Detailed investigation of thermal convection in a liquid metal under a horizontal magnetic field: Suppression of oscillatory flow observed by velocity profiles

Thermal convection experiments in a liquid gallium layer were carried out with various intensities of uniform horizontal magnetic fields. The gallium layer was in a rectangular vessel with a 4:1:1 length ratio (1 is the height), where the magnetic field is applied in the direction normal to the longest vertical wall. An ultrasonic velocity profiling method was used to visualize the spatiotemporal variations in the flow pattern, and the temperature fluctuations in the gallium layer were also monitored. The observed flow pattern without a magnetic field shows oscillating rolls with axes normal to the longest vertical wall of the vessel. The oscillatory motion of the flow pattern was suppressed when increasing the applied magnetic field. The flow behavior was characterized by the fluctuation amplitude of the oscillation and the frequency in the range of Rayleigh numbers from 9.3 x 10^[3] to 3.5 x 10^[5] and Chandrasekhar numbers 0-1900. The effect of the horizontal magnetic field on the flow pattern may be summarized into three regimes with increases in the magnetic intensity: (1) no effect of the magnetic field, (2) a decrease in the oscillation of the roll structure, and (3) a steady two-dimensional roll structure with no oscillation. These regimes may be explained as a result of an increase in the dominance of Lorentz forces over inertial forces. The power spectrum from the temperature time series showed the presence of a convective-inertial subrange above Rayleigh numbers of 7 x 10^[4], which suggests that turbulence has developed, and such a subrange was commonly observed above this Rayleigh number even with applied magnetic fields when the rolls oscillate

Structure of large-scale flows and their oscillation in the thermal convection of liquid gallium

This investigation observed large-scale flows in liquid gallium and the oscillation with Rayleigh-Bénard convection. An ultrasonic velocity profiling method was used to visualize the spatiotemporal flow pattern of the liquid gallium in a horizontally long rectangular vessel. Measuring the horizontal component of the flow velocity at several lines, an organized roll-like structure with four cells was observed in the 1 x 10^[4]-2 x 10-[5] range of Rayleigh numbers, and the rolls show clear oscillatory behavior. The long-term fluctuations in temperature observed in point measurements correspond to the oscillations of the organized roll structure. This flow structure can be interpreted as the continuous development of the oscillatory instability of two-dimensional roll convection that is theoretically investigated around the critical Rayleigh number. Both the velocity of the large-scale flows and the frequency of the oscillation increase proportional to the square root of the Rayleigh number. This indicates that the oscillation is closely related to the circulation of large-scale flow

A retrospective analysis of 30 patients with spontaneous spinal epidural hematoma

Background: Spontaneous spinal epidural hematoma (SSEH) is a rare disease. Despite numerous case reports, the clinical characteristics and prognosis of patients with SSEH in the contemporary aging population are unknown. The purpose of this study was to clarify the clinical characteristics, prognostic factors, and optimal management of SSEH. Methods: We retrospectively reviewed and analyzed patients with SSEH who were admitted to Shinshu University Hospital between July 2009 and October 2019. The modified Rankin Scale (mRS) was used to measure the degree of disability in patients with SSEH at discharge as a functional outcome and patients were classified accordingly. Clinical variables of patients with good (mRS 0–2) and poor (mRS > 2) outcomes were compared. Results: We identified 30 patients with SSEH (17 men and 13 women) aged 36–89 years (median age, 67 years). Twelve patients had hypertension. Surgical treatment was performed in 11 patients. The number of patients who had taken anticoagulants was higher in the poor outcome group than in the good outcome group (p = 0.01). The poor outcome group were older (p = 0.048), had a higher operation rate (p = 0.04) and longer lengths of hospitalization (p < 0.001) than the good outcome group. Anticoagulants were the only factor associated with poor outcome in the univariate analysis (odds ratio, 16 [1.45–176], p = 0.02). Conclusions: SSEH patients who had been taking anticoagulants had a worse functional outcome. Physicians should consider that SSEH patients who have been taking anticoagulants require timely management, including surgery

Ternary Complexes of pDNA, Neuron-Binding Peptide, and PEGylated Polyethyleneimine for Brain Delivery with Nano-Bubbles and Ultrasound

In brain-targeted delivery, the transport of drugs or genes across the blood−brain barrier (BBB) is a major obstacle. Recent reports found that focused ultrasound (FUS) with microbubbles enables transient BBB opening and improvement of drug or gene delivery. We previously developed nano-sized bubbles (NBs), which were prepared based on polyethylene glycol (PEG)-modified liposomes containing echo-contrast gas, and showed that our NBs with FUS could also induce BBB opening. The aim of this study was to enhance the efficiency of delivery of pDNA into neuronal cells following transportation across the BBB using neuron-binding peptides. This study used the RVG-R9 peptide, which is a chimeric peptide synthesized by peptides derived from rabies virus glycoprotein and nonamer arginine residues. The RVG peptide is known to interact specifically with the nicotinic acetylcholine receptor in neuronal cells. To enhance the stability of the RVG-R9/pDNA complex in vivo, PEGylated polyethyleneimine (PEG-PEI) was also used. The ternary complexes composed of RVG-R9, PEG-PEI, and pDNA could interact with mouse neuroblastoma cells and deliver pDNA into the cells. Furthermore, for the in vivo experiments using NBs and FUS, gene expression was observed in the FUS-exposed brain hemispheres. These results suggest that this systemic gene delivery system could be useful for gene delivery across the BBB