The Complexity of Flow Expansion and Electrical Flow Expansion

FlowExpansion is a network design problem, in which the input consists of a flow network and a set of candidate edges, which may be added to the network. Adding a candidate incurs given costs. The goal is to determine the cheapest set of candidate edges that, if added, allow the demands to be satisfied. FlowExpansion is a variant of the Minimum-Cost Flow problem with non-linear edge costs. We study FlowExpansion for both graph-theoretical and electrical flow networks. In the latter case this problem is also known as the Transmission Network Expansion Planning problem. We give a structured view over the complexity of the variants of FlowExpansion that arise from restricting, e.g., the graph classes, the capacities, or the number of sources and sinks. Our goal is to determine which restrictions have a crucial impact on the computational complexity. The results in this paper range from polynomial-time algorithms for the more restricted variants over NP-hardness proofs to proofs that certain variants are NP-hard to approximate even within a logarithmic factor of the optimal solution

Deleterious variants in TRAK1 disrupt mitochondrial movement and cause fatal encephalopathy

This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.The corrigendum to this article is in ORE: http://hdl.handle.net/10871/33588Cellular distribution and dynamics of mitochondria are regulated by several motor proteins and a microtubule network. In neurons, mitochondrial trafficking is crucial because of high energy needs and calcium ion buffering along axons to synapses during neurotransmission. The trafficking kinesin proteins (TRAKs) are well characterized for their role in lysosomal and mitochondrial trafficking in cells, especially neurons. Using whole exome sequencing, we identified homozygous truncating variants in TRAK1 (NM_001042646:c.287-2A > C), in six lethal encephalopathic patients from three unrelated families. The pathogenic variant results in aberrant splicing and significantly reduced gene expression at the RNA and protein levels. In comparison with normal cells, TRAK1-deficient fibroblasts showed irregular mitochondrial distribution, altered mitochondrial motility, reduced mitochondrial membrane potential, and diminished mitochondrial respiration. This study confirms the role of TRAK1 in mitochondrial dynamics and constitutes the first report of this gene in association with a severe neurodevelopmental disorder.D.M.E. and J.K. are supported by the Office of Naval Research (ONR) Grant N000141410538. M.S. is supported by the BBSRC (BB/K006231/1), a Wellcome Trust Institutional Strategic Support Award (WT097835MF, WT105618MA), and a Marie Curie Initial Training Network (ITN) action PerFuMe (316723). M.C.V.M., J.S., H.P., C.F., T.V. and W.A.G. are supported by the NGHRI Intramural Research Program. G.R. is supported by the Kahn Family Foundation and the Israeli Centers of Excellence (I-CORE) Program (ISF grant no. 41/11)

Constructing Near Spanning Trees with Few Local Inspections

Constructing a spanning tree of a graph is one of the most basic tasks in graph theory. Motivated by several recent studies of local graph algorithms, we consider the following variant of this problem. Let G be a connected bounded-degree graph. Given an edge $e$ in $G$ we would like to decide whether $e$ belongs to a connected subgraph $G'$ consisting of $(1+\epsilon)n$ edges (for a prespecified constant $\epsilon >0$), where the decision for different edges should be consistent with the same subgraph $G'$. Can this task be performed by inspecting only a {\em constant} number of edges in $G$? Our main results are: (1) We show that if every $t$-vertex subgraph of $G$ has expansion $1/(\log t)^{1+o(1)}$ then one can (deterministically) construct a sparse spanning subgraph $G'$ of $G$ using few inspections. To this end we analyze a "local" version of a famous minimum-weight spanning tree algorithm. (2) We show that the above expansion requirement is sharp even when allowing randomization. To this end we construct a family of $3$-regular graphs of high girth, in which every $t$-vertex subgraph has expansion $1/(\log t)^{1-o(1)}$

