"Soft and rigid" dithiols and Au nanoparticles grafting on plasma-treated polyethyleneterephthalate

ABSTRACT: Surface of polyethyleneterephthalate (PET) was modified by plasma discharge and subsequently grafted with dithiols (1, 2-ethanedithiol (ED) or 4, 4'-biphenyldithiol) to create the thiol (-SH) groups on polymer surface. This "short" dithiols are expected to be fixed via one of -SH groups to radicals created by the plasma treatment on the PET surface. "Free" -SH groups are allowed to interact with Au nanoparticles. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and electrokinetic analysis (EA, zeta potential) were used for the characterization of surface chemistry of the modified PET. Surface morphology and roughness of the modified PET were studied by atomic force microscopy (AFM). The results from XPS, FTIR, EA and AFM show that the Au nanoparticles are grafted on the modified surface only in the case of biphenyldithiol pretreatment. The possible explanation is that the "flexible" molecule of ethanedithiol is bounded to the activated PET surface with both -SH groups. On the contrary, the "rigid" molecule of biphenyldithiol is bounded via only one -SH group to the modified PET surface and the second one remains "free" for the consecutive chemical reaction with Au nanoparticle. The gold nanoparticles are distributed relatively homogenously over the polymer surface.     

Restraining of calcium contamination in near‐net shape alumina ceramics during slip casting

The traditional method for shaping ceramics is by slip casting on gypsum molds; however, its application for near‐net shaping of ceramic components is limited due to contamination by calcium ions. The focus of this study is the modification of the mold to limit Ca²⁺ contamination and to maintain favorable sucking properties. Cement was added to a standard gypsum mold to suppress its erosion, and a decrease in the sucking rate was observed due to its reduced macroporosity. The highest values of green densities were obtained at gypsum/cement weight ratios of 90/10 and 70/30. The microstructure analysis showed that alumina blocks prepared from the molds containing higher quantities of cement (30 or 50 wt%) were resistant to abnormal grain growth caused by Ca²⁺ contamination from the gypsum. The gypsum/cement mixtures for making molds for slip casting significantly limit mold erosion due to a lower sucking rate and abnormal grain growth of the slip cast samples because of the decreased diffusivity of Ca²⁺ ions. Therefore, the present modification of the mold renders the slip casting method more suitable for the near‐net shaping of ceramics.     

Thermal Conductivity Measurement of Bulk Solids

The coefficient of thermal conductivity of particulates and powders is of great importance in process engineering. The prediction of thermal properties of powders using empirical equations is still difficult due to the wide range of specific attributes. This article describes a new measurement methodology for a laboratory device that can be used to determine the thermal conductivity of bulk solids. The presented results show that the created device is highly applicable in industrial practice. It is possible to examine the coefficient of thermal conductivity depending on the sample temperature, the granulometry results and the morphological composition, the moisture content, the degree of consolidation, and other variables that may enter into the entire process and affect it significantly.     

翻新轮胎胎面胶配方和胎面花纹对汽车主动安全性的影响

轮胎翻新是废旧轮胎的一种利用手段。在轮胎翻新过程中,旧轮胎胎面花纹是通过覆盖一层胎面胶料进行修复的。翻新轮胎性能的完善以及其价格比新轮胎低使其被相当频繁地使用,但安装翻新轮胎的汽车经常发生车祸。在轮胎翻新时,关于翻新轮胎性能如何影响交通安全方面的信息非常重要。在给定路况条件下,轮胎的制动性能、抓着性能和行驶操纵性能等方面的知识令人关注。     

Electrocrystallisation of metallic films under the influence of an external homogeneous magnetic field—Early stages of the layer growth

The effects of a uniform magnetic field on the early stages of Ag, Fe and CoFe alloys electrocrystallisation have been investigated. It was found for Fe and CoFe alloys, irrespective of the applied parameters, that early stages of the layer growth can be characterised by a nucleation and 3D diffusion controlled growth. The influence of the deposition parameters on the nucleation behaviour was studied on the basis of the Sharifker-Mostany (SM) model. A modification to the existing model has been proposed in order to model alloy systems. It is reported that a magnetic field superposed parallel to the electrode surface has a significant influence on the early stages of Fe and CoFe alloys growth. The growth of the nuclei is enhanced by the Lorentz-force-driven convection, while the nucleation processes remain unaffected. The hydrodynamic origin of these phenomena is confirmed by independent rotating disk electrode (RDE) investigations. Moreover, the proposed mechanism of a magnetic field influence on the 3D diffusion controlled growth is supported by a microscopic investigation of Ag deposits. It was found that Ag deposits obtained without a magnetic field superposition are characterised by a relatively large number of small 3D growth centres, whereas the deposits obtained in a field show fewer 3D centres but their size is greatly increased.     

