ABSTRACT
Today clinicians may diagnose hundreds of people with coronavirus disease 2019 (COVID-19). We report the case of a child with asthma who sought care for COVID-19 symptoms whose condition did not improve despite appropriate treatment for asthma, pneumonia and COVID-19. Further examination revealed a surprising underlying disease. It is important to consider that in pandemics such as COVID-19, because all attention is paid to the disease, underlying hidden causes may be neglected.
ABSTRACT
Owing to its severe hydrophobicity, graphene (G) as on dispersed in a fluid usually deposits therein after a short interval of time. Understanding the G-behavior and the factors affecting its deposition could pave a way for creating a substantially stable nanofluid (NF). In this work, a novel method of stabilizing a G-NF is described with selective examples. The results can be extended to develop the science and technology of G-NFs in general. Electrohydrodynamic forces are used as a controlling factor in the presence of magnetic nanoparticles (MNPs). Contrary to common chemical methods employed for preparing G-NFs, which depend on establishing bonds between the components, the physical method introduced in this article could be used as a novel approach not only to dispersing G in a fluid carrier but also to resolve the common problems originating from utilizing such chemical methods as increasing thermal resistance through adding various types of surfactants. The effects of various factors on the stability of the G-NFs are described. By increasing 50%, 100% and 170% of G, the G sitting rate increased by 43%, 82%, and 109%, respectively. With the addition of one, two and three layers to a G-monolayer, the G sitting rate grew by 77%, 153%, and 263%, respectively. Further, the G-behavior in the presence of MNPs and varied intensive electric fields were studied to optimize an electric field that could stabilize a single-layer G sheet in aqueous NFs. Adding MNPs promptly stabilizes a water/ethylene glycol/G NF in an applied electric field of 0.05 V/Å.
ABSTRACT
A unique tunable microwave resonator with a pair of half-rings is introduced and validated by experimental data. The capacitive gap between the overlapping areas can be controlled accurately using a magnetic actuator for tunability. The design geometry is scalable to cover different bands of electromagnetic spectrum. Transmission characteristics of the resonators have been modeled using finite-element analysis and have been measured. The experimental results indicate the resonant frequency can be controlled with a resolution of a few MHz in a tuning range of 38%. The resonator exhibits sharp transmission dips within the tuning range with measured quality factors larger than 2500.