1,168 research outputs found
Exploring the potential X-ray counterpart of the puzzling TeV gamma-ray source HESS J1507-622 with new Suzaku observations
The unidentified VHE (E>100 GeV) gamma-ray source HESS J1507-622 seems to not
fit into standard models for sources related to young supernova remnants,
pulsar wind nebulae, or young stellar populations in general. This is due to
its intrinsically extended, but yet compact morphology, coupled with a relative
large offset (~3.5 deg) from the Galactic plane. Therefore, it has been
suggested that this object may be the first representative of a new distinct
class of extended off-plane gamma-ray sources. The distance to HESS J1507-622
is the key parameter to constrain the source's most important properties, such
as age and energetics of the relativistic particle population.
In this article we report on results of follow-up observations of the
potential X-ray counterpart with Suzaku. We present detailed measurements of
its spectral parameters and find a high absorbing hydrogen column density,
compatible with the total amount of Galactic gas in this direction. In
comparisons to measurements and models of the Galactic three-dimensional gas
distribution we show that the potential X-ray counterpart of HESS J1507-622 may
be located at the far end of the Galaxy. If the gamma-ray source is indeed
physically connected to this extended X-ray source, this in turn would place
the object outside of the usual distribution of Galactic VHE gamma-ray
emitters.Comment: 12 pages, 7 figures, accepted for publication by MNRA
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Towards a change process planning tool
The relationship between a product and its design process is generally complex and not fully understood. When modifying a product, industry still rarely considers the implementation process and its consequences for other design activities in the company, which is hard to assess with conventional planning methods. Although change processes are highly constrained, product and process constraints are not usually considered together or traded off against each other when planning the change. Inadequate assessment and planning of the change implementation process can lead to costly knock-on effects across the product and the design process. This paper argues for a combination of change and process research and discusses requirements for a change process planning tool. It proposes a system for the analysis of the impact of change on the product as well as other company activities. Then, a more informed selection between change alternatives is possible
A functional analysis of change propagation
A thorough understanding of change propagation is fundamental to effective change management during product redesign. A new model of change propagation, as a result of the interaction of form and function is presented and used to develop an analysis method that determines how change is likely to propagate. The analysis produces a Design Structure Matrix, which clearly illustrates change propagation paths and highlights connections that could otherwise be ignored. This provides the user with an in-depth knowledge of product connectivity, which has the potential to support the design process and reduce the product's susceptibility to future change
Spatially Invariant Coding of Numerical Information in Functionally Defined Subregions of Human Parietal Cortex
Macaque electrophysiology has revealed neurons responsive to number in lateral (LIP) and ventral (VIP) intraparietal areas. Recently, fMRI pattern recognition revealed information discriminative of individual numbers in human parietal cortex but without precisely localizing the relevant sites or testing for subregions with different response profiles. Here, we defined the human functional equivalents of LIP (feLIP) and VIP (feVIP) using neurophysiologically motivated localizers. We applied multivariate pattern recognition to investigate whether both regions represent numerical information and whether number codes are position specific or invariant. In a delayed number comparison paradigm with laterally presented numerosities, parietal cortex discriminated between numerosities better than early visual cortex, and discrimination generalized across hemifields in parietal, but not early visual cortex. Activation patterns in the 2 parietal regions of interest did not differ in the coding of position-specific or position-independent number information, but in the expression of a numerical distance effect which was more pronounced in feLIP. Thus, the representation of number in parietal cortex is at least partially position invariant. Both feLIP and feVIP contain information about individual numerosities in humans, but feLIP hosts a coarser representation of numerosity than feVIP, compatible with either broader tuning or a summation cod
A Search for Diffuse X-ray Emission from GeV Detected Galactic Globular Clusters
Recently, diffuse and extended sources in TeV gamma-rays as well as in X-rays
have been detected in the direction of the Galactic globular cluster (GC)
Terzan 5. Remarkably, this is among the brightest GCs detected in the GeV
regime. The nature of both the TeV and the diffuse X-ray signal from Terzan 5
is not settled yet. These emissions most likely indicate the presence of
several non-thermal radiation processes in addition to these giving rise to the
GeV signal.
The aim of this work is to search for diffuse X-ray emission from the GeV
detected GCs M 62, NGC 6388, NGC 6541, M 28, M 80 and NGC 6139 to compare the
obtained results with the signal detected from Terzan 5. This study will help
to determine whether Terzan 5 stands out amongst other GC or whether a whole
population of globular clusters feature similar properties.
None of the six GCs show significant diffuse X-ray emission on similar scales
as observed from Terzan 5 above the particle and diffuse galactic X-ray
background components. The derived upper limits allow to assess the validity of
different models that were discussed in the interpretation of the
multi-wavelength data of Terzan 5. A scenario based on synchrotron emission
from relativistic leptons provided by the millisecond pulsar population can not
be securely rejected if a comparable magnetic field strength as in Terzan 5 is
assumed for every GC. However, such a scenario seems to be unlikely for NGC
6388 and M 62. An inverse-Compton scenario relying on the presence of a
putative GRB remnant with the same properties as the one proposed for Terzan 5
can be ruled out for all of the six GCs. Finally, the assumption that each GC
hosts a source with the same luminosity as in Terzan 5 is ruled out for all GCs
but NGC 6139. (abridged)Comment: 8 pages, 1 Figure, accepted for publication by Astronomy &
Astrophysics, final version after language editin
The Policy of Enforcement: Red Light Cameras and Racial Profiling
The article of record as published may be located at http://dx.doi.org/10.1177/1098611115586174We explore the question of whether some of the often conflicting evidence of
racial profiling can be cleared up using red light camera observations to measure
racial disparities in traffic violations. Using data from cameras at intersections
matched to census data, we find that although citations from the red light cameras
are issued to a disproportionate number of minorities based on the racial composition
of the surrounding location, the racial composition of the violator is consistent
with the racial composition of the block group in which they reside. Our study
indicates that red light cameras may have a present and future role in assisting
public policy makers on issues of racial profiling thresholds
The ideal gas as an urn model: derivation of the entropy formula
The approach of an ideal gas to equilibrium is simulated through a
generalization of the Ehrenfest ball-and-box model. In the present model, the
interior of each box is discretized, {\it i.e.}, balls/particles live in cells
whose occupation can be either multiple or single. Moreover, particles
occasionally undergo random, but elastic, collisions between each other and
against the container walls. I show, both analitically and numerically, that
the number and energy of particles in a given box eventually evolve to an
equilibrium distribution which, depending on cell occupations, is binomial
or hypergeometric in the particle number and beta-like in the energy.
Furthermore, the long-run probability density of particle velocities is
Maxwellian, whereas the Boltzmann entropy exactly reproduces the
ideal-gas entropy. Besides its own interest, this exercise is also relevant for
pedagogical purposes since it provides, although in a simple case, an explicit
probabilistic foundation for the ergodic hypothesis and for the maximum-entropy
principle of thermodynamics. For this reason, its discussion can profitably be
included in a graduate course on statistical mechanics.Comment: 17 pages, 3 figure
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