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When the wavelength of the Raman scattered light coincides with the absorption spectrum of the sample, a phenomenon known as Raman self-absorption occurs. If the absorption wavelength range matches completely with the Raman wavenumber range for a given excitation line (high absorption), this process causes spectra with poor signal-to-noise-ratio, making the acquisition nearly impossible. When the absorption of the sample and the Raman scattered are partially coincident (low absorption), smaller modifications in the band-profile of the Raman spectrum are expected difficult to be detected. If a different excitation wavelength is available in order to avoid or minimize this phenomenon, a correction method is customary. The correction methods developed so far in quantitative analysis are still very complex and require the knowledge of several sampling parameters. In this work, we present a very simple but reliable method based on the Beer-Lambert law to correct low self-absorption effects. This method uses simple concepts, a straightforward methodology and the concentration of the Raman active component in the liquid matrix is the only parameter required to perform the correction. This method may be extremely useful in different fields in which Raman spectroscopy is used to obtain molecular and structural information from a band profile analysis. As an example, the method is applied here to successfully correct the Raman spectra of different CuSO4 aqueous solutions excited at 532 nm.

Raman spectra of methanol-water mixtures were measured over the whole composition range at room conditions. The spectra are used to quantify the strength of intermolecular interactions in terms of local internal pressures. The conclusions derived from the spectroscopic analysis are discussed within the framework of the solvation pressure model using values of the cohesion energy density expected in the mixture. This work demonstrates that an appropriate analysis of Raman spectroscopy experiments can be used to quantify the local internal pressures due to intermolecular interactions in liquid mixtures, provided that high pressure results of the pure liquids are available.

Introducción: el objetivo de este trabajo de investigación fue explicar cuáles son las técnicas más utilizadas para extraer una pieza que se fractura en el transquirúrgico, en el área de cirugía de la Universidad Iberoamericana, durante el período febrero-mayo del 2013, y demostrar si los estudiantes del pregrado son capaces o no de resolver este tipo de complicación. Métodos: para este estudio se diseñó un cuestionario, el cual fue dispuesto en el área de cirugía de la clínica dental de la Universidad Iberoamericana; los doctores responsables de cada tanda de cirugía debieron contestarlo y firmarlo al momento en que se fracturara una pieza durante el transquirúrgico. También fue realizada una encuesta a los doctores del área, para corroborar y obtener sus puntos de vista sobre los datos recolectados con el cuestionario. Resultados: la odontosección, el levantamiento de un colgajo, ostectomía y el uso de elevadores apicales son las técnicas utilizadas en esta área para extraer un fragmento fracturado. Conclusiones: se demostró que la odontosección fue la técnica más utilizada. A su vez se determinó que en la mayoría de los casos de fractura, el doctor responsable tuvo que intervenir en la extracción.

We have carried out a systematic study of abiotic precipitation at different temperatures of several Mg and Ca carbonates (calcite, nesquehonite, hydrocalcite) present in carbonaceous chondrites. This study highlights the capability of Raman spectroscopy as a primary tool for performing full mineralogical analysis. The precipitation reaction and the structure of the resulting carbonates were monitored and identified with Raman spectroscopy. Raman spectroscopy enabled us to confirm that the precipitation reaction is very fast (minutes) when Ca(II) is present in the solution, whereas for Mg(II) such reactions developed at rather slow rates (weeks). We also observed that both the composition and the reaction mechanisms depended on temperature, which might help to clarify several issues in the fields of planetology and geology, because of the environmental implications of these carbonates on both terrestrial and extraterrestrial objects.

Raman spectra of 1,2-ethylenediamine (EDA) in aqueous solutions are used to demonstrate that EDA molecules experience an anti–gauche conformational change resulting from the interactions with water. The observed Raman shift reveals a compressive (hydrophobic) effect of water on both methylene and amino groups of EDA. Raman spectra of EDA at high pressures are used as reference to quantify the intermolecular EDA–H2O interactions in terms of local pressures. These results are compared with macroscopic solvation pressures calculated from the cohesive energy parameter. We compare and discuss all our observations with available computational and experimental studies.

