低分子质量褐藻寡糖的高效酶法制备及其抗氧化活性评价     

张明杰  李恒  蒋敏  郝瑶  许正宏  史劲松 《海洋科学》2016,40(12):62-70

褐藻寡糖具有多种生理活性,本研究通过酶解与分级条件的优化,获得了低分子质量褐藻寡糖的酶法制备工艺,并在体外模型上评价了不同分子质量组分的抗氧化活性。结果表明,优化后的褐藻寡糖制备条件为:底物浓度1.20%,酶底比4.35 U/mg,酶解时间4 h。进一步采用乙醇沉淀和超滤分离后,获得了重均分子质量分别为0.84、1.40、2.25和34.56 k Da的4种组分,其得率分别为50.82%、5.15%、11.48%和12.00%。各组分均具有一定的还原能力,可有效清除DPPH和羟自由基,其中低分子质量组分A的抗氧化活性最为显著,其清除羟自由基的能力与维生素C相近。  相似文献   

Statistical analyses of Global U-Pb Database 2017     

Stephen J.Puetz  Carlos E.Ganade  Udo Zimmermann  Glenn Borchardt 《地学前缘(英文版)》2018,9(1):121-145

The method of obtaining zircon samples affects estimation of the global U-Pb age distribution.Researchers typically collect zircons via convenience sampling and cluster sampling.When using these techniques,weight adjustments proportional to the areas of the sampled regions improve upon unweighted estimates.Here,grid-area and modern sediment methods are used to weight the samples from a new database of 418,967 U-Pb ages.Preliminary tests involve two age models.Model-1 uses the most precise U-Pb ages as the best ages.Model-2 uses the~(206)Pb/~(238)U age as the best age if it is less than a1000 Ma cutoff,otherwise it uses the~(207)Pb/~(206)Pb age as the best age.A correlation analysis between the Model-1 and Model-2 ages indicates nearly identical distributions for both models.However,after applying acceptance criteria to include only the most precise analyses with minimal discordance,a histogram of the rejected samples shows excessive rejection of the Model-2 analyses around the1000 Ma cutoff point.Because of the excessive rejection rate for Model-2,we select Model-1 as the preferred model.After eliminating all rejected samples,the remaining analyses use only Model-1 ages for five rock-type subsets of the database:igneous,meta-igneous,sedimentary,meta-sedimentary,and modern sediments.Next,time-series plots,cross-correlation analyses,and spectral analyses determine the degree of alignment among the time-series and their periodicity.For all rock types,the U-Pb age distributions are similar for ages older than 500 Ma,but align poorly for ages younger than 500 Ma.The similarities(500 Ma)and differences(500 Ma)highlight how reductionism from a detailed database enhances understanding of time-dependent sequences,such as erosion,detrital transport mechanisms,lithification,and metamorphism.Time-series analyses and spectral analyses of the age distributions predominantly indicate a synchronous period-tripling sequence of~91-Myr,~273-Myr,and~819-Myr among the various rock types.  相似文献   

进口爆破孔钻机配套钻塔的研制          下载免费PDF全文

张西坤  宋秋锋  申寿长  刘大仲  浦静怡  曹继玉  魏少军 《探矿工程》2021,48(6):80-86

进口DMH90型爆破孔钻机配套钻塔整体性强,起落塔快捷方便,钻塔高度满足不换杆一次成孔,即钻塔有效高度略大于钻孔深度,承受振动冲击力大,施工工作环境恶劣。基于这些特点和难点,爆破塔长期依赖进口,导致成本增高、周期加长,为此进行了进口DMH90型爆破孔钻机配套钻塔的替代进口研究工作。本文介绍了DMH90型爆破孔钻机配套ZT27-45型爆破孔钻塔的研制过程,主要对ZT27-45型爆破孔钻塔的设计要点、结构型式、塔体选材、焊接工艺、防止变形、消除应力、质量检验等方面进行了探索、试验和总结。生产施工实践表明,ZT27-45型钻塔制造质量达到了设计要求,满足爆破孔施工的需要,实现了替代进口,达到了降低成本、缩短工期和提高机械性能的目的。  相似文献   

Pushover analysis procedure for systems considering SSI effects based on capacity spectrum method     

王凤霞  欧进萍 《地震工程与工程振动(英文版)》2007,6(3):269-279

This paper presents a new procedure to transform an SSI system into an equivalent SDOF system using twice equivalence. A pushover analysis procedure based on the capacity spectrum method for buildings with SSI effects （PASSI） is then established based on the equivalent SDOF system, and the modified response spectrum and equivalent capacity spectrum are obtained. Furthermore, the approximate formulas to obtain the dynamic stiffness of foundations are suggested. Three steel buildings with different story heights （3, 9 and 20） including SSI effects are analyzed under two far-field and two near-field historical records and an artificial seismic time history using the two PASSI procedures and the nonlinear response history analysis （NLhRHA） method. The results are compared and discussed. Finally, combined with seismic design response spectrum, the nonlinear seismic response of a 9-story building with SSI effects is analyzed using the PASSI procedures, and its seismic performance is evaluated according to the Chinese ＇Code for Seismic Design of Buildings. The feasibility of the proposed procedure is verified.  相似文献   

