Studying liquid-crystal systems with impurities using matrix-formalism methods

We use the matrix formalism to investigate a liquid-crystal system containing impurities. As an example, we calculate correlation functions for fluctuations of the director orientation and of the order parameter, which characterizes an isotropic subsystem. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 147, No. 2, pp. 323–327, May, 2006.     

Influence of hydrostatic pressure on the diffusion of hydrogen in n-GaAs : Si

Hydrogen diffusion experiments have been performed in buried silicon doped GaAs epilayers under hydrostatic pressure. The deuterium diffusion profile in n-GaAs : Si depends on the hydrostatic pressure: a plateau followed by a steep decrease progressively appears as the pressure is increased. This has been interpreted as being due to the increasing importance of the trapping-detrapping process of H⁻ on Si⁺ donors during the hydrogen diffusion. This increase has been attributed to a deepening of the hydrogen acceptor level with respect to the bottom of the Γ conduction band of GaAs as the hydrostatic pressure increases.     

等离子体质谱(ICP-MS)测定高纯氧化镱中痕量稀土和非稀土杂质研究

本文报道ＩＣＰ－ＭＳ直接测定高纯（５Ｎ～６Ｎ）氧化镱中稀土和非稀土杂质的新方法．对ＩＣＰ－ＭＳ测定中的光谱干扰和基体效应进行了详细考察，结果表明：用镓作内标，可有效地补偿因氧化镱引起的基体效应．方法的检出限在０．０Ｘ－０．Ｘｎｇ／ｍＬ范围；相对标准偏差（ＲＳＤ）（ｎ＝７）＜１０％．已应用于高纯氧化镱的工艺流程及其产品分析．     

Influence of annealing conditions on impurity species in arsenic-doped HgCdTe grown by molecular beam epitaxy

Based on our previous work,the influence of annealing conditions on impurity species in in-situ arsenic (As)-doped Hg 1 x Cd x Te (x ≈ 0.3) grown by molecular beam epitaxy has been systematically investigated by modulated photoluminescence spectra.The results show that (i) the doped-As acting as undesirable shallow/deep levels in as-grown can be optimized under proper annealing conditions and the physical mechanism of the disadvantage of high activation temperature,commonly assumed to be more favourable for As activation,has been discussed as compared with the reports in the As-implanted HgCdTe epilayers (x ≈ 0.39),(ii) the density of V Hg has an evident effect on the determination of bandgap (or composition) of epilayers and the excessive introduction of V Hg will lead to a short-wavelength shift of epilayers,and (iii) the V Hg prefers forming the V Hg-As Hg complex when the inactivated-As (As Hg or related) coexists in a certain density,which makes it difficult to annihilate V Hg in As-doped epilayers.As a result,the bandedge electronic structures of epilayers under different conditions have been drawn as a brief guideline for preparing extrinsic p-type epilayers or related devices.     

Aktivierungsanalytische Untersuchung von Zirkoniumlegierungen

Durch Aktivierungsanalyse mit Reaktorneutronen (zerstörungsfrei und mit chemischer Aufarbeitung) sowie mittels zerstörungsfreier Untersuchungen an einem Neutronengenerator wurden O, Al, Si, P, Mn, Cu, Nb, Mo, Cd, Ti, Cr und Hf in Zirkoniumlegierungen bestimmt.     

Theory of Systems of Rodlike Particles: I. Athermal systems

An improved treatment of the lattice model proposed in 1956 is presented for a system of hard rods, with axial ratio x, dispersed in a diluent. Interparticle forces, apart from repulsions on contact, are deliberately ignored within the scope of the present paper. The equilibrium distribution of orientations of the rodlike particles in a phase with nematic order is derived and explicitly taken into account. Thermodynamic properties in the asymptotic limit of high degree of order reduce approximately. to those obtained previously. Calculations carried out for equilibrium between anistropic (nematic) and isotropic phases yield ν′_x/ν_x = 1.4653 for the ratio of volume fractions in the respective phases in the limit x → ∞. The product xν_x, expressing the combined covolume of solute species in the isotropic phase at coexistence is 7.89 in the same limit. The calculated critical value of the axial ratio for coexistence of the two phases in the neat liquid is x_crit, = 6.417. Results are compared with those of other theories. Those that rely on the virial expansion are subject to errors implicit in treating the solvent as a continuum.     