OBJETIVO: Conocer la frecuencia de portadores nasales de cepas de Staphylococcus aureus resistentes a meticilina (SARM) y el patron de resistencia antimicrobiana de esas cepas obtenidas de trabajadores de la salud de cuatro hospitales de Nicaragua. METODOS: Se realizo un estudio descriptivo, transversal, en el periodo del 1 de junio de 2009 al 30 de septiembre de 2010. Los hisopados nasales de los trabajadores de la salud que aceptaron voluntariamente participar en el estudio fueron cultivados en medio agar base de deteccion de resistencia a oxacilina (ORSAB). La identificacion de los aislados de S. aureus se realizo por metodos cotidianos y la resistencia a meticilina se determino por la presencia del gen mecA con la tecnica de reaccion en cadena de polimerasa. El patron de resistencia antimicrobiana se detecto por difusion en disco. Cada participante firmo un consentimiento informado con anterioridad a la toma de la muestra. RESULTADOS: Participaron en el estudio 569 trabajadores de la salud, de los cuales 208 eran del hospital de Leon, 155 de dos hospitales de Chinandega y 206 del de Managua. La frecuencia de portadores nasales de SARM fue de 9,6% en Leon, 11,6% en Chinandega y 6,7% en Managua. El perfil de resistencia de las cepas SARM fue similar en los cuatro hospitales y todas las cepas fueron sensibles a vancomicina. Del total de cepas SARM aisladas, 15% fueron multirre-sistentes. El porcentaje de resistencia a eritromicina fue el mas alto, seguido del de clindamicina. CONCLUSIONES: Los resultados del estudio se pueden considerar una advertencia sobre la circulacion de cepas SARM entre el personal de salud de los hospitales participantes y aportan informacion relevante en relacion al perfil de resistencia de las cepas SARM.

Despite the widespread use of the 4:1 methanol–ethanol mixture as a hydrostatic medium by the high-pressure community, its equation of state (EOS) is usually substituted by that of pure methanol. Here we report accurate direct volumetric measurements of the room temperature EOS for this mixture up to 5 GPa. A brief description of the optical technique (imaging+interferometric) specifically developed for this purpose is given, as well as the general characteristics of the required miniature diamond anvil cell. Our results are compared with the available data of similar pure fluids’ EOS in the same pressure range. We find that there exist noticeable differences between the EOS of the mixture and that of pure methanol in terms of molar quantities.

En los últimos años se ha observado un incremento de la incidencia de la Resistencia Antimicrobiana entre patógenos que causan infecciones intra-hospitalarias principalmente y también en la comunidad. La Resistencia antimicrobiana es un problema global de salud pública, promovido básicamente por el uso y abuso de los antibióticos. El fenómeno de la Resistencia antimicrobiana es un área prioritaria de investigación del Centro de investigación de enfermedades infecciosas y como parte de sus actividades se realizó un estudio en tres hospitales noroccidentales (León, Chinandega y Estelí) con el objetivo de conocer el perfil de resistencia o sensibilidad antimicrobiana de bacterias aerobias aisladas de pacientes que fueron atendidos en estos hospitales en el periodo comprendido entre Mayo 2003 a Mayo 2006. Se incluyó en el estudio 1181 cepas de bacterias aerobias y se utilizó el método Kirby Bauer según recomendaciones del NCCLS, para determinar el perfil de resistencia. Las más frecuentes especies bacterianas estudiadas fueron, Estafilococos aureus (385 cepas), E. coli (209 cepas), Pseudomona spp. (180 cepas) seguidas por un menor número de cepas de Shígella spp., Streptococos beta hemolìticos del grupo A y otros bacilos Gram negativos obtenidas principalmente de muestras biológicas de infecciones de piel y tejidos blandos, bacteriemia neonatal, infecciones de vías urinarias y Faringoamigdalitis. Los Resultados obtenidos fueron los siguientes: Penicilina fué el fármaco de menor efectividad contra E. aureus; un porcentaje importante mayor del 25% fueron resistentes a Meticilina principalmente cepas de Estelí. Sin embargo estos antibioticos fueron altamente efectivos contra Streptococos, no se presentó resistencia a Vancomicina. En relaciòn a las bacterias Gram negativas, T. sulfa fue el antimicrobiano de menor efectividad contra E. coli aislados de urocultivos, con un porcentaje similar en los tres hospitales, e igualmente contra Klebsiella spp. y otros Gram negativos, excepto Pseudomona spp. para el que no esta indicado su análisis. Pseudomona spp. fue resistente principalmente a Cloranfenicol y Ceftriaxona en Estelí, a Ceftriaxona y Gentamicina en León y Chinandega. Los resultados de este estudio muestran la importancia del problema y ofrecen la posibilidad a la comunidad médica de utilizarlos para adecuar las pautas de tratamiento y contribuir a modificar conductas de riesgo que promueven la Resistencia antimicrobiana.DOI: http://dx.doi.org/10.5377/universitas.v1i1.1630

We present direct measurements of the isothermal compressibility (κT) and thermal expansion coefficient (αp) of liquid methanol using an expansion technique. The measurements of κT were carried out along six isotherms from (208.17 to 298.16) K at pressures up to 101 MPa. For αp, we have measured four isobars from (0.59 to 80.03) MPa from 195 K up to 300 K. Our experimental results of αp(T) for the 0.59 MPa isobar exhibit a minimum around 224 K. A clear shift of the minimum to higher temperatures is observed as the pressure increases along the different isobars. Interestingly, the minima for the isobars of αp(ρ) take place within a narrow range of densities, around 26.5 mol·dm-3 (about 3.15 times the critical density).

