525 research outputs found

    The position of graptolites within Lower Palaeozoic planktic ecosystems.

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    An integrated approach has been used to assess the palaeoecology of graptolites both as a discrete group and also as a part of the biota present within Ordovician and Silurian planktic realms. Study of the functional morphology of graptolites and comparisons with recent ecological analogues demonstrates that graptolites most probably filled a variety of niches as primary consumers, with modes of life related to the colony morphotype. Graptolite coloniality was extremely ordered, lacking any close morphological analogues in Recent faunas. To obtain maximum functional efficiency, graptolites would have needed varying degrees of coordinated automobility. A change in lifestyle related to ontogenetic changes was prevalent within many graptolite groups. Differing lifestyle was reflected by differing reproductive strategies, with synrhabdosomes most likely being a method for rapid asexual reproduction. Direct evidence in the form of graptolithophage 'coprolitic' bodies, as well as indirect evidence in the form of probable defensive adaptations, indicate that graptolites comprised a food item for a variety of predators. Graptolites were also hosts to a variety of parasitic organisms and provided an important nutrient source for scavenging organisms

    Ab-initio calculation of Kerr spectra for semi-infinite systems including multiple reflections and optical interferences

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    Based on Luttinger's formulation the complex optical conductivity tensor is calculated within the framework of the spin-polarized relativistic screened Korringa-Kohn-Rostoker method for layered systems by means of a contour integration technique. For polar geometry and normal incidence ab-initio Kerr spectra of multilayer systems are then obtained by including via a 2x2 matrix technique all multiple reflections between layers and optical interferences in the layers. Applications to Co|Pt5 and Pt3|Co|Pt5 on the top of a semi-infinite fcc-Pt(111) bulk substrate show good qualitative agreement with the experimental spectra, but differ from those obtained by applying the commonly used two-media approach.Comment: 32 pages (LaTeX), 5 figures (Encapsulated PostScript), submitted to Phys. Rev.

    Driving a motor vehicle and psychogenic nonepileptic seizures: ILAE Report by the Task Force on Psychogenic Nonepileptic Seizures

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    Objectives This International League Against Epilepsy (ILAE) Report: (a) summarizes the literature about “driving and psychogenic nonepileptic seizures (PNES)”; (b) presents the views of international experts; and (c) proposes an approach to assessing the ability of persons with PNES (PwPNES) to drive. Methods Phase 1: Systematic literature review. Phase 2: Collection of international expert opinion using SurveyMonkey®. Experts included the members of the ILAE PNES Task Force and individuals with relevant publications since 2000. Phase 3: Joint analysis of the findings and refinement of conclusions by all participants using email. As an ILAE Report, the resulting text was reviewed by the Psychiatry Commission, the ILAE Task Force on Driving Guidelines, and Executive Committee. Results Eight studies identified by the systematic review process failed to provide a firm evidence base for PNES‐related driving regulations, but suggest that most health professionals think restrictions are appropriate. Twenty‐six experts responded to the survey. Most held the view that decisions about driving privileges should consider individual patient and PNES characteristics and take account of whether permits are sought for private or commercial driving. Most felt that those with active PNES should not be allowed to drive unless certain criteria were met and that PNES should be thought of as “active” if the last psychogenic seizure had occurred within 6 months. Significance Recommendations on whether PwPNES can drive should be made at the individual patient level. Until future research has determined the risk of accidents in PwPNES a proposed algorithm may guide decisions about driving advice

    Occultation observations of Saturn's rings with Cassini VIMS

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    We describe the prediction, design, execution and calibration of stellar and solar occultation observations of Saturn's rings by the Visual and Infrared Mapping Spectrometer (VIMS) instrument on the Cassini spacecraft. Particular attention is paid to the technique developed for onboard acquisition of the stellar target and to the geometric and photometric calibration of the data. Examples of both stellar and solar occultation data are presented, highlighting several aspects of the data as well as the different occultation geometries encountered during Cassini's 13-year orbital tour. Complete catalogs of ring stellar and solar occultations observed by Cassini-VIMS are presented, as a guide to the standard data sets which have been delivered to the Planetary Data System's Ring Moon Systems Node (Hedman and Nicholson, 2019b)

