Aed01

AED-01 Bachelor’s Degree Programme (BDP) Also for: B. Com (A & F) B. Com (CA & A) B. Com (F & CA) ASSIGNMENT 2012-13 Application Oriented Course AED-01: EXPORT PROCEDURES AND DOCUMENTATION For July 2012 and January 2013 admission cycle School of Management Studies Indira Gandhi National Open University Maidan Garhi, New Delhi-110 068 Application Oriented Course AED-01: Export Procedures and Documentation ASSIGNMENT – 2012-13 Dear Students, As explained in the Programme Guide, you have to do one Tutor Marked Assignment in this Course.Assignment is given 30% weightage in the final assessment. To be eligible to appear in the Term-end examination, it is compulsory for you to submit the assignment as per the schedule. Before attempting the assignments, you should carefully read the instructions given in the Programme Guide. This assignment is valid for two admission cycles (July 2012 and January 2013. ) The validity is given below: 1. Those who are enrolled in July 2012, it is valid upto June 2013. . Those who are enrolled in, January 2013 it is valid upto December 2013. You have to submit the assignment of all the courses to The Coordinator of your Study Centre. For appearing in June Term-end Examination, you must submit assignment to the Coordinator of your study centre latest by 15th March Similarly for appearing in December Term-end Examination, you must submit assignments to the Coordinator of your study centre latest by 15th SeptemberNote : In case you receive the study material and assignments late, you can submit the assignment responses within one month after receiving the study material. 2 TUTOR MARKED ASSIGNMENT Course Code Course Title Assignment Code Assignment Coverage : : : : AED-01 Export Procedures and Documentation AED-01/TMA/2012-13 All Blocks Maximum Marks : 100 Attempt all the questions 1. 2. Describe the various kinds of commercial documents used in export. Discuss the significance of commercial invoice and bill of lading. 10+10) (a) Describe the various factors which may motivate a firm to export. (b) Discuss the methods of dispute settlement in international trade. (10+10) (a) (b) Discuss the foreign trade policy related to export. What do you mean by cargo insurance? Why should the goods be insured? 3. (10+10) 4. Distinguish between the following: (a) FOB Contract and CIF Contract (b) Total Loss and Particular Loss Write short notes on the following: (a) Export Licensing (b) Procedure for Claiming Duty Drawback (10+10) 5. (10+10) 3

Importance of computer in education system Essay

The computer and its related technologies are now such an integral part of every day life that it must be an ingredient in educating for participation in present and future society. For educators it is a tool for lesson preparation: – research information on any topic – find activities to print and use – gather ideas used by other teachers for presenting lessons – using word processing, page layout and presentation software to produce activity pages and audio/video lesson presentations The internet in particular keeps teachers up to date when they join in on forums and blogs about teaching practices etc. Online courses are also available for adding to teaching credentials. (This is a boon for those who are not living close enough to a large city centre where classes, conferences and meetings can easily be attended. ) For students, access to computer (and in particular internet technology) at school can be a great leveler. While most students are comfortable using the computer, those who do not have one at home are at a disadvantage for completing assignments that require research and producing a printed document. The computer can be a tool for learning in many areas of the curriculum: – math teachers should take advantage of the opportunity to allow students to create spreadsheets to manipulate data – formal teaching in the finer points of using word processing and presentation software to produce polished presentations of creative writing or research reports would prepare students to meet the expectations of the business world – music classes can be dynamic when students are given the opportunity to explore composition using computer software. Learn about varieties of music by listening to files available on the internet – set up pen pals in another city or country for their students to learn communication skills (also a great way for students who are learning another language to practise by â€Å"chatting’ with another student Teachers are constantly discovering new ways to integrate computers into their programs. In today’s education the computer has become the new pencil and paper, text book, library and in many cases   teacher.

Bringing a Change in Organizational Culture Essay

Critically explain why changing organisational culture is so difficult and how managers can do it. Culture can be defined as â€Å"a set of basic tacit assumptions about how the world is and ought to be that a group of people share and that determines their perceptions, thoughts, feelings, and, to some degree, their overt behaviour† (Schein, 1996). Organizational culture is depend on differences in norms and shared values which are learned in workplace and to direct behaviour of members in the particular organisation. Cabrera, Cabrera& Barajas 2001) Organisational culture was built on its shared beliefs and values which was the guidance to solve problems. This essay will introduce the definition of organisational culture and explain why changing organisational culture is so difficult. The main reasons are the fear of uncertain future and difficult to establish the organisational culture. In addition, the essay is to interpret how managers can change organisational culture and how does it work. Managers can change organisational culture through communication and management strategies. This essay may introduce the detail about changing organisational culture. Most scholars think that changing organisational culture is difficult; however a few people think it is easy to change organisational culture. As Chu (2003) stated that organizational culture is contributed to change. In his opinion, organisational culture can collect different values and actions to form a frame to guide the behaviour of members within an organisation. In other words, organisational culture can shape what employees do in the company and control tendency of company. For example, a company may have employees who are unwilling to change and who are conductive to change, if managers recruit staff that are innovated and willing to change, they may be the new power to change organisational culture. Therefore, to form a â€Å"change† culture can make changing organisational culture easier. However, it is also difficult to establish an organisational culture. It is need to experience a long time and face lots of difficult and challenges. According to levels of cultural analysis (Wood 2004), it shows how difficult to form the organisational culture, especially the deepest level of cultural analysis: common assumption. Common assumptions are to collect truths that organisational employees shares as a result of their common experiences and that direct beliefs and behaviours. It is extremely hard to isolate these modes, but it is interpret why culture is full of organisational life. It is hard to shape common assumptions if members of the organisation do not experience same ups and downs or cooperate long time. As Ferrara-Love (1997) stated that organizational culture does not appear in a night. On the contrary, organisational culture evolves during the time, and is the collective beliefs of individuals who worked together. Therefore, it is hard to establish organisational culture, to say nothing of changing organisational culture. At the same time, it is debatable to recruit plenty employees when the company want to change organisational culture. The new power is unstable to the company. It is hard for managers to control the new employees and it still need to cost much time. To conclude, it is difficult to change organisational culture. Organisational culture plays an ineradicable role to different kinds of organisational behaviours and members within organisations. Thus, it is always failure if certain problems of organisational culture were not being considered. Moreover, if managers want to change organisational culture which focuses on shared values or beliefs, it will be more difficult; because on the deepest of organisational culture, it formed invisible and omnipresent old guard or power which makes organisational change failure. As Locus and Kline (2008) stated that organizations always appear â€Å"learning disability† and â€Å"defensive routines† which obstruct the learning and organizational change. It shows the strong of conservative power. When managers try to change the organizational culture, they always face opposition. What was worse, the conservative power always important to the organisation. They make huge contribution to the company, which used to promote the development of company. Therefore, they play an important role to organisation. It is difficult for managers to challenge their authority. Moreover, the reason people do not want to change is the nature of people. People are easy to be used to do one thing and do not want to accept new thing. They are afraid of the unknown thing after change. As Ferrara-Love (1997) stated that people are comfortable with exist ways to finish the work. In their opinion, change is just the threat to their peaceful. Thus, they do not want to change organisational culture and dispute to change. It is obvious that changing organisational culture is so difficult. Leadership is the key to change organisational culture. The achievements of an organisation mostly depend on the leadership of managers. As Fishman and Kavanaugh (1989) stated that the culture of an organization and how employees want to change was formed substantially by leader. For example, if managers uphold to change organisational culture steady and have enough ability to direct staff, it will achieve maximum results with little effort to change organisational culture. Thus, managers are the guidance of the company; they are main factor to change organisational culture. Clement (1994) also expounded that management leadership is basic factor in a major organisational change effort. From this, it can be seen that the importance of leadership in change organisational culture. However, it is hard to change managers. If managers are not satisfied with their employees, employees can be changed, but managers will not changed unless the company go bankrupt. Thus, the most difficult to change organisational culture is to change the mind of managers. For instance, if managers make no attempt to make progress and milk-toast, it will be the most resistance to change organisational change. For this reason, the best way to change is from up to bottom. At the same time, change the mind and ability of leader is the difficult demand for changing organisational culture. To change organisational culture, managers have lot of things to do it. The role of managers is very important through up down system. As Ott (1989) suggested that the leader can do lots of things included staff selection, socialization, removal of deviating members, cultural communication and role model to guide behaviour. For example, managers can choose employees who will support to change organisational culture. Although it will not change the situation directly, they can be the power push the step of changing organisational culture. In the same way, managers can fire part of staff who opposes to change. It is not only reducing resistance to change organisational culture, but also overawe the opponent to change their minds. Furthermore, managers need to be the role model to change organisational culture. The behaviour of managers can be the maximum power to guide behaviour of managers. For example, when managers try to change organisational culture but not to do anything to change it, employees will not follow managers with any anxiety. To sum up, it is important to be the role model of changing organisational culture for managers. Furthermore, communication is an important tool for managers to change organisational culture. According to Fry (2003), he examined that leadership as motivation to change; managers need to communicate with employees about their feelings. In other words, managers should get in touch with employees and let them know core values of changing organisational culture and the need of changing organisational culture. The employees may understand the determination of managers and why to change organisational culture. Then, they can have their decision about changing organisational culture. In this way, it can reduce the distance between managers and employees, and let employees think they are also the participants to change organisational culture, they are not insignificant. When employees think they are the part of changing organisational culture, they will follow managers and try their best to help managers. At the same time, managers communicate with employees also can understand what employees think about and then do well about interactive. In addition, it can reduce the fear of employees about unknown future. As Kanter, Stein and Jick (1992) stated that communication is basic tool within any change process and failure to change always because of the feeling uncertain and anxious about their future. Thus, communication is very significant for managers to change organizational culture. In addition, to help employees to change organisational culture, managers need to teach them related skills and knowledge to work differently. As Ke and Wei (2007) suggested that employees thought to learn skills and knowledge as their main responsibility. Thus, employees may accept skills and knowledge easier than accept directly new culture. When they understand how to do, it may easy for them to accept to change organisational culture. At the same time, it is also the good way to remove their fear to uncertain future. When they master relevant skills and knowledge, they will be confident to deal with change of organisational culture. In this way, they will not fight against to change organisational culture as before. Then they can be the power help to change organisational culture. The most important things to change organisational culture are to change origin perception and beliefs. According to the definition of organisational culture, if managers want to change organisational culture, they must change shared values. The same as Whitely (1995) said that, managers need to be able to help employees to remove the past values which are not consistent with current shared vision of future organizational arrangements. The shared values and beliefs are keys of the organisational culture. Thus, managers need to change origin values of employees to change organisational culture. For example, managers can change new uniform to show the new the new appearance of company. According to Wood (2006), managers can create processes, systems and ways of working that enable to put the new values into practice. The new values can take place of the past one. In addition, managers can recruit and select new employees to help change origin values. As Harris and Metallinos (2002) stated that new employees were outside the company who did not affect by origin organizational culture, thus they were easy to accept new culture. That is why managers to select new employees to enlarge the power to change organizational culture. The new values and beliefs can be brought into the company in this way. In the same way, managers can retrain employees and engraft new rules to them, although it will not have better effect than new employees, it also can help to change organizational culture. In a word, managers need to create new values and beliefs to substitute origin one. Technology change also can promote to change organisational change. Although Weick (1990) thought technology change may make people anxiety about the values of new technology to their work, the new technology is the progress to organisational culture. There is no doubt technology change may improve work efficiency which may improve organisational culture. As Harris and Metallinos (2002) suggested that the application of new technology and subsequent development of system would promote standardization. The implementation of new technology can make employees understand new things which break routine. It also can be the sally port to open the mind of employees, let them know advantages of changing. When they can accept technology change, it is easy for them to support to change organisational change. Thus, managers can first bring in advanced technology to improve organisational change. Then teaching them to learn about it and establish new values in this process. This essay introduces what are the organisational culture and two main parts of organisational culture, the reason why changing organisational culture is difficult and how managers do to change it. This essay support to change organisational culture is so difficult because of the fear of unknown and difficult process to form organisational culture.

