Influence of mode conversions in the skull on transcranial focused ultrasound and temperature fields utilizing the wave field separation method： A numerical study

Transcranial focused ultrasound is a booming noninvasive therapy for brain stimuli. The Kelvin–Voigt equations are employed to calculate the sound field created by focusing a 256-element planar phased array through a monkey skull with the time-reversal method. Mode conversions between compressional and shear waves exist in the skull. Therefore, the wave field separation method is introduced to calculate the contributions of the two waves to the acoustic intensity and the heat source, respectively. The Pennes equation is used to depict the temperature field induced by ultrasound. Five computational models with the same incident angle of 0？and different distances from the focus for the skull and three computational models at different incident angles and the same distance from the focus for the skull are studied. Numerical results indicate that for all computational models, the acoustic intensity at the focus with mode conversions is 12.05%less than that without mode conversions on average. For the temperature rise, this percentage is 12.02%. Besides, an underestimation of both the acoustic intensity and the temperature rise in the skull tends to occur if mode conversions are ignored. However, if the incident angle exceeds 30？, the rules of the over-and under-estimation may be reversed. Moreover,shear waves contribute 20.54% of the acoustic intensity and 20.74% of the temperature rise in the skull on average for all computational models. The percentage of the temperature rise in the skull from shear waves declines with the increase of the duration of the ultrasound.

Mn-Co oxide decorated on Cu nanowires as efficient catalysts for catalytic oxidation of toluene

Mn-Co mixed oxides were electrodeposited on Cu nanowires generated on Cu foam(CF)and used for effectively catalytic oxidation of toluene.The physical and chemical properties of the prepared catalysts were characterized by SEM,TEM,XRD,H_(2)-TPR,O_(2)-TPD and XPS.It is found that the Mn-Co mixed metal oxides were uniformly coated on the Cu nanowires by the electrochemical method,whose Mn/Co ratio can be tuned by adjusting the molar ratio of Mn/Co in the initial solution for the electrodeposition.The intimate contact between Mn and Co nanocrystals was found by HRTEM,which is important for realizing synergetic effects on improving catalytic activity.Meanwhile,the formation of the active surface oxygen species and the increase of the active species of Mn^(4+)and Co^(3+)were considered to make significant contribution to the catalytic oxidation of toluene.Mn-Co mixed metal oxide catalysts exhibited higher performance than the single metal oxide,and especially 0.10Mn-0.01Co/CF catalyst with the Mn/Co molar ratio of 10:1 in the initial solution for the electrodeposition achieved the highest catalytic activity with a low toluene conversion temperature(T_(90%))of 251℃,and displayed excellent catalytic stability even in the presence of water vapor.It is expected that such a simply-electrodeposited mixed metal oxides based catalysts could be applied for the oxidation of volatile organic compounds(VOCs)in a practical process.

Facile synthesis of nitrogen-doped graphene aerogels functionalized with chitosan for supercapacitors with excellent electrochemical performance

Three-dimensional porous nitrogen-doped graphene aerogels（NGAs） were synthesized by using graphene oxide（GO） and chitosan via a self-assembly process by a rapid method.The morphology and structure of the as-prepared aerogels were characterized.The results showed that NGAs possesed the hierarchical pores with the wide size distribution ranging from mesopores to macropores.The NGAs carbonized at different temperature all showed excellent electrochemical performance in 6 mol/L KOH electrolyte and the electrochemical performance of the NGA-900 was the best.When working as a supercapacitor electrode,NGA-900 exhibited a high specific capacitance（244.4 F/g at a current density of 0.2 A/g）,superior rate capability（51.0% capacity retention） and excellent cycling life（96.2% capacitance retained after 5000 cycles）.