Morocco Country Risk Assessment Essay Example | Topics and Well Written Essays - 1000 words

Morocco Country Risk Assessment - Essay Example Having been inhabited back in the Paleolithic times, most of the citizens are either Arabs or Berbers with the latter ethnic group forming the bulk of the population. Other ethnic groups that form part of the population include Haratin and Gnaoua. Additionally, the country is inhibited by more that 100,000 foreigners including Spanish and French who have invested in various sectors thus improving the country economic performance. Culturally, Morocco is known for being an ethnically diverse nation based on its hosting various foreigners who come from the East, South and other regions. Some of the key visitors who have contributed to the cultural growth of the country include Carthaginians, Arabs, Phoenicians, Romans, Andalusians, Jews and Vandals among others. Due to the interaction of the various groups in the country, Moroccan literature has continued to experience an expansive growth. For example, western and Middle East literary models have enhanced the growth of poetry and tradit ional Moroccan genres (Yahya 49). Similarly, the country rich cultural values have attracted expatriates academic and social writers such as Paul Bowles and Pierre Loti among others. Infrastructure One of the major factors that make Morocco a good country for investors is the highly developed infrastructure system as compared to other African countries. For instance, the country is served by more that 35, 946 miles and 18,800 miles of primary roads and secondary roads respectively. As a result, the cost of transporting raw materials and finished products within the country is low thus resulting to high profits by the local and foreign investors. Additionally, the government has continued to issues large number of licenses to... This paper stresses that a vital factor that makes Morocco a viable country for investors is the electrical power development. National Office of Electricity is the main government-owned firm that is responsible for providing electricity power in the country. Even though the country has significant oil reserves, most of the power was earlier generated from imported fuels from Saudi Arabia. This report makes a conclusion that Morocco is ruled under the constitutional monarchy with the prime minister holding major powers while the king hold few executive powers including dissolving the parliament. Two major chambers in Morocco parliament are the assembly of councilors and the assembly of representatives. To ensure justice in the country judicial system, the country constitution provides for an independent judiciary. In this way, politicians do not have much impact on the country court system thus reducing the level of corruption in the country. One of the remarkable political initiatives that occurred in 2011 was the drafting of new constitution that brought about major reforms in the country political system. For example, the king was given power to appoint a prime minister from the party with the majority seats in parliament. Similarly, the prime minister was given power to appoint high level diplomats and chief executive officers of the government owned organizations. It is worth noting that the constitutional also gave power to all citizens by ensuring freedom of creation, ideas, thought among others.

In what ways may disagreement aid the pursuit of knowledge in the Essay

In what ways may disagreement aid the pursuit of knowledge in the natural and human sciences - Essay Example However, from the past, they solely relied on empirical evidence and analysis in the absence of enhanced gadgets and technologies. They were challenged to do almost the impossible because they were motivated to think outside the box so as to discover new learning, idea or concept. Outstandingly, Maslow managed to interpret the hierarchy of the human needs, but other psychologists believe that there are other important points that one could use to explain â€Å"motivation.† Understanding motivation requires knowing human’s complex emotions and personality. One, therefore, should expect that this area of academic interest should involve myriads of ideas that have to be taken into account prior to forming concrete information on the whole thought about human needs and motivation. It is, therefore, clear that disagreements involved in pursuit of knowledge in the natural and human sciences could provide a substantial advantage not just for the preservation of the body of kno wledge but for taking it to the next level in an upward spiral. It is, thus, the main concern in this paper to explicate the ways on how disagreements aid the pursuit of knowledge in the natural and human sciences. ... Empirical evidence in this area is a significant requirement in order to prove that something like important claims concerning certain ideas, events, observations or concepts potentially exist. However, various other thoughts using empirical scientific inquiry sometimes would put each other in a clash, leading to a significant consideration about the situation. Let us take the case behind Genetically Modified (GM) crops. Just before the end of 2012, in September, Monsanto was bombarded with another controversial issue concerning the safety of their products. A study from French scientists revealed that Monsanto’s genetically modified corn or top-selling weedkiller was found to cause rat mortality due to tumors, multiple organ damage and premature death (Palma). The implication of this result could lead to the idea that Monsanto’s top-selling weedkiller GM crops might have a potential impending toxicity level that could be detrimental to the human health. Rumors were abl e to spread concerning this report leading to the point that there is a need to consider further investigations on the actual methodology used in the entire research process, and to initiate other series or relevant independent studies so as to confirm the reliability of the published results. There are more other potential concerns aside from these. However, it is also good to look at the side of Monsanto, particularly at their strong stand on GM crops, stating that their safety is the same with existing food crops, so they do not exactly make a difference (Monsanto Company). Monsanto remarkably offered a high level of confidence in their GM crops because they also initiated relevant scientific inquiries in order to prove the safety of their product offerings. Any

Critical management perspectives Essay Example | Topics and Well Written Essays - 2500 words

Critical management perspectives - Essay Example When 70 percent of the surveyed individuals prefer to buy Company A’s products and services over the Company B’s competing products and services, Company A’s products and services has more value over the value of Company B. Value includes the value of the supply chaini. Academic theory /literature to justify my idea One research shows that the company must exert efforts to create and enhance business valueii. For the business entity, value equates to the quality of the services offered. A company that delivers the same product within two days has a lower value when compared to another company that offers to deliver the same product or service within a lesser time period. The research shows that value includes quality of the factors that contribute supplying the immediate needs of the company’s current and future customers. The factors include the suppliers’ delivery of the company’s raw materials and other quality supply needs on time. Furthe r, another research states that value creation and enhancement includes implementing the best alternative marketing and management plansiii. The research shows that value creation in the contemporary business organization is complex and many-phased topic that incorporates changing factors. For example, outsourcing will increase the company’s revenues. ... Economic principles dictate that as the demand for the company’s products and services decrease, the current and future customers demand for the company’s products and services increaseiv. Furthermore, another research