Characterization of different diamond-like carbon electrodes for biosensor design.

Diamond-like carbon (DLC) films are gaining big interest in electrochemistry research area. DLC electrodes made with different ratio of sp(3)/sp(2) carbon hybridization or doped with different percentages of nickel were characterized electrochemically by cyclic voltammetry and by amperometric measurements towards hydrogen peroxide. SiCAr1 and SiCNi5% were chosen as sensitive transducers for the elaboration of amperometric glucose biosensors. Immobilization of glucose oxidase was carried out by cross-linking with glutaraldehyde. Measurements were made at a fixed potential+1.0V in 40mM phosphate buffer pH 7.4. SiCAr1 seems to be more sensitive for glucose, 0.6875muA/mM, than SiCNi5%, 0.3654muA/mM. Detections limits were 20muM and 30muM, respectively. Apparent Michaelis-Menten constants were found around 3mM. Forty-eight percent and 79% of the original response for 0.5mM glucose remained after 10 days for both biosensors, respectively.

Identification and simultaneous determination of Azorubin, Allura red and Ponceau 4R by differential pulse polarography: application to soft drinks.

Azorubin (E 122), Ponceau 4R (E 124) and Allura red (E 129), are the most used red dyes in soft drinks manufacturing, and in some cases two dyes are present. The aim of this work is to show that using differential pulse polarography, it was possible to distinguish these synthetic dyes from the natural dyes providing from fruits. In addition, in an appropriate supporting electrolyte, identification and quantitative analysis of these three red dyes were possible, even when they were mixed. Various electrolytes were tested such as potassium chloride, which is a classical supporting electrolyte, citric acid which is one of the components of the soft beverages, sodium citrate and a phosphate buffer. It was shown that the peak intensities and potentials, and consequently their resolution, depend greatly on the pH values. In potassium chloride and sodium citrate the peaks of Azorubin, Allura red and Ponceau 4R were well separated and dyes were identified without ambiguity. Buffer solutions with pH close to 8 and 9 appeared to be appropriate, as the potentials and the intensities of the peaks were slightly changed when small amounts of soft drinks, usually at pH close to 3, were introduced in the cell. A procedure using the standard addition technique was developed, tested with model syrups and then applied to commercial syrups, soda and non-alcoholic bitters.

Potentiometric study of Cd(II) and Pb(II) complexation with two high molecular weight poly(acrylic acids); comparison with Cu(II) and Ni(II).

The cadmium (II) or lead (II) complex formation with two poly(acrylic acids) of high molecular weight (Mw=2.5 x 10(5) and 3 x 10(6)) was investigated in dilute aqueous solution (NaNO(3) 0.1 mol l(-1); 25 degrees C). Potentiometric titrations were carried out to determine the stability constants of the MA and MA(2) complex species formed. Bjerrum's method, modified by Gregor et al. (J. Phys. Chem. 59 (1955) 34-39), for the study of polymeric acids was used. The results were compared to those previously obtained in the same conditions with copper (II) and nickel (II) [1]. It appeared that the two polymers under study present similar binding properties and that the stability constants of the complex species formed increased in the following order, depending on the metal ion: Ni(II)

Potentiometric study of Cu(II) and Ni(II) complexation with two high molecular weight poly(acrylic acids).

The copper (II) or nickel (II) complex formation with two poly(acrylic acids) of high molecular weight (Mw=2.5x10(5) and 3x10(6)) was investigated in aqueous dilute solution (NaNO(3) 0.1 mol l(-1); 25 degrees C). Potentiometric titrations were carried out, first to precise the acid-base properties of the two polymers, and secondly to determine the stability constants of the MA and MA(2) complex species formed. The Bjerrum's method, modified by Gregor et al. (J. Phys. Chem., 59 (1955) 34-39), for the study of polymeric acids was used. The results obtained showed that both polymers present very similar properties. As expected, copper(II) is more readily bound to poly(acrylic acids). CuA(2) was the predominant observed species; the global stability constant logbeta(102) was found to be close to 6.6. With nickel(II), none of the complex species MA or MA(2) becomes predominant (logbeta(102)=5.5). Finally, the PAA complexes present a greater stability compared with that of monomeric analogs.

