Suppression of low-frequency ultrasound broadband vibration using star-shaped single-phase metamaterials

In order to suppress the low-frequency ultrasound vibration in the broadband range of 20 k Hz—100 k Hz,this paper proposes and discusses an acoustic metamaterial with low-frequency ultrasound vibration attenuation properties,which is configured by hybrid arc and sharp-angle convergent star-shaped lattices.The effect of the dispersion relation and the bandgap characteristic for the scatterers in star-shaped are simulated and analyzed.The target bandgap width is extended by optimizing the geometry parameters of arc and sharp-angle convergent lattices.The proposed metamaterial configured by optimized hybrid lattices exhibits remarkable broad bandgap characteristics by bandgap complementarity,and the simulation results verify a 99%vibration attenuation amplitude can be obtained in the frequency of20 k Hz—100 k Hz.After the fabrication of the proposed hybrid configurational star-shaped metamaterial by 3D printing technique,the transmission loss experiments are performed,and the experimental results indicate that the fabricated metamaterial has the characteristics of broadband vibration attenuation and an amplitude greater than 85%attenuation for the target frequency.These results demonstrate that the hybrid configurational star-shaped metamaterials can effectively widen the bandgap and realize high efficiency attenuation,which has capability for the vibration attenuation in the application of highprecise equipment.

Effect of Occupational Extremely Low-Frequency Electromagnetic Field Exposure on the Thyroid Gland of Workers:A Prospective Study

Objective:The aim of this study was to investigate the biological effects of occupational extremely low-frequency electromagnetic field(ELF-EMF)exposure on the thyroid gland.Methods:We conducted a prospective analysis of 85 workers(exposure group)exposed to an ELF-EMF(100μT,10-100 Hz)produced by the electromagnetic aircraft launch system and followed up on thyroid function indices,immunological indices,and color Doppler images for 3 years.Additionally,116 healthy volunteers were randomly selected as controls(control group),the thyroid function of whom was compared to the exposure group.Results:No significant difference was observed in thyroid function between the exposure and control groups.During the follow-up of the exposure group,the serum free triiodothyronine(FT3)level was found to slowly decrease and free thyroxine(FT4)level slowly increase with increasing exposure time.However,no significant difference was found in thyroid-stimulating hormone(TSH)over the three years,and no significant difference was observed in the FT3,FT4 and TSH levels between different exposure subgroups.Furthermore,no significant changes were observed in thyroid autoantibody levels and ultrasound images between subgroups or over time.Conclusion:Long-term exposure to ELF-EMF may promote thyroid secretion of T4 and inhibit deiodination of T4 to T3.ELF-EMF has no significant effect on thyroid immune function and morphology.

Topical Delivery of Modified Da-Cheng-Qi Decoction(加味大承气汤) Using Low-Frequency Ultrasound Sonophoresis for Refractory Metastatic Malignant Bowel Obstruction:An Open-Label Single-Arm Clinical Trial

Objective:To evaluate the efficacy and safety of topical delivery of modified Da-Cheng-Qi Decoction(加味大承气汤,MDCQD)by low-frequency ultrasound sonophoresis(LFUS)in patients with refractory metastatic malignant bowel obstruction(MBO)using an objective performance criteria(OPC)design.Methods:Fifty patients with refractory metastatic MBO were enrolled in this open-label single-arm clinical trial.Alongside fasting,gastrointestinal decompression,glycerol enema,intravenous nutrition and antisecretory therapy,a 50 g dose of MDCQD(prepared as a hydrogel)was applied through topical delivery at the site of abodminal pain or Tianshu(S 25)using LFUS for 30 min,twice daily for 5 consecutive days.The overall outcomes were the remission of intestinal obstruction,improvement on abdominal pain,abdominal distention,nausea and vomiting scores.Indicators of safety evaluation included liver and renal function as well as blood coagulation indicators.Results:Among 50 patients,5 patients(10%)showed complete remission of intestinal obstruction and 21 patients(42%)showed improvement of intestinal obstruction.The overall remission rate of bowel obstruction was 52%.The results of the symptom score,based on the severity and frequency of the episode,were as follows:26 patients(52%)showed improvment on symptom scores,20 patients(40%)did not respond to treatment,and 4 patients(8%)discontinued treatment due to intolerance.No serious adverse effects or abnormal changes on liver and renal functions or blood coagulation were observed.Conclusion:Topical delivery of MDCQD at 100 g/day using LFUS can improve the treatment response in patients with refractory metastatic MBO.