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1.
Keller Teichmann Hans Pfeiffer W. Langenbeck A. Reid Heinrich Menzel Th. Höpner W. Mühlsteph M. Ulmann Geib R. E. Liesegang 《Colloid and polymer science》1939,87(1):100-104
Ohne Zusammenfassung 相似文献
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Ohne Zusammenfassung 相似文献
3.
Zusammenfassung Die alternierende Copolymerisation von Styrol und Benzylmethacrylat in Gegenwart von Ethylaluminiumsesquichlorid als Katalysator zeigt im Anfangsstadium der Reaktion ein vom weiteren Verlauf abweichendes Verhalten. So nehmen die Zusammensetzung und die Grenzviskositäten der Produkte sowie die Reaktionsgeschwindigkeit erst nach der Anfangsphase konstante Werte an.Die1H-NMR-Spektren von alternierenden und statistischen Copolymeren gleicher Bruttozusammensetzung zeigen deutliche Unterschiede. Das Spektrum des alternierenden Copolymeren bestätigt die alternierende Struktur und spricht gleichzeitig für einen ataktischen Kettenaufbau.
The alternating copolymerization of styrene and benzylmethacrylate shows a different behaviour at the beginning of the reaction and later on. Thus the composition and the intrinsic viscosity of the products as well as the reaction rate become constant only after the initial stage.The1H-NMR-spectra of alternating and statistical copolymers with equal composition show distinct differences. The spectrum of the alternating copolymer confirms the alternating structure as well as an atactic chain configuration.相似文献
4.
A. Bärwolff R. Puchert P. Enders U. Menzel D. Ackermann 《Journal of Thermal Analysis and Calorimetry》1995,45(3):417-436
New results of steady-state two-dimensional finite-element computations of temperature distributions of high power semiconductor laser arrays are presented. The influence of different thermal loads on the 2D temperature distribution in AlGaAs/GaAs gain-guided laser arrays is investigated. TheFEM model is tested by comparing it with analytical solutions. For numerical convenience, the latter is rewritten in a novel form, which is free of overflow problems. The maximum temperatures calculated by both methods agree within 1%. Several factors determining the thermal resistance of the device are quantitatively examined: the ratio of light emitting to non-emitting areas along the active zone, the amount of Joule losses, the current spreading, the solder thickness, and voids in the solder. This yields design rules for optimum thermal performance. 相似文献
5.
E. Kaiser J. de Vries H. Steger C. Menzel W. Kamke I. V. Hertel 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):193-196
A reflecting time of flight mass spectrometer (RETOF) is used to study unimolecular and collision induced fragmentation of ammonia cluster ions. Synchrotron radiation from the BESSY electron storage ring is used in a range of photon energies from 9.08 up to 17.7 eV for single photon ionisation of neutral clusters in a supersonic beam. The threshold photoelectron photoion coincidence technique (TPEPICO) is used to define the energy initially deposited into the cluster ions. Metastable unimolecular decay (µs range) is studied using the RETOF's capacity for energy analysis. Under collision free conditions the by far most prominent metastable process is the evaporation of one neutral NH3 monomer from protonated clusters (NH3) n ? 2NH 4 + . Abundance of homogeneous vs. protonated cluster ions and of metastable fragments are reported as a function of photon energy and cluster size up ton=10. 相似文献
6.
