Coherent electron-phonon coupling and polaron-like transport in molecular wires

We present a technique to calculate the transport properties through one-dimensional models of molecular wires. The calculations include inelastic electron scattering due to electron-lattice interaction. The coupling between the electron and the lattice is crucial to determine the transport properties in one-dimensional systems subject to Peierls transition since it drives the transition itself. The electron-phonon coupling is treated as a quantum coherent process, in the sense that no random dephasing due to electron-phonon interactions is introduced in the scattering wave functions. We show that charge carrier injection, even in the tunneling regime, induces lattice distortions localized around the tunneling electron. The transport in the molecular wire is due to polaron-like propagation. We show typical examples of the lattice distortions induced by charge injection into the wire. In the tunneling regime, the electron transmission is strongly enhanced in comparison with the case of elastic scattering through the undistorted molecular wire. We also show that although lattice fluctuations modify the electron transmission through the wire, the modifications are qualitatively different from those obtained by the quantum electron-phonon inelastic scattering technique. Our results should hold in principle for other one-dimensional atomic-scale wires subject to Peierls transitions.Comment: 21 pages, 8 figures, accepted for publication in Phys. Rev. B (to appear march 2001

Female chromosome X mosaicism is age-related and preferentially affects the inactivated X chromosome

To investigate large structural clonal mosaicism of chromosome X, we analysed the SNP microarray intensity data of 38,303 women from cancer genome-wide association studies (20,878 cases and 17,425 controls) and detected 124 mosaic X events42Mb in 97 (0.25%) women. Here we show rates for X-chromosome mosaicism are four times higher than mean autosomal rates; X mosaic events more often include the entire chromosome and participants with X events more likely harbour autosomal mosaic events. X mosaicism frequency increases with age (0.11% in 50-year olds; 0.45% in 75-year olds), as reported for Y and autosomes. Methylation array analyses of 33 women with X mosaicism indicate events preferentially involve the inactive X chromosome. Our results provide further evidence that the sex chromosomes undergo mosaic events more frequently than autosomes, which could have implications for understanding the underlying mechanisms of mosaic events and their possible contribution to risk for chronic diseases

Detectable clonal mosaicism and its relationship to aging and cancer

In an analysis of 31,717 cancer cases and 26,136 cancer-free controls from 13 genome-wide association studies, we observed large chromosomal abnormalities in a subset of clones in DNA obtained from blood or buccal samples. We observed mosaic abnormalities, either aneuploidy or copy-neutral loss of heterozygosity, of >2 Mb in size in autosomes of 517 individuals (0.89%), with abnormal cell proportions of between 7% and 95%. In cancer-free individuals, frequency increased with age, from 0.23% under 50 years to 1.91% between 75 and 79 years (P = 4.8 × 10(-8)). Mosaic abnormalities were more frequent in individuals with solid tumors (0.97% versus 0.74% in cancer-free individuals; odds ratio (OR) = 1.25; P = 0.016), with stronger association with cases who had DNA collected before diagnosis or treatment (OR = 1.45; P = 0.0005). Detectable mosaicism was also more common in individuals for whom DNA was collected at least 1 year before diagnosis with leukemia compared to cancer-free individuals (OR = 35.4; P = 3.8 × 10(-11)). These findings underscore the time-dependent nature of somatic events in the etiology of cancer and potentially other late-onset diseases

Penetration of 14C-DDT into and through the cockroach integument

1. 1. The penetration of DDT into and through the integument of Periplaneta americana (L.) is not a simple first-order function, but may be an aggregate of first-order events. 2. 2. Partitioning of DDT from the epicuticular grease into lower phases is the rate-limiting step in penetration. 3. 3. About 8 per cent of the DDT injected into the haemolymph back-diffuses into the epicuticular lipids. 4. 4. About 3 per cent of the DDT applied to the integument is recoverable from the haemolymph

From monopoly to markets: Milestones along the road. Occasional paper {number_sign}25

This report analyzes developments in the electric utility industry using the tools of transaction cost economics. During the last thirty years, the tools of economic analysis have been substantially expanded--notably, Oliver Williamson, building on the insights of Coase and others, has made significant contributions through his work in developing the new institutional economics, of which transaction cost economics reasoning plays a major role. Because of the relevance of the new institutional economics to public utilities and public utility regulation, the theoretical insights of the new institutional economics have been applied to many aspects of public utility industry structure, governance, and regulation. The contributions of Joskow and Schmalensee are most notable, but many other economists have made theoretical and empirical contributions. These insights are very applicable to the issues that policymakers and regulators are likely to address as electric restructuring progresses. The goal of this report is to synthesize the theoretical work on the new institutional economics with the recent developments in the electric utility industry--most notably, the rapid trend toward competition in electric generation, both in the US and abroad. Transaction-cost-economics reasoning provides an analytical structure for understanding the implications of asset specificity, asymmetric and imperfect information, reputation effects, ex ante contracting costs, ex post contract maladaption issues, and issues that arise because contracts are incomplete. The insights that transaction cost economics can provide are very timely to the debates currently going on with respect to electric restructuring issues

DNA Sequence Analysis of Regions Surrounding \u3ci\u3ebla\u3c/i\u3e\u3csub\u3eCMY-2\u3c/sub\u3e from Multiple \u3ci\u3eSalmonella\u3c/i\u3e Plasmid Backbones

The emergence in the United States of resistance to expanded-spectrum cephalosporin (e.g., ceftriaxone) within the salmonellae has been associated primarily with three large (\u3e100-kb) plasmids (designated types A, B, and C) and one 10.1-kb plasmid (type D) that carry the blaCMY-2 gene. In the present study, the distribution of these four known blaCMY-2-carrying plasmids among 35 ceftriaxone-resistant Salmonella isolates obtained from 1998 to 2001 was examined. Twenty-three of these isolates were Salmonella enterica serotype Newport, 10 were Salmonella enterica serotype Typhimurium, 1 was Salmonella enterica serotype Agona, and 1 was Salmonella enterica serotype Reading. All 23 serotype Newport isolates carried a type C plasmid, and 5, 4, and 1 serovar Typhimurium isolate carried type B, A, and C plasmids, respectively. Both the serotype Agona and serotype Reading isolates carried type A plasmids. None of the isolates carried a type D plasmid. Hybridization data suggested that plasmid types A and C were highly related replicons. DNA sequencing revealed that the region surrounding blaCMY-2 was highly conserved in all three plasmid types analyzed (types B, C, and D) and was related to a region surrounding blaCMY-5 from the Klebsiella oxytoca plasmid pTKH11. These findings are consistent with a model in which blaCMY-2 has been disseminated primarily through plasmid transfer, and not by mobilization of the gene itself, to multiple Salmonella chromosomal backbones