Showing papers by "Autonomous University of Barcelona published in 1995"

IMOMM: A new integrated ab initio + molecular mechanics geometry optimization scheme of equilibrium structures and transition states

Abstract: A new computational scheme integrating ab initio and molecular mechanics descriptions in different parts of the same molecule is presented. In contrast with previous approaches, this method is especially designed to allow the introduction of molecular mechanics corrections in full geometry optimizations concerning problems usually studied through ab initio calculations on model systems. The scheme proposed in this article intends to solve some of the systematic error associated with modeling through the use of molecular mechanics corrections. This method, which does not require any new parameter, evaluates explicitly the energy derivatives with respect to geometrical parameters and therefore has a straightforward application to geometry optimization. Examples of its performance on two simple cases are provided: the equilibrium geometry of cyclopropene and the energy barriers on SN2 reactions of alkyl chloride systems. Results are in satisfactory agreement with those of full ab initio calculations in both cases. © 1995 by John Wiley & Sons, Inc.

The Spanish version of the SF-36 Health Survey (the SF-36 health questionnaire): an instrument for measuring clinical results

Abstract: Background The present study, performed within the International Quality of Life Assessment project (including researchers from 15 countries) presents preliminary results of the process of adaptation of the SF-36 to be used in Spain. Methods The adaptation was based on the translation/back-translation methodology. Meetings of translators, researchers and patients were organized in order to produce successive versions. A study involving 47 individuals was carried out to assess the relative value (through a visual analogue scale) of each response choice of the questionnaire items. Finally, internal consistency and reproducibility of the Spanish version of the SF-36 was assessed by administering the questionnaire to 46 patients with stable coronary heart disease in two different occasions 2 weeks apart. Results The average ratings of equivalence of the translated version with the original were high regardless of the difficulty of translation. The rank ordering of mean scores for each responses choice agreed with the ranking assigned in the questionnaire in all cases. Cronbach's Alpha was higher than 0.7 for all dimensions (range: 0.71-0.94) except for Social Functioning scale (alpha = 0.45). Intraclass correlation coefficients between both administrations of the questionnaire ranged from 0.58 to 0.99. Conclusions The adaptation process of the SF-36 has concluded with an instrument apparently equivalent to the original and with an acceptable level of reliability. Nevertheless, other basic characteristics of the adapted questionnaire (i.e. validity and sensitivity to changes) should be also assessed.

Induction of micronuclei by five pyrethroid insecticides in whole-blood and isolated human lymphocyte cultures.

Abstract: Five pyrethroid insecticides: cypermethrin, deltamethrin, fenpropathrin, fenvalerate and permethrin, were tested for their ability to induce micronuclei in both whole-blood (WB; three donors) and isolated human lymphocyte (IL, 2 donors) cultures, by using the cytokinesis-block method with 6 micrograms/ml cytochalasin B (Cyt-B). Fenvalerate and permethrin were tested with two different concentrations of Cyt-B (3 and 6 micrograms/ml). At the concentration ranges tested, all the five pyrethroids induced clear dose dependent cytotoxic effects, fenpropathrin being the most toxic. Nuclear division index (NDI) and the newly introduced index of cytotoxicity, the cytokinesis block proliferation index (CBPI), reflected the dose dependency more accurately than the percentage of binucleated cells did. CBPI is similar to NDI except that it estimates the average number of cell divisions that the cell population has gone through, and, therefore, classifies both trinucleate and tetranucleate cells into the same category. Cypermethrin and fenpropathrin slightly increased the number of MN and micronucleated cells in WB lymphocyte cultures from two out of the three donors. Deltamethrin produced a positive response only in WB cultures of one donor and in IL cultures of another donor. Permethrin gave mostly negative results, although it increased the MN frequency in WB cultures of one donor when 6 micrograms/ml Cyt-B was used. Fenvalerate did not significantly induce MN. With certain reservations to the purity and isomer composition of each pesticide, the existing information appears to support the idea that pyrethroid insecticides have a weak (cypermethrin, deltamethrin and fenpropathrin) or nule (fenvalerate and permethrin) genotoxic activity in vitro.

