Magnetoelectric effect in cobalt ferrite-barium titanate composites and their electrical properties

CoFe₂O₄-BaTiO₃ composites were prepared using conventional ceramic double sintering process with various compositions. Presence of two phases in the composites was confirmed using X-ray diffraction. The dc resistivity and thermoemf as a function of temperature in the temperature range 300 K to 600 K were measured. Variation of dielectric constant (ɛ′) with frequency in the range 100 Hz to 1 MHz and also with temperature at a fixed frequency of 1 kHz was studied. The ac conductivity was derived from dielectric constant (ɛ′) and loss tangent (tan δ). The nature of conduction is discussed on the basis of small polaron hopping model. The static value of magnetoelectric conversion factor has been studied as a function of magnetic field.     

Palladium supported on structured and nonstructured carbon: a consideration of Pd particle size and the nature of reactive hydrogen

This study sets out a comprehensive characterization of bulk Pd and Pd (ca. 8% w/w) supported on activated carbon (AC), graphite and graphitic nanofibers (GNF). Catalyst activation has been examined by temperature programmed reduction (TPR) analysis and the activated catalysts analyzed in terms of BET area, TEM, H2 chemisorption/TPD, and XRD measurements. While H2 chemisorption and TEM delivered the same sequence of increasing (surface area weighted) average Pd particle sizes, a significant difference (by up to a factor of 3) in the values obtained from both techniques has been recorded and is attributed to an unwarranted (but widely adopted) assumption of an exclusive H2/Pd adsorption stoichiometry=1/2. It is demonstrated that TEM analysis provides a valid mean particle size once it is established that the associated standard deviation is small and insensitive to additional particle counting. XRD line broadening yielded an essentially equivalent Pd size (20-25 nm) for each supported catalyst. The nature of the hydrogen associated with the supported catalysts has been probed and is shown to comprise of chemisorbed (on Pd), spillover (on the carbon support), and hydride (associated with Pd) species. Physical mixtures of bulk Pd + support (AC, graphite, and GNF) were also considered in order to assess hydrogen spillover by H2 TPD analysis. Generation of spillover hydrogen at room temperature is established where temperatures in excess of 740 K are required for effective desorption from the supported Pd catalysts, i.e., 280 K higher than that required for the desorption of chemisorbed hydrogen. Pd hydride formation (at room temperature) is shown to be reversible with decomposition occurring at ca. 380 K. Taking the hydrodechlorination of chlorobenzene as a test reaction, the capability of Pd hydride to promote a hydrogen scission of C-Cl in the absence of an external supply of H2 is demonstrated with a consequent consumption of the hydride. This catalytic response was entirely recoverable once the Pd hydride was replenished during a subsequent reactivation step.     

On‐Site Determination of Carbendazim,Cathecol and Hydroquinone in Tap Water Using a Homemade Batch Injection Analysis Cell for Screen Printed Electrodes

In this work, we present a simple homemade batch‐injection analysis cell for screen‐printed electrodes (BIA‐SPE). The potential of the proposed system for on‐site analysis was demonstrated by the determination of carbendazim, catechol, and hydroquinone in tap water. The system provided reduced injection volume (30 µL), high analytical frequency (≈200 h^?1) and low detection limits (nanomolar level). Moreover, the BIA‐SPE cell presented better stability (RSD≈0.4 %) than a conventional flow injection cell for SPE (RSD≈5.0 %) in organic media. The proposed homemade BIA‐SPE cell is very simple, inexpensive and can be easily constructed in any laboratory.     

A novel antinociceptive sulphated polysaccharide of the brown marine alga Spatoglossum schroederi

Sulfated polysaccharides (SP) of brown algae (Phaeophyta) are composed mainly of alpha- L-fucose, being classified as fucans, with recognized role in inflammation but not in nociception, which was already described for SP obtained from red algae. Here the SP of the brown marine alga S. schroederi (named Ss-SP) was isolated and assayed for the antinociceptive effect. Ss-SP was isolated by DEAE-cellulose, analyzed by agarose gel electrophoresis and evaluated in nociception models (Formalin, Hot plate, Von Frey) using Swiss mice (20-25g). Anion exchange chromatography provided four major fractions being F1 (Ss-SP) that of highest metachromatic activity and sugar content. Ss-SP inhibited both phases of the formalin test. In the first phase the paw licking (55.2 +/- 8.07s) was reduced by 45% (30.5 +/- 6.51s) and 40% (32.85 +/- 8.66s) at 0.1 and 1 mg/kg, respectively. In the second phase, Ss-SP was also inhibitory about 39%, but only at 1 mg/kg (83.0 +/- 15.70s) compared to formalin (136.8 +/- 10.27s). This inhibitory effect suggests a mixed mechanism similar to morphine, which was not confirmed in the hot plate test, a model of pain associated with central neurotransmission. However, Ss-SP reduced the animal reaction in response to stimulation withVon Frey filament at the 2nd and 3rd h (20.8 +/- 6.86% versus carrageenan: 47.9 +/- 5.83%; 33.3 +/- 7.71% versus carrageenan: 62.5 +/- 9.83%). Accordingly, the paw edema induced by carrageenan (0.08 +/- 0.01g) was potently reduced in 45.35% by Ss-SP pre-treatment (0.02 +/- 0.003g), corroborating the anti-inflammatory activity demonstrated for brown seaweed polysaccharides. In conclusion our data revealed for the first time the antinociceptive effect of Ss-SP which could be used as a new source of analgesic substances.     

