Kinetics of dissolution of β-uranium trioxide in acid and carbonate solutions

The kinetics of dissolution of β-UO3 in acid and carbonate solutions have been studied as functions of stirring rate, hydrogen-ion concentration, carbonate concentration, various other cations and anions in solution, and temperature. The dissolution rates are: (i) independent of stirring rate, (ii) dependent on the 0.5 order in [H+] in acid solutrons and a substantially lower order in carbonate solutions; (iii) inhibited by the presence of cations in solution in the order Mg2+ > Li+ > Na+ > [NH4]+ > K+[gt-or-equal] Cs+ in acid solutions and Na+ > [NH4]+ > Cs+[gt-or-equal] K+ in carbonate solutions, the relative effects of the cations in the acid and carbonate solutions being very similar; (iv) increased by sulphate but unaffected by chloride, nitrate, and perchlorate ions in acid solutions; and (v) characterised by activation energies of ca. 12 kcal mol–1 in acid solutions and 15 kcal mol–1 in carbonate solutions. The observed kinetic data have been rationalised in terms of a charge-transfer (c.t.) mechanism, in which the transfer of charged complexes of the uranyl and oxide ions of the β-UO3 lattice across the electrochemical-potential barrier at the solid–solution phase boundary is the rate determining step during the dissolution reaction. In HCl, HClO4, and HNO3 the c.t. species are the uranyl and protonated oxide ions of the lattice, while in H2SO4 sulphatouranate complexes are also involved. In carbonate solution the dicarbonatouranate ion and the protonated oxide ion are the c.t. species. The β-UO3 dissolution reactions are interesting examples of c.t. kinetics since the oxide anions and uranyl cations of the β-UO3 lattice form complexes with the cations and anions in the solutions in the process of dissolution and these complex-formation reactions are mirrored in the rate expressions for dissolution

A Handheld Texel Camera for Acquiring Near-Instantaneous 3D Images

A Texel camera is a device which synchronously captures depth information via a ladar and digital imagery of the same scene. The ladar and digital camera are co-boresighted to eliminate parallax. This configuration fuses the ladar data to the digital image at the pixel level, eliminating complex post-processing to register the datasets. This paper describes a handheld version of a Texel Camera which can be used to create near-instantaneous 3D imagery. The hardware configuration of the Texel Camera, issues and method associated with ladar/camera calibration, and representative imagery are presented

Real-Time Image Analysis of Living Cellular-Biology Measurements of Intelligent Chemistry

This paper reports on the Pacific Northwest National Laboratory (PNNL) DOE Initiative in Image Science and Technology (ISAT) research, which is developing algorithms and software tool sets for remote sensing and biological applications. In particular, the PNNL ISAT work is applying these research results to the automated analysis of real-time cellular biology imagery to assist the biologist in determining the correct data collection region for the current state of a conglomerate of living cells in three-dimensional motion. The real-time computation of the typical 120 MB/sec multi-spectral data sets is executed in a Field Programmable Gate Array (FPGA) technology, which has very high processing rates due to large-scale parallelism. The outcome of this artificial vision work will allow the biologist to work with imagery as a creditable set of dye-tagged chemistry measurements in formats for individual cell tracking through regional feature extraction, and animation visualization through individual object isolation/characterization of the microscopy imagery

Spirituality and attitudes towards nature in the Pacific Islands: insights for enabling climate - change adaptation

A sample of 1226 students at the University of the South Pacific, the premier tertiary institution in the Pacific Islands, answered a range of questions intended to understand future island decision-makers’ attitudes towards Nature and concern about climate change. Questions asking about church attendance show that the vast majority of participants have spiritual values that explain their feelings of connectedness to Nature which in turn may account for high levels of pessimism about the current state of the global/Pacific environment. Concern about climate change as a future livelihood stressor in the Pacific region is ubiquitous at both societal and personal levels. While participants exhibited a degree of understanding matching objective rankings about the vulnerability of their home islands/countries, a spatial optimism bias was evident in which ‘other places’ were invariably regarded as ‘worse’. Through their views on climate change concern, respondents also favoured a psychological distancing of environmental risk in which ‘other places’ were perceived as more exposed than familiar ones. Influence from spirituality is implicated in both findings. Most interventions intended to reduce exposure to environmental risk and to enable effective and sustainable adaptation to climate change in the Pacific Islands region have failed to acknowledge influences on decision making of spirituality and connectedness to Nature. Messages that stress environmental conservation and stewardship, particularly if communicated within familiar and respected religious contexts, are likely to be more successful than secular ones

Nonclassical statistics of intracavity coupled χ(2)\chi^{(2)} waveguides: the quantum optical dimer

