Lightcone fluctuations in quantum gravity and extra dimensions

We discuss how compactified extra dimensions may have potentially observable effects which grow as the compactification scale decreases. This arises because of lightcone fluctuations in the uncompactified dimensions which can result in the broadening of the spectral lines from distant sources. We analyze this effect in a five dimensional model, and argue that data from gamma ray burst sources require the compactification length to be greater than about $10^5$ cm in this model.Comment: Two additional references adde

Cognitive changes during the menopausal transition: a longitudinal study in women with and without HIV

OBJECTIVE: To assess longitudinal changes in cognitive performance across menopause stages in a sample comprised primarily of low-income women of color, including women with HIV (WWH). METHODS: A total of 443 women (291 WWH; 69% African American; 18% Hispanic; median age = 42 y) from the Women's Interagency HIV Study completed tests of verbal learning and memory, attention/working memory, processing speed, verbal fluency, motor skills, and executive function first at an index premenopausal visit and thereafter once every 2 years for up to six visits (mean follow-up = 5.7 y). General linear-mixed effects regression models were run to estimate associations between menopause stages and cognition, in the overall sample and in WWH. We examined both continuous scores and categorical scores of cognitive impairment (yes/no >1 standard deviation below the mean). RESULTS: Adjusting for age and relevant covariates, the overall sample and WWH showed longitudinal declines in continuous measures of learning, memory, and attention/working memory domains from the premenopause to the early perimenopause and from the premenopause to the postmenopause, Ps < 0.05 to < 0.001. Effects on those same domains were also evident in categorical scores of cognitive impairment, with the increased odds of impairment ranging from 41% to 215%, Ps < 0.05 to < 0.001. The increase in predicted probability of impairment by menopausal stage (% affected) ranged from 4% to 13%. CONCLUSIONS: Menopause stage was a key determinant of cognition in a sample of low-income women of color, including WWH. Many of these changes reached a clinically significant level of cognitive impairment

Use of Nonantiretroviral Medications That May Impact Neurocognition: Patterns and Predictors in a Large, Long-Term HIV Cohort Study

Background: Neurocognitive impairment is a frequent and often disabling comorbidity of HIV infection. In addition to antiretroviral therapies, individuals with HIV infection may commonly use nonantiretroviral medications that are known to cause neurocognitive adverse effects (NC-AE). The contribution of NC-AE to neurocognitive impairment is rarely considered in the context of HIV and could explain part of the variability in neurocognitive performance among individuals with HIV. Setting: Women’s Interagency HIV Study, a prospective, multisite, observational study of US women with and without HIV. Methods: After a literature review, 79 medications (excluding statins) with NC-AE were identified and reported by Women’s Interagency HIV Study participants. We examined factors associated with self-reported use of these medications over a 10-year period. Generalized estimating equations for binary outcomes were used to assess sociodemographic, behavioral, and clinical characteristics associated with NC-AE medication use. Results: Three thousand three hundred women (71% with HIV) and data from ~42,000 visits were studied. HIV infection was associated with NC-AE medication use (odds ratio = 1.52; 95% confidence interval: 1.35 to 1.71). After adjustment for HIV infection status, other predictors of NC-AE medication use included having health insurance, elevated depressive symptoms, prior clinical AIDS, noninjection recreational drug use, and an annual household income of <$12,000 (Ps < 0.004). NC-AE medication use was less likely among women who drank 1–7 or 8–12 alcoholic drinks/week (vs. abstaining) (P < 0.04). Conclusions: HIV infection was associated with NC-AE medication use, which may influence determinations of HIV-associated neurocognitive impairment. Providers should consider the impact of NC-AE medications when evaluating patients with HIV and concurrent neurocognitive symptoms

Factors Predicting Detrimental Change in Declarative Memory Among Women With HIV: A Study of Heterogeneity in Cognition

Objective: Statistical techniques used to study cognitive function in HIV typically yield normative estimates and can mask the heterogeneity in cognitive trajectories over time. We applied a novel statistical approach to identify clusters of individuals with distinct patterns of change in declarative memory in HIV-seropositive (HIV+) and HIV-seronegative (HIV−) women. Methods: 1731 women from the Women’s Interagency HIV Study, a multi-center, prospective cohort study, completed the Hopkins Verbal Learning Test-Revised (HLVT-R) at >2 visits. To derive subgroups with similar patterns of decline by HIV-serostatus, we used a mixed-effects framework that modeled the trajectory of multiple declarative memory outcomes over time, while simultaneously clustering individuals. Results: Of the 1731 participants, 1149 were HIV+ (70% Black/African American [AA]; 30% White/Other [W/O]) and 582 were HIV− (68% AA; 32% W/O). Race stratification was necessary to optimize clustering. Among HIV+AA’s, four subgroups emerged: a subgroup with minimal decline, two with accelerated decline, and one with stable but low performance. In HIV− AA, three subgroups emerged: one with minimal decline and two with accelerated decline. In multivariable-adjusted models among HIV+, individuals with accelerated decline were less educated (P < 0.001) and more likely to have a history of depression (P < 0.001) versus those with minimal decline. Similar subgroups were identified in W/O HIV+ and W/O HIV− participants. Conclusion: We identified clinically meaningful subgroups of women with distinct phenotypes of declarative memory decline, which depend on race and HIV-serostatus using a data driven approach. Identification of underlying mechanisms and risk factors contributing to the observed differences are warranted. More broadly our modeling approach could be other populations to identify risk factors for accelerated cognitive decline and to personalize interventions

