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PubMed1996

Dissolution of Barium from Barite in Sewage Sludges and Cultures of Desulfovibrio desulfuricans.

High concentrations of total barium, ranging from 0.42 to 1.58 mg(middot)g(sup-1) (dry weight) were found in sludges of two sewage treatment plants near Florence, Italy. Barium concentrations in the suspended matter decreased as redox potential values changed from negative to positive. An anoxic sewage sludge sample was aerated, and 30% of the total barium was removed in 24 h. To demonstrate that barium was solubilized from barite by sulfate-reducing bacteria, a strain of Desulfovibrio desulfuricans was used to study the solubilization of barium from barite under laboratory conditions. During cell growth with different concentrations of barite from 0.01 to 0.3 g(middot)liter(sup-1) (the latter is the MIC) as the only source of sulfates in the cultures, the D. desulfuricans strain accumulated barium up to 0.58 (mu)g(middot)mg(sup-1) (dry weight). Three times the quantity of barium was dissolved by bacteria than in the uninoculated medium (control). The unexpectedly low concentration of soluble barium (1.2 mg of Ba(middot)liter(sup-1)) with respect to the quantity expected (109 mg of Ba(middot)liter(sup-1)), calculated on the basis of the free H(inf2)S evolved from the dissimilatory reduction of sulfate from barite, was probably due to the formation of other barium compounds, such as witherite (BaCO(inf3)) and the transient species barium sulfide (BaS). The D. desulfuricans strain, growing on barite, formed visible aggregates. Confocal microscopy analysis showed that aggregates consisted of bacteria and barite. After 3 days of incubation, several autofluorescent crystals surrounded by a dissolution halo were observed. The crystals were identified as BaS by comparison with the commercial compound.

Journal Article↗
PubMed2003

Chemical and X-ray analyses of five brands of dental gutta-percha cone.

AIM: To determine the chemical composition of five commercially available nonstandardized gutta-percha points. METHODOLOGY: The organic fraction (gutta-percha polymer and wax/resin) of nonstandardized gutta-percha points (Dentsply, Tanari, Konne, Obtura Spartan and Analytic Endodontics) was separated from the inorganic fraction (ZnO and BaSO4) by dissolution in chloroform. Gutta-percha polymer was precipitated with acetone. Zinc oxide was partially separated from barium sulphate by reaction with HCl. Energy-dispersive X-ray microanalysis and X-ray diffraction were employed to identify the chemical elements and compounds (barium sulphate and zinc oxide). The barium sulphate content was calculated by percentage of sulphur from elemental microanalysis. All analyses were repeated three times. RESULTS: The means and standard deviations of the percentage by weight of gutta-percha in the points were: Dentsply (14.5 +/- 0.70%), Tanari (15.6 +/- 0.66%), Obtura (17.7 +/- 0.35%), Konne (18.9 +/- 0.32%) and Analytic (20.4 +/- 0.40%). The mean and SD of the zinc oxide content were: Dentsply (84.3 +/- 0.50%), Tanari (82.0 +/- 0.72%), Obtura (69.5 +/- 0.21%), Konne (78.0 +/- 0.05%) and Analytic (66.5 +/- 0.50%). CONCLUSIONS: The method was appropriate to quantify gutta-percha and resin/wax components of gutta-percha points, but not barium sulphate and zinc oxide. An alternative procedure to determine barium sulphate and zinc oxide contents has been proposed based on elemental microanalysis of sulphur. Some brands of gutta-percha did not contain barium sulphate.

Electron Probe Microanalysis↗
PubMed2006

Homoleptic alkaline earth metal bis(trifluoromethanesulfonyl)imide complex compounds obtained from an ionic liquid.

The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which coordinate in a bidentate chelating fashion. Three further oxygen atoms of the same ligands are linking the Ba2+ cations to infinite (infinity)(1)[Ba(Tf2N)3] chains.

Journal Article↗
PubMed1979

[Routine double-contrast radiographic examination of the esophagus].