In a previous work, we analysed some regularities found in the behaviour of the thermal expansion coefficient, αp, in compressed liquids. We confirmed that a given liquid presents a characteristic pressure range in which the condition is fulfilled within a narrow range of reduced densities. We also found that the density at which the condition is satisfied, ρα, decreases with temperature, a key feature not described before. Earlier studies by other authors suggested that similar regularities are expected for the reduced bulk modulus, B. We present here a detailed analysis of the temperature and density dependence of B from existing experimental results at high pressures. Several liquids have been analysed: argon, krypton, xenon, ethylene, tetrafluoromethane, trifluoromethane, carbon dioxide, carbon disulfide, n-butane, n-hexane, toluene, ethanol, 1-hexanol, m-cresol, and quinoline. We locate that the density ρB that fulfils the condition occurs at a particular region of the phase diagram, between 3.4 and 2.4 times the critical density of each liquid. Interestingly, the previously found density ρα is close to ρB, in a similar region of the reduced phase diagram. However, we note that ρB typically decreases to a lesser extent with temperature than ρα. In addition, we have found that ρB(T) behaves in a parallel fashion for the different liquids, showing larger values of ρB as the complexity of the molecules increases. These findings provide a strong basis for developing general equation of state models to describe the behaviour of liquids in the high-pressure regime.

Measurements of the refractive index from 293 to 321 K at four fixed wavelengths, from 587.6 to 404.7 nm, are reported for valeric acid (pentanoic acid), caproic acid (hexanoic acid), oenantic acid (heptanoic acid), caprylic acid (octanoic acid), and pelargonic acid (nonanoic acid). We also report the temperature and wavelength dependencies of the refractive index obtained from a least-squares routine. The agreement between the measured and calculated refractive indices lies within the experimental uncertainty.

Measurements of the refractive index from 288 to 318 K at five fixed wavelengths, from 656.3 to 404.7 nm, are reported for benzene, toluene (methylbenzene), o-xylene (1,2-dimethylbenzene), m-xylene (1,3-dimethylbenzene), and p-xylene (1,4-dimethylbenzene). We also report the temperature and wavelength dependencies of the refractive index obtained from a least-squares routine. The agreement between the measured and calculated refractive indices lies within the experimental uncertainty.

We analyse here the thermodynamic behaviour of the thermal expansion coefficient for a number of liquids. The purpose of this work is to provide some general rules to develop equations of state models meeting the following criteria: thermodynamic consistency, generality, predictive power and accuracy to represent derived properties over wide ranges of pressure and temperature. The liquids included into our analysis have been selected to meet two criteria: (1) available experimental data over wide ranges of pressure and temperature (from the melting point up to the critical point), and (2) liquids composed of molecules with different geometries and interactions.

We propose a new Raman pressure scale based on the shift with pressure of the fundamental Raman band of micrometer-sized diamonds. First, we confirmed that the pressure slope of the triply degenerate diamond phonon behaves in a similar fashion to that of the bulk. Our measurements were calibrated Raman against the Sm:YAG fluorescence pressure scale up to 5 GPa using a gasketed sapphire anvil cell. The most relevant features regarding the design of the anvil cell are briefly outlined. Measurements were performed under hydrostatic conditions using 4 : 1 methanol–ethanol as pressure-transmitting medium. The calibration pressures according to the relationship p(GPa) = 0.356[ν(cm−1) − 1332.3] are considered to be accurate within about 0.1 GPa. The convenience of using micrometer-sized diamonds as pressure sensors in Raman studies using gem anvil devices is demonstrated with several examples. Copyright © 2003 John Wiley & Sons, Ltd.

A general method to include temperature effects into the equation of state (EOS) of solids is discussed. A universal model based on a pseudo-spinodal approach is used to predict the pressure and temperature dependencies of the thermodynamic properties for a variety of solids: n -H 2 , Ar, Kr, Xe, NaCl, LiF, NaF, KCl, CsCl, Li, Na, K, Rb, Cs, Al, Fe, Cu, Zn, Ag, Cd, Pt, Au, and Pb. The predictive capabilities of the complete EOS are discussed and compared with available models.

