Preface

Wenk, Hans‐Rudolf; Bulakh, Andrei

doi:10.1017/9781316226889.001

Cited by 4 publications

(21 citation statements)

References 227 publications

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“…Eight oxygen atoms coordinate the calcium site in zirconolite, but the calcium site in perovskite is larger and coordinated by 12 oxygen atoms [19]. Hence, calcium within perovskite undergoes extensive isomorphous substitution with uranium, thorium and REEs [20]. Perovskite is commonly formed as a side-product in the synthesis of zirconolite and other titanate ceramics [14,21] and is an intentional phase in Synroc C, to host Sr-90.…”

Section: Sem Edxmentioning

confidence: 99%

Chemical Stability of Zirconolite for Proliferation Resistance under Conditions Typically Required for the Leaching of Highly Refractory Uranium Minerals

Nikoloski

Gilligan

Squire

et al. 2019

Metals

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In this study, synthetic zirconolite samples with a target composition Ca0.75Ce0.25ZrTi2O7, prepared using two different methods, were used to study the stability of zirconolite for nuclear waste immobilisation. Particular focus was on plutonium, with cerium used as a substitute. The testing of destabilisation was conducted under conditions previously applied to other highly refractory uranium minerals that have been considered for safe storage of nuclear waste, brannerite and betafite. Acid (HCl, H2SO4) leaching for up to 5 h and alkaline (NaHCO₃, Na2CO3) leaching for up to 24 h was done to enable comparison with brannerite leached under the same conditions. Ferric ion was added as an oxidant. Under these conditions, the synthetic zirconolite dissolved much slower than brannerite and betafite. While the most intense conditions were observed previously to result in near complete dissolution of brannerite in under 5 h, zirconolite was not observed to undergo significant attack over this timescale. Fine zirconolite dissolved faster than the coarse material, indicating that dissolution rate is related to surface area. This data and the long term stability of zirconolite indicate that it is a good material for long-term sequestration of radioisotopes. Besides its long term durability in the disposal environment, a wasteform for fissile material immobilisation must demonstrate proliferation resistance such that the fissile elements cannot be retrieved by leaching of the wasteform. This study, in conjunction with the previous studies on brannerite and betafite leaching, strongly indicates that the addition of depleted uranium to the wasteform, to avert long term criticality events, is detrimental to proliferation resistance. Given the demonstrated durability of zirconolite, long term criticality risks in the disposal environment seem a remote possibility, which supports its selection, above brannerite or betafite, as the optimal wasteform for the disposition of nuclear waste, including of surplus plutonium.

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Section: Sem Edxmentioning

confidence: 99%

Chemical Stability of Zirconolite for Proliferation Resistance under Conditions Typically Required for the Leaching of Highly Refractory Uranium Minerals

Nikoloski

Gilligan

Squire

et al. 2019

Metals

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“…9,10 To that end, microwave irradiation is applied to saturate electron paramagnetic resonance (EPR) transitions, causing polarization transfer via several distinct mechanisms. 11,12 The theoretically attainable highest DNP enhancement factors, ε, are approximately equal to the ratio of gyromagnetic ratios of the electron to the nuclear spins; for the common biologically relevant atoms --1 H, 13 C, and 15 N --these factors are ~660, 2,624, and 6,511, respectively. 1 H enhancements as high as 250 have been experimentally observed in biological solids.…”

Section: Introductionmentioning

confidence: 99%

“…1 H enhancements as high as 250 have been experimentally observed in biological solids. 13 In practice, transferring electron polarization in DNP-enhanced NMR spectroscopy requires the presence of paramagnetic centers in the samples. These can be endogenous paramagnetic groups 14 or externally introduced paramagnetic species.…”

Section: Introductionmentioning

confidence: 99%

“…15 DNP-enhanced MAS NMR spectroscopy of biological systems is an area of intense interest and active development, following in the footsteps of the seminal work from the Griffin group on bacteriorhodopsin and bacteriophages. 16,17 With the availability of commercial instrumentation at magnetic fields of up to 21.1 T, DNP has since been applied to a variety of biological systems, including nanocrystalline peptides, 18 membrane proteins, 17 amyloid fibrils, 19 nucleic acids, 13 biomaterials, [20][21][22] cells, 23,24 and viral capsid assemblies. 25,26 DNP enhancements were found to depend strongly on the detailed experimental conditions, such as magnetic field, temperature, nature and concentration of the radical, to name a few.…”

