Direct production of D-arabinose from D-xylose by a coupling reaction using D-xylose isomerase, D-tagatose 3-epimerase and D-arabinose isomerase

Klebsiella pneumoniae 40bXX, a mutant strain that constitutively produces D-arabinose isomerase (D-AI), was isolated through a series of repeated subcultures from the parent strain on a mineral salt medium supplemented with L-Xylose as the sole carbon source. D-AI could be efficiently immobilized on chitopearl beads. The optimum temperature for the activity of the immobilized enzyme was 40 degrees C and the enzyme was stable up to 50 degrees C. The D-Al was active at pH 10.0 and was stable in the range of pH 6.0-11.0. The enzyme required manganese ions for maximum activity. Three immobilized enzymes, D-xylose isomerase (D-XI), D-tagatose 3-epimerase (D-TE and D-AI were used for the preparation of D-arabinose from D-xylose in a coupling reaction. After completion of the reaction, degradation of D-xylulose was carried out by Saccharomyces cerevisiae. The reaction mixture containing D-Xylose, D-ribulose and the product was then separated by ion exchange column chromatography. After crystallization, the product was checked by HPLC, IR spectroscopy, NMR spectroscopy and optical rotation measurements. Finally, 2.0 g of D-arabinose could be obtained from 5 g of the substrate.     

Plasma effects in semiconducting nanowire growth

Three case studies are presented to show low-temperature plasma-specific effects in the solution of (i) effective control of nucleation and growth; (ii) environmental friendliness; and (iii) energy efficiency critical issues in semiconducting nanowire growth. The first case (related to (i) and (iii)) shows that in catalytic growth of Si nanowires, plasma-specific effects lead to a substantial increase in growth rates, decrease of the minimum nanowire thickness, and much faster nanowire nucleation at the same growth temperatures. For nucleation and growth of nanowires of the same thickness, much lower temperatures are required. In the second example (related to (ii)), we produce Si nanowire networks with controllable nanowire thickness, length, and area density without any catalyst or external supply of Si building material. This case is an environmentally-friendly alternative to the commonly used Si microfabrication based on a highly-toxic silane precursor gas. The third example is related to (iii) and demonstrates that ZnO nanowires can be synthesized in plasma-enhanced CVD at significantly lower process temperatures than in similar neutral gas-based processes and without compromising structural quality and performance of the nanowires. Our results are relevant to the development of next-generation nanoelectronic, optoelectronic, energy conversion and sensing devices based on semiconducting nanowires.     

Design and application of an efficient scheme for wafer transfer procedure during ion implantation process

Ion implantation is widely used in semiconductor manufacturing to modify electrical properties of the near-surface region of silicon wafers. The efficiency of ion implantation process deeply relies on wafer transfer procedure. Increasing wafer transfer speed is one of the most efficient ways to accelerate the ion implantation process for higher productivity of silicon chips. This study focuses on developing an efficient scheme for wafer transfer procedure to acquire higher transfer speed and reduce cycle time during ion implantation process. The scheme we proposed improves the layout of the vacuum chamber in currently used ion implanter by introducing an additional wafer transfer robot inside while placing the alignment station outside, planning optimal motion sequence of three wafer transfer robots in order to make all of them keep working without spending a long time waiting for other robots. Experimental platform has been established and the results show that wafer transfer speed based on the proposed scheme is over three times faster than the commonly used apparatus.     

Effect of lime treatment and subsequent carbonation on gelatinization and saccharification of starch granules

The present study was aimed to improve the efficiency of bioconversion process, namely the calcium capturing by carbonation at room temperature (RT‐CaCCO) process. Rice endosperm starch was used as a model substance to observe the effects of lime treatments on the gelatinization of starch granules. Effect of subsequent carbonation and saccharification behaviors were also evaluated. With increasing lime concentration, significant rise in the gelatinization temperatures, and decrease in the gelatinization enthalpy were observed, suggesting enhanced granule stability and disruption of hydrogen bonds. These changes appeared to be leveling off near 9% lime concentration, at which the binding effect of calcium ions may be saturated. The mild heat treatment further promoted changes in gelatinization. It was postulated that it was not an annealing effect, but that mild heat treatment disrupted hydrogen bonds and provided more available sites for calcium binding. Carbondioxide (CO₂) neutralization led to decrease in gelatinization temperatures. The optimum pretreatment conditions for efficient hydrolysis of mild heat treatment at 50°C for 24 h subsequent to lime pretreatment is effective in accelerating saccharification by 1.9‐fold and CO₂ neutralization should be carried out after heat treatment. This approach can be useful in improving the recovery of liberated glucose when applying the RT‐CaCCO process to feedstocks which contain both starch and lignocellulosic material.     

