Modified f(G) gravity models with curvature-matter coupling

A modified f(G) gravity model with coupling between matter and geometry is proposed, which is described by the product of the Lagrange density of the matter and an arbitrary function of the Gauss-Bonnet term. The field equations and the equations of motion corresponding to this model show the non-conservation of the energy-momentum tensor, the presence of an extra-force acting on test particles and the non-geodesic motion. Moreover, the energy conditions and the stability criterion at de Sitter point in the modified f(G) gravity models with curvature-matter coupling are derived, which can degenerate to the well-known energy conditions in general relativity. Furthermore, in order to get some insight on the meaning of these energy conditions, we apply them to the specific models of f(G) gravity and the corresponding constraints on the models are given. In addition, the conditions and the candidate for late-time cosmic accelerated expansion in the modified f(G) gravity are studied by means of conditions of power-law expansion and the equation of state of matter less than -1/ 3 .Comment: 13 pages, 4 figure

Exploring definitions of retention in care for people living with HIV in the United States in the modern treatment era

Objective: To describe retention in HIV care based on various definitions of retention in the modern treatment era. Design: A cohort study of people enrolled in care at seven mostly urban HIV clinics across the United States, 2010 - 2018. Methods: We estimated retention based on missed visits, kept visits, kept encounters (clinical visits, CD4þ cell counts, and viral loads), and HIV labs. We contrasted risk factors for retention by different definitions and estimated odds ratios for viral suppression and hazard ratios for mortality in 2 years immediately following the year in which retention was defined (the study year). Results: Across 108 171 person-years (N ¼ 21 481 people), in 71% of years, people kept ≥75% of scheduled visits; in 78%, people kept ≥2 visits >90 days apart; in 74%, people had ≥2 HIV labs >90 days apart; and in 47%, people had no gaps >6 months in clinic visits. Missing >25% of scheduled visits despite attending ≥2 visits >90 days apart was associated with nonwhite non-Hispanic race/ethnicity, history of injection drug use, and prior AIDS diagnosis. In contrast, attending ≥75% of scheduled visits while not attending ≥2 visits >90 days apart was associated with male sex, white race, no injection drug use history, and no prior AIDS diagnosis. Subsequent viral nonsuppression was more strongly associated with missed- than kept-visit measures of retention; 2-year mortality was only associated with failure to be retained by missed-visit measures. Discussion: Missed and kept-visit definitions of retention capture different constructs. Missed-visit measures are more strongly associated with poor HIV outcomes

Alcohol consumption upon direct-acting antiviral therapy for hepatitis C among persons with human immunodeficiency virus in the United States

Background: Direct-acting antivirals (DAA) are highly effective against hepatitis C virus (HCV) infection among persons with human immunodeficiency virus (PWH). However, alcohol use post-DAA treatment poses a continued threat to the liver. Whether the focus on liver health alone during HCV treatment can impact alcohol consumption is unclear. Therefore, we examined the change in alcohol use among HCV-coinfected PWH who received DAA therapy by non-addiction medical providers. Methods: In our longitudinal clinical cohort study, we identified HCV-coinfected PWH who received interferon-free DAA therapy between January 2014 and June 2019 in the Centers for AIDS Research Network of Integrated Clinical Systems. The Alcohol Use Disorders Identification Test—Consumption (AUDIT-C) was the alcohol screening instrument. We used mixed-effects logistic regression models to estimate the longitudinal change in alcohol use upon DAA therapy. Results: Among 738 HCV-coinfected PWH, 339 (46 %) reported any alcohol use at the end of HCV treatment, including 113 (15 %) with high-risk use (i.e., AUDIT-C ≥3 for women, ≥4 for men). Concurrently, 280 (38 %) PWH noted active drug use, and 357 (48 %) were currently smoking. We observed no changes in the odds of any alcohol or high-risk alcohol use over time with DAA therapy. Findings were similar in the PWH subgroup with a history of alcohol use before DAA treatment. Conclusions: For PWH with HCV, alcohol use did not change following interferon-free DAA treatment by non-addiction medical providers. Thus, clinicians should consider integrating targeted alcohol use interventions into HCV care to motivate reduced alcohol consumption and safeguard future liver health

