What You Dont Know About Essay Topics on Climate Change Could Be Costing to More Than You Think

What You Don't Know About Essay Topics on Climate Change Could Be Costing to More Than You Think You have to make sure you get your points right. The change that has happened in the recent past is also known as outcome of global warming. It is simple to say such things. With the assistance of our governments, there's hope. Want to Know More About Essay Topics on Climate Change? If your aim is developing an excellent climate change essay for your college or university, it is an excellent place to master the abilities and tricks required to present a strong analysis to the general public. No matter your reasons are, it's great if you're passionate about the matter of climate change as it will be simpler to conduct research and persuade the reader to adopt your viewpoint. Knowing what sort of paper you have to write will shape the format, content, and clearly, the kind of sources you will have to support your claims. You ought to be acquainted with the concepts behind climate change if you're planning on writing a paper on it. The students that are engaged in too many works and would like to seek the services of a proper writer, then students assignment help is the very best choice for them. Your teacher may also request that you craft an informative international climate change essay where you need to just inform the reader about the present problem without expressing your own personal opinion. For instance, you might find there are 3 sub-topics under the very first major topic that you want to discuss, and that means you will create sub-headings for them. So, you should choose a topic that you may write a lot about. Quite frequently, the ideal topic is one which you truly care about, but you also will need to get ready to research it. Picking an excellent topic is an ambitious undertaking. Also, do not forget that you're able to pay for essay, just order original and superior quality papers from MyEssayWriting on a huge variety of topics. Before you write your descriptive essay, you should lay the basis of the full work. Furthermore, many students discover that it's tough to distinguish the kind of paper they are writing. If you're a working student or only have zero time for the research work we'll let you create a robust and winning essay. Furthermore, it lays out the intention behind the essay. When you start writing your essay you'll have all info you have to make accurate direct quotations. All the written essays are extremely easy and easy to be able to help students. Unlike in different essays, writing narrative essays permit the writer to use a very first person point of view as it is based on personal experiences. Climate change, in actuality, has come to be a cause of concern particularly over the past few decades. It will play a major role in animal health. It has the potential to drastically impact the future of the human race, and is intrinsically linked to the water supply across the world. It is one of the most important global issues facing the world today. The capacity for human suffering would be huge, and it's possible that we'd observe outbreaks of disease and famine, along with increased homelessness and poverty. A massive industrial revolution in today's time has largely impacted the inte rnational climate system by boosting the total amount of greenhouse gases in the earth's atmosphere. For instance, it can be scientific research on the causes and potential consequences of the worldwide warming. The clearest is climate warming. Future tropical cyclones will grow more intense. Finally, climate change is creating a rise in desertification. It is also known as global warming. Climatic changes have become more prominent now on account of the global warming that's a worldwide concern. There are numerous elements to take into account on several fronts, but with plants, here are a number of key aspects that affect their life cycles. There are a lot of factors that result in a change in the climate. Both are hot issues of the present time and it's the opportunity to analyse causes and prevention methods to stop the international warming. A good example is the greater sea levels because of the melting ice caps caused by global warming. Folks should cut power consumption in order to decrease the effects of global warming. Some folks feel that instead of preventing climate change, we have to obtain a means to live with this. If the planet's temperatures continue to rise later on, living things on earth would become extinct as a result of high temperatures. Also people with heart problems are going to be at high risk with the growing temperature and diseases due to the increase of stress on their entire body.

