167 research outputs found
Report of the x ray and gamma ray sensors panel
Overall five major areas of technology are recommended for development in order to meet the science requirements of the Astrotech 21 mission set. These are: detectors for high resolution gamma ray spectroscopy, cryogenic detectors for improved x ray spectral and spatial resolution, advanced x ray charge coupled devices (CCDs) for higher energy resolution and larger format, extension to higher energies, liquid and solid position sensitive detectors for improving stopping power in the energy range 5 to 500 keV and 0.2 to 2 MeV. Development plans designed to achieve the desired capabilities on the time scales required by the technology freeze dates have been recommended in each of these areas
Coordinated surface activities in Variovorax paradoxus EPS
<p>Abstract</p> <p>Background</p> <p><it>Variovorax paradoxus </it>is an aerobic soil bacterium frequently associated with important biodegradative processes in nature. Our group has cultivated a mucoid strain of <it>Variovorax paradoxus </it>for study as a model of bacterial development and response to environmental conditions. Colonies of this organism vary widely in appearance depending on agar plate type.</p> <p>Results</p> <p>Surface motility was observed on minimal defined agar plates with 0.5% agarose, similar in nature to swarming motility identified in <it>Pseudomonas aeruginosa </it>PAO1. We examined this motility under several culture conditions, including inhibition of flagellar motility using Congo Red. We demonstrated that the presence of a wetting agent, mineral, and nutrient content of the media altered the swarming phenotype. We also demonstrated that the wetting agent reduces the surface tension of the agar. We were able to directly observe the presence of the wetting agent in the presence and absence of Congo Red, and found that incubation in a humidified chamber inhibited the production of wetting agent, and also slowed the progression of the swarming colony. We observed that swarming was related to both carbon and nitrogen sources, as well as mineral salts base. The phosphate concentration of the mineral base was critical for growth and swarming on glucose, but not succinate. Swarming on other carbon sources was generally only observed using M9 salts mineral base. Rapid swarming was observed on malic acid, d-sorbitol, casamino acids, and succinate. Swarming at a lower but still detectable rate was observed on glucose and sucrose, with weak swarming on maltose. Nitrogen source tests using succinate as carbon source demonstrated two distinct forms of swarming, with very different macroscopic swarm characteristics. Rapid swarming was observed when ammonium ion was provided as nitrogen source, as well as when histidine, tryptophan, or glycine was provided. Slower swarming was observed with methionine, arginine, or tyrosine. Large effects of mineral content on swarming were seen with tyrosine and methionine as nitrogen sources. Biofilms form readily under various culture circumstances, and show wide variance in structure under different conditions. The amount of biofilm as measured by crystal violet retention was dependent on carbon source, but not nitrogen source. Filamentous growth in the biofilm depends on shear stress, and is enhanced by continuous input of nutrients in chemostat culture.</p> <p>Conclusion</p> <p>Our studies have established that the beta-proteobacterium <it>Variovorax paradoxus </it>displays a number of distinct physiologies when grown on surfaces, indicative of a complex response to several growth parameters. We have identified a number of factors that drive sessile and motile surface phenotypes. This work forms a basis for future studies using this genetically tractable soil bacterium to study the regulation of microbial development on surfaces.</p
Advanced techniques for high resolution spectroscopic observations of cosmic gamma-ray sources
An advanced gamma-ray spectrometer that is currently in development is described. It will obtain a sensitivity of 0.0001 ph/sq cm./sec in a 6 hour balloon observation and uses innovative techniques for background reduction and source imaging
Temperature Sensitivity of Surface Channels on High-Purity Germanium Detectors
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Radiation Damage Effects on High-Purity Germanium Detectors
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Formation of Re-Aggregated Neonatal Porcine Islet Clusters Improves In Vitro Function and Transplantation Outcome
