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1.
J Sci Food Agric ; 101(9): 3564-3574, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33280107

RESUMO

BACKGROUND: Granny Smith (GS) apple has low protein content and poor antimicrobial properties; hence it has been blended with Aloe vera (AV; high ascorbic acid, antimicrobial and antioxidant properties) and soybean flour (SF; rich in phenols, flavonoids, ascorbic acid, total antioxidant and protein) in different proportions to obtain fortified GS, i.e. GSAVSF. Moreover, GS being a perishable fruit, its moisture content should be reduced to enhance shelf life. Accordingly, this GSAVSF was osmotically pre-dehydrated and finally dried through energy-efficient quartz-halogen radiation (QHR) assisted vacuum-drying (QHRVD) to produce dried GSAVSF i.e. (DGSAVSF) under optimized conditions. RESULTS: The optimally dehydrated DGSAVSF product resulted in minimum moisture (4.85% w/w) and maximum protein (6.24 g kg-1 ) content. The application of osmotic dehydration and QHRVD afforded acceptable colour of DGSAVSF compared to GSAVSF (ΔEI * = 10.07 ± 0.21). A parametric drying model was formulated that corroborated well with Fick's equation. QHRVD rendered high moisture diffusivity (1.49 × 10-8 m2 s-1 ) and low activation energy (27.64 kJ mol-1  K-1 ). Appreciable quality improvements with respect to fresh GS concerning ascorbic acid (176.05%), total phenolic (579.07%), total flavonoid (333.33%) contents and 2,2'-diphenyl-1-picrylhydrazyl radical scavenging activity (446.71%) could be achieved. The product demonstrated satisfactory shelf life (1 × 104 CFU g-1 : aerobic mesophilic; 1 × 104 CFU g-1 : mould and yeast) and high rehydration ratio (4.25 ± 0.1). CONCLUSION: The enrichment of GS with AV and SF along with optimal drying protocols could provide a quality fortified DGSAVSF through an energy-proficient sustainable process. The highly nutritious product with suitable colour, microbial stability and rehydration ratio also satisfied a 9-point hedonic scale, thus confirming consumer acceptability. © 2020 Society of Chemical Industry.


Assuntos
Aloe/química , Dessecação/métodos , Farinha/análise , Conservação de Alimentos/métodos , Glycine max/química , Halogênios/química , Malus/química , Quartzo/química , Dessecação/instrumentação , Conservação de Alimentos/instrumentação , Alimentos Fortificados/análise , Frutas/química , Cinética , Vácuo
2.
Food Chem ; 310: 125825, 2020 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-31753689

RESUMO

Preconcentration of cobalt was carried out with deep eutectic solvent based liquid phase microextraction (DES-LPME) for trace determination by a slotted quartz tube (SQT) attached flame atomic absorption spectrometry (FAAS) system. Choline chloride and phenol in a 1:2 M ratio was used as a green solvent to extract cobalt from the aqueous sample solution. Key parameters influencing the extraction efficiency of cobalt were examined and optimized. Under the conditions optimized, the linear dynamic range was found between 5.0 and 50 µg L-1, and the limits of detection and quantification (LOD and LOQ) were calculated as 2.0 and 6.6 µg L-1, respectively. The detection power of the conventional FAAS was improved upon by 67 folds using the optimized DES-LPME-SQT-FAAS method. The developed analytical method was successfully applied for the determination of cobalt in linden tea samples and the recovery results obtained for different spiked concentrations (20, 30 and 40 µg L-1) were remarkable (≈100%).


Assuntos
Cobalto/análise , Análise de Alimentos/métodos , Microextração em Fase Líquida/métodos , Espectrofotometria Atômica/métodos , Cobalto/isolamento & purificação , Química Verde , Limite de Detecção , Quartzo/química , Solventes/química , Espectrofotometria Atômica/instrumentação , Chás de Ervas/análise , Tilia/química , Água/química
3.
Food Chem ; 297: 124947, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253290

