5,634 research outputs found
Quenching massive galaxies across cosmic time with the semi-analytic model SHARK v2.0
We introduce version 2.0 of the SHARK semi-analytic model of galaxy formation
after many improvements to the physics included. The most significant being:
(i) a model describing the exchange of angular momentum (AM) between the
interstellar medium and stars; (ii) a new active galactic nuclei feedback model
which has two modes, a quasar and a radio mode, with the radio mode tied to the
jet energy production; (iii) a model tracking the development of black hole
(BH) spins; (iv) more sophisticated modelling of environmental effects on
satellite galaxies; and (v) automatic parameter exploration using Particle
Swarm Optimisation. We focus on two timely research topics: the structural
properties of galaxies and the quenching of massive galaxies. For the former,
SHARK v2.0 is capable of producing a more realistic stellar size-mass relation
with a plateau marking the transition from disk- to bulge-dominated galaxies,
and scaling relations between specific AM and mass that agree well with
observations. For the quenching of massive galaxies, SHARK v2.0 produces
massive galaxies that are more quenched than the previous version, reproducing
well the observed relations between star formation rate (SFR) and stellar mass,
and specific SFR and BH mass at . SHARK v2.0 produces a number density of
massive-quiescent galaxies >1dex higher than the previous version, in good
agreement with JWST observations at ; predicts a stellar mass function
of passive galaxies in reasonably good agreement with observations at
; and environmental quenching to already be effective at .Comment: Submitted for publication in MNRAS. Supplementary material with
additional comparisons with observations can be found here
https://clagos.com/files/Shark_v2_SupplementaryMaterial.pd
Neutralino-Nucleon Cross Section and Charge and Colour Breaking Constraints
We compute the neutralino-nucleon cross section in several supersymmetric
scenarios, taking into account all kind of constraints. In particular, the
constraints that the absence of dangerous charge and colour breaking minima
imposes on the parameter space are studied in detail. In addition, the most
recent experimental constraints, such as the lower bound on the Higgs mass, the
branching ratio, and the muon are considered. The
astrophysical bounds on the dark matter density are also imposed on the
theoretical computation of the relic neutralino density, assuming thermal
production. This computation is relevant for the theoretical analysis of the
direct detection of dark matter in current experiments. We consider first the
supergravity scenario with universal soft terms and GUT scale. In this scenario
the charge and colour breaking constraints turn out to be quite important, and
\tan\beta\lsim 20 is forbidden. Larger values of can also be
forbidden, depending on the value of the trilinear parameter . Finally, we
study supergravity scenarios with an intermediate scale, and also with
non-universal scalar and gaugino masses where the cross section can be very
large.Comment: Final version to appear in JHE
Leishmania isoenzyme polymorphisms in Ecuador: Relationships with geographic distribution and clinical presentation
Background: Determinants of the clinical presentation of the leishmaniases are poorly understood but Leishmania species and strain differences are important. To examine the relationship between clinical presentation, species and isoenzyme polymorphisms, 56 Leishmania isolates from distinct presentations of American tegumentary leishmaniasis (ATL) from Ecuador were analyzed.
Methods: Isolates were characterized by multilocus enzyme electrophoresis for polymorphisms of 11 isoenzymes. Patients were infected in four different ecologic regions: highland and lowland jungle of the Pacific coast, Amazonian lowlands and Andean highlands.
Results: Six Leishmania species constituting 21 zymodemes were identified: L. (Viannia) panamensis (21 isolates,
7 zymodemes), L. (V.) guyanensis (7 isolates, 4 zymodemes), L. (V.) braziliensis (5 isolates, 3 zymodemes), L.
(Leishmania) mexicana (11 isolates, 4 zymodemes), L. (L.) amazonensis (10 isolates, 2 zymodemes) and L. (L.) major
(2 isolates, 1 zymodeme). L. panamensis was the species most frequently identified in the Pacific region and was
associated with several clinical variants of cutaneous disease (CL); eight cases of leishmaniasis recidiva cutis (LRC) found in the Pacific highlands were associated with 3 zymodemes of this species. Mucocutaneous leishmaniasis
found only in the Amazonian focus was associated with 3 zymodemes of L. braziliensis. The papular variant of CL,
Uta, found in the Andean highlands was related predominantly with a single zymodeme of L. mexicana.
