Degradation of hexacyanoferrate (III) ion by the coupling of the ultraviolet light and the activation of persulfate at basic pH

The ultraviolet light activation of persulfate (PS) under alkaline conditions was evaluated for treating hexacyanoferrate (III) ion ([Fe(CN)6]3-). The effect of the wavelength type (i.e., UVA and UVC), initial PS concentration (0.3, 0.6, and 0.9 g L−1), and pH value (11 and 13) on the degradation of 50 mg L−1 of [Fe(CN)6]3- were studied. Finally, the role of the main degrading agents (SO4•-, O2•-, or HO•) involved in the degradation process was determined using scavengers and a degradation pathway for [Fe(CN)6]3- was proposed. Results show that [Fe(CN)6]3- can be decomposed by UVC light, while UVA is not effective neither in [Fe(CN)6]3- photolysis nor in the activation of PS. Alkaline activation alone at pH 13 can also not degrade the cyanocomplex. However, the combination of UVC with PS (0.3 g L−1) at pH 13 showed high efficiency in the elimination of [Fe(CN)6]3-, achieving 93.3% of removal after 125 min of treatment. The highest CN- release and Fe dissolved removal also occurs at pH 13 and 0.3 g L−1 PS. Further increases in initial PS concentrations may lead to an excess of radicals in solution, resulting in detrimental recombination reactions that affect the efficiency of the process. Quenching tests showed that the importance of radicals involved in the degradation of [Fe(CN)6]3- follows the order: HO• > O2•- >>> 1O2 or SO4•-, and allowed to demonstrate that singlet oxygen could participate in the UVC photolysis of [Fe(CN)6]3-. All these results suggest the feasibility of this technology to treat this type of industrial wastewater efficiently

Optically controlled spin-polarization memory effect on Mn delta-doped heterostrucutres

We investigated the dynamics of the interaction between spin-polarized photo-created carriers and Mn ions on InGaAs/GaAs:Mn structures. The carriers are confined in an InGaAs quantum well and the Mn ions come from a Mn delta-layer grown at the GaAs barrier close to the well. Even though the carriers and the Mn ions are spatially separated, the interaction between them is demonstrated by time-resolved spin-polarized photoluminescence measurements. Using a pre-pulse laser excitation with an opposite circular-polarization clearly reduces the polarization degree of the quantum-well emission for samples where a strong magnetic interaction is observed. The results demonstrate that the Mn ions act as a spin-memory that can be optically controlled by the polarization of the photocreated carriers. On the other hand, the spin-polarized Mn ions also affect the spin-polarization of the subsequently created carriers as observed by their spin relaxation time. These effects fade away with increasing time delays between the pulses as well as with increasing temperatures.Comment: 12 pages, 5 figure

Acceleration of the precession frequency for optically-oriented electron spins in ferromagnetic/semiconductor hybrids

Time-resolved Kerr rotation measurements were performed in InGaAs/GaAs quantum wells nearby a doped Mn delta layer. Our magneto-optical results show a typical time evolution of the optically-oriented electron spin in the quantum well. Surprisingly, this is strongly affected by the Mn spins, resulting in an increase of the spin precession frequency in time. This increase is attributed to the variation in the effective magnetic field induced by the dynamical relaxation of the Mn spins. Two processes are observed during electron spin precession: a quasi-instantaneous alignment of the Mn spins with photo-excited holes, followed by a slow alignment of Mn spins with the external transverse magnetic field. The first process leads to an equilibrium state imprinted in the initial precession frequency, which depends on pump power, while the second process promotes a linear frequency increase, with acceleration depending on temperature and external magnetic field. This observation yields new information about exchange process dynamics and on the possibility of constructing spin memories, which can rapidly respond to light while retaining information for a longer period.Comment: 7 pages, 5 figure

Enhancement of carrier lifetimes in type-II quantum dot/quantum well hybrid structures

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORWe investigate optical transitions and carrier dynamics in hybrid structures containing type-I GaAs/AlGaAs quantum wells (QWs) and type-II GaSb/AlGaAs quantum dots (QDs). We show that the optical recombination of photocreated electrons confined in the QWs with holes in the QDs and wetting layer can be modified according to the QW/QD spatial separation. In particular, for low spacer thicknesses, the QW optical emission can be suppressed due to the transference of holes from the QW to the GaSb layer, favoring the optical recombination of spatially separated carriers, which can be useful for optical memory and solar cell applications. Time-resolved photoluminescence (PL) measurements reveal non-exponential recombination dynamics. We demonstrate that the PL transients can only be quantitatively described by considering both linear and quadratic terms of the carrier density in the bimolecular recombination approximation for type-II semiconductor nanostructures. We extract long exciton lifetimes from 700 ns to 5 mu s for QDs depending on the spacer layer thickness. Published by AIP Publishing.We investigate optical transitions and carrier dynamics in hybrid structures containing type-I GaAs/AlGaAs quantum wells (QWs) and type-II GaSb/AlGaAs quantum dots (QDs). We show that the optical recombination of photocreated electrons confined in the QWs with holes in the QDs and wetting layer can be modified according to the QW/QD spatial separation. In particular, for low spacer thicknesses, the QW optical emission can be suppressed due to the transference of holes from the QW to the GaSb layer, favoring the optical recombination of spatially separated carriers, which can be useful for optical memory and solar cell applications. Time-resolved photoluminescence (PL) measurements reveal non-exponential recombination dynamics. We demonstrate that the PL transients can only be quantitatively described by considering both linear and quadratic terms of the carrier density in the bimolecular recombination approximation for type-II semiconductor nanostructures. We extract long exciton lifetimes from 700 ns to 5 mu s for QDs depending on the spacer layer thickness.120817FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR2012/11382-9 , 2014/17141-9Sem informaçãoSem informaçã

