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Fluoridation of HfO2 was carried out with three commonly used solid-state fluoridation agents: PVDF, PTFE, and NH4HF2. Clear and reproducible differences are observed in the reaction products of the fluoropolymer reagents and NH4HF2 with the latter more readily reacting in air. Strong evidence of distinct, previously unreported hafnium oxyfluoride phases is produced by both reactions, and efforts to isolate them were successful for the air-NH4HF2 reaction. Synchrotron XRD, 19F NMR, and elemental analysis were employed to characterize the phase-pure material which appears to be analogous to known Zr-O-F phases with anion-deficient α-UO3 structures such as Zr7O9F10. Comparison with the hydrolysis of β-HfF4 under identical conditions depicts that the NH4HF2 route produces the oxyfluoride with greater selectivity and at lower temperatures. Thermodynamic calculations were employed to explain this result. Potential reaction pathways for the NH4HF2 fluoridation of HfO2 are discussed.

Single crystals of LiIn2SbO6 have been synthesized using a Li2MoO4 flux and characterized with X-ray diffraction. The compound crystallizes in a new structure-type with a rutile-related framework. ...

The anion-deficient fluorite-related family of materials exhibits a number of commercially useful properties arising from the specific arrangement of anion vacancies in each structure. One recently reported member, Zn0.456In1.084Ge0.46O3, is the only known example with its particular complex structure in which cation coordinations span one 4-coordinate (4b), two 6-coordinate (8e and 16f), and one 8-coordinate (4a) site. A new, complete, solid solution (CuxZn1–x)0.456In1.084Ge0.46O3, (0 ≤ x ≤ 1) has been discovered via the isovalent substitution of Cu2+ for Zn2+, significantly expanding the known phase space of this structure. Synchrotron X-ray data confirm the ZIGO structure over the entire composition range. Inclusion of Cu in the structure is found to occur exclusively at the 16f site, increasing the number of cations mixed on that site from three to four, while all others remain singly occupied, including the other 6-coordinate (8e) position. Furthermore, transmission electron microscopy investigations...

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications. 115In and 209Bi are both I = 9/2 nuclei with high natural abundances and moderately high frequencies but large nuclear electric quadrupole moments. Leveraging the quadrupolar interaction as a measure of local symmetry and polyhedral distortions for these nuclei could provide powerful insights on a range of applied materials. However, the absence of reported NMR parameters on these nuclei, particularly in oxides, hinders their use by the broader materials community. In this contribution, solid-state 115In and 209Bi NMR of three recently discovered quaternary bismuth or indium oxides are reported, supported by density functional theory calculations, numerical simulations, diffraction, and additional multinuclear (27Al, 69,71Ga, 121Sb) solid-state NMR measurements. The compounds LiIn2SbO6, BiAlTeO6, and BiGaTeO6 are measured without special equipment at 9.4 T, demonstrating that wideline techniques such as the QCPMG pulse sequence and frequency-stepped acquisition can enable straightforward extraction of quadrupolar tensor information in I = 9/2 115In and 209Bi even in sites with large quadrupolar coupling constants. Relationships are described between the NMR observables and local site symmetry. These are amongst the first reports of the NMR parameters of 115In, 121Sb, and 209Bi in oxides.

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications.

Fluoridation of HfO

In this paper, we consider the semi-classical setting constructed on nilpotent graded Lie groups by means of representation theory. We analyze the effects of the pull-back by diffeomorphisms on pseudodifferential operators. We restrict to diffeomorphisms that preserve the filtration and prove that they are Pansu differentiable. We show that the pull-back of a semi-classical pseudodifferential operator by such a diffeomorphism has a semi-classical symbol that is expressed at leading order in terms of the Pansu differential. We interpret the geometric meaning of this invariance in the setting of filtered manifolds., Comment: 25 pages

We initiate the study of X-ray tomography on sub-Riemannian manifolds, for which the Heisenberg group exhibits the simplest nontrivial example. With the language of the group Fourier Transform, we prove an operator-valued incarnation of the Fourier Slice Theorem, and apply this new tool to show that a sufficiently regular function on the Heisenberg group is determined by its line integrals over sub-Riemannian geodesics. We also consider the family of taming metrics $g_\epsilon$ approximating the sub-Riemannian metric, and show that the associated X-ray transform is injective for all $\epsilon>0$. This result gives a concrete example of an injective X-ray transform in a geometry with an abundance of conjugate points., Comment: References added; some sections partially revised; minor errors fixed; results unchanged

The crystal structures of LiM2SbO6 (M ​= ​Sc, Fe, Mn, In) were originally described as ordered, Pnn2 variants of the Pnna LiSbO3 structure. Recently, however, a single crystal study on the M ​= ​In analogue revealed that its structure is better described as rutile-related with alternating-width chains and Pnnm symmetry. Here, the structure of LiSc2SbO6 (M ​= ​Sc) is similarly revisited with single crystal X-ray diffraction which indicates that it is an Li-ordered variant of the LiIn2SbO6 (M ​= ​In) structure with polar Pmn21 symmetry and a Flack parameter value of 0.5. Solid-state NMR confirms that Li is tetrahedrally coordinated, a key difference between the ordered LiSbO3 and rutile-related models structures. Differential thermal analysis reveals a second-order phase transition between 460 and 480 ​K. With this context, the implications of the low-temperature Flack parameter and powder diffraction data are discussed.

The anion-deficient fluorite-related family of materials exhibits a number of commercially useful properties arising from the specific arrangement of anion vacancies in each structure. One recently reported member, Zn

Elevated levels of fluoride (F(-)) in groundwaters of granitic and basaltic terrains pose a major environmental problem and are affecting millions of people all over the world. Hydroxyapatite (HA) has been shown to be a strong sorbent for F(-); however, low permeability of synthetic HA results in poor sorption efficiency. Here we provide a novel method of synthesizing nano- to micrometer sized HA on the surfaces of granular limestone to improve the sorption efficiency of the HA-based filter. Our experiments with granular limestone (38-63, 125-500 μm) and dissolved PO4(3-) (0.5-5.3 mM) as a function of pH (6-8) and temperature (25-80 °C) indicated rapid formation of nano- to micrometer sized HA crystals on granular limestone with the maximum surface coverage at lower pH and in the presence of multiple additions of aqueous PO4(3-). The HA crystal morphology varied with the above variables. The sorption kinetics and magnitude of F(-) sorption by HA-coated-fine limestone are comparable to those of pure HA, and the F(-) levels dropped to below the World Health Organization's drinking water limit of 79 μM for F(-) concentrations commonly encountered in contaminated potable waters, suggesting that these materials could be used as effective filters. Fluorine XANES spectra of synthetic HA reacted with F(-) suggest that the mode of sorption is through the formation of fluoridated-HA or fluorapatite at low F(-) levels and fluorite at high F(-) loadings.

California’s passage of the Nonprofit Integrity Act in 2004, followed by the enactment of similar legislation in other American states, has resulted in a series of new financial reporting requirements for many larger nonprofit organizations. Chief among the provisions of several of these legislative pieces is the requirement for nonprofit entities to form separate audit committees. Following the lead established in the for-profit sector, advocates have strongly urged nonprofit organizations to include at least one financial expert among audit committee members to augment actual and perceived financial reporting integrity. However, advocates’ acknowledgement of the challenge of recruiting these individuals leads one to question their ultimate worth to nonprofit organizations. Recognizing the significance of this issue, this study investigates individual donors’ impressions regarding the inclusion of financial experts among nonprofit audit committee members. Using an experimental case as the basis for exploration, the study finds that donors generally do not perceive financial experts as enhancing the credibility of nonprofit organizations’ financial statements. In light of the significance of individual donor contributions to entities’ continued financial sustainability, these findings represent potentially important considerations for nonprofit organizations as they weigh the costs and benefits of enlisting busy financial professionals for audit committee service.

The magnetoresistance effect in WTe2, a layered semimetal, is extremely large: the electrical resistance can be changed by more than 13 million per cent at very high magnetic fields and low temperatures. Apply a magnetic field to a magnetoresistive material and its electrical resistance changes — a technologically useful phenomenon that is harnessed, for example, in the data-reading sensors of hard drives. Mazhar Ali and colleagues have now identified a material (tungsten ditelluride or WTe2) in which the magnetoresistance effect is unusually large: the electrical resistance can be changed by more than 13 million per cent. Its remarkable magnetoresitance is evident at very high magnetic fields and at extremely low temperatures, so practical applications are not yet in prospect. But this finding suggests new directions in the study of magnetoresistivity that could ultimately lead to new uses of this effect. Magnetoresistance is the change in a material’s electrical resistance in response to an applied magnetic field. Materials with large magnetoresistance have found use as magnetic sensors1, in magnetic memory2, and in hard drives3 at room temperature, and their rarity has motivated many fundamental studies in materials physics at low temperatures4. Here we report the observation of an extremely large positive magnetoresistance at low temperatures in the non-magnetic layered transition-metal dichalcogenide WTe2: 452,700 per cent at 4.5 kelvins in a magnetic field of 14.7 teslas, and 13 million per cent at 0.53 kelvins in a magnetic field of 60 teslas. In contrast with other materials, there is no saturation of the magnetoresistance value even at very high applied fields. Determination of the origin and consequences of this effect, and the fabrication of thin films, nanostructures and devices based on the extremely large positive magnetoresistance of WTe2, will represent a significant new direction in the study of magnetoresistivity.

‘What did you get on number one?’ Instinctively, I looked up and made eye contact with Student X, a recent immigrant from a communist country in Asia. Was this student really attempting to compare ...

High-quality single crystals of WTe2 were grown using a Te flux followed by a cleaning step involving self-vapor transport. The method is reproducible and yields consistently higher-quality single crystals than are typically obtained via halide-assisted vapor transport methods. Magnetoresistance (MR) values at 9 tesla and 2 kelvin as high as 1.75 million %, nearly an order of magnitude higher than previously reported for this material, were obtained on crystals with residual resistivity ratio (RRR) of approximately 1250. The MR follows a near B 2 law and, assuming a semiclassical model, the average carrier mobility for the highest-quality crystal was found to be at 2 K. A correlation of RRR, MR ratio and average carrier mobility is found with the cooling rate during the flux growth.

A 32-year-old white male presented to the Jones Eye Institute at the University of Arkansas for Medical Sciences with blurred vision of the right eye (OD) and severe bilateral retrobulbar pain. He had an eight-year history of Wegener's granulomatosis. On examination there was optic disc edema OD and extensive bilateral orbital involvement with compression of the right optic nerve by neuroimaging studies. Optic nerve compression is rare in Wegener's granulomatosis. The ophthalmic manifestations are reviewed.

A 22-year-old white female presented to the Jones Eye Institute (JEI) complaining of pain and blurred vision in her left eye (OS). Slit-lamp examination revealed Lisch's nodules, and physical examination revealed multiple cutaneous neurofibromas and café-au-lait spots leading to a new diagnosis of neurofibromatosis type 1 (NF-1).

Primary osteogenic sarcoma of the bladder is an extremely rare disease. Fewer than 30 cases of tumors of the bladder containing bone or cartilage have been reported. Only 14 cases of well-documented primary osteogenic sarcoma of the bladder appear in the world's literature. The authors describe the first detailed description of such a patient treated with radiotherapy and chemotherapy as well as provide a review of this rare and interesting entity.