Zur Kenntnis der Kjeldahl-Reaktion III

Zusammenfassung Chromatographische Versuche zeigen, daß die Zwischenprodukte der Kjeldahlisierung des Anilins mit denen der Anilinschwarz-Bildung verwandt sind. Die Elementaranalyse von Polymerisationsprodukten dieser Zwischenstoffe weist darauf hin, daß es sich um sulfonierte Oxyemeraldine handelt. Kinetische Versuche und Überlegungen führen zu dem Ergebnis, daß alle diese Zwischenstufen erst durchlaufen werden, nachdem Anilin zu Sulfanilsäure sulfoniert worden ist, wobei ein der weiteren Oxydation vorgelagertes Gleichgewicht erreicht wird. Emil Abel zum 80. Geburtstag zugeeignet.     

Lyman-α absorption photometry at high pressure and atom density kinetic results for H recombination

Atomic absorption and fluorescence spectrophotometry have been routinely used in kinetic investigations as probes of relative, rather than absolute, atom concentration. The calibration of a Lyman-α photometer for measurement of absolute hydrogen atom concentrations at levels [H] ι ≤ 1.8 × 10¹⁴ atoms/cm² and total pressure of 1.5 torr He is described. The photometer is characterized in terms of a two-level emission source and an absorption region in which only Doppler broadening of the transition is considered. The modifications due to pressure broadening by high pressures (500 ≤ P ≤ 1500 torr) in the absorption region are discussed in detail. Application of the technique is reported for the recombination of hydrogen atoms in the presence of six nonreactive heat bath gases. Experiments were performed in a static reaction cell at pressures of 500–1500 torr of heat bath gas, and hydrogen atoms were produced by Hg (³P₁) photosensitization of H₂. The technique is critically evaluated and the mechanistic implications of the hydrogen atom recombination results are examined. The measured room temperature recombination rate constants in H₂, He, Ne, Ar, Kr, and N₂ are 8.5 ± 1.2, 6.9 ± 1.5, 5.9 ± 1.5, 8.0 ± 0.8, 10.2 ± 0.9, and 9.6 ± 1.4, respectively, where the units are 10³³ cm⁶/molec² · sec.     

Normal persistent currents

This article reviews recent advances in mesoscopic physics, namely experimental and theoretical investigations of persistent (equilibrium) currents in normal metal rings. While theory and experiment are consistent in the ballistic regime, theoretical studies so far have not been able to account for the unexpectedly huge currents observed experimentally in disordered (diffusive) samples, in which the elastic mean free path is much less than the circumference of the rings.     

On Incidence Algebras of Combinatorial Inverse Monoids

We study the incidence algebra of the reduced standard division category of a combinatorial bisimple inverse monoid [with (E(S), ≤) locally finite], and we describe semigroups of poset type (i.e., a combinatorial inverse semigroup for which the corresponding Möbius category is a poset) as being combinatorial strict inverse semigroups. Up to isomorphism, the only Möbius-division categories are the reduced standard division categories of combinatorial inverse monoids.     

Multicomponent Self‐Assembly with a Shape‐Persistent N‐Heterotriangulene Macrocycle on Au(111)

Multicomponent network formation by using a shape‐persistent macrocycle ( MC6 ) at the interface between an organic liquid and Au(111) surface is demonstrated. MC6 serves as a versatile building block that can be coadsorbed with a variety of organic molecules based on different types of noncovalent interactions at the liquid–solid interface. Scanning tunneling microscopy (STM) reveals the formation of crystalline bicomponent networks upon codeposition of MC6 with aromatic molecules, such as fullerene (C₆₀) and coronene. Tetracyanoquinodimethane, on the other hand, was found to induce disorder into the MC6 networks by adsorbing on the rim of the macrocycle. Immobilization of MC6 itself was studied in two different noncovalently assembled host networks. MC6 assumed a rather passive role as a guest and simply occupied the host cavities in one network, whereas it induced a structural transition in the other. Finally, the central cavity of MC6 was used to capture C₆₀ in a complex three‐component system. Precise immobilization of organic molecules at discrete locations within multicomponent networks, as demonstrated here, constitutes an important step towards bottom‐up fabrication of functional surface‐based nanostructures.     

