Organic geochemistry of particulate matter in the eastern tropical North Pacific Ocean: Implications for particle dynamics

Samples of marine particulate matter were collected in sediment traps and by in-situ filtration to depths of 1500 m during VERTEX II and III cruises in the eastern tropical North Pacific. Wax esters, triacylglycerols, fatty acids, sterols and steroidal ketones were analyzed in these samples to compare the compositions of organic matter associated with large sinking particulate aggregates sampled by sediment traps and with fine suspended material obtained by in-situ filtration. Distributions of specific compounds indicated that the organic chemical composition of large sinking particles and small suspended particles both in the euphotic zone and at mid-depth result from very distinct particle pools, not only in terms of particle size but also in their sources and transport mechanisms. Suspended particles in the epipelagic zone contain a mix of organic compounds derived from both phytoplankton and zooplankton sources, whereas sinking particles are dominated by zooplankton-derived compounds. In the mesopelagic zone, large, sinking particles contain organic compounds which are indicative of intensive alteration of organic matter, even though transport from the euphotic zone may have been rapid. On the other hand, it is the suspended particle pool which contains a remarkable abundance of labile organic compounds which can be attributed to undegraded phytoplankton cells rapidly delivered from surface waters. These organic geochemical results lead to a modified model of particle dynamics in which there are two distinct large, sinking particle pools which are differentially sampled by the two sampling techniques

The nature of organic carbon in density-fractionated sediments in the Sacramento-San Joaquin River Delta (California)

Rivers are the primary means by which sediments and carbon are transported from the terrestrial biosphere to the oceans but gaps remain in our understanding of carbon associations from source to sink. Bed sediments from the Sacramento-San Joaquin River Delta (CA) were fractionated according to density and analyzed for sediment mass distribution, elemental (C and N) composition, mineral surface area, and stable carbon and radiocarbon isotope compositions of organic carbon (OC) and fatty acids to evaluate the nature of organic carbon in river sediments. OC was unevenly distributed among density fractions. Mass and OC were in general concentrated in mesodensity (1.6-2.0 and 2.0-2.5 g cm(-3)) fractions, comprising 84.0 +/- 1.3% of total sediment mass and 80.8 +/- 13.3% of total OC (TOC). Low-density (\u3c 1.6 g cm(-3)) material, although rich in OC (34.0 +/- 2.0% OC) due to woody debris, constituted only 17.3 +/- 12.8% of TOC. High-density (\u3e2.5 g cm(-3) /organic-poor, mineral-rich material made-up 13.7 +/- 1.4% of sediment mass and 2.0 +/- 0.9% of TOC. Stable carbon isotope compositions of sedimentary OC were relatively uniform across bulk and density fractions (delta C-13 27.4 +/- 0.5 parts per thousand). Radiocarbon content varied from Delta C-14 values of 382 (radiocarbon age 3800 yr BP) to C 94 parts per thousand(modern) indicating a mix of young and old OC. Fatty acids were used to further constrain the origins of sedimentary OC. Short-chain n-C-14-n-C-18 fatty acids of algal origin were depleted in 13C (delta C-13 37.5 to 35.2 parts per thousand) but were enriched in C-14 (Delta C-14 \u3e 0) compared to long-chain n-C-24-n-C-28 acids of vascular plant origins with higher delta C-13 (33.0 to 31.0 parts per thousand) but variable Delta C-14 values (180 and 61 %). These data demonstrate the potentially complex source and age distributions found within river sediments and provide insights about sediment and organic matter supply to the Delta

Viscosity of R134a, R32, and R125 at saturation

This paper reports the results of the measurement of the viscosity of R134a close to the saturation line in the vapor phase. The new measurements were carried out in a vibrating-wire viscometer specially constructed for the purpose, and the results have an accuracy of ±2%. In addition, the opportunity is taken to present a reevaluation of earlier measurements along the saturation line of the viscosity of R32 and R125. Improved equations of state for these fluids are now available and can be employed to generate improved values for the viscosity

Isotopic compositions of lipid biomarker compounds in estuarine plants and surface sediments

We examined the isotopic compositions of fatty acids, sterols, and hydrocarbons isolated from three coastal macrophytes (Zostera marina, Spartina alterniflora, and Juncus roemerianus) in order to investigate the relative contribution of these vascular plants as sources of organic matter in coastal sediments such as Cape Lookout Eight, North Carolina. On average, lipid biomarker compounds extracted from the plants were depleted in C-13 by 3-5 parts per thousand relative to delta(13)C total organic carbon (TOC). However, individual compounds within each lipid class varied by up to 5.6 parts per thousand. Trends in the isotopic compositions of lipids were consistent with delta(13)C(TOC); compounds obtained from Z. marina were the most enriched in C-13 and those from J. roemerianus were the most depleted. The range in isotopic abundances and molecular compositions of the sediments was greater than that obtained from the plants, indicating that additional, presently unidentified sources of organic matter contribute to the Cape Lookout Eight sediments. Similarity between the signatures for suspended particulate matter and the sediments indicates that much of the sedimentary organic matter is derived from algal and bacterial sources. Bacterial sources of organic matter are Likely greater during summer/early fall, and incorporation of C-13-enriched bacterial biomass may contribute to observed seasonal shifts in delta(13)C(TOC) in the surficial sediments

HLA-B-associated transcript 3 (Bat3)/Scythe is essential for p300-mediated acetylation of p53.

