The Filed-rate Doctrine: Leaving Regulation to the Regulators

NT Library Week, 14-19 May 1984. Opening party at Darwin Botanic Gardens. Julii Tyson (Conservation Commission Library) looking at votes in Best Book Poll.Suttor, T

Many-body localization and the area law in two dimensions

We study the high-energy phase diagram of a two-dimensional spin-$\frac{1}{2}$ Heisenberg model on a square lattice in the presence of disorder. The use of large-scale tensor network numerics allows us to compute the bi-partite entanglement entropy for systems of up to $30\times7$ lattice sites. We demonstrate the existence of a finite many-body localized phase for large disorder strength $W$ for which the eigenstate thermalization hypothesis is violated. Moreover, we show explicitly that the area law holds for excited states in this phase and determine an estimate for the critical $W_{\rm{c}}$ where the transition to the ergodic phase occurs.Comment: 5 pages, 5 figure

Vascular Dysfunction and Posttraumatic Stress Disorder: Examining the Role of Oxidative Stress and Sympathetic Activity

Purpose: The physiological manifestations of posttraumatic stress disorder (PTSD) have been associated with an increase in risk of cardiovascular disease (CVD) independent of negative lifestyle factors. The goal of the study was to better elucidate the mechanisms behind the increased CVD risk by examining peripheral vascular function, a precursor to CVD. Moreover, this study sought to determine the role of oxidative stress and sympathetic nervous system (SNS) activity in PTSD-induced vascular dysfunction. Methods: Sixteen individuals with PTSD (10 women, 6 men; age 24 ± 4 years), and twenty-four healthy controls (CTRL; 15 women, 9 men, 24 ± 4 years), participated in the study. The PTSD group participated in two visits, consuming either a placebo or antioxidant cocktail (AO - vitamins C and E and alpha lipoic acid) prior to their visits, in a randomized order. Arm vascular function was assessed via the reactive hyperemia- induced flow mediated dilation of the brachial artery (BAFMD) technique and evaluated with Doppler ultrasonography. Brachial artery and arm microvascular function were determined by percent change of diameter from baseline normalized for BA shear rate (BAD/Shear), and blood flow area under the curve (BF AUC), respectively. Heart rate variability (HRV) was used to assess autonomic nervous system activity. Results: BF AUC was significantly lower (p = 0.02) and SNS activity was significantly higher (p = 0.02) in the PTSD group when compared to the CTRL group. BAD/Shear was not different between groups. Following the acute AO supplementation, BF AUC was augmented to which it was no longer significantly different (p = 0.16) when compared to the CTRL group. SNS activity within the PTSD group was significantly reduced (p=.007) following the AO supplementation when compared to the PL condition, and the difference between PTSD and CTRL was no longer significant (p=.41). Conclusion: Young individuals with PTSD demonstrated lower arm microvascular, but not brachial artery, function as well as higher sympathetic activity when compared to healthy controls matched for age, sex, and physical activity level. Furthermore, this microvascular dysfunction and SNS activity was attenuated by an acute AO supplementation to the level of the healthy controls. Taken together, this study revealed that the modulation of oxidative stress, via an acute AO supplementation, improved vascular dysfunction in individuals with PTSD, potentially by reducing the substantial SNS activity associated with this disorder.https://scholarscompass.vcu.edu/gradposters/1084/thumbnail.jp

Effects of Dietary Sodium Intake on Blood Flow Regulation During Exercise in Salt Resistant Individuals

PURPOSE: Dietary sodium intake guidelines is ≤2,300 mg/day, yet is exceeded by 90% of Americans. This study examined the impact of a high sodium diet on blood flow regulation during exercise. METHODS: Six males (25 ± 2 years) consumed dietary sodium intake guidelines for two weeks, with one week salt-capsule supplemented (HS: 6,900 mg/day of sodium) and the other week placebo-capsule supplemented (LS: 2,300 mg/day of sodium). At the end of each week, peripheral hemodynamic measurements [blood flow (BF), shear rate (SR), and flow mediated dilation (FMD)/SR)] of the brachial and superficial femoral artery were taken during handgrip (HG) and plantar flexion (PF) exercise, respectively. Each exercise workload was 3 minutes and progressed by 8 kilograms until exhaustion. RESULTS: There were no differences between LS and HS in blood pressure (82 ± 4 v 80 ± 5 mmHg; p = 0.3) or heart rate (56 ± 6 v 59 ± 10 bpm; p = 0.4). HG and PF exercise increased BF, SR, and FMD/SR across workload (p \u3c 0.03 for all), but no difference between diets (p \u3e 0.05 for all). CONCLUSION: Despite previous reports that HS impairs resting vascular function, this study revealed that peripheral vascular function and blood flow regulation during exercise is not impacted by a HS diet.https://scholarscompass.vcu.edu/gradposters/1082/thumbnail.jp

Gentamicin pharmacokinetics and pharmacodynamics during short-daily hemodialysis

BACKGROUND/AIMS: Gentamicin pharmacokinetics have not been described in patients undergoing short-daily hemodialysis (SDHD). The aim of this study is to describe gentamicin pharmacokinetics and dialytic clearance (Cl(dial)) in SDHD patients and simulate gentamicin exposure after six dosing regimens to help guide future dosing. METHODS: Six anuric patients undergoing SDHD were enrolled. Patients received intravenous infusion of 2 mg/kg gentamicin on day 1 after the first HD session followed by HD sessions on days 2, 3, and 4. Blood samples for determination of gentamicin concentrations were serially collected. Gentamicin pharmacokinetic parameters and Cl(dial) and interindividual variability terms (IIV) were estimated using NONMEM VII. Influence of patient weight on systemic clearance (Cl(s)) and central volume of distribution (V(c)) and influence of urea removal estimates on Cl(dial) were assessed. The model was used to simulate gentamicin concentrations after six dosing regimens including pre- and postdialysis as well as daily and every-other-day dosing. RESULTS: A two-compartment model with first-order elimination from central compartment described gentamicin pharmacokinetics. Population estimates for Cl(s) and Cl(dial) were 7.6 and 134 ml/min, respectively. Patient weight was statistically significantly associated with Cl(s) and V(c). Predialysis every-other-day regimens were as effective (C(max) ≥8 mg/l and AUC(48 h) ≥140 mg·h/l) and less toxic (C(min) <2 mg/l and AUC(48 h) <240 mg·h/l) than postdialysis regimens. CONCLUSIONS: Estimated gentamicin Cl(dial) is higher than previous estimates with thrice-weekly regimens. Predialysis every-other-day dosing may be recommended during SDHD