Conclusion: Our data show a high degree of phenotypic variation within species, and some evidence for associations between specific variants of ATL (i.e. Uta and LRC) and specific Leishmania zymodemes. This study
further defines the geographic distribution of Leishmania species and clinical variants of ATL in Ecuador
First measurement of the CP-violating phase in B0s→J/ψ( → e+e−)ϕ decays
A flavour-tagged time-dependent angular analysis of B0 s → J/ψφ decays is presented where the J/ψ meson is reconstructed through its decay to an e +e − pair. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1 . The CP-violating phase and lifetime parameters of the B0 s system are measured to be φs = 0.00 ± 0.28 ± 0.05 rad, ∆Γs = 0.115 ± 0.045 ± 0.011 ps−1 and Γs = 0.608 ± 0.018 ± 0.011 ps−1 where the first uncertainty is statistical and the second systematic. This is the first time that CP-violating parameters are measured in the B0 s → J/ψφ decay with an e +e − pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions
The Determination of alpha_s from Tau Decays Revisited
We revisit the determination of alpha_s(m_tau) using a fit to inclusive tau
hadronic spectral moments in light of (1) the recent calculation of the
fourth-order perturbative coefficient K_4 in the expansion of the Adler
function, (2) new precision measurements from BABAR of e+e- annihilation cross
sections, which decrease the uncertainty in the separation of vector and
axial-vector spectral functions, and (3) improved results from BABAR and Belle
on tau branching fractions involving kaons. We estimate that the fourth-order
perturbative prediction reduces the theoretical uncertainty, introduced by the
truncation of the series, by 20% with respect to earlier determinations. We
discuss to some detail the perturbative prediction and show that the effect of
the incomplete knowledge of the series is reduced by using the so-called
contour-improved calculation, as opposed to fixed-order perturbation theory
which manifests convergence problems. The corresponding theoretical
uncertainties are studied at the tau and Z mass scales. Nonperturbative
contributions extracted from the most inclusive fit are small, in agreement
with earlier determinations. Systematic effects from quark-hadron duality
violation are estimated with simple models and found to be within the quoted
systematic errors. The fit gives alpha_s(m_tau) = 0.344 +- 0.005 +- 0.007,
where the first error is experimental and the second theoretical. After
evolution to M_Z we obtain alpha_s(M_Z) = 0.1212 +- 0.0005 +- 0.0008 +- 0.0005,
where the errors are respectively experimental, theoretical and due to the
evolution. The result is in agreement with the corresponding NNNLO value
derived from essentially the Z width in the global electroweak fit. The
alpha_s(M_Z) determination from tau decays is the most precise one to date.Comment: 22 pages, 7 figure
Amphotericin B plasma monitoring for one burn child using high-performance liquid chromatography
A bioanalytical micromethod was described for the quantification of amphotericin B in plasma by HPLC. The method showed high absolute recovery, good linearity (0.1-10.0 μg/mL, r2 = 0.999), sensitivity (limits of quantification: 0.1 μg/mL), and acceptable stability. Inter/intraday precisions were 6.8 %/2.3 % and mean accuracy was 94.3 %. The method was applied to plasma monitoring of one burn child, 3 years old, 25 kg, thermal injury (18 % total burn surface area - TBSA). Amphotericin B (1 mg/kg) was prescribed from 24th to 35th day of the accident and plasma monitoring and pharmacokinetics was performed by serial blood collections on 27th and 35th days post burn. Plasma concentrations obtained were respectively 0.7 μg/mL and 1.2 μg/mL. Pharmacokinetics at both periods (27th vs 35th day) also was compared: 13.8 vs 14.3 h (t1/2β ); 0.5 vs 0.3 mL/min.kg (CLT) and 0.65 vs 0.38 L/kg (Vdss ). In conclusion, drug plasma monitoring by HPLC was quite useful to guarantee low risk and drug efficacy in a paediatric burn patient.Colegio de Farmacéuticos de la Provincia de Buenos Aire
