4,871 research outputs found

    Properties of oscillatory motions in a facular region

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    We study the properties of waves in a facular region of moderate strength in the photosphere and chromosphere. Our aim is to analyse statistically the wave periods, power and phase relations as a function of the magnetic field strength and inclination. Our work is based on observations obtained at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife) using two different instruments: the Triple Etalon SOlar Spectrometer (TESOS), in the BaII 4554 A line to measure velocity and intensity variations through the photosphere; and, simultaneously, the Tenerife Infrared Polarimeter (TIP-II), in the FeI 1.56 mm lines to the measure the Stokes parameters and magnetic field strength in the lower photosphere. Additionally, we use the simultaneous broad-band filtergrams in the CaIIH line to obtain information about intensity oscillations in the chromosphere. We find several clear trends in the oscillation behaviour: (i) the period of oscillation increases by 15-20 % with the magnetic field increasing from 500 to 1500 G; (ii) the temperature-velocity phase shifts show a strikingly different distribution in the facular region compared to the quiet region, a significant number of cases in the range from -180 to 180 degrees is detected in the facula. (iii) the most powerful chromospheric CaIIH intensity oscillations are observed at locations with strong magnetic fields (1.3-1.5 kG) inclined by 10-12 degrees, as a result of upward propagating waves with rather small phase speeds, and temperature-velocity phase shifts between 0 and 90 degrees; (iv) the power of the photospheric velocity oscillations from the \BaII\ line increases linearly with decreasing magnetic field inclination, reaching its maximum at strong field locations.Comment: Astronomy and Astrophysics, accepte

    High-dimensional estimation with geometric constraints

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    Consider measuring an n-dimensional vector x through the inner product with several measurement vectors, a_1, a_2, ..., a_m. It is common in both signal processing and statistics to assume the linear response model y_i = + e_i, where e_i is a noise term. However, in practice the precise relationship between the signal x and the observations y_i may not follow the linear model, and in some cases it may not even be known. To address this challenge, in this paper we propose a general model where it is only assumed that each observation y_i may depend on a_i only through . We do not assume that the dependence is known. This is a form of the semiparametric single index model, and it includes the linear model as well as many forms of the generalized linear model as special cases. We further assume that the signal x has some structure, and we formulate this as a general assumption that x belongs to some known (but arbitrary) feasible set K. We carefully detail the benefit of using the signal structure to improve estimation. The theory is based on the mean width of K, a geometric parameter which can be used to understand its effective dimension in estimation problems. We determine a simple, efficient two-step procedure for estimating the signal based on this model -- a linear estimation followed by metric projection onto K. We give general conditions under which the estimator is minimax optimal up to a constant. This leads to the intriguing conclusion that in the high noise regime, an unknown non-linearity in the observations does not significantly reduce one's ability to determine the signal, even when the non-linearity may be non-invertible. Our results may be specialized to understand the effect of non-linearities in compressed sensing.Comment: This version incorporates minor revisions suggested by referee

    Identifying, measuring and management risks in Russian secondary stock markets

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    : This paper outlines the changes and challenges of Emerging Russian Stock Market and investment strategy of portfolio management for the period 1996-1998 . It also taste the West models of optimization of portfolio risks and investment decisions for Russia. The major purpose of this article was to enhance the understanding of the participants in securities markets and enhance the performance of its stock and Emerging securities. This article will review the trends in the markets and help focus on the corporate risks and management and a detailed and developed conception of the mechanism of the initial public offerings and public placement of securities the global stock markets such as the U.S., Western Europe and emerging markets. It also outlined the regulatory structure and investor?s risk management tools required by western investors. In light of the recent ?financial crisis? in Russia and other major markets such as Asia, these tools will be increasing important. During much of the past decade the Russian Securities market has been developing into a number of areas including federal securities (GKO-OFZ), sub-federal (oblast) and municipal issues, corporate securities, Ag Bonds, futures, forward contracts and currency instruments. This article is developing in all those areasm .These will be increasing important in light of the new banking environment and securities laws and regulations. In 1997 Russia has joined the league of the few emerging markets that have market capitalizations of over 100Billion.AsofJune30,1997thecapitalizationis100 Billion. As of June 30, 1997 the capitalization is 104 Billion and has a YTD of 134 %. The recent ?Asian induced? corrections in the markets have reduced this by 20-40% according to private estimates. Nevertheless, it remains one of the most vibrant emerging securities markets in the world. The training focused on a number of issues related to emerging market securities including privatization, auctions, IPO?s and new products in the securities markets.

    The Approach to Development the Human Resources Intellectual Management System. Management Procedures

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    The Article suggests an approach to designing the Human Resources Intellectual Management System in order to increase Human Resources reliability, using the management methods known from the Theory of Management.. The Article examines the realization of the Subsystem of implementing management methods by the number of management procedures, executing the corresponding management method

    Implanting germanium into graphene

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    Incorporating heteroatoms into the graphene lattice may be used to tailor its electronic, mechanical and chemical properties. Direct substitutions have thus far been limited to incidental Si impurities and P, N and B dopants introduced using low-energy ion implantation. We present here the heaviest impurity to date, namely 74^{74}Ge+^+ ions implanted into monolayer graphene. Although sample contamination remains an issue, atomic resolution scanning transmission electron microscopy imaging and quantitative image simulations show that Ge can either directly substitute single atoms, bonding to three carbon neighbors in a buckled out-of-plane configuration, or occupy an in-plane position in a divacancy. First principles molecular dynamics provides further atomistic insight into the implantation process, revealing a strong chemical effect that enables implantation below the graphene displacement threshold energy. Our results show that heavy atoms can be implanted into the graphene lattice, pointing a way towards advanced applications such as single-atom catalysis with graphene as the template.Comment: 20 pages, 5 figure

    Regional Innovation Policy beyond ‘Best Practice’: Lessons from Sweden

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    This paper deals with policy measures in the regional innovation system of Scania, Southern Sweden. Focus is dedicated to requirements on innovation policy from actors representing different industries. Previous studies have identified profound differences with regard the organization of knowledge sourcing between firms and other actors in industries drawing on different knowledge bases. In correspondence with these findings, industries differ also with regard to how policy measures aiming to support innovation are perceived and acquired. Despite this, there is a tendency among regional policy programs to base their strategies on one ‘best practice’-model, inspired by successful (or sometimes less successful) cases in other parts of the world. The paper presents an in-depth analysis of such policy support targeting three industries located in one region, and ends with a suggestion to how those should be adapted to render influence on the institutional framework of the regional innovation system

    Morphofunctional changes in the rat's liver of different ages after L-methionine administration

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    Background: Literature data on the effect of methionine on functional activity and, especially, on morphological changes in the liver parenchyma in animals of different ages are sporadic, and research results are often ambiguous. Aim: The purpose of this work was to study and compare the morphofunctional changes in the liver of rats of different ages on prolonged administration of L-methionine. Material and Methods: The experiment was performed on 48 male Wistar rats of 3 and 15 months of age. Animals of the experimental group received L-methionine at a dose of 250 mg/kg body weight in addition to the standard diet, daily for 21 days. Histological preparations were prepared from liver tissue by a standard technique. Morphometry was performed on digital images using the computer program «Image J». Succinate dehydrogenase activity and protein concentration were determined in the suspension of hepatocyte mitochondria. Results: It was revealed that 21-day administration of L-methionine to rats led to hypertrophy of the hepatocyte nucleus, an increase in the nuclear-cytoplasmic ratio, the number of binuclear hepatocytes, and the nucleolus in the cell nucleus. The relative area of ​​the sinusoids network increased by 50% in 3-month-old animals. This indicated a better blood filling of the liver parenchyma. The increase in succinate dehydrogenase activity and protein concentration was revealed in the suspension of hepatocyte mitochondria of the experimental rats. This indicated an increase in the mitochondria energy potential and protein-synthetic activity. Conclusions: The administration of prophylactic doses of methionine to healthy rats leads to the appearance of pronounced morphological and functional signs of increased activity of hepatocytes. The severity of this effect has a distinct age-dependent character. In young rats, it is more pronounced than in mature rats. The results of the study are important for practical medicine when using methionine for therapeutic and prophylactic purposes
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