Skoog Solution of Chapter 15

Crouch Principles of Instrumental Analysis, 6th ed. Chapter 15 Instructor’s Manual CHAPTER 15 15-1. In a fluorescence emission spectrum, the excitation wavelength is held constant and the emission intensity is measured as a function of the emission wavelength. In an excitation spectrum, the emission is measured at one wavelength while the excitation wavelengths are scanned. The excitation spectrum closely resembles an absorption spectrum since the emission intensity is usually proportional to the absorbance of the molecule. 15-2. a) Fluorescence is the process in which a molecule, excited by the absorption of radiation, emits a photon while undergoing a transition from an excited singlet electronic state to a lower state of the same spin multiplicity (e. g. , a singlet > singlet transition).Phosphorescence is the process in which a molecule, excited by the absorption of radiation, emits a photon while undergoing a transition from an excited triplet state to a lower state of a different spin multiplicity (e. g. , a triplet > singlet transition). (c) Resonance fluorescence is observed when an excited species emits radiation of he same frequency at used to cause the excitation. (d) A singlet state is one in which the spins of the electrons of an atom or molecule are all paired so there is no net spin angular momentum (e) A triplet state is one in which the spins of the electrons of an atom or molecule are unpaired so that their spin angular moments add to give a net non-zero moment. (f) Vibrational relaxation is the process by which a molecule loses its excess vibrational energy without emitting radiation. 1 Principles of Instrumental Analysis, 6th ed. (g) Chapter 15Internal conversion is the intermolecular process in which a molecule crosses to a lower electronic state with emitting radiation. (h) External conversion is a radiationless process in which a molecule loses electronic energy while transferring that energy to the solvent or another solute. (i) I ntersystem crossing is the process in which a molecule in one spin state changes to another spin state with nearly the same total energy (e. g. , singlet > triplet). (j) Predissociation occurs when a molecule changes from a higher electronic state to n upper vibrational level of a lower electronic state in which the vibrational energy is great enough to rupture the bond. (k) Dissociation occurs when radiation promotes a molecule directly to a state with sufficient vibrational energy for a bond to break. (l) Quantum yield is the fraction of excited molecules undergoing the process of interest. For example, the quantum yield of fluorescence is the fraction of molecules which have absorbed radiation that fluoresce.Chemiluminescence is a process by which radiation is produced as a result of a chemical reaction. 5-3. For spectrofluorometry, the analytical signal F is proportional to the source intensity P0 and the transducer sensitivity. In spectrophotometry, the absorbance A is proporti onal to the ratio of P0 to P. Increasing P0 or the transducer sensitivity to P0 produces a corresponding increase in P or the sensitivity to P. Thus the ratio does not change. As a result, the sensitivity of fluorescence can be increased by increasing P0 or transducer sensitivity, but the that of absorbance does not change. 2 Principles of Instrumental Analysis, 6th ed. Chapter 15 5-4. (a) Fluorescein because of its greater structural rigidity due to the bridging –O– groups. (b) o,o’-Dihdroxyazobenzene because the –N=N– group provides rigidity that is absent in the –NH–NH– group. 15-5. Compounds that fluoresce have structures that slow the rate of nonradiative relaxation to the point where there is time for fluorescence to occur. Compounds that do not fluoresce have structures that permit rapid relaxation by nonradiative processes. 15-6. The triplet state has a long lifetime and is very susceptible to collisional deactivation.T hus, most phosphorescence measurements are made at low temperature in a rigid matrix or in solutions containing micelles or cyclodextrin molecules. Also, electronic methods must be used to discriminate phosphorescence from fluorescence. Not as many molecules give good phosphorescence signals as fluorescence signals. As a result, the experimental requirements to measure phosphorescence are more difficult than those to measure fluorescence and the applications are not as large.3 Principles of Instrumental Analysis, 6th ed. 15-7. Chapter 15 4 Principles of Instrumental Analysis, 6th ed. 5-8. Chapter 15 15-9. Q = quinine ppm Q in diluted sample = 100 ppm ? 245 = 196 125 mass Q = 196 mg Q 500 mL ? 100 mL ? = 490 mg Q 10 mL solution 20 mL 3 5 Principles of Instrumental Analysis, 6th ed. 15-10. cQ = A1csVs (448)(50 ppm)(10. 0 mL) = = 145. 45 ppm ( A2 ? A1 )VQ ( 525 ? 448) (20. 0 mL) Chapter 15 145. 45 ppm ? 1 mg quinine 1 g solution ? ? 1000 mL = 145. 45 mg quinine 3 1 mL 1 ? 10 g solution 0. 225 g Q ? 100% = 3. 43% 4. 236 g tablet 15-11. Assume that the luminescent intensity L is proportional to cx, the concentration of iron in the original sample.Then, L1 = kcxVx / Vt where Vx and Vt are the volume of sample and of the final solution, and k is a proportionality constant. For the solution after addition of Vs mL of a standard of concentration cs, the luminescence L2 is L2 = kcxVx / Vt + kcsVs / Vt Dividing the second equation by the first yields, after rearrangement, cx = L1csVs (14. 3)(3. 58 ? 10? 5 )(1. 00) = = 1. 35 ? 10? 5 M ( L2 ? L1 )Vx (33. 3 ? 14. 3)(2. 00) 15-12. Assume that the luminescence intensity L is proportional to the partial pressure of S* . 2 We may then write L = k[S* ] 2 and K = S* ][H 2 O]4 2 [SO 2 ]2 [H 2 ]4 where the bracketed terms are all partial pressures and k and K are constants.The two equations can be combined to give after rearrangement 6 Principles of Instrumental Analysis, 6th ed. Chapter 15 [SO 2 ] = [H 2 O]2 [H 2 ]2 L kK In a hydr ogen-rich flame, the pressure of H2O and H2 should be more or less constant. Thus, [SO 2 ] = k ? L where k? = 1 kK 15-13. The fluorescent center is the rigid quinoline ring, which is rich in ? electrons. 15-14. From Equation 15-7, we can write F = 2. 303 ? f K bcP0 = 2. 303 ? K cP0 ? 0 Dividing both sides by the lifetime ? yields F = 2. 303K bcP0 ? ?0 Since K? , ? , b, ? 0 and P0 are constants, we can write F ? = Kc where K is a compilation of all the constants in the previous equation. 7 Principles of Instrumental Analysis, 6th ed. 15-15. (a) Chapter 15 (b) (c) The corrected fluorescence Fcorr would be Fcorr = F? 0/? , where F is the observed fluorescence, ? 0 is the lifetime for [Cl–] = 0. 00, and ? is the observed lifetime. The results are in the spreadsheet. 8 Principles of Instrumental Analysis, 6th ed. Chapter 15 9