    Enhanced Secretion of Amylase from Exocrine Pancreas of Connexin32-deficient Mice

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    To determine whether junctional communication between pancreatic acinar cells contributes to their secretory function in vivo, we have compared wild-type mice, which express the gap junctional proteins connexin32 (Cx32) and connexin26, to mice deficient for the Cx32 gene. Pancreatic acinar cells from Cx32 (−/−) mice failed to express Cx32 as evidenced by reverse transcription–PCR and immunolabeling and showed a marked reduction (4.8- and 25-fold, respectively) in the number and size of gap junctions. Dye transfer studies showed that the extent of intercellular communication was inhibited in Cx32 (−/−) acini. However, electrical coupling was detected by dual patch clamp recording in Cx32 (−/−) acinar cell pairs. Although wild-type and Cx32 (−/−) acini were similarly stimulated to release amylase by carbamylcholine, Cx32 (−/−) acini showed a twofold increase of their basal secretion. This effect was caused by an increase in the proportion of secreting acini, as detected with a reverse hemolytic plaque assay. Blood measurements further revealed that Cx32 (−/−) mice had elevated basal levels of circulating amylase. The results, which demonstrate an inverse relationship between the extent of acinar cell coupling and basal amylase secretion in vivo, support the view that the physiological recruitment of secretory acinar cells is regulated by gap junction mediated intercellular communication

    Influence of aggregate mineralogical composition on water resistance of aggregate–bitumen adhesion

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    The effects of aggregate mineralogical composition on moisture sensitivity of aggregate–bitumen bonds were investigated using four aggregate types (two limestone and two granite) and two bitumen grades (40/60 pen and 70/100 pen). Moisture sensitivity (or water resistance) of the aggregate–bitumen bonds were characterized using retained strength obtained from three different tensile tests (peel, PATTI and pull-off). The results showed significant differences in the amount of moisture absorbed by a given aggregate which suggested strong correlations between aggregate mineral composition and moisture absorption. For most of the aggregate–bitumen bonds, failure surfaces transformed from cohesive to adhesive with conditioning time thereby confirming the strong influence of moisture on aggregate bonds. The three tensile tests used in this study showed similar rankings in terms of moisture sensitivity but the pull-off test was found to be the most sensitive. The effect of bitumen on moisture sensitivity was found to be lower than the effect of aggregates, with the moisture absorption properties of the aggregates depending strongly on certain key minerals including clay, anorthite and calcite. Strong correlations were also found between mineral compositions and moisture sensitivity with clay and anorthite having strong negative influence while calcite showed positive effect on moisture sensitivity. Previous studies have identified various mineral phases like albite, quartz, and k-feldspar, as detrimental in terms of moisture sensitivity. The results appear to support the extension of the existing list of detrimental aggregate minerals to include anorthite and clay while supporting the case of calcite as a moisture resistant mineral

    Analysis of LIGO data for gravitational waves from binary neutron stars

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    We report on a search for gravitational waves from coalescing compact binary systems in the Milky Way and the Magellanic Clouds. The analysis uses data taken by two of the three LIGO interferometers during the first LIGO science run and illustrates a method of setting upper limits on inspiral event rates using interferometer data. The analysis pipeline is described with particular attention to data selection and coincidence between the two interferometers. We establish an observational upper limit of R<\mathcal{R}<1.7 \times 10^{2}peryearperMilkyWayEquivalentGalaxy(MWEG),with90coalescencerateofbinarysystemsinwhicheachcomponenthasamassintherange13 per year per Milky Way Equivalent Galaxy (MWEG), with 90% confidence, on the coalescence rate of binary systems in which each component has a mass in the range 1--3 M_\odot$.Comment: 17 pages, 9 figure

    Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

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    This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

    Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

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    The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

    Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

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    We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters
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