自限温电热带在液碱输送管线上的伴热应用

本文简要介绍了自限温电热带的特点及限温原理,并从投资、施工、操作、管理等方面与蒸汽和热水伴热进行技术经济比较。成功地将自限温伴热带应用于48%液碱管道伴热,确保48%液碱冬季出口。     

HDPE/PVDF/CB复合体系PTC性能的研究

以HDPE/PVDF共混物为基体 ,研究了两种不同类型炭黑 (CB)的用量 ,以及HDPE/PVDF配比对复合物的正电阻温度系数 (PTC)的影响。结果表明 ,HDPE/PVDF/CB三元复合体系具有很强的PTC特性 ,可用于制作电致发热稳定性良好、自限温度 ( 85± 5 )℃、具有商业用途的自控温伴热带     

安全电压自控温电热带的研制

研究了安全电压自控温电热带的制备和性能，介绍了该电热带的结构、性能、制作及工作原理，同时讨论了一些关键技术，如：自控温原理、化学交联工艺等。以ＰＥ、橡胶、碳黑、交联剂、抗氧剂及镀锡铜导线等为原料研制了自控温电热带。结果表明，所研制的安全电压自控温电加热带的具有最佳的导电性及ＰＴＣ特性，最低室温电阻达２０Ω/m。经过近两年的通电试验表明，具备良好的功率稳定，限温效果极限佳。     

粘接性树脂在PTC自限温伴热带中应用

研究了以乙炔炭黑为导电粒子,ＨＤＰＥ、ＬＬＤＰＥ及粘接性树脂（接枝高密度聚乙烯（ｇ ＨＤＰＥ））为基体的导电复合物ＰＴＣ行为,电致发热特性及电压循环冲击试验。结果发现,ｇ ＨＤＰＥ／ＣＢ导电复合材料、ＬＬＤＰＥ／ｇ ＨＤＰＥ／ＣＢ复合物的ＰＴＣ复演性及电阻稳定性均优于ＬＬＤＰＥ／ＣＢ及ＨＤＰＥ／ＣＢ导电体系     

LLDPE/EVA/CB复合体系的导电和发热性能

对LLDPE/EVA(乙烯醋酸乙烯酯共聚物)/CB(碳黑)三元复合材料的导电性能及发热特性进行了研究。讨论了碳黑种类及含量对复合导电材料性能的影响,探讨了复合材料的伏-安特性、功率-温度特性以及辐照交联工艺对复合材料稳定性的影响。结果表明,添加乙炔碳黑,可使复合材料具有最佳的导电性及PTC(正电阻温度系数)特性,辐照交联使材料具有良好的电阻稳定性,由此制得的电缆经过一年的通电试验,其工作温度稳定在70℃±5℃,具有良好的限温作用。     

正温度系数自限温加热电缆放大效应研究

研究LDPE／CB（低密度聚乙烯／炭黑）导电复合材料经50L密炼机塑化造粒，再以Φ45挤出机制备自限温加热电缆的放大效应，考察了工艺放大对导电复合材料体积电阻率及其重复稳定性的影响。结果表明，1L密炼配方放大后可适当降低炭黑含量，得到均匀分散的LDPE／CB正温度系数（PTC）导电复合材料；而挤出放大工艺参数，如加工温度及螺杆速度提高，长径比小时，电缆的电阻率下降，与小试实验结果一致，且所得加热电缆轴向电阻均匀性及发热稳定性良好，可用于批量生产。     

高密度聚乙烯/炭黑自限温发热管的电热特性

介绍了一种新型的可连续化批量生产的复合型高分子自限温发热元件－自限温发热管的电热特性,其发热功率,发热温度,热功转换效率,使用寿命的试验结果表明,这一智能型功能元件除用于伴热保温之外,有望成为实用的低温发热热源,在许多领域替代传统的金属发热元件。     

复合型高分子自限温发热材料及元器件在汽车冷启动方面的应用

采用HDPE／CB复合型高分子自限温发热材料制备了适于在汽车上使用的自限温加热带、发热管及相应的加热器，通过实验室模拟试验，研究了加热器的电热特性。在冬季的柴油车冷启动试验表明，组合加热装置对柴油车的冷启动及正常运行非常奏效，所研制的复合型高分子自限温发热材料及元器件用于汽车领域是可行的。     

乙炔炭黑在智能PTC自限温伴热带中的应用

研究了高导电炭黑、乙炔炭黑、油炉法炭黑、高耐磨炭黑、槽法炭黑与ＬＬＤＰＥ（ 线性低密度聚乙烯） 共混复合导电材料的逾渗行为及ＰＴＣ（ 正温度系数） 特性,并借助ＴＥＭ 观察了几种典型炭黑的粒子形貌。结果发现,乙炔炭黑用于制备ＰＴＣ 导电复合材料具有ＰＴＣ 效应强、炭黑逾渗值适中、加工便利的优点;由乙炔炭黑／ＬＬＤＰＥ 复合物可制得具有发热温度（６５ ±５ ） ℃、稳态发热功率４ ～８ Ｗ／ ｍ 、并可长期使用的智能ＰＴＣ 自限温伴热带。     

