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The current investigation reports the influence of the addition of CdFeO nanoparticles on the structural and superconducting properties of the (Bi,Pb)-2212 phase. The formation of an orthorhombic phase of Bi-2212 superconductor is confirmed by the X-ray powder diffraction measurements. The scanning electron microscope measurements show an improvement in the grain connectivity and a decline of voids due to the CdFeO nanoparticles addition. The Fourier transform infra-red spectroscopy is used to associate the absorption bands to equivalent functional groups. The DC-electrical resistivity and the I-V characteristic measurements show an enhancement of the superconducting transition temperature (Tc) and the critical current density (Jc) up to 0.02 wt% addition of CdFeO, respectively. The elemental composition and oxidation states are determined using X-ray photoelectron emission spectroscopy. The results suggest a correlation between the electric behavior and the cationic equilibrium reactions among Pb2+ ions in Bi3+ or Cu2+ sites. [ABSTRACT FROM AUTHOR]

(BaSnO3)x/Cu0.5Tl0.5Ba2Ca2Cu3O10-δ superconducting composites (0.00 ≤ x ≤ 1.50 wt.%) were prepared by the solid-state reaction technique. The crystalline structure and superconducting transition temperature were investigated by X-ray powder diffraction (XRD) and dc-electrical resistivity measurements, respectively. X-Band electron spin resonance (ESR) measurements were carried out at different temperatures 103 ≤ T ≤ 298 K. ESR spectra are dominated by a single asymmetric line corresponding to Cu2+ ions at the rhombic site. The temperature dependence of the g factors allowed the determination of the pseudo-gap onset temperature T*. The results of T* are compatible with those obtained from resistivity and thermoelectric power measurements. The contribution of delocalized electrons from Cu2+ ions in the disordered part of the impurity phases BaCuO2 and Ba2CuO3 is significant for the high addition of nanoparticles. Moreover, the number of spins N participating in ESR and the activation energy Ea were enhanced with the addition of BaSnO3. [ABSTRACT FROM AUTHOR]

The effect of Arsenic substitution on the properties of Bi-2212 superconductors was studied. Solid-state reaction technique was used for the synthesis of Bi2−xAsxSr2Ca1.1Cu2.1O8 samples, x = 0, 0.1, 0.2 and 0.4. The X-ray diffraction confirmed the formation of the tetragonal phase of Bi-2212 superconductors. The decrement in the c parameter confirmed that As insertions were introduced into the Bi sites of the system. The grain morphology of the surface was analysed by scanning electron microscopy, where the amount of arsenic increases with As substitution. The superconducting transition temperature (Tc) was determined from the DC-electrical resistivity by the standard four-probe technique. Tc was enhanced up to x = 0.1 above which it was suppressed. For magnetism, half magnetic-hysteresis loops were obtained by SQUID magnetometer at different temperatures (5 and 30 K). The hysteresis loops sizes increased with increasing As-concentrations. The critical current density (Jc) and the flux pinning mechanisms were investigated via different models. [ABSTRACT FROM AUTHOR]

(Mn2O3)x SmBa2Cu3O7-δ composite samples (0.00 ≤ x ≤ 0.08 wt.%) were prepared using solid state reaction technique, and investigated using resistivity measurements and the Vickers microhardness. The characterisation of the prepared samples was accomplished using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and Brunauer-Emmett-Teller (BET). The Mn2O3 nanoparticles do not influence the orthorhombic structure of SmBa2Cu3O7- δ and stay as adhering material producing a filling up of the voids and reducing the cracks. BET measurements show a decrease in the specific surface area as well as in the total pore volume for x = 0.02 wt.%, confirming the SEM results. The superconducting transition temperature Tc of the prepared samples was investigated using electrical resistivity measurements. Results showed that Tc increases from 91.68 K to 94.43 K as x increases from 0.00 to 0.02 wt.%, then it decreases as nano-Mn2O3 wt.% concentration increases. The mechanical properties of (Mn2O3)xSmBa2Cu3O7-δ samples were measured using Vickers microhardness in order to investigate the effect of Mn2O3 nanoparticles on Vickers microhardness number Hv. The Vickers microhardness data were analysed using Meyer's law, Hays and Kendall (HK), and Modified Proportional Specimen Resistance (MPSR) models. The analysis showed that the HK is the best model to describe the load dependence of Hv for all samples. [ABSTRACT FROM AUTHOR]

