Drawing graphs with vertices and edges in convex position

A graph has strong convex dimension $2$, if it admits a straight-line drawing in the plane such that its vertices are in convex position and the midpoints of its edges are also in convex position. Halman, Onn, and Rothblum conjectured that graphs of strong convex dimension $2$ are planar and therefore have at most $3n-6$ edges. We prove that all such graphs have at most $2n-3$ edges while on the other hand we present a class of non-planar graphs of strong convex dimension $2$. We also give lower bounds on the maximum number of edges a graph of strong convex dimension $2$ can have and discuss variants of this graph class. We apply our results to questions about large convexly independent sets in Minkowski sums of planar point sets, that have been of interest in recent years.Comment: 15 pages, 12 figures, improved expositio

Fully polynomial-time approximation schemes for time–cost tradeoff problems in series–parallel project networks

2009-2010 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Automatizability and Simple Stochastic Games

The complexity of simple stochastic games (SSGs) has been open since they were dened by Condon in 1992. Despite intensive eort, the complexity of this problem is still unresolved. In this paper, building on the results of [4], we establish a connection between the complexity of SSGs and the complexity of an important problem in proof complexity{the proof search problem for low depth Frege systems. We prove that if depth-3 Frege systems are weakly automatizable, then SSGs are solvable in polynomial-time. Moreover we identify a natural combinatorial principle, which is a version of the well-known Graph Ordering Principle (GOP), that we call the integer-valued GOP (IGOP). This principle states that for any graph G with nonnegative integer weights associated with each node, there exists a locally maximal vertex (a vertex whose weight is at least as large as its neighbors). We prove that if depth-2 Frege plus IGOP is weakly automatizable, then SSG is in P. Supported by NSERC.

Religiosity and corporate financial reporting: evidence from a European country

Using a sample of Portuguese privately-held firms, I examine the association between religiosity and financial reporting quality. The results suggest that firms headquartered in Portuguese areas with strong religious adherence and in the core area of the Portuguese religious cult (the district where the Fátima Sanctuary is located) generally experience lower incidence of earnings management. I provide further evidence that the results are robust to alternative measures of religiosity, and that are not driven by firms headquartered in rural areas. I also conclude that religious social norms, together with other forms of external financial monitoring, represent a mechanism for reducing costly agency conflicts. While the religious practice declined in the last decades in Portugal, I provide evidence that, even in a such context, religiosity is associated with reduced acceptance of unethical business practices, in particular, with reduced acceptance of aggressive accounting practices.I thank participants of the Second Paris Financial Management Conference (PFMC, 2014) and the 3RD Workshop on Business Ethics (EIASM, 2015) for their helpful insights.info:eu-repo/semantics/publishedVersio

Muslim Integration into Western Cultures: Between Origins and Destinations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91196/1/j.1467-9248.2012.00951.x.pd

Changes over time in the effect of marital status on cancer survival

<p>Abstract</p> <p>Background</p> <p>Rates of all-cause and cause-specific mortality are higher among unmarried than married individuals. Cancer survival is also poorer in the unmarried population. Recently, some studies have found that the excess all-cause mortality of the unmarried has increased over time, and the same pattern has been shown for some specific causes of death. The objective of this study was to investigate whether there has been a similar change over time in marital status differences in cancer survival.</p> <p>Methods</p> <p>Discrete-time hazard regression models for cancer deaths among more than 440 000 women and men diagnosed with cancer 1970-2007 at age 30-89 were estimated, using register data encompassing the entire Norwegian population. More than 200 000 cancer deaths during over 2 million person-years of exposure were analyzed.</p> <p>Results</p> <p>The excess mortality of the never-married compared to the married has increased steadily for men, in particular the elderly. Among elderly women, the excess mortality of the never-married compared to the married has increased, and there are indications of an increasing excess mortality of the widowed. The excess mortality of divorced men and women, however, has been stable.</p> <p>Conclusions</p> <p>There is no obvious explanation for the increasing disadvantage among the never-married. It could be due to a relatively poorer general health at time of diagnosis, either because of a more protective effect of partnership in a society that may have become less cohesive or because of more positive selection into marriage. Alternatively, it could be related to increasing differentials with respect to treatment. Today's complex cancer therapy regimens may be more difficult for never-married to follow, and health care interventions directed and adapted more specifically to the broad subgroup of never-married patients might be warranted.</p

School sector variation on non-cognitive dimensions: are denominational schools different?

Denominational schooling makes up an important part of European educational systems. Given its specificity, denominational schooling can be expected to place a greater weight on values teaching and moral education. As such, it may be more effective in bringing about certain attitudes and opinions. It also may be more successful in creating a warm and caring atmosphere, thus helping students to better emotionally connect to the school community. This paper set out to empirically test some of these hypotheses by making use of three waves of data collected in the framework of the Program for International Student Assessment study. We compare public and publicly supported private (as a proxy to denominational) schools on two dimensions, namely the emotional integration with the rest of the school community, and the concern and feelings of responsibility towards the environment. But for Austria, Belgium and Spain, no evidence could be found that the type of the school has any impact on the reported psychological adaptation to the school. In these three countries, publicly supported private schools tend to be more successful in integrating their students. Also students in public and private dependent schools were equally environment oriented, taking into account several student and school characteristics. The lack of schooling sector differences in attaining non-cognitive aims may have at least three causes. First, ecological issues could be salient enough not to necessitate any special religious or moral reinforcement in order to gain traction. Second, public schools may use religious education or ethics just as fruitfully and consequently, they are just as successful in values and norms transmission. Third, it is possible that schools play a minor role in introducing students to environmental dilemmas and concerns, this role being taken over by the family or the media

Television pictures of Phobos: first results

In February-March 1989, 37 television images of the Martian satellite Phobos were obtained by the Phobos 2 spacecraft from distances of 200-1100 km. These images provide an important supplement to the TV data from the American Mariner 9 and Viking spacecraft in coverage of t4e surface of Phobos and in resolution in certain regions, in spectral range, and in range of phase angles. They make it possible to refine the figure and topographic and geological maps of the surface of Phobos, its spectral and angular reflective characteristics, the surface composition and texture, and characteristics of the orbital and librational motion