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  • Instrumentation and Photography  (12)
  • Lunar and Planetary Science and Exploration  (3)
  • Cytoplasm/metabolism
  • Geosciences (General)
  • 1
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    Mechanism of Na+/H+ antiporting (2007)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2007-08-11
    Description: Na+/H+ antiporters are central to cellular salt and pH homeostasis. The structure of Escherichia coli NhaA was recently determined, but its mechanisms of transport and pH regulation remain elusive. We performed molecular dynamics simulations of NhaA that, with existing experimental data, enabled us to propose an atomically detailed model of antiporter function. Three conserved aspartates are key to our proposed mechanism: Asp164 (D164) is the Na+-binding site, D163 controls the alternating accessibility of this binding site to the cytoplasm or periplasm, and D133 is crucial for pH regulation. Consistent with experimental stoichiometry, two protons are required to transport a single Na+ ion: D163 protonates to reveal the Na+-binding site to the periplasm, and subsequent protonation of D164 releases Na+. Additional mutagenesis experiments further validated the model.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Arkin, Isaiah T -- Xu, Huafeng -- Jensen, Morten O -- Arbely, Eyal -- Bennett, Estelle R -- Bowers, Kevin J -- Chow, Edmond -- Dror, Ron O -- Eastwood, Michael P -- Flitman-Tene, Ravenna -- Gregersen, Brent A -- Klepeis, John L -- Kolossvary, Istvan -- Shan, Yibing -- Shaw, David E -- New York, N.Y. -- Science. 2007 Aug 10;317(5839):799-803.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉D. E. Shaw Research, New York, NY 10036, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17690293" target="_blank"〉PubMed〈/a〉
    Keywords: Aspartic Acid/metabolism ; Binding Sites ; Computer Simulation ; Crystallization ; Cytoplasm/metabolism ; Escherichia coli/growth & development/*metabolism ; Escherichia coli Proteins/*chemistry/*metabolism ; Hydrogen Bonding ; Hydrogen-Ion Concentration ; Ion Transport ; *Models, Biological ; Models, Molecular ; Mutagenesis ; Periplasm/metabolism ; Protein Conformation ; Protein Structure, Secondary ; *Protons ; Sodium/*metabolism ; Sodium-Hydrogen Antiporter/*chemistry/*metabolism
    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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  • 2
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    Thermal Stability of the AVIRIS On-Board Calibrator (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The AVIRIS On-Board Calibrator (OBC) provides essential data for refining the calibration of each AVIRIS data run. Annual improvement to the AVIRIS sensor and laboratory calibration accuracy has resulted in increasingly high demands on the stability of the OBC. Since the 1995 flight season, the OBC could track the stability of the spectrometer alignment to the 2% level, a significant improvement over previous years. The major contributor to this 2% stability was the conversion from a constant-current bulb power supply to an intensity-based active feedback power supply. Given the high sensor signal-to-noise ratio, improving the OBC to track 1% or 0.5% changes was highly desirable. Achieving stability better than 2% required an examination of the mechanisms affecting stability.
    Keywords: Instrumentation and Photography
    Type: Summaries of the Seventh JPL Airborne Earth Science Workshop January 12-16, 1998; Volume 1; 105-110; JPL-Publ-97-21-Vol-1
    Format: text
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  • 3
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    Calibration of the Airborne Visible/Infrared Imaging Spectrometer in the Laboratory (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Imaging spectrometry data must be spectrally, radiometrically and geometrically calibrated in order to: 1) derive physical parameters from measured spectral radiance, 2) compare data acquired from different regions and at different times, 3) compare and analyze the imaging spectrometry data with data acquired from other calibrated sensors, and 4) compare and analyze data with results from computer models. The calibration of AVIRIS data is the process by which laboratory characterization data are applied to raw instrument data (digitized number versus spectral channels) to produce quantitative spectra (radiance versus wavelength) for each image pixel in units of spectral radiance. The AVIRIS sensor and calibration process are described by Vane and the application of the calibration data to the raw digital data is described by Green. This calibration process is validated for in-flight performance of the sensor using a rigorous ground-truth campaign. This workshop paper reviews the laboratory characterization data set that is used in the AVIRIS calibration process. The laboratory measurements used to acquire the calibration data are divided into three classes: 1) spectral calibration, 2) radiometric calibration, and 3) spatial calibration.
    Keywords: Instrumentation and Photography
    Type: Summaries of the Sixth Annual JPL Airborne Earth Science Workshop; Volume 1; 39-48; NASA/CR/96-113073
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  • 4
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    Quantum Efficient Detectors for Use in Absolute Calibration (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The trap or quantum efficient detector has a quantum efficiency of greater than 0.98 for the region from 450 to 900 nm. The region of flattest response is from 600 to 900 nm. The QED consists of three windowless Hamamatsu silicon detectors. The QED was mounted below AVIRIS to monitor the Spectralon panel for changes in radiance during radiometric calibration. The next step is to permanently mount the detector to AVIRIS and monitor the overall radiance of scenes along with calibration.
    Keywords: Instrumentation and Photography
    Type: Summaries of the Seventh JPL Airborne Earth Science Workshop January 12-16, 1998; Volume 1; 97-103; JPL-Publ-97-21-Vol-1
    Format: text
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  • 5
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    Backscattering enhancement for Marshall-Palmer distributed rains for a W-band nadir-pointing radar with a finite beam width (2005)
    In:  Other Sources
    Details
    Publication Date: 2018-06-11
    Description: In this paper, we expand the previous theory to be applied to a generic drop size distribution with spheroidal raindrops including spherical raindrops. Results will be used to discuss the multiple scattering effects on the backscatter measurements acquired by a W-band nadir-pointing radar.
