17,309 research outputs found
Study of outgassing and decomposition of Space Shuttle heat protection tiles, fillers and adhesive
A purge and trap technique which was employed to collect and separate the chemicals desorbing from the space shuttle heat protection tiles is described. The instrumentation included a mass spectrometer and gas chromatograph
Bottom-Up Reconstruction Scenarios for (un)constrained MSSM Parameters at the LHC
We consider some specific inverse problem or "bottom-up" reconstruction
strategies at the LHC for both general and constrained MSSM parameters,
starting from a plausibly limited set of sparticle identification and mass
measurements, using mainly gluino/squark cascade decays, plus eventually the
lightest Higgs boson mass. For the three naturally separated sectors of:
gaugino/Higgsino, squark/slepton, and Higgs parameters, we examine different
step-by-step algorithms based on rather simple, entirely analytical, inverted
relations between masses and basic MSSM parameters. This includes also
reasonably good approximations of some of the relevant radiative correction
calculations. We distinguish the constraints obtained for a general MSSM from
those obtained with universality assumptions in the three different sectors.
Our results are compared at different stages with the determination from more
standard "top-down" fit of models to data, and finally combined into a global
determination of all the relevant parameters. Our approach gives complementary
information to more conventional analysis, and is not restricted to the
specific LHC measurement specificities. In addition, the bottom-up
renormalization group evolution of general MSSM parameters, being an important
ingredient in this framework, is illustrated as a new publicly available option
of the MSSM spectrum calculation code "SuSpect".Comment: 52 pages, 22 figures. Slight reorganization of sections, a few more
results for the neutralino sector, one appendix added on neutralino sector
calculation details. Version to appear in Phys. Rev.
The Infrared Massive Stellar Content of M83
We present an analysis of archival Spitzer images and new ground-based and
Hubble Space Telescope (HST) near-infrared (IR) and optical images of the field
of M83 with the goal of identifying rare, dusty, evolved massive stars. We
present point source catalogs consisting of 3778 objects from
Infrared Array Camera (IRAC) Band 1 (3.6 m) and Band 2 (4.5 m), and
975 objects identified in Magellan 6.5m FourStar near-IR and
images. A combined catalog of coordinate matched near- and mid-IR point sources
yields 221 objects in the field of M83. Using this photometry we identify 185
massive evolved stellar candidates based on their location in color-magnitude
and color-color diagrams. We estimate the background contamination to our
stellar candidate lists and further classify candidates based on their
appearance in Wide Field Camera 3 (WFC3) observations of M83. We find 49
strong candidates for massive stars which are very promising objects for
spectroscopic follow-up. Based on their location in a versus
diagram, we expect at least 24, or roughly 50%, to be confirmed as red
supergiants.Comment: 32 pages, 23 figures, accepted for publication in A&
The Practitioner\u27s Corner: An exploration of municipal active living charter development and advocacy
Background: Numerous municipal active living-‐related charters have been adopted to promote physical activity in Canada throughout the past decade. Despite this trend, there are few published critical examinations of the process through which charters are developed and used.
Purpose: Thus, the purpose of this study was to establish greater understanding of active living charter development and advocacy.
Methods: Semi-‐structured interviews were conducted with eight primary contributors to different active living-‐related charters across Ontario, Canada. Interview questions explored participants’ experiences developing and advocating for an active living charter. Interviews were analyzed using open, axial, and selective coding.
