铁矿选矿产品中低微量钍的X射线荧光光谱分析

本文介绍用粉末内标压片Ｘ射线荧光光谱法测定铁矿选矿工艺流程产品中的低微量钍，方法简便、快速、准确、经济，较之化学分析法，有它独到之处，满足了选矿研究对于分析的快速、准确的要求。本法以钼为内标元素，硼酸为低吸收粘结剂，与粉末试样混合均匀后，用１５吨压片机压制成直径２５ｍｍ的圆片状的样品，即可进机测量。     

s-对数凸函数的Hermite-Hadamard型积分不等式

该文定义了"s-对数凸函数"的概念,并给出了可微s-对数凸函数的若干个HermiteHadamard型积分不等式,作为应用给出了平均数的几个不等式.     

A rapid fluorescence based method for the quantitative analysis of cell culture media photo-degradation

Cell culture media are very complex chemical mixtures that are one of the most important aspects in biopharmaceutical manufacturing. The complex composition of many media leads to materials that are inherently unstable and of particular concern, is media photo-damage which can adversely affect cell culture performance. This can be significant particularly with small scale transparent bioreactors and media containers are used for process development or research. Chromatographic and/or mass spectrometry based analyses are often time-consuming and expensive for routine high-throughput media analysis particularly during scale up or development processes.     

Noise perturbation in functional principal component analysis filtering for two-dimensional correlation spectroscopy: its theory and application to infrared spectra of a poly(3-hydroxybutyrate) thin film

A method based on noise perturbation in functional principal component analysis (NPFPCA) is for the first time introduced to overcome the noise interference problem in two-dimensional correlation spectroscopy (2D-COS). By the systematic addition of synthetic noise to the dynamic multivariate spectral data, the functional principal component analysis (FPCA) described in this report is able to accurately determine which eigenvectors are representing significant signals instead of noise in the original data. This feature is especially useful for the data reconstruction and noise filtering. Reconstructed data resulted from the smooth eigenvectors can produce much more reliable 2D correlation spectra by removing the correlation artifacts from noise, which in turn enable more accurate interpretation of the spectral variations. The usefulness of this method is demonstrated with a theoretical framework and applications to the 2D correlation analyses of both simulated data and temperature-dependent reflection-absorption infrared spectra of a poly(3-hydroxybutyrate) (PHB) thin film.     

Peptide plane can flip in two opposite directions: implication in amyloid formation of transthyretin

Transthyretin (TTR) is one of the known 20 or so human proteins that form fibrils in vivo, which is a hallmark of amyloid diseases. Recently, molecular dynamics simulations using ENCAD force field have revealed that under low pH conditions, the peptide planes of several amyloidogenic proteins can flip in one direction to form an alpha-pleated structure which may be a common conformational transition in the fibril formation. We performed molecular dynamics simulations with AMBER force fields on a recently engineered double mutant TTR, which was shown experimentally to form amyloid fibrils even under close to physiological conditions. Our simulations have demonstrated that peptide-plane flipping can occur even under neutral pH and room temperature for this amyloidogenic TTR variant. Unlike previously reported peptide-plane flipping of TTR using ENCAD force field, we have found two-way flipping using AMBER force field. We propose a new mechanism of amyloid formation based on the two-way flipping, which gives a better explanation of various experimental and computational results. In principle, the residual dipolar and hydrogen-bond scalar coupling techniques can be applied to the wild-type TTR and the variant to study the peptide-plane flipping of amyloidogenic proteins.     

Two-dimensional liquid chromatographic methods to examine phenylboronate interactions with recombinant antibodies

A two-dimensional liquid chromatography (2D-LC) system incorporating Agilent 1100 components was set up and 2D-LC methods were developed to determine how recombinant antibodies (rAbs) interact with a commercial boronate column. Analyses of ten rAbs demonstrated that a simple boronate affinity chromatography method cannot be generalized to separate or detect the glycation level for all of rAbs as the aggregates were also retained on the boronate column. A quantitative boronate affinity chromatography method was developed to examine the extent of glycation of a recombinant humanized monoclonal antibody (rhuMAb). With the method, only the glycated components of intact or papain-treated rhuMAb were bound to the boronate column. When denatured, rhuMAb heavy chain was also bound. However, enzymatic removal of the N-oligosaccharides did not delete the binding, indicating that the interaction between the heavy chain and the phenylboronate functionality is not mediated through the N-oligosaccharides. Two-stage 2D-LC analysis with boronate affinity chromatography in the first dimension and reversed-phase chromatography in the second demonstrated that the interaction between the antibody heavy chain and boronate column is not specific, as urea is able to selectively elute retained heavy chain without disrupting the retention of glycated light chain. Quantum mechanic calculations show that the vicinal cis-diols in β-pyranose conformations in N-glycosylated antibodies need to overcome at least 7.172 kcal/mol to become co-planar (zero-dihedral angle). However, the cis-diols on β-furanose rings of glycated species only have to overcome a 0.885 kcal/mol energy barrier to achieve the co-planar configuration that facilitates its complex formation with the phenylboronate groups. This minimal energy barrier, coupled with the stabilizing effect from the electrostatic interaction between the oppositely charged phenylboronate group on the column and the fructosamine group of glycated species, explains why the boronate column exhibits high binding selectivity towards the glycated proteins.     

构建色满骨架的简便方法: (–)-4’-羟基-7-甲氧基黄烷的不对称合成

通过不对称还原产生手性中心以及微波催化的芳环上C―O键的生成构建出苯并吡喃骨架,首次对映选择性地合成了天然产物(–)-4’-羟基-7-甲氧基黄烷. 主要的合成特色包括路线简短, 反应过程手性中心的ee值保持, 有两种可供选择的关环前体.     

Finite p-Groups with Few Non-major k-Maximal Subgroups

A subgroup of index p ^k of a finite p-group G is called a k-maximal subgroup of G. Denote by d(G) the number of elements in a minimal generator-system of G and by δ _k (G) the number of k-maximal subgroups which do not contain the Frattini subgroup of G. In this paper, the authors classify the finite p-groups with δ_d(G)(G) ≤ p² and δ_d(G)?1(G) = 0, respectively.     

Least Energy Solitary Waves for a System of Nonlinear Schrödinger Equations in $${\mathbb{R}^n}$$

In this paper we consider systems of coupled Schrödinger equations which appear in nonlinear optics. The problem has been considered mostly in the one-dimensional case. Here we make a rigorous study of the existence of least energy standing waves (solitons) in higher dimensions. We give: conditions on the parameters of the system under which it possesses a solution with least energy among all multi-component solutions; conditions under which the system does not have positive solutions and the associated energy functional cannot be minimized on the natural set where the solutions lie.