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991.
《Magnetic resonance in chemistry : MRC》2003,41(2):107-114
NMR relaxation measurement of perfluorocarbons (PFCs), such as perfluorotributylamine (FTBA), is a convenient method for the determination of oxygen concentrations in tissues and tumors. Previous relaxation studies of FTBA used different 19F NMR assignments causing some confusion. Fluorine‐detected 19F, 13C HMQC and HMBC and selectively 19F‐decoupled 13C NMR provided unequivocal 19F and 13C assignments for FTBA and perfluoropentanoic acid (FPA). Based on those assignments, 13C spin–lattice relaxation time constants (T1) and effective correlation times for FTBA and FPA are reported and discussed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
992.
Consider the tessellation of the hyperbolic plane by m-gons, ℓ per vertex. In its 1-skeleton, we compute the growth series of vertices, geodesics, tuples of geodesics with common
extremities. We also introduce and enumerate holly trees, a family of proper loops in these graphs. We then apply Grigorchuk’s result relating cogrowth and random walks to obtain
lower estimates on the spectral radius of the Markov operator associated with a symmetric random walk on these graphs.
Received 19 September 2001; in revised form 23 December 2001 相似文献
993.
C. Léonard 《Probability Theory and Related Fields》1995,101(1):1-44
Summary We consider a dynamical interacting particle system whose empirical distribution tends to the solution of a spatially homogeneous Boltzmann type equation, as the number of particles tends to infinity. These laws of large numbers were proved for the Maxwellian molecules by H. Tanaka [Tal] and for the hard spheres by A.S. Sznitman [Szl]. In the present paper we investigate the corresponding large deviations: the large deviation upper bound is obtained and, using convex analysis, a non-variational formulation of the rate function is given. Our results hold for Maxwellian molecules with a cutoff potential and for hard spheres. 相似文献
994.
E. Ballico 《Annali dell'Universita di Ferrara》2002,48(1):21-23
LetX be a smooth complex compact surface without non-constant meromorphic functions. Here we prove the existence of rank holomorphic
vector bundles onX containing exactly one rank one saturated subsheaf.
Sunto SiaX una superficie complessa compatta non singolare senza funzioni meromorfe non costanti. In questo lavoro si domstra cheX possiede molti fibrati olomorfi di rango 2 contenenti un unico fibrato in rette.相似文献
995.
Summary. We have discovered a new implementation of the
qd algorithm that has a far wider domain of stability than Rutishauser's version. Our algorithm was
developed from an examination of the {Cholesky~LR} transformation and can be adapted
to parallel computation in stark contrast to traditional qd. Our algorithm also yields
useful a posteriori upper and lower bounds on the smallest singular
value of a bidiagonal matrix.
The zero-shift bidiagonal QR of Demmel and Kahan computes the smallest singular
values to maximal relative accuracy and the others to maximal absolute accuracy
with little or no degradation in efficiency when compared with the
LINPACK code. Our algorithm obtains maximal relative accuracy for all
the singular values and runs at least four times faster than the LINPACK code.
Received August 8, 1993/Revised version received May 26, 1993 相似文献
996.
M. Marshall 《Aequationes Mathematicae》1994,48(2-3):306-316
Summary The paper looks at certain open problems in the theory of minimal generation of semi-algebraic sets and constructible sets in the real spectrum: problems about thet-invariant and the associatedp-invariant for separating families, and about the extension of the theory to arbitrary commutative rings. 相似文献
997.
We consider numerical methods for the incompressible Reynolds averaged Navier–Stokes equations discretized by finite difference
techniques on non-staggered grids in body-fitted coordinates. A segregated approach is used to solve the pressure–velocity
coupling problem. Several iterative pressure linear solvers including Krylov subspace and multigrid methods and their combination
have been developed to compare the efficiency of each method and to design a robust solver. Three-dimensional numerical experiments
carried out on scalar and vector machines and performed on different fluid flow problems show that a combination of multigrid
and Krylov subspace methods is a robust and efficient pressure solver.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
998.
999.
Periodic and almost periodic solutions of nonlinear discrete Volterra equations with unbounded delay
The existence of periodic and almost periodic solutions of nonlinear discrete Volterra equations with unbounded delay is obtained by using stability properties of a bounded solution. 相似文献
1000.
Brian H. Bowditch 《Mathematische Zeitschrift》2007,255(1):35-76
Let Γ be the fundamental group of a compact surface group with non-empty boundary. We suppose that Γ admits a properly discontinuous strictly type preserving action on hyperbolic 3-space such that there is a positive lower bound on the translation lengths of loxodromic elements. We describe the Cannon–Thurston map in this case. In particular, we show that there is a continuous equivariant map of the circle to the boundary of hyperbolic 3-space, where the action on the circle is obtained by taking any finite-area complete hyperbolic structure on the surface, and lifting to the boundary of hyperbolic 2-space. We deduce that the limit set is locally connected, hence a dentrite in the singly degenerate case. Moreover, we show that the Cannon–Thurston map can be described topologically as the quotient of the circle by the equivalence relations arising from the ends of the quotient 3-manifold. For closed surface bundles over the circle, this was obtained by Cannon and Thurston. Some generalisations and variations have been obtained by Minsky, Mitra, Alperin, Dicks, Porti, McMullen and Cannon. We deduce that a finitely generated kleinian group with a positive lower bound on the translation lengths of loxodromics has a locally connected limit set assuming it is connected. 相似文献