RESUMEN
Electron paramagnetic resonance (EPR) signals generated by ionizing radiation in touch-screen glasses have been reported as useful for personal dosimetry in people accidently exposed to ionizing radiation. This article describes the effect of light exposure on EPR spectra of various glasses obtained from mobile phones. This effect can lead to significant inaccuracy of the radiation doses reconstructed by EPR. The EPR signals from samples unexposed and exposed to X-rays and/or to natural and artificial light were numerically separated into three model spectra: those due to background (BG), radiation-induced signal (RIS), and light-induced signal (LIS). Although prolonged exposures of mobile phones to UV light are rather implausible, the article indicates errors underestimating the actual radiation doses in dose reconstruction in glasses exposed to UV light even for low fluences equivalent to several minutes of sunshine, if one neglects the effects of light in applied dosimetric procedures. About 5 min of exposure to sunlight or to light from common UV lamps reduced the intensity of the dosimetric spectral components by 20-60% as compared to non-illuminated samples. This effect strongly limits the achievable accuracy of retrospective dosimetry using EPR in glasses from mobile phones, unless their exposure to light containing a UV component can be excluded or the light-induced reduction in intensity of the RIS can be quantitatively estimated. A method for determination of a correction factor accounting for the perturbing light effects is proposed on basis of the determined relation between the dosimetric signal and intensity of the light-induced signal.
Asunto(s)
Teléfono Celular , Vidrio/efectos de la radiación , Luz Solar , Rayos Ultravioleta , Espectroscopía de Resonancia por Spin del Electrón , Rayos XRESUMEN
PURPOSE: Radiation scattering from bone reconstruction materials can cause problems from prolonged healing to osteoradionecrosis. Glass fiber reinforced composite (FRC) has been introduced for bone reconstruction in craniofacial surgery but the effects during radiotherapy have not been previously studied. The purpose of this study was to compare the attenuation and back scatter caused by different reconstruction materials during radiotherapy, especially FRC with bioactive glass (BG) and titanium. METHODS: The effect of five different bone reconstruction materials on the surrounding tissue during radiotherapy was measured. The materials tested were titanium, glass FRC with and without BG, polyether ether ketone (PEEK) and bone. The samples were irradiated with 6 MV and 10 MV photon beams. Measurements of backscattering and dose changes behind the sample were made with radiochromic film and diamond detector dosimetry. RESULTS: An 18% dose enhancement was measured with a radiochromic film on the entrance side of irradiation for titanium with 6 MV energy while PEEK and FRC caused an enhancement of 10% and 4%, respectively. FRC-BG did not cause any measurable enhancement. The change in dose immediately behind the sample was also greatest with titanium (15% reduction) compared with the other materials (0-1% enhancement). The trend is similar with diamond detector measurements, titanium caused a dose enhancement of up to 4% with a 1 mm sample and a reduction of 8.5% with 6 MV energy whereas FRC, FRC-BG, PEEK or bone only caused a maximum dose reduction of 2.2%. CONCLUSIONS: Glass fiber reinforced composite causes less interaction with radiation than titanium during radiotherapy and could provide a better healing environment after bone reconstruction.
Asunto(s)
Huesos/efectos de la radiación , Anomalías Craneofaciales/cirugía , Vidrio/efectos de la radiación , Ensayo de Materiales/métodos , Fantasmas de Imagen , Procedimientos de Cirugía Plástica/métodos , Titanio/efectos de la radiación , Materiales Biocompatibles , Dosimetría por Película/instrumentación , Humanos , Fotones , Dispersión de RadiaciónRESUMEN
The treatment with high doses of ionizing radiation is prescribed for the terminal sterilization of many healthcare products. In order to check the product irradiation, it may be useful to develop suitable detection methods. The aim of this work was to verify the suitability of the thermoluminescence (TL) and electron paramagnetic resonance (EPR) techniques to reveal illegal omission of radiation sterilization in glass used for blood test tubes. In particular, this work reports the results of the analysis performed on two batches of glass tubes provided by the same manufacturer. The results indicated that both TL and EPR techniques could reveal the damage induced by high doses of ionizing radiation in the glass allowing the identification of the tubes which were irradiated at the manufacture stage. The study provided also some information about the chemical composition of the two-batch glass.
