A stability limit for the atmospheres of giant extrasolar planets

Recent observations of the planet HD209458b indicate that it is surrounded by an expanded atmosphere of atomic hydrogen that is escaping hydrodynamically. Theoretically, it has been shown that such escape is possible at least inside an orbit of 0.1 au (refs 4 and 5), and also that H3+ ions play a crucial role in cooling the upper atmosphere. Jupiter's atmosphere is stable, so somewhere between 5 and 0.1 au there must be a crossover between stability and instability. Here we show that there is a sharp breakdown in atmospheric stability between 0.14 and 0.16 au for a Jupiter-like planet orbiting a solar-type star. These results are in contrast to earlier modelling that implied much higher thermospheric temperatures and more significant evaporation farther from the star. (We use a three-dimensional, time-dependent coupled thermosphere-ionosphere model and properly include cooling by H3+ ions, allowing us to model globally the redistribution of heat and changes in molecular composition.) Between 0.2 and 0.16 au cooling by H3+ ions balances heating by the star, but inside 0.16 au molecular hydrogen dissociates thermally, suppressing the formation of H3+ and effectively shutting down that mode of cooling.     

Research on the atomic force microscopy-based fabrication of nanochannels on silicon oxide surfaces

The atomic force microscopy (AFM)-based nanomachining of nanochannels on silicon oxide surfaces is investigated both theo-retically and experimentally. The relationships of nanochannel depth versus cutting velocity, nanochannel depth versus normal force, friction force versus cutting velocity, and friction force versus normal force are systematically studied. Using the derived theory and fabrication method, a nanochannel with an expected depth can be machined simply by controlling the vertical deflection signal on the position sensitive detector of AFM. The theoretical analysis and fabrication method can be effectively used for AFM-based fabrication of nanochannels.     

Colorado's rare flora

Distribution, status, habitat, elevational range, original literature citations, synonymy, and specimens deposited at Brigham Young University (BRY), University of Colorado (COLO), Colorado State University (CS),Denver Botanical Garden (KHD), Kansas State University (KSC), University of Kansas (KANU), Missouri Botanical Garden (MO), and the Rocky Mountain Herbarium (RM) are given for 79 species of rare Colorado plants. Species federally listed by the U.S. Fish and Wildlife Service under the Endangered Species Act, candidates for listing, and species that qualify as federal candidates because of limited range, small populations, or known threats are included. Suggested changes in status are offered where appropriate. Maps and tables indicating the Colorado range of these species are provided.     

万物之理

有没有一个单独的统一了自然界显著多样性的深刻的理论？是不是正发现了粒子物理线索到万物之理的一个有趣的模式？某些物理学家正想回答这两个问题。爱因斯坦曾经说过“宇宙中最不可理解的事情，实际上是都可以理解的。”宇宙的体积之大不可相信，其所包含事物之多不可想象。至今我们已能模拟出它的大部分历史，阐明它的结构，预测它的未来，了解其所含有客体的迷惑多变的行为。我们之所以能做这些事是因为我们了解到所有事物都是通过一个关系网把它们联结在一起的。我们把它们称之为物理定律。万物归一个好的物理学定律或理论的工作就是用…     

Planning for smallpox outbreaks

Mathematical models of viral transmission and control are important tools for assessing the threat posed by deliberate release of the smallpox virus and the best means of containing an outbreak. Models must balance biological realism against limitations of knowledge, and uncertainties need to be accurately communicated to policy-makers. Smallpox poses the particular challenge that key biological, social and spatial factors affecting disease spread in contemporary populations must be elucidated largely from historical studies undertaken before disease eradication in 1979. We review the use of models in smallpox planning within the broader epidemiological context set by recent outbreaks of both novel and re-emerging pathogens.     

New estimates of trends in births by birth order in England and Wales

A greater understanding of past, present and future trends in fertility can be gained from analysing trends in birth order; that is whether a birth is a first, second, third or higher order birth. However, under current legislation, birth order information is not collected at registration for births outside marriage and birth order recorded within marriage is not the true birth order. This article presents revised and updated estimates of true birth order. It discusses the construction of the new estimates and presents analysis relating the births by true birth order to the population of women by parity on both a period (fertility in a particular year) and cohort (fertility of women born in a particular year) basis. The new true birth order figures are also compared to the previous set of estimates.     

Deletion of brain dystroglycan recapitulates aspects of congenital muscular dystrophy

Fukuyama congenital muscular dystrophy (FCMD), muscle-eye-brain disease (MEB), and Walker-Warburg syndrome are congenital muscular dystrophies (CMDs) with associated developmental brain defects. Mutations reported in genes of FCMD and MEB patients suggest that the genes may be involved in protein glycosylation. Dystroglycan is a highly glycosylated component of the muscle dystrophin-glycoprotein complex that is also expressed in brain, where its function is unknown. Here we show that brain-selective deletion of dystroglycan in mice is sufficient to cause CMD-like brain malformations, including disarray of cerebral cortical layering, fusion of cerebral hemispheres and cerebellar folia, and aberrant migration of granule cells. Dystroglycan-null brain loses its high-affinity binding to the extracellular matrix protein laminin, and shows discontinuities in the pial surface basal lamina (glia limitans) that probably underlie the neuronal migration errors. Furthermore, mutant mice have severely blunted hippocampal long-term potentiation with electrophysiologic characterization indicating that dystroglycan might have a postsynaptic role in learning and memory. Our data strongly support the hypothesis that defects in dystroglycan are central to the pathogenesis of structural and functional brain abnormalities seen in CMD.     

The Need for a Systemic Approach to Change Management—A Case Study

Change is now a constant feature of organizational life, but the effectiveness of change management initiatives is often open to question. By reflecting on a case of change management involving a Higher Education Institution (HEI), this paper argues that, to be more effective, organizational change must be managed systemically. The paper first provides a systemic conceptual underpinning to change management, and then examines the case by comparing what had really happened with what might have happened if organizational change had been managed systemically. The analysis helps build an improved understanding of change management, and provides implications for future change management practice.