超声辐射对PVA/CB导电复合材料气敏性能的影响

以聚乙烯醇(PVA)为基体,填充各种类型炭黑导电粒子,制备了导电复合薄膜。研究了超声作用下导电复合薄膜在不同溶剂蒸气中的气敏性能。考察了PVA与炭黑的比例、炭黑种类、超声时间、超声功率等条件对导电薄膜响应性能与响应稳定性的影响,并对这种导电复合薄膜产生气敏响应性的机理作了分析。结果表明,以PVA/乙炔炭黑组成的导电复合薄膜具有较强气敏响应性。当将其置于丙酮、正丁醇、乙醇、水极性溶剂中,电阻急剧提高102~103倍,表现为正蒸气系数效应(PVC);随炭黑含量提高,复合材料薄膜室温电阻下降,对溶剂蒸气的响应强度提高;超声时间、功率对导电粒子分散行为及复合材料的气敏性有影响,随超声时间延长及功率增大,接枝改性效果明显,导电薄膜的响应性及重复稳定性提高。     

欧盟公布染料化学名称

该文根据欧盟2000年公布的第五版和2002年公布的第六版《欧洲化学物质申报清单》，选择一些重要的染料品种，介绍了他们的化学名称，以及可供参考的结构式。     

An efficient method for creation and functional analysis of libraries of hybrid type I polyketide synthases

Bacterial type I polyketide synthases (PKSs) generate a structurally diverse group of natural products with a wide range of biological activities. Hybrid type I PKSs in which domains of one multifunctional polypeptide are replaced with components from heterologous systems have generated significant interest over the past decade. Almost invariably only one or several specific hybrids are made at a time and tested for functionality. This approach is slow, dependent upon a fortuitous choice of specific fusions points, and often leads to inactive or minimally active hybrid systems. We describe herein a method for generating and screening a library of hybrid pikAI complementation plasmids (encoding the loading domain and the first two extension domains of pikromycin PKS) able to restore pikromycin in a BB138 Streptomyces venezuelae pikAI-deletion mutant. In the first step the plasmid sequence encoding the loading domain AT(0)-ACP(0) was replaced by a counter selectable marker, sacB. DNA family shuffling was then used to generate a diverse library of chimeric AT(0)-ACP(0) fragments, which were used to replace sacB by lambda-Red-mediated in vivo recombination in an Escherichia coli host. This method resulted in the rapid and efficient generation of a large number of hybrid pikAI complementation plasmids, which were used to transform S.venezuelae BB138. A bioassay of over 4000 of these transformants successfully revealed three different PikAI hybrids which were able to lead to pikromycin production. The study suggests that most of the hybrids are not detectably functional, and underscores the need to generate and screen large and diverse libraries in which different fusion points are tried. The methodologies applied in this study address this need and can be used for directed evolution of any component of the PikPKS, and potentially other type I PKS systems.     

Prediction of proprotein convertase cleavage sites

Many secretory proteins and peptides are synthesized as inactive precursors that in addition to signal peptide cleavage undergo post-translational processing to become biologically active polypeptides. Precursors are usually cleaved at sites composed of single or paired basic amino acid residues by members of the subtilisin/kexin-like proprotein convertase (PC) family. In mammals, seven members have been identified, with furin being the one first discovered and best characterized. Recently, the involvement of furin in diseases ranging from Alzheimer's disease and cancer to anthrax and Ebola fever has created additional focus on proprotein processing. We have developed a method for prediction of cleavage sites for PCs based on artificial neural networks. Two different types of neural networks have been constructed: a furin-specific network based on experimental results derived from the literature, and a general PC-specific network trained on data from the Swiss-Prot protein database. The method predicts cleavage sites in independent sequences with a sensitivity of 95% for the furin neural network and 62% for the general PC network. The ProP method is made publicly available at http://www.cbs.dtu.dk/services/ProP.     

