Identification of auxotrophic mutants of the yeast Kluyveromyces marxianus by non‐homologous end joining‐mediated integrative transformation with genes from Saccharomyces cerevisiae

The isolation and application of auxotrophic mutants for gene manipulations, such as genetic transformation, mating selection and tetrad analysis, form the basis of yeast genetics. For the development of these genetic methods in the thermotolerant fermentative yeast Kluyveromyces marxianus, we isolated a series of auxotrophic mutants with defects in amino acid or nucleic acid metabolism. To identify the mutated genes, linear DNA fragments of nutrient biosynthetic pathway genes were amplified from Saccharomyces cerevisiae chromosomal DNA and used to directly transform the K. marxianus auxotrophic mutants by random integration into chromosomes through non‐homologous end joining (NHEJ). The appearance of transformant colonies indicated that the specific S. cerevisiae gene complemented the K. marxianus mutant. Using this interspecific complementation approach with linear PCR‐amplified DNA, we identified auxotrophic mutations of ADE2, ADE5,7, ADE6, HIS2, HIS3, HIS4, HIS5, HIS6, HIS7, LYS1, LYS2, LYS4, LYS9, LEU1, LEU2, MET2, MET6, MET17, TRP3, TRP4 and TRP5 without the labour‐intensive requirement of plasmid construction. Mating, sporulation and tetrad analysis techniques for K. marxianus were also established. With the identified auxotrophic mutant strains and S. cerevisiae genes as selective markers, NHEJ‐mediated integrative transformation with PCR‐amplified DNA is an attractive system for facilitating genetic analyses in the yeast K. marxianus. Copyright © 2013 John Wiley & Sons, Ltd.     

Prediction of pyrolysis kinetic parameters from biomass constituents based on simplex-lattice mixture design

The aim of this study is to determine the effect of the main chemical components of biomass:cel ulose, hemicel-lulose and lignin, on chemical kinetics of biomass pyrolysis. The experiments were designed based on a simplex-lattice mixture design. The pyrolysis was observed by using a thermogravimetric analyzer. The curves obtained from the employed analytical method fit the experimental data (R2 N 0.9). This indicated that this method has the potential to determine the kinetic parameters such as the activation energy (Ea), frequency factor (A) and re-action order (n) for each point of the experimental design. The results obtained from the simplex-lattice mixture design indicated that cellulose had a significant effect on Ea and A, and the interaction between cellulose and lignin had an important effect on the reaction order, n. The proposed models were then proved to be useful for predicting pyrolysis behavior in real biomass and so could be used as a simple approximation for predicting the overall trend of chemical reaction kinetics.     

A majority-density approach to developing testing and diagnostic systems with the cooperation of multiple experts based on an enhanced concept–effect relationship model

In the recent years, diagnosing students’ learning problems after testing and providing learning suggestions for them are an important research issue. Many studies have been conducted to develop a method for analyzing learning barriers of students such that helpful learning suggestions or guidance can be provided based on the analysis results. In this paper, we present a new procedure for integrating test item–concept relationship opinions based on majority density of multiple experts in order to enhance a concept–effect relationship model used for generating personalized feedback. It provides a useful and practical way to decrease inconsistencies in the weighting criteria of multiple experts and to enhance the entire learning-diagnosis procedure for developing testing and diagnostic systems.     

Durable compliant electrode based on graphene and natural rubber

A compliant electrode is a stretchable electronic device that retains good conductivity under stretching or bending. It has been used in various electro‐actuating applications which require large deformations under electrical field. The objective of this work was to fabricate a compliant electrode possessing high electrical conductivity and good mechanical properties. Due to the excellent mechanical properties of natural rubber (NR), it was used as a matrix for the compliant electrode. Graphene was used as a new and innovative conductive filler to provide excellent electrical conductivity. The mechanical properties and electrical properties were investigated by using a rheometer in the tension mode. Both mechanical and electrical properties were improved drastically by introducing graphene into the matrix. The highest electrical conductivity of 0.61 S/cm was obtained from the 35.0 %vol/vol graphene/NR composite, two orders of magnitude higher than that of the commercial compliant electrode. The 5.0 %vol/vol graphene/NR composite was shown and identified here as a promising material for using as a compliant electrode. POLYM. ENG. SCI., 57:129–136, 2017. © 2016 Society of Plastics Engineers     

