Ringed impact craters on Venus: An analysis from Magellan images

We have analyzed cycle 1 Magellan images covering approximately 90 percent of the venusian surface and have identified 55 unequivocal peak-ring craters and multiringed impact basins. This comprehensive study (52 peak-ring craters and at least 3 multiringed impact basins) complements our earlier independent analysis of Arecibo and Venera images and initial Magellan data and that of the Magellan team

Triton's surface age and impactor population revisited in light of Kuiper Belt fluxes: Evidence for small Kuiper Belt objects and recent geological activity

Neptune's largest satellite, Triton, is one of the most fascinating and enigmatic bodies in the solar system. Among its numerous interesting traits, Triton appears to have far fewer craters than would be expected if its surface was primordial. Here we combine the best available crater count data for Triton with improved estimates of impact rates by including the Kuiper Belt as a source of impactors. We find that the population of impactors creating the smallest observed craters on Triton must be sub-km in scale, and that this small-impactor population can be best fit by a differential power-law size index near -3. Such results provide interesting, indirect probes of the unseen small body population of the Kuiper Belt. Based on the modern, Kuiper Belt and Oort Cloud impactor flux estimates, we also recalculate estimated ages for several regions of Triton's surface imaged by Voyager 2, and find that Triton was probably active on a time scale no greater than 0.1-0.3 Gyr ago (indicating Triton was still active after some 90% to 98% of the age of the solar system), and perhaps even more recently. The time-averaged volumetric resurfacing rate on Triton implied by these results, 0.01 km$^3$ yr$^{-1}$ or more, is likely second only to Io and Europa in the outer solar system, and is within an order of magnitude of estimates for Venus and for the Earth's intraplate zones. This finding indicates that Triton likely remains a highly geologically active world at present, some 4.5 Gyr after its formation. We briefly speculate on how such a situation might obtain.Comment: 14 pages (TeX), plus 2 postscript figures Stern & McKinnon, 2000, AJ, in pres

Factors That Influence High School Student Participation in United States Department of Agriculture School Lunch Nutrition Programs

The survey investigated factors that influenced high school student participation in the National School Lunch Program. The National School Lunch program provides nutritionally balanced meals based on the Dietary Guidelines for Americans, the Recommended Dietary Allowances, and the Food Guide Pyramid. This nutrition program contributes significantly to the nutrient needs of adolescents, however, participation rates are low and students do not receive the health benefits associated with this nutrition program when they do not participate. The survey was conducted in two high schools, both with grades sophomore through senior. The two high schools had distinct differences in location, cafeteria design and seating arrangement, number of lunch periods, and proximity to additional eating establishments. The survey asked the high school students to rate their school lunch program from Very Good to Poor in the areas of taste, appearance, temperature and amount of the food, and the courtesy of the foodservice staff. The survey also asked students to rate the variety and selection offered in the school, the time spent waiting in line, and the frequency which the student participated in the school lunch program. Questions regarding the current grade in school, the type of food typically selected, and any comments the students chose to add were also on the survey. Students with the newer cafeteria design were more likely to rate the food appearance as very good compared to students with an older cafeteria design. The temperature of the food, and the variety and selection were viewed more positively by the school with the more attractive cafeteria design than the school with the older cafeteria. Taste, frequency of participation, amount of food, time spent waiting in line, and the courtesy of the foodservice staff were rated similarly by both schools. The survey showed that the school lunchroom environment can influence student participation

Flight and tunnel test results of the MDC mechanical jet noise suppressor nozzle

The flight and wind tunnel tests to determine the acoustic and performance effects of a mechanical jet noise suppressor nozzle mounted on a Viper engine of an HS-125 airplane are discussed. Flyover noise measurements were made with microphones mounted on top of a 137.5 m bridge tower. Seven nozzle configurations including two references nozzles, two suppressors, and three ejector inlets were tested. The suppressor nozzle of interest for an advanced supersonic transport, the suppressor/treated ejector, achieved a measured noise reduction of 14 EPNdB relative to a conventional conical reference nozzle at the highest pressure ratio tested (approximately 2.5). The unique engine nacelle, flight hardware, and nacelles from the HS-125 flight test program, combined with a simulated HS-125 fuselage were windtunnel tested. Both propulsion and acoustic data were recorded. Preliminary thrust data results from the wind tunnel tests are summarized and compared to other mechanical suppressor test results. The test results indicate that a noise reduction of at least 16 EPNdB would be possible for the suppressor/ejector nozzle scaled to typical AST engine size with a 5% thrust loss at a typical takeoff climb speed

Prospective genetic screening decreases the incidence of Abacavir hypersensitivity reactions in the Western Australian HIV cohort study

Abacavir therapy is associated with significant drug hypersensitivity in ∼8% of recipients, with retrospective studies indicating a strong genetic association with the HLA-B*5701 allelle. In this prospective study, involving 260 abacavir-naive individuals (7.7% of whom were positive for HLA-B*5701), we confirm the usefulness of genetic risk stratification, with no cases of abacavir hypersensitivity among 148 HLA-B*5701–negative recipients

Association between low 25(OH) vitamin D levels, antiretroviral therapy and metabolic profile in a cohort of treated ahd therapy naive HIV positive patients in Western Australia

See Attache

Simultaneous single-pulse observations of radio pulsars III. The behaviour of circular polarization

We investigate circular polarization in pulsar radio emission through simultaneous observations of PSR B1133+16 at two frequencies. In particular, we investigate the association of the handedness of circular polarization with the orthogonal polarization mode phenomenon at two different frequencies. We find the association to be significant across the pulse for PSR B1133+16, making a strong case for orthogonal polarization modes determining the observed circular polarization. The association however is not perfect and decreases with frequency. Based on these results and assuming emission occurs in superposed orthogonal polarization modes, we present a technique of mode decomposition based on single pulses. Average profiles of the polarization of each mode can then be computed by adding the individual mode-separated single pulses. We show that decomposing single pulses produces different average profiles for the orthogonal polarization modes from decomposing average profiles. Finally, we show sample single pulses and discuss the implications of the frequency dependence of the correlation of the circular polarization with the orthogonal polarization mode phenomenon.Comment: accepted for publication in A&

Surviving well together: post development, maternity care and the politics of ontological pluralism

Londo