Abstract
Simulated images of a black hole surrounded by optically thin emission typically display two main features: a central brightness depression and a narrow “photon ring” consisting of strongly ...lensed images superimposed over the direct emission. The photon ring closely tracks a theoretical curve on the image plane corresponding to light rays that asymptote to bound photon orbits. The size and shape of this critical curve are purely governed by the Kerr geometry; in contrast, the size, shape, and depth of the observed brightness depression depend on the details of the emission region. For instance, images of spherical accretion models display a distinctive dark region—the “black hole shadow”—that completely fills the photon ring. By contrast, in models of equatorial disks extending to the event horizon, the darkest region in the image is restricted to a much smaller area—an
inner shadow
—whose edge lies near the direct lensed image of the equatorial horizon. Using both general relativistic MHD simulations and semi-analytic models, we demonstrate that the photon ring and inner shadow may be simultaneously visible in submillimeter images of M87
*
, where magnetically arrested disk simulations predict that the emission arises in a thin region near the equatorial plane. We show that the relative size, shape, and centroid of the photon ring and inner shadow can be used to estimate the black hole mass and spin, breaking degeneracies in measurements of these quantities from the photon ring alone. Both features may be accessible to direct observation via high-dynamic-range images with a next-generation Event Horizon Telescope.
We explore a simple spherical model of optically thin accretion on a Schwarzschild black hole, and study the properties of the image as seen by a distant observer. We show that a dark circular region ...in the center-a shadow-is always present. The outer edge of the shadow is located at the photon ring radius , where is the gravitational radius of the accreting mass M. The location of the shadow edge is independent of the inner radius at which the accreting gas stops radiating. The size of the observed shadow is thus a signature of the spacetime geometry and it is hardly influenced by accretion details. We briefly discuss the relevance of these results for the Event Horizon Telescope image of the supermassive black hole in M87.
Sodium-Ion Batteries Slater, Michael D.; Kim, Donghan; Lee, Eungje ...
Advanced functional materials,
February 25, 2013, Letnik:
23, Številka:
8
Journal Article
Recenzirano
The status of ambient temperature sodium ion batteries is reviewed in light of recent developments in anode, electrolyte and cathode materials. These devices, although early in their stage of ...development, are promising for large‐scale grid storage applications due to the abundance and very low cost of sodium‐containing precursors used to make the components. The engineering knowledge developed recently for highly successful Li ion batteries can be leveraged to ensure rapid progress in this area, although different electrode materials and electrolytes will be required for dual intercalation systems based on sodium. In particular, new anode materials need to be identified, since the graphite anode, commonly used in lithium systems, does not intercalate sodium to any appreciable extent. A wider array of choices is available for cathodes, including high performance layered transition metal oxides and polyanionic compounds. Recent developments in electrodes are encouraging, but a great deal of research is necessary, particularly in new electrolytes, and the understanding of the SEI films. The engineering modeling calculations of Na‐ion battery energy density indicate that 210 Wh kg−1 in gravimetric energy is possible for Na‐ion batteries compared to existing Li‐ion technology if a cathode capacity of 200 mAh g−1 and a 500 mAh g−1 anode can be discovered with an average cell potential of 3.3 V.
The research and development of ambient temperature Na‐ion batteries is progressing quickly and is now poised to penetrate the energy storage landscape. The combination of new electrode materials, electrochemical couples, and engineering advances coupled with a potential for low‐cost and long‐life make them attractive candidates for grid storage.
ABSTRACT Just as turbulence in the Earth's atmosphere can severely limit the angular resolution of optical telescopes, turbulence in the ionized interstellar medium fundamentally limits the ...resolution of radio telescopes. We present a scattering mitigation framework for radio imaging with very long baseline interferometry (VLBI) that partially overcomes this limitation. Our framework, "stochastic optics," derives from a simplification of strong interstellar scattering to separate small-scale ("diffractive") effects from large-scale ("refractive") effects, thereby separating deterministic and random contributions to the scattering. Stochastic optics extends traditional synthesis imaging by simultaneously reconstructing an unscattered image and its refractive perturbations. Its advantages over direct imaging come from utilizing the many deterministic properties of the scattering-such as the time-averaged "blurring," polarization independence, and the deterministic evolution in frequency and time-while still accounting for the stochastic image distortions on large scales. These distortions are identified in the image reconstructions through regularization by their time-averaged power spectrum. Using synthetic data, we show that this framework effectively removes the blurring from diffractive scattering while reducing the spurious image features from refractive scattering. Stochastic optics can provide significant improvements over existing scattering mitigation strategies and is especially promising for imaging the Galactic Center supermassive black hole, Sagittarius A*, with the Global mm-VLBI Array and with the Event Horizon Telescope.