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Productos Biológicos/análisis , Espectroscopía de Resonancia por Spin del Electrón/métodos , Vidrio/química , Vidrio/efectos de la radiación , Radiometría/métodos , Dosimetría Termoluminiscente/métodos , Relación Dosis-Respuesta en la Radiación , Humanos , Mediciones Luminiscentes , Radiación IonizanteRESUMEN
In this work, we report some preliminary results regarding the analysis of electron spin resonance (ESR) response of soda-lime samples used for retrospective dosimetry. Six different soda-lime glass batches were evaluated after irradiation. We compared several dose reconstruction techniques: saturation method, subtraction method and g-effective, geff, approach. The differences were observed and discussed. ESR signal responses of soda-lime glass samples to different radiation doses for the triage application were investigated. Results confirmed that geff approach has potential for the identification and dosimetry of irradiated soda-lime glass samples using either additive dose method or only calibration curve.
Asunto(s)
Compuestos de Calcio/efectos de la radiación , Espectroscopía de Resonancia por Spin del Electrón/métodos , Espectroscopía de Resonancia por Spin del Electrón/estadística & datos numéricos , Vidrio/efectos de la radiación , Óxidos/efectos de la radiación , Radiometría/métodos , Hidróxido de Sodio/efectos de la radiación , Triaje/métodos , Compuestos de Calcio/química , Relación Dosis-Respuesta en la Radiación , Rayos gamma , Vidrio/química , Humanos , Óxidos/química , Hidróxido de Sodio/químicaRESUMEN
Storm water culverts are integral for U.S. public safety and welfare, and their mechanical failure can cause roadways to collapse. To repair these buried assets, ultraviolet (UV) light cured-in-place-pipes (CIPP) are being installed. Chemical emission and residual material left behind from the installation process was investigated in New York and Virginia, USA. Samples of an uncured resin tube and field-cured styrene-based resin CIPPs were collected and analyzed. Also collected were air and water samples before, during, and after installations. Chemicals were emitted into air because of the installation and curing processes. Particulates emitted into the air, water, and soil contained fiberglass, polymer, and contaminants, some of which are regulated by state-level water quality standards. The uncured resin tube contained more than 70 chemical compounds, and 19 were confirmed with analytical standards. Compounds included known and suspected carcinogens, endocrine disrupting compounds, hazardous air pollutants, and other compounds with little aquatic toxicity data available. Compounds (14 of 19 confirmed) were extracted from the newly installed CIPPs, and 11 were found in water samples. Aqueous styrene (2.31â¯mg/L), dibutyl phthalate (12.5⯵g/L), and phenol (16.7⯵g/L) levels exceeded the most stringent state water quality standards chosen in this study. Styrene was the only compound that was found to have exceed a 48â¯h aquatic toxicity threshold. Newly installed CIPPs contained a significant amount volatile material (1.0 to > 9.0â¯wt%). Recommendations provided can reduce chemical emission, as well as improve worksite and environmental protection practices. Recommended future research is also described.
Asunto(s)
Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente/métodos , Plásticos/química , Rayos Ultravioleta , Contaminantes Químicos del Agua/análisis , Agua/química , Vidrio/química , Vidrio/efectos de la radiación , New York , Plásticos/efectos de la radiación , Estireno/química , Estireno/efectos de la radiación , VirginiaRESUMEN
Two different spectra deconvolution methods have been compared on samples of Gorilla® Glass (GG) irradiated in the dose range 0-20 Gy and measured with X-band EPR. The first method used a matrix deconvolution procedure using sample-specific sets of reference signals. The second method used a 'universal' set of eight reference signals (due to five electron centers, two hole centers and a background) to fit EPR spectra from any GG sample. Dose-responses curves were constructed for each individual reference signal. These were then used to test reconstruction of a laboratory-administered dose of 2 Gy. For the matrix method, the values of the reconstructed and nominal doses were within ± 20% after averaging measurements from three aliquots of each sample. For the universal method, the most promising results were obtained with E1, E4 and H1 signals. The fitting failed for one sample, due to dominance of the background signal.
