一种度量细胞网络结构的方法

文题释义： 复杂网络：是指具有自组织、自相似、小世界、无标度中部分或全部特征的网络。小世界效应和无标度特性是复杂网络最显著的特点。小世界是指网络具有大的簇系数和较小的平均路径长度，无标度是指网络节点的连接度分布服从幂律分布。 细胞网络：在多细胞生物体中，单个细胞除了完成自身功能外，各个细胞间的通讯联络是必不可少的，如维持生物体的生长发育、各种生理活动的协调等。如果将每个细胞抽象为一个节点，每两个细胞间的通讯抽象为一条边，那么众多细胞及其之间的通讯将抽象成为一个巨大的细胞网络。 背景：在多细胞组成的生物体社会中，细胞之间的通讯必不可少。众多细胞之间相互通讯、相互联系，形成了一个复杂的细胞网络结构。对细胞网络结构相关属性值进行度量和评价，显得极其重要。 目的：基于复杂网络，提出了一种细胞网络结构的度量方法。 方法：结合文献研究及实际应用，搭建细胞网络结构的度量框架，分别从细胞节点的度、细胞网络的度分布、细胞网络的平均路径长度、细胞网络的簇系数等方面对细胞网络结构进行度量。以某小型实验为例，进行了实例验证。 结果与结论：细胞网络的度分布中，绝大部分细胞节点的度值比较小，只有较少量细胞节点的度值较高。细胞网络中细胞节点的度分布P(k)的幂律分布特点越是明显，则此细胞网络结构越是合理，细胞网络越正常；同时，许多细胞网络结构具有较小的平均路径长度。细胞网络的簇系数越大，表明该细胞网络具有较高的聚集特性。一般情况下，细胞网络结构越“紧密”，细胞网络结构的“集团化”特性越明显，细胞网络越正常。 ORCID: 0000-0002-2483-032X(张雨) 中国组织工程研究杂志出版内容重点：干细胞；骨髓干细胞；造血干细胞；脂肪干细胞；肿瘤干细胞；胚胎干细胞；脐带脐血干细胞；干细胞诱导；干细胞分化；组织工程     

基于离散型地理信息的H7N9流感病毒动态时空传播模式

目的 基于离散型的地理信息构建了H7N9病毒时空动态传播模式图，探索H7N9病毒的空间传播路径。方法 选取全球共享禽流感数据倡议组织（GISAID）中中国以人类为宿主的H7N9流感病毒血凝素（HA）和神经酰胺酶（NA）基因序列，利用BioEdit 7.0软件进行多序列比对。在贝叶斯理论框架下，运用BEAST 1.8.2软件构建H7N9时空传播模型，采用symmetric substitution model和贝叶斯随机搜索变量选择（BBSVS）方法，对H7N9的历史传播轨迹进行推断和检验。以Google Earth软件展现H7N9病毒的时空传播动态图。结果 感染人类的H7N9病毒起源于上海或杭州，最早可追溯到2012年10月。并在2013年3、4月份开始传向邻近省份，同年8、9月份传播加剧，3个月内传向10余处地区。结论 基于基因核苷酸序列和空间地理信息，追踪了H7N9病毒历史传播轨迹，为早期流感疫情的防控及病毒的溯源提供线索。     

Reduction of silver complexes: towards an ever more elaborated insight in the influence of the type of ligand on the reaction rate

The present work deals with the investigation of the electrochemical reduction of silver thiosulphate (1,2-Ag(S₂O₃)₂^3?), thiocyanate (1,3-Ag(SCN)₃^2?) and 1,8-dihydroxy-3,6-dithiaoctane (1,2-Ag(DTO)₂⁺) complexes. The influence of the ligand type on the charge transfer rate is explained by the changing positions of the density distributions of electronic energy levels of the three complexes. The basics for this approach are the theories of energy band models (EBMs). An experimental methodology is developed to determine the energy density distributions. A Ti/TiO₂ substrate, obtained by galvanostatically anodising Ti, is put forward as an appropriate substrate for this investigation, and its semiconducting properties are determined. On this substrate, charge transfer (CT) controlled currents can be measured in a sufficiently large potential domain for the three systems. A method of pre-plating is optimised such that the overall semiconducting character of the substrate is kept during the monitoring of the (quasi-)stationary current/voltage diagrams. The active surface areas, necessary for the calculation of the current density/potential curves, are calculated. The positions of the energy density distributions, obtained by the derivation of the current density/voltage diagrams, of the three complexes, show that thiosulphate exhibits the smallest density of accepting energy levels in the given potential domain. For potentials above 0.5 V vs. SCE, the DTO complex has the largest density of vacant energy levels, but for lower potentials the situation is reversed.     

