Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 3.726
Filtrar
1.
Braz Oral Res ; 34: e018, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32187304

RESUMO

The objective of this study was to evaluate the influence of hydrofluoric acid (HF) concentration, etching time, and application of phosphoric acid (PA) followed by neutralization with sodium bicarbonate on the bond strength between a feldspar ceramic and resin cement. Thus, 80 blocks (10 x 12 x 2 mm) of glass ceramic (VM - Vita Mark II - Vita Zahnfabrik) were made and randomly assigned to eight groups (n = 10) according to the factors: HF concentration (5 and 10%), etching time (60 and 120 s), and use of phosphoric acid (PA) (with and without). According to the experimental group, 37% PA (Condac, FGM) was applied after HF etching for 60s. Afterwards, samples were immersed in sodium bicarbonate for 1 min then in an ultrasonic bath in distilled water (5 min) for cleaning. After surface bonding treatment, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block. The samples were then stored in water (37ºC) for 90 days and submitted to the shear bond test (50 KgF, 1 mm/min). Failure analysis was performed by stereomicroscope and scanning electron microscopy. Data (MPa) were analyzed with 3-way ANOVA and Tukey's test. Only the factor "HF concentration" was significant (p = 0.02). Most failures were of cohesive in ceramic (40%) and mixed types (42.5%). The 10% HF resulted in higher shear bond strength value than the 5% HF. Surface cleaning with phosphoric acid followed by sodium bicarbonate and HF time (60 or 120 seconds) did not influence the resin bond strength to feldspar ceramic.


Assuntos
Silicatos de Alumínio/química , Colagem Dentária/métodos , Ácido Fluorídrico/química , Ácidos Fosfóricos/química , Compostos de Potássio/química , Análise de Variância , Porcelana Dentária/química , Teste de Materiais , Metacrilatos/química , Microscopia Eletrônica de Varredura , Valores de Referência , Reprodutibilidade dos Testes , Cimentos de Resina/química , Resistência ao Cisalhamento/efeitos dos fármacos , Silanos/química , Propriedades de Superfície , Fatores de Tempo
2.
Chemphyschem ; 21(3): 188-193, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31912640

RESUMO

Tip-enhanced Raman spectroscopy (TERS) is a promising technique for structural studies of biological systems and biomolecules, owing to its ability to provide a chemical fingerprint with sub-diffraction-limit spatial resolution. This application of TERS has thus far been limited, due to difficulties in generating high field enhancements while maintaining biocompatibility. The high sensitivity achievable through TERS arises from the excitation of a localized surface plasmon resonance in a noble metal atomic force microscope (AFM) tip, which in combination with a metallic surface can produce huge enhancements in the local optical field. However, metals have poor biocompatibility, potentially introducing difficulties in characterizing native structure and conformation in biomolecules, whereas biocompatible surfaces have weak optical field enhancements. Herein, a novel, biocompatible, highly enhancing surface is designed and fabricated based on few-monolayer mica flakes, mechanically exfoliated on a metal surface. These surfaces allow the formation of coupled plasmon enhancements for TERS imaging, while maintaining the biocompatibility and atomic flatness of the mica surface for high resolution AFM. The capability of these substrates for TERS is confirmed numerically and experimentally. We demonstrate up to five orders of magnitude improvement in TERS signals over conventional mica surfaces, expanding the sensitivity of TERS to a wide range of non-resonant biomolecules with weak Raman cross-sections. The increase in sensitivity obtained through this approach also enables the collection of nanoscale spectra with short integration times, improving hyperspectral mapping for these applications. These mica/metal surfaces therefore have the potential to revolutionize spectromicroscopy of complex, heterogeneous biological systems such as DNA and protein complexes.


Assuntos
Silicatos de Alumínio/química , Materiais Biocompatíveis/química , Ouro/química , Microscopia de Força Atômica/instrumentação , DNA/análise , Microscopia de Força Atômica/métodos , Análise Espectral Raman/métodos , Ressonância de Plasmônio de Superfície/métodos
3.
Chemosphere ; 245: 125643, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31877460

