Time-resolved Fourier transform infrared spectroscopy: Application to pulsed discharges

Time-resolved Fourier transform spectroscopy (TR-FTS) is reviewed, with emphasis on synchronous FTS using continuously scanning interferometers. By using a high-resolution Bruker IFS 120 HR, a TR-FTS method has been developed with the help of a microcontroller SX, where a maximum of 64 time-resolved data are recorded with a preset time interval in a single scan of the interferometer. The time resolution is 1 μs, limited by the response time of the detector system used. This method has been applied to a pulsed discharge in an Ar and H₂ mixture to observe time profiles of ArH⁺ and ArH emission spectra. Electronic transitions of He₂ have been observed in the infrared region with this method, and from the time profiles, He₂ in Rydberg states with higher energy than the b³Π state is found to be produced efficiently in afterglow plasma. Fifteen bands in the 2300-8000 cm⁻¹ region have been assigned by using previously reported data from the optical region. A new band from the 5f state has been assigned for the first time through the 5f-4d band in the 2600 cm⁻¹ region.     

A new method to evaluate the unfolding activity of chaperone unit ClpA based on Fe-S cluster disruption

ATP-dependent proteases unfold their substrates and then refold (via chaperone activity) or degrade (via protease activity) them. The proteases choose between these two activities by selecting their substrates; however, little is known about their substrate selection mechanism. The present study attempts to clarify this mechanism by investigating the role of the Escherichia coli (E. coli) ATP-dependent protease ClpAP. To address this, a reaction system that can measure both chaperone and protease activities simultaneously must be constructed. However, the chaperone activities cannot be evaluated in the presence of protease units. Green fluorescent protein (GFP) is usually used as a model substrate of ClpAP; the fluorescence decrease reflects the degradation of substrates. However, it is difficult to evaluate the chaperone activity of ClpAP using this system, because it cannot distinguish between intact and refolded substrates. Therefore, it is necessary to evaluate the exact unfolding activity while avoiding restoration of substrate spectroscopic characteristics due to chaperone activity. In this study, E. coli Ferredoxin (Fd) was used as a new model substrate for ClpAP to evaluate its unfolding activity. Intact and refolded substrates may be distinguished by the existence of an Fd Fe-S cluster. To verify this hypothesis, the absorption spectrum of Fd complexed with ClpA, the chaperone unit of ClpAP, was measured. A decrease in two peaks derived from the Fe-S cluster was observed, indicating that the Fe-S cluster of Fd was disrupted by the ClpA chaperone. This reaction system should prove useful to evaluate the exact unfolding activity of ATP-dependent proteases.     

Crystal-plasticity finite-element analysis of inelastic behavior during unloading in a magnesium alloy sheet

A crystal-plasticity finite-element analysis of the loading-unloading process under uniaxial tension of a rolled magnesium alloy sheet was carried out, and the mechanism of the inelastic response during unloading was examined, focusing on the effects of basal and nonbasal slip systems. The prismatic and basal slip systems were mainly activated during loading, but the activation of the prismatic slip systems was more dominant. Thus the overall stress level during loading was determined primarily by the prismatic slip systems. The prismatic slip systems were hardly activated during unloading because the stress level was of course lower than that during loading. On the other hand, because the strength of the basal slip systems was much lower than that of the prismatic slip systems, the basal slip systems would be easily activated under the stress level during unloading in the opposite direction when their Schmid’s resolved shear stresses changed signs because of the inhomogeneity of the material. These results indicated that one explanation for the inelastic behavior during unloading was that the basal slip systems were primarily activated owing to their low strengths compared to that of the prismatic slip systems. Numerical tests using the sheets with random orientations and with the more pronounced texture were conducted to further examine the mechanism.     

Hydrodynamics: Fluctuating initial conditions and two-particle correlations

Event-by-event hydrodynamics (or hydrodynamics with fluctuating initial conditions) has been developed in the past few years. Here we discuss how it may help to understand the various structures observed in two-particle correlations.     