Sports Essay Example | Topics and Well Written Essays - 750 words - 1

Sports - Essay Example In his Sport: A Cultural History, Richard Mandell leads the reader through the history of sports and really gets at the core of what makes sports such a quintessentially human activity and enterprise. For the Greeks, for example, sports were a time for ritual and pageantry. They set their calendars according to the various sporting events that they loved so much. Sports and sporting events were inherently tied to religious practice and offerings to the gods would be made at the various Olympic games. Indeed, the Olympics began as a way of honouring the important gods whom the Greeks loved so much. Athletes were worshipped as paragons of physical beauty and power and their deeds were written about in epic poems. Indeed, some athletes were even seen as human gods and were worshipped by their followers. There was of course an additional element to the athletic prowess, as Mandell clearly indicates in his fine book: Athletic talent, potential or proved, was a precious commodity in the economic and political commerce of Greece. Established or promising athletes were therefore worth nurturing. The superior athlete, then, functioned in a quasi-sacred atmosphere, his performances ritualistically arranged and reverentially viewed. The awesome semi-divine status given the victor . . . has never been equalled subsequently. (53) Mandell's book was written in 1984, before the rise of celebrity cult that surrounds many athletes today. Just as in the ancient world a cult would develop around a god or a goddess, so today many athletes have thousands of fans. In the past, gods and saints would have icons-today fans cover themselves in logos and put posters on the wall. There are a lot of similarities between gods and athletes in today's contemporary world. So while athletes such as David Beckham and Alex Rodriguez may not literally be considered divine in today's world, they certainly do occupy a position of significant power and fame-more so than nearly anyone else on the planet. They are often involved with beautiful women, fast cars, and advertising campaigns. They make tens of millions of dollars and can do virtually anything they like. Indeed, it is fair to say that in today's world the culture of sports celebrity has never been so vibrant. We truly live in unique times. In the 20th century sports have been about celebrity, but they have also been about politics too. This is another important point made by Mandell in his book. He compares the rivalries between Communist countries and capitalist countries throughout the last one hundred years. He shows how much governments and people invested in their athletes as representatives of their political ideologies and their nationalist hopes. Sports was in a way an extension of war by other means. The Soviet Union especially is an interesting case study in the subject. Mandell writes: There was no indigenous sports tradition acceptable for the vast empire of many cultures, so the Soviets adopted all those sports that since 1896 had been steadily integrated into the Olympic program. The thorough recruiting of potential stars, the scientific investigation of principles of movement and performance, the refinement of apparatus and training that had characterized American and then Japanese and Nazi sport were pushed much further. Fitness exercises were introduced at all levels of education and even on the job. (265) Sports for the Soviets were politics. Sports were international prestige and a

OPPORTUNITY COSTS Coursework Example | Topics and Well Written Essays - 1000 words

OPPORTUNITY COSTS - Coursework Example EXPLAIN THE CONCEPTS OF COMPARATIVE AND ABSOLUTE ADVANTAGE The concept of ‘Comparative and Absolute Advantage’ holds primary importance being closely related to profit maximization and increased productivity. It principally indicates the capability of a producer to manufacture products and/or services at a lesser opportunity cost than other producers operating in almost identical conditions. A comparative advantage provides a company the capacity to trade goods, products and services at a lower fee than other players in the market for the purpose of attaining higher sales margins and revenues. In the similar context, the concept of obsolete advantage can be identified when a company produces larger volume of goods than that of its competitors with a given amount of resources. In both these situations, companies are affirmed to obtain advantages over its competitors in terms of cost of production and profit margin (Horsley 1-99). For example, in case the USA and Canada ha ve been producing differing quantities of potatoes and rice in a year [as illustrated in the below table], both the producers will have to incur differing opportunity cost. ... Assessing both these situations, it can be observed that Canada will have a comparative advantage in producing larger volume of potatoes, with the given amount of resources and also by incurring lesser opportunity cost. Thus, Canada should produce potatoes. HOW DOES TRADE AFFECT THE PRODUCTION POSSIBILITIES FRONTIER? EXPLAIN Production possibilities frontier, in simple terms, can be referred to as a frontier or a graph indicating the maximum output producing possibilities for a particular producer to manufacture two products at a given point of time. Indicating all possible combinations of the given two products, the production possibilities frontier tends to conclude the possible points at which the producer can manufacture at a greater production level in comparison to the other commodity’s normal production level with the fixed amount of resources (Horsley 1-99). Trade can affect the production possibilities frontier in a positive as well as in a negative manner. For instan ce, if the activities related to trade and commerce increases in a country, the requirement of the resources and production capacity with respect to two given commodities is also quite likely to increase (Horsley 1-99). Precisely, the concept of production possibilities frontier indicates the points at which a producer can make the maximum use of the resources allocated to produce one or more commodities. Notably, the points on the curved line of production possibilities frontier [refer to the diagram below] depicts efficiency of the producer to use the given amount of resources to produce maximum amount of product A and product B. On the contrary, the points below the curved line depict the inefficiency of the producer to make effective use of the resources allocated.

Journal entry Essay Example | Topics and Well Written Essays - 250 words - 6

Journal entry - Essay Example at the solicitation of japan, was still in conversation with its government and emperor looking toward the maintenance of peace in the pacific† the speakers character of being a peaceful person trying to seek peaceful ways of solving a conflict is brought out. He tries to convince the congress that his government made all the peaceful attempts to find amicable solution and indeed it’s the government of japan that is at fault and therefore drastic action should be taken against them (Gross et al 78). â€Å"Yesterday the Japanese Government also launched an attack against Malaya. Last night Japanese forces attacked Hong Kong. Last night Japanese forces attacked Guam. Last night Japanese forces attacked the Philippine Islands. Last night the Japanese attacked Wake Island. And this morning the Japanese attacked Midway Island.Japan has, therefore, undertaken a surprise offensive extending throughout the Pacific area. The facts of yesterday and today speak for themselves† the speaker uses a lot of repetition employing the artistic style of logic, giving supportive evidences to bring out the facts that indeed japan is offensive due to the many attacks and congress should declare war with them (Gross et al 88) The other rhetorical technique employed by the speaker is the use of pathos when he says â€Å"The attack yesterday on the Hawaiian Islands has caused severe damage to American naval and military forces. I regret to tell you that very many American lives have been lost† the speaker tries to bring out the damage and loss of lives caused by the attack therefore tries to invoke emotions of sympathy and anger for the lives lost and anger about the attack hence the reason why congress should act(Gross et al 90). The speaker used evidence based arguments that he illustrated with a lot of emotions to bring out the urgency of the matter to congress and the American people. The use of artistic techniques such as logos pathos and ethos brought out the speakers character

AN INDIVIDUAL PROJECT PROPOSAL Dissertation Example | Topics and Well Written Essays - 1000 words

AN INDIVIDUAL PROJECT PROPOSAL - Dissertation Example The Standards for acquiring accessibility through technical specifications and interface design have been laid down for the conventional Web, but, how far e-learning systems are conforming to these standards is still unclear. More so, there remains conflicts between educational features and usability. There is a need for Institutions to meet recent accessibility andb fulfil government targets to deliver growing access to Higher Education. It can only be achieved by evaluating e-learning system usability and identifying the arising accessibility needs. Aims of the research The project intends to fulfil certain objectives. The research project will look at the current levels of accessibility in e-learning systems, that is the Virtual Learning Environments. It will go ahead to assess theproblems faced by disabled users in accessing system features these will include textual resources, interactive content, navigation features and tools for communication. The other things that will be car ried out may include semi-structured interviews with educational support staff, among them lecturers and Information Services staff that support the disabled users example, disability support staff,e-learning support. When it comes to the empirical research with learners, six to seven university sites will be taken to assess practices and policies in accessibility support that is within different e-learning systems. This practical investigation and research activities will help gain user views and perspectives on system usability example through questionnaires or interviews. There is a need for Institutions to know which features should be avoided or used with care so that to enable disabled students to access e-learning systems. They should also be able to know the features that are educationally valuable and if they can be supported with more training for disabled learners. General context descr?pt?on This project is personal research in the field of Information Science,especially within the area of end-user systems accessibility. It a coomon issue that in Higher Education there is constant innovation and changing methods to provision of online services, but , there remains grey areas when it comes to issue of user accessibility. This issue has turned into a neede requires secondary consideration. This research looks towards underpinning improved provision of accessible systems for disabled adult learners. It has been discovered that one of the major barriers for people with intellectual disabilities in accessing electronic programmes is due to the lack of accessible adult training material and information in simple language. Through focusing directly on people with disabilities, and also on the staff of adult education or e-learning providers, this Project tackles this problem and focuses on improving the accessibility of lifelong learning programmes. Research questions The research is aimed at answering the following questions: 1. What are the major obstac le faced by students when undertaking learning in an online setting? 2. What are the usability and accessibility issues in e-learning systems? 3. What are the training needs of disabled users in facilitating online learning? 4. How can usability and access issues be practically addressed? Research methodology The research will go for a practical research element to investigate questions outlined in the study mainly targeted at

Beach resorts Essay Example | Topics and Well Written Essays - 3500 words

Beach resorts - Essay Example In this context, the analysis of the characteristics of beach resorts requires the reference to beach, which is a prerequisite for the establishment of a beach resort. Beaches are areas that meet the following criteria: ‘a) they are common property, b) they are highly dynamic energy systems and c) tourism is the main coastal activity on them’ (Botero and Hurtado 2009: 133). Beach resorts have been related to specific issues as of their development, management and operations. These issues are highlighted in the literature. In regard to their development, beach resorts need to be aligned with the standards set by local authorities for establishing a business in beach resorts. The above requirement is necessary only for beach resorts that are also used as centers of business activities. This means that all businesses established near beach resorts have to meet specific conditions and cannot expand their operations above the limits set by the relevant laws. When referring to beach resort as a coastal system, then a different approach would be used for explaining its development. The development of such system refers to a series of activities that need to take place so that a beach can be used by people for recreational purposes, which are among the key purposes of the specific systems. In the above case, the term development refers to projects for cleaning the beach and for taking measures so that the safety of any person that would use the beach is secured, as possible. Of course, they are coastal areas in which no development task has taken place and which are often characterized as beaches just because the have the characteristics of such ecosystem. For example, a coastal area which is not organized, being far from a residential area with no access to facilities for covering basic needs, such as food or cleaning, can be considered as a beach, a practice that would not be correct: such place is not a beach but it is a coastal area. Beaches are usuall y organized for providing to their visitors access to basic facilities. In the context of this study emphasis is given on beach resorts as systems related to business activities, such as the Marriott’s Marbella Beach Resort the characteristics of which are explored below. The development of beach resorts as areas where business activities are developed, needs to be combined with appropriate management plans otherwise any expected benefits would be eliminated. More specifically, in the case of beach resorts, management refers to activities such as the monitoring, periodically, of the condition of the beach in terms of litter accumulated, of damages that have been possible caused on certain of the area’s elements due to weather or due to human activities, of pollution caused by residential or business blocks that are established near to the coast and so on. Other activities, such as the gathering of funds for supporting projects required for keeping the beach clean or fo r other needs of the beach, can be also incorporated in beach resort management. In regard to the operations of beach resorts, emphasis should be given to the following fact: the conditions on which the daily operations of a beach resort will be based are set in the context of the resort’s management plan. In the specific plan the objectives that the particular resort has to achieve are defined; these objectives can be achieved only if an effective management plan

Terrorism in the 21st century Essay Example | Topics and Well Written Essays - 1000 words

