多元统计分析中一类矩阵迹函数最小化问题的有效算法

研究来源于多元统计分析中的一类矩阵迹函数最小化问题$\min c+ tr(AX)+\sum\limits_{j=1}^{m}tr(B_j X C_jX^{T}),\ \ {\rm s. t.} \ X^TX=I_p,$其中$c$为常数, $A\in R^{p\times n}\ (n\geq p)$, $B_j\in R^{n\times n}, C_j\in R^{p\times p}$为给定系数矩阵. 数值实验表明已有的Majorization算法虽可行, 但收敛速度缓慢且精度不高. 本文从黎曼流形的角度重新研究该问题, 基于Stiefel流形的几何性质, 构造一类黎曼非单调共轭梯度迭代求解算法, 并给出算法收敛性分析.数值实验和数值比较验证所提出的算法对于问题模型是高效可行的.     

基于视觉辐条图案识别方法的蓝宝石引晶机制研究

工业生产蓝宝石晶体过程中,引晶步骤有着至关重要的地位。引晶必须在温度梯度较小,温度分布趋于稳定的条件下进行。目前,工业生产蓝宝石主要依靠人工经验操控籽晶杆实现引晶操作,但是人工引晶操作的准确性不高会导致成品品质不佳、资源浪费。为此,本文提出一种基于蓝宝石视觉辐条图案识别方法来检测蓝宝石熔体状态自由液面状态,从而实现一种高效率引晶的机制。此方法利用经典骨架化算法细化辐条图案,Harris算子实现特征信息的提取,提取的特征信息放入运动轨迹模型中判断熔体稳定性,分析液面温度分布稳定性从而实现引晶。结果表明,此算法具有有效性,蓝宝石晶体引晶效率大大提高,生产出的成品良率也有提升,可有效指导蓝宝石的工业生产。     

A rapid,spatially dispersive frequency comb spectrograph aimed at gas phase chemical reaction kinetics

This New Views article will highlight some recent advances in high sensitivity gas detection using direct infrared absorption frequency comb laser spectroscopy, with a focus on frequency comb use in chemical reaction kinetics and our own contribution to this field. Our recently implemented detection technique uses a combination of a 12.9?GHz free spectral range virtually imaged phased array and diffraction grating to spatially disperse the mid-infrared frequency comb onto a camera. Individual frequencies or ‘comb teeth’ of a 250?MHz repetition-rate frequency comb are able to be resolved. High molecular sensitivity is achieved by increasing the interaction path length using a Herriott multipass cell. High spectral resolution, broadband spectral coverage, and high molecular sensitivity are all achieved on an adjustable 1–50 µs timescale, making this frequency comb apparatus ideal for measuring chemical reaction kinetics where multiple absorbing species can be monitored simultaneously. This New Views article will also discuss some of the challenges and decisions that chemists might face in implementing this advanced physics technology in their own laboratory.

Spatially dispersed 250 MHz mid-infrared frequency comb laser, with absorption of some frequencies by a dilute sample of methane.     

Distinct effect of xenobiotics on the metal‐binding properties of protein molecules

The X‐ray standing‐wave method was applied to study the elemental composition and molecular organization of ordered protein films of alkaline phosphatase exposed to different xenobiotics (drug compounds, lead). Binding of metal ions from triply distilled water to protein molecules has been experimentally observed. Definite differences in the arrangement of impurity metal ions in the films have been established. The considerable enhancement of protein–metal interactions is attributed to partial rearrangement of the protein native structure, induced by xenobiotics.     

Homogeneous variable exponent Besov and Triebel–Lizorkin spaces

We introduce homogeneous Besov and Triebel–Lizorkin spaces with variable indexes. We show that their study reduces to the study of inhomogeneous variable exponent spaces and homogeneous constant exponent spaces. Corollaries include trace space characterizations and Sobolev embeddings.     

甲基膦酸(濒)哪酯分子印迹聚合物的合成与识别特性研究

利用~(31)P{~1H}NMR谱和~1H NMR谱、FT-IR谱等技术手段,研究了化学毒剂梭曼的降解产物(甲基膦酸■哪酯)与甲基丙烯酸、丙烯酰胺功能单体的分子间作用力。通过预组装体系设计,合成了多孔性材料甲基膦酸■哪酯分子印迹聚合物。通过Scatchard模型分析,得到该聚合物对甲基膦酸■哪酯的最大表观结合量Q_(max)为661μg/g(AM为单体),在低吸附量(Q500μg/g)范围内,吸附量对模板浓度的比值与吸附量呈线性相关。通过静态吸附分配实验发现,该聚合物对同系的5种烷基膦酸单烷基酯存在选择性,对结构不同的其他化合物的识别因子显著降低。将该分子印迹聚合物制成固相萃取柱,用于含大量背景干扰的样品中痕量甲基膦酸■哪酯的萃取分离,取得显著效果。该研究为复杂基质中该类化合物的痕量分析鉴定提供了技术手段。     

Microfluidic chip-inductively coupled plasma mass spectrometry for trace elements and their species analysis in cells

