Alkaliphilic lysine decarboxylases for effective synthesis of cadaverine from L-lysine

The enzymatic decarboxylation of L-lysine using lysine decarboxylase is a promising biological approach for producing cadaverine, a versatile platform chemical for bio-polyamides. However, due to the problem with elevated pH in the reaction solution during the enzymatic process, it is desirable to use lysine decarboxylases effectively active in alkaline conditions. In this study, the catalytic properties of three lysine decarboxylases from Selenomonas ruminantium (srLDC), Vibrio vulnificus (vvLDC), and Geobacillus thermodenitrificans (gtLDC) were characterized, and the applicability of the enzymes in alkaline conditions was investigated. Among the three enzymes, only vvLDC exhibited effective activity in alkaline pH conditions. The conversion rate of vvLDC was 1.5-fold higher than that of srLDC and 5.3-fold higher than that of gtLDC in pH 9.0. The results indicate that vvLDC is more advantageous than srLDC and gtLDC for the enzymatic conversion of L-lysine to cadaverine in alkaline conditions.     

A low Reynolds number dissipation rate equation model using the dissipation rate tensor equation and elliptic-blending equation

The purpose of this study is to theoretically supplement the dissipation rate equation model that has been adopted and used for the elliptic-blending second-moment closure widely and currently used for analysis of turbulent flow, and eventually to enhance the theoretical validity of the model. The new dissipation rate equation model was derived by using the dissipation rate equation in terms of length scale that can be applied both in the near-wall region and to homogeneous flow and by using the dissipation rate tensor equation model. The newly derived dissipation rate equation model is applied in the existing elliptic-blending model as it is. To test the model equation we conducted a numerical analysis of non-rotating and rotating channel flows, channel flow with uniform transpiration, square duct flow, and 3-dimensional curved duct flow before comparing the analysis results with DNS data and the measurements. In regard to all flow fields adopted in this study, the expected results showed a high satisfaction in comparison with DNS data and measurements, thereby proving the theoretical validity of the new model.     

Synergistic improvement of oxygen reduction reaction on gold/cerium-phosphate catalysts

The main challenge in fuel cells lies in improving slow oxygen reduction reaction (ORR) kinetics causing low conversion efficiencies. Here, we introduce the Au/CePO₄-binary nanocomposites as effective oxygen reduction catalysts in alkaline media. The ORR activity comparable with Pt is achieved through the serial 4-electron reduction pathway. The bi-functionality of CePO₄ is suggested to explain the remarkably enhanced activity on the Au/CePO₄ nanocomposites. Significantly, the own catalytic activity of CePO₄ for hydrogen peroxide is demonstrated, validating synergistic effects with Au for complete ORR.     

A framework for the segmentation of high-resolution satellite imagery using modified seeded-region growing and region merging

Image segmentation is becoming increasingly important in areas such as object-oriented image classification in the field of remote-sensing image analysis. We present a new approach for the image segmentation of a high-resolution pan-sharpened satellite image based on modified seeded-region growing and region merging. First, we conduct some pre-processing prior to image segmentation to improve segmentation quality. The initial seeds are automatically selected using the proposed block-based seed-selection method. After automatic selection of significant seeds, initial segmentation is achieved by applying the modified seeded-region growing procedure. Finally, region merging, based on a region-adjacency graph, is carried out in post-processing to obtain the final segmentation result. Experimental results demonstrate that the proposed method shows better performance than other approaches, and has good potential for its application to the segmentation of high-resolution satellite imagery.     

An inventory model-based spectrum pooling for wireless service provider and unlicensed users

In order to comply with more opportunistic and transient service requirements, many research literatures have paid attention to an approach called spectrum pooling. If we imagine a scenario in which wireless service providers (WSPs) manage the spectrum pool, the radio spectrum itself will be traded as done in a market-based scenario, and moreover, every WSP will likely require new strategies in order to make more profits under such dynamic service requirements. Up to now, most researches have concentrated on investigating the inter-WSP strategies such as market equilibrium under the consideration of noncooperative or cooperative WSPs. In this paper, we direct our attentions to an intra-WSP strategy: a WSP coordinates the spectrum order in order to minimize its cost. To this end, we deploy a probabilistic inventory model that helps WSPs to determine economic order quantity and reorder point yielding minimum total expected cost. The total cost is composed of ordering cost, holding cost, and stockout cost. We believe that this model will be the first investigation of intra-WSP strategy that manages and estimates economic aspects of the spectrum pooling.     

Ellipsometric study on the optical property of UV exposed MEH-PPV polymer film

We performed ellipsometric analysis on the effect of Ultra-Violet (UV) light exposure to the poly(2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylenevinylene) (MEH-PPV) films. The measured dielectric function spectrum of the MEH-PPV film showed the consistent decrease of absorption coefficients with the UV light exposure time, especially at the ordinary axis. This work notes that UV light protection method should be included in the process of MEH-PPV films for the optical device applications to prevent the significant change of optical property of the film and to maintain its efficient absorption of sunlight for solar cell devices.     

Occurrence of biogenic amines in Doubanjiang and Tofu

This study was performed to analyze biogenic amine contents and other parameters in doubanjiang and tofu. Through this study, it was found that doubanjiang contained considerably large amounts of most biogenic amines (>30 mg/kg of β-phenylethylamine in particular), and tofu had a relatively high level of spermidine (>20 mg/ kg). Therefore, the amounts of biogenic amines in the foods seem to be occasionally beyond the safe level for human consumption. Meanwhile, the biogenic amine contents in doubanjiang showed a good relationship with salt content (R²=0.89). The spermidine content in tofu samples was closely related to that in soybean, the raw material of tofu. There also appeared to be a good relationship (R²=0.82) between the biogenic amine contents and total plate counts in doubanjiang, but not in tofu. Most strains from the foods were capable of producing biogenic amines, and the identification revealed that bacterial ability to produce biogenic amines was determined at the level of strains rather than species. Taken together, it seems that biogenic amine contents in doubanjiang are mainly affected by fermentation processes, whereas those in tofu are primarily affected by raw materials.