Performance of the ALEPH detector at LEP

Abstract: The performance of the ALEPH detector at the LEP e+e− collider is reviewed. The accuracy of the tracking detectors to measure the impact parameter and momentum of charged tracks is specified. Calorimeters are used to measure photons and neutral hadrons, and the accuracy obtained in energy and angle is given. An essential property of the detector is its ability to identify particles; the performance in identification of electrons, muons, neutrinos (from missing energy), charged hadrons, π0's and V0's is described.

Clinical pharmacokinetics and pharmacodynamics of zolpidem. Therapeutic implications.

Abstract: Zolpidem is an imidazopyridine which differs in structure from the benzodiazepines and zopiclone. It is a strong sedative with only minor anxiolytic, myorelaxant and anticonvulsant properties, and has been shown to be effective in inducing and maintaining sleep in adults. The available evidence suggests that zolpidem produces no rebound or withdrawal effects, and patients have experienced good daytime alertness. Zolpidem 10mg in non-elderly and a reduced dose of 5mg in elderly individuals are clinically effective. In humans, the major metabolic routes include oxidation and hydroxylation; none of the metabolites appears to be pharmacologically active. The pharmacological activity of zolpidem results from selective binding to the central benzo-diazepine receptors of the ωl subtype. Zolpidem is approximately 92% bound to plasma proteins; absolute bioavailability of zolpidem is about 70%. After single 20mg oral doses, typical values of pharmacokinetic variables for zolpidem in humans are: a peak plasma concentration of 192 to 324 µg/L occurring 0.75 to 2.6 hours postdose; a terminal elimination half-life of 1.5 to 3.2 hours; and total clearance of 0.24 to 0.27 ml/min/kg. Zolpidem pharmacokinetics are unchanged during multiple-dose treatment. Zolpidem pharmacokinetics are not significantly influenced by gender. Clearance of zolpidem in children is 3 times higher than in young adults, and is lower in very elderly people. There are no significant differences in the pharmacokinetic parameters between various racial groups. Dosage reduction appears to be prudent in patients with renal disease, and caution should be exercised when prescribing zolpidem to elderly patients with hepatic impairment. Coadministration of haloperidol, cimetidine, ranitidine, chlorpromazine, warfarin, digoxin or flumazenil do not alter the pharmacokinetics of zolpidem; flumazenil predictably antagonises the hypnotic effects of zolpidem. Alertness tends to be reduced when cimetidine is combined with zolpidem. Volunteers treated with imipramine plus zolpidem developed anterograde amnesia.

Ecology of Phototrophic Sulfur Bacteria

Abstract: Phototrophic sulfur bacteria often form mass developments in aquatic environments, either planktonic or benthic, where anoxic layers containing reduced sulfur compounds are exposed to light. This chapter summarizes a number of reports from the literature, collecting the information on the abundance of these bacteria as well as on their contribution to primary production. From the point of view of population dynamics, the abundance of these organisms is the consequence of a certain balance between growth and losses. Both specific growth rates, and specific rates of loss through several processes are analyzed in several environments, in an attempt to generalize on the growth status of blooms of phototrophic sulfur bacteria. The information available indicates the existence of an upper limit for the production of these bacteria in nature, and seems to suggest the existence of an upper limit for biomass based in the balance between growth and losses.

L-arginine: nitric oxide pathway in endotoxemia and human septic shock.

Abstract: Objective To investigate the relationship between nitric oxide production, endotoxemia, and hemodynamic alterations in human septic shock.Design Prospective study.Setting A 32-bed intensive care unit in a university referral hospital.Patients Two groups of septic patients with shock (n=13) or withou

An anatomical study and ontogenetic explanation of 23 cases with variations in the main pattern of the human brachio-antebrachial arteries.

