A Photon Force and Flow for Dissipative Structuring: Application to Pigments, Plants and Ecosystems.

Through a modern derivation of Planck's formula for the entropy of an arbitrary beam of photons, we derive a general expression for entropy production due to the irreversible process of the absorption of an arbitrary incident photon spectrum in material and its dissipation into an infrared-shifted grey-body emitted spectrum, with the rest being reflected or transmitted. Employing the framework of Classical Irreversible Thermodynamic theory, we define the generalized thermodynamic flow as the flow of photons from the incident beam into the material and the generalized thermodynamic force is, then, the entropy production divided by the photon flow, which is the entropy production per unit photon at a given wavelength. We compare the entropy production of different inorganic and organic materials (water, desert, leaves and forests) under sunlight and show that organic materials are the greater entropy-producing materials. Intriguingly, plant and phytoplankton pigments (including chlorophyll) reach peak absorption exactly where entropy production through photon dissipation is maximal for our solar spectrum 430<λ<550 nm, while photosynthetic efficiency is maximal between 600 and 700 nm. These results suggest that the evolution of pigments, plants and ecosystems has been towards optimizing entropy production, rather than photosynthesis. We propose using the wavelength dependence of global entropy production as a biosignature for discovering life on planets of other stars.

Transcutaneous Electrical Nerve Stimulation in Nerve Regeneration: A Systematic Review of In Vivo Animal Model Studies.

OBJECTIVE: Transcutaneous electrical nerve stimulation (TENS) is a noninvasive electrical stimulation therapy indicated for pain control that has been applied for the regeneration of nerves. This systematic review aimed to analyze the evidence on TENS effectiveness on nerve regeneration. MATERIALS AND METHODS: A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria: PubMed/MEDLINE, Web of Science, ScienceDirect, and SciELO data bases. Primary research that evaluated TENS on nerve regeneration was considered. RESULTS: Several studies have investigated the use of TENS for pain treatment. A total of six animal studies analyzed TENS for nerve regeneration. The selected articles showed high quality (Animal Research: Reporting of In Vivo Experiments guidelines), with many unclear points related to bias opportunities (Systematic Review Center for Laboratory Animal Experimentation Risk of Bias tool). In general, TENS accelerated functional and motor recovery and increased axon quantity and diameter. More specifically, the application of low-frequency TENS resulted in a continuous basal lamina; a higher density of fibers with normal diameters, indicating normal myelination, showed signs of deterioration and delayed nerve regeneration. In contrast, the high-frequency TENS application stimulated motor regeneration and increased the diameter of the regenerated axons but revealed a small number of axons, demyelination, dark axoplasm, and an increase in the predisposition of neuropathic pain. CONCLUSIONS: Although there is some heterogeneous evidence in animal research, TENS seems to be a promising treatment for nerve injury that should be better explored. It is still necessary to improve the analysis of its application parameters, which can lead to the most satisfactory regeneration results and improve the understanding of its mechanisms on peripheral nerve regeneration.

Respuestas fotosintéticas de cacao cultivado sin sombra a alta y baja radiación en áreas de baja demanda evaporativa / Photosynthetic response to low and high light of cacao growing without shade in an area of low evaporative demand

ABSTRACT Cacao (Theobroma cacao L.) breeding programmes in Ecuador have focused on obtaining high-yield clones with improved disease resistance. Cacao clones should also have photosynthetic characteristics which support increased productivity. Regarding the weather conditions at the coast of Ecuador, where most of the year there are overcasts and low air evaporative demand, there is the possibility to grow cacao without overhead shade. This study focused on the photosynthetic response at two different photosynthetic photon flux densities (PPFD) of Ecuadorian cacao clones. Seven-year old cacao clones were evaluated: eight clones of Nacional type and two commercial clones (CCN 51 and EET 103), used as controls. All clones showed an increase of 35 % on average in net photosynthetic rate (A)with increasing PPFD from the light saturation point for cacao (i.e. 400 μmol m-2 s-1) to high values (1000 μmol 2 s-1). Such light responsiveness in A has not been reported before. Higher A was associated with higher apparent electron transport rate, while high stomatal conductance was maintained under both PPFD conditions. Under high PPFD, low non-photochemical quenching values were found, suggesting low energy dissipation. All clones showed high maximum quantum yields of PSII (Fv/Fm), suggesting the absence of damage of the photochemical system.