Lasioglossins: Three Novel Antimicrobial Peptides from the Venom of the Eusocial Bee Lasioglossum laticeps (Hymenoptera: Halictidae)

Three novel structurally related pentadecapeptides, named lasioglossins, were isolated from the venom of the eusocial bee Lasioglossum laticeps. Their primary sequences were established as H‐Val‐Asn‐Trp‐Lys‐Lys‐Val‐Leu‐Gly‐Lys‐Ile‐Ile‐Lys‐Val‐Ala‐Lys‐NH₂ (LL‐I), H‐Val‐Asn‐Trp‐Lys‐Lys‐Ile‐Leu‐Gly‐Lys‐Ile‐Ile‐Lys‐Val‐Ala‐Lys‐NH₂ (LL‐II) and H‐Val‐Asn‐Trp‐Lys‐Lys‐Ile‐Leu‐Gly‐Lys‐Ile‐Ile‐Lys‐Val‐Val‐Lys‐NH₂ (LL‐III). These lasioglossins exhibited potent antimicrobial activity against both Gram‐positive and Gram‐negative bacteria, low haemolytic and mast cell degranulation activity, and a potency to kill various cancer cells in vitro. The lasioglossin CD spectra were measured in the presence of trifluoroethanol and sodium dodecyl sulfate solution and indicated a high degree of α‐helical conformation. NMR spectroscopy, which was carried out in trifluoroethanol/water confirmed a curved α‐helical conformation with a concave hydrophobic and convex hydrophilic side. To understand the role of this bend on biological activity, we studied lasioglossin analogues in which the Gly in the centre of the molecule was replaced by other amino acid residues (Ala, Lys, Pro). The importance of the N‐terminal part of the molecule to the antimicrobial activity was revealed through truncation of five residues from both the N and C termini of the LL‐III peptide. C‐terminal deamidation of LL‐III resulted in a drop in antimicrobial activity, but esterification of the C terminus had no effect. Molecular modelling of LL‐III and the observed NOE contacts indicated the possible formation of a bifurcated H‐bond between hydrogen from the Lys15 CONH peptide bond and one H of the C‐terminal CONH₂ to the Ile11 oxygen atom. Such interactions cannot form with C‐terminal esterification.     

Milling as a method of surface pre-treatment of steel for adhesive bonding

The paper analyses the impact of mechanical milling pre-treatment parameters on adhesive joint strength. Comparison of surface roughness of adherends after milling and its effect on adhesive joint strength is analysed in strength tests. The tests were performed on C45 structural steel specimens, which were subjected to machining at different parameters, with two types of milling cutters. Adherends were degreased prior to adhesive joining. Two types of end mills used in tests were NFPaφ20 high-speed steel cutter and R390-020B20-11L indexable milling cutter. The machining was carried out at three cutting speeds: 0.05, 0.15 and 0.30 mm/tooth. Adherends were joined with an adhesive composition of Epidian 57 epoxy resin and Z-1 curing agent.     

Development of Microsatellite Markers Using Pyrosequencing in Galium trifidum (Rubiaceae), a Rare Species in Central Europe

We identify a large number of microsatellites from Galium trfidum, a plant species considered rare and endangered in Central and Western Europe. Using a combination of a total enriched genomic library and small-scale 454 pyrosequencing, we determined 9755 contigs with a length of 100 to 6192 bp. Within this dataset, we identified 153 SSR motifs in 144 contigs. Here, we tested 14 microsatellite loci in 2 populations of G. trifidum. The number of alleles and expected heterozygosity were 1-8 (mean 3.2) and 0.00-0.876 (0.549 on average), respectively. The markers described in this study will be useful for evaluating genetic diversity within and between populations, and gene flow between G. trifidum populations. These markers could also be applied to investigate the biological aspects of G. trifidum, such as the population dynamics and clonal structure, and to develop effective conservation programs for the Central European populations of this species.     

Globals of unary algebras

In the present paper, we investigate the question on the reconstructability (up to isomorphism) of a finite unary algebra from its global. It is proved that the class of all finite unary algebras is not globally determined.     

Effects of an agonist, allosteric modulator, and antagonist on guanosine-gamma-[35S]thiotriphosphate binding to liposomes with varying muscarinic receptor/Go protein stoichiometry

We investigated whether alcuronium, an allosteric modulator of muscarinic acetylcholine receptors, can induce receptor-mediated activation of Go proteins in liposomal membranes incorporating purified M2 receptors and Go proteins and whether its action is affected by the receptor/Go protein (R/Go) ratio. The binding of guanosine-gamma-[35S]thiotriphosphate ([35S]GTPgammaS) served as the indicator of G protein activation. It was stimulated by empty receptors at high receptor densities, and the dose-response curve was shifted to the left by the agonist carbachol and to the right by the antagonist atropine. At an R/Go ratio of 300:100, the rate of [35S]GTPgammaS binding was the same in the presence or absence of 0. 1 mM carbachol. Alcuronium increased the binding of [35S]GTPgammaS at R/Go ratios of <3:100 and diminished it at R/Go ratios of >10:100, similar to previous observations on intact cells expressing muscarinic receptors at different densities. The apparent biphasicity of alcuronium action indicates that the allosteric modulator has at least two effects on muscarinic receptor/G protein interaction but its mechanistic basis is unclear. The "active state" of muscarinic receptors induced by alcuronium probably is different from that induced by carbachol. Changes in the densities of receptors and Go proteins had little effect on the kinetics of [35S]GTPgammaS binding and on receptor affinity for carbachol, provided the R/Go ratio was kept constant. This suggests that the receptors and G proteins are located in microdomains in which their concentrations remain constant, despite variations in the amounts of lipidic membranes in the system.