160 research outputs found
Ergodic vs diffusive decoherence in mesoscopic devices
We report on the measurement of phase coherence length in a high mobility
two-dimensional electron gas patterned in two different geometries, a wire and
a ring. The phase coherence length is extracted both from the weak localization
correction in long wires and from the amplitude of the Aharonov-Bohm
oscillations in a single ring, in a low temperature regime when decoherence is
dominated by electronic interactions. We show that these two measurements lead
to different phase coherence lengths, namely and . This difference
reflects the fact that the electrons winding around the ring necessarily
explore the whole sample (ergodic trajectories), while in a long wire the
electrons lose their phase coherence before reaching the edges of the sample
(diffusive regime).Comment: LaTeX, 5 pages, 4 pdf figures ; v2: revised versio
Quantum Coherence at Low Temperatures in Mesoscopic Systems: Effect of Disorder
We study the disorder dependence of the phase coherence time of quasi
one-dimensional wires and two-dimensional (2D) Hall bars fabricated from a high
mobility GaAs/AlGaAs heterostructure. Using an original ion implantation
technique, we can tune the intrinsic disorder felt by the 2D electron gas and
continuously vary the system from the semi-ballistic regime to the localized
one. In the diffusive regime, the phase coherence time follows a power law as a
function of diffusion coefficient as expected in the Fermi liquid theory,
without any sign of low temperature saturation. Surprisingly, in the
semi-ballistic regime, it becomes independent of the diffusion coefficient. In
the strongly localized regime we find a diverging phase coherence time with
decreasing temperature, however, with a smaller exponent compared to the weakly
localized regime.Comment: 21 pages, 30 figure
The diagnostic value of biomarkers (SteatoTest) for the prediction of liver steatosis
BACKGROUND: Biopsy is the usual gold standard for liver steatosis assessment. The aim of this study was to identify a panel of biomarkers (SteatoTest), with sufficient predictive values, for the non-invasive diagnosis of steatosis in patients with or without chronic liver disease. Biomarkers and panels were assessed in a training group of consecutive patients with chronic hepatitis C and B, alcoholic liver disease, and non-alcoholic fatty liver disease, and were validated in two independent groups including a prospective one. Steatosis was blindly assessed by using a previously validated scoring system. RESULTS: 310 patients were included in the training group; 434 in three validation groups; and 140 in a control group. SteatoTest was constructed using a combination of the 6 components of FibroTest-ActiTest plus body mass index, serum cholesterol, triglycerides, and glucose adjusted for age and gender. SteatoTest area under the ROC curves was 0.79 (SE = 0.03) in the training group; 0.80 (0.04) in validation group 1; 0.86 (0.03) in validation group 2; and 0.72 (0.05) in the validation group 3 – all significantly higher than the standard markers: γ-glutamyl-transpeptidase or alanine aminotransferase. The median SteatoTest value was 0.13 in fasting controls; 0.16 in non-fasting controls; 0.31 in patients without steatosis; 0.39 in grade 1 steatosis (0–5%); 0.58 in grade 2 (6–32%); and 0.74 in grade 3–4 (33–100%). For the diagnosis of grade 2–4 steatosis, the sensitivity of SteatoTest at the 0.30 cut-off was 0.91, 0.98, 1.00 and 0.85 and the specificity at the 0.70 cut-off was 0.89, 0.83, 0.92, 1.00, for the training and three validation groups, respectively. CONCLUSION: SteatoTest is a simple and non-invasive quantitative estimate of liver steatosis and may reduce the need for liver biopsy, particularly in patients with metabolic risk factor
A focus reduction neutralization assay for hepatitis C virus neutralizing antibodies
BACKGROUND/AIM: The role of humoral immunity in hepatitis C virus (HCV) infection is poorly understood. Nevertheless, there is increasing interest in characterizing the neutralizing antibodies in the serum of HCV-infected patients. Focus reduction assays have been widely used to evaluate neutralizing antibody responses against a range of non-cytopathic viruses. Based on the recent development of a HCV cell culture system using the genotype 2 JFH-1-strain, we developed a focus reduction assay for HCV-neutralizing antibodies. METHODS: The focus reduction assay was based on a standard microneutralization assay in which immunostained foci on tissue culture plates are counted. The neutralizing anti-HCV antibodies titers of purified serum immunoglobulin samples from seventy-seven individuals were determined using a 50% focus reduction neutralization assay. Each titer was determined as the log value of the reciprocal antibody dilution that reduced the number of viral foci by 50%. IgG antibodies were first purified from each serum in order to avoid the facilitating effect of HDL on HCV entry. RESULTS: The assay's cut-off using an ELISA and RNA HCV-negative samples was found to be 1.25 log, corresponding to a dilution of 1:18. The assay was compared with a commercial HCV ELISA and exhibited specificity and sensitivity values of 100% and 96.5%, respectively, and good reproducibility (with intra-assay and inter-assay coefficients of variation of 6.7% and 12.6%, respectively). The assay did not show any cross-reactivity with anti-HIV, anti-HBs or heterophile antibody-positive samples. The neutralizing antibodies titers were 2.13 log (1:134) for homologous samples from HCV genotype 2 infected patients harboring the same genotype as JFH-1 and 1.93 log (1:85) for heterologous samples from patients infected by genotypes other than type 2. These results confirm the presence of broadly cross-neutralizing antibodies already reported using the HCV pseudoparticles system. CONCLUSION: This study presents a simple, specific and reproducible cell culture-based assay for determination of HCV-neutralizing antibodies in human sera. The assay should be an important tool for gauging the relationship between the neutralizing antibodies response and viral load kinetics in acutely or chronically infected patients and for investigating the possible eradication or prevention of HCV infection by neutralizing antibodies
Low temperature dephasing in irradiated metallic wires
We present phase coherence time measurements in quasi-one-dimensional Ag
wires implanted with Ag ions with an energy of . The
measurements have been carried out in the temperature range from up to
; this has to be compared with the Kondo temperature of iron in silver,
i.e. , used in recent experiments on dephasing in
Kondo systems\cite{mallet_prl_06,birge_prl_06}. We show that the phase
coherence time is not affected by the implantation procedure, clearly proving
that ion implantation process by itself \emph{does not lead to any extra
dephasing} at low temperature.Comment: 4 pages, 4figure
Longitudinal liver stiffness assessment in patient with chronic hepatitis C undergoing antiviral therapy.
