A smooth variation of Baas–Sullivan theory and positive scalar curvature

Let $M$ be a smooth closed spin (resp. oriented and totally non-spin) manifold of dimension $n\ge 5$ with fundamental group $\pi $ . It is stated, e.g. by Rosenberg and Stolz (Surv Surg Theory 2, pp. 353–370, 2001), that $M$ admits a metric of positive scalar curvature (pscm) if its orientation class in $ko_n(B\pi )$ (resp.  $H_n(B\pi ;\mathbb Z )$ ) lies in the subgroup consisting of elements which contain pscm representatives. This is $2$ -locally verified loc. cit. and by Stolz (Topology 33, pp. 159–180, 1994). After inverting $2$ it was announced that a proof would be carried out by Jung (uncompleted Ph.D. thesis), but this work has never appeared in print. The purpose of our paper is to present a self-contained proof of the statement with $2$ inverted.     

An electrochemical thermometer: voltammetric measurement of temperature and its application to amperometric gas sensing

We report a temperature sensing system incorporated into an amperometric oxygen sensor. In the first part of this work, we introduce temperature sensing systems based upon voltammetric responses of both single molecule (1,2-diferrocenylethylene in 1-propyl-3-methylimidazolium bistrifluoromethylsulfonylimide) and two independent molecules (decamethylferrocene and N,N,N',N'-tetramethyl-p-phenylenediamine in 1-ethyl-3-methylimidazolium tetracyanoborate) respectively. In both systems, the difference in the formal potentials of two redox centres was measured as a function of temperature. The former was recorded as the peak difference in square wave voltammetry with the peak potential difference increases linearly with the increasing temperature. In order to show proof-of-concept in relation to a gas sensor, the latter system was investigated in the presence of oxygen, where the concentration and diffusion coefficient of oxygen varied with temperature, as well as the peak difference discussed previously, were studied in the presence of pure oxygen and dried air using chronoamperometry. A negligible variation of concentration of oxygen from both sources with temperature over the range 298 K to 318 K is demonstrated. These results obtained from pure oxygen and dried air were compared and a ca. 79% drop of cathodic signal from pure oxygen to dried air was found which is consistent with the percentage of oxygen in air. The diffusion coefficient of oxygen was related to temperature using an Arrhenius plot (natural log of diffusion coefficient as a function of reciprocal temperature), yielding a linear graph with high correlation. All experiments gave a high reproducibility.     

Internal Flow Analysis for Slow Moving Small Droplets in Contact with Hydrophobic Surfaces

Internal fluid flow behavior for slow moving small droplets in contact with hydrophobic surfaces is analyzed. The shape of the droplet is first computed using the Young-Laplace equation. For this purpose a Finite Element (FE) model [1], in which contact constraints are enforced through Penalty and Augmented Lagrange Multiplier methods, is used. The flow field within the droplet is then analyzed using the Stokes flow model, considering a de-coupled approach. Similar to the membrane deformation model, the formulation for the flow analysis is also expressed in the framework of FE analysis. Both, stabilized (Pressure Stabilizing/Petrov-Galerkin PSPG) and Galerkin FE formulations are considered. The motion of the fluid inside the droplet is governed by the slip condition enforced on the membrane of the droplet. Numerical examples for droplets rolling steadily are presented. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stabilization of Laminar Boundary-Layer Flow using Dielectric Barrier Discharge Plasma Actuators

A numerical method is developed to study the stabilizing effect of dielectric barrier discharge plasma actuators on laminar boundary-layer flow. A finite difference approach based on a Keller box discretization is chosen to solve the Falkner-Skan transformed boundary-layer equations. The fluid dynamic effect of the flow-control device is implemented as a body-force field, derived quantitatively from previous measurements using particle image velocimetry. The resulting laminar boundary-layer flow is compared to experimental wind tunnel measurements and the effect on hydrodynamic stability is investigated in the framework of linear stability theory. A good agreement between experimentally acquired and numerically predicted transition locations based on an empirical function is obtained, rendering the numerical scheme valuable as a design tool for DBD based flow control applications. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Automorphic Equivalence within Gapped Phases of Quantum Lattice Systems

Gapped ground states of quantum spin systems have been referred to in the physics literature as being ‘in the same phase’ if there exists a family of Hamiltonians H(s), with finite range interactions depending continuously on \({s\in [0,1]}\), such that for each s, H(s) has a non-vanishing gap above its ground state and with the two initial states being the ground states of H(0) and H(1), respectively. In this work, we give precise conditions under which any two gapped ground states of a given quantum spin system that ’belong to the same phase’ are automorphically equivalent and show that this equivalence can be implemented as a flow generated by an s-dependent interaction which decays faster than any power law (in fact, almost exponentially). The flow is constructed using Hastings’ ‘quasi-adiabatic evolution’ technique, of which we give a proof extended to infinite-dimensional Hilbert spaces. In addition, we derive a general result about the locality properties of the effect of perturbations of the dynamics for quantum systems with a quasi-local structure and prove that the flow, which we call the spectral flow, connecting the gapped ground states in the same phase, satisfies a Lieb-Robinson bound. As a result, we obtain that, in the thermodynamic limit, the spectral flow converges to a co-cycle of automorphisms of the algebra of quasi-local observables of the infinite spin system. This proves that the ground state phase structure is preserved along the curve of models H(s), 0 ≤ s ≤ 1.     

