电感耦合等离子体-原子发射光谱法测定红景天中锌、铁、锰和钛

用电感耦合等离子体-原子发射光谱法测定红景天中锌、铁、锰和钛等元素。使用与分析样品基体相接近的标准样品和控制一致的测定条件,克服了物理干扰和基体效应的影响,选择波长为233.0,273.9,257.6,334.9nm4条谱线分别作为测定锌、铁、锰和钛的分析线,测得4种元素的检出限(3s)为0.004—0.05μg/mL。本法测定红景天中4种金属元素的含量,相对标准偏差(n=7)在2.2%—4.2%之间,加标回收率在96.4%—115.2%之间。     

Magnetic hysteresis and refrigeration capacity of Ni-Mn-Ga alloys near Martensitic transformation

This paper studies the magnetic hysteresis and refrigeration capacity of Ni-Mn-Ga alloys in detail during heating and cooling isothermal magnetisation processes. The Ni-Mn-Ga alloys show larger magnetic hysteresis when they transform from austenite to martensite, but smaller magnetic hysteresis when they transform from martensite to austenite. This behaviour is independent of either the pure Ni-Mn-Ga alloys or the alloys doped with other elements. Because of the existence of the magnetic hysteresis, the relation between the magnetic entropy change and refrigeration capacity is not simply linear. For practical consideration, magnetocaloric effect of Ni-Mn-Ga alloys should be investigated both on cooling and heating processes.     

Luminescence of Ce3+ in lanthanum silicon oxynitride

The luminescence properties of lanthanum silicon oxynitride(La-Si-O-N) series doped by trivalent Ce ions have been investigated to seek for tunable wavelength-conversion phosphor for white light emitting diode applications.Four compound hosts of LaSiO2N,La4Si2O7N2,La5Si3O12 N,and La2Si6O3N8 were synthesized and examined in this work.Crystallographic examination for the equal amount of Ce 3+ substitution indicated that the covalency degree decreased in a sequence LaSiO2 N > La2Si6O3N8 > La4Si2O7N2 > La5Si3O12 N,not simply in correlation to the ratio of N3/O2.Excitation and emission spectrum measurements showed the main features of Ce3+ luminescence in the series:the centre of gravity of 5d bands depends on crystal-field splitting more strongly than that on covalency of Ce-N bonding;nephelauxetic effect could not be observed clearly for the investigated series;to some extent Stokes shift was dominated by crystal-field splitting rather than Ce-N covalency degree.     

In silico analysis of microdomain-mediated trimer formation in the T cell membrane

We consider stochastic reaction-diffusion dynamics involved in the formation of a trimeric protein receptor complex, where diffusion is modulated by the presence of small, fixed membrane microdomains. Compartmentalisation of cell membrane signalling proteins may optimise signal transduction but previous modelling work suggests that signalling is only augmented if microdomains are highly mobile. Using a Gillespie algorithm-based spatial numerical simulation, we examine the effect of the presence, size and total coverage of microdomains, which either slow protein diffusion or trap proteins at their boundary. We examine scenarios where protein-protein interactions take place within microdomains, and also where interactions are favoured at the microdomain boundary. This model is motivated by the formation of the high-affinity receptor for the cytokine IL-2. Proliferation requires a threshold number of bound receptors, but pleiotropic effects of IL-2 on other cell types means that high ligand concentrations are undesirable. Hence, optimising T cell sensitivity to IL-2 is essential. In agreement with earlier models, we find that small microdomain sizes result in the greatest augmentation in receptor formation, but that static microdomains can also confer an increased sensitivity in the case of heterotrimeric receptor complex formation.     

Inflationary scenario in the supersymmetric economical 3-3-1 model

We construct the supersymmetric economical 3-3-1 model which contains inflationary scenario and avoids the monopole puzzle. Based on the spontaneous symmetry breaking pattern (with three steps), the F-term inflation is derived. The slow-roll parameters ∈ and η are calculated. By imposing as experimental five-year WMAP data on the spectral index n, we have derived a constraint on the number of e-folding N _Q to be in the range from 25 to 50. The scenario for large-scale structure formation implied by the model is a mixed scenario for inflation and cosmic string, and the contribution to the CMBR temperature anisotropy depends on the ratio M _X /M _Pl. From the COBE data, we have obtained the constraint on the M _X to be M _X ∈ [1.22 × 10¹⁶, 0.98 × 10¹⁷] GeV. The upper value M _X ≃ 10¹⁷ GeV is a result of the analysis in which the inflationary contribution to the temperature fluctuations measured by the COBE is 90%. The coupling α varies in the range: 10⁻⁷−10⁻¹. This value is not so small, and it is a common characteristics of the supersymmetric unified models with the inflationary scenario. The spectral index n is a little bit smaller than 0.98. The SUGRA corrections are slightly different from the previous consideration. When ξ ≪ 1 and α lies in the above range, the spectral index gets the value consistent with the experimental five-year WMAP data. Comparing with string theory, one gets ξ < 10⁻⁸. Numerical analysis shows that α ≈ 10⁻⁶. To get inflation contribution to the CMBR temperature anisotropy ≈90%, the mass scale M _X < 3.5 × 10¹⁴ GeV.     

