Use of electrochemical methods to examine different surface preparation methods for organic coatings on steel

For preparation of steel surfaces before applying an organic coating, waterjetting is a modern, effective and environmentally friendly method. However there is a lack of data on its performance in terms of the subsequent protection afforded by the paint compared with more conventional methods. Hence previously exposed steel panels had their surfaces prepared in a variety of ways (abrasion, blasting with garnet entrained in water (10 K psi) and waterjetting without garnet at two velocities (20 K psi and 40 K psi)) prior to coating with two typical maintenance coatings. These were then exposed under immersion condition in the laboratory and monitored using the DC resistance method. Another set of samples were exposed in a salt spray test in accordance with ASTM B 117 for 500 h. At the end of both tests DC measurements were carried out and the samples were inspected visually in terms of blistering and rust. Results showed that both the immersion test and the salt spray test differentiated the surface preparations methods in the same order. Thus control panels performed the best. Nearly as good though were the two (20 K psi and 40 K psi) sets of waterjetted samples. The abraded samples were variable but overall provided less protection. The panels blasted with garnet entrained in water (10 K psi) samples proved to be the worst. Characterisation of the surfaces prior to coatings using the scanning electron microscope was also conducted. A tentative explanation for the differing protection afforded involving the integrity of the oxide film was suggested. Further work is needed to substantiate this. Overall, with samples in the immersion test, results using electrochemical methods proved themselves to be very effective in assessing and even predicting performance in a relatively short period of time. The results also correlated with the salt spray test. Also the work showed that waterjetting is a very effective way of preparing the surface prior to maintenance painting.     

The effect of linker of electrodes prepared from sol–gel ionic liquid precursor and carbon nanoparticles on dioxygen electroreduction bioelectrocatalysis

The effect of linker of three-dimensional, hydrophilic-carbon-nanoparticle film-electrodes prepared by layer-by-layer method on redox probe accumulation and bioelectrocatalytic dioxygen reduction was studied and compared for two different electrode scaffolds. The linker in both of these scaffolds was based on the same ionic liquid sol–gel precursor, 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium bis(trifluoromethyl-sulfonyl)imide. The first electrode type was prepared by alternative immersion of tin doped indium oxide substrate in an aqueous suspension of carbon nanoparticles modified with phenyl sulphonic groups and a sol composed of ionic liquid sol–gel precursor and tetramethoxysilane. For the second electrode type sol was replaced by a methanolic suspension of silicate submicroparticles with appended imidazolium functional groups. In both films 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) anions accumulate irreversibly. In the case of the first electrode electrostatic attraction plays the more important role in comparison to the case of the second where stable adsorption of the redox probe takes place. After adsorption of bilirubin oxidase, electrodes obtained from sol and carbon nanoparticles exhibit modest bioelectrocatalytic activity towards dioxygen reduction at pH 4.8, however those obtained from oppositely charged particles are much more efficient. The magnitude of the associated catalytic current in both cases depends on the number of immersion and withdrawal steps. Interestingly, mediatorless catalysis at electrodes obtained from oppositely charged particles is more efficient than mediated catalysis.     

Antioxidative activity of rosemary extract using connective tissue proteins as carriers

In the research the activity of rosemary extract introduced using connective tissue proteins was investigated, taking into consideration the effect of the type of carrier (collagen and elastin), carrier concentration (1%, 2%, 4%) and the method of its introduction to fat substrate (rehydrated or unhydrated). Antioxidative activity was assessed using the Oxidograph instrumental test. The activity of rosemary extract on protein preparations was significantly affected by the rehydration of these preparations. The application of collagen as carrier of rosemary extract had an advantageous effect on the activity of this antioxidant. In turn, under the adopted testing conditions the application of elastin resulted in partial masking of antioxidative activity of rosemary extract. Amounts of the carriers, onto which the antioxidant was introduced, did not have a statistically significant effect on this activity.     

Granulation of sludge under different loads of a glycerol fraction from biodiesel production

The aim of the research was to evaluate the possibility of using the crude glycerol fraction from biodiesel manufacturing processes for granular sludge production. The experiment was carried out simultaneously in four sequencing batch reactors (SBRs) at different carbon loads: 0.2 ± 0.08, 0.6 ± 0.16, 1.1 ± 0.27, and 1.3 ± 0.35 g COD/g TSS per cycle (COD – chemical oxygen demand, TSS – total suspended solids). Granulation did not occur in the reactor with the lowest organic carbon load. In the remaining reactors small granules began to appear after 25 cycles of reactor operation. In all reactors the efficiency of carbon removal remained at ca. 80%. The highest granular sludge production per cycle was 0.31 ± 0.28 g TSS/L; it was obtained at an organic load of 1.1 ± 0.27 g COD/g TSS per cycle. Most of the introduced COD was removed in the reactors during the first 5 h of aeration; the COD removal rate was correlated with the organic load and varied from 123.12 to 472.76 mg COD per litre and hour. Practical applications: With the increasing production of biodiesel fuel a problem arises with the utilization of glycerol that is a by‐product of the process. By‐product glycerol fraction from small agricultural installations is usually contaminated. Its composition varies depending on parameters of the transesterification process and it is unprofitable to purify it. In the present research we investigated one possible way of dealing with the by‐product. The glycerol fraction was successfully used as a carbon source for the production of aerobic granular sludge. The granules obtained can be used as a seed sludge in granule‐based reactors, or can be cofired with coal or directly combusted. Since aerobic granular sludge is one of the most promising technologies investigated during the last few years it appears to possess high utility.     