Electrochemical response of a carbon paste electrode containing an adsorbed species on incorporated alumina.

The electrochemical response of carbon paste electrode was investigated containing an inorganic and a non-electroactive compound on which an electro- active organic molecule was adsorbed. Alizarin S was chosen as the test molecule adsorbed on 150 m(2)/g of alumina, because this molecule is either easily reduced or oxidized on carbon. The electrode response was found to be linear for low amounts of alumina containing a known amount of Alizarin S. The electrical yield was never higher than 50%, but was reproducible. An increasing alumina amount in the paste increased the response, but lowered the electrical yield.

[Diagnostic imaging of Budd-Chiari syndrome in adults and children]. / Diagnostica per immagini della sindrome di Budd-Chiari nell'adulto e nel bambino.

Budd-Chiari syndrome is caused by the obstruction of the hepatic veins or of the inferior vena cava. It is characterized by the classic symptomatological triad: ascites, hepatomegaly, and abdominal pain. In 2/3 cases its etiology remains unknown. Budd-Chiari syndrome may be associated with polycythemia vera, neoplasms, chronic leukemia, congenital abnormalities, hypercoagulation conditions, pregnancy, oral contraceptives, and constrictive pericarditis. Even though its clinical diagnosis is difficult, radiology plays a decisive role with US, CT, MR imaging and, above all, angiography; the latter, together with liver biopsy, generally provides with an unquestionable diagnosis. Through the definition of stage of the disease, of level (intrahepatic, venous, caval, cardiac), of type (intrinsic or extrinsic), and degree of both obstruction and consequent development of collateral channels, radiology determines which patients should undergo a medical or a surgical treatment. In some case, percutaneous angioplasty can be performed. Four cases of Budd-Chiari syndrome, including two children, were investigated with US, CT, angiography, and liver biopsy; MR imaging was also employed in one case. The underlying cause was identified in 3 patients: constrictive pericarditis of probable congenital origin and web occlusion of the inferior vena cava near the right atrium in the 2 children; hepatic vein thrombosis due to essential thrombocythemia in the third case. In the fourth patient, thrombosis of the inferior vena cava and hepatic veins was unexplained. The diagnosis was established by means of liver biopsy and phlebography of the hepatic veins. Good diagnostic information was also supplied by non-invasive techniques, such as US, CT, and MR imaging.(ABSTRACT TRUNCATED AT 250 WORDS)

A phase I study of human natural interferon-beta in cancer patients.

In this phase I study 15 patients with metastatic tumors were given interferon (IFN)-beta by i.v. bolus injections. Twelve individual doses of 1, 2, 3.3, 5, 7, 9, 12, 16, 21, 27, 35, and 46 x 10(6) IU were administered every other day. The single maximal tolerated dose ranged from 9 to 46 x 10(6) IU. Eight patients tolerated the dose of 46 x 10(6) IU without side effects. Disturbances of cardiac rhythm were observed, but were closely related temporally to severe chills and appeared to be the consequence of adrenergic stimulation associated with this side-effect. In addition, no significant variations in the left ventricular function as assessed by nuclear stethoscope were observed. Neurotoxicity was not a major side-effect. The toxicity of IFN-beta given as scheduled in this study was significant, but acceptable.

Venice: sea-lagoon exchange in a modified tide regime.

Salinity and tide heights recorded for a month at P(0), a point in the northern section of the Venetian lagoon, are the basic experimental data used to construct a numerical model which describes the salinity variations at P(0) as a function of the tides measured at the Lido entrance. The time variation of the salinity pattern iss interpreted in terms of a lagoon system in which a freshwater source of constant intensity is in a quasi-steady equilibrium with a tide-modulated sink. The mean residence time of a contaminant in this simulated lagoon is predicted from the change in the salinity pattern due to a reduction in the entrance size.