Silica Crystals Research Articles

Study on antibacterial active components from Viola yedoensis

Study on the antibacterial activity of Viola yedoensis and the antibacterial active compounds. The chemical compositions were isolated by means of solvent extraction, column chromatography on silica gel, sephadex LH-20 and crystallization. The antibacterial activities were tested by Neo-Sensitab disk-diffusion method, nephelometric analysis and plating method. One new compound (4) along with three known compounds were isolated from this plant for the first time and were identified as aesculetin (1), 6,7-dimethoxycoumarin (2), scopoletin (3) and 5-methoxy-7-hydroxymethylcoumarin (4), respectively. All the compounds showed antibacterial and antibactericidal activities at varying degree on Streptococcus Aureas, S. agalactiae, S. uberis, S. dysgalactiae, E. coli and Salmonella, of which 1 was most active with 0.031- 0.313 g x L(-1) of minimal inhibitory concentrations (MIC) and 0.313 - 0.625 g x L(-1) of minimal bactericidal concentrations (MBC). Viola yedoensis has a broad spectrum of antibacterial activity on animal pathogenic bacteria, and coumarins may be the main antibacterial activity ingredients.

Nano encapsulation of hematite into silica matrix as a red inclusion ceramic pigment

The hematite as a natural and non toxic red inorganic pigment has been known since prehistoric times but color shade of hematite becomes unstable with temperature and need to protect with a suitable matrix. The best red shades are obtained by the inclusion of hematite in silica matrixes. A co-precipitation method has been applied in order to improve the inclusion efficiency of hematite into silica crystals; iron sulfate was used as Fe precursor and precipitating agent was ammonia. Effects of the single flux agent (NaF and NaCl) and binary flux agent (NaF·NaCl), have been studied. Continuous changes in color were measured by comparing L*- a*- b* values of the heated samples. TEM analysis on heat treated powders shows some hematite single crystals that were occluded with silica crystals successfully. Due to its chemical and thermal stability, the hematite/silica pigment may be considered as a suitable red pigment for ceramic manufacturing by fast firing cycles.

Improved PCR-RFLP for the Detection of Diminazene Resistance in Trypanosoma congolense under Field Conditions Using Filter Papers for Sample Storage

Improved PCR-RFLP for the Detection of Diminazene Resistance in Trypanosoma congolense under Field Conditions Using Filter Papers for Sample Storage

A STUDY OF GLASS BEADS FROM THE HALLSTATT C–D FROM SOUTHWESTERN POLAND: IMPLICATIONS FOR GLASS TECHNOLOGY AND PROVENANCE*

Eighty‐one samples taken from 68 glass beads found in southwestern Poland on sites of the Lusatian culture from the Hallstatt C and Hallstatt D subphases were analysed by EPMA. A subsample of 18 of these were additionally subjected to analysis by means of LA–ICP–MS in order to validate the results obtained by EPMA. Some glass was made using mineral soda and some using plant ash rich in sodium. Both high‐magnesium soda–lime glass (HMG) and low‐magnesium soda–lime glass (LMG) were identified. A large number of samples are characterized by low MgO content and medium K2O content (LMMK glass), combined with low concentrations of CaO and high Fe2O3 and Al2O3. All the LMMK glass contains numerous silica crystals and inclusions composed of a number of elements (most frequently Cu, Co, Sb, As, Ag, Ni and Fe). The LMMK glass was presumably made in Europe during the Hallstatt C.

Highly ordered macroporous carbon spheres and their catalytic application for methanol oxidation

Highly ordered three dimensionally macroporous carbon spheres (3DMPCS) were successfully prepared against removable colloidal silica crystal bead templates by carbonization of glucose. The unique structural characteristics of the well-developed three dimensionally interconnected macropores were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption. The 3DMPCS have uniform large pore structures with size about 250nm. Pt nanoparticles were supported on the macroporous carbon spheres by two aqueous impregnation methods, and it was found that the 3DMPCS supported Pt exhibited high electrocatalytic activity for methanol oxidation.