Section: Introductionmentioning

confidence: 99%

“…25,26 DNP enhancements were found to depend strongly on the detailed experimental conditions, such as magnetic field, temperature, nature and concentration of the radical, to name a few. 27 Reported sensitivity gains for 1 H polarization vary widely, from relatively modest factors of ε~4-10 for membrane proteins 28 and at high magnetic fields of 18.8 T 25 to impressive ε~148 for direct 13 C excitation in a perdeuterated microcrystalline SH3 protein. 29 In our work on non-crystalline HIV-1 capsid tubular assemblies, we observed very large sensitivity gains of up to ε=64 at 14.1 T, permitting detection of resonances from dynamically disordered residues and low-concentration conformers, which are not observable in roomtemperature MAS NMR experiments.…”

Section: Introductionmentioning

confidence: 99%

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¹⁹F Dynamic Nuclear Polarization at Fast Magic Angle Spinning for NMR of HIV-1 Capsid Protein Assemblies

Wang

Sergeyev

et al. 2019

J. Am. Chem. Soc.

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We report remarkably high, up to 100-fold, signal enhancements in 19 F dynamic nuclear polarization (DNP) magic angle spinning (MAS) spectra at 14.1 T on HIV-1 CA capsid protein assemblies. These enhancements correspond to absolute sensitivity ratios of 12-29 and are of similar magnitude as seen for 1 H signals in the same samples. At MAS frequencies above 20 kHz, it was possible to record 2D 19 F-13 C HETCOR spectra, which contain long-range intra-and intermolecular correlations. Such correlations provide unique distance restraints, inaccessible in conventional experiments without DNP for protein structure determination. Furthermore, systematic quantification of the DNP enhancements as a function of biradical concentration, MAS frequency, temperature, and microwave power is reported. Our work establishes the power of DNP-enhanced 19 F MAS NMR spectroscopy for structural characterization of HIV-1 CA assemblies and this approach is anticipated to be applicable to a wide range of large biomolecular systems.

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Significance of Formamidinium Incorporation in Perovskite Composition and Its Impact on Solar Cell Efficiency: A Mini‐Review

Sekar,

Manisekaran,

Nwakanma

et al. 2024

Adv Energy and Sustain Res

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Perovskite solar cells (PSCs) have gained tremendous research interest recently owing to several advantages, including low material cost, facile solution processability, bandgap tunability, and alluring device efficiency. The organic formamidinium (FA) cation‐based perovskites are mainly considered as one of the potential candidates for charge carrier generation due to their excellent properties, such as bandgap and thermal stability than traditional perovskites. However, the inevitable unfavorable polymorphism (i.e., α to δ) at room temperature still forms the basis for numerous research works to allow the fabrication of a high‐quality absorber and enhances the PSCs performance. The studies to resolve the polymorphism and several contemporary techniques (e.g., passivation strategy) with several recent novel fabrication methods presented in this review form the essence of the improvements in PSCs. The absorber morphology also influences the charge‐transfer behavior and the device's lifetime. Therefore, understanding these properties is essential to improve the absorber quality and avoid many defects. This review focuses on the structure and properties of pure and mixed FA perovskites with various halides, mainly the FA cation's role in the absorber composition. And a comprehensive overview of recent FA cation‐based double, triple, and quadrupole PSCs results with proper scientific explanations to understand the device physics.

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Preface

Cited by 4 publications

References 227 publications

Chemical Stability of Zirconolite for Proliferation Resistance under Conditions Typically Required for the Leaching of Highly Refractory Uranium Minerals

Chemical Stability of Zirconolite for Proliferation Resistance under Conditions Typically Required for the Leaching of Highly Refractory Uranium Minerals

¹⁹F Dynamic Nuclear Polarization at Fast Magic Angle Spinning for NMR of HIV-1 Capsid Protein Assemblies

Significance of Formamidinium Incorporation in Perovskite Composition and Its Impact on Solar Cell Efficiency: A Mini‐Review

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Preface

Cited by 4 publications

References 227 publications

Chemical Stability of Zirconolite for Proliferation Resistance under Conditions Typically Required for the Leaching of Highly Refractory Uranium Minerals

Chemical Stability of Zirconolite for Proliferation Resistance under Conditions Typically Required for the Leaching of Highly Refractory Uranium Minerals

19F Dynamic Nuclear Polarization at Fast Magic Angle Spinning for NMR of HIV-1 Capsid Protein Assemblies

Significance of Formamidinium Incorporation in Perovskite Composition and Its Impact on Solar Cell Efficiency: A Mini‐Review

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Product

Resources

About

¹⁹F Dynamic Nuclear Polarization at Fast Magic Angle Spinning for NMR of HIV-1 Capsid Protein Assemblies