Degradation and silicon excretion of the calcium silicate bioactive ceramics during bone regeneration using rabbit femur defect model.

PubMed

Lin, Kaili; Liu, Yong; Huang, Hai; Chen, Lei; Wang, Zhen; Chang, Jiang

2015-06-01

The investigation of the bone regeneration ability, degradation and excretion of the grafts is critical for development and application of the newly developed biomaterials. Herein, the in vivo bone-regeneration, biodegradation and silicon (Si) excretion of the new type calcium silicate (CaSiO3, CS) bioactive ceramics were investigated using rabbit femur defect model, and the results were compared with the traditional β-tricalcium phosphate [β-Ca3(PO4)2, β-TCP] bioceramics. After implantation of the scaffolds in rabbit femur defects for 4, 8 and 12 weeks, the bone regenerative capacity and degradation were evaluated by histomorphometric analysis. While urine and some organs such as kidney, liver, lung and spleen were resected for chemical analysis to determine the excretion of the ionic products from CS implants. The histomorphometric analysis showed that the bioresorption rate of CS was similar to that of β-TCP in femur defect model, while the CS grafts could significantly stimulate bone formation capacity as compared with β-TCP bioceramics (P < 0.05). The chemical analysis results showed that Si concentration in urinary of the CS group was apparently higher than that in control group of β-TCP. However, no significant increase of the Si excretion was found in the organs including kidney, which suggests that the resorbed Si element is harmlessly excreted in soluble form via the urine. The present studies show that the CS ceramics can be used as safe, bioactive and biodegradable materials for hard tissue repair and tissue engineering applications.

Calcium Phosphate Cement with Antimicrobial Properties and Radiopacity as an Endodontic Material

PubMed Central

Shieh, Tzong-Ming; Hsu, Shih-Ming; Chang, Kai-Chi; Lin, Dan-Jae

2017-01-01

Calcium phosphate cements (CPCs) have several advantages for use as endodontic materials, and such advantages include ease of use, biocompatibility, potential hydroxyapatite-forming ability, and bond creation between the dentin and appropriate filling materials. However, unlike tricalcium silicate (CS)-based materials, CPCs do not have antibacterial properties. The present study doped a nonwashable CPC with 0.25–1.0 wt % hinokitiol and added 0, 5, and 10 wt % CS. The CPCs with 0.25–0.5 wt % hinokitiol showed appreciable antimicrobial properties without alterations in their working or setting times, mechanical properties, or cytocompatibility. Addition of CS slightly retarded the apatite formation of CPC and the working and setting time was obviously reduced. Moreover, addition of CS dramatically increased the compressive strength of CPC. Doping CS with 5 wt % ZnO provided additional antibacterial effects to the present CPC system. CS and hinokitiol exerted a synergic antibacterial effect, and the CPC with 0.25 wt % hinokitiol and 10 wt % CS (doped with 5 wt % ZnO) had higher antibacterial properties than that of pure CS. The addition of 10 wt % bismuth subgallate doubled the CPC radiopacity. The results demonstrate that hinokitiol and CS can improve the antibacterial properties of CPCs, and they can thus be considered for endodontic applications. PMID:29088119

Ion release and mechanical properties of calcium silicate and calcium hydroxide materials used for pulp capping.

PubMed

Natale, L C; Rodrigues, M C; Xavier, T A; Simões, A; de Souza, D N; Braga, R R

2015-01-01

To compare the ion release and mechanical properties of a calcium hydroxide (Dycal) and two calcium silicate (MTA Angelus and Biodentine) cements. Calcium and hydroxyl ion release in water from 24-h set cements were calculated from titration with HCl (n = 3). Calcium release after 7, 14, 21 and 28 days at pH 5.5 and 7.0 was measured using ICP-OES (n = 6). Flexural strength (FS) and modulus (E) were tested after 48-h storage, and compressive strength (CS) was tested after 48 h and 7 days (n = 10). Ion release and mechanical data were subjected to anova/Tukey and Kruskal-Wallis/Mann-Whitney tests, respectively (α = 0.05). Titration curves revealed that Dycal released significantly fewer ions in solution than calcium silicates (P < 0.001). Calcium release remained constant at pH 7.0, whilst at pH 5.5, it dropped significantly by 24% after 21 days (P < 0.05). At pH 5.5, MTA Angelus released significantly more calcium than Dycal (P < 0.01), whilst Biodentine had superior ion release than Dycal at pH 7.0 (P < 0.01). Biodentine had superior flexural strength, flexural modulus and compressive strength than the other cements, whilst MTA Angelus had higher modulus than Dycal (P < 0.001). Immediate calcium and hydroxyl ion release in solution was significantly lower for Dycal. In general, all materials released constant calcium levels over 28 days, but release from Dycal was significantly lower than Biodentine and MTA Angelus depending on pH conditions. Biodentine had substantially higher strength and modulus than MTA Angelus and Dycal, both of which demonstrated low stress-bearing capabilities. © 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Preliminary study on removing Cs⁺/Sr²⁺ by activated porous calcium silicate-A by-product from high-alumina fly ash recycling industry.

PubMed

Chu, Yingying; Wang, Rong; Chen, Mengjun

2015-01-01

¹³⁷Cs⁺/⁹⁰Sr²⁺-containing radioactive wastewater is one of the most important problems that the world has been facing with. A by-product, activated porous calcium silicate, is generated at high levels by the pre-desiliconizing and soda-lime-sintering processes for producing Al₂O₃from high-alumina fly ash. In order to examine if this by-product could be used as an absorbent for removal of ¹³⁷Cs⁺/⁹⁰Sr²⁺ from radioactive wastewater, various parameters, such as pH, adsorbent dose, contact time, and initial concentration, were discussed. Results indicated that the equilibrium reached in about 2 hr. Activated porous calcium silicate was highly pH sensitive and able to remove Cs(+)/Sr²⁺ in a near-neutral environment. The adsorption equilibrium was best described by Freundlich isotherm equations, and the adsorption of Cs⁺/Sr²⁺ was a physical process. The adsorption kinetic data could be better fitted by the pseudo-second-order model, and the adsorption was controlled by multidiffusion. Current study showed that activated porous calcium silicate has a good adsorption of Cs⁺/Sr²⁺ for their removal. However, other characteristics, such as selectivity because of coexisting cations, elution and regeneration, thermal stability, and acid resistance, should be discussed carefully before using it in an actual field.

The effect of sodium chloride on the dissolution of calcium silicate hydrate gels.

PubMed

Hill, J; Harris, A W; Manning, M; Chambers, A; Swanton, S W

2006-01-01

The use of cement based materials will be widespread in the long-term management of radioactive materials in the United Kingdom. One of the applications could be the Nirex reference vault backfill (NRVB) as an engineered barrier within a deep geological repository. NRVB confers alkaline conditions, which would provide a robust chemical barrier through the control of the solubility of some key radionuclides, enhanced sorption and minimised corrosion of steel containers. An understanding of the dissolution of C-S-H gels in cement under the appropriate conditions (e.g., saline groundwaters) is necessary to demonstrate the expected evolution of the chemistry over time and to provide sufficient cement to buffer the porewater conditions for the required time. A programme of experimental work has been undertaken to investigate C-S-H gel dissolution behaviour in sodium chloride solutions and the effect of calcium/silicon ratio (C/S), temperature and cation type on this behaviour. Reductions in calcium concentration and pH values were observed with samples equilibrated at 45 degrees C compared to those prepared at 25 degrees C. The effect of salt cation type on salt-concentration dependence of the dissolution of C-S-H gels was investigated by the addition of lithium or potassium chloride in place of sodium chloride for gels with a C/S of 1.0 and 1.8. With a C/S of 1.0, similar increases in dissolved calcium concentration with increasing ionic strength were recorded for the different salts. However, at a C/S of 1.8, anomalously high calcium concentrations were observed in the presence of lithium.

21 CFR 172.410 - Calcium silicate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely...

21 CFR 172.410 - Calcium silicate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely...

21 CFR 172.410 - Calcium silicate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely...

21 CFR 172.410 - Calcium silicate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely...

21 CFR 172.410 - Calcium silicate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 172.410 Section 172.410 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used in food in accordance with the...

Measurement of the efficacy of calcium silicate for the protection and repair of dental enamel.

PubMed

Parker, Alexander S; Patel, Anisha N; Al Botros, Rehab; Snowden, Michael E; McKelvey, Kim; Unwin, Patrick R; Ashcroft, Alexander T; Carvell, Mel; Joiner, Andrew; Peruffo, Massimo

2014-06-01

To investigate the formation of hydroxyapatite (HAP) from calcium silicate and the deposition of calcium silicate onto sound and acid eroded enamel surfaces in order to investigate its repair and protective properties. Calcium silicate was mixed with phosphate buffer for seven days and the resulting solids analysed for crystalline phases by Raman spectroscopy. Deposition studies were conducted on bovine enamel surfaces. Acid etched regions were produced on the enamel surfaces using scanning electrochemical cell microscopy (SECCM) with acid filled pipettes and varying contact times. Following treatment with calcium silicate, the deposition was visualised with FE-SEM and etch pit volumes were measured by AFM. A second set of bovine enamel specimens were pre-treated with calcium silicate and fluoride, before acid exposure with the SECCM. The volumes of the resultant acid etched pits were measured using AFM and the intrinsic rate constant for calcium loss was calculated. Raman spectroscopy confirmed that HAP was formed from calcium silicate. Deposition studies demonstrated greater delivery of calcium silicate to acid eroded than sound enamel and that the volume of acid etched enamel pits was significantly reduced following one treatment (p<0.05). In the protection study, the intrinsic rate constant for calcium loss from enamel was 0.092 ± 0.008 cm/s. This was significantly reduced, 0.056 ± 0.005 cm/s, for the calcium silicate treatments (p<0.0001). Calcium silicate can transform into HAP and can be deposited on acid eroded and sound enamel surfaces. Calcium silicate can provide significant protection of sound enamel from acid challenges. Calcium silicate is a material that has potential for a new approach to the repair of demineralised enamel and the protection of enamel from acid attacks, leading to significant dental hard tissue benefits. © 2014 Elsevier Ltd. All rights reserved.

21 CFR 182.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 182.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 582.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 582.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 582.2227 - Calcium silicate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

21 CFR 582.2227 - Calcium silicate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

21 CFR 582.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 582.2227 - Calcium silicate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

21 CFR 182.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 582.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 582.2227 - Calcium silicate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

21 CFR 582.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 182.2227 - Calcium silicate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2227 Calcium silicate. (a) Product. Calcium silicate...

21 CFR 582.2227 - Calcium silicate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

21 CFR 182.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Aluminum calcium silicate. 182.2122 Section 182...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This...

21 CFR 182.2122 - Aluminum calcium silicate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

21 CFR 182.2227 - Calcium silicate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

21 CFR 182.2227 - Calcium silicate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

21 CFR 182.2227 - Calcium silicate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

21 CFR 182.2227 - Calcium silicate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

Ash fusion characteristics during co-gasification of biomass and petroleum coke.

PubMed

Xiong, Qing-An; Li, Jiazhou; Guo, Shuai; Li, Guang; Zhao, Jiantao; Fang, Yitian

2018-06-01

In this study, the effect of biomass ash on petroleum coke ash fusibility was investigated at a reducing atmosphere. Some analytical methods, such as ash fusion temperatures (AFTs) analysis, X-ray diffraction (XRD), FactSage and scanning electron microscopy (SEM), were applied to determine the characteristics of ash fusion and transformation of mineral matters. The results indicated that AFTs were closely associated with ash mineral compositions. It was found that the formations of high melting point calcium silicate, vanadium trioxide and coulsonite resulted in the high AFTs of Yanqing petroleum coke (YQ). When blending with certain proportional pine sawdust (PS), corn stalk (CS), the AFTs of mixture could be decreased significantly. For PS addition, the formations of low-melting point calcium vanadium oxide should be responsible for the reduction of AFTs, whereas for CS addition the reason was ascribed to the formation of low-melting point leucite and the disappearance of high-melting V 2 O 3 . Copyright © 2018. Published by Elsevier Ltd.

Calcium silicate-based drug delivery systems.

PubMed

Zhu, Ying-Jie; Guo, Xiao-Xuan; Sham, Tsun-Kong

2017-02-01

Compared with other inorganic materials such as silica, metal oxides, noble metals and carbon, calcium silicate-based materials, especially nanostructured calcium silicate materials, have high biocompatibility, bioactivity and biodegradability, high specific surface area, nanoporous/hollow structure, high drug-loading capacity, pH-responsive drug release behavior and desirable drug release properties, and thus they are promising for the application in drug delivery. Calcium silicate-based drug delivery systems have a long drug-release time, which can significantly prolong the therapeutic effect of drugs. Another advantage of calcium silicate-based drug delivery systems is their pH-responsive drug release property, which can act as an ideal platform for targeted drug delivery. Areas covered: In recent years, studies have been carried out on calcium silicate-based drug delivery systems, and important results and insights have been documented. This article is not intended to offer a comprehensive review on the research on calcium silicate-based drug delivery systems, but presents some examples reported in the literature, and includes new insights obtained by tracking the interactions between drug molecules and calcium silicate carriers on the molecular level using the synchrotron-based X-ray spectroscopy. Expert opinion: Finally, our opinions on calcium silicate-based drug delivery systems are provided, and several research directions for the future studies are proposed.

Combined effect of magnesia and zirconia on the bioactivity of calcium silicate ceramics at C\\S ratio less than unity.

PubMed

Ewais, Emad M M; Amin, Amira M M; Ahmed, Yasser M Z; Ashor, Eman A; Hess, Ulrike; Rezwan, Kurosch

2017-01-01

This paper describes the effect of magnesia in the presence of zirconia on the bioactivity, microstructure and physico-mechanical properties of calcium silicate composition adjusted at calcia/silica ratio(C/S) of 0.5. A mixture from calcium carbonate and silica was conducted at C/S of 0.5. 20wt.% of magnesia and 5-25wt.% of ZrO 2 were added. Each mixture was mixed with ethanol in a planetary ball mill, dried, formed and fired at a temperature of 1325±5°C. Phase composition, FE-SEM, and physico-mechanical properties of the fired specimens were determined and explained. The in vitro bioactivities of these specimens were investigated by analysis of their abilities to form apatite in the simulated body fluid (SBF) for a short time (7days) using SEM-EDS. The findings indicated that the surface of the specimens containing 5 and 15wt.% ZrO 2 were completely covered by single and multilayered hydroxyapatite (HA) precipitate typical to "cauliflower" morphology, respectively. The surface of the specimen containing 25wt.% ZrO 2 did not cover, but there are some scattered HA precipitate. The differences among the results were rationalized based on the phase composition. Vickers hardness and fracture toughness of the specimens of highly promised bioactivity were 2.32-2.57GPa and 1.80-1.50MPa. m 1/2 , respectively. The properties of these specimens are similar to the properties of human cortical bone. Consequently, these composites might be used as bone implant materials. Copyright © 2016 Elsevier B.V. All rights reserved.

Hydrothermal synthesis and characterization of Si and Sr co-substituted hydroxyapatite nanowires using strontium containing calcium silicate as precursors.

PubMed

Zhang, Na; Zhai, Dong; Chen, Lei; Zou, Zhaoyong; Lin, Kaili; Chang, Jiang

2014-04-01

In the absence of any organic surfactants and solvents, the silicon (Si) and strontium (Sr) co-substituted hydroxyapatite [Ca10(PO4)6(OH)2, Si/Sr-HAp] nanowires were synthesized via hydrothermal treatment of the Sr-containing calcium silicate (Sr-CS) powders as the precursors in trisodium phosphate (Na3PO4) aqueous solution. The morphology, phase, chemical compositions, lattice constants and the degradability of the products were characterized. The Si/Sr-HAp nanowires with diameter of about 60nm and up to 2μm in length were obtained after hydrothermal treatment of the Sr-CS precursors. The Sr and Si substitution amount of the HAp nanowires could be well regulated by facile tailoring the Sr substitution level of the precursors and the reaction ratio of the precursor/solution, respectively. The SiO4 tetrahedra and Sr(2+) ions occupied the crystal sites of the HAp, and the lattice constants increased apparently with the increase of the substitution amount. EDS mapping also suggested the uniform distribution of Si and Sr in the synthetic nanowires. Moreover, the Si/Sr-substitution apparently improved the degradability of the HAp materials. Our study suggested that the precursor transformation method provided a facile approach to synthesize the Si/Sr co-substituted HAp nanowires with controllable substitution amount, and the synthetic Si/Sr-HAp nanowires might be used as bioactive materials for hard tissue regeneration applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Hydration of Concrete: The First Steps.

PubMed

Thissen, Peter; Natzeck, Carsten; Giraudo, Nicolas; Weidler, Peter; Wöll, Christof

2018-04-12

Concrete is the most important construction material used by mankind and, at the same time, one of the most complex substances known in materials science. Since this mineral compound is highly porous, a better understanding of its surface chemistry, and in particular the reaction with water, is urgently required to understand and avoid corrosion of infrastructure like buildings and bridges. We have gained insight into proton transfer from concrete upon contact with water by applying the so-called Surface Science approach to a well-defined mineral, Wollastonite. Data from IR (infrared) spectroscopy reveal that exposure of this calcium-silicate (CS) substrate to H 2 O leads to dissociation and the formation of OH-species. This proton transfer is a chemical reaction of key importance, since on the one hand it triggers the conversion of cement into concrete (a calcium-silicate-hydrate phase), but on the other hand also governs the corrosion of concrete. Interestingly, we find that no proton transfer takes place when the same surface is exposed to methanol. In order to understand this unexpected difference, the analysis of the spectroscopic data obtained was aided by a detailed, first-principles computational study employing density functional theory (DFT). The combined experimental and theoretical effort allows derivation of a consistent picture of proton transfer reactions occurring in CS and CSH phases. Implications for strategies to protect this backbone of urban infrastructure from corrosion in harsh, aqueous environments will be discussed. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of temperature on hydration kinetics and polymerization of tricalcium silicate in stirred suspensions of CaO-saturated solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grant, Steven A.; Boitnott, Ginger E.; Korhonen, Charles J.

2006-04-15

Tricalcium silicate was hydrated at 274, 278, 283, 298, and 313 K in stirred suspensions of saturated CaO solutions under a nitrogen-gas atmosphere until the end of deceleratory period. The suspension conductivities and energy flows were measured continuously. The individual reaction rates for tricalcium silicate dissolution, calcium silicate hydrate precipitation, and calcium hydroxide precipitation were calculated from these measurements. The results suggest that the proportion of tricalcium silicate dissolved was determined by the rate of tricalcium silicate dissolution and the time to very rapid calcium hydroxide precipitation. The time to very rapid calcium hydroxide precipitation was more sensitive to changesmore » in temperature than was the rate of tricalcium silicate dissolution, so that the proportion of tricalcium silicate hydration dissolved by the deceleratory period increased with decreasing temperature. The average chain length of the calcium silicate hydrate ascertained by magic-angle spinning nuclear magnetic resonance spectroscopy increased with increasing temperature.« less

40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Calcium hydroxide oxide silicate (Ca6... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate (Ca6(OH)2O2... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...

40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Calcium hydroxide oxide silicate (Ca6... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate (Ca6(OH)2O2... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...

40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Calcium hydroxide oxide silicate (Ca6... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate (Ca6(OH)2O2... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...

40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Calcium hydroxide oxide silicate (Ca6... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate (Ca6(OH)2O2... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...

40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Calcium hydroxide oxide silicate (Ca6... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate (Ca6(OH)2O2... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Pei; Wei, Pingpin; Li, Pengjian

Calcium silicate possessed excellent biocompatibility, bioactivity and degradability, while the high brittleness limited its application in load-bearing sites. Hydroxyapatite whiskers ranging from 0 to 30 wt.% were incorporated into the calcium silicate matrix to improve the strength and fracture resistance. Porous scaffolds were fabricated by selective laser sintering. The effects of hydroxyapatite whiskers on the mechanical properties and toughening mechanisms were investigated. The results showed that the scaffolds had a uniform and continuous inner network with the pore size ranging between 0.5 mm and 0.8 mm. The mechanical properties were enhanced with increasing hydroxyapatite whiskers, reached a maximum at 20more » wt.% (compressive strength: 27.28 MPa, compressive Young's modulus: 156.2 MPa, flexural strength: 15.64 MPa and fracture toughness: 1.43 MPa·m{sup 1/2}) and then decreased by addition of more hydroxyapatite whiskers. The improvement of mechanical properties was due to whisker pull-out, crack deflection and crack bridging. Moreover, the degradation rate decreased with the increase of hydroxyapatite whisker content. A layer of bone-like apatite was formed on the scaffold surfaces after being soaked in simulated body fluid. Human osteoblast-like MG-63 cells spread well on the scaffolds and proliferated with increasing culture time. These findings suggested that the calcium silicate scaffolds reinforced with hydroxyapatite whiskers showed great potential for bone regeneration and tissue engineering applications. - Highlights: • HA whiskers were incorporated into CS to improve the properties. • The scaffolds were successfully fabricated by SLS. • Toughening mechanisms was whisker pull-out, crack deflection and bridging. • The scaffolds showed excellent apatite forming ability.« less

Biocompatibility of new nanostructural materials based on active silicate systems and hydroxyapatite: in vitro and in vivo study.

PubMed

Petrović, V; Opačić-Galić, V; Živković, S; Nikolić, B; Danilović, V; Miletić, V; Jokanović, V; Mitić-Ćulafić, D

2015-10-01

To evaluate in vitro cytotoxicity and in vivo inflammatory response to new nanostructural materials based on active calcium silicate systems (CS) and hydroxyapatite (HA-CS). Cytotoxicity of eluates of new nanostructural noncommercial materials CS and HA-CS, and MTA (White MTA, Angelus(®) Soluções Odontológicas, Londrina, Brazil) as a control, were tested using the MTT assay on MRC-5 cells. Eluates of set materials were tested in 100% and 50% concentrations, 24 h, 7 days and 21 days post-elution. The pH values were determined for undiluted eluates of set materials. Polyethylene tubes containing the test materials (CS, HA-CS, MTA) were implanted in subcutaneous tissue of Wistar rats. Histopathological examinations were conducted at 7, 15, 30 and 60 days after the implantation. Data were statistically analyzed using three-way and one-way anova Tukey's post hoc test as well as Kruskall-Wallis test with Dunn's post hoc test at α = 0.05. All materials significantly reduced cell viability; especially when undiluted eluates were used (P < 0.001). After 24 h elution, cell viability was 10 ± 1.8%, 49.5 ± 4.2% and 61 ± 7.4%, for MTA, and HA-CS, respectively. However, CS and HA-CS were significantly less toxic than the control material MTA (P < 0.05). Cytotoxicity could be at least partially attributed to pH kinetics over time. Dilution of eluates of all tested materials resulted in better cell survival. Histopathological examination indicated similar inflammatory reaction, vascular congestion and connective tissue integrity associated with CS, HA-CS and MTA at each observation period (P > 0.05). The only significant difference was found for capsule thickness, that is thicker capsule was associated with HA-CS compared to MTA at 60 days (P = 0.0039). HA-CS induced moderately thick capsules (median score 3, score range 2-3), whereas MTA resulted in thin capsule formation (median score 2, score range 1-3). Evaluation of cytotoxicity and inflammatory response indicated better biocompatibility of CS and HA-CS, in comparison with MTA (White MTA, Angelus(®) Soluções Odontológicas, Londrina, Brazil). © 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Ceramic modifications of porous titanium: effects on macrophage activation.

PubMed

Scislowska-Czarnecka, A; Menaszek, E; Szaraniec, B; Kolaczkowska, E

2012-12-01

Porous titanium is one of the most widely used implant materials because of its mechanical properties, however, it is also characterised by low bioactivity. To improve the above parameter we prepared three modifications of the porous (30 wt%) titanium (Ti) surface by covering it with bioactive hydroxyapatite (HA), bioglass (BG) and calcium silicate (CS). Subsequently we tested the impact of the modifications on macrophages directing the inflammatory response that might compromise the implant bioactivity. In the study we investigated the in vitro effects of the materials on murine cell line RAW 264.7 macrophage adherence, morphology and activation (production/release of metalloproteinase MMP-9 and pro- and anti-inflammatory cytokines). CS Ti decreased the macrophage adherence and up-regulated the release of several pro-inflammatory mediators, including TNF-α, IL-6, IL-12. Also HA Ti reduced the cell adherence but other parameters were generally not increased, except of TNF-α. In contrast, BG Ti improved macrophage adherence and either decreased production of multiple mediators (MMP-9, TNF-α, IFN-γ, MCP-1) or did not change it in comparison to the porous titanium. We can conclude that analyzing the effects on the inflammatory response initiated by macrophages in vitro, calcium silicate did not improve the biological properties of the porous titanium. The improved bioactivity of titanium was, however, achieved by the application of the hydroxyapatite and bioglass layers. The present in vitro results suggest that these materials, HA Ti and especially BG Ti, may be suitable for in vivo application and thus justify their further investigation. Copyright © 2012 Elsevier Ltd. All rights reserved.

The utilization of waste by-products for removing silicate from mineral processing wastewater via chemical precipitation.

PubMed

Kang, Jianhua; Sun, Wei; Hu, Yuehua; Gao, Zhiyong; Liu, Runqing; Zhang, Qingpeng; Liu, Hang; Meng, Xiangsong

2017-11-15

This study investigates an environmentally friendly technology that utilizes waste by-products (waste acid and waste alkali liquids) to treat mineral processing wastewater. Chemical precipitation is used to remove silicate from scheelite (CaWO 4 ) cleaning flotation wastewater and the waste by-products are used as a substitute for calcium chloride (CaCl 2 ). A series of laboratory experiments is conducted to explain the removal of silicate and the characterization and formation mechanism of calcium silicate. The results show that silicate removal reaches 90% when the Ca:Si molar ratio exceeds 1.0. The X-ray diffraction (XRD) results confirm the characterization and formation of calcium silicate. The pH is the key factor for silicate removal, and the formation of polysilicic acid with a reduction of pH can effectively improve the silicate removal and reduce the usage of calcium. The economic analysis shows that the treatment costs with waste acid (0.63 $/m 3 ) and waste alkali (1.54 $/m 3 ) are lower than that of calcium chloride (2.38 $/m 3 ). The efficient removal of silicate is confirmed by industrial testing at a plant. The results show that silicate removal reaches 85% in the recycled water from tailings dam. Copyright © 2017 Elsevier Ltd. All rights reserved.

Interaction of Nanostructured Calcium Silicate Hydrate with Ibuprofen Drug Molecules: X-ray Absorption Near Edge Structure (XANES) Study at the Ca, Si and O K-edge

NASA Astrophysics Data System (ADS)

Guo, X. X.; Sham, T. K.; Zhu, Y. J.; Hu, Y. F.

2013-04-01

Mesoporous calcium silicate hydrate (CSH) nanostructure has been proven to be bioactive and biocompatible, and has a bright future in the application of bone treatment among other applications. X-ray absorption near edge structure (XANES) is a powerful tool for the study of the interactions of calcium silicate hydrates with drug molecules because it is element specific and it probes the unoccupied electronic states. Herein, we report the use of the calcium, silicon and oxygen K-edge XANES spectroscopy to identify how drug molecules interact with different groups in calcium silicate hydrate mesoporous nano-carriers with different morphologies. Significant changes are observed in XANES spectra after drug loading into the calcium silicate hydrate system, especially at the Si and O K-edge. The implications of these findings are discussed.

Cs-137 immobilization in C-S-H gel nanopores.

PubMed

Duque-Redondo, Eduardo; Kazuo, Yamada; López-Arbeloa, Iñigo; Manzano, Hegoi

2018-04-04

Cementation is a widespread technique to immobilize nuclear waste due to the low leachability of cementitious materials. The capacity of calcium silicate hydrate (C-S-H), the main component of cement, to retain radionuclide Cs has been empirically studied at the macroscale, yet the specific molecular scale mechanisms that govern the retention have not been determined. In this work, we employed molecular dynamics simulations to investigate the adsorption and diffusivity of Cs into a C-S-H gel nanopore. From the simulations, it was possible to distinguish three types of Cs adsorption configurations on the C-S-H: an inner-sphere surface site where Cs is strongly bound, an outer-sphere surface site where Cs is loosely bound, and Cs free in the nanopore. For each configuration, we determined the sorption energy, and the diffusion coefficients, up to two orders of magnitude lower than in bulk water due to the effect of nanoconfinement in the worst case scenario. It has also proved that Cs cannot displace the intrinsic Ca from the C-S-H surface, and we calculated the binding strength and the residence time of the cations in the surface adsorption sites. Finally, we quantified the average number of adsorption sites per nm2 of the C-S-H surface. All these results are the first insights into Cs retention in cement at the molecular scale and will be useful to build macroscopic diffusion models and devise cement formulations to improve radionuclide Cs retention from spent nuclear fuel.

Dehydration and dehydroxylation of C-S-H phases synthesized on silicon wafers

NASA Astrophysics Data System (ADS)

Giraudo, Nicolas; Bergdolt, Samuel; Laye, Fabrice; Krolla, Peter; Lahann, Joerg; Thissen, Peter

2018-03-01

In this work, the synthesis of specific ultrathin Calcium-Silicate-Hydrate (C-S-H) phases on silicon wafers and their transformation into C-S phases is achieved. Specific mineral phases are identified, and the synthesis is successful controlled. Samples are investigated by means of Fourier Transform Infrared (FTIR) spectroscopy and X-ray Diffraction (XRD) and the results are analyzed based on first-principles calculations. When C-S-H phases are transformed into C-S phases, only a few reflexes are detected on XRD, and the coherent scattering domains decrease with the increment of the temperature and time of exposure. This behavior is explained by the Ca/Si changes, which are identified by changes in the FTIR spectra. A thermodynamic analysis is performed with the help of first-principles calculations to underline the influence of the calcium-to-silicon (Ca/Si) ratio in the process of dehydroxylation. To increase the Ca/Si ratio water is partially substituted by methanol at the synthesis. This is observed in the FTIR spectra and is confirmed by lower temperatures of dehydroxylation. The catalytic nature of calcium towards the dehydroxylation is confirmed. The core of this work lies in the preparation of a model, which perfection makes possible to model reactivity, stability and mechanical properties using first-principles calculations, and is the starting point for the synthesis of many others.

In vitro studies of degradation and bioactivity of aliphatic polyester composites

NASA Astrophysics Data System (ADS)

Chouzouri, Georgia

In spite of numerous publications on the potential use of combinations of aliphatic polyester composites containing bioactive fillers for bone regeneration, little information exists on the combined in vitro mechanisms involving simultaneously diffusion for polymer degradation and bioactivity through nucleation and growth of apatite in simulated body fluid (SBF) solution. The objective of this study is to contribute to the understanding of the fundamentals in designing non-porous, solid materials for bone regeneration, from experimental data along with their engineering interpretation. Bioactivity, in terms of apatite growth, was assessed through several experimental methods such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray-diffraction (XRD) and changes in ion concentration. In the case of the six neat fillers evaluated, the filler shape, form and chemical structure showed significant differences in bioactivity response. Bioglass and calcium silicate fillers showed faster nucleation and growth rates in the screening experiments. Composites at 30% by weight filler were prepared by solution and/or melt mixing. Polycaprolactone (PCL) composites containing five different fillers were evaluated. Solution processed PCL/calcium silicate (CS) samples showed faster bioactivity, as determined by apatite growth, compared to melt mixed samples. The onset time for bioactivity was different for all PCL composites. The limited bioactivity in the PCL composites over longer periods of time could be attributed to the PCL hydrophobicity leading to a slow polymer degradation rate, and also to the lack of SBF replenishment. For both polylactic acid (PLA) composites containing CS and bioglass, significant growth was observed after one week and in the case of CS was still evident after four weeks immersion. However, at prolonged time periods no further bioactivity was observed, although ion release results indicated a faster release rate that would eventually lead to a faster polymer degradation and possibly continuing bioactivity. The presence of silicate fillers enhanced the hydrolytic degradation rate of both PCL and PLA as shown from kinetic data calculations based on molecular weight measurements. Unfilled PLA samples showed significant embrittlement after two weeks immersion, whereas for the CS filled system more significant changes could be observed in the compressive strength and modulus after the same time period. Experimental data were also fitted into an equation proposed to calculate erosion number; in the case of unfilled PLA predictions were found to agree with literature results suggesting bulk erosion. By assuming impermeable, randomly dispersed glass flakes, water transport in a composite system, prior to significant polymer degradation could be modeled. However, modeling of transport in the case of the composite consisting of a degrading polymer and a reactive decaying filler was challenging, particularly in the case of directional bioactive reinforcements, due to the occurrence of simultaneous time dependent diffusion phenomena that altered the integrity of the sample.

The inhibitory effects of potassium chloride versus potassium silicate application on (137)Cs uptake by rice.

PubMed

Fujimura, Shigeto; Yoshioka, Kunio; Ota, Takeshi; Ishikawa, Tetsuya; Sato, Makoto; Satou, Mutsuto

2016-03-01

After the accident at the Fukushima Dai-ichi Nuclear Power Plant owned by the Tokyo Electric Power Company on 11 March 2011, potassium fertilizer was applied to agricultural fields in the southern Tohoku and northern Kanto regions of Japan to reduce the uptake of radiocesium by crops. In this study, we examined the effects of two types of potassium fertilizers, potassium chloride (a readily available potassium fertilizer) and potassium silicate (a slow-release potassium fertilizer), as well as a split application of potassium, on the accumulation of (137)Cs by rice plants in two pot experiments. The (137)Cs concentrations in the brown rice and in the above-ground plants were significantly lower after potassium chloride application than after potassium silicate application. The potassium ion (K(+)) concentrations in soil solutions sampled 9 and 21 d after transplanting were significantly higher for the potassium chloride application than for the potassium silicate application. The K(+) concentrations in soil solutions observed in the application of potassium silicate were similar to those in the treatment when no potassium was applied. This finding indicates that the application of potassium silicate did not sufficiently increase the available K(+) for rice plants in the soil, which led to a greater uptake of (137)Cs after the potassium silicate application than after the application of potassium chloride. The (137)Cs concentration in brown rice was higher in the split application of potassium fertilizer with the second application at the full heading stage than that without split application and the split application with the second application before heading. Copyright © 2016 Elsevier Ltd. All rights reserved.

Revised Atomistic Models of the Crystal Structure of C-S-H with high C/S Ratio

NASA Astrophysics Data System (ADS)

Kovačević, Goran; Nicoleau, Luc; Nonat, André; Veryazov, Valera

2016-09-01

The atomic structure of calcium-silicate-hydrate (C1.67-S-Hx) has been studied. Atomistic C-S-H models suggested in our previous study have been revised in order to perform a direct comparison of energetic stability of the different structures. An extensive set of periodic structures of C-S-H with variation of water content was created, and then optimized using molecular dynamics with reactive force field ReaxFF and quantum chemical semiempirical method PM6. All models show organization of water molecules inside the structure of C-S-H. The new geometries of C-S-H, reported in this paper, show lower relative energy with respect to the geometries from the original definition of C-S-H models. Model that corresponds to calcium enriched tobermorite structure has the lowest relative energy and the density closest to the experimental values.

Calcium silicates synthesised from industrial residues with the ability for CO2 sequestration.

PubMed

Morales-Flórez, Victor; Santos, Alberto; López, Antonio; Moriña, Isabel; Esquivias, Luis

2014-12-01

This work explored several synthesis routes to obtain calcium silicates from different calcium-rich and silica-rich industrial residues. Larnite, wollastonite and calcium silicate chloride were successfully synthesised with moderate heat treatments below standard temperatures. These procedures help to not only conserve natural resources, but also to reduce the energy requirements and CO2 emissions. In addition, these silicates have been successfully tested as carbon dioxide sequesters, to enhance the viability of CO2 mineral sequestration technologies using calcium-rich industrial by-products as sequestration agents. Two different carbon sequestration experiments were performed under ambient conditions. Static experiments revealed carbonation efficiencies close to 100% and real-time resolved experiments characterised the dynamic behaviour and ability of these samples to reduce the CO2 concentration within a mixture of gases. The CO2 concentration was reduced up to 70%, with a carbon fixation dynamic ratio of 3.2 mg CO2 per g of sequestration agent and minute. Our results confirm the suitability of the proposed synthesis routes to synthesise different calcium silicates recycling industrial residues, being therefore energetically more efficient and environmentally friendly procedures for the cement industry. © The Author(s) 2014.

The flame photometric determination of calcium in phosphate, carbonate, and silicate rocks

USGS Publications Warehouse

Kramer, H.

1957-01-01

A flame photometric method of determining calcium in phosphate, carbonate, and silicate locks has been developed Aluminum and phosphate interference was overcome by the addition of a large excess of magnesium. The method is rapid and suitable for routine analysis Results obtained are within ?? 2% of the calcium oxide content. ?? 1957.

Fluoride-containing nanoporous calcium-silicate MTA cements for endodontics and oral surgery: early fluorapatite formation in a phosphate-containing solution.

PubMed

Gandolfi, M G; Taddei, P; Siboni, F; Modena, E; Ginebra, M P; Prati, C

2011-10-01

To test the chemical-physical properties and apatite-forming ability of experimental fluoride-doped calcium silicate cements designed to create novel bioactive materials for use in endodontics and oral surgery. A thermally treated calcium silicate cement (wTC) containing CaCl(2) 5%wt was modified by adding NaF 1%wt (FTC) or 10%wt (F10TC). Cements were analysed by environmental scanning electron microscopy with energy-dispersive X-ray analysis, IR and micro-Raman spectroscopy in wet conditions immediately after preparation or after ageing in a phosphate-containing solution (Dulbecco's phosphate-buffered saline). Calcium and fluoride release and pH of the storage solution were measured. The results obtained were analysed statistically (Tukey's HSD test and two-way anova). The formation of calcium phosphate precipitates (spherulites) was observed on the surface of 24 h-aged cements and the formation of a thick bone-like B-type carbonated apatite layer (biocoating) on 28 day-aged cements. The rate of apatite formation was FTC>F10TC>wTC. Fluorapatite was detected on FTC and F10TC after 1 day of ageing, with a higher fluoride content on F10TC. All the cements released calcium ions. At 5 and 24 h, the wTC had the significantly highest calcium release (P<0.001) that decreased significantly over the storage time. At 3-28 days, FTC and F10TC had significantly higher calcium release than wTC (P<0.05). The F10TC had the significantly highest fluoride release at all times (P<0.01) that decreased significantly over storage time. No significant differences were observed between FTC and wTC. All the cements had a strong alkalinizing activity (OH(-) release) that remained after 28 days of storage. The addition of sodium fluoride accelerated apatite formation on calcium silicate cements. Fluoride-doped calcium silicate cements had higher bioactivity and earlier formation of fluorapatite. Sodium fluoride may be introduced in the formulation of mineral trioxide aggregate cements to enhance their biological behaviour. F-doped calcium silicate cements are promising bone cements for clinical endodontic use. © 2011 International Endodontic Journal.

Determination of thermodynamic parameters for complexation of calcium and magnesium with chondroitin sulfate isomers using isothermal titration calorimetry: Implications for calcium kidney-stone research

NASA Astrophysics Data System (ADS)

Rodgers, Allen L.; Jackson, Graham E.

2017-04-01

Chondroitin sulfate (CS) occurs in human urine. It has several potential binding sites for calcium and as such may play an inhibitory role in calcium oxalate and calcium phosphate (kidney stone disease by reducing the supersaturation (SS) and crystallization of these salts. Urinary magnesium is also a role player in determining speciation in stone forming processes. This study was undertaken to determine the thermodynamic parameters for binding of the disaccharide unit of two different CS isomers with calcium and magnesium. These included the binding constant K. Experiments were performed using an isothermal titration calorimeter (ITC) at 3 different pH levels in the physiological range in human urine. Data showed that interactions between the CS isomers and calcium and magnesium occur via one binding site, thought to be sulfate, and that log K values are 1.17-1.93 and 1.77-1.80 for these two metals respectively. Binding was significantly stronger in Mg-CS than in Ca-CS complexes and was found to be dependent on pH in the latter but not in the former. Furthermore, binding in Ca-CS complexes was dependent on the location of the sulfate binding site. This was not the case in the Mg-CS complexes. Interactions were shown to be entropy driven and enthalpy unfavourable. These findings can be used in computational modeling studies to predict the effects of the calcium and magnesium CS complexes on the speciation of calcium and the SS of calcium salts in real urine samples.

