257 research outputs found
LZS/Al2O3 nanostructured composites obtained by colloidal processing and spark plasma sintering
[EN] Li2O-SiO2-ZrO2 (LZS) glass-ceramics have high mechanical strength, hardness, resistance to abrasion and chemical attack, but also a high coefficient of thermal expansion (CTE), which can be reduced adding alumina nanoparticles. The conventional glass-ceramic production is relatively complex and energy consuming, since it requires the melting of the raw materials to form a glass frit and a two-step milling process to obtain particle sizes adequate for compaction. This study describes the preparation of LZS glass-ceramics through a colloidal processing approach from mixtures of SiO2 and ZrO2 nanopowders and a Li precursor (lithium acetate obtained by reaction of the carbonate with acetic acid). Concentrated suspensions were freeze-dried to obtain homogeneous mixtures of powders that were pressed (100 MPa) and sintered conventionally and by spark plasma sintering. The effect of the alumina nanoparticles additions on suspensions rheology, sintering behavior and properties such as thermal expansion, thermal conductivity, hardness and Young's modulus were evaluated. (C) 2017 Elsevier Ltd. All rights reserved.This work has been supported by Ministerio de Economia y Competitividad (MINECO) and FEDER Funds under grant No MAT2016-67586-C3-R. Authors greatly acknowledge the financial Support of CAPES in the frame of the International Cooperation Program Science without Borders for Special Visiting Researcher PVE (MEC/MCTI/CAPES/CNPQ/FAPs/No 71/2013), Project no. A011/2013. A. Borrell acknowledges the MINECO for her Juan de la Cierva-Incorporacion contract (IJCI-2014-19839).Arcaro, S.; Novaes De Oliveira, A.; Gutierrez-Gonzalez, C.; Salvador Moya, MD.; Borrell TomĂĄs, MA.; Moreno, R. (2017). LZS/Al2O3 nanostructured composites obtained by colloidal processing and spark plasma sintering. Journal of the European Ceramic Society. 37(16):5139-5148. https://doi.org/10.1016/j.jeurceramsoc.2017.03.023S51395148371
Impact of non-respect of SYNTAX score II recommendation for surgery in patients with left main coronary artery disease treated by percutaneous coronary intervention: an EXCEL substudy
OBJECTIVES: The SYNTAX score II (SSII) was developed from the SYNTAX trial to predict the 4-year all-cause mortality after left main or multivessel disease revascularization and to facilitate the decision-making process. The SSII provides the following treatment recommendations: (i) coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) (equipoise risk), (ii) CABG preferred (excessive risk for PCI) or (iii) PCI preferred (excessive risk for CABG). We sought to externally validate SSII and to investigate the impact of not abiding by the SSII recommendations in the randomized EXCEL trial of PCI versus CABG for left main disease. METHODS: The calibration plot of predicted versus observed 4-year mortality was constructed from individual values of SSII in EXCEL. To assess overestimation versus underestimation of predicted mortality risk, an optimal fit regression line with slope and intercept was determined. Prospective treatment recommendations based on SSII were compared with actual treatments and all-cause mortality at 4âyears. RESULTS: SSII variables were available from EXCEL trial in 1807/1905 (95%) patients. For the entire cohort, discrimination was possibly helpful (C statisticâ=â0.670). SSII-predicted all-cause mortality at 4âyears overestimated the observed mortality, particularly in the highest-risk percentiles, as confirmed by the fit regression line [intercept 2.37 (1.51-3.24), Pâ=â0.003; slope 0.67 (0.61-0.74), Pâ<â0.001]. When the SSII-recommended treatment was CABG, randomized EXCEL patients treated with PCI had a trend towards higher mortality compared with those treated with CABG (14.1% vs 5.3%, Pâ=â0.07) in the as-treat population. In the intention-to-treat population, patients randomized to PCI had higher mortality compared with those randomized to CABG (15.1% vs 4.1%, Pâ=â0.02), when SSII recommended CABG. CONCLUSIONS: In the EXCEL trial of patients with left main disease, the SSII-predicted 4-year mortality overestimated the 4-year observed mortality with a possibly helpful discrimination. Non-compliance with SSII CABG treatment recommendations (i.e. randomized to PCI) was associated with higher 4-year all-cause mortality
Towards Noncommutative Fuzzy QED
We study in one-loop perturbation theory noncommutative fuzzy quenched QED_4.
