688 research outputs found
Pippi - painless parsing, post-processing and plotting of posterior and likelihood samples
Interpreting samples from likelihood or posterior probability density
functions is rarely as straightforward as it seems it should be. Producing
publication-quality graphics of these distributions is often similarly painful.
In this short note I describe pippi, a simple, publicly-available package for
parsing and post-processing such samples, as well as generating high-quality
PDF graphics of the results. Pippi is easily and extensively configurable and
customisable, both in its options for parsing and post-processing samples, and
in the visual aspects of the figures it produces. I illustrate some of these
using an existing supersymmetric global fit, performed in the context of a
gamma-ray search for dark matter. Pippi can be downloaded and followed at
http://github.com/patscott/pippi .Comment: 4 pages, 1 figure. v3: Updated for pippi 2.0. New features include
hdf5 support, out-of-core processing, inline post-processing with arbitrary
Python code in the input file, and observable-specific data cuts. Pippi can
be downloaded from http://github.com/patscott/pipp
Inflationary power asymmetry from primordial domain walls
We study the asymmetric primordial fluctuations in a model of inflation in
which translational invariance is broken by a domain wall. We calculate the
corrections to the power spectrum of curvature perturbations; they are
anisotropic and contain dipole, quadrupole, and higher multipoles with
non-trivial scale-dependent amplitudes. Inspired by observations of these
multipole asymmetries in terms of two-point correlations and variance in real
space, we demonstrate that this model can explain the observed anomalous power
asymmetry of the cosmic microwave background (CMB) sky, including its
characteristic feature that the dipole dominates over higher multipoles. We
test the viability of the model and place approximate constraints on its
parameters by using observational values of dipole, quadrupole, and octopole
amplitudes of the asymmetry measured by a local-variance estimator. We find
that a configuration of the model in which the CMB sphere does not intersect
the domain wall during inflation provides a good fit to the data. We further
derive analytic expressions for the corrections to the CMB temperature
covariance matrix, or angular power spectra, which can be used in future
statistical analysis of the model in spherical harmonic space.Comment: 22 pages, 7 figures. Version published in JCA
The biomechanics of pregnancy: a systematic review
This is the final version. Available from the publisher via the DOI/link in this record.During pregnancy, a number of biomechanical and hormonal changes occur that can alter
spinal curvature, balance, and gait patterns by affecting key areas of the human body. This can
greatly impact quality of life (QOL) by increasing back pain and the risk of falls. These effects are
likely to be the ultimate result of a number of hormonal and biomechanical changes that occur
during pregnancy. Research Question and Methodology: Using the Preferred Reporting Items for
Systematic reviews and Meta-Analyses (PRISMA) guidelines, this systematic review sets out to
analyse all available literature relating to the biomechanics factors caused by pregnancy and assess
how this might reduce QOL. Fifty papers were deemed eligible for inclusion in this review based
on the PUBMED and SCOPUS databases. Results: Angles of lordosis and kyphosis of the spine are
significantly increased by pregnancy, but not consistently across all studies. Back pain is
significantly increased in pregnant women, although this is not significantly correlated with spinal
changes. Increased movements of centre of pressure (COP) and increased stability indexes indicate
postural control is reduced in pregnancy. Trunk range of motion, hip flexion, and extension are
reduced, as well as decreased stride length, decreased gait velocity, and increased step width; again,
not consistently. It is likely that each woman adopts unique techniques to minimise the effects, for
example increasing step width to improve balance. Further research should focus on how altered
limb kinematics during gait might affect QOL by influencing the human body, as well as assessing
parameters in all planes to develop a wider understanding of pregnant biomechanical alteration
Seminatural propagation and rearing of roach (Rutilus rutilus caspicus)
A research experiment was conducted to provide a protocol for seminatural propagation and rearing of Roach up to release size. The attempt was made to combat the declining trend in the population size and catch of the fish in the Caspian Sea. The optimum temperature for spawning brood-stocks lasts from middle March to late April when the ambient temperature range is 12-17°C. During the four months research period, brood stocks were caught in the estuary of the Gorganrood in Golestan Province, north east Iran. The stocks were released into 2 hectare earthen ponds enriched with manure and fertilizers. Artificial spawning grounds made of pine branches were placed in the ponds. Ponds were stocked with 700 female breeders with an average weight of 150 grams and around 350 male breeders weighing 100 grams on average. Spawning and fertilization of eggs occurred in the ponds of which an estimated 80-90% eyed that were observed from the fifth day onwards. The starting of hatching was observed in the 6th day and yolk sac absorption was observed in day 4 to 6. The lame were fed on natural zooplankton and artificial food. Assessment of 146 fries for ingested food indicated that the fries fed on Rotifer (Rotatoria sp. and Daphnia sp.) in the ponds. The length-weight relationship was not significantly different among the ponds and also specific growth rates (SGR) did not show any difference in the fries. The relative gut length in the fries were smaller than I (RLG<l) and fries with an average weight of 0.5 to 1 gram were released into their natural habitat
Bimetric gravity is cosmologically viable
Bimetric theory describes gravitational interactions in the presence of an
extra spin-2 field. Previous work has suggested that its cosmological solutions
are generically plagued by instabilities. We show that by taking the Planck
mass for the second metric, , to be small, these instabilities can be
pushed back to unobservably early times. In this limit, the theory approaches
general relativity with an effective cosmological constant which is,
remarkably, determined by the spin-2 interaction scale. This provides a
late-time expansion history which is extremely close to CDM, but with
a technically-natural value for the cosmological constant. We find should
be no larger than the electroweak scale in order for cosmological perturbations
to be stable by big-bang nucleosynthesis. We further show that in this limit
the helicity-0 mode is no longer strongly-coupled at low energy scales.Comment: 8+2 pages, 2 tables. Version published in PLB. Minor typo corrections
from v
An EF2X Allocation Protocol for Restricted Additive Valuations
We study the problem of fairly allocating a set of indivisible goods to aset of agents. Envy-freeness up to any good (EFX) criteria -- whichrequires that no agent prefers the bundle of another agent after removal of anysingle good -- is known to be a remarkable analogous of envy-freeness when theresource is a set of indivisible goods. In this paper, we investigate EFXnotion for the restricted additive valuations, that is, every good has somenon-negative value, and every agent is interested in only some of the goods. We introduce a natural relaxation of EFX called EFkX which requires that noagent envies another agent after removal of any goods. Our maincontribution is an algorithm that finds a complete (i.e., no good is discarded)EF2X allocation for the restricted additive valuations. In our algorithm wedevise new concepts, namely "configuration" and "envy-elimination" that mightbe of independent interest. We also use our new tools to find an EFX allocation for restricted additivevaluations that discards at most goods. This improvesthe state of the art for the restricted additive valuations by a factor of .<br
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