188 research outputs found
Millisecond Pulsar Velocities
We present improved timing parameters for 13 millisecond pulsars (MSPs)
including 9 new proper motion measurements. These new proper motions bring to
23 the number of MSPs with measured transverse velocities. In light of these
new results we present and compare the kinematic properties of MSPs with those
of ordinary pulsars. The mean transverse velocity of MSPs was found to be
85+/-13 km/s; a value consistent with most models for the origin and evolution
of MSPs and approximately a factor of four lower than that of ordinary pulsars.
We also find that, in contrast to young ordinary pulsars, the vast majority of
which are moving away from the Galactic plane, almost half of the MSPs are
moving towards the plane. This near isotropy would be expected of a population
that has reached dynamic equilibrium. Accurate measurements of MSP velocities
have allowed us to correct their measured spin-down rates for Doppler
acceleration effects, and thereby derive their intrinsic magnetic field
strengths and characteristic ages. We find that close to half of our sample of
MSPs have a characteristic age comparable to or greater than the age of the
Galaxy.Comment: 10 pages LaTeX including 2 LaTeX tables and 3 postscript figures;
submitted to MNRA
Predictive simulations for plasma scenarios in the SMART tokamak
The SMall Aspect Ratio Tokamak (SMART) is a new spherical machine that is currently being constructed at the University of Seville (Mancini et al., 2021; Agredano-Torres et al., 2021). The operation of SMART will cover three different phases reaching an inductive plasma current (IP) of more than 500 kA, a toroidal magnetic field (BT) of 1 T and a pulse length of 500 ms (Mancini et al., 2021; Agredano-Torres et al., 2021). The main goal of the SMART tokamak is to study high plasma confinement regimes in a broad triangularity range (-0.5≤δ≤0.5) (Doyle et al., 2021; Doyle et al., 2021). While in phase 1 the ohmic heating alone is expected to provide enough power to access the H-mode, in phase 2 and phase 3 the access to the H-mode will be ensured by applying Neutral Beam Injection (NBI) as external heating system. The NBI will consist of one injector at 25 keV and 1 MW of power. The overall design of the NBI, including injection geometry, energy and power have been optimized using the ASCOT5 code (Hirvijoki et al., 2021). The SMART scenarios have been developed with the help of the free boundary equilibrium solver code FIESTA (Cunningham, 2013) coupled to the linear time independent, rigid plasma model RZIP (Lazarus et al., 1990) to calculate the target equilibria for all the different operational phases. To assess the feasibility of those scenarios, predictive modelling needs to be included to evaluate properly the evolution of the temperatures, density profiles for both electrons and ions. To this extent, the 1.5D transport code ASTRA (Pereverzev and Yushmanov, 2002) has been used including models for the ohmic current, bootstrap current and current driven by NBI. This contribution discusses the electron and ion density and temperature profiles obtained for various scenarios for phase 1 and 2 and presents the design study of the NBI.his work received funding from the Fondo Europeo de Desarollo Regional (FEDER) by the European Commission under grant agreement numbers IE17-5670 and US-15570. The authors gratefully acknowledge the financial support of the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 805162).Peer reviewe
Neutrophil count is associated with reduced gray matter and enlarged ventricles in first-episode psychosis
Although there is recent evidence that cells from the peripheral immune system can gain access to the central nervous system in certain conditions such as multiple sclerosis, their role has not been assessed in psychosis. Here, we aimed to explore whether blood cell count was associated with brain volume and/or clinical symptomatology. A total of 218 participants (137 first-episode psychosis patients [FEP] and 81 healthy controls [HC]) were included in the study. For each participant, a T1 structural image was acquired, from which brain tissue volumes were calculated. We found that, in FEP, neutrophil count was associated with reduced gray matter (GM) volume (ß = -0.117, P < .001) and increased cerebrospinal fluid volume (ß = 0.191, P = .007). No associations were observed in HC. GM reduction was generalized but more prominent in certain regions, notably the thalamus, the anterior insula, and the left Heschl''s gyrus, among many others. Neutrophil count was also associated with the total PANSS score (ß = 0.173, P = .038), including those items assessing hallucinations (ß = 0.182, P = .028) and avolition (ß = 0.197, P = .018). Several confounders, such as antipsychotic medication, body mass index, and smoking, were controlled for. Overall, the present study may represent the first indirect evidence of brain tissue loss associated with neutrophils in psychosis, and lends support to the hypothesis of a dysregulated immune system. Higher neutrophil count was also associated with more severe clinical symptomatology, which renders it a promising indicator of schizophrenia severity and could even give rise to new therapies
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at , 2.76 and 7 TeV
Measurements of the sphericity of primary charged particles in minimum bias
proton--proton collisions at , 2.76 and 7 TeV with the ALICE
detector at the LHC are presented. The observable is linearized to be collinear
safe and is measured in the plane perpendicular to the beam direction using
primary charged tracks with GeV/c in . The
mean sphericity as a function of the charged particle multiplicity at
mid-rapidity () is reported for events with different
scales ("soft" and "hard") defined by the transverse momentum of the leading
particle. In addition, the mean charged particle transverse momentum versus
multiplicity is presented for the different event classes, and the sphericity
distributions in bins of multiplicity are presented. The data are compared with
calculations of standard Monte Carlo event generators. The transverse
sphericity is found to grow with multiplicity at all collision energies, with a
steeper rise at low , whereas the event generators show the
opposite tendency. The combined study of the sphericity and the mean with multiplicity indicates that most of the tested event generators
produce events with higher multiplicity by generating more back-to-back jets
resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with
tune PERUGIA-2011 exhibits a noticeable improvement in describing the data,
compared to the other tested generators.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16,
published version, figures from
http://aliceinfo.cern.ch/ArtSubmission/node/308
Binary and Millisecond Pulsars at the New Millennium
We review the properties and applications of binary and millisecond pulsars.
Our knowledge of these exciting objects has greatly increased in recent years,
mainly due to successful surveys which have brought the known pulsar population
to over 1300. There are now 56 binary and millisecond pulsars in the Galactic
disk and a further 47 in globular clusters. This review is concerned primarily
with the results and spin-offs from these surveys which are of particular
interest to the relativity community.Comment: 59 pages, 26 figures, 5 tables. Accepted for publication in Living
Reviews in Relativity (http://www.livingreviews.org
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
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
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