Determine the Compressive Strength of Calcium Silicate Bricks by Combined Nondestructive Method

PubMed Central

2014-01-01

The paper deals with the application of combined nondestructive method for assessment of compressive strength of calcium silicate bricks. In this case, it is a combination of the rebound hammer method and ultrasonic pulse method. Calibration relationships for determining compressive strength of calcium silicate bricks obtained from nondestructive parameter testing for the combined method as well as for the L-type Schmidt rebound hammer and ultrasonic pulse method are quoted here. Calibration relationships are known for their close correlation and are applicable in practice. The highest correlation between parameters from nondestructive measurement and predicted compressive strength is obtained using the SonReb combined nondestructive method. Combined nondestructive SonReb method was proved applicable for determination of compressive strength of calcium silicate bricks at checking tests in a production plant and for evaluation of bricks built in existing masonry structures. PMID:25276864

Calcium silicate-based cements and functional impacts of various constituents

PubMed Central

SAGHIRI, Mohammad Ali; ORANGI, Jafar; ASATOURIAN, Armen; GUTMANN, James L.; Garcia-Godoy, Franklin; LOTFI, Mehrdad; SHEIBANI, Nader

2016-01-01

Calcium silicate-based cements have superior sealing ability, bioactivity, and marginal adaptation, which make them suitable for different dental treatment applications. However, they exhibit some drawbacks such as long setting time and poor handling characteristics. To overcome these limitations calcium silicates are engineered with various constituents to improve specific characteristics of the base material, and are the focus of this review. An electronic search of the PubMed, MEDLINE, and EMBASE via OVID databases using appropriate terms and keywords related to the use, application, and properties of calcium silicate-based cements was conducted. Two independent reviewers obtained and analyzed the full texts of the selected articles. Although the effects of various constituents and additives to the base Portland cement-like materials have been investigated, there is no one particular ingredient that stands out as being most important. Applying nanotechnology and new synthesis methods for powders most positively affected the cement properties. PMID:27773894

Decreased water flowing from a forest amended with calcium silicate

Treesearch

Mark B. Green; Amey S. Bailey; Scott W. Bailey; John J. Battles; John L. Campbell; Charles T. Driscoll; Timothy J. Fahey; Lucie C. Lepine; Gene E. Likens; Scott V. Ollinger; Paul G. Schaberg

2013-01-01

Acid deposition during the 20th century caused widespread depletion of available soil calcium (Ca) throughout much of the industrialized world. To better understand how forest ecosystems respond to changes in a component of acidification stress, an 11.8-ha watershed was amended with wollastonite, a calcium silicate mineral, to restore available soil Ca to preindustrial...

Mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells following their exposure to a discoloration-free calcium aluminosilicate cement.

PubMed

Niu, Li-Na; Pei, Dan-Dan; Morris, Matthew; Jiao, Kai; Huang, Xue-Qing; Primus, Carolyn M; Susin, Lisiane F; Bergeron, Brian E; Pashley, David H; Tay, Franklin R

2016-10-01

An experimental discoloration-free calcium aluminosilicate cement has been developed with the intention of maximizing the beneficial attributes of tricalcium silicate cements and calcium aluminate cements. The present study examined the effects of this experimental cement (Quick-Set2) on the mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells (hDPSCs), by comparing the cellular responses with a commercially available tricalcium silicate cement (white mineral trioxide aggregate (ProRoot(®) MTA); WMTA). The osteogenic potential of hDPSCs exposed to the cements was examined using qRT-PCR for osteogenic gene expressions, Western blot for osteogenic-related protein expressions, alkaline phosphatase enzyme activity, Alizarin red S staining, Fourier transform infrared spectroscopy and transmission electron microscopy of extracellular calcium deposits. Results of the six assays indicated that osteogenic differentiation of hDPSCs was significantly enhanced after exposure to the tricalcium silicate cement or the experimental calcium aluminosilicate cement, with the former demonstrating better mineralogenic stimulation capacity. The better osteogenic stimulating effect of the tricalcium silicate cement on hDPSCs may be due to its relatively higher silicate content, or higher OH(-) and Ca(2+) release. Further investigations with the use of in vivo animal models are required to validate the potential augmenting osteogenic effects of the experimental discoloration-free calcium aluminosilicate cement. Published by Elsevier Ltd.

Thermodynamics, kinetics, and mechanics of cesium sorption in cement paste: A multiscale assessment

NASA Astrophysics Data System (ADS)

Arayro, Jack; Dufresne, Alice; Zhou, Tingtao; Ioannidou, Katerina; Ulm, Josef-Franz; Pellenq, Roland; Béland, Laurent Karim

2018-05-01

Cesium-137 is a common radioactive byproduct found in nuclear spent fuel. Given its 30 year half life, its interactions with potential storage materials—such as cement paste—is of crucial importance. In this paper, simulations are used to establish the interaction of calcium silicate hydrates (C-S-H)—the main binding phase of cement paste—with Cs at the nano- and mesoscale. Different C-S-H compositions are explored, including a range of Ca/Si ratios from 1.0 to 2.0. These calculations are based on a set of 150 atomistic models, which qualitatively and quantitatively reproduce a number of experimentally measured features of C-S-H—within limits intrinsic to the approximations imposed by classical molecular dynamics and the steps followed when building the models. A procedure where hydrated Ca2 + ions are swapped for Cs1 + ions shows that Cs adsorption in the C-S-H interlayer is preferred to Cs adsorption at the nanopore surface when Cs concentrations are lower than 0.19 Mol/kg. Interlayer sorption decreases as the Ca/Si ratio increases. The activation relaxation technique nouveau is used to access timescales out of the reach of traditional molecular dynamics (MD). It indicates that characteristic diffusion time for Cs1 + in the C-S-H interlayer is on the order of a few hours. Cs uptake in the interlayer has little impact on the elastic response of C-S-H. It leads to swelling of the C-S-H grains, but mesoscale calculations that access length scales out of the range of MD indicate that this leads to practically negligible expansive pressures for Cs concentrations relevant to nuclear waste repositories.

Effect of phase composition of calcium silicate phosphate component on properties of brushite based composite cements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sopcak, T., E-mail: tsopcak@imr.saske.sk; Medvecky, L.; Giretova, M.

The composite cement mixtures were prepared by mixing brushite (B) with, the amorphous hydrated calcium silicate phosphate (CSPH) or annealed calcium silicate phosphate (CSP composed of Si-saturated hydroxyapatite, wollastonite and silica) phases and water as liquid component. The contents of the silicate-phosphate phase in composites were 10.30 and 50 wt%. The significant effect of both the Ca/P ratio and different solubility of calcium silicate phosphate component in starting cement systems on setting time and phase composition of the final composite cements was demonstrated. The compressive strength of the set cements increased with the filler addition and the highest value (~more » 48 MPa) exhibited the 50CSP/B cement composite. The final setting times of the composite cements decreased with the CSPH addition from about 25 to 17 min in 50CSHP/B and setting time of CSP/B composites was around 30 min. The higher content of silica in cements caused the precipitation of fine hydroxyapatite particles in the form of nanoneedles or thin plates perpendicularly oriented to sample surface. The analysis of in vitro cement cytotoxicity demonstrated the strong reduction in cytotoxicity of 10CSPH/B composite with time of cultivation (a low cytotoxicity after 9 days of culture) contrary to cements with higher calcium silicate-phosphate content. These results were attributed to the different surface topography of composite substrates and possible stimulation of cell proliferation by the slow continuously release of ions from 10CSPH/B cement. - Highlights: • Ca/P ratio and solubility of calcium silicate-phosphate components affect the self-setting properties of cements. • Strong relationship between the composite in vitro cytotoxicity and surface microtopography was demonstrated. • Plate-like morphology of coarser particles allowed cells to better adhere and proliferate as compared with nanoneedles.« less

SINTERING AND SULFATION OF CALCIUM SILICATE-ALUMINATE

EPA Science Inventory

The effect of sintering on the reactivity of solids at high temperature was studied. The nature of the interaction was studied with calcium silicate-aluminate reacting with SO2 between 665 and 800 C. The kinetics of the sintering and sulfation processes were measured independentl...

Remineralisation effect of a dual-phase calcium silicate/phosphate gel combined with calcium silicate/phosphate toothpaste on acid-challenged enamel in situ.

PubMed

Joiner, Andrew; Schäfer, Fred; Naeeni, Mojgan M; Gupta, Ashok K; Zero, Domenick T

2014-06-01

To test if a novel dual-phase gel system (calcium silicate and phosphate with 1450 ppmF, as NaF/MFP; TG) combined with a toothpaste (calcium silicate and sodium phosphate with 1450 ppmF, as MFP; TG) was able to re-harden previously acid-challenged enamel to a greater extent than other toothpastes. The study consisted of a double-blind, randomised, cross-over design with four 7-day treatment legs. In each leg, subjects wearing a partial denture holding four demineralised enamel specimens (25 min in 0.3% citric acid, pH3.8) used either the test regimen (TG+TP) or one of the three controls. (placebo TG+TP; Positive Control - placebo TG+marketed 1450 ppmF toothpaste; Negative Control - placebo TG+placebo TP). Enamel specimens were removed after 1, 2, 3 and 7 days. The gel systems were applied once per day for the first three days during which subjects also brushed with the corresponding toothpaste; this was followed by four days use of the toothpastes only. Toothpastes were used in the conventional way brushing twice per day throughout the seven days. The outcome variable was %Surface Microhardness Recovery calculated after three and seven days of in situ treatment. The results showed a statistically significant (p<0.001) re-hardening effect for all treatments compared to pre-treatment hardness. After three days and after seven days of in situ treatment significantly greater hardening (p<0.05) was found in the samples treated with calcium silicate/phosphate gel system plus calcium silicate/phosphate toothpaste than in the control groups. It is concluded that the test regimen based on the novel dual-phase gel system combined with toothpaste was able to re-harden acid-challenged tooth enamel to a greater extent than a normal fluoride toothpaste. The novel oral care products containing calcium silicate, sodium phosphate salts and fluoride is a new approach to the repair of demineralised enamel. © 2014 Elsevier Ltd. All rights reserved.

Desulfurization of fuel gases in fluidized bed gasification and hot fuel gas cleanup systems

DOEpatents

Steinberg, M.; Farber, G.; Pruzansky, J.; Yoo, H.J.; McGauley, P.

1983-08-26

A problem with the commercialization of fluidized bed gasification is that vast amounts of spent sorbent are generated if the sorbent is used on a once-through basis, especially if high sulfur coals are burned. The requirements of a sorbent for regenerative service in the FBG process are: (1) it must be capable of reducing the sulfur containing gas concentration of the FBG flue gas to within acceptable environmental standards; (2) it must not lose its reactivity on cyclic sulfidation and regeneration; (3) it must be capable of regeneration with elimination of substantially all of its sulfur content; (4) it must have good attrition resistance; and, (5) its cost must not be prohibitive. It has now been discovered that calcium silicate pellets, e.g., Portland cement type III pellets meet the criteria aforesaid. Calcium silicate removes COS and H/sub 2/S according to the reactions given to produce calcium sulfide silicate. The sulfur containing product can be regenerated using CO/sub 2/ as the regenerant. The sulfur dioxide can be conveniently reduced to sulfur with hydrogen or carbon for market or storage. The basic reactions in the process of this invention are the reactions with calcium silicate given in the patent. A convenient and inexpensive source of calcium silicate is Portland cement. Portland cement is a readily available, widely used construction meterial.

Preparation of the fast setting and degrading Ca-Si-Mg cement with both odontogenesis and angiogenesis differentiation of human periodontal ligament cells.

PubMed

Chen, Yi-Wen; Hsu, Tuan-Ti; Wang, Kan; Shie, Ming-You

2016-03-01

Develop a fast setting and controllable degrading magnesium-calcium silicate cement (Mg-CS) by sol-gel, and establish a mechanism using Mg ions to stimulate human periodontal ligament cells (hPDLs) are two purposes of this study. We have used the diametral tensile strength measurement to obtain the mechanical strength and stability of Mg-CS cement; in addition, the cement degradation properties is realized by measuring the releasing amount of Si and Mg ions in the simulated body fluid. The other cell characteristics of hPDLs, such as proliferation, differentiation and mineralization were examined while hPDLs were cultured on specimen surfaces. This study found out the degradation rate of Mg-CS cements depends on the Mg content in CS. Regarding in vitro bioactivity; the CS cements were covered with abundant clusters of apatite spherulites after immersion of 24h, while less apatite spherulites were formatted on the Mg-rich cement surfaces. In addition, the authors also explored the effects of Mg ions on the odontogenesis and angiogenesis differentiation of hPDLs in comparison with CS cement. The proliferation, alkaline phosphatase, odontogenesis-related genes (DSPP and DMP-1), and angiogenesis-related protein (vWF and ang-1) secretion of hPDLs were significantly stimulated when the Mg content of the specimen was increased. The results in this study suggest that Mg-CS materials with this modified composition could stimulate hPDLs behavior and can be good bioceramics for bone substitutes and hard tissue regeneration applications as they stimulate odontogenesis/angiogenesis. Copyright © 2015 Elsevier B.V. All rights reserved.

Apatite formation on bioactive calcium-silicate cements for dentistry affects surface topography and human marrow stromal cells proliferation.

PubMed

Gandolfi, Maria Giovanna; Ciapetti, Gabriela; Taddei, Paola; Perut, Francesca; Tinti, Anna; Cardoso, Marcio Vivan; Van Meerbeek, Bart; Prati, Carlo

2010-10-01

The effect of ageing in phosphate-containing solution of bioactive calcium-silicate cements on the chemistry, morphology and topography of the surface, as well as on in vitro human marrow stromal cells viability and proliferation was investigated. A calcium-silicate cement (wTC) mainly based on dicalcium-silicate and tricalcium-silicate was prepared. Alpha-TCP was added to wTC to obtain wTC-TCP. Bismuth oxide was inserted in wTC to prepare a radiopaque cement (wTC-Bi). A commercial calcium-silicate cement (ProRoot MTA) was tested as control. Cement disks were aged in DPBS for 5 h ('fresh samples'), 14 and 28 days, and analyzed by ESEM/EDX, SEM/EDX, ATR-FTIR, micro-Raman techniques and scanning white-light interferometry. Proliferation, LDH release, ALP activity and collagen production of human marrow stromal cells (MSC) seeded for 1-28 days on the cements were evaluated. Fresh samples exposed a surface mainly composed of calcium-silicate hydrates CSH (from the hydration of belite and alite), calcium hydroxide, calcium carbonate, and ettringite. Apatite nano-spherulites rapidly precipitated on cement surfaces within 5 h. On wTC-TCP the Ca-P deposits appeared thicker than on the other cements. Aged cements showed an irregular porous calcium-phosphate (Ca-P) coating, formed by aggregated apatite spherulites with interspersed calcite crystals. All the experimental cements exerted no acute toxicity in the cell assay system and allowed cell growth. Using biochemical results, the scores were: fresh cements>aged cements for cell proliferation and ALP activity (except for wTC-Bi), whereas fresh cements

Calcium-43 chemical shift tensors as probes of calcium binding environments. Insight into the structure of the vaterite CaCO3 polymorph by 43Ca solid-state NMR spectroscopy.

PubMed

Bryce, David L; Bultz, Elijah B; Aebi, Dominic

2008-07-23

Natural-abundance (43)Ca solid-state NMR spectroscopy at 21.1 T and gauge-including projector-augmented-wave (GIPAW) DFT calculations are developed as tools to provide insight into calcium binding environments, with special emphasis on the calcium chemical shift (CS) tensor. The first complete analysis of a (43)Ca solid-state NMR spectrum, including the relative orientation of the CS and electric field gradient (EFG) tensors, is reported for calcite. GIPAW calculations of the (43)Ca CS and EFG tensors for a series of small molecules are shown to reproduce experimental trends; for example, the trend in available solid-state chemical shifts is reproduced with a correlation coefficient of 0.983. The results strongly suggest the utility of the calcium CS tensor as a novel probe of calcium binding environments in a range of calcium-containing materials. For example, for three polymorphs of CaCO3 the CS tensor span ranges from 8 to 70 ppm and the symmetry around calcium is manifested differently in the CS tensor as compared with the EFG tensor. The advantages of characterizing the CS tensor are particularly evident in very high magnetic fields where the effect of calcium CS anisotropy is augmented in hertz while the effect of second-order quadrupolar broadening is often obscured for (43)Ca because of its small quadrupole moment. Finally, as an application of the combined experimental-theoretical approach, the solid-state structure of the vaterite polymorph of calcium carbonate is probed and we conclude that the hexagonal P6(3)/mmc space group provides a better representation of the structure than does the orthorhombic Pbnm space group, thereby demonstrating the utility of (43)Ca solid-state NMR as a complementary tool to X-ray crystallographic methods.

Analysis of a Sheet Silicate.

ERIC Educational Resources Information Center

Adams, J. M.; Evans, S.

1980-01-01

Describes a student project in analytical chemistry using sheet silicates. Provides specific information regarding the use of phlogopite in an experiment to analyze samples for silicon, aluminum, magnesium, iron, potassium, and fluoride. (CS)

21 CFR 573.260 - Calcium silicate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

21 CFR 573.260 - Calcium silicate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

21 CFR 573.260 - Calcium silicate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

21 CFR 573.260 - Calcium silicate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

21 CFR 573.260 - Calcium silicate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

MTA and F-doped MTA cements used as sealers with warm gutta-percha. Long-term study of sealing ability.

PubMed

Gandolfi, M G; Prati, C

2010-10-01

To evaluate the long-term sealing ability (up to 6 months) of two experimental calcium silicate MTA cements used as root canal sealers in association with warm gutta-percha. Calcium silicate (MTA) and calcium-fluoro-silicate powders were prepared. Sodium fluoride was included in FMTA (Fluoride-doped Mineral Trioxide Aggregate) as an expansive and retardant agent. Single-rooted teeth were instrumented with NiTi rotary instruments, filled with warm gutta-percha in association with one of the experimental sealers or with AH Plus as a control (n = 20 for each sealer) and stored at 37 °C. Sealing was assessed at 24, 48 h, 1, 2 weeks and 1, 3, 6 months by a fluid filtration method. Scanning electron microscopy with energy dispersive analysis (SEM/EDX) was used to study the dentine/sealer interface of roots stored for 6 months and the surface of cement disks stored for 24 h. All sealers revealed a statistically significant reduction (P < 0.05) in fluid filtration after the first 2 weeks. No statistically significant differences were observed between FMTA and AH Plus at all analysis times. At short times (24, 48-h), no statistically significant differences were found between the experimental cements and AH Plus. At long-term evaluations (1, 3, 6 months), FMTA and AH Plus sealed significantly better (P < 0.05) than MTA. FMTA was associated with lower fluid filtration rates, and the seal was stable from 48 h to 6 months, thus proving the most effective material. Scanning electron microscopy with energy dispersive analysis of root sections filled with calcium silicate sealers revealed the formation of a blend layer of gutta-percha and cement consequent to the warm gutta-percha condensation technique. Scanning electron microscopy with energy dispersive analysis of 24-h-stored disks identified a Ca-rich coating on the outer surface consisting of globular particles (calcium hydroxide and calcium carbonate), and a deeper internal Ca- and Si-rich region consisting of needle-like ettringite crystals and round formations of calcium silicate hydrate gel. Fluoride-doped MTA demonstrated stable sealing during a period of up to 6 months and significantly better than conventional calcium silicate MTA cements and comparable to AH Plus. The study supports the suitability of calcium silicate MTA cements as sealers in association with warm gutta-percha for root filling. © 2010 International Endodontic Journal.

Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering.

PubMed

Quirk, Joe; Beerling, David J; Banwart, Steve A; Kakonyi, Gabriella; Romero-Gonzalez, Maria E; Leake, Jonathan R

2012-12-23

Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to 'trenching' of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO(2) and climate history.

Physicochemical properties of calcium silicate cements associated with microparticulate and nanoparticulate radiopacifiers.

PubMed

Bosso-Martelo, Roberta; Guerreiro-Tanomaru, Juliane M; Viapiana, Raqueli; Berbert, Fabio Luiz C; Duarte, Marco Antonio Hungaro; Tanomaru-Filho, Mário

2016-01-01

The objective of this paper was to evaluate the physicochemical properties of calcium silicate cements with different chemical compositions, associated with radiopacifying agents. Mineral trioxide aggregate (MTA) Angelus, calcium silicate cement with additives (CSC), and resinous calcium silicate cement (CSCR) were evaluated, with the addition of the following radiopacifiers: microparticles (micro) or nanoparticles (nano) of zirconium oxide (ZrO(2)), niobium oxide (Nb(2)O(5)), bismuth oxide (Bi(2)O(3)), or calcium tungstate (CaWO(4)). Setting time was evaluated using Gilmore needles. Solubility was determined after immersion in water. The pH and calcium ion release were analyzed after 3, 12, and 24 h and 7, 14, and 21 days. The data obtained were submitted to analysis of variance and Tukey's test, at a level of significance of 5 %. CSC + CaWO(4) and CSCR + ZrO(2) micro, Nb(2)O(5) and CaWO(4) presented results similar to MTA, with a shorter final setting time than the other associations. CSC and CSCR+ ZrO(2) micro presented a higher degree of flow. All the cements evaluated presented low solubility. The materials presented alkaline pH and released calcium ions. ZrO(2) micro radiopacifier may be considered a potential substitute for Bi(2)O(3) when associated with CSC or CSCR. The proposed materials, especially when associated with ZrO(2), are potential materials for use as alternatives to MTA.

Calcium-silicate mesoporous nanoparticles loaded with chlorhexidine for both anti- Enterococcus faecalis and mineralization properties.

PubMed

Fan, Wei; Li, Yanyun; Sun, Qing; Ma, Tengjiao; Fan, Bing

2016-10-21

In infected periapical tissues, Enterococcus faecalis is one of the most common dominant bacteria. Chlorhexidine has been proved to show strong antibacterial ability against E. faecalis but is ineffective in promoting mineralization for tissues around root apex. Mesoporous calcium-silicate nanoparticles are newly synthesized biomaterials with excellent ability to promote mineralization and carry-release bioactive molecules in a controlled manner. In this study, mesoporous calcium-silicate nanoparticles were functionalized with chlorhexidine and their releasing profile, antibacterial ability, effect on cell proliferation and in vitro mineralization property were evaluated. The chlorhexidine was successfully incorporated into mesoporous calcium-silicate nanoparticles by a mixing-coupling method. The new material could release chlorhexidine as well as Ca 2+ and SiO 3 2- in a sustained manner with an alkaline pH value under different conditions. The antimicrobial ability against planktonic E. faecalis was dramatically improved after chlorhexidine incorporation. The nanoparticles with chlorhexidine showed no negative effect on cell proliferation with low concentrations. On dentin slices, the new synthesized material demonstrated a similar inhibitory effect on E. faecalis as the chlorhexidine. After being immersed in SBF for 9 days, numerous apatite crystals could be observed on surfaces of the material tablets. Mesoporous calcium-silicate nanoparticles loaded with chlorhexidine exhibited release of ions and chlorhexidine, low cytotoxicity, excellent antibacterial ability and in vitro mineralization. This material could be developed into a new effective intra-canal medication in dentistry or a new bone defect filling material for infected bone defects.

Premixed calcium silicate cement for endodontic applications

PubMed Central

Persson, Cecilia; Engqvist, Håkan

2011-01-01

Calcium silicate-based materials (also called MTA) are increasingly being used in endodontic applications. However, the handling properties of MTA are not optimal when it comes to injectability and cohesion. Premixing the cements using glycerol avoids these issues. However, there is a lack of data on the effect of common cement variables on important properties of premixed cements for endodontic applications. In this study, the effects of liquid-to-powder ratio, amount of radiopacifier and amount of calcium sulfate (added to control the setting time) were screened using a statistical model. In the second part of the study, the liquid-to-powder ratio was optimized for cements containing three different amounts of radiopacifier. Finally, the effect of using glycerol rather than water was evaluated in terms of radiopacity. The setting time was found to increase with the amount of radiopacifier when the liquid-to-powder ratio was fixed. This was likely due to the higher density of the radiopacifier in comparison to the calcium silicate, which gave a higher liquid-to-powder ratio in terms of volume. Using glycerol rather than water to mix the cements led to a decrease in radiopacity of the cement. In conclusion, we were able to produce premixed calcium silicate cements with acceptable properties for use in endodontic applications. PMID:23507729

Premixed calcium silicate cement for endodontic applications: injectability, setting time and radiopacity.

PubMed

Persson, Cecilia; Engqvist, Håkan

2011-01-01

Calcium silicate-based materials (also called MTA) are increasingly being used in endodontic applications. However, the handling properties of MTA are not optimal when it comes to injectability and cohesion. Premixing the cements using glycerol avoids these issues. However, there is a lack of data on the effect of common cement variables on important properties of premixed cements for endodontic applications. In this study, the effects of liquid-to-powder ratio, amount of radiopacifier and amount of calcium sulfate (added to control the setting time) were screened using a statistical model. In the second part of the study, the liquid-to-powder ratio was optimized for cements containing three different amounts of radiopacifier. Finally, the effect of using glycerol rather than water was evaluated in terms of radiopacity. The setting time was found to increase with the amount of radiopacifier when the liquid-to-powder ratio was fixed. This was likely due to the higher density of the radiopacifier in comparison to the calcium silicate, which gave a higher liquid-to-powder ratio in terms of volume. Using glycerol rather than water to mix the cements led to a decrease in radiopacity of the cement. In conclusion, we were able to produce premixed calcium silicate cements with acceptable properties for use in endodontic applications.

Cesium titanium silicate and method of making

DOEpatents

Balmer, Mari L.

1997-01-01

The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs.sub.2 Ti.sub.2 Si.sub.4 O.sub.13 pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs.sub.2 O and TiO.sub.2 loadings and are durable glass and ceramic materials. The amount of TiO.sub.2 and Cs.sub.2 that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass.

Cesium titanium silicate and method of making

DOEpatents

Balmer, M.L.

1997-01-07

The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs{sub 2}Ti{sub 2}Si{sub 4}O{sub 13} pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs{sub 2}O and TiO{sub 2} loadings and are durable glass and ceramic materials. The amount of TiO{sub 2} and Cs{sub 2} that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass. 10 figs.

Testing Urey's carbonate-silicate cycle using the calcium isotopic composition of sedimentary carbonates

NASA Astrophysics Data System (ADS)

Blättler, Clara L.; Higgins, John A.

2017-12-01

Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.

Calcium silicate insulation structure

DOEpatents

Kollie, Thomas G.; Lauf, Robert J.

1995-01-01

An insulative structure including a powder-filled evacuated casing utilizes a quantity of finely divided synthetic calcium silicate having a relatively high surface area. The resultant structure-provides superior thermal insulating characteristics over a broad temperature range and is particularly well-suited as a panel for a refrigerator or freezer or the insulative barrier for a cooler or a insulated bottle.

Microstructure, Porosity and Mechanical Property Relationships of Calcium-Silicate-Hydrate

DTIC Science & Technology

1991-02-15

feasibility of producing S ,,zeolite-cement composites . calcium silicate hydrate (C-S-H) structure, NAS NMR, C3S, pH, zeolites, aluminosilicate hydrate...3 S pH- Composition Plots......................................... 6 X-ray Diffraction...6 The System CaO-A1203-SiO 2 -H2 0................................. 8 pH- Composition Plots......................................... 8 MASNMR

Imaging of drug loading distributions in individual microspheres of calcium silicate hydrate - an X-ray spectromicroscopy study

NASA Astrophysics Data System (ADS)

Guo, Xiaoxuan; Wang, Zhiqiang; Wu, Jin; Wang, Jian; Zhu, Ying-Jie; Sham, Tsun-Kong

2015-04-01

Imaging is one of the most direct and ideal ways to track drug loading distributions in drug carriers on the molecular level, which will facilitate the optimization of drug carriers and drug loading capacities. Herein, we report the mapping of an individual mesoporous calcium silicate hydrate (CSH) microsphere before and after the loading of ibuprofen (IBU) and the interactions between drug carriers and drug molecules simultaneously by scanning transmission X-ray microscopy (STXM). Nanoscaled X-ray absorption near edge structure (XANES) spectroscopy clearly indicates that IBU is bonded to calcium and silicate sites via carboxylic acid groups. More importantly, STXM has been successfully used to determine the absolute thickness of IBU, revealing its distribution in the CSH microsphere.Imaging is one of the most direct and ideal ways to track drug loading distributions in drug carriers on the molecular level, which will facilitate the optimization of drug carriers and drug loading capacities. Herein, we report the mapping of an individual mesoporous calcium silicate hydrate (CSH) microsphere before and after the loading of ibuprofen (IBU) and the interactions between drug carriers and drug molecules simultaneously by scanning transmission X-ray microscopy (STXM). Nanoscaled X-ray absorption near edge structure (XANES) spectroscopy clearly indicates that IBU is bonded to calcium and silicate sites via carboxylic acid groups. More importantly, STXM has been successfully used to determine the absolute thickness of IBU, revealing its distribution in the CSH microsphere. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07471h

Present and future of glass-ionomers and calcium-silicate cements as bioactive materials in dentistry: Biophotonics-based interfacial analyses in health and disease

PubMed Central

Watson, Timothy F.; Atmeh, Amre R.; Sajini, Shara; Cook, Richard J.; Festy, Frederic

2014-01-01

Objective Since their introduction, calcium silicate cements have primarily found use as endodontic sealers, due to long setting times. While similar in chemistry, recent variations such as constituent proportions, purities and manufacturing processes mandate a critical understanding of service behavior differences of the new coronal restorative material variants. Of particular relevance to minimally invasive philosophies is the potential for ion supply, from initial hydration to mature set in dental cements. They may be capable of supporting repair and remineralization of dentin left after decay and cavity preparation, following the concepts of ion exchange from glass ionomers. Methods This paper reviews the underlying chemistry and interactions of glass ionomer and calcium silicate cements, with dental tissues, concentrating on dentin–restoration interface reactions. We additionally demonstrate a new optical technique, based around high resolution deep tissue, two-photon fluorescence and lifetime imaging, which allows monitoring of undisturbed cement–dentin interface samples behavior over time. Results The local bioactivity of the calcium-silicate based materials has been shown to produce mineralization within the subjacent dentin substrate, extending deep within the tissues. This suggests that the local ion-rich alkaline environment may be more favorable to mineral repair and re-construction, compared with the acidic environs of comparable glass ionomer based materials. Significance The advantages of this potential re-mineralization phenomenon for minimally invasive management of carious dentin are self-evident. There is a clear need to improve the bioactivity of restorative dental materials and these calcium silicate cement systems offer exciting possibilities in realizing this goal. PMID:24113131

Characterization of un-hydrated and hydrated BioAggregate™ and MTA Angelus™.

PubMed

Camilleri, J; Sorrentino, F; Damidot, D

2015-04-01

BioAggregate™ is a novel material introduced for use as a root-end filling material. It is tricalcium silicate-based, free of aluminium and uses tantalum oxide as radiopacifier. BioAggregate contains additives to enhance the material performance. The purpose of this research was to characterize the un-hydrated and hydrated forms of BioAggregate using a combination of techniques, verify whether the additives if present affect the properties of the set material and compare these properties to those of MTA Angelus™. Un-hydrated and hydrated BioAggregate and MTA Angelus were assessed. Un-hydrated cement was tested for chemical composition, specific surface area, mineralogy and kinetics of hydration. The set material was investigated for mineralogy, microstructure and bioactivity. Scanning electron microscopy, X-ray energy dispersive spectroscopic analysis, X-ray fluorescence spectroscopy, X-ray diffraction and isothermal calorimetry were employed. The specific surface area was investigated using a gas adsorption method with nitrogen as the probe. BioAggregate was composed of tricalcium silicate, tantalum oxide, calcium phosphate and silicon dioxide and was free of aluminium. On hydration, the tricalcium silicate produced calcium silicate hydrate and calcium hydroxide. The former was deposited around the cement grains, while the latter reacted with the silicon dioxide to form additional calcium silicate hydrate. This resulted in reduction of calcium hydroxide in the aged cement. MTA Angelus reacted in a similar fashion; however, since it contained no additives, the calcium hydroxide was still present in the aged cement. Bioactivity was demonstrated by deposition of hydroxyapatite. BioAggregate exhibited a high specific surface area. Nevertheless, the reactivity determined by isothermal calorimetry appeared to be slow compared to MTA Angelus. The tantalum oxide as opposed to bismuth oxide was inert, and tantalum was not leached in solution. BioAggregate exhibited high calcium ion release early, which was maintained over the 28-day period as opposed to MTA Angelus, which demonstrated low early calcium ion release which increased as the material aged. The mineralogical composition of BioAggregate was different to MTA Angelus. As opposed to MTA Angelus, BioAggregate did not contain aluminium and contained additives such as calcium phosphate and silicon dioxide. As a consequence, BioAggregate reacted more slowly and formation of calcium hydroxide and leaching of calcium ions in solution were not evident as the material aged. The additives in BioAggregate modify the kinetics and the end products of hydration. Although newer generation tricalcium silicate-based materials contain similar constituents to MTA, they do not undergo the same setting reactions, and thus, their clinical performance will not be comparable to that of MTA.

Preliminary study of raw material for calcium silicate/PVA coating on Ti-6Al-4V alloy

NASA Astrophysics Data System (ADS)

Azam, Farah Atiqah bt Abdul; Shamsudin, Roslinda

2015-09-01

Calcium silicate bioceramic was prepared from the rice husk and limestone resources using the sol gel method. The preparations of CaSiO3 formulation were differ from the previous study due CaO/SiO2 amount with 45:55 ratio. X-Ray Fluorescence analysis was carried out to clarify the amount of SiO2 and CaO content in the limestone and rice husk ash. The high amount of CaO was found in the limestone with the percentages of 97.22%, whereby 89% of SiO2 content of the rice husk ash. Several milling time were studied to obtain the optimized milling ti me and speed in progress to obtain nano size particle. The particle size analysis result confirms that increase in milling time does not certainly reduce the size of particle. The addition of 0.05% polyvinyl alcohol as a binder did not change the phases or composition of calcium silicates after examined by X-Ray diffraction analysis which make it suitable to be used as a binder for calcium silicate coating without changing the chemical structure.

Vibrational investigation of calcium-silicate cements for endodontics in simulated body fluids

NASA Astrophysics Data System (ADS)

Taddei, Paola; Modena, Enrico; Tinti, Anna; Siboni, Francesco; Prati, Carlo; Gandolfi, Maria Giovanna

2011-05-01

Calcium-silicate MTA (Mineral Trioxide Aggregate) cements have been recently developed for oral and endodontic surgery. This study was aimed at investigating commercial (White ProRoot MTA, White and Grey MTA-Angelus) and experimental (wTC-Bi) accelerated calcium-silicate cements with regards to composition, hydration products and bioactivity upon incubation for 1-28 days at 37 °C, in Dulbecco's Phosphate Buffered Saline (DPBS). Deposits on the surface of the cements and the composition changes during incubation were investigated by micro-Raman and ATR/FT-IR spectroscopy, and pH measurements. Vibrational techniques disclosed significant differences in composition among the unhydrated cements, which significantly affected the bioactivity as well as pH, and hydration products of the cements. After one day in DPBS, all the cements were covered by a more or less homogeneous layer of B-type carbonated apatite. The experimental cement maintained a high bioactivity, only slightly lower than the other cements and appears a valid alternative to commercial cements, in view of its adequate setting time properties. The bioactivity represents an essential property to favour bone healing and makes the calcium-silicate cements the gold standard materials for root-apical endodontic surgery.

Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering

PubMed Central

Quirk, Joe; Beerling, David J.; Banwart, Steve A.; Kakonyi, Gabriella; Romero-Gonzalez, Maria E.; Leake, Jonathan R.

2012-01-01

Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to ‘trenching’ of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO2 and climate history. PMID:22859556

Multiscale understanding of tricalcium silicate hydration reactions.

PubMed

Cuesta, Ana; Zea-Garcia, Jesus D; Londono-Zuluaga, Diana; De la Torre, Angeles G; Santacruz, Isabel; Vallcorba, Oriol; Dapiaggi, Monica; Sanfélix, Susana G; Aranda, Miguel A G

2018-06-04

Tricalcium silicate, the main constituent of Portland cement, hydrates to produce crystalline calcium hydroxide and calcium-silicate-hydrates (C-S-H) nanocrystalline gel. This hydration reaction is poorly understood at the nanoscale. The understanding of atomic arrangement in nanocrystalline phases is intrinsically complicated and this challenge is exacerbated by the presence of additional crystalline phase(s). Here, we use calorimetry and synchrotron X-ray powder diffraction to quantitatively follow tricalcium silicate hydration process: i) its dissolution, ii) portlandite crystallization and iii) C-S-H gel precipitation. Chiefly, synchrotron pair distribution function (PDF) allows to identify a defective clinotobermorite, Ca 11 Si 9 O 28 (OH) 2 . 8.5H 2 O, as the nanocrystalline component of C-S-H. Furthermore, PDF analysis also indicates that C-S-H gel contains monolayer calcium hydroxide which is stretched as recently predicted by first principles calculations. These outcomes, plus additional laboratory characterization, yielded a multiscale picture for C-S-H nanocomposite gel which explains the observed densities and Ca/Si atomic ratios at the nano- and meso- scales.

Simple technology for recycling phosphate from wastewater to farmland in rural areas.

PubMed

Ohtake, Hisao; Okano, Kenji; Kunisada, Masashi; Takano, Hiroyuki; Toda, Masaya

2018-01-01

A simple technology for phosphate (P i ) recovery has been developed using a bifunctional adsorption-aggregation agent. The bifunctional agent was prepared by soaking calcium silicates in hydrochloric acid solution. Importantly, recyclable calcium silicates were available almost free of charge from the cement industry and also from the steel industry. The acid treatment was essential not only for enhancing the ability of calcium silicates to remove P i from aqueous solution but also for enabling the high settleability of removed P i . On-site experiments using a mobile plant showed that approximately 80% P i could be recovered from anaerobic sludge digestion liquor at a wastewater treatment plant. This technology has the potential to offer a simple, compact service for recycling P i from wastewater to farmland in rural areas.

Reactive molecular simulation on the calcium silicate hydrates/polyethylene glycol composites

NASA Astrophysics Data System (ADS)

Zhou, Yang; Hou, Dongshuai; Jiang, Jinyang; She, Wei; Yu, Jiao

2017-11-01

Calcium silicate hydrates (C-S-H) may potentially exhibit extraordinary performance when modified by polymers, in which way the properties of cement-based materials can be improved from the genetic level. In this molecular dynamics simulation of the interaction between C-S-H and polyethylene glycol, apart from the H bond network connection in the interface, another chemical adsorption was observed. Calcium of C-S-H broke the Csbnd O bond of PEG and formed a new Casbnd C connection, which created a stronger link between the organic and inorganic phases.

Mechanical Properties and Durability of Advanced Environmental Barrier Coatings in Calcium-Magnesium-Alumino-Silicate Environments

NASA Technical Reports Server (NTRS)

Miladinovich, Daniel S.; Zhu, Dongming

2011-01-01

Environmental barrier coatings are being developed and tested for use with SiC/SiC ceramic matrix composite (CMC) gas turbine engine components. Several oxide and silicate based compositons are being studied for use as top-coat and intermediate layers in a three or more layer environmental barrier coating system. Specifically, the room temperature Vickers-indentation-fracture-toughness testing and high-temperature stability reaction studies with Calcium Magnesium Alumino-Silicate (CMAS or "sand") are being conducted using advanced testing techniques such as high pressure burner rig tests as well as high heat flux laser tests.

Regenerable sorbents for CO.sub.2 capture from moderate and high temperature gas streams

DOEpatents

Siriwardane, Ranjani V [Morgantown, WV

2008-01-01

A process for making a granular sorbent to capture carbon dioxide from gas streams comprising homogeneously mixing an alkali metal oxide, alkali metal hydroxide, alkaline earth metal oxide, alkaline earth metal hydroxide, alkali titanate, alkali zirconate, alkali silicate and combinations thereof with a binder selected from the group consisting of sodium ortho silicate, calcium sulfate dihydrate (CaSO.sub.4.2H.sub.2O), alkali silicates, calcium aluminate, bentonite, inorganic clays and organic clays and combinations thereof and water; drying the mixture and placing the sorbent in a container permeable to a gas stream.

Cesium and strontium ion exchange on the framework titanium silicate M2Ti2O3SiO4.nH2O (M = H, Na).

PubMed

Solbrå, S; Allison, N; Waite, S; Mikhalovsky, S V; Bortun, A I; Bortun, L N; Clearfield, A

2001-02-01

The ion exchange properties of the titanium silicate, M2Ti2O3SiO4.nH2O (M = H, Na), toward stable and radioactive 137Cs+ and 89Sr2+, have been examined. By studying the cesium and strontium uptake in the presence of NaNO3, CaCl2, NaOH, and HNO3 (in the range of 0.01-6 M) the sodium titanium silicate was found to be an efficient Cs+ ion exchanger in acid, neutral, and alkaline media and an efficient Sr2+ ion exchanger in neutral and alkaline media, which makes it promising for treatment of contaminated environmental media and biological systems.

Mitigating global warming potentials of methane and nitrous oxide gases from rice paddies under different irrigation regimes.

