Convex Hull of Arithmetic Automata

Arithmetic automata recognize infinite words of digits denoting decompositions of real and integer vectors. These automata are known expressive and efficient enough to represent the whole set of solutions of complex linear constraints combining both integral and real variables. In this paper, the closed convex hull of arithmetic automata is proved rational polyhedral. Moreover an algorithm computing the linear constraints defining these convex set is provided. Such an algorithm is useful for effectively extracting geometrical properties of the whole set of solutions of complex constraints symbolically represented by arithmetic automata

Mountain trail formation and the active walker model

We extend the active walker model to address the formation of paths on gradients, which have been observed to have a zigzag form. Our extension includes a new rule which prohibits direct descent or ascent on steep inclines, simulating aversion to falling. Further augmentation of the model stops walkers from changing direction very rapidly as that would likely lead to a fall. The extended model predicts paths with qualitatively similar forms to the observed trails, but only if the terms suppressing sudden direction changes are included. The need to include terms into the model that stop rapid direction change when simulating mountain trails indicates that a similar rule should also be included in the standard active walker model.Comment: Introduction improved. Analysis of discretization errors added. Calculations from alternative scheme include

Efficient Algorithms for Asymptotic Bounds on Termination Time in VASS

Vector Addition Systems with States (VASS) provide a well-known and fundamental model for the analysis of concurrent processes, parameterized systems, and are also used as abstract models of programs in resource bound analysis. In this paper we study the problem of obtaining asymptotic bounds on the termination time of a given VASS. In particular, we focus on the practically important case of obtaining polynomial bounds on termination time. Our main contributions are as follows: First, we present a polynomial-time algorithm for deciding whether a given VASS has a linear asymptotic complexity. We also show that if the complexity of a VASS is not linear, it is at least quadratic. Second, we classify VASS according to quantitative properties of their cycles. We show that certain singularities in these properties are the key reason for non-polynomial asymptotic complexity of VASS. In absence of singularities, we show that the asymptotic complexity is always polynomial and of the form $\Theta(n^k)$, for some integer $k\leq d$, where $d$ is the dimension of the VASS. We present a polynomial-time algorithm computing the optimal $k$. For general VASS, the same algorithm, which is based on a complete technique for the construction of ranking functions in VASS, produces a valid lower bound, i.e., a $k$ such that the termination complexity is $\Omega(n^k)$. Our results are based on new insights into the geometry of VASS dynamics, which hold the potential for further applicability to VASS analysis.Comment: arXiv admin note: text overlap with arXiv:1708.0925

Évaluation de lignées de sorgho (Sorghum bicolor) pour leur résistance à la mauvaise herbe parasite Striga hermonthica au Burkina Faso

Des essais en pots et au champ ont été réalisés au Burkina Faso en 1987 pour évaluer la résistance de lignées de sorgho (Sorghum bicolor) vis-à-vis la mauvaise herbe parasite Striga hermonthica. Dans l'expérience en pots, les lignées de cycle court ICSV-1079 BF et ICSV-1078 BF ont présenté un nombre et une biomasse de S. hermonthica inférieurs à ceux du témoin sensible. Cette réaction n'a pas été confirmée dans l'expérience au champ. Aucune lignée ne s'est avérée résistante. Parmi les lignées de cycle moyen, aucune lignée ne s'est démarquée du témoin sensible dans l'expérience en pots. Dans l'expérience au champ, la lignée ICSV-1089 BF a présenté une faible sensibilité au S. hermonthica. Cependant, cette lignée a obtenu de faibles rendements. Aucune des lignées testées ne semble pouvoir être recommandée pour la lutte envers le S. hermonthica dans le sorgho au Sahel. Le cultivar Framida ne saurait être utilisé comme source de résistance au S. hermonthica. Il est urgent d'identifier de nouvelles sources de résistance afin de répondre aux besoins des programmes d'amélioration du sorgho.Pot and field experiments were performed in Burkina Faso in 1987 in order to evaluate sorghum (Sorghum bicolor) lines for their resistance to the parasitic weed Striga hermonthica. In pot experiments, low duration lines ICSV-1079 BF and ICSV-1078 BF presented a lower number and biomass of S. hermonthica than the susceptible check. This reaction was notconfirmed in field experiments. No line was resistant. Among medium duration lines, no line was significantly different from the susceptible check in pot experiments. ICSV-1089 BF exhibited a low susceptibility to S. hermonthica attack in field experiments. However, its yield was low. No line could be recommended in the perspective of controlling S. hermonthica sorghum in Sahelian countries. The cultivar Framida is not an appropriate source of resistance to S. hermonthica. Other sources of resistance are urgently required to satisfy the needs of sorghum breeding programs

Optomechanical Cavity Cooling of an Atomic Ensemble

We demonstrate cavity sideband cooling of a single collective motional mode of an atomic ensemble down to a mean phonon occupation number of 2.0(-0.3/+0.9). Both this minimum occupation number and the observed cooling rate are in good agreement with an optomechanical model. The cooling rate constant is proportional to the total photon scattering rate by the ensemble, demonstrating the cooperative character of the light-emission-induced cooling process. We deduce fundamental limits to cavity-cooling either the collective mode or, sympathetically, the single-atom degrees of freedom.Comment: Paper with supplemental material: 4+6 pages, 4 figures. Minor revisions of text. Supplemental material shortened by removal of supplementary figur

Pregnancy has a minimal impact on the acute transcriptional signature to vaccination.

Vaccination in pregnancy is an effective tool to protect both the mother and infant; vaccines against influenza, pertussis and tetanus are currently recommended. A number of vaccines with a specific indication for use in pregnancy are in development, with the specific aim of providing passive humoral immunity to the newborn child against pathogens responsible for morbidity and mortality in young infants. However, the current understanding about the immune response to vaccination in pregnancy is incomplete. We analysed the effect of pregnancy on early transcriptional responses to vaccination. This type of systems vaccinology approach identifies genes and pathways that are altered in response to vaccination and can be used to understand both the acute inflammation in response to the vaccine and to predict immunogenicity. Pregnant women and mice were immunised with Boostrix-IPV, a multivalent vaccine, which contains three pertussis antigens. Blood was collected from women before and after vaccination and RNA extracted for analysis by microarray. While there were baseline differences between pregnant and non-pregnant women, vaccination induced characteristic patterns of gene expression, with upregulation in interferon response and innate immunity gene modules, independent of pregnancy. We saw similar patterns of responses in both women and mice, supporting the use of mice for preclinical screening of novel maternal vaccines. Using a systems vaccinology approach in pregnancy demonstrated that pregnancy does not affect the initial response to vaccination and that studies in non-pregnant women can provide information about vaccine immunogenicity and potentially safety