RESUMO

The cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) can exert inhibitory effects on micro-organisms responsible for their biodegradation. However, under environmentally relevant exposure scenarios the presence of and sorption to organic and inorganic matter can lead to significant reduction of inhibitory effects. In our studies we investigated silica gel and seven clays as inert sorbents to mitigate these inhibitory effects in a 28 day manometric respirometry biodegradation test. CTAB was not inhibitory to the used inoculum, but we did observe that seven out of eight sorbents increased maximum attainable biodegradation, and four out of eight decreased the lag phase. The strongly inhibitory effect of CPC was successfully mitigated by most sorbents, with five out of eight allowing >50% biodegradation within 28 days. Results further indicate that bioaccessibility of the sorbed fractions in the stirred manometric test systems was higher than in calmly shaken headspace test systems. Bioaccessibility might also be limited depending on characteristics of test chemical and sorbent type, with montmorillonite and bentonite apparently providing the lowest level of bioaccessibility with CPC. Clay sorbents can thus be used as environmentally relevant sorbents to mitigate potential inhibitory effects of test chemicals, but factors that impede bioaccessibility should be considered. In addition to apparently increased bioaccessibility due to stirring, the automated manometric respirometry test systems give valuable and highly cost-effective insights into lag phase and biodegradation kinetics; information that is especially relevant for test chemicals of gradual biodegradability.


Assuntos
Biodegradação Ambiental , Argila/química , Desinfetantes/química , Adsorção , Silicatos de Alumínio/química , Bentonita/química , Cátions , Cetilpiridínio , Tensoativos/química
4.
Chemosphere ; 240: 124838, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31542582

RESUMO

Modified sodium vermiculite, an iron-rich clay mineral, has been used in novel heterogeneous electrochemical Fenton-based treatments, so-called electro-Fenton (EF)-vermiculite, UVA photoelectro-Fenton (PEF)-vermiculite and solar photoelectro-Fenton (SPEF)-vermiculite. Tests were made with 130 mL of 0.150 mM Ponceau SS diazo dye in 0.050 M Na2SO4 at pH 3.0, in the presence of 1.0 g L-1 catalyst microparticles. The electrolyses were performed in an undivided cell with a boron-doped diamond anode (BDD) and air-diffusion cathode for H2O2 production, at 33.3 mA cm-2. Decolorization and mineralization were upgraded in the sequence: EF-vermiculite < PEF-vermiculite < SPEF-vermiculite. The removal of organics occurred by the combined action of OH oxidant formed at the BDD surface and homogeneous and heterogeneous Fenton's reactions, along with the photolysis caused by UVA light or sunlight. The homogeneous Fenton's reaction resulted from iron ions leaching, but the heterogeneous mechanism was prevalent. Comparative treatments by anodic oxidation in the presence of H2O2 and homogeneous EF were less effective than EF-vermiculite. The diazo dye absorbance decays agreed with a pseudo-first-order kinetics. SPEF-vermiculite was the most powerful process, yielding total decolorization and 84.1% mineralization after 300 and 360 min, respectively. The influence of catalyst concentration, current density and diazo dye content on PEF-vermiculite performance was examined. Oxalic, oxamic, malic, tartronic and acetic acids were detected as final short-linear carboxylic acids.


Assuntos
Silicatos de Alumínio/química , Compostos Azo/química , Técnicas Eletroquímicas/métodos , Catálise
5.
Braz Oral Res ; 33: e095, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31618283

RESUMO

This study evaluates the shear bond strength (SBS) of various resin cements to different ceramics. Composite resin cylinders of Z100 were fabricated and cemented to disks of feldspathic ceramic (Creation), leucite-reinforced feldspathic ceramic (Empress I), and densely sintered aluminum oxide ceramic (Procera AllCeram) using five resin cements: Panavia F (PAN), RelyX ARC (ARC), RelyX Unicem (RXU), RelyX Veneer, and Variolink II. SBS was measured after three days of water storage (baseline) and after artificial aging (180 days of water storage along with 12,000 thermal cycles). Failure mode of fractured specimens also was evaluated. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (α=0.05). RXU showed 1) the lowest baseline median SBS to feldspathic ceramic, which was not statistically different from PAN; 2) the lowest median baseline SBS to leucite-reinforced feldspathic and densely sintered aluminum-oxide ceramics. All cements performed similarly after aging, except for ARC (median 0.0 MPa) and PAN (median 16.2 MPa) in the densely sintered aluminum-oxide ceramic group. Resin cements perform differently when bonded to different ceramic substrates. While all test resin cements worked similarly in the long-term to feldspathic and leucite-reinforced feldspathic ceramics, only the MDP-containing resin cement provided durable bonds to densely sintered aluminum-oxide ceramic.


