Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Dent Mater J ; 38(4): 547-554, 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31105163

RESUMO

This study evaluated shear bond strengths of two gingiva-colored layering resin composites to zirconia frameworks coated with feldspathic porcelain. Airborne-particle abraded porcelain-coated zirconia disks were treated with one of the following primers: Clearfil Photo Bond, Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB+Activator), Estenia Opaque Primer, Porcelain Liner M Liquid B (PLB), or no primer. A light-polymerizing (CER) or a photo/heat-polymerizing gingiva-colored indirect resin composite (EST) was bonded to the porcelain-coated zirconia disks in each group (n=11). Shear bond strength was measured. For both CER and EST specimens, bond strengths in CPB+Act group were significantly higher than those in the other groups. In all priming groups, bond strength was significantly higher for EST specimens than for CER specimens. Combined application of a phosphate monomer and silane enhanced initial bond strength of light-polymerized and photo/heat-polymerized gingiva-colored layering resin composites to porcelain-coated zirconia ceramics.


Assuntos
Colagem Dentária , Porcelana Dentária , Resinas Compostas , Gengiva , Teste de Materiais , Cimentos de Resina , Resistência ao Cisalhamento , Silanos , Propriedades de Superfície , Zircônio
2.
J Prosthodont Res ; 63(2): 140-144, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30446411

RESUMO

PURPOSE: To determine the effect of veneering material and framework design on fracture loads of implant-supported zirconia molar fixed dental prostheses (FDPs). METHODS: Sixty-six zirconia FDPs were manufactured onto two implants and classified as uniform thickness (UT) or anatomic design (AD). These framework design groups were then further divided into three subgroups (n=11): feldspathic porcelain-veneered zirconia FDPs (PVZ), indirect composite-veneered zirconia FDPs (IVZ), and metal-ceramic FDPs (MC). The FDPs were luted on the implant abutments and underwent fracture load testing. Significant differences were assessed by the Kruskal-Wallis test and Mann-Whitney U-test (α=0.05). RESULTS: For UT group, median fracture load was significantly higher for the IVZ (1.87kN) and MC (1.90kN) specimens than for the PVZ specimens (1.38kN) (p<0.05). In the AD group, the IVZ specimens had the highest median fracture load (4.10kN) of the three groups tested. The AD group exhibited higher median fracture loads than the UT group in all subgroups. CONCLUSIONS: Indirect composite appears to be a useful alternative to feldspathic porcelain as the layering material for implant-supported zirconia FDPs. The AD group had higher fracture loads than UT group. In addition, implant-supported indirect composite-veneered zirconia-based FDPs appear to be clinically feasible.


Assuntos
Implantes Dentários , Materiais Dentários , Planejamento de Prótese Dentária , Prótese Dentária Fixada por Implante , Análise do Estresse Dentário , Facetas Dentárias , Teste de Materiais , Dente Molar , Zircônio , Desenho Assistido por Computador , Porcelana Dentária , Humanos , Estresse Mecânico
3.
Forensic Sci Int ; 291: 23-38, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30125768

RESUMO

The Raman spectra of twenty-two chemical warfare agents (CWAs) were measured: eleven nerve agents and their precursor, five blister agents, three lachrymators, one choking agent, and one vomit agent, in liquid or solid state in colorless transparent vials were analyzed using a portable Raman spectrometer, Xantus-2 from Rigaku Corporation, equipped with selectable excitation lasers (785nm and 1064nm). With 785nm excitation, characteristic Raman spectra composed of many sharp peaks were observed for twenty CWAs, but nitrogen mustard 3 (HN3) and adamsite (DM) did not show particular peaks owing to broad and intense mountain-like baselines. With 1064nm excitation, Raman spectra similar to those with 785nm excitation were observed for the twenty CWAs, where the wavenumbers of the peak tops and comparative heights were similar to those with 785nm excitation. Characteristic Raman spectra with several sharp peaks could be even obtained for HN3 and DM with 1064nm excitation. The resolutions of the peaks in the spectral region below 1000cm-1 were higher with 785nm excitation than those with 1064nm excitation. In contrast, those above 1000cm-1 were almost compatible with both excitations. The heights of the peaks in the spectral region lower than 1000cm-1 were significantly higher with 785nm excitation than those with 1064nm excitation, but those higher than 1000cm-1 were almost compatible with both excitations. The CWAs could be discriminated based on the Raman spectra showing respective unique fingerprint patterns, even among six alkyl methylphosphonofluoridate congeners. Structural assignment to Raman bands observed in the spectra was also proposed. The influence of mixing with gasoline to match the quality of library search was examined for seven representative CWAs. With 785nm excitation, the hit quality index (HQI) of sarin was higher than 50% when the concentration (V/V) was higher than 25%. Meanwhile, with 1064nm excitation, HQI of sarin was higher than 50% even when the concentration was as low as 15%. With 785nm excitation, the HQI of L1 was higher than 50% when the concentration was higher than 80%. However, with 1064nm excitation, the HQI of L1 was higher than 50% when the concentration was 20%. Measurements with 1064nm excitation seemed superior in identifying CWAs in a gasoline mixture using the library search. The Raman spectra with 785nm and 1064nm excitation were compared in the measurement in the amber glass containers.


