Adaptive smearing for Brillouin zone integration

We suggest a simple scheme for automatically determining the width parameter of smearing methods of the Brillouin zone integration in electronic structure calculation. The scheme retains one free parameter that at any time can be eliminated by choosing a denser k‐space mesh until the desired accuracy is obtained. The tests are carried out in the context of Methfessel‐Paxton smearing. This adaptive Gaussian smearing (AGS) is easily implemented, variational with respect to partial occupancies and free from spurious occupancies that are negative or larger than one. Its convergence properties are similar to those obtained with the modified tetrahedron method for energy resolution of ≥0.1 meV. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Water-promoted one-pot vinylogous Mannich-type reaction of trimethylsilyloxyfuran

Water, produced in situ during the formation of imines from aldehydes 1 and amines 2, is employed to promote the one-pot Mannich reaction of trimethylsilyloxyfuran 3a without addition of extra solvent or catalyst. This clean and quick reaction allows the obtention of a series of 5-substituted γ-butenolides 4 with good yields and modest diastereomeric ratio. A large panel of substituents is tolerated ranging from aliphatic chains to aromatic or heteroaromatic rings.     

Glycosylated Nanoscale Surfaces: Preparation and Applications in Medicine and Molecular Biology

Carbohydrates on cell surfaces are critical components of the extracellular landscape and contribute to cell signalling, motility, adhesion and recognition. Multivalent effects are essential to these interactions that are inherently weak. Carbohydrate‐functionalised surfaces meet an important need for studying the multivalent interactions between carbohydrates and other biomolecules. Innovations in nanomaterials are revolutionising how these carbohydrate interfaces are studied and underscore their importance in the cosmos of biochemical interactions.     

Structure and electrocompression of chloride adlayers on Cu(111)

The specific adsorption of chloride on Cu(111) from acidic aqueous electrolyte (pH 3) was investigated by in-situ surface X-ray diffraction, revealing an incommensurate hexagonal rotated adlayer. The structure and its potential dependence suggest a strong adsorbate–adsorbate interaction as compared to other halide adlayers on (111)-oriented metal electrode surfaces. The orientational epitaxy can be rationalized by the model suggested by Grey and Bohr (Europhys. Lett. 18, 171, 1992), which is based on symmetry considerations.     

An impulse control approach for optimal maintenance scheduling of a gas turbine

Today gas turbine outages are determined by one global life counter and deterministic life times. In the future the gas turbine will be equipped with multiple life counters for outage determination. Therefore we present an impulse control approach which takes the probabilistic nature of the damage mechanism into account to calculate an optimized maintenance schedule. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Propagation mechanism of dust detonations

This paper summarizes the studies on dust detonations at the Stosswellenlabor of RWTH Aachen since 1987. The onset and propagation mechanism of heterogeneous dust detonations are similar to those of marginal gas phase detonations. A self-sustained dust detonation has transverse wave structures that provide the coupling between shock and reaction. Large transition distances and transverse wave spacings require large sized tubes for the propagation of self-sustained dust detonations. The Hugoniot analysis of the Chapman-Jouguet detonation predicts equilibrium detonation states being in reasonable agreement with the self-sustained dust detonations observed. Shock matching calculations at the triple point adequately determine the wave structures of those stable dust detonations.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

Low jitter reliable nanosecond spark source for optical short-duration measurements

A simple nanosecond spark source (Nanospark) has been constructed from several small ceramic capacitors, one thyratron and one coaxial cable. During operation, a 500 pF capacitor in the spark head is pulsecharged in about 70 ns with automatic preionization from a high-voltage pulse generator switched by a thyratron. This charge is available for discharge when the gas breakdown starts. The preionization is useful to start the gas breakdown easily and to decrease the pulse to pulse jitter. This Nanospark produces 12–15 ns (FWHM) light pulses with a time jitter of less than 60 ns when operated at 8–11 kV and at air of atmospheric pressure. The initiation of the spark discharge is highly reliable. The spark has adequately exposed polaroid film (ASA 3000).     

Fluctuation–Dissipation Relation for Systems with Spatially Varying Friction

When a particle diffuses in a medium with spatially dependent friction coefficient \(\alpha (r)\) at constant temperature \(T\) , it drifts toward the low friction end of the system even in the absence of any real physical force \(f\) . This phenomenon, which has been previously studied in the context of non-inertial Brownian dynamics, is termed “spurious drift”, although the drift is real and stems from an inertial effect taking place at the short temporal scales. Here, we study the diffusion of particles in inhomogeneous media within the framework of the inertial Langevin equation. We demonstrate that the quantity which characterizes the dynamics with non-uniform \(\alpha (r)\) is not the displacement of the particle \(\Delta r=r-r^0\) (where \(r^0\) is the initial position), but rather \(\Delta A(r)=A(r)-A(r^0)\) , where \(A(r)\) is the primitive function of \(\alpha (r)\) . We derive expressions relating the mean and variance of \(\Delta A\) to \(f\) , \(T\) , and the duration of the dynamics \(\Delta t\) . For a constant friction coefficient \(\alpha (r)=\alpha \) , these expressions reduce to the well known forms of the force-drift and fluctuation–dissipation relations. We introduce a very accurate method for Langevin dynamics simulations in systems with spatially varying \(\alpha (r)\) , and use the method to validate the newly derived expressions.     

An extension theorem for planar semimodular lattices

We prove that every finite distributive lattice \(D\) can be represented as the congruence lattice of a rectangular lattice \(K\) in which all congruences are principal. We verify this result in a stronger form as an extension theorem.