PubMed

Ali, Muhammad Aslam; Hoque, M Anamul; Kim, Pil Joo

2013-04-01

A field experiment was conducted in Bangladesh Agricultural University Farm to investigate the mitigating effects of soil amendments such as calcium carbide, calcium silicate, phosphogypsum, and biochar with urea fertilizer on global warming potentials (GWPs) of methane (CH4) and nitrous oxide (N2O) gases during rice cultivation under continuous and intermittent irrigations. Among the amendments phosphogypsum and silicate fertilizer, being potential source of electron acceptors, decreased maximum level of seasonal CH4 flux by 25-27 % and 32-38 % in continuous and intermittent irrigations, respectively. Biochar and calcium carbide amendments, acting as nitrification inhibitors, decreased N2O emissions by 36-40 % and 26-30 % under continuous and intermittent irrigations, respectively. The total GWP of CH4 and N2O gases were decreased by 7-27 % and 6-34 % with calcium carbide, phosphogypsum, and silicate fertilizer amendments under continuous and intermittent irrigations, respectively. However, biochar amendments increased overall GWP of CH4 and N2O gases.

Analysis of the color alteration and radiopacity promoted by bismuth oxide in calcium silicate cement.

PubMed

Marciano, Marina Angélica; Estrela, Carlos; Mondelli, Rafael Francisco Lia; Ordinola-Zapata, Ronald; Duarte, Marco Antonio Hungaro

2013-01-01

The aim of the study was to determine if the increase in radiopacity provided by bismuth oxide is related to the color alteration of calcium silicate-based cement. Calcium silicate cement (CSC) was mixed with 0%, 15%, 20%, 30% and 50% of bismuth oxide (BO), determined by weight. Mineral trioxide aggregate (MTA) was the control group. The radiopacity test was performed according to ISO 6876/2001. The color was evaluated using the CIE system. The assessments were performed after 24 hours, 7 and 30 days of setting time, using a spectrophotometer to obtain the ΔE, Δa, Δb and ΔL values. The statistical analyses were performed using the Kruskal-Wallis/Dunn and ANOVA/Tukey tests (p<0.05). The cements in which bismuth oxide was added showed radiopacity corresponding to the ISO recommendations (>3 mm equivalent of Al). The MTA group was statistically similar to the CSC/30% BO group (p>0.05). In regard to color, the increase of bismuth oxide resulted in a decrease in the ΔE value of the calcium silicate cement. The CSC group presented statistically higher ΔE values than the CSC/50% BO group (p<0.05). The comparison between 24 hours and 7 days showed higher ΔE for the MTA group, with statistical differences for the CSC/15% BO and CSC/50% BO groups (p<0.05). After 30 days, CSC showed statistically higher ΔE values than CSC/30% BO and CSC/50% BO (p<0.05). In conclusion, the increase in radiopacity provided by bismuth oxide has no relation to the color alteration of calcium silicate-based cements.

Present and future of glass-ionomers and calcium-silicate cements as bioactive materials in dentistry: biophotonics-based interfacial analyses in health and disease.

PubMed

Watson, Timothy F; Atmeh, Amre R; Sajini, Shara; Cook, Richard J; Festy, Frederic

2014-01-01

Since their introduction, calcium silicate cements have primarily found use as endodontic sealers, due to long setting times. While similar in chemistry, recent variations such as constituent proportions, purities and manufacturing processes mandate a critical understanding of service behavior differences of the new coronal restorative material variants. Of particular relevance to minimally invasive philosophies is the potential for ion supply, from initial hydration to mature set in dental cements. They may be capable of supporting repair and remineralization of dentin left after decay and cavity preparation, following the concepts of ion exchange from glass ionomers. This paper reviews the underlying chemistry and interactions of glass ionomer and calcium silicate cements, with dental tissues, concentrating on dentin-restoration interface reactions. We additionally demonstrate a new optical technique, based around high resolution deep tissue, two-photon fluorescence and lifetime imaging, which allows monitoring of undisturbed cement-dentin interface samples behavior over time. The local bioactivity of the calcium-silicate based materials has been shown to produce mineralization within the subjacent dentin substrate, extending deep within the tissues. This suggests that the local ion-rich alkaline environment may be more favorable to mineral repair and re-construction, compared with the acidic environs of comparable glass ionomer based materials. The advantages of this potential re-mineralization phenomenon for minimally invasive management of carious dentin are self-evident. There is a clear need to improve the bioactivity of restorative dental materials and these calcium silicate cement systems offer exciting possibilities in realizing this goal. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Application of soil block without burning process and calcium silicate panels as building wall in mountainous area

NASA Astrophysics Data System (ADS)

Noerwasito, Vincentius Totok; Nasution, Tanti Satriana Rosary

2017-11-01

Utilization of local building materials in a residential location in mountainous area is very important, considering local material as a low-energy building material because of low transport energy. The local building materials used in this study are walls made from soil blocks. The material was made by the surrounding community from compacted soil without burning process. To maximize the potential of soil block to the outdoor temperature in the mountains, it is necessary to add non-local building materials as an insulator from the influence of the outside air. The insulator was calcium silicate panel. The location of the research is Trawas sub-district, Mojokerto regency, which is a mountainous area. The research problem is on applying the composition of local materials and calcium silicate panels that it will be able to meet the requirements as a wall building material and finding to what extent the impact of the wall against indoor temperature. The result from this research was the application of soil block walls insulated by calcium silicate panels in a building model. Besides, because of the utilization of those materials, the building has a specific difference between indoor and outdoor temperature. Thus, this model can be applied in mountainous areas in Indonesia.

Chitosan-magnesium aluminum silicate composite dispersions: characterization of rheology, flocculate size and zeta potential.

PubMed

Khunawattanakul, Wanwisa; Puttipipatkhachorn, Satit; Rades, Thomas; Pongjanyakul, Thaned

2008-03-03

Composite dispersions of chitosan (CS), a positively charged polymer, and magnesium aluminum silicate (MAS), a negatively charged clay, were prepared and rheology, flocculate size and zeta potential of the CS-MAS dispersions were investigated. High and low molecular weights of CS (HCS and LCS, respectively) were used in this study. Moreover, the effects of heat treatment at 60 degrees C on the characteristics of the CS-MAS dispersions and the zeta potential of MAS upon addition of CS at different pHs were examined. Incorporation of MAS into CS dispersions caused an increase in viscosity and a shift of CS flow type from Newtonian to pseudoplastic flow with thixotropic properties. Heat treatment brought about a significant decrease in viscosity and hysteresis area of the composite dispersions. Microscopic studies showed that flocculation of MAS occurred after mixing with CS. The size and polydispersity index of the HCS-MAS flocculate were greater than those of the LCS-MAS flocculate. However, a narrower size distribution and the smaller size of the HCS-MAS flocculate were found after heating at 60 degrees C. Zeta potentials of the CS-MAS flocculates were positive and slightly increased with increasing MAS content. In the zeta potential studies, the negative charge of the MAS could be neutralized by the addition of CS. Increasing the pH and molecular weight of CS resulted in higher CS concentrations required to neutralize the charge of MAS. These findings suggest that the electrostatic interaction between CS and MAS caused a change in flow behavior and flocculation of the composite dispersions, depending on the molecular weight of CS. Heat treatment affected the rheological properties and the flocculate size of the composite dispersions. Moreover, pH of medium and molecular weight of CS influence the zeta potential of MAS.

Incorporation of bitumen and calcium silicate in cement and lime stabilized soil blocks

NASA Astrophysics Data System (ADS)

Kwan, W. H.; Cheah, C. B.; Ramli, M.; Al-Sakkaf, Y. K.

2017-04-01

Providing affordable housing is the most critical problem in many of the developing countries. Using earth materials in building construction is one of the feasible methods to address this issue and it can be a way towards sustainable construction as well. However, the published information on the stabilized soil blocks is limited. Therefore, the present study is conducted to examine the characterization of the soils and engineering properties of the stabilized soil blocks. Four types of stabilizer were used in the study, namely; cement, slaked lime, bitumen emulsion and calcium silicate. Cement and slaked lime were added at different percentages in the range of 5% to 15%, with interval of 2.5%. The percentage was determined based on weight of soil. Meanwhile, bitumen emulsion and calcium silicate were incorporated at various percentages together with 10% of cement. Dosage of bitumen emulsion is in the range of 2% to 10% at interval of 2% while calcium silicate was incorporated at 0.50%, 0.75%, 1.00%, 1.25%, 1.50% and 2.00%. Results show that cement is the most viable stabilizer for the soil block among all stabilizers in this study. The bulk density, optimum moisture content and compressive strengths were increased with the increasing cement content. The most suitable cement content was 10% added at moisture content of 12%. Lime, bitumen and calcium contents were recommended at 5.0%, 6.0% and 1.25%, respectively.

Corrosion resistant thermal barrier coating. [protecting gas turbines and other engine parts

NASA Technical Reports Server (NTRS)

Levine, S. R.; Miller, R. A.; Hodge, P. E. (Inventor)

1981-01-01

A thermal barrier coating system for protecting metal surfaces at high temperature in normally corrosive environments is described. The thermal barrier coating system includes a metal alloy bond coating, the alloy containing nickel, cobalt, iron, or a combination of these metals. The system further includes a corrosion resistant thermal barrier oxide coating containing at least one alkaline earth silicate. The preferred oxides are calcium silicate, barium silicate, magnesium silicate, or combinations of these silicates.

New nanostructural biomaterials based on active silicate systems and hydroxyapatite: characterization and genotoxicity in human peripheral blood lymphocytes.

PubMed

Opačić-Galić, V; Petrović, V; Zivković, S; Jokanović, V; Nikolić, B; Knežević-Vukčević, J; Mitić-Ćulafić, D

2013-06-01

To characterize and investigate the genotoxic effect of a new endodontic cement based on dicalcium- and tricalcium-silicate (CS) with hydroxyapatite (HA) on human lymphocytes. Hydrothermal treatment was applied for synthesis of CS and HA. The final mixture HA-CS, with potential to be used in endodontic practice, is composed of CS (34%) and HA (66%). Human lymphocytes were incubated with HA, HA-CS and CS for 1 h, at 37 °C and 5% CO2. Cell viability was determined using the trypan blue exclusion assay. To evaluate the level of DNA damage comet assay (single cell gel electrophoresis) was performed. For the statistical analysis anova and Duncan's Post Hoc Test were used. The SEM analysis indicated that CS consisted mostly of agglomerates of several micrometers in size, built up from smaller particles, with dimensions between 117 and 477 nm. This is promising because dimensions of agglomerates are not comparable with channels inside the cell membranes, whereas their nano-elements provide evident activity, important for faster setting of these mixtures compared to MTA. Values of DNA damage obtained in the comet assay indicated low genotoxic risk of the new endodontic materials. The significantly improved setting characteristics and low genotoxic risk of the new material support further research. © 2012 International Endodontic Journal.

A Comparative Chemical Study of Calcium Silicate-Containing and Epoxy Resin-Based Root Canal Sealers.

PubMed

Reszka, Przemysław; Nowicka, Alicja; Lipski, Mariusz; Dura, Włodzimierz; Droździk, Agnieszka; Woźniak, Krzysztof

2016-01-01

Objective. The present study assessed the chemical elements in two novel calcium silicate-containing root canal sealers, BioRoot RCS and Well-Root ST, compared to a calcium silicate-containing root canal sealer that has been on the market for several years, MTA Fillapex, and epoxy resin-based sealer AHPlus. Material and Methods. The sealers were mixed and manipulated according to the manufacturers' instructions. Twelve cylindrical molds (inner diameter 4 mm; height 3 mm) were placed on a glass petri dish and packed with the materials. The dish was transferred to an incubator. After 72 h the molds were examined by scanning electron microscopy and energy dispersive X-ray microanalysis. Results. BioRoot RCS and Well-Root ST had high peaks of calcium, zirconium, oxygen, carbon, silicon, and chlorine. Well-Root ST also had sodium, magnesium, aluminum, and titanium peaks. MTA Fillapex and AHPlus had carbon, oxygen, calcium, titanium, and bismuth peaks. A silicon peak was also observed for MTA Fillapex, and zirconium and tungsten peaks for AHPlus. Conclusion. BioRoot RSC had the highest degree of purity. The clinical implication of metals contained in the other sealers needs to be investigated.

A Comparative Chemical Study of Calcium Silicate-Containing and Epoxy Resin-Based Root Canal Sealers

PubMed Central

Reszka, Przemysław; Dura, Włodzimierz; Droździk, Agnieszka; Woźniak, Krzysztof

2016-01-01

Objective. The present study assessed the chemical elements in two novel calcium silicate-containing root canal sealers, BioRoot RCS and Well-Root ST, compared to a calcium silicate-containing root canal sealer that has been on the market for several years, MTA Fillapex, and epoxy resin-based sealer AHPlus. Material and Methods. The sealers were mixed and manipulated according to the manufacturers' instructions. Twelve cylindrical molds (inner diameter 4 mm; height 3 mm) were placed on a glass petri dish and packed with the materials. The dish was transferred to an incubator. After 72 h the molds were examined by scanning electron microscopy and energy dispersive X-ray microanalysis. Results. BioRoot RCS and Well-Root ST had high peaks of calcium, zirconium, oxygen, carbon, silicon, and chlorine. Well-Root ST also had sodium, magnesium, aluminum, and titanium peaks. MTA Fillapex and AHPlus had carbon, oxygen, calcium, titanium, and bismuth peaks. A silicon peak was also observed for MTA Fillapex, and zirconium and tungsten peaks for AHPlus. Conclusion. BioRoot RSC had the highest degree of purity. The clinical implication of metals contained in the other sealers needs to be investigated. PMID:28097154

Doped Calcium Silicate Ceramics: A New Class of Candidates for Synthetic Bone Substitutes

PubMed Central

No, Young Jung; Li, Jiao Jiao; Zreiqat, Hala

2017-01-01

Doped calcium silicate ceramics (DCSCs) have recently gained immense interest as a new class of candidates for the treatment of bone defects. Although calcium phosphates and bioactive glasses have remained the mainstream of ceramic bone substitutes, their clinical use is limited by suboptimal mechanical properties. DCSCs are a class of calcium silicate ceramics which are developed through the ionic substitution of calcium ions, the incorporation of metal oxides into the base binary xCaO–ySiO2 system, or a combination of both. Due to their unique compositions and ability to release bioactive ions, DCSCs exhibit enhanced mechanical and biological properties. Such characteristics offer significant advantages over existing ceramic bone substitutes, and underline the future potential of adopting DCSCs for clinical use in bone reconstruction to produce improved outcomes. This review will discuss the effects of different dopant elements and oxides on the characteristics of DCSCs for applications in bone repair, including mechanical properties, degradation and ion release characteristics, radiopacity, and biological activity (in vitro and in vivo). Recent advances in the development of DCSCs for broader clinical applications will also be discussed, including DCSC composites, coated DCSC scaffolds and DCSC-coated metal implants. PMID:28772513

Calcium silicate-based sealers: Assessment of physicochemical properties, porosity and hydration.

PubMed

Marciano, Marina Angélica; Duarte, Marco Antonio Hungaro; Camilleri, Josette

2016-02-01

Investigation of hydration, chemical, physical properties and porosity of experimental calcium silicate-based sealers. Experimental calcium silicate-based sealers with calcium tungstate and zirconium oxide radio-opacifiers were prepared by mixing 1g of powder to 0.3 mL of 80% distilled water and 20% propylene glycol. MTA and MTA Fillapex were used as controls. The raw materials and set sealers were characterized using a combination of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Physical properties were analyzed according to ANSI/ADA. The pH and calcium ion release were assessed after 3, 24, 72 and 168 h. The porosity was assessed using mercury intrusion porosimetry. The analysis of hydration of prototype sealers revealed calcium hydroxide as a by-product resulting in alkaline pH and detection of calcium ion release, with high values in initial periods. The radiopacity was similar to MTA for the sealers containing high amounts of radio-opacifiers (p>0.05). Flowability was higher and film thickness was lower for resinous MTA Fillapex sealer (p<0.05). The test sealers showed water sorption and porosity similar to MTA (p>0.05). The prototype sealers presented adequate hydration, elevated pH and calcium ion release. Regarding physical properties, elevated proportions of radio-opacifiers were necessary to accomplish adequate radiopacity, enhance flowability and reduce film thickness. All the tested sealers presented water sorption and porosity similar to MTA. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Constituent elements and their distribution in the radioactive Cs-bearing silicate glass microparticles released from Fukushima nuclear plant.

PubMed

Kogure, Toshihiro; Yamaguchi, Noriko; Segawa, Hiroyo; Mukai, Hiroki; Motai, Satoko; Akiyama-Hasegawa, Kotone; Mitome, Masanori; Hara, Toru; Yaita, Tsuyoshi

2016-10-01

Microparticles of radioactive cesium (Cs)-bearing silicate glass emitted from the Fukushima Daiichi nuclear power plant were investigated mainly using state-of-the-art energy-dispersive X-ray spectroscopy in scanning transmission electron microscopes. Precise elemental maps of the particles were obtained using double silicon drift detectors with a large collection angle of X-rays, and qualitative elemental analysis was performed using high-resolution X-ray spectroscopy with a microcalorimetry detector. Beside the substantial elements (O, Si, Cl, K, Fe, Zn, Rb, Sn and Cs) as previously reported, Mn and Ba were also common, though their amounts were small. The atomic ratios of the substantial elements were not the same but varied among individual particles. Fe and Zn were relatively homogeneously distributed, whereas the concentration of alkali ions varied radially. Generally, Cs was rich and K and Rb were poor outward of the particles but the degree of such radial dependence was considerably different among the particles. A concentration of Sn on the particle surface was observed. High-resolution imaging indicated the formation of SnO 2 (cassiterite) nanocrystals on the surface. Synthesis of the bulk glass with a similar composition to the microparticles was attempted by quenching the silicate melt from ∼1600°C. However, homogeneous silicate glass like that of the microparticles could not be obtained due to the segregation of nano-spherules rich in Fe and Zn, suggesting that the microparticles were formed in a very specific condition in the nuclear reactor. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved.For permissions, please e-mail: journals.permissions@oup.com.

Synthesis, characterization and modelling of zinc and silicate co-substituted hydroxyapatite

PubMed Central

Friederichs, Robert J.; Chappell, Helen F.; Shepherd, David V.; Best, Serena M.

2015-01-01

Experimental chemistry and atomic modelling studies were performed here to investigate a novel ionic co-substitution in hydroxyapatite (HA). Zinc, silicate co-substituted HA (ZnSiHA) remained phase pure after heating to 1100°C with Zn and Si amounts of 0.6 wt% and 1.2 wt%, respectively. Unique lattice expansions in ZnSiHA, silicate Fourier transform infrared peaks and changes to the hydroxyl IR stretching region suggested Zn and silicate co-substitution in ZnSiHA. Zn and silicate insertion into HA was modelled using density functional theory (DFT). Different scenarios were considered where Zn substituted for different calcium sites or at a 2b site along the c-axis, which was suspected in singly substituted ZnHA. The most energetically favourable site in ZnSiHA was Zn positioned at a previously unreported interstitial site just off the c-axis near a silicate tetrahedron sitting on a phosphate site. A combination of experimental chemistry and DFT modelling provided insight into these complex co-substituted calcium phosphates that could find biomedical application as a synthetic bone mineral substitute. PMID:26040597

Evaluation of European District Heating Systems for Application to Army Installations in the United States

DTIC Science & Technology

2006-07-01

pipes in hooded channels, and the steel insulated pipes are insulated with mineral wool . In the thermo- concrete laying system the insulation...depends on the type foam insulation used. • Class “A” steel carrier pipe with a mineral wool , foam glass, fiber glass, or calcium silicate insulation...with a mineral wool , foam glass, fiber glass, or calcium silicate insulation covered by a steel con- duit, which has a polyurethane foam insulation

Development of the foremost light-curable calcium-silicate MTA cement as root-end in oral surgery. Chemical-physical properties, bioactivity and biological behavior.

PubMed

Gandolfi, Maria Giovanna; Taddei, Paola; Siboni, Francesco; Modena, Enrico; Ciapetti, Gabriela; Prati, Carlo

2011-07-01

An innovative light-curable calcium-silicate cement containing a HEMA-TEGDMA-based resin (lc-MTA) was designed to obtain a bioactive fast setting root-end filling and root repair material. lc-MTA was tested for setting time, solubility, water absorption, calcium release, alkalinizing activity (pH of soaking water), bioactivity (apatite-forming ability) and cell growth-proliferation. The apatite-forming ability was investigated by micro-Raman, ATR-FTIR and ESEM/EDX after immersion at 37°C for 1-28 days in DPBS or DMEM+FBS. The marginal adaptation of cement in root-end cavities of extracted teeth was assessed by ESEM/EDX, and the viability of Saos-2 cell on cements was evaluated. lc-MTA demonstrated a rapid setting time (2min), low solubility, high calcium release (150-200ppm) and alkalinizing power (pH 10-12). lc-MTA proved the formation of bone-like apatite spherulites just after 1 day. Apatite precipitates completely filled the interface porosities and created a perfect marginal adaptation. lc-MTA allowed Saos-2 cell viability and growth and no compromising toxicity was exerted. HEMA-TEGDMA creates a polymeric network able to stabilize the outer surface of the cement and a hydrophilic matrix permeable enough to allow water absorption. SiO(-)/Si-OH groups from the mineral particles induce heterogeneous nucleation of apatite by sorption of calcium and phosphate ions. Oxygen-containing groups from poly-HEMA-TEGDMA provide additional apatite nucleating sites through the formation of calcium chelates. The strong novelty was that the combination of a hydraulic calcium-silicate powder and a poly-HEMA-TEGDMA hydrophilic resin creates the conditions (calcium release and functional groups able to chelate Ca ions) for a bioactive fast setting light-curable material for clinical applications in dental and maxillofacial surgery. The first and unique/exclusive light-curable calcium-silicate MTA cement for endodontics and root-end application was created, with a potential strong impact on surgical procedures. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Influence of substrate mineralogy on bacterial mineralization of calcium carbonate: implications for stone conservation.

PubMed

Rodriguez-Navarro, Carlos; Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnación; González-Muñoz, María Teresa

2012-06-01

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed.

Influence of Substrate Mineralogy on Bacterial Mineralization of Calcium Carbonate: Implications for Stone Conservation

PubMed Central

Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnación; González-Muñoz, María Teresa

2012-01-01

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed. PMID:22447589

Properties of a novel polysiloxane-guttapercha calcium silicate-bioglass-containing root canal sealer.

PubMed

Gandolfi, M G; Siboni, F; Prati, C

2016-05-01

Root canal filling sealers based on polymethyl hydrogensiloxane or polymethyl hydrogensiloxane-guttapercha--introduced to improve the quality of conventional guttapercha-based and resin-based systems--showed advantages in handiness and clinical application. The aim of the study was to evaluate the chemical-physical properties of a novel polysiloxane-guttapercha calcium silicate-containing root canal sealer (GuttaFlow bioseal). GuttaFlow bioseal was examined and compared with GuttaFlow2, RoekoSeal and MTA Fillapex sealers. Setting times, open and impervious porosity and apparent porosity, water sorption, weight loss, calcium release, and alkalinizing activity were evaluated. ESEM-EDX-Raman analyses of fresh materials and after soaking in simulated body fluid were also performed. Marked differences were obtained among the materials. GuttaFlow bioseal showed low solubility and porosity, high water sorption, moderate calcium release and good alkalinizing activity. MTA Fillapex showed the highest calcium release, alkalinizing activity and solubility, RoekoSeal the lowest calcium release, no alkalinizing activity, very low solubility and water sorption. Only GuttaFlow bioseal showed apatite forming ability. GuttaFlow bioseal showed alkalinizing activity together with negligible solubility and slight calcium release. Therefore, the notable nucleation of apatite and apatite precursors can be related to the co-operation of CaSi particles (SiOH groups) with polysiloxane (SiOSi groups). The incorporation of a calcium silicate component into polydimethyl polymethylhydrogensiloxane guttapercha sealers may represent an attractive strategy to obtain a bioactive biointeractive flowable guttapercha sealer for moist/bleeding apices with bone defects in endodontic therapy. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Hydrothermal Synthesis of Dicalcium Silicate Based Cement

NASA Astrophysics Data System (ADS)

Dutta, N.; Chatterjee, A.

2017-06-01

It is imperative to develop low energy alternative binders considering the large amounts of energy consumed as well as carbon dioxide emissions involved in the manufacturing of ordinary Portland cement. This study is on the synthesis of a dicalcium silicate based binder using a low temperature hydrothermal route.The process consists of synthesizing an intermediate product consisting of a calcium silicate hydrate phase with a Ca:Si ratio of 2:1 and further thermal treatment to produce the β-Ca2SiO4 (C2S) phase.Effect of various synthesis parameters like water to solid ratio, dwell time and temperature on the formation of the desired calcium silicate hydrate phase is reported along with effect of heating conditions for formation of the β-C2S phase. Around 77.45% of β-C2S phase was synthesized by thermal treatment of the intermediate phase at 820°C.

Preparation of reactive beta-dicalcium silicate

DOEpatents

Shen, M.S.; Chen, J.M.; Yang, R.T.

1980-02-28

This invention relates to the preparation of fine particles of reactive beta-dicalcium silicate by means of a solid state process which comprises firing a mixture of calcium sulfate, silica, and a reducing additive selected from the group consisting of calcium sulfide, carbon, carbon monoxide, methane, and hydrogen, at a temperature of about 850 to 1000/sup 0/C. A carrier gas such as nitrogen or carbon dioxide may also be added, if desired. A high concentration of sulfur dioxide is a by-product of this process.

Preparation of reactive beta-dicalcium silicate

DOEpatents

Shen, Ming-Shing; Chen, James M.; Yang, Ralph T.

1982-01-01

This invention relates to the preparation of fine particles of reactive beta-dicalcium silicate by means of a solid state process which comprises firing a mixture of calcium sulfate, silica and a reducing additive selected from the group consisting of calcium sulfide, carbon, carbon monoxide, methane and hydrogen, at a temperature of about 850.degree.-1000.degree. C. A carrier gas such as nitrogen or carbon dioxide may also be added, if desired. A high concentration of sulfur dioxide is a by-product of this process.

The risk of coronary artery disease estimated non-invasively in patients with essential hypertension environmentally exposed to cigarette smoke.

PubMed

Gać, Paweł; Jaźwiec, Przemysław; Poręba, Małgorzata; Mazur, Grzegorz; Pawlas, Krystyna; Sobieszczańska, Małgorzata; Poręba, Rafał

2017-12-01

The relationship between environmental exposure of non-smokers to cigarette smoke and the coronary artery calcium scores has not been sufficiently documented. The aim of the study was to identify the relationship between environmental exposure to cigarette smoke and the risk of coronary artery disease (CAD) estimated non-invasively through measurement of coronary artery calcium score by computed tomography in patients with essential hypertension. The study was conducted on 67 patients with essential hypertension, non-smokers environmentally exposed to cigarette smoke (group A) and on 67 patients with essential hypertension, non-smokers not exposed to cigarette smoke (group B), selected using the case to case. Environmental exposure to cigarette smoke was evaluated using a questionnaire. The risk of development of coronary artery disease was estimated non-invasively through measurement of coronary artery calcium score (CA CS ) by computed tomography. Group A was characterised by significantly higher CA CS and left anterior descending (LAD CS ) calcium scores than group B. Compared to group B, group A had significantly higher percentage of patients with significant risk of CAD estimated on the basis of CA CS values, and significantly lower percentage of patients with practically no risk of CAD estimated with the same method. Advanced age, peripheral artery diseases and environmental exposure to cigarette smoke are independent risk factors associated with increased CA CS and LAD CS values. In addition, higher BMI and hypercholesterolemia are independent risk factors for increased values of LAD CS . In patients with essential hypertension environmental exposure to cigarette smoke may result in elevated risk of coronary artery disease estimated non-invasively through measurement of coronary artery calcium score by computed tomography. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis, characterization and modelling of zinc and silicate co-substituted hydroxyapatite.

PubMed

Friederichs, Robert J; Chappell, Helen F; Shepherd, David V; Best, Serena M

2015-07-06

Experimental chemistry and atomic modelling studies were performed here to investigate a novel ionic co-substitution in hydroxyapatite (HA). Zinc, silicate co-substituted HA (ZnSiHA) remained phase pure after heating to 1100 °C with Zn and Si amounts of 0.6 wt% and 1.2 wt%, respectively. Unique lattice expansions in ZnSiHA, silicate Fourier transform infrared peaks and changes to the hydroxyl IR stretching region suggested Zn and silicate co-substitution in ZnSiHA. Zn and silicate insertion into HA was modelled using density functional theory (DFT). Different scenarios were considered where Zn substituted for different calcium sites or at a 2b site along the c-axis, which was suspected in singly substituted ZnHA. The most energetically favourable site in ZnSiHA was Zn positioned at a previously unreported interstitial site just off the c-axis near a silicate tetrahedron sitting on a phosphate site. A combination of experimental chemistry and DFT modelling provided insight into these complex co-substituted calcium phosphates that could find biomedical application as a synthetic bone mineral substitute. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Dentin-cement Interfacial Interaction

PubMed Central

Atmeh, A.R.; Chong, E.Z.; Richard, G.; Festy, F.; Watson, T.F.

2012-01-01

The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline caustic effect of the calcium silicate cement’s hydration products degrades the collagenous component of the interfacial dentin. This degradation leads to the formation of a porous structure which facilitates the permeation of high concentrations of Ca2+, OH-, and CO32- ions, leading to increased mineralization in this region. Comparison of the dentin-restorative interfaces shows that there is a dentin-mineral infiltration with the Biodentine, whereas polyacrylic and tartaric acids and their salts characterize the penetration of the GIC. A new type of interfacial interaction, “the mineral infiltration zone”, is suggested for these calcium-silicate-based cements. PMID:22436906

Process for production desulfurized of synthesis gas

DOEpatents

Wolfenbarger, James K.; Najjar, Mitri S.

1993-01-01

A process for the partial oxidation of a sulfur- and silicate-containing carbonaceous fuel to produce a synthesis gas with reduced sulfur content which comprises partially oxidizing said fuel at a temperature in the range of 1900.degree.-2600.degree. F. in the presence of a temperature moderator, an oxygen-containing gas and a sulfur capture additive which comprises a calcium-containing compound portion, a sodium-containing compound portion, and a fluoride-containing compound portion to produce a synthesis gas comprising H.sub.2 and CO with a reduced sulfur content and a molten slag which comprises (1) a sulfur-containing sodium-calcium-fluoride silicate phase; and (2) a sodium-calcium sulfide phase.

Silicon based substrate with calcium aluminosilicate/thermal barrier layer

NASA Technical Reports Server (NTRS)

Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Miller, Robert Alden (Inventor); Jacobson, Nathan S. (Inventor); Smialek, James L. (Inventor); Opila, Elizabeth J. (Inventor); Lee, Kang N. (Inventor); Nagaraj, Bangalore A. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

2001-01-01

A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a calcium alumino silicate.

Brain aluminium accumulation and oxidative stress in the presence of calcium silicate dental cements.

PubMed

Demirkaya, K; Demirdöğen, B Can; Torun, Z Öncel; Erdem, O; Çırak, E; Tunca, Y M

2017-10-01

Mineral trioxide aggregate (MTA) is a calcium silicate dental cement used for various applications in dentistry. This study was undertaken to test whether the presence of three commercial brands of calcium silicate dental cements in the dental extraction socket of rats would affect the brain aluminium (Al) levels and oxidative stress parameters. Right upper incisor was extracted and polyethylene tubes filled with MTA Angelus, MTA Fillapex or Theracal LC, or left empty for the control group, were inserted into the extraction socket. Rats were killed 7, 30 or 60 days after operation. Brain tissues were obtained before killing. Al levels were measured by atomic absorption spectrometry. Thiobarbituric acid reactive substances (TBARS) levels, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were determined using spectrophotometry. A transient peak was observed in brain Al level of MTA Angelus group on day 7, while MTA Fillapex and Theracal LC groups reached highest brain Al level on day 60. Brain TBARS level, CAT, SOD and GPx activities transiently increased on day 7 and then returned to almost normal levels. This in vivo study for the first time indicated that initial washout may have occurred in MTA Angelus, while element leaching after the setting is complete may have taken place for MTA Fillapex and Theracal LC. Moreover, oxidative stress was induced and antioxidant enzymes were transiently upregulated. Further studies to search for oxidative neuronal damage should be done to completely understand the possible toxic effects of calcium silicate cements on the brain.

Rapid hydrothermal flow synthesis and characterisation of carbonate- and silicate-substituted calcium phosphates

PubMed Central

Knowles, Jonathan C; Rehman, Ihtesham; Darr, Jawwad A

2013-01-01

A range of crystalline and nano-sized carbonate- and silicate-substituted hydroxyapatite has been successfully produced by using continuous hydrothermal flow synthesis technology. Ion-substituted calcium phosphates are better candidates for bone replacement applications (due to improved bioactivity) as compared to phase-pure hydroxyapatite. Urea was used as a carbonate source for synthesising phase pure carbonated hydroxyapatite (CO3-HA) with ≈5 wt% substituted carbonate content (sample 7.5CO3-HA) and it was found that a further increase in urea concentration in solution resulted in biphasic mixtures of carbonate-substituted hydroxyapatite and calcium carbonate. Transmission electron microscopy images revealed that the particle size of hydroxyapatite decreased with increasing urea concentration. Energy-dispersive X-ray spectroscopy result revealed a calcium deficient apatite with Ca:P molar ratio of 1.45 (±0.04) in sample 7.5CO3-HA. For silicate-substituted hydroxyapatite (SiO4-HA) silicon acetate was used as a silicate ion source. It was observed that a substitution threshold of ∼1.1 wt% exists for synthesis of SiO4-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy. PMID:22983020

Sol-Gel Synthesis and Crystallization of Magnesium and Calcium Rich Silicate Dust Analogs

NASA Astrophysics Data System (ADS)

Gillot, J.; Roskosz, M.; Depecker, C.; Roussel, P.; Leroux, H.

2009-03-01

A new sol-gel method optimized to synthesize amorphous and porous silicate dust analogs is proposed. The crystallization of such analogs is metastable and polyphasic. Their high reactivity is probably due to high surface/volume ratio.

A realistic molecular model of cement hydrates.

PubMed

Pellenq, Roland J-M; Kushima, Akihiro; Shahsavari, Rouzbeh; Van Vliet, Krystyn J; Buehler, Markus J; Yip, Sidney; Ulm, Franz-Josef

2009-09-22

Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially unexplored. Together these characteristics of C-S-H define and modulate the physical and mechanical properties of this "liquid stone" gel phase. With the recent determination of the calcium/silicon (C/S = 1.7) ratio and the density of the C-S-H particle (2.6 g/cm(3)) by neutron scattering measurements, there is new urgency to the challenge of explaining these essential properties. Here we propose a molecular model of C-S-H based on a bottom-up atomistic simulation approach that considers only the chemical specificity of the system as the overriding constraint. By allowing for short silica chains distributed as monomers, dimers, and pentamers, this C-S-H archetype of a molecular description of interacting CaO, SiO2, and H2O units provides not only realistic values of the C/S ratio and the density computed by grand canonical Monte Carlo simulation of water adsorption at 300 K. The model, with a chemical composition of (CaO)(1.65)(SiO2)(H2O)(1.75), also predicts other essential structural features and fundamental physical properties amenable to experimental validation, which suggest that the C-S-H gel structure includes both glass-like short-range order and crystalline features of the mineral tobermorite. Additionally, we probe the mechanical stiffness, strength, and hydrolytic shear response of our molecular model, as compared to experimentally measured properties of C-S-H. The latter results illustrate the prospect of treating cement on equal footing with metals and ceramics in the current application of mechanism-based models and multiscale simulations to study inelastic deformation and cracking.

Silicon based substrate with calcium aluminosilicate environmental/thermal barrier layer

NASA Technical Reports Server (NTRS)

Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Miller, Robert Alden (Inventor); Jacobson, Nathan S. (Inventor); Smialek, James L. (Inventor); Opila, Elizabeth J. (Inventor); Lee, Kang N. (Inventor); Nagaraj, Bangalore A. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

2001-01-01

A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a calcium alumino silicate.

Formulation and characterization of a compacted multiparticulate system for modified release of water-soluble drugs--part 1--acetaminophen.

PubMed

Cantor, Stuart L; Hoag, Stephen W; Augsburger, Larry L

2009-03-01

The aim of this study was to characterize and evaluate a modified release, multiparticulate tablet formulation consisting of placebo beads and drug-loaded beads. Acetaminophen (APAP) bead formulations containing ethylcellulose (EC) from 40-60% and placebo beads containing 30% calcium silicate and prepared using 0-20% alcohol were developed using extrusion-spheronization and studied using a central composite experimental design. Particle size and true density of beads were measured. Segregation testing was performed using the novel ASTM D6940-04 method on a 50:50 blend of uncoated APAP beads (60%EC) : calcium silicate placebo beads (10% alcohol). Tablets were prepared using an instrumented Stokes-B2 rotary tablet press and evaluated for crushing strength and dissolution rate. Compared with drug beads (60%EC), placebo beads (10% alcohol) were smaller but had higher true densities: 864.8 mum and 1.27 g/cm(3), and 787.1 mum and 1.73 g/cm(3), respectively. Segregation testing revealed that there was approximately a 20% difference in drug content (as measured by the coefficient of variation) between initial and final blend samples. Although calcium silicate-based placebo beads were shown to be ineffective cushioning agents in blends with Surelease(R)-coated APAP beads, they were found to be very compactibile when used alone and gave tablet crushing strength values between 14 and 17 kP. The EC in the APAP bead matrix minimally suppressed the drug release from uncoated beads (t(100%) = 2 h). However, while tablets containing placebo beads reformulated with glycerol monostearate (GMS) showed a slower release rate (t(60%)= 5 h) compared with calcium silicate-based placebos, some coating damage ( approximately 30%) still occurred on compression as release was faster than coated APAP beads alone. While tablets containing coated drug beads can be produced with practical crushing strengths (>8 kP) and low compression pressures (10-35 MPa), dissolution studies revealed that calcium silicate-based placebos are ineffective as cushioning agents. Blend segregation was likely observed due to the particle size and the density differences between APAP beads and calcium silicate-based placebo beads; placebo bead percolation can perhaps be minimized by increasing their size during the extrusion-spheronization process. The GMS- based placebos offer greater promise as cushioning agents for compacted, coated drug beads; however, this requires an optimized compression pressure range and drug bead : placebo bead ratio (i.e., 50:50).

Na, Rb and Cs partitioning between metal, silicate and sulfide: Implications for volatile depletion in terrestrial planets

NASA Astrophysics Data System (ADS)

Boujibar, A.; Fei, Y.; Du, Z.; Righter, K.; Bullock, E. S.

2017-12-01

Inner Solar System materials are known for their depletion in volatile elements, including the moderately volatile alkalis: Na, K, Rb, and Cs. The origin of this depletion is still uncertain, as several processes could have been involved, during the nebular condensation or planetary accretion. Volatile depletion is commonly estimated through comparison of alkali concentrations relatively to those of chondrites, assuming they remain in planetary mantles during core segregation. However, experimental studies show that substantial K can partition into metals that are enriched in sulfur and oxygen. Several models have also suggested that sulfides may have played an important role during episodes of sulfide segregation from a crystallizing magma ocean (sulfide matte) or accretion of S-rich planetary embryos. For Mercury, a sulfide layer could be present between core and mantle, due to immiscibility between Si-rich and S-rich metals. Therefore, here we investigate whether alkali elements (Na, Cs and Rb) could be partly sequestered in planetary cores during their differentiation. We conducted experiments at high pressure and temperature (1 to 5 GPa and up to 1900 °C) to determine partition coefficients of Na, Rb and Cs between metal and silicate. Our results show that pressure, temperature, sulfur and oxygen in metals enhance the partitioning of Na, Rb and Cs into metals, as previously found for K. For all three investigated alkalis (Na, Rb and Cs), we found a maximum partition coefficient of 1 between sulfides containing 13 wt% O and silicate melt. Therefore, S-rich cores or sulfide layers formed due to immiscibility in Fe-S-O systems could have acted as important geochemical reservoirs for alkali elements. Using our experimental data and different assumptions on initial bulk abundances, we evaluate volatile depletion in terrestrial planets, by comparing resulting mantle alkali concentrations after core segregation, with actual concentrations in the Earth's mantle.

