Bayesian consensus clustering for multivariate longitudinal data

In clinical and epidemiological studies, there is a growing interest in studying the heterogeneity among patients based on longitudinal characteristics to identify subtypes of the study population. Compared to clustering a single longitudinal marker, simultaneously clustering multiple longitudinal markers allow additional information to be incorporated into the clustering process, which reveals co-existing longitudinal patterns and generates deeper biological insight. In the current study, we propose a Bayesian consensus clustering (BCC) model for multivariate longitudinal data. Instead of arriving at a single overall clustering, the proposed model allows each marker to follow marker-specific local clustering and these local clusterings are aggregated to find a global (consensus) clustering. To estimate the posterior distribution of model parameters, a Gibbs sampling algorithm is proposed. We apply our proposed model to the primary biliary cirrhosis study to identify patient subtypes that may be associated with their prognosis. We also perform simulation studies to compare the clustering performance between the proposed model and existing models under several scenarios. The results demonstrate that the proposed BCC model serves as a useful tool for clustering multivariate longitudinal data.     

A reaction route graph analysis of the electrochemical hydrogen oxidation and evolution reactions

The reaction route (RR) graph approach recently developed by us for complex, non-linear kinetic mechanisms is applied to the hydrogen oxidation and evolution reactions. A corresponding RR graph is constructed and translated into an equivalent electrical circuit network by associating each elementary step with a characteristic resistance for the steady-state case and considering the overall reaction as a power source. It is further shown that the steady-state kinetics of the reaction can be investigated employing the conventional methods of the electrical network theory. Using a set of rate constants for the hydrogen evolution reaction (her) in alkaline solutions from the literature, the dominant RRs are identified and simplified mechanisms and kinetics derived.     

Multivariate modelling of responses to conditional items: New possibilities for latent class analysis

Questionnaire data may contain missing values because certain questions do not apply to all respondents. For instance, questions addressing particular attributes of a symptom, such as frequency, triggers or seasonality, are only applicable to those who have experienced the symptom, while for those who have not, responses to these items will be missing. This missing information does not fall into the category ‘missing by design’, rather the features of interest do not exist and cannot be measured regardless of survey design. Analysis of responses to such conditional items is therefore typically restricted to the subpopulation in which they apply. This article is concerned with joint multivariate modelling of responses to both unconditional and conditional items without restricting the analysis to this subpopulation. Such an approach is of interest when the distributions of both types of responses are thought to be determined by common parameters affecting the whole population. By integrating the conditional item structure into the model, inference can be based both on unconditional data from the entire population and on conditional data from subjects for whom they exist. This approach opens new possibilities for multivariate analysis of such data. We apply this approach to latent class modelling and provide an example using data on respiratory symptoms (wheeze and cough) in children. Conditional data structures such as that considered here are common in medical research settings and, although our focus is on latent class models, the approach can be applied to other multivariate models. Copyright © 2009 John Wiley & Sons, Ltd.     

地黄合剂降血糖作用的实验性研究

本文通过用四氧嘧啶复制小白鼠糖尿病模型,以血清中血糖及胰岛素水平为指标,研究了地黄合剂对高糖动物的降血糖作用。结果表明,注射四氧嘧啶前小白鼠血糖为173.47±5.23mg/100ml注射后血糖升高至419.78±22.70mg/100ml(P<0.01),差异有高度显著性。实验组服用地黄合剂后,血糖值从410.25±2739mg/100ml下降至313.51±29.39mg/100ml(P<0.05)差异有显著性。因而认为地黄合剂对于四氧嘧啶性糖尿病有显著的降血糖作用。     

Determination of diffusion coefficient of hydrogen in metals and their elastic modulus by generalised impedance

Transport of hydrogen in elastic metals has been analysed in terms of an impedance-like non-linear transfer function (TF). The equilibrium in a membrane specimen is perturbed by a sinusoidal signal of the concentration of hydrogen, of large amplitude, applied to one of its surfaces. The fundamental harmonics of periodically reproducible flux at the same surface is considered as a response. The TF is defined as the ratio of the signal to the response. The power of the said TF in determining the diffusion coefficient of hydrogen in a metal–hydrogen system and its bulk elastic modulus was analysed for the example of α-phase Pd–H and Pd₈₁Pt₁₉–H systems. It has been found that such a TF is suitable for determination of the above parameters. Also, the sensitivity of these estimates to the uncertainty of concentration of hydrogen in the metal, its partial molar volume and the thickness of the specimen has been explored.     

