58 research outputs found
Non-Gaussianity in Loop Quantum Cosmology
We extend the phenomenology of loop quantum cosmology (LQC) to second order
in perturbations. Our motivation is twofold. On the one hand, since LQC
predicts a cosmic bounce that takes place at the Planck scale, the second order
contributions could be large enough to jeopardize the validity of the
perturbative expansion on which previous results rest. On the other hand, the
upper bounds on primordial non-Gaussianity obtained by the Planck Collaboration
are expected to play a significant role on explorations of the LQC
phenomenology. We find that the bounce in LQC produces an enhancement of
non-Gaussianity of several orders of magnitude, on length scales that were
larger than the curvature radius at the bounce. Nonetheless, we find that one
can still rely on the perturbative expansion to make predictions about
primordial perturbations. We discuss the consequences of our results for LQC
and its predictions for the cosmic microwave background.Comment: Minor updates: current version matches the accepted PRD manuscrip
Ekpyrosis and inflationary dynamics in heavy ion collisions: the role of quantum fluctuations
We summarize recent significant progress in the development of a
first-principles formalism to describe the formation and evolution of matter in
very high energy heavy ion collisions. The key role of quantum fluctuations
both before and after a collision is emphasized. Systematic computations are
now feasible to address early time dynamics essential to quantifying properties
of strongly interacting quark-gluon matter.Comment: Talk by R.V. at Quark Matter 2011, Annecy, France, May 23-28, 2011.
LaTex, 4 pages; v2, final version to appear in J. Phys.
Spectral Distortions of the CMB as a Probe of Inflation, Recombination, Structure Formation and Particle Physics
Following the pioneering observations with COBE in the early 1990s, studies
of the cosmic microwave background (CMB) have focused on temperature and
polarization anisotropies. CMB spectral distortions - tiny departures of the
CMB energy spectrum from that of a perfect blackbody - provide a second,
independent probe of fundamental physics, with a reach deep into the primordial
Universe. The theoretical foundation of spectral distortions has seen major
advances in recent years, which highlight the immense potential of this
emerging field. Spectral distortions probe a fundamental property of the
Universe - its thermal history - thereby providing additional insight into
processes within the cosmological standard model (CSM) as well as new physics
beyond. Spectral distortions are an important tool for understanding inflation
and the nature of dark matter. They shed new light on the physics of
recombination and reionization, both prominent stages in the evolution of our
Universe, and furnish critical information on baryonic feedback processes, in
addition to probing primordial correlation functions at scales inaccessible to
other tracers. In principle the range of signals is vast: many orders of
magnitude of discovery space could be explored by detailed observations of the
CMB energy spectrum. Several CSM signals are predicted and provide clear
experimental targets, some of which are already observable with present-day
technology. Confirmation of these signals would extend the reach of the CSM by
orders of magnitude in physical scale as the Universe evolves from the initial
stages to its present form. The absence of these signals would pose a huge
theoretical challenge, immediately pointing to new physics.Comment: Astro2020 Science White Paper, 5 pages text, 13 pages in total, 3
Figures, minor update to reference
Ontogeny of the circadian system during embryogenesis in rainbow trout (Oncorhynchus mykiss) and the effect of prolonged exposure to continuous illumination on daily rhythms of per1, clock, and aanat2 expression
It is widely held that the development of the circadian system during embryogenesis is important for future survival of an organism. Work in teleosts has been, to date, limited to zebrafish, which provides little insight into the diversity of this system within such a large vertebrate class. In this study, we analyzed the diel expression of per1, clock, and aanat2 in unfertilized rainbow trout oocytes and embryos maintained under either a 12:12 light:dark (LD) cycle or continuous illumination (LL) from fertilization. 24-h profiles in expression were measured at fertilization as well as 8, 21 42, and 57 days postfertilization (dpf). Both per1 and clock were expressed in unfertilized oocytes and all embryonic stages, while aanat2 expression was only measureable from 8 dpf. A reduction in both per1 and clock mean expression level between unfertilized oocytes/0-1dpf embryos and 8-9dpf embryos was suggestive of a transition from maternal RNA to endogenous mRNA expression. While aanat2 expression was not clearly associated with photic conditions, photoperiod treatment did alter the expression of per1 and clock expression/rhythmicity from as early as 8 dpf (per1), which could suggest the presence and functionality of an as yet unidentified âphotoreceptorâ. As a whole, this work demonstrates that clock systems are present and functional during embryonic development in rainbow trout. Further studies of their expression and regulation will help understand how the environment interacts with embryonic development in the species
Higher Flow Harmonics in Heavy Ion Collisions from STAR
We report STAR measurements relating to higher flow harmonics including the
centrality dependence of two- and four-particle cumulants for harmonics 1 to 6.
