229 research outputs found
Electromagnetic dissociation of relativistic B nuclei in nuclear track emulsion
Experimental data on fragmentation channels in peripheral interactions of
B nuclei in nuclear track emulsions are presented. A detailed analysis made
it possible to justify selections of events of the electromagnetic-dissociation
process B Be + \emph{p} and to estimate its cross section. Events of
C peripheral dissociation that were observed in the same exposure are
described.Comment: 12 pages, 10 figures, 4 tables, Published in
Phys.Atom.Nucl.72:690-701,200
Clustering in light nuclei in fragmentation above 1 A GeV
The relativistic invariant approach is applied to analyzing the 3.3 A GeV
Ne fragmentation in a nuclear track emulsion. New results on few-body
dissociations have been obtained from the emulsion exposures to 2.1 A GeV
N and 1.2 A GeV Be nuclei. It can be asserted that the use of the
invariant approach is an effective means of obtaining conclusions about the
behavior of systems involving a few He nuclei at a relative energy close to 1
MeV per nucleon. The first observations of fragmentation of 1.2 A GeV B
and C nuclei in emulsion are described. The presented results allow one
to justify the development of few-body aspects of nuclear astrophysics.Comment: 7 pages, 8 figures, 3 tables, Nuclear Physics in Astrophysics-2,
16-20 May, 2005 (ATOMKI), Debrecen, Hungar
Fragmentation of relativistic nuclei in peripheral interactions in nuclear track emulsion
The technique of nuclear track emulsions is used to explore the fragmentation
of light relativistic nuclei down to the most peripheral interactions - nuclear
"white" stars. A complete pattern of therelativistic dissociation of a B
nucleus with target fragment accompaniment is presented. Relativistic
dissociation Be is explored using significant statistics and
a relative contribution of Be decays from 0 and 2 states is
established. Target fragment accompaniments are shown for relativistic
fragmentation N3He+H and Ne5He. The leading role of the
electromagnetic dissociation on heavy nuclei with respect to break-ups on
target protons is demonstrated in all these cases. It is possible to conclude
that the peripheral dissociation of relativistic nuclei in nuclear track
emulsion is a unique tool to study many-body systems composed of lightest
nuclei and nucleons in the energy scale relevant for nuclear astrophysics.Comment: 15 pages, 4 figures, 4 tables, conference: Relativistic nuclear
physics: from Nuclotron to LHC energies, Kiev, June 18-22, 200
Topology of "white" stars in relativistic fragmentation of light nuclei
In the present paper, experimental observations of the multifragmentation
processes of light relativistic nuclei carried out by means of emulsions are
reviewed. Events of the type of "white" stars in which the dissociation of
relativistic nuclei is not accompanied by the production of mesons and the
target-nucleus fragments are considered.
A distinctive feature of the charge topology in the dissociation of the Ne,
Mg, Si, and S nuclei is an almost total suppression of the binary splitting of
nuclei to fragments with charges higher than 2. The growth of the nuclear
fragmentation degree is revealed in an increase in the multiplicity of singly
and doubly charged fragments with decreasing charge of the non-excited part of
the fragmenting nucleus.
