PURPOSE The integration of a low field biplanar magnetic resonance (MR) imager and linear accelerator (linac) causes magnetic interference at the linac due to the MR fringe fields. In order to eliminate this interference, passive and active magnetic shielding designs are investigated. METHODS The optimized design of passive magnetic shielding was performed using the finite element method. The...

F or a shielded cable, an approximate relationship valid from few kHz up to the first cable resonance can be derived from its Transfer Impedance (Zt ) allowing to predict the cable shielding factor. This Cable Shielding factor, as a figure of merit, is often preferred by engineers dealing with product specifications and early design. Being not necessarily EMC specialists, they can relate it dir...

An extensive study of 13C and “B shielding values of icosahedral heteroatom boranes is described. Shielding effects on polyhedral atoms due to variations (a) in directly bonded exopolyhedral groups, (b) in ortho cage groups, (c) in meta cage groups, and (d) in para cage groups are outlined. A linear relationship between ‘“C and llB shielding values of isoelectronic and isostructural icosahedral...

Introduction: In radiation therapy centers across Iran, protection of normal tissues is usually accomplished by either Cerrobend or lead block shielding. In this study, the influence of these two shielding methods on central axis dose distribution of photon beam a Cobalt unit was investigated in clinical conditions. Materials and Methods: All measurements were performed for 60Co γ-ray beams an...

Background: Monte Carlo simulations play a vital role in the calculation of the necessary shielding both for neutrons and photons. Advanced and simple shielding materials against neutron and gamma rays were compared by simulation using the MCNB4B Monte Carlo code. The simulations were carried out for the three common neutron sources, namely the 252Cf, the 241Am/Be and the DD neutron generator w...

Background: Polymer composites when reinforced with heavy metals in the form of micro/nano particles are efficient gamma- and X-ray shielding materials providing such advantageous features as cost-effectiveness, light-weight factor, flexibility, non-toxicity, conformability over conventional shields. Materials and Methods: In this paper the influence of weight percentages and particle sizes of ...

We have measured the magnetic susceptibility of the ironsulfur proteins, ferredoxin from both spinach and parsley, and high potential protein from Chromafium in the oxidized and reduced state. Over the temperature range 1.4-201” K the oxidized plant proteins are either totally diamagnetic or exhibit trace paramagnetism. The reduced proteins are strongly pararnagnetic with a susceptibility appro...

Crack tip shielding phenomena, whereby the "effective crack-driving force" actually experienced at the crack tip is locally reduced, are examined with reference to fatigue crack propagation behavior in metals, composites and ceramics. Sources of shielding are briefly described in terms of mechanisms relying on the production of elastically constrained zones which envelop the crack (zone shieldi...

Effective radiation shielding is imperative to safe operation of modern Medical Cyclotrons producing large activities of short-lived radioisotopes on a commercial basis. Like the containment shielding of Medical Linear Accelerators (1), the optimal shielding design of Medical Cyclotrons demands a careful balance between the radiological, economical and often the sociopolitical factors. One is r...