50,232 research outputs found
The Classification of Extragalactic X-ray Jets
The overall classification of X-ray jets has clung to that prevalent in the
radio: FRI vs. FRII (including quasars). Indeed, the common perception is that
X-ray emission from FRI's is synchrotron emission whereas that from FRII's may
be IC/CMB and/or synchrotron. Now that we have a sizable collection of sources
with detected X-ray emission from jets and hotspots, it seems that a more
unbiased study of these objects could yield additional insights on jets and
their X-ray emission. The current contribution is a first step in the process
of analyzing all of the relevant parameters for each detected component for the
sources collected in the XJET website. This initial effort involves measuring
the ratio of X-ray to radio fluxes and evaluating correlations with other jet
parameters. For single zone synchrotron X-ray emission, we anticipate that
larger values of fx/fr should correlate inversely with the average magnetic
field strength (if the acceleration process is limited by loss time equals
acceleration time). Beamed IC/CMB X-rays should produce larger values of fx/fr
for smaller values of the angle between the jet direction and the line of sight
but will also be affected by the low frequency radio spectral index.Comment: 4 pages; to appear in the conference proceedings: "X-Ray Astronomy
2009: Present Status, Multiwavelength Approach and Future Perspectives";
Bologna, Italy, September 2009, Editors: A. Comastri, M. Cappi, L. Angelini,
2010 AIP (in press
GdRhSi: An exemplary tetragonal system for antiferromagnetic order with weak in-plane anisotropy
The anisotropy of magnetic properties commonly is introduced in textbooks
using the case of an antiferromagnetic system with Ising type anisotropy. This
model presents huge anisotropic magnetization and a pronounced metamagnetic
transition and is well-known and well-documented both, in experiments and
theory. In contrast, the case of an antiferromagnetic - system with weak
in-plane anisotropy is only poorly documented. We studied the anisotropic
magnetization of the compound GdRhSi and found that it is a perfect
model system for such a weak-anisotropy setting because the Gd ions in
GdRhSi have a pure spin moment of S=7/2 which orders in a simple AFM
structure with . We observed experimentally in a
continuous spin-flop transition and domain effects for field applied along the
- and the -direction, respectively. We applied a mean field model
for the free energy to describe our data and combine it with an Ising chain
model to account for domain effects. Our calculations reproduce the
experimental data very well. In addition, we performed magnetic X-ray
scattering and X-ray magnetic circular dichroism measurements, which confirm
the AFM propagation vector to be and indicate the absence of
polarization on the rhodium atoms
Vacuum ultraviolet holography
The authors report the first demonstration of holographic techniques in the vacuum ultraviolet spectral region. Holograms were produced with coherent 1182 A radiation. The holograms were recorded in polymethyl methacrylate and read out with an electron microscope. A holographic grating with a fringe spacing of 836 A was produced and far-field Fraunhofer holograms of sub-micron particles were recorded
Role of Micro-CT in the Visualization, Measurement, and Quantification of Bone Structure in Osteogenesis Imperfecta
Statistical properties of entropy production derived from fluctuation theorems
Several implications of well-known fluctuation theorems, on the statistical
properties of the entropy production, are studied using various approaches. We
begin by deriving a tight lower bound on the variance of the entropy production
for a given mean of this random variable. It is shown that the Evans-Searles
fluctuation theorem alone imposes a significant lower bound on the variance
only when the mean entropy production is very small. It is then nonetheless
demonstrated that upon incorporating additional information concerning the
entropy production, this lower bound can be significantly improved, so as to
capture extensivity properties. Another important aspect of the fluctuation
properties of the entropy production is the relationship between the mean and
the variance, on the one hand, and the probability of the event where the
entropy production is negative, on the other hand. Accordingly, we derive upper
and lower bounds on this probability in terms of the mean and the variance.
