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  • Polymer and Materials Science  (3)
  • Estuaries  (2)
  • 03. Hydrosphere::03.01. General::03.01.07. Physical and biogeochemical interactions  (1)
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 39 (1996), S. 591-614 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular dynamics simulations of the water-solvated, β-hairpin-forming linear peptide Y-Q-N-P-D-G-S-Q-A (one-letter amino acid code) [F. J. Blanco et al. (1993) J. Am. Chem. Soc. 115, 5887-5888] were performed at simulation temperatures of 278 K and 270 K. At 278 K, the overall β-hairpin state remained stable for approximately 2.06 ns, after which it underwent an unfolding transition to a more disordered, random coil-like state that was maintained for the remainder of the 3.50-ns simulation. A comparison of experimental Hα-Cα order parameters determined at 278 K with order parameters derived from the simulation revealed that the β-hairpin state is consistent with the experimental results, whereas the random coil-like state yields order parameters that are all much lower than the experimental values. This indicates that the random coil-like state is not highly populated in the experimental system. An examination of the dynamic behavior of the simulated peptide/solvent system indicated that a lower temperature may yield a more stable trajectory. At 270 K, the β-hairpin conformation remained stable for approximately 2.32 ns, after which the peptide again unfolded and maintained a less-ordered state for the remainder of the 3.50-ns simulation. The less-ordered state observed at 270 K is more compact than the disordered state observed at 278 K; the former may represent a folding intermediate. The folded state is stabilized primarily by a number of transient hydrogen bonding interactions, including hydrogen bonds between Tyr-1 O and Ala-9 HN, between Asn-3 HN and Ser-7 O, and between the side chain of Asn-3 and backbone groups of Asp-5, Gly-6, and Ser-7. The 270 K simulation was restarted at 2.10 ns, with a single loose nuclear Over-hauser effect (NOE) upper-bound distance restraint of 5.5 Å added between Gln-2 Hα and Gln-8 Hα. This single restraint maintained folded conformations for the remaining 10.50 ns of the trajectory. The restraint was frequently violated (i.e., the restraint potential frequently took on nonzero values) during the period between about 0.24 and 6.51 ns of the restrained trajectory. Between about 6.51 and 8.04 ns of the restrained trajectory, the restraint remained well-satisfied, demonstrating a transiently stable, alternate-folded conformational state during this period. These results indicate that even long (by today's standards), ∼ 1 ns timescale trajectories may not always be sufficient to prove the long-term stability of the native state in simulations of biomolecules, and that apparently converged states may only be metastable. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 25 (1980), S. 2435-2438 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 390-396 
    ISSN: 0142-2421
    Keywords: Environmental AES ; Electron-Stimulated Desorption ; insulating surfaces ; aluminium oxide ; silicon oxide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Charging processes on the bulk oxides Al2O3, ZrO2 and SiO2 occurring during Auger Electron Spectroscopy (AES) are studied. All samples experience a negative charge-up under the following parameters: electron beam energy 〉1 keV, current density 〉10-2 A cm-2 and different angles of incidence. The samples show strong history effects as a function of previous irradiation damage. For charge compensation, Environmental Auger Electron Spectroscopy with O2 gas is applied; several traditional methods were applied for comparison. Charging of SiO2 and ZrO2 could be reduced considerably in an O2 environmental pressure of 〈5×10-8 Torr. Charging of Al2O3 could be compensated completely in this oxygen environment. It is shown that for the compensation of the electron beam effects, including electron-stimulated desorption and carbon contamination of the surface, an O2 atmosphere of 5×10-8 Torr is more efficient than using an auxiliary electron gun or low-energy positive ions. It is also more efficient than an Ar environment of 1×10-4 Torr. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
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  • 4
    Publication Date: 2012-02-03
    Description: The performance of 36 models (22 ocean color models and 14 biogeochemical ocean circulation models (BOGCMs)) that estimate depth-integrated marine net primary productivity (NPP) was assessed by comparing their output to in situ 14C data at the Bermuda Atlantic Time series Study (BATS) and the Hawaii Ocean Time series (HOT) over nearly two decades. Specifically, skill was assessed based on the models' ability to estimate the observed mean, variability, and trends of NPP. At both sites, more than 90% of the models underestimated mean NPP, with the average bias of the BOGCMs being nearly twice that of the ocean color models. However, the difference in overall skill between the best BOGCM and the best ocean color model at each site was not significant. Between 1989 and 2007, in situ NPP at BATS and HOT increased by an average of nearly 2% per year and was positively correlated to the North Pacific Gyre Oscillation index. The majority of ocean color models produced in situ NPP trends that were closer to the observed trends when chlorophyll-a was derived from high-performance liquid chromatography (HPLC), rather than fluorometric or SeaWiFS data. However, this was a function of time such that average trend magnitude was more accurately estimated over longer time periods. Among BOGCMs, only two individual models successfully produced an increasing NPP trend (one model at each site). We caution against the use of models to assess multiannual changes in NPP over short time periods. Ocean color model estimates of NPP trends could improve if more high quality HPLC chlorophyll-a time series were available
    Description: Published
    Description: GB3020
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: restricted
    Keywords: marine primary productivity models ; BATS HOT trends ; multidecadal climate forcing ; 03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling ; 03. Hydrosphere::03.01. General::03.01.07. Physical and biogeochemical interactions ; 03. Hydrosphere::03.04. Chemical and biological::03.04.01. Biogeochemical cycles ; 03. Hydrosphere::03.04. Chemical and biological::03.04.04. Ecosystems
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 32 (2018): 389-416, doi:10.1002/2017GB005790.