Mixed binary-continuous copula regression models with application to adverse birth outcomes

Bivariate copula regression allows for the flexible combination of two arbitrary, continuous marginal distributions with regression effects being placed on potentially all parameters of the resulting bivariate joint response distribution. Motivated by the risk factors for adverse birth outcomes, many of which are dichotomous, we consider mixed binary-continuous responses that extend the bivariate continuous framework to the situation where one response variable is discrete (more precisely, binary) whereas the other response remains continuous. Utilizing the latent continuous representation of binary regression models, we implement a penalized likelihood–based approach for the resulting class of copula regression models and employ it in the context of modeling gestational age and the presence/absence of low birth weight. The analysis demonstrates the advantage of the flexible specification of regression impacts including nonlinear effects of continuous covariates and spatial effects. Our results imply that racial and spatial inequalities in the risk factors for infant mortality are even greater than previously suggested.     

Predictive distributions for between‐study heterogeneity and simple methods for their application in Bayesian meta‐analysis

Numerous meta‐analyses in healthcare research combine results from only a small number of studies, for which the variance representing between‐study heterogeneity is estimated imprecisely. A Bayesian approach to estimation allows external evidence on the expected magnitude of heterogeneity to be incorporated. The aim of this paper is to provide tools that improve the accessibility of Bayesian meta‐analysis. We present two methods for implementing Bayesian meta‐analysis, using numerical integration and importance sampling techniques. Based on 14 886 binary outcome meta‐analyses in the Cochrane Database of Systematic Reviews, we derive a novel set of predictive distributions for the degree of heterogeneity expected in 80 settings depending on the outcomes assessed and comparisons made. These can be used as prior distributions for heterogeneity in future meta‐analyses. The two methods are implemented in R, for which code is provided. Both methods produce equivalent results to standard but more complex Markov chain Monte Carlo approaches. The priors are derived as log‐normal distributions for the between‐study variance, applicable to meta‐analyses of binary outcomes on the log odds‐ratio scale. The methods are applied to two example meta‐analyses, incorporating the relevant predictive distributions as prior distributions for between‐study heterogeneity. We have provided resources to facilitate Bayesian meta‐analysis, in a form accessible to applied researchers, which allow relevant prior information on the degree of heterogeneity to be incorporated. © 2014 The Authors. Statistics in Medicine published by John Wiley & Sons Ltd.     

A mixed‐effect model for positive responses augmented by zeros

In this research article, we propose a class of models for positive and zero responses by means of a zero‐augmented mixed regression model. Under this class, we are particularly interested in studying positive responses whose distribution accommodates skewness. At the same time, responses can be zero, and therefore, we justify the use of a zero‐augmented mixture model. We model the mean of the positive response in a logarithmic scale and the mixture probability in a logit scale, both as a function of fixed and random effects. Moreover, the random effects link the two random components through their joint distribution and incorporate within‐subject correlation because of the repeated measurements and between‐subject heterogeneity. A Markov chain Monte Carlo algorithm is tailored to obtain Bayesian posterior distributions of the unknown quantities of interest, and Bayesian case‐deletion influence diagnostics based on the q‐divergence measure is performed. We apply the proposed method to a dataset from a 24hour dietary recall study conducted in the city of São Paulo and present a simulation study to evaluate the performance of the proposed methods. Copyright © 2015 John Wiley & Sons, Ltd.     

A method for multiparametric statistical quantification of the heterogeneity of free Na+ concentration by 19F MR spectroscopy: Proof of principle in silico and in vitro

