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Wyświetlanie 1-10 z 193
Tytuł:
Poprawa jakości obrazu rentgenowskiego w oparciu o grubość ludzkiego ciała i rozpoznawanie struktury
Improving X-ray image quality based on human-body thickness and structure recognition
Autorzy:
Takahashi, T.
Yamada, M.
Ohara, Y.
Tematy:
Dynamic Visualization II
przetwarzanie obrazu
sztuczna inteligencja
image processing
artificial intelligence
Pokaż więcej
Wydawca:
Indygo Zahir Media
Powiązania:
https://bibliotekanauki.pl/articles/112281.pdf  Link otwiera się w nowym oknie
Opis:
Kompatybilność „wyższego kontrastu” oraz „pełnej wizualizacji struktury anatomicznej” jest trudna do osiągnięcia w konwencjonalnym przetwarzaniu. Dynamic Visualization II (DV II) jest nową metodą przetwarzania obrazu i pozwala na rozwiązanie tego problemu. Metoda ta oparta jest na nowej technologii, która szacuje grubość i strukturę na podstawie informacji z obrazu RTG, gdzie promienie X penetrują ciało pacjenta. Przedstawiona w tym artykule technika przetwarzania może poprawić wizualizację całej części ciała i może zminimalizować potrzebę dodatkowej korekty gęstości i kontrastu obrazu RTG.
The compatibility of “higher contrast” and “whole anatomic structure visualization” is difficult to achieve in conventional processing. Dynamic Visualization II, which is a new image-processing method, solves this problem. This processing method is based on a new technology that estimates a patient’s thickness and structure from X-ray image information, which penetrates through the patient’s body. This processing method can improve the visualization of an entire body part and can minimize the need for additional adjustments in the X-ray image’s density and contrast.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Time-dependent modeling of gamma-ray flares in blazar PKS1510–089
Autorzy:
Stawarz, Łukasz
Saito, S.
Moderski, R.
Takahashi, T.
Sikora, M.
Tanaka, Y. T.
Opis:
Here we present a new approach for constraining luminous blazars, incorporating fully time-dependent and selfconsistent modeling of bright $\gamma$-ray flares of PKS 1510–089, resolved with Fermi-LAT, in the framework of the internal shock scenario. The results of our modeling imply the location of the $\gamma$-ray flaring zone to be outside of the broad-line region, namely around \simeq 3 pc from the core for a free-expanding jet with the opening angle $\Gamma\Theta_{jet}\simeq 1$ (where $\Gamma$ is the jet bulk Lorentz factor), up to $\simeq 3$ pc for a collimated outflow with \Gamma\Theta_{jet}\simeq 0.1. Moreover, under the $\Gamma\Theta_{jet}\simeq 1$ condition, our modeling indicates the maximum efficiency of the jet production during the flares, with the total jet energy flux strongly dominated by protons and exceeding the available accretion power in the source. This is in contrast to the quiescence states of the blazar, characterized by lower jet kinetic power and an approximate energy equipartition between different plasma constituents. We demostrate how strictly simultaneous observations of flaring PKS 1510–089 at optical, X-ray, and GeV photon energies, on hourly timescales, augmented by extensive simulations as presented in this paper, may help to impose further precise constraints on the magnetization and opening angle of the emitting region. In addition, our detailed modeling implies that a nonuniformity of the Doppler factor across the jet, caused by the radial expansion of the outflow, may lead to a pronounced time distortion in the observed $\gamma$-ray light curves, resulting, in particular, in asymmetric flux profiles with substantially extended decay phases.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Very rapid high-amplitude gamma-ray variability in luminous blazar PKS 1510–089 studied with Fermi-LAT
Autorzy:
D’Ammando, F.
Stawarz, Łukasz
Saito, S.
Madejski, G.
Takahashi, T.
Tanaka, Y. T.
