7,220 research outputs found

    Middle Atmosphere Temperature and Dynamics as Revealed from D-region Observations

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    The concept of so-called meteorological control of the ionospheric D-region is presently undergoing development. According to this concept the electron concentration in this region is governed not only by solar and geomagnetic parameters but strongly depends on the temperature and dynamical regime of the mesosphere and stratosphere. How this connection between D-region and meteorological parameters can be used to obtain some information about middle atmosphere temperature and dynamics is examined. The essential points of the meteorological control concept are reviewed and the influence of turbulence on nitric oxide distribution and thus the ion production rate is discussed

    Rates of Basic Ion-molecular Processes in the Ionosphere

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    Literature review on basic ion-molecular reaction rates in ionospher

    General overview of the solar activity effects on the lower ionosphere

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    Solar activity influences the ionospheric D region. That influence manifests itself both in the form of various solar induced disturbances and in the form of the D region dependence on solar activity parameters (UV-flux, interplanetary magnetic field, solar wind etc.) in quiet conditions. Relationship between solar activity and meteorological control of the D region behavior is considered in detail and examples of strong variations of aeronomical parameters due to solar or meteorological events are given

    Discrete convexity and unimodularity. I

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    In this paper we develop a theory of convexity for a free Abelian group M (the lattice of integer points), which we call theory of discrete convexity. We characterize those subsets X of the group M that could be call "convex". One property seems indisputable: X should coincide with the set of all integer points of its convex hull co(X) (in the ambient vector space V). However, this is a first approximation to a proper discrete convexity, because such non-intersecting sets need not be separated by a hyperplane. This issue is closely related to the question when the intersection of two integer polyhedra is an integer polyhedron. We show that unimodular systems (or more generally, pure systems) are in one-to-one correspondence with the classes of discrete convexity. For example, the well-known class of g-polymatroids corresponds to the class of discrete convexity associated to the unimodular system A_n:={\pm e_i, e_i-ej} in Z^n.Comment: 26 pages, Late

    The Russian corporation: patterns of behavior during the crisis

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    This paper considers the behavior patterns of Russian firms before and during the financial crisis of 2008-2009. To facilitate comparison, we define three main groups of actors at the firm level in the Russian economy – large, politically connected companies; mid-size firms that expanded in the 2000s with the help of administrative support, and successful mid-size firms driven by market factors. Many of the large companies practiced highly risky financial policy and experienced a decrease in efficiency before the crisis, and the managers and owners of some Russian firms have been engaging in opportunistic behavior during the crisis; the forms and causes of this behavior are analyzed here. We conclude by proposing some policy implications with emphasis on supporting successful mid-size firms driven by market factors
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