Phase evolution of slag-rich cementitious grouts for immobilisation of nuclear wastes

An updated calcium silicate hydrate (C–S–H) model incorporating aluminium-containing end-members was used for thermodynamic modelling of blended cements using blast-furnace slag and Portland cement (BFS:PC) with ratios of 1:1, 3:1 and 9:1, using GEMSelektor. Selective dissolution and magic angle spinning nuclear magnetic resonance (MAS NMR) studies were performed to determine the degree of hydration (DoH) of the anhydrous material as an input parameter for the modelling work. Both techniques showed similar results for determining the DoH of the BFS within each sample. Characterisation of the hardened cement pastes over 360 days, using X-ray diffraction analysis and MAS NMR, demonstrated that the use of the updated C–S–H model can highlight the effect of different blend ratios and curing ages on the phase assemblages in these cements. Validation using this modelling approach was performed on 20 year old specimens from the literature to highlight its applicability for modelling later-age blended cements

Management practices as risk factors for the presence of bulk milk antibodies to Salmonella, Neospora caninum and Leptospira interrogans serovar hardjo in Irish dairy herds

peer-reviewedA survey of management practices in 309 Irish dairy herds was used to identify risk factors for the presence of antibodies to Salmonella, Neospora caninum and Leptospira interrogans serovar hardjo in extensively managed unvaccinated dairy herds. A previous study documented a herd-level seroprevalence in bulk milk of 49%, 19% and 86% for Salmonella, Neospora caninum and leptospira interrogans serovar hardjo, respectively in the unvaccinated proportion of these 309 herds in 2009. Association analyses in the present study were carried out using multiple logistic regression models. Herds where cattle were purchased or introduced had a greater likelihood of being positive to leptospira interrogans serovar hardjo (P<0.01) and Salmonella (P<0.01). Larger herds had a greater likelihood of recording a positive bulk milk antibody result to leptospira interrogans serovar hardjo (P<0.05). Herds that practiced year round calving were more likely to be positive to Neospora caninum (P<0.05) compared to herds with a spring-calving season, with no difference in risk between herds that practiced split calving compared to herds that practiced spring calving. No association was found between presence of dogs on farms and prevalence of Neospora caninum possibly due to limited access of dogs to infected materials including afterbirths. The information from this study will assist in the design of suitable control programmes for the diseases under investigation in pasture-based livestock systems

Thermodynamic modelling of BFS-PC cements under temperature conditions relevant to the geological disposal of nuclear wastes

Intermediate level waste produced in UK nuclear power generation is encapsulated or immobilised in blended cements comprising blast furnace slag (BFS) and Portland cement (PC), to be emplaced in a proposed geological disposal facility (GDF). The wasteforms are expected to be exposed to temperatures from 35 to 80 °C during the initial 150 years of GDF operation. Thermodynamic modelling is applied here to describe the phase assemblages of hydrated 1:1, 3:1 and 9:1 BFS-PC blends, with the participation of hydrogarnet as an important phase above 60 °C. The chemical composition of the main phase forming in these systems, an aluminium rich calcium silicate hydrate (C-A-S-H), was well described by a solid-solution model with explicit Al incorporation, although the Al/Si ratio was systematically slightly under-predicted. The developed thermodynamic model predicts the correct phase assemblage across varying temperature regimes, making it a valuable tool to assess the effects of temperature on cements

A scalable quantum computer with an ultranarrow optical transition of ultracold neutral atoms in an optical lattice

We propose a new quantum-computing scheme using ultracold neutral ytterbium atoms in an optical lattice. The nuclear Zeeman sublevels define a qubit. This choice avoids the natural phase evolution due to the magnetic dipole interaction between qubits. The Zeeman sublevels with large magnetic moments in the long-lived metastable state are also exploited to address individual atoms and to construct a controlled-multiqubit gate. Estimated parameters required for this scheme show that this proposal is scalable and experimentally feasible.Comment: 6 pages, 6 figure

Mediation of detention trauma via perceived locus of control

Political detention in South Africa has been documented to contain conditions inherently detrimental to psychological health. Reports indicate high levels of stress reponses associated with conditions of solitary confinement, and physical and psychological abuse — particularly in the form of Post-Traumatic Stress Disorder. Amongst the moderating variables that may mediate between detention stress and post-detention trauma is perceived locus of control. In the present study the author aimed to determine post-detention sequelae and the moderating influence of perceived locus of control in this specific context. A Post-Traumatic Stress Disorder scale was combined with an Index of Well-being scale and correlated with a Detention Locus of Control scale to assess mediation significance of experienced ‘traumatization’. Results indicated a positive correlation with those who are internal in their perceived locus of control suffering reduced post-stress sequelae, compared to those who are more externally oriented. Implications and limitations of the study are discussed with specific reference to therapeutic intervention in the clinical context. © 1990, South African Psychological Association and the Psychological Institute of the Republic of South Africa. All rights reserved