1,642 research outputs found

    Forest habitats on the territory of the National Park „Central Balkan" Bulgaria

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    Identifaction and characterization of forest habitats on the territory of the "Central Balkan" National Park in Bulgaria was carried out. The national park is one of the most valuable and largest protected areas in Europe – second category according to the International Union for Conservation of Nature (IUCN). Based on 786 phytosociological relevés, a total of 17 different habitat types, according to EUNIS were identified and mapped. The habitats were ecologically characterized by Ellenberg indicator values and their area was determined. A comparison was made with the areas determined in previous works. The applied method is suitable for the purposes of managing protected territories and zones, for monitoring the status and especially the conservation status of the habitats. The results and especially the established new habitats support this point of view

    Classificaton of the relict forest communites of Palla’s Black Pine (Pinus nigra subsp. pallasiana) in Bulgaria

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    New approach for the classifcation of the Black Pine forest communities in Bulgaria was made in the paper. Te analysis of forest pytocoenoses from Vlahina, East and West Rhodopi and Balkan Range Mountains confrmed their separation into two classes – Quercetea pubescentis (low-altitudinal) and Erico-Pinetea (high altitudinal). Te second class is represented from one polymorphic association Seslerio latifoliae-Pinetum nigrae whereas the other group is represented from two new associations. Te association Junipero deltoidi-Pineteum pallasianae is more related to the surrounding thermophilous oak forests as well as the association Lathyro laxiflori-Pinetum pallasianae is more similar to the hornbeam and beechforests

    Forest vegetation diversity of Slivenska Mountain (eastern Stara planina, Bulgaria)

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    This study deals with the diversity of forest vegetation in the Slivenska Mountain (Eastern Stara planina) and presents a contemporary classification scheme for the identified syntaxa. A total of 137 relevés were collected and analyzed using specialized software (JUICE 7.0 and PC-ORD Version 4). As a result, forest vegetation is classified into 10 associations, 3 subassociations, 4 variants and 5 communities They belong to 7 alliances, 5 orders and 3 classes: Carpino-Fagetea sylvaticae, Quercetea pubescentis and Alno glutinosae-Populetea albae. The recorded 18 distinguished vegetation groups show a relatively high diversity of forest plant communities of the study area

    Resolving spin currents and spin densities generated by charge-spin interconversion in systems with reduced crystal symmetry

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    The ability to control the generation of spins in arbitrary directions is a long-sought goal in spintronics. Charge to spin interconversion (CSI) phenomena depend strongly on symmetry. Systems with reduced crystal symmetry allow anisotropic CSI with unconventional components, where charge and spin currents and the spin polarization are not mutually perpendicular to each other. Here, we demonstrate experimentally that the CSI in graphene-WTe induces spins with components in all three spatial directions. By performing multi-terminal nonlocal spin precession experiments, with specific magnetic fields orientations, we discuss how to disentangle the CSI from the spin Hall and inverse spin galvanic effects.We acknowledge support of the European Union's Horizon 2020 FET-PROACTIVE project TOCHA under Grant No. 824140 and of the Spanish Research Agency (AEI), Ministry of Science and Innovation, under Contracts No. PID2019-111773RB-I00/AEI/10.13039/501100011033, and SEV-2017-0706 Severo Ochoa. J F S acknowledges support from AEIunder contract RYC2019-028368-I/AEI/10.13039/50110001103, W S T and M V C from the European Union Horizon 2020 research and innovation program, Grant No. 881603 (Graphene Flagship), and I F A of a fellowship from 'la Caixa' Foundation (ID 100010434) with code LCF/BQ/DI18/11660030 and of H2020 Marie Skłodowska-Curie Grant No. 713673. J S acknowledges funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 754558

    Development of Agricultural Market and Trade Policies in the CEE Candidate Countries.