RESUMO

Newly developed combination of magnetic cobalt particles based dispersive solid-phase microextraction (Co-MP-DSPME) and slotted quartz tube attached flame atomic absorption spectrometry (SQT-FAAS) was utilized to determine lead at trace levels in tea samples. Co-MPs' adsorbent properties were tested and validated for their selectiveness to lead. Only with a few and short extraction steps (i.e. adding MPs, mixing, decanting and eluting) analyte was extracted from sample solution rapidly and efficiently. Limit of detection (LOD) and limit of quantification (LOQ) for the developed method (Co-MP-DSPME-SQT-FAAS) were found to be 7.77 µg/L and 25.9 µg/L, respectively. Matrix matching strategy was performed and outcomes indicated that the developed method is applicable with the high percent recovery values of 110.1 ±â€¯4.5 and %102.9 ±â€¯4.2 for 100 and 300 µg/kg lead standard spiked black tea samples, respectively. The method was also applied to standard reference material to check the accuracy of the method.


Assuntos
Contaminação de Alimentos/análise , Chumbo/análise , Microextração em Fase Sólida/métodos , Espectrofotometria Atômica/métodos , Chá/química , Cobalto/química , Análise de Alimentos/métodos , Limite de Detecção , Quartzo/química , Sensibilidade e Especificidade , Microextração em Fase Sólida/instrumentação , Espectrofotometria Atômica/instrumentação
4.
J Oleo Sci ; 68(2): 121-129, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30651412

RESUMO

A Fourier transform infrared (FTIR) spectroscopy with infrared quartz cuvette (IQC) as spectral accessory method was developed to determine acid value (AV) of edible oils. The absorption peak at 5680 cm-1/5487 cm-1 ascribed to the C-H stretching band was a substitute for the peak of an internal standard. Partial least square (PLS) regression was used for AV calibration, and samples were validated by titrated method. Results showed dilution calibration was feasible for randomly dilution among 6-13:1 (CCl4: oils, v/v). PLS calibration was optimal by a spectral wavenumber (3603 cm-1-3250 cm-1) as the first derivative treatment. Correlation coefficient and root mean square error of calibration were 0.9967 and 0.135, respectively. Calibrated validation, blind sample validation and precision analysis presented a good correlation between IQC-FTIR and titrated methods. Based on the dilution calibration, randomly diluted oil samples can be employed by IQC-FTIR.


Assuntos
Óleos de Plantas/química , Quartzo/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Calibragem , Magnoliopsida/química , Oxirredução , Espectroscopia de Infravermelho com Transformada de Fourier/instrumentação
5.
Magn Reson Imaging ; 56: 86-89, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30336200

RESUMO

We have applied diffusion and relaxation Nuclear Magnetic Resonance experiments to investigate the translational and rotational mobility of adsorbents on quartz and calcite mineral surfaces. On both surfaces it was found that water is the dominant molecule. On the quartz surface the majority of water molecules have a relatively high degree of both rotational and translational mobility, while a minor fraction of water molecules, and all hydrocarbon molecules, have a significantly lower mobility. On the calcite surface the translational mobility is very low for all the adsorbed molecules, while there is a large diversity in rotational mobility, indicating that the hydrocarbon molecules are strongly attached to the surface, but that some part of each molecule still have a large degree of rotational mobility. Diffusion and relaxation experiments give a detailed description of both the molecular mobility of adsorbed species on these mineral surfaces, which leads to new insight with respect to aging processes on a molecular level.


Assuntos
Hidrocarbonetos/química , Espectroscopia de Ressonância Magnética/métodos , Minerais/química , Petróleo , Água/química , Adsorção , Difusão , Imageamento por Ressonância Magnética , Pós , Quartzo/química , Rotação , Software
6.
Environ Sci Pollut Res Int ; 25(33): 33298-33308, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30259319

