2,538 research outputs found
Higher order correction to the neutrino self-energy in a medium and its astrophysical applications
We have calculated the 1/M^4 (M the vector boson mass) order correction to
the neutrino self-energy in a medium. The possible application of this higher
order contribution to the neutrino effective potential is considered in the
context of the Early Universe hot plasma and of the cosmological Gamma Ray
Burst fireball. We found that, depending on the medium parameters and on the
neutrino properties (mixing angle and mass square difference) the resonant
oscillation of active to active neutrinos is possible.Comment: 10 pages, revtex style, uses axodraw.sty, 1 figur
Microextraction of ochratoxin A in raw wheat with supramolecular solvents
II Encuentro sobre nanociencia y nanotecnología de investigadores y tecnólogos de la Universidad de Córdoba. NANOUC
Chronic Stress Triggers Expression of Immediate Early Genes and Differentially Affects the Expression of AMPA and NMDA Subunits in Dorsal and Ventral Hippocampus of Rats
Indexación: Web of Science; Scopus.Previous studies in rats have demonstrated that chronic restraint stress triggers anhedonia, depressive-like behaviors, anxiety and a reduction in dendritic spine density in hippocampal neurons. In this study, we compared the effect of repeated stress on the expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptor subunits in dorsal and ventral hippocampus (VH). Adult male Sprague-Dawley rats were randomly divided into control and stressed groups, and were daily restrained in their motion (2.5 h/day) during 14 days. We found that chronic stress promotes an increase in c-Fos mRNA levels in both hippocampal areas, although it was observed a reduction in the immunoreactivity at pyramidal cell layer. Furthermore, Arc mRNAs levels were increased in both dorsal and VH, accompanied by an increase in Arc immunoreactivity in dendritic hippocampal layers. Furthermore, stress triggered a reduction in PSD-95 and NR1 protein levels in whole extract of dorsal and VH. Moreover, a reduction in NR2A/NR2B ratio was observed only in dorsal pole. In synaptosomal fractions, we detected a rise in NR1 in dorsal hippocampus (DH). By indirect immunofluorescence we found that NR1 subunits rise, especially in neuropil areas of dorsal, but not VH. In relation to AMPA receptor (AMPAR) subunits, chronic stress did not trigger any change, either in dorsal or ventral hippocampal areas. These data suggest that DH is more sensitive than VH to chronic stress exposure, mainly altering the expression of NMDA receptor (NMDAR) subunits, and probably favors changes in the configuration of this receptor that may influence the function of this area.https://www.frontiersin.org/articles/10.3389/fnmol.2017.00244/ful
Nanostructured-solvent for the extraction of ochratoxin A in Andalusian wines
II Encuentro sobre nanociencia y nanotecnología de investigadores y tecnólogos de la Universidad de Córdoba. NANOUC
Effects of overstorey canopy, plant-plant interactions and soil properties on Mediterranean maritime pine seedling dynamics
Seedling emergence, survival and early growth of the Mediterranean conifer P. pinaster were
studied under closed canopy and open canopy (gaps) cover conditions in a Mediterranean
forest of central Spain during two consecutive years (March 2008 to January 2010). Our main
objective was to understand how overstorey structure, shrubs and soil properties influence
recruitment in this species. Natural emergence and seedling survival were significantly better
under closed canopy cover than under open canopy during the two consecutive years of the
study; survival increased as radiation decreased. Proximity to shrubs under closed canopy
cover was associated with lower mortality rates as well as a positive and apparently transitive
effect on early growth. Amelioration of microclimatic conditions is hypothesized as the
primary facilitation agent of those observed. Younger seedlings established during the spring
of 2008 experienced higher mortality rates than older seedlings established before 2008, and
soil properties affected seedling survival significantly. Water stress during summer appeared
to be the main cause of seedling mortality in both years. Our study suggests that seedlings of
shade-intolerant species may require overstorey cover to establish successfully, and that
positive plant-plant interactions in forest communities may be more important than expected
in the milder conditions provided by overstorey canopy cover.Instituto Universitario de Gestión Forestal Sostenibl
Resonant transmission of light through finite chains of subwavelength holes
In this paper we show that the extraordinary optical transmission phenomenon
found before in 2D hole arrays is already present in a linear chain of
subwavelength holes, which can be considered as the basic geometrical unit
showing this property. In order to study this problem we have developed a new
theoretical framework, able to analyze the optical properties of finite
collections of subwavelength apertures and/or dimples (of any shape and placed
in arbitrary positions) drilled in a metallic film.Comment: Accepted for publication in Phys. Rev. Let
Gravitational settling of 22Ne and white dwarf evolution
We study the effects of the sedimentation of the trace element 22Ne in the
cooling of white dwarfs. In contrast with previous studies, which adopted a
simplified treatment of the effects of 22Ne sedimentation, this is done
self-consistently for the first time, using an up-to-date stellar evolutionary
code in which the diffusion equation is coupled with the full set of equations
of stellar evolution. Due the large neutron excess of 22Ne, this isotope
rapidly sediments in the interior of the white dwarf. Although we explore a
wide range of parameters, we find that using the most reasonable assumptions
concerning the diffusion coefficient and the physical state of the white dwarf
interior the delay introduced by the ensuing chemical differentation is minor
for a typical 0.6 Msun white dwarf. For more massive white dwarfs, say M_Wd
about 1.0 Msun, the delay turns out to be considerably larger. These results
are in qualitatively good accord with those obtained in previous studies, but
we find that the magnitude of the delay introduced by 22Ne sedimentation was
underestimated by a factor of about 2. We also perform a preliminary study of
the impact of 22Ne sedimentation on the white dwarf luminosity function.