Posthumus and Innogene Essay

The following passage is from Shakespeare’s ‘Cymbeline’ Act 4 Scene 2. In the quoted lines Innogen identifies Clotens to be Posthumus due to Posthumus’ garment worn by Clotens. Innogen looks at Clotens’ body and his garments and says â€Å"I know the shape of`s leg; this is his hand†. According to her, his foot is ‘Mercurial’ and thighs â€Å"Marcial’. From the first act the audience is accustomed to see a chaste Innogen who is attracted only to her husband, Postumus. However in this passage Innogene is made to speak admiring words about Clotens which is ironic to the audience. Her instant decision based on the garment is a kind of an amusement to the audience who is aware of the identity of the corpse. Innogene believes that she know Posthumus well enough to identify him without the head or the ‘jovial face’. The audience may expect better judgment from Innogene who till then did show good judgment in choosing Postumus to Clotens. This passage shows that Postumus and Clotens were more similar looking than Innogene would want to believe. These similarities are mentioned by Clotens in â€Å"I mean, the lines of my body are as well drawn as his;† in Act 4, Scene 1(9-10). She tries to see some logical reason for the gruesome murder of her husband. The first possibility that comes to her mind is Pisanio’s involvement. She suspects him to have revealed the details about Posthumous to Clotens. Everyone except Innogene knows that Pisanio has got nothing to do with this murder. Moreover Innogene is unable to think logically, for, if Pisanio was the culprit he may not have helped and sent her in pursuit of Posthumus. She concludes that Pisanio has joined with Clotens to kill Posthumus. In the passage Innogene call Clotens, â€Å"irregulous devil Clotens†. Clotens is interested in marrying Innogen. When he found out that this was not possible because she chose to be the wife of Posthumus, Clotens decided to murder Posthumus and rape her. He goes to the wilderness in search of Posthumous with pure hatred in his heart. Nevertheless he wears Posthumus’ garments while seeking out Posthumus and Innogene. This is ironic that he chose to wear the dress of his opponent in subduing him. He may have thought this would be a nice way to torture Innogene with the thoughts of her dead husband when he uses force on her. This may heighten the misery. This however goes a long way to show the cruel nature of Clotens. On the other hand the audience sees that Posthumus is aggrieved for ordering the death of his wife. He is repentant and tries to seek his own punishment by surrendering as a Roman soldier in to the hand of British troops. During the battle he takes the side of his motherland and protects it from the enemy attack, fulfilling the duty of the son of the soil. Deception in costume plays its part here again when he dresses as an Englishman and fights with Iachimo. Posthumus and Clotens are two opposite forces juxtaposed to bring out their contrasting natures to intensify the final good over evil concept. However Innogenes’ misunderstanding in identifying the corpse is the climax of this parallelism. This is an important scene in this play due to the death of Clotens and his misidentification as Postumous. Clotens has been the shadow of Posthumus throughout the play. At every mention of Posthumus there is a direct comparison drawn with Clotens as both are interested in noble Innogene. Death of Clotens signifies the death of evil and victory of good. However at this stage not all threads in the play are brought to a conclusive end. Moreover the difference between both is so strong that it needs to have a lingering effect for some time until alls well. Hence this scene is a good device to conclude the play in a progressive gradation.

