The Effect of Planarization on Width

We study the effects of planarization (the construction of a planar diagram $D$ from a non-planar graph $G$ by replacing each crossing by a new vertex) on graph width parameters. We show that for treewidth, pathwidth, branchwidth, clique-width, and tree-depth there exists a family of $n$-vertex graphs with bounded parameter value, all of whose planarizations have parameter value $\Omega(n)$. However, for bandwidth, cutwidth, and carving width, every graph with bounded parameter value has a planarization of linear size whose parameter value remains bounded. The same is true for the treewidth, pathwidth, and branchwidth of graphs of bounded degree.Comment: 15 pages, 6 figures. To appear at the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Entre o texto e a vida: uma leitura sobre as políticas de educação especial

On the sidelines of the State political agenda, special education has traditionally been organized as the specialized educational catering that substitutes regular teaching in special classes and schools. In the last decades, Brazil, in tune with international movements, has established a series of laws, policies and programs to tackle inequalities and social exclusion. In such movement, subjects with global learning difficulties (GLD), traditionally excluded from schooling processes, are accepted in the classroom, and in the old school yard. What rationalities give support to the forms of naming and identifying who are these pupils? How do we understand the relation between the diagnostics, the policies, and the inscription of the school (im) possibilities? To what extent inclusive policies of special education deconstruct the meanings that associate GLDs with ineducability or, still, difference with abnormality and inferiority? This essay discusses the implementation of guidelines of inclusion considering the political text and its effects on the context of the practice. Philosophical hermeneutics offers the times and focus for this reading. The argument is woven with and from the speeches of a pupil and of teachers in different fields of research. From text to life, the increase in enrolments; the proliferation of the meanings about these pupils and the school possibilities; the re-enactment of old impasses faced with the new, the different. Although within the sphere of principles equality and differences are both recognized, in the concrete life in schools the notion of the different as unequal still endures. From inclusion to belonging, we put our hopes here in the dialogue as valuation of alterity and requirement of belonging.À margem da agenda política do Estado, a educação especial tradicionalmente se organizou como atendimento educacional especializado substitutivo ao ensino comum, em classes e escolas especiais. Nas últimas décadas, o Brasil, em consonância com movimentos internacionais, estabeleceu uma série de leis, políticas e programas para combater as desigualdades e a exclusão escolar. Nesse movimento, sujeitos com transtornos globais do desenvolvimento (TGD), tradicionalmente apartados dos processos de escolarização, são recebidos nas salas de aula e no velho pátio da escola. Quais racionalidades sustentam as formas de nomear e identificar esses alunos? Como compreender as relações entre os diagnósticos, as políticas e a inscrição das (im)possibilidades escolares? Em que medida as políticas inclusivas de educação especial desconstroem sentidos que relacionam os TGD à ineducabilidade, ou, ainda, a diferença à anormalidade e à inferioridade? O presente ensaio discute a implementação das diretrizes inclusivas considerando o texto político e seus efeitos no contexto da prática. A hermenêutica filosófica oferece os tempos e os focos da leitura. O argumento é tecido com e a partir das falas de um aluno e de professores, em diferentes campos de pesquisa. Do texto à vida, o incremento das matrículas; a proliferação dos sentidos sobre esses alunos e as possibilidades escolares; a atualização de antigos impasses perante o novo, o diferente. Se, no âmbito dos princípios, são reconhecidas a igualdade e as diferenças, na concretude das escolas ainda persiste a noção do diferente como desigual. Da inclusão ao pertencimento, aposta-se no diálogo como valoração da alteridade e condição de pertença

Onset of Convection in Two Liquid Layers with Phase Change

We perform linear stability calculations for horizontal fluid bilayers that can undergo a phase transformation, taking into account both buoyancy effects and thermocapillary effects in the presence of a vertical temperature gradient. We compare the familiar case of the stability of two immiscible fluids in a bilayer geometry with the less-studied case that the two fluids represent different phases of a single-component material, e.g., the water-steam system. The two cases differ in their interfacial boundary conditions: the condition that the interface is a material surface is replaced by the continuity of mass flux across the interface, together with an assumption of thermodynamic equilibrium that in the linearized equations represents the Clausius-Clapeyron relation relating the interfacial temperature and pressures. For the two-phase case, we find that the entropy difference between the phases plays a crucial role in determining the stability of the system. For small values of the entropy difference between the phases, the two-phase system can be linearly unstable to either heating from above or below. The instability is due to the Marangoni effect in combination with the effects of buoyancy (for heating from below). For larger values of the entropy difference the two-phase system is unstable only for heating from below, and the Marangoni effect is masked by effects of the entropy difference. To help understand the mechanisms driving the instability on heating from below we have performed both long-wavelength and short-wavelength analyses of the two-phase system. The short-wavelength analysis shows that the instability is driven by a coupling between the flow normal to the interface and the latent heat generation at the interface. The mechanism for the large wavelength instability is more complicated, and the detailed form of the expansion is found to depend on the Crispation and Bond numbers as well as the entropy difference. The two-phase system allows a conventional Rayleigh-Taylor instability if the heavier fluid overlies the lighter fluid; applying a temperature gradient allows a stabilization of the interface

Partial Homology Relations - Satisfiability in terms of Di-Cographs

Directed cographs (di-cographs) play a crucial role in the reconstruction of evolutionary histories of genes based on homology relations which are binary relations between genes. A variety of methods based on pairwise sequence comparisons can be used to infer such homology relations (e.g.\ orthology, paralogy, xenology). They are \emph{satisfiable} if the relations can be explained by an event-labeled gene tree, i.e., they can simultaneously co-exist in an evolutionary history of the underlying genes. Every gene tree is equivalently interpreted as a so-called cotree that entirely encodes the structure of a di-cograph. Thus, satisfiable homology relations must necessarily form a di-cograph. The inferred homology relations might not cover each pair of genes and thus, provide only partial knowledge on the full set of homology relations. Moreover, for particular pairs of genes, it might be known with a high degree of certainty that they are not orthologs (resp.\ paralogs, xenologs) which yields forbidden pairs of genes. Motivated by this observation, we characterize (partial) satisfiable homology relations with or without forbidden gene pairs, provide a quadratic-time algorithm for their recognition and for the computation of a cotree that explains the given relations

