浆体极限切应力的研究

本文基于絮凝发育图式,提出浆体在宾汉极限切应力行将呈现时,亦已具有恒大于零的临界粒间粘着力(τ_(Fk))的观点。换言之,宾汉极限切应力τ_B的大小取决于形成絮网结构时的粒间粘着应力τ_F与τ__(Fk)之差值的大小。并由此建立了包含有流型转化因素(临界含沙浓度)的宾汉极限切应力计算公式。并经大量实测资料验证表明,公式与实测资料吻合较好;其次还利用实测资料进一步对临界含沙浓度的大小进行了测算,获得了有益的认识。     

黄孢平革霉（Phanerochaete chrysosporium）木质素过氧化物酶基因的克隆与分析

用大肠杆菌克隆载体ｐＵＣ１０构建白腐丝状担子真菌黄孢平革霉（Ｐｈａｎｅｒｏｃｈａｅｔｅｃｈｒｙｓｏｓｐｏｒｉｕｍ）ＭＥ４４６基因组文库，用分离自ＢＫＭ－Ｆ１７６７菌株的木质素过氧化物酶ｃＤＮＡ片段ＣＬＧ４和ＣＬＧ５为探针，从构建的基因组文库中分离到一个含木质素过氧化物酶基因的重组子ｐＧＬＧ－Ｍ１。对该重组子插入片段所作的限制酶谱分析结果表明，它与来自ＢＫＭ－Ｆ１７６７的ＧＬＧ２片段的限制酶谱十分相似。     

弱Hopf Galois扩张的Cotorsion维数

考虑在Ext群上构造Grothendieck谱序列揭示弱Hopf Galois扩张的cotorsion维数. 设H为有限维弱Hopf代数, A/B为弱H-Galois扩张, 给出A,B的左cotorsion维数与H的右整体维数之间的关系, 并讨论当B为可换的或H*为半单时, A,B的左cotorsion维数的性质.     

基于旋转矩阵的加密解密算法

利用舍入误差分析的方法及计算机浮点运算的特性, 构造一种基于旋转矩阵的加密解密算法, 并提出了保证算法有效的充分条件. 应用实例验证了算法的可行性.     

Cloning and Characterization of Gene Promoters from Bacillus pumilus

DNA fragments obtained from Sau3AI partially digested total DNA of Bacillus pumilus UN31-C-42 are first inserted into BamHI site of pSUPV4, a promoter-probe vector. The recombinant DNA molecules are transformed into Escherichia coli cells and eight-three Kanr clones (named pSUBp1-pSUBp83) are obtained. The inserted fragments in pSUBp53, pSUBp57, pSUBp21, which showed high level of kanamycin- resistance, are sequenced and analyzed, respectively. These fragments contain some con-served sequences of prokaryotic gene promoters, such as TATAAT and TIGACA box. The promoter frag-ment Bp53 could efficiently promote the alkaline protease gene of B. pumilus expression not only in E.coli but also in B. subtilis cells.     

Purification and Partial Characterization of a Collagenolytic Enzyme Produced by Pseudomonas aeraginosa SCU Screened from Rotten Hides

Strain Pseudomonas Aeraginosa SCU isolated from rotten hides is shown to produce various gelatinolytic enzymes with molecular masses ranging from - 50 to - 200 kD. A gelatinolytic enzyme called PAC exhibiting collagenolytic activity is purified by SP sepharose fast flow, Sephadex G-200 gel filtration and native PAGE cutting method. The purified enzyme has an apparent molecular weight of about 110 kD by SDS PAGE without β-mercaptoethanol. Treatment withtβ-Me suggests that PAC is dissociated into three subunits approximately 33 kD, 25 kD and 20 kD with a ratio of 2:1:1, named sub A, sub B and sub C repectively. EDFA and EGTA display a significant inhibitory effect on the enzyme activity while PMSF, leupeptin and pepstain do not appreciably inhibit it. The first 15 amino acid residues of the major subunit (subA) are determined and the sequence is Ala-Glu-Ala-Gly-Gly-Pro-Gly-Gly-Asn-Gln-Lys-Ile-Gly -Lys-Tyr. This sequence is identical to that of elastase of P. aeruginosa. The fragment of encoding mature sub A is cloned and its sequence is determined, which has a high homology with the gene of elastase. These results indicate that PAC is a novel collagenolytic metalloprotease composed of three kinds of subunits, of which elastase is the major one.     

小熊猫脑源性神经营养因子（BDNF）基因的克隆与序列分析

参照人的ＢＤＮＦ基因序列设计了一对引物，利用聚合酶链式反应（ＰＣＲ），从小熊猫基因组ＤＮＡ中扩增和克隆到ＢＤＮＦ基因。序列分析表明，小熊猫和人的ＢＤＮＦ基因核苷酸序列同源性为９３％，而与大熊猫ＢＤＮＦ基因的核苷酸序列同源性高达９８％。在推导的多肽序列中，除在前导肽区有两个氨基酸的差异外，小熊猫ＢＤＮＦ的成熟区与人和其他报道的哺乳动物ＢＤＮＦ成熟区的氨基酸序列完全一致，显示了极高的保守性。     

用酵母生产麦角固醇发酵动力学的研究

研究了酵母以蔗糖为废物发酵生产麦角固醇的动力学模型：菌体生长模型．拟合值和实验值之间的平均相对误差１３．５％；底物庶糖消耗动力学模型．拟合值和实验值之间的平均相对误差９．８８％；麦角固醇合成动力学模型：拟合值和实验值之间的平均相对误差９．０％．     

马铃薯专性寄生真菌内生集壶菌的研究进展

内生集壶菌是引起马铃薯癌肿病的一种低等专性寄生真菌。本文首先对国内外马铃薯癌肿病病原菌的分布及危害、生物学特征、致病型及检测、分子生物学研究现状、病害防控等方面的研究进行了综述。针对该病菌是专性寄生真菌,至今仍未见全基因组序列的报道,提出加紧研究不同发生地病原菌的基因组序列,了解基因组序列差异及其与抗病马铃薯品种间的关系的展望,这将有利于推动马铃薯癌肿病抗性基因研究及相关育种工作的开展,为马铃薯癌肿病的发生防患于未然。     

Effect of boehmite sol on the crystallization behavior and densification of mullite formed from a sol–gel precursor

Hybrid mullite sol was synthesized from an aqueous solution of aluminum nitrate (AN), aluminum isopropoxide (AIP) and tetraethylorthosilicate (TEOS), doped with boehmite sol with different ratios. Pressureless sintering of the xerogel was carried out at different temperatures in the presence of boehmite doping. The xerogel and sintered powder were characterized by FTIR, TG-DSC, XRD, SEM and bulk density. The addition of boehmite caused the formation of metaphase spinel (6Al2O3·SiO2) crystal before the appearance of mullite phase, which could lead to the formation of amorphous phase and suppress the premature formation of mullite. Both of these effects improve the densification of mullite. A maximum density about 98% of the theoretical density (TD, 3.01 g/cm3 ) of mullite could be obtained for 5 wt% boehmite addition at 1200 1C pressureless sintering.