Lifetime of vibrational levels from Fourier grid calculations: RbCs example.

We present systematic calculations of the lifetimes of vibrational levels of excited Rb(5s)Cs(6p(1/2)) 0(+) electronic states. We show that a precise description of the variation with the internuclear distance of the transition dipole moment between electronic states is essential. It is also crucial to account precisely for the spin-orbit coupling between the Rb(5s)Cs(6p) A (1)Σ(+) and b (3)Π states. We describe the general trends of the probability of formation of stable molecules in the Rb(5s)Cs(6s) X (1)Σ(+) and a (3)Σ(+) electronic states, through radiative decay from the 0(+)v' levels, together with the branching ratios for the obtention of singlet or triplet molecules, stable with respect to dissociation. Furthermore, this analysis allows us to demonstrate the efficiency of the Mapped Fourier Grid Hamiltonian Representation method (MFGHR) to determine rigorously the energy variation, throughout the continuous part of the spectrum, of the density of an observable connecting bound vibrational levels and continuum states. The resolution in energy can be adapted to the studied problem through a judicious choice of the grid parameters.

Nervio laríngeo no recurrente en cirugía de tiroides: reporte de dos casos / Non recurrent laryngeal nerve during thyroid surgery: Two cases report

La lesión del nervio laríngeo recurrente (NLR) durante la cirugía de tiroides o de las paratiroides es la causa iatrogénica más común de la parálisis de cuerda vocal. La identificación del NLR y de una técnica quirúrgica meticulosa puede disminuir perceptiblemente la incidencia de esta complicación. El nervio laríngeo inferior no recurrente es excesivamente raro (1%). Los cirujanos necesitan conocer ampliamente la anatomía y las variantes anatómicas para evitar lesiones, ya que su existencia no es diagnosticada prequirúrgicamente. El nervio laríngeo no recurrente se asocia generalmente a una arteria subclavia derecha retroesofágica que se desprende del arco aórtico distal. El conocimiento de su existencia y técnica quirúrgica correcta prevendrá al cirujano de lesiones accidentales durante la cirugía de tiroides o paratiroides.

The damage to the recurrent laryngeal nerve (RLN) during thyroid or parathyroid surgery is the most common iatrogenic cause of vocal cord paralysis. Identification of the recurrent laryngeal nerve and meticulous surgical technique can significantly decrease the incidence of this complication. Nonrecurrent laryngeal nerve is exceedingly rare (1%). Surgeons need know the anatomy and the anatomic anomalies to avoid injuries; the nerve anomaly is never preoperatively diagnosed. The nonrecurent laryngeal nerve is associated with a retroesophageal right subclavian artery from distal aortic arch. The awarereness of their existence combine with the correct surgical technique will prevent the surgeon from accidentally harmit during thyroid or parathyroid surgery.

HIV-related high risk sexual behaviors and practices among women in Bogotá, Colombia.

Determinants associated with high-risk sexual behaviors were investigated in 1,133 sexually active women in Bogotá, Colombia. A self-administered questionnaire was completed by two groups of women: 721 representing the general population (GP), and 412 commercial sex workers (CSWs). High-risk sexual behaviors for HIV/AIDS were evident in both groups. Nevertheless, consistent condom use was reported by only 6% of the GP group, as compared to 67% of the CSWs. Failure to recognize high-risk routes for HIV infection was indicated in 69% of the GP women for anal sex, and by the majority of both groups for intercourse during menses (56% GP women and 54% CSWs). Multivariate analysis revealed that education level, actual age, and age of first sex experience were significant predictors of high-risk sexual practices. The necessity for educational programs regarding high-risk sexual practices and risk of HIV/ AIDS is evident for HIV/AIDS prevention.

'Air hunger' from increased PCO2 persists after complete neuromuscular block in humans.