Black hole images present an annular region of enhanced brightness. In the absence of propagation effects, this "photon ring" has universal features that are completely governed by general relativity ...and independent of the details of the emission. Here, we show that the polarimetric image of a black hole also displays universal properties. In particular, the photon ring exhibits a self-similar pattern of polarization that encodes the black hole spin. We explore the corresponding universal polarimetric signatures of the photon ring on long interferometric baselines, and propose a method for measuring the black hole spin using a sparse interferometric array. These signatures could enable spin measurements of the supermassive black hole in M87, as well as precision tests of general relativity in the strong field regime, via a future extension of the Event Horizon Telescope to space.
We draw on eight different lab and field samples to delineate the effects of expressed humility on several important organizational outcomes, including performance, satisfaction, learning goal ...orientation, engagement, and turnover. We first review several literatures to define the construct of expressed humility, discuss its implications in social interactions, and distinguish expressed humility from related constructs. Using five different samples, Study 1 develops and validates an observer-report measure of expressed humility. Study 2 examines the strength of expressed humility predictions of individual performance and contextual performance (i.e., quality of team member contribution) relative to conscientiousness, global self-efficacy, and general mental ability. This study also reveals that with regard to individual performance, expressed humility may compensate for lower general mental ability. Study 3 reports insights from a large field sample that examines the relationship between leader-expressed humility and employee retention as mediated by job satisfaction and employee engagement as mediated by team learning orientation. We conclude with recommendations for future research.
Genetically modified T cells expressing chimeric antigen receptors (CARs) demonstrate robust responses against lineage restricted, non-essential targets in hematologic cancers. However, in solid ...tumors, the full potential of CAR T cell therapy is limited by the availability of cell surface antigens with sufficient cancer-specific expression. The majority of CAR targets have been normal self-antigens on dispensable hematopoietic tissues or overexpressed shared antigens. Here, we established that abnormal self-antigens can serve as targets for tumor rejection. We developed a CAR that recognized cancer-associated Tn glycoform of MUC1, a neoantigen expressed in a variety of cancers. Anti-Tn-MUC1 CAR T cells demonstrated target-specific cytotoxicity and successfully controlled tumor growth in xenograft models of T cell leukemia and pancreatic cancer. These findings demonstrate the therapeutic efficacy of CAR T cells directed against Tn-MUC1 and present aberrantly glycosylated antigens as a novel class of targets for tumor therapy with engineered T cells.
•Cancer cells of many tissues express an abnormal glycoform of MUC1, Tn-MUC1•Normal human tissue does not express detectable Tn-MUC1 on the cellular surface•CAR T cells are engineered to target Tn-MUC1 lyse tumor cells in vitro and in vivo•Abnormal glycoform epitopes are valid clinical targets for CAR T cells
Posey and colleagues developed a CAR T cell therapy to break immune tolerance to solid tumors by targeting an aberrantly glycosylated, cancer-specific glycoprotein in multiple cancer histotypes and demonstrated efficacy and safety in tumors as diverse as leukemia and pancreatic cancer.
The pneumococcus is one of the most prodigious producers of hydrogen peroxide amongst bacterial pathogens. Hydrogen peroxide production by the pneumococcus has been implicated in antibiotic ...synergism, competition between other bacterial colonizers of the nasopharynx, and damage to epithelial cells. However, the role during invasive disease has been less clear with mutants defective in hydrogen peroxide production demonstrating both attenuation and heightened invasive disease capacity depending upon strain and serotype background. This work resolves these conflicting observations by demonstrating that the main hydrogen peroxide producing enzyme of the pneumococcus, SpxB, is required for capsule formation in a strain dependent manner. Capsule production by strains harboring capsules with acetylated sugars was dependent upon the presence of spxB while capsule production in serotypes lacking such linkages were not. The spxB mutant had significantly lower steady-state cellular levels of acetyl-CoA, suggesting that loss of capsule arises from dysregulation of this intermediary metabolite. This conclusion is corroborated by deletion of pdhC, which also resulted in lower steady-state acetyl-CoA levels and phenocopied the capsule expression profile of the spxB mutant. Capsule and acetyl-CoA levels were restored in the spxB and lctO (lactate oxidase) double mutant, supporting the connection between central metabolism and capsule formation. Taken together, these data show that the defect in pathogenesis in the spxB mutant is due to a metabolic imbalance that attenuates capsule formation and not to reduced hydrogen peroxide formation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract Although amyloid imaging with PiB-PET (C-11Pittsburgh Compound-B positron emission tomography), and now with F-18-labeled tracers, has produced remarkably consistent qualitative findings ...across a large number of centers, there has been considerable variability in the exact numbers reported as quantitative outcome measures of tracer retention. In some cases this is as trivial as the choice of units, in some cases it is scanner dependent, and of course, different tracers yield different numbers. Our working group was formed to standardize quantitative amyloid imaging measures by scaling the outcome of each particular analysis method or tracer to a 0 to 100 scale, anchored by young controls (≤45 years) and typical Alzheimer's disease patients. The units of this scale have been named “Centiloids.” Basically, we describe a “standard” method of analyzing PiB PET data and then a method for scaling any “nonstandard” method of PiB PET analysis (or any other tracer) to the Centiloid scale.
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