نتایج جستجو برای: chemical shielding

تعداد نتایج: 386370  

2011
Chen-Ching Ting Chien-Chih Chen

This article presents some new experimental data for study the shielding effect of electromagnetic wave. The frequencies of electromagnetic wave are mainly focused on emission of daily electrical equipments, which are normally called “low frequency electromagnetic waves”. In this work, a water pump with maximum magnetic field intensity of ca. 2300 mG was applied as emission source of the electr...

2013
Ekkasit Tharavichitkul Somsak Wanwilairat Anirut Watcharawipha Damrongsak Tippanya Rungtip Jayasvasti Somvilai Chakrabandhu Pitchayaponne Klunklin Wimrak Onchan Razvan Galalae Imjai Chitapanarux

PURPOSE To evaluate the cumulative dose at point A for three and four centimeters central shielding. MATERIAL AND METHODS The plans of external beam radiotherapy plus conventional intracavitary brachytherapy were performed. Three or four centimeters central shieldings (after 44 Gy) were applied to the standard whole pelvis irradiation. Additional intracavitary brachytherapy 4 × 7 Gy at point ...

Journal: :journal of physical & theoretical chemistry 2005
m. monajemi m.a seyed sajjadi r. sayyadi g. ghassemi

structural and magnetic properties of purine and pyrimidine nucleotides (cmp, ump, dtmp, amp, gmp, imp) were studied at different levels of ab initio molecular orbital theory. these calculations were performed at the hartree-fock level and density functional b3lyp methods. geometries were fully optimized by following cs symmetry restrictions. the standard 6-31g** basis set which includes polari...

ژورنال: سلامت کار ایران 2016

Background and aims: X-band with 8-12.5 frequencies range has various applications such as air control traffic, navy communication and etc. Uncontrolled exposure with microwave can lead to adverse effect on workers. Application of the shielding is superior control for prevention of microwave exposure, now. This study investigated the effect of dispersion on shielding effectiveness improvement a...

Introduction: Development of higher energy modalities such as positron emission tomography/computed tomography (PET/CT), has led to more complex shielding problems. This is due to several factors, such as the radiopharmaceutical relatively high-administered activity, high patient throughput, and high energies of 511 kilo-electron volt (keV) positron annihilation photon...

Journal: :iranian journal of radiation research 0
f. bouzarjomehri shahid sadoughi university of medical sciences, yazd, iran m. kiani tabriz university of medical sciences, medical physics, tabriz, iran a.r. farajollahi tabriz university of medical sciences, medical physics, tabriz, iran

background: the shielding methods in radiotherapy due to delivering an accurate radiation dose to cancer tissues and avoiding unnecessary dose to normal tissues are very important. these methods include lead standard blocks, individual molding and multi leaf collimator (mlc). the mlc method is not still common in iran radiotherapy centers. individual molding is better than the lead block shield...

2001
R. P. Drake R. S. Marjoribanks

The oscillation of electrons, in a sufficiently intense pump wave, frustrates Debye shielding in the direction of the oscillation. One finds that such oscillating electrons cannot shield charge fluctuations over distances smaller than the distance they sample in a plasma period. One consequence is that the frequency of ion waves can be increased from the ion acoustic frequency to the ion plasma...

Journal: :The journal of physical chemistry. A 2006
Mark Strohmeier Dewey H Barich David M Grant Joel S Miller Ronald J Pugmire Jack Simons

The principal (13)C chemical-shift values for the pi-[TCNE](2)(2-) dimer anion within an array of counterions have been measured to understand better the electronic structure of these atypical chemical species in several related TCNE-based structures. The structure of pi-[TCNE](2)(2-) is unusual as it contains two very long C-C bond lengths (ca. 2.9 Angstroms) between the two monomeric units an...

2017
Shuxu Zhang Shaohui Jiang Quanbin Zhang Shengqu Lin Ruihao Wang Xiang Zhou Guoqian Zhang Huaiyu Lei Hui Yu

With the purpose of reducing stray radiation dose (SRD) in out-of-field region (OFR) during radiotherapy with 6 MV intensity-modulated radiation therapy (IMRT), a body-shielding device (BSD) was prepared according to the measurements obtained in experimental testing. In experimental testing, optimal shielding conditions, such as 1 mm lead, 2 mm lead, and 1 mm lead plus 10 mm bolus, were investi...

2013
Kazuaki Kosako Koji Oishi Takashi Nakamura Yoshiaki Kiyanagi

When considering the space limit of high energy LINAC facility in a hospital, the design of shielding wall is strongly required to optimize the wall thickness. Shielding wall usually consists of concrete, and iron plate is sometimes added in concrete to decrease the wall thickness. We investigated the optimum design of the shielding wall in medical LINAC facility by simulation. The calculations...

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