144 research outputs found
Thirty-day mortality after elective and emergency total colectomy in Danish patients with inflammatory bowel disease: a population-based nationwide cohort study
Inference for reaction networks using the Linear Noise Approximation
We consider inference for the reaction rates in discretely observed networks
such as those found in models for systems biology, population ecology and
epidemics. Most such networks are neither slow enough nor small enough for
inference via the true state-dependent Markov jump process to be feasible.
Typically, inference is conducted by approximating the dynamics through an
ordinary differential equation (ODE), or a stochastic differential equation
(SDE). The former ignores the stochasticity in the true model, and can lead to
inaccurate inferences. The latter is more accurate but is harder to implement
as the transition density of the SDE model is generally unknown. The Linear
Noise Approximation (LNA) is a first order Taylor expansion of the
approximating SDE about a deterministic solution and can be viewed as a
compromise between the ODE and SDE models. It is a stochastic model, but
discrete time transition probabilities for the LNA are available through the
solution of a series of ordinary differential equations. We describe how a
restarting LNA can be efficiently used to perform inference for a general class
of reaction networks; evaluate the accuracy of such an approach; and show how
and when this approach is either statistically or computationally more
efficient than ODE or SDE methods. We apply the LNA to analyse Google Flu
Trends data from the North and South Islands of New Zealand, and are able to
obtain more accurate short-term forecasts of new flu cases than another
recently proposed method, although at a greater computational cost
Quantum Separability of Thermal Spin One Boson Systems
Using the temperature Green's function approach we investigate entanglement
between two non-interacting spin 1 bosons in thermal equilibrium. We show that,
contrary to the fermion case, the entanglement is absent in the spin density
matrix. Separability is demonstrated using the Peres-Horodecki criterion for
massless particles such as photons in black body radiation. For massive
particles, we show that the density matrix can be decomposed with separable
states.Comment: References & comments related to AQFT added. no figure, revtex4, to
be published in Phys. Lett.
Fine-mapping QTL for mastitis resistance on BTA9 in three Nordic red cattle breeds
A QTL affecting clinical mastitis and/or somatic cell score (SCS) has been reported previously on chromosome 9 from studies in 16 families from the Swedish Red and White (SRB), Finnish Ayrshire (FA) and Danish Red (DR) breeds. In order to refine the QTL location, 67 markers were genotyped over the whole chromosome in the 16 original families and 18 additional half-sib families. This enabled linkage disequilibrium information to be used in the analysis. Data were analysed by an approach that combines information from linkage and linkage disequilibrium, which allowed the QTL affecting clinical mastitis to be mapped to a small interval (<1 cM) between the markers BM4208 and INRA084. This QTL showed a pleiotropic effect on SCS in the DR and SRB breeds. Haplotypes associated with variations in mastitis resistance were identified. The haplotypes were predictive in the general population and can be used in marker-assisted selection. Pleiotropic effects of the mastitis QTL were studied for three milk production traits and eight udder conformation traits. This QTL was also associated with yield traits in DR but not in FA or SRB. No QTL were found for udder conformation traits on chromosome 9
Constraints on decaying Dark Matter from XMM-Newton observations of M31
We derive constraints on parameters of the radiatively decaying Dark Matter
(DM) particles, using XMM-Newton EPIC spectra of the Andromeda galaxy (M31).
Using the observations of the outer (5'-13') parts of M31 we improve the
existing constraints. For the case of sterile neutrino DM, combining our
constraints with the latest computation of abundances of sterile neutrino in
the Dodelson-Widrow (DW) scenario, we obtain the lower mass limit m_s < 4 keV,
which is stronger than the previous one m_s < 6 kev, obtained recently by Asaka
et al. (2007) [hep-ph/0612182]. Comparing this limit with the most recent
results on Lyman-alpha forest analysis of Viel et al. (2007) [arXiv:0709.0131]
(m_s > 5.6 kev), we argue that the scenario in which all the DM is produced via
DW mechanism is ruled out. We discuss however other production mechanisms and
note that the sterile neutrino remains a viable candidate of Dark Matter,
either warm or cold.Comment: 13 pages, 12 figure
Constraining DM properties with SPI
Using the high-resolution spectrometer SPI on board the International
Gamma-Ray Astrophysics Laboratory (INTEGRAL), we search for a spectral line
produced by a dark matter(DM) particle with a mass in the range 40keV < M_DM <
14MeV, decaying in the DM halo of the Milky Way. To distinguish the DM decay
line from numerous instrumental lines found in the SPI background spectrum, we
study the dependence of the intensity of the line signal on the offset of the
SPI pointing from the direction toward the Galactic Centre. After a critical
analysis of the uncertainties of the DM density profile in the inner Galaxy, we
find that the intensity of the DM decay line should decrease by at least a
factor of 3 when the offset from the Galactic Centre increases from 0 to 180
degrees. We find that such a pronounced variation of the line flux across the
sky is not observed for any line, detected with a significance higher than 3
sigma in the SPI background spectrum. Possible DM decay origin is not ruled out
only for the unidentified spectral lines, having low (~3 sigma) significance or
coinciding in position with the instrumental ones. In the energy interval from
20 keV to 7 MeV, we derive restrictions on the DM decay line flux, implied by
the (non-)detection of the DM decay line. For a particular DM candidate, the
sterile neutrino of mass MDM, we derive a bound on the mixing angle.Comment: Minor changes; v.2 - Final version appeared in MNRA
Genetic and environmental influences on human height from infancy through adulthood at different levels of parental education
Genetic factors explain a major proportion of human height variation, but differences in mean stature have also been found between socio-economic categories suggesting a possible effect of environment. By utilizing a classical twin design which allows decomposing the variation of height into genetic and environmental components, we tested the hypothesis that environmental variation in height is greater in offspring of lower educated parents. Twin data from 29 cohorts including 65,978 complete twin pairs with information on height at ages 1 to 69 years and on parental education were pooled allowing the analyses at different ages and in three geographic-cultural regions (Europe, North America and Australia, and East Asia). Parental education mostly showed a positive association with offspring height, with significant associations in mid-childhood and from adolescence onwards. In variance decomposition modeling, the genetic and environmental variance components of height did not show a consistent relation to parental education. A random-effects meta-regression analysis of the aggregate-level data showed a trend towards greater shared environmental variation of height in low parental education families. In conclusion, in our very large dataset from twin cohorts around the globe, these results provide only weak evidence for the study hypothesis.Peer reviewe
Active bacterial community structure along vertical redox gradients in Baltic Sea sediment
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