Noise analysis of an electro-optic sensor system

Optical Review - This paper describes the noise analysis of an electro-optic (EO) sensor system based on experimental and simulation results. We developed a polarization simulator of the EO sensor...     

XAFS spectra from X-ray fluorescence Kβ line using conventional energy-discriminating detector

X-ray fluorescence spectra of copper (Cu) metal, copper monoxide (CuO), and potassium chromate (K₂CrO₄) were recorded as a function of incident X-ray energy near the Cu K-edge and chromium (Cr) K-edge, respectively, using a conventional silicon drift detector. The spectra contained components due to elastic, inelastic, and multiple scattering, in addition to the Kα and Kβ lines. Cu and Cr K-edge X-ray absorption fine structure (XAFS) spectra of Cu, CuO, and K₂CrO₄ were obtained by an intensity analysis of the Kα and Kβ lines. The intensity of the Kβ line for the different incident photon energies was obtained by numerically removing the additional scattering components using the MUSCAT program. These spectra exhibited a jump near the K absorption edges, which reproduced the spectral features obtained in transmission mode for both Cu, CuO, and K₂CrO₄. A chemical shift was also clearly identified in the X-ray absorption near edges structure using the X-ray fluorescence Kβ line. In addition, the Cr K-edge extended XAFS spectrum of K₂CrO₄ was clearly observed using the Cr Kβ fluorescent line. The XAFS measurements on the Kα and Kβ lines are possible, and they carry equally valuable information.     

Deprotection of dithioacetals with 30% hydrogen peroxide catalyzed by tantalum(V) chloride–sodium iodide or niobium(V) chloride–sodium iodide

The reaction of dithioacetals with 30% hydrogen peroxide in the presence of catalytic amounts of tantalum(V) and iodide ion effectively produced carbonyl compounds in high yields. Dithioacetals also can be deprotected using the niobium(V) catalyzed oxidation of iodide ion by hydrogen peroxide under mild conditions.     

Accurate intensity calibration for low wavenumber (−150 to 150 cm−1) Raman spectroscopy using the pure rotational spectrum of N2

We report on an accurate intensity calibration method for low wavenumber Raman spectroscopy. It uses the rotational Raman spectrum of N₂. The intensity distributions in the rotational Raman spectra of diatomic molecules are theoretically well established. They can be used as primary intensity standards for intensity calibration. The intensity ratios of the Stokes and anti‐Stokes transitions originating from the same rotational levels are not affected by thermal population. Taking the effect of rotation–vibration interactions appropriately into account, we are able to calculate these intensity ratios theoretically. The comparison between the observed and calculated ratios of the N₂ pure rotational spectrum provides an accurate relative sensitivity curve (error ~5 × 10⁻⁴) in the wavenumber region of −150 to 150 cm⁻¹. We determine the temperature of water solely from the low wavenumber Raman spectra, using a thus calibrated spectrometer. The Raman temperature shows an excellent agreement with the thermocouple temperature, with only 0.5 K difference. The present calibration technique will be highly useful in many applications of low wavenumber quantitative Raman spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

Geometrical Evolution and Formation of the Photoproduct in the Cycloreversion Reaction of a Diarylethene Derivative Probed by Vibrational Spectroscopy

The geometrical evolution of the reactant and formation of the photoproduct in the cycloreversion reaction of a diarylethene derivative were probed using time-resolved absorption spectroscopies in the visible to near-infrared and mid-infrared regions. The time-domain vibrational data in the visible region show that the initially formed Franck-Condon state is geometrically relaxed into the minimum in the excited state potential energy surface, concomitantly with the low-frequency coherent vibrations. Theoretical calculations indicate that the nuclear displacement in this coherent vibration is nearly parallel to that in the geometrical relaxation. Time-resolved mid-infrared spectroscopy directly detected the formation of the open-ring isomer with the same time constant as the decrease of the closed-ring isomer in the excited state minimum. This observation reveals that no detectable intermediate, in which the population is accumulated, is present between the excited closed-ring isomer and the open-ring isomer in the ground state.     

