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At least 109 records · Page 6Linked to original sources

PubMed2002

Formation of a new crystalline silicate structure by grafting dialkoxysilyl groups on layered octosilicate.

Dialkoxydichlorosilanes ((RO)2SiCl2, R = alkyl) react almost completely with interlayer silanol groups in a layered silicate octosilicate to create a new crystalline silicate structure consisting of new five-membered rings arranged regularly on both sides of the silicate layers. The introduction of dialkoxysilyl groups to the interlamellar region of layered silicates with regular reaction sites provides a new methodology for the design and construction of novel crystalline silicate frameworks by a soft chemical route.

Journal Article↗

PubMed2004

Stardust silicates from primitive meteorites.

Primitive chondritic meteorites contain material (presolar grains), at the level of a few parts per million, that predates the formation of our Solar System. Astronomical observations and the chemical composition of the Sun both suggest that silicates must have been the dominant solids in the protoplanetary disk from which the planets of the Solar System formed, but no presolar silicates have been identified in chondrites. Here we report the in situ discovery of presolar silicate grains 0.1-1 microm in size in the matrices of two primitive carbonaceous chondrites. These grains are highly enriched in 17O (delta17O(SMOW) > 100-400 per thousand ), but have solar silicon isotopic compositions within analytical uncertainties, suggesting an origin in an oxygen-rich red giant or an asymptotic giant branch star. The estimated abundance of these presolar silicates (3-30 parts per million) is higher than reported for other types of presolar grains in meteorites, consistent with their ubiquity in the early Solar System, but is about two orders of magnitude lower than their abundance in anhydrous interplanetary dust particles. This result is best explained by the destruction of silicates during high-temperature processing in the solar nebula.

Journal Article↗

PubMed2005

[Intracavitary application of silics for the treatment of inflammatory-purulent processes].

The results of clinical application of Silics--new sorbent of polydirected action, based on highly disperse amorphous silica, were presented. Silics owes unique properties, which are manifested while its intracavitary application for treatment of inflammatory-purulent processes. Osmotic activity of sorbent is more than 500%, waterabsorbability--up to 1000%, it sorbates up to 800 mg/g of proteins, microorganisms--up to 10(10) of the colony forming units on 1 g. Silics promotes lysis of necrotized tissues. In clinical application of Silics in 146 patients with retroperitoneal space phlegmon in an acute destructive pancreatitis, in 23--with abdominal cavity abscess, in 34--with inflammatory-purulent pleuropulmonary diseases it was established, that this preparation promotes the intoxication severity lowering, the reduction of microbal sowing of purulent cavities and resistance of the wound microflora to antibotics. The securing of fragmentation of necrotized tissues and the fibrin deposits, lowering of the exudate viscosity rises efficacy of the inflammatory focus drainage. Application of Silics for the treatment of inflammatory-purulent processes permits to improve essentially its results on the account of lowering of mortality and the treatment cost, and the shortage of the patients stationary treatment.

Abdominal Abscess↗

PubMed2006

[Structure changes of lead silicate glasses induced by UV laser irradiation].

The structure changes of lead silicate glasses induced by UV laser irradiation were studied by UV-visible spectra and electron spin resonance (ESR). The Urbach energies of lead silicate glasses exposed to the 266 nm UV laser increased. This implied that the disorder of the lead silicate glasses was increased. The electron spin resonance experiments showed that the oxygen deficiency centers in lead silicate glass did not change to paramagnetic defects after exposure to 266 nm laser beam, and the absorption peak near 235 nm for lead silicate glass film did not change either. But this absorption peak was bleached after exposure to the 248 nm UV laser.

English Abstract↗

PubMed1979

Comparative pathology of silicate pneumoconiosis.

A simple pneumoconiosis with lamellar birefringent crystals was observed in animals dying in the San Diego Zoo. We studied 100 autopsies from 11 mammalian and eight avian species. In mammals, mild pulmonary lesions comprised crystal-laden macrophages in alveoli and lymphatics. Interstitial fibrosis was present in 20% of cases. There were no nodules. In birds, dust retention produced large granulomas around tertiary bronchi without fibrosis. Mineralogic analysis using scanning and transmission electron microscopy showed most of the crystals to be silicates. Ninety percent were complex silicates, with aluminum-potassium silicates comprising 70% of the analyzed particles. Electron and x-ray diffraction showed the silicates to be muscovite mica and its hydrothermal degradation product, ie, illite clay. This mica was also present on filtration membranes of atmospheric air samples obtained from the San Diego Zoo. The amount of dust retention was related to the animal's age, anatomic or ecologic variances, and length of stay in the San Diego Zoo. Its semidesert atmosphere is rich in silicates, which are inhaled and deposited in the lungs. Similar mica-induced lesions are found in humans living in this region or the Southwest of the USA. This simple pneumoconiosis is likely to be widespread in human populations living in desert or semidesert climates.

