Preparation and characterization of novel nanometer-scale platinum electrodes

Observation of the oxidation–reduction processes occurring at the nanoelectrode–solution interface demonstrates how electrochemical behavior depends upon nanoelectrode size. The use of a modified form of pulsed laser ablation as an improved method to synthesize nanometer-scaled electrode materials easily and consistently is reported. This method of fabrication enables platinum metal nanoparticles averaging 3 nm in diameter and approximately 5.0 × 10¹¹ particles/cm² to be deposited onto silicon substrates using optimum ablation parameters. A platinum silicide phase exists at the interface of the platinum and silicon as a result of the ablation process. Electrochemical results demonstrate the presence of a large number of isolated platinum particles (1.1 × 10⁷ particles/cm²), separated by an average edge to edge distance of 14 nm, which are electrochemically active nanoelectrodes.     

Using 15N‐Ammonium to Characterise and Map Potassium Binding Sites in Proteins by NMR Spectroscopy

A variety of enzymes are activated by the binding of potassium ions. The potassium binding sites of these enzymes are very specific, but ammonium ions can often replace potassium ions in vitro because of their similar ionic radii. In these cases, ammonium can be used as a proxy for potassium to characterise potassium binding sites in enzymes: the ¹H,¹⁵N spin‐pair of enzyme‐bound ¹⁵NH₄⁺ can be probed by ¹⁵N‐edited heteronuclear NMR experiments. Here, we demonstrate the use of NMR spectroscopy to characterise binding of ammonium ions to two different enzymes: human histone deacetylase 8 (HDAC8), which is activated allosterically by potassium, and the bacterial Hsp70 homologue DnaK, for which potassium is an integral part of the active site. Ammonium activates both enzymes in a similar way to potassium, thus supporting this non‐invasive approach. Furthermore, we present an approach to map the observed binding site onto the structure of HDAC8. Our method for mapping the binding site is general and does not require chemical shift assignment of the enzyme resonances.     

Extensive N‐methylation of chitosan: evaluating the effects of the reaction conditions by using response surface methodology

The effects of reaction time, concentration of aqueous sodium hydroxide and molar ratio iodomethane/chitosan on the yield of the reaction of chitosan with iodomethane in N‐methyl‐2‐pyrrolidone (NMP) at 25.0 ± 0.1 °C, as well as on the characteristics of the resulting N,N,N‐trimethylchitosan (TMCh), were evaluated by using full‐factorial 2³ design analysis and response surface methodology. This study also aimed to determine the reaction conditions allowing the production of water‐soluble TMCh presenting a high average degree of quaternization and intrinsic viscosity at high reaction yield. ¹H NMR spectroscopy was employed for structural characterization, including the determination of average degrees of acetylation () and quaternization (), while capillary viscometry was used to determine intrinsic viscosity [η]. The results show that when the extensive N‐methylation is carried out for 24 h in NMP/15% NaOH (w/v) employing a lower excess of iodomethane (CH₃I/Ch = 9), water‐soluble highly substituted ( = 46.0%) TMCh ([η] = 213.0 mL g^?1) can be produced in high yield (81.8%). The highly significant mathematical models resulting from this study describe the dependence of the experimental responses on the reaction conditions and allow the characteristics and properties of the resulting TMCh to be defined by properly choosing the reaction conditions. © 2015 Society of Chemical Industry     

2种防腐工艺技术在长庆油田的应用

简述了传统环氧酚醛清漆浸涂技术和高速旋转喷涂技术的工艺原理,工艺流程、以及2种技术处理的油管在中国石油长庆油田公司的应用现状。结合实验室评价结果和具体案例,综合对比了2种工艺的使用效果,为评价2种工艺的差别提供了必要的支持,对长庆油田今后选择和确定防腐油管类型也有一定的指导意义。     