Zn-Co ferrites doped with Er3+ and Pr3+ with different concentrations were synthesised by co-precipitation method at constant calcination temperature. XRD results show an increase in the lattice parameter. Particle sizes determined from TEM are close to those determined from XRD, confirming PVP acts as controlling of the nanoparticles growth. Electron paramagnetic resonance (EPR) spectra analysis indicates that the spin-spin relaxation time T2 increases and the g-factor decreases with increasing Er3+ and Pr3+ content. The saturation magnetisation and the coercivity decrease with increasing RE3+ content. The dielectric constants ε' and ε" and the dielectric loss tangent (tanδ) decrease, and the a.c. conductivity increases with the increase of Er3+ concentration between 0.00 wt% and 0.20 wt%; the same trend is observed for samples doped with Pr3+ of concentrations 0.04, 0.12 and 0.20 wt%, while that doped with 0.08 wt% of Pr3+ shows a peak at low frequency. [ABSTRACT FROM AUTHOR]

The corrosion behavior of (SnO2)x(Bi1.6Pb0.4)Sr2Ca2Cu3O10-δ, (SnO2)x(Bi,Pb)-2223, in 0.5 M NaCl solutions at 30°C was studied using potentiodynamic polarization curves measurements, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques as well as scanning electron microscopy (SEM) and energy dispersive X-ray emission spectroscopy (EDX). The polarization data indicated that SnO2nanoparticles behave as a cathodic type inhibitor for the corrosion of (Bi–Pb)-2223 phase superconductors in simulating seawater solutions. The corrosion current density of (SnO2)x(Bi,Pb)-2223 in a NaCl solution decreases with the time elapsed from sample preparation. The CV of (SnO2)x(Bi–Pb)-2223 phase superconductors showed features similar to those of ideal capacitive behavior. The results indicated that a pure (Bi,Pb)-2223 phase superconductor is the most suitable choice for electrochemical capacitor applications in simulating seawater solutions. However, EIS measurements at different potentials revealed that the corrosion process is controlled not only by charge transfer but also by the diffusion process. These measurements also confirm that the corrosion rate of a cathodically polarized phase superconductor is less than that of an anodically polarized phase superconductor. SEM images and EDX analysis showed that the reduction of SnO2nanoparticles to Sn decreases the corrosion rates of the superconducting materials. [ABSTRACT FROM AUTHOR]

Two new proanthocyanidin trimers have been isolated from Cistus incanus herb; gallocatechin-(4α→6)-gallocatechin-(4α→8)-gallocatechin (compound 1) and epigallocatechin-3-O-gallate-(4ß→8)-epigallocatechin-3-O-gallate-(4ß→8)-gallocatechin (compound 2). The structures were determined on the basis of 1D- and 2D-NMR (HSQC, HMBC) of their peracetylated derivatives, MALDI-TOF-MS and by acid-catalysed degradation with phloroglucinol. A more abundant proanthocyanidin oligomer was also isolated, purified and its chemical constitution studied by 13C-NMR and phloroglucinol degradation. The mean molecular weight of the polymer was estimated to be about 7 to 8 flavan-3-ol-units with a ratio of procyanidin : prodelphinidin units at 1:5, some of which are derivatised by gallic acid. Water extract and higher oligomeric proanthocyanidin fractions of C. incanus significantly inhibited TPA-induced oedema when applied topically at doses of 0.5 and 1 mg/ear in mice. Furthermore, the extracts and the pure compounds inhibited COX-1 and COX-2 activities. In addition, compound 2 exhibited an IC50 of 4.5 μM against COX-2 indicating its high selectivity towards COX-2. [ABSTRACT FROM AUTHOR]

