Generating facets for the independence system

In this paper, we present procedures to obtain facet-defining inequalities for the independence system polytope. These procedures are defined for inequalities which are not necessarily rank inequalities. We illustrate the use of these procedures by der iving strong valid inequalities for the acyclic induced subgraph, triangle free induced subgraph, bipartite induced subgraph, and knapsack polytopes. Finally, we derive a new family of facet-defining ineq ualities for the independence system polytope by adding a set of edges to antiwebs.© 2009 Society for Industrial and Applied Mathematics

Securing virtual network function placement with high availability guarantees

Virtual Network Functions as a Service (VNFaaS) is currently under attentive study by telecommunications and cloud stakeholders as a promising business and technical direction consisting of providing network functions as a service on a cloud (NFV Infrastructure), instead of delivering standalone network appliances, in order to provide higher scalability and reduce maintenance costs. However, the functioning of such NFVI hosting the VNFs is fundamental for all the services and applications running on top of it, forcing to guarantee a high availability level against attacks and software failures. Indeed the availability of an VNFaaS relies on the failure rate of its single components, namely the servers, the virtualization software, and the communication network. The proper assignment of the virtual machines implementing network functions to NFVI servers and their protection from both endogenous and exogenous threats is essential to guarantee high availability. We model the High Availability Virtual Network Function Placement (HA- VNFP) as the problem of finding the best assignment of virtual machines to servers guaranteeing protection by replication. We propose a probabilistic approach to measure the real availability of a system and design both efficient and effective algorithms that can be used by stakeholders for both online and offline planning

Survivability in hierarchical telecommunications networks

The survivable hierarchical telecommunications network design problem consists of locating concentrators, assigning user nodes to concentrators, and linking concentrators in a reliable backbone network. In this article, we study this problem when the backbone is 2-edge connected and when user nodes are linked to concentrators by a point-to-point access network. We formulate this problem as an integer linear program and present a facial study of the associated polytope. We describe valid inequalities and give sufficient conditions for these inequalities to be facet defining. We investigate the computational complexity of the corresponding separation problems. We propose some reduction operations to speed up the separation procedures. Finally, we devise a branch-and-cut algorithm based on these results and present the outcome of a computational study. © 2011 Wiley Periodicals, Inc

On the fixed parameter tractability and approximability of the minimum error correction problem

Haplotype assembly is the computational problem of reconstructing the two parental copies, called haplotypes, of each chromosome starting from sequencing reads, called fragments, possibly affected by sequencing errors. Minimum Error Correction (MEC) is a prominent computational problem for haplotype assembly and, given a set of fragments, aims at reconstructing the two haplotypes by applying the minimum number of base corrections. By using novel combinatorial properties of MEC instances, we are able to provide new results on the fixed-parameter tractability and approximability of MEC. In particular, we show that MEC is in FPT when parameterized by the number of corrections, and, on “gapless” instances, it is in FPT also when parameterized by the length of the fragments, whereas the result known in literature forces the reconstruction of complementary haplotypes. Then, we show that MEC cannot be approximated within any constant factor while it is approximable within factor O(log nm) where nm is the size of the input. Finally, we provide a practical 2-approximation algorithm for the Binary MEC, a variant of MEC that has been applied in the framework of clustering binary data

Disentangling molecular and clinical stratification patterns in beta-galactosidase deficiency

INTRODUCTION: This study aims to define the phenotypic and molecular spectrum of the two clinical forms of β-galactosidase (β-GAL) deficiency, GM1-gangliosidosis and mucopolysaccharidosis IVB (Morquio disease type B, MPSIVB). METHODS: Clinical and genetic data of 52 probands, 47 patients with GM1-gangliosidosis and 5 patients with MPSIVB were analysed. RESULTS: The clinical presentations in patients with GM1-gangliosidosis are consistent with a phenotypic continuum ranging from a severe antenatal form with hydrops fetalis to an adult form with an extrapyramidal syndrome. Molecular studies evidenced 47 variants located throughout the sequence of the GLB1 gene, in all exons except 7, 11 and 12. Eighteen novel variants (15 substitutions and 3 deletions) were identified. Several variants were linked specifically to early-onset GM1-gangliosidosis, late-onset GM1-gangliosidosis or MPSIVB phenotypes. This integrative molecular and clinical stratification suggests a variant-driven patient assignment to a given clinical and severity group. CONCLUSION: This study reports one of the largest series of b-GAL deficiency with an integrative patient stratification combining molecular and clinical features. This work contributes to expand the community knowledge regarding the molecular and clinical landscapes of b-GAL deficiency for a better patient management

Generating facets for the independence system polytope

info:eu-repo/semantics/publishe

Neurological manifestations in adults with phenylketonuria: new cases and review of the literature

Early Access: NOV 2019International audienceOBJECTIVE: Phenylketonuria (PKU) is a rare autosomal recessive disease characterised by high plasma phenylalanine levels inducing, if untreated, serious neurological manifestations in children but also, rarely, in adults who stopped their diet. The objective of the study was to describe the neurological manifestations observed in adults with PKU. METHODS: We analysed cases reported in French reference centres for inborn errors of metabolism and cases already reported in the literature. RESULTS: We report 8 new cases of neurological manifestations and 22 cases in the literature, which occurred in adult PKU patients, associated with chronic or rapid increase of phenylalanine levels, mostly when strict low-phenylalanine diet was stopped early in life. Neurological symptoms consisted in cerebellar ataxia, tremor, brisk reflexes, visual loss, sensory manifestations, and/or headaches. Visual loss was more frequent in the new cases (4/8) of the present series than in the literature (4/22). These neurological complications were associated with leucopathy on brain magnetic resonance imaging (27/29). The start of a low-phenylalanine diet improved or fully reversed neurological manifestations, even in patients with late diagnosis during adulthood. CONCLUSION: Neurological manifestations can complicate PKU in adult patients with elevated phenylalanine levels, after long or short period of diet discontinuation. Neurologists should be aware of this diagnosis, and measure phenylalaninemia in case of neurological symptoms associated with non-specific leucopathy on brain MRI. PKU patients should be systematically encouraged to continue their diet and their medical follow-up to avoid neurological complications

Agglutinines froides et cryoglobulinemie chez un patient avec une hepatite C. [Cold agglutinins and cryoglobulinemia in a patient with hepatitis C]

OBJECTIVES: Cold agglutinins and cryoglobulins are uncommon in the same patient as observed in our case. CASE REPORT: A 74-year-old patient suffered repeated episodes of hemolytic anemia for one year and had hepatitis C anti-virus antibodies. Mixed cryoglobulinemia was found at levels which increased during episodes of acute hemolysis in addition to anti-I cold agglutinins. Two-dimensional electrophoresis revealed identical oligoclonal cold agglutinins and cryoglobulins. DISCUSSION: Unlike mixed cryoglobulinemia, cold agglutinins are not known to occur subsequent to hepatitis C infection. The identical immunoglobulins observed in our patient suggest a common origin. Chronic anti-I cold oligoclonal agglutinins are rarely observed and could be an intermediary step towards monoclonal lymphopathy as has been described in prolonged hepatitis C infection