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

About the coherent fraction of synchrotron emission

Coherent fraction is a concept widely used in the synchrotron radiation community. Here I discuss the meaning of coherent fraction, an accurate way to define it, and the different formulations found in literature to calculate it. After several comparisons using values from the present and future ESRF lattices, an approximated way to quickly compute it is proposed.Comment: 6 pages, 3 figures, to be submitted to Journal of Synchrotron Radiatio

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