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  • Geophysics  (137)
  • Female  (39)
  • Instrumentation and Photography  (38)
  • 2000-2004  (214)
  • 2000  (214)
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  • 2000-2004  (214)
Year
  • 11
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    Natural selection and parallel speciation in sympatric sticklebacks (2000)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2000-01-15
    Description: Natural selection plays a fundamental role in most theories of speciation, but empirical evidence from the wild has been lacking. Here the post-Pleistocene radiation of threespine sticklebacks was used to infer natural selection in the origin of species. Populations of sticklebacks that evolved under different ecological conditions show strong reproductive isolation, whereas populations that evolved independently under similar ecological conditions lack isolation. Speciation has proceeded in this adaptive radiation in a repeatable fashion, ultimately as a consequence of adaptation to alternative environments.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rundle, H D -- Nagel, L -- Wenrick Boughman, J -- Schluter, D -- New York, N.Y. -- Science. 2000 Jan 14;287(5451):306-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4 Canada. rundle@zoology.ubc.ca〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10634785" target="_blank"〉PubMed〈/a〉
    Keywords: Adaptation, Physiological ; Animals ; *Biological Evolution ; British Columbia ; DNA, Mitochondrial/genetics ; Female ; Fishes/classification/*genetics/physiology ; Male ; Phylogeny ; Probability ; Reproduction ; *Selection, Genetic ; Sexual Behavior, Animal
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 12
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    Reduced food intake and body weight in mice treated with fatty acid synthase inhibitors (2000)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2000-07-06
    Description: With the escalation of obesity-related disease, there is great interest in defining the mechanisms that control appetite and body weight. We have identified a link between anabolic energy metabolism and appetite control. Both systemic and intracerebroventricular treatment of mice with fatty acid synthase (FAS) inhibitors (cerulenin and a synthetic compound C75) led to inhibition of feeding and dramatic weight loss. C75 inhibited expression of the prophagic signal neuropeptide Y in the hypothalamus and acted in a leptin-independent manner that appears to be mediated by malonyl-coenzyme A. Thus, FAS may represent an important link in feeding regulation and may be a potential therapeutic target.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Loftus, T M -- Jaworsky, D E -- Frehywot, G L -- Townsend, C A -- Ronnett, G V -- Lane, M D -- Kuhajda, F P -- DC02979/DC/NIDCD NIH HHS/ -- DK09623/DK/NIDDK NIH HHS/ -- New York, N.Y. -- Science. 2000 Jun 30;288(5475):2379-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10875926" target="_blank"〉PubMed〈/a〉
    Keywords: Acetyl-CoA Carboxylase/antagonists & inhibitors/metabolism ; Animals ; Appetite/*drug effects ; Appetite Depressants/administration & dosage/chemical synthesis/*pharmacology ; Cerulenin/pharmacology ; Dose-Response Relationship, Drug ; Eating/drug effects ; Enzyme Inhibitors/administration & dosage/chemical synthesis/*pharmacology ; Fasting ; Fatty Acid Synthases/*antagonists & inhibitors/metabolism ; Female ; Hypothalamus/drug effects/metabolism ; Injections, Intraventricular ; Leptin/metabolism ; Liver/drug effects/metabolism ; Male ; Malonyl Coenzyme A/metabolism ; Mice ; Mice, Inbred BALB C ; Neurons/drug effects/metabolism ; Neuropeptide Y/administration & dosage/genetics/metabolism/pharmacology ; RNA, Messenger/genetics/metabolism ; Weight Loss/*drug effects
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 13
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    Transmission of vesicular stomatitis virus from infected to noninfected black flies co-feeding on nonviremic deer mice (2000)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2000-01-22
    Description: Vesicular stomatitis is an economically important arboviral disease of livestock. Viremia is absent in infected mammalian hosts, and the mechanism by which insects become infected with the causative agents, vesicular stomatitis viruses, remains unknown. Because infected and noninfected insects potentially feed on the same host in nature, infected and noninfected black flies were allowed to feed on the same host. Viremia was not detected in the host after infection by a black fly bite, but because noninfected black flies acquired the virus while co-feeding on the same host with infected black flies, it is concluded that a viremic host is not necessary for an insect to be infected with the virus. Thus co-feeding is a mechanism of infection for an insect-transmitted virus.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mead, D G -- Ramberg, F B -- Besselsen, D G -- Mare, C J -- New York, N.Y. -- Science. 2000 Jan 21;287(5452):485-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Veterinary Science and Microbiology, and University Animal Care, 1117 East Lowell, University of Arizona, Tucson, AZ 85721, USA. dmead@u.arizona.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10642550" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Disease Reservoirs ; Feeding Behavior ; Female ; Insect Vectors/physiology/*virology ; *Peromyscus/virology ; Random Allocation ; Rhabdoviridae Infections/*transmission/virology ; Simuliidae/physiology/*virology ; Vesicular stomatitis Indiana virus/isolation & purification/*physiology ; Viremia
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 14
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    Compact CH4 sensor based on difference frequency mixing of diode lasers in quasi-phasematched LiNbO3 (2000)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A compact, portable and robust room temperature CH4 sensor is reported. By difference frequency mixing a 500 mW alpha-DFB diode laser at 1066 nm and an erbium-doped fiber amplified 1574 nm DFB diode laser in periodically poled lithium niobate up to 7 (mu)W of narrowband radiation at 3.3 microns is generated. Real-time monitoring of CH4 over a 7 day period using direct absorption in an open-path multipass cell (L = 36 m) demonstrates a detection precision of +/- 14 ppb.
