18,709 research outputs found

    Elastic Form Factors of 3,4^{3,4}He up to Large Q2Q^2

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    Elastic electron scattering off 3^3He and 4^4He has recently been studied at forward and backward scattering angles in Hall A at JLab. The results will provide accurate data on the elastic form factors, charge and magnetic for 3^3He and charge only for 4^4He, up to squared momentum transfer Q2Q^2-values of 3.2 GeV2^2.Comment: 3 pages, Proceedings of EFB2

    Proposed method for searches of gravitational waves from PKS 2155-304 and other blazar flares

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    We propose to search for gravitational waves from PKS 2155-304 as well as other blazars. PKS 2155-304 emitted a long duration energetic flare in July 2006, with total isotropic equivalent energy released in TeV gamma rays of approximately 104510^{45} ergs. Any possible gravitational wave signals associated with this outburst should be seen by gravitational wave detectors at the same time as the electromagnetic signal. During this flare, the two LIGO interferometers at Hanford and the GEO detector were in operation and collecting data. For this search we will use the data from multiple gravitational wave detectors. The method we use for this purpose is a coherent network analysis algorithm and is called {\tt RIDGE}. To estimate the sensitivity of the search, we perform numerical simulations. The sensitivity to estimated gravitational wave energy at the source is about 2.5×10552.5 \times 10^{55} ergs for a detection probability of 20%. For this search, an end-to-end analysis pipeline has been developed, which takes into account the motion of the source across the sky.Comment: 10 pages, 7 figures. Contribution to 12th Gravitational Wave Data Analysis Workshop. Submitted to Classical and Quantum Gravity. Changes in response to referee comment

    Evaluation of Mechanisms of Alteration and Humification of PAHs for Water Quality Management

