Accelerated Gossip in Networks of Given Dimension using Jacobi Polynomial Iterations

Consider a network of agents connected by communication links, where each agent holds a real value. The gossip problem consists in estimating the average of the values diffused in the network in a distributed manner. We develop a method solving the gossip problem that depends only on the spectral dimension of the network, that is, in the communication network set-up, the dimension of the space in which the agents live. This contrasts with previous work that required the spectral gap of the network as a parameter, or suffered from slow mixing. Our method shows an important improvement over existing algorithms in the non-asymptotic regime, i.e., when the values are far from being fully mixed in the network. Our approach stems from a polynomial-based point of view on gossip algorithms, as well as an approximation of the spectral measure of the graphs with a Jacobi measure. We show the power of the approach with simulations on various graphs, and with performance guarantees on graphs of known spectral dimension, such as grids and random percolation bonds. An extension of this work to distributed Laplacian solvers is discussed. As a side result, we also use the polynomial-based point of view to show the convergence of the message passing algorithm for gossip of Moallemi \& Van Roy on regular graphs. The explicit computation of the rate of the convergence shows that message passing has a slow rate of convergence on graphs with small spectral gap

Advanced survival models for risk-factor analysis in scrapie

Because of the confounding effects of long incubation duration and flock management, accurate epidemiological studies of scrapie outbreaks are difficult to carry out. In this study, 641 Manech red-faced sheep from six scrapie-affected field flocks in Pyrénées Atlantiques, France, were monitored for clinical scrapie over a 6–9 year period. Over this period, 170 scrapie clinical cases were recorded and half of the culled animals were submitted for post-mortem transmissible spongiform encephalopathy diagnosis to assess their infectious status. Collected data were analysed using a ‘mixture cure model’ approach, which allowed for the discriminating effect of PrP genotype and flock origin on incidence and incubation period. Simulations were performed to evaluate the applicability of such a statistical model to the collected data. As expected, ARR heterozygote sheep were less at risk of becoming infected than ARQ/ARQ individuals and had a greater age at clinical onset. Conversely, when compared with ARQ/ARQ, the VRQ haplotype was associated with an increased infection risk, but not a shorter incubation period. Considering the flock effect, we observed that a high incidence rate was not associated with shorter incubation periods and that the incubation period could be significantly different in flocks harbouring similar infection risks. These results strongly support the conclusion that other parameters, such as the nature of the agent or flock management, could interfere with epidemiological dynamics of the infection in scrapie-affected flocks

Québec's Childcare Universal Low Fees Policy 10 Years After: Effects, Costs and Benefits

More than ten years ago the province of Québec implemented a universal early childhood education and care policy. This paper examines if the two objectives pursued, to increase mothers’ participation in the labour market (balance the needs of workplace and home) and to enhance child development and equality of opportunity for children, were reasonable meet. A non-experimental evaluation framework based on multiple pre- and post-treatment periods is used to estimate the policy effects. First, year after year the number of children and their weekly of hours in childcare have increased. More preschool children are in non-parental childcare at a younger age and the intensity of childcare has increased over the years. Second, the policy has significantly increased the labour force participation and annual weeks worked for mothers with at least a child aged 1 to 4 years compared to mothers in the same situation in the Rest of Canada. Third, the evidence presented show that the policy has not enhanced school readiness or child early literacy skills in general, with negative significant effects on the PPVT scores of children aged 5 and possibly negative for children of age 4. Simulations show the bounds of the public benefits in terms of additional net taxes (income taxes less refundable credits and transfers based on household’s “net” income). Unless one suppose that mothers in the upper part of the earnings distribution are those who returned early to the labour market after giving birth or a maternity leave, and who have worked more weeks, the effect on governments revenues are modest. The main beneficiary of the larger tax base of a higher labour supply of mothers with young children is the federal government which do not support the significant public funding of the program. The policy has some drawbacks in terms of social efficiency and equity. The structure of the program with its very low $7/day fee before taxes creates strong incentives for families to use long hours of daycare for children at a very young age, which may not be the best mechanism for children development. The high transfers in-kind (1.9 billion in 2009) to families using subsidized childcare raise the question of their horizontal and vertical equity. The paper concludes on three modifications to the program that could correct some of its weaknesses.Childcare policy, mother’s labour supply, preschool children and school readiness, treatment effects, natural experiment

Conjugated linolenic acid (CLnA), conjugated linoleic acid (CLA) and other biohydrogenation intermediates in plasma and milk fat of cows fed raw or extruded linseed