Asunto(s)
Calibración , Espectroscopía de Resonancia por Spin del Electrón/métodos , Espectroscopía de Resonancia por Spin del Electrón/estadística & datos numéricos , Vidrio/química , Vidrio/efectos de la radiación , Radiometría/métodos , Algoritmos , Relación Dosis-Respuesta en la Radiación , Rayos gamma , Humanos , Estándares de ReferenciaRESUMEN
Electron Paramagnetic Resonance (EPR) and Thermoluminescence (TL) signals have been studied in samples of Gorilla® Glass (GG) from different smartphones as well as some online stores and vendors. Background, radiation-induced and ultraviolet-induced signals were compared between the samples. Significant variability of both EPR and TL signals (in shape and intensity) was observed between samples from different screens as well as over the surface of the same screen, from the same phone. Both the EPR and TL background signals appear to be due to UV exposure during phone manufacture; some phones have higher EPR and TL signals around the edge of the screen, indicating more UV exposure at the edge than in the center. EPR and TL signals in the same GG samples appear correlated: they decayed over the same temperature region; and both hole- and electron-related EPR and TL signals were made up of stable and unstable components (at room temperature).
Asunto(s)
Espectroscopía de Resonancia por Spin del Electrón/métodos , Vidrio/química , Vidrio/efectos de la radiación , Radiometría/métodos , Dosimetría Termoluminiscente/métodos , Relación Dosis-Respuesta en la Radiación , Humanos , Mediciones Luminiscentes , Rayos UltravioletaRESUMEN
The aim of this study was to analyze the efficiency of experimental light-curing resin cements (ERCs) with a ternary photo-initiator system containing diphenyliodonium hexafluorphosphate (DPI) and different amines on retention of glass-fiber posts to dentin (GFP). ERCs formulations: a 1:1 mass ratio of 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenylpropane and triethyleneglycol dimethacrylate. Camphorquinone was used as initiator. Six experimental groups were established according to the amine used: [ethyl-4-(dimethylamino)benzoate-EDMAB or 2-(dimethylamino)ethyl methacrylate-DMAEMA] and the concentration of DPI (0, 0.5 mol%, 1 mol%). The resin cements Variolink II (dual- and light-cured versions) were used as commercial reference. Eighty recently extracted bovine incisors (n = 10) were selected for this study. The roots were prepared and the fiber posts were cemented with the resin cement specified for each experimental group. Specimens from coronal, middle, and apical thirds of the root were subjected to push-out bond strength test 24 hours after bonding. Data were subjected to split-plot ANOVA and the Tukey test (p = 0.05). ERCs containing DPI showed statistically significant higher bond strengths compared with ERCs without DPI. ERCs containing DPI were statistically similar to VARIOLINK II - dual-cured and superior to VARIOLINK II - light-cured (except for EDMAB - 1DPI in the medium third and DMAEMA - 1DPI in the coronal third). Different amines did not influence post retention. The apical root region showed the lowest bond strength for the groups EDAB-0DPI, DMAEMA-0DPI and VARIOLINK II light-cured. Light-cured ERCs containing DPI were efficient for GFP retention to radicular dentin, with similar behaviour to that of dual-curing commercial resin cement.
Asunto(s)
Compuestos de Bifenilo/química , Dentina/efectos de los fármacos , Curación por Luz de Adhesivos Dentales/métodos , Compuestos Onio/química , Fotoiniciadores Dentales/química , Técnica de Perno Muñón , Cementos de Resina/química , Ápice del Diente/efectos de los fármacos , Análisis de Varianza , Compuestos de Bifenilo/efectos de la radiación , Luces de Curación Dental , Dentina/efectos de la radiación , Vidrio/química , Vidrio/efectos de la radiación , Ensayo de Materiales , Metacrilatos/química , Metacrilatos/efectos de la radiación , Compuestos Onio/efectos de la radiación , Fotoiniciadores Dentales/efectos de la radiación , Polimerizacion , Cementos de Resina/efectos de la radiación , Factores de Tiempo , Ápice del Diente/efectos de la radiación , Fracturas de los Dientes , para-Aminobenzoatos/química , para-Aminobenzoatos/efectos de la radiaciónRESUMEN
STATEMENT OF PROBLEM: The use of photosensitizers in photodynamic therapy promotes intraradicular microbial reduction during nonsurgical endodontic therapy. However, studies are lacking on the consequences of the application of these agents on the mechanical properties of intraradicular dentin and on the bond strength of glass-fiber posts. PURPOSE: The purpose of this in vitro study was to evaluate the influence of photodynamic therapy on the bond strength of glass-fiber posts using a push-out test and, additionally, to measure the Martens hardness (MH) and elastic indentation modulus (Eit) of intraradicular dentin when different photosensitizers are used. MATERIAL AND METHODS: Eighty bovine teeth were used to simulate experimental endodontic treatments. Biomechanical instrumentation was performed for all root canals, and the teeth were distributed into 5 groups: control-deionized water; methylene blue 50 mg/L + red laser; methylene blue 100 mg/L + red laser; curcumin 500 mg/L + blue LED; and curcumin 1000 mg/L + blue LED. The MH and Eit of intraradicular dentin were measured using an ultramicrohardness tester under a load of 3 mN (n=8). The push-out bond strength of glass-fiber posts to dentin was measured using a universal testing machine (n=8). Mechanical properties and bond strength data were subjected to the Kruskal-Wallis test, ANOVA, and Fisher least significant difference test (α=.05). Images of representative specimens were obtained using a scanning electron microscope. RESULTS: The MH, Eit, and bond strength of intraradicular dentin were influenced by the photosensitizer used. In general, curcumin promoted lower mechanical properties values but higher bond strength values. CONCLUSIONS: Photosensitizers influenced the mechanical properties of intraradicular dentin and the bond strength of glass-fiber posts, and methylene blue at 50 mg/L had no marked effect on the mechanical properties of the dentin or the bond strength values.
