Photoexcited energy relaxation and vibronic couplings in π-conjugated carbon nanorings.

Conjugated carbon nanorings exhibit unique photophysical properties that, combined with their tunable sizes and conformations, make them suitable for a variety of practical applications. These properties are intimately associated to their strained, bent and sterically hindered cyclic structures. Herein we perform a comparative analysis of the photoinduced dynamics in carbon nanorings composed of nine phenyl units([9]CPP) and nine naphthyl units ([9]CN) respectively. The sterically demanding naphthyl units lead to large dihedral angles between neighboring units. Nevertheless, the ultrafast electronic and vibrational energy relaxation and redistribution is found to be similar for both systems. We observe that vibronic couplings, introduced by nonadiabatic energy transfer between electronic excited states, ensure the intramolecular vibrational energy redistribution through specific vibrational modes. The comparative impact of the internal conversion process on the exciton spatial localization and intra-ring migration indicates that naphthyl units in [9]CN achieve more efficient but less dynamical self-trapping compared to that of phenyl units in [9]CPP. That is, during the photoinduced process, the exciton in [9]CN is more static and localized than the exciton in [9]CPP. The internal conversion processes take place through a specific set of middle- to high-frequency normal modes, which directly influence the spatial exciton redistribution during the internal conversion, self-trapping and intra-ring migration.

Chitosan/pvp-based mucoadhesive membranes as a promising delivery system of betamethasone-17-valerate for aphthous stomatitis.

Mucoadhesive membranes were proposed in this study as drug delivery system for betamethasone-17-valerate (BMV) in the treatment of recurrent aphthous stomatitis (RAS). The membranes were obtained by using the polymers chitosan (CHI) in both presence and absence of polyvinilpyrrolidone (PVP), following the solvent evaporation method. The presence of PVP in the membranes causes significant modifications in its thermal properties. Changes in the thermal events at 114 and 193 °C (related to BMV melting point), and losses in mass (39.38 and 30.68% for CH:PVP and CH:PVP-B, respectively), suggests the incorporation of BMV in these membranes. However, the morphological aspects of the membranes do not change after adding PVP and BMV. PVP causes changes in swelling ratios (>80%) of the membranes, and it is suggested that the reorganization of the polymer mesh was highlighted by the chemical interactions between the polymers leading to different percentages of BMV released ∼40% and ∼80% from CH-B and CH:PVP-B. BMV release profile follows Korsmeyer and Peppas model (n > 0.89) which suggests that the diffusion of the drug in the swollen matrix is driven by polymer relaxation. In addition, the membranes containing PVP (higher swelling ability) present high rates of tensile strength, and therefore, higher mucoadhesion. Moreover, given the results presented, the developed mucoadhesive membranes are a promising system to deliver BMV for the treatment of RAS.

Relaxation dynamics in quantum dissipative systems: the microscopic effect of intramolecular vibrational energy redistribution.

We investigate the effect of inter-mode coupling on the vibrational relaxation dynamics of molecules in weak dissipative environments. The simulations are performed within the reduced density matrix formalism in the Markovian regime, assuming a Lindblad form for the system-bath interaction. The prototypical two-dimensional model system representing two CO molecules approaching a Cu(100) surface is adapted from an ab initio potential, while the diatom-diatom vibrational coupling strength is systematically varied. In the weak system-bath coupling limit and at low temperatures, only first order non-adiabatic uni-modal coupling terms contribute to surface-mediated vibrational relaxation. Since dissipative dynamics is non-unitary, the choice of representation will affect the evolution of the reduced density matrix. Two alternative representations for computing the relaxation rates and the associated operators are thus compared: the fully coupled spectral basis, and a factorizable ansatz. The former is well-established and serves as a benchmark for the solution of Liouville-von Neumann equation. In the latter, a contracted grid basis of potential-optimized discrete variable representation is tailored to incorporate most of the inter-mode coupling, while the Lindblad operators are represented as tensor products of one-dimensional operators, for consistency. This procedure results in a marked reduction of the grid size and in a much more advantageous scaling of the computational cost with respect to the increase of the dimensionality of the system. The factorizable method is found to provide an accurate description of the dissipative quantum dynamics of the model system, specifically of the time evolution of the state populations and of the probability density distribution of the molecular wave packet. The influence of intra-molecular vibrational energy redistribution appears to be properly taken into account by the new model on the whole range of coupling strengths. It demontrates that most of the mode mixing during relaxation is due to the potential part of the Hamiltonian and not to the coupling among relaxation operators.

