The Experts below are selected from a list of 437601 Experts worldwide ranked by ideXlab platform
Marlon R Lewis - One of the best experts on this subject based on the ideXlab platform.
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gross community production and metabolic balance in the south pacific gyre using a non intrusive bio Optical Method
Biogeosciences, 2007Co-Authors: Herve Claustre, Yannick Huot, Ingrid Obernosterer, Bernard Gentili, D Tailliez, Marlon R LewisAbstract:Abstract. The very clear waters of the South Pacific Gyre likely constitute an end-member of oligotrophic conditions which remain essentially unknown with respect to its impact on carbon fixation and exportation. We describe a non-intrusive bio-Optical Method to quantify the various terms of a production budget (Gross community production, community losses, net community production) in this area. This Method is based on the analysis of the diel cycle in Particulate Organic Carbon (POC), derived from high frequency measurements of the particle attenuation coefficient c p . We report very high integrated rates of Gross Community Production within the euphotic layer (average of 846±484 mg C m −2 d −1 for 17 stations) that are far above any rates determined using incubation techniques for such areas. Furthermore we show that the daily production of POC is essentially balanced by the losses so that the system cannot be considered as net heterotrophic. Our results thus agree well with geochemical Methods, but not with incubation studies based on oxygen Methods. We stress to the important role of deep layers, below the euphotic layer, in contributing to carbon fixation when incident irradiance at the ocean surface is high (absence of cloud coverage). These deep layers, not considered up to know, might fuel part of the heterotrophic processes in the upper layer, including through dissolved organic carbon. We further demonstrate that, in these extremely clear and stratified waters, integrated gross community production is proportional to the POC content and surface irradiance via an efficiency index ψ GCP * , the water column cross section for Gross Community Production. We finally discuss our results in the context of the role of oligotrophic gyre in the global carbon budget and of the possibility of using Optical proxies from space for the development of growth community rather than primary production global models.
Herve Claustre - One of the best experts on this subject based on the ideXlab platform.
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gross community production and metabolic balance in the south pacific gyre using a non intrusive bio Optical Method
Biogeosciences, 2007Co-Authors: Herve Claustre, Yannick Huot, Ingrid Obernosterer, Bernard Gentili, D Tailliez, Marlon R LewisAbstract:Abstract. The very clear waters of the South Pacific Gyre likely constitute an end-member of oligotrophic conditions which remain essentially unknown with respect to its impact on carbon fixation and exportation. We describe a non-intrusive bio-Optical Method to quantify the various terms of a production budget (Gross community production, community losses, net community production) in this area. This Method is based on the analysis of the diel cycle in Particulate Organic Carbon (POC), derived from high frequency measurements of the particle attenuation coefficient c p . We report very high integrated rates of Gross Community Production within the euphotic layer (average of 846±484 mg C m −2 d −1 for 17 stations) that are far above any rates determined using incubation techniques for such areas. Furthermore we show that the daily production of POC is essentially balanced by the losses so that the system cannot be considered as net heterotrophic. Our results thus agree well with geochemical Methods, but not with incubation studies based on oxygen Methods. We stress to the important role of deep layers, below the euphotic layer, in contributing to carbon fixation when incident irradiance at the ocean surface is high (absence of cloud coverage). These deep layers, not considered up to know, might fuel part of the heterotrophic processes in the upper layer, including through dissolved organic carbon. We further demonstrate that, in these extremely clear and stratified waters, integrated gross community production is proportional to the POC content and surface irradiance via an efficiency index ψ GCP * , the water column cross section for Gross Community Production. We finally discuss our results in the context of the role of oligotrophic gyre in the global carbon budget and of the possibility of using Optical proxies from space for the development of growth community rather than primary production global models.
