Colossal magnetodielectric effect in SmFe<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> multiferroic

The colossal (more than threefold) decrease in the dielectric constant ɛ in the easy-plane SmFe₃(BO₃)₄ ferroborate in a magnetic field of ∼5 kOe applied in the basal ab plane of the crystal has been found. A close relation of this effect to anomalies in the field dependence of the electric polarization has been established. It has been shown that this magnetodielectric effect is due to the contribution to ɛ from the electric susceptibility, which is related to the rotation of spins in the ab plane, arises in the region of the antiferromagnetic ordering T < T _N = 33 K, and is suppressed by the magnetic field. A theoretical model describing the main features of the behavior of ɛ and electric polarization in the magnetic field has been proposed, taking into account the additional anisotropy in the basal plane induced by the magnetoelastic stresses.     

Chiral N-phosphonyl imine chemistry:asymmetric additions of glycine enolate to diphenyl diamine-based phosphonyl imines

Diphenyl diamine-based phosphonyl imines attached by the N-isopropyl group in the auxiliary have been synthesized in good yields under convenient reaction conditions.These new chiral N-phosphonyl imines can react with glycine enolate smoothly to give chiral α-β diamino esters in good yields(72%-90%) and up to excellent diastereoselectivity(>99:1 dr).By treatment with HBr,the chiral auxiliary can be readily removed.The absolute structure has been unambiguously determined by converting a product to a known sa...     

Wear kinetics of high-strength activated granulated carbons based on peat

The wear kinetics of activated carbons made of raw formulations based on peat with furfural and lignin additives was studied in comparison with the wear kinetics of the FAS-3 sample, a top-strength domestic activated carbon.     

Bayesian Approach to Retrieving a Vertical Ozone Profile from Radiometric Measurement Data

We propose a technique for retrieving a vertical profile of the atmospheric ozone number density from ground-based radiometry data. The technique is based on the Bayesian approach to solving inverse problems and permits one, by allowing for measurement noise and using certain a priori information on the retrieved profile, to construct the probability distribution of the ozone number density in the entire altitude range being monitored. Using the proposed technique, we compare the retrieval results obtained for various (both well-known and suggested for the first time in this paper) methods of approximation and regularization of retrieved profiles. Model examples demonstrate that the proposed technique is capable of retrieving ozone-profile disturbances which accompany the formation of ozone holes.     

Influence of the orientation of a crystal on thermal polarization effects in high-power solid-state lasers

The polarization thermal self-action of laser radiation propagating in an isotropic crystal has been studied experimentally. New nonlinear effects have been observed for the first time. These effects include a change in the symmetry of the depolarized-field distribution and the qualitative dependence of the degree of the self-induced depolarization on the geometry of the beam and crystal. The classical problem of self-induced depolarization has been analytically solved in the general form for an arbitrary orientation of any cubic crystal. The theoretical results agree well with the experimental data. The optimum orientation of the laser crystal has been determined, which can be effectively used in lasers with high average power.     

The nature of magnetoelastic anomalies in Nd<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>MnO<Subscript>3</Subscript> upon suppression of charge ordering by a magnetic field

This paper reports on the results of investigations into the magnetic and magnetoelastic properties of Nd_0.5Sr_0.5MnO₃ single crystals in pulsed magnetic fields up to 250 kOe, the magnetic and kinetic properties of these crystals in weak static magnetic fields, and their thermal expansion. It is demonstrated that the studied properties exhibit a number of anomalies due to a transition from the antiferromagnetic semiconducting state to the ferromagnetic metallic state upon suppression of charge ordering.     

深圳某电厂H型钢桩沉桩与效果测试

在上部为花岗岩块石填土、下部为相对软弱的粘性土 ,地下水与海水相通的地区进行大型工程建设 ,主要建 (构 )筑物采用桩基础是安全可靠的措施 ,但采用何种桩型、沉桩时怎样才能顺利穿过花岗岩块石填土是一个值得研究的课题。采用潜孔锤引孔穿过花岗岩块石填土 ,往孔内回填碎石 ,然后打H型钢桩 ,在深圳某电厂地基处理中获得了较好的效果     

顶空气相色谱-质谱联用结合同位素峰形校正检索技术鉴别芝麻油风味成分

采用顶空气相色谱-质谱联用(GC-MS)仪结合同位素峰形校正检索技术鉴别了市售芝麻油风味成分中的71种化合物,占总检出化合物的90.2%。检出化合物可分为吡嗪、吡咯、吡啶、噻唑、噻吩、吲哚、唑、呋喃、醛类和酚类等,其中醛、酚、吡嗪和呋喃类化合物的含量较高,分别占风味成分含量的37.4%,20.1%,10.0%和6.7%。同位素峰形校正检索技术在低分辨率质谱上可对化合物的相对分子质量实现精确测量,从而为低分辨率四极杆质谱确定化合物的元素组成和解析化合物结构提供了重要依据,同时也为芝麻油的成分分析提供了新的技术手段。     

Study of the quality of carbon nanotubes produced by chemical vapor deposition

Method for obtaining carbon nanotubes by the method of chemical vapor deposition with varied amount of catalyst, reaction duration, and temperature is considered. The synthesis of carbon nanotubes with various mode parameters was experimentally studied. The quality of the carbon nanotubes was examined by Raman spectroscopy. It was found that the defectiveness of the carbon nanotubes depends on the synthesis parameters.     

三项指数和四次均值的精确计算公式(2)

本文进一步深入研究了三项指数和四次均值的计算问题.运用指数和的相关性质并结合求解同余方程组的方法与技巧,利用两种不同的方法获得了两个精确的均值计算公式,揭示了三项指数和的计算与同余方程组解的个数之间的本质联系,推广了已有的结果.