Assuntos
Cerâmica/química , Colagem Dentária/métodos , Cimentos de Resina/química , Alumínio/química , Silicatos de Alumínio/química , Teste de Materiais , Compostos de Potássio/química , Valores de Referência , Reprodutibilidade dos Testes , Resistência ao Cisalhamento , Estatísticas não Paramétricas , Propriedades de Superfície
6.
Chemosphere ; 226: 907-914, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31509920

RESUMO

The isomorphous substitution in the structure of phyllosilicate minerals plays an important role in regulating of surface chemical properties. In this work, iron muscovite nanoparticles with various Al species were successfully prepared to explore the structural Fe and Al species on the capture of Cd(II) from solutions. The synthesized nanocrystals have irregular shapes with diameters of 10-50 nm. The incorporation of Al(III) into the iron muscovite nanostructure has slight effect on the species of Fe and the crystal phase of the products. The degree of Al(III) substituting Si(IV) in the tetrahedral sheets of the minerals obviously increased with increasing of Al doping levels. For the samples with low Al doping levels (5% and 10%), the adsorption capacity of the iron muscovite nanoparticles for Cd(II) increased slightly. With increasing of Al doping ratio to 15%, the obtained iron muscovite nanoparticles exhibited a maximal uptake of 41.4 mg g-1 for Cd(II), which is about two times that of the undoped samples (22.8 mg g-1). The solution pH had a slight effect on the Cd (II) capture at a wide pH range from 4 to 8. The adsorption of Cd(II) is very fast and reached a steady state within 5 min. Desorption results showed that the binding strength between Cd(II) and iron muscovite nanoparticles was obviously enhanced by incorporation of Al at a high level. The ion exchange and surface complexation are principal mechanisms in the Cd(II) capture by the iron muscovite nanomaterials with various structural Al species.


Assuntos
Silicatos de Alumínio/química , Alumínio/química , Cádmio/isolamento & purificação , Ferro/química , Nanopartículas/química , Adsorção , Cádmio/química , Concentração de Íons de Hidrogênio , Propriedades de Superfície
7.
Environ Sci Pollut Res Int ; 26(27): 28294-28308, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31368068

RESUMO

Stable Hg(II)-containing flue gas has been successfully simulated by the plasma oxidation of Hg(0), and an effective solution for Hg(0) mercury fumes was obtained by combining the plasma with a ceramic nanomaterial. Characterization tests showed that the ceramic nanomaterial was mainly composed of silicon dioxide (SiO2) with other minor constituents, including potassium mica (KAl3Si3O11), iron magnesium silicate (Fe0.24Mg0.76SiO3) and dolomite (CaMg(CO3)2). The nanomaterial had many tube bank structures inside with diameters of approximately 8-10 nm. The maximum sorption capacity of Hg(II) was 5156 µg/g, and the nanomaterial can be regenerated at least five times. During the adsorption, chemical adsorption first occurred between Hg(II) and sulfydryl moieties, but these were quickly exhausted, and Hg(II) was then removed by surface complexation and wrapped into Fe moieties. The pseudo-first-order kinetic model and the Langmuir equation had the best fitting results for the kinetics and isotherms of adsorption. This work suggests that the ceramic nanomaterial can be used as an effective and recyclable adsorbent in the removal of gaseous Hg(II).


Assuntos
Carbonato de Cálcio/química , Ferro/química , Magnésio/química , Mercúrio/análise , Nanoestruturas/química , Dióxido de Silício/química , Adsorção , Silicatos de Alumínio/química , Cerâmica/química , Gases , Cinética , Mercúrio/química , Minerais/química
8.
Environ Sci Pollut Res Int ; 26(28): 28860-28870, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31385252

RESUMO

Nowadays, most of mineral-based adsorbents are powder form, which makes them inconvenient to collect and always easy to cause secondary pollution. In this work, an organic rectorite composite nanofiber membrane (SRt-PAN) was designed and prepared by electrospinning technique. The as-received composite nanofiber membranes were characterized by XRD and SEM analysis, proving the homodisperse and existence of SRt in PAN nanofiber membrane. A series of batch experiments for BPA adsorption were carried out to investigate the effect of different adsorption parameters, including initial concentration, pH, and temperature of pollutant solution. The influences of modifier dosage and adsorbent dosage on the adsorption performance were investigated as well. On the basis of the experiment results, the adsorption process could be well described by the pseudo-second-order model and the Langmuir isotherm. In addition, the thermodynamic parameters indicate that this adsorption process is exothermic and spontaneous. Moreover, compared with pure nanofiber membranes and organic rectorite powders, the resultant SRt-PAN adsorbents exhibited higher adsorption capacity, superior reusability, and adsorption stability. It is indicated that the hydrophobicity surface of organic rectorite should be the key factor to not only the intimate interfacial combination between the mineral and PAN, but also the enhancement of BPA adsorption capacity.


