Utsunomiya University

About: Utsunomiya University is a education organization based out in Utsunomiya, Japan. It is known for research contribution in the topics: Laser & Holography. The organization has 4139 authors who have published 6812 publications receiving 91975 citations. The organization is also known as: Utsunomiya daigaku.

Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers

Abstract: Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers.

Identification and Molecular Characterization of Viruses Infecting Cucurbits in Pakistan

Abstract: Cucurbits are grown throughout the North-West Frontier Province of Pakistan as summer and winter crops. Plants having mosaic, mottling, chlorosis and leaf distortion symptoms were frequently found in most of the cucurbit fields during the survey. Using dot immunobinding assay, Cucumber green mottle mosaic virus (CGMMV), Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV) and Papaya ringspot virus (PRSV) were found infecting cucurbits. CGMMV was widespread, infecting 46.9% of the samples tested followed by ZYMV (14.8%), WMV (12.5%) and PRSV (7.8%). Multiple infections were common with 42% of the samples being infected with two viruses and 8% with three viruses. The nucleotide sequences of the coat protein (CP) genes of these four viruses were determined and deduced amino acid sequence comparisons revealed 88.3-99% similarity of the ZYMV-Pak isolate with other isolates of ZYMV reported worldwide. The amino acid sequence identity of Pakistani isolates of WMV, CGMMV and PRSV ranged from 96.8 to 98.4%, 98.1 to 99.4% and 79.3 to 84.2%, respectively, with other isolates reported elsewhere. Little variability was observed in the sequences of WMV and CGMMV. ZYMV-Pak was very close to the USA isolate, and the PRSV-Pak isolate was close to Indian isolates of PRSV possibly reflecting the geographical relationship between these isolates.

Upgrading of bitumen with formic acid in supercritical water

Abstract: Upgrading of bitumen was examined with formic acid in supercritical water (SCW) from 673 to 753 K and at a water/oil ratio from 0 to 3. Decomposition of bitumen in SCW + HCOOH gave higher conversions of asphaltene and lower coke yields than those of pyrolysis or with only SCW. Decomposition of bitumen was also conducted in SCW + H2, SCW + CO, toluene and tetralin, which revealed that decomposition of asphaltene was promoted and coke formation was suppressed when using SCW + HCOOH. In SCW + HCOOH, an increase in the water/oil ratio promoted both decomposition of asphaltene and suppression of coke formation. Formic acid in SCW seemed to enhance the conversion of bitumen to lower molecular weight compounds because formic acid seems to produce active species in SCW. The low temperature region (ca. 723 K) was suitable for upgrading bitumen with formic acid in SCW since coke formation was strongly promoted at high temperature (>753 K). A reaction model was proposed and the model predicted that hydrogenation of the asphaltene core was important for the suppression of coke formation.

Effect of a laser prepulse on fast ion generation in the interaction of ultra-short intense laser pulses with a limited-mass foil target

Abstract: Fast electrons generated in ultra-intense laser interaction with a solid target can produce multi-MeV ions from laser-induced plasmas. These fast ions can have different applications ranging from ion implantation to nuclear reactions. The most important parameter is the efficiency of fast ion production. An analytical model and particle-in-cell simulations were employed to examine acceleration mechanisms that can provide an optimal plasma density distribution due to a laser prepulse. We considered the acceleration of ions leaving a plasma layer with different density gradients, from a step-like overdense plasma to an underdense plasma with a smooth density gradient. The effects of the plasma initial scale length and density on the ion acceleration were analysed, and we found that the optimal case should have some plasma parameters. It is shown that overdense plasmas provide a higher density of accelerated ion energy than underdense plasmas at intensities below 1019 W cm−2.