Low-Intensity Focused Ultrasound Stimulation on Fingertip Can Evoke Fine Tactile Sensations and Different Local Hemodynamic Responses

Low-intensity focused ultrasound stimulation (LIFUS) has been proved effective in eliciting vibrotactile in addition to warm, cold and nociceptive pain when applied to human peripheral endings. However, if it can evoke fine tactile sensations has been rarely investigated by far despite the importance of fine tactile feedback in motor control. To explore this issue, 14 healthy volunteers were recruited in this study. A psychophysical experiment was firstly conducted to determine the appropriate range of pulse repetition frequency (PRF) and acoustic intensity (AI). Then, participants were asked to perceive and discriminate different tactile stimulations under LIFUS, so as to evaluate if multiple fine tactile sensations could be reliably elicited by modulating the PRF and AI. For objective assessment, the local blood perfusion volume (BPV) response beneath stimulated fingertip was recorded and characterized. Our results showed that four types of tactile sensations, including tapping, vibrating, electrical, and pressure could be reliably elicited by modulating the PRF and AI within a specific range, and there was a significant impact of PRF and AI on both participants’ tactile discrimination and amplitude features of BPV response. This study would facilitate the application of LIFUS to some human-machine interaction scenarios, and shed valuable insights on the physiological mechanisms of peripherally applied ultrasound stimulation

Template-free synthesis of helical hexagonal microtubes of indium nitride

Single crystalline indium nitride (InN) helical microtubes with a hexagonal hollow cross section have been synthesized in bulk quantities by nitriding indium oxide powder in ammonia flux. As-prepared InN microtubes grow along the [0001] direction with typical outer diameters of 1–3 μm, wall thickness of 50–80 nm and lengths up to hundreds of microns. The InN microtubes exhibit both right-handed and left-handed helicities with helical angles ranging from zero to about 30°. Variation of helicity can be observed in a single tube. A number of observations demonstrate that the growth of the tubular structure occurs by the spiraling of the warped InN nanobelts. Photoluminescence spectrum of the microtubes presents a strong emission peak centered at 700 nm at room temperature

Poisoning Effects of H₂S, CS₂, and COS on Hydrogen Oxidation Reaction over Pt/C Catalysts

Hydrogen used in proton exchange membrane fuel cells (PEMFCs) mainly originates from refinery resources in which inevitable S-containing impurities possibly reduce the fuel cell life. Herein, the poisonous influence of trace impurities of H2S, carbon disulfide (CS2), and carbonyl sulfide (COS) on the performance of Pt/C catalysts in hydrogen oxidation reaction (HOR) is investigated by a combination of electrochemical measurements, structural characterization, and DFT calculations. Rotating disk electrode (RDE) half-cell electrochemical experiments were used to determine the impact of H2S, CS2, and COS on the HOR activity and the recovery capability of a commercial Pt/C catalyst. The experimental results indicate that CS2 even poses a more severe threat to the HOR activity than H2S, while COS poses a weaker threat than H2S. Moreover, all of H2S, CS2, and COS have a deteriorative impact on the regeneration of Pt/C catalysts. The theoretical calculation results reveal that CS2 and COS can decrease the activity of HOR by decreasing the d-band center of Pt atoms except for occupying the active sites of Pt, while H2S deactivates the catalyst solely by occupying the active sites. Based on the analysis, the presence of trace CS2 and COS, as well as H2S, will result in the serious degeneration of the Pt/C catalysts. These results provide insights into the deactivation mechanism of Pt-based catalysts and are significant for the practical applications of PEMFCs