The effect of ceramic nanoparticles on tribological properties of alumina sol–gel thin coatings

Thin alumina coatings containing zirconia or alumina nanoparticles having diameter of ～20–30 nm were deposited by the sol–gel dip-coating process on silicon wafers. The mass content of nanoparticles in the alumina coating was fixed at 15% in relation to the theoretical mass of alumina matrix resulted from the amount of the applied precursor. Atomic force microscopy (AFM) was used to image the surface topography of as-made coatings and find out the wear level after frictional tests. Tribological tests were performed with the use of a microtribometer operating in the load range of 30–100 mN. It was found that the presence of α-alumina (corundum) or zirconia nanoparticles enhances the tribological performance of alumina layers annealed at 100 °C by decreasing the average wear rate by 20% and 63% for zirconia and corundum nanoparticles, respectively. No wear was observed for samples containing both types of nanoparticles annealed at 500 °C.     

A survey of MAC layer solutions to the hidden node problem in ad-hoc networks

Ad-hoc networks suffer from the problem of hidden nodes (terminals), which leads to severe degradation of network throughput. This survey gives a comprehensive overview of Medium Access Control (MAC) protocols which directly or indirectly address this problem. The presented protocols are grouped in several categories and are described in the order of their publication date. To give the reader a deep understanding of the progress made in the area of alleviating the hidden node problem a brief summary of the key ideas as well as a detailed comparison of different protocols are presented. Open research directions are also discussed to serve as a starting point for future protocol design and evaluation.     

EFFECT OF KCL EXCESS AND INERT CARRIER ON THE YIELD OF KVO3 SYNTHESIS

Investigation was carried out on the optimal conditions of the synthesis of KVO₃ and Cl₂ from KCl and V₂O₅ in the presence of atmospheric oxygen. The influence of the excess of KCl relative to V₂O₅ was investigated. Also, the effect of quartz sand introduced into the reaction mixture on the yield of KVO₃ synthesis was determined. The obtained product of synthesis was isolated from the post-reaction mixture.     

Wettability of polytetrafluoroethylene and polymethyl methacrylate by aqueous solutions of TX-100 and TX-165 mixture with propanol

The measurements of the contact angle of the aqueous solutions of TX-100 and TX-165 mixture with propanol on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA) were carried out. On the basis of the obtained results, the dependence between the cosine of contact angle and surface tension as well as between the adhesion and surface tension of the solutions in the light of the work of adhesion of the solutions to the PTFE and PMMA surface was discussed. The dependence between the adhesion and surface tension for PMMA was correlated to the surface concentration of propanol as well as TX-100 and TX-165 mixture concentration determined from the Frumkin equation at the PMMA-air, PMMA-solution and solution–air interfaces. For this purpose, the surface tension of PMMA covered by a surface active agent film was determined using the Neumann et al. equation and next the PMMA–solution interface tension was evaluated from the Young equation. The values of the surface tension of PMMA covered by propanol and surfactants mixture layer were applied to describe the changes of the adhesion work of solutions to PMMA surface as a function of propanol and surfactants mixture concentration. The adhesion work of the aqueous solutions of TX-100 and TX-165 mixture with propanol to the PTFE and PMMA surfaces was discussed in the light of the adhesion work of particular components of the solutions. On the basis of the results obtained from the contact angle measurements, the standard Gibbs free energy of adsorption of particular components of solution was also considered.     

The Mode of SN38 Derivatives Interacting with Nicked DNA Mimics Biological Targeting of Topo I Poisons

The compounds 7-ethyl-9-(N-methylamino)methyl-10-hydroxycamptothecin (2) and 7-ethyl-9-(N-morpholino)methyl-10-hydroxycamptothecin (3) are potential topoisomerase I poisons. Moreover, they were shown to have favorable anti-neoplastic effects on several tumor cell lines. Due to these properties, the compounds are being considered for advancement to the preclinical development stage. To gain better insights into the molecular mechanism with the biological target, here, we conducted an investigation into their interactions with model nicked DNA (1) using different techniques. In this work, we observed the complexity of the mechanism of action of the compounds 2 and 3, in addition to their decomposition products: compound 4 and SN38. Using DOSY experiments, evidence of the formation of strongly bonded molecular complexes of SN38 derivatives with DNA duplexes was provided. The molecular modeling based on cross-peaks from the NOESY spectrum also allowed us to assign the geometry of a molecular complex of DNA with compound 2. Confirmation of the alkylation reaction of both compounds was obtained using MALDI–MS. Additionally, in the case of 3, alkylation was confirmed in the recording of cross-peaks in the ¹H/¹³C HSQC spectrum of ¹³C-enriched compound 3. In this work, we showed that the studied compounds—parent compounds 2 and 3, and their potential metabolite 4 and SN38—interact inside the nick of 1, either forming the molecular complex or alkylating the DNA nitrogen bases. In order to confirm the influence of the studied compounds on the topoisomerase I relaxation activity of supercoiled DNA, the test was performed based upon the measurement of the fluorescence of DNA stain which can differentiate between supercoiled and relaxed DNA. The presented results confirmed that studied SN38 derivatives effectively block DNA relaxation mediated by Topo I, which means that they stop the machinery of Topo I activity.