Abstract: Twenty-three cases with variations in the brachio-antebrachial arterial pattern of the human upper limb are reported. According to the artery which showed a variation, 4 groups were recognised: (1) isolated persistence of the median artery; (2) high origin of the ulnar artery; (3) high origin of the radial artery; and (4) duplication of the brachial artery, either with or without anastomosis at the cubital fossa. In addition, in groups 2, 3 and 4 the median artery may have persisted. Based on these arterial variations an anatomical and embryological correlation was established from a morphogenetic pattern which is proposed as being normal. Thus the terminal branches of the superficial brachial artery take part in the development of the radial, ulnar and median arteries, joining with the trunks of deep origin of these arteries in the primitive axial artery. Regression of the superficial arterial segments located proximal to this anastomosis gives rise to the definitive arterial pattern. Either the total or partial persistence of the superficial arterial segments explains those cases of high origin of either the radial or ulnar arteries as well as the duplications of the brachial artery. We postulate that the persistence of the median artery is independent of the presence or absence of any other variation in the arterial pattern.

Feature structure of Romance clitics

Abstract: The combination of pronominal clitics in Romance often triggers the appearence of unexpected (opaque) form, which always coincide with clitics that exist independently in the language. In this article, which analyzes opaque forms in Italian, Spanish, and, especially, Catalan, it is proposed that pronominal clitics constitute hierarchical structures of monovalent morphological features. This hierarchy reflects markedness relations. Most opaque forms are obtained through morphological rules that delink or insert morphological features, thus rendering the target structure identical to the structure of another clitic. Morphological rules take place within the Morphology Component, between S-structure and PF (cf. Halle 1990, 1991). Phonological information, not present in the syntax, is introduced by spell-out rules very late in the Morphology Component and provides the input to PF. Clitic order is determined through mapping to a template. Some other opaque forms arise at that point.

Population Awareness and Control of Hypertension and Hypercholesterolemia: The Atherosclerosis Risk in Communities Study

Abstract: Background: A national program for hypertension detection and control was implemented in the 1970s, whereas a similar program for control of hypercholesterolemia has been implemented in recent years. We studied the levels of awareness, treatment, and control of these conditions in US population samples during a 3-year period (1987 to 1989). Methods: The levels of awareness, treatment (by medication), and adequate control of hypertension (systolic blood pressure, ≥140 mm Hg; diastolic blood pressure, ≥90 mm Hg; or antihypertensive medication) and hypercholesterolemia (serum cholesterol level, ≥6.21 mmol/L [≥240 mg/dL], or lipid-lowering medication) were studied among participants in the baseline examination of the Atherosclerosis Risk in Communities Study, including 15 739 individuals aged 45 to 64 years. Results: Eighty-four percent of the hypertensive subjects and 42% of the hypercholesterolemic subjects were aware of their conditions. Overall, 50% of the hypertensive subjects and only 4% of the hypercholesterolemic subjects had their conditions both treated and controlled. Rates of hypertension prevalence, awareness, and control remained stable during the 3-year study period. Hypercholesterolemia prevalence decreased from 30% in 1987 to 25% in 1989; its awareness increased from 31% to 50% during the same period. Hypertensive women were more likely than hypertensive men to be aware and treated, whereas hypercholesterolemia awareness was higher in men than in women. Hypertension awareness was highest in black women, but black hypertensive subjects were less likely than whites to be treated and to have their hypertension controlled. Black hypercholesterolemic subjects were less likely to be either aware or treated. Conclusions: After the recent implementation of the National Cholesterol Education Program, the levels of awareness, treatment, and control of hypercholesterolemia are improving at a high rate, although they are still substantially lower than those for hypertension. Further improvement is necessary, particularly among certain population groups, such as blacks. (Arch Intern Med. 1995;155:677-684)

Mixed Risk Aversion

Abstract: We analyze the class of increasing utility functions exhibiting all derivatives of alternating sign. This property, that we call mixed risk aversion, is satisfied by the utility functions most commonly used in financial economics. The utility functions displaying mixed risk aversion can be expressed as mixtures of exponential functions. We characterize stochastic dominance and we find conditions for both mutual aggravation and mutual amelioration of risks when agents are mixed risk averse. Finally, the analysis of the distribution function describing a mixed utility allows one to characterize the behaviour of its indexes of risk aversion and to discuss its implications for portfolio selection. Journal of Economic Literature Classification Numbers: D81, G11.

