On the nonexistence of Liouvillian first integrals for generalized Liénard polynomial differential systems

International audienceWe consider generalized Liénard polynomial differential systems. In their work, Llibre and Valls have shown that, except in some particular cases, such systems have no Liouvillian first integral. In this letter, we give a direct and shorter proof of this result

Localizing limit cycles : from numeric to analytical results

Presentation given by participants of the joint international multidisciplinary workshop MURPHYS-HSFS-2016 (MUltiRate Processes and HYSteresis; Hysteresis and Slow-Fast Systems), which was dedicated to the mathematical theory and applications of multiple scale systems and systems with hysteresis, and held at the Centre de Recerca Matemàtica (CRM) in Barcelona from June 13th to 17th, 2016This note presents the results of [4]. It deals with the problem of location and existence of limit cycles for real planar polynomial differential systems. We provide a method to construct Poincaré-Bendixson regions by using transversal curves, that enables us to prove the existence of a limit cycle that has been numerically detected. We apply our results to several known systems, like the Brusselator one or some Liénard systems, to prove the existence of the limit cycles and to locate them very precisely in the phase space. Our method, combined with some other classical tools can be applied to obtain sharp bounds for the bifurcation values of a saddle-node bifurcation of limit cycles, as we do for the Rychkov syste

Molecular Dynamics Simulation Study of Nonconcatenated Ring Polymers in a Melt: I. Statics

Molecular dynamics simulations were conducted to investigate the structural properties of melts of nonconcatenated ring polymers and compared to melts of linear polymers. The longest rings were composed of N=1600 monomers per chain which corresponds to roughly 57 entanglement lengths for comparable linear polymers. For the rings, the radius of gyration squared was found to scale as N to the 4/5 power for an intermediate regime and N to the 2/3 power for the larger rings indicating an overall conformation of a crumpled globule. However, almost all beads of the rings are "surface beads" interacting with beads of other rings, a result also in agreement with a primitive path analysis performed in the following paper (DOI: 10.1063/1.3587138). Details of the internal conformational properties of the ring and linear polymers as well as their packing are analyzed and compared to current theoretical models.Comment: 15 pages, 14 figure

Perceptions and practice of personal protective behaviors to prevent COVID-19 transmission in the G7 nations

Introduction: To combat the transmission of COVID-19, countries have endorsed a series of non-pharmaceutical measures. We evaluated the practice and perceptions of personal protective measures and social distancing across the G7 countries. Methods: Data were collected during 19–21 March 2020, from 7005 of Kantar’s online panelists aged >16 years across the G7 countries: Canada, France, Great Britain, Germany, Italy, Japan, and the United States. Data were post-stratified and weighted to match population distributions of the respective countries. Descriptive and multivariable analyses were conducted in late March 2020. Results: Males (vs females) and those less educated (vs college graduates) were less likely to practice personal protective measures and social distancing. Younger adults were also less likely to practice social distancing (vs adults >65 years old). Respondents who expressed concern about the impact of COVID-19 on their health, income or education had higher odds of practicing personal protective measures (AOR=2.81, 1.74, and 1.54, respectively) and social distancing (AOR=3.18, 1.68, and 1.89, respectively) compared to those who did not. Those who perceived precautionary measures as highly effective were also more likely to practice personal protective measures (AOR=2.05) and social distancing (AOR=3.99) compared to those who perceived them as ineffective. Conclusions: Concerns about COVID-19 and perceived effectiveness of precautionary measures strongly predict practice of protective measures, regardless of the types of behaviors. Population-wide interventions should focus on ensuring increased adherence and tailoring communications to groups that are less likely to practice protective behaviors

On the number of limit cycles of the Lienard equation

In this paper, we study a Lienard system of the form dot{x}=y-F(x), dot{y}=-x, where F(x) is an odd polynomial. We introduce a method that gives a sequence of algebraic approximations to the equation of each limit cycle of the system. This sequence seems to converge to the exact equation of each limit cycle. We obtain also a sequence of polynomials R_n(x) whose roots of odd multiplicity are related to the number and location of the limit cycles of the system.Comment: 10 pages, 5 figures. Submitted to Physical Review

