Basicity of the amino groups of the aminoglycoside amikacin using capillary electrophoresis and coupled CE-MS-MS techniques

This paper describes the use of capillary electrophoresis (CE), and coupled CE and mass spectrometric techniques, to measure the values of the pKa of the amino groups of the aminoglycoside antibiotic amikacin and of its acetylated derivatives. These values of pKa (8.4, 6.7, 9.7, 8.4) were determined by measuring the electrophoretic mobilities of the molecules as a function of pH; they are within 0.7 unit of certain values reported in the literature (by 13C and 15N NMR spectroscopies) but resolved ambiguities left by these earlier studies. The range of values of pKa of amino groups also indicates the complex dependence of the acidity of a functional group (and thus the extent of ionization at a specified value of pH) on the molecular environment of that group.     

德士古水煤浆气化中氨生成量的探讨

通过分析某德士古水煤浆气化合成氨厂的实测数据,提出了德士古水煤浆气化中氨生成量和原料煤中氮含量的关系。     

Hydroxyapatite-reinforced polymer biocomposites for synthetic bone substitutes

Hydroxyapatite (HA)-reinforced polymer biocomposites offer a robust system to engineer synthetic bone substitutes with tailored mechanical, biological, and surgical functions. The basic design rationale has been to reinforce a tough, biocompatible polymer matrix with a bioactive HA filler. A large number of studies have investigated modifications to the biocomposite structure and composition, aimed at improving the mechanical properties, often through modified or novel processing methods. In this article, the effects of the polymer composition and molecular orientation; the HA/polymer interface; and the HA-reinforcement content, morphology, preferred orientation, and size are reviewed with respect to mechanical properties, drawing frequent comparisons between various HA-reinforced polymer composites and bone tissue.     

Additive Manufacturing of Metallic Materials: A Review

In this review article, the latest developments of the four most common additive manufacturing methods for metallic materials are reviewed, including powder bed fusion, direct energy deposition, binder jetting, and sheet lamination. In addition to the process principles, the microstructures and mechanical properties of AM-fabricated parts are comprehensively compared and evaluated. Finally, several future research directions are suggested.     

Sulfur and Nitrogen Co‐Doped Graphene for Metal‐Free Catalytic Oxidation Reactions

Sulfur and nitrogen co‐doped reduced graphene oxide (rGO) is synthesized by a facile method and demonstrated remarkably enhanced activities in metal‐free activation of peroxymonosulfate (PMS) for catalytic oxidation of phenol. Based on first‐order kinetic model, S–N co‐doped rGO (SNG) presents an apparent reaction rate constant of 0.043 ± 0.002 min^?1, which is 86.6, 22.8, 19.7, and 4.5‐fold as high as that over graphene oxide (GO), rGO, S‐doped rGO (S‐rGO), and N‐doped rGO (N‐rGO), respectively. A variety of characterization techniques and density functional theory calculations are employed to investigate the synergistic effect of sulfur and nitrogen co‐doping. Co‐doping of rGO at an optimal sulfur loading can effectively break the inertness of carbon systems, activate the sp²‐hybridized carbon lattice and facilitate the electron transfer from covalent graphene sheets for PMS activation. Moreover, both electron paramagnetic resonance (EPR) spectroscopy and classical quenching tests are employed to investigate the generation and evolution of reactive radicals on the SNG sample for phenol catalytic oxidation. This study presents a novel metal‐free catalyst for green remediation of organic pollutants in water.     

Frictional performance of silica microspheres

We present a fundamental study of the frictional performance of silica microspheres, either 4, 2, or 0.5 μm in diameter, on a silicon substrate. The tribological properties of these rolling systems were measured with a ball-on-flat tribometer at various loads. The frictional performance of the rolling systems is found to be highly dependent on load and sphere diameter. Rolling motion was confirmed by imaging the surface of microsphere systems that have been coated with a thin layer of gold. In addition, the surface energy of the lubrication scheme was altered using coatings containing octadecyltrichlorosilane or (tridecafluoro-1,1,2,2-tetrahydrooctyl)-1-trichlorosilane precursors.     

Microstructural characterization and pore structure analysis of nuclear graphite

Graphite will be used as a structural and moderator material in next-generation nuclear reactors. While the overall nature of the production of nuclear graphite is well understood, the historic nuclear grades of graphite are no longer available. This paper reports the virgin microstructural characteristics of filler particles and macro-scale porosity in virgin nuclear graphite grades of interest to the Next Generation Nuclear Plant program. Optical microscopy was used to characterize filler particle size and shape as well as the arrangement of shrinkage cracks. Computer aided image analysis was applied to optical images to quantitatively determine the variation of pore structure, area, eccentricity, and orientation within and between grades. The overall porosity ranged between ∼14% and 21%. A few large pores constitute the majority of the overall porosity. The distribution of pore area in all grades was roughly logarithmic in nature. The average pore was best fit by an ellipse with aspect ratio of ∼2. An estimated 0.6-0.9% of observed porosity was attributed to shrinkage cracks in the filler particles. Finally, a preferred orientation of the porosity was observed in all grades.     