Beyond the ‘East-West’ dichotomy: global variation in cultural models of selfhood

Markus and Kitayama’s (1991) theory of independent and interdependent self-construals had a major influence on social, personality, and developmental psychology by highlighting the role of culture in psychological processes. However, research has relied excessively on contrasts between North American and East Asian samples, and commonly used self-report measures of independence and interdependence frequently fail to show predicted cultural differences. We revisited the conceptualization and measurement of independent and interdependent self-construals in 2 large-scale multinational surveys, using improved methods for cross-cultural research. We developed (Study 1: N = 2924 students in 16 nations) and validated across cultures (Study 2: N = 7279 adults from 55 cultural groups in 33 nations) a new 7-dimensional model of self-reported ways of being independent or interdependent. Patterns of global variation support some of Markus and Kitayama’s predictions, but a simple contrast between independence and interdependence does not adequately capture the diverse models of selfhood that prevail in different world regions. Cultural groups emphasize different ways of being both independent and interdependent, depending on individualism-collectivism, national socioeconomic development, and religious heritage. Our 7-dimensional model will allow future researchers to test more accurately the implications of cultural models of selfhood for psychological processes in diverse ecocultural contexts

Musculoskeletal Deficits and Cognitive Impairment: Epidemiological Evidence and Biological Mechanisms

Purpose of review: Cognitive impairment is associated with obesity, sarcopenia, and osteoporosis. However, no critical appraisal of the literature on the relationship between musculoskeletal deficits and cognitive impairment, focusing on the epidemiological evidence and biological mechanisms, has been published to date. Herein, we critically evaluate the literature published over the past 3 years, emphasizing interesting and important new findings, and provide an outline of future directions that will improve our understanding of the connections between the brain and the musculoskeletal system. Recent findings: Recent literature suggests that musculoskeletal deficits and cognitive impairment share pathophysiological pathways and risk factors. Cytokines and hormones affect both the brain and the musculoskeletal system; yet, lack of unified definitions and standards makes it difficult to compare studies. Interventions designed to improve musculoskeletal health are plausible means of preventing or slowing cognitive impairment. We highlight several musculoskeletal health interventions that show potential in this regard

Los hongos como determinantes de la calidad alimentaria

Los Hongos son un grupo de organismos eucariotas, que se pueden presentar como hongos filamentosos (mohos) y hongos levaduriformes (levaduras), se caracterizan por segregar enzimas para realizar una digestión externa y absorber los nutrientes de sustancias disueltas. Los hongos han acompañado la vida productiva del hombre desde la antigüedad y cada día su importancia aumenta en campos como la agroindustria, la medicina y la biotecnología, debido a su capacidad de producción de una gran variedad de enzimas y metabolitos secundarios. En este libro se presenta a los lectores los resultados de algunas de las investigaciones realizadas con este importante grupo de organismos, un enfoque desde la Agroindustria y la Biotecnología llevadas a cabo por los grupos de investigación Biotecnología de la Universidad de San Buenaventura Cali y Microbiología, Industria y Ambiente de la Universidad Santiago de Cali. Aquí se refleja el trabajo interinstitucional e interdisciplinario, que reúne los esfuerzos de estudiantes de pregrado y posgrado, al igual que el de los docentes quienes desde diferentes espacios como los semilleros de investigación, los trabajos de grado, las tesis y los proyectos de investigación logran demostrar que en nuestra región es posible realizar investigación para dar un uso biotecnológico a los hongos y mostrar la gran diversidad biológica con la que se cuenta para desarrollar investigaciones que potencien el sector agroindustrial e impacten el mundo. El presente título se compone de seis capítulos en los cuales se exponen los muchos usos que se pueden dar a los hongos y sus aplicaciones agroindustriales, permitiendo así al lector tener una visión general del gran potencial de los microorganismos en la solución de los problemas que afectan el sector y las oportunidades que se pueden presentar. Cada capítulo tiene un breve cuadro de los elementos teóricos que detallan la problemática y los resultados de investigación asociados. Así, el primer capítulo muestra la capacidad de los hongos de actuar como controladores biológicos, describe los diferentes métodos de infección de hongos a insectos y otros hongos, y se enfoca en su utilidad en el control de plagas, enfocándose en la investigación del desarrollo de un bionsecticida para el control de la hormiga arriera (Atta cephalotes). El segundo capítulo contiene una descripción de la funcionalidad y las fuentes de las enzimas pectiolíticas en el reino fungi y un análisis investigativo de algunas especies fúngicas aisladas en Valle del Cauca con capacidad para degradar pectinas. El tercer capítulo muestra un lado negativo de los hongos, las micotoxinas, metabolitos secundarios que son capaces de generar riesgos para la salud de los consumidores, esto es sujeto de investigación en una materia prima prometedora para la agroindustria en Colombia, el Cacao. El capítulo Los capítulos 4, 5 y 6 corresponden a resultados de investigación científica presentados en formato tipo artículo, el capítulo cuatro muestra como la producción de enzimas puede convertirse en un aliado estratégico para mitigar el impacto ambiental generado por algunas industrias, el capítulo cinco muestra la suceptibilidad de los hongos a ser controlados por metabolitos producidos por las plantas como los son los aceites esenciales y en el capítulo seis la investigación sobre la producción de Orellana, muestra la importancia de los hongos en la producción de alimentos y su potencial en la producción de metabolitos como la lovastatina