Negative Cigarette Smoking And Consumption â€Myassignmenthelp.Com

Question: Discuss About The Negative Cigarette Smoking And Consumption? Answer: Introduction Beer consumption and cigarettes smoking are some of the factors that are responsible for many deaths in the world every year. Beer consumers have resulted in many accidents that has taken the life of many innocent individuals. The smoking of cigarettes has resulted in many health issues such as cancers and has resulted in many deaths as well. Cigarettes are less expensive than beer and thus are more likely to be abused. There are more deaths that results from cigarettes consumption in comparison to beer consumption. There is a need for the government to raise the social welfare of the citizens by ensuring that it saves as many lives as possible. Saving of these life means discouraging their consumption; it is only achievable through marketing these products more expensive. This paper will determine their relationship and confirm whether the argument posed by the Washington University that discouraging cigarette could reduce beer consumption is true. The beer and wine markets are faced by reduced regulations compared to the cigarette markets. The number of alcohol consumers are lesser than those for cigarette consumers; this explains why there are more cigarette-related deaths compared to alcohol-related deaths. Beer and cigarettes have a complementarity in consumption (Moore, 2010); wines and cigarettes have no close relationship. It is with a high possibility to get a person who is taking beer to be smoking as well. People who are dependent on wine consumption belong to a higher class of life and thus they choose better living standards and thus its difficult for them to indulge in unhealthy behaviors such as cigarettes smoking (Ingraham, 2014). However, for the case of beer and cigarettes smoking the two goods are complements, thus, an increase in cigarettes tax to discourage its consumption also discourages the consumption of beer but at a lesser proportion that the reduction in cigarette smoking. Some people are not satisfie d with just the consumption of beer alone; they feel much better when they complement the beer with other substances as well (Moore, 2010); cigarette is the major choice of complement for beer consumption. Assuming that initially the demand for beer was equal to Q* and the price was P*, initial demand D*, the introduction of health warning on the cigarettes packaging will have the following impact on beer demand. The warning will make the cigarettes consumers to be more cautious and thus their demand for cigarettes will fall at every price level (White, Williams, Faulkner Wakefield, 2014). Since the change in the cigarettes demand results from a change in preference rather than price, the initial demand curve D* shifts leftwards to D1. There is a shift in demand curve for all non-price demand influencers (Chand, 2016). The quantity of beer demanded falls from Q* to Q1 as observed above. Thus the impact of health warning on cigarettes is to reduce the consumption of beer (Wigg Stafford, 2016). Quantity of Cigarettes The initial cigarettes demand was Q* when the price of beer was P*. The shortage of yeast will cause a reduction in the amount of beer produced since yeast is an input for beer production; supply shifts from S* to S1. When supply is low, the selling price rises (Ritenour, 2010). The new beer price will be P1 and will make beer less attractive. Since beer and cigarettes are complementary goods, the demand for cigarettes will also fall. There is a great addiction on cigarettes such that it is difficult for a smoker to spend a day without smoking a few cigarettes. Addictive smokers may prefer cigarettes over food or drinks. The cravings that they have for cigarettes cannot be satisfied by anything else apart from cigarettes. Non cigarette smokers may not be impacted by the presence of such a jail business their normal states will still be maintained at the initial position. New jailers are given only one choice when they arrive in this jail; they have to keep of the cigarettes. According to Dailymail.co.uk (2009), there has been a decline in all kind on crimes since most criminals are cigarette smokers and are frightened to face the tough consequences. Most people who avoid crimes are not fearing the presence of the non-smoking jail, what they fear is the smoking ban. This fear of smoking ban and the sub-sequential decline in crime rate explains the inelastic nature of cigarette demand to the changes in its prices. Even if price was raised to high levels, smokers will always smoke nearly the same quantity smoked before the prices went up. There will be a small decline in cigarette demand after the tax causing the prices to hike. packaging. Conclusion If alcohol and cigarettes are complement goods, then an increase in the cigarette prices will not result in an increment in alcohol consumption but rather a reduction. Beer and cigarettes are inelastic to price changes and thus no matter the price charged, there is still a greater demand by the consumers. This is because these products cause addiction to the users. Their inelastic nature is an advantage to the government as it can be able to raise higher revenues as it saves many lives. References Chand, S. (2016). Effect of Demand Curve on Substitute Goods and Complementary Goods. YourArticleLibrary.com. Retrieved 11 September 2017, from https://www.yourarticlelibrary.com/economics/effect-of-demand-curve-on-substitute-goods-and-complementary-goods-micro-economics/8914/. Dailymail.co.uk. (2009). Drop in crime on Isle of Man attributed to Europe's only non-smoking prison. Mail Online. Retrieved 11 September 2017, from https://www.dailymail.co.uk/news/article-1239209/Drop-crime-Isle-Man-attributed-Europes-non-smoking-prison.html. Ingraham, C. (2014). Want people to drink less? Make their cigarettes more expensive. Washington Post. Retrieved 11 September 2017, from https://www.washingtonpost.com/news/wonk/wp/2014/10/27/want-people-to-drink-less-make-their-cigarettes-more-expensive/?utm_term=.a22995e37523. Moore, S. (2010). Substitution and Complementarity in the Face of Alcohol-Specific Policy Interventions. Oup.com. Retrieved 11 September 2017, from https://academic.oup.com/alcalc/article/45/5/403/184976. Ritenour, S. (2010). Foundations of economics: A Christian view. Eugene, Or: Wipf Stock. White, V., Williams, T., Faulkner, A., Wakefield, M. (2014). Do larger graphic health warnings on standardized cigarette packs increase adolescents cognitive processing of consumer health information and beliefs about smoking-related harms? Bmj.com. Retrieved 11 September 2017, from https://tobaccocontrol.bmj.com/content/24/Suppl_2/ii50. Wigg, S., Stafford, L. (2016). Health Warnings on Alcoholic Beverages: Perceptions of the Healthcare Risks and Intentions towards Alcohol Consumption. Ncbi.nlm.nih.gov. Retrieved 11 September 2017, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4841515/.

