奶牛初乳的热稳定性

研究奶牛初乳的热稳定性并对其加以改进,其成分分析表明,初乳的蛋白质、脂肪、灰分、密度均高于常乳,并随着泌乳期的延长而下降,并逐渐接近常乳水平。而添加蔗糖和脱脂粉后的初乳其热稳定性也有所提高。     

初乳早断方案初探

<正> 初乳(colostral milk)又称血奶或胶乳,是指母牛产犊后一周内,特别是前三天内所产的乳汁。它对新生犊牛具有十分重要的生物学意义,是犊牛理想的全价饲料,含有犊牛所必需的营养素——脂肪、酪蛋白、球蛋白、多种维生素、矿物质、以及促生长因子。一公斤初乳约含20％干物质,5％脂肪。维生素是常乳的几倍甚至是十几倍,蛋白质相当于常乳的三倍,特别是球蛋白是常乳的十一倍,可使犊牛获得被动免疫,以抵抗多种病原菌的侵袭     

奶山羊初乳孕酮和17β—雌二醇的含量及注射初乳对乳中激素水平的影响

应用放射免疫分析法(Radioimmunoassay.RIA),首次测定了14只西农萨能奶山羊初乳中17β—雌二醇(17β—E_2)和孕酮(P_4)的水平。结果表明,分娩0时17β—E_2含量最高(549.05±156.51pg/ml),为10天后均值的12.2倍;分娩后最初6小时17β—E_2水平波动在549.05—408.01pg/ml的范围内,然后陡然下降;2天后下降幅度逐渐减慢,到分娩5天以后,下降到较低水平。P_4的水平在分娩0时为1.883±0.937ng/ml,分娩后最初2天下降较快,随后逐渐变慢,6天后维持在0.7—0.8ng/ml的水平。用山羊初乳对12只西农萨能奶山羊实施颈部皮下注射。结果表明,与注射0天比较,注射后P_4水平立即下降,持续13天。其中第1、5、6、12天显著下降(P<0.05),其余9天均值下降到注射0天均值的80.3％,而对照组无变化(P>0.10)。17β—E_2水平变化不显著(P>0.05)。注射初乳后最初13天,注射组的17β—E_2/P_4的比值极显著地高于对照组(P<0.001)。以上研究结果表明,奶山羊初乳中17β—E_2和P_4水平的分泌范型与牛类似;给奶山羊注射初乳后,能引起其乳汁P_4水平下降和17β—E_2/P_4比值升高,但显示不出诱导发情的作用。     

免疫初乳对正常和实验性糖尿病小鼠血糖的影响

目的研究免疫初乳对正常小鼠和四氧嘧啶致糖尿病小鼠血糖的影响.方法用正常小鼠和糖尿病模型小鼠研究免疫初乳调节血糖的作用.连续30d给予正常小鼠和四氧嘧啶糖尿病模型小鼠免疫初乳,30d后眼眶取血,取其血清测定小鼠空腹血清血糖.结论免疫初乳能显著降低四氧嘧啶致高血糖小鼠的血糖水平并提高其糖耐量,且高剂量免疫初乳组的效果好于低剂量组的效果.但免疫初乳对正常小鼠的血清血糖及糖耐量没有影响.     

免疫初乳对大鼠血液某些生理指标和激素水平的影响

24只健康成年SD大鼠,雌雄对半,随机分成对照组(C组)、普通初乳组(NC组)、免疫初乳组(IC组),每组8只.NC和IC组每天分别灌服普通初乳和免疫初乳(1 mL/100 g体重),C组灌服生理盐水.连续6 d.在第6天观察了灌胃免疫初乳后大鼠血液某些生理指标和激素水平的变化,探讨免疫初乳在参与机体生理活动和内分泌功能活动过程中的作用.结果显示,在整个实验期内,IC组大鼠血液中性粒细胞显著高于C、NC组;NC和IC组大鼠血浆中Ins水平极显著高于对照组;IC组大鼠T3水平显著高于对照组;然而,在整个实验期,大鼠血浆T4、IL-2水平各组间无显著差异.提示免疫初乳可提高正常机体非特异性免疫功能,促进机体代谢激素的分泌,但对细胞免疫没有明显效应.     

