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排序方式: 共有1448条查询结果,搜索用时 15 毫秒
11.
W. Nierle W. Feldheim H. G. Maier P. Schreier W. Grosch G. -W. v. Rymon Lipinski H. -P. Thier W. Feldheim W. Seibel J. Buchberger E. Schlimme G. Engel U. Sacher F. Siewek R. Frommberger R. Frommberger G. -W. v. Rymon Lipinski F. I. Schäfers F. I. Schäfers R. Matissek H. Klostermeyer F. Kiermeier H. -P. Thier M. Miller M. Miller H. Wieczorek F. Jekat W. Feldheim K. Eichner M. Petz D. Gottschalk und W. Nierle 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1987,185(2):134-144
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W Maier 《Canadian Metallurgical Quarterly》1993,79(3):279-299
Both ontogenetically and phylogenetically the facial skull of primates consists of two components: the endocranial nasal capsule, and the exocranial membrane bones. The cartilaginous nasal capsule of the fetal period constitutes the framework for the nasal cavity, and it also functions as an expansive basis for the developing facial skull. In adult animals, its ossified parts form the fragile ethmoid bone. The structure of the nasal capsule is determined on the one hand by the spatial requirements of the orbits and of the nasal cavity (with respiratory and olfactory components), and on the other hand by the biomechanical properties of the chewing apparatus. The interaction of these heterogeneous factors results in complex, species-specific compromises. Primates are characterized by a gradual reduction of their olfactory system throughout evolution and by binocular vision. Their chewing apparatus shows constructional adaptations to a varying herbivorous diet. Viewed within a phylogenetic-systematic framework, primate evolution may be taken as a natural experiment that demonstrates the influence of various factors on a complex structural system such as the nasal and facial skeleton. 相似文献
14.
An improved antenna for a wireless mobile broadband system (e.g. as realised by Bosch as a demonstrator) is proposed. By means of a shaped dielectric lens the radiation pattern of a primary antenna (e.g. a short helical structure) can be shaped to optimise the power distribution across an indoor cell. The calculated performance of lenses designed for the 30 and 60 GHz bands by using geometric optics shows good agreement with measured results 相似文献
15.
An existing extensive database on the isothermal and thermomechanical fatigue behaviour of high-temperature titanium alloy
EVII 834 and dispersoid-strengthened aluminum alloy X8019 in SiC particle-reinforced as well as unreinv conditions was used
to evaluate both the adaptability of fracture mechanics approaches to TMF and the resulting predictive capabilities of determining
material life by crack propagation consideration. Selection of the correct microstructural concepts was emphasised and these
concepts were, then adjusted by using data from independent experiments in order to avoid any sort of fitting. It is shown
that the cyclic /-integral (δJeff concept) is suitable to predict the cyclic lifetime for conditions where the total crack propagation rate is approximately
identical to pure fatigue crack growth velocity. In the case that crack propagation is strongly affected by creep, the creep-fatigue
damage parameter δCF introduced by Riedel can be successfully applied. If environmental effects are very pronounced, the accelerating influence
of corrosion on fatigue crack propagation can no longer implicitly be taken into account in the fatigue crack growth law.
Instead, a linear combination of the crack growth rate contributions from plain fatigue (determined in vacuum) and from environmental
attack is assumed and found to yield a satisfactory prediction, if the relevant corrosion process is taken into account. 相似文献
16.
The open circuit voltage of the electrochemical cell Ag (nano)|solid silver electrolyte|Ag (macro) is found to be inherently unstable. Even under conditions which support the morphological stability of the arrangement of nanocrystalline silver, the particles grow significantly as soon as they function as electrodes; i.e. when they are in contact with a silver electrolyte and connected electronically at the same time. The process is shown to be due to electrochemical Ostwald ripening with the interfacial transfer of Ag+ through the Ag/electrolyte interface being the rate limiting step. Its activation energy is 0.01 eV. The decay is in good agreement with modelling results. 相似文献
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I Beck-Speier N Dayal C Denzlinger C Haberl KL Maier A Ziesenis J Heyder 《Canadian Metallurgical Quarterly》2003,71(3-4):217-234
Recent studies have shown that long-term in vivo exposure of dogs to neutral sulfur(IV)/sulfite aerosols induces mild inflammatory reactions, whereas the combination of neutral sulfite with acidic sulfur(VI)/sulfate aerosols evokes less pronounced effects. To understand underlying mechanisms, we studied in vitro the role of lipid mediators in the responses of alveolar macrophages (AMs) to sulfur-related compounds under neutral (pH 7) or moderate acidic (pH 6) conditions. Canine AMs incubated with sulfite at pH 7 released threefold higher amounts of platelet-activating factor than control (P < 0.005). Generation of arachidonic acid, leukotriene B4, 5-hydroxy-eicosatetraenoic acid, prostaglandin E2, thromboxane B2 and 12-hydroxyheptadecatrienoic acid increased twofold (P < 0.0005). However, these metabolites remained unchanged following incubation of AMs with sulfite at pH 6 or with sulfate at pH 7 or pH 6. Mediator release by sulfite-treated AMs at pH 7 stimulated respiratory burst activity of neutrophils. Inhibition of MAPK pathway by PD 98059, of cytosolic (cPLA2) and secretory phospholipases A2 by AACOCF3 and thioetheramide-PC, respectively, reduced sulfite-induced eicosanoid formation in AMs. Sulfite activated cPLA2 activity twofold at pH 7. This mechanism of sulfite-stimulated responses in phospholipid metabolism predicts that chronic exposure to sulfur(IV)/sulfite is associated with a considerable health risk. 相似文献
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20.
R. Niebuhr K. H. Bachem U. Kaufmann M. Maier C. Merz B. Santic P. Schlotter H. Jürgensen 《Journal of Electronic Materials》1997,26(10):1127-1130
Oxygen doped GaN has been grown by metalorganic chemical vapor deposition using N2O as oxygen dopant source. The layers were deposited on 2″ sapphire substrates from trimethylgallium and especially dried
ammonia using nitrogen (N2) as carrier gas. Prior to the growth of the films, an AIN nucleation layer with a thickness of about 300? was grown using
trimethylaluminum. The films were deposited at 1085°C at a growth rate of 1.0 μm/h and showed a specular, mirrorlike surface.
Not intentionally doped layers have high resistivity (>20 kW/square). The gas phase concentration of the N2O was varied between 25 and 400 ppm with respect to the total gas volume. The doped layers were n-type with carrier concentrations
in the range of 4×1016 cm−3 to 4×1018 cm−3 as measured by Hall effect. The observed carrier concentration increased with increasing N2O concentration. Low temperature photoluminescence experiments performed on the doped layers revealed besides free A and B
exciton emission an exciton bound to a shallow donor. With increasing N2O concentration in the gas phase, the intensity of the donor bound exciton increased relative to that of the free excitons.
These observations indicate that oxygen behaves as a shallow donor in GaN. This interpretation is supported by covalent radius
and electronegativity arguments. 相似文献