2,101 research outputs found
Plasmon channels in the electronic relaxation of diamond under high-order harmonics femtosecond irradiation
We used high order harmonics of a femtosecond titanium-doped sapphire system
(pulse duration 25 fs) to realise Ultraviolet Photoelectron Spectroscopy (UPS)
measurements on diamond. The UPS spectra were measured for harmonics in the
range 13 to 27. We also made ab initio calculations of the electronic lifetime
of conduction electrons in the energy range produced in the UPS experiment.
Such calculations show that the lifetime suddenly diminishes when the
conduction electron energy reaches the plasmon energy, whereas the UPS spectra
show evidence in this range of a strong relaxation mechanism with an increased
production of low energy secondary electrons. We propose that in this case the
electronic relaxation proceeds in two steps : excitation of a plasmon by the
high energy electron, the latter decaying into individual electron-hole pairs,
as in the case of metals. This process is observed for the first time in an
insulator and, on account of its high efficiency, should be introduced in the
models of laser breakdown under high intensity
Evo-devo of human adolescence: beyond disease models of early puberty
Despite substantial heritability in pubertal development, much variation remains to be explained, leaving room for the influence of environmental factors to adjust its phenotypic trajectory in the service of fitness goals. Utilizing evolutionary development biology (evo-devo), we examine adolescence as an evolutionary life-history stage in its developmental context. We show that the transition from the preceding stage of juvenility entails adaptive plasticity in response to energy resources, other environmental cues, social needs of adolescence and maturation toward youth and adulthood. Using the evolutionary theory of socialization, we show that familial psychosocial stress fosters a fast life history and reproductive strategy rather than early maturation being just a risk factor for aggression and delinquency. Here we explore implications of an evolutionary-developmental-endocrinological-anthropological framework for theory building, while illuminating new directions for research
Conical refraction healing after partially blocking the input beam
In conical refraction, when a focused Gaussian beam passes along one of the
optic axes of a biaxial crystal it is transformed into a pair of concentric
bright rings at the focal plane. We demonstrate both theoretically and
experimentally that this transformation is hardly affected by partially
blocking the Gaussian input beam with an obstacle. We analyze the influence of
the size of the obstruction both on the transverse intensity pattern of the
beam and on its state of polarization, which is shown to be very robust
Investigation of the effect of combined thermomechanical processing on the brass microstructure evolution and the microhardness change
The article investigates the effect of combined thermomechanical processing, including pre-heat treatment and radial-shear rolling on the brass microstructure evolution and the microhardness change. The microstructure analysis of heat-treated samples according to various modes showed that the most optimal heat treatment before radialshear rolling for L63 brass is annealing at a temperature of 500 °C. As a result of combined thermomechanical processing, a gradient structure was obtained, so in the resulting rods with a diameter of 16 mm in the surface layer, a structure with an average grain size of 9 μm was obtained. In rods with a diameter of 12 mm, a fine–grained, equalgrained structure of 3 μm was obtained in the surface layer
Investigation of the effect of combined thermomechanical processing on the brass microstructure evolution and the microhardness change
The article investigates the effect of combined thermomechanical processing, including pre-heat treatment and radial-shear rolling on the brass microstructure evolution and the microhardness change. The microstructure analysis of heat-treated samples according to various modes showed that the most optimal heat treatment before radialshear rolling for L63 brass is annealing at a temperature of 500 °C. As a result of combined thermomechanical processing, a gradient structure was obtained, so in the resulting rods with a diameter of 16 mm in the surface layer, a structure with an average grain size of 9 μm was obtained. In rods with a diameter of 12 mm, a fine–grained, equalgrained structure of 3 μm was obtained in the surface layer
Differential susceptibility to plasticity: a 'missing link' between gene-culture co-evolution and neuropsychiatric spectrum disorders?
