Single-photon emission computed tomography (SPECT) is based on the measurement of radiation emitted by a radiotracer injected into the patient. Because of photoelectric absorption and Compton scatter, the γ photons are attenuated inside the body before arriving at the detector. A quantitative reconstruction must consider the attenuation, which is usually non-uniform. Novikov and Natterer had de...

Dielectric laser-driven accelerators (DLAs) based on gratings confine an electromagnetic field induced by a drive laser into a narrow vacuum channel where electrons travel and are accelerated. This can provide an alternative acceleration scheme compared to conventional RF cavity accelerators. Due to the achievable high accelerating gradient of up to several GV/m this could pave the way for futu...

It is shown that enantiomorph structures of a noncentrosymmetric crystal can be determined, in the absence of anomalous diffraction signals, by measuring two series of reference-beam oscillation diffraction patterns related by an inverse-beam geometry. The corresponding intensities of the Friedel pairs recorded on the two sets of images exhibit the characteristic three-beam interference effects...

Cone-beam computed tomography systems have been developed to provide in situ imaging for the purpose of guiding radiation therapy. Clinical systems have been constructed using this approach, a clinical linear accelerator (Elekta Synergy RP) and an iso-centric C-arm. Geometric calibration involves the estimation of a set of parameters that describes the geometry of such systems, and is essential...

for dynamic analyses of railway track structures, the algorithm of solution is very important. for estimating the important problems in the railway tracks such as the effects of rail joints, rail supports, rail modeling in the nearness of bridge and other problems, the models of the axially beam model on the elastic foundation can be utilized. for studying the effects of axially beam on the ela...

A novel method for beam manipulation, compression, and stacking using a broad band RF system in circular accelerators is described. The method uses a series of linear voltage ramps in combination with moving barrier pulses to azimuthally compress, expand, or cog the beam. Beam manipulations can be accomplished rapidly and, in principle, without emittance growth. The general principle of the met...

We study Wigner phase-space distributions W (x, p) in position (x) and momentum (p) for light undergoing multiple small-angle scattering in a turbid medium. Smoothed Wigner phase-space distributions are measured by using a heterodyne technique that achieves position and momentum resolution determined by the width and the diffraction angle of the local oscillator beam. The sample consists of 5.7...

Context: An electron-positron beam escaping from the magnetospheric vacuum gap of an accreting black hole interacts with recombination-line photons surrounding gas clouds. Inverse-Compton scattering and subsequent pair production initiate unsaturated electromagnetic cascades exhibiting a characteristic spectral energy distribution. Aims: By modelling interactions electrons (positrons) hydrogen ...