Ultrafast isomerization-induced cooperative motions to higher molecular orientation in smectic liquid-crystalline azobenzene molecules

The photoisomerization of molecules is widely used to control the structure of soft matter in both natural and synthetic systems. However, the structural dynamics of the molecules during isomerization and their subsequent response are difficult to elucidate due to their complex and ultrafast nature. Herein, we describe the ultrafast formation of higherorientation of liquid-crystalline (LC) azobenzene molecules via linearly polarized ultraviolet light (UV) using ultrafast time-resolved electron diffraction. The ultrafast orientation is caused by the trans-to-cis isomerization of the azobenzene molecules. Our observations are consistent with simplified molecular dynamics calculations that revealed that the molecules are aligned with the laser polarization axis by their cooperative motion after photoisomerization. This insight advances the fundamental chemistry of photoresponsive molecules in soft matter as well as their ultrafast photomechanical applications

Comparison of properties between Pr-Fe-B and Nd-Fe-B thick-film magnets applied to MEMS

We investigated the possibility of R (Nd or Pr)-Fe-B thick-film magnets applied to MEMS. First, an enhancement in the thickness of the Si oxide layer on a Si substrate enabled us to increase the adhesion force between the Si substrate and Nd-Fe-B film. Then, after depositing a glass buffer layer on the Si substrate to obtain a thicker Si oxide layer, we compared the mechanical characteristics and magnetic properties of both Pr-Fe-B and Nd-Fe-B films. As the thickness of the glass buffer layer increased, the thickness of the Pr-Fe-B film could be enhanced without mechanical destruction. We had difficulty in exceeding the thickness of 100 μm in Nd-Fe-B films. Moreover, the (BH)max value of a 127-μm-Thick Pr-Fe-B film was higher by approximately 30 kJ m-3 than that of a 92-μm-Thick Nd-Fe-B film. The obtained results suggest that a Pr-Fe-B thick-film magnet is more suitable for MEMS applications

Identification of cis-acting promoter sequences required for expression of the glycerol-3-phosphate acyltransferase 1 gene in mice

Glycerol-3-phosphate acyltransferase 1 (GPAT1) is a rate limiting enzyme in de novo glycerophospholipid synthesis. The murine GPAT1 promoter sequence (the “classical” sequence) was reported previously. However, the organization of this DNA sequence does not fully match the mouse genome sequences on NCBI/GenBank. Here we have identified net cis-acting promoter sequences for the mouse GPAT1 gene: promoter 1a which includes part of the classical sequence and the downstream promoter 1b. Promoter 1a facilitates transcription of two alternative GPAT1 transcript variants, GPAT1-V1 and V2, while promoter 1b produces a third transcript variant, GPAT1-V3. Upstream stimulating factor-1 (USF-1) controlled both promoters whereas sterol regulatory element-binding protein-1 (SREBP-1) exclusively regulated promoter 1a activity in vitro. Feeding increased GPAT1-V1 and V2, but not V3 mRNA levels in mouse liver. The obese condition of db/db mice did not alter the hepatic expression levels of any of the three GPAT1 variants. Feeding enhanced hepatic mRNA levels, intranuclear protein levels and promoter 1a-binding levels of SREBP-1, but not of USF-1. Thus, promoter 1a was exclusively activated by routine feeding in vivo. Our results indicate differential roles of the two promoters in the regulation of hepatic GPAT1 gene expression in mice

Nanomaterials by severe plastic deformation: review of historical developments and recent advances

International audienceSevere plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such as high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, and multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover, numerous alloys, glasses, semiconductors, ceramics, polymers, and their composites were processed. The SPD methods were used to synthesize new materials or to stabilize metastable phases with advanced mechanical and functional properties. High strength combined with high ductility, low/room-temperature superplasticity, creep resistance, hydrogen storage, photocatalytic hydrogen production, photocatalytic CO2 conversion, superconductivity, thermoelectric performance, radiation resistance, corrosion resistance, and biocompatibility are some highlighted properties of SPD-processed materials. This article reviews recent advances in the NanoSPD field and provides a brief history regarding its progress from the ancient times to modernity

Elimination of Systematic Error in Diffusion Measurement Using In-situ X-ray Fluorescence Analysis for Liquid Alloys

The objective of the present study is to quantify and eliminate the error factors in the measurement of diffusion coefficients in liquid alloys by using in-situ X-ray fluorescence analysis (in-situ XRF). Averaging effect, initial mass transport, and matrix effect were investigated. The impurity diffusion coefficient of Bi in liquid Sn was measured at 573 K using a combination of the long capillary technique and in-situ XRF. The apparent diffusion coefficient was obtained as the time-series data by fitting an analytical solution of Fick’s second law to the temporal variation in Bi concentration in the capillary. In the present measurement, matrix effect did not induce a significant error in the measured diffusion coefficient. Averaging effect can be eliminated by convoluting the analytical solution with the distribution of the X-ray fluorescence intensity scanned from the rod sample. Furthermore, the initial mass transport can be eliminated by shifting the point of time origin to the latter time in the temporal variation in the measured concentration by fitting the analytical solution. By performing the above corrections, the systematic error in the measured diffusion coefficient can be reduced