    Keywords: Instrumentation and Photography
    Type: Optics communications (ISSN 0030-4018); Volume 175; 4-6; 461-8
    Format: text
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  • 15
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    Martian Neutron Energy Spectrometer (MANES) (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: High energy charged particles of extragalactic, galactic, and solar origin collide with spacecraft structures and planetary atmospheres. These primaries create a number of secondary particles inside the structures or on the surfaces of planets to produce a significant radiation environment. This radiation is a threat to long term inhabitants and travelers for interplanetary missions and produces an increased risk of carcinogenesis, central nervous system (CNS) and DNA damage. Charged particles are readily detected; but, neutrons, being electrically neutral, are much more difficult to monitor. These secondary neutrons are reported to contribute 30-60% of the dose equivalent in the Shuttle and MIR station. The Martian atmosphere has an areal density of 37 g/sq cm primarily of carbon dioxide molecules. This shallow atmosphere presents fewer mean free paths to the bombarding cosmic rays and solar particles. The secondary neutrons present at the surface of Mars will have undergone fewer generations of collisions and have higher energies than at sea level on Earth. Albedo neutrons produced by collisions with the Martian surface material will also contribute to the radiation environment. The increased threat of radiation damage to humans on Mars occurs when neutrons of higher mean energy traverse the thin, dry Martian atmosphere and encounter water in the astronaut's body. Water, being hydrogeneous, efficiently moderates the high energy neutrons thereby slowing them as they penetrate deeply into the body. Consequently, greater radiation doses can be deposited in or near critical organs such as the liver or spleen than is the case on Earth. A second significant threat is the possibility of a high energy heavy ion or neutron causing a DNA double strand break in a single strike.
    Keywords: Instrumentation and Photography
    Type: Concepts and Approaches for Mars Exploration; Part 2; 213-214; LPI-Contrib-1062-Pt-2
    Format: text
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    NASA TECHNICAL REPORTS
  • 16
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    Acousto-Optic Imaging Spectrometers for Mars Surface Science (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: NASA's long term plan for Mars sample collection and return requires a highly streamlined approach for spectrally characterizing a landing site, documenting the mineralogical make-up of the site and guiding the collections of samples which represent the diversity of the site. Ideally, image data should be acquired at hundreds of VIS and IR wavelengths, in order to separately distinguish numerous anticipated species, using principal component analysis and linear unmixing. Cameras with bore-sighted point spectrometers can acquire spectra of isolated scene elements, but it requires 10(exp 2) to 10(exp 2) successive motions and precise relative pointing knowledge in order to create a single data cube which qualifies as a spectral map. These and other competing science objectives have to be accomplished within very short lander/rover operational lifetime (a few sols). True, 2-D imaging spectroscopy greatly speeds up the data acquisition process, since the spectra of all pixels in the scene are collected at once. This task can be accomplished with cameras that use electronically tunable acousto-optic tunable filters (AOTFs) as the optical tuning element. AOTFs made from TeO2 are now a mature technology, and operate at wavelengths from near-UV to about 5 microns. Because of incremental improvements in the last few years, present generation devices are rugged, radiation-hard and operate at temperatures down to at least 150K so they can be safely integrated into the ambient temperature optics of in-situ instruments such as planetary or small-body landers. They have been used for ground-based astronomy, and were also baselined for the ST-4 Champollion IR comet lander experiment (CIRCLE), prior to cancellation of the ST-4 mission last year. AIMS (for Acousto-optic Imaging spectrometer), is a prototype lander instrument which is being built at GSFC with support by the NASA OSS Advanced Technologies and Mission Studies, Mars Instrument Definition and Development Program (MIDP). AIMS is capable of tunable spectroscopic imaging of surface mineralogy, ices and dust between 0.5 and 2.4 microns, at a resolving power (lambda/delta lambda) which is typically several hundred. The design spatial resolution, similar to IMP and SSI, will allow mapping at scales down to about 1 cm.