Gold Standard Paper Research Example | Topics and Well Written Essays - 1000 words

Gold Standard - Research Paper Example This paper will discuss both advantages and disadvantages that could be incurred if the United States economy returns to the Gold Standard, by presenting a brief history on US economy’s use of the Gold Standard and the circumstances surrounding the standard’s dismissal. From early centuries, Gold has always been placed at an esteemed position due to its use and functionality. Among the various precious metals that are found here on earth, Gold is considered the most 'valuable' as it has many applications, from being used in Jewelry to being the main tool in International financial transactions. The major nations of the world including United States from the latter half of 19th century till 1920’s used Gold to pay for all the trade that was carried out between them. To standardize this form of gold transaction, a Gold standard was adopted. Under the Gold Standard, currencies of the countries, using gold for transaction, are tied to a specific amount of gold. So, w hen a country redeems or pays its money in the form of gold, it is said to be following or using the Gold Standard. This way, the government of the country which redeems gold and its counterparts who receive the gold will share a fixed-currency relationship. The advantage, the nations were able achieve due to the use of earlier introduced Gold Standard was the adjustment of their Balance of payments. That is, when a nation has a trade deficit while doing trade with a particular country, they could balance it by paying in gold, as currencies were convertible to gold. This advantage could also be garnered, if the Gold Standard is reintroduced again, particularly in relation to United States Economy. The pro-group for the introduction of Gold Standard state that if the standard is introduced in United States, preferably within next 5 years, it could solve number of fiscal and monetary problems that has been plaguing the US economy in the recent past. One of the main advantages that cou ld be incurred is stabilization of the US’ Dollar value, which in a way could restore the confidence among the â€Å"foreign investors in U.S. government bonds,† and importantly could also â€Å"discourage reckless federal spending.† (Dykewicz, 2011). That is, with the Dollar serving as the world's reserve currency, it enables other countries to use it for all types of trade and even stockpile it, thus providing the U.S. Federal Reserve to print as much Dollar as it needs to fiddle with its economy as it sees fit. The downside of such loose monetary policies includes higher inflation rates and a weaker Dollar, and so certain sections of experts advocate the return to the Gold Standard, with the hope that it could force the government to live within its means. (Jones and Walter, 2011). In a way, the return of Gold Standard could bring stability and strengthening of the US Dollar, thereby having many positive impacts on the economy. The positive impacts include so lutions to the current unemployment problem, because strengthened or expensive Dollar would lead to people using more labor, and importantly would lead to fiscal discipline. Thus, it is being pointed out that the current Fed’s policy of pouring trillions of Dollars into the economy to stimulate growth, will only lead to more inflation and weakening of Dollar, and so if the Gold Stand

In the paper, analyze Vincents claims about how men and women are Essay

In the paper, analyze Vincents claims about how men and women are differentsimilar from the book, SelfMade Man by Norah Vincent - Essay Example Disguised as "Ned," Vincent entered an all-male world in which she joined a bowling league, dated women, worked as a door-to-door salesman, spent almost a month in a male catholic monastery, visited strip clubs and, to put the cherry on the top of the cake, joined a men-only therapy group. I her book, Vincent creates rich, experience-proof portraits of all the men she met in all these places and managed to describe male behavior in a very pictorial way. One should not forget though, that being a lesbian, she successfully separates sexuality from gender issues. It is fascinating how Vincent describes the internal reflections of this experiment on her self image. The result from censoring her emotions, while hiding under the mask of a male, was a deep psychological breakdown, a crisis of identity, which threw her into the depths of depression. Vincent's first daring act as a newborn male was to join a bastion of male friendship - she became a member of a local bowling team in a typical working-class Pennsylvania neighborhood. Her major problem was that she was a terrible bowler. Astonishingly, the men accepted her in the team. From this point on, her observations on the male world could begin. Among the first things to notice were the amazing generosity and support that they had. The bowling experience turned some of Vincent's perceptions about men being cruel and rejecting and women being warm and welcoming upside down. After nine months with the bowling team Vincent gained entrance to the inner sanctum of the masculine world. She found out that cursing and what seems to be verbal aggression among men is just a way for them to show affection for each another, without being too intimate. Her in-depth exploration of male friendship doesn't stop here. Unveiling the mystery of boys' nights out is one thing, but explaining the explicit nature of male sexuality is quite another. In order to gain a deeper understanding of the male sex drive, Vincent visited several strip clubs, accompanied by a male friend. She describes this experience as hellish. According to her, it was very demeaning for the strippers, but even worse for the men. Vincent says that the activities she witnessed there describe the essence of pure, male sex drive. Men who visit these clubs are completely depraved of any meaningful interaction, although naked women are dancing in their laps. Though she is attracted to women as a lesbian, she could never get sexually aroused from these visits. Vincent realized that there are major differences between male and female sexuality. According to her, female sexuality is a mental experience, while for a man, it is physical urge. This primitive urge can be a great disadvantage for men in modern society. Vincent claims that the act of simply hearing "no" from a woman can devastate a man. Women don't have to cope with the humiliating part of fighting for female approval. Men have to gather a lot of self esteem and courage, in order to cross the room and to introduce themselves to a total stranger who can easily degrade them in front of everybody by rejection. Saying the first words is a task which men are expected to fulfill and it is not a simple task. In most cases, she found out, saying those first words is very hard without sounding like a total jerk. If the opposite side is cruel enough, consequences can be very harmful