RESUMO

Mixed media design is key factor that affects the operation of bioretention systems. In this study, four types of modifiers, namely, water treatment residual (WTR), green zeolite, fly ash, and coconut bran, were mixed with traditional bioretention soil (65% sand + 30% soil + 5% sawdust, by mass). Consequently, four kinds of modified media were obtained. Ten pilot-scale bioretention basins were constructed by setting different configurations. The steady infiltration rates of the modified packing bioretention systems were 3.25~62.78 times that of plant soil, which was 2.88~55.75 m/day. Results showed that the average concentration removal (ACR) of both mixed and layered fly ash and WTR were better than those of the other media, and the effects could reach over 61.92%. In the bioretention basins with WTR as the modifier, the treatment efficiency of nitrogen under the submerged zone height of 150 mm was relatively optimal, and ACR could reach 65.46%. Outflow total nitrogen (TN) load was most influenced by inflow load, and the correlation coefficient was above 0.765. Relative to the change of inflow concentration (IC), the change of recurrence interval (RI) and discharge ratio (DR) was more sensitive to TN load reduction. The reduction rate of TN load decreased by approximately 15% when the recurrence interval increased from 0.5 to 3 years. It decreased by approximately 12% when the discharge ratio increased from 10 to 20. This study will provide additional insights into the treatment performance of retrofit bioretention systems, and thus, can guide media and configuration design, effect evaluation, and related processes.


Assuntos
Nitrogênio/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Biodegradação Ambiental , Cinza de Carvão/química , Cocos/química , Desnitrificação , Projetos Piloto , Quartzo/química , Solo/química , Movimentos da Água , Zeolitas/química
7.
PLoS One ; 12(6): e0179029, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28582427

RESUMO

The Talbragar Fish Bed is one of Australia's most important Jurassic deposits for freshwater fishes, land plants and aquatic and terrestrial insects. The site has yielded many well preserved fossils, which has led to the formal description of numerous new species and higher taxa. The excellent preservation of many fossils has allowed detailed anatomical studies, e.g. of the early teleost fish Cavenderichthys talbragarensis (Woodward, 1895). Here we report on the fluorescent characteristics and mineral composition of a range of Talbragar fossils. Most specimens fluoresce under ultraviolet, blue and green light. Elemental and mineralogical analyses revealed that the Talbragar fossils consist predominantly of quartz (SiO2), a mineral that is likely to account for the observed fluorescence, with trace kaolinite (Al2Si2O5(OH)4) in some of the fish fossils. Rock matrices are predominantly composed of quartz and goethite (FeO(OH)). Closer inspection of a plant leaf (Pentoxylon australicum White, 1981) establishes fluorescence as a useful tool for the visualisation of anatomical details that are difficult to see under normal light conditions.


Assuntos
Peixes/anatomia & histologia , Fósseis , Insetos/anatomia & histologia , Folhas de Planta/anatomia & histologia , Plantas/anatomia & histologia , Animais , Austrália , Evolução Biológica , História Antiga , Insetos/química , Compostos de Ferro/análise , Compostos de Ferro/química , Compostos de Ferro/história , Caulim/análise , Caulim/química , Caulim/história , Medições Luminescentes , Metais Pesados/análise , Metais Pesados/química , Metais Pesados/história , Minerais/análise , Minerais/química , Minerais/história , Folhas de Planta/química , Plantas/química , Quartzo/análise , Quartzo/química , Quartzo/história , Espectrometria de Fluorescência
8.
Chemosphere ; 144: 1358-64, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26490430

RESUMO

Addition of granular materials to floating crude oil slicks can be effective in capturing and densifying the floating hydrophobic phase, which settles by gravity. Interaction of light hydrophobic liquids (LHL) with quartz sand was investigated in LHL-salt water systems. The LHLs studied were decane, tetradecane, hexadecane, benzene, toluene, ethylbenzene, m-xylene, and 2-cholorotoluene. Experiments were conducted with fine quartz sand (passing sieve No. 40 with openings 0.425 mm). Each LHL was dyed with few crystals of Sudan IV dye for ease of visual observation. A volume of 0.5 mL of each LHL was added to 100 mL salt water (34 g/L). Addition of one gram of quartz sand to the floating hydrophobic liquid layer resulted in formation of sand-encapsulated globules, which settled due to increased density. All LHLs (except for a few globules of decane) formed globules covered with fine sand particles that were heavy enough to settle by gravity. The encapsulated globules were stable and retained their shape upon settling. Polarity of hydrophobic liquids as the main factor of aggregation with minerals was found to be insufficient to explain LHL aggregation with sand. Contact angle measurements were made by submerging a large quartz crystal with the LHL drop on its surface into salt water. A positive correlation was observed between the wetting angle of LHL and the LHL volume captured (r = 0.75). The dependence of the globule density on globule radius was analyzed in relation to the coverage (%) of globule surface (LHL-salt water interface) by fine quartz particles.


