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The dynamics of a bubble in a pressure gradient is investigated experimentally and numerically with particular emphasis on the behavior at reentrant jet impact and break through the opposite side of the bubble with corresponding energy loss and vorticity generation. High speed photography observations of a bubble generated by electric spark energy deposit in a low ambient pressure tank are coupled with wavelet based Optical Flow Velocimetry (wOFV) and Boundary Element Method (BEM) numerical analysis to examine the flow field resulting from the reentrant jet formation and break through. We study, as an illustration, the effects of the constant pressure gradient due to gravity on the bubble dynamics. Energy losses between the first and second cycle are measured for the bubbles generated under various conditions characterized by a non-dimensional pressure gradient parameter, and the corresponding measured energy loss is used in the numerical simulations. Good correspondence is seen between the image analysis, the wOFV computations, and the BEM results and insight is gained on the involved physics., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Bryan Schmidt reports administrative support was provided by Naval Surface Warfare Center Carderock Division. Georges Chahine reports a relationship with Naval Surface Warfare Center Indian Head Explosive Ordnance Disposal Technology Division that includes: funding grants., (Copyright © 2023 Dynaflow, inc. Published by Elsevier B.V. All rights reserved.)

Background: Adrenoleukodystrophy (ALD) is an X-linked peroxisomal disorder caused by mutations in the ABCD1 gene. The clinical manifestations of ALD vary widely with some patients presenting with adrenomyeloneuropathy (AMN) that resembles the phenotype of hereditary spastic paraplegia (HSP). The aim of this study is to investigate the frequency, spectrum, and clinical features of ABCD1 mutations in Taiwanese patients with HSP phenotype., Methods: Mutational analysis of the ABCD1 gene was performed in 230 unrelated Taiwanese patients with clinically suspected HSP by targeted resequencing. Clinical, electrophysiological, and neuroimaging features of the patients carrying an ABCD1 pathogenic mutation were characterized., Results: Ten different ABCD1 mutations were identified in eleven patients, including two novel mutations (p.Q177Pfs*17 and p.Y357*) and eight ever reported in ALD cases of other ethnicities. All patients were male and exhibited slowly progressive spastic paraparesis with onset ages ranging from 21 to 50 years. Most of them had additional non-motor symptoms, including autonomic dysfunction in nine patients, sensory deficits in seven, premature baldness in seven, skin hyperpigmentation in five, psychiatric symptoms in one and cerebellar ataxia in one. Seven of the ten patients who ever received nerve conduction studies showed axonal polyneuropathy. Magnetic resonance imaging (MRI) revealed diffuse spinal cord atrophy in seven patients, cerebral white matter hyperintensity in one patient, and cerebellar involvement in one patient., Conclusions: ABCD1 mutations account for 4.8% (11/230) of the cases with HSP phenotype in Taiwan. This study highlights the importance to consider ABCD1 mutations in patients with clinically suspected HSP of unknown genetic causes., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Introduction: Mutations in the PUM1 gene were recently identified to cause spinocerebellar ataxia type 47 (SCA47). However, their role in cerebellar ataxia in various populations remains elusive. The aim of this study was to elucidate the frequency and spectrum of PUM1 mutations in a cohort of Taiwanese patients with molecularly undetermined cerebellar ataxia., Methods: Mutational analyses of PUM1 were performed by Sanger sequencing in a cohort of 248 unrelated patients with cerebellar ataxia of unknown cause, including 108 with autosomal-dominantly inherited cerebellar ataxia, 45 with autosomal-recessively inherited cerebellar ataxia, and 95 with apparently sporadic cerebellar ataxia. Among them, the genetic causes of ataxia remained unknown after excluding mutations responsible for SCA1, 2, 3, 6, 7, 8, 10, 12, 17, 19/22, 23, 26, 27, 28, 31, 35, 36, dentatorubral-pallidoluysian atrophy and Friedreich's ataxia., Results: Two heterozygous missense PUM1 variants were identified in two patients with apparently sporadic cerebellar ataxia, including a known disease-causing mutation (p.R1139W) and a variant of uncertain significance (p.K151R). The patient carrying the p.R1139W mutation had a slowly progressive, relatively