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71.
Ulrich Dierkes 《Inventiones Mathematicae》1995,122(1):453-473
We here prove pointwise curvature estimates for minimal hypersurfaces in singular spaces, using the integral curvature estimate and a generalized Simons inequality which were established recently. A further basic ingredient is a new Sobolev type inequality for stationary hypersurfaces.Oblatum 19-IX-1994This research was supported by the Deutsche Forschungsgemeinschaft through a Heisenberg award. Part of the work described here was carried out during visits to Dipartimento Matematica Applicata, University of Firenze and Department of Mathematics, Stanford University. The author would like to express his gratitude to both institutions for their kind hospitality and support. Also it is a pleasure to thank the referee for his useful comments concerning the formulation of the main theorem. 相似文献
72.
Ulrich Kohlenbach 《Archive for Mathematical Logic》1995,34(4):279-283
It is well-known (due to C. Parsons) that the extension of primitive recursive arithmeticPRA by first-order predicate logic and the rule of
2
0
-induction
2
0
-IR is
2
0
-conservative overPRA. We show that this is no longer true in the presence of function quantifiers and quantifier-free choice for numbersAC
0,0-qf. More precisely we show that :=PRA
2 +
2
0
-IR+AC
0,0-qf proves the totality of the Ackermann function, wherePRA
2 is the extension ofPRA by number and function quantifiers and
2
0
-IR may contain function parameters.This is true even forPRA
2 +
1
0
-IR+
2
0
-IR
–+AC
0,0-qf, where
2
0
-IR
– is the restriction of
2
0
-IR without function parameters.I am grateful to an anonymous referee whose suggestions led to an improved discussion of our results 相似文献
73.
A Ginzburg-Landau model with a scalar and a vector order parameter, which describe the concentration and orientation of the amphiphile, respectively, is used to study the phase diagram and the scattering intensity of binary amphiphilic systems. With increasing amphiphile concentration, the calculated phase diagram shows the typical sequence of ordered phases observed experimentally, that is micellar liquid cubic micellar hexagonal lamellar cubic bicontinuous invers hexagonal. The scattering intensity in the homogeneous phase is calculated in the oneloop approximation. In the vicinity of a phase transition to an ordered phase, the intensity is found to show a 1/q behavior for not too small wave vectorsq, followed by a small peak, and a 1/q
2 decay for large wave vectors, in agreement with experimental observations in theL
3-(or sponge-)phase.Dedicated to Prof. H. Wagner on the occasion of his 60th birthday 相似文献
74.
Volkmar Nejedl Michael Panzner Stefan Baunack Ulrich Franz Arnold Luft Klaus Wetzig 《Mikrochimica acta》1998,130(1-2):89-95
The laser induced modification of iron surfaces with atmospheric species was investigated by means of Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Different laser systems were used for irradiating iron samples in a wide range of the laser processing parameters up to small foci and ultra short pulses.A nitriding of iron connected with an oxidation of the near surface region was observed in the wavelength range between 193 nm and 10.6 m using large foci (0.1 cm2) and short pulses (10...1400ns). In case of small foci (7·10–6cm2) with ns-pulses (50 ns) an enrichment of the iron melt with nitrogen and an advanced oxidation of the surrounding area of the laser spot were detected. When using shorter pulses (200 fs, 40 ps) no indications for a nitriding were found. 相似文献
75.
This study addresses the phenomenon of persistent countergradient (PCG) fluxes of momentum and heat (density) as observed in homogeneous turbulence forced by shear and stratification. Countergradient fluxes may occur at large scales when stratification is strong. However, they always occur at small scales, independently of stratification. A conceptional model is introduced to explain PCG fluxes at small scales as the result of the collision of large-scale fluid parcels. The large parcels collide under the driving force of inclined vortex structures (in a shear-dominated flow) or of buoyancy (in a strongly stratified shear flow). This collision model also explains the PCG heat flux in an unsheared stratified flow with zero average momentum flux. It is found that the energy of the small-scale PCG motions is provided (i) by quick transport of kinetic energy from the scales of production to relatively slowly dissipating scales if the flow is shear-driven and (ii) by conversion of available potential energy to kinetic energy at small scales when the flow is stratified. The collision mechanism is an inherent property of the turbulence dynamics. Therefore, the PCG fluxes at small scales reflect a universal character of homogeneous turbulence, and are found over a large range of Reynolds numbers. The Prandtl (or Schmidt) number influences the rate of dissipation of temperature (or density) variance but not the dissipation rate of the velocity variance. In stratified flows, therefore, the number directly affects the strength of the PCG heat flux at small scales. It is found, however, that the PCG momentum flux is also altered slightly when the Prandtl number is large enough to sustain small buoyantly moving parcels after collision. 相似文献
76.
77.
78.
79.
1,3-Dienes and electron deficient alkenes are coupled in a one pot carbon-carbon bond formation reaction under mild conditions. 相似文献
80.