Ultrashort laser induced spatial redistribution of silver species and nano-patterning of etching selectivity in silver-containing glasses.

Femtosecond laser-induced spatial redistribution of silver species (ions, clusters, and hole centers) in a silver-containing phosphate glass is investigated by correlative means of near-field scanning optical microscopy (NSOM) images, numerical simulations, chemical micro-probe analysis, and nanoscale spatial profiles after soft etching. In particular, we found that the chemical etching selectivity for nanoscale patterning is strongly dependent upon the irradiation of femtosecond laser due to the spatial redistribution of silver species within the affected area. These results strongly indicate that controlling the distribution of silver species by femtosecond laser irradiation may open new routes for surface nanoscale chemical and/or spatial patterning for the fabrication of 2D surface photonic crystals.

Laser writing of nonlinear optical properties in silver-doped phosphate glass.

The formation of both local second- and third-harmonic generations (SHG and THG) induced by a train of femtosecond laser pulses in silver-doped phosphate glasses is addressed. Based on modeling calculations, including various diffusion and kinetic processes, THG is shown to result from the formation of silver clusters. The latter organize into a ring-shape structure, leading to the emergence of a static electric field. By breaking the glass centro-symmetry, this field gives rise to a local effective second-order susceptibility, inducing SHG. Both theoretically predicted SHG and THG evolutions with respect to the number of pulses in the train are in good agreement with experimental observations. In particular, the observed reaching of a maximum in the nonlinear optical responses after a few thousands of pulses is explained by the competition of various physical processes. A cooling of the glass is shown to improve the process efficiency of the laser writing of second-order nonlinearity.

Satellite cells isolated from aged or dystrophic muscle exhibit a reduced capacity to promote angiogenesis in vitro.

Deficits in skeletal muscle function exist during aging and muscular dystrophy, and suboptimal function has been related to factors such as atrophy, excessive inflammation and fibrosis. Ineffective muscle regeneration underlies each condition and has been attributed to a deficit in myogenic potential of resident stem cells or satellite cells. In addition to reduced myogenic activity, satellite cells may also lose the ability to communicate with vascular cells for coordination of myogenesis and angiogenesis and restoration of proper muscle function. Objectives of the current study were to determine the angiogenic-promoting capacity of satellite cells from two states characterized by dysfunctional skeletal muscle repair, aging and Duchenne muscular dystrophy. An in vitro culture model composed of satellite cells or their conditioned media and rat adipose tissue microvascular fragments (MVF) was used to examine this relationship. Microvascular fragments cultured in the presence of rat satellite cells from adult muscle donors (9-12 month of age) exhibited greater indices of angiogenesis (endothelial cell sprouting, tubule formation and extensive branching) than MVF co-cultured with satellite cells from aged muscle donors (24 month of age). We sought to determine if the differential degree of angiogenesis we observed in the co-culture setting was due to soluble factors produced by each satellite cell age group. Similar to the co-culture experiment, conditioned media produced by adult satellite cells promoted greater angiogenesis than that of aged satellite cells. Next, we examined differences in angiogenesis-stimulating ability of satellite cells from 12 mo old MDX mice or age-matched wild-type mice. A reduction in angiogenesis activity of media conditioned by satellite cells from dystrophic muscle was observed as compared to healthy muscle. Finally, we found reduced gene expression of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) in both aged and dystrophic satellite cells compared to their adult and normal counterparts, respectively. These results indicate that functional deficits in satellite cell activities during aging and diseased muscle may extend to their ability to communicate with other cells in their environment, in this case cells involved in angiogenesis.

Thermal properties and surface reactivity in simulated body fluid of new strontium ion-containing phosphate glasses.