Antifouling coatings: recent developments in the design of surfaces that prevent fouling by proteins, bacteria, and marine organisms

The major strategies for designing surfaces that prevent fouling due to proteins, bacteria, and marine organisms are reviewed. Biofouling is of great concern in numerous applications ranging from biosensors to biomedical implants and devices, and from food packaging to industrial and marine equipment. The two major approaches to combat surface fouling are based on either preventing biofoulants from attaching or degrading them. One of the key strategies for imparting adhesion resistance involves the functionalization of surfaces with poly(ethylene glycol) (PEG) or oligo(ethylene glycol). Several alternatives to PEG-based coatings have also been designed over the past decade. While protein-resistant coatings may also resist bacterial attachment and subsequent biofilm formation, in order to overcome the fouling-mediated risk of bacterial infection it is highly desirable to design coatings that are bactericidal. Traditional techniques involve the design of coatings that release biocidal agents, including antibiotics, quaternary ammonium salts (QAS), and silver, into the surrounding aqueous environment. However, the emergence of antibiotic- and silver-resistant pathogenic strains has necessitated the development of alternative strategies. Therefore, other techniques based on the use of polycations, enzymes, nanomaterials, and photoactive agents are being investigated. With regard to marine antifouling coatings, restrictions on the use of biocide-releasing coatings have made the generation of nontoxic antifouling surfaces more important. While considerable progress has been made in the design of antifouling coatings, ongoing research in this area should result in the development of even better antifouling materials in the future.     

Micromolding Surface‐Initiated Polymerization: A Versatile Route for Fabrication of Coatings with Microscale Surface Features of Tunable Height

This article introduces a process termed micromolding surface‐initiated polymerization (μMSIP) as a versatile route to provide surface‐bound, partially fluorinated polymer coatings with a homogeneous array of microscale surface features. The process employs hard‐polydimethylsiloxane (h‐PDMS) to mold the surface structure of master substrates exhibiting patterned microscale features. Upon filling the mold with the monomer 5‐(perfluorooctyl)norbornene (NBF8) and placing against a surface that is pre‐activated for surface‐initiated ring‐opening metathesis polymerization (SI‐ROMP), a partially fluorinated polymer film propagates from the surface with features that grow into the recesses of the mold to produce the final microtextured coating. The heights of these features can be tuned from 20–100% of the full height of the mold features based on the amount of initiator employed as well as the polymerization time and temperature. Reproduced topographies include pyramidal and inverted pyramidal structures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images show that the final polymer film exhibits a homogeneously microstructured surface that resembles that of its corresponding master.     

Integrins Increase Sarcoplasmic Reticulum Activity for Excitation—Contraction Coupling in Human Stem Cell-Derived Cardiomyocytes

Engagement of the sarcoplasmic reticulum (SR) Ca²⁺ stores for excitation–contraction (EC)-coupling is a fundamental feature of cardiac muscle cells. Extracellular matrix (ECM) proteins that form the extracellular scaffolding supporting cardiac contractile activity are thought to play an integral role in the modulation of EC-coupling. At baseline, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) show poor utilisation of SR Ca²⁺ stores, leading to inefficient EC-coupling, like developing or human CMs in cardiac diseases such as heart failure. We hypothesised that integrin ligand–receptor interactions between ECM proteins and CMs recruit the SR to Ca²⁺ cycling during EC-coupling. hiPSC-CM monolayers were cultured on fibronectin-coated glass before 24 h treatment with fibril-forming peptides containing the integrin-binding tripeptide sequence arginine–glycine–aspartic acid (2 mM). Micropipette application of 40 mM caffeine in standard or Na⁺/Ca²⁺-free Tyrode’s solutions was used to assess the Ca²⁺ removal mechanisms. Microelectrode recordings were conducted to analyse action potentials in current-clamp. Confocal images of labelled hiPSC-CMs were analysed to investigate hiPSC-CM morphology and ultrastructural arrangements in Ca²⁺ release units. This study demonstrates that peptides containing the integrin-binding sequence arginine–glycine–aspartic acid (1) abbreviate hiPSC-CM Ca²⁺ transient and action potential duration, (2) increase co-localisation between L-type Ca²⁺ channels and ryanodine receptors involved in EC-coupling, and (3) increase the rate of SR-mediated Ca²⁺ cycling. We conclude that integrin-binding peptides induce recruitment of the SR for Ca²⁺ cycling in EC-coupling through functional and structural improvements and demonstrate the importance of the ECM in modulating cardiomyocyte function in physiology.