Brüne's proposal that erstwhile 'vulnerability' genes need to be reconsidered as 'plasticity' genes, given the potential for certain environments to yield increased positive function in the same domain as potential dysfunction, has implications for psychiatric nosology as well as a more dynamic understanding of the relationship between genes and culture. In addition to validating neuropsychiatric spectrum disorder nosologies by calling for similar methodological shifts in gene-environment-interaction studies, Brüne's position elevates the importance of environmental contexts - inclusive of socio-cultural variables - as mechanisms that contribute to clinical presentation. We assert that when models of susceptibility to plasticity and neuropsychiatric spectrum disorders are concomitantly considered, a new line of inquiry emerges into the co-evolution and co-determination of socio-cultural contexts and endophenotypes. This presents potentially unique opportunities, benefits, challenges, and responsibilities for research and practice in psychiatry
Conical refraction healing after partially blocking the input beam
In conical refraction, when a focused Gaussian beam passes along one of the optic axes of a biaxial crystal, it is transformed into a pair of concentric bright rings at the focal plane. We demonstrate both theoretically and experimentally that this transformation is hardly affected by partially blocking the Gaussian input beam with an obstacle. We analyze the influence of the size of the obstruction both on the transverse intensity pattern of the beam and on its state of polarization, which is shown to be very robust
Child's oxytocin response to mother-child interaction: the contribution of child genetics and maternal behavior
The oxytocinergic system is a primary biological system involved in regulating a child’s needs for bonding and for protection from threats. It is responsive to social experiences in close relationships, though evidence across studies is not entirely consistent. Guided by previous literature, we investigated individual and environmental factors predicting and presumably affecting children’s oxytocin (OT) response during mother-child interaction. by focusing on children’s OXTR genotype, and maternal behavior, respectively. This was achieved by assessing salivary OT levels of 88 Portuguese preschoolers prior to and following a mother-child interaction task, and by genotyping children’s OXTR SNP rs53576. Maternal interactive behavior was assessed using Ainsworth scales.
Results indicated that child genotype and mother’s sensitive responsiveness interacted in predicting change in child OT concentrations from before to after the interaction. Specifically, Genotypic differences emerged under conditions of low maternal sensitive responsiveness: OT levels increased over time for children with the GG genotype when maternal sensitive responsiveness was low, but no such genotypic differences were evident when mothers were highly sensitive responsive.
Findings provide preliminary support for the notion that increased understanding of children’s OT and close relationships requires consideration of both individual and environmental factors.info:eu-repo/semantics/acceptedVersio
Differential susceptibility in youth: evidence that 5-HTTLPR x positive parenting is associated with positive affect ‘for better and worse'
Positive affect has been implicated in the phenomenological experience of various psychiatric disorders, vulnerability to develop psychopathology and overall socio-emotional functioning. However, developmental influences that may contribute to positive affect have been understudied. Here, we studied youths' 5-HTTLPR genotype and rearing environment (degree of positive and supportive parenting) to investigate the differential susceptibility hypothesis (DSH) that youth carrying short alleles of 5-HTTLPR would be more influenced and responsive to supportive and unsupportive parenting, and would exhibit higher and lower positive affect, respectively. Three independent studies tested this gene–environment interaction (GxE) in children and adolescents (age range 9–15 years; total N=1874). In study 1 (N=307; 54% girls), positive/supportive parenting was assessed via parent report, in study 2 (N=197; 58% girls) via coded observations of parent–child interactions in the laboratory and in study 3 (N=1370; 53% girls) via self report. Results from all the three studies showed that youth homozygous for the functional short allele of 5-HTTLPR were more responsive to parenting as environmental context in a ‘for better and worse' manner. Specifically, the genetically susceptible youth (that is, S'S' group) who experienced unsupportive, non-positive parenting exhibited low levels of positive affect, whereas higher levels of positive affect were reported by genetically susceptible youth under supportive and positive parenting conditions. These GxE findings are consistent with the DSH and may inform etiological models and interventions in developmental psychopathology focused on positive emotion, parenting and genetic susceptibility
The organic geochemistry of ancient sediments, part II
Chemical analysis of sediment and oil hydrocarbon content by gas chromatography and mass spectrometry to establish inception period of bio-organic evolutio
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