Relationship between Weather Temperature and Mortality: A Time Series Analysis Approach in Barcelona

Abstract: Background. Many studies have reported that heatwaves increase mortality. However, it is not certain whether less pronounced rises in temperature also increase it. Such information might be important for predicting the impact of potential weather changes on mortality. We have assessed the relationship between daily mortality and moderate increases in weather temperature in Barcelona, Spain, following a time series approach. Methods. The study included the period from 1 January 1985 to 30 December 1989. For all the population resident in Barcelona, Spain, we considered the following daily data : total mortality, mortality of those >65 years, and cardiovascular and respiratory mortality. The meteorological variables were : minimum temperature, maximum temperature, dew point temperature and relative humidity. Several transfer function (ARIMA) models were estimated for the entire period and for both winters and summers separately. Results. We found that unusual periods of at least three consecutive days of increased weather temperature increased mortality, independently of the V-shaped relationship also found. The occurrence of an unusual period increased total daily mortality by 2% on average (1.7% on summers) and by 2.6% in those over 65 (2% on summers). Cardiovascular mortality rose by 4.6% (4.2% on summers) and respiratory mortality by 21.6% (13.2% on summers). However, only those unusual periods with an excess temperature and humidity were associated with mortality increases. Conclusions. The unusual periods observed in the present study cannot be classified as heatwaves because the weather temperature never reached high values and most of them occurred during the winter. The association of unusual periods with mortality was stronger during winters than in summers, maybe because unusual winter periods showed a temperature deviation from the average twice that in summer or because humidity during unusual winter periods was higher than in summer.

Short-term association between air pollution and emergency room visits for asthma in Barcelona.

Abstract: BACKGROUND--Several studies have assessed the association between urban air pollutants and hospital admissions or emergency room visits for asthma with inconsistent results. The objective of this study was to assess the relation between levels of black smoke, sulphur dioxide, nitrogen dioxide, and ozone and adult emergency room visits for asthma in Barcelona, Spain during the five year period 1985-9. METHODS--The daily number of emergency room visits for asthma was obtained from a register of respiratory emergencies designed to study the asthma outbreaks occurring in Barcelona. The association between asthma visits and levels of pollutants was assessed separately for summers and winters with Poisson regression models controlling for meteorological and time related variables. RESULTS--Black smoke was associated with asthma visits in summer but not in winter. The relative risk (RR) of asthma visits for a 25 micrograms/m3 increase of current day concentrations of black smoke was 1.082 (95% CI 1.011 to 1.157). The mean current and previous three day levels of black smoke led to a stronger association (RR = 1.114 (95% CI 1.010 to 1.160). In addition, nitrogen dioxide was associated with asthma visits in both summer (RR = 1.045, 95% CI 1.009 to 1.081) and winter (RR = 1.056, 95% CI 1.011 to 1.104). These associations were slightly higher for the previous day's level of nitrogen dioxide. No associations were found for sulphur dioxide or for ozone. CONCLUSIONS--This study provides further evidence of the effect of particulate pollution on asthma, and it suggests that nitrogen dioxide may have a role in the exacerbation of bronchial asthma in adults.

A model of physiologically structured population dynamics with a nonlinear individual growth rate

Abstract: In this article we consider a size structured population model with a nonlinear growth rate depending on the individual's size and on the total population. Our purpose is to take into account the competition for a resource (as it can be light or nutrients in a forest) in the growth of the individuals and study the influence of this nonlinear growth in the population dynamics. We study the existence and uniqueness of solutions for the model equations, and also prove the existence of a (compact) global attractor for the trajectories of the dynamical system defined by the solutions of the model. Finally, we obtain sufficient conditions for the convergence to a stationary size distribution when the total population tends to a constant value, and consider some simple examples that allow us to know something about their global dynamics.