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111.
By a totally regular parallelism of the real projective 3-space
P3:=PG(3, \mathbb R){\Pi_3:={{\rm PG}}(3, \mathbb {R})} we mean a family T of regular spreads such that each line of Π
3 is contained in exactly one spread of T. For the investigation of totally regular parallelisms the authors mainly employ Klein’s correspondence λ of line geometry and the polarity π
5 associated with the Klein quadric H
5 (for details see Chaps. 1 and 3). The λ-image of a totally regular parallelism T is a hyperflock of H
5, i.e., a family H of elliptic subquadrics of H
5 such that each point of H
5 is on exactly one subquadric of H. Moreover, {p5(span l(X))|X ? T}=:HT{\{\pi_5({{\rm span}} \,\lambda(\mathcal {X}))\vert\mathcal {X}\in\bf{T}\}=:\mathcal {H}_{\bf{T}}} is a hyperflock determining line set, i.e., a set Z{\mathcal {Z}} of 0-secants of H
5 such that each tangential hyperplane of H
5 contains exactly one line of Z{\mathcal {Z}} . We say that dim(span HT)=:dT{{{\rm dim}}({{\rm span}}\,\mathcal {H}_{\bf{T}})=:d_{\bf{T}}} is the dimension of
T and that T is a d
T
- parallelism. Clifford parallelisms and 2-parallelisms coincide. The examples of non-Clifford parallelisms exhibited in Betten
and Riesinger [Result Math 47:226–241, 2004; Adv Geom 8:11–32, 2008; J Geom (to appear)] are totally regular and of dimension
3. If G{\mathcal{G}} is a hyperflock determining line set, then {l-1 (p5(X) ?H5) | X ? G}{\{\lambda^{-1}\,{\rm (}\pi_5(X){\,\cap H_5)\,|\, X\in\mathcal{G}\}}} is a totally regular parallelism. In the present paper the authors construct examples of topological (see Definition 1.1)
4- and 5-parallelisms via hyperflock determining line sets. 相似文献
112.
Rolf R. Gerhardts 《Surface science》1976,58(1):227-234
The validity of assumptions involved in experimental evaluations of the g-factor of electrons in (100) surface inversion layers of p-silicon from Shubnikov-De Haas oscillations of the surface conductivity by the method of tilted megnetic fields is discussed on the basis of the transport theory of a two-dimensional electron-impurity system. The self-consistent Born approximation is shown to be insufficient to this task, and an alternative cumulant approach is discussed. Contrary to recent work, the cumulant approach is introduced in a simple manner, avoiding the path-integral formalism. 相似文献
113.
114.
Rolf Klein 《Computational Geometry》1992,1(6):325-351
A polygon with two distinguished vertices, s and g, is called a street if the two boundary chains from s to g are mutually weakly visible. For a mobile robot with on-board vision system we describe a strategy for finding a short path from s to g in a street not known in advance, and prove that the length of the path created does not exceed 1 +
π times the length of the shortest path from s to g. Experiments suggest that our strategy is much better than this, as no ratio bigger than 1.8 has yet been observed. This is complemented by a lower bound of 1.41 for the relative detour each strategy can be forced to generate. 相似文献
115.
Anna K. Migglautsch Melissa Willim Bettina Schweda Anton Glieder Rolf Breinbauer Margit Winkler 《Tetrahedron》2018,74(43):6199-6204
Microbial cytochrome P450 enzymes (CYPs) are able to mimic the metabolism of human CYPs. One challenge is to identify the respective drug metabolites and to compare substrate specificities to those of the human enzymes. In this study, a class VIII self-sufficient CYP from Aspergillus fumigatus (CYP505X) and variants of this enzyme were heterologously expressed in E. coli. The substrate scope of the variants was determined using active pharmaceutical ingredients (APIs) and (hetero)cyclic compounds. Capsaicin – the active compound in chili peppers – was oxidized most efficiently (4.36?μM/min) in a whole cell mediated biotransformation. The products were isolated, purified and their structures elucidated by 1D and 2D NMR. The two major metabolites showed modifications on the lipophilic side chain. Specifically, capsaicin was hydroxylated at position 8 to give (E)-8-hydroxy-N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-6-enamide and epoxidized at the double bond to give N-(4-hydroxy-3-methoxybenzyl)-5-(3-isopropyloxiran-2-yl)-pentanamide. 相似文献
116.
