Influence of nuclear data uncertainties on thorium fusion-fission hybrid blanket nucleonic performance

The fusion-fission hybrid blanket proposed for the Tandem Mirror Hybrid Reactor employs thorium metal as the fertile material. Based on the ENDF/B-IV nuclear data, the /sup 233/U and tritium production rate and blanket energy multiplication averaged over the blanket lifetime of about 9 MW-yr/m/sup 2/ are 0.76 and 1.12 per D-T neutron and 4.8, respectively. At the time of the blanket discharge, the /sup 233/U enrichment in the thorium metal is about 3%. The thorium cross sections given by the ENDF/B-IV and V were reviewed, and the important partial cross sections such as (n,2n), (n,3n), and (n,..gamma..) were found to be known to +-10 to 20% in the respective energy range of interest. A sensitivity study showed that the /sup 233/U and tritium production rate and blanket energy multiplication are relatively sensitive to the thorium capture and fission cross section uncertainties. In order to predict the above parameters within +-1%, the Th(n,..gamma..) and Th(n,..nu..f) cross sections must be measured within about +-2% in the energy range 3 to 3000 keV and 13.5 to 15 MeV, respectively

Recoil-Induced-Resonances in Nonlinear, Ground-State, Pump-Probe Spectroscopy

A theory of pump-probe spectroscopy is developed in which optical fields drive two-photon Raman transitions between ground states of an ensemble of three-level $\Lambda$ atoms. Effects related to the recoil the atoms undergo as a result of their interactions with the fields are fully accounted for in this theory. The linear absorption coefficient of a weak probe field in the presence of two pump fields of arbitrary strength is calculated. For subrecoil cooled atoms, the spectrum consists of eight absorption lines and eight emission lines. In the limit that $\chi_{1}\ll \chi_{2}$, where $\chi_{1}$ and $\chi_{2}$ are the Rabi frequencies of the two pump fields, one recovers the absorption spectrum for a probe field interacting with an effective two-level atom in the presence of a single pump field. However when $\chi_{1}\gtrsim \chi_{2}$, new interference effects arise that allow one to selectively turn on and off some of these recoil induced resonances.Comment: 30 pages, 8 figures. RevTex. Submitted to Phys. Rev. A, Revised versio

Herd-level risk factors of bovine tuberculosis in England and Wales after the 2001 foot-and-mouth disease epidemic

We present the results of a 2005 case–control study of bovine tuberculosis (bTB) breakdowns in English and Welsh herds. The herd management, farming practices, and environmental factors of 401matched pairs of case and control herds were investigated to provide a picture of herd-level risk factors in areas of varying bTB incidence. A global conditional logistic regression model, with region-specific variants, was used to compare case herds that had experienced a confirmed bTB breakdown to contemporaneous control herds matched on region, herd type, herd size, and parish testing interval. Contacts with cattle from contiguous herds and sourcing cattle from herds with a recent history of bTB were associated with an increased risk in both the global and regional analyses. Operating a farm over several premises, providing cattle feed inside the housing, and the presence of badgers were also identified as significantly associated with an increased bTB risk. Steps taken to minimize cattle contacts with neighboring herds and altering trading practices could have the potential to reduce the size of the bTB epidemic. In principle, limiting the interactions between cattle and wildlife may also be useful; however this study did not highlight any specific measures to implement

Quantum gauge models without classical Higgs mechanism

We examine the status of massive gauge theories, such as those usually obtained by spontaneous symmetry breakdown, from the viewpoint of causal (Epstein-Glaser) renormalization. The BRS formulation of gauge invariance in this framework, starting from canonical quantization of massive (as well as massless) vector bosons as fundamental entities, and proceeding perturbatively, allows one to rederive the reductive group symmetry of interactions, the need for scalar fields in gauge theory, and the covariant derivative. Thus the presence of higgs particles is explained without recourse to a Higgs(-Englert-Brout-Guralnik-Hagen-Kibble) mechanism. Along the way, we dispel doubts about the compatibility of causal gauge invariance with grand unified theories.Comment: 20 pages in two-column EPJC format, shortened version accepted for publication. For more details, consult version

Evaluating the Population Impact on Racial/Ethnic Disparities in HIV in Adulthood of Intervening on Specific Targets: A Conceptual and Methodological Framework

