343 research outputs found
Effects of acceleration on the collision of particles in the rotating black hole spacetime
We study the collision of two geodesic particles in the accelerating and
rotating black hole spacetime and probe the effects of the acceleration of
black hole on the center-of-mass energy of the colliding particles and on the
high-velocity collision belts. We find that the dependence of the
center-of-mass energy on the acceleration in the near event-horizon collision
is different from that in the near acceleration-horizon case. Moreover, the
presence of the acceleration changes the shape and position of the
high-velocity collision belts. Our results show that the acceleration of black
holes brings richer physics for the collision of particles.Comment: 7 pages, 2 figures, The corrected version accepted for publication in
EPJ
A novel determination of the local dark matter density
We present a novel study on the problem of constructing mass models for the
Milky Way, concentrating on features regarding the dark matter halo component.
We have considered a variegated sample of dynamical observables for the Galaxy,
including several results which have appeared recently, and studied a 7- or
8-dimensional parameter space - defining the Galaxy model - by implementing a
Bayesian approach to the parameter estimation based on a Markov Chain Monte
Carlo method. The main result of this analysis is a novel determination of the
local dark matter halo density which, assuming spherical symmetry and either an
Einasto or an NFW density profile is found to be around 0.39 GeV cm with
a 1- error bar of about 7%; more precisely we find a for the Einasto profile and for the NFW. This is in contrast to the
standard assumption that is about 0.3 GeV cm with an
uncertainty of a factor of 2 to 3. A very precise determination of the local
halo density is very important for interpreting direct dark matter detection
experiments. Indeed the results we produced, together with the recent accurate
determination of the local circular velocity, should be very useful to
considerably narrow astrophysical uncertainties on direct dark matter
detection.Comment: 31 pages,11 figures; minor changes in the text; two figures adde
PPPC 4 DM ID: A Poor Particle Physicist Cookbook for Dark Matter Indirect Detection
We provide ingredients and recipes for computing signals of TeV-scale Dark
Matter annihilations and decays in the Galaxy and beyond. For each DM channel,
we present the energy spectra of electrons and positrons, antiprotons,
antideuterons, gamma rays, neutrinos and antineutrinos e, mu, tau at
production, computed by high-statistics simulations. We estimate the Monte
Carlo uncertainty by comparing the results yielded by the Pythia and Herwig
event generators. We then provide the propagation functions for charged
particles in the Galaxy, for several DM distribution profiles and sets of
propagation parameters. Propagation of electrons and positrons is performed
with an improved semi-analytic method that takes into account
position-dependent energy losses in the Milky Way. Using such propagation
functions, we compute the energy spectra of electrons and positrons,
antiprotons and antideuterons at the location of the Earth. We then present the
gamma ray fluxes, both from prompt emission and from Inverse Compton scattering
in the galactic halo. Finally, we provide the spectra of extragalactic gamma
rays. All results are available in numerical form and ready to be consumed.Comment: 57 pages with many figures and tables. v4: updated to include a 125
higgs boson, computation and discussion of extragalactic spectra corrected,
some other typos fixed; all these corrections and updates are reflected on
the numerical ingredients available at
http://www.marcocirelli.net/PPPC4DMID.html they correspond to Release 2.