La investigacion en salud: Una herramienta para contribuir al desarrollo de la poblacion El desarrollo social y economico del pais, guarda estrecha relacion con los factores que condicionan y determinan el nivel de salud de la poblacion nicaraguense. La investigacion en salud sirve para dos propositos fundamentales en el desarrollo para la salud. a) Investigacion basica tradicional necesaria para generar nuevos conocimientos tecnologicos y terapeuticos para mejorar los grandes problemas no resueltos. b) Investigacion Aplicada para identificar los problemas prioritarios y para disenar y evaluar las politicas y programas que sean de mayor beneficio. Por ejemplo: Es atraves de la investigacion que hemos podido obtener la evidencia cientifica que demuestra que la vigilancia y control de riesgos inherentes a la contaminacion del ambiente fisico y social, de los alimentos, del agua y del aire, entre otros redundan en mejor nivel de salud de la poblacion y del propio ambiente, lo que se traduce en un mejor desarrollo de la poblacion. Es mediante los resultados de las investigaciones que podemos fundamentar las prioridades y avanzar en la busqueda de respuestas para los problemas sanitarios, que evolucionan en la medida que tambien cambian las necesidades de la poblacion. Si se ha comprendido la importancia de la busqueda y utilizacion de la informacion en la toma de decisiones en salud, es facil entender la necesidad de difundir los conocimientos generados a partir de los resultados de una investigacion. Este proceso podemos entenderlo desde el momento en que se analizan e interpretan los resultados hasta que las conclusiones se hacen publicas. Existen diversas formas de hacer conocida una investigacion, algunas mas eficientes que otras, asi se puede recurrir a la presentacion de resultados a los pares (en reuniones clinicas o congresos cientificos) y a la divulgacion a traves de la publicacion en revistas cientificas. Este Volumen de la Revista Cientifica UNIVERSITAS, esta dedicado a la publicacion de los mejores trabajos de investigacion realizados por estudiantes y maestros de la Facultad de Ciencias Medicas en el ano 2007, en las investigaciones presentadas en este revista se abordan temas de gran importancia en salud publica de la poblacion nicaraguense tales como estado nutricional, infecciones perinatales, VIH-SIDA e infecciones parasitarias. En la publicacion de este volumen dedicado a la investigacion en salud podemos observar una actitud comprometida de las autoridades de esta magna casa de estudios. Quienes estan consientes que para que el perfil del profesional de la salud egresado sea integral y se adapte a las demandas del mundo actual es necesario incorporar las actividades de investigacion, que le permitiran el mantenimiento de la competencia profesional y mejorar la calidad de la atencion medica. Asi mismo para entender e interpretar los nuevos hallazgos cientificos y aplicar los principios eticos que se requieren en el ambito de trabajo. La investigacion contribuye a la excelencia academica que es el supremo objetivo de la Facultad de Ciencias Medicas de la UNAN-Leon, para formar un buen profesional de la salud, quien a su vez es un instrumento social en el desarrollo de la poblacion. Dra. Mercedes Caceres, Ph.D. Vice Decana Facultad de Ciencias Medicas, UNAN-Leon DOI: http://dx.doi.org/10.5377/universitas.v2i2.1686

Anais do III Encontro de Iniciação Científica da Unila - Sessão de Engenharia Civil - 06/11/14 – 13h30 às 15h50 - Unila-PTI - Bloco 09 – Espaço 02 – Sala 02 El presente trabajo analiza los aspectos técnicos que interfieren en la calidad del pavimento asfáltico en tres escenarios diferentes respecto al clima y sus políticas de mantenimiento. El proyecto de investigación presenta los resultados de la aplicación de un nuevo instrumento de inspección para pavimentos asfálticos aplicado a 3 casos de estudio como son: Colombia, Brasil y México. Para el nuevo algoritmo de evaluación se han concebido 4 ejes principales: fisuras, deformaciones, pérdida de la capa superficial y daños superficiales. Se concluye que una adecuada visión de la normativa permite orientar un uso racional de la infraestructura viaria, generando estrategias preventivas en el deterioro de pavimentos urbanos. Además, se concluye que las condiciones climatológicas pueden direccionar en el comportamiento del material bituminoso durante el ciclo de vida de la misma. Si bien, las administraciones públicas han manifestado diversidad en sus políticas de mantenimiento, la climatología direcciona notablemente el estado de las vías interurbanas en ambas ciudades estudiadas. Respecto a los resultados cuantitativos el equipo de levantamiento de Brasil identificó que el 40 % son patologías asociadas a fisuras transversales, contra un 60 % en pérdidas de capas asfálticas (llamadas piel de cocodrilo). Para el caso Colombia, el 94.5% de los deterioros encontrados están asociados principalmente al comportamiento frágil que experimentan mezclas asfálticas sometidas a climas de bajas temperaturas. Lo anterior induce a pensar que en un clima como el de la ciudad de Bogotá D.C., las mezclas asfálticas tienden a experimentar un comportamiento frágil que genera principalmente fallas por fatiga. En zonas de clima frío, este mecanismo de daño incrementa en mezclas asfálticas sometidas a envejecimiento a largo plazo (especialmente en vías con escaso mantenimiento superficial en donde el daño por humedad y fenómenos como el stripping se hacen evidentes). En el caso de México, se estima que cerca del 60% del área evaluada presenta deterioro por fisuración, de los cuales el 88% presenta severidad alta, 6% con severidad media y 6% severidad baja. Por otro lado, tanto patologías como pérdida de la capa estructural como deformaciones presentan cerca del 18% y 16% respectivamente. Si bien el deterioro o daño superficial presenta solamente el 4% del total de las patologías el grado de severidad ha sido identificado como 100%. Finalmente, el grado de deterioro tanto de fisuraciones, pérdida de la capa estructural, deformaciones y daños superficiales son menores a las zonas estudiadas en Brasil y Colombia, el grado de severidad en su mayoría son altas, con cerca del 76%. En síntesis, el 62% de los deterioros encontrados están asociados principalmente al comportamiento frágil que experimentan mezcla asfáltica sometida a climas de bajas temperaturas y bajo clima seco desértica, traduciéndose en fisuración en la mayoría de los casos. Universidade Federal da Integração Latino-Americana (UNILA)

Brillouin spectra of liquid toluene have been measured between 288 and 358 K using a dynamic light scattering technique. The polarized spectra have been modeled according to Mountain’s theory. The most relevant quantity of the theory, namely the relaxation time, has been used to check the validity of several molecular models proposed to interpret vibrational–translational energy exchanges observed in nonassociated liquids.

