Temperature compensating Elinvar character in Fe-Mn-Si alloys

Young's modulus-temperature and thermal expansion curves were measured in γ-Fe-31Mn-(0.25-8.67) Si-0.77C (at%) alloys by dynamic audio resonance method and in a light dilatometer. The results show that the anomalies in Young's modulus and thermal expansion appear near the Néel temperature. The temperature coefficient of Young's modulus, (1/E_p)(dE_p/dT), is controlled by Si content below the Néel temperature. When Si content increases to 5.31 at%, (1/E_p)(dE_p/dT) is close to zero in temperature range from 260 to 335 K, i.e. the Fe-31Mn-5.31Si-0.67C (at%) alloy shows Elinvar character. The temperature range in which the Elinvar character appears is wider than that of γ-Fe-Mn Elinvar alloys. The change in exchange energy and the ΔE effect result from the effect of Si on the antiferromagnetic behavior in γ-Fe-Mn alloys since it induces or enhances localized magnetic moment. When the increase in normal Young's modulus due to lowering temperature is compensated by the ΔE effect caused by the antiferromagnetic ordering, Elinvar character appears.     

Asymptotic distributions of maxima of complete and incomplete samples from multivariate stationary Gaussian sequences

Let be a sequence of d-dimensional stationary Gaussian vectors, and let denote the partial maxima of . Suppose that there are missing data in each component of and let denote the partial maxima of the observed variables. In this note, we study two kinds of asymptotic distributions of the random vector where the correlation and cross-correlation satisfy some dependence conditions.     

Almost sure limit theorems of extremes of complete and incomplete samples of stationary sequences

Let \((X_{n}^{\ast})\) be an independent identically distributed random sequence. Let \(M_{n}^{\ast}\) and \(m_{n}^{\ast}\) denote, respectively, the maximum and minimum of \(\{X_{1}^{\ast},\cdots,X_{n}^{\ast}\}\). Suppose that some of the random variables \(X_1^{\ast},X_2^{\ast},\cdots\) can be observed and let \(\widetilde{M}_n^{\ast}\) and \(\widetilde{m}_n^{\ast}\) denote, respectively, the maximum and minimum of the observed random variables from the set \(\{X_1^{\ast},\cdots,X_n^{\ast}\}\). In this paper, we consider the asymptotic joint limiting distribution and the almost sure limit theorems related to the random vector \((\widetilde{M}_n^{\ast}, \widetilde{m}_n^{\ast}, M_n^{\ast}, m_n^{\ast})\). The results are extended to weakly dependent stationary Gaussian sequences.     

Structure and characterization of hexakis(imidazole) cobalt(II) complexes: [Co(Im)6(OBz)2] and [Co(Im)6(mB)2] (Im = imidazole, OBz = benzoate, mB = p-methoxybenzoate)

The crystal and molecular structures of the complexes of [Co(Im)₆(OBz)₂] and [Co(Im)₆(mB)₂] (Im = imidazole, OBz = benzoate, mB = p-methoxybenzoate) have been determined by X-ray crystallography. The crystal structures are very similar and consist of discrete molecules of [Co(Im)₆(OBz)₂] and [Co(Im)₆(mB)₂], respectively. They both crystallize in the triclinic system, space group the former with lattice parameters a = 7.6934(3), b = 10.4518(5), c = 11.6088(5) Å, = 73.920(1), = 79.023(1), = 73.681(1)°, and Z = 1; the latter with a = 9.8336(3), b = 10.5509(2), c = 10.8889(3) Å, = 61.450(1), = 76.832(1), = 71.157(1)°, and Z = 1. The cobalt(II) ions have octahedral geometry with a CoN₆ chromophore. In the solid state, the complexes all form a three-dimensional network through N—H···O hydrogen bonds. The electronic spectra and IR spectra data are in agreement with the structural data.     

