Computational investigations of the thermodynamic properties of size-selected water and Ar-water clusters: high-pressure transitions.

Classical parallel-tempering Monte Carlo simulations in the isothermal-isobaric ensemble were carried out for the (H2O)20 and Ar(H2O)20 clusters, over a wide range of temperatures (30-1000 K) and pressures (3 kPa-10 GPa) in order to study their thermodynamic properties and structural changes. The TIP4P/ice water model is employed for the water-water interactions, while both semiempirical and ab initio-based potentials are used to model the interaction between the rare-gas atoms and the water molecules. Temperature-pressure phase diagrams for these cluster systems were constructed by employing a two-dimensional multiple-histogram method. Structural changes were detected by analyzing the heat capacity landscape and the Pearson correlation coefficient profile for the interaction energy and volume. Those at high pressure correspond to solid-to-solid transitions and are found to be related to clathrate-like cages around the Ar atom. It is also shown that the formation and thermodynamic stability of such structures are determined by the intermolecular interaction between the rare-gas atoms and the host water molecules.

Effect of country-of-origin contextual factors and length of stay on immigrants' substance use in Spain.

BACKGROUND: Factors explaining disparities in risk of substance use between immigrants and natives and between immigrant subgroups are poorly understood. We aimed to describe such disparities and identify some explanatory factors in Spain. METHODS: Participants were residents aged 15-64 years from 2005 to 07 nationally representative surveys. Outcomes were prevalences of alcohol, tobacco, sedative-hypnotics, cannabis and other illegal substance use. Immigrants were recent if <5 years of Spanish stay and long term if ≥10 years. Country-of-origin income per capita and population level of substance use were taken from international databases. Adjusted prevalence ratios (aPRs) and percent change from Poisson regression with robust variance were used to estimate risk disparities and effects of immigration variables. RESULTS: Most immigrants had lower substance use than natives, although it generally increased with increasing Spanish stay, especially for illegal substances. This lower risk could be partially explained by country-of-origin contextual factors as a lower level of income or substance use and religious or cultural factors such as Islam. By origin, recent immigrant aPRs and convergence-divergence risk patterns were, respectively, as follows: lower aPRs with upward convergence (often incomplete) toward natives' risk in immigrants from Muslim area, Eastern-Europe and Latin-America excluding South-Cone, lower/similar aPRs with upward overtaking or divergent patterns in South-Cone Americans and similar/higher aPRs with stable or upward divergent patterns in Non-Eastern-Europeans. CONCLUSION: Spain is a host context that seems to facilitate increased substance use among immigrants, even those from countries with prevalences close to Spain. However, country-of-origin context is important in explaining disparities in substance use among immigrants.

Spin-polarized Rb2 interacting with bosonic He atoms: potential energy surface and quantum structures of small clusters.

A new full-dimension potential energy surface of the three-body He-Rb2(³Σ(u)(+)) complex and a quantum study of small (4He)(N)-Rb2(³Σ(u)(+)) clusters, 1 ≤ N ≤ 4, are presented. We have accurately fitted the ab initio points of the interaction to an analytical form and addressed the dopant's vibration, which is found to be negligible. A Variational approach and a Diffusion Monte Carlo technique have been applied to yield energy and geometric properties of the selected species. Our quantum structure calculations show a transition in the arrangements of the helium atoms from N = 2, where they tend to be separated across the diatomic bond, to N = 4, in which a closer packing of the rare gas particles is reached, guided by the dominance of the He-He potential over the weaker interaction of the latter adatoms with the doping dimer. The deepest well of the He-Rb2 interaction is placed at the T-shape configuration, a feature which causes the dopant to be located as parallel to the helium "minidroplet". Our results are shown to agree with previous findings on this and on similar systems.

No effect of the Penalty Point System on road traffic accident mortality among men with a high socioeconomic status in Spain.

