Reconstruction and future trends of the AIDS epidemic in the United States

There has been considerable uncertainty in estimates of past and current human immunodeficiency virus (HIV) infection rates in the United States. Statistical estimates of historical infection rates can be obtained from acquired immunodeficiency syndrome (AIDS) incidence data and the incubation period. However, this approach is subject to a number of sources of uncertainty and two other approaches, epidemic models of HIV transmission and surveys of HIV prevalence, are used to corroborate and refine the statistical estimates. Analyses suggest the HIV infection rate in the United States grew rapidly in the early 1980s, peaked in the mid-1980s, and subsequently declined markedly. Due both to the decline in the underlying infection rate and to the development of effective therapies that may delay AIDS diagnosis, overall AIDS incidence may plateau during the next 5 years. However, the number of individuals with advanced HIV disease without a diagnosis of AIDS who could potentially benefit from therapy is expected to increase 40% by 1995 as infected individuals progress to more advanced stages of HIV disease. Thus, although the overall HIV infection rate has declined, the demands on the U.S. health care system for treatment and care of HIV-infected individuals remain enormous.     

“If you study,the last thing you want to be is working under the sun:” an analysis of perceptions of agricultural education and occupations in four countries

Agriculture plays a key role in national economies and individual livelihoods in many developing countries, and yet agriculture as a field of study and an occupation remain under-emphasized in many educational systems. In addition, working in agriculture is often perceived as being less desirable than other fields, and not a viable or compelling option for students who have received a post-secondary education. This article explores the historical and contemporary perceptions of agriculture as a field of study and an occupation globally, and applies themes from the literature to analyze primary data from focus groups with international students studying for university degrees in the United States. The article analyzes students’ perceptions and experiences in four countries—Bangladesh, Nepal, Honduras and Haiti—in order to make recommendations about how best to address challenges and develop capacity in agricultural education and employment in low-income countries.     

Number of siblings and educational attainment

Family background continues to be closely related to individuals' educational attainment in the United States. A notable change in one aspect of this background, number of siblings, is occurring as fertility is becoming extremely low. Examination of the negative relation between individuals' sibling number and years of schooling indicates that education among those with many siblings is disproportionately cut short before high school graduation. Because there is a strong negative relation between number of siblings and scores on tests measuring verbal ability, recent reductions in sibling number would be expected to contribute to enhanced verbal ability and increasing years of schooling for those born now in the United States.     

Epidemiology of HIV infection and AIDS in the United States

By the end of 1987, nearly 50,000 cases of acquired immunodeficiency syndrome (AIDS) had been reported since 1981, 20,745 in the past year alone. Black and Hispanic adults and children have reported rates 3 to 12 times as high as whites. This can be largely attributed to higher reported rates in black and Hispanic intravenous (IV) drug abusers, their sex partners, and infants. In 1986, reported AIDS deaths increased adult male and female mortality in the United States by an estimated 0.7 and 0.07%, respectively, with much greater increases in selected age groups or areas of the country. The greatest variation in infection with the human immunodeficiency virus (HIV) (0 to 70%) has been found in surveys of IV drug abusers, while surveys of homosexual men reveal infection rates of 20 to 50%. Infection with HIV ranged from 0 to 2.6% in limited sexually transmitted disease clinic surveys of heterosexual men and women without a history of IV drug abuse or known sexual contact with persons at increased risk. The modes of HIV transmission are now well understood, but a large amount of biologic variability in efficiency of transmission remains to be explained. The period between initial infection with HIV and the development of AIDS is variable, but the risk for disease progression increases with duration of infection.     

The syphilis epidemic and its relation to AIDS

This article presents an overview of the history of medical and public health responses to syphilis in the 20th-century United States and briefly evaluates the relevance and significance of these approaches for the AIDS epidemic. The parallels are numerous: they relate to science, public health, civil liberties, and social attitudes concerning sexually transmitted infection. The strengths and limits of past approaches to controlling sexually transmitted diseases are explored as a possible guide for AIDS policy.     

Is AIDS in Africa a distinct disease?

In Africa, opportunistic infections, transmission patterns, and viral subtypes differ from what is seen in the AIDS epidemics of the United States and Europe, yet 2 decades into the epidemic, AIDS researchers have only a shaky handle on the fundamental question: What accounts for these differences? The answers have potentially important implications for both prevention and treatment strategies.     

