178,535 research outputs found
Seasonal variation in marine C:N:P stoichiometry: can the composition of seston explain stable Redfield ratios?
No full textSeston is suspended particulate organic matter, comprising a mixture of autotrophic, heterotrophic and detrital material. Despite variable proportions of these components, marine seston often exhibits relatively small deviations from the Redfield ratio (C:N:P = 106:16:1). Two time-series from the Norwegian shelf in Skagerrak are used to identify drivers of the seasonal variation in seston elemental ratios. An ordination identified water mass characteristics and bloom dynamics as the most important drivers for determining C:N, while changes in nutrient concentrations and biomass were most important for the C:P and N:P relationships. There is no standardized method for determining the functional composition of seston and the fractions of POC, PON and PP associated with phytoplankton, therefore any such information has to be obtained by indirect means. In this study, a generalized linear model was used to differentiate between the live autotrophic and non-autotrophic sestonic fractions, and for both stations the non-autotrophic fractions dominated with respective annual means of 76 and 55%. This regression model approach builds on assumptions (e.g. constant POC:Chl-a ratio) and the robustness of the estimates were explored with a bootstrap analysis. In addition the autotrophic percentage calculated from the statistical model was compared with estimated phytoplankton carbon, and the two independent estimates of autotrophic percentage were comparable with similar seasonal cycles. The estimated C:nutrient ratios of live autotrophs were, in general, lower than Redfield, while the non-autotrophic C:nutrient ratios were higher than the live autotrophic ratios and above, or close to, the Redfield ratio. This is due to preferential remineralization of nutrients, and the P content mainly governed the difference between the sestonic fractions. Despite the seasonal variability in seston composition and the generally low contribution of autotrophic biomass, the variation observed in the total seston ratios was low compared to the variation found in dissolved and particulate pools. Sestonic C:N:P ratios close to the Redfield ratios should not be used as an indicator of phytoplankton physiological state, but could instead reflect varying contributions of sestonic fractions that sum up to an elemental ratio close to Redfield
CDC Director Dr. Robert R. Redfield and HHS Chief Information Officer Jose Arrieta remarks on HHS Protect
No full textOn Wednesday, July 15, CDC Director Robert Redfield and HHS Chief Information Officer Jose Arrieta provided an update for members of the media on HHS efforts to gather and disseminate real-time hospital data on COVID-19. Below are their statements as prepared for delivery.2020799
Men by Train, Redfield, Spink County
No full text4 x 6 photograph, a group of men standing in front of a train car3 Photo Album H2009-101 5644 R.C. Lathrop Coll Box No 334A Chicago Northwestern Railroad Train No 106 Pierre to Tracy at Redfield, S D Taken summer 1948 Dakota Division Looking West from Depot L to R. Bill Lucas - Sorn Dealer Redfield Roy Rhiem Rdm Ben Rhode Tracy Baggage man Carl Gommer Section Fmn Redfield Max Hill opr. Day Shift Redfield Dick Wiest REAMAN Redfield Unknown Big Charlie Marsten Redfield Trainma
for immediate release
No full textOn Wednesday, October 21, U.S. Department of Health and Human Services (HHS) Secretary Alex Azar will meet with CDC Director Robert R. Redfield, M.D. and agency leadership to discuss the ongoing COVID-19 response and Operation Warp Speed. Following the meeting, the Secretary and Dr. Redfield will host a press briefing.2020859
Local generation of entanglement with Redfield dynamics
No full textIn phenomenological applications, time evolutions of Bloch-Redfield type are
widely adopted for modelling open system dynamics, despite their non-positive
preserving character: this physical inconsistency, that in general shows up at
small times, is usually cured by suitably restricting the space of allowed
initial states. Nevertheless, additional problems may arise in relation to
entanglement: specifically, we show that Redfield dynamics can generate
entanglement through a purely local action, and this unphysical effect can
persist for finite times.Comment: 17 pages, 1 fig, LaTe
Front and Side Façade of Depot, Redfield SD, Spink County
No full text35 mm slide, a farming implement and a sign bearing the text "D.H.M. Builders & Equipment [?] Buildings Concrete Work Grain and Livestock Equip. Redfield, S.D. Ph. 472-2550" next to a single-story brick building with a false frontDrawer info: Pennington -Turner; RedfieldEktachrome Slide Spink Co. Redfield Depot C. Sands 16 Sep 79 R
Side Façade of CNW Depot, Redfield SD, Spink County
No full text35 mm slide, a sign bearing the text "D.H.M. Builders & Equipment Buildings Concrete Work Grain and Livestock Equip. Redfield, S. D. Ph. 472-2550" in front of a single-story brick building with two wingsDrawer info: Pennington -Turner; National Register PropertiEktachrome Slide Spink Co. Redfield Depot C. Sands 24 Sep 79 R
for immediate release
No full textOn Wednesday, October 21, U.S. Department of Health and Human Services (HHS) Secretary Alex Azar will meet with CDC Director Robert R. Redfield, M.D. and agency leadership to discuss the ongoing COVID-19 response and Operation Warp Speed. Following the meeting, the Secretary and Dr. Redfield will host a press briefing.2020859
Front Façade of CNW Depot, Redfield SD, Spink County
No full text35 mm slide, a single-story brick building with two wingsDrawer info: Pennington -Turner; National Register PropertiEktachrome Slide Spink Co. Redfield Depot C. Sands 26 Sep 79 R
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