Abstract
IMPACT (Isotope and Muon Production with Advanced Cyclotron and Target Technologies) is a proposed initiative envisaged for the high-intensity proton accelerator facility (HIPA) at the Paul ...Scherrer Institute (PSI). As part of IMPACT, a radioisotope target station, TATTOOS (Targeted Alpha Tumour Therapy and Other Oncological Solutions) will allow the production of terbium radionuclides for therapeutic and diagnostic purposes. The proposed TATTOOS beamline and target will be located near the UCN (Ultra Cold Neutron source) target area, branching off from the main UCN beamline. In particular, the beamline is intended to operate at a beam intensity of 100 μA, requiring a continuous splitting of the main beam via an electrostatic splitter. Realistic beam loss simulations to verify safe operation have been performed and optimised using Beam Delivery Simulation (BDSIM), a Geant4 based tool enabling the simulation of beam transportation through magnets and particle passage through the accelerator. In this study, beam profiles, beam transmission and power deposits are generated and studied.
The High Intensity Proton Accelerator facility (HIPA) delivers a 590 MeV cw (50.6 MHz) proton beam with up to 1.4 MW beam power (2.4 mA) to spallation and meson production targets serving particle ...physics experiments and material research. The main accelerator is the ring cyclotron, an isochronous proton machine accelerating an injected 72 MeV beam to a final 590 MeV. A few meters downstream of the ring cyclotron, an electrostatic beam splitter was installed in the 1980s and originally designed to peel off from a 200 μA beam up to 20 μA (12 kW beam power). Future initiatives will also make use of the splitter. Specifically, as part of the Isotope and Muon Production using Advanced Cyclotron and Target technologies (IMPACT) upgrade project, Targeted Alpha Tumour Therapy and Other Oncological Solutions (TATTOOS), an online isotope separation facility will allow to produce promising radionuclides for diagnosis and therapy of cancer in quantities sufficient for clinical studies. The TATTOOS facility includes a dedicated beamline intended to operate at a beam intensity of 100 μA (60 kW beam power), requiring continuous splitting of the high-power main beam via the splitter. As a step forward toward reaching the desired beam intensity, a beam study was carried out to test the viability of the existing splitter for TATTOOS. The results of this study show that a record of 90 μA (53 kW beam power) was peeled off a horizontally and vertically enlarged beam by the splitter. The successful beam strategy employed during the study as well as the results of several key measurements are presented in this paper, with particular emphasis on diagnostic measurements. Additionally, to support the measurements, a computational model of the splitter has been implemented using Monte Carlo simulation tools, including realistic geometry, electrostatic fields, beam optics, and power deposition calculations. Overall, the results of this paper show that through the combination of beam measurements and simulations, the existing splitter can be used to reach the 100-μA beam intensity requirement for TATTOOS.
The brain can flexibly filter out sensory information in a manner that depends on behavioral state. In the visual thalamus and cortex, arousal and locomotion are associated with changes in the ...magnitude of responses to visual stimuli. Here, we asked whether such modulation of visual responses might already occur at an earlier stage in this visual pathway. We measured neural activity of retinal axons using wide-field and two-photon calcium imaging in awake mouse thalamus across arousal states associated with different pupil sizes. Surprisingly, visual responses to drifting gratings in retinal axonal boutons were robustly modulated by arousal level in a manner that varied across stimulus dimensions and across functionally distinct subsets of boutons. At low and intermediate spatial frequencies, the majority of boutons were suppressed by arousal. In contrast, at high spatial frequencies, boutons tuned to regions of visual space ahead of the mouse showed enhancement of responses. Arousal-related modulation also varied with a bouton’s preference for luminance changes and direction or axis of motion, with greater response suppression in boutons tuned to luminance decrements versus increments, and in boutons preferring motion along directions or axes of optic flow. Together, our results suggest that differential modulation of distinct visual information channels by arousal state occurs at very early stages of visual processing, before the information is transmitted to neurons in visual thalamus. Such early filtering may provide an efficient means of optimizing central visual processing and perception across behavioral contexts.
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•Visual responses of most retinothalamic axonal boutons are suppressed by arousal•Greater arousal-related suppression of information at lower spatial frequencies•Greater arousal-related suppression of boutons preferring luminance decrements•Greater arousal-related suppression of boutons preferring posterior/upward motion
Using calcium imaging of retinal axonal boutons, Liang et al. reveal differential modulation of distinct visual information channels by arousal state at very early stages of visual processing. Such early filtering may provide an efficient means of optimizing central visual processing and perception across behavioral contexts.
Eritrocitose primária em cão: relato de caso Gonçalves, S.; Reggiani, D.; Moreira, M.B.
