Continuum thermodynamic models for crystal plasticity including the effects of geometrically-necessary dislocations

The purpose of this work is the formulation of constitutive models for the inelastic material behaviour of single crystals and polycrystals in which geometrically necessary dislocations (GNDs) may develop and influence this behaviour. To this end, we focus on the dependence of the development of such dislocations on the inhomogeneity of the inelastic deformation in the material. More precisely, in the crystal plasticity context, this is a relation between the density of GNDs and the inhomogeneity of inelastic deformation in glide systems. In this work, two models for GND density and its evolution, i.e., a glide-system-based model, and a continuum model, are formulated and investigated. As it turns out, the former of these is consistent with the original two-dimensional GND model of Ashby (Philos. Mag. 21 (1970) 399), and the latter with the more recent model of Dai and Parks (Proceedings of Plasticity ’97, Neat Press, 1997, p. 17). Since both models involve a dependence of the inelastic state of a material point on the (history of the) inhomogeneity of the glide-system inelastic deformation, their incorporation into crystal plasticity modelling necessarily implies a corresponding non-local generalization of this modelling. As it turns out, a natural quantity on which to base such a non-local continuum thermodynamic generalization, i.e., in the context of crystal plasticity, is the glide-system (scalar) slip deformation. In particular, this is accomplished here by treating each such slip deformation as either (1), a generalized “gradient” internal variable, or (2), as a scalar internal degree-of-freedom. Both of these approaches yield a corresponding generalized Ginzburg-Landau- or Cahn-Allen-type field relation for this scalar deformation determined in part by the dependence of the free energy on the dislocation state in the material. In the last part of the work, attention is focused on specific models for the free energy and its dependence on this state. After summarizing and briefly discussing the initial-boundary-value problem resulting from the current approach as well as its algorithmic form suitable for numerical implementation, the work ends with a discussion of additional aspects of the formulation, and in particular the connection of the approach to GND modelling taken here with other approaches.     

MALDI‐TOF mass spectrometry of hordeins: rapid approach for identification of malting barley varieties

A procedure for identification of malting barley varieties using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) of ethanol‐soluble barley proteins (hordeins) is described. The hordeins were first extracted from milled barley grains by several extraction protocols (using different extraction agents and conditions). Hordein extracts were then analyzed directly via MALDI‐TOF MS without any preliminary purification or separation step, and the protein profiles of analyzed hordein extracts were compared in order to find out the most suitable extraction procedure for mass spectrometric analysis. The optimized procedure was successfully applied to identification of 13 malting barley varieties. Our results revealed that the proposed mass spectrometry‐based approach provides characteristic mass patterns of extracted hordeins, which can be advantageously used for barley variety identification. Copyright © 2009 John Wiley & Sons, Ltd.     

Early tables resembling those of natural logarithms

That natural logarithms may be constructed from Napier's logarithms is no surprise to a modern mathematician, but the thought that this might have been done within ten years of Napier's original publication seems a historical impossibility, since by that time, most of the modern constituents of the notion had not been conceived. Nonetheless the practical use of Napier's tables required interpolation, and the systematization of that interpolation generated a new table with a remarkable similarity to natural logarithms. This interpolation table was later extended by Speidell to stand alongside his ‘New Logarithms’, as an alternative form.     

Submillimeter wave detector workshop

A brief report on the results of a workshop concerning submillimeter wave detection held September 34, 1985.     

Three-dimensional fluid-suppressed T2-prep flow-independent peripheral angiography using balanced SSFP

Accurate depiction of the vessels of the lower leg, foot or hand benefits from suppression of bright MR signal from lipid (such as bone marrow) and long-T1 fluid (such as synovial fluid and edema). Signal independence of blood flow velocities, good arterial/muscle contrast and arterial/venous separation are also desirable. The high SNR, short scan times and flow properties of balanced steady-state free precession (SSFP) make it an excellent candidate for flow-independent angiography. In this work, a new magnetization-prepared 3D SSFP sequence for flow-independent peripheral angiography is presented. The technique combines a number of component techniques (phase-sensitive fat detection, inversion recovery, T2-preparation and square-spiral phase-encode ordering) to achieve high-contrast peripheral angiograms at only a modest scan time penalty over simple 3D SSFP. The technique is described in detail, a parameter optimization performed and preliminary results presented achieving high contrast and 1-mm isotropic resolution in a normal foot.     