Predictive Mechanical Characterization of Macro-Molecular Material Chemistry Structures of Cement Paste at Nano Scale - Two-phase Macro-Molecular Structures of Calcium Silicate Hydrate, Tri-Calcium Silicate, Di-Calcium Silicate and Calcium Hydroxide

NASA Astrophysics Data System (ADS)

Padilla Espinosa, Ingrid Marcela

Concrete is a hierarchical composite material with a random structure over a wide range of length scales. At submicron length scale the main component of concrete is cement paste, formed by the reaction of Portland cement clinkers and water. Cement paste acts as a binding matrix for the other components and is responsible for the strength of concrete. Cement paste microstructure contains voids, hydrated and unhydrated cement phases. The main crystalline phases of unhydrated cement are tri-calcium silicate (C3S) and di-calcium silicate (C2S), and of hydrated cement are calcium silicate hydrate (CSH) and calcium hydroxide (CH). Although efforts have been made to comprehend the chemical and physical nature of cement paste, studies at molecular level have primarily been focused on individual components. Present research focuses on the development of a method to model, at molecular level, and analysis of the two-phase combination of hydrated and unhydrated phases of cement paste as macromolecular systems. Computational molecular modeling could help in understanding the influence of the phase interactions on the material properties, and mechanical performance of cement paste. Present work also strives to create a framework for molecular level models suitable for potential better comparisons with low length scale experimental methods, in which the sizes of the samples involve the mixture of different hydrated and unhydrated crystalline phases of cement paste. Two approaches based on two-phase cement paste macromolecular structures, one involving admixed molecular phases, and the second involving cluster of two molecular phases are investigated. The mechanical properties of two-phase macromolecular systems of cement paste consisting of key hydrated phase CSH and unhydrated phases C3S or C2S, as well as CSH with the second hydrated phase CH were calculated. It was found that these cement paste two-phase macromolecular systems predicted an isotropic material behavior. Also, these systems exhibited a high bulk modulus, compared to the elastic modulus. These results are an indication and concur with the high compression strength of cement paste seen at engineering length scale. In addition, the bulk modulus of two-phase systems consisting of hydrated CSH and unhydrated C3S or C2S was found to increase with higher levels of unhydrated components. The interaction energies of two-phase cement paste molecular structures studied in the present work were calculated, showing that a higher interaction is attained when the two phases are admixed as small components instead of cluster of phases. Finally, the mechanical behavior under shear deformation was predicted by using a quasi-static deformation method and analyzed for a representative two-phase (CSH and C2S) macromolecular structure of cement paste.

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development,more » and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C–S–H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C–S–H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C–S–H’s nanostructure. We identify that confinement is dictated by the topology of the C–S–H’s atomic network. Altogether, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.« less

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

PubMed

Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

2016-12-28

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

CaCl 2 -Accelerated Hydration of Tricalcium Silicate: A STXM Study Combined with 29 Si MAS NMR

DOE PAGES

Li, Qinfei; Ge, Yong; Geng, Guoqing; ...

2015-01-01

Tmore » he effect of calcium chloride (CaCl 2 ) on tricalcium silicate (C 3 S) hydration was investigated by scanning transmission X-ray microscopy (SXM) with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra and 29 Si MAS NMR. SXM is demonstrated to be a powerful tool for studying the chemical composition of a cement-based hydration system. he Ca L 3,2 -edge NEXAFS spectra obtained by examining C 3 S hydration in the presence of CaCl 2 showed that this accelerator does not change the coordination of calcium in the calcium silicate hydrate (C-S-H), which is the primary hydration product. O K-edge NEXAFS is also very useful in distinguishing the chemical components in hydrated C 3 S. Based on the Ca L 3,2 -edge spectra and chemical component mapping, we concluded that CaCl 2 prefers to coexist with unhydrated C 3 S instead of C-S-H. In Si K-edge NEXAFS analysis, CaCl 2 increases the degree of silicate polymerization of C-S-H in agreement with the 29 Si CP/MAS NMR results, which show that the presence of CaCl 2 in hydrated C 3 S considerably accelerates the formation of middle groups ( Q 2 ) and branch sites ( Q 3 ) in the silicate chains of C-S-H gel at 1-day hydration.« less

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

DOE PAGES

Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel; ...

2016-12-06

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development,more » and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C–S–H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C–S–H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C–S–H’s nanostructure. We identify that confinement is dictated by the topology of the C–S–H’s atomic network. Altogether, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.« less

Modeling Nanomechanical Behavior of Calcium-Silicate-Hydrate

DTIC Science & Technology

2012-08-01

applicability to hardened pastes of tricalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag , metakaolin, or silica...Hydrated Nanocomposites: Concrete, Bone, and Shale. J. Am. Ceram . Soc., 90(9): 2677-2692. Wu, Jianzhong. and John M. Prausnitz. 2002. Generalizations for

CURRENT STATUS OF ADVACATE PROCESS FOR FLUE GAS DESULFURIZATION

EPA Science Inventory

The following report discusses current bench- and pilot-plant advances in preparation of ADVAnced siliCATE (ADVACATE) calcium silicate sorbentsfor flue gas desulfurization. It also discusses current bench- and pilot-plant advances in sorbent preparation. Fly ash was ground in a l...

Addition of a Fluoride-containing Radiopacifier Improves Micromechanical and Biological Characteristics of Modified Calcium Silicate Cements.

PubMed

Antonijevic, Djordje; Jeschke, Anke; Colovic, Bozana; Milovanovic, Petar; Jevremovic, Danimir; Kisic, Danilo; vom Scheidt, Annika; Hahn, Michael; Amling, Michael; Jokanovic, Vukoman; Busse, Björn; Djuric, Marija

2015-12-01

Calcium silicate cements (CSCs) with the addition of nanohydroxyapatite and calcium carbonate play a critical role in dental applications. To further improve their properties, particularly radiopacity and biointeractivity, the fluoride-containing radiopacifier ytterbium trifluoride (YbF3) was added to their composition, and biological and mechanical characteristics were evaluated. YbF3 was added to 3 different CSCs: cement I (CSC + calcium carbonate), cement II (CSC + nanohydroxyapatite), and Portland cement. Material characterization encompassed measurements of pH, calcium, ytterbium, and fluoride ion release; radiopacity; setting time; porosity; microindentation properties; wettability; and Fourier transform infrared spectroscopic, x-ray diffraction, and scanning electron microscopic analyses. Osteoblast- and osteoclast-like cells were grown on the materials' surface to evaluate their adherence. The addition of calcium carbonate, nanohydroxyapatite, and 30 wt% of YbF3 improved radiopacity and the setting time of experimental cements. The pH values did not differ among the groups. The greatest ytterbium and fluoride releases occurred in the Portland cement + YbF3 group. Combined x-ray diffraction and Fourier transform infrared spectroscopic analysis showed the presence of calcium hydroxide and calcium silicate hydrates. In addition, the presence of calcium ytterbium fluoride and ytterbium oxide proved that YbF3 reacted with cement compounds. Wettability of cement I + YbF3 was superior to other formulations, but its porosity and microindentation properties were weaker than in the Portland cement + YbF3 mixture. Cement II + YbF3 presented micromechanical indentation and porosity characteristics similar to the Portland-based cement formulation. Osteoclast- and osteoblast-like cells adhered to the cements' surfaces without alteration of the cell structural integrity. YbF3-containing CSCs with nanostructured hydroxyapatite and calcium carbonate are well suited for dental application. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Enhancement of biodegradation and osseointegration of poly(ε-caprolactone)/calcium phosphate ceramic composite screws for osteofixation using calcium sulfate.

PubMed

Wu, Chang-Chin; Hsu, Li-Ho; Tsai, Yuh-Feng; Sumi, Shoichiro; Yang, Kai-Chiang

2016-04-04

Internal fixation devices, which can stabilize and realign fractured bone, are widely used in fracture management. In this paper, a biodegradable composite fixator, composed of poly(ε-caprolactone), calcium phosphate ceramic and calcium sulfate (PCL/CPC/CS), is developed. The composition of CS, which has a high dissolution rate, was expected to create a porous structure to improve osteofixation to the composite fixator. PCL, PCL/CPC, and PCL/CPC/CS samples were prepared and their physical properties were characterized in vitro. In vivo performance of the composite screws was verified in the distal femurs of rabbits. Results showed that the PCL/CPC/CS composite had a higher compressive strength (28.55 ± 3.32 MPa) in comparison with that of PCL (20.64 ± 1.81 MPa) (p < 0.05). A larger amount of apatite was formed on PCL/CPC/CS than on PCL/CPC, while no apatite was found on PCL after simulated body fluid immersion. In addition, PCL/CPC/CS composites also had a faster in vitro degradation rate (13.05 ± 3.42% in weight loss) relative to PCL (1.79 ± 0.23%) and PCL/CPC (4.32 ± 2.18%) (p < 0.001). In animal studies, PCL/CPC/CS screws showed a greater volume loss than that of PCL or PCL/CPC at 24 weeks post-implantation. Under micro-computerized tomography observation, animals with PCL/CPC/CS implants had better osseointegration in terms of the structural parameters of the distal metaphysis, including trabecular number, trabecular spacing, and connectivity density, than the PCL screw. This study reveals that the addition of CS accelerates the biodegradation and enhanced apatite formation of the PCL/CPC composite screw. This osteoconductive PCL/CPC/CS is a good candidate material for internal fixation devices.

A novel sol-gel-derived calcium silicate cement with short setting time for application in endodontic repair of perforations

PubMed Central

Lee, Bor-Shiunn; Lin, Hong-Ping; Chan, Jerry Chun-Chung; Wang, Wei-Chuan; Hung, Ping-Hsuan; Tsai, Yu-Hsin; Lee, Yuan-Ling

2018-01-01

Mineral trioxide aggregate (MTA) is the most frequently used repair material in endodontics, but the long setting time and reduced mechanical strength in acidic environments are major shortcomings. In this study, a novel sol-gel-derived calcium silicate cement (sCSC) was developed using an initial Ca/Si molar ratio of 3, with the most effective mixing orders of reactants and optimal HNO3 catalyst volumes. A Fourier transform infrared spectrometer, scanning electron microscope with energy-dispersive X-ray spectroscopy, and X-ray powder diffractometer were used for material characterization. The setting time, compressive strength, and microhardness of sCSC after hydration in neutral and pH 5 environments were compared with that of MTA. Results showed that sCSC demonstrated porous microstructures with a setting time of ~30 min, and the major components of sCSC were tricalcium silicate, dicalcium silicate, and calcium oxide. The optimal formula of sCSC was sn200, which exhibited significantly higher compressive strength and microhardness than MTA, irrespective of neutral or pH 5 environments. In addition, both sn200 and MTA demonstrated good biocompatibility because cell viability was similar to that of the control. These findings suggest that sn200 merits further clinical study for potential application in endodontic repair of perforations. PMID:29386894

A novel sol-gel-derived calcium silicate cement with short setting time for application in endodontic repair of perforations.

PubMed

Lee, Bor-Shiunn; Lin, Hong-Ping; Chan, Jerry Chun-Chung; Wang, Wei-Chuan; Hung, Ping-Hsuan; Tsai, Yu-Hsin; Lee, Yuan-Ling

2018-01-01

Mineral trioxide aggregate (MTA) is the most frequently used repair material in endodontics, but the long setting time and reduced mechanical strength in acidic environments are major shortcomings. In this study, a novel sol-gel-derived calcium silicate cement (sCSC) was developed using an initial Ca/Si molar ratio of 3, with the most effective mixing orders of reactants and optimal HNO 3 catalyst volumes. A Fourier transform infrared spectrometer, scanning electron microscope with energy-dispersive X-ray spectroscopy, and X-ray powder diffractometer were used for material characterization. The setting time, compressive strength, and microhardness of sCSC after hydration in neutral and pH 5 environments were compared with that of MTA. Results showed that sCSC demonstrated porous microstructures with a setting time of ~30 min, and the major components of sCSC were tricalcium silicate, dicalcium silicate, and calcium oxide. The optimal formula of sCSC was sn200, which exhibited significantly higher compressive strength and microhardness than MTA, irrespective of neutral or pH 5 environments. In addition, both sn200 and MTA demonstrated good biocompatibility because cell viability was similar to that of the control. These findings suggest that sn200 merits further clinical study for potential application in endodontic repair of perforations.

Effect of tetracalcium phosphate/monetite toothpaste on dentin remineralization and tubule occlusion in vitro.

PubMed

Medvecky, L; Stulajterova, R; Giretova, M; Mincik, J; Vojtko, M; Balko, J; Briancin, J

2018-03-01

To investigate the tubule occlusion and remineralization potential of a novel toothpaste with active tetracalcium phosphate/monetite mixtures under de/remineralization cycling. Dentin de/remineralization cycling protocol consisted of demineralization in 1% citric acid at pH 4.6 with following remineralization with toothpastes and soaking in artificial saliva. Effectiveness of toothpastes to promote remineralization was evaluated by measurement of microhardness recovery, analysis of surface roughness, thickness of coating and scanning electron microscopy. The novel tetracalcium phosphate/monetite dentifrice had comparable remineralization potential as commercial calcium silicate/phosphate (SENSODYNE ® ) and magnesium aluminum silicate (Colgate ® ) toothpastes and significantly higher than control saliva (p<0.02). Surface roughness was significantly lower after treatment with prepared and SENSODYNE ® dentifirice (p<0.05). The coatings on dentin surfaces was significantly thicker after applying toothpastes as compared to negative control (p<0.001). The new fluoride toothpaste formulation with bioactive tetracalcium phosphate/monetite calcium phosphate mixture effectively occluded dentin tubules and showed good dentin remineralization potential under de/remineralization cycling. It could replace professional powder preparation based on this mixture. It was demonstrated that prepared dentifrice had comparable properties with commercial fluoride calcium silicate/phosphate or magnesium aluminum silicate dentifrices. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effects of Incorporating High-Volume Fly Ash into Tricalcium Silicate on the Degree of Silicate Polymerization and Aluminum Substitution for Silicon in Calcium Silicate Hydrate

DOE PAGES

Bae, Sungchul; Taylor, Rae; Kilcoyne, David; ...

2017-02-04

This study assesses the quantitative effects of incorporating high-volume fly ash (HVFA) into tricalcium silicate (C 3S) paste on the hydration, degree of silicate polymerization, and Al substitution for Si in calcium silicate hydrate (C–S–H). Thermogravimetric analysis and isothermal conduction calorimetry showed that, although the induction period of C 3S hydration was significantly extended, the degree of hydration of C 3S after the deceleration period increased due to HVFA incorporation. Synchrotron-sourced soft X-ray spectromicroscopy further showed that most of the C 3S in the C 3S-HVFA paste was fully hydrated after 28 days of hydration, while that in the puremore » C 3S paste was not. The chemical shifts of the Si K edge peaks in the near-edge X-ray fine structure of C–S–H in the C 3S-HVFA paste directly indicate that Al substitutes for Si in C–S–H and that the additional silicate provided by the HVFA induces an enhanced degree of silicate polymerization. This new spectromicroscopic approach, supplemented with 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectroscopy and transmission electron microscopy, turned out to be a powerful characterization tool for studying a local atomic binding structure of C–S–H in C 3S-HVFA system and presented results consistent with previous literature.« less

Effects of Incorporating High-Volume Fly Ash into Tricalcium Silicate on the Degree of Silicate Polymerization and Aluminum Substitution for Silicon in Calcium Silicate Hydrate

PubMed Central

Bae, Sungchul; Taylor, Rae; Kilcoyne, David; Moon, Juhyuk; Monteiro, Paulo J. M.

2017-01-01

This study assesses the quantitative effects of incorporating high-volume fly ash (HVFA) into tricalcium silicate (C3S) paste on the hydration, degree of silicate polymerization, and Al substitution for Si in calcium silicate hydrate (C–S–H). Thermogravimetric analysis and isothermal conduction calorimetry showed that, although the induction period of C3S hydration was significantly extended, the degree of hydration of C3S after the deceleration period increased due to HVFA incorporation. Synchrotron-sourced soft X-ray spectromicroscopy further showed that most of the C3S in the C3S-HVFA paste was fully hydrated after 28 days of hydration, while that in the pure C3S paste was not. The chemical shifts of the Si K edge peaks in the near-edge X-ray fine structure of C–S–H in the C3S-HVFA paste directly indicate that Al substitutes for Si in C–S–H and that the additional silicate provided by the HVFA induces an enhanced degree of silicate polymerization. This new spectromicroscopic approach, supplemented with 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectroscopy and transmission electron microscopy, turned out to be a powerful characterization tool for studying a local atomic binding structure of C–S–H in C3S-HVFA system and presented results consistent with previous literature. PMID:28772490

Effects of Incorporating High-Volume Fly Ash into Tricalcium Silicate on the Degree of Silicate Polymerization and Aluminum Substitution for Silicon in Calcium Silicate Hydrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bae, Sungchul; Taylor, Rae; Kilcoyne, David

This study assesses the quantitative effects of incorporating high-volume fly ash (HVFA) into tricalcium silicate (C 3S) paste on the hydration, degree of silicate polymerization, and Al substitution for Si in calcium silicate hydrate (C–S–H). Thermogravimetric analysis and isothermal conduction calorimetry showed that, although the induction period of C 3S hydration was significantly extended, the degree of hydration of C 3S after the deceleration period increased due to HVFA incorporation. Synchrotron-sourced soft X-ray spectromicroscopy further showed that most of the C 3S in the C 3S-HVFA paste was fully hydrated after 28 days of hydration, while that in the puremore » C 3S paste was not. The chemical shifts of the Si K edge peaks in the near-edge X-ray fine structure of C–S–H in the C 3S-HVFA paste directly indicate that Al substitutes for Si in C–S–H and that the additional silicate provided by the HVFA induces an enhanced degree of silicate polymerization. This new spectromicroscopic approach, supplemented with 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectroscopy and transmission electron microscopy, turned out to be a powerful characterization tool for studying a local atomic binding structure of C–S–H in C 3S-HVFA system and presented results consistent with previous literature.« less

The Effect of Specific Surface Area of Chitin-Metal Silicate Coprocessed Excipient on the Chemical Decomposition of Cefotaxime Sodium.

PubMed

Al-Nimry, Suhair S; Alkhamis, Khouloud A; Alzarieni, Kawthar Z

2017-02-01

Chitin-metal silicates are multifunctional excipients used in tablets. Previously, a correlation between the surface acidity of chitin-calcium and chitin-magnesium silicate and the chemical decomposition of cefotaxime sodium was found but not with chitin-aluminum silicate. This lack of correlation could be due to the catalytic effect of silica alumina or the difference in surface area of the excipients. The objective of this study was to investigate the effect of the specific surface area of the excipient on the chemical decomposition of cefotaxime sodium in the solid state. Chitin was purified and coprocessed with different metal silicates to prepare the excipients. The specific surface area was determined using gas adsorption. The chemical decomposition was studied at constant temperature and relative humidity. Also, the degradation in solution was studied. A correlation was found between the degradation rate constant and the surface area of chitin-aluminum and chitin-calcium silicate but not with chitin-magnesium silicate. This was due to the small average pore diameter of this excipient. Also, the degradation in solution was slower than in solid state. In conclusion, the stability of cefotaxime sodium was dependent on the surface area of the excipient in contact with the drug. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Calcium silicate hydrates: Solid and liquid phase composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lothenbach, Barbara, E-mail: Barbara.lothenbach@empa.ch; Nonat, André

This paper presents a review on the relationship between the composition, the structure and the solution in which calcium silicate hydrate (C–S–H) is equilibrated. The silica chain length in C–S–H increases with the silicon concentration and the calcium content in the interlayer space with the calcium concentrations. Sodium and potassium are taken up in the interlayer space, preferentially at low calcium concentrations and thus by low Ca/Si C–S–H. Aluminium uptake in C–S–H increases strongly at higher aluminium concentrations in the solution. At low Ca/Si, aluminium substitutes silica in the bridging position, at Ca/Si > 1 aluminium is bound in TAH.more » Recently developed thermodynamic models are closely related to the structure of C–S–H and tobermorite, and able to model not only the solubility and the chemical composition of the C–S–H, but also to predict the mean silica chain length and the uptake of aluminium.« less

Tooth Discoloration Induced by Different Calcium Silicate-based Cements: A Systematic Review of In Vitro Studies.

PubMed

Możyńska, Joanna; Metlerski, Marcin; Lipski, Mariusz; Nowicka, Alicja

2017-10-01

On the basis of many clinical observations, some calcium silicate-based cements have a high potential for staining tooth tissue. This feature greatly limits the use of those cements, particularly for anterior teeth. This review aimed to provide a systematic evaluation of published in vitro studies to determine the effect of different calcium silicate-based cements on dental tissue discoloration. This literature review was developed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The literature search was based on all publications without a year limit. The last search was performed on October 22, 2016. An electronic search was performed on MEDLINE (PubMed), Cochrane, and Scopus. The articles were selected to address the following research question: Which materials based on calcium silicate-based cements have hard tissue staining potential? The necessary information was extracted by 2 authors independently using a standardized form. The search resulted in 390 titles from all databases. Twenty-three studies met the inclusion criteria. Most of the studies exhibited a moderate risk of bias. The results indicated that some materials showed a strong potential for staining, including gray and white MTA Angelus (Londrina, PR, Brazil), gray and white ProRoot MTA (Dentsply, Tulsa, OK), and Ortho MTA (BioMTA, Seoul, Korea). Individual study results showed that Biodentine (Septodont, Saint Maur des Fosses, France), Retro MTA (BioMTA), Portland cement, EndoSequence Root Repair Material (Brasseler USA, Savannah, GA), Odontocem (Australian Dental Manufacturing, Brisbane, Australia), MM-MTA (Micro Mega, Besancon Cedex, France), and MTA Ledermix (Riemser Pharma GmbH, Greiswald-Insel Riems, Germany) were materials with the smallest staining potential. This review clearly showed that some calcium silicate-based cements have a high potential for staining hard tissue. On the other hand, some showed only a small change in color, which was nearly invisible to the human eye (ΔE <3.3). However, more long-term clinical studies are needed. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Kinetics of apatite formation on a calcium-silicate cement for root-end filling during ageing in physiological-like phosphate solutions.

PubMed

Gandolfi, Maria Giovanna; Taddei, Paola; Tinti, Anna; De Stefano Dorigo, Elettra; Rossi, Piermaria Luigi; Prati, Carlo

2010-12-01

The bioactivity of calcium silicate mineral trioxide aggregate (MTA) cements has been attributed to their ability to produce apatite in presence of phosphate-containing fluids. This study evaluated surface morphology and chemical transformations of an experimental accelerated calcium-silicate cement as a function of soaking time in different phosphate-containing solutions. Cement discs were immersed in Dulbecco's phosphate-buffered saline (DPBS) or Hank's balanced salt solution (HBSS) for different times (1-180 days) and analysed by scanning electron microscopy connected with an energy dispersive X-ray analysis (SEM-EDX) and micro-Raman spectroscopy. SEM-EDX revealed Ca and P peaks after 14 days in DPBS. A thin Ca- and P-rich crystalline coating layer was detected after 60 days. A thicker multilayered coating was observed after 180 days. Micro-Raman disclosed the 965-cm(-1) phosphate band at 7 days only on samples stored in DPBS and later the 590- and 435-cm(-1) phosphate bands. After 60-180 days, a layer approximately 200-900 μm thick formed displaying the bands of carbonated apatite (at 1,077, 965, 590, 435 cm(-1)) and calcite (at 1,088, 713, 280 cm(-1)). On HBSS-soaked, only calcite bands were observed until 90 days, and just after 180 days, a thin apatite-calcite layer appeared. Micro-Raman and SEM-EDX demonstrated the mineralization induction capacity of calcium-silicate cements (MTAs and Portland cements) with the formation of apatite after 7 days in DPBS. Longer time is necessary to observe bioactivity when cements are immersed in HBSS.

Cytotoxicity and Bioactivity of Calcium Silicate Cements Combined with Niobium Oxide in Different Cell Lines.

PubMed

Mestieri, Leticia Boldrin; Gomes-Cornélio, Ana Lívia; Rodrigues, Elisandra Márcia; Faria, Gisele; Guerreiro-Tanomaru, Juliane Maria; Tanomaru-Filho, Mário

2017-01-01

The aim of this study was to evaluate the cytotoxicity and bioactivity of calcium silicate-based cements combined with niobium oxide (Nb2O5) micro and nanoparticles, comparing the response in different cell lines. This evaluation used four cell lines: two primary cultures (human dental pulp cells - hDPCs and human dental follicle cells - hDFCs) and two immortalized cultures (human osteoblast-like cells - Saos-2 and mouse periodontal ligament cells - mPDL). The tested materials were: White Portland Cement (PC), mineral trioxide aggregate (MTA), white Portland cement combined with microparticles (PC/Nb2O5µ) or nanoparticles (PC/Nb2O5n) of niobium oxide (Nb2O5). Cytotoxicity was evaluated by the methylthiazolyldiphenyl-tetrazolium bromide (MTT) and trypan blue exclusion assays and bioactivity by alkaline phosphatase (ALP) enzyme activity. Results were analyzed by ANOVA and Tukey test (a=0.05). PC/Nb2O5n presented similar or higher cell viability than PC/Nb2O5µ in all cell lines. Moreover, the materials presented similar or higher cell viability than MTA. Saos-2 exhibited high ALP activity, highlighting PC/Nb2O5µ material at 7 days of exposure. In conclusion, calcium silicate cements combined with micro and nanoparticles of Nb2O5 presented cytocompatibility and bioactivity, demonstrating the potential of Nb2O5 as an alternative radiopacifier agent for these cements. The different cell lines had similar response to cytotoxicity evaluation of calcium silicate cements. However, bioactivity was more accurately detected in human osteoblast-like cell line, Saos-2.

Corticosteroid treatment exacerbates bone osteopenia in mice with gonadal hormone deficiency-induced osteoporosis.

PubMed

Badraoui, Riadh; Amri, Nahed; Zammel, Nourhène; Chaabane, Rim; Rebai, Tarek

2017-07-15

Gonadic deficiency and corticotherapy are important risk factors in the pathogenesis of osteoporosis. This study was outlined to assess the effects of combined orchidectomy (ORX) and corticosteroid (cortisol; CS) administration on bone remodeling and metabolism. Twenty-week-old male Swiss mice were randomized into four groups: either sham operated (sham), ORX, CS injected (CS), or ORX and CS injected (ORX+CS). After 28days, mice were euthanized. Both ORX and CS resulted in reduced trabecular volume, and mineral apposition rate and increased osteoclast number and activity. TRAcP levels were increased in ORX and CS mice, but reached highest values in ORX+CS. Bone and serum mineral content (calcium and phosphorus) were disrupted in ORX and CS groups when compared to Sham, and were more affected in ORX+CS group. Urinary calcium measures were increased in ORX, CS, and ORX+CS during the time course of the study. Increases were more prominent in ORX+CS. The differences between groups were generally more accentuated at ORX+CS group. Biochemical data showed a parallel extent to the histologic and histomorphometric changes. This study provides a valid pre-clinical model for severe and rapid osteopenia by ORX associated corticotherapy in which bone loss was significantly higher than either ORX or CS alones. Copyright © 2017 Elsevier B.V. All rights reserved.

Drying-induced atomic structural rearrangements in sodium-based calcium-alumino-silicate-hydrate gel and the mitigating effects of ZrO 2 nanoparticles

DOE PAGES

Yang, Kengran; Özçelik, V. Ongun; Garg, Nishant; ...

2018-01-01

Drying-induced nanoscopic alterations to the local atomic structure of silicate-activated slag and the mitigated effects of nano-ZrO2 are elucidated using in situ X-ray pair distribution function analysis.

Drying-induced atomic structural rearrangements in sodium-based calcium-alumino-silicate-hydrate gel and the mitigating effects of ZrO 2 nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Kengran; Özçelik, V. Ongun; Garg, Nishant

Drying-induced nanoscopic alterations to the local atomic structure of silicate-activated slag and the mitigated effects of nano-ZrO2 are elucidated using in situ X-ray pair distribution function analysis.

Mechanical and physical properties of calcium silicate/alumina composite for biomedical engineering applications.

PubMed

Shirazi, F S; Mehrali, M; Oshkour, A A; Metselaar, H S C; Kadri, N A; Abu Osman, N A

2014-02-01

The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000°C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0-50w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150°C and 1250°C with a 5h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15wt% of Al2O3 powder at 1250°C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500-700nm after sintering process. © 2013 Published by Elsevier Ltd.

Calcium carbonate precipitation by heterotrophic bacteria isolated from biofilms formed on deteriorated ignimbrite stones: influence of calcium on EPS production and biofilm formation by these isolates.

PubMed

López-Moreno, Angélica; Sepúlveda-Sánchez, José David; Mercedes Alonso Guzmán, Elia Mercedes; Le Borgne, Sylvie

2014-01-01

Heterotrophic CaCO3-precipitating bacteria were isolated from biofilms on deteriorated ignimbrites, siliceous acidic rocks, from Morelia Cathedral (Mexico) and identified as Enterobacter cancerogenus (22e), Bacillus sp. (32a) and Bacillus subtilis (52g). In solid medium, 22e and 32a precipitated calcite and vaterite while 52g produced calcite. Urease activity was detected in these isolates and CaCO3 precipitation increased in the presence of urea in the liquid medium. In the presence of calcium, EPS production decreased in 22e and 32a and increased in 52g. Under laboratory conditions, ignimbrite colonization by these isolates only occurred in the presence of calcium and no CaCO3 was precipitated. Calcium may therefore be important for biofilm formation on stones. The importance of the type of stone, here a siliceous stone, on biological colonization is emphasized. This calcium effect has not been reported on calcareous materials. The importance of the effect of calcium on EPS production and biofilm formation is discussed in relation to other applications of CaCO3 precipitation by bacteria.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azam, Farah 'Atiqah bt Abdul; Shamsudin, Roslinda, E-mail: linda@ukm.edu.my

Calcium silicate bioceramic was prepared from the rice husk and limestone resources using the sol gel method. The preparations of CaSiO{sub 3} formulation were differ from the previous study due CaO/SiO{sub 2} amount with 45:55 ratio. X-Ray Fluorescence analysis was carried out to clarify the amount of SiO{sub 2} and CaO content in the limestone and rice husk ash. The high amount of CaO was found in the limestone with the percentages of 97.22%, whereby 89% of SiO{sub 2} content of the rice husk ash. Several milling time were studied to obtain the optimized milling ti me and speed inmore » progress to obtain nano size particle. The particle size analysis result confirms that increase in milling time does not certainly reduce the size of particle. The addition of 0.05% polyvinyl alcohol as a binder did not change the phases or composition of calcium silicates after examined by X-Ray diffraction analysis which make it suitable to be used as a binder for calcium silicate coating without changing the chemical structure.« less

Crystalline phases involved in the hydration of calcium silicate-based cements: Semi-quantitative Rietveld X-ray diffraction analysis.

PubMed

Grazziotin-Soares, Renata; Nekoofar, Mohammad H; Davies, Thomas; Hübler, Roberto; Meraji, Naghmeh; Dummer, Paul M H

2017-08-30

Chemical comparisons of powder and hydrated forms of calcium silicate cements (CSCs) and calculation of alterations in tricalcium silicate (Ca 3 SiO 5 ) calcium hydroxide (Ca(OH) 2 ) are essential for understanding their hydration processes. This study aimed to evaluate and compare these changes in ProRoot MTA, Biodentine and CEM cement. Powder and hydrated forms of tooth coloured ProRoot MTA, Biodentine and CEM cement were subjected to X-ray diffraction (XRD) analysis with Rietveld refinement to semi-quantitatively identify and quantify the main phases involved in their hydration process. Data were reported descriptively. Reduction in Ca 3 SiO 5 and formation of Ca(OH) 2 were seen after the hydration of ProRoot MTA and Biodentine; however, in the case of CEM cement, no reduction of Ca 3 SiO 5 and no formation of Ca(OH) 2 were detected. The highest percentages of amorphous phases were seen in Biodentine samples. Ettringite was detected in the hydrated forms of ProRoot MTA and CEM cement but not in Biodentine. © 2017 Australian Society of Endodontology Inc.

Physiology of Calcium and Phosphate Metabolism: 1980 Refresher Course, Syllabus.

ERIC Educational Resources Information Center

Knox, Franklyn G., Ed.

1980-01-01

This syllabus reviews information concerning calcium and phosphate regulation. Topics of interest include the following: calcium metabolism, phosphorus metabolism, bone, parathyroid hormone, calcitonin, and vitamin D. (CS)

Ion-Doped Silicate Bioceramic Coating of Ti-Based Implant

PubMed Central

Mohammadi, Hossein; Sepantafar, Mohammadmajid

2016-01-01

Titanium and its alloy are known as important load-bearing biomaterials. The major drawbacks of these metals are fibrous formation and low corrosion rate after implantation. The surface modification of biomedical implants through various methods such as plasma spray improves their osseointegration and clinical lifetime. Different materials have been already used as coatings on biomedical implant, including calcium phosphates and bioglass. However, these materials have been reported to have limited clinical success. The excellent bioactivity of calcium silicate (Ca-Si) has been also regarded as coating material. However, their high degradation rate and low mechanical strength limit their further coating application. Trace element modification of (Ca-Si) bioceramics is a promising method, which improves their mechanical strength and chemical stability. In this review, the potential of trace element-modified silicate coatings on better bone formation of titanium implant is investigated. PMID:26979401

Inorganic Corrosion-Inhibitive Pigments for High-Temperature Alkali-activated Well Casing Foam Cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugama, T.; Pyatina, T.

2014-11-01

This study evaluates inorganic pigments for improving carbon steel (CS) brine-corrosion protection by the sodium metasilicate-activated calcium aluminate cement/Fly Ash blend at 300°C. Calcium borosilicate (CBS) and zinc phosphate, significantly improved CS corrosion-protection by decreasing cement’s permeability for corrosive ions and inhibiting anodic corrosion. An amorphous Na 2O-Al 2O 3-SiO 2-H 2O phase tightly attached to CS surface formed at 300oC in CBS-modified cement pore solution. The corrosion rate of the CS covered with this phase was nearly 4-fold lower than in the case of nonmodified cement pore solution where the major phase formed on the surface of CS wasmore » crystalline analcime.« less

Inorganic Corrosion-Inhibitive Pigments for High-Temperature Alkali-activated Well Casing Foam Cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugama, T.; Pyatina, T.

2014-11-14

This study evaluates inorganic pigments for improving carbon steel (CS) brine-corrosion protection by the sodium metasilicate-activated calcium aluminate cement/Fly Ash blend at 300°C. Calcium borosilicate (CBS) and zinc phosphate, significantly improved CS corrosion-protection by decreasing cement’s permeability for corrosive ions and inhibiting anodic corrosion. An amorphous Na 2O-Al 2O 3-SiO 2-H 2O phase tightly attached to CS surface formed at 300oC in CBS-modified cement pore solution. The corrosion rate of the CS covered with this phase was nearly 4-fold lower than in the case of nonmodified cement pore solution where the major phase formed on the surface of CS wasmore » crystalline analcime.« less

Techno - economic and leachability effect of Ca2SiO4 interlocking composite brick

NASA Astrophysics Data System (ADS)

Namboonruang, Weerapol; Yongam-nuai, Prayoon; Suphadon, Nutthanun

2017-07-01

This work studied the possibility to produce the new novel calcium silicate ceramic kiln ash composite brick (CSCACB) which was the combination of the local Ratchaburi soil and calcium silicate kiln ash (CSCA) wasted from the ceramic industry. The chemical and physical properties of the composite brick were investigated. Also, the mechanical properties such as the compressive strength, flexural strength and as well as the leachability property were determined. By summary, this invented materials has enough quality to produce as local commercial products considered by the strength properties, environmental effect, price and appropriated implementation.

The determination of calcium in phosphate, carbonate, and silicate rocks by flame photometer

USGS Publications Warehouse

Kramer, Henry

1956-01-01

A method has been developed for the determination of calcium in phosphate, carbonate, and silicate rocks using the Beckman flame photometer, with photomultiplier attachement. The sample is dissolved in hydrofluoric, nitric, and perchloric acids, the hydrofluoric and nitric acids are expelled, a radiation buffer consisting of aluminum, magnesium, iron, sodium, potassium, phosphoric acid, and nitric acid is added, and the solution is atomized in an oxy-hydrogen flame with an instrument setting of 554 mµ. Measurements are made by comparison against calcium standards, prepared in the same manner, in the 0 to 50 ppm range. The suppression of calcium emission by aluminum and phosphate was overcome by the addition of a large excess of magnesium. This addition almost completely restores the standard curve obtained from a solution of calcium nitrate. Interference was noted when the iron concentration in the aspirated solution (including the iron from the buffer) exceeded 100 ppm iron. Other common rock-forming elements did not interfere. The results obtained by this procedure are within ± 2 percent of the calcium oxide values obtained by other methods in the range 1 to 95 percent calcium oxide. In the 0 to 1 percent calcium oxide range the method compares favorably with standard methods.

Cs(2)K(UO)(2)Si(4)O(12): a mixed-valence uranium(IV,V) silicate.

PubMed

Lee, Cheng-Shiuan; Wang, Sue-Lein; Lii, Kwang-Hwa

2009-10-28

The first mixed-valence uranium(IV,V) silicate is synthesized under high-temperature, high-pressure hydrothermal conditions. The structure contains chains of corner-sharing U(IV,V)O(6) octahedra which are interconnected by Si(4)O(12) four-membered rings to form a 3-D framework. XPS and XANES spectra were measured to identify the valence state of uranium.

Pseudowollastonite Carbonation Could Enable New Frontiers in Carbon Storage

NASA Astrophysics Data System (ADS)

Plattenberger, D.; Tao, Z.; Ling, F. T.; Peters, C. A.; Clarens, A. F.

2017-12-01

One of the primary challenges of CO2 mineral trapping is that precipitation reactions are reversible. A wide range of solid magnesium, iron, or calcium carbonates (such as magnesite, MgCO3) can be synthesized by reacting mineral silicates (such as olivine, Mg2SiO4) with CO2 to produce mineral carbonates. However, if CO2 remains present at high concentrations, as would be the case in many subsurface environments, the carbonate minerals could re-dissolve, making the precipitated carbonates impermanent forms of storage. In this work, we study pseudowollastonite (CaSiO3), a crystalline form of calcium silicate that is common in slags, cement, and calcium-rich volcanic formations, for its potential to produce other secondary mineral phases that may be resistant to dissolution under low pH conditions. These secondary mineral precipitation phases have morphologies and X-ray diffraction patterns that resemble both calcium silicate hydrate gels as well as crystalline calcium silicate carbonate hydrates. The combination of these phases forms a complex system that may resist acid attack while providing strength and limiting flow in the subsurface environment. High pressure and temperature column experiments carried out in our lab show that pseudowollastonite carbonation effectively lowers permeability in columns of sintered glass beads. Many of the pore throats are clogged by precipitates, as seen using micro X-ray tomography of intact columns and electron microscopy of thin sections. The spatial distribution of the products suggests that calcite forms toward the inlet of the columns where the pCO2 is highest. This forms a barrier that reduces, but does not eliminate, the availability of CO2 deeper in the porous media where the secondary phases precipitate. The existence of the calcite zone drives the reduction in permeability and the depth of this zone is self-limiting, which could have important implications for limiting leakage and unwanted migration of CO2 in some instances.

Physicochemical properties of calcium silicate-based formulations MTA Repair HP and MTA Vitalcem.

PubMed

Guimarães, Bruno Martini; Prati, Carlo; Duarte, Marco Antonio Hungaro; Bramante, Clovis Monteiro; Gandolfi, Maria Giovanna

2018-04-05

This study aimed to analyze the following physicochemical properties: radiopacity, final setting time, calcium release, pH change, solubility, water sorption, porosity, surface morphology, and apatite-forming ability of two calcium silicate-based materials. We tested MTA Repair HP and MTA Vitalcem in comparison with conventional MTA, analyzing radiopacity and final setting time. Water absorption, interconnected pores and apparent porosity were measured after 24-h immersion in deionized water at 37°C. Calcium and pH were tested up to 28 d in deionized water. We analyzed data using two-way ANOVA with Student-Newman-Keuls tests (p<0.05). We performed morphological and chemical analyses of the material surfaces using ESEM/EDX after 28 d in HBSS. MTA Repair HP showed similar radiopacity to that of conventional MTA. All materials showed a marked alkalinizing activity within 3 h, which continued for 28 d. MTA Repair HP showed the highest calcium release at 28 d (p<0.05). MTA Vitalcem showed statistically higher water sorption and solubility values (p<0.05). All materials showed the ability to nucleate calcium phosphate on their surface after 28 d in HBSS. MTA Repair HP and MTA Vitalcem had extended alkalinizing activity and calcium release that favored calcium phosphate nucleation. The presence of the plasticizer in MTA HP might increase its solubility and porosity. The radiopacifier calcium tungstate can be used to replace bismuth oxide.

Effect of Exposed Surface Area, Volume and Environmental pH on the Calcium Ion Release of Three Commercially Available Tricalcium Silicate Based Dental Cements.