Finally, we hypothesize as well on the possibility of detecting the
sedimentation of 22Ne using pulsating white dwarfs in the appropriate effective
temperature range with accurately determined rates of change of the observed
periods.Comment: To apper in The Astrophysical Journa
MicroRNA Profiling and Bioinformatics Target Analysis in Dorsal Hippocampus of Chronically Stressed Rats: Relevance to Depression Pathophysiology
Indexación: Scopus.1Laboratory of Neuroplasticity and Neurogenetics, Faculty of Chemical and Pharmaceutical Sciences, Department of Biochemistry and Molecular Biology, Universidad de Chile, Santiago, Chile, 2National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Durham, NC, United States, 3Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile, 4Millennium Institute for Integrative Biology (iBio), FONDAP Center for Genome Regulation, Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago, Chile, 5Department of Kinesiology, Faculty of Health Sciences, Universidad Católica del Maule, Talca, Chile, 6Escuela de Química y Farmacia, Facultad de Medicina, Universidad Andres Bello, Santiago, Chile.This study was supported by the following grants: FONDECYT 1120528 (JLF), Fondo Central de Investigación, Universidad de Chile ENL025/16 (JLF), ES090079 (JAC). Research in RG and EV laboratories is funded by Instituto Milenio iBio – Iniciativa Científica Milenio MINECON.Studies conducted in rodents subjected to chronic stress and some observations in humans after psychosocial stress, have allowed to establish a link between stress and the susceptibility to many complex diseases, including mood disorders. The studies in rodents have revealed that chronic exposure to stress negatively affects synaptic plasticity by triggering changes in the production of trophic factors, subunit levels of glutamate ionotropic receptors, neuron morphology, and neurogenesis in the adult hippocampus. These modifications may account for the impairment in learning and memory processes observed in chronically stressed animals. It is plausible then, that stress modifies the interplay between signal transduction cascades and gene expression regulation in the hippocampus, therefore leading to altered neuroplasticity and functioning of neural circuits. Considering that miRNAs play an important role in post-transcriptional-regulation of gene expression and participate in several hippocampus-dependent functions; we evaluated the consequences of chronic stress on the expression of miRNAs in dorsal (anterior) portion of the hippocampus, which participates in memory formation in rodents. Here, we show that male rats exposed to daily restraint stress (2.5 h/day) during 7 and 14 days display a differential profile of miRNA levels in dorsal hippocampus and remarkably, we found that some of these miRNAs belong to the miR-379-410 cluster. We confirmed a rise in miR-92a and miR-485 levels after 14 days of stress by qPCR, an effect that was not mimicked by chronic administration of corticosterone (14 days). Our in silico study identified the top-10 biological functions influenced by miR-92a, nine of which were shared with miR-485: Nervous system development and function, Tissue development, Behavior, Embryonic development, Organ development, Organismal development, Organismal survival, Tissue morphology, and Organ morphology. Furthermore, our in silico study provided a landscape of potential miRNA-92a and miR-485 targets, along with relevant canonical pathways related to axonal guidance signaling and cAMP signaling, which may influence the functioning of several neuroplastic substrates in dorsal hippocampus. Additionally, the combined effect of miR-92a and miR-485 on transcription factors, along with histone-modifying enzymes, may have a functional relevance by producing changes in gene regulatory networks that modify the neuroplastic capacity of the adult dorsal hippocampus under stress. © 2018 Muñoz-Llanos, García-Pérez, Xu, Tejos-Bravo, Vidal, Moyano, Gutiérrez, Aguayo, Pacheco, García-Rojo, Aliaga, Rojas, Cidlowski and Fiedler.https://www.frontiersin.org/articles/10.3389/fnmol.2018.00251/ful
Retention of three fissure sealants and a dentin bonding system used as fissure sealant in caries prevention: 12-month follow-up results
Background. Bonding agents could be used as fissure sealants. This study compares the retention three fissure sealants (Delton®, Delton Plus® and Concise®) and a filled dentin bonding system (Optibond Solo®). Methods. Fifty-six children aged 7-8 years received fissure sealants either in the four permanent first molars, in the four deciduous second molars, or in all eight of these teeth. Every child received a different sealing material in each quadrant on a random basis. Clinical evaluation at 12 months was performed by a single blind examiner, and the retention was classified as either a success (total retention) or a failure (partial retention or not present). Results: There were no statistically significant differences among the four materials in permanent maxillary molars or deciduous molars. In permanent mandibular molars, Optibond Solo® showed a lower percentage of retention (40.9%), significantly different (p=0.002) to that of Delton® (89.5%), Delton Plus® (87.5%) and Concise® (76.5%). Conclusion: One bottle dentin bonding system used as a sealant does not improve the retention of conventional fissure sealants. Clinical Implication: Because of the scarcity of studies on the use of dental adhesives as sealants, further studies are warranted for the final support of that conclusion
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