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Introduction :-
Concentration of solar radiation is achieved using a reflecting arrangements of mirrors or glass and a refracting arrangements of lenses. The optical system directs the solar radiation on to an absorber of smaller area. The smaller area is surrounded by a transparent cover. Because of the optical system, some losses are introduced. It include reflection or absorption losses in the mirrors or lenses and some losses are caused due to geometrical imperfections in the optical system. The optical losses is compensated by the flux incident on a smaller area of the absorber surface by concentrating. Thermal loss terms not like a flat-plate collector and the collection efficiency is usually higher. Some of the features of a flat plate collector are simple in design and easy for maintenance but not same for concentrating collector. In the presence of the optical system concentrator usually has to track the sun so the beam radiation is concentrate on to the absorber surface. For gaining a high degree of concentration, it’s necessary to maintain continuous adjustments of the collector orientation. In tracking system there are some complexity in design so it’s maintenance requirements are also increased. In the last few years there are many significant advances have been made in the development of concentrating collectors.

Solar concentrator :-
Solar concentrator is a device that allows the collection of sunlight from a large area and focusing its on a small area. A conceptual representation of a solar concentrator used to harnessing the power from the sun to generate heat for application purpose.
Solar concentrators are made of number of flat shaped mirror, glass or reflective films which are mounted on a structural frame. They are moves to north-south axis parallel to earth’s axis to track the sun’s movement. The axis of rotation passes through the center of gravity of the reflectors and that’s how reflectors always manage its gravitational equilibrium. The frame also performs change in inclination angle , while staying in front of sun in order to obtain sharp focal point. Receiver is fixed at the focal point . receiver captures the concentrated heat and transfers to the object according to it’s application .

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Classification of solar concentrator :-
Imaging concentrator:-
Imaging concentrators reflects the light from the mirror on to a receiver to produce the optical image means to concentrate. They are mainly used for achieving the highest temperature. It enable a very large aperture area into a small absorber area, effectively reducing thermal losses at high temperature. Sun rays tracing is used to evaluate concentrator during the design process.
Line focus type ( one axis tracking ) :-
Concentrator with one axis tracking are used to achieve moderate concentration.
1. Cylindrical parabolic concentrator :-
It is a very common optical imaging instrument which is used as a solar concentrator.it is rotated about one axis to track the sun’s motion. Here at focal plane metal tube receiver is used. The absdorer tube carries the heat and transfer top the fluid. Mostly mild steel or copper is used to make absorber and it is coated with the black paint. Anodised aluminium sheet, aluminized mylar or curved silvered glass are used to make the reflector.
2. Fixed mirror solar concentrator :-
This type of concentrator are having a fixed mirror which is associated with a tracking receiver system. The mirrors are made from long, narrow, flat strips of mirror. These mirrors are arranged on a circular cylinder of the radius.the focal line can be easily tracked by the movable receiver pipe which is made to rotate about the center curvature of the reflector module.
3. Linear Fresnel lens concentrator :-
Fresnel lens are similar to the conventional lens , which is refracting the rays and focusing them at on focal point. Generally there are two sections in the concentrator ; a flat upper surface and a back surface that employs canted facets. The facet is an nearly to the curvature of a lens. This concentrator is able to separate the direct and diffuse light. It is thinner than the conventional lens. Plastic and glass both are used as refracting material. For fabricating the Fresnel lens, glass is seldom used because it is difficult to mold and has large surface tension.
Point focus type ( two axis tracking ) :-
1. Hemispherical bowl mirror concentrator :-
Fixed hemispherical mirror, a tracking linear absorber and a supportive structure are the main components of this concentrator. The hemisphere produces aberrated optical image. Because of its symmetry all rays entering in to the hemisphere after reflection cross the paraxial line at some point between the focus and mirror surface. An absorber pivoted about the center of the curvature of the hemisphere. Because of spherical aberration this type of concentrator gives a lesser concentration.
2. Circular Fresnel lens concentrator :-
These type of lenses are usually not used in solar energy application due to cost and weight. These are used where high temperature is required. The circular fresenel lens provided very high concentration. Fresnel lenses are made from the glass and plastic.
3. Parabolic dish collector :-
The two dimensional design of a parabolic concentrator is equal to a parabola . it is used as a reflecting solar concentrator. A distinct property of that it can focus all the parallel rays from the sun to a single focus point . it is not necessary to use the full part of the parabola curve to construct the concentrator. It’s requires larger field of view and need a good tracking system. this concentrator provides a higher concentration.
4. Central tower receiver :-
The system consists of a central stationary receiver in which the solar radiation is reflected by heliostats. A heliostat is composed of a large erray of mirrors fixed to a supporting frame. This frame move as sun is move. The heliostats are installed in the open space. They focus solar radiation on a central receiver, which is fixed at some height. The receiver must be able to interrupt the focused radiation, adsorb this heat and transfer to the working fluid with minimum heat loss.

