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81.
Stian Svelle Morten Bjørgen Stein Kolboe Dietmar Kuck Matthias Letzel Unni Olsbye Osamu Sekiguchi Einar Uggerud 《Catalysis Letters》2006,109(1-2):25-35
In order to reach a deeper insight into the reaction mechanism of the zeolite catalyzed methanol to hydrocarbons reaction
(MTH), the proposed reaction intermediates, i.e., a series of multiply methyl-substituted benzenium ions has been generated
in the gas phase by chemical ionization. The fragmentations of the corresponding long-lived (metastable) ions have been investigated.
While expulsion of H2 dominates for the lower homologues, elimination of methane dominates for the higher homologues, accompanied by increasing
amounts CH3·. Loss of larger fragments relevant to the MTH-reaction, in particular ethene, propene and even butene, is also observed in
minor amounts. This latter finding is consistent with a proposed reaction cycle in the MTH reaction known as the paring mechanism, and the feasibility of this mechanism has thus been demonstrated. The metastable gas-phase ions studied here are considerably
more energetic than those residing in a zeolite catalyst, but they were found to decompose with markedly higher selectivity
towards alkenes as compared to those activated by collision-induced dissociation (CID). 相似文献
82.
An accurate method for the quantitative determination of hydroperoxy and hydroxy fatty acids in liver microsomes is presented
which involves the use of18O-labeled internal standards. The method is employed for the determination of hydroperoxides in rat liver microsomes after
aerobic incubation with Fe2+/ADP and in microsomes from animals exposed to 75 mg tetrachloromethane/kg body weight. The amounts found after artificial
microsomal “lipid peroxidation” are almost two orders of magnitude larger than those in microsomes from tetrachloromethaneexposed
animals. 相似文献
83.
Ulrich Reiners Rudolf Jeschar Reinhard Scholz Dietmar Zebrowski Wolfgang Reichelt 《国际钢铁研究》1985,56(5):239-246
Within the framework of research investigations described in this paper, a measuring method for the determination of heat transfer coefficients in the range of stable film boiling has been developed for water spray cooling in the secondary cooling zone of continuous casting machines. Based on investigations by 3), a water cooled test sample with a measuring field of 20 × 20 mm2 was constructed. For this sample geometry, a special evaluation method has been developed which permits quick evaluation in on-line procedure. Result of measurements are sections for the heat transfer coefficient arising from different spray water distributions. On the one hand, these can be used as calculation figures for the determination of the solidification profile and the solidification rate. On the other hand, the measuring results serve as an assessment basis for nozzle constructions. Practical use of the measuring results confirms the usefulness of the measuring method on a laboratory scale. In addition, the validity of the measuring results has been demonstrated by comparing them with an unsteady state method in accordance with 2). 相似文献
84.
85.
Dietmar Salamon 《Theory of Computing Systems》1988,21(1):147-164
A representation theorem for infinite-dimensional, linear control systems is proved in the context of strongly continuous
semigroups in Hilbert spaces. The result allows for unbounded input and output operators and is used to derive necessary and
sufficient conditions for the realizability in a Hilbert space of a time-invariant, causal input-output operator ℐ. The relation
between input-output stability and stability of the realization is discussed. In the case of finite-dimensional input and
output spaces the boundedness of the output operator is related to the existence of a convolution kernel representing the
operator ℐ.
This research has been supported by the Nuffields Foundation. 相似文献
86.
87.
Einfluß der Abschreckalterung auf Streckgrenze und Übergangstemperatur der Kerbschlagzähigkeit. Deutungsmöglichkeiten mit Hilfe der Cottrell-Theorie. Einfluß der Ausscheidungen auf die Größen σi, ky und k bzw. k0 sowie deren Einfluß auf Tü. 相似文献
88.
89.
Schantz JT Brandwood A Hutmacher DW Khor HL Bittner K 《Journal of materials science. Materials in medicine》2005,16(9):807-819
Biomimetic scaffolds offer great potentials in the development of bone analogs for tissue engineering. The studies presented in this paper focus specifically on the osteogenic potential of the novel PCL/CaP matrices and its degradation behavior. Biodegradable Polymer-ceramic Scaffolds were fabricated using the solid free form fabrication technology: Fused Deposition Modeling (FDM). The scaffold architecture was characterized by a honeycomb-like design and a complete interconnectivity of the pores. Human mesenchymal stem cells (MSCs) were seeded together with fibrin glue into PCL/CaP scaffolds and cultured in vitro for periods of up to eight weeks. Cellular adhesion, proliferation and osteogenic differentiation were assessed in these constructs using a range of histological and microscopic techniques. In additional experiments, degradation was assessed by measuring mass loss, diameter change, molecular weight change and by scanning electron micrographs. MSCs were able to adhere, migrate, and differentiate along the osteogenic lineage with in these scaffolds. The PCL/CaP scaffolds showed up to 27 fold increased degradation of compared to PCL scaffolds. 相似文献
90.
Among other waveguide elements directional couplers are required in integrated millimeterwave circuits in image guide technique. Hereby an I-guide is used which consists of a dielectric slab between two conducting plates on which the electric field is perpendicularily. Flat coupling behaviour and better isolation can be reached by use of a dielectric coupling element and absorber materials. Thereby the frequency dependence is reduced significantly. Further the coupling can be steered by an additional premagnetized ferrite slab. In this way switched couplers can be realized. 相似文献