Stochastic processes with orthogonal polynomial eigenfunctions

Markov processes which are reversible with either Gamma, Normal, Poisson or Negative Binomial stationary distributions in the Meixner class and have orthogonal polynomial eigenfunctions are characterized as being processes subordinated to well-known diffusion processes for the Gamma and Normal, and birth and death processes for the Poisson and Negative Binomial. A characterization of Markov processes with Beta stationary distributions and Jacobi polynomial eigenvalues is also discussed.     

Vacancy filling effect of graphene on photoluminescence behavior of ZnO/graphene nanocomposite

We report on the aerosol synthesis and optical characterization of ZnO/unoxidized graphene (UG) platelets nanocomposite films with high optical transparency (>85% at visible wavelengths). The ZnO/UG composite films, in which UG nanoplatelets are embedded in nano‐grained ZnO, were fabricated from colloidal suspensions of UG platelets with an aqueous zinc precursor. From photoluminescence (PL) spectra of the UG composite films, it was found that PL intensity decreases with the addition of UG platelets. The features of PL intensity in the UG composites are in contrast to that of ZnO/graphene oxide (G‐O) platelets composites, and can be explained by the absence of an oxygen vacancy filling effect, due to the unoxidized nature of UG and an increase in defect sites in its composites. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

NMR at earth's magnetic field using para-hydrogen induced polarization

A method to achieve NMR of dilute samples in the earth's magnetic field by applying para-hydrogen induced polarization is presented. Maximum achievable polarization enhancements were calculated by numerically simulating the experiment and compared to the experimental results and to the thermal equilibrium in the earth's magnetic field. Simultaneous 19F and 1H NMR detection on a sub-milliliter sample of a fluorinated alkyne at millimolar concentration (～10(18) nuclear spins) was realized with just one single scan. A highly resolved spectrum with a signal/noise ratio higher than 50:1 was obtained without using an auxiliary magnet or any form of radio frequency shielding.     

cis‐ and trans‐Dichloro(3,6‐dihydro‐1,2‐oxazine‐N)(dimethyl sulfoxide‐S)‐platinum(II)

Both the cis, (I), and trans, (II), isomers of the title complex, [PtCl₂(C₄H₇NO)(C₂H₆OS)], possess relatively undistorted square‐planar geometries about the Pt atoms. For (I), cisL—Pt—L angles are in the range 88.8 (2)–91.08 (8)°, while trans angles are 178.61 (8) and 179.4 (2)°. For (II), cisL—Pt—L 86.1 (3)–93.7 (1)°, and transL—Pt—L 175.5 (1) and 179.1 (3)°. The di­methyl sulfoxide (dmso) ligand adopts a normal pyramidal geometry in both complexes. In (I), the S=O bond essentially eclipses the adjacent Pt—N bond, while the oxazine ligand in (I) is twisted so as to avoid steric interactions with the adjacent chloride ligand. By contrast, the dmso ligand in (II) is rotated such that the S=O bond is approximately perpendicular to the square plane, while the oxazine ligand is once again twisted out of the plane by a similar amount as in (I). These are the first structural examples of square‐planar platinum(II) complexes containing a 1,2‐oxazine ligand.     

cis‐Bis(3,6‐di­hydro‐2H‐1,2‐oxazine‐N)­di­iodo­platinum(II) and cis‐bis(3,4,5,6‐tetra­hydro‐2H‐1,2‐oxazine‐N)­di­iodo­platinum(II)

The title complexes, [Pt(C₄H₇NO)₂I₂], (I), and [Pt(C₄H₉NO)₂I₂], (II), possess similar square‐planar coordination geometries with modest distortions from ideality. For (I), the cis‐L—Pt—L angles are in the range 87.0 (4)–94.2 (3)°, while the trans angles are 174.4 (3) and 176.4 (3)°. For (II), cis‐L—Pt—L are 86.1 (8)–94.2 (6)° and trans‐L—Pt—L are 174.4 (6) and 177.4 (5)°. One 3,6‐di­hydro‐2H‐1,2‐oxazine ligand in (I) is rotated so that the N—O bond is out of the square plane by approximately 70°, while the N—C bond is only ca 20° out of the plane. The other oxazine ligand is rotated so that the N—C bond is about 80° out of the plane, while the N—O bond is out of the plane by approximately 24°. In (II), the 3,4,5,6‐tetra­hydro‐2H‐1,2‐oxazine ligands are also positioned with one having the N—O bond further out of the plane and the other having the N—C bond positioned in that fashion. Both ligands, however, are rotated approximately 90° compared with their positions in (I). In both complexes, this results in an unsymmetrical distortion of the I—Pt—N bond angles in which one is expanded and the other contracted. These features are compared to those of reported cis‐di­amine­di­iodo­platinum(II) complexes.