3,273 research outputs found

    The emission line near 1319 A in solar and stellar spectra

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    An emission line near 1319 A is one of the strongest unidentified lines in the ultraviolet spectra of cool dwarf stars. In most line lists it is identified as a transition in N I, although its intensity would then be anomalous and the observed wavelength does not fit precisely that expected for N I. The line is also observed in cool giant stars. The measured wavelength of the line in stellar spectra is 1318.94 (+,- 0.01) A. Observations of giant stars provide further evidence that this line is not due to N I. It is proposed that this line is a decay from a previously unknown level in S I, which lies above the first ionization limit. This is identified with the 3d singlet D (odd parity) term. The previous tentative assignment of this term to the S I line at 1309.3 A then needs to be revised. The 1309.3 A line has been identified here for the first time in an astrophysical source. The singlet D (odd parity) level could, in principle, be populated by collisions from nearby autoionizing levels that have large number-densities, through population by di-electronic capture. Spin-orbit interaction with the autoionizing triplet D (odd parity) term might also lead to di-electronic capture into the singlet D (odd parity) level. A line at 1309.87 A observed in cool giant stars is identified as a transition in P II, pumped by the O I resonance lines.Comment: 9 pages, 3 figures, to be published in Monthly Notices of the Royal Astronomical Societ

    Ram Opportunity

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    RAM Opportunity is a self-sustaining mentoring and experiential learning program designed to serve high school students in the local community through programs led by graduate student mentors. RAM Opportunity operates using a plug-and-play structure that can be implemented in the arts, business, education, humanities, sciences, or any other discipline. Partnerships will be formed with local high schools and their guidance counseling services to develop a pipeline for potential students to participate in the program. The program benefits VCU by enhancing engagement with the local community, generating interest in high school students pursuing post-secondary education at VCU, and developing graduate students by providing professional development funding and real-world teaching and mentoring experience

    Uncertainties in atmospheric chemistry modelling due to convection parameterisations and subsequent scavenging

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    Moist convection in global modelling contributes significantly to the transport of energy, momentum, water and trace gases and aerosols within the troposphere. Since convective clouds are on a scale too small to be resolved in a global model their effects have to be parameterised. However, the whole process of moist convection and especially its parameterisations are associated with uncertainties. In contrast to previous studies on the impact of convection on trace gases, which had commonly neglected the convective transport for some or all compounds, we investigate this issue by examining simulations with five different convection schemes. This permits an uncertainty analysis due to the process formulation, without the inconsistencies inherent in entirely neglecting deep convection or convective tracer transport for one or more tracers. <br><br> Both the simulated mass fluxes and tracer distributions are analysed. Investigating the distributions of compounds with different characteristics, e.g., lifetime, chemical reactivity, solubility and source distributions, some differences can be attributed directly to the transport of these compounds, whereas others are more related to indirect effects, such as the transport of precursors, chemical reactivity in certain regions, and sink processes. <br><br> The model simulation data are compared with the average regional profiles of several measurement campaigns, and in detail with two campaigns in fall and winter 2005 in Suriname and Australia, respectively. <br><br> The shorter-lived a compound is, the larger the differences and consequently the uncertainty due to the convection parameterisation are, as long as it is not completely controlled by local production that is independent of convection and its impacts (e.g. water vapour changes). Whereas for long-lived compounds like CO or O<sub>3</sub> the mean differences between the simulations are less than 25%), differences for short-lived compounds reach up to ±100% with different convection schemes. <br><br> A rating of an overall "best" performing scheme is difficult, since the optimal performance depends on the region and compound

    a A convergent and modular synthesis of dienyl and diynyl isobutylamide natural products from echinacea and spilanthes herbal medicines

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    ""Echinacea" and "Spilanthes" are popular over-the-counter herbal supplements derived from raw tissue or tissue extracts from plants such as Echinacea purpurea and Spilanthes acmella, respectively. Several chemical constituents have been identified as possible candidates for these plants' supposed medicinal activities, and include the "alkylamides," of which dienyl and diynyl analogs are prominent members. Isolation of these compounds from the plants is often difficult and results in poor yields. The goal of our research was to develop an encompassing synthesis scheme for dienyl and diynyl alkylamides (Figure 1) addressing consistent functional groups, using a Wittig reaction, a Horner-Wadsworth-Emmons reaction and a Sonogashira reaction. The total syntheses for these compounds are not novel, but have been known to be rather lengthy procedures. We are pleased to offer a novel synthesis that can synthesize a derivative of Spilanthol which involves only three reactions and well developed method for the diynyl structures using the Sonogashira coupling reaction."--Abstract from author supplied metadata

    The nondual level: the cosmopolitan imagination of liquid modernity as visual midrash.

