Turbulent diffusion of a buoyant layer at a wall

Summary When a light fluid is injected at a steady rate at the roof of a tunnel in which there is a turbulent main flow of a heavier fluid, the turbulent diffusion of the light layer may be considerably reduced due to buoyancy. For large Richardson numbers turbulent mixing ceases altogether.The equations of motion and diffusion were solved by introducing an eddy diffusivity which is dependant on the Richardson number. Experiments were made on brine (floor) layers in a water flow, and on methane (roof) layers in an air flow. Results were essentially in agreement with theory.The motion and mixing of the layers depend mainly on the inclination of the tunnel and on a dimensionless combination of main-flow velocity, gravity, relative density difference, volume input rate of layer fluid, and tunnel width. Values of the dimensionless parameter are suggested to overcome the effects of buoyancy on mixing, and to prevent layers from moving up a slope against the main flow.     

Detoxifying CO2 Capture Reclaimer Waste by Anaerobic Digestion

The decrease in toxicity of carbon capture reclaimer monoethanolamine (MEA) waste (MEAw) during anaerobic degradation of such waste together with easily degradable organics was investigated. Samples were collected from a bioreactor at steady state with 86 % organic chemical oxygen demand removal at room temperature, which had been running on MEAw for 2 years. The toxicity of the digester effluents were 126, 42 and 10 times lower than that of the MEAw to the tested freshwater trophic groups of Pseudokirchneriella subcapitata, Daphnia magna and embryos of Danio rerio, respectively. The toxicity of the tested taxonomic groups after anaerobic digestion was mainly attributed to the ammonia generated by the degradation of MEAw.     

Gravitational geometric phase in the presence of torsion

We investigate the relativistic and non-relativistic quantum dynamics of a neutral spin-1/2 particle subject to an external electromagnetic field in the presence of a cosmic dislocation. We analyze the explicit contribution of the torsion in the geometric phase acquired in the dynamics of this neutral spinorial particle. We discuss the influence of the torsion in the relativistic geometric phase. Using the Foldy–Wouthuysen approximation, the non-relativistic quantum dynamics is studied and the influence of the torsion on the Aharonov–Casher and He–McKellar–Wilkens effects are discussed. An erratum to this article can be found at     

Bound states for a Coulomb-type potential induced by the interaction between a moving electric quadrupole moment and a magnetic field

We discuss the arising of bound states solutions of the Schrödinger equation due to the presence of a Coulomb-type potential induced by the interaction between a moving electric quadrupole moment and a magnetic field. Furthermore, we study the influence of the Coulomb-type potential on the harmonic oscillator by showing a quantum effect characterized by the dependence of the angular frequency on the quantum numbers of the system, whose meaning is that not all values of the angular frequency are allowed.     

Torsion and noninertial effects on a nonrelativistic Dirac particle

We investigate torsion and noninertial effects on a spin-1/2$1/2$ quantum particle in the nonrelativistic limit of the Dirac equation. We consider the cosmic dislocation spacetime as a background and show that a rotating system of reference can be used out to distances which depend on the parameter related to the torsion of the defect. Therefore, we analyse torsion effects on the spectrum of energy of a nonrelativistic Dirac particle confined to a hard-wall potential in a Fermi–Walker reference frame.     

On the interaction of the Dirac oscillator with the Aharonov–Casher system in topological defect backgrounds

In this paper, we study the influence of the Aharonov–Casher effect [Y. Aharonov, A. Casher, Phys. Rev. Lett. 53 (1984) 319] on the Dirac oscillator in three different scenarios of general relativity: the Minkowski spacetime, the cosmic string spacetime and the cosmic dislocation spacetime. In this way, we solve the Dirac equation and obtain the energy levels for bound states and the Dirac spinors for positive-energy solutions. We show that the relativistic energy levels depend on the Aharonov–Casher geometric phase. We also discuss the influence of curvature and torsion on the relativistic energy levels and the Dirac spinors due to the topology of the cosmic string and cosmic dislocation spacetimes.     

1,3‐Dihydro‐2H‐imidazo[4,5‐c]pyridin‐2‐one

A facile acid catalysed cyclisation method for the preparation of the cyclic urea 2H‐imidazo[4,5‐c]pyridin‐2‐one ( 2 ) in > 95 % yield is reported. The biologically active compound 2 can be obtained by heating (3‐amino‐4‐pyridinyl)‐carbamic acid methyl, ethyl or tert‐butyl esters ( 1a‐c ) in sulfuric acid (0.1 %) or in aqueous HBF₄ (3.5 equivalents) for 10 min. ‐ 3 hrs at 90 °C. The corresponding microwave‐promoted (MW) reactions afforded the pure product 2 within few minutes. The 6‐butylamino‐substituted analogue ( 2a ) was correspondingly obtained by MW irradiation in 99 % yield by cyclisation of 2‐(butylamino)‐5‐amino‐4‐pyridylcarbamic acid isopropyl ester ( 1d ). Quantitative precipitation of product 2 was obtained by pH adjustment. The process represents a solvent‐free, “green” method for the preparation of 2 .     

On the harmonic-type and linear-type confinement of a relativistic scalar particle yielded by Lorentz symmetry breaking effects

Based on the Standard Model Extension, we investigate relativistic quantum effects on a scalar particle in backgrounds of the Lorentz symmetry violation defined by a tensor field. We show that harmonic-type and linear-type confining potentials can stem from Lorentz symmetry breaking effects, and thus, relativistic bound state solutions can be achieved. We first analyse a possible scenario of the violation of the Lorentz symmetry that gives rise to a harmonic-type potential. In the following, we analyse another possible scenario of the breaking of the Lorentz symmetry that induces both harmonic-type and linear-type confining potentials. In this second case, we also show that not all values of the parameter associated with the intensity of the electric field are permitted in the search for polynomial solutions to the radial equation, where the possible values of this parameter are determined by the quantum numbers of the system and the parameters associated with the violation of the Lorentz symmetry.