Assuntos
Silicatos de Alumínio/síntese química , Compostos Benzidrílicos/química , Minerais/síntese química , Nanofibras/química , Fenóis/química , Adsorção , Silicatos de Alumínio/química , Cinética , Minerais/química , Temperatura , Termodinâmica
9.
J Phys Chem Lett ; 10(15): 4192-4196, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31305079

RESUMO

We report the successful one-pot synthesis of adenosine mono-, di-, and triphosphate in the confined space of a mordenite zeolite. This is also the first report of ATP synthesized onto a porous mineral surface. The results revealed a plausible prebiotic route to ribonucleotides and highlighted the contribution of microporous minerals in the origins of life.


Assuntos
Difosfato de Adenosina/síntese química , Monofosfato de Adenosina/síntese química , Trifosfato de Adenosina/síntese química , Silicatos de Alumínio/química , Nanopartículas/química , Técnicas de Síntese em Fase Sólida/métodos , Zeolitas/química , Adenina/química , Organofosfatos/química , Origem da Vida , Porosidade , Ribose/química , Propriedades de Superfície , Termodinâmica , Fatores de Tempo
10.
Nature ; 571(7764): 251-256, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31292559

RESUMO

The ability of proteins and other macromolecules to interact with inorganic surfaces is essential to biological function. The proteins involved in these interactions are highly charged and often rich in carboxylic acid side chains1-5, but the structures of most protein-inorganic interfaces are unknown. We explored the possibility of systematically designing structured protein-mineral interfaces, guided by the example of ice-binding proteins, which present arrays of threonine residues (matched to the ice lattice) that order clathrate waters into an ice-like structure6. Here we design proteins displaying arrays of up to 54 carboxylate residues geometrically matched to the potassium ion (K+) sublattice on muscovite mica (001). At low K+ concentration, individual molecules bind independently to mica in the designed orientations, whereas at high K+ concentration, the designs form two-dimensional liquid-crystal phases, which accentuate the inherent structural bias in the muscovite lattice to produce protein arrays ordered over tens of millimetres. Incorporation of designed protein-protein interactions preserving the match between the proteins and the K+ lattice led to extended self-assembled structures on mica: designed end-to-end interactions produced micrometre-long single-protein-diameter wires and a designed trimeric interface yielded extensive honeycomb arrays. The nearest-neighbour distances in these hexagonal arrays could be set digitally between 7.5 and 15.9 nanometres with 2.1-nanometre selectivity by changing the number of repeat units in the monomer. These results demonstrate that protein-inorganic lattice interactions can be systematically programmed and set the stage for designing protein-inorganic hybrid materials.


Assuntos
Silicatos de Alumínio/química , Proteínas Imobilizadas/química , Biossíntese de Proteínas , Nanofios/química , Ligação Proteica
11.
Chemosphere ; 235: 670-678, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31276880

RESUMO

Extracellular DNA (eDNA) is widely present in soil, with potential ecological impacts. Metal cations are naturally present on the surface of soil clay minerals, although the adsorption mechanism of eDNA on clay minerals saturated with metal cations is still not fully understood. The research investigated the adsorption of eDNA, using salmon sperm DNA as a representative, on metal cation (Na+, Ca2+, and Fe3+)-saturated montmorillonites (Mt). Metal cation-saturated Mt have higher adsorption capacities for DNA. Compared with Mt (3500 mg⋅kg-1), the amounts of DNA adsorption on metal cation-saturated Mt (pH = 7.0) were increased by 0.74-5.38 times, and followed the descending order of Fe-Mt > Na-Mt > Ca-Mt > Mt. A temperature of 25 °C was found to be more suitable than 15 and 35 °C for DNA adsorption, while an increasing pH value (3.0-9.0) reduced DNA adsorption on Mt and metal cation-saturated Mt. Microscopic and spectroscopic analyses, together with a model computation technique, confirmed that metal cations saturated on the surface of Mt work like a "cation bridge" linking oxygen atoms in the phosphate groups of DNA and the negatively charged moieties of Mt, which were predominantly bound through electrostatic forces, thus, facilitating DNA adsorption at pH > 5. The results of this investigation provide valuable insight into eDNA adsorption on soil clay minerals and the transport and fate of eDNA in the natural soil environment.


