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931.
Larivière D Tremblay M Durand-Jézéquel M Tolmachev S 《Analytical and bioanalytical chemistry》2012,403(2):409-418
This article describes a robust methodology using the combination of instrumental design (high matrix interface—HMI), sample
dilution and internal standardization for the quantification of beryllium (Be) in various digested autopsy tissues using inductively
coupled plasma mass spectrometry. The applicability of rhodium as a proper internal standard for Be was demonstrated in three
types of biological matrices (i.e., femur, hair, lung tissues). Using HMI, it was possible to achieve instrumental detection
limits and sensitivity of 0.6 ng L−1 and 157 cps L ng−1, respectively. Resilience to high salt matrices of the HMI setup was also highlighted using bone mimicking solution ([Ca2+] = 26 to 1,400 mg L−1), providing a 14-fold increase in tolerance and a 2.7-fold decrease in method detection limit compared to optimized experimental
conditions obtained without the HMI configuration. Precision of the methodology to detect low levels of Be in autopsy samples
was demonstrated using hair and blood certified reference materials. Be concentration ranging from 0.015 to 255 μg kg−1 in autopsy samples obtained from the U.S. Transuranium and Uranium Registries were measured using the methodology presented. 相似文献
932.
Pilar Ferrer Iván da Silva Juan Rubio‐Zuazo Belén F. Alfonso Camino Trobajo Sergei Khainakov Jose R. Garcia Santiago Garcia‐Granda Germán R. Castro 《Journal of synchrotron radiation》2012,19(1):93-100
A portable powder–liquid high‐corrosion‐resistant reaction cell has been designed to follow in situ reactions by X‐ray powder diffraction (XRD) and X‐ray absorption spectroscopy (XAS) techniques. The cell has been conceived to be mounted on the experimental stations for diffraction and absorption of the Spanish CRG SpLine‐BM25 beamline at the European Synchrotron Radiation Facility. Powder reactants and/or products are kept at a fixed position in a vertical geometry in the X‐ray pathway by a porous membrane, under forced liquid reflux circulation. Owing to the short pathway of the X‐ray beam through the cell, XRD and XAS measurements can be carried out in transmission configuration/mode. In the case of the diffraction technique, data can be collected with either a point detector or a two‐dimensional CCD detector, depending on specific experimental requirements in terms of space or time resolution. Crystallization processes, heterogeneous catalytic processes and several varieties of experiments can be followed by these techniques with this cell. Two experiments were carried out to demonstrate the cell feasibility: the phase transformations of layered titanium phosphates in boiling aqueous solutions of phosphoric acid, and the reaction of copper carbonate and l ‐isoleucine amino acid powders in boiling aqueous solution. In this last case the shrinking of the solid reactants and the formation of Cu(isoleucine)2 is observed. The crystallization processes and several phase transitions have been observed during the experiments, as well as an unexpected reaction pathway. 相似文献
933.
Trushina AP Goldort VG Kochubei SA Baklanov AV 《The journal of physical chemistry. A》2012,116(25):6621-6629
The mechanism and spectral dependence of the quantum yield of singlet oxygen O(2)(a (1)Δ(g)) photogenerated by UV radiation in gaseous oxygen at elevated pressure (32-130 bar) have been experimentally investigated within the 238-285 nm spectral region overlapping the range of the Wulf bands in the absorption spectrum of oxygen. The dominant channel of singlet oxygen generation with measured quantum yield up to about 2 is attributed to the one-quantum absorption by the encounter complexes O(2)-O(2). This absorption gives rise to oxygen in the Herzberg III state O(2)(A' (3)Δ(u)), which is assumed to be responsible for singlet oxygen production in the relaxation process O(2)(A' (3)Δ(u), υ) + O(2)(X (3)Σ(g)(-)) → O(2)({a (1)Δ(g)}, {b (1)Σ(g)(+)}) + O(2)({a (1)Δ(g), υ = 0}, {b (1)Σ(g)(+), υ = 0}) with further collisional relaxation of b to a state. This mechanism is deduced from the analysis of the avoiding crossing locations on the potential energy surface of colliding O(2)-O(2) pair. The observed drop of the O(2)(a (1)Δ(g)) yield near spectral threshold for O(2) dissociation is explained by the competition between above relaxation and reaction giving rise to O(3) + O (O + O + O(2)) supposed in literature. The quantum yield of O(2)(a (1)Δ(g)) formation from encounter complex N(2)-O(2) measured at λ = 266 nm was found to be the same as that for O(2)-O(2). 相似文献
934.