Assessing in the Field of Marriage and Family Therapy

Introduction Assessment refers to the treatment process of identifying the signs and symptoms, which are associated with mental and emotional disorders. The disorders are then compared with the standardized disorders.Advertising We will write a custom essay sample on Assessing in the Field of Marriage and Family Therapy specifically for you for only $16.05 $11/page Learn More It should be noted that the treatment process should be based on the health condition of the patient because patients differ based on their coping abilities. The therapist develops a treatment plan after completing the process of diagnosis. The treatment plan helps in the process of alleviating the symptoms. Some instruments are utilized in the process of diagnosis and measuring the condition of the patient, including psychometric instruments (Barraca, Yarto, Olea, 2000). Family therapy is a process that uses systemic and relational theories in diagnosing and treating patients, inc luding couples, family members, and families in general. The Purpose of Assessment Family therapy entails identifying some of the factors that make it difficult for family members to coexist in unity and harmony. The process helps those in relationships in resolving issues that may lead to serious conflicts or divorce. It is noted that assessment helps in identifying those problems before they escalate into serious problems. Problems are resolved so easily once they are identified as opposed to leaving them until they bring about major problems in a family unit. The assessment process is of essence in relationships because it assists in nurturing change and development in families. Family psychoanalysis perceives family change in terms of the structures of relations among individuals.Advertising Looking for essay on psychology? Let's see if we can help you! Get your first paper with 15% OFF Learn More In psychological wellbeing, the interactions among family members ar e considered one of the critical factors. A number of schools of thoughts exist as regards to the importance of assessment in family therapy. However, all scholars and practitioners confirm that family members must be involved in finding the main problem affecting them. In this case, the origin of the problem does not matter, but what matters is the quality of solution and the process utilized in arriving at the solution. Assessment is the first step towards unraveling the problem affecting an individual or a family member. In other words, assessment is the basic stage that a therapist must consider before moving in to provide any help to a troubled individual or family member (Caldwell, Woolley, Caldwell, 2007). Through assessment, the family therapist can influence the outcome of the conversations in a consultative meeting between the troubled individual and the therapist. The assessment process has helped therapists understand that the family is not defined in narrower sense, bu t instead it should be understood in broader terms meaning that the family should be defined based on the roles and relationships of closely related individuals, which may even include friends. The assessment process in family therapy is of great importance as far as establishing formal interventions are concerned. Each culture had its own ways through which family members could be helped get out the problem, but they techniques were ineffective because they lacked assessment. The traditional therapies included performing some rituals with the help of the extended families. There was some development when societal leaders such as the chiefs and priests conducted family therapies. However, the problems could not be addressed amicably because there were no assessments conducted on the affected.Advertising We will write a custom essay sample on Assessing in the Field of Marriage and Family Therapy specifically for you for only $16.05 $11/page Learn More Th e emergence of child guidance and marriage counseling introduced the idea of assessment because individuals had to be cross-examined in a laboratory setting to outline the problems affecting them. Assessment process is very important because it gives a distinctive feature related to analytical framework meaning that it does not rely on the number of people present. Assessment without Judging The main role of family therapy professionals is to offer professional advice without interfering with the welfare of the families. This implies that they have to respect the rights of the clients and keep off from unnecessary judgments. For instance, they have to take caution when it comes to offering subjective verdicts. They have to be objective in whatever they do meaning that they have to avoid using a certain form of language that may sound discriminative or judgmental. In this regard, family and marriage psychoanalysts are warned to keep away from evaluating clients based on their races, age, cultural backgrounds, riches, physical statuses, healthiness, wellbeing, and faith. A therapist might be tempted to conclude that a certain condition is associated with a certain ethnic group or gender. This would be wrong because it may injure the client emotional, given the fact that family therapists deal with those who are already discriminated against. For a family and marriage therapist to offer quality services without offering his or her own insights, he or she must exercise restraint and observe professional codes of conducts.Advertising Looking for essay on psychology? Let's see if we can help you! Get your first paper with 15% OFF Learn More In particular, the therapist should refer the patient to the necessary department or therapist if he or she realizes that the situation can no longer be handled in his or her officer. This would prevent the therapist from offering defective or harmful advice to the client. If the client turns out to be stubborn or he or she is unwilling to disclose critical information needed for diagnosis, the therapist should simply terminate the conversation in a very professional manner instead of giving wrong advice. When handling clients, the family and marriage therapist is