Iodoarene-Catalyzed Cyclizations of Unsaturated Amides

The cyclization of N-alkenylamides catalyzed by iodoarenes under oxidative conditions is presented. Five-, six-, and seven-membered rings with a range of substitutions can be prepared by this route. Preliminary data from the use of chiral iodoarenes as precatalysts show that enantiocontrol is feasible

HS Hya about to turn off its eclipses

Aims: We aim to perform the first long-term analysis of the system HS Hya. Methods: We performed an analysis of the long-term evolution of the light curves of the detached eclipsing system HS Hya. Collecting all available photometric data since its discovery, the light curves were analyzed with a special focus on the evolution of system's inclination. Results: We find that the system undergoes a rapid change of inclination. Since its discovery until today the system's inclination changed by more than 15 deg. The shape of the light curve changes, and now the eclipses are almost undetectable. The third distant component of the system is causing the precession of the close orbit, and the nodal period is about 631 yr. Conclusions: New precise observations are desperately needed, preferably this year, because the amplitude of variations is decreasing rapidly every year. We know only 10 such systems on the whole sky at present.Comment: 4 pages, 3 figures, published in 2012A&A...542L..23

Rendezvous of Heterogeneous Mobile Agents in Edge-weighted Networks

We introduce a variant of the deterministic rendezvous problem for a pair of heterogeneous agents operating in an undirected graph, which differ in the time they require to traverse particular edges of the graph. Each agent knows the complete topology of the graph and the initial positions of both agents. The agent also knows its own traversal times for all of the edges of the graph, but is unaware of the corresponding traversal times for the other agent. The goal of the agents is to meet on an edge or a node of the graph. In this scenario, we study the time required by the agents to meet, compared to the meeting time $T_{OPT}$ in the offline scenario in which the agents have complete knowledge about each others speed characteristics. When no additional assumptions are made, we show that rendezvous in our model can be achieved after time $O(n T_{OPT})$ in a $n$-node graph, and that such time is essentially in some cases the best possible. However, we prove that the rendezvous time can be reduced to $\Theta (T_{OPT})$ when the agents are allowed to exchange $\Theta(n)$ bits of information at the start of the rendezvous process. We then show that under some natural assumption about the traversal times of edges, the hardness of the heterogeneous rendezvous problem can be substantially decreased, both in terms of time required for rendezvous without communication, and the communication complexity of achieving rendezvous in time $\Theta (T_{OPT})$

Byzantine Gathering in Networks

This paper investigates an open problem introduced in [14]. Two or more mobile agents start from different nodes of a network and have to accomplish the task of gathering which consists in getting all together at the same node at the same time. An adversary chooses the initial nodes of the agents and assigns a different positive integer (called label) to each of them. Initially, each agent knows its label but does not know the labels of the other agents or their positions relative to its own. Agents move in synchronous rounds and can communicate with each other only when located at the same node. Up to f of the agents are Byzantine. A Byzantine agent can choose an arbitrary port when it moves, can convey arbitrary information to other agents and can change its label in every round, in particular by forging the label of another agent or by creating a completely new one. What is the minimum number M of good agents that guarantees deterministic gathering of all of them, with termination? We provide exact answers to this open problem by considering the case when the agents initially know the size of the network and the case when they do not. In the former case, we prove M=f+1 while in the latter, we prove M=f+2. More precisely, for networks of known size, we design a deterministic algorithm gathering all good agents in any network provided that the number of good agents is at least f+1. For networks of unknown size, we also design a deterministic algorithm ensuring the gathering of all good agents in any network but provided that the number of good agents is at least f+2. Both of our algorithms are optimal in terms of required number of good agents, as each of them perfectly matches the respective lower bound on M shown in [14], which is of f+1 when the size of the network is known and of f+2 when it is unknown

Performances de systèmes viticoles à faible niveau d’intrants phytopharmaceutiques dans le vignoble bordelais

Afin de répondre aux exigences de réduction de l'usage des produits phytosanitaires, ce projet vise à concevoir et à évaluer des systèmes viticoles qui en sont très économes. Ces systèmes, menés en agriculture conventionnelle ou biologique, sont basés essentiellement sur des leviers d'efficience de la lutte chimique pour la gestion des maladies et des ravageurs (règles de décision de traitement), et de substitution pour la maîtrise des adventices (travail du sol, couverts végétaux). Un autre type de système teste aussi le levier de la résistance variétale contre le mildiou et l'oïdium. Une évaluation multicritères de ces systèmes est effectuée pendant 5 ans au vignoble (réduction d’IFT, présence de résidus, maîtrise des bioagresseurs, atteinte des objectifs de rendement, coûts de production, temps de travail). Les résultats montrent que des systèmes basés essentiellement sur l'efficience permettent de réduire significativement l'IFT en maintenant des performances agronomiques et économiques satisfaisantes. Néanmoins, compte tenu d'une certaine prise de risque engendrée par ces systèmes, la diffusion des règles de décisions doit impliquer les viticulteurs. En viticulture biologique, il apparaît difficile de réduire les doses de cuivre et de soufre par rapport aux pratiques actuelles en maintenant des performances agronomiques stables. La mise en œuvre de variétés résistantes au mildiou et à l'oïdium permet de réduire l’IFT de 90 % par rapport aux références régionales