985 resultados para Small clusters
Resumo:
By using a simplified model of small open liquid-like clusters with surface effects, in the gas phase, it is shown how the statistical thermodynamics of small systems can be extended to include metastable supersaturated gaseous states not too far from the gas–liquid equilibrium transition point. To accomplish this, one has to distinguish between mathematical divergence and physical convergence of the open-system partition function.
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Ten novel small nucleolar RNA (snoRNA) gene clusters, consisting of two or three snoRNA genes, respectively, were identified from Arabidopsis thaliana. Twelve of the 25 snoRNA genes in these clusters are homologous to those of yeast and mammals according to the conserved antisense sequences that guide 2′-O-ribose methylation of rRNA. The remaining 13 snoRNA genes, including two 5.8S rRNA methylation guides, are new genes identified from A.thaliana. Interestingly, seven methylated nucleotides, predicted by novel snoRNAs Z41a–Z46, are methylated neither in yeast nor in vertebrates. Using primer extension at low dNTP concentration the six methylation sites were determined as expected. These snoRNAs were recognized as specific guides for 2′-O-ribose methylation of plant rRNAs. Z42, however, did not guide the expected methylation of 25S rRNA in our assay. Thus, its function remains to be elucidated. The intergenic spacers of the gene clusters are rich in uridine (up to 40%) and most of them range in size from 35 to 100 nt. Lack of a conserved promoter element in each spacer and the determination of polycistronic transcription from a cluster by RT–PCR assay suggest that the snoRNAs encoded in the clusters are transcribed as a polycistron under an upstream promoter, and individual snoRNAs are released after processing of the precursor. Numerous snoRNA gene clusters identified from A.thaliana and other organisms suggest that the snoRNA gene cluster is an ancient gene organization existing abundantly in plants.
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The hydrophobic interaction, the tendency for nonpolar molecules to aggregate in solution, is a major driving force in biology. In a direct approach to the physical basis of the hydrophobic effect, nanosecond molecular dynamics simulations were performed on increasing numbers of hydrocarbon solute molecules in water-filled boxes of different sizes. The intermittent formation of solute clusters gives a free energy that is proportional to the loss in exposed molecular surface area with a constant of proportionality of 45 ± 6 cal/mol⋅Å2. The molecular surface area is the envelope of the solute cluster that is impenetrable by solvent and is somewhat smaller than the more traditional solvent-accessible surface area, which is the area transcribed by the radius of a solvent molecule rolled over the surface of the cluster. When we apply a factor relating molecular surface area to solvent-accessible surface area, we obtain 24 cal/mol⋅Å2. Ours is the first direct calculation, to our knowledge, of the hydrophobic interaction from molecular dynamics simulations; the excellent qualitative and quantitative agreement with experiment proves that simple van der Waals interactions and atomic point-charge electrostatics account for the most important driving force in biology.
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We discuss the impact of the results from the recent Hipparcos astrometric satellite on distance estimates of galactic globular clusters. Recalibrating the clusters not only implies a relatively small change in the distance to the Large Magellanic Cloud, and hence a rescaling of several estimates of the Hubble constant, but also leads to significantly younger cluster ages. Although the data are not yet conclusive, the results so far point to a likely resolution of the apparent paradox of a universe younger than its constituents, without requiring significant modifications to simple cosmological models.
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Recent major advances in x-ray imaging and spectroscopy of clusters have allowed the determination of their mass and mass profile out to ≈1/2 the virial radius. In rich clusters, most of the baryonic mass is in the gas phase, and the ratio of mass in gas/stars varies by a factor of 2–4. The baryonic fractions vary by a factor of ≈3 from cluster to cluster and almost always exceed 0.09 h50−[3/2] and thus are in fundamental conflict with the assumption of Ω = 1 and the results of big bang nucleosynthesis. The derived Fe abundances are 0.2–0.45 solar, and the abundances of O and Si for low redshift systems are 0.6–1.0 solar. This distribution is consistent with an origin in pure type II supernova. The amount of light and energy produced by these supernovae is very large, indicating their importance in influencing the formation of clusters and galaxies. The lack of evolution of Fe to a redshift of z ≈ 0.4 argues for very early enrichment of the cluster gas. Groups show a wide range of abundances, 0.1–0.5 solar. The results of an x-ray survey indicate that the contribution of groups to the mass density of the universe is likely to be larger than 0.1 h50−2. Many of the very poor groups have large x-ray halos and are filled with small galaxies whose velocity dispersion is a good match to the x-ray temperatures.
