6,367 research outputs found
The pattern of genetic and environmental variation in relation to ageing in laying hens
International audienc
The probability density function tail of the Kardar-Parisi-Zhang equation in the strongly non-linear regime
An analytical derivation of the probability density function (PDF) tail
describing the strongly correlated interface growth governed by the nonlinear
Kardar-Parisi-Zhang equation is provided. The PDF tail exactly coincides with a
Tracy-Widom distribution i.e. a PDF tail proportional to , where is the the width of the interface. The PDF tail is
computed by the instanton method in the strongly non-linear regime within the
Martin-Siggia-Rose framework using a careful treatment of the non-linear
interactions. In addition, the effect of spatial dimensions on the PDF tail
scaling is discussed. This gives a novel approach to understand the rightmost
PDF tail of the interface width distribution and the analysis suggests that
there is no upper critical dimension.Comment: 17 pages, 2 figure
High Excitation Molecular Gas in the Magellanic Clouds
We present the first survey of submillimeter CO 4-3 emission in the
Magellanic Clouds. The survey is comprised of 15 6'x6' maps obtained using the
AST/RO telescope toward the molecular peaks of the Large and Small Magellanic
Clouds. We have used these data to constrain the physical conditions in these
objects, in particular their molecular gas density and temperature. We find
that there are significant amounts of molecular gas associated with most of
these molecular peaks, and that high molecular gas temperatures are pervasive
throughout our sample. We discuss whether this may be due to the low
metallicities and the associated dearth of gas coolants in the Clouds, and
conclude that the present sample is insufficient to assert this effect.Comment: 18 pages, 3 figures, 5 tables. To appear in Ap
Thermal fluctuations in pinned elastic systems: field theory of rare events and droplets
Using the functional renormalization group (FRG) we study the thermal
fluctuations of elastic objects, described by a displacement field u and
internal dimension d, pinned by a random potential at low temperature T, as
prototypes for glasses. A challenge is how the field theory can describe both
typical (minimum energy T=0) configurations, as well as thermal averages which,
at any non-zero T as in the phenomenological droplet picture, are dominated by
rare degeneracies between low lying minima. We show that this occurs through an
essentially non-perturbative *thermal boundary layer* (TBL) in the (running)
effective action Gamma[u] at T>0 for which we find a consistent scaling ansatz
to all orders. The TBL resolves the singularities of the T=0 theory and
contains rare droplet physics. The formal structure of this TBL is explored
around d=4 using a one loop Wilson RG. A more systematic Exact RG (ERG) method
is employed and tested on d=0 models. There we obtain precise relations between
TBL quantities and droplet probabilities which are checked against exact
results. We illustrate how the TBL scaling remains consistent to all orders in
higher d using the ERG and how droplet picture results can be retrieved.
Finally, we solve for d=0,N=1 the formidable "matching problem" of how this T>0
TBL recovers a critical T=0 field theory. We thereby obtain the beta-function
at T=0, *all ambiguities removed*, displayed here up to four loops. A
discussion of d>4 case and an exact solution at large d are also provided
Criteria of efficiency for conformal prediction
We study optimal conformity measures for various criteria of efficiency of
classification in an idealised setting. This leads to an important class of
criteria of efficiency that we call probabilistic; it turns out that the most
standard criteria of efficiency used in literature on conformal prediction are
not probabilistic unless the problem of classification is binary. We consider
both unconditional and label-conditional conformal prediction.Comment: 31 page
Estimation of absorption line indices of early-type galaxies using colours
Context. Absorption line indices are widely used to determine the stellar
population parameters such as age and metallicity of galaxies, but it is not
easy to obtain the line indices of some distant galaxies that have colours
available. Aims. This paper investigates the correlations between absorption
line indices and colours. Methods. A few statistical fitting methods are mainly
used, via both the observational data of Sloan Digital Sky Survey and a widely
used theoretical stellar population model. Results. Some correlations between
widely used absorption line indices and ugriz colours are found from both
observational data of early-type galaxies and a theoretical simple stellar
population model. In particular, good correlations between colours and widely
used absorption line indices such as Dn(4000), HgammaA, HgammaF, HdeltaA, Mg1,
Mg2, and Mgb, are shown in this paper. Conclusions. Some important absorption
line indices of early-type galaxies can be estimated from their colours using
correlations between absorption line indices and colours. For example,
age-sensitive absorption line indices can be estimated from (u-r) or (g-r)
colours and metallicity-sensitive ones from (u - z) or (g - z). This is useful
for studying the stellar populations of distant galaxies, especially for
statistical investigations.Comment: 9 pages, 21 figures, will be shown in A&
Understanding mountain soils : a contribution from mountain areas to the International Year of Soils 2015
Smallholder farmers in the Taita hills and Mount Kilimanjaro recognize the need to conserve soil nutrients of fields and farms located in the upper, middle and lower zones of mountainous areas. These mountain communities depend on rain-fed subsistence agriculture which means that for sustainable subsistence crop production, they also depend on nutrient availability and use efficiency in farming households. A study under way in the area has looked at loss of land cover and infestations of plant pests and diseases and is using this information to raise farmers’ awareness of soil fertility and to introduce best cropping practices
Polymorphism in glutathione S-transferase P1 is associated with susceptibility to chemotherapyinduced leukemia
Glutathione S-transferases (GSTs) detoxify potentially mutagenic and toxic DNA-reactive electrophiles, including metabolites of several chemotherapeutic agents, some of which are suspected human carcinogens. Functional polymorphisms exist in at least three genes that encode GSTs, including GSTM1, GSTT1, and GSTP1. We hypothesize, therefore, that polymorphisms in genes that encode GSTs alter susceptibility to chemotherapy-induced
carcinogenesis, specifically to therapy-related acute myeloid leukemia (t-AML), a devastating complication of long-term cancer survival. Elucidation of genetic determinants may help to identify individuals at increased risk of developing t-AML. To this end, we have examined 89 cases of t-AML, 420 cases of de novo AML, and
1,022 controls for polymorphisms in GSTM1, GSTT1, and GSTP1. Gene deletion of GSTM1 or GSTT1 was not specifically associated with susceptibility to t-AML. Individuals with at least one GSTP1 codon 105 Val allele were significantly over-represented in t-AML
cases compared with de novo AML cases [odds ratio (OR), 1.81; 95% confidence interval (CI), 1.11–2.94]. Moreover, relative to de novo AML, the GSTP1 codon 105 Val allele occurred more often among t-AML patients with prior exposure to chemotherapy (OR, 2.66; 95% CI, 1.39–5.09), particularly among those with prior exposure to known GSTP1 substrates (OR, 4.34; 95% CI, 1.43–13.20), and not
among those t-AML patients with prior exposure to radiotherapy alone (OR,1.01; 95% CI, 0.50–2.07). These data suggest that inheritance of at least one Val allele at GSTP1 codon 105 confers a significantly increased risk of developing t-AML after cytotoxic chemotherapy, but not after radiotherapy
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