Assuntos
Bentonita/química , DNA/química , Metais/química , Poluentes do Solo/química , Adsorção , Silicatos de Alumínio/química , Cátions/química , Argila , Minerais/química , Fosfatos , Sódio , Solo
12.
J Microbiol Biotechnol ; 29(7): 1071-1077, 2019 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-31337188

RESUMO

Natural gamma-decalactone (GDL) produced by biotransformation is an essential food additive with a peach-like aroma. However, the difficulty of effectively controlling the concentration of the substrate ricinoleic acid (RA) in water limits the biotransformation productivity, which is a bottleneck for industrialization. In this study, expanded vermiculite (E-V) was utilized as a carrier of RA to increase its distribution in the medium. E-V and three commonly used organic compounds were compared with respect to their effects on the biotransformation process, and the mechanism was revealed. Scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis indicated that RA was physically adsorbed onto the surface of and inside E-V instead of undergoing a chemical reaction, which increased the opportunity for interactions between microorganisms and the substrate. The highest concentration of GDL obtained in the medium with E-V was 6.2 g/l, which was 50% higher than that in the reference sample. In addition, the presence of E-V had no negative effect on the viability of the microorganisms. This study provides a new method for producing natural GDL through biotransformation on an industrial scale.


Assuntos
Silicatos de Alumínio/química , Biotransformação , Lactonas/metabolismo , Ácidos Ricinoleicos/química , Ácidos Ricinoleicos/metabolismo , Adsorção , Microbiologia Industrial , Viabilidade Microbiana , Yarrowia/metabolismo , Yarrowia/fisiologia
13.
ACS Appl Mater Interfaces ; 11(26): 23050-23064, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31180643

RESUMO

Alterations in the normal gastrointestinal microbial community caused by unhealthy diet, environmental factors, and antibiotic overuse may severely affect human health and well-being. Novel antimicrobial drug formulations targeting pathogenic microflora while not affecting or even supporting symbiotic microflora are urgently needed. Here we report fabrication of a novel antimicrobial nanocontainer based on halloysite nanotubes loaded with curcumin and protected with a dextrin outer layer (HNTs+Curc/DX) and its effective use to suppress the overgrowth of pathogenic bacteria in Caenorhabditis elegans nematodes. Nanocontainers have been obtained using vacuum-facilitated loading of hydrophobic curcumin into halloysite lumens. We have applied UV-vis and infrared spectroscopy, thermogravimetry and microscopy to characterize the HNTs+Curc/DX nanocontainers. In experiments in vitro we found that HNTs+Curc/DX effectively suppressed the growth of Serratia marcescens cells, whereas Escherichia coli bacteria were not affected. We applied HNTs+Curc/DX nanocontainers to alleviate the S. marcescens infection in C. elegans nematodes in vivo. The nematodes ingest HNTs+Curc/DX at 4-6 ng per worm, which results in improvement of the nematodes' fertility and life expectancy. Remarkably, treatment of S. marcescens-infected nematodes with HNTs+Curc/DX nanocontainers completely restored the longevity, demonstrating the enhanced bioavailability of hydrophobic curcumin. We believe that our results reported here open new avenues for fabrication of effective antimicrobial nanoformulations based on hydrophobic drugs and clay nanotubes.


