Galois groups of multivariate Tutte polynomials

The multivariate Tutte polynomial $\hat Z_M$ of a matroid $M$ is a generalization of the standard two-variable version, obtained by assigning a separate variable $v_e$ to each element $e$ of the ground set $E$. It encodes the full structure of $M$. Let \bv = \{v_e\}_{e\in E}, let $K$ be an arbitrary field, and suppose $M$ is connected. We show that $\hat Z_M$ is irreducible over K(\bv), and give three self-contained proofs that the Galois group of $\hat Z_M$ over K(\bv) is the symmetric group of degree $n$, where $n$ is the rank of $M$. An immediate consequence of this result is that the Galois group of the multivariate Tutte polynomial of any matroid is a direct product of symmetric groups. Finally, we conjecture a similar result for the standard Tutte polynomial of a connected matroid.Comment: 8 pages, final version, to appear in J. Alg. Comb. Substantial revisions, including the addition of two alternative proofs of the main resul

From Isotopes to TK Interviews: Towards Interdisciplinary Research in Fort Resolution and the Slave River Delta, Northwest Territories

Evolving research in Fort Resolution and the Slave River Delta, Northwest Territories, aims to improve understanding of how the natural ecosystem functions and responds to various environmental stressors, as well as to enhance the stewardship of natural resources and the capacity of local residents to respond to change. We seek to integrate approaches that span the natural and social sciences and traditional knowledge understandings of change, employing a research design developed in response to the concerns of a northern community. In doing so, we have strived for a research process that is collaborative, interdisciplinary, policy-oriented, and reflective of northern priorities. These elements characterize the new northern research paradigm increasingly promoted by various federal funding agencies, northern partners, and communities. They represent a holistic perspective in the pursuit of solutions to address complex environmental and socioeconomic concerns about impacts of climate change and resource development on northern societies. However, efforts to fulfill the objectives of this research paradigm are associated with a host of on-the-ground challenges. These challenges include (but are not restricted to) developing effective community partnerships and collaboration and documenting change through interdisciplinary approaches. Here we provide an overview of the components that comprise our interdisciplinary research program and offer an accounting of our formative experiences in confronting these challenges

Trying to predict the unpredictable: Variations in device-based daily monitored diagnostic parameters can predict malignant arrhythmic events in patients undergoing cardiac resynchronization therapy

Background: The aim of this study was to evaluate the value of device-based diagnostic parameters in predicting ventricular arrhythmias in cardiac resynchronization therapy (CRT) recipients. Methods: Ninety-six CRT-D patients participating in TRUST CRT Trial were analyzed. The inclusion criteria were: heart failure in NYHA ≥ 3 class, QRS ≥ 120 ms, LVEF £ 35% and significant mechanical dyssynchrony. Patients were divided into those with (n = 31, 92 arrhyth­mias) and without (n = 65) appropriate ICD interventions within follow-up of 12.03 ± 6.7 months. Daily monitored device-based parameters: heart rate (HR), thoracic impedance (TI), HR variability and physical activity were analyzed in 4 time windows: within 10, 7, 3 days and 1 day before appropriate ICD interventions. Results: A consistent pattern of changes in three monitored factors was observed prior to ar­rhythmia: 1) a gradual increase of day HR (from 103.43% of reference within 10-day window to 105.55% one day before, all p < 0.05 vs. reference); 2) variations in night HR (104.75% in 3 days, 107.65% one day before, all p < 0.05) and 3) TI decrease (from 97.8% in 10 days to 96.81% one day before, all p < 0.05). The combination of three parameters had better pre­dictive value, which improved further after exclusion of patients with atrial fibrillation (AF). The predictive model combining HR and TI together with LVEF and NT-proBNP was more prognostic than the model involving LVEF and NT-proBNP alone (difference in AUC 0.05, 95% CI 0.0005–0.09, p = 0.04). Conclusions: Daily device-monitored parameters show significant variations prior to ven­tricular arrhythmia. Combination of multiple parameters improves arrhythmia predictive performance by its additive value to baseline risk factors, while presence of AF diminishes it.

