Film resonance on acoustic wave devices: the roles of frequency and contacting fluid.

The dynamics of composite films of polypyrrole and sodium poly(styrenesulfonate) were studied by means of the electrochemical quartz crystal microbalance. Admittance spectra recorded after successive cycles of electrodeposition showed dramatic changes, which were interpreted in terms of acoustic resonance of the film. Reports of this phenomenon are rare and unquantified, presenting a unique opportunity for the first test of a recently reported theoretical model. The model, valid at frequencies in the vicinity of film resonance, is represented in terms of an equivalent electrical circuit with parallel LCR elements in the motional arm of the resonator. Since it was developed for viscoelastic films exposed to a vacuum, this provides an opportunity to test the importance of the fluid necessarily present in in situ electrochemical experiments. Measurements at the fundamental frequency and at higher harmonics reveal the sensitivity of film resonance effects to frequency and provide insights into film dynamics through the variation of shear moduli with time scale (frequency).

Characterization of self-assembled redox polymer and antibody molecules on thiolated gold electrodes.

Multilayer immobilization of antibody and redox polymer molecules on a gold electrode was achieved, as a strategy for the potential development of an amperometric immunosensor. The step-by-step assembly of antibiotin IgG on Os(bpy)(2)ClPyCH(2)NH poly(allylamine) redox polymer (PAH-Os) adsorbed on thiolated gold electrodes was proved by quartz crystal microbalance (QCM) and atomic force microscopy (AFM) experiments, confirming the electrochemical evidence. The increase of redox charge during the layer-by-layer deposition demonstrated that charge propagation within the layers is feasible. The multilayer structure proved to be effective for the molecular recognition of horseradish peroxidase-biotin conjugate (HRP-biotin), as confirmed by the QCM measurements and the electrocatalytic reduction current obtained upon H(2)O(2) addition. The catalytic current resulting from PAH-Os mediation was shown to increase with the number of assembled layers. Furthermore, the inventory of IgG molecules on the supramolecular self-assembled structure and the specific and non-specific binding of HRP-biotin conjugate were confirmed by the QCM transient studies, giving information on the kinetics of IgG deposition and HRP-biotin conjugate binding to the IgG.

Voltammetric iodometric titration of ascorbic acid with dead-stop end-point detection in fresh vegetables and fruit samples.

The present work describes a method for determining ascorbic acid, which combines iodometry with a voltammetric technique to detect the end point of the titration. In addition, the validity of the method applied to natural vegetable or fruit samples was assessed. The results were compared with those obtained by an accurate method such as HPLC using UV detection. Similar values of ascorbic acid for different natural samples were obtained by means of this approach (p > 0.05). The limit of quantification was 0.1 mg. This technique presents the advantage of other electroanalytical methods such as avoiding filtration or ultracentrifugation steps, with the additional benefit of using the platinum electrodes, which are routinely used in the laboratory. These facts allow a rapid and efficient quantification of ascorbic acid with very low cost of reagents and equipment.

Retrieval of solid-state 31P nuclear magnetic resonance (NMR) chemical shielding parameters: proposal of an approach concerning variable-temperature 31P NMR mass spectra of urea phosphate and comparison of different methods.

Several methods are used to retrieve the principal components of the 31P chemical shielding tensor from variable-temperature 31P NMR spectra of urea phosphate (both static and spinning at the magic angle at low speeds). A complementary approach is proposed for the study of small changes in these parameters, based on the measurement of selected side-band intensities which are most sensitive to changes in sigma.

Magic-angle-spinning 31P NMR spectra of solid dihydrogen phosphates. Comparison of ordered and dynamically disordered compounds.

High-resolution 31P NMR spectra are reported for several dihydrogen phosphates in the solid state. Shielding tensor components were retrieved by analysis of the sideband intensities. The results, together with previously published data, can be grouped according to the presence and type of proton exchange occurring in the crystals. Static MH2PO4 samples (M = Na, Li) show a shielding anisotropy delta sigma of approximately 120 ppm. In the case of M = Cs (one static P-OH bond and two oxygens attached to "half" hydrogens on the average) delta sigma is smaller (approximately 75 ppm) and can be understood in terms of the accepted, proton-exchange model. For highly disordered samples (M = K, NH4, Rb), where all four oxygens have nearby hydrogens with 50% occupancy, delta sigma is even smaller (approximately 30 ppm) but not zero. In the last-mentioned cases, 31P NMR information suggests that local PO4 environments may not have the symmetry that could be expected on the basis of the known crystal structures.

[The development of psychoses: results of a clinical survey concerning 383 cases followed during 10 years (1975-1985)]. / Evolution des psychoses: résultats d'une enquête clinique portant sur 383 cas suivis pendant 10 ans (1975-1985).

383 psychotics patients were selected in 1975 according to the french classification (INSERM). These initial population was simultaneously subdivided according 2 types of criteria: Diagnosis criteria (DSM III Axis 1), Psychosocial adaptation criteria (DSM III axis V). For each subjects we investigates in 1985 evolution of following data previously collected in 1975: Diagnosis and psychosocial adaptation, Marital status and presence of social welfare work, Treatment variable (Hospitalization and out patient department care, neuroleptic treatment). Results indicate than: psychosocial adaptation criteria are better than diagnosis criteria for outcome judgment. most of the time there is no correlation between high quantity of care and better outcome, furthermore some time there is a correlation between high quantity of care and negative outcome, We must consider, as one explanation of this fact, that it's the more severe patients who use the higher quantity of care.

[Aspects of the crossed thoracobrachial syndrome as seen in rheumatology]. / Aspects du syndrome de la traversée thoraco-brachiale vu en milieu rhumatologique.

On the basis of 12 personal observations it is pointed out that the thoracobrachial syndrome may become apparent from pain or paraesthesia of the arm. These symptoms typically appear in certain positions or on effort. Essential arterial or venous complications require early diagnosis, which is only possible by vascular exploration (arteriography or phlebography with radiographs with abduction of the arm). The value of clinical changes appears to be very restricted. Simple surgery-resection of the first rib- eliminates all possible multiple compression causes and is indicated in serious or very incapaciting forms of the syndrome.

[Cyclical chemotherapy of myeloma with cell synchronization: therapeutic trial. Apropos of 13 cases]. / Chimiothérapie cyclique du myélome avec synchronisation cellulaire: essai thérapeutique. A propos de 13 observations

The authors report the results obtained from the treatment of 13 cases of myeloma by cyclic chemotherapy (melphalan) applied after cellular synchronization with vincristine. The clinical results (maximum 2 years after treatment) were good in 11 cases out of 13. The following laboratory values quickly returned to normal: sedimentation and calcaemia, but there was little change in the immunoglobulins.