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  • 1
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    Marine vibrators: the new phase of seismic exploration (2018)
    Wiley
    Details
    Publication Date: 2018
    Description: ABSTRACT Marine seismic vibrators are generally considered to be less intrusive than airguns from an environmental perspective. This is because they emit their energy spread out in time, rather than in a single, high‐intensity pulse. There are also significant geophysical benefits associated with marine vibrators, and they stem from the ability to specify in detail the output acoustic waveform. The phase can be specified independently at each frequency. Such detailed control cannot be achieved with conventional airgun sources, where the phase can only be modified using simple overall time delays. The vibrator phase can be employed in several different ways: it can be applied to the overall source phase in a sequence so that it varies from one source point to the next; it can be applied to the individual vibrators within the source array so the source directivity is changed; it can be applied to the overall source phase of each source in a simultaneous source acquisition. Carefully designed phase sequences can attenuate the residual source noise, and this in turn allows extra source points to be interleaved between the conventional ones. For these extra source points, the relative phase of the vibrators within the array can be chosen to create a transverse gradient source, which illuminates the earth predominantly in directions out of the plane of the sail line without left/right ambiguity. If seismic vibrator data are acquired using interleaved conventional and transverse gradient sweeps, more information is collected per kilometre of vessel travel than is the case in conventional acquisition. This richer data acquisition leads to the possibility of acquiring all the necessary seismic data in a shorter time. Three‐dimensional reconstruction techniques are used to recover the same image quality that would have been obtained using the conventional, more time‐consuming acquisition. For a marine vibrator to be suitable for these techniques it must, in general terms, have ‘high fidelity’. The precise device specifications are defined through realistic end‐to‐end simulations of the physical systems and the processing. The specifications are somewhat more onerous than for a conventional vibrator, but they are achievable. A prototype vibrator that satisfies these requirements has been built. In a simulated case study of a three‐dimensional deep‐water ocean bottom node survey, the seismic data could have been acquired using marine vibrators in one third of the time that it would have taken using airguns.
    Print ISSN: 0016-8025
    Electronic ISSN: 1365-2478
    Topics: Geosciences , Physics
    Published by Wiley
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  • 2
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    High temperature intensifies negative density dependence of fitness in red flour beetles (2015)
    Wiley
    Details
    Publication Date: 2015-02-09
    Description: Competition for food, space, or other depletable resources has strong impacts on the fitness of organisms and can lead to a pattern known as negative density dependence, where fitness decreases as population density increases. Yet, many resources that have strong impacts on fitness are nondepletable (e.g., moisture or temperature). How do these nondepletable resources interact with depletable resources to modify negative density dependence? We tested the hypothesis that negative density dependence is modulated by temperature in red flour beetles and tested the prediction that the strength of negative density dependence should decrease as temperature decreases. We measured the number of eggs laid, offspring development time, and the number of offspring that reached maturity at three temperatures and two food treatment combinations as we simultaneously manipulated adult population density. We demonstrated that low temperatures weaken negative density dependence in the number of eggs laid; this pattern was most evident when food was abundant. Density had no effect on development time, but low temperatures increased development time. The percent of eggs that emerged as adults decreased with both density and temperature and increased with food. Temperature, an abiotic driver, can thus modulate density-dependent processes in ectotherms. Therefore, models of population growth for ectotherms should incorporate the effects of temperature. Ectotherms rely on external temperature to optimize many processes, from locomotion to metabolism, and even reproductive success. We demonstrate that competition for resources is also a temperature-dependent process. Negative density dependence nearly disappears at low temperatures, and is strongest at optimal temperatures.