Effect of Low-Saline Aqueous Solutions and pH on the Desorption of Crude Oil Fractions from Silica Surfaces

Desorption of interfacially active crude oil components was studied by exposing coated silica surfaces to aqueous solutions with different composition. The measurements were carried out for two North Sea crude oils as well as for fractions where the acidic and basic components were removed, respectively. One crude oil was acidic in nature, while the other was basic. Initially, the amount of adsorption onto the silica crystals was determined by a quartz crystal microbalance (QCM). Contact angle measurements showed small changes in wettability when the silica surfaces coated with components from the acidic oil were exposed to high-salinity solutions. On the other hand, considerable changes in wettability were seen when the surfaces coated with components from the basic crude oil were exposed to similar solutions. Consequently, significant desorption occurred in the latter case. Subsequent desorption was followed by QCM for both cases upon exposing the surfaces to low-salinity solutions. Generally, the acidi...

Silica Crystals and Aluminum Salts Regulate the Production of Prostaglandin in Macrophages via NALP3 Inflammasome-Independent Mechanisms

Particulates such as silica crystal (silica) and aluminum salts (alum) activate the inflammasome and induce the secretion of proinflammatory cytokines in macrophages. These particulates also induce the production of immunoglobulin E via a T helper 2 (Th2) cell-associated mechanism. However, the mechanism involved in the induction of type 2 immunity has not been elucidated. Here, we showed that silica and alum induced lipopolysaccharide-primed macrophages to produce the lipid mediator prostaglandin E₂ (PGE₂) and interleukin-1β (IL-1β). Macrophages deficient in the inflammasome components caspase 1, NALP3, and ASC revealed that PGE₂ production was independent of the NALP3 inflammasome. PGE₂ expression was markedly reduced in PGE synthase-deficient (Ptges⁻/⁻) macrophages, and Ptges⁻/⁻ mice displayed reduced antigen-specific serum IgE concentrations after immunization with alum or silica. Our results indicate that silica and alum regulate the production of PGE₂ and that the induction of PGE₂ by particulates controls the immune response in vivo.

Fabrication of SAPO-34 Crystals with Different Morphologies by Microwave Heating

The crystal size and shape of the silicoaluminophosphate molecular sieve SAPO-34 have been effectively controlled in the reaction system of Al2O3–P2O5–SiO2–TEAOH–H2O under microwave radiations. Nano sheet-like SAPO-34 crystals are obtained when using colloidal silica as the silica source. When TEOS is used as the source of silica, homogeneous SAPO-34 crystals with a particle size of about 100 nm are formed, and the morphology of the crystals changes from uniform nano particles (~100 nm) to microspheres (~1.5 μm) by varying the H2O/Al2O3 molar ratio. To further investigate the morphology control of SAPO-34, the synthetic factors, such as the silica source, water content, crystallization time and aging time have been studied in detail.

Production of rice husk ash for use in concrete as a supplementary cementitious material

Rice husk ash (RHA), rich in silica content, can be produced from rice husk using appropriate combustion technique for use in concrete as a supplementary cementitious material. This paper discusses production process of RHA from rice husk and the quality of RHA produced using rudimentary furnace of the National University of Malaysia (UKM). Three combustion methods and two grinding methods were used to investigate physical characteristics and chemical aspects of RHA produced. Combustion temperature distribution of the furnace, ash particle size, silica crystallization phase and chemical content of the produced RHA were studied using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). From the investigation, it was found that combustion period, chilling duration, and grinding process and duration are important in obtaining RHA of standard fineness and quality. In addition, air ducts in the furnace are very useful in order to supply air for proper burning of rice husk.

Location of Alkali Ions and their Relevance to Crystallization of Low Silica X Zeolite

A novel method of intermediate addition of alkali ions is proposed to give phase selectivity of zeolite in crystallization stages. Location of alkali metal ions in formed zeolite A, low silica zeol...

High-temperature oxidation of MoSi2

Oxidation behavior of MoSi2 was investigated in air over the temperature range of 1400–1700 °C. Spallation of the SiO2 scale did not occur at any temperature, and Mo5Si3 formation did not happen below 1700 °C. A change in the rate-controlling mechanism was detected within the temperature range of this study. Activation energy for oxidation of MoSi2 at high temperatures was determined to be 204 kJ/mol. This value is less than the value of activation energy for oxidation of MoSi2 controlled by diffusion of O2 through amorphous SiO2 layer reported at lower temperatures. The decrease in activation energy is attributed to the increased degree of crystallization of amorphous silica to β-cristobalite at high temperatures resulting in enhanced O2 diffusion through SiO 4 −4 tetrahedral structure.

