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  • 1
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    Settling Velocity and Grain Shape of Maerl Biogenic Gravel (2014)
    Society for Sedimentary Geology (SEPM)
    Details
    Publication Date: 2014-08-28
    Description: A bstract :  The importance of a grain-size-dependent shape metric, convexity, for determining the unusual settling velocity characteristics of maërl, a variety of unattached coralline algae, has been quantified by modeling of settling-tube data. A modification of the general settling-velocity equation of Ferguson and Church (2004) , involving a dependence of the drag coefficient-related constant, C 2 , on grain size, produces a satisfactory fit to the experimental observations. For a given grain size and at Reynolds numbers greater than ~ 220, maërl grains experience greater drag than is predicted for natural quartz grains by Ferguson and Church (2004) because of this grain-size-dependent roughness. Subsequent detailed measurements of maërl grain shape using microscopic image analysis confirm a strong positive linear relationship between grain roughness, quantified by the reciprocal of convexity, and grain size. This departure from the ideal settling characteristics of siliciclastic gravel is hypothesized to explain the observed propensity of maërl, under suitable hydrodynamic conditions, to form beach deposits with a low percentage of sand. Maërl samples from three different sedimentary environments (open marine, intertidal, and beach) exhibit different linear relationships between roughness and grain size, probably resulting from different degrees of abrasion due to a combination of different wave climates and transport histories. This spatial variability in grain texture suggests that a general equation for maërl settling velocity is not possible. However, for maërl, and other branched sediment types, it may only be necessary to measure the convexity of the middle and largest size fractions to estimate the linear variation of C 2 with grain size, resulting in an accurate estimate of the settling-velocity curve. In the broader context of physical sedimentology, our results indicate that, over a range of bottom current conditions between 200 and 250 mm s –1 , where the settling curve of maërl is flat and grain-size invariant relative to siliciclastic sediment, a larger part of the maërl grain-size distribution can remain in suspension compared to the siliciclastic sediment. This contrast in physical properties may be an effective process for the spatial separation of coarse siliciclastic and biogenic sediment.
    Print ISSN: 1527-1404
    Topics: Geosciences
    Published by Society for Sedimentary Geology (SEPM)
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  • 2
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    Gating of CaMKII by cAMP-regulated protein phosphatase activity during LTP (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-06-25
    Description: Long-term potentiation (LTP) at the Schaffer collateral-CA1 synapse involves interacting signaling components, including calcium (Ca2+)/calmodulin-dependent protein kinase II (CaMKII) and cyclic adenosine monophosphate (cAMP) pathways. Postsynaptic injection of thiophosphorylated inhibitor-1 protein, a specific inhibitor of protein phosphatase-1 (PP1), substituted for cAMP pathway activation in LTP. Stimulation that induced LTP triggered cAMP-dependent phosphorylation of endogenous inhibitor-1 and a decrease in PP1 activity. This stimulation also increased phosphorylation of CaMKII at Thr286 and Ca2+-independent CaMKII activity in a cAMP-dependent manner. The blockade of LTP by a CaMKII inhibitor was not overcome by thiophosphorylated inhibitor-1. Thus, the cAMP pathway uses PP1 to gate CaMKII signaling in LTP.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Blitzer, R D -- Connor, J H -- Brown, G P -- Wong, T -- Shenolikar, S -- Iyengar, R -- Landau, E M -- DK52054/DK/NIDDK NIH HHS/ -- GM54508/GM/NIGMS NIH HHS/ -- NS33646/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1998 Jun 19;280(5371):1940-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Bronx VA Medical Center and Department of Psychiatry, Mount Sinai School of Medicine, New York, NY 10029, USA. rb2@doc.mssm.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9632393" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium-Calmodulin-Dependent Protein Kinase Type 2 ; Calcium-Calmodulin-Dependent Protein Kinases/antagonists & inhibitors/*metabolism ; *Carrier Proteins ; Cyclic AMP/analogs & derivatives/*metabolism/pharmacology ; Cyclic AMP-Dependent Protein Kinases/metabolism ; Electric Stimulation ; Enzyme Inhibitors/metabolism/pharmacology ; Hippocampus/*metabolism ; In Vitro Techniques ; *Intracellular Signaling Peptides and Proteins ; *Long-Term Potentiation ; Male ; Phosphoprotein Phosphatases/antagonists & inhibitors/*metabolism ; Phosphorylation ; Protein Phosphatase 1 ; RNA-Binding Proteins/metabolism/pharmacology ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; Synapses/*metabolism ; Thionucleotides/pharmacology
    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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  • 3
    Electronic Resource
    Electronic Resource
    Amorphous m-Phenoxylenes as Potential Lubricants. (1961)
