Einstein-Weyl Gravity from a Topological {{\rm SL}(5, \mathbb{R})} Gauge Invariant Action

A topological field theory of gravity in four-dimension is proposed which is finite after quantization. Since such ‘minimal’ BF type models for the high energy limit are physically not quite realistic, a tiny symmetry breaking is needed to recover standard Einsteinian gravity for the macroscopic metrical background.     

Study on the Mechanism of Formation of 1‐Methylheptyl Phenyl Ether by the Isourea Method

The formation of (1R)‐1‐methylheptyl phenyl ether from (2S)‐octan‐2‐ol via its isourea derivative (S)‐ 1 follows a borderline mechanism. The intermediacy of a carbocation (see (S)‐ 2 ) can be demonstrated (Scheme 1). However, the extremely high inversion of configuration and the olefinic by‐products are also indicative of an S_N2 mechanism.     

Algebra for a BRST Quantization of Metric-Affine Gravity

For a general gauge-theoretical formulation of gravitational interactions, we analyze the first algebraic steps towards a quantization via BRST ghost operators, replacing the Lagrange multipliers of the classical Hamiltonian constraints. From the nilpotency of the BRST charge, we deduce new restrictions on torsion and curvature of Yang-Mills type metric-affine models.     

Coherence resonance and stochastic synchronization in a nonlinear circuit near a subcritical Hopf bifurcation

We analyze noise-induced phenomena in nonlinear dynamical systems near a subcritical Hopf bifurcation. We investigate qualitative changes of probability distributions (stochastic bifurcations), coherence resonance, and stochastic synchronization. These effects are studied in dynamical systems for which a subcritical Hopf bifurcation occurs. We perform analytical calculations, numerical simulations and experiments on an electronic circuit. For the generalized Van der Pol model we uncover the similarities between the behavior of a self-sustained oscillator characterized by a subcritical Hopf bifurcation and an excitable system. The analogy is manifested through coherence resonance and stochastic synchronization. In particular, we show both experimentally and numerically that stochastic oscillations that appear due to noise in a system with hard excitation, can be partially synchronized even outside the oscillatory regime of the deterministic system.     

Heat Transfer Experiments in a Rotary Drum for a Variety of Granular Materials

The influence of material properties on the contact heat transfer coefficient between the covered wall surface and the solid bed was investigated. The contact heat transfer coefficients were calculated from the measured radial and circumferential temperature profiles. Experiments were carried out with six different materials, including steel spheres, animal powder, cement clinker, quartz sand, glass beads, and expanded clay. The rotational speeds were varied from 1 to 6 rpm to evaluate the influence of rotational speed on the contact heat transfer coefficient. The measured contact heat transfer coefficients were compared with four models from the literature.     

Notes on a Recent Paper About the Cleavage of N,N-Dimethylhydrazones and Tosylhydrazones

The reaction of dimethylhydrazones with dimethyl sulfate and potassium carbonate gives the N,N,N-trimethyl methylsulfate (e.g. 3a) primarily which may be hydrolyzed to the ketone subsequently. Tosylhydrazones give the N-methyl derivatives only and not the related ketones. Deviating results by A. Kamal et al. cannot be reproduced.     

Characterization of the boiling width on metal quenching with spray cooling

A hot aluminum alloy AA6082 and nickel disc of 560°C and 850°C was cooled by water spray of various spray flux under different condition of experiment. Temperature history was recorded with use of an infrared camera. During the quenching process, it was observed that the area with no apparent boiling and the outer annular region with vigorous liquid boiling have formed the boiling region. The width of the boiling region is essential as the maximum heat flux point is within the boiling region. Boiling width increases with initial temperature but decreases with water subcooling, spray flux and salinity.     

13C-NMR-spektroskopische und stereochemische Untersuchungen. XXIII.—Konformationen, 13C-NMR-Verschiebungen- und 13C?1H- Kopplungen bei Pinanverbindungen

¹³C NMR shifts of bicyclo[3.1.1]heptanes are discussed on the basis of geometries which are largely obtained by application of a molecular mechanics force field. For the basic hydrocarbon chair geometry minima are observed; their interconversion, however, is so fast [ΔH*～0.6 kcal (2.51 kJ) for fully relaxed molecular states] that an average flat Y form should be assumed for the ground state. In pinanes bearing equatorial substituents approximate chair geometries are obtained which, upon introduction of axial groups, appear very much flattened. In cosequence, conformationally transmitted substituent induced shieldings are observed, which can reach, e.g. + 7.45 ppm deshielding for a γ-methyl substituent. One bond ¹³C—¹H coupling constants, obtained in some cases from {¹H} off-resonance decoupled ¹³C spectra, are compared to calculated hybridization of C? H bonds. Their values of up to 145 Hz\documentclass{article}\pagestyle{empty}\begin{document}$ \buildrel \wedge \over = $\end{document}29% s for the cyclobutane part of pinanes are also useful for ¹³C signal assignments. Some literature assignments have to be revised, also on the basis of measurements with specifically deuterated compounds.