indicates that business value investing and improvement should be prioritizedv. The value investing and improvement included companies are forecasted to have high value. There are many factors that contribute to increasing and retaining the company’s high business value. The factors include the company’s historical revenue trend. The company that shows it generated three prior year’s high revenue will have a higher business value compared to the company that has a tract record of three years of lackluster (low) revenue outputs. Additionally, the company that has shows it generated net profits for the past three years has a higher business value compared to a company that had generated net losses for the past three years. Moreover, bus iness combinations contribute to higher business valuevi. When a big company acquires a smaller company, the business value of the smaller company is catapulted to higher levels. Normally, big companies merge or combine with some of its competitors in order to increase its market presence. The increased market presence increase the company’s revenues and profits. Often, the fair market values of the separate companies are used when determining the higher business value of the merged or combined company. Further, the merger or consolidation of the two companies includes adding one company’s goodwill or good name in the new combined company’s higher business value. Goodwill can be defined as the popularity of the company’s name among

Leisure and Tourism Maqnagement Project Coursework

Leisure and Tourism Maqnagement Project - Coursework Example This has implications for the events industry in general, and for the way the events industry ought to capitalize on social media trends in order to remain relevant. These developments also augur well for the industry, as they represent new opportunities that the industry can exploit in order to thrive moving forward (Neff; Smith and Zook; Kaplan and Heinlein; Agichtein et al.; Gilbert and Karahalios). Gaping holes in the marketing mix can result from events industry participants ignoring recent trends relating to the growing power and influence of social media in the lives and the finances of its customers. An understanding of the intricacies of social media as they are used to supplement or to make up the core of the important promotions and place aspects of the marketing mix can have profound implications for the events industry as a whole (Mangold and Faulds; Asur and Huberman; Xiang and Gretzel; Correa et al; Eyrich et al.; Kietzmann er al.; Thakeray et al.; Bian et al.). How does social media impact the UK events industry? What are the implications of the explosion in social media use on the events industry in the UK, as they pertain specifically to the way the industry markets itself and provides services to its customers? (Neff; Smith and Zook; Kaplan and Heinlein; Agichtein et al.; Gilbert and Karahalios). This paper aims to derive insights from recent research relating to the impacts of social media on the UK events industry in particular, and the intricacies of social media use and how such affects the way the UK industry markets itself and provides services to its customer bases (Neff; Smith and Zook; Kaplan and Heinlein; Agichtein et al.; Gilbert and Karahalios). There is the growing sense that social media is of vital importance in many aspects of businesses that have to do with facing and relating to customers, as evidenced, for instance, in

Analyzing Brazilian Movie Essay Example for Free

Analyzing Brazilian Movie Essay The movie â€Å"Behind the Sun† is a Brazilian film, entitles â€Å"Abril Despedacado† in Portuguese, based to the novel â€Å"Shattered April† originally written by multi awarded Albanian writer â€Å"Ismail Kadare†. The film was released in the year 2001, directed by a multi-talented and reputable Brazilian movie director â€Å"Walter Salles†, and produced by an Academy film producer â€Å"Arthur Cohn†. Although, the movie was not able to garner major movie awards and recognition, director Walter Salless Behind the Sun, had received a bunch of positive feedbacks from different movie critics and fanatics from countries across the globe. (IGN Entertainment, Inc. ) Nevertheless, the Brazilian motion picture â€Å"Behind the Sun† is said to be one of the successful movie, produced and done in Brazil. Technically, the movie Behind the Sun is a thematic drama and thrilling film, which tells the story between the bloods battle of two Brazilian families, who are battling for land rights. Essentially, the storyline of the film is a depiction of the family struggles, which shows the extent of family desire to revenge for their aggravated member of the clan, a result of personal and objective desire to own a merely useless and forgotten land. The movie shows the true color of elderly Brazilian family members to chase their desire to own a land, specifically, the movie tells the bloody battle tale of two Brazilian family, the â€Å"Breeves Family† and the â€Å"Ferreiras Family†, as they struggle for long been quarrel on the unproductive land. Moreover, the story line runs through the bloody family conflict, as the scenes are depictions of offensive actions against the two different oppositions in the movie. Most of the scenes in the movie, are the bloody picture of killing between the two young Brazilian gentlemen (teenagers) from both side of the family, as they act their revenge for their murdered family member, cause by their long been family quarrel over a destitute land. Nonetheless, the story line of the movie Behind the Sun is a depiction of the long been bloody tale for land rights, between two Brazilian families, the â€Å"Breeves† and the â€Å"Ferreiras†, and a struggle for honor. Moreover, the story of the movie â€Å"Behind the Sun† had happened way back 1910, as the Breeves and the Ferreiras argued for a merely useless land. The movie takes place in the â€Å"Northeast part of Brazil†, which is also known as the†badland†. Technically, the Northeast of part Brazil is the settings of the movie, where the two families quarrel over a property right of a dying sugarcane land. Since, the movie happened in the year 1910 and in the northeast of Brazil, the primary characters or the two families finds their way of living through the blessings of their land. Meaning, the Breeves and the Ferreiras makes their living through agriculture. In addition to this, the movie tells a profound family relationship, on which the Breeves and Ferreiras show in-depth family relationship and closed family links. Nevertheless, the movie is depiction of the true color of Brazilian family, which is united, loving and brave, ready to fight for their family members and honor. Movie Production, on the other hand, is awesomely amazing, as the directors, actors and the rest of the people responsible for the movie do their job really well for this project. Starting from camera angles, the director and camera man had done a great job, as the shots in the movie are appropriately done to give superb detail in every scene or event. The camera angles are perfect, as far as I can say that it gives the right shot, which the specific scene and happenings requires. Technically, the Cinematography of the movie is equally great as the camera angles and shot. The films cinematography gives fine details for every scene, as the movie introduces a profound definition of cinematography for the movie Behind the Sun. Since, the movie is a tale of bloody family battle, happened in the early 19th century (1910), in the Northeast part of Brazil, the lights and colors of the movie, supports, enhances and provide the needed emotions in every scenes. Nevertheless, The cinematography or the lighting and the color of the movie, makes the story, every scene and the whole film realistic, as if it was shoot way back 1910. Costumes props and the settings of the movie, on the other hand, are all timely and appropriate with the portrayal of 1910 era. The props men and the creative director, have definitely done their job at the very best they can. The costumes and the cultural settings of the movie, like early Brazilian agricultural materials are reproduce appropriate