The enthalpies of dilution for aqueous solutions of [Co(en)3]Br3, [Co(pn)3]Cl3, and [Co(tn)3]Cl3 (where en = 1,2-diaminoethane, pn = 1,2-diaminopropane, and tn = 1,3-diaminopropane) have been measured at 25°C, and up to m = 1 mol-kg−1, using an isoperibol calorimeter by the “long-jump” method. Relative apparent molar enthalpies Lφ have been extracted as an empirical equation relating Lφ and m. Previously reported experimental data and theoretical predictions in the restricted primitive model (RPM) for 3:1 and 1:3 aqueous electrolytes are shown together with the new experimental material.

Enterotoxigenic Bacteroides fragilis (ETBF) strains have been reported as a cause of diarrhoeal diseases. Diarrhoea is an important cause of morbidity and mortality in children from developing countries. This study was conducted to determine the prevalence and antimicrobial susceptibility of ETBF in children from Leon, Nicaragua. Faecal specimens from 106 children under ten years of age with diarrhoea and 60 asymptomatic, age-matched controls were examined for presence of ETBF using an assay based on immunomagnetic separation (IMS) in combination with PCR (IMS-PCR) and HT29/C1 cell assay. ETBF was present in nine children with diarrhoea (8.4%) and was more often identified in children ≤1 year (7/63, 11.1%) but all ETBF positive children were under 2 years of age. ETBF was isolated as the only pathogen in five of nine positive children (55.5%). The agar dilution method was used to determine the antimicrobial susceptibility pattern of the ETBF strains. All strains were resistant to ampicillin (range 8–1024 mg/L) and one strain was also resistant to clindamycin MIC 256 mg/L. All the other antimicrobial agents were active against the strains (MIC50and MIC90): 8 and 16 mg/L for cefoxitin, 0.004 and 0.008 mg/L for imipenem, 0.5 and 0.5 mg/L for clindamycin and for metronidazole, 2 and 4 mg/L for chloramphenicol. A majority (77%) of the ETBF strains were β-lactamase producers.

We estimated the incidence of watery diarrhea in the community before and after introduction of the pentavalent rotavirus vaccine in León, Nicaragua. A random sample of households was selected before and after rotavirus vaccine introduction. All children < 5 years of age in selected households were eligible for inclusion. Children were followed every 2 weeks for watery diarrhea episodes. The incidence rate was estimated as numbers of episodes per 100 child-years of exposure time. A mixed effects Poisson regression model was fit to compare incidence rates in the pre-vaccine and vaccine periods. The pre-vaccine cohort (N = 726) experienced 36 episodes per 100 child-years, and the vaccine cohort (N = 826) experienced 25 episodes per 100 child-years. The adjusted incidence rate ratio was 0.60 (95% confidence interval [CI] 0.40, 0.91) during the vaccine period versus the pre-vaccine period, indicating a lower incidence of watery diarrhea in the community during the vaccine period.

We provide evidence of a universal equation of state for solids using a pseudospinodal hypothesis. A simple model to estimate the pseudospinodal curve is presented. This model combined with a previously reported (isothermal) volumetric equation [Baonza et al., Phys. Rev. B 51, 28 (1995)] yields a complete equation of state applicable over the whole range of temperature. The resulting equation appears to be a well-behaved equation of state over the whole range of temperatures using a single reference thermodynamic state of the solid at atmospheric pressure as input data. Comparison with experimental results of molar volume, bulk modulus, and thermal- (volumetric) expansion coefficient are presented. Comparison with previous equations of state are also presented and discussed. Our results imply that the thermodynamics of any solid are governed by its pseudospinodal curve. \textcopyright{} 1996 The American Physical Society.

Experimental excess volume, surface tension and isothermal compressibility measurements at atmospheric pressure are reported for ethanol–methylcyclopentane at 298.15 K. These data have been used to estimate the molar volume of the mixture up to 200 MPa through a novel procedure. Surface tension measurements at 293.15 K for carbon disulfide–tetramethylsilane are also reported. These data, together with measurements of molar volume and isothermal compressibility at atmospheric pressure previously reported for this mixture, have been used to make an analogous study up to 100 MPa. Comparison with experimental data is rather satisfactory for both systems. Differences between experimental and calculated volumes are commonly less than 1%, which allow us to predict adequately the pressure behaviour of the molar excess volume.

