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971.
Alexander V. Evteev Elena V. Levchenko Leila Momenzadeh Irina V. Belova Graeme E. Murch 《哲学杂志》2016,96(6):596-619
Using results of equilibrium molecular dynamics simulation in conjunction with the Green–Kubo formalism, we present a general treatment of thermal impedance of a crystal lattice with a monatomic unit cell. The treatment is based on an analytical expression for the heat current autocorrelation function which reveals, in a monatomic lattice, an energy gap between the origin of the phonon states and the beginning of the energy spectrum of the so-called acoustic short-range phonon modes. Although, we consider here the f.c.c. Al model as a case example, the analytical expression is shown to be consistent for different models of elemental f.c.c. crystals over a wide temperature range. Furthermore, we predict a frequency ‘window’ where the thermal waves can be generated in a monatomic lattice by an external periodic temperature perturbation. 相似文献
972.
973.
《Analytical letters》2012,45(12):1954-1964
A novel, simple, sensitive, and efficient method for the speciation of inorganic antimony by dispersive liquid–liquid microextraction (DLLME) combined with graphite furnace atomic absorption spectrometry (GF-AAS) is reported. The method uses a hydrophobic complex of antimony(III) with a new chelating agent, 1,2,6-hexanetriol trithioglycolate, at neutral pH. The complex was extracted into the organic phase, whereas antimony(V) remained in aqueous solution. The concentration of antimony(V) was obtained by subtracting the antimony(III) concentration from the total antimony concentration following the reduction of antimony(V) to antimony(III) by L-cysteine. The pH, extraction and dispersive solvents and volumes, and concentration of 1,2,6 -hexanetriol trithioglycolate were optimized. Under the optimized conditions, the analytical curve was linear from 0.26 to 3.2 micrograms per liter with a limit of detection of 27.0 nanograms per liter for antimony(III). The relative standard deviation was 6.8 percent at 0.52 microgram per liter antimony(III) with an enrichment factor of twenty-six. The method was employed for the speciation of antimony in leaching solution in contact with plastic; and the recoveries in fortified samples were between 94.2 and 118.0 percent. 相似文献
974.
Green light emitting Mn2+ doped Zn2SiO4 particles embedded in SiO2 host matrix were synthesized by a sol–gel method. After the incorporation of ZnO:Mn nanoparticles in a silica monolith using sol–gel method with supercritical drying of ethyl alcohol in two steps, it was heat treated in air at 1200 °C for 2 h in order to obtain the SiO2/α-Zn2SiO4:Mn nanocomposites. The microstructure of phosphor crystals was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). XRD results indicate that the pure phase α-Zn2SiO4 with rhombohedral structure was obtained after thermal treatment at 1200 °C. The SiO2/α-Zn2SiO4:Mn nanocomposites with a Mn doping concentration of 1.5 at% exhibit two broadband emissions in the visible range: a strong green emission at around 525 nm and a second one in the range between 560 and 608 nm. This nanocomposite with a Mn doping concentration of 0.05 shows the highest relative emission intensity. Upon 255 nm excitation, the luminescence decay time of the green emission of Zn2SiO4:Mn around 525 nm is 11 ms. The luminescence spectra at 525 nm (4T1–6A1) and lifetime of the excited state of Mn2+ ions-doped Zn2SiO4 nanocrystals are investigated. 相似文献
975.
M. Dutta 《Journal of statistical physics》1972,5(1-2):127-131
In an essentially statistical approach to statistical mechanics, it is seen that the Gauss principle of the arithmetic mean may be taken as the starting point. The equations from which the subject can be built up are deduced from the Gauss principle of the arithmetic mean. 相似文献
976.
Muhammad Akhyar Farrukh Noureen Siraj Iftikhar Imam Naqvi 《Journal of Saudi Chemical Society》2010,14(2):209-212
Iron has been determined in apple and vegetables spectrophotometrically, by complexing it with xylenol orange. 1:1 complex formed in a highly acidic medium is measured for its absorbance at its λmax of 585 nm. The results have been compared by employing atomic absorption technique. Apples and vegetable samples were collected from local markets of Pakistan. Statistical manipulations, t-test and F-test, were performed and it was found that the results from the two techniques have an excellent agreement. 相似文献
977.
C. Rossi C. Bonechi S. Martini M. Ricci G. Corbini P. Corti A. Donati 《Magnetic resonance in chemistry : MRC》2001,39(8):457-462
Proton NMR selective and non-selective spin–lattice relaxation rate measurements were used to monitor the strength of the overall complexation behaviour of a ligand (carbamazepine) toward a macromolecular receptor (albumin). The ‘affinity index,’ a quantitative parameter related to the strength of the ligand–macromolecule interaction, was determined from the experimental contribution of the bound ligand molar fraction to the observed selective spin–lattice relaxation rate. The effect of a second ligand (lamotrigine) on the carbamazepine–albumin interaction was also investigated and was found to have a modulation effect on the carbamazepine–albumin interaction. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
978.
In this paper, we study a second order variational problem for locally convex hypersurfaces, which is the affine invariant analogue of the classical Plateau problem for minimal surfaces. We prove existence, regularity and uniqueness results for hypersurfaces maximizing affine area under appropriate boundary conditions.
979.
Min Wu 《Journal of Mathematical Analysis and Applications》2008,339(2):1425-1431
We provide sufficient conditions for the convergence of the Newton-like methods in the assumption that the derivative satisfies some kind of weak Lipschitz conditions. Consequently, some important convergence theorems follow from our main result in this paper. 相似文献
980.
在正项级数Gauss判别法的基础上,定义了正数列an的Gauss指标G=lim[n ln(an/an+1)-1]ln n.从而得到了正项级数的Gauss指标判别法.通过具体计算已有各种判别法的Gauss指标,结果表明,Gauss指标判别法是达朗贝尔、柯西、拉贝、高斯和Bertrand等5种判别法的推广. 相似文献