益生菌抗氧化活性及菌体抗氧化相关成分的分析

目的比较乳杆菌、双歧杆菌、嗜热链球菌和乳酸乳球菌的抗氧化活性,分析抗氧化活性较高菌株内与抗氧化相关的成分。方法采用清除DPPH自由基、清除羟自由基以及抗脂质过氧化能力3种方法评价40株益生菌的抗氧化活性,选出抗氧化活性较高的菌株分析其超氧化物歧化酶(SOD)、谷胱甘肽(GSH)和总巯基化合物(TTG)的含量。结果所比较的40株益生菌的抗氧化能力差别较大,既具有种属特异性,又具有菌株特异性;7株嗜热链球菌和11株乳酸乳球菌中的SOD活性最高[(平均分别为124.02U/mg(蛋白质)和107.10U/mg(蛋白质)]、2株双歧杆菌中GSH的含量最高(平均为311.03μmol/L细胞破碎液),所分析的菌株中TTG含量均较高。研究结果表明,实验菌乳酸乳球菌清除自由基能力最强,其次是嗜热链球菌,所试验的乳杆菌和双歧杆菌最弱;SOD对益生菌的抗氧化起主要作用;GSH的存在因种属和菌株的不同而差别较大;TTG对益生菌的抗氧化起了积极作用。     

Formation and catalytic performance of supported ni nanoparticles via self‐reduction of hybrid NiAl‐LDH/C composites

In the present work, hybrid NiAl‐layered double hydroxide/carbon (LDH/C) composites with adjustable compositions were successfully assembled by crystallization of LDH in combination with carbonization of glucose under hydrothermal conditions, and further utilized as an integrated catalyst for the growth of carbon nanotubes (CNTs) in catalytic chemical vapor deposition (CCVD) of acetylene. The materials were characterized by X‐ray diffraction, Fourier transform infrared, elemental analysis, thermogravimetric and differential thermal analysis, SEM, transmission electron microscopy, X‐ray photoelectron spectra, and Raman spectroscopy. The results revealed that the supported Ni nanoparticles with the small crystallite size of about 10 nm could be obtained by in situ self‐reduction of as‐assembled hybrid LDH/C composites in the course of CCVD. The carbon in the hybrid structure as a reducing agent played a key role for the high dispersion of resulting Ni nanoparticles. Furthermore, the Ni nanoparticles obtained here exhibited excellent activity for catalytic growth of CNTs, which could be delicately tuned by varying the compositions of hybrid composites. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Thermal fluorination effects on carbon nanotubes for preparation of a high-performance gas sensor

A high-performance NO gas sensor was prepared by inducing thermal fluorination of carbon nanotube semiconductors. Thermal fluorination of multi-walled carbon nanotubes (MWCNTs) was carried out at various temperatures (100 ∼ 1000 °C) to investigate the effects of the reaction temperature. The mechanism of high-performance NO gas sensor electrode was shown to depend on the fluorination temperature in a way that can be divided into three regions, separated at 400 and 1000 °C. In the first temperature region, the induction of fluorine functional groups onto MWCNTs showed the opposite trend in electrical resistance change comparing with traditional p-type MWCNTs. In the second temperature region, the induced fluorine functional groups were attenuated by generated fluorinated carbon gases resulting in the decomposition of MWCNTs and the recovery of traditional p-type gas sensor behavior. In the highest temperature region above 1000 °C, reoriented carbon structure was observed, showing bent nanotubes produced from destruction by fluorination and subsequent reorientation due to the high temperature. The gas sensing responsiveness was significantly improved by the thermal fluorination, which causes electrophilic attraction, creates adsorption sites for target NO gases and improve hydrophobicity for gas sensing stability in humid condition. In conclusion, a high-performance gas sensor was obtained by thermal-fluorination of MWCNTs.     

关于冷凝器封头的有限元局部应力分析

制冷设备冷凝器管程介质为水,壳程介质为制冷剂。管箱形式多种多样,尤其封头的形式,主要有冲压、铸造、板材加工等。文章针对这一问题,对其中一种特殊形式的封头结构进行受力分析。     

Soil nutrient content and nutrient balances in newly-built solar greenhouses in northern China