Assuntos
Alcanos/isolamento & purificação , Derivados de Benzeno/isolamento & purificação , Petróleo/análise , Quartzo/química , Água do Mar/química , Poluentes Químicos da Água/isolamento & purificação , Interações Hidrofóbicas e Hidrofílicas , Modelos Teóricos , Tamanho da Partícula , Molhabilidade
9.
Mar Pollut Bull ; 91(1): 107-12, 2015 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-25555617

RESUMO

When granular materials are applied to hydrophobic liquids floating over another liquid (i.e., water), particles form aggregates which can be separated from the floating phase. This concept can be used for controlling mobility of floating oils, especially after oil spills near coastal areas. The objectives of this research were to characterize oil capture efficiency and determine effectiveness of particles for converting the floating phase to a heavier phase for effective separation. Experiments were conducted with South Louisiana crude oil contaminated salt water, limestone and quartz sand. Although the oil removal efficiency increased with the increasing amount of granular material applied, it did not increase linearly. About 50% of the floating oil was removed by aggregates, regardless of the material used, when granular material to floating oil ratio was about 1 g/g. The aggregates separated had higher amounts of oil content when smaller amounts of granular materials were added.


Assuntos
Carbonato de Cálcio/química , Recuperação e Remediação Ambiental/métodos , Poluição por Petróleo/prevenção & controle , Petróleo/análise , Quartzo/química , Interações Hidrofóbicas e Hidrofílicas , Louisiana
10.
Chemosphere ; 119: 242-249, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25016557

RESUMO

Molecular dynamic (MD) simulation was applied to evaluate the mobility, diffusivity and partitioning of SARA (saturates, aromatics, resins, asphaltenes) fractions of heavy crude oil on soil organic matter (SOM) coated quartz surface. Four types of SOM were investigated including Leonardite humic acid, Temple-Northeastern-Birmingham humic acid, Chelsea soil humic acid and Suwannee river fulvic acid. The SOM aggregation at oil-quartz interface decreased the adsorption of SARA on the quartz surface by 13-83%. Although the SOM tended to promote asphaltenes aggregation, the overall mobility of SARA was significantly greater on SOM-quartz complex than on pure quartz. Particularly, the diffusion coefficient of asphaltenes and resins increased by up to one-order of magnitude after SOM addition. The SOM increased the overall oil adsorption capacity but also mobilized SARA by driving them from the viscous oil phase and rigid quartz to the elastic SOM. This highlighted the potential of SOM addition for increasing the bioavailability of heavy crude oil without necessarily increasing the environmental risks. The MD simulation was demonstrated to be helpful for interpreting the role of SOM and the host oil phase for the adsorption and partitioning of SARA molecules, which is the key for developing more realistic remediation appraisal for heavy crude oil in soils.


Assuntos
Petróleo , Quartzo/química , Poluentes do Solo/química , Solo/química , Adsorção , Benzopiranos/química , Difusão , Substâncias Húmicas , Simulação de Dinâmica Molecular
11.
J Environ Sci (China) ; 26(2): 466-77, 2014 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-25076539

RESUMO

The choice of substrates with high phosphorus adsorption capacity is vital for sustainable phosphorus removal from waste water in constructed wetlands. In this study, four substrates were used: quartz sand, anthracite, shale and biological ceramsite. These substrate samples were characterized by Xray diffractometry and scanning electron microscopy studies for their mineral components (chemical components) and surface characteristics. The dynamic experimental results revealed the following ranking order for total phosphorus (TP) removal efficiency: anthracite > biological ceramsite > shale > quartz sand. The adsorptive removal capacities for TP using anthracite, biological ceramsite, shale and quartz sand were 85.87, 81.44, 59.65, and 55.98 mg/kg, respectively. Phosphorus desorption was also studied to analyze the substrates' adsorption efficiency in wastewater treatment as well as the substrates' ability to be reused for treatment. It was noted that the removal performance for the different forms of phosphorus was dependent on the nature of the substrate and the adsorption mechanism. A comparative analysis showed that the removal of particulate phosphorus was much easier using shale. Whereas anthracite had the highest soluble reactive phosphorus (SRP) adsorptive capacity, biological ceramsite had the highest dissolved organic phosphorus (DOP) removal capacity. Phosphorus removal by shale and biological ceramsite was mainly through chemical adsorption, precipitation or biological adsorption. On the other hand, phosphorus removal through physical adsorption (electrostatic attraction or ion exchange) was dominant in anthracite and quartz sand.