Terrorism in the 21st century - Essay Example This paper examines the Israel-Palestine conflict and terrorism in Middle East as well as all over the world. The paper also argues the role of western foreign policies and the strengthening extremist groups in the growth of world-wide terrorism. There are many countries i.e. the USA that tried to mediate the Israel-Palestine issue but at the end they remained unsuccessful. This conflict is a big terror for the world peace as the extremist groups of both Israel and Palestine are being strengthened. If the conflict does not get resolved within next few years, it would definitely cost a lot and whole world have to suffer. Extremists should not be given an opportunity to govern their respective states. They need to be discouraged by both sides through the right to vote. (Berrebi and Klor, 2006). The only way to make this world safer and terrorism free is the dialogue. The cross-cultural dialogues are the only things that can mediate the conflicts including Israel Palestine conflict. The Israeli operations in Palestine give birth to new terrorist attacks. The Israel-Palestine conflict is leading to the growth of terrorism not only in the region but also to a large extent all over the globe. The conflict started soon after Jews entered the Palestinian territory. The Arab nationalists joined the ground to defend the Palestinian homeland. This conflict became more vivid with the passage of time. There are many fundamental and extremist groups like Hamas still determined to keep the Israelis out of their territories. These types of extremist groups are at the both end. Israel also have religious extremist. These are extremist known as Jews Zionist (Naqib, 2003). Another reason that boosts terrorism in the region but all over the world happens to be the unemployment and rate of poverty. The rate of poverty and unemployment is rising day by day in the Israel and Palestine. The situation in Israel is still satisfactory but the circumstance in Palestine is something

Session Hijacking Essay Example | Topics and Well Written Essays - 1250 words

Session Hijacking - Essay Example There are two types of attacks in session hijacking namely; the active and passive attack. In active attack, the hacker identifies a session that is active and takes over by force by forcing one member to be inactive (offline). In passive attack, there is hijacking of a session by a hacker who remains inactive and observes information being transmitted from and to the computers. The attack strategy known as the denial of service is used as a common component in these attacks to either crash it or jamming its network connection. In some instances a hybrid method of attack exists which the hacker may either watch an active session for sometime before taking over or the attacker may decide to inactively watch a session for sometime before becoming active and hijacking it (Hope & Walther, 2008). Another form of the hybrid method is where one watches a session and introduces data into the session that is active periodically with no intentions of hijacking the session In perpetrating a session hijack, four methods are used. These are session fixation, session side jacking, and cross-side scripting. In session fixation, the attacker sets the id of the user’s session to another one, which is known to him. For instance, he can send an email to the user containing a link that has an id of a particular session and wait for the user to log in.

How E-Commerce Has Changed the Way to Do Business Research Paper

How E-Commerce Has Changed the Way to Do Business - Research Paper Example This essay will also give a brief history concerning E-Commerce and also state the advantages and disadvantages of E-Commerce to customers/ businesses. Earlier on, E-Commerce was branded as the facilitation of marketable business electronically by means of technologies like Electronic Funds Transfer (EFT) and Electronic Data Interchange (EDI). These technologies were introduced early in the 1970s. Technological advancement led to introduction of other systems like automated teller machines (ATM), telephone banking, airline reservation system and credit cards which are also forms of E-Commerce (Reynolds, 2009). In the early 90s, Tim Berners-Lee invented the World Wide Web which profoundly altered a scholarly telecommunication system to a global communication system named www or the internet (Plant, 2012). In time, many European and American business firms offered their services through the Worldwide Web. Since then, people are much conversant to E-Commerce with the ability to purchase various goods through the internet using electronic payment services and secure protocols. As defined earlier, E-Commerce is the process of buying and selling products and services from the internet, especially the World Wide Web. When retail selling is used, then the term e-tailing can be used. E-Commerce is divided into several categories. They include E-tailing, Electronic Data Interchange (EDI), business-to-business transactions, gathering and use of demographic data through Web contacts, E-Mail and fax and the security of business transactions (Plant, 2012). E-Commerce has a number of benefits to customers and other businesses. They include efficient buying and selling procedures as well as an easy way of finding products. Buying and selling of products is not limited. The customers are able to purchase products and get services 24 hours daily. E-Commerce also allows customers to select products from various providers without the need of moving physically from one point to ano ther. This process, therefore, cuts down the rate associated with processing, inventory management, marketing, customer care and information storage (Reynolds, 2009). This in turn, reduces the burden influenced by infrastructure to conduct businesses. This form of business is easier to start and run. Moreover, this invention allows more customers to find products and services without hypothetical geographic boundaries. Lastly, there is no need for physical company setups since the business is run on a network. Since the early 1990s, the internet has tremendously grown as a technologically enthusiastic tool to many corporations. Improvement in technology and other forms of E-Commerce also came in play. There are four principal categories of E-Commerce business models. They are business to consumer (B2C), business to business (B2B), consumer to business (C2B) and consumer to consumer (C2C) (Plant, 2012). In E-Commerce, there are eight unique features that enable this web shopping proc ess run successfully. They are global reach, ubiquity, richness, universal standards, interactivity, personalization and customization and information density (Plant, 2012). Ubiquity is the leading factor in the success of any E-Commerce business. Online stores never close and they are available every time and anytime. Global reach is also essential in ensuring a successful E-Commerce busines

General Principles of Ecology Essay Example for Free

General Principles of Ecology Essay The term ecology refers to the study of abundance and distribution of living organism in an ecosystem, together with the interaction that exists between them and the natural environment. The distribution of organisms is usually influenced by the adaptation of a certain organism to the environment. An adaptation refers to an organism’s ability to exist successfully in a given environment. Therefore, organisms can only exist in environments that they are adapted to. When a given species of animal or plant is adapted in a given natural environment, then it becomes distributed in that environment densely and in high numbers. Those that lack the ability to adapt well are poorly distributed, since they cannot cope with the pressures or stress that emanate from the environmental conditions. Different species of plants can be adapted to low and high –nutrient environments. Plants always try to adapt to the environments in several ways. The plants that inhabit low –nutrient areas grow at a slow rate, as an adaptation to the scarcity of nutrients. These plants also have the ability to recycle nutrients internally. Those in high nutrient areas on the other hand grow fast. They have the ability to control the absorption of nutrients at minimum levels. The breakdown of dead organic matter in the soil undergoes several processes. The first process of breakdown involves the alteration of the organic matter chemical components. This is then followed by another process, whereby the chemical components are split or fragmented. After undergoing these two processes, the organic matter mineral nutrients are then released into the soil and they are then converted into simpler components that can be absorbed by the plants. The day length influences the seasonal activity of plants and animals, because the length of the day length triggers certain changes. These changes include the climatic patterns in an area. Both plants and animals synchronize their behavioral and physiological activities with the seasonal changes. By doing this, they are able to carry out certain activities based on the season of the year. For example, the migration in animals is sometimes synchronized with the seasonal changes. Plants on the other hand, synchronize activities such as pollination with seasons when the activity can be easily facilitated by the pollinators. Temperature conditions in a given natural ecosystem affect the response of both the homeotherms and the poikilotherms. While the homeotherms have the ability to maintain their internal environment temperature at a stable level, the poikilotherms on the other hand cannot regulate their internal environment temperature. Changes in temperature triggers behavioral changes in poikilotherms as they try to regulate their body temperature depending on the external temperature. For example, some poikilotherms may bask out in the sun so as to regulate body temperature by warming their bodies. The homeotherms try to regulate their body temperature using feedback mechanisms in their body systems. For instance, their blood vessels may undergo dilatation or constriction as their bodies try to conserve heat. Climatic changes may trigger an inactive state in animals, especially during the cold season or winter. Hibernation and torpor are two examples behavioral adaptations in animals to very low temperatures. In both, animals go into a state of inactivity and they lower their body metabolism as a strategy of conserving energy . However, there is one major difference between the two. In hibernation, the animals’ body temperature at a significant level. Animals that hibernate become inactive for a long period of time. Torpor on the other hand is whereby animals lower their body temperature but at minimal levels as compared to that in hibernators. Animals that undergo torpor may be inactive but usually wake up several times. The Black Bear is not considered as a true hibernator because its body temperature does not reduce significantly as that of a true hibernator . Furthermore, the bear remains alert and active during the period of â€Å"hibernation†. References Odum, E. P. (1971) . General Principles of Ecology, Third Edition W. B. Suanders Company. Smith, T. M. , and Smith, R. L. (2005). Elements of Ecology. (6th Edition). Benjamin Cummings Publishers

