Results 1 - 10 of 149
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[en] Gas target systems have been used for decades on cyclotrons to produce radionuclides for medical imaging. However, the activity recovered from such targets is often lower than its theoretically predicted value. Past research has suggested that nuclide interactions with the walls of the target body may play a key role in the loss of recoverable radionuclide activity. Here, we consider gas targets and modify the standard radionuclide production equation by adding a loss term representing radionuclides depositing on the walls of the target. We derive the form of the deposition term based on a simple adsorption model which is then linearized by solving for leading order terms. The resulting production equation uses one fitting parameter to give an estimate of the recoverable activity produced in a target system, taking adsorption into account. The model is then fit to six data series, taken in-house and reported in the literature and a parity plot compares model predictions to experimental data. The model is able to better track the data than any previous models, and points towards a phenomenological understanding of adsorption in target systems. (paper)
[en] We present a novel way to apply the singularity confinement property as a discrete integrability criterion. We shall use what we call a full deautonomization approach, which consists in treating the free parameters in the mapping as functions of the independent variable, applied to a mapping complemented with terms that are absent in the original mapping but which do not change the singularity structure. We shall show, on a host of examples including the well-known mapping of Hietarinta–Viallet, that our approach offers a way to compute the algebraic entropy for these mappings exactly, thereby allowing one to distinguish between the integrable and non-integrable cases even when both have confined singularities. (fast track communication)
[en] The formation of a common mycorrhizal network (CMN) between roots of different plant species enables nutrient transfers from one plant to another and their coexistence. However, almost all studies on nutrient transfers between CMN-connected plants have separately, but not simultaneously, been demonstrated under the same experimentation. Both conspecific and heterospecific seedlings of Cinnamomum camphora, Bidens pilosa, and Broussonetia papyrifera native to a karst habitat in southwest China were concurrently grown in a growth microcosm that had seven hollowed compartments (six around one in the center) being covered by 35.0-μm and/or 0.45-μm nylon mesh. The Ci. camphora in the central compartment was supplied with or without Glomus etunicatum and 15N to track N transfers between CMN-connected conspecific and heterospecific seedlings. The results showed as follows: significant greater nitrogen accumulations, biomass productions, 15N content, % Ntransfer, and the Ntransfer amount between receiver plant species ranked as Br. papyrifera≈Bi. pilosa > Ci. camphora under both M+ and M−, and as under M+ than under M− for Ci. camphora but not for both Bi. Pilosa and Br. papyrifera; the CMN transferred more nitrogen (15N content, % Ntransfer, and Ntransfer amount) from the donor Ci. camphora to the heterospecific Br. papyrifera and Bi. pilosa, with a lower percentage of nitrogen derived from transfer (%NDFT). These findings suggest that the CMN may potentially regulate the nitrogen transfer from a donor plant to individual heterospecific receiver plants, where the ratio of nitrogen derived from transfer depends on the biomass strength of the individual plants.
[en] A confocal scanner for selective observation of the vertical particle tracks in the nuclear photoemulsion is described. The particle track being searched for is imaging at an angle of 45° with respect to the optical axis of the system. The confocal scanner is provided with a new optical element, an “image orthogonalizator,” by means of which the extended image of the inclined vertical particle track is rotated through an angle of 90°. The stereoscopic version of the confocal scanner is presented as well. The described systems will be used in experiments for the investigation of neutrino oscillations in the accelerator.
[en] Conductive tracks represent a critically important class of component for high-performance transient electronics. However, the fabrication of transient conductors normally employs expensive and complex sputtering or evaporation process. Herein, we prepared novel silver nanowire (AgNW) and PEDOT:PSS transient tracks by sintering at 100 °C for only 10 min. It is demonstrated that the AgNW/PEDOT:PSS tracks are highly conductive with resistance of 8.5 μOhm·m and highly flexible. Impressively, the AgNW/PEDOT:PSS tracks fall off the glass substrates in only 170 s after being immersed in water due to the swelling of PEDOT:PSS. The rapid failure of the AgNW/PEDOT:PSS tracks makes it a potential candidate for conductors in transient electronics. (paper)
[en] The results of the creation of a transition radiation detector—a “B” tracker on the basis of thin-walled drift tubes (straw tubes) for the inner detector of the ATLAS Large Hadron Collider (LHC)—are presented. The results of preliminary detector testing are described. The basic components and procedures of assembly for 17 eight-layer TRT modules manufactured at JINR are described.
