Surface analysis with scanning electrochemical microscopy in the feedback mode: Monitoring of reactivity and pitting precursor sites on the Nd-Fe-B-type magnet

Scanning electrochemical microscopy (SECM) in the feedback mode was utilized for monitoring the surface reactivity and the localized corrosion processes occurring on the Nd_13.5Fe_79.5Si₁B₆ permanent magnet (intrinsically comprising iron inclusions). SECM imaging experiments, performed with the application of ferrocenecarboxylic acid as the mediator, revealed distinctly reactive areas at the magnet surface during early stages of its immersion in 0.1 mol dm⁻³ phosphate buffer (pH = 7). It was demonstrated that the iron inclusions were responsible for the existence of these reactive areas whereas the bulk material surface was practically unreactive (insulating). It was observed that the surface reactivity of the iron inclusions gradually decreased with time and after 7 h immersion the whole magnet surface became uniformly unreactive (insulating). The results were explained in terms of differences in the dynamics of the passive film formation on the iron inclusions and on the bulk material. Another factor that might be responsible for the observed non-uniform surface reactivity was also considered, namely, the differences in abilities to charge propagation through passive films existing on the iron inclusions and on the bulk material. The role of the iron inclusions as pitting precursor sites in the presence of chlorides in the phosphate buffer solution was also examined.     

An experimental optimization study on a tube-in-shell latent heat storage

Thermal energy storage (TES) using phase change materials (PCMs) has recently received considerable attention in the literature, due to its high storage capacity and isothermal behaviour during the storage (melting or charging) and removal (discharging or solidification). In this study, a novel modification on a tube-in-shell-type storage geometry is suggested. In the proposed geometry, the outer surface of the shell is inclined and it is the objective of this study to determine the optimum range for the inclination angle of the shell surface. Paraffin with a melting temperature of 58.06°C, which is supplied by the Merck Company, is used as the PCM. The PCM is stored in the vertical annular space between an inner tube through which the heat transfer fluid (HTF), hot water, is flowing and a concentrically placed outer shell. At first, the thermophysical properties of this paraffin are determined through the differential scanning calorimeter (DSC) analysis. Temporal behaviour of the PCM undergoing a non-isothermal solid–liquid phase change during its melting or charging by the HTF are determined for different values of the inlet temperature and the mass flow rate of the HTF. The new geometry is shown to respond well with the melting characteristics of the PCM and to enhance heat transfer inside the PCM for a specific range of the shell inclination angle. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of the oat,horse chestnut,cowherb, soy,quinoa and soapwort extracts on skin-mimicking monolayers and cell lines

The main goal of the study was to compare the effect of aqueous extracts of oat (Avena sativa L.), horse chestnut (Aesculus hippocastanum L.), quinoa (Chenopodium quinoa Willd.), soapwort (Saponaria officinalis L.), cowherb (Vaccaria hispanica [P. Mill.] Rauschert) and soy (Glycine max L.) on model lipid monolayers mimicking the lipid membrane of keratinocytes and intercellular lipids of stratum corneum, and on human skin-related cell lines. Two lipid monolayers, consisting of a dipalmitoylphosphatidylcholine (DPPC) and cholesterol mixture in a molar ratio of 7:3 and Ceramide VI, stearic acid and cholesterol in a molar ratio of 1:1:0.7, and two cell lines (human keratinocyte HaCaT and human skin malignant melanoma A375) were employed. None of the extracts reduced surface pressure below the level achieved for bare monolayers. The strength of the effect on the lipid monolayers (horse chestnut > cowherb > soapwort > soy) points to the existence of some specific interactions responsible for the observed affinity of biosurfactants from the extracts to the lipids in the monolayers. The cytotoxicity tests performed with two model skin cell lines showed that all six plants extracts significantly reduced the cells' viability in a concentration-dependent way. The model lipid monolayers were not solubilized by the investigated surface-active extracts. The latter thus proved interesting candidates for application in mild cleansing cosmetic formulations. Penetration of the monolayers by surface-active components of some extracts, especially horse chestnut, cowherb and soapwort, opens new possibilities for topical delivery of active components.     

Combined EBSD and Computer-Assisted Quantitative Analysis of the Impact of Spark Plasma Sintering Parameters on the Structure of Porous Materials

Metallurgical and Materials Transactions A - The paper presents the experimental, numerical, and theoretical investigation of the microstructure of nickel aluminide samples manufactured by spark...     

