Effect of tacticity of poly(methyl methacrylate) on interfacial region with silica in polymer nanocomposite

The effect of tacticity on the interfacial region between poly(methyl methacrylate) (PMMA) and silica in a PMMA/silica nanocomposite was investigated by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The glass transition temperature (T_g) values of the syndiotactic (st-) and atactic (at-) PMMA/silica nanocomposites are higher than those of the neat PMMA. Conversely, the T_g of the isotactic (it-) PMMA/silica nanocomposite is slightly higher than that of the neat it-PMMA. DSC and XRD results suggest that the restriction of the PMMA chain mobility in the silica nanoparticle interfacial region heightens as the syndiotactic content increases. FT-IR results show that this phenomenon is caused by the interaction between the carbonyl group of PMMA and the silanol group on the silicon dioxide surface. Therefore, it can be concluded that the syndiotactic-rich PMMA has a significantly different molecular mobility from that of the neat PMMA in the interfacial region with silica nanoparticle surface than isotactic-rich PMMA.     

Radiation damage of SiC Schottky diodes by electron irradiation

The impact of radiation damage on the device performance of 4H-SiC Schottky diodes, which are irradiated at room temperature with 2-MeV electrons is studied. After irradiation the reverse current increases, while the forward current and the capacitance decrease with barrier height and carrier density. The decrease of the barrier height is mainly responsible for the increase of the reverse current, while the decrease of the forward current for a high fluence is caused by the increase of the resistance in the bulk of the crystal. Although no electron capture levels are observed before irradiation, three electron capture levels (E₁, E₂, and E₃) are induced after irradiation. It is noted that the decrease in carrier density is partly caused by the contribution of non-observed electron capture level in the DLT spectrum, which compensates the free carriers.     

Radiation source dependence of performance degradation in thin gate oxide fully-depleted SOI n-MOSFETs

The degradation of the electrical performance of thin gate oxide fully depleted SOI n-MOSFETs and its dependence on the radiation particles are investigated. The transistors are irradiated with 7.5-MeV protons and 2-MeV electrons at room temperature without bias. The shift of threshold voltage and the coupling effect with the degraded opposite gate are clarified. A remarkable reduction of the floating body effects is observed after irradiation. The degradation of the extracted parameters is discussed by a comparison with the damage coefficients.     

Evaporation rate effect on starting point of shrinkage stress development during drying process in solvent cast polymer film

To reveal the effect of drying conditions on shrinkage stress existing between a film and a substrate, a polystyrene/toluene solution was coated on a glass substrate, and the volume fraction of toluene at the time when the stress starts to grow (?_S) was measured at various drying temperatures and evaporation rates. ?_S decreased with increase of drying temperature at a constant evaporation rate, while ?_S increased with increase of evaporation rate at a constant drying temperature. From these results, it was suggested that the dominant factors affecting the starting point of stress were both the chain mobility and the measurement time‐scale. Considering the two factors, the tendency of ?_S with the drying conditions is quite similar to that of the solvent content at glass transition point, and this fact indicates a strong correlation between the starting point of stress and the glass transition of coated solution. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of electron irradiation on SiGe devices

The degradation and the recovery behavior of the device performance for SiGe diodes and p-MOSFETs irradiated by 2-MeV electrons are reported. For diodes, it is noted that both the reverse and forward current increase by irradiation. An interesting observation is that the forward current decreases after irradiation for a forward voltage larger than ~ 0.7 V. This reduction can be explained by an increased resistivity of the Si substrate. The degradation recovers by thermal annealing after irradiation. For a fluence of 1 × 10¹⁵ e/cm², the diode performance almost recovers to the initial condition after 250 °C annealing. For the transistors, after irradiation, a slight negative shift of the threshold voltage and a decrease of the drain current for input and output characteristics have been observed together with a decrease of hole mobility. This is mainly due to the increase of the threshold voltage induced by positive charge trapping in the gate oxide.     

Degradation of SiC-MESFETs by irradiation

The impact of radiation source dependence on the device performance degradation of 4H-SiC MESFETs (Metal Schottky Field Effect Transistors), which have been irradiated at room temperature with 2-MeV electrons and 20-MeV protons, is studied. The damage coefficient for protons is about three orders of magnitude larger than that for electrons. The radiation source dependence of the device performance degradation is attributed to the difference of mass and the possibility of nuclear collision for the formation of lattice defects. From thermal annealing of electron-irradiated MESFETs, it is found that the recovery of the drain current characteristics principally takes place from 100 °C, and that the drain current recovers to the pre-rad value after 200 °C annealing. It is concluded that the degradation of the drain current is mainly sensitive to the radiation-induced decrease of the Schottky barrier height at the gate contact.     