Fixed-Parameter and Approximation Algorithms: A New Look

A Fixed-Parameter Tractable (FPT) ρ-approximation algorithm for a minimization (resp. maximization) parameterized problem P is an FPT algorithm that, given an instance (x,k) ∈ P computes a solution of cost at most k · ρ(k) (resp. k/ρ(k)) if a solution of cost at most (resp. at least) k exists; otherwise the output can be arbitrary. For well-known intractable problems such as the W[1]-hard Clique and W[2]hard Set Cover problems, the natural question is whether we can get any FPT-approximation. It is widely believed that both Clique and Set-Cover admit no FPT ρ-approximation algorithm, for any increasing function ρ. However, to the best of our knowledge, there has been no progress towards proving this conjecture. Assuming standard conjectures such as the Exponential Time Hypothesis (ETH) [19] and the Projection Games Conjecture (PGC) [29], we make the first progress towards proving this conjecture by showing that • Under the ETH and PGC, there exist constants F1,F2> 0 such that the Set Cover problem does not admit a FPT approximation algorithm with ratio k F1 in 2 kF 2 · poly(N,M) time, where N is the size of the universe and M is the number of sets. • Unless NP ⊆ SUBEXP, for every 1> δ> 0 there exists a constant F(δ)> 0 such that Clique has no FPT cost approximation with ratio k1−δ in 2kF · poly(n) time, where n is the number of vertices in the graph. In the second part of the paper we consider various W[1]-hard problems such as Directed Steiner Tree, Directed Steiner Forest, Directed Steiner Network and Minimum Size Edge Cover. For all these problem we give polynomial time f (OPT)-approximation algorithms for some small function f (the largest approximation ratio we give is OPT 2). Our results indicate a potential separation between the classes W[1] and W[2]; since no W[2]-hard problem is known to have a polynomial time f (OPT)-approximation for any function f. Finally, we answer a question by Marx [25] by showing the well-studied Strongly Connected Steiner Subgraph problem (which is W[1]-hard and does not have any polynomial time constant factor approximation) has a constant factor FPT-approximation.

A dimens?o espiritual no processo de viver envelhecendo

Made available in DSpace on 2015-04-14T13:53:28Z (GMT). No. of bitstreams: 1 417994.pdf: 10736925 bytes, checksum: ab0a171195946960874f79dffe355973 (MD5) Previous issue date: 2009-08-21Introdu??o: O envelhecimento ? um est?gio vital e natural de todo ser humano, ocorrendo durante toda a vida. A espiritualidade ? inata ao ser humano e possui qualidades fundamentais como a bondade, benevol?ncia, respeito, compaix?o e interesse pelo outro e pode ser vivenciada atrav?s da religiosidade. Objetivo: Investigar como os indiv?duos de faixas et?rias diferentes vivenciam a espiritualidade no seu processo de envelhecimento. M?todo: Foi realizado um estudo transversal nos trinta bairros de Chapec? SC de julho a janeiro de 2009, com 2.160 pessoas nas faixas et?rias de 20 aos 39 anos, 40 aos 59 anos e acima de 60 anos. Resultados: Houve predom?nio do sexo feminino, de casados, cat?licos e 82,3% praticam sua religi?o. 28,2% participam de outras atividades religiosas, o que lhes confere gratifica??o e sentido ? sua vida. 68,5% acreditam na exist?ncia de elementos espirituais e afirmam que eles os auxiliam em diferentes situa??es. Os pesquisados oram/rezam como forma de agradecimento e o fazem em diferentes locais e de prefer?ncia deitados. Acreditam na B?blia e n?o praticam a religiosidade social. Praticam o habito de leitura de livros religiosos relacionados ? sua religi?o. 67,0% j? tiveram experi?ncia confirmando a exist?ncia de Deus e 26,0% dos pesquisados relataram que esta experi?ncia esta ligada a obten??o e melhora da sa?de em casos de doen?as graves. Para 71,5% dos pesquisados o homem ? um ser espiritual. O nascimento dos filhos foi o evento mais feliz para os pesquisados e relataram sensa??o de felicidade. A perda familiar foi o evento mais triste e marcante relatado por 58,9% dos pesquisados e o choro foi a atitude tomada frente a este evento. 32,2% dos pesquisados conversam com Deus e pedem auxilio para a supera??o das dificuldades que encontram na vida. Em rela??o ao recebimento de uma not?cia de doen?a grave, piora da sa?de ou pouco tempo de vida, 18,1% dos pesquisados afirmam que iriam aproveitar a vida intensamente. A espiritualidade ? importante na vida de 72,2% dos pesquisados. Para 31,6% dos pesquisados, a concep??o de ter sa?de consiste em n?o ter dor e aus?ncia de doen?a. 41,8% apontam que para ter sa?de ? necess?rio manter h?bitos saud?veis como alimenta??o, higiene adequada e atividades f?sicas. 31,3% dos pesquisados apontam que a religi?o ou a sua cren?a fortalece e auxilia na supera??o dos problemas independente de sua origem. Conclus?es: 1)Os indiv?duos de diferentes faixas et?rias vivenciam a espiritualidade no processo de viver envelhecendo de forma diferenciada, mas ela ? apontada como uma dimens?o importante e presente na vida de cada um. 2)Observa-se que indiv?duos de 40 a 59 anos se reconhecem mais espiritualizados do que os de 60 a 69 anos. Ap?s esta idade verifica-se que o processo de envelhecer traz uma maior signific?ncia a dimens?o espiritual, al?m disso, os mais idosos tendem a dar uma maior import?ncia a esta dimens?o do que indiv?duos mais jovens. A espiritualidade para os mais idosos proporciona seguran?a nos momentos de inseguran?a de const?ncia na fragilidade do envelhecimento. 3)As pr?ticas espirituais mais evidenciadas foram: rezar em qualquer lugar, freq?entar atividades religiosas (missas, cultos), atividades em prol da comunidade, e a realiza??o de leituras relacionadas com a sua religi?o. 4)A exist?ncia de elementos espirituais ? aceitos em todas as faixas et?rias pesquisadas, e observou-se que quanto maior a faixa et?ria a cren?a na exist?ncia de elementos espirituais ? mais s?lida. 5)A maioria dos pesquisados pertencem ? religi?o cat?lica, entretanto mesmo em outras religi?es observa-se a pratica religiosa. 6) Observou-se que os pesquisados informam participar de outras atividades religiosas em prol da comunidade tais como: pastor, ministros, catequizador, grupos de ora??o, palestrantes e organizador de campanhas solid?rias. Referem-se a estas atividades como gratificantes e que lhes proporciona sentido a vida. S?o exercidas pelos pesquisados em diferentes atividades e obedecem a sua condi??o f?sica e disponibilidade de tempo. 7) Evidenciou-se que a pr?tica religiosa mais comum entre todas as faixas et?rias ? a ora??o/reza para o enfrentamento das situa??es de tristeza e alegria, independente do local e posi??o, sendo que a mais praticada ? orar/rezar na posi??o deitada. 8) As maiorias dos entrevistados rezam para agradecimento e fortalecimento pessoal. Pode-se observar que para os idosos a ora??o/reza ? uma forma de remiss?o dos pecados e um pedido para a melhoria da sa?de, ? significativamente diferente das outras faixas et?rias. 9) Em rela??o aos objetos de f? e de cren?a, a leitura da B?blia ? o elemento mais significativo, seguido da cren?a em santos que ocorre em maior propor??o nos adultos jovens e adultos. 10) Apartir dos resultados sugere-se que a pr?tica da espiritualidade/religiosidade intimamente relacionada ao processo sa?de/doen?a influenciando positivamente para a melhoria e aquisi??o de h?bitos saud?veis, fortalecendo e auxiliando na supera??o dos problemas. 11) Observou-se diferen?as significativas entre os indiv?duos de diferentes faixas et?rias com rela??o ? espiritualidade no processo de viver envelhecendo, sendo que se pode evidenciar que o idoso torna mais valorizada a espiritualidade

