Space program: Space debris a potential threat to Space Station and shuttle

Experts estimate that more than 3.5 million man-made objects are orbiting the earth. These objects - space debris - include whole and fragmentary parts of rocket bodies and other discarded equipment from space missions. About 24,500 of these objects are 1 centimeter across or larger. A 1-centimeter man-made object travels in orbit at roughly 22,000 miles per hour. If it hit a spacecraft, it would do about the same damage as would a 400-pound safe traveling at 60 miles per hour. The Government Accounting Office (GAO) reviews NASA's plans for protecting the space station from debris, the extent and precision of current NASA and Defense Department (DOD) debris-tracking capabilities, and the extent to which debris has already affected shuttle operations. GAO recommends that the space debris model be updated, and that the findings be incorporated into the plans for protecting the space station from such debris. GAO further recommends that the increased risk from debris to the space shuttle operations be analyzed

Koinonia

Reclaiming Discipline, Stephen Beers President\u27s Corner Critical Years: A look at a new era in Faith Development CoCCA: A Christian Response to Multiculturalism; Guest Editorial; Hot Programs ACSD Lake Regional Conference Report ACSD Placement Service Research Grant Applicationshttps://pillars.taylor.edu/acsd_koinonia/1047/thumbnail.jp

The Frequency of Carbon Stars Among Extremely Metal-Poor Stars

We demonstrate that there are systematic scale errors in the [Fe/H] values determined by the Hamburg/ESO Survey (and by inference by the HK Survey in the past) for certain extremely metal poor highly C-enhanced giants. The consequences of these scale errors are that a) the fraction of carbon stars at extremely low metallicities has been overestimated in several papers in the recent literature b) the number of extremely metal poor stars known is somewhat lower than has been quoted in the recent literature c) the yield for extremely metal poor stars by the HES Survey is somewhat lower than is stated in the recent literature. A preliminary estimate for the frequency of Carbon stars among the giants in the HES sample with -4 < [Fe/H] < -2.0 dex is 7.4 +-2.9%; adding an estimate for the C-enhanced giants with [C/Fe] > 1.0 dex without detectable C2 bands raises the fraction to 14 +-4$%. We rely on the results of an extensive set of homogeneous detailed abundance analyses of stars expected to have [Fe/H] < -3.0 dex selected from the HES to establish these claims. We have found that the Fe-metallicity of the cooler (Teff < 5200K) C-stars as derived from spectra taken with HIRES at Keck are a factor of ~10 higher than those obtained via the algorithm used by the HES project to analyze the moderate resolution follow-up spectra, which is identical to that used until very recently by the HK Survey. This error in Fe-abundance estimate for C-stars arises from a lowering of the emitted flux in the continuum bandpasses of the KP (3933 A line of CaII) and particularly the HP2 (Hdelta) indices used to estimate [Fe/H] due to absorption from strong molecular bands.Comment: Accepted to the ApJL after a very lengthly duel with the 3 simultaneous referee

Spatial patterns of western flower thrips (Thysanoptera: Thripidae) in apple orchards and associated fruit damage

Western flower thrips, Frankliniella occidentalis (Pergande), is an economic pest of apples in orchards of North America. Western flower thrips causes damage (“pansy spot”) to apples by its egglaying activities during the bloom and immediate post—bloom periods. Difficulties in monitoring this pest and incomplete understanding of its biology during the bloom period have complicated control efforts in apple orchards. Densities of western flower thrips were monitored in seven (2003) or eight (2004) apple orchards at each of four bloom stages; in each orchard, thrips counts in blossom clusters were estimated at four to six distances into the orchard from an orchard edge that abutted native sagebrush-steppe habitat. We hypothesized that numbers of thrips in blossoms would decline with increasing distance along transects into orchards if the native habitat acted as a source of thrips. Thrips numbers in blossom clusters peaked at full bloom and petal fall. Densities showed a linear drop with increasing distance into the orchard, which we interpreted as evidence that the native habitat adjacent to each orchard did indeed act as a source of thrips moving into the orchards. Pansy spot incidence declined with increasing distance into the orchard. The major drop in damage occurred between the border row trees and samples taken at the adjacent distance (nine m away), suggesting that border rows adjacent to native habitats should be monitored with particular care. Regression analyses showed that damage and thrips density were positively correlated, albeit with substantial levels of unexplained variation in levels of damage

Extremely Metal-Poor Stars: The Local High Redshift Universe

Extremely metal-poor (EMP) stars can only have formed early in the history of the Galaxy, and represent the local equivalent of the high redshift universe. With them, we can study the early supernovae, the early chemical evolution of the Galaxy, and the history of star formation in the Milky Way. By analogy we can learn about those epochs of galaxy formation in the distant past that are currently at such high redshifts that they are beyond the reach of even the largest existing telescopes, a technique some call “near-field cosmology”. While H, He, and some Li came out of the Big Bang, all other elements were formed in stars, and were dispersed by supernovae and stellar winds into the gas from which subsequent stellar generations formed. The ejecta from supernovae played the most important role in the early Universe. SN models have many parameters, including the history of the progenitor star (initial mass, mass loss history, internal nucleosynthesis history prior to the explosion, etc), the details of the explosion (energy, ejected mass, mixing) etc. There are vigorous groups pursuing the details of these models both theoretically and computationally in the US and abroad. But there are so many free or poorly known parameters that these efforts are best guided by observations of metal-poor stars

Multi-scale immunoepidemiological modeling of within-host and between-host HIV dynamics: systematic review of mathematical models.

OBJECTIVE: The objective of this study is to conduct a systematic review of multi-scale HIV immunoepidemiological models to improve our understanding of the synergistic impact between the HIV viral-immune dynamics at the individual level and HIV transmission dynamics at the population level. BACKGROUND: While within-host and between-host models of HIV dynamics have been well studied at a single scale, connecting the immunological and epidemiological scales through multi-scale models is an emerging method to infer the synergistic dynamics of HIV at the individual and population levels. METHODS: We reviewed nine articles using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) framework that focused on the synergistic dynamics of HIV immunoepidemiological models at the individual and population levels. RESULTS: HIV immunoepidemiological models simulate viral immune dynamics at the within-host scale and the epidemiological transmission dynamics at the between-host scale. They account for longitudinal changes in the immune viral dynamics of HIV+ individuals, and their corresponding impact on the transmission dynamics in the population. They are useful to analyze the dynamics of HIV super-infection, co-infection, drug resistance, evolution, and treatment in HIV+ individuals, and their impact on the epidemic pathways in the population. We illustrate the coupling mechanisms of the within-host and between-host scales, their mathematical implementation, and the clinical and public health problems that are appropriate for analysis using HIV immunoepidemiological models. CONCLUSION: HIV immunoepidemiological models connect the within-host immune dynamics at the individual level and the epidemiological transmission dynamics at the population level. While multi-scale models add complexity over a single-scale model, they account for the time varying immune viral response of HIV+ individuals, and the corresponding impact on the time-varying risk of transmission of HIV+ individuals to other susceptibles in the population