Local ionic motion in the superionic conductor Li3N

Anisotropic dielectric behavior of the superionic conductor lithium nitride (Li₃N) is reported for low temperature where the dc ionic conductivity can be neglected (T<17oK). For E ⊥ c the static dielectric constant followed a Langevin-Debye (ε ∝ 1/T) type law from 170 to 80K which changed to a temperature independent value below 40K. Debye relaxations were measured between 10 and 50K in the frequency range 10Hz to 1MHz. The observed properties are discussed in terms of a locally restricted ionic motion in shallow potentials. Different types of potentials are considered and an overdamped oscillator model is proposed.     

Time-lapse STM studies of diastereomeric cinchona alkaloids on platinum metals

The adsorption of cinchonidine (CD) and cinchonine (CN) on Pt(111) and Pd(111) single crystals has been investigated by means of scanning tunneling microscopy (STM) in an ultrahigh vacuum system. In time-lapse series the mobilities of different adsorption species have been determined on a single molecule basis and with varying hydrogen background pressures in the system. The diastereomeric cinchona alkaloids, CD and CN, which are widely used as chiral modifiers of platinum group metals in catalytic enantioselective hydrogenation, showed similar adsorption modes and diffusion behavior on Pt(111), except that the flatly adsorbed CN molecules which were free (not in a dimer/cluster) were significantly more mobile than their CD analogues. CD adsorbed on Pd(111) showed similar adsorption modes as observed on Pt(111) but at considerably higher mobility of the flatly absorbed species already in the low-pressure region. The observed adsorption behaviors are discussed in the context of independent ATR-IR measurements and theoretical calculations. Special emphasis is put on the nonlinear effect observed in hydrogenation reactions with CD/CN mixtures. Our observations corroborate that this effect is mainly a consequence of the different adsorption strengths of CD and CN on Pt.     

Local pressure-induced metallization of a semiconducting carbon nanotube in a crossed junction

The electronic and vibrational density of states of a semiconducting carbon nanotube in a crossed junction was investigated by elastic and inelastic scanning tunneling spectroscopy. The strong radial compression of the nanotube at the junction induces local metallization spatially confined to a few nanometers. The local electronic modifications are correlated with the observed changes in the radial breathing and G band phonon modes, which react very sensitively to local mechanical deformation. In addition, the experiments reveal the crucial contribution of the image charges to the contact potential at nanotube-metal interfaces.     

Measuring surface pressure with far field acoustics

This paper presents measurements of the wavenumber frequency spectrum of wall pressure fluctuations under a turbulent boundary layer made using sound radiated from hydrodynamically smooth ridges in the surface. The measurements also serve as a test of the scattering theory of roughness noise. The radiated sound reveals a cut through the full three-dimensional wavenumber frequency spectrum of the wall pressure at the wavenumber of the surface. Since ridges can be made with very small wavelengths, this technique can be used to probe the structure of the wall pressure spectrum on scales far smaller than those that can be reached using conventional wall-mounted transducers. Furthermore, the method reveals the wavenumber frequency spectrum directly, without the need for multi-point measurements or the spatial Fourier transforming of data. Measured spectra bear a close similarity to Corcos’ and Chase's model forms, and confirm the applicability of the theory of roughness noise and its prediction of roughness noise directivity.     

Energy deposition distributions caused by fast neutrons in converter type silicon detectors

Polyethylene converter silicon detectors have been developed as part of a dosimetry system for the application in neutron fields. Signals have been investigated which are mainly caused by reactions occurring when neutrons hit the PE converter or the silicon diode directly. In this work, neutron interactions in the components of a PE converter silicon sensor have been calculated to determine energy deposition distributions for neutron energies from 1.2 v MeV to 14.8 v MeV. Experiments in quasi-monoenergetic neutron fields have been performed. For the simulation of the neutron interactions with the detector layers, the GSF neutron interaction code NISD has been applied. The transport of ions has been calculated separately by means of the program TRIM. It has been shown that by the use of these concepts and models, a rather good agreement of measured and computed pulse height distributions can be obtained and, consequently, the response of converter type detectors to neutron radiation can be determined.     

Antisense-mediated isoform switching of steroid receptor coactivator-1 in the central nucleus of the amygdala of the mouse brain

Background

Antisense oligonucleotide (AON)-mediated exon skipping is a powerful tool to manipulate gene expression. In the present study we investigated the potential of exon skipping by local injection in the central nucleus of the amygdala (CeA) of the mouse brain. As proof of principle we targeted the splicing of steroid receptor coactivator-1 (SRC-1), a protein involved in nuclear receptor function. This nuclear receptor coregulator exists in two splice variants (SRC-1a and SRC-1e) which display differential distribution and opposing activities in the brain, and whose mRNAs differ in a single SRC-1e specific exon.

Methods

For proof of principle of feasibility, we used immunofluorescent stainings to study uptake by different cell types, translocation to the nucleus and potential immunostimulatory effects at different time points after a local injection in the CeA of the mouse brain of a control AON targeting human dystrophin with no targets in the murine brain. To evaluate efficacy we designed an AON targeting the SRC-1e-specific exon and with qPCR analysis we measured the expression ratio of the two splice variants.

