1,097 research outputs found

    Responses of salmonids to habitat changes

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    Streams in western North America provide spawning and rearing habitats for several species of salmon and trout that are of substantial economic importance in the region. Timber that grows on lands through which these streams flow is also economically important, and its harvest can substantially change habitat conditions and aquatic production in salmonid streams. Undisturbed forests, the streams that flow through them, and the salmonid communities in these streams have intrinsic scientific, genetic, and cultural values in addition to their economic importance. The complex relations between salmonids and their physical environment, and the changes in these relations brought about by timber harvest, have been investigated extensively (see the bibliography by Macdonald et al. 1988). However, in spite of considerable evidence of profound changes in channel morphology and in light, temperature, and flow regimes associated with timber harvests, much uncertainty exists about the responses of salmonids to these changes

    Material Characterization and Real-Time Wear Evaluation of Pistons and Cylinder Liners of the Tiger 131 Military Tank

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    Material characterisation and wear evaluation of the original and replacement pistons and cylinder-liners of Tiger 131 is reported. Original piston and cylinder-liner were operative in the Tigers’ engine during WWII. The replacement piston and cylinder-liner were used as substitutes and were obtained after failure in two hours of operation in the actual engine. Material characterisation revealed that the original piston was aluminium silicon hypereutectic alloy whereas the replacement piston was aluminium copper alloy with very low silicon content. Both original and replacement cylinder-liners consisted of mostly iron which is indicative of cast iron, a common material for this application. The replacement piston average surface roughness was found to be 9.09 ÎŒm while for replacement cylinder-liner it was 5.78 ÎŒm

    Lost but Not Forgotten—The Economics of Improving Patient Retention in AIDS Treatment Programs

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    Gregory Bisson and Jeffrey Stringer discuss the implications of a new study showing how loss to follow-up affects the effectiveness of a public sector HIV program in CĂŽte d'Ivoire

    Isoniazid resistance and death in patients with tuberculous meningitis: retrospective cohort study

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    Objective To determine whether initial isoniazid resistance is associated with death during the treatment of tuberculous meningitis

    Etude des variations de maturité des grappes de vigne selon leur position sur la souche Recherche d'une méthode d'échantillonnage

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    La valeur de diffĂ©rentes grappes comme Ă©chantillon reprĂ©sentatif des caractĂ©ristiques de maturitĂ©, teneur en sucre et aciditĂ© totale, de la souche entiĂšre est analysĂ©e. Les rĂ©sultats montrent que le meilleur Ă©chantillonnage est constituĂ© par le prĂ©lĂšvement de la grappe basale d'un rameau situĂ©e Ă  Ă©gale distance du tronc et de l'extrĂ©mitĂ© de la branche Ă  fruit. Ce type de prĂ©lĂšvement, particuliĂšrement satisfaisant dans les expĂ©riences oĂč l'on dĂ©sire surtout comparer et Ă©tablir un classement, semble avoir une valeur assez gĂ©nĂ©rale dans diffĂ©rentes conditions (modes de conduite, annĂ©es, localitĂ©s).Untersuchungen ĂŒber die VariabilitĂ€t der Beerenreife in Beziehung zur Stellung der Traube am WeinstockEntwicklung einer Methode fĂŒr die Entnahme von StichprobenEs wurde analysiert, welche Trauben eines Weinstockes eine reprasentative Aussage ĂŒber die Beerenreife der ganzen Rebe ermöglichen (Reifekriterien: Zucker- und Gesamtsauregehalt).FĂŒr eine reprĂ€sentative Stichprobe wird am zweckmĂ€ĂŸigsten die basale Traube eines Triebes entnommen, der gleich weit vom Stamm und von der Spitze der Tragrute entspringt. Dieser Art der Probenahme, die sich besonders fĂŒr den Vergleich und die Klassifizierung von Reben eignet, dĂŒrfte eine allgemeinere Bedeutung, auch bei unterschiedlichen Erziehungsformen, JahrgĂ€ngen und Standorten, zukommen

    Statistics of electromagnetic transitions as a signature of chaos in many-electron atoms

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    Using a configuration interaction approach we study statistics of the dipole matrix elements (E1 amplitudes) between the 14 lower odd states with J=4 and 21st to 100th even states with J=4 in the Ce atom (1120 lines). We show that the distribution of the matrix elements is close to Gaussian, although the width of the Gaussian distribution, i.e. the root-mean-square matrix element, changes with the excitation energy. The corresponding line strengths are distributed according to the Porter-Thomas law which describes statistics of transition strengths between chaotic states in compound nuclei. We also show how to use a statistical theory to calculate mean squared values of the matrix elements or transition amplitudes between chaotic many-body states. We draw some support for our conclusions from the analysis of the 228 experimental line strengths in Ce [J. Opt. Soc. Am. v. 8, p. 1545 (1991)], although direct comparison with the calculations is impeded by incompleteness of the experimental data. Nevertheless, the statistics observed evidence that highly excited many-electron states in atoms are indeed chaotic.Comment: 16 pages, REVTEX, 4 PostScript figures (submitted to Phys Rev A