Reducing racial/ethnic disparities in human immunodeficiency virus (HIV) disease is a high priority. Reductions in HIV racial/ethnic disparities can potentially be achieved by intervening on important intermediate factors. The potential population impact of intervening on intermediates can be evaluated using observational data when certain conditions are met. However, using standard stratification-based approaches commonly employed in the observational HIV literature to estimate the potential population impact in this setting may yield results that do not accurately estimate quantities of interest. Here we describe a useful conceptual and methodological framework for using observational data to appropriately evaluate the impact on HIV racial/ethnic disparities of interventions. This framework reframes relevant scientific questions in terms of a controlled direct effect and estimates a corresponding proportion eliminated. We review methods and conditions sufficient for accurate estimation within the proposed framework. We use the framework to analyze data on 2,329 participants in the CFAR [Centers for AIDS Research] Network of Integrated Clinical Systems (2008-2014) to evaluate the potential impact of universal prescription of and ≥95% adherence to antiretroviral therapy on racial disparities in HIV virological suppression. We encourage the use of the described framework to appropriately evaluate the potential impact of targeted interventions in addressing HIV racial/ethnic disparities using observational data

Cumulative Human Immunodeficiency Viremia, Antiretroviral Therapy, and Incident Myocardial Infarction

Background: People living with HIV are at risk of increased myocardial infarction (MI). Cumulative HIV viral load (VL) has been proposed as a better measure of HIV inflammation than other measures of VL, like baseline VL, but its associations with MI are not known. Methods: The multisite Centers for AIDS Research Network of Integrated Clinical Systems (CNICS) cohort includes clinical data and centrally adjudicated MI with distinction between atheroembolic MI (type 1) and MI related to supply-demand mismatch (type 2). We examined CNICS participants who were not on antiretroviral therapy (ART) at enrollment. Cumulative VL (copy-days of virus) from 6 months after enrollment was estimated with a time-weighted sum using the trapezoidal rule. We modeled associations of cumulative and baseline VL with MI by type using marginal structural Cox models. We contrasted the 75% percentile of the VL distribution with the 25% percentile. Results: Among 11,324 participants, 218 MIs occurred between 1996 and 2016. Higher cumulative VL was associated with risk of all MI (hazard ratio [HR] = 1.72; 95% confidence interval [CI] = 1.26, 2.36), type 1 MI (HR = 1.23; 95% CI = 0.78, 1.96), and type 2 MI (HR = 2.52; 95% CI = 1.74, 3.66). While off ART, cumulative VL had a stronger association with type 1 MI (HR = 2.13; 95% CI = 1.15, 3.94) than type 2 MI (HR = 1.25; 95% CI = 0.70, 2.25). Baseline VL was associated with all MI (HR = 1.60; 95% CI = 1.28, 2.01), type 1 MI (HR = 1.73; 95% CI = 1.26, 2.38), and type 2 MI (HR = 1.51; 95% CI = 1.10, 2.08). Conclusions: Higher cumulative and baseline VL is associated with all MI, with a particularly strong association between cumulative VL and type 2 MI

Recent abacavir use increases risk of type 1 and type 2 myocardial infarctions among adults with HIV

Background: There is persistent confusion as to whether abacavir (ABC) increases the risk of myocardial infarction (MI), and whether such risk differs by type 1 (T1MI) or 2 (T2MI) MI in adults with HIV. Methods: Incident MIs in North American Cohort Collaboration on Research and Design participants were identified from 2001 to 2013. Discrete time marginal structural models addressed channeling biases and time-dependent confounding to estimate crude hazard ratio (HR) and adjusted hazard ratio (aHR) and 95% confidence intervals; analyses were performed for T1MI and T2MI separately. A sensitivity analysis evaluated whether Framingham risk score (FRS) modified the effect of ABC on MI occurrence. Results: Eight thousand two hundred sixty-five adults who initiated antiretroviral therapy contributed 29,077 person-years and 123 MI events (65 T1MI and 58 T2MI). Median follow-up time was 2.9 (interquartile range 1.4-5.1) years. ABC initiators were more likely to have a history of injection drug use, hepatitis C virus infection, hypertension, diabetes, impaired kidney function, hyperlipidemia, low (,200 cells/mm3) CD4 counts, and a history of AIDS. The risk of the combined MI outcome was greater for persons who used ABC in the previous 6 months [aHR = 1.84 (1.17-2.91)]; and persisted for T1MI (aHR = 1.62 [1.01]) and T2MI [aHR = 2.11 (1.08-4.29)]. FRS did not modify the effect of ABC on MI (P = 0.14) and inclusion of FRS in the MSM did not diminish the effect of recent ABC use on the combined outcome. Conclusions: Recent ABC use was associated with MI after adjustment for known risk factors and for FRS. However, screening for T1MI risks may not identify all or even most persons at risk of ABC use-associated MIs

Prevalence and Factors Associated with Hazardous Alcohol Use Among Persons Living with HIV Across the US in the Current Era of Antiretroviral Treatment

