169 research outputs found
Morphological differentiation of leaves in the relict tree Zelkova carpinifolia (Ulmaceae)
Zelkova carpinifolia is a relict tree occurring in refugial zones of south-western Eurasia. The main aim of the study was the biometrical comparison of the leaf characteristics of the species sampled in three regions of Transcaucasia. We aimed to test the hypotheses that (1) leaves from vegetative (L) shoots would be larger and more variable than those from fertile (S) shoots, (2) the leaves from the same shoot type express geographic patterns of morphological differentiation, similar to pattern described for genetic markers and (3) to verify the systematic position of Z. hyrcana and Z. carpinifolia subsp. yomraensis. The plant material was collected from 5 populations of Z. carpinifolia, one of Z. hyrcana and one of Z. carpinifolia subsp. yomraensis. The total 1482 leaves, 713 from L- and 769 S-type were measured using 26 characters. Our results show very high level of differences between leaves from the L- and S-type of shoots. The majority of leaf characters did not reveal dependence neither on geographic latitude, longitude and altitude nor on the basic climatic data. The results of multivariate analyses of S leaves revealed three group of populations, namely from (1) Colchis, (2) eastern Caucasus (3) Talysh. Thus, our biometric analyses revealed similar pattern to the haplotypic differentiation of Z. carpinifolia detected using chloroplast markers described in the literature. We did not detected significant differences in the leaf characters between supposed Z. hyrcana and/or Z. carpinifolia subsp. yomraensis, when compared to Z. carpinifolia, thus not confirming their separate taxonomic status
Morphological differentiation supports the genetic pattern of the geographic structure of Juniperus thurifera (Cupressaceae)
12 p., mapas, tablas, grĂĄf.Juniperus thurifera is an important component of woodland communities of dry sites within the West Mediterranean region and is characterised by a strongly disjunctive geographic range. Two subspecies were recognised, subsp. thurifera in Europe and subsp. africana in Africa. The aim of the study was the comparison of phenetic diversity to the pattern of AFLP geographic differentiation of the species described in the literature. The examination of phenetic diversity was based on the biometrical analysis of 17 populations using 12 morphological characters of cone and seed. The differences among populations were analysed using Studentâs t test, analysis of discrimination, UPGMA agglomeration and hierarchical analysis of variance. The majority of morphological characters differentiated at a statistically significant level between populations and between J. thurifera subsp. thurifera and subsp. africana. Three groups of populations were detected using multivariate statistical analyses. The first, well separated, is subsp. africana, while the following two concern subsp. thurifera. The morphological differentiation of populations appeared similar to that described on the AFLP. The Gibraltar Straight appeared to be the most important barrier.Funding the work was partly sponsored by the Institute of Dendrology of the Polish Academy of Sciences. The collection of material was made possible due to the bilateral cooperation of the Polish Academy of Sciences with the Spanish National Research Council "Consejo Superior de Investigaciones CientĂficas".Peer reviewe
Simulation studies of annihilation-photon's polarisation via Compton scattering with the J-PET tomograph
J-PET is the first positron-emission tomograph (PET) constructed from plastic
scintillators. It was optimized for the detection of photons from
electron-positron annihilation. Such photons, having an energy of 511 keV,
interact with electrons in plastic scintillators predominantly via the Compton
effect. Compton scattering is at most probable at an angle orthogonal to the
electric field vector of the interacting photon. Thus registration of multiple
photon scatterings with J-PET enables to determine the polarization of the
annihilation photons. In this contribution we present estimates on the physical
limitation in the accuracy of the polarization determination of ~keV
photons with the J-PET detector.Comment: Submitted to Hyperfine Interaction
Feasibility studies of the polarization of photons beyond the optical wavelength regime with the J-PET detector
J-PET is a detector optimized for registration of photons from the
electron-positron annihilation via plastic scintillators where photons interact
predominantly via Compton scattering. Registration of both primary and
scattered photons enables to determinate the linear polarization of the primary
photon on the event by event basis with a certain probability. Here we present
quantitative results on the feasibility of such polarization measurements of
photons from the decay of positronium with the J-PET and explore the physical
limitations for the resolution of the polarization determination of 511 keV
photons via Compton scattering. For scattering angles of about 82 deg (where
the best contrast for polarization measurement is theoretically predicted) we
find that the single event resolution for the determination of the polarization
is about 40 deg (predominantly due to properties of the Compton effect).
However, for samples larger than ten thousand events the J-PET is capable of
determining relative average polarization of these photons with the precision
of about few degrees. The obtained results open new perspectives for studies of
various physics phenomena such as quantum entanglement and tests of discrete
symmetries in decays of positronium and extend the energy range of polarization
measurements by five orders of magnitude beyond the optical wavelength regime.Comment: 10 pages, 14 figures, submitted to EPJ
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
Three-dimensional image reconstruction in J-PET using Filtered Back Projection method
We present a method and preliminary results of the image reconstruction in
the Jagiellonian PET tomograph. Using GATE (Geant4 Application for Tomographic
Emission), interactions of the 511 keV photons with a cylindrical detector were
generated. Pairs of such photons, flying back-to-back, originate from e+e-
annihilations inside a 1-mm spherical source. Spatial and temporal coordinates
of hits were smeared using experimental resolutions of the detector. We
incorporated the algorithm of the 3D Filtered Back Projection, implemented in
the STIR and TomoPy software packages, which differ in approximation methods.
Consistent results for the Point Spread Functions of ~5/7,mm and ~9/20, mm were
obtained, using STIR, for transverse and longitudinal directions, respectively,
with no time of flight information included.Comment: Presented at the 2nd Jagiellonian Symposium on Fundamental and
Applied Subatomic Physics, Krak\'ow, Poland, June 4-9, 2017. To be published
in Acta Phys. Pol.
Evaluation of Single-Chip, Real-Time Tomographic Data Processing on FPGA - SoC Devices
A novel approach to tomographic data processing has been developed and
evaluated using the Jagiellonian PET (J-PET) scanner as an example. We propose
a system in which there is no need for powerful, local to the scanner
processing facility, capable to reconstruct images on the fly. Instead we
introduce a Field Programmable Gate Array (FPGA) System-on-Chip (SoC) platform
connected directly to data streams coming from the scanner, which can perform
event building, filtering, coincidence search and Region-Of-Response (ROR)
reconstruction by the programmable logic and visualization by the integrated
processors. The platform significantly reduces data volume converting raw data
to a list-mode representation, while generating visualization on the fly.Comment: IEEE Transactions on Medical Imaging, 17 May 201
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