Asunto(s)
Recubrimiento Dental Adhesivo , Dentina/efectos de la radiación , Vidrio/efectos de la radiación , Fotoquimioterapia/métodos , Técnica de Perno Muñón , Resistencia a la Tracción/efectos de la radiación , Análisis de Varianza , Animales , Bismuto , Hidróxido de Calcio , Bovinos , Resinas Compuestas , Recubrimiento Dental Adhesivo/métodos , Materiales Dentales/química , Materiales Dentales/efectos de la radiación , Cavidad Pulpar , Dentina/ultraestructura , Recubrimientos Dentinarios/química , Recubrimientos Dentinarios/efectos de la radiación , Ensayo de Materiales , Cementos de Resina/química , Estrés Mecánico , Diente no VitalRESUMEN
Ultrashort electric pulses (ns-ps) are useful in gaining understanding as to how pulsed electric fields act upon biological cells, but the electric field intensity to induce biological responses is typically higher than longer pulses and therefore a high voltage ultrashort pulse generator is required. To deliver 1 ns pulses with sufficient electric field but at a relatively low voltage, we used a glass-encapsulated tungsten wire triple-point electrode (TPE) at the interface among glass, tungsten wire, and water when it is immersed in water. A high electric field (2 MV/cm) can be created when pulses are applied. However, such a high electric field was found to cause bubble emission and temperature rise in the water near the electrode. They can be attributed to Joule heating near the electrode. Adherent cells on a cover slip treated by the combination of these stimuli showed two major effects: (1) cells in a crater (<100 µm from electrode) were fragmented and the debris was blown away. The principal mechanism for the damage is presumed to be shear forces due to bubble collapse; and (2) cells in the periphery of the crater were permeabilized, which was due to the combination of bubble movement and microstreaming as well as pulsed electric fields. These results show that ultrashort electric fields assisted by microbubbles can cause significant cell response and therefore a triple-point electrode is a useful ablation tool for applications that require submillimeter precision.
Asunto(s)
Permeabilidad de la Membrana Celular/efectos de la radiación , Membrana Celular/efectos de la radiación , Campos Electromagnéticos , Electrodos , Vidrio/efectos de la radiación , Microburbujas , Tungsteno/efectos de la radiaciónRESUMEN
CONTEXT: Light transmission (LT) into deeper areas of the dentin root is limited. AIM: The aim of this study is to perform a quantitative investigation of the radial transmission of light (LT) through different fiber posts and its influence on the Knoop hardness number (KHN) and bond strength (BS) of a dual-cure self-adhesive resin cement at 3 different depths. MATERIALS AND METHODS: Four types of fiber posts (2 translucent and 2 conventional) were used. LT and KHN analyses were performed in a specially designed matrix, which allowed measurements at 3 different depths. LT was measured using a volt-ampere meter while KHN tests were performed in a microhardness tester. For BS analysis, endodontically treated bovine roots were divided into 4 groups, each group receiving one type of post. After cementation, cross sections of the root were tested for resistance to displacement using a universal testing machine. STATISTICAL ANALYSIS USED:: Statistical analysis was performed by using this ANOVA and Tukey's test. RESULTS: For LT, translucent posts showed significantly higher values at all depths compared to the conventional ones. For all posts, LT decreased at the deeper depths. The KHN results showed no statistical differences among the different posts, regardless of depth. For BS, a translucent post showed the highest values, and comparative analyses between the different depths of posts also showed statistically significant differences while comparisons among the different depths of the same post showed no differences. CONCLUSIONS: LT depended on the type of post and on depth. The type of post did not significantly influence the cement KHN. A translucent post showed higher BS in pooled data.
