436 research outputs found
Quasifree Knockout Of Deuterons In The â¶Li(α,αd)âŽHe Reaction At 23.6 MeV
αâd correlations in quasi-elastic scattering of 23.6-MeV α particles on the deuteron cluster of the â¶Li target were measured in and off the principal reaction plane. Despite the low c.m. energy of 14.2 MeV, the impulse approximation provides a reasonable description of the quasifree process. Computations were based on the asymptotic αâd S-state wave function and on the cluster-model wave function of â¶Li. Insensitivity of the fits to the details of the â¶Li cluster-model wave function indicates an extreme surface reaction mechanism. The full width at half-maximum of the spectator momentum distribution was found to be 48±6 MeV/c. By comparing the experimental cross section for the quasifree process at the maximum of the angular correlation ((d2Ï/dΩddΩ)=68±9 mb/srÂČ at Ξ=25°,Ξ(d)=45°) with the corresponding cross section for the free process, the probability of finding â¶Li as an αâd cluster was evaluated
Neuroprotective strategies for ischemic strokeâFuture perspectives
Ischemic stroke is the main cause of death and the most common cause of acquired physical disability worldwide. Recent demographic changes increase the relevance of stroke and its sequelae. The acute treatment for stroke is restricted to causative recanalization and restoration of cerebral blood flow, including both intravenous thrombolysis and mechanical thrombectomy. Still, only a limited number of patients are eligible for these time-sensitive treatments. Hence, new neuroprotective approaches are urgently needed. Neuroprotection is thus defined as an intervention resulting in the preservation, recovery, and/or regeneration of the nervous system by interfering with the ischemic-triggered stroke cascade. Despite numerous preclinical studies generating promising data for several neuroprotective agents, successful bench-to-bedside translations are still lacking. The present study provides an overview of current approaches in the research field of neuroprotective stroke treatment. Aside from âtraditionalâ neuroprotective drugs focusing on inflammation, cell death, and excitotoxicity, stem-cell-based treatment methods are also considered. Furthermore, an overview of a prospective neuroprotective method using extracellular vesicles that are secreted from various stem cell sources, including neural stem cells and bone marrow stem cells, is also given. The review concludes with a short discussion on the microbiotaâgutâbrain axis that may serve as a potential target for future neuroprotective therapies
The H1 Forward Proton Spectrometer at HERA
The forward proton spectrometer is part of the H1 detector at the HERA
collider. Protons with energies above 500 GeV and polar angles below 1 mrad can
be detected by this spectrometer. The main detector components are
scintillating fiber detectors read out by position-sensitive photo-multipliers.
These detectors are housed in so-called Roman Pots which allow them to be moved
close to the circulating proton beam. Four Roman Pot stations are located at
distances between 60 m and 90 m from the interaction point.Comment: 20 pages, 10 figures, submitted to Nucl.Instr.and Method
Colour reconnections in Herwig++
We describe the implementation details of the colour reconnection model in
the event generator Herwig++. We study the impact on final-state observables in
detail and confirm the model idea from colour preconfinement on the basis of
studies within the cluster hadronization model. Moreover, we show that the
description of minimum bias and underlying event data at the LHC is improved
with this model and present results of a tune to available data.Comment: 19 pages, 21 figures, 2 tables. Matches with published versio
A 3D track finder for the Belle II CDC L1 trigger
Machine learning methods are integrated into the pipelined first level (L1) track trigger of the upgraded flavor physics experiment Belle II at KEK in Tsukuba, Japan. The novel triggering techniques cope with the severe background from events outside the small collision region provided by the new SuperKEKB asymmetric-energy electron-positron collider. Using the precise drift-time information of the central drift chamber which provides axial and stereo wire layers, a neural network L1 trigger estimates the 3D track parameters of tracks, based on input from the axial wire planes provided by a 2D track finder. An extension of this 2D Hough track finder to a 3D finder is proposed, where the single hit representations in the Hough plane are trained using Monte Carlo. This 3D finder improves the track finding efficiency by including the stereo sense wires as input. The estimated polar track angle allows a specialization of the subsequent neural networks to sectors in the polar angle