[en] This paper presents the methodology and results of the national radon survey in Bulgaria and its spatial variability. The measurements were carried out in 2778 dwellings using CR-39 track detectors over two successive 9 and 3-month periods from April 2015 to March 2016. The arithmetic (AM) and geometric (GM) means of annual indoor radon concentration were 111 ± 105 Bq/m3 and 81 Bq/m3 (GSD = 2.15), respectively. The distribution of data has been accepted to be log-normal. Two hypotheses have been investigated in the paper. The first one was a spatial variation of indoor radon concentration and the second was spatiality of the factor that influences radon variation. The indoor radon concentrations in the 28 districts have been significantly different, which prove the first hypothesis. The influence of the factors, geology (geotectonic unit, type of rock, and faults distance of the measuring site), type of the region, and the presence of the basement in the building on radon spatial variation, was examined. The analyses have been shown that they significantly affect radon variations but with a relatively small contribution in comparison to the radon variation between district. Furthermore, the significance and contribution of the investigated factors were different in each district, which confirmed the second hypothesis for their spatiality.
[en] Highlights: • The controversy between TD mechanism and shuffling mechanism is raised in explaining TB departing from K1 plane. • BP/PB interfaces can accommodate the deviations, thus twinning growth is still ascribed to TD. • Based on the track record of publishing on twinning, a few scientific problems and further works on twinning in HCP metals are propose. Besides coordinating plastic deformation, the frequently observed twins can cause the change of microstructure and texture of hexagonal close-packed (HCP) metals, influencing the mechanical properties. Thus, understanding twinning mechanism is essential. In this paper, we review the recent basic research on twinning growth process by experiments, modeling and theory. The structural characterization of twinning boundaries and exploring twinning growth mechanism are summarized in detail. Finally, for this research topic, a few critical scientific problems and further works on deformation twinning in HCP metals are proposed.
[en] The structural information of coronary arteries has important clinical value for quantitative diagnosis and treatment of coronary artery disease. In this study, a deep feature regression (DFR) method based on a convolutional regression network (CRN) and a stable point clustering mechanism for 3D vessel segmentation is proposed. First, the vessel model is constructed by a vessel section generator and a series of deviation parameter estimators. The generator provides 2D images for the training and prediction processes, while the estimators calculate pose parameters of an input vessel section. Second, estimators are trained by a series of CRNs, in which deep vessel features are automatically learned from 600 000 sample images. Third, we propose a stable point clustering mechanism that evaluates the reliability of the CRN estimation through iterative regression of vessel parameters. This mechanism eliminates the outliers, thereby increasing tracking robustness. Finally, we present a vessel segmentation algorithm using trained deviation parameter estimators. And, the termination criteria are designed based on both the number of stable points and an intensity constraint. The proposed method is evaluated on a public coronary artery data set. The average overlapping ratio and error are 97.5% and 0.27 mm, respectively. A quantitative test on a public cerebral artery data set demonstrates that the proposed DFR method tracks the vessel centerline with high accuracy, for which the average error is less than 0.33 mm. (paper)
[en] Energetic heavy ions during their passage through a material medium lose their energy via the processes of ionization and excitation of the target atoms resulting in the process of crosslinking and chain-scissoring, finally leading to the formation of latent tracks in polymers. The track recording property of polymers has led to their utility in many scientific and technological applications. In the present talk we have focused on certain important studies carried out in our group based on the recorded ion tracks in polymers. In the first study, we observed that the track recording properties of polymers provides an excellent way to measure average energy loss, range and straggling. In the second study, we noticed that the ion tracks recorded in the polymers provide the excellent way for the fabrication of membranes with controlled pore size and also as templates for the fabrication of nano/micro structure. In the third study, we have synthesized PVA-Ag nano-composites by in-situ chemical reduction method and preparation of their films by solution casting method. On irradiation, due to the formation of ion tracks the properties of such nano-composites can be tuned to the desired extent. All these studies and many other studies involving ion tracks have opened many new channels for the research activities in diverse fields