Maximal induced matchings in triangle-free graphs

An induced matching in a graph is a set of edges whose endpoints induce a $1$-regular subgraph. It is known that any $n$-vertex graph has at most $10^{n/5} \approx 1.5849^n$ maximal induced matchings, and this bound is best possible. We prove that any $n$-vertex triangle-free graph has at most $3^{n/3} \approx 1.4423^n$ maximal induced matchings, and this bound is attained by any disjoint union of copies of the complete bipartite graph $K_{3,3}$. Our result implies that all maximal induced matchings in an $n$-vertex triangle-free graph can be listed in time $O(1.4423^n)$, yielding the fastest known algorithm for finding a maximum induced matching in a triangle-free graph.Comment: 17 page

A biomechanical assessment of superior shoulder translation after reconstruction of anterior glenoid bone defects: The Latarjet procedure versus allograft reconstruction

BACKGROUND: The coracoacromial ligament (CAL) is an important restraint to superior shoulder translation. The effect of CAL release on superior stability following the Latarjet is unknown; therefore, our purpose was to compare the effect of two Latarjet techniques and allograft reconstruction on superior instability. MATERIALS AND METHODS: Eight cadaveric specimens were tested on a simulator. Superior translation was monitored following an axial force in various glenohumeral rotations (neutral, internal, and external) with and without muscle loading. Three intact CAL states were tested (intact specimen, 30% glenoid bone defect, and allograft reconstruction) and two CAL deficient states (classic Latarjet (classicLAT) and congruent-arc Latarjet (congruentLAT)). RESULTS: In neutral without muscle loading, a significant increase in superior translation occurred with the classicLAT as compared to 30% defect (P = 0.046) and allograft conditions (P = 0.041). With muscle loading, the classicLAT (P = 0.005, 0.002) and the congruentLAT (P = 0.018, 0.021) had significantly greater superior translation compared to intact and allograft, respectively. In internal rotation, only loaded tests produced significant results; specifically, classicLAT increased translation compared to all intact CAL states (P < 0.05). In external rotation, only unloaded tests produced significant results with classicLAT and congruentLAT allowing greater translations than intact (P ≤ 0.028). For all simulations, the allograft was not significantly different than intact (P > 0.05) and no differences (P = 1.0) were found between classicLAT and congruentLAT. DISCUSSION: In most simulations, CAL release with the Latarjet lead to increased superior humeral translation. CONCLUSION: The choice of technique for glenoid bone loss reconstruction has implications on the magnitude of superior humeral translation. This previously unknown effect requires further study to determine its clinical and kinematic outcomes

O processo de profissionalização dos Osteopatas em Portugal: as forças e as debilidades de uma profissão em construção

Sendo certo que os profissionais de saúde têm suscitado enorme interesse junto dos sociólogos que se interessam pela problemática das profissões, não será despiciendo afirmar que as áreas das medicinas alternativas ou não convencionais estão ainda muito pouco estudadas entre nós. Assim sendo, o objectivo principal deste artigo será o de dar a conhecer os aspectos mais marcantes do processo de profissionalização dos Osteopatas em Portugal, tendo como referencial teórico de base o paradigma do poder na análise das profissões. Segundo Mike Saks (2000), o facto de existir um elevado número de profissionais da medicina alternativa e complementar, tal não significa que as práticas alternativas estejam consolidadas no quadro das ofertas dos sistemas de saúde europeus. Entre nós, a inserção no mercado de trabalho dos profissionais em Osteopatia é ainda relativamente recente e revela algumas especificidades, ao aceitar pessoas sem qualquer formação estruturada e consolidada, ou reconhecimento profissional acreditado pelo Estado. Sabendo que a qualidade da inserção no mercado de trabalho dos profissionais em Osteopatia pode determinar em grande medida a qualidade da carreira a ser construída, o objectivo deste trabalho consistiu em analisar o processo de profissionalização e de formação identitária dos actuais Osteopatas que trabalham em Portugal. Tendo por base a caracterização do conceito de profissão apresentado por E. Freidson e a partir de um conjunto de entrevistas realizadas junto de indivíduos de ambos os sexos a trabalhar em Portugal e assumindo diferentes experiências e formações ditas Osteopáticas, tanto a nível nacional como internacional, foi possível concluir que sem a regulamentação da profissão por parte do Estado e sem a formação de cursos a tempo inteiro devidamente estruturados e oficialmente reconhecidos, dificilmente será possível ultrapassar uma imagem muito débil de percepcionar o que é a Osteopatia e qual o seu verdadeiro “métier”. Desta forma poder-se-á estar a criar um problema de natureza e formação identitária entre os profissionais e na imagem que estes transmitem para a opinião pública. O poder profissional desta classe apresentar-se-á debilitado e enfraquecido por falta de uma consolidação da profissão, ao gerar valores e formas muito diferenciadas de apropriação da profissão e das suas actividades de trabalho

Predictors and trajectory of performance status in patients with advanced cancer: A secondary data analysis of the international European Palliative Care Cancer Symptom study.

