The effects of washing a collagen sample prior to TEM examination

Transmission electron microscopy (TEM) is an important analysis technique to visualize (bio)macromolecules and their assemblies, including collagen fibers. Many protocols for TEM sample preparation of collagen involve one or more washing steps to remove excess salts from the dispersion that could hamper analysis when dried on a TEM grid. Such protocols are not standardized and washing times as well as washing solvents vary from procedure to procedure, with each research group typically having their own protocol. Here, we investigate the influence of washing with water, ethanol, but also methanol and 2-propanol, for both mineralized and unmineralized collagen samples via a protocol based on centrifugation. Washing with water maintains the hydrated collagen structure and the characteristic banding pattern can be clearly observed. Conversely, washing with ethanol results in dehydration of the fibrils, often leading to aggregation of the fibers and a less obvious banding pattern, already within 1 min of ethanol exposure. As we show, this process is fully reversible. Similar observations were made for methanol and propanol. Based on these results, a standardized washing protocol for collagenous samples is proposed.     

STRONG METAL-CERAMIC JOINTS

In this paper the technology for joining metals to ceramics is reviewed. The technologies of metal powder sintering, liquid phase joining with activated brazing alloys and with ceramic frit, solid-state joining, friction welding and mechanical fixation are described. In order to put some perspective on the mechanical data given in the literature, some evaluating remarks on mechanical testing are made.     

A model material approach to the study of fracture process zone of quasi-brittle materials

A new approach to study the fracture of quasi-brittle materials is introduced: the design and testing of model materials. By model material is understood a material with enlarged microstructure and which material parameters, such as stacking and mechanical properties of particles and cohesion force, can be fully controlled. In this paper a first example to the model materials approach is presented, consisting in 5 mm steel particles bonded in a precise stacking with an epoxy-based glue. It is shown how it is possible to correlate the different fracture mechanisms and ultimate peak load of the model material to the particle pair force and to the fracture process zone size. It is also seen how a quasi-brittle behaviour is produced in the presence of mechanisms that induced the crack to shift fracture planes, that is, in presence of energy dissipative mechanisms.     

Cr、Ni/γ-Al_2O_3-SiO_2催化聚合α-烯烃制润滑油基础油

研究了新型α-烯烃聚合制润滑油基础油的催化剂。在最佳实验条件下考察了活性组分负载量、磷酸含量、水蒸气处理时间及H_2还原时间的不同对催化性能的影响。结果表明,当活性组分Ni、Cr质量比为4时,产品运动粘度(20℃)最大,向载体中添加酸性组分,增强了其对Cr、Ni/r-Al_2O_3-SiO_2催化剂的调变作用,当酸体积分数为7％时催化剂活性最高。水蒸气处理时间不同时催化剂活性影响不同,但与未处理的催化剂性能相比较,活性有了显著提高,当水蒸气处理时间为40h时,产品的运动粘度达到最大。氢气还原处理可将催化剂中负载的金属还原为较低价态,增强了催化剂的活性,同时该催化剂再生性能较好,再生后催化剂的稳定性及寿命均优于新鲜催化剂。     

Hydrogenation of p‐Nitrophenol to p‐Aminophenol as a Test Reaction for the Catalytic Activity of Supported Pt Catalysts

Hydrogenation of p‐nitrophenol (PNP) to p‐aminophenol (PAP) using NaBH₄ as a reducing agent was studied as a test reaction for determining the catalytic activity of supported Pt catalysts. The initial reaction rate, which is accessible within less than 10 min via online UV‐vis spectroscopy at room temperature, ambient pressure, and in water as solvent, was applied as measure for catalytic activity. For three Pt catalysts supported on porous SiO₂, porous glass, and Al₂O₃, respectively, significant differences in the catalytic activity by almost one order of magnitude were observed. However, especially in the case of very active catalysts, limitations of the reaction by internal or external mass transfer have to be considered.     

Wetting forces and meniscus pinning at geometrical edges

It is shown that complications in currently used optical measurements for wetting and flow resistance over edges can be circumvented by surface tension force measurements. These forces are measured by employing a modified Wilhelmy plate testing technique in which a plate with rectangular holes is immersed. The forces measured during immersion and emersion are subdivided into mass, buoyancy, and surface tension related parts, where the flow resistance when the meniscus passes horizontal faces and edges of the plate receives particular attention. Combining this experimental method with wetting theory, we show that we can predict and measure the full force curve for meniscus shape transitions over edge geometries under quasi‐static conditions. Moreover, wetting effects directly linked to surface defects can be detected qualitatively. We also point to the speed‐dependent rupture of metastable films formed during emersion. The measurement method designed is most relevant in cases where optical methods cannot be used. © 2016 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 62: 4453–4465, 2016     

