Approximation algorithms for maximally balanced connected graph partition

Given a simple connected graph $G = (V, E)$, we seek to partition the vertex set $V$ into $k$ non-empty parts such that the subgraph induced by each part is connected, and the partition is maximally balanced in the way that the maximum cardinality of these $k$ parts is minimized. We refer this problem to as {\em min-max balanced connected graph partition} into $k$ parts and denote it as {\sc $k$-BGP}. The general vertex-weighted version of this problem on trees has been studied since about four decades ago, which admits a linear time exact algorithm; the vertex-weighted {\sc $2$-BGP} and {\sc $3$-BGP} admit a $5/4$-approximation and a $3/2$-approximation, respectively; but no approximability result exists for {\sc $k$-BGP} when $k \ge 4$, except a trivial $k$-approximation. In this paper, we present another $3/2$-approximation for our cardinality {\sc $3$-BGP} and then extend it to become a $k/2$-approximation for {\sc $k$-BGP}, for any constant $k \ge 3$. Furthermore, for {\sc $4$-BGP}, we propose an improved $24/13$-approximation. To these purposes, we have designed several local improvement operations, which could be useful for related graph partition problems.Comment: 23 pages, 7 figures, accepted for presentation at COCOA 2019 (Xiamen, China

Etude de la durabilité des assemblages collés bois-béton soumis à des chargements hydriques

L'étude a pour objectif de déterminer les paramètres qui gouvernent les mécanismes d'endommagement d'un assemblage collé bois/béton soumis à des chargements hydriques. Des mesures des déformations globales par palmer et locales par la technique de corrélation d'image ont été réalisées lors du chargement hydrique. On analyse le comportement global de la structure en liaison avec des aspects plus locaux notamment les déformations du bois liées à sa teneur en eau (via des mesures par IRM) et les propriétés de la colle pour comprendre les couplages hygro-mécaniques

Algorithms for the minimum non-separating path and the balanced connected bipartition problems on grid graphs (With erratum)

For given a pair of nodes in a graph, the minimum non-separating path problem looks for a minimum weight path between the two nodes such that the remaining graph after removing the path is still connected. The balanced connected bipartition (BCP$_2$) problem looks for a way to bipartition a graph into two connected subgraphs with their weights as equal as possible. In this paper we present an algorithm in time $O(N\log N)$ for finding a minimum weight non-separating path between two given nodes in a grid graph of $N$ nodes with positive weight. This result leads to a 5/4-approximation algorithm for the BCP$_2$ problem on grid graphs, which is the currently best ratio achieved in polynomial time. We also developed an exact algorithm for the BCP$_2$ problem on grid graphs. Based on the exact algorithm and a rounding technique, we show an approximation scheme, which is a fully polynomial time approximation scheme for fixed number of rows.Comment: With erratu

Dietary Fish Hydrolysate Improves Memory Performance Through Microglial Signature Remodeling During Aging

Brain aging is characterized by a chronic low-grade inflammation, which significantly impairs cognitive function. Microglial cells, the immunocompetent cells of the brain, present a different phenotype, switching from a homeostatic signature (M0) to a more reactive phenotype called “MGnD” (microglial neurodegenerative phenotype), leading to a high production of pro-inflammatory cytokines. Furthermore, microglial cells can be activated by age-induced gut dysbiosis through the vagus nerve or the modulation of the peripheral immune system. Nutrients, in particular n-3 long chain polyunsaturated fatty acids (LC-PUFAs) and low molecular weight peptides, display powerful immunomodulatory properties, and can thus prevent age-related cognitive decline. The objective of this study was to investigate the effects of n-3 LC-PUFAs and low molecular weight peptides contained in a marine by-product-derived hydrolysate on microglial phenotypes and intestinal permeability and their consequences on cognition in mice. We demonstrated that the hydrolysate supplementation for 8 weeks prevented short- and long-term memory decline during aging. These observations were linked to the modulation of microglial signature. Indeed, the hydrolysate supplementation promoted homeostatic microglial phenotype by increasing TGF-β1 expression and stimulated phagocytosis by increasing Clec7a expression. Moreover, the hydrolysate supplementation promoted anti-inflammatory intestinal pathway and tended to prevent intestinal permeability alteration occurring during aging. Therefore, the fish hydrolysate appears as an interesting candidate to prevent cognitive decline during aging

The Maraichine Cattle Breed Supports Breeders and Researchers in the Atlantic Coastal Marshlands

The Maraichine breed of cattle originates from the Loire region of France and has been under a conservation programme since 1986. This programme links the conservation of the breed with the conservation of its traditional environment of wet grasslands. In this case report, we describe the different steps of this programme, each of which had its own successes and challenges. We also describe how, throughout this process, researchers have been involved in the generation and dissemination of information covering areas such as stakeholder perspectives, animal performance, and socio-economics. Under the conservation programme, the Maraichine population has expanded in both size and scale. Simultaneously, stakeholder perspectives have also developed, continually shifting the balance between the productivity, conservation, and maintenance of heritage traits. The conservation programme also provided the opportunity to utilise the breed�s desirable traits, such as easy calving and disease resistance. Whilst the carcasses are not necessarily as valuable as those of other breeds, farmers have implemented novel economic practices to capitalise on market opportunities. Today, Maraichine cattle and Maraichine breeders offer researchers the opportunity to deepen and enrich our knowledge on sustainable ruminant livestock farming systems

Nackter Phosphor als gewinkelt verbrückender Ligand

Die Metathesereaktion von [W2(OAr)6] (Ar=2,6-Me2C6H3) mit tBuCP führt zur Bildung eines Komplexes, der den ersten gewinkelt verbrückenden P1-Liganden der Koordinationszahl 2 enthält (siehe Struktur, Atom P2). Dieser Koordinationstyp war bisher ausschließlich dem Stickstoff vorbehalten und bei den schweren Homologen unbekannt. Das freie Elektronenpaar des Phosphidoliganden ist koordinationschemisch aktiv und koordiniert Lewis-saure {M(CO)5}-Fragmente (M=Cr, W)