Sedimentation field flow fractionation of DNA's

Sedimentation field flow fractionation (SFFF) is a method for purifying and providing mass or size distribution information on samples containing particulates or soluble macromolecules. Since SFFF separations are based on simple physical phenomena related to first principles, molecular weight (or particle sizes) can be determined without calibration standards. SFFF is a gentle technique suited for fractionating biomolecules. Studies with the fragile lambda DNA (molecular weight, 33 X 10(6] and smaller supercoiled plasmids have shown that these materials are not altered during SFFF separation; molecular weights and conformation remain unchanged, and biological activity is not reduced. Recoveries of nucleic acids approach 100 percent. Typically, components with about 20 percent difference in mass can be separated essentially to baseline if required. Fractionation time is usually independent of molecular weight, and separations often can be carried out within an hour.     

High-Resolution Density Gradient Sedimentation Analysis

The principle of stability for a sample layered in a density-gradient liquid column is discussed, and a method for separating ribonucleoprotein particles by means of sedimentation in the ultracentrifuge is described.     

Deep seismic expression of an ancient plate boundary in europe

Seismological results on the structure of the upper mantle below Europe reveal a marked contrast in seismic properties between Precambrian and younger parts of Europe. The Precambrian craton in eastern Europe is characterized by high shear-wave velocities, which can be explained by low temperatures. The transition to low seismic velocities below Phanerozoic Europe coincides with the crustal boundary zone of the craton and exists to depths of at least 140 kilometers. Despite the long and complex tectonic history of the plate boundary zone, the transition is remarkably sharp, which rules out any significant lateral transport of asthenospheric material across the suture zone.     

一种热雾施药专用沉降稳定剂的研发

为解决热雾机施药时热雾微粒飘逸及发烟载体与常规商品农药不相容的问题,通过对发烟载体、表面活性剂、凝结核物质及防冻剂、分散剂、增稠剂、消泡剂等助剂进行筛选和组配,开发出一种热雾沉降稳定剂,为热雾施药技术在农作物病虫害防治上的推广应用提供技术支持.     

Sedimentation field flow fractionation: applications

Sedimentation field flow fractionation is a powerful, new, high-resolution separation method for a wide variety of colloids, micelles, particulates, and soluble macromolecules of biological interest. Advances in instrumentation allow sedimentation field flow fractionation operation with rotor speeds up to 32,000 revolutions per minute ( approximately 85,000 gravities), which permits separation of materials as small as 5 x 10(5) molecular weight, depending on sample density. Compared to conventional centrifugation techniques, the gentle, mass-separating sedimentation field flow fractionation method is capable of higher resolution in shorter times.     

Mineralogic evidence for an impact event at the cretaceous-tertiary boundary

A thin claystone layer found in nonmarine rocks at the palynological Cretaceous-Tertiary boundary in eastern Montana contains an anomalously high value of iridium. The nonclay fraction is mostly quartz with minor feldspar, and some of these grains display planar features. These planar features are related to specific crystallographic directions in the quartz lattice. The shocked quartz grains also exhibit asterism and have lowered refractive indices. All these mineralogical features are characteristic of shock metamorphism and are compelling evidence that the shocked grains are the product of a high velocity impact between a large extraterrestrial body and the earth. The shocked minerals represent silicic target material injected into the stratosphere by the impact of the projectile.     

Major earthquakes occur regularly on an isolated plate boundary fault

The scarcity of long geological records of major earthquakes, on different types of faults, makes testing hypotheses of regular versus random or clustered earthquake recurrence behavior difficult. We provide a fault-proximal major earthquake record spanning 8000 years on the strike-slip Alpine Fault in New Zealand. Cyclic stratigraphy at Hokuri Creek suggests that the fault ruptured to the surface 24 times, and event ages yield a 0.33 coefficient of variation in recurrence interval. We associate this near-regular earthquake recurrence with a geometrically simple strike-slip fault, with high slip rate, accommodating a high proportion of plate boundary motion that works in isolation from other faults. We propose that it is valid to apply time-dependent earthquake recurrence models for seismic hazard estimation to similar faults worldwide.     

榨菜废水的混凝处理研究

采用混凝法对榨菜废水进行了处理试验.结果表明,混凝剂投加量、混凝剂种类、搅拌速率及沉降时间等对处理效果都起着重要作用.选用CaO作混凝剂,聚丙烯酰胺(PAM)作助凝剂,其处理效果明显优于其他几种混凝剂.当CaO,PAM的投加量分别为700,5 mg/L,以250 r/min的速度搅拌30 min,则COD,TP,浊度的去除率分别为36.54%,52.03%和97.85%,处理成本较低,中试试验结果与小试试验参数相吻合;用CaO,PAM联合处理榨菜废水能自动调节废水pH值,节省混凝剂的用量、减轻废水的刺激性气味、提高榨菜废水的可生化性,减轻后续处理系统的负担,同时沉降形成的絮体较大,易于被回收开发成饲料或有机肥料,为榨菜废水的处理提供了依据.     