Flavour Violation in SUSY SU(5) GUT at Large tan beta
We study flavour violation in the minimal SUSY SU(5) GUT assuming all the
third generation Yukawa couplings to be due to the renormalizable physics above
GUT scale. At large as suggested by Yukawa unification in SU(5),
sizable flavour violation in the left (right) slepton (down squark) sector is
induced due to renormalization effects of down type Yukawa couplings between
GUT and Planck scales in addition to the flavour violation in the right slepton
sector. The new flavour physics contribution to mixing
is small but might be of phenomenological interest in the case of The sign of the latter contribution is the same as the sign of the
dominant chargino contribution, thus making the constraints on SUSY scale
coming from somewhat more restrictive. The most important
feature of the considered scenario is the large rate of lepton flavour
violation. Given the present experimental constraints, the and
conversion branching ratios are above the sensitivity of the planned
experiments unless the SUSY scale is pushed above one TeV.Comment: 22 pages, 7 figure
2D-Tasks for Cognitive Rehabilitation
Neuropsychological Rehabilitation is a complex clinic process which tries to restore or compensate cognitive and behavioral disorders in people suffering from a central nervous system injury. Information and Communication Technologies (ICTs) in Biomedical Engineering play an essential role in this field, allowing improvement and expansion of present rehabilitation programs.
This paper presents a set of cognitive rehabilitation 2D-Tasks for patients with Acquired Brain Injury (ABI). These tasks allow a high degree of personalization and individualization in therapies, based on the opportunities offered by new technologies
Search for the Higgs boson in events with missing transverse energy and b quark jets produced in proton-antiproton collisions at s**(1/2)=1.96 TeV
We search for the standard model Higgs boson produced in association with an
electroweak vector boson in events with no identified charged leptons, large
imbalance in transverse momentum, and two jets where at least one contains a
secondary vertex consistent with the decay of b hadrons. We use ~1 fb-1
integrated luminosity of proton-antiproton collisions at s**(1/2)=1.96 TeV
recorded by the CDF II experiment at the Tevatron. We find 268 (16) single
(double) b-tagged candidate events, where 248 +/- 43 (14.4 +/- 2.7) are
expected from standard model background processes. We place 95% confidence
level upper limits on the Higgs boson production cross section for several
Higgs boson masses ranging from 110 GeV/c2 to 140 GeV/c2. For a mass of 115
GeV/c2 the observed (expected) limit is 20.4 (14.2) times the standard model
prediction.Comment: 8 pages, 2 figures, submitted to Phys. Rev. Let
Measurement of the Helicity Fractions of W Bosons from Top Quark Decays Using Fully Reconstructed top-antitop Events with CDF II
We present a measurement of the fractions F_0 and F_+ of longitudinally
polarized and right-handed W bosons in top quark decays using data collected
with the CDF II detector. The data set used in the analysis corresponds to an
integrated luminosity of approximately 318 pb -1. We select ttbar candidate
events with one lepton, at least four jets, and missing transverse energy. Our
helicity measurement uses the decay angle theta*, which is defined as the angle
between the momentum of the charged lepton in the W boson rest frame and the W
momentum in the top quark rest frame. The cos(theta*) distribution in the data
is determined by full kinematic reconstruction of the ttbar candidates. We find
F_0 = 0.85 +0.15 -0.22 (stat) +- 0.06 (syst) and F_+ = 0.05 +0.11 -0.05 (stat)
+- 0.03 (syst), which is consistent with the standard model prediction. We set
an upper limit on the fraction of right-handed W bosons of F_+ < 0.26 at the
95% confidence level.Comment: 11 pages, 2 figures, submitted to Phys. Rev.
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