We write down the effective action on fuzzy S**2 x S**2 and show the existence
of a gauge-invariant UV-IR mixing in the model in the large N planar limit. We
also give a derivation of the beta function and comment on the limit of large
mass of the normal scalar fields. We also discuss topology change in this 4
fuzzy dimensions arising from the interaction of fields (matrices) with
spacetime through its noncommutativity.Comment: 33 page
Matrix Models, Gauge Theory and Emergent Geometry
We present, theoretical predictions and Monte Carlo simulations, for a simple
three matrix model that exhibits an exotic phase transition. The nature of the
transition is very different if approached from the high or low temperature
side. The high temperature phase is described by three self interacting random
matrices with no background spacetime geometry. As the system cools there is a
phase transition in which a classical two-sphere condenses to form the
background geometry. The transition has an entropy jump or latent heat, yet the
specific heat diverges as the transition is approached from low temperatures.
We find no divergence or evidence of critical fluctuations when the transition
is approached from the high temperature phase. At sufficiently low temperatures
the system is described by small fluctuations, on a background classical
two-sphere, of a U(1) gauge field coupled to a massive scalar field. The
critical temperature is pushed upwards as the scalar field mass is increased.
Once the geometrical phase is well established the specific heat takes the
value 1 with the gauge and scalar fields each contributing 1/2.Comment: 41 pages,23 figures,two references added,typos corrected, extra
comments include
A first estimate of triply heavy baryon masses from the pNRQCD perturbative static potential
Within pNRQCD we compute the masses of spin-averaged triply heavy baryons
using the now-available NNLO pNRQCD potentials and three-body variational
approach. We focus in particular on the role of the purely three-body
interaction in perturbation theory. This we find to be reasonably small and of
the order 25 MeV Our prediction for the Omega_ccc baryon mass is 4900(250) in
keeping with other approaches. We propose to search for this hitherto
unobserved state at B factories by examining the end point of the recoil
spectrum against triple charm.Comment: 18 figures, 21 page
Measurement of the Lifetime of the Tau Lepton
The tau lepton lifetime is measured with the L3 detector at LEP using the
complete data taken at centre-of-mass energies around the Z pole resulting in
tau_tau = 293.2 +/- 2.0 (stat) +/- 1.5 (syst) fs. The comparison of this result
with the muon lifetime supports lepton universality of the weak charged current
at the level of six per mille. Assuming lepton universality, the value of the
strong coupling constant, alpha_s is found to be alpha_s(m_tau^2) = 0.319 +/-
0.015(exp.) +/- 0.014 (theory)
Measurement of the Tau Branching Fractions into Leptons
Using data collected with the L3 detector near the Z resonance, corresponding
to an integrated luminosity of 150pb-1, the branching fractions of the tau
lepton into electron and muon are measured to be
B(tau->e nu nu) = (17.806 +- 0.104 (stat.) +- 0.076 (syst.)) %,
B(tau->mu nu nu) = (17.342 +- 0.110 (stat.) +- 0.067 (syst.)) %.
From these results the ratio of the charged current coupling constants of the
muon and the electron is determined to be g_mu/g_e = 1.0007 +- 0.0051. Assuming
electron-muon universality, the Fermi constant is measured in tau lepton decays
as G_F = (1.1616 +- 0.0058) 10^{-5} GeV^{-2}. Furthermore, the coupling
constant of the strong interaction at the tau mass scale is obtained as
alpha_s(m_tau^2) = 0.322 +- 0.009 (exp.) +- 0.015 (theory)
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV
The Lambda(b) differential production cross section and the cross section
ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum
pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7
TeV using data collected by the CMS experiment at the LHC. The measurements are
based on Lambda(b) decays reconstructed in the exclusive final state J/Psi
Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and
Lambda to proton pion, using a data sample corresponding to an integrated
luminosity of 1.9 inverse femtobarns. The product of the cross section times
the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls
faster than that of b mesons. The measured value of the cross section times the
branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06
+/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for
anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are
statistical and systematic, respectively.Comment: Submitted to Physics Letters
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