Hydrogen adsorption and hydrogen evolution reaction on a polycrystalline Pt electrode studied by surface-enhanced infrared absorption spectroscopy

Hydrogen evolution reaction (HER) on a polycrystalline Pt electrode has been investigated in Ar-purged acids by surface-enhanced infrared absorption spectroscopy and electrochemical kinetic analysis (Tafel plot). A vibrational mode characteristic to H atom adsorbed at atop sites (terminal H) was observed at 2080-2095 cm⁻¹. This band appears at 0.1 V (RHE) and grows at more negative potentials in parallel to the increase in hydrogen evolution current. Good signal-to-noise ratio of the spectra enabled us to establish the quantitative relation between the band intensity (equivalently, coverage) of terminal H and the kinetics of HER, from which we conclude that terminal H atom is the reaction intermediate in HER and the recombination of two terminal H atoms is the rate-determining step. The quantitative analysis of the infrared data also revealed that the adsorption of terminal H follows the Frumkin isotherm with repulsive interaction.     

High-speed melt spinning of bicomponent fibers: Mechanism of fiber structure development in poly(ethylene terephthalate)/polypropylene system

High-speed bicomponent spinning of poly(ethylene terephthalate)(PET)(core) and poly-propylene (PP) (sheath) was carried out and the structure development in the individual components, PET and PP, was investigated. The orientation and crystallinity development in the PET component was enhanced as compared to that of the single-component spinning while the PP component remained in a low orientation state and had a pseudohexagonal crystal structure even at high take-up speeds. To clarify the mutual interaction between the two components in bicomponent spinning, a semiquantitative numerical simulation was performed. The simulation results obtained using the Newtonian fluid model showed that the solidification stress in the PET component was enhanced while that of the PP component was decreased in comparison with the corresponding single-component spinning. This is due to the difference in the temperature dependence of their elongational viscosity. Simulation with an upper-convected Maxwell model as the constitutive equation suggested that significant stress relaxation of the PP component can occur in the spinline if the PET component solidifies earlier than does PP. Based on the structural characterization results, and the simulation results, it was concluded that the difference in the activation energy of the elongational viscosity and solidification temperature between the two polymers are the main factors influencing the mutual interaction in the bicomponent spinning process. © 1996 John Wiley & Sons, Inc.     

Speed limit of all-optical gate switches using cascaded second-order nonlinear effect in quasi-phase-matched LiNbO/sub 3/ devices

In all-optical gate switches that employ the cascaded second-order nonlinear effect in quasi-phase-matched (QPM) LiNbO/sub 3/ devices, walkoff between the fundamental and second harmonic pulses is very large. The authors experimentally show that crosstalk of the switch induced by such walkoff limits the switching speed, but that the switching speed can significantly be enhanced by walkoff compensation. Using a 20-mm-long QPM LiNbO/sub 3/ waveguide device, the authors switch one of twin pulses separated by 6.25 ps without crosstalk, showing the possibility of switching a 160-Gb/s signal.     

Passively mode-locked laser diodes with bandgap-wavelength detunedsaturable absorbers

We fabricated monolithic passively mode-locked laser diodes with bandgap-wavelength detuned saturable absorbers using selective growth. The pulsewidth shortened with increasing detuning of the absorber toward shorter wavelengths. For the detuned absorber, the pulsewidth was reduced to 1.2 ps, compared to 2.6 ps for the nondetuned absorber. This originated in broadened mode-locked spectra and reduced absorption recovery time under larger reverse bias voltages for detuned saturable absorbers     

Influence of anti-LDL receptor antibody on the transfer of cholesterol from LDL to isolated lymphocytes in normal subjects

Results 2 1/2 years after an enuresis nocturna training are presented, including rate of success, percentage and duration of relapse for 113 children (mean age 11.6 year at the start of the training). The bibliotherapeutic treatment by parents did not require any intervention by a professional. Behaviour of parents in the event of a relapse differed between training conditions. Children in the Arousal condition recovered faster from a relapse, 90% of their parents used the Arousal training again at relapse or did not intervene at all and none of them consulted a professional. Clearly they had confidence in the method of Arousal training: combining the alarm device with reinforcement for correct behaviour at the time the alarm goes off. Parents in control conditions did not use the alarm device as often as the parents in the Arousal condition, but tried other means with less success, including consulting professionals.     

Generation of synchronized subterahertz optical pulse trains byrepetition-frequency multiplication of a subharmonic synchronousmode-locked semiconductor laser diode using fiber dispersion

We describe the generation of a synchronized, low-jitter, subterahertz optical pulse train by repetition-frequency multiplication of a subharmonic synchronous mode-locked semiconductor laser diode using the group-velocity dispersion (GVD) of optical fiber. A 49-196 GHz optical pulse train was generated with low intensity fluctuation and with low timing jitter, by adjusting fiber length in accordance with the mode-locking frequency and the fiber's GVD     

Energy analysis of a Kori-tofu plant

Consumption of energy was analysed on a Kori-tofu plant which processed 6 tons of soybeans per day, involving 13 operations such as wetmilling, extraction-denaturation of soy protein, coagulation, compression, freezing, thawing, drying and waste-water treatment. Total energy consumption per 1 kg of the dry Kori-tofu was 27·1 MJ of fuel energy (27·9 MJ of exergy) plus 8·3 MJ of electrical energy. Energy-intensive operations were the extraction-denaturation of soy protein and the drying for thermal energy, and the refrigeration and the waste-water treatment for electrical energy. The extraction-denaturation of soy protein consumed twice as much thermal energy as the drying. The waste-water treatment consumed more electrical energy than the whole manufacturing process. Points for energy conservation are discussed.     

Microfluidic device for the detection of glucose using a micro direct methanol fuel cell as an amperometric detection power source

We designed and prepared a novel microbiosensing system consisting of a microbioreactor fabricated using photosensitive sheets intercalated between Pyrex wafers as a dam structure, together with a micro fuel cell as a power source device between the electrodes for amperometric detection. The dam structure retains enzyme (glucose oxidase, GOx)-immobilized microbeads in a microchannel. Microelectrodes are used as an integrated detector within a microchannel located downstream of the dam structure, and these are used to detect the oxidation current of hydrogen peroxide produced from a glucose sample and GOx. A micro direct methanol fuel cell (mu-DMFC, i.d. 500 microm) was fabricated on a polymeric substrate and was used to supply a potential for the electrochemical detector. In this case, two mu-DMFCs were stacked on one substrate to increase the voltage for the oxidation of hydrogen peroxide. A linear response curve was obtained in range from 0.1 to 10 mM glucose for the designed microbiosensing system. These results show that a microfluidic biosensing system designed with a mu-DMFC device is useful and has the potential to assist minuaturization and simplification of the sensing system, in addition to increasing disposability of the device.