encouraged to follow the manual instead of using his or her own knowledge to diagnose a disorder. Some professionals might be tempted to serve their own interests instead of addressing the needs of the client. At this point, the therapist would be fulfilling his or her own interests, which amounts to subjectivity instead of striving to be objective. The therapist should always be mindful of the interests of the client if h e or she is to keep off from value judgment and promote objective assessment. Why Marriage and Family Therapists should be allowed to Diagnose Before addressing the consequences of any disorder or disease, it must be diagnosed for proper analysis and recommendation. Studies show that family therapy is an effective tool of addressing psychological problems such as depression, digestive disorders, chronic disorders, drug abuse, issues related to parenting, and issues that come about in relations. Family therapy is effective as compared to other traditional therapies because it involves all family members in resolving issues affecting them. Scholars in the field of mental health appreciate the role of family therapy meaning that they also endorse family and marriage therapists to conduct diagnosis. Some observe that there is no adequate literature in the field of family and marriage therapy, which prevents effective diagnosis. Moreover, misunderstanding the process of assessment and di agnosis among family therapists is another reason cited. However, family and marriage therapy may not utilize the diagnosis of other practitioners to arrive at critical conclusions because it family therapy involves understanding human behavior. Human behavior is subject to change meaning that diagnosis should b conducted at the time of therapy. Relying on diagnosis from other places may mislead the expert because the patient could have gone through many experiences since the time he or she was diagnosed to the time of therapy. In the American society, the role played by marriage and family therapists is not yet recognized, even though there is a consensus that their presence is highly valued. In fact, the training offered to family and marriage therapists is very high as compared to that offered to other mental therapists, including social workers and counselors. To worsen the matter, the law does not permit family and marriage therapists to charge clients meaning that they offer t heir services on mutual basis. This is unacceptable because those trained in the field lack employment since the profession does not fetch any substantial funds. It is therefore recommended that marriage and family therapists should be allowed to exercise their profession just the way others are doing in the market. They should be allowed to offer professional services, including diagnosing the problems facing individuals in marriages and families. The family is the most basic unit of social organization meaning that its failure would imply the failure of the whole society. Philosophical Challenges in Marriage and Family Diagnosis One of the challenges is that there is no data related to marriage and family therapy, which means that there is no existing body of knowledge as regards to the processes of diagnosis in the field. This is a major problem among scholars because it is claimed in the philosophy that knowledge is cumulative implying that the problem must have existed for year s for it to be accepted. In other words, the marriage and family therapy diagnosis does not have clear theories and methodologies. Others claim that marriage and family therapy simply relies on subjective knowledge, which cannot be depended upon to sustain a discourse. There is no established method or technique used in treating similar problems in the family and marriage therapy. DSM is not systematic meaning that it cannot be relied upon to offer a comprehensive solution to relational disorders. A method must be consistent for it to be considered scientific. Family and marriage therapy methods are not systematic because they offer different results whenever they are applied to understand a similar problem. Each case is different because human behavior is highly unpredictable (Kreppner, 2005). Human behavior is influenced by very many variables, including culture, individual orientation to the world, gender, role, place, and education. For instance, an educated sick individual coul d be suffering from a similar disorder as an uneducated individual. Their behavior would not be similar, given their differences in the level of education. The methods applied in diagnosing their problems would not be the same, even though their conditions are similar. Impacts of Diagnosis on Marriage and Family Therapist Allowing marriage and family therapists to diagnose a disorder would be one way of empowering them since it would give them an advantage over other practitioners. They would be in a position to deal with various problems affecting those in relationships and family members. Diagnosing a problem is critical to understanding the best technique to be applied in treatment. Relying on others for diagnosis might give wrong results because the diagnosis could have been conducted wrongly. If marriage and family therapists diagnoses disorders, they will come up with a patterned and structured technique that would be consistent in addressing similar disorders. References Barr aca, J., Yarto, L., Olea, J. (2000). Psychometric properties of a new family life satisfaction scale. European Journal of Psychological Assessment, 16(2), 98–100. Caldwell, B., Woolley, S., Caldwell, C. (2007). Preliminary estimates of cost-effectiveness for marital therapy. Journal of Marital and Family Therapy, 33(3), 392–406. Kreppner, K. (2005). Family assessment and methodological issues: Discussion. European Journal of Psychological Assessment, 21(4), 249–254. This essay on Assessing in the Field of Marriage and Family Therapy was written and submitted by user Charity Beasley to help you with your own studies. You are free to use it for research and reference purposes in order to write your own paper; however, you must cite it accordingly. You can donate your paper here.