Asunto(s)
Resinas Compuestas/uso terapéutico , Recubrimiento Dental Adhesivo/métodos , Técnica de Perno Muñón , Análisis del Estrés Dental , Vidrio/química , Vidrio/efectos de la radiación , Dureza , Humanos , Luz , Técnica de Perno Muñón/instrumentaciónRESUMEN
BACKGROUND: Glass fiber-reinforced posts have been preferred frequently because of some physical properties similar to the dentin, chemically bonding to dentin, biocompatibility, and esthetics. OBJECTIVE: This study aimed to evaluate the microleakage and bond strength of glass fiber posts cemented with various adhesive systems on laser-etched root canal walls. METHODS: Roots of 120 human mandibular premolars were divided into two groups for push-out bond strength test and the microleakage test (n = 60). Erbium-doped yttrium-aluminum-garnet (Er:YAG) laser etching of the root canal walls was carried out on half of the specimens in both test groups. The laser-treated and laser-nontreated groups were divided again into three subgroups (n = 10). Glass fiber posts (everStick Post) were luted using three different resin cements: total-etch (Variolink N), self-etch (Panavia F 2.0), and self-adhesive (Rely X Unicem). Three dentin discs were obtained from each root, and the bond strength of the glass fiber posts was measured by push-out tests. The dye penetration method was used to investigate coronal microleakage. In addition, surface treatments and the bonding interfaces were observed using scanning electron microscope. RESULTS: The highest bond strengths were observed for the total-etch and self-adhesive resin cement groups with laser etching (p < 0.05), and the lowest bond strength was obtained for the self-etch resin cement group (p < 0.05). There were no statistically significant differences in terms of microleakage (p > 0.05), except for the self-adhesive resin cement group (p < 0.05). CONCLUSIONS: Er:YAG laser etching enhances the bonding strength of glass fiber posts. In addition, laser etching can reduce microleakage of self-adhesive resin cement.
Asunto(s)
Recubrimiento Dental Adhesivo/métodos , Cavidad Pulpar/efectos de la radiación , Láseres de Estado Sólido/uso terapéutico , Terapia por Luz de Baja Intensidad/métodos , Técnica de Perno Muñón , Cementos de Resina/efectos de la radiación , Análisis del Estrés Dental , Vidrio/química , Vidrio/efectos de la radiación , Humanos , Cementos de Resina/química , Muestreo , Resistencia al Corte/efectos de la radiaciónRESUMEN
Abstract The aim of this study was to analyze the efficiency of experimental light-curing resin cements (ERCs) with a ternary photo-initiator system containing diphenyliodonium hexafluorphosphate (DPI) and different amines on retention of glass-fiber posts to dentin (GFP). ERCs formulations: a 1:1 mass ratio of 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenylpropane and triethyleneglycol dimethacrylate. Camphorquinone was used as initiator. Six experimental groups were established according to the amine used: [ethyl-4-(dimethylamino)benzoate-EDMAB or 2-(dimethylamino)ethyl methacrylate-DMAEMA] and the concentration of DPI (0, 0.5 mol%, 1 mol%). The resin cements Variolink II (dual- and light-cured versions) were used as commercial reference. Eighty recently extracted bovine incisors (n = 10) were selected for this study. The roots were prepared and the fiber posts were cemented with the resin cement specified for each experimental group. Specimens from coronal, middle, and apical thirds of the root were subjected to push-out bond strength test 24 hours after bonding. Data were subjected to split-plot ANOVA and the Tukey test (p = 0.05). ERCs containing DPI showed statistically significant higher bond strengths compared with ERCs without DPI. ERCs containing DPI were statistically similar to VARIOLINK II - dual-cured and superior to VARIOLINK II - light-cured (except for EDMAB - 1DPI in the medium third and DMAEMA - 1DPI in the coronal third). Different amines did not influence post retention. The apical root region showed the lowest bond strength for the groups EDAB-0DPI, DMAEMA-0DPI and VARIOLINK II light-cured. Light-cured ERCs containing DPI were efficient for GFP retention to radicular dentin, with similar behaviour to that of dual-curing commercial resin cement.