and was used accordingly. Even the food, are all timely to the 1910 era and the way of living as well as the whole surroundings are likely the same in the year 1910. The House of Sand, on the other hand, is another Brazilian film, which was released four years after â€Å"Behind the Sun†, in 2005. (Netflix, Inc. ) Just like the movie â€Å"Behind the Sun† by â€Å"Walter Salles†, The House of Sand is a movie, which also tells a family Brazilian family story. Essentially, these two Brazilian movies are both produced in the early 20th century and for that fact these two films had been successful on their own ways. Apart from being the same as Brazilian movies,† Behind the Sun† and â€Å" The House of Sand† both happened in the northern part of Brazil. In addition, these two Brazilian movies share a likely family tale in their story. Although, the movies â€Å"Behind the Sun† and â€Å"The House of Sand† are the alike in different aspects, these two Brazilian movies still vary in some manner. First, in the movie Behind the Sun, the focal point of the story is through the connection or relationship between the father and son, while on the movie The House of Sand, the storyline evolves essentially between the mother and daughter relationship. Second, The House of Sand has lighter conflict or dilemma in its story, while the movie Behind the Sun has more serious and critical family conflict or dilemma in its tale. Nevertheless, these two movies are effectively positive, on which a depiction of social and moral lessons on certain issues in our community today. Works Cited IGN Entertainment, Inc. (2008), Behind the Sun (2001): Retrieved May 13, 2008 from http://www. rottentomatoes. com/m/behind_the_sun/#synopsis Netflix, Inc. (2008), The House of Sand (2005): Retrieved May 13, 2008 from http://www. netflix. com/Movie/The_House_of_Sand/70043822? mqso=80012394

Middle-Class Homelessness in America Essay Example for Free

Middle-Class Homelessness in America Essay Can you imagine yourself standing in line in hope for a cot at a shelter to share with your family, or waiting for a warm meal in a soup kitchen? This is what many middle-class American citizens have succumbed to. Has the American dream been lost, has the middle-class lost its position in the American economy, and has the inequality of income cause the demise of the middle-class? By focusing on the health care reform and record low unemployment rate we overlook the underlying problem; the dwindling middle-class, the backbone of our country. Many studies have been conducted to define middle-class without much success. It has been attempted to relate it to annual income. One study states that yearly incomes between $32,900 and $64,000, another between $50,800 and $122,000, and the U. S. census bureau middle 60% of incomes is the largest range of all lies between$ 20600, and $102,000 as what defines middle-class. Dan Horn notes in the Cincinnati Enquirer â€Å"Psychologist Ken Eisold, a contributor to Psychology today, said, though, that the way people describe their social status has more to do with what’s going on in their heads than their wallets. † Eisold goes on to say that â€Å"it’s really more about identity†. Horn adds that Julie Heath, director of the University of Cincinnati’s Economics Center agrees with Eisold that saying, â€Å"We’re a middle-class family has more than a financial connotations to it, it has a salt-of the earth to it. That’s the bed rock. Essentially this shows that Americans do not base their social status on their income alone, but also on their personal accomplishments and views of where they have come from and where they are going. That being said, the bed rock of the middle-class comes from one of the most common descriptions what living in America is all about; the great American Dream. History tells us that this emotion connected with being middle-class started showing up in the 1830’s. In these times people came to America hoping for the best, and they clung to ideas of how they would make it. They believed that if those ideas and values were kept, that they were middle-class, even if they were not financially. This is how the idea of the Leave it to Beaver life style came into being. In the 1950’s men took white collar jobs while women stayed home and maintained their house and families. They bought homes in the suburbs, nice family cars, and made safe investments. This provided them a sense of stability and many believed this is what the American dream is all about. Today, in pursuit of the dream, to maintain their middle-class status many Americans have higher incomes than their parents did but both parents are working. Yet while doing the best that they that they can possibly do, many are watching their dreams shatter. Erin Currier, director of the Pew Economic Mobility Project, said â€Å"stability is one of the biggest threats to the middle class today. † She goes on to say, â€Å"Though born into middle-class, many fall out by adulthood. † This is due to inflation of basic needs such as health care, day care, college funding, and the rise of the inequality of income. One term often referred to when relating to the middle-class crisis is Income Gap. As defined on the internet by investapedia. om, the income gap is the unequal distribution of household and individual income across the various participants in an economy. A sociology and political science professor at the University of Arizona who studies income inequality and poverty, says that over the past three decades â€Å"is slow income growth compared to general economic growth†¦ a bigger and bigger portion of economic growth has occurred to the wealthiest 1 %, whether the measure is basic wages or total compensation,† says Lane Kenworthy. (CQ researcher 3) There is political risk involved with this shift that is greater than economics and family finances. A large middle class, especially one that is politically active, tends to be a kind of anchor that keeps our country from swinging back and forth. There are typical values that middle-class families acquire and pass on to their children and those values tend to be good for democracy,† states Teresa Sullivan, provost and executive vice president for academic affairs at the University of Michigan, and the co-author of The Fragile Middle Class: Americans in Debt. (CQ Researche r 2) The new millennium looked very hopeful for the war on poverty in America. The federal poverty rate was the lowest it had been since 1974 according to CQ Researcher. The next 4 years even better with Housing prices doubling in many cities and increase in home equity loans that brought the Home-ownership rate up to an all time high of 69 percent. In 2008 we would not only see the sand shift out from the false growth of the economy led by the banks and lending companies but our government bail the banks out with $700 billion rescue bill, They did not however bail out the borrower and many lost their homes. Leading to the current middle class crisis. These issues, the rise of the inequality of income and the shattering of the American dream, have led us to the downfall of the middle class. In more recent years the middle-class are finding themselves not only having a decrease in their income due to layoffs and downsizing, but while not able to maintain their dream are losing their homes due to foreclosures. They are now finding themselves sleeping in their cars, if fortunate to still have one. They are waiting in lines for food and shelter, and bathing in gas station rest rooms, standing on street corners and highway exit’s begging for money or work. I have a personal interest in this research because I consider myself a middleclass American who lived through these years of the housing crisis and recession, I have lost a business, I am dealing with the short sale of my home and a threat of foreclosure, I have suffered through divorce and currently I am a struggling single mother. In conclusion the decline of the middle-class has hit very close to home. Although the hope of the American dream dies a slow death in my own heart, because of the continual economic status and burden of the cost of living rising, many like me are losing hope.