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The appearance of ferromagnetic correlations among π electrons of phenanthrene (C14H10) molecules in the herringbone structure is proven for K doped clusters both by ab initio quantum-chemistry calculations and by the direct solution of the many-body Pariser-Parr-Pople Hamiltonian. Magnetic ground states are predicted for one or three additional electrons per phenanthrene molecule. These results are a consequence of the small overlap between the lowest unoccupied molecular orbitals (and lowest unoccupied molecular orbitals + 1) of neutral neighboring phenanthrene molecules, which makes the gain in energy by delocalization similar to the corresponding increase due to the Coulomb interaction.
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We are undertaking a program to measure the characteristics of the intracluster light ( ICL; total flux, profile, color, and substructure) in a sample of 10 galaxy clusters with a range of cluster mass, morphology, and redshift. We present here the methods and results for the first cluster in that sample, A3888. We have identified an ICL component in A3888 in V and r that contains 13% +/- 5% of the total cluster light and extends to 700 h(70)(-1) kpc (similar to 0.3r(200)) from the center of the cluster. The ICL color in our smallest radial bin is V - r 0.3 +/- 0.1, similar to the central cluster elliptical galaxies. The ICL is redder than the galaxies at 400 h(70)(-1) kpc < r < 700 h(70)(-1) kpc, although the uncertainty in any one radial bin is high. Based on a comparison of V - r color with simple stellar models, the ICL contains a component that formed more than 7 Gyr ago ( at z less than 1) with a high-metallicity ( 1.0 Z(circle dot) < Z(ICL) less than or similar to 2.5 Z(circle dot)) and a more centralized component that contains stars formed within the past 5 Gyr ( at z similar to 1). The profile of the ICL can be roughly fitted by a shallow exponential in the outer regions and a steeper exponential in the central region. We also find a concentration of diffuse light around a small group of galaxies 1.4 h(70)(-1) Mpc from the center of the cluster. In addition, we find three low surface brightness features near the cluster center that are blue ( V - r 0.0) and contain a total flux of 0.1M*. Based on these observations and X-ray and galaxy morphology, we suggest that this cluster is entering a phase of significant merging of galaxy groups in the core, whereupon we expect the ICL fraction to grow significantly with the formation of a cD galaxy, as well as the infall of groups.
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The spatial heterogeneity in the risk of Ross River virus (family Togaviridae, genus Alphavirus, RRV) disease, the most common mosquito-borne disease in Australia, was examined in Redland Shire in southern Queensland, Australia. Disease cases, complaints from residents of intense mosquito biting exposure, and human population data were mapped using a geographic information system. Surface maps of RRV disease age-sex standardized morbidity ratios and mosquito biting complaint morbidity ratios were created. To determine whether there was significant spatial variation in disease and complaint patterns, a spatial scan analysis method was used to test whether the number of cases and complaints was distributed according to underlying population at risk. Several noncontiguous areas in proximity to productive saline water habitats of Aedes vigilax (Skuse), a recognized vector of RRV, had higher than expected numbers of RRV disease cases and complaints. Disease rates in human populations in areas which had high numbers of adult Ae. vigilax in carbon dioxide- and octenol-baited light traps were up to 2.9 times those in areas that rarely had high numbers of mosquitoes. It was estimated that targeted control of adult Ae. vigilax in these high-risk areas could potentially reduce the RRV disease incidence by an average of 13.6%. Spatial correlation was found between RRV disease risk and complaints from residents of mosquito biting. Based on historical patterns of RRV transmission throughout Redland Shire and estimated future human population growth in areas with higher than average RRV disease incidence, it was estimated that RRV incidence rates will increase by 8% between 2001 and 2021. The use of arbitrary administrative areas that ranged in size from 4.6 to 318.3 km2, has the potential to mask any small scale heterogeneity in disease patterns. With the availability of georeferenced data sets and high-resolution imagery, it is becoming more feasible to undertake spatial analyses at relatively small scales.