Asunto(s)
Compuestos Onio/química , Compuestos de Bifenilo/química , Técnica de Perno Muñón , Ápice del Diente/efectos de los fármacos , Cementos de Resina/química , Dentina/efectos de los fármacos , Curación por Luz de Adhesivos Dentales/métodos , Fotoiniciadores Dentales/química , Compuestos Onio/efectos de la radiación , Factores de Tiempo , Fracturas de los Dientes , Compuestos de Bifenilo/efectos de la radiación , Ensayo de Materiales , Análisis de Varianza , Ápice del Diente/efectos de la radiación , Cementos de Resina/efectos de la radiación , Dentina/efectos de la radiación , Luces de Curación Dental , Fotoiniciadores Dentales/efectos de la radiación , Polimerizacion , para-Aminobenzoatos/efectos de la radiación , para-Aminobenzoatos/química , Vidrio/efectos de la radiación , Vidrio/química , Metacrilatos/efectos de la radiación , Metacrilatos/químicaRESUMEN
OBJECTIVES: to determine the mode of light transmission and its impact on the polymerisation kinetic in modern bulk-fill resin-based composites (B-RBC). MATERIALS AND METHODS: Four low-viscosity methacrylate-based and one high-viscosity ormocer-based B-RBCs were considered. One material was available in three different shades that were all analyzed. Polymerization kinetic and light transmittance were assessed in 2 and 4mm specimen depths. Incident and transmitted irradiance and radiant exposure were measured in real-time on a laboratory-grade spectrometer. RESULTS: A progressive enhanced light transmittance during polymerisation was identified in all materials except for TetricEvoFlow BulkFill, which became progressively opaque in all shades. One-way ANOVA and multivariate analysis (α=0.05) were performed. The parameter material has a significant (p<0.001) effect on DC (ηP2=0.856) and light transmittance parameters (irradiance, ηP2=0.965; radiant exposure, ηP2=0.956); specimen depth influences only transmittance (ηP2=0.978; 0.980). DC variation in time was best described by an exponential sum function (R2>0.95), differentiating between the gel- and the glass-phase and revealing a faster initiation of polymerization and a slower transition into the glass-phase by lowering the filler volume. Depth retarded the transition into the glass-phase, but did not alter DC measured 300s post-irradiation. Moderate inverse correlation was identified among DC and filler volume% (-0.646) or filler weight% (-0.403), while no correlation among DC and light transmittance (p=0.141; 0.125). The maximal rate of carbon-carbon double bond conversion varied within the analyzed materials but was independent from specimen's depths. CONCLUSIONS: Light transmission changes during polymerization do not alter polymerization kinetics in modern B-RBCs. DC 300s post-irradiation was maintained with depth, while light was attenuated, the faster the more translucent the material was. DC and quality of curing cannot be related to light transmittance in B-RBCs.
Asunto(s)
Resinas Compuestas/química , Resinas Compuestas/efectos de la radiación , Luces de Curación Dental , Materiales Dentales/química , Materiales Dentales/efectos de la radiación , Ensayo de Materiales , Transición de Fase/efectos de la radiación , Polimerizacion/efectos de la radiación , Cementos Dentales/química , Cementos Dentales/efectos de la radiación , Vidrio/química , Vidrio/efectos de la radiación , Cinética , Curación por Luz de Adhesivos Dentales/métodos , Metacrilatos/química , Metacrilatos/efectos de la radiación , Análisis Multivariante , Cerámicas Modificadas Orgánicamente , Dosis de Radiación , Espectroscopía Infrarroja por Transformada de Fourier , Estrés Mecánico , Propiedades de Superficie , Factores de Tiempo , ViscosidadRESUMEN
Surface interactions with pollutants and photons are key factors that affect the applications of TiO2 in environmental remediation. In this study, the solubilizing agents dimethylsulfoxide and polyoxyethylene sorbitan monooleate, which act as photon competitors, had no effect on the photocatalytic activity of TiO2-C-Ag film in phenanthrene (PHE) removal. Fiberglass with TiO2-C-Ag coating removed 91.1 ± 5.2 and 99.7 ± 0.4% of PHE in treatments using UVA (365-465 nm) and UVC (254 nm) irradiation, respectively. The use of fiberglass as a support increased the superficial area, thus allowing PHE sorption. C and Ag, which are electrically active impurities in TiO2, enhanced its photocatalytic activity and thus the attraction of the pollutant to its surface. The use of high-frequency UV light (UVC) decreased the amount of carbon species deposited on the TiO2CAg film surface. X-ray photoelectron spectroscopy of the TiO2-C-Ag film revealed extensive oxidation of the carbon deposited on the film under UVC light and loss of electrons from Ag clusters by conversion of Ag0 to Ag3+.
