The Repeater Tree Construction Problem

A tree-like substructure on a computer chip whose task it is to carry a signal from a source circuit to possibly many sink circuits and which consists only of wires and so-called repeater circuits is called a repeater tree. We present a mathematical formulation of the optimization problems related to the construction of such repeater trees. Furthermore, we prove theoretical properties of a simple iterative procedure for these problems which was successfully applied in practice

European public health policies for managing contacts of invasive meningococcal disease cases better harmonized in 2013 than 2007,” Eurosurveillance

In 2007, a European survey identified variation in country policies on public health management of invasive meningococcal disease (IMD). In 2009-10, the European Centre for Disease Prevention and Control (ECDC) published evidence-based guidance on IMD. We therefore surveyed again European countries to describe policies for managing IMD cases and contacts in 2013. We asked national IMD public health experts from 32 European countries to complete a questionnaire focusing on post-exposure prophylaxis (PEP) for IMD contacts and meningococcal vaccination. Proportions in 2007 and 2013 were compared using the chi-squared test. All 32 countries responded, with responses from two regions for Belgium and Italy; half stated having used ECDC guidance to update national recommendations. PEP was recommended to close contacts in 33 of 34 countries/regions, mainly ciprofloxacin for adults (29/32 countries) and rifampicin for children (29/32 countries). ECDC guidance for managing IMD contacts in airplanes was strictly followed by five countries/regions. Twenty-three countries/regions participated in both surveys. Compared with 2007, in 2013, more countries/regions recommended i) ceftriaxone for children (15/23 vs 6/20; p = 0.03), ii) PEP for all children in the same preschool group (8/23 vs 17/23; p = 0.02). More countries/regions recommended evidence-based measures for IMD public health management in 2013 than 2007. However, some discrepancies remain and they call for further harmonisation

Ongoing outbreak of invasive listeriosis, Germany, 2012 to 2015

Listeriosis patient isolates in Germany have shown a new identical pulsed-field gel electrophoresis (PFGE) pattern since 2012 (n = 66). Almost all isolates (Listeria monocytogenes serotype 1/2a) belonged to cases living in southern Germany, indicating an outbreak with a so far unknown source. Case numbers in 2015 are high (n = 28). No outbreak cases outside Germany have been reported. Next generation sequencing revealed the unique cluster type CT1248 and confirmed the outbreak. Investigations into the source are ongoing

Parameterized tractability of edge-disjoint paths on directed acyclic graphs

Given a graph and terminal pairs (si, ti), i ∈ [k], the edge-disjoint paths problem is to determine whether there exist siti paths, i ∈ [k], that do not share any edges. We consider this problem on acyclic digraphs. It is known to be NP-complete and solvable in time n O(k) where n is the number of nodes. It has been a long-standing open question whether it is fixed-parameter tractable in k, i.e. whether it admits an algorithm with running time of the form f(k) n O(1). We resolve this question in the negative: we show that the problem is W [1]-hard, hence unlikely to be fixed-parameter tractable. In fact it remains W [1]-hard even if the demand graph consists of two sets of parallel edges. On a positive side, we give an O(m+k O(1) k! n) algorithm for the special case when G is acyclic and G + H is Eulerian, where H is the demand graph. We generalize this result (1) to the case when G + H is “nearly ” Eulerian, (2) to an analogous special case of the unsplittable flow problem, a generalized version of disjoint paths that has capacities and demands. Keywords. Disjoint paths, fixed-parameter tractability, W[1]-hardness, Eulerian graphs, unsplittable flow

Cluster of two cases of botulism due to Clostridium baratii type F in France, November 2014.

International audienceThe first two cases in France of botulism due to Clostridium baratii type F were identified in November 2014, in the same family. Both cases required prolonged respiratory assistance. One of the cases had extremely high toxin serum levels and remained paralysed for two weeks. Investigations strongly supported the hypothesis of a common exposure during a family meal with high level contamination of the source. However, all analyses of leftover food remained negative