Spatial extension is an important characteristic for correctly associating gamma-ray-emitting sources with their counterparts at other wavelengths and for obtaining an unbiased model of their ...spectra. We present a new method for quantifying the spatial extension of sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi). We perform a series of Monte Carlo simulations to validate this tool and calculate the LAT threshold for detecting the spatial extension of sources. We then test all sources in the second Fermi-LAT catalog for extension. We report the detection of seven new spatially extended sources.
Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio ...beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic field. We modeled the radio profiles using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase, we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best-fit parameters and confidence intervals are determined using a maximum likelihood technique. We divide the light curves into three model classes, with gamma-ray peaks trailing (Class I), aligned (Class II), or leading (Class III) the radio peaks. Outer gap and slot gap (two-pole caustic) models best fit roughly equal numbers of Class I and II, while Class III are exclusively fit with pair-starved polar cap models. Distinguishing between the model classes based on typical derived parameters is difficult. We explore the evolution of the magnetic inclination angle with period and spin-down power, finding possible correlations. While the presence of significant off-peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed.
After almost three years of data taking in sky-survey mode, the Fermi Large Area Telescope has detected gamma-ray emission toward Tycho's supernova remnant (SNR). The Tycho SNR is among the youngest ...remnants in the Galaxy, originating from a Type Ia Supernova in AD 1572. The gamma-ray integral flux from 400 MeV up to 100 GeV has been measured to be (3.5 + or - 1.1 sub(stat) + or - 0.7 sub(syst))x 10 super(-9) cm super(-2) s super(-1) with a photon index of 2.3 + or - 0.2 sub(stat) + or - 0.1 sub(syst). A simple model consistent with TeV, X-ray, and radio data is sufficient to explain the observed emission as originating from pi super(0) decays as a result of cosmic-ray acceleration and interaction with the ambient medium.
Mental structures Lande, Kevin J.
Noûs (Bloomington, Indiana),
September 2021, 2021-09-00, 20210901, Letnik:
55, Številka:
3
Journal Article
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An ongoing philosophical discussion concerns how various types of mental states fall within broad representational genera—for example, whether perceptual states are “iconic” or “sentential,” “analog” ...or “digital,” and so on. Here, I examine the grounds for making much more specific claims about how mental states are structured from constituent parts. For example, the state I am in when I perceive the shape of a mountain ridge may have as constituent parts my representations of the shapes of each peak and saddle of the ridge. More specific structural claims of this sort are a guide to how mental states fall within broader representational kinds. Moreover, these claims have significant implications of their own about semantic, functional, and epistemic features of our mental lives. But what are the conditions on a mental state's having one type of constituent structure rather than another? Drawing on explanatory strategies in vision science, I argue that, other things being equal, the constituent structure of a mental state determines what I call its distributional properties—namely, how mental states of that type can, cannot, or must co‐occur with other mental states in a given system. Distributional properties depend critically on and are informative about the underlying structures of mental states, they in important ways from aspects of how mental states are processed, and they can yield significant insights into the variegation of psychological capacities.
Perception involves the processing of content or information about the world. In what form is this content represented? I argue that perception is widely compositional. The perceptual system ...represents many stimulus features (including shape, orientation, and motion) in terms of combinations of other features (such as shape parts, slant and tilt, common and residual motion vectors). But compositionality can take a variety of forms. The ways in which perceptual representations compose are markedly different from the ways in which sentences or thoughts are thought to be composed. I suggest that the thesis that perception is compositional is not itself a concrete hypothesis with specific predictions; rather it affords a productive framework for developing and evaluating specific empirical hypotheses about the form and content of perceptual representations. The question is not just whether perception is compositional, but how. Answering this latter question can provide fundamental insights into perception. This article is categorized under: Philosophy > Representation Philosophy > Foundations of Cognitive Science Psychology > Perception and Psychophysics.
Complications of endoscopic biliary sphincterotomy Freeman, M L; Nelson, D B; Sherman, S ...
New England journal of medicine/The New England journal of medicine,
09/1996, Letnik:
335, Številka:
13
Journal Article
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Endoscopic sphincterotomy is commonly used to remove bile-duct stones and to treat other problems. We prospectively investigated risk factors for complications of this procedure and their outcomes.
...We studied complications that occurred within 30 days of endoscopic biliary sphincterotomy in consecutive patients treated at 17 institutions in the United States and Canada from 1992 through 1994.
