两种磁性纳米颗粒(Fe_3O_4、Fe_3O_4@柠檬酸)的制备及其在DNA提取分离中的应用

采用溶剂热法制备表面修饰柠檬酸的磁性Fe_3O_4纳米粒子和磁性Fe_3O_4纳米粒子,并对其粒径大小、晶体结构和磁性能进行表征,并考察其用于DNA提取分离的效果。结果表明,两产物均为立方晶系的Fe_3O_4纳米颗粒。磁性Fe_3O_4纳米粒子和表面修饰柠檬酸的磁性Fe_3O_4纳米粒子的平均粒径为411.1nm和586.3nm。当全血体积200μL、磁性纳米粒子用量2.0mg时,提取的DNA浓度最高分别为270.6ng/μL(Fe_3O_4)和466.4ng/μL(Fe_3O_4@柠檬酸)。     

纳米生物活性玻璃颗粒的制备及形态控制

采用溶胶-凝胶技术制备纳米生物活性玻璃颗粒, 通过在溶胶中加入柠檬酸来控制生物活性玻璃的形态结构。利用比表面积分析仪、 透射电子显微镜和扫描电子显微镜对纳米生物活性玻璃的结构和形成机制进行了表征。研究结果表明:采用柠檬酸作为水解催化剂可以方便地控制生物活性玻璃的纳米结构形态, 有利于制备较小粒径、 大比表面积和孔体积的生物活性玻璃。这种制备技术提供了一种简单、 低成本制备纳米生物活性玻璃并控制其纳米粒子形态的方法。      

快速热解法制备炭包覆纳米金属磁性颗粒(英文)

以简单金属前躯体为原料通过快速热解法制备炭包覆纳米金属磁性颗粒,通过透射电镜、X-射线衍射、热重-示差扫描同步热分析及振动样品磁强计等对产物形貌、结构、成分与磁性能进行表征。结果表明:采用该方法制备的炭包覆纳米金属磁性颗粒形状为近球形颗粒,粒径均一,其中炭包覆镍纳米磁性颗粒的粒径集中在10nm～30nm范围,炭包覆铁纳米磁性颗粒粒径则在50nm～60nm范围;所制炭包覆纳米金属磁性颗粒在室温下具有顺磁性,其磁性能随金属颗粒含量的变化而改变。该方法有望发展成一种工艺简单,可进行连续工业化生产炭包覆纳米金属磁性颗粒的方法。     

乳液聚合法制备P(NIPAM-co-St)温敏纳米粒子的性能与应用

采用乳液聚合法制备P(NIPAM-co-St)温敏纳米粒子。利用红外光谱对纳米粒子成分进行表征,用动态光散射对纳米粒子粒径和最低临界溶解温度(LCST)进行研究,并用扫描电子显微镜对P(NIPAM-co-St)纳米粒子的形貌进行观察。研究反应过程中苯乙烯(St)加入量、交联剂和乳化剂加入量对P(NIPAM-co-St)纳米粒子的LCST、粒径大小、溶胀性能的影响。结果表明,随着St含量和交联剂用量增加,LCST、粒径呈减小趋势,溶胀性能越来越差;随着乳化剂用量增加,LCST和溶胀性能几乎不变,粒径在添加0～3%的乳化剂用量情况下急剧减小,在乳化剂用量超过3%后,粒径无明显变化。     

合成工艺对水相合成金纳米颗粒的影响

分别采用柠檬酸三钠和硼氢化钠为还原剂在水相中还原氯金酸制备了稳定的金纳米溶胶。通过透射电子显微镜、激光粒度分析仪、紫外-可见分光光度计对所制备的金纳米颗粒的形貌、结构、粒度分布以及光学特性进行表征,研究了还原剂用量、加热反应时间、反应温度、pH值对水相制备金纳米颗粒的影响。结果表明通过调节合成工艺,可以实现金纳米颗粒的可控生长,制备出平均粒径在5～70nm粒度分布均匀的球形金纳米颗粒。     