The purpose of this study was to assess the effect of the Penalty Point System (PPS) on road traffic accident mortality by gender and socioeconomic status. We conducted a nationwide prospective study covering adult people living in Spain on November 2001. They were followed up until 30 Nov 2007 to determine vital status and cause of death. An interrupted time-series analysis was used to assess whether PPS (explanatory variable) had both immediate and long-term effect on the rates of road traffic accident mortality (RTAMs) separately by gender. Subjects were classified by socioeconomic status (low and high) using two indicators: educational attainment (up to lower secondary education; upper secondary education or more) and occupation (manual and non-manual workers). We performed several segmented Poisson regression models, controlling for trend, seasonality, 2004 road safety measures and fuel consumption as proxy for traffic exposure. Among men, we found a decrease on the RTAMs immediately after PPS in those with low educational level (16.2 %, IC95 %: 6.1 %-25.2 %) and manual workers (16.3 %, IC95 %: 2.8 %-27.8 %), and a non-significant increase among those with high education level and non-manual workers (6.2 % and 1.8 %). Among women, there were no significant differences in the immediate effect of PPS by socioeconomic status. We did not identify significant trend changes between pre-PPS and post-PPS periods in any socioeconomic group. In a context of downward trend of traffic mortality, the PPS implementation led to an immediate reduction on death rates only among men with a low socioeconomic status.

Long-term impact of the 2008 economic crisis in Spain on road traffic collisions mortality by socioeconomic position.

We aimed to assess the effect of the 2008 crisis on road traffic collision (RTC) mortality in Spain, by socioeconomic position (SEP) and type of road use. This prospective, country-wide study covered all adults living in Spain and aged ≥30 years in November 2001. The long-term effect of the crisis was assessed by measuring the monthly percentage change (MPC) in RTC mortality between the pre-crisis (2002-2007) and crisis period (2008-2011). During the recession, RTC mortality fell more in people with low compared to high SEP, so MPCs difference between periods were of a higher magnitude in the low compared to high SEP groups, especially among men motorcyclists. RTC mortality trends were favorable following the 2008 crisis, particularly among low-SEP groups. In men motorcyclists, the upward trend of the pre-crisis period reversed course.

A new accurate and full dimensional potential energy surface of H5(+) based on a triatomics-in-molecules analytic functional form.

In this work a reliable full nine-dimensional potential energy surface for studying the dynamics of H(5)(+) is constructed, which is completely symmetric under any permutation of the nuclei. For this purpose, we develop a triatoms-in-molecules method as an extension of the more common diatoms-in-molecules one, which allows a very accurate description of the asymptotic regions by including correctly the charge-induced dipole and quadrupole interactions. Moreover, this treatment provides a semiquantitative description of all the topological features of the global potential compared with coupled cluster results. In particular, the hop of the proton between two H(2) fragments produces a double well in the potential. This resonant structure involving the five atoms produces a stabilization, lowering the barrier, and the triatoms-in-molecules yields to a barrier significantly higher than the ab initio results. Therefore, to improve the triatomics-in-molecules potential surface, two five-body terms are added, which are fitted to more than 110,000 coupled-cluster ab initio points. The global potential energy surface thus obtained in this work has an overall root mean square error of 0.079 kcal/mol for energies below 27 kcal/mol above the global well. The features of the potential are described and compared with previous available surfaces.

A path-integral Monte Carlo study of a small cluster: The Ar trimer.

The Ar(3) system has been studied between T=0 K and T=40 K by means of a path-integral Monte Carlo (PIMC) method. The behavior of the average energy in terms of the temperature has been explained by comparison with results obtained with the thermal averaged rovibrational spectra estimated via: (i) a quantum mechanical method based on distributed Gaussian functions for the interparticle distances and (ii) an analytical model which precisely accounts for the participation of the dissociative continua Ar(2)+Ar and Ar+Ar+Ar. Beyond T approximately 20 K, the system explores floppier configurations than the rigid equilateral geometry, as linear and Ar-Ar(2)-like arrangements, and fragmentates around T approximately 40 K. A careful investigation of the specific heat in terms of a confining radius in the PIMC calculation seems to discard a proper phase transition as in larger clusters, in apparent contradiction with previous reports of precise values for a liquid-gas transition. The onset of this noticeable change in the dynamics of the trimer occurs, however, at a remarkably low value of the temperature in comparison with Ar(n) systems formed with more Ar atoms. Quantum mechanical effects are found of relevance at T

An optimized full-configuration-interaction nuclear orbital approach to a "hard-core" interaction problem: application to (3He)(N)-Cl2(B) clusters (N < or = 4).