Assuntos
Fósforo/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Carvão Mineral , Materiais de Construção , Cinética , Modelos Químicos , Quartzo/química , Termodinâmica
12.
Acta Odontol Scand ; 72(8): 1010-6, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25139129

RESUMO

PURPOSE: Debonding at the post-adhesive interface is a major problem for quartz fiber posts. The objective of this study was to evaluate surface roughness and bond strength of quartz fiber posts after various surface treatments. MATERIALS AND METHODS: Sixty-six quartz fiber posts were randomly divided into six experimental groups (n = 11) including group C, untreated (control); group SB, sandblasted; group SC, silica coated; group HF, hydrofluoric acid-etched; group N, Nd:YAG laser irradiated; group E, Er:YAG laser irradiated. Surface roughness of the posts was measured before and after pre-treatment. They were then bonded to resin cement and tensile bond strength was determined in a universal testing machine. Furthermore, two-way ANOVA and post hoc comparison tests (α = 0.05) were performed on all data. RESULTS: The highest mean force value was observed in group SB and followed by group E. Tukey's HSD test showed that there was no statistical difference between group SB and group E (p = 0.673). The highest mean roughness value was observed in group SB and a significant difference was found between group SB and all other groups (p < 0.001). This study reveals that sandblasting and Er:YAG laser irradiation provided a significant increase in bond strength between quartz fiber posts and resin cement. CONCLUSIONS: Sandblasting or Er:YAG laser-irradiation of the surface of the quartz fiber post before cementation is recommended for increasing retention.


Assuntos
Colagem Dentária , Materiais Dentários/química , Técnica para Retentor Intrarradicular/instrumentação , Quartzo/química , Condicionamento Ácido do Dente/métodos , Óxido de Alumínio/química , Corrosão Dentária/métodos , Planejamento de Prótese Dentária , Análise do Estresse Dentário/instrumentação , Resinas Epóxi/química , Humanos , Ácido Fluorídrico/química , Lasers de Estado Sólido , Teste de Materiais , Microscopia Eletrônica de Varredura , Distribuição Aleatória , Cimentos de Resina/química , Dióxido de Silício/química , Estresse Mecânico , Propriedades de Superfície , Resistência à Tração
13.
Environ Sci Technol ; 48(14): 7766-73, 2014 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-24979668

RESUMO

A batch and cryogenic laser-induced time-resolved luminescence spectroscopy investigation of U(VI) adsorbed on quartz-chlorite mixtures with variable mass ratios have been performed under field-relevant uranium concentrations (5×10(-7) M and 5×10(-6) M) in pH 8.1 synthetic groundwater. The U(VI) adsorption Kd values steadily increased as the mass fraction of chlorite increased, indicating preferential sorption to chlorite. For all mineral mixtures, U(VI) adsorption Kd values were lower than that calculated from the assumption of component additivity possibly caused by surface modifications stemming from chlorite dissolution; The largest deviation occurred when the mass fractions of the two minerals were equal. U(VI) adsorbed on quartz and chlorite displayed characteristic individual luminescence spectra that were not affected by mineral mixing. The spectra of U(VI) adsorbed within the mixtures could be simulated by one surface U(VI) species on quartz and two on chlorite. The luminescence intensity decreased in a nonlinear manner as the adsorbed U(VI) concentration increased with increasing chlorite mass fraction-likely due to ill-defined luminescence quenching by both structural Fe/Cr in chlorite, and trace amounts of solubilized and reprecipitated Fe/Cr in the aqueous phase. However, the fractional spectral intensities of U(VI) adsorbed on quartz and chlorite followed the same trend of fractional adsorbed U(VI) concentration in each mineral phase with approximate linear correlations, offering a method to estimate of U(VI) concentration distribution between the mineral components with luminescence spectroscopy.


