Deeply virtual Compton scattering off nuclei

We consider the hard leptoproduction of a photon off nuclei up to spin-1. As a new result we present here the general azimuthal angular dependence of the differential cross section for a spin-1 target. Its twist-two Fourier coefficients of the interference and squared deeply virtual Compton scattering amplitude are evaluated in leading order approximation of perturbation theory in terms of generalized parton distributions, while the pure Bethe-Heitler cross section is exactly calculated in terms of electromagnetic form factors. Relying on a simple model for the nucleon generalized parton distribution H, which describes the existing DVCS data for a proton target, we estimate the size of unpolarized cross sections, beam and longitudinal target spin as well as unpolarized charge asymmetries for the present fixed target experiments with nuclei. These estimates are confronted with preliminary HERMES data for deuterium and neon.Received: 1 October 2003, Published online: 3 December 2003     

Speaking rate of adventitiously deaf male cochlear implant candidates

No objective group data on speaking rate or speaking duration have been reported on the speech of adventitiously profoundly hearing-impaired adults. Results of the present study showed that speaking rate, i.e., number of syllables per second, was significantly slower and speaking duration was significantly longer for 25 adventitiously profoundly hearing-impaired adult male cochlear implant candidates than for 10 normal-hearing control subjects. The factors of length of time since onset of profound hearing loss and hearing aid use did not significantly affect speaking rate. Based on these objective data, a rationale and method are presented for aural rehabilitation of the profoundly hearing-impaired who exhibit speaking rate abnormalities.     

Boussinesq–Cerruti problems for the hexagonally symmetric system of elasticity in n–dimensional half-space

The Poisson matrices of the analoga to the Boussinesq–Cerruti boundary value problems for the operator of transversely isotropic elastostatics in n–dimensional half-space are computed by Fourier transformation and given in explicit form. (Received: May 4, 2004; revised: January 30, 2006)     

Triphilic Ionic‐Liquid Mixtures: Fluorinated and Non‐fluorinated Aprotic Ionic‐Liquid Mixtures

We present here the possibility of forming triphilic mixtures from alkyl‐ and fluoroalkylimidazolium ionic liquids, thus, macroscopically homogeneous mixtures for which instead of the often observed two domains—polar and nonpolar—three stable microphases are present: polar, lipophilic, and fluorous ones. The fluorinated side chains of the cations indeed self‐associate and form domains that are segregated from those of the polar and alkyl domains. To enable miscibility, despite the generally preferred macroscopic separation between fluorous and alkyl moieties, the importance of strong hydrogen bonding is shown. As the long‐range structure in the alkyl and fluoroalkyl domains is dependent on the composition of the liquid, we propose that the heterogeneous, triphilic structure can be easily tuned by the molar ratio of the components. We believe that further development may allow the design of switchable, smart liquids that change their properties in a predictable way according to their composition or even their environment.     

Acceleration of Acetal Hydrolysis by Remote Alkoxy Groups: Evidence for Electrostatic Effects on the Formation of Oxocarbenium Ions

In contrast to observations with carbohydrates, experiments with 4‐alkoxy‐substituted acetals indicate that an alkoxy group can accelerate acetal hydrolysis by up to 20‐fold compared to substrates without an alkoxy group. The acceleration of ionization in more flexible acetals can be up to 200‐fold when compensated for inductive effects.     

Beitrag zur Kenntnis der Wärmeleitfähigkeit poröser Stoffe Teil II

Zusammenfassung Die in einem ersten Teil dieser Untersuchung erhaltenen Ergebnisse werden durch zusätzliche neue Versuche kontrolliert. Der Meßbereich wird auf Rohdichten von 9,5 kg/m³ erweitert; die notwendigen Versuchsdaten für reines Polystyrol werden experimentell neu ermittelt. Ein Vergleich mit den Meßwerten anderer Beobachter ergibt gute Übereinstimmung aller Daten, wenn gleichartige Versuchsbedingungen eingehalten wurden. Der Verlauf der gemessenen (effektiven) Wärmeleitfähigkeit von Polystyrolpartikel-Hartschaumplatten (Styropor) in Abhängigkeit von Rohdichte und Schichtdicke wird aufgezeigt und diskutiert. Zusätzliche Messungen der Absorptionsspektren von Polystyrol und Polystyrol-Schaumstoff ergänzen die Messung der Wärmeleitfähigkeit und mögen zur Klärung des Wärmetransportes in porösen Schaumstoffen beitragen.

---

A contribution to the knowledge of heat conductivity of porous materials part II

The results obtained in the first part of this experimental research are controlled by new measurements. The range of apparent over-all density was enlarged till 9.5 kg/m³. The necessary dates for pure polystyrene were experimentally determined. A comparison with the results of other observers shows good agreement, if equal measuring conditions are given. The behaviour of the measured (effective) thermal conductivity of polystyrene foam as function of apparent over-all density and the thickness of the layer may be learned from several diagrams; these are discussed. Additional measurements of some optical absorption spectra of pure polystyrene and polystyrene foam follow the measurement of thermal conductivity; they may contribute to the clearing up of heat transfer through porous materials.

---

---

Herrn Dr.-Ing. F. Stastny, Ludwigshafen/Rh. und der BASF haben wir für sehr entgegenkommende Lieferung der verschiedenartigen Proben zu danken, ferner Herrn Techn. Reg. Amtmann Jugel für sorgfältige Kontrollversuche.     

Reactivity of coordinatively unsaturated iron complexes towards carbon monoxide: to bind or not to bind?

An overview of the reactivity of coordinatively unsaturated iron complexes (in most cases Fe(II)) towards carbon monoxide is presented. Unsaturated iron complexes are known with coordination numbers (CN) of two to five adopting linear or slightly bent (CN = 2), trigonal (CN = 3), tetrahedral, square planar or trigonal pyramidal (CN = 4), and square-pyramidal or trigonal-bipyramidal geometries (CN = 5), respectively. The binding of CO depends strongly on the number and the nature of co-ligands (overall ligand field strength), the charge of the complex, the complex geometry, and the spin state of the unsaturated metal center. In many cases, CO addition to high-spin iron complexes takes place with concomitant spin state changes forming compounds in the lowest possible spin state, i.e., with S = 0. In several other cases, however, the addition of CO is reversible or is even totally rejected altogether for either thermodynamic or kinetic reasons. In the case of the latter such reactions are termed "spin-blocked" or "spin forbidden".     

Exo-cyclopamine--a stable and potent inhibitor of hedgehog-signaling

The combination of theoretical and computational studies with organic synthesis and biological investigations has led to exo-cyclopamine. This stable and highly potent derivative of cyclopamine promises big potential as an experimental drug against several types of human cancer.