Polynomial spline estimation of partially linear single-index proportional hazards regression models

The Cox proportional hazards (PH) model usually assumes linearity of the covariates on the log hazard function, which may be violated because linearity cannot always be guaranteed. We propose a partially linear single-index proportional hazards regression model, which can model both linear and nonlinear covariate effects on the log hazard in the proportional hazards model. We adopt a polynomial spline smoothing technique to model the structured nonparametric single-index component for the nonlinear covariate effects. This method can reduce the dimensionality of the covariates being modeled, while, at the same time, can provide efficient estimates of the covariate effects. A two-step iterative algorithm to estimate the nonparametric component and the covariate effects is used for facilitating implementation. Asymptotic properties of the estimators are derived. Monte Carlo simulation studies are presented to compare the new method with the standard Cox linear PH model and some other comparable models. A case study with clinical trial data is presented for illustration.     

Specification-based data reduction in dimensional data warehouses

Many data warehouses contain massive amounts of data, accumulated over long periods of time. In some cases, it is necessary or desirable to either delete “old” data or to maintain the data at an aggregate level. This may be due to privacy concerns, in which case the data are aggregated to levels that ensure anonymity. Another reason is the desire to maintain a balance between the uses of data that change as the data age and the size of the data, thus avoiding overly large data warehouses. This paper presents effective techniques for data reduction that enable the gradual aggregation of detailed data as the data ages. With these techniques, data may be aggregated to higher levels as they age, enabling the maintenance of more compact, consolidated data and the compliance with privacy requirements. Special care is taken to avoid semantic problems in the aggregation process. The paper also describes the querying of the resulting data warehouses and an implementation strategy based on current database technology.     

Incorporating multiple patterns of activity into the design of cognitive work support systems

The design of support systems for cognitive work needs to account for the different patterns of activity resulting from changes in context. The contextual control modes from Hollnagel’s model of control are presented as a suitable framework to describe these patterns and to identify the implications for design of support systems. The design and evaluation of a prototype support system for airline operations is used as a case study in supporting multiple cognitive control modes. The evaluation of the prototype with experts illustrated clear and distinguishable changes in the patterns of activity in different contextual control modes. Notably, different designs were demonstrated to support particular contextual control modes and to disrupt cognitive activity in contextual control modes which they were not intended to support.     

Introduction to the Special Section on Dissemination: Dissemination Research and Research Dissemination: How Can We Close the Gap?

One of the greatest challenges facing health promotion and disease prevention is translating research findings into evidence-based public health and clinical practices that are actively disseminated and widely adopted. Despite the tremendous strides made in developing effective disease prevention and control programs, there has been little study of effective dissemination of evidence-based programs to and adoption by community, public health, and clinical practice settings. This special section provides a venue in which to highlight exemplary dissemination research efforts while also identifying limitations in research to date and framing important future research questions. This issue establishes a resource for investigators interested in dissemination research, with relevance to health psychology. In this sense, it can serve as a benchmark by which to examine subsequent progress. The 6 articles reflect the state of the science in dissemination research for the promotion and adoption of health behavior change interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of d-amphetamine and smoking abstinence on cue-induced cigarette craving.

In this study, the authors investigated the effects of the indirect dopamine agonist d-amphetamine (AMPH) on cue-induced cigarette craving in smokers. Abstinent or nonabstinent cigarette smokers (N=21) rated their cravings for cigarettes and for food (control) after pretreatment with AMPH (15 mg) or placebo and before and after viewing blocks of smoking-related, food-related, and neutral pictures. Before the cues were presented, AMPH increased cigarette craving and decreased food craving. Smoking and food cues increased craving for cigarettes and for food, respectively. AMPH also further increased cigarette craving (and decreased food craving) after cue presentation, but it did so regardless of cue type (food or smoking). Smoking abstinence markedly increased craving regardless of cue presentation or drug condition. These results suggest that both AMPH and smoking abstinence can increase cigarette craving, but they do not appear to specifically affect responses to conditioned smoking-related cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wheat Starch Modification Through Biotechnology

Natural mutations that affect the amylose/amylopectin ratio in starch are unlikely to develop naturally in wheat due to its allohexaploid genome (2n=6x; AABBDD). One of the strategies to modify wheat starch structure involves identification of germplasms with null alleles for starch biosynthetic genes, followed by exchange of functional alleles with the identified null alleles through classical plant breeding. This technique has successfully been used to combine the three null alleles for granule-bound starch synthase I (GBSSI) to develop a wheat line that produces amylopectin-rich (>95%) starch (waxy starch). Another strategy to alter expression levels of starch biosynthetic genes employs recent advances in molecular biology and genetic engineering of wheat. For this approach, various monocot vectors have been developed that drive expression of wheat starch branching enzyme I (SBEI) cDNA sequences in the anti-sense orientation. Several of the wheat cell lines transformed with the anti-sense vectors express branching enzyme (BE) activity at a significantly lower level than non-transformed cells. One transgenic wheat plant expressing the anti-sense SBEI RNA produces a ten-fold lower level of BE activity in kernels than wild-type wheat. Analysis of starch produced from the transgenic plant shows that starch structure and properties have been altered.