Ranking and Social Inequality

Ranking and Social Inequality Ranking is a characteristic of complex societies in which different persons within a society have different quantities or qualities of power, rights and responsibilities. As societies grow in complexity, different tasks are assigned to specific people, called craft specialization. Sometimes specialization leads to status changes. The study of ranking and social inequality in archaeology is based on the anthropological and economic studies of Elman Service (Primitive Social Organization, 1962) and Morton Fried (Evolution of Political Societies, 1967). Service and Fried argued that there are two ways in which ranking of people in a society is arrived at: achieved and ascribed status. Achieved status results from being a warrior, artisan, shaman, or other useful profession or talent. and ascribed status (inherited from a parent or other relative). Ascribed status is based on kinship, which as a form of social organization ties the status of an individual within a group to descent, such as dynastic kings or hereditary rulers. Ranking and Archaeology In egalitarian societies, goods and services are spread relatively evenly among the population. High-ranking individuals in a community can be identified archaeologically by studying human burials, where differences in grave contents, the health of an individual or his or her diet can be examined. Ranking can also be established by the difference sizes of houses, the locations within a community, or the distribution of luxury or status items within a community. Sources for Ranking This glossary entry is a part of the About.com Guide to the Characteristics of Ancient Civilizations, and part of the Dictionary of Archaeology. A fairly brief bibliography of ranking and social stratification has been collected for this entry.

Managing Knowledge Essay Example | Topics and Well Written Essays - 2500 words

Managing Knowledge - Essay Example Knowledge is passive, analytic and atomistic (Thomas, Kellogg & Erickson, 2001). This does not imply that knowledge is power, rather applied knowledge is power. To apply knowledge, to use the abundance of information that is available in any organization today, codification of knowledge is essential. Codification of knowledge into information implies making knowledge portable, re-usable and transferable within the organization (Hall, 2006). Only when this is possible can knowledge become power. Organizational knowledge can then be used to gain competitive edge over the rivals but the organization should know how to use that power. Technological advancements have made it possible to retain knowledge and transmit it to the persons concerned within the organization. Knowledge can be a powerful weapon when retained, transmitted, disseminated and applied. It is thus important to understand the implications and the ways of retaining and applying knowledge. Knowledge has been classified into two categories - tacit and explicit. Explicit knowledge is that which has been previously defined and codified. It is usually gained through formal education, training, books and now the internet. Explicit knowledge is static and does not have the capacity to renew itself (Ehin, 2008). It requires an outside entity to keep it current. Tacit knowledge on the other hand is acquired by interacting with others and is connected to life's experiences. Tacit knowledge is the basis for generation of new knowledge or "the key to knowledge creation lies in the mobilization and conversion of tacit knowledge" (Nonaka cited by Marwick, 2001). The individual tacit knowledge characterizes the human capital of an organization. Human capital is the combination of genetic inheritance, education, experience and attitude towards life and business (Bontis & Fitz-enz, 2002). Human capital is the source of innovation and strategy. Sustained competitive advantage can accr ue from a pool of human capital. Human capital adds value and is not substitutable. An organization is not a passive repository of knowledge. The tacit knowledge in the form of organization culture may interact with the explicit knowledge of the individual. The core competencies of an organization incorporate both tacit and explicit knowledge and should be conceived as a mix of skills and technologies (Lindgren & Wallstrom, 2000). These interactions and combinations result in new knowledge as organizational learning or innovation. This knowledge has to be efficiently managed so as to derive competitive advantage. Managing knowledge Managing knowledge or knowledge management (KM) is nothing more than getting the right information to the right people at the right time. It is also known by other terms like organizational learning, organizational memory and expertise management. Most organizations may not even be aware of the knowledge they have, let alone knowing how to manage knowledge. They may under estimate the value and creation of knowledge; they may even unknowingly give away what they possess (Earl & Scott, 2001). They may defer the sharing of knowledge or under invest in the utilization of the knowledge. As organizations started recognizing these facts, they created the post of a Chief Knowledge Officer (CKO), whose popularity and demand has increased in the recent

Dietary Intake, Gender and Activity Factors Influenced on BMI Essay

Dietary Intake, Gender and Activity Factors Influenced on BMI - Essay Example Nevertheless, overweight is most importantly attributable to excess intake of energy, which lead to not only a positive energy balance but also an accumulation of body fats (Moore, 2000). Also, a sedentary lifestyle is the other factors that can contribute to a gain in weight. BMI is a reliable and easily obtainable indicator of relative body size. At most times, BMI is directly associated with LDL and total cholesterol plasma concentrations. However, an inverse relationship has been reported between BMI and HDL-cholesterol (McNamara et al. 1992). On the other hand, the effect of gender on the association between blood lipid constraint and BMI has not been evidently recognized because most of the studies that have been conducted in this area are hardly consistent. Participating in physical activities is commonly used as a valuable way of preventing a number of health risks that are especially caused by heavyweight across all genders (Eaton and Eaton, 2003). There are a number of reports that have indicated that youth and children spend most of their leisure time in sedentary engagements such as playing video games or watching television (Moore, 2000). Mounting evidence reveals that sedentary behaviors, which are characterized by lack of physical activities, are attributed to increased risk of physical problems Sedentary behaviors have been proved to, be associated with physical activities, eating habits, and obesity when correlation designs are used (Gortmaker et al., 1996). Although these designs are valuable in determining associations between variables, experimental designs that entail the manipulation of sedentary behaviors are important in determining the causal impact of sedentary habits on energy consumption (Robinson, 1999).  