de Meijere A Khlebnikov AF Kozhushkov SI Kostikov RR Schreiner PR Wittkopp A Rinderspacher C Menzel H Yufit DS Howard JA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(4):828-842
(M)-(-)- and (P)-(+)-Trispiro[2.0.0.2.1.1]nonanes [(M)- and (P)-3] as well as (M)-(-)- and (P)-(+)-tetraspiro[2.0.0.0.2.1.1.1]undecanes [(M)- and (P)-4]-enantiomerically pure unbranched [4]- and [5]triangulanes-have been prepared starting from racemic bicyclopropylidenecarboxylic [(1RS)-12] and exo-dispiro[2.0.2.1]heptane-1-carboxylic [(1RS,3SR)-13] acids. The optical resolutions of rac-12 and rac-13 furnished enantiomerically pure acids (S)-(+)-12, (R)-(-)-12, (1R,3S)-(-)-13, and (1S,3R)-(+)-13. The ethyl ester (R)-25 of the acid (R)-(-)-12 was cyclopropanated to give carboxylates (1R,3R)-26 and (1R,3S)-26. The ester (1R,3S)-26 and acids (1R,3S)-13 and (1S,3R)-13 were converted into enantiomerically pure methylene[3]triangulanes (S)-(-)- and (R)-(+)-28. An alternative approach consisted of an enzymatic deracemization of endo-[(1SR,3SR)-dispiro[2.0.2.1]heptyl]methanol (rac-20) or anti-[(1SR,3RS)-4-methylenespiropentyl]methanol (rac-18). This afforded (S)-(-)- and (R)-(+)-28 (starting from rac-20), as well as enantiomerically pure (M)-(-)- and (P)-(+)-1,4-dimethylenespiropentanes [(M)- and (P)-23] starting from rac-18. The methylenetriangulanes (S)-(-)- and (R)-(+)-28 were cyclopropanated furnishing (M)- and (P)-3. The rhodium-catalyzed cycloaddition of ethyl diazoacetate onto (S)-(-)- and (R)-(+)-28 yielded four diastereomeric ethyl trispiro[2.0.0.2.1.1]nonane-1-carboxylates in approximately equal proportions. The enantiomerically pure esters (1R,3S,4S)- and (1S,3R,4R)-30 were isolated by careful distillation and then transformed into [5]triangulanes (M)- and (P)-4 using the same sequence of reactions as applied for (M)- and (P)-3. The structures of the key intermediates (R)-12 and rac-31 were confirmed by X-ray analyses. Although [4]- and [5]triangulanes have no chromophore which would lead to any significant absorption above 200 nm, they have remarkably high specific rotations even at 589 nm with [alpha](20)D=-192.7 [(M)-3, c=1.18, CHCl(3))] or +373.0 [(P)-4, c=1.18, CHCl(3))]. This remarkable optical rotatation is in line with their helical arrangement of sigma bonds, as confirmed by a full valence space single excitation configuration interaction treatment (SCI) in conjunction with DFT computations at the B3LYP/TZVP//B3LYP/6-31+G(d,p) level of theory which reproduce the ORD very well. Thus, it is appropriate to call the helically shaped unbranched [n]triangulanes the "sigma-[n]helicenes", representing the sigma-bond analogues of the aromatic [n]helicenes. 相似文献
7.
The oxygen chemisorption on Ni, Cu and Ag is studied by comparing PE spectra of these systems and SCF-Xα scattered-wave cluster models. Consideration of octahedral clusters M6 (M = Ni, Cu, Ag) shows that they are large enough to reproduce trends in energy differences, such as the width of the d-bands and the distance from the top of the d-bands to the Fermi level, as found in experiment and in bulk energy band calculations. Substrate model clusters for the interaction of oxygen with different metal surfaces are derived from an octahedron by removing one ((100) face) or two adjacent metal atoms ((110) face). Comparing the UPS difference spectrum for O/Ag (110) with several Ag4O cluster models makes it possible to interpret the peaks above the Ag d-band as O-Ag anti-bonding levels. These peaks are caused by O 2p-Ag 4d and O 2p-Ag 5s interaction. The corresponding bonding levels fall in the Ag d-bands and cannot therefore be identified with confidence in the spectra. The decreasing intensity of the oxygen derived peak below the metal d-band in the UPS spectra when going from Ni to Cu to Ag, and the simultaneously increasing O peaks above the d-band correlate with the changes of the localization of the corresponding bonding and anti-bonding levels in the oxygen sphere and the decreasing strength of the chemisorption bond. 相似文献
8.
B.K. Ystenes F. Menzel W. Brockner 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):485-488
The dimeric title compound decomposes upon heating to give the monomer and desulphurized monomer as shown by FT-Raman and quantum chemical means. 相似文献
9.
A finite deformation framework for nonlinear magneto-viscoelasticity is introduced and applied to the constitutive and structural modeling of magnetoactive polymer (MAP) response. In this thermodynamically-consistent formulation the free energy function consists of purely elastic, purely magnetic and coupling contributions, where the rate-dependence is fully attributed to the non-magnetizable matrix material. The model consistently accounts for saturation in the magnetic as well as the magnetostrictive behavior. The identification of material parameters from experimental data is briefly described. Finally, a finite element model for the large strain magneto-mechanical problem is established and tested considering MAP behavior. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
Metal sheet forming processes like deep drawing are applied in order to produce carriage parts in mass production. Therefore, forming tools are required that are well protected against wear. For such forming tools, wear resistant surfaces are, e.g., produced by thermal spraying of hard material coatings. The thermal spraying process itself is a highly transient thermo-mechanical process. In order to gain a better understanding of the heat input and transfer during thermal spraying, a simulation framework for thermal spraying processes is presented. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献