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Gross community production and metabolic balance in the South Pacific Gyre, using a non intrusive bio-Optical Method
Biogeosciences Discussions, 2007Co-Authors: Herve Claustre, Yannick Huot, Ingrid Obernosterer, Bernard Gentili, D Tailliez, M. LewisAbstract:The very clear waters of the South Pacific Gyre likely constitute an end-member of oligotrophic conditions which remain essentially unknown with respect to its impact on carbon fixation and exportation. We describe a non-intrusive bio-Optical Method to quantify the various terms of a production budget (Gross Community Production, community losses, net community production) in this area. This Method is based on the analysis of the diel cycle in Particulate Organic Carbon (POC), derived from high frequency measurements of the particle attenuation coefficient cp. We report very high integrated rates of Gross Community Production within the euphotic layer (average of 846±484 mg C m-2 d-1 for 17 stations) that are far above any rates determined using incubation techniques for such areas. Furthermore we show that the daily production of POC is essentially balanced by the losses so that the system cannot be considered as net heterotoph. Our results thus agree well with geochemical Methods, but not with incubation studies based on oxygen Methods. We stress to the important role of deep layers, below the euphotic layer, in contributing to carbon fixation when incident irradiance at the ocean surface is high (absence of cloud coverage). These deep layers, not considered up to now, might fuel a part of the heterotrophic processes in the upper layer, in particular through dissolved organic carbon release. We further demonstrate that, in these extremely clear and stratified waters, integrated Gross Community Production is proportional to the POC content and surface irradiance via an efficiency index ?GCP*, the water column cross section for Gross Community Production. We finally discuss our results in the context of the role of oligotrophic gyre in global carbon budget and of the possibility of using Optical proxy from space for the development of gross community rather than primary production global models.
M.s.j. Hashmi - One of the best experts on this subject based on the ideXlab platform.
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An Optical Method and neural network for surface roughness measurement
Optics and Lasers in Engineering, 1997Co-Authors: Z Yilbas, M.s.j. HashmiAbstract:The measurement of surface roughness using stylus equipment has several disadvantages. A non-contact Optical Method is needed for measuring the surface roughness of engineering metals with improved accuracy. One candidate for an Optical Method is the use of a laser source, where the laser light intensity reflected from the surface represents the surface roughness of the illuminated area. A relation can be developed between the reflected laser beam intensity and the surface roughness of the metal. The present study examines the measurement of the surface roughness of the stainless steel samples using a He-Ne laser beam. In the measurement a Gaussian curve parameter of a Gaussian function approximating the peak of the reflected intensity is measured with a fast response photodetector. In order to achieve this, an experimental setup is designed and built. In the experimental apparatus, fiber-optic cables are used to collect the reflected beam from the surface. The output of the fiber-optic system is fed to a back-propagation neural network to classify the resulting surface profile and predict the surface roughness value. The results obtained from the present study are then compared with the stylus measurement results. It is found that the resolution of the surface texture improves considerably in the case of Optical Method and the neural network developed for this purpose can classify the surface texture according to the control charts developed mathematically.
Liaquat Husain - One of the best experts on this subject based on the ideXlab platform.
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Measurement of black carbon (BC) by an Optical Method and a thermal-Optical Method: Intercomparison for four sites
Atmospheric Environment, 2009Co-Authors: Tanveer Ahmed, Vincent A. Dutkiewicz, Akhtar Shareef, Gürdal Tuncel, Semra G. Tuncel, Liaquat HusainAbstract:Abstract Comparison of black carbon (BC) measurements obtained by two Methods was performed for aerosols samples collected on Whatman 41 (W-41) filters, using an Optical Method (Magee Scientific Optical Transmissometer Model OT-21) and a thermal-Optical Method (Sunset Laboratory Thermal-Optical analyzer). Samples were collected from four sites: Albany (a small urban site, NY), Antalya (coastal site, Turkey), Whiteface Mountain (remote site, NY) and Mayville (rural site, NY). At Albany, comparison between the two Methods showed excellent agreement; a least-squares regression line yielded a slope of 1.02, and r 2 = 0.88. Similar comparisons at Antalya (slope of 1.02, r 2 = 0.5) and Whiteface Mountain (slope of 0.92 and r 2 = 0.58) also gave very good relationship. At Mayville, the relationship between the two Methods yielded somewhat lower regression: a slope of 0.75, and r 2 = 0.44. The data from the four locations, when plotted together, yielded an excellent agreement: a slope of 0.91, and r 2 of 0.84. Based on our measurements, it appears that Optical measurement using the OT-21 can be successfully applied to determination of BC in W-41 filters. However, because of the variability in the chemical composition of BC aerosol at different locations, it is suggested that the calibration of OT-21 when using W-41 filters should be performed with a statistically significant numbers of samples for specific sites.
