Immunoprobes for thermally-induced alterations in whey protein structure and their application to the analysis of thermally-treated milks

Polyclonal antisera have been raised to the whey proteins α-lactalbumin [α-La] and β-lactoglobulin [β-Lg], variants A and B. These antibody preparations have been used to develop enzyme-linked immunosorbent assays (ELISAs) for each of these proteins, which had limits of detection of 13 ng/ml [α-La], 27 ng/ml [β-Lg, variant A], and 20 ng/ml [β-Lg, variant B]. The α-La ELISA did not show any cross-reaction with β-Lg, and neither of the β-Lg ELISAs showed a cross-reactivity with α-La. However, despite the almost identical sequences of variants A and B of β-Lg, the variant A ELISA had a cross-reactivity of 66% with variant B, whilst the variant B ELISA had a cross-reactivity of more than 200% with variant A. The effect of thermal treatment on the immunoreactivity of purified whey proteins was studied by ELISA and related to changes in secondary and tertiary structure determined using CD and fluorescence spectroscopy. The immunoreactivity of α-La determined by ELISA decreased on heating above 90°C, these changes coinciding with the protein denaturation as indicated by a loss of secondary structure. In contrast, the ELISA immunoreactivity of both β-Lg variants increased after heating, a change that also coincided with changes in β-Lg secondary and tertiary structure as determined by intrinsic fluorescence of the protein. Similar thermally-induced changes in whey protein immunoreactivity were observed following heat-treatment of raw milk, the immunoreactivity of α-La being reduced whilst that of the β-Lg variants increased. When used in combination these ELISAs were able to discriminate between milks which had been pasteurized or subjected to more severe heat-treatments such as sterilization and ultra heat treatments (UHT). These data demonstrate that such immunoassays have the potential to be used as quality control methods for determining the thermal history of milks.     

铜合金上渗硅层的耐磨耐蚀性

介绍了铜合金在渗剂粉末中高效渗硅,获得无孔的渗硅层。对渗硅层的组织、零件的表面形状和保温时间对渗硅层厚度的影响、摩擦学行为、腐蚀电位等进行了测定,并进行了初步的探讨,说明铜合金上的渗硅层在硫酸介质中具有耐蚀、耐磨(耐磨性提高3倍以上)、减摩等良好性能。     

Wear Resistance of Medium Carbon Steel with Different Microstructures

In this research, the tribological properties of different microstructures of medium carbon steel produced by either an austempered process or quenched-tempered process are investigated. The as-received samples with annealed microstructure (spherodized) are austempered to obtain a bainite microstructure or quenched-tempered to obtain a tempered martensite microstructure. The tribological performance of these microstructures was studied using a ball-on-disk UMT3 tribometer. The results indicated that both bainite microstructures and tempered-martensite microstructures produced better wear resistance than pearlite microstructures. At the same hardness level, the austempered disk specimens have less cracking due to higher fracture toughness compared to quenched and tempered steel. For the disks, tempered martensite microstructures produced more plastic deformation compared with bainite microstructures. Mild abrasive wear was observed on the harder disks, however, smearing wear was observed on the softer disks. Adhered debris particles were observed on the balls.     

蒲菜热加工中的护绿效果

实验研究了不同热处理条件对保持蒲菜绿色的效果,结果表明:当热处理条件为120℃加热10min,热处理溶液pH值为7.0;十二烷基硫酸钠质量浓度为1g/L;Zn2+质量浓度为100mg/L;料液体积比为1∶3;锌盐为ZnCl2时,蒲菜表皮色泽的-a值达7,在贮藏中能很好地保持绿色.     

蒲菜热烫的工艺条件

通过对过氧化物酶的残留酶活、色差、剪切强度和剪切功的分析,研究了热烫时间和贮藏温度对蒲菜的过氧化物酶、色泽和质构的影响.结果表明,在100℃的热烫温度下随着热烫时间的延长,过氧化物酶活降低,而贮藏2 d后酶活的再生量先增大后降低,在热处理时间为1.0-1.5min时达到最大值;热烫时间为4 min时,可基本破坏蒲菜中的过氧化物酶,且蒲菜的质构和色泽较好.     