Of 2347 patients, 229 (9.8 percent) had a complication, including pancreatitis in 127 (5.4 percent) and hemorrhage in 48 (2.0 Percent). There were 55 deaths from all causes within 30 days; death was directly or indirectly related to the procedure in 10 cases. Of five significant risk factors for complications identified in a multivariate analysis, two were characteristics of the patients (suspected dysfunction of the sphincter of Oddi as an indication for the procedure and the presence of cirrhosis) and three were related to the endoscopic technique (difficulty in cannulating the bile duct achievement of access to the bile duct by "precut" sphincterotomy, and use of a combined percutaneous-endoscopic procedure). The overall risk of complications was not related to the patient's age, the number of coexisting illnesses, or the diameter of the bile duct. The rate of complications was highest when the indication for the procedure was suspected dysfunction of the sphincter of Oddi (21.7 percent) and lowest when the indication was removal of bile-duct stones within 30 days of laparoscopic cholecystectomy (4.9 percent). As compared with those who performed fewer procedures, endoscopists who performed more than one sphincterotomy per week had lower rates of all complications (8.4 percent vs. 11.1 percent, P=0.03) and severe complications (0.9 percent vs. 2.3 percent, P=0.01).
The rate of complications after endoscopic biliary sphincterotomy can vary widely in different circumstances and is primarily related to the indication for the procedure and to endoscopic technique, rather than to the age or general medical condition of the patients.
In perception, one can transcend the limitations imposed by one's perspective and see things, in many respects, as they really are. For example, a circular coin can reflect dramatically different ...patterns of light to your eyes, depending on the angle from which you view it. Each of these patterns of light could have been reflected by infinitely many different types of surfaces of different shapes and sizes. On the face of it, these ever-changing and always ambiguous patterns of light at the eye carry little information about the shape and size of the coin. Yet you normally can see the coin as having a unique size and shape. The size and shape you see the coin as having normally remains the same from one viewpoint to the next -- this is known as size constancy and shape constancy. And, normally, you can see the size and shape of the coin accurately.
Abstract
Deep excavation and foundation works in soft clays can cause large settlements, resulting in damage to neighboring buildings and structures. The costs related to these types of damage can be ...substantial. There is significant potential for reducing such costs if the causes are better understood and the risk is assessed during planning, design and execution. The research project “BegrensSkade II” (“REMEDY”) focuses on developing guidelines for the main causes of excavation-induced damage related to installation effects, drainage and pore pressure lowering, and vibration effects. In addition, tools to support risk management and decision making in the building process are developed. The project is funded by the Norwegian Research Council with participation from a wide range of consultants, contractors, clients and research institutes in Norway. This paper provides an overview of the work carried out in BegrensSkade II and highlights some initial findings.
We present an analysis of gamma-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope in the region around supernova remnant (SNR) S147 (G180.0-1.7). A ...spatially extended gamma-ray source detected in an energy range of 0.2-10 GeV is found to coincide with SNR S147. We confirm its spatial extension at >5sigma confidence level. The gamma-ray flux is (3.8 + or - 0.6) x 10 super(-8) photons cm super(-2) s super(-1), corresponding to a luminosity of 1.3 x 10 super(34) (d/1.3 kpc) super(2) erg s super(-1) in this energy range. The gamma-ray emission exhibits a possible spatial correlation with the prominent H alpha filaments of SNR S147. There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538 + 2817. The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral pi mesons produced through the proton-proton collisions in the filaments. The reacceleration of the pre-existing cosmic rays and subsequent adiabatic compression in the filaments is sufficient to provide the energy density required of high-energy protons.
Self-direction is an approach to human service delivery within long-term services and supports that aims to provide greater control for individuals with disabilities and their closest supporters. The ...purpose of this study was to understand the implementation of self-directed supports for individuals with intellectual and developmental disabilities. Researchers interviewed state developmental disabilities administrators in 34 of 42 states that currently operate self-directed service options and used qualitative analysis to arrive at a thematic map of the strengths and challenges currently experienced by state administrators. Common strengths identified by state administrators were increased opportunities for participant self-determination and improved relationships with support staff. Common challenges included restructuring case management relationships, as well as rulemaking and enforcement. Administrators’ suggestions for the future of self-direction focused on increasing program size and streamlining services using technology.
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