Some experimental studies indicate that the isothermal compressibility, κT, of molecular liquids follows a power law up to very high pressures along isothermal paths. We show here that the high-pressure behavior of κT can be characterized from surface tension and κT data measured at low pressures. Our method is based on a pseudospinodal hypothesis. Comparison with experimental is satisfactory up to very high pressures for different molecular liquids. The results are also studied in terms of the reduced bulk modulus. B. Our method reproduces adequately the intersections experimentally found for the isotherms of B versus molar volume of molecular liquids.

Most of useful estimation techniques for surface tension of liquids are based on empirical correlations and general methods with molecular basis are rare in the literature. In this paper we show how combining an expression derived from the hole theory of Furth with an statistical-mechanical based equation of state, an estimation of surface tension and its behavior with temperature is easily obtained.

Accurate thermal expansion coefficient αp, speed-of-sound and density measurements found in the literature have been used to characterize the general behavior with pressure of the constant pressure heat capacity Cp of benzene and toluene. The results agree well with direct measurements of Cp found in the literature. Indirect methods for estimating Cp at high pressures are discussed. αp results obtained with an expansion technique using a differential method have been used to characterize the high-pressure behavior of Cp for mesitylene.

Experimental pρT measurements and derived thermodynamic properties of p-xylene (1,4-dimethylbenzene) have been obtained with an expansion technique for temperatures between 288 and 303 K and pressures up to 43 MPa, or freezing pressure when lower. The solid-liquid coexistence curve of this compound was also measured up to 40 MPa. The experimental results have been correlated in terms of a recently derived equation of state, which is introduced here and has been used to calculate the isothermal compressibility, κT, and the thermal expansion coefficient, αp, as functions of pressure and temperature. The equation of state depends only on six parameters, all of which are physically meaningful. Comparisons of several properties show good agreement with literature values.

pρT values for liquid o-xylene have been measured with an expansion technique at temperatures between 258 and 298 K and pressures up to 108 MPa. Isothermal compressibility and thermal expansion coeffcient data are reported as functions of pressure and temperature. The pρT results have been used to test the performance of two recently developed equations of state and to study the physical significance of their characteristic parameters. The extrapolation capabilities of both equations have been checked with experimental results from the literature at higher pressures and temperatures.

Experimental pρT measurements of m-xylene obtained with an expansion technique are reported from 230 to 298 K and up to 110 MPa, or freezing pressure when lower. The experimental results have been correlated in terms of a recently proposed equation of state which has been used to calculate the isothermal compressibility, κT, and the thermal expansion coefficient, αp, as functions of pressure and temperature. Experimental density results for liquid toluene, which was used to calibrate our experimental device, are also reported for the isotherms of 223 and 303 K. The ability of simple power functions recently proposed to correlate high-pressure results has been tested. The extrapolation capabilities of these functions have been confirmed using experimental results from the literature for the two compounds studied.

To determine the frequency of nasal carriers of strains of methicillin-resistant Staphylococcus aureus (MRSA) and the antimicrobial resistance pattern of these strains, obtained from health workers from four hospitals in Nicaragua.A descriptive cross-sectional study was conducted between 1 June 2009 and 30 September 2010. Nasal swabs were taken from health workers who voluntarily agreed to participate in the study, and were cultured on an oxacillin-resistant screening agar base (ORSAB) medium. The S. aureus isolates were identified using ordinary methods, and methicillin resistance was confirmed based on the presence of the mecA gene using the polymerase chain reaction technique. The antimicrobial resistance pattern was detected by the disk diffusion method. Each participant signed an informed consent form before the samples were taken.A total of 569 health workers participated in the study: 208 from one hospital in León, 155 from two hospitals in Chinandega, and 206 from one hospital in Managua. The frequency of nasal MRSA carriers was 9.6% in León, 11.6% in Chinandega, and 6.7% in Managua. The MRSA resistance profile was similar in the four hospitals, and all the strains were sensitive to vancomycin. Of the total MRSA strains isolated, 15% were multi-drug resistant. Erythromycin had the highest percentage of resistance, followed by clindamycin.The results of the study may be regarded as a warning that MRSA strains are circulating among health workers in the participating hospitals. The study also contributes important information regarding the resistance profile of MRSA strains.

Experimental and theoretical studies suggest that the thermal expansion coefficients α p of liquids follow a power law up to extremely high pressures along isothermal paths. Accurate experiments reveal that intersections between α p isotherms occur at high pressure for many liquids. It is shown how the high-pressure behavior of α p can be accurately predicted for real liquids from surface tension and low-pressure α p measurements. The method proposed here is based on the assumption that the spinodal curve does exist and can be estimated from surface tension measurements using Furth's hole theory.

