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  • *Protons  (1)
  • Cytoplasm/metabolism  (1)
  • Fluctuations  (1)
  • Geosciences (General)  (1)
  • 2005-2009  (3)
  • 1
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    Sound scattering by several zooplankton groups. I. Experimental determination of dominant scattering mechanisms (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1998. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 103 (1998): 225-235, doi:10.1121/1.421469.
    Description: The acoustic scattering properties of live individual zooplankton from several gross anatomical groups have been investigated. The groups involve (1) euphausiids (Meganyctiphanes norvegica) whose bodies behave acoustically as a fluid material, (2) gastropods (Limacina retroversa) whose bodies include a hard elastic shell, and (3) siphonophores (Agalma okeni or elegans and Nanomia cara) whose bodies contain a gas inclusion (pneumatophore). The animals were collected from ocean waters off New England (Slope Water, Georges Bank, and the Gulf of Maine). The scattering properties were measured over parts or all of the frequency range 50 kHz to 1 MHz in a laboratory-style pulse-echo setup in a large tank at sea using live fresh specimens. Individual echoes as well as averages and ping-to-ping fluctuations of repeated echoes were studied. The material type of each group is shown to strongly affect both the overall echo level and pattern of the target strength versus frequency plots. In this first article of a two-part series, the dominant scattering mechanisms of the three animal types are determined principally by examining the structure of both the frequency spectra of individual broadband echoes and the compressed pulse (time series) output. Other information is also used involving the effect on overall levels due to (1) animal orientation and (2) tissue in animals having a gas inclusion (siphonophores). The results of this first paper show that (1) the euphausiids behave as weakly scattering fluid bodies and there are major contributions from at least two parts of the body to the echo (the number of contributions depends upon angle of orientation and shape), (2) the gastropods produce echoes from the front interface and possibly from a slow-traveling circumferential (Lamb) wave, and (3) the gas inclusion of the siphonophore dominates the echoes, but the tissue plays a role in the scattering and is especially important when analyzing echoes from individual animals on a ping-by-ping basis. The results of this paper serve as the basis for the development of acoustic scattering models in the companion paper [Stanton et al., J. Acoust. Soc. Am. 103, 236–253 (1998)].
    Description: This work was supported by the National Science Foundation Grant No. OCE- 9201264, the U.S. Office of Naval Research Grant Nos. N00014-89-J-1729 and N00014-95-1-0287, and the MIT/ WHOI Joint Graduate Education Program.
    Keywords: Bioacoustics ; Acoustic wave scattering ; Fluctuations
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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    PAPER (OA)
  • 2
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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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    PAPER CURRENT
  • 3
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    Earth Science Programs (2007)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This slide presentation reviews the JPL missions that enabling Earth Sciences, past, present and future. Included is a list of the National Academy of Sciences Space Studies Board of the recommended missions that are of interest to JPL.
    Keywords: Geosciences (General)
    Type: Japan Aerospace Exploration Agency (JAXA); Jun 15, 2007; Pasadena, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
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