Direct interpretation of the X-ray and neutron three-dimensional difference pair distribution functions (3D-ΔPDFs) of yttria-stabilized zirconia.

Three-dimensional difference pair distribution functions (3D-ΔPDFs) from X-ray and neutron diffraction experiments are reported for yttria-stabilized zirconia (Zr0.82Y0.18O1.91). A quantitative analysis of the signatures in the three-dimensional difference pair distribution functions is used to establish that oxygen ions neighbouring a vacancy shift by 0.525 (5) Šalong ⟨1, 0, 0⟩ towards the vacancy while metal ions neighbouring a vacancy shift by 0.465 (2) Šalong ⟨1, 1, 1⟩ away from the vacancy. The neutron 3D-ΔPDF shows a tendency for vacancies to cluster along ⟨½, ½, ½⟩, which results in sixfold coordinated metal ions.

Understanding the Water-in-Salt to Salt-in-Water Characteristics across the Zinc Chloride : Water Phase Diagram.

Using a series of time- and temperature-resolved synchrotron diffraction experiments, the relationship between multiple polymorphs of ZnCl2 and its respective hydrates is established. The δ-phase is found to be the pure anhydrous phase, while the α, ß, and γ phases result from partial hydration. Diffraction, gravimetric, and calorimetric measurements across the entire ZnCl2·R H2O, 0 > R > ∞ composition range using ultrapure, doubly sublimed ZnCl2 establish the ZnCl2 : H2O phase diagram. The results are consistent with the existence of crystalline hydrates at R = 1.33, 3, and 4.5 and identify a mechanistic pathway for hydration. All water is not removed from hydrated ZnCl2 until the system is heated above its melting point. While hydration/dehydration is reversible in concentrated solutions, dehydration from dilute aqueous solutions can result in loss of HCl, the source of hydroxide impurities commonly found in commercial ZnCl2 preparations. The strong interaction between ZnCl2 and water exerts a significant impact on the solvent water such that the system exhibits a deep eutectic at a composition of about R = 7 (87.5 mol %) and a eutectic temperature below -60 °C.

Aligning Practice to Policies: Changing the Culture to Recognize and Reward Teaching at Research Universities.

Recent calls for improvement in undergraduate education within STEM (science, technology, engineering, and mathematics) disciplines are hampered by the methods used to evaluate teaching effectiveness. Faculty members at research universities are commonly assessed and promoted mainly on the basis of research success. To improve the quality of undergraduate teaching across all disciplines, not only STEM fields, requires creating an environment wherein continuous improvement of teaching is valued, assessed, and rewarded at various stages of a faculty member's career. This requires consistent application of policies that reflect well-established best practices for evaluating teaching at the department, college, and university levels. Evidence shows most teaching evaluation practices do not reflect stated policies, even when the policies specifically espouse teaching as a value. Thus, alignment of practice to policy is a major barrier to establishing a culture in which teaching is valued. Situated in the context of current national efforts to improve undergraduate STEM education, including the Association of American Universities Undergraduate STEM Education Initiative, this essay discusses four guiding principles for aligning practice with stated priorities in formal policies: 1) enhancing the role of deans and chairs; 2) effectively using the hiring process; 3) improving communication; and 4) improving the understanding of teaching as a scholarly activity. In addition, three specific examples of efforts to improve the practice of evaluating teaching are presented as examples: 1) Three Bucket Model of merit review at the University of California, Irvine; (2) Evaluation of Teaching Rubric, University of Kansas; and (3) Teaching Quality Framework, University of Colorado, Boulder. These examples provide flexible criteria to holistically evaluate and improve the quality of teaching across the diverse institutions comprising modern higher education.

Ionic Liquid Character of Zinc Chloride Hydrates Define Solvent Characteristics that Afford the Solubility of Cellulose.

The recently described ionic liquid structure of the three equivalent hydrate of zinc chloride (ZnCl2·R H2O, R = 3, existing as [Zn(OH2)6][ZnCl4]) explains the solubility of cellulose in this medium. Only hydrate compositions in the narrow range of 3 - x < R < 3 + x with x ≈ 1 dissolve cellulose. Once dissolved, the cellulose remains in solution up to the R = 9 hydrate. Neutron diffraction and differential pair distribution function analysis of cellulose and model compound solutions (1 wt % cellulose in the R = 3 hydrate and 1 wt % ethanol in the R = 3 hydrate and the ZnCl2·3 ethanol liquid) coupled with detailed solubility measurements suggest that cellulose solubility occurs via coordination of the primary OH to the hydrated zinc cation with ring hydroxyls forming part of a second coordination shell around the cation of the ionic liquid.

