Supermassive Binaries and Extragalactic Jets

Some quasars show Doppler shifted broad emission line peaks. I give new statistics of the occurrence of these peaks and show that, while the most spectacular cases are in quasars with strong radio jets inclined to the line of sight, they are also almost as common in radio-quiet quasars. Theories of the origin of the peaks are reviewed and it is argued that the displaced peaks are most likely produced by the supermassive binary model. The separations of the peaks in the 3C 390.3-type objects are consistent with orientation-dependent "unified models" of quasar activity. If the supermassive binary model is correct, all members of "the jet set" (astrophysical objects showing jets) could be binaries.Comment: 31 pages, PostScript, missing figure is in ApJ 464, L105 (see http://www.aas.org/ApJ/v464n2/5736/5736.html

Atomic X-ray Spectroscopy of Accreting Black Holes

Current astrophysical research suggests that the most persistently luminous objects in the Universe are powered by the flow of matter through accretion disks onto black holes. Accretion disk systems are observed to emit copious radiation across the electromagnetic spectrum, each energy band providing access to rather distinct regimes of physical conditions and geometric scale. X-ray emission probes the innermost regions of the accretion disk, where relativistic effects prevail. While this has been known for decades, it also has been acknowledged that inferring physical conditions in the relativistic regime from the behavior of the X-ray continuum is problematic and not satisfactorily constraining. With the discovery in the 1990s of iron X-ray lines bearing signatures of relativistic distortion came the hope that such emission would more firmly constrain models of disk accretion near black holes, as well as provide observational criteria by which to test general relativity in the strong field limit. Here we provide an introduction to this phenomenon. While the presentation is intended to be primarily tutorial in nature, we aim also to acquaint the reader with trends in current research. To achieve these ends, we present the basic applications of general relativity that pertain to X-ray spectroscopic observations of black hole accretion disk systems, focusing on the Schwarzschild and Kerr solutions to the Einstein field equations. To this we add treatments of the fundamental concepts associated with the theoretical and modeling aspects of accretion disks, as well as relevant topics from observational and theoretical X-ray spectroscopy.Comment: 63 pages, 21 figures, Einstein Centennial Review Article, Canadian Journal of Physics, in pres

Strengthening altitude knowledge: a delphi study to define minimum knowledge of altitude illness for laypersons traveling to high altitude

Introduction: A lack of knowledge among laypersons about the hazards of high-altitude exposure contributes to morbidity and mortality from acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) among high-altitude travelers. There are guidelines regarding the recognition, prevention, and treatment of acute-altitude illness for experts, but essential knowledge for laypersons traveling to high altitudes has not been defined. We sought expert consensus on the essential knowledge required for people planning to travel to high altitudes. Methods: The Delphi method was used. The panel consisted of two moderators, a core expert group and a plenary expert group. The moderators made a preliminary list of statements defining the desired minimum knowledge for laypersons traveling to high altitudes, based on the relevant literature. These preliminary statements were then reviewed, supplemented, and modified by a core expert group. A list of 33 statements was then presented to a plenary group of experts in successive rounds. Results: It took three rounds to reach a consensus. Of the 10 core experts invited, 7 completed all the rounds. Of the 76 plenary experts, 41 (54%) participated in Round 1, and of these 41 a total of 32 (78%) experts completed all three rounds. The final list contained 28 statements in 5 categories (altitude physiology, sleeping at altitude, AMS, HACE, and HAPE). This list represents an expert consensus on the desired minimum knowledge for laypersons planning high-altitude travel. Conclusion: Using the Delphi method, the STrengthening Altitude Knowledge initiative yielded a set of 28 statements representing essential learning objectives for laypersons who plan to travel to high altitudes. This list could be used to develop educational interventions

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

The acute effects of MDMA and ethanol administration on electrophysiological correlates of performance monitoring in healthy volunteers

Item does not contain fulltextRATIONALE: Knowing how commonly used drugs affect performance monitoring is of great importance, because drug use is often associated with compromised behavioral control. Two of the most commonly used recreational drugs in the western world, 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") and ethanol (alcohol), are also often used in combination. The error-related negativity (ERN), correct-related negativity (CRN), and N2 are electrophysiological indices of performance monitoring. OBJECTIVES: The present study aimed to investigate how ethanol, MDMA, and their co-administration affect performance monitoring as indexed by the electrophysiological correlates. METHODS: Behavioral and EEG data were obtained from 14 healthy volunteers during execution of a speeded choice-reaction-time task after administration of ethanol, MDMA, and combined ethanol and MDMA, in a double-blind, placebo-controlled, randomized crossover design. RESULTS: Ethanol significantly reduced ERN amplitudes, while administration of MDMA did not affect the ERN. Co-administration of MDMA and ethanol did not further impair nor ameliorate the effect of ethanol alone. No drug effects on CRN nor N2 were observed. DISCUSSION: A decreased ERN following ethanol administration is in line with previous work and offers further support for the impairing effects of alcohol intoxication on performance monitoring. This impairment may underlie maladaptive behavior in people who are under influence. Moreover, these data demonstrate for the first time that MDMA does not affect performance monitoring nor does it interact with ethanol in this process. These findings corroborate the notion that MDMA leaves central executive functions relatively unaffected

Biogeochemical and edaphic data from burned peat soil on the Stalybridge estate (UK), October 2018

