Sensitivity and significance of disease outcome measures in inflammatory bowel disease

In inflammatory bowel disease (IBD), proxy measures of clinical outcome are often collected into summary indices of qualitative self-rated disease markers, clinical observations, and quantitative biochemical analyses. In Crohn's disease (CD), a frequently used index is the Crohn's disease activity index (DCAI). This index consists of six qualitative variables and two quantitative variables. The aim of this presentation is to illustrate the use of this index to calculate its range, to estimate errors in the index, its sensitivity, and the number of significant steps in the index. The measure of sensitivity of the summary index was analyzed for the signal-to-noise ratio (SNR), the reference change value (RCV) and the confidence interval (CI). If identical errors were assumed in patient self-rated health and clinically judged disease manifestations, such as tumours and fistulas, the majority of the variance of the index was caused by the self-rated experience of health, the number of days over which the individual variable was rated, and the prognostic multiplier of each variable.The range of the index has no upper limit, but can be estimated to 403 units, of which patient self-rating of well-being account for up to one-third of the summary index maximal score range. The median signal noise measure of index sensitivity was 18 SDs. The two disease classification limits of 150 units for moderate disease and 450 for severe disease on average cover an interval of limit ±41.5 units vs. ±60.5 units. In judgments on change in clinical outcome the RCV interval of steps of 121 units are valid. Conclusion: Both variance and range of the CDAI summary score are primarily decided by the self-rated experience of well-being. Variables on disease signs have a minor impact on the index. Rating of the two important outcome parameters: Self-experienced health and medical outcome would favourably be given in two individual scores.Presented at the 10th Conference Quality in the Spotlight, March 2005, Antwerp, Belgium.     

Bayesian Model Assessment in Joint Modeling of Longitudinal and Survival Data With Applications to Cancer Clinical Trials

Joint models for longitudinal and survival data are routinely used in clinical trials or other studies to assess a treatment effect while accounting for longitudinal measures such as patient-reported outcomes. In the Bayesian framework, the deviance information criterion (DIC) and the logarithm of the pseudo-marginal likelihood (LPML) are two well-known Bayesian criteria for comparing joint models. However, these criteria do not provide separate assessments of each component of the joint model. In this article, we develop a novel decomposition of DIC and LPML to assess the fit of the longitudinal and survival components of the joint model, separately. Based on this decomposition, we then propose new Bayesian model assessment criteria, namely, ΔDIC and ΔLPML, to determine the importance and contribution of the longitudinal (survival) data to the model fit of the survival (longitudinal) data. Moreover, we develop an efficient Monte Carlo method for computing the conditional predictive ordinate statistics in the joint modeling setting. A simulation study is conducted to examine the empirical performance of the proposed criteria and the proposed methodology is further applied to a case study in mesothelioma. Supplementary materials for this article are available online.     

制动器管裂纹原因分析

重型汽车制动器管在潮湿的环境中使用时发生破裂,采用化学成分分析、力学性能试验、断口分析和金相分析等方法对破裂的制动器管进行分析.结果表明,制动器管的裂纹主要产生于存在加工应力的弯曲部位,应力腐蚀是造成其破裂的主要原因.同时在选材方面提出建议.     

科技保险中项目投资损失保险投保比例优化决策

针对我国科技保险第二批推行险种--项目投资损失保险,以科技企业为研究主体,综合考虑其期望利润和科技风险(方差),构建了投保比例模型.在对武汉市迪源光电科技有限公司投保科技保险的具体案例中,运用线性不等式组的旋转算法进行求解,计算出企业在项目组合投资中如何优化各项投保比例,使其以最小的风险承担得到最大的期望利润.     

Adaptive collision meshing and satellite droplet formation in spray simulations

Improved numerical methods and physical models have been applied to droplet collision modeling. Numerically, an adaptive collision mesh method is developed to calculate collision rate. This method produces a collision mesh that is independent of the gas phase mesh and adaptively refined according to local parcel number density. An existing model describing the satellite droplet formation during the collision process is improved to reflect the experimental findings that the satellite droplets are much smaller than the parent droplets. The adaptive collision mesh and the improved satellite model have been used to simulate three impinging spray experiments. The model was able to qualitatively predict the occurrence of small satellite drops and bi-modal post-collision drop size distributions. The effect of the collision mesh and the satellite droplet model on a high-speed non-evaporating diesel spray is also assessed.     

