4,485 research outputs found
Wp-2 basic investigation of transition effect
An important goal of the TFAST project was to study the effect of the location of transition in relation to the shock wave on the separation size, shock structure and unsteadiness of the interaction area. Boundary layer tripping (by wire or roughness) and flow control devices (Vortex Generators and cold plasma) were used for boundary layer transition induction. As flow control devices were used here in the laminar boundary layer for the first time, their effectiveness in transition induction was an important outcome. It was intended to determine in what way the application of these techniques induces transition. These methods should have a significantly different effect on boundary layer receptivity, i.e. the transition location. Apart from an improved understanding of operation control methods, the main objective was to localize the transition as far downstream as possible while ensuring a turbulent character of interaction. The final objective, involving all the partners, was to build a physical model of transition control devices. Establishing of such model would simplify the numerical approach to flow cases using such devices. This undertaking has strong support from the industry, which wants to include these control devices in the design process. Unfortunately only one method of streamwise vortices was developed and investigated in the presented study
Linear ubiquitin assembly complex regulates lung epithelial–driven responses during influenza infection
Influenza A virus (IAV) is among the most common causes of pneumonia-related death worldwide. Pulmonary epithelial cells are the primary target for viral infection and replication and respond by releasing inflammatory mediators that recruit immune cells to mount the host response. Severe lung injury and death during IAV infection result from an exuberant host inflammatory response. The linear ubiquitin assembly complex (LUBAC), composed of SHARPIN, HOIL-1L, and HOIP, is a critical regulator of NF-κB–dependent inflammation. Using mice with lung epithelial–specific deletions of HOIL-1L or HOIP in a model of IAV infection, we provided evidence that, while a reduction in the inflammatory response was beneficial, ablation of the LUBAC-dependent lung epithelial–driven response worsened lung injury and increased mortality. Moreover, we described a mechanism for the upregulation of HOIL-1L in infected and noninfected cells triggered by the activation of type I IFN receptor and mediated by IRF1, which was maladaptive and contributed to hyperinflammation. Thus, we propose that lung epithelial LUBAC acts as a molecular rheostat that could be selectively targeted to modulate the immune response in patients with severe IAV-induced pneumonia.Fil: Brazee, Patricia L.. Northwestern University; Estados UnidosFil: Morales Nebreda, Luisa. Northwestern University; Estados UnidosFil: Magnani, Natalia Daniela. Northwestern University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; ArgentinaFil: Garcia, Joe G. N.. University of Arizona; Estados UnidosFil: Misharin, Alexander V.. Northwestern University; Estados UnidosFil: Ridge, Karen M.. Northwestern University; Estados UnidosFil: Budinger, G.R. Scott. Northwestern University; Estados UnidosFil: Iwai, Kazuhiro. Kyoto University; JapónFil: Dada, Laura Andrea. Northwestern University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; ArgentinaFil: Sznajder, Jacob I.. Northwestern University; Estados Unido
Transverse-momentum-dependent Multiplicities of Charged Hadrons in Muon-Deuteron Deep Inelastic Scattering
A semi-inclusive measurement of charged hadron multiplicities in deep
inelastic muon scattering off an isoscalar target was performed using data
collected by the COMPASS Collaboration at CERN. The following kinematic domain
is covered by the data: photon virtuality (GeV/), invariant
mass of the hadronic system GeV/, Bjorken scaling variable in the
range , fraction of the virtual photon energy carried by the
hadron in the range , square of the hadron transverse momentum
with respect to the virtual photon direction in the range 0.02 (GeV/ (GeV/). The multiplicities are presented as a
function of in three-dimensional bins of , , and
compared to previous semi-inclusive measurements. We explore the
small- region, i.e. (GeV/), where
hadron transverse momenta are expected to arise from non-perturbative effects,
and also the domain of larger , where contributions from
higher-order perturbative QCD are expected to dominate. The multiplicities are
fitted using a single-exponential function at small to study
the dependence of the average transverse momentum on , and . The power-law behaviour of the
multiplicities at large is investigated using various
functional forms. The fits describe the data reasonably well over the full
measured range.Comment: 28 pages, 20 figure
Multiplicities of charged pions and unidentified charged hadrons from deep-inelastic scattering of muons off an isoscalar target
Multiplicities of charged pions and unidentified hadrons produced in
deep-inelastic scattering were measured in bins of the Bjorken scaling variable
, the relative virtual-photon energy and the relative hadron energy .
Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam and
an isoscalar target (LiD). They cover the kinematic domain in the photon
virtuality > 1(GeV/c, , and . In addition, a leading-order pQCD analysis was performed using the
pion multiplicity results to extract quark fragmentation functions
Longitudinal double spin asymmetries in single hadron quasi-real photoproduction at high
We measured the longitudinal double spin asymmetries for single
hadron muo-production off protons and deuterons at photon virtuality <
1(GeV/) for transverse hadron momenta in the range 0.7
GeV/ to 4 GeV/ . They were determined using COMPASS data taken
with a polarised muon beam of 160 GeV/ or 200 GeV/ impinging on
polarised or targets. The experimental
asymmetries are compared to next-to-leading order pQCD calculations, and are
sensitive to the gluon polarisation inside the nucleon in the range
of the nucleon momentum fraction carried by gluons
Interplay among transversity induced asymmetries in hadron leptoproduction
In the fragmentation of a transversely polarized quark several left-right
asymmetries are possible for the hadrons in the jet. When only one unpolarized
hadron is selected, it exhibits an azimuthal modulation known as Collins
effect. When a pair of oppositely charged hadrons is observed, three
asymmetries can be considered, a di-hadron asymmetry and two single hadron
asymmetries. In lepton deep inelastic scattering on transversely polarized
nucleons all these asymmetries are coupled with the transversity distribution.
From the high statistics COMPASS data on oppositely charged hadron-pair
production we have investigated for the first time the dependence of these
three asymmetries on the difference of the azimuthal angles of the two hadrons.
The similarity of transversity induced single and di-hadron asymmetries is
discussed. A new analysis of the data allows to establish quantitative
relationships among them, providing for the first time strong experimental
indication that the underlying fragmentation mechanisms are all driven by a
common physical process.Comment: 6 figure
Interplay among transversity induced asymmetries in hadron leptoproduction
In the fragmentation of a transversely polarized quark several left-right
asymmetries are possible for the hadrons in the jet. When only one unpolarized
hadron is selected, it exhibits an azimuthal modulation known as Collins
effect. When a pair of oppositely charged hadrons is observed, three
asymmetries can be considered, a di-hadron asymmetry and two single hadron
asymmetries. In lepton deep inelastic scattering on transversely polarized
nucleons all these asymmetries are coupled with the transversity distribution.
From the high statistics COMPASS data on oppositely charged hadron-pair
production we have investigated for the first time the dependence of these
three asymmetries on the difference of the azimuthal angles of the two hadrons.
The similarity of transversity induced single and di-hadron asymmetries is
discussed. A new analysis of the data allows to establish quantitative
relationships among them, providing for the first time strong experimental
indication that the underlying fragmentation mechanisms are all driven by a
common physical process.Comment: 6 figure
First Measurement of Chiral Dynamics in \pi^- \gamma -> \pi^- \pi^- \pi^+
The COMPASS collaboration at CERN has investigated the \pi^- \gamma -> \pi^-
\pi^- \pi^+ reaction at center-of-momentum energy below five pion masses,
sqrt(s) < 5 m(\pi), embedded in the Primakoff reaction of 190 GeV pions
impinging on a lead target. Exchange of quasi-real photons is selected by
isolating the sharp Coulomb peak observed at smallest momentum transfers, t' <
0.001 (GeV/c)^2. Using partial-wave analysis techniques, the scattering
intensity of Coulomb production described in terms of chiral dynamics and its
dependence on the 3\pi-invariant mass m(3\pi) = sqrt(s) were extracted. The
absolute cross section was determined in seven bins of with an
overall precision of 20%. At leading order, the result is found to be in good
agreement with the prediction of chiral perturbation theory over the whole
energy range investigated.Comment: 10 pages, 5 figure
The Spin Structure Function of the Proton and a Test of the Bjorken Sum Rule
New results for the double spin asymmetry and the proton
longitudinal spin structure function are presented. They were
obtained by the COMPASS collaboration using polarised 200 GeV muons scattered
off a longitudinally polarised NH target. The data were collected in 2011
and complement those recorded in 2007 at 160\,GeV, in particular at lower
values of . They improve the statistical precision of by
about a factor of two in the region . A next-to-leading order
QCD fit to the world data is performed. It leads to a new determination
of the quark spin contribution to the nucleon spin, ranging
from 0.26 to 0.36, and to a re-evaluation of the first moment of .
The uncertainty of is mostly due to the large uncertainty in
the present determinations of the gluon helicity distribution. A new evaluation
of the Bjorken sum rule based on the COMPASS results for the non-singlet
structure function yields as ratio of the axial and
vector coupling constants , which validates the sum rule to an accuracy of about
9\%.Comment: 19 pages, 8 figures and table
Resonance Production and S-wave in at 190 GeV/c
The COMPASS collaboration has collected the currently largest data set on
diffractively produced final states using a negative pion
beam of 190 GeV/c momentum impinging on a stationary proton target. This data
set allows for a systematic partial-wave analysis in 100 bins of three-pion
mass, GeV/c , and in 11 bins of the reduced
four-momentum transfer squared, (GeV/c) . This
two-dimensional analysis offers sensitivity to genuine one-step resonance
production, i.e. the production of a state followed by its decay, as well as to
more complex dynamical effects in nonresonant production. In this paper,
we present detailed studies on selected partial waves with , , , , and . In these waves, we observe
the well-known ground-state mesons as well as a new narrow axial-vector meson
decaying into . In addition, we present the results
of a novel method to extract the amplitude of the subsystem with
in various partial waves from the
data. Evidence is found for correlation of the and
appearing as intermediate isobars in the decay of the known
and .Comment: 96 page
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