A new bomb-combustion system for tritium extraction

Quantitative extraction of tritium from a sample matrix is critical to efficient measurement of the low-energy pure beta emitter. Oxidative pyrolysis using a tube furnace (Pyrolyser) has been adopted as an industry standard approach for the liberation of tritium (Warwick et al. in Anal Chim Acta 676:93–102, 2010) however pyrolysis of organic-rich materials can be problematic. Practically, the mass of organic rich sample combusted is typically limited to <1 g to minimise the possibility of incomplete combustion. This can have an impact on both the limit of detection that can be achieved and how representative the subsample is of the bulk material, particularly in the case of heterogeneous soft waste. Raddec International Ltd (Southampton, UK), in conjunction with GAU-Radioanalytical, has developed a new high-capacity oxygen combustion bomb (the Hyperbaric Oxidiser; HBO₂) to address this challenge. The system is capable of quantitatively combusting samples of 20–30 g under an excess of oxygen, facilitating rapid extraction of total tritium from a wide range sample types.     

Reservoir storage and containment of greenhouse gases, II: Vapour-entry pressures

This paper investigates the role of a nonzero vapour entry pressure on reservoir storage and containment of the greenhouse gas carbon dioxide. Two effects are observed: vapour storage under confining layers, and enhanced lateral spreading of gas under confining layers. Lateral flow of gas under both impermeable and permeable confining layers is solved analytically using Buckley-Leverett assumptions. A full numerical analysis of gas and water transport is also presented, using results from the simulator TOUGH. We consider the injection of CO₂ from a thermal power plant at a rate of 100 kg/s for 10 years, at a depth of 3000 metres. Inclusion of a nonzero vapour entry pressure shows that containment of this gas for at least 5000 years can be expected. The CO₂ is stored predominantly in a high density vapour phase (about 600 kg/m³) under lower permeability confining layers, and also is dissolved in liquid at about 40 kg/m³.     

A Rigorous ODE Solver and Smale's 14th Problem

We present an algorithm for computing rigorous solutions to a large class of ordinary differential equations. The main algorithm is based on a partitioning process and the use of interval arithmetic with directed rounding. As an application, we prove that the Lorenz equations support a strange attractor, as conjectured by Edward Lorenz in 1963. This conjecture was recently listed by Steven Smale as one of several challenging problems for the twenty-first century. We also prove that the attractor is robust, i.e., it persists under small perturbations of the coefficients in the underlying differential equations. Furthermore, the flow of the equations admits a unique SRB measure, whose support coincides with the attractor. The proof is based on a combination of normal form theory and rigorous computations. July 27, 2000. Final version received: June 30, 2001.     

Enclosing all zeros of an analytic function — A rigorous approach

We present a method to find all zeros of an analytic function in a rectangular domain. The approach is based on finding guaranteed enclosures rather than approximations of the zeros. Well-isolated simple zeros are determined fast and with high accuracy. Clusters of zeros can in many cases be distinguished from multiple zeros by applying the argument principle to sufficiently high-order derivatives of the function. We illustrate the proposed method through five examples of varying levels of complexity.     

Transition metal-alkane σ-complexes with oxygen donor co-ligands

A new family of long-lived alkane σ-complexes of the type (L(OEt))Re(CO)(2)(alkane) [alkane = cyclopentane, cyclohexane, pentane; L(OEt) = cyclopentadienyltris(diethylphosphito)cobaltate(III)] has been observed using both IR and NMR spectroscopies and computationally interrogated with DFT methods. The oxygen-rich coordination spheres makes these complexes perhaps more relevant as models for intermediates in metal oxide mediated hydrocarbon transformations than other known alkane σ-complexes.     

Colourimetric Carboxylate Anion Sensors Derived from Viologen‐Based Receptors

A series of tri‐ and tetrapodal viologen‐based anion receptors showing a colourimetric response to carboxylates, such as acetate, have been synthesised. Alteration of the anion binding sites allows for binding site competition within a receptor. This results in a delayed colourimetric response for urea derivatives compared with pyridinium systems because the anions are initially bound to the periphery of the receptor, away from the viologen unit. DFT calculations and experimental measurements allow the colour change to be assigned to an anion–receptor charge‐transfer process, facilitated by the exceptionally low reduction potential of the cationic host compounds. Evidence for electron transfer to give the viologen radical cation is also seen in some cases.     

Harmonic entanglement with second-order nonlinearity

We investigate the second-order nonlinear interaction as a means to generate entanglement between fields of differing wavelengths and show that perfect entanglement can, in principle, be produced between the fundamental and second-harmonic fields in these processes. Neither pure second-harmonic generation nor parametric oscillation optimally produce entanglement; such optimal entanglement is rather produced by an intermediate process.     

Four-wave mixing from Fe3+ spins in sapphire

Fe(3+) ions in sapphire exhibit an electron spin resonance which interacts strongly with high-Q whispering gallery modes at microwave frequencies. We report the first observation of a third-order paramagnetic nonlinear susceptibility in such a resonator at cryogenic temperatures and the first demonstration of four-wave mixing using this parametric nonlinearity. This observation of an all-microwave nonlinearity is an enabling step towards a host of quantum measurement and control applications which utilize spins in solids.     

Rapid scan UV/visible detection in liquid chromatography-application to environmental analysis

Summary The use of a rapid-scan UV/visible, diode-array spectrophotometer for the trace analysis of environmental pollutants is of great importance when qualitative as well as quantitative information is required. This spectrophotometric technique may be used to determine peak purity and identity as well as the concentrations of chromatographically unresolved mixtures. Examples are given of this technique applied to the analysis of some organic compounds found in factory atmospheres.