2,717 research outputs found
NASA Flight Planning Branch Space Shuttle Lessons Learned
Planning products and procedures that allowed the mission Flight Control Teams and the Astronaut crews to plan, train and fly every Space Shuttle mission were developed by the Flight Planning Branch at the NASA Johnson Space Center in Houston, Texas. As the Space Shuttle Program came to a close, lessons learned were collected from each phase of the successful execution of these Space Shuttle missions. Specific examples of how roles and responsibilities of console positions that develop the crew and vehicle attitude timelines have been analyzed and will be discussed. Additionally, the relationships and procedural hurdles experienced through international collaboration have molded operations. These facets will be explored and related to current and future operations with the International Space Station and future vehicles. Along with these important aspects, the evolution of technology and continual improvement of data transfer tools between the Space Shuttle and ground team has also defined specific lessons used in improving the control team s effectiveness. Methodologies to communicate and transmit messages, images, and files from the Mission Control Center to the Orbiter evolved over several years. These lessons were vital in shaping the effectiveness of safe and successful mission planning and have been applied to current mission planning work in addition to being incorporated into future space flight planning. The critical lessons from all aspects of previous plan, train, and fly phases of Space Shuttle flight missions are not only documented in this paper, but are also discussed regarding how they pertain to changes in process and consideration for future space flight planning
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"The dearest of our possessions": applying Floridi's information privacy concept in models of information behavior and information literacy
This conceptual paper argues for the value of an approach to privacy in the digital information environment informed by Luciano Floridi's philosophy of information and information ethics. This approach involves achieving informational privacy, through the features of anonymity and obscurity, through an optimal balance of ontological frictions. This approach may be used to modify models for information behavior and for information literacy, giving them a fuller and more effective coverage of privacy issues in the infosphere. For information behavior, the Information Seeking and Communication Model, and the Information Grounds conception, are most appropriate for this purpose. For information literacy, the metaliteracy model, using a modification a privacy literacy framework, is most suitable
Methamphetamine and Viagra Use: Relationship to Sexual Risk Behaviors
Recent studies show that Viagra and methamphetamine use are associated with unprotected anal intercourse among men who have sex with men (MSM). In Long Beach, California, we have reported on an association between Viagra use and the use of amphetamines during sex. The current research investigated the use of both Viagra and amphetamine in men in Long Beach, California. Data on 1,839 men recruited into HIV prevention and testing programs were collected using the Risk Behavior Assessment. A generalized logit model was constructed comparing ever having used both amphetamine and Viagra together and separately, as compared to never having used either (referent). Men who used both methamphetamine and Viagra showed a significantly higher prevalence of hepatitis B, syphilis, and HIV compared to those who used only one or neither drug. Of the 1,794 complete cases, 11.1% (199/1794) had used both amphetamine and Viagra. Of 20 potential risk and protective factors for use of amphetamine and Viagra, 12 were significant predictors: ever used gamma-hydroxybutyrate (GHB), ever used cocaine, ever used ecstasy, being infected with HIV, race = White compared to other, ever having hepatitis B, ever using crack, ever given money to have sex, living in a hotel, ever been in drug treatment, and ever using heroin. The protective factor was being heterosexual. Viagra use was associated with insertive, and methamphetamine was associated with receptive, anal intercourse. GHB use appears to play a more important role than previously thought
Integer quantum Hall transition in the presence of a long-range-correlated quenched disorder
We theoretically study the effect of long-ranged inhomogeneities on the
critical properties of the integer quantum Hall transition. For this purpose we
employ the real-space renormalization-group (RG) approach to the network model
of the transition. We start by testing the accuracy of the RG approach in the
absence of inhomogeneities, and infer the correlation length exponent nu=2.39
from a broad conductance distribution. We then incorporate macroscopic
inhomogeneities into the RG procedure. Inhomogeneities are modeled by a smooth
random potential with a correlator which falls off with distance as a power
law, r^{-alpha}. Similar to the classical percolation, we observe an
enhancement of nu with decreasing alpha. Although the attainable system sizes
are large, they do not allow one to unambiguously identify a cusp in the
nu(alpha) dependence at alpha_c=2/nu, as might be expected from the extended
Harris criterion. We argue that the fundamental obstacle for the numerical
detection of a cusp in the quantum percolation is the implicit randomness in
the Aharonov-Bohm phases of the wave functions. This randomness emulates the
presence of a short-range disorder alongside the smooth potential.Comment: 10 pages including 6 figures, revised version as accepted for
publication in PR
The effect of Ku on telomere replication time is mediated by telomere length but is independent of histone tail acetylation
Peer reviewedPublisher PD
Searches for very high energy gamma rays from blazars with CANGAROO-III telescope in 2005-2009
We have searched for very high energy (VHE) gamma rays from four blazars
using the CANGAROO-III imaging atmospheric Cherenkov telescope. We report the
results of the observations of H 2356-309, PKS 2155-304, PKS 0537-441, and 3C
279, performed from 2005 to 2009, applying a new analysis to suppress the
effects of the position dependence of Cherenkov images in the field of view. No
significant VHE gamma ray emission was detected from any of the four blazars.