A Valuable Tool for Learning Essay Example | Topics and Well Written Essays - 4250 words

A Valuable Tool for Learning - Essay Example It is worth noting that in recent years, CIT has been utilized in newer settings, including the determination of poor and effective service episodes in the retail and healthcare industries. A comprehensive review of these contemporary uses of CIT specifically in the healthcare sector is provided by Kemppainen (2000). Critical incident analysis permits the emergence –instead of the imposition – of an evaluative framework and concentrates on the occurrences and dimensions of the patient experience that are most prominent, striking, and with a greater likelihood to be recounted to others (Ruben, 1993). This paper thus presents a critical incident and uses reflective analysis to draw insights from the incident, with the ultimate goal of improving patient service. A secondary goal is to derive personal lessons which I may use for my own professional development. The following portion expounds on the value of reflective learning and analysis, as a means of gaining insight from a critical incident. †¦ the process of internally examining and exploring an issue of concern, triggered by an experience, which creates and clarifies meaning in terms of self and which results in a changed conceptual perspective. As a process, reflection is integrated into numerous conceptual frameworks (Hutchinson & Allen, 1997; Kember et al., 1999; Riley-Doucet & Wilson, 1997). I have chosen Johns’ (1994) framework for structured reflection for this analyzing the critical incident. Johns model for structured reflection can be utilized as a guide for reflecting on a critical incident or general reflection on an experience. This would be useful for more complicated decision making and analysis at levels 3 and 4. Johns (1994) advocates the need for the learner to work with a supervisor throughout their learning experience. He refers to this as guided reflection and recommends that students use a structured diary.

Adonis musati project Article Example | Topics and Well Written Essays - 500 words

Adonis musati project - Article Example The Adonis Musati is a name that has a great significance for the project as it points to the mission of the project. Adonis Musati is the name of refugee who died in a line while queuing to have his application of being a South African Asylum seeker verified. His death, which resulted from fatigue and hunger, touched the heart of many and hence this project was launched to ensure that such an incidence did not happen again in the history of this country. From a broad look, refugees in South Africa have always been face of major challenges after escaping from the neighboring countries. For instance, there is a high inflow of Asylum seekers from Zimbabwe, a country that has constantly been involved in war. Unfortunately, these refugees end up suffering from torture and discrimination in the government. The process of becoming an asylum seeker has always been rough and punctuated by strings of corruption. Consequently, the rights of these marginalized groups have always been suppressed and this only makes the situation worse for them. Adonis Musati Project is an interventional project that aims at alleviating any form of suffering from those who escape their countries due to harsh conditions. The aim of the project is to ensure that Asylum seekers are provided with basic necessities such as food, clothes and shelter and to ensure that they are free from any form of suffering. The project has pulled a large number of sponsors to help in funding the project and support the welfare of this minority group. The project also seeks for the rights of the refugees in their process of applying to be South African Asylum seekers. They protect especially the females who are vulnerable to harassment and the old who cannot take care of themselves. The project has continuously taken an initiative to improve the lifestyle of the marginalized in an effort to make them equal humans in the face of the world. The

What do you think has been the most profound and enduring consequence Essay

What do you think has been the most profound and enduring consequence of colonialism in Africa Can it be said that colonialism had positive consequences - Essay Example onists normally govern the possessions, work force, and the trading aspects of the colony, and may enforce certain rules on the local people of that particular colony. In Africa, colonialism has most profound and enduring consequences that can either be positive or negative consequences. This paper, therefore, highlights some of the most profound and enduring consequences of colonialism, in Africa. It further argues whether or not colonialism had positive consequences, in Africa. The process of colonialism on the African land significantly transformed its account forever. Every way of living of the Africans changed completely from the way they think to culture, which were forever put in place by the change in their political system that was brought about by the process of colonialism (Thomson 67). The economy of Africa also transformed due to the slave trade through imperialism and the economic strategies that were imposed by the colonists. The major impacts and long lasting effects of colonialism, in Africa, include racial discrimination to Africans, tribal violence, and total poverty. According to Ali Mazrui, racial expression is the major lasting effect of colonialism in Africa, taking the example of the South African’s apartheid era, which took a long time to end even after they got their independent from the European colonists (Mazrui 116). The Europeans most awful heritage was the presence of the White racist state, which existed up to the year 1994, in South Africa. Apartheid was an acceptable racial discrimination method that was centered upon different ethnic backgrounds in South Africa. The people of South Africa were discriminated according to their races, and the local black population was denied the citizenship (Mazrui 112). The Whites were offered quality education, proper housing, good jobs, and excellent medical care. The apartheid system was so unreasonable with only whites who were less than te n percent trying to rule upon a larger population

