Cloning and characterization of an n-alkane-inducible cytochrome P450 gene essential for n-decane assimilation by Yarrowia lipolytica

A gene encoding cytochrome P450 involved in n-alkane utilization was cloned from an n-alkane assimilating yeast, Yarrowia lipolytica CX161-1B. The RT-PCR was performed on the mRNA prepared from the cells grown on n-alkane as a template using degenerated PCR primers designed for the conserved amino acid sequences of the CYP52 family. The RT-PCR amplified fragment was then used as a probe to isolate genes coding for P450 of the CYP52 family from the genomic DNA library of the strain CX161-1B. The nucleotide sequence of one of the positive clones was determined. An open reading frame which had the same nucleotide sequence as the RT-PCR-amplified fragment was identified. It was of 523 amino acid residues, 60·2 kDa in molecular mass, and had 30–45% sequence identity with the other members of the CYP52 family of Candida species so far analysed. The expression of the P450 gene that was named as YlALK1 was induced by n-tetradecane and repressed by glycerol. A YlALK1 gene disruptant did not grow well on n-decane, but grew on longer-chain n-alkanes such as hexadecane as a sole carbon source. Introduction of YlALK1 on a plasmid to the disruptant restored the decane assimilation. These results suggest that the YlALK1 gene product is the major P450Alk to metabolize short-chain n-alkanes such as decane and dodecane in Y. lipolytica. © 1998 John Wiley & Sons, Ltd.     

Catalytic activity of pitch-based activated carbon fiber of large surface area heat-treated at high temperature and its regeneration for NO–NH3 reaction at ambient temperatures

The catalytic activity of a pitch-based activated carbon fiber (ACF) of very large surface area (OG-20A) was studied for NO–NH₃ reaction in a flow reactor at ambient temperatures. The ACF exhibited the highest activity in wet as well as dry gas among heat-treated ACFs so far examined by the present authors. The calcination at 1100°C was essential to exhibit the highest activity especially in wet gas. Although high humidity always retarded the reaction very markedly, its retardation was very much emphasized against NO of low concentration around 10 ppm. Sufficient amount of OG-20A-H1100 (3 g) allowed complete removal of 10–200 ppm NO by reduction and adsorption for initial 6 h even at least in wet gas at 25–30°C depending on NO concentration. The removal conversion decreased gradually for several hours following to the stationary one. The reactivity of adsorbed NO and NH₃ was examined in air to regenerate the period of complete NO removal over the ACF. The regeneration at 30°C was found optimum after the removal reaction at 25 or 30°C to provide the same period of complete removal by 3 h, leaking minimum amounts of adsorbed NO and NH₃. A higher reaction temperature of 35°C shortened the period of complete NO removal, and the successive regeneration at 30°C by 3 h failed in the complete NO removal in the second run. Oxygen appears necessary to regenerate the activity through enhancing the reaction of adsorbed NO and NH₃. NH₃ in the regeneration gas appears to inhibit the reaction of adsorbed species, increasing NH₃ leak.     

Fatty Acid Desaturation and Elongation Reactions of <Emphasis Type="Italic">Trichoderma</Emphasis> sp. 1-OH-2-3

The fatty acid desaturation and elongation reactions catalyzed by Trichoderma sp. 1-OH-2-3 were investigated. This strain converted palmitic acid (16:0) mainly to stearic acid (18:0), and further to oleic acid (c9-18:1), linoleic acid (c9,c12-18:2), and α-linolenic acid (c9,c12,c15-18:3) through elongation, and Δ9, Δ12, and Δ15 desaturation reactions, respectively. Palmitoleic acid (c9-16:1) and cis-9,cis-12-hexadecadienoic acid were also produced from 16:0 by the strain. This strain converted n-tridecanoic acid (13:0) to cis-9-heptadecenoic acid and further to cis-9,cis-12-heptadecadienoic acid through elongation, and Δ9 and Δ12 desaturation reactions, respectively. trans-Vaccenic acid (t11-18:1) and trans-12-octadecenoic acid (t12-18:1) were desaturated by the strain through Δ9 desaturation. The products derived from t11-18:1 were identified as the conjugated linoleic acids (CLAs) of cis-9,trans-11-octadecadienoic acid and trans-9,trans-11-octadecadienoic acid. The product derived from t12-18:1 was identified as cis-9,trans-12-octadecadienoic acid. cis-6,cis-9-Octadecadienoic acid was desaturated to cis-6,cis-9,cis-12-octadecatrienoic acid by this strain through Δ12 desaturation. The broad substrate specificity of the elongation, and Δ9 and Δ12 desaturation reactions of the strain is useful for fatty acid biotransformation.     