Assuntos
Cloretos/química , Minerais/química , Quartzo/química , Urânio/isolamento & purificação , Poluentes Radioativos da Água/isolamento & purificação , Adsorção , Água Subterrânea/química , Concentração de Íons de Hidrogênio , Luminescência , Análise Espectral , Fatores de Tempo
14.
Environ Sci Technol ; 48(12): 6569-77, 2014 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-24865372

RESUMO

Many aquifers contaminated by U(VI)-containing acidic plumes are composed predominantly of quartz-sand sediments. The F-Area of the Savannah River Site (SRS) in South Carolina (USA) is an example. To predict U(VI) mobility and natural attenuation, we conducted U(VI) adsorption experiments using the F-Area plume sediments and reference quartz, goethite, and kaolinite. The sediments are composed of ∼96% quartz-sand and 3-4% fine fractions of kaolinite and goethite. We developed a new humic acid adsorption method for determining the relative surface area abundances of goethite and kaolinite in the fine fractions. This method is expected to be applicable to many other binary mineral pairs, and allows successful application of the component additivity (CA) approach based surface complexation modeling (SCM) at the SRS F-Area and other similar aquifers. Our experimental results indicate that quartz has stronger U(VI) adsorption ability per unit surface area than goethite and kaolinite at pH ≤ 4.0. Our modeling results indicate that the binary (goethite/kaolinite) CA-SCM under-predicts U(VI) adsorption to the quartz-sand dominated sediments at pH ≤ 4.0. The new ternary (quartz/goethite/kaolinite) CA-SCM provides excellent predictions. The contributions of quartz-sand, kaolinite, and goethite to U(VI) adsorption and the potential influences of dissolved Al, Si, and Fe are also discussed.


Assuntos
Sedimentos Geológicos/química , Modelos Teóricos , Quartzo/química , Dióxido de Silício/química , Poluentes Radioativos do Solo/isolamento & purificação , Urânio/isolamento & purificação , Adsorção , Substâncias Húmicas , Compostos de Ferro/química , Caulim/química , Cinética , Minerais/química , South Carolina , Propriedades de Superfície , Temperatura , Poluentes Radioativos da Água/isolamento & purificação
15.
Nanotechnology ; 24(25): 255603, 2013 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-23727692

RESUMO

We report a new, novel and universal method to fabricate high-quality titanium dioxide (TiO2) nanofilms on different substrates by a solid phase growth process of ion implantation and subsequent annealing in oxygen atmosphere. Ti ions were implanted into fused silica, soda lime glass, Z-cut quartz, or (0001) α-sapphire by a metal vapor vacuum arc (MEVVA) ion source implanter to fluences of 0.75, 1.5 and 3 × 10(17) ions cm(-2) with a nominal accelerating voltage of 20 kV. To understand the influence of the annealing temperature, time, and substrate on the formation and phase transformation of the TiO2 nanofilms, the Ti-ion-implanted substrates were annealed in oxygen atmosphere from 500 to 1000 °C for 1-6 h. The formation of TiO2 nanofilms resulted from the slow out-diffusion of implanted Ti ions from the substrates which were then oxidized at the surfaces. The thickness and phase of the nanofilms can be tailored by controlling the implantation and annealing parameters. Since the TiO2 nanofilms are formed under high temperature and low growth rate, they show good crystallinity and antibacterial properties, with good film adhesion and stability, suggesting that the TiO2 nanofilms formed by this method have great potential in applications such as antibacterial and self-cleaning transparent glass.


Assuntos
Antibacterianos/química , Nanoestruturas/química , Titânio/química , Óxido de Alumínio/química , Antibacterianos/farmacologia , Catálise , Escherichia coli/efeitos dos fármacos , Infecções por Escherichia coli/tratamento farmacológico , Vidro/química , Temperatura Alta , Humanos , Azul de Metileno/isolamento & purificação , Nanoestruturas/ultraestrutura , Oxirredução , Oxigênio/química , Fotólise , Quartzo/química , Dióxido de Silício/química , Titânio/farmacologia
17.
Environ Sci Technol ; 46(3): 1565-71, 2012 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-22191402