矿产地质勘查项目研判ABC     

冯建忠  续婧 《地质找矿论丛》2007,22(4):287-293,302

矿产地质勘查是高投入、高风险、高回报的投资活动,如何引进经济、优质的矿权是矿产地质勘查的先决条件和企业赖以发展的基础.对项目高效、快速、准确的研判是项目研发最重要的一步.文章把矿权分为3种矿权来源和4种项目类型.通过3种矿权来源点评和4种项目类型的剖析,探讨了项目研判的内容、研判的准则、研判的工作程序,把研判过程分为初判、普判、详判3个阶段.在此基础上研究了研判各阶段时间安排与具体工作内容,普判阶段编图方法、取样间距和取样方法,普判阶段工作量及费用概略估计,以及详判阶段的几个关键问题.  相似文献   

迭代逼近科学方法在速度估算中的作用     

陈宝孚  李貅 《地球科学与环境学报》2000,22(2):67-70

以地球物理中的速度为题 ,在详细描述了速度参数重要作用、各类速度基本概念及其应用范围、影响速度估算的各种因素的基础上 ,以模型和处理流程的叠加速度分析为例 ,在两个层面上展现了迭代逼近方法。又以剩余层速度分析为例 ,说明了具有反馈控制思想的迭代逼近算法 ,从而指出该方法在速度估算中的重要作用  相似文献   

Experimental study on a sampling technique based on a freeze-sediments valve for deep-sea microorganism     

《Applied Ocean Research》2019

Deep-sea microorganism research has become a hot topic in life science, owing to its special value in high pressure and low temperature environment. If not kept the in-situ low temperature and high pressure, it will cause the microorganism to lose its activity and lead to a waste of resources. A freeze-sediments valve presents a promising solution to maintain the low temperature and high pressure in situ, improve the success rate of sampling and shorten the sampling time. A series of experiments were conducted to characterize the freeze-sediments valve, including the sampling time without leakage, adaptation to different sediments and the effect of the length, etc. Most important of all, temperature change of sediments is observed in all experiments. Experimental results indicated that the freeze-sediments valve was formed in 5 min without leakage and the freeze-sediments valve could be applied to different sediments without limitations on sediments type and mineral content. Considering the pressure retaining capacity and formation time of freeze-sediments valve, it was found that the freeze-sediments valve with a length of 60–80 mm has good pressure retaining capacity whose value was 41.3–48.4 Mpa and short formation time which was 5 min. Precooling the sampler could be used to shorten the sampling time in the actual environment application. This sampling technique can play a vital role in maintaining in-situ low temperature at −2 to −4 ° Celsius in all the experiments. According to the tests, the sampling technique based on the freeze-sediments valve had the potential to solve the problem of keeping in-situ temperature, low sampling success rate and long sampling time in the future.  相似文献   

复合加载模式作用下地基承载性能数值分析   总被引：14，自引：3，他引：11  

栾茂田  赵少飞  袁凡凡  吕爱钟  武科 《海洋工程》2006,24(1):34-40

确定竖向荷载(V)、水平荷载(H)和力矩(M)共同作用下建筑物地基的破坏模式及在荷载空间(H,V,M)中的破坏包络面是地基设计中的关键问题。为提高Swipe试验方法计算精度,提出了改进方案,进而利用有限元方法分析了复合加载模式作用下均质粘性土地基上条形基础的破坏包络面。计算表明,基于改进Swipe试验方法的数值模拟结果明显好于常规Swipe试验方法。针对海洋工程中实际复合加载模式的特点,探讨了竖向荷载分量V对地基破坏模式和H-M荷载平面上的破坏包络线的影响,结果表明竖向荷载分量显著地改变了地基的破坏模式及包络线的形状。  相似文献   

Reply: Bulk sampling of coarse clastic sediments for particle-size analysis     

Stephen J. Gale  Peter G. Hoare 《地球表面变化过程与地形》1994,19(3):263-268

The work of Gale and Hoare (1992) provides a guide to the minimum mass of bulk sample required to obtain a reproducible measure of the complete particle-size distribution of coarse clastic sediments such as till, fluvial gravel and beach gravel. Dunkerley (1994) makes a number of criticisms and misrepresentations of this procedure. These are systematically refuted and corrected here, and further data obtained from till and beach gravel are provided to support the criterion adopted by Gale and Hoare (1992) for sample reliability. The procedure of Gale and Hoare (1992) is confirmed as a practical guide to the mass of bulk sample required to obtain a reliable measure of the particle-size distribution of coarse clastic sediment.  相似文献   

钱塘江口涌潮的二维数值模拟   总被引：16，自引：1，他引：16       下载免费PDF全文

谭维炎  韩曾萃 《水科学进展》1995,6(2):83-93

应用二维有限体积法、Osher格式及间断拟合法,计算了钱塘江河口涌潮产生、发展到消亡的全过程。该算法能保证水量和动量守恒,且能适应水深巨大变化和动边界。根据钱塘江涌潮的特点,可将其合理概化为一线潮。在网格尺寸较大情况下,计算的一线潮仍保持高分辨率,能准确满足水力学间断条件,且计算量小,可以在微机上实现。在对某实测半日小潮进行率定后,对随后的大潮进行了验证计算,涌潮的主要特征(如涌潮高度、移速、水位和流场等)与实测资料符合良好,证实了模型的合理性和模拟能力。  相似文献