RADIal versus femoral approach for percutaneous coronary interventions in patients with Acute Myocardial Infarction (RADIAMI): A prospective, randomized, single-center clinical trial

Background: The transradial approach for percutaneous coronary intervention (PCI) seems to be superior to transfemoral. The safety and efficacy of transradial approach for PCI in acute myocardial infarction is not well-established. Methods: Hundred patients with acute myocardial infarction qualified to PCI were randomly assigned to transradial (group I; n = 50) and transfemoral (group II; n = 50) approaches. Results: PCI was successful for almost all patients, except one from group II. There were no significant differences between groups in X-ray exposition, volume of contrast and total procedure duration. Small but significant elongation of door to stent time in group I was caused mostly by a longer time between beginning of procedure and arterial sheath introduction. Major bleeding complications occurred in three patients from group I and seven from group II. There were no significant differences observed between the two groups. Time to ambulation in group I was significantly shorter then in group II (22.6 ± 10.3 h vs. 34.7 ± 34.6 h; p = 0.003). Conclusions: The transradial approach for PCI in acute myocardial infarction has the same efficacy as transfemoral. There are no differences in total procedure duration, X-ray exposition or volume of contrast between the two approaches. A longer time from the patient’s admission to the individual stages of the PCI procedure in group I was mostly due to the longer times of the initial stages of the procedure. The use of transradial approach reduces the time to ambulation and allows rehabilitation to begin sooner. In both groups, bleeding complications occurred rarely

Long-term outcomes of cardiac resynchronization therapy are worse in patients who require atrioventricular junction ablation for atrial fibrillation than in those with sinus rhythm

Background: The aim of the study was to assess the impact of atrial fibrillation (AF) with and without the need for atrioventricular junction (AVJ) ablation on outcomes in patients undergoing cardiac resynchronization therapy (CRT).Methods: A single center cohort of 200 consecutive CRT patients was divided into three groups: 1) AF with CRT pacing < 95% in which AVJ ablation was performed (AF-ABL, n = 40; 20%), 2) AF without the need for AVJ ablation (AF-non ABL, n = 40; 20%), 3) sinus rhythm (SR, n = 120; 60%). All patients were assessed before CRT implantation and at 6-month follow-up. Positive clinical response to CRT was considered alive status without the need for heart transplantation and improvement ≥ 1 NYHA after 6 months. The comparative analysis among all study groups with respect to response-rate and long-term survival was performed.Results: The 6-month response-rate in both AF-ABL and AF-nonABL was significantly lower than in SR (52.5 and 50 vs.77.5%, respectively; both p < 0.017), though there were no differences in baseline characteristics among study groups apart from higher baseline NT-proBNP levels in AF-ABL. However, after adjustment for this confounder, and despite optimal CRT pacing burden in study groups, the remote all-cause mortality during median follow-up of 36.1 months was significantly higher in AF-ABL than in SR (adjusted HR = 2.57, 95% CI 1.09–6.02, p = 0.03). What is more, no difference in long-term survival between SR and AF-nonABL was observed.Conclusions: Despite the improvement of CRT pacing burden and thus response-rate up to the level of AF subjects without the need for ablation, the long-term survival of AF patients requiring AVJ ablation remains still worse than in SR

Left ventricular scar and the acute hemodynamic effects of multivein and multipolar pacing in cardiac resynchronization

Background We sought to determine whether presence, amount and distribution of scar impacts the degree of acute hemodynamic response (AHR) with multisite pacing. Multi-vein pacing (MVP) or multipolar pacing (MPP) with a multi-electrode left ventricular (LV) lead may offer benefits over conventional biventricular pacing in patients with myocardial scar. Methods In this multi-center study left bundle branch block patients underwent an hemodynamic pacing study measuring LV dP/dtmax. Patients had cardiac magnetic resonance scar imaging to assess the effect of scar presence, amount and distribution on AHR. Results 24 patients (QRS 171 ± 20 ms) completed the study (83% male). An ischemic etiology was present in 58% and the mean scar volume was 6.0 ± 7.0%. Overall discounting scar, MPP and MVP showed no significant AHR increase compared to an optimized “best BiV” (BestBiV) site. In a minority of patients (6/24) receiver-operator characteristic analysis of scar volume (cut off 8.48%) predicted a small AHR improvement with MPP (sensitivity 83%, specificity 94%) but not MVP. Patients with scar volume > 8.48% had a MPP-BestBiV of 3 ± 6.3% vs. −6.4 ± 7.7% for those below the cutoff. There was a significant correlation between the difference in AHR and scar volume for MPP-BestBiV (R = 0.49, p = 0.02) but not MVP-BestBiV(R = 0.111, p = 0.62). The multielectrode lead positioned in scar predicted MPP AHR improvement (p = 0.04). Conclusions Multisite pacing with MPP and MVP shows no AHR benefit in all-comers compared to optimized BestBiV pacing. There was a minority of patients with significant scar volume in relation to the LV site that exhibited a small AHR improvement with MPP

