光脉冲在非啁啾光纤光栅中的透射传输研究

基于均匀布拉格光纤光栅的色散特性,阐述丁激光啁啾脉冲的传输演变特性,研究了工作于传输方式的非啁啾光纤光栅的透射传输特性。讨论了光源线宽、光栅长度、光栅耦合系数等光栅参数以及初始脉宽、初始啁啾等参量对补偿光纤长度的影响,通过理论计算和模拟实验研究光栅对脉冲的补偿能力。     

Lipase-catalyzed synthesis of O-lauroyl l-serinamide and O-lauroyl l-threoninamide

O-Lauroyl l-serinamide and O-lauroyl l-threoninamide were synthesized with an immobilized lipase using lauric acid and l-serinamide or l-threoninamide in water-miscible organic solvents, of which 2-methyl-2-propanol gave the highest conversion of 93% for O-lauroyl l-serinamide at 50 mmol-l-serinamide/L and 100 mmol-lauric acid/L. The addition of 4 Å 1/16 molecular sieves at 50 mg/mL increased the conversion to 53% for O-lauroyl l-threoninamide at 50 mmol-l-threoninamide/L and 150 mmol-lauric acid/L in 2-methyl-2-butanol. The difference of conversion between the two products was exactly proportional to the difference of solubility of aminoacid amides.     

Effects of modified atmosphere packaging with various sizes of silicon gum film window on the storage of Agrocybe Chaxingu Huang and the modelling of its respiration rate

An Agrocybe chaxingu Huang packaged in 5% O₂‐ and 10% CO₂‐modified atmospheres with different sizes (0, 0.5, 1.0 and 1.5cm²) of silicon gum film window was stored at a temperature of 3 ± 1°C for 20 days. Changes of ascorbic acid content, titratable acidity, electrolyte leakage and sensory characteristic were evaluated. Significant differences were found among the packages with different sizes of silicon gum film window on ascorbic acid content, titratable acidity, electrolyte leakage, general appearance, firmness and odour after 8, 8, 12, 12, 12 and 4 days of storage, respectively. The package with a 1.0cm² silicon gum film window was the most effective for keeping the quality of Agrocybe chaxingu Huang. Based on the optimum storage condition in this study, an enzyme kinetics respiration model was set successfully and the applicability of the enzyme kinetics respiration model was verified by using the packages of Agrocybe chaxingu Huang with weights of 105 and 125g, respectively. Copyright © 2007 John Wiley & Sons, Ltd.     

一种新的虹膜定位算法

提出了一种新的虹膜预处理方法，即使用联合扩散滤波器对虹膜进行平滑处理，利用其保边光滑的特性提取虹膜内边缘的若干点，再使用3点确定圆心的方法计算虹膜圆心，最后使用标准Hough变换进行小范围精确定位。仿真结果显示，该算法性能优于文献中提出的算法，稳定性、速度和精度已经达到较高程度。     

葡萄籽原花青素降低小鼠血清中胆固醇作用的研究

通过采用双总体t检验方法,比较了高脂组和低脂组小白鼠血清中胆固醇含量的变化和差异。研究发现,灌药(血脂康和原花青素)组小鼠血清中的总胆固醇和低密度脂蛋白胆固醇明显降低,下降率达25%以上,与高脂对照组(阳性组)相比有显著性差异。经过小鼠肝脏解剖和肝细胞病理切片,发现高脂对照组小鼠已明显发生肝脂肪变,高脂给药组和阴性对照组小鼠未发现明显的肝脂肪变,说明原花青素具有降低小鼠血清中胆固醇和抑制肝脂肪变等作用,而且中剂量组(50mg原花青素/kg体重·d)的效果最好,其降低低密度脂蛋白胆固醇能力甚至强于血脂康。灌药20d的小鼠,其血清中胆固醇含量低于10d和30d的小鼠。     

Purification and characterization of two types of chitosanase from Aspergillus sp. CJ22-326