An efficient full-configuration-interaction nuclear orbital treatment has been recently developed as a benchmark quantum-chemistry-like method to calculate ground and excited "solvent" energies and wave functions in small doped DeltaE(est) clusters (N < or = 4) [M. P. de Lara-Castells, G. Delgado-Barrio, P. Villarreal, and A. O. Mitrushchenkov, J. Chem. Phys. 125, 221101 (2006)]. Additional methodological and computational details of the implementation, which uses an iterative Jacobi-Davidson diagonalization algorithm to properly address the inherent "hard-core" He-He interaction problem, are described here. The convergence of total energies, average pair He-He interaction energies, and relevant one- and two-body properties upon increasing the angular part of the one-particle basis set (expanded in spherical harmonics) has been analyzed, considering Cl(2) as the dopant and a semiempirical model (T-shaped) He-Cl(2)(B) potential. Converged results are used to analyze global energetic and structural aspects as well as the configuration makeup of the wave functions, associated with the ground and low-lying "solvent" excited states. Our study reveals that besides the fermionic nature of (3)He atoms, key roles in determining total binding energies and wave-function structures are played by the strong repulsive core of the He-He potential as well as its very weak attractive region, the most stable arrangement somehow departing from the one of N He atoms equally spaced on equatorial "ring" around the dopant. The present results for N = 4 fermions indicates the structural "pairing" of two (3)He atoms at opposite sides on a broad "belt" around the dopant, executing a sort of asymmetric umbrella motion. This pairing is a compromise between maximizing the (3)He-(3)He and the He-dopant attractions, and suppressing at the same time the "hard-core" repulsion. Although the He-He attractive interaction is rather weak, its contribution to the total energy is found to scale as a power of three and it thus increasingly affects the pair density distributions as the cluster grows in size.

A theoretical investigation on the spectrum of the Ar trimer for high rotational excitations.

A detailed study of the rovibrational spectrum of the Ar trimer is performed by means of an exact hyperspherical coordinate (HC) method and a variational approach based on distributed Gaussian functions (DGFs) to describe the interparticle distances. The good agreement observed between the energy levels obtained with both procedures for high values of the total angular momentum (J=15 and 20) reveals the quality of the DGF method to describe the rotation of the title system. Rotational constants for the lowest bound states, obtained as averages for each vibrational state, have been obtained and compared to previous results. A detailed analysis of density probability functions obtained by means of the HC approach for rovibrational states at J=0 and 20 shows close similitudes thus supporting the vibration-rotation separation adopted within the DGF scheme for the Ar(3) system.

Men who pay for sex in Spain and condom use: prevalence and correlates in a representative sample of the general population.

OBJECTIVE: To estimate the percentage of men who have paid for heterosexual sex in Spain and the percentage who used condoms. To identify the main factors associated with these behaviours and to describe opinions about condoms. METHODS: Sexual behaviour probability sample survey in men aged 18-49 years resident in Spain in 2003 (n = 5153). Computer-assisted face to face and self interview was used. Bivariate and multivariate logistic regression analyses were performed. RESULTS: 25.4% (n = 1306) of the men had paid for heterosexual sex at some time in their lives; 13.3% (n = 687) in the last 5 years and 5.7% (n = 295) in the last 12 months. In the logistic analysis this behaviour was associated with older age, lower education, being unmarried, foreign birth, being a practicing member of a religious group, unsatisfactory communication with parents about sex, age under 16 years at first sexual intercourse and having been drunk in the last 30 days. Of the men who had paid for sex in the previous 5 years, 95% (n = 653) had used a condom in the most recent paid contact. In the multivariate analysis, not using a condom was associated with age over 30 years and first sexual intercourse before age 16 years. Men who did not use condoms in the last commercial intercourse had more negative opinions about condoms. CONCLUSIONS: The prevalence of paying for heterosexual sex among Spanish men is the highest ever described in developed countries. The many variables associated with paying for sex and condom use permit the characterisation of male clients of prostitution and should facilitate targeting HIV prevention policies.

