Discrete pulse orthogonal functions for the analysis,parameter estimation and optimal control of linear time-varying digital systems

The analysis, parameter estimation and optimal control of linear time-varying digital systems are facilitated in this study. The discrete pulse orthogonal functions (DPOFs) and their operational matrices are taken as a sharp tool. The applications of DPOFs to digital control systems are analogous to those of the known block pulse functions (BPFs) in continuous systems. By applying the DPOFs, approximate solutions of digital time-varying systems can easily be obtained by convenient algorithms. Three examples are illustrated to demonstrate the proposed DPOF technique, and the approximate results are very accurate and satisfactory.     

ANTIRADICAL EFFICIENCY OF TEA COMPONENTS

Tea contains antioxidant compounds, such as (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin gallate (EGCG), gallic acid and caffeine. The antioxidant activity of these compounds as well as 1,3,7-trimethyluric acid (the major metabolite of caffeine) was evaluated using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The antiradical ability according to the EC₅₀ was EGCG > ECG > EGC > gallic acid > EC > BHT > 1,3,7-trimethyluric acid > caffeine. The time for these compounds to reach the steady state was considered, and the concept of antioxidant efficiency (AE₅₀) involving the EC₅₀ and the time to reach the steady state was used to evaluate the antiradical efficacy. The order of antiradical efficiency according to AE₅₀ was ECG gallic acid > EGCG > EC > EGC > BHT > 1,3,7-trimethyluric acid > caffeine.     

A SURVEY OF ARYLAMINE N-ACETYLTRANSFERASE ACTIVITY IN COMMON FRUITS AND VEGETABLES

The N-acetyltransferase activity was determined in 58 common fruits and vegetables. The assay was based on acetylation of 2-aminofluorene or p-amino-benzoic acid, followed by high pressure liquid chromatographic analysis of products and remaining nonacetylated substrate. The highest specific activities were observed in Balsam pear which contained 17.37 ± 1.45 N-acetyl aminofluorene nmole/min/mg protein and 46.27 ± 6.87 N-acetyl p-aminobenzoic acid nmole/min/mg protein. N-acetyltransferase activities within the remaining 57 foodstuffs analyzed ranged from none detected to 3.39 ± 0.72 N-acetyl aminofluorene nmole/min/mg protein and none detected to 32.45 ± 6.55 N-acetyl p-aminobenzoic acid nmole/min/mg protein. This is the first demonstration of acetyl CoA: arylamine N-acetyltransferase activity in common foodstuffs.     

Cr-Si粉末冶金工艺及其物理-力学性能

粉末冶金制作法主要有热压(HP)、热等静压(HIP)及常压烧结(Sinter)三种.采用热压及热等静压法可以很容易地得到高致密化的高温金属硅化物,但若要进行大尺寸的产品烧结,必须提升生产设备的规格和能力,例如加大热压机力吨位、扩大热压炉腔体等,致使设备投资及生产成本相对昂贵.所以大部分厂商宁可采用常压烧结法,虽然该法的高致密化工艺条件不易控制,却因可以制作大尺寸金属硅化物,加上设备投资及生产成本相对降低,使许多大厂已投入相当大的人力和物力在开发此工艺.该文作者试用不同真空烧结温度,造成Cr-Si合金粉末烧结性质的差异,探讨稳定而可大量生产的可行性;并通过对温度的控制,来改善Cr-Si的物理性质与力学性质.结果表明,提高烧结温度会使Cr-Si合金产生部分液相烧结的现象,从而使孔隙率显著下降;但显微结构也随之有偏析与晶粒粗化的现象.     