1996～2000年《武汉大学学报(自然科学版)》引文分析

以1996-2000年《武汉大学学报（自然科学版）》上发表的917篇科技论文为统计样本，据义献计量学的方法对其引文进行了统计分析．结果表明：《武汉大学学报（自然科学版）》篇均引文节为7．83，引文主要类型为期刊。占76．6％。外文文献占引文总数的66．77％，最大中文引文年限为2年，半哀期为7年，衰减系数为31．30％．最大外义引文年限为3年，半哀期为10年，哀减系数为17．08％．刊载论文的总被引量和总影响因子在逐年增加。     

Optimum properties of extruding paste powders on the basis of TiO2, Al2O3 and other substances for production of honeycomb supports

Structure-mechanical and rheological characteristics of pastes on the basis of TiO₂ and Al₂O₃ are discussed. Optinum values to prepare honeycomb supports are determined.     

The time path of the marginal cost of oil: The turning point and the subsequent upward drift

The gradual exhaustion of existing deposits of a depletable non-renewable resource such as oil tends to shift the supply price curve of the resource upwards, increasing its marginal cost. Advances in technologies for exploration and production act as a brake on such upward shifts. Thus, there is a tug-of-war between the gradual exhaustion of existing deposits and technological progress. Using a recently developed constrained least-squares regression technique, we demonstrate that technological progress was the dominant force of the two during the first part of this century, causing a secular drop in marginal costs, but that this situation eventually was reversed, and that the gradual exhaustion of deposits gained the upper hand, causing marginal costs to increase. The turning point occurred around 1971–72. We also discuss the forecasting of the possible current upward drift of marginal costs.     

The acquisition of new technology and its impact on a firm's competitive position

The strategic decision concerning the optimal and dynamic acquisition of new technology is examined. The model focuses on a profit maximizing firm that optimally derives its price, level of output, and its level and composition of productive capacity over time. The acquisition of new technology and reduction of existing capacity may occur simultaneously, so that the composition of the firm's productive resources may be upgraded over time. It is assumed that the acquisition of new technology causes a reduction in production costs and a direct increase in the firm's demand. The demand experienced by the firm may be directly increased as a result of acquiring new technology due to benefits such as expanded product-mix or volume capabilities, improved quality of output, or improved customer service (shorter production lead time). In addition, it is shown that demand is indirectly increased due to the reduced production costs that enable the firm to charge a lower price. Therefore, the strategic impact of acquiring new technology is captured, since its effect on future demand and the firm's ability to meet the demand are considered. The importance of capturing the increased demand potential offered by the new technology is demonstrated through the analysis of numerical examples. In addition, the effect on the optimal solution caused by a variety of environmental conditions is examined. For example, the impact of technological innovation is observed by defining (i) the cost of acquiring technology as a decreasing function of time, and (ii) the effectiveness of new technology on reducing operating costs as an increasing function of time.     

ICT integration in mathematics initial teacher training and its impact on visualization: the case of GeoGebra

This case study investigates the impact of the integration of information and communications technology (ICT) in mathematics visualization skills and initial teacher education programmes. It reports on the influence GeoGebra dynamic software use has on promoting mathematical learning at secondary school and on its impact on teachers’ conceptions about teaching and learning mathematics. This paper describes how GeoGebra-based dynamic applets – designed and used in an exploratory manner – promote mathematical processes such as conjectures. It also refers to the changes prospective teachers experience regarding the relevance visual dynamic representations acquire in teaching mathematics. This study observes a shift in school routines when incorporating technology into the mathematics classroom. Visualization appears as a basic competence associated to key mathematical processes. Implications of an early integration of ICT in mathematics initial teacher training and its impact on developing technological pedagogical content knowledge (TPCK) are drawn.