A photodiode amplifier system for pulse-by-pulse intensity measurement of an x-ray free electron laser

We have developed a single-shot intensity-measurement system using a silicon positive-intrinsic-negative (PIN) photodiode for x-ray pulses from an x-ray free electron laser. A wide dynamic range (10(3)-10(11) photons/pulse) and long distance signal transmission (>100 m) were required for this measurement system. For this purpose, we developed charge-sensitive and shaping amplifiers, which can process charge pulses with a wide dynamic range and variable durations (ns-μs) and charge levels (pC-μC). Output signals from the amplifiers were transmitted to a data acquisition system through a long cable in the form of a differential signal. The x-ray pulse intensities were calculated from the peak values of the signals by a waveform fitting procedure. This system can measure 10(3)-10(9) photons/pulse of ~10 keV x-rays by direct irradiation of a silicon PIN photodiode, and from 10(7)-10(11) photons/pulse by detecting the x-rays scattered by a diamond film using the silicon PIN photodiode. This system gives a relative accuracy of ~10(-3) with a proper gain setting of the amplifiers for each measurement. Using this system, we succeeded in detecting weak light at the developmental phase of the light source, as well as intense light during lasing of the x-ray free electron laser.     

An inorganic electroluminescent device using calcium phosphate doped with Eu3+ as the luminescent layer

In this work, the availability of calcium phosphates for the light emitting layer of a thin-film electroluminescent (TFEL) device was investigated. The goal of this work was to develop an electronic device with ordinary materials such as a calcium phosphate, the principal ingredient of the skeleton of the vertebrate. Compositions of 2CaO·P₂O₅ (Ca₂P₂O₇), 3CaO·P₂O₅ (Ca₃(PO₄)₂) and 4CaO·P₂O₅ (Ca₄O(PO₄)₂) were examined as the candidates for the light emitting layer. Before composing the TFEL device, the photoluminescence (PL) properties of the three compositions were investigated in the powder form to evaluate the performance as the light emitting layer. Among the examined calcium phosphates, Eu-doped β-Ca₃(PO₄)₂ showed the best PL properties. It showed typical red-emission from Eu³⁺. The PL intensity was enhanced with the heat-treatment temperature and the optimal temperature was 1250 °C. Then, a TFEL device was prepared by a spray pyrolysis method with the β-Ca₃(PO₄)₂:Eu³⁺ phosphor layer on a BaTiO₃ disk. The TFEL device exhibited the red emission originating in Eu³⁺ at 610 nm under applying alternating voltage. Different from the power sample, the intensity of EL decreased with the heat-treatment temperature from 1000 to 1250 °C. The deterioration of EL at the higher temperatures was attributed to chemical interaction between the phosphor layer and the BaTiO₃ disk.     

Flexible air-stable three-dimensional polymer field-effect transistors with high output current density

Flexible air-stable short-channel polymer organic field-effect transistor (OFET) arrays with high saturated output current density are demonstrated by utilizing a novel solution-processed naphthobisthiadiazole (NTz) based donor–acceptor semiconducting polymer (PNTz4T) and designing a three-dimensional vertical channel structure with an extremely large ratio of channel width to channel length. The saturated mean field-effect mobility of 0.16 cm²/V s of the short-channel polymer devices remains over one month resulting in air-stable OFET arrays with high on/off ratio over 10⁶ and powerful current–density exceeding 0.3 A/cm² under low operation voltage, both of which meet the requirements for such applications as driving organic light-emitting diodes in active-matrix displays.     

Cycloartenyl trans-ferulate,a component of the bran byproduct of sake-brewing rice,inhibits mammalian DNA polymerase and suppresses inflammation

During the screening of selective DNA polymerase (pol) inhibitors, we isolated cycloartenyl trans-ferulate (CAF), which is a major component of γ-oryzanol, which is a byproduct formed during the production of Japanese rice wine “sake”. CAF selectively inhibited the activity of mammalian A, B, and X pol families, but Y family pols were not affected. CAF did not influence the activities of plant or prokaryotic pols, nor the activity of other DNA metabolic enzymes tested. Individual chemical components of CAF, including cycloartenol (CA) and ferulic acid (FA), did not inhibit pol enzyme activities. CAF suppressed TPA (12-O-tetradecanoylphorbol-13-acetate)-induced inflammation in the mouse ear, but CA and FA did not. The ability to inhibit mammalian pol enzymes in vitro was positively correlated with their propensity to suppress inflammation in vivo. These results suggest that this byproduct formed during the sake-brewing process is useful as an anti-inflammatory agent.     

Contrast Enhancement of Gaussian Speckles Produced by Centrosymmetrical Objects

Abstract

It is well known that the contrast of Gaussian speckles produced under ordinary optical configurations is at most 1. It is also known, however, that under some special situations even Gaussian speckles can have contrast values higher than 1. As an example of such a situation, this paper discusses the first-order statistics of speckle patterns produced in the Fraunhofer region of objects having centrosymmetrical structures. The first-order statistics of Gaussian speckles is first reviewed with special emphasis on the optical conditions which produce the contrast enhancement. Enhanced contrast and the intensity distributions which deviate from the negative exponential density are elucidated theoretically in the case of speckles produced by random objects containing centrosymmetrical structures. Some experimental verifications are also given for the speckle patterns produced by randomly distributed circular apertures containing some symmetrical pairs.