منابع مشابه
Quadrantids and the lunar Na atmosphere
Enhancements of the Na emission and temperature from the lunar atmosphere were reported during the Leonids meteor showers of 1995, 1997 and 1998. Here we report a search for similar enhancement during the 1999 Quadrantids, which have the highest mass flux of any of the major streams. No enhancements were detected. We suggest that different chemical-physical properties of the Leonid and Quadrant...
متن کاملMeteor stream activity V. The Quadrantids, a very young stream
This paper presents the first large set of precisely reduced orbits of Quadrantid meteoroids. These orbits were obtained from photographic observations during the 1995 return of the Quadrantid stream. The orbits refer to the main peak of the activity curve, with an unidentified few being part of a broad background component. The measured dispersion of orbits is less than from previous data obta...
متن کاملThe relative coincidence
We define a relative coincidence Nielsen number Nrel(f, g) for pairs of maps between manifolds, prove a Wecken type theorem for this invariant and give some formulae expressing Nrel(f, g) by the ordinary Nielsen numbers. Introduction. In [S2] pairs of spaces A ⊂ X and maps f : X → X such that f(A) ⊂ A were considered. A relative Nielsen number of such maps was defined, i.e. a lower bound of the...
متن کاملThe Coincidence Problem
Discrete point sets S such as lattices or quasiperiodic Delone sets may permit, beyond their symmetries, certain isometries R such that S ∩ RS is a subset of S of finite density. These are the so-called coincidence isometries. They are important in understanding and classifying grain boundaries and twins in crystals and quasicrystals. It is the purpose of this contribution to introduce the corr...
متن کاملThe Interprocedural Coincidence Theorem
We present an interprocedural generalization of the well-known (intraprocedural) Coincidence Theorem of Kam and Ullman, which provides a suucient condition for the equivalence of the meet over all paths (MOP) solution and the maximal xed point (MFP) solution to a data ow analysis problem. This generalization covers arbitrary imperative programs with recursive procedures, global and local variab...
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ژورنال
عنوان ژورنال: Nature
سال: 1903
ISSN: 0028-0836,1476-4687
DOI: 10.1038/067535b0