Cyclic Voltammetry Principle

Cyclic Voltammetry Principle Cyclic voltammetry is the most widely used technique for acquiring qualitative information about electrochemical reactions [34, 35]. The power of cyclic voltammetry results from its ability to provide considerable information on the thermodynamics and kinetics of heterogeneous electron transfer reactions [47, 48], and coupled chemical reactions [36, 37]. It also provides mathematical analysis of an electron transfer process at an electrode [41, 49, 50]. Basic Principle of Cyclic voltammetry An electron transfer process with a single step may be represented as; O + ne à ¢Ã¢â‚¬ ¡Ã¢â‚¬ ¹ R (2.1) where O and R are oxidized and reduced form of electoractive species respectively, which either is soluble in solution or absorbed on the electrode surface and are transported by diffusion alone. Cyclic voltammetry consists of scanning linearly the potential of a stationary working electrode (in an unstirred solution), using a triangular potential waveform. Depending on the information sought, single or multiple cycles can be used. During the potential sweep, the potentiostat measures the current resulting from the applied potential. The resulting plot of current vs. potential is termed as cyclic voltammogram. The excitation signal in cyclic voltammetry is given in Fig. 2.1a. Initially the potential of the electrode is Ei. Then the potential is swept linearly at the rate of ÃŽÂ ½ volts per second. In cyclic voltammetry reversal technique is carried out by reversing direction of scan after a certain time t =ÃŽÂ » .The potential at any time E (t) is given by E (t) = Ei ÃŽÂ ½t t E (t) = Ei 2ÃŽÂ ½ÃƒÅ½Ã‚ » + ÃŽÂ ½t tà ¢Ã¢â‚¬ °Ã‚ ¥ÃƒÅ½Ã‚ » (2.2b) HereÃŽÂ ½ is scan rate in V/s. The shape of the resulting cyclic voltammogram can be qualitatively explained as follows: When potential is increased from the region where oxidized form O is stable, cathodic current starts to flow as potential approaches E0 for R/O couple until a cathodic peak is reached. After traversing the potential region in which the reduction process takes place, the direction of potential sweep is reversed. The reaction-taking place in the forward scan can be expressed as O + e- à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ R During the reverse scan, R molecule (generated in the forward half cycle, and accumulated near the surface) is reoxidized back to O and anodic peak results. R à ¯Ã¢â‚¬Å¡Ã‚ ¾Ãƒ ¯Ã¢â‚¬Å¡Ã‚ ® O + e- In the forward scan as potential moves past Eo, the near-electrode concentration of O falls to zero, the mass transfer of O reaches a maximum rate, in unstirred solution, this rate then declines as the depletion of O further and further from electrode takes place. Before dropping again current passes through a maximum. Reversal of scan repeats the above sequence of events for the oxidation of electrochemically generated R that now predominates in near-electrode region. The continuous change in the surface concentration is coupled with an expansion of the diffusion layer thickness (as expected in the quiescent solutions). The resulting current peaks thus reflect the continuous change of the concentration gradient with time, hence, the increase to the peak current corresponds to the achievement of diffusion control, while the current drop (beyond the peak) exhibits a t-1/2 dependence (independent of the applied potential). For the above reasons, the reversal current has the same shape as the forward one. Electrochemical Cell Electrochemical cell is a sealed vessel which is designed to prevent the entry of air. It has an inlet and outlet to allow the saturation of solution with an inert gas, N2 or Ar. Removal of O2 is usually necessary to prevent currents due to the reduction of O2 interfering with response from system under study. The standard electrochemical cell consists of three electrodes immersed in an electrolyte; Working electrode (WE) Reference electrode (RE) Counter electrode (CE) Working Electrode (WE) The performance of the voltammetric procedure is strongly influenced by the working electrode material. Since the reaction of interest (reduction or oxidation) takes place on working electrode, it should provide high signal to noise characteristics, as well as a reproducible response. Thus, its selection depends primarily on two factors: the redox behaviour of the target analyte and the background current over the potential region required for the measurement. Other considerations include the potential window, electrical conductivity, surface reproducibility, mechanical properties, cost, availability and toxicity. A range of materials have found application as working electrodes for electroanalysis, the most popular are those involving mercury, carbon or noble metals (particularly platinum and gold). Reference Electrode (RE) This functional electrode has a constant potential so it can be used as reference standard against which potential of other electrode present in the cell can be measured. Commonly used reference electrodes are silver-silver chloride or the calomel electrode. Counter of Auxiliary Electrode (CE) It is also termed as auxiliary electrode and serves as source or sink for electrons so that current can be passed from external circuit through the cell. The potential at WE is monitored and controlled very precisely with respect to RE via potentiostat. This may be controlled in turn via interfacing with a computer. The desired waveform is imposed on the potential at the WE by a waveform generator. The potential drop V is usually measured by the current flowing between the WE and CE across a resistor R (from which (I=V/R), the latter connected in series with the two electrodes. The resulting I/V trace, termed as a voltammogram is then either plotted out via an XY chart recorder or, where possible, retained in a computer to allow any desired data manipulation prior to hard copy being taken. Single Electron Transfer Process Three types of single electron transfer process can be studied. Reversible process Irreversible