Neonatal porcine islet-like cell clusters (NPICCs) are a promising source for islet cell transplantation. Excellent islet quality is important to achieve a cure for type 1 diabetes. We investigated formation of cell clusters from dispersed NPICCs on microwell cell culture plates, evaluated the composition of re-aggregated porcine islets (REPIs) and compared in vivo function by transplantation into diabetic NOD-SCID IL2rγ−/− (NSG) mice with native NPICCs. Dissociation of NPICCs into single cells and re-aggregation resulted in the formation of uniform REPI clusters. A higher prevalence of normoglycemia was observed in diabetic NSG mice after transplantation with a limited number (n = 1500) of REPIs (85.7%) versus NPICCs (n = 1500) (33.3%) (p < 0.05). Transplanted REPIs and NPICCs displayed a similar architecture of endocrine and endothelial cells. Intraperitoneal glucose tolerance tests revealed an improved beta cell function after transplantation of 1500 REPIs (AUC glucose 0–120 min 6260 ± 305.3) as compared to transplantation of 3000 native NPICCs (AUC glucose 0–120 min 8073 ± 536.2) (p < 0.01). Re-aggregation of single cells from dissociated NPICCs generates cell clusters with excellent functionality and improved in vivo function as compared to native NPICCs
Spectra of GRB 970228 from the Transient Gamma-Ray Spectrometer
Visible afterglow counterparts have now been detected for two GRBs (970228
and 970508) but are absent, with ratios at least two
orders of magnitude lower, for other GRBs, e.g., 970828. The causes of this
variation are unknown. Any correspondence which could be discovered between the
gamma-ray properties of a GRB and its would be useful,
both in determining the GRB mechanisms, and in allocating resources for
counterpart searches and studies. This paper presents the gamma-ray spectra of
GRB 970228 as measured by the Transient Gamma-Ray Spectrometer and comments on
characteristics of this GRB compared to others that do and do not have
observable counterparts.Comment: To appear in "Gamma-Ray Bursts", Proceedings of the 4th Huntsville
Symposium, 1997, eds. C. Meegan, R. Preece, and T. Koshut, 5 pages, LaTeX
(aipproc.sty incl.), 3 figs. (epsfig.sty
The CO2 reduction potential for the Europeanindustry via direct electrification of heat supply(power-to-heat)
The decarbonisation of industry is a bottleneck for the EU's 2050 target of climate neutrality. Replacing fossil fuels with low-carbon electricity is at the core of this challenge; however, the aggregate electrification potential and resulting system-wide CO2 reductions for diverse industrial processes are unknown. Here, we present the results from a comprehensive bottom-up analysis of the energy use in 11 industrial sectors (accounting for 92% of Europe's industry CO2 emissions), and estimate the technological potential for industry electrification in three stages. Seventy-eight per cent of the energy demand is electrifiable with technologies that are already established, while 99% electrification can be achieved with the addition of technologies currently under development. Such a deep electrification reduces CO2 emissions already based on the carbon intensity of today's electricity (∼300 gCO2 kWhel-1). With an increasing decarbonisation of the power sector IEA: 12 gCO2 kWhel-1 in 2050), electrification could cut CO2 emissions by 78%, and almost entirely abate the energy-related CO2 emissions, reducing the industry bottleneck to only residual process emissions. Despite its decarbonisation potential, the extent to which direct electrification will be deployed in industry remains uncertain and depends on the relative cost of electric technologies compared to other low-carbon options
TGRS Observation of the Galactic Center Annihilation Line
The TGRS (Transient Gamma-Ray Spectrometer) experiment is a high-resolution
germanium detector launched on the WIND satellite on Nov. 1, 1994. Although
primarily intended to study gamma-ray bursts and solar flares, TGRS also has
the capability of studying slower transients (e.g. x-ray novae) and certain
steady sources. We present here results on the narrow 511 keV annihilation line
from the general direction of the Galactic Center accumulated over the period
Jan. 1995 through Oct. 1995. These results were obtained from the TGRS
occultation mode, in which a lead absorber occults the Galactic Center region
for 1/4 of each spacecraft rotation, thus chopping the 511 keV signal. The
occulted region is a band in the sky of width 16 degrees that passes through
the Galactic Center. We detect the narrow annihilation line from the galactic
center with flux = .
The data are consistent with a single point source at the galactic center, but
a distributed source of extent up to ~30 degrees cannot be ruled out. No
evidence for temporal variability on time scales longer than 1 month was found.Comment: 11 pages + 5 Postscript figure
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