Diagrammatic description for the categories of perverse sheaves on isotropic Grassmannians

For each integer \(k\ge 4\), we describe diagrammatically a positively graded Koszul algebra \(\mathbb {D}_k\) such that the category of finite dimensional \(\mathbb {D}_k\)-modules is equivalent to the category of perverse sheaves on the isotropic Grassmannian of type \(\mathrm{D}_k\) or \(\mathrm{B}_{k-1}\), constructible with respect to the Schubert stratification. The algebra is obtained by a (non-trivial) “folding” procedure from a generalized Khovanov arc algebra. Properties such as graded cellularity and explicit closed formulas for graded decomposition numbers are established by elementary tools.     

Actinide incorporation in a zirconia based pyrochlore (Nd1.8An0.2)Zr2O7+x (An=Th, U, Np, Pu, Am)

Actinides (thorium, uranium, neptunium, plutonium, and americium) were infiltrated into a porous Nd_1.8Zr₂O_6.7 matrix, prepared by gel-supported precipitation. (Nd_1.8An_0.2)Zr₂O_7+x pyrochlores were formed after sintering in Ar/H₂ and the pyrochlore structure remains during oxidation at 800 °C in air. X-ray diffraction reveals a linear relationship between the pyrochlore lattice parameter and the ionic radii of the actinides. EXAFS measurements on actinide L₃-edge show a split shell of nearest neighbour oxygen atoms similar to that surrounding of Nd. The actinide-oxygen bond distances decrease with the actinide ionic radii, which verifies that these actinides adopt the Nd site in the (Nd_1.8An_0.2)Zr₂O_7+x pyrochlore. The oxidation susceptibility of Np is related to the availability of oxygen vacancies and in contrast to stabilised zirconia Np(V) can be obtained in zirconia based pyrochlore.     

Perpendicular ultrasound velocity measurement by 2D cross correlation of RF data. Part B: volume flow estimation in curved vessels

A novel axial velocity profile integration method, obtained from ultrasonic perpendicular velocimetry, for flow estimation in curved tubes was validated. In an experimental set-up, physiologically relevant curved geometries and flows were considered. Axial velocity profile measurements were taken by applying particle imaging velocimetry-based methods to ultrasound data acquired by means of a linear array transducer positioned perpendicular to the axial velocity component. Comparison of the assessed asymmetric velocity profiles to computational fluid dynamics calculations showed excellent agreement. Subsequently, the recently introduced cos θ-integration method for flow estimation was compared to the presently applied Poiseuille and Womersley models. The average deviation between the cos θ-integration-based unsteady flow estimate and the reference flow was about 5%, compared to an average deviation of 20% for both the Poiseuille and Womersley approximation. Additionally, the effect of off-centre measurement was analysed for the three models. It was found that only for the cos θ-integration method, an accurate flow estimation is feasible, even when it is measured off centre.     

Fracture in single crystal NiTi

This paper presents an investigation of the pseudoelastic transformation of two crystallographic orientations of a single crystal NiTi shape memory alloy (SMA). Both uniaxial tension and notched tension samples are considered with the tensile axes along the [1 0 0] and [1 1 1] directions. The phase transformation is observed using optical techniques in situ. For the uniaxial tension samples, martensite plates and Lüders-band structures are observed. For the notched samples, transformation structures in the [1 0 0] sample appeared predominantly on the sides of the notch and crack tip with stable crack propagation. In the [1 1 1] notched samples transformation occurs directly ahead of the notch and unstable crack propagation is observed. An available work criterion is used to predict the location of the transformation, with good agreement to the experimental observations. The different fracture behavior of the two notched sample orientations is explained utilizing the available work calculations.     

