LiNbO3 optical waveguides formed in a new proton source

Proton-exchanged planar waveguides have been fabricated on Z-cut and X-cut lithium niobate crystals by using a new proton source formed by a mixture of benzoic and adipic acids. Waveguide index profiles and optical characteristics have been obtained at different values of the adipic-benzoic acid concentration ratio. The samples have been structurally characterized by Raman and infrared (IR) absorption spectroscopy and double-crystal X-ray diffraction. Good quality samples have been fabricated by using 30 mol% ratio dilution, showing very low scattering levels (<0.1 dB/cm), relatively high electrooptic coefficient (r₃₃=0.88 pm/V), and low relative percentage of interstitial protons (26%). The main factor limiting the waveguide optical properties is the substitutional-interstitial proton ratio, which can be easily controlled to produce good quality waveguides. A demonstration of the repeatability of the exchange process in the acid mixture is also provided     

The Role of Testosterone in the Elderly: What Do We Know?

Testosterone is the most important hormone in male health. Aging is characterized by testosterone deficiency due to decreasing testosterone levels associated with low testicular production, genetic factors, adiposity, and illness. Low testosterone levels in men are associated with sexual dysfunction (low sexual desire, erectile dysfunction), reduced skeletal muscle mass and strength, decreased bone mineral density, increased cardiovascular risk and alterations of the glycometabolic profile. Testosterone replacement therapy (TRT) shows several therapeutic effects while maintaining a good safety profile in hypogonadal men. TRT restores normal levels of serum testosterone in men, increasing libido and energy level and producing beneficial effects on bone density, strength and muscle as well as yielding cardioprotective effects. Nevertheless, TRT could be contraindicated in men with untreated prostate cancer, although poor findings are reported in the literature. In addition, different potential side effects, such as polycythemia, cardiac events and obstructive sleep apnea, should be monitored. The aim of our review is to provide an updated background regarding the pros and cons of TRT, evaluating its role and its clinical applicability in different domains.     

Scattering effect in optical microring resonators

In this paper we present an investigation of detrimental effects due to roughness-induced scattering and their influence on the properties of both passive and active optical microring resonators. The theoretical analysis involves different mathematical models, such as the volume current method to determine the scattering influence, and the quantum mechanical approach based on density matrix to investigate the active ring dynamics.     

Single-mode and polarization-independent silicon-on-insulator waveguides with small cross section

The fabrication restrictions that must be imposed on the geometry of optical waveguides to make them behave as single-mode devices are well known for relatively large waveguides, with shallow etch depth. However, the restrictions for small waveguides (/spl sim/1 /spl mu/m or less in cross section) are not well understood. Furthermore, it is usually a requirement that these waveguides are polarization independent, which further complicates the issues. This paper reports on the simulations of the conditions for both single-mode behavior and polarization independence, for small and deeply etched silicon-on-insulator (SOI) waveguides. The aim is to satisfy both conditions simultaneously. The results show that at larger waveguide widths, waveguide etch depth has little effect on the mode birefringence because the transverse-electric (TE) mode (horizontal-polarized mode) is well confined under the rib region. However, at smaller rib widths, the etch depth has a large influence on birefringence. An approximate equation relating the rib-waveguide width and etch depth to obtain polarization-independent operation is derived. It is possible to achieve single-mode operation at both polarizations while maintaining polarization independence for each of the waveguide heights used in this paper but may be difficult for other dimensions. For example, a 1-/spl mu/m SOI rib waveguide with an etch depth of 0.64 /spl mu/m and rib width of 0.52 /spl mu/m is predicted to exhibit such characteristics.     