Dehydrogenation and hydrogenation activity of palladium-tin-silica and nickel-tin-silica

The dehydrogenation of cyclohexanone, cyclohexylamine, cyclohexane, and 2-propanol and the hydrogenation of ethylene on palladium-tin-silica and the hydrogenation of benzene on nickel-tin-silica were studied. With nickel-silica and nickel-tin-silica, the deposition of carbonaceous materials was studied kinetically. The X-ray photoelectron spectra of palladiumtin and nickel-tin were observed. The catalytic activities of both of the catalyst systems changed in similar ways with the change of the $\text{Pd}\text{Sn}$ and $\text{Ni}\text{Sn}$ ratios (atomic) of the catalysts. The dehydrogenation activity increased to a maximum and then decreased, with a decrease in the $\text{Pd}\text{Sn}$ and $\text{Ni}\text{Sn}$ ratios. The hydrogenation activity of the tin-containing catalysts was much lower than that of the tin-free catalysts. Carbonaceous materials were observed to be deposited more easily on the nickel-silica than on the nickel-tin-silica. The palladium-4d and nickel-3d band peaks of the alloy systems obtained by X-ray photoelectron spectroscopy were observed to shift to higher binding energies as the $\text{Pd}\text{Sn}$ and $\text{Ni}\text{Sn}$ ratios decreased. From the amount of carbon monoxide adsorbed, the surface concentration of palladium and that of nickel on the catalysts were suggested to be the minor determining factor of the catalytic activity studied here. It is concluded that tin is not just a diluent for the active metal but is an effective component to weaken the adsorption bond.     

Influence of achievement need on goal setting, performance, and feedback effectiveness.

91 undergraduates set their own goal to be attained on a perceptual speed task lasting 15 min and received feedback after 7? min of work. Ss' achievement need, as assessed through the Manifest Needs Questionnaire, significantly correlated with the goals set and total number attempted. Partial correlation between achievement need and the total number attempted was nonsignificant when goal difficulty was held constant, suggesting that achievement need affected the total number attempted through its effect on goal difficulty. Only the Ss who were higher in achievement need performed better after than before feedback. The rationale for the moderating effect of achievement need on the feedback–performance relationship and its implication for previous goal-setting findings are discussed. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The mechanisms of fission gas release from (Th,U)O2

The releases of xenon from three (Th, U)O₂ specimens with different U contents were measured over a wide range of fission dose from $\text{2.9 × 10}{}^{19}$ to $\text{2.2 × 10}{}^{22}$ fissions m^?3 by using a post-irradiation technique. The releases were found to decrease with dose and to level off at higher doses. Measurements of the changes in lattice parameter and specific surface area of the same specimens enabled one to conclude that the decrease in release originates in the trapping of xenon by the vacancies and vacancy clusters induced by fission fragments. And the release mechanisms of fission gas were proposed based on the proper evaluation of the observation on radiation damage and recovery in oxide fuel.     

