نتایج جستجو برای: collimation
تعداد نتایج: 1626 فیلتر نتایج به سال:
Context. The bipolar HH 212 outflow has been mapped in SiO using the extended configuration of the Plateau de Bure Interferometer (PdBI), revealing a highly collimated SiO jet closely associated with the H2 jet component. Aims. We study at unprecedented resolution (0. ′′34 across the jet axis) the properties of the innermost SiO “microjet” within 1000 AU of this young Class 0 source, to compare...
OBJECTIVE Unnecessary exposure of the abdomen, arms or head may lead to a substantial increase of the radiation dose in portable chest X-rays on the neonatal intensive care unit. The objective was to identify potential factors influencing inappropriate exposure of non-thoracic structures in two teaching hospitals. METHODS The study analysed 200 consecutive digital chest radiographs in 20 pret...
Conventional single photon emission computed tomography (SPECT) relies on mechanical collimation whose resolution and sensitivity are interdependent, the best performance a SPECT system can attain is only compromise of these two equally desired properties. To simultaneously achieve high sensitivity, we propose to use sensitive detectors constructed in multi-layer inter spaced mosaicdetectors (M...
A key question in the formation of the relativistic jets in active galactic nuclei (AGNs) is the collimation process of their energetic plasma flow launched from the central supermassive black hole (SMBH). Recent observations of nearby low-luminosity radio galaxies exhibit a clear picture of parabolic collimation inside the Bondi accretion radius. On the other hand, little is known of the obser...
INTRODUCTION Collimating the primary beam to the area of diagnostic interest (ADI) has been strongly recommended as an effective method to reduce patient's radiation dose and to improve image quality during radiology practice. Lack or inadequate collimation results in excessive radiation dose to patients and deterioration image quality. OBJECTIVE To assess the quality of beam collimation duri...
Super-collimation is the propagation of a light beam without spreading that occurs when the light beam is guided by the dispersion properties of a photonic crystal, rather than by defects in the photonic crystal. Super-collimation has many potential applications, the most straight-forward of which is in the area of integrated optical circuits, where super-collimation can be utilized for optical...
Molecular imaging with radionuclides is a very sensitive technique because it allows to obtain images with nanomolar or picomolar concentrations. This has generated a rapid growth of interest in radionuclide imaging of small animals. Indeed radiolabeling of small molecules, antibodies, peptides and probes for gene expression enables molecular imaging in vivo, but only if a suitable imaging syst...
Cover: Generation of an intensity modulated field by using dynamic multileaf collimation.
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