Assuntos
Substâncias para a Guerra Química/química , Lasers , Análise Espectral Raman/métodos , Ciências Forenses , Humanos , Estrutura Molecular , Análise Espectral Raman/instrumentação
4.
J Am Soc Mass Spectrom ; 27(7): 1219-26, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27098411

RESUMO

We propose detecting a fragment ion (Ph2As(+)) using counter-flow introduction atmospheric pressure chemical ionization ion trap mass spectrometry for sensitive air monitoring of chemical warfare vomiting agents diphenylchloroarsine (DA) and diphenylcyanoarsine (DC). The liquid sample containing of DA, DC, and bis(diphenylarsine)oxide (BDPAO) was heated in a dry air line, and the generated vapor was mixed into the humidified air flowing through the sampling line of a mass spectrometer. Humidity effect on the air monitoring was investigated by varying the humidity of the analyzed air sample. Evidence of the in-line conversion of DA and DC to diphenylarsine hydroxide (DPAH) and then BDPAO was obtained by comparing the chronograms of various ions from the beginning of heating. Multiple-stage mass spectrometry revealed that the protonated molecule (MH(+)) of DA, DC, DPAH, and BDPAO could produce Ph2As(+) through their in-source fragmentation. Among the signals of the ions that were investigated, the Ph2As(+) signal was the most intense and increased to reach a plateau with the increased air humidity, whereas the MH(+) signal of DA decreased. It was suggested that DA and DC were converted in-line into BDPAO, which was a major source of Ph2As(+). Graphical Abstract ᅟ.

5.
J Chromatogr A ; 1406: 279-90, 2015 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-26118803

RESUMO

A field-portable gas chromatograph-mass spectrometer (Hapsite ER system) was evaluated for the detection of chemical warfare agents (CWAs) in the vapor phase. The system consisted of Tri-Bed concentrator gas sampler (trapping time: 3s(-1)min), a nonpolar low thermal-mass capillary gas chromatography column capable of raising temperatures up to 200°C, a hydrophobic membrane-interfaced electron ionization quadrupole mass spectrometer evacuated by a non-evaporative getter pump for data acquisition, and a personal computer for data analysis. Sample vapors containing as little as 22µg sarin (GB), 100µg soman (GD), 210µg tabun (GA), 55µg cyclohexylsarin (GF), 4.8µg sulfur mustard, 390µg nitrogen mustard 1, 140µg of nitrogen mustard 2, 130µg nitrogen mustard 3, 120µg of 2-chloroacetophenone and 990µg of chloropicrin per cubic meter could be confirmed after Tri-Bed micro-concentration (for 1min) and automated AMDIS search within 12min. Using manual deconvolution by background subtraction of neighboring regions on the extracted ion chromatograms, the above-mentioned CWAs could be confirmed at lower concentration levels. The memory effects were also examined and we found that blister agents showed significantly more carry-over than nerve agents. Gasoline vapor was found to interfere with the detection of GB and GD, raising the concentration limits for confirmation in the presence of gasoline by both AMDIS search and manual deconvolution; however, GA and GF were not subject to interference by gasoline. Lewisite 1, and o-chlorobenzylidene malononitrile could also be confirmed by gas chromatography, but it was hard to quantify them. Vapors of phosgene, chlorine, and cyanogen chloride could be confirmed by direct mass spectrometric detection at concentration levels higher than 2, 140, and 10mg/m(3) respectively, by bypassing the micro-concentration trap and gas chromatographic separation.