Animals↗

PubMed1979

Silicate pneumoconiosis of farm workers.

Abnormal numbers of birefringent particles have been found in the lungs of seven patients (five vineyard workers, one farmer, and one rural resident) in association with a spectrum of early to late interstitial inflammation and fibrosis. Nodular granulomas of the type seen in silicosis were absent. Scanning electron microscopy and energy dispersive x-ray analysis of 177 individual particles (less than 5 micrometer.) in situ in the lungs of four of the patients showed mostly silicates (notably aluminum, silicon, and potassium), with 5 to 10 per cent silicon dioxide. An analysis of particles less than 5 micrometer. from both vineyard and non-vineyard soil showed lung and soil particles to have a similar composition. The presence of large amounts of silicates in the lung tissues, in association with chronic inflammation and fibrosis, implicates the silicates in the causation of the fibrosis. The silicate deposits may, in large part, be a marker, reflecting a mixture of toxic soil additives or pesticides found in commercial clay silicate products or in dusts from the soil itself. The findings do not exclude lung pathology of a similar nature in regions outside of the farm.

Aged↗

PubMed1999

Spectrophotometric determination of silicate traces in hemodialysis solutions.

Reliable methods for the analysis of silicon are of great importance, because it seems that the silicate anion can reduce aluminum bioavailability in patients undergoing dialysis. Thus, a simple and sensitive spectrophotometric method is described for the determination of silicate traces in dialysis solutions. The method is based on the reaction between silicate ions and excess ammonium molybdate reagent to give a yellow silico-molybdic complex. This complex is then reduced to the heteropoly blue compound by means of ascorbic acid. Absorbance values are measured at 830 nm, and are stable for more than 2 h. A good linearity was obtained up to 300 ng ml(-1) of silicon concentration. The accuracy and the precision of the method were good; relative standard deviation values of 2% intraday and of 3.9% interday for six replicates on 40 ng ml(-1) standard silicate solutions were found. Results of the analysis of some commercial hemodialysis solution samples, obtained by means of the 'standard additions' method, are provided.

Aluminum↗

PubMed2006

Selective and simultaneous determination of phosphate and silicate ions in leaching process waters for ceramics glaze raw materials of narutal origin by ion-exclusion chromatography coupled with UV-detection after postcolumn derivatization.

The selective and simultaneous ion-exclusion chromatography (IEC) with UV-detection on a weakly acidic cation-exchange resin column in the H+ -form (TSKgel Super IC-A/C) was developed and applied for the simultaneous determination of phosphate and silicate ions as the water quality parameters required for optimizing the water-leaching process for ceramics glaze raw materials of natural origin including feldspar, woods-ash, and straw-ash. Phosphate and silicate ions in these water-leaching process water samples were separated selectively from the coexisting anions such as sulfate, chloride, nitrate and carbonate ions, based on the ion-exclusion separation mechanism. They were detected selectively and simultaneously by a postcolumn derivatization with molybdenum-yellow using the UV-detector. Under the optimized separation and detection conditions (eluent, 0-1 mM sulfuric acid; reactant, 10 mM sodium molybdate-25 mM sulfuric acid; detector, UV at 370 nm; temperature, 45 degrees C), the linearity of calibration was in the range 0.1 - 10 ppm for both phosphate and silicate ions, and the detection limits at S/N = 3 were 2.58 ppb for silicate ions and 4.75 ppb for phosphate ions. The effectiveness of this method was demonstrated in practical applications to the water-leaching process for some ceramics glaze raw materials.

Aluminum Silicates↗

PubMed1983

The effect of sodium fluoride and sodium silicate on growth and bone strength of broilers.

Two experiments were conducted using 300 broilers each. Standard broiler diets were supplemented by adding to the drinking water either sodium fluoride or sodium meta-silicate. Sodium fluoride provided 120 ppm Na and 100 ppm F and 120 ppm Na and 74 ppm Si were provided by the sodium silicate. Control groups received tap water. All groups received a standard corn-soybean meal diet and drinking water ad libitum. All broilers were reared in floor pens, and hardwood shavings were used for bedding. Live weights and feed conversion were determined every 2 weeks. Growth rates, feed conversions, and mortality were not affected by the sodium salts in either experiment. Litter conditions in the pens were closely observed, and no differences were found resulting from the addition of either sodium salt to the drinking water. A significant decrease in humeri strength was observed when one wing of broilers in the control and sodium fluoride treated groups was immobilized with tape during the last 2 weeks of each experiment. This loss of strength was not significant in the sodium silicate group. In both experiments, breaking strength and ash content of humeri and tibiae were significantly increased in birds fed the sodium fluoride when compared to the control group. The sodium silicate group yielded intermediate results.