Black Hole Thermodynamics and Statistical Mechanics

We have known for more than thirty years that black holes behave as thermodynamic systems, radiating as black bodies with characteristic temperatures and entropies. This behavior is not only interesting in its own right; it could also, through a statistical mechanical description, cast light on some of the deep problems of quantizing gravity. In these lectures, I review what we currently know about black hole thermodynamics and statistical mechanics, suggest a rather speculative "universal" characterization of the underlying states, and describe some key open questions.Comment: 35 pages, Springer macros; for the Proceedings of the 4th Aegean Summer School on Black Hole

Factors Associated with Severity of COVID-19 Disease in a Multicenter Cohort of People with HIV in the United States, March-December 2020

Background: Understanding the spectrum of COVID-19 in people with HIV (PWH) is critical to provide clinical guidance and risk reduction strategies.Setting:Centers for AIDS Research Network of Integrated Clinic System, a US multisite clinical cohort of PWH in care.Methods:We identified COVID-19 cases and severity (hospitalization, intensive care, and death) in a large, diverse HIV cohort during March 1, 2020-December 31, 2020. We determined predictors and relative risks of hospitalization among PWH with COVID-19, adjusted for disease risk scores. Results: Of 16,056 PWH in care, 649 were diagnosed with COVID-19 between March and December 2020. Case fatality was 2%; 106 (16.3%) were hospitalized, and 12 died. PWH with current CD4 count <350 cells/mm3[aRR 2.68; 95% confidence interval (CI): 1.93 to 3.71; P < 0.001] or lowest recorded CD4 count <200 cells/mm3(aRR 1.67; 95% CI: 1.18 to 2.36; P < 0.005) had greater risks of hospitalization. HIV viral load and antiretroviral therapy status were not associated with hospitalization, although most of the PWH were suppressed (86%). Black PWH were 51% more likely to be hospitalized with COVID-19 compared with other racial/ethnic groups (aRR 1.51; 95% CI: 1.04 to 2.19; P = 0.03). Chronic kidney disease, chronic obstructive pulmonary disease, diabetes, hypertension, obesity, and increased cardiovascular and hepatic fibrosis risk scores were associated with higher hospitalization risk. PWH who were older, not on antiretroviral therapy, and with current CD4 count <350 cells/mm3, diabetes, and chronic kidney disease were overrepresented among PWH who required intubation or died. Conclusions: PWH with CD4 count <350 cells/mm3, and a history of CD4 count <200 cells/mm3, have a clear excess risk of severe COVID-19, accounting for comorbidities associated with severe outcomes. PWH with these risk factors should be prioritized for COVID-19 vaccination and early treatment and monitored closely for worsening illness

Racial and ethnic disparities in coronavirus disease 2019 disease incidence independent of comorbidities, among people with HIV in the United States

Objectives: To define the incidence of clinically detected coronavirus disease 2019 (COVID-19) in people with HIV (PWH) in the United States and evaluate how racial and ethnic disparities, comorbidities, and HIV-related factors contribute to risk of COVID-19. Design: Observational study within the CFAR Network of Integrated Clinical Systems cohort in seven cities during 2020. Methods: We calculated cumulative incidence rates of COVID-19 diagnosis among PWH in routine care by key characteristics including race/ethnicity, current and lowest CD4þ cell count, and geographic area. We evaluated risk factors for COVID-19 among PWH using relative risk regression models adjusted with disease risk scores. Results: Among 16 056 PWH in care, of whom 44.5% were black, 12.5% were Hispanic, with a median age of 52 years (IQR 40 - 59), 18% had a current CD4þ cell count less than 350 cells/ml, including 7% less than 200; 95.5% were on antiretroviral therapy (ART), and 85.6% were virologically suppressed. Overall in 2020, 649 PWH were diagnosed with COVID-19 for a rate of 4.94 cases per 100 person-years. The cumulative incidence of COVID-19 was 2.4-fold and 1.7-fold higher in Hispanic and black PWH respectively, than non-Hispanic white PWH. In adjusted analyses, factors associated with COVID-19 included female sex, Hispanic or black identity, lowest historical CD4þ cell count less than 350 cells/ml (proxy for CD4þ nadir), current low CD4þ : CD8þ ratio, diabetes, and obesity. Conclusion: Our results suggest that the presence of structural racial inequities above and beyond medical comorbidities increased the risk of COVID-19 among PWH. PWH with immune exhaustion as evidenced by lowest historical CD4þ cell count or current low CD4þ : CD8þ ratio had greater risk of COVID-19