Estructura molecular y predicción de propiedades fisicoquímicas de líquidos iónicos

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Física AplicadaLos líquidos iónicos (LIs) son sistemas que siguen despertando un gran interés tanto desde el punto de vista científico como en sus aplicaciones. Así, debido a su baja presión de vapor, que evita las emisiones en procesos químicos, son considerados como una alternativa a los disolventes orgánicos convencionales. Estructuralmente los LIs están constituidos únicamente por iones, y existe un gran número de combinaciones posibles de iones que dan lugar a LIs con propiedades características muy diferentes. Por ello, son considerados como disolventes de diseño en el sentido de que es posible desarrollar distintos LIs con funciones específicas para cada aplicación. Este elevado número de combinaciones posibles, unido a la escasez de datos experimentales disponibles en la literatura científica, justifica la aplicación de modelos predictivos para estimar sus propiedades termofísicas. El hecho de que se trate de sistemas en fase líquida dificulta su tratamiento con los métodos convencionales desarrollados para el cálculo de la estructura molecular. En este sentido, los métodos COSMO y COSMO-RS han abierto una alternativa en la que se tiene en cuenta esta estructura a la hora de elaborar predicciones sobre su comportamiento químico y sus propiedades. En el caso del método COSMO-RS, los valores de las propiedades termofísicas de los fluidos puros y de las mezclas se pueden predecir utilizando únicamente información estructural de las moléculas. Para el trabajo teórico, los LIs pueden ser considerados a partir de dos modelos: el de pares iónicos, en el que cada par catión-anión se considera como un todo desde el punto de vista estructural, o el de iones independientes, en el que se considera como una mezcla de iones. En este trabajo se han tenido en cuenta ambos modelos para estudiar la estructura molecular de un conjunto de LIs y se han aplicado diferentes métodos para analizar su densidad electrónica. El tamaño de los sistemas hace que la aplicación de los métodos de cálculo más rigurosos sea inviable. Por este motivo, se ha encontrado un compromiso razonable entre calidad y coste del cálculo en los métodos basados en la teoría del funcional de la densidad. Con estos métodos, se han llevado a cabo cálculos de la estructura molecular de diferentes LIs y se ha analizado la influencia de esta estructura en las predicciones de sus propiedades fisicoquímicas realizadas mediante COSMO-RS. Dentro de la gran variedad de LIs, son especialmente interesantes los LIs bioderivados, entre cuyas propiedades más significativas destacan su elevada biodegradabilidad y su baja toxicidad. La parte aniónica de estos LIs es el aminoácido y la parte catiónica suele estar formada por derivados de imidazolios, aminas, pirrolidinios o fosfonios. Este trabajo se ha centrado en el estudio de algunas de sus propiedades más interesantes como son la densidad y la viscosidad. En definitiva, el objetivo de esta Tesis Doctoral ha sido el análisis de la estructura molecular de diversos LIs, y una relación con sus propiedades químicas y termofísicas, la elaboración de una metodología para predicción de éstas mediante COSMO y COSMO-RS, y validación de esta metodología por comparación con resultados disponibles en la bibliografía.Ionic liquids (ILs) are systems which are still getting great interest from the scientific point of view, as well as in their practical applications. In particular, due to negligible vapor pressure that prevents emissions in chemical processes, these systems are considered as an alternative to conventional organic solvents. Structurally ILs are composed of ions, and there is a huge number of possible combinations of ions that result in ILs with very different properties. Therefore, they are termed designer solvents because it is possible to develop ILs with specific functions for each application. This huge number of possible combinations and the scarcity of experimental data available in the literature justifies the application of predictive models to estimate their thermophysical properties. The fact that these systems are in liquid phase makes it difficult their treatment with conventional methods developed for the calculation of molecular structure. In this regard, COSMO and COSMO-RS methods have provided an alternative which takes into account this structure to make predictions of their chemical behavior and properties. With COSMO-RS, the values of thermophysical properties of pure fluids and mixtures can be predicted using only structural information of molecules. In theoretical studies, ILs can be treated with two models: ion pairs, in which each cation-anion pair is considered as a whole from a structural point of view, or independent ions, in which the IL is considered as a mixture of ions. This work takes into account both models to study the molecular structure of a set of ILs and different methods have been used for analyzing their electron density. The size of the system makes the application of rigorous calculation methods unfeasible. For this reason, a reasonable compromise between quality and computational cost was found with methods based on the density functional theory. Molecular structure calculations for different ILs were carried out with these methods, and the influence of this structure on predictions of their physicochemical properties was analyzed by COSMO-RS. Within the wide variety of ILs, bioderived ILs are especially interesting due to their high biodegradability and low toxicity. The anionic part of these ILs is the aminoacid and the cationic part is usually formed by imidazolium, amines, pyrrolidinium or phosphonium derivatives. This work was focused on the study of some of their most interesting properties, such as density and viscosity. Finally, the goal of this Doctoral Thesis is to analyze the molecular structure of different ILs, and the relationship with their chemical and thermophysical properties, the development of a methodology for predictions of their properties using COSMO and COSMO-RS, and the validation of this methodology by comparison with results available in the literature