In-situ measurements of gas permeability in fuel cell membranes using a cylindrical microelectrode

A new method to study permeation of gases in proton conducting membranes using a cylindrical microelectrode is presented. The focus of this work was to develop an in-situ method to study transport properties of hydrogen and oxygen close to real fuel cell operating conditions. The gas permeability is strongly affected by the change of water content in the membrane and it is therefore of advantage that, by using this method, measurements can be carried out over a wide range of relative humidities. The numerical method makes it possible to separate the diffusion coefficient and the concentration of dissolved gas in the membrane and also allows kinetic limitations to be taken into account. Chronoamperometric measurements on Nafion® 117 were successfully evaluated numerically. Experiments at temperatures of 25 and 60 °C with respect to oxygen permeation and at 60 °C for hydrogen permeation at relative humidities in the range 30–94% are presented. The reproducibility of data was excellent when measuring with different microelectrodes on the same membrane sample, but differed when measuring on different samples. In general, the permeability increases with increasing temperature and relative humidity.     

Fluctuations in Tumor Blood Flow under Normotension and the Effect of Angiotensin II-induced Hypertension

To elucidate the significance of angiotensin II (AID-induced hypertension chemotherapy, changes of tissue blood flow both in normal subcutis and in tumors (AH109A, LY80) were measured with the hydrogen gas clearance method. A newly-developed anesthetic machine was used to keep the animals' condition constant. Tissue blood flow in normal subcutis and tumors always fluctuated with time under normotension. The nature and the rate of fluctuation in tumor Wood flow were almost identical in two different types of tumors. However, the fluctuation of blood flow in tumor and that in normal subcutis were almost always inversely related when blood flows in these different tissues were measured simultaneously, i.e., when tissue blood flow in normal subcutis decreased, tumor blood flow increased, and vice versa. The findings supported the idea that the connection mode between the tumor vascular bed and normal vascular bed is a parallel circuit. Vascular resistance in the normal vascular bed under All-induced hypertension seemed to be greater than that under normotension, because the All-increased tumor blood flow always exceeded the maximum tumor blood flow under normotension. Due to the fluctuations of tumor blood flow, no-flow or low-flow areas, resistant to delivery of anti-cancer drugs, moved sporadically within the tumor under the normotensive condition. However, good conditions for drug delivery to tumor tissue were induced by All-induced hypertension.     

急性阑尾炎术中外用过氧化氢液冲洗疗效观察─—附50例报告

本文报导采用过氧化氢液在急性阑尾炎术对局部腹腔及切口进行冲洗的方法。并用５０个病例进行了对比分析。认为此法简单、可靠。对腹腔脓肿，预防切口感染有一定效果。可适用于一般基层医院。     

过氧化氢对血管平滑肌细胞的作用

目的　研究过氧化氢 (H2 O2 )对兔血管平滑肌细胞的作用机制。方法　兔血管平滑肌细胞 (VSMCs)原代培养 ,微量细胞培养四甲基偶氮唑蓝法 (MTT)检测不同浓度H2 O2 在不同时段对其增殖影响 ,确定进一步研究的H2 O2 浓度 ,并应用流式细胞仪检测此浓度H2 O2 对VSMCs细胞周期和细胞凋亡的作用。结果　MTT法检测 ,H2 O2 浓度≥ 10 0 μmol/L(10 0～ 14 0 0 μmol/L)时 ,与VSMCs作用仅 1h ,即出现吸光度值显著降低 (P <0 .0 1) ;流式细胞仪细胞周期检测 ,H2 O2 浓度≥ 10 0 μmol/L时 ,与VSMCs作用 2 4h后 ,其G1期细胞数显著高于对照组 (94.65 %和 79.97% ) (P <0 .0 1) ,以H2 O2浓度在 10 0 μmol/L时尤为明显 ;流式细胞仪AnnexinV PI双标细胞凋亡检测 ,10 0 μmol/LH2 O2 有促进VSMCs凋亡作用 ,并在作用 48h左右达到高峰 ,占 2 6.76% ,与对照组相比 ,差异有显著性 (P <0 .0 1)。结论　H2 O2 浓度≥ 10 0 μmol/L时 ,可显著抑制VSMCs增殖 ;当H2 O2 浓度为 10 0 μmol/L时 ,有促进VSMCs凋亡作用。     

Continuous flow synthesis of peptides using a polyacrylamide gel resin (Expansin™)

The continuous flow syntheses of endothelin 1, proendothelin 2. ATP binding site of the CDC2 kinase 3, and fragment 18-30 of an actin 4, have been performed by using a polyacrylamide gel resin Expansin? (about 0.6 mmol NH₂/g) with the glycolamidic ester handle as labile anchorage. In addition, we report here a method of air oxidation which reduces the formation of side-products related to the formation of intermolecular disulfide bridges.