The GeV gamma-ray spectra of these objects were obtained by analyzing Fermi/LAT
archival data. Non-simultaneous wide range (radio to VHE gamma-ray bands)
spectral energy distributions (SEDs) including CANGAROO-III upper limits, GeV
gamma-ray spectra, and archival data are discussed using a one-zone synchrotron
self-Compton (SSC) model in combination with a external Compton (EC) radiation.
The HBLs (H 2356-309 and PKS 2155-304) can be explained by a simple SSC model,
and PKS 0537-441 and 3C 279 are well modeled by a combination of SSC and EC
model. We find a consistency with the blazar sequence in terms of strength of
magnetic field and component size.Comment: 11 pages, 8 figures, Accepted for publication in Astroparticle
Physic
Hepatic gene expression in flounder chronically exposed to multiply polluted estuarine sediment: Absence of classical exposure âbiomarkerâ signals and induction of inflammatory, innate immune and apoptotic pathways
The effects of chronic long term exposure to multiply-polluted environments on fish are not well understood, but environmental surveys suggest that such exposure may cause a variety of pathologies, including cancers. Transcriptomic profiling has recently been used to assess gene expression in European flounder (Platichthys flesus) living in several polluted and clean estuaries. However, the gene expression changes detected were not unequivocally elicited by pollution, most likely due to the confounding effects of natural estuarine ecosystem variables. In this study flounder from an uncontaminated estuary were held on clean or polluted sediments in mesocosms, allowing control of variables such as salinity, temperature, and diet. After 7 months flounder were removed from each mesocosm and hepatocytes prepared from fish exposed to clean or polluted sediments. The hepatocytes were treated with benzo(a)pyrene (BAP), estradiol (E2), copper, a mixture of these three, or with the vehicle DMSO. A flounder cDNA microarray was then used to measure hepatocyte transcript abundance after each treatment. The results show that long term chronic exposure to a multiply-polluted sediment causes increases in the expression of mRNAs coding for proteins of the endogenous apoptotic program, of innate immunity and inflammation. Contrary to expectation, the expression of mRNAs which are commonly used as biomarkers of environmental exposure to particular contaminants were not changed, or were changed contrary to expectation. However, acute treatment of hepatocytes from flounder from both clean and polluted sediments with BAP or E2 caused the expected changes in the expression of these biomarkers. Thus transcriptomic analysis of flounder exposed long-term to chronic pollution causes a different pattern of gene expression than in fish acutely treated with single chemicals, and reveals novel potential biomarkers of environmental contaminant exposure. These novel biomarkers include Diablo, a gene involved in apoptotic pathways and highly differentially regulated by both chronic and acute exposure to multiple pollutants
Trading or coercion? Variation in male mating strategies between two communities of East African chimpanzees
Across taxa, males employ a variety of mating strategies, including sexual coercion and the provision, or trading, of resources. Biological Market theory (BMT) predicts that trading of commodities for mating opportunities should exist only when males cannot monopolise access to females and/or obtain mating by force, in situations where power differentials between males are low; both coercion and trading have been reported for chimpanzees (Pan troglodytes). Here, we investigate whether the choice of strategy depends on the variation in male power differentials, using data from two wild communities of East African chimpanzees (P.t. schweinfurthii): the structurally despotic Sonso community (Budongo, Uganda) and the structurally egalitarian M-group (Mahale, Tanzania). We found evidence of sexual coercion by male Sonso chimpanzees, and of tradingâof grooming for matingâby M-group males; females traded sex for neither meat nor protection from male aggression. Our results suggest that the despotismâegalitarian axis influences strategy choice: male chimpanzees appear to pursue sexual coercion when power differentials are large and trading when power differentials are small and coercion consequently ineffective. Our findings demonstrate that trading and coercive strategies are not restricted to particular chimpanzee subspecies; instead, their occurrence is consistent with BMT predictions. Our study raises interesting, and as yet unanswered, questions regarding female chimpanzeesâ willingness to trade sex for grooming, if doing so represents a compromise to their fundamentally promiscuous mating strategy. It highlights the importance of within-species cross-group comparisons and the need for further study of the relationship between mating strategy and dominance steepness
A review of elliptical and disc galaxy structure, and modern scaling laws
A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their
models to describe the radial distribution of stars in `nebulae'. This article
reviews the progress since then, providing both an historical perspective and a
contemporary review of the stellar structure of bulges, discs and elliptical
galaxies. The quantification of galaxy nuclei, such as central mass deficits
and excess nuclear light, plus the structure of dark matter halos and cD galaxy
envelopes, are discussed. Issues pertaining to spiral galaxies including dust,
bulge-to-disc ratios, bulgeless galaxies, bars and the identification of
pseudobulges are also reviewed. An array of modern scaling relations involving
sizes, luminosities, surface brightnesses and stellar concentrations are
presented, many of which are shown to be curved. These 'redshift zero'
relations not only quantify the behavior and nature of galaxies in the Universe
today, but are the modern benchmark for evolutionary studies of galaxies,
whether based on observations, N-body-simulations or semi-analytical modelling.
For example, it is shown that some of the recently discovered compact
elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to
appear in "Planets, Stars and Stellar
Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references
incl. many somewhat forgotten, pioneer papers. Original submission to
Springer: 07-June-201
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