PubMed

Rajasekharan, Sivaprakash; Vercruysse, Chris; Martens, Luc; Verbeeck, Ronald

2018-01-13

Tricalcium silicate cements (TSC) are used in dental traumatology and endodontics for their bioactivity which is mostly attributed to formation of calcium hydroxide during TSC hydration and its subsequent release of calcium and hydroxide ions. The aim of this study was to determine the effect of volume (Vol), exposed surface area (ESA) and pH of surrounding medium on calcium ion release. Three commercially available hydraulic alkaline dental cements were mixed and condensed into cylindrical tubes of varying length and diameter ( n = 6/group). For the effect of ESA and Vol, tubes were immersed in 10 mL of deionized water. To analyze the effect of environmental pH, the tubes were randomly immersed in 10 mL of buffer solutions with varying pH (10.4, 7.4 or 4.4). The solutions were collected and renewed at various time intervals. pH and/or calcium ion release was measured using a pH glass electrode and atomic absorption spectrophotometer respectively. The change of pH, short-term calcium ion release and rate at which calcium ion release reaches maximum were dependent on ESA ( p < 0.05) while maximum calcium ion release was dependent on Vol of TSC ( p < 0.05). Maximum calcium ion release was significantly higher in acidic solution followed by neutral and alkaline solution ( p < 0.05).

Effect of Exposed Surface Area, Volume and Environmental pH on the Calcium Ion Release of Three Commercially Available Tricalcium Silicate Based Dental Cements

PubMed Central

Rajasekharan, Sivaprakash; Vercruysse, Chris; Martens, Luc; Verbeeck, Ronald

2018-01-01

Tricalcium silicate cements (TSC) are used in dental traumatology and endodontics for their bioactivity which is mostly attributed to formation of calcium hydroxide during TSC hydration and its subsequent release of calcium and hydroxide ions. The aim of this study was to determine the effect of volume (Vol), exposed surface area (ESA) and pH of surrounding medium on calcium ion release. Three commercially available hydraulic alkaline dental cements were mixed and condensed into cylindrical tubes of varying length and diameter (n = 6/group). For the effect of ESA and Vol, tubes were immersed in 10 mL of deionized water. To analyze the effect of environmental pH, the tubes were randomly immersed in 10 mL of buffer solutions with varying pH (10.4, 7.4 or 4.4). The solutions were collected and renewed at various time intervals. pH and/or calcium ion release was measured using a pH glass electrode and atomic absorption spectrophotometer respectively. The change of pH, short-term calcium ion release and rate at which calcium ion release reaches maximum were dependent on ESA (p < 0.05) while maximum calcium ion release was dependent on Vol of TSC (p < 0.05). Maximum calcium ion release was significantly higher in acidic solution followed by neutral and alkaline solution (p < 0.05). PMID:29342837

Evaluation of the radiopacity of calcium silicate cements containing different radiopacifiers.

PubMed

Camilleri, J; Gandolfi, M G

2010-01-01

To identify the suitable ratio of alternative radiopacifiers to impart the necessary radiopacity to calcium silicate cements (CSC) and assess the purity of the radiopacifying agents. Alternative radiopacifying materials for incorporation into CSC included barium sulphate, titanium oxide, zinc oxide, gold powder and silver/tin alloy. The chemical composition of the alternative radipacifying materials and bismuth oxide, which is used in mineral trioxide aggregate (MTA), was determined using energy dispersive X-ray analysis. In addition, using an aluminium step-wedge and densitometer, the radiopacity of each material was evaluated as recommended by international standards. The optical density was compared with the relevant thickness of aluminium (Al). A commercial MTA and CSC were used as controls. Statistical analysis comparing the radiodensity of the different cements to MTA was performed using anova with P = 0.05 and post hoc Tukey test. All percentage replacements of bismuth oxide, gold and silver-tin alloy powder, and the 25% and 30% replacements with barium sulphate and zinc oxide had radiopacities greater than 3 mm thickness of aluminium (Al) recommended by ISO 6876 (2002). The 25% replacement of cement with gold powder and 20% replacement of cement with silver/tin alloy powder exhibited radiopacity values of 8.04 mm Al and 7.52 mm Al, respectively, similar to MTA (P > 0.05). The cement replaced with 20% bismuth oxide showed a radiopacity of 6.83 mm Al, lower than MTA (P = 0.003). Silver/tin alloy and gold powder imparted the necessary radiopacity to a calcium silicate-based cement. Barium sulphate was also a suitable radiopacifier together with a lower concentration of silver/tin alloy and gold powder that achieved the radiodensity recommended by ISO 6876. Further research is required to investigate the broader properties of the calcium silicate-based cement with the different radiopacifiers.

Long term mechanical properties of alkali activated slag

NASA Astrophysics Data System (ADS)

Zhu, J.; Zheng, W. Z.; Xu, Z. Z.; Leng, Y. F.; Qin, C. Z.

2018-01-01

This article reports a study on the microstructural and long-term mechanical properties of the alkali activated slag up to 180 days, and cement paste is studied as the comparison. The mechanical properties including compressive strength, flexural strength, axis tensile strength and splitting tensile strength are analyzed. The results showed that the alkali activated slag had higher compressive and tensile strength, Slag is activated by potassium silicate (K2SiO3) and sodium hydroxide (NaOH) solutions for attaining silicate modulus of 1 using 12 potassium silicate and 5.35% sodium hydroxide. The volume dosage of water is 35% and 42%. The results indicate that alkali activated slag is a kind of rapid hardening and early strength cementitious material with excellent long-term mechanical properties. Single row of holes block compressive strength, single-hole block compressive strength and standard solid brick compressive strength basically meet engineering requirements. The microstructures of alkali activated slag are studied by X-ray diffraction (XRD). The hydration products of alkali-activated slag are assured as hydrated calcium silicate and hydrated calcium aluminate.

TiO2 induced structural modifications in Cs containing borosilicate glasses: Raman and infrared studies

NASA Astrophysics Data System (ADS)

Pandey, M.; Banerjee, D.; Sudarsan, V.; Kshirsagar, R. J.

2018-04-01

Effect of TiO2 addition in Cs containing Sodium-borosilicate glasses is studied using Raman and infrared spectroscopic techniques. As revealed from infrared and Raman studies, TiO2 does not form segregated phase, but instead enters into the borosilicate network. It is further observed that TiO2 addition results in modifications of the borate and silicate structural units by transforming into tetraborates and metasilicate structural units. These structural modifications are responsible for Cs immobilization, leach rate and chemical durability of these glasses.

Calcium-Magnesium-Alumino-Silicates (CMAS) Reaction Mechanisms and Resistance of Advanced Turbine Environmental Barrier Coatings for SiC/SiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Costa, Gustavo; Harder, Bryan J.; Wiesner, Valerie L.; Hurst, Janet B.; Puleo, Bernadette J.

2017-01-01

Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) systems will play a crucial role in future turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is an essential requirement to enable the applications of the 2700-3000 F EBC - CMC systems. This presentation primarily focuses on the reaction mechanisms of advanced NASA environmental barrier coating systems, when in contact with Calcium-Magnesium Alumino-Silicates (CMAS) at high temperatures. Advanced oxide-silicate defect cluster environmental barrier coatings are being designed for ultimate balanced controls of the EBC temperature capability and CMAS reactivity, thus improving the CMAS resistance. Further CMAS mitigation strategies are also discussed.

Effects of cement on redistribution of trace metals and dissolution of organics in sewage sludge and its inorganic waste-amended products.

PubMed

Lim, T T; Chu, J; Goi, M H

2006-01-01

The suitability of using cement-stabilized sludge products as artificial soils in earth works was evaluated. The sludge products investigated were cemented sludge, cement-treated clay-amended sludge (SS+MC), and cement-treated copper slag-amended sludge (SS+CS). The leachability of lead (Pb), zinc (Zn), copper (Cu), and chromium (Cr) were assessed using the sequential extraction technique, toxicity characteristic leaching procedure (TCLP), NEN 7341 availability test, and column leaching test. The results indicated that Zn leachability was reduced in all the cement-stabilized sludge products. In contrast, Cu was transferred from the organic fraction to the readily leachable phases in the cement-stabilized sludge products and therefore exhibited increased leachability. The increased Cu leachability could be attributed to dissolution of humic substances in the sludge as a result of elevated pH. Good correlation between dissolved organic carbon (DOC) and heavy metal leaching from the cement-stabilized sludge products was observed in the column leaching experiment. Even with a cement percentage as small as 12.5%, calcium silicate hydrate (C-S-H) was formed in the SS+MC and SS+CS products. Inclusion of the marine clay in the SS+MC products could reduce the leaching potentials of Zn, and this was the great advantage of the marine clay over the copper slag for sludge amendment.

Kondogogu gum-Zn+2-pectinate emulgel matrices reinforced with mesoporous silica for intragastric furbiprofen delivery.

PubMed

Bera, Hriday; Nadimpalli, Jhansirani; Kumar, Sanoj; Vengala, Pavani

2017-11-01

Flurbiprofen (FLU), a non-steroidal anti-inflammatory drug, exhibits limited clinical response due to its poor physicochemical properties. This study aimed at developing reliable drug carriers for intrgastric FLU delivery with a view to improve biopharmaceutical characteristics of drug and modulate its release in a controlled manner. In this context, FLU-loaded kondogogu gum (KG)-Zn +2 -low methoxyl (LM) pectinate emulgel matrices reinforced with calcium silicate (CS) were accomplished by ionotropic gelation technique employing zinc acetate as cross-linker and characterized for their in vitro performances. All the formulations demonstrated excellent drug encapsulation efficiency (DEE, 46-87%) and sustained drug release behavior (Q 7h , 70-91%). These quality attributes were remarkably influenced by polymer-blend (LM pectin:KG) ratios, low-density oil types and CS inclusion. The drug release profile of the FLU-loaded optimized matrices (F-7) was best fitted in Korsmeyer-Peppas model with Fickian diffusion driven mechanism. It also conferred excellent in vitro gastroretention capabilities. Moreover, the drug-excipient compatibility, alteration of crystallinity and thermal behavior of drug and surface morphology of matrices were evidenced with the results of FTIR, XRD, DSC and SEM analyses, respectively. Thus, the newly developed matrices are appropriate for sustained intragastric FLU delivery and simultaneous zinc supplementation for effective inflammation and arthritis management. Copyright © 2017 Elsevier B.V. All rights reserved.

Active Dendrites and Differential Distribution of Calcium Channels Enable Functional Compartmentalization of Golgi Cells.

PubMed

Rudolph, Stephanie; Hull, Court; Regehr, Wade G

2015-11-25

Interneurons are essential to controlling excitability, timing, and synaptic integration in neuronal networks. Golgi cells (GoCs) serve these roles at the input layer of the cerebellar cortex by releasing GABA to inhibit granule cells (grcs). GoCs are excited by mossy fibers (MFs) and grcs and provide feedforward and feedback inhibition to grcs. Here we investigate two important aspects of GoC physiology: the properties of GoC dendrites and the role of calcium signaling in regulating GoC spontaneous activity. Although GoC dendrites are extensive, previous studies concluded they are devoid of voltage-gated ion channels. Hence, the current view holds that somatic voltage signals decay passively within GoC dendrites, and grc synapses onto distal dendrites are not amplified and are therefore ineffective at firing GoCs because of strong passive attenuation. Using whole-cell recording and calcium imaging in rat slices, we find that dendritic voltage-gated sodium channels allow somatic action potentials to activate voltage-gated calcium channels (VGCCs) along the entire dendritic length, with R-type and T-type VGCCs preferentially located distally. We show that R- and T-type VGCCs located in the dendrites can boost distal synaptic inputs and promote burst firing. Active dendrites are thus critical to the regulation of GoC activity, and consequently, to the processing of input to the cerebellar cortex. In contrast, we find that N-type channels are preferentially located near the soma, and control the frequency and pattern of spontaneous firing through their close association with calcium-activated potassium (KCa) channels. Thus, VGCC types are differentially distributed and serve specialized functions within GoCs. Interneurons are essential to neural processing because they modulate excitability, timing, and synaptic integration within circuits. At the input layer of the cerebellar cortex, a single type of interneuron, the Golgi cell (GoC), carries these functions. The extent of inhibition depends on both spontaneous activity of GoCs and the excitatory synaptic input they receive. In this study, we find that different types of calcium channels are differentially distributed, with dendritic calcium channels being activated by somatic activity, boosting synaptic inputs and enabling bursting, and somatic calcium cannels promoting regular firing. We therefore challenge the current view that GoC dendrites are passive and identify the mechanisms that contribute to GoCs regulating the flow of sensory information in the cerebellar cortex. Copyright © 2015 the authors 0270-6474/15/3515492-13$15.00/0.

Trigeminal ganglion neuron subtype-specific alterations of CaV2.1 calcium current and excitability in a Cacna1a mouse model of migraine

PubMed Central

Fioretti, B; Catacuzzeno, L; Sforna, L; Gerke-Duncan, M B; van den Maagdenberg, A M J M; Franciolini, F; Connor, M; Pietrobon, D

2011-01-01

Abstract Familial hemiplegic migraine type-1 (FHM1), a monogenic subtype of migraine with aura, is caused by gain-of-function mutations in CaV2.1 (P/Q-type) calcium channels. The consequences of FHM1 mutations on the trigeminovascular pathway that generates migraine headache remain largely unexplored. Here we studied the calcium currents and excitability properties of two subpopulations of small-diameter trigeminal ganglion (TG) neurons from adult wild-type (WT) and R192Q FHM1 knockin (KI) mice: capsaicin-sensitive neurons without T-type calcium currents (CS) and capsaicin-insensitive neurons characterized by the expression of T-type calcium currents (CI-T). Small TG neurons retrogradely labelled from the dura are mostly CS neurons, while CI-T neurons were not present in the labelled population. CS and CI-T neurons express CaV2.1 channels with different activation properties, and the CaV2.1 channels are differently affected by the FHM1 mutation in the two TG neuron subtypes. In CI-T neurons from FHM1 KI mice there was a larger P/Q-type current density following mild depolarizations, a larger action potential (AP)-evoked calcium current and a longer AP duration when compared to CI-T neurons from WT mice. In striking contrast, the P/Q-type current density, voltage dependence and kinetics were not altered by the FHM1 mutation in CS neurons. The excitability properties of mutant CS neurons were also unaltered. Congruently, the FHM1 mutation did not alter depolarization-evoked CGRP release from the dura mater, while CGRP release from the trigeminal ganglion was larger in KI compared to WT mice. Our findings suggest that the facilitation of peripheral mechanisms of CGRP action, such as dural vasodilatation and nociceptor sensitization at the meninges, does not contribute to the generation of headache in FHM1. PMID:22005682

Evaluation of the phase properties of hydrating cement composite using simulated nanoindentation technique

NASA Astrophysics Data System (ADS)

Gautham, S.; Sindu, B. S.; Sasmal, Saptarshi

2017-10-01

Properties and distribution of the products formed during the hydration of cementitious composite at the microlevel are investigated using a nanoindentation technique. First, numerical nanoindentation using nonlinear contact mechanics is carried out on three different phase compositions of cement paste, viz. mono-phase Tri-calcium Silicate (C3S), Di-calcium Silicate (C2S) and Calcium-Silicate-Hydrate (CSH) individually), bi-phase (C3S-CSH, C2S-CSH) and multi-phase (more than 10 individual phases including water pores). To reflect the multi-phase characteristics of hydrating cement composite, a discretized multi-phase microstructural model of cement composite during the progression of hydration is developed. Further, a grid indentation technique for simulated nanoindentation is established, and employed to evaluate the mechanical characteristics of the hydrated multi-phase cement paste. The properties obtained from the numerical studies are compared with those obtained from experimental grid nanoindentation. The influence of composition and distribution of individual phase properties on the properties obtained from indentation are closely investigated. The study paves the way to establishing the procedure for simulated grid nanoindentation to evaluate the mechanical properties of heterogeneous composites, and facilitates the design of experimental nanoindentation.

A Multidisciplinary Evaluation of the Effectiveness of Cyclosporine A in Dystrophic Mdx Mice

PubMed Central

De Luca, Annamaria; Nico, Beatrice; Liantonio, Antonella; Paola Didonna, Maria; Fraysse, Bodvael; Pierno, Sabata; Burdi, Rosa; Mangieri, Domenica; Rolland, Jean-François; Camerino, Claudia; Zallone, Alberta; Confalonieri, Paolo; Andreetta, Francesca; Arnoldi, Elisa; Courdier-Fruh, Isabelle; Magyar, Josef P.; Frigeri, Antonio; Pisoni, Michela; Svelto, Maria; Conte-Camerino, Diana

2005-01-01

Chronic inflammation is a secondary reaction of Duchenne muscular dystrophy and may contribute to disease progression. To examine whether immunosuppressant therapies could benefit dystrophic patients, we analyzed the effects of cyclosporine A (CsA) on a dystrophic mouse model. Mdx mice were treated with 10 mg/kg of CsA for 4 to 8 weeks throughout a period of exercise on treadmill, a protocol that worsens the dystrophic condition. The CsA treatment fully prevented the 60% drop of forelimb strength induced by exercise. A significant amelioration (P < 0.05) was observed in histological profile of CsA-treated gastrocnemius muscle with reductions of nonmuscle area (20%), centronucleated fibers (12%), and degenerating area (50%) compared to untreated exercised mdx mice. Consequently, the percentage of normal fibers increased from 26 to 35% in CsA-treated mice. Decreases in creatine kinase and markers of fibrosis were also observed. By electrophysiological recordings ex vivo, we found that CsA counteracted the decrease in chloride conductance (gCl), a functional index of degeneration in diaphragm and extensor digitorum longus muscle fibers. However, electrophysiology and fura-2 calcium imaging did not show any amelioration of calcium homeostasis in extensor digitorum longus muscle fibers. No significant effect was observed on utrophin levels in diaphragm muscle. Our data show that the CsA treatment significantly normalized many functional, histological, and biochemical endpoints by acting on events that are independent or downstream of calcium homeostasis. The beneficial effect of CsA may involve different targets, reinforcing the usefulness of immunosuppressant drugs in muscular dystrophy. PMID:15681831

SIMULTANEOUS CONTROL OF HG(0), SO2, AND NOX BY NOVEL OXIDIZED CALCIUM-BASED SORBENTS

EPA Science Inventory

The paper gives results of an investigation of two classes of calcium (Ca)-based sorbents (hydrated limes and silicate compounds). {NOTE: Efforts to develop multipollutant control strategies have demonstrated that adding certain oxidants to different classes of Ca-based sorbents ...

SIMULTANEOUS CONTROL OF HGO, SO2, AND NOX BY NOVEL OXIDIZED CALCIUM-BASED SORBENTS

EPA Science Inventory

The paper gives results of an investigation of two classes of calcium (Ca)-based sorbents (hydrated limes and silicate compounds). (NOTE: Efforts to develop multipollutant control strategies have demonstrated that adding certain oxidants to different classes of Ca-based sorbents...

Aqueous solubility diagrams for cementitious waste stabilization systems. 3. Mechanism of zinc immobilizaton by calcium silicate hydrate.

PubMed

Tommaseo, C E; Kersten, M

2002-07-01

Zinc oxide was added during hydration of alite (C3S) as an analogue for solidification/stabilization by cement of metal-bearing hazardous waste. Curing of samples was stopped at various intervals between 8 h and 100 d, and the reaction products were analyzed by both X-ray diffraction (XRD) and X-ray absorption spectroscopy (EXAFS at Zn, Ca, and Si K-edges). Calcium zincate hydrate (CaZn2(OH)6 x 2H2O) initially formed together with calcium silicate hydrate (CSH) vanishes from X-ray diffractograms after 14 d, and no other crystalline Zn-bearing phase could be detected thereafter. EXAFS Zn K-edge data analysis reveals that Zn(O,OH)4 tetrahedra continue to determine the first shell coordination. However, a new Zn-Si bond appears in the second coordination shell as indicated by both Zn K-edge and Si K-edge EXAFS. Together with the Ca-Zn and Ca-Ca shells derived from the Ca K-edge EXAFS spectra, a structural model for the site occupation of Zn in CSH is proposed, whereby the Zn(O,OH)4 tetrahedra are bound in layer rather than interlayer positions substituting for the silicate bridging tetrahedra and/or at terminal silicate chain sites. This structural model enables ultimately the formulation of a thermodyamic Lippmann model to predict the aqueous solubility of Zn in solid solution with a CSH phase of a Ca/Si ratio fixed to unity.

The effect of divalent salt in chondroitin sulfate solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aranghel, D., E-mail: daranghe@nipne.ro; Extreme Light Intrastructure Nuclear Physics; Badita, C. R.

Chondroitin-4 sulfate (CS4) is the main glycosaminoglycan extracted from bovine trachea. CS4 play an important role in osteoarthritis treatment, anticoagulant activity, reduces the degradation of cartilage matrix components, reduces necrosis and apoptosis of chondrocytes and reduces the activity of collagenase. Chondroitin sulfate is also responsible for proteoglycans degradation. Chondroitin sulfate can bind calcium ions with different affinities, depending on their sulfation position. The purpose of this study was to determine the structural properties and the influence of Ca{sup 2+} cations. We carried out measurements on CS4 solutions and mixtures of liquid CS4 with Ca{sup 2+} by Small-Angle Neutron Scattering (SANS).more » CS4 have a mass fractal behavior and the addition of a salt (CaCl{sub 2}) in CS4 solutions generates the appearance of a correlation peak due to local ordering between adjacent chains with inter-chain distances between 483 Å and 233 Å for a calcium concentration of 0.01% w/w.« less

The effect of divalent salt in chondroitin sulfate solutions

NASA Astrophysics Data System (ADS)

Aranghel, D.; Badita, C. R.; Radulescu, A.; Moldovan, L.; Craciunescu, O.; Balasoiu, M.

2016-03-01

Chondroitin-4 sulfate (CS4) is the main glycosaminoglycan extracted from bovine trachea. CS4 play an important role in osteoarthritis treatment, anticoagulant activity, reduces the degradation of cartilage matrix components, reduces necrosis and apoptosis of chondrocytes and reduces the activity of collagenase. Chondroitin sulfate is also responsible for proteoglycans degradation. Chondroitin sulfate can bind calcium ions with different affinities, depending on their sulfation position. The purpose of this study was to determine the structural properties and the influence of Ca2+ cations. We carried out measurements on CS4 solutions and mixtures of liquid CS4 with Ca2+ by Small-Angle Neutron Scattering (SANS). CS4 have a mass fractal behavior and the addition of a salt (CaCl2) in CS4 solutions generates the appearance of a correlation peak due to local ordering between adjacent chains with inter-chain distances between 483 Å and 233 Å for a calcium concentration of 0.01% w/w.

Effects of calcium hydroxide addition on the physical and chemical properties of a calcium silicate-based sealer.

PubMed

Kuga, Milton Carlos; Duarte, Marco Antonio Hungaro; Sant'anna-Júnior, Arnaldo; Keine, Kátia Cristina; Faria, Gisele; Dantas, Andrea Abi Rached; Guiotti, Flávia Angélica

2014-06-01

Recently, various calcium silicate-based sealers have been introduced for use in root canal filling. The MTA Fillapex is one of these sealers, but some of its physicochemical properties are not in accordance with the ISO requirements. The aim of this study was to evaluate the flowability, pH level and calcium release of pure MTA Fillapex (MTAF) or containing 5% (MTAF5) or 10% (MTAF10) calcium hydroxide (CH), in weight, in comparison with AH Plus sealer. The flowability test was performed according to the ISO 6876:2001 requirements. For the pH level and calcium ion release analyses, the sealers were placed individually (n=10) in plastic tubes and immersed in deionized water. After 24 hours, 7 and 14 days, the water in which each specimen had been immersed was evaluated to determine the pH level changes and calcium released. Flowability, pH level and calcium release data were analyzed statistically by the ANOVA test (α=5%). In relation to flowability: MTAF>AH Plus>MTAF5>MTAF10. In relation to the pH level, for 24 h: MTAF5=MTAF10=MTAF>AH Plus; for 7 and 14 days: MTAF5=MTAF10>MTAF>AH Plus. For the calcium release, for all periods: MTAF>MTAF5=MTAF10>AH Plus. The addition of 5% CH to the MTA Fillapex (in weight) is an alternative to reduce the high flowability presented by the sealer, without interfering in its alkalization potential.

Physicochemical properties of calcium silicate-based formulations MTA Repair HP and MTA Vitalcem

PubMed Central

Guimarães, Bruno Martini; Prati, Carlo; Duarte, Marco Antonio Hungaro; Bramante, Clovis Monteiro; Gandolfi, Maria Giovanna

2018-01-01

Abstract Objective This study aimed to analyze the following physicochemical properties: radiopacity, final setting time, calcium release, pH change, solubility, water sorption, porosity, surface morphology, and apatite-forming ability of two calcium silicate-based materials. Material and methods We tested MTA Repair HP and MTA Vitalcem in comparison with conventional MTA, analyzing radiopacity and final setting time. Water absorption, interconnected pores and apparent porosity were measured after 24-h immersion in deionized water at 37°C. Calcium and pH were tested up to 28 d in deionized water. We analyzed data using two-way ANOVA with Student-Newman-Keuls tests (p<0.05). We performed morphological and chemical analyses of the material surfaces using ESEM/EDX after 28 d in HBSS. Results MTA Repair HP showed similar radiopacity to that of conventional MTA. All materials showed a marked alkalinizing activity within 3 h, which continued for 28 d. MTA Repair HP showed the highest calcium release at 28 d (p<0.05). MTA Vitalcem showed statistically higher water sorption and solubility values (p<0.05). All materials showed the ability to nucleate calcium phosphate on their surface after 28 d in HBSS. Conclusions MTA Repair HP and MTA Vitalcem had extended alkalinizing activity and calcium release that favored calcium phosphate nucleation. The presence of the plasticizer in MTA HP might increase its solubility and porosity. The radiopacifier calcium tungstate can be used to replace bismuth oxide. PMID:29641748

Examination of Calcium Silicate Cements with Low-Viscosity Methyl Cellulose or Hydroxypropyl Cellulose Additive.

PubMed

Baba, Toshiaki; Tsujimoto, Yasuhisa

2016-01-01

The purpose of this study was to improve the operability of calcium silicate cements (CSCs) such as mineral trioxide aggregate (MTA) cement. The flow, working time, and setting time of CSCs with different compositions containing low-viscosity methyl cellulose (MC) or hydroxypropyl cellulose (HPC) additive were examined according to ISO 6876-2012; calcium ion release analysis was also conducted. MTA and low-heat Portland cement (LPC) including 20% fine particle zirconium oxide (ZO group), LPC including zirconium oxide and 2 wt% low-viscosity MC (MC group), and HPC (HPC group) were tested. MC and HPC groups exhibited significantly higher flow values and setting times than other groups ( p < 0.05). Additionally, flow values of these groups were higher than the ISO 6876-2012 reference values; furthermore, working times were over 10 min. Calcium ion release was retarded with ZO, MC, and HPC groups compared with MTA. The concentration of calcium ions was decreased by the addition of the MC or HPC group compared with the ZO group. When low-viscosity MC or HPC was added, the composition of CSCs changed, thus fulfilling the requirements for use as root canal sealer. Calcium ion release by CSCs was affected by changing the CSC composition via the addition of MC or HPC.

Examination of Calcium Silicate Cements with Low-Viscosity Methyl Cellulose or Hydroxypropyl Cellulose Additive

PubMed Central

Tsujimoto, Yasuhisa

2016-01-01

The purpose of this study was to improve the operability of calcium silicate cements (CSCs) such as mineral trioxide aggregate (MTA) cement. The flow, working time, and setting time of CSCs with different compositions containing low-viscosity methyl cellulose (MC) or hydroxypropyl cellulose (HPC) additive were examined according to ISO 6876-2012; calcium ion release analysis was also conducted. MTA and low-heat Portland cement (LPC) including 20% fine particle zirconium oxide (ZO group), LPC including zirconium oxide and 2 wt% low-viscosity MC (MC group), and HPC (HPC group) were tested. MC and HPC groups exhibited significantly higher flow values and setting times than other groups (p < 0.05). Additionally, flow values of these groups were higher than the ISO 6876-2012 reference values; furthermore, working times were over 10 min. Calcium ion release was retarded with ZO, MC, and HPC groups compared with MTA. The concentration of calcium ions was decreased by the addition of the MC or HPC group compared with the ZO group. When low-viscosity MC or HPC was added, the composition of CSCs changed, thus fulfilling the requirements for use as root canal sealer. Calcium ion release by CSCs was affected by changing the CSC composition via the addition of MC or HPC. PMID:27981048

Electron Microscopic Analysis of Surface Inorganic Substances on Oral and Combustible Tobacco Products

PubMed Central

Halstead, Mary M.; Watson, Clifford H.; Pappas, R. Steven

2015-01-01

Though quantitative trace toxic metals analyses have been performed on tobacco products, little has been published on inorganic particulate constituents on and inside the products. We analyzed these constituents using scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS). The nature of SEM-EDS instrumentation makes it an ideal choice for inorganic particulate analyses and yields relevant information to potential exposures during consumption of oral tobacco products, and possibly as a consequence of smoking. Aluminum silicates, silica, and calcium compounds were common inorganic particulate constituents of tobacco products. Aluminum silicates and silica from soil were found on external leaf surfaces. Phytolithic silica, found in the lumen of the plant leaf, is of biogenic origin. Calcium oxalate was also apparently of biogenic origin. Small mineral deposits on tobacco could have health implications. Minerals found on the surfaces of smokeless tobacco products could possibly abrade the oral mucosa and contribute to the oral inflammatory responses observed with smokeless tobacco product use. If micron and sub-micron size calcium particles on cigarette filler were transported in mainstream smoke, they could potentially induce a pulmonary irritant inflammation when inhaled. The transport of aluminum silicate and silica in smoke could potentially also contribute to chronic inflammatory disease. PMID:26286581

Cluster formation of network-modifier cations in cesium silicate glasses

NASA Astrophysics Data System (ADS)

Jardón-Álvarez, Daniel; Sanders, Kevin J.; Phyo, Pyae; Baltisberger, Jay H.; Grandinetti, Philip J.

2018-03-01

Natural abundance 29Si two-dimensional magic-angle flipping (2D MAF) NMR spectra were measured in a series of ten cesium silicate glass compositions xCs2O.(1 - x)SiO2, where x is 0.067, 0.113, 0.175, 0.179, 0.218, 0.234, 0.263, 0.298, 0.31, and 0.36. The Q3 shielding anisotropy decreases with increasing Cs content—interpreted as an increase in the non-bridging oxygen (NBO) bond length from increasing Cs coordination (clustering) around the NBO. The 29Si 2D MAF spectra for four glass compositions x = 0.218, 0.234, 0.263, 0.298 exhibit a second co-existing and distinctly smaller shielding anisotropy corresponding to a significantly longer Si-NBO length arising from a higher degree of Cs clustering around the NBO. This second Q3 site appears at a Cs2O mole fraction close to the critical mole fraction of x = 0.24 associated with the percolation threshold of non-bridging oxygen in random close packing of oxygen, thus suggesting that the longer Si-NBO length is associated with an infinite size spanning cluster while the sites with larger anisotropies are associated with shorter Si-NBO lengths and belong to finite size clusters. The equilibrium constant of the Q3 disproportionation reaction was determined as k3 = 0.005, indicating a Qn anionic species distribution close to a binary model as expected for a low field strength modifier such as cesium. It is also found that evolution of the isotropic Q4 and line shapes with increasing Cs content are consistent with a random connectivity model between Qn of differing number of bridging oxygen, n.

Loss of radioactivity in radiocesium-bearing microparticles emitted from the Fukushima Dai-ichi nuclear power plant by heating.

PubMed

Okumura, Taiga; Yamaguchi, Noriko; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro

2018-06-26

Radiocesium-bearing microparticles (CsPs) substantially made of silicate glass are a novel form of radiocesium emitted from the broken containment vessel of Fukushima Dai-ichi nuclear power plant. CsPs have a potential risk of internal radiation exposure caused by inhalation. Radiation-contaminated waste including CsPs is being burned in incinerators; therefore, this study has investigated the responses of CsPs to heating in air. The radioactivity of CsPs gradually decreased from 600 °C and was almost lost when the temperature reached 1000 °C. The size and spherical morphology of CsPs were almost unchanged after heating, but cesium including radiocesium, potassium and chlorine were lost, probably diffused away from the CsPs. Iron, zinc and tin originally dissolved in the glass matrix were crystallized to oxide nanoparticles inside the CsPs. When the CsPs were heated together with weathered granitic soil that is common in Fukushima, the radiocesium released from CsPs was sorbed by the surrounding soil. From these results, it is expected that the radioactivity of CsPs will be lost when radiation-contaminated waste including CsPs is burned in incinerators.

Push-out bond strength of three calcium silicate cements to root canal dentine after two different irrigation regimes.

PubMed

Çelik, Davut; Er, Kürşat; Serper, Ahmet; Taşdemir, Tamer; Ceyhanlı, Kadir Tolga

2014-05-01

The aim of this study was to compare the push-out bond strength of three calcium silicate cements to dentine after two different irrigation regimes. One hundred eighty 2-mm-thick root sections were prepared. The sections were divided into three main groups (n = 60). In group A, the sections were immersed in 1 % NaOCl for 3 min. In group B, the sections were immersed in 17 % EDTA for 3 min followed by 1 % NaOCl for the same period of time. In group C (control group), no irrigation was applied to the sections. The samples from each group were divided into four subgroups (n = 15). In subgroups A1, B1 and C1, DiaRoot BioAggregate; in subgroups A2, B2 and C2, MTA-Angelus and in subgroups A3, B3 and C3, MM-MTA were mixed with hand-mixing. In subgroups A4, B4 and C4, MM-MTA was mixed with auto-mixing. The mixed cements were then placed into cavities with a carrier. The samples were submitted to the push-out test and were loaded. All the data were analysed with one-way analysis of variance and the Tukey HSD multiple comparisons (p < 0.05). There were no statistically significant differences between the irrigation regimes regardless of the used materials. The resistance to displacement in subgroup B4 was significantly greater than that presented by subgroups A3, B3 and C3 (p < 0.05) while not different than all other groups. Irrigation regimes had not affected the push-out bond strength of the calcium silicate cements. Also, strength of auto-mixed MM-MTA was similar to the other cements. The novel calcium silicate cements would be a potentially useful material in endodontic procedures with favourable properties.

Biocompatibility and bioactivity of calcium silicate-based endodontic sealers in human dental pulp cells.

PubMed

Mestieri, Leticia Boldrin; Gomes-Cornélio, Ana Lívia; Rodrigues, Elisandra Márcia; Salles, Loise Pedrosa; Bosso-Martelo, Roberta; Guerreiro-Tanomaru, Juliane Maria; Tanomaru-Filho, Mário

2015-10-01

Mineral Trioxide Aggregate (MTA) is a calcium silicate-based material. New sealers have been developed based on calcium silicate as MTA Fillapex and MTA Plus. The aim of this study was to evaluate biocompatibility and bioactivity of these two calcium silicate-based sealers in culture of human dental pulp cells (hDPCs). The cells were isolated from third molars extracted from a 16-year-old patient. Pulp tissue was sectioned into fragments with approximately 1 mm3 and kept in supplemented medium to obtain hDPCs adherent cultures. Cell characterization assays were performed to prove the osteogenic potential. The evaluated materials were: MTA Plus (MTAP); MTA Fillapex (MTAF) and FillCanal (FC). Biocompatibility was evaluated with MTT and Neutral Red (NR) assays, after hDPCs exposure for 24 h to different dilutions of each sealer extract (1:2, 1:3 and 1:4). Unexposed cells were the positive control (CT). Bioactivity was assessed by alkaline phosphatase (ALP) enzymatic assay in cells exposed for one and three days to sealer extracts (1:4 dilution). All data were analyzed by ANOVA and Tukey post-test (p≤0.05%). MTT and NR results showed suitable cell viability rates for MTAP at all dilutions (90-135%). Cells exposed to MTAF and FC (1:2 and 1:4 dilutions) showed significant low viability rate when compared to CT in MTT. The NR results demonstrated cell viability for all materials tested. In MTAP group, the cells ALP activity was similar to CT in one and three days of exposure to the material. MTAF and FC groups demonstrated a decrease in ALP activity when compared to CT at both periods of cell exposure. The hDPCs were suitable for the evaluation of new endodontic materialsin vitro. MTAP may be considered a promising material for endodontic treatments.

Effects of calcium hydroxide addition on the physical and chemical properties of a calcium silicate-based sealer

PubMed Central

KUGA, Milton Carlos; DUARTE, Marco Antonio Hungaro; SANT'ANNA-JÚNIOR, Arnaldo; KEINE, Kátia Cristina; FARIA, Gisele; DANTAS, Andrea Abi Rached; GUIOTTI, Flávia Angélica

2014-01-01

Recently, various calcium silicate-based sealers have been introduced for use in root canal filling. The MTA Fillapex is one of these sealers, but some of its physicochemical properties are not in accordance with the ISO requirements. Objective The aim of this study was to evaluate the flowability, pH level and calcium release of pure MTA Fillapex (MTAF) or containing 5% (MTAF5) or 10% (MTAF10) calcium hydroxide (CH), in weight, in comparison with AH Plus sealer. Material and Methods The flowability test was performed according to the ISO 6876:2001 requirements. For the pH level and calcium ion release analyses, the sealers were placed individually (n=10) in plastic tubes and immersed in deionized water. After 24 hours, 7 and 14 days, the water in which each specimen had been immersed was evaluated to determine the pH level changes and calcium released. Flowability, pH level and calcium release data were analyzed statistically by the ANOVA test (α=5%). Results In relation to flowability: MTAF>AH Plus>MTAF5>MTAF10. In relation to the pH level, for 24 h: MTAF5=MTAF10=MTAF>AH Plus; for 7 and 14 days: MTAF5=MTAF10>MTAF>AH Plus. For the calcium release, for all periods: MTAF>MTAF5=MTAF10>AH Plus. Conclusions The addition of 5% CH to the MTA Fillapex (in weight) is an alternative to reduce the high flowability presented by the sealer, without interfering in its alkalization potential. PMID:25025558

Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.

PubMed

Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

2012-12-18

The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 °C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 °C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 °C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses.

Involvement of endoplasmic reticulum in hepatitis B virus replication.

PubMed

Xia, Weiliang; Shen, Yan; Xie, Haiyang; Zheng, Shusen

2006-11-01

The mitochondrial calcium and downstream proline-rich tyrosine kinase-2 (PyK2) signaling pathway are critical to hepatitis B virus (HBV) replication, and the endoplasmic reticulum (ER) plays an important role in intracellular calcium regulation. To investigate the role of ER in HBV replication, the HBV genome transfected HepG2.2.15 cells were treated by cyclosporine A (CsA), cyclopiazonic acid (CPA), ryanodine and U73122, which are all specific blockers of calcium channels located in either ER or mitochondria. The HBV replication level was evaluated by two methods: slot blot hybridization analysis of intracellular HBV DNA and real-time polymerase chain reaction (PCR) analysis of secreted HBV DNA in supernatant; the activation of PyK2 kinase was detected by Western blot analysis. Results indicated that the HBV replication was inhibited when mitochondrial permeability transition pore, ER Ca2+ -ATPase and ER inositol 1,4,5-trisphosphate receptor (IP3R) were blocked by CsA, CPA and U73122, respectively; but not inhibited when ER ryanodine receptor was blocked by ryanodine. The PyK2 phosphorylation level declined after treatment of 2 microg/ml CsA, 5 microM CPA and 25 microM U73122, but not changed apparently after 50 microM ryanodine treatment. Compared with monotreatment, a more powerful inhibitory effect was achieved when the CsA, CPA and U73122 were combined used in twosome or triple manner, while the HBV replication level did not change apparently when ryanodine combined with CsA, CPA or U73122. In conclusion, besides the mitochondria, the ER also participates in the HBV replication through calcium-PyK2 signaling pathway; the calcium channels of ER Ca2+ -ATPase and ER IP3R are responsible for this role; during this complicated process, an interaction between ER and mitochondria maybe involved.

Proton tunneling in low dimensional cesium silicate LDS-1

NASA Astrophysics Data System (ADS)

Matsui, Hiroshi; Iwamoto, Kei; Mochizuki, Dai; Osada, Shimon; Asakura, Yusuke; Kuroda, Kazuyuki

2015-07-01

In low dimensional cesium silicate LDS-1 (monoclinic phase of CsHSi2O5), anomalous infrared absorption bands observed at 93, 155, 1210, and 1220 cm-1 are assigned to the vibrational mode of protons, which contribute to the strong hydrogen bonding between terminal oxygen atoms of silicate chain (O-O distance = 2.45 Å). The integrated absorbance (oscillator strength) for those modes is drastically enhanced at low temperatures. The analysis of integrated absorbance employing two different anharmonic double-minimum potentials makes clear that proton tunneling through the potential barrier yields an energy splitting of the ground state. The absorption bands at 93 and 155 cm-1, which correspond to the different vibrational modes of protons, are attributed to the optical transition between the splitting levels (excitation from the ground state (n = 0) to the first excited state (n = 1)). Moreover, the absorption bands at 1210 and 1220 cm-1 are identified as the optical transition from the ground state (n = 0) to the third excited state (n = 3). Weak Coulomb interactions in between the adjacent protons generate two types of vibrational modes: symmetric mode (93 and 1210 cm-1) and asymmetric mode (155 and 1220 cm-1). The broad absorption at 100-600 cm-1 reveals an emergence of collective mode due to the vibration of silicate chain coupled not only with the local oscillation of Cs+ but also with the proton oscillation relevant to the second excited state (n = 2).