In response to DNA damage, p53 undergoes post-translational modifications (including acetylation) that are critical for its transcriptional activity. However, the mechanism by which p53 acetylation is regulated is still unclear. Here, we describe an essential role for HLA-B-associated transcript 3 (Bat3)/Scythe in controlling the acetylation of p53 required for DNA damage responses. Depletion of Bat3 from human and mouse cells markedly impairs p53-mediated transactivation of its target genes Puma and p21. Although DNA damage-induced phosphorylation, stabilization, and nuclear accumulation of p53 are not significantly affected by Bat3 depletion, p53 acetylation is almost completely abolished. Bat3 forms a complex with p300, and an increased amount of Bat3 enhances the recruitment of p53 to p300 and facilitates subsequent p53 acetylation. In contrast, Bat3-depleted cells show reduced p53-p300 complex formation and decreased p53 acetylation. Furthermore, consistent with our in vitro findings, thymocytes from Bat3-deficient mice exhibit reduced induction of puma and p21, and are resistant to DNA damage-induced apoptosis in vivo. Our data indicate that Bat3 is a novel and essential regulator of p53-mediated responses to genotoxic stress, and that Bat3 controls DNA damage-induced acetylation of p53

Viscosity measurements on Ionic liquids : a cautionary tale

The vibrating-wire viscometer has proven to be an exceedingly effective means of determining the viscosity of liquids over a wide range of temperature and pressure. The instrument has a long history but a variety of technological and theoretical developments over a number of years have improved its precision and most recently have enabled absolute measurements of high accuracy. However, the nature of the electrical measurements required for the technique has inhibited its widespread use for electrically conducting liquids so that there have been only a limited number of measurements. In the particular context of ionic liquids, which have themselves attracted considerable attention, this is unfortunate because it has meant that one primary measurement technique has seldom been employed for studies of their viscosity. In the last 2 years systematic efforts have been made to explore the applicability of the vibrating-wire technique by examining a number of liquids of increasing electrical conductivity. These extensions have been successful. However, in the process we have had cause to review previous studies of the viscosity and density of the same liquids at moderate temperatures and pressures and significant evidence has been accumulated to cause concern about the application of a range of viscometric techniques to these particular fluids. Because the situation is reminiscent of that encountered for a new set of environmentally friendly refrigerants at the end of the last decade, in this paper the experimental methods employed with these liquids have been reviewed which leads to recommendations for the handling of these materials that may have consequences beyond viscometric measurements. In the process new viscosity and density data for 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide [C6mim][NTf2], 1-ethyl-3-methylimidazolium ethyl sulfate [C2mim][EtSO4], and 1-ethyl-3-methylpyridinium ethyl sulfate [C2mpy][EtSO4] have been obtained

Epoxy-cross-linked Polyamine CO2 Sorbents Enhanced via Hydrophobic Functionalization

Optimizing sorption capacity and amine efficiency are among the major challenges in developing solid carbon dioxide sorbents. Such materials frequently feature polyamines impregnated onto supports adding weight to the sorbents. This work presents the cross-linking of polyethyleneimine (PEI) by the industrially available epoxy resin, bisphenol-A diglycidyl ether (DER) to form support-free sorbent materials. Prior to cross-linking, the polyamine chain is functionalized with hydrophobic additives; one material modified with the branched chain hydrocarbon 2-ethylhexyl glycidyl ether displays CO2 uptake of 0.195 g/g, 4.43 mmol CO2/g (1 atm single component CO2, 90 °C). The additive loading affects the cross-linking, with the lesser cross-linked materials showing more favorable sorption capacities and higher amine efficiencies. The type of additive also influences sorption, with the larger, longer and bulkier additives better able to free the amine from their hydrogen bonding network, generally promoting better sorption. As well as increasing CO2 uptake, the additives also reduce the optimum sorption temperature, offering a handle to tune sorbents for specific working conditions. The best performing material shows high selectivity for CO2 sorption, and under sorption cycles in a 10% CO2/90% N2 mixture, utilizing temperature swing desorption, demonstrates a good working capacity of 9.5% CO2 uptake over the course of 29 cycles. Furthermore, humidity has been found to promote CO2 sorption at lower temperatures with a CO2 uptake of 0.235 g/g, 5.34 mmol/g (1 atm single component CO2, 25 °C) using a pre-hydrated sample. Overall, these findings confirm the value of our approach where cross-linking emerges as a valid and practical alternative to loading polyamines onto solid supports. This work demonstrates the versatility of these types of materials and their potential for use in large scale carbon capture systems