    Assessing future vent opening locations at the Somma-Vesuvio volcanic complex:1. A new information geodatabase with uncertainty characterizations

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    This study presents new and revised data sets about the spatial distribution of past volcanic vents, eruptive fissures, and regional/local structures of the Somma‐Vesuvio volcanic system (Italy). The innovative features of the study are the identification and quantification of important sources of uncertainty affecting interpretations of the data sets. In this regard, the spatial uncertainty of each feature is modeled by an uncertainty area, i.e., a geometric element typically represented by a polygon drawn around points or lines. The new data sets have been assembled as an updatable geodatabase that integrates and complements existing databases for Somma‐Vesuvio. The data are organized into 4 data sets and stored as 11 feature classes (points and lines for feature locations and polygons for the associated uncertainty areas), totaling more than 1700 elements. More specifically, volcanic vent and eruptive fissure elements are subdivided into feature classes according to their associated eruptive styles: (i) Plinian and sub‐Plinian eruptions (i.e., large‐ or medium‐scale explosive activity); (ii) violent Strombolian and continuous ash emission eruptions (i.e., small‐scale explosive activity); and (iii) effusive eruptions (including eruptions from both parasitic vents and eruptive fissures). Regional and local structures (i.e., deep faults) are represented as linear feature classes. To support interpretation of the eruption data, additional data sets are provided for Somma‐Vesuvio geological units and caldera morphological features. In the companion paper, the data presented here, and the associated uncertainties, are used to develop a first vent opening probability map for the Somma‐Vesuvio caldera, with specific attention focused on large or medium explosive events.Published4336-43566V. Pericolosità vulcanica e contributi alla stima del rischioJCR Journa

    Non-linear susceptibilities of spherical models

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    The static and dynamic susceptibilities for a general class of mean field random orthogonal spherical spin glass models are studied. We show how the static and dynamical properties of the linear and nonlinear susceptibilities depend on the behaviour of the density of states of the two body interaction matrix in the neighbourhood of the largest eigenvalue. Our results are compared with experimental results and also with those of the droplet theory of spin glasses.Comment: 20 pages, 2 fig

    Timeliness of Clinic Attendance is a good predictor of Virological Response and Resistance to Antiretroviral drugs in HIV-infected patients

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    Ensuring long-term adherence to therapy is essential for the success of HIV treatment. As access to viral load monitoring and genotyping is poor in resource-limited settings, a simple tool to monitor adherence is needed. We assessed the relationship between an indicator based on timeliness of clinic attendance and virological response and HIV drug resistance

    DAAM1 and DAAM2 are co-required for myocardial maturation and sarcomere assembly

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    AbstractWnt ligands regulate heart morphogenesis but the underlying mechanisms remain unclear. Two Formin-related proteins, DAAM1 and 2, were previously found to bind the Wnt effector Disheveled. Here, since DAAM1 and 2 nucleate actin and mediate Wnt-induced cytoskeletal changes, a floxed-allele of Daam1 was used to disrupt its function specifically in the myocardium and investigate Wnt-associated pathways. Homozygous Daam1 conditional knockout (CKO) mice were viable but had misshapen hearts and poor cardiac function. The defects in Daam1 CKO mice were observed by mid-gestation and were associated with a loss of protrusions from cardiomyocytes invading the outflow tract. Further, these mice exhibited noncompaction cardiomyopathy (NCM) and deranged cardiomyocyte polarity. Interestingly, Daam1 CKO mice that were also homozygous for an insertion disrupting Daam2 (DKO) had stronger NCM, severely reduced cardiac function, disrupted sarcomere structure, and increased myocardial proliferation, suggesting that DAAM1 and DAAM2 have redundant functions. While RhoA was unaffected in the hearts of Daam1/2 DKO mice, AKT activity was lower than in controls, raising the issue of whether DAAM1/2 are only mediating Wnt signaling. Daam1-floxed mice were thus bred to Wnt5a null mice to identify genetic interactions. The hearts of Daam1 CKO mice that were also heterozygous for the null allele of Wnt5a had stronger NCM and more severe loss of cardiac function than Daam1 CKO mice, consistent with DAAM1 and Wnt5a acting in a common pathway. However, deleting Daam1 further disrupted Wnt5a homozygous-null hearts, suggesting that DAAM1 also has Wnt5a-independent roles in cardiac development
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