Assuntos
Anti-Infecciosos/farmacologia , Caenorhabditis elegans/efeitos dos fármacos , Curcumina/farmacologia , Sistemas de Liberação de Medicamentos , Silicatos de Alumínio/química , Animais , Anti-Infecciosos/química , Anti-Infecciosos/farmacocinética , Caenorhabditis elegans/microbiologia , Argila/química , Curcumina/química , Dextrinas/química , Humanos , Nanotubos/química , Termogravimetria
14.
Int J Mol Sci ; 20(12)2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31234409

RESUMO

Crystallite aluminosilicates are inorganic microporous materials with well-defined pore-size and pore-structures, and have important industrial applications, including gas adsorption and separation, catalysis, etc. Crystallite aluminosilicates are commonly synthesized via hydrothermal processes, where the oligomerization of silicic acids is crucial. The mechanisms for the oligomerization of poly-silicic acids in neutral aqueous solution were systematically investigated by extensive first-principles-based calculations. We showed that oligomerization of poly-silicic acid molecules proceeds through the lateral attacking and simultaneously proton transfer from the approaching molecule for the formation of a 5-coordinated Si species as the transition state, resulting in the ejection of a water molecule from the formed poly-silicic acid. The barriers for this mechanism are in general more plausible than the conventional direct attacking of poly-silicic acid with reaction barriers in the range of 150-160 kJ/mol. The formation of linear or branched poly-silicic acids by intermolecular oligomerization is only slightly more plausible than the formation of cyclic poly-silicic acids via intramolecular oligomerization according to the reaction barriers (124.2-133.0 vs. 130.6-144.9 kJ/mol). The potential contributions of oligomer structures, such as the length of the linear oligomers, ring distortions and neighboring linear branches, etc., to the oligomerization were also investigated but found negligible. According to the small differences among the reaction barriers, we proposed that kinetic selectivity of the poly-silicic acids condensation would be weak in neutral aqueous solution and the formation of zeolite-like structures would be thermodynamics driven.


Assuntos
Ácido Silícico/química , Água/química , Zeolitas/química , Silicatos de Alumínio/química , Dimerização , Cinética , Modelos Moleculares , Soluções , Termodinâmica
15.
Appl Biochem Biotechnol ; 189(2): 437-447, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31049882

RESUMO

Depending on its purity, feldspar has a wide application in industry. Fungi play an important role in the feldspar purification. A bacterial leaching study of feldspar sample from Aydin, Turkey, was conducted to obtain a suitable raw material for industrial applications. XRD analyses indicated that albite (NaAlSi3O8) with minor amounts of orthoclase (KAlSi3O8), quartz (SiO2), muscovite (KAl2(Si3AlO10)(OH)2), rutile (TiO2), and small quantities of weathered clay minerals. This study evaluates bacterial leaching treatment to iron removal from feldspar using Aspergillus niger and Aspergillus ficuum to attain a product suitable for industrial uses. These funguses were tested for organic acid (oxalic and citric acid) production and leaching capabilities of feldspar. The leaching performances of two funguses were compared. Bacterial leaching experiments were performed in 500-mL Erlenmeyer flask at 30 ± 2 °C and 180 rpm agitation under aseptic conditions. In bacterial leaching experiments using A. niger and A. ficuum, 70.13% and 85.09% of the total iron oxides in the feldspar were removed, respectively. As a result, the final iron oxide concentrations in bacterial leaching experiments using A. niger and A. ficuum were 0.095% and 0.047%, respectively (at 5% w/v pulp density, temperature 30 ± 2 °C, A. niger 3 × 107 spores, A. ficuum 5 × 107 spores, and particle size < 63 µm). The use of fungi to remove iron from feldspar has the potential to be an effective method for upgrading the content and the commercial value of the feldspar. The experimental results of this study have provided significant opportunity to use biotechnological approach for producing the feldspar as a feed material for the high-quality ceramic industry.


Assuntos
Silicatos de Alumínio/química , Aspergillus niger/crescimento & desenvolvimento , Microbiologia Industrial , Compostos de Potássio/química
16.
Chemosphere ; 228: 513-520, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31051354

RESUMO

We explored the effects of gas emission by mixtures undergoing alkali-activation of municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite (the mixtures included dehydrated pyrophyllite, MSWIFA, 14 mol/L aqueous sodium hydroxide, and sodium silicate; curing proceed at 105 °C for 24 h). We measured the compressive strengths of the derived solid composites. The causes of gas emission, and the physical and chemical properties of products created under controlled gas emission, were investigated. Hydrogen was emitted after mixing MSWIFA and alkali. The compressive strength of products prepared when gas emission was complete was 2-3.4-fold greater than that of products prepared when gas emission was incomplete. X-ray micro-tomography and mercury intrusion porosimetry showed that products formed during complete gas emission tended to have smaller pores. X-ray diffraction and nuclear magnetic resonance (27Al and 29Si) indicated that the aluminum substitution levels in tectosilicate differed under such conditions, although the minerals were identical. Thus, complete gas emission after mixing improved ultimate products.