不同胎次和泌乳天数对牦牛初乳营养品质的影响

分析了天祝白牦牛初乳中常规营养成分随胎次及泌乳天数的变化规律. 结果表明1胎牦牛初乳中蛋白质含量低于其他胎次，差异不显著-p＞005-, 干物质含量低于其他胎次，除第1, 4天外其余均无显著性差异, 乳糖含量始终高于其他胎次，差异不显著-p＞005-; 第1, 5胎牦牛初乳中脂肪含量低于其他胎次，差异不显著-p＞005-; 所有胎次牦牛初乳中灰分含量差异不显著-p＞005-. 白牦牛初乳中蛋白质、脂肪、干物质和灰分含量在泌乳的第1天最高，随着泌乳期的延长呈下降趋势，乳糖含量在泌乳的第1天最低，之后逐渐上升. 掌握牦牛初乳基本组成成分的变化规律，不仅可以探索牦牛的泌乳性能，还可以为开发利用牦牛初乳产品提供理论参考.     

初乳搅拌速率对复乳法制备载蛋白微球性质的影响

采用复乳法制备载牛血清白蛋白的聚乳酸聚乙醇酸(PLGA)微球,研究初乳搅拌速率(5 000、10 000和15 000 r/min)对微球性质的影响。以包封率、载药量、粒径等为指标,评价其理化性质;扫描电镜观察微球内外形态,并通过图像分析软件计算其结构参数;激光共聚焦显微镜观察蛋白在微球表面及骨架内的分布情况;荧光摄取实验考察孔洞与微球表面连通情况;并考察微球体外释药行为及降解过程中微球的内外形态变化。随着搅拌速率的增加,微球表面及内部孔洞增加,内部孔洞孔径减小,微球释药及降解速率减慢,但对微球粒径及截面孔隙率无显著影响。10 000 r/min组,微球包封率有最大值,1 d的突释率最低,且有最低的表面孔洞连通率;5 000 r/min和15 000 r/min组,微球突释率较高。不同初乳搅拌速率所得微球的内外形态在载蛋白的PLGA微球的释放中发挥重要作用。     

兰州市哺乳期妇女初乳与产后三个月乳汁中几种元素比较分析

比较分析兰州地区产妇产后3个月乳汁与初乳中的钙、铜、铁、镁、锌等多种微量元素的含量变化。收集352例产妇产后3个月的母乳与其初乳标本,采用原子吸收光谱法测定其中所含的钙(Ca)、铜(Cu)、铁(Fe)、镁(Mg)、锌(Zn)、钾(K)与钠(Na)的含量,得出了兰州地区产妇产后3个月母乳中与初乳中钙(Ca)、铜(Cu)、铁(Fe)、镁(Mg)、锌(Zn)、钾(K)与钠(Na)元素的参考范围,并且对其差异性进行了比较分析。兰州地区产妇产后初乳中所含的铜(Cu)、镁(Mg)、锌(Zn)、钾(K)与钠(Na)元素的含量均极显著或显著高于其产后3个月的乳汁中的含量(P0.01),钙(Ca)、铁(Fe)差异不显著(P0.05)。兰州地区产妇初乳中所含的微量元素含量明显高于产后3个月,因此,建议随着产妇生产后时间的推移,应定期检测乳汁微量元素,以保证婴幼儿健康成长。     

用双向电泳-质谱初步分析大熊猫初乳和常乳中差异表达的乳清蛋白

目的 是分析大熊猫初乳和常乳中差异表达的乳清蛋白.利用双向电泳-质谱技术首次对一只大熊猫产后第1d和第22 d的乳清蛋白进行初步的分离与鉴定,结果成功得到11种差异表达的蛋白质,值得注意的是,其中有3种蛋白质与免疫、抗菌有关,包括抗白细胞蛋白酶、溶菌酶C,C反应蛋白.推测这3种蛋白质可能参与大熊猫乳腺或幼仔的防御功能.研究结果表明,用双向电泳-质谱技术可以分析大熊猫初乳和常乳中的差异表达蛋白质,有助于认识大熊猫乳的组成和功能特性.     