Improving Kings Medical Center

Improving Kings Medical Center Kings Medical Center provides various health services within the City and its locality. They have sites in three location (Staten Island, Queens, and Manhattan) spread across the City and have enlisted our service to develop their Information System. Their requirement included elements covering a Web site, Networking, Management Information System (MIS) and a Database. They have reviewed their organization structure and their strategic plan has revealed the need to reconstruct their functions, services and human resources application We are a dedicated medical institution, aiming to provide the highest quality care for our patients and maintain a relaxed, friendly and comfortable work environment for our staff and other users. We guarantee the well-fare and safety of our patients as our priority and ensure confidentiality of all nature. The commitment of our staff, physicians, volunteers and community partners to our mission, allows us to maintain a quality standard of caring, promoting wellness, relieve suffering and restore health as humanely as can be done. In consistence with the best service available we will ensure the highest value to all our users. We endeavor to treat all our patience and client fairly, efficiently and with the care and respect required to satisfy their needs and accordingly. Vision The vision of king medical center is to provide place for extraordinary achievements and Significant infrastructure growth. The vision of the king medical center is to provide large facilities of medical therapy. Organizational Chart The organizational chart of the medical center describes the overall organizational structure .This describe the administrative structure from top to the bottom like director to the peon. The director is the top of the organizational structure and there is multiple divisions like energy and plan divisions. Current Situation and Problem/ Opportunity Statement à ¢Ã¢â€š ¬Ã‚ ¢Improving the appointment system and reducing walk-ins to a minimum à ¢Ã¢â€š ¬Ã‚ ¢Assigning doctors to patient à ¢Ã¢â€š ¬Ã‚ ¢Creating and implementing a web site à ¢Ã¢â€š ¬Ã‚ ¢Eliminate redundancy within the filing system and implement software and applications to regulate normalcy and consistency Critical Assumption and Constraints .There must be specified proposal which include identifying the earliest possible state including critical assumptions and revenue drivers, operating cost, social and environmental factors. .There is regularity, legislative and relevant acts which may impinge the proposal need. Which may identify including information? .There is information which can describe sensitivity of assumption need which is to be provided. Analysis of Options and Recommendation à ¢Ã¢â€š ¬Ã‚ ¢Keeping machines on standby when not in use à ¢Ã¢â€š ¬Ã‚ ¢Ensure all medical closet are secured à ¢Ã¢â€š ¬Ã‚ ¢Accessories should be stored in designated area and appropriately to eliminate risk à ¢Ã¢â€š ¬Ã‚ ¢Provide security at each site à ¢Ã¢â€š ¬Ã‚ ¢Sign posting at each location PROJECT INTEGRATION MANAGEMENT Preliminary Project Requirement There must be more attractive environment and higher perceived quality. There should no time gap for significant relationship between the perceived wait times. There should be project and its impact on existing infrastructure. Budget Estimate and Financial Analysis The project was allocated a budget of $800,000. The labor cost percent includes a forty hours per week at a rate of $100 per hour for the project manager, other team members between $80 $90 per hour (according to experience and qualification) and consultants at a rate of $150 per hour. Other consideration of the project will cover the outsourcing of software and other services costs. The discount rate for this project is 8%, reflecting the estimate after the discounted costs and benefits have been implemented. Schedule Estimate We estimate one year to complete the project and will be providing additional maintenance and technical support throughout an agreed period. We will be managing and monitoring the operation of applications and recommendations across the organization. Potential Risks There are several potential risks on project evaluation like cost assessment risk and time bound project have the overrun risks. The potential risks are the risk that can occur simultaneously which can identified during running phase. This type of risk can affect the running schedule of the project and also affect the cost of the project. Weighted Decision Matrix Initiating Assign a project manager Develop a business case Identify key stakeholders Prepare project charter Hold project kick-off meeting Planning Hold team planning meeting Prepare team contract Prepare scope statement Prepare WBS 2.4.1 Create Milestones Prepare schedule and cost baseline Determine task resources Determine task durations Determine task dependencies Create Gantt chart Identify, discuss and prioritize risks Develop project plans Review project plans Approve project plans Executing Analysis Task Collect data on organization Collect information on project User inputs Internet site contents Templates and tools Articles Links User requests feature Web site design Web site construction Web site testing Web site promotion Web site roll-out Project benefits measurement Design Task 3.2.1 Collect detailed requirement for all programs 3.2.2 Design network program 3.2.3 Design database 3.2.4 Design MIS 3.2.5 Design Web site 3.10 Implementation Task 3.10.1 Network 3.10.2 Database 3.10.3 MIS 3.10.4 Website 3.11 Training 3.11.1 Employees training 3.11.2 Technical Support 3.11.3 Access Security Specification 3.4 Testing 3.4.1 Test programs 3.5 Roll Out and Support 3.5.1 Support User 3.5.2 Roll out New programs 3.5.3 Technical Support Monitoring and Controlling Project reports 4.2.1 Change request report 4.2.2 Organizational process assets updates 4.2.3 Project document updates 4.2.4 Project management plan updates 4.2.5 Status Reports 3.2.6 Control changes Closing Final project report Final presentation Sign-off on project Lesson learnt reports Financial Analysis for Kings Medical Center Project The financial Analysis for the king medical center is depend on recourse and the financial fund and time validation ,human effort etc. The financial analysis is depend on operational cost and the project risk assessment ,project structure and managerial elements of project. The risk type and identification affect the project cost and running time and risk exposure is time taking process so financial schedule affected by risk. The financial analysis depends on the risk assessments. Project Charter Project Title: Kings Medical Center Project Project Start Date: April 28, 2010 Projected Finish Date: April 28, 2011 Budget Information: A budget of $800,000 has been allocated to fund the project over a one year period. This cost will be used up to fund the All in One (AIO) Tech development team, consulting personnel, hardware and software purchase, and utility fees. An initial estimate requires a total of 40 hours per week labor cost, considering that the team works a standard eight hour day shift. Project Manager: Foxy Brown, 646-238-1224, [emailprotected] Project Objectives: The goal is to provide a complete IT Infrastructure overhaul to Monroe Medical Center. In doing so, employees will be able to retrieve and update patients file and information accordingly, assign a doctor to groups of patients, produce departmental reports, and share information across all locations within a reasonable time frame. An online appointment system will also be created to minimize patient waiting time and improve the system for walk-in patients. Main Project Success Criteria: The project is scheduled to be completed within one year at the provisional cost of $800,000. The end product of this project is guaranteed to support the overall functionality of Kings Medical Center operations. This will assist them to negotiate lower premiums and track improvements in patients waiting time among other requirements they have stipulated. It will also provide solid evidence for other benefits, such as improving morale and productivity. Additionally, the project should be able to pay for itself within two years of completion. It must also have a positive net present value (NPV) and a 50% or greater return on investment, in order to be considered a successful project. Additionally, the project payback must not be beyond 2 years. Approach:  · Select a project manager and project team  · Identify project requirements and list milestones to meet accordingly  · Incorporate best practices methodologies  · Incorporate excellent testing procedures  · Use corporate standards in all application development  · Using a prototyping approach to development  · Provide training and develop support procedures  · creating a highly specific and detailed documentation Integrated Change Control The integrated change control is the process which can be implemented during the all changes which involves in running state in project. It is quite often implement over the course of a project life cycle. PROJECT SCOPE MANAGEMENT Requirements Document The requirement document for project scope document is resource, financial status, time schedule, and operational cost structure, estimation time for each module. The requirement document must have the work breakdown structure and time estimation graph. It can also describe the overall structure with financial status. Requirements Management Plan The requirement management plan utilize the proper resource for running status of any hospital effectively and efficiently. It can also describe the requirement of different modules and resource management. Requirements Matrix for Kings Medical Center Project The requirement matrix for king medical center project depends on several phase and resource allocation graph .The requirement matrix is depend on supply and demand of resource and operational cost. The requirement matrix is sparse matrix for resource allocation to different module and reduces the overall operational cost. Scope Statement (Version 1) PROJECT TIME MANAGEMENT Work Breakdown Structure for Kings Medical Center Project The work breakdown structure is known as hierarchical discrete structure which divides the work task in different small module. Thus work breakdown structure for the kings medical college project can be subdivided task like operational cost which having subtask the doctors fee and medicine cost, bed charge, equipments cost etc. WBS Dictionary The WBS dictionary must include the overall subdivided task and which type of structure tree or list .The WBS dictionary describes the how the work breakdown structure correlate to each other which is the master task and which one is slave task. Milestone Report Kings Medical Center Project The milestone report of kings medical center project is describe the achievement of the center which is the best of the previous report .The milestone report is known as master copy every other report must be compare from this milestone report ,this can give estimation cost and resource handling idea in brief. Gantt chart The Gantt chart is known as the chart which can specify the project completion time and resource allocation to different module. The Gantt chart describe the different small module start and end time this also describe analysis time and result this contains the day by day data and store it and compare by historical data. Network Diagram The network diagram describe the day by day activity and recourse allocation by network diagram by network diagram we describe the minimum activity path to reduce the cost effort there is critical path method and project evaluation review technique use for estimation. Work Schedule The work schedule describe the overall running schedule for different task and it can specify the resource allocation to each activity the work schedule is to use reduce cost time effort . Activity Assignments The activity assignment is known as assign resource to different task and activity. The activity assignment insures that the correct task is handling by the specified specialist person. Time Management Contingency Strategies The time management contingency strategies is to use the reduce time effort and make project effective and beneficial. These Strategies is to use assumption of minimum time effort in which sequence we can gain minimum time effort. PROJECT COST MANAGEMENT Project cost estimate The project cost estimation is done by Gantt chat or by the histogram or by the CPM PERT. The project cost estimation is done with respect to the earned value and actual cost or planning cost. There is graph analysis between the earned value and the actual cost. Project cost baseline The project baseline cost is theoretical or real construct it capture and approved budget structure distributed overtime. The baseline may incorporate during changes in the project running schedule. Earned value The earned value describes the how much part of cost and time is spent till the analysis time. The earned value analysis is useful for estimation how much time and cost in feature needed to complete the project in under budget and specified time. PROJECT QUALITY MANAGEMENT Quality Standards/ Requirements The quality standard is measured by quality assurance like ISO 9000.The quality assurance is achieved by The effectiveness and efficiency .Quality standard /requirement is gain by the ISO certificate for the health care the IWA 4:2009 certificate issued, for medical devices ISO 13485:2003 certificate needed. The Seven Basic Tools of Quality The seven basic tools for quality control is Pareto chart which shows the bar graph and insures which factors are more significant. The Histogram which represent the bar diagram and histogram representation of each activity. Scattered data which represents the graph pair of numerical datas. Control chart and check sheet for analyzing the data. Cause and affect diagram and stratification which control the study of individual data. PROJECT NETWORK MANAGEMENT This is the tool for the understand to project management cycle there is the graphical representation of the project life cycle various activity in the project form a network diagram which specify the project duration for each separate activity. PROJECT DATABASE MANAGEMENT The project database management stores the every information during project execution state and keeps each activity record day by day. Thus the project database management system stores information of resources and the durations to complete a task. PROJECT WEBSITE MANAGEMENT Project website management is done according to database and information which is retrieval day by day activity the database updating can also be done by the website .Thus the project website management must insure to display current database. Appendix The UNICEF child protection program The king George medical College, Department of cancer therapy India. The all India medical Association, New Delhi India Policies There is research center establishment for H.I.V To provide best facility perform cancer chemical therapy. Glossary Glossary of Genetic Terms, Genetics Education Center, Univ. Kansas Medical Center Biotechnology Glossary, SDPatel and S Maulik, GeneEd, Celera (not available Sept 2002) Genome Glossary, Department of Energy (DOE) Dictionary of Genetics, Science and Technology, graphics, searchable, Academic Press (not available Sept 2002)