Measuring Black Hole Spin using X-ray Reflection Spectroscopy
I review the current status of X-ray reflection (a.k.a. broad iron line)
based black hole spin measurements. This is a powerful technique that allows us
to measure robust black hole spins across the mass range, from the stellar-mass
black holes in X-ray binaries to the supermassive black holes in active
galactic nuclei. After describing the basic assumptions of this approach, I lay
out the detailed methodology focusing on "best practices" that have been found
necessary to obtain robust results. Reflecting my own biases, this review is
slanted towards a discussion of supermassive black hole (SMBH) spin in active
galactic nuclei (AGN). Pulling together all of the available XMM-Newton and
Suzaku results from the literature that satisfy objective quality control
criteria, it is clear that a large fraction of SMBHs are rapidly-spinning,
although there are tentative hints of a more slowly spinning population at high
(M>5*10^7Msun) and low (M<2*10^6Msun) mass. I also engage in a brief review of
the spins of stellar-mass black holes in X-ray binaries. In general,
reflection-based and continuum-fitting based spin measures are in agreement,
although there remain two objects (GROJ1655-40 and 4U1543-475) for which that
is not true. I end this review by discussing the exciting frontier of
relativistic reverberation, particularly the discovery of broad iron line
reverberation in XMM-Newton data for the Seyfert galaxies NGC4151, NGC7314 and
MCG-5-23-16. As well as confirming the basic paradigm of relativistic disk
reflection, this detection of reverberation demonstrates that future large-area
X-ray observatories such as LOFT will make tremendous progress in studies of
strong gravity using relativistic reverberation in AGN.Comment: 19 pages. To appear in proceedings of the ISSI-Bern workshop on "The
Physics of Accretion onto Black Holes" (8-12 Oct 2012). Revised version adds
a missing source to Table 1 and Fig.6 (IRAS13224-3809) and corrects the
referencing of the discovery of soft lags in 1H0707-495 (which were in fact
first reported in Fabian et al. 2009
<i>Pseudomonas aeruginosa</i> intensive care unit outbreak:winnowing of transmissions with molecular and genomic typing
Bioinformatics and computational biology analyses were supported by the University of St Andrews Bioinformatics Unit which is funded by a Wellcome Trust ISSF award [grant 097831/Z/11/Z]. BJP, KO, MP, MTGH, GP and SHG are funded by the Chief Scientist Office through the Scottish Infection Research Network, a part of the SHAIPI consortium grant reference number SIRN/10.Background: Pseudomonas aeruginosa healthcare outbreaks can be time consuming and difficult to investigate. Guidance does not specify which typing technique is most practical to base decisions on. Aim: We explore the usefulness of whole genome sequencing (WGS) in the investigation of a Pseudomonas aeruginosa outbreak describing how it compares with pulsed-field gel electrophoresis (PFGE) and variable number tandem repeat (VNTR) analysis. Methods: Six patient isolates and six environmental samples from an Intensive Care Unit (ICU) positive for P. aeruginosa over two years underwent VNTR, PFGE and WGS. Findings: VNTR and PFGE were required to fully determine the potential source of infection and rule out others. WGS results unambiguously distinguished linked isolates giving greater assurance of the transmission route between wash hand basin (WHB) water and two patients supporting control measures employed. Conclusion: WGS provided detailed information without need for further typing. When allied to epidemiological information it can be used to understand outbreak situations rapidly and with certainty. Implementation of WGS in real-time would be a major advance in day-to-day practice. It could become a standard of care as it becomes more widespread due to its reproducibility and reduction in costs.Publisher PDFPeer reviewe
Effect of liraglutide on cardiovascular outcomes in elderly patients: A post hoc analysis of a randomized controlled trial
Background: Comorbidities and complications associ-ated with type 2 diabetes mellitus (T2DM) increase with age, making treatment of elderly persons with this condition chal-lenging. Clinical data on the effect of antihyperglycemic treat-ment on cardiovascular (CV) events in elderly persons are limited (1). The U.S. Food and Drug Administration and Euro-pean Medicines Agency recommend collecting comprehen-sive data on elderly patients with diabetes, particularly those aged 75 years or older, to inform appropriate treatment of this growing populatio
Supporting knowledge transfer in web-based managed IT support
