Comparison between the impedance spectra of Li/SOCl2 batteries obtained using the time and the frequency domain measurement techniques

A comparison between the impedance spectra of Li/SOCl₂ batteries obtained in the time and frequency domains is reported. It is demonstrated that by averaging over several responses the accuracy in the time domain is greatly improved. On the other hand, it was found that the time domain technique caused nonlinearity in the system response even at very small amplitudes of excitation (for example corresponding to a potential drop of 30 mV). The method is useful for routine characterization of the quality of galvanic cells in industrial production. The accuracy compared with market-available impedance spectrometers operating in the frequency domain is satisfactory (±10%), the price being much lower.Nomenclature g _i parameters of model frequency response - g _id parametersg _i obtained by deconvolution - g _ir parametersg _i obtained by frequency domain method - H frequency response - H _m model frequency response - H _r reference frequency response - i(t) excitation current - I() Fourier transform of thei(t) - Im imaginary part - j imaginary unit - M Number of independent measurements - N number of samples - Re real part - R resistance - R ₀ ohmic resistance - T sampling time - u(t) response voltage - U() Fourier transform ofu(t) - dispersion factor - angular frequency - () phase spectrum - _a relative amplitude error - _gi relative error ofg _i - average relative amplitude error - _p relative phase error - average relative phase error - ₀ mean relaxation time     

Single‐Step Deposition of Au‐ and Pt‐Nanoparticle‐Functionalized Tungsten Oxide Nanoneedles Synthesized Via Aerosol‐Assisted CVD,and Used for Fabrication of Selective Gas Microsensor Arrays

Tungsten oxide nanostructures functionalized with gold or platinum NPs are synthesized and integrated, using a single‐step method via aerosol‐assisted chemical vapour deposition, onto micro‐electromechanical system (MEMS)‐based gas‐sensor platforms. This co‐deposition method is demonstrated to be an effective route to incorporate metal nanoparticles (NP) or combinations of metal NPs into nanostructured materials, resulting in an attractive way of tuning functionality in metal oxides (MOX). The results show variations in electronic and sensing properties of tungsten oxide according to the metal NPs introduced, which are used to discriminate effectively analytes (C₂H₅OH, H₂, and CO) that are present in proton‐exchange fuel cells. Improved sensing characteristics, in particular to H₂, are observed at 250 °C with Pt‐functionalized tungsten oxide films, whereas non‐functionalized tungsten oxide films show responses to low concentrations of CO at low temperatures. Differences in the sensing characteristics of these films are attributed to the different reactivities of metal NPs (Au and Pt), and to the degree of electronic interaction at the MOX/metal NP interface. The method presented in this work has advantages over other methods of integrating nanomaterials and devices, of having fewer processing steps, relatively low processing temperature, and no requirement for substrate pre‐treatment.     

Electrochemical binding and wiring in battery materials

Binders in battery electrodes not only provide mechanical cohesiveness during battery operation but can also affect the electrode properties via the surface modification. Using atomic force microscopy (AFM), we study the surface structuring of three binders: polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC) and gelatin. We try to find correlation between the observed structures and the measured electrochemical charge–discharge characteristics. We further measure the binding ability of gelatin adsorbed from solutions of different pHs. While the best binding ability of gelatin is obtained at pH about 9, the least polarization is observed at pH 12. Both properties are explained based on the observed gelatin structuring as a function of pH. In the second part of this study, gelatin is used as a surface agent that dictates the organization of nanometre-sized carbon black particles around micrometre-sized cathodic active particles. Using microcontact impedance measurements on polished pellets we show that using gelatin-forced carbon black deposition the average electronic resistance around LiMn₂O₄ particles is decreased by more than two orders of magnitude. We believe that it is this decrease in resistance that improves significantly the rate performance of various cathode materials, such as LiMn₂O₄ and LiCoO₂.     

A chamber for biomechanical,electrochemical and electrophysiological measurements in functional segments of peripheral nerves

The aim of the work was to develop the chamber to be used in biomechanical, electrochemical and electrophysiological measurements in functional segments of peripheral nerves, when electrical stimulating pulses are selectively applied to preselected locations along the nerve and neural responses are measured.     

The control of the diameter and length of α-MnO2 nanorods by regulation of reaction parameters and their thermogravimetric properties

α-MnO₂-type single-crystal nanorods were synthesized under hydrothermal conditions based on the redox reaction of KMnO₄ in an acidic environment. Several reaction parameters, like the reaction temperature, the reaction time and the concentration of KMnO₄ in the reaction mixture, were varied in order to determine their impact on the structure, the dimensions of the synthesized nanorods, and as well on their thermogravimetric properties. It was found that the reaction time has no significant influence on the diameter, although it has a strong influence on the length of the obtained nanorods. On the other hand, the concentration of KMnO₄ in the reaction mixture has a strong impact on both the diameter and the length. With an increasing concentration of KMnO₄ in the reaction mixture the average lengths and diameters of the isolated MnO₂ nanorods are reduced. The change in dimensions of the synthesized nanorods is reflected in their thermogravimetric properties.     

Reproducibility of the acetylene rebreathe technique for determining cardiac output

Acute and subacute extrapyramidal movement disorders are rarely reported in uremic patients. We report three such cases with basal ganglia lesions. All three had advanced renal failure with high serum creatinine levels. One of the patients had a history of ischemic heart disease and acute pulmonary edema with hypoxemia. Another patient had experienced arterial hypotension during previous hemodialysis. The third had prominent metabolic acidosis. One of the patients developed generalized dyskinesias, whereas the other two developed gait disturbances. Neuroimaging studies in all three cases showed bilateral changes in the basal ganglia. The natural history was self-limiting with gradual improvement. Diminution of the basal ganglia lesions was demonstrated on follow-up imaging in two of the three cases. We conclude that acute or subacute movement disorders with bilateral basal ganglia lesions may occur in uremia. Hypoperfusion with global brain ischemia and selective vulnerability of the basal ganglia to uremic toxins may account for these lesions.     

Robustness as a criterion for use of hollow clay masonry units in seismic zones: an attempt to propose the measure

In order to provide adequate seismic behavior of masonry walls, local brittle failure of masonry units in the most stressed zones of structural walls should be prevented. Although robust behavior is required by the code, no specifications are given regarding the criteria to fulfill this requirement. To propose such criteria, a series of 28 masonry walls, built with six different types of hollow clay masonry units, currently available on the market, have been tested by subjecting them to cyclic lateral load at two levels of constant precompression. Besides, the strength characteristics of the units, like compressive strength orthogonal and parallel to the bed joints and tensile and shear strength of the units have been determined by standardized and specifically designed testing procedures. By correlating the parameters of seismic resistance of the walls and strength characteristics of the units, no specific indicator for robustness could have been determined on the basis of the mechanical characteristics of the tested units. It has been found that in all cases the level of precompression, i.e. the ratio between the compressive stresses in the walls and the compressive strength of masonry, represents the governing parameter.