AIDS: an international perspective

The acquired immunodeficiency syndrome (AIDS) and infection with the human immunodeficiency virus type 1 (HIV-1) constitute a worldwide public health problem. Whereas in Europe and in most of the Americas transmission of HIV-1 has occurred predominantly among homosexual men and intravenous drug abusers, in Africa a distinct epidemiologic pattern has emerged that indicates that HIV-1 infection is mainly heterosexually acquired. Heterosexual transmission appears to be increasing in some parts of Latin America and the Caribbean, and possibly in the United States. In addition to HIV-1, at least one other human retrovirus, namely HIV-2, has been implicated as a cause of AIDS in Africa and Europe. Factors that influence heterosexual transmission of HIV-1 include genital ulcerations, early or late stages of HIV-1 infection in the index case, and possibly oral contraception and immune activation. The rate of perinatal transmission is enhanced when the mother's illness is more advanced. AIDS and HIV-1 infection may have a significant impact not only on public health, but also on the demography and socioeconomic conditions of some developing countries. Programs for the prevention and control of AIDS should be an immediate priority in all countries.     

Human T-lymphotropic virus type 4 and the human immunodeficiency virus in West Africa

A new human T-lymphotropic virus (HTLV-4) was recently described in healthy people from Senegal. This virus has many properties in common with members of the human T-lymphotropic viruses, particularly the human immunodeficiency virus or HIV, the etiologic agent of acquired immune deficiency syndrome (AIDS), but does not appear to be associated with immunodeficiency-related disorders. In the present study, serum samples were obtained from 4248 individuals from six West African countries, including Senegal, Guinea, Guinea Bissau, Mauritania, Burkina Faso, and Ivory Coast. These samples, collected during 1985-1987, were from people categorized as healthy control, sexually active risk, and disease populations. All samples were analyzed for reactivity to HTLV-4 and HIV by radioimmunoprecipitation-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. Evidence for HTLV-4 infection was found in five of the six countries. The seroprevalence varied markedly from country to country. Healthy sexually active individuals in the risk category had the highest levels of HTLV-4 infection compared to individuals in the healthy control category and the disease category, the latter including AIDS patients. The seroprevalence of HIV infection in most of these countries was quite low, although tightly associated with the rare cases of AIDS. The biology of HTLV-4 infection thus differs from that of HIV in Central Africa or the United States and Europe. The presence of these viruses and their different pathogenicities in several countries of West Africa indicate the necessity for serologic assays that will distinguish between them. Further studies of their origin and distribution as well as of their biology will be important in advancing our understanding of AIDS.     

New physicians: a natural experiment in market organization

The National Resident Matching Program is a centralized clearinghouse through which new medical graduates in the United States obtain their first positions. The history of this market, from the market failures that the centralized system was designed to address, to the present, is discussed, and a hypothesis about the behavior of such markets is presented. New evidence is then presented from a set of similar centralized markets in the United Kingdom. Because some of these latter markets have failed, while others have succeeded, they provide a natural experiment that permits the hypothesis to be tested. The new evidence also suggests directions in which modifications of existing procedures might be considered.     

Prevalence and patterns of same-gender sexual contact among men

The prevalence and patterns of same-gender sexual contact among men are key components of models of the spread of HIV infection and AIDS in the U.S. population. Previous estimates by Kinsey et al. from data collected between 1938 and 1948 have been widely criticized for inadequacies of sample design. New lower-bound estimates of prevalence developed from data from a national sample survey conducted in 1970 indicate that minimums of 20.3 percent of adult men in the United States in 1970 had sexual contact to orgasm with another man at some time in life; 6.7 percent had such contact after age 19; and between 1.6 and 2.0 percent had such contact within the previous year. Although these estimates incorporate adjustments for missing data, the likelihood of underreporting suggests that these estimates might be lower bounds on the prevalence of same-gender sex among men. Two sets of alternative estimates are derived to assess the sensitivity of these estimates to the assumptions made in imputing values to missing data. Detailed estimates are presented by frequency of contact, age, education, and marital status; and supporting estimates are derived from a 1988 national survey. Data from both the 1970 and 1988 surveys indicate that never-married men are more likely than other men to have had same-gender sexual contacts within the last year. The 1970 survey also indicates, however, that approximately half the men estimated to have such contacts are found among the more numerous population of currently or previously married men.     