    Electronic ISSN: 2045-7758
    Topics: Biology
    Published by Wiley
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  • 3
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    Regulation of leucine metabolism in man: a stable isotope study (1981)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1981-12-04
    Description: Leucine catabolism is regulated by either of the first two degradative steps: (reversible) transamination to the keto acid or subsequent decarboxylation. A method is described to measure rates of leucine transamination, reamination, and keto acid oxidation. The method is applied directly to humans by infusing the nonradioactive tracer, L-[15N,1-13C]leucine. Leucine transamination was found to be operating several times faster than the keto acid decarboxylation and to be of equal magnitude in adult human males under two different dietary conditions, postabsorptive and fed. These results indicate that decarboxylation, not transamination, is the rate-limiting step in normal human leucine metabolism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Matthews, D E -- Bier, D M -- Rennie, M J -- Edwards, R H -- Halliday, D -- Millward, D J -- Clugston, G A -- AM-25994/AM/NIADDK NIH HHS/ -- HD-10667/HD/NICHD NIH HHS/ -- RR-00954/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1981 Dec 4;214(4525):1129-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7302583" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Carbon Isotopes ; Humans ; Kinetics ; Leucine/*metabolism ; Male ; Models, Biological ; Nitrogen Isotopes ; Oxidation-Reduction
    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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  • 4
    Electronic Resource
    Electronic Resource
    Time resolved photoluminescence studies in a reverse biased quantum well laser structure (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2497-2499 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of photoluminescence decay time in a reverse biased GaAs/AlGaAs graded index separate confined heterostructure single quantum well (GRINSCH-SQW) laser, as a function of bias voltage at temperatures of 20, 70, and 150 K. For certain bias voltages and temperatures, we observe extremely fast escape times of optically generated carriers. We propose a simple model based on photogenerated electron recombination in the quantum well, and escape via direct tunneling out of the lower bound electronic level, thermally assisted tunneling out of the upper weakly bound state, or thermionic emission over the barrier. We have performed a theoretical calculation of each of these processes and show that the data agrees well with the direct and thermally assisted tunneling times and that the thermionic emission term underestimates the times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108160
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  • 5
    Electronic Resource
    Electronic Resource
    Herbicides and Selective Phytotoxicity (1951)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology 2 (1951), S. 199-230 
    Details
    ISSN: 0066-4294
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pp.02.060151.001215
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  • 6
    Electronic Resource
    Electronic Resource
    Recent advances in the use of labelled amino-acids to quantitate protein metabolism in man
    Amsterdam : Elsevier
    International Journal of Radiation Applications & Instrumentation. Part 39 (1988), S. 523 
    Details
    ISSN: 0883-2889
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0883-2889(88)90229-8
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  • 7
    Electronic Resource
    Electronic Resource
    A resin-based method for the preparation of molecular nitrogen for ^1^5N analysis from urinary and plasma components
    Amsterdam : Elsevier
    Analytical Biochemistry 123 (1982), S. 249-254 
    Details
    ISSN: 0003-2697
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0003-2697(82)90442-0
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  • 8
    Electronic Resource
    Electronic Resource
    Geodetic Measurements by Radar (1949)
    [s.l.] : Nature Publishing Group
    Nature 164 (1949), S. 1005-1006 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] HART1 has referred to the potential uses of radar in geodesy and photogrammetry. The War Office has now granted permission to publish details of geodetic observations made in Italy by radar during May–June 1945. The general principle of these observations was that an aircraft, a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1641005a0
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of Duchenne muscular dystrophy on muscle protein synthesis (1982)
    [s.l.] : Nature Publishing Group
    Nature 296 (1982), S. 165-167 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We studied seven normal fed adult men aged 22-65 yr and five boys with Duchenne muscular dystrophy, aged 12-1 Syr. Three of the patients were wheelchair bound and the two youngest were on the verge of becoming so. Investigations of these subjects using radioactive isotopes would not have been ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/296165a0
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular analysis of eight mutations in FBN1 (1999)
    Springer
    Human genetics 〈Berlin〉 105 (1999), S. 587-597 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Mutations in the gene encoding extracellular glycoprotein fibrillin-1 (FBN1) cause Marfan syndrome (MFS) and other related connective tissue disorders. In this study, eight mutations have been detected in MFS patients by heteroduplex analysis. These comprise two missense mutations, C1835Y and C2258Y in calcium-binding epidermal growth factor-like domains, two nonsense mutations, R1541X and R2394X in transforming growth factor β1-binding protein-like domains, one splice site mutation, which has been detected previously, and three small insertions or deletions resulting in a frameshift. Fibroblast cells have been established from seven of the MFS patients and the biochemical effects of the mutations on fibrillin-1 synthesis and secretion assessed by pulse-chase analysis. Each cysteine mutation resulted in the delayed secretion of fibrillin-1 and both nonsense and frameshift mutations caused reduced levels of synthesis and/or deposition of fibrillin-1. Indirect immunofluorescence and rotary shadowing electron microscopy analysis of fibrillin microfibrils revealed no major differences between normal and patient samples. We discuss the relative merits of the biochemical techniques used in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004399900190
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