The U.K Identity Cards Bill and its implcations Essay

The U.K Identity Cards Bill and its implcations - Essay Example While the Bill and the stated objectives seem reasonable, and a large majority of the general public believe it to be good idea, there remains confusion and apprehension on the potential implications of the Bill to their privacy and civil liberties, not to mention the cost and policy implications.3 Unlike other means of individual identification, the proposed use of biometric technologies utilising biological information, and the introduction of a computerised National Identity Register, which permits users to track anybody, anytime, anywhere, in the modern networked society, apparently present far-reaching implications on the privacy and security of the individual, as well as the society. A research is deemed necessary to understand the implications of the Bill including that of the technology involved, in terms of the privacy and security concerns, as well as to look at alternative techniques or modes of identification, which may be considered by the government for successful imple mentation of the identity project. Researchers observe that biometric techniques, such as fingerprint verification, retina analysis, iris or face recognition, voice recognition, hand-written signature verification, are increasingly used in individual authentication and identification systems.4 While researchers are generally in agreement on the efficacy of the technology, experts in information technology and data security caution the possibility of errors including false matches and multiple identities, and the dangers of manipulations and misuse.5 Many researchers, both in the U.K and elsewhere, have studied the impact of biometric technologies on individual privacy and security.6 Researchers like Zorkadis and Donos observe that, "too wide utilisation of biometrics creates general concern for the protection of the fundamental rights and freedoms of individuals."7 According to them any human physiological or behavioural traits used in biometric technologies are personal data protected by privacy protection legislation. The U.K. Identity Cards Bill and the use of biometrics have received widespread criticism by policy analysts and academic researchers.8 The report by Joint Committee on Human Rights (JCHR) raises "a number of concerns relating to the human rights compatibility of the Bill"9. According to academics from the London School of Economics and Political Science the identity card bill proposals are "too complex, technically unsafe, overly prescriptive and lack a foundation of public trust and confidence."10 While the researchers support the concept of a national identity system for the UK, it considers the present legislation and the scheme "as a potential danger to the public interest and to the legal rights of individuals."11 Other policy analysts also condemn the Bill as an unwarranted state intervention in individual freedom and privacy-Dolan Cummings states that the ID card proposals are in effect trying to "reconstitute the public as membership organisation" 12 creating a society in which the members have to constantly prove their identity to

Rebellion or Revolution Essay Example | Topics and Well Written Essays - 1000 words

Rebellion or Revolution - Essay Example In this paper I will take a specific position on the two concepts and aim to define each one of them. There have been numerous revolution and rebellions in the past. There has been confusion to some extent in terming an event a rebellion or a revolution. Numerous authors, researchers, historians, have all tried to establish a difference between a rebellion and a revolution. In the following paragraphs I will attempt to establish the difference between the two by taking a specific position on each. In order to do so, I have fallen back on the work of other scholars and some real life examples from the past. First, I will define each of them individually and then try to establish the difference between the two. According to me, a rebellion is an act of protesting or defying the higher authority. In most cases rebellion is a protest or against an ideology, requirement or a restriction. Through a rebellion, an attempt is made at changing a part of a system (for example part of a governme nt). A rebellion is always associated with a negative attitude if not a destructive one. Rebellions lack a proper direction and in most cases lack an affirmative program. Rebellion in most cases is associated with violence. Brinkley (2010) in his article points how to rebellion attitude is associated with negative emotions. But a rebellion is not always violent and negative. But a rebellion is an aggressive attempt to walk away from the routine and the accepted. Rebellion is a fight against the flaws or loopholes in a system that is accepted by majority of the society. It is aimed at changing or refining a part of the system. Rebellion is not associated with majority of the population but is supported only by a few. Hence, the scale of a rebellion is small. A rebellion unlike the common belief can be both violent and non-violent. Example of violent rebellion is rebellion against the Gaddafi government in Libya. A very good example of a non-violent rebellion is the protest by Gandhi against the injustice SA against the Indians. This is very well depicted in the 1982 movie Gandhi (Gandhi, 1982). This is will addressed again later. A revolution on the other hand is much larger in scale and is aimed at overthrowing the entire system or bringing in a major change in the way a system works. A revolution is associated with a positive attitude and is supported by majority of the society. As a result of a revolution there is a fundamental change being brought about with respect to power in a system. Revolution is mainly associated with political change and is much shorter with respect to duration but on a much bigger scale than a rebellion. A revolution brings in a major reform and attracts huge support from different quarters of the society. World has seen numerous revolutions in the past which has resulted in a total change. A revolution can be both violent and non-violent but it is always associated with positive emotion. Russian revolution was a violent revolution which bought a major political change in Russia while the Indian independence movement was a non-violent revolution which got India freedom. Now that the definitions and concepts of the two have been established, let’s see how they are different from each other. To put in a simplest way, revolution is born put of a rebellion. Rebellion is on a smaller scale and is aimed at showing discontent about the system while revolution is aimed at completely overthrowing a system. Rebellion is a narrow domain while revolution is a much broader field. A rebellion becomes a revolution when it gains momentum and realize its capability to bring in change on a large scale. A rebellion can happen at a individual level and might consider individual interests or interests of a small section of the society. Rebellion attitudes are

