Search results for "S-phase"
showing 10 items of 56 documents
Measurement of high order Kerr refractive index of major air components
2009
International audience; We measure the instantaneous electronic nonlinear refractive index of N2 , O2 , and Ar at room temperature for a 90 fs and 800 nm laser pulse. Measurements are calibrated by post-pulse molecular alignment through a polarization technique. At low intensity, quadratic coefficients n2 are determined. At higher intensities, a strong negative contribution with a higher nonlinearity appears, which leads to an overall negative nonlinear Kerr refractive index in air above 26 TW/cm2 .
Incoherent solitons and condensation processes
2006
International audience; We study the nonlinear interaction of partially incoherent nonlinear optical waves. We show that, in spite of the incoherence of the waves, coherent phase effects may play a relevant role during the propagation, in contrast with the usual wave turbulence description of the interaction. These nonlinear phase effects may lead the system to unexpected processes of self-organization, such as condensation, or incoherent soliton generation in instantaneous response nonlinear media. Such self-organization processes may be characterized by a reduction of the non-equilibrium entropy, which violates the Boltzmann's H-theorem of entropy growth inherent to the wave turbulence th…
Gas-phase hydrogenation of propionitrile on copper-lanthanide oxides
2009
Abstract The hydrogenation of propionitrile on copper-lanthanide oxide catalysts (2Cu·CeO 2 and 4Cu·Ln 2 O 3 (Ln = La, Pr, Nd)) was studied in the gas phase. The activity of the catalysts varies with the lanthanide in the order 2Cu·CeO 2 > 4Cu·Pr 2 O 3 > 4Cu·La 2 O 3 ≥ 4Cu·Nd 2 O 3 , while the activation energies varies in the opposite order, except for 2Cu·CeO 2 . The main product was the primary amine, n -propylamine. The formation of the unstable imine CH 3 CH 2 N CHCH 3 as a major product over 2Cu·CeO 2 seems to be consistent with the acidity of the catalyst. The catalysts were more selective than conventional copper impregnation catalysts, Cu (10 wt.%) on SiO 2 , La 2 O 3 or CeO 2 ,…
DNA aneuploidy and high proliferative activity but not K-ras-2 mutations as independent predictors of clinical outcome in operable gastric carcinoma:…
2001
BACKGROUND The prognostic value of DNA ploidy, S-phase fraction (SPF) and K-ras-2 mutations in gastric carcinoma (GC) has not yet been clearly defined. The aim of this study was to clarify the association between biomolecular variables, tumor characteristics, and clinical outcome in GC patients. METHODS Resected specimens from a consecutive series of 69 patients with GC who underwent potentially curative surgery were studied prospectively. DNA ploidy and SPF were assessed by flow cytometry on multiple frozen tumor samples, whereas K-ras-2 mutations were detected by polymerase chain reaction followed by single-strand conformation polymorphism. All the patients involved in this study were fol…
Modulational instability processes in optical isotropic fibers under dual-frequency pumping
2001
Experiments are presented showing that under dual-frequency, circular polarization pumping, a host modulational instability processes can be generated in a single isotropic fiber, by carefully tuning the frequency spacing between the pumps.
A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland
2015
Atmospheric concentrations of nitrous acid (HONO), one of the major precursors of the hydroxyl radical (OH) in the troposphere, significantly exceed the values predicted by the assumption of a photostationary state (PSS) during daytime. Therefore, additional sources of HONO were intensively investigated in the last decades. This study presents budget calculations of HONO based on simultaneous measurements of all relevant species, including HONO and OH at two different measurement heights, i.e. 1 m above the ground and about 2 to 3 m above the canopy (24 m above the ground), conducted in a boreal forest environment. We observed mean HONO concentrations of about 6.5 × 108 molecules cm−3 (26 p…
Self-phase modulation-based 2R regenerator including pulse compression and offset filtering for 42.6 Gbit/s RZ-33% transmission systems
2009
International audience; We report on the experimental and theoretical study of a self-phase-modulation-based regenerator at 42.6 Gbit/s with a return-to-zero 33% format. We point out some detrimental effects such as intrachannel interactions and Brillouin scattering. An efficient solution, relying on a self-phase-modulation-based pulse compressor in combination with the regenerator, is proposed to overcome these detrimental phenomena. The experimental demonstration shows the effectiveness of a wavelength-transparent regenerator at 42.6 Gbit/s with a sensitivity-improvement of more than 5 dB and an eye-opening improvement of 2.3 dB in a back-to-back configuration, as well as a 10 times maxim…
Collisions between similaritons in optical fiber amplifiers
2009
We consider the self-similar amplification of two optical pulses of different wavelengths in order to investigate the effects of a collision between two similaritons. We theoretically demonstrate that similaritons are stable against collisions in a Raman amplifier: similaritons evolve separately in the amplifier without modification of the scaling of their temporal width and chirp and by conserving their velocities, only interact during their overlap and regain their parabolic form after collision. We show both theoretically and experimentally that the collision of two similaritons induces a sinusoidal modulation inside the overlap region, whose frequency decreases during the interaction. T…
Regenerative 40 Gbit/s wavelength converter based on similariton generation.
2005
International audience; We present an all-optical regeneration technique based on spectral filtering of self-similar parabolic pulses (similaritons). In particular, we demonstrate numerically and experimentally that ghost pulses, which occur in the zero bit slots of telecommunication pulse trains, can be effectively suppressed. These results are obtained with a 40 Gbit/s pulse train.
Demonstration of Stimulated-Raman-scattering suppression in optical fibers in a multifrequency pumping configuration
1999
International audience; We analyze the stimulated-Raman-scattering-(SRS) process induced by a linearly polarized multifrequency pump field in a normally dispersive single-mode fiber. We show, by theoretical analysis and numerical simulations, that the SRS process may be either controlled by switching all the generated Stokes radiations to the lowest-frequency pump or suppressed for all the frequency components of the pump field. The suppression process is achieved by an appropriate choice of the frequency separation between the pumps and a particular power distribution among the frequency components of the pump field. We present experimental spectra showing the effectiveness of this suppres…