Thin Film Nanocrystalline TiO2 Electrodes: Dependence of Flat Band Potential on pH and Anion Adsorption.

Thin nanocrystalline TiO2 films were produced on ITO conductive glass by dip-coating of a sol-gel TiO2 precursor. The transparent films were characterized from the optical and structural point of view with UV-Vis, Spectroscopic Ellipsometry, Raman and X-ray photoelectron spectroscopies, the roughness of the coating by AFM. The changes in the electrochemical properties features of ITO/TiO2 electrodes were evaluated in the presence of different electrolytes (KCI, Na2SO4 and phosphate buffer) with the aim to clarify the role of the ion adsorption on the structure of the electrical double layer. Electrochemical tests (Cyclic Voltammetry, CV, and Impedance Electrochemical Spectroscopy, EIS) showed a strong influence of the electrolyte properties on the semiconductor band edge position in the electrochemical scale and on band bending. The CV profiles recorded can be explained by considering that the interface capacity is due to the charging of surface states (e.g., Ti(IV) surface sites coordinated by oxygen atoms, ≡Ti-OH or Ti-O-Ti). The surface charge is strongly affected also by the density and nature of adsorbed ions and by dissociation of surficial OH. Of interest the fact that for the produced nanocrystalline electrodes the flat band potential, measured from the Mott-Schottky analysis of the space charge layer capacity obtained with EIS, showed a non Nernstian behavior with the pH probably caused by a change in the surface acidity as a consequence of specific anion adsorption. The modulation of flat band potential with adsorbed ions is of interest for many applications, in particular for photocatalysis (change in the redox potential of photogenerated carriers) and for photovoltaic applications like DSSC (change in the photopotentials).

[Control of plasma aluminium in hemodialyzed patients. Optimization of the method]. / Controllo dell'alluminio plasmatico nei pazienti in emodialisi. Ottimizzazione del metodo.

As concerning biological matrix, the analytic technique in AA-ETA if on one hand shows remarkable sensitivity, on the other it offers reasons that make it not much reproducible. Our aim has been to optimize and standardize the methodic for the dosage of the Al-s paying a special attention on the contamination risks and on the interference problems in reading phase. If we choose accurately consumption materials and the reagents, aluminium contamination problems may be remarkably reduced avoiding all those decontamination operations often complicated; besides it is possible optimize a thermical program which allows the dosage of the Al-s without using chemical modificator. In this work has been practiced a quality control on 103 couples of samples relative to 62 dialyzed patients and blinded compared to the operator, obtaining a CV of 5.4% on the total average of 45.2 micrograms/l. We are convinced that at the present state the high quality of reagents and the utilisation of disposable materials individually wrapped, and even less the remarkable progress of electronics instrumentation of the last generation allow the use of this technique in a widespread way also in laboratories not particularly specialized.

Primary prevention: HBV vaccination in hemodialysis unit.

The authors evaluated the response rate to HBV vaccination in 27 dialyzed patients. In the 1st stage, the response was 70.37%; nonresponder patients (n = 8) were treated with thymostimulin and revaccinated. The total percentage increased to 85.18%. In order to restore a normal response, the authors suggest to treat nonresponder patients with thymostimulin before revaccination.

Localization of thymostimulin in mouse and rat thymuses.

Anti-bovine thymostimulin serum reacts with reticulo-epithelial cells in the cortex and in the medulla of rat and mouse thymuses. The immuno-reaction is present in a smaller number of cells which have more pallid color than those found in calf thymus. Comparative examination as to the distribution of other thymic factors and as to species-specificity was conducted.

Respiration-dependent ventricular pacing compared with fixed ventricular and atrial-ventricular synchronous pacing: aerobic and hemodynamic variables.

A pacemaker that adapts heart rate in response to the patient's metabolic requirements has been developed. The pacemaker uses breathing frequency and tidal volume as the indicators of physiologic demand. Maximal physical work capacity, anaerobic threshold, oxygen uptake (16 patients) and hemodynamic variables (9 patients) were assessed with fixed rate (VVI), atrial synchronous (VDT/I) and respiration-dependent ventricular (VVI-RD) pacing. All subjects attained their anaerobic threshold in stress tests with VVI pacing. The maximal physical capacity (p less than 0.001), work time to attain the anaerobic threshold (p less than 0.01) and oxygen uptake (p less than 0.001) were significantly greater with VVI-RD than with VVI pacing. The transition from the supine to the standing position was characterized by a significant increase of cardiac index at rest with both VDT/I and VVI-RD pacing as compared with VVI pacing. Progressive increments in the cardiac index and average left ventricular stroke work index were significantly different at submaximal and maximal exercise when VVI and VVI-RD were compared. At maximal exercise, mean cardiac output was also significantly different: 10.21 +/- 2.5 (SD) liters/min with VVI, 11.2 +/- 0.8 liters/min with VDT/I (p less than 0.05) and 12.65 +/- 3.1 liters/min with VVI-RD (p less than 0.05) pacing. Maximal oxygen extraction values were greater with VVI and VVI-RD pacing than with VDT/I pacing. Pulmonary artery end-diastolic pressures at maximal exercise were within the normal range with the three different modes of pacing. In conclusion, there is a significant (25%) improvement in exercise performance with VVI-RD pacing as compared with VVI pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

[Non-invasive recording of the His bundle electrogram: choice of leads and reliability of the "averaging" technic]. / Riconoscimento non invasivo dell'elettrogramma hisiano: scelta delle derivazioni e attendibilità della tecnica di "averaging".

An improvement in detecting His bundle activity using a Marquette high resolution Mac unit, without pharmacologic depression of AV node conduction, was obtained with two surface lead systems, which were selected on the basis of the His bundle anatomical position and its electrostimulation axis. In 8 patients the direction of the His bundle bipolar stimulation vector was evaluated in the frontal plane, on the orthogonal leads and with map of the chest potential. In 39 patients the surface recording, using high-gain amplification, filtering between 50-300 Hz and an averaging of 256-512 cycles, was obtained by positioning the electrodes in the following sites: manubrium sterni-xiphisternum-V4. When this lead system failed, it was replaced by another one, which included V4-right sternal and right vertebral border at the level of the 3rd intercostal space. In 24 patients (PR less than 0.16" in 4 cases) intracavitary and surface H-V recording were compared. The surface interval was measured between the apex of the surface "blip" and onset of the QRS. Sensitivity was 86% with a good correlation (r = 0.94) between invasive and non-invasive measurements. The surface leads, in which the His bundle activity was best detected, were the manubrium-xiphisternum (on the midsternal line) and V4-right vertebral border at the 3rd intercostal space level. Our external measurement technique avoids subjective misinterpretations; the surface H-V interval was on an average 6 msec. shorter than the invasive one. The upper normal value of non-invasive H-V interval is therefore 50 msec in our measurement method.

[Automatic method for the evaluation of the extent of myocardial infarct from the serum of CPK curve]. / Sistema automatico per valutare l'estensione dell'infarto miocardico dalla curva del CPK serico.

An off-line system for calculating the extent of infarct from serial serum CPK determinations based on Sobel et al.'s compartmental model is presented. Results in 40 patients with acute infarct in a coronary unit showed that the index of infarct extent had an appreciable prognostic significance. Employment of the MB isoenzyme in the calculation could, it is felt improve the sensitivity of the method.