Background: Due to the small size of the beamlets in IMRT (intensity modulated radiotherapy), physical penumbra is one of the important dosimetric parameters and small changes in the penumbra have a notable impact on the results. The physical penumbra width is defined as the lateral distance between two specified isodose curves at a specified depth of phantom. In this study, after demonstrating...

Introduction: Because of small size of the beamlets in IMRT, physical penumbra is one of the important dosimetric parameters and small changes in the penumbra will have a great impact on the results. The physical penumbra width is defined as the lateral distance between two specified isodose curves at a specified depth of phantom. In this study, after demonstrating the inconsi...

Introduction: Stereotactic radiosurgery (SRS) is one of the conformal radiotherapy methods and Gamma Knife is a non-invasive SRS technique to treat intracranial lesions with 201 Co- 60 sources without need to surgery and bleeding. Beam penumbra phenomenon leads to irradiation outside the field and normal tissues. Therefore, considering it is momentous to attain the acceptable t...

Context. It is unclear why there a rather sharp boundary in sunspots between the umbra and penumbra. Both regions exhibit magnetoconvection, which manifests penumbral filaments penumbra umbral dots umbra. Aims. Here we compare physical properties of filaments. Our goal to understand how these convective features change across this related rapid increase brightness at umbra-penumbra boundary. Me...

The uncombed penumbral model explains the structure of the sunspot penumbra in terms of thick magnetic fibrils embedded in a magnetic surrounding atmosphere. This model has been successfully applied to explain the polarization signals emerging from the sunspot penumbra. Thick penumbral fibrils face some physical problems, however. In this contribution we will offer possible solutions to these s...

ABSTRACT A light bridge is a magnetic intrusion into sunspot, it interacts with the main field and excites variety of dynamical processes. In letter, we studied connectivity between coronal loops rooted at sunspot. We used data Atmospheric Imaging Assembly onboard Solar Dynamics Observatory(SDO) to study features sunspots bridges. It found that if anchors umbra-penumbra boundary, could not be f...

Background: Recently, multileaf collimators (MLC) have become an important part of any LINAC collimation system because they reduce the treatment planning time and improve the conformity. Important factors that affect MLCs collimation performance are leaves material composition and their thickness.Objective: In this study, we investigate main dosimetric parameters of a typical MLC includi...

Environment maps are a popular method of reproducing complex natural lighting. However, current methods for hardware environment map shadows depend on significant pre-computation and cannot support dynamic objects. This work presents a pre-process that decomposes an environment map into two components: a set of area lights and an ambient map. Once the map is split into these components, each is...

Prel iminary results of tbe measurements of the electroQ and ion components of plasma obtained by means of wide-angle detectors onboard the Venera-9 and Venera-l0 satell ites are presented. Stable electron and fluctuating ion fluxes were detected in the optical and corpuscular umbra. As a result of the plasma characteristics ob­ served at a few hundred kilometers above the optical umbra, we ref...