Preparation of medicated polylactide micropieces by means of ultrasonic technology

A technology based on the application of ultrasound as an energy source was applied to get polylactide (PLA) micropieces with minimum degradation and processing time. This requirement could be even shorter than 1.5 s. The ultrasound technology was also demonstrated to be efficient for the incorporation of drugs with a pharmacological activity. Thus, the loading of two representative bactericide agents (i.e., triclosan (TCS), and chlorhexidine (CHX)), having differentiated chemical properties was evaluated. Typical physicochemical characterization included mechanical and thermal properties together with the evaluation of molecular degradation during processing for both unloaded and loaded specimens. Results pointed out that the thermally stable TCS could be loaded into the specimens without any problem, but cautions should be taken into account for CHX. Nevertheless, degradation could in this case be avoided when the drug load was lower than 3 wt-%, a result that contrasts with the significant decomposition attained by using conventional melting processes, which required long processing times at high temperatures. Morphologic analyses of loaded specimens did not reveal significant defects, while spectroscopic analyses showed that a good dispersion of drugs inside pieces could be attained. Drugs were slowly released from micropieces with a rate that was dependent on their hydrophilic character. Thus, release in a phosphate buffered saline (PBS)-ethanol medium (70% of PBS) followed a first order kinetics with constants of 0.0356 h-1 and 0.027 h-1 for CHX and TCS, respectively. A clear bactericide effect against both Gram-positive and Gram-negative bacteria was achieved at the beginning of exposure to the corresponding culture media, while a bacteriostatic effect was interestingly still detected after long exposure times. In fact, bacterial growth could be reduced to near 20% when micropieces were loaded with only 3 wt-% of any of the selected CHX and TCS drugsPostprint (published version

Biodegradable polylactides scaffolds with pharmacological activity by means of ultrasound micromolding technology

Ultrasound micromolding technology has been applied to get microporous polylactide scaffolds from the subsequent leaching of incorporated NaCl salts. A small amount of water-soluble polyethylene glycol (PEG) was required in order to improve the leaching process and get compact pieces with interconnected pores. Distribution of polymers in the processed specimens was quite homogeneous due to the small PEG content, although it was more concentrated in the regions close to the feeding channels due to its higher viscosity. Hydrophobic drugs like triclosan could be incorporated causing a minimum degradation during ultrasound processing and suffering an insignificant solubilization during the leaching step. Final scaffolds showed clear bactericide or bacteriostatic effects before and after 10 h of exposure. Cell proliferation of MDCK epithelial cells was higher for TCS loaded porous scaffolds (200%) than for unloaded samples (170%) and non-porous polylactide (PLA) specimens (100%, control). Micrographs showed the absence of non-inhibition areas in both the specimens and the container, confirming the biocompatibility of PLA specimensPeer ReviewedPostprint (published version