BACKGROUND/AIMS:Liver stiffness (LS) measurement by means of transient elastography (TE) is accurate to predict fibrosis stage. The effect of antiviral treatment and virologic response on LS was assessed and compared with untreated patients with chronic hepatitis C (CHC). METHODS: TE was performed at baseline, and at weeks 24, 48, and 72 in 515 patients with CHC. RESULTS: 323 treated (62.7%) and 192 untreated patients (37.3%) were assessed. LS experienced a significant decline in treated patients and remained stable in untreated patients at the end of study (P<0.0001). The decline was significant for patients with baseline LS ≥ 7.1 kPa (P<0.0001 and P 0.03, for LS ≥ 9.5 and ≥ 7.1 kPa vs lower values, respectively). Sustained virological responders and relapsers had a significant LS improvement whereas a trend was observed in nonresponders (mean percent change -16%, -10% and -2%, for SVR, RR and NR, respectively, P 0.03 for SVR vs NR). In multivariate analysis, high baseline LS (P<0.0001) and ALT levels, antiviral therapy and non-1 genotype were independent predictors of LS improvement. CONCLUSIONS: LS decreases during and after antiviral treatment in patients with CHC. The decrease is significant in sustained responders and relapsers (particularly in those with high baseline LS) and suggests an improvement in liver damage
The treatment response of chronically hepatitis C virus-infected patients depends on interferon concentration but not on interferon gene expression in peripheral blood mononuclear cells.
International audienceThe current treatment of chronic hepatitis C is based on pegylated alpha interferon (PEG-IFN-α) and ribavirin. The aim of this study was to identify biological and clinical variables related to IFN therapy that could predict patient outcome. The study enrolled 47 patients treated with PEG-IFN and ribavirin combined therapy. The interferon concentration was measured in serum by a bioassay. The expression of 93 interferon-regulated genes in peripheral blood mononuclear cells was quantified by real-time quantitative reverse transcription-PCR (RT-PCR) before and after 1 month of treatment. The interferon concentration in the serum was significantly lower in nonresponders than in sustained virological responders. Moreover, a significant correlation was identified between interferon concentration and interferon exposition as well as body weight. The analysis of interferon-inducible genes in peripheral blood mononuclear cells among the genes tested did not permit the prediction of treatment outcome. In conclusion, the better option seems to be to treat patients with weight-adjusted PEG-IFN doses, particularly for patients with high weight who are treated with PEG-IFN-α2a. Although the peripheral blood mononuclear cell samples are the easiest to obtain, the measurement of interferon-inducible genes seems not be the best strategy to predict treatment outcome
DMTs and Covid-19 severity in MS: a pooled analysis from Italy and France
We evaluated the effect of DMTs on Covid-19 severity in patients with MS, with a pooled-analysis of two large cohorts from Italy and France. The association of baseline characteristics and DMTs with Covid-19 severity was assessed by multivariate ordinal-logistic models and pooled by a fixed-effect meta-analysis. 1066 patients with MS from Italy and 721 from France were included. In the multivariate model, anti-CD20 therapies were significantly associated (OR = 2.05, 95%CI = 1.39–3.02, p < 0.001) with Covid-19 severity, whereas interferon indicated a decreased risk (OR = 0.42, 95%CI = 0.18–0.99, p = 0.047). This pooled-analysis confirms an increased risk of severe Covid-19 in patients on anti-CD20 therapies and supports the protective role of interferon
Transferring an optimized TAP-toolbox for the isolation of protein complexes to a portfolio of rice tissues
EVALUATION DES MARQUEURS BIOLOGIQUES DE FIBROSE HEPATIQUE DANS LE BILAN INITIAL DES PATIENTS ATTEINTS D'INFECTION CHRONIQUE PAR LE VIRUS DE L'HEPATITE C
AMIENS-BU Santé (800212102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
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