A Fundamental and Systematic Investigation into the Solid State Chemistry of Some Ternary Uranium Oxides

This Ph.D. dissertation explores the solid state chemistry of the AUO4 family of oxides (A = divalent or trivalent cation), addressing the role uranyl bonding and 5f electron chemistry play in influencing their physicochemical properties using high resolution measurement methods and ab initio calculations. The irreversible phase transformation that occurs between the rhombohedral and orthorhombic variants of SrUO4 is examined and demonstrated to be first order and reconstructive. The transformation is shown to involve a sequential reduction and oxidation process related to reducing the activation energy barrier that can be traced to the respective ability and inability for the rhombohedral and orthorhombic variants to host oxygen defects. The defect inventory in AUO4 rhombohedral structures is shown to be modulated by the size of the A site cation. When isostructural rhombohedral CaUO4, α-Sr0.4Ca0.6UO4 and SrUO4 obtain a critical amount of oxygen defects they can access novel reversible symmetry lowering and defect ordering transformations forming phases denoted δ. The transformations are purely thermodynamic where the origin is proposed to be related to decreasing entropy from defect ordering balanced by increasing electronic entropy with heating. AUO4 oxides that had been previously poorly described were examined at high resolution. This includes elucidation of NiUO4 polymorphs which provide the transformative “missing link" between the Pbcn and Ibmm orthorhombic variants. Consequently a structural hierarchy is developed for the family of AUO4 oxides that can be used for structure prediction for specific A and U cations. High pressure studies of SrUO4 found anomalous U-O bond lengthening to occur with increasing pressure related to electron delocalisation. This demonstrates the inapplicability of Badger’s rule to all uranyl bearing compounds. With the structural topology of rhombohedral SrUO4, this lengthening process produces bulk moduli comparable to diamon

Structure and phase transition in BaThO3: A combined neutron and synchrotron X-ray diffraction study

The structure of BaThO3, obtained by solid state synthesis, was refined for the first time by the Rietveld method using a combination of synchrotron X-ray and neutron powder diffraction data. BaThO3 has an orthorhombic structure at room temperature, in space group Pbnm with a = 6.3491(5), b = 6.3796(4) and c = 8.9907(7) Å. Heating BaThO3 to above 700 °C results in a continuous transition to a second orthorhombic structure, in space group Ibmm, demonstrated by both in situ neutron and synchrotron X-ray powder diffraction measurements. The coefficient of volumetric thermal expansion for BaThO3 is determined to be 1.04 x 10-5 oC-1 from 50 to 625 oC (Pbnm phase), and 9.43 x 10-6 oC-1 from 800 to 1000 oC (Ibmm phase). BaThO3 was found to decompose upon exposure to atmospheric moisture resulting in the formation of ThO2. The thermal expansion of ThO2, which invariably co-exists with BaThO3, is also described.Australian Synchrotron Australian Research Council2019-12-1

Structure and phase transition in BaThO3: A combined neutron and synchrotron X-ray diffraction study

The structure of BaThO3, obtained by solid state synthesis, was refined for the first time by the Rietveld method using a combination of synchrotron X-ray and neutron powder diffraction data. BaThO3 has an orthorhombic structure at room temperature, in space group Pbnm with a = 6.3491(5), b = 6.3796(4) and c = 8.9907(7) Å. Heating BaThO3 to above 700 °C results in a continuous transition to a second orthorhombic structure, in space group Ibmm, demonstrated by both in situ neutron and synchrotron X-ray powder diffraction measurements. The coefficient of volumetric thermal expansion for BaThO3 is determined to be 1.04 x 10-5 oC-1 from 50 to 625 oC (Pbnm phase), and 9.43 x 10-6 oC-1 from 800 to 1000 oC (Ibmm phase). BaThO3 was found to decompose upon exposure to atmospheric moisture resulting in the formation of ThO2. The thermal expansion of ThO2, which invariably co-exists with BaThO3, is also described.Australian Synchrotron Australian Research Counci

Probing the Long- and Short-Range Structural Chemistry in the C‑Type Bixbyite Oxides Th0.40Nd0.48Ce0.12O1.76, Th0.47Nd0.43Ce0.10O1.785, and Th0.45Nd0.37Ce0.18O1.815 via Synchrotron X‑ray Diffraction and Absorption Spectroscopy

The long- and short-range structural chemistry of the C-type bixbyite compounds Th0.40Nd0.48Ce0.12O1.76, Th0.47Nd0.43Ce0.10O1.785, and Th0.45Nd0.37Ce0.18O1.815 is systematically examined using synchrotron X-ray powder diffraction (S-PXRD), high-energy resolution fluorescence detection X-ray absorption near edge (HERFD-XANES), and extended X-ray absorption fine structure spectroscopy (EXAFS) measurements supported by electronic structure calculations. S-PXRD measurements revealed that the title compounds all form classical C-type bixbyite structures in space group Ia3̅ that have disordered cationic crystallographic sites with further observation of characteristic superlattice reflections corresponding to oxygen vacancies. Despite the occurrence of oxygen vacancies, HERFD-XANES measurements on the Ce L3-edge revealed that Ce incorporates as Ce4+ into the structures but involves local distortion that resembles cluster behavior and loss of nearest-neighbors. In comparison, HERFD-XANES measurements on the Nd L3-edge supported by electronic structure calculations reveal that Nd3+ adopts a local coordination environment similar to the long-range C-type structure while providing charge balancing for the formation of oxygen defects. Th L3-edge EXAFS analysis reveals shorter average Th–O distances in the title compounds in comparison to pristine ThO2 in addition to shorter Th–O and Th–Ce distances compared to Th–Th or Ce–Ce in the corresponding F-type binary oxides (ThO2 and CeO2). These distances are further found to decrease with the increased Nd content of the structures despite simultaneous observation of the overall lattice structure progressively expanding. Linear combination calculations of the M-O bond lengths are used to help explain these observations, where the role of oxygen defects, via Nd3+ incorporation, induces local bond contraction and enhanced Th cation valence, leading to the observed increased lattice expansion with progressive Nd3+ incorporation. Overall, the investigation points to the significance of dissimilar cations exhibiting variable short-range chemical behavior and how it can affect the long-range structural chemistry of complex oxides

Three-Dimensional FDTD Simulation of Biomaterial Exposure to Electromagnetic Nanopulses

Ultra-wideband (UWB) electromagnetic pulses of nanosecond duration, or nanopulses, have been recently approved by the Federal Communications Commission for a number of various applications. They are also being explored for applications in biotechnology and medicine. The simulation of the propagation of a nanopulse through biological matter, previously performed using a two-dimensional finite difference-time domain method (FDTD), has been extended here into a full three-dimensional computation. To account for the UWB frequency range, a geometrical resolution of the exposed sample was $0.25 mm$, and the dielectric properties of biological matter were accurately described in terms of the Debye model. The results obtained from three-dimensional computation support the previously obtained results: the electromagnetic field inside a biological tissue depends on the incident pulse rise time and width, with increased importance of the rise time as the conductivity increases; no thermal effects are possible for the low pulse repetition rates, supported by recent experiments. New results show that the dielectric sample exposed to nanopulses behaves as a dielectric resonator. For a sample in a cuvette, we obtained the dominant resonant frequency and the $Q$-factor of the resonator.Comment: 15 pages, 8 figure

Taking the next step: a systematic review and meta-analysis of physical activity and behavior change interventions in recent post-treatment breast cancer survivors

Research has shown that recent post-treatment breast cancer survivors face significant challenges around physical activity as they transition to recovery. This review examined randomized controlled trials targeting physical activity behavior change in breast cancer survivors <5 years post-treatment and describes 1) characteristics of interventions for breast cancer survivors as well as 2) effect size estimates for these studies

The Grizzly, January 27, 1989

Constructium Ursini • Ad Hoc Hoists Honor • New GPA: 2.25 or Dive! • Letter: Green Shirt Makes Reed Red • Fair Not Just for Freshmen • Security Shacks in Reimert • Beverly Oehlert Named to Pottstown Board of Directors • Final Red and Gold Day • Hoopsters Stunning in Second • Lady Bears Go For Title • U.C. Hockey Bids Boyd Bon Voyage • A \u27bears Recover from Fla. • Dryfoos, Knauer Newest Dirs. • Bailey Bandies With Bush • Grim Gripes: Wismer Hard to Swallow • Quintet Jazzes Up First Forum • Greenstein to Performhttps://digitalcommons.ursinus.edu/grizzlynews/1226/thumbnail.jp

Genome-wide signatures of complex introgression and adaptive evolution in the big cats.

The great cats of the genus Panthera comprise a recent radiation whose evolutionary history is poorly understood. Their rapid diversification poses challenges to resolving their phylogeny while offering opportunities to investigate the historical dynamics of adaptive divergence. We report the sequence, de novo assembly, and annotation of the jaguar (Panthera onca) genome, a novel genome sequence for the leopard (Panthera pardus), and comparative analyses encompassing all living Panthera species. Demographic reconstructions indicated that all of these species have experienced variable episodes of population decline during the Pleistocene, ultimately leading to small effective sizes in present-day genomes. We observed pervasive genealogical discordance across Panthera genomes, caused by both incomplete lineage sorting and complex patterns of historical interspecific hybridization. We identified multiple signatures of species-specific positive selection, affecting genes involved in craniofacial and limb development, protein metabolism, hypoxia, reproduction, pigmentation, and sensory perception. There was remarkable concordance in pathways enriched in genomic segments implicated in interspecies introgression and in positive selection, suggesting that these processes were connected. We tested this hypothesis by developing exome capture probes targeting ~19,000 Panthera genes and applying them to 30 wild-caught jaguars. We found at least two genes (DOCK3 and COL4A5, both related to optic nerve development) bearing significant signatures of interspecies introgression and within-species positive selection. These findings indicate that post-speciation admixture has contributed genetic material that facilitated the adaptive evolution of big cat lineages

Lumpability Abstractions of Rule-based Systems

The induction of a signaling pathway is characterized by transient complex formation and mutual posttranslational modification of proteins. To faithfully capture this combinatorial process in a mathematical model is an important challenge in systems biology. Exploiting the limited context on which most binding and modification events are conditioned, attempts have been made to reduce the combinatorial complexity by quotienting the reachable set of molecular species, into species aggregates while preserving the deterministic semantics of the thermodynamic limit. Recently we proposed a quotienting that also preserves the stochastic semantics and that is complete in the sense that the semantics of individual species can be recovered from the aggregate semantics. In this paper we prove that this quotienting yields a sufficient condition for weak lumpability and that it gives rise to a backward Markov bisimulation between the original and aggregated transition system. We illustrate the framework on a case study of the EGF/insulin receptor crosstalk.Comment: In Proceedings MeCBIC 2010, arXiv:1011.005

TEN Team

There is a growing realisation that to better understand and intervene in the interconnected political, cultural and psycho-social dynamics that constitute the contexts for these current global challenges requires transdisciplinary and intersectoral approaches; approaches that include and value diverse perspectives and pay particular attention to the perspectives and experiences of those who are the most vulnerable and those who are currently excluded from the knowledge creation processes. This article discusses the learning gained from an inter-disciplinary and inter-institutional project entitled Transformative Engagement Network (TEN). &nbsp