New silicate-germanate Cs2Pb2[(Si0.6Ge0.4)2O7] from the series A2Pb2[B2O7], A = K, Cs, B = Si, Ge with the umbrella-like [PbO3]4- group

NASA Astrophysics Data System (ADS)

Belokoneva, Elena L.; Morozov, Ivan A.; Volkov, Anatoly S.; Dimitrova, Olga V.; Stefanovich, Sergey Yu.

2018-04-01

New silicate-germanate Cs2Pb2[(Si0.6Ge0.4)2O7] was synthesized in multi-components hydrothermal solution with 20 w.% concentration of Cs2CO3 mineralizer, pH = 10. Novel mixed compound belongs to the structure type A2Pb2[B2O7] previously indicated for powders with A = K, B=Si or Ge. Singe crystal structure determination of Cs2Pb2[(Si0.6Ge0.4)2O7] revealed the need for the correction of the space group of the earlier suggested structural model from P-3 to P-3m1, as well as for the splitting of the Pb-atom position. Umbrella-like groups [PbO3]4- are located between [(Si,Ge)O4]4- tetrahedra in mica-like honeycomb layers and play the role of tetrahedra with the Pb-lone-pair as the forth apex. Crystal chemical comparison revealed similarities and differences with the classical structure type of α-celsian Ba[Al2Si2O8] with the tetrahedral double layer. Recently investigated nonlinear optical acentric borates Pb2(BO3)(NO3) and Pb2(BO3)Cl are both related to this structural type, possessing umbrella-like groups [PbO3]4- and honeycomb layers [Pb2(BO3)]+ with the BO3-triangles on the tetrahedral positions.

Water quality characterization in some birimian aquifers of the Birim Basin, Ghana

USGS Publications Warehouse

Bruce, B.-Y.; Yidana, S.M.; Anku, Y.; Akabzaa, T.; Asiedu, D.

2009-01-01

The objective of this study was to determine the main controls on the hydrochemistry of groundwater in the study area. Mass balance modeling was used simultaneously with multivariate R-mode hierarchical cluster analysis to determine the significant sources of variation in the hydrochemistry. Two water types have been revealed in this area: (1) waters influenced more significantly by the weathering of silicate minerals from the underlying geology, and are rich in silica, sodium, calcium, bicarbonate, and magnesium ions, and (2) waters that have been influenced by the effects of fertilizers and other anthropogenic activities in the area. Mineral speciation and silicate mineral stability diagrams generated from the data suggest that montmorillonite, probably derived from the incongruent dissolution of feldspars and micas, is the most stable silicate phase in the groundwater. The apparent incongruent weathering of silicate minerals in the groundwater system has led to the enrichment of sodium, calcium, magnesium and bicarbonate ions as well as silica, leading to the supersaturation of calcite, aragonite, dolomite and quartz. Stability in the montmorillonite field suggests restricted flow conditions whereby groundwater residence time is relatively high, leading to greater contact of groundwater with the rock to enhance weathering. Cation exchange processes have also been determined to play minor roles in the hydrochemistry.

Spectroscopic study of biologically active glasses

NASA Astrophysics Data System (ADS)

Szumera, M.; Wacławska, I.; Mozgawa, W.; Sitarz, M.

2005-06-01

It is known that the chemical activity phenomenon is characteristic for some inorganic glasses and they are able to participate in biological processes of living organisms (plants, animals and human bodies). An example here is the selective removal of silicate-phosphate glass components under the influence of biological solutions, which has been applied in designing glasses acting as ecological fertilizers of controlled release rate of the nutrients for plants. The structure of model silicate-phosphate glasses containing the different amounts of the glass network formers, i.e. Ca 2+ and Mg 2+, as a binding components were studied. These elements besides other are indispensable of the normal growth of plants. In order to establish the function and position occupied by the particular components in the glass structure, the glasses were examined by FTIR spectroscopy (with spectra decomposition) and XRD methods. It has been found that the increasing amount of MgO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes systematically from a structure of the cristobalite type to a structure corresponding to forsterite type. Whilst the increasing content of CaO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes from a structure typical for cristobalite through one similar to the structure of calcium orthophosphate, to a structure corresponding to calcium silicates. The changing character of domains structure is the reason of different chemical activity of glasses.

Cytotoxicities and genotoxicities of cements based on calcium silicate and of dental formocresol.

PubMed

Ko, Hyunjung; Jeong, Youngdan; Kim, Miri

2017-03-01

Increasing interest is being paid to the toxicities of dental materials. The purpose of this study was to determine the cytotoxicities and genotoxicities of endodontic compounds to Chinese hamster ovary (CHO-K1) reproductive cells. Cultured CHO-K1 cells were treated with dental formocresol, two types of calcium hydroxide paste, and two types of mineral trioxide aggregate cement for 24h. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay was performed on each culture, and the micronucleus frequency was determined by performing a micronucleus assay. Alkaline comet assay and γ-H2AX immunofluorescence assay were used to detect DNA damage. Out of the five materials tested, only dental formocresol significantly increased DNA damage. The mineral trioxide aggregate cements based on calcium silicate were not found to be potentially genotoxic. The data suggest that dental formocresol should not be recommended for use in vital pulp therapy on young teeth. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of Calcium Sulfate Combined with Platelet-rich Plasma on Restoration of Long Bone Defect in Rabbits

PubMed Central

Chen, Hua; Ji, Xin-Ran; Zhang, Qun; Tian, Xue-Zhong; Zhang, Bo-Xun; Tang, Pei-Fu

2016-01-01

Background: The treatment for long bone defects has been a hot topic in the field of regenerative medicine. This study aimed to evaluate the therapeutic effects of calcium sulfate (CS) combined with platelet-rich plasma (PRP) on long bone defect restoration. Methods: A radial bone defect model was constructed through an osteotomy using New Zealand rabbits. The rabbits were randomly divided into four groups (n = 10 in each group): a CS combined with PRP (CS-PRP) group, a CS group, a PRP group, and a positive (recombinant human bone morphogenetic protein-2) control group. PRP was prepared from autologous blood using a two-step centrifugation process. CS-PRP was obtained by mixing hemihydrate CS with PRP. Radiographs and histologic micrographs were generated. The percentage of bone regenerated bone area in each rabbit was calculated at 10 weeks. One-way analysis of variance was performed in this study. Results: The radiographs and histologic micrographs showed bone restoration in the CS-PRP and positive control groups, while nonunion was observed in the CS and PRP groups. The percentages of bone regenerated bone area in the CS-PRP (84.60 ± 2.87%) and positive control (52.21 ± 4.53%) groups were significantly greater than those in the CS group (12.34 ± 2.17%) and PRP group (16.52 ± 4.22%) (P < 0.001). In addition, the bone strength of CS-PRP group (43.10 ± 4.10%) was significantly greater than that of the CS group (20.10 ± 3.70%) or PRP group (25.10 ± 2.10%) (P < 0.001). Conclusion: CS-PRP functions as an effective treatment for long bone defects through stimulating bone regeneration and enhancing new bone strength. PMID:26904990

High chloride content calcium silicate glasses.

PubMed

Chen, Xiaojing; Karpukhina, Natalia; Brauer, Delia S; Hill, Robert G

2017-03-08

Chloride is known to volatilize from silicate glass melts and until now, only a limited number of studies on oxychloride silicate glasses have been reported. In this paper we have synthesized silicate glasses that retain large amounts of CaCl 2 . The CaCl 2 has been added to the calcium metasilicate composition (CaO·SiO 2 ). Glasses were produced via a melt quench route and an average of 70% of the chloride was retained after melting. Up to 31.6 mol% CaCl 2 has been successfully incorporated into these silicate glasses without the occurrence of crystallization. 29 Si MAS-NMR spectra showed the silicon being present mainly as a Q 2 silicate species. This suggests that chloride formed Cl-Ca(n) species, rather than Si-Cl bonds. Upon increasing the CaCl 2 content, the T g reduced markedly from 782 °C to 370 °C. Glass density and glass crystallization temperature decreased linearly with an increase in the CaCl 2 content. However, both linear regressions revealed a breakpoint at a CaCl 2 content just below 20 mol%. This might be attributed to a significant change in the structure and is also correlated with the nature of the crystallizing phases formed upon heat treatment. The glasses with less than 19.2 mol% CaCl 2 crystallized to wollastonite, whilst the compositions with CaCl 2 content equal to or greater than 19.2 mol% are thought to crystallize to CaCl 2 . In practice, the crystallization of CaCl 2 could not occur until the crystallization temperature fell below the melting point of CaCl 2 . The implications of the results along with the high chloride retention are discussed.

Microstructure and mechanical properties of stainless steel/calcium silicate composites manufactured by selective laser melting.

PubMed

Zheng, Zeng; Wang, Lianfeng; Jia, Min; Cheng, Lingyu; Yan, Biao

2017-02-01

Selective laser melting (SLM) is raised as one kind of additive manufacturing (AM) which is based on the discrete-stacking concept. This technique can fabricate advanced composites with desirable properties directly from 3D CAD data. In this research, 316L stainless steel (316L SS) and different fractions of calcium silicate (CaSiO 3 ) composites (weight fractions of calcium silicate are 0%, 5%,10% and 15%, respectively) were prepared by SLM technique with a purpose to develop biomedical metallic materials. The relative density, tensile, microhardness and elastic modulus of the composites were tested, their microstructures and fracture morphologies were observed using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the addition of CaSiO 3 particles influenced the microstructure and mechanical properties of specimens significantly. The CaSiO 3 precipitates from the overlap of adjacent tracks and became the origin of the defects. The tensile strength of specimens range 320-722MPa. The microhardness and elastic modulus are around 250HV and 215GPa respectively. These composites were ductile materials and the fracture mode of the composites was mixed mode of ductile and brittle fracture. The 316L SS/CaSiO 3 composites can be a potential biomedical metallic materials in the medical field. Copyright © 2016. Published by Elsevier B.V.

Experimental Calcium Silicate-Based Cement with and without Zirconium Oxide Modulates Fibroblasts Viability.

PubMed

Slompo, Camila; Peres-Buzalaf, Camila; Gasque, Kellen Cristina da Silva; Damante, Carla Andreotti; Ordinola-Zapata, Ronald; Duarte, Marco Antonio Hungaro; de Oliveira, Rodrigo Cardoso

2015-01-01

The aim of this study was to verify whether the use of zirconium oxide as a radiopacifier of an experimental calcium silicate-based cement (WPCZO) leads to cytotoxicity. Fibroblasts were treated with different concentrations (10 mg/mL, 1 mg/mL, and 0.1 mg/mL) of the cements diluted in Dulbecco's modified Eagle's medium (DMEM) for periods of 12, 24, and 48 h. Groups tested were white Portland cement (WPC), white Portland cement with zirconium oxide (WPCZO), and white mineral trioxide aggregate Angelus (MTA). Control group cells were not treated. The cytotoxicity was evaluated through mitochondrial-activity (MTT) and cell-density (crystal violet) assays. All cements showed low cytotoxicity. In general, at the concentration of 10 mg/mL there was an increase in viability of those groups treated with WPC and WPCZO when compared to the control group (p<0.05). A similar profile for the absorbance values was noted among the groups: 10 mg/mL presented an increase in viability compared to the control group. On the other hand, smaller concentrations presented a similar or lower viability compared to the control group, in general. A new dental material composed of calcium silicate-based cement with 20% zirconium oxide as the radiopacifier showed low cytotoxicity as a promising material to be exploited for root-end filling.

Electron Microscopic Analysis of Surface Inorganic Substances on Oral and Combustible Tobacco Products.

PubMed

Halstead, Mary M; Watson, Clifford H; Pappas, R Steven

2015-01-01

Although quantitative trace toxic metal analyses have been performed on tobacco products, little has been published on inorganic particulate constituents on and inside the products. We analyzed these constituents using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The nature of SEM-EDS instrumentation makes it an ideal choice for inorganic particulate analyses and yields relevant information to potential exposures during consumption of oral tobacco products, and possibly as a consequence of smoking. Aluminum silicates, silica and calcium compounds were common inorganic particulate constituents of tobacco products. Aluminum silicates and silica from soil were found on external leaf surfaces. Phytolithic silica, found in the lumen of the plant leaf, is of biogenic origin. Calcium oxalate was also apparently of biogenic origin. Small mineral deposits on tobacco could have health implications. Minerals found on the surfaces of smokeless tobacco products could possibly abrade the oral mucosa and contribute to the oral inflammatory responses observed with smokeless tobacco product use. If micron and sub-micron size calcium particles on cigarette filler were transported in mainstream smoke, they could potentially induce a pulmonary irritant inflammation when inhaled. The transport of aluminum silicate and silica in smoke could potentially also contribute to chronic inflammatory disease. Published by Oxford University Press 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Chitosan-coated mesoporous microspheres of calcium silicate hydrate: environmentally friendly synthesis and application as a highly efficient adsorbent for heavy metal ions.

PubMed

Zhao, Jing; Zhu, Ying-Jie; Wu, Jin; Zheng, Jian-Qiang; Zhao, Xin-Yu; Lu, Bing-Qiang; Chen, Feng

2014-03-15

Chitosan-coated calcium silicate hydrate (CSH/chitosan) mesoporous microspheres formed by self-assembly of nanosheets have been synthesized in aqueous solution under ambient conditions without using any toxic surfactant or organic solvent. The method reported herein has advantages of simplicity, low cost and being environmentally friendly. The BET specific surface area of CSH/chitosan mesoporous microspheres is measured to be as high as ~356 m(2) g(-1), which is considerably high among calcium silicate materials. The as-prepared CSH/chitosan mesoporous microspheres are promising adsorbent and exhibit a quick and highly efficient adsorption behavior toward heavy metal ions of Ni(2+), Zn(2+), Cr(3+), Pb(2+) Cu(2+) and Cd(2+) in aqueous solution. The adsorption kinetics can be well fitted by the pseudo second-order model. The maximum adsorption amounts of Ni(2+), Zn(2+), Pb(2+), Cu(2+) and Cd(2+) on CSH/chitosan mesoporous microspheres are extremely high, which are 406.6, 400, 796, 425 and 578 mg/g, respectively. The CSH/chitosan adsorbent exhibits the highest affinity for Pb(2+) ions among five heavy metal ions. The adsorption capacities of the CSH/chitosan adsorbent toward heavy metal ions are relatively high compared with those reported in the literature. Copyright © 2013 Elsevier Inc. All rights reserved.

Dynamical behaviors of structural, constrained and free water in calcium- and magnesium-silicate-hydrate gels

DOE PAGES

Le, Peisi; Fratini, Emiliano; Ito, Kanae; ...

2016-01-28

We present the hypothesis that the mechanical properties of cement pastes depend strongly on their porosities. In a saturated paste, the porosity links to the free water volume after hydration. Structural water, constrained water, and free water have different dynamical behavior. Hence, it should be possible to extract information on pore system by exploiting the water dynamics. With our experiments we investigated the slow dynamics of hydration water confined in calcium- and magnesium-silicate-hydrate (C-S-H and M-S-H) gels using high-resolution quasi-elastic neutron scattering (QENS) technique. C-S-H and M-S-H are the chemical binders present in calcium rich and magnesium rich cements. Wemore » measured three M-S-H samples: pure M-S-H, M-S-H with aluminum-silicate nanotubes (ASN), and M-S-H with carboxyl group functionalized ASN (ASN-COOH). A C-S-H sample with the same water content (i.e. 0.3) is also studied for comparison. We found that structural water in the gels contributes to the elastic component of the QENS spectrum, while constrained water and free water contribute the quasi-elastic component. The quantitative analysis suggests that the three components vary for different samples and indicate the variance in the system porosity, which controls the mechanical properties of cement pastes.« less

TheraCal LC: From Biochemical and Bioactive Properties to Clinical Applications

PubMed Central

Rabi, Tarek

2018-01-01

Background Direct pulp capping is a popular treatment modality among dentists. TheraCal LC is a calcium silicate-based material that is designed as a direct/indirect pulp capping material. The material might be very attractive for clinicians because of its ease of handling. Unlike other calcium silicate-based materials, TheraCal LC is resin-based and does not require any conditioning of the dentine surface. The material can be bonded with different types of adhesives directly after application. There has been considerable research performed on this material since its launching; however, there are no review articles that collates information and data obtained from these studies. This review discusses the various characteristics of the material with the aim of establishing a better understanding for its clinical use. Methods A search was conducted using search engines (PubMed and Cochrane databases) in addition to reference mining of the articles that was used to locate other papers. The process of searching for the relevant studies was performed using the keywords pulp protection, pulp capping, TheraCal, and calcium silicates. Only articles in English published in peer-reviewed journals were included in the review. Conclusion This review underlines the fact that further in vitro and in vivo studies are required before TheraCal LC can be used as a direct pulp capping material. PMID:29785184

Compressive strength and magnetic properties of calcium silicate-zirconia-iron (III) oxide composite cements

NASA Astrophysics Data System (ADS)

Ridzwan, Hendrie Johann Muhamad; Shamsudin, Roslinda; Ismail, Hamisah; Yusof, Mohd Reusmaazran; Hamid, Muhammad Azmi Abdul; Awang, Rozidawati Binti

2018-04-01

In this study, ZrO2 microparticles and γ-Fe2O3 nanoparticles have been added into calcium silicate based cements. The purpose of this experiment was to investigate the compressive strength and magnetic properties of the prepared composite cement. Calcium silicate (CAS) powder was prepared by hydrothermal method. SiO2 and CaO obtained from rice husk ash and limestone respectively were autoclaved at 135 °C for 8 h and sintered at 950°C to obtain CAS powder. SiO2:CaO ratio was set at 45:55. CAS/ZrO2 sample were prepared with varying ZrO2 microparticles concentrations by 0-40 wt. %. Compressive strength value of CAS/ZrO2 cements range from 1.44 to 2.44 MPa. CAS/ZrO2/γ-Fe2O3 sample with 40 wt. % ZrO2 were prepared with varying γ-Fe2O3 nanoparticles concentrations (1-5 wt. %). The additions of γ-Fe2O3 nanoparticles showed up to twofold increase in the compressive strength of the cement. X-Ray diffraction (XRD) results confirm the formation of mixed phases in the produced composite cements. Vibrating sample magnetometer (VSM) analysis revealed that the ferromagnetic behaviour has been observed in CAS/ZrO2/γ-Fe2O3 composite cements.

Dynamical behaviors of structural, constrained and free water in calcium- and magnesium-silicate-hydrate gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le, Peisi; Fratini, Emiliano; Ito, Kanae

We present the hypothesis that the mechanical properties of cement pastes depend strongly on their porosities. In a saturated paste, the porosity links to the free water volume after hydration. Structural water, constrained water, and free water have different dynamical behavior. Hence, it should be possible to extract information on pore system by exploiting the water dynamics. With our experiments we investigated the slow dynamics of hydration water confined in calcium- and magnesium-silicate-hydrate (C-S-H and M-S-H) gels using high-resolution quasi-elastic neutron scattering (QENS) technique. C-S-H and M-S-H are the chemical binders present in calcium rich and magnesium rich cements. Wemore » measured three M-S-H samples: pure M-S-H, M-S-H with aluminum-silicate nanotubes (ASN), and M-S-H with carboxyl group functionalized ASN (ASN-COOH). A C-S-H sample with the same water content (i.e. 0.3) is also studied for comparison. We found that structural water in the gels contributes to the elastic component of the QENS spectrum, while constrained water and free water contribute the quasi-elastic component. The quantitative analysis suggests that the three components vary for different samples and indicate the variance in the system porosity, which controls the mechanical properties of cement pastes.« less

[Endodontics in motion: new concepts, materials and techniques 1. Hydraulic Calcium Silicate Cements].

PubMed

Moinzadeh, A T; Jongsma, L; de Groot-Kuin, D; Cristescu, R; Neirynck, N; Camilleri, J

2015-01-01

Hydraulic Calcium Silicate Cements (HCSCs) constitute a group of materials that have become increasingly popular in endodontics since the introduction of Mineral Trioxide Aggregate (MTA) in the 1990s. MTA is Portland cement to which bismuth oxide has been added to increase its radiopacity. The most important property of MTA is its capacity to set in water or a humid environment. However, MTA also has important limitations, for example, it's difficult to work with and can discolour teeth. Recently, numerous products based on HCSC chemistry, which can be considered as modifications of MTA intended to reduce its limitations, have become available on the market. Despite their potential advantages, all of these materials have their own specific limitations that are currently insufficiently known and investigated.

Effect of replacing calcium salts of palm oil with camelina seed at 2 dietary ether extract levels on digestion, ruminal fermentation, and nutrient flow in a dual-flow continuous culture system.

PubMed

Brandao, V L N; Dai, X; Paula, E M; Silva, L G; Marcondes, M I; Shenkoru, T; Poulson, S R; Faciola, A P

2018-06-01

Camelina is a drought- and salt-tolerant oil seed, which in total ether extract (EE) contains up to 74% polyunsaturated fatty acids. The objective of this study was to assess the effects of replacing calcium salts of palm oil (Megalac, Church & Dwight Co. Inc., Princeton, NJ) with camelina seed (CS) on ruminal fermentation, digestion, and flows of fatty acids (FA) and AA in a dual-flow continuous culture system when supplemented at 5 or 8% dietary EE. Diets were randomly assigned to 8 fermentors in a 2 × 2 factorial arrangement of treatments in a replicated 4 × 4 Latin square design, with four 10-d experimental periods consisting of 7 d for diet adaptation and 3 d for sample collection. Treatments were (1) calcium salts of palm oil supplementation at 5% EE (MEG5); (2) calcium salts of palm oil supplementation at 8% EE (MEG8); (3) 7.7% CS supplementation at 5% EE (CS5); and (4) 17.7% CS supplementation at 8% EE (CS8). Diets contained 55% orchardgrass hay, and fermentors were fed 72 g of dry matter/d. On d 8, 9, and 10 of each period, digesta effluent samples were taken for ruminal NH 3 , volatile fatty acids, nitrogen metabolism analysis, and long-chain FA and AA flows. Statistical analysis was performed using the MIXED procedure (SAS Institute Inc., Cary, NC). We detected an interaction between FA source and dietary EE level for acetate, where MEG8 had the greatest molar proportion of acetate. Molar proportions of propionate were greater and total volatile fatty acids were lower on CS diets. Supplementation of CS decreased overall ruminal nutrient true digestibility, but dietary EE level did not affect it. Diets containing CS had greater biohydrogenation of 18:2 and 18:3; however, biohydrogenation of 18:1 was greater in MEG diets. Additionally, CS diets had greater ruminal concentrations of trans-10/11 18:1 and cis-9,trans-11 conjugated linoleic acid. Dietary EE level at 8% negatively affected flows of NH 3 -N (g/d), nonammonia N, and bacterial N as well as the overall AA outflow. However, treatments had minor effects on individual ruminal AA digestibility. The shift from acetate to propionate observed on diets containing CS may be advantageous from an energetic standpoint. Moreover, CS diets had greater ruminal outflow of trans-10/11 18:1 and cis-9,trans-11 conjugated linoleic acid than MEG diets, suggesting a better FA profile available for postruminal absorption. However, dietary EE at 8% was deleterious to overall N metabolism and AA outflow, indicating that CS can be fed at 5% EE without compromising N metabolism. Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Internal structure of cesium-bearing radioactive microparticles released from Fukushima nuclear power plant

PubMed Central

Yamaguchi, Noriko; Mitome, Masanori; Kotone, Akiyama-Hasegawa; Asano, Maki; Adachi, Kouji; Kogure, Toshihiro

2016-01-01

Microparticles containing substantial amounts of radiocesium collected from the ground in Fukushima were investigated mainly by transmission electron microscopy (TEM) and X-ray microanalysis with scanning TEM (STEM). Particles of around 2 μm in diameter are basically silicate glass containing Fe and Zn as transition metals, Cs, Rb and K as alkali ions, and Sn as substantial elements. These elements are homogeneously distributed in the glass except Cs which has a concentration gradient, increasing from center to surface. Nano-sized crystallites such as copper- zinc- and molybdenum sulfide, and silver telluride were found inside the microparticles, which probably resulted from the segregation of the silicate and sulfide (telluride) during molten-stage. An alkali-depleted layer of ca. 0.2 μm thick exists at the outer side of the particle collected from cedar leaves 8 months after the nuclear accident, suggesting gradual leaching of radiocesium from the microparticles in the natural environment. PMID:26838055

Interfacial Connection Mechanisms in Calcium-Silicate-Hydrates/Polymer Nanocomposites: A Molecular Dynamics Study.

PubMed

Zhou, Yang; Hou, Dongshuai; Manzano, Hegoi; Orozco, Carlos A; Geng, Guoqing; Monteiro, Paulo J M; Liu, Jiaping

2017-11-22

Properties of organic/inorganic composites can be highly dependent on the interfacial connections. In this work, molecular dynamics, using pair-potential-based force fields, was employed to investigate the structure, dynamics, and stability of interfacial connections between calcium-silicate-hydrates (C-S-H) and organic functional groups of three different polymer species. The calculation results suggest that the affinity between C-S-H and polymers is influenced by the polarity of the functional groups and the diffusivity and aggregation tendency of the polymers. In the interfaces, the calcium counterions from C-S-H act as the coordination atoms in bridging the double-bonded oxygen atoms in the carboxyl groups (-COOH), and the Ca-O connection plays a dominant role in binding poly(acrylic acid) (PAA) due to the high bond strength defined by time-correlated function. The defective calcium-silicate chains provide significant numbers of nonbridging oxygen sites to accept H-bonds from -COOH groups. As compared with PAA, the interfacial interactions are much weaker between C-S-H and poly(vinyl alcohol) (PVA) or poly(ethylene glycol) (PEG). Predominate percentage of the -OH groups in the PVA form H-bonds with inter- and intramolecule, which results in the polymer intertwining and reduces the probability of H-bond connections between PVA and C-S-H. On the other hand, the inert functional groups (C-O-C) in poly(ethylene glycol) (PEG) make this polymer exhibit unfolded configurations and move freely with little restrictions. The interaction mechanisms interpreted in this organic-inorganic interface can give fundamental insights into the polymer modification of C-S-H and further implications to improving cement-based materials from the genetic level.

Cytotoxicity and osteogenic potential of silicate calcium cements as potential protective materials for pulpal revascularization.

PubMed

Bortoluzzi, Eduardo A; Niu, Li-Na; Palani, Chithra D; El-Awady, Ahmed R; Hammond, Barry D; Pei, Dan-Dan; Tian, Fu-Cong; Cutler, Christopher W; Pashley, David H; Tay, Franklin R

2015-12-01

In pulpal revascularization, a protective material is placed coronal to the blood clot to prevent recontamination and to facilitate osteogenic differentiation of mesenchymal stem cells to produce new dental tissues. Although mineral trioxide aggregate (MTA) has been the material of choice for clot protection, it is easily displaced into the clot during condensation. The present study evaluated the effects of recently introduced calcium silicate cements (Biodentine and TheraCal LC) on the viability and osteogenic differentiation of human dental pulp stem cells (hDPSCs) by comparing with MTA Angelus. Cell viability was assessed using XTT assay and flow cytometry. The osteogenic potential of hDPSCs exposed to calcium silicate cements was examined using qRT-PCR for osteogenic gene expressions, alkaline phosphatase enzyme activity, Alizarin red S staining and transmission electron microscopy of extracellular calcium deposits. Parametric statistical methods were employed for analyses of significant difference among groups, with α=0.05. The cytotoxic effects of Biodentine and TheraCal LC on hDPSCs were time- and concentration-dependent. Osteogenic differentiation of hDPSCs was enhanced after exposure to Biodentine that was depleted of its cytotoxic components. This effect was less readily observed in hDPSCs exposed to TheraCal LC, although both cements supported extracellular mineralization better than the positive control (zinc oxide-eugenol-based cement). A favorable tissue response is anticipated to occur with the use of Biodentine as a blood clot-protecting material for pulpal revascularization. Further investigations with the use of in vivo animal models are required to validate the potential adverse biological effects of TheraCal LC on hDPSCs. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Cytotoxicity and Osteogenic Potential of Silicate Calcium Cements as Potential Protective Materials for Pulpal Revascularization

PubMed Central

Bortoluzzi, Eduardo A.; Niu, Li-na; Palani, Chithra D.; El-Awady, Ahmed R.; Hammond, Barry D.; Pei, Dan-dan; Tian, Fu-cong; Cutler, Christopher W.; Pashley, David H.; Tay, Franklin R.

2016-01-01

Objectives In pulpal revascularization, a protective material is placed coronal to the blood clot to prevent recontamination and to facilitate osteogenic differentiation of mesenchynal stem cells to produce new dental tissues. Although mineral trioxide aggregate (MTA) has been the material of choice for clot protection, it is easily displaced into the clot during condensation. The present study evaluated the effects of recently-introduced calcium silicate cements (Biodentine and TheraCal LC) on the viability and osteogenic differentiation of human dental pulp stem cells (hDPSCs) by comparing with MTA Angelus. Methods Cell viability was assessed using XTT assay and flow cytometry. The osteogenic potential of hDPSCs exposed to calcium silicate cements was examined using qRT-PCR for osteogeic gene expressions, alkaline phosphatase enzyme activity, Alizarin red S staining and transmission electron microscopy of extracellular calcium deposits. Parametric statistical methods were employed for analyses of significant difference among groups, with α=0.05. Results The cytotoxic effects of Biodentine and TheraCal LC on hDPSCs were time- and concentration-dependent. Osteogenic differentiation of hDPSCs was enhanced after exposure to Biodentine that was depleted of its cytotoxic components. This effect was less readily observed in hDPSCs exposed to TheraCal LC, although both cements supported extracelluar mineralization better than the positive control (zinc oxide-eugenol–based cement). Significance A favorable tissue response is anticipated to occur with the use of Biodentine as a blood clot-protecting material for pulpal revascularizaiton. Further investigations with the use of in vivo animal models are required to validate the potential adverse biological effects of TheraCal LC on hDPSCs. PMID:26494267

Experimental and theoretical study of the structural environment of magnesium in minerals and silicate glasses using X-ray absorption near-edge structure

NASA Astrophysics Data System (ADS)

Trcera, Nicolas; Cabaret, Delphine; Rossano, Stéphanie; Farges, François; Flank, Anne-Marie; Lagarde, Pierre

2009-05-01

X-ray absorption spectroscopy at the Mg K-edge is used to obtain information on magnesium environment in minerals, silicate and alumino-silicate glasses. First-principles XANES calculations are performed for minerals using a plane-wave density functional formalism with core-hole effects treated in a supercell approach. The good agreement obtained between experimental and theoretical spectra provides useful information to interpret the spectral features. With the help of calculation, the position of the first peak of XANES spectra is related to both coordination and polyhedron distortion changes. In alumino-silicate glasses, magnesium is found to be mainly 5-fold coordinated to oxygen whatever the aluminum saturation index value. In silicate glasses, magnesium coordination increases from 4 in Cs-, Rb- and K-bearing glasses to 5 in Na- and Li-bearing glasses but remains equal as the polymerization degree of the glass varies. The variation of the C feature (position and intensity) is strongly related to the alkali type providing information on the medium range order.

Sulfation and Cation Effects on the Conformational Properties of the Glycan Backbone of Chondroitin Sulfate Disaccharides

PubMed Central

Faller, Christina E.; Guvench, Olgun

2015-01-01

Chondroitin sulfate (CS) is one of several glycosaminoglycans that are major components of proteoglycans. A linear polymer consisting of repeats of the disaccharide -4GlcAβ1-3GalNAcβ1-, CS undergoes differential sulfation resulting in five unique sulfation patterns. Because of the dimer repeat, the CS glycosidic “backbone” has two distinct sets of conformational degrees of freedom defined by pairs of dihedral angles: (ϕ1, ψ1) about the β1-3 glycosidic linkage and (ϕ2, ψ2) about the β1-4 glycosidic linkage. Differential sulfation and the possibility of cation binding, combined with the conformational flexibility and biological diversity of CS, complicate experimental efforts to understand CS three-dimensional structures at atomic resolution. Therefore, all-atom explicit-solvent molecular dynamics simulations with Adaptive Biasing Force sampling of the CS backbone were applied to obtain high resolution, high precision free energies of CS disaccharides as a function of all possible backbone geometries. All ten disaccharides (β1-3 vs. β1-4 linkage x five different sulfation patterns) were studied; additionally, ion effects were investigated by considering each disaccharide in the presence of either neutralizing sodium or calcium cations. GlcAβ1-3GalNAc disaccharides have a single, broad, thermodynamically important free-energy minimum whereas GalNAcβ1-4GlcA disaccharides have two such minima. Calcium cations but not sodium cations bind to the disaccharides, and binding is primarily to the GlcA –COO− moiety as opposed to sulfate groups. This binding alters the glycan backbone thermodynamics in instances where a calcium cation bound to –COO− can act to bridge and stabilize an interaction with an adjacent sulfate group, whereas, in the absence of this cation, the proximity of a sulfate group to –COO− results in two like charges being both desolvated and placed adjacent to each other and is found to be destabilizing. In addition to providing information on sulfation and cation effects, the present results can be applied to building models of CS polymers and as a point of comparison in studies of CS polymer backbone dynamics and thermodynamics. PMID:25906376

Sulfation and cation effects on the conformational properties of the glycan backbone of chondroitin sulfate disaccharides.

PubMed

Faller, Christina E; Guvench, Olgun

2015-05-21

Chondroitin sulfate (CS) is one of several glycosaminoglycans that are major components of proteoglycans. A linear polymer consisting of repeats of the disaccharide -4GlcAβ1-3GalNAcβ1-, CS undergoes differential sulfation resulting in five unique sulfation patterns. Because of the dimer repeat, the CS glycosidic "backbone" has two distinct sets of conformational degrees of freedom defined by pairs of dihedral angles: (ϕ1, ψ1) about the β1-3 glycosidic linkage and (ϕ2, ψ2) about the β1-4 glycosidic linkage. Differential sulfation and the possibility of cation binding, combined with the conformational flexibility and biological diversity of CS, complicate experimental efforts to understand CS three-dimensional structures at atomic resolution. Therefore, all-atom explicit-solvent molecular dynamics simulations with Adaptive Biasing Force sampling of the CS backbone were applied to obtain high-resolution, high-precision free energies of CS disaccharides as a function of all possible backbone geometries. All 10 disaccharides (β1-3 vs β1-4 linkage × five different sulfation patterns) were studied; additionally, ion effects were investigated by considering each disaccharide in the presence of either neutralizing sodium or calcium cations. GlcAβ1-3GalNAc disaccharides have a single, broad, thermodynamically important free-energy minimum, whereas GalNAcβ1-4GlcA disaccharides have two such minima. Calcium cations but not sodium cations bind to the disaccharides, and binding is primarily to the GlcA -COO(-) moiety as opposed to sulfate groups. This binding alters the glycan backbone thermodynamics in instances where a calcium cation bound to -COO(-) can act to bridge and stabilize an interaction with an adjacent sulfate group, whereas, in the absence of this cation, the proximity of a sulfate group to -COO(-) results in two like charges being both desolvated and placed adjacent to each other and is found to be destabilizing. In addition to providing information on sulfation and cation effects, the present results can be applied to building models of CS polymers and as a point of comparison in studies of CS polymer backbone dynamics and thermodynamics.

Coronary Artery Calcium as an Independent Surrogate Marker in the Risk Assessment of Patients With Atrial Fibrillation and an Intermediate Pretest Likelihood for Coronary Artery Disease Admitted to a German Chest Pain Unit.

PubMed

Breuckmann, Frank; Olligs, Jan; Hinrichs, Liane; Koopmann, Matthias; Lichtenberg, Michael; Böse, Dirk; Fischer, Dieter; Eckardt, Lars; Waltenberger, Johannes; Garvey, J Lee

2016-03-01

About 10% of patients admitted to a chest pain unit (CPU) exhibit atrial fibrillation (AF). To determine whether calcium scores (CS) are superior over common risk scores for coronary artery disease (CAD) in patients presenting with atypical chest pain, newly diagnosed AF, and intermediate pretest probability for CAD within the CPU. In 73 subjects, CS was related to the following risk scores: Global Registry of Acute Coronary Events (GRACE) score, including a new model of a frequency-normalized approach; Thrombolysis In Myocardial Infarction score; European Society of Cardiology Systematic Coronary Risk Evaluation (SCORE); Framingham risk score; and Prospective Cardiovascular Münster Study score. Revascularization rates during index stay were assessed. Median CS was 77 (interquartile range, 1-270), with higher values in men and the left anterior descending artery. Only the modified GRACE (ρ = 0.27; P = 0.02) and the SCORE (ρ = 0.39; P < 0.005) were significantly correlated with CS, whereas the GRACE (τ = 0.21; P = 0.04) and modified GRACE (τ = 0.23; P = 0.02) scores were significantly correlated with percentile groups. Only the CS significantly discriminated between those with and without stenosis (P < 0.01). Apart from modified GRACE score, overall correlations between risk scores and calcium burden, as well as revascularization rates during index stay, were low. By contrast, the determination of CS may be used as an additional surrogate marker in risk stratification in AF patients with intermediate pretest likelihood for CAD admitted to a CPU. © 2016 Wiley Periodicals, Inc.

Cesium distribution and phases in proxy experiments on the incineration of radioactively contaminated waste from the Fukushima area.

PubMed

Saffarzadeh, Amirhomayoun; Shimaoka, Takayuki; Kakuta, Yoshitada; Kawano, Takashi

2014-10-01

After the March 11, 2011 Tohoku earthquake and Fukushima I Nuclear Power Plant accident, incineration was initially adopted as an effective technique for the treatment of post-disaster wastes. Accordingly, considerable amounts of radioactively contaminated residues were immediately generated through incineration. The level of radioactivity associated with radiocesium in the incineration ash residues (bottom ash and fly ash) became significantly high (several thousand to 100,000 Bq/kg) as a result of this treatment. In order to understand the modes of occurrence of radiocesium, bottom ash products were synthesized through combusting of refuse-derived fuel (RDF) with stable Cs salts in a pilot incinerator. Microscopic and microanalytical (SEM-EDX) techniques were applied and the following Cs categories were identified: low and high concentrations in the matrix glass, low-level partitioning into some newly-formed silicate minerals, partitioning into metal-sulfide compounds, and occurring in newly-formed Cs-rich minerals. These categories that are essentially silicate-bound are the most dominant forms in large and medium size bottom ash particles. It is expected that these achievements provide solutions to the immobilization of radiocesium in the incineration ash products contaminated by Fukushima nuclear accident. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Cesium Rare-Earth Silicate Cs3 RESi6 O15 (RE=Dy-Lu, Y, In): The Parent of an Unusual Structural Class Featuring a Remarkable 57 Å Unit Cell Axis.

PubMed

Terry, Rylan; Vinton, Daniel; McMillen, Colin D; Kolis, Joseph W

2018-02-19

The structure of Cs 3 RESi 6 O 15 , where RE=Dy-Lu, Y, In, is unusual in that it contains octahedrally coordinated rare-earth ions; their relative orientation dictates the structure, as they rotate about the c-axis supported by the cyclic Si 6 O 15 framework. The repeat unit of the rotation is eight units generating a very long (ca. 57 Å) unit cell axis. This unusual repeat unit is created by the structural flexibility of the hexasilicate ring, which is in turn affected by the size of the rare earth ion as well as the size of alkali ion residing within the silicate layers. Previous work showed for the smaller Sc 3+ ion, the rotation of the octahedra is not sufficient to achieve closure at an integral repeat unit and an incommensurate structure results. The products are prepared as large, high quality single crystals using a high-temperature (650 °C) hydrothermal method with CsOH and F - mineralizers. The presence of fluoride is essential to the formation of the product. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Co-crystallization of cholesterol and calcium phosphate as related to atherosclerosis

NASA Astrophysics Data System (ADS)

Hirsch, Danielle; Azoury, Reuven; Sarig, Sara

1990-09-01

Calcification of atherosclerotic plaques occurs very frequently and aggravates the disease. In biological systems, epitaxial relationships between crystal structures may be important in nucleating the deposit of a solid phase. The biologically preferred calcium phosphate species, apatite, and cholesterol crystal have structurally compatible crystallographic faces which allow epitaxial growth of one crystal upon another. The present study describes a new approach to explore, in vitro, the crystallization processes of calcium phosphate (CaP) with cholesterol (CS) and cholestanol (CN) which are related to atherosclerosis. Aqueous solutions containing calcium and phosphate ions or CaP crystals as hydroxyapatite were added into saturated ethanolic solutions of CS or CS and 10% CN. After precipitation, crystals were collected and analyzed by nuclear magnetic resonance (NMR), infra-red (IR), X-ray, scanning electron microscope (SEM-LINK), differential scanning calorimeter (DSC) and atomic absorption. The principal result is the well-formed crystals precipitation when an aqueous solution and CaP seed crystals were added to saturated solutions of CS and 10% CN. Cholesterol-cholestanol dihydrate (CC2W) crystals precipitated in the presence of CaP seeds were compared to the CC2W crystals obtained without the mineral compound. The results of this comparison indicate a special link between crystals of CaP and CC2W, and support the epitaxial relationship between the two kinds of crystals. The potential of CC2W crystals to be precipitated by CaP seed crystals prove likewise the possible significant role of the cholestanol metabolite in the process of cholesterol crystallization and calcification in the arteries.