Crystalline and liquid structure of zinc chloride trihydrate: a unique ionic liquid.

The water/ZnCl(2) phase diagram in the vicinity of the 75 mol % water composition is reported, demonstrating the existence of a congruently melting phase. Single crystals of this 3-equiv hydrate were grown, and the crystal structure of [Zn(OH(2))(6)][ZnCl(4)] was determined. Synchrotron X-ray and neutron diffraction and IR and Raman spectroscopy along with reverse Monte Carlo modeling demonstrate that a CsCl-type packing of the molecular ions persists into the liquid state. Consistent with the crystalline and liquid structural data, IR spectroscopy demonstrates that the O-H bonds of coordinated water do not exhibit strong intermolecular hydrogen ion bonding but are significantly weakened because of the water's coordination to Lewis acidic zinc ions. The O-H bond weakening makes this system a very strong hydrogen-bond donor, whereas the ionic packing along with the nonpolar geometry of the molecular ions makes this system a novel nonpolar, hydrogen-bonding, ionic liquid solvent.

Mixed anion (phosphate/oxalate) bonding to iron(III) materials.

A novel phosphate/oxalate inorganic-organic hybrid material has been prepared to elucidate synthesis and bonding characteristics of iron(III) with both phosphate and organic matter (OM). Such mixed anion bonding of inorganic oxyanions and OM to iron(III) and aluminum(III) in environmental systems has been proposed but not proven, mainly because of the complexity of natural geochemical matrices. The compound reported here with the molecular formula of [C(3)H(12)N(2)](2)[Fe(5)(C(2)O(4))(2)(H(x)PO(4))(8)] (I) was hydrothermally synthesized and characterized by single crystal X-ray diffraction and X-ray absorption spectroscopy (XAS). In this new structure, Fe-O octahedra and P-O tetrahedra are connected by corner-sharing to form a 2-D network in the a-b plane. Oxalate anions cross-link these Fe-P layers constructing a 3-D anionic framework. A diprotonated structure-directing template, DAP (1,3-diaminopropane), resides in the oxalate layer of the structure and offsets the negative charge of the anionic framework. Iron K-edge XANES spectra confirmed that the iron in I is Fe(III). The crystal structure of I is used to successfully fit its Fe K-edge EXAFS spectrum, which exhibits spectral signatures that unambiguously identify iron-phosphate and iron-OM bonding. Such molecular spectroscopic features will be invaluable for the evaluation of complex environmental systems. Furthermore, syntheses demonstrated the critical role of the templating amine to mediate whether or not the iron(III) is reduced by the organic acid.

Magnetic bistability in a cobalt bis(dioxolene) complex: long-lived photoinduced valence tautomerism.

The thermal- and photoinduced valence tautomerism of a cobalt bis(dioxolene) complex is described. The thermal conversion is precipitous, complete within 10 K, and is accompanied by a 5 K hysteresis loop (107 K < T(1/2) < 112 K). Rapid thermal quenching (300 K --> 10 K in ca. 5 s) and photoinduced valence tautomerism result in trapping of the metastable Co(II)-state at low temperatures through intermolecular hydrogen bonding. This lattice stabilization results in unmatched kinetic and thermal stability for a valence tautomer from 10-50 K, with residual hs-Co(II) persisting until about 90 K.

Effect of matrix crystal structure on ion abundance of carbohydrates by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry.

Sample preparation techniques for carbohydrate analysis using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) are explored, with particular emphasis on analyte/matrix co-crystallization procedures. While carbohydrates are known to prefer 2,5-dihydroxybenzoic acid (2,5-DHB) as the matrix of choice, these analytes are quite specific about matrix crystal structure, which in turn is dependent on the rate of drying of analyte/matrix spots on the MALDI target. With N-acetylglucosamine (GlcNAc) and N-acetylneuraminic acid (sialic acid or NeuAc) as test monosaccharides, significant increases in ion abundances are demonstrated with 2,5-DHB/NeuAc spots (>10-fold improvement) and 2,5-DHB/GlcNAc spots ( approximately 5-fold improvement) with active drying. The fine structure of crystals generated in active and passive drying was investigated using powder diffraction. Passively dried samples were shown to consist of an ordered polymorph, crystallizing in the space group P2(1)/a, while the actively dried samples produced a disordered phase crystallizing in the space group Pa. These data provide the wherewithal to engineer a matrix best suited for carbohydrate analyses.

