68 research outputs found
Visible-light-assisted selective catalytic reduction of NO with NH[3] on porphyrin derivative-modified TiO[2] photocatalysts
Accepted 16 Sep 2014.Porphyrin-derivative-modified TiO[2] photocatalysts showed high photocatalytic activity for the selective catalytic reduction of NO with NH[3] in the presence of O[2] under visible-light irradiation. Tetra(p-carboxyphenyl)porphyrin (TCPP) was the most effective photosensitizer among the five porphyrin derivatives investigated. NO conversion and N[2] selectivity of 79.0% and 100%, respectively, were achieved at a gas hourly space velocity of 50 000 h[−1]. UV–Vis and photoluminescence spectroscopies revealed the presence of two species of TCPP on the TiO2surface; one was a TCPP monomer and the other was an H-aggregate of the TCPP molecules. It was concluded that the TCPP monomer is an active species for the photo-assisted selective catalytic reduction (photo-SCR). Moreover, an increase in the fraction of H-aggregates with increasing TCPP loading amount resulted in a decrease in the photocatalytic activity of the photo-SCR
Estimation of the detected background by the future gamma ray transient mission CAMELOT
This study presents a background estimation for the CubeSats Applied for MEasuring and LOcalising Transients (CAMELOT), which is a proposed fleet of nanosatellites for the all-sky monitoring and timing-based localization of gamma ray transients with precise localization capability at low Earth orbits. CAMELOT will allow us to observe and precisely localize short gamma ray bursts (GRBs) associated with kilonovae, long GRBs associated with core-collapse massive stars, magnetar outbursts, terrestrial gamma ray flashes, and gamma ray counterparts to gravitational wave sources. A fleet of at least nine 3U CubeSats is proposed to be equipped with large and thin CsI(Tl) scintillators read out by multipixel photon counters (MPPC). A careful study of the radiation environment in space is necessary to optimize the detector casing, estimate the duty cycle due to the crossing of the South Atlantic Anomaly and polar regions, and minimize the effect of the radiation damage of MPPCs
A replication-competent smallpox vaccine LC16m8Δ-based COVID-19 vaccine
金沢大学医薬保健研究域薬学系Viral vectors are a potent vaccine platform for inducing humoral and T-cell immune responses. Among the various viral vectors, replication-competent ones are less commonly used for coronavirus disease 2019 (COVID-19) vaccine development compared with replication-deficient ones. Here, we show the availability of a smallpox vaccine LC16m8Δ (m8Δ) as a replication-competent viral vector for a COVID-19 vaccine. M8Δ is a genetically stable variant of the licensed and highly effective Japanese smallpox vaccine LC16m8. Here, we generated two m8Δ recombinants: one harbouring a gene cassette encoding the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) glycoprotein, named m8Δ-SARS2(P7.5-S)-HA; and one encoding the S protein with a highly polybasic motif at the S1/S2 cleavage site, named m8Δ-SARS2(P7.5-SHN)-HA. M8Δ-SARS2(P7.5-S)-HA induced S-specific antibodies in mice that persisted for at least six weeks after a homologous boost immunization. All eight analysed serum samples displayed neutralizing activity against an S-pseudotyped virus at a level similar to that of serum samples from patients with COVID-19, and more than half (5/8) also had neutralizing activity against the Delta/B.1.617.2 variant of concern. Importantly, most serum samples also neutralized the infectious SARS-CoV-2 Wuhan and Delta/B.1.617.2 strains. In contrast, immunization with m8Δ-SARS2(P7.5-SHN)-HA elicited significantly lower antibody titres, and the induced antibodies had less neutralizing activity. Regarding T-cell immunity, both m8Δ recombinants elicited S-specific multifunctional CD8+ and CD4+ T-cell responses even after just a primary immunization. Thus, m8Δ provides an alternative method for developing a novel COVID-19 vaccine
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
Hitomi (ASTRO-H) X-ray Astronomy Satellite
The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month
Hitomi X-Ray Studies of Giant Radio Pulses from the Crab Pulsar
To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2300 keV band and the Kashima NICT radio telescope in the 1.41.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 fluctuations of the X-ray fluxes at the pulse peaks, and the 3 upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.510 keV and 70300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) 10(exp 11) erg cm(exp 2), respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a >0.02% brightening of the pulse-peak flux under such conditions
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