173,759 research outputs found
On the Erdős-Pósa property for long holes in C_4-free graphs
No full textWe prove that there exists a function f(k)=O(k^2logk) such that for every C4-free graph G and every k∈N, G either contains k vertex-disjoint holes of length at least 6, or a set X of at most f(k) vertices such that G−X has no hole of length at least 6. This answers a question of Kim and Kwon [Erdős-Pósa property of chordless cycles and its applications. JCTB 2020
Obstructions for bounded shrub-depth and rank-depth
No full textShrub-depth and rank-depth are dense analogues of the tree-depth of a graph.
It is well known that a graph has large tree-depth if and only if it has a long
path as a subgraph. We prove an analogous statement for shrub-depth and
rank-depth, which was conjectured by Hlin\v{e}n\'y, Kwon, Obdr\v{z}\'alek, and
Ordyniak [Tree-depth and vertex-minors, European J.~Combin. 2016]. Namely, we
prove that a graph has large rank-depth if and only if it has a vertex-minor
isomorphic to a long path. This implies that for every integer , the class
of graphs with no vertex-minor isomorphic to the path on vertices has
bounded shrub-depth.Comment: 19 pages, 5 figures; accepted to Journal of Combinatorial Theory Ser.
Unilateral partial nephrectomy with warm ischemia results in acute Hypoxia inducible factor 1-alpha (HIF-1α) and toll-like receptor 4 (TLR4) overexpression in a porcine model
No full textPurpose: Ischemia/reperfusion (I/R) during partial nephrectomy (PN) contributes to acute kidney injury (AKI), which is inaccurately assessed using existent clinical markers of renal function. We evaluated I/R-related changes in expression in hypoxia inducible factor 1α (HIF-1α) and toll-like receptor 4 (TLR4), within kidney tissue and peripheral blood leukocytes (PBL) in a porcine model of PN.
Materials and Methods: Three adult pigs each underwent unilateral renal hilar cross clamping for 180 min followed by a 15 min reperfusion. The contralateral kidney served as control. Biopsies of clamped kidneys were obtained at baseline (time 0), every 60 min during the hypoxic phase, and post-reperfusion. Control kidneys were biopsied once at 180 min. Peripheral blood was sampled at time 0, every 30 min during the hypoxic phase, and post-reperfusion. HIF-1α and TLR4 expression in kidney tissue and PBL were analyzed by Western blotting. I/R-related histological changes were assessed.
Results: Expression of HIF-1α in clamped kidneys and PBL was below detection level at baseline, rising to detectable levels after 60 min of hypoxia, and continuing to rise throughout the hypoxic and reperfusion phases. Expression of TLR-4 in clamped kidneys followed a similar trend with initial detection after 30–60 min of hypoxia. Control kidneys exhibited no change in HIF-1α or TLR-4 expression. I/R-related histologic changes were minimal, primarily mild tubular dilatation.
Conclusions: In a porcine model of PN, HIF-1α and TLR4 exhibited robust, I/R-related increases in expression in kidney tissue and PBL. Further studies investigating these molecules as potential markers of AKI are warranted.Peer reviewe
Fast peak quench of the exciton transition in extremely shallow quantum well structures
No full textThe radius and binding energy of exciton in an extremely shallow quantum well (ESQW) structure are calculated theoretically. As the strength of applied electric field increases, the exciton radius increases and the binding energy decreases rapidly compared with a conventional quantum well, which explains the rapid peak quench in ESQW structures.X11sci
The exciton transition in extremely shallow quantum well structures: Strong coupling between the distributions in the quantized and in-plane directions
No full textThe planar radius and the binding energy of excitons in extremely shallow quantum well (ESQW) structures are calculated theoretically. As the strength of an applied electric field increases, the exciton planar radius increases and the binding energy decreases rapidly compared with a conventional quantum well, which explains the rapid peak quench in ESQW structures. We also calculate the energy difference between heavy hole and light hole exciton transitions in quantum wells with various barrier heights. Due to the small energy difference in ESQW structures, the light hole peak is not clearly resolved from heavy hole peak by room-temperature photocurrent experiments. (C) 1996 American Institute of Physics.open114sciescopu
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A Polynomial Kernel for Block Graph Deletion