A model is proposed where two $\chi^{(2)}$ nonlinear waveguides are contained in a cavity suited for second-harmonic generation. The evanescent wave coupling between the waveguides is considered as weak, and the interplay between this coupling and the nonlinear interaction within the waveguides gives rise to quantum violations of the classical limit. These violations are particularly strong when two instabilities are competing, where twin-beam behavior is found as almost complete noise suppression in the difference of the fundamental intensities. Moreover, close to bistable transitions perfect twin-beam correlations are seen in the sum of the fundamental intensities, and also the self-pulsing instability as well as the transition from symmetric to asymmetric states display nonclassical twin-beam correlations of both fundamental and second-harmonic intensities. The results are based on the full quantum Langevin equations derived from the Hamiltonian and including cavity damping effects. The intensity correlations of the output fields are calculated semi-analytically using a linearized version of the Langevin equations derived through the positive-P representation. Confirmation of the analytical results are obtained by numerical simulations of the nonlinear Langevin equations derived using the truncated Wigner representation.Comment: 15 pages, 8 figures, submitted to Phys. Rev.

Isogeometric Boundary-Element Analysis for the Wave-Resistance Problem using T-splines

In this paper we couple collocated Boundary Element Methods (BEM) with unstructured analysis suitable T-spline surfaces for solving a linear Boundary Integral Equation (BIE) arising in the context of a ship-hydrodynamic problem, namely the so-called Neumann-Kelvin problem, following the formulation by Brard (1972) [1] and Baar & Price (1988) [2]. The local-refinement capabilities of the adopted T-spline bases, which are used for representing both the geometry of the hull and approximating the solution of the associated BIE, in accordance with the Isogeometric concept proposed by Hughes et al. (2005) [3], lead to a solver that achieves the same error level for many fewer degrees of freedom as compared with the corresponding NURBS-based Isogeometric-BEM solver recently developed in Belibassakis et al. (2013) [4]. In this connection, this paper makes a step towards integrating modern CAD representations for ship-hulls with hydrodynamic solvers of improved accuracy and efficiency, which is a prerequisite for building efficient ship-hull optimizers

Unitary designs and codes

A unitary design is a collection of unitary matrices that approximate the entire unitary group, much like a spherical design approximates the entire unit sphere. In this paper, we use irreducible representations of the unitary group to find a general lower bound on the size of a unitary t-design in U(d), for any d and t. We also introduce the notion of a unitary code - a subset of U(d) in which the trace inner product of any pair of matrices is restricted to only a small number of distinct values - and give an upper bound for the size of a code of degree s in U(d) for any d and s. These bounds can be strengthened when the particular inner product values that occur in the code or design are known. Finally, we describe some constructions of designs: we give an upper bound on the size of the smallest weighted unitary t-design in U(d), and we catalogue some t-designs that arise from finite groups.Comment: 25 pages, no figure

A cohort study of post-weaning multisystemic wasting syndrome and PCV2 in 178 pigs from birth to 14 weeks on a single farm in England

Our hypothesis was that pigs that develop post-weaning multisystemic wasting syndrome (PMWS) are detectable from an early age with signs of weight loss and other clinical and serological abnormalities. Therefore, the objective of this study was to investigate the temporally varying and fixed events linked with the clinical incidence of PMWS by comparing affected and unaffected pigs in a cohort of 178 male piglets. Piglets were enrolled at birth and examined each week. Samples of blood were collected at regular intervals. The exposures measured were porcine circovirus type 2 (PCV2) antibody titres in all 178 and PCV2 antigen in a subset of 75 piglets. We also observed piglet health and measured their weight, and a post-mortem examination was performed by an external laboratory on all pigs between 6 and 14 weeks of age that died. From the cohort, 14 (8%) pigs died from PMWS and 4% from other causes. A further 37 pigs between 6 and 14 weeks of age died from PMWS (30) and ileitis and other causes (7). PMWS was only apparent in pigs from 1 to 2 weeks before death when they wasted rapidly. There were no other characteristic clinical signs and no obvious gross clinical lesions post-mortem. There was no strong link with PCV2 antibody throughout life but PCV2 antigen level was higher from 4 to 6 weeks of age in pigs that died from PMWS compared with pigs that died from other causes

A terminal assessment of stages theory : introducing a dynamic states approach to entrepreneurship

Stages of Growth models were the most frequent theoretical approach to understanding entrepreneurial business growth from 1962 to 2006; they built on the growth imperative and developmental models of that time. An analysis of the universe of such models (N=104) published in the management literature shows no consensus on basic constructs of the approach, nor is there any empirical confirmations of stages theory. However, by changing two propositions of the stages models, a new dynamic states approach is derived. The dynamic states approach has far greater explanatory power than its precursor, and is compatible with leading edge research in entrepreneurship