Degree of Polypharmacy and Cognitive Function in Older Women with HIV

The number of people with HIV (PWH) experiencing age-associated comorbidities including those treated with medications and cognitive impairment is increasing. We examined associations between polypharmacy and cognition in older women with HIV (WWH) given their vulnerability to this comorbidity. Cross-sectional analysis capitalizing on Women's Interagency HIV Study data collected between 2014 and 2017. WWH meeting the following criteria were analyzed: age ≥50 years; availability of self-reported non-antiretroviral therapy (ART) medications data; and neuropsychological data. The number of non-ART medications used regularly in the prior 6 months was summed. Polypharmacy was categorized as none/low (0-4), moderate (5-9), or severe (≥10). Multivariable linear regression analyses examined polypharmacy-cognition (T-score) associations in the total sample and among virally suppressed (VS; < 20 copies/mL)-WWH after covariate adjustment for enrollment site, income, depressive symptoms, substance use (smoking, heavy alcohol, marijuana, crack, cocaine, and/or heroin), the Veterans Aging Cohort Study index (indicators of HIV disease and organ system function, hepatitis C virus serostatus), ART use, nadir CD4 count, and specific ART drugs (efavirenz, integrase inhibitors). We included 637 women (median age = 55 years; 72% Black). Ninety-four percent reported ART use in the past 6 months and 75% had HIV RNA <20 copies/mL. Comorbidity prevalence was high (61% hypertension; 26% diabetes). Moderate and severe polypharmacy in WWH were 34% and 24%. In WWH, severe polypharmacy was associated with poorer executive function (p = .007) and processing speed (p = .01). The same pattern of findings remained among VS-WWH. Moderate polypharmacy was not associated with cognition. Moderate and severe polypharmacy were common and associated with poorer executive function and processing speed in WWH. Severe polypharmacy may be a major contributor to the persistence of domain-specific cognitive complications in older WWH above and beyond the conditions that these medications are used to treat

Midlife body mass index, central adiposity and neuropsychological performance over 10 years in women living with and without HIV

Background and objective: Observations of overweight and obesity in association with neuropsychological performance (NP) vary over the adult life course depending on baseline levels, biological sex, age, race, temporality of measurements, and other factors. Therefore, similar published analyses across cohorts are inconsistent. In our sample of women living with HIV (WLWH) and women without HIV (WWOH), we conducted comparable analyses as those published in men with and without HIV. We examined cross-sectional and longitudinal associations between body mass index (BMI) and waist circumference (WC) and NP. Methods: Four hundred thirty two 432 virologically-suppressed WLWH and 367 WWOH, ≥40 years in the Women’s Interagency HIV Study (WIHS) with anthropometry and NP assessments every two years from 2009-2019 were included in the study. Demographically-adjusted T-scores were calculated for six NP domains: learning, memory, executive function, processing speed, attention and working memory, and motor function. Multivariable linear regression models stratified by HIV status were used to examine cross-sectional associations of BMI and WC by NP domain; repeated measures analyses assessed baseline BMI and WC in association with longitudinal change in NP. Covariates included sociodemographic, behavioral, and HIV-related characteristics. Results: At baseline among all women, the median age was 45 years, 65% were Non-Latinx Black women, and 45% were obese women. Obese WLWH (BMI≥30.0 kg/m2) had poorer executive function (β=-2.27, 95%CI [-4.46, -0.07]) versus WLWH with healthy BMI (18.5–24.9 kg/m2). Longitudinally over ~8 years, obese versus overweight WWOH improved on memory (β=2.19, 95%CI [0.13, 4.26]), however overweight versus healthy WWOH experienced declining memory (β= -2.67, 95%CI [-5.40, -0.07]). Increasing WC was associated with declining executive, processing speed, and motor function (p’s<0.05); an at-risk WC was associated with improved memory (β=1.81, 95%CI [0.19, 3.44]) among WWOH. Among WLWH, increasing BMI was associated with improved learning (β=0.07, 95%CI [0.00, 0.15]. Conclusion: Our cross-sectional and longitudinal analyses evaluating the associations of BMI and WC and NP were mixed compared to previous reports. This illustrates the importance of sociodemographic characteristics, baseline levels of exposures and outcomes, HIV status, temporality of measurements, and other factors when evaluating aging HIV epidemiology study results

Observation of exclusive DVCS in polarized electron beam asymmetry measurements

We report the first results of the beam spin asymmetry measured in the reaction e + p -> e + p + gamma at a beam energy of 4.25 GeV. A large asymmetry with a sin(phi) modulation is observed, as predicted for the interference term of Deeply Virtual Compton Scattering and the Bethe-Heitler process. The amplitude of this modulation is alpha = 0.202 +/- 0.028. In leading-order and leading-twist pQCD, the alpha is directly proportional to the imaginary part of the DVCS amplitude.Comment: 6 pages, 5 figure

Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV

The three-body photodisintegration of 3He has been measured with the CLAS detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first time to cover a wide momentum and angular range for the two outgoing protons. Three kinematic regions dominated by either two- or three-body contributions have been distinguished and analyzed. The measured cross sections have been compared with results of a theoretical model, which, in certain kinematic ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications: removed 2 figures, improvements on others, a few minor modifications to the tex

A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments

We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.Comment: revtex4 18 pp., 12 figure

eta-prime photoproduction on the proton for photon energies from 1.527 to 2.227 GeV

Differential cross sections for the reaction gamma p -> eta-prime p have been measured with the CLAS spectrometer and a tagged photon beam with energies from 1.527 to 2.227 GeV. The results reported here possess much greater accuracy than previous measurements. Analyses of these data indicate for the first time the coupling of the etaprime N channel to both the S_11(1535) and P_11(1710) resonances, known to couple strongly to the eta N channel in photoproduction on the proton, and the importance of j=3/2 resonances in the process.Comment: 6 pages, 3 figure