Image transfer through cirrus clouds. I. Ray trace analysis and wave-front reconstruction.

A new technique for modeling image transfer through cirrus clouds is presented. The technique uses a ray trace to model beam propagation through a three-dimensional volume of polydisperse, hexagonal ice crystals. Beyond the cloud, the technique makes use of standard Huygens-Fresnel propagation methods. At the air-cloud interface, each wave front is resolved into a ray distribution for input to the ray trace software. Similarly, a wave front is reconstructed from the output ray distribution at the cloud-air interface. Simulation output from the ray trace program is presented and the modulation transfer function for stars imaged through cirrus clouds of varying depths is discussed.

An evaluation of the effectiveness of a videotape programme on interobserver reliability in outcome assessment for fibromyalgia.

AIMS: A study was designed to assess the effects of a standardized instructional videotape on training senior medical students to acceptable levels of reliability in performing several commonly used observer dependent outcome measures in patients with fibromyalgia (FM). METHODS: During a single day, six third-year medical students independently examined six patients with FM in predetermined order using a Latin Square design, before and after viewing a standardized videotape which demonstrated methods for performing doiorimelry and for delecting skinfold tenderness and reactive hyperaemia. Reliability coefficients were calculated based on the variance components of the Analysis of Variance (ANOVA) table. RESULTS: Prestandardization reliability coefficients were <0.80 for 8 measures. Following standardization all reliability coefficients, but one, approximated or exceeded 0.80. CONCLUSIONS: An important and beneficial effect of the standardization procedure was noted for several outcome variables. Such improvements in observer agreement have important implications for training senior medical students to perform quantitative measurement in the longitudinal management of FM patients in clinical practice. The use of a videotape to achieve this goal has obvious cost and convenience advantages compared with personal onc-on-one or small group training procedures.

Class, health and justice.

Class inequalities in health are intuitively unjust. Although the link between social class and health status has been fully documented, the precise nature of the injustice has not been made clear. Four alternative views are presented, corresponding to four goals: (1) maximizing the sum total of health; (2) equalizing the health status of higher and lower social classes; (3) maximizing the health status of the lowest social class; and (4) maximizing the health status of the sickest individuals in society. The nature of the injustice is further obscured by several theoretical and empirical questions, like the degree and significance of personal responsibility for illness and the relation of the degree of economic inequality to sum total of health.

Active Imaging through Cirrus Clouds.

The presence of clouds of ice particles in the uplink and downlink path of an illumination beam can severely impede the performance of an active imaging system. Depending on the optical depth of the cloud, i.e., its density and depth, the beam can be completely scattered and extinguished, or the beam can pass through the cloud with some fraction attenuated, scattered, and depolarized. In particular, subvisual cirrus clouds, i.e., high, thin cirrus clouds that cannot be observed from the ground, can affect the properties and alignment of both uplink and downlink beams. This paper discusses the potential for active imaging in the presence of cirrus clouds. We document field data results from an active imaging experiment conducted several years ago, which the authors believe to show the effects of cirrus clouds on an active imaging system. To verify these conclusions, we include the results of a simulation of the interaction of a coherent illumination scheme with a cirrus cloud.

An outbreak of infections caused by strains of Staphylococcus aureus resistant to methicillin and aminoglycosides. I. Clinical studies.

In a 22-month period, strains of Staphylococcus aureus resistant to methicillin and multiple aminoglycosides, (designated MARS) were recovered from 108 inpatients with nosocomial infections at a hospital in the midwestern United States. Sixty-six of these patients were staying in a burn unit, and 42 were on other hospital wards. Among the patients with burns, MARS were recovered from the burn wounds of 64%; 32% of the patients with burns had MARS bacteremia. The patients without burns were age-matched with patients with nosocomial infections caused by antibiotic-susceptible strains of S. aureus. Patients from whom MARS were isolated had a longer mean hospital stay (79.6 days vs. 36.9 days; P less than 0.01), developed infection later (26.5 days vs. 13.5 days after admission; P less than 0.01), and had received antibiotic therapy before infection more often (81% vs. 38% of patients; P less than 0.01) than patients in the comparative population. Types of infection and incidences of death and bacteremia were similar in the two groups. Antibiotic-resistant strains of S. aureus may cause serious infections and significant mortality.

An outbreak of infections caused by strains of Staphylococcus aureus resistant to methicillin and aminoglycosides. II. Epidemiologic studies.

Studies to determine the epidemiologic behavior of strains of Staphylococcus aureus resistant to methicillin and aminoglycosides (MARS) were conducted over a period of two and one-half years, during which MARS were isolated from 201 patients at a hospital in the midwestern United States. Most cases of infection or colonization with MARS (156 of 201) occurred in patients with burns. In the burn unit, MARS were recovered from the air, from the hair and hands of personnel, and from inanimate objects. Nasal (72%) and rectal (66%) colonization were common among burned patients with infected or colonized burn wounds but occurred in only six of 74 burn unit personnel. When compared with two control periods, the prophylactic use of antistaphylococcal agents in patients with burns increased markedly at the time the outbreak began. Of the 45 patients without burns from whom MARS were isolated, 42 (93%) were surgical patients. MARS were not demonstrated in the air or environment of patients with infected surgical wounds. None of 334 non-burn unit hospital personnel were found to be carriers of MARS. Four phage types (83A, 6/75/85, 29/52/80, and 92) were recovered during the outbreak. A determinant of antibiotic resistance was probably transmitted among strains of S. aureus.