具有良好可再生性的新型二氧化硅磁性氧化石墨烯纳米复合材料

Graphene oxide (GO) wrapped Fe₃O₄ nanoparticles (NPs) were prepared by coating the Fe₃O₄ NPs with a SiO₂ layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO₂ coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO₂ on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO₂ layer can effectively induce the GO nanosheets to completely wrap the Fe₃O₄ NPs, forming a core-shell Fe₃O₄@SiO₂@GO composite where Fe₃O₄@SiO₂ NPs are firmly encapsulated by GO nanosheets. The optimized Fe₃O₄@SiO₂@GO sample exhibits a high saturated adsorption capacity of 253 mg·g?1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.     

微波预处理对复杂铜矿磨矿及浮选动力学的影响

The effect of CaCO₃, Na₂CO₃, and CaF₂ on the reduction roasting and magnetic separation of high-phosphorus iron ore containing phosphorus in the form of Fe₃PO₇ and apatite was investigated. The results revealed that Na₂CO₃ had the most significant effect on iron recovery and dephosphorization, followed by CaCO₃, the effect of CaF₂ was negligible. The mechanisms of CaCO₃, Na₂CO₃, and CaF₂ were investigated using X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS). Without additives, Fe₃PO₇ was reduced to elemental phosphorus and formed an iron–phosphorus alloy with metallic iron. The addition of CaCO₃ reacted with Fe₃PO₇ to generate an enormous amount of Ca₃(PO₄)₂ and promoted the reduction of iron oxides. However, the growth of iron particles was inhibited. With the addition of Na₂CO₃, the phosphorus in Fe₃PO₇ migrated to nepheline and Na₂CO₃ improved the reduction of iron oxides and growth of iron particles. Therefore, the recovery of iron and the separation of iron and phosphorus were the best. In contrast, CaF₂ reacted with Fe₃PO₇ to form fine Ca₃(PO₄)₂ particles scattered around the iron particles, making the separation of iron and phosphorus difficult.     

不同硅饱和系数水榴石的碳酸化分解动力学

Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method, which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method. In this study, the effect of the silica saturation coefficient (x) on the carbonation of hydrogarnet was investigated from the kinetic perspective. The results indicated that the carbonation of hydrogarnets with different x values (x = 0.27, 0.36, 0.70, and 0.73) underwent two stages with significantly different rates, and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3. The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and 14.80–34.84 kJ/mol, respectively. Moreover, the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion.     

一种超重力燃烧合成制备高性能高熵合金的新方法

A new method of high-gravity combustion synthesis (HGCS) followed by post-treatment (PT) is reported for preparing high-performance high-entropy alloys (HEAs), Cr_0.9FeNi_2.5V_0.2Al_0.5 alloy, whereby cheap thermite powder is used as the raw material. In this process, the HEA melt and the ceramic melt are rapidly formed by a strong exothermic combustion synthesis reaction and completely separated under a high-gravity field. Then, the master alloy is obtained after cooling. Subsequently, the master alloy is sequentially subjected to conventional vacuum arc melting (VAM), homogenization treatment, cold rolling, and annealing treatment to realize a tensile strength, yield strength, and elongation of 1250 MPa, 1075 MPa, and 2.9%, respectively. The present method is increasingly attractive due to its low cost of raw materials and the intermediate product obtained without high-temperature heating. Based on the calculation of phase separation kinetics in the high-temperature melt, it is expected that the final alloys with high performance can be prepared directly across master alloys with higher high-gravity coefficients.     

利用皮秒激光烧蚀制备非球形铝纳米颗粒

We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid (chloroform, CHCl₃) with ~2 ps laser pulses at an input energy of ~350 μJ. The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at ~340 nm. Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of (27 ± 3.6) nm. The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles. In addition to spherical aluminum nanoparticles, triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution. Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures (LIPSSs), which were the high spatial frequency LIPSSs (HSF-LIPSSs) since their grating period was ~280 nm. Additionally, coarse structures with a period of ~700 nm were observed.     

窄板坯结晶器内连铸工艺参数对钢液流场的影响

Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting (CC) molds with narrow widths for the production of automobile exposed panels. Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process. The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold. Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone. The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min?1 and casting speed of 1.7 m·min?1. Under the present experimental conditions, the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm.     