RESUMO

The mobility of an acidic uranium waste plume in the F-Area of Savannah River Site is of great concern. In order to understand and predict uranium mobility, U(VI) adsorption experiments were performed as a function of pH using background F-Area aquifer sediments and reference goethite and kaolinite (major reactive phases of F-Area sediments), and a component-additivity (CA) based surface complexation model (SCM) was developed. Our experimental results indicate that the fine fractions (≤45 µm) in sediments control U(VI) adsorption due to their large surface area, although the quartz sands show a stronger adsorption ability per unit surface area than the fine fractions at pH < 5.0. Kaolinite is a more important sorbent for U(VI) at pH < 4.0, while goethite plays a major role at pH > 4.0. Our CA model combines an existing U(VI) SCM for goethite and a modified U(VI) SCM for kaolinite along with estimated relative surface area abundances of these component minerals. The modeling approach successfully predicts U(VI) adsorption behavior by the background F-Area sediments. The model suggests that exchange sites on kaolinite dominate U(VI) adsorption at pH < 4.0, goethite and kaolinite edge sites cocontribute to U(VI) adsorption at pH 4.0-6.0, and goethite dominates U(VI) adsorption at pH > 6.0.


Assuntos
Sedimentos Geológicos/química , Água Subterrânea/química , Modelos Químicos , Poluentes Radioativos/análise , Urânio/análise , Adsorção , Georgia , Concentração de Íons de Hidrogênio , Compostos de Ferro/química , Caulim/química , Minerais/química , Quartzo/química , Poluentes Radioativos/química , Urânio/química
18.
J Contam Hydrol ; 124(1-4): 57-67, 2011 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-21458880

RESUMO

Mineralogical studies of coatings on quartz grains and bulk sediments from an aquifer on Western Cape Cod, Massachusetts, USA were carried out using a variety of transmission electron microscopy (TEM) techniques. Previous studies demonstrated that coatings on quartz grains control the adsorption properties of these sediments. Samples for TEM characterization were made by a gentle mechanical grinding method and focused ion beam (FIB) milling. The former method can make abundant electron-transparent coating assemblages for comprehensive and quantitative X-ray analysis and the latter technique protects the coating texture from being destroyed. Characterization of the samples from both a pristine area and an area heavily impacted by wastewater discharge shows similar coating textures and chemical compositions. Major constituents of the coating include Al-substituted goethite and illite/chlorite clays. Goethite is aggregated into well-crystallized domains through oriented attachment resulting in increased porosity. Illite/chlorite clays with various chemical compositions were observed to be mixed with goethite aggregates and aligned sub-parallel to the associated quartz surface. The uniform spatial distribution of wastewater-derived phosphorus throughout the coating from the wastewater-contaminated site suggests that all of the coating constituents, including those adjacent to the quartz surface, are accessible to groundwater solutes. Both TEM characterization and chemical extraction results indicate there is a significantly greater amount of amorphous iron oxide in samples from wastewater discharge area compared to those from the pristine region, which might reflect the impact of redox cycling of iron under the wastewater-discharge area. Coating compositions are consistent with the moderate metal and oxy-metalloid adsorption capacities, low but significant cation exchange capacities, and control of iron(III) solubility by goethite observed in reactive transport experimental and modeling studies conducted at the site.


Assuntos
Sedimentos Geológicos/química , Quartzo/química , Dióxido de Silício/química , Poluentes Químicos da Água/química , Adsorção , Alumínio/química , Cloretos/química , Microanálise por Sonda Eletrônica , Compostos Férricos/química , Sedimentos Geológicos/análise , Compostos de Ferro/química , Massachusetts , Microscopia Eletrônica de Transmissão , Minerais/química , Fósforo/química , Silício/química
19.
J Prosthodont ; 20(3): 180-9, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21323785