Sublayers for Pt catalyst electrodeposition electrodes in PEMFC

The effect of sublayers on the deposited platinum (Pt) catalyst layer fabricated by electrodeposition, and on the resulting fuel cell performance, was investigated. The substrate was prepared by applying a hydrophobic sublayer, composed of polytetrafluoroethylene (PTFE) and carbon black, and a hydrophilic sublayer, composed of Nafion and glycerol, onto an uncatalyzed gas diffusion layer prior to the electrodeposition of the Pt catalyst. The hydrophilic sublayer was found to play a substantial role in the Pt electrodeposition, since the structure of the resultant Pt catalyst significantly depended on the presence of the hydrophilic sublayer, the total loading amount and the Nafion to glycerol weight ratio, which in turn affected the fuel cell performance. The hydrophobic sublayer, which did not directly contact with the plating solution, did not show as marked an effect on the Pt deposit structure compared to that of the hydrophilic sublayer, except at high PTFE to carbon black weight ratios (≥70:30). However, the suitable PTFE to carbon black weight ratio in the hydrophobic sublayer was still important for the water management, mass transport of reactant gases and ohmic resistance of the membrane electrode assembly (MEA) during fuel cell operation. In this study, a total hydrophilic loading of 0.8 mg cm⁻² with a Nafion to glycerol weight ratio of 50:50, and a PTFE to carbon black weight ratio in the hydrophobic sublayer of 30:70 was found to yield the best Pt catalyst layer for PEMFC.     

Variation of atmospheric optical depth for remote sensing radiance calculations

An analysis of the radiative transfer processes in the atmosphere suggests that the ratio between the diffuse radiance flux and the directly transmitted flux may be a useful parameter for investigating the variation of atmospheric optical depth. The radiative parameter is derived for an observer at the top of the atmosphere in the position of a satellite. One of the important variables required in the computations of the radiative parameter is the aerosol phase function which can be satisfactorily fitted by the two-term Henyey-Greenstein function. When the surface reflectance equals zero, representing the atmospheric radiance alone without any influence from an oceanic surface, the study shows that the variation of the optical depth is associated with the changing of aerosol size distribution. The optical depth increases with the presence of large aerosol particles. The results indicate that inhomogeneities in aerosol optical properties, such as the variation of the scattering phase function due to the changes in aerosol size distribution, can affect the magnitude of the optical depth.     

Enumeration of coliforms and Escherichia coli in frozen black tiger shrimp Penaeus monodon by conventional and rapid methods

Conventional (most probable number, MPN) and rapid methods-including Chromocult coliform agar (CCA), Fluorocult(R) LMX broth (LMX), and Petrifilm Escherichia coli count plates (PEC) for enumeration of coliforms and E. coli in frozen black tiger shrimp from Thailand were compared in order to assess the possibility of using one of the rapid methods for routine analysis. Enumeration of coliforms and E. coli from 18 samples of regular frozen black tiger shrimp and 156 samples of frozen black tiger shrimp experimentally contaminated with coliforms or E. coli at concentrations of approximately 10, approximately 10(2), and approximately 10(3) CFU g(-1) revealed that at the level of approximately 10 CFU g(-1), coliform numbers ranked as LMX>CCA>MPN=PEC and E. coli as MPN=LMX=PEC=CCA. At the level of approximately 10(2) CFU g(-1), coliform numbers ranked as LMX>MPN=PEC=CCA and E. coli as MPN=LMX>PEC=CCA. At the level of 10(3) CFU g(-1), coliforms ranked as LMX>MPN=CCA>PEC and E. coli as MPN>LMX>CCA>PEC. Agreements with the conventional MPN method for coliforms were LMX 108%, PEC 87.2%, and CCA 91.2% and agreements for E. coli were LMX 101%, PEC 95.7%, and CCA 96.3%. Sensitivities (%) ranked LMX>MPN>CCA=PEC for coliforms and E. coli, whereas equal specificities (100%) of all methods for coliforms and E. coli were demonstrated. Rankings for the other parameters compared were: convenience, PEC>CCA=LMX>MPN; time to detection, MPN>LMX=PEC=CCA; expense, MPN=PEC>CCA>LMX; labor, MPN>LMX=CCA>PEC; accuracy for coliforms, PEC>CCA>MPN>LMX; and accuracy for E. coli, PEC=CCA>LMX>MPN.