Long-lived neutral-kaon flux measurement for the KOTO experiment

The KOTO ($K^0$ at Tokai) experiment aims to observe the CP-violating rare decay $K_L \rightarrow \pi^0 \nu \bar{\nu}$ by using a long-lived neutral-kaon beam produced by the 30 GeV proton beam at the Japan Proton Accelerator Research Complex. The $K_L$ flux is an essential parameter for the measurement of the branching fraction. Three $K_L$ neutral decay modes, $K_L \rightarrow 3\pi^0$, $K_L \rightarrow 2\pi^0$, and $K_L \rightarrow 2\gamma$ were used to measure the $K_L$ flux in the beam line in the 2013 KOTO engineering run. A Monte Carlo simulation was used to estimate the detector acceptance for these decays. Agreement was found between the simulation model and the experimental data, and the remaining systematic uncertainty was estimated at the 1.4\% level. The $K_L$ flux was measured as $(4.183 \pm 0.017_{\mathrm{stat.}} \pm 0.059_{\mathrm{sys.}}) \times 10^7$ $K_L$ per $2\times 10^{14}$ protons on a 66-mm-long Au target.Comment: 27 pages, 16 figures. To be appeared in Progress of Theoretical and Experimental Physic

Public perspective on the governmental response, communication and trust in the governmental decisions in mitigating COVID-19 early in the pandemic across the G7 countries

The COVID-19 pandemic poses a threat to global health and security inciting governments with the responsibility to respond with measures that ensure the health and safety of their communities. We assessed public attitudes towards governmental actions to combat the COVID-19 pandemic in the G7 countries. Data were collected during 19th–21st March 2020, from 7005 Kantar's online panelists aged >16 years across the G7 countries: Canada, France, Great Britain, Germany, Italy, Japan, and the United States. Data were post-stratified and weighted to match population distributions of the respective countries. Descriptive and multivariable analyses were conducted. Amongst the G7, Japan had the lowest level of approval of governmental response to the pandemic, rating governmental communication as good, and trusting governmental decisions (35.0%, 33.6%, and 38.0%, respectively), followed by the U.S. (52.9%, 64.6%, and 59.9%, respectively). Understanding of which measures one can personally take to help limit the spread of the coronavirus was significantly associated with approving governmental response (aOR = 2.88), rating government communication as good (aOR = 2.70) and trust in future governmental decisions (aOR = 2.73). Those who reported government/politicians and friends/family as their most trusted information source were more likely to report approval, higher rating, and/or trust toward governmental actions. Public attitudes towards governmental actions against COVID-19 varied substantially across the G7 countries and were associated with the understanding of measures and source of information that respondents most trusted. Timely and accurate communication is essential to enhance public engagement to control the COVID-19 pandemic

ARG098, a novel anti-human Fas antibody, suppresses synovial hyperplasia and prevents cartilage destruction in a severe combined immunodeficient-HuRAg mouse model

<p>Abstract</p> <p>Background</p> <p>The anti-human Fas/APO-1/CD95 (Fas) mouse/human chimeric monoclonal IgM antibody ARG098 (ARG098) targets the human Fas molecule. The cytotoxic effects of ARG098 on cells isolated from RA patients, on normal cells <it>in vitro</it>, and on RA synovial tissue and cartilage <it>in vivo </it>using implanted rheumatoid tissues in an SCID mouse model (SCID-HuRAg) were investigated to examine the potential of ARG098 as a therapy for RA.</p> <p>Methods</p> <p>ARG098 binding to each cell was analyzed by cytometry. The effects of ARG098 on several cells were assessed by a cell viability assay <it>in vitro</it>. Effects on the RA synovium, lymphocytes, and cartilage were assessed <it>in vivo </it>using the SCID-HuRAg mouse model.</p> <p>Results</p> <p>ARG098 bound to cell surface Fas molecules, and induced apoptosis in Fas-expressing RA synoviocytes and infiltrating lymphocytes in the RA synovium in a dose-dependent manner. However, ARG098 did not affect the cell viability of peripheral blood mononuclear cells of RA patients or normal chondrocytes. ARG098 also induced apoptosis in RA synoviocytes and infiltrating lymphocytes in the RA synovium <it>in vivo</it>. The destruction of cartilage due to synovial invasion was inhibited by ARG098 injection in the modified SCID-HuRAg mouse model.</p> <p>Conclusions</p> <p>ARG098 treatment suppressed RA synovial hyperplasia through the induction of apoptosis and prevented cartilage destruction <it>in vivo</it>. These results suggest that ARG098 might become a new therapy for RA.</p