Molar densities have been measured by using an expansion technique at pressures up to 104 MPa and temperatures from 198 to 298 K for the mixture {x CS2 + (1-x) Si(CH3)4}(1) over the whole composition range. Several thennodynamic properties (isothermal compressibility, thermal expansivity, and molar internal energy, enthalpy and entropy increments relative to liquid at saturation) have been directly obtained from the experimental densities. The isothermal compressibility and the thermal expansivity are both smooth functions of pressure, temperature and composition, although the isotherms of the thermal expansivity exhibit a characteristic crossover at high pressures. The intersection of isotherms of thermal expansivity seems to occur at a single point of the (p,αp) diagram, showing a nearly linear dependence with the composition.

Studying the behavior with pressure and temperature of thermal expansivity data derived from (p,p,T) measurements of liquids, we found that a previously derived analytical equation of state is inapplicable under certain thermodynamic conditions. The main obstacle is that these conditions are determined by characteristic constants of the liquid under study. Following the same scheme used to derive the original equation of state, we propose a new analytical expression which removes this restriction. Three different substances have been used to test the ability of the new equation of state to represent the volumetric properties of compressed liquids

Rheumatic heart disease (RHD) results in morbidity and mortality that is disproportionate among individuals in developing countries compared to those living in economically developed countries. The global burden of disease is uncertain because most previous studies to determine the prevalence of RHD in children relied on clinical screening criteria that lacked the sensitivity to detect most cases. The present study was performed to determine the prevalence of RHD in children and young adults in Leon, Nicaragua, an area previously thought to have a high prevalence of RHD. This was an observational study of 3,150 children aged 5 to 15 years and 489 adults aged 20 to 35 years randomly selected from urban and rural areas of Leon. Cardiopulmonary examinations and Doppler echocardiographic studies were performed on all subjects. Doppler echocardiographic diagnosis of RHD was based on predefined consensus criteria that were developed by a working group of the World Health Organization and the National Institutes of Health. The overall prevalence of RHD in children was 48 in 1,000 (95% confidence interval 35 in 1,000 to 60 in 1,000). The prevalence in urban children was 34 in 1,000, and in rural children it was 80 in 1,000. Using more stringent Doppler echocardiographic criteria designed to diagnose definite RHD in adults, the prevalence was 22 in 1,000 (95% confidence interval 8 in 1,000 to 37 in 1,000). In conclusion, the prevalence of RHD among children and adults in this economically disadvantaged population far exceeds previously predicted rates. The findings underscore the potential health and economic burden of acute rheumatic fever and RHD and support the need for more effective measures of prevention, which may include safe, effective, and affordable vaccines to prevent the streptococcal infections that trigger the disease.

The Deiters equation of state has been used to predict the vapor-liquid equilibrium and second virial coefficient for several pure substances. The equation of state depends on three characteristic parameters which can be calculated from the critical constants. A general procedure to determine the characteristic parameters is reported. The predictions are very satisfactory, being within the experimental uncertainties in most cases.

The densities of dilute aqueous solutions of [CoL3]X3 [L=1,2-diaminoethane(en), 1,2-diaminopropane(pn), 1,3-diaminopropane(tn) X=Cl−, Br− and (ClO4)−] have been measured at 25°C from 0 to 5×10−2m. The apparent molar volumes were calculated and extrapolated to infinite dilution. Ion-solvent interactions were detected from the change of the ionic partial molar volumes with concentration. These interactions depend both on the properties of the ion (polarization charge density at the surface, hydrophobic groups, etc.) and the characteristics and structure of the solvent.

Osmotic coefficients of aqueous solutions of tris(ethylenediamine)cobalt(III) chloride, tris(ethylenediamine)cobalt(III) bromide, tris(ethylenediamine)cobalt(III) iodide, tris(ethylenediamine)cobalt(III) nitrate, and tris(ethylenediamine)cobalt(III) perchlorate have been measured from 0.000 to 0.025 mol-kg −1 . The freezing-point method was used for the determination of the osmotic coefficients. These results were fitted to semiempirical least-squares equations, and these equations were used to calculate the mean molal activity coefficients

Brillouin spectra obtained in dynamic light-scattering experiments are reported for the three isomeric xylenes (ortho-, meta-, and paradimethylbenzenes) between 288 and 363 K. Limiting sound velocities and relaxation times, as obtained from the polarized spectra using the theory developed by Mountain [J. Res. Natl. Bur. Stand. 70A, 207 (1966)], reveal the existence of a relaxation process. Our results suggest that the relaxation process in liquid xylenes has a purely vibrational nature. Vibrational-translational energy exchanges in xylenes are analyzed in terms of available molecular models and compared to those previously obtained for toluene and benzene. The results presented here confirm the important role played by the molecular geometry in the vibrational relaxation process, as the relative arrangement of the methyl groups has significant effect in determining the relaxing vibrational modes.

