Portland cement-based grouts used for radioactive waste immobilisation contain a Ca- and Si-rich binder phase, known as calcium-silicate-hydrate (C-S-H). Depending on the blend of cement used, the ...Ca/Si ratio can vary considerably. A range of C-S-H minerals with Ca/Si ratios from 0.6 to 1.6 were synthesised and contacted with aqueous U(VI) at 0.5 mM and 10 mM concentrations. Solid-state
Si MAS-NMR spectroscopy was applied to probe the Si coordination environment in U(VI)-contacted C-S-H minerals and, in conjunction with U L
-edge X-ray absorption spectroscopy analysis, inferences of the fate of U(VI) in these systems were made. At moderate or high Ca/Si ratios, uranophane-type uranyl silicates or Ca-uranates dominated, while at the lowest Ca/Si ratios, the formation of a Ca-bearing uranyl silicate mineral, similar to haiweeite (Ca(UO
)
Si
O
(OH)
·3H
O) or Ca-bearing weeksite (Ca
(UO
)
Si
O
·10H
O) was identified. This study highlights the influence of Ca/Si ratio on uranyl sequestration, of interest in the development of post-closure safety models for U-bearing radioactive waste disposal.
Many scenarios of physics beyond the standard model predict the existence of new gauge singlets, which might be substantially lighter than the weak scale. The experimental constraints on additional ...scalars with masses in the MeV to GeV range could be significantly weakened if they interact predominantly with leptons rather than quarks. At an e+e− collider, such a leptophilic scalar (ϕL) would be produced predominantly through radiation from a τ lepton. We report herein a search for e+e−→τ+τ−ϕL, ϕL→ℓ+ℓ− (ℓ=e, μ) using data collected by the BABAR experiment at SLAC. No significant signal is observed, and we set limits on the ϕL coupling to leptons in the range 0.04<mϕL<7.0 GeV. These bounds significantly improve upon the current constraints, excluding almost entirely the parameter space favored by the observed discrepancy in the muon anomalous magnetic moment below 4 GeV at 90% confidence level.
Objective
To determine whether a policy of offering cffDNA testing to all RhD‐negative women at about 16 weeks’ gestation to avoid anti‐D administration when the fetus is RhD‐negative could be ...implemented successfully in the NHS without additional funding.
Design
Prospectively planned observational service implementation pilot and notes audit.
Setting
Three maternity services in the South West of England.
Population
All RhD‐negative women in a 6‐month period.
Methods
Prospective, intervention, cross‐sectional observational study, using pre‐intervention data as controls.
Main outcome measures
Proportion of suitable women who offered and accepted the test. Accuracy of the cffDNA result as assessed by cord blood group result. Fall in anti‐D doses administered.
Results
529 samples were received; three were unsuitable. The results were reported as RhD‐positive (n = 278), RhD‐negative (n = 185) or inconclusive, treat as positive (n = 63). Cord blood results were available in 502 (95%) and the only incorrect result was one case of a false positive (cffDNA reported as positive, cord blood negative – and so given anti‐D unnecessarily). The notes audit showed that women who declined this service were correctly managed and that anti‐D was not given when the fetus was predicted to be RhD‐negative. The total use of anti‐D doses fell by about 29% which equated to about 35% of RhD‐negative women not receiving anti‐D in their pregnancy unnecessarily.
Conclusions
We recommend this service is extended to all UK NHS services.
A unique set of high-quality downhole shallow subsurface well log data combined with industry standard 3D seismic data from the Alaminos Canyon area has enabled the first detailed description of a ...concentrated gas hydrate accumulation within sand in the Gulf of Mexico. The gas hydrate occurs within very fine grained, immature volcaniclastic sands of the Oligocene Frio sand. Analysis of well data acquired from the Alaminos Canyon Block 818 #1 (“Tigershark”) well shows a total gas hydrate occurrence 13 m thick, with inferred gas hydrate saturation as high as 80% of sediment pore space. Average porosity in the reservoir is estimated from log data at approximately 42%. Permeability in the absence of gas hydrates, as revealed from the analysis of core samples retrieved from the well, ranges from 600 to 1500 millidarcies. The 3-D seismic data reveals a strong reflector consistent with significant increase in acoustic velocities that correlates with the top of the gas-hydrate-bearing sand. This reflector extends across an area of approximately 0.8 km
2 and delineates the minimal probable extent of the gas hydrate accumulation. The base of the inferred gas-hydrate zone also correlates well with a very strong seismic reflector that indicates transition into units of significantly reduced acoustic velocity. Seismic inversion analyses indicate uniformly high gas-hydrate saturations throughout the region where the Frio sand exists within the gas hydrate stability zone. Numerical modeling of the potential production of natural gas from the interpreted accumulation indicates serious challenges for depressurization-based production in settings with strong potential pressure support from extensive underlying aquifers.
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