美国高校计算机基础教学的启示

研究总结了美国高校计算机基础教学与我国相比的差异,分析其教学特点,如教学内容注重应用、使用有利于培养应用型人才的嵌入式的教学模式、以展开实例的方式教学组织形式等,借鉴美国高校计算机基础教学的经验以促进我国高校计算机基础教学的发展。     

The current situation in mexican immigration

By 1988, the Mexican-origin population of the United States had grown to 12.1 million, largely from recent, sharp increases in immigration. The policy concerns raised by this phenomenon have been influenced by some perceptions that available research contradicts. Today most Mexican immigrants come to stay, about half are female, and they have increasingly less schooling compared to the native-born population and other immigrants. Nationally, they do not cause adverse economic effects for native-born workers and, across generations, their language and political assimilation is proceeding well. They put greater demands on education than on other public services. However, the Mexican-origin population affects the economy and public services more and differently in the areas where it is concentrated, primarily in the western United States and large urban areas. Further, the recent legalization of 2.3 million Mexican immigrants can be expected to increase the demand on public services, especially in those areas.     

Legal rights and duties in the AIDS epidemic

This article provides an overview of some major areas of legal concern in which the AIDS epidemic is having an impact. The rights of infected individuals to testing, treatment, and confidentiality are reviewed, and emphasis is given to their claims to nondiscrimination regarding access to health care, employment, housing, education, insurance, and related interests. Infected persons' duties to contain transmission of AIDS are outlined under principles of criminal and civil law, including liability for provision of contaminated blood products. Uninfected people's general rights to protection are considered, and health professionals' and authorities' rights and duties are given more detailed attention. In conclusion, some legal developments outside the United States are reviewed.     

Agricultural structure and economic adjustment

There has been much discussion of changing agricultural structure in the United States. In this paper, the author reviews some of the factors contributing to structural change in the United States and describes the policies adopted by the European Community with respect to agricultural structure. The European experience with structural policies suggests that this approach is not very promising for the United States where no specific structural policies exist. The argument developed in this paper is that structural changes in agriculture are simply one example of economic adjustment in a capitalist economy, that economic adjustments are generally desirable although they are not costless, and that discussions of agricultural structure should focus on methods to alleviate the costs of adjustment rather than on efforts to prevent change.     

Warming and earlier spring increase western U.S. forest wildfire activity

Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt.     

论新时期农业推广中农民行为规律变化及对策

我国农业正从传统农业向现代农业转变,在农业推广中农民的行为规律呈现出了新的变化,农民行为的改变越来越多地受到教育程度、经济收入以及市场因素和社会环境的影响。农业推广工作应该通过提高农民的受教育程度,改善农民的生产环境、生活环境、经营环境等途径,避免过多地使用强制性方法改变农民的行为,引导农民更多地自愿改变自己的行为。     

ECOLOGY: Forest Fire Plan Kindles Debate

Forest fires burning in the western United States have already scorched over 2.5 million hectares this summer. Now a federal proposal to prevent them by paying loggers to cut smaller trees is generating heat among ecologists, who say the approach may not be right for all forests--or all fires.     

Physicists find windows of opportunity in plasmas

The 1500 physicists from Europe, the United States, the Pacific Rim, and the former Soviet Union who gathered in Minneapolis from 7 to 11 November had many messages but one medium: plasmas. As the presentations at the meeting of the American Physical Society's division of plasma physics showed, the windows that laboratory plasmas can provide into space, turbulent liquids, and matter-antimatter interactions are opening wider than ever.     

Development of vegetation and climate in the southwestern United States

Plant macrofossils in ancient packrat middens document the presence of woodland communities in most of the present Chihuahuan, Sonoran, and Mohave deserts in the southwestern United States during the late Wisconsinan (22,000 to 11,000 years before present by radiocarbon dating). Warm desert species were common in the woodlands at lower elevations and mixed conifer and subalpine forests were present at high elevations. Inferred mild, wet winters and cool summers produced unusual plant and animal associations compared to those of today. Montane communities acquired modern aspects and more mesophytic species disappeared from lower woodlands about 11,000 years ago. Early Holocene xeric woodlands and an inferred winter precipitation regime persisted until about 8000 years ago. The present circulation patterns, rainfall regimes, and biotic distributions probably formed as a result of the melting of the continental ice sheets. Southwestern communities appear to have responded quickly to climatic changes compared to the gradual responses of central and eastern United States forest communities.     

中国大学开放性建设刍议——世界一流大学的经验与启示

开放性是大学发展的必然要求,是创建世界一流大学的必然选择,社会需求和知识探索分别为大学开放性的外在和内在要求。美、英、德等国的世界一流大学在开放性建设上进行了卓有成效的实践,值得借鉴。当前中国大学的思想保守化、人才家族化、学术封闭化和评价功利化等问题严重,为促使中国大学向世界一流大学迈进,大学的胸怀姿态,招生招聘,教育理念和模式,教学内容和形式,教育科研评价五大方面应更加开放。