We use a dynamic light scattering technique to measure both polarized (VV) and depolarized (VH) spectra of liquid diphenylmethane (DPM) between 288 and 362 K, covering both normal and supercooled liquid ranges. Our results allow extracting information on structural relaxation processes, rotational motions, rotation–translation couplings, and molecular reorientation phenomena in liquid DPM. The VV spectra are modeled according to the microscopic theory of Wang [J. Chem. Phys. 70, 3796 (1979)], which assumes that a structural relaxation process dominates the spectrum. We find that the relaxation time of the structural relaxation in DPM follows an Arrhenius behavior. The Rayleigh dip was observed in the VH spectra, which are described using the Andersen–Pecora [J. Chem. Phys. 54, 2584 (1971)] theory. Our results are discussed in terms of the rotation–translation coupling parameter, which we find independent of temperature over the experimental range. The collective reorientation time also follows an Arrhenius behavior with temperature. Finally, we calculate the hydrodynamic volumes for the reorientation process from geometric molecular models in two hydrodynamic limits: slip and stick boundary conditions. Our results suggest that the DMP molecule reorientates in quasi-slipping conditions in the bulk liquid.

El objetivo del trabajo es la descripcion de un equipo experimental que permite obtener el espectro de luz difundida por un liquido, tanto polarizada como despolarizada, a temperaturas entre 288 y 368 K. El analisis de los espectros se realiza utilizando una tecnica interferometrica. Se describen, en primer lugar, los elementos esenciales del equipo, asi como el procedimiento utilizado para obtener el espectro experimental. El buen funcionamiento del equipo experimental ha sido comprobado midiendo algunos espectros VV y VH de liquidos previamente estudiados por otros autores. La comparacion entre nuestros resultados y los de la literatura para el n-hexadecano liquido muestra una buena concordancia. Por lo tanto, se concluye que el dispositivo experimental propuesto permite obtener aceptables espectros VV y VH de liquidos.

El objetivo del trabajo presentado fue la construcción de un calorímetro de envoltura isotérmica destinado a medir entalpía de dilución de disoluciones acuosas de electrolitos de alta carga. Para verificar la capacidad del calorímetro se ha medido la entalpía de dilución de cloruro de potasio a 25ºC, y hasta concentraciones (m) de 1.6 mol·kg-1, obteniéndose una concordancia satisfactoria con los datos de la literatura. Con este calorímetro se han medido las entalpías de dilución de los sistemas acuosos [Co(en)3]Cl3 y [Co(tn)3]Cl3. Los resultados obtenidos para estos sistemas se muestran como entalpía molar aparente relativa frente la raíz cuadrada de la concentración, m½. Los resultados de este estudio confirman que el calorímetro es idóneo para la medida de entalpías de dilución de complejos del tipo cobaltoamina. The goal of this work was the development of an isothermal jacket calorimeter to measure enthalpies of dilution for aqueous solution of high charge electrolytes. The accuracy of the calorimeter has been verified with the aqueous system potassium chloride at 25ºC and up to concentrations (m) of 1.6 mol·kg-1, finding satisfactory agreement with literature data. Enthalpies of dilution have been measured with this calorimeter for aqueous systems [Co(en)3]Cl3 and [Co(tn)3]Cl3, The experimental values for these systems are shown as relative apparent molar enthalpy against the square root of the concentration, m½. This work confirms that the calorimeter is suitable to measure the enthalpy of dilution for cobalt-amine-type salts.

The enthalpies of dilution of aqueous solutions of {Co(en)3}Cl3and {Co(tn)3}Cl3(where en = 1,2-diaminoethane andtn = 1,3-diaminopropane) have been measured up to m = 1 mol · kg − 1at T = 278.15 K and atmospheric pressure with an isoperibol calorimeter by the long-jump method. Relative apparent molar enthalpies Lφ,mhave been extracted from an empirical polynomial of the molality square root. Previously reported data at T = 298.15 K are compared with the new experimental dilution results. A noticeable decrease in Lφ,mwas observed at every experimental concentration when temperature diminished from 298.15 K to 278.15 K. An inversion in the relative layout for the Lφ,mcurves of aqueous {Co(en)3}Cl3and {Co(tn)3}Cl3was also found., This research was supported by DGESIC (M.E.C., Spain) under Research ProjectNo.: PB98-0832.

We recently proposed an isothermal equation of state that was successfully applied to study the high-pressure behavior of molecular liquids. In this work we extend its applicability to liquid metals, polymers, molten salts, and solids. The possibility of considering this equation as an alternative to long-standing equations such as those of Tait and Birch-Murnaghan is emphasized. This suggestion is firmly supported by comparisons with experimental data up to pressures of several GPa. A new physical interpretation of the pressure coefficient of the Tait equation ${\mathit{B}}_{\mathit{T}}$ is given. It can be identified to the divergence pressure along a pseudospinodal curve. We also compare the performance of our equation with the most successful equations of state used to represent isothermal data of solids, with excellent results. Our equation can be applied to systems with phase transitions. An interesting observation is that it seems that the different pseudospinodal curves obtained for the different phases can be put together into the same curve except for characteristic jumps occurring at the phase transitions.