Evaluating the impact of methadone maintenance programmes on mortality due to overdose and aids in a cohort of heroin users in Spain.

AIMS: To assess the relationship between methadone treatment (MT) and overdose and HIV/AIDS mortality among heroin users resident in Barcelona city. DESIGN: All patients who started treatment in any treatment centre between 1992 and 1997 were included in a cohort the first time they were admitted for heroin addiction treatment. Follow-up controls were carried out every 9 months, on average, until 31 December 1999. Variables, both constant and varying over time, were fitted into Cox regression models. FINDINGS: The study recruited 5049 patients, which provided 23,048.2 person-years. Fifty per cent were in MT during the study period; of the total cohort 1005 patients died: 38.4% due to AIDS, 34.7% to overdose and 27% to other causes. Overall mortality decreased from 5.9 deaths per 100 person-years in 1992 to 1.6 in 1999. Globally, life expectancy at birth was 39 years, 38 years lower than that of the general population. The main factor for overdose mortality was not being in MT at the time of death [relative ratio (RR) = 7.1]; other factors were being a current injector at baseline and being HIV positive. For AIDS mortality, the main factor was the calendar year (RR for 1996 versus 1999 = 4.6), the next major factor was more than 10 years of heroin consumption, followed by not being in MT, being unemployed, then having a prison record. CONCLUSIONS: The observed mortality decline could be linked to the effectiveness of low-threshold MT. The life expectancy of heroin users increased by 21 years during the study period.

Toxoplasma peritonitis in a patient with acquired immunodeficiency syndrome.

Toxoplasma gondii was identified in a stained slide preparation of, and isolated from, peritoneal fluid specimens obtained from a patient with the acquired immunodeficiency syndrome (AIDS). At the time of admission to the hospital, the patient's serologic tests were positive for Toxoplasma. Toxoplasma was isolated from samples of the patient's blood by mouse inoculation. Findings of newly developed methods for diagnosis of the presence of T gondii in body fluids by assay for Toxoplasma-specific antigen and by use of a DNA probe were positive.

Inicio y progresión en el consumo de sustancias en la población general de Cataluña, España / Onset and progression of drug use in the general population of Catalonia, Spain

Este estudio tuvo como finalidad realizar un análisis retrospectivo de la secuencia de inicio y progresión de las vías más comunes del inicio del consumo de sustancias en una muestra de la población general española. Recopilamos datos de la encuesta nacional de las viviendas del año 2011 sobre el consumo de sustancias en Cataluña, España, respecto de personas no-institucionalizadas de la población general con edades entre los 15-64 años. La muestra final estaba compuesta de 2.069 personas con la misma distribución de edad que la población general. Mostramos la progresión en el inicio de consumo de sustancias mediante la cuantificación de los cambios de un estado anterior, en términos de número de personas y porcentajes ponderados. Aplicamos análisis de supervivencia para valorar las vías más prevalentes halladas en el análisis descriptivo usando modelos de regresión aditivos. La edad media de inicio de consumo fue decreciendo en todas las cohortes desde 1965 hasta 1985-1996: de 17 a 15 para tabaco, de 20 a 16 para cannabis y de 21 a 18 para cocaína. En las personas que usaban las tres sustancias estudiadas, la vía más frecuente fue "tabaco-uso diario de tabaco-cannabis-cocaína". Dichos resultados requieren políticas de salud y estrategias de prevención para aumentar la percepción de los riesgos de las sustancias legales e ilegales. Esto, unido a intervenciones de compañeros bien diseñadas, podría reducir el riesgo de exposición de sustancias ilegales, como cannabis y cocaína, y, por tanto, reducir la probabilidad de un problema de consumo de sustancias en un futuro