电渣重熔脱硫技术研究进展

Electroslag remelting (ESR) gives a combination of liquid metal refining and solidification structure control. One of the typical aspects of liquid metal refining during ESR for the advanced steel and alloy production is desulfurization. It involves two patterns, i.e., slag–metal reaction and gas–slag reaction (gasifying desulfurization). In this paper, the advances in desulfurization practices of ESR are reviewed. The effects of processing parameters, including the initial sulfur level of consumable electrode, remelting atmosphere, deoxidation schemes of ESR, slag composition, melting rate, and electrical parameters on the desulfurization in ESR are assessed. The interrelation between desulfurization and sulfide inclusion evolution during ESR is discussed, and advancements in the production of sulfur-bearing steel at a high-sulfur level during ESR are described. The remaining challenges for future work are also proposed.     

Mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al2O3?Na2O system during high-temperature sintering

The mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al₂O₃?Na₂O system during the high-temperature sintering process were systematically investigated using DSC?TG, XRD, SEM?EDS, FTIR, and Raman spectra, and the crystal structure of Na₄Ca₃(AlO₂)₁₀ was also simulated by Material Studio software. The results indicated that the minerals formed during the sintering process included Na₄Ca₃(AlO₂)₁₀, CaO·Al₂O₃, and 12CaO·7Al₂O₃, and the content of Na₄Ca₃(AlO₂)₁₀ could reach 92wt% when sintered at 1200°C for 30 min. The main formation stage of Na₄Ca₃(AlO₂)₁₀ occurred at temperatures from 970 to 1100°C, and the content could reach 82wt% when the reaction temperature increased to 1100°C. The crystal system of Na₄Ca₃(AlO₂)₁₀ was tetragonal, and the cells preferred to grow along crystal planes (110) and (210). The formation of Na₄Ca₃(AlO₂)₁₀ was an exothermic reaction that followed a secondary reaction model, and its activation energy was 223.97 kJ/mol.     

含细夹层的分矿充填层中流动特性的可视化

Ore particles, especially fine interlayers, commonly segregate in heap stacking, leading to undesirable flow paths and changeable flow velocity fields of packed beds. Computed tomography (CT), COMSOL Multiphysics, and MATLAB were utilized to quantify pore structures and visualize flow behavior inside packed beds with segregated fine interlayers. The formation of fine interlayers was accompanied with the segregation of particles in packed beds. Fine particles reached the upper position of the packed beds during stacking. CT revealed that the average porosity of fine interlayers (24.21%) was significantly lower than that of the heap packed by coarse ores (37.42%), which directly affected the formation of flow paths. Specifically, the potential flow paths in the internal regions of fine interlayers were undeveloped. Fluid flowed and bypassed the fine interlayers and along the sides of the packed beds. Flow velocity also indicated that the flow paths easily gathered in the pore throat where flow velocity (1.8 × 10?5 m/s) suddenly increased. Fluid stagnant regions with a flow velocity lower than 0.2 × 10?5 m/s appeared in flow paths with a large diameter.     

气体扩散层集流体对Ni(OH)2纳米结构电化学性能的影响

We report the electrochemical performance of Ni(OH)₂ on a gas diffusion layer (GDL). The Ni(OH)₂ working electrode was successfully prepared via a simple method, and its electrochemical performance in 1 M NaOH electrolyte was investigated. The electrochemical results showed that the Ni(OH)₂/GDL provided the maximum specific capacitance value (418.11 F·g?1) at 1 A·g?1. Furthermore, the Ni(OH)₂ electrode delivered a high specific energy of 17.25 Wh·kg?1 at a specific power of 272.5 W·kg?1 and retained about 81% of the capacitance after 1000 cycles of galvanostatic charge–discharge (GCD) measurements. The results of scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed the occurrence of sodium deposition after long-time cycling, which caused the reduction in the specific capacitance. This study results suggest that the light-weight GDL, which can help overcome the problem of the oxide layer on metal–foam substrates, is a promising current collector to be used with Ni-based electroactive materials for energy storage applications.