Validación de la Escala de Depresión de Zung en personas con VIH / Validation of the Zung Depression Scale in persons with HIV

Se describen las propiedades psicométricas de la escala de depresión de Zung, que fue administrada a 62 personas con VIH que al momento del estudio eran vistos en el Centro Ambulatorio para la Prevención y Atención a VIH/SIDA e ITS en la ciudad de Hermosillo, México. La edad promedio de los participantes fue de 37,02 años, de los cuales 59,7 por ciento eran personas del sexo masculino y 40,3 por ciento del sexo femenino. Para la evaluación de las propiedades psicométricas de la escala se utilizaron en orden sucesivo los siguientes procedimientos: la prueba de la t de Student de comparación de medias para la comprensión de las preguntas; un análisis factorial exploratorio con rotación varimax para estudiar la validez de constructo y el coeficiente a de Cronbach para valorar la confiabilidad. Con la prueba de la t de Student se obtuvieron valores de significancia estadística en 19 de las 20 preguntas. El análisis factorial exploratorio arrojó una estructura de tres factores, con valores propios superiores a 1 y que en conjunto explican 56,13 por ciento) de la varianza. Finalmente, en el análisis de confiabilidad de la medida se obtuvo un a de Cronbach global de 0.887. Según los resultados obtenidos, la escala de depresión de Zung posee óptimas propiedades psicométricas de validez de constructo y confiabilidad en personas con VIH.

We describe the psychometric properties of the Zung's depression scale, which was administered to 62 persons with HIV who were being treated in the Ambulatory Center of Prevention and Attention at HIV/AIDS and STI in Hermosillo, Mexico. Participants mean age was 37.02 year old, 59.7 percent> were male and 40.3 percent> females. Three consecutive statistical testing procedures were applied for data analysis: the Student t test for comparison of means and for assesing the comprehensibility of the questions; an exploratory factorial analysis with varimax rotation for determining construct validity; Cronbach's a coefficient for determining reliability. In 19 out of a total of 20 questions, the Student t test for comparison of means gave statistically significant values. A three-factors structure was found with the factorial analysis, with values above 1 that, taken as a whole, explain 56.13 percent> of the variance. An overall a coefficient of 0.887 was obtained with the test of reliability. According with the results obtained, the Zung' depression scale has optimal psychometric properties of construct validity and reliability for people with HIV

Estudio etiológico de enfermedades en vias respiratorias de niños / Etiologic study of respiratory tract diseases in children

"De Diciembre de 1982 a Marzo de 1983 fueron estudiados 401 niños menores de 6 años en la ciudad de La Ceiba, Honduras: 226 niños con síntomas de vías respiratorias y un grupo control (asintomático) de 175 niños. Se determinó la incidencia y prevalencia de diferentes tipos de virus y bacterias en la población estudiada, mediante aislamiento de antígenos y/o detección de anticuerpos séricos. Se obtuvo una incidencia de un 6l,06

de los pacientes estudiados con enfermedad respiratoria de etiología viral, ocupando el primer lugar el Virus Sincitial Respiratorio (RSV) con un 27,13

y en segundo lugar el Parainfuenza Virus (Para Flu) con un 22,19

. Otros virus fueron identificados en menor porcentaje. Se obtuvo una prevalencia de un 91,27

de pacientes con enfermedad respiratoria de etiología viral en la población estudiada. Tambiém aquí el virus más frecuentemente diagnosticado fue el RSV (70,07

). No se encontró gran diferencia en la distribución viral según nivel socio-económico ni sexo. También se detectaron anticuerpos séricos para el Mycoplasma pneumoniae en un 5,48

de los pacientes estudiados, para el Haemophilus Influenzae tipo b (H. flu b) en un 0,99

, para Chlamydiae en un 3,99

y para el Streptococcus pneumoniae 93 (Sp 93) en 1,99

de los pacientes, mostrando relativamente una mayor incidencia entre el grupo de niños en edad pre-escolar (2 a 6 años) (AU)

Estudio etiológico de enfermedades en vias respiratorias de niños / Etiologic study of respiratory tract diseases in children

"De Diciembre de 1982 a Marzo de 1983 fueron estudiados 401 niños menores de 6 años en la ciudad de La Ceiba, Honduras: 226 niños con síntomas de vías respiratorias y un grupo control (asintomático) de 175 niños. Se determinó la incidencia y prevalencia de diferentes tipos de virus y bacterias en la población estudiada, mediante aislamiento de antígenos y/o detección de anticuerpos séricos. Se obtuvo una incidencia de un 6l,06% de los pacientes estudiados con enfermedad respiratoria de etiología viral, ocupando el primer lugar el Virus Sincitial Respiratorio (RSV) con un 27,13% y en segundo lugar el Parainfuenza Virus (Para Flu) con un 22,19%. Otros virus fueron identificados en menor porcentaje. Se obtuvo una prevalencia de un 91,27% de pacientes con enfermedad respiratoria de etiología viral en la población estudiada. Tambiém aquí el virus más frecuentemente diagnosticado fue el RSV (70,07%). No se encontró gran diferencia en la distribución viral según nivel socio-económico ni sexo. También se detectaron anticuerpos séricos para el Mycoplasma pneumoniae en un 5,48% de los pacientes estudiados, para el Haemophilus Influenzae tipo b (H. flu b) en un 0,99%, para Chlamydiae en un 3,99% y para el Streptococcus pneumoniae 93 (Sp 93) en 1,99% de los pacientes, mostrando relativamente una mayor incidencia entre el grupo de niños en edad pre-escolar (2 a 6 años)