ABSTRACT
Harmonic generation from linearly polarized high-intensity short-pulse laser normally impacting a solid plasma grating is investigated using analytical modeling and particle-in-cell simulation. It is found that when the radiation excited by the relativistic electron quiver motion in the laser fields suitably matches a harmonic of the grating periodicity, it will be significantly enhanced and peak with narrow angular spread in specific directions. The corresponding theory shows that the phenomenon can be attributed to an interference effect of the periodic grating on the excitation.
ABSTRACT
The X-ray findings in 51 cases of neuroblastoma were analysed. The aim of plain film of abdomen is to search for fine sandy calcifications in the abdominal mass, paravertebral widening at lower thoracic region, and bone metastases. Displacement and deformity of kidney by extrinsic pressure seen in IVU are useful in differentiating an extrarenal tumor from intrarenal one. Ultrasound and CT are superior to IVU in localization diagnosis and defining the extent of abdominal neuroblastoma. Thoracic neuroblastoma usually manifests as a posterior mediastinal tumor associated with rib changes and the chest film remains valuable in diagnosis of this condition. It is mandatory to screen the patient for skeletal metastases radiographically and to investigate the bone marrow, and urine VMA whenever abnormalities are found in abdominal or thoracic imaging. The significance of combined imaging techniques in staging of neuroblastoma was discussed, and a simple diagnostic approach was proposed.
