Influence of Incorporated Pt-Fe2O3 Core-Shell Nanoparticles on the Resistive Switching Characteristics of ZnO Thin Film.

The resistance-switching characteristics of metal oxides have attracted great interest for the non-volatile memory applications such as resistive random access memory. A basic resistive random access memory device has a metal/insulator/metal structure, and its memory effect is achieved by applying voltage to change the resistance of the insulating layer. One of the promising candidates for explaining the resistance-switching mechanism is the formation and rupture of nanoscale conductive filaments. However, this model has an issue that needs to be addressed: the wide distribution of switching voltage due to randomly formed filaments. Therefore, some researchers have reported a decrease in switching voltage distribution and an increase in switching stability by incorporating nanoparticles into the insulating layer. In this study, we investigated influence of incorporated Pt-Fe2O3 core-shell nanoparticles on the resistive switching characteristics of ZnO thin films. Devices were fabricated on SiO2 wafers. A 100-nm-thick Cr layer was used as the bottom electrode. A 50-nm-thick ZnO layer was deposited using the sputtering method, and Pt-Fe2O3 nanoparticles were deposited on it by the dip coating method. A 50-nm-thick ZnO layer was then deposited again. A top Cr electrode (size: 100 µm x 100 µm) was deposited using a shadow mask and sputtering system. All the devices showed bipolar resistance-switching behavior that is observed in Cr/ZnO/Cr structures. However, the on/off voltage was dramatically lowered by incorporating nanoparticles into the insulating layer when compared with that of the devices without nanoparticles. In addition, the switching stability of the devices was improved upon the incorporation of nanoparticles. On the basis of these results, we can conclude that Pt-Fe2O3 nanoparticles may be used to enhance the resistance switching properties of ZnO thin films by incorporating them into the films.

Resistive switching characteristics of the Cr/ZnO/Cr structure.

Resistive random access memory (ReRAM) with conductor-dielectric-conductor structures has attracted extensive attention for next generation nonvolatile memory devices. The resistive switching effect has been observed in various materials, such as metal oxides and chalcogenide oxides. From our findings, we advocate the resistive switching characteristics of zinc oxide thin film, due to its simple composition and ease of manipulation. In this study, we investigated the current-voltage (I-V) characteristics of the Cr/ZnO/Cr capacitor structure. The Cr electrode and ZnO thin film were deposited by radio frequency magnetron sputtering at room temperature. The top electrode layers were patterned by 100 microm x 100 microm. The fabricated devices of the Cr/ZnO/Cr structures exhibited bipolar switching behavior. In addition, using the Cr-coated AFM tip replaced with the top electrode enabled us to map the local current image and measure the current flow at each point. This gave us more information to verify the resistive switching mechanism of ZnO thin film.

Changes in the cutaneous silent period by paired stimulation.

OBJECTIVE: The cutaneous silent period (CSP) corresponds to the inhibition of motor neuronal activity that is induced by electrical cutaneous stimulation. This motor neuronal inhibition might be useful as a therapeutic strategy for modulating the excitability of motor neurons. Therefore, we investigated the CSP changes that can be observed using the paired-stimulation method. METHODS: Fifteen healthy adults were recruited. The digital cutaneous nerve of the right index finger was stimulated, and the CSP was recorded at the right thenar muscle. During the stimulation, contraction of the opposing right thumb and third finger was maintained at 20% of maximal voluntary contraction. A single stimulation was applied at the right index finger, and the duration and latency of the CSP (CSP1) was recorded. Paired electrical stimulations were then delivered with 60-, 80-, 100-, 120-, 140-, 160-, 180-, and 200-ms interstimulus intervals (ISI), and the latency and duration of a second CSP (CSP2) was measured and compared with that for the single stimulation. RESULTS: The CSP2 onset latencies were delayed in the 60-, 80-, and 100-ms ISI when compared to CSP1. CSP2 durations were shorter in the 60-, 80-, and 100-ms ISI. No significant differences in the latencies and durations between CSP1 and CSP2 were observed for ISI durations greater than 120 ms. CONCLUSIONS: We found that repetitive electrical stimulation changed the latency and duration of the CSP. These results suggest that the refractory period of the spinal inhibitory circuit in CSP is less than 100 ms.

Minimal electrical stimulation intensity and duration to elicit maximal cutaneous silent period in hand.

