Incipient order in the t-J model at high temperatures

We analyze the high-temperature behavior of the susceptibilities towards a number of possible ordered states in the t-J-V model using the high-temperature series expansion. From all diagrams with up to ten edges, reliable results are obtained down to temperatures of order J, or (with some optimism) to J/2. In the unphysical regime, t<J, large superconducting susceptibilities are found, which moreover increase with decreasing temperatures, but for t>J, these susceptibilities are small and decreasing with decreasing temperature; this suggests that the t-J model does not support high-temperature superconductivity. We also find modest evidence of a tendency toward nematic and d-density wave orders. ERRATUM: Due to an error in the calculation, the series for d-wave supeconducting and extended s-wave superconducting orders were incorrect. We recalculate the series and give the replacement figures. In agreement with our earlier findings, we still find no evidence of any strong enhancement of the superconducting susceptibility with decreasing temperature. However, because different Pade approximants diverge from each other at somewhat higher temperatures than we originally found, it is less clear what this implies concerning the presence or absence of high-temperature superconductivity in the t-J model.Comment: 4 pages, 5 eps figures included; ERRATUM 2 pages, 3 eps figures correcting the error in the series for superconducting susceptibilitie

Complexity of childhood sexual abuse: predictors of current post-traumatic stress disorder, mood disorders, substance use, and sexual risk behavior among adult men who have sex with men

Men who have sex with men (MSM) are the group most at risk for HIV and represent the majority of new infections in the United States. Rates of childhood sexual abuse (CSA) among MSM have been estimated as high as 46 %. CSA is associated with increased risk of HIV and greater likelihood of HIV sexual risk behavior. The purpose of this study was to identify the relationships between CSA complexity indicators and mental health, substance use, sexually transmitted infections, and HIV sexual risk among MSM. MSM with CSA histories (n = 162) who were screened for an HIV prevention efficacy trial completed comprehensive psychosocial assessments. Five indicators of complex CSA experiences were created: CSA by family member, CSA with penetration, CSA with physical injury, CSA with intense fear, and first CSA in adolescence. Adjusted regression models were used to identify relationships between CSA complexity and outcomes. Participants reporting CSA by family member were at 2.6 odds of current alcohol use disorder (OR 2.64: CI 1.24–5.63), two times higher odds of substance use disorder (OR 2.1: CI 1.02–2.36), and 2.7 times higher odds of reporting an STI in the past year (OR 2.7: CI 1.04–7.1). CSA with penetration was associated with increased likelihood of current PTSD (OR 3.17: CI 1.56–6.43), recent HIV sexual risk behavior (OR 2.7: CI 1.16–6.36), and a greater number of casual sexual partners (p = 0.02). Both CSA with Physical Injury (OR 4.05: CI 1.9–8.7) and CSA with Intense Fear (OR 5.16: CI 2.5–10.7) were related to increased odds for current PTSD. First CSA in adolescence was related to increased odds of major depressive disorder. These findings suggest that CSA, with one or more complexities, creates patterns of vulnerabilities for MSM, including post-traumatic stress disorder, substance use, and sexual risk taking, and suggests the need for detailed assessment of CSA and the development of integrated HIV prevention programs that address mental health and substance use comorbidities.This study was supported by a Grant from the NIMH (R01 MH095624) PI: O'Cleirigh; Author time (Safren) was supported, in part, by Grant 5K24MH094214. (R01 MH095624 - NIMH; 5K24MH094214)Accepted manuscrip

Validation of a single biopsy approach and bolus protein feeding to determine myofibrillar protein synthesis in stable isotope tracer studies in humans

<p>Abstract</p> <p>Background</p> <p>Minimizing the number of muscle biopsies has important methodological implications and minimizes subject discomfort during a stable isotope amino acid infusion. We aimed to determine the reliability of obtaining a single muscle biopsy for the calculation of muscle protein fractional synthetic rate (FSR) as well as the amount of incorporation time necessary to obtain that biopsy after initiating a stable isotope infusion (Study 1). The calculation of muscle protein FSR requires tracer steady-state during the stable isotope infusion. Therefore, a second aim was to examine if steady-state conditions are compromised in the precursor pools (plasma free or muscle intracellular [IC]) after ingestion of a tracer enriched protein drink and after resistance exercise (Study 2).</p> <p>Methods</p> <p>Sixteen men (23 ± 3 years; BMI = 23.8 ± 2.2 kg/m², means ± SD) were randomized to perform Study 1 or Study 2 (n = 8, per study). Subjects received a primed, constant infusion of L-[<it>ring</it>-¹³C₆]phenylalanine coupled with muscle biopsies of the vastus lateralis to measure rates of myofibrillar protein synthesis (MPS). Subjects in Study 2 were fed 25 g of whey protein immediately after an acute bout of unilateral resistance exercise.</p> <p>Results</p> <p>There was no difference (P = 0.3) in rates of MPS determined using the steady-state precursor-product equation and determination of tracer incorporation between sequential biopsies 150 min apart or using plasma protein as the baseline enrichment, provided the infusion length was sufficient (230 ± 0.3 min). We also found that adding a modest amount of tracer (4% enriched), calculated based on the measured phenylalanine content of the protein (3.5%) in the drink, did not compromise steady-state conditions (slope of the enrichment curve not different from zero) in the plasma free or, more importantly, the IC pool (both P > 0.05).</p> <p>Conclusions</p> <p>These data demonstrate that the single biopsy approach yields comparable rates of muscle protein synthesis, provided a longer incorporation time is utilized, to that seen with a traditional two biopsy approach. In addition, we demonstrate that enriching protein-containing drinks with tracer does not disturb isotopic steady-state and thus both are reliable techniques to determine rates of MPS in humans.</p

Preventing Leader Derailment—A Strategic Imperative for Public Health Agencies

Public health leaders, such as those who serve as state health officials (SHOs), routinely face challenges that are uncertain and complex. Those who reflect on the challenges they face and use those reflections to improve themselves and their teams develop into more effective leaders. Not addressing challenges can lead to the risk of premature “derailment.” In this column, we review research from the Center for Creative Leadership (CCL), a global authority in leadership development, which explores the underlying dynamics of derailment. We also share insights gained from ongoing research into SHO success discussed in prior Management Moment columns.1 , 2 Finally, we offer several thoughts on strategies for preventing derailment among senior public health leaders