Measuring self-steepening with the photon-conserving nonlinear Schrödinger equation.

We propose an original, simple, and direct method to measure self-steepening (SS) in nonlinear waveguides. Our proposal is based on results derived from the recently introduced photon-conserving nonlinear Schrödinger equation (NLSE) and relies on the time shift experienced by soliton-like pulses due to SS upon propagation. In particular, a direct measurement of this time shift allows for a precise estimation of the SS parameter. Furthermore, we show that such an approach cannot be tackled by resorting to the NLSE. The proposed method is validated through numerical simulations, in excellent agreement with the analytical model, and results are presented for relevant spectral regions in the near infrared, the telecommunication band, and the mid infrared, and for realistic parameters of available laser sources and waveguides. Finally, we demonstrate the robustness of the proposed scheme against deviations expected in real-life experimental conditions, such as pulse shape, pulse peak power, pulsewidth, and/or higher-order linear and nonlinear dispersion.

Modulation instability in waveguides doped with anisotropic nanoparticles.

We exploit the anisotropic plasmonic behavior of gold nanorods (AuNRs) to obtain a waveguide with a nonlinear coefficient dependent on both the frequency and polarization of incident light. The optical properties of the waveguide are described by an extension of the Maxwell Garnett model to nonlinear optics and anisotropic nanoparticles. Then, we perform a study of modulation instability (MI) in this system by resorting to the recently introduced photon-conserving nonlinear Schrödinger equation (pcNLSE), as the pcNLSE allows us to model propagation in nonlinear waveguides of arbitrary sign and frequency dependence of the nonlinear coefficient. Results show that the anisotropy of the nanorods leads to two well-differentiated MI regimes, a feature that may find applications in all-optical devices.

Modulation instability in waveguides with an arbitrary frequency-dependent nonlinear coefficient.

In this Letter, we present, for the first time, to the best of our knowledge, the modulation instability (MI) gain spectrum of waveguides with an arbitrary frequency-dependent nonlinear coefficient ensuring strict energy and photon-number conservation of the parametric process. This is achieved by starting from a linear stability analysis of the recently introduced photon-conserving nonlinear Schrödinger equation. The derived MI gain is shown to predict some unique features, such as a nonzero gain extending beyond a zero-nonlinearity wavelength and a complex structure of the MI gain spectrum. Analytical results are shown to be in excellent agreement with numerical simulations.

Association between vitamin D deficiency and common variants of Vitamin D binding protein gene among Mexican Mestizo and indigenous postmenopausal women.

PURPOSE: Vitamin D deficiency (VDD) and polymorphisms in the group-specific component (GC) gene are known to be associated in different populations. However, the effects of such genetic variants may vary across different populations. Thus, the objective of this study was to estimate the association between Vitamin D-Binding Protein (VDBP) haplotypes and VDD in mestizo postmenopausal women and Mexican Amerindian ethnic groups. METHODS: This was a cross-sectional study of 726 postmenopausal Mexican women from the Health Workers Cohort Study (HWCS) and 166 postmenopausal women from the Metabolic Analysis in an Indigenous Sample (MAIS) cohort in Mexico. GC polymorphisms (rs7045 and rs4588) were analyzed by TaqMan probes. Serum 25-hydroxyvitamin D [25(OH)D] levels were measured by Chemiluminescent Microparticle Immuno Assay. RESULTS: The prevalence of VDD serum 25(OH)D < 20 ng/mL was 43.7% in mestizo women and 44.6% in indigenous women. In HWCS, the single nucleotide polymorphisms (SNPs) rs7041 and rs4588 were associated with VDD. In addition, women from the HWCS, carrying the haplotypes GC2/2 and GC1f/2 had higher odds of VDD (OR = 2.83, 95% CI 1.14, 7.02; and OR = 2.30, 95% CI 1.40, 3.78, respectively) compared to women with haplotype 1f/1 s. These associations were not statistically significant in the MAIS cohort. CONCLUSIONS: Our results show genetic association of the analyzed SNPs and related haplotypes, on the GC gene, with VDD in mestizo Mexican postmenopausal women. Moreover, a high prevalence of VDD with high genetic variability within the country was observed. Our results support the need for national policies for preventing VDD.

