Mitigating disruptions, and scalability of radiation oncology physics work during the COVID-19 pandemic

PURPOSE: The COVID-19 pandemic has led to disorder in work and livelihood of a majority of the modern world. In this work, we review its major impacts on procedures and workflow of clinical physics tasks, and suggest alternate pathways to avoid major disruption or discontinuity of physics tasks in the context of small, medium, and large radiation oncology clinics. We also evaluate scalability of medical physics under the stress of social distancing . METHODS: Three models of facilities characterized by the number of clinical physicists, daily patient throughput, and equipment were identified for this purpose. For identical objectives of continuity of clinical operations, with constraints such as social distancing and unavailability of staff due to system strain, however with the possibility of remote operations, the performance of these models was investigated. General clinical tasks requiring on-site personnel presence or otherwise were evaluated to determine the scalability of the three models at this point in the course of disease spread within their surroundings. RESULTS: The clinical physics tasks within three models could be divided into two categories. The former, which requires individual presence, include safety-sensitive radiation delivery, high dose per fraction treatments, brachytherapy procedures, fulfilling state and nuclear regulatory commission\u27s requirements, etc. The latter, which can be handled through remote means, include dose planning, physics plan review and supervision of quality assurance, general troubleshooting, etc. CONCLUSION: At the current level of disease in the United States, all three models have sustained major system stress in continuing reduced operation. However, the small clinic model may not perform if either the current level of infections is maintained for long or staff becomes unavailable due to health issues. With abundance, and diversity of innovative resources, medium and large clinic models can sustain further for physics-related radiotherapy services

Nanostructured soft magnetic materials synthesized via mechanical alloying: a review

Soft magnetic materials are widely used in electrical and electronic industries due to their desirable electromagnetic features, i.e. relatively high electrical resistivity and low eddy current loss at high frequencies. From industrial point of view, once the size of grains is reduced to micron scale regimes, their performance is only narrowed to a few megahertz frequencies, due to their higher conductivity and domain wall resonance. Thus, one way to resolve this issue and utilize these materials at high frequency applications, is to reduce the size of grains from micron to sub or nanoscale before they are being compacted for sintering. In this aspect, however, several methods are employed to synthesize these nanoparticles, a mechanical alloying is found to be a proven route to produce a vast variety of materials with both non-equilibrium and equilibrium phases in a controlled size and shape of powder particles at desired tonnages. Mechanical alloying (MA) is a solid-state powder metallurgy route which involves a repeated action of fracturing and re-welding of powder particles in a high-energy ball mill. The final products characteristics are strongly dependent on the variable parameters of the process, i.e. milling time, ball-to-powder weight ratio, rotation speed, grinding media and milling atmosphere. Thus, this work reviews the key role of these parameters on the structure and magnetic behaviors of soft magnetic materials. Eventually, the mechanism of mechanical alloying and effect of diffusivity are also highlighted

Fabrication of spherical cofe2o4 nanoparticles with a sol-gel and hydrothermal method and their magnetorheological characteristics

CoFe2O4 nanoparticles are synthesized through sol-gel and facile hydrothermal methods, and their magnetorheological (MR) characteristics are evaluated. X-ray diffraction results indicate the formation of single phase CoFe2O4 after the prepared samples were sintered at 550 degrees C for 2 h, which was further confirmed by DSC, TG and FT-IR analysis. TEM results exhibit a narrow particle size distribution in the range of 5-40 nm with an average size of 21 nm for the samples prepared via the hydrothermal method. On the other hand, the particle size distribution was in the range of 15-120 nm and an average size of 42 nm was obtained via the sol-gel method. To prepare an MR fluid, CoFe2O4 nanoparticles were added to a micron-sized soft magnetic carbonyl iron (CI)-based suspension and MR effects were measured via rotational tests under different magnetic field strengths. The results reveal that the CoFe2O4-CI-based MR fluids present a higher yield stress with an enhanced MR effect compared to the CI-based MR fluid due to increased magnetic properties. This suggests that the CoFe2O4 nanoparticles fill the cavities of micron-sized CI particles and form chain-like structures, which orient in the direction of the applied magnetic field. On the other hand, depending on the employed synthetic route, the obtained results display slightly higher stress behaviors in the samples prepared via the hydrothermal method. The sedimentation ratio was also evaluated to further confirm the effects of the nanoparticle additive

Laser welding of nickel-titanium (NiTi) shape memory alloys

Nickel-titanium (NiTi) shape memory alloys (SMAs) with outstanding shape memory and superelasticity effects are interesting candidates for a multitude of applications ranging from small-scale structures, such as microsensors and stents, to large-scale components used in aviation and automotive industries. After a mechanical deformation, SMAs can resume their initial shape which makes them an ideal candidate material to be used in smart components for various applications. A practical method for joining similar and dissimilar NiTi SMAs is laser welding. However, the thermal effect associated with the laser welding procedure influences the transformation temperature of the welded parts that will significantly impact their super elasticity and/or shape memory effect characteristics. This chapter deals with the microstructural, metallurgical, and mechanical investigations of the laser welding process as well as suggesting effective methods to improve the functionality of the welded parts of NiTi alloys