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Abstract  

Three ferromanganese crusts from different locations of the Indian Ocean were analysed by neutron activation analysis using thek 0 method (k 0 NAA method) for studying the distribution of some trace elements along with Fe and Mn. Another crust from the Lau basin of the Pacific Ocean was investigated for comparison of the influence of different oceanic conditions on the trace element distributions in ferromanganese crusts. Variation in Co concentration along with the Mn/Fe ratio were discussed in terms of the hydrogenous/hydrothermal nature of the crusts. The normalised REE content was used to identify possible anomalies. The observed Ce anomaly is discussed in the light of the depositional environment. The precision and accuracy of the method were confirmed by measuring the elemental concentrations in a USGS nodule standard NOD A-1.

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Analysis of a symmetric neopolyol ester

II. Solid state13C NMR and X-ray measurements

Journal of Thermal Analysis and Calorimetry
Authors:
W. Chen
,
A. Habenschuss
,
M. Pyda
,
Monika Varma-Nair
,
H. S. Aldrich
, and
B. Wunderlich

The symmetric neopolyol ester tetra[methyleneoxycarbonyl(2,4,4-trirnethyl)pentyl]methane (MOCPM) has been studied by variable-temperature solid-state13C NMR and X-ray powder diffraction and compared to molecular mechanics calculations of the molecular structure. Between melting and glass transition temperatures the material is semicrystalline, consisting of two conformationally and motionally distinguishable phases. The more mobile phase is liquid-like and is, thus attributed to an amorphous phase (≈16%). The branches of the molecules in the crystal exhibit two conformationally distinguishable behaviors. In one, the branches are well ordered (≈56%), in the other, the branches are conformationally disordered (≈28%). Different branches of the same molecule may show different conformational order. This unique character of the rigid phase is the reason for the deficit of the entropy of fusion observed earlier by DSC. In the melt, solid state NMR can identify two bonds that are rotationally immobile, even though the molecules as a whole have liquid-like mobility. This partial rigidity of the branches accounts quantitatively for the observed increase in heat capacity at the glass transition. The reason for this unique behavior of MOCPM, a small molecule, is the existence of one chiral centers in each of the four arms of the molecule. A statistical model assuming that at least two of the chiral centers must fit into the order of the crystal can explain the crystallization behavior and would require 12.5% amorphous phase, 28.1% conformational disorder, and 59.4% crystallinity, close to the observed maximum perfection.

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Abstract  

Extraction of trivalent (Pu3+, Am3+, actinides and Eu3+, a representative of lanthanides) and tetravalent (Np4+ and Pu4+) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP) in combination with TBP in benzene from 2M nitric acid. The stoichiometries of the species extracted were found to be M(NO3)3·(3–n) TBP·n DHDECMP (for trivalent ions) and M(NO3)4·(2–n) TBP·n DHDECMP (for tetravalent ions) by the slope ratio method. The extraction constants evaluated (from the distribution data) indicate that for tetravalent ions (with solvation number two) the extraction constant increases when TBP (Kh=0.17) molecules are successively replaced by more basic DHDECMP (Kh=0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHDECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu3+ and Am3+, a lesser decrease being observed for Pu3+ (larger ion).

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
R.N. Acharya
,
K. Sudarshan
,
A.G.C. Nair
,
Y.M. Scindia
,
A. Goswami
,
A.V.R. Reddy
, and
S.B. Manohar

Abstract  

The guided thermal neutron beam at 100 MW Dhruva research reactor facility of Bhabha Atomic Research Centre (BARC) was used to carry out prompt gamma-ray neutron activation analysis (PGNAA). The prompt k 0-factors have been determined for the isotopes of the elements H, B, K, Co, Cu, Ca, Ti, Cr, Cd, Ba, Hg and Gd with respect to 1951 keV gamma-line of 36Cl. The prompt k 0-factors for H, Cl and Cu were also measured with respect to the 1381 keV gamma-line of 49Ti. Different samples like NH4Cl, Ti metal, cobalt chloride and other stoichiometric compounds and pure metals were used for this purpose. Prompt gamma-rays were accumulated using a 22% HPGe detector connected to a PC based 8k MCA in single mode counting. The energy calibration in the range of 100–8500 keV was carried out using gamma-rays from 152Eu and 60Co, and the prompt gamma-rays from 36Cl whereas the absolute detection efficiency for this energy range was determined using 152Eu and prompt gamma-rays from 36Cl and 49Ti.

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