The pharmacological activity of neuroactive phytochemicals on recombinant human glutamic acid decarboxylase 65 (hGAD65) was investigated. GAD catalyzes the conversion of glutamic acid to γ-aminobutyric acid (GABA), which acts as an important inhibitory neurotransmitter in the central nervous system (CNS). We describe an improved method in which recombinant hGAD65 was expressed at high levels using a maltose binding protein (MBP) fusion system. The expression and purification process was superior to the commonly used glutathioneS-transferase (GST) fusion partner. The in vitro system developed here detected both enzyme inhibition and stimulation, under varying pyridoxal-5'-phosphate (PLP) concentrations. The known GAD inhibitor, 3-mercaptopropionic acid, was tested as a positive control and had an IC50 = 12.3 μ M. Phytochemicals were tested (10 μ g/mL) for their effects on in vitro hGAD65 activity. Minor inhibition was seen with the ethanol extract of Panax quinquefolius L. (ginsenosides) (23%), betulinic acid (27%), and valerenic acid (20%). An increase in hGAD65 activity by approximately 20% was observed with bilobalide and asiaticoside. As a result, these small changes in GAD activity may have physiologic implications. The possibility that phytochemicals influence GABAergic neurotransmission in vivo and the mechanisms by which it may occur is discussed. [ABSTRACT FROM AUTHOR]

Various emulsifying salt mixtures were used in making block type processed cheeses. Ras cheese was used as the cheese base with two salt mixtures: (i) Na-diphosphate + Na-polyphosphate + Na-tripolyphosphate and (ii) Na-polyphosphate + Na-citrate + Na-orthophosphate + Na-diphosphate comparing to commercial salts Joha SE and PZO respectively. The resultant processed cheeses were analyzed when fresh and monthly during storage at 7 and 20°C for water activity (aw), oil separation, meltability, flow behavior, color parameters, and sensory properties. There were no significant differences in water activity values among all treatments. The differences were significant in oil index and meltability values. The samples exhibited different shear stress values and it was highest in treatments with commercial salts. Consistency coefficient (k-value) of processed cheese samples was affected by emulsifying salt mixture being almost two folds higher with salt mixtures (i) than those of salt mixtures (ii). The color parameters L, a, b, Chroma and hue angle showed slight differences among treatments and the cheese was shinier and whiter with increasing pyrophosphate content in the salt mixture. The stored samples became less white especially when stored at room temperature (20°C). Sensory evaluation showed that all cheeses were acceptable but the most acceptable samples were produced with mixtures in the ratio of (i) 30:40:30 and (ii) 50:20:20:10. [ABSTRACT FROM AUTHOR]

This paper reports experimental results from the use of pure natural honey for drag reduction in capillary tubes, with particular reference to biomedical engineering. The effects of the capillary tube diameter, the Reynolds numbers, concentration percentages, and honey type on the drag reduction were investigated. The maximum drag reduction obtained in this investigation is very much dependent on both the diameter of the capillary tubes and the concentration of the honey. Maximum drag reductions of 17.1%, 46.9%, and 37.3% at concentrations of 1000 ppm were obtained for the tube diameters of 1 mm, 1.3 mm, and 1.5 mm, respectively. Increasing the concentrations to 2000 ppm gave maximum reductions of 43%, 36.5%, and 50% for the tube diameters of 2 mm, 2.5 mm, and 3 mm, respectively. [ABSTRACT FROM PUBLISHER]

This paper reports some experimental results of using a new additive solution for reducing drag in thermoplastic pipes. It was found that the amount of drag achieved is very much dependent on the diameter of the pipe, Reynolds number, and concentrations of the additives. In general it was found that the drag is higher in small-diameter thermoplastic pipes. The maximum drag reduction obtained was 29.4%. [ABSTRACT FROM PUBLISHER]