241 research outputs found
On negative higher-order Kerr effect and filamentation
As a contribution to the ongoing controversy about the role of higher-order
Kerr effect (HOKE) in laser filamentation, we first provide thorough details
about the protocol that has been employed to infer the HOKE indices from the
experiment. Next, we discuss potential sources of artifact in the experimental
measurements of these terms and show that neither the value of the observed
birefringence, nor its inversion, nor the intensity at which it is observed,
appear to be flawed. Furthermore, we argue that, independently on our values,
the principle of including HOKE is straightforward. Due to the different
temporal and spectral dynamics, the respective efficiency of defocusing by the
plasma and by the HOKE is expected to depend substantially on both incident
wavelength and pulse duration. The discussion should therefore focus on
defining the conditions where each filamentation regime dominates.Comment: 22 pages, 11 figures. Submitted to Laser physics as proceedings of
the Laser Physics 2010 conferenc
PAH under XUV excitation: an ultrafast XUV- photochemistry experiment for astrophysics
International audienceUnderstanding processes induced by XUV excitation of Polycyclic Aromatic Hydrocarbons (PAHs) is at the heart of molecular astrophysics, which aims at understanding molecular evolution in interstellar media. We used ultrashort XUV pulses to produce highly excited PAHs cations. The photo-induced dynamics is probed using a pump-probe XUV-IR spectroscopy. By studying PAH from small (naphthalene) to large (hexabenzocoronene) PAHs, we show that the dynamic is governed by the large density of states, in which many-body quantum effects are dominant
Phase-ordering dynamics of the Gay-Berne nematic liquid crystal
Phase-ordering dynamics in nematic liquid crystals has been the subject of
much active investigation in recent years in theory, experiments and
simulations. With a rapid quench from the isotropic to nematic phase a large
number of topological defects are formed and dominate the subsequent
equilibration process. We present here the results of a molecular dynamics
simulation of the Gay-Berne model of liquid crystals after such a quench in a
system with 65536 molecules. Twist disclination lines as well as type-1 lines
and monopoles were observed. Evidence of dynamical scaling was found in the
behavior of the spatial correlation function and the density of disclination
lines. However, the behavior of the structure factor provides a more sensitive
measure of scaling, and we observed a crossover from a defect dominated regime
at small values of the wavevector to a thermal fluctuation dominated regime at
large wavevector.Comment: 18 pages, 16 figures, animations available at
http://www.physics.brown.edu/Users/faculty/pelcovits/lc/coarsening.htm
Occult Hepatitis B Infection in Patients With Cryptogenic Liver Cirrhosis in Southwest of Iran
Background: Chronic hepatitis B virus (HBV) infection has a broad spectrum of manifestation, ranging from silent carrier state to
advanced cirrhosis and hepatocellular carcinoma. The persistence of HBV DNA in serum and hepatocytes of the cirrhotic patient could be
detected by molecular techniques in spite of negative HBV serologic markers.
Objectives: This case-control study was designed to evaluate the prevalence of occult HBV infection (OBI) in patients with cryptogenic liver
cirrhosis in comparison with healthy subjects.
Patients and Methods: Of 165 patients with liver cirrhosis, 50 consecutive patients with cryptogenic cirrhosis and 80 healthy individual
without any risk factors as a control group were enrolled in this study. Their sera were tested for HBV DNA using nested PCR method.
Results: Of 50 patients with cryptogenic cirrhotic, 36 (72%) were male. The mean age of patients was 53.34 ± 14.73 years; 80 healthy subjects
were selected as control group with mean age of 32.65 ± 8.51 years; 7 (14%) of the patients with cryptogenic cirrhosis showed positive HBV
DNA by PCR, while HBV DNA was negative for the control group (P = 0.0001); 4 (57%) cases with positive HBV shown by PCR were negative for
anti-HBc and anti-HBs tests. The mean level of transaminases was significantly higher in patients with cirrhosis. There were no significant
differences in demographic parameters, transaminases level and degree of hepatic failure among cirrhotic patients with and without OBI.
Conclusions: The prevalence of OBI was relatively high in patients with cryptogenic cirrhosis. OBI was found among the patients above 40
years old. Prospective cohort studies are needed to evaluate the clinical significance of OBI
Ultrafast vibrational relaxation dynamics in XUV-excited Polycyclic Aromatic Hydrocarbon molecules
Interstellar matter and star formatio
Ultrafast dynamics of correlation bands following XUV molecular photoionization
Interstellar matter and star formatio
Event-Free Survival, a Prostate-Specific Antigen-Based Composite End Point, Is Not a Surrogate for Overall Survival in Men With Localized Prostate Cancer Treated With Radiation
PURPOSE: Recently, we have shown that metastasis-free survival is a strong surrogate for overall survival (OS) in men with intermediate- and high-risk localized prostate cancer and can accelerate the evaluation of new (neo)adjuvant therapies. Event-free survival (EFS), an earlier prostate-specific antigen (PSA)-based composite end point, may further expedite trial completion. METHODS: EFS was defined as the time from random assignment to the date of first evidence of disease recurrence, including biochemical failure, local or regional recurrence, distant metastasis, or death from any cause, or was censored at the date of last PSA assessment. Individual patient data from trials within the Intermediate Clinical Endpoints in Cancer of the Prostate-ICECaP-database with evaluable PSA and disease follow-up data were analyzed. We evaluated the surrogacy of EFS for OS using a 2-stage meta-analytic validation model by determining the correlation of EFS with OS (patient level) and the correlation of treatment effects (hazard ratios [HRs]) on both EFS and OS (trial level). A clinically relevant surrogacy was defined a priori as an R2 ≥ 0.7. RESULTS: Data for 10,350 patients were analyzed from 15 radiation therapy-based trials enrolled from 1987 to 2011 with a median follow-up of 10 years. At the patient level, the correlation of EFS with OS was 0.43 (95% CI, 0.42 to 0.44) as measured by Kendall's tau from a copula model. At the trial level, the R2 was 0.35 (95% CI, 0.01 to 0.60) from the weighted linear regression of log(HR)-OS on log(HR)-EFS. CONCLUSION: EFS is a weak surrogate for OS and is not suitable for use as an intermediate clinical end point to substitute for OS to accelerate phase III (neo)adjuvant trials of prostate cancer therapies for primary radiation therapy-based trials
UDP-glucuronosyltransferase UGT1A7 genetic polymorphisms in hepatocellular carcinoma: a differential impact according to seropositivity of HBV or HCV markers?
<p>Abstract</p> <p>Background:</p> <p>We conducted a case-control study to evaluate the role of UDP-glucuronosyltransferase 1A7 (UGT1A7) polymorphisms in the onset of hepatocellular carcinoma (HCC).</p> <p>Methods:</p> <p>The study included 165 patients with HCC, 134 with cirrhosis and 142 controls without liver disease, matched for age and hospital. All were men younger than 75 years. HCC and cirrhosis patients were stratified according to time since cirrhosis diagnosis.</p> <p>Results:</p> <p>We found a positive association between the UGT1A7*3/*3 genotype and HCC when the comparison was restricted to patients whose disease was of viral origin [OR = 3.4 (0.3–45)] but a negative association when it included only alcoholic patients [OR = 0.1 (0.02–0.6), p = 0.01].</p> <p>Conclusion:</p> <p>Our study shows that UGT1A7 may play a role in hepatocellular carcinogenesis and that this role may differ according to the primary cause of the cirrhosis.</p
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