178 research outputs found
Recent Labour Market Trends in the Visegrad Group Countries
The large declines in the Slovak and Czech employment appeared because the countries' GDPs grew smaller while real wages grew bigger. Shorter working hours and limitations on labour productivity that the two countries introduced could not reverse the unfavourable employment trends that occurred during economic downturn.Duże spadki zatrudnienia w Słowacji i Czechach były związane ze słabym wzrostem PKB i silnym wzrostem płac realnych. Redukcje czasu pracy i wydajności pracy nie były w stanie odwrócić niekorzystnych tendencji w zatrudnieniu
Featured Snippets Results in Google Web Search: An Exploratory Study
In this paper authors analyzed 163412 keywords and results with featured
snippets collected from localized Polish Google search engine. A method-ology
for retrieving data from Google search engine was proposed in terms of
obtaining necessary data to study featured snippets. It was observed that
almost half of featured snippets (48%) is taken from result on first ranking
position. Furthermore, some correlations between prepositions and the most
often appearing content words in keywords was discovered. Results show that
featured snippets are often taken from trustworthy websites like e.g.,
Wikipedia and are mainly presented in form of a paragraph. Paragraph can be
read by Google Assistant or Home Assistant with voice search. We conclude our
findings with discussion and research limitations.Comment: 10 pages, 6 tables, accepted to conference ICMarktech'1
Beam profile investigation of the new collimator system for the J-PET detector
Jagiellonian Positron Emission Tomograph (J-PET) is a multi-purpose detector
which will be used for search for discrete symmetries violations in the decays
of positronium atoms and for investigations with positronium atoms in
life-sciences and medical diagnostics. In this article we present three methods
for determination of the beam profile of collimated annihilation gamma quanta.
Precise monitoring of this profile is essential for time and energy calibration
of the J-PET detector and for the determination of the library of model signals
used in the hit-time and hit-position reconstruction. We have we have shown
that usage of two lead bricks with dimensions of 5x10x20 cm^3 enables to form a
beam of annihilation quanta with Gaussian profile characterized by 1 mm FWHM.
Determination of this characteristic is essential for designing and
construction the collimator system for the 24-module J-PET prototype.
Simulations of the beam profile for different collimator dimensions were
performed. This allowed us to choose optimal collimation system in terms of the
beam profile parameters, dimensions and weight of the collimator taking into
account the design of the 24 module J-PET detector.Comment: 14 pages, 9 figure
Topological effects in the thermal properties of knotted polymer rings
The topological effects on the thermal properties of several knot
configurations are investigated using Monte Carlo simulations. In order to
check if the topology of the knots is preserved during the thermal fluctuations
we propose a method that allows very fast calculations and can be easily
applied to arbitrarily complex knots. As an application, the specific energy
and heat capacity of the trefoil, the figure-eight and the knots are
calculated at different temperatures and for different lengths. Short-range
repulsive interactions between the monomers are assumed. The knots
configurations are generated on a three-dimensional cubic lattice and sampled
by means of the Wang-Landau algorithm and of the pivot method. The obtained
results show that the topological effects play a key role for short-length
polymers. Three temperature regimes of the growth rate of the internal energy
of the system are distinguished.Comment: 7 pages, 12 figures, LaTeX + RevTeX. With respect to the first
version, in the second version the text has been improved and all figures are
now in black and whit
Analysis framework for the J-PET scanner
J-PET analysis framework is a flexible, lightweight, ROOT-based software
package which provides the tools to develop reconstruction and calibration
procedures for PET tomography. In this article we present the implementation of
the full data-processing chain in the J-PET framework which is used for the
data analysis of the J-PET tomography scanner. The Framework incorporates
automated handling of PET setup parameters' database as well as high level
tools for building data reconstruction procedures. Each of these components is
briefly discussed.Comment: 6 pages, 1 figur
Processing optimization with parallel computing for the J-PET tomography scanner
The Jagiellonian-PET (J-PET) collaboration is developing a prototype TOF-PET
detector based on long polymer scintillators. This novel approach exploits the
excellent time properties of the plastic scintillators, which permit very