Extreme wet adhesion of a novel epoxy-amine coating on aluminum alloy 2024-T3

Amine-epoxy polymer systems are widely used, for example as matrix materials for structural composites employed in aerospace industry and in industrial coatings on metal substrates for corrosion protection. This work focuses on the investigation of different epoxy-amine coatings on the adhesion performance on aluminum AA-2024 substrates. Two different epoxies (Epikote 828 (aromatic) and Eponex 1510 (aliphatic)) and four different amines (1,8-diaminooctane, Dytek A, Jeffamine EDR148 and Jeffamine D230) as curing agent were used in different stoichiometric ratios. These different epoxy-amine coatings were characterized using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile tests (pull-off) and water-uptake measurements. Pull-off tests in dry conditions showed comparable adhesion of the coatings. Surprisingly, pull-off results showed after water soaking a higher wet adhesion of the coatings prepared with Eponex 1510 as compared to coatings prepared with Epikote 828. Moreover, the combination of Eponex 1510-Jeffamine EDR148 coatings resulted in high adhesion values (∼7 MPa) with pull-off tests and these values did not change after immersion for two weeks in water. This combination shows extreme good wet adhesion performance as compared to any other epoxy-amine coating. Complete recovery was demonstrated of the adhesion of Eponex 1510-Jeffamine D230 coating after being immersed for two weeks in water and dried for two weeks. Furthermore, in contrast with Epikote 828 water uptake measurements showed almost nil water uptake for all coatings prepared with Eponex 1510. Optical microscopy investigations on the residues of the coatings after pull-off tests revealed adhesive failure in wet condition for Epikote 828, while coatings prepared with Eponex 1510 showed cohesive failure.     

延续奔腾的力量——揭密Intel下一代处理器

处理器工作频率越高越好?虽然现在要回答这个问题看似很简单,但是在不久的过去,很多人都会不假思索地说出肯定的答案——这现象产生的原因很大程度在于厂商宣传。Pentium 4与Athlon XP的较量中,同频率条件下根本不是Athlon XP的对手。虽然 Intel可能已经认识到了NetBurst构架效率低下的缺点,但依然没有抛弃NetBurst架构而是继续坚持自己“频率至上”的理念,于是Prescott诞生了。由于 Intel将流水线(Pipelining)由先前的20级猛然提升到 31级,使得产品的频率提升更为容易。虽然Prescott 核心在其上一代核心的基础上进行了多项改进,比如增大了二级缓存的等,但是在同等频率下却不是前辈的对手。由于流水线的增长,处理指令的操作步骤也会随之增多,消耗的电能也会提升,加上处理器工作频率的提升,这样就导致处理器容易出现功耗过高的情况——Pentium 4 4．0GHz也就成了“无法完成的任务”。为了缓解Prescott核心Pentium 4进一步带来的效率低下问题、增强自身产品的竞争力,Intel于去年初引入双核心处理器Pentium D。根据Intel微处理器研究实验室高层的说法:如果继续开发单核心架构的 Tejas,其芯片面积会比Prescott增加90％,而多任务性能则提升40％左右;但如果开发多核心架构的 Smithfield,其芯片面积同样增加90％,但是多任务性能就能比Prescott提升接近一倍,单任务也能提高几个百分点。正是这样的原因促使Intel最终选择了双核心作为Prescott核心后一阶段的发展方向。在Intel没有正式发布双核心架构之前,人们一直认为将两块Dothan核心集成起来是Intel当时制造双核心处理器的最好选择,因为该核心具备了高性能与低功耗两大优势。但是当Intel在IDF Spring 2005上正式发布Pentium D的时候让人大失所望,它采用的是将两颗Prescott集成的方式生产Pentium D。根据著名硬件网站Anand对其进行的功耗测试来看,当进行满负荷运行时,Pentium D 2．8GHz的功耗高达 244W,而其对手Athlon 64 3500+(2．2GHz)只有 143W,足足多出了101W!按照这样的趋势发展下去,对于Intel产品来说将是致命的。还好,这种趋势并没有变成现实。在半年后的 IDF Fall 2005上,Intel郑重宣布——将桌面平台、移动平台和服务器平台所使用的处理器在架构上进行统一,推出新的处理器架构!     

The effect of Bi2O3 on the electrical and mechanical properties of ZrO2-Y2O3 ceramics

ZrO₂-Y₂O₃ ceramics with varying Bi₂O₃ content have been prepared and their microstructure, electrical conductivity and mechanical properties investigated. The sintering rate is strongly increased at low temperatures (1270 to 1420 K) due to the occurrence of a reactive phase the amount of which decreases during the sintering process. The main fluorite phase has an approximately constant composition at 0.85 ZrO₂-0.13 Y₂O₃-0.02 Bi₂O₃ while the amount of second phase depends on overall composition and sintering procedure. The electrical conductivity is also approximately constant but about a factor of five lower than in ZrO₂-Y₂O₃ ceramics. Typical strength and fracture toughness values are 160 MPa and 1.8 MPa m^1/2, respectively. However, the non-reproducibility of the second phase content and morphology seriously influences both mechanical properties.