Efficiency assessment of primary care providers: A conditional nonparametric approach

This paper uses a fully nonparametric approach to estimate efficiency measures for primary care units incorporating the effect of (exogenous) environmental factors. This methodology allows us to account for different types of variables (continuous and discrete) describing the main characteristics of patients served by those providers. In addition, we use an extension of this nonparametric approach to deal with the presence of undesirable outputs in data, represented by the rates of hospitalization for ambulatory care sensitive condition (ACSC). The empirical results show that all the exogenous variables considered have a significant and negative effect on efficiency estimates.     

1‐Factor and Cycle Covers of Cubic Graphs

Let G be a bridgeless cubic graph. Consider a list of k 1‐factors of G. Let be the set of edges contained in precisely i members of the k 1‐factors. Let be the smallest over all lists of k 1‐factors of G. Any list of three 1‐factors induces a core of a cubic graph. We use results on the structure of cores to prove sufficient conditions for Berge‐covers and for the existence of three 1‐factors with empty intersection. Furthermore, if , then is an upper bound for the girth of G. We also prove some new upper bounds for the length of shortest cycle covers of bridgeless cubic graphs. Cubic graphs with have a 4‐cycle cover of length and a 5‐cycle double cover. These graphs also satisfy two conjectures of Zhang 18 . We also give a negative answer to a problem stated in 18 .     

Nonvertex‐Balanced Factors in Random Graphs

We prove part of a conjecture by Johansson, Kahn, and Vu (Factors in random graphs, Random Struct. Algorithms 33 (2008), 1, 1–28.) regarding threshold functions for the existence of an H‐factor in a random graph . We prove that the conjectured threshold function is correct for any graph H which is not covered by its densest subgraphs. We also demonstrate that the main result of Johansson, Kahn, and Vu (Factors in random graphs, Random Struct. Algorithms 33 (2008), 1, 1–28) generalizes to multigraphs, digraphs, and a multipartite model.     

Derivatization-free determination of aminoglycosides by CZE–UV in pharmaceutical formulations

Aminoglycosides are a relevant class of antibiotics widely used by medics and veterinaries. There are a variety of reasons that make their determination relevant, such as quality control, environment and food contamination assessment, drug-release studies, among others. The lack of a chromophore makes aminoglycoside spectrophotometric detection particularly challenging, often requiring derivatization. In this work, an indirect detection method, making use of imidazole as a probe, applying CZE was successfully tested. It did not require derivatization, which simplified the sample preparation. Suitable figures of merit were obtained; recoveries between 95 and 105%, adequate repeatability and precision, correlation coefficients (r) above 0.998, and limits of detection (LODs) of 3.2 and 11 mg/L for gentamicin and paromomycin, respectively. As a proof-of-concept, it was also applied in a simple controlled release experiment that was well fitted using the Hill equation.     

金属有机骨架薄膜用于小分子和离子的高效分离

综述了近几年金属有机骨架（MOF）薄膜在小分子和离子高效分离应用中的研究进展.MOF膜材料因具有结晶度良好、结构可设计、孔径可调和可功能化等特点,在分离领域展现出极大的潜在应用价值而受到广泛关注.鉴于近年来MOF膜材料在分离领域取得的巨大进展,对这一领域的前沿进展进行及时系统的总结,并对未来的发展趋势进行展望,具有重要的学术价值,也为科研工作者对MOF膜材料的研究提供了参考.本文首先总结了MOF膜的4种制备方法,包括LBL自组装法（液相外延和Langmuir-Blodgett沉积）、真空制备法（化学气相沉积和原子层沉积）、电化学沉积法和粉末沉积法;而后,详述了MOF膜在气体分离、液体分离及离子/质子传导等方面的应用;最后,总结了MOF膜材料领域当前存在的挑战及潜在解决途径,并对该领域的未来发展方向进行了展望.     

Nonclassical nucleation towards separation and recycling science: Iron and aluminium (Oxy)(hydr)oxides

Separation, analysis and recycling technologies are of high interest for our modern societies, where colloidal iron and aluminium (hydr)oxides have important applications. However, there are significant gaps in the fundamental understanding of how these phases form in real systems. Classical nucleation theory cannot account for many experimental observations, and there is a dichotomy between the chemistry of hydrolysing/condensating systems and the physical notion of supersaturation. Reviewing parts of the established and recent literature, we demonstrate that concepts of nonclassical nucleation pathways can overcome these issues. This broader, chemistry-based conceptual framework has a high potential for advancing current applications, and developing new strategies towards separation, analysis and recycling applications, which seem to be urgently required for the future.     

罗汉果水提取物的高效液相色谱分离研究

采用超声强化水提取法进行样品前处理,用高效液相色谱(HPLC)法对罗汉果水提取物进行分离,用罗汉果苷Ⅴ作为参照物进行指标成分峰的定位,以建立全面评价罗汉果质量的方法。实验比较了水-甲醇、冰乙酸水溶液-甲醇、磷酸水溶液-甲酸、水-乙腈、磷酸水溶液-乙腈、三氟乙酸水溶液-乙腈6种体系的等度、梯度洗脱效果。结果表明:在上述6种流动相体系中,以三氟乙酸水溶液-乙腈的洗脱效果最好,色谱条件:梯度洗脱、Sinochrom ODS-BP柱、检测波长为205 nm,流速0.8 mL/min,柱温25℃。采用本法得到的分离度和重现性均较好。     

咪唑啉纤维树脂分离富集/ICP-MS测定矿石中的痕量铂(Ⅳ)

本文提出了咪唑啉纤维树脂分离富集/ICP-MS测定矿石中痕量铂(Ⅳ)的方法。实验考察了影响咪唑啉纤维树脂分离富集痕量Pt(Ⅳ)的酸度、流速、洗脱液的组成、体积等因素,结果发现:在20%的王水介质中,Pt(Ⅳ)能定量吸附于树脂上并与大量其它金属分离;被吸附的Pt(Ⅳ)可用5%硫脲-1%HCl溶液定量洗脱,ICP-MS测定Pt(Ⅳ)的回收率为87%~102%。所建立的方法应用于硫镍矿管理样分析,其测定结果与推荐值吻合。     

中学化学教学中的科学思维与逻辑辨析

化学是一门具有创造性的基础科学,是环境、生命、医药、材料等科学的基础,在思维逻辑上彰显和蕴含了丰富的科学思维方法。系统总结化学科学思维方法,可以有效破解中学化学学习中的“繁,难,乱”。在多年的教学实践中,提出了化学科学多向思维方法体系,强调多层次思维过程中对多因素的立体逻辑思维辨析。重点介绍了与中学化学教学相关的零阶、初阶、中阶和高阶逻辑思维辨析的内涵,期望化学教学中重视化学思维逻辑过程,实现化学教与学在思维模式上的深层次发展与提升。     

相干梯度敏感干涉测量技术及在静态断裂力学实验中的应用

介绍了相干梯度敏感(CGS)干涉测量技术的基本原理及其在静态Ⅰ型断裂实验中的应用,验证了该方法对裂纹尖端局部变形场和断裂特性进行定量研究的可行性。给出了代表静态Ⅰ型裂纹尖端奇异场光力学信息的CGS控制方程,模拟并分析了Ⅰ型裂纹尖端的CGS条纹模式,对静态Ⅰ型裂纹尖端变形场和断裂特性进行了三点弯曲的CGS试验,并提取了应力强度因子KⅠ。结果表明,试验结果与理论分析结果相吻合。