Animals↗

PubMed1982

Ulcerative contact dermatitis caused by sodium silicate. Coexistence of primary irritant contact dermatitis and contact urticaria.

A 57-year-old man had had recurrent ulcerative lesions on his left hand for two years. The ulcers were associated with chronic eczematous changes resulting from primary irritant contact dermatitis to sodium silicate, as indicated by positive patch tests. The patient also had another type of cutaneous reaction to sodium silicate, ie, contact urticaria. An immediate wheal and flare reaction was found 15 minutes after application of sodium silicate to a scratch test site. This response was not seen in healthy control subjects. To our knowledge, the coexistence of primary irritant contact dermatitis and contact urticaria, both induced by sodium silicate, has not previously been described.

Dermatitis, Contact↗

PubMed2005

Early apatite deposition and osteoblast growth on plasma-sprayed dicalcium silicate coating.

Dicalcium silicate coating was deposited onto a Ti-6Al-4V substrate using plasma-spraying technology. The coating was immersed in simulated body fluid (SBF) for 1, 3, 6, 12, 24, and 48 h to investigate early apatite formation on the coating. Osteoblasts were also seeded onto the surface of the dicalcium silicate coating to evaluate its biocompatibility. Cold field-emission scanning electron microscopy and energy-dispersive X-ray spectrometry were used to evaluate the morphologies and determine the chemical composition of the coatings. The surface structural changes caused by immersion in SBF were analyzed using thin-film X-ray diffraction. After the dicalcium silicate coating was soaked in SBF solution 1-6 h, two types of particles containing calcium and phosphorus were formed on the surface. One type consisted of relatively larger particles (P1) precipitated on the surface of the coating from the precursor cluster formed in the SBF solution. The second type was composed of particles (P2) nucleated on the surface of the coating. With increasing immersion time, the particles coalesced to form a surface Ca-P layer. The Ca-P layer was composed of amorphous calcium phosphate that was not transformed to crystalline apatite until the immersion time in SBF exceeded 24 h. The formation mechanism of the Ca-P layer and apatite on the surface of the coating is believed to be involved in the formation of the Si 3-ring active surface site with negative charge. The cell-seeding test revealed that osteoblasts grew and proliferated very well on the surface of the dicalcium silicate coating.

Animals↗

PubMed2007

Self-setting properties of a beta-dicalcium silicate reinforced calcium phosphate cement.

Beta-dicalcium silicate was used to reinforce the injectable calcium phosphate cement (iCPC) for the first time in this study. The influence of the content of beta-dicalcium silicate on the mechanical properties, setting time, rheological properties, injectability, phase evolution, microstructure, and biodegradability of iCPC was systematically investigated. The results demonstrated that the addition of 8 wt % beta-dicalcium silicate obviously enhanced the compressive strength of the CPC from 26.5 to 47.5 MPa, and did not significantly influence the biodegradability, setting time, injectability, phase evolution, and microstructure of the CPC. The beta-dicalcium silicate-reinforced iCPC with relatively high mechanical property should have potential prospects for the wider applications in surgery such as orthopedics, oral, and maxillofacial surgery.

Bone Cements↗

PubMed1976

Electron probe microanalysis of secondary carious lesions adjacent to silicate fillings.

Secondary caries associated with silicate fillings is characterized by lesions at the tooth surface and lesions of the cavity wall. The mineral content of the cavity wall lesions and the penetration of elements originating from the silicate fillings were studied in experimental in vitro and in vivo lesions as well as in natural carious lesions. Dentine wall lesions, where microradiographs had shown increased radiopacity relative to intact tissue, exhibited increased Ca and P values. Elements derived from the silicate fillings were regularly found in enamel and dentine. The concentrations of fluorine (F) and of zinc (Zn) amounted to 2-3% by weight close to the cavity wall and decreased gradually to less than 0.1% at depths of 600 mum and 400 mum, respectively, from the cavity. Aluminum (Al) most often occurred in a 20-40 mum-wide zone, showing a maximum concentration of 2-3% near the cavity. Sulfur (S) was often present in the dentinal cavity walls of natural secondary caries, but not in the in vitro specimens. The findings indicate that F released from the silicate filling significantly modifies the progress of a carious lesion in the adjacent enamel and dentine. Through its tendency to form complexes with F, Al may possibly enhance the cariostatic effect of F.

Aluminum↗

PubMed2005

A novel complex of arginine-silicate improves micro- and macrovascular function and inhibits glomerular sclerosis in insulin-resistant JCR:LA-cp rats.

