Edge plane sites on highly ordered pyrolytic graphite as templates for making palladium nanowires via electrochemical decoration

An approach for the fabrication of metal nanowires is presented. Palladium wires with diameters less than 50 nm were produced by electrochemical decoration of step edge sites on the surface of highly ordered pyrolytic graphite via the following three steps. First an electrochemical activation step was used to oxidize the edge plane sites on highly ordered pyrolytic graphite surfaces in 0.5 M Na(2)SO(4). Second, a potential cycling step in a 1 mM PdCl(2) solution in 0.1 M H(2)SO(4) was used to form palladium oxide (s) and/or complexes of Pd on the step edges. Third, Pd nanowires were formed by electroreduction after transfer of the graphite to 0.1 M H(2)SO(4). The resulting wires showed a high degree of uniformity. A merit of this approach is that it allowed metal nanowires to be fabricated without the simultaneous formation of nanoparticles on the basal plane terraces, in contrast to other studies of this type. The mesoscopic palladium wires are shown to be useful for the electrochemical sensing of hydrazine.     

Kinetics and thermodynamics of the reaction of deoxyhemerythrin with nitric oxide

Deoxyhemerythrin reacts with NO to form a 1:1 adduct shown spectrophotometrically. The kinetics of the formation have been studied directly by stopped-flow measurements at four different temperatures (0.0-23.6 degrees C). The kinetics of the dissociation have been studied, also by stopped-flow techniques, at five different temperatures (4.0-35.1 degrees C) using three different scavengers [Fe(II)(edta)2-, O2 and sperm whale deoxymyoglobin], which gave similar values. For the formation kf = (4.2 +/- 0.2) x 10(6) M-1 s-1, delta Hf not equal = 44.3 +/- 2.3 kJ mol-1, delta Sf not equal to = 30 +/- 8 J mol-1 K-1 and for the dissociation kd = 0.84 +/- 0.02 s-1, delta Hd not equal to 95.6 +/- 2.1 kJ mol-1 delta Sd not equal to = 74 +/- 7 J mol-1 K-1 (25 degrees C, I = 0.2 M and pH 7-8.1). From the kinetic data the thermodynamic data for the formation of HrNO were calculated: Kf = (5.0 +/- 0.3) x 10(6) M-1, delta H = -51.3 +/- 3.1 kJ mol-1 and delta S = -44 +/- 11 J mol-1 K-1 (25 degrees C). The kinetic data suggest that NO occupies the same iron(II) site in deoxyhemerythrin as oxygen does. The equilibrium constant for the formation of Fe(II)(edta)(NO)2- has been redetermined: K1 = (1.45 +/- 0.07) x 10(7) M-1, delta H = -77.5 +/- 1.5 kJ and mol-1 and delta S = -123.5 J mol-1 K-1 (25 degrees C).     

Graphite powder and multiwalled carbon nanotubes chemically modified with 4-nitrobenzylamine.

We demonstrate that graphite powder and multiwalled carbon nanotubes (MWCNTs) can be derivatised by 4-nitrobenzylamine (4-NBA) simply by stirring the graphite powder or MWCNTs in a solution of acetonitrile containing 10 mM 4-NBA. We propose that 4-NBA partially intercalates at localised edge-plane or edge-plane-like defect sites and this hypothesis with a range of experimental data provided by electrochemistry in both aqueous and nonaqueous media, electron microscopy and X-ray powder diffraction.     

A variational problem in Hilbert space

Let? be a Hilbert space over the field of complex numbers, with inner product (g,h). Letf be a fixed element in?, and letH be a compact, self-adjoint linear operator on?. We find the maximum value ofQ _f (u)=|(f,u)|² in the classU of elementsu in? for which (u,u)=1, (u, Hu)=0.     

A field study to assess the effects of wearing hearing protectors on the perception of warning sounds in an industrial environment

A field study has been performed which assessed the effectiveness of two warning sounds under realistic factory conditions. The thirty subjects were press operators who were involved in their regular work activities during the course of the experiment. The noise levels at their work stations were in the range 85 to 95 dB(A). The warning sound, plus four other irrelevant sounds, each at one of five different intensities, were presented via a loudspeaker in random order and at random time intervals (mean inter-stimulus interval, 30 s; range, 10 to 50 s). The influence of the factors hearing level and age of the subjects and use of hearing protection were investigated.The results showed significant differences between the intentional and incidental warning sounds investigated. Whilst the perception of the intentional horn warning sound was unaffected by the hearing sensitivity of the subjects and the wearing of hearing protectors, these two factors had a significant effect on the perception, as a warning, of the clinking sound of metal components. Subjects classified as having a substantial hearing loss perceived, on average, 18 percent fewer clinking sounds than those subjects with normal hearing or a mild hearing loss and, when wearing hearing protectors, the subjects overall perceived, on average, 9 percent fewer clinks. It is of note that the results of the field study differ from those of earlier laboratory-based experiments in finding that the distinctive intentional warning sound was not entirely reliable as a warning, even at levels substantially above its masked threshold, and in observing more than double the adverse effect of wearing hearing protection.