HLA-G as a new tumor biomarker: detection of soluble isoforms of HLA-G in the serum and saliva of patients with colorectal cancer.

INTRODUCTION: Recent medical investigations suggest that HLA-G, due to its tolerogenic properties, can be used as a biomarker in the diagnosis, treatment, and prognosis of different neoplasms. This observational prospective pilot study aims at detecting sHLA-G in the serum and saliva of patients diagnosed with colorectal cancer (CRC). For this purpose, we compared the expression of sHLA-G from patients with a control sample from a healthy population. MATERIALS AND METHODS: Using the specific enzyme-linked immunosorbent assay (ELISA) method, the expression of sHLA-G in the serum and saliva samples from patients affected by CRC (n = 20) and in a control sample (n = 10) were analyzed. RESULTS: The data showed that in patients with CRC, salivary sHLA-G values were significantly higher than in the control group (18.84 U/ml versus 6.3 U/ml, p = 0.036). In addition, higher levels of sHLA-G were observed in the saliva of patients with CRC in more advanced stages, compared with patients in early stages (24.2 U/ml vs. 8.1 U/ml, p = 0.019). A significant correlation was observed between the concentration of sHLA-G in the serum and saliva of the analyzed samples (Spearman correlation 0.7, p = 0.004). CONCLUSIONS: This study demonstrates, for the first time, the possibility of detecting sHLA-G in the saliva of patients with CRC, resulting in a less invasive alternative to venipuncture. Likewise, we propose that sHLA-G could be an attractive molecular target based on its significant high levels in advanced stages.

Simple method for estimating the fractional Raman contribution.

We propose a novel and simple method for estimating the fractional Raman contribution, fR, based on an analysis of a full model of modulation instability (MI) in waveguides. An analytical expression relating fR to the MI peak gain beyond the cutoff power is explicitly derived, allowing for an accurate estimation of fR from a single measurement of the Raman gain spectrum.

Stochastic resonance between dissipative structures in a bistable noise-sustained dynamics.

We study an extended system that without noise shows a monostable dynamics, but when submitted to an adequate multiplicative noise, an effective bistable dynamics arises. The stochastic resonance between the attractors of the noise-sustained dynamics is investigated theoretically in terms of a two-state approximation. The knowledge of the exact nonequilibrium potential allows us to obtain the output signal-to-noise ratio. Its maximum is predicted in the symmetric case for which both attractors have the same nonequilibrium potential value.

Trapping reactions for mobile particles and a trap in the laboratory frame.

We have used a stochastic model to obtain the exact spatial particle density profile for the trapping process A+B-->B in a one-dimensional lattice with a single trap, as seen from the laboratory frame. We obtain the profile for either perfect or imperfect reactions when A particles are immobile, but only for perfect absorption in the general case where both particles are mobile with different diffusivities. This profile is found to be similar to that seen from the reference system attached to the trap, the most noticeable difference being near the origin.

Reaction kinetics of diffusing particles injected into a reactive substrate.

We analyze the kinetics of trapping (A+B-->B) and annihilation (A+B-->0) processes on a one-dimensional substrate with homogeneous distribution of immobile B particles while the A particles are supplied by a localized source. For the imperfect reaction case, we analyze both problems by means of a stochastic model and compare the results with numerical simulations. In addition, we present the exact analytical results of the stochastic model for the case of perfect trapping.

Transverse myelitis as a first manifestation of systemic lupus erythematosus: a case report.

Transverse myelitis as a first manifestation of systemic lupus erythematosus (SLE) is very uncommon. No pathognomonic clinical or biochemical characteristics exist, and therefore an early diagnosis is often difficult. Therapy with intravenous pulses of methylprednisolone and cyclophosphamide has been shown to improve the prognosis. However, morbidity and mortality rates in transverse myelitis are still high due to the fact that complications such as opportunistic infections and pulmonary embolism are still frequent causes of death. We report a woman with relapsing transverse myelitis which was the first manifestation of SLE. A good response to pulse methylprednisolone and cyclophosphamide therapy was obtained but she died later as a result of a pulmonary embolism. We conclude that intravenous pulse methylprednisolone and cyclophosphamide therapy improve the prognosis of transverse myelitis associated with SLE but that a careful follow-up is needed to avoid complications due to the illness itself or secondary to the therapy.