Salt effect on sensitized photooxidations. A kinetic approch to environmental decomposition of marine contaminants

The salt effect on the kinetics of singlet molecular oxygen [O2(1Δg)]-mediated photooxidations of sea water contaminants was investigated. Two families of photooxidizable compounds were employed in the study: anthracene derivatives and phenols. The presence of salt (NaCl in H2O and LiCl in MeCN, in both cases in the range 0-0.45 M) produces changes in the photooxidation rate. For solvent-polarity-dependent reactions, this behavior can be predicted, by knowing the solvent-polarity dependence of the rate constant for chemical reaction of the substrates with O2(1Δ g) in non-saline solutions (kr). For the cases of photooxidations possessing solvent-polarity-independent or scantily-dependent kr values, the photooxidation rates decrease as the salt content in the solution increases, mainly due to a predominance of the physical quenching pathway. In addition, the quantum yield for O2(1 Δg) generation (ΦΔ) was determined in a series of saline solutions, in the range of 0-0.45 M in water and MeCN solutions, in the presence of NaCl and LiCl respectively. The Δ values are independent, within the experimental error on the salt content.No disponibl

Hallazgos electromiográficos y electroneurográficos en el pie cavo esencial

La etiología del pie cavo cuando ésta es conocida, suele ser debida a un trastorno de tipo neurológico o miopático, aunque en determinados casos nos encontramos con pacientes que padecen esta deformidad en el pie, en los cuales no podemos descubrir ningún antecedente de este tipo, por lo que lo calificamos de pie cavo «esencial». A un grupo de estos pacientes con pie cavo «esencial», en los que no hemos encontrado ningún tipo de antecedente neurológico, lo hemos sometido a una exploración electroneurográfica, encontrando que la mitad de ellos padecían algún trastorno neuropático/miopático, que no había sido detectado en la exploración clínica inicial.Neurological or myopathic diseases are frequently involved in the etiology of flat foot. In some cases, no antecedents of disease can be found and therefore these flat foots are classified as «essential». We have undertaken an electrophysiologic study in a series of patients with «essential» flat food in order to explore unsuspected neurological disorders. In half of the patients, neuropathic and myopathic electroneurographic patterns of different severity were detected

Thermal transport in glassy selenium: The role of low-frequency librations

7 págs.; 3 figs.The experimental curves giving the temperature dependence of the thermal conductivity of glassy selenium are considered in detail. The observed behavior can be taken into account quantitatively if the densities of states for short-wavelength phonons as well as for low-energy librations arising from computer simulations are used for the calculations. In particular, it is shown that the lowest frequency excitations of a chain of selenium atoms can give due account of the plateau observed at temperatures about 2-10 K. The implications of the present findings for the current debate regarding the mechanisms for thermal transport in glasses are finally discussed. © 1994 The American Physical Society.This work has been supported by DGICYT Grant No. PB92-0114-C03Peer Reviewe

Oxy-fired fluidized bed combustors with a flexible power output using circulating solids for thermal energy storage

This paper presents a power plant concept based on an oxy-fired circulating fluidized bed combustor (oxy-CFBC) combined with thermal energy storage on a large scale. The concept exploits to full advantage the large circulation flows of high temperature solids that are characteristic of these systems. Two solid storage silos (one for high temperature and the other for low temperature solids) connected to the oxy-fired CFBC allow variability in power output without the need to modify the fuel firing rate and/or the mass flow of O2 to the combustor. During the periods of high power demand the system can deliver additional thermal power by extracting heat from a series of fluidized bed heat exchangers fed with solids from the high temperature silo. Likewise, during period of low power demand, the thermal power output can be reduced by using the energy released in the combustor to heat up the low temperature solids on their way from the low temperature silo to the oxy-CFBC and storing them in the high temperature silo located below the cyclone. A preliminary economic analysis of two designs indicates that this highly flexible system could make this type of power plant more competitive in the electricity markets where fossil fuels with CCS will be required to respond to a large variability in power output.Y.A. Criado thanks the Government of the Principality of Asturias for a Ph.D. fellowship (Severo Ochoa Program). B. Arias thanks the Spanish MINECO for the award of a Ramon y Cajal contract.Peer reviewe

La cámara oscura en la clase de ciencias: fundamento y utilidades didácticas

Se describe el uso didáctico de una cámara oscura, construida con una gran caja de cartón, donde se introduce la cabeza. La construcción del recurso y su uso didáctico admiten diferentes niveles de complejidad: desde asomarse al interior y mirar, hasta el desarrollo de un control de variables, como trabajo de investigación escolar. Así, se puede abordar el problema de cómo influyen en la imagen atributos de la cámara, u otros factores como la distancia del objeto a la misma.Palabras clave: aprendizaje por investigación; cámara oscura.The darkroom in science classroom: foundation and didactic utilitiesThis paper describes how to use in the classroom a darkroom, which can be obtained by modifying a big cardboard box into which the head is put. The making of the resource itself and its didactic use allow different levels of complexity: from leaning into the interior and simply looking at it, to the development of a control of variables in the contexts of an inquiry–based school work. This way we tackle the problem of how attributes of the camera or other factors, like the distance to it, influence the image.Keywords: inquiry based learning; darkroom, pinhole camera

GPS, LiDAR and VNIR data to monitor the spatial behavior of grazing sheep

Traditional knowledge about the behavior of grazing livestock is about to disappear. Shepherds well know that sheep behavior follows non-random patterns. As a novel alternative to seeking behavioral patterns, this study quantified the grazing activities of two sheep flocks of Churra breed (both in the same area but separated by 10 years) based on Global Position System (GPS) monitoring and remote monitoring sensing techniques. In the first monitoring period (2009-10), geolocations were recorded every 5 min (4, 240 records), while in the second one (2018-20), records were taken every 30 min (7, 636 records). The data were clustered based on the day/night and the activity (resting, moving, or grazing). An airborne LiDAR dataset was used to study the slope, aspect, and vegetation height. Four visible-infrared orthophotographs were mosaicked and classified to obtain the land use/land cover (LU/LC) map. Then, GPS locations were overlain on the terrain features, and a Chi-square test evaluated the relationships between locations and terrain features. Three spatial statistics (directional distribution, Kernel density, and Hot Spot analysis) were also calculated. Results in both monitoring periods suggested that the spatial distribution of free-grazing ewes was non-random. The flocks showed strong preferences for grazing areas with gentle north-facing slopes, where the herbaceous layer formed by pasture predominates. The geostatistical analyses of the sheep locations corroborated those preferences. Geotechnologies have emerged as a potent tool to demonstrate the influence of environmental and terrain attributes on the non-random spatial behavior of grazing sheep. © 2022 Malque Publishing. All rights reserved

Low-frequency excitations in glassy selenium: A comparison of neutron-scattering and molecular-dynamics results

12 págs.; 9 figs.; 1 tab.The microscopic low-frequency dynamics of glassy selenium is investigated by means of the concurrent use of neutron inelastic scattering and computer simulations. A separation of the dynamic response in terms of intra- and interchain processes is achieved from the analysis of the simulation results. The S(Q,E) dynamic structure factors are analyzed in terms of the frequency moments or from a model scattering law, and the wave-vector dependence of the relevant quantities is established. Finally, the anomalous behavior of the heat capacity at moderately low temperatures is shown to be originated by mostly interchain interactions. © 1993 The American Physical Society.This work has been supported in part by DGICYT Grant No. PB89-0037-C03.Peer Reviewe