1,528 research outputs found

    N2H+(1-0) survey of massive molecular cloud cores

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    We present the results of N2H+(1-0) observations of 35 dense molecular cloud cores from the northern and southern hemispheres where massive stars and star clusters are formed. Line emission has been detected in 33 sources, for 28 sources detailed maps have been obtained. The optical depth of (23-12) component toward peak intensity positions of 10 sources is ~ 0.2-1. In total, 47 clumps have been revealed in 26 sources. Integrated intensity maps with aspect ratios < 2 have been fitted with a power-law radial distribution r−pr^{-p} convolved with the telescope beam. Mean power-law index is close to unity corresponding to the ∌r−2\sim r^{-2} density profile provided N2H+ excitation conditions do not vary inside these regions. Line widths of the cores either decrease or stay constant with distance from the center. The ratio of rotational to gravitational energy is too low for rotation to play a significant role in the dynamics of the cores. A correlation between mean line widths and sizes of clumps has been found.Comment: 17 pages, Late

    Ellagitannins with Glucopyranose Cores Have Higher Affinities to Proteins than Acyclic Ellagitannins by Isothermal Titration Calorimetry

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    The thermodynamics of the interactions of different ellagitannins with two proteins, namely, bovine serum albumin (BSA) and gelatin, were studied by isothermal titration calorimetry. Twelve individual ellagitannins, including different monomers, dimers, and a trimer, were used. The studies showed that several structural features affected the interaction between the ellagitannin and the protein. The interactions of ellagitannins with proteins were stronger with gelatin than with BSA. The ellagitannin-gelatin interactions contained both the primary stronger and the secondary weaker binding sites. The ellagitannin-BSA interactions showed very weak secondary interactions. The ellagitannins with glucopyranose cores had stronger interaction than C-glycosidic ellagitannins with both proteins. In addition, the observed enthalpy change increased as the degree of oligomerization increased. The stronger interactions were also observed with free galloyl groups in the ellagitannin structure and with higher molecular flexibility. Other smaller structural features did not show any overall trend

    Research Data Management 'Green Shoots' Pilot Programme, Final Reports

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    This document contains the final reports of six Research Data Management Green Shoots projects run at Imperial College in 2014

    Decomposition and nutrient release of leguminous plants in coffee agroforestry systems.

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    Leguminous plants used as green manure are an important nutrient source for coffee plantations, especially for soils with low nutrient levels. Field experiments were conducted in the Zona da Mata of Minas Gerais State, Brazil to evaluate the decomposition and nutrient release rates of four leguminous species used as green manures (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum and Stylosanthes guianensis) in a coffee agroforestry system under two different climate conditions. The initial N contents in plant residues varied from 25.7 to 37.0 g kg-1 and P from 2.4 to 3.0 g kg-1. The lignin/N, lignin/polyphenol and(lignin+polyphenol)/N ratios were low in all residues studied. Mass loss rates were highest in the first 15 days, when 25 % of the residues were decomposed. From 15 to 30 days, the decomposition rate decreased on both farms. On the farm in Pedra Dourada (PD), the decomposition constant k increased in the order C. mucunoides < S. aterrimum < S. guianensis < A. pintoi. On the farm in Araponga (ARA), there was no difference in the decomposition rate among leguminous plants. The N release rates varied from 0.0036 to 0.0096 d-1. Around 32 % of the total N content in the plant material was released in the first 15 days. In ARA, the N concentration in the S. aterrimum residues was always significantly higher than in the other residues. At the end of 360 days, the N released was 78 % in ARA and 89 % in PD of the initial content. Phosphorus was the most rapidly released nutrient (k values from 0.0165 to 0.0394 d-1). Residue decomposition and nutrient release did not correlate with initial residue chemistry and biochemistry, but differences in climatic conditions between the two study sites modified the decomposition rate constants
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