The processes of dissociation of stable Li, Be, B, C, N, and O isotopes to
charged fragments were used to study special features of the formation of
systems consisting of the lightest , d, and t nuclei. Clustering in
form of the He nucleus can be detected in "white" stars via the
dissociation of neutron-deficient Be, B, C, and N isotopes.Comment: 20 pages, 3 figures, 9 tables, conference: Conference on Physics of
Fundamental Interactions, Moscow, Russia, 1-5 Mar 2004.(Author's translation
The alpha 7 nicotinic receptor agonist PHA-543613 hydrochloride inhibits <i>Porphyromonas gingivalis</i>-induced expression of interleukin-8 by oral keratinocytes
Objective:
The alpha 7 nicotinic receptor (α7nAChR) is expressed by oral keratinocytes. α7nAChR activation mediates anti-inflammatory responses. The objective of this study was to determine if α7nAChR activation inhibited pathogen-induced interleukin-8 (IL-8) expression by oral keratinocytes.<p></p>
Materials and methods:
Periodontal tissue expression of α7nAChR was determined by real-time PCR. OKF6/TERT-2 oral keratinocytes were exposed to <i>Porphyromonas gingivalis</i> in the presence and absence of a α7nAChR agonist (PHA-543613 hydrochloride) alone or after pre-exposure to a specific α7nAChR antagonist (α-bungarotoxin). Interleukin-8 (IL-8) expression was measured by ELISA and real-time PCR. Phosphorylation of the NF-κB p65 subunit was determined using an NF-κB p65 profiler assay and STAT-3 activation by STAT-3 in-cell ELISA. The release of ACh from oral keratinocytes in response to <i>P. gingivalis</i> lipopolysaccharide was determined using a GeneBLAzer M3 CHO-K1-blacell reporter assay.<p></p>
Results:
Expression of α7nAChR mRNA was elevated in diseased periodontal tissue. PHA-543613 hydrochloride inhibited <i>P. Gingivalis</i>-induced expression of IL-8 at the transcriptional level. This effect was abolished when cells were pre-exposed to a specific α7nAChR antagonist, α-bungarotoxin. PHA-543613 hydrochloride downregulated NF-κB signalling through reduced phosphorylation of the NF-κB p65-subunit. In addition, PHA-543613 hydrochloride promoted STAT-3 signalling by maintenance of phosphorylation. Furthermore, oral keratinocytes upregulated ACh release in response to <i>P. Gingivalis</i> lipopolysaccharide.<p></p>
Conclusion:
These data suggest that α7nAChR plays a role in regulating the innate immune responses of oral keratinocytes.<p></p>
Emulsion sheet doublets as interface trackers for the OPERA experiment
New methods for efficient and unambiguous interconnection between electronic
counters and target units based on nuclear photographic emulsion films have
been developed. The application to the OPERA experiment, that aims at detecting
oscillations between mu neutrino and tau neutrino in the CNGS neutrino beam, is
reported in this paper. In order to reduce background due to latent tracks
collected before installation in the detector, on-site large-scale treatments
of the emulsions ("refreshing") have been applied. Changeable Sheet (CSd)
packages, each made of a doublet of emulsion films, have been designed,
assembled and coupled to the OPERA target units ("ECC bricks"). A device has
been built to print X-ray spots for accurate interconnection both within the
CSd and between the CSd and the related ECC brick. Sample emulsion films have
been extensively scanned with state-of-the-art automated optical microscopes.
Efficient track-matching and powerful background rejection have been achieved
in tests with electronically tagged penetrating muons. Further improvement of
in-doublet film alignment was obtained by matching the pattern of low-energy
electron tracks. The commissioning of the overall OPERA alignment procedure is
in progress.Comment: 19 pages, 19 figure
Limits on muon-neutrino to tau-neutrino oscillations induced by a sterile neutrino state obtained by OPERA at the CNGS beam
The OPERA experiment, exposed to the CERN to Gran Sasso beam,
collected data from 2008 to 2012. Four oscillated Charged Current
interaction candidates have been detected in appearance mode, which are
consistent with oscillations at the atmospheric within the "standard" three-neutrino framework. In this paper, the OPERA
appearance results are used to derive limits on the mixing
parameters of a massive sterile neutrino.Comment: 11 pages, 4 figures; reference to Planck result updated in the
Introduction. Submitted to JHE
First events from the CNGS neutrino beam detected in the OPERA experiment
The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS)
was designed to perform the first detection of neutrino oscillations in
appearance mode, through the study of nu_mu to nu_tau oscillations. The
apparatus consists of a lead/emulsion-film target complemented by electronic
detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam
(CNGS) 730 km away from the neutrino source. In August 2006 a first run with
CNGS neutrinos was successfully conducted. A first sample of neutrino events
was collected, statistically consistent with the integrated beam intensity.
After a brief description of the beam and of the various sub-detectors, we
report on the achievement of this milestone, presenting the first data and some
analysis results.Comment: Submitted to the New Journal of Physic
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