Late Quaternary beach deposits and archaeological relicts on the coasts of Cyprus, and the possible implications of sea-level changes and tectonics on the early populations

<p>Late Pleistocene beach deposits in 22 selected sites around Cyprus demonstrate the vertical changes in the Earth's crust in that island over the last 125 ka. The beach/shallow-marine deposits were observed on the abraded coastal cliffs at 3–22 m above the present sea-level. They overlie Pliocene marls, and some of them contain the Senegalese marine gastropods <em>Persististrombus latus</em>, <em>Bursa granularis</em> and <em>Conus ermineus</em> that no longer live in the Mediterranean. These are index fossils for the Marine Isotope Stage (MIS) 5e in the Mediterranean and, as such, suggest an uplift of up to 15.5 m over about the last 125 ka: that is a maximal rate of 0.12 mm a⁻¹. These findings are in accordance with Holocene beachrocks, abrasion platforms, wave notches and Roman/Byzantine fish tanks that retained their elevations, and thus enable the reconstruction of the coast encountered by the early colonizers. While the maximal uplift since the early Holocene has been minor and did not exceed 1.2–1.5 m, the sea-level changes have reached 40–50 m. The transition between the impermeable Pliocene marls and the porous Late Pleistocene deposits above them is the origin of freshwater springs and associated vegetation. The early colonizers seemed to recognize the potential of that essential permanent source of water and excavated wells, the earliest wells known so far. The locations of the Early Neolithic settlements (Mylouthkia and Akanthou) adjacent to visible water springs along the coastal cliffs may not be incidental. Not surprisingly, recent wells dug in the coastal Pleistocene deposits rely on the very same hydrological setting. </p