Theory of coherent acoustic phonons in InGaN/GaN multi-quantum wells

A microscopic theory for the generation and propagation of coherent LA phonons in pseudomorphically strained wurzite (0001) InGaN/GaN multi-quantum well (MQW) p-i-n diodes is presented. The generation of coherent LA phonons is driven by photoexcitation of electron-hole pairs by an ultrafast Gaussian pump laser and is treated theoretically using the density matrix formalism. We use realistic wurzite bandstructures taking valence-band mixing and strain-induced piezo- electric fields into account. In addition, the many-body Coulomb ineraction is treated in the screened time-dependent Hartree-Fock approximation. We find that under typical experimental conditions, our microscopic theory can be simplified and mapped onto a loaded string problem which can be easily solved.Comment: 20 pages, 17 figure

An evaluation of the endophytic colonies present in pathogenic and non-pathogenic Vanguerieae using electron microscopy

Fadogia homblei, Pavetta harborii, Pavetta schumanniana, Vangueria pygmaea (=Pachystigma pygmaeum), Vangueria latifolia (=Pachystigma latifolium) and Vangueria thamnus (=Pachystigma thamnus) all induce one of the most important cardiotoxicoses of domestic ruminants in southern Africa, causing the sickness gousiekte. All the plants which cause gousiekte have previously been shown to contain bacterial endophytes. However, in this study other plants within the Vanguerieae tribe that have not been reported to cause gousiekte; namely Vangueria infausta, Vangueria macrocalyx and Vangueria madagascariensis, have now been shown to also contain endophytes within the inter-cellular spaces of the leaves. The disease gousiekte is difficult to characterise due to fluctuations in plant toxicity. The majority of reported cases of gousiekte poisoning are at the beginning of the growing season; and thus the plants are thought to be more toxic at this time. By using both transmission and scanning electron microscopy the endophytes within these Vanguerieae plants were compared visually. Using the plant reported most often for gousiekte poisoning, V. pygmaea, a basic seasonal comparison of the presence of endophytes was done. It was found that the bacterial endophyte colonies were most abundant during the spring season.The National Research Foundation of South Africa and Professor T. Coutinho.http:// www.elsevier.com/ locate/sajbam201

Beyond the Heartlands: Deindustrialization, Naturalization and the Meaning of an 'Industrial' Tradition

Deindustrialization is a complex and multifaceted series of processes and transitions, reflecting the equally complicated web of social relationships and interdependencies that constitute(d) an industrial society. Contemporary scholars have looked beyond just the economic impact of industrial loss, to the cultural, temporal and spatial legacies and impacts wrought by the mass closures of the 1980s, as well as the continuing presence of an industrial identity in struggles over representation and regeneration. However, deindustrialization has a history that precedes the volatility and culmination of that period, and has impacted upon a more geographically diverse range of former industrial locations than are commonly represented. The narratives that surround some sites are complicated by their displacement in time, place and discourse; they lack the political capital of an ‘industrial’ identity through this disassociation. In this article I aim to go beyond what we might consider the industrial ‘heartlands’ of the UK to a place that has felt the impact of deindustrialization, but which falls outside of the usual representations of the UK’s industrial past. I explore how the industrial identity and memory of a place can be naturalized and selectively re-worked for the needs of the hour, the very meaning of ‘industrial’ altered in the process. I argue that for sites unable to access or utilize the imagery of modern, heavy industry for community or promotional aims, deindustrialization becomes a process of re-writing an historic identity – one that sheds new light on industrial loss in diverse situations, and at an ever-increasing distance from closure

Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV

We report the results of a study of color coherence effects in ppbar collisions based on data collected by the D0 detector during the 1994-1995 run of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8 TeV. Initial-to-final state color interference effects are studied by examining particle distribution patterns in events with a W boson and at least one jet. The data are compared to Monte Carlo simulations with different color coherence implementations and to an analytic modified-leading-logarithm perturbative calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters

Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits

The WWgamma triple gauge boson coupling parameters are studied using p-pbar -> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were collected with the DO detector from an integrated luminosity of 162 pb^{-1} delivered by the Fermilab Tevatron Collider. The cross section times branching fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum) pb. The one-dimensional 95% confidence level limits on anomalous couplings are -0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events

We present a measurement of the top quark pair ttbar production cross section in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1} of data collected by the DO detector at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), large missing transverse energy, and at least four jets, and extract the ttbar content of the sample based on the kinematic characteristics of the events. For a top quark mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1} (syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging

We present a measurement of the top quark pair ($t\bar{t}$) production cross section ($\sigma_{t\bar{t}}$) in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using 230 pb$^{-1}$ of data collected by the D0 experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the $t\bar{t}$ purity of the selected sample. For a top quark mass of 175 GeV, we measure $\sigma_{t\bar{t}}=8.6^{+1.6}_{-1.5}(stat.+syst.)\pm 0.6(lumi.)$ pb, in agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let

Improved W boson mass measurement with the D0 detector

We have measured the W boson mass using the D0 detector and a data sample of 82 pb^-1 from the Tevatron collider. This measurement used W -> e nu decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such 'edge' electrons have not been used in any previous D0 analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous D0 W boson mass measurements, we obtain M_W = 80.483 +/- 0.084 GeV. The 8% improvement from the previous D0 measurement is primarily due to the improved determination of the response parameters for non-edge electrons using the sample of Z bosons with non-edge and edge electrons.Comment: submitted to Phys. Rev. D; 20 pages, 18 figures, 9 table

An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics

For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types