Results and Conclusions: Participants consistently described a process whereby an impetus triggered the development of a charter, which was subsequently adopted by regional or municipal council. Continued advocacy to develop awareness of the charter and to promote desired outcomes in the community was valued and the capacity of the working group as well as the local political context played pivotal roles in determining how the charter was implemented. Outcomes were, however, only objectively evaluated in one case that was described – evaluation being a process that many participants thought was omitted in regard to their own charter. This work provides practical guidance for health professionals developing regional active living charters as a component of broader advocacy efforts
Qualitative evaluation of a flush air data system at transonic speeds and high angles of attack
Flight tests were performed on an F-14 aircraft to evaluate the use of flush pressure orifices on the nose section for obtaining air data at transonic speeds over a large range of flow angles. This program was part of a flight test and wind tunnel program to assess the accuracies of such systems for general use on aircraft. It also provided data to validate algorithms developed for the shuttle entry air data system designed at NASA Langley. Data were obtained for Mach numbers between 0.60 and 1.60, for angles of attack up to 26.0 deg, and for sideslip angles up to 11.0 deg. With careful calibration, a flush air data system with all flush orifices can provide accurate air data information over a large range of flow angles. Several orificies on the nose cap were found to be suitable for determination of stagnation pressure. Other orifices on the nose section aft of the nose cap were shown to be suitable for determination of static pressure. Pairs of orifices on the nose cap provided the most sensitive measurements for determining angles of attack and sideslip, although orifices located farther aft on the nose section could also be used
Advanced Silicon Avalanche Photodiodes on NASA's Global Ecosystem Dynamics Investigation (GEDI) Mission
Silicon Avalanche Photodiodes (APDs) are used in NASAs Global Ecosystem Dynamics Investigation (GEDI) which was launched in December 2018 and is currently measuring the Earths vegetation vertical structure from the International Space Station. The APDs were specially made for space lidar with a much lower hole-to-electron ionization coefficient ratio (k-factor ~0.008) than that of commercially available silicon APDs in order to reduce the APD excess noise from the randomness of the avalanche gain. A silicon heater resistor was used under the APD chip to heat the device up to 70C and improve its quantum efficiency at 1064 nm laser wavelength while maintaining a low dark current such that the overall signal to noise ratio is improved. Special APD protection circuits were used to raise the overload damage threshold to prevent device damage from strong laser return by specular surfaces, such as still water bodies, and space radiation events. The APD and a hybrid transimpedance amplifier circuit were hermetically sealed in a package with a sufficiently low leak rate to ensure multi-year operation lifetime in space. The detector assemblies underwent a series of pre-launch tests per NASA Goddard Environmental Verification Standard for space qualification. They have performed exactly as expected with GEDI in orbit. A detailed description of the GEDI detector design, signal and noise model, and test results are presented in this paper
Constitutional Law - Equal Protection - School Desegregation - Keyes v. School District Number One
Feedback control of thermal lensing in a high optical power cavity
This paper reports automatic compensation of strong thermal lensing in a suspended 80 m optical cavity with sapphire test mass mirrors. Variation of the transmitted beam spot size is used to obtain an error signal to control the heating power applied to the cylindrical surface of an intracavity compensation plate. The negative thermal lens created in the compensation plate compensates the positive thermal lens in the sapphire test mass, which was caused by the absorption of the high intracavity optical power. The results show that feedback control is feasible to compensate the strong thermal lensing expected to occur in advanced laser interferometric gravitational wave detectors. Compensation allows the cavity resonance to be maintained at the fundamental mode, but the long thermal time constant for thermal lensing control in fused silica could cause difficulties with the control of parametric instabilities.This research was supported by the Australian
Research Council and the Department of Education,
Science and Training and by the U.S. National Science Foundation,
through LIGO participation in the HOPF
Unusual Metabolism and Hypervariation in the Genome of a Gracilibacterium (BD1-5) from an Oil-Degrading Community.
The candidate phyla radiation (CPR) comprises a large monophyletic group of bacterial lineages known almost exclusively based on genomes obtained using cultivation-independent methods. Within the CPR, Gracilibacteria (BD1-5) are particularly poorly understood due to undersampling and the inherent fragmented nature of available genomes. Here, we report the first closed, curated genome of a gracilibacterium from an enrichment experiment inoculated from the Gulf of Mexico and designed to investigate hydrocarbon degradation. The gracilibacterium rose in abundance after the community switched to dominance by Colwellia Notably, we predict that this gracilibacterium completely lacks glycolysis, the pentose phosphate and Entner-Doudoroff pathways. It appears to acquire pyruvate, acetyl coenzyme A (acetyl-CoA), and oxaloacetate via degradation of externally derived citrate, malate, and amino acids and may use compound interconversion and oxidoreductases to generate and recycle reductive power. The initial genome assembly was fragmented in an unusual gene that is hypervariable within a repeat region. Such extreme local variation is rare but characteristic of genes that confer traits under pressure to diversify within a population. Notably, the four major repeated 9-mer nucleotide sequences all generate a proline-threonine-aspartic acid (PTD) repeat. The genome of an abundant Colwellia psychrerythraea population has a large extracellular protein that also contains the repeated PTD motif. Although we do not know the host for the BD1-5 cell, the high relative abundance of the C. psychrerythraea population and the shared surface protein repeat may indicate an association between these bacteria.IMPORTANCE CPR bacteria are generally predicted to be symbionts due to their extensive biosynthetic deficits. Although monophyletic, they are not monolithic in terms of their lifestyles. The organism described here appears to have evolved an unusual metabolic platform not reliant on glucose or pentose sugars. Its biology appears to be centered around bacterial host-derived compounds and/or cell detritus. Amino acids likely provide building blocks for nucleic acids, peptidoglycan, and protein synthesis. We resolved an unusual repeat region that would be invisible without genome curation. The nucleotide sequence is apparently under strong diversifying selection, but the amino acid sequence is under stabilizing selection. The amino acid repeat also occurs in a surface protein of a coexisting bacterium, suggesting colocation and possibly interdependence
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