Kondo resonance effect on persistent currents through a quantum dot in a mesoscopic ring

The persistent current through a quantum dot inserted in a mesoscopic ring of length L is studied. A cluster representing the dot and its vicinity is exactly diagonalized and embedded into the rest of the ring. The Kondo resonance provides a new channel for the current to flow. It is shown that due to scaling properties, the persistent current at the Kondo regime is enhanced relative to the current flowing either when the dot is at resonance or along a perfect ring of same length. In the Kondo regime the current scales as $L^{-1/2}$, unlike the $L^{-1}$ scaling of a perfect ring. We discuss the possibility of detection of the Kondo effect by means of a persistent current measurement.Comment: 11 pages, 3 Postscript figure

Transport in Coupled Quantum Dots: Kondo Effect Versus Anti-Ferromagnetic Correlation

The interplay between the Kondo effect and the inter-dot magnetic interaction in a coupled-dot system is studied. An exact result for the transport properties at zero temperature is obtained by diagonalizing a cluster, composed by the double-dot and its vicinity, which is connected to leads. It is shown that the system goes continuously from the Kondo regime to an anti-ferromagnetic state as the inter-dot interaction is increased. The conductance, the charge at the dots and the spin-spin correlation are obtained as a function of the gate potential.Comment: 4 pages, 3 postscript figures. Submitted to PR

High awareness of hepatitis C virus (HCV) but limited knowledge of HCV complications among HIV-positive and HIV-negative men who have sex with men

Hepatitis C virus (HCV) has emerged as a sexually transmitted infection among HIV-positive men who have sex with men (MSM) in high-income countries. Little is reported about HCV awareness among MSM, although this is essential for developing targeted prevention strategies. We, therefore, studied HCV awareness and knowledge among HIV-positive and HIV-negative MSM from the Amsterdam Cohort Studies (ACS). During two visits, 1 year apart and starting in October 2007, MSM from the ACS answered questions regarding HCV awareness, knowledge of HCV transmission (7 items), complications (8 items) and sexual risk behaviour. We examined the percentage of HCV awareness and correctly answered knowledge items, and whether awareness and knowledge improved significantly over time. Using logistic regression, we studied whether HIV status and sexual risk behaviour were associated with awareness. Seventy percent (312/444) of HIV-negative and 80% (74/92) of HIV-positive MSM reported to have ever heard of HCV on the first visit. Overall, awareness increased with 9% between the first and second visit (p < 0.001). In multivariate analysis the association of group sex with HCV awareness was borderline significant (OR 1.49, 95% CI 0.97-2.30). Compared with knowledge of transmission routes, knowledge of complications appeared to be limited. In the ACS, awareness of HCV is high, particularly among those reporting group sex, an important risk factor for HCV transmission. The majority of participants had good knowledge of transmission routes, but limited knowledge of complications of chronic HCV infection. HCV prevention messages could be strengthened, therefore, by further addressing the complications of HCV infectio

Changes in substance use among HIV-negative MSM: A longitudinal analysis, 1995-2019

Background: Research suggests shifting patterns of recreational drug consumption among MSM in recent decades. The present study evaluates population-level mean trajectories of substance use among HIV-negative MSM from 1995 to 2019. Methods: Using open cohort study data following MSM in the Netherlands (n=1495) since 1995, we applied generalized estimating equations to examine population-averaged estimates of five substances – alcohol, cannabis, ecstasy, cocaine, and poppers – from 1995 to 2019, as well as their use during sexual encounters. Results: Recent alcohol use decreased; predicted probabilities declined from 1995 to 2019 (.96 to .87). During the same period, cocaine and poppers use increased – (.10 to .23 and .37 to .47, respectively) and use during sex also increased (.05 to .16, and .32 to .41, respectively). Ecstasy use increased over time (.23 to .38), although not during sex. No significant changes in cannabis use occurred. Conclusions: While changes in use of various substances were mixed, increases in cocaine and poppers use during sexual encounters occurred among HIV-negative MSM over time. Efforts to intervene on substance use in connection with sex remain critical for health promotion

A COMBINED MORPHOMETRIC AND MOLECULAR APPROACH TO IDENTIFYING METACERCARIAE OF EUCLINOSTOMUM HETEROSTOMUM (DIGENEA: CLINOSTOMIDAE)

Metacercariae of species of Euclinostomum have been found encysted in kidney, liver and muscles of several fish species while adults occur in the mouth, pharynx, larynx, trachea and upper esophagus of fish-eating birds. The aim of this work was to gather molecular and morphological data from the type species, Euclinostomum heterostomum, as a starting point for needed revisions of the genus. Metacercariae were collected from cichlids in Lake Kinneret, Israel and all were identified as E. heterostomum based on morphology. This identification was further confirmed by principal components analyses that revealed no partitions in morphometric resemblance, indicating that the material represents a single species, and that the specimens were morphometrically similar to other descriptions of E. heterostomum. In phylogenetic analysis of concatenated partial internal transcribed spacer 1 and 2, and 5.8S rDNA, and partial cytochrome c oxidase I barcode sequences, the isolates of Euclinostomum obtained in this study form a single, monophyletic group separate from recently published data from Euclinostomum sp. from Thailand, and from Clinostomum species, which are also monophyletic. The morphological and molecular data reported in the present work can provide a useful point of reference for future studies

Less decrease in risk behaviour from pre-HIV to post-HIV seroconversion among MSM in the combination antiretroviral therapy era compared with the pre-combination antiretroviral therapy era

Objective: To gain insight in the ongoing HIV transmission, we compared sexual risk behaviour pre-HIV and post-HIV seroconversion in 206 MSM participating in the Amsterdam Cohort Studies (1984-2008) before and after the introduction of combination antiretroviral therapy (cART). Design and methods: MSM completed behavioural questionnaires and were tested for HIV antibodies every 6 months. Trends in anal intercourse and number of sex partners from 4 years before HIV seroconversion until 4 years after diagnosis were analysed with latent class random effects logistic regression models. Results: The risk of having unprotected anal intercourse (UAI) 1 year after HIV diagnosis decreased significantly when compared with 1 year before diagnosis in both the pre-cART era [difference, 30%; 95% confidence interval (CI), 22-36%] and cART era (difference, 19%; 95% CI, 9-30%). In contrast to a continuing decrease of UAI in the pre-cART era, the probability of UAI in the cART era increased again to preseroconversion levels (61%; 95% CI, 48-74%)) 4 years after diagnosis. Conclusion: This study provides evidence that recently seroconverted MSM reduce their sexual risk behaviour following HIV diagnosis both in the pre-cART as well as the cART period. However, in the cART period this reduction in sexual risk behaviour is less and returns to pre-cART levels within 4 years. These findings not only confirm the need for early HIV testing but also make it clear that much more effort should go into identifying, counselling, and possibly treating recently seroconverted MSM who have been found to be one of the most important drivers of HIV transmission among MSM. (C) 2012 Wolters Kluwer Health broken vertical bar Lippincott Williams & Wilkin