    Keywords: Lunar and Planetary Science and Exploration
    Type: International Geoscience and Remote Sensing Symposium
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  • 6
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    In-Situ Radars For Sounding of Mars and Europa (1998)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: One of fundamental problems in the Mars science is the determination of Martian volatile budget. Of Primary importance is the knowledge of the planetwide distribution of ground ice.
    Keywords: Lunar and Planetary Science and Exploration
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  • 7
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    Mercury-Cadmium-Telluride Focal Plane Array Performance Under Non-Standard Operating Conditions (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper highlights a new technique that allows the Teledyne Scientific & Imaging LLC TCM6604A Mercury-Cadmium-Telluride (MCT) Focal Plane Array (FPA) to operate at room temperature. The Teledyne MCT FPA has been a standard in Imaging Spectroscopy since its creation in the 1980's. This FPA has been used in applications ranging from space instruments such as CRISM, M3 and ARTEMIS to airborne instruments such as MaRS and the Next Generation AVIRIS Instruments1. Precise focal plane alignment is always a challenge for such instruments. The current FPA alignment process results in multiple cold cycles requiring week-long durations, thereby increasing the risk and cost of a project. These alignment cycles are necessary because optimal alignment is approached incrementally and can only be measured with the FPA and Optics at standard operating conditions, requiring a cold instrument. Instruments using this FPA are normally cooled to temperatures below 150K for the MCT FPA to properly function. When the FPA is run at higher temperatures the dark current increases saturating the output. This paper covers the prospect of warm MCT FPA operation from a theoretical and experimental perspective. We discuss the empirical models and physical laws that govern MCT material properties and predict the optimal settings that will result in the best MCT PA performance at 300K. Theoretical results are then calculated for the proposed settings. We finally present the images and data obtained using the actual system with the warm MCT FPA settings. The paper concludes by emphasizing the strong positive correlation between the measured values and the theoretical results.
    Keywords: Instrumentation and Photography
    Type: IEEE Aerospace; Mar 05, 2011 - Mar 12, 2011; Big Sky, MT; United States
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  • 8
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    AXIOM: Advanced X-Ray Imaging of the Magnetosphere (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Planetary plasma and magnetic field environments can be studied in two complementary ways by in situ measurements, or by remote sensing. While the former provide precise information about plasma behaviour, instabilities and dynamics on local scales, the latter offers the global view necessary to understand the overall interaction of the magnetospheric plasma with the solar wind. Some parts of the Earth's magnetosphere have been remotely sensed, but the majority remains unexplored by this type of measurements. Here we propose a novel and more elegant approach employing remote X-ray imaging techniques, which are now possible thanks to the relatively recent discovery of solar wind charge exchange X-ray emissions in the vicinity of the Earth's magnetosphere. In this article we describe how an appropriately designed and located X-ray telescope, supported by simultaneous in situ measurements of the solar wind, can be used to image the dayside magnetosphere, magnetosheath and bow shock, with a temporal and spatial resolution sufficient to address several key outstanding questions concerning how the solar wind interacts with the Earth's magnetosphere on a global level. Global images of the dayside magnetospheric boundaries require vantage points well outside the magnetosphere. Our studies have led us to propose AXIOM: Advanced X-ray Imaging Of the Magnetosphere, a concept mission using a Vega launcher with a LISA Pathfinder-type Propulsion Module to place the spacecraft in a Lissajous orbit around the Earth Moon L1 point. The model payload consists of an X-ray Wide Field Imager, capable of both imaging and spectroscopy, and an in situ plasma and magnetic field measurement package. This package comprises a Proton-Alpha Sensor, designed to measure the bulk properties of the solar wind, an Ion Composition Analyser, to characterize the minor ion populations in the solar wind that cause charge exchange emission, and a Magnetometer, designed to measure the strength and direction of the solar wind magnetic field. We also show simulations that demonstrate how the proposed X-ray telescope design is capable of imaging the predicted emission from the dayside magnetosphere with the sensitivity and cadence required to achieve the science goals of the mission.
    Keywords: Instrumentation and Photography
    Type: GSFC.JA.5094.2011
    Format: application/pdf
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  • 9
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    Silicon micromachined broad band light source (2004)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: A micro electromechanical system (MEMS) broad band incandescent light source includes three layers: a top transmission window layer; a middle filament mount layer; and a bottom reflector layer. A tungsten filament with a spiral geometry is positioned over a hole in the middle layer. A portion of the broad band light from the heated filament is reflective off the bottom layer. Light from the filament and the reflected light of the filament are transmitted through the transmission window. The light source may operate at temperatures of 2500 K or above. The light source may be incorporated into an on board calibrator (OBC) for a spectrometer.
    Keywords: Instrumentation and Photography
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  • 10
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    The Portable Remote Imaging Spectrometer (PRISM) Coastal Ocean Sensor (2012)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Instrumentation and Photography
    Type: Optical Remote Sensing of the Environment (ORS); Jun 24, 2012 - Jun 28, 2012; Monterey, CA; United States
    Format: text
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