Sorptive reconstruction of CuMCl4 (M = Al and Ga) upon small-molecule binding and the competitive binding of CO and ethylene.

Carbonyl adducts to CuMCl(4) (M = Al and Ga) have been characterized by single-crystal and/or powder X-ray diffraction, IR and diffuse reflectance UV/vis spectroscopy. Up to two equivalents of carbon monoxide ( approximately 200 cm(3)/g relative to stp) are sorbed at room temperature, with equilibrium binding pressures of below 0.5 atm of CO. The carbonyl bonding is shown to be nonclassical, implicating the dominance of sigma-bonding and absence of pi-back-bonding. Analysis of the crystalline structures of the parent and adduct phases provides an atomistic picture of the sorptive reconstruction reaction. Comparison of the reactivity of CO and ethylene with these CuMCl(4) materials, as well as other copper(I) halide compounds that exhibit classical and nonclassical modes of bonding, demonstrates the ability to tune the reactivity of the crystalline frameworks with selectivity for carbon monoxide or olefins, respectively.

Frequency response of pig intervertebral disc cells subjected to dynamic hydrostatic pressure.

The pathogenesis of vibration-induced disorders of intervertebral disc at the cellular level is largely unknown. Dynamic loads with frequencies close to that of the in vivo human spine resonant frequency (4-6 Hz) have a destructive effect, which may induce extracellular disc matrix (ECM) degradation. To investigate this issue, three-dimensional (3D) alginate cultures of normal pig intervertebral disc nucleus and inner annulus cells were tested under dynamic hydrostatic loading. Alginate cultures of each region were divided into six groups; five groups were exposed to cyclic hydrostatic pressures of frequencies 1, 3, 5, 8, and 10 Hz with the same amplitude (1 MPa), and group 6 was the control group (no loading). Cultures of different groups were loaded for 3 days (30 min daily) in a hydraulic chamber. Effects of loading frequency on disc collagen and protein metabolism were investigated by measuring 3H-proline-labeled proteins associated with the cells in the extracellular matrix and release of 3H-proline-labeled molecules into culture medium. The results indicated a poor synthesis rate and more degradation near the 5 Hz frequency. The repeatability of experiments was verified by performing two experiments with the same protocol. Both experiments indicated that a threshold frequency of around 5 Hz disrupted protein metabolism.

Metallotropic liquid crystals formed by surfactant templating of molten metal halides.

Liquid crystals consist of anisotropic molecular units, and most are organic molecules. Materials incorporating metals into anisotropic molecules, described as metallomesogens, have been prepared. Anisotropic structures such as one-dimensional chains and two-dimensional layers are frequently observed in solid-state inorganic materials, however, little is understood about structural organization in melts of such materials. Achieving liquid-crystalline behaviour in inorganic fluids should be possible if the anisotropic structure can be retained or designed into the molten phase. We demonstrated the ability to engineer zeolite-type structures into metal halide glasses and liquids. In this work we have engineered lamellar, cubic and hexagonal liquid-crystalline structure in metal-halide melts by controlling the volume fraction and nature of the inorganic block (up to 80 mol%) with respect to alkylammonium surfactants. The high metal content of these liquid-crystalline systems significantly advances the field of metallomesogens, which seeks to combine magnetic, electronic, optical, redox and catalytic properties common to inorganic materials with the fluid properties of liquid crystals.

Tuning the band gap in hybrid tin iodide perovskite semiconductors using structural templating.

Structural distortions within the extensive family of organic/inorganic hybrid tin iodide perovskite semiconductors are correlated with their experimental exciton energies and calculated band gaps. The extent of the in- and out-of-plane angular distortion of the SnI4(2-) perovskite sheets is largely determined by the relative charge density and steric requirements of the organic cations. Variation of the in-plane Sn-I-Sn bond angle was demonstrated to have the greatest impact on the tuning of the band gap, and the equatorial Sn-I bond distances have a significant secondary influence. Extended Hückel tight-binding band calculations are employed to decipher the crystal orbital origins of the structural effects that fine-tune the band structure. The calculations suggest that it may be possible to tune the band gap by as much as 1 eV using the templating influence of the organic cation.