Scheffler dish :-
It is a point focus type of concentrator. The basic concept to the development of the scheffler reflector was to solar cooking as comfortable as possible. The reflector is a small lateral section of a large paraboloid. The inclined cut of the large paraboloid produces the typical elliptical shape of scheffler reflector. The axis of daily rotation is located exactly in north-south direction which is parallel to the earth axis and runs through the center of gravity of the reflector.
That way the reflector always maintains it’s gravitational equilibrium. The mechanical tracking device doesn’t require to be driven by much force to rotate it with the sun. The focus is located on the axis of rotation to prevent it from moving when the reflector is moving. The distance between focus and center of the parabolic reflector depends on the selected parabola. During the day the concentrated light will only rotate around its own center but not move in any direction. So the focus stays fixed, which is very useful, it means the cooking pot doesn’t have to moved either.
The paraboloid has to perform the change of inclination in order to stay directed at the sun. So the it’s possible to obtain a Sharp for point. It is possible by shaping the reflector after an other parabola for different seasonal inclination angle of the sun. For changing the inclination angle mirror support structure and dish stand is used. The efficiency for the cooking depends on the cleanliness of the reflector surface and the state of insulation of the cooking pot. It’s optical efficiency is up to 75%. On an average a 8m^2 reflector can bring 22 litres of cold water to boiling temperature within one hour after consuming the 700W/m^2 direct solar radiation. At the focal point backing oven, steam generator or heat storage can be installed.
Scheffler dish are build in varieties of 2.7m^2, 8m^2, 10m^2 and 12m^2. The standard size of the scheffler dish is 8m^2.

Applications :-
1. Bolier feed water preheating
2. Washing in laundries
3. Oil heating for cooking or industrial applications
4. Milk pasteurization
5. Cooking
6. Generating steam
Advantages :-
1. No any type of pollution.
2. Renewable source of energy.
3. Saves wood, electricity and other fuels.
4. Adaption to changing season.
5. Highly durable.
Disadvantages :-
1. initial cost is high.
2. Requires maintaince.
3. Replacement of parts are not easily available.
4. Not locally available.

Components :-
1. Collector:-
The collector of scheffler dish’s shape is paraboloid. All the assembly of flat shaped glass, mirrors or reflective films are arranged on a structural steel framework. The frame is mirrors support structure . it consists of bars and angles sections to form a shape of parabola. The mirrors are arranged to give paraboloidal shape and reflect the solar radiation on to focusing point or receiver.
2. Receiver :-
The receiver of scheffler dish is placed at the focusing point of the dish. it captures the solar radiation and transfer it to the thermal medium used in the system. Mostly this component is spherical dome type absorber fixed on the structural steel frame. The receiver works on thermo siphon principle. The receiver’s size is depends on the size of the focus and storage requirement. The receiver are designed according to its application of the user.
3. Dish stand :-
The basic framework of the dish stand is rectangular/triangular conical shape steel structure. The framework is made of pipes and angles. This structure is designed to withstand wind speed in operating conditions as well as rotates as sun’s movement.the rotary support, counter weight and other equipments are attached on the stand.
4. Tracking system :-
Tracking system enables the dish to focused towards the sun to capture maximum direct radiation during the day. It also tracks the sun as it change its position during the year. In tracking system many equipments are arranged like electric motor, gear box, sprockets and chains, counter weight with rope, screw shaft, solar radiation sensor, wind sensor and timer.

