Key Relationships (key + relationships)

Distribution by Scientific Domains

Selected Abstracts

Robust estimation and testing of haplotype effects in case-control studies,,

Andrew S. Allen
Abstract Haplotype-based analyses are thought to play a major role in the study of common complex diseases. This has led to the development of a variety of statistical methods for detecting disease-haplotype associations from case-control study data. However, haplotype phase is often uncertain when only genotype data is available. Methods that account for haplotype ambiguity by modeling the distribution of haplotypes can, if this distribution is misspecified, lead to substantial bias in parameter estimates even when complete genotype data is available. Here we study estimators that can be derived from score functions of appropriate likelihoods. We use the efficient score approach to estimation in the presence of nuisance parameters to a derive novel estimators that are robust to the haplotype distribution. We establish key relationships between estimators and study their empirical performance via simulation. Genet. Epidemiol. 2007. Published 2007 Wiley-Liss, Inc. [source]

Impact of climate change on runoff from a mid-latitude mountainous catchment in central Japan

Yoshinori Shinohara
Abstract Hydrologic balance in high-altitude, mid-latitude mountain areas is important in terms of the water resources available to associated lowlands. This study examined how current and historical shifts in precipitation (P) patterns and concurrent increases in temperature (T) affected runoff (Q) and other hydrologic components in a mid-latitude mountain catchment of central Japan, using a combination of long-term data and a simplified hydrologic model, along with their stochastic treatment. The availability of intensive meteorological and hydrological data from the period 1997,2001 allowed the derivation of key relationships for the current climate that tie the forcing term to the parameters or state variables. By using the data recorded in the period 1965,2001, the force for driving the historical simulation was generated. Based on this model and historical shifts in P and T, the probability density functions of Q (pdf(Q)) was computed. A main novelty in this study is that such a stochastic representation, which is useful for considering the influence of projected shifts in environmental factors on the hydrologic budget, was provided. Despite the large increase in the rate of T in winter and spring, pdf(Q) in spring and summer varied appreciably during the time studied mainly because of an increase in snowmelt. An interannual change in whole-year Q was robust to shifts in T because while Q in spring increased, in summer it decreased, implying a crucial effect of global warming on mountain hydrologic regimes is change in the timing of Q. Copyright 2009 John Wiley & Sons, Ltd. [source]

The Role of Processing in the Fabrication and Optimization of Plastic Solar Cells

ADVANCED MATERIALS, Issue 14-15 2009
Jeffrey Peet
Abstract The development of high-efficiency plastic solar cells is rapidly accelerating as the need for economically viable alternative energy sources becomes evident. Polymer-based bulk-heterojunction (BHJ) solar cells are attractive in that they can be coated from solution onto flexible substrates by a variety of techniques and thus inexpensive large-volume manufacturing should be possible. Further, the inherent flexibility of the polymeric materials combined with thin photovoltaic active layers results in devices that can be adapted to a variety of unique aesthetics and form factors. Recent advances in key relationships between thin-film casting methods, bulk-heterojunction morphology, and device performance have occurred in tandem with the synthesis of novel polymer semiconductors that possess increased optical-absorption breadth and optoelectronic performance. This Research News article highlights a few techniques developed to optimize the BHJ nanomorphology and performance of solar cells fabricated by various solution-processing methods. [source]


G.W. Saunders
Algae of the Alariaceae, Laminariaceae and Lessoniaceae are the largest, most complex, and, arguably, most fascinating of the seaweeds. It is, therefore, a profound paradox that these species remain in taxonomic chaos despite the contemporary emphases on systematics. Setchell and Gardner established the classification system in 1925, recognizing these families on the basis of clear morphological features. At that time, however, they acknowledged that some species had features consistent with placement in two families, or that obscured logical placement in any of the families. Ironically, the problems noted by Setchell and Gardner have been ignored and the system has become entrenched in kelp literature. Initial molecular studies highlighted the shortcomings noted by Setchell and Gardner, and further indicated that little of the morphology-based system was natural. It was obvious that the diagnostic morphological features, presence or absence of sporophylls and ontogenetic splitting, were ,noisy' being gained and lost independently many times in kelp evolution. Despite the insights of the initial molecular studies, they had limitations and key relationships remained unresolved. The investigations used the Internal Transcribed Spacers (ITS) of the ribosomal cistron that have phylogenetic limitations owing to their short length, which is exacerbated by the many variable regions that can't be aligned confidently and must be removed prior to phylogenetic analyses. Many molecular publications have appeared subsequent to the first ITS results, and their contribution towards elucidating kelp phylogeny will be assessed. Current investigations using the Large Subunit ribosomal DNA (LSU) for kelp systematics will also be discussed. [source]