Hazardous alcohol use is associated with detrimental health outcomes among persons living with HIV (PLWH). We examined the prevalence and factors associated with hazardous alcohol use in the current era using several hazardous drinking definitions and binge drinking defined as ≥5 drinks for men versus ≥4 for women. We included 8567 PLWH from 7 U.S. sites from 2013 to 2015. Current hazardous alcohol use was reported by 27% and 34% reported binge drinking. In adjusted analyses, current and past cocaine/crack (odd ratio [OR] 4.1:3.3–5.1, p < 0.001 and OR 1.3:1.1–1.5, p < 0.001 respectively), marijuana (OR 2.5:2.2–2.9, p < 0.001 and OR 1.4:1.2–1.6, p < 0.001), and cigarette use (OR 1.4:1.2–1.6, p < 0.001 and OR 1.3:1.2–1.5, p < 0.001) were associated with increased hazardous alcohol use. The prevalence of hazardous alcohol use remains high in the current era, particularly among younger men. Routine screening and targeted interventions for hazardous alcohol use, potentially bundled with interventions for other drugs, remain a key aspect of HIV care

Associations between At-Risk Alcohol Use, Substance Use, and Smoking with Lipohypertrophy and Lipoatrophy among Patients Living with HIV

To examine associations between lipohypertrophy and lipoatrophy and illicit drug use, smoking, and at-risk alcohol use among a large diverse cohort of persons living with HIV (PLWH) in clinical care. 7,931 PLWH at six sites across the United States completed 21,279 clinical assessments, including lipohypertrophy and lipoatrophy, drug/alcohol use, physical activity level, and smoking. Lipohypertrophy and lipoatrophy were measured using the FRAM body morphology instrument and associations were assessed with generalized estimating equations. Lipohypertrophy (33% mild, 4% moderate-to-severe) and lipoatrophy (20% mild, 3% moderate-to-severe) were common. Older age, male sex, and higher current CD4 count were associated with more severe lipohypertrophy (p values <.001-.03). Prior methamphetamine or marijuana use, and prior and current cocaine use, were associated with more severe lipohypertrophy (p values <.001-.009). Older age, detectable viral load, and low current CD4 cell counts were associated with more severe lipoatrophy (p values <.001-.003). In addition, current smoking and marijuana and opiate use were associated with more severe lipoatrophy (p values <.001-.03). Patients with very low physical activity levels had more severe lipohypertrophy and also more severe lipoatrophy than those with all other activity levels (p values <.001). For example, the lipohypertrophy score of those reporting high levels of physical activity was on average 1.6 points lower than those reporting very low levels of physical activity (-1.6, 95% CI:-1.8 to-1.4, p <.001). We found a high prevalence of lipohypertrophy and lipoatrophy among a nationally distributed cohort of PLWH. While low levels of physical activity were associated with both lipohypertrophy and lipoatrophy, associations with substance use and other clinical characteristics differed between lipohypertrophy and lipoatrophy. These results support the conclusion that lipohypertrophy and lipoatrophy are distinct, and highlight differential associations with specific illicit drug use

Association Between Bilirubin, Atazanavir, and Cardiovascular Disease Events Among People Living With HIV Across the United States

Objective: Bilirubin is an antioxidant that may suppress lipid oxidation. Elevated bilirubin is associated with decreased cardiovascular events in HIV-uninfected populations. We examined these associations in people living with HIV (PLWH). Methods: Potential myocardial infarctions (MIs) and strokes were centrally adjudicated. We examined MI types: type 1 MI (T1MI) from atherosclerotic plaque instability and type 2 MI (T2MI) in the setting of oxygen demand/supply mismatch such as sepsis. We used multivariable Cox regression analyses to determine associations between total bilirubin levels and outcomes adjusting for traditional and HIV-specific risk factors. To minimize confounding by hepatobiliary disease, we conducted analyses limited to bilirubin values <2.1 mg/dL; among those with fibrosis-4 values <3.25; and among everyone. We repeated analyses stratified by hepatitis C status and time-updated atazanavir use. Results: Among 25,816 PLWH, there were 392 T1MI and 356 T2MI during follow-up. Adjusted hazard ratios for the association of higher bilirubin levels with T1MI were not significant. Higher bilirubin levels were associated with T2MI. By contrast, among PLWH on atazanavir, higher bilirubin levels were associated with fewer T2MI (hazard ratio 0.56:0.33-1.00). Higher bilirubin levels among those on atazanavir were associated with fewer T1MI combined with ischemic stroke. Limitations: Analyses were conducted with total rather than unconjugated bilirubin. Conclusions: Among PLWH, higher bilirubin levels were associated with T2MI among some subgroups. However, among those on atazanavir, there was a protective association between bilirubin and T2MI. These findings demonstrate different associations between outcomes and elevated bilirubin due to diverse causes and the importance of distinguishing MI types