242 research outputs found
Az erdĂ©szeti genetikai erĆforrĂĄsok ĂĄllapota Ă©s szerepe a XXI. szĂĄzad elejĂ©n MagyarorszĂĄgon
Multidimensional analysis of Fermi GBM gamma-ray bursts
The Fermi GBM catalog provides a large database with many measured variables
that can be used to explore and verify gamma-ray burst classification results.
We have used Principal Component Analysis and statistical clustering techniques
to look for clustering in a sample of 801 gamma-ray bursts described by sixteen
classification variables. The analysis recovers what appears to be the Short
class and two long-duration classes that differ from one another via peak flux,
with negligible variations in fluence, duration and spectral hardness. Neither
class has properties entirely consistent with the Intermediate GRB class.
Spectral hardness has been a critical Intermediate class property. Rather than
providing spectral hardness, Fermi GBM provides a range of fitting variables
for four different spectral models; it is not intuitive how these variables can
be used to support or disprove previous GRB classification results.Comment: accepte
Effect of Linalool and Piperine on Chicken Meat Quality During Refrigerated Conditions
This study was conducted to evaluate the effect of bioactive compounds (BACs): linalool (LIN) and piperine (PIP) on chicken meat characteristics. The meat was treated with 500, 1000 ppm of BACs, vacuum packaged and stored at 4 °C for 8 days. Physicochemical characteristics, lipid oxidation (thiobarbituric acid reactive substances, TBARS), microbiological status, and sensorial (electronic-nose based) properties were investigated. Both BACs significantly increased the redness (a*) and chroma (C*) values in meat compared to increased lightness (L*) and higher TBARS in control. Although both BACs showed overlapping aroma profile, the E-nose was able to distinguish between the different meat groups. LIN with various dilution ratios, particularly 1:10 (v:v), showed in vitro growth inhibition against Escherichia coli, Staphylococcus aureus, Salmonella Typhimurium, and Bacillus cereus, concomitantly Listeria monocytogenes required 1:80 (v:v) to be inhibited, and no inhibition was detected for Pseudomonas lundensis. In contrast, PIP at different dilutions did not exhibit inhibitory activity. Regarding aerobic mesophilic counts (AMC), less than 7 log CFU gâ1 were recorded except for control showing higher log. Both BACs have potential to improve quality characteristics and increase the shelf life of meat and meat products
Development and calibration of a currency trading strategy using global optimization
We have developed a new financial indicatorâcalled the Interest Rate Differentials Adjusted for Volatility (IRDAV) measureâto assist investors in currency markets. On a monthly basis, we rank currency pairs according to this measure and then select a basket of pairs with the highest IRDAV values. Under positive market conditions, an IRDAV based investment strategy (buying a currency with high interest rate and simultaneously selling a currency with low interest rate, after adjusting for volatility of the currency pairs in question) can generate significant returns. However, when the markets turn for the worse and crisis situations evolve, investors exit such money-making strategies suddenly, andâas a resultâsignificant losses can occur. In an effort to minimize these potential losses, we also propose an aggregated Risk Metric that estimates the total risk by looking at various financial indicators across different markets. These risk indicators are used to get timely signals of evolving crises and to flip the strategy from long to short in a timely fashion, to prevent losses and make further gains even during crisis periods. Since our proprietary model is implemented in Excel as a highly nonlinear âblack boxâ computational procedure, we use suitable global optimization methodology and softwareâthe Lipschitz Global Optimizer solver suite linked to Excelâto maximize the performance of the currency basket, based on our selection of key decision variables. After the introduction of the new currency trading model and its implementation, we present numerical results based on actual market data. Our results clearly show the advantages of using global optimization based parameter settings, compared to the typically used âexpert estimatesâ of the key model parameters.post-prin
Classifying GRB 170817A/GW170817 in a Fermi durationâhardness plane
GRB 170817A, associated with the LIGO-Virgo GW170817 neutron-star merger event, lacks the short duration and hard spectrum of a Short gamma-ray burst (GRB) expected from long-standing classification models. Correctly identifying the class to which this burst belongs requires comparison with other GRBs detected by the Fermi GBM. The aim of our analysis is to classify Fermi GRBs and to test whether or not GRB 170817A belongsâas suggestedâto the Short GRB class. The Fermi GBM catalog provides a large database with many measured variables that can be used to explore gamma-ray burst classification. We use statistical techniques to look for clustering in a sample of 1298 gamma-ray bursts described by duration and spectral hardness. Classification of the detected bursts shows that GRB 170817A most likely belongs to the Intermediate, rather than the Short GRB class. We discuss this result in light of theoretical neutron-star merger models and existing GRB classification schemes. It appears that GRB classification schemes may not yet be linked to appropriate theoretical models, and that theoretical models may not yet adequately account for known GRB class properties. We conclude that GRB 170817A may not fit into a simple phenomenological classification scheme. © 2018, Springer Science+Business Media B.V., part of Springer Nature
Constraints on the thickness and seismic properties of the lithosphere in an extensional setting (Nógråd-Gömör Volcanic Field, Northern Pannonian Basin)
TheNógråd-GömörVolcanic Field (NGVF) is one of the five mantle xenolith bearing
alkaline basalt locations in the Carpathian Pannonian Region. This allows us to constrain
the structure and properties (e.g. composition, current deformation state, seismic anisotropy,
electrical conductivity) of the upper mantle, including the lithosphere-asthenosphere boundary
(LAB) using not only geophysical, but also petrologic and geochemical methods. For
this pilot study, eight upper mantle xenoliths have been chosen from BĂĄrna-NagykËo, the
southernmost location of the NGVF. The aim of this study is estimating the average seismic
properties of the underlying mantle. Based on these estimations, the thickness of the
anisotropic layer causing the observed average SKS delay time in the area was modelled
considering five lineation and foliation end-member orientations. We conclude that a 142â
333km thick layer is required to explain the observed SKS anisotropy, assuming seismic
properties calculated by averaging the properties of the eight xenoliths. It is larger than the
thickness of the lithospheric mantle. Therefore, the majority of the delay time accumulates
in the sublithospheric mantle. However, it is still in question whether a single anisotropic
layer, represented by the studied xenoliths, is responsible for the observed SKS anisotropy,as it is assumed beneath the BakonyâBalaton Highland Volcanic Field (KovĂĄcs et al. 2012),
or the sublithospheric mantle has different layers. In addition, the depths of the Moho and
the LAB (25 ± 5, 65 ± 10 km, respectively) were estimated based on S receiver function
analyses of data from three nearby permanent seismological stations
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