Cloning of cDNA and chromosomal location of genes encoding the three types of subunits of the wheat tetrameric inhibitor of insect a-amylase

We have characterized three cDNA clones corresponding to proteins CM1, CM3 and CM16, which represent the three types of subunits of the wheat tetrameric inhibitor of insect -amylases. The deduced amino acid sequences of the mature polypeptides are homologous to those of the dimeric and monomeric -amylase inhibitors and of the trypsin inhibitors. The mature polypeptides are preceded by typical signal peptides. Southern blot analysis of appropriate aneuploids, using the cloned cDNAs as probes, has revealed the location of genes for subunits of the CM3 and of the CM16 type within a few kb of each other in chromosomes 4A, 4B and 4D, and those for the CM1 type of subunit in chromosomes 7A, 7B and 7D. Known subunits of the tetrameric inhibitor corresponding to genes from the B and D genomes have been previously characterized. No proteins of this class have been found to be encoded by the A genome in hexaploid wheat (genomes AA, BB, DD) or in diploid wheats (AA) and no anti -amylase activity has been detected in the latter, so that the A-genome genes must be either silent (pseudogenes) or expressed at a much lower level

Recent and historical recombination in the admixed Norwegian Red cattle breed

<p>Abstract</p> <p>Background</p> <p>Comparison of recent patterns of recombination derived from linkage maps to historical patterns of recombination from linkage disequilibrium (LD) could help identify genomic regions affected by strong artificial selection, appearing as reduced recent recombination. Norwegian Red cattle (NRF) make an interesting case study for investigating these patterns as it is an admixed breed with an extensively recorded pedigree. NRF have been under strong artificial selection for traits such as milk and meat production, fertility and health.</p> <p>While measures of LD is also crucial for determining the number of markers required for association mapping studies, estimates of recombination rate can be used to assess quality of genomic assemblies.</p> <p>Results</p> <p>A dataset containing more than 17,000 genome-wide distributed SNPs and 2600 animals was used to assess recombination rates and LD in NRF. Although low LD measured by r²was observed in NRF relative to some of the breeds from which this breed originates, reports from breeds other than those assessed in this study have described more rapid decline in r²at short distances than what was found in NRF. Rate of decline in r²for NRF suggested that to obtain an expected r²between markers and a causal polymorphism of at least 0.5 for genome-wide association studies, approximately one SNP every 15 kb or a total of 200,000 SNPs would be required. For well known quantitative trait loci (QTLs) for milk production traits on <it>Bos Taurus </it>chromosomes 1, 6 and 20, map length based on historic recombination was greater than map length based on recent recombination in NRF.</p> <p>Further, positions for 130 previously unpositioned contigs from assembly of the bovine genome sequence (Btau_4.0) found using comparative sequence analysis were validated by linkage analysis, and 28% of these positions corresponded to extreme values of population recombination rate.</p> <p>Conclusion</p> <p>While LD is reduced in NRF compared to some of the breeds from which this admixed breed originated, it is elevated over short distances compared to some other cattle breeds. Genomic regions in NRF where map length based on historic recombination was greater than map length based on recent recombination coincided with some well known QTL regions for milk production traits.</p> <p>Linkage analysis in combination with comparative sequence analysis and detection of regions with extreme values of population recombination rate proved to be valuable for detecting problematic regions in the Btau_4.0 genome assembly.</p