Camelina sativa phosphatidylcholine:diacylglycerol cholinephosphotransferase-catalyzed interconversion does not discriminate between substrates

Phosphatidylcholine:diacylglycerol cholinephosphotransferases (PDCT) regulate the fatty acid composition of seed oil (triacylglycerol, TAG) by interconversion of diacylglycerols (DAG) and phosphatidylcholine (PtdCho). PtdCho is the substrate for polyunsaturated fatty acid biosynthesis, as well as for a number of unusual fatty acids. By the action of PDCT, these fatty acids can be transferred into the DAG pool to be utilized in TAG biosynthesis by the action of acyl-CoA:DAG and phospholipid:diacylglycerol acyltransferases. Despite its importance in regulating seed oil composition, biochemical characterization of PDCT enzymes has been lacking. We characterized Camelina sativa PDCT in microsomal preparations of a yeast strain expressing Camelina PDCT and lacking the capacity of producing TAG. Camelina PDCT was specific for PtdCho and the sn-1,2 enantiomer of DAG and could not utilize ceramide. The interconversion reaches equilibrium within 15 min of incubation, indicating that only distinct pools of DAG and PtdCho were available for exchange. However, the pool sizes of DAG and PtdCho involved in the exchange were not fixed but increased with the amount of exogenous DAG or PtdCho added. Camelina PDCT showed about the same selectivity for di-oleoyl, di-linoleoyl, and di-linolenoyl species in both PtdCho and DAG substrates, suggesting that no unidirectional transfer of particular unsaturated substrates occurred. Camelina PDCT had a good activity with erucoyl-DAG as a substrate despite low erucic acid levels in PtdCho in plant species accumulating a high amount of this fatty acid in the seed oil.     

Structural phase instability,mixed-phase,and energy band gap change in BiFeO3 under lattice strain effect from first-principles investigation

Lattice strain effects drive a variety of novel functional responses in epitaxial BiFeO₃ thin films and have attracted significant interest and attention from researchers in experimental and theoretical studies. However, the difficulty in designing experimental techniques in addition to facing problems in the first principles approach, such as output accuracy and high computational costs, constitute the discovery of new functional responses in epitaxial BiFeO₃ thin films not entirely understood. Therefore, in this study, we perform a first principles calculation based on the less expensive LDA+U method to investigate the structural phase instability and electronic properties change in BiFeO₃ under the lattice strain effect. The structural phase transformation of BiFeO₃ under volumetric and compressive/tensile lattice strain was examined established on the calculated lower energy phases. Importantly, we demonstrated that the change of crystal structure phases of BiFeO₃ was extremely sensitive to the volumetric and compressive/tensile lattice strain, comparable with various experiment data, as reported in the literature. Moreover, we revealed for the first time from the first principles prediction the coexistence of mixed R-T phases in the region of moderate compressive ζ_in-plane of ?2.9% (e.g. LaAlO₃ substrates with ɑ = 3.79 Å). From the prediction of electronic properties obtained by the LDA+U and PBE0 methods, we found that the energy band gap increased when the compressive in-plane lattice strain is increased while, in contrast, the energy band gap decreased when BiFeO₃ was under the tensile in-plane lattice strain effect. We also demonstrate that our computational technique based on the first principles study was sufficiently accurate enough, helping to speed up the process of designing new materials having an excellent multifunctional response (piezoelectric, magnetic, photovoltaic, spintronic).     

Unleashing the performance of ccNUMA multiprocessor architectures in heterogeneous stencil computations

The Journal of Supercomputing - This paper meets the challenge of harnessing the heterogeneous communication architecture of ccNUMA multiprocessors for heterogeneous stencil computations, an...     

Detection of ROS and translocation of ERP-57 in apoptotic induced human neuroblastoma (SH-SY5Y) cells

Several toxic compounds are known to induce apoptosis in mammalian cell lines. The human neuroblastoma cells (SH-SY5Y) were exposed to the phosphatase inhibiting toxin okadaic acid (OA) or hydrogen peroxide (H2O2) to induce apoptosis as well as generate reactive oxygen species (ROS). Mitoxantrone (MXT) was used as a positive control for apoptosis. The SH-SY5Y cells were transfected with eukaryotic expression plasmid pHyPer-dMito encoding mitochondrial-targeted fluorescent or pHyPer-dCito encoding cytoplasmic-targeted fluorescent sensor for hydrogen peroxide (HyPer). The ERp57, also called GRP58 (Glucose-regulated protein 58), is a stress protein induced in conditions like glucose starvation and viral infection. Recently ERp57 was shown to translocate from the endoplasmatic reticulum to the cell surface in anthracycline-induced apoptotic cells. ERp57 co-translocation together with calreticulin has been suggested to be crucial for recognizing tumor cells to induce immunogenic cell death. ERp57 translocation after exposure to okadaic acid was studied using immunofluorescence and confocal microscopy. These studies indicated that okadaic acid has induced the translocation of ERp57 to the cellular membrane.     

Morphologic characterization and fractal analysis of lapped and polished surfaces of quartz single crystals

Lapping and polishing are industrial processes sometimes used alternatively for surface finishing of hard and brittle materials. This article presents advanced image analysis of surfaces of quartz crystal blanks finished by lapping and polishing. Scanning electron micrographs were obtained from workpiece surfaces parallel to Y-, AT-, and Z-cut crystal planes treated with different normal stress and abrasive grit size, and stereometric and fractal/multifractal approaches were used to analyze the respective surfaces. Fractal dimensions and segmentation parameters were able to decode the effect of normal stress increasing on the surface roughness of lapped and polished samples. Moreover, the texture isotropy and the bifractal—hence agglomerated—nature of the surface patterns, suggest that both treatments dismiss the anisotropic signature of hardness and fracture toughness inherent to each crystal plane. This study provides promising results regarding the applicability of fractal analysis in the assessment of surfaces severely worn by the combined effect of brittle microcracking and plastic deformation mechanisms.