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A busca por maior competitividade frente ao mercado cada vez mais concorrido, a perseguição pela maximização dos lucros nas organizações, e as maneiras para tornar as organizações mais eficientes são assuntos largamente debatidos em discussões nos ambientes empresariais e acadêmicos, áreas em que a administração é requerida para analisar o universo de possibilidades em busca dos objetivos acima. Principalmente sobre as pequenas e médias empresas (PME), os impactos dos custos decorrentes de falta de infraestruturas adequadas em transportes, movimentação de materiais e em logística em geral, tornam estas organizações menos competitivas. Uma das alternativas que deve ser apresentada é um agrupamento destas organizações em um mesmo espaço físico, os denominados clusters, a fim de compartilharem alguns destes custos, além de experiências para atingirem alguns ganhos também em escala. Na logística, existe a possibilidade de compartilhamento de diversos serviços, onde deverá ser identificada boa parte do potencial de ganho com este modelo, que é aplicado para diversos segmentos inclusive ao redor do mundo. Em especial no Brasil onde a carga tributária é elevada e muito complexa, quando se opta pelo modelo de cluster, haverá ganhos em escala inclusive na tributação fiscal das movimentações de mercadorias. Através do levantamento bibliográfico e a comparação de dados de diversos artigos e de instituições públicas e privadas, objetiva-se apresentar as vantagens das operações no modelo cluster, a possibilidade dos ganhos pelo cooperativismo existente nestes empreendimentos entre outras formas de benefícios possíveis na logística compartilhada pelas empresas do cluster, além de possíveis desvantagens e limitações. .
Resumo:
A cikk azt a kérdést vizsgálja, hogy milyen szerepet töltenek be a multinacionális vállalatok leányvállalatai a hazai klaszterekben, milyen a kapcsolatuk a klasztertag kis- és középvállalatokkal többek között a közös innovációban, a tudásközvetítésben, a klaszterek reputációjának növelésében. A felderítő kutatás a témát a hazai klaszterfejlesztési program, a Pólus Program által életre hívott három, úgynevezett akkreditált klaszter menedzsereivel, a klasztertag multinacionális vállalatok (MNV-k) hazai leányvállalatainak képviselőivel és a klasztertag KKV-k vezetőivel készült interjúk alapján mutatja be. A téma relevanciáját a program által potenciálisan indukált együttműködési folyamatok adják, mivel a klaszterfejlesztési pályázati konstrukciók úgy lettek kialakítva, hogy a klasztertag KKV-knak érdemes legyen nagyvállalatot is bevonniuk a közös innovációs és kutatás-fejlesztési projektekbe. A kutatási eredmények alapján az MNV leányvállalatainak leginkább a globális trendek és standardok klaszterbeli elterjesztésében van meghatározó szerepük, illetve a KKV-k és leányvállalatok közötti üzleti kapcsolatok alakításában kiemelt szerepe van a klasztermenedzsment szervezet tevékenységének. / === / The paper focuses on the topic which deals with the role of subsidiaries of multinational companies (MNC’s) in Hungarian industrial clusters in the fields of common innovation, knowledge transfer, and increasing the cluster’s reputation. The findings of the paper are based on an explorative research. Interviews were made with cluster managers, representatives of MNC’s subsidiaries, leaders of small and medium size (SME’s) enterprises operating in three accredited clusters created by the Hungarian cluster development program, the Pole Program. The relevance of the topic is given by the Program, which has induced potential cooperation between MNC’s subsidiaries and domestic SME’s in cluster environment in a way so the members of the cluster – SME’s and subsidiaries – were driven to cooperate in common innovation and R+D projects. The author’s research results suggest that MNC’s subsidiaries in Hungarian clusters seem to play a key role in the dissemination of global industrial trends and standards between the cluster members. The national cluster management organization can also play a decisive role in shaping business relationship between MNC’s and SME’s.
