Particulate organic carbon : natural radionuclide ratios in zooplankton and their freshly produced fecal pellets from the NW Mediterranean (MedFlux 2005)

To discern controls on particulate organic carbon (POC) : natural radionuclide (RN) ratio variability in order to enhance the accuracy of water column radionuclide‐based carbon flux estimates, 234Th, 210Po, and POC were analyzed in seven size classes of mixed micro‐ and mesoplankton (1‐1,500‐µm size range), in larger zooplankton from different taxa (salps, euphausiids, copepods, pteropods), and in freshly produced feces from zooplankton collected during spring in the NW Mediterranean. POC:RN ratios in zooplankton ranged between 120 and 11,600 and between 89 and 9,200 µmol dpm−1 for 234Th and 210Po, respectively. In fecal pellets, POC:RN ratios were one to three orders of magnitude lower for 234Th and 3‐fold to 30‐fold lower for 210Po; the only exception was euthecosome pteropods, which had a higher POC: 210Po ratio in their pellets than in their whole bodies. Significant increases in POC:RN ratios with organism size were best described by a power relationship for POC: 234Th (p 33‐µm size classes, 210Po specific activity correlates negatively with the surface : volume ratio, while 234Th correlates positively with it (p < 0.004 and p < 0.001, respectively). POC:RN ratios vary greatly among species and to a lesser extent among fecal pellet types, most probably due to differences in zooplankton feeding strategies. Partial removal of most zooplankton "wimmers" from trap samples would not likely confound assessment of 234Th flux; however, it could considerably bias similar measurements of 210Po flux as well as those of POC:RN ratios

Release rates of trace elements and protein from decomposing planktonic debris. 2. Copepod carcasses and sediment trap particulate matter

In experiments designed to relate the release kinetics of various elements with that of protein from biogenic particles, 110mAg, 241Am, 109Cd, 60Co, 75Se and protein were measured over time in radiolabeled copepod carcasses and particles caught in unpoisoned sediment traps (mostly zooplankton fecal pellets and amorphous marine snow). Log-linear release rate constants (k) of 110mAg, 241Am, 109Cd, and 60Co from carcasses ranged from 0.079 d−1 for 60Co at 2°C to 0.130 d−1 for 109Cd at 15°C, and did not vary significantly with temperature. 75Se was lost most rapidly from copepod carcasses at 2°C, with k = 0.168 d−1; however, at 15°C, 75Se was in two compartments, with 56% in a rapidly exchanging pool (k = 0.391 d−1) and 44% in a slowly exchanging pool (k = 0.107 d−1). Protein displayed loss from two compartments at both temperatures. At 2°C, protein was lost slowly (k = 0.065 d−1) for 1 wk, after which it was released from the carcasses very rapidly (k = 0.245 d−1). At 15°C, however, the loss of protein from carcasses was more rapid over the first 2 d (k = 0.627 d−1) than thereafter (k = 0.127 d−1). The k values of 110mAg, 241Am, and 60Co from sediment trap particles (15°C) ranged from 0.008 to 0.011 d−1. Protein was lost twice as fast as 110mAg, 241Am, and 60Co, more slowly than half of the particulate 109Cd and 75Se in rapidly exchanging pools (k = 0.168 and 0.237 d−1, respectively), and at rates comparable to 109Cd and 75Se in slowly exchanging pools. Overall, copepod carcasses and fecal pellets could act as vectors of these five elements and protein to the deep ocean, the vertical flux being dependent on settling velocity and water column temperature structure. Of the elements considered here, Se follows the cycling of protein most closely

Vegetative Erosion Control Project : Final Report

The Vegetative Erosion Control (VEC) project is a four-year study with coordinated efforts by the Virginia Soil and Water Conservation Commmission (VS&WCC) through their Shoreline Erosion Advisory Service (SEAS), the Soil Conservation Service (SCS) and the Virginia Institute of Marine Science (VIMS). Initial funding was appropriated in 1980 following the recommendation of the Coastal Erosion Abatement Commission and contracted out to the SCS and VIMS by the VS&WCC, the lead agency. (...) The purpose of the VEC project is to supplement previous research with detailed site analysis of the early stages of marsh development and to more precisely define the physical limits of marsh implantation for shoreline erosion control. The project also provides demonstration sites which will help the average land owner, the advisory and regulatory agencies in determining whether or not a property is conducive to this low cost erosion control method

