Adding Isolated Vertices Makes some Online Algorithms Optimal

An unexpected difference between online and offline algorithms is observed. The natural greedy algorithms are shown to be worst case online optimal for Online Independent Set and Online Vertex Cover on graphs with 'enough' isolated vertices, Freckle Graphs. For Online Dominating Set, the greedy algorithm is shown to be worst case online optimal on graphs with at least one isolated vertex. These algorithms are not online optimal in general. The online optimality results for these greedy algorithms imply optimality according to various worst case performance measures, such as the competitive ratio. It is also shown that, despite this worst case optimality, there are Freckle graphs where the greedy independent set algorithm is objectively less good than another algorithm. It is shown that it is NP-hard to determine any of the following for a given graph: the online independence number, the online vertex cover number, and the online domination number.Comment: A footnote in the .tex file didn't show up in the last version. This was fixe

Quantitative proteomics of a B12 -dependent alga grown in coculture with bacteria reveals metabolic tradeoffs required for mutualism

The unicellular green alga Lobomonas rostrata requires an external supply of vitamin B12 (cobalamin) for growth, which it can obtain in stable laboratory cultures from the soil bacterium Mesorhizobium loti in exchange for photosynthate. We investigated changes in protein expression in the alga that allow it to engage in this mutualism. We used quantitative isobaric tagging (iTRAQ) proteomics to determine the L. rostrata proteome grown axenically with B12 supplementation or in coculture with M. loti. Data are available via ProteomeXchange (PXD005046). Using the related Chlamydomonas reinhardtii as a reference genome, 588 algal proteins could be identified. Enzymes of amino acid biosynthesis were higher in coculture than in axenic culture, and this was reflected in increased amounts of total cellular protein and several free amino acids. A number of heat shock proteins were also elevated. Conversely, photosynthetic proteins and those of chloroplast protein synthesis were significantly lower in L. rostrata cells in coculture. These observations were confirmed by measurement of electron transfer rates in cells grown under the two conditions. The results indicate that, despite the stability of the mutualism, L. rostrata experiences stress in coculture with M. loti, and must adjust its metabolism accordingly.The work in this manuscript was supported by funding from the Biotechnology and Biological Sciences Research Council (BBSRC) of the UK (grant BB/I013164/1, a CASE studentship for M.B.C. joint with PML Applications Ltd, Plymouth, UK, and a DTP studentship for F.B.); an EU FP7 Marie Curie ITN Photo.Comm, no. 317184 for U.J.K.; Engineering and Physical Science Research Council (EPSRC) grant EP/E036252/1; and the Natural Environment Research Council (NERC) grant NE/J024767/1

Les émotions en politique à Aix en Provence – Le bilan

La section 8 du 13ème Congrès de l’Association Française de Science Politique (juin 2015 – Aix en Provence) a été consacrée à la place des émotions dans la politique. Légèrement dépassés par le succès initial de l’appel à communication (plus de cinquante réponses), ses initiateurs Alain Faure et Emmanuel Négrier ont sélectionné 25 textes en optant pour une organisation des débats en quatre séquences : d’abord trois temps de discussion thématisés, animés à chaque fois par deux lecteurs critiqu..

Discovering real options in the optimal control of foot-and-mouth disease

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