Will nuclear power pay for itself?

Will nuclear power ever generate enough revenue to cover its costs? Historical data covering capital, fuel, operations, maintenance, decommissioning, and waste disposal costs, and generation and revenue figures during the period 1953 through 1991 were analyzed and compared. The analysis shows that nuclear power is currently nowhere near meeting its costs. Scenarios projecting future costs and revenues were developed. Analysis of these projections suggests that even under the most optimistic conditions (where costs are cut considerably and revenues climb substantially), the current generation of the nuclear option over its lifetime may be best be economically marginal.     

Detecting a changed segment in DNA sequences

Non-coding deoxyribonucleic acid (DNA) can typically be modelled by a sequence of Bernoulli random variables by coding one base, e.g. T, as 1 and other bases as 0. If a segment of a sequence is functionally important, the probability of a 1 will be different in this changed segment from that in the surrounding DNA. It is important to be able to see whether such a segment occurs in a particular DNA sequence and to pin-point it so that a molecular biologist can investigate its possible function. Here we discuss methods for testing the occurrence of such a changed segment and how to estimate the end points of it. Maximum-likelihood-based methods are not very tractable and so a nonparametric method based on the approach of Pettitt has been developed. The problem and its solution are illustrated by a specific DNA example.     

Detecting homogeneous segments in DNA sequences by using hidden Markov models

In recent years there has been a rapid growth in the amount of DNA being sequenced and in its availability through genetic databases. Statistical techniques which identify structure within these sequences can be of considerable assistance to molecular biologists particularly when they incorporate the discrete nature of changes caused by evolutionary processes. This paper focuses on the detection of homogeneous segments within heterogeneous DNA sequences. In particular, we study an intron from the chimpanzee α-fetoprotein gene; this protein plays an important role in the embryonic development of mammals. We present a Bayesian solution to this segmentation problem using a hidden Markov model implemented by Markov chain Monte Carlo methods. We consider the important practical problem of specifying informative prior knowledge about sequences of this type. Two Gibbs sampling algorithms are contrasted and the sensitivity of the analysis to the prior specification is investigated. Model selection and possible ways to overcome the label switching problem are also addressed. Our analysis of intron 7 identifies three distinct homogeneous segment types, two of which occur in more than one region, and one of which is reversible.     

Associations between multiscale landscape characteristics and breeding bird abundance and diversity across urban-rural gradients in Northeastern Georgia, USA

Urbanization is rapidly changing the southeastern US landscape, particularly in Georgia within and around the Atlanta metropolitan area, the fastest-growing Southeastern population center. Landscape characteristics related to human disturbance, landscape composition, and landscape configuration vary across the urban-rural gradient and are easily and inexpensively evaluated using geographic information systems (GIS). Previous studies have suggested that avian communities and populations respond in scale-dependent ways to urbanization-related landscape changes through changes in abundance and diversity. We conducted a 2-year study (2007?C2008) of the response of breeding bird population abundance, community abundance, species richness, and relative diversity in young and mature single-family residential areas to 15 landscape characteristics measured at multiple spatial scales across urban-rural development intensity gradients near Athens, Georgia. We grouped birds by species, entire site assemblage, and by functional guild affiliation. Our models suggest strong relationships between the landscape and both community and population abundance of birds, as well as a somewhat weaker relationship with species richness. We detected only a weak relationship between breeding season relative diversity and landscape characteristics; we hypothesize a possible seasonal component to that relationship based on an earlier study. Our results suggest that widely available geospatial metrics of human disturbance and landscape pattern can be used to model breeding bird abundance and diversity across urban-rural gradients. This study sets the framework for a landscape scale understanding of the effects of housing developments and development intensity on breeding birds in northeastern Georgia and such a landscape-based approach to modeling species numbers represents a valuable tool in natural resources management.     

Relations between stressors and group perceptions: Main and mediating effects

Most orgnizations these days utilize groups for the performance of at least some tasks. There is therefore a need to examine the relationthip between job stressors and group functioning. Until now it has been proposed that employees who perceive high levels of stress in their jobs will have negative perceptions of the groups in which they work, in the form of reduced altruism and collective efficacy. They may also have higher levels of psychological strain. This study examined relations between job-related stressors and group perceptions (collective efficacy 3rd the prevalence of altruistic behaviour) in a sample of 2403 mililitary personnel, comprising 31 companies in two US Anny combat brigades. We also examined whether group perceptions mediated the relationship between stressors and both job satisfaction and subjective well-being. Results indicated that stressors were negatively associated with measures of group perceptions, and both job satisfiction and well-being. Furthermore, mediated regression analyses suggested that relations between interpersonal conflict and both job satitfaction and well-being were partially mediated by both group perception measures. These finding suggest that work-related stressors may negatively impact on group functioning, which may lead to employee strains. Implications of these finding are discussed, and suggestions are made for future research.     

永远的“希腊小庙”——英译《边城》序

曾经因为沈从文的乡村中国的故事如此贴近乡下人的生活及其重要场景,以至一本1947年的沈从文英译选集就被题名为<中国土地>.伴随着沈从文的文学声名,那片土地在1949年的共产主义革命中被推翻了.30年后,当激进的毛思想终结之时,中国的批评家们重新发现了沈从文.他们称他为唯一的中国战前本土文学或乡土文学流派的代表性作家,也许还是奠基者.1980年代将乡土主题和轻柔风格相结合的沈从文式的写作手法,随中国后毛时代的文艺复兴而颇受追捧.     

Ethnic power mobilised

Mobilizing Ethnic Power: Can South Africa Change? by Heribert Adam and Herman Giliomee New Haven and London, Yale University Press, 1979. Distributed by David Philip: Cape Town.     

It Takes a Village (Perhaps a Nation): Families,States, and Educational Achievement

Research in the United States has shown that children growing up in 2‐parent households do better in school than children from single‐parent households. We used the Trends in International Mathematics and Science Study (TIMSS) data to test whether this finding applied to other countries as well (N = 100,307). We found that it did, but that the educational gap was greater in the United States than in the other 13 countries considered. Results from 2‐level hierarchical linear models demonstrated that international differences in the educational gap were associated with several indicators of national policy and demographic contexts. No single policy appeared to have a large effect, but several policy combinations were associated with substantially reduced educational gaps between children from different family structures.