Low‐temperature fabrication of 5‐in. QVGA flexible AMOLED display driven by OTFTs using olefin polymer as the gate insulator

Abstract— A 5‐in. QVGA flexible AMOLED display driven by OTFTs has been fabricated at a low temperature of 130°C. A polyethylene naphthalate film was used as the flexible substrate and an olefin polymer was used as the gate insulator for the OTFT. This layer was formed by spin‐coating and baking at 130°C. Pentacene was used as the organic semiconductor layer. The OTFT performance to drive the flexible display with QVGA pixels in terms of current on/off ratio, carrier mobility, and spatial uniformity on the backplane have been obtained. Phosphorescent and fluorescent OLEDs were used as light‐emitting devices on a flexible display. Those layers were formed by vacuum deposition. After the flexible display was fabricated, a clear and uniform moving image was obtained on the display. The display also showed a stable moving image even when it was bent.     

Gigabit optical transmitter GaAs MESFET IC

A GaAs optical transmitter IC consisting of input buffers, a D-type flip-flop, an NRZ/RZ code convertor and a light source current driver has been developed for use in fibre-optic communication systems, employing D-MESFET SCFL by the Pt buried gate FET process. 1.1 Gbit/s modulation of an LD in RZ format with 20 mA peak drive current has been demonstrated.     

Electrochemistry and electrocatalytic activities of superoxide dismutases at gold electrodes modified with a self-assembled monolayer

In this article, the electrochemical properties and electrocatalytic activity of three kinds of superoxide dismutases (SODs), that is, bovine erythrocyte copper-zinc superoxide dismutase (Cu/Zn-SOD), iron superoxide dismutase from Escherichia coli (Fe-SOD), and manganese superoxide dismutase from E. coli (Mn-SOD), in the SOD family were studied. It was revealed that the direct electron transfer of the three kinds of SODs could be efficiently promoted by a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (MPA) confined on a gold electrode. The electrochemical properties of the SODs at the MPA-SAM electrode vary with the sort of SOD with respect to the formal potential, reversibility of electrode reactions, kinetic parameters, and pH dependence, suggesting different mechanisms for the electrode reactions of the individual SODs. A combination of the facilitated direct electron transfer and the bifunctional enzymatic catalytic activities of the SODs via a redox cycle of their active metals substantially offered a flexible electrochemical route to determination of O(2)(*)(-) where O(2)(*)(-) can be sensed with the SOD-based biosensors in both anodic and cathodic polarizations. Such an intrinsic feature of the SOD-based biosensors successfully enabled a sensitive determination scheme for O(2)(*)(-) free from the interference from some coexisting electroactive species, such as ascorbic acid (AA) and uric acid (UA). Further potential applications for in vivo determination of O(2)(*)(-) is also suggested.     

Scalable high-resolution integral videography autostereoscopic display with a seamless multiprojection system

We propose a scalable high-resolution autostereoscopic display that uses integral videography (IV) and a seamless multiprojection system. IV is an animated extension of integral photography (IP). Although IP and IV are ideal ways to display three-dimensional images, their spatial viewing resolution needs improvement; the pixel pitch of the display and the lens pitch are the main factors affecting IV image quality. We improved the quality by increasing the number and density of the pixels. Using multiple projectors, we create a scalable high-resolution image and project it onto a small screen using long-focal-length projection optics. To generate seamless IV images, we developed an image calibration method for geometric correction and color modulation. We also fabricated a lens array especially for the display device. Experiments were conducted with nine XGA projectors and nine PCs for parallel image rendering and displaying. A total of 2868 x 2150 pixels were displayed on a 241 mm x 181 mm (302.4 dots/in.) rear-projection screen. The lens pitch was 1.016 mm, corresponding to 12 pixels of the projected image. Measurement of the geometric accuracy of the reproduced IV images demonstrated that the spatial resolution of the display system matched that of the theoretical analysis.     

Effect of crosslinked core on minimum film formation temperature and morphology of composite microspheres

Effect of crosslinking on minimum film formation temperature (MFT) and particle morphology was investigated using the latices composed by the combination of crosslinked soft core-hard shell. n-Butyl acrylate (nBA) and ethylene glycol dimethacrylate (EGDMA) were used to prepare crosslinked rubber with methylmethacrylate (MMA) or styrene (ST) as a hard plastic component. Ordinary batch (flooded with secondary monomer) and semicontinuous (starved feed) operations were employed to compare the thermal properties of composite latices resulting from the different mode of secondary polymerization. As the degree of crosslinking increases, MFT of the latices obtained by batch operation became higher than those by semibatch operation. Observation of microtomed sections of particles stained with RuO₄ did not reveal much difference in particle morphologies between the two operations. There was a definite relationship between MFT and molecular weight of THF soluble fraction of composite polymers regardless the mode of operation.     

