222 research outputs found
The Effects of Micro-vessel Curvature Induced Elongational Flows on Platelet Adhesion
The emerging profile of blood flow and the cross-sectional distribution of blood cells have far reaching biological consequences in various diseases and vital internal processes, such as platelet adhesion. The effects of several essential blood flow parameters, such as red blood cell free layer width, wall shear rate, and hematocrit on platelet adhesion were previously explored to great lengths in straight geometries. In the current work, the effects of channel curvature on cellular blood flow are investigated by simulating the accurate cellular movement and interaction of red blood cells and platelets in a half-arc channel for multiple wall shear rate and hematocrit values. The results show significant differences in the emerging shear rate values and distributions between the inner and outer arc of the channel curve, while the cell distributions remain predominantly uninfluenced. The simulation predictions are also compared to experimental platelet adhesion in a similar curved geometry. The inner side of the arc shows elevated platelet adhesion intensity at high wall shear rate, which correlates with increased shear rate and shear rate gradient sites in the simulation. Furthermore, since the platelet availability for binding seems uninfluenced by the curvature, these effects might influence the binding mechanics rather than the probability. The presence of elongational flows is detected in the simulations and the link to increased platelet adhesion is discussed in the experimental results
Intracranial atherosclerotic burden and cerebral parenchymal changes at 7T MRI in patients with transient ischemic attack or ischemic stroke
The relevance of intracranial vessel wall lesions detected with MRI is not fully established. In this study (trial identification number: NTR2119; ), 7T MRI was used to investigate if a higher vessel wall lesion burden is associated with more cerebral parenchymal changes in patients with ischemic stroke or transient ischemic attack (TIA). MR images of 82 patients were assessed for the number of vessel wall lesions of the large intracranial arteries and for cerebral parenchymal changes, including the presence and number of cortical, small subcortical, and deep gray matter infarcts; lacunes of presumed vascular origin; cortical microinfarcts; and periventricular and deep white matter hyperintensities (WMHs). Regression analyses showed that a higher vessel wall lesion burden was associated with the presence of small subcortical infarcts, lacunes of presumed vascular origin, and deep gray matter infarcts (relative risk 1.18; 95% CI, 1.03-1.35) and presence of moderate-to-severe periventricular WMHs (1.21; 95% CI, 1.03-1.42), which are all manifestations of small vessel disease (SVD). The burden of enhancing vessel wall lesions was associated with the number of cortical microinfarcts only (1.48; 95% CI, 1.04-2.11). These results suggest an interrelationship between large vessel wall lesion burden and cerebral parenchymal manifestations often linked to SVD or, alternatively, that vascular changes occur in both large and small intracranial arteries simultaneously.Neuro Imaging Researc
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
Measurement of Transverse Single-Spin Asymmetries for Di-Jet Production in Proton-Proton Collisions at GeV
We report the first measurement of the opening angle distribution between
pairs of jets produced in high-energy collisions of transversely polarized
protons. The measurement probes (Sivers) correlations between the transverse
spin orientation of a proton and the transverse momentum directions of its
partons. With both beams polarized, the wide pseudorapidity () coverage for jets permits separation of Sivers functions for the valence
and sea regions. The resulting asymmetries are all consistent with zero and
considerably smaller than Sivers effects observed in semi-inclusive deep
inelastic scattering (SIDIS). We discuss theoretical attempts to reconcile the
new results with the sizable transverse spin effects seen in SIDIS and forward
hadron production in pp collisions.Comment: 6 pages total, 1 Latex file, 3 PS files with figure
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at = 2.76 TeV
The yield of charged particles associated with high- trigger
particles ( GeV/) is measured with the ALICE detector in
Pb-Pb collisions at = 2.76 TeV relative to proton-proton
collisions at the same energy. The conditional per-trigger yields are extracted
from the narrow jet-like correlation peaks in azimuthal di-hadron correlations.