Gestión de Empresas 2.0. Desde la Estructura Jerárquica hasta las Redes de Conocimiento. El Modelo CIACO_RED

[ESP] En este trabajo se abordan tres de los principales fenómenos que convierten a la empresa en una estructura en constante cambio y donde las personas participativas, colaborativas, abiertas, con visión global, y sin miedo a lo nuevo e insólito, se convierten en los protagonistas principales y agentes capaces de dar respuestas a los nuevos desafíos. El resultado es una nueva organización, donde pueden participar agentes desconocidos hasta el momento, que deberá aprender a reinventarse de forma permanente y en clara sintonía con tales cambios. A este respecto, no es mucho decir, que el éxito de la empresa, su fuerza, energía y permanencia no está en sus fuentes de producción, sino en el conocimiento, talento y competencias de sus trabajadores, actuando colectivamente, adaptados a las nuevas tecnologías y sin miedo a lo nuevo e inesperado. Obviamente, ante esta coyuntura, los modelos o formas de gestión tradicionales no sirven y deben ser sustituidos por otros que presten su atención de manera prioritaria en los lazos que articulan la empresa y que, además, son los facilitadores del uso pleno de las capacidades y conocimientos de los trabajadores. Este planteamiento organizativo, en el pasado, sencillamente, no era posible. Se habla, así, de empresas 2.0, modelos de gestión abiertos, redes de conocimiento como alternativas de interacción y colaboración para acometer los nuevos desafíos y todo un conjunto de tecnologías para la información, relaciones y comunicaciones al servicio de los “trabajadores del conocimiento

Accuracy of urea breath test performed immediately after emergency endoscopy in peptic ulcer bleeding

Producción CientíficaThe aim of this work is to investigate the accuracy of the urea breath test (UBT) performed immediately after emergency endoscopy in peptic ulcer bleeding (PUB). METHODS: Urea breath test was carried out right after emergency endoscopy in patients with PUB. The accuracy of this early UBT was compared to a delayed one after hospital discharge that was considered the gold standard. Clinical and epidemiological factors were analyzed in order to study their influence on the accuracy of the early UBT. RESULTS: Early UBT was collected without any complication and good acceptance from all the 74 patients included. In 53 of the patients (71.6%), a delayed UBT was obtained. Comparing concordance between the two tests we have calculated an accuracy of 83% for the early UBT. Sensibility and specificity were 86.36 and 66%, respectively, with a positive predictive value of 92.68% and negative predictive value of 50% (Kappa index = 0.468; p = 0.0005; CI: 95%). We found no influence of epidemiological factors, clinical presentation, drugs, times to gastroscopy, Forrest classification, endoscopic therapy, hemoglobin, and urea levels over the accuracy of early UBT. CONCLUSIONS: Urea breath test carried out right after emergency endoscopy in PUB is an effective, safe, and easy-to-perform procedure. The accuracy of the test is not modified by clinical or epidemiological factors, ulcer stage, or by the type of therapy applied. However, we have found a low negative predictive value for early UBT, so a delayed test is mandatory for all negative cases

Effect of dielectric constant on estimation of properties of ionic liquids: an analysis of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

A series of different cationic structures based on 1-alkyl-3-methylimidazolium were combined with a single anion, bis(trifluoromethylsulfonyl)imide (CnmimNTf2, n = 1 to 12) for analyzing the quality of COSMO-RS based estimations. For this purpose, we have studied the structure as well as the estimations of several properties of one ionic liquid (IL). These estimations are obtained from polarization charge distribution in which the IL is embedded. Special attention has been paid to the effect of the dielectric constant value in the predictions. For this purpose, polarization charge density has been modeled using several values of dielectric constant, and properties have been estimated in each case. Thus, σ-profiles and, σ-potentials have been computed and used with COSMO-RS for estimating vapor pressure, as a function of temperature, as well as theoretical values of vaporization enthalpy, density, and viscosity at 298.15 K. The influence of the length of the alkyl chain of ionic liquid in the estimation of these properties has also been tested. Finally, the results have been compared with experimental dataThe authors thank the “Ministerio de Ciencia e Innovación” (Project: CTQ2010-19232) and “Comunidad de Madrid” (Project: LIQUORGAS-S2013/MAE-2800) financial suppor