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    Introduction: Creosote-pentachlorophenol (PCP) is a mixture commonly used as a wood preservative in the U.S. (1). A 1988 survey (2) indicated that 1,397 wood preserving waste contaminated sites exist in the United States consisting of 555 active wood treatment plants and 842 inactive plants. Stinson (3) indentifed 58 wood preserving sites on the National Priorities List, of which 51 have PCP and/or creosote or polycyclic aromatic hydrocarbon (PAH) contamination. Principal classes of organic constituents present in creosote waste are PAHs (~85% by weight) and phenolics. PAHs with less than three fused benzene rings comprise 69% (i.e., naphthalene, anthracene and phenanthrene); PAHs with more than three rings, such as pyrne, benzo(a)pyrene, and benz(a)anthracene, dibenz(a,h)anthracene, and indeno(1,2,3-c,d)pyrene comprise 16% by weight of creosote. Phenolics comprise 2% to 17% of creosote. Nitrogen- and sulfur- containing heterocyclic compounds may comprise up to 13% of creosote by weight. Creosote and creosote components including phenol and several PAHs have been reported to be mutagenic, teratogenic, fetotoxic and/or toxic (4,5) and have been designated as hazardous wastes under the Resource Conservation and Recovery Act of 1976 (6) and as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980. PCP is often added to creosote to enhace the wood preservation potential due to its bactericidal and fungicidal properties. PCP is also toxic to lower and higher plants (algicide, herbicide), to invertegrate and vertebrate animals (insecticide, molluscicide), and to man. Toxicity of PCP and potentical for uptake by organisms are pH-dependent, since PCP is a weak acid with a Ka of about 10^-5. Both bioaccumulation and toxicity increase as pH decreases due to the greated penetration of cell membranes by non-ionized PCP molecules than by pentachlorophenate ions (1). Therefore PCP may inhibit microbial degradation of other compounds in creosote-PCP waste, including oil and grease. Contaminated vadose zone soil systems generally consist of four phases: 1)aqueous; 2) gas; 3) oil (commonly referred to as non-aqueous phase liquid, or NAPL); and 4)solid, which has two components, and inorganic mineral compartment and an organic matter compartment (organic carbon-humic substances). Interphase tranfer potential for waste constituents among oil (waste or NAPL), water, air, and solid (organic and inorganic) phase of a soil system is affected by the relative affinity of the waste constituents for each phase. Measurement of waste constitutents in all four phases is generally not done in treatability studies, especially in complex environmental samples (7). High molecular weight (greater than 3 rings) PAHs are hydrophobic and essentially not mobile dur to their low volatilities and water solubilities. Bulman et al. (8) and Keck et al. (9) observed that sorption of B(a)P to soil was the dominant mechanism of loss. Studies have shown that immobilization of some xenobiotics can be accomplished by incorporation into soil humus, or sorption into the clay lattice of soil (10). Humification and sorption have not been extensively evaluated for PAHs in creosote contaminated soil. PCP is, in general, more mobile in high pH soils than in acidic soils. At low pH, PCP exists as a free acid (non-ionized) and readily adsorbs to soil particles. At high pH, PCP exists in the ionized form (pKa = 4.7) as the negatively charged pentachlorophenate anion, and is more mobile. In a study by Choi and Aomine (11), apparent adsorption of PCP was greatest in strongly acid soil and in soils with high organic matter content. Apparent adsoprtion was shown to include both the mechanisms of adsorption on soil colloids and precipitation in the soil micelle and in the external liquid phase, depending on the soil pH. Pionteck (12) also observed that although soil organic matter is important in determining the extent of odsorption of PCP, an even more important soil property is pH. Adsorption of PCP was shown to be reversible. Therefore, PCP may not be permanently immobilized in the soil phase, but may be slowly released into and move through the soil (1). A wide range of soil organisms, including bacteria, fungi, cyanobacteria and eukaryotic algae, have been shown to have the enzymatic capacity to oxidize PAHs. Metabolites from the degradation of large PAHs identified in these studies are responsible for toxic, mutagenic, and/or carcinogenic responses in animal species and many indicate epoxide intermediates (13-20). Presense of PCP may inhibit microbial degradation of other organics, including PAHs, oil and grease, etc. Despite a high degree of chlorination, PCP has been shown to be degraded in soil. Microbial deconposition appears to be the primary detoxification mechanism. Success was the highest in those studies that used acclimated or inoculated (with acclimated species) systems. The ability to degrade PCP may not be uniform among microorganisms, and adaptation of microbial populations to PCP and control of pH may play important roles in its degradation (1). Laboratory studies (7, 12) of the biodegradation potential of creosote wood preservative waste have shown that hazardous parent components were degraded, transformed, or immobilized in certain soil systems. In a study by Aprill et al. (21) on the biodegradation potential of creosote, the apparent degradation of four non-carcinogenic PAHs and four carcinogenic PAHs ranged from 54% to 90% and 24% to 53% of mass added, respectively. Aprill et al. (21) defined apparent degradation as the measurement of changes in concentrations of specific constituents in solvent extracts of soil samples with time of incubation. The reduction in concentration of the higher molecular weight PAHs was correlated with oil and grease content of the waste. Degradation of a chemical in soil may not result in the complete mineralization of a hazardous waste, but may render waste constituents less harzardous or nonhazardous through transformations (1,7,21). However in some cases detoxification does not occur (22). Studies (23-30_ conducted with 14C labeled compounds often report collection of the radiolabelled carbon in carbon dioxide trapping solutions to indicate degradation or mineralization. However, collection of the radiolabelled carbon in a carbon dioxide trapping solution may be misleading in two ways, i.e., 1) liberation of CO2 may not be concurrent with complete degradation of the total mass present because of accumulation of metabolites in the soil (31), or 2) measurement of radiolabelled carbon may not indicate mineralization if colatilized parent compound or labeled metabolites are collected in the trapping solution in addition to 14C2 (32, 33). Torstensson and Stenstrom (31) recommend that the rate of decomposition of a substance should be defined by direct measurement of its disappearance. However, direct measurement of the disappearance of hydrophobic organics from soil systems cannot be defined as degration because of other loss mechanisms including volatilization or soption to soil solids. Sorbed organics that cannot be removed from soil by organic solvents cannot be easily identified or analyzed. There is a current lack of knowledge concering the behavior of PAHs in complex environmental vadose zone soil samples. This study was undertaken, using a chemical mass balance appreaoch, to determine the distribution of radiolabelled carbon, parent compounds, and transformation products of the radiolabelled PAH compounds, benzo(a)pyrene (B(a)P) and pyrene, among aqueous, gas, and solid phases of a non-contaminated and contaminated (creosote-PCP) vadose zone soil over time of incubation. The apparent degradation of unlabeled PAHs and changes in the toxicity of the water-soluble (aqueous) fraction were also measured

    Search for continuous gravitational waves from 20 accreting millisecond x-ray pulsars in O3 LIGO data

