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Protected by the chiral symmetry, three dimensional chiral topological insulators are characterized by an integer-valued topological invariant. How this invariant could emerge in physical observables is an important question. Here we show that the magneto-electric polarization can identify the integer-valued invariant if we gap the system without coating a quantum Hall layer on the surface. The quantized response is demonstrated to be robust against weak perturbations. We also study the topological properties by adiabatically coupling two nontrivial phases, and find that gapless states appear and are localized at the boundary region. Finally, an experimental scheme is proposed to realize the Hamiltonian and measure the quantized response with ultracold atoms in optical lattices.
Abstract Background The combination of sarcopenia and obesity has been associated with physical impairment in older people. However, previous research has relied on assessments of lean mass as a surrogate for muscle mass. We postulate that inaccurate measures of muscle mass may have obscured the role of obesity in sarcopenia and related outcomes. Our aim was to clarify the interactions of muscle and fat with physical performance and adverse outcomes using an accurate measure of muscle mass. Methods In a longitudinal study of >1,300 older men (mean age 84 years), we compared a direct measurement of muscle mass (D3 creatine dilution; D3Cr) with an approximation of muscle mass (appendicular lean mass [ALM] by dual-energy x-ray absorptiometry [DXA]) and their associations with measures of physical performance (gait speed, chair stand time) and adverse outcomes (incident injurious falls and mobility problems). We measured percent fat mass by DXA. Results Low D3Cr muscle mass was strongly associated with decreased performance and increased risk of adverse outcomes. Increased fat mass had little association after accounting for D3Cr muscle mass. In contrast, DXA ALM was minimally associated with performance or adverse outcomes, and fatness remained associated with both outcomes after accounting for DXA ALM. Conclusions When an accurate assessment of muscle mass (rather than lean mass) is used, reduced muscle mass is highly associated with important outcomes and the negative effects of adiposity are minimal, suggesting that obesity has little relevance for the understanding of important adverse health outcomes of sarcopenia in older men.
Organic electronics are broadly anticipated to impact the development of flexible thin-film device technologies. Among these, solution-processable π-conjugated polymers and small molecules are proving particularly promising in field-effect transistors and bulk heterojunction solar cells. This Perspective analyzes some of the most exciting strategies recently suggested in the design and structural organization of π-functional materials for transistor and solar cell applications. Emphasis is placed on the interplay between molecular structure, self-assembling properties, nanoscale and mesoscale ordering, and device efficiency parameters. A critical look at the various approaches used to optimize both materials and device performance is provided to assist in the identification of new directions and further advances.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPreparation of the first stable formylsilane, (Me3Si)3SiCHO, from a zirconium .eta.2-silaacyl complexFrederick H. Elsner, Hee Gweon. Woo, and T. Don. TilleyCite this: J. Am. Chem. Soc. 1988, 110, 1, 313–314Publication Date (Print):January 1, 1988Publication History Published online1 May 2002Published inissue 1 January 1988https://doi.org/10.1021/ja00209a063RIGHTS & PERMISSIONSArticle Views337Altmetric-Citations49LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (305 KB) Get e-Alerts Get e-Alerts
A set of catalytic, intermolecular hydroaminations of strained bicyclic olefins and dienes are reported that occur in both high yield and high enantioselectivity. These reactions occur with a catalyst generated from [Ir(cyclooctene)Cl]2, sterically hindered and electron-rich derivatives of the Segphos and BIPHEP family of ligands, and a soluble base. This system catalyzes the addition of various anilines to norbornene, norbornadiene, and other bicyclic olefins. The products from addition of p-anisidine can be transformed to BOC-protected norbornylamine and to substituted cyclopentanes in nearly enantiopure form. Mechanistic studies show that addition of aniline-d2 occurs in a syn fashion and suggest that the catalytic cycle comprises oxidative addition of aniline to form a bis-anilide hydride complex, followed by migratory insertion of olefin and reductive elimination of product in a series of steps involving iridium complexes containing ancillary bisphosphine and arylamide ligands.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Global industrial production continues to recover – something for which policy deserves considerable credit (as we have argued on this site, see Almunia et al 2009 and O’Rourke and Eichengreen 2009). But before indulging in selfcongratulation, policymakers should note that the level of industrial production is still 6% below its previous peak (figure 1). (At the trough it was 13% below its previous peak.) It follows that considerable excess capacity remains in a number of important economies. Exiting now from policies of stimulus in those countries would therefore be premature.
This chapter examines the military applications of nuclear power plants. It examines their historical dimension, their present status and likely future applications. The US armed forces are looking at reducing power supply vulnerabilities and operating costs, and also reducing petroleum dependence. During their operations in Iraq and Afghanistan, the US armed forces had difficulty in getting huge quantities of fuel for the power needs of remote operating bases. The National Aeronautical and Space Administration (NASA) reportedly uses some of these to power satellites and other spacecraft. The nuclear reactors and/or fissile material will also have to be safeguarded from possible theft or capture by terrorist groups. Nuclear-powered submarines have small reactors that provide propulsion. Their advantage over conventional diesel-electric submarines is based on the fact that they are independent of air and do not need to surface off and on to run the diesel generator to charge the batteries.