衛生陶器上の釉薬―ガラス二層構造に及ぼすガラス組成の影響

The surface of a conventional sanitary ware was covered with the glaze that was a glassy phase containing silica and zircon crystals. Therefore, the surface of the glassy region was eroded selectively by using it for long time, which made a rough surface of a sanitary ware that causes adhesion of dirt on the surface. In this study, we investigated a double layer structure constituted of a conventional graze layer and a coating glass layer on the sanitary ware surface for improvement of durability and anti-contamination of the sanitary ware. We selected seven glasses constituted of SiO2-Al2O3-CaO-MgO-K2O-Na2O system for the coating glasses on the conventional glaze layer, and fabricated a double layer structure on a sanitary ware by firing. We also investigated the physical properties (glass transition temperature Tg, crystallization temperature Tc, liquidus temperature T1, and viscosity of the glass melts (η)) of the coating glass were measured. The microscopic observations of the cross-section at the interface between the graze layer and the coating glass layer showed three different mixing patterns as follows.(1) The graze layer and the coating glass layer were completely separated.(2) The graze layer and the coating glass layer were partially mixed.(3) The graze layer was partially exposed to the surface of the coating glass layer.From the results of the physical properties measurements of the coating glasses, it was found that the formation of double layer structure was controlled by the viscosity of glass melts and the thickness of the coating glass layer. Finally, we concluded that the accomplished double layer on the sanitary ware surface was suitable for improvement of durability and anti-contamination.

204 籾殻と炭素繊維端材に由来する複合材料の摩擦特性(循環型廃棄物処理技術(1))

The composites were fabricated from agricultural waste of rice husk (RH) and industrial waste of carbon fiber (CF) ends. The powder-state RH mixed with chopped CF ends (0 to 40 mass%) was molded into a disk by means of hot pressing in an inert condition without using any binders, and then heated at high temperatures by using an electric furnace. The surface static and kinetic friction coefficients of the composites were evaluated under the contact with a SUS304 ball. The composite added with 20 mass% of chopped CF and heated to 1000℃ displayed the lowest static and kinetic friction coefficients, which were respectively 0.14 and 0.12. It was found that frictional properties of the composite were affected by thermal shrinkage of the matrix material derived from RH, the level of the added chopped CF, and crystallization of silica provided from RH.

Crystallization of silica glass upon heating by contact with a NaCl crystal grain

Silica glass might be crystallized from the surface under existence of contaminants such as alkali metal compounds at high temperatures.1) The crystallization of glass from the surface upon heating is called devitrification. Devitrification of silica glass depends closely on the temperature, the holding time, impurities in the silica glass, and contaminants2) from the ambient materials. Wagstaff et al. reported dynamics of devitrification of silica glasses.3)­6) They measured the crystallization rate of stoichiometric and oxygendeficient silica glasses. Under a humidified atmosphere, the activation energy of the crystallization becomes approximately half that in a dry atmosphere. In general, vitreous silica is crystallized at temperatures higher than about 1100°C without contaminants.7) Therefore, the studies reported in the literature are limited to temperatures higher than approximately 1200°C. Devitrification is promoted when in contact with alkali metal compounds; amorphous silica is devitrified at temperatures as low as 1000°C when in contact with alkali metal compounds.8)­11) Bassett12) and Higuchi13) reported crystallization of silica glasses conducted with alkali metal compounds of various types. These studies specifically addressed the phase transitions of the silica crystal, and did not address the dynamics of the crystallization. In these studies, silica glass powder was used for quantitative analyses to assess the dynamics of the devitrification; plate-type samples must be used, as in the case of the study of Wagstaff and colleagues described above. Therefore, in this study, devitrification of the silica glass occurred when a grain of NaCl crystal contacted the silica glass plate. Four commercially available silica glasses provided by Tosoh Corp.®ES, ED-B, HR, and N®were used for samples. The ES and ED-B are synthetic fused silica containing ca. 1000 and <1 wt. ppm of OH, respectively. The N and HR are produced respectively by melting quartz powder containing ca. 200 and 1 wt. ppm of OH. These samples were cut to 20 © 20 © 1 mm and optically polished on two facing surfaces. The NaCl crystal grain was placed on the center of the silica glass substrate. Then the substrate was heated in a tubular electric furnace (type ARF-50K; Asahi Rika Co. Ltd.). The soaking area length («5°C) was 62 mm. The temperatures can thereby be controlled to within «2°C. The heating time was counted after the furnace temperature reached the target temperature. Heat treatments are repeated after measuring the morphology and depth. The heat-treated sample was cooled to room temperature without temperature control before measurements. The devitrification depth was determined from the distance from the backside of the substrate to the bottom of the devitrification region using a digital optical microscope (VH7000; Keyence Co.) with correction of the effect of the refractive index. Figure 1 portrays a photograph of the devitrification of samples that had been heat-treated at 1150°C for 10 min. The devitrified region consisted of double concentric circles around the NaCl grain (0.14 « 0.01 mg). Cross-section profiles of the devitrified region of ED-B heat-treated for 8 h at various temperatures are presented in Fig. 2. The mass of the NaCl in this measurement was 0.12 « 0.01 mg. At 800°C, the devitrification profile is flat throughout the devitrified region. At temperatures higher than 1000°C, the