Cryptococcus gattii: in vitro susceptibility to photodynamic inactivation

Cryptococus gattii is an emergent primary human pathogen that causes meningismus, papilledema, high intracranial pressure and focal involvement of the central nervous system in immunocompetent hosts. Prolonged antifungal therapy is the conventional treatment, but it is highly toxic, selects for resistant strains, contributes to therapy failure and has a poor prognosis. Photodynamic inactivation (PDI) offers a promising possibility for the alternative treatment of cryptococcosis. The aim of this study was to test the effectiveness of toluidine blue O (TBO) and light-emitting diode (LED) against C. gattii strains with distinct susceptibility profile to antifungal drugs (amphotericin B: 0.015-1.0 μg mL(-1); itraconazole: 0.015-2 μg mL(-1); fluconazole: 4-64 μg mL(-1)). Using 25 μM (6.76 μg mL(-1)) TBO and LED energy density of 54 J cm(-2) these fungal isolates presented variable susceptibility to PDI. The production of reactive oxygen species (ROS)/peroxynitrite was determined, and the catalase and peroxidase activities were measured. After PDI, high amounts of ROS/peroxynitrite are produced and higher catalase and peroxidase activities could be correlated with a lower susceptibility of C. gattii isolates to PDI. These results indicate that PDI could be an alternative to C. gattii growth inhibition, even of isolates less susceptible to classical antifungal drugs, also pointing to mechanisms related to their variable susceptibility behavior.     

Back-to-back Schottky diodes: the generalization of the diode theory in analysis and extraction of electrical parameters of nanodevices

We report on the analysis of nonlinear current-voltage characteristics exhibited by a set of blocking metal/SnO(2)/metal. Schottky barrier heights in both interfaces were independently extracted and their dependence on the metal work function was analyzed. The disorder-induced interface states effectively pinned the Fermi level at the SnO(2) surface, leading to the observed Schottky barriers. The model is useful for any two-terminal device which cannot be described by a conventional diode configuration.     

Determination of carrier mobility in MEH-PPV thin-films by stationary and transient current techniques

Charge transport and shelf-degradation of MEH-PPV thin-films were investigated through stationary (e.g. current versus voltage — JxV) and transient (e.g. Time-of-Flight — ToF, Dark-Injection Space-Charge-Limited Current — DI-SCLC, Charge Extraction by Linearly Increasing Voltage — CELIV) current techniques. Charge carrier mobility in nanometric films was best characterized through JxV and DI-SCLC. It approaches 10^? 6 cm²/Vs under a SCLC regime with deep traps for light-emitting diode applications. ToF measurements performed on micrometric layers (i.e. ~ 3 μm) confirmed studies in 100 nm-thick films as deposited in OLEDs. All results were comparable to a similar poly(para-phenylene vinylene) derivative, MDMO-PPV. Electrical properties extracted from thin-film transistors demonstrated mobility dependence on carrier concentration in the channel (~ 10^? 7–10^? 4 cm²/Vs). At low accumulated charge levels and reduced free carrier concentration, a perfect agreement to the previously cited techniques was observed. Degradation was verified through mobility reduction and changes in trap distribution of states.     

The Linear Stability of Shock Waves for the Nonlinear Schrödinger–Inviscid Burgers System

We investigate the coupling between the nonlinear Schrödinger equation and the inviscid Burgers equation, a system which models interactions between short and long waves, for instance in fluids. Well-posedness for the associated Cauchy problem remains a difficult open problem, and we tackle it here via a linearization technique. Namely, we establish a linearized stability theorem for the Schrödinger–Burgers system, when the reference solution is an entropy-satisfying shock wave to Burgers equation. Our proof is based on suitable energy estimates and on properties of hyperbolic equations with discontinuous coefficients. Numerical experiments support and expand our theoretical results.