Hydrogels for Wound Healing Applications

Hydrogels for Wound Healing Applications Abstract This chapter discusses about the hydrogels both natural and synthetic that can be used for wound healing applications. Also it discusses briefly about the various novel techniques that have been developed recently. Keywords: Hydrogels; Chitosan, Antimicrobial; Grafting; Blending; Wound dressing; Wound healing; Gene therapy, Stem cell therapy, Skin Engineering, pH and Thermosensitive polymers. 1 Introduction Healthcare is an essential aspect of human survival. So many biopolymers have generated interest in a number of biomedical applications. Wound management is one such area where management of cuts, ulcers, and sores needs dressings which help in promoting rapid wound healing in order to obtain both functional and cosmetic results. [45] There are different kinds of wound management products: staples or sutures, dressings or bandages, surgical sealants and adhesives, skin substitutes, and other biomaterials. [51] Human skin provides an effective barrier to microbial penetration and subsequent infection. However, once the wound has been developed in this barrier, the infection chances increases. In case of chronic wounds, the colonization and infection potential increases as the result of the presence of avascular eschar which provides an environment for the uninhibited growth of microorganisms. [89] The rate of infection is related to the type of wound, general wound care, and local health of the patient. [88, 90] For avoiding infection, good clinical practices are needed. The management of chronic wounds is a very costly practice and it also places an enormous drain on healthcare resources; studies have calculated the cost of wounds to the NHS to be about  £1bn a year. [166] So for lowering this cost such wound management products are needed that are more economical and effective. Out of all the above wound management products, here in this chapter we will discuss more about the wound dressings that will provide an optimal healing environment to the wound. A dressing is an adjunct used by a person for application to a wound in order to promote healing and/or prevent further harm. It is designed to be in direct contact with the wound, so it is different from the bandage in the manner that bandages are normally used to hold dressing in place. A wound is a break in the epithelial integrity of the skin and may be accompanied by disruption of the structure and function of underlying normal tissue. Wounds can be divided into four categories based on their appearance and stage of healing: Necrotic, sloughing, granulating and epithelializing wounds. [87] Wounds cause discomfort and are more prone to infection and other troublesome complications. [75] Some diseases like diabetes, ischaemia and conditions like malnourishment, ageing, local infection, local tissue damage due to burn leads to delay in wound healing. Infection is a major complication of burn injury and is responsible for 50-75% of hospital deaths. [76] Human skin has one of the greatest capacities to regenerate itself amongst all of the tissues in our body. It constantly replaces old cells with new cells, enabling it to repair itself when damaged. Wound healing is a complex-physiologic process, which consists of three overlapping phases: inflammatory, proliferative and remodeling phases. The normal healing response begins the moment the tissue is injured. As the blood components spill into the site of injury, the platelets come into contact with exposed collagen and other elements of the extracellular matrix. This contact triggers the platelets to release clotting factors as well as essential growth factors. During the inflammation process, neutrophils are the first leukocytes which come at the site of injury to rid it from bacterial contamination. Then, the monocytes and their conversion to macrophages initiate tissue repair by releasing a number of biologically active substances and growth factors that are necessary for the initi ation of tissue formation process. In the third process, fibroblasts proliferate and migrate into the wound space and started the deposition of the loose extracellular matrix. Endothelial cells grow into a wound simultaneously with fibroblasts and undergo angiogenesis. Finally, tissue remodeling takes place to reconstruct the basement membrane by the differentiation of keratinocytes as well as the formation of follicle cells. [43, 49, 50] A scar is an essential part of this natural healing process following any type of damage to the skin. This can occur after a surgical incision or the healing of a wound. As your body makes an effort to close an open wound and protect itself from infection, it replaces injured skin tissue with rapidly generated scar tissue. Scarring is slight when the damaged outer layer of skin is healed by rebuilt tissue. When we damage the thick layer of tissue beneath the skin, rebuilding is more complicated. Our bodies lay down collagen fibers (a protein which is naturally produced by the body) and this usually results in a highly obvious scar. A permanent reminder of the injury is left behind. So, a dressing that can induce scarless healing is needed. Historically, a dressing was usually a piece of material, sometimes cloth, but the use of cobwebs, dung, leaves and honey has also been described. However, modern dressings include gauzes, semipermeable films, low adherent dressings, gels, foams, hydrocolloids, alginates, hydrogels and polysaccharide pastes. Wound dressings are passive, active or interactive. Passive dressings simply provide cover while active or interactive dressings are capable of modifying the physiology of the wound environment. Interactive dressings include hydrocolloids, hydrogels, alginates, foam dressings and antimicrobial dressings. [17, 20, 85] Traditionally dry wound dressings are considered to be good for healing wounds i.e. the wound should be covered with gauze or left open. But it has been observed by Winter [191] that when wound is left open to air without any dressing, a scab i.e. a dry covering covers the wound and decreases the rate of epithelialization. On the other hand, if moist dressing is used in place of dry dressings scab will not form and rate of healing increases as moist dressings provide low oxygen tension which helps in wound healing, these dressings not only keep cells viable which enables them to release growth factors while maintaining contact between them and the healing tissues, but may also modulate or stimulate their proliferation, these dressings decrease the pain at rest, during ambulation and during dressing changes also moist environment allows rapid and efficient delivery of any added antimicrobial agent thus prevent the wound from infection. So, the dressings that create and maintain a mois t environment, however, are now considered to provide the optimal conditions for wound healing. 2 Requirements of an ideal wound care system These characteristics should be present in the ideal wound care system (a) it should be capable of maintaining a high humidity at the wound site, (b) it should be non-toxic, (c) non-allergenic, (d) it can be removed without causing trauma to the wound, (e) it should pe impermeable to bacteria, (f) Thermally insulating, (g) it should be soft to touch, (h) it should allow proper gaseous exchange, (i) it should be free from particulate and toxic product, (j) promote tissue reconstruction processes and (k) it should be cost effective. [20, 165, 177] Out of all the dressings hydrocolloids, alginates and hydrogels each one has its own advantages and limitations but hydrogels are best and have all the characteristics that are needed in an ideal wound dressing. All the above mentioned characteristics can be achieved in hydrogel wound dressings. 3 Hydrogels for Wound Healing Applications Hydrogels are natural or synthetic cross-linked polymers used in a variety of medical and biomedical applications. Hydrogels consist of a matrix of insoluble polymers with up to 96% water content enabling them to donate water molecules to the wound surface and to maintain a moist environment at the wound bed. They are used in the construction of contact lenses, drug-delivery vehicles, wound dressings and as physiological electrodes or sensors. [17] Examples of hydrogel include Aquaform, Intrasite, GranuGel, Nu-Gel, Purilon, Sterigel. These also have the ability to absorb a degree of wound exudate. They transmit moisture vapour and oxygen, but their bacterial and fluid permeability is dependent on the type of secondary dressing used. [20] Hydrogels swell or shrink in aqueous solutions due to the association, dissociation and binding of various ions to polymer chains. These systems may swell in water until an equilibrium state is reached and retain their original shape. The interactions responsible for water sorption by hydrogels include the process of hydration, which is connected to the presence of such chemical groups as -OH, -COOH, -CONH2, -CONH-, and -SO3H and the existence of capillary areas and differences in osmotic pressure. The forces that make hydrogel dissolution impossible are presence of covalent bonds between individual polymer chains, hydrophobic and electrostatic interactions. [46] These are hydrophilic polymer networks which may absorb from 10-20% (an arbitrary lower limit) up to thousands of times their dry weight in water. These may be chemically stable or they may degrade and dissolve. They are called ‘reversible, or ‘physical gels when the networks are held together by molecular entanglements, and/or secondary forces including ionic, H-bonding or hydrophobic forces. [13, 14, 15] Hydrogels are called ‘permanent or ‘chemicalgels when they are covalently-crosslinked networks as shown in 1. Hydrogels can be made by irradiation, freeze-thawing or chemical methods. Out of all the methods, irradiation is considered as a suitable tool for the formation of hydrogels as in this method there is easy control of processing, no need of adding initiators or cross-linkers which are harmful, and have the possibility of formation and sterilization in one step. But as everything has its own advantages and disadvantages this method also has a disadvantage which is hydrogels formed by this method have poor mechanical strength. Nowadays, Freeze thawing technique is generally used to prepare hydrogels having good strength, stability and no crosslinkers and initiators. But the main disadvantage is that the prepared hydrogels have opaque appearance and limited swelling and thermal stability. [120] In comparison to the traditional gauze therapy the application of a hydrogel seems to significantly stimulate wound healing. [11] Various natural and synthetic polymers having good biocompatibility are used to develop hydrogel wound dressing. These polymers include natural polymers such as alginate, chitosan, gelatin and collagen and synthetic polymers such as polyurethane, poly(ethylene glycol), polycaprolactone, poly vinyl pyrrolidone, poly(lactide-co-glycolide), polyacrylonitrile , poly(amino acid), etc. Table 1 below shows different hydrophilic polymers used to synthesize hydrogel matrices. Table 1 Hydrophilic polymers used to synthesize hydrogel matrices. [13] Hydrogels may be classified as homopolymer hydrogels, copolymer hydrogels, multipolymer hydrogels, and interpenetrating polymeric hydrogels. Homopolymer hydrogels are crosslinked networks of one type of hydrophilic monomer unit, whereas copolymer hydrogels are produced by the crosslinking of two comonomer units, one of which must be hydrophilic. Multipolymer hydrogels are produced by the crosslinking of more than three monomers. Finally, interpenetrating polymeric hydrogels are produced by the swelling of a first network in a monomer and the reaction of the latter to form a second intermeshing network structure. [46, 47] Also, it has been shown that the blending of a natural polymer with a synthetic polymer seems to be a good method for obtaining materials having required mechanical and thermal properties in comparison to pure components. It is also a simple method by which suitable shapes such as films, sponges and hydrogels can be obtained easily to realize a variety of biomedical devices. 2 shows healing is faster with the hydrogel dressing than with the gauze dressing. Wound area covered by hydrogel decreases faster with increasing healing period. On the contrary, the wound covered by gauze dressing reduces by only half a percent even after 14 days. [192] 3.1 Natural Hydrogels Natural polymers, such as chitin, chitosan, alginate, collagen, elastin, genipin, gelatin, cellulose etc. have been used for dressing wounds because they play an important role in the healing process. [47] Chitosan is a partially deacetylated form of chitin. Chitin as BeschitinÃ’, Unitika, is also commercially available as dressing in Japan. [28] But as far as chitosan is concerned it is biocompatible, biodegradable, haemostatic, fungistatic [54] and non-toxic and can be successfully used as gels, films, fibres etc. This polymer also show antibacterial properties and possess good wound healing properties. [60, 61, 62] It has many applications as wound dressing, drug delivery device and as scaffold for tissue engineering. [63, 64] Some of the examples of wound dressings are given below which use chitosan as one of the biomaterial. Asymmetric chitosan membranes have been developed by using immersion-precipitation phase-inversion method. [123, 124, 125] These asymmetric chitosan membranes are homogeneous and have porous structure. This membrane was prepared by preheating casted chitosan solution in oven for different time periods for dry phase separation and then immersed in to coagulant tank for wet phase separation and were subsequently freeze-dried. The skin layer acts as the rate controlling barrier for the release of drug and the porous layer provide mechanical support to the skin layer. The water vapor transmission rate, gas permeability, PBS solution absorption, in-vitro degradation, cell culture, bacterial penetration and wound healing test of this dressing were carried out. These membranes are effective in controlling evaporative water loss, showed excellent oxygen permeability and also antibacterial in nature. These are also found to be an urgent hemostat. In another study, silver sulphadiazine was inc orporated as an antimicrobial agent to this asymmetric dressing. The release behaviour of both silver and sulphadiazine ions were studied and found to be significantly different from one another. Silver ions displayed a slow release behavior while sulphadiazine ions exhibited burst effect on first day of the drug release and then slowly tapered off. It is because of the interaction of silver with amino group of chitosan leading to its slow release throughout whereas, as the sulphadiazine ions were free to diffuse through the membrane to reach the wound site thus they showed a burst release. The membranes were further found effective against P. aerugniosa and S. aureus. In one of the papers, novel wound dressings were formed that composed of chitosan film and Minocycline Hydrochloride (MH) and commercial polyurethane film (Tegaderm) as a backing. It is also a useful formulation for the treatment of severe burn wounds. Water vapor and oxygen can permeate the Tegaderm film but water cannot. The tegaderm film support the polymer membrane. [126] In