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Inductively coupled Argon Plasma Spectrometry is used for the indirect determination of sulphate in iron(III) chloride leach solution of Elliot Lake uranium ores via addition of a known amount of barium ions and analyzing for excess of barium. The ore contains approximately 7 wt% pyrite, FeS(2) as the major mineral which oxidizes to generate sulphate during leaching with fe(III). The effects of pH, the concentrations of Fe(III) and chloride ions and for presence of ethanol in the test samples on the accuracy of analysis are studied. It is found that unlike the Rhodizonate method, removal of iron(III) from or addition of ethanol to the test sample prior to analysis are not required. Linear calibration curves are obtained. 相似文献
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Measurements of synchrotron radiation emitted by 30-MeV runaway electrons in the TEXTOR-94 tokamak show that the runaway population decays after switching on neutral beam injection (NBI). The decay starts only with a significant delay, which decreases with increasing NBI heating power. This delay provides direct evidence of the energy dependence of runaway confinement, which is expected if magnetic modes govern the loss of runaways. Application of the theory by Mynick and Strachan [Phys. Fluids 24, 695 (1981)] yields estimates for the "mode width" (delta) of magnetic perturbations: delta<0.5 cm in Ohmic discharges, increasing to delta = 4.4 cm for 0. 6 MW NBI. 相似文献
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Ultrasonic pulse echo-overlap technique at 300 K (9 MHz) has been employed to study the elastic properties of Al3+-substituted CuFe2O4 spinel ferrite system. The longitudinal and transverse wave velocities are used to compute elastic moduli and these are corrected to the zero porosity by employing different models. Contrary to expectation, the magnitude of elastic moduli is found to decrease by 75% with only 30% of Al3+-substitution for Fe3+ in the system. The lowering of elastic stiffness is mainly due to residual stress-induced spontaneous cracking and presence of oxygen vacant sites in the material. The lower value of lattice energy for polycrystalline specimens as compared to their single crystalline counterparts have been explained in the light of an increase degree of disorientation at the grain boundary with Al3+-substitution. 相似文献
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Joohyun Kim Josef Kapitán Ahmed Lakhani Petr Bouř Timothy A. Keiderling 《Theoretical chemistry accounts》2008,119(1-3):81-97
Vibrational circular dichroism (VCD) has had a large impact on configurational studies of organic molecules largely due to
the theoretical advances made by Philip Stephens and co-workers. For peptides, the structural issue is not one of the configuration,
but of conformation, and the flexibility of the oligomeric structure raises major computational challenges. Turns are a vital
aspect of peptide and protein conformation that allow such structures to fold into a compact unit. However, unlike helices
and sheets, they are not extended repeating structures, but each residue has a different local conformation. Also, when turns
are part of larger peptides their termini are connected to completely different structural elements. We have done extended
comparative density functional theory (DFT) computations to characterize the expected spectral contributions of selected turn
structures to the amide IR and VCD spectra of peptides. The isolated vacuum results for tri-amide turns (Ac-X-Y-NH2) of a few different sequences are compared with calculations involving correction for solvation effects. In particular, we
looked at the sequence variation in spectra and structure between Ala-Ala, Aib-Gly and D-Pro-Gly for the turn-specific X–Y
residues. The nature of some turn-associated, amide originating, spectral transitions are developed and tested. 相似文献
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The electrical conductivity at 10GHz, the dielectric constant, and the thermoelectric power (TEP) of [(C6H5)3PCH3]+(TCNQ)-2, from 230 up to 400 K, have been measured. This organic quasi-one-dimensional solid undergoes a first order phase transition at 314 K. At the transition the conductivity increases by a factor of 2.2 and the activation energy drops to 0.26 from 0.31 eV. At 314 K TEP decreases abruptly from -75 to -60μVK-1 and remains almost constant for T > 314 K. The dielectric permeability ?0 is constant and equal to 5 in the low temperature phase, increases abruptly by 7% at the transition, and then depends strongly on temperature in the high temperature phase. Results of the high temperature phase are interpreted in terms of a strongly correlated salt. 相似文献
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The amplitude of the quantum oscillations in the magnetoconductance of a silicon inversion layer has been studied as a function of gate voltage Vg, for different values of the temperature T, applied magnetic field strength H and substrate bias Vs. By analyzing the amplitude of the oscillations at fixed Vg and Vg as a function of T and H, the dependence of the cyclotron effective mass m1 and the Dingle temperature TD on Vg and Vs can be obtained. The dependence of m1 on Vg for different values of Vs is compared with the prediction of theory. 相似文献
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Observation of π Berry phase in quantum oscillations of three‐dimensional Fermi surface in topological insulator Bi2Se3
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We report the quantum transport studies on Bi2Se3 single crystal with bulk carrier concentration of ~1019 cm–3. The Bi2Se3 crystal exhibits metallic character, and at low temperatures, the field dependence of resistivity shows clear Shubnikov–de Haas (SdH) oscillations above 6 T. The analysis of these oscillations through Lifshitz–Kosevich theory reveals a non‐trivial π Berry phase coming from three‐dimensional (3D) Fermi surface, which is a strong signature of Dirac fermions with three‐dimensional dispersion. The large Dingle temperature and non zero slope of Williamson–Hall plot suggest the presence of enhanced local strain field in our system which possibly transforms the regions of topological insulator to 3D Dirac fermion metal state. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
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We have used the technique of chemical vapour transport to prepare needle shaped single crystal of ZrS3. Results of the measurements of d.c. resistivity. Hall coefficient and thermoelectric power of the temperature range 100–500 K are reported. All the samples exhibited semiconducting behaviour with a room temperature resistivity of about 15 Ω-cm and an activation energy of 0.20±0.02 eV. Room temperature thermoelectric power is -850 μVK?1 and the dominant carriers are electrons. The thermoelectric power varies as (1/T), a behaviour associated with a typical semiconductor. Mobility at low temperatures is limited by ionized impurity scattering and is given by μ1 = 6.5 × 10?2T3/2 cm2V7-1 sec?1. At high temperatures, phonon scattering is dominant and the mobility is given by μ2 = 1.35 × 10+5T?32 cm2V?1 sec?1. 相似文献