In the 5% most central collisions, we observe that the yield of associated
charged particles with transverse momenta GeV/ on the
away-side drops to about 60% of that observed in pp collisions, while on the
near-side a moderate enhancement of 20-30% is found.Comment: 15 pages, 2 captioned figures, 1 table, authors from page 10,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/350
Detector Technologies for CLIC
The Compact Linear Collider (CLIC) is a high-energy high-luminosity linear
electron-positron collider under development. It is foreseen to be built and
operated in three stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3
TeV, respectively. It offers a rich physics program including direct searches
as well as the probing of new physics through a broad set of precision
measurements of Standard Model processes, particularly in the Higgs-boson and
top-quark sectors. The precision required for such measurements and the
specific conditions imposed by the beam dimensions and time structure put
strict requirements on the detector design and technology. This includes
low-mass vertexing and tracking systems with small cells, highly granular
imaging calorimeters, as well as a precise hit-time resolution and power-pulsed
operation for all subsystems. A conceptual design for the CLIC detector system
was published in 2012. Since then, ambitious R&D programmes for silicon vertex
and tracking detectors, as well as for calorimeters have been pursued within
the CLICdp, CALICE and FCAL collaborations, addressing the challenging detector
requirements with innovative technologies. This report introduces the
experimental environment and detector requirements at CLIC and reviews the
current status and future plans for detector technology R&D.Comment: 152 pages, 116 figures; published as CERN Yellow Report Monograph
Vol. 1/2019; corresponding editors: Dominik Dannheim, Katja Kr\"uger, Aharon
Levy, Andreas N\"urnberg, Eva Sickin
Energy dependence of charged pion, proton and anti-proton transverse momentum spectra for Au+Au collisions at \sqrt{s_NN} = 62.4 and 200 GeV
We study the energy dependence of the transverse momentum (pT) spectra for
charged pions, protons and anti-protons for Au+Au collisions at \sqrt{s_NN} =
62.4 and 200 GeV. Data are presented at mid-rapidity (|y| < 0.5) for 0.2 < pT <
12 GeV/c. In the intermediate pT region (2 < pT < 6 GeV/c), the nuclear
modification factor is higher at 62.4 GeV than at 200 GeV, while at higher pT
(pT >7 GeV/c) the modification is similar for both energies. The p/pi+ and
pbar/pi- ratios for central collisions at \sqrt{s_NN} = 62.4 GeV peak at pT ~ 2
GeV/c. In the pT range where recombination is expected to dominate, the p/pi+
ratios at 62.4 GeV are larger than at 200 GeV, while the pbar/pi- ratios are
smaller. For pT > 2 GeV/c, the pbar/pi- ratios at the two beam energies are
independent of pT and centrality indicating that the dependence of the pbar/pi-
ratio on pT does not change between 62.4 and 200 GeV. These findings challenge
various models incorporating jet quenching and/or constituent quark
coalescence.Comment: 19 pages and 6 figure
Ï production in pâPb collisions at âsNN=8.16 TeV
Ï production in pâPb interactions is studied at the centre-of-mass energy per nucleonânucleon collision âsNN = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals 2.03 < ycms < 3.53 and â4.46 < ycms < â2.96, down to zero transverse momentum. In this work, results on the Ï(1S) production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the Ï(1S) yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. Furthermore, the Ï(2S) nuclear modification factor is evaluated, suggesting a suppression similar to that of the Ï(1S). A first measurement of the Ï(3S) has also been performed. Finally, results are compared with previous ALICE measurements in pâPb collisions at âsNN = 5.02 TeV and with theoretical calculations.publishedVersio
Energy dependence of Ï meson production at forward rapidity in pp collisions at the LHC
The production of mesons has been studied in pp collisions at LHC energies with the ALICE detector via the dimuon decay channel in the rapidity region . Measurements of the differential cross section are presented as a function of the transverse momentum () at the center-of-mass energies , 8 and 13 TeV and compared with the ALICE results at midrapidity. The differential cross sections at and 13 TeV are also studied in several rapidity intervals as a function of , and as a function of rapidity in three intervals. A hardening of the -differential cross section with the collision energy is observed, while, for a given energy, spectra soften with increasing rapidity and, conversely, rapidity distributions get slightly narrower at increasing . The new results, complementing the published measurements at and 7 TeV, allow one to establish the energy dependence of meson production and to compare the measured cross sections with phenomenological models. None of the considered models manages to describe the evolution of the cross section with and rapidity at all the energies.publishedVersio
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