Analysis of saturation velocity and energy relaxation time of electrons in Si using full-band Monte Carlo simulation

In this paper, we have investigated the influence of optical phonon energy on electron saturation velocity and energy relaxation time by using a full band Monte Carlo simulator. The energy band structure is obtained using the first principle calculation. The scattering probability is calculated so as to conserve the energy and momentum in the full band structure. It is found that the range of optical phonon energy from 56.2 to 63.9 meV allows experimental saturation velocity and energy relaxation time. Electron saturation velocity is more sensitive than relaxation time to the optical phonon energy.     

Growing neural gas based navigation system in unknown terrain environment for an autonomous mobile robot

Artificial Life and Robotics - Recently, various types of autonomous robots have been expected in many fields such as a disaster site, forest, and so on. The autonomous robots are assumed to be...     

An application of polyalcohols prepared from diols. I. Elastic polymers with functional groups prepared by chemical modifications

An elastic polymer with hydroxymethyl side chains, which contains some crosslinked structure, has been prepared by treating its prepolymer with maleic anhydride and styrene in the presence of an initiator. Its mechanical properties were varied largely by the molar ratio of the hydroxyl group:maleic anhydride:styrene. A typical example of the polymer showed elongation 69%, tensile strength 0.85 kgf/mm², and Young's modulus 9.4 kgf/mm². Some other modifications are also examined.     

Solidification microstructures selection of Fe-Cr-Ni and Fe-Ni alloys

The transition of solidified phases in Fe–Cr–Ni and Fe–Ni alloys was investigated from low to high growth rate ranges using a Bridgman type furnace, laser resolidification and casting into a substrate from superheated or undercooled melt. The ferrite-austenite regular eutectic growth, which is difficult to find in typical production conditions of stainless steels, was confirmed under low growth rate conditions. The transition velocity between eutectic and ferrite cell growth had a good agreement predicted by the phase selection criterion. Which of either ferrite or austenite is easier to form in the high growth range was discussed from the point of nucleation and growth. Metastable austenite formation in stable primary ferrite composition was mainly a result of growth competition between ferrite and austenite. For a binary Fe–Ni system, a planar metastable austenite in the steady state, simultaneous growth such as eutectic and banded growth between ferrite and austenite in an initial transient region are confirmed.     

Shear Thinning of Nanometer-Thick Liquid Lubricant Films Measured at High Shear Rates

Viscosities of liquid films that were confined and sheared in a nanometer-scale gap were higher than those in the bulk state, and decreased with increasing shear rate, which is called shear thinning. However, the previous findings were based on the experimental results obtained at shear rates of 10^?1–10⁶ s^?1 by using a surface force apparatus (SFA). In this study, we succeeded in measuring shear rate dependence of viscous friction at the high shear rates of 10⁵–10⁸ s^?1. To measure the viscous friction at high shear rates, we used a fiber wobbling method that is a highly sensitive shear force measurement method we developed. The confined polymer lubricant (PFPE Z03) showed shear thinning behavior even at high shear rates up to 10⁸ s^?1, and the relationship between effective viscosity η and shear rate $\dot{\gamma }$ was well expressed by the equation that was $\log_{10} \eta = C - n\log_{10} \dot{\gamma }$ where C ≈ 4.6 ± 0.6 and n ≈ 1.1 ± 0.1. This equation agreed well with the universal curve of shear thinning determined based on the SFA measurements conducted at shear rates of 10^?1–10⁶ s^?1. This result indicates the measured shear thinning behavior was consistent at wide range of shear rates from 10^?1–10⁸ s^?1.     

Effect of Polyethylene Glycol Modification of TiO2 Nanoparticles on Cytotoxicity and Gene Expressions in Human Cell Lines

Nanoparticles (NPs) are tiny materials used in a wide range of industrial and medical applications. Titanium dioxide (TiO(2)) is a type of nanoparticle that is widely used in paints, pigments, and cosmetics; however, little is known about the impact of TiO(2) on human health and the environment. Therefore, considerable research has focused on characterizing the potential toxicity of nanoparticles such as TiO(2) and on understanding the mechanism of TiO(2) NP-induced nanotoxicity through the evaluation of biomarkers. Uncoated TiO(2) NPs tend to aggregate in aqueous media, and these aggregates decrease cell viability and induce expression of stress-related genes, such as those encoding interleukin-6 (IL-6) and heat shock protein 70B' (HSP70B'), indicating that TiO(2) NPs induce inflammatory and heat shock responses. In order to reduce their toxicity, we conjugated TiO(2) NPs with polyethylene glycol (PEG) to eliminate aggregation. Our findings indicate that modifying TiO(2) NPs with PEG reduces their cytotoxicity and reduces the induction of stress-related genes. Our results also suggest that TiO(2) NP-induced effects on cytotoxicity and gene expression vary depending upon the cell type and surface modification.     

Metformin Protects against NMDA-Induced Retinal Injury through the MEK/ERK Signaling Pathway in Rats

Metformin, an anti-hyperglycemic drug of the biguanide class, exerts positive effects in several non-diabetes-related diseases. In this study, we aimed to examine the protective effects of metformin against N-methyl-D-aspartic acid (NMDA)-induced excitotoxic retinal damage in rats and determine the mechanisms of its protective effects. Male Sprague–Dawley rats (7 to 9 weeks old) were used in this study. Following intravitreal injection of NMDA (200 nmol/eye), the number of neuronal cells in the ganglion cell layer and parvalbumin-positive amacrine cells decreased, whereas the number of CD45-positive leukocytes and Iba1-positive microglia increased. Metformin attenuated these NMDA-induced responses. The neuroprotective effect of metformin was abolished by compound C, an inhibitor of AMP-activated protein kinase (AMPK). The AMPK activator, AICAR, exerted a neuroprotective effect in NMDA-induced retinal injury. The MEK1/2 inhibitor, U0126, reduced the neuroprotective effect of metformin. These results suggest that metformin protects against NMDA-induced retinal neurotoxicity through activation of the AMPK and MEK/extracellular signal-regulated kinase (ERK) signaling pathways. This neuroprotective effect could be partially attributable to the inhibitory effects on inflammatory responses.     

Airborne Monoterpenes Emitted from a <Emphasis Type="Italic">Cupressus lusitanica</Emphasis> Cell Culture Induce a Signaling Cascade that Produces β-Thujaplicin

A cell culture of Cupressus lusitanica was used to investigate the reaction of a plant to certain airborne chemicals. Compared with laboratory and field methods using intact plants or tissues, a cell culture is advantageous because it is not affected by environmental factors, and the experiments are easier to reproduce. When exposed to an elicitor, our cell line produces 10 monoterpenes and β-thujaplicin, which is a strong phytoalexin. These monoterpenes are emitted into the vapor phase and are expected to play a role in airborne signaling. In the present study, the cells were exposed to monoterpene vapors, and the volatiles present in the culture flasks were monitored. When the culture cells were exposed to low doses of sabinene, we detected γ-terpinene and p-cymene. After exposure to γ-terpinene, we found p-cymene and terpinolene, whereas p-cymene exposure resulted in terpinolene emission. By contrast, the other seven monoterpenes we investigated did not induce any emissions of other monoterpenes. These results strongly suggest that in C. lusitanica a signaling cascade exists that starts with the emission of sabinene and moves to γ-terpinene, p-cymene, and finally to terpinolene, which accelerates the production of the phytoalexin β-thujaplicin.