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    This thesis is an exploration of the cosmopolitan imagination in liquid modernity. The artworks are responses to text, memory and images as a form of visual midrash. These visual responses are not hierarchal, but rather part of an infinite relationship of Everything and Nothingness

    Knowledge, Capabilities and Human Capital Formation in Economic Growth

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    This monograph, which has been prepared as a Research Report to the New Zealand (New Zealand) Treasury, undertakes three main tasks: (1) describing the various forms of tangible and intangible human capital, their relationship to "capabilities" affecting human well-being, and the channels through which they may contribute to economic growth; (2) reviewing the major theoretical and empirical findings on the microeconomic determinants, and macroeconomic growth effects of investment in human capital; (3) reviewing salient general implications for policies affecting human capital, and indicating measures specifically germane to the situation of the New Zealand economy. For these purposes, the concept of human capital is defined comprehensively, so that it embraces capacities for interpreting flows of sensory data and structured information required for goal-directed individual actions and inter-personal transactions, and for providing various physical labour service- inputs in ordinary production processes. More conventionally, it subsumes the creative faculties for generating new scientific and technological knowledge, the cognitive basis of entrepreneurship, and the competences for managing market and non-market production as well as household consumption activities. The report is organised in three main Parts that address the three major objectives, taking each in its turn. A detailed Table of Contents and an Executive Summary precede the text, which is followed by extensive bibliographic references. A unifying conceptual framework is developed to (a) identify the micro-level processes involved in human capital formation; (b) implicitly aggregate the resulting qualities and capabilities of individuals belonging to successive population cohorts; (c) trace the interrelated influences that the forms of human capital have upon macroeconomic performance. The review of empirical evidence at the macroeconomic level features a discussion of the deficiencies of data and methods in many of the international cross-section studies, and contrasts recent econometric findings on the role of education in economic growth among the developed economies with the conclusions derived through more detailed analyses of their historical experiences. Significant policy implications do emerge from the modern macroeconomic growth literature, but these are very broad in nature and not particularly germane to the situation of small, open economies that may lack a substantial industrial base or the extensive human and institutional infrastructure required to generate the knowledge-base needed for their peoples' well-being and their firms' competitive success in international markets. Nor does the received literature adequately treat the implications of such economies' potential to rapidly alter their respective human resource endowments through differential population migration. Consideration of human capital policies geared more closely to the specific challenges and opportunities facing New Zealand's economy leads to the formulation of a number of novel proposals. These would reform tax treatment of education and training investments by residents and immigrants alike; subsidise new voluntary institutions developing on-the-job training programs under industry sponsorship; undertake public information infrastructure investments in order to reduce the costs of effective access to global knowledge bases in science and technology. Proposals also are considered for integrated government programmes to accelerate the closing of persistent socio-economic disparities within New Zealand society, such as those between Maori and non-Maori.human capital; capabilities; knowledge; education; on-the-job training; R&D; productivity; macroeconomic growth theory; investment taxation and subsidies

    Search for new phenomena with the monojet and missing transverse momentum signature using the ATLAS detector in √s = 7 TeV proton-proton collisions

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    A search for new phenomena in events featuring a high energy jet and large missing transverse momentum in proton–proton collisions at √s = 7 TeV is presented using a dataset corresponding to an integrated luminosity of 33 pb−1 recorded with the ATLAS detector at the Large Hadron Collider. The number of observed events is consistent with the Standard Model prediction. This result is interpreted in terms of limits on a model of Large Extra Dimensions.Facultad de Ciencias Exacta

    Measurements of underlying-event properties using neutral and charged particles in pp collisions at √s = 900 GeV and √s = 7 TeV with the ATLAS detector at the LHC

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    We present first measurements of charged and neutral particle-flow correlations in pp collisions using the ATLAS calorimeters. Data were collected in 2009 and 2010 at centre-of-mass energies of 900 GeV and 7 TeV. Events were selected using a minimum-bias trigger which required a charged particle in scintillation counters on either side of the interaction point. Particle flows, sensitive to the underlying event, are measured using clusters of energy in the ATLAS calorimeters, taking advantage of their fine granularity. No Monte Carlo generator used in this analysis can accurately describe the measurements. The results are independent of those based on charged particles measured by the ATLAS tracking systems and can be used to constrain the parameters of Monte Carlo generators.Facultad de Ciencias Exacta

    A measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at √s = 7 TeV with ATLAS

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    The ratio of production cross sections of the W and Z bosons with exactly one associated jet is presented as a function of jet transverse momentum threshold. The measurement has been designed to maximise cancellation of experimental and theoretical uncertainties, and is reported both within a particle-level kinematic range corresponding to the detector acceptance and as a total cross-section ratio. Results are obtained with the ATLAS detector at the LHC in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of 33 pb−1. The results are compared with perturbative leading-order, leading-log, and next-to-leading-order QCD predictions, and are found to agree within experimental and theoretical uncertainties. The ratio is measured for events with a single jet with pT > 30 GeV to be 8.73 ± 0.30(stat) ± 0.40(syst) in the electron channel, and 8.49 ± 0.23(stat) ± 0.33(syst) in the muon channel.Facultad de Ciencias Exacta

    Measurements of the electron and muon inclusive cross-sections in proton–proton collisions at √s = 7 TeV with the ATLAS detector

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    This Letter presents measurements of the differential cross-sections for inclusive electron and muon production in proton–proton collisions at a centre-of-mass energy of √s = 7 TeV, using data collected by the ATLAS detector at the LHC. The muon cross-section is measured as a function of pT in the range 4 < pT < 100 GeV and within pseudorapidity |η| < 2.5. In addition the electron and muon cross-sections are measured in the range 7 < pT < 26 GeV and within |η| < 2.0, excluding 1.37 < |η| < 1.52. Integrated luminosities of 1.3 pb−1 and 1.4 pb−1 are used for the electron and muon measurements, respectively. After subtraction of the W /Z/γ ∗ contribution, the differential cross-sections are found to be in good agreement with theoretical predictions for heavy-flavour production obtained from Fixed Order NLO calculations with NLL high-pT resummation, and to be sensitive to the effects of NLL resummation.Facultad de Ciencias Exacta
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