Arquivo brasileiro de medicina veterinária e zootecnia,
10/2018, Letnik:
70, Številka:
5
Journal Article
Recenzirano
Odprti dostop
RESUMO A eritrocitose absoluta primária, também denominada de policitemia vera, é um distúrbio mieloproliferativo crônico de causa desconhecida, caracterizado pela proliferação clonal de ...células-tronco eritróides neoplásicas. Acomete cães de meia-idade entre seis e sete anos. As manifestações clínicas mais comuns são letargia, fraqueza, poliúria, polidipsia, sangramentos como epistaxe, hematúria, hematoemese, hematoquezia, até mesmo convulsões e ataxia. O diagnóstico é baseado em valores altos de hematócrito, geralmente acima de 70%, excluindo-se as causas de eritrocitose secundária. As concentrações séricas de eritropoietina estão normais ou diminuídas. O tratamento consiste em flebotomia e administração de hidroxiuréia. Relata-se o caso de uma cadela, raça Bichon Frise, 11 anos, que, no início do quadro, apresentou hematócrito de 84%, letargia, ataxia, mucosas congestas, cianose de língua, poliúria e polidipsia. Realizou-se o tratamento com hidroxiuréia durante oito anos, na dose de 15 a 30 mg/kg, a cada 24 horas, sem ocorrência de efeitos colaterais ou recidiva das manifestações clínicas.
Detectors of scientific instruments on spacecraft flying through Jupiter radiation belts need to be protected from high fluxes of penetrating radiation by means of radiation shields. Electrons ...constitute the most difficult component of Jupiter's magnetosphere to shield from, because of their abundance, penetration depth in matter, and intensity of bremsstrahlung radiation generated upon interaction with the shielding material. For the Neutral and Ion Mass spectrometer (NIM) of the Particle Environment Package (PEP) instrument suite on board the European Space Agency's mission JUpiter Icy moons Explorer (JUICE), we devised a shielding design made of an aluminum and tantalum stack to reduce the radiation-induced noise on its Micro-Channel Plate (MCP) detector. To predict the expected radiation background in the mass spectra in space, we manufactured a flight-like shielded detector and submitted it to radiation testing at the Paul Scherrer Institut with an electron beam in the energy range ~ 30 to ~ 345 MeV. The results of this test provide a verification of the NIM capability to fulfill its science requirements in the mission's worst-case scenario (the Europa flyby), and give insights into new directions of optimization of shielding elements' design for NIM and similar instrument bound to operate in a harsh radiation environment.
Neutral Ion Mass spectrometer (NIM) is one of the instruments in the Particle Environmental Package (PEP) designed for the JUICE mission of ESA to the Jupiter system. NIM, equipped with a sensitive ...MCP ion detector, will conduct detailed measurements of the chemical composition of Jovian icy moons exospheres. To achieve high sensitivity of the instrument, radiation effects due to the high radiation background (high-energy electrons and protons) around Jupiter have to be minimised. We investigate the performance of an Al–Ta–Al composite stack as a potential shielding against high-energy electrons. Experiments were performed at the PiM1 beam line of the High Intensity Proton Accelerator Facilities located at the Paul Scherrer Institute, Villigen, Switzerland. The facility delivers a particle beam containing e−, μ− and π− with momentum from 17.5 to 345MeV/c (Hajdas et al., 2014). The measurements of the radiation environment generated during the interaction of primary particles with the Al–Ta–Al material were conducted with dedicated beam diagnostic methods and with the NIM MCP detector. In parallel, modelling studies using GEANT4 and GRAS suites were performed to identify products of the interaction and predict ultimate fluxes and particle rates at the MCP detector. Combination of experiment and modelling studies yields detailed characterisation of the radiation fields produced by the interaction of the incident e− with the shielding material in the range of the beam momentum from 17.5 to 345MeV/c. We derived the effective MCP detection efficiency to primary and secondary radiation and effective shielding transmission coefficients to incident high-energy electron beam in the range of applied beam momenta. This study shows that the applied shielding attenuates efficiently high-energy electrons. Nevertheless, owing to nearly linear increase of the bremsstrahlung production rate with incident beam energy, above 130MeV their detection rates measured by the MCP detector compares to the MCP rate of the incident electron beam. We define key performance parameters for the shielding and show direction of its improvements by introducing additional layer of material to attenuate γ-rays and reduce the MCP sensitivity to the penetrating radiation. The experiments also verify the predictions by modelling tools used currently for optimisation of shielding against high-energy particles.
Retinal ganglion cell (RGC) types relay parallel streams of visual feature information. We hypothesized that neuromodulators might efficiently control which visual information streams reach the ...cortex by selectively gating transmission from specific RGC axons in the thalamus. Using fiber photometry recordings, we found that optogenetic stimulation of serotonergic axons in primary visual thalamus of awake mice suppressed ongoing and visually evoked calcium activity and glutamate release from RGC boutons. Two-photon calcium imaging revealed that serotonin axon stimulation suppressed RGC boutons that responded strongly to global changes in luminance more than those responding only to local visual stimuli, while the converse was true for suppression induced by increases in arousal. Converging evidence suggests that differential expression of the 5-HT1B receptor on RGC presynaptic terminals, but not differential density of nearby serotonin axons, may contribute to the selective serotonergic gating of specific visual information streams before they can activate thalamocortical neurons.
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•Serotonin suppresses retinal axon spike-evoked presynaptic Ca2+ and glutamate release•Suppression was stronger in retinal axons driven by full-field luminance change•Serotonin and arousal suppress different subsets of retinal axons in thalamus•Serotonergic suppression may scale with 5-HT1B expression in retinal axonal boutons
Reggiani et al. find that, in awake mouse primary thalamus, serotonin from brainstem inputs suppresses retinal axon bouton presynaptic calcium signals and glutamate release. Different retinal axon classes were more strongly suppressed by serotonin versus by pupil-linked arousal, indicating diverse gating of visual information streams before they activate thalamocortical neurons.
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