How to Write a Good Dental School Essay Example for Free

How to Write a Good Dental School Essay This article was created by a professional writer and edited by experienced copy editors, both qualified members of the Demand Media Studios community. All articles go through an editorial process that includes subject matter guidelines, plagiarism review, fact-checking, and other steps in an effort to provide reliable information. By WayneS, eHow Contributor Writing a good dental school essay may may be the difference between being accepted and rejected. An important part of applying to dental schools is writing a personal essay. The essay provides applicants with a chance to relate the attributes they would bring to the school and show their commitment to the field. It also offers applicants a chance to demonstrate how dental school will fulfill their professional and personal goals. Essays can be a deciding factor when schools make admission decisions, so applicants should put a lot of careful time and effort into writing them. Instructions Devote a lot of time to brainstorming. A clear understanding of exactly what you want to say is a necessary step when writing a compelling and effective dental school essay. While brainstorming, keep the three major goals of the essay in mind. First, establish exactly why you want to be a dentist. Second, think of any personal experiences that will prove helpful in dental school. Finally, search for qualities that would make you a good dentist. These can include schoolwork, clinical experience and community activities. Think of personal stories that will show you can be successful in dental school and dentistry. These stories should demonstrate the compassion needed to be a good dentist and identify experiences and skills youwill bring to dental school. Start the essay by using one of these stories. This will draw the reader into the essay more effectively than a list of accomplishments. Organize the essay. Determine the major points that you need to make in the essay and organize stories and information around those points. Instead of just relating all the stories at one time, organize the essay by topics. One topic can be how you have enthusiasm for the field. Then, use stories and information to demonstrate that enthusiasm. Â  Write the essay so it reflects the way you speak. It should flow naturally and be easy to read, not pedantic and full of jargon. The purpose is to sell yourself to show how you would be a great asset to the school and the field of dentistry. Â  Avoid cliches and worn-out themes. Use stories and practical examples to show the why the school should admit you. Do not just say that the you are committed or enjoy helping people. Provide practical examples of this commitment and desire to help. Have someone with a solid journalism or English background proofread the essay. Typos and misspellings can make you appear unprofessional and increase the chances of rejection.