The aim of the present study was to retrospectively study the onset and progression sequence of the most frequent pathways of drug use initiation in a sample of the Spanish general population. Data come from the 2011 household survey on drug use in Catalonia, Spain, on non-institutionalized individuals aged 15-64 in the general population. The final sample was of 2,069 individuals and had the same age distribution as the general population. Progressions of drug initiation were pictured by quantifying transitions from a previous state in terms of the number of individuals and weighted percentages. Survival analyses were employed to assess the most prevalent pathways found in the descriptive analysis using additive regression models. Median ages of onset were decreasing in every cohort from 1965 to 1985-1996: from 17 to 15 in tobacco, 20 to 16 in cannabis and 21 to 18 in cocaine. In people who consumed the three drugs studied, the most frequent pathway was "tobacco-daily tobacco-cannabis-cocaine". These results demand health policies and prevention strategies in order to increase perception of the risks of legal and illegal substances. This, together with well-designed peer interventions could reduce the risk of exposure to illegal drugs such as cannabis and cocaine, thus reducing the likelihood of future problem drug use

Lessons from the history of the human immunodeficiency virus/acquired immunodeficiency syndrome epidemic among Spanish drug injectors.

In Spain, approximately 10 years passed between the time when human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) harm-reduction programs should have been developed with sufficient coverage to have an optimum impact on public health (before the HIV/AIDS epidemic's explosion in 1984) and the date of their actual implementation. This delay yielded an enormous cost for the country. The introduction of the virus in drug injector networks during a period of widespread diffusion of heroin injection and the lack of political awareness of the growing problem were 2 important factors that contributed to the important diffusion of the HIV infection among Spanish injection drug users. Lessons can be learned that may be of great interest in countries or territories facing similar challenges now and in the future.

Matrix elements for anharmonic potentials: Application to I2 morse oscillator.

Many authors have contributed expressions for obtaining analytical matrix elements for Morse oscillators. In this work, we discuss the advantages of using these expressions. At the same time, we propose a full numerical method to calculate these matrix elements and we compare, for the I2 system, the different results given by Gallas, Vasan, and Cross, and the variational method.

Intravenous administration among heroin users having treatment in Spain.

BACKGROUND: Of critical importance to AIDS control in Spain is the analysis of geographical variation and trend over time in the prevalence of intravenous administration in heroin users, as well as the factors associated with the use of this route. METHODS: We carried out a cross-sectional study of 27,655 people admitted to outpatient treatment for heroin dependence in 15 of the 17 Autonomous Communities of Spain during 1991, using data provided by the State Information System on Drug Abuse (SEIT). To assess the association of some factors with use of the intravenous route crude and logistic analysis was performed. RESULTS: The prevalence of intravenous administration in this population was 64.4% with regional differences ranging between 33% and 90%. Crude and logistic analysis demonstrated a strong association with two factors in addition to geography: the year of first use and the age at first use (the earlier the first use, the greater the strength of the association). CONCLUSIONS: These findings are of paramount importance for the control of the HIV epidemic in Spain and further study in this area could help to guide policy development.

Loading of plasmid DNA into PLGA microparticles using TROMS (Total Recirculation One-Machine System): evaluation of its integrity and controlled release properties.