Measuring Concentration of Natural Gas in Air

Measuring Concentration of Natural Gas in Air Valentin Haemmerli Measuring concentration of natural gas in air using a catalytic bead sensor and a Wheatstone bridge circuit Abstract. A vacuum system and a catalytic bead combustible gas sensor were used to calibrate and test an apparatus for measuring the concentration of natural gas in air. Total concentrations ranged between 0%-5% and total pressure from 0.5 bar to 1.5 bar. A Wheatstone bridge circuit was used to measure the output voltage of the sensors and relate this to concentration over the range of pressures. The linear relationship between reaction rate (given by initial rate of change of output voltage) and concentration was most strongly observed at pressures of 1 bar and above. The constant of proportionality for the equation (1) was found to be 8.7  ±0.4 10-4 Vs-1 per % methane for a total system pressure of 1 bar. The relationship broke down for pressures significantly below 1 bar, indicating that the sensors are not reliable in this range. Introduction Catalytic bead sensors, also known as pellistors [1], are used in a wide range of applications in industry to monitor levels of combustible gases. One such combustible gas is the mixture consisting mainly of methane referred to as natural gas. The catalytic bead sensors can be used to monitor the concentration of natural gas in production facilities, coal mines and industrial processes. This is important because if the concentration of natural gas in air exceeds 5% it becomes explosive [2]. It is especially important to monitor methane concentration because it is usually colourless and odourless [3], making it very difficult to detect without sensors. An apparatus to measure concentration of natural gas in air can be used to trigger an alarm when there is a concentration greater than the Lower Explosive Limit (LEL), given as a percentage. At this concentration the mixture of gas and air becomes explosive. The apparatus may need to be applied for different pressure environments, not only atmospheric pressure, for example in applications with chemical processes requiring lower or higher pressures. The apparatus has therefore been tested for a range of pressures from 0.5 -1.5 bar. Theory Sensors The sensors used are catalytic bead sensors. One sensor is made up of two elements, one sensitive and one non-sensitive. The sensors work by catalysing the oxidation reaction of combustible hydrocarbons in the sensitive element which consists of a platinum wire coated in a compound which facilitates the oxidation reaction and also contains the catalyst for this reaction. The non-sensitive element is identical in most regards, but crucially is missing the oxidizing chemical or has had it poisoned, depending on the specific sensor design used. Poisoning means that the catalyst has been reacted with another chemical to make it inert. The non-sensitive element does not react with combustible gases. The elements are supplied with 3V, and heated up to 400-500ËÅ ¡C to speed up the reaction. When the oxidation reaction of combustible gases occurs on the sensitive element, the heat of reaction increases the temperature of the element, which changes the resistance in the platinum wire. Th e non-sensitive element acts as a control for ambient temperature, meaning that in the absence of any combustible gas, the two elements will output exactly the same voltage. This is very useful as it means that change in temperature due to external factors is controlled and the difference in output between the sensitive and non-sensitive elements can be measured using a Wheatstone bridge circuit as described below. This design means that these sensors detect a multitude of different combustible gases and are therefore not useful for distinguishing between them, meaning they are nonspecific [4]. However, they are very useful for situations where monitoring combustibility is of importance, and they can be applied readily to the task of measuring concentration as they are accurate and have a fast response time. The sensors used are sensitive, with a measurement range of 0-100% of the LEL. This corresponds to 0-5% concentration of methane. One downside of these sensors is that they cannot operate in a vacuum as they rely on combustion, which usually requires at least 15% oxygen [4]. They are also at risk of poisoning since they rely on a coat of catalyst and the presence of certain chemicals can result in a reaction with this catalyst, meaning the sensitive element would no longer facilitate the oxidation reaction and the difference in output between the elements would always be zero. Wheatstone Bridge Circuit Jeong-Yeol Yoon states that â€Å"A Wheatstone bridge is an electrical circuit used to measure a very small change in resistance† [5]. A circuit as shown in Figure 1 can be used to measure the output from the sensors, where a small resistance change is expected as a result of the sensitive element heating up due to the presence