Asunto(s)
Carbono/química , Vidrio/química , Fenantrenos/análisis , Plata/química , Titanio/química , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Adsorción , Carbono/efectos de la radiación , Catálisis , Dimetilsulfóxido/química , Vidrio/efectos de la radiación , Oxidación-Reducción , Espectroscopía de Fotoelectrones , Fotones , Polisorbatos/química , Plata/efectos de la radiación , Solubilidad , Soluciones , Propiedades de Superficie , Titanio/efectos de la radiación , Rayos UltravioletaRESUMEN
OBJECTIVE: The aim of this study was to evaluate the influence of laser irradiation on flexural strength, elastic modulus, and surface roughness and morphology of glass fiber posts (GFPs). BACKGROUND DATA: Laser treatment of GFPs has been introduced to improve its adhesion properties. MATERIALS AND METHODS: A total of 40 GFPs were divided into 4 groups according to the irradiation protocol: GC-no irradiation, GYAG-irradiation with erbium:yttrium-aluminum-garnet [Er:YAG], GCR-irradiation with erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG), and GDI-irradiation with diode laser. The GFP roughness and morphology were evaluated through laser confocal microscopy before and after surface treatment. Three-point bending flexural test measured flexural strength and elastic modulus. Data about elastic modulus and flexural strength were subjected to one-way ANOVA and Bonferroni test (p < 0.05). The effect of roughness was evaluated using the linear mixed effects model and Bonferroni test (p < 0.05). RESULTS: Laser treatment changed surface roughness in the groups GCR (p = 0.000) and GDI (p = 0.007). The mean flexural strength in GYAG (995.22 MPa) was similar to that in GC (980.48 MPa) (p = 1.000) but different from that in GCR (746.83 MPa) and that in GDI (691.34 MPa) (p = 0.000). No difference was found between the groups GCR and GDI (p = 0.86). For elastic modulus: GYAG (24.47 GPa) was similar to GC (25.92 GPa) (p = 1.000) but different from GCR (19.88 GPa) (p = 0.002) and GDI (17.20 GPa) (p = 0.000). CONCLUSIONS: The different types of lasers, especially Er,Cr:YSGG and 980 ηm diode, influenced the mechanical properties of GFPs.
Asunto(s)
Vidrio/efectos de la radiación , Rayos Láser , Técnica de Perno Muñón , Láseres de Estado Sólido , Ensayo de Materiales , Propiedades de SuperficieRESUMEN
In order to develop a high spatial resolution (micron level) thermal neutron detector, a detector assembly composed of cerium doped lithium glass microfibers, each with a diameter of 1 µm, is proposed, where the neutron absorption location is reconstructed from the observed charged particle products that result from neutron absorption. To suppress the cross talk of the scintillation light, each scintillating fiber is surrounded by air-filled glass capillaries with the same diameter as the fiber. This pattern is repeated to form a bulk microfiber detector. On one end, the surface of the detector is painted with a thin optical reflector to increase the light collection efficiency at the other end. Then the scintillation light emitted by any neutron interaction is transmitted to one end, magnified, and recorded by an intensified CCD camera. A simulation based on the Geant4 toolkit was developed to model this detector. All the relevant physics processes including neutron interaction, scintillation, and optical boundary behaviors are simulated. This simulation was first validated through measurements of neutron response from lithium glass cylinders. With good expected light collection, an algorithm based upon the features inherent to alpha and triton particle tracks is proposed to reconstruct the neutron reaction position in the glass fiber array. Given a 1 µm fiber diameter and 0.1mm detector thickness, the neutron spatial resolution is expected to reach σâ¼1 µm with a Gaussian fit in each lateral dimension. The detection efficiency was estimated to be 3.7% for a glass fiber assembly with thickness of 0.1mm. When the detector thickness increases from 0.1mm to 1mm, the position resolution is not expected to vary much, while the detection efficiency is expected to increase by about a factor of ten.