Influence of impurities on the fracture behaviour of tungsten

Ten tungsten materials with different impurity concentrations and different microstructures have been investigated by Auger electron spectroscopy and scanning electron microscopy with respect to their fracture behaviour. For almost all samples, both inter- and transgranular fracture are observed, and the proportion of each type varies. Due to the difference in their impurity content and grain boundary area, a large variation in the grain boundary impurities can be expected. By analysing the fracture surfaces the effect of grain boundary impurities, especially phosphorous and oxygen, on the fracture resistance of the boundaries was determined. The results indicate that for the analysed tungsten materials, grain boundary impurities do not have a significant influence on the fracture resistance of the boundaries. Other factors such as the size and shape of the grains, the amount of deformation and therefore the density of dislocations within the grains have a greater impact on the fracture behaviour of tungsten.     

超高效液相色谱-四极杆-飞行时间质谱法定性分析奥利司他氢化液中的杂质

建立了定性分析奥利司他氢化液中杂质的超高效液相色谱-四极杆-飞行时间质谱法(UPLC-Q-TOF-MS)。采用Thermo Hypersil gold aq C_(18)色谱柱(2.1 mm×150 mm,1.9μm),以0.1%乙酸水-0.1%乙酸乙腈(25∶75)为流动相进行等度分析。质谱使用电喷雾离子源(ESI),正离子模式检测,扫描范围为m/z 50～600,雾化气温度为300℃,干燥气流速为10 L/min。样品经UPLC分离后,用Q-TOF-MS测定了16个杂质的精确分子量与质谱碎片离子,推测了杂质结构,并分析了杂质来源。结果表明,奥利司他氢化液中的杂质主要由发酵过程引入,且含量均大于0.1%,需进行纯化以除去杂质。该研究为奥利司他的工艺纯化与质量控制提供了参考。     

Multifunctional Sulfur-Hyperdoped Silicon Nanoparticles with Engineered Mid-Infrared Sulfur-Impurity and Free-Carrier Absorption

Si nanoparticles (NPs), which are innovative promising light-harvesting components of thin-film solar cells and key-enabling biocompatible theranostic elements of infrared-laser and radiofrequency hyperthermia-based therapies of cancer cells in tumors and metastases, are significantly advanced in their near/mid-infrared band-to-band and free-carrier absorption via donor sulfur-hyperdoping during high-throughput facile femtosecond-laser ablative production in liquid carbon disulfide. High-resolution transmission electron microscopy and Raman microscopy reveal their mixed nanocrystalline/amorphous structure, enabling the extraordinary sulfur content of a few atomic percents and very minor surface oxidation/carbonization characterized by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. A 200-nm thick layer of the nanoparticles exhibits near−mid-infrared absorbance, comparable to that of the initial 380-micron thick n-doped Si wafer (phosphor-dopant concentration ≈10¹⁵ cm⁻³), with the corresponding extinction coefficient for the hyperdoped NPs being 4–7 orders higher over the broadband spectral range of 1–25 micrometers. Such ultimate, but potentially tunable mid-IR structured, multi-band absorption of various sulfur-impurity clusters and smooth free-carrier absorption are break through advances in mid-infrared (mid-IR) laser and radiofrequency (RF) hyperthermia-based therapies, as envisioned in the RF-heating tests, and in fabrication of higher-efficiency thin-film and bulk photovoltaic devices with ultra-broad (UV−mid-IR) spectral response.