and reaction of combustible gases. A voltage is supplied at the top and bottom of the diamond of resistors, and the voltage across the middle, between V1 and V2 is measured. The right leg of the bridge should have a large resistance compared to the other leg so that a small change can be detected. The variable resistor allows one to slightly vary the resistance on one leg and so balance the bridge before measurements, zeroing the output. Experimental Method The first step was to test how sensor output related to concentration for a total pressure of 1bar (atmospheric). Care was taken to ensure that all joints and seals of the vacuum system were tight and that all valves were firmly closed. The vacuum system used to prepare test mixtures is shown in Figure 2. P1 and P2, the pressure sensors shown in the figure, were used to measure concentration of natural gas and air. P1 had a range of 3 bar, with the zero set to atmospheric pressure (1bar), and vacuum (0bar) set to -1. This was not very precise, with an uncertainty of  ±0.1bar and was used to fill up the system with compressed air and the pressure shown by this corresponded to total pressure. P2 was a more precise pressure sensor, ranging from 0 to 50 mbar with uncertainty  ±0.5mbar. It was used to carefully add the correct proportion of natural gas to the vacuum, before topping up with compressed air. Using this vacuum system, concentrations ranging from 0-5% natural gas were prepared. Figure 2 also shows the position of the pellistor sensor’s two elements and the connection to the Wheatstone bridge circuit. The output of this circuit was connected to a ÃŽ ¼V meter which was connected to a computer for dat a logging. This had a range of -30.00 to 30.00mV with uncertainty  ±0.01mV. Data logging was carried out for 5 minutes and 30s for concentrations of 1%, 2%, 3%, 4% and 5% at a total pressure of 1 bar. Errors were reduced by zeroing the Wheatstone bridge output using the variable resistor between measurements. This was done to reduce the effect of a natural drift in the output due to very slightly varying conditions in the lab such as temperature and the resistance in the circuit, as well as mechanical vibrations. The bridge circuit supply voltage was kept at a constant 3.00V. Care was taken to leave little time between sealing the system under vacuum and filling with natural gas and air as the seals were not perfect and pressure rose slowly, but noticeably if the system was left at vacuum for an extended period. This procedure was then repeated for a suitable range of concentrations at total pressures of 0.5, 0.75, 1.25, and 1.5 bar. The same considerations were made for reducing error as above. One thing to note is that at total pressures of less than atmospheric there was always a slight influx of outside air, due to the imperfect seals, however the effect of this was negligible. Experimental Results To find a correlation between the concentration of methane and the bridge output voltage we took the gradient of the initial increasing linear section of the raw data. Figure 3 below shows this for the case with concentration 5% of methane with a total pressure of 1 bar. As can be seen, the measured data falls away as reactant, the natural gas, is used up in the reaction. Figure 3 also shows that there is a very sharp spike as the output voltage varied greatly when the sensor was first switched on. This illustrates that care was needed when selecting which section of the curve to use to calculate the gradient. This is the right method to use to find concentration because, according to Hammett, â€Å"the rate of any chemical reaction is proportional to the product of the concentrations of the substances actually involved in the reaction.† [7] and the gradient of Figure 3 is a rate of reaction. The next step was to establish the gradients, or initial reaction rates, of 1%, 2%, 3%, and 4% methane mixtures. These are shown in Figure 4, along with 5%, for a total pressure of 1 bar. Figure 5 shows these gradients again, but all in order and passing through the origin to better show the steady increase in gradient. Figure 6 shows processed data for 1 bar total pressure. The gradients of the lines from Figures 4 and 5 are plotted against their concentration. This allows us to find a constant linking the raw data to the concentration for this pressure. Table 1 goes on to show the values of this constant for the other pressures analysed. The raw data for these is not shown here, but the process and data is similar to that for 1 bar. Figure 7 shows the relation between the pressure and the concentration. Also included are a second order polynomial and a linear trend line (fitted by least squares). Vertical error bars are from standard error in Table 1 and horizontal error bars from  ±0.1bar uncertainty in total pressure. Discussion Figure 6 shows the gradients of the lines in Figures 4 and 5, meaning the rates of reactions at different concentrations, plotted against the concentration of methane. This