Working of scheffler dish system :-
The scheffler dish system works on the different principles :-
1. The reflective dish turns about North-south axis parallel to earth’s axis. It track the sun’s movement from morning (East) to evening (West) and maintaining gravitational equilibrium of the dish.
2. The parabolic reflector also performs changes in inclination angle while staying in fornt to the sun, in order to maintain a sharp focal point.
3. The Focus lies on to the axis of rotation. It remains at a fixed position, where concentrated heat is capture and it is received by the receiver.
4. The receiver pass the heat to the thermal medium of the system.

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INTRODUCTION: EPIDEMIOLOGY OF HIV INFECTION AND AIDS WORLDWIDE

HIV infection/AIDS is a global pandemic, with cases reported from virtually every country. At the end of 2013, an estimated 35.0 million individuals were living with HIV infection, according to the Joint United Nations Programme on HIV/AIDS (UNAIDS). An estimated 95% of people living with HIV/AIDS reside in low- and middle-income countries; ~50% are female, and 3.2 million are children 1%. However, the populations of many Asian nations are so large (especially India and China) that even low infection and seroprevalence rates result in large numbers of people living with HIV. Although Asia’s epidemic has been concentrated for some time among specific populations—sex workers and their clients, men who have sex with men, and IDUs—it is expanding to the heterosexual partners of those most at risk.
The epidemic is expanding in Eastern Europe and Central Asia, where ~1.1 million people were living with HIV at the end of 2013. The Russian Federation and Ukraine account for the majority of HIV cases in the region. Driven initially by injection drug use and increasingly by heterosexual transmission, the number of new infections in this region has increased dramatically over the past decade (WHO, 2014).
Approximately 1.9 million people are living with HIV/AIDS in Central and South America and the Caribbean. Brazil is home to the largest number of HIV-infected people in the region. However, the epidemic has been slowed in that country due to successful treatment and prevention efforts. Men who have sex with men account for the largest proportion of HIV infections in Central and South America. The Caribbean region has the highest regional adult seroprevalence rate after Africa. Heterosexual transmission, often tied to sex work, is the main driver of transmission in the region.
Approximately 2.3 million people are living with HIV/AIDS in North America and western and central Europe. The number of new infections among men who have sex with men has increased over the past decade in these mostly high-income areas, while rates of new infections among heterosexuals have stabilized and infections among women and IDUs have fallen (WHO, 2014).

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PATHOPHYSIOLOGY AND PATHOGENESIS

The hallmark of HIV disease is a profound immunodeficiency resulting primarily from a progressive quantitative and qualitative deficiency of the subset of T lymphocytes referred to as helper T cells occurring in a setting of polyclonal immune activation. The helper subset of T cells is defined phenotypically by the presence on its surface of the CD4 molecule, which serves as the primary cellular receptor for HIV. A co-receptor must also be present together with CD4 for efficient binding, fusion, and entry of HIV-1 into its target cells. HIV uses two major co-receptors, CCR5 and CXCR4, for fusion and entry; these co-receptors are also the primary receptors for certain chemoattractive cytokines termed chemokines and belong to the seven-transmembrane-domain G protein–coupled family of receptors. A number of mechanisms responsible for cellular depletion and/or immune dysfunction of CD4+ T cells have been demonstrated in vitro; these include direct infection and destruction of these cells by HIV, as well as indirect effects such as immune clearance of infected cells, cell death associated with aberrant immune activation, and immune exhaustion due to aberrant cellular activation with resulting cellular dysfunction. Patients with CD4+ T cell levels below certain thresholds are at high risk of developing a variety of opportunistic diseases, particularly the infections and neoplasms that are AIDS-defining illnesses. Some features of AIDS, such as Kaposi’s sarcoma and certain neurologic abnormalities, cannot be explained completely by the immunodeficiency caused by HIV infection, since these complications may occur prior to the development of severe immunologic impairment.
The combination of viral pathogenic and immunopathogenic events that occurs during the course of HIV disease from the moment of initial (primary) infection through the development of advanced stage disease is complex and varied. It is important to appreciate that the pathogenic mechanisms of HIV disease are multifactorial and multiphasic and are different at different stages of the disease. Therefore, it is essential to consider the typical clinical course of an untreated HIV infected individual in order to more fully appreciate these pathogenic events.