The authors evaluate the opportunity of extending the double-contrast technique to the X-rays examination of the esophagus, with particular regard to physical and chemical features of barium compounds used at present for the X-rays study of digestive tract. The authors expose the results of this kind of X-rays examination in the most important fields of esophageal pathology. Personal experience actually demonstrate the opportuny of extending the double-contrast technique to routine practice, as a first approach to the double-contrast study of the upper digestive tract.

Air↗
PubMed1996

Prolonged intraocular pressure reduction following intravitreal barium injection in rabbits.

The isolated ciliary epithelium contains barium-inhibitable potassium channels. The present study was aimed at testing the in vivo effects of barium on aqueous humor dynamics in rabbits. BaCl2 was administered to one eye by topical delivery or intravitreal injection. Dynamic measurements included intraocular pressure, outflow facility, episcleral venous pressure and aqueous flow (fluorophotometry). Barium dynamics were studied using 133Ba. Intraocular pressure was not altered after topical administration of BaCl2. 133Ba was not detected in the aqueous after delivery of eyedrops containing the radiochemical. Intraocular pressure decreased following intravitreal injection of BaCl2 (0.15 microgram). The onset of this pressure reduction was 12 to 16 hr, the maximum decrease (-11.3 mmHg) occurred at 2 days, and the effect persisted (-4.2 mmHg) for approximately 12 days after the injection. Outflow facility and episcleral venous pressure were not altered. However, aqueous humor flow 5 to 6 days after the injection was decreased by 42% to 63% as determined by fluorophotometry or calculated tonographic data. The injection was not associated with findings of intraocular inflammation. Radioactivity was detected in the vitreous within the first 3 days after the injection; however, activity was present in the ciliary body, equally distributed between the cell membrane and soluble fractions, seven days after the injection. Intravitreally injected BaCl2 results in a prolonged intraocular pressure decrease relating to reduced aqueous formation. While the mechanism(s) for the BaCl2-induced decrease in pressure are not clear, possibilities include a Ba2+ interaction with ciliary epithelial K+ or N-type Ca2+ channels.

Animals↗
PubMed1982

The relationship of weight loss to surface roughness of composite resins from simulated toothbrushing.

This study was designed to measure percentage of weight loss during simulated toothbrushing of five different composite resins. The surface roughness of each composite resin was also measured after each year of simulated toothbrushing for a period of 5 years. The following conclusions were reached: 1. Despite the loss of toothbrush efficiency, all composite resins tested tended to have a decreasing wear rate with the increasing time of toothbrushing. 2. Profile (with a soft filler) and Isopast (with a microsized filler) showed the greatest resistance to abrasion and retained the smoothest surface. 3. Prestige, which demonstrated the greatest percent weight loss, also has a soft barium filler. Loss of the filler as an alkaline reaction in water due to soluble barium compounds may cause the binder to release filler particles prematurely.

Acrylic Resins↗
PubMed1991

Barium sulfate suspension as a negative oral MRI contrast agent: in vitro and human optimization studies.

In vitro proton spectroscopy with line-width measurements and MR imaging were performed on various concentrations of commercially available single contrast (SC), double contrast, oral and rectal barium sulfate suspensions, as well as potassium sulfate, barium chloride, barium hydroxide, and 97% pure barium sulfate suspensions. Approximately 500 ml of 20%, 40%, 60%, and 70% w/w suspensions of SC oral barium sulfate suspensions were administered to four normal volunteers, respectively, and MR images were obtained at both 1.5 T and 0.15 T. Subsequently, 500 ml of 60% w/w suspensions of SC oral barium sulfate suspensions were administered to five normal volunteers and imaged at 1.5 T. All of the inert suspensions produced line-width broadening but the SC oral barium sulfate suspension at 50% and 70% stayed in suspension even after hours of standing undisturbed. As much as 80% of the small bowel and the entire colon were well visualized using the combination of 60% or 70% w/w SC barium sulfate suspensions with SE 550/22 and FISP pulse sequences. The effect was less at 0.15 T and also with the SE 2000/45/90 pulse sequences. We conclude that barium sulfate suspensions are useful as oral MRI contrast agents.

Administration, Oral↗
PubMed1999

The effects of disordered structure on the solubility and dissolution rates of some hydrophilic, sparingly soluble drugs.

