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Institution

Rio de Janeiro State University

EducationRio de Janeiro, Brazil
About: Rio de Janeiro State University is a education organization based out in Rio de Janeiro, Brazil. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 16631 authors who have published 30919 publications receiving 465753 citations. The organization is also known as: UERJ & Rio de Janeiro State University.


Papers
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Journal ArticleDOI
TL;DR: It is shown that a reasonable density resolution can be achieved with a relatively small dose, which is comparable to or even lower than that of x-ray CT.
Abstract: Conformal proton radiation therapy requires accurate prediction of the Bragg peak position. Protons may be more suitable than conventional x rays for this task since the relative electron density distribution can be measured directly with proton computed tomography (CT). However, proton CT has its own limitations, which need to be carefully studied before this technique can be introduced into routine clinical practice. In this work, we have used analytical relationships as well as the Monte Carlo simulation tool GEANT4 to study the principal resolution limits of proton CT. The noise level observed in proton CT images of a cylindrical water phantom with embedded tissue-equivalent density inhomogeneities, which were generated based on GEANT4 simulations, compared well with predictions based on Tschalar's theory of energy loss straggling. The relationship between phantom thickness, initial energy, and the relative electron density resolution was systematically investigated to estimate the proton dose needed to obtain a given density resolution. We show that a reasonable density resolution can be achieved with a relatively small dose, which is comparable to or even lower than that of x-ray CT.

171 citations

Journal ArticleDOI
TL;DR: In this article, a coating of crystalline monetite oriented along the [112] axis was electrochemically deposited on titanium substrates and was subsequently converted to hydroxyapatite by immersion in alkaline solutions.
Abstract: Calcium phosphates have a wide range of pH stability, depending on their Ca/P ratio. Under physiological conditions (pH ≈7), the most stable calcium phosphate is hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 . Acidic calcium phosphates, like dicalcium phosphate, CaHPO 4 (monetite) and dicalcium phosphate dihydrate, CaHPO 4 ·2H 2 O (brushite), are thermodynamically unstable under pH values greater than 6–7 and undergo transformation into more stable calcium phosphates. It means that, when placed in vivo (pH ≈7), acidic calcium phosphates convert to hydroxyapatite. In the present study, a coating of crystalline monetite oriented along the [112] axis was electrochemically deposited on titanium substrates. This monetite coating was subsequently converted to hydroxyapatite by immersion in alkaline solutions. The result was a crystalline hydroxyapatite coating oriented along the [002] axis. Different alkaline solutions produced the same result. Studying the effect of immersion time on the transformation indicated that 4 h were required to complete the conversion from monetite to hydroxyapatite. The transformation occurred by a dissolution–reprecipitation mechanism, i.e. the monetite coating was continuously dissolved and reprecipitated as hydroxyapatite. This combined electrochemical deposition and chemical conversion process produced hydroxyapatite coatings with satisfactory adhesion to the substrate and a thickness between 10 and 30 μm.

170 citations

Journal ArticleDOI
TL;DR: In this paper, a search for a Higgs boson decaying into a Z boson and a photon was performed using proton-proton collision datasets recorded by the CMS detector at the LHC.

170 citations

Journal ArticleDOI
Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam, Federico Ambrogi  +2272 moreInstitutions (160)
TL;DR: A search for Higgs boson pair production using the combined results from four final states: bbγγ, bbττ, bbbb, and bbVV, where V represents a W or Z boson, is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions.
Abstract: This Letter describes a search for Higgs boson pair production using the combined results from four final states: bbγγ, bbττ, bbbb, and bbVV, where V represents a W or Z boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at s=13 TeV, corresponding to an integrated luminosity of 35.9 fb-1. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250–3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.

169 citations


Authors

Showing all 16818 results

NameH-indexPapersCitations
Hyun-Chul Kim1764076183227
Maria Elena Pol139141499240
Wagner Carvalho135139594184
Alberto Santoro1351576100629
Andre Sznajder134146498242
Luiz Mundim133141389792
Helio Nogima132127484368
D. De Jesus Damiao128116282707
Magdalena Malek12859867486
Sudha Ahuja127101675739
Helena Malbouisson125115182692
Jose Chinellato123111664267
Flavia De Almeida Dias12059059083
Gilvan Alves11982969382
C. De Oliveira Martins11988066744
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20241
202362
2022281
20212,251
20202,453
20192,072