非航海类轮机工程专业实践教学改革的探讨

轮机模拟器训练是轮机工程专业实践教学的重要环节,在详细分析非航海类轮机工程专业教学特点和现状的基础上,提出了整合教学内容、改进教学方法与手段的措施,以提高非航海类轮机工程专业学生理论知识应用及工程实践的能力和培养他们的创新精神.     

Novel pathway for assimilation of dimethylsulphoniopropionate widespread in marine bacteria

Dimethylsulphoniopropionate (DMSP) accounts for up to 10% of carbon fixed by marine phytoplankton in ocean surface waters, producing an estimated 11.7-103?Tmol S per year, most of which is processed by marine bacteria through the demethylation/demethiolation pathway. This pathway releases methanethiol (MeSH) instead of the climatically active gas dimethylsulphide (DMS) and enables marine microorganisms to assimilate the reduced sulphur. Despite recognition of this critical microbial transformation for over two decades, the biochemical pathway and enzymes responsible have remained unidentified. Here we show that three new enzymes related to fatty acid β-oxidation constitute the pathway that assimilates methylmercaptopropionate (MMPA), the first product of DMSP demethylation/demethiolation, and that two previously unknown coenzyme A (CoA) derivatives, 3-methylmercaptopropionyl-CoA (MMPA-CoA) and methylthioacryloyl-CoA (MTA-CoA), are formed as novel intermediates. A member of the marine roseobacters, Ruegeria pomeroyi DSS-3, requires the MMPA-CoA pathway for MMPA assimilation and MeSH production. This pathway and the ability to produce MeSH from MMPA are present in diverse bacteria, and the ubiquitous SAR11 clade bacterium Pelagibacter ubique possesses enzymes for at least the first two steps. Analysis of marine metagenomic data indicates that the pathway is widespread among bacterioplankton in the ocean surface waters, making it one of the most important known routes for acquisition of reduced carbon and sulphur by surface ocean heterotrophs.     

红树林内生真菌2524号中分离的新神经酰胺

红树林内生真菌2524号，采自香港红树Auicennia marina的种子中。从该菌的培养液提取物中分离得到两个新的神经酰胺：[2′，3′-dihydroxytetracosanolyamino]-1,3-dihydroxy-octadecane和[2′，3′-dihydroxydocosanoylami-no]-1,3-dihydroxy-octadecane，化合物的结构通过IR，1D和2DNMR，FAB-MS，ESI-MS^n等实验确定。这两个化合物对肿瘤细胞系Bel-7402，NCI-4460和人体正常细胞系L-02不显示有意义的细胞毒性。     

Novel materials from protein-polymer grafts

Proteins are the most underrated and under-used polymers: their impressive properties include infusibility, great mechanical strength and inherent adhesive capability due to a highly flexible backbone and many functional side chains. The notion of moisture sensitivity of proteins is not universally true. Barnacle cement (which can adhere to Teflon) and mussel and clam byssus, all of which are 99% protein, set in the presence of water and resist enzymatic as well as chemical degradation at ambient temperature. This observation suggests that proteins that are capable of tight three-dimensional cross-linking can overcome sensitivity to moisture and enzymatic attack. It should then be possible to achieve similar resistance by appropriate chemical manipulation of proteins, leading to cross-linking. We have achieved such a result with an ordinary protein, commercially available gelatin, which was chemically modified and then epoxidized. When cured such a material binds to metals and plastics. Any protein that has modifiable amino acids can be used for this purpose.     

南海海洋真菌2492号中的甾体成分

对南海海洋真菌2492分离自香港红树林植物Phramites australi,从其菌丝体的乙醇粗提物分离出3个甾体化合物：(22E,24R)—麦角甾—5,7,22—三烯—3β醇;5a,8a—表二氧—(22E,24R)—麦角甾—6,22—二烯—3β醇和(22E,24R)—24—甲基麦角甾—7,22—三烯—3β,5a,6a—三醇。它们的结构通过IR,FABMS和NMR谱图得到确定。     

海洋真菌Aspergillus flavipes中新神经胺成分

从黄海葵Anthopleura xanthogtammica(Berkly)中分离出海洋附生真菌Aspergillus flavipes,经实验室培养和化学分离纯化,分离得到四种新颖结构的神经酰胺同系物(1-4),它们的化学结构经波谱解析(1R、UV、2D NMR、MS等)和化学降解得以确定.     

试论"乡土小说"向"农村小说"的转换

20世纪前期的“乡土小说”与新中国成立后的“农村小说”是有很大区别的。从经济形态之别和基本主题与题材转换，社会关系之别和基本场景与情节转换，价值体系之别和主要人物与主导风格转换这三方面论述“乡土小说”向“农村小说”转换的历程。     

中国海上船舶垃圾管理策略

介绍海上垃圾污染情况,阐述中国关于船舶垃圾污染防治的管理程序及采取的应对措施.提出减少及根除污染物排放的建议.     

Biochemistry: a cadmium enzyme from a marine diatom

The ocean biota contains a vast reservoir of genomic diversity. Here we present the sequence and preliminary characterization of a protein that is a cadmium-containing carbonic anhydrase from the marine diatom Thalassiosira weissflogii. The existence of a cadmium enzyme in marine phytoplankton may indicate that there is a unique selection pressure for metalloenzymes in the marine environment, and our discovery provides a long-awaited explanation for the nutrient-like behaviour of cadmium in the oceans.     