one of the studies, a silver nanocrystalline chitosan (SNC) wound dressing composed of nano-silver and chitosan was constructed by self-assembly and nanotechnology and used for treating deep partial-thickness wounds. In this, sterility and pyrogen testing were performed to ensure biosafety. These dressings promote wound healing and combat infection, and also decrease the risk of silver absorption in comparison with silver sulphadiazine (SSD) dressings. [127] There is also one more method of forming wound dressing composed of chitosan i.e. the formation of polyelectrolyte complex of gum kondagogu (GKG) and chitosan. This complex is formed by the electrostatic interaction between carboxyl group of gum and amine group of chitosan. This method is more advantageous as it avoids the use of organic solvents, chemical crosslinking agents and thus reduces the toxicity and undesirable side effects. In this, diclofenac sodium is used as model drug. The diclofenac loaded complex of gum kondagogu/ chitosan shows drug release which changes with change in pH. The drug release was higher at pH 6.8 as compared to pH 1.2, due to higher swelling of complex at higher pH. This holds a great potential as a natural polymer based delivery device for controlled delivery of drugs like diclofenac sodium for two reasons: (i) to reduce dosing frequency and (ii) lower the gastric toxicity. [152] Semi-interpenetrating polymer networks (SIPNs) composed of chitosan (CS) and poloxamer were prepared in order to improve the mechanical strength of CS. The WVTR was found to be 2508.2 ±65.7 gm−2 day−1, i.e. these can maintain a moist environment at wound site which enhance epithelial cell migration. Also, the in vitro assessment of SIPNs showed proper biodegradation and low cytotoxicity and in vivo is carried out on experimental full thickness wounds in a mouse model and found that the wounds covered with these were completely filled with new epithelium without any significant adverse reactions after 3 weeks. In one of the papers, a kind of surgical wound dressing, the chitosan-gelatin sponge wound dressing (CGSWD) having good antibacterial property is prepared. The in vitro test showed that the antibacterial effect of CGSWD on E. coli K88 is better than that of penicillin, and the effect on S. aureus is also better than that of cefradine. [137] One more wound dressing consists of two separate layers were prepared in which the upper layer is a swellable hydrogel material which can absorb exudates and also serve as mechanical and microbial barrier while lower layer is a chitosan acetate foam incorporated with the anti-microbial agent chlorherxidine gluconate. [183] The antimicrobial activity is checked by the Bauer-Kirby Disk Diffusion Test, inhibition zones can be clearly seen around the discs of chitosan acetate foams incorporated with chlorhexidine gluconate, in culture plates inoculated with either Gram-negative or positive bacteria showing that the dressing is antimicrobial in nature. Blending is a convenient and effective method to improve physical and mechanical properties of hydrogels. So modification of chitosan is done by blending with other polymers like cellulose. [178] In this, E. coli and S. aureus were used as the test bacteria to examine the antibacterial properties of chitosan, cellulose and chitosan/cellulose blends. The numbers of colony of these bacteria formed on the test membranes are shown in s 5 and 6. It was noted that the numbers of colony of all test bacteria formed on the chitosan/cellulose blend membranes were decreased with the increase of chitosan concentration. These blends are more effective against E. coli than that of S. aureus, as indicated by the lower colony unit. Thus these dressings are suitable to use as an antimicrobial wound dressing. Chitosan due to its structural properties has the ability to heal wounds without scar formation. [198] Since chitosan is composed of D-glucosamine, which is also the component present in the disaccharide subunits of hyaluronic acid, chitosan tries to structurally mimic hyaluronic acid and exerts similar effects. [197] It has been known that the fetal wound healing takes place without fibrosis or scar formation due to the presence of hyaluronic acid. [199] In one of the studies, Chitosan as a semi-permeable biological dressing maintains a moist environment and prevent the wound site from dehydration and contamination. In addition, digital colour separation analysis of donor site scars demonstrated an earlier return to normal skin colour at chitosan-treated areas as shown in 7. [196] Collagen is also a biopolymer that is used as a polymer for making wound dressing and drug delivery devices as it is biocompatible and biocompatibility of a material applied to wound tissue is a prerequisite for optimal wound environment and facilitation of the healing processes. A new collagen dressing with gentamycin or amikacin was prepared in one of the research work and these follow the basic requirement of antibacterial bandages. The dressing is composed of two collagen biomaterials—membrane and sponge—both possessing good tissue biocompatibility. These dressing released antibiotics slowly and show the antibacterial treatment in experimentally infected superficial wounds in mice. Thus, it can be used for the treatment of infected wounds in humans. [26] As discussed previously that both chitosan and collagen are excellent materials that can be used as wound dressing materials. So it has been seen that if both are used simultaneously then what will be the effect. It is found that the wound dressings composed of chitosan crosslinked collagen sponge (CCCS) enhance the diabetic wound healing. Collagen crosslinked with chitosan showed several advantages required for wound dressing, including the uniform and porous ultrastructure, less water imbibition, small interval porosity, and high resistance to collagenase digestion and slow release of FGF from CCCS/FGF. [138] Following moist healing concept, alginates which are able to absorb exudates from wound have become one of the most important materials for wound management. [52, 53, 54, 55, 56] In this particular field, the properties of alginate fibers are unparalleled in many respects. Alginate based products form a gel and effective in removing out of the wound on the contrary to traditional cotton and viscose fibres, which can entrap in the wound developing discomfort during dressing removal. [55] Also, the alginate fibres are non-toxic, non-carcinogenic, non-allergic, haemostatic, biocompatible, of reasonable strength, capable of being sterilized and easily processable. Sorbsanâ„ ¢ was first commercialized in 1981 and after that there were many dressings launched. The alginate fibers can be converted into wound dressings by using a number of textile processes. Because of its simplicity and also the high absorbency of the product, nonwoven is the main form of alginate wound dressings. [19] The antimicrobial action of alginate dressing can be seen as in 8 which shows the antimicrobial action of silver containing alginate fibers against E. Coli. There was 100% reduction in bacteria count within 5 hr after the fibers were placed in contact with solutions containing the bacteria. Sorbsan alginate fibers showed some antimicrobial activity while AquacelTM (made of carboxymethyl cellulose), does not show any antimicrobial effect. [18] Gelatin widely found in nature and is the major constituent of skin, bones, and connective tissue. Gelatin can easily be obtained by a controlled hydrolysis of the fibrous insoluble protein, collagen. [195] This is also used in number of biomedical applications like wound dressings. Hydrogel wound dressing from gelatin, oxidized alginate and borax were prepared and the composite matrix promotes wound healing because of alginate, has haemostatic effect of gelatin and is antiseptic because of borax. The water vapour transmission rate (WVTR) of the hydrogel was calculated and found to be 2686 ±124 g/m2/day indicating that this hydrogel can maintain a proper fluid balance at the wound site which helps in cell migration. 2 shows the loss of water vapour with time through the hydrogel when placed in a moisture rich environment. [119] Genipin has been used to crosslink chitosan membranes to control swelling ratio and mechanical properties. It increased its ultimate tensile strength but significantly reduced its strain-at-fracture and swelling ratio. It had significantly less cytotoxicity for human fibroblasts and slower degradation rate compared to the glutaraldehyde-crosslinked membrane. This genipin crosslinked chitosan membrane can be successfully used as a wound dressing. [132] Bacterial cellulose is a natural polymer consisting of microfibrils containing glucan chains bound together by hydrogen bonds. Bacterial cellulose with chitosan combines properties such as bioactivity, biocompatibility, and biodegradability of the two biopolymers and form an ideal material for dressing wounds. [66, 67] These are antibacterial and scar preventive in nature too. Since natural polymers have been considered limited in their applications for wound-dressing materials as their low mechanical properties and shortage of processing. So we move towards the synthetic polymers that can be used for wound healing applications. 3.2 Synthetic Hydrogels Synthetic polymers are also being used successfully in biomedical applications as one of the materials because of their wide range of mechanical properties, suitability for easily forming into a variety of different shapes, and low production costs. In an ideal dressing both the characteristics i.e. antimicrobial ability and moist healing environment should be present, so in order to prevent the wound from dehydration and bacterial penetration a new dressing composed of polyurethane is designed in such a way that the upper layer of the dressing is microporous (pore size Polyvinyl pyrrolidone (PVP) is one of the most widely used synthetic polymers in medicine because of its solubility in water and its extremely low cytotoxicity. Hydrogels prepared by radiation crosslinking of an aqueous solution of polyvinyl pyrrolidone (PVP) have been used as wound dressing. [21] These are biocompatible, reduces pain, easily replacable, permeable to oxygen, maintain moist environment at the wound site. Polyvinyl alcohol (PVA) is a well-known polymer because it is biocompatible and have required mechanical properties and polyethylene oxide (PEO) is a hydrophilic semicrystalline polyether which is biocompatible, non toxic, non polar, non antigenic and non immunogenic and is highly desirable in most biomedical applications requiring contact with physiological fluids. A hydrogel composed of PEO for wound dressing is prepared and PVA is added to give toughness to the hydrogel by electron beam irradiation and found that these hydrogels showed satisfactory properties for wound dressing that has been evaluated by creating wound on the back of the marmots. [157] The hydrogel gives a wet environment to wounds which causes faster healing compared with the gauze dressing with a dry environment. The weight of the hydrogel increases quickly at the earlier stages, up to 4 days, due to absorption of effusion produced from the wound as shown in Table 2. After that, the production of effusion from the wound ceases and the weight of the hydrogel decreases due to evaporation of the water in the hydrogel. This means that the healing of wound proceeds smoothly with time. The hydrogel can be peeled off easily from the wound at the time of removal. Table 2 Absorption of effusion from wound of dressing during healing. [157] The toughness of PEO hydrogel is improved by the addition of PVA and tensile strength is measured and found that as shown in 10 and 11, the tensile strength and elongation decrease with increasing dose because of the increase of crosslinking. Various synthetic polymers as discussed above are used for wound dressing applications. But the major problem with these materials is their biocompatibility characteristics are often unsatisfactory and their interaction with living tissues is a major problem. So a combination of both natural and synthetic polymers is the better option to make a hydrogel having biocompatibility and desired mechanical strength. 3.3 Blended hydrogels Since both the natural and synthetic polymers have their own advantages and disadvantages so a combination of natural and synthetic polymers can endow the optimal properties necessary for wound repair. [47] The combination of natural and synthetic polymers is used in the biomedical, bioengineering and biotechnology field nowadays because of their great potential. A blended hydrogel composed of polyvinyl alcohol/polyvinyl pyrrolidone and charcoal were prepared by single ‘‘freezing and thawing or two-step ‘‘freezing and thawing and ÃŽ ³-ray irradiation and applied as wound dressing. It is found that the absorption of S. aureus and P. aeruginosa by charcoal/PVA/PVP hydrogels was larger than those by PVA/PVP hydrogels, this is due to the absorption and attachment capability of bacteria by charcoal, this can be shown in 12 given below. [22] The most classical way of fabricating a CS based wound dressing has been to design an asymmetric composite structure. In this method, the Cotton fabric was coated with chitosan (CS) and polyethylene glycol (PEG) followed by freeze-drying. The outer dense layer helps in preventing the microbial passage across the dressing and provides a rate controlling barrier for water vapor permeation, while the inner porous layer provides a high surface area for the exudates absorption. For the absorption of wound exudates porosity is the prime requirement in a dressing. It has been found that these dressings have the porosity 54-70% and the pore size was in the range of 75-120 µm. [45] The increase in the PEG content in the blend composition led to an enhanced destabilization of pores, leading to an increase in the pore size with elongated morphology. There seems to be phase separation between the two components which is an important factor for the observed behavior of the porous structure. Cot ton fabric has been used as the support layer for the CS-PEG layer and leads to very thin and light weight structures. The structure of the dressing has been designed in such a way that it leads to the high porosity of the bulk structure. The thickness of CS coating plays an important role in the development of the porosity on the surface. The influence of the CS thickness on the surface morphology is presented in 13 given below. PEG addition to CS makes significant alteration in the surface morphology of this CS-PEG/cotton membrane (freeze-dried), henceforth known as CPC membrane. There is a distinct trend in the loss of inherent elongated porous structure in membranes and formation of the partially collapsed porosity takes place due to the PEG addition. This suggests that a very limited interaction between CS and PEG exists which is reflected in the observed surface morphology. It has been observed that higher the amount of PEG, the higher is the pore destabilization leading to larger pores. This is evident from the morphology of the CPC membrane at 50% PEG-20 content as shown in 14.45 On the above matrix, the addition of PVP and drug followed by coating on the cotton fabric and freeze drying of the coated matrix is also done. It has been found that the drug Hydrogels for Wound Healing Applications Hydrogels for Wound Healing Applications Abstract This chapter discusses about the hydrogels both natural and synthetic that can be used for wound healing applications. Also it discusses briefly about the various novel techniques that have been developed recently. Keywords: Hydrogels; Chitosan, Antimicrobial; Grafting; Blending; Wound dressing; Wound healing; Gene therapy, Stem cell therapy, Skin Engineering, pH and Thermosensitive polymers. 