Percutaneous treatment of a duodenocutaneous high-flow fistula using a new biological plug

Enterocutaneous fistula is a challenging entity and a gold-standard treatment is not settled so far. Here, we describe the successful closure of a duodenocutaneous fistula with the use of the Biodesign enterocutaneous fistula plug (Cook Medical), which is derived from a biological plug that has been used in recent years in order to close anorectal fistula tracts

El ingreso hospitalario de desintoxicación en pacientes graves en programa de mantenimiento con metadona: resultados a corto y medio plazo

Introducción: Se analiza naturalísticamente la evolución durante seis meses de pacientes graves en Programas de Mantenimiento con Metadona (PMM) que presentan recaídas en el consumo de opiáceos y/o cocaína y requieren un ingreso hospitalario de desintoxicación. El diseño es prospectivo y la estadística descriptiva. Resultados: Se realiza el seguimiento de 15 personas que cumplían los criterios de inclusión durante 18 meses consecutivos. La mayoría de los pacientes (11:15) recaen precozmente en el consumo de drogas. El patrón de reinicio de consumo es similar: primero reinician el consumo de cocaína y posteriormente de opiáceos. El tiempo medio de recaída en cocaína es de 1.8 meses, y de heroína es de 2.8 meses. Conclusiones: La efectividad a corto y medio plazo del ingreso hospitalario de desintoxicación en PMM, que han recaído en el consumo de drogas es baja. El patrón de nuevas recaídas es predecible y típico

Disturbed, diffuse, or just missing? A global study of the H I content of Hickson compact groups

Context. Hickson compact groups (HCGs) are dense configurations of four to ten galaxies, whose H I morphology appears to follow an evolutionary sequence of three phases, with gas initially confined to galaxies, then significant amounts spread throughout the intra-group medium, and finally with almost no gas remaining in the galaxies themselves. It has also been suggested that several groups may harbour a diffuse H I component that is resolved out by interferometric observations. Aims. The H I deficiency of HCGs is expected to increase as the H I morphological phase progresses along the evolutionary sequence. If this is the case, H I deficiency would be a rough proxy for the age and evolutionary state of a HCG. We aim to test this hypothesis for the first time using a large sample of HCGs and to investigate the evidence for diffuse H I in HCGs. Methods. We performed a uniform reduction of all publicly available VLA H I observations (38 HCGs) with a purpose-built pipeline that also maximises the reproducibility of this study. The resulting H I data cubes were then analysed with the latest software tools to perform a manual separation of emission features into those belonging to galaxies and those extending into the intra-group medium. We thereby classified the H I morphological phase of each group as well as quantified their H I deficiency compared to galaxies in isolation. Results. We find little evidence that H I deficiency can be used as a proxy for the evolutionary phase of a compact group in either of the first two phases, with the distribution of H I deficiency being consistent in both. However, for the final phase, the distribution clearly shifts to high H I deficiencies, with more than 90% of the expected H I content typically missing. Across all HCGs studied, we identify a few cases where there is strong evidence for a diffuse gas component in the intra-group medium, which might be detectable with improved observations. We also classify a new sub-phase where groups contain a lone H I-bearing galaxy, but are otherwise devoid of gas. Conclusions. The new morphological phase we have identified is likely the result of an evolved, gas-poor group acquiring a new, gas-rich member. The large spread of H I deficiencies in the first two morphological phases suggests that there is a broad range of initial H I content in HCGs, which is perhaps influenced by large-scale environment, and that the timescale for morphological changes is, in general, considerably shorter than the timescale for the destruction or consumption of neutral gas in these systems