Opis:
Here we report on the detailed analysis of the $\gamma$-ray light curve of a luminous blazar PKS 1510−089 observed in the GeV range with the Large Area Telescope (LAT) on board the Fermi satellite during the period 2011 September–December. By investigating the properties of the detected three major flares with the shortest possible time binning allowed by the photon statistics, we find a variety of temporal characteristics and variability patterns. This includes a clearly asymmetric profile (with a faster flux rise and a slower decay) of the flare resolved on sub-daily timescales, a superposition of many short uncorrelated flaring events forming the apparently coherent longer-duration outburst, and a huge single isolated outburst unresolved down to the timescale of 3 hr. In the latter case we estimate the corresponding $\gamma$-ray flux doubling timescale to be below 1 hr, which is extreme and never previously reported for any active galaxy in the GeV range. The other unique finding is that the total power released during the studied rapid and high-amplitude flares constitutes the bulk of the power radiatively dissipated in the source and a significant fraction of the total kinetic luminosity of the underlying relativistic outflow. Our analysis allows us to access directly the characteristic timescales involved in shaping the energy dissipation processes in the source, and to provide constraints on the location and the structure of the blazar emission zone in PKS 1510−089.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Evaluation of portable blood glucose meters using canine and feline pooled blood samples
Autorzy:
Mori, A.
Oda, H.
Onozawa, E.
Shono, S.
Takahashi, T.
Yamashita, S.
Fujimoto, H.
Sako, T.
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/30884.pdf  Link otwiera się w nowym oknie
Opis:
This study evaluated the accuracy and reproducibility of a human portable blood glucose meter (PBGM) for canine and feline whole blood. Reference plasma glucose values (RPGV) were concurrently measured using glucose oxidation methods. Fifteen healthy dogs and 6 healthy cats were used for blood sampling. Blood glucose concentrations and hematocrits were adjusted using pooled blood samples for our targeted values. A positive correlation between the PBGM and RPGV was found for both dogs (y = 0.877, x = −24.38, r = 0.9982, n = 73) and cats (y = 1.048, x = −27.06, r = 0.9984, n = 69). Acceptable results were obtained in error grid analysis between PBGM and RPGV in both dogs and cats; 100% of these results were within zones A and B. Following ISO recommendations, a PBGM is considered accurate if 95% of the measurements are within ± 15 mg/dl of the RPGV when the glucose concentration is <100 mg/dl and within ±15% when it is ≥100 mg/dl; however, small numbers of samples were observed inside the acceptable limits for both dogs (11%, 8 of 73 dogs) and cats (39%, 27 of 69 cats). Blood samples with high hematocrits induced lower whole blood glucose values measured by the PBGM than RPGV under hypoglycemic, normoglycemic, and hyperglycemic conditions in both dogs and cats. Therefore, this device is not clinically useful in dogs and cats. New PBGMs which automatically compensate for the hematocrit should be developed in veterinary practice.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the merging cluster Abell 578 and its central radio galaxy 4C+67.13
Autorzy:
Cheung, C. C.
Szostek, Anna
Madejski, G.
Siemiginowska, A.
Kozieł-Wierzbowska, Dorota
Simionescu, A.
Hagino, K.
Takahashi, T.
Stawarz, Łukasz
Harris, D. E.
Opis:
Here we analyze radio, optical, and X-ray data for the peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy (BCG), CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation $\sim$10 kpc, the brighter of which hosts the radio source 4C+67.13. The Fanaroff–Riley type-II radio morphology of 4C+67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to the Eddington ratio $\sim 10^{-4}$ (for the estimated black hole masses of $\sim 3 \times 10^{8} M_{\bigodot }$ and $\sim 10^{9} M_{\bigodot }$. The gathered X-ray (Chandra) data allowed us to confirm and to quantify robustly the previously noted elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a large spatial offset ($\sim$ 60 kpc projected) between the position of the BCG and the cluster center inferred from the modeling of the X-ray surface brightness distribution. Detailed analysis of the brightness profiles and temperature revealed also that the cluster gas in the vicinity of 4C+67.13 is compressed (by a factor of about $\sim$ 1.4) and heated (from $\simeq$ 2.0 keV up to 2.7 keV), consistent with the presence of a weak shock (Mach number $\sim$ 1.3) driven by the expanding jet cocoon. This would then require the jet kinetic power of the order of $\sim 10 ^{45}erg s^{-1}$, implying either a very high efficiency of the jet production for the current accretion rate, or a highly modulated jet/accretion activity in the system.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Fermi-LAT and Suzaku observations of the radio galaxy Centaurus B
Autorzy:
Cheung, C. C.
Funk, S.
Kataoka, J.
Takahashi, T.
Svoboda, J.
Odaka, H.
Stawarz, Łukasz
Tanaka, Y. T.
Yuasa, T.
