Ein Ansatz zur Lösung von Spannungsrandwertproblemen bei flachen doppelt gekrümmten Membranen und dünnen Schalen

übersicht Für doppelt gekrümmte orthogonal anisotrope Membranen wird das System von zwei partiellen Differentialgleichungen für die Durchbiegungw und die Spannungsfunktion ϕ durch eine Transformation auf eine partielle Differentialgleichung zurückgeführt. Durch Spezialisierungen kann diese Gleichung in die Form einer verzerrten homogenen Bipotentialgleichung gebracht werden. Damit ist die Kl?rung der Einflüsse von Anisotropie und Krümmung auf die Spannungen unter Belastung m?glich. Au?erdem kann damit für allgemeine Schalen ein direktes Finite-Element-Verfahren für die Berechnung des Membranspannungszustands begründet werden.

---

Summary The system of two partial differential equations for orthogonal anisotropic membranes in the case of nonvanishing gaussian curvature is transformed to one equation. In special cases this equation can further be simplified up to the form of a distorted bipotential equation. Thus the influence of shape and anisotropy to the stresses under loading can be discussed. Furthermore one can get the foundation of a Finite-Element-Method for the computation of the membran stresses of arbitrary shells with orthogonal anisotropy parallel to the main axes of curvature.

     

Die Anlaufströmung eines Binghamschen Stoffes zwischen zwei parallelen Wänden

Summary The initial flow of a Bingham plastic between two parallel plates is considered. First the stress distribution by applying Laplace transforms to the equation of motion is obtained To find the corresponding velocity distribution the stress distribution is integrated.     

Laser properties of bis-styryle compounds

The class of bis-styryle dyes was systematically investigated for its application in N₂ laser-pumped dye lasers. All tested dyes showed good lasing characteristics in methanolic and aqueous solution if they contained sulphonate groups, and in dioxane without sulphonate groups. Many of these dyes, all lasing in the blue and violet spectral region, were demonstrated to be superior to other common dyes. Broad tuning ranges, high photochemical stability and good efficiencies were found.     

Local degrees of freedom and nuclear quadrupolar spin relaxation in liquid metals and alloys

We discuss the temperature dependence of the nuclear quadrupolar spin relaxation rate in metals and alloys. Four different relaxation processes must be distinguished: Hard collisions, diffusion, decay of associates and rotational diffusion. The latter two processes are important in alloys of strongly interacting alloying partners, the former in pure metals (collision) and ideal or regular mixtures. Diffusion is important if the alloying partners produce different electrical field gradients.     

Nuclear magnetic resonance of 27Al in the lutetium aluminum garnet

By NMR, the quadrupole coupling constants of ²⁷Al for the a- and d-sites in Lu₃Al₂ (AlO₄)₃ have been determined at 300 and 4.2 K. Structural consequences are discussed and compared with other rare earth aluminum garnets.     

Orienting Semi‐Conducting π‐Conjugated Polymers

The present review focuses on the recent progress made in thin film orientation of semi‐conducting polymers with particular emphasis on methods using epitaxy and shear forces. The main results reported in this review deal with regioregular poly(3‐alkylthiophene)s and poly(dialkylfluorenes). Correlations existing between processing conditions, macromolecular parameters and the resulting structures formed in thin films are underlined. It is shown that epitaxial orientation of semi‐conducting polymers can generate a large palette of semi‐crystalline and nanostructured morphologies by a subtle choice of the orienting substrates and growth conditions.

     

A semi-classical model of attosecond electron localization in dissociative ionization of hydrogen

In the development of attosecond molecular science, a series of experiments have recently been performed where ionic fragment asymmetries in the dissociative ionization of H(2) into H(+) + H and that of D(2) into D(+) + D were used to uncover electron localization processes that occur on the attosecond and few-femtosecond timescale. Electron localization was observed both in strong-field dissociative ionization using carrier envelope phase-stable few-cycle laser pulses [Kling et al., Science, 2006, 312, 246] and in a two-color extreme ultra-violet + infrared attosecond pump-probe experiment [Sansone et al., Nature, 2010, 465, 763]. Here we show that the observed electron localization can be well understood using a semi-classical model that describes the dynamics in terms of quasi-static states that take the interaction of the molecule with the laser field instantaneously into account. The electron localization is shown to be determined by the passage of the dissociating molecule through a regime where the laser-molecule interaction is neither diabatic nor adiabatic.     

The Molecular Pathway to ZIF‐7 Microrods Revealed by In Situ Time‐Resolved Small‐ and Wide‐Angle X‐Ray Scattering,Quick‐Scanning Extended X‐Ray Absorption Spectroscopy,and DFT Calculations

We present an in situ small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) and quick‐scanning extended X‐ray absorption fine‐structure (QEXAFS) spectroscopy study on the crystallization of the metal–organic framework ZIF‐7. In combination with DFT calculations, the self‐assembly and growth of ZIF‐7 microrods together with the chemical function of the crystal growth modulator (diethylamine) are revealed at all relevant length scales, from the atomic to the full crystal size.     

Complexity behind CO2 capture on NH2-MIL-53(Al)

Some Metal Organic Frameworks (MOFs) show excellent performance in extracting carbon dioxide from different gas mixtures. The origin of their enhanced separation ability is not clear yet. Herein, we present a combined experimental and theoretical study of the amino-functionalized MIL-53(Al) to elucidate the mechanism behind its unusual high efficiency in CO(2) capture. Spectroscopic and DFT studies point out only an indirect role of amine moieties. In contrast to other amino-functionalized CO(2) sorbents, no chemical bond between CO(2) and the NH(2) groups of the structure is formed. We demonstrate that the functionalization modulates the "breathing" behavior of the material, that is, the flexibility of the framework and its capacity to alter the structure upon the introduction of specific adsorbates. The absence of strong chemical interactions with CO(2) is of high importance for the overall performance of the adsorbent, since full regeneration can be achieved within minutes under very mild conditions, demonstrating the high potential of this type of adsorbents for PSA like systems.