159,955 research outputs found

    Pyrite oxidation under initially neutral pH conditions and in the presence of Acidithiobacillus ferrooxidans and micromolar hydrogen peroxide

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    Hydrogen peroxide (H2O2) at a micromolar level played a role in the microbial surface oxidation of pyrite crystals under initially neutral pH. When the mineral-bacteria system was cyclically exposed to 50 μM H2O2, the colonization of Acidithiobacillus ferrooxidans onto the mineral surface was markedly enhanced, as compared to the control(no added H2O2). This can be attributed to the effects of H2O2 on increasing the roughness of the mineral surfaces, as well as the acidity and Fe2+ concentration at the mineral-solution interfaces. All of these effects tended to create more favourable nanoto micro-scale environments in the mineral surfaces for the cell adsorption. However, higher H2O2 levels inhibited the attachment of cells onto the mineral surfaces, possibly due to the oxidative stress in the bacteria when they approached the mineral surfaces where high levels of free radicals are present as a result of Fenton-like reactions. The more aggressive nature of H2O2 as an oxidant caused marked surface flaking of the mineral surface. The XPS results suggest that H2O2 accelerated the oxidation of pyrite-S and consequently facilitated the overall corrosion cycle of pyrite surfaces. This was accompanied by pH drop in the solution in contact with the pyrite cubes

    Projecting the voice : audience responses to ICT-mediated contemporary opera

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    This paper examines how audiences experience live opera performance and the behaviours they exhibit during live-streaming of the performance. It aims to contribute to our understanding of how audiences, who increasingly inhabit an environment saturated with digital media, respond to contemporary opera performance. Based on a comparative study of audience experiences and behaviours during a live opera performance and the streamed opera screening, we investigate whether digital mediation affects audience appreciation, and whether streaming live opera means the same thing to an audience as the unmediated performance. We firstly outline the conception, design and performance of a contemporary opera and its simultaneous streaming to nearby digital screens. Then, we report the evaluation of the project as measured by a mix of qualitative and quantitative methods during the rehearsals, the live performance and the screening. As one of the few social studies of contemporary classical music in Britain, our study of opera audience behaviours sheds light on the challenges and opportunities afforded by digital technologies for opera companies. Understanding how audiences appreciate digital operas offers practical advice on how theatres and opera companies could respond to new forms of digital activities

    A sharp stability criterion for the Vlasov-Maxwell system

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    We consider the linear stability problem for a 3D cylindrically symmetric equilibrium of the relativistic Vlasov-Maxwell system that describes a collisionless plasma. For an equilibrium whose distribution function decreases monotonically with the particle energy, we obtained a linear stability criterion in our previous paper. Here we prove that this criterion is sharp; that is, there would otherwise be an exponentially growing solution to the linearized system. Therefore for the class of symmetric Vlasov-Maxwell equilibria, we establish an energy principle for linear stability. We also treat the considerably simpler periodic 1.5D case. The new formulation introduced here is applicable as well to the nonrelativistic case, to other symmetries, and to general equilibria

    Crumpling wires in two dimensions

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    An energy-minimal simulation is proposed to study the patterns and mechanical properties of elastically crumpled wires in two dimensions. We varied the bending rigidity and stretching modulus to measure the energy allocation, size-mass exponent, and the stiffness exponent. The mass exponent is shown to be universal at value DM=1.33D_{M}=1.33. We also found that the stiffness exponent α=0.25\alpha =-0.25 is universal, but varies with the plasticity parameters ss and θp\theta_{p}. These numerical findings agree excellently with the experimental results