Ingrid Obernosterer - One of the best experts on this subject based on the ideXlab platform.
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gross community production and metabolic balance in the south pacific gyre using a non intrusive bio Optical Method
Biogeosciences, 2007Co-Authors: Herve Claustre, Yannick Huot, Ingrid Obernosterer, Bernard Gentili, D Tailliez, Marlon R LewisAbstract:Abstract. The very clear waters of the South Pacific Gyre likely constitute an end-member of oligotrophic conditions which remain essentially unknown with respect to its impact on carbon fixation and exportation. We describe a non-intrusive bio-Optical Method to quantify the various terms of a production budget (Gross community production, community losses, net community production) in this area. This Method is based on the analysis of the diel cycle in Particulate Organic Carbon (POC), derived from high frequency measurements of the particle attenuation coefficient c p . We report very high integrated rates of Gross Community Production within the euphotic layer (average of 846±484 mg C m −2 d −1 for 17 stations) that are far above any rates determined using incubation techniques for such areas. Furthermore we show that the daily production of POC is essentially balanced by the losses so that the system cannot be considered as net heterotrophic. Our results thus agree well with geochemical Methods, but not with incubation studies based on oxygen Methods. We stress to the important role of deep layers, below the euphotic layer, in contributing to carbon fixation when incident irradiance at the ocean surface is high (absence of cloud coverage). These deep layers, not considered up to know, might fuel part of the heterotrophic processes in the upper layer, including through dissolved organic carbon. We further demonstrate that, in these extremely clear and stratified waters, integrated gross community production is proportional to the POC content and surface irradiance via an efficiency index ψ GCP * , the water column cross section for Gross Community Production. We finally discuss our results in the context of the role of oligotrophic gyre in the global carbon budget and of the possibility of using Optical proxies from space for the development of growth community rather than primary production global models.
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Gross community production and metabolic balance in the South Pacific Gyre, using a non intrusive bio-Optical Method
Biogeosciences Discussions, 2007Co-Authors: Herve Claustre, Yannick Huot, Ingrid Obernosterer, Bernard Gentili, D Tailliez, M. LewisAbstract:The very clear waters of the South Pacific Gyre likely constitute an end-member of oligotrophic conditions which remain essentially unknown with respect to its impact on carbon fixation and exportation. We describe a non-intrusive bio-Optical Method to quantify the various terms of a production budget (Gross Community Production, community losses, net community production) in this area. This Method is based on the analysis of the diel cycle in Particulate Organic Carbon (POC), derived from high frequency measurements of the particle attenuation coefficient cp. We report very high integrated rates of Gross Community Production within the euphotic layer (average of 846±484 mg C m-2 d-1 for 17 stations) that are far above any rates determined using incubation techniques for such areas. Furthermore we show that the daily production of POC is essentially balanced by the losses so that the system cannot be considered as net heterotoph. Our results thus agree well with geochemical Methods, but not with incubation studies based on oxygen Methods. We stress to the important role of deep layers, below the euphotic layer, in contributing to carbon fixation when incident irradiance at the ocean surface is high (absence of cloud coverage). These deep layers, not considered up to now, might fuel a part of the heterotrophic processes in the upper layer, in particular through dissolved organic carbon release. We further demonstrate that, in these extremely clear and stratified waters, integrated Gross Community Production is proportional to the POC content and surface irradiance via an efficiency index ?GCP*, the water column cross section for Gross Community Production. We finally discuss our results in the context of the role of oligotrophic gyre in global carbon budget and of the possibility of using Optical proxy from space for the development of gross community rather than primary production global models.