聚酚藏花红功能碳纳米管生物阳极制备及其在乙醇传感器应用

应用电化学法聚合酚藏花红（PPS）功能化的单壁碳纳米管,以其作为烟酰胺辅酶（NADH）氧化的电化学催化剂（电极）,构建基于乙醇脱氢酶的安培型乙醇生物电化学传感器.该电极于0.0 V时,对NADH具有很好的催化性能.而单体酚藏花红则由于其电位过低（-0.48 V）,不能显示催化性能.循环伏安和计时安培法测试表明：该传感器...     

Quantitative analysis of inhomogeneous luminance effect on visibility of text

In the present study, we measured the visibility of several types of Japanese text on a liquid crystal display (LCD) with a spatially inhomogeneous luminance and extended the visibility index function (VIF) to explain the current experimental results with a higher degree of accuracy. We quantitatively analyzed the effect of an inhomogeneous luminance, which was produced by the graphical representation of a background without reflected light and by reflected light on a homogeneous background. These results showed that the visibility of text was influenced by the inhomogeneity of the background luminance in a domain that depended on text size. Then we applied a weighted average background luminance with a two dimensional Gaussian function, whose distribution width was related to the text size, to VIF. Finally, we proposed a modified VIF and showed that the new method was able to precisely estimate the actual visibility of text with an inhomogeneous luminance.     

Optical simulation of reduced retinal illuminance caused by senile miosis

In order to simulate elderly vision for young observers, we developed an optical goggle using filters whose transmittance optically simulates the senile miosis: reduction in retinal illuminance as a function of ambient illuminance. First, we measured the pupil size of young and elderly subjects (mean age were 21.8 and 67.1 years, respectively) under six illuminance conditions (from 0.03 to 4850 lx), and formulated the relationship between illuminance and pupillary area functions in both age groups. Next, the transmittance formulae for the filter simulating the senile miosis were derived based on the properties of the pupillary area and visual functions of the elderly and the young subjects including the effect of mydriasis induced by the reduction of light due to the filter in young observers. Finally, we developed a goggle-type simulator using active optical devices which enables young people to experience senile miosis in any environment in real time.     

WIDE RANGE DETECTOR USING PARABOLIC CYLINDRICAL MIRROR FOR THz APPLICATIONS

A new, wide-band, high-speed and high-sensitivity THz detector has been developed. The prototype detector consists of a parabolic cylindrical mirror, a long wire antenna and a Schottky barrier diode. Direct detection measurements have shown a stable sensitivity of 150 ± 50 V/W for 1–2 THz without any adjustments. The long wire antenna was fixed at the focus of parabolic cylindrical mirror then it has been realized less operation steps, easy coupling to the external THz signals and a dramatic enhancement in the practicality of this system. The optically polished mirror and frosted surface one showed comparable sensitivities, thus easy polishing and less cost mirror fabrication can be applied for this system. The radiation pattern showed a maximum radiation angle of approximately 23° with its dominant main lobe, which was attributed to the wire antenna character and confirmed good agreements with classical antenna theory.     

Injection seeding for single-mode operation in an optically pumped high-power D2O laser

Spectrally narrow, pulsed outputs consisting of almost a single mode have been obtained from an optically-pumped high-power (200kW) D₂O laser by adopting the injection seeding method, where single-mode radiation (seed pulse) from a low-power, compact D₂O laser has been injected into the main D₂O laser. Spectrally narrow outputs with high power having spectral widths as narrow as 5 MHz have been obtained, when the seed pulses with frequency tuned to one longitudinal mode of the main D₂O laser have been injected at a time sufficiently before the lasing of the main laser took place. The experimental results have been compared with those of numerical simulation modified to include the injection field with varying injection times.