precise time measurements. The very fast, FPGA-based front-end electronics and
the data acquisition system, as well as, low- and high-level reconstruction
algorithms were specially developed to be used with the J-PET scanner. The
TOF-PET data processing and reconstruction are time and resource demanding
operations, especially in case of a large acceptance detector, which works in
triggerless data acquisition mode. In this article, we discuss the parallel
computing methods applied to optimize the data processing for the J-PET
detector. We begin with general concepts of parallel computing and then we
discuss several applications of those techniques in the J-PET data processing.Comment: 8 page
Searches for discrete symmetries violation in ortho-positronium decay using the J-PET detector
In this paper we present prospects for using the J-PET detector to search for
discrete symmetries violations in a purely leptonic system of the positronium
atom. We discuss tests of CP and CPT symmetries by means of ortho-positronium
decays into three photons. No zero expectation values for chosen correlations
between ortho-positronium spin and momentum vectors of photons would imply the
existence of physics phenomena beyond the Standard Model. Previous measurements
resulted in violation amplitude parameters for CP and CPT symmetries consistent
with zero, with an uncertainty of about 10-3. The J-PET detector allows to
determine those values with better precision thanks to a unique time and
angular esolution combined with a high geometrical acceptance. Achieving the
aforementioned is possible due to application of polymer scintillators instead
of crystals as detectors of annihilation quanta.Comment: in Nukleonika 201
Studies of unicellular micro-organisms Saccharomyces cerevisiae by means of Positron Annihilation Lifetime Spectroscopy
Results of Positron Annihilation Lifetime Spectroscopy (PALS) and microscopic
studies on simple microorganisms: brewing yeasts are presented. Lifetime of
ortho - positronium (o-Ps) were found to change from 2.4 to 2.9 ns (longer
lived component) for lyophilised and aqueous yeasts, respectively. Also
hygroscopicity of yeasts in time was examined, allowing to check how water -
the main component of the cell - affects PALS parameters, thus lifetime of o-Ps
were found to change from 1.2 to 1.4 ns (shorter lived component) for the dried
yeasts. The time sufficient to hydrate the cells was found below 10 hours. In
the presence of liquid water an indication of reorganization of yeast in the
molecular scale was observed.
Microscopic images of the lyophilised, dried and wet yeasts with best
possible resolution were obtained using Inverted Microscopy (IM) and
Environmental Scanning Electron Microscopy (ESEM) methods. As a result visible
changes to the surface of the cell membrane were observed in ESEM images.Comment: Nukleonika (2015
Trilateration-based reconstruction of ortho-positronium decays into three photons with the J-PET detector
This work reports on a new reconstruction algorithm allowing to reconstruct
the decays of ortho-positronium atoms into three photons using the places and
times of photons recorded in the detector. The method is based on trilateration
and allows for a simultaneous reconstruction of both location and time of the
decay. Results of resolution tests of the new reconstruction in the J-PET
detector based on Monte Carlo simulations are presented, which yield a spatial
resolution at the level of 2 cm (FWHM) for X and Y and at the level of 1 cm
(FWHM) for Z available with the present resolution of J-PET after application
of a kinematic fit. Prospects of employment of this method for studying angular
correlations of photons in decays of polarized ortho-positronia for the needs
of tests of CP and CPT discrete symmetries are also discussed. The new
reconstruction method allows for discrimination of background from random
three-photon coincidences as well as for application of a novel method for
determination of the linear polarization of ortho-positronium atoms, which is
also introduced in this work.Comment: 18 pages, 5 figures. Accepted for publication in Nuclear
Instrumentation and Methods in Physics Research
Calculation of time resolution of the J-PET tomograph using the Kernel Density Estimation
In this paper we estimate the time resolution of the J-PET scanner built from
plastic scintillators. We incorporate the method of signal processing using the
Tikhonov regularization framework and the Kernel Density Estimation method. We
obtain simple, closed-form analytical formulas for time resolutions. The
proposed method is validated using signals registered by means of the single
detection unit of the J-PET tomograph built out from 30 cm long plastic
scintillator strip. It is shown that the experimental and theoretical results,
obtained for the J-PET scanner equipped with vacuum tube photomultipliers, are
consistent.Comment: 25 pages, 11 figure
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