Aspergillus CJ22-326, a fungi strain capable of utilizing chitosan as a carbon source, was isolated from soil samples. Two types of chitosanase (ChiA and ChiB) produced from the culture supernatant of Aspergillus CJ22-326 were purified to an apparent homogeneity identified by SDS–PAGE through ammonium sulfate precipitation, CM-Sepharose FF chromatography, and Sephacryl S-200 gel filtration. Molecular weights of the enzymes were 109 kDa (ChiA) and 29 kDa (ChiB). Optimum pH values and temperature of ChiA were 4.0 and 50 °C, respectively, those of ChiB were 6.0 and 65 °C. The enzyme activities of ChiA and ChiB were increased by about 0.5-fold and 1.5-fold, respectively, by the addition of 1 mM Mn²⁺. However, 2.5 mM Ag⁺, Hg²⁺ and Fe³⁺strongly inhibited ChiA and ChiB activities. Viscosimetric assay and analysis of reaction products of these enzymes, using chitosan as a substrate, by TLC indicated endo- and exo-type cleavage of chitosan by ChiB and ChiA, respectively. ChiB catalysed the hydrolysis of glucosamine (GlcN) oligomers larger than pentamer, and chitosan with a low degree of acetylation (0–30%), and formed chitotriose with chitohexaose as the major products. ChiA released a single glucosamine residue from chitosan and glucosamine oligomers. Both of the activities of ChiA and ChiB increased with the degree of deacetylation of chitosan. The enzyme ChiB had a useful reactivity and a high specific activity for producing functional chitooligosaccharides with high degree of polymerization.     

Aqueous extraction of corncob xylan and production of xylooligosaccharides

Xylooligosaccharide, which is usually produced from xylan by enzymatic hydrolysis, is a newly developed functional oligosaccharide having many beneficial biomedical and health effects. In this study, a process for producing xylooligosaccharides from corncob was developed. The procedure consisted of soaking the corncob in 1.0 g/l H₂SO₄ at 60 °C for 12 h, followed by filtrating and washing with tap water to pH 6 and steaming at 135–140 °C for 0.5 h. The steamed corncob was mashed and hydrolysed by xylanase. The cumulative yield of xylooligosaccharides after enzymatic hydrolysis was close to 67.7 g/100 g by steaming (based on xylan in raw material), and the purity of xylooligosaccharides was over 70 g/100 g (based on the total sugars in the hydrolysate). This study demonstrated that the xylan–lignin complex present in the corncob was affected during steaming at 135 °C for 30 min. Almost all of the xylan was removed from the lignin after steam application and subsequent enzymatic hydrolysis.     

耐热性黄原胶的制备与性能

油田油藏条件下使用的黄原胶在高温下易发生降解、黏度下降。文中研究了除氧剂(硫代硫酸钠)对黄原胶耐热稳定性的影响,结果表明,当硫代硫酸钠的使用浓度为1.5 g/L时,黄原胶溶液经121℃高温处理3 h,其黏度下降幅度变小,黏度保留率得到明显的提高,耐热稳定性提高了1.85倍。通过包埋硫代硫酸钠,制备出了具有较高耐热性的黄原胶。采用热重分析仪(TGA)对其耐热性进行了研究,研究表明,黄原胶(包埋硫代硫酸钠)的耐热稳定性得到有效的改善。     

空调压缩机用滚子的中凸磨削研究

利用现有无心磨床的仿形板式砂轮修整器,通过使仿形板产生一定量的微量弹性变形,从而成功解决了空调压缩机滚子零件外圆磨削的微量中凸工艺问题.介绍了使仿形板产生微量中凸的调整与检测方法,砂轮的修整参数和砂轮的选择.     

基于超高压对撞式均质技术的物料粉碎机理的研究

重点研究了物料在超高压对撞式均质机内部的粉碎机理,以陶瓷烧结的均质管为研究对象,把内部流道分成引流区、分流区、撞击区、射流区和扩流区等5个部分,对其粉碎机理进行了初步分析,为超高压均质机关键结构均质头的设计提供一定的参考依据.