75 research outputs found
FPGA applications for single dish activity at Medicina radio telescopes
FPGA technologies are gaining major attention in the recent years in the field of radio astronomy. At Medicina radio telescopes, FPGAs have been used in the last ten years for a number of purposes and in this article we will take into exam the applications developed and installed for the Medicina Single Dish 32m Antenna: these range from high performance digital signal processing to instrument control developed on top of smaller FPGAs
On the evolution of the Gamma- and X-ray luminosities of Pulsar Wind Nebulae
Pulsar wind nebulae are a prominent class of very high energy (E > 0.1 TeV)
Galactic sources. Their Gamma-ray spectra are interpreted as due to inverse
Compton scattering of ultrarelativistic electrons on the ambient photons,
whereas the X-ray spectra are due to synchrotron emission. We investigate the
relation between the Gamma- and-X-ray emission and the pulsars' spin-down
luminosity and characteristic age. We find that the distance-independent Gamma-
to X-ray flux ratio of the nebulae is inversely proportional to the spin-down
luminosity, (\propto \dot{E}^-1.9), while it appears proportional to the
characteristic age, (\propto tau_c^2.2), of the parent pulsar. We interpret
these results as due to the evolution of the electron energy distribution and
the nebular dynamics, supporting the idea of so-called relic pulsar wind
nebulae. These empirical relations provide a new tool to classify unidentified
diffuse Gamma-ray sources and to estimate the spin-down luminosity and
characteristic age of rotation powered pulsars with no detected pulsation from
the X- and Gamma-ray properties of the associated pulsar wind nebulae. We apply
these relations to predict the spin-down luminosity and characteristic age of
four (so far unpulsing) candidate pulsars associated to wind nebulae.Comment: Accepted for publication in ApJ (6 pages, 2 figures
Efeitos do exercĂcio fĂsico na cognição de idosos: Uma revisĂŁo sistemática
O objetivo deste estudo foi analisar os efeitos de intervenções realizadas com exercĂcio fĂsico na cognição de idosos a partir da análise sistemática de artigos cientĂficos. Trata-se de uma revisĂŁo sistemática da literatura e as bases de dados utilizadas na busca foram o Portal de PeriĂłdicos da Capes, a Biblioteca Virtual em SaĂşde (BVS) e o Medline, seguindo as exigĂŞncias do modelo Prisma
de checklist e escala PEDro. A busca foi realizada mediante os descritores “physical exercise” OR “physical activity” AND “cognition” AND “elderly”. ApĂłs o refinamento, o escore total foi de nove artigos. Na análise dos estudos encontrados percebeu-se que os estudos publicados durante esse perĂodo apresentam diferentes formas de intervenção e de treinamento, quando se destaca a
prática de diferentes tipos de exercĂcios como forma de prevenção e manutenção das capacidades cognitivas na população idosa. Conclui-se que intervenções contendo a prática de exercĂcio fĂsico, independentemente do tempo de intervenção, possuem efeito positivo em fatores relacionados Ă cognição de idosos
DEMON: a Proposal for a Satellite-Borne Experiment to study Dark Matter and Dark Energy
We outline a novel satellite mission concept, DEMON, aimed at advancing our
comprehension of both dark matter and dark energy, taking full advantage of two
complementary methods: weak lensing and the statistics of galaxy clusters. We
intend to carry out a 5000 sqdeg combined IR, optical and X-ray survey with
galaxies up to a redshift of z~2 in order to determine the shear correlation
function. We will also find ~100000 galaxy clusters, making it the largest
survey of this type to date. The DEMON spacecraft will comprise one IR/optical
and eight X-ray telescopes, coupled to multiple cameras operating at different
frequency bands. To a great extent, the technology employed has already been
partially tested on ongoing missions, therefore ensuring improved reliability.Comment: 12 pages, 3 figures, accepted for publication in the SPIE conference
proceeding
Radio frequency over fiber technology for SKA-low receiver
The signal reception chain is an essential element for achieving the square kilometer array-low (SKA-low) system requirements in terms of high sensitivity and dynamic range. The balance between gain, linearity, and low power consumption, as well as the cost, are fundamental parameters that influence the selection of the most suitable technology for SKA-low. Further factors, such as low self-generated radio frequency (RF) interference, high reliability, robustness under extreme environment, and last but not least, the distance between the antennas and the acquisition systems, have impacts on the selection for both architecture and receiver system design. The selected technology for the SKA-low RF signal transportation is RF-over-fiber systems, where the preamplified RF signal picked up by the antennas is carried via analogue modulation over optical fiber. The rationales behind the selection are reported, along with descriptions on the development of the receiver prototypes. The prototypes were deployed and installed on the demonstrator arrays at the selected SKA-low site in Western Australian. Particular attention has been put on the thermal characterization of the receiver system under the actual operating temperature on site, especially when both transmitting part and the optical medium are subjected to external ambient temperature variations. Performance issues encountered in the demonstrator arrays are also discussed along with some proposals for future activities
Preliminary tests to design an ad hoc signal acquisition chain for the Sardinia Aperture Array Demonstrator
The Sardinia Aperture Array Demonstrator (SAD) is an Italian facility, which is composed of 128 prototypical Vivaldi antennas, specifically designed to operate across the 50-500 MHz frequency range. As well known, one of the major burden at low frequency are the radio frequency interferences, thus after several accurate measurement campaigns we realized that a specific signal conditioning is needed in order to feed the digital beamformer with the proper signal level. In this paper, we report the results of the preliminary tests that we carried out in order to design an ad hoc receiving chain for the SAD array
Procedura di montaggio del sistema di movimentazione e controllo del ramo N/S per il sistema BIRALES
Lo scopo di questo documento è quello di descrivere la procedura dell’installazione del nuovo sistema di movimentazione delle antenne cilindrico paraboliche del ramo Nord/Sud del radiotelescopio “Croce del Nord”, studiato per venire incontro alle esigenze del programma “Space Surveillance and Tracking”, oltre a programmi scientifici quale la ricerca degli FRB. Oltre alla procedura di installazione, è indicata la lista del materiale necessario alla replicazione e i disegni costruttivi, e viene inoltre descritta la procedura di manutenzione
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