Shift of zero-dispersion wavelength in bent optical fibers.

The understanding of how bending modifies the dispersion of optical fibers, in particular, the zero-dispersion wavelength (λ0), is essential in the development of compact nonlinear optical devices such as parametric amplifiers, wavelength converters, soliton lasers and frequency comb generators. Typically, substantial variations in the parametric gain and/or conversion efficiency are significant for changes in λ0 of ~0.1 nm, which occur for variations on the bending radius (Rb) of 1 cm or less. Measuring λ0 as a function of bending radius (Rb) is challenging, as it requires detecting changes < 0.1 nm and in short fibers. By using a method based on four-wave mixing (FWM) generated by an incoherent-pump with relatively broad spectrum and a weak laser, we report measurements of λ0 as a function of Rb in a dispersion-shifted fiber with <0.1 nm accuracy on λ0. This method is sensitive enough to measure small variations in λ0 of ~0.04 nm in very short fibers (~20 m). We observe that λ0 increases by 12 nm when Rb is decreased from 10 cm to 1 cm, and a change of 1 nm is obtained for Rb = 3 cm. We also present numerical simulations of the bent fiber that are in good agreement with our measurements, and help us to explain the observations and to predict how high-order dispersion is modified with bending. This study can provide insights for dispersion engineering, in which bending could be used as a tuning, equalization, or tailoring mechanism for λ0, which can be used in the development of compact nonlinear optical devices based on fibers or other bent-waveguide structures.

Osteonecrosis bilateral de cadera tras shock séptico refractario / Bilateral hip osteonecrosis following refractory septic shock

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Tetraparesia fláccida y desconexión del medio tras neumonía bilateral en un paciente alcohólico / Flaccid tetraparesia and disconnection in an alcoholic patient affected by pneumonia

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Effect of zinc supplementation on ethanol-mediated bone alterations.

Ethanol consumption leads to bone alterations, mainly osteoporosis. Ethanol itself may directly alter bone synthesis, but other factors, such as accompanying protein malnutrition--frequently observed in alcoholics, chronic alcoholic myopathy with muscle atrophy, alcohol induced hypogonadism or hypercortisolism, or liver damage, may all contribute to altered bone metabolism. Some data suggest that zinc may exert beneficial effects on bone growth. Based on these facts, we analyzed the relative and combined effects of ethanol, protein malnutrition and treatment with zinc, 227 mg/l in the form of zinc sulphate, on bone histology, biochemical markers of bone formation (osteocalcin) and resorption (urinary hydroxyproline excretion), and hormones involved in bone homeostasis (insulin growth factor 1 (IGF-1), vitamin D, parathormone (PTH), free testosterone and corticosterone), as well as the association between these parameters and muscle fiber area and liver fibrosis, in eight groups of adult Sprague Dawley rats fed following the Lieber de Carli model during 5 weeks. Ethanol showed an independent effect on TBV (F=14.5, p<0.001), causing it to decrease, whereas a low protein diet caused a reduction in osteoid area (F=8.9, p<0.001). Treatment with zinc increased osteoid area (F=11.2, p<0.001) and serum vitamin D levels (F=3.74, p=0.057). Both ethanol (F=45, p<0.001) and low protein diet (F=46.8, p<0.01) decreased serum osteocalcin levels. Ethanol was the only factor independently related with serum IGF-1 (F=130.24, p<0.001), and also showed a synergistic interaction with protein deficiency (p=0.027). In contrast, no change was observed in hydroxyproline excretion and serum PTH levels. No correlation was found between TBM and muscle atrophy, liver fibrosis, corticosterone, or free testosterone levels, but a significant relationship was observed between type II-b muscle fiber area and osteoid area (rho=0.34, p<0.01). Osteoporosis is, therefore, present in alcohol treated rats. Both alcohol and protein deficiency lead to reduced bone formation. Muscle atrophy is related to osteoid area, suggesting a role for chronic alcoholic myopathy in decreased bone mass. Treatment with zinc increases osteoid area, but has no effect on TBV.

Valor de la determinacion de la subunidad beta de gonadotropina corionica en el diagnostico de neoplasias malignas no trofoblasticas. / Value of determination of beta subunit of chorionic gonadotrophin in the diagnosis of malignant non trophoblastic neoplasms

Con el proposito de establecer el valor de la determinacion de la gonadotropina corionica (HCG) como marcador tumoral, se estudiaron 100 pacientes con diagnostico de neoplasia maligna no trofoblastica, incluyendose 40 controles sanos; a todos se les realizo cuantificacion en suero de HCG por medio de la subunidad beta, por radioinmunoalisis (RIA) empleando la tecnica de doble anticuerpo. El 10 por ciento de los casos, presento niveles detectables de dicha hormona; el tipo de neoplasia y la frecuencia de positividad encontrados fueron los siguientes: dermatofibrosarcoma: 100 por ciento, seminoma y teratoma testicular 66.6 por ciento, hepatoma 25 por ciento, carcinoma renal 25 por ciento, carcinoma cervicouterino 14.8 por ciento, carcinoma de mama 14.2 por ciento; en el resto de pacientes como en los casos control, las determinaciones para beta HCG fueron negativas. Se concluye, que aunque la produccion de beta HCG por diversas neoplasias malignas no trofoblasticas, puede variar del 0 al 100 por ciento, la positividad para esta fraccion hormonal en ausencia de embarazo, es sugestiva de algun proceso tumoral