Characteristics of post-annealed SrTiO3 thin films prepared by mirror-confinement-type ECR plasma sputtering

SrTiO₃ films were synthesized on Pt/Ti/SiO₂/Si multilayer substrates by mirror-confinement-type ECR plasma sputtering without substrate heating. All films were found to be well crystallized at a substrate temperature below 450 K. A low temperature post-annealing of the films by electromagnetic-wave radiation drastically improved the crystallographic and electric properties of Pt/SrTiO₃/Pt/Ti/SiO₂/Si capacitors. The crystallinity of the films indicated little variation by post-annealing, but irradiation of electromagnetic wave was confirmed to be effective for decreasing the post-annealing time and temperature. The electric properties of films annealed without Pt upper electrodes were better than those with them, and the film dielectric constant reached a value of 260, which is nearly equal to thebulk one, at an annealing temperature of 573 K.     

模块化可重构足式仿生机器人设计

在应用仿生学原理和拓扑理论对足类生物骨骼结构进行简化和模块化分的基础上,开发了一套模块化可重构足式机器人系统,此套系统能够构造出多种不同构形的足式机器人,并且由于采用了均一化的设计,在一定程度上降低了生产成本。     

Geophysical monitoring of hydrological and biogeochemical transformations associated with Cr(VI) bioremediation

Understanding how hydrological and biogeochemical properties change over space and time in response to remedial treatments is hindered by our ability to monitor these processes with sufficient resolution and over field relevant scales. Here, we explored the use of geophysical approaches for monitoring the spatiotemporal distribution of hydrological and biogeochemical transformations associated with a Cr(VI) bioremediation experiment performed at Hanford, WA. We first integrated hydrological wellbore and geophysical tomographic data sets to estimate hydrological zonation at the study site. Using results from laboratory biogeophysical experiments and constraints provided by field geochemical data sets, we then interpreted time-lapse seismic and radar tomographic data sets, collected during thirteen acquisition campaigns over a three year experimental period, in terms of hydrological and biogeochemical transformations. The geophysical monitoring data sets were used to infer: the spatial distribution of injected electron donor; the evolution of gas bubbles; variations in total dissolved solids (nitrate and sulfate) as a function of pumping activity; the formation of precipitates and dissolution of calcites; and concomitant changes in porosity. Although qualitative in nature, the integrated interpretation illustrates how geophysical techniques have the potential to provide a wealth of information about coupled hydrobiogeochemical responses to remedial treatments in high spatial resolution and in a minimally invasive manner. Particularly novel aspects of our study include the use of multiple lines of evidence to constrain the interpretation of a long-term, field-scale geophysical monitoring data set and the interpretation of the transformations as a function of hydrological heterogeneity and pumping activity.     

接龙铁矿地质特征及成因探讨

通过对接龙铁矿的矿床地质特征和控矿因素的分析和总结,分析了矿床的形成环境和成矿机理,形成了矿床成因方面的初步认识。     

Low-damage surface modification of polymethylmethacrylate with argon-oxygen mixture plasmas driven by multiple low-inductance antenna units

Surface modification of polymethylmethacrylate (PMMA) films has been investigated with argon-oxygen mixture plasmas sustained with multiple low-inductance antenna units. PMMA films were exposed to argon-oxygen mixture (20%) plasmas on a water-cooled substrate holder. Average ion energies bombarding onto the PMMA films was estimated to be as low as 6 eV, which was evaluated from the gap between plasma potential and floating potential. The etching depth of PMMA surface increased linearly with increasing plasma-exposure time and the etching rate was 170 nm/min. Surface roughness of PMMA slightly increased from 0.3 nm to 1.4 nm with increasing exposure time. Hard X-ray photoelectron spectroscopy (HXPES) was carried out to examine chemical bonding states of the PMMA surface in deeper regions (about 54 nm) as compared with those observed in shallower regions (27 nm).