水稻白叶枯病菌无毒新基因的克隆和序列分析

从菲律宾水稻白叶枯病菌9a生理小种的代表菌株PX0339中克隆到一个新的无毒基因,全长2118bp,编码705个氨基酸,分子质量和等电点分别约为74．7ku和6．585．NCBI网站BLAST表明,该基因属于avrBs3基因家族,命名为arp3．与所有avrBs3同源基因的Alignment分析发现,arp3的5’端缺少了两个长度分别是144bp和45bp的片断,但在水稻白叶枯病菌中,arp3基因的5’端的特征很普遍．全长的arp3基因中间区域是一个特异的只有5．5次102bp的重复区,是已克隆的avrBs3基因家族中重复次数最少的一个,C-端有3个核定位信号NLSs和1个酸性转录激活域AAD．     

海洋链霉菌生物活性物质的研究

海洋微生物的种类繁多、数量巨大、代谢产物结构奇特、复杂多样、很多具有很好活性的特点吸引着人们的目光.由于海洋环境的特殊性和微生物在生态系统的功能,海洋微生物已发展出独特的代谢方式,也提供了在陆地微生物中未遇到过的新代谢产物.链霉菌是一类革兰氏阳性细菌,具有很强的再生、防御和识别能力,海洋环境下的进化过程造就其独特的代谢方式,其结构类型及生物活性等方面都呈现出与陆生链霉菌多样性.按化合物结构类型介绍了近年来在海洋中分离得到的链霉菌及其生物活性物质的研究概况.     

Reduced nitrogen fixation in the glacial ocean inferred from changes in marine nitrogen and phosphorus inventories.

To explain the lower atmospheric CO2 concentrations during glacial periods, it has been suggested that the productivity of marine phytoplankton was stimulated by an increased flux of iron-bearing dust to the oceans. One component of this theory is that iron-an essential element/nutrient for nitrogen-fixing organisms-will increase the rate of marine nitrogen fixation, fuelling the growth of other marine phytoplankton and increasing CO2 uptake. Here we present data that questions this hypothesis. From a sediment core off the northwestern continental margin of Mexico, we show that denitrification and phosphorite formation-processes that occur in oxygen-deficient upwelling regions, removing respectively nitrogen and phosphorus from the ocean-declined in glacial periods, thus increasing marine inventories of nitrogen and phosphorus. But increases in phosphorus were smaller and less rapid, leading to increased N/P ratios in the oceans. Acknowledging that phytoplankton require nitrogen and phosphorus in constant proportions, the Redfield ratio, and that N/P ratios greater than the Redfield ratio are likely to suppress nitrogen fixation, we suggest therefore that marine productivity did not increase in glacial periods in response to either increased nutrient inventories or greater iron supply.     

New public key cryptosystems from combinatorial group theory

0 IntroductionThe security of most commonly used cryptographicschemesis essentially based onthree families of compu-tational problems :the integer factoring problem(RSAprob-lem) ,the Diffie-Hell man problemand the discrete logarithmproblem,andthe elliptic curve variants thereof .Inthe middleof 1990s , Shor[1], Bonehet al[2]presented some remarkablequantumalgorithms which can solveinteger factoring problemand discrete logarithmproblemover any group including Ga-lois fields and elliptic curve…     

Identity Based Group Key Agreement from Bilinear Pairing

0 IntroductionMulticast isthe core component of the groupcommunica-tions .There are several schemes proposed for securemulticast . The logical key hierarchy (LKH) was proposed byWonget al[1].Inthat ,the groupcontroller (GC) maintains alogical key tree where each node represents a key encryptionkey. An opti mizationthat haves the size of the rekeying mes-sages is described by Canettiet al[2]using a pseudo-randomgenerator tree(OFCT) . Another methodis the one-wayfunc-tion protocol (OFT)[3…     

小白芸豆凝集素的分离纯化及性质研究

从小白芸豆中分离纯化出一种新的凝集素,对其部分理化性质和生物活性进行研究.小白芸豆经过去皮粉碎、浸提、硫酸铵分段盐析、SP Sepharose阳离子交换、Q Sepharose阴离子交换和Superdex 200凝胶过滤层析后可得到小白芸豆凝集素(Phaseolus vulgaris var.albuslectin,PVAL)纯品.测定了PVAL的表观分子质量、亚基分子质量、糖含量、等电点、氨基酸组成、酸碱稳定性以及抗癌性.PVAL的表观分子质量为136 ku,是由2种分子质量分别为36.2 ku和32.2 ku的亚基组成的四聚体,糖含量为4.93%,等电点分布在pH5.3~6.0之间.PVAL分子无半胱氨酸,也无二硫键,疏水性氨基酸质量分数约为37%.PVAL对酸碱的耐受性比较好,并且对肿瘤细胞MDA-MB-435S有较好的抗性.     

一株渤海丝状海洋真菌的分子生物学复核鉴定

采用真菌形态观察的标准培养条件,结合18S rDNA—ITS片段克隆测序和序列特征GeneBank比较分析,对本实验室分离保藏的海洋真菌Penicillium sp．BH06进行了培养特征和显微形态的复核鉴定研究,依据分子生物学和形态结构特征,认定该菌株应修订为桔青霉（Penicillium citrinum）．研究结果提示,基于传统形态学观察并结合ITS序列分析,可为丝状真菌的分类鉴定提供可靠的分子生物学依据．