The effects of experimental design on the apparent solubility of two sparingly soluble hydrophilic compounds (barium sulphate and calcium carbonate) were studied in this paper. The apparent solubility appeared to be primarily dependent on the amount of solute added to the solvent in each experiment, increasing with increased amounts. This effect seems to be due to the existence of a peripheral disordered layer. However physico-chemical methods used in the present study were not able to unambiguously verify the existence of any disorder in the solid state structure of the drugs. At higher proportions of solute to solvent, the solubility reached a plateau corresponding to the solubility of the disordered or amorphous molecular form of the material. Milling the powders caused the plateau to be reached at lower proportions of solute to solvent, since this further disordered the surface of the drug particles. It was also found that the apparent solubility of the drugs tested decreased after storage at high relative humidities. A model for describing the effects of a disordered surface layer of varying thickness and continuity on the solubility of a substance is presented. This model may be used as a method for detection of minute amount of disorder, where no other technique is capable of detecting the disordered structure. It is suggested that recrystallisation of the material occurs via slow solid-state transition at the surface of the drug particle; this would slowly reduce the apparent solubility of the substance at the plateau level to the thermodynamically stable value. A biphasic dissolution rate profile was obtained. The solubility of the disordered surface of the particles appeared to be the rate-determining factor during the initial dissolution phase, while the solubility of the crystalline core was the rate-determining factor during the final slower phase.

Barium↗
PubMed2004

Curing depths of a universal hybrid and a flowable resin composite cured with quartz tungsten halogen and light-emitting diode units.

This in vitro study evaluated curing depths of a universal hybrid resin composite with two viscosities (Tetric Ceram and Tetric Flow) after curing with 6 different quartz tungsten halogen and light-emitting diode curing units. Irradiance (light intensity) of the curing units varied between 200 and 700 mW/cm2. The curing units were used for standard, soft-start, or pulse curing. Curing times were 20 and 40 s for standard curing, 3 + 10 s and 3 + 30 s for pulse curing, and 40 s for soft-start. Resin composite specimens, 5 in each group, with a diameter of 4 mm and a height of 6 mm, were made in brass molds and cured from one side at a distance of 6 mm. After 2 weeks, the specimens were ground longitudinally half through the specimen. Curing depth was then determined by measurement of Wallace hardness for each half millimeter starting at 0.5 mm from the top surface. For all curing units and for both resin composites an increased curing time led to statistically significantly higher depth of cure (P < 0.0005). Tetric Flow showed a statistically significantly higher depth of cure than Tetric Ceram (P < 0.0005). All curing units cured more than 2.0 mm of both composites from a distance of 6 mm at 20 s curing time. The value for 40 s was 3.0 mm. The composite closer to the surface than the depth of cure value was equally well cured with all curing units investigated. There was a significant linear correlation between the determined irradiance of the curing units and the depths of cure obtained (20s: r = 0.89, P < 0.025; 40 s: r = 0.91, P < 0.01).

Aluminum Compounds↗
PubMed2005

Brazilian gutta-percha points. Part I: chemical composition and X-ray diffraction analysis.

Eight nonstandardized gutta-percha points commercially available in Brazil (Konne, Tanari, Endopoint, Odous, Dentsply 0.04, Dentsply 0.06, Dentsply TP and Dentsply FM) were analysed chemically and by X-ray diffraction, and their chemical compositions were compared. The organic fraction (gutta-percha polymer and wax/resin) of the gutta-percha points was separated from the inorganic fraction (ZnO and BaSO4) by dissolving them in chloroform. The gutta-percha polymer was precipitated with acetone. The inorganic fraction was analysed by elemental microanalysis. Energy-dispersive X-ray microanalysis (EDX) and X-ray diffraction were employed to identify the chemical elements and compounds (barium sulfate and zinc oxide). The barium sulfate content was calculated based on the percentage of sulfur found in the elemental microanalysis. All analyses were repeated three times. The means and standard deviations of the percentage by weight of gutta-percha in the points were: Konne (17.6 +/- 0.30), Tanari (15.2 +/- 0.30), Endopoint (16.7 +/- 0.23), Odous (18.8 +/- 0.20), Dentsply 0.04 (15.7 +/- 0.17), Dentsply 0.06 (16.6 +/- 0.17), Dentsply TP (21.6 +/- 0.15) and Dentsply FM (16.3 +/- 0.23). The means and standard deviations of the zinc oxide content were: Konne (79.9 +/- 0.10), Tanari (81.9 +/- 0.07), Endopoint (81.3 +/- 0.40), Odous (79.7 +/- 0.26), Dentsply 0.04 (77.9 +/- 0.03), Dentsply 0.06 (78.2 +/- 0.07), Dentsply TP (69.8 +/- 0.19) and Dentsply FM (72.6 +/- 0.70). The method utilized was appropriate to quantify gutta-percha, wax/resin, zinc oxide and barium sulfate. Cone brands without barium sulfate were found. An unusual high wax/resin percentage was detected in Dentsply FM (p = 0.0003). Dentsply TP showed the highest gutta-percha percentage.