In this paper, we investigate the effect of SrO substitution for CaO in 50P2O5-10Na2-(40-x)CaO-xSrO glass system (x from 0 to 40) on the thermal and structural properties and also on the glass reactivity in simulated body fluid (SBF) in order to find new glass candidates for biomedical glass fibers. The addition of SrO at the expense of CaO seems to restrain the leaching of phosphate ions in the solution limiting the reduction of the solution pH. We observed the formation of an apatite layer at the surface of the glasses when in contact with SBF. SrO and MgO were found in the apatite layer of the strontium ion-containing glasses, the concentration of which increases with an increase of SrO content. We think that it is the presence of MgO and SrO in the layer which limits the leaching of phosphate in the solution and thus the glass dissolution in SBF.

Two-photon excited fluorescence in the LYB:Eu monoclinic crystal: towards a new scheme of single-beam dual-voxel direct laser writing in crystals.

We report on two-photon excited fluorescence in the oriented Eu(3+)doped LYB monoclinic crystal under femtosecond laser tight focusing. Due to spatial walk-off, the two polarization modes of the incident femtosecond beam simultaneously provide the independent excitation of two distinct focuses, leading to a single-beam dual-voxel nonlinear excitation of fluorescence below material modification threshold. These observations emphasize on the anisotropy of both two-photon absorption as well as fluorescence emission. They demonstrate the localized control of the nonlinear energy deposit, thanks to the adjustment of both the input power and polarization, by properly balancing the injected energy in each voxel. Such approach should be considered for future direct laser writing of waveguides in propagation directions out of the dielectric axes, so as to optimally cope with the highly probable anisotropy of laser-induced material modification thresholds in these crystals. These results open new ways for further potential developments in direct laser writing as the simultaneous inscription of double-line structures for original waveguides processes.

Modified electrical transport probe design for standard magnetometer.

Making electrical transport measurements on a material is often a time consuming process that involves testing a large number of samples. It is thus inconvenient to wire up and rewire samples onto a sample probe. We therefore present a method of modifying Quantum Design's MPMS SQUID magnetometer transport probe that simplifies the process of sample mounting. One of the difficulties to overcome is the small diameter of the sample space. A small socket is designed and mounted on the probe so that various samples mounted on individual headers can be readily exchanged in the socket. We also present some test results on the topological insulator Bi(2)Te(2)Se using the modified probe.

Agreement and association between the phase angle and parameters of nutritional status assessment in surgical patients.

BACKGROUND & AIMS: To assess the agreement and the association between phase angle (PA) and parameters of nutritional status in surgical patients. METHODS: This was a cross-sectional study that involved 98 patients admitted for elective gastrointestinal or hernia repair surgery. The risk and nutritional status were evaluated through Nutritional Risk Screening 2002 (NRS 2002), Subjective Global Assessment (SGA), Body Mass Index (BMI) and Total Lymphocytes Count (TLC). These assessments were compared with the mean standardized PA (SPA), obtained by Bioelectrical Impedance Analysis (BIA). Statistical analysis included kappa coefficient, Student's t-test, Mann-Whitney test, and the construction of a ROC Curve. RESULTS: The highest kappa agreement was obtained between the SPA and the SGA (0.27; CI95% 0.06-0.48). Malnourished patients diagnosed by NRS 2002, SGA and TLC had a significantly lower mean SPA as compared to those who were well-nourished. A cut-off point of 0.8 for SPA showed 82.6% (CI95% 65.0-100.0%) sensitivity and 40.6% (CI95% 23.0-58.2%) specificity. CONCLUSION: The SPA presented weak agreement with the methods of nutritional assessment, as well as low specificity, and could not be recommended as a marker of nutritional status, despite the fact that the lowest values for SPA were found in malnourished patients.

