226 research outputs found
An inhomogeneous universe with thick shells and without cosmological constant
We build an exact inhomogeneous universe composed of a central flat Friedmann
zone up to a small redshift , a thick shell made of anisotropic matter, an
hyperbolic Friedmann metric up to the scale where dimming galaxies are observed
() that can be matched to a hyperbolic Lema\^{i}tre-Tolman-Bondi
spacetime to best fit the WMAP data at early epochs. We construct a general
framework which permits us to consider a non-uniform clock rate for the
universe. As a result, both for a uniform time and a uniform Hubble flow, the
deceleration parameter extrapolated by the central observer is always positive.
Nevertheless, by taking a non-uniform Hubble flow, it is possible to obtain a
negative central deceleration parameter, that, with certain parameter choices,
can be made the one observed currently. Finally, it is conjectured a possible
physical mechanism to justify a non-uniform time flow.Comment: Version published in Class. Quantum gra
Epidemiology of invasive fungal diseases among patients with haematological disorders in the Asia-Pacific: a prospective observational study
AbstractWe conducted a 2-year multicentre prospective observational study to determine the epidemiology of and mortality associated with invasive fungal diseases (IFDs) among patients with haematological disorders in Asia. Eleven institutions from 8 countries/regions participated, with 412 subjects (28.2% possible, 38.3% probable and 33.5% proven IFDs) recruited. The epidemiology of IFDs in participating institutions was similar to Western centres, with Aspergillus spp. (65.9%) or Candida spp. (26.7%) causing the majority of probable and proven IFDs. The overall 30-day mortality was 22.1%. Progressive haematological disorder (odds ratio [OR] 5.192), invasive candidiasis (OR 3.679), and chronic renal disease (OR 6.677) were independently associated with mortality
LTB solutions in Newtonian gauge: from strong to weak fields
Lemaitre-Tolman-Bondi (LTB) solutions are used frequently to describe the
collapse or expansion of spherically symmetric inhomogeneous mass distributions
in the Universe. These exact solutions are obtained in the synchronous gauge
where nonlinear dynamics (with respect to the FLRW background) induce large
deviations from the FLRW metric. In this paper we show explicitly that this is
a gauge artefact (for realistic sub-horizon inhomogeneities). We write down the
nonlinear gauge transformation from synchronous to Newtonian gauge for a
general LTB solution using the fact that the peculiar velocities are small. In
the latter gauge we recover the solution in the form of a weakly perturbed FLRW
metric that is assumed in standard cosmology. Furthermore we show how to obtain
the LTB solutions directly in Newtonian gauge and illustrate how the Newtonian
approximation remains valid in the nonlinear regime where cosmological
perturbation theory breaks down. Finally we discuss the implications of our
results for the backreaction scenario.Comment: 17 page
"Swiss-Cheese" Inhomogeneous Cosmology & the Dark Energy Problem
We study an exact swiss-cheese model of the Universe, where inhomogeneous LTB
patches are embedded in a flat FLRW background, in order to see how
observations of distant sources are affected. We find negligible integrated
effect, suppressed by (L/R_{H})^3 (where L is the size of one patch, and R_{H}
is the Hubble radius), both perturbatively and non-perturbatively. We
disentangle this effect from the Doppler term (which is much larger and has
been used recently \cite{BMN} to try to fit the SN curve without dark energy)
by making contact with cosmological perturbation theory.Comment: 35 pages, 6 figure
Left gaze bias in humans, rhesus monkeys and domestic dogs
While viewing faces, human adults often demonstrate a natural gaze bias towards the left visual field, that is, the right side of the viewee’s face is often inspected first and for longer periods. Using a preferential looking paradigm, we demonstrate that this bias is neither uniquely human nor limited to primates, and provide evidence to help elucidate its biological function within a broader social cognitive framework. We observed that 6-month-old infants showed a wider tendency for left gaze preference towards objects and faces of different species and orientation, while in adults the bias appears only towards upright human faces. Rhesus monkeys showed a left gaze bias towards upright human and monkey faces, but not towards inverted faces. Domestic dogs, however, only demonstrated a left gaze bias towards human faces, but not towards monkey or dog faces, nor to inanimate object images. Our findings suggest that face- and species-sensitive gaze asymmetry is more widespread in the animal kingdom than previously recognised, is not constrained by attentional or scanning bias, and could be shaped by experience to develop adaptive behavioural significance
Use of wild Pennisetum species for improving biotic and abiotic stress tolerance in pearl millet
Pearl millet [Pennisetum glaucum (L.) R. Br.] is one of the world’s hardiest warmseason
cereal crop cultivated for food and animal feed in the semi-arid tropics of
Asia and Africa. This crop faces terminal drought during rainy and flowering-stage
heat stress during summer seasons. Blast is emerging as a serious threat affecting
its production and productivity in India. Using wild P. violaceum (Lam) Rich. and
pearl millet cultivars, prebreeding populations were developed following backcross
method. These populations were evaluated in target ecologies in India at three locations
during the 2018 summer season for flowering-stage heat stress and at two locations
during the 2018 rainy season for terminal drought stress.Atotal 18 introgression
lines (ILs) from Population (Pop) 3 exhibited improved seed set under high heat stress
vs. the cultivated parent, whereas no IL was better than the cultivated parent in Pop
4. Under rainfed conditions at Hisar and Bawal, India, 19 ILs from Pop 3 and 16 ILs
from Pop 4 showed significantly higher dry fodder yield than the cultivated parents.
Further, screening of ILs for five diverse pathotype isolates—Pg 45, Pg 138, Pg 186,
Pg 204, and Pg 232—of blast resulted in the identification of resistant ILs. Use of
these promising ILs in breeding programs will assist in developing new varieties and
hybrids with improved tolerance to biotic and abiotic stresses. The study indicated
the genetic differences between the parents involved in crossing and also highlighted
the importance of precise phenotyping of wild species for target trait prior to use in
prebreeding work
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