pure cerebellar ataxia, presenting with gait unsteadiness, limb dysmetria, ataxic dysarthria and saccadic pursuit., Conclusion: Our findings support the pathogenic role of PUM1 mutations in cerebellar ataxia and emphasize the importance of considering PUM1 mutations as a possible etiology of cerebellar ataxia., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The dynamics of a bubble cloud excited by a sinusoidal pressure field near a rigid wall is studied using a novel Eulerian/Lagrangian two-phase flow model. The effects of key parameters such as the amplitude and frequency of the excitation pressure, the cloud and bubble sizes, the void fraction, and the initial standoff distance on the bubbles' collective behavior and the resulting pressure loads on the nearby wall are investigated. The study shows that nonlinear bubble cloud dynamics becomes more pronounced and results in higher pressure loading at the wall as the excitation pressure amplitude increases. The strongest collective bubble behavior occurs at a preferred resonance frequency. At this resonance frequency, pressure peaks orders of magnitudes higher than the excitation pressure result from the bubble interaction when the amplitude of the pressure excitation is high. The numerically obtained resonance frequency is significantly different from the reported natural frequency of a spherical cloud derived from linear theory, which assumes small amplitude oscillations in an unbounded medium. At high amplitudes of the excitation, the resonance frequency decreases almost linearly with the ratio of excitation pressure amplitude to ambient pressure until the ratio is larger than one., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Surface cleaning using cavitation bubble dynamics is investigated numerically through modeling of bubble dynamics, dirt particle motion, and fluid material interaction. Three fluid dynamics models; a potential flow model, a viscous model, and a compressible model, are used to describe the flow field generated by the bubble all showing the strong effects bubble explosive growth and collapse have on a dirt particle and on a layer of material to remove. Bubble deformation and reentrant jet formation are seen to be responsible for generating concentrated pressures, shear, and lift forces on the dirt particle and high impulsive loads on a layer of material to remove. Bubble explosive growth is also an important mechanism for removal of dirt particles, since strong suction forces in addition to shear are generated around the explosively growing bubble and can exert strong forces lifting the particles from the surface to clean and sucking them toward the bubble. To model material failure and removal, a finite element structure code is used and enables simulation of full fluid-structure interaction and investigation of the effects of various parameters. High impulsive pressures are generated during bubble collapse due to the impact of the bubble reentrant jet on the material surface and the subsequent collapse of the resulting toroidal bubble. Pits and material removal develop on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress or its ultimate strain. Cleaning depends on parameters such as the relative size between the bubble at its maximum volume and the particle size, the bubble standoff distance from the particle and from the material wall, and the excitation pressure field driving the bubble dynamics. These effects are discussed in this contribution., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Cavitating jet technologies (DynaJets®) were investigated as a means of disinfection of gram-negative Escherichia coli, Klebsiellapneumoniae, Pseudomonas syringae, and Pseudomonas aeruginosa, and gram-positive Bacillus subtilis. The hydrodynamic cavitating jets were found to be very effective in reducing the concentrations of all of these species. In general, the observed rates of disinfection of gram-negative species were higher than for gram-positive species. However, different gram-negative species also showed significant differences (P. syringae 6-log(10) reduction, P. aeruginosa 2-log(10) reduction) under the same conditions. Disinfection of E. coli repeatedly showed five orders of magnitude reduction in concentration within 45-60-min at low nozzle pressure (2.1 bar). Optimization of nozzle design and operating pressures increased disinfection rates per input energy by several orders of magnitude. The power efficiencies of the hydrodynamic cavitating jets were found to be 10-100 times greater than comparable ultrasonic systems., (Copyright © 2011 Elsevier B.V. All rights reserved.)