Katsuta, J.
O’Sullivan, S. P.
Opis:
Centaurus B is a nearby radio galaxy positioned in the southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months of accumulated Fermi-LAT data of the $\gamma$-ray counterpart of the source initially reported in the 2nd Fermi-LAT catalog, and of newly acquired Suzaku X-ray data. We confirm its detection at GeV photon energies and analyze the extension and variability of the $\gamma$-ray source in the LAT dataset, in which it appears as a steady $\gamma$-ray emitter. The X-ray core of Centaurus B is detected as a bright source of a continuum radiation. We do not detect, however, any diffuse X-ray emission from the known radio lobes, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. Two scenarios that connect the X-ray and $\gamma$-ray properties are considered. In the first one, we assume that the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. In this case, modeling the inverse-Compton emission shows that the observed $\gamma$-ray flux of the source may in principle be produced within the lobes. This association would imply that efficient in-situ acceleration of the radiating electrons is occurring and that the lobes are dominated by the pressure from the relativistic particles. In the second scenario, with the diffuse X-ray emission well below the Suzaku upper limits, the lobes in the system are instead dominated by the magnetic pressure. In this case, the observed $\gamma$-ray flux is not likely to be produced within the lobes, but instead within the nuclear parts of the jet. By means of synchrotron self-Compton modeling, we show that this possibility could be consistent with the broad-band data collected for the unresolved core of Centaurus B, including the newly derived Suzaku spectrum.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Giant lobes of Centaurus a radio galaxy observed with the Suzaku X-ray satellite
Autorzy:
Cheung, C. C.
Madejski, G.
Reville, B.
Feain, I. J.
Siemiginowska, A.
Simionescu, A.
Kataoka, J.
Hardcastle, M. J.
Ostrowski, Michał
Takahashi, T.
Takeuchi, Y.
Werner, N.
Tanaka, Y. T.
Stawarz, Łukasz
Fukazawa, Y.
Gandhi, P.
Takei, Y.
O’Sullivan, S. P.
Opis:
We report on Suzaku observations of selected regions within the southern giant lobe of the radio galaxy Centaurus A. In our analysis we focus on distinct X-ray features detected with the X-ray Imaging Spectrometer within the range 0.5-10 keV, some of which are likely associated with fine structure of the lobe revealed by recent high-quality radio intensity and polarization maps. With the available photon statistics, we find that the spectral properties of the detected X-ray features are equally consistent with thermal emission from hot gas with temperatures kT > 1 keV, or with a power-law radiation continuum characterized by photon indices $\Gamma \sim 2.0 \pm 0.5$. However, the plasma parameters implied by these different models favor a synchrotron origin for the analyzed X-ray spots, indicating that a very efficient acceleration of electrons up to $_{\sim }^{>} 10$ TeV energies is taking place within the giant structure of Centaurus A, albeit only in isolated and compact regions associated with extended and highly polarized radio filaments. We also present a detailed analysis of the diffuse X-ray emission filling the whole field of view of the instrument, resulting in a tentative detection of a soft excess component best fitted by a thermal model with a temperature of $\mathit{kT} \sim 0.5$ keV. The exact origin of the observed excess remains uncertain, although energetic considerations point to thermal gas filling the bulk of the volume of the lobe and mixed with the non-thermal plasma, rather than to the alternative scenario involving a condensation of the hot intergalactic medium around the edges of the expanding radio structure. If correct, this would be the first detection of the thermal content of the extended lobes of a radio galaxy in X-rays. The corresponding number density of the thermal gas in such a case is ng $\mathit{n_{g}} \sim 10^{-4} \mathrm{cm}^{-3}$, while its pressure appears to be in almost exact equipartition with the volume-averaged non-thermal pressure provided by the radio-emitting electrons and the lobes' magnetic field. A prominent large-scale fluctuation of the Galactic foreground emission, resulting in excess foreground X-ray emission aligned with the lobe, cannot be ruled out. Although tentative, our findings potentially imply that the structure of the extended lobes in active galaxies is likely to be highly inhomogeneous and non-uniform, with magnetic reconnection and turbulent acceleration processes continuously converting magnetic energy to internal energy of the plasma particles, leading to possibly significant spatial and temporal variations in the plasma \beta parameter around the volume-averaged equilibrium condition \beta.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Wyświetlanie 1-10 z 193

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