解放汽车驾驶员座椅防尘罩研制

介绍了解放汽车驾驶员座椅防尘罩的研制经过。配方采用丙烯腈质量分数为19％的NBR并用NR和马来酸酐化聚丁二烯MLPB。模具采用多产品组合设计，三开注射模结构。用橡胶注射成型工艺制造的汽车驾驶员座椅防尘罩，外观美观，性能达到标准要求。     

Identification of potent human anti-IL-1RI antagonist antibodies

Interleukin-1 (IL-1) blockade by IL-1 receptor antagonist benefits some arthritis patients by reducing joint damage. This fact inspired us to develop antagonist human therapeutic antibodies against IL-1R(I) using phage libraries that display single-chain variable fragment (scFv) antibody fragments. Panning libraries against human IL-1R(I) generated 39 unique scFv-phage whose binding to IL-1R(I) was competed by IL-1 ligands. Fifteen of these scFv-phage, identified using IL-1R(I)-binding assays and dissociation rate ranking, were reformatted as scFv-Fc and IgG(4) molecules. The ease of producing antibodies in the scFv-Fc format permitted rapid identification of four lead clones (C10, C13, C14, C15) that inhibit NF-kappaB nuclear translocation induced by IL-1. Reformatting these clones as IgG(4) molecules increased their inhibition potency by 相似文献   

Determination of Algerian Hassi-Messaoud asphaltene aromaticity with different solid-state NMR sequences

Algerian oil well deposit derived asphaltene fraction was characterized by different MAS/NMR sequences to investigate asphaltene aromaticity and the best cross-polarization contact time. The aromaticity was estimated by single pulse sequence (SP), Hahn-echo (HE), cross-polarization (CP) and variable cross-polarization (VACP) sequences. The values found ranging from 0.58 to 0.48 are of the same order of magnitude as ones published in the literature. The discrepancies between the values are thought to be relevant to both the specificity of each sequence and the asphaltene structure. Spectra band de-convolution enables us the determination of the average number of carbon atoms per side chain according to each sequence. The obtained values spanning from 3 to 7 are also sequence nature dependent.     

Structural and kinetic studies of a series of mutants of galactose oxidase identified by directed evolution

Galactose oxidase (GO; E.C. 1.1.3.9) is a copper- containing enzyme that oxidizes a range of primary alcohols to aldehydes. This broad substrate specificity is reflected in a high K(M) for substrates. Directed evolution has previously been used to select variants of GO that exhibit enhanced expression and kinetic properties. In assays using unpurified enzyme samples, the variant C383S displayed a 5-fold lower K(M) than wild-type GO. In the present study, we have constructed, expressed, purified and characterized a number of single, double and triple mutants at residues Cys383, Tyr436 and Val494, identified in one of the directed evolution studies, to examine their relative contributions to improved catalytic activity of GO. We report kinetic studies on the various mutant enzymes. In addition, we have determined the three-dimensional structure of the C383S variant. As with many mutations identified in directed evolution experiments, the availability of structural information does not provide a definitive answer to the reason for the improved K(M) in the C383S variant protein.     

Transglutaminase-mediated N- and C-terminal fluorescein labeling of a protein can support the native activity of the modified protein

Fluorescein and its analogs are among the best fluorophores to label proteins and the labeling generally involves chemical modification of a translated protein. Using this methodology, labeling at a specific position remains difficult. It is known that the guinea pig liver transglutaminase (TGase)-catalyzed enzymatic modification method can allow terminal-specific fluorophore labeling of a protein by monodansylcadaverine. However, native activity of the fluorescent protein has not been investigated so far, nor has direct comparison between the chemical modification and the TGase-catalyzed modification been attempted. Therefore, we compared the possibility of fluorescein labeling via chemical labeling and via TGase-catalyzed modification. The latter method was found to be very practical and overcame some of the problems associated with the specificity of the former; fluorescein was covalently attached only to the N- or C-terminal site of glutathione S-transferase when the reaction was catalyzed by TGase and the resulting labeled protein completely retained its native activity. The TGase-mediated labeling occurred not only at room temperature but also at 4 degrees C to the same extent, which is more desirable for preventing the inactivation of proteins.     

Improvement of cyclodextrin glucanotransferase as an antistaling enzyme by error-prone PCR

In an effort to improve the properties of cyclodextrin glucanotransferase (CGTase) as an antistaling enzyme, error-prone PCR was used to introduce random mutations into a CGTase cloned from alkalophilic Bacillus sp. I-5 (CGTase I-5). A mutant CGTase[3-18] with the three mutations M234T, F259I and V591A was selected by agar plate assay. Sequence alignment of various CGTases indicated that M234 and F259 are located in the vicinity of the catalytic sites of the enzyme and V591 in the starch binding domain E. The cyclization activity of CGTase[3-18] was dramatically decreased by 10-fold, while the hydrolyzing activity was increased by up to 15-fold. These mutations near subsite +1 (M234T) and at subsite +2 (F259I) are likely to alter the enzyme activity in a concerted manner, promoting hydrolysis of substrate while retarding cyclization. The addition of CGTase[3-18] reduced the retrogradation rate of bread by as much as did the commercial antistaling enzyme Novamyl during 7-day storage at 4 degrees C. No cyclodextrin (CD) was detected in bread treated with CGTase[3-18], whereas 21 mg of CD per 10 g of bread was produced in bread treated with wild-type CGTase.