Probing anomalous top quark interactions at the Fermilab Tevatron Collider

We study the effects of dimension-six operators contributing to the $gt\bar t$ vertex in top quark pair production at the Tevatron collider. We derive both the limits from Run 1 data and the potential bounds from future runs (Run 2 and 3). Although the current constraints are not very strong, the future runs are quite effective in probing these operators. We investigate the possibility of disentangling different operators with the $t\bar t$ invariant mass distribution and the top quark polarization asymmetry. We also study the effects of a different set of operators contributing to single top production via the $Wt\bar b$ coupling. We derive the current and potential future bounds on these anomalous operators and find that the upgraded Tevatron can improve the existing constraints from $R_b$ for one of the operators.Comment: 20 pages, 2 figures, REVTEX, some clarifying remarks adde

R-parity violation and top quark polarization at the Fermilab Tevatron collider

The lepton or baryon number violating top quark interactions in the supersymmetric standard model with R parity violation contribute to the process d dbar to t tbar at the tree level via the t- or u-channel sfermion exchange. Since these interactions are chiral, they induce polarization to the top quark in the t tbar events at hadron colliders. We show in this article that the polarization can be a useful observable for probing these interactions at the upgraded Fermilab Tevatron collider, because the polarization is expected to be very small in the standard model.Comment: 15 pages, 5 figure

The fully differential single-top-quark cross section in next-to-leading order QCD

We present a new next-to-leading order calculation for fully differential single-top-quark final states. The calculation is performed using phase space slicing and dipole subtraction methods. The results of the methods are found to be in agreement. The dipole subtraction method calculation retains the full spin dependence of the final state particles. We show a few numerical results to illustrate the utility and consistency of the resulting computer implementations.Comment: 37 pages, latex, 2 ps figure

2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation: executive summary.

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2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation: executive summary.

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withdrawn 2017 hrs ehra ecas aphrs solaece expert consensus statement on catheter and surgical ablation of atrial fibrillation

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Stimulating a Canadian narrative for climate

ABSTRACT: This perspective documents current thinking around climate actions in Canada by synthesizing scholarly proposals made by Sustainable Canada Dialogues (SCD), an informal network of scholars from all 10 provinces, and by reviewing responses from civil society representatives to the scholars' proposals. Motivated by Canada's recent history of repeatedly missing its emissions reduction targets and failing to produce a coherent plan to address climate change, SCD mobilized more than 60 scholars to identify possible pathways towards a low-carbon economy and sustainable society and invited civil society to comment on the proposed solutions. This perspective illustrates a range of Canadian ideas coming from many sectors of society and a wealth of existing inspiring initiatives. Solutions discussed include climate change governance, low-carbon transition, energy production, and consumption. This process of knowledge synthesis/creation is novel and important because it provides a working model for making connections across academic fields as well as between academia and civil society. The process produces a holistic set of insights and recommendations for climate change actions and a unique model of engagement. The different voices reported here enrich the scope of possible solutions, showing that Canada is brimming with ideas, possibilities, and the will to act

Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Abstract: In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M ⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded

Singlet Oxygen Generation in Classical Fenton Chemistry

The Fenton reaction, the Fe-catalyzed conversion of hydrogen peroxide to reactive oxygen species (ROS) was discovered more than a century ago. It occurs widely in nature because of the ubiquity of Fenton reagents, i.e., Fe and H2O2, and ROS in environmental and biological systems; however, its mechanisms and the identity of the ROS generated under varying conditions have remained controversial. The widely accepted mechanism is that of successive oxidation and reduction of Fe2+ and Fe3+ by hydrogen peroxide to form ·OH and O2-·, respectively, where ·OH is implicated as the primary oxidant. However, the formation of high-valent Fe4+=O species has also been implicated. Herein, by systematically dissecting the contributions of various ROS species generated in the classical Fenton reaction by using specific ROS traps and scavengers, we identified that singlet oxygen (1O2) is the main ROS from pH 4–7. In contrast, although ·OH is produced in measurable quantities, it was not a major contributor to the oxidation of organic molecules.</div