    s.l. : American Chemical Society
    Journal of chemical & engineering data 6 (1961), S. 125-127 
    Details
    ISSN: 1520-5134
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/je60009a025
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  • 4
    Electronic Resource
    Electronic Resource
    Electrical Properties of Phenothiazine (1962)
    [s.l.] : Nature Publishing Group
    Nature 193 (1962), S. 361-362 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the present work, phenothiazine was purified by chromatography, multiple vacuum sublimations and zone-refining. Fig. 1 shows the results obtained at potential stresses of 76 and 760 V./cm. on a sample of phenothiazine which had been chromatographed, sublimed, zone-refined and re-sublimed. Using ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/193361a0
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic Properties of Imidazole (1961)
    [s.l.] : Nature Publishing Group
    Nature 191 (1961), S. 379-380 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1. Specific resistivity of imidazole. O, run 2, 720 V./cm.; ?, run 3, 72 V./cm.; Q, run 4, 72 V./cm. Supporting evidence for this view has now been found in a study of the resistivity of imidazole. Imidazole is extensively hydrogen-bonded as adduced from its relatively high melting and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/191379a0
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic Properties of Phenazine (1961)
    [s.l.] : Nature Publishing Group
    Nature 189 (1961), S. 827-828 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We have now found that this relationship apparently also holds true for the heterocyclic compound phenazine. From the dependence on temperature of the resistivity (Fig. la) of phenazine in the range of 98-143 C., we determined the energy gap as 2-1 eV. This compares favourably with the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/189827a0
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  • 7
    Electronic Resource
    Electronic Resource
    Weak surface anchoring of liquid crystals (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 399 (1999), S. 338-340 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Current nematic liquid-crystal (LC) displays rely on voltage-induced reorientation of the director (the average molecular direction) within the bulk of the LC layer. In these devices, the surface region of the LC is strongly anchored to the cell walls and does not undergo reorientation at normal ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/20646
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  • 8
    Electronic Resource
    Electronic Resource
    Voltage-dependent anchoring of a nematic liquid crystal on a grating surface (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 392 (1998), S. 365-367 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The switching properties of most liquid-crystal electro-optic devices rely mainly on the reorientation of the average molecular direction (director) within the bulk of the liquid-crystal layer. Reorientation of the director at or near the surfaces of the layer usually has an insignificant ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/32849
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  • 9
    Electronic Resource
    Electronic Resource
    Grating coupled liquid crystal waveguides using nematics and smectics (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3603-3607 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical properties of grating coupled waveguides are theoretically modeled and practically demonstrated using nematic and smectic liquid crystals as thin (0.7 μm) waveguide layers. Voltage induced reorientation of the liquid crystal is shown to lead to large changes in reflectivity and transmissivity when the angle of incidence initially corresponds to a guided mode resonance. Time resolved measurements using these thin cells show that the switching time for the nematic phase can be faster than the smectic phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352918
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  • 10
    Electronic Resource
    Electronic Resource
    Diffraction grating pitch modulation using lead lanthanum zirconate titanate (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1691-1693 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interferographic exposure followed by fast atom etching is used to write a sinusoidal diffraction grating into the surface of a lead lanthanum zirconium titanate (PLZT) wafer. A silver overlayer evaporated onto the grating allows the excitation of surface plasmon polaritons by incident radiation thus leading to sharp resonance dips in the angular dependent reflectivity. A second silver layer is evaporated onto the back of the wafer to allow ac electric fields to be applied across the sample. The large electrostrictive effect in PLZT causes a significant modulation in the grating groove pitch and hence surface plasmon polariton resonance angle which is very accurately quantified using a lock-in differential measurement. This simple configuration is able to measure pitch changes as small as 4.2×10−4 nm (a strain of 4.8×10−7).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109578
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