INTRODUCTION: The cutaneous silent period (CSP) is an interruption of electromyographic activity produced by a painful stimulation delivered in homotopic cutaneous territory. It may be useful in evaluating small afferent fibers. However, standardized parameters of stimulation still need to be carefully defined before using this technique in routine clinical application. In this study, we investigated the effects of stimulus intensity and duration on the CSP. METHODS: Twenty healthy adults were included. The digital cutaneous nerve of the right index finger was stimulated and the CSP was measured from the right thenar muscle. The voluntary contraction of thenar muscle was maintained at 50% of maximal voluntary contraction, and the digital cutaneous nerve was stimulated using 0.1, 0.2, 0.5, and 1.0 ms durations and, for each stimulus duration, intensities increasing from 30 to 80 mA in 10 mA steps. RESULTS: CSP duration first increased with increasing stimulus intensity and duration and then reached a plateau. Maximal CSP duration ranged from 34.7 to 71.0 ms (mean +/- S.D.: 51.2 +/- 9.5 ms). CSP duration was not significantly different for intensities varying between 40 and 80 mA and for stimulus durations varying between 0.2 and 1.0 ms. CONCLUSION: This study demonstrates a high inter-individual variability of maximal CSP duration, and that CSP duration first increased with stimulus intensity and duration and then reached a plateau. We suggest to use a minimal stimulus intensity of 40 mA, and a minimal stimulus duration of 0.2 ms in order to elicit maximal CSP duration.

Evaluations of inhibitory effect on the motor cortex by cutaneous pain via application of capsaicin.

To evaluation the effect of experimental tonic cutaneous pain on motor cortex excitability by means of transcranial magnetic stimulation (TMS). Thirty healthy adults (male: 12, female: 18) were tested with TMS. Cutaneous pain was induced by topical application of capsaicin cream (0.025%) on the skin overlying the flexor carpi radialis of dominant limb. And the cream had been under an occlusive dressing for 40 minutes until we removed it. Magnetic stimulation was performed to the contralateral cortex with a circular coil at 80% intensity of maximum stimulator output. MEPs were recorded at flexor carpi radialis (FCR), extensor carpi radialis (ECR) and opponens pollicis (OP) with constant isometric contraction of 10%, 30% maximal voluntary contraction (MVC). Main outcome measures the intensity of pain by visual analog scale (VAS). The latency, amplitude and silent period of motor evoked potentials (MEPs). Values at baseline and 20, 40, 60, 80 minutes from applying capsaicin were compared. VAS score reached the peak value at 40 minutes. Amplitudes of MEPs at FCR progressively decreased up to 40 minutes than returned to nearly baseline value at 80 minutes. The decrease in MEP amplitude at FCR was accompanied by the increase in VAS score significantly and sustained for 20 min after washing out capsaicin cream. At ECR & OP, we could not demonstrate any changes in amplitude with time. Silent period at FCR only was significantly prolonged with the increase in VAS score. The present findings support that noxious cutaneous stimulation inhibit motor cortex excitability by so-called cortico-cortical circuits.

A non-peptide angiotensin II receptor antagonist: 2-butyl-6-dimethoxymethyl-5-phenyl-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4- yl]methyl]-1H-imidazo[5,4-b]pyridine.

The title compound, C33H33N7O2, is one of a series of imidazo[4,5-b]pyridine-based angiotensin II receptor antagonists showing high antihypertensive activity. The biphenyltetrazole moiety assumes the same conformation as in related compounds, but its relative orientation with respect to the central fused ring is different to that in these compounds, indicating that there is considerable conformational flexibility about the methylene bridge joining the two ring systems.

Effect of wheelchair ergometer training on spinal cord-injured paraplegics.

The purpose of this study was to investigate the effect of wheelchair ergometer training on spinal cord-injured paraplegics. Eleven male paraplegics with a mean age of 30.9 years (range, 20 to 49 years) participated in the wheelchair ergometer training for the period of 5 weeks. The mean peak heart rate, the mean peak systolic blood pressure and the mean time required for 100m wheelchair propelling at resistance level 1 were significantly decreased at the end of 5 weeks of training as compared with those at pre-training. There was no statistically significant difference in pulmonary function test at pre- and post-training. The peak torque of shoulder flexor and the total work of shoulder flexor and extensor at 180 degrees/sec after training were increased more significantly than those prior to the training. In accordance with the findings as revealed above, it is deemed that the endurance and strength of the upper body and the cardiac fitness for spinal cord-injured paraplegics may be improved by the wheelchair ergometer exercise.

Isometric and isokinetic torque curves at the knee joint.

Isometric and isokinetic torques of bilateral quadriceps and hamstrings were measured with Isokinetic Rehabilitation and Testing System (Model No. Cybex 340) on 40 normal untrained subjects, 20 males and 20 females, ranging between the ages of 23 and 35 years. The mean peak isometric and isokinetic torque values of both muscle groups showed no significant differences between dominant (right) and nondominant (left) limbs in both sexes; however there were significant differences between the male and the female. As the angular velocity increased, the peak torque significantly decreased, and the point of peak torque output occurred significantly later in the range of motion for quadriceps and hamstrings (p less than 0.01). There were no significant changes in the hamstrings to quadriceps (H/Q) ratios as the angular velocity increased. However, there were significant differences of mean H/Q ratio between male and female (p less than 0.01). Height had significant positive correlation with peak isometric and isokinetic torques for both quadriceps and hamstrings (p less than 0.01). Weight was found to correlate significantly with peak isometric and isokinetic torques (p less than 0.01). The mean isometric torques were significantly higher than the mean isokinetic torques for any joint angles in both sexes (p less than .01).