Localized states and non-variational Ising–Bloch transition of a parametrically driven easy-plane ferromagnetic wire

A time-periodic magnetic field applied transversally to the hard axis of an extended easy-plane ferromagnetic sample can produce parametric resonance. For the 2:1 resonance, the prototype order-parameter-equation derived from the Landau–Lifshitz–Gilbert dynamical model for the precessional motion is the parametrically driven damped nonlinear Schrödinger equation. Unfortunately this standard approximation fails to meet the stability feature of the synchronized precession states, and we propose some amendment. Localized solutions supported by the uniform states are characterized and classified into two types: motionless and propagative states, rising through a non-variational Ising–Bloch transition. We propose and investigate a dynamical model ruling this transition.     

Acid-induced dimerisation of 1,2-di(thien-2-yl)ethanone

Treatment of 1,2-di(thien-2-yl)ethanone with aqueous 75% (v/v) sulfuric acid gives a dimer in which the units are linked head-to-head via a thiophene-tetrahydrothiophene bond.     

1,4‐Dilithio‐1,1,4,4‐tetraphenylbutane in diethyl ether: An effective initiator for the living anionic polymerization of dienes

The anionic polymerization of butadiene initiated with 1,4‐dilithio‐1,1,4,4‐tetraphenylbutane (LiTPB) in diethyl ether (DEE) gives polybutadiene (PBD) with high 1,2 content (>70%), narrow polydispersities (1.04 < M_w/M_n < 1.20), and predicted molecular weights. In THF, this polymerization does not work very well. After removal of DEE and addition of THF, the PBD dianion is end capped quantitatively by addition of 1,1‐diphenylethylene (DPE) to give the diphenylalkyl end capped PBD dianion. Subsequent addition of methyl methacrylate at low temperatures results in the formation of well‐defined PMMA‐b‐PBD‐b‐PMMA triblock copolymers. The results are accounted for by taking into account the effects of Li ion solvation on the BD initiation and end capping of the PBD anion by DPE. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2198–2206, 2009     

Synthesis and Properties of Oligodeoxynucleotide Analogs with Bis(methylene) Sulfone Bridges

A convergent, solution‐phase synthesis was developed for the bis(methylene) sulfone‐bridged oligodeoxynucleotide analogs (SNA) 5′‐d(HOCH₂‐Tso ₂Tso ₂Tso ₂Cso ₂Tso ₂Tso ₂Tso ₂T‐CH₂SO )‐3′ ( 35b ) and 5′‐d(HOCH₂‐Tso ₂Tso ₂Tso ₂Tso ₂Tso ₂Tso ₂Tso ₂T‐CH₂SO )‐3′ ( 34c ) (SO₂ corresponds to CH₂SO₂CH₂ instead of OP(?O)(O^?)(O). In these, the phosphodiester linkages are replaced by non‐ionic bis(methylene) sulfone linkers. The general strategy involved convergent coupling of 3′,5′‐bishomo‐β‐D ‐deoxyribonucleotide analogs functionalized at the 6′‐end (?CH₂? C(5′)) as bromides or mesylates and at the CH₂? C(3′) position as thiols, with the resulting thioether being oxidized to the corresponding sulfone. A single charge was introduced at the terminal CH₂? C(3′) position of the octamers to increase their solubility in water. During the synthesis, it became apparent that the key intermediates generated secondary structures through either folding or aggregation in a variety of solvents. This generated unusual reactivity and was unique for very similar structures. For example, although the dimeric thiol d(BzOCH₂‐Tso ₂C‐CH₂SH) ( 14b ) was a well‐behaved synthetic intermediate, the tetrameric thiol d(TrOCH₂‐Tso ₂Tso ₂Tso ₂^toC‐CH₂SH) derived from the corresponding thioacetate was rapidly converted to a disulfide by very small amounts of oxidant ( 28 → 29 , Scheme 6), while the analogous tetrameric thiol d(BzOCH₂‐Tso ₂Ts Tso ₂T‐CH₂SH) ( 26 ), differing only by a single heterocycle, was oxidized much more slowly (Bz=PhCO, Tr=Ph₃C, to=2‐MeC₆H₄CO (at N⁴ of dc)). The sequence‐dependent reactivity, well known in many classes of natural products (including polypeptides), is not prominent in natural oligonucleotides. These results are discussed in light of the proposal that the repeating negative charge in nucleic acids is key to their ability to serve as genetic molecules, in particular, their capability to support Darwinian evolution. The ability of 5′‐d(HOCH₂‐Tso ₂Tso ₂Tso ₂Cso ₂Tso ₂Tso ₂Tso ₂T‐CH₂SO )‐3′ ( 35b ) to bind as a third strand to duplex DNA was also examined. No triple‐helix‐forming propensity was detected in this molecule.     

Analysis of surface layers of an iron axe from Early Medieval Age

An ancient axe from Early Medieval Age which was unearthed on a territory of the archaeological excavation site near the village Borovce (Slovakia) is investigated. The surface of the axe was supposed to be covered with a sort of glassy system. Mössbauer effect measurements performed in backscattering and transmission geometry upon original as well as powdered pieces of the axe confirmed that the surface layers of the axe consist of goethite, lepidocrite, akageneite, and/or magnetite. After temperature treatment at 400°C/100 min hematite and maghemite were found; these are products of thermal decomposition of the above mentioned iron phases. These findings ruled out the hypothesis that the surface covering substance was put on the axe by intention.