Surfaces, Tree-Width, Clique-Minors, and Partitions

In 1971, Chartrand, Geller, and Hedetniemi conjectured that the edge set of a planar graph may be partitioned into two subsets, each of which induces an outerplanar graph. Some partial results towards this conjecture are presented. One such result, in which a planar graph may be thus edge partitioned into two series-parallel graphs, has nice generalizations for graphs embedded onto an arbitrary surface and graphs with no large clique-minor. Several open questions are raised. © 2000 Academic Press

Transonic airframe propulsion integration

This chart shows the time line for HSR propulsion/airframe integration program. HSR Phase 1 efforts are underway in both propulsion and aerodynamics. The propulsion efforts focus on cycles, inlets combustors and nozzles that will be required to reduce nitrogen oxide (NOX) at cruise and noise at takeoff and landing to acceptable levels. The aerodynamic efforts concentrate on concepts that will reduce sonic booms and increase the lift/drag (L/D) ratio for the aircraft. The Phase 2 critical propulsion component technology program will focus on large scale demonstrators of the inlet, fan, combustor, and nozzle. The hardware developed here will feed into the propulsion system program which will demonstrate overall system technology readiness, particularly in the takeoff and supersonic cruise speed ranges. The Phase 2 aerodynamic performance and vehicle integration program will provide a validated data base for advanced airframe/control/integration concepts over the full HSR speed range. The results of this program will also feed into the propulsion system demonstration program, particularly in the critical transonic arena

Prevention of Undesirable Isomerization during Olefin Metathesis

1,4-Benzoquinones have been found to prevent olefin isomerization of a number of allylic ethers and long-chain aliphatic alkenes during ruthenium-catalyzed olefin metathesis reactions. Electron-deficient benzoquinones are the most effective additives for the prevention of olefin migration. This mild, inexpensive, and effective method to block olefin isomerization increases the synthetic utility of olefin metathesis via improvement of overall product yield and purity

Excluding any graph as a minor allows a low tree-width 2-coloring

This article proves the conjecture of Thomas that, for every graph G, there is an integer k such that every graph with no minor isomorphic to G has a 2-coloring of either its vertices or its edges where each color induces a graph of tree-width at most k. Some generalizations are also proved. © 2003 Elsevier Inc. All rights reserved

Gastrointestinal Perforations: Examining the Overlooked Unintentional Consequences of Our Nation’s Epidemic of Antibiotic Exposure

Objective: More than 266 million courses of antibiotics are dispensed to outpatients annually in the US, with the rising elderly population consuming a substantial number of antibiotics. At least 30% of these antibiotics prescribed are unnecessary. Alterations in gut microbiome are known to cause stomach and small intestine (SSI) perforations. However, the impact of antibiotic exposure outcomes of SSI perforations among the elderly has not been studied. We examined the relationship between antibiotic exposure, as a proxy for microbiome modulation, and SSI perforation outcomes in a nationwide sample of elderly patients. Methods: A 5% random sample of Medicare beneficiaries (2009-2011) was queried to identify patients with SSI perforations. Previous outpatient antibiotic exposure (0-30, 31-60, 61-90 days prior to admission) was assessed. Clinical characteristics were compared between no previous antibiotic exposure (NPA) and previous antibiotic exposure (PA) patients. Primary outcome was in-hospital mortality. Secondary outcomes included length of stay and 30-day readmission. Univariate and multivariable regression analyses were performed. Results: Overall, 401 patients ≥ 65 years had SSI perforations (68.3% with NPA and 31.7 % with PA). Mean age (± SD) was 80 years (± 8). Overall in-hospital mortality was 13%. There was a significant difference in the rates of mortality (12% in NPA vs. 18 % in 0-30 days PA, 17% 31-60 days PA, and 8% 61-90 days PA, P= 0.002). After adjustment of other factors, a trend toward increased in-hospital mortality was observed among patients in 0-30 days PA (odds ratio [OR] 2.0, 95% confidence interval [CI] (0.9, 4.7) and was significantly associated with ICU admission (OR 4.3, 95% CI (1.8, 10.2). Conclusion: Recent antibiotic use increases illness severity and may increase mortality among elderly patients with SSI perforations. Exposure to antibiotics, one of the most modifiable determinants of microbiota, should be minimized in the outpatient setting

A controlled evaluation of an enhanced self-directed behavioural family intervention for parents of children with conduct problems in rural and remote areas.

Few studies have examined the impact of parenting interventions for families in rural and isolated areas who have children with conduct problems, where-access to professional services can be difficult. The present investigation compared the effects of three conditions, two levels of self-directed behavioral family intervention: an enhanced self-directed program that combined a self-help program using written materials and a weekly telephone consultation (ESD), a self-help program (SD) and a waitlist control group (WL). At postintervention the ESD group reported significantly lower levels of disruptive behaviour, and lower levels of dysfunctional parenting than the SD and WL controls, and higher levels of consumer satisfaction. At 6 months follow-up the main effects for the ESD group had been maintained. The SD group continued to evidence improvement from postintervention to follow-up such that 65% of children in the ESD condition and 57% of children in the SD condition showed clinical reliable change on measures of disruptive behaviour. Implications of findings and directions for future research are discussed