Electrochemical behavior of Ti/Al2O3 interfaces produced by diffusion bonding

In the field of biomedical applications a special interest exists regarding the study of the physicochemical and mechanical behaviour of materials, with special focus on the electrochemical degradation of metal/ceramic interfaces. In fact, etal/ceramic interfaces may be present in several biomedical devices, ranging from external or implantable sensors, to dental implants. Diffusion bonding represents an important technique since, in opposition to other production technologies, such as active metal brazing, avoid the possible liberation of certain chemical components harmful to health. The aim of this work is to study the electrochemical degradation of the interface formed between commercially pure Ti and Al2O3 produced by diffusion bonding, in contact with a physiological solution. The present approach included the evaluation of the contribution of individual and pairs of interfacial layers on the global degradation processes. For this propose d.c. electrochemical techniques were used to monitor the open-circuit potential, and to perform potentiodynamic polarization and galvanic corrosion evaluation. Also, electrochemical impedance spectroscopy was used as a complementary technique of the corrosion behaviour of the interface. Chemical composition and morphology of samples and corrosion products were evaluated by SEM and EDS analysis. According to experimental results, two principal reaction layers were formed in the interface: TiAl and Ti3Al. The TiAl layer appears to be the responsible for the strong increase in corrosion rate of the interface.Fundação para a Ciência e Tecnologia -POCTI/CTM/33384/2000; SFRH/BPD/ 5518/2001

The holographic superconductors in higher-dimensional AdS soliton

We explore the behaviors of the holographic superconductors at zero temperature for a charged scalar field coupled to a Maxwell field in higher-dimensional AdS soliton spacetime via analytical way. In the probe limit, we obtain the critical chemical potentials increase linearly as a total dimension $d$ grows up. We find that the critical exponent for condensation operator is obtained as 1/2 independently of $d$, and the charge density is linearly related to the chemical potential near the critical point. Furthermore, we consider a slightly generalized setup the Einstein-Power-Maxwell field theory, and find that the critical exponent for condensation operator is given as $1/(4-2n)$ in terms of a power parameter $n$ of the Power-Maxwell field, and the charge density is proportional to the chemical potential to the power of $1/(2-n)$.Comment: LaTeX, 16 pages, 5 figures, typos corrected, one reference added, version to appear in European Physical Journal

Prevalência de fatores de risco coronariano em praticantes de futebol recreacional

