Documented AIDS Cases as the Basis for Projections of Adolescence HIV Infections in the US

Twenty percent of AIDS cases in the U.S. occur in individuals in the age range 20 to 29. The mean incubation time, the time from infection to the onset of AIDS, is in the order of 8 years. Therefore, most of these AIDS cases represent HIV infections that occurred during mid- to late-adolescence. About 800 officially reported cases in the age group 13 to 19 have occurred in the U.S. This low occurrence of AIDS should not be a source of complacency in assessing the need to provide education and behavioral alternatives to this age group. As the predominate mode of transmission of HIV infection shifts from gay-male behaviors and intravenous drug abuse (IVDA) to heterosexual intercourse, adolescents may be at significantly increased risk. The occurrence of STDs and early pregnancies indicate a significant rate of high-risk sexual behaviors in adolescents in the U.S. The rate of adolescent HIV infections can be projected by extrapolation from historical data and by epidemiological modeling and computer simulation. The rates of infection projected by these methods are sufficiently congruent to lend credibility to them. A rate of new HIV infections, in individuals in the age range of 13 to 19, in the order of 300,000 annually should be anticipated within the next 10 years

Seismic effects of sonic booms

Measurement and interpretation of ground vibrations, produced by seismic effect of sonic boo

Flexible body dynamic stability for high performance aircraft

Dynamic equations which include the effects of unsteady aerodynamic forces and a flexible body structure were developed for a free flying high performance fighter aircraft. The linear and angular deformations are assumed to be small in the body reference frame, allowing the equations to be linearized in the deformation variables. Equations for total body dynamics and flexible body dynamics are formulated using the hybrid coordinate method and integrated in a state space format. A detailed finite element model of a generic high performance fighter aircraft is used to generate the mass and stiffness matrices. Unsteady aerodynamics are represented by a rational function approximation of the doublet lattice matrices. The equations simplify for the case of constant angular rate of the body reference frame, allowing the effect of roll rate to be studied by computing the eigenvalues of the system. It is found that the rigid body modes of the aircraft are greatly affected by introducing a constant roll rate, while the effect on the flexible modes is minimal for this configuration

The Spanish and Mexican Baseline of California Tree and Shrubland Distributions Since the Late 18th Century

Historical distributions of 31 tree species, chaparral, and coastal sage scrub described by Spanish land explorers in the late eighteenth and early nineteenth centuries (1769–1806) and in land grant diseños (1784–1846) are reconstructed at 634 localities across central and southern California. This baseline predates most formal botanical surveys by nearly a century, allowing for assessment of vegetation change over the broadest time frame for comparison with pre-historical evidences and future distributions. Spanish accounts are compared with historical sources in the Mexican era (1821–1848), American settlement (1848–1929), and modern range maps of the 1929–1934 Vegetation Type Map (VTM) survey. Among tree species that were recorded in Spanish explorations, the site-specific localities are consistent with VTM maps at the spatial resolution of the land expeditions. In contrast with massive deforestation across eastern North America since European colonization, hardwood and conifer forests in California sustained inconsequential cutting during Hispanic settlement. Spanish accounts and Mexican diseños occasionally provide remarkable detail of fine-scale distributions which have not changed over the past two centuries, including Pinus radiata forest at Cambria and Monterey, the eastern limit of Quercus lobata and Q. agrifolia woodlands with Aesculus californica in the Salinas Valley, as well as isolated stands of Cupressus macrocarpa and C. sargentii. Disjunct occurrences of trees in southern California were recorded at the same places they occur today, including an isolated grove of Q. engelmannii at the Baldwin Park Arboretum, and the Pinus coulteri stand in the mountains above Santa Barbara. The southern margin of mixed conifer forest in the San Bernardino Mountains has remained on the crest of the range since Garcés’ account in 1776. Long-term tree distributions are evaluated with respect to land use, grazing and climate change. We advocate the use of historical records as proxy data for climate change studies

Diets of Invasive Channel Catfish are Subsidized by Invasive Riparian Trees

Russian olive (Elaeagnus angustifolia) is an invasive, fruit- bearing riparian tree that dominates riparian zones of the San Juan River in the southwestern United States. Previous research in this river suggests olive fruit is common in diets of invasive channel catfish (Ictalurus punctatus), but its energetic importance is unknown (i.e. critical for catfish fitness vs. incidental consumption). We assessed Russian olive consumption in channel catfish diets bimonthly for 1 year, hypothesizing that olive consumption would be greatest during periods of high olive availability and low benthic aquatic invertebrate availability. We found that catfish consumed olive fruit throughout the year and that olive comprised up to 44% of total stomach contents by mass, with peaks in spring and fall. Regression models revealed the presence and mass of olive fruit in catfish stomachs were positively associated with catfish total length, with a significant interaction between water temperature and river discharge. Catfish were more likely to consume olive fruit during higher flows, regardless of temperature and at low discharge with higher temperature. Contrary to our hypothesis, neither olive nor benthic invertebrate availability were associated with olive presence in channel catfish diets. Nutrition analysis indicated that olive alone was a low-quality diet item but has the potential to provide a reliable energy source. We used seasonal data to estimate the energetic contribution of olive fruit to catfish populations using a bioen-ergetic model, which estimated that olive fruit accounted for 35.6% of energy (Joules) consumed by catfish populations and satisfied 38% of their metabolic demand. Our results suggest that Russian olive fruit is a significant subsidy to channel catfish in the San Juan River. However, more research is needed to determine the indirect effects of this interaction on native fishes and ecosystem function

Venus/Mercury swingby with Venus capsule. Preliminary science objectives and experiments for use in advanced mission studies

Venus/Mercury swingby with Venus capsule - preliminary science objectives and experiments for use in advanced mission studie

Flight and analytical investigations of a structural mode excitation system on the YF-12A airplane

A structural excitation system, using an oscillating canard vane to generate force, was mounted on the forebody of the YF-12A airplane. The canard vane was used to excite the airframe structural modes during flight in the subsonic, transonic, and supersonic regimes. Structural modal responses generated by the canard vane forces were measured at the flight test conditions by airframe-mounted accelerometers. Correlations of analytical and experimental aeroelastic results were made. Doublet lattice, steady state double lattice with uniform lag, Mach box, and piston theory all produced acceptable analytical aerodynamic results within the restrictions that apply to each. In general, the aerodynamic theory methods, carefully applied, were found to predict the dynamic behavior of the YF-12A aircraft adequately

A brief description of geological and geophysical exploration of the Marysville geothermal area

Extensive geological and geophysical surveys were carried out at the Marysville geothermal area during 1973 and 1974. The area has high heat flow (up to microcalories per square centimeter-second, a negative gravity anomaly, high electrical resistivity, low seismic ground noise, and nearby microseismic activity. Significant magnetic and infrared anomalies are not associated with the geothermal area. The geothermal anomaly occupies the axial portion of a dome in Precambrian sedimentary rocks intruded by Cretaceous and Cenozoic granitic rocks. The results from a 2.4-km-deep test well indicate that the cause of the geothermal anomaly is hydrothermal convection in a Cenozoic intrusive. A maximum temperature of 95 C was measured at a depth of 500 m in the test well