Soil nutrient content and nutrient balances in newly-built solar greenhouses in the southern part of China??s Loess Plateau were investigated over two consecutive years. Farmers applied manure and inorganic fertilizers at average annual rates of 1,907?kg?N ha^?1, 1,601?kg?P₂O₅?ha^?1 and 1,742?kg?K₂O?ha^?1. Manure accounted for 65?% of the total N input, 57?% of the total P input and 55?% of the total K input. The average annual nutrient surpluses were 1,374?kg?N?ha^?1, 1,468?kg?P₂O₅?ha^?1 and 881?kg?K₂O?ha^?1. Soil organic matter, total N, available P, available K and electrical conductivity (EC) increased significantly across time in the topsoil (0?C20?cm depth), but not in the subsoil (20?C100?cm depth). The nitrate?CN concentrations (mg?N?kg^?1) of the 0?C100?cm depth increased by 163?C336?% over 2?years. The average accumulation of nitrate?CN (kg?N?ha^?1) of the 0?C100?cm depth increased by 241?% and leveled out at 511?kg?N?ha^?1; and it was 1,015?kg?N?ha^?1 in the 0?C200?cm depth. In conclusion, over-fertilization led to large nutrient surpluses in the soil of newly-built greenhouses.     

Importance of N-Glycosylation on CD147 for Its Biological Functions

Glycosylation of glycoproteins is one of many molecular changes that accompany malignant transformation. Post-translational modifications of proteins are closely associated with the adhesion, invasion, and metastasis of tumor cells. CD147, a tumor-associated antigen that is highly expressed on the cell surface of various tumors, is a potential target for cancer diagnosis and therapy. A significant biochemical property of CD147 is its high level of glycosylation. Studies on the structure and function of CD147 glycosylation provide valuable clues to the development of targeted therapies for cancer. Here, we review current understanding of the glycosylation characteristics of CD147 and the glycosyltransferases involved in the biosynthesis of CD147 N-glycans. Finally, we discuss proteins regulating CD147 glycosylation and the biological functions of CD147 glycosylation.     

高效液相色谱法测定烟丝及烟气中多元酸的方法研究

本研究建立了高效液相色谱法定量测定烟丝及烟气中的多元酸,确定的色谱条件如下:HP Hypersil ODS柱(125mm×4.6mm×5μm),流动相流速为1.0mL/min,紫外检测波长为210nm。进样量1μL,柱温40℃。该方法的精密度RSD<4%,回收率大于97%。在此色谱条件下20min内完成了多元酸(草酸、苹果酸、丙二酸、柠檬酸、丁二酸、富马酸)的分离,结果比较理想,表明此新建方法准确而快速,并能适用于烟丝及烟气中单多元酸的测定。     

塑料网印常见问题分析

塑料在电子产品中应用越来越广泛，如外壳、控制面板、铭牌等。为达到装饰目的，普遍采用丝网印刷工艺。丝网印刷在塑料零件表面的装饰手段中占据重要位置。塑料是各种不同性质的高分子化合物的统称，种类非常多。在其表面印刷涉及许多工艺要素，常出现各种各样的质量问题。本文仅对丝网印刷涉及到的热塑性塑料经常出现的问题及解决办法作一介绍。一、附着力塑料网印后，附着力是一项最主要的检查标准。附着力常用的检查方法是：先将膜层用锐利的刀片划成10×10个1 mm×1 mm的方格，然后用PP胶带纸用力粘贴膜层，符合要求的附着力不允许有…     

转基因玉米的七重PCR鉴定方法

以玉米内源基因IVR、外源抗除草剂基因(BAR、PAT)、抗虫基因Cry1Ab、筛选基因NPTII、CaMV35S启动子和NOS终止子为检测的目的片段,分别设计了7对引物,通过研究较佳引物终浓度配比和退火温度,建立了玉米转基因成分七重PCR检测体系。结果表明,建立的七重PCR体系用于同时检测内源基因和转基因成分是可行的,检测方法效率高、稳定性好。     

小麦DH群体馒头主要品质性状之间的相关分析

依照行业标准SB/T 10139—1993制作馒头,采用感官评定、色彩色差计测定、质构分析相结合的方法测定分析馒头主要品质性状之间的相关性。分析结果表明:对馒头评分影响最主要的因素分别为硬度、体积、L*值、A*值和B*值,其中与评分呈极显著正相关的为体积和L*值,呈极显著负相关的为硬度、A*值和B*值;馒头主要品质性状间的相关性分析表明:硬度与黏着性、弹性、黏聚性、回复性均呈极显著负相关水平,而与胶着性和咀嚼度的相关性为极显著正相关;L*值与A*值、B*值、l*值、a*值的相关性均为极显著正相关,并且,L*值与l*值,A*值与a*值,B*值与b*值之间均存在极显著正相关关系;体积与弹性、黏聚性、胶着性、咀嚼度以及回复性间的相关性均为极显著负相关。