Assuntos
Silicatos de Alumínio/química , Cinza de Carvão/química , Incineração/métodos , Indústria de Petróleo e Gás/métodos , Resíduos Sólidos/análise , Carbono/química
17.
Braz Oral Res ; 33: e029, 2019 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-31038566

RESUMO

Orthodontic bonding systems are submitted to demineralization and remineralization dynamics that might compromise their surface smoothness, and favor biofilm aggregation and caries development. The aim of the present study was to evaluate the effects of a cariogenic challenge model (in vitro pH-cycling model) on the surface roughness and topography of 3 bonding materials: Transbond™ XT (XT), Transbond™ Plus Color Change (PLUS) and Fuji Ortho™ LC (FUJI), by means of Atomic Force Microscopy (AFM). Six specimens with standardized dimensions and surface smoothness were fabricated per group, and the materials were manipulated in accordance with the manufacturers' instructions. No polishing was necessary. AFM tests were performed before and after pH-cycling, taking 3 readouts per specimen. The roughness results (Ra) were obtained at nanometric levels (nm) and surface records were acquired in two- and three-dimensional images of height and lock-in phase of the material components. The surfaces of all groups analyzed in the study were morphologically altered, presenting images suggestive of matrix degradation and loss of matrix-load integrity. FUJI presented the greatest increase in surface roughness, followed by XT and PLUS, respectively (p≤0.001). Nevertheless, the roughness values found did not present sufficient degradation to harbor bacteria. The surface roughness of all tested materials was increased by pH-cycling. The use of materials capable of resisting degradation in the oral environment is recommended, in order to conserve their integrity and of the surrounding tissues.


Assuntos
Resinas Acrílicas/química , Silicatos de Alumínio/química , Cariogênicos/química , Colagem Dentária/métodos , Cimentos de Resina/química , Análise de Variância , Concentração de Íons de Hidrogênio , Imageamento Tridimensional , Teste de Materiais , Microscopia de Força Atômica , Valores de Referência , Estatísticas não Paramétricas , Propriedades de Superfície
18.
World J Gastroenterol ; 25(17): 2133-2143, 2019 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-31114139

RESUMO

BACKGROUND: Patients with neuroendocrine tumors (NETs) of the gastrointestinal tract suffer frequently from chronic diarrhea. A well characterized medical advice containing zeolite (Detoxsan® powder) was applied to patients suffered from therapy-refractory diarrhea either by its frequency or by watery stool, despite receiving standard pharmacotherapy according to the guidelines for carcinoid syndrome and comorbidities. Detoxsan® powder acts as an adsorbent and might reduce significantly symptoms of diarrhea in patients suffering from NETs. AIM: To overcome the therapy-refractory diarrhea of patients with NETs by the zeolite containing medical advice Detoxsan® powder. METHODS: A total of 20 patients (12 female and 8 male) suffering from diarrhea either by its frequency or from watery stool caused by NETs were included. In each patient, the diagnosis had been confirmed by histology and somatostatin receptors expression proven by positron emission tomography/computed tomography using Ga-68-labeled somatostatin analogs. All patients received standard-of-care pharmacotherapy and were additionally given Detoxsan® powder as an extemporaneous drug containing 90% natural Cuban zeolite and 10% magnesium aspartate. Recommended daily dosage ranges between 3 g once to three times per day. Each day dose and bowel movements were documented by the patients themselves in a pre-defined table. Additionally to the bowel movements quantitative determinations of serotonin, urea, creatinine and single ions were performed within the serum of the patients by commercially available equipment used as a matter of routine in the clinic. RESULTS: All patients enrolled in this pilot study did not only suffer from NETs, but also from comorbidities and treatment-resistant diarrhea. There was insufficient control of diarrhea, most probably due to the secretion of hormones like serotonin produced by the slowly growing and highly differentiated NETs. All patients only took Detoxsan® powder as an antidiarrheal drug. In general, response effects need several days to become perceptible and require an intake of Detoxsan® powder for an extended time period or intermittently, if persisting stabilization of bowel movements could not be achieved. A correlation between NET grade, part and size of bowel resection and functionality of the tumor could not be demonstrated. Therefore, diarrhea seemed to be based on the metabolic activity of the well-differentiated NETs, which eventually led to treatment resistance. In summary, 14 out of the 20 patients (70%) declared to be very content with using Detoxsan® powder and observed a significant reduction of diarrhea, while the effective dose and intake period that resulted in a symptom relief varied individually. CONCLUSION: Detoxsan® powder is able to reduce significantly symptoms of NET-related diarrhea in the majority of patients. The duration of taking Detoxsan® powder and its dosage vary individually.