XANES investigation of phosphate sorption in single and binary systems of iron and aluminum oxide minerals.

Phosphate sorption on Fe- and Al-oxide minerals helps regulate the solubility and mobility of P in the environment. The objective of this study was to characterize phosphate adsorption and precipitation in single and binary systems of Fe- and Al-oxide minerals. Varying concentrations of phosphate were reacted for 42 h in aqueous suspensions containing goethite, ferrihydrite, boehmite, or noncrystalline (non-xl) Al-hydroxide, and in 1:1 (by mass) mixed-mineral suspensions of goethite/boehmite and ferrihydrite/ non-xl Al-hydroxide at pH 6 and 22 degrees C. X-ray absorption near edge structure (XANES) spectroscopy was used to detect precipitated phosphate and distinguish PO4 associated with Fe(III) versus Al(III) in mixed-mineral systems. Changes in the full width at half-maximum height (fwhm) in the white-line peak in P K-XANES spectra provided evidence for precipitation in Al-oxide single-mineral systems, but not in goethite or ferrihydrite systems. Similarly, adsorption isotherms and XANES data showed evidence for precipitation in goethite/boehmite mixtures, suggesting that mineral interactive effects on PO4 sorption were minimal. However, sorption in ferrihydrite/non-xl Al-hydroxide systems and a lack of XANES evidence for precipitation indicated that mineral interactions inhibited precipitation in these binary mixtures.

Property and morphology development in nanocomposite thermoplastic elastomer gels.

Thermoplastic elastomer gels (TPEGs), molecular networks composed of a microphase-separated multiblock copolymer swollen to a large extent by a low-volatility midblock-selective solvent, are ubiquitous in a wide range of contemporary technologies, including home and office products, athletic equipment, and telecommunications devices. In this work, we investigate the effect of several network-forming nanoscale modifiers-two different silica nanoparticles, three different nanoclays, and a multiwalled carbon nanotube-on the property and morphology development of a TPEG prepared from a microphase-ordered poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) triblock copolymer imbibed with an EB-compatible aliphatic mineral oil. Dynamic rheological measurements of the resultant nanocomposite TPEGs confirm that addition of these modifiers affects the linear viscoelastic threshold and increases, to different extents, the dynamic elastic modulus, the dynamic yield stress, and the maximum operating temperature of the parent TPEG. X-ray diffraction analysis reveals that the nanoclays used to generate three series of modified TPEGs are generally swollen with copolymer and/or solvent.

Synthesis of [NH(4)]MnCl(2)(OAc) and [NH(4)](2)MnCl(4)(H(2)O)(2) by solvothermal dehydration and structure/property correlations in a one-dimensional antiferromagnet.

The utility of the solvothermal dehydration strategy whereby superheated acetonitrile reacts with water of hydration to form ammonium acetate is demonstrated in the synthesis of [NH(4)]MnCl(2)(OAc), I, and [NH(4)](2)MnCl(4)(H(2)O)(2), II, from MnCl(2).4H(2)O. The structure of I is shown to crystallize in the monoclinic space group C2/c (No. 15) with a = 15.191(6) A, b = 7.044(2) A, c = 13.603(6) A, beta = 107.31 degrees, V = 1389.7(9) cm(-)(1), and Z = 8. The structure of II crystallizes in the space group I4/mmm (No. 139) with a = 7.5250(5) A, b = 8.276(2) A, V = 468.6(1) cm(-)(1), and Z = 2. Both structures exhibit extensive hydrogen bonding that controls both local Mn-Cl bonding and the interchain organization. I is shown to be a one-dimensional Heisenberg antiferromagnet with an intrachain exchange constant J/k = -2.39 K. This structure exhibits exchange coupling intermediate between the well-studied triply and doubly chloride-bridged one-dimensional manganese Heisenberg antiferromagnets. The structure/property correlation demonstrates a linear dependence of the exchange constant on the Mn-Cl-Mn bond angle, alpha, for alpha < 94 degrees.

Sorptive reconstruction of the CuAlCl(4) framework upon reversible ethylene binding.

Three ethylene adducts to CuAlCl(4) have been characterized by single crystal and/or powder X-ray diffraction, (13)C, (27)Al and (63)Cu MAS NMR and diffuse reflectance UV-vis spectroscopy. (C(2)H(4))(2)CuAlCl(4), a = 7.1274(5) b = 12.509(1) c = 11.997(3) beta = 91.19 degrees, Pc, Z = 4; alpha-(C(2)H(4))CuAlCl(4), a =7.041(3) b = 10.754(8) c =11.742(9) beta = 102.48(6), P2(1), Z = 4 and beta-(C(2)H(4))CuAlCl(4), a = 7.306(2), b = 16.133(3), c = 7.094(1), Pna2(1), Z = 4. Up to 2 equiv of ethylene ( approximately 200 cm(3)/g relative to stp) are sorbed at room temperatures and pressures as low as 300 Torr. The ethylene ligands are bound to copper (I) primarily through a sigma-interaction, because the AlCl(4)(-) groups also bound to copper prevent any significant pi-back-bonding. The olefin binding is reversible and has been characterized by gravimetric and volumetric adsorption analysis and by time and pressure resolved synchrotron powder X-ray diffraction. Comparison of the parent crystal structure to those of the adduct phases provide an atomistic picture of the sorptive reconstruction reactions. These are proposed to proceed by a classic substitution mechanism that is directed by the van der Waals channels of the parent crystalline lattice.

Diabetes, hypertension and birth injuries: a complex interrelationship.

Seemingly coincidental occurrence of various pathological conditions may derive from common etiologic denominators. While reviewing 240 malpractice claims involving shoulder dystocia related fetal injuries, we found two antenatal complications in the background conspicuously often. Chronic or pregnancy induced hypertension was identifiable in 80 instances (33%). Pregnancy induced or preexisting diabetes was diagnosed 48 times (20%). Many of these patients were poorly controlled. The blood pressure was usually checked during the antenatal visits. However, about one-half of all patients received no diabetic screening. Therefore, this study may underestimate the actual incidence of diabetes. It has been calculated that the frequency of diabetes in pregnancy and that of hypertension, is about 5% in the United States. Thus, the rates of these complications in this selected group of gravidas was severalfold higher than in the general population. Since hypertension causes retarded fetal growth, it cannot be a direct cause of arrest of the shoulders at delivery. The likely common denominator is maternal diabetes a known predisposing factor both for preeclampsia and shoulder dystocia at birth. In the course of litigations for fetal injuries, demonstration of the predisposing role of seemingly unrelated shortcomings of the medical management may profoundly influence the outcome. This principle is demonstrated by the presentation of an actual malpractice action which resulted in a substantial settlement.

Electronic structure, electrical and magnetic properties of RMo(8)O(14) compounds (R = La, Ce, Pr, Nd, Sm) containing bicapped Mo(8) clusters.

Magnetic and electrical resistivity properties of RMo(8)O(14) (R = La, Ce, Pr, Nd, Sm) compounds containing different bicapped-octahedral Mo(8) clusters are discussed. Extended Hückel (EH) molecular calculations were carried out in order to study the influence of the position of metal capping atoms on the electronic structure of different Mo(8) isomers. Different optimal metal electron counts are possible for these clusters. Periodic density functional calculations confirm the molecular character of these compounds and allow the understanding of their semiconducting and magnetic properties.

Designing intermediate-range order in amorphous materials.

Amorphous materials are commonly understood to consist of random organizations of molecular-type structural units. However, it has long been known that structural organizations intermediate between discrete chemical bonds and periodic crystalline lattices are present even in liquids. Numerous models--including random networks and crystalline-type structures with networks composed of clusters and voids--have been proposed to account for this intermediate-range order. Nevertheless, understanding and controlling structural features that determine intermediate-range order in amorphous materials remain fundamental, yet presently unresolved, issues. The most characteristic signature of such order is the first peak in the total structure factor, referred to as the first sharp diffraction peak or 'low Q' structure. These features correspond to large real-space distances in the materials, and understanding their origin is key to unravelling details of intermediate-range order. Here we employ principles of crystal engineering to design specific patterns of intermediate-range order within amorphous zinc-chloride networks. Using crystalline models, we demonstrate the impact of various structural features on diffraction at low values of Q. Such amorphous network engineering is anticipated to provide the structure/property relationships necessary to tailor specific optical, electronic and mechanical properties.