These bounds are tighter than previous bounds that can be found in the
literature. Moreover, they are tight in the sense that there exist probability
distributions, satisfying the Evans-Searles fluctuation theorem, that achieve
them with equality. Finally, we present a general method for generating a wide
class of inequalities that must be satisfied by the entropy production. We use
this method to derive several new inequalities which go beyond the standard
derivation of the second law.Comment: 14 pages, 1 figure; Submitted to Journal of Statistical Mechanios:
Theory and Experimen
A Bond Length ā Bond Valence Relationship for Carbon ā Nitrogen Bonds
In a recent study, Paulingās relationship between bond length and valence was derived along with a definition for his fitting parameter b that incorporates the orbital exponents for each atom contributing to the bond of interest. The values of b for various bonds, including C-N bonds, were calculated using the orbital exponent data. In this study, Paulingās correlation between bond length and bond valence, as well as his valence sum rule, were used with the recently-derived definition for b in order to produce a relationship specifically applicable to C-N bonds. The resulting equation was checked against published x-ray diffraction data for 430 C-N bonds. It is expected, and shown by the data presented in this study, that these equations relating the bond length and bond valence of C-N bonds have sufficient applicability and accuracy for use in any bonding environment, regardless of physical state or oxidation number
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On the Interface Between LENSĀ® Deposited Stainless Steel 304L Repair Geometry and Cast or Machined Components
Laser Engineered Net Shapingā¢ (LENSĀ®) is being evaluated for use as a metal component
repair/modification process. A component of the evaluation is to better understand the characteristics of
the interface between LENS deposited material and the substrate on which it is deposited. A processing
and metallurgical evaluation was made on LENS processed material fabricated for component
qualification tests. A process parameter evaluation was used to determine optimum build parameters
and these parameters were used in the fabrication of tensile test specimens to study the characteristics of
the interface between LENS deposited material and several types of substrates. Analyses of the
interface included mechanical properties, microstructure, and metallurgical integrity. Test samples
were determined for a variety of geometric configurations associated with interfaces between LENS
deposited material and both wrought base material or previously deposited LENS material. Thirteen
different interface configurations were fabricated for evaluation representing a spectrum of deposition
conditions from complete part build, to hybrid substrate-LENS builds, to repair builds for damaged or
re-designed housings. Good mechanical properties and full density were observed for all configurations.
When tested to failure, fracture occurred by ductile microvoid coalescence. The repair and hybrid
interfaces showed the same metallurgical integrity as, and had properties similar to, monolithic LENS
deposits.Mechanical Engineerin
A qualitative study of primary care professionalsā views of case finding for depression in patients with diabetes or coronary heart disease in the UK
<p>Background
Routinely conducting case finding (also commonly referred to as screening) in patients with chronic illness for depression in primary care appears to have little impact. We explored the views and experiences of primary care nurses, doctors and managers to understand how the implementation of case finding/screening might impact on its effectiveness.</p>
<p>Methods
Two complementary qualitative focus group studies of primary care professionals including nurses, doctors and managers, in five primary care practices and five Community Health Partnerships, were conducted in Scotland.</p>
<p>Results
We identified several features of the way case finding/screening was implemented that may lead to systematic under-detection of depression. These included obstacles to incorporating case finding/screening into a clinical review consultation; a perception of replacing individualised care with mechanistic assessment, and a disconnection for nurses between management of physical and mental health. Far from being a standardised process that encouraged detection of depression, participants described case finding/screening as being conducted in a way which biased it towards negative responses, and for nurses, it was an uncomfortable task for which they lacked the necessary skills to provide immediate support to patients at the time of diagnosis.</p>
<p>Conclusion
The introduction of case finding/screening for depression into routine chronic illness management is not straightforward. Routinized case finding/screening for depression can be implemented in ways that may be counterproductive to engagement (particularly by nurses), with the mental health needs of patients living with long term conditions. If case finding/screening or engagement with mental health problems is to be promoted, primary care nurses require more training to increase their confidence in raising and dealing with mental health issues and GPs and nurses need to work collectively to develop the relational work required to promote cognitive participation in case finding/screening.</p>
Application of remote sensing to state and regional problems
There are no author-identified significant results in this report
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