Effects of ferrocenyl group on refractive index of colloidal crystal system formed by polymer-grafted silica in organic solvent

Colloidal crystallization of copolymer-grafted silica containing ferrocenyl groups in organic solvents and effects of ferrocenyl groups on effective refractive index of colloidal crystal systems were investigated. Poly(ferrocenyl metharylate (FeMA)-co-methyl methacrylate (MMA)-grafted silica gave colloidal crystallization in dimethylformamide and acetonitrile. The colloidal crystals exhibited characteristic coloration due to cooperative effects of specific absorption at 400–500 nm by ferrocenyl group and transmission of 700–800-nm light through the crystals. It was observed that effective refractive index of colloidal crystals systems of poly(FeMA-co-MMA)-grafted silica was higher than that of poly(MMA)-grafted silica. Normalized effective refractive index of the system linearly increased with mole fraction of FeMA in grafted copolymer. However, poly(FeMA-block-MMA) did not bring effective increase of the index because of bias formation of ferrocenyl group on silica.

Synthesis of Ordered Macroporous Co3O4 Microspheres via an Easy Melt Infiltration Route

Abstract Uniform Co3O4 microspheres with ordered macroporous structure were synthesized via an easy melt infiltration method. Colloidal silica crystal was used as a hard template and Co(NO3)2·6H2O as the precursor. The samples were characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. A formation mechanism was also proposed.

Os gêneros Chaetomorpha Kütz. nom. cons. e Rhizoclonium Kütz. (Chlorophyta) do litoral do Estado da Bahia, Brasil

O presente trabalho refere-se ao estudo taxonomico dos generos Chaetomorpha e Rhizoclonium ocorrentes no litoral da Bahia. As especies foram delimitadas com base no habito, presenca ou ausencia de rizoides laterais, tipo de celula basal, forma e dimensoes celulares. A presenca de inclusoes cristalinas nas celulas tambem foi verificada. Foram identificadas nove especies, sete para o genero Chaetomorpha (C. aerea (Dillwyn) Kutz., C. antennina (Bory) Kutz., C. brachygona Harv., C. clavata Kutz., C. crassa (C. Agardh) Kutz., C. minima Collins & Herv. e C. nodosa Kutz.) e duas para o genero Rhizoclonium (R. africanum Kutz. and R. riparium (Roth) Kutz. ex Harv.). Chaetomorpha crassa, C. minima e C. nodosa sao novas adicoes para o litoral nordeste do Brasil e C. aerea, C. clavata e R. africanum sao adicoes para o litoral da Bahia. Tres tipos de cristais foram encontrados: 1. cristais de silica, em forma de finas agulhas agrupadas, presentes em C. aerea, C. antennina, C. brachygona, C. clavata e C. crassa; 2. cristais de oxalato de calcio, em forma de octaedros, encontrados em C. antennina e C. clavata e, 3. cristais de carbonato de calcio, em forma de cones formando agregados globosos, observados em C. clavata. Talos ferteis de C. antennina, C. clavata, C. nodosa, R. africanum e R. riparium sao ilustrados pela primeira vez para o Brasil. Descricoes detalhadas das estruturas vegetativas e reprodutivas das especies e comparacoes com taxons afins sao apresentadas.