Porous ZnO nanobelts: synthesis,mechanism, and morphological evolutions

Porous ZnO nanobelts with rough surface and poly-crystalline nature have been developed from a facile wet chemical method. The as-prepared products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), cold field emission scanning electron microscopy (CFE-SEM), and energy dispersive analysis of X-rays (EDAX). The ZnO nanobelts were synthesized with usually 5 to 6 nm in thickness, 10 to 40 nm in width, and about several micrometers in length. A PVP promoted self-assembly mechanism is believed to be responsible for the morphology shaping process of the ZnO nanostructures. This first wet chemical synthesis of such hierarchical structures without any hard templates implies a simple and inexpensive way to prepare transition metal superstructures on a large scale for modern chemical synthesis. Optical characterization by a confocal laser Raman were also carried out to explore their optical properties; the PL and Raman results showed both good agreement with the characters of our samples and potential for future applications such as sensors and other modern technologies.     

Stoichiometry of BaTiO3 nanoparticles

Barium titanate nanoparticles with various nominal Ba/Ti ratios were prepared through direct synthesis from solution (DSS) and further annealed at different temperatures. Their deviation from stoichiometry was studied through XRD analysis, and a large deviation from stoichiometry has been observed. The grain size we studied ranges from 50 nm to 1 μm. For the as-prepared particles, the grain size is about 50 nm, and the maximum excess of Ti is over 15%. For the samples annealed at 800 °C, the grain size is increased to 100 nm, and the maximum excesses of Ba and Ti are 8 and 9%, respectively. The defects formed during synthesis and surface effect of nanoparticles are both estimated for their contributions to the deviation from stoichiometry, and the defects have been found to be mainly responsible for the large deviation observed.     

相位延迟器在四频激光陀螺中的应用研究

介绍了典型相位延迟器1／4波片和90°相位延迟膜的工作原理,定义了四频激光陀螺输出信号解调信噪比,分析了相位延迟量对其造成的影响,并就此结果进行了MATLAB仿真。从两种相位延迟器的工作原理出发,阐述了温度、入射角、入射光波长等因素对两者相位延迟量的影响。结合激光陀螺在实际应用中的要求,对两者进行了比较,并得出结论：90°相位延迟膜更适合作为四频激光陀螺输出解调系统中的相位延迟器。     

LITTLEWOOD-PALEY THEOREM FOR SCHR(O)DINGER OPERATORS

Let H be a Schr(o)dinger operator on Rn. Under a polynomial decay condition for the kernel of its spectral operator, we show that the Besov spaces and Triebel-Lizorkin spaces associated with H are well defined. We further give a Littlewood-Paley characterization of Lp spaces in terms of dyadic functions of H. This generalizes and strengthens the previous result when the heat kernel of H satisfies certain upper Gaussian bound.     

Symmetry-breaking substitutions of [Re(CN)8]3- into the centered, face-capped octahedral clusters (CH3OH)24M9M'6(CN)48 (M = Mn, Co; M = Mo, W)

The diamagnetic complex [Re(CN)8]3- is shown to react with Mn2+ ions in methanol to generate the centered, face-capped octahedral cluster (CH3OH)24Mn9Re6(CN)48, which is structurally analogous to (CH3OH)24Mn9Mo6(CN)48. Related reactions involving stoichiometric mixtures of octacyanometalate complexes generate the substituted species (CH3OH)24Mn9Mo5Re(CN)48, (CH3OH)24Co9Mo5Re(CN)48, (CH3OH)24Mn9Mo3Re3(CN)48, (CH3OH)24Mn9W5Re(CN)48 and (CH3OH)24Co9W5Re(CN)48, in which the O(h) symmetry of the cluster core is broken. Reassessment of the magnetic properties of the Mn9Mo6(CN)48 cluster confirm that it possesses a ground state spin of S = 39/2, but does not exhibit single-molecule-magnet behavior. Lowering the symmetry of the molecule by substitutions of ReV at one or three of the MoV sites does not lead to an overall increase in the magnetic anisotropy, as probed by ac magnetic susceptibility measurements. A similar result occurs for the other substituted species, with the important exception of the new single-molecule magnet (CH3OH)24Co9W5Re(CN)48, for which the spin reversal barrier is significantly reduced relative to that observed previously in (CH3OH)24Co9W6(CN)48.