Sodium(I) (Na⁺) is one of the most important cations in mammalian tissues. Since Na⁺ plays a key role in basic cell function, noninvasive methods for measuring intracellular concentrations of free sodium ions in biological tissue have been developed on the basis of ¹⁹F NMR spectroscopy. However, intracellular Na⁺ levels are often not uniform throughout a tissue volume (or voxel) being measured. In such cases, [Na⁺] heterogeneity is not reflected in results obtained by the classical technique, and may even result in biased average values. For this reason, we have designed an approach for quantifying [Na⁺] heterogeneity. First, the ¹⁹F MRS resonance from FCrown‐1 serving as a “Na⁺ probe” is transformed into a [Na⁺] curve. Then the digital points of the resulting [Na⁺] profile are used to construct a histogram with specially developed algorithms. From each [Na⁺] histogram, at least eight quantitative parameters describing the underlying statistical [Na⁺] distribution were computed: weighted median, weighted mean, standard deviation, range, mode(s), kurtosis, skewness, and entropy. In addition to our new paradigm, we present a first validation based on (i) computer simulations and (ii) experimentally obtained ¹⁹F MR spectra of model solutions. This basic proof of principle warrants future in vivo experiments, in particular because of its ability to provide quantitative information complementary to that made available by commonly used ²³Na MRI: (i) multiparametric statistical characterization of [Na⁺] distributions; (ii) total [Na⁺] heterogeneity analysis not intrinsically limited by the size of any MRI voxels; and (iii) analysis of unequivocally intracellular [Na⁺], as opposed to measurement of a combination of intra‐ and extracellular [Na⁺].     

Global burden of thermal burns, 1990–2017: Unbalanced distributions and temporal trends assessed from the Global Burden of Disease Study 2017

BackgroundMany studies demonstrate that being burned has both physical and psychological sequelae that affect quality of life. Further, these effects may be more prevalent in some regions and populations. We sought to access the unbalanced distributions and temporal trends concerning the health burden of thermal burns.MethodsData were collected from the Global Burden of Disease Study 2017, and the disability-adjusted life year (DALY)¹ was used as a measure of health burden. Linear regression was used to evaluate the relationship between the age-standardized DALY rate and socio-demographic index.² Joinpoint regression analysis and comparison line charts were all applied to assess the temporal trends of burns.ResultsThe age-standardized DALY rate of global thermal burns decreased by 43.7%, from 197 (95% CI: 152–228) per 100,000 in 1990 to 111 (95% CI: 93–129) per 100,000 in 2017. The burden was borne mainly by children 1–4 years of age and people over 80 years. Socio-demographic index was negatively correlated with the age-standardized DALY rate. In low-middle and low socio-demographic index regions, the decreasing trends were slower than other regions with an average annual percentage change of ?2.1% (95% CI: ?2.2 to ?2.0) and ?2.1% (95% CI: ?2.1 to ?2.0), respectively. Among six geographical regions, Africa presented the highest age-standardized DALY rates of 352 (95% CI: 275–410) per 100,000 in 1990 and 208 (95% CI: 175–236) per 100,000 in 2017, and also the slowest average decreasing trend, with an average annual percentage change of ?1.9% (95% CI: ?2 to ?1.8).ConclusionsThe global burden of thermal burns shows a downward trend from 1990 to 2017, and regions with lower socio-demographic index and Africa show greater burdens and smaller downward trends.     

Beyond speed: Gait changes after botulinum toxin injections in chronic stroke survivors (a systematic review)

BackgroundThe mechanisms by which spasticity reductions after botulinum toxin A (BoNT) affect gait in stroke are not well understood. We systematically reviewed the effects of BoNT on spatiotemporal, kinematic, kinetic and electromyographic (EMG) measures during gait.QuestionWhat are the effects of botulinum toxin on gait mechanics in stroke patients?MethodsSystematic search using PubMed and Web of Science. We considered all studies that reported laboratory-based and instrumented gait measures as primary or secondary outcomes to determine the effects of BoNT on walking performance in stroke populations only. Selected studies were classified and analysed based on the injection sites.ResultsA total of 240 articles were identified of which 22 were selected for analysis. Overall, 91% of the studies reported spatiotemporal, 64% kinematics, 23% kinetics, 32% EMG and 23% other gait measures. All but one study found significant effects of BoNT on gait measures using instrumented assessments even when clinical measures (i.e. speed) did not significantly improve. However, the majority of the studies had a high risk of bias. Overall, BoNT improved: a) dorsiflexion during stance, propulsive forces and timing and activity of more proximal musculature with injections in the plantarflexors; b) hip, knee and ankle angles and velocities, coordination and energetic cost with injections in the rectus femoris; c) segmental coordination and energetic cost when several lower limb muscles were injected; and, d) elbow and trunk angles when upper limb muscles were injected.ConclusionInstrumented and laboratory measures of gait improve after BoNT injections in different muscle groups even in the absence of clinical changes.