1 Introduction Healthcare is an essential aspect of human survival. So many biopolymers have generated interest in a number of biomedical applications. Wound management is one such area where management of cuts, ulcers, and sores needs dressings which help in promoting rapid wound healing in order to obtain both functional and cosmetic results. [45] There are different kinds of wound management products: staples or sutures, dressings or bandages, surgical sealants and adhesives, skin substitutes, and other biomaterials. [51] Human skin provides an effective barrier to microbial penetration and subsequent infection. However, once the wound has been developed in this barrier, the infection chances increases. In case of chronic wounds, the colonization and infection potential increases as the result of the presence of avascular eschar which provides an environment for the uninhibited growth of microorganisms. [89] The rate of infection is related to the type of wound, general wound care, and local health of the patient. [88, 90] For avoiding infection, good clinical practices are needed. The management of chronic wounds is a very costly practice and it also places an enormous drain on healthcare resources; studies have calculated the cost of wounds to the NHS to be about  £1bn a year. [166] So for lowering this cost such wound management products are needed that are more economical and effective. Out of all the above wound management products, here in this chapter we will discuss more about the wound dressings that will provide an optimal healing environment to the wound. A dressing is an adjunct used by a person for application to a wound in order to promote healing and/or prevent further harm. It is designed to be in direct contact with the wound, so it is different from the bandage in the manner that bandages are normally used to hold dressing in place. A wound is a break in the epithelial integrity of the skin and may be accompanied by disruption of the structure and function of underlying normal tissue. Wounds can be divided into four categories based on their appearance and stage of healing: Necrotic, sloughing, granulating and epithelializing wounds. [87] Wounds cause discomfort and are more prone to infection and other troublesome complications. [75] Some diseases like diabetes, ischaemia and conditions like malnourishment, ageing, local infection, local tissue damage due to burn leads to delay in wound healing. Infection is a major complication of burn injury and is responsible for 50-75% of hospital deaths. [76] Human skin has one of the greatest capacities to regenerate itself amongst all of the tissues in our body. It constantly replaces old cells with new cells, enabling it to repair itself when damaged. Wound healing is a complex-physiologic process, which consists of three overlapping phases: inflammatory, proliferative and remodeling phases. The normal healing response begins the moment the tissue is injured. As the blood components spill into the site of injury, the platelets come into contact with exposed collagen and other elements of the extracellular matrix. This contact triggers the platelets to release clotting factors as well as essential growth factors. During the inflammation process, neutrophils are the first leukocytes which come at the site of injury to rid it from bacterial contamination. Then, the monocytes and their conversion to macrophages initiate tissue repair by releasing a number of biologically active substances and growth factors that are necessary for the initi ation of tissue formation process. In the third process, fibroblasts proliferate and migrate into the wound space and started the deposition of the loose extracellular matrix. Endothelial cells grow into a wound simultaneously with fibroblasts and undergo angiogenesis. Finally, tissue remodeling takes place to reconstruct the basement membrane by the differentiation of keratinocytes as well as the formation of follicle cells. [43, 49, 50] A scar is an essential part of this natural healing process following any type of damage to the skin. This can occur after a surgical incision or the healing of a wound. As your body makes an effort to close an open wound and protect itself from infection, it replaces injured skin tissue with rapidly generated scar tissue. Scarring is slight when the damaged outer layer of skin is healed by rebuilt tissue. When we damage the thick layer of tissue beneath the skin, rebuilding is more complicated. Our bodies lay down collagen fibers (a protein which is naturally produced by the body) and this usually results in a highly obvious scar. A permanent reminder of the injury is left behind. So, a dressing that can induce scarless healing is needed. Historically, a dressing was usually a piece of material, sometimes cloth, but the use of cobwebs, dung, leaves and honey has also been described. However, modern dressings include gauzes, semipermeable films, low adherent dressings, gels, foams, hydrocolloids, alginates, hydrogels and polysaccharide pastes. Wound dressings are passive, active or interactive. Passive dressings simply provide cover while active or interactive dressings are capable of modifying the physiology of the wound environment. Interactive dressings include hydrocolloids, hydrogels, alginates, foam dressings and antimicrobial dressings. [17, 20, 85] Traditionally dry wound dressings are considered to be good for healing wounds i.e. the wound should be covered with gauze or left open. But it has been observed by Winter [191] that when wound is left open to air without any dressing, a scab i.e. a dry covering covers the wound and decreases the rate of epithelialization. On the other hand, if moist dressing is used in place of dry dressings scab will not form and rate of healing increases as moist dressings provide low oxygen tension which helps in wound healing, these dressings not only keep cells viable which enables them to release growth factors while maintaining contact between them and the healing tissues, but may also modulate or stimulate their proliferation, these dressings decrease the pain at rest, during ambulation and during dressing changes also moist environment allows rapid and efficient delivery of any added antimicrobial agent thus prevent the wound from infection. So, the dressings that create and maintain a mois t environment, however, are now considered to provide the optimal conditions for wound healing. 2 Requirements of an ideal wound care system These characteristics should be present in the ideal wound care system (a) it should be capable of maintaining a high humidity at the wound site, (b) it should be non-toxic, (c) non-allergenic, (d) it can be removed without causing trauma to the wound, (e) it should pe impermeable to bacteria, (f) Thermally insulating, (g) it should be soft to touch, (h) it should allow proper gaseous exchange, (i) it should be free from particulate and toxic product, (j) promote tissue reconstruction processes and (k) it should be cost effective. [20, 165, 177] Out of all the dressings hydrocolloids, alginates and hydrogels each one has its own advantages and limitations but hydrogels are best and have all the characteristics that are needed in an ideal wound dressing. All the above mentioned characteristics can be achieved in hydrogel wound dressings. 3 Hydrogels for Wound Healing Applications Hydrogels are natural or synthetic cross-linked polymers used in a variety of medical and biomedical applications. Hydrogels consist of a matrix of insoluble polymers with up to 96% water content enabling them to donate water molecules to the wound surface and to maintain a moist environment at the wound bed. They are used in the construction of contact lenses, drug-delivery vehicles, wound dressings and as physiological electrodes or sensors. [17] Examples of hydrogel include Aquaform, Intrasite, GranuGel, Nu-Gel, Purilon, Sterigel. These also have the ability to absorb a degree of wound exudate. They transmit moisture vapour and oxygen, but their bacterial and fluid permeability is dependent on the type of secondary dressing used. [20] Hydrogels swell or shrink in aqueous solutions due to the association, dissociation and binding of various ions to polymer chains. These systems may swell in water until an equilibrium state is reached and retain their original shape. The interactions responsible for water sorption by hydrogels include the process of hydration, which is connected to the presence of such chemical groups as -OH, -COOH, -CONH2, -CONH-, and -SO3H and the existence of capillary areas and differences in osmotic pressure. The forces that make hydrogel dissolution impossible are presence of covalent bonds between individual polymer chains, hydrophobic and electrostatic interactions. [46] These are hydrophilic polymer networks which may absorb from 10-20% (an arbitrary lower limit) up to thousands of times their dry weight in water. These may be chemically stable or they may degrade and dissolve. They are called ‘reversible, or ‘physical gels when the networks are held together by molecular entanglements, and/or secondary forces including ionic, H-bonding or hydrophobic forces. [13, 14, 15] Hydrogels are called ‘permanent or ‘chemicalgels when they are covalently-crosslinked networks as shown in 1. Hydrogels can be made by irradiation, freeze-thawing or chemical methods. Out of all the methods, irradiation is considered as a suitable tool for the formation of hydrogels as in this method there is easy control of processing, no need of adding initiators or cross-linkers which are harmful, and have the possibility of formation and sterilization in one step. But as everything has its own advantages and disadvantages this method also has a disadvantage which is hydrogels formed by this method have poor mechanical strength. Nowadays, Freeze thawing technique is generally used to prepare hydrogels having good strength, stability and no crosslinkers and initiators. But the main disadvantage is that the prepared hydrogels have opaque appearance and limited swelling and thermal stability. [120] In comparison to the traditional gauze therapy the application of a hydrogel seems to significantly stimulate wound healing. [11] Various natural and synthetic polymers having good biocompatibility are used to develop hydrogel wound dressing. These polymers include natural polymers such as alginate, chitosan, gelatin and collagen and synthetic polymers such as polyurethane, poly(ethylene glycol), polycaprolactone, poly vinyl pyrrolidone, poly(lactide-co-glycolide), polyacrylonitrile , poly(amino acid), etc. Table 1 below shows different hydrophilic polymers used to synthesize hydrogel matrices. Table 1 Hydrophilic polymers used to synthesize hydrogel matrices. [13] Hydrogels may be classified as homopolymer hydrogels, copolymer hydrogels, multipolymer hydrogels, and interpenetrating polymeric hydrogels. Homopolymer hydrogels are crosslinked networks of one type of hydrophilic monomer unit, whereas copolymer hydrogels are produced by the crosslinking of two comonomer units, one of which must be hydrophilic. Multipolymer hydrogels are produced by the crosslinking of more than three monomers. Finally, interpenetrating polymeric hydrogels are produced by the swelling of a first network in a monomer and the reaction of the latter to form a second intermeshing network structure. [46, 47] Also, it has been shown that the blending of a natural polymer with a synthetic polymer seems to be a good method for obtaining materials having required mechanical and thermal properties in comparison to pure components. It is also a simple method by which suitable shapes such as films, sponges and hydrogels can be obtained easily to realize a variety of biomedical devices. 2 shows healing is faster with the hydrogel dressing than with the gauze dressing. Wound area covered by hydrogel decreases faster with increasing healing period. On the contrary, the wound covered by gauze dressing reduces by only half a percent even after 14 days. [192] 3.1 Natural Hydrogels Natural polymers, such as chitin, chitosan, alginate, collagen, elastin, genipin, gelatin, cellulose etc. have been used for dressing wounds because they play an important role in the healing process. [47] Chitosan is a partially deacetylated form of chitin. Chitin as BeschitinÃ’, Unitika, is also commercially available as dressing in Japan. [28] But as far as chitosan is concerned it is biocompatible, biodegradable, haemostatic, fungistatic [54] and non-toxic and can be successfully used as gels, films, fibres etc. This polymer also show antibacterial properties and possess good wound healing properties. [60, 61, 62] It has many applications as wound dressing, drug delivery device and as scaffold for tissue engineering. [63, 64] Some of the examples of wound dressings are given below which use chitosan as one of the biomaterial. Asymmetric chitosan membranes have been developed by using immersion-precipitation phase-inversion method. [123, 124, 125] These asymmetric chitosan membranes are homogeneous and have porous structure. This membrane was prepared by preheating casted chitosan solution in oven for different time periods for dry phase separation and then immersed in to coagulant tank for wet phase separation and were subsequently freeze-dried. The skin layer acts as the rate controlling barrier for the release of drug and the porous layer provide mechanical support to the skin layer. The water vapor transmission rate, gas permeability, PBS solution absorption, in-vitro degradation, cell culture, bacterial penetration and wound healing test of this dressing were carried out. These membranes are effective in controlling evaporative water loss, showed excellent oxygen permeability and also antibacterial in nature. These are also found to be an urgent hemostat. In another study, silver sulphadiazine was inc orporated as an antimicrobial agent to this asymmetric dressing. The release behaviour of both silver and sulphadiazine ions were studied and found to be significantly different from one another. Silver ions displayed a slow release behavior while sulphadiazine ions exhibited burst effect on first day of the drug release and then slowly tapered off. It is because of the interaction of silver with amino group of chitosan leading to its slow release throughout whereas, as the sulphadiazine ions were free to diffuse through the membrane to reach the wound site thus they showed a burst release. The membranes were further found effective against P. aerugniosa and S. aureus. In one of the papers, novel wound dressings were formed that composed of chitosan film and Minocycline Hydrochloride (MH) and commercial polyurethane film (Tegaderm) as a backing. It is also a useful formulation for the treatment of severe burn wounds. Water vapor and oxygen can permeate the Tegaderm film but water cannot. The tegaderm film support the polymer membrane. [126] In