Preparation and properties of calcium-silicate filled resins for dental restoration. Part II: Micro-mechanical behaviour to primed mineral-depleted dentine.

PubMed

Profeta, Andrea Corrado

2014-11-01

Evaluating microtensile bond strength (μTBS) and Knoop micro-hardness (KHN) of resin bonded-dentine interfaces created with two methacrylate-based systems either incorporating Bioglass 45S5 (3-E&RA/BG) or MTA (3-E&RA/WMTA). Solvated resins (50% ethanol/50% co-monomers) were used as primers while their neat counterparts were filled with the two calcium-silicate compounds. Application of neat resin adhesive with no filler served as control (3-E&RA). μTBS, KHN analysis and confocal tandem scanning microscopy (TSM) micropermeability were carried out after 24 h and 10 months of storage in phosphate buffer solution (DPBS). Scanning electron microscopy (SEM) was also performed after debonding. High μTBS values were achieved in all groups after 24 h of DPBS storage. On the contrary, solely the specimens created using 3-E&RA/BG and 3-E&RA/WMTA agents showed no significant reduction in terms of μTBS even after 10 months in DPBS; similarly, they did not restore the average superficial micro-hardness to the level of sound dentine, but maintained unchanged KHN values, and no statistical decrease was found following 10 months of DPBS storage. The only statistically significant changes occurred in the resin-dentine interfaces bonded with 3-E&RA that were subjected to a reduction of both μTBS and KHN values with ageing. In terms of micropermeability, adverse results were obtained with 3-E&RA while 3-E&RA/BG and 3-E&RA/WMTA demonstrated a beneficial effect after prolonged DPBS storage. Calcium-silicate filled composite resins performed better than a current etch-and-rinse adhesive and had a therapeutic/protective effect on the micro-mechanical properties of mineral-depleted resin-dentine interfaces. The incorporation of calcium-silicates into dental restorative and bonding agents can create more biomimetic (life-like) restorations. This will not only enable these materials to mimic the physical characteristics of the tooth structure, but will also stabilize and protect the remaining dental hard tissues.

DNA adsorption onto glass surfaces

NASA Astrophysics Data System (ADS)

Carlson, Krista Lynn

Streaming potential measurements were performed on microspheres of silica, lime silicate (SLS) and calcium aluminate (CA) glasses containing silica and iron oxide (CASi and CAFe). The silicate based glasses exhibited acidic surfaces with isoelectric points (IEP) around a pH of 3 while the calcium aluminates displayed more basic surfaces with IEP ranging from 8--9.5. The surface of the calcium aluminate microspheres containing silica reacted with the background electrolyte, altering the measured zeta potential values and inhibiting electrolyte flow past the sample at ˜ pH 4 due to formation of a solid plug. DNA adsorption experiments were performed using the microspheres and a commercially available silicate based DNA isolation filter using a known quantity of DNA suspended in a chaotropic agent free 0.35 wt% Tris(hydroxymethyl)aminomethane (Tris) buffer solution. The microspheres and commercial filter were also used to isolate DNA from macrophage cells in the presence of chaotropic agents. UV absorbance at ˜260 nm and gel electrophoresis were used to quantify the amount and size of the DNA strands that adsorbed to the microsphere surfaces. In both experiments, the 43--106 microm CAFe microspheres adsorbed the largest quantity of DNA. However, the 43--106 microm SLS microspheres isolated more DNA from the cells than the <43 microm CAFe microspheres, indicating that microsphere size contributes to isolation ability. The UV absorbance of DNA at ˜260 nm was slightly altered due to the dissolution of the calcium aluminate glasses during the adsorption process. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) determined that calcium and aluminum ions leached from the CA and CAFe microsphere surfaces during these experiments. Circular dichroism (CD) spectroscopy showed that the leached ions had no effect on the conformation of the DNA, and therefore would not be expected to interfere in downstream applications such as DNA replication. The 0.35 wt% Tris solution completely inhibited the formation of the hydrated crystalline layer that develops when the calcium aluminate glassess are incubated in deionized water. A Tris concentration of 0.24 wt% allowed for the formation of both hexagonal and cubic hydrates, however they were severely distorted and present in low amounts such that they were undectable by XRD.

Properties of Tricalcium Silicate Sealers.

PubMed

Khalil, Issam; Naaman, Alfred; Camilleri, Josette

2016-10-01

Sealers based on tricalcium silicate cement aim at an interaction of the sealer with the root canal wall, alkalinity with potential antimicrobial activity, and the ability to set in a wet field. The aim of this study was to characterize and investigate the properties of a new tricalcium silicate-based sealer and verify its compliance to ISO 6876 (2012). A new tricalcium silicate-based sealer (Bio MM; St Joseph University, Beirut, Lebanon), BioRoot RCS (Septodont, St Maure de Fosses, France), and AH Plus (Dentsply, DeTrey, Konstanz, Germany) were investigated. Characterization using scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analysis was performed. Furthermore, sealer setting time, flow, film thickness, and radiopacity were performed following ISO specifications. pH and ion leaching in solution were assessed by pH analysis and inductively coupled plasma. Bio MM and BioRoot RCS were both composed of tricalcium silicate and tantalum oxide in Bio MM and zirconium oxide in BioRoot RCS. In addition, the Bio MM contained calcium carbonate and a phosphate phase. The inorganic components of AH Plus were calcium tungstate and zirconium oxide. AH Plus complied with the ISO norms for both flow and film thickness. BioRoot RCS and Bio MM exhibited a lower flow and a higher film thickness than that specified for sealer cements in ISO 6876. All test sealers exhibited adequate radiopacity. Bio MM interacted with physiologic solution, thus showing potential for bioactivity. Sealer properties were acceptable and comparable with other sealers available clinically. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Advanced ceramic coating development for industrial/utility gas turbines

NASA Technical Reports Server (NTRS)

Vogan, J. W.; Stetson, A. R.

1982-01-01

A program was conducted with the objective of developing advanced thermal barrier coating (TBC) systems. Coating application was by plasma spray. Duplex, triplex and graded coatings were tested. Coating systems incorporated both NiCrAly and CoCrAly bond coats. Four ceramic overlays were tested: ZrO2.82O3; CaO.TiO2; 2CaO.SiO2; and MgO.Al2O3. The best overall results were obtained with a CaO.TiO2 coating applied to a NiCrAly bond coat. This coating was less sensitive than the ZrO2.8Y2O3 coating to process variables and part geometry. Testing with fuels contaminated with compounds containing sulfur, phosphorus and alkali metals showed the zirconia coatings were destabilized. The calcium titanate coatings were not affected by these contaminants. However, when fuels were used containing 50 ppm of vanadium and 150 ppm of magnesium, heavy deposits were formed on the test specimens and combustor components that required frequent cleaning of the test rig. During the program Mars engine first-stage turbine blades were coated and installed for an engine cyclic endurance run with the zirconia, calcium titanate, and calcium silicate coatings. Heavy spalling developed with the calcium silicate system. The zirconia and calcium titanate systems survived the full test duration. It was concluded that these two TBC's showed potential for application in gas turbines.

Calcium-Magnesium-Aluminosilicate (CMAS) Reactions and Degradation Mechanisms of Advanced Environmental Barrier Coatings

NASA Technical Reports Server (NTRS)

Ahlborg, Nadia L.; Zhu, Dongming

2013-01-01

The thermochemical reactions between calcium-magnesium-aluminosilicate- (CMAS-) based road sand and several advanced turbine engine environmental barrier coating (EBC) materials were studied. The phase stability, reaction kinetics and degradation mechanisms of rare earth (RE)-silicates Yb2SiO5, Y2Si2O7, and RE-oxide doped HfO2 and ZrO2 under the CMAS infiltration condition at 1500 C were investigated, and the microstructure and phase characteristics of CMAS-EBC specimens were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Experimental results showed that the CMAS dissolved RE-silicates to form crystalline, highly non-stoichiometric apatite phases, and in particular attacking the silicate grain boundaries. Cross-section images show that the CMAS reacted with specimens and deeply penetrated into the EBC grain boundaries and formed extensive low-melting eutectic phases, causing grain boundary recession with increasing testing time in the silicate materials. The preliminary results also showed that CMAS reactions also formed low melting grain boundary phases in the higher concentration RE-oxide doped HfO2 systems. The effect of the test temperature on CMAS reactions of the EBC materials will also be discussed. The faster diffusion exhibited by apatite and RE-doped oxide phases and the formation of extensive grain boundary low-melting phases may limit the CMAS resistance of some of the environmental barrier coatings at high temperatures.

Hydrochemical characterization of groundwater in the Akyem area, Ghana

USGS Publications Warehouse

Banoeng-Yakubo, B.; Yidana, S.M.; Anku, Y.; Akabzaa, T.; Asiedu, D.

2008-01-01

The Akyem area is a small farming community located in southeastern Ghana. Groundwater samples from wells in the area were analyzed for concentrations of the major ions, silica, electrical conductivity and pH. The objective was to determine the main controls on the hydrochemistry of ground-water. Mass balance modeling was used together with multivariate R-mode hierarchical cluster analysis to determine the significant sources of variation in the hydrochemistry. Two water types exist in this area. The first is influenced most by the weathering of silicate minerals from the underlying geology, and is thus rich in silica, sodium, calcium, bicarbonate, and magnesium ions. The second is water that has been influenced by the effects of fertilizers and other anthropogenic activities in the area. Mineral speciation and silicate mineral stability diagrams suggest that montmorillonite, probably derived from the incongruent dissolution of feldspars and micas, is the most stable silicate phase in the groundwaters. The apparent incongruent weathering of silicate minerals in the groundwater system has led to the enrichment of sodium, calcium, magnesium and bicarbonate ions as well as silica, leading to the supersaturation of calcite, aragonite, dolomite and quartz. Stability in the montmorillonite field suggests restricted flow conditions and a long groundwater residence time, leading to greater exposure of the rock to weathering. Cation exchange processes appear to play minor roles in the hydrochemistry of groundwater.

Evaluation of certain food additives and contaminants. Eightieth report of the Joint FAO/WHO Expert Committee on Food Additives.

PubMed

2016-01-01

This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives and contaminants and to prepare specifications for identity and purity. The first part of the report contains a brief description of general considerations addressed at the meeting, including updates on matters of interest to the work of the Committee. A summary follows of the Committee's evaluations of technical, toxicological and/or dietary exposure data for seven food additives (benzoates; lipase from Fusarium heterosporum expressed in Ogataea polymorpha; magnesium stearate; maltotetraohydrolase from Pseudomonas stutzeri expressed in Bacillus licheniformis; mixed β-glucanase, cellulase and xylanase from Rasamsonia emersonii; mixed β-glucanase and xylanase from Disporotrichum dimorphosporum; polyvinyl alcohol (PVA)- polyethylene glycol (PEG) graft copolymer) and two groups of contaminants (non-dioxin-like polychlorinated biphenyls and pyrrolizidine alkaloids). Specifications for the following food additives were revised or withdrawn: advantame; annatto extracts (solavnt extracted bixin, ad solvent-extracted norbixin); food additives containing aluminium and/or silicon (aluminium silicate; calcium aluminium silicate; calcium silicate; silicon dioxide, amorphous; sodium aluminium silicate); and glycerol ester of gum rosin. Annexed to the report are tables or text summarizing the toxicological and dietary exposure information and information on specifications as well as the Committees recommendations on the food additives and contaminants considered at this meeting.

Uptake of Silicon by Sugarcane from Applied Sources May Not Reflect Plant-Available Soil Silicon and Total Silicon Content of Sources.

PubMed

Keeping, Malcolm G

2017-01-01

Soils of the tropics and sub-tropics are typically acid and depleted of soluble sources of silicon (Si) due to weathering and leaching associated with high rainfall and temperatures. Together with intensive cropping, this leads to marginal or deficient plant Si levels in Si-accumulating crops such as rice and sugarcane. Although such deficiencies can be corrected with exogenous application of Si sources, there is controversy over the effectiveness of sources in relation to their total Si content, and their capacity to raise soil and plant Si concentrations. This study tested the hypothesis that the total Si content and provision of plant-available Si from six sources directly affects subsequent plant Si uptake as reflected in leaf Si concentration. Two trials with potted cane plants were established with the following Si sources as treatments: calcium silicate slag, fused magnesium (thermo) phosphate, volcanic rock dust, magnesium silicate, and granular potassium silicate. Silicon sources were applied at rates intended to achieve equivalent elemental soil Si concentrations; controls were untreated or lime-treated. Analyses were conducted to determine soil and leaf elemental concentrations. Among the sources, calcium silicate produced the highest leaf Si concentrations, yet lower plant-available soil Si concentrations than the thermophosphate. The latter, with slightly higher total Si than the slag, produced substantially greater increases in soil Si than all other products, yet did not significantly raise leaf Si above the controls. All other sources did not significantly increase soil or leaf Si concentrations, despite their high Si content. Hence, the total Si content of sources does not necessarily concur with a product's provision of soluble soil Si and subsequent plant uptake. Furthermore, even where soil pH was raised, plant uptake from thermophosphate was well below expectation, possibly due to its limited liming capacity. The ability of the calcium silicate to provide Si while simultaneously and significantly increasing soil pH, and thereby reducing reaction of Si with exchangeable Al 3+ , is proposed as a potential explanation for the greater Si uptake into the shoot from this source.

Uptake of Silicon by Sugarcane from Applied Sources May Not Reflect Plant-Available Soil Silicon and Total Silicon Content of Sources

PubMed Central

Keeping, Malcolm G.

2017-01-01

Soils of the tropics and sub-tropics are typically acid and depleted of soluble sources of silicon (Si) due to weathering and leaching associated with high rainfall and temperatures. Together with intensive cropping, this leads to marginal or deficient plant Si levels in Si-accumulating crops such as rice and sugarcane. Although such deficiencies can be corrected with exogenous application of Si sources, there is controversy over the effectiveness of sources in relation to their total Si content, and their capacity to raise soil and plant Si concentrations. This study tested the hypothesis that the total Si content and provision of plant-available Si from six sources directly affects subsequent plant Si uptake as reflected in leaf Si concentration. Two trials with potted cane plants were established with the following Si sources as treatments: calcium silicate slag, fused magnesium (thermo) phosphate, volcanic rock dust, magnesium silicate, and granular potassium silicate. Silicon sources were applied at rates intended to achieve equivalent elemental soil Si concentrations; controls were untreated or lime-treated. Analyses were conducted to determine soil and leaf elemental concentrations. Among the sources, calcium silicate produced the highest leaf Si concentrations, yet lower plant-available soil Si concentrations than the thermophosphate. The latter, with slightly higher total Si than the slag, produced substantially greater increases in soil Si than all other products, yet did not significantly raise leaf Si above the controls. All other sources did not significantly increase soil or leaf Si concentrations, despite their high Si content. Hence, the total Si content of sources does not necessarily concur with a product's provision of soluble soil Si and subsequent plant uptake. Furthermore, even where soil pH was raised, plant uptake from thermophosphate was well below expectation, possibly due to its limited liming capacity. The ability of the calcium silicate to provide Si while simultaneously and significantly increasing soil pH, and thereby reducing reaction of Si with exchangeable Al3+, is proposed as a potential explanation for the greater Si uptake into the shoot from this source. PMID:28555144

pH-controlled drug loading and release from biodegradable microcapsules.

PubMed

Zhao, Qinghe; Li, Bingyun

2008-12-01

Microcapsules made of biopolymers are of both scientific and technological interest and have many potential applications in medicine, including their use as controlled drug delivery devices. The present study makes use of the electrostatic interaction between polycations and polyanions to form a multilayered microcapsule shell and also to control the loading and release of charged drug molecules inside the microcapsule. Micron-sized calcium carbonate (CaCO3) particles were synthesized and integrated with chondroitin sulfate (CS) through a reaction between sodium carbonate and calcium nitrate tetrahydrate solutions suspended with CS macromolecules. Oppositely charged biopolymers were alternately deposited onto the synthesized particles using electrostatic layer-by-layer self-assembly, and glutaraldehyde was introduced to cross-link the multilayered shell structure. Microcapsules integrated with CS inside the multilayered shells were obtained after decomposition of the CaCO3 templates. The integration of a matrix (i.e., CS) permitted the subsequent selective control of drug loading and release. The CS-integrated microcapsules were loaded with a model drug, bovine serum albumin labeled with fluorescein isothiocyanate (FITC-BSA), and it was shown that pH was an effective means of controlling the loading and release of FITC-BSA. Such CS-integrated microcapsules may be used for controlled localized drug delivery as biodegradable devices, which have advantages in reducing systemic side effects and increasing drug efficacy.

The geologic classification of the meteorites

USGS Publications Warehouse

Elston, Donald Parker

1968-01-01

The meteorite classes of Prior and Mason are assigned to three proposed genetic groups on the basis of a combination of compositional, mineralogical, and elemental characteristics: l) the calcium-poor, volatile-rich carbonaceous chondrites and achondrites; 2) the calcium-poor, volatile-poor chondrites (enstatite, bronzite, hypersthene, and pigeonite), achondrites (enstatite, hypersthene, and pigeonite), stonyirons (pallasites, siderophyre), and irons; and, 3) the calcium-rich (basaltic) achondrites. Chondrites are correlated with calcium-poor achondrites and the silicate phase of the pallasitic meteorites on Fe contents of olivine and pyroxene; and with metal of the stony-irons and irons on the basis of trace elements (Ga and Ge). Transitions in structure and texture between the chondrites and achondrites are recognized. The Van Schmus-Wood chemical-petrologic classification of the chondrites has been modified and expanded to a mineralogic-petrologic classification of the chondrites and calcium-poor achondrites. Chondrites apparently are the first rocks of the solar system. Paragenetic and textural relations in the Murray carbonaceous chondrite shed new light on the manner of accretion, and on the character of dispersed solid materials ('dust', and chondrules and metal) that existed in the solar system before accretion. Two pre-accretionary mineral assemblages (components) are recognized in the carbonaceous chondrites and in the unequilibrated volatile-poor chondrites. They are: 1) a 'low temperature' water-, rare gas-, and carbon-bearing component; and, 2) a high temperature anhydrous silicate and metal component. Paragenetic relations indicate that component 2 materials predate chondrite formation. An accretionary assemblage (component 3) also is recognized in the carbonaceous chondrites and in the unequilibrated volatile-poor chondrites. Component 3 consists of very fine grains of olivine and pyroxene, which occur as pervasive disseminations, as small irregular aggregates of grains, and as large subround to round, finely granular accretional chondrules. Evidence in Murray indicates that component 3 silicates precipitated abruptly and at low pressures, possibly from a high temperature gas, in an environment that contained dispersed component 1 and 2 materials. All component 3 aggregates in Murray contain component 1 material, most commonly as flakes, and locally as tiny granules and larger spherules, some of which are hollow and some of which were broken prior to their mechanical incorporation in accretionary chondrules. Accretion may have occurred as ices associated with dispersed water-bearing component 1 materials temporarily melted during the precipitation of component 3 silicates, and then abruptly refroze to form an icy cementing material. Group 1 materials may be cometary, and group 2 materials may be asteroidal. Schematic models are proposed. Evidence is reviewed for the lunar origin of the pyroxeneplagioclase achondrites. On the basis of natural remanent magnetism, it is suggested that the very scarce diopside-olivine achondrites may be samples from Mars. A classification of the meteorite breccias, including the calcium-poor and calcium-rich mesosiderites, and irons that contain silicate fragments, is proposed. A fragmentation history of the meteorites is outlined on the basis of evidence in the polymict breccias, and from gas retention ages in stones and exposure ages in irons. Cometal impacts appear to have caused the initial fragmentation, stud possibly the perturbation of orbits, of two inferred asteroidal bodies (enstatite and bronzite), one and possibly both events occurring before 2000 m.y. ago. Several impacts apparently occurred on the inferred hypersthene body in the interval 1000 to 2000 m.y. ago. Major breakups of the three bodies apparently occurred as the result of interasteroidal collisions at about 900 m.y. ago, and 600 to 700 m.y. ago. The breakups were followed by a number of fr

Bonelike apatite formation on ethylene-vinyl alcohol copolymer modified with silane coupling agent and calcium silicate solutions.

PubMed

Oyane, Ayako; Kawashita, Masakazu; Nakanishi, Kazuki; Kokubo, Tadashi; Minoda, Masahiko; Miyamoto, Takeaki; Nakamura, Takashi

2003-05-01

An ethylene-vinyl alcohol copolymer (EVOH) was treated with a silane coupling agent and calcium silicate solutions, and then soaked in a simulated body fluid (SBF) with ion concentrations approximately equal to those of human blood plasma. A smooth and uniform bonelike apatite layer was successfully formed on both the EVOH plate and the EVOH-knitted fibers in SBF within 2 days. Part of the structure of the resulting apatite-EVOH fiber composite was similar to that of natural bone. If this kind of composite can be fabricated into a three-dimensional structure similar to natural bone, the resultant composite is expected to exhibit both mechanical properties analogous to those of natural bone and bone-bonding ability. Hence, it has great potential as a bone substitute. Copyright 2003 Elsevier Science Ltd.

Thermodynamics and kinetics of the sulfation of porous calcium silicate

NASA Technical Reports Server (NTRS)

Miller, R. A.; Kohl, F. J.

1981-01-01

The sulfation of plasma sprayed calcium silicate in flowing SO2/air mixtures at 900 and 1000 C was investigated thermogravimetrically. Reaction products were analyzed using electron microprobe and X-ray diffraction analysis techniques, and results were compared with thermodynamic predictions. The percentage, by volume, of SO2 in air was varied between 0.036 and 10 percent. At 10 percent SO2 the weight gain curve displays a concave downward shoulder early in the sulfation process. An analytical model was developed which treats the initial process as one which decays exponentially with increasing time and the subsequent process as one which decays exponentially with increasing weight gain. At lower SO2 levels the initial rate is controlled by the reactant flow rate. At 1100 C and 0.036 percent SO2 there is no reaction, in agreement with thermodynamic predictions.

Evaluation of nutrient equivalency of microbial phytase in hens in late lay given maize-soybean or distiller's dried grains with solubles (DDGS) diets.

PubMed

Deniz, G; Gezen, S S; Kara, C; Gencoglu, H; Meral, Y; Baser, E

2013-01-01

1. An experiment was conducted with 360 Lohmann LSL-Classic White Leghorn layers (64 weeks old) to evaluate the effects of supplementation of microbial phytase on production, egg quality, bone, selected manure parameters and feed costs. 2. Experimental diets were formulated as follows: (1) maize-soybean (CS), (2) CS+300 units of phytase (FTU)/kg diet which was formulated to recoup only calcium and available phosphorus equivalency for phytase (CS+PHYCa+P), (3) CS+300 FTU/kg diet which was formulated to recoup total nutrient equivalency for phytase (CS+PHYtotal), (4) CS+100 g/kg distiller's dried grains with solubles (DDGS), (5) DDGS+300 FTU/kg diet which was formulated to recoup only calcium and available phosphorus equivalency for phytase (DDGS+PHYCa+P), or (6) DDGS+300 FTU/kg diet which was formulated to recoup total nutrient equivalency for phytase (DDGS+PHYtotal). 3. Each dietary treatment was assigned to 4 replicate groups with 3 cages and 5 hens per cage. The hens were provided with feed and water ad libitum. The experiment lasted for 8 weeks. 4. CS+PHYCa+P, CS+PHYtotal, DDGS+PHYCa+P and DDGS+PHYtotal diets supplemented with phytase provided similar percentage egg production, egg weight, egg mass, exterior egg quality, initial and final body weight compared with phytase-free diets. 5. However, supplementation of phytase to the experimental diets and calculation of the total nutrient equivalency for enzyme caused increased feed intake and decreased feed conversion ratio and Haugh unit. 6. No differences in manure dry matter, crude ash, total nitrogen, tibia crude ash, calcium and phosphorus contents were found among the experimental diets. On the other hand, manure total phosphorus content was significantly decreased in the DDGS diet and diets supplemented with phytase in comparison to the CS diet. 7. It was concluded that the addition of microbial phytase to the CS-based diets or diets with DDGS of hens in late lay and using Ca and available P equivalency of enzyme in feed; formulation may provide an economic benefit and decrease the amount of phytate P excretion in the manure without compromising production and egg quality parameters.

Q-Speciation and Network Structure Evolution in Invert Calcium Silicate Glasses.

PubMed

Kaseman, Derrick C; Retsinas, A; Kalampounias, A G; Papatheodorou, G N; Sen, S

2015-07-02

Binary silicate glasses in the system CaO-SiO2 are synthesized over an extended composition range (42 mol % ≤ CaO ≤ 61 mol %), using container-less aerodynamic levitation techniques and CO2-laser heating. The compositional evolution of Q speciation in these glasses is quantified using (29)Si and (17)O magic angle spinning nuclear magnetic resonance spectroscopy. The results indicate progressive depolymerization of the silicate network upon addition of CaO and significant deviation of the Q speciation from the binary model. The equilibrium constants for the various Q species disproportionation reactions for these glasses are found to be similar to (much smaller than) those characteristic of Li (Mg)-silicate glasses, consistent with the corresponding trends in the field strengths of these modifier cations. Increasing CaO concentration results in an increase in the packing density and structural rigidity of these glasses and consequently in their glass transition temperature Tg. This apparent role reversal of conventional network-modifying cations in invert alkaline-earth silicate glasses are compared and contrasted with that in their alkali silicate counterparts.

Tableting properties of silica aerogel and other silicates.

PubMed

Hentzschel, C M; Alnaief, M; Smirnova, I; Sakmann, A; Leopold, C S

2012-04-01

In solid oral dosage forms silicates are commonly used as glidants in low concentration. However, due to their large specific surface area, silicates may also be used as carrier materials for drugs. Moreover, silicates allow amorphisation of drugs by co-grinding or processing with supercritical fluids. The aim of this study was to investigate the physical and the tableting properties of Silica Aerogel (special type of silica with an extremely large specific surface area), Neusilin(®) US2 (magnesium aluminometasilicate), Florite(®) (calcium silicate) and Aerosil(®) 200 (colloidal silica). Powder blends of Avicel(®) PH102 (microcrystalline cellulose) and different amounts of the respective silicate were compacted and analyzed for their tabletability (tensile strength vs. compaction pressure) as well as their Heckel plot. With Neusilin(®) the tabletability appeared to be independent of the silicate concentration, whereas with Florite(®) an increasing silicate concentration led to a higher tensile strength. In contrast, the addition of Silica Aerogel and Aerosil(®) resulted in a decrease of the tensile strength. With Aerosil(®) a maximum tolerable concentration of 20% [w/w] was determined. Plastic deformation of all powder blends decreased with increasing silicate concentration. This effect was most pronounced with Aerosil(®) and least with Florite(®). Tablets with acceptable tensile strength were obtained with all plain silicates except for Aerosil(®). Therefore, these silicates may be used in tablet formulations, e.g. as carrier materials for liquid or amorphous drugs.

Atomic Structure of a Cesium Aluminosilicate Geopolymer: A Pair Distribution Function Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bell, J.; Sarin, P; Provis, J

2008-01-01

The atomic pair distribution function (PDF) method was used to study the structure of cesium aluminosilicate geopolymer. The geopolymer was prepared by reacting metakaolin with cesium silicate solution followed by curing at 50C for 24 h in a sealed container. Heating of Cs-geopolymer above 1000C resulted in formation of crystalline pollucite (CsAlSi{sub 2}O{sub 6}). PDF refinement of the pollucite phase formed displayed an excellent fit over the 10-30 {angstrom} range when compared with a cubic pollucite model. A poorer fit was attained from 1-10 {angstrom} due to an additional amorphous phase present in the heated geopolymer. On the basis ofmore » PDF analysis, unheated Cs-geopolymer displayed structural ordering similar to pollucite up to a length scale of 9 {angstrom}, despite some differences. Our results suggest that hydrated Cs{sup +} ions were an integral part of the Cs-geopolymer structure and that most of the water present was not associated with Al-OH or Si-OH bonds.« less

A Kinetic Model for Calcium Dynamics in RAW 264.7 Cells: 1. Mechanisms, Parameters, and Subpopulational Variability

PubMed Central

Maurya, Mano Ram; Subramaniam, Shankar

2007-01-01

Calcium (Ca2+) is an important second messenger and has been the subject of numerous experimental measurements and mechanistic studies in intracellular signaling. Calcium profile can also serve as a useful cellular phenotype. Kinetic models of calcium dynamics provide quantitative insights into the calcium signaling networks. We report here the development of a complex kinetic model for calcium dynamics in RAW 264.7 cells stimulated by the C5a ligand. The model is developed using the vast number of measurements of in vivo calcium dynamics carried out in the Alliance for Cellular Signaling (AfCS) Laboratories. Ligand binding, phospholipase C-β (PLC-β) activation, inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) dynamics, and calcium exchange with mitochondria and extracellular matrix have all been incorporated into the model. The experimental data include data from both native and knockdown cell lines. Subpopulational variability in measurements is addressed by allowing nonkinetic parameters to vary across datasets. The model predicts temporal response of Ca2+ concentration for various doses of C5a under different initial conditions. The optimized parameters for IP3R dynamics are in agreement with the legacy data. Further, the half-maximal effect concentration of C5a and the predicted dose response are comparable to those seen in AfCS measurements. Sensitivity analysis shows that the model is robust to parametric perturbations. PMID:17483174

Chemical kinetics of Cs species in an alkali-activated municipal solid waste incineration fly ash and pyrophyllite-based system using Cs K-edge in situ X-ray absorption fine structure analysis

NASA Astrophysics Data System (ADS)

Shiota, Kenji; Nakamura, Takafumi; Takaoka, Masaki; Nitta, Kiyofumi; Oshita, Kazuyuki; Fujimori, Takashi; Ina, Toshiaki

2017-05-01

We conducted in situ X-ray absorption fine structure (in situ XAFS) analysis at the Cs K-edge to investigate the chemical kinetics of Cs species during reaction in an alkali-activated municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite-based system. Understanding the kinetics of Cs is essential to the design of appropriate conditions for Cs stabilization. In situ XAFS analysis of four pastes, prepared from NaOHaq, sodium silicate solution, pyrophyllite, and MSWIFA with the addition of CsCl, was conducted in custom-built reaction cells at four curing temperatures (room temperature, 60 °C, 80 °C, 105 °C) for approximately 34 h. The results indicated that the change in Cs species during reaction at room temperature was small, while changes at higher temperatures were faster and more extreme, with the fastest conversion to pollucite occurring at 105 °C. Further analysis using a leaching test and a simple reaction model for Cs species during reaction showed that the pollucite formation rate was dependent on the curing temperature and had a significant negative correlation with Cs leaching. The activation energy of pollucite formation was estimated to be 31.5 kJ/mol. These results revealed that an important change in the chemical state of Cs occurs during reaction in the system.

Stabilization of cesium in alkali-activated municipal solid waste incineration fly ash and a pyrophyllite-based system.

PubMed

Shiota, Kenji; Nakamura, Takafumi; Takaoka, Masaki; Aminuddin, Siti Fatimah; Oshita, Kazuyuki; Fujimori, Takashi

2017-11-01

Environmentally sound treatments are required to dispose of municipal solid waste incineration fly ash (MSWIFA) contaminated with radioactive cesium (Cs) from the Fukushima Daiichi nuclear power plant accident in Japan. This study focuses on the stabilization of Cs using an alkali-activated MSWIFA and pyophyllite-based system. Three composite solid products were synthesized after mixtures of raw materials (dehydrated pyrophyllite, MSWIFA, 14 mol/L aqueous sodium hydroxide, and sodium silicate solution) were cured at 105 °C for 24 h. Three types of MSWIFAs were prepared as raw fly ash, raw fly ash with 0.1% CsCl, and raw fly ash with 40% CsCl to understand the stabilization mechanism of Cs. Cs stabilization in two solid products was successful, with less than 6.9% leaching observed from two types tests, and was partly successful for the solid product with the highest concentration of Cs. X-ray diffraction showed that all of the solid products produced several crystalline phases, and that pollucite was formed in the highest Cs concentration product. The X-ray absorption fine structure and scanning electron microscopy with X-ray analysis suggested that most Cs species formed pollucite in the two solid products from MSWIFA with added CsCl. This system provides a technique for the direct stabilization of Cs in MSWIFA. Copyright © 2017 Elsevier Ltd. All rights reserved.

Early Age Carbonation Heat and Products of Tricalcium Silicate Paste Subject to Carbon Dioxide Curing.

PubMed

Li, Zhen; He, Zhen; Shao, Yixin

2018-05-04

This paper presents a study on the carbonation reaction heat and products of tricalcium silicate (C₃S) paste exposed to carbon dioxide (CO₂) for rapid curing. Reaction heat was measured using a retrofitted micro-calorimeter. The highest heat flow of a C₃S paste subject to carbonation curing was 200 times higher than that by hydration, and the cumulative heat released by carbonation was three times higher. The compressive strength of a C₃S paste carbonated for 2 h and 24 h was 27.5 MPa and 62.9 MPa, respectively. The 24-h carbonation strength had exceeded the hydration strength at 28 days. The CO₂ uptake of a C₃S paste carbonated for 2 h and 24 h was 17% and 26%, respectively. The X-ray diffraction (XRD), transmission electron microscope coupled with energy dispersive spectrometer (TEM-EDS), and 29 Si magic angle spinning⁻nuclear magnetic resonance ( 29 Si MAS-NMR) results showed that the products of a carbonated C₃S paste were amorphous silica (SiO₂) and calcite crystal. There was no trace of calcium silicate hydrate (C⁻S⁻H) or other polymorphs of calcium carbonate (CaCO₃) detected.

Composition characteristics and regularities of dissolving of hydroxyapatite materials obtained in water solutions with varied content of silicate ions

NASA Astrophysics Data System (ADS)

Solonenko, A. P.

2018-01-01

Research aimed at developing new bioactive materials for the repair of defects in bone tissues, do not lose relevance due to the strengthening of the regenerative approach in medicine. From this point of view, materials based on calcium phosphates, including silicate ions, consider as one of the most promising group of substances. Methods of synthesis and properties of hydroxyapatite doped with various amounts of SiO4 4- ions are described in literature. In the present work synthesis of a solid phase in the systems Ca(NO3)2 - (NH4)2HPO4 - Na2SiO3 - NH4OH - H2O (Cca/CP = 1.70) performed with a wide range of sodium silicate additive concentration (y = CSi/CP = 0 ÷ 5). It is established that under the studied conditions at y ≥ 0.3 highly dispersed poorly crystallized apatite containing isomorphic impurities of CO3 2- and SiO4 4- precipitates in a mixture with calcium hydrosilicate and SiO2. It is shown that the resulting composites can gradually dissolve in physiological solution and initiate passive formation of the mineral component of hard tissues.

Developing a novel magnesium glycerophosphate/silicate-based organic-inorganic composite cement for bone repair.

PubMed

Ding, Zhengwen; Li, Hong; Wei, Jie; Li, Ruijiang; Yan, Yonggang

2018-06-01

Considering that the phospholipids and glycerophosphoric acid are the basic materials throughout the metabolism of the whole life period and the bone is composed of organic polymer collagen and inorganic mineral apatite, a novel self-setting composite of magnesium glycerophosphate (MG) and di-calcium silicate(C2S)/tri-calcium silicate(C3S) was developed as bio-cement for bone repair, reconstruction and regeneration. The composite was prepared by mixing the MG, C2S and C3S with the certain ratios, and using the deionized water and phosphoric acid solution as mixed liquid. The combination and formation of the composites was characterized by FTIR, XPS and XRD. The physicochemical properties were studied by setting time, compressive strength, pH value, weight loss in the PBS and surface change by SEM-EDX. The biocompatibility was evaluated by cell culture in the leaching solution of the composites. The preliminary results showed that when di- and tri-calcium silicate contact with water, there are lots of Ca(OH) 2 generated making the pH value of solution is higher than 9 which is helpful for the formation of hydroxyapatite(HA) that is the main bone material. The new organic-inorganic self-setting bio-cements showed initial setting time is ranged from 20 min to 85 min and the compressive strength reached 30 MPa on the 7th days, suitable as the bone fillers. The weight loss was 20% in the first week, and 25% in the 4th week. Meanwhile, the new HA precipitated on the composite surface during the incubation in the SBF showed bioactivity. The cell cultured in the leaching liquid of the composite showed high proliferation inferring the new bio-cement has good biocompatibility to the cells. Copyright © 2018 Elsevier B.V. All rights reserved.

A study of the formation of amorphous calcium phosphate and hydroxyapatite on melt quenched Bioglass using surface sensitive shallow angle X-ray diffraction.

PubMed

Martin, R A; Twyman, H; Qiu, D; Knowles, J C; Newport, R J

2009-04-01

Melt quenched silicate glasses containing calcium, phosphorous and alkali metals have the ability to promote bone regeneration and to fuse to living bone. These glasses, including 45S5 Bioglass((R)) [(CaO)(26.9)(Na(2)O)(24.4)(SiO(2))(46.1)(P(2)O(5))(2.6)], are routinely used as clinical implants. Consequently there have been numerous studies on the structure of these glasses using conventional diffraction techniques. These studies have provided important information on the atomic structure of Bioglass((R)) but are of course intrinsically limited in the sense that they probe the bulk material and cannot be as sensitive to thin layers of near-surface dissolution/growth. The present study therefore uses surface sensitive shallow angle X-ray diffraction to study the formation of amorphous calcium phosphate and hydroxyapatite on Bioglass((R)) samples, pre-reacted in simulated body fluid (SBF). Unreacted Bioglass((R)) is dominated by a broad amorphous feature around 2.2 A(-1) which is characteristic of sodium calcium silicate glass. After reacting Bioglass((R)) in SBF a second broad amorphous feature evolves ~1.6 A(-1) which is attributed to amorphous calcium phosphate. This feature is evident for samples after only 4 h reacting in SBF and by 8 h the amorphous feature becomes comparable in magnitude to the background signal of the bulk Bioglass((R)). Bragg peaks characteristic of hydroxyapatite form after 1-3 days of reacting in SBF.

Method for scavenging mercury

DOEpatents

Chang, Shih-ger [El Cerrito, CA; Liu, Shou-heng [Kaohsiung, TW; Liu, Zhao-rong [Beijing, CN; Yan, Naiqiang [Berkeley, CA

2009-01-20

Disclosed herein is a method for removing mercury from a gas stream comprising contacting the gas stream with a getter composition comprising bromine, bromochloride, sulphur bromide, sulphur dichloride or sulphur monochloride and mixtures thereof. In one preferred embodiment the getter composition is adsorbed onto a sorbent. The sorbent may be selected from the group consisting of flyash, limestone, lime, calcium sulphate, calcium sulfite, activated carbon, charcoal, silicate, alumina and mixtures thereof. Preferred is flyash, activated carbon and silica.

Method for scavenging mercury

DOEpatents

Chang, Shih-Ger [El Cerrito, CA; Liu, Shou-Heng [Kaohsiung, TW; Liu, Zhao-Rong [Beijing, CN; Yan, Naiqiang [Berkeley, CA

2011-08-30

Disclosed herein is a method for removing mercury from a gas stream comprising contacting the gas stream with a getter composition comprising bromine, bromochloride, sulphur bromide, sulphur dichloride or sulphur monochloride and mixtures thereof. In one preferred embodiment the getter composition is adsorbed onto a sorbent. The sorbent may be selected from the group consisting of flyash, limestone, lime, calcium sulphate, calcium sulfite, activated carbon, charcoal, silicate, alumina and mixtures thereof. Preferred is flyash, activated carbon and silica.

