1,146 research outputs found
Probing Shadowed Nuclear Sea with Massive Gauge Bosons in the Future Heavy-Ion Collisions
The production of the massive bosons and could provide an
excellent tool to study cold nuclear matter effects and the modifications of
nuclear parton distribution functions (nPDFs) relative to parton distribution
functions (PDFs) of a free proton in high energy nuclear reactions at the LHC
as well as in heavy-ion collisions (HIC) with much higher center-of mass
energies available in the future colliders. In this paper we calculate the
rapidity and transverse momentum distributions of the vector boson and their
nuclear modification factors in p+Pb collisions at TeV and in
Pb+Pb collisions at TeV in the framework of perturbative QCD
by utilizing three parametrization sets of nPDFs: EPS09, DSSZ and nCTEQ. It is
found that in heavy-ion collisions at such high colliding energies, both the
rapidity distribution and the transverse momentum spectrum of vector bosons are
considerably suppressed in wide kinematic regions with respect to p+p reactions
due to large nuclear shadowing effect. We demonstrate that in the massive
vector boson productions processes with sea quarks in the initial-state may
give more contributions than those with valence quarks in the initial-state,
therefore in future heavy-ion collisions the isospin effect is less pronounced
and the charge asymmetry of W boson will be reduced significantly as compared
to that at the LHC. Large difference between results with nCTEQ and results
with EPS09 and DSSZ is observed in nuclear modifications of both rapidity and
distributions of and in the future HIC.Comment: 13 pages, 21 figures, version accepted for publication in Eur. Phys.
J.
Top-Level Categories of Constitutively Organized Material Entities - Suggestions for a Formal Top-Level Ontology
Application oriented ontologies are important for reliably communicating and managing data in databases. Unfortunately, they often differ in the definitions they use and thus do not live up to their potential. This problem can be reduced when using a standardized and ontologically consistent template for the top-level categories from a top-level formal foundational ontology. This would support ontological consistency within application oriented ontologies and compatibility between them. The Basic Formal Ontology (BFO) is such a foundational ontology for the biomedical domain that has been developed following the single inheritance policy. It provides the top-level template within the Open Biological and Biomedical Ontologies Foundry. If it wants to live up to its expected role, its three top-level categories of material entity (i.e., 'object', 'fiat object part', 'object aggregate') must be exhaustive, i.e. every concrete material entity must instantiate exactly one of them.By systematically evaluating all possible basic configurations of material building blocks we show that BFO's top-level categories of material entity are not exhaustive. We provide examples from biology and everyday life that demonstrate the necessity for two additional categories: 'fiat object part aggregate' and 'object with fiat object part aggregate'. By distinguishing topological coherence, topological adherence, and metric proximity we furthermore provide a differentiation of clusters and groups as two distinct subcategories for each of the three categories of material entity aggregates, resulting in six additional subcategories of material entity.We suggest extending BFO to incorporate two additional categories of material entity as well as two subcategories for each of the three categories of material entity aggregates. With these additions, BFO would exhaustively cover all top-level types of material entity that application oriented ontologies may use as templates. Our result, however, depends on the premise that all material entities are organized according to a constitutive granularity
Upper atmospheres and ionospheres of planets and satellites
The upper atmospheres of the planets and their satellites are more directly
exposed to sunlight and solar wind particles than the surface or the deeper
atmospheric layers. At the altitudes where the associated energy is deposited,
the atmospheres may become ionized and are referred to as ionospheres. The
details of the photon and particle interactions with the upper atmosphere
depend strongly on whether the object has anintrinsic magnetic field that may
channel the precipitating particles into the atmosphere or drive the
atmospheric gas out to space. Important implications of these interactions
include atmospheric loss over diverse timescales, photochemistry and the
formation of aerosols, which affect the evolution, composition and remote
sensing of the planets (satellites). The upper atmosphere connects the planet
(satellite) bulk composition to the near-planet (-satellite) environment.