RESUMEN Los programas de mejoramiento de cacao (Theobroma cacao L.) en Ecuador se han centrado en la obtención de clones de alto rendimiento con mayor resistencia a las enfermedades. Estos clones también deben tener características fotosintéticas que apoyen una mayor productividad. En las condiciones climáticas en la costa de Ecuador, donde la mayor parte del año hay alta densidad de nubes y baja demanda evaporativa, existe la posibilidad de cultivar cacao sin sombra. Este estudio se centró en la respuesta fotosintética de clones de cacao del Ecuador en dos diferentes densidades de flujo de fotones fotosintéticos (PPFD). Se evaluaron diez clones de cacao de siete años de edad: ocho clones de tipo Nacional recientemente desarrollados por el Instituto Nacional de investigaciones Agropecuarias, y dos clones comerciales utilizados como controles (CCN 51 y EET 103). Todos los clones de cacao mostraron un aumento del 35 % en promedio en la tasa fotosintética neta (A) con el incremento del PPFD desde el punto de saturación de luz para el cacao (400 μmol m -2 s -1) hasta valores altos (1000 μmol m -2 s- 1). Dicha respuesta de A a estas condiciones de luz alta no se ha reportado en cacao. La tasa fotosintética neta se asoció con una mayor velocidad aparente de transporte de electrones (J), mientras que la alta conductancia estomática (gs) se mantuvo en ambas condiciones de PPFD. En condiciones de alto PPFD, se encontraron bajos valores del coeficiente de extinción no fotoquímico (NPQ), lo que sugiere una baja disipación de energía, además de presentarse altos rendimientos cuánticos máximos de PSII (Fv / Fm), indicando la ausencia de daño del sistema fotoquímico.

Effect of damping and yielding on the seismic response of 3D steel buildings with PMRF.

The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions.

Evaluación de normas técnicas: subprograma de enjuagatorios fluorados en 16 escuelas de Temuco, IX Región, Chile, 2003 / Evaluation of technical standards assessment: fluoride mouthwash subprogram in 16 primary schools in Temuco, IX Región, Chile, 2003

La aplicación masiva de medidas preventivas en base a vehículos fluorados, lleva más de 50 años de discusión en los escenarios científicos. Dentro de las estrategias preventivas el Ministerio de Salud de Chile desde el año 1992 formuló, el Subprograma de Enjuagatorios Fluorados (S.E.F.). La finalidad del estudio es evaluar el cumplimiento de la aplicación de las normas técnicas de Ministerio de Salud para la realización del S.E.F. Se realizó un estudio transversal retrospectivo, tipo descriptivo a través de revisión de informes de práctica profesional controlada de los alumnos de sexto año de la carrera de Odontología durante el año 2003. La muestra fue determinada por conveniencia, la unidad de análisis correspondió a 16 escuelas urbanas de Temuco. Los datos fueron registrados en una ficha y analizados bajo el Programa Estadístico de Stata 8.0. El 100 por ciento presentó a lo menos una falta en el cumplimiento de las normas técnicas; el enjuagatorio no se realiza en todos los cursos, siendo esta la norma que más informalidad mostró (68.75 por ciento). El 50 por ciento de las escuelas presentaba tres o más contravención de los parámetros, siendo imposible analizar a largo plazo los resultados de la efectividad del programa. En conclusión, la planificación de medidas preventivas deben considerar tanto su efectividad, su relación costo-beneficio y su correcta ejecución sostenida en el tiempo, los métodos deben ser correctamente señalados por profesionales del área de Promoción de la Salud y cautelando la motivación e interés todos los actores del programa.

Evaluación al M.E.B. de la interfase resina diente al usar tres sistemas de unión a dentina: un estudio in vitro / Evaluation to M.E.B. of the resin teeth interface when using 3 systems of dentin union: in vitro study

Se propone, evaluar microscopio electrónico de barrido, la zola de unión entre las resinas compuesta y la dentina, utilizando adhesivos dentinarios comerciales, para determinar el grado de separación entre la restauración y la dentina

Embarazadas adolescentes: análisis del problema en el área sur de Tucumán / Pregnant adolescent: analysis of the problem in the South of Tucuman area

Se analiza el problema de la adolescente embarazada en un hospsital regional de la provincia que es centro de derivación, atendiendo población urbano y rural. Sobre 1265 partos ocurridos en un año, 310 (24,56%) fueron de madres adolescentes. la mortalidad fetal fue sorpresivamente menor en este grupo que en la población general (16,11% o vs. 36,59%0) encontencontrándose que más del 50% de las muertes en este grupo ocurre en fetos con peso superior a los 2.500 g. Esto indica que por razones de distancia, económicas y/o culturales, no se efectúa en la zona un adecuado control prenatal, debiendo considerarse a la población obstétrica como de alto riesgo. Otro hecho llamtivo es el elevado número de adolescente con más de un hijo (36% aproximadamente) que se da, lógicamente, en forma más frecuente en el grupo de 16 a 20 años

Esquema diagnóstico de actinomicosis pulmonar: estudio retrospectivo de pacientes / Diagnostic scheme of pulmonary actinomycosis: retrospective study of patients

The review of the five clinical cases and the analysis of the few articles that has been written about pulmonary Actinomyces showed us stricking similarities specially from the diagnostical and epidemiologycal point of view. Personal antecedents specially those concerning thoraxic trauma of surgical procedures appeared as high risk factors, nevertheless we still believe that new studies should be made in order to determine the presence of other determinants such as immunosupression. Smoking 10 or more cigarettes a day in fact suggest a relation that cannot be explained randomly. Time between the appearence of first symptoms and diagnosis is vital, when there is a big suspicious of a pneumological infectious disease one must consider the use of the scheme we suggest so as to begin the adequate treatment on time and prevent complications (i.e. disemination) and lower cost