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The accumulation of Cd(II), Cu(II), Pb(II) and Zn(II) at mg L(-1) concentration levels by inactive freeze-dried biomass of Pseudomonas Putida has been investigated. These metals could be efficiently removed from diluted aqueous solutions. A contact time of 10 min was sufficient to reach equilibrium. The pH has a strong effect on metal biosorption and the optimal pH values were 6.0, 5.0-6.0, 6.0-6.5 and 7.0-7.5 for Cd(II), Cu(II), Pb(II) and Zn(II) respectively. Under these conditions there was 80% removal for all metals studied. The process of biosorption can be described by a Langmuir-type adsorption model. This model accounts for 98% of the data variance. The K(A) and q(max) parameters for each metal are strongly correlated (at confidence levels greater than 98%) with the metal acidity, quantified by the constant of the corresponding M(OH)(+) complex, thus confirming previous assertions by other authors.

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A new procedure for the direct determination of picomolar levels of cobalt in seawater is presented. Cathodic stripping voltammetry is preceded by adsorptive accumulation of the cobalt-nioxime (cyclohexane-1,2-dione dioxime) complex from seawater containing 6 μM nioxime and 80 mM ammonia at pH 9.1, onto a hanging mercury drop electrode, followed by reduction of the adsorbed species. The reduction current is catalytically enhanced by the presence of 0.5 M nitrite. Optimized conditions for cobalt include a 30 s adsorption period at -0.7 V and a voltammetric scan using differential pulse modulation. According to the proposed reaction mechanism, dissolved Co(II) is oxidized to Co(III) upon addition of nioxime and high concentrations of ammonia and nitrite; a mixed Co(III)-ammonia-nitrite complex is adsorbed on the electrode surface; the Co(III) is reduced to Co(II) (complexed by nioxime) during the voltammetric scan, followed by its chemical reoxidation by the nitrite, initiating a catalytically enhanced current. A detection limit of 3 pM cobalt (at an adsorption period of 60 s) enables the detection of this metal in uncontaminated seawater using a very short adsorption time. UV digestion of seawater is essential, as part of the cobalt may occur strongly complexed by organic matter and rendered nonlabile. The method was applied successfully to the determination of the distribution of cobalt in the water column of the Mediterranean.

With the increasing use of concomitant chemoradiotherapy (CCRT) in the treatment of advanced head and neck carcinoma, surgery has lost ground as the first therapy and is reserved as a salvage treatment in cases of locoregional failure. The objective of our study was to review our experience in patients who had a local or regional recurrence after treatment with CCRT. Thirty-two patients underwent salvage surgery after CCRT: 24 were treated with a local or locoregional resection and 8 patients with a neck dissection only. In patients who had surgery involving the primary location of the tumor, some kind of reconstruction was required in 83% of cases. One or more postoperative complications occurred in nine patients. The median hospital stay was 18.5 days. There was a significant difference in hospital stay in relation to the appearance of surgical complications. Five-year adjusted survival after salvage surgery was 34.2% (CI 95% 13.2-55.2%). Adjusted survival was related to the status of the resection margins and appearance of neck nodes with extracapsular spread in the neck dissection. In conclusion, salvage surgery after CCRT involves extensive resections, requiring reconstruction techniques with regional or microanastomosed free flaps in most cases, achieving acceptable outcomes.

The electrochemical behaviour of ytterbium ions was investigated in the eutectic LiCl-KCl at 723 K at the surface of tungsten, glassy carbon, aluminium and aluminium coated tungsten electrodes. On inert electrodes (W and GC) the electroreduction of Yb(III) to Yb(II) takes place in a quasi-reversible electrochemical mode within the electroactive window. The electrochemical system Yb(II)/Yb (0) is not observed because it is similar or more negative in potential than the Li(I)/Li(0) couple. As a result Yb metal in contact with the melt could react to give Li(0) according to the reaction:On the contrary, on reactive Al electrodes the electrochemical system Yb(II)/Yb(0) was observed within the electroactive range. The potential shift of the redox couple is caused by the decrease of Yb activity in the metal phase due to the formation of Yb-Al alloys at the interface. The formation mechanism of the alloys was determined in a melt containing both Yb(III) and Al(III) ions, using W, Al and Al coated tungsten electrodes. X-ray diffraction analysis and scanning electron microscopy (SEM) after potentiostatic electrolysis runs allowed the identification of Al 3 Yb and Al 2 Yb. Potentiometric titrations of Yb(III) solutions with oxide donors, using a ytria stabilized circonia membrane electrode "YSZME" as a pO 2À indicator electrode, have shown the formation of ytterbium oxychloride and ytterbium oxide and their solubility products have been determined at 723 K (pk s (Yb 2 O 3 ) = 7.6 AE 0.3 and pk s -(YbOCl) = 18.5 AE 0.7.

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