one of the studies, a silver nanocrystalline chitosan (SNC) wound dressing composed of nano-silver and chitosan was constructed by self-assembly and nanotechnology and used for treating deep partial-thickness wounds. In this, sterility and pyrogen testing were performed to ensure biosafety. These dressings promote wound healing and combat infection, and also decrease the risk of silver absorption in comparison with silver sulphadiazine (SSD) dressings. [127] There is also one more method of forming wound dressing composed of chitosan i.e. the formation of polyelectrolyte complex of gum kondagogu (GKG) and chitosan. This complex is formed by the electrostatic interaction between carboxyl group of gum and amine group of chitosan. This method is more advantageous as it avoids the use of organic solvents, chemical crosslinking agents and thus reduces the toxicity and undesirable side effects. In this, diclofenac sodium is used as model drug. The diclofenac loaded complex of gum kondagogu/ chitosan shows drug release which changes with change in pH. The drug release was higher at pH 6.8 as compared to pH 1.2, due to higher swelling of complex at higher pH. This holds a great potential as a natural polymer based delivery device for controlled delivery of drugs like diclofenac sodium for two reasons: (i) to reduce dosing frequency and (ii) lower the gastric toxicity. [152] Semi-interpenetrating polymer networks (SIPNs) composed of chitosan (CS) and poloxamer were prepared in order to improve the mechanical strength of CS. The WVTR was found to be 2508.2 ±65.7 gm−2 day−1, i.e. these can maintain a moist environment at wound site which enhance epithelial cell migration. Also, the in vitro assessment of SIPNs showed proper biodegradation and low cytotoxicity and in vivo is carried out on experimental full thickness wounds in a mouse model and found that the wounds covered with these were completely filled with new epithelium without any significant adverse reactions after 3 weeks. In one of the papers, a kind of surgical wound dressing, the chitosan-gelatin sponge wound dressing (CGSWD) having good antibacterial property is prepared. The in vitro test showed that the antibacterial effect of CGSWD on E. coli K88 is better than that of penicillin, and the effect on S. aureus is also better than that of cefradine. [137] One more wound dressing consists of two separate layers were prepared in which the upper layer is a swellable hydrogel material which can absorb exudates and also serve as mechanical and microbial barrier while lower layer is a chitosan acetate foam incorporated with the anti-microbial agent chlorherxidine gluconate. [183] The antimicrobial activity is checked by the Bauer-Kirby Disk Diffusion Test, inhibition zones can be clearly seen around the discs of chitosan acetate foams incorporated with chlorhexidine gluconate, in culture plates inoculated with either Gram-negative or positive bacteria showing that the dressing is antimicrobial in nature. Blending is a convenient and effective method to improve physical and mechanical properties of hydrogels. So modification of chitosan is done by blending with other polymers like cellulose. [178] In this, E. coli and S. aureus were used as the test bacteria to examine the antibacterial properties of chitosan, cellulose and chitosan/cellulose blends. The numbers of colony of these bacteria formed on the test membranes are shown in s 5 and 6. It was noted that the numbers of colony of all test bacteria formed on the chitosan/cellulose blend membranes were decreased with the increase of chitosan concentration. These blends are more effective against E. coli than that of S. aureus, as indicated by the lower colony unit. Thus these dressings are suitable to use as an antimicrobial wound dressing. Chitosan due to its structural properties has the ability to heal wounds without scar formation. [198] Since chitosan is composed of D-glucosamine, which is also the component present in the disaccharide subunits of hyaluronic acid, chitosan tries to structurally mimic hyaluronic acid and exerts similar effects. [197] It has been known that the fetal wound healing takes place without fibrosis or scar formation due to the presence of hyaluronic acid. [199] In one of the studies, Chitosan as a semi-permeable biological dressing maintains a moist environment and prevent the wound site from dehydration and contamination. In addition, digital colour separation analysis of donor site scars demonstrated an earlier return to normal skin colour at chitosan-treated areas as shown in 7. [196] Collagen is also a biopolymer that is used as a polymer for making wound dressing and drug delivery devices as it is biocompatible and biocompatibility of a material applied to wound tissue is a prerequisite for optimal wound environment and facilitation of the healing processes. A new collagen dressing with gentamycin or amikacin was prepared in one of the research work and these follow the basic requirement of antibacterial bandages. The dressing is composed of two collagen biomaterials—membrane and sponge—both possessing good tissue biocompatibility. These dressing released antibiotics slowly and show the antibacterial treatment in experimentally infected superficial wounds in mice. Thus, it can be used for the treatment of infected wounds in humans. [26] As discussed previously that both chitosan and collagen are excellent materials that can be used as wound dressing materials. So it has been seen that if both are used simultaneously then what will be the effect. It is found that the wound dressings composed of chitosan crosslinked collagen sponge (CCCS) enhance the diabetic wound healing. Collagen crosslinked with chitosan showed several advantages required for wound dressing, including the uniform and porous ultrastructure, less water imbibition, small interval porosity, and high resistance to collagenase digestion and slow release of FGF from CCCS/FGF. [138] Following moist healing concept, alginates which are able to absorb exudates from wound have become one of the most important materials for wound management. [52, 53, 54, 55, 56] In this particular field, the properties of alginate fibers are unparalleled in many respects. Alginate based products form a gel and effective in removing out of the wound on the contrary to traditional cotton and viscose fibres, which can entrap in the wound developing discomfort during dressing removal. [55] Also, the alginate fibres are non-toxic, non-carcinogenic, non-allergic, haemostatic, biocompatible, of reasonable strength, capable of being sterilized and easily processable. Sorbsanâ„ ¢ was first commercialized in 1981 and after that there were many dressings launched. The alginate fibers can be converted into wound dressings by using a number of textile processes. Because of its simplicity and also the high absorbency of the product, nonwoven is the main form of alginate wound dressings. [19] The antimicrobial action of alginate dressing can be seen as in 8 which shows the antimicrobial action of silver containing alginate fibers against E. Coli. There was 100% reduction in bacteria count within 5 hr after the fibers were placed in contact with solutions containing the bacteria. Sorbsan alginate fibers showed some antimicrobial activity while AquacelTM (made of carboxymethyl cellulose), does not show any antimicrobial effect. [18] Gelatin widely found in nature and is the major constituent of skin, bones, and connective tissue. Gelatin can easily be obtained by a controlled hydrolysis of the fibrous insoluble protein, collagen. [195] This is also used in number of biomedical applications like wound dressings. Hydrogel wound dressing from gelatin, oxidized alginate and borax were prepared and the composite matrix promotes wound healing because of alginate, has haemostatic effect of gelatin and is antiseptic because of borax. The water vapour transmission rate (WVTR) of the hydrogel was calculated and found to be 2686 ±124 g/m2/day indicating that this hydrogel can maintain a proper fluid balance at the wound site which helps in cell migration. 2 shows the loss of water vapour with time through the hydrogel when placed in a moisture rich environment. [119] Genipin has been used to crosslink chitosan membranes to control swelling ratio and mechanical properties. It increased its ultimate tensile strength but significantly reduced its strain-at-fracture and swelling ratio. It had significantly less cytotoxicity for human fibroblasts and slower degradation rate compared to the glutaraldehyde-crosslinked membrane. This genipin crosslinked chitosan membrane can be successfully used as a wound dressing. [132] Bacterial cellulose is a natural polymer consisting of microfibrils containing glucan chains bound together by hydrogen bonds. Bacterial cellulose with chitosan combines properties such as bioactivity, biocompatibility, and biodegradability of the two biopolymers and form an ideal material for dressing wounds. [66, 67] These are antibacterial and scar preventive in nature too. Since natural polymers have been considered limited in their applications for wound-dressing materials as their low mechanical properties and shortage of processing. So we move towards the synthetic polymers that can be used for wound healing applications. 3.2 Synthetic Hydrogels Synthetic polymers are also being used successfully in biomedical applications as one of the materials because of their wide range of mechanical properties, suitability for easily forming into a variety of different shapes, and low production costs. In an ideal dressing both the characteristics i.e. antimicrobial ability and moist healing environment should be present, so in order to prevent the wound from dehydration and bacterial penetration a new dressing composed of polyurethane is designed in such a way that the upper layer of the dressing is microporous (pore size Polyvinyl pyrrolidone (PVP) is one of the most widely used synthetic polymers in medicine because of its solubility in water and its extremely low cytotoxicity. Hydrogels prepared by radiation crosslinking of an aqueous solution of polyvinyl pyrrolidone (PVP) have been used as wound dressing. [21] These are biocompatible, reduces pain, easily replacable, permeable to oxygen, maintain moist environment at the wound site. Polyvinyl alcohol (PVA) is a well-known polymer because it is biocompatible and have required mechanical properties and polyethylene oxide (PEO) is a hydrophilic semicrystalline polyether which is biocompatible, non toxic, non polar, non antigenic and non immunogenic and is highly desirable in most biomedical applications requiring contact with physiological fluids. A hydrogel composed of PEO for wound dressing is prepared and PVA is added to give toughness to the hydrogel by electron beam irradiation and found that these hydrogels showed satisfactory properties for wound dressing that has been evaluated by creating wound on the back of the marmots. [157] The hydrogel gives a wet environment to wounds which causes faster healing compared with the gauze dressing with a dry environment. The weight of the hydrogel increases quickly at the earlier stages, up to 4 days, due to absorption of effusion produced from the wound as shown in Table 2. After that, the production of effusion from the wound ceases and the weight of the hydrogel decreases due to evaporation of the water in the hydrogel. This means that the healing of wound proceeds smoothly with time. The hydrogel can be peeled off easily from the wound at the time of removal. Table 2 Absorption of effusion from wound of dressing during healing. [157] The toughness of PEO hydrogel is improved by the addition of PVA and tensile strength is measured and found that as shown in 10 and 11, the tensile strength and elongation decrease with increasing dose because of the increase of crosslinking. Various synthetic polymers as discussed above are used for wound dressing applications. But the major problem with these materials is their biocompatibility characteristics are often unsatisfactory and their interaction with living tissues is a major problem. So a combination of both natural and synthetic polymers is the better option to make a hydrogel having biocompatibility and desired mechanical strength. 3.3 Blended hydrogels Since both the natural and synthetic polymers have their own advantages and disadvantages so a combination of natural and synthetic polymers can endow the optimal properties necessary for wound repair. [47] The combination of natural and synthetic polymers is used in the biomedical, bioengineering and biotechnology field nowadays because of their great potential. A blended hydrogel composed of polyvinyl alcohol/polyvinyl pyrrolidone and charcoal were prepared by single ‘‘freezing and thawing or two-step ‘‘freezing and thawing and ÃŽ ³-ray irradiation and applied as wound dressing. It is found that the absorption of S. aureus and P. aeruginosa by charcoal/PVA/PVP hydrogels was larger than those by PVA/PVP hydrogels, this is due to the absorption and attachment capability of bacteria by charcoal, this can be shown in 12 given below. [22] The most classical way of fabricating a CS based wound dressing has been to design an asymmetric composite structure. In this method, the Cotton fabric was coated with chitosan (CS) and polyethylene glycol (PEG) followed by freeze-drying. The outer dense layer helps in preventing the microbial passage across the dressing and provides a rate controlling barrier for water vapor permeation, while the inner porous layer provides a high surface area for the exudates absorption. For the absorption of wound exudates porosity is the prime requirement in a dressing. It has been found that these dressings have the porosity 54-70% and the pore size was in the range of 75-120 µm. [45] The increase in the PEG content in the blend composition led to an enhanced destabilization of pores, leading to an increase in the pore size with elongated morphology. There seems to be phase separation between the two components which is an important factor for the observed behavior of the porous structure. Cot ton fabric has been used as the support layer for the CS-PEG layer and leads to very thin and light weight structures. The structure of the dressing has been designed in such a way that it leads to the high porosity of the bulk structure. The thickness of CS coating plays an important role in the development of the porosity on the surface. The influence of the CS thickness on the surface morphology is presented in 13 given below. PEG addition to CS makes significant alteration in the surface morphology of this CS-PEG/cotton membrane (freeze-dried), henceforth known as CPC membrane. There is a distinct trend in the loss of inherent elongated porous structure in membranes and formation of the partially collapsed porosity takes place due to the PEG addition. This suggests that a very limited interaction between CS and PEG exists which is reflected in the observed surface morphology. It has been observed that higher the amount of PEG, the higher is the pore destabilization leading to larger pores. This is evident from the morphology of the CPC membrane at 50% PEG-20 content as shown in 14.45 On the above matrix, the addition of PVP and drug followed by coating on the cotton fabric and freeze drying of the coated matrix is also done. It has been found that the drug