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91.
92.
93.
The electric response of several isolated rat hearts in a controlled environment was studied experimentally. The correlation dimension D(2) was estimated and was found to be between 4 and 6.5 when the response was nearly periodic. The variation of D(2) with the concentration of calcium was studied and a general trend of its increase with increasing concentration was found. Two types of ventricular fibrillation (VF) were observed, one that corresponds to a stochastic signal where D(2) is unbounded and the other to a low dimensional dynamical system with 3.5=D(2)=4. It was found also that for the heart the correlation dimension is only an approximate concept. A new method for the estimation of D(2), that is suitable for the case when it is only approximate was introduced. A surrogate data method suitable for the analysis of nearly periodic series was implemented. (c) 2000 American Institute of Physics. 相似文献
94.
Gelmini and Roncadelli have proposed a model of neutrino masses in which B?L symmetry is spontaneously broken by a small vacuum expectation value of a Higgs triplet. We give an exegesis of this model. We show that the massive neutrinos in this model cannot be cosmologically relevant today and that conflicting analyses of double beta decay experiments can be reconciled. 相似文献
95.
Shmuel Weinberger 《Israel Journal of Mathematics》1987,59(1):1-7
This paper studies the question of which manifolds fiber over the circle in dimensions four and five.
Partially supported by an NSF Postdoctoral Fellowship. 相似文献
96.
97.
Letf
0(x) be a function of one variable with a simple zero atr
0. An iteration scheme is said to be locally convergent if, for some initial approximationsx
1, ...,x
s nearr
0 and all functionsf which are sufficiently close (in a certain sense) tof
0, the scheme generates a sequence {x
k} which lies nearr
0 and converges to a zeror off. The order of convergence of the scheme is the infimum of the order of convergence of {x
k} for all such functionsf. We study iteration schemes which are locally convergent and use only evaluations off,f, ...,f
[d] atx
1, ...,x
k–1 to determinex
k, and we show that no such scheme has order greater thand+2. This bound is the best possible, for it is attained by certain schemes based on polynomial interpolation.This work was supported (in part) by the Office of Naval Research under contract numbers N0014-69-C-0023 and N0014-71-C-0112. 相似文献
98.
99.
100.
Shmuel Friedland 《Linear and Multilinear Algebra》1978,6(2):123-143
It Is shown here that a permanent of n× ndoubly stochastic matrix is not less than 1/ n!. The proof of this inequality follows from the study of a generalized van der Waerden problem on the set of doubly stochastic matrices. 相似文献