Results

We found that AONs were taken up by corticotropin releasing hormone expressing neurons and other cells in the CeA, and translocated into the cell nucleus. Immune responses after AON injection were comparable to those after sterile saline injection. A successful shift of the naturally occurring SRC-1a:SRC-1e expression ratio in favor of SRC-1a was observed, without changes in total SRC-1 expression.

Conclusions

We provide a proof of concept for local neuropharmacological use of exon skipping by manipulating the expression ratio of the two splice variants of SRC-1, which may be used to study nuclear receptor function in specific brain circuits. We established that exon skipping after local injection in the brain is a versatile and useful tool for the manipulation of splice variants for numerous genes that are relevant for brain function.     

Bz-Oxy-Indolinone

Zusammenfassung Durch diese Untersuchung wurde festgestellt, daß sich auch solche Hydrazide durch Erhitzen mit Kalk in Indolinone überführen lassen, welche im Benzolkern in der Ortho- und Parastellung zur Hydrazingruppe ein Methoxyl enthalten. Im Hinblick auf die antipyretischen und antineuralgischen Eigenschaften, welche einige Indolinone aufweisen sollen, könnten vielleicht auch diese Indolinone als Heilmittel Beachtung verdienen.Es wurden dabei folgende Verbindungen, die bisher nicht bekannt sind, erhalten und analysiert: F. P.B-3-Methoxy-Pr-3, 3-Dimethyl-2-Indolinon 150° Monobromprodukt dieses Indolinons 218° Acetylprodukt dieses Indolinons 84° Benzoylprodukt dieses. Indolinons 82°B-3-Hydroxyl-Pr-3,3-Dimethyl-2-Indolinon 244° Diacetylprodukt dieses Indolinons 126° Monobenzoylprodukt dieses Indolinons 240°B- Methoxy-Pr-3, 3-Dimethyl-2-Indolinon 101° Monobromprodukt dieses Indolinons 200°B-1-Hydroxyl-Pr-3, 3-Dimethyl-2-Indolinon 250°     

Synthesis of a polyrotaxane-based macroporous polymer as stationary phase for capillary electrochromatography via host-guest complexation of N,N '-ethylenedianilinediacrylamide with statistically methylated beta-cyclodextrin

A synthetic route to acrylamide-based monolithic stationary phases for CEC with rotaxane-type immobilized derivatized beta-CD was explored. N,N'-Ethylenedianilinediacrylamide was synthesized as the water-insoluble crosslinker forming water-soluble inclusion complexes with statistically methylated beta-CD. Mixed-mode stationary phases were synthesized by free radical copolymerization of the bisacrylamide-CD host-guest complex with water-soluble monomers and an additional water-soluble crosslinker in aqueous solution. Complex formation in solution and inclusion of the pseudorotaxane into the polymeric network (formation of a polyrotaxane architecture) were studied by means of (1)H-NMR chemical shift analysis, CD modified micellar EKC (CD-MEKC), 2D-NOESY spectroscopy, and solid state( 13)C-NMR spectroscopy. The presence of a mixed-mode selectivity of the stationary phase based on hydrophobic and hydrophilic interaction was confirmed by CEC with neutral polar and nonpolar solutes.     

Wacker Oxidation of Methylenecyclobutanes: Scope and Selectivity in an Unusual Setting

Methylenecyclobutanes are found to undergo Wacker oxidation via a semi-pinacol-type rearrangement. Key to a successful process is the use of tert-butyl nitrite as oxidant, which not only enables efficient catalyst turn-over but also ensures high Markovnikov-selectivity under mild conditions. Thus, cyclopentanones (26 examples) can be accessed in an overall good yield and excellent selectivity (up to 97 % yield, generally >99 : 1 ketone:aldehyde ratio). Stereochemical analysis of the reaction sequence reveals migration aptitudes in line with related 1,2-shifts. By introducing a pyox ligand to palladium, prochiral methylenecyclobutanes can be desymmetrized, thus realizing the first enantioselective Wacker oxidation.     

Small silicon memories: confinement, single-electron,. and interface state considerations

Memories that utilize single-electron effects are an attempt at combining the discreteness observable in transport of electrons on to very small capacitances (∼10^-18 F) and into three-dimensionally quantum-confined states, with the reproducibility, architecture and integration of the field-effect devices. We discuss the role size plays in the operation and its variability for such memories. In particular, we discuss the implications of size effects through barriers on speed; through electrostatics on variability, acceptability and reproducibility of properties desired; through random variations and of tunneling on limits in the use of the field-effect, and through interface-states on the time-domain operation. For device properties and their variations, using silicon-on-insulator substrates, silicon and back-insulator thicknesses matter through the linear variations introduced in the electrostatic potential and quadratic variations introduced in the subband energies, the quantum-dots and nano-crystals matter secondarily through the electrostatics and the linear dependence of capacitance on size and the quadratic dependence of the allowed eigen-energies on size. We also discuss the implications of tunneling on time constants of charging of the confined states and in between the source and the drain for the ultimate structure size limit. Received: 14 April 2000 / Accepted: 17 April 2000 / Published online: 6 September 2000