In order to conduct sound comparison, I have selected the United States of America from developed countries and Ethiopia from developing countries. Below I have tried to elaborate the two countries national HIV prevention, treatment and care policy and strategy.
HIV INFECTION AND AIDS IN THE UNITED STATES OF AMERICA

About 1.7 million people have been infected with HIV in the United States since the beginning of the epidemic, of whom >630,000 have died. Approximately 1.1 million individuals in the United States are living with HIV infection, ~16–18% of whom are unaware of their infection, according to recent estimates. Only a fraction of HIV-infected people are able to negotiate the steps in the HIV “care continuum,” from diagnosis, to entering into and staying in care, to receiving antiretroviral therapy, and ultimately to achieving a suppressed viral load.More than 60% of those living with HIV/AIDS are Black/African American or Hispanic/Latino, and more than half are men who have sex with men. The estimated HIV seroprevalence rate among
all individuals age 13 years or older in the United States is ~0.5%. Approximately 2% of Black/African-American adults are HIV-infected in the United States, higher than any other group.

The number of new HIV infections in the United States, HIV incidence, peaked at about 130,000 per year in the late 1980s, followed by declines. For more than a decade, HIV incidence has remained stable at approximately 50,000 per year, with the proportion of new infections increasing in recent years among men who have sex with men and falling among women and IDUs. Among adults and adolescents newly diagnosed with HIV infection in 2011 (regardless of stage of infection), ~79% were males and ~21% were women. Of new HIV diagnoses among men, ~79% were attributed to male-to-male sexual contact, ~12% to heterosexual contact, ~6% to injection drug use, and ~4% to a combination of male-to-male sexual contact and injection drug use. Of new HIV diagnoses among women, ~86% were due to heterosexual contact and ~14% to injection drug use. Perinatal HIV transmission, from an HIV-infected mother to her baby, has declined significantly in the United States, largely due to the implementation of guidelines for the universal counseling and voluntary HIV testing of pregnant women and the use of antiretroviral therapy for pregnant women and newborn infants to prevent infection. In 2011, fewer than 200 children were diagnosed with HIV infection in the United States.

HIV infection and AIDS have disproportionately affected minority populations in the United States. Among those diagnosed with HIV (regardless of stage of infection) in 2011, 47% percent were Blacks/African Americans, a group that constitutes only 12% of the U.S. population. The estimated rate of new HIV diagnoses in 2011 by race/ethnicity per 100,000 population in the United States.

The number of individuals diagnosed with AIDS and deaths among persons with AIDS in the United States rose steadily through the 1980s; AIDS cases peaked in 1993 and deaths in 1995.
Since then, the annual numbers of AIDS-related deaths in the United States have fallen ~70%. This trend is due to several factors, including improved prophylaxis and treatment of opportunistic infections, growing experience among the health professions in caring for HIV infected individuals, improved access to health care, and a decrease in new infections due to saturational effects and prevention efforts However, the most influential factor clearly has been 1227 the increased use of potent antiretroviral drugs, generally administered in a combination of three or four agents.

Although the HIV/AIDS epidemic on the whole is plateauing in the United States, it is spreading rapidly among certain populations, stabilizing in others, and decreasing in others. Similar to other STIs, HIV infection will not spread homogeneously throughout the population of the United States. However, it is clear that anyone who practices high-risk behavior is at risk for HIV infection. In addition, recent increases in infections and AIDS cases among young men who
have sex with men as well as the spread in pockets of poverty in both urban and rural regions (particularly among underserved minority populations in the southern United States with inadequate access to health care) testify that the epidemic of HIV infection in the United States remains a public health problem of major proportion (Harrison 19th ed,2015).

HIV/AIDS POLICY AND PROGRAMS OF UNITED STATES OF AMERICA

In June 2001, at the United Nations General Assembly Special Session on HIV/AIDS (UNGASS), 189 national governments, including the United States, adopted the Declaration of Commitment on HIV/AIDS. The document commits governments to improve responses to their domestic AIDS epidemics and sets targets for AIDS-related financing, policy, and programming.
The Declaration also stipulates that governments conduct periodic reviews to assess progress on realizing their UNGASS commitments. In recognition of the crucial role civil society plays in the response to HIV/AIDS, the Declaration calls on governments to include civil society, particularly people living with HIV/AIDS, in the review process.

