Freezing vortex rivers

We demonstrate experimentally and theoretically that the dissipative state at high current densities of superconducting samples with a periodic array of holes consist of flux rivers resulting from a short range attractive interaction between vortices. This dynamically induced vortex–vortex attraction results from the migration of quasiparticles out of the vortex core. We have directly visualized the formation of vortex chains by scanning Hall microscopy after freezing the dynamic state by a field cooling procedure at constant bias current. Similar experiments carried out in a sample without holes show no hint of flux river formation.     

Synthesis and Properties of Oligonucleotides Containing 2,4‐Dihydroxycyclohexyl Nucleosides

Cyclohexyl nucleosides with an adenine and uracil base have been synthesized from 2‐azidocyclohexane‐1,5‐diol. The obtained racemic nucleosides were resolved using (R)‐O‐methylmandelic acid. Short oligonucleotides were synthesized using phorphoramidite chemistry. However, these oligonucleotides do not show self‐hybridization, and duplexes are less stable than those of ribopyranosyl‐(4′ → 2′)‐oligonucleotides.     

Random field forward interest rate models,market price of risk and their statistics

In this paper we consider discrete time forward interest rate models. In our approach, unlike in the classical Heath–Jarrow–Morton framework, the forward rate curves are driven by a random field. Hence we get a general interest rate structure. Our aim is to give an overview of our results in such a model on the following questions: no-arbitrage conditions, maximum likelihood estimation of the volatility, as well as the joint estimation of the parameters and the asymptotic behaviour of the estimators, relationship with continuous models. Finally we give discussion on the practical problems of the estimation and we show several numerical results on the statistics of such models. This research has been supported by the Hungarian Scientific Research Fund under Grants No. OTKA–F046061/2004 and OTKA–T048544/2005.     

Incorporation of a conjugated side‐chain in regioregular polythiophenes: Chiroptical properties and selective oxidation

The synthesis, aggregation, and optical properties of a chiral, regioregular polythiophene, substituted with a conjugated substituent, are described. The polymer was prepared using a Stille coupling reaction. The fact that the side‐chain contributes to the absorption (UV‐vis), emission (fluorescence), and redox behavior (cyclic voltammetry) of the material demonstrates that the substituent contributes to the electronic properties. It was shown that the conjugated side‐chain chirally stacks in conditions in which the polymer backbone aggregates, which demonstrates the ability of conjugated polymers to induce a (chiral) lamellar organization of conjugated moieties, present in their side‐chain. The aggregation of both the side‐chain and the backbone was monitored using UV‐vis and CD spectroscopy. Finally, it is shown that the conjugated side‐chain can selectively be oxidized, without oxidizing the polythiophene backbone. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1891–1900, 2009     

1‐(3‐Methoxy­benzoyl)‐3,3‐diethyl­thiourea

The title compound, C₁₃H₁₈N₂O₂S, crystallizes in the thio­amidic form. The mol­ecules are connected by N—H?S interactions forming dimers with N?S and H?S distances of 3.487 (4) and 2.76 Å, respectively.