Abstract

Accurate identification and quantification of trace elements and their species in cells is an important prerequisite for the exploration of their physiological function and related mechanisms of process involving trace elements/species in human body. Inductively coupled plasma mass spectrometry (ICP-MS) is a powerful analytical instrument for trace elements detection, while it still suffers from insufficient limits of detection, interference from complex cell matrix, and incompatible sample consumption in cells analysis. Microfluidic chips which possess advantages of low sample/reagent consumption, rapid analysis speed and high spatial resolution provide perfect miniaturized and integrated platforms for cell analysis. In this article, microfluidic chip-ICP-MS techniques for trace elements and their species analysis in cells were reviewed. Both chip-based pretreatment techniques (e.g., magnetic solid phase microextraction (MSPME), monolithic capillary microextraction (MCME), liquid phase microextraction (LPME)) including chip-based array microextraction techniques for trace elements and their species analysis and droplet chip for single cell analysis were introduced. The newly developed methods of microfluidic chips in combination with ICP-MS for trace elements and their species analysis in small numbers of cells and even single cell were critically discussed, including chip-based MSPME/MCME/LPME-(electrothermal vaporization-ICP-)MS, on-line chip-based array MSPME/MCME-ICP-MS, on-line chip-based array MSPME-high performance liquid chromatography-ICP-MS and online droplet chip-time-resolved ICP-MS. These methodologies were demonstrated with high sensitivity, high throughput, good matrix resistance and low sample/reagent consumption, contributing to the quantification of trace elements/species in cells and even single cells. Relevant 20 references are included herein, and the development trend of microfluidic chip-ICP-MS techniques for cells analysis is prospected.     

Uptake,Translocation, and Bioaccumulation of Elements in Forest Nettle (Laportea alatipes)

Elements found in the edible parts of plants are considered to be the main source of nutrients for humans and animals. However, there is insufficient information on the relationship between heavy metal pollution in the growing soil of most edible plants. In this study, the distribution of elements in the edible forest nettle (Laportea alatipes) was evaluated as a function of geographical location. Forest land soils had higher concentrations of minor elements (Cu, Cr, Ni, and Zn) compared to soils from rural and suburban areas. Translocation factors for Cd and Pb showed effective translocation from the roots to the leaves; however, these heavy metals in leaves were still above South African maximum permissible levels for vegetables. Atmospheric depositions may play a significant role in higher Cd and Pb concentrations in the leaves. Bioaccumulation factors showed the plant to accumulate Cu, Mn, and Zn to meet physiological requirement levels. Geoaccumulation indices and enrichment factors showed no soil contamination or minimal enrichment by trace metals. Principal component analysis showed Co, Cr, Cu, Fe, Ni, Pb, and Zn in soil to originate from a common source which may be soil silicates and other minerals.     

Explicit uniform bounds on integrals of Bessel functions and trace theorems for Fourier transforms

Explicit and partly sharp estimates are given of integrals over the square of Bessel functions with an integrable weight which can be singular at the origin. They are uniform with respect to the order of the Bessel functions and provide explicit bounds for some smoothing estimates as well as for the L² restrictions of Fourier transforms onto spheres in which are independent of the radius of the sphere. For more special weights these restrictions are shown to be Hölder continuous with a Hölder constant having this independence as well. To illustrate the use of these results a uniform resolvent estimate of the free Dirac operator with mass in dimensions is derived.     

Method validation for direct determination of some trace and toxic elements in soft drinks by inductively coupled plasma mass spectrometry

The consumption of soft drink beverages has increased in the last few years around the world and it is related to the diversity of brands and flavours available, increasing also the risk of ingestion of compounds considered non-beneficial to the health of consumers. In this study, fast, easy and simple method of analysis for direct determination of As, Pb, Cd, Sb, Hg, Cu, Zn, Fe, Al, Cr, Sn, Co, Mn and Ni in soft drink samples using quadrupole inductively coupled plasma mass spectrometry (Q-ICP–MS) was validated. The estimated detection limits, practical quantification limits, linearity (linear dynamic ranges and method linearity), accuracy (trueness and precision) and measurement uncertainty parameters were studied under optimised (Q-ICP–MS) conditions. The method showed that the estimated detection limits were varied between 0.02 and 2.403 µg/L, and the quantification limits were varied between 0.5 and 20 µg/L. The mean recoveries ± standard deviations at different spiking levels were varied between 75.03 ± 0.62% and 117.07 ± 2.83% and the coefficients of variation were varied between 0.49% and 9.79%. The method trueness was confirmed by using four different certified reference materials (soft drinks and treated water) purchased from FAPAS (Food Analysis Performance Assessment Scheme) and all obtained results were within satisfactory ranges and had acceptable recovery and Z-score values. The method precision, in terms of relative standard deviation, was below 4.88%. The method uncertainty expressed as expanded uncertainty of all validated elements was found to be ≤22.52%. The results obtained make the method suitable for accurate determination of validated elements in different kinds of soft drink samples at these low concentration values. Validated method was used for the determination of metallic contaminants in 40 commercial soft drink samples and the results were compared with the provisional guideline of the elements stated by Egyptian, WHO and European standards in drinking and potable bottled natural mineral water.