We applied external high pressure to ambient water in liquid-phase laser ablation. As a result, it was found that the maximum volume V max of a cavitation bubble induced by laser ablation satisfied a scaling law of V max / P À1 ext with P ext being the pressure applied to water. The effect of the pressurization was also observed in the shape of the second bubble induced by the collapse of the first cavitation bubble. These experimental results indicate that the dynamics of a cavitation bubble induced by liquid-phase laser ablation is controlled by the external pressure. #
The solution of the conventional Rayleigh–Plesset equation did not agree with the experimental results on the temporal variations of the sizes of cavitation bubbles produced by laser ablation in water. In this work, we modified the conventional Rayleigh–Plesset theory in the following two points to reproduce the experimental observation theoretically. One was to introduce the effect of the contact angle among the water, the cavitation bubble, and the ablation target. The other was to treat the surface tension and the kinematic viscosity coefficient of water as additional adjusting parameters to fit the theoretical result with the experimental observation. The latter modification was effective especially for laser ablation in the pressurized water. Better agreement between the theoretical and the experimental results was realized with the help of these modifications, but anomalous thermodynamic parameters were necessary to obtain the best fitting. We evaluated the pressures and the temperatures inside the cavitation bubbles.
BackgroundVariants in the type IV collagen gene (COL4A1/2) cause early-onset cerebrovascular diseases. Most individuals are diagnosed postnatally, and the prenatal features of individuals with COL4A1/2 variants remain unclear.MethodsWe examined COL4A1/2 in 218 individuals with suspected COL4A1/2-related brain defects. Among those arising from COL4A1/2 variants, we focused on individuals showing prenatal abnormal ultrasound findings and validated their prenatal and postnatal clinical features in detail.ResultsPathogenic COL4A1/2 variants were detected in 56 individuals (n=56/218, 25.7%) showing porencephaly (n=29), schizencephaly (n=12) and others (n=15). Thirty-four variants occurred de novo (n=34/56, 60.7%). Foetal information was available in 47 of 56 individuals, 32 of whom (n=32/47, 68.1%) had one or more foetal abnormalities. The median gestational age at the detection of initial prenatal abnormal features was 31 weeks of gestation. Only 14 individuals had specific prenatal findings that were strongly suggestive of features associated with COL4A1/2 variants. Foetal ventriculomegaly was the most common initial feature (n=20/32, 62.5%). Posterior fossa abnormalities, including Dandy-Walker malformation, were observed prenatally in four individuals. Regarding extrabrain features, foetal growth restriction was present in 16 individuals, including eight individuals with comorbid ventriculomegaly.ConclusionsPrenatal observation of ventriculomegaly with comorbid foetal growth restriction should prompt a thorough ultrasound examination and COL4A1/2 gene testing should be considered when pathogenic variants are strongly suspected.
A high-temperature superconducting (HTS) power cable demonstration project was started in 2007 to evaluate the cable's performance, stability, and reliability. This project aims to operate a 66-kV 200-MVA HTS cable system in a real power grid of the Tokyo Electric Power Company. A 240-m-long HTS cable was successfully installed, and other system components, such as a cable-to-cable joint, terminations, and a cooling system, were also constructed at the Asahi Substation in Yokohama. After several completion and performance tests on the system, the HTS cable was connected to a real grid from October 29, 2012 to December 25, 2013. The in-grid operation had continued for more than one year without any accidental interruption of the operation or troubles of this system. The temperatures and pressures of liquid nitrogen flowing in the HTS cable were controlled to within the target values. After the in-grid operation, the critical current of the HTS cable was measured, and it was confirmed that there was no degradation compared with the initial results. In addition, no partial discharge was observed in periodical measurements. It is concluded that the HTS cable system has good performance and stability for long-term in-grid operation.
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