Magnetic resonance-guided focused ultrasound for essential tremor:a prospective,single center,single-arm study

The safety and effectiveness of magnetic resonance-guided focused ultrasound thalamotomy has been broadly established and validated for the treatment of essential tremor.In 2018,the first magnetic resonance-guided focused ultrasound system in Chinese mainland was installed at the First Medical Center of the PLA General Hospital.This prospective,single center,open-label,single-arm study was part of a worldwide prospective multicenter clinical trial(ClinicalTrials.gov Identifier:NCT03253991)conducted to confirm the safety and efficacy of magnetic resonance-guided focused ultrasound for treating essential tremor in the local population.From 2019 to 2020,10 patients with medication refractory essential tremor were recruited into this open-label,single arm study.The treatment efficacy was determined using the Clinical Rating Scale for Tremor.Safety was evaluated according to the incidence and severity of adverse events.All of the subjects underwent a unilateral thalamotomy targeting the ventral intermediate nucleus.At the baseline assessment,the estimated marginal mean of the Clinical Rating Scale for Tremor total score was 58.3±3.6,and this improved after treatment to 23.1±6.4 at a 12-month follow-up assessment.A total of 50 adverse events were recorded,and 2 were defined as serious.The most common intraoperative adverse events were nausea and headache.The most frequent postoperative adverse events were paresthesia and equilibrium disorder.Most of the adverse events were mild and usually disappeared within a few days.Our findings suggest that magnetic resonance-guided focused ultrasound for the treatment of essential tremor is effective,with a good safety profile,for patients in Chinese mainland.

Effect of grain size on gas bubble evolution in nuclear fuel:Phase-field investigations

Numerous irradiation-induced gas bubbles are created in the nuclear fuel during irradiation, leading to the change of microstructure and the degradation of mechanical and thermal properties. The grain size of fuel is one of the important factors affecting bubble evolution. In current study, we first predict the thermodynamic behaviors of point defects as well as the interplay between vacancy and gas atom in both UO_(2) and U_(3)Si_(2) according to ab initio approach. Then, we establish the irradiation-induced bubble phase-field model to investigate the formation and evolution of intra-and inter-granular gas bubbles. The effects of fission rate and temperature on the evolutions of bubble morphologies in UO_(2) and U_(3)Si_(2) have been revealed. Especially, a comparison of porosities under different grain sizes is examined and analyzed. To understand the thermal conductivity as functions of grain size and porosity, the heat transfer capability of U_(3)Si_(2) is evaluated.

Modeling of Mesoscale Creep Behaviors and Macroscale Creep Responses of Composite Fuels Under Irradiation Conditions

A finite-strain homogenization creep model for composite fuels under irradiation conditions is developed and verified,with the irradiation creep strains of the fuel particles and matrix correlated to the macroscale creep responses,excluding the contributions of volumetric strain induced by the irradiation swelling deformations of fuel particles.A finite element(FE)modeling method for uniaxial tensile creep tests is established with the irradiation effects of nuclear materials taken into account.The proposed models and simulation strategy are numerically implemented to a kind of composite nuclear fuel,and the predicted mesoscale creep behaviors and the macroscale creep responses are investigated.The research results indicate that:(1)the macroscale creep responses and the mesoscale stress and strain fields are all greatly affected by the irradiation swelling of fuel particles,owing to the strengthened mechanical interactions between the fuel particles and the matrix.(2)The effective creep rates for a certain case are approximately two constants before and after the critical fission density,which results from the accelerated fission gas swelling after fuel grain recrystallization,and the effects of macroscale tensile stress will be more enhanced at higher temperatures.(3)The macroscale creep contributions from the fuel particles and matrix depend mainly on the current volume fractions varying with fission density.(4)As a function of the macroscale stress,temperature,initial particle volume fraction and particle fission rate,a multi-variable mathematical model for effective creep rates is fitted out for the considered composite fuels,which matches well with the FE predictions.This study supplies important theoretical models and research methods for the multi-scale creep behaviors of various composite fuels and provides a basis for simulation of the thermal–mechanical behavior in related composite fuel elements and assemblies.