Assuntos
Diarreia/complicações , Neoplasias Gastrointestinais/complicações , Tumores Neuroendócrinos/complicações , Zeolitas/uso terapêutico , Adsorção , Adulto , Idoso , Idoso de 80 Anos ou mais , Silicatos de Alumínio/química , Tumor Carcinoide/terapia , Comorbidade , Diarreia/terapia , Feminino , Radioisótopos de Gálio/química , Neoplasias Gastrointestinais/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Tumores Neuroendócrinos/fisiopatologia , Projetos Piloto , Pós , Somatostatina/química , Resultado do Tratamento , Zeolitas/química
19.
Colloids Surf B Biointerfaces ; 180: 457-465, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31100672

RESUMO

A simple method for preparing AgNPs/clay nanocomposites using an adsorption process without any reducing agent was developed in which saponite iron-rich clay was both the solid inorganic support and reducing agent. Silver adsorption by ion exchange of silver ions and saponite ferrous ions resulted in simultaneous silver reduction and silver nanoparticle formation. The maximum loading of silver was determined as 48 mg/g (4.8 mass %). Microscopy showed a homogeneous distribution of sphere-like silver nanoparticles which are composed from smaller crystallites in the form of twinned triangular prisms. The silver particle sizes ranged from 1 nm to 50 nm but predominantly between 8 and 10 nm. The optimum pH range for silver immobilization on saponite support was between 4 and 8. Characterization of the clay samples and synthesized AgNPs/saponite nanocomposites was performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), porosimetry (low temperature nitrogen adsorption-desorption) and zeta potential measurements. The antibacterial activities of raw saponite and AgNPs/saponite nanocomposite samples were tested against clinical relevant Gram-positive Staphylococcus aureus, Staphylococcus epidermidis, and Gram-negative Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis bacteria by the well diffusion method.


Assuntos
Antibacterianos/farmacologia , Nanopartículas Metálicas/química , Nanocompostos/química , Substâncias Redutoras/química , Prata/farmacologia , Adsorção , Silicatos de Alumínio/química , Concentração de Íons de Hidrogênio , Cinética , Nanopartículas Metálicas/ultraestrutura , Testes de Sensibilidade Microbiana , Nanocompostos/ultraestrutura , Espectroscopia de Infravermelho com Transformada de Fourier , Fatores de Tempo , Difração de Raios X
20.
Nanoscale ; 11(17): 8210-8218, 2019 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-30973561

RESUMO

Water in nanoscale-confined geometries has unique physicochemical properties in contrast to bulk water, and is believed to play important roles in biological processes although there is less direct information available in the literature. Here, we report the self-assembly behaviors of a neurodegenerative disease related peptide termed GAV-9 encapsulated in mica-graphene nanocapillaries interacting with water nanofilms condensed under ambient conditions, based on atomic force microscopy (AFM) imaging and molecular dynamics (MD) simulations. The results revealed that, upon increase in the humidity, the GAV-9 peptide monomers adsorbed the confined water molecules and transitioned to unexpected hydrogel-like structures. Our MD simulations also suggested that in the confined mica-graphene nanocapillaries, the GAV-9 peptide monomers would indeed form water-rich hydrogel structures instead of highly ordered nanofilaments. The interfacial water confined in the mica-graphene nanocapillary is found to be crucial for such a transition. Moreover, the distribution of confined water layers largely depended on the locations of the preformed peptide nanofilaments, and the peptide nanofilaments further assembled into nanosheets with the water layer increasing, but depolymerized to amorphous peptide assemblies with the water layer decreasing. The polymerization and depolymerization of the peptide nanofilaments could be controlled in a reversible manner. Our results have supplied a simplified model system to uncover the effects of the confined interfacial water on the biological process at the molecular level.


Assuntos
Silicatos de Alumínio/química , Grafite/química , Nanoestruturas/química , Oligopeptídeos/química , Água/química , Microscopia de Força Atômica , Simulação de Dinâmica Molecular , Oligopeptídeos/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA