Quantifying multiple trace elements in uranium ore concentrates: an interlaboratory comparison

An intercomparison was organized, with six laboratories tasked to quantify sixty-nine impurities in two uranium materials. The main technique employed for analysis was inductively coupled plasma mass spectrometry in combination with matrix-matched external calibration. The results presented highlight the current state-of-the-practice; lessons learned include previously unaccounted polyatomic interferences, issues related to sample dissolution, blank correction and calibration, and the challenge of estimating measurement uncertainties. The exercise yielded consensus values for the two analysed materials, suitable for use as laboratory standards to partially fill a gap in the availability of uranium reference materials characterized for impurities.     

A two-phase computational biomechanics model for successful rehabilitation after hip and knee surgery

Nonlinear Dynamics - We propose a two-phase computational biomechanical model for a successful rehabilitation after hip and/or knee replacement surgery. The first phase, conducted before the...     

A quantitative study of orthokinetic flocculation in suspensions

Colloid and Polymer Science - A theoretical study of orthokinetic flocculation in suspensions is presented. Mathematical derivations suggest that an exponential distribution of non-flocculated...     

Crystal structure determination of 2′-nitro-10-phenylphenothiazine

The structure of the titled compound, 4 , has been solved by x-ray analysis. One of the important structural features of 4 is that the 2′-nitrophenyl group is in the plane bisecting the phenothiazine ring which is in contrast to that of 10-(2′-pyrazyl)phenothiazine of 4′-nitro-10-phenylphenothiazine in which the 10-aryl group is perpendicular to the plane bisecting the phenothiazine ring. The structure of 4 is in agreement with its ¹H and ¹³C nmr data which indicate that resonance interactions between the 2′-nitrophenyl group and the lone pair of electrons on N₁₀ are hindered sterically by the 2′-nitro group.     

Laboratory authorization versus accreditation in transitional economies: case study of Serbia

Many CEE governments are still using various systems of laboratory authorization together with ISO/IEC 17025 laboratory accreditation. It is difficult to understand from the EU prospective, the existence of two parallel laboratory competence verification systems. The basic relations between laboratory accreditation and authorization: independence and succession have been defined. The case study of testing laboratory accreditation versus authorization in Serbia, has been presented and discussed. Relevant requests and procedures for water quality, food and air quality testing laboratory authorization were analysed in detail. Comparative analyses of accreditation and authorization have established: (i) independent relations, (ii) relevant regulation is in collision and barely legal, (iii) authorization is (technically) on the far lower level than accreditation is, and (iv) authorization requests cause high space and personnel costs. It has been concluded that it is not adequate to perform two policies at the same time: one EU oriented—laboratory accreditation, and one non-EU oriented—laboratory authorization. The policy proposal is that all CEE countries should abandon existing laboratory authorization procedures and replace them by accreditation. Proposed goal could be reached in rather a short transition process of 2–3 years.     

Reduction of Pertechnetate by Chemical and Photochemical Approaches and Incorporation of Tc(IV) into Titanium Dioxide

Technetium-99 is a prevalent fission product from nuclear waste. The long half-life (211,000 yr) and environmental mobility of pertechnetate (TcO₄⁻) render Tc particularly challenging to isolate and stabilize. Here we present two approaches for development of potential wasteforms using titanium dioxide, TiO₂. Approach 1 is a low temperature chemical synthesis of TiO₂ doped with Tc(IV) from TcO₄⁻ intended to mimic the Tc waste stream from the UREX family of separations and removes 98.5 % of the Tc, mainly present as edge-shared Tc(IV) pairs. Approach 2 utilizes TiO₂ to photocatalytically reduce TcO₄⁻ to Tc(IV) stabilized on the surface of or within the TiO₂ lattice. The %Tc removed from solution and adsorbed to TiO₂ is pH dependent, with the maximum Tc(IV) adsorbed at pH 3–4 as either TcO₂ or edge-sharing Tc(IV) octahedra. The Tc(IV)-TiO₂ composites materials formed by both approaches are suitable for consolidation into a dense wasteform by Hot Isostatic Pressing (HIPing).     

Investigation of the structure and 13C NMR spectrum of 5-phenylbarbituric acid

Crystals of 5-phenylbarbituric acid, 2 , are monoclinic, space group C2/c. There are 8 molecules in the unit cell of dimensions a = 20.218(3), b = 7.477(1), c, = 12.443(2), β = 111.54° and V = 1749.6(4) ų. Full-matrix least-squares refinement has reached R = 0.039. This is the first barbiturate reported to exist in the enol form in the solid state. There is extensive hydrogen bonding between adjacent molecules which gives rise to very dense crystals. The ¹³C-nmr spectroscopy shows that 2 exists in both enol and keto forms in DMSO solution.