On the structure of polyurethane hard segments based on MDI and butanediol-1,4: X-ray diffraction analysis of oriented elastomers and of single crystals of a model compound

Single-crystal x-ray diffraction analysis is performed on a model compound (bisurethane of diphenylmethane-4–monoisocyanate and butanediol-1,4) for the thermoplastic polyurethane (TPU) hard segment formed from diphenylmethane-4,4′-diisocyanate and butanediol-1,4. The resulting structure is compared to structure models of corresponding TPU hard segments, especially to the structure proposed by Blackwell and Ross. Our results confirm this structure model showing a planar zigzag of the (CH₂)₄ group and planar hydrogen bonding between the urethane groups of adjacent molecules. X-ray diffraction analyses of polymeric TPU hard segments and of TPU elastomers with noncrystallizing soft segments lead to a revision of the dimensions of the proposed lattice cell, resulting in a more plausible value of 1.3226g/cm³ for the crystal density.     

TiO2−CeOx−Pt Hollow Nanosphere Catalyst for Low-Temperature CO Oxidation

TiO₂−CeO₂−Pt hollow nanospheres (1 wt-% Pt) are realized using a liquid-phase strategy using NaCl as a template. The NaCl template is first coated with TiO₂ and thereafter with CeO₂ via the hydrolyzation of TiCl(OiPr)₃ and Ce(OiPr)₄ as suitable alkoxides. Finally, the NaCl template is removed by washing with water. The resulting @TiO₂−CeO₂ hollow nanospheres (□: inner cavity) exhibit an outer diameter of 140–180 nm, a wall thickness of 30–40 nm, an inner cavity of 80–100 nm, a specific surface area of 210 m²/g, a pore volume and area of 0.08 cm³/g and 191 m²/g, mainly with micropores ≥5 Å and ≤14 Å. The hollow nanosphere support is impregnated with Pt nanoparticles, using two different methods – a wet-chemical deposition (Pt(ac)₂, acetone, 25 °C) and a supercritical fluid reactive deposition (SFRD) process ([Pt(COD)Me₂], supercritical CO₂, 80 °C, 15.6 MPa) resulting in an uniform size distribution with Pt nanoparticles 2.5±0.1 nm (TiO₂−CeO₂−Pt_WCD) and 2.3±0.1 nm (TiO₂−CeO₂−Pt_SFRD) in size. The catalytic properties of the TiO₂−CeO₂−Pt hollow nanospheres are evaluated for CO oxidation between 50 and 500 °C. A promising catalytic activity and stable light-out/light-off temperatures are observed especially for the TiO₂−CeO₂−Pt_SFRD sample, indicating the suitability of hollow nanospheres as high-porosity catalyst material.     

Sample preparation and determination of ginkgo terpene trilactones in selected beverage, snack, and dietary supplement products by liquid chromatography with evaporative light-scattering detection

Ginkgo biloba leaf extract has been widely used in dietary supplements and more recently in some foods and beverages. Sample preparation procedures for determination of ginkgo terpene trilactones (including bilobalide and ginkgolides A, B, C, and J) in various sample matrixes were developed in this study. Ginkgo leaves and capsules were extracted with 5% KH2PO4 aqueous solution under sonication. Tea bags were extracted with boiling water, whereas drink samples were taken directly from the bottles. After filtration and the addition of NaCl to approximately 30% (w/v), the terpene trilactones in aqueous solutions were quantitatively extracted with ethyl acetate-tetrahydrofuran (4 + 1, v/v). Puff samples (a cereal-based fried snack item) were first defatted by using hexane or by using supercritical fluid extraction and then extracting under sonication with methanol-acetic acid (99 + 1, v/v). After evaporation of the organic phase, the terpene trilactones were redissolved in methanol and determined on a C18 reversed-phase column by liquid chromatography (LC) with evaporative light-scattering detection. The method of standard additions and gas chromatography with flame ionization detection were used for method validation. For most samples, the relative standard deviation was <10%. The identities of target compounds in ginkgo leaves and drink samples were confirmed by LC/electrospray ionization-tandem mass spectrometry.