短程反硝化耦合厌氧氨氧化工艺及其应用前景研究进展

短程反硝化以其碳源消耗量、废污泥产量、温室气体排量极低及无需曝气等优势,被认为是最具研究潜势的厌氧氨氧化底物供给技术,成为近年来研究热点。本文首先介绍了短程反硝化工艺原理;其次从污泥源、反应时间、碳源类型、碳源量及pH等5个方面总结了影响短程反硝化工艺启动因素;随后综述了短程反硝化耦合厌氧氨氧化工艺的重要研究进展,同时指出了耦合工艺实验研究与工程应用的不足,并提出了解决实验与工程应用缺陷的方案;最后展望了耦合工艺处理城市污水和工业硝酸盐废水的可行性及应用前景,认为全面分析工业硝酸盐废水化学组分与基于分子生物学水平的宏基因组学测序、元转录组学技术是未来耦合工艺同步处理城市污水和工业硝酸盐废水的研究重点。     

无规共聚聚丙烯的结构与性能研究

通过核磁共振(13CNMR),红外光谱(IR)和差示扫描量热法(DSC)等表征分析手段对无规共聚聚丙烯(PPR)的物理结构与机械性能进行研究。结果表明:PPR具有典型的无规共聚物的结构,乙烯基团较均匀的无规分散于丙烯分子长链中;在分子序列结构中,EE和EEE联排的结构并不多;乙烯含量低的EP接点的含量偏低,相应的抗冲击强度偏低,乙烯含量高的EP接点的含量偏高,相应的抗冲击强度较高。乙烯在丙烯分子长链中的无规插入也适当的降低了共聚物的熔点。     

Accumulation of magnetic iron oxide nanoparticles coated with variably sized polyethylene glycol in murine tumors

Iron oxide nanoparticles have found widespread applications in different areas including cell separation, drug delivery and as contrast agents. Due to water insolubility and stability issues, nanoparticles utilized for biological applications require coatings such as the commonly employed polyethylene glycol (PEG). Despite its frequent use, the influence of PEG coatings on the physicochemical and biological properties of iron nanoparticles has hitherto not been studied in detail. To address this, we studied the effect of 333-20,000 Da PEG coatings that resulted in larger hydrodynamic size, lower surface charge, longer circulation half-life, and lower uptake in macrophage cells when the particles were coated with high molecular weight (M(w)) PEG molecules. By use of magnetic resonance imaging, we show coating-dependent in vivo uptake in murine tumors with an optimal coating M(w) of 10,000 Da.     

Alternating Cationic-Hydrophobic Peptide/Peptoid Hybrids: Influence of Hydrophobicity on Antibacterial Activity and Cell Selectivity

The influence of hydrophobicity on antibacterial activity versus the effect on the viability of mammalian cells for peptide/peptoid hybrids was examined for oligomers based on the cationic Lys-like peptoid residue combined with each of 28 hydrophobic amino acids in an alternating sequence. Their relative hydrophobicity was correlated to activity against both Gram-negative and Gram-positive species, human red blood cells, and HepG2 cells. This identified hydrophobic side chains that confer potent antibacterial activity (e. g., MICs of 2–8 μg/mL against E. coli) and low toxicity toward mammalian cells (<10 % hemolysis at 400 μg/mL and IC₅₀>800 μg/mL for HepG2 viability). Most peptidomimetics retained activity against drug-resistant strains. These findings corroborate the hypothesis that for related peptidomimetics two hydrophobicity thresholds may be identified: i) it should exceed a certain level in order to confer antibacterial activity, and ii) there is an upper limit, beyond which cell selectivity is lost. It is envisioned that once identified for a given subclass of peptide-like antibacterials such thresholds can guide further optimisation.     

Indentation cracking and deformation mechanism of sodium aluminoborosilicate glasses

Developing less brittle oxide glasses is a grand challenge in the field of glass science and technology, as it would pave the way toward new glass applications and limit the overall raw material usage and energy consumption. However, in order to achieve this goal, more insight into the correlation between the chemical composition and material properties is required. In this work, we focus on the mechanical properties of quaternary sodium aluminoborosilicate glasses, wherein systematic changes in glass chemistry yield different resistances to indentation crack initiation. We discuss the origin of the composition dependence of indentation cracking based on an evaluation of the deformation mechanism taking place during the indentation event. To this end, we use a simple metric, the extent of indent side length recovery upon annealing, to quantify the extent of reversible volume deformation. Finally, we also compare the compositional trend in crack initiation resistance to that in crack growth resistance (fracture toughness), showing no simple correlation among the two.