The Open Society Public Health Watch HIV/AIDS Monitoring Project partners with civil society organizations in the United States to monitor and advocate for improved governmental efforts to comply with the UNGASS Declaration of Commitment on HIV/AIDS. This report provides an overview of Public Health Watch partners’ findings in country, as well as a lengthier assessment of U.S. HIV/AIDS policy.

The Office of National AIDS Policy (ONAP), which was formed under President Clinton in 1993, coordinates the continuing domestic efforts to implement the President’s National HIV/AIDS Strategy. In addition, the Office works to coordinate an increasingly integrated approach to the prevention, care and treatment of HIV/AIDS. As a unit of the Domestic Policy Council, ONAP coordinates with other White House offices. ONAP is led by the Director, who is appointed by the President.

Following the inauguration of President Trump on January 20, 2017, the website for ONAP became inaccessible and it was reported the office was closed with the departure of the previous director, Amy Lansky, with no clear plans if or when President Trump planned to reopen it. In June 2017, six members of the council filed letters of resignation, citing that above all things the current administration “…simply does not care…” about the HIV/AIDS situation in the United States (ONAP,2010).

Function
The Office of National AIDS Policy is part of the White House Domestic Policy Council and is tasked with coordinating the continuing efforts of the government to reduce the number of HIV infections across the United States. The Office emphasizes prevention through wide-ranging education initiatives and helps to coordinate the care and treatment of citizens with HIV/AIDS.
ONAP also coordinates with the National Security Council and the Office of the Global AIDS Coordinator, and works with international bodies to ensure that America’s response to the global pandemic is fully integrated with other prevention, care, and treatment efforts around the world. Through the U.S. President’s Emergency Plan for AIDS Relief (PEPFAR) initiative, the U.S. has taken steps in responding to the global HIV/AIDS pandemic, working with countries heavily impacted by HIV/AIDS to help expand access to treatment, care, and prevention.

US National HIV/AIDS Strategy

In July 2010, President Obama released the National HIV/AIDS Strategy for the United States, the first comprehensive strategy to achieve a coordinated response to domestic HIV. The National HIV/AIDS Strategy sought to reduce the number of new infections in the United States, improve health outcomes for people living with HIV, and reduce HIV-related disparities by coordinating the response across Federal agencies. The Strategy was implemented across U.S. departments and agencies, including the Department Health and Human Services (HHS), Department of Justice (DOJ), Department of Labor (DOL), Housing and Urban Development (HUD), and Department of Veterans Affairs (VA). The Strategy had four main goals:
1) To reduce new HIV infections;
2) To increase access to care and improve health outcomes for people living with HIV;
3) To reduce HIV-related disparities;
4) To achieve a more coordinated response.

HIV INFECTION AND AIDS IN ETHIOPIA

The first evidence of HIV epidemic in Ethiopia was detected in 1984. Since then, AIDS has claimed the lives of millions and has left behind hundreds of thousands of orphans. The Government of Ethiopia took several steps in preventing further disease spread, and in increasing accessibility to HIV care, treatment and support for persons living with HIV.

According to single point HIV related estimates and projections for Ethiopia 2014, the national HIV prevalence is 1.14%. The recent 2011 EDHS shown that the urban prevalence is 4.2% which is seven times higher than that of the rural (0.6%). The 2011 EDHS also shows that the HIV prevalence varies from region to region ranging from 0.9% in SNNPR to 6.5% in Gambela. Furthermore, the HIV related estimates and projections indicate that the 2013 HIV prevalence in regions ranges from 0.8% to 5.8%.

Currently 523,000 patients, including 23,400 children under the age of 15, are taking ART. Based on the 2014 estimate, the 2014 ART need is 751,121for adults and 178,500 for children under 15 years of age (WHO 2013 and UNAIDS ,2015).

Free ARV service was launched in January 2005 and public hospitals started providing free ARVs in March 2005. Currently, ART service is available in 1045 Health facilities. On the basis of the 2010-2014 strategic plan, ART coverage for adults (age 15+) has reached 76% but the coverage remains low (23.5%) for children (age

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