In vitro dissolution study of uranium dioxide and uranium ore with different particle sizes in simulated lung fluid

Inhalation is one of the most important routes for aerosol particles of uranium compounds to enter the body. The main step for uranium to be available for blood circulation and for interaction with bio-molecules is the dissolution of the particles. Particle size effects on dissolution of uranium dioxide and uranium ore were studied in simulated lung fluid using the “batch/filter” method. Samples were fractionated to ten size ranges from <0.43 μm to >10 μm by cascade impaction prior to dissolution experiments. Dependence of dissolution kinetics on particle size and on the amount of uranium trioxide contained in the particles was observed.     

A measurement of the beam asymmetry parameter Σ for neutral pion photoproduction in the energy range 1.2–2.8 GeV

An experiment has been completed at the Daresbury synchrotron to measure the asymmetry in the photoproduction cross section of neutral pions on hydrogen, for photons polarised normal to and in the production plane. The source of polarised photons was coherent bremsstrahlung of electrons traversing the lattice structure of diamond and the polarisation P of the γ beam was calculated from the measured intensity of the coherent spike. The asymmetry parameter Σ, defined as Σ = (σ⊥ ? σ|)/(σ⊥ + σ|) where σ⊥(σ|) are the cross sections for photons polarised perpendicular (parallel) to the production plane, has been measured over a range of photon energies from 1.2 to 2.8 GeV and over a range of ?t (the square of the four-momentum transfer) from 0.13 (GeV/c)² to 1.4 (GeV/c)². A marked energy variation in the value of Σ is found over the energy region 1.6–1.8 GeV.     

Interaction of rhodium(i) bisphosphine complexes with semicarbazones to give orthometallated rhodium(iii) complexes

Interaction of the cis-[Rh(PR₃)₂(Solv)₂]PF₆ complexes (R = Ar or R₃ = Ph₂Me, Solv — solvent) under Ar with semicarbazones bearing a phenyl group on the imine-C atom gives the rhodium(iii)-hydrido-bis(phosphine)-orthometallated semicarbazone species [RhH(PR₃)₂{(o-C₆H₄(R")C=N—N(H)CONH₂}]PF₆ (R" = Me or Et), which are characterized generally by elemental analysis, ³¹P{¹H} and ¹H NMR spectroscopy, and mass-spectrometry. The PPh₃-containing complex with R" = Me, structurally characterized by X-ray analysis, reveals coordination of the semicarbazone by the ortho-C atom, the imine-N atom, and the amide-carbonyl group. For a semicarbazone containing no Ph group, the rhodium(i) complex [Rh(PR₃)₂(Et(Me)C=N—N(H)CONH₂)]PF₆, containing the ²-semicarbazone bonded via the imine-N and carbonyl, is formed. Attempts to hydrogenate the C=N moiety in the complexes or to catalytically hydrogenate the semicarbazones were unsuccessful.     

The polarised beam asymmetry in photoproduction of eta mesons from protons at 2.5 GeV and 3.0 GeV

Measurements of the polarised beam asymmetry parameter Σ for eta photoproduction from protons, have been carried out at incident energies of 2.5 GeV and 3.0 GeV, and for various t-values between ?0.2 (GeV/c)² and ?1.2 (GeV/c)². The values of Σ are close to +1 for values of |t| less than 0.7 (GeV/c)², showing that there can be little contribution from unnatural parity exchange in any Regge exchange model of the process, in disagreement with present theories. Differential cross sections for the process werre also measured, and are consistent with those from other experiments.     

Optimal Investment by the Principal in Order to Increase the Probability of Favourable States of Nature in the Principal-Agent Model with Moral Hazard

In this paper we analyse the single agent, principal-agent model with moral hazard. This model differs from other models that have been formulated in that in this model the principal is allowed to make an investment that increases the probability of higher levels of output. The principal must take into account the agent's reaction to the investment in making the investment decision. We also show that conventional wisdom about the relationship between compensation and uncertainty, and the optimal level of investment may only hold under restrictive assumptions when the principal is allowed to invest.     

Tax-Adjusted Replacement Models

The 1984 UK Finance Act introduced changes in tax legislation with consequences for both capital and revenue expenditure on plant. The one- and two-cycle rent models for capital equipment replacement and the infinite-cycle discounted-cost model are extended here to incorporate the new tax features. A specific replacement problem is used as the basis of an analyis of the sensitivity of the optimal replacement period to parameters. Whilst all these models are consistently insensitive to the new tax legislation, there is no consistency across models with respect to which parameters dominate choice of optimal replacement period.     

An Operational Research Approach to Planned Maintenance: Modelling P.M. for a Vehicle Fleet

A methodology is advanced for modelling the problem of planned preventive maintenance, thereby relating plant performance to maintenance activity. Ideas are discussed and developed within the context of a P.M. system for the maintenance of a vehicle fleet. Three specific questions are addressed: first, the omission of any desirable activities from the P.M. schedule, secondly, the presence of redundant items in the schedule, and thirdly, the consequences of different frequencies of application of the P.M. schedule. A fleet model is obtained relating the P.M. period to measures such as proportion of breakdown repairs and the cost per vehicle year.     

An improved cell for in-situ electrochemical ESR

An improved cell for simultaneous electrochemical ESR based on a coaxial cylindrical cavity is described and shown to have high sensitivity whilst behaving as a satisfactory hydrodynamic electrode as evidenced by Tafel analysis, by Levich analysis and comparison with theory for the dependence of the ESR signal on electrode currents and electrolyte flow rate.