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    This synthesis report focuses on the evolution of agricultural market and trade policies in the Central and Eastern European (CEE) candidate countries in the period 1997 to 2001. The developments were crucially influenced by (OECD, 2000a): ⢠the situation in world agricultural markets; ⢠the overall macroeconomic development in the countries considered; ⢠the prospective EU accession; ⢠bringing domestic agricultural policy in line with the Uruguay Agreement on Agriculture (URAA). High 1997 agricultural prices on world commodity markets were followed by a marked depression in 1998. With the exemption of milk products this trend continued in 1999. Likewise the economic and financial crisis in Russia had a considerable impact on agricultural policies. It hit the regions´ exports resulting in a decline in industrial as well as agricultural output1. Thus, compared to the previous years most of the CEE candidate countries experienced a slow down or even negative rates of growth in their Gross Domestic Product (GDP) in 1998 and 1999. In addition those countries felt increased budgetary pressures. Agricultural market and trade policies largely reacted to these developments. Border protection was increased in many countries in 1998. This was combined in some cases with export subsidies, and ad hoc producer aids to mitigate the adverse effects. The prospect of EU accession also had an influence on the agricultural policy design in the region with many countries implementing EU-type policy instruments. Thus, the importance of per hectare and per head payments increased in the region, quota like measures were implemented in some countries and as part of this development Estonia introduced tariffs for agro-food imports. Finally, many countries also continued to adjust their policies to comply with their commitments agreed to in the World Trade Organisation (WTO). Despite these general tendencies there are also differences in the development of agricultural policies between the various CEE candidates. Chapter 2 therefore provides an overview of the changes of agricultural market and trade policies in each of the 10 accession countries. It addresses the policy issues market access (e.g. tariffs, special safeguard measures), export subsidies (value and quantities) and domestic support (intervention policies, direct payments, input subsidies, production quotas). Chapter 3 provides a brief assessment of recent policy developments in the region in the light of EU accession and WTO commitments. The development of prices and values, e.g. export subsidies, agricultural support expenditure, were presented in the background papers provided by the country experts in current prices in national currencies. In this synthesis report they are in addition converted in Euro. This firstly allows for a better comparison among the CEE candidate countries as well as between those countries and the EU. Some of the accession countries still suffer from high inflation and thus a strong depreciation of their currency. Thus secondly, the conversion to Euros allows the comparisons to be made in real terms.Industrial Organization, International Development, Productivity Analysis,

    Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV

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    Many measurements and searches for physics beyond the standard model at the LHC rely on the efficient identification of heavy-flavour jets, i.e. jets originating from bottom or charm quarks. In this paper, the discriminating variables and the algorithms used for heavy-flavour jet identification during the first years of operation of the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, are presented. Heavy-flavour jet identification algorithms have been improved compared to those used previously at centre-of-mass energies of 7 and 8 TeV. For jets with transverse momenta in the range expected in simulated tt\mathrm{t}\overline{\mathrm{t}} events, these new developments result in an efficiency of 68% for the correct identification of a b jet for a probability of 1% of misidentifying a light-flavour jet. The improvement in relative efficiency at this misidentification probability is about 15%, compared to previous CMS algorithms. In addition, for the first time algorithms have been developed to identify jets containing two b hadrons in Lorentz-boosted event topologies, as well as to tag c jets. The large data sample recorded in 2016 at a centre-of-mass energy of 13 TeV has also allowed the development of new methods to measure the efficiency and misidentification probability of heavy-flavour jet identification algorithms. The heavy-flavour jet identification efficiency is measured with a precision of a few per cent at moderate jet transverse momenta (between 30 and 300 GeV) and about 5% at the highest jet transverse momenta (between 500 and 1000 GeV)

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

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    Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

    Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon

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    The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe

    Search for heavy resonances decaying to two Higgs bosons in final states containing four b quarks

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    A search is presented for narrow heavy resonances X decaying into pairs of Higgs bosons (H) in proton-proton collisions collected by the CMS experiment at the LHC at root s = 8 TeV. The data correspond to an integrated luminosity of 19.7 fb(-1). The search considers HH resonances with masses between 1 and 3 TeV, having final states of two b quark pairs. Each Higgs boson is produced with large momentum, and the hadronization products of the pair of b quarks can usually be reconstructed as single large jets. The background from multijet and t (t) over bar events is significantly reduced by applying requirements related to the flavor of the jet, its mass, and its substructure. The signal would be identified as a peak on top of the dijet invariant mass spectrum of the remaining background events. No evidence is observed for such a signal. Upper limits obtained at 95 confidence level for the product of the production cross section and branching fraction sigma(gg -> X) B(X -> HH -> b (b) over barb (b) over bar) range from 10 to 1.5 fb for the mass of X from 1.15 to 2.0 TeV, significantly extending previous searches. For a warped extra dimension theory with amass scale Lambda(R) = 1 TeV, the data exclude radion scalar masses between 1.15 and 1.55 TeV
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