Loading plasmid DNA into poly(ester) microparticles usually involves the formation of a multiple emulsion, using homogenisation techniques such as sonication or Ultra-Turrax. These procedures may negatively affect the integrity of the macromolecule and consequently its activity. The aim of this study was to prepare and evaluate DNA-loaded microparticles by TROMS (Total Recirculation One-Machine System), a new procedure that is based on the formation of a multiple emulsion by the injection of the phases under a turbulent regime. Microparticles were prepared with either Resomer) RG 502 (MP 502) or RG 756 (MP 756) and DNA loading was quantified fluorimetrically. DNA loading in MP 756 was almost twice as high as in MP 502 (510 vs. 285 ng/mg, respectively). Under both formulations, the loaded plasmid was released while maintaining its integrity for at least 24 days (MP 502) and 40 days (MP 756). Finally, the transfection efficiency was studied after injection of the microparticles (MP 502) into rat skeletal muscle and compared with naked DNA injection. Injection of naked DNA (150 microg DNA per muscle) achieved higher but variable expression levels that decreased after 3 weeks. In contrast, the muscles injected with microparticles (6.8 microg DNA per muscle) showed lower but homogeneous expression values, which were maintained for at least 3 weeks.

The transition from injecting to smoking heroin in three Spanish cities. The Spanish Group for the Study of the Route of Heroin Administration.

AIMS: To measure the current prevalence of different routes of heroin administration among users and to describe the most frequent patterns in the evolution of the main route from the time of first use to the present and their implications for the control of the HIV epidemic. DESIGN: Cross-sectional study. Face-to-face interviews using a structured questionnaire. SETTING AND PARTICIPANTS: Nine hundred and nine regular heroin users from Madrid, Barcelona and Seville (about 300 per city), half of them recruited in treatment centres and the other half out of treatment. MEASUREMENTS: Socio-demographic characteristics, current and historical behaviours related to route of administration. FINDINGS: Before 1980 injection was the first main route of heroin administration for most users in Barcelona and Madrid; in Seville smoking already predominated, although 40% of users began by injecting. Sniffing subsequently became predominant in Barcelona, while smoking became the predominant first route in Madrid and Seville (smoking has been the only first route in Seville since 1991). The prevalence of injection as the main route of administration during the last 30 days was 77.3% in Barcelona, 24.3% in Madrid and 23.9% in Seville; smoking predominated in the latter two cities. The factors most strongly associated with injection as the preferred route were city of recruitment and having a partner who injected. Some 73% of those who stopped injecting in their last change of route stated that the results of their HIV test or fear of becoming infected had been important in making this decision. CONCLUSIONS: The change from injecting to smoking will greatly facilitate the control of HIV infection in Spain. However, the main causal factor does not appear to be the perception of HIV risk, but rather other, ecological factors (cultural or market-related). The absence of these factors in some areas may impede the spread of smoking.

IV drug users: changes in risk behaviour according to HIV status in a national survey in Spain.

STUDY OBJECTIVE: To determine whether HIV positive intravenous drug users (IVDUs) who were receiving outpatient treatment for opiate and cocaine abuse or dependence used practices aimed at reducing the spread of HIV. DESIGN: Cross sectional study of behaviour and HIV serostatus in IVDUs. SETTING: A nationwide sample, from 83 health centres for outpatient treatment, stratified by autonomous regions. PARTICIPANTS: Altogether 1074 IVDUs were recruited. HIV serostatus could be verified in 738 (68.7%) of these. MEASUREMENTS AND MAIN RESULTS: Crude and adjusted odds ratios and their 95% confidence intervals were estimated to assess the association between HIV serostatus and behavioural changes. In their daily interactions with other members of the same household, seropositive subjects more frequently used preventive methods aimed at avoiding transmission than seronegative patients. Treatment for abuse or dependency before the current regimen had a greater impact in HIV positive than HIV negative subjects in terms of abstaining from risk behaviours. There was a significant trend toward lower drug consumption in HIV positive subjects, and the number of seropositive and seronegative IVDUs who stopped injecting their drugs was significantly higher among the former. Seropositive subjects were also more likely to stop sharing drug injecting equipment and to change their sexual habits; they reported an increased consistent use of condoms. CONCLUSIONS: HIV positive IVDUs were more likely to change their risk behaviours than their HIV negative counterparts.