Understanding the relevant physics and chemistry provides insight to the past
and future conditions of these objects, which is critical for understanding
their evolution. This chapter introduces the basic concepts of upper
atmospheres and ionospheres in our solar system, and discusses aspects of their
neutral and ion composition, wind dynamics and energy budget. This knowledge is
key to putting in context the observations of upper atmospheres and haze on
exoplanets, and to devise a theory that explains exoplanet demographics.Comment: Invited Revie
Impact-parameter dependent nuclear parton distribution functions: EPS09s and EKS98s and their applications in nuclear hard processes
We determine the spatial (impact parameter) dependence of nuclear parton
distribution functions (nPDFs) using the -dependence of the spatially
independent (averaged) global fits EPS09 and EKS98. We work under the
assumption that the spatial dependence can be formulated as a power series of
the nuclear thickness functions . To reproduce the -dependence over the
entire range we need terms up to . As an outcome, we release two
sets, EPS09s (LO, NLO, error sets) and EKS98s, of spatially dependent nPDFs for
public use. We also discuss the implementation of these into the existing
calculations. With our results, the centrality dependence of nuclear
hard-process observables can be studied consistently with the globally fitted
nPDFs for the first time. As an application, we first calculate the LO nuclear
modification factor for primary partonic-jet production in
different centrality classes in Au+Au collisions at RHIC and Pb+Pb collisions
at LHC. Also the corresponding central-to-peripheral ratios are
studied. We also calculate the LO and NLO nuclear modification factors for
single inclusive neutral pion production, , at mid- and
forward rapidities in different centrality classes in d+Au collisions at RHIC.
In particular, we show that our results are compatible with the PHENIX
mid-rapidity data within the overall normalization uncertainties given by the
experiment. Finally, we show our predictions for the corresponding
modifications in the forthcoming p+Pb collisions at LHC.Comment: 36 page
Z' Bosons at Colliders: a Bayesian Viewpoint
We revisit the CDF data on di-muon production to impose constraints on a
large class of Z' bosons occurring in a variety of E_6 GUT based models. We
analyze the dependence of these limits on various factors contributing to the
production cross-section, showing that currently systematic and theoretical
uncertainties play a relatively minor role. Driven by this observation, we
emphasize the use of the Bayesian statistical method, which allows us to
straightforwardly (i) vary the gauge coupling strength, g', of the underlying
U(1)'; (ii) include interference effects with the Z' amplitude (which are
especially important for large g'); (iii) smoothly vary the U(1)' charges; (iv)
combine these data with the electroweak precision constraints as well as with
other observables obtained from colliders such as LEP 2 and the LHC; and (v)
find preferred regions in parameter space once an excess is seen. We adopt this
method as a complementary approach for a couple of sample models and find
limits on the Z' mass, generally differing by only a few percent from the
corresponding CDF ones when we follow their approach. Another general result is
that the interference effects are quite relevant if one aims at discriminating
between models. Finally, the Bayesian approach frees us of any ad hoc
assumptions about the number of events needed to constitute a signal or
exclusion limit for various actual and hypothetical reference energies and
luminosities at the Tevatron and the LHC.Comment: PDFLaTeX, 24 pages, 7 figures. Version with improved tables and
figure
Galactic and Extragalactic Samples of Supernova Remnants: How They Are Identified and What They Tell Us
Supernova remnants (SNRs) arise from the interaction between the ejecta of a
supernova (SN) explosion and the surrounding circumstellar and interstellar
medium. Some SNRs, mostly nearby SNRs, can be studied in great detail. However,
to understand SNRs as a whole, large samples of SNRs must be assembled and
studied. Here, we describe the radio, optical, and X-ray techniques which have
been used to identify and characterize almost 300 Galactic SNRs and more than
1200 extragalactic SNRs. We then discuss which types of SNRs are being found
and which are not. We examine the degree to which the luminosity functions,
surface-brightness distributions and multi-wavelength comparisons of the
samples can be interpreted to determine the class properties of SNRs and
describe efforts to establish the type of SN explosion associated with a SNR.