Purpose – The purpose of this paper is to highlight the importance and complexities of the knowledge transfer process in the provision of effective managed after-sales IT support, when the web is used for service delivery.Design/methodology/approach – The paper features an interpretive case study of a multinational Managed Service Provider (MSP) and a focus group of representatives from five comparable MSPs.Findings – The paper finds that MSPs that use web-based channels for the provision of after-sales IT support services need to address a range of important social and organisational issues in order to realise cost and efficiency-based benefits.Research limitations/implications – The paper provides a four stage processual model of knowledge transfer in the provision of web-based managed after-sales IT support services. The barriers and enablers of knowledge transfer at each stage are identified. The paper adopts a MSP perspective and suggests that further research from the customer perspective is required.Practical implications – The paper highlights some important social and organisational enablers and barriers, which will guide MSPs when providing managed after-sales IT support using webbased channels.Originality/value – The paper provides the first staged model of inter-organisational knowledge transfer in a complex multi-organisational and multi-channel web-based context.<br /
Presence of Epstein-Barr virus latency type III at the single cell level in post- transplantation lymphoproliferative disorders and AIDS related lymphomas
AIMS: To investigate the expression pattern of Epstein-Barr virus (EBV) latent genes at the single cell level in post-transplantation lymphoproliferative disorders and acquired immunodefiency syndrome (AIDS) related lymphomas, in relation to cellular morphology. METHODS: Nine post-transplantation lymphoproliferative disorders and three AIDS related lymphomas were subjected to immunohistochemistry using monoclonal antibodies specific for EBV nuclear antigen 1 (EBNA1) (2H4), EBNA2 (PE2 and the new rat anti-EBNA2 monoclonal antibodies 1E6, R3, and 3E9), and LMP1 (CS1-4 and S12). Double staining was performed combining R3 or 3E9 with S12. RESULTS: R3 and 3E9 anti-EBNA2 monoclonal antibodies were more sensitive than PE2, enabling the detection of more EBNA2 positive lymphoma cells. Both in post-transplantation lymphoproliferative disorders and AIDS related lymphomas, different expression patterns were detected at the single cell level. Smaller neoplastic cells were positive for EBNA2 but negative for LMP1. Larger and more blastic neoplastic cells, sometimes resembling Reed-Sternberg cells, were LMP1 positive but EBNA2 negative (EBV latency type II). Morphologically intermediate neoplastic cells coexpressing EBNA2 and LMP1 (EBV latency type III), were detected using R3 and 3E9, and formed a considerable part of the neoplastic population in four of nine post-transplantation lymphoproliferative disorders and two of three AIDS related lymphomas. All samples contained a subpopulation of small tumour cells positive exclusively for Epstein-Barr early RNA and EBNA1. The relation between cellular morphology and EBV expression patterns in this study was less pronounced in AIDS related lymphomas than in post-transplantation lymphoproliferative disorders, because the AIDS related lymphomas were less polymorphic than the post-transplantation lymphoproliferative disorders. CONCLUSIONS: In post-transplantation lymphoproliferative disorders and AIDS related lymphomas, EBV latency type III can be detected by immunohistochemistry in a subpopulation of tumour cells using sensitive monoclonal antibodies R3 and 3E9. Our data suggest that EBV infected tumour cells in these lymphomas undergo gradual changes in the expression of EBV latent genes, and that these changes are associated with changes in cellular morphology
Genome-wide Association Study of Platelet Count Identifies Ancestry-Specific Loci in Hispanic/Latino Americans
Platelets play an essential role in hemostasis and thrombosis. We performed a genome-wide association study of platelet count in 12,491 participants of the Hispanic Community Health Study/Study of Latinos by using a mixed-model method that accounts for admixture and family relationships. We discovered and replicated associations with five genes (ACTN1, ETV7, GABBR1-MOG, MEF2C, and ZBTB9-BAK1). Our strongest association was with Amerindian-specific variant rs117672662 (p value = 1.16 × 10−28) in ACTN1, a gene implicated in congenital macrothrombocytopenia. rs117672662 exhibited allelic differences in transcriptional activity and protein binding in hematopoietic cells. Our results underscore the value of diverse populations to extend insights into the allelic architecture of complex traits
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