1,634 research outputs found
Coherent modes of X-ray beams emitted by undulators in new storage rings
Synchrotron radiation emitted by electrons passing through an undulator
placed in a storage ring is decomposed in coherent modes. The case of ultimate
storage rings where the electron emittance is comparable to the emittance of
the photon fan is analyzed by means of the cross spectral density and the
coherent mode spectrum. The proposed method permits naturally the statistical
analysis and propagation of the cross spectral density along the beamline
optics. The coherence properties of the X-ray beam at any point of the beamline
are completely given in terms of the eigenvalues and coherent modes of the
cross spectral density.Comment: 5 pages, 6 Figures, 17 reference
X-ray polarization: General formalism and polarization analysis
The polarization of x-rays plays an outstanding role in experimental
techniques such as non-resonant magnetic x-ray scattering and resonant x-ray
scattering of magnetic and multipolar order. Different instrumental methods
applied to synchrotron light can transform its natural polarization into an
arbitrary polarization state. Several synchrotron applications, in particular
in the field of magnetic and resonant scattering rely on the improvement in the
signal/noise ratio or the deeper insight into the ordered state and the
scattering process made possible through these polarization techniques. Here,
we present the mathematical framework for the description of fully and
partially polarized x-rays, with some applications such as linear x-ray
polarization analysis for the determination of the scattered beam's
polarization, and the Ge K-edge resonant scattering.Comment: 12 pages, 6 figures and 1 table. To be published in proceedings of
the workshop "Resonant Elastic X-ray Scattering", Aussois, France (2011
Gas turbine power cycles for retrofitting and repowering coal plants with post-combustion carbon dioxide capture
A widely-proposed way to retrofit coal-fired power plants with post-combustion CO2 capture (PCC) is to supply all the electricity and heat required to operate the capture equipment from the existing steam cycle (an ‘integrated retrofit’), at the expense of a reduction in site power output. As an alternative, it is possible to add a gas turbine (GT) plant to maintain, or even increase, the net site power output. The GT can be integrated with the capture plant in various ways to supply all or part of the heat and power required for the capture and compression systems. But there is then the issue of how to capture the CO2 emissions from the added GT plant. In this study a novel retrofit configuration is proposed. The exhaust gas of the GT replaces part of the secondary air for the coal boiler and a common capture system is used for both coal- and natural gas-derived CO2. This new ‘GT flue gas windbox retrofit’ is based on the principles of previous hot windbox repowering proposals, with additional modifications to permit operation without extensive coal boiler modifications. To achieve this, the heat recovery steam generator (HRSG) attached to GT is designed to maintain the main steam turbine flow rates and temperatures, to compensate for a necessary reduction in coal feed rates, and this, with the GT output, maintains the net power output of the site A techno-economic analysis of coal plants retrofitted with GT power cycles shows that these ‘power matched’ retrofits can be competitive with integrated retrofits at lower natural gas prices (as is now the case in North America). In particular, the novel GT flue gas windbox retrofit provides a promising alternative for adapting integrated capture retrofits that are initially designed for flexible operation with zero to full (~90%) capture (as at the Boundary Dam 3 unit) for subsequent operation only with full capture. In this case the addition of a GT flue gas windbox retrofit will restore the full power output of the site with full CO2 capture and using the original capture plant. In general, techno-economic analysis shows that the economic performance of GT retrofit options depends on the site power export capacity. If there is no limit on power export then retrofits may advantageously also include an additional steam cycle, to give a combined cycle with the GT, otherwise retrofits with a single pressure HRSG producing process steam only are preferred
Measuring Population Transmission Potential for HIV: An Alternative Metric of Transmission Risk in Men who have Sex with Men (MSM) in the US
Background Various metrics for HIV burden and treatment success [e.g. HIV prevalence, community viral load (CVL), population viral load (PVL), percent of HIV-positive persons with undetectable viral load] have important public health limitations for understanding disparities. Methods and Findings Using data from an ongoing HIV incidence cohort of black and white men who have sex with men (MSM), we propose a new metric to measure the prevalence of those at risk of transmitting HIV and illustrate its value. …See full text for complete abstract
Electromiograph Parameters in Thedysfunctional Patient with Open Bite
INTRODUCTION: Open bite is an occlusal problem that appears in 0.5% of the population, and is more frequent in women. There is correlation between open bite and dysfunctional syndrome with TMJ disorders.
AIM OF THE STUDY: We attempted to analyze muscular parameters in patients with open bite treated with an occlusal splint by EMG recordings.
MATERIAL AND METHODS: Myotronics K6 electromiograph can provide information in the following situations: maximum force bite, lateral and protrusion movements, with and without an occlusal splint.
RESULTS: In maximum force bite with the occlusal splint more activity was found in the elevator muscles with a lack of dygastric activity. There was less EMG activity in protrusive and lateral
movements with occlusal splint.
CONCLUSION: With better support between the dental arches (occlusal splint) more activity was obtained in the elevators when biting, and when interferences were eliminated activity in the contralateral muscles was reduced
Tilting refractive x-ray lenses for fine-tuning their focal length
In this work, we measure and model tilted x-ray refractive lenses to
investigate their effects on an x-ray beam. The modelling is benchmarked
against at-wavelength metrology obtained with x-ray speckle vector tracking
experiments (XSVT) at the BM05 beamline at the ESRF-EBS light source, showing
very good agreement. This validation permits us to explore possible
applications of tilted x-ray lenses in optical design: we demonstrate that
tilting 1D lenses around their focusing direction can be used for fine-tuning
their focal length with possible applications in beamline optical design.Comment: 15 pages, 13 figures, 38 references to be submitted to Optics Expres
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