Two-particle correlation functions vs. \Delta\eta and \Delta\phi are presented
for pT and number correlations. We find the power spectra (Fourier Transforms
of the correlation functions) for central collisions drop quickly for higher
harmonics. The \Delta\eta dependence of v3{2}2 and the pT and centrality
dependence of v2 and v3 are studied. Trends are conistent with expectations
from models including hot-spots in the initial energy density and an expansion
phase. We also present v3 and v2{2}2 - v2{4}2 vs. \surdsNN .Comment: 8 pages. Conference proceedings for Quark Matter 201
Ontogeny of central serotonergic neurons in the directly developing frog, Eleutherodactylus coqui
Embryonic development of the central serotonergic neurons in the directly developing frog, Eleutherodactylus coqui , was determined by using immunocytochemistry. The majority of anuran amphibians (frogs) possess a larval stage (tadpole) that undergoes metamorphosis, a dramatic post-embryonic event, whereby the tadpole transforms into the adult phenotype. Directly developing frogs have evolved a derived life-history mode where the tadpole stage has been deleted and embryos develop directly into the adult bauplan. Embryonic development in E. coqui is classified into 15 stages (TS 1â15; 1 = oviposition / 15 = hatching). Serotonergic immunoreactivity was initially detected at TS 6 in the raphe nuclei in the developing rhombencephalon. At TS 7, immunopositive perikarya were observed in the paraventricular organ in the hypothalamus and reticular nuclei in the hindbrain. Development of the serotonergic system was steady and gradual during mid-embryogenesis. However, starting at TS 13 there was a substantial increase in the number of serotonergic neurons in the paraventricular, raphe, and reticular nuclei, a large increase in the number of varicose fibers, and a differentiation of the reticular nuclei in the hindbrain. Consequentially, E. coqui displayed a well-developed central serotonergic system prior to hatching (TS 15). In comparison, the serotonergic system in metamorphic frogs typically starts to develop earlier but the surge of development that transpires in this system occurs post-embryonically, during metamorphosis, and not in the latter stages of embryogenesis, as it does in E. coqui . Overall, the serotonergic development in E. coqui is similar to the other vertebrates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47526/1/429_2005_Article_22.pd
Recruitment abundance estimation : role of glass eel (Anguilla anguilla L.) response to light
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Endocrine control of Anguilla anguilla glass eel dispersal: Effect of thyroid hormones on locomotor activity and rheotactic behavior
Dispersal, one of the most important processes in population ecology, is an issue linking physiological and behavioral features. However, the endocrine control of animal dispersal remains poorly understood. Here, we tested whether and how thyroid hormones may influence dispersal in glass eels of Anguilla anguilla, by testing their influence on locomotor activity and rheotactic behavior. Glass eels were caught during their estuarine migration and treated by immersion in either a l-thyroxine (T4) or a thiourea (TU) solution. As measured by radioimmunoassay, T4 and TU treatments induced, respectively, increased and decreased whole-body thyroid hormone levels relative to untreated controls. We tested a total of 960 glass eels distributed into control, and T4 and TU treatment groups, on their swimming behavior in experimental flume tanks equipped with upstream and downstream traps that allowed us to concurrently measure both the locomotor activity and the rheotactic behavior. Compared to controls, locomotor activity significantly increased among the hyperthyroid, T4-treated eels, but significantly decreased among the hypothyroid, TU-treated eels. The results on rheotactic behavior suggested a more complex regulatory mechanism, since TU but not T4 treatment significantly affected rheotactic behavior. The influence of thyroid hormones on locomotor activity suggests a central role for these hormones in the regulation of mechanisms leading to the colonization of continental habitats by glass eels. Thyroid hormones are also implicated in the control of locomotor activity in mammals and migratory behavior in birds, suggesting that these hormones represent conserved, proximate mediators of dispersal in vertebrates
Micro-pollutant content in Anguilla anguilla glass eels and relationship with migratory behaviour
cited By 2International audienceThe concentrations of ten trace elements (barium, cadmium, cobalt, copper, lead, manganese, nickel, strontium, vanadium and zinc) were determined in the whole-body of glass eels caught in the Adour estuary, and exhibiting different levels of activity in laboratory. Glass eels that become "active" in response to a decrease in light intensity in flume present significantly lower values than those remaining buried in the substratum for Ph (p = 0.010) and Zn (p = 0.049). Results are discussed in relation to migratory behaviour
Multiple circadian oscillators in the photosensitive pike pineal gland : a study using organ and cell culture
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