Near NP-Completeness for Detecting p-adic Rational Roots in One Variable

We show that deciding whether a sparse univariate polynomial has a p-adic rational root can be done in NP for most inputs. We also prove a polynomial-time upper bound for trinomials with suitably generic p-adic Newton polygon. We thus improve the best previous complexity upper bound of EXPTIME. We also prove an unconditional complexity lower bound of NP-hardness with respect to randomized reductions for general univariate polynomials. The best previous lower bound assumed an unproved hypothesis on the distribution of primes in arithmetic progression. We also discuss how our results complement analogous results over the real numbers.Comment: 8 pages in 2 column format, 1 illustration. Submitted to a conferenc

Genetic heterogeneity of residual variance in broiler chickens

Aims were to estimate the extent of genetic heterogeneity in environmental variance. Data comprised 99 535 records of 35-day body weights from broiler chickens reared in a controlled environment. Residual variance within dam families was estimated using ASREML, after fitting fixed effects such as genetic groups and hatches, for each of 377 genetically contemporary sires with a large number of progeny ($>$100 males or females each). Residual variance was computed separately for male and female offspring, and after correction for sampling, strong evidence for heterogeneity was found, the standard deviation between sires in within variance amounting to 15–18% of its mean. Reanalysis using log-transformed data gave similar results, and elimination of 2–3% of outlier data reduced the heterogeneity but it was still over 10%. The correlation between estimates for males and females was low, however. The correlation between sire effects on progeny mean and residual variance for body weight was small and negative (-0.1). Using a data set bigger than any yet presented and on a trait measurable in both sexes, this study has shown evidence for heterogeneity in the residual variance, which could not be explained by segregation of major genes unless very few determined the trait

Does the transition to grandparenthood influence the health and well-being of older people? Evidence from the CHARLS study in China.

•Transitioning to grandmotherhood was associated with a higher probability of reporting ≥1 functional limitations in ADLs.•Transitioning to grandparenthood was associated with higher life satisfaction.•Role enhancement and role strain may generate mixed impacts of transitioning to grandparenthood on older adults' health

Ecotypic Adaptation of Medicago Polymorpha along a Gradient in Central Chile: Growth and Seed Production

Relative growth rate, total dry weight and seed yield on 19 accessions of burr medic (Medicago polymorpha L.) from different bioclimatic conditions, were assessed at Cauquenes (35°58’;72°17’W) in the subhumid mediterranean region. The accessions were sown in microplots over raised beds during two years (1991 and 1992), and swards cut periodically at 2, 6 and 10 cm height. There were significant differences between accessions in both total dry weight and seed yield (P \u3c 0.001, Table 1), but the interaction between accessions and height of cutting was not significant (P \u3e 0.05). Total dry weight was positive correlated with days to flowering (r2 = 0.81; P \u3e 0.01)

Normal Stresses and Interface Displacement: Influence of Viscoelasticity on Enhanced Oil Recovery Efficiency

International audienceOne of chemical Enhanced Oil Recovery (EOR) methods consists in injecting aqueous solutions of polymers into the reservoir in order to improve mobility ratio between the injected fluid and the remaining oil. This "polymer flooding" process is usually only characterized with the low shear viscosity of the injected fluid, even if these aqueous solutions are strongly shear thinning and may show high elastic properties evidenced by normal stresses appearance. In order to study the mechanisms at the interface level, we develop simple model experimentations with the goal of quantifying the influence of viscoelastic properties on fluid displacement in a simple geometry. For this purpose, we propose and characterize a model fluid formulation, for which elastic and viscous effects can be tuned systematically. We study then the displacement of a viscous oil by a Newtonian non elastic, a viscoelastic or a purely shear thinning fluid in a two dimensional flow cell. Observing the shape of the interface between aqueous fluids and displaced oil permits to appreciate viscoelasticity effects on the displacement. Using model geometries and controlled rheology fluids, we show that viscoelastic fluids tend to better displace immiscible liquids than Newtonian fluids and that those effects are closely related to the apparitions of normal stresses independently of shear thinning property or variation of interfacial tension as soon as viscous effects govern the flow

CONDUCTIVE PATHWAYS CONSTRUCTION USING GENETIC ALGORITHM AND CONSTRUCTAL DESIGN

In this work, Constructal Design and Genetic Algorithms are used to construct high conductivity paths connected to a heat sink and inserted in a square plate of low conductivity material with internal heat generation. The objective is propose a methodology that leads to minimize the maximum solid domain temperature. Total volume of the plate, amount of high thermal conductivity material and thermal ratio between high and low conductivities are fixed. The high conductive pathway forms found in this work greately resembles to the tree-forms found in nature, on which temperature is efficiently minimized by the application of the Genetic Algorithm and the Constructal Theory combined

Social participation and depression in old age: a fixed-effects analysis in 10 European countries

We examined whether changes in different forms of social participation were associated with changes in depressive symptoms in older Europeans. We used lagged individual fixed effects models based on data from 9,068 individuals aged 50+ in wave 1 (2004/05), wave 2 (2006/07) and wave 4 (2010/11) of the Survey of Health, Ageing and Retirement in Europe (SHARE). Controlling for a wide set of confounders, increased participation in religious organizations predicted a decline in depressive symptoms four years later (β =-0.190 units, 95% confidence interval: -0.365, -0.016), while participation in political/community organizations was associated with an increase in depressive symptoms (β =0.222, 95% confidence interval: 0.018, 0.428). There were no significant differences between European regions in these associations. Our findings suggest that social participation is associated with depressive symptoms, but the direction and strength of the association depends on the type of social activity. Participation in religious organizations may offer benefits to mental health beyond those offered by other forms of social participation