Au dissolution during the anodic response of short-chain alkylthiols with polycrystalline Au electrodes

The electrochemical characteristics of polycrystalline Au in LiClO₄ electrolyte solutions containing 3-mercaptopropionic acid (MPA) or meso-2,3-dimercaptosuccinic acid (DMSA) were studied with linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) over a wide range of positive potentials vs. Ag/AgCl. The EIS data exhibited linear capacitive behaviour at 0.0 V with either MPA or DMSA added directly to the electrolyte suggesting the formation of an adsorbed layer of the alkylthiol on the electrode surface. Above this potential, a single well-defined impedance loop appeared for electrolyte solutions containing DMSA or MPA, an observation indicative of a charge transfer reaction that could be related to several processes including oxidative desorption, oxidation of the alkylthiol, or Au oxidation/dissolution. To test for Au dissolution, the electrode was held at 0.8 V vs. Ag/AgCl for 12 h in electrolytes containing MPA or DMSA followed by surface analysis with Atomic Force Microscopy and solution analysis with Atomic Absorption Spectroscopy. When the electrolyte contained MPA, the extended potential holding procedure resulted in significant roughening of the electrode with no detectable quantities of Au in the electrolyte. X-ray photoelectron spectroscopy (XPS) analysis of the Au surface revealed an additional species in the Au 4f_7/2 spectrum indicating the presence of an insoluble electrochemically generated Au(I)–MPA species. When the electrolyte contained DMSA, the Au electrode appeared smoother, 56.6 ± 9.6 ppb of Au was detected in the electrolyte and the XPS analysis displayed a single species in the Au 4f_7/2 spectrum indicative of metallic Au after the potential holding procedure. Both observations with MPA and DMSA support the charge transfer resistance to be at least partially related to the corrosion of Au, but also suggest that an electrochemically generated Au–DMSA species is soluble and of potential industrial relevance.     

Multifunctional fiberglass-reinforced PMMA-BaTiO3 structural/dielectric composites

Fiberglass-reinforced polymer composites were investigated for potential use as structural dielectrics in multifunctional capacitors that require simultaneous excellent mechanical properties and good energy storage characteristics. Composites were fabricated employing poly(methyl methacrylate), PMMA, as the structural matrix. While barium titanate (BaTiO₃) nanopowder was added to the composites for its high room temperature dielectric constant, fiberglass was employed to confer high stiffness. A conductive polymer blend of poly (3,4-ethylenedioxythiophene) and polystyrene sulfonate (PEDOT:PSS) was used to coat the BaTiO₃ nanoparticles with the purpose of further elevating the dielectric constant of the resultant PMMA-composites. FTIR spectroscopy, TGA and SEM measurements were conducted to prove the successful coating of BaTiO₃ nanoparticles with the PEDOT:PSS blend. TEM measurements revealed a good dispersion of coated nanoparticles throughout the PMMA matrix. The fiberglass-reinforced-PMMA composites containing neat and coated BaTiO₃ were found to exhibit excellent stiffness. In addition, the use of PEDOT:PSS in conjunction with BaTiO₃ was observed to improve the dielectric constant of the composites. Finally, the dielectric constant of the structural composites was found to vary only slightly with temperature.     

Doping-induced broadening of the hole density-of-states in conducting polymers

The density-of-states distribution in conducting polymers reflects the energy disorder caused by electrostatic and steric interactions resulting from the different environment in which each molecule is placed. In case of p-doping (oxidation), the highest occupied molecular orbital (HOMO) manifold spreads in energy following a distribution as a result of long-range electrostatic (dipolar) interactions with the surrounding disordered host. In this paper the repercussion of the dipolar disorder on electrochemical signals of standard polypyrrole films is explored. The analysis is based on the chemical capacitance variation with the applied potential in experiments performed in quasi-equilibrium conditions. In addition to the Gaussian shape of cyclic voltammograms at low-doping levels, the model is able to qualitatively account for the current plateau usually observed at high oxidation potentials. This approach allows to estimating the dipolar moment associated to the polymer/dopant complex.     

Wet air oxidation in a catalytic membrane reactor: Model and industrial wastewaters in single tubes and multichannel contactors

Recent results on catalytic wet air oxidation applied to a membrane contactor are presented that give new insight following a series of previous publications. Model and industrial effluents are treated in both single tube and multichannel catalytic systems. Characterisation of the catalytic material (solid analyses, electron microscopy, EDS and EPMA) is carried out, in order to determine the catalyst distribution. Catalytic results show performances heavily dependent on the nature of the effluent and the operating conditions, and to a lesser extent on the catalytic membrane characteristics. At 80 °C, an industrial effluent is oxidised at a membrane surface related rate of 3.8 mmol/s/m². This result is achieved using a membrane containing about 0.1 wt.% Pt. This allows a revised and improved technico-economical evaluation of the Watercatox process.     

Aspekte der künstlichen Ernährung bei demenzkranken Patienten in der Geriatrie

Definition of the problem: The discussion of the appropriateness of artificial nutrition in patients with advanced dementia seems to be solved on medical grounds. If it is taken for granted that a solid and valid moral judgement in medical practice rests on actual medical facts, then one needs to consider normative arguments more carefully if it can be shown that the common medical understanding of the connection between advanced dementia and artificial nutrition seems misleading. This includes a critical discussion of recently published empirical studies, which are used to justify the belief that tube feeding is useless for elderly patients in terms of their nutritional state, quality of life, and mortality. Arguments and Conclusion: This paper puts forward a threefold approach: (1) the interdependence of nutritional state and type and grade of dementia is shown, (2) a working model is presented that should avoid the poor outcomes reported in the recent medical literature, and (3) it is argued that the discussion cannot be grounded solely in medical facts because of the limitations of recently published medical evidence. Normative aspects should be given more weight.     

Very low noise mixer at 115 GHz using a Mott diode cooled to 20 K

Measurements on a cooled resistive mixer are reported using a Mott-barrier diode cooled to 20 K, operating at 115 GHz and pumped with a local oscillator power as low as 150 ?W. The mixer noise temperature of 200 K is not only the lowest reported for a resistive mixer above 90 GHz but indicates that some improvement in shot-noise models for resistive mixers is desirable.     

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