Ascent of dinosaurs linked to an iridium anomaly at the Triassic-Jurassic boundary

Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per trillion, with an average maximum of 141 parts per trillion) and a fern spore spike, suggesting that a bolide impact was the cause. Eastern North American dinosaurian diversity reached a stable maximum less than 100,000 years after the boundary, marking the establishment of dinosaur-dominated communities that prevailed for the next 135 million years.     

Holocene mean uplift rates across an active plate-collision boundary in taiwan

Samples of Holocene fossil coral from uplifted reefs of three tectonically distinct, yet geographically proximal regions of Taiwan have been dated by uranium-series and (14)C isotopes. Applying corrections for altitude change caused by sea level fluctuations enables evaluation of long-term average Holocene uplift rates for three areas across an active convergent margin: (i) the Hengchun Peninsula of the Eurasian tectonic plate; (ii) the Eastern Coastal Range of Taiwan, a plate boundary; and (iii) two offshore islands, Lanyu and Lutao, both situated on the leading edge of the adjoining Philippine Plate. The data indicate that while all three areas have experienced uplift through the Holocene, plate collision has caused significantly higher uplift rates in the region directly along the plate boundary.     

基于企业边界理论的图书馆边界分析

借鉴经济学中的企业边界和边界扩展理论,结合图书馆的特点和发展规律,探讨了图书馆的核心能力和要素、效率,总结图书馆边界扩展的优势维度,并以面向科研嵌入式学科服务和学术社交网络Ami ner为例进行剖析,探讨了图书馆边界扩展限制,可作为图书馆新业务开展或边界扩展时的参考。     

带弯头弯管段不停输沉降的设计与施工

将弯头弯管段视为一个整体,应用CAESARⅡ软件对弯头弯管段的沉降进行了应力分析和计算,该软件不仅可以满足应力分析的要求,而且还可以给出相应的位移数据,有利于设计和施工过程中采取相应的安全措施,保证带弯头弯管段不停输沉降施工的安全性.介绍了带弯头弯管段不停输沉降的施工步骤和注意事项,指出在施工过程中,应根据现场施工的实际情况,合理调整施工进度和采取必要的技术措施.     

辽河中下游泥沙沉积特性分析

为了确定辽河中下游泥沙主要沉积区及对其起控制作用的水沙来源区,以有关水文站年系列资料为基础.运用泥沙收支平衡法、统计学方法,研究辽河中下游泥沙时空分布及主要沉积区沉积量与上游不同水沙来源区水沙量相关关系.结果表明:巨流河一六间房河段为辽河中下游强烈沉积区,支流柳河产沙量的变化对辽河下游泥沙沉积量的变化起着主要的控制作用,为缓解辽河下游泥沙沉积问题,亟待加强柳河水土流失的治理.     

小麦种质资源沉淀值的研究

本研究测定了中国15个地区的11286份不同类型的普通小麦种质材料的沉淀值(小麦面筋强度和食品加工品质的一种重要标志)。发现来自不同地区小麦样本的沉淀位有自南向北和自平原到高原逐渐增高的趋势。就不同类型材料而言,我国农家品种,育成品种和国外引进品种的平均测定值无明显差异,但其变异系数依次增大,说明国外品种作为优质源有较大的潜力。     

絮凝沉降法采收小球藻的研究

考察了明矾、硫酸铝、聚合氯化铝、三氯化铁、硫酸亚铁、壳聚糖6种常用絮凝剂对小球藻(Chlorella vulgaris)细胞采收的效果,并研究了p H对絮凝采收效果的影响。结果表明,三氯化铁和明矾的絮凝效果较好,当絮凝剂浓度分别为0.6、1.6 g/L时,小球藻细胞采收率分别达到98.3%和98.2%。p H对小球藻细胞最大采收率的影响差异显著,以三氯化铁和明矾为絮凝剂时,p H分别为10和8时为最佳,此时细胞采收率最大。     

辽宁省汤河水库淤积分析研究

我国江河大多泥沙量大,造成水库淤积严重,由此带来了一系列问题:库容损失影响水库效益的发挥;坝前泥沙淤积影响枢纽的安全运行等。结合辽宁省汤河水库淤积测量项目,对水库淤积现状进行分析,探讨水库水位与淤积量之间的关系,确定在88.00～89.00m、91.00～95.00m、104.00～110.00m3个片断的淤积量特别突出。并结合水库的日常运行及相关工程措施,对水库淤积进行系统分析,指出目前水库淤积存在的问题并提出相关建议。     

小麦高分子量谷蛋白亚基积累量与沉降值的关系

应用 SDS-PAGE技术对 6种亚基组合类型的 42份品种 (系 ) HMW-GS组成及含量与沉降值的关系进行了分析。结果表明 ,HMW-GS百分含量以及占总蛋白的比例均与沉降值呈正相关 ,且在 7 8、2 1 2 ,1、7 8、2 1 2 ,1、7 8、5 1 0和 1、7 9、5 1 0组合中达到了显著水平 ;单个亚基含量对沉降值有一定的正向作用 ,且同一亚基在不同带型中对沉降值的作用不完全一致 ;从 Glu-1各位点亚基含量与沉降值的相关强度和相关性质来看 ,Glu-D1位点含量的增高有利于籽粒品质的改善