RESUMO

PURPOSE: Unresolved controversy exists concerning the optimum restorative material to reinforce the thin-walled roots of endodontically treated teeth to improve their fracture resistance under occlusal load. This study evaluated the effectiveness of irrigant, dowel type, and root-reinforcing material on the fracture resistance of thin-walled endodontically treated teeth. MATERIALS AND METHODS: The root canals of 140 maxillary central incisors were enlarged and equally divided into seven groups according to the canal irrigant: no irrigant (control), 5% hydrogen peroxide, 5% sodium hypochlorite, a combination of 5% hydrogen peroxide and sodium hypochlorite, 15% ethylenediaminotetraacetic acid (EDTA), 10% lactic acid, or 20% lactic acid. Within each group, root canals were lined with composite resin (PermaFlo) or glass ionomer cement (Fuji II LC). A light-transmitting plastic dowel (Luminex) was used to create space for a quartz fiber-reinforced dowel (Aestheti Post) or a titanium alloy dowel (ParaPost XH) and to cure the restorative materials. Following dowel cementation and restoration of the roots with composite core, the teeth were submitted to fracture resistance testing, and data were analyzed with 3-way ANOVA followed by Ryan-Einot-Gabriel-Welsch Multiple Range Test (α= 0.05). RESULTS: Fracture resistance values were significantly different among irrigants, restorative materials, and their interaction (p < 0.001); however, the dowel type was not significantly different (p= 0.51). CONCLUSIONS: Thin-walled roots that had the smear layer removed with lactic acid and that were then lined with composite resin had a higher fracture resistance.


Assuntos
Resinas Compostas/química , Materiais Dentários/química , Cavidade Pulpar/fisiopatologia , Cimentos de Ionômeros de Vidro/química , Técnica para Retentor Intrarradicular/instrumentação , Irrigantes do Canal Radicular/uso terapêutico , Preparo de Canal Radicular/métodos , Fraturas dos Dentes/fisiopatologia , Dente não Vital/fisiopatologia , Fenômenos Biomecânicos , Ligas Dentárias/química , Análise do Estresse Dentário/instrumentação , Dentina/fisiopatologia , Ácido Edético/uso terapêutico , Guta-Percha/uso terapêutico , Humanos , Peróxido de Hidrogênio/uso terapêutico , Incisivo/fisiopatologia , Ácido Láctico/uso terapêutico , Teste de Materiais , Microscopia Eletrônica de Varredura , Quartzo/química , Resinas Sintéticas/química , Materiais Restauradores do Canal Radicular/uso terapêutico , Preparo de Canal Radicular/instrumentação , Hipoclorito de Sódio/uso terapêutico , Estresse Mecânico , Titânio/química
20.
J Dent ; 39(2): 171-9, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21115098

RESUMO

OBJECTIVES: The aim of this study was to evaluate the effects of surface treatments on bond strength of resin-core materials to three different types of fibre posts. METHODS: Prefabricated glass (FRC Postec, Ivoclar), quartz (DT light, Bisco) and individually formed glass (Everstick, Stick Tech) fibre posts with a coronal diameter of 1.5 mm were randomly divided into three groups according to the surface treatment performed. In Group 1 sandblasting with aluminium oxide particles (Rocatec Pre, 3M Espe) was followed by the application of a silane coupling agent. In Group 2, posts were immersed in 9.6% hydrofluoric acid gel for 60 s and silanized for 60 s. In Group 3, no surface treatment was performed and it served as control. The resin-core material (Biscore, Bisco) or resin composites (Admira, Voco) were applied to the tube in 2-mm thick increments and light-cured for 40 s using a halogen light curing unit. 1 mm thick discs (n=10/per group) were prepared for the micropush-out test. The discs were pushed out in a universal testing machine (Lloyd Instruments). Statistical significance was determined by a multifactorial analysis of variance followed by Tukey's post hoc test or independent t tests. RESULTS: ANOVA revealed that fibre posts and core materials had a significant effect on micropush-out bond strength values (p<0.001). The surface treatment with hydrofluric acid gel and sandblasting with aluminium oxide particles significantly enhanced bond strength values of fibre posts except Everstick post (p<0.05). CONCLUSION: Different surface treatments of fibre posts might affect the bonding capacity of resin-core systems to these posts.


Assuntos
Resinas Compostas/química , Colagem Dentária , Materiais Dentários/química , Vidro/química , Técnica para Retentor Intrarradicular/instrumentação , Condicionamento Ácido do Dente/métodos , Óxido de Alumínio/química , Lâmpadas de Polimerização Dentária/classificação , Corrosão Dentária/métodos , Análise do Estresse Dentário/instrumentação , Humanos , Ácido Fluorídrico/química , Teste de Materiais , Metacrilatos/química , Quartzo/química , Cimentos de Resina/química , Silanos/química , Siloxanas/química , Estresse Mecânico , Propriedades de Superfície , Temperatura , Fatores de Tempo , Água/química
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