艾叶精油化学成分研究

本文用水蒸气蒸馏法提取了不同产地艾叶精油,采用GC-MS技术分析了艾叶精油的化学成分。结果不同产地艾叶精油的质量收率为0.29%～0.56%,都含有特征成分:α-蒎烯、β-蒎烯、α-松油烯、γ-松油烯、桉叶素、蒿酮、蒿醇、2-环己烯-1-醇、樟脑、龙脑、4-松油醇、反式-石竹烯、丁子香酚。其中具有药效作用的成分有桉叶素(14.32%～26.12%,质量百分数,下同),樟脑(3.66%～14.97%)、龙脑(0.51%～10.53%)、甘菊环(0.00%～23.95%)等,有毒成分侧柏酮含量为0.32%～3.62%。     

Multipoint scanning dual‐detection confocal microscopy for fast 3D volumetric measurement

We propose a multipoint scanning dual‐detection confocal microscopy (MS‐DDCM) system for fast 3D volumetric measurements. Unlike conventional confocal microscopy, MS‐DDCM can accomplish surface profiling without axial scanning. Also, to rapidly obtain 2D images, the MS‐DDCM employs a multipoint scanning technique, with a digital micromirror device used to produce arrays of effective pinholes, which are then scanned. The MS‐DDCM is composed of two CCDs: one collects the conjugate images and the other collects nonconjugate images. The ratio of the axial response curves, measured by the two detectors, provides a linear relationship between the height of the sample surface and the ratio of the intensity signals. Furthermore, the difference between the two images results in enhanced contrast. The normalising effect of the MS‐DDCM provides accurate sample heights, even when the reflectance distribution of the surface varies. Experimental results confirmed that the MS‐DDCM achieved high‐speed surface profiling with improved image contrast capability.     

Numerical Modeling of a Spar Platform Tethered by a Mooring Cable

Virtual simulation is an economical and efficient method in mechanical system design. Numerical modeling of a spar platform, tethered by a mooring cable with a spherical joint is developed for the dyna...     

Antibacterial Effect of Glucose Oxidase on Growth of Pseudomonas fragi as Related to pH

The effect of glucose oxidase (GOX) catalyzed reaction with glucose on Pseudomonas fragi was analyzed in nutrient broth and fish extract media. Growth of P. fiugi in nutrient broth was clearly suppressed by 1.0, 2.0 and 4.0 mg/mL glucose when combined with 0.5–2.0 U/mL GOX. The same GOX/glucose combinations inhibited P. frasi growth in fish extract media. Viable cell numbers in fish media showed clear growth inhibition with combinations of l.0–2.0 U/mL GOX and 8.0–16.0 mg/mL glucose. Higher GOX and glucose rapidly produced 2.0–2.5 unit decreases in pH, but produced enough gluconic acid to precipitate fish proteins. Use of 0.5 U/mL GOX in fish extract media resulted in slow, sustained activity with potential for inhibition of microbial growth in foods without excessive acidity.     

Relation between etching profile and voltage–current shape of sintered SiC etching by atmospheric pressure plasma

Sintered silicon carbide (SiC) was etched by a dielectric barrier discharge source. A high voltage bipolar pulse was used with helium gas for the plasma generation. One stable filament plasma was generated and could be used for SiC etching. As the processing gas (NF₃) mixing rate increased, the width and depth of the etching profile became narrower and deeper. The differentiated V–Q Lissajous method was used for measuring the capacitances (C_eq) of the electrode after the plasma turned on. The width of the etching profile was proportional to C_eq. As the current peak value I_smx of the substrate current increased, the volume removal rate of SiC increased. The etch depth was proportional to the ratio of I_smx to C_eq. Additionally, because of the different characteristics of the plasma disks on SiC substrate by the voltage polarity, the etching profile was unstable. However, in high NF₃ mixing process, the etching profile became stable and deeper.     

Distributed Virtual Inertia Based Control of Multiple Photovoltaic Systems in Autonomous Microgrid

The large inertia of a traditional power system slows down system's frequency response but also allows decent time for controlling the system. Since an autonomous renewable microgrid usually has much smaller inertia, the control system must be very fast and accurate to fight against the small inertia and uncertainties. To reduce the demanding requirements on control, this paper proposes to increase the inertia of photovoltaic (PV) system through inertia emulation. The inertia emulation is realized by controlling the charging/discharging of the direct current (DC)-link capacitor over a certain range and adjusting the PV generation when it is feasible and/or necessary. By well designing the inertia, the DC-link capacitor parameters and the control range, the negative impact of inertia emulation on energy efficiency can be reduced. The proposed algorithm can be integrated with distributed generation setting algorithms to improve dynamic performance and lower implementation requirements. Simulation studies demonstrate the effectiveness of the proposed solution.      

CLONING, EXPRESSION AND CHARACTERIZATION OF NOVEL LECTIN FROM ORYZA SATIVA

A lectin gene homolog of Oryza sativa was successfully cloned and expressed in Escherichia coli. The deduced amino acid sequence of the protein product showed a significant similarity with known chitin‐binding lectins. Most of the recombinant lectin was found in an insoluble aggregated form as inclusion bodies and only a small part was in the culture medium in a soluble active form. Functional recombinant lectin was recovered from the inclusion bodies by solubilization with 8 M urea in Tris/HCl buffer, pH 7.0 and renaturation by 10‐fold dilution in the same buffer. The recombinant lectin with His‐tag was simply purified to homogeneity by the process of affinity chromatography and was obtained with a yield of 6–8 mg/L culture. The recombinant lectin was a homo‐dimer composed of 22 kDa. The hemagglutination activity of the recombinant lectin was optimal at pH 4.0–7.0 and it was very sensitive to inhibition by N‐acetylneuraminic acid and thyroglobulin.     

利用ICP设备制备图形化蓝宝石基底的工艺控制

该文对利用感应耦合等离子体(ICP)刻蚀设备来制作图形化蓝宝石基底(PSS)的工艺控制进行了研究。在工艺制作过程中,选用了C轴(0001)取向的100 mm蓝宝石平片作为实验样品,通过光刻工艺和ICP刻蚀工艺控制,制作出了具有圆锥状图形结构的图形化蓝宝石基底。借助扫描电子显微镜,对该图形化蓝宝石基底进行了测量和分析。测量结果显示,基底表面上的单粒圆锥状图形结构的底部直径为(3.45±0.25) μm,刻蚀高度/深度为(1.75±0.25) μm,整个图形化蓝宝石基底成品片的均匀性控制在3%以内。