Fe_3O_4/Au复合磁性纳米颗粒的制备及其表征

首先通过化学共沉淀法制备出Fe3O4磁性纳米颗粒,考察了表面活性剂的用量、碱的用量、陈化时间以及三价铁与二价铁的摩尔比等因素对Fe3O4纳米颗粒性能的影响。制备出饱和磁化强度为73.85A.m2/kg、粒径大小为10nm以下的Fe3O4纳米颗粒。在此基础上,制备出Fe3O4/Au复合纳米颗粒,通过VSM、TEM、XRD、XPS对产物进行了表征,研究了HAuCl4的用量、还原剂的种类、硅烷偶联剂以及包金之前的Fe3O4纳米颗粒对复合颗粒的影响,结果表明所制得的Fe3O4/Au复合磁性纳米颗粒包覆良好,粒径大小为50～200nm,饱和磁化强度为10.08A.m2/kg。     

纳米Fe颗粒的化学还原制备及结构与磁性表征

室温下通过NaBH4还原FeCl2溶液,在实验过程中加入聚丙烯酸(PAA)作为表面活性剂,制备了粒径大小为3～5nm的Fe纳米颗粒,并在不同温度下对得到的颗粒进行退火。对比了在不同温度下退火对样品的结构及磁性能的影响。结果表明,通过化学还原法制备的Fe纳米颗粒为非晶态,其磁性表现为超顺磁和铁磁的混磁态,随着退火温度的增加Fe纳米颗粒的晶化程度越来越高,其饱和磁化强度和矫顽力逐渐增大,磁性由混磁态逐渐向铁磁态转变。     

PCL/Fe_3O_4磁性复合纳米纤维的结构与性能

将纳米Fe_3O_4磁性颗粒加入到N,N-二甲基甲酰胺(DMF)和氯仿溶解聚己内酯(PCL)的聚合物溶液中,通过静电纺丝制备PCL/Fe_3O_4磁性复合纳米纤维。利用扫描电子显微镜、X射线衍射仪、红外光谱仪、差示扫描量热分析及磁性演示对复合纤维的形貌尺寸、化学结构、热稳定性和磁性进行了表征。结果表明:所制得的磁性纳米纤维成型良好,且Fe_3O_4磁性颗粒分散在纳米纤维中,其与PCL是物理复合,复合纳米纤维具有一定的磁性,为PCL磁性复合纳米纤维的实际应用做了有益的探索研究。     

烧结温度和升温速率对铁氧体粉体粒径的影响

采用柠檬酸盐溶胶-凝胶法制备尖晶石型铁氧体粉体,通过扫描电子显微镜和粒度分析仪表征产物的粒径大小,研究烧结温度和升温速率对铁氧体粒径的影响。结果表明:多步升温的方式更有利于形成粒径小且均匀的铁氧体粉体,得到的产物粒径约为300 nm;随着烧结温度的升高,铁氧体颗粒的粒径呈先减小后增大的趋势,850℃为最佳烧结温度,适用于制备颗粒均匀、粒径小的尖晶石型铁氧体粉体。     

Fe3O4 包覆聚苯乙烯磁性微球的制备及性能

为研究一种应用于磁稳定流化床反应器的新型高分子磁性微球的制备方法及性能,采用悬浮聚合法制备了Fe_3O_4纳米粒子包覆聚苯乙烯磁性微球,研究了搅拌速率、加入磁性Fe_3O_4纳米粒子的时间等因素对复合微球粒径及性能的影响,运用扫描电子显微镜(SEM)、X射线衍射(XRD)、振动样品磁强计(VSM)、热重(TGA)等测试手段,表征了磁性聚苯乙烯微球的形貌特征、结构、粒径、磁学性能及Fe_3O_4的包覆量.实验结果表明:在搅拌转速为600 r/min,80℃保温10 min加入修饰Fe_3O_4纳米粒子,制备所得的磁性聚苯乙烯微球为粒径分布均匀的球状微粒;Fe_3O_4的包覆量达到5%,最高饱和磁化强度为3.73 emu/g,具有较好的超顺磁性,可应用于磁稳定流化床反应器.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...