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201.
Mustafa Korkmaz Burak Ozbagci 《Proceedings of the American Mathematical Society》2001,129(5):1545-1549
There exists a (relatively minimal) genus Lefschetz fibration with only one singular fiber over a closed (Riemann) surface of genus iff and . The singular fiber can be chosen to be reducible or irreducible. Other results are that every Dehn twist on a closed surface of genus at least three is a product of two commutators and no Dehn twist on any closed surface is equal to a single commutator.
202.
Roman Drnovšek 《Integral Equations and Operator Theory》2001,39(3):253-266
Let
be a collection of bounded operators on a Banach spaceX of dimension at least two. We say that
is finitely quasinilpotent at a vectorx
0X whenever for any finite subset
of
the joint spectral radius of
atx
0 is equal 0. If such collection
contains a non-zero compact operator, then
and its commutant
have a common non-trivial invariant, subspace. If in addition,
is a collection of positive operators on a Banach lattice, then
has a common non-trivial closed ideal. This result and a recent remarkable theorem of Turovskii imply the following extension of the famous result of de Pagter to semigroups. Let
be a multiplicative semigroup of quasinilpotent compact positive operators on a Banach lattice of dimension at least two. Then
has a common non-trivial invariant closed ideal.This work was supported by the Research Ministry of Slovenia. 相似文献
203.
Roman Frič 《International Journal of Theoretical Physics》2000,39(3):677-686
We propose a simple set-theoretic model of a generalized probability spaceadmitting intrinsic incompatible events and incompatible observables. It is acoproduct in the category D of D-posets and D-homomorphisms each factor ofwhich is a classical Kolmogorovian probability space. Since classical events,random functions, and probability measures can be treated within D in a canonicalway, the Kolmogorovian model becomes a special case. We show that -additivityand other -notions can be replaced in a natural way by sequential continuity. 相似文献
204.
Oxidative-reductive properties on the acid-base surfaces of the oxide compositions Sn-Ce-Rh-O and Zr-Mg-Y-O, active as catalysts in the ketonization of secondary alcohols were determined based on the isopropanol conversion selectivity. The kinetics of isopropanol conversion was measured in the oxygen-free atmosphere. Activation energies for both directions of conversion (dehydration to propylene and dehydrogenation to acetone) were calculated. The results were compared with the kinetics over SnO2 and ZrO2. Both oxide compositions, Sn-Ce-Rh-O and Zr-Mg-Y-O are oxidative-reductive catalysts containing Lewis acid centers. 相似文献
205.
Jiri Pechousek Miroslav Mashlan Jiri Frydrych Dalibor Jancik Roman Prochazka 《Hyperfine Interactions》2007,175(1-3):1-8
A plenty of different programming techniques and instrument solutions are used in the development of Mössbauer spectrometers. Each of them should provide a faster spectrum accumulation process, increased productivity of measurements, decreased nonlinearity of the velocity scale, etc. The well known virtual instrumentation programming method has been used to design a computer-based Mössbauer spectrometer. Hardware solution was based on two commercially-available PCI modules produced by National Instruments Co. Virtual Mössbauer spectrometer is implemented by the graphical programming language LabVIEW 7 Express. This design environment allows to emulate the multichannel analyzer on the digital oscilloscope platform. This is a novel method based on Waveform Peak Detection function which allows detailed analysis of the acquired signal. The optimal treatment of the detector signal from various detector types is achieved by mathematical processing only. As a result, the possibility of an increase of signal/noise ratio is presented. 相似文献
206.
Nikita M. Podvalnyy Alexander I. Zinin Nelly N. Malysheva Roman A. Kunetskiy 《Journal of carbohydrate chemistry》2013,32(5):213-224
A convenient synthesis and separation of α- and β-anomers of methyl (phenyl 3,5-dideoxy-2-thio-5-trifluoroacetamido-D-glycero-D-galacto-nonulopyranosid)onate (6a and 6b) on a multigram scale was developed. Both α- and β-isomers of 6 were obtained as crystals suitable for safe storage. The β-isomer forms a crystalline solvate with methanol. Fully O-trichloroacetylated and O-trifluoroacetylated N-trifluoroacetyl thiosialosides were synthesized in an efficient manner from the β-tetraol 6b. 相似文献
207.
Nichole Cates Miller Roman Gysel Chad E. Miller Eric Verploegen Zach Beiley Martin Heeney Iain McCulloch Zhenan Bao Michael F. Toney Michael D. McGehee 《Journal of Polymer Science.Polymer Physics》2011,49(7):499-503
Polymer:fullerene blends have been widely studied as an inexpensive alternative to traditional silicon solar cells. Some polymer:fullerene blends, such as blends of poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene (pBTTT) with phenyl‐c71‐butyric acid methyl ester (PC71BM), form bimolecular crystals due to fullerene intercalation between the polymer side chains. Here we present the determination of the eutectic pBTTT:PC71BM phase diagram using differential scanning calorimetry (DSC) and two‐dimensional grazing incidence X‐ray scattering (2D GIXS) with in‐situ thermal annealing. The phase diagram explains why the most efficient pBTTT:PC71BM solar cells have 75–80 wt % PC71BM since these blends lie in the center of the only room‐temperature phase region containing both electron‐conducting (PC71BM) and hole‐conducting (bimolecular crystal) phases. We show that intercalation can be suppressed in 50:50 pBTTT:PC71BM blends by using rapid thermal annealing to heat the blends above the eutectic temperature, which forces PC71BM out of the bimolecular crystal, followed by quick cooling to kinetically trap the pure PC71BM phase. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
208.
The multipole-to-local (M2L) operator is the most time-consuming part of the far field computation in the fast multipole method for Laplace equation. Its natural expression, though commonly used, does not respect a sharp error bound: we here first prove the correctness of a second expression. We then propose a matrix formulation implemented with basic linear algebra subprograms (BLAS) routines in order to speed up its computation for these two expressions. We also introduce special data storages in memory to gain greater computational efficiency. This BLAS scheme is finally compared, for uniform distributions, to other M2L improvements such as block FFT, FFT with polynomial scaling, rotations and plane wave expansions. When considering runtime, extra memory storage, numerical stability and common precisions for Laplace equation, the BLAS version appears as the best one. 相似文献
209.
We show that the conjectures by Matthews and Sumner (every 4-connected claw-free graph is Hamiltonian), by Thomassen (every 4-connected line graph is Hamiltonian) and by Fleischner (every cyclically 4-edge-connected cubic graph has either a 3-edge-coloring or a dominating cycle), which are known to be equivalent, are equivalent to the statement that every snark (i.e. a cyclically 4-edge-connected cubic graph of girth at least five that is not 3-edge-colorable) has a dominating cycle.We use a refinement of the contractibility technique which was introduced by Ryjá?ek and Schelp in 2003 as a common generalization and strengthening of the reduction techniques by Catlin and Veldman and of the closure concept introduced by Ryjá?ek in 1997. 相似文献