Assuntos
Substâncias para a Guerra Química/análise , Técnicas de Química Analítica/instrumentação , Técnicas de Química Analítica/métodos , Cromatografia Gasosa-Espectrometria de Massas , Gases/química , Mecloretamina/análise , Gás de Mostarda/análise , Organofosfatos/análise , Sarina/análise , Soman/análise
6.
Anal Chem ; 87(2): 1314-22, 2015 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-25553788

RESUMO

A new method enabling sensitive real-time air monitoring of highly reactive chemical warfare agents, namely, mustard gas (HD) and Lewisite 1 (L1), by detecting ions of their in-line reaction products instead of intact agents, is proposed. The method is based on corona discharge-initiated atmospheric pressure chemical ionization coupled with ion trap tandem mass spectrometry (MS(n)) via counterflow ion introduction. Therefore, it allows for highly sensitive and specific real-time detection of a broad range of airborne compounds. In-line chemical reactions, ionization reactions, and ion fragmentations of these agents were investigated. Mustard gas is oxygenated in small quantity by reactive oxygen species generated in the corona discharge. With increasing air humidity, the MS(2) signal intensity of protonated molecules of mono-oxygenated HD decreases but exceeds that of dominantly existing intact HD. This result can be explained in view of proton affinity. Lewisite 1 is hydrolyzed and oxidized. As the humidity increases from zero, the signal of the final product, namely, didechlorinated, dihydroxylated, and mono-oxygenated L1, quickly increases and reaches a plateau, giving the highest MS(2) and MS(3) signals among those of L1 and its reaction products. The addition of minimal moisture gives the highest signal intensity, even under low humidity. The method was demonstrated to provide sufficient analytical performance to meet the requirements concerning hygienic management and counter-terrorism. It will be the first practical method, in view of sensitivity and specificity, for real-time air monitoring of HD and L1 without sample pretreatment.

7.
Artigo em Inglês | MEDLINE | ID: mdl-24211802

RESUMO

A portable mass spectrometer with an electron cyclotron resonance ion source (miniECRIS-MS) was developed. It was used for in situ monitoring of trace amounts of chemical warfare agents (CWAs) in atmospheric air. Instrumental construction and parameters were optimized to realize a fast response, high sensitivity, and a small body size. Three types of CWAs, i.e., phosgene, mustard gas, and hydrogen cyanide were examined to check if the mass spectrometer was able to detect characteristic elements and atomic groups. From the results, it was found that CWAs were effectively ionized in the miniECRIS-MS, and their specific signals could be discerned over the background signals of air. In phosgene, the signals of the 35Cl+ and 37Cl+ ions were clearly observed with high dose-response relationships in the parts-per-billion level, which could lead to the quantitative on-site analysis of CWAs. A parts-per-million level of mustard gas, which was far lower than its lethal dosage (LCt50), was successfully detected with a high signal-stability of the plasma ion source. It was also found that the chemical forms of CWAs ionized in the plasma, i.e., monoatomic ions, fragment ions, and molecular ions, could be detected, thereby enabling the effective identification of the target CWAs. Despite the disadvantages associated with miniaturization, the overall performance (sensitivity and response time) of the miniECRIS-MS in detecting CWAs exceeded those of sector-type ECRIS-MS, showing its potential for on-site detection in the future.


Assuntos
Ar/análise , Substâncias para a Guerra Química/análise , Cianeto de Hidrogênio/análise , Espectrometria de Massas/instrumentação , Gás de Mostarda/análise , Fosgênio/análise , Ciclotrons/instrumentação , Desenho de Equipamento , Sensibilidade e Especificidade
8.
J Am Chem Soc ; 127(29): 10400-5, 2005 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-16028953

RESUMO

Monolayer arrays of a series of meso-tetra-substituted porphyrins containing octadecyloxy and carboxyl (or pyridyl) groups were prepared on the highly oriented pyrolytic graphite surface at the liquid/solid interface. It was found by means of scanning tunneling microscopy that some porphyrins from this family assemble into various patterns. Specifically, slightly undulated rows are obtained from 5,10,15-tris(4-octadecyloxyphenyl)-20-(4-pyridyl)porphyrin. Meanwhile, rows with more pronounced kinks result from 5-(4-carboxyphenyl)-10,15,20-tris(4-octadecyloxyphenyl)porphyrin. The occurrence of the kinks is dependent on the arrangement of surrounding porphyrin molecules and is determined by intricate interplay between directional hydrogen-bonding interactions and packing forces, including molecule-molecule and molecule-substrate interactions. A double-layer structure is obtained from 5,10-bis(4-carboxyphenyl)-15,20-bis(4-octadecyloxyphenyl)porphyrin, probably through cyclic hydrogen bond formation. This work proves the concept that programmed surface patterning is possible by using porphyrins incorporating directional intermolecular interaction sites.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA