67 research outputs found

    Hopping conduction in strong electric fields: Negative differential conductivity

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    Effects of strong electric fields on hopping conductivity are studied theoretically. Monte-Carlo computer simulations show that the analytical theory of Nguyen and Shklovskii [Solid State Commun. 38, 99 (1981)] provides an accurate description of hopping transport in the limit of very high electric fields and low concentrations of charge carriers as compared to the concentration of localization sites and also at the relative concentration of carriers equal to 0.5. At intermediate concentrations of carriers between 0.1 and 0.5 computer simulations evidence essential deviations from the results of the existing analytical theories. The theory of Nguyen and Shklovskii also predicts a negative differential hopping conductivity at high electric fields. Our numerical calculations confirm this prediction qualitatively. However the field dependence of the drift velocity of charge carriers obtained numerically differs essentially from the one predicted so far. Analytical theory is further developed so that its agreement with numerical results is essentially improved.Comment: 12 pages, 12 figures. References added, figures improve

    Spin-dependent pbar-d cross sections at low and intermediate energies

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    Antiproton-deuteron (pˉd{\bar p}d) scattering is calculated at beam energies below 300 MeV within the Glauber approach, utilizing the amplitudes of the J\"ulich NˉN\bar N N models. A good agreement is obtained with available experimental data on upolarized differential and integrated pˉd\bar p d cross sections. Predictions for polarized total pˉd{\bar p}d cross sections are presented, obtained within the single scattering approximation including Coulomb-nuclear interference effects. It is found that the total longitudinal and transversal pˉd{\bar p}d cross sections are comparable in absolute value to those for pˉp{\bar p}p scattering. The kinetics of polarization buildup is considered.Comment: 8 pages, 5 figures, to appear in proceedings of the 19th international Spin Physics Symposium, September 27 - October 2, 2010, Juelich, German

    Proton--induced deuteron breakup at GeV energies with forward emission of a fast proton pair

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    A study of the deuteron breakup reaction pd(pp)npd \to (pp)n with forward emission of a fast proton pair with small excitation energy Epp<E_{pp}< 3 MeV has been performed at the ANKE spectrometer at COSY--J\"ulich. An exclusive measurement was carried out at six proton--beam energies Tp=T_p=~0.6,~0.7,~0.8,~0.95,~1.35, and 1.9 GeV by reconstructing the momenta of the two protons. The differential cross section of the breakup reaction, averaged up to 88^{\circ} over the cm polar angle of the total momentum of the pppp pairs, has been obtained. Since the kinematics of this process is quite similar to that of backward elastic pddppd \to dp scattering, the results are compared to calculations based on a theoretical model previously applied to the pddppd \to dp process.Comment: 17 pages including 6 figures and 1 table v2: minor changes; v3: minor change of author list; v4: changes in accordance with referee remark

    Incarceration history and risk of HIV and hepatitis C virus acquisition among people who inject drugs: a systematic review and meta-analysis

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    Background People who inject drugs (PWID) experience a high prevalence of incarceration and might be at high risk of HIV and hepatitis C virus (HCV) infection during or after incarceration. We aimed to assess whether incarceration history elevates HIV or HCV acquisition risk among PWID. Methods In this systematic review and meta-analysis, we searched MEDLINE, Embase, and PsycINFO databases for studies in any language published from Jan 1, 2000 until June 13, 2017 assessing HIV or HCV incidence among PWID. We included studies that measured HIV or HCV incidence among community-recruited PWID. We included only studies reporting original results and excluded studies that evaluated incident infections by self-report. We contacted authors of cohort studies that met the inclusion or exclusion criteria, but that did not report on the outcomes of interest, to request data. We extracted and pooled data from the included studies using random-effects meta-analyses to quantify the associations between recent (past 3, 6, or 12 months or since last follow-up) or past incarceration and HIV or HCV acquisition (primary infection or reinfection) risk among PWID. We assessed the risk of bias of included studies using the Newcastle-Ottawa Scale. Between-study heterogeneity was evaluated using the I2 statistic and the P-value for heterogeneity. Findings We included published results from 20 studies and unpublished results from 21 studies. These studies originated from Australasia, western and eastern Europe, North and Latin America, and east and southeast Asia. Recent incarceration was associated with an 81% (relative risk [RR] 1·81, 95% CI 1·40–2·34) increase in HIV acquisition risk, with moderate heterogeneity between studies (I2=63·5%; p=0·001), and a 62% (RR 1·62, 95% CI 1·28–2·05) increase in HCV acquisition risk, also with moderate heterogeneity between studies (I2=57·3%; p=0·002). Past incarceration was associated with a 25% increase in HIV (RR 1·25, 95% CI 0·94–1·65) and a 21% increase in HCV (1·21, 1·02–1·43) acquisition risk. Interpretation Incarceration is associated with substantial short-term increases in HIV and HCV acquisition risk among PWID and could be a significant driver of HCV and HIV transmission among PWID. These findings support the need for developing novel interventions to minimise the risk of HCV and HIV acquisition, including addressing structural risks associated with drug laws and excessive incarceration of PWID

