171 research outputs found
UHECR narrow clustering correlating IceCube through-going muons
The recent UHECR events by AUGER and the Telescope Array (TA) suggested that
wide clusterings as the North and South, named Hot Spot, are related to near
AGNs such as the one in M82 and Cen A. In the same frame since 2008 we assumed
that the UHECR are made by light and lightest nuclei to explain the otherwise
embarrassing absence of the huge nearby Virgo cluster, absence due to the
fragility and the opacity of lightest nuclei by photo-dissociation from Virgo
distances. Moreover UHECR map exhibits a few narrow clustering, some near the
galactic plane, as toward SS 433 and on the opposite side of the plane at
celestial horizons: we tagged them in 2014 suggesting possible near source
active also as a UHE neutrino. Indeed since last year, 2015, highest IceCube
trough-going muons, UHE up-going neutrino events at hundreds TeV energy, did
show (by two cases over three tagged in North sky) the expected overlapping of
UHE neutrinos signals with narrow crowding UHECR. New data with higher energy
threshold somehow re-confirmed our preliminary proposal; new possible sources
appear by a additional correlated UHE-neutrino versus UHE-neutrino and-or with
narrow UHECR clustering events. A possible role of relic neutrino mass
scattering by ZeV neutrino arised.Comment: 6 pages, 5 figure
Upward Tau Air Showers from Earth
We estimate the rate of observable Horizontal and Upward Tau Air-Showers
(HORTAUs, UPTAUS) considering both the Earth opacity and the finite size of the
terrestrial atmosphere. We calculate the effective target volumes and masses
for Tau air-showers emerging from the Earth. The resulting model-independent
masses for satellite experiments such as EUSO may encompass at E_nu_tau = 10^19
eV a very large volume, V= 1020 km^3. Adopting simple power law neutrino
fluxes, E^-2 and E^-1, calibrated to GZK-like and Z-Burst-like models, we
estimate that at E= 10^19 eV nearly half a dozen horizontal shower events
should be detected by EUSO in three years of data collection by the
"guaranteed" GZK neutrino flux. We also find that the equivalent mass for an
Earth outer layer made of rock is dominant compared to the water, contrary to
simplified all-rock/all-water Earth models and previous Montecarlo simulations.
Therefore we expect an enhancement of neutrino detection along continental
shelves nearby the highest mountain chains, also given the better geometrical
acceptance for Earth skimming neutrinos. The Auger experiment might reveal such
a signature at E_nu= 10^{18} eV (with 26 events in 3 yr) towards the Andes, if
the angular resolution at the horizon (both in azimuth and zenith) would reach
an accuracy of nearly one degree needed to disentangle tau air showers from
common UHECR. The number of events increases at lower energies; therefore we
suggest an extension of the EUSO and Auger sensitivity down to (or even below)
E_nu = 10^19 eV and E_nu = 10^18 eV respectively.Comment: New version resubmitted to ApJ on the 6th April 2004; 55 Pages,20
figures, major changes following referee reques
UHECR Signatures and Sources
Abstract. We discuss recent results on the clustering, composition and
distribution of Ultra-High Energy Cosmic Rays (UHECR) in the sky; from the
energy of several tens of EeV in the dipole anisotropy, up to the highest
energy of a few narrow clusters, those of Hot Spots. Following the early UHECR
composition records deviations from proton, we noted that the UHECR events
above 40 EeV can be made not just by any light or heavy nuclei, but mainly by
the lightest ones as He,D, Li,Be. The remarkable Virgo absence and the few
localized nearby extragalactic sources, such as CenA, NGC 253 and M82, are
naturally understood: lightest UHECR nuclei cannot reach us from the Virgo
distance of twenty Mpc, due to their nuclei fragility above a few Mpc
distances. Their deflection and smearing in wide hot spots is better tuned to
the lighter nuclei than to the preferred proton or heavy nuclei candidate
courier. We note that these lightest nuclei still suffer of a partial
photodistruction even from such close sources. Therefore, their distruption in
fragments, within few tens EeV multiplet chain of events, have been expected
and later on observed by Auger collaboration, nearly a decade ago. These
multiplet presences, strongly correlate with the same CenA, NGC253 sources. The
statistical weight of such correlation is reminded. We conclude that the same
role of NGC 253 clustering at lower energies could also feed the Auger dipole
anisotropy at lower energy ranges, integrated by nearest Vela, Crab, LMC and
Cas A contributes. In our present UHECR model, based on lightest nuclei in
local volumes of a few Mpcs, closest AGN, Star-Burst or very close SNR are
superimposing their signals, frozen in different epochs, distances and
directions, feeding small and wide anisotropy. Possible tests to confirm, or
untangle the current model from alternative ones, are suggested and updated.Comment: 4 pages, 4 figure
Overproduction, crystallization and preliminary X-ray characterization of Abn2, an endo-1,5-alpha-arabinanase from Bacillus subtilis.
Acta Crystallographica F64 (2008) 636-638Two Bacillus subtilis extracellular endo-1,5-alpha-L-arabinanases, AbnA and Abn2, belonging to glycoside hydrolase family 43 have been identified. The recently characterized Abn2 protein hydrolyzes arabinan and has low identity to other reported 1,5-alpha-L-arabinanases. Abn2 and its selenomethionine (SeMet) derivative have been purified and crystallized. Crystals appeared in two different space groups: P1, with unit-cell parameters a = 51.9, b = 57.6, c = 86.2 A, alpha = 82.3, beta = 87.9, gamma = 63.6 degrees , and P2(1)2(1)2(1), with unit-cell parameters a = 57.9, b = 163.3, c = 202.0 A. X-ray data have been collected for the native and the SeMet derivative to 1.9 and 2.7 A resolution, respectively. An initial model of Abn2 is being built in the SeMet-phased map.This work was partially supported by grant No. POCI/AGR/60236/2004 from Fundacao para a Ciencia e Tecnologia (FCT) and FEDER to IdS-N and fellowship SFRH/BD/18238/2004 from FCT to JMI
Functional Implications of Second-Shell Basic Residues for dUTPase DR2231 Enzymatic Specificity
Nucleotide-processing enzymes are key players in biological processes. They often operate through high substrate specificity for catalysis. How such specificity is achieved is unclear. Here, we dea..
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