活性焦表面改性及其常温催化氧化NO的性能研究

使用不同的氧化剂和不同的热处理温度对活性焦（AC）进行改性,采用低温N₂吸附法、傅里叶变换红外光谱（FT-IR）、氨气-程序升温脱附（NH₃-TPD）和非水酸碱滴定法对样品的孔结构和表面化学性质进了表征,并考察了样品在不同湿度下的NO常温催化氧化活性。结果表明,氧化改性减小了样品的微孔孔容,降低了样品的表面碱性基团含量和NO转化率。热处理改性则增加了样品的微孔孔容,提高了样品的表面碱性基团含量和不同湿度下的NO催化氧化活性。在相对湿度为0~80%范围内,氧化-热处理组合改性样品的NO转化率均高于活性焦直接热处理样品,且提高热处理温度,有利于增强样品在湿气（相对湿度为80%）条件下的NO催化氧化活性。     

天然与合成紫晶的光谱学特征及其呈色机理

采用X射线荧光光谱(XRF)、紫外可见光光谱(UV-Vis)、红外光谱(FT-IR)和拉曼光谱(RM)多种光谱学分析方法对天然与合成紫晶样品进行测试。XRF结果显示,天然与合成紫晶的成分均为w=99 % SiO₂,分别含有致色的Fe元素和其他微量金属杂质;红外光谱图显示天然紫晶在3 560~3 200 cm^-1区间内有一强宽吸收带,合成紫晶在3 600~3 000 cm^-1 区间内有2个较尖锐的水吸收峰,分别位于3 583 cm^-     

The Characteristics of SnO Coatings on Titanium.at Different Heat-Treatment Temperature

Objective The aim of this investigation is to study the characteristics of SnO coatings deposited on titanium at different heat-treatment temperature. Methods SnO coatings were produced by sol-gel method with the heat-treatment progress at 300℃, 500℃ and 700℃. Their properties were identified by using DSC, IR, EDS and XRD. Results The SnO gel composed by SnO and SnO2 in the form of an uniform film formed completely at 300℃. Conclusion The Sol-gel method should be prospective to be served as a surface treatment method of titanium substrates to reduce the excessive oxidation of titanium surface during dental porcelain fused to titanium surface.     

热处理对PVDF-PFSA中空纤维共混超滤膜结构及性能的影响

以聚偏氟乙烯(PVDF)与全氟磺酸(PFSA)为共混膜材料,采用湿法纺丝制备了中空纤维共混超滤膜,考察了热处理温度与热处理时间对共混膜的渗透性能、膜结构、受热收缩率及机械性能的影响。结果表明：随热处理温度的升高,截留率先增加后降低,纯水通量先降低后升高,分别在80 ℃时达到最大值与最小值,80 ℃时PEG4000的截留率为95.0%,纯水通量为231 L/(m2·h·MPa);膜的渗透性能随热处理时间变化而变化,在15 min时出现极值;热处理使膜的支撑层结构发生转变,膜径向壁厚收缩率较大,轴向膜长度收缩率较小;热处理后中空纤维膜的断裂伸长率降低,而杨氏模量与断裂强度跟热处理后的膜支撑层结构密切相关;湿法纺制的PVDFPFSA膜,经70 ℃热处理15 min后,制得截留分子量为4 000的中空纤维共混超滤膜,其纯水通量为261 L/(m2·h·MPa)。     

碱热处理制备生物活性钛种植体

钛或钛合金具有良好的生物相容性，临床上常被用作骨内种植体，为了使其更好地与骨组织结合，出现了多种钛表面活化处理的方法，碱热处理是最近出现的一种钛表面活化处理方法。本文就碱热处理活化钛种植体的机制及活化后钛种植体的生物学表现进行综述。