Magnon excitation by spin injection in thin Fe/Cr/Fe films

The technique of Brillouin light scattering is used to observe strong excitation of magnons in antiferromagnetically coupled trilayers of Fe/Cr/Fe at room temperature. The magnons are driven out of equilibrium by a microwave current applied in the trilayer through point contacts. The magnitude of the scattering intensity is investigated as a function of the magnon wave number and applied magnetic field. Confirming recent theoretical predictions, the observations provide strong evidence of electronic spin injection in the rf driving field.     

Cardiac valve prosthesis flow performances measured by 2D and 3D-stereo particle image velocimetry

The present paper reports the design and performance tests of a new artificial heart valve test bench that was specially devised to employ Particle Image Velocimetry (PIV) to perform flow analysis. Among the useful characteristics of this new test bench are the repeatable high quality of the developed flow, the generation of time-variable flow with a feedback-controlled actuator, high versatility in changing and controlling the flow parameters (average rate and the beat frequency), and good optical access for PIV measurements. Different chambers and flow conditions have been used to perform tests using 2D-PIV and 3D-StereoPIV. The aim of such tests were to study the fluid dynamical characteristics of mechanical and biological cardiac prostheses, and to evaluate the procedures used to reduce measurement uncertainty due to the 3D components of the pulsatilee flow through the cardiac valve prostheses. It has been possible to observe the evolution of the complete 2D and 3D flow disturbance induced by the valve prostheses for each phase of their cycle on the upstream and downstream volumes.Abbreviations Re Reynold Number - St Strouhal Number - Q volumetric flow rate - density - dynamic viscosity - pulsatile flow parameter - f pulse rate - d nominal pipe diameter - d _i internal pipe diameter - d _e external pipe diameter - s pipe thickness - t -time - v -velocity - Scheimpflug condition angle     

A Green Analytical Method Combined with Chemometrics for Traceability of Tomato Sauce Based on Colloidal and Volatile Fingerprinting

Tomato sauce is a world famous food product. Despite standards regulating the production of tomato derivatives, the market suffers frpm fraud such as product adulteration, origin mislabelling and counterfeiting. Methods suitable to discriminate the geographical origin of food samples and identify counterfeits are required. Chemometric approaches offer valuable information: data on tomato sauce is usually obtained through chromatography (HPLC and GC) coupled to mass spectrometry, which requires chemical pretreatment and the use of organic solvents. In this paper, a faster, cheaper, and greener analytical procedure has been developed for the analysis of volatile organic compounds (VOCs) and the colloidal fraction via multivariate statistical analysis. Tomato sauce VOCs were analysed by GC coupled to flame ionisation (GC-FID) and to ion mobility spectrometry (GC-IMS). Instead of using HPLC, the colloidal fraction was analysed by asymmetric flow field-fractionation (AF4), which was applied to this kind of sample for the first time. The GC and AF4 data showed promising perspectives in food-quality control: the AF4 method yielded comparable or better results than GC-IMS and offered complementary information. The ability to work in saline conditions with easy pretreatment and no chemical waste is a significant advantage compared to environmentally heavy techniques. The method presented here should therefore be taken into consideration when designing chemometric approaches which encompass a large number of samples.     

Kinetics of aquation of Co(III) complex in binary aqueous mixtures and effect of multiparameters of the solvent on the reaction rate

Kinetics and solvent effects of the aquation of trans[Co(4‐(Etpy)₄Cl₂]⁺ have been studied in ethanol + water ranging from 0 to 60% (v/v) and urea + water of various solvent compositions up to 40% (w/w) of organic solvent. Thermodynamic activation parameters were computed and discussed in terms of the solvation effect. Isokinetic temperature within the experimental range revealed that the existence of the compensation effect arising from the solute–solvent interaction. Nonlinear plots of log k with D^?1 suggest that changes in the solvent structure are an important factor that influences these rates. The influence of the added cosolvent on reactivity was analyzed in light of various simple and multiple regression equations using Kirkwood, E_T(30), and Kamlet–Taft parameters. The obtained results showed that the solvation phenomenon plays a dominant role in the aquation. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 230–237, 2011     

Electrochemical characterization of a lithiated mixed nickel-cobalt oxide (LiNi0.5Co0.5O2) prepared by sol-gel process

Lithiated transition metal oxides having a layered structure and general formula LiMO₂, have been extensively studied as positive electrode active materials for lithium or lithium-ion batteries. In particular, lithium nickel dioxide (LiNiO₂) and lithium cobalt dioxide (LiCoO₂) present a layered structure with high diffusion coefficients for the lithium ion. This latter property is very important in order to realize practical devices having high discharge rates. LiNiO₂, compared with LiCoO₂, has the advantage to be a cheaper material with a higher specific capacity for lithium cycling, but its stability upon cycling can be greatly influenced by the displacement of Ni ions from the Ni layers to the Li planes as the content in lithium is reduced over a certain value. Recently, solid solutions such as LiNi_xCo_1−xO₂ have been proposed to offer a compromise between stability, cost and capacity. In this work we have studied LiNi_0.5Co_0.5O₂ prepared by the Complex Sol-Gel Process (CSGP). The advantage of this procedure toward the solid-state process is the high homogeneity in composition and in particle dimension of the synthesized compounds. The samples have been characterized electrochemically using chronopotentiometric, voltammetric and impedance measurements in liquid electrolyte. The results indicates that CSGP-synthesized LiNi_0.5Co_0.5O₂ shows good cyclability (after 1000 cycles about 2/3 of the initial capacity can still be cycled) only if the anodic potential is limited to about 4.2 V. The quite low values of the specific capacity (∼70 mAh/g at C/1 charge-discharge rate) can be justified by the non-complete calcination reaction, as suggested by X-ray measurements. Kinetic properties have been evaluated by Electrochemical Impedance Spectroscopy measurements, which have shown quite high values for the lithium chemical diffusion coefficient (10⁻⁷÷10⁻⁸ cm²s⁻¹) and its unexpected decrease as deintercalation proceeds from x=0.5 in LiNi_0.5Co_0.5O₂. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

A voltammetric and chronopotentiometric study of molten alkali acetates

The electrochemical behaviour of water, hydrogen ion, and molecular hydrogen has been investigated in (Na,K) acetate melt at 250 degrees with bright platinum electrodes by means of chronopotentiometry and voltammetry.     

A regular perturbation approach to the problem of diffusion towards a growing mercury drop electrode

Summary The problem of diffusion of an electroactive species towards a growing mercury drop electrode is treated. An approximate solution for the complete differential equation is given using a regular perturbation technique.

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Riassunto Il lavoro tratta il problema della diffusione di una specie elettroattiva verso un elettrodo a goccia di mercurio che cresce nel tempo. Una tecnica di perturbazione regolare è stata utilizzata per ricavare una soluzione approssimata.