Characterization of nanometer-sized Pt-dendrite structures fabricated on insulator Al2O3 substrate by electron-beam-induced deposition

Nanometer-sized Pt-dendrite structures were fabricated on an insulator Al₂O₃ substrate using an electron-beam-induced deposition (EBID) process in a transmission electron microscope (TEM). The as-fabricated structures were characterized using conventional and high-resolution transmission electron microscopies (CTEM and HRTEM) and X-ray energy dispersive spectroscopy (EDS). The as-fabricated nanodendrites consisted of many nano-grains and amorphous state structures. The nanometer-sized grains were determined to be Pt crystals with face-centered cubic (fcc) structure. The formation of the nanodendrite structures are discussed to relate to a mechanism involving charge-up produced on surface of the substrate, movement of charges to and accumulation at the convex surface of the substrate and the tips of the deposits.     

Properties of electrical insulating materials at cryogenictemperatures: A literature review

Many insulating materials and systems for superconducting electrical equipment have been developed in response to the severe demands of safe usage, such as in cryogenic temperature, high mechanical stresses, high radiation, etc. They have been designed to fulfill very extreme service conditions, either at liquid helium or liquid nitrogen temperatures. Whatever the future industrial development, there is already abundant knowledge about insulating materials at cryogenic temperatures, and the feasibility has been proven. Many laboratories in the world continue research to increase this knowledge and to fill in the remaining gaps     

Effects of TA-0910, an orally active TRH analog, on the spinal reflex in spinal rats

Effects of TA-0910 (1-methyl-(S)-4,5-dihydroorotyl-L-histidyl-L-prolinamide), a new thyrotropin releasing hormone (TRH) analog, on spinal reflex potentials and flexor reflexes were compared with those of TRH in C1-spinal rats. Intravenously administered TA-0910 and TRH produced dose-dependent increases in the amplitudes of mono- and polysynaptic reflex potentials and withdrawal flexor reflexes. TA-0910 was more potent and more long-lasting than TRH. The stimulating actions of TA-0910 and TRH on the monosynaptic reflex potential were not antagonized by pretreatment with atropine, cyproheptadine, haloperidol or prazosin, suggesting no involvement of the cholinergic, serotonergic, dopaminergic or noradrenergic system. Intraduodenally administered TA-0910 also produced a lasting potentiation of the withdrawal flexor reflex, but intraduodenally administered TRH showed no effect. These results suggest that TA-0910 may be a more useful drug than TRH for spinal functional disorders.     

Pathogenic role of glutamate in hyperthermia-induced seizures

Hyperthermia induces seizures in both humans and rodents, but the underlying mechanism remains unknown. The present study showed that hyperthermia, causing rapid increase in body temperature, increases the concentration of glutamate (Glu) released into a cortical perfusate before onset of seizures in rats and that this increase in Glu concentration correlated with a decrease in seizure threshold temperature. These results indicate that increased cortical extracellular Glu induced by hyperthermia contributes to onset of seizures. The same mechanism may be involved in clinical seizures induced by fever in patients with febrile convulsions or epilepsy.     

Gunn-effect high-speed carry finding device for 8 bit binary adder

A high-speed carry finding device consisting of seven inhibitors, each an integrated Schottky electrode-triggered Gunn device and an m.e.s.f.e.t., was fabricated monolithically. The device could find and store carry signals of all digits in 330 ps at the worst logic case. The anode-voltage margin was 11%     

High-field dielectric properties of polyethylene in the high-temperature region

Nonpolar polymers such as polyethylene or polypropylene are widely used as insulation materials, often under conditions involving strong electric fields and high temperatures. Under these conditions, the conduction loss due to DC-like carrier transport may give rise to a high-field AC dissipation factor (tan δ). This paper describes the high-field dielectric properties of polyethylene films at frequencies from 50 to 400 Hz and temperatures from room temperature to 100°C, as measured with a new type electrode design developed by the authors. In the high-temperature region, the AC dissipation current waveform at 50 Hz was also measured. At room temperature, the electric-field dependence of tan δ is almost unaffected by the frequency of the applied field. But at high temperatures and strong electric fields, tan δ tends to have a large field dependence and to be almost inversely proportional to the frequency. Thus the AC conductivity becomes independent of the frequency of the applied field in the region of strong fields and high temperatures. A theoretical analysis shows that the high-field dielectric loss is governed by two processes, namely, the dielectric relaxation loss inherent to the AC field and the DC-like carrier transport loss that becomes prominent in the high-temperature region, where AC dissipation current waveform becomes significantly nonsinusoidal.     

Age-related changes in intracranial artery velocity measured by transcranial Doppler sonography in normotensive, hypertensive and diabetic patients

We measured mean blood flow velocity (MFV) and Fourier pulsatility index (PI) of the M1 portion of the middle cerebral artery (MCA) by transcranial Doppler mapping technique (2 MHz, Trans-scan, EME Co., Ltd.). The correlations between these parameters and arteriosclerotic risk factors such as aging, hypertension and diabetes mellitus were examined. Healthy volunteers as well as patients suffering from hypertension and diabetes mellitus were studied. A total of 59 persons (85 MCAs) consisting of 30 males (mean age 54.4, 24-81 years) and 29 females (mean age 54.8, 20-75 years) were enrolled in this study. Some hypertensive or diabetic subjects had previous cerebrovascular disease, therefore cases who had only minor stroke or asymptomatic infarction without significant lesions in carotid artery system were included. After excluding brain embolism, these subjects were divided into three groups as normotensive/non diabetic group (NT/non DM), hypertensive group (HT) and diabetic group (DM). In each group, MFV decreased with aging, being more evident in the HT and DM groups than in the NT/non DM group. Fourier PI also showed a significant increase with aging, and the correlation was stronger than that between MFV and age. Moreover, these trends of age-Fourier PI relationship were more highly significant in HT and DM groups than NT/non DM group. In cases with HT or DM, age-related arterial changes appeared to be more severe than in those without. Fourier PI seemed valuable for detecting arterial lesions with aging, HT and DM.