Structure and orbital ordering of ultrathin LaVO3 probed by atomic resolution electron microscopy and Raman spectroscopy

Orbital ordering has been less investigated in epitaxial thin films, due to the difficulty to evidence directly the occurrence of this phenomenon in thin film samples. Atomic resolution electron microscopy enabled us to observe the structural details of the ultrathin LaVO₃ films. The transition to orbital ordering of epitaxial layers as thin as ≈4 nm was probed by temperature‐dependent Raman scattering spectroscopy of multilayer samples. From the occurrence and temperature dependence of the 700 cm^–1 Raman active mode it can be inferred that the structural phase transition associated with orbital ordering takes place in ultrathin LaVO₃ films at about 130 K.     

Towards the column bed stabilization of columns in capillary electroendosmotic chromatography. Immobilization of microparticulate silica columns to a continuous bed

This article discusses a novel method generating a continuous bed inside the CEC column. The column bed composed of microparticulate reversed-phase silica is completely immobilized by a hydrothermal treatment using water for the immobilization process. This process eliminates the manufacture of frits of both ends of the column and all problems associated with their preparation. Fundamental studies on operational parameters will be presented such as the dependence of the immobilization on the column temperature, the type of stationary phase and the column back pressure. The immobilized CEC columns show the same high column efficiency as packed columns with frits.     

Tests of QED and elektroweak theories at PETRA

We review experimental results from PETRA on the reactions:e ⁺ e ^?→e ⁺ e ^?, μ⁺ μ^?, τ⁺ τ^?, and γγ at centre-of-mass energies up to 36.7 GeV. The data are compared with the predictions of quantum electrodynamics and electroweak theories. The implication of the total cross section measurements fore ⁺ e ^?→q \(\bar q\) →hadrons with respect to the weak mixing angle is discussed.     

Yang-Mills Equation and Bures Metric

It is shown that the connection form (gauge field) related to the generalization of the Berry phase to mixed states proposed by Uhlmann satisfies the source-free Yang–Mills equation * D * D = 0, where the Hodge operator is taken with respect to the Bures metric on the space of finite-dimensional nondegenerate density matrices.     

Packing density,permeability, and separation efficiency of packed microchips at different particle-aspect ratios

HPLC microchips are investigated experimentally with respect to packing density, pressure drop–flow rate relation, hydraulic permeability, and separation efficiency. The prototype microchips provide minimal dead volume, on-chip UV detection, and a 75 mm long separation channel with a ca. 50 μm × 75 μm trapezoidal cross-section. A custom-built stainless-steel holder allowed to adopt optimized packing conditions. Separation channels were slurry-packed with 3, 5, and 10 μm-sized spherical, porous C8-silica particles. Differences in interparticle porosity, permeability, and plate height data are analyzed and consistently explained by different microchannel-to-particle size (particle-aspect) ratios and particle size distributions.     

Novel Copolymers of Trisubstituted Ethylenes and Styrene. 9. Some Ring-Substituted Ethyl 2-Cyano-1-oxo-3-phenyl-2-propenylcarbamates

Electrophilic trisubstituted ethylenes, ring-substituted ethyl 2-cyano-1-oxo-3-phenyl-2-propenylcarbamates, RC₆H₃CH = C(CN)CONHCO₂C₂H₅(where R is 2-CN, 3-CN, 4-CN, 3-Br- 4-CH₃O, 5-Br-2-CH₃O, 5-Br-2,3-(CH₃O)₂, 5-Br-2,4-(CH₃O)₂), were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and N-cyanoacetylurethane, and characterized by CHN analysis, IR, ¹H- and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H- and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 5-Br-2-CH₃O (3.4) > 5-Br-2,3-(CH₃O)₂ (1.7) > 3-Br- 4-CH₃O (1.4) > 5-Br-2,4-(CH₃O)₂ (0.7) > 4-CN (0.4) > 3-CN (0.4) > 2-CN (0.3). High T _g of the copolymers in comparison with that of polystyrene indicates decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene structural unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 250–420°C with residue (5–15% wt), which then decomposed in the 420–650°C range.     

Denseness results in the theory of algebraic fields

We study when the property that a field is dense in its real and p-adic closures is elementary in the language of rings and deduce that all models of the theory of algebraic fields have this property.     

Observation of a charge asymmetry in e+e− → μ+μ−

The angular distribution and the s dependence of the total cross section for the process e⁺e^? → μ⁺μ^? have been measured using the JADE detector at PETRA. After radiative corrections, a forward-backward asymmetry of ?(11.8±3.8) % was observed at an average centre of mass energy of 33.5 GeV. For comparison, an asymmetry of ?7.8 % is expected on the basis of the standard Glashow-Salam-Weinberg model.     

Prompt muons in multiparticle events from e+e− annihilation at petra

We have observed the production of prompt muons in e⁺e^? annihilation in the centre of mass energy range 33.0 GeV to 35.8 GeV. The rate of such muons with momentum greater than 1.4 GeV was measured to be 0.069 ± 0.024 per multiparticle event. When compared with currently accepted models, this rate is consistent with that expected from charm and bottom decays, but does not support the production also of a top quark of mass less than about 15 GeV.