Olefination of α,α'-divinyl ketones through catalytic Meyer-Schuster rearrangement

The direct olefination of 1,4-dien-3-ones remains a synthetic challenge. A two-step protocol, employing acetylide addition followed by catalytic Meyer-Schuster rearrangement has been developed for the olefination of 1,4-pentadien-3-ones to afford [3]dendralenes. Many of the traditional methods for the Meyer-Schuster rearrangement of alkynyl carbinols are not suitable with these highly unsaturated substrates because of their acid sensitivity. Unexpected reactivity during attempted rearrangement, including Nazarov-type electrocyclizations, is presented, along with conditions to promote the Meyer-Schuster rearrangement of ethoxyacetylene adducts using catalytic VO(acac)(2).     

On Bayesian group sequential sampling procedures

A general group sequential statistical decision model is investigated. Using a Bayesian approach and Bayesian dynamic programming, we examine structural properties of the cost functions and of optimal sampling procedures. In particular, we consider variable-sample-size-sequential probability ratio tests and show that the so-called onion-skins conjecture is false.     

MANIPULATION OF ATOMS, MOLECULES AND CLUSTERS FOR CONSTRUCTION OF NANOSYSTEMS

Controlled manipulations with the scanning tunneling microscope (STM) down to the scale of small molecules and single atoms allow to built molecular and atomic nanosystems, leading to the fascinating possibility of creating manmade structures on atomic scale. Here we present a short review on atomic scale manipulation investigations. Upon soft lateral manipulation of adsorbed species, in which only tip/particle forces are used, three different manipulation modes (pushing, pulling, sliding) can be discerned. We show that even the manipulation of highly coordinated native substrate atoms is possible and we demonstrate how this can be applied as local analytic and synthetic chemistry tools, with important consequences on surface structure research. Vertical manipulation of Xe and CO is demonstrated, leading to improved imaging with functionalized tips. With CO deliberately transferred to the tip, we have also succeeded to perform vibrational spectroscopy on single molecules. Furthermore, we describe how we have reproduced a full chemical reaction with single molecules, whereby all basic steps, namely preparation of the reactants, diffusion and association, are induced with the STM tip. Finally, we have extended the manipulation techniques to large specially designed molecules by performing lateral manipulation in constant height and realizing the principle of a conformational molecular switch.     

Reconstruction behaviour of fcc(110) transition metal surfaces and their vicinals

The fcc(110) surfaces are well known for their strong tendency to missing-row (MR) type reconstructions either in the clean state (Au, Pt) or driven by adsorbates (Ni, Cu, Pd, Ag). The present knowledge on the different reconstruction behaviour of flat (110) surfaces is reviewed. The survey focuses on recent scanning tunneling microscopy (STM) studies, which for the first time also elucidate the dynamics of the reconstruction process for the various systems. An overview of our recent STM and low energy electron diffraction studies on vicinal Au(110) and Ni(110) surfaces is given, aiming for a deeper understanding of the influence of steps on reconstruction behaviour of fcc(110) surfaces on the one hand, and on the stability of reconstructing vicinal surfaces on the other. Finally, we report on the reconstruction behaviour of Ir(110), which stabilizes in the clean state by formation of mesoscopic (331) facets and dereconstructs to the (1×1) phase upon oxygen adsorption at 700–900 K.     

Detection of human and rodent 5-HT3B receptor subunits by anti-peptide polyclonal antibodies

Background  

The 5-HT₃ receptor is a member of a neurotransmitter-gated ion channel family which includes nicotinic acetylcholine, GABA_A, and glycine receptors. While antibodies specific for the 5-HT_3A receptor subunit are plentiful, and have revealed a wealth of structural and functional information, few antisera exist for the detection of 5-HT_3B receptor subunits. Here we describe the generation and characterisation of a rabbit polyclonal antiserum that specifically recognises 5-HT_3B receptor subunits     

Single atomic manipulation and writing with scanning tunnelling microscopy at low temperatures

In the work reported in this paper,we have used a low-temperature scanning tunnelling microscope (LT-STM) system to manipulate accurately single atoms.We show how we can use a LT-STM to image and modify a bulk Ag(111) surface and manipulate Ag atoms from substrate and evaporated adsorbates on Ag(111) substrates.We present a synergistic combination of SM-induced modification and ordered arrays of nanometre-scale structures.In particular,we demonstrate the ability to modify Ag atomic nanometre structures on the Ag(111) substrate,and some English letters and a Chinese character can be written by single Ag atoms coming from the substrate and evaporated adsorbates on Ag(111),In this way ,we supply an effective basis to explore the fundamental physical properties of a nanometre structure and to develop nanotechnology with a bottom-up approach,     

Über die Konvergenz eines Iterationsverfahrens der ebenen Elastizitätstheorie

Zusammenfassung und Ausblick Für ein von kubo und Seika I aufgestelltes Iterationsverfahren zur Bestimmung von Spannungen in periodisch nichthomogenen unendlichen Scheiben wurde die Konvergenz nachgewiesen für den Fall, daß die Airysche Spannungsfunktion periodisch ist. kubo und Seika geben an, daß sich dieses Verfahren auch auf Randwertprobleme erweitern läßt. Dies ist ohne Zweifel der Fall für starre Einschlüsse. Zwar ist dann das Kriterium (16) nicht mehr erfüllt; der Konvergenzbeweis läßt sich jedoch mit Hilfe der Überlegungen von II § 4 auch auf diesen Fall ausdehnen. Dagegen wachsen in Löchern und über alle Grenzen, so daß dort F() in (9) seinen Sinn verliert. Für diesen Fall gibt es jedoch ein Iterationsverfahren, dessen Prinzip von Hetényi und Neas für Randwertprobleme angegeben wurde. Es läßt sich auch auf Nichthomogenitätsprobleme erweitern (II, § 3.5); bei diesem Verfahren der sukzessiven Belastung spielen dann die Verschiebungen eine ähnliche Rolle wie die Airysche Spannungsfunktion beim Verfahren von kubo und Seika. Auch Kombinationen beider Verfahren sind denkbar; doch sind für diesen Fall noch einige Einzelheiten zu klären (II, § 1.4, § 3.7–8).     

Die Auflösung einer Klasse verallgemeinerter Abelscher Integralgleichungen

Ohne Zusammenfassung     

Engineering electronic lifetimes in artificial atomic structures

By means of atomic manipulation, 51 Ag atoms have been precisely positioned to form a triangle with a base length of 245 A on a Ag(111) substrate. The scattering of the surface electrons at these adatoms results in a complex interference pattern. Spectroscopic data and dI/dV maps taken inside the triangle have been quantitatively evaluated by multiple scattering calculations of the wave pattern. Adjustment of the scattering parameters to the data yields the properties of the scatterers and the electron lifetimes. The experimental results for the electron lifetimes deviate from a (E-E(F))(-2) dependence and reflect the electronic band structure at the surface as well as the local influence of the triangle.