Time-periodic phases in populations of nonlinearly coupled oscillators with bimodal frequency distributions

The mean field Kuramoto model describing the synchronization of a population of phase oscillators with a bimodal frequency distribution is analyzed (by the method of multiple scales) near regions in its phase diagram corresponding to synchronization to phases with a time periodic order parameter. The richest behavior is found near the tricritical point were the incoherent, stationarily synchronized, ``traveling wave'' and ``standing wave'' phases coexist. The behavior near the tricritical point can be extrapolated to the rest of the phase diagram. Direct Brownian simulation of the model confirms our findings.Comment: Revtex,16 pag.,10 fig., submitted to Physica

Broadband NIR-emitting Te cluster-doped glass for smart light source towards night-vision and NIR spectroscopy applications

Broadband near-infrared (NIR)-emitting materials are crucial components of the next generation of smart NIR light sources based on blue light-emitting diodes (LEDs). Here, we report a Te cluster-doped borate glass, which exhibits ultra-broadband emission around 980 nm with a full-width at half-maximum (FWHM) of 306 nm under blue light excitation. We propose adjustments of glass chemistry and processing condition as a means for topo-chemical tailoring of the NIR photoemission characteristics in such materials. Through implementing strongly reducing conditions during glass melting, Te clusters with broad NIR photoluminescence can be generated and stabilized once the melt is vitrified to the glassy state. Tunability of the NIR emission peak over the wavelength range of 904 to 1026 nm is possible in this way, allowing for fine adjustments of spectral properties relative to the stretching vibrations of common chemical bonds, for example, in water, proteins, and fats. This potentially enables high sensitivity in NIR spectroscopy. We further demonstrate potential application of glass-converted LEDs in night vision.</p

Expression of Pseudomonas amyloderamosa isoamylase gene in Saccharomyces cerevisiae

Isoamylase gene (iso) of Pseudomonas amyloderamosa was amplified by polymerase chain reaction and cloned into Saccharomyces cerevisiae vectors under the control of alcohol dehydrogenase gene and glyceraldehyde-3-phosphate dehydrogenase gene promoters. The signal sequence of iso gene was also replaced with that of Schwanniomyces occidentalis alpha-amylase gene. The extracellular isoamylase activity of transformed Sacc. cerevisiae could reach 86 U ml(-1) after a 4-days cultivation

High-level expression of Trigonopsis variabilis D-amino acid oxidase in Escherichia coli using lactose as inducer

The use of lactose as inducer for the expression of Trigonopsis variabilis D-amino acid oxidase gene (daao) was investigated in Escherichia coli regulated by T7 or T5 promoter. The daao gene was prepared by reverse transcriptase-polymerase chain reaction and cloned into pET21b and pQE-30 to yield pET-DAAO and pQE-DAAO, respectively. The His(6)-tagged DAAO was expressed in E. coli and had a M-r value of approximately 39.3 kDa. In lactose-induced E. coli BL21 (DE3) (pET-DAAO), the expressed DAAO could comprise up to 15% of total soluble proteins and a productivity of 23.4 U ml(-1) was obtained

A study of rationality of slopeland use in view of land preservation

In recent years, frequent attacks of heavy rain and typhoon have severely devastated the vulnerable mountains of Taiwan; slopelands are artificially disturbed by improper development and utilization. People are getting more aware of the importance of slopeland preservation as well as disaster prevention and mitigation. The government, realizing the criticality of gradually worsened land safety issues, has also set forth the &quot;Draft of National Land Planning Act&quot; and the &quot;Draft of Regulations on Land Preservation Act&quot; in the purposes of rehabilitating the excessively explored ecosystems and diminishing the development extent of environmentally susceptible areas, so as to effectively preserve soil, water, and organism resources and to achieve perpetual development of national lands. &quot;Classification of Slopeland Utilization Limitations&quot; is a critical link to national land preservation. The classification is based on four factors, namely average slope, effective soil depth, soil erosion, and parent rock, with different utilization zones defined as bases of landuse planning. However, current classification results of the environmentally susceptible and disaster-prone mountain lands are mostly defined as suitable for forestry or husbandry. Scattered allocation of these lands results in critical issues such as segmented landuse and impaired landscape and ecotype. It is necessary to re-adjust land resources planning and usage management. Therefore a review of the current standards for classifying slopeland utilization limitations is proposed to facilitate rational allocation of slopeland use. Jhuoshuei River is selected as the scope of the case study, with data of debris flows induced by the typhoon Toraji in 2001 as the training data. Eight susceptibility factors, which include form factor of watershed, integral hypsometric, slope of main stream, density of stream network, density of road network, area ratio of historical landslide, and area ratio of triggered landslide, together with the total rainfall of the storm event as the triggering factor, are selected for creating the debris flow susceptibility model by employing the logistic regression within the multivariate geostatistics analysis. This model interprets the curve of success ratio of debris flows triggered by typhoon Toraji, of which the area under the curve is as high as 74.3%. The debris flow susceptibility model created in the study takes the Feng-Chiu section of Sinyi Township, Nantou County, Taiwan within the Jhuoshuei River as the scope of research. GIS technology has been applied in the feasibility study of classification standards. New concepts have been further proposed in view of national land preservation addressing the medium and high elevation disaster-prone areas that are not suitable for agricultural use, for standard revision reference

Substitution of the critical methionine residues in Trigonopsis variabilis D-amino acid oxidase with leucine enhances its resistance to hydrogen peroxide

Each of the six oxidative-sensitive methionine residues in Trigonopsis variabilis D-amino acid oxidase (DAAO) was changed to leucine by site-directed mutagenesis. The wild-type and mutant enzymes with an apparent molecular mass of about 39.3 kDa were expressed in Escherichia coli. The specific activity of four mutant DAAOs (Met(104)Leu, Met(226)Leu, Met(245)Leu, and Met(339)Leu) was decreased by more than 96% while Met(156)Leu and Met(209)Leu showed about 23% and 96% higher activity, respectively, than the wild-type enzyme. The kinetic parameters of the two mure active enzymes were determined and a 2.2-fold increase in K(m) was observed for Met(209)Leu. Comparison of Met(156)Leu and wild-type DAAO revealed a 95% increase in k(cat)/K(m). Met(156)Leu, Met(209)Leu, and Met(226)Leu were resistant to inactivation by 50 mM H(2)O(2) The other three mutant DAAOs were also slightly more resistant than the wild-type enzyme to chemical oxidation. These observations indicate that the oxidative stability in T. variabilis DAAO can be improved by substitution of methionine residues with leucine. (C) 2000 Published by Elsevier Science B.V. All rights reserved