The structure of epitaxial V2O3 films and their surfaces: A medium energy ion scattering study

Medium energy ion scattering, using 100 keV H⁺ incident ions, has been used to investigate the growth of epitaxial films, up to thicknesses of ~ 200 Å, of V₂O₃ on both Pd(111) and Au(111). Scattered-ion energy spectra provide a measure of the average film thickness and the variations in this thickness, and show that, with suitable annealing, the crystalline quality is good. Plots of the scattering yield as a function of scattering angle, so-called blocking curves, have been measured for two different incidence directions and have been used to determine the surface structure. Specifically, scattering simulations for a range of different model structures show poor agreement with experiment for half-metal (….V′O₃V) and vanadyl (….V′O₃V=O) terminations, with and without surface interlayer relaxations. However, good agreement with experiment is found for the modified oxygen-termination structure, first proposed by Kresse et al., in which a subsurface V half-metal layer is moved up into the outermost V buckled metal layer to produce a VO₂ overlayer on the underlying V₂O₃, with an associated layer structure of ….O₃VV′′V ′O₃. This result is consistent with the predictions of thermodynamic equilibrium at the surface under the surface preparation conditions, but is at variance with the conclusions of earlier studies of this system that have favoured the vanadyl termination. The results of these previous studies are re-evaluated in the light of the new result.     

Mass spectrometry based analysis of nucleotides, nucleosides, and nucleobases—application to feed supplements

In this work, accurate MS-based methods for quantitative profiling of nucleotides, nucleosides, and nucleobases in yeast extracts used as additives in animal feedstuff are presented. Reversed-phase chromatography utilizing a stationary phase compatible with 100% aqueous mobile phases resulted in superior analytical figures of merit than HILIC or ion-pair reversed-phase separation. The novel separation method was combined with both molecular and elemental mass spectrometry. By use of RP-LC-MS-MS, excellent limits of detection <1 μmol L(-1) could be obtained for all the compounds investigated. The elemental speciation analysis approach enabled determination of nucleotides by phosphorus detection. Sensitivity of LC-ICP-MS was 1-2 orders of magnitude lower than that of LC-MS-MS. Quantitative analysis of yeast products using complementary MS detection furnished values in good agreement.     

Quantification of low fat contents: a comparison of MR imaging and spectroscopy methods at 1.5 and 3 T

Magnetic resonance spectroscopy (MRS) has long been considered the golden standard for non-invasive measurement of tissue fat content. With improved techniques for fat/water separation, imaging has become an alternative to MRS for fat quantification. Several imaging models have been proposed, but their performance relative to MRS at very low fat contents is yet not fully established. In this work, imaging and spectroscopy were compared at 1.5 T and 3 T in phantoms with 0-3% fat fraction (FF). We propose a multispectral model with individual a priori R₂ relaxation rates for water and fat, and a common unknown R₂′ relaxation. Magnitude and complex image reconstructions were also compared. Best accuracy was obtained with the imaging method at 1.5 T. At 3 T, the FFs were underestimated due to larger fat-water phase shifts. Agreement between measured and true FF was excellent for the imaging method at 1.5 T (imaging: FF_meas= 0.98 FF_true− 0.01%, spectroscopy: FF_meas= 0.77 FF_true+ 0.08%), and fair at 3 T (imaging: FF_meas= 0.91 FF_true− 0.19%, spectroscopy: FF_meas= 0.79 FF_true+ 0.02%). The imaging method was able to quantify FFs down to approx. 0.5%. We conclude that the suggested imaging model is capable of fat quantification with accuracy and precision similar to or better than spectroscopy and offers an improvement vs. a model with a common R₂* relaxation only.     

Electronic and optical properties of Cu, CuO and Cu2O studied by electron spectroscopy

The electronic and optical properties of Cu, CuO and Cu(2)O were studied by x-ray photoelectron spectroscopy (XPS) and reflection electron energy-loss spectroscopy (REELS). We report detailed Cu 2p, Cu LVV, O 1s and O KLL spectra which are in good agreement with previous results. REELS spectra, recorded for primary energies in the range from 150 to 2000 eV, were corrected for multiple inelastically scattered electrons to determine the effective inelastic scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(-1/ε) by using the QUEELS-ε(k,ω)-REELS software package. By Kramers-Kronig transformation of the determined Im(-1/ε), the real and imaginary parts (ε(1) and ε(2)) of the dielectric function, and the refractive index n and extinction coefficient k were determined for Cu, CuO, and Cu(2)O in the 0-100 eV energy range. Observed differences between Cu, CuO and Cu(2)O are mainly due to modifications of the 3d and O 2p electron configurations.