No full textIn the Block Graph Deletion problem, we are given a graph G on n vertices and a positive integer k, and the objective is to check whether it is possible to delete at most k vertices from G to make it a block graph, i.e., a graph in which each block is a clique. In this paper, we obtain a kernel with O(k^{6}) vertices for the Block Graph Deletion problem. This is a first step to investigate polynomial kernels for deletion problems into non-trivial classes of graphs of bounded rank-width, but unbounded tree-width. Our result also implies that Chordal Vertex Deletion admits a polynomial-size kernel on diamond-free graphs. For the kernelization and its analysis, we introduce the notion of 'complete degree' of a vertex. We believe that the underlying idea can be potentially applied to other problems. We also prove that the Block Graph Deletion problem can be solved in time 10^{k} * n^{O(1)}
Respostas hemodinâmicas na vigília e sono de mulheres hipertensas após uma sessão de Tae Kwon Do
No full textIntroduction: Tae Kwon Do, Korean martial art with over 80 million practitioners worldwide. Cardiovascular Coma Syndrome of Hypertensive Women Purpose: To analyze the acute effect of a Tae Kwon Do of the Born Cardiovascular of hypertensive women. Methods: 23 women (60.8 ± 6 years) hypertensive, attended by the drug form, were submitted to a control session and adjusted through breathing classes. postural. Cardiovascular variables were evaluated as systemic arterial hypertension after a 24-hour period, wakefulness and outpatient radiological control after blood flow control. Results: A demonstrative analysis of Tae Kwon Do compared to control, keeping blood pressure lower by 10.5mHg for six hours after the stimulus, reducing DBP by 5.6mmHg 75min after term, as well as maintaining the frequency cardiac output at 6bpm up to four hours. In wake and sleep no differences were found between Tae Kwon Do and control. Conclusion: the behavior of blood pressure and cardiopulmonary function after the Tae Kwon Do session demonstrates that the modality can be adopted as an auxiliary form of drug control of arterial hypertension in hypertensive women.Introdução: O Tae Kwon Do, arte marcial coreana com mais de 80 milhões de praticantes em todo o mundo. Contudo, pouco se sabe sobre seu efeito nas respostas cardiovasculares de mulheres hipertensas. Objetivo: Analisar o efeito agudo de uma sessão de Tae Kwon Do nas respostas cardiovasculares de mulheres hipertensas. Métodos: 23 mulheres (60,8±6 anos) hipertensas, previamente tratadas pela forma medicamentosa, foram submetidas a uma sessão controle e Tae Kwon Do composto por exercícios tradicionais de movimentos balísticos de ataque e defesa em posições e movimentos que requerem coordenação e controle postural. Foram avaliadas as variáveis cardiovasculares como pressão arterial e frequência cardiaca em um período de 24 horas, vigília e sono pela monitorização ambulatorial após o Tae Kwon Do e o controle. Resultados: A análise demonstrou que o Tae Kwon Do, comparado com o controle, mantem a pressão arterial sistólica mais baixa em 10,5mHg até seis horas após o estimulo, reduz a PAD em 5,6 mmHg 75 min após o estimulo tão como mantem a frequência cardiaca mais alta em 6bpm até quatro horas. Na vigília e sono não foram encontradas diferenças entre o Tae Kwon Do e o controle. Conclusão: o comportamento da pressão arterial e frequência cardiaca após uma sessão de Tae Kwon Do demonstra que essa modalidade pode ser adotada como forma auxiliar a forma medicamentosa no controle da pressão arterial em mulheres hipertensas.São Cristóvão, S
Erdos-Posa property of chordless cycles and its applications
No full textA chordless cycle, or equivalently a hole, in a graph G is an induced subgraph of G which is a cycle of length at least 4. We prove that the Erdos-Posa property holds for chordless cycles, which resolves the major open question concerning the Erdos-Posa property. Our proof for chordless cycles is constructive: in polynomial time, one can find either k + 1 vertex-disjoint chordless cycles, or c(1)k(2) log k + c(2) vertices hitting every chordless cycle for some constants c(1) and c(2). It immediately implies an approximation algorithm of factor 0(opt log opt) for CHORDAL VERTEX DELETION. We complement our main result by showing that chordless cycles of length at least P for any fixed l >= 5 do not have the Erdos-Posa property. (C) 2020 The Authors. Published by Elsevier Inc.
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