Characteristics of Hurricanes: Analyses and calculations made from measurements by aircraft result in a fairly complete description.

Tropical cyclones derive their energy from the release of latent heat of condensation; they have been compared to simple heat engines (6), although they are not very efficient ones since only about 3 percent or less of the heat released within the cyclone is converted into kinetic energy. Tropical cyclones are warm-core, direct circulations in the sense that ascent takes place at warmer temperatures than does descent, thus converting heat energy into potential energy and potential energy to kinetic energy.

Mutation-specific functional impairments in distinct tau isoforms of hereditary FTDP-17.

Tau proteins aggregate as cytoplasmic inclusions in a number of neurodegenerative diseases, including Alzheimer's disease and hereditary frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). Over 10 exonic and intronic mutations in the tau gene have been identified in about 20 FTDP-17 families. Analyses of soluble and insoluble tau proteins from brains of FTDP-17 patients indicated that different pathogenic mutations differentially altered distinct biochemical properties and stoichiometry of brain tau isoforms. Functional assays of recombinant tau proteins with different FTDP-17 missense mutations implicated all but one of these mutations in disease pathogenesis by reducing the ability of tau to bind microtubules and promote microtubule assembly.

Augmentation of mortality risk discriminating power of left ventricular ejection fraction by measures of nonuniformity in systolic emptying on radionuclide ventriculography.

Employing equilibrium-gated radionuclide ventriculography in the left anterior oblique view, six geometric models and five mathematic coefficients of nonuniformity in regional left ventricular emptying were tested for their relative mortality risk-stratifying power and capacity to augment the risk-discriminating potency of the continuous and dichotomized global ejection fraction. Radionuclide ventriculography was performed an average of 7.6 days after acute myocardial infarction. All geometric models significantly separated 20 normal subjects from 137 patients with recent infarction (p less than 0.001). Cumulative mortality data demonstrated that significant independent univariate dichotomizing potency and augmentation of the mortality risk-discriminating power of the global ejection fraction were provided by models of regional emptying that 1) conformed to coronary artery perfusion areas, 2) encompassed total ventricular counts, 3) expressed variability in regional relative to global ejection fraction, and 4) simulated a pattern of emptying directed toward the center of geometry of the left ventricle. The combination of a four quadrant geometric model with axes drawn 45 degrees above the horizontal and a coefficient of variation calculated as square root of sigma(GEF - REF)2/4 x 100/GEF (where GEF = global ejection fraction and REF = regional ejection fraction) proved to be optimal. This coefficient averaged 12.2% in normal subjects and 32.2% in patients with recent acute myocardial infarction (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Tuberculosis prevention and control activities in the United States: an overview of the organization of tuberculosis services.

After a 20% increase in tuberculosis (TB) cases between 1986 and 1992, TB cases in the United States have declined from 1993 through 1997, an average of 5 to 7 per cent per year. In this paper, we review trends and the current epidemiology of TB in the US, present a brief history of TB control efforts in the country, and present the key strategies for TB control in the US. We describe the current organizational structure of TB services in the US, the role of the private sector in TB control, and how TB control is funded. Finally we discuss the mechanisms by which TB policy is developed. The US model represents a categorical disease program that combines a centralized role of the national government in development of policy, funding, and in the maintenance of national surveillance, and a decentralized role of state and local jurisdictions, which adapt and implement national guidelines and which are responsible for day-to-day program activities. Given the relative success of this combined approach, other countries facing the challenge of maintaining an effective TB control program in the face of increased decentralization of health services may find this description useful.

Estimating HIV levels and trends among patients of tuberculosis clinics.

Symptomatic tuberculosis (TB) can occur as an opportunistic disease in immunosuppressed persons who are infected with human immunodeficiency virus (HIV) and who have been previously infected with Mycobacterium tuberculosis. Increases in TB cases have occurred in areas which have reported large numbers of cases of the acquired immunodeficiency syndrome (AIDS), and a high proportion of these TB cases have been HIV seropositive. Therefore, increasing numbers of HIV-infected persons may be found in TB clinics and hospitals. HIV serologic surveys in TB clinics and hospitals providing clinical services to TB patients are needed to assess the local prevalence of HIV infection in TB patients and the consequent need for public health intervention to prevent further spread of HIV and TB infection. The Centers for Disease Control (CDC), in collaboration with State and local health departments, has initiated HIV surveillance of patients with confirmed and suspected TB in TB clinics and hospitals in the United States. Blinded (serologic test results not linked to identifiable persons) HIV seroprevalence surveys are conducted in sentinel TB clinics and hospitals that provide TB clinical services each year to obtain estimates of the level of HIV infection in TB patients and to follow trends in infection over time. Nonblinded (voluntary) surveys will also be conducted to evaluate behaviors that have placed TB patients at risk for or protected them against HIV infection. Data from these surveys will be used to target education and prevention and control programs for TB and HIV infection and to monitor changes in behavior in response to such programs.

Acquired immunodeficiency syndrome in the United States: an analysis of cases outside high-incidence groups.

From 1 June 1981 through 31 January 1984, 201 cases of the acquired immunodeficiency syndrome were reported involving persons who could not be classified into a group identified to be at increased risk for this syndrome. Thirty-five had received transfusions of single-donor blood components in the 5 years preceding diagnosis of the syndrome and 30 were sexual partners of persons belonging to a high-risk group. Information was incomplete for most remaining patients, but because many of these patients were demographically similar to populations recognized to be at increased risk for the syndrome, previously identified risk factors may have been present but not reported for some of them. Additionally, a few persons who met the case definition for the syndrome probably had other reasons for their opportunistic disease and did not have the acquired immunodeficiency syndrome. The slow emergence of the acquired immunodeficiency syndrome in new populations is consistent with transmission mediated through sexual contact or parenteral exposure to blood.