Resumo:
A tanulmány célja a Magyarországon működő exportáló vállalatok jellemzőinek feltárása volt a 2009-es vállalati versenyképességi felmérés alapján. Több tanulmány vizsgálta a vállalatok exportteljesítményét vállalati méret és tulajdonosi szerkezet szerinti bontásban, az elemzésben a szerző viszont ettől eltérő szemléletmódot alkalmazott. A vállalatok exportteljesítménye áll (exportértékesítés volumene, aránya, exportárbevétel változása, jövedelmezőség), a vállalati csoportképzés, klaszterelemzés középpontjában. Három jól elkülöníthető klasztert sikerült azonosítani: a jelentős exporthányaddal és folyamatos növekedéssel jellemezhető sikeres exportáló vállalatok csoportját, a stagnálással, s gyakran csökkenő exportértékesítéssel jellemezhető vállalatcsoportot, s végül a harmadik klasztert azok a jelenleg még alacsony export-ár bevétellel és alacsony exportaránnyal jellemezhető vállalatok képezték, melyekre a növekedés és a kiugróan magas jövedelmezőség volt a jellemző. Az elemzés egyediségét az adja, hogy a vállalati versenyképességi felmérés adatbázisa lehetővé tette a különböző exportteljesítmények hátterében álló működési jellemzők vizsgálatát, amelynek eredményeit a cikk bemutatja. Fő következtetésként megállapítható, hogy a sikeres exportáló vállalatok csoportja mindegyik jellemző szerint jobb működési jellemzőkkel rendelkezik a másik két csoporthoz viszonyítva. / === / The purpose of the paper is to reveal the main characteristics of the Hungarian export oriented firms. It is based on the Hungarian Competitiveness Research Survey 2009. 85% of enterprises were small or medium size in the sample. The aim of the analysis was to identify main factors and tendencies of the overall export performance. Several papers discussed the export activities of firms according to their size and ownership structure in Hungary. A different method was used here. The overall export performance (measured by volume, change, and share of export revenues, and firm profitability ratios) was put in the centre of cluster analysis. Three different clusters were identified. Firms in the firstcluster had significant export performance and growth rate. The second cluster was the group of stagnating firms and the third one contained those whose export performance was low but signaled growth with excellent profitability ratios. The uniqueness of the paper derived from the Competitiveness Research Survey because it provided an opportunity to analyse the connection between export performance and other management and operational characteristics of enterprises. The paper may induce futher research in exploring main enterprise level factors of export performance of the Hungarian firms.
Resumo:
A cikk azt a kérdést vizsgálja, hogy milyen szerepet töltenek be a multinacionális vállalatok leányvállalatai a hazai klaszterekben, milyen a kapcsolatuk a klasztertag kis- és középvállalatokkal többek között a közös innovációban, a tudásközvetítésben, a klaszterek reputációjának növelésében. A felderítő kutatás a témát a hazai klaszterfejlesztési program, a Pólus Program által életre hívott három, úgynevezett akkreditált klaszter menedzsereivel, a klasztertag multinacionális vállalatok (MNV-k) hazai leányvállalatainak képviselőivel és a klasztertag KKV-k vezetőivel készült interjúk alapján mutatja be. A téma relevanciáját a program által potenciálisan indukált együttműködési folyamatok adják, mivel a klaszterfejlesztési pályázati konstrukciók úgy lettek kialakítva, hogy a klasztertag KKV-knak érdemes legyen nagyvállalatot is bevonniuk a közös innovációs és kutatás-fejlesztési projektekbe. A kutatási eredmények alapján az MNV leányvállalatainak leginkább a globális trendek és standardok klaszterbeli elterjesztésében van meghatározó szerepük, illetve a KKV-k és leányvállalatok közötti üzleti kapcsolatok alakításában kiemelt szerepe van a klasztermenedzsment-szervezet tevékenységének. ----- Abstract: The paper focuses on the topic which deals with the role of subsidiaries of multinational companies (MNC’s) in Hungarian industrial clusters in the fields of common innovation, knowledge transfer, and increasing the cluster’s reputation. The findings of the paper are based on an explorative research. Interviews were made with cluster managers, representatives of MNC’s subsidiaries, leaders of small and medium size (SME’s) enterprises operating in three accredited clusters created by the Hungarian cluster development program, the Pole Program. The relevance of the topic is given by the Program, which has induced potential cooperation between MNC’s subsidiaries and domestic SME’s in cluster environment in a way so the members of the cluster – SME’s and subsidiaries – were driven to cooperate in common innovation and R+D projects. Our research results suggest that MNC’s subsidiaries in Hungarian clusters seem to play a key role in the dissemination of global industrial trends and standards between the cluster members. The national cluster management organization can also play a decisive role in shaping business relationship between MNC’s and SME’s.
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This article investigates the attitudes to inter-firm co-operation in Hungary by analysing a special group of business networks: the business clusters. Following an overview of cluster policy, a wide range of selfproclaimed business clusters are identified. A small elite of these business networks evolves into successful, sustainable innovative business clusters. However, in the majority of cases, these consortia of interfirm co-operation are not based on a mutually satisfactory model, and as a consequence, many clusters do not survive in the longer term. The paper uses the concepts and models of social network theory in order to explain, why and under what circumstances inter-firm co-operation in clusters enhances the competitiveness of the network as a whole, or alternatively, under what circumstances the cluster remains dependent on Government subsidies. The empirical basis of the study is a thorough internet research about the Hungarian cluster movement; a questionnaire based expert survey among managers of clusters and member companies and a set of in-depth interviews among managers of self-proclaimed clusters. The last chapter analyises the applicability of social network theory in the analysis of business networks and a model involving the value chain is recommended.