Inflammasome-activating nanoparticles as modular systems for optimizing vaccine efficacy

Innate immune system activation is a critical step in the initiation of an effective adaptive immune response; therefore, activation of a class of innate pathogen receptors called pattern recognition receptors (PRR) is a central feature of many adjuvant systems. It has recently been shown that one member of an intracellular PRR, the NLRP3 inflammasome, is activated by a number of classical adjuvants including aluminum hydroxide and saponins [Eisenbarth SC, Colegio OR, O’Connor W, Sutterwala FS, Flavell RA. Crucial role for the Nalp3 inflammasome in the immunostimulatory properties of aluminium adjuvants. Nature 2008;453(June (7198)):1122–6; Li H, Willingham SB, Ting JP, Re F. Cutting edge: inflammasome activation by alum and alum's adjuvant effect are mediated by NLRP3. J Immunol 2008;181(July (1)):17–21]. Inflammasome activation in vitro requires signaling of both the Toll-like receptor (TLR) and NLRP3 in antigen-presenting cells. Here we present a class of nanomaterials endowed with these two signals for rapid optimization of vaccine design. We constructed this system using a simple approach that incorporates lipopolysaccharides (LPS) onto the surface of nanoparticles constructed from a biocompatible polyester, poly(lactic-co-glycolic acid) (PLGA), loaded with antigen. We demonstrate that LPS-modified particles are preferentially internalized by dendritic cells compared to uncoated nanoparticles and the system, when administered to mice, elicits potent humoral and cellular immunity against a model antigen, ovalbumin. Wild-type macrophages pulsed with LPS-modified nanoparticles resulted in production of the proinflammatory cytokine IL-1β consistent with inflammasome activation. In comparison, NLRP3-deficient and caspase-1-deficient macrophages showed negligible production of IL-1β. Furthermore, when endocytosis and lysosomal destabilization were inhibited, inflammasome activity was diminished, supporting the notion that nanoparticles rupture lysosomal compartments and behave as ‘danger signals’ [Hornung V, Bauernfeind F, Halle A, Samstad EO, Kono H, Rock KL, et al. Silica crystals and aluminum salts activate the NALP3 inflammasome through phagosomal destabilization. Nat Immunol 2008;9(August (8)):847–56]. The generality of this vaccination approach is tested by encapsulation of a recombinant West Nile envelope protein and demonstrated by protection against a murine model of West Nile encephalitis. The design of such an antigen delivery mechanism with the ability to stimulate two potent innate immune pathways represents a potent new approach to simultaneous antigen and adjuvant delivery.

A comparative study of optical fibre types for application in a laser-induced ignition system

Various types of optical fibres have been investigated and compared for delivering high power laser beams to an optical plug (comprising of lenses and an optical window) for the application of laser-induced ignition of gasoline and air mixtures in an automotive internal combustion engine. Three main types of optical fibre were examined: multi-mode step index silica, sapphire and photonic crystal. The fibres had various core sizes ranging from 35 to 600 μ ma nd numerical apertures between 0.046 and 0.64. A Q-switched Nd:YAG laser operating at the fundamental wavelength 1064 nm with a pulse length of 15 ns was used for the testing. Fibre output beam properties, including beam mode quality, output divergence, transmission losses, beam energy thresholds and effects of engine vibration were investigated. These fibre beam properties were compared with known beam parameters for laser ignition to assess the suitability of such fibres for a laser ignition system. Online fibre delivery laser ignition engine tests were performed with the most suitable fibres, which showed that combustion could be achieved with this system despite a relatively large percentage of misfires.

Effect of Al dopant on the hydrothermal oxidation behavior of Ti 3SiC 2 powders

Experimental and thermodynamic studies of the hydrothermal oxidation behavior of Ti 3Si 0.9Al 0.1C 2 powders were performed at 500–700 °C under a hydrostatic pressure of 50 MPa. Titanium, silicon and aluminum were selectively extracted from Ti 3Si 0.9Al 0.1C 2 during hydrothermal oxidation, resulting in the formation of oxides and disordered carbon. A comparative investigation with Ti 3SiC 2 disclosed the evident influence of Al dopant on the hydrothermal oxidation process, i.e. delaying the phase transformation from anatase to rutile, promoting the formation of carbon, the crystallization of silica and decomposition of Ti 3Si 0.9Al 0.1C 2. The corresponding mechanism was discussed.