412 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
New Prognostic factors for second-line targeted therapy (TT) in metastatic renal cell carcinoma (mRCC).
No abstract availabl
Viscosities of the Gay-Berne nematic liquid crystal
We present molecular dynamics simulation measurements of the viscosities of
the Gay-Berne phenomenological model of liquid crystals in the nematic and
isotropic phases. The temperature dependence of the rotational and shear
viscosities, including the nonmonotonic behavior of one shear viscosity are in
good agreement with experimental data. The bulk viscosities are significantly
larger than the shear viscosities, again in agreement with experiment.Comment: 11 pages, 4 Postscript figures, Revte
Identification of IMDC intermediate-risk subgroups in patients with metastatic clear-cell renal cell carcinoma (ccRCC).
e16577Background: Majority of patients (pts) with ccRCC at first line (1L) treatment are classified in the IR subgroup according to International Metastatic Renal Cell Carcinoma Database Consortium..
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
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XUV excitation followed by ultrafast non-adiabatic relaxation in PAH molecules as a femto-astrochemistry experiment
Highly excited molecular species are at play in the chemistry of interstellar media and are involved in the creation of radiation damage in a biological tissue. Recently developed ultrashort extreme ultraviolet light sources offer the high excitation energies and ultrafast time-resolution required for probing the dynamics of highly excited molecular states on femtosecond (fs) (1 fs=10−15s) and even attosecond (as) (1 as=10−18 s) timescales. Here we show that polycyclic aromatic hydrocarbons (PAHs) undergo ultrafast relaxation on a few tens of femtoseconds timescales, involving an interplay between the electronic and vibrational degrees of freedom. Our work reveals a general property of excited radical PAHs that can help to elucidate the assignment of diffuse interstellar absorption bands in astrochemistry, and provides a benchmark for the manner in which coupled electronic and nuclear dynamics determines reaction pathways in large molecules following extreme ultraviolet excitation
Ultrafast vibrational relaxation dynamics in XUV-excited Polycyclic Aromatic Hydrocarbon molecules
Interstellar matter and star formatio
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