Verificar a prevalência dos fatores de risco coronariano em praticantes de futebol recreacional e comparar o risco coronariano de acordo com a faixa etária. Avaliaram- se 201 homens que praticavam futebol recreacionalmente, com idade média de 25.3 ± 6.0 anos. Todos responderam ao questionário RISKO, que é um questionário contendo 8 fatores de risco, sendo o risco coronariano representado pela soma dos escores obtidos nos 8 fatores de risco. O tratamento estatístico constou da exploração descritiva e da ANOVA oneway, com post hoc Tuckey, para comparação entre as faixas etárias. Adotou- se um nível de significância de p < 0.05. O escore médio de risco coronariano encontrado foi de 18.22 ± 3.49 pontos (12- 29 pontos), classificado como risco médio. Em relação às faixas etárias o risco coronariano médio obtido foi de: 16.58 ± 3.11 pontos para os indivíduos entre 18- 20 anos; 18.21 ± 3.08 pontos para aqueles entre 21- 30 anos; 20.58 ± 3.89 pontos para os sujeitos entre 31- 40 anos; e 21.00 ± 4.53 para aqueles com idade superior a 40 anos. Em relação a cada fator de risco isoladamente, as prevalências observadas, em ordem decrescente, foram: excesso de peso (44.78%), sedentarismo (38.31%), hipercolesterolemia (24.38%), tabagismo (17.41%), hereditariedade (12.94%) e hipertensão (8.46%). Os fatores de risco coronariano mais prevalentes nos praticantes de futebol recreacional foram o excesso de peso, o sedentarismo e a hipercolesterolemia, apresentando classificação de risco médio e crescimento com o aumento da idade, sobretudo após os 31 anos.Investigar la prevalencia de factores de riesgo coronario en jugadores recreacionales de fútbol y comparar el riesgo coronario según grupo de edad. Métodos: Se evaluaron 201 hombres que practicaban fútbol de forma recreativa, con edad media de 25.3 ± 6.0 años. Todos respondieron el cuestionario RISKO, que contiene 8 factores de riesgo y representándose el riesgo coronario por la suma de las puntuaciones obtenidas en los 8 factores. El análisis estadístico incluyó descripción de los datos y ANOVA one way, con post hoc Tukey, para comparaciones entre grupos de edad, con nivel de significación de p < 0.05. Se encontró una media de puntuación de riesgo coronario de 18.22 ± 3.49 puntos (12- 29 puntos), que se clasifica como riesgo medio. En cuanto a grupos de edad el riesgo coronario reportado fue de 16.58 ± 3.11 puntos para los individuos del grupo 18- 20 años, 18.21 ± 3.08 puntos para 21- 30 años, 20.58 ± 3.89 puntos para 31- 40 años, y 21.00 ± 4.53 para los mayores de 40 años. Para cada factor de riesgo, la prevalencia observada, en orden descendente, fue: sobrepeso (44.78%), inactividad física (38.31%), hipercolesterolemia (24.38%), tabaquismo (17.41%), herencia (12.94%) e hipertensión (8.46%). Los factores de riesgo coronario de mayor prevalencia en los jugadores recreacionales de fútbol fueron la inactividad física, el sobrepeso y la hipercolesterolemia, con una clasificación de riesgo medio y con aumento del riesgo con la edad, especialmente después de 31 años.To determine the prevalence of coronary risk factors in recreational soccer players and compare the coronary risk according to age. Methods: 201 men who practiced soccer recreationally eere evaluated, with a mean age of 25.26 ± 5.96 years. All individuals answered the questionnaire RISKO, which is a questionnaire containing eight risk factors. The coronary risk is represented by the sum of the scores obtained in the eight risk factors. Statistical analysis consisted of descriptive exploration and one way ANOVA with post hoc Tukey, to compare coronary risk between age groups. We adopted a significance level of p < 0.05. The mean coronary risk was 18.22 ± 3.49 points (12- 29 points), classified as medium risk. Regarding age groups the mean coronary risk obtained was: 16.58 ± 3.11 points for individuals between 18 and 20 years; 18.21 ± 3.08 points for those between 21 and 30 years, 20.58 ± 3.89 points for subjects between 31 and 40 years, and 21.00 ± 4.53 for those aged over 40 years. For each risk factor, the prevalence observed in descending order, was: overweight (44.78%), physical inactivity (38.31%), hypercholesterolemia (24.38%), smoking (17.41%), inheritance (12.94%) and hypertension (8.46%). The coronary risk factors more prevalent in recreational soccer players were overweight, physical inactivity and hypercholesterolemia, showing increased with increasing age, especially after 31 years

Measurement of the correlation between flow harmonics of different order in lead-lead collisions at √sNN = 2.76 TeV with the ATLAS detector

Correlations between the elliptic or triangular flow coefficients vm (m=2 or 3) and other flow harmonics vn (n=2 to 5) are measured using √sNN=2.76 TeV Pb+Pb collision data collected in 2010 by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 7 μb−1. The vm−vn correlations are measured in midrapidity as a function of centrality, and, for events within the same centrality interval, as a function of event ellipticity or triangularity defined in a forward rapidity region. For events within the same centrality interval, v3 is found to be anticorrelated with v2 and this anticorrelation is consistent with similar anticorrelations between the corresponding eccentricities, ε2 and ε3. However, it is observed that v4 increases strongly with v2, and v5 increases strongly with both v2 and v3. The trend and strength of the vm−vn correlations for n=4 and 5 are found to disagree with εm−εn correlations predicted by initial-geometry models. Instead, these correlations are found to be consistent with the combined effects of a linear contribution to vn and a nonlinear term that is a function of v22 or of v2v3, as predicted by hydrodynamic models. A simple two-component fit is used to separate these two contributions. The extracted linear and nonlinear contributions to v4 and v5 are found to be consistent with previously measured event-plane correlations

Search for W′→tb→qqbb decays in pp collisions at √s=8 TeV with the ATLAS detector

A search for a massive W′ gauge boson decaying to a top quark and a bottom quark is performed with the ATLAS detector in pp collisions at the LHC. The dataset was taken at a centre-of-mass energy of √s=8 TeV and corresponds to 20.3 fb−1 of integrated luminosity. This analysis is done in the hadronic decay mode of the top quark, where novel jet substructure techniques are used to identify jets from high-momentum top quarks. This allows for a search for high-mass W′ bosons in the range 1.5–3.0 TeV. b-tagging is used to identify jets originating from b-quarks. The data are consistent with Standard Model background-only expectations, and upper limits at 95 % confidence level are set on the W′→tb cross section times branching ratio ranging from 0.16pb to 0.33pb for left-handed W′ bosons, and ranging from 0.10pb to 0.21pb for W′ bosons with purely right-handed couplings. Upper limits at 95 % confidence level are set on the W′-boson coupling to tb as a function of the W′ mass using an effective field theory approach, which is independent of details of particular models predicting a W′boson

