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  • 1
  • 2
    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zang, Z., Xue, Z. G., Xu, K., Bentley, S. J., Chen, Q., D'Sa, E. J., Zhang, L., & Ou, Y. The role of sediment-induced light attenuation on primary production during Hurricane Gustav (2008). Biogeosciences, 17(20), (2020): 5043-5055, doi:10.5194/bg-17-5043-2020.
    Beschreibung: We introduced a sediment-induced light attenuation algorithm into a biogeochemical model of the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system. A fully coupled ocean–atmospheric–sediment–biogeochemical simulation was carried out to assess the impact of sediment-induced light attenuation on primary production in the northern Gulf of Mexico during the passage of Hurricane Gustav in 2008. When compared with model results without sediment-induced light attenuation, our new model showed a better agreement with satellite data on both the magnitude of nearshore chlorophyll concentration and the spatial distribution of offshore bloom. When Hurricane Gustav approached, resuspended sediment shifted the inner shelf ecosystem from a nutrient-limited one to a light-limited one. Only 1 week after Hurricane Gustav's landfall, accumulated nutrients and a favorable optical environment induced a posthurricane algal bloom in the top 20 m of the water column, while the productivity in the lower water column was still light-limited due to slow-settling sediment. Corresponding with the elevated offshore NO3 flux (38.71 mmol N m−1 s−1) and decreased chlorophyll flux (43.10 mg m−1 s−1), the outer shelf posthurricane bloom should have resulted from the cross-shelf nutrient supply instead of the lateral dispersed chlorophyll. Sensitivity tests indicated that sediment light attenuation efficiency affected primary production when sediment concentration was moderately high. Model uncertainties due to colored dissolved organic matter and parameterization of sediment-induced light attenuation are also discussed.
    Beschreibung: This research has been supported by the National Science Foundation (grant nos. CCF-1856359, EnvS-1903340, OCE-1635837 and EAR-1427389), NASA (grant no. NNH17ZHA002C), the Louisiana Board of Regents (grant no. NASA/LEQSF(2018-20)-Phase3-11) and the LSU Foundation Billy and Ann Harrison Endowment for Sedimentary Geology.
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(9), (2020): e2019JC015269, doi:10.1029/2019JC015269
    Beschreibung: Wave‐supported fluid mud (WSFM) plays an important role in sediment downslope transport on the continental shelves. In this study, we incorporated WSFM processes in the wave boundary layer (WBL) into the Community Sediment Transport Modeling System (CSTMS) on the platform of the Coupled Ocean‐Atmosphere‐Wave‐and‐Sediment Transport modeling system (COAWST). The WSFM module was introduced between the bottommost water layer and top sediment layer, which accounted for the key sediment exchange processes (e.g., resuspension, vertical settling, diffusion, and horizontal advection) at the water‐WBL and WBL‐sediment bed boundaries. To test its robustness, we adapted the updated model (CSTMS + WBL) to the Atchafalaya shelf in the northern Gulf of Mexico and successfully reproduced the sediment dynamics in March 2008, when active WSFM processes were reported. Compared with original CSTMS results, including WSFM module weakened the overall intensity of sediment resuspension, and the CSTMS + WBL model simulated a lutocline between the WBL and overlying water due to the formation of WSFM. Downslope WSFM transport resulted in offshore deposition (〉4 cm), which greatly changed the net erosion/deposition pattern on the inner shelf off the Chenier Plain. WSFM flux was comparable with suspended sediment flux (SSF) off the Atchafalaya Bay, and it peaked along the Chenier Plain coast where wave activities were strong and the bathymetric slope was steep. The influence of fluvial sediment supply on sediment dynamics was limited in the Atchafalaya Bay. Sensitivity tests of free settling, flocculation, and hindered settling effects suggested that sediments were transported further offshore due to reduced settling velocity in the WBL once fluid mud was formed. Although sediment concentration in the WBL was sensitive to surface sediment critical shear stress, cohesive bed behavior was less important in WSFM dynamics when compared with strong hydrodynamic during cold fronts.
    Beschreibung: Research support provided through NSF CyberSEES (Award CCF‐1856359), NASA (Award NNH17ZHA002C), Louisiana Board of Regents (award number NASA/LEQSF(2018‐20)‐Phase3‐11), Bureau of Ocean Energy Management (Cooperative Agreement Award M20AC00007), NSF Coastal SEES (Award EAR‐1427389 ), NSF (Award OCE‐20203676), and LSU Foundation Billy and Ann Harrison Endowment for Sedimentary Geology.
    Beschreibung: 2021-02-19
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 4
    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Liu, H., Xu, K., Ou, Y., Bales, R., Zang, Z., & Xue, Z. G. Sediment transport near ship shoal for coastal restoration in the Louisiana Shelf: a model estimate of the year 2017-2018. Water, 12(8), (2020): 2212, doi:10.3390/w12082212.
    Beschreibung: Ship Shoal has been a high-priority target sand resource for dredging activities to restore the eroding barrier islands in LA, USA. The Caminada and Raccoon Island pits were dredged on and near Ship Shoal, which resulted in a mixed texture environment with the redistribution of cohesive mud and noncohesive sand. However, there is very limited knowledge about the source and transport process of suspended muddy sediments near Ship Shoal. The objective of this study is to apply the Regional Ocean Modeling System (ROMS) model to quantify the sediment sources and relative contribution of fluvial sediments with the estuary and shelf sediments delivered to Ship Shoal. The model results showed that suspended mud from the Atchafalaya River can transport and bypass Ship Shoal. Only a minimal amount of suspended mud from the Atchafalaya River can be delivered to Ship Shoal in a one-year time scale. Additionally, suspended mud from the inner shelf could be transported cross Ship Shoal and generate a thin mud layer, which is also considered as the primary sediment source infilling the dredge pits near Ship Shoal. Two hurricanes and one tropical storm during the year 2017–2018 changed the direction of the sediment transport flux near Ship Shoal and contributed to the pit infilling (less than 10% for this specific period). Our model also captured that the bottom sediment concentration in the Raccoon Island pit was relatively higher than the one in Caminada in the same period. Suspended mud sediment from the river, inner shelf, and bay can bypass or transport and deposit in the Caminada pit and Raccoon Island pit, which showed that the Caminada pit and Raccoon Island pits would not be considered as a renewable borrow area for future sand dredging activities for coastal restoration.
    Beschreibung: Funding for this study was provided by the U.S. Department of the Interior, Bureau of Ocean Energy Management, Coastal Marine Institute, Washington DC, under Cooperative Agreement Numbers M16AC00018 and M17AC00019.
    Schlagwort(e): sediment transport ; ROMS modeling ; Ship Shoal ; Caminada pit ; Raccoon Island pit ; coastal restoration
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2227-2231 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ag–O–Cs thin films with internal field-assisted structure were fabricated, and enhanced photoemission was observed when the internal electric field was applied to the thin films. The increase of photoelectronic quantum yield, corresponding to the applied 30 V bias, was about 15.7%, while the thin films were irradiated by the light with wavelength of 510 nm. From an analysis of the electric potential distribution in the Ag–O–Cs thin films with the applied internal electric field, it is found that the interfacial barrier between the Ag nanoparticles and the Cs2O matrix is decreased and the vacuum level at the surface is degraded. The calculated barrier curves for various applied biases are illustrated to show the thinning effect of internal electric field on the interfacial barrier width. The theoretical lowering of interfacial barrier height is obtained as 0.08 and 0.22 eV when the thin films are stimulated by applied bias of 1 and 30 V, respectively. Further, a group of formulas as well, based upon the electric potential distribution in the Ag–O–Cs thin films, is deduced to describe the relationship between the applied bias and the degradation of the surface vacuum level. The enhanced photoemission of Ag–O–Cs thin films is attributed to the field-induced variations in the energy band structure which are considered to result in the increased probabilities for the photoexcited electrons to travel through the interfacial barrier and escape into the vacuum. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3752-3753 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Nanometer-scale recording on an organic-complex thin film with a scanning tunneling microscope (STM) under ambient conditions is demonstrated. The recording marks are made by applying external voltage pulses between the tip and the highly ordered pyrolytic graphite substrate. A 30×30 nm2 STM image with recorded marks is given. The average recorded mark is 1.3 nm in diameter, which corresponds to a data storage density of about 1013 bits/cm2. The current–voltage characteristics measured by the STM show an insulator behavior for the unrecorded regions, and a conductor behavior for the recorded regions, which indicates that the data are recorded by local change of the electrical property of the films. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1747-1749 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The scanning tunneling microscope (STM) has been used to fabricate grooves a few nm wide at room temperature by extracting atoms one by one from the Si(111)7×7 surfaces. When the direction of modification is parallel to the basic vector of Si(111)7×7 surfaces, grooves formed by such a process have atomically straight edges and lateral features as small as one 7×7 unit cell wide. The critical current under various voltages for fabricating grooves is measured. The modification mechanism is discussed based on the experiment data in this letter. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2192-2194 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report an ionized-cluster-beam (ICB) deposition and the electrical bistability of C60–tetracyanoquinodimethane (TCNQ) thin films. The films are fabricated by using an ionized-cluster-beam deposition method in a high vacuum system. The as-deposited films were characterized by transmission electron microscopy and optical absorption spectroscopy, which verified the formation of the charge-transfer complex system in C60–TCNQ thin films and the microstructure of these thin films. The structure and the electrical property of the ICB deposited Ag-TCNQ thin films are also presented. The possible conductive mechanism of these ICB deposited thin films is discussed in the letter. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2441-2443 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A novel complex thin film of 2,6-bis(2,2-bicyanovinyl)pyridine (BDCP) and C60 has been fabricated by vacuum coevaporation of BDCP and C60 from two different evaporation sources. The C60-BDCP thin films have shown totally different optical and electronic properties from the films of both the BDCP and C60. Stable and reproducible electric bistable properties have been observed in sandwichlike device Ag/C60-BDCP/Ag. The films are characterized by several methods including high-resolution scanning electron microscopy, x-ray diffraction, UV-visible absorption and infrared transmission spectroscopy. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2532-2534 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A thin film of 1,1-dicyano-2,2-(4-dimethylaminophenyl) ethylene (DDME) has been grown by a modified vacuum deposition. The films were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning tunneling microscopy (STM). Highly ordered parallel molecular stacks were repeatedly observed with STM under ambient conditions. The dc current–voltage (I–V) characteristics of device Au/DDME/Au were measured, and the film was found to possess good electrical bistability and electrochromic properties. Nanometer-scale recording was realized on the film by applying pulse voltage between the STM tip and substrate. The possible switching mechanism is discussed. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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