高功率微波高斯馈源口面场分析

 用波导本征模展开方法对用于高功率微波发射系统的方角锥高斯馈源口面场进行分析，提出结合馈源远场辐射特性和避免高功率击穿折衷选定相应的高斯模注腰半径，进而确定多个波导模幅值，从而为运用模匹配或耦合波理论设计高斯馈源提供依据。     

饲喂频率对鲈鱼生长及体生化成分的影响

选取同一种饵料设置1次·d-1、2次·d-1、3次·d-1、4次·d-14个饲喂频率,采用静水连续充气养殖系统,在盐度为26.0%～27.0%、温度为26～30℃条件下对鲈鱼(85.95±2.04)g进行为期40d的生长实验.结果表明:(1)饲喂频率影响鲈鱼的生长是由食物转化率和摄食率的提高共同引起的.(2)水分含量随饲喂频率的增高而保持不变;蛋白质含量随饲喂频率的增加,基本保持不变;脂肪含量随饲喂频率的增高而明显减少;灰分含量随饲喂频率的增多而明显增加.(3)鲈鱼的适宜饲喂频率为2次·d-1.     

预测气吹精密播种机排种质量的一种简易方法

通过对气吹式精密播种机田间试验资料的相关分析，发现合格指数Ａ与｜Ｄ－Ｍ｜（重播指数与漏播指数之差的绝对值）之间里极显著负相关（ｒ＝－０．９３１２）。在对数据作进一步回归分析的基础上，本文建立了一套“由排种粒数预测排种质量”的方法。     

A supported gold catalyst for the elimination of hydrogen from CO2 feed gas in the production of urea

Supported gold catalyst for eliminating hydrogen from CO₂ feed gas in the production of urea is found to be superior to other industrial catalysts (e.g. Pt/Al₂O₃ and PdPt/Al₂O₃) in catalytic activity and resistance to sulfur poisoning.     

TEQ-value determinations of animal feed; emphasis on the CALUX bioassay validation

Polyhalogenated aromatic hydrocarbons, such as polychlorinated dibenzo-p-dioxins are a large and diverse group of environmental pollutants. Their tendency to accumulate in the food chain and their toxicity make monitoring necessary. The reference analysis method is laborious and very expensive, therefore cheap and rapid bioassays have been developed. The chemical-activated luciferase bioassay (CALUX) bioassay uses a recombinant cell line, which responds to dioxins and dioxin-like molecules with Ah receptor (AhR)-dependent induction of firefly luciferase in a dose related response. The CALUX was tested for its use in the screening of feed. Aliquots of 20 g of enriched feed were extracted with a toluene:methanol mixture (20:4 v/v) and extracts were defatted on 33% H₂SO₄ silica columns and purified on carbon columns. Only the dioxin and furan fraction was analysed, the PCB fraction was discarded. The precision of the method is acceptable and in compliance with an R.S.D. <30% as suggested for cell-based bioassays in the Commission Directive 2002/70/EC of July 2002. The results evidence good agreement between TEQ-values obtained by either CALUX or GC–HRMS. The method is now routinely in use for a feed screening programme designed by the Federal Agency for the Safety of the Food chain. Approximately, 25 samples are analysed weekly. From the obtained results approximately 10% was confirmed by GC–HRMS. The false positive ratio is 1% and no false negatives were found, making the use of the CALUX technology advantageous.     

Independent exponential feeding of glycerol and methanol for fed-batch culture of recombinant Hansenula polymorpha DL-1

As a novel feeding strategy for aptomizing human epidermal growth factor (hEGF) production with a recombinant Hansenula polymorpha DL-1 using the methanol oxidase (MOX) promoter in H. polymorpha DL-1, independent exponential feeding of two substrates was used. A simple kinetic model considering the cell growth on two substrates was established and used to calculate the respective feeding rates of glycerol and methanol. In the fedbatch culture with methanol-only feeding, the optimal set point of specific growth rate on methanol was found to be 0.10 h⁻¹. When the fed-batch cultures were conducted by the independent feeding of glycerol and methanol, the actual specific growth rate on glycerol and methanol was slightly lower than the set point of specific growth rate. By the uncoupled feeding of glycerol and methanol the volumetric productivity of hEGF increased from 6.4 to 8.0 mg/(L·h), compared with methanol-only feeding.     

