Overtone spectra of 2-mercaptoethanol and 1,2-ethanedithiol

Vibrational spectra of vapor-phase 1,2-ethanedithiol and 2-mercaptoethanol were recorded to investigate weak intramolecular interactions. The spectra were recorded with conventional absorption spectroscopy and laser photoacoustic spectroscopy in the 2000-11,000 cm(-1) region. The room temperature spectra of each molecule are complicated by contributions from several conformers. Anharmonic oscillator local-mode calculations of the OH- and SH-stretching transitions have been performed to facilitate assignment of the different conformers in the spectra. We observe evidence of hydrogen-bond-like interactions from OH to S, but not from SH to O or S. The OH to S intramolecular interaction in 2-mercaptoethanol is weak and comparable to that found in the OH to O interaction in ethylene glycol.     

Synthesis and molecular modelling of double-functionalised nucleosides with aromatic moieties in the 5'-(S)-position and minor groove interactions in DNA zipper structures

A series of six double-functionalised nucleosides, in which aromatic moieties were inserted into the 5'-(S)-C-position, were synthesised and incorporated into DNA duplexes. The aromatic moieties were thymine-1-yl, phenyl, 1,2,3-triazol-1-yl, 1,2,3-triazol-4-yl, 4-(uracil-5-yl)-1,2,3-triazol-1-yl and 4-phenyl-1,2,3-triazol-1-yl. The DNA duplexes were studied with UV melting curves, CD spectroscopy and molecular modelling. The results showed that the aromatic moieties in some cases interact in the minor groove forming DNA zipper structures. The strongest specific interaction was found between two thymines or between a thymine and a phenyl group in a crossed (-3)-zipper motif (i.e., with two base pairs interspacing the modifications). Modelling revealed that the interaction is aromatic stacking across the minor groove. Also, the extended uracil-triazole moiety demonstrated zipper contacts in the minor groove as well as binding to the floor of the groove.     

DFT+U study of defects in bulk rutile TiO(2)

We present a systematic study of electronic gap states in defected titania using our implementation of the Hubbard-U approximation in the grid-based projector-augmented wave density functional theory code, GPAW. The defects considered are Ti interstitials, O vacancies, and H dopants in the rutile phase of bulk titanium dioxide. We find that by applying a sufficiently large value for the Hubbard-U parameter of the Ti 3d states, the excess electrons localize spatially at the Ti sites and appear as states in the band gap. At U=2.5?eV, the position in energy of these gap states are in fair agreement with the experimental observations. In calculations with several excess electrons and U=2.5?eV, all of these end up in gap states that are spatially localized around specific Ti atoms, thus effectively creating one Ti(3+) ion per excess electron. An important result of this investigation is that regardless of which structural defect is the origin of the gap states, at U=2.5?eV, these states are found to have their mean energies within a few hundredths of an eV from 0.94 eV below the conduction band minimum.     

Implementing combined uncertainty according to GUM into a commercial gamma spectrometric software

Measurement uncertainty is an important part of a measurement result that still often is neglected. A complete combined uncertainty budget can be calculated for non-routine measurements. However, for routine measurements, this work becomes time-consuming since every measurement result requires an uncertainty analysis. By analysing the uncertainty on a measurement system level in e.g. high resolution gamma spectrometry, the uncertainty analysis will be universal for a particular measurement geometry. The problem is then reduced to implementing the combined uncertainty into measurement software. This work shows how this analysis can be done and implemented into a commercial software for gamma spectrometric measurements.     

Uniform Regularity Close to Cross Singularities in an Unstable Free Boundary Problem

We introduce a new method for the analysis of singularities in the unstable problem $$ \Delta u = -\chi_{\{u >0 \}}, $$ which arises in solid combustion as well as in the composite membrane problem. Our study is confined to points of “supercharacteristic” growth of the solution, i.e. points at which the solution grows faster than the characteristic/invariant scaling of the equation would suggest. At such points the classical theory is doomed to fail, due to incompatibility of the invariant scaling of the equation and the scaling of the solution. In the case of two dimensions our result shows that in a neighborhood of the set at which the second derivatives of u are unbounded, the level set {u = 0} consists of two C ¹-curves meeting at right angles. It is important that our result is not confined to the minimal solution of the equation but holds for all solutions.     

Adsorption of molecular SiO2 on a clean Si(1 0 0) surface

We have investigated the adsorption of molecular (gaseous) SiO₂ on a clean Si(1 0 0) p(2 × 2) reconstructed surface using density functional theory based methods. The SiO₂ molecule is found to be chemisorbed on various sites on the Si surface and the most energetically favourable structure is on top of the dimers. The minimum energy pathways for the various adsorption channels indicate that the reaction is barrierless in all cases. The corresponding vibrational spectrum is also calculated and the adsorbed molecules are, as expected, found to have red-shifted vibrational frequencies. The energetically favourable adsorption sites and adsorption energies are comparable to the results found for SiO.     

Geometric Counting on Wavefront Real Spherical Spaces

We provide L~p-versus L~∞-bounds for eigenfunctions on a real spherical space Z of wavefront type. It is shown that these bounds imply a non-trivial error term estimate for lattice counting on Z. The paper also serves as an introduction to geometric counting on spaces of the mentioned type.     

Compact operator semigroups applied to dynamical systems

A right chain ordered semigroup is an ordered semigroup whose right ideals form a chain. In this paper we study the ideal theory of right chain ordered semigroups in terms of prime ideals, completely prime ideals and prime segments, extending to these semigroups results on right chain semigroups proved in Ferrero et al. (J Algebra 292:574–584, 2005).     

Algebras that satisfy Auslander’s condition on vanishing of cohomology

Auslander conjectured that every Artin algebra satisfies a certain condition on vanishing of cohomology of finitely generated modules. The failure of this conjecture—by a 2003 counterexample due to Jorgensen and Şega—motivates the consideration of the class of rings that do satisfy Auslander’s condition. We call them AC rings and show that an AC Artin algebra that is left-Gorenstein is also right-Gorenstein. Furthermore, the Auslander–Reiten Conjecture is proved for AC rings, and Auslander’s G-dimension is shown to be functorial for AC rings that are commutative or have a dualizing complex.