process Quasi-reversible process Based on values of electrochemical parameters, i.e. peak potential Ep, half peak potential (Ep/2), half wave potential (E1/2), peak current (ip), anodic peak potential Epa, cathodic peak potential Epc etc, it can be ascertained whether a reaction is reversible, irreversible or quasi-reversible. Ep is the potential corresponding to peak current ip, Ep/2 is the potential corresponding to 0.5 ip, E1/2 is the potential corresponding to 0.85 ip. These  electrochemical parameters can be graphically obtained from the voltammogram as shown in the Fig. 2.2. Reversible Process The heterogeneous transfer of electron from an electrode to a reducible species and vice versa O + ne à ¢Ã¢â‚¬ ¡Ã¢â‚¬ ¹ R is a form of Nernstian electrode reaction with assumption that at the surface of electrode, rate of electron transfer is so rapid that a dynamic equilibrium is established and Nernstian condition holds i.e. CO(0,t) à ¢Ã‹â€ Ã¢â‚¬ ¢ CR(0,t) = Exp[(nFà ¢Ã‹â€ Ã¢â‚¬ ¢RT)(Ei-ÃŽÂ ½t-Eo)] (2.3) In equation (2.3), Co and CR are concentration of oxidized and reduced species at the surface of electrode as a function of time, Eo is the standard electrode potential, Ei is the initial potential and ÃŽÂ ½ is the scan rate in volts per second. Under these conditions, the oxidized and reduced species involved in an electrode reaction are in equilibrium at the electrode surface and such an electrode reaction is termed as a reversible reaction. Current Expression Due to difference in concentration of electroactive species at the surface of electrode and the concentration in the bulk, diffusion controlled mass transport takes place. Ficks second law can be applied to obtain time dependent concentration distribution in one dimension of expanding diffusion layer. à ¢Ã‹â€ Ã¢â‚¬Å¡Ci(x, t) à ¢Ã‹â€ Ã¢â‚¬ ¢Ãƒ ¢Ã‹â€ Ã¢â‚¬Å¡t = Dià ¢Ã‹â€ Ã¢â‚¬Å¡2Ci(x, t) à ¢Ã‹â€ Ã¢â‚¬ ¢Ãƒ ¢Ã‹â€ Ã¢â‚¬Å¡x2 (2.4) Peak current is a characteristic quantity in reversible cyclic voltammetric process. The current expression is obtained by solving Ficks law [51]. i = nFACo*(à Ã¢â€š ¬Doa)1/2 à Ã¢â‚¬ ¡(at) (2.5) where i = current, n = number of electrons transferred, A is the area of electrode, Co* is the bulk concentration of oxidized species, Do is the diffusion coefficient, à Ã¢â‚¬ ¡ (at) is the current function and a = nFÃŽÂ ½/RT At 298K, function à Ã¢â‚¬ ¡(at) and the current potential curve reaches their maximum for the reduction process at a potential which is 28.5/n mV more negative than the half wave potential i.e. at n(Ep-E1/2) = 28.50 mV, à Ã¢â€š ¬1/2à Ã¢â‚¬ ¡(at) = 0.4463 ( Table 2.1). Then the current expression for the forward potential scan becomes (2.6) where ip is the peak current or maximum current. Using T=298K, Area (A) in cm2, Diffusion coefficient (Do) in cm2/s, concentration of species O (Co*) in moles dm-3 and Scan rate (ÃŽÂ ½) in volts sec-1, equation (2.6) takes the following form, (2.7) Equation (2.7) is called Randles Sevick equation [39, 40]. Diagnostic Criteria of Reversibility Certain well-defined characteristic values can be obtained from the voltammogram, for a reversible electrochemical reaction. Relationship between peak potential (Ep) and half wave potential (E1/2) for a reversible reaction is given by, (2.8a) (2.8b) Where E1/2 is potential corresponding to i = 0.8817ip [41]. At 298 K (2.8c) From equations (2.8a) and (2.8b) one obtains, (2.9a) At 298K (2.9b) The peak voltage position does not alter as scan rate varies. In some cases, the precise determination of peak potential Ep is not easy because the observed CV peak is somewhat broader. So it is sometimes more convenient to report the potential at i = 0.5ip called half peak potential, which can be used for E1/2 determination [52]. (2.10a) At 298 K (2.10b) (2.10c) From equations (2.8a) and (2.10a) we obtain, (2.11a) At 298K (2.11b) The diagnostic criterion of single electron transfer reversible reaction is often sufficient to get qualitative as well as quantitative information about the thermodynamic and kinetic parameters of the system. For a reversible system, should be independent of the scan rate, however, it is found that generally increases with à ¯Ã‚ Ã‚ ®. This is due to presence of finite solution resistance between the reference and the working electrode. Irreversible Process For a totally irreversible process, reverse reaction of the electrode process does not occur. Actually for this type of reaction the charge transfer rate constant is quite small, i.e. ksh à ¯Ã¢â‚¬Å¡Ã‚ £ 10-5cm sec-1, hence charge transfer is extremely low and current is mainly controlled by the rate of charge transfer reaction. Nernst equation is not applicable for such type of reaction. The process can be best described by the following reaction O + ne à ¯Ã¢â‚¬Å¡Ã‚ ¾Ãƒ ¯Ã¢â‚¬Å¡Ã‚ ® R Delahay [51] and later on Mastuda, Ayabe [48], and Reinmuth [53] described the stationary electrode voltammetric curves of the irreversible process. Irreversibility can be diagnosed by three major criteria. A shift in peak potential occurs as the scan rate varies. Half peak width for an irreversible process is given by (2.12) Here ÃŽÂ ± is transfer coefficient and na is the number of electrons involved in rate determining step of charge transfer process. At 298K (2.13) Current expression is given as, i = nFACo*(à Ã¢â€š ¬Dob)1/2 à Ã¢â‚¬ ¡(bt) (2.14) The function à Ã¢â‚¬ ¡(bt) goes through a maximum at à Ã¢â€š ¬1/2à Ã¢â‚¬ ¡(bt) = 0.4958.