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- Author or Editor: A. Varga x
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Abstract
We investigate the functional equation
The role of spatial proximity to innovation inputs (such as industrial R&D or academic research) in technological change has been widely studied in the economics literature. However, most of the papers in this research area are based on data for technologically advanced countries such as the US and parts of the EU. During transition recently accessed countries of Central Europe have undergone a dramatic restructuring process that significantly affected their systems of innovation: R&D expenditures, academic research and patenting activity have declined. According to some research results FDI constituted the most significant drive of technological change during the 1990s. Is there any role of spatially mediated knowledge spillovers in innovation in these countries? To what extent regional systems of innovation have started to develop in Central European new EU member countries? These questions have rarely been raised in the relevant literature. Using regional data this paper adopts econometric modelling techniques commonly applied in innovation research to study the role of localised knowledge inputs in technological change in Hungary.
Abstract
Blends were prepared from isotactic polypropylene (iPP) along with its b-nucleated form and poly(vinylidene-fluoride) (PVDF). Melting, and crystallization characteristics as well as structure of the blends were studied by polarized light microscopy (PLM) and differential scanning calorimetry. According to PLM studies, the phase structure of these blends is heterogeneous in the molten state. The temperature range of crystallization of PVDF during cooling is higher than that of iPP. PVDF has a strong α-nucleating effect on iPP. The crystallization of iPP starts on the surface of dispersed PVDF droplets and an α-transcrystalline layer forms on the surface of the crystalline PVDF phase. The iPP matrix crystallizes predominantly in a-form in spite of the presence of a highly active b-nucleating agent.
Abstract
The energy distribution of the alpha particles emitted from a source is in general complex. Only under particular circumstances, as in the case of very thin sources measured at large distances from the detector, can the energy distribution be approximated theoretically. In this work, we used the well-known code SRIM to simulate the interaction of alpha particles within a thin radioactive source and within the entrance window of a typical Si semiconductor detector. We considered several thin alpha particle sources measured at a large source-to-detector distance (small solid angle), in order to compare the distributions obtained by simulation with those determined by the theoretical model applied to this case. The study was performed for a variety of realistic alpha particle sources: UF4, UO2, U3O8, Gd2O3, and BaSO4, considering as alpha emitters 235U, 233U, 148Gd and 226Ra. For all these cases, we obtained the distributions due to the source and due to the entrance window of the detector, and also the final distribution given by the convolution of these two distributions. All the energy distributions obtained by simulation showed, in general, good agreement with the predictions given by the theoretical model, which includes corrections for Bohr straggling.
Baker's yeast (Saccharomyces cerevisiae-Sz1) enriched in chromium, iron, selenium or zinc was prepared by shaken cultivation and laboratory fermentation. Determination of the cellular distribution of microelements indicated that a considerable portion (68-88%) was bound to the cell constituents, a very little part was solved only in the cytosol and vacuole. More than half of the original vitamins B content has been lost during the general guarantee time (12 months) and the microelements had only little influence on it. Enrichment of yeast cells with iron was accompanied by considerable increase in vitamin B2
The present study was carried out at a dune slack meadow near Mórahalom town in the Southern part of the Great Hungarian Plain. The area of the grassland is approximately 840,000 m 2 . The vegetation is mosaic-like in accordance with the variable microrelief and water content. The lower part of the grassland consists of various types of saltmarshes and wet meadows and at the upper microrelief, Pannonic sand steppe patches occur. True bug assemblages were sampled at 16 patches using 5×50 sweeps at each sampling site. The sampling was repeated three times in both 2007 and 2008. The area, the perimeter, the shape index of the sampled patches as well as the diversity of the surrounding patches were assessed as “landscape parameters”. The plant species number and diversity of the sampled patches were estimated from the data of 5×5 m coenological quadrats. Altogether 66,087 adult individuals belonging to 153 species were collected. The ordination methods showed that the true bug assemblages of the sampling patches differ from each other in accordance with the vegetation type. These assemblages differed in their species composition and diversity as well as in their assemblage structure. The results suggested that the vegetation type based on plant species composition determined the true bug assemblages.
For Lotka-Volterra population systems, a general model of state monitoring is presented. The model includes time-dependent environmental effects or direct human intervention (treatment) as control functions and, instead of the whole state vector, the densities of certain indicator species (distinguished or lumped together) are observed. Mathematical systems theory offers a sufficient condition for local observability in such systems. The latter means that, based on the above (dynamic) partial observation, the state of the population can be recovered, at least near equilibrium. The application of this sufficient condition is illustrated by three-species examples such as a one-predator two-prey system and a simple food chain.
Abstract
Determination of very low-level activity in samples using 
-spectrometry is possible due to the low background. In order to determine the chemical yield in the separation of the element of interest, a spike must be added to the sample. In many practical cases there is no adequate spike or it is not available in the laboratory. In these cases a spike of the radionuclide already pesent in the sample can be used as the so-called inner standard method. In order to achieve the best results the optimal quantity and the spike to choose must be determined to reduce the uncertainties associated with the activities. The present work is a systematic study of these problems. These considerations were used to the determination of thorium in environmental samples.