    Updating the Unitarity Triangle: Top Quark Mass Versus Nonperturbative Uncertainties

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    We summarize the present knowledge on the non-perturbative hadronic inputs needed in the analysis of B0B^0-Bˉ0\bar B^0 mixing and the CP-violating parameter ε\varepsilon of the K0K^0-Kˉ0\bar K^0 system. Using this information, together with the recently determined value of the top-quark mass, we update the phenomenological constraints on the unitarity triangle.Comment: 21 pages, Plain LateX, 7 figures included, preprint FTUV/94-37, IFIC/94-32, NBI-94-3

    Nucleon charge exchange on the deuteron: A critical review

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    The existing experimental data on the d(n,p)nn and d(p,n)pp cross sections in the forward direction are reviewed in terms of the Dean sum rule. It is shown that the measurement of the ratio of the charge exchange on the deuteron to that on the proton might, if taken together with other experimental data, allow a direct construction of the np -> np scattering amplitude in the backward direction with few ambiguities.Comment: 7 pages with 3 figure

    Incidence of HIV and hepatitis C virus among people who inject drugs, and associations with age and sex or gender: a global systematic review and meta-analysis

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    Background: Measuring the incidence of HIV and hepatitis C virus (HCV) infection among people who inject drugs (PWID) is key to track progress towards elimination. We aimed to summarise global data on HIV and primary HCV incidence among PWID and associations with age and sex or gender. Methods: In this systematic review and meta-analysis, we updated an existing database of HIV and HCV incidence studies among PWID by searching MEDLINE, Embase, and PsycINFO, capturing studies published between Jan 1, 2000, and Dec 12, 2022, with no language or study design restrictions. We contacted authors of identified studies for unpublished or updated data. We included studies that estimated incidence by longitudinally re-testing people at risk of infection or by using assays for recent infection. We pooled incidence and relative risk (RR; young [generally defined as ≤25 years] vs older PWID; women vs men) estimates using random-effects meta-analysis and assessed risk of bias with a modified Newcastle–Ottawa scale. This study is registered with PROSPERO, CRD42020220884. Findings: Our updated search identified 9493 publications, of which 211 were eligible for full-text review. An additional 377 full-text records from our existing database and five records identified through cross-referencing were assessed. Including 28 unpublished records, 125 records met the inclusion criteria. We identified 64 estimates of HIV incidence (30 from high-income countries [HICs] and 34 from low-income or middle-income countries [LMICs]) and 66 estimates of HCV incidence (52 from HICs and 14 from LMICs). 41 (64%) of 64 HIV and 42 (64%) of 66 HCV estimates were from single cities rather than being multi-city or nationwide. Estimates were measured over 1987–2021 for HIV and 1992–2021 for HCV. Pooled HIV incidence was 1·7 per 100 person-years (95% CI 1·3–2·3; I2=98·4%) and pooled HCV incidence was 12·1 per 100 person-years (10·0–14·6; I2=97·2%). Young PWID had a greater risk of HIV (RR 1·5, 95% CI 1·2–1·8; I2=66·9%) and HCV (1·5, 1·3–1·8; I2=70·6%) acquisition than older PWID. Women had a greater risk of HIV (RR 1·4, 95% CI 1·1–1·6; I2=55·3%) and HCV (1·2, 1·1–1·3; I2=43·3%) acquisition than men. For both HIV and HCV, the median risk-of-bias score was 6 (IQR 6–7), indicating moderate risk. Interpretation: Although sparse, available HIV and HCV incidence estimates offer insights into global levels of HIV and HCV transmission among PWID. Intensified efforts are needed to keep track of the HIV and HCV epidemics among PWID and to expand access to age-appropriate and gender-appropriate prevention services that serve young PWID and women who inject drugs. Funding: Canadian Institutes of Health Research, Fonds de recherche du Québec–Santé, Canadian Network on Hepatitis C, UK National Institute for Health and Care Research, and WHO

