27 research outputs found
Risk factors for vaginal fistula symptoms in Sub-Saharan Africa: a pooled analysis of national household survey data
Sarcoptes scabiei infestation does not alter the stability of ectoparasite communities
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Single-dose BNT162b2 vaccine protects against asymptomatic SARS-CoV-2 infection
The BNT162b2 mRNA COVID-19 vaccine (Pfizer-BioNTech) is being utilised internationally for mass COVID-19 vaccination. Evidence of single-dose protection against symptomatic disease has encouraged some countries to opt for delayed booster doses of BNT162b2, but the effect of this strategy on rates of asymptomatic SARS-CoV-2 infection remains unknown. We previously demonstrated frequent pauci- and asymptomatic SARS-CoV-2 infection amongst healthcare workers (HCWs) during the UK’s first wave of the COVID-19 pandemic, using a comprehensive PCR-based HCW screening programme (Rivett et al., 2020; Jones et al., 2020). Here, we evaluate the effect of first-dose BNT162b2 vaccination on test positivity rates and find a fourfold reduction in asymptomatic infection amongst HCWs ≥12 days post-vaccination. These data provide real-world evidence of short-term protection against asymptomatic SARS-CoV-2 infection following a single dose of BNT162b2 vaccine, suggesting that mass first-dose vaccination will reduce SARS-CoV-2 transmission, as well as the burden of COVID-19 disease
INFLUENCE OF NATURAL AND SYNTHETIC ORGANIC LIGANDS ON THE STABILITY AND MOBILITY OF REDUCED TC(IV)
The primary objectives were (1) to quantify the interactions of organic ligands with Tc(IV) through the generation of thermodynamic (complexation) and kinetic parameters needed to assess and predict the mobility of reduced Tc(IV) at DOE contaminated sites; and (2) to determine the impact of organic ligands on the mobility and fate of reduced Tc(IV) under field geochemical conditions
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Chemical Trends in Solid Alkali Pertechnetates.
Insight into the solid-state chemistry of pure technetium-99 (99Tc) oxides is required in the development of a robust immobilization and disposal system for nuclear waste stemming from the radiopharmaceutical industry, from the production of nuclear weapons, and from spent nuclear fuel. However, because of its radiotoxicity and the subsequent requirement of special facilities and handling procedures for research, only a few studies have been completed, many of which are over 20 years old. In this study, we report the synthesis of pure alkali pertechnetates (sodium, potassium, rubidium, and cesium) and analysis of these compounds by Raman spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), solid-state nuclear magnetic resonance (static and magic angle spinning), and neutron diffraction. The structures and spectral signatures of these compounds will aid in refining the understanding of 99Tc incorporation into and release from nuclear waste glasses. NaTcO4 shows aspects of the relatively higher electronegativity of the Na atom, resulting in large distortions of the pertechnetate tetrahedron and deshielding of the 99Tc nucleus relative to the aqueous TcO4-. At the other extreme, the large Cs and Rb atoms interact only weakly with the pertechnetate, have closer to perfect tetrahedral symmetry at the Tc atom, and have very similar vibrational spectra, even though the crystal structure of CsTcO4 is orthorhombic while that of RbTcO4 is tetragonal. Further trends are observed in the cell volume and quadrupolar coupling constant
Chemical Trends in Solid Alkali Pertechnetates
Insight into the solid-state chemistry of pure technetium-99 (99Tc) oxides is required in the development of a robust immobilization and disposal system for nuclear waste stemming from the radiopharmaceutical industry, from the production of nuclear weapons, and from spent nuclear fuel. However, because of its radiotoxicity and the subsequent requirement of special facilities and handling procedures for research, only a few studies have been completed, many of which are over 20 years old. In this study, we report the synthesis of pure alkali pertechnetates (sodium, potassium, rubidium, and cesium) and analysis of these compounds by Raman spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), solid-state nuclear magnetic resonance (static and magic angle spinning), and neutron diffraction. The structures and spectral signatures of these compounds will aid in refining the understanding of 99Tc incorporation into and release from nuclear waste glasses. NaTcO4 shows aspects of the relatively higher electronegativity of the Na atom, resulting in large distortions of the pertechnetate tetrahedron and deshielding of the 99Tc nucleus relative to the aqueous TcO4 –. At the other extreme, the large Cs and Rb atoms interact only weakly with the pertechnetate, have closer to perfect tetrahedral symmetry at the Tc atom, and have very similar vibrational spectra, even though the crystal structure of CsTcO4 is orthorhombic while that of RbTcO4 is tetragonal. Further trends are observed in the cell volume and quadrupolar coupling constant