Thirty lactating dairy cows were used in a 333 Latin-square design to investigate the effects of a raw or extruded blend of linseed and wheat bran (70:30) on plasma and milk fatty-acids (FA). Linseed diets, containing 16.6% linseed blend on a dry-matter basis, decreased milk yield and protein percentage. They decreased the proportions of FA with less than 18 carbons in plasma and milk and resulted in cis-9, cis-12, cis-15 18:3 proportions that were more than three and four times higher in plasma and milk, respectively, whereas cis-9, cis-12 18:2 proportions were decreased by 10–15%. The cis-9, trans-11, cis-15 18:3 isomer of conjugated linolenic acid was not detected in the milk of control cows, but was over 0.15% of total FA in the milk fat of linseed-supplemented cows. Similarly, linseed increased plasma and milk proportions of all biohydrogenation (BH) intermediates in plasma and milk, including the main isomer of conjugated linoleic acid cis-9, trans-11 18:2, except trans-4 18:1 and cis-11, trans-15 18:2 in plasma lipids. In milk fat, compared with raw linseed, extruded linseed further reduced 6:0–16:0 even-chain FA, did not significantly affect the proportions of 18:0, cis-9 18:1 and cis-9, cis-12 18:2, tended to increase cis-9, cis-12, cis-15 18:3, and resulted in an additional increase in the proportions of most BH intermediates. It was concluded that linseed addition can improve the proportion of conjugated linoleic and linolenic acids, and that extrusion further increases the proportions of intermediates of ruminal BH in milk fat

Stability comparison of two absolute gravimeters: optical versus atomic interferometers

We report the direct comparison between the stabilities of two mobile absolute gravimeters of different technology: the LNE-SYRTE Cold Atom Gravimeter and FG5X\#216 of the Universit\'e du Luxembourg. These instruments rely on two different principles of operation: atomic and optical interferometry. The comparison took place in the Walferdange Underground Laboratory for Geodynamics in Luxembourg, at the beginning of the last International Comparison of Absolute Gravimeters, ICAG-2013. We analyse a 2h10 duration common measurement, and find that the CAG shows better immunity with respect to changes in the level of vibration noise, as well as a slightly better short term stability.Comment: 6 page

ON THE ASYMPTOTIC LIMIT OF THE THREE DIMENSIONAL VLASOV-POISSON SYSTEM FOR LARGE MAGNETIC FIELD : FORMAL DERIVATION

International audienceIn this paper we establish the asymptotic limit of the three dimensional Vlasov–Poisson equation with strong external magnetic field. The guiding center approximation is investigated in the three dimensional case with a non-constant magnetic field. In the long time asymptotic limit, the motion canbe split in two parts : one stationary flow along the lines of the magnetic field and the guiding center motion in the orthogonal plane of the magnetic field where classical drift velocities and invariants (magnetic moment) are recovered

Cis-15 intermediates of biohydrogenation in the duodenal flow of cows receiving linseed

Duodenal samples from a previous experiment (Akraim et al., 2006) were reanalysed for determination of cis-15 intermediates of ruminal biohydrogenation (BH). Three dry Holstein cows fitted with a duodenal cannula received a diet with 14% (dry matter basis) raw linseed. C18 fatty acids (C18FA) represented 6.3% of dietary dry matter, and contained 57.8% of C18:3. After 18 days adaptation, on each cow, twelve samples of duodenal flow were taken over 3 days, composited, and analysed for FA composition. Cis-9,trans-11,cis-15C18:3 and trans-11,cis-15C18:2 (CLnA) were identified by GC-MS. The proportion of CLnA was low, in spite of the high C18:3 intake. The first step of C18:3 BH, isomerisation to CLnA, was extensive because the C18:3 proportion was 13.5 times lower in the duodenum than in the diet (Akraim et al., 2006). The extensive C18:3 BH and the low proportion of CLnA suggest a rapid ruminal reduction of this FA. The proportion of the product of this first reduction, trans-11,cis-15C18:2, was much higher than that of CLnA, but quite variable among cows. This suggests that the reduction of this FA was slower than that of CLnA, although this reduction is supposed to be due to a broad range of bacteria. According to responsible bacteria, this reduction can lead to trans-11C18:1, or cis-15C18:1 and trans-15C18:1. Cis-15C18:1 represented only half the proportion of trans-15C18:1, suggesting either a direct BH of trans-11,cis-15C18:2 to trans-15C18:1, or a rapid isomerisation of cis-15C18:1 to trans-15C18:1