AIMS/HYPOTHESIS: The metabolic syndrome, with associated vasculopathy, is a major cause of cardiovascular disease and nephropathy. Impaired nitric oxide (NO) metabolism and endothelial function is an important component of the disease process. Increasing the availability of arginine, the precursor of NO, might enhance vascular function and protect against end-stage disease. MATERIALS AND METHODS: Insulin-resistant JCR:LA-cp rats were treated with arginine-silicate-inositol complex or arginine-HCl at 1.0 g kg(-1) day(-1) (expressed as arginine-HCl) from 8 to 13 weeks of age. The contractile/relaxant function of thoracic aortae and coronary arteries was assessed in vitro. Kidneys were assessed for severity of glomerular sclerosis. RESULTS: Arginine-silicate complex, but not arginine-HCl, normalised the hypercontractile response of the aorta to phenylephrine via an NO-dependent pathway. Coronary artery function, as indicated by reactive hyperaemia to warm ischaemia, was enhanced by both arginine compounds. In addition, the arginine-silicate complex increased coronary vasodilatation in response to bradykinin. Glomerular sclerosis was significantly reduced in rats treated with the arginine-silicate complex. CONCLUSIONS/INTERPRETATION: Treatment with exogenous arginine, in an efficiently absorbed form, improves vascular function and reduces nephropathy in an animal model of insulin resistance and cardiovascular disease, via mechanism(s) independent of insulin concentration. Enhancement of NO metabolism through increased availability of the precursor arginine appears to offer protection against micro- and macrovascular disease associated with the metabolic syndrome and insulin resistance.

Acetylcholine↗

PubMed1989

C-O-H ratios of silicate melt inclusions in basalts from the Galapagos Spreading Center near 95 degrees W: a laser decrepitation mass spectrometry study.

Volatile ratios (primarily of H2O and CO2) in individual silicate melt (glass) inclusions in minerals have been analyzed using laser volatilization and mass spectrometry. A Nd-glass laser was used to produce 50-micrometer diameter pits in silicate melt inclusions. Released volatiles were analyzed directly with a computer-controlled quadrupole mass spectrometer. The detection limits for CO2 and H2O were on the order of 3 x 10(-14) and 3 x 10(-13) moles, respectively. The reproducibility for CO2/H2O was better than +/- 9%. The total range of volatile ratios from vitreous silicate glass inclusions contained in a suite of Galapagos lavas were: 0.018 to 1.193 for CO2/H2O; 0.002 to 0.758 for CO/H2O; 0 to 0.454 for CH4/H2O; and 0 to 0.432 for Ar/H2O. The mean CO2/H2O from the propagating rift (0.245 +/- 0.068) silicate glass inclusions is significantly lower than that of the actively failing rift (0.641 +/- 0.241); this difference probably reflects different degrees of degassing during magmatic histories for the two regions. Relatively undifferentiated failing rift magmas must have relatively short crustal residence times prior to eruption and, therefore, have not undergone significant degassing of CO2, as would appear to be the case for the more highly fractionated propagating rift magmas. The laser-mass spectrometric system described herein has the ability to act as a point-source probing device that can differentiate between the various volatile sites in minerals and rocks (as well as synthetic materials) on a micrometer scale.

Carbon↗

PubMed1977

Chromatographic patterns of prostaglandins using different lots of silicic acid.

The chromatographic patterns of prostaglandin E2 chromatographed on various lots of silicic acid are presented. Two lots of Mallinckrodt silicic acid tested give totally unsatisfactory separation of PGE2. Sigma silicic acid SIL-R gives better separation than any of the Mallinckrodt lots tested. Increasing the size of the "E" fraction of solvent can give satisfactory separation on Mallinckrodt silicic acid.

Chromatography↗

PubMed1994

Novel polyalkenoate (glass-ionomer) dental cements based on zinc silicate glasses.

Powdered zinc silicate glasses were investigated for cement formation with aqueous poly(acrylic acid). Alkali metal zinc silicate glasses and calcium zinc silicate glasses gave polyalkenoate cements which were hydrolytically unstable, whilst alumino-zinc-silicate glasses gave hydrolytically stable cements with short setting times (under 10 min) and high compressive strengths (above 90 MPa). The aluminium to silicon ratio was not important in determining the cement forming ability of the glass. The ability to form a cement was, instead, determined largely by the network connectivity of the glass.

Aluminum↗

PubMed1988

Strand breakage in DNA by silicic acid.

The alkaline unwinding assay has been used to demonstrate the formation of single-strand breaks in DNA on treatment with silicic acid. Double-stranded DNA, containing no single-strand breaks, when incubated with increasing concentrations of silicic acid, showed the formation of an increasing number of strand breaks per molecule. Experiments on reduction of silicic acid-treated DNA with NaBH4 suggested the possibility of creation of apurinic or apyrimidinic sites. The significance of silicic acid interaction with cellular DNA during asbestos exposure is discussed.

Borohydrides↗