Construction of the road

Construction of the road 1. Introduction Roads are constructed to bring benefits to the people. Investment in roads is huge for which funding most time is limited. Therefore the decision to invest and protect the investment in form of maintenance is important so as to bring optimal benefits and value for money. In order to maximise the benefits in the choice of investment, road investment appraisal may well be part of the planning process. The purpose of economic appraisal is to determine the investment cost and economic returns expected from such investment. Investment cost consists of construction and annual maintenance costs and are normally shouldered by the road agency. While economic returnsis in form of savings to the road users resulting from new road facility. These costs are referred to as total (road) transport cost or whole life cycle cost (HDM-4 documentation). It is therefore necessary to determine the works that will minimise the total transport cost over the extended analysis period, say expected life of the road. This report presents the economic analysis of a project to upgrade an existing gravel road to a bituminous pavement. The aim is to assess the economic benefit resulting from the proposed investment. This is to be carried out using Highway Development and Management (HDM-4), a road investment appraisal tool. HDM-4 is known to have the capability which assist with the selection of appropriate road design and maintenance standards that minimises the total transport cost. The support system will also indicate the economic viability of the proposed upgrading. The run will include sensitivity analysis, which involves repeated economic evaluation changing one parameter at a time, to identify the parameter(s) which affect the viability of the road project. 2. Literature review: 2.1 Economic appraisal of a road project. Economic appraisal is very important in planning a road project. It enables the road agency knows the investment cost as well as the economic returns of various alternatives, thereby assisting them in the selection of that which gives the highest returns. Total transport cost, also referred to as whole life cycle cost, includes construction and annual maintenance costs as well as road user costs (RUC). The RUC, in most cases, is the benefit due to the provision of a better road facility i.e VOC, travel time, comfort, reduction in accident. HDM-4 is a decision support tool for the analysis of road management, evaluation of investment alternatives and strategic planning among others. It has four models that are used to predict the effects of road construction and operation. Road deterioration model considers pavement structure, traffic loading and climate condition to analyse and predict the progression of structural and surface condition variables. Works effects model uses these variables and application of maintenance and construction measures to predict the physical quantities of resources required. These are used to multiply the unit costs specified to obtain the construction and maintenance cost for the analysis period. Road user effect model uses vehicle characteristics, geometric data and the forecast condition variables (e.g. IRI) to calculate the expected travel speeds of the different vehicle types, which in turn affect the vehicle and owners costs. The social and environmental effect model can forecast vehicle emissions and energy consumption. 2.2 Method of economic appraisal of a road project. This is usually done in HDM-4 for at least for two mutually alternatives road construction, rehabilitation or upgrade, one of which is referred to Do nothing or base alternative. While others are do something or project alternatives. The Do nothing or base alternative is where minimum investment is carried out in form of continuation of current maintenance strategy. This alternative has no construction component but has high maintenance cost and RUC. On the other hand, the do something or alternative project is when the road standard is improved, the choice of which depend on many factors such as the road agencys standard, traffic level, political and social consideration etc. This would normally have construction cost with both low maintenance cost and RUC. 3. Methodology. Create Project Define road network Section 2 Section 1 Define road sections Improvement Standard Mtce Standard (After) Mtce Standard (Before) Mtce Standard (Gravel) Define Work standards With Project Without Project Define Project alternatives Run analysis with sensitivity Generate Outputs The above flow describes the procedure for the economic analysis of the project using HMD-4. 4. Procedure for project analysis. 4.1 Project description: This Project is a 49.9 km gravel road classed secondary road and it is situated in sub-tropical/humid climate. It passes through varying topography. The road is divided into two sections based on geometric, pavement condition and traffic volume. The traffic and condition data obtained in 2008 are represented in table 4.1. The road is proposed to be upgraded to bituminous pavement. Both the degree of conflict between motorised and non-motorised transport and the effect of the road side activities on traffic flow were insignificant. 4.2 Data Input: Using the flow chart in paragraph 3 above all the necessary data require for the project analysis is stored in the system in the appropriate folders. These include detailed traffic composition and growth rate which are provided in the Vehicle fleet folder. A uniform growth rate of 4% was used for all vehicle classes on this project. The sections of the roads are defined under the road network folder. Each of the sections is considered homogenous in terms of geometric, pavement condition, traffic volume and composition. Therefore the physical details of the sections (length, width, and surface class), traffic direction and pattern, pavement type and condition, horizontal and vertical alignment information are among data set in the road network definition. However, only motorised traffic is considered in this analysis. 4.3 Defining the works standards: This is where both the maintenance and improvement standards are defined. The details are on Table 4.3. The maintenance standards are in the works standard/maintenance standards folder while the improvement standards are specified in the works standard/improvement standards folders. The maintenance standard has great effect on rate of deterioration of a road. Road will continue to perform to standard throughout its design life only when adequate and timely maintenance is carried out. Defining maintenance standard in the system imposes a limit to which deterioration could reach before a trigger. Furthermore the long term performance of a road is also affected by the improvement standard 4.3.1 Maintenance standard: There are three maintenance standards under the study. These are Gravel road maintenance, Maintenance before upgrading and routine maintenance after upgrade (crack sealing and patching paved road). These are effective at different time for the two sections of the road as detailed in Table 4.4. Scheduled for specified years. Duration is one year. Both economic and financial costs for each of the work items were stored in the system. 4.3.2 Improvement standard: The improvement standard is to upgrade the gravel road to bituminous pavement. However the year of implementation for each of sections 1 and 2 are 2011 and 2012 respectively. These are indicated at the intervention tab while keying the information for each of the section. Furthermore the financial cost for sections 1 and 2 are US$120,000 and US$150,050. The economic costs were estimated as 85% of the financial costs. These were stored in the cost tab. 4.4 Defining the project alternatives. There are two project alternatives Without project (maintaining the gravel road) and With project (upgrade gravel road). Each of the alternatives has works standards specified for each of the two sections. The analysis type (by project), start year (2009) as well as analysis period (20 years) were specified. The currency output of US$ was also selected. 