Naoki Kobayashi

A synthesis of (−)-sitophilate by utilizing yeast-mediated reduction of an enol ester☆

Abstract The microbial reduction of 1′-ethylpropyl 2-methyl-3-oxopentanoate, a β-keto ester possessing bulky substituent, as well as the corresponding enol ester was examined. Epimeric mixture of hydroxy ester, containing (2S,3S-isomer as the major product (92%e.e., 43%d.e.) was obtained via the reduction of enol ester with growing cells of Pichia farinosa IAM 4682 in 63% yield. The resulting β-hydroxy ester was converted to (2S,3R)-isomer (88%e.e., 96%d.e.), of which e.e. was further enhanced by the lipase-catalyzed partial hydrolysis of the corresponding chloroacetate to give (−)-sitophilate, (99%e.e., 98%d.e.) an aggregation pheromone of Sitophillus granarius L.

Halftoning technique using genetic algorithm

A new method for the halftoning technique using genetic algorithms (GA) is proposed. For representing gray-tone images on bilevel displays or printers, the gray-tone images need to be transformed into binary images by using halftoning techniques. Visually pleasing halftone images must have both a high spatial resolution and a high gray level resolution. In this method, a halftoning technique is regarded as an optimizing problem that is to search for a visually pleasing distribution of white and black pixels. In the study, spatial and gray level resolutions of halftone images are evaluated, and then the evaluated value is optimized by using GA. For demonstrating an efficacy of the proposed two halftoning techniques, the results obtained by a computer simulation are shown.<<ETX>>

Evolutionary computation approaches to halftoning algorithm

In this paper, evolutionary computation approaches to halftoning algorithm is described. The halftoning technique is required for representing gray-tone images on bilevel displays or printers. Using the halftoning techniques, gray-tone images are transformed into binary representations. In general, visually pleasing halftone images must have high spatial and gray-level resolution. In this study, the halftoning algorithm is regarded as a optimization problem that is to search for the visually pleasing placement of black pixel in the halftoning image. For solving the problem, a Simple GA (SGA) and a Single Populated GA (SPGA) are applied to the halftoning algorithm. Some halftone images obtained by the evolutionary computation are shown, and their performances are demonstrated.<<ETX>>

Halftoning technique using genetic algorithms

A new halftoning technique using genetic algorithm (GA) has been proposed. GA is the optimal search algorithm based on natural selection. An original gray-tone image is divided into some equally sized blocks. A binary block of the halftone image is coded as the string in GA. The fitness value for the string is defined according to the visual quality of the halftone image. By using GA, the binary block having the highest fitness value is searched for among every block. The efficacy of the proposed halftoning technique is demonstrated by the results obtained by computer simulation.

Catalytic control requirements for the stable operation of the closed‐cycle, transversely excited atmospheric CO2 laser

Using a comprehensive theoretical CO2 laser model, we calculated the amount of the catalytic conversion from CO to CO2, which is required for the stable and long‐life operation of the closed‐cycle, transversely excited atmospheric CO2 laser. The amount of the catalytic conversion was evaluated by the fractional conversion (η) defined as η=([CO]in−[CO]out)/[CO]in, where [CO]in and [CO]out are the CO molecules number density at the entrance and exit of the CO2 regenerator in the laser chamber, respectively. For the laser gas mixture of CO2/N2/He=15/15/70(%) and the output coupler reflectivity of 80%, an η of the CO2 regenerator greater than 0.22 is theoretically required to maintain the 95% level of the initial laser output energy at an input energy density and a laser gas clearing ratio CR of 176.1 J/l and 2.0, respectively.

Reduction of Acyl Enolates of α-Substituted β-Keto Esters by Bakers’ Yeast

Enol esters of 2-substituted-3-oxoalkanoates of (Z)-configuration were reduced by bakers yeast to chiral 2-substituted-3-hydroxyalkanoates. The syn-selectivities of this reaction increased compared with those of the reduction of the corresponding racemic keto esters. The reaction may proceed via an asymmetric hydrolysis of the enol esters, followed by the reduction of the resulting carbonyl group.

A study on iterative video coding rate–distortion optimization and its rate control

Encoding a video clip with as large a compression ratio as possible within a framework of established standards is a key technology for digital TV broadcasting, content creation, distribution, and storage. Optimization, encoding a video clip at the highest possible quality within a given bit rate, is expected to become increasingly important in the future. As this process repeats encoding many times, rate control should converge quickly. This paper proposes an iterative encoding (N-pass) optimization strategy based on the Lagrange multiplier method. It focuses on local coding units and knowledge about optimal multipliers within an MPEG-2 framework. We also propose and demonstrate an affiliated accurate rate control algorithm. Simulation results show the PSNR gain for this optimization method is 1.0 to 1.9 dB higher than that offered by the TM5 method, and is significantly higher than the 0.03 to 0.7 dB gain improvement over TM5 we achieved with quantization-parameter-based optimization. The rate control framework is highly accurate; the error is less than 1% within one or two rate control iterations.

Analysis of gas degradation under a closed-cycle high-repetition-rate operation of a transversely excited atmospheric CO2 laser

Using the newly developed 1 kHz closed-cycle TEA CO2 laser with the efficient CO2 regenerator including the Pt/Al2O3 solid catalyst, we experimentally determined the minimum operational performance of the CO2 regenerator which is required for the stable and long-life operation of the closed-cycle TEA CO2 laser. The operational performance of the CO2 regenerator was evaluated by the fractional conversion (eta) from CO to CO2, which is defined as the ratio of the differential CO2 concentration increased by the CO2 regenerator to the total CO concentration introduced into the CO2 regenerator. The minimum eta of 0.07 was at least required to keep the laser output power at 95 percent of the initial laser output for the laser gas mixture of CO2/N2/He = 15/15/70 (percent) and at an input energy density and a clearing ratio of 150 J/l and 6.0, respectively. When operating the CO2 regenerator at eta of 0.10, no appreciable reduction of the initial laser output of 570 W due to CO2 decomposition was observed up to 1.8 x 10 exp 7 shots (5 hrs). At this time, gas analysis showed that the CO and O2 concentration in the laser gas mixture was maintained about at 0.17 percent and 0.055 percent, respectively.

Plasma chemistry of the closed-cycle 1 kHz transversely excited atmospheric CO/sub 2/ laser with an efficient catalytic CO/sub 2/ regenerator

A high-power closed-cycle 1 kHz transversely excited atmospheric (TEA) CO/sub 2/ laser with an efficient catalytic CO/sub 2/ regenerator was used to investigate the variations of the average laser output power and the concentrations of the CO/sub 2/, CO, and O/sub 2/ molecules in the laser gas mixture with the operational performance of the CO/sub 2/ regenerator. It was experimentally shown that for the laser gas mixture of CO/sub 2/-N/sub 2/-He=15-15-70% and the output coupler reflectivity of 70%, eta of 0.1 was required to maintain the laser output power greater than 90% of the initial laser output power of 570 W at an input energy density and a clearing ratio of 150 J/L and 3.0, respectively. >