Asunto(s)
Diseño Asistido por Computadora , Modelos Estadísticos , Método de Montecarlo , Neutrones , Radiometría/instrumentación , Conteo por Cintilación/instrumentación , Algoritmos , Simulación por Computador , Diseño de Equipo , Análisis de Falla de Equipo , Vidrio/química , Vidrio/efectos de la radiación , Miniaturización , Dosis de Radiación , Reproducibilidad de los Resultados , Dispersión de Radiación , Sensibilidad y Especificidad , Programas InformáticosRESUMEN
In the welding process between similar or dissimilar materials, inserting an intermediate layer and pressure assistance are usually thought to be necessary. In this paper, the direct welding between alumina-silicate glass and metal (aluminum, copper, and steel), under exposure from 1 kHz femtosecond laser pulses without any auxiliary processes, is demonstrated. The micron/nanometer-sized metal particles induced by laser ablation were considered to act as the adhesive in the welding process. The welding parameters were optimized by varying the pulse energy and the translation velocity of the sample. The shear joining strength characterized by a shear force testing equipment was as high as 2.34 MPa. This direct bonding technology has potential for applications in medical devices, sensors, and photovoltaic devices.
Asunto(s)
Vidrio/química , Vidrio/efectos de la radiación , Rayos Láser , Metales/química , Metales/efectos de la radiación , Soldadura/métodos , Relación Dosis-Respuesta en la Radiación , Materiales Manufacturados/efectos de la radiación , Ensayo de Materiales , Nanopartículas/química , Nanopartículas/efectos de la radiación , Tamaño de la Partícula , Dosis de Radiación , Resistencia al Corte/efectos de la radiación , Estrés Mecánico , Propiedades de Superficie/efectos de la radiación , Resistencia a la Tracción/efectos de la radiaciónRESUMEN
Highly mineralized biological materials such as nacre (mother of pearl), tooth enamel or conch shell boast unique and attractive combinations of stiffness, strength and toughness. The structures of these biological materials and their associated mechanisms are now inspiring new types of advanced structural materials. However, despite significant efforts, no bottom up fabrication method could so far match biological materials in terms of microstructural organization and mechanical performance. Here we present a new 'top down' strategy to tackling this fabrication problem, which consists in carving weak interfaces within a brittle material using a laser engraving technique. We demonstrate the method by fabricating and testing borosilicate glasses containing nacre-like microstructures infiltrated with polyurethane. When deformed, these materials properly duplicate the mechanisms of natural nacre: combination of controlled sliding of the tablets, accompanied with geometric hardening, strain hardening and strain rate hardening. The nacre-like glass is composed of 93 volume % (vol%) glass, yet 700 times tougher and breaks at strains as high as 20%.
Asunto(s)
Materiales Biomiméticos/síntesis química , Vidrio/química , Vidrio/efectos de la radiación , Rayos Láser , Nácar/química , Módulo de Elasticidad/efectos de la radiación , Dureza/efectos de la radiación , Ensayo de Materiales , Propiedades de Superficie/efectos de la radiación , Resistencia a la Tracción/efectos de la radiación , Viscosidad/efectos de la radiaciónRESUMEN
In this work, we studied the effect of gamma irradiation on nano-bioactive glass (NBG) structure, bioactivity, drug loading efficiency, and drug release kinetic. Gamma irradiation was mainly introduced as a safe and cheap method to tailor the drug loading and release efficiencies. NBG was investigated before and after gamma irradiation with two doses 25 and 50 kGy. Vancomycin antibiotic was used as a drug model, and different kinetic models (first order, Higuchi, Hixson-Crowell, and Baker-Lonsdale models) were used to study the mechanism of drug release. It was found that G25 sample showed the lowest affinity for vancomycin adsorption, but it showed the highest release rate. Also, vancomycin was released from all samples by diffusion mechanism from spherically shaped carrier. On the other hand, the bioactivity of NBG was not altered by gamma irradiation; in contrary, newly formed apatite layers were more well-crystalline.