Mössbauer effect study of antiferromagnetic Fe–Mn–Si alloys

Antiferromagnetic Fe–30Mn–Si alloys containing 2.0–8.7 at.% Si are known to exhibit several attractive physical properties at Néel temperatures which render them candidate materials for functional alloys applications. The Néel transitions and anomalous transport phenomena have been studied extensively in a wide temperature range. In the present work, the hyperfine interactions are studied by Mössbauer spectroscopy measured at temperatures 95–623 K. It is found that the Mössbauer spectra are singlets at temperatures above the Néel temperature and doublets below the Néel temperature. The alloys have a small hyperfine field around the Fe nuclei below the Néel temperature and the hyperfine field increases linearly with increasing silicon concentration. This can be explained by the presence of a localised net magnetic moment on the Fe nuclei which is induced by the silicon atoms. A decrease in isomer shift with increasing silicon concentration is observed and this can be accounted for by the change in the occupation of the Fe 3d shell. There is a small quadrupole splitting, it increases with increasing silicon concentration, and is consistent with the lattice shrinking and magnetostriction.     

A new modified walnut shell by grafting l-aspartic acid: Synthesis and kinetics

A new modified walnut shell was prepared by grafting l -aspartic acid (ASP) to walnut shell (WNS) in the hydrochloric acid solution (1.0 M). The effects of stirring speed, particle size, solid-liquid ratio, temperature, and modifying agent concentration on grafting yield were studied. The grafting process conditions were optimized, and the grafting yield of WNS reached ∼14 wt%. The kinetics of the grafting reaction was investigated in the temperature range of 348-368 K. A three-step hypothesis was proposed to describe the grafting process: The ASP molecules diffuse to the out surface of WNS through the liquid film, then attend to the internal surface and react with WNS. The shrinking core models with different controlling steps were used to fit the kinetic data of the grafting process, and the results showed that the model controlled by a product layer fitted well with the experimental data. The internal diffusion coefficient D_A of ASP in WNS has been calculated, and it was applied to predict the grafting yield at different ASP concentrations by a shrinking core model. The results showed that the shrinking core model controlled by internal diffusion is suitable.     

极谱双点滴定法测定奎宁类药物

本文提出以0.1 mol/KI、0.025％聚乙烯醇为底液,以CdCl_2标准溶液为滴定剂,用极谱双点滴定法测定奎宁。该方法具有简便、快速等优点。     

The model of the action mechanism of SP-C in the lung surfactant monolayers

The action mechanism of surfactant protein C (SP-C) in the lung surfactant monolayers is studied. On the basis of the SP-C molecular structure, a detailed interaction model is developed to describe the interaction of phospholipids/SP-C in the lung surfactant monolayers. It is supposed that: (1) in an alveolus monolayer, SP-C molecules are surrounded by phosphatidylglycerol (PG). When the monolayer is compressed, SP-C molecules can promote PG molecules to be squeezed out; (2) during compressing of the monolayer, unsaturated-PG molecules form a collapse pit firstly when liquid-expanded state (LE) components achieve the collapse pressure. Then, SP-C's alpha-helix is attracted by the collapse pit and both alpha-helix and PG molecules are squeezed out speedily. Finally, the squeezed-out matters can form a lipid-protein aggregation in the subphase. The lipid-protein aggregation, in the centre of which, there is the hydrophobic alpha-helix section surrounded by PG molecules; (3) during the monolayer expanding, because of the increasing of the monolayer's surface tension, the structure of the lipid-protein aggregation is disturbed and reinserts into the surface of the monolayer rapidly. On the basis of analyzing the energies change of the squeeze-out process, a mathematical model is obtained to calculate the squeezed-out number of DPPG molecules when a SP-C molecule squeezes out in a monolayer. According to the model, it is concluded that SP-C has the capability to promote the squeeze-out and the reinsertion of most of PG component in an alveolus monolayer, the prediction data agree well with the experimental data.     

On convergence of extremes under power normalization

In this note, we discuss two aspects of convergence of extremes under power normalization: convergence of moments and convergence of densities. The moments convergence is established for four p-max-stable laws according to conditions imposed on the considered distributions or on the parameter of the p-max-stable laws. For densities convergence, local uniform convergence of the densities is shown to coincide with some von Mises conditions.