Centro Universitario Of Volta Redonda

Volta Redonda, Brazil

Centro Universitario Of Volta Redonda

Volta Redonda, Brazil

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Cerqueira A.,Centro Universitario Of Volta Redonda | Rodrigues B.O.,Brazilian Center for Research in Physics (CBPF) | Bracco M.E.,State University of Rio de Janeiro
Journal of Physics: Conference Series | Year: 2015

In this work, we calculated the form factors and coupling constant of the vertex DsDK∗ using the QCD Sum Rules. The calculation of the form factors were performed for the cases D, Ds and K∗ off shell. Using the similarities between B and D mesons, we also calculated the form factors and coupling constant of the vertex BsBK∗. The coupling constants of the vertices BsBK∗ and DsDK∗ were compared with each other through the Heavy Hadron Chiral Perturbation Theory(HHChPT). We found a difference of 19% between BsBK∗ and DsDK∗ coupling constants using the HHChPT relation. © Published under licence by IOP Publishing Ltd.

Senna A.R.,Centro Universitario Of Volta Redonda | Mugnai R.,Federal University of Rio de Janeiro | Reddy Y.R.,Acharya Nagarjuna University
Zoologia | Year: 2013

A new amphipod species of Bogidiellidae Hertzog, 1936 is described and illustrated based on specimens collected from bore wells in the state of Andhra Pradesh, Southern India. The new species is closely related to those belonging to a group of Bogidiella species with inner rami of pleopods reduced or absent. Bogidiella totakura sp. nov. differs from all the other species in the group mainly by the shape, size and ornamentation on gnathopods and telson. This is the second Indian species of Bogidiella.

Hirayama D.,University of Sao Paulo | Hirayama D.,Centro Universitario Of Volta Redonda | Saron C.,University of Sao Paulo | Saron C.,Centro Universitario Of Volta Redonda
Industrial and Engineering Chemistry Research | Year: 2012

Microwave devulcanization has been studied as a method for elastomer recycling, which is based on the conversion of the reticulated and infusible structure of thermosetting rubbers in free polymeric chains able to be remolded by thermomechanical processing in recycling operations for the manufacture of other products. Elastomeric wastes are often irregularly discarded in nature, producing serious environmental damage, and their mechanical recycling is still considered a challenge. Thus, the development of alternatives for elastomer recycling is directly related to the actions of sustainable development and economic benefits to companies that pay to discard their wastes. The aim of this work is to evaluate the chemical modifications occurring in styrene-butadiene rubber (SBR) after microwave devulcanization. Compounds of SBR were vulcanized in the presence of vulcanization agents and variable amounts of carbon black, and then the rubbers were milled and submitted to microwave treatment. Only the SBR with high carbon black content shows some portion of devulcanized material. However, the rubber with lower content of carbon black which was devulcanized by microwave radiation shows an increase in cross-link density. The microwave treatment also causes cross-link breaks mainly in polysulfidic bonds as well as decomposition of chemical groups containing sulfur attached to the chemical structure of SBR, while the chemical bonds of higher energy such as monosulfidic bonds remain preserved. The improvement of the microwave method for rubber devulcanization represents a way for viable recycling of thermosetting rubbers. © 2012 American Chemical Society.

Azevedo e Silva P.R.S.,University of Sao Paulo | Baldan R.,University of Sao Paulo | Nunes C.A.,University of Sao Paulo | Coelho G.C.,University of Sao Paulo | And 2 more authors.
Materials Characterization | Year: 2012

MAR-M247 superalloy has excellent mechanical properties and good oxidation resistance at elevated temperatures. Niobium is an element known as γ' phase hardener in nickel-based superalloys, besides promoting homogeneous distribution of MC carbides. This work is inserted in a project that aims to evaluate the total replacement of tantalum by niobium atoms in MAR-M247 superalloy (10.2 Co, 10.2 W, 8.5Cr, 5.6 Al, 1.6 Nb, 1.4 Hf, 1.1 Ti, 0.7 Mo, 0.15 C, 0.06 Zr, 0.015 B, Ni balance-wt.%). Based on microstructural characterizations (SEM and FEG-SEM, both with EDS) of the as-cast material and heat-treated materials as well as utilizing Thermocalc simulations and experiments of differential thermal analysis (DTA), heat-treatment at 1260. °C for 8. h was chosen as an ideal condition for the solution of Nb-modified MAR-M247 superalloy. The hardness of as-cast and ideally solution treated materials was 390. ±. 14. HV and 415. ±. 6. HV, respectively. © 2012 Elsevier Inc.