ANTIOXIDANT PROPERTIES OF POLYPHENOLS EXTRACTED FROM GREEN AND BLACK TEAS

The catechins, including epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG), and the theaflavins, including theaflavin (TF), theaflavin monogallate (TF-1), and theaflavin digallate (TF-2), were extracted from green tea and black tea, respectively. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging ability, superoxide-scavenging efficiency, and lipid oxidation-inhibition ability of the pure compounds listed above as well as epicatechin (EC), carnosol, carnosic acid, and butylated hydroxytoluene (BHT) were investigated.
The DPPH radical-scavenging ability of the catechins was EGCG > ECG > EGC > EC and of the theaflavins was TF-2 > TF-1 > TF. EGCG, ECG, EGC, TF-2, TF-1, and TF showed higher DPPH radical- and superoxide-scavenging abilities than carnosol, carnosic acid, and BHT. EGCG, ECG, EGC, carnosol, and carnosic acid showed higher lipid oxidation-inhibition activity, as measured by the Rancimat method, than BHT and theaflavins.     

Reactor technology options for distributed hydrogen generation via ammonia decomposition: A review

Hydrogen (H₂) fuel obtained via thermo-catalytic ammonia (NH₃) decomposition is rapidly attracting considerable interest for portable and distributed power generation systems. Consequently, a variety of reactor technologies are being developed in view of the current lack of infrastructure to generate H₂ for proton exchange membrane (PEM) fuel cells. This paper provides an extensive review of the state-of-the-art reactor technology (also referred to as reactor infrastructure) for pure NH₃ decomposition. The review strategy is to survey the open literature and present reactor technology developments in a chronological order. The primary objective of this paper is to provide a condensed viewpoint and basis for future advances in reactor technology for generating H₂ via NH₃ decomposition. Also, this review highlights the prominent issues and prevailing challenges that are yet to be overcome for possible market entry and subsequent commercialization of various reactor technologies. To our knowledge, this work presents for the first time a review of reactor infrastructure for distributed H₂ generation via NH₃ decomposition. Despite commendable research and development progress, substantial effort is still required if commercialization of NH₃ decomposition reactor infrastructure is to be realized.     

Efficient Enzymatic Cyclization of Disulfide-Rich Peptides by Using Peptide Ligases

Disulfide-rich macrocyclic peptides—cyclotides, for example—represent a promising class of molecules with potential therapeutic use. Despite their potential their efficient synthesis at large scale still represents a major challenge. Here we report new chemoenzymatic strategies using peptide ligase variants—inter alia, omniligase-1—for the efficient and scalable one-pot cyclization and folding of the native cyclotides MCoTI-II, kalata B1 and variants thereof, as well as of the θ-defensin RTD-1. The synthesis of the kB1 variant T20K was successfully demonstrated at multi-gram scale. The existence of several ligation sites for each macrocycle makes this approach highly flexible and facilitates both the larger-scale manufacture and the engineering of bioactive, grafted cyclotide variants, therefore clearly offering a valuable and powerful extension of the existing toolbox of enzymes for peptide head-to-tail cyclization.     

Impact of nanoparticles on the process-induced distortions of carbon fiber reinforced plastics: An experimental and simulative approach

This article investigates the potential of aluminum oxide nanoparticles for the reduction of process-induced distortions of carbon fiber reinforced plastics (CFRP). Therefore the matrix properties, which affect the distortions, are experimentally and mechanistically analyzed in detail at various particle contents. The results clearly show an increasing impact of raised particle content on gelation, chemical and thermal shrinkage, on Young's modulus, as well as on Poisson's ratio. These alterations can be successfully transferred to reduce spring-in of L-shaped CFRP brackets, which are manufactured by infusion technology. However, it is found that particle contents higher than 5 wt % are needed to influence these parameters. For further understanding of the parameters controlling spring-in, a numerical sensitivity analysis is performed by the correlation of various matrix parameters and the induced distortions. The results from a structural simulation reveal that changes in thermal and chemical shrinkage as well as in gelation have a major impact on the distortions, but the modes of action of the particles also have to be taken into consideration. These mechanistical insights about nanoparticle impacts might be a valuable approach to lower or overcome distortions in composite materials in the future. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47031.