Background: Performance status, a predictor of cancer survival, and ability to maintain independent living deteriorate in advanced disease. Understanding predictors of performance status trajectory could help identify those at risk of functional deterioration, target support for independent living and reduce service costs. The relationship between symptoms, analgesics and performance status is poorly delineated. Aim: The aim of this study is to determine whether demographics, analgesics, disease characteristics, quality-of-life domains and C-reactive protein predict the trajectory of Karnofsky Performance Status (KPS) in patients with advanced cancer. Design: The study design is the secondary data analysis of the international prospective, longitudinal European Palliative Care Cancer Symptom study (ClinicalTrials.gov: NCT01362816). A multivariable regression model was built for KPS area under the curve per day (AUC). Setting and participants: This included adults with advanced, incurable cancer receiving palliative care, without severe cognitive impairment and who were not imminently dying (n = 1739). Results: The mean daily KPS AUC (n = 1052) was 41.1 (standard deviation = 14.1). Opioids (p < 0.001), co-analgesics (p = 0.023), poorer physical functioning (p < 0.001) and appetite loss (p = 0.009) at baseline were explanatory factors for lower KPS AUC. A subgroup analysis of participants with C-reactive protein data (n = 240) showed that only C-reactive protein (p = 0.040) and physical function (p < 0.001) were associated with lower KPS AUC. Conclusion: This study is novel in determining explanatory factors for subsequent functional trajectories in an international dataset and identifying systemic inflammation as a candidate therapeutic target to improve functional performance. The effect of interventions targeting physical function, appetite and inflammation, such as those used for cachexia management, on maintaining functional status in patients with advanced cancer needs to be investigated

Estimation of adjusted rate differences using additive negative binomial regression

Rate differences are an important effect measure in biostatistics and provide an alternative perspective to rate ratios. When the data are event counts observed during an exposure period, adjusted rate differences may be estimated using an identity-link Poisson generalised linear model, also known as additive Poisson regression. A problem with this approach is that the assumption of equality of mean and variance rarely holds in real data, which often show overdispersion. An additive negative binomial model is the natural alternative to account for this, however, standard model-fitting methods are often unable to cope with the constrained parameter space arising from the non-negativity restrictions of the additive model. In this paper, we propose a novel solution to this problem using a variant of the ECME algorithm. Our method provides a reliable way to fit an additive negative binomial regression model and also permits flexible generalisations using semi-parametric regression functions. We illustrate the method using a placebo-controlled clinical trial of fenofibrate treatment in patients with type II diabetes, where the outcome is the number of laser therapy courses administered to treat diabetic retinopathy. An R package is available that implements the proposed method. Copyright c 2015 John Wiley & Sons, Ltd

Saltmarsh plants, but not fertilizer, facilitate invertebrate recolonization after an oil spill

Foundation species contribute to the recovery of animal communities from disturbance by engineering, by improving habitat quality, and by regulating food availability. In a salt marsh impacted by the Deepwater Horizon oil spill, we tested the hypothesis that nutrient subsidies would enhance the positive effects of the foundation species Spartina alterniflora on the initial recolonization of benthic invertebrate communities (e.g., copepods, annelids, nematodes) by augmenting food (i.e., microalgae) availability. After two months, plantings of S.alterniflora significantly elevated the densities of the polychaete Capitella capitata, meiofauna-sized annelids, and total macroinfauna over unplanted plots. After 7months, the significant effect of plantings persisted for meiofauna-sized annelids, but not for C.capitata and total macroinfauna. Plantings had no effect on copepods (including Nannopus palustris, the dominant species), nematodes, or microalgal biomass for either month. Nutrient additions did not influence any taxon, despite initial increases in benthic microalgal biomass after 2months. We hypothesize that the structural effects of plants were important to early colonization, possibly by facilitating larval settlement or ameliorating temperature and desiccation stress. Our results emphasize the importance of re-establishing foundation species in oil-impacted sites to enhance recolonization of saltmarsh annelids, but suggest that recolonization is not promoted by the addition of nutrients

Risk of seizure recurrence in people with single seizures and early epilepsy - Model development and external validation

PURPOSE: Following a single seizure, or recent epilepsy diagnosis, it is difficult to balance risk of medication side effects with the potential to prevent seizure recurrence. A prediction model was developed and validated enabling risk stratification which in turn informs treatment decisions and individualises counselling. METHODS: Data from a randomised controlled trial was used to develop a prediction model for risk of seizure recurrence following a first seizure or diagnosis of epilepsy. Time-to-event data was modelled via Cox's proportional hazards regression. Model validity was assessed via discrimination and calibration using the original dataset and also using three external datasets - National General Practice Survey of Epilepsy (NGPSE), Western Australian first seizure database (WA) and FIRST (Italian dataset of people with first tonic-clonic seizures). RESULTS: People with neurological deficit, focal seizures, abnormal EEG, not indicated for CT/MRI scan, or not immediately treated have a significantly higher risk of seizure recurrence. Discrimination was fair and consistent across the datasets (c-statistics: 0.555 (NGPSE); 0.558 (WA); 0.597 (FIRST)). Calibration plots showed good agreement between observed and predicted probabilities in NGPSE at one and three years. Plots for WA and FIRST showed poorer agreement with the model underpredicting risk in WA, and over-predicting in FIRST. This was resolved following model recalibration. CONCLUSION: The model performs well in independent data especially when recalibrated. It should now be used in clinical practice as it can improve the lives of people with single seizures and early epilepsy by enabling targeted treatment choices and more informed patient counselling