Oligonucleotides Functionalized by Fluorescein and Rhodamine Dyes: Michael Addition of Methyl Acrylate to 2′‐Deoxypseudouridine

The 2′‐deoxypseudouridine ( 5 ) was functionalized at N(1) with methyl acrylate by Michael addition. The resulting methyl 2′‐deoxypseudouridine‐1‐propanoate ( 6 ) was converted to the phosphoramidite 8 and to the amino‐functionalized derivative 9 , which was transformed into the fluorescein‐labeled phosphoramidites 14 and 16 . Fluorescent oligonucleotides were synthesized either from these building blocks or by post‐synthetic modification of oligomers containing 2′‐deoxypseudouridine subunits. The stability of oligonucleotide duplexes was determined from the melting profiles, measured by UV‐ or VIS‐light absorbance, as well as from the fluorescence emission spectra. While small spacer residues did not affect the thermal stability of the 2′‐deoxypseudouridine‐containing duplexes, large dye residues led to destabilization.     

The mystery of the alkali metals; the induced anomalous Hall effect in thin Cs films

Sandwiches made from Fe and Cs films are investigated as a function of the magnetic field and the Cs thickness. Conduction electrons which cross from the Fe to the Cs are marked by a drift velocity component perpendicular to the electric field. The anomalous Hall effect in the Fe provides this “non-diagonal” kick to the electrons that cross from the Fe into the Cs. The ballistic propagation of the conduction electrons can be monitored as a function of the Cs film thickness. The free propagation into the Cs is measured in terms of the non-diagonal conductance L_xy which we denote as the “induced anomalous Hall conductance”L _xy ⁰. For a normal (non-magnetic) metal in contact with Fe, L_xy increases with the thickness of the normal metal until the film thickness exceeds (half) the mean free path of the conduction electrons. For Cs on top of Fe the induced anomalous Hall conductance increases up to a Cs coverage of about 100 A, then, in contrast to other non-magnetic metals, L _xy ⁰ decreases for larger Cs coverage and approaches zero. This behavior cannot be explained with the free electron model. The strange behavior of the induced AHC in Cs films adds an even more challenging mystery to the already poorly understood properties of thin Cs films. These results defy explanation in the free electron model. Received 29 April 1999 and Received in final form 10 July 1999     

Crystalline Si thin-film solar cells: a review

The present review summarizes the results of research efforts in the field of crystalline silicon thin-film solar cells on foreign substrates. The large number of competing approaches can be broadly classified according to the grain size of the crystalline Si films and the doping of the crystalline absorber. Currently, solar cells based on microcrystalline Si films on glass with an intrinsic or moderately doped absorber film achieve efficiencies around 10%, whereas thin-film cells fabricated from large-grained polycrystalline Si on high-temperature-resistant substrates have efficiencies in the range of 15%. The paper discusses the limitations of various approaches and describes recent developments in the area of thin, monocrystalline Si films that may open the way towards 20% efficient thin-film Si solar cells. Received: 1 March 1999 / Accepted: 28 March 1999 / Published online: 24 June 1999     

Electrical properties of transparent carbon nanotube networks prepared through different techniques

Ultra‐thin, optically transparent and electrically conducting films of pure carbon nanotubes (CNTs) are widely studied thanks to their promise for broad applications. In the present work, we study and compare different deposition techniques for the production of these networks: dip‐coating, spray‐coating, vacuum filtration and electrophoretic deposition on a quartz glass using single‐walled carbon nanotubes (SWCNTs) produced by the HiPCo method. In order to optimize the networks, besides the various deposition techniques we also investigate how the optical and electrical properties vary if the networks are fabricated from different CNTs, all synthesized by the CVD method: SWCNTs, DWCNTs and MWCNTs. As the main criteria for evaluating the quality of these CNT networks we measure the electrical surface resistance at a certain optical transmittance and correlate it to the morphology (homogeneity and roughness) of the networks. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spektralanalyse von Metallegierungen

Ohne Zusammenfassung     

ALS-associated mutant SOD1<Superscript>G93A</Superscript> causes mitochondrial vacuolation by expansion of the intermembrane space and by involvement of SOD1 aggregation and peroxisomes

Background  

Amyotrophic lateral sclerosis (ALS) is an age-dependent neurodegenerative disease that causes motor neuron degeneration, paralysis and death. Mutations in Cu, Zn superoxide dismutase (SOD1) are one cause for the familial form of this disease. Transgenic mice expressing mutant SOD1 develop age-dependent motor neuron degeneration, skeletal muscle weakness, paralysis and death similar to humans. The mechanism whereby mutant SOD1 induces motor neuron degeneration is not understood but widespread mitochondrial vacuolation has been observed during early phases of motor neuron degeneration. How this vacuolation develops is not clear, but could involve autophagic vacuolation, mitochondrial permeability transition (MPT) or uncharacterized mechanisms. To determine which of these possibilities are true, we examined the vacuolar patterns in detail in transgenic mice expressing mutant SOD1^G93A.     

Role of kinetic effects on the polarization current around a magnetic island

The polarization current due to a magnetic island rotating in a tokamak plasma is believed to play a central role in the initial evolution of the neoclassical tearing mode. Monte Carlo delta f simulations are performed which also cover a parameter range that is not amenable to analytic treatment but is relevant to experiments. It is shown that the polarization current can change sign when the island rotation frequency is of the order of the ion parallel streaming around the island. Moreover, the current is reduced when the island width is of the order of the ion banana width. Finally, the transition to the enhanced high-collisionality regime is shown to occur for collision frequencies higher than those typical of today's experiments.     

Revealing antiferromagnetic order of the Fe monolayer on W(001): spin-polarized scanning tunneling microscopy and first-principles calculations

We prove that the magnetic ground state of a single monolayer Fe on W(001) is c(2x2) antiferromagnetic, i.e., a checkerboard arrangement of antiparallel magnetic moments. Real space images of this magnetic structure have been obtained with spin-polarized scanning tunneling microscopy. An out-of-plane easy magnetization axis is concluded from measurements in an external magnetic field. The magnetic ground state and anisotropy axis are explained based on first-principles calculations.