Integrated Computational and Experimental Protocol for Understanding Rh(III) Speciation in Hydrochloric and Nitric Acid Solutions
Platinum
group metals (PGMs), including rhodium, generated by the fission of <sup>235</sup>U are present in significant quantities within spent nuclear
fuel located on power generation sites in the United States, the amount
of which is expected to exceed natural reserves by 2030. Yet, spent
fuel raffinates are highly acidic media that may result in complex
speciation of the PGM. This work provides an understanding of Rh(III)
speciation up to 9 M HCl and HNO<sub>3</sub>, and utilizes a combination
of ultraviolet–visible (UV-vis) and capillary zone electrophoresis
data, along with computationally predicted thermochemistry and simulated
UV-vis spectra to approximate the relative concentrations of potential
species in solution as a function of acid concentration. One Rh(III)
species, [Rh(NO<sub>3</sub>)<sub>3</sub>], is observed under all conditions
in HNO<sub>3</sub> and for Rh(III) concentrations smaller than 10<sup>–3</sup> M. In contrast, a variety of chloridated Rh(III)
species may exist simultaneously in a HCl medium. The species [RhCl<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]<sup>+</sup> and [RhCl<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub>] are observed in HCl solutions of concentrations
ranging from 0 to 1 M; the species [RhCl<sub>4</sub>(H<sub>2</sub>O)<sub>2</sub>]<sup>−</sup>, [RhCl<sub>5</sub>(H<sub>2</sub>O)]<sup>2–</sup>, and [Rh<sub>2</sub>Cl<sub>9</sub>]<sup>3–</sup> are observed between 2 and 9 M HCl
Synthesis and Crystal Structures of Volatile Neptunium(IV) β‑Diketonates
Production
of certified reference materials in support of domestic nuclear forensics
programs require volatile precursors for introduction into electromagnetic
isotopic separation instruments. β-Diketone chelates of tetravalent
actinides are known for their high volatility, but previously developed
synthetic approaches require starting material (NpCl<sub>4</sub>)
that is prohibitively difficult and hazardous to prepare. An alternative
strategy was developed here that uses controlled potential electrolysis
to reduce neptunium to the tetravalent state in submolar concentrations
of hydrochloric acid. Four different β-diketone ligands of varying
degrees of fluorination were reacted with an aqueous solution of Np<sup>4+</sup>. Products of this reaction were characterized via X-ray
diffraction and infrared spectroscopy, and were found to be neutral
8-coordinate complexes that adopt square antiprismatic crystal geometry.
Synthesis of Np β-diketonates by this approach circumvents the
necessity of using NpCl<sub>4</sub> in tetravalent Np coordination
compound synthesis. The volatility of the complexes was assessed using
thermogravimetric analysis, where the temperature of sublimation was
determined to be in the range of 180° to 205 °C. The extent
of fluorination did not appreciably alter the sublimation temperature
of the complex. Thermal decomposition of these compounds was not observed
during sublimation. High volatility and thermal stability of Np β-diketonates
make them ideal candidates for gaseous introduction into isotopic
separation instruments
Batch Comparisons of Sr and Ba Retention and Capacities on AnaLig® Sr-01 and Eichrom Sr Resins
Association of mutations in FLNA with craniosynostosis
Mutations of FLNA, an X-linked gene that encodes the cytoskeletal protein filamin A, cause diverse and distinct phenotypes including periventricular nodular heterotopia and otopalatodigital spectrum disorders (OPDS). Craniofacial abnormalities associated with OPDS include supraorbital hyperostosis, down-slanting palpebral fissures and micrognathia; craniosynostosis was previously described in association with FLNA mutations in two individual case reports. Here we present four further OPDS subjects who have pathological FLNA variants and craniosynostosis, supporting a causal link. Together with the previously reported patients, frontometaphyseal dysplasia was the most common clinical diagnosis (four of six cases overall); five patients had multiple suture synostosis with the sagittal suture being the most frequently involved (also five patients). No genotype–phenotype correlation was evident in the distribution of FLNA mutations. This report highlights the need to consider a filaminopathy in the differential diagnosis of craniosynostosis, especially in the presence of atypical cranial or skeletal features