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    Results are presented of searches for continuous gravitational waves from 20 accreting millisecond x-ray pulsars with accurately measured spin frequencies and orbital parameters, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. The search algorithm uses a hidden Markov model, where the transition probabilities allow the frequency to wander according to an unbiased random walk, while the J-statistic maximum-likelihood matched filter tracks the binary orbital phase. Three narrow subbands are searched for each target, centered on harmonics of the measured spin frequency. The search yields 16 candidates, consistent with a false alarm probability of 30% per subband and target searched. These candidates, along with one candidate from an additional target-of-opportunity search done for SAX J1808.4 - 3658, which was in outburst during one month of the observing run, cannot be confidently associated with a known noise source. Additional follow-up does not provide convincing evidence that any are a true astrophysical signal. When all candidates are assumed nonastrophysical, upper limits are set on the maximum wave strain detectable at 95% confidence, h(0)(95%). The strictest constraint is h(0)(95%) = 4.7 x 10(-26) from IGR J17062 - 6143. Constraints on the detectable wave strain from each target lead to constraints on neutron star ellipticity and r-mode amplitude, the strictest of which are epsilon(95%) = 3.1 x 10(-7) and alpha(95%) = 1.8 x 10(-5) respectively. This analysis is the most comprehensive and sensitive search of continuous gravitational waves from accreting millisecond x-ray pulsars to date

    Action learning and healthcare: affinities and challenges

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    Action learning has been used in healthcare settings to bring about changes to how services are delivered, to help individuals to develop their knowledge and skills, including leadership development, and to enable the development of collective abilities and communities of practice. It is evident that there are some positive elements in the healthcare environment that support the processes of action learning – what we might call affinities between the environment and these processes. However, those who have practised action learning in these environments also know that difficulties and disablers can arise, to derail or block the processes – what we might, perhaps optimistically, call challenges

    Search for Gravitational-wave Signals Associated with Gamma-Ray Bursts during the Second Observing Run of Advanced LIGO and Advanced Virgo

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    We present the results of targeted searches for gravitational-wave transients associated with gamma-ray bursts during the second observing run of Advanced LIGO and Advanced Virgo, which took place from 2016 November to 2017 August. We have analyzed 98 gamma-ray bursts using an unmodeled search method that searches for generic transient gravitational waves and 42 with a modeled search method that targets compact-binary mergers as progenitors of short gamma-ray bursts. Both methods clearly detect the previously reported binary merger signal GW170817, with p-values of <9.38 × 10−6 (modeled) and 3.1 × 10−4 (unmodeled). We do not find any significant evidence for gravitational-wave signals associated with the other gamma-ray bursts analyzed, and therefore we report lower bounds on the distance to each of these, assuming various source types and signal morphologies. Using our final modeled search results, short gamma-ray burst observations, and assuming binary neutron star progenitors, we place bounds on the rate of short gamma-ray bursts as a function of redshift for z ≤ 1. We estimate 0.07–1.80 joint detections with Fermi-GBM per year for the 2019–20 LIGO-Virgo observing run and 0.15–3.90 per year when current gravitational-wave detectors are operating at their design sensitivities

    The Prediction of Mass of Z'-Boson from bq0−bq0barb_q^0-b_q^0 bar Mixing

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    B_q^0-B_^0 bar mixing offers a profound probe into the effects of new physics beyond the Standard Model. In this paper, Bs0−Bs0barB_s^0-B_s^0 bar and Bd0−Bd0barB_d^0-B_d^0 bar mass differences are considered taking the effect of both Z-and Z' -mediated flavour-changing neutral currents in the Bq0−Bq0barB_q^0-B_q^0 bar mixing (q = d, s). Our estimated mass of Z' boson is accessible at the experiments LHC and B-factories in near future.Comment: 11 pages, 02 Figure

    First Search for Nontensorial Gravitational Waves from Known Pulsars

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    We present results from the first directed search for nontensorial gravitational waves. While general relativity allows for tensorial (plus and cross) modes only, a generic metric theory may, in principle, predict waves with up to six different polarizations. This analysis is sensitive to continuous signals of scalar, vector, or tensor polarizations, and does not rely on any specific theory of gravity. After searching data from the first observation run of the advanced LIGO detectors for signals at twice the rotational frequency of 200 known pulsars, we find no evidence of gravitational waves of any polarization. We report the first upper limits for scalar and vector strains, finding values comparable in magnitude to previously published limits for tensor strain. Our results may be translated into constraints on specific alternative theories of gravity
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