Rolf W. Berg 《应用光谱学评论》2018,53(6):503-515
The common substance Hydrohalite has a role to play in as diverse areas as Geology, Earth Climatology, Universe Cosmology, and Cryobiology. In this review, the occurrences under very different occasions are described. These relations are not commonly appreciated. During the work, we realized that there is yet an aspect that has been overlooked. Hydrohalite formed sometimes on icy roads resists common salt deicing procedures. Also, hydrohalite can be detected by rather simple Raman spectroscopy instrumentation. It means that it is possible to avoid accidents on icy roads in the following way: Common salt deicing trucks may be equipped with “artificial intelligence” based on a duel deicing system that switches between normal NaCl deicing and non-NaCl deicing based on Raman spectroscopy. The advantages are first of all less traffic accidents and lower environmental impact and corrosion from NaCl, but disadvantages are increased costs of investments and consumption of non-NaCl deicing agents. 相似文献
117.
Sabina Ronneteg Rolf Berger Gilles André 《Journal of magnetism and magnetic materials》2010,322(6):681-685
The magnetic layer structure of TlCo2Se2−xSx has been thoroughly re-investigated with neutron powder diffraction. The cobalt magnetic moments are ferromagnetically arranged within the layers, but the interlayer coupling differs profoundly with varying composition (x): the spins in TlCo2Se2 form a helix along the c-axis with a turning-angle of ∼119° at 1.4 K. This kind of helical structure prevails for 0≤x≤1.5 with a gradual decrease of the angle with increasing sulphur content, down to 34°, showing an almost linear relationship with the interlayer distance of Co-Co. For x≥1.75 the interlayer coupling changes to ferromagnetic. Unexpectedly, two helices were found to coexist at x=0.5 and x=1.0. The interaction between adjacent cobalt layers is there characterized by an incommensurate angle (106°, resp., 73°) together with a commensurate angle of 90°. The magnetic structures have been refined as two magnetic phases, each having a characteristic wave vector. A tentative model where the symmetry of the structure and the interlayer distance compete is considered for explaining the simultaneous occurrence of the two kinds of diffraction profile satellites. 相似文献
118.
119.
Michael Zech Matthias Saurer Mario Tuthorn Katja Rinne Roland A. Werner Rolf Siegwolf 《Isotopes in environmental and health studies》2013,49(4):492-502
Although the instrumental coupling of gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) for compound-specific δ18O analysis has been commercially available for more than a decade, this method has been hardly applied so far. Here we present the first GC-Py-IRMS δ18O results for trimethylsilyl-derivatives of plant sap-relevant sugars and a polyalcohol (glucose, fructose, sucrose, raffinose and pinitol). Particularly, we focus on sucrose, which is assimilated in leaves and which is the most important transport sugar in plants and hence of utmost relevance in plant physiology and paleoclimate studies. Replication measurements of sucrose standards and concentration series indicate that the GC-Py-IRMS δ18O measurements are not stable over time and that they are amount (area) dependent. We, therefore, suggest running sample batch replication measurements in alternation with standard concentration series of reference material. This allows for carrying out (i) a drift correction, (ii) a calibration against reference material and (iii) an amount (area) correction. Tests with 18O-enriched water do not provide any evidence for oxygen isotope exchange reactions affecting sucrose and raffinose. We present the first application of GC-Py-IRMS δ18O analysis for sucrose from needle extract (soluble carbohydrate) samples. The obtained δ18Osucrose/ Vienna Standard Mean Ocean Water (VSMOW) values are more positive and vary in a wider range (32.1–40.1 ‰) than the δ18Obulk/ VSMOW values (24.6–27.2 ‰). Furthermore, they are shown to depend on the climate parameters maximum day temperature, relative air humidity and cloud cover. These findings suggest that δ18Osucrose of the investigated needles very sensitively reflects the climatically controlled evaporative 18O enrichment of leaf water and thus highlights the great potential of GC-Py-IRMS δ18Osucrose analysis for plant physiology and paleoclimate studies. 相似文献
120.
During stress-induced transformation NiTi shows a distinct generation of transformation bands. A simple one-dimensional model for superelastic NiTi wires has been developed to show exemplarily methods to account for these bands in plasticitybased models. To clarify the dependence of the transformation bands on the distribution of latent heat and therefore on the mechanical behaviour, optical and thermographical experiments have been performed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献