Agreement and association between the phase angle and parameters of nutritional status assessment in surgical patients / Concordancia y asociación entre el ángulo de fase y los parámetros de evaluación del estado nutricional en pacientes quirúrgicos

Background & aims: To assess the agreement and the association between phase angle (PA) and parameters of nutritional status in surgical patients. Methods: This was a cross-sectional study that involved 98 patients admitted for elective gastrointestinal or hernia repair surgery. The risk and nutritional status were evaluated through Nutritional Risk Screening 2002 (NRS 2002), Subjective Global Assessment (SGA), Body Mass Index (BMI) and Total Lymphocytes Count (TLC). These assessments were compared with the mean standardized PA (SPA), obtained by Bioelectrical Impedance Analysis (BIA). Statistical analysis included kappa coefficient, Student's t-test, Mann-Whitney test, and the construction of a ROC Curve. Results: The highest kappa agreement was obtained between the SPA and the SGA (0.27; CI95% 0.06-0.48). Malnourished patients diagnosed by NRS 2002, SGA and TLC had a significantly lower mean SPA as compared to those who were well-nourished. A cut-off point of 0.8 for SPA showed 82.6% (CI95% 65.0-100.0%) sensitivity and 40.6% (CI95% 23.0-58.2%) specificity. Conclusion: The SPA presented weak agreement with the methods of nutritional assessment, as well as low specificity, and could not be recommended as a marker of nutritional status, despite the fact that the lowest values for SPA were found in malnourished patients (AU)

Introducción y objetivos: Evaluar la concordancia y asociación entre el ángulo de fase (AF) y los parámetros del estado nutricional en pacientes quirúrgicos. Métodos: Se desarrolló un estudio de sección transversal con 98 pacientes admitidos para una cirugía gastrointestinal o de hernia. Se evaluó el riesgo y el estado nutricional a través del Rastreo de Riesgo Nutricional 2002 (RRN 2002), la Valoración Global Subjetiva (VGS), el Índice de Masa Corporal (IMC) y el Recuento Total de Linfocitos (RTL). Estos métodos fueron comparados con la media del AF estandarizado (AFE) obtenido por medio del Análisis de Impedancia Bioeléctrica (AIB). Los Análisis estadísticos incluyeron el coeficiente kappa , el test t Student, el test de Mann-Whitney, y la construcción de la Curva ROC. Resultados: La concordancia kappa más alta se obtuvo entre el AFE y el VGS (0,27; CI95% 0,06-0,48). Los pacientes desnutridos diagnosticados por el RRN 2002, VGS y el RTL, tuvieron una media estadística de AFE significativamente menor comparado con aquellos que estaban bien nutridos. Un punto de corte del 0.8 para un AFE mostró 82,6% (CI95% 65,0-100,0%) de sensibilidad y 40,6% (CI95% 23,0-58,2%) de especificidad. Conclusión: El AFE presentó una concordancia débil con los métodos de evaluación nutricional, así como una baja especificidad y no pudo ser recomendado como un indicador del estado nutricional, a pesar de que los valores más bajos del AFE fueron encontrados en pacientes desnutridos (AU)

Coherent acoustic vibration of metal nanoshells.

Using time-resolved pump-probe spectroscopy, we have performed the first investigation of the vibrational modes of gold nanoshells. The fundamental isotropic mode launched by a femtosecond pump pulse manifests itself in a pronounced time-domain modulation of the differential transmission probed at the frequency of nanoshell surface plasmon resonance. The modulation amplitude is significantly stronger, and the period is longer than that in a gold nanoparticle of the same overall size, in agreement with theoretical calculations. This distinct acoustical signature of nanoshells provides a new and efficient method for identifying these versatile nanostructures and for studying their mechanical and structural properties.

Photodarkening and photobleaching of an ytterbium-doped silica double-clad LMA fiber.

We studied the temporal evolution of the photodarkening effect in an Yb-doped silica LMA fiber. The absorption spectra exhibit an increase in absorption in the visible and in the near infrared spectral range when the fiber is exposed to pump light around 980 nm. We show the influence of the photodarkening on the cw lasing properties of the fiber, and demonstrate photobleaching of the same fiber by exposure to UV light at 355 nm. The corresponding absorption spectra and lasing performances are shown and are entirely comparable to those of a new fiber.