Linear Time LexDFS on Cocomparability Graphs

Lexicographic depth first search (LexDFS) is a graph search protocol which has already proved to be a powerful tool on cocomparability graphs. Cocomparability graphs have been well studied by investigating their complements (comparability graphs) and their corresponding posets. Recently however LexDFS has led to a number of elegant polynomial and near linear time algorithms on cocomparability graphs when used as a preprocessing step [2, 3, 11]. The nonlinear runtime of some of these results is a consequence of complexity of this preprocessing step. We present the first linear time algorithm to compute a LexDFS cocomparability ordering, therefore answering a problem raised in [2] and helping achieve the first linear time algorithms for the minimum path cover problem, and thus the Hamilton path problem, the maximum independent set problem and the minimum clique cover for this graph family

Life History of the Butternut Curculio, \u3ci\u3eConotrachelus Juglandis\u3c/i\u3e (Coleoptera: Curculionidae), in Michigan

(excerpt) The butternut curculio, Conotrachelus juglandis LeConte (Coleoptera: Curculionidae), injures the shoots and nuts of various species and hybrids of Juglans in eastern North America This insect was described in 1876 (LeConte, 1876); its life history has been studied in Connecticut (Britton and Kirk, 1912) and in West Virginia (Brooks, 1922). Its range, however, extends from the New England states through southern Canada to the Great Plains and south to Kansas, Alabama, and Georgia, contiguous with the natural range of butternut (J. cinema), its native host

Some Light and Temperature Effects on the Behavior of the Adult Pales Weevil, Hylobius Pales (Coleoptera: Curculionidae)

Adult pales weevils react to light and temperature cues regarding their movements in pine plantations. They remain at the base of their host trees during the day and move onto the trees after dark. A drop in light intensity to 2 fc triggers this response. Ambient temperature below 10°C curtails their movements. Weevils placed on the ground are photophobic at temperatures below 20°C and photophobic and thermophobic above 35°C. Orientation is erratic above 40°C and heat stupor occurs in a few minutes

Live Branches on Pine Stumps Deter Pales Weevil Breeding in Michigan (Coleoptera: Curculionidae)

Eastern white pine and Scotch pine stumps with living branches were unattractive to pales weevil for breeding. When feasible, leaving a few lower branches on Christmas tree stumps during harvest should prevent weevil buildup

Lessons and consequences of the evolving 2007-? Credit Crunch

We are neither economists nor academic scholars; however we are students of the markets having experienced the credit crunch on the front lines as institutional investors from a country that is neither in Europe nor is the United States (i.e. Canada). The credit crunch and related “Great Recession” have instilled havoc on the global economy. The crisis has led to a large contraction of the real economy of approximately 1% of real GDP in 2009, which could have been considerably larger without massive government sponsored stimulus plans. In the aftermath of every crisis there are always lessons to be learned. The main takeaways from the most recent credit crunch centre on risk distortion, the flawed counterparty risk offset model, excessive leverage, inherent conflicts of interest and the legacy of creating “too big to fail” financial institutions. As financial markets appear to have stepped back from the brink of destruction, we believe that there are three major consequences that we are currently facing. First the global financial system will likely be irrevocably changed by new regulations. Second, on the economic front, we are facing a post-recession period of relatively low global growth. Third, developing countries’ governments are facing massive budget deficits and their debt/GDP levels are likely unsustainable and therefore requiring severe fiscal austerity programs.Credit Crisis, Solutions, Securitization, CDS

Practical and Efficient Split Decomposition via Graph-Labelled Trees

Split decomposition of graphs was introduced by Cunningham (under the name join decomposition) as a generalization of the modular decomposition. This paper undertakes an investigation into the algorithmic properties of split decomposition. We do so in the context of graph-labelled trees (GLTs), a new combinatorial object designed to simplify its consideration. GLTs are used to derive an incremental characterization of split decomposition, with a simple combinatorial description, and to explore its properties with respect to Lexicographic Breadth-First Search (LBFS). Applying the incremental characterization to an LBFS ordering results in a split decomposition algorithm that runs in time $O(n+m)\alpha(n+m)$, where $\alpha$ is the inverse Ackermann function, whose value is smaller than 4 for any practical graph. Compared to Dahlhaus' linear-time split decomposition algorithm [Dahlhaus'00], which does not rely on an incremental construction, our algorithm is just as fast in all but the asymptotic sense and full implementation details are given in this paper. Also, our algorithm extends to circle graph recognition, whereas no such extension is known for Dahlhaus' algorithm. The companion paper [Gioan et al.] uses our algorithm to derive the first sub-quadratic circle graph recognition algorithm

A Characterization of Mixed Unit Interval Graphs

We give a complete characterization of mixed unit interval graphs, the intersection graphs of closed, open, and half-open unit intervals of the real line. This is a proper superclass of the well known unit interval graphs. Our result solves a problem posed by Dourado, Le, Protti, Rautenbach and Szwarcfiter (Mixed unit interval graphs, Discrete Math. 312, 3357-3363 (2012)).Comment: 17 pages, referees' comments adde