Compact Labelings For Efficient First-Order Model-Checking

We consider graph properties that can be checked from labels, i.e., bit sequences, of logarithmic length attached to vertices. We prove that there exists such a labeling for checking a first-order formula with free set variables in the graphs of every class that is \emph{nicely locally cwd-decomposable}. This notion generalizes that of a \emph{nicely locally tree-decomposable} class. The graphs of such classes can be covered by graphs of bounded \emph{clique-width} with limited overlaps. We also consider such labelings for \emph{bounded} first-order formulas on graph classes of \emph{bounded expansion}. Some of these results are extended to counting queries

Exploring concurrency and reachability in the presence of high temporal resolution

Network properties govern the rate and extent of spreading processes on networks, from simple contagions to complex cascades. Recent advances have extended the study of spreading processes from static networks to temporal networks, where nodes and links appear and disappear. We review previous studies on the effects of temporal connectivity for understanding the spreading rate and outbreak size of model infection processes. We focus on the effects of "accessibility", whether there is a temporally consistent path from one node to another, and "reachability", the density of the corresponding "accessibility graph" representation of the temporal network. We study reachability in terms of the overall level of temporal concurrency between edges, quantifying the overlap of edges in time. We explore the role of temporal resolution of contacts by calculating reachability with the full temporal information as well as with a simplified interval representation approximation that demands less computation. We demonstrate the extent to which the computed reachability changes due to this simplified interval representation.Comment: To appear in Holme and Saramaki (Editors). "Temporal Network Theory". Springer- Nature, New York. 201

Entre o texto e a vida: uma leitura sobre as políticas de educação especial

À margem da agenda política do Estado, a educação especial tradicionalmente se organizou como atendimento educacional especializado substitutivo ao ensino comum, em classes e escolas especiais. Nas últimas décadas, o Brasil, em consonância com movimentos internacionais, estabeleceu uma série de leis, políticas e programas para combater as desigualdades e a exclusão escolar. Nesse movimento, sujeitos com transtornos globais do desenvolvimento (TGD), tradicionalmente apartados dos processos de escolarização, são recebidos nas salas de aula e no velho pátio da escola. Quais racionalidades sustentam as formas de nomear e identificar esses alunos? Como compreender as relações entre os diagnósticos, as políticas e a inscrição das (im)possibilidades escolares? Em que medida as políticas inclusivas de educação especial desconstroem sentidos que relacionam os TGD à ineducabilidade, ou, ainda, a diferença à anormalidade e à inferioridade? O presente ensaio discute a implementação das diretrizes inclusivas considerando o texto político e seus efeitos no contexto da prática. A hermenêutica filosófica oferece os tempos e os focos da leitura. O argumento é tecido com e a partir das falas de um aluno e de professores, em diferentes campos de pesquisa. Do texto à vida, o incremento das matrículas; a proliferação dos sentidos sobre esses alunos e as possibilidades escolares; a atualização de antigos impasses perante o novo, o diferente. Se, no âmbito dos princípios, são reconhecidas a igualdade e as diferenças, na concretude das escolas ainda persiste a noção do diferente como desigual. Da inclusão ao pertencimento, aposta-se no diálogo como valoração da alteridade e condição de pertença.On the sidelines of the State political agenda, special education has traditionally been organized as the specialized educational catering that substitutes regular teaching in special classes and schools. In the last decades, Brazil, in tune with international movements, has established a series of laws, policies and programs to tackle inequalities and social exclusion. In such movement, subjects with global learning difficulties (GLD), traditionally excluded from schooling processes, are accepted in the classroom, and in the old school yard. What rationalities give support to the forms of naming and identifying who are these pupils? How do we understand the relation between the diagnostics, the policies, and the inscription of the school (im) possibilities? To what extent inclusive policies of special education deconstruct the meanings that associate GLDs with ineducability or, still, difference with abnormality and inferiority? This essay discusses the implementation of guidelines of inclusion considering the political text and its effects on the context of the practice. Philosophical hermeneutics offers the times and focus for this reading. The argument is woven with and from the speeches of a pupil and of teachers in different fields of research. From text to life, the increase in enrolments; the proliferation of the meanings about these pupils and the school possibilities; the re-enactment of old impasses faced with the new, the different. Although within the sphere of principles equality and differences are both recognized, in the concrete life in schools the notion of the different as unequal still endures. From inclusion to belonging, we put our hopes here in the dialogue as valuation of alterity and requirement of belonging

Clique-width : harnessing the power of atoms.

Many NP-complete graph problems are polynomial-time solvable on graph classes of bounded clique-width. Several of these problems are polynomial-time solvable on a hereditary graph class G if they are so on the atoms (graphs with no clique cut-set) of G . Hence, we initiate a systematic study into boundedness of clique-width of atoms of hereditary graph classes. A graph G is H-free if H is not an induced subgraph of G, and it is (H1,H2) -free if it is both H1 -free and H2 -free. A class of H-free graphs has bounded clique-width if and only if its atoms have this property. This is no longer true for (H1,H2) -free graphs, as evidenced by one known example. We prove the existence of another such pair (H1,H2) and classify the boundedness of clique-width on (H1,H2) -free atoms for all but 18 cases