An academic hospitalist model to improve healthcare worker communication and learner education: Results from a quasi‐experimental study at a veterans affairs medical center

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102160/1/jhm2105.pd

Performance analysis of packet layer FEC codes and interleaving in FSO channels

The combination of forward-error-correction (FEC) and interleaving can be used to improve free-space optical (FSO) communication systems. Recent research has optimized the codeword length and interleaving depth under the assumption of a fixed buffering size, however, how the buffering size influences the system performance remains unsolved. This paper models the system performance as a function of buffering size and FEC recovery threshold, which allows system designers to determine optimum parameters in consideration of the overhead. The modelling is based on statistics of temporal features of correct data reception and burst error length through the measurement of the channel good time and outage time. The experimental results show good coherence with the theoretical values. This method can also be applied in other channels if a Continuous-Time-Markov-Chain (CTMC) model of the channel can be derive

An assessment of the use of sediment traps for estimating upper ocean particle fluxes

Author Posting. © Sears Foundation for Marine Research, 2007. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 65 (2007): 345–416, doi: 10.1357/002224007781567621This review provides an assessment of sediment trap accuracy issues by gathering data to address trap hydrodynamics, the problem of zooplankton "swimmers," and the solubilization of material after collection. For each topic, the problem is identified, its magnitude and causes reviewed using selected examples, and an update on methods to correct for the potential bias or minimize the problem using new technologies is presented. To minimize hydrodynamic biases due to flow over the trap mouth, the use of neutrally buoyant sediment traps is encouraged. The influence of swimmers is best minimized using traps that limit zooplankton access to the sample collection chamber. New data on the impact of different swimmer removal protocols at the US time-series sites HOT and BATS are compared and shown to be important. Recent data on solubilization are compiled and assessed suggesting selective losses from sinking particles to the trap supernatant after collection, which may alter both fluxes and ratios of elements in long term and typically deeper trap deployments. Different methods are needed to assess shallow and short- term trap solubilization effects, but thus far new incubation experiments suggest these impacts to be small for most elements. A discussion of trap calibration methods reviews independent assessments of flux, including elemental budgets, particle abundance and flux modeling, and emphasizes the utility of U-Th radionuclide calibration methods.WG meetings and production of this report was partially supported by the U.S. National Science Foundation via grants to the SCOR. Individuals and science efforts discussed herein were supported by many national science programs, including the U.S. National Science Foundation, Swedish Research Council, the International Atomic Energy Agency through its support of the Marine Environmental Laboratory that also receives support from the Government of the Principality of Monaco, and the Australian Antarctic Science Program. K.B. was supported in part by a WHOI Ocean Life Institute Fellowship

Functional Amyloid Formation within Mammalian Tissue

Amyloid is a generally insoluble, fibrous cross-β sheet protein aggregate. The process of amyloidogenesis is associated with a variety of neurodegenerative diseases including Alzheimer, Parkinson, and Huntington disease. We report the discovery of an unprecedented functional mammalian amyloid structure generated by the protein Pmel17. This discovery demonstrates that amyloid is a fundamental nonpathological protein fold utilized by organisms from bacteria to humans. We have found that Pmel17 amyloid templates and accelerates the covalent polymerization of reactive small molecules into melanin—a critically important biopolymer that protects against a broad range of cytotoxic insults including UV and oxidative damage. Pmel17 amyloid also appears to play a role in mitigating the toxicity associated with melanin formation by sequestering and minimizing diffusion of highly reactive, toxic melanin precursors out of the melanosome. Intracellular Pmel17 amyloidogenesis is carefully orchestrated by the secretory pathway, utilizing membrane sequestration and proteolytic steps to protect the cell from amyloid and amyloidogenic intermediates that can be toxic. While functional and pathological amyloid share similar structural features, critical differences in packaging and kinetics of assembly enable the usage of Pmel17 amyloid for normal function. The discovery of native Pmel17 amyloid in mammals provides key insight into the molecular basis of both melanin formation and amyloid pathology, and demonstrates that native amyloid (amyloidin) may be an ancient, evolutionarily conserved protein quaternary structure underpinning diverse pathways contributing to normal cell and tissue physiology