Gabriel S.B.,Federal University of Rio de Janeiro | Gabriel S.B.,Centro Universitario Of Volta Redonda | De Almeida L.H.,Federal University of Rio de Janeiro | Nunes C.A.,University of Sao Paulo | And 2 more authors.
Materials Science and Engineering C | Year: 2013

Alloys for orthopaedic and dentistry applications require high mechanical strength and a low Young's modulus to avoid stress shielding. Metastable β titanium alloys appear to fulfil these requirements. This study investigated the correlation of phases precipitated in a Ti-12Mo-13Nb alloy with changes in hardness and the Young's modulus. The alloy was produced by arc melting under an argon atmosphere, after which, it was heat treated and cold forged. Two different routes of heat treatment were employed. Phase transformations were studied by employing X-ray diffraction and transmission electron microscopy. Property characterisation was based on Vickers microhardness tests and Young's modulus measurements. The highest ratio of microhardness to the Young's modulus was obtained using thermomechanical treatment, which consists of heating at 1000 C for 24 h, water quenching, cold forging to reduce 80% of the area, and ageing at 500 C for 24 h, where the final microstructure consisted of an α phase dispersed in a β matrix. The α phase appeared in two different forms: as fine lamellas (with 240 ± 100 nm length) and massive particles of 200-500 nm size. © 2013 Elsevier B.V.

De Almeida L.H.,Federal University of Rio de Janeiro | Bastos I.N.,State University of Rio de Janeiro | Santos I.D.,Instituto Tecnologico Vale Vale S.A. | Dutra A.J.B.,Federal University of Rio de Janeiro | And 3 more authors.
Journal of Alloys and Compounds | Year: 2014

Metastable β-Ti alloys combine low elastic modulus, excellent mechanical strength as well as good corrosion resistance. Wherever, the presence of nontoxic elements such as Nb, Ta, Mo, and Zr is an important advantage. With such properties this type alloy has been developed for orthopedic applications. Previous studies had shown that the Ti-12Mo-13Nb and Ti-10Mo-20Nb alloys aged at 500 °C presented higher hardness/elastic modulus ratio compared to commercially Ti-6Al-4V, indicating a great potential for biomedical application. However, additional studies are needed such as corrosion resistance. Therefore, the objective of this work was to analyze the electrochemical behavior of the Ti-12Mo-13Nb and Ti-10Mo-20Nb alloys aged at 500 °C/24 h and 500 °C/4 h, respectively. The electrochemical behavior was carried through by potentiodynamic polarization curves in Ringer's solutions to simulate the body fluid. The Ti-10Mo-20Nb alloy showed to be more resistant to corrosion when compared to Ti-12Mo-13Nb alloy and the commercially Ti-6Al-4V alloy. © 2014 Elsevier B.V. All rights reserved.

Bicalho L.A.,University of Sao Paulo | Baptista C.A.R.P.,University of Sao Paulo | Souza R.C.,Federal University of São Paulo | Santos C.,University of Sao Paulo | And 3 more authors.
Ceramics International | Year: 2013

This work investigates the characteristics of ZrO2 based ceramics (Y-TZP) doped with bioglass developed for dental prostheses. Powder mixtures composed of zirconia and 3 or 5 wt% of 3CaO·P2O 5-SiO2-MgO bioglass were sintered at 1300 °C for 2 h. The samples were characterized by their phase composition using X-Ray diffraction (XRD) and analysis of their microstructure by scanning electronic microscopy (SEM). Hardness and fracture toughness were evaluated using the Vickers indentation method, while bending strength and fatigue resistance were determined using the four-point bending testing. The mechanical properties indicate that the samples achieved high density under the applied sinter conditions. X-ray diffraction analysis revealed tetragonal ZrO2 as a major crystalline phase. Hardness, fracture toughness and bending strength of the sintered samples containing 3% or 5% bioglass were 1167and 1134 HV, 6.3 and 6.1 MPa m1/2 and 453 and 636 MPa, respectively. The fatigue results presented large scattering, which is attributed to a heterogeneous distribution of the secondary glassy phase in the zirconia matrix. The non-uniform dispersion of the glass may result in the formation of stress gradients, possibly responsible for crack initiation and their respective subcritical growth during fatigue testing. The fatigue limit determined was superior to stresses developed during mastication, turning its use in dental prostheses viable. Weibull statistics were applied on the fatigue results obtained at average stress levels of 255, 270 and 285 MPa in order to calculate the subcritical crack growth. A life expectancy of over 20 years under severe cyclic pressure conditions has been calculated. © 2012 Elsevier Ltd and Techna Group S.r.l.