    Description: Carbon cycling in the coastal zone affects global carbon budgets and is critical for understanding the urgent issues of hypoxia, acidification, and tidal wetland loss. However, there are no regional carbon budgets spanning the three main ecosystems in coastal waters: tidal wetlands, estuaries, and shelf waters. Here we construct such a budget for eastern North America using historical data, empirical models, remote sensing algorithms, and process‐based models. Considering the net fluxes of total carbon at the domain boundaries, 59 ± 12% (± 2 standard errors) of the carbon entering is from rivers and 41 ± 12% is from the atmosphere, while 80 ± 9% of the carbon leaving is exported to the open ocean and 20 ± 9% is buried. Net lateral carbon transfers between the three main ecosystem types are comparable to fluxes at the domain boundaries. Each ecosystem type contributes substantially to exchange with the atmosphere, with CO2 uptake split evenly between tidal wetlands and shelf waters, and estuarine CO2 outgassing offsetting half of the uptake. Similarly, burial is about equal in tidal wetlands and shelf waters, while estuaries play a smaller but still substantial role. The importance of tidal wetlands and estuaries in the overall budget is remarkable given that they, respectively, make up only 2.4 and 8.9% of the study domain area. This study shows that coastal carbon budgets should explicitly include tidal wetlands, estuaries, shelf waters, and the linkages between them; ignoring any of them may produce a biased picture of coastal carbon cycling.
    Description: NASA Interdisciplinary Science program Grant Number: NNX14AF93G; NASA Carbon Cycle Science Program Grant Number: NNX14AM37G; NASA Ocean Biology and Biogeochemistry Program Grant Number: NNX11AD47G; National Science Foundation's Chemical Oceanography Program Grant Number: OCE‐1260574
    Description: 2018-10-04
    Keywords: Carbon cycle ; Coastal zone ; Tidal wetlands ; Estuaries ; Shelf waters
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 37 (2007): 1496-1511, doi:10.1175/jpo3071.1.
    Description: Measurements collected in the York River estuary, Virginia, demonstrate the important impact that tidal and lateral asymmetries in turbulent mixing have on the tidally averaged residual circulation. A reduction in turbulent mixing during the ebb phase of the tide caused by tidal straining of the axial density gradient results in increased vertical velocity shear throughout the water column during the ebb tide. In the absence of significant lateral differences in turbulent mixing, the enhanced ebb-directed transport caused by tidal straining is balanced by a reduction in the net seaward-directed barotropic pressure gradient, resulting in laterally uniform two-layer residual flow. However, the channel–shoal morphology of many drowned river valley estuaries often leads to lateral gradients in turbulent mixing. Tidal straining may then lead to tidal asymmetries in turbulent mixing near the deeper channel while the neighboring shoals remain relatively well mixed. As a result, the largest lateral asymmetries in turbulent mixing occur at the end of the ebb tide when the channel is significantly more stratified than the shoals. The reduced friction at the end of ebb delays the onset of the flood tide, increasing the duration of ebb in the channel. Conversely, over the shoal regions where stratification is more inhibited by tidal mixing, there is greater friction and the transition from ebb to flood occurs more rapidly. The resulting residual circulation is seaward over the channel and landward over the shoal. The shoal–channel segregation of this barotropically induced estuarine residual flow is opposite to that typically associated with baroclinic estuarine circulation over channel–shoal bathymetry.
    Description: Support for this research was provided by the National Science Foundation Division of Ocean Sciences Grant OCE- 9984941.
    Keywords: Tides ; Ocean circulation ; Estuaries ; Turbulence
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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