Studies on modified phenolic resin. Iv: Properties of phenolic resin modified with 4-hydroxyphenyl- maleimide/n-butylacrylate copolymers

Three 4-hydroxyphenylmaleimide/ n-butylacrylate (HPMI/n-BuA) copolymers with different monomer ratios were synthesized. Their average molecular weights, glass transition temperatures (T,_g), and thermal decomposition temperatures were measured. It was found that these copolymers had higher average molecular weights and higher thermal decomposition temperatures than novolac. Modified phenolic resins were prepared by transfer moulding from moulding compounds consisting of novolac, the copolymer, hexamethylenetetramine (hexamine), and glass fibre. Properties of the three kinds of modified phenolic resins were examined by flexural test, impact test, dynamic thermomechanometry, and observation of morphology. It was found that phenolic resin modified with HPMI/ n-BuA (1/3-6) copolymer and modified with HPMI/n-BuA (1/7-0) copolymer showed good toughness and good heat resistance. It was also found that the heat resistance of modified phenolic resins was improved by after-cure, but the mechanical properties were decreased by after-cure: similar behaviour was observed for unmodified phenolic resin.     

Duplication and partial evaluation

This paper presents a general implementation framework for reflective languages. It allows us to systematically build reflective languages which have the following favorable properties: (1) user programs are allowed to access and change (parts of) metalevel interpreters, (2) reflective facilities are available at every level, (hence there exists conceptually an infinite tower of interpreters), and (3) the interpreter runs as efficiently as the conventional (directly implemented) metacircular interpreter when reflection is not used. Our scheme is divided into three stages. First, we define interpreters which give the operational semantics of each level, and conceptually construct the infinite tower of these interpreters. They are thenduplicated to obtain directly executed interpreters, while introducing double interpretation to maintain redefinability of interpreters. Finally, partial evaluation is employed to collapse the double interpretation into single interpretation. We illustrate our scheme by implementing a particular reflective language calledBlack in Scheme, but it is general enough to be applied to other reflective languages. The paper gives the complete Scheme implementation of Black and demonstrates some examples. We also show how a system with the delta abstraction introduced by Blond can be constructed in our framework.     

Semisupervised learning for a hybrid generative/discriminative classifier based on the maximum entropy principle

This paper presents a method for designing semi-supervised classifiers trained on labeled and unlabeled samples. We focus on probabilistic semi-supervised classifier design for multi-class and single-labeled classification problems, and propose a hybrid approach that takes advantage of generative and discriminative approaches. In our approach, we first consider a generative model trained by using labeled samples and introduce a bias correction model, where these models belong to the same model family, but have different parameters. Then, we construct a hybrid classifier by combining these models based on the maximum entropy principle. To enable us to apply our hybrid approach to text classification problems, we employed naive Bayes models as the generative and bias correction models. Our experimental results for four text data sets confirmed that the generalization ability of our hybrid classifier was much improved by using a large number of unlabeled samples for training when there were too few labeled samples to obtain good performance. We also confirmed that our hybrid approach significantly outperformed generative and discriminative approaches when the performance of the generative and discriminative approaches was comparable. Moreover, we examined the performance of our hybrid classifier when the labeled and unlabeled data distributions were different.     

Genetic algorithm with dynamic variable number of individuals and accuracy

This paper proposes a novel processor for genetic algorithm (GA) that can dynamically change number of individuals and accuracy. In conventional GA, number of population and accuracy are fixed. However, the accuracy of solution is low at first-half stage. Therefore, the number of population is doubled at expense of the accuracy of solution, and the searching ability is improved at first-stage in the proposed GA processor. Then, the number of population is reduced by half, and the accuracy is improved at second-half stage. As a result, the searching ability is improved. The proposed GA processor was designed and verified. The effectiveness of proposed method was confirmed by applying to the knapsack problem. Recommended by Guest Editor Phill Kyu Rhee. This work was supported by the grant from Research Institute for Science and Technology, Tokyo Denki University (Q06J-03). Akihiko Tsukahara received the B.E. degree in Electronic Engineering from Tokyo Denki University in 2005. He is currently a M.E. student in Tokyo Denki University. His research interests include VLSI design for genetic algorithm and rough sets. Akinori Kanasugi received the B.E., M.E. and Ph.D. degrees from Saitama University, Japan, in 1983, 1985 and 1994, respectively. After a research associate in Saitama University, he moved to Tokyo Denki University in 2002, where he is currently a Professor in the Faculty of Engineering. His current research interests are in the development of VLSI systems such as reconfigurable processor, GA processor, and rough sets processor.