(Table 2.2). Introduction of this value in equation (2.14) yields the expression (2.15) for the peak  current. A plot of ln ip vs. (Ep-Eo) for different scan rates would be a straight line with a slope proportional to -à ¯Ã‚ Ã‚ ¡naF and an intercept proportional to ks,h. Quasi-reversible Process Quasi-reversible process is termed as a process which shows intermediate behaviour between reversible and irreversible processes. Both charge transfer and mass transfer control current of the reaction. For quasi-reversible process value of standard heterogeneous electron transfer rate constant, ks,h lies between 10-1 to 10-5 cm sec-1[42]. Cyclic voltammogram for quasi-reversible process is shown in Fig. 2.3. An expression relating the current to potential dependent charge transfer rate was first provided by Matsuda and Ayabe [48]. (2.17) where, ksh is the heterogeneous electron transfer rate constant at standard potential Eo of redox system,is the transfer coefficient and à ¯Ã‚ Ã‚ ¢ = 1- à ¯Ã‚ Ã‚ ¡. In this case, the shape of the peak and the various peak parameters are functions of à ¯Ã‚ Ã‚ ¡ and the dimensionless parameter à ¯Ã‚ Ã…’, defined as [54] (2.18) For quasi-reversible process current value is expressed as a function of. (2.19) where is expressed as (2.20) is shown in Fig. 2.4. It is observed that when à ¯Ã‚ Ã…’ > 10, the behavior approaches that of a reversible system. It is observed that for a quasi-reversible reaction, ip is not proportional to à ¯Ã‚ Ã‚ ®1/2. For half peak potential we have at 298K (2.21) This implies, These parameters attain limiting values characteristic of reversible or totally irreversible processes as à ¯Ã‚ Ã…’ varies. For à ¯Ã‚ Ã…’ >10, à ¯Ã‚ Ã¢â‚¬Å¾(à ¯Ã‚ Ã…’,à ¯Ã‚ Ã‚ ¡) = 2.2 which gives Ep-Ep/2 = 56.5mV (value characteristic of a reversible wave). For Variation of Ά with Άº and ÃŽÂ ± is shown in Fig. 2.5. For three types of electrode processes Matsuda and Ayabe [48] suggested following zone boundaries. a) Reversible (Nernstian) ΆºÃƒ ¯Ã¢â‚¬Å¡Ã‚ ³15; ksh à ¯Ã¢â‚¬Å¡Ã‚ ³ 0.3 à Ã¢â‚¬ ¦1/2cm s-1 b) Quasi-Reversible 15à ¯Ã¢â‚¬Å¡Ã‚ ³ Άº à ¯Ã¢â‚¬Å¡Ã‚ ³ 10-2 (1+ÃŽÂ ±); 0.3 à Ã¢â‚¬ ¦1/2 à ¯Ã¢â‚¬Å¡Ã‚ ³ ksh à ¯Ã¢â‚¬Å¡Ã‚ ³ 2 10-5 à Ã¢â‚¬ ¦1/2 cm s-1 c) Totally Irreversible Άº Source: Bard, A.J.; Faulkner, L.R. Electrochemical Methods, Fundamentals and Applications, John Wiley, New York, 1980, pp 225. Source: Bard, A.J.; Faulkner, L.R. Electrochemical Methods, Fundamentals and Applications, John Wiley, New York, 1980, pp 227. Multi Electron Transfer Process Multi-electron transfer process usually takes place in two separate steps. Two-steps mechanism, each step characterized by its own electrochemical parameters is called EE mechanism. Stepwise reversible EE mechanism is given by following reaction, A + n1e à ¢Ã¢â‚¬ ¡Ã¢â‚¬ ¹ B (E10) (2.22a) B + n2e à ¢Ã¢â‚¬ ¡Ã¢â‚¬ ¹ C (E20) (2.22b) where, A and B are electroactive species and n1 and n2 are the number of electrons involved in successive steps. If A and B react at sufficiently separated potentials with A more easily reducible than B, the voltammogram for overall reduction of A to C consists of two separated waves. The first wave corresponds to the reduction of A to B with n1 electrons and in this potential range the substance B diffuses into the solution. As potential is scanned towards more cathodic values, a second wave appears which is made up of two superimposed parts. The current related to substance A, which is still diffusing toward electrode increases since this species now is reduced directly to substance C by (n1+n2) electrons. In addition, substance B, which was the product of the first wave, can be reduced in this potential region and a portion of this material diffuses back towards the electrode and reacts. Each heterogeneous electron transfer step is associated with its own electrochemical parameters i.e. ks,hi and ÃŽÂ ±i, where i =1, 2 for the 1st and 2nd electron transfer respectively. Based on the value of à ¯Ã‚ Ã¢â‚¬Å¾Eo, we come across three different types of cases [50] as shown in the Fig. 2.6. Types of Two Electron Transfer Reactions [50] Case 1: Separate Peaks When à ¯Ã‚ Ã¢â‚¬Å¾Eo à ¯Ã¢â‚¬Å¡Ã‚ ³ -150mV the EE mechanism is termed as disproportionate mechanism [55]. Cyclic voltammogram consists of two typical one-electron reduction waves. The heterogeneous electron transfer reaction may simultaneously be accompanied by homogenous electron transfer reactions, which in multi-electron system leads to disproportionation. Each disproportionation reaction can be described as, 2R1 à ¢Ã¢â‚¬ ¡Ã¢â‚¬ ¹ O+ R2 (2.23) The equilibrium constant K (disproportionation constant) is given by (2.24) It can be derived from the difference between the standard potentials using (2.25) Case 2: In this case, the individual waves merge into one broad distorted wave whose peak height and shape are no longer characteristics of a reversible wave. The wave is broadened similar to an irreversible wave, but can be distinguished from the irreversible voltammogram, in that the distorted wave does not shift on the potential axis as a function of the scan rate. Case 3: = 0mV Single peak In this case, in cyclic voltammogram, only a single wave would appear with peak current intermediate between those of a single step one electron and two electron transfer reactions and Ep-Ep/2 = 21 mV. Case 4: E1o If the energy required for the first second electron transfer is less than that for the first, one wave is observed having peak height equal to 23/2 times that of a single electron transfer process. In this case, Ep E1/2 = 14.25 mV. The effective E0 for the composite two electron wave is given by [50]. Source: Polcyn, D.S.; Shain, I. J. Anal. Chem. 1966, 38, 370. Cyclic Voltammetric Methods for the Determination of Heterogeneous Electron Transfer Rate Constant Cyclic voltammetry provides a systematic approach to solution of diffusion problems and determination of different kinetic parameters including ks,h. Various methods are reported in literature to determine heterogeneous rate constants. Nicholson [41, 42], Gileadi [56] and Kochi [37] developed different equations to calculate heterogeneous electron transfer rate constants. Nicholsons Method [41, 42] Nicholson derived an expression for determination of heterogeneous electron transfer rate constant ksh. This method is based on correlation between and ks,h through a dimensionless parameter by following equation, (2.26) where is scan rate. for different values of ΆEp can be obtained from the Table 2.3. Hence, if ΆEp (Epa-Epc) is determined from the voltammogram, can be known from Table 2.3. From the knowledge of, , ksh can be calculated using equation (2.27). If D o= DR then ÃŽÂ ³=1 (2.27) This method is applied for voltammograms having peak separation in the range of 57mV to 250mV, and between this range, the electrode process progresses from reversible to irreversible. With increasing scan rate, the peak separation and hence à Ã‹â€  decreases. It can be seen from the Table 2.3, that for reversible reactions i.e. for the current voltage curves and is independent of . For totally irreversible reaction i.e. for the back reaction becomes unimportant, anodic peak and is not observed. For quasi-reaction i.e. for 0. 