    2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure: The Task Force for the diagnosis and treatment of acute and chronic heart failure of the European Society of Cardiology (ESC). Developed with the special contribution of the Heart Failure Association (HFA) of the ESC

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    2016 ESC on Acute and Chronic H

    European Society of Cardiology: Cardiovascular Disease Statistics 2017

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    Background: The European Society of Cardiology (ESC) Atlas has been compiled by the European Heart Agency to document cardiovascular disease (CVD) statistics of the 56 ESC member countries. A major aim of this 2017 data presentation has been to compare high income and middle income ESC member countries, in order to identify inequalities in disease burden, outcomes and service provision. Methods: The Atlas utilizes a variety of data sources, including the World Health Organization, the Institute for Health Metrics and Evaluation, and the World Bank to document risk factors, prevalence and mortality of cardiovascular disease and national economic indicators. It also includes novel ESC sponsored survey data of health infrastructure and cardiovascular service provision provided by the national societies of the ESC member countries. Data presentation is descriptive with no attempt to attach statistical significance to differences observed in stratified analyses. Results: Important differences were identified between the high income and middle income member countries of the ESC with regard to CVD risk factors, disease incidence and mortality. For both women and men, the age-standardised prevalence of hypertension was lower in high income countries (18.3% and 27.3%) compared with middle income countries (23.5% and 30.3%). Smoking prevalence in men (not women) was also lower (26% vs 41.3%), and together these inequalities are likely to have contributed to the higher CVD mortality in middle income countries. Declines in CVD mortality have seen cancer becoming a more common cause of death in a number of high income member countries, but in middle income countries declines in CVD mortality have been less consistent where CVD remains the leading cause of death. Inequalities in CVD mortality are emphasised by the smaller contribution they make to potential years of life lost in high income compared with middle income countries both for women (13% vs. 23%) and men (20% vs. 27%). The downward mortality trends for CVD may, however, be threatened by the emerging obesity epidemic that is seeing rates of diabetes increasing across all ESC member countries. Survey data from the National Cardiac Societies (n=41) showed that rates of cardiac catheterization and coronary artery bypass surgery, as well as the number of specialist centres required to deliver them, were greatest in the high income member countries of the ESC. The Atlas confirmed that these ESC member countries, where the facilities for the contemporary treatment of coronary disease were best developed, were often those in which declines in coronary mortality have been most pronounced. Economic resources were not the only driver for delivery of equitable cardiovascular healthcare, as some middle income ESC member countries reported rates for interventional procedures and device implantations that matched or exceeded the rates in wealthier member countries. Conclusion: In documenting national CVD statistics, the Atlas provides valuable insights into the inequalities in risk factors, healthcare delivery and outcomes of CVD across ESC member countries. The availability of these data will underpin the ESC’s ambitious mission “to reduce the burden of cardiovascular disease” not only in its member countries, but also in nation states around the world

    Incarceration history and risk of HIV and hepatitis C virus acquisition among people who inject drugs: a systematic review and meta-analysis

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    Background: People who inject drugs (PWID) experience high rates of incarceration and may be at high risk of HIV and hepatitis C (HCV) virus infection during or after incarceration. We conducted a systematic review and meta-analysis to assess whether incarceration history elevates HIV or HCV acquisition risk among PWID.Methods: MEDLINE, Embase and PsycINFO databases were searched for studies in any language published since 2000 assessing HIV or HCV incidence among PWID. Studies were included if they reported the association between recent (in last 3, 6 or 12 months or since last follow-up) or past incarceration and HIV or HCV (primary or reinfection) incidence. Authors of incidence studies not reporting these outcomes were contacted for data. Data were extracted and pooled using random-effects meta-analyses. Findings: Twenty published and 21 unpublished studies were included, originating from Australasia, Western and Eastern Europe, North and Latin America and East and Southeast Asia. Recent incarceration was associated with an 81% (rate ratio (RR):1.81, 95%CI: 1.40-2.34) and 62% (RR:1.62, 95%CI:1.28-2.05) increase in HIV and HCV acquisition risk, respectively. Past incarceration was associated with a 25% and 21% increase in HIV (RR:1.25, 95%CI:0.94-1.66) and HCV (RR:1.21, 95%CI:1.02-1.43) and acquisition risk, respectively.Interpretation: Incarceration is associated with substantial short-term HIV and HCV acquisition risk among PWID and could be a significant driver for HCV and HIV transmission among PWID. These findings support the need for developing novel interventions to minimise the risk of HCV acquisition – including addressing structural risks associated with drug laws and excessive incarceration of PWID
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