Efficient preparation of DHMF and HMFA from biomass-derived HMF via a Cannizzaro reaction in ionic liquids

2,5-Dihydroxymethylfuran (DHMF) and 5-hydroxymethylfuranoic acid (HMFA) are the versatile intermediate chemicals of high industrial potential. An efficient preparation of both DHMF and HMFA is reported from biomass-derived HMF via a Cannizzaro reaction using ionic liquids as a reusable reaction solvent under the water-free conditions. The operationally simple and environment-friendly process produces both DHMF and HMFA from HMF consistently in good to high yields up to five runs with the recycled ionic liquid.     

OPT: optimal human visual system-aware and power-saving color transformation for mobile AMOLED displays

Organic light-emitting diode (OLED) displays have a high power efficiency; however, the frequent use of user interaction-based applications such as instant messengers, video players, and games contributes strongly to the total power consumption. The power consumption varies significantly depending on the display contents, and thus, color transformation, which is a representative low-power technique, is used for OLED displays. Previously developed low-power color transformation methods have not been thoroughly researched for satisfying the human visual system and have not considered optimal visual satisfaction and power consumption simultaneously. In this paper, a novel low-power color transformation approach is proposed, which is aimed at simultaneously optimizing both visual satisfaction and power consumption. In addition, it is implemented on an active-matrix OLED (AMOLED) display-based Android smartphone at runtime. Experimental results show that the proposed technique achieves better human visual satisfaction and shows up to 22.32% power saving on average on the AMOLED display and offers 6.23% more extended battery life over that of an existing leading technique.

     

Multi-wavelength emitting InGan/GaN quantum well grown on V-shaped gan(1101) microfacet

InGaN/GaN multiple quantum wells (MQWs) were successfully grown on the inclined GaN(1101) microfacets. Conventional photolithography and subsequent growth of GaN were employed to generate the V-shaped microfacets along (1120) direction. The well-developed microfacets observed by scanning electron microscopy and the clear transmission electron microscope interfacial images indicated that the MQW was successfully grown on the GaN microfacets. Interestingly, cathodoluminescence (CL) spectra measured on the microfacets showed a continuous change in the luminescence peak positions. The CL peaks were shifted to a longer wavelength from 420 nm to 440 nm as the probing points were changed along upward direction. This could be attributed to the nonuniform distribution of the In composition and/or the wavefunction overlapping between adjacent wells. Present works thus propose a novel route to fabricate a monolithic white light emitting diode without phosphors by growing the InGaN/GaN MQWs on (1101) facet.     

Overexpression of ethionine resistance gene for maximized production of S-adenosylmethionine in Saccharomyces cerevisiae sake kyokai No. 6

In our previous work, we developed an auxotrophic mutant of Saccharomyces cerevisiae sake kyokai No. 6 strain for the selection of recombinant DNA. Sake yeast can accumulate high amount of S-adenosylmethionine (SAM) that is effective for treating depression, Alzheimer’s disease and so on. In this work, we further introduced SAM2 gene and ERC1, a frame-shift mutant of YHR032w, to maximize the production of S-adenosylmethionine in S. cerevisiae sake K6. The recombinant strain accumulated SAM about half of its dry cell weight.     

Increased production of S-adenosyl-L-methionine using recombinant <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> sake K6

S. cerevisiae sake K6 was the firstly isolated industrial strain to overproduce S-adenosyl-L-methionine (SAM). Although the strain has advantages over other strains, such as GRAS (generally recognized as safe) property, the S. cerevisiae K6 has not been further developed with DNA recombinant technology due to the lack of a proper genetic marker. In this study, UV mutagenesis was conducted with S. cerevisiae sake K6. With the method, a mutant of sake yeast with leucine auxotroph, K6-1, was isolated. The mutant showed comparable growth rate and SAM productivity with its wild type. Using the auxotroph as a genetic marker, a SAM synthase in S. cerevisiae, SAM2, was overexpressed in the mutant strain. This recombinant DNA technology successfully increased SAM productivity in sake yeast. This article is dedicated to Professor Chul Soo Lee in commemoration of his retirement from Department of Chemical and Biological Engineering of Korea University.