Dusp3 and Psme3 are associated with murine susceptibility to Staphylococcus aureus infection and human sepsis.

Using A/J mice, which are susceptible to Staphylococcus aureus, we sought to identify genetic determinants of susceptibility to S. aureus, and evaluate their function with regard to S. aureus infection. One QTL region on chromosome 11 containing 422 genes was found to be significantly associated with susceptibility to S. aureus infection. Of these 422 genes, whole genome transcription profiling identified five genes (Dcaf7, Dusp3, Fam134c, Psme3, and Slc4a1) that were significantly differentially expressed in a) S. aureus -infected susceptible (A/J) vs. resistant (C57BL/6J) mice and b) humans with S. aureus blood stream infection vs. healthy subjects. Three of these genes (Dcaf7, Dusp3, and Psme3) were down-regulated in susceptible vs. resistant mice at both pre- and post-infection time points by qPCR. siRNA-mediated knockdown of Dusp3 and Psme3 induced significant increases of cytokine production in S. aureus-challenged RAW264.7 macrophages and bone marrow derived macrophages (BMDMs) through enhancing NF-κB signaling activity. Similar increases in cytokine production and NF-κB activity were also seen in BMDMs from CSS11 (C57BL/6J background with chromosome 11 from A/J), but not C57BL/6J. These findings suggest that Dusp3 and Psme3 contribute to S. aureus infection susceptibility in A/J mice and play a role in human S. aureus infection

An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of 234Th as a POC flux proxy

Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 100 (2006): 213-233, doi:10.1016/j.marchem.2005.10.013.Thorium-234 is increasingly used as a tracer of ocean particle flux, primarily as a means to estimate particulate organic carbon export from the surface ocean. This requires determination of both the 234Th activity distribution (in order to calculate 234Th fluxes) and an estimate of the C/234Th ratio on sinking particles, to empirically derive C fluxes. In reviewing C/234Th variability, results obtained using a single sampling method show the most predictable behavior. For example, in most studies that employ in situ pumps to collect size fractionated particles, C/234Th either increases or is relatively invariant with increasing particle size (size classes >1 to 100’s μm). Observations also suggest that C/234Th decreases with depth and can vary significantly between regions (highest in blooms of large diatoms and highly productive coastal settings). Comparisons of C fluxes derived from 234Th show good agreement with independent estimates of C flux, including mass balances of C and nutrients over appropriate space and time scales (within factors of 2-3). We recommend sampling for C/234Th from a standard depth of 100 m, or at least one depth below the mixed layer using either large volume size fractionated filtration to capture the rarer large particles, or a sediment trap or other device to collect sinking particles. We also recommend collection of multiple 234Th profiles and C/234Th samples during the course of longer observation periods to better sample temporal variations in both 234Th flux and the characteristic of sinking particles. We are encouraged by new technologies which are optimized to more reliably sample truly settling particles, and expect the utility of this tracer to increase, not just for upper ocean C fluxes but for other elements and processes deeper in the water column.Individuals and science efforts discussed herein were supported by many national science programs, including the U.S. National Science Foundation and U.S. Department of Energy. S.F. and J.C.M. acknowledge the support provided to the International Atomic Energy Agency (IAEA) Marine Environment Laboratory by the Government of the Principality of Monaco. T.T. acknowledges support from the Australian Antarctic Science Program. K.B. was supported in part by a WHOI Ocean Life Institute Fellowship