Ion chamber measurements of transverse gamma knife beam profiles

A microchamber, PTW Pinpoint 31006, was used to measure transverse beam profiles for an Elekta Gamma Knife, Model B, and compared with profiles measured with film dosimetry. The microchamber sensitive volume has a diameter of 2 mm, which is smaller than the gamma knife beams, and a length of 5 mm. The chamber was mounted in a custom cassette in a spherical plastic phantom, supplied by Elekta, and oriented in a sagittal plane with the 2-mm dimension at right angles to the transverse plane. The phantom was manually moved across the beam, using the gamma knife x-coordinate trunnions, to measure the profiles. Profiles were also measured with V-film placed in a cassette mounted in the spherical plastic phantom. The films were scanned with a Scanditronix film scanner and converted to dose with a density to dose calibration curve. The results were superimposed for comparison. The beam width at the 50% intensity was measured from the film profiles to give the dimensions of the beams in the orthagonal planes. The ion chamber measurements are compared with the film results for the transverse, x profiles. Good agreement between the film and ion chamber transverse profiles is observed

Assignment of the 71‐cm−1 Band in Polyethylene

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70272/2/JCPSA6-42-11-4059-1.pd

Superimposition of beams to vary shot size in gamma knife stereotactic radiosurgery

The Leksell Gamma Knife [Elekta Corp] uses helmets as collimators to produce four standard beam sizes. The nominal beam diameters are 18, 14, 8, and 4 mm. During computer treatment planning for gamma knife stereotactic radiosurgery, the size of the treated volume may differ from the standard beam sizes. To maintain conformality of the isodose curves to the treated volume, beam sizes may be superimposed during computer treatment planning to produce beam diameters that are intermediate to the standard beams. A study of superimposed gamma knife beams was performed to confirm the accuracy of this method and to verify the accuracy of the GammaPlan treatment planning computer. Superimposed beams were simulated on the Elekta treatment planning computer, GammaPlan, version 4.12, and tested by film measurements of beam profiles for single helmet sizes and superimposed shots with various beam weightings. The weighting for each beam size is varied to attain the beam size diameter desired. The beams were defined at the 50% isodose line. The profiles of the superimposed beams were obtained and compared with the single helmet shots. The uniformity of the resulting beams was measured. The results show a linear relationship between beam size and beam weighting for the superimposed beams. The film measurements confirm the computer calculations

Convergence of simple adaptive Galerkin schemes based on h − h/2 error estimators

We discuss several adaptive mesh-refinement strategies based on (h − h/2)-error estimation. This class of adaptivemethods is particularly popular in practise since it is problem independent and requires virtually no implementational overhead. We prove that, under the saturation assumption, these adaptive algorithms are convergent. Our framework applies not only to finite element methods, but also yields a first convergence proof for adaptive boundary element schemes. For a finite element model problem, we extend the proposed adaptive scheme and prove convergence even if the saturation assumption fails to hold in general

An Empirical Study of the Telecommunication and Economic Growth in Nigeria

This study examines the impact of telecommunication on economic growth in Nigeria.  The study’s model is based on Solow’s augmented growth theory where labor, capital and technology are the sole determinants of economic growth. Thus, economic growth is estimated through classical least squares and fully modified ordinary least squares techniques co integration and error correction model. The finding shows that labor employed, capital stock, real investment in telecommunication and electricity supply are statistically significant to economic growth in the short run equilibrium in Nigeria. Therefore, positive economic growth is attainable when efficient and well-coordinated policies are implemented on labor productivity, price management, investment promotion and constant electricity supply. The study used GDP as a proxy of economic growth. Secondary data from NBS, CBN and NCC which were corroborated with data from ITU, WTO and World Bank Development Indicators were used for the analysis. Based on established theories, existing empirical studies and available data, six independent variables (Telecommunications revenue, telecommunications Investments, Teledensity, Agriculture, Unemployment and Electricity consumption) were regressed on the dependent variable (GDP) using Multiple Regression Analysis. The study includes labor employed, capital stock, real investment in telecommunication and electricity supply to be the repressors and real economic growth to be the regress and using a time series data from 1999 – 2018

Korea-vocational schools development project

노트 : This document has a restricted distribution and may be used by recipients only in the performance of their official duties. Its contents may not otherwise be disclosed without World Bank authorization

Risk attitudes and informal employment in a developing economy

© 2012 Bennett et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License(http://creativecommons.org/licenses/by/2.0),which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.We model an urban labour market in a developing economy, incorporating workers’ risk attitudes. Trade-offs between risk aversion and ability determine worker allocation across formal and informal wage employment, and voluntary and involuntary self employment. Greater risk of informal wage non-payment can raise or lower informal wage employment, depending on the source of risk. Informal wage employment can be reduced by increasing detection efforts or by strengthening contract enforcement for informal wage payment. As the average ability of workers rises, informal wage employment first rises, then falls. Greater demand for formal production may lead to more involuntary self employment

Korea-science education and libraries computerization project

노트 : This document has a restricted distribution and may be used by recipients only in the performance of their official duties. Its contents may not otherwise be disclosed without World Bank authorization

Korea-vocational education project

노트 : This document has a restricted distribution and may be used by recipients only in the performance of their official duties. Its contents may not otherwise be disclosed without World Bank authorization