The tolerance of totally curarized subjects for prolonged breath hold is viewed by many as evidence that respiratory muscle contraction is essential to generate the sensation of breathlessness. Although conflicting evidence exists, none of it was obtained during total neuromuscular block. We completely paralyzed four normal, unsedated subjects with vecuronium (a non-depolarizing neuromuscular blocker). Subjects were mechanically ventilated with hyperoxic gas mixtures at fixed rate and tidal volume. End-expiratory PCO2 (PETCO2) was varied surreptitiously by changing inspired PCO2. Subjects rated their respiratory discomfort or 'air hunger' every 45 sec. At low PETCO2 (median 35 Torr) they felt little or no air hunger. When PETCO2 was raised (median 44 Torr) all subjects reported severe air hunger. They had reported the same degree of air hunger at essentially the same PETCO2 before paralysis. When questioned afterwards all subjects said the sensation could be described by the terms 'air hunger', 'urge to breathe', and 'shortness of breath', and that is was like breath holding. They reported no fundamental difference in the sensation before and after paralysis. We conclude that respiratory muscle contraction is not important in the genesis of air hunger evoked by hypercapnia.

Velocity structure and a seismic model for nevado del Ruiz Volcano (Colombia)

A seismic tomographic study was done for Nevado del Ruiz Volcano (NRV). More than 1500 high-quality local and regional earthquakes were used for this tomographic study. Three low P wave velocity (low-Vp) and low S wave velocity (low-Vs) zones were found, one low-Vs zone at depths 2-4km located beneath the volcano, a second low-Vp and low-Vs zone at depths 5-10km located beneath the crater, elongated and dipping to the E-SE, and a third low-Vp and low-Vs zone at 10 to 12 km farther to the east. This three low Vp and low-Vs zones are believed to be the location of heat sources. A high velocity zone for both P and S waves was found at shallow depths (05km) around the active crater. The upper part (02km depth) of the high-Vp and high-Vs zone was characterized by low Vp/Vs ratios (<1.68), while the deeper part (210km) had high Vp/Vs ratios (>1.80). The upper part with low Vp/Vs ratios is correlated with a steam-dominated geothermal system. The high Vp/Vs zone extending from to 2 to 10km depth associated with a high-Vp zone beneath the active vent are interpreted as an intrusive body of magmatic origin which include partial melting zones associated with low-Vs anomalies . A small low-Vp zone was found to the southwest of the volcano. This zone seems to be the source of Long-Period (LP) earthquakes. Based on the data obtained with the tomography in combination with the seismicity, geochemistry, geology and gravimetry, we suggest a model for the seismic activity of NRV. Volcano-tectonic (VT) earthquakes that occurred very often in swarm-like patterns located in several clusters around the volcano, seem to be due to changes in stress produced by the passing of fluids and/or gas through many small cracks. A fault and a caldera-like structure in separate the VT swarms located to the west of the volcano from the source of Longperiod (LP) earthquakes. The LP earthquakes are located above a high Vp/Vs zone. The LP events seemed to be interacting with the western VT seismicity. (AU)

A warning model based on temporal changes of coda q for volcanic activity at Nevado del Ruiz volcano, Colombia

The coda Q has been calculated for Nevado del Ruiz Volcano, Colombia (NRV) from 1985 to 1999 by using a single scattering model. During this period, the inverse of Q (Q-1 proportional to attenuation) exhibited a long-term decrease with time, as well as shorter-term variations related to the volcanic activity. Q-1 increased prior to volcanic crises and decreased afterward. Based on these observations, a warning seismic criterion has been developed. The parameters (frequency band, size of moving average window, and threshold levels) necessary to evidence clear and significant short-term changes in Q-1 have been investigated and appropiated values are proposed. We suggest a phenomenological model with three stages for the short-term temporal changes in Q-1 at NRV. Firstly, Q-1 increases before volcanic crises due to accumulation of gas and/or liquid, which decreases the aspect ratio of fluid pockets and increases the fractional volume of fluid in the rocks and the pore aspect ratio. Secondly, Q-1 starts to decrease during the crises by the discharging of fluids from the volcano such as gas, water, etc. Finally, Q-1 became more stable after the crisis at a lower value due to the degassing and/or increasing of rigidity of the medium because of the long-term crystallization and cooling processes. Q-1 seems a promising monitoring tool at NRV. It is possible that the observed temporal changes of Q-1, combined with other parameters, may help to predict with more accuracy a volcanic crisis at NRV. The model has been tested with a recent volcanic crisis occurred in June 9 2002. The results showed that the model is a good tool for forecasting volcanic activity at NRV. (AU)