Vasiliev ES Loukhovitskaya EE Morozov II Savilov SV Lunin VV 《The journal of physical chemistry. A》2012,116(24):6107-6112
The uptake of ClO radicals on KBr, NaCl, and NaBr dry solid films was studied at 1 Torr pressure of helium over the temperature range 290-350 K using a flow tube technique with a modulated molecular beam mass spectrometer as the detection method. A Pyrex tube with the deposited salt sample was introduced into the flow reactor along its axis. The ClO uptake coefficient on the KBr surface did not depend on temperature within the experimental accuracy of ~20%. Chlorine oxide radicals were prepared using the reaction of Cl with ozone. It was found out that the ClO uptake coefficient strongly depended on ozone concentration. The uptake coefficients at T = 293 K and [O(3)] = 4.6 × 10(13) molecules cm(-3) were found to be (9.6 ± 5.7) × 10(-4), (3.7 ± 1.5) × 10(-4), and (12.3 ± 3.6) × 10(-4) for KBr, NaCl, and NaBr, respectively. Bromine-containing species were not observed during the interaction of ClO radicals with KBr film. The results obtained indicate that the ClO loss through heterogeneous interaction with salt surface is not sufficiently rapid to compete with gas-phase self-reaction in the atmosphere. 相似文献
935.
Shainyan BA Kirpichenko SV Shlykov SA Kleinpeter E 《The journal of physical chemistry. A》2012,116(1):784-789
Structure and the conformational properties of 1,3,3-trimethyl-1,3-azasilinane have been studied. According to gas electron diffraction (GED), the molecule exists in a slightly distorted chair conformation with the N-Me group in equatorial position. High-level quantum chemical calculations excellently reproduce the experimental geometry. Employing variable temperature (1)H and (13)C NMR spectroscopy down to 103 K, the conformational equilibrium could be frozen and the barrier to ring inversion determined. 相似文献
936.
MA Worsley SO Kucheyev HE Mason MD Merrill BP Mayer J Lewicki CA Valdez ME Suss M Stadermann PJ Pauzauskie JH Satcher J Biener TF Baumann 《Chemical communications (Cambridge, England)》2012,48(67):8428-8430
We report the synthesis of a three-dimensional (3D) macroassembly of graphene sheets with electrical conductivity (~10(2) S m(-1)) and Young's modulus (~50 MPa) orders of magnitude higher than those previously reported, super-compressive deformation behavior (~60% failure strain), and surface areas (>1300 m(2) g(-1)) approaching theoretically maximum values. 相似文献
937.
Grigory Adamovsky Sergei F. Lyuksyutov Jeffrey R. Mackey Bertram M. Floyd Ujitha Abeywickrema Igor Fedin Mindaugas Rackaitis 《Optics Communications》2012,285(5):766-773
Direct experimental measurements of the thermo-optic for fixed temperature intervals (20–200 °C, 200–500 °C, 500–660 °C, 660–780 °C) in fused silica fiber containing fiber Bragg gratings (FBGs) were conducted. The diffraction efficiency of a FBG fluctuated with temperature between 2.01 × 10? 4 and 0.17 × 10? 4 while the temperature shift of the Bragg's peak was monitored between 1300 and 1311 nm with sub-Angstrom precision. Numerical simulations were focused on FBG's diffraction efficiency calculations accounting for the temperature drift of the gratings, and found to be in excellent agreement with obtained experimental data.It was found that the first-order thermo-optic coefficient changes between 1.29 and 1.85 × 10? 5 K? 1 for the linear fit and at T = 0 °C its value was found to be close to 2.37 × 10? 5 K? 1 for the polynomial fit of experimental data. The average thermo-optic coefficient undergoes a minimum in the vicinity of 440 °C. Additional observation indicates a negative sign of the second-order thermo-optic coefficient. The value of thermal expansion coefficient was much less (0.5 × 10? 6 K? 1) than that for the average thermo-optic coefficient. Based on the energy dispersive spectroscopy it was determined that thermal erasing of the FBGs at a temperature around 780 °C corresponds to germanium monoxide diffusion out of core in silica-based fibers. 相似文献
938.
We prove that, under certain conditions, the capacity of an optical communication channel with in-line, nonlinear filtering (regeneration) elements can be higher than the Shannon capacity for the corresponding linear Gaussian white noise channel. 相似文献
939.
Dispersion-dominated nonlinear fiber-optic channel 总被引:1,自引:0,他引:1
We propose to apply a large predispersion (having the same sign as the transmission fiber) to an optical signal before the uncompensated fiber transmission in coherent communication systems. This technique is aimed at simplification of the following digital signal processing of nonlinear impairments. We derive a model describing pulse propagation in the dispersion-dominated nonlinear fiber channel. In the limit of very strong initial predispersion, the nonlinear propagation equations for each Fourier mode become local and decoupled. This paves the way for new techniques to manage fiber nonlinearity. 相似文献
940.
Astashenok Artyom V. Elizalde Emilio Odintsov Sergei D. Yurov Artyom V. 《The European Physical Journal C - Particles and Fields》2012,72(12):1-10
The European Physical Journal C - The d-dimensional scalar field action may be reduced, in the background geometry of a black hole, to a two-dimensional effective action. In the near-horizon... 相似文献