704 research outputs found
Bounce Loop Quantum Cosmology Corrected Gauss-Bonnet Gravity
We develop a Gauss-Bonnet extension of Loop Quantum Cosmology, by introducing
holonomy corrections in modified theories of gravity. Within
the context of our formalism, we provide a perturbative expansion in the
critical density, a parameter characteristic of Loop Quantum Gravity theories,
and we result in having leading order corrections to the classical
theories of gravity. After extensively discussing the
formalism, we present a reconstruction method that makes possible to find the
Loop Quantum Cosmology corrected theory that can realize
various cosmological scenarios. Specifically, we studied exponential and
power-law bouncing cosmologies, emphasizing on the behavior near the bouncing
point and in some cases, the behavior for all the values of the cosmic time is
obtained. We exemplify our theoretical constructions by using bouncing
cosmologies, and we investigate which Loop Quantum Cosmology corrected
Gauss-Bonnet modified gravities can successfully realize such cosmologies.Comment: Revised version, to appear in PR
Corrections to Gravity due to a Sol Manifold Extra Dimensional Space
The corrections to the gravitational potential due to a Sol extra dimensional
compact manifold, denoted as , are studied. The total spacetime is of
the form . The range of the Sol corrections is investigated
and compared to the range of the corrections.Comment: 13 pages, 10 figures, published versio
Viable Inflationary Models in a Ghost-free Gauss-Bonnet Theory of Gravity
In this work we investigate the inflationary phenomenological implications of
a recently developed ghost-free Gauss-Bonnet theory of gravity. The resulting
theory can be viewed as a scalar Einstein-Gauss-Bonnet theory of gravity, so by
employing the formalism for cosmological perturbations for the latter theory,
we calculate the slow-roll indices and the observational indices, and we
compare these with the latest observational data. Due to the presence of a
freely chosen function in the model, in principle any cosmological evolution
can be realized, so we specify the Hubble rate and the freely chosen function
and we examine the phenomenology of the model. Specifically we focus on de
Sitter, quasi-de Sitter and a cosmological evolution in which the Hubble rate
evolves exponentially, with the last two being more realistic choices for
describing inflation. As we demonstrate, the ghost-free model can produce
inflationary phenomenology compatible with the observational data. We also
briefly address the stability of first order scalar and tensor cosmological
perturbations, for the exponential Hubble rate, and as we demonstrate,
stability is achieved for the same range of values of the free parameters that
guarantee the phenomenological viability of the models.Comment: EPJC Accepte
The Electron Glass in a Switchable Mirror: Relaxation, Aging and Universality
The rare earth hydride YH can be tuned through the
metal-insulator transition both by changing and by illumination with
ultraviolet light. The transition is dominated by strong electron-electron
interactions, with transport in the insulator sensitive to both a Coulomb gap
and persistent quantum fluctuations. Via a systematic variation of UV
illumination time, photon flux, Coulomb gap depth, and temperature, we
demonstrate that polycrystalline YH serves as a model system for
studying the properties of the interacting electron glass. Prominent among its
features are logarithmic relaxation, aging, and universal scaling of the
conductivity
Developing policy-relevant river fish monitoring in Greece: Insights from a nation-wide survey
A wide-ranging river fish survey was executed in the summer of 2009 as part of the preparatory actions for the establishment of a monitoring programme for the EU Water Framework Directive (WFD). This was the first extensive electrofishing campaign for WFD standardized bioassessment in Greece and the experience and insights gained are used here to provide a review of fish-based assessment conditions and requirements in this country. The survey sampled 85 sites on 25 rivers throughout mainland Greece, collecting 70 species of freshwater fish. Quantitative site-based assemblage data is used for taxonomic and ordination analyses revealing a strong biogeographic regionalization in the distribution of the ichthyofauna. The structural and spatial organisation of the fish fauna through the use of species-level and community-level data analyses is explored in three ecoregions where data was deemed sufficient. Transitions in community taxonomic composition among ecoregions were abrupt and concordant with geographical barriers and reflect the influence of historical biogeographic processes. Community-based analysis revealed a substantial degree of variation in quantitative attributes of the fish assemblages among ecoregions. Key conclusions of this work are: (a) the fish-based bioassessment system must be regionalised to reflect biogeographic variation, (b) high faunal heterogeneity among ecoregions (taxonomic, structural), and to a lower degree among basins, constrain the transferability of bioassessment metrics and indices created for explicit regions to other regional frameworks; (c) faunal depauperation in most of the study areas reduce the utility of functional bioassessment metrics and also limits the utilization of rare species and the applicability of the classical form of the “Index of Biotic Integrity” concept. Recommendations to cope with these problems are discussed
Hybrid integration of microfabricated chemοcapacitor arrays with miniaturized read-out electronics towards low-power gas sensing module
AbstractA hybrid gas sensing module consisting of an array of 8 polymer coated capacitive sensors and low power read-out electronics is introduced. The chemocapacitor array is fabricated with standard microelectronics/micromachining processes allowing for the realization of planar InterDigitated Electrodes (IDEs). The read-out electronics sub- module consists of an analog multiplexer for the sequential measurement of the sensor array elements, a capacitance to 24-bit converter and a USB to I2C interface. The compact hybrid module has been successfully applied in the detection of sub-100ppm concentrations of p-xylene and toluene. The responses to various humidity levels have been also evaluated
Linkage mapping, comparative genome analysis, and QTL detection for growth in a non-model teleost, the meagre Argyrosomus regius, using ddRAD sequencing
Meagre (Argyrosomus regius), is a benthopelagic species rapidly emerging in aquaculture, due to its low food to biomass conversion rate, good fillet yield and ease of production. Tracing a species genomic background along with describing the genetic basis of important traits can greatly influence both conservation strategies and production perspectives. In this study, we employed ddRAD sequencing of 266 fish from six F1 meagre families, to construct a high-density genetic map comprising 4529 polymorphic SNP markers. The QTL mapping analysis provided a genomic appreciation for the weight trait identifying a statistically significant QTL on linkage group 15 (LG15). The comparative genomics analysis with six teleost species revealed an evolutionarily conserved karyotype structure. The synteny observed, verified the already well-known fusion events of the three-spine stickleback genome, reinforced the evidence of reduced evolutionary distance of Sciaenids with the Sparidae family, reflected the evolutionary proximity with Dicentrarchus labrax, traced several putative chromosomal rearrangements and a prominent putative fusion event in meagre’s LG17. This study presents novel elements concerning the genome evolutionary history of a non-model teleost species recently adopted in aquaculture, starts to unravel the genetic basis of the species growth-related traits, and provides a high-density genetic map as a tool that can help to further establish meagre as a valuable resource for research and production.info:eu-repo/semantics/publishedVersio
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