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81.
Purpose
The objective of this study was to compare multiple methods for estimation of PWV from 4D flow MRI velocity data and to investigate if 4D flow MRI-based PWV estimation with piecewise linear regression modeling of travel-distance vs. travel time is sufficient to discern age-related regional differences in PWV.Methods
4D flow MRI velocity data were acquired in 8 young and 8 older (age: 23 ± 2 vs. 58 ± 2 years old) normal volunteers. Travel-time and travel-distance were measured throughout the aorta and piecewise linear regression was used to measure global PWV in the descending aorta and regional PWV in three equally sized segments between the top of the aortic arch and the renal arteries. Six different methods for extracting travel-time were compared.Results
Methods for estimation of travel-time that use information about the whole flow waveform systematically overestimate PWV when compared to methods restricted to the upslope-portion of the waveforms (p < 0.05). In terms of regional PWV, a significant interaction was found between age and location (p < 0.05). The age-related differences in regional PWV were greater in the proximal compared to distal descending aorta.Conclusion
Care must be taken as different classes of methods for the estimation of travel-time produce different results. 4D flow MRI-based PWV estimation with piecewise linear regression modeling of travel-distance vs. travel time can discern age-related differences in regional PWV well in line with previously reported data. 相似文献82.
83.
84.
F Matthaei S Heidorn K Boom C Bertram A Safiei J Henzl K Morgenstern 《J Phys Condens Matter》2012,24(35):354006
The submonolayer growth of NaCl bilayer high-rectangular shaped islands on Ag(111) is investigated at around room temperature by using low temperature scanning tunneling microscopy. The growth at the step edges is preferred. Two kinds of islands are observed. They either grow with their non-polar edge at the step edge of Ag(111) or the islands overgrow in a carpet-like mode with the polar direction parallel to the edge. In the latter case, the Ag step is rearranged and considerable, while the NaCl layer is bent. This study clarifies the nature of the interaction of an alkali halide nanostructure with a metal step edge. 相似文献
85.
The DNA base thymine is deposited at 100?K on Cu(111) and investigated and manipulated by low-temperature scanning tunneling microscopy at 5?K. At submonolayer coverage paired rows are observed. At monolayer coverage a hexagonal commensurate self-assembled layer with the methyl group pointing away from the surface forms. A reversible local manipulation of molecules within the self-assembled layer is demonstrated. This manipulation is interpreted as an out-of-plane relaxation of molecules within the layer induced by the change of the adsorption geometry of individual molecules between two meta-stable orientations. A positive field of 2-4?V leads to this local change in the molecular arrangement, while a field larger than 4?V restores the original geometry. 相似文献
86.
T. Schlathölter O. Hadjar R. Hoekstra R. Morgenstern 《Applied Physics A: Materials Science & Processing》2001,72(3):281-287
The electronic friction experienced by a multiply charged ion interacting with the valence electrons of a single fullerene
is an important aspect of the collision dynamics. It manifests itself in a considerable loss of projectile kinetic energy
transferred to the target, resulting in excitation. The latter mainly leads to direct ionization and multifragmentation and
can be recognized in specific patterns of the fragmentation spectra. These fingerprints can be used to quantify electronic
stopping and to identify its typical properties as known from particle–solid interactions, such as the oscillation of the
electronic stopping with the projectile atomic number Z. These essentially many-body effects can therefore be studied in a
well-defined system of finite size.
Received: 4 April 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001 相似文献
87.
H. Kühne Th. Morgenstern A. Fischer G. Kissinger D. Krüger 《Crystal Research and Technology》1994,29(2):199-206
In multi-wafer deposition of Si/Ge thin films from silane, germane mixtures at low-temperature epitaxy conditions not only the depletion of the silicon source but also of the germanium source along the reactor tube axis has to be counteracted in order to get homogeneous layer thickness as well as composition. Carrier gas throughput must be minimized to have a sufficient effective chemical reaction rate at low temperature. Thus it cannot be used to flatten layer growth along the susceptor. Yet the addition of a chemically reactive gas, as for instance hydrogen chloride, is suitable to ensure a nearly constant content of the layer forming source gases along the reactor tube. On the other hand hydrogen chloride may infiltrate additional contaminants leading for instance to high oxygen concentration in the deposited layer. However, oxygen soluted or precipitated changes particular features of Si/Ge behaviour for instance during the thin film growth, the following technological stress of the wafer, or the running electronic structures of microelectronic devices. 相似文献
88.
89.
Mateusz Piontek Bernd Morgenstern Nils Steinbrück Bastian Oberhausen Guido Kickelbick Kaspar Hegetschweiler 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(6):678-685
Liu et al. [Chin. J. Struct. Chem. (1996). 15 , 371–373] reported the structure of 6‐hydroxy‐1,4‐diazepane di(hydrogen bromide), C5H12N2O·2HBr, which was interpreted in terms of neutral diazepane and HBr molecules. We found, however, ample evidence that the formation of an organic salt, consisting of a diammonium cation and two bromide anions, is more plausible. This interpretation is also in agreement with thermogravimetric analysis and with the observed solution behaviour. The crystal structure of 6‐hydroxy‐1,4‐diazepane‐1,4‐diium dibromide, C5H14N2O2+·2Br?, measured at 142 K, crystallized in the orthorhombic space group P212121. The structure displays O—H…Br and N—H…Br hydrogen bonding. Contact distances are given. A search in the Cambridge Structural Database for the singly‐bonded H—Br moiety revealed a total of 69 structures. The question, whether these structures really include HBr as neutral molecules or rather Br? anions and a protonated substrate such as an amine, is addressed. 相似文献
90.
Kacwin Christopher Oettershagen Jens Ullrich Mario Ullrich Tino 《Foundations of Computational Mathematics》2021,21(3):849-889
Foundations of Computational Mathematics - In this paper, we deal with several aspects of the universal Frolov cubature method, which is known to achieve optimal asymptotic convergence rates in a... 相似文献