    Keywords: Instrumentation and Photography
    Type: Concepts and Approaches for Mars Exploration; Part 1; 125-126; LPI-Contrib-1062
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  • 17
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    The Next Generation MOD: A Microchip Amino Acid Analyzer for Detecting Extraterrestrial Life (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The MOD (Mars Organic Detector) instrument which has selected for the definition phase of the BEDS package on the 2005 Mars Explorer Program spacecraft is designed to simply detect the presence of amino acids in Martian surface samples at a sensitivity of a few parts per billion (ppb). An additional important aspect of amino acid analyses of Martian samples is identifying and quantifying which compounds are present, and also distinguishing those produced abiotically from those synthesized by either extinct or extant life. Amino acid homochirality provides an unambiguous way of distinguishing between abiotic vs. biotic origins. Proteins made up of mixed D- and L-amino acids would not likely have been efficient catalysts in early organisms because they could not fold into bioactive configurations such as the a-helix. However, enzymes made up of all D-amino acids function just as well as those made up of only L-amino acids, but the two enzymes use the opposite stereoisomeric substrates. There are no biochemical reasons why L-amino acids would be favored over Damino acids. On Earth, the use of only L-amino acids in proteins by life is probably simply a matter of chance. We assume that if proteins and enzymes were a component of extinct or extant life on Mars, then amino acid homochirality would have been a requirement. However, the possibility that Martian life was (or is) based on D-amino acids would be equal to that based on L-amino acids. The detection of a nonracemic mixture of amino acids in a Martian sample would be strong evidence for the presence of an extinct or extant biota on Mars. The finding of an excess of D-amino acids would provide irrefutable evidence of unique Martian life that could not have been derived from seeding the planet with terrestrial life (or the seeding of the Earth with Martian life). In contrast, the presence of racemic amino acids, along with non-protein amino acids such as alpha-aminoisobutyric acid and isovaline, would be indicative of an abiotic origin, although we have to consider the possibility that the racemic amino acids were generated from the racemization of biotically produced amino acids.
    Keywords: Instrumentation and Photography
    Type: Concepts and Approaches for Mars Exploration; Part 2; 209-210; LPI-Contrib-1062-Pt-2
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    NASA TECHNICAL REPORTS
  • 18
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    Forecasts and postanalysis of mountain wave temperature fluctuations during SOLVE (2000)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Fall Meeting; San Francisco, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 19
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    General Differences between Early and Late Stages of BATSE Gamma-Ray Bursts (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The early and late stages of gamma-ray bursts are studied in a statistical analysis of the large sample of long BATSE events. The primary peak is used as the boundary between the early and late stages of emission. Significant differences are found between the stages: the early stage is shorter, it has harder emission, and it becomes a smaller fraction of the total burst duration for burst groups of decreasing intensity.
    Keywords: Geophysics
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    NASA TECHNICAL REPORTS
  • 20
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    8-9 and 14-15 Micron Two-Color 640x486 GaAs/AlGaAs Quantum Well Infrared Photodetector (QWIP) Focal Plane Array Camera (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: An optimized long-wavelength two-color Quantum Well Infrared Photodetector (QWIP) device structure has been designed. This device structure was grown on a three inch semi-insulating GaAs substrate by molecular beam epitaxy (MBE). This wafer was processed into several 640x486 format monolithically integrated 8-9 and 14-15 micron two color (or dual wavelength) QWIP focal plane arrays (FPAs). These FPAs were then hybridized to 640x486 silicon CMOS readout multiplexers. A thinned (i.e., substrate removed) FPA hybrid was integrated into a liquid helium cooled dewar to perform electrical and optical characterization and to demonstrate simultaneous two-color imagery. The 8-9 micron detectors in the FPA have shown background limited performance (BLIP) at 70 K operating temperature, at 300 K background with f/2 cold stop. The 14-15 micron detectors of the FPA have reached BLIP at 40 K operating temperature at the same background conditions. In this presentation we discuss the performance of this long-wavelength dualband QWIP FPA in quantum efficiency, detectivity, noise equivalent temperature difference (NEAT), uniformity, and operability.
    Keywords: Instrumentation and Photography
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