Über die Auswirkung der (geordneten) Rekombination freier Ladungsträger und einen äquivalenten Effekt

Zeitschrift für Physik A Hadrons and nuclei - Auf der früher gewonnenen Basis wird eine Reihe bisher abseits stehender Beobachtungen — betreffend die Ausbreitung einer Explosion im...     

Structural and variable-temperature NMR studies of 9-diisopropylphosphanylanthracenes and 9,10-bis(diisopropylphosphanyl)anthracenes and their oxidation products

The diisopropylphosphanyl-substituted anthracenes i-Pr2P(C14H9) (1a), i-Pr2P(C14H8)Br (2a), and (i-Pr2P)2(C14H8) (3a) and some of their oxidation products were prepared from 9-bromoanthracene and 9,10-dibromoanthracene, respectively. Low-temperature (1)H NMR spectra of the 9-monophosphanyl-substituted anthracenes 1a and 2a are in accordance with a staggered conformer, while above room temperature dynamic processes occur. The low-temperature NMR spectrum of the 9,10-diphosphanylanthracene 3a indicates the presence of two different rotational isomers. The rotational barrier for 1a was determined from variable-temperature (1)H NMR spectra to be 56 kJ mol(-1) (DeltaG(298K)). The crystal structure determinations show the solid-state conformers to be consistent with the prevailing conformer at low temperature.     

Convergence rates for sparse chaos approximations of elliptic problems with stochastic coefficients

^** Email: todor{at}math.ethz.ch^*** Corresponding author. Email: schwab{at}math.ethz.ch A scalar, elliptic boundary-value problem in divergence formwith stochastic diffusion coefficient a(x, ) in a bounded domainD ^d is reformulated as a deterministic, infinite-dimensional,parametric problem by separation of deterministic (x D) andstochastic ( ) variables in a(x, ) via Karhúnen–Loèveor Legendre expansions of the diffusion coefficient. Deterministic,approximate solvers are obtained by projection of this probleminto a product probability space of finite dimension M and sparsediscretizations of the resulting M-dimensional parametric problem.Both Galerkin and collocation approximations are considered.Under regularity assumptions on the fluctuation of a(x, ) inthe deterministic variable x, the convergence rate of the deterministicsolution algorithm is analysed in terms of the number N of deterministicproblems to be solved as both the chaos dimension M and themultiresolution level of the sparse discretization resp. thepolynomial degree of the chaos expansion increase simultaneously.     

Production of charged pions, kaons and antikaons in relativistic C + C and C + Au collisions

Production cross-sections of charged pions, kaons and antikaons have been measured in C+C and C+Au collisions at beam energies of 1.0 and 1.8 AGeV for different polar emission angles. The kaon and antikaon energy spectra can be described by Boltzmann distributions whereas the pion spectra exhibit an additional enhancement at low energies. The pion multiplicity per participating nucleon M(π⁺)/<A _part> is a factor of about 3 smaller in C+Au than in C+C collisions at 1.0 AGeV whereas it differs only little for the C and the Au target at a beam energy of 1.8 AGeV. The K⁺ multiplicities per participating nucleon M(K⁺)/ <A _part> are independent of the target size at 1 AGeV and at 1.8 AGeV. The K^- multiplicity per participating nucleon M(K^-)/ <A _part> is reduced by a factor of about 2 in C+Au as compared to C+C collisions at 1.8 AGeV. This effect might be caused by the absorption of antikaons in the heavy target nucleus. Transport model calculations underestimate the K^-/K⁺ ratio for C+C collisions at 1.8 AGeV by a factor of about 4 if in-medium modifications of K-mesons are neglected. Received: 10 December 1999 / Accepted: 14 November 2000