001 Separation of cathodic and anodic peak potential as a function of the kinetic parameter à ¯Ã‚ Ã‚ ¹ in the cyclic voltammogram at room temperature. Kochis Method Kochi and Klinger [37] formulated another correlation between the rate constant for heterogeneous electron transfer and peak separation. The expression for ksh given by Kochi was (2.28) The standard rate constant ksh can be calculated from the difference of peak potentials and the sweep rates directly. This equation applies only to sweep rates which are large enough to induce electrode irreversibility. The relation derived by Kochi is based on following expressions derived by Nicholson and Shain [41]. (2.29a) (2.29b) where ÃŽÂ ² = 1-ÃŽÂ ± , and à Ã¢â‚¬ ¦ is the scan rate. Equations (2.29a) and (2.29b) yield (2.30) This expression is used for the determination of the transfer coefficient. Assuming that (for reversible reaction). We have, (2.31) Gileadis Method Gileadi [56] formulated a more sophisticated method for the determination of heterogeneous electron transfer rate constant, ks,h, using the idea of critical scan rate, c. This method can be used in the case where anodic peak is not observed. When reversible heterogeneous electron transfer process is studied at increasing scan rates, peak potential values also vary and process progresses towards irreversible. If are plotted against the logarithm of scan rates, a straight line at low scan rates and ascending curve at higher scan rate is obtained. Extrapolation of both curves intersects them at a point known as toe. This toe corresponds to the logarithm of critical scan rate, c. as shown in Fig. 2.7. Hence critical scan rate can be calculated experimentally. ks,h can be calculated as, (2.32) where à Ã¢â‚¬ ¦c is the critical scan rate, ÃŽÂ ± is a dimensionless parameter, called transfer coefficient and Do is the diffusion coefficient. Coupled Chemical Reactions Although charge transfer processes are an important part of entire spectrum of chemical reactions, they seldom occur as isolated elementary steps. Electron transfer reactions coupled with new bond formation or bond breaking steps are very frequent. The occurrence of such chemical reactions, which directly affect the available surface concentration of the electroactive species, is common to redox processes of many important organic and inorganic compounds. Changes in the shape of the cyclic voltammogram resulting from the chemical competition for the electrochemical reactant  or product, can be extremely useful for elucidating the reaction pathways and for providing reliable chemical information about reactive intermediates [35]. It is convenient to classify the different possible reaction schemes in which homogeneous reactions are associated with the heterogeneous electrons transfer steps by using letters to signify the nature of the step. E represents an electron transfer at the electrode surface, and C represents a homogenous chemical reaction. While O and R indicate oxidized and reduced forms of the electroactive species, other non electroactive species which result from the coupled chemical complication are indicated by W, Y, Z, etc [57]. The order of C with respect to E then follows the chronological order in which the two events occur [58]. So according to sequence of step, the systems are classified as EC, ECE, CE etc. These reactions are further classified on basis of reversibility. For example, subclasses of EC reactions can be distinguished depending on whether the reactions are reversible (r), quasi-reversible (q), or irreversible (i), for example Er Cr, ErCi, EqCi, etc. Two Steps Coupled Chemical Reactions In two steps reactions, a variety of possibilities exist, which include chemical reactions following or preceding a reversible or an irreversible electron transfer [59, 60, 61, 62]. The chemical reactions themselves may be reversible or irreversible. a) Preceding Chemical Reactions (CE) In a preceding chemical reaction, the species O is the product resulting from a chemical reaction. Such a reaction influences the amount of O to be reduced so forward peak is perturbed. For a preceding chemical reaction, two mechanisms are possible, depending on whether the electron transfer is reversible CrEr or irreversible CrEi [58]. Reversible Electrode Process Preceded by a Reversible Chemical Reaction (CrEr Reaction) The process in which a homogeneous chemical reaction precedes a reversible electron transfer is schematized as follows: (2.33) where Y represents the non electroactive species and O and R are the electroactive congeners. Since the supply of electroactive species O results from the chemical reaction, it is important to know that how much of O is formed during the time scale of cyclic voltammogram. In this connection, it must be noted that the time scale of voltammetry is measured by the parameter a = nFà Ã¢â‚¬ ¦/RT for a reversible process and b = ÃŽÂ ±naFà Ã¢â‚¬ ¦/RT for a quasi reversible or an irreversible process It means that the time scale of cyclic voltammetry is a function of the scan rate, in the sense that higher the scan rate, the higher is the competition of the voltammetric intervention with respect to the rate of chemical complication. The limit at which the chemical complication can proceed is governed either by the equilibrium constant K or the kinetics of the homogeneous reaction (l = kf+kr). In this regard, it is convenient to distinguish three limiting cases depending on the rate of chemical complication [41]. Slow preceding