Search for vectorlike B quarks in events with one isolated lepton, missing transverse momentum, and jets at √s = 8 TeV with the ATLAS detector

A search has been performed for pair production of heavy vectorlike down-type (B) quarks. The analysis explores the lepton-plus-jets final state, characterized by events with one isolated charged lepton (electron or muon), significant missing transverse momentum, and multiple jets. One or more jets are required to be tagged as arising from b quarks, and at least one pair of jets must be tagged as arising from the hadronic decay of an electroweak boson. The analysis uses the full data sample of pp collisions recorded in 2012 by the ATLAS detector at the LHC, operating at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb −1 . No significant excess of events is observed above the expected background. Limits are set on vectorlike B production, as a function of the B branching ratios, assuming the allowable decay modes are B → Wt/Zb/Hb. In the chiral limit with a branching ratio of 100% for the decay B → Wt, the observed (expected) 95% C.L. lower limit on the vectorlike B mass is 810 GeV (760 GeV). In the case where the vectorlike B quark has branching ratio values corresponding to those of an SU(2) singlet state, the observed (expected) 95% C.L. lower limit on the vectorlike B mass is 640 GeV (505 GeV). The same analysis, when used to investigate pair production of a colored, charge 5/3 exotic fermion T 5/3 , with subsequent decay T 5/3 → Wt, sets an observed (expected) 95% C.L. lower limit on the T 5/3 mass of 840 GeV (780 GeV)

A search for prompt lepton-jets in pp collisions at root s=8 TeV with the ATLAS detector

A search is presented for a new, light boson with a mass of about 1 GeV and decaying promptly to jets of collimated electrons and/or muons (lepton-jets). The analysis is performed with 20.3 fb−1 of data collected by the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a centre-of-mass energy of 8 TeV. Events are required to contain at least two lepton-jets. This study finds no statistically significant deviation from predictions of the Standard Model and places 95% confidence-level upper limits on the contribution of new phenomena beyond the SM, incuding SUSY-portal and Higgs-portal models, on the number of events with lepton-jets.We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF, DNSRC and Lundbeck Foundation, Denmark; IN2P3-CNRS, CEADSM/IRFU, France; GNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZ. S, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, CANARIE, CRC, Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC, FP7, Horizon 2020 and Marie Sklodowska-Curie Actions, European Union; Investissements d'Avenir Labex and Idex, ANR, Region Auvergne and Fondation Partager le Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF; BSF, GIF and Minerva, Israel; BRF, Norway; the Royal Society and Leverhulme Trust, United Kingdom

Search for the production of single vector-like and excited quarks in the Wt final state in pp collisions at √s=8 TeV with the ATLAS detector

A search for vector-like quarks and excited quarks in events containing a top quark and a W boson in the final state is reported here. The search is based on 20.3 fb−1 of proton-proton collision data taken at the LHC at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector. Events with one or two leptons, and one, two or three jets are selected with the additional requirement that at least one jet contains a b-quark. Single-lepton events are also required to contain at least one large-radius jet from the hadronic decay of a high-pTW boson or a top quark. No significant excess over the expected background is observed and upper limits on the cross-section times branching ratio for different vector-like quark and excited-quark model masses are derived. For the excited-quark production and decay to Wt with unit couplings, quarks with masses below 1500 GeV are excluded and coupling-dependent limits are set

Measurement of jet charge in dijet events from √s = 8 TeV pp collisions with the ATLAS detector

The momentum-weighted sum of the charges of tracks associated to a jet is sensitive to the charge of the initiating quark or gluon. This paper presents a measurement of the distribution of momentum-weighted sums, called jet charge, in dijet events using 20.3 fb−¹ of data recorded with the ATLAS detector at √s = 8 TeV in pp collisions at the LHC. The jet charge distribution is unfolded to remove distortions from detector effects and the resulting particle-level distribution is compared with several models. The pT dependence of the jet charge distribution average and standard deviation are compared to predictions obtained with several leading-order and next-to-leading-order parton distribution functions. The data are also compared to different Monte Carlo simulations of QCD dijet production using various settings of the free parameters within these models. The chosen value of the strong coupling constant used to calculate gluon radiation is found to have a significant impact on the predicted jet charge. There is evidence for a pT dependence of the jet charge distribution for a given jet flavor. In agreement with perturbative QCD predictions, the data show that the average jet charge of quark-initiated jets decreases in magnitude as the energy of the jet increases