Wpływ zakłóceń elektromagnetycznych na funkcje wszczepialnych urządzeń kontrolujących rytm serca

Wraz z rozwojem techniki medycznej co roku rośnie liczba wszczepialnych urządzeń kontrolujących rytm serca. Zwiększa się również stopień komplikacji implantowanych urządzeń, co w połączeniu z pojawianiem się w codziennym życiu oraz środowisku zawodowym i szpitalnym coraz to nowych emiterów zakłóceń elektromagnetycznych sprawia, że problem ewentualnych interferencji między tymi urządzeniami a środowiskiem zewnętrznym jest coraz bardziej istotny. Do najczęstszych reakcji urządzenia wszczepialnego na zewnętrzne zakłócenia elektromagnetyczne należą: wyhamowanie lub wytworzenie pojedynczego pobudzenia, całkowite zahamowanie stymulacji, przejście do trybu stymulacji awaryjnej oraz zwiększenie częstości rytmu lub nieprawidłowa częstość rytmu. Możliwe źródła zakłóceń elektromagnetycznych można podzielić na: wewnątrzszpitalne, środowiskowe i zawodowe. W pierwszej grupie do najczęściej spotykanych urządzeń medycznych emitujących zakłócenia elektromagnetyczne należą: magnetyczny rezonans jądrowy oraz urządzenia do diatermii i radioterapii. W środowisku zewnątrzszpitalnym najczęściej spotykanym źródłami interferencji elektromagnetycznych są telefony komórkowe oraz systemy zabezpieczenia przed kradzieżą. W niniejszej pracy omówiono aktualny stan wiedzy na temat możliwych interferencji oraz ich konsekwencji klinicznych. (Folia Cardiol. 2005; 12: 261–272

From Isotopes to TK Interviews: Towards Interdisciplinary Research in Fort Resolution and the Slave River Delta, Northwest Territories

Evolving research in Fort Resolution and the Slave River Delta, Northwest Territories, aims to improve understanding of how the natural ecosystem functions and responds to various environmental stressors, as well as to enhance the stewardship of natural resources and the capacity of local residents to respond to change. We seek to integrate approaches that span the natural and social sciences and traditional knowledge understandings of change, employing a research design developed in response to the concerns of a northern community. In doing so, we have strived for a research process that is collaborative, interdisciplinary, policy-oriented, and reflective of northern priorities. These elements characterize the new northern research paradigm increasingly promoted by various federal funding agencies, northern partners, and communities. They represent a holistic perspective in the pursuit of solutions to address complex environmental and socioeconomic concerns about impacts of climate change and resource development on northern societies. However, efforts to fulfill the objectives of this research paradigm are associated with a host of on-the-ground challenges. These challenges include (but are not restricted to) developing effective community partnerships and collaboration and documenting change through interdisciplinary approaches. Here we provide an overview of the components that comprise our interdisciplinary research program and offer an accounting of our formative experiences in confronting these challenges.Des travaux de recherche en cours à Fort Resolution et dans le delta de la rivière des Esclaves, aux Territoires du Nord-Ouest, visent à mieux comprendre le fonctionnement de l’écosystème naturel, à réagir aux divers facteurs d’agression environnementaux ainsi qu’à rehausser la gérance des ressources naturelles et la capacité des habitants de la région à réagir au changement. Nous cherchons à intégrer des méthodes qui englobent les sciences naturelles et sociales et favorisent la compréhension du changement du point de vue des connaissances traditionnelles. Nous cherchons également à employer une méthodologie respectueuse des inquiétudes de la collectivité du Nord. Ce faisant, nous avons abouti à un processus de recherche caractérisé par la collaboration, l’interdisciplinarité et les politiques, processus qui tient également compte des priorités dans le Nord. Ces éléments définissent le nouveau paradigme de recherche dans le Nord qui est de plus en plus préconisé par divers organismes de subvention fédéraux, partenaires du Nord et collectivités. Ils représentent une perspective holistique en guise de solutions à des enjeux environnementaux et socioéconomiques complexes portant sur les incidences du changement climatique et de l’exploitation des ressources sur les sociétés du Nord. Toutefois, les efforts visant à concrétiser les objectifs de ce paradigme de recherche font face à une multitude de défis. Ces défis comprennent (mais sans s’y restreindre) la formation de partenariats efficaces avec les collectivités, des efforts de collaboration et la prise de notes sur les changements qui s’opèrent grâce à des méthodes interdisciplinaires. Ici, nous fournissons un aperçu des éléments de notre programme de recherche interdisciplinaire et donnons un aperçu de l’expérience formative qui a découlé de ces défis