On dynamic effects at folding of coated papers

Folding of coated papers is examined numerically using the finite element method. The analysis is focused on the influence from dynamic effects on the folding process. In particular, the behaviour of field variables relevant for cracking of the coating layers are studied in some detail. The results presented indicate that dynamic effects are of little importance as regards maximum strain levels in the coating but will influence the stress and strain distributions. Accordingly, a quasi-static analysis of the problem will be sufficient in order to describe many of the important features related to cracking.     

A new 3-D finite-element model based on thin-film approximation for microelectrode array recording of extracellular action potential.

A transient finite-element model has been developed to simulate an extracellular action potential recording in a tissue slice by a planar microelectrode array. The thin-film approximation of the active neuron membrane allows the simulation within single finite-element software of the intracellular and extracellular potential fields. In comparison with a compartmental neuron model, it is shown that the thin-film approximation-based model is able to properly represent the neuron bioelectrical behavior in terms of transmembrane current and potential. Moreover, the model is able to simulate extracellular action potential recordings with properties similar to those observed in biological experiments. It is demonstrated that an ideal measurement system model can be used to represent the recording microelectrode, provided that the electronic recording system adapts to the electrode-tissue interface impedance. By comparing it with a point source approximated neuron, it is also shown that the neuron three-dimensional volume should be taken into account to simulate the extracellular action potential recording. Finally, the influence of the electrode size on the signal amplitude is evaluated. This parameter, together with the microelectrode noise, should be taken into account in order to optimize future microelectrode designs in terms of the signal-to-noise ratio.     

Stereospecific analysis of human plasma triglycerides

Brockerhoff-type procedures were used to determine the amounts of each fatty acid at each position of plasma triglycerides from normal and hyperlipemic humans. Statistically significant differences between both groups are found for the 2 and 3 positions.     

Mise en oeuvre des methodes d'impusions galvanostatiques rapides: determination de la resistance de transfert de charge et de la capacite differentielle d'une electrode

Reading within a very short time the voltage response to galvanostatic pulses requires the use of a microelectrode having a suitable geometry and an area not exceeding a few mm². The comparison of different methods (single, double pulse, charge step-decay) applied to the H⁺/H system and to some Me^z+/Me systems show that the double pulse method is the only one to yield the determination of the R_t and C_d characteristic parameters 60–80 ns after the beginning of polarization.     

ETude cinetique des systemes Cd---Cd(II) et Fe(II)---Fe(II) en milieu aqueux par trace d'oscillogrammes lineaires au moyen de la methode de double impulsion potentiostatique

The principle and construction of a quadratic function generator are described. The voltage output, supplying the oscilloscope time-base, gives a linear i(√t) oscillogram and allows the transfer cd i_a to be read on the oscilloscope screen.

The kinetic parameters of the Cd---Cd(II0 and Fe(II)---fe(III) sytsems are determined in this way. In these two examples, the second Fick equation is solved numerically in order to establish the validity of the formula used to calculate T₀, the time corresponding to the cd i_a.

Zusammenfassung

Man beschreibt die Einstellung von einem Quadratischfunktiongenerator. Wenn die Klemmenspannung dieses Generators mit der Zeitablenkung des Oszillographes angeschaltet wird, erreicht man ein lineares Oszillogramm i(√t); die Durchtrittstromdichte i_a wird sofort auf dem Oszilloskopschrim gelesen.

Mann kann mit dieser Methode die elektrolytischen Konstanten der Reaktionen Cd---Cd(II) und Fe(II)---Fe(III) bestimmen. Jedenfalls integriert man die Zweite Diffusion differentialgleichung zahlenmässig und so, kann man die Richtigkeit der die Zeit gebenden Formel, welcher Zeit die Ordinate i_a auf die Linie i(√t) entspricht, bestätigen.     

Electrochemical behaviour of copper in a NaF-AlF3-BaCl2 ternary melt at 750° C

Voltammetric and chronopotentiometric methods were used to study the electrochemical behaviour of copper in the NaF-AlF₃-BaCl₂ ternary melt at 750° C. Copper, graphite and platinum were used as electrode materials. It was shown that the electrochemical reduction of copper ions is a single step process, with the reversible exchange of one electron at a copper electrode. The value of the diffusion coefficient of the cuprous ion, determined by means of chronopotentiometry, isD =(2.8±0.3)× 10^–5 cm² s^–1.     

Evaluation of the gastrotoxicity of anti-inflammatory drugs: contribution of general registries of digestive endoscopy

The evaluation of the rate of gastroduodenal toxicity of anti inflammatory drugs is a difficult problem. We tried to analyse that question by studying the general endoscopic registers of the Gastro-Enterologic department of the hospital. This retrospective study concerns 2,945 endoscopies performed during the year 1988 and 1992 randomly chosen among the last 5 years. 992 results show injuries suggestive of non steroidal anti inflammatory drugs (NSAID) toxicity, however only in 65 cases the potential role of an anti inflammatory drug is mentioned: 36 men and 29 women, mean age: 50.6 +/- 19.6 years. Concerning the drugs, only the pharmacological classes they belong to are mentioned except for Aspirin. Acetyl salicylate acid 7 cases, NSAIDS 36 and Steroids 22. In the drug group 63% of injuries are located to the stomach (ulcers 13%, gastritis 50%), 37% to the duodenum (19% ulcers, 18% duodenitis). Compared to the groups with the same kind of injuries, but without any mention of drugs, there are no statistical difference in the proportion of ulcers. Aging and sex are not influent in our results on the genesis of drug induced ulcers. These results must be discussed because a lot of datas are missing in the registers and so the number of patients taking drugs is probably underestimated. This means that unless a prospective study is held with someone enquiring for all the risk factors, the study of the general endoscopic registers is not a good way to estimate gastrointestinal damages due to drugs.     

Radial echo-planar imaging

A new ultrafast magnetic resonance imaging pulse sequence named radial echo-planar imaging (rEPI) is introduced. The sequence is based on a modification of the echo-planar imaging (EPI) sequence to scan k-space radially, in an attempt to combine the speed of EPI with the benefits of radial sampling. Like in EPI, all the desired lines in k-space are scanned consecutively in opposite directions. The unique feature of this new sequence, however, is that the orientation of the readout gradient is incrementally rotated, so that all the echoes are refocused through the center of k-space. Therefore, rEPI data are acquired in a polar grid, and image reconstruction can be done either by means of filtered back-projection or by regridding the data to a Cartesian matrix followed by 2D Fourier transform. First results show that rEPI images can be acquired with the same speed and signal-to-noise ratio of EPI images. rEPI images are also shown to be less sensitive to off-resonance effects than EPI images. Further studies are underway to investigate the usefulness of rEPI for spectroscopic imaging and applications affected by motion.     

Meaningful electronic signatures based on an automatic indexing method

Legal information certification and secured storage combined with documents electronic signature are of great interest when digital documents security and conservation are in concern. Therefore, these new and evolving technologies offer powerful abilities, such as identification, authentication and certification. The latter contribute to increase the global security of legal digital archives conservation and access. However, currently used cryptographic and hash coding concepts cannot intrinsically enclose cognitive information about both the signer and the signed content. Indeed, an evolution of these technologies may be necessary to achieve full text researches within hundreds or thousands of electronically signed documents. This article aims at describing a possible model along with associated processes to create and make use of these new electronic signatures called “meaningful electronic signatures” as opposed to traditional electronic signatures based on bit per bit computation.