Barium Sulfate↗
PubMed1983

Barium bioavailability as the chloride, sulfate, or carbonate salt in the rat.

This study was conducted to determine how the bioavailability of a low concentration of barium (Ba) in drinking water is affected by the anion. Male Sprague Dawley rats weighing 250-300 grams were maintained on a diet of less than 1 mg Ba/kg of food for at least 1 month prior to experimentation. Rats were given 10.0 mg 131Ba/liter as sulfate (SO4), chloride (Cl), or carbonate (CO3) at pH 7.0. Animals were sacrificed at 2, 5, 10, 20, 30, 60, and 120 minutes and 24 hours after intubation. When 131Ba was administered, as Cl, 131Ba in blood rose linearly for 10 minutes and then less rapidly until the highest number of counts was measured at 60 minutes. At 24 hours 131Ba was still at 90% of peak levels. Five tissues were tested 24 hours after dosing for 131Ba. In decreasing order of 131Ba concentration they were heart, eye, skeletal muscle, kidney, and liver. 131Ba in the heart reached 8x that observed in blood 24 hours after dosing. In the eye, 131Ba increased linearly for 1 hour. Isotope concentrations in the eye eventually reached 2.5x that observed in blood. When 131Ba was administered as SO4 or CO3, 131Ba in blood was respectively 85% or 45% of levels, of 131Ba from 131BaCl2. Initial uptake of 131Ba and deposition in the eye were not different when administered as Cl or SO4.

Absorption↗
PubMed1958

[Baryta lungs].

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Barium Compounds↗
PubMed1997

[Scanning electron microscopic studies on mucosal coating by barium mixtures].

The purpose of this study was to observe and evaluate mucosal coating by barium mixtures using electron microscopy. Specimens from the ileum of two pigs, about 50cm in length from the terminal ileum, were divided into 3 groups with different in concentrations and additives of barium mixture. The 50cm length of ileum was cut into 10cm long pieces. Four specimens from each group were evaluated by double contrast study for coating by the barium layer. Then the specimen was frozen with liquid nitrogen solution, and fixed. Afterward, the specimen was cut into about 1cm sections, fixed again, dehydrated, dried, and observed by scanning electron microscopy (SM). In the double contrast study, the differences in barium coating were correlated with the concentration of barium sulphate. The scanning electron microscopic findings were correlated with those of the double contrast study. The various additives in the barium mixture did not cause any distinctive differences. Although barium particles have been studied by electron microscopy, barium mixture coating state on the mucosa of biological materials has not been reported. In conclusion, a correlation of the coated barium layer on double contrast study and the images of scanning electron microscopy was observed using pig ileum specimens.

Animals↗
PubMed1998

[Safety health conditions for disposal of waste generated during the production of barium and boron compounds].

The authors proposed an approach to calculating maximum concentrations of dust in the ambient air that may occur during digging, loading and transportation of barium and boron wastes containing a variety of metallic compounds, including arsenic and nickel. In addition, they listed conditions which should be fulfilled in view of binding legal regulations, in order to ensure that the work performed does not create any health risk. It was recognized that maintaining dust concentrations in the air below 5 mg/m3 should protected workers against the potential risk during their work.

Air Pollutants, Occupational↗