Experimental results with mobile antennas having cross-polarizationcomponents in urban and rural areas

The receiving performance of mobile antenna systems that have vertical and horizontal elements at the 920-MHz band has been investigated by measurements in both rural and urban areas in Japan. Three types of inverted-F antennas for a car and three types of antenna elements, a monopole, a bent-slot and an inverted-F antenna, for portable equipment were used in the experiments. The average received power and its probability density function are obtained as the parameter to evaluate the performance of antenna systems. The performances of the bent-slot antenna system for portable equipment and the inverted-F antenna system mounted on a car are compared with those of the monopole or dipole antenna systems used as reference antennas. A notable increase in the average received power has been observed in operation in an urban area where the field distributes randomly and consists of cross-polarized components     

Urinary bladder carcinoma was induced in a patient treated with cyclophosphamide for malignant lymphoma

A major responsibility of any Quality Assurance Unit (QUA) is to ensure data integrity. Errors made during data entry can lead to many problems in the study review process and decrease the quality, accuracy, and overall efficiency of data management. One technique that can reduce the number of data entry errors in computer data sets is the use of a dual entry data system. Currently available software allows creation of customized data entry screens that either closely resemble or duplicate the data collection forms used during studies. Two data entry operators enter data into two independent data sets. The use of an on-screen display that resembles the data collection form reduces the potential for keypunch errors. The two data sets can then be electronically compared. The comparison reports differences between the two data sets. When differences exist, the correct values can be determined by reference to the original data sheets and the two data files can then be corrected. Theoretically, the only key punch errors that will exist after making these corrections are when the two independent entry operators make the same exact data entry error. Typically, the time required for two people to enter data is minimal compared to the time required to manually identify and correct data entry discrepancies. With error-free data entry, we have found that electronic data quality, accuracy, and audit efficiency are improved at every subsequent step of data management, analysis, quality assurance auditing, and report generation.     

Formation of hydrogen-capped polyynes by laser ablation of C60 particles suspended in solution

Laser ablation of C₆₀ particles suspended in hexane or methanol solution has been studied using a Nd:YAG laser (266, 355, 532, and 1064 nm). Insoluble product analysis by Raman spectroscopy showed that C₆₀ particles transformed to graphite-like ones. On the other hand, soluble product analysis by HPLC coupled with UV absorption spectroscopy and GC/MS demonstrated that linear hydrogen-capped polyynes (C_nH₂: n=8, 10, 12) were formed. The dominant C_nH₂ polyyne was C₈H₂ in all cases. The relative abundance of polyynes decreased with increasing wavelength of the Nd:YAG laser, except for 266-nm irradiation in hexane, where the relative abundance of polyynes at 355 nm was greater than that at 266 nm. It was therefore concluded that photochemical processes are more important than thermal ones for the formation of polyynes. The relative abundance of polyynes in hexane was greater than that in methanol. The dependence of relative abundance of polyynes on the particles concentration, laser irradiation time, and laser power was measured in order to obtain information on formation mechanism of polyynes. These results and reported laser photochemical processes of C₆₀ molecules in the gas phase suggested that C₂ radicals produced from C₆₀ are polymerized and hydrogenated to form C₈H₂ and much smaller amounts of C₁₀H₂ and C₁₂H₂.     

Fabrication of high precision microstructure using ICP etching for capacitive inclination sensor

Capacitive inclination sensors have the advantage because it could easily provide a linear analog output with respect to inclination. Since the dimensions of the sensing region are very small, then this sensor is expected to be widely used in fields where efficient and reliable position control is a primary factor to be considered if this sensor could be mass produced at low cost. Therefore, we proposed fabrication process based on transfer to resin using mold. We successfully fabricated a micro capacitive inclination sensor by a combination of a resin forming method and a mold. The sensor consists of a gap distance of 80 μm between its electrodes. The sensor detects difference of capacitance, which varied with movement of silicone oil accompanying with inclination. When the sensor was inclined, linear analog output was obtained within the range of ?45 to +45°