gives us a relationship between concentration and the initial rate of reaction, the quantity derived from the raw data, for a specific total pressure. For 1 bar this was 8.7 ±0.4 10-4 Vs-1 per % methane. The error in this comes from a combination of the uncertainty in the pressure measurement leading to uncertainty in concentration corresponding to  ±0.1% in the worst case and a small random error in the output voltage of the bridge circuit corresponding to  ±2Ãâ€"10-4V. Figure 7 includes both a polynomial fit and a linear fit. It is unclear if the relationship remains linear or takes some other form at low pressure. The polynomial is almost linear for the three higher pressures, which indicates a strong relationship between pressure and reaction rate for higher pressures. The values and their associated errors in Table 1 come from each plot of initial reaction rate (rate of change of voltage) against concentration for the different pressures. The error is the standard error for these plots. There was a breakdown of the relationship at low pressures. Data for 0.5 bar total pressure was not included in the results because no clear relationship between output and concentration was found. This indicates that the sensors are not suitable for low pressures, especially when coupled with low concentrations. This resulted in very little output from the sensors, making it difficult to reliably determine an initial reaction rate, which is vital for obtaining a relationship between the raw data and the concentration. The reason for this lack of output was that not enough natural gas particles were interacting with the sensitive element to cause it to heat up and also due to a lower oxygen concentration also slowing down the reaction. This is not a problem in the commercial applications of these types of sensors as they are typically used to detect high concentrations of combustible gases at atmospheric pressure. This does highlight a weakness in the apparatus when used for finding unknown concentrations, however. Another weakness was the inability to measure large pressures precisely, leading to large errors in the total pressure measurements. This has an increased effect on low pressures, which is a further reason for the less reliable data. Empirical Relationship If we give the initial rate of reaction a constant,, and a function of pressure, , then (2) where is the concentration of methane, is determined experimentally from the sensor data and is the polynomial relationship from Figure 7, (3) with the appropriate total pressure, found experimentally from the pressure sensors on the vacuum system, substituted. Using this equation it is possible to use the sensors to determine the concentration of an unknown mixture. Conclusions The aim was to build an apparatus capable of determining the concentration of natural gas in air up to 5%. In order to do this it was necessary to first establish the relationship between sensor output and concentration. This was then repeated at different pressures to understand the effect of a different pressure on the relationship between sensor output and concentration. Finally it was possible to use these relationships to determine the concentration of an unknown mixture of gas and air. The constant of proportionality for 1 bar pressure was found to be 8.7 ±0.4 10-4 Vs-1 per % methane. For 0.75 bar it was found to be 6.5 ±1.6 10-4 Vs-1 per % methane, 1.25 bar was 16.2 ±0.8 10-4 Vs-1 per % methane, and 1.5 bar was 25.3 ±1.9 10-4 Vs-1 per % methane. No correlation was found between sensor output and concentration for 0.5 bar. Appendix Division of labour among group members: Giuseppe Guarino –main tasks were constructing bridge circuit on protoboard and constructing and soldering strip board circuit which was finally used in data collection David Griggs –main tasks were configuring CassyLab software and importing raw data into Microsoft Excel Valentin Haemmerli –main tasks were preparing mixtures of natural gas and compressed air in vacuum system and researching sensor operation guidelines Shared responsibilities –everyone shared the tasks of checking the circuit, building the vacuum system apparatus and preliminary data analysis. References [1]Operating Combustible Gas Sensors, ed: Sixth Sense (sensor manufacturer). [2]Material Safety Data Sheet: Methane, ed: Air Products, 1999. [3]J. G. Speight, CHAPTER 1: History and Uses, in Natural Gas: A Basic Handbook, ed: Euromoney Institutional Investor PLC / Gulf Publishing Company, 2007, pp. 1-33. [4]L. T. White, 4 Hazardous Gas Monitoring Sensors, in Hazardous Gas Monitoring (Fifth Edition), L. T. White, Ed., ed Norwich, NY: William Andrew Publishing, 2001, pp. 81-116. [5]J.-Y. Yoon, Wheatstone Bridge, in Introduction to Biosensors, ed: Springer New York, 2013, pp. 75-86. [6]Catalytic Elements CAT16, ed: Sixth Sense (sensor manufacturer). [7]L. P. Hammett, Physical organic chemistry reaction rates, equilibria, and mechanisms. New York; St. Louis; San Francisco [etc.]: McGraw-Hill, 1970.