A Monte-Carlo generator for statistical hadronization in high energy e+e- collisions
We present a Monte-Carlo implementation of the Statistical Hadronization
Model in e+e- collisions. The physical scheme is based on the statistical
hadronization of massive clusters produced by the event generator Herwig within
the microcanonical ensemble. We present a preliminary comparison of several
observables with measurements in e+e- collisions at the Z peak. Although a fine
tuning of the model parameters is not carried out, a general good agreement
between its predictions and data is found.Comment: 19 pages, 28 figures, 6 tables. v2: added sections on comparison
between the Statistical Hadronization Model and the Cluster Model and on the
interplay between Herwig cluster splitting algorithm and Statistical
Hadronization Model predictions. Fixed typos and references added. Version
accepted for publication in EPJ
Vasoactive intestinal peptide, whose receptor-mediated signalling may be defective in alopecia areata, provides protection from hair follicle immune privilege collapse
Background: Alopecia areata (AA) is an autoimmune disorder whose pathogenesis involves the collapse of the relative immune privilege (IP) of the hair follicle (HF). Given that vasoactive intestinal peptide (VIP) is an immunoinhibitory neuropeptide released by perifollicular sensory nerve fibres, which play a role in IP maintenance, it may modulate human HF-IP and thus be therapeutically relevant for AA. Objectives: To answer the following questions: Do human HFs express VIP receptors, and does their stimulation protect from or restore experimentally induced HF-IP collapse? Is VIP signalling defective in AA HFs?. Methods: Firstly, VIP and VIP receptor (VPAC1, VPAC2) expression in human scalp HFs and AA skin was assessed. In HF organ culture, we then explored whether VIP treatment can restore and/or protect from interferon-Îł-induced HF-IP collapse, assessing the expression of the key IP markers by quantitative (immuno-)histomorphometry. Results: Here we provide the first evidence that VIP receptors are expressed in the epithelium of healthy human HFs at the gene and protein level. Furthermore, VIP receptor protein expression, but not VIP+ nerve fibres, is significantly downregulated in lesional hair bulbs of patients with AA, suggesting defects in VIP receptor-mediated signalling. Moreover, we show that VIP protects the HF from experimentally induced IP collapse in vitro, but does not fully restore it once collapsed. Conclusions: These pilot data suggest that insufficient VIP receptor-mediated signalling may contribute to impairing HF-IP in patients with AA, and that VIP is a promising candidate âHF-IP guardianâ that may be therapeutically exploited to inhibit the progression of AA lesions.</p
Jet vetoing and Herwig++
We investigate the simulation of events with gaps between jets with a veto on
additional radiation in the gap in Herwig++. We discover that the
currently-used random treatment of radiation in the parton shower is generating
some unphysical behaviour for wide-angle gluon emission in QCD 2 to 2
scatterings. We explore this behaviour quantitatively by making the same
assumptions as the parton shower in the analytical calculation. We then modify
the parton shower algorithm in order to correct the simulation of QCD
radiation.Comment: 18 pages, 11 figure
SUSY parameter determination at the LHC using cross sections and kinematic edges
We study the determination of supersymmetric parameters at the LHC from a
global fit including cross sections and edges of kinematic distributions. For
illustration, we focus on a minimal supergravity scenario and discuss how well
it can be constrained at the LHC operating at 7 and 14 TeV collision energy,
respectively. We find that the inclusion of cross sections greatly improves the
accuracy of the SUSY parameter determination, and allows to reliably extract
model parameters even in the initial phase of LHC data taking with 7 TeV
collision energy and 1/fb integrated luminosity. Moreover, cross section
information may be essential to study more general scenarios, such as those
with non-universal gaugino masses, and distinguish them from minimal,
universal, models.Comment: 22 pages, 8 figure
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