44 research outputs found
The peak-flux of GRB 221009A measured with GRBAlpha
The brightest gamma-ray burst ever observed, long-duration GRB 221009A, was
detected by GRBAlpha nano-satellite without saturation. We present light curves
of the prompt emission in 13 energy bands, from 80 keV to 950 keV, and perform
a spectral analysis to calculate the peak flux and peak isotropic-equivalent
luminosity. Since the satellite's attitude information is not available for the
time of this GRB, more than 200 incident directions were probed in order to
find the median luminosity and its systematic uncertainty. We found that the
peak flux in the keV range (observer frame) was
ph cms or
erg cms
and the fluence in the same energy range of the first GRB episode lasting 300
s, which was observable by GRBAlpha, was erg
cm or erg cm for
the extrapolated range of keV. We infer the isotropic-equivalent
released energy of the first GRB episode to be
erg in the
keV band (rest frame at ). The peak isotropic-equivalent luminosity in
the keV range (rest frame) was
erg s and the
bolometric peak isotropic-equivalent luminosity was
erg s (4 s
scale) in the keV range (rest frame). The peak emitted energy is
keV. Our measurement of
is consistent with the Yonetoku relation. It is
possible that, due to the spectral evolution of this GRB and orientation of
GRBAlpha at the peak time, the true values of peak flux, fluence,
, and are even higher. [abridged]Comment: 7 pages, 7 figures, 1 table, accepted for publication in Astronomy &
Astrophysic
GRBAlpha: the smallest astrophysical space observatory -- Part 1: Detector design, system description and satellite operations
Aims. Since launched on 2021 March 22, the 1U-sized CubeSat GRBAlpha operates
and collects scientific data on high-energy transients, making it the smallest
astrophysical space observatory to date. GRBAlpha is an in-obit demonstration
of a gamma-ray burst (GRB) detector concept suitably small to fit into a
standard 1U volume. As it was demonstrated in a companion paper, GRBAlpha adds
significant value to the scientific community with accurate characterization of
bright GRBs, including the recent outstanding event of GRB 221009A. Methods.
The GRB detector is a 75x75x5 mm CsI(Tl) scintillator wrapped in a reflective
foil (ESR) read out by an array of SiPM detectors, multi-pixel photon counters
by Hamamatsu, driven by two separate, redundant units. To further protect the
scintillator block from sunlight and protect the SiPM detectors from particle
radiation, we apply a multi-layer structure of Tedlar wrapping, anodized
aluminium casing and a lead-alloy shielding on one edge of the assembly. The
setup allows observations of gamma radiation within the energy range of 70-890
keV with an energy resolution of ~30%. Results. Here, we summarize the system
design of the GRBAlpha mission, including the electronics and software
components of the detector, some aspects of the platform as well as the current
way of semi-autonomous operations. In addition, details are given about the raw
data products and telemetry in order to encourage the community for expansion
of the receiver network for our initiatives with GRBAlpha and related
experiments.Comment: Accepted for publication in Astronomy & Astrophysics, 9 pages, 10
figure
A Method to Assign Spread Codes Based on Passive RFID Communication for Energy Harvesting Wireless Sensors Using Spread Spectrum Transmission
Considerable research has been conducted on systems that collect real-world information by using numerous energy harvesting wireless sensors. The sensors need to be tiny, cheap, and consume ultra-low energy. However, such sensors have some functional limits, including being restricted to wireless communication transmission. Therefore, when more than one sensor simultaneously transmits information in these systems, the receiver may not be able to demodulate if the sensors cannot accommodate multiple access. To solve this problem, a number of proposals have been made based on spread spectrum technologies for resistance to interference. In this paper, we point out some problems regarding the application of such sensors, and explain the assumption of spread codes assignment based on passive radio frequency identification (RFID) communication. During the spread codes assignment, the system cannot work. Hence, efficient assignment method is more appropriate. We consider two assignment methods and assessed them in terms of total assignment time through an experiment. The results show the total assignment time in case of Electronic Product Code (EPC) Global Class-1 Generation-2 which is an international standard for wireless protocols and the relationship between the ratio of the time taken by the read/write command and the ratio of total assignment time by the two methods. This implies that more efficient methods are obtained by considering the time ratio of read/write command
Auditory cortical areas activated by slow frequency-modulated sounds in mice.
Species-specific vocalizations in mice have frequency-modulated (FM) components slower than the lower limit of FM direction selectivity in the core region of the mouse auditory cortex. To identify cortical areas selective to slow frequency modulation, we investigated tonal responses in the mouse auditory cortex using transcranial flavoprotein fluorescence imaging. For differentiating responses to frequency modulation from those to stimuli at constant frequencies, we focused on transient fluorescence changes after direction reversal of temporally repeated and superimposed FM sweeps. We found that the ultrasonic field (UF) in the belt cortical region selectively responded to the direction reversal. The dorsoposterior field (DP) also responded weakly to the reversal. Regarding the responses in UF, no apparent tonotopic map was found, and the right UF responses were significantly larger in amplitude than the left UF responses. The half-max latency in responses to FM sweeps was shorter in UF compared with that in the primary auditory cortex (A1) or anterior auditory field (AAF). Tracer injection experiments in the functionally identified UF and DP confirmed that these two areas receive afferent inputs from the dorsal part of the medial geniculate nucleus (MG). Calcium imaging of UF neurons stained with fura-2 were performed using a two-photon microscope, and the presence of UF neurons that were selective to both direction and direction reversal of slow frequency modulation was demonstrated. These results strongly suggest a role for UF, and possibly DP, as cortical areas specialized for processing slow frequency modulation in mice
Characteristics of the BDNF Val66Met polymorphism in competitive swimmers and judo athletes
Studies have demonstrated that motivation, aggression, excitation intensity, competitive spirit, and tolerance to psychological stress are included in major psychological factors affecting the performance of athletes. However, to date, there have not been sufficient scientific studies on the relationship between genetic polymorphisms affecting psychological abilities and competitive strength/sport. In this study, we compared the distribution of the brain-derived neurotrophic factor (BDNF) gene polymorphism(Val66Met) in athletes between competitive swimming, which needs closed skill without opponents, and judo, which needs open skill with opponents, in order to investigate the genetic basis of sports performance and related psychological factors. The results showed that the prevalence of Met carriers of the BDNF polymorphism associated with vulnerability to psychological stress was lower in judo players, suggesting that judo athletes had a higher stress tolerance. In addition, the prevalence of the BDNFheterozygous group was higher in competitive swimmers, supporting the hypothesis that closed skill sports without opponents receive less stress than open skill sports with opponents, furthre suggesting that they are excellent in motor control and motor learning