Khan A.U.,University of Vienna | Nunes C.A.,University of Sao Paulo | C. Coelho G.,University of Sao Paulo | C. Coelho G.,Centro Universitario Of Volta Redonda | And 5 more authors.
Journal of Solid State Chemistry | Year: 2012

X-ray single crystal (XSC) and neutron powder diffraction data (NPD) were used to elucidate boron site preference for five ternary phases. Ta 3Si 1-xB x (x=0.112(4)) crystallizes with the Ti 3P-type (space group P4 2/n) with B-atoms sharing the 8g site with Si atoms. Ta 5Si 3-x (x=0.03(1); Cr 5B 3- type) crystallizes with space group I4/mcm, exhibiting a small amount of vacancies on the 4a site. Both, Ta 5(Si 1-xB x) 3, x=0.568(3), and Nb 5(Si 1-xB x) 3, x=0.59(2), are part of solid solutions of M 5Si 3 with Cr 5B 3-type into the ternary M-Si-B systems (M=Nb or Ta) with B replacing Si on the 8h site. The D8 8-phase in the Nb-Si-B system crystallizes with the Ti 5Ga 4-type revealing the formula Nb 5Si 3B 1-x (x=0.292(3)) with B partially filling the voids in the 2b site of the Mn 5Si 3 parent type. © 2012 Elsevier Inc.

Bimestre B.H.,University of Sao Paulo | Saron C.,University of Sao Paulo | Saron C.,Centro Universitario Of Volta Redonda
Materials Research | Year: 2012

Poly(ethylene tereftalate) (PET) is a polymer highly susceptible to the hydrolytic reactions that occur during applications and mainly in thermomechanical processing. These reactions lead to the decrease of molecular weight of the polymer, limiting the recycling number of the material. The reactive extrusion of the PET in presence of chain extenders is an alternative to recover mechanical and rheological properties that were depreciated by the polymer degradation. In this study, PET wastes from nonwoven fabrics production were extruded in presence of the secondary stabilizer Irgafos 126 (IRG) on variable concentrations. The results showed that Irgafos 126 increased molecular weight, decreased crystallinity and changed processing behavior of the PET, similarly to the effects produced by the well-known chain extender pyromellitic dianhydride (PMDA), showing that the secondary stabilizer Irgafos 126 can also act as a chain extender for the PET.

PubMed | Federal University of Fluminense, Centro Universitario Of Volta Redonda and Hospital Pro Cardiaco
Type: Journal Article | Journal: Arquivos brasileiros de cardiologia | Year: 2015

Recent studies have suggested that B-type Natriuretic Peptide (BNP) is an important predictor of ischemia and death in patients with suspected acute coronary syndrome. Increased levels of BNP are seen after episodes of myocardial ischemia and may be related to future adverse events.To determine the prognostic value of BNP for major cardiac events and to evaluate its association with ischemic myocardial perfusion scintigraphy (MPS).This study included retrospectively 125 patients admitted to the chest pain unit between 2002 and 2006, who had their BNP levels measured on admission and underwent CPM for risk stratification. BNP values were compared with the results of the MPS. The chi-square test was used for qualitative variables and the Student t test, for quantitative variables. Survival curves were adjusted using the Kaplan-Meier method and analyzed by using Cox regression. The significance level was 5%.The mean age was 63.9 13.8 years, and the male sex represented 51.2% of the sample. Ischemia was found in 44% of the MPS. The mean BNP level was higher in patients with ischemia compared to patients with non-ischemic MPS (188.3 208.7 versus 131.8 88.6; p = 0.003). A BNP level greater than 80 pg/mL was the strongest predictor of ischemia on MPS (sensitivity = 60%, specificity = 70%, accuracy = 66%, PPV = 61%, NPV = 70%), and could predict medium-term mortality (RR = 7.29, 95% CI: 0.90-58.6; p = 0.045) independently of the presence of ischemia.BNP levels are associated with ischemic MPS findings and adverse prognosis in patients presenting with acute chest pain to the emergency room, thus, providing important prognostic information for an unfavorable clinical outcome.

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