Method for scavenging mercury

DOEpatents

Chang, Shih-ger; Liu, Shou-heng; Liu, Zhao-rong; Yan, Naiqiang

2010-07-13

Disclosed herein is a method for removing mercury from a gas stream comprising contacting the gas stream with a getter composition comprising bromine, bromochloride, sulphur bromide, sulphur dichloride or sulphur monochloride and mixtures thereof. In one preferred embodiment the getter composition is adsorbed onto a sorbent. The sorbent may be selected from the group consisting flyash, limestone, lime, calcium sulphate, calcium sulfite, activated carbon, charcoal, silicate, alumina and mixtures thereof. Preferred is flyash, activated carbon and silica.

Concept Study for Military Port Design Using Natural Processes.

DTIC Science & Technology

1982-06-15

exchange methods are so good in this ocean heat sink with its diffused materials because it uses its chemicals to attach the ions and then to make acids...H.L., "Saturation State of Calcium Carbonate in Seawater and its Possible Significance for Scale Formation on OTEC Heat Exchanger ," Abstract...Which Harvest Calcium and Magnesium as Structural Materials E. Forming Structures from Silicates After Ion Exchanging , Using Hot and Cold Forming

Optical characteristics of novel bulk and nanoengineered laser host materials

NASA Astrophysics Data System (ADS)

Prasad, Narasimha S.; Sova, Stacey; Kelly, Lisa; Bevan, Talon; Arnold, Bradley; Cooper, Christopher; Choa, Fow-Sen; Singh, N. B.

2018-02-01

The hexagonal apatite single crystals have been investigated for their applications as laser host materials. Czochralksi and flux growth methods have been utilized to obtain single crystals. For low temperature processing (<100 0C), several techniques for crystal growth have been developed. The hexagonal apatite structure (space group P63/m) is characteristic of several compounds, some of which have extremely interesting and useful properties as laser hosts and bone materials. Calcium lanthanum silicate (Nd-doped) and lanthanum aluminate material systems were studied in detail. Nanoengineered calcium and lanthanum based silicates were synthesized by a solution method and their optical and morphological characteristics were compared with Czochralski grown bulk hydroxyapatite single crystals. Materials were evaluated by absorbance, fluorescence and Raman characteristics. Neodymium, iron and chromium doped crystals grown by a solution method showed weak but similar optical properties to that of Czochralski grown single crystals.

Calcium silicate-based cements: composition, properties, and clinical applications.

PubMed

Dawood, Alaa E; Parashos, Peter; Wong, Rebecca H K; Reynolds, Eric C; Manton, David J

2017-05-01

Mineral trioxide aggregate (MTA) is a calcium silicate-based cement (CSC) commonly used in endodontic procedures involving pulpal regeneration and hard tissue repair, such as pulp capping, pulpotomy, apexogenesis, apexification, perforation repair, and root-end filling. Despite the superior laboratory and clinical performance of MTA in comparison with previous endodontic repair cements, such as Ca(OH) 2 , MTA has poor handling properties and a long setting time. New CSC have been commercially launched and marketed to overcome the limitations of MTA. The aim of the present review was to explore the available literature on new CSC products, and to give evidence-based recommendations for the clinical use of these materials. Within the limitations of the available data in the literature regarding the properties and performance of the new CSC, the newer products could be promising alternatives to MTA; however, further research is required to support this assumption. © 2015 Wiley Publishing Asia Pty Ltd.

Docking 90Sr radionuclide in cement: An atomistic modeling study

NASA Astrophysics Data System (ADS)

Youssef, Mostafa; Pellenq, Roland J.-M.; Yildiz, Bilge

Cementitious materials are considered to be a waste form for the ultimate disposal of radioactive materials in geological repositories. We investigated by means of atomistic simulations the encapsulation of strontium-90, an important radionuclide, in calcium-silicate-hydrate (C-S-H) and its crystalline analog, the 9 Å-tobermorite. C-S-H is the major binding phase of cement. Strontium was shown to energetically favor substituting calcium in the interlayer sites in C-S-H and 9 Å-tobermorite with the trend more pronounced in the latter. The integrity of the silicate chains in both cementitious waste forms were not affected by strontium substitution within the time span of molecular dynamics simulation. Finally, we observed a limited degradation of the mechanical properties in the strontium-containing cementitious waste form with the increasing strontium concentration. These results suggest the cement hydrate as a good candidate for immobilizing radioactive strontium.

Biodentine™ material characteristics and clinical applications: a 3 year literature review and update.

PubMed

Rajasekharan, S; Martens, L C; Cauwels, R G E C; Anthonappa, R P; Verbeeck, R M H

2018-02-01

Biodentine™ has frequently been acknowledged in the literature as a promising material and serves as an important representative of tricalcium silicate based cements used in dentistry. To provide an update on the physical and biological properties of Biodentine™ and to compare these properties with those of other tricalcium silicate cements namely, different variants of mineral trioxide aggregate (MTA) such as ProRoot MTA, MTA Angelus, Micro Mega MTA (MM-MTA), Retro MTA, Ortho MTA, MTA Plus, GCMTA, MTA HP and calcium enriched mixture (CEM), Endosequence and Bioaggregate™. A comprehensive literature search for publications from November 20, 2013 to November 20, 2016 was performed by two independent reviewers on Medline (PubMed), Embase, Web of Science, CENTRAL (Cochrane), SIGLE, SciELO, Scopus, Lilacs and clinicaltrials.gov. Electronic and hand search was carried out to identify randomised control trials (RCTs), case control studies, case series, case reports, as well as in vitro and animal studies published in the English language. The enhanced physical and biologic properties of Biodentine™ could be attributed to the presence of finer particle size, use of zirconium oxide as radiopacifier, purity of tricalcium silicate, absence of dicalcium silicate, and the addition of calcium chloride and hydrosoluble polymer. Furthermore, as Biodentine™ overcomes the major drawbacks of MTA it has great potential to revolutionise the different treatment modalities in paediatric dentistry and endodontics especially after traumatic injuries. Nevertheless, high quality long-term clinical studies are required to facilitate definitive conclusions.

Source apportionment of aerosol particles near a steel plant by electron microscopy.

PubMed

Ebert, Martin; Müller-Ebert, Dörthe; Benker, Nathalie; Weinbruch, Stephan

2012-12-01

The size, morphology and chemical composition of 37,715 individual particles collected over 22 sampling days in the vicinity of a large integrated steel production were studied by scanning and transmission electron microscopy. Based on the morphology, chemistry and beam stability the particles were classified into the following fourteen groups: silicates, sea salt, calcium sulfates, calcium carbonates, carbonate-silicate mixtures, sulfate-silicate mixtures, iron oxides, iron mixtures, metal oxide-metals, complex secondary particles, soot, Cl-rich particles, P-rich particles, and other particles. The majority of iron oxide (≈85%) and metal oxide-metal (≈70%) particles as well as ≈20% of the silicate particles are fly ashes from high temperature processes. The emissions from the steel work are dominated by iron oxide particles. For source apportionment, seven source categories and two sectors of local wind direction (industrial and urban background) were distinguished. In both sectors PM₁₀ consists of four major source categories: 35% secondary, 20% industrial, 17% soil and 16% soot in the urban background sector compared to 45% industrial, 20% secondary, 13% soil, and 9% soot in the industrial sector. As the secondary and the soot components are higher in the urban background sector than in the industrial sector, it is concluded that both components predominantly originate from urban background sources (traffic, coal burning, and domestic heating). Abatement measures should not only focus on the steel work but should also include the urban background aerosol.

Localization of cesium on montmorillonite surface investigated by frequency modulation atomic force microscopy

NASA Astrophysics Data System (ADS)

Araki, Yuki; Satoh, Hisao; Okumura, Masahiko; Onishi, Hiroshi

2017-11-01

Cation exchange of clay mineral is typically analyzed without microscopic study of the clay surfaces. In order to reveal the distribution of exchangeable cations at the clay surface, we performed in situ atomic-scale observations of the surface changes in Na-rich montmorillonite due to exchange with Cs cations using frequency modulation atomic force microscopy (FM-AFM). Lines of protrusion were observed on the surface in aqueous CsCl solution. The amount of Cs of the montmorillonite particles analyzed by energy dispersive X-ray spectrometry was consistent with the ratio of the number of linear protrusions to all protrusions in the FM-AFM images. The results showed that the protrusions represent adsorbed Cs cations. The images indicated that Cs cations at the surface were immobile, and their occupancy remained constant at 10% of the cation sites at the surface with different immersion times in the CsCl solution. This suggests that the mobility and the number of Cs cations at the surface are controlled by the permanent charge of montmorillonite; however, the Cs distribution at the surface is independent of the charge distribution of the inner silicate layer. Our atomic-scale observations demonstrate that surface cations are distributed in different ways in montmorillonite and mica.

Effects of dietary supplementation of arginine-silicate-inositol complex on absorption and metabolism of calcium of laying hens

PubMed Central

Orhan, Cemal; Tuzcu, Mehmet; Hayirli, Armagan; Komorowski, James R.; Sahin, Nurhan

2018-01-01

The effects of supplementation of arginine-silicate-inositol complex (ASI; 49.5–8.2–25 g/kg, respectively) to laying hens were investigated with respect to eggshell quality, calcium (Ca) balance, and expression of duodenal proteins related to Ca metabolism (calbindin and tight junction proteins). A total of 360 laying hens, 25 weeks old, were divided into 3 groups consisting of 6 replicate of cages, 20 birds per cage. The groups were fed a basal diet and the basal diet supplemented with 500 or 1000 mg ASI complex per kilogram for 90 days. Data were analyzed by ANCOVA using data during the first week of the adaptation period as covariates. As the ASI complex supplementation level increased, there were increases in feed intake (P < 0.0001), egg production (P < 0.001), egg weight (P < 0.0001) and eggshell weight (P < 0.001) weight, and shell thickness (P < 0.001) and decreases in feed conversion ratio and cracked egg percentage (P < 0.0001 for both). Concentrations of serum osteocalcin (P < 0.0001), vitamin D (P < 0.0001), calcium (P < 0.001), phosphorus (P < 0.001), and alkaline phosphatase (P < 0.008) as well as amounts of calcium retention (P < 0.0001) and eggshell calcium deposition (P < 0.001), and Ca balance (P < 0.0001) increased, whereas amount of calcium excretion (P < 0.001) decreased linearly in a dose-dependent manner. The ASI complex supplementation increased expressions of calcium transporters (calbindin-D28k, N sodium-calcium exchanger, plasma membrane calcium ATPase, and vitamin D receptor) and tight junction proteins (zonula occludens-1 and occludin) in the duodenum in a linear fashion (P < 0.0001 for all). In conclusion, provision of dietary ASI complex to laying hens during the peak laying period improved eggshell quality through improving calcium utilization as reflected by upregulation of genes related to the calcium metabolism. Further studies are needed to elucidate the contribution of each of the ASI complex ingredients. PMID:29360830

Preparation and evaluation of squid ink polysaccharide-chitosan as a wound-healing sponge.

PubMed

Huang, Na; Lin, Jiali; Li, Sidong; Deng, Yifeng; Kong, Songzhi; Hong, Pengzhi; Yang, Ping; Liao, Mingneng; Hu, Zhang

2018-01-01

A new type of wound healing agent was developed using two marine biomaterials (squid ink polysaccharide and chitosan) as carriers and calcium chloride as an initiator for coagulation. Based on central composite design-response surface methodology, comprehensive evaluation of appearance quality for composite sponges and water absorbency were used as evaluation indices to identify the optimized preparation conditions and further evaluate the performance of the squid ink polysaccharide-chitosan sponge (SIP-CS). The optimized formulation of SIP-CS was as follows: chitosan concentration, 2.29%; squid ink polysaccharide concentration, 0.55%; and calcium chloride concentration, 2.82%, at a volume ratio of 15:5:2. SIP-CS was conducive to sticking on the wound, characterized by the spongy property, strong absorptivity, and tackiness. Rabbit ear arterial, hepatic, and femoral artery hemorrhage experiments indicated that, compared with chitosan dressings and absorbable gelatin, the hemostatic times were shorter and the bleeding volume was smaller. Furthermore, SIP-CS absorbed a large amount of hemocytes, leading to rapid hemostasis. The healing areas and wound pathological sections in scalded New Zealand rabbits indicated that SIP-CS promoted wound healing more rapidly than chitosan and better than commercially available burn cream. Thus, SIP-CS is a good wound healing agent for rapid hemostasis, promoting burn/scalded skin healing, and protecting from wound infection. Copyright © 2017 Elsevier B.V. All rights reserved.

Material transport in laser-heated diamond anvil cell melting experiments

NASA Technical Reports Server (NTRS)

Campbell, Andrew J.; Heinz, Dion L.; Davis, Andrew M.

1992-01-01

A previously undocumented effect in the laser-heated diamond anvil cell, namely, the transport of molten species through the sample chamber, over distances large compared to the laser beam diameter, is presented. This effect is exploited to determine the melting behavior of high-pressure silicate assemblages of olivine composition. At pressures where beta-spinel is the phase melted, relative strengths of partitioning can be estimated for the incompatible elements studied. Iron was found to partition into the melt from beta-spinel less strongly than calcium, and slightly more strongly than manganese. At higher pressures, where a silicate perovskite/magnesiowuestite assemblage is melted, it is determined that silicate perovskite is the liquidus phase, with iron-rich magnesiowuestite accumulating at the end of the laser-melted stripe.

In vitro effects of two silicate-based materials, Biodentine and BioRoot RCS, on dental pulp stem cells in models of reactionary and reparative dentinogenesis

PubMed Central

Loison-Robert, Ludwig Stanislas; Berbar, Tsouria; Isaac, Juliane; Berdal, Ariane; Simon, Stéphane

2018-01-01

Background Calcium silicate-based cements are biomaterials with calcium oxide and carbonate filler additives. Their properties are close to those of dentin, making them useful in restorative dentistry and endodontics. The aim of this study was to evaluate the in vitro biological effects of two such calcium silicate cements, Biodentine (BD) and Bioroot (BR), on dental stem cells in both direct and indirect contact models. The two models used aimed to mimic reparative dentin formation (direct contact) and reactionary dentin formation (indirect contact). An original aspect of this study is the use of an interposed thin agarose gel layer to assess the effects of diffusible components from the materials. Results The two biomaterials were compared and did not modify dental pulp stem cell (DPSC) proliferation. BD and BR showed no significant cytotoxicity, although some cell death occurred in direct contact. No apoptosis or inflammation induction was detected. A striking increase of mineralization induction was observed in the presence of BD and BR, and this effect was greater in direct contact. Surprisingly, biomineralization occurred even in the absence of mineralization medium. This differentiation was accompanied by expression of odontoblast-associated genes. Exposure by indirect contact did not stimulate the induction to such a level. Conclusion These two biomaterials both seem to be bioactive and biocompatible, preserving DPSC proliferation, migration and adhesion. The observed strong mineralization induction through direct contact highlights the potential of these biomaterials for clinical application in dentin-pulp complex regeneration. PMID:29370163

Effect of the calcium silicate-based sealer removal protocols and time-point of acid etching on the dentin adhesive interface.

PubMed

Morais, Jéssika Mayhara Pereira; Victorino, Keli Regina; Escalante-Otárola, Wilfredo Gustavo; Jordão-Basso, Keren Cristina Fagundes; Palma-Dibb, Regina Guenka; Kuga, Milton Carlos

2018-06-15

The aim of the study was to evaluate the effects when acid etching on the dentin surface was immediately performed (I) or 7 days (D) after calcium silicate-based sealer (MTA Fillapex) removal, using 95% ethanol (E) or xylol (X). First study, 60 bovine incisor dentin specimens were impregnated with sealer and divided into six groups (n = 10): (EI), E + I; (XI), X + I; (ED), E + D; (XD), X + D, (UN), untreated and (MR), mechanical removal of sealer. Scanning electron microscopy (SEM) images (500×) were obtained from each specimen and scores assessed the sealer residues persistence. Second study, 60 specimens were similarly treated; however, the specimens were restored with composite resin after the removal protocols. Hybrid layer formation was evaluated using confocal laser microscopy (1,024×). Third study, 60 specimens were similarly obtained and subjected to micro-shear test to evaluate the effects of removal protocols on the bond strength of etch-and- rinse adhesive system to dentin. XI showed the highest persistence of sealer residues (p < .05), similar to MR (p > .05). EI showed the greatest hybrid layer extension, except in relation to UN (p < .05). XI and MR presented the lowest bond strength adhesive system to dentin (p < .05). Acid etching immediately after calcium silicate-based endodontic sealer removal using xylol presented the highest residues persistence and negatively affected the adhesive interface between dentin and etch-and-rinse adhesive system. © 2018 Wiley Periodicals, Inc.

Thermodynamics and Kinetics of Boron Removal from Metallurgical Grade Silicon by Addition of High Basic Potassium Carbonate to Calcium Silicate Slag

NASA Astrophysics Data System (ADS)

Wu, Jijun; Wang, Fanmao; Ma, Wenhui; Lei, Yun; Yang, Bin

2016-06-01

In this study, we investigated the thermodynamics and kinetics of boron removal from metallurgical grade silicon (MG-Si) using a calcium silicate slag containing a high basic potassium carbonate. The distribution of boron between slag and silicon was theoretically derived and the distribution coefficients ( L B) of boron with different compositions of CaO, SiO2, and K2CO3 in slag reagents were determined. The maximal value of L B reached 2.08 with a high basicity slag of 40 pctCaO-40 pctSiO2-20 pctK2CO3 (Λ = 0.73). The boron removal rates from MG-Si using CaO-SiO2 and CaO-SiO2-K2CO3 slags at 1823 K (1550 °C) were investigated in an electromagnetic induction furnace. The results showed that the boron concentration in MG-Si can be reduced from 22 to 1.8 ppmw at 1823 K (1550 °C) with 20 pct K2CO3 addition to calcium silicate slag, where the removal efficiency of boron reached 91.8 pct. The mass transfer coefficient ( β S) of boron in binary 50 pctCaO-50 pctSiO2 slag was 3.16 × 10-6 m s-1 at 1823 K (1550 °C) and was 2.43 × 10-5 m s-1 in ternary 40 pctCaO-40 pctSiO2-20 pctK2CO3 slag.

Transformation of silicate gels during heat treatment in air and in argon - Spectroscopic studies

NASA Astrophysics Data System (ADS)

Rokita, M.; Mozgawa, W.; Adamczyk, A.

2014-07-01

The sol-gel method offers the possibility of obtaining silicate materials with different chemical compositions. When using TEOS or other organic precursor to silica capable of hydrolysis and poly-condensation, it is possible to use inorganic or organic precursors to produce other ingredients. This paper presents results of studying two series of silicate sols with the addition of calcium, in which the molar ratio of calcium to silicon was Ca/Si = x/(100 - x), where x was, respectively, 0-40 (x = 0-control sample). The resulting gels were subjected to heat treatment, wherein the heating was carried out simultaneously in air or in argon. To study the various stages of transformation of the gels, IR spectroscopy was used as the main research method to observe gradual disappearance of bands associated with bonds typical of organic materials and formation of bands characteristic of Si-O-Si bridging bonds. Due to the amorphous or fine crystalline nature of the resulting material, as confirmed in XRD studies, the different bands on the IR spectra were characterized by large full width at half maximum, hence an attempt was made to decompose the spectra into component bands. The analytic parameters of the resulting bands warranted the conclusion that there had been structural changes caused by the varying synthesis parameters. A comparison of the sol spectra after heat treatment in air and in argon at different temperatures showed a clear decrease in the full width at half maximum in the case of bands of samples with calcium content x ⩾ 30. The resulting spectra were compared with spectra of crystalline tobermorite, quartz and pseudowollastonite, which suggested the possibility of existence of areas with quartz-like ordering in the case of materials with calcium content x ⩾ 20 for the samples heated in argon and areas with pseudowollastonite-like ordering in the case of materials with calcium content x ⩾ 10 for the samples heated in air atmosphere. The conclusions drawn on the basis of infrared spectra were confirmed by XRD - prolonged heating of gels at 700 °C allowed us to obtain fine quartz and pseudowollastonite.

New high-capacity, calcium-based sorbents, calcium silicate sorbents. Final report, 1993--August 31, 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenney, M.C.; Chiang, R.K.; Fillgrove, K.L.

1995-02-01

A search is being carried out for new calcium-based S0{sub 2} sorbents for induct injection. More specifically, a search is being carried out for induct injection calcium silicate sorbents that are highly cost effective. The objectives for the current year include the study of sorbents made from Ca(OH){sub 2}, from mixtures of Ca(OH){sub 2} and SiO{sub 2}, and from portland cement. They also include the study of sorbents made from model compounds. During this year, sorbents prepared from Ca(OH){sub 2} and from mixtures of Ca(OH){sub 2} and fumed SiO{sub 2} were investigated. The results show that very good SiO{sub 2}-modifiedmore » Ca(OH){sub 2} sorbents in which the Si-to-Ca reactant ratio is low can be prepared from Ca(OH){sub 2} and fumed SiO{sub 2}. Sorbents prepared from Ca(OH){sub 2} and natural SiO{sub 2} or natural SiO{sub 2} sources were also studied. The results obtained show that very good SiO{sub 2}-modified Ca(OH){sub 2} sorbents and calcium silicate hydrate sorbents, C-S-H sorbents, can be prepared from Ca(OH){sub 2} and diatomite, pumice or perlite, minerals that are readily available. In addition. sorbents prepared from Ca{sub 3}SiO{sub 5} and {beta}-Ca{sub 2}SiO{sub 4} and from mixtures of these compounds and SiO{sub 2} were studied. The results secured demonstrate that very good C-S-H rich sorbents can be prepared from these compounds and from mixtures of them with SiO{sub 2}. They also provide information useful for interpreting the cement sorbent results. Sorbents prepared from cement and from mixtures of cement and natural SiO{sub 2} or SiO{sub 2} sources were investigated as well. The results secured show that cement and mixtures of it with diatomite, pumice or perlite rapidly yield excellent sorbents with the proper reaction conditions.« less

Identification of a novel cyclosporin-sensitive element in the human tumor necrosis factor alpha gene promoter

PubMed Central

1993-01-01

Tumor necrosis factor alpha (TNF-alpha), a cytokine with pleiotropic biological effects, is produced by a variety of cell types in response to induction by diverse stimuli. In this paper, TNF-alpha mRNA is shown to be highly induced in a murine T cell clone by stimulation with T cell receptor (TCR) ligands or by calcium ionophores alone. Induction is rapid, does not require de novo protein synthesis, and is completely blocked by the immunosuppressant cyclosporin A (CsA). We have identified a human TNF-alpha promoter element, kappa 3, which plays a key role in the calcium-mediated inducibility and CsA sensitivity of the gene. In electrophoretic mobility shift assays, an oligonucleotide containing kappa 3 forms two DNA protein complexes with proteins that are present in extracts from unstimulated T cells. These complexes appear in nuclear extracts only after T cell stimulation. Induction of the inducible nuclear complexes is rapid, independent of protein synthesis, and blocked by CsA, and thus, exactly parallels the induction of TNF-alpha mRNA by TCR ligands or by calcium ionophore. Our studies indicate that the kappa 3 binding factor resembles the preexisting component of nuclear factor of activated T cells. Thus, the TNF-alpha gene is an immediate early gene in activated T cells and provides a new model system in which to study CsA-sensitive gene induction in activated T cells. PMID:8376940

Liposomes coated with thiolated chitosan enhance oral peptide delivery to rats.

PubMed

Gradauer, K; Barthelmes, J; Vonach, C; Almer, G; Mangge, H; Teubl, B; Roblegg, E; Dünnhaupt, S; Fröhlich, E; Bernkop-Schnürch, A; Prassl, R

2013-12-28

The aim of the present study was the in vivo evaluation of thiomer-coated liposomes for an oral application of peptides. For this purpose, salmon calcitonin was chosen as a model drug and encapsulated within liposomes. Subsequently, the drug loaded liposomes were coated with either chitosan-thioglycolic acid (CS-TGA) or an S-protected version of the same polymer (CS-TGA-MNA), leading to an increase in the particle size of about 500 nm and an increase in the zeta potential from approximately -40 mV to a maximum value of about +44 mV, depending on the polymer. Coated liposomes were demonstrated to effectively penetrate the intestinal mucus layer where they came in close contact with the underlying epithelium. To investigate the permeation enhancing properties of the coated liposomes ex vivo, we monitored the transport of fluoresceinisothiocyanate-labeled salmon calcitonin (FITC-sCT) through rat small intestine. Liposomes coated with CS-TGA-MNA showed the highest effect, leading to a 3.8-fold increase in the uptake of FITC-sCT versus the buffer control. In vivo evaluation of the different formulations was carried out by the oral application of 40 μg of sCT per rat, either encapsulated within uncoated liposomes, CS-TGA-coated liposomes or CS-TGA-MNA-coated liposomes, or given as a solution serving as negative control. The blood calcium level was monitored over a time period of 24h. The highest reduction in the blood calcium level, to a minimum of 65% of the initial value after 6h, was achieved for CS-TGA-MNA-coated liposomes. Comparing the areas above curves (AAC) of the blood calcium levels, CS-TGA-MNA-coated liposomes led to an 8.2-fold increase compared to the free sCT solution if applied orally in the same concentration. According to these results, liposomes coated with S-protected thiomers have demonstrated to be highly valuable carriers for enhancing the oral bioavailability of salmon calcitonin. © 2013. Published by Elsevier B.V. All rights reserved.

Mode of action studies on the formation of enamel minerals from a novel toothpaste containing calcium silicate and sodium phosphate salts.

PubMed

Sun, Yuekui; Li, Xiaoke; Deng, Yan; Sun, Jianing N; Tao, DanYing; Chen, Hui; Hu, Qinghong; Liu, Renjiang; Liu, Weining; Feng, Xiping; Wang, Jinfang; Carvell, Mel; Joiner, Andrew

2014-06-01

To investigate in vitro and in situ the deposition and formation of hydroxyapatite (HAP) on enamel surfaces following brushing with a novel toothpaste containing calcium silicate (CaSi), sodium phosphate salts and fluoride. Polished enamel blocks were brushed in vitro with a slurry of the CaSi toothpaste. After one brush and four weeks simulated brushing the enamel surfaces were analysed. In an in situ protocol, enamel blocks were attached to first or second molar teeth of healthy subjects, exposed to 4 weeks twice per day brushing with the CaSi toothpaste and then analysed. The surface deposits were analysed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). In addition, the CaSi toothpaste was slurried in simulated oral fluid (SOF) over a 3 hour period and the solids were isolated and analysed by Fourier transform infrared spectroscopy (FTIR). The FTIR study demonstrated that calcium phosphate phases had formed and these became increasingly crystalline over 3 hours. CaSi was deposited onto enamel surfaces following one brushing with the toothpaste in vitro.The deposited particles showed evidence of HAP crystalline phases associated with the CaSi. Following 4 weeks brushing in vitro, the deposition increased and analyses showed that the deposited material was HAP. These results were confirmed by the in situ study. Calcium silicate can be deposited onto enamel surfaces from a novel toothpaste formulation where it can form the enamel mineral HAP. A novel toothpaste formulation containing CaSi can form HAP on enamel surfaces. The potential of this technology is for a novel approach to the repair of demineralised enamel and the protection of enamel during acid exposure. © 2014 Elsevier Ltd. All rights reserved.

Intrinsic differences in atomic ordering of calcium (alumino)silicate hydrates in conventional and alkali-activated cements

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Claire E., E-mail: whitece@princeton.edu; Andlinger Center for Energy and the Environment, Princeton University, Princeton; Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos

2015-01-15

The atomic structures of calcium silicate hydrate (C–S–H) and calcium (–sodium) aluminosilicate hydrate (C–(N)–A–S–H) gels, and their presence in conventional and blended cement systems, have been the topic of significant debate over recent decades. Previous investigations have revealed that synthetic C–S–H gel is nanocrystalline and due to the chemical similarities between ordinary Portland cement (OPC)-based systems and low-CO{sub 2} alkali-activated slags, researchers have inferred that the atomic ordering in alkali-activated slag is the same as in OPC–slag cements. Here, X-ray total scattering is used to determine the local bonding environment and nanostructure of C(–A)–S–H gels present in hydrated tricalcium silicatemore » (C{sub 3}S), blended C{sub 3}S–slag and alkali-activated slag, revealing the large intrinsic differences in the extent of nanoscale ordering between C–S–H derived from C{sub 3}S and alkali-activated slag systems, which may have a significant influence on thermodynamic stability, and material properties at higher length scales, including long term durability of alkali-activated cements.« less

Rietveld refinement of the crystal structures of Rb2 XSi5O12 (X = Ni, Mn).

PubMed

Bell, Anthony M T; Henderson, C Michael B

2016-02-01

The synthetic leucite silicate framework mineral analogues Rb2 XSi5O12 {X = Ni [dirubidium nickel(II) penta-silicate] and Mn [dirubidium manganese(II) penta-silicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu Kα X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetra-hedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework. Extraframework Rb(+) cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetra-hedrally coordinated sites (T-sites). However, the Ni displacement parameter and the Ni-O bond lengths suggest that for the X = Ni sample, there may actually be some T-site cation disorder.

Rietveld refinement of the crystal structures of Rb2 XSi5O12 (X = Ni, Mn)

PubMed Central

Bell, Anthony M. T.; Henderson, C. Michael B.

2016-01-01

The synthetic leucite silicate framework mineral analogues Rb2 XSi5O12 {X = Ni [dirubidium nickel(II) penta­silicate] and Mn [dirubidium manganese(II) penta­silicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu Kα X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetra­hedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework. Extraframework Rb+ cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetra­hedrally coordinated sites (T-sites). However, the Ni displacement parameter and the Ni—O bond lengths suggest that for the X = Ni sample, there may actually be some T-site cation disorder. PMID:26958399

Properties of calcium silicate-monobasic calcium phosphate materials for endodontics containing tantalum pentoxide and zirconium oxide.

PubMed

Zamparini, Fausto; Siboni, Francesco; Prati, Carlo; Taddei, Paola; Gandolfi, Maria Giovanna

2018-05-08

The aim of the study was to evaluate chemical-physical properties and apatite-forming ability of three premixed calcium silicate materials containing monobasic calcium phosphate (CaH 4 P 2 O 8 ) bioceramic, tantalum pentoxide and zirconium oxide, recently marketed for endodontics (TotalFill BC-Sealer, BC-RRM-Paste, BC-RRM-Putty). Microchemical and micromorphological analyses, radiopacity, initial and final setting times, calcium release and alkalising activity were tested. The nucleation of calcium phosphates (CaPs) and/or apatite after 28 days ageing was evaluated by ESEM-EDX and micro-Raman spectroscopy. BC-Sealer and BC-RRM-Paste showed similar initial (23 h), prolonged final (52 h) setting times and good radiopacity (> 7 mm Al); BC-RRM-Putty showed fast initial (2 h) and final setting times (27 h) and excellent radiopacity (> 9 mm Al). All materials induced a marked alkalisation (pH 11-12) up to 28 days and showed the release of calcium ions throughout the entire test period (cumulative calcium release 641-806 ppm). After 28 days ageing, a well-distributed mineral layer was present on all samples surface; EDX demonstrated relevant calcium and phosphorous peaks. B-type carbonated apatite and calcite deposits were identified by micro-Raman spectroscopy on all the 28-day-aged samples; the deposit thickness was higher on BC-RRM-Paste and BC-RRM-Putty, in agreement with calcium release data. These materials met the required chemical and physical standards and released biologically relevant ions. The CaSi-CaH 4 P 2 O 8 system present in the materials provided Ca and OH ions release with marked abilities to nucleate a layer of B-type carbonated apatite favoured/accelerated by the bioceramic presence. The ability to nucleate apatite may lead many clinical advantages: In orthograde endodontics, it may improve the sealing ability by the deposition of CaPs at the material-root dentine interface, and in endodontic surgery, it could promote bone and periodontal tissue regeneration. As premixed materials, their application in endodontics may result easier in several complex endodontic situations (apicoectomy, root perforation, presence of wide/wet apices).

Calcium Sulphate/Hydroxyapatite Carrier for Bone Formation in the Femoral Neck of Osteoporotic Rats.

PubMed

Sirka, Aurimas; Raina, Deepak Bushan; Isaksson, Hanna; Tanner, K Elizabeth; Smailys, Alfredas; Kumar, Ashok; Tarasevicius, Sarunas; Tägil, Magnus; Lidgren, Lars

2018-06-01

We investigated bone regeneration in the femoral neck canal of osteoporotic rats using a novel animal model. We used a calcium sulphate (CS)/ Hydroxyapatite (HA) carrier to locally deliver a bisphosphonate, zoledronic acid (ZA), with or without added recombinant human bone morphogenic protein-2 (rhBMP-2). Ovariectomized Sprague-Dawley rats of 28 weeks age were used. A 1 mm diameter and 8 mm long defect was created in the femoral neck by drilling from the lateral cortex in the axis of the femoral neck leaving the surrounding cortex intact. Three treatment groups and one control group were used 1) CS/HA alone, 2) CS/HA+ ZA (10 μg) 3) CS/HA+ZA (10 μg)+rhBMP-2 (4 μg) and 4) Empty defect. The bone formation was assessed at 4 weeks post-surgery using in vivo micro computed tomography (micro-CT). At 8 weeks post-surgery, the animals were sacrificed and both defect and contralateral femurs were subjected to micro-CT, mechanical testing and histology. Micro-CT results showed that the combination of CS/HA with ZA or ZA+rhBMP-2 increased the bone formation in the defect when compared to the other groups and to the contralateral hips. Evidence of new dense bone formation in CS/HA+ZA and CS/HA+ZA+rhBMP-2 groups was seen histologically. Mechanical testing results showed no differences in the load to fracture between the treatments in either of the treated or contralateral legs. The CS/HA biomaterial can be used as a carrier for ZA and rhBMP-2 to regenerate bone in the femoral neck canal of osteoporotic rats.

Releasing effects in flame photometry: Determination of calcium

USGS Publications Warehouse

Dinnin, J.I.

1960-01-01

Strontium, lanthanum, neodymium, samarium, and yttrium completely release the flame emission of calcium from the depressive effects of sulfate, phosphate, and aluminate. Magnesium, beryllium, barium, and scandium release most of the calcium emission. These cations, when present in high concentration, preferentially form compounds with the depressing anions when the solution is evaporated rapidly in the flame. The mechanism of the interference and releasing effects is explained on the basis of the chemical equilibria in the evaporating droplets of solution and is shown to depend upon the nature of the compounds present in the aqueous phase of the solution. The need for background correction techniques is stressed. The releasing effect is used in the determination of calcium in silicate rocks without the need for separations.

Early Age Carbonation Heat and Products of Tricalcium Silicate Paste Subject to Carbon Dioxide Curing

PubMed Central

Li, Zhen; He, Zhen; Shao, Yixin

2018-01-01

This paper presents a study on the carbonation reaction heat and products of tricalcium silicate (C3S) paste exposed to carbon dioxide (CO2) for rapid curing. Reaction heat was measured using a retrofitted micro-calorimeter. The highest heat flow of a C3S paste subject to carbonation curing was 200 times higher than that by hydration, and the cumulative heat released by carbonation was three times higher. The compressive strength of a C3S paste carbonated for 2 h and 24 h was 27.5 MPa and 62.9 MPa, respectively. The 24-h carbonation strength had exceeded the hydration strength at 28 days. The CO2 uptake of a C3S paste carbonated for 2 h and 24 h was 17% and 26%, respectively. The X-ray diffraction (XRD), transmission electron microscope coupled with energy dispersive spectrometer (TEM-EDS), and 29Si magic angle spinning–nuclear magnetic resonance (29Si MAS-NMR) results showed that the products of a carbonated C3S paste were amorphous silica (SiO2) and calcite crystal. There was no trace of calcium silicate hydrate (C–S–H) or other polymorphs of calcium carbonate (CaCO3) detected. PMID:29734681

Effect of carbonic anhydrase on silicate weathering and carbonate formation at present day CO2 concentrations compared to primordial values

PubMed Central

Xiao, Leilei; Lian, Bin; Hao, Jianchao; Liu, Congqiang; Wang, Shijie

2015-01-01

It is widely recognized that carbonic anhydrase (CA) participates in silicate weathering and carbonate formation. Nevertheless, it is still not known if the magnitude of the effect produced by CA on surface rock evolution changes or not. In this work, CA gene expression from Bacillus mucilaginosus and the effects of recombination protein on wollastonite dissolution and carbonate formation under different conditions are explored. Real-time fluorescent quantitative PCR was used to explore the correlation between CA gene expression and sufficiency or deficiency in calcium and CO2 concentration. The results show that the expression of CA genes is negatively correlated with both CO2 concentration and ease of obtaining soluble calcium. A pure form of the protein of interest (CA) is obtained by cloning, heterologous expression, and purification. The results from tests of the recombination protein on wollastonite dissolution and carbonate formation at different levels of CO2 concentration show that the magnitudes of the effects of CA and CO2 concentration are negatively correlated. These results suggest that the effects of microbial CA in relation to silicate weathering and carbonate formation may have increased importance at the modern atmospheric CO2 concentration compared to 3 billion years ago. PMID:25583135

Melting relations and elemental distribution of portion of the system Fe-S-Si-O to 32 KB with planetary application

NASA Technical Reports Server (NTRS)

Huang, W. L.

1980-01-01

The melting relations and distribution of K and Cs in portions of the system was determined at high pressures. Ferrosilite is stable as a primary phase at high pressures because of the incongruent melting of ferrosilite to quartz plus liquid and the boundary between the one and two liquid fields on the joint Fe(1-x) O-FeS-SiO2 shifts away from silica with increasing pressures. Potassium K was found to have limited solubility in metal sulfide liquids at pressures up to 45 kb. The speculation that K may dissolve significantly in metal-metal sulfide liquids after undergoing first order isomorphic transition was tested by determining the distribution of Cs between sulfide and silicate liquids as an analogy to K. At 45 kb, 1400 C and 27 kb, 1300 C only limited amounts of Cs were detected in quench sulfide liquids even at pressures beyond the isomorphic transition of Cs.

Chemical-garden formation, morphology, and composition. II. Chemical gardens in microgravity.

PubMed

Cartwright, Julyan H E; Escribano, Bruno; Sainz-Díaz, C Ignacio; Stodieck, Louis S

2011-04-05

We studied the growth of metal-ion silicate chemical gardens under Earth gravity (1 g) and microgravity (μg) conditions. Identical sets of reaction chambers from an automated system (the Silicate Garden Habitat or SGHab) were used in both cases. The μg experiment was performed on board the International Space Station (ISS) within a temperature-controlled setup that provided still and video images of the experiment downlinked to the ground. Calcium chloride, manganese chloride, cobalt chloride, and nickel sulfate were used as seed salts in sodium silicate solutions of several concentrations. The formation and growth of osmotic envelopes and microtubes was much slower under μg conditions. In 1 g, buoyancy forces caused tubes to grow upward, whereas a random orientation for tube growth was found under μg conditions.

Sealing of cracks in cement using microencapsulated sodium silicate

NASA Astrophysics Data System (ADS)

Giannaros, P.; Kanellopoulos, A.; Al-Tabbaa, A.

2016-08-01

Cement-based materials possess an inherent autogenous self-healing capability allowing them to seal, and potentially heal, microcracks. This can be improved through the addition of microencapsulated healing agents for autonomic self-healing. The fundamental principle of this self-healing mechanism is that when cracks propagate in the cementitious matrix, they rupture the dispersed capsules and their content (cargo material) is released into the crack volume. Various healing agents have been explored in the literature for their efficacy to recover mechanical and durability properties in cementitious materials. In these materials, the healing agents are most commonly encapsulated in macrocontainers (e.g. glass tubes or capsules) and placed into the material. In this work, microencapsulated sodium silicate in both liquid and solid form was added to cement specimens. Sodium silicate reacts with the calcium hydroxide in hydrated cement paste to form calcium-silicate-hydrate gel that fills cracks. The effect of microcapsule addition on rheological and mechanical properties of cement is reported. It is observed that the microcapsule addition inhibits compressive strength development in cement and this is observed through a plateau in strength between 28 and 56 days. The improvement in crack-sealing for microcapsule-containing specimens is quantified through sorptivity measurements over a 28 day healing period. After just seven days, the addition of 4% microcapsules resulted in a reduction in sorptivity of up to 45% when compared to specimens without any microcapsule addition. A qualitative description of the reaction between the cargo material and the cementitious matrix is also provided using x-ray diffraction analysis.

Cement and concrete

NASA Technical Reports Server (NTRS)

Corley, Gene; Haskin, Larry A.

1992-01-01

To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

Involvement of heme oxygenase-1 in β-cyclodextrin-hemin complex-induced cucumber adventitious rooting process.

PubMed

Lin, Yuting; Li, Meiyue; Huang, Liqin; Shen, Wenbiao; Ren, Yong

2012-09-01

Our previous results showed that β-cyclodextrin-hemin complex (CDH) exhibited a vital protective role against cadmium-induced oxidative damage and toxicity