chemical reaction (kf+kr When K is large (i.e. K > 20) most of O will already be present in solution, the response is apparently not disturbed by the latter, i.e. it appears as a simple reversible electron transfer. When K is small, the small electron transfer again appears as a simple reversible process except that the peak current will be smaller than is expected on the basis of quantity of Y in the solution. This results because the concentration of the electroactive species CO, being determined by the equilibrium of the preceding reaction is equal to a fraction of species Y placed in the solution. where C* = CO (x,0) +CY(x,0) Fast preceding chemical reaction (kf+kr >> nFà Ã¢â‚¬ ¦/RT) When K is large, once again the response appears as a simple reversible electron transfer, but the measured standard potential Eo/* is shifted toward more negative values compared to the standard potential Eo/ of the couple O/ R by a factor of . When K is small, because of the fast continuous maintaining of the small equilibrium amount of O, the complete depletion of O at the electrode surface will never be reached, so that the forward profile no longer maintains the peak shape form, rather assumes a sigmoidal S-shaped curve, the height of which remains constant at all scan rates. Intermediate preceding chemical reaction (kf+kr = nFà Ã¢â‚¬ ¦/RT) In this case, the kinetics can be studied using the ratio between the kinetic and the diffusive currents according to the relationship (2.34) Irreversible Electrode Process Preceded by a Reversible Chemical Reaction (CrEi Reaction) This process is schematizes as. (2.35) In this case, not only the thermodynamic K (kf / kr) and kinetic (kf + kr) parameters of preceding chemical reaction but also the kinetic parameters of the electron transfer (ÃŽÂ ±, k0) play a role. Obviously the lack of reverse peak is immediately apparent, due to the irreversibility of the charge transfer. The curves are also more drawn out because of the electron transfer coefficient, ÃŽÂ ±. Slow preceding chemical reaction (kf+kr In this case, the process appears as a simple irreversible electron transfer. The peak height of the process depends on the equilibrium constant because, as mentioned in the previous case, the concentration of the active species CO is a fraction of the amount C* put in the solution: Fast preceding chemical reaction (kf+kr >> nFà Ã¢â‚¬ ¦/RT) If instead the reaction kinetics is fast, there are two possibilities: If K is large, again the response appears as if the preceding chemical reaction would be absent. However, the peak potential is shifted towards more negative values than those that would be recorded in the absence of the chemical complication by a factor equal to . If K is small, as in the preceding case, an easily recognizable S-like curve voltammogram is obtained having a limiting current independent from the scan rate (2.36) Intermediate preceding chemical reaction (kf+kr = nFà Ã¢â‚¬ ¦/RT) Here again, the kinetics can be studied using the ratio between the kinetic and diffusive currents according to the relationship (2.37) b) Following Chemical Reactions (EC) The process in which the primary product of an electron transfer becomes involved in a chemical reaction is indicated by EC mechanism. It can be represented by O + ne à ¢Ã¢â‚¬ ¡Ã¢â‚¬ ¹ R R à ¢Ã¢â‚¬ ¡Ã¢â‚¬ ¹ Z (2.38) where O and R are the electroactive congeners and Z represents the non electroactive species. Several situations are possible depending on the extent of electrochemical reversibility of the electron transfer and on the reversibility or irreversibility of the chemical reaction following the electron transfer. As a general criterion, in cyclic voltammetry, the presence of a following reaction has little influence on the forward peak, whereas it has a considerable effect on the reverse peak. Reversible Electrode Process Followed by a Reversible Chemical Reaction (ErCr Reaction) ErCr mechanism can be written as (2.39) Once again the voltammetric response will differ to a greater or lesser extent with respect to a simple electron transfer depending on the values of either the equilibrium constant, K, or the kinetics of the chemical complication (kf+kr) [58]. Analogously to that discussed for preceding equilibrium reactions, three limiting cases can be distinguished. Slow following chemical reaction (kf+kr If the rate of chemical reaction is low, it has a little effect on the process, thus reducing it a simple reversible electron transfer. Fast following chemical reaction (kf+kr >> nFà Ã¢â‚¬ ¦/RT) If the rate of the chemical complication is high, the system will always be in equilibrium and the voltammogram will apparently look like a non complicated reversible electron transfer. However, as a consequence of the continual partial removal of the species R from the electrode surface, the reduction occurs at potential values less negative than that of a simple electron transfer by an amount of . Due to the fast kinetics of the chemical complication, the potential will remain at this value regardless of the scan rate. Intermediate following chemical reaction (kf+kr=nFà Ã¢â‚¬ ¦/RT) If the kinetics of the chemical reaction are intermediate with the scan rate the response gradually shifts from previous value for a fast chemical reaction [which was more anodic by w.r.t. to value of the couple O/R] towards the Eo/ value assuming more and more the values predicted by the relationship (2.40) In other words, the response (which for the fast kinetics is more anodic compared to E0/) due to the competitive effects of the potential scan rate moves towards more cathodic values by 30/n (mV) for every ten fold increase in the scan rate. However, it is noted that at the same time, the reversible peak tends to disappear, in that on increasing the scan rate, the species Z does not have time to restore R. This is demonstrated by the current ratio which is about one at low scan rates, but it tends to zero at high scan rates. Reversible Electrode Process Followed by an Irreversible Chemical R