Esophago-jejuno-gastroplasty in the treatment of peptic stenosis of the esophagus]

Resistance to benzalkonium chloride (BC) among Pseudomonas spp. isolated from poultry carcasses was determined and strategies for elimination of resistant strains evaluated. This investigation showed that resistance was quite common, about 30% of the isolates being able to grow in 200 micrograms ml-1 BC. Pseudomonas fluorescens strains were generally less susceptible than strains of Ps. lundensis and Ps. fragi. An overnight incubation in medium containing 200 micrograms ml-1 BC was sufficient to reduce the susceptibility of two Pseudomonas strains to the lethal effect of BC significantly. Adding EDTA enhanced the lethal effect of BC, but the effect was reduced after growing cells in medium containing BC and EDTA. Growth in medium with a quaternary ammonium compound (QAC) rendered the cells more susceptible to chlorine, phenolics, and alkylaminoacetate. These results indicate that alternating use of QACs with these compounds can be used to avoid build-up of resistant strains. In addition, increased temperatures improved the lethal effect of BC and should be considered when planning disinfection routines.     

Modeling of noncollinear multifrequency acoustooptic interaction inguided-wave Bragg cells

We present an original detailed theoretical modeling of guided-wave noncollinear acoustooptic (AO) interaction produced by a multifrequency surface acoustic wave (SAW) in planar guided-wave structures. The modeling of the multifrequency AO interaction is based on a modified version of the coupled-mode theory. The first- and third-order diffraction efficiency and optimum dynamic range of the Bragg cell have been calculated as a function of acoustic power, acoustic radiofrequency, and optical waveguide parameters in Y-cut Ti:LiNbO₃ planar waveguides. Polynomial approximations, describing the first and third order diffraction efficiency versus normalized acoustic power in the cases of two- and three-frequency interactions, are derived and presented for the first time for arbitrarily large RF signals     

Sigmoidovesicocutaneous fistula complicating diverticular disease of the colon

A sixty-six year old diabetic male had a draining sinus tract from the lateral portion of a fourteen year old left herniorrhaphy scar. The diagnosis of sigmoidovesicocutaneous fistula was confirmed by a sinogram and the patient was treated in one stage with left hemicolectomy and resection of the fistula site from the dome of the bladder. To our knowledge this is the first report of a sigmoidovesicocutaneous fistula.     

Analysis of radiation loss in grating-assisted codirectionalcouplers

In this paper, we present a new accurate numerical method, named leaky mode propagation method, to analyze the radiation loss in grating-assisted codirectional couplers. The complex propagation constant and electromagnetic field distribution of the normal modes are evaluated by using a space harmonic field expansion derived from the Floquet theorem. In order to prove the accuracy of our method, a comparison between our results and those calculated by the most used method, i.e., the transfer matrix method, is carried out in terms of power attenuation coefficient and total radiation loss. Quantitative and qualitative discrepancies between the two methods are widely discussed. In particular, an oscillatory variation of radiation loss with grating depth and gap thickness in contrast to the monotonic behavior predicted by the transfer matrix method has been found     

Effect of paternal alcohol consumption before conception on infant birth weight. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood

Previous studies of paternal drinking and fetal growth in both animals and human have produced conflicting results. We evaluated the association between paternal drinking before conception and infant birth weight in a cohort of 9,845 liveborn singleton infant born to couples who participated in the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC), ALSPAC is a population-based cohort study in which women and their partners completed several self-administered questionnaires over the course of pregnancy. Of participating male partners, 20% were reportedly daily drinkers before conception, and 8% were considered moderately heavy or very heavy drinkers. Because maternal drinking is highly correlated with paternal, the analyses were stratified by maternal drinking in early pregnancy. We also adjusted for confounders and known predictors of birth weight. For all three maternal drinking strata, all adjusted mean differences in birth weight across levels of paternal drinking were similar, and all had confidence intervals that included zero. These findings persisted even after adjustment for other covariates and after stratification by parental smoking, race, and education. The size of the ALSPAC cohort, the large number of heavy drinkers, and the availability of data from the fathers themselves support the conclusion that paternal drinking before conception is not an important predictor of infant birth weight in humans.