Construction of a plasmid vector for the regulatable high level expression of eukaryotic genes in Escherichia coli: an application to overproduction of chicken lysozyme

A novel expression vector pKPl500 for synthesizing unfused proteinin Escherichia coli was constructed. pKP1500 perserves the tacpromoter, the lacZ SD sequence, unique restriction sites (EcoRI,SmaI, BamHI, SalI, PstI and HindIII) and the rrnB terminatorsof pKK223-3, but the replication origin is replaced with thatof pUC9. Construction of this plasmid is based upon the observationthat the copy number control of pUC9 is temperature dependent.At 28°C, the copy number of pKP1500 is less than 25 perchromosome, approximately the same copy number as that of pKK223-3,which contains the replication origin of pBR322, whereas at42°C, the copy number increases about 10 times and reachesup to 230 copies per chromosome. The main advantage of thissystem is that the temperature-dependent copy control and regulatableexpression of the tac promoter make cells car rying pKPl500derivatives stable against selective pressure by detrimentaloverproduction of foreign proteins at a low temperature andpermits high expression of cloned DNAs at a high temperature.When chicken lysozyme cDNA carrying the initiation codon (ATG)immediately upstream from the Lys¹ codon was inserted downstreamfrom the tac promoter and the SD sequence, the pKP1500 derivativeproduced lysozyme at about 25% of the total cellular proteins.This value is more than 10 times higher than that obtained withthe pKK223-3 derivative carrying the same lysozyine cDNA. Bycomparison, the expression of eukaryotic genes from the tacpromoter reported by others has usually been less than a few% of the total cellular protein. pKPl500 would therefore beuseful for the high level production of unfused proteins fromeukaryotic cDNAs in E. coli.     

Broadband method for precise microwave spectroscopy of superconducting thin films near the critical temperature

We present a high-resolution microwave spectrometer to measure the frequency- dependent complex conductivity of a superconducting thin film near the critical temperature. The instrument is based on a broadband measurement of the complex reflection coefficient, S 11, of a coaxial transmission line, which is terminated to a thin film sample with the electrodes in a Corbino disk shape. In the vicinity of the critical temperature, the standard calibration technique using three known standards fails to extract the strong frequency dependence of the complex conductivity induced by the superconducting fluctuations. This is because a small unexpected difference between the phase parts of S 11 for a short and load standards gives rise to a large error in the detailed frequency dependence of the complex conductivity near the superconducting transition. We demonstrate that a new calibration procedure using the normal-state conductivity of a sample as a load standard resolves this difficulty. The high quality performance of this spectrometer, which covers the frequency range between 0.1 and 10 GHz, the temperature range down to 10 K, and the magnetic field range up to 1 T, is illustrated by the experimental results on several thin films of both conventional and high temperature superconductors.     

DRYING OF SLICED RAW POTATOES IN SUPERHEATED STEAM AND HOT AIR

Drying experiments were conducted on raw potato slices, using atmospheric pressure superheated steam and hot air as drying media at 170 and 240°C. Mass changes of the material were continuously measured, the conditions of cross section near the surfaces were observed with an electron microscope, also color changes of their surface were measured during drying. The respective drying methods and temperature conditions were compared and it was found that, in the case of superheated steam drying, moisture content temporarily increases due to steam condensation in the initial stage of drying, therewith, as well as starch gelatinization rapidly develops. Meanwhile, in case of hot air drying, starch gelatinization occurs more slowly than with superheated steam drying and that non-gelatinized starch granules remain on the surface when drying was completed. Furthermore, surface color measurements showed that samples dried by superheated steam were more reddish than ones dried by hot air and the surfaces were more glossy, because no starch granules remain on the surface in case of superheated steam drying.     

Effect of load, temperature and humidity on the pH of the water drained out from H2/air polymer electrolyte membrane fuel cells

The effect of the operating conditions, e.g., load, temperature, relative humidity (RH), and the MEA's aging condition on the pH of the water drained out from the cathode and anode sides of a H₂/air PEM fuel cell was studied. Also the effect of the pollutants’ existence in natural air on the measured pH and the performance of the fuel cell was investigated. pH values as low as 1 were measured for the water drained out from the cathode side under a low temperature–low RH condition. Increasing the load, temperature or RH value resulted in an increase of the measured pH except for the low temperature–low RH condition where increasing the load resulted in a decrease in the measured pH. On the other hand, the pH value of the water drained out from the anode side was around 4 under the same low temperature–low RH condition. Aging of the MEA at 90 °C and RH of 100% for at least 30 h resulted in low measured pH values for the water drained out from the cathode side. The polarization behaviors of the cathode under these different conditions were measured and correlated to the pH change and the performance of the MEA. Measuring the pH using a flow pH meter for the water droplets drained out from the cathode side can be used as an alarm for the onset of the chemical degradation of the Nafion membrane.     

Effects of micro-phase-separated structures on proton conductivity and methanol permeability in polymer electrolyte membranes

The effects of micro-phase-separated structures in hydrocarbon-based polymer electrolyte membrane on its proton conductivity and methanol permeability were investigated to obtain a membrane with high proton conductivity and low methanol permeability. Membrane with low methanol permeability had low water content, which indicates that methanol permeated through swollen areas in the membranes. Membranes with gyroid-like structure exhibited high proton conductivity and low methanol permeability. These results indicate that continuous hydrophilic domains functioned as proton paths, therefore higher proton conductivities were shown in the structures, in which continuous hydrophobic domains existed. In contrast, continuous hydrophobic domains played a role as frameworks that prevented membranes from swelling due to water and lower methanol permeability coefficients were found in structures, in which continuous hydrophilic domains existed. Therefore, we can conclude that the most suitable structures obtaining high proton conductivities and low methanol permeability were the gyroid-like structure.