Single-shot two-dimensional spectral interferometry for ultrafast laser-produced plasmas

Coherent white light was used as a light source for spectral interferometry of ultrafast laser-produced plasmas. Using a narrowband filter, two-dimensional images of field ionization in helium were obtained with a 14 fs time resolution.     

Development and Application of Different Non-thermal Plasma Reactors for the Removal of Perfluorosurfactants in Water: A Comparative Study

Plasma Chemistry and Plasma Processing - The degradation of perfluorosurfactants (PFS), particularly of PFOS, has been studied in dielectric barrier discharge (DBD) and nano-pulse corona discharge...     

Optical testing of star sensor (I): Defocus spot measuring technique for ground-based test

We developed a technique for measuring the intensity distribution of a point image in sub-pixel resolution even after assembly of a lens and an image sensor, which is especially suitable for defocus adjustment of a star sensor used to determine the attitude of a spacecraft. The star sensor optical system is usually aligned in a defocused position to calculate the luminance centroid of a star image in sub-pixel resolution. In the measurement technique, the point image is carefully scanned around a certain pixel on the image sensor, and the intensity change of the pixel is recorded during the scanning. We applied this technique to the alignment of our star sensor’s optical system, and we were able to suppress the spot size in a range between 1.2 and 2.2 pixels at 1/e² diameter at a certain defocus position, making it appropriate for luminance centroid calculation.     

Lipase-catalyzed kinetic resolution of cyclic trans-1,2-diols bearing a diester moiety: synthetic application to chiral seven-membered-ring alpha,alpha-disubstituted alpha-amino acid

Chiral cycloalkane-trans-1,2-diols (+/-)-3 and (+/-)-8 having a diester moiety have been prepared from dimethyl dialkenylmalonate using olefin metathesis by Grubbs catalyst, followed by epoxidation and acidic hydrolysis. Kinetic resolution of racemic cyclopentane-trans-1,2-diol (+/-)-3 by lipase-catalyzed transesterification afforded an optically active monoacetate (-)-5 of 95% ee in 46% yield and the recovered diol (-)-3 of 92% ee in 51% yield, and that of cycloheptane-trans-1,2-diol (+/-)-8 gave a monoacetate (+)-10 of 95% ee in 51% yield and the diol (-)-8 of >99% ee in 43% yield, respectively. The enantiomer selectivity of racemic cyclic trans-1,2-diols bearing a diester moiety by lipases (Amano PS and Amano AK) was opposite to that of the reported simple racemic cycloalkane-trans-1,2-diols. To explain the lipase-catalyzed enantiomer selectivity, computer modeling of lipase-substrate complexes was performed. Furthermore, the optically active diester (-)-8 could be efficiently converted into an optically active seven-membered-ring alpha,alpha-disubstituted amino acid (4R,5R)-(-)-15.     

Characterization of polypropylenes prepared with bis‐indenyl type metallocene and MgCl2‐supported TiCl4 catalyst systems

The homo‐polypropylene: m‐PP, prepared with rac‐Me₂Si[2‐n‐Pr‐4‐(9‐Phenanthryl)‐Ind]₂ZrCl₂, showed 99.6% of [mmmm] and 162.8°C of melting temperature (Tm). This polymer was compared by TREF analysis with the homo‐polypropylene: Ti‐PP, which was produced by our latest MgCl₂‐supported TiCl₄ catalyst system and showed 99.0% of [mmmm] and 165.7°C of Tm. It was indicated that m‐PP has narrower stereoregurality distribution than Ti‐PP and Tm of the fraction eluted from m‐PP at the highest temperature range is 163.6°C, while that from Ti‐PP reaches to 167.3°C. The characters and advantages of each polymer are discussed on the basis of these results. In addition, an advantage of this metallocene was made clear by characterization of polypropylenes copolymerized with ethylene.