Z-scan for thin media with more than one nonlocal nonlinear response.

A model to characterize the response of a thin media that can exhibit more than one nonlocal nonlinear response when it is illuminated with a Gaussian beam in a z-scan experiment is proposed. The model considers that these nonlocal contributions can be treated as independent contributions in the refractive or absorptive nonlinear response. Numerical results for two nonlocal nonlinear contributions with different magnitudes between them are presented. Experimental results obtained from a hydrogenated amorphous silicon sample are used to corroborate this model.

Far-field diffraction patterns by a thin nonlinear absorptive nonlocal media.

In this work we present numerical results of the far field intensity distributions obtained for a Gaussian beam after crossing a thin nonlinear nonlocal material that exhibit nonlinear refraction and absorption. The distributions are obtained for different positions along the Z axis and different signs of the nonlinear absorption. The results demonstrate that the far field intensity patterns obtained for strong nonlocal media are more affected by the presence of the nonlinear absorption than weak nonlocal media.

Analytical expressions for Z-scan with arbitrary phase change in thin nonlocal nonlinear media.

Analytical expressions for the normalized transmittance of a thin material with simultaneous nonlocal nonlinear change in refraction and absorption are reported. Gaussian decomposition method was used to obtain the formulas that are adequate for any magnitude of the nonlinear changes. Particular cases of no locality are compared with the local case. Experimental results are reproduced (fitted) with the founded expressions.

New asymmetric propagation invariant beams obtained by amplitude and phase modulation in frequency space.

In this paper, we demonstrate, numerically and experimentally that using the mask-lens setup used by Durnin to generate Bessel beams Durnin [Phys. Rev. Lett. 58, 1499 (1987)], it is possible to generate different kinds of propagation invariant beams. A modification in the amplitude or phase of the field that illuminates the annular slit is proposed that corresponds to modulation in frequency space. In particular, we characterize the new invariant beams that were obtained by modulating the amplitude of the annular mask and when the incident field was modulated with a one-dimensional quadratic or cubic phase. Experimental results using an amplitude mask are shown in order to corroborate the numerical predictions.

Nonlocal nonlinear refractive index of gold nanoparticles synthesized by ascorbic acid reduction: comparison of fitting models.

In this paper, the nonlinear refractive index of colloidal gold nanoparticles under continuous wave illumination is investigated with the z-scan technique. Gold nanoparticles were synthesized using ascorbic acid as reductant, phosphates as stabilizer and cetyltrimethylammonium chloride (CTAC) as surfactant agent. The nanoparticle size was controlled with the CTAC concentration. Experiments changing incident power and sample concentration were done. The experimental z-scan results were fitted with three models: thermal lens, aberrant thermal lens and the nonlocal model. It is shown that the nonlocal model reproduces with exceptionally good agreement; the obtained experimental behaviour.

Waveguide properties of the asymmetric collision between two bright spatial solitons in Kerr media.

In this work, we numerically characterize the waveguide properties of the asymmetric collision between two bright spatial solitons in a nonlinear Kerr media. The results demonstrate that the energy carried by a probe beam guided by one soliton can be transferred after the collision to the waveguide created by the other soliton depending on the initial separation between the solitons, the angle of their collision, and in some cases, the particular soliton that initially guides the probe beam. The observed behavior is equivalent to that obtained for the symmetrical collision when there is an initial relative phase between the solitons.

Far field intensity distributions due to spatial self phase modulation of a Gaussian beam by a thin nonlocal nonlinear media.

In this work we present a simple model that can be used to calculate the far field intensity distributions when a Gaussian beam cross a thin sample of nonlinear media but the response can be nonlocal.

Polarization-controlled contrasted images using dye-doped nematic liquid crystals.

We explore the polarization dependence of the nonlinear response of a planar nematic liquid crystal cell doped with 1% wt of methyl red dye. The results obtained show that the refractive index change can be switched from a positive value to a negative one as the polarization of the beam changes from parallel to perpendicular with respect to the rubbing direction. This property is exploited in a phase contrast system, where a dynamic phase filter is photoinduced in a liquid crystal cell placed in the system's Fourier plane. Real-time contrast inversion in the resulting images is demonstrated.

Varón de 46 años con clínica de insuficiencia cardíaca / 46-year old male patient with heart failure symptoms

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Expression of heterologous genes from an IRES translational cassette in replication competent murine leukemia virus vectors.

We describe replication competent retroviruses capable of expressing heterologous genes during multiple rounds of infection. An internal ribosome entry site (IRES) from encephalomyocarditis virus was inserted in the U3 region of Akv- and SL3-3-murine leukemia viruses (MLV) to direct translation of neo or the enhanced green fluorescence protein gene (EGFP). Akv-MLV's with IRES-neo and IRES-EGFP cassettes replicated with titers of about 10(6) infectious units/ml while SL3-3-MLV with IRES-neo gave about 10(3)-fold lower titers. Interestingly, RNA analysis showed a drastic reduction in the amount of spliced env mRNA for the SL3-3 derived vector relative to the Akv derived vectors, seemingly contributing to its low replication capacity. The EGFP expressing Akv-MLV was genetically stable for multiple rounds of infection; marker-cassette deletion revertants appeared after several replication rounds and these revertants only slowly became dominant in the virus population.

Differential effects of IL-1 beta and ibuprofen after endotoxic challenge in mice.

Interleukin-1 (IL-1) and ibuprofen modulate the host response in different models after endotoxic challenge. A comparative study was made between the two drugs, as they were jointly administered, to explore a potentiation of their therapeutic effects. Endotoxic challenge was provoked in CBA/H mice with lipopolysaccharide (LPS) from Escherichia coli (125 mg/kg), with administration of recombinant murine IL-1 beta (80 ng/mouse) 24 hr pre-LPS. Two doses of ibuprofen (1 mg/kg) were administered 1 hr before and 30 min after the septic challenge. Serum levels of IL-1 alpha, tumor necrosis factor-alpha (TNF alpha), and interleukin-6 (IL-6) were determined 1,2, and 4 hr, post-LPS, and prostaglandin E2 (PGE2) urine levels 4,8, and 12 hr post-LPS, and a comparative mortality study was performed. IL-1 beta treatment provoked a reduction of IL-1 alpha, TNF alpha, and IL-6 without affecting PGE2, while ibuprofen provoked a later increase of IL-1 alpha, TNF alpha, and IL-6, with a decrease of PGE2. Both drugs caused a notable enhancement of survival, with no difference between them, but their combined administration caused no improvement. We conclude that both drugs exert a similar therapeutic effect in endotoxic shock by different mechanisms.

[Effect of several inhalation anesthetics on ectopic cardiac automaticity. Intervention of the calcium ion]. / Efecto de diferentes anestésicos inhalatorios sobre el automatismo cardíaco ectópico. Intervención del ion calcio.

The effect of halothane, enflurane and isoflurane (at concentrations ranging from 0.1 v/v% to 5 v/v%) on ventricular automaticity induced by a local injury, has been studied in the isolated right ventricle of the rat. Both, halothane and isoflurane, effectively reduces ventricular frequency at all concentrations tested. On the contrary, enflurane (0.3, 0.5 and 1 v/v%) increases ventricular automaticity. The effect of enflurane was either potentiated or reduced respectively in the presence of lower or higher calcium concentrations.