801 research outputs found

    Kinetics of Deposition of Oriented Superdisks

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    We use numerical Monte Carlo simulation to study kinetics of deposition of oriented superdisks, bounded by the Lame curves of the form x2p+y2p=1|x|^{2p}+|y|^{2p}=1, on regular planar substrate. It was recently shown that the maximum packing density, as well as jamming density ρJ\rho_{J}, exhibit discontinuous derivative at p=0.5p=0.5, when the shape changes from convex to concave form. By careful examination of the late-stage approach to the jamming limit, we find that the leading term in temporal development is also nonanalytic at p=0.5p=0.5, and offer heuristic excluded-area arguments for this behavior

    Family-specific vs. Universal PCR primers for the study of mitochondrial DNA in plants

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    Mitochondrial genomes (mtDNAs or mitogenomes) of seed plants are characterized by a notoriously unstable organization on account of which available so-called universal or consensus primers may fail to fulfil their foreseen function-amplification of various mtDNA regions in a broad range of plant taxa. Thus, the primers developed for groups assumed to have similar organization of their mitogenomes, such as families, may facilitate a broader usage of more variable non-coding portions of these genomes in group members. Using in silico PCR method and six available complete mitogenomes of Fabaceae, it has been demonstrated that only three out of 36 published universal primer and three Medicago sativa-specific primer pairs that amplify various mtDNA regions are suitable for six representatives of the Fabaceae family upon minor modifications, and develop 21 Fabaceae-specific primer pairs for amplification of all 14 cis-splicing introns in genes of NADH subunits (nad genes) which represent the most commonly used noncoding mtDNA regions in various studies in plants. Using the same method and six available complete mitogenomes of representatives of related families Cucurbitaceae, Euphorbiaceae and Rosaceae and a model plant, Arabidopsis thaliana, it has further been demonstrated that applicability of newly developed primer pairs for amplification of nad introns in more or less related taxa was dependent not only on species evolutionary distances but also on their genome sizes. A reported set of 24 primer pairs is a valuable resource which may facilitate a broader usage of mtDNA variability in future studies at both intra- and inter-specific levels in Fabaceae, which is the third largest family of flowering plants rarely studied at the mtDNA level, and in other more or less related taxa

    Vortex Bubble Formation in Pair Plasmas

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    It is shown that delocalized vortex solitons in relativistic pair plasmas with small temperature asymmetries can be unstable for intermediate intensities of the background electromagnetic field. Instability leads to the generation of ever-expanding cavitating bubbles in which the electromagnetic fields are zero. The existence of such electromagnetic bubbles is demonstrated by qualitative arguments based on a hydrodynamic analogy, and by numerical solutions of the appropriate Nonlinear Schr\"odinger equation with a saturating nonlinearity.Comment: 4 pages of two-column text, 2 figure

    Human dimension of strategic partnerships

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    This paper aims to point to the widespread practice of neglecting behavioral aspects of different forms of fusions and integrations of enterprises that have emerged in the process of privatization through strategic partnerships with foreign companies among Serbian enterprises. The initial hypothesis in this paper is that the process of privatization, restructuring and transformation in Serbian enterprises cannot be completely successful and equally advantageous for all the subjects involved if there is no concern for human dimension of these processes. Without this concern there is a possibility for behavioral problems to arise, and the only way to resolve them is through post festum respecting and introducing elements that should never have been neglected in the first place. This paper refers to the phenomenon of collision of cultures and the ways of resolving it while forming strategic partnerships

    Response of rare and endangered species Picea omorika to climate change: The need for speed

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    Serbian spruce (Picea omorika (Pančić) Purk.) is a rare and endangered tertiary relict and endemic species, with restricted and fragmented natural range in Serbia and Bosnia and Herzegovina, mainly around the mid-course of the Drina river. Since the middle of the 19th century, its natural range declines constantly, followed by a decline in the number of mature individuals. The decline of this forest species is slow and mainly attributed to poor regeneration and low competing ability. Given the foreseen worsening of the climate in forthcoming decades, this decline can only accelerate. In recent years, dieback related to drought has been observed as response to extreme weather events suggesting that Serbian spruce will face difficulties in adapting to climate change within its natural range. However, successful use of Serbian spruce in Central and Northern Europe indicates potentially large adaptive potential of this species which, along with the high genetic variability, outweigh the limited morphological variation, self-fertilization, and limitations related to the restricted natural range in the first place, and, indicates possible directions of migration in the second place. In this paper, current conservation actions are discussed, and strategies for the species survival in a changing environment are suggested. Since migration and adaptation are the least likely responses of this species to climate change, measures such as assisted migration may be the only strategy which will enable persistence of Serbian spruce. Current conservation programs, limited to in-situ actions, need to be supplemented with ex-situ actions and strategies. In the worst case scenario, i.e. for species such as Serbian spruce which are unable to migrate and/or adapt to changing climate, the most suitable sites should be identified and colonized in order to prevent extinction in the near future

    Udarni presek za reakciju 9Be (6He, 4He) 11Be

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    The energy averaged cross section of the 9Be (6He, 4He) 11Be reaction is measured. The determined value 11 ± 4 mb compared with the theoretically calculated indicates that this reaction proceeds via a direct mechanism.lzmeren je srednji efikasni presek za energije O < E6_He < 10.6 MeV-a 9Be(6He, 4He) 11Be reakcije. Dobivena vrednost 11 ± 4 mb slaže se s teorijski izračunatim efikasnim presekom ove reakcije, što daje indikacije da se reakcija odigrava direktnim mehanizmom

    Campanula cichoracea (Campanulaceae), a neglected species from the Balkan-Carpathian C-lingulata complex as inferred from molecular and morphological characters

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    The taxonomically intricate Campanula lingulata complex confined to the Balkan Peninsula is reviewed using molecular and morphological data. An extensive sample of 62 individuals for phylogenetic analyses and 402 individuals for morphometric analysis from 17 populations across the species range was used. The phylogenetic analyses based on two chloroplast intergenic spacers (trnG(UCC)-trnS(GCU) and psbA-trnH) and morphological analysis based on 50 characters revealed two allopatrically distributed lineages of the C. lingulata complex that comprise individuals from the C and S Balkans, respectively. Both molecular and morphological data allowed us to re-establish C. cichoracea Sm., a species endemic to Thessaly in Greece. This species can easily be distinguished from C. lingulata s.str. by its calyx appendages hairy on the margins and adaxial side, and ovary continuously downwards hairy all over the surface. Molecular characters that can be used to distinguish these two species comprise four parsimony-informative substitutions within trnG(UCC)-trnS(GCU), and a microsatellite with a dinucleotide (AT) motif present only within the psbA-trnH region in C. lingulata. Further studies are required for resolving the taxonomic status of the remaining Macedonian and Rhodopean sub-lineages from the S Balkans
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