This dataset contains biogeochemical and edaphic information from burned peat soil on the Stalybridge estate located near Manchester (UK), commonly referred to as Saddleworth moor. This study was conducted after a wildfire fire on the Saddleworth moor in June 2018. The sample plots included areas with deep and shallow peat burn. The data includes geographical information (location, elevation and slope), soil temperature and soil chemical composition (carbon, nitrogen and 22 other elements). The dataset is the result of research funded by a NERC Urgency grant entitled 'RECOUP-Moor: Restoring Ecosystem CarbOn Uptake of Post-fire Moorland' (NE/S011943/1, led by Dr. Bjorn Robroek of the University of Southampton (now Radboud University Nijmegen, the Netherlands).,We established 10 plots in October 2018 at the post-fire site. Each plot was 10 m x 10 m in size. We identified 5 of these plots as suffering a less severe (shallow) burn. The other 5 plots were in areas where a more severe (deep) burn was identified. In all plots the surface vegetation had been removed by the fire exposing the bare peat. We determined the geographical properties of each plot. This included their geographical location, elevation and slope. We also measured soil temperature at each location at multiple time points over the following 24 months. On July 23rd 2019 we extracted small peat samples from the surface of each plot. Each sample was 5 cm x 5 cm in diameter and 2 cm in depth. The samples were homogenized and kept at c. 5oC until further analysis was completed to determine their chemical composition. In preparation for the chemical analysis of each sample we dried the peat at 70 oC for 72 hours. This was then crushed forming a fine homogenous powder. To determine the carbon and nitrogen content of each sample we extracted three sub-samples of the fine peat powder. Each sample was then combusted at 1800 oC and the percentage of carbon and nitrogen released was quantified. This was performed using a Vario Micro Cube (Elementar). For each plot, the content of each sub-sample was compared to ensure that the observed values were consistent, and the samples were homogenous. An average of the three sub-samples was then taken to provide one value per plot. To determine the composition of other elements within the samples, we extracted two sub-samples from each plot sample and performed Inductively Coupled Plasma-Mass-Spectrometry (ICP-MS) analysis on each of the sub-samples. This was used to determine the relative composition of 22 elements. For each plot, an average of the two sub-samples was taken., We established 10 plots in October 2018 at the post-fire site. Each plot was 10 m x 10 m in size. We identified 5 of these plots as suffering a less severe (shallow) burn. The other 5 plots were in areas where a more severe (deep) burn was identified. In all plots the surface vegetation had been removed by the fire exposing the bare peat. We determined the geographical properties of each plot. This included their geographical location, elevation and slope. We also measured soil temperature at each location at multiple time points over the following 24 months. On July 23rd 2019 we extracted small peat samples from the surface of each plot. Each sample was 5 cm x 5 cm in diameter and 2 cm in depth. The samples were homogenized and kept at c. 5oC until further analysis was completed to determine their chemical composition. In preparation for the chemical analysis of each sample we dried the peat at 70 oC for 72 hours. This was then crushed forming a fine homogenous powder. To determine the carbon and nitrogen content of each sample we extracted three sub-samples of the fine peat powder. Each sample was then combusted at 1800 oC and the percentage of carbon and nitrogen released was quantified. This was performed using a Vario Micro Cube (Elementar). For each plot, the content of each sub-sample was compared to ensure that the observed values were consistent, and the samples were homogenous. An average of the three sub-samples was then taken to provide one value per plot. To determine the composition of other elements within the samples, we extracted two sub-samples from each plot sample and performed Inductively Coupled Plasma-Mass-Spectrometry (ICP-MS) analysis on each of the sub-samples. This was used to determine the relative composition of 22 elements. For each plot, an average of the two sub-samples was taken

Quantifying the effect of gape and morphology on bite force: biomechanical modelling and in vivo measurements in bats

Maximum bite force is an important metric of feeding performance that defines the dietary ecology of many vertebrates. In mammals, theoretical analyses and empirical studies suggest a trade‐off between maximum bite force and gape at behavioural and evolutionary scales; in vivo bite force is expected to decrease at wide gapes, and cranial morphologies that enable high mechanical advantage are thought to have a lower ability to generate high bite forces at wide gapes, and vice versa. However, very few studies have confirmed these relationships in free‐ranging mammals. This study uses an ecologically diverse sample of bats to document the variation in bite force with respect to gape angle, and applies three‐dimensional models of the feeding apparatus to identify the major morphological and biomechanical predictors of the gape‐bite force relationship. In vivo and model data corroborated that bite force decreases significantly at wide gapes across species, but there is substantial intraspecific variation in the data obtained from live bats. Results from biomechanical models, analysed within a phylogenetic framework, revealed that species with larger temporalis muscles, higher temporalis stretch factors and high mechanical advantages experience a steeper reduction in bite force with increasing gape. These trends are illustrated by short‐faced durophagous frugivores. The results from this study suggest that gape‐mediated changes in bite force can be explained both by behavioural effects and cranial morphology, and that these link are relevant for functional analyses of mammal dietary ecology

Dataset for: Propagule availability drives post-wildfire recovery of peatland plant communities

This dataset contains results from an on-site vegetation survey data and off-site seed-germination experiment conducted a UK blanket bog (Stalybridge Moors) that had previously undergone a wildfire in June 2018. There is additional data from soil collected at a neighbouring unburned site that was added to the offside seed-germination experiment. There are various levels of spatial location within the data that is distinguished by various identifiers. There also information on the mass of soil extracted for each sample when surveying seed bank composition

Propagule availability drives post-wildfire recovery of peatland plant communities

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