We conclude that in order to better understand the class properties of SNRs, it
is more important to study (and obtain additional data on) the SNRs in galaxies
with extant samples at multiple wavelength bands than it is to obtain samples
of SNRs in other galaxiesComment: Final 2016 draft of a chapter in "Handbook of Supernovae" edited by
Athem W. Alsabti and Paul Murdin. Final version available at
https://doi.org/10.1007/978-3-319-20794-0_90-
Pregnancy and Maternal Behavior Induce Changes in Glia, Glutamate and Its Metabolism within the Cingulate Cortex
An upregulation of the astrocytic proteins GFAP and bFGF within area 2 of the cingulate cortex (Cg2) occurs within 3 hours of parturition in rats. These changes are the result of an interaction between hormonal state and maternal experience and are associated with increased dendritic spine density in this area. Here, we examined whether this upregulation of astrocytic proteins generalized to other glial markers and, in particular those associated with glutamate metabolism. We chose glial markers commonly used to reflect different aspects of glial function: vimentin, like GFAP, is a marker of intermediate filaments; glutamine synthetase (GS), and S-100beta, are used as markers for mature astrocytes and GS has also been used as a specific marker for glutamatergic enzymatic activity. In addition, we examined levels of proteins associated with glutamine synthetase, glutamate, glutamine and two excitatory amino acid transporters found in astrocytes, glt-1 and glast. S100beta immunoreactivity did not vary with reproductive state in either Cg2 or MPOA suggesting no change in the number of mature astrocytes across these conditions. Vimentin-ir did not differ across groups in Cg2, but expression of this protein decreased from Day 1 postpartum onwards in the MPOA. By contrast, GS-ir was increased within 24 h postpartum in Cg2 but not MPOA and similarly to GFAP and bFGF this upregulation of GS resulted from an interaction between hormonal state and maternal experience. Within Cg2, upregulation of GS was not accompanied by changes in the astrocytic glutamatergic transporters, glt-1 and glast, however, an increase in both glutamate and glutamine proteins were observed within the Cg2 of postpartum animals. Together, these changes suggest postpartum upregulation of glutamatergic activity and metabolism within Cg2 that is stimulated by pregnancy hormones and maternal experience
Novel STAT1 Alleles in Otherwise Healthy Patients with Mycobacterial Disease
The transcription factor signal transducer and activator of transcription-1 (STAT1) plays a key role in immunity against mycobacterial and viral infections. Here, we characterize three human STAT1 germline alleles from otherwise healthy patients with mycobacterial disease. The previously reported L706S, like the novel Q463H and E320Q alleles, are intrinsically deleterious for both interferon gamma (IFNG)–induced gamma-activating factor–mediated immunity and interferon alpha (IFNA)–induced interferon-stimulated genes factor 3–mediated immunity, as shown in STAT1-deficient cells transfected with the corresponding alleles. Their phenotypic effects are however mediated by different molecular mechanisms, L706S affecting STAT1 phosphorylation and Q463H and E320Q affecting STAT1 DNA-binding activity. Heterozygous patients display specifically impaired IFNG-induced gamma-activating factor–mediated immunity, resulting in susceptibility to mycobacteria. Indeed, IFNA-induced interferon-stimulated genes factor 3–mediated immunity is not affected, and these patients are not particularly susceptible to viral disease, unlike patients homozygous for other, equally deleterious STAT1 mutations recessive for both phenotypes. The three STAT1 alleles are therefore dominant for IFNG-mediated antimycobacterial immunity but recessive for IFNA-mediated antiviral immunity at the cellular and clinical levels. These STAT1 alleles define two forms of dominant STAT1 deficiency, depending on whether the mutations impair STAT1 phosphorylation or DNA binding
General practitioners' beliefs about effectiveness and intentions to prescribe smoking cessation medications: qualitative and quantitative studies
BACKGROUND: General practitioners' (GPs) negative beliefs about nicotine dependence medications may act as barriers to prescribing them. METHODS: Study1: Twenty-five GPs from 16 practices across London were interviewed in this qualitative study. Framework analysis was used to identify key themes. Study 2: A convenience sample of 367 GPs completed an internet-based survey. Path-analysis was used to examine the relations between beliefs and intentions to prescribe smoking cessation medications. RESULTS: Study 1: Whilst nicotine replacement therapy (NRT) and bupropion were generally perceived as effective and cost-effective, the effectiveness of NRT was seen as critically dependent on behavioural support for smoking cessation. This dependence appeared to be influenced by perceptions that without support smokers would neglect psychological aspects of smoking and use NRT incorrectly. GPs perceived bupropion as dangerous and were concerned about its side-effects. Study 2: GPs' beliefs had medium (NRT, f(2 )= .23) to large (bupropion, f(2)=.45; NRT without support, f(2)=.59) effects on their intentions to prescribe medications. Beliefs about effectiveness of NRT and bupropion and the perceived danger of bupropion were the key predictors of intentions to prescribe NRT and bupropion, respectively. Beliefs about neglecting psychological aspects of smoking and incorrect use had indirect effects on intentions to prescribe NRT without support, operating via beliefs about effectiveness. CONCLUSION: GPs vary in their beliefs about the effectiveness and safety of smoking cessation medications. Their intentions to prescribe these medications vary in line with these beliefs. Interventions aimed at increasing the likelihood with which GPs prescribe these medications may be more effective if they addressed these beliefs
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