4.4.1 Analysis method: There are two methods of analysing road investment in HDM-4 Analysis by section and analysis by project. The formal (analysis by section) is when the sections in the road are considered separately and analyse against a base section. While the latter (analysis by project) is when the entire sections in an alternative are considered against a base alternative. For this case study the analysis is by project. In this instance, the annual cost and benefit are added for the sections in the With project to give the year total. The economic indicators so obtained are then used to compare the base alternative. 4.4.2 Without project alternative: This is the base alternative representing a continuation of current maintenance practice. The two sections were defined and assigned a maintenance standard Gravel road maintenance earlier defined under the works standard/maintenance standards folder. 4.4.3 With project alternative: This is the alternative where the road is to be upgraded to bituminous pavement. The two sections were defined with both maintenance and improvement standards. Both sections are to be upgraded in 2011 and 2012 respectively. However, they are to be maintained before upgrade according to maintenance before upgrading standard as defined. Furthermore, the period of maintenance after upgrade is also specified. 4.4.4 Sensitivity analysis: It is a technique used to find out the effect on the whole project of changes in value of each variable which is considered potentially serious risk to the project. In this case study, three variables Traffic growth rates, Construction cost and Initial AADT were considered as sensitive to the project. Therefore each of them was changed at a time by  ±20% from 20% to 80% to verify their impact on economic indicators. 5. Analysis concept, summary result and discussion. 5.1 Project analysis concept The concept of the project analysis, using HMD-4, is assessing the physical, functional and economic feasibility of the With project alternative and compares it with Without project considered as base case. The system uses Life cycle costing for the analysis period of 20 years. In achieving this cost, the system models and predict the road deterioration, estimates the road user cost, model the road works effects and the cost of these to the road agency as well as calculate the economic and financial benefits from the comparison of the alternatives. 5.2 Road Deterioration and road works effect modelling For each year of the analysis period, HDM-4 models the road condition and assigns road works effect using predefined works strategies. Road deterioration prediction is based on the data provided on such variables as the original design, material type, construction quality, traffic volume, axle load characteristics, road geometry, environmental conditions, age of pavement and maintenance standard. HDM-4 does predict change in condition, i.e. distresses, from the initial set conditions as a function of the above named variables. 5.2.1 Average roughness (IRIav) of project: The deterioration of gravel road is characterised by roughness and material loss. Therefore grading every six months was specified as one of the work items for its maintenance to keep the roughness within tolerable limit. Spot regravelling work item was to repair areas of severe depression, while gravel resurfacing is performed to augment gravel surfacing due to loss of material. These work items followed intervention criteria specified by the users. This is the logic HDM-4 uses to predict the gravel road deterioration and it is presented in graph 5.2. This graph correlates Appendix I which shows the pavement condition summary. The pavement condition of Without project is a reflection of the interventions of the work items under continuous maintenance of the gravel road. Grading and Spot regravelling were effective every six month with no significant improvement to IRI values. However, gravel resurfacing was done in 2013, 2016, 2019, 2023 a nd 2025. There is a drop in IRI value each time the work item was carried out. In general the IRI was consistently high at between 7-13m/km throughout the analysis period for Without project alternative. HDM-4 also predicts the deterioration of the road after improvement. This is done through surface distresses (cracking and potholing) and deformation distress (roughness). Out of the three work items for the maintenance of the paved (bituminous) road only resealing work item was triggered throughout the analysis period. This is a reflection of the intervention criteria specified. Under the With project alternative there is a drop in IRI values in 2011 and 2012 following the upgrading of sections 1 and 2 at these years respectively. For instance, for section 1 the IRI value was 11.26m/km in 2010 but drastically reduced to 3.01m/km after upgrade in 2011. This is similar to the effect of upgrading section 2 in 2012. However, it is noticed that IRI continued to increase steadily subsequently but at low rate. In 2018, 2019, 2025 and 2026 there was resealing which changed the rate of increase in IRI (between 2018 and 2019) and actually reduced the value (between 2025 and 2026). Surface dre ssing does not necessarily improve the smoothness of road surface hence its effect on IRI is not significant. 5.2.2 Road works summary: This summary, as contained in Appendix 2, confirmed graph 5.1 and reflects the pavement condition summary in appendix 1. It shows the works items as they were triggered with associate quantities and costs (economic and financial). For the With project the maintenance standard before upgrade is reflected in the two sections before the upgrade. Furthermore resealing was also carried out in 2018 and 2025 for section 1, while that for section 2 was in 2019 and 2026. On the other hand in the Without project the average roughness for the project is shown in graph 4.1. This graph correlates Appendix 1 which shows the pavement condition summary. Road User Cost (RUC): From the economic indicator shown in Table 4.3 there is a decrease of US$3.828 million in Road User Cost (RUC) compared to US$3.105 million increase in Road Agency Cost (RAC) for the proposed upgrade. This is an indication of the viability for the upgrade. Cost Streams and Economic Evaluation Table 4.3 reflects the economic indicator showing a positive Net Present Value (NPV) of US$0.723 million, indicative of the project viability. The Internal Rate of Return (EIRR) is US$12.6 million. The economic indicator summary with sensitivity included in the analysis is provided in Appendix 3 Sensitivity Analysis As discussed in paragraph 5.2.2 above Tables 5.4a, 5.4b and 5.4c show the effects in economic indicators (NPV and EIRR) of changing the percentages of Initial AADT, Construction cost and Traffic growth rates considered as sensitive to the project. Increasing both initial AADT and Growth rate indicates positive values of NPV and EIRR, while reduction in their values gives negative economic indicators. On the other hand, increase construction cost gives negative NPV and its reduction gives positive NPV. NPV sensitivity diagram in figure 5.3 below indicates that the three variables have various degrees of sensitivity on the project, with AADT being most sensitive. An increase in construction cost as well as drop in AADT will affect the chances of achieving the positive NPV values. Therefore the accuracy of their estimation and forecast is important. Switching Values: A reduction in percentage of AADT and Growth rate beyond 11.5% and 25.6% respectively changes the NPV values from positive to negative. Whereas increase in construction cost beyond 19.5% also changes NPV from positive to negative. 6. Conclusion: The economic analysis, using HDM-4, indicates that upgrading the gravel road to bituminous pavement is viable because of the positive NPV value obtained for the analysis period. In implementing the project the gain in RUC outweighs the increase in the RAC when this is compared with do minimum alternative. However, this result can only be achieved if the works are carried out according to the programme. The Initial AADT, Construction cost and vehicle growth rate have various levels of sensitivity on the NPV. However, AADT is the most sensitive. An increase in construction cost as well as drop in AADT is likely to affect the chances of achieving a positive NPV values. There is also an indication that more benefit could be derived from the project when AADT value grows even as high as by 80% of the initial value. Therefore the accuracy of the construction cost, AADT and its projection are important to getting the benefit from the proposed project