We have studied the polarization of photoemission from an In0.15Ga0.85As–GaAs
strained-layer superlattice. The polarization of 82.7±0.3(stat.)±6.1(syst.)%
was observed at laser wavelengths from 911 to 916 nm at room temperature. The quantum
efficiency at the wavelength of 911 nm was ∼0.015% in the vacuum of ∼6×10-10 Torr with high cathode voltage of -4 kV.
In order to increase the quantum efficiency of the strained GaAs photocathode for a highly polarized electron source, we designed a new type of photocathode with a distributed Bragg reflector (DBR). A Fabry-Perot cavity is formed by the DBR and the GaAs surface. A large enhancement of quantum efficiency was observed at the laser wavelength which satisfied the condition for the resonant absorption of incident laser light. Based on this experiment, it appears promising to make a photocathode which has the quantum efficiency of more than ∼1% together with electron spin polarization higher than 80%.
Artificial lipid bilayer single-channel recording technique has been employed to determine the biophysical and pharmacological properties of various ion channels. However, its measurement efficiency is very low, as it requires two time-consuming processes: preparation of lipid bilayer membranes and incorporation of ion channels into the membranes. In order to address these problems, we previously developed a technique based on hydrophilically modified gold probes on which are immobilized ion channels that can be promptly incorporated into the bilayer membrane at the same time as the membrane is formed on the probes’ hydrophilic area. Here, we improved further this technique by optimizing the gold probe and developed an automated channel current measurement system. We found that use of probes with rounded tips enhanced the efficiency of channel current measurements, and introducing a hydrophobic area on the probe surface, beside the hydrophilic one, further increased measurement efficiency by boosting membrane stability. Moreover, we developed an automated measurement system using the optimized probes; it enabled us to automatically measure channel currents and analyze the effects of a blocker on channel activity. Our study will contribute to the development of high-throughput devices to identify drug candidates affecting ion channel activity.
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