NMR and NQR Fluctuation Effects in Layered Superconductors

We study the effect of thermal fluctuations of the s-wave order parameter of a quasi two dimensional superconductor on the nuclear spin relaxation rate near the transition temperature Tc. We consider both the effects of the amplitude fluctuations and the Berezinskii-Kosterlitz-Thouless (BKT) phase fluctuations in weakly coupled layered superconductors. In the treatment of the amplitude fluctuations we employ the Gaussian approximation and evaluate the longitudinal relaxation rate 1/T1 for a clean s-wave superconductor, with and without pair breaking effects, using the static pair fluctuation propagator D. The increase in 1/T1 due to pair breaking in D is overcompensated by the decrease arising from the single particle Green's functions. The result is a strong effect on 1/T1 for even a small amount of pair breaking. The phase fluctuations are described in terms of dynamical BKT excitations in the form of pancake vortex-antivortex (VA) pairs. We calculate the effect of the magnetic field fluctuations caused by the translational motion of VA excitations on 1/T1 and on the transverse relaxation rate 1/T2 on both sides of the BKT transitation temperature T(BKT)<Tc. The results for the NQR relaxation rates depend strongly on the diffusion constant that governs the motion of free and bound vortices as well as the annihilation of VA pairs. We discuss the relaxation rates for real multilayer systems where the diffusion constant can be small and thus increase the lifetime of a VA pair, leading to an enhancement of the rates. We also discuss in some detail the experimental feasibility of observing the effects of amplitude fluctuations in layered s-wave superconductors such as the dichalcogenides and the effects of phase fluctuations in s- or d-wave superconductors such as the layered cuprates.Comment: 38 pages, 12 figure

COVAD survey 2 long-term outcomes: unmet need and protocol

Vaccine hesitancy is considered a major barrier to achieving herd immunity against COVID-19. While multiple alternative and synergistic approaches including heterologous vaccination, booster doses, and antiviral drugs have been developed, equitable vaccine uptake remains the foremost strategy to manage pandemic. Although none of the currently approved vaccines are live-attenuated, several reports of disease flares, waning protection, and acute-onset syndromes have emerged as short-term adverse events after vaccination. Hence, scientific literature falls short when discussing potential long-term effects in vulnerable cohorts. The COVAD-2 survey follows on from the baseline COVAD-1 survey with the aim to collect patient-reported data on the long-term safety and tolerability of COVID-19 vaccines in immune modulation. The e-survey has been extensively pilot-tested and validated with translations into multiple languages. Anticipated results will help improve vaccination efforts and reduce the imminent risks of COVID-19 infection, especially in understudied vulnerable groups

Routine preoperative abdominal computed tomography in colon cancer : a utility study

Background: There is currently little proven utility for the preoperative scanning of intraperitoneal colonic cancer using computerized tomography (CT). A prospective study was conducted where CT scanning was preoperatively incorporated into the management algorithm to ascertain its role in patient management. Methods: Thoracoabdominal CT scanning was performed in both the elective and emergency settings in an unselected group of 73 patients referred to a coloproctology unit established over the last 30 months at the Queen Elizabeth Hospital, Barbados with in-hospital and electronic correlation of the CT and operative findings to determine the influence that the preoperative CT scan made on surgical decision making. Results: Unexpected additional pathology was found in 6.8% of patients with a sensitivity for the detection of visceral metastatic disease of 91.7%. The preoperative scan was deemed to be of clinical value in 24.7% of cases and to definitively alter surgical management in 13.7% of patients. These alterations in management included several types of multivisceral resections, the need for ureteric stenting or reimplantation, the utilization of stomas alone and the avoidance of resection in known metastatic disease. Conclusion: Preoperative CT scanning of intraperitoneal colonic cancer adds important technical information to the conduct of the surgery and alters therapy in a selected patient grou

Improved Characterization of Healthy and Malignant Tissue by NMR Line-Shape Relaxation Correlations

We performed a relaxation-line-shape correlation NMR experiment on muscle, liver, kidney, and spleen tissues of healthy mice and of mouse tumor tissue. In each tissue studied, five spin groups were resolved and characterized by their relaxation parameters. We report a previously uncharacterized semi-solid spin group and discuss briefly the value of this method for the identification of malignant tissues

Structure-based identification of small-molecule angiotensin-converting enzyme 2 activators as novel antihypertensive agents

Angiotensin-converting enzyme 2 (ACE2) is a key renin-angiotensin system enzyme involved in balancing the adverse effects of angiotensin II on the cardiovascular system, and its overexpression by gene transfer is beneficial in cardiovascular disease. Therefore, our objectives were 2-fold: to identify compounds that enhance ACE2 activity using a novel conformation-based rational drug discovery strategy and to evaluate whether such compounds reverse hypertension-induced pathophysiologies. We used a unique virtual screening approach. In vitro assays revealed 2 compounds (a xanthenone and resorcinolnaphthalein) that enhanced ACE2 activity in a dose-dependent manner. Acute in vivo administration of the xanthenone resulted in a dose-dependent transient and robust decrease in blood pressure (at 10 mg/kg, spontaneously hypertensive rats decreased 71±9 mm Hg and Wistar-Kyoto rats decreased 21±8 mm Hg; P<0.05). Chronic infusion of the xanthenone (120 μg/day) resulted in a modest decrease in the spontaneously hypertensive rat blood pressure (17 mm Hg; 2-way ANOVA; P<0.05), whereas it had no effect in Wistar-Kyoto rats. Strikingly, the decrease in blood pressure was also associated with improvements in cardiac function and reversal of myocardial, perivascular, and renal fibrosis in the spontaneously hypertensive rats. We conclude that structure-based screening can help identify compounds that activate ACE2, decrease blood pressure, and reverse tissue remodeling. Administration of ACE2 activators may be a valid strategy for antihypertensive therapy. © 2008 American Heart Association, Inc