色谱分离分光光度法测定饲料中的叶黄素

用色谱法分离和分光光度法测定饲料产品中的叶黄素含量。以硅胶为固定相,分别洗脱胡萝卜素和叶黄素,叶黄素的测定波长为474nm,该测定方法的相对标准偏差为0.023%,测量不确定度为1%~2%。     

正烷酵母作为饲料的最近研究

本文叙述了近十年来我国对正烷烃酵母研究的进展。我们用的菌种是热带假丝酵母Y-17,本所实验厂的生产规模是年产一百吨酵母。发酵罐为6米~3的内或外循环空气提升式,两级连续发酵,50％废水循环利用。生产能力为2克/升·小时。酵母产品的化学分析,包括蛋白质、氨基酸、脂肪、核酸、维生素等,都证明该产品为一优良蛋白饲料。有毒物质含量(如苯骈(a)芘、重金属)符合国际标准。动物试验(包括用大白鼠、鸡、猪的营养试验,慢性毒性试验,传代试验)证明该正烷烃酵母为安全可靠的优良饲料。我们也研究了酵母的核酸和脂肪的综合利用、并筛选了一株高产新菌株球拟嗜烷烃酵母(新种)4B-2,使生产能力提高至2.8克/升·小时。     

Biocatalytic synthesis of polymers. III. Formation of a high molecular weight polyester through limitation of hydrolysis by enzyme-bound water and through equilibrium control

Enzyme-catalyzed preparation of polymers offers several potentially valuable advantages over the usual polymerization procedures and has been studied for several years. A significant limitation on the polyesters prepared to date has been the low molecular weights achieved. The present studies have established that, in the polycondensation of bis(2,2,2-trifluoroethyl) glutarate with 1,4-butanediol using porcine pancreatic lipase as the catalyst, this limitation arises from at least two sources: hydrolysis of activated ester end groups by water introduced along with the enzyme and the polymerization's reaching equilibrium despite using the poorly nucleophilic 2,2,2-trifluoroethanol as the leaving group. Evidence is also developed that the presence of trifluoroethanol accelerates the release of the enzyme-bound water which hydrolyzes the activated ester end groups. The hydrolysis could be avoided by choosing a relatively high-boiling solvent, such as bis(2-ethoxyethyl) ether, then removing the trifluoroethanol by placing the reaction mixture under vacuum periodically or by drying the enzyme rigorously. The vacuum method also removed the limitation on molecular weight resulting from the reaction's reaching equilibrium. A further improvement in the molecular weight to nearly 40,000 daltons, well within the range that is technically interesting, was achieved by using 1,2-dimethoxybenzene or 1,3-dimethoxybenzene as the polymerization solvent. © 1995 John Wiley & Sons, Inc.     

Analysis of Nitrofuran Residues in Animal Feed Using Liquid Chromatography and Photodiode-Array Detection

The analysis of four nitrofuran veterinary drugs, nitrofurantoin, furazolidone, furaltadone and nitrofurazone, was optimized using reversed-phase liquid chromatography with a monolithic column and photo-diode array detection. The antibiotics were extracted from animal feeds by heating with acetonitrile. The isocratic mobile phase consisted of a 8:92 (v/v) acetonitrile/phosphate buffer (pH 4.5) at a flow-rate of 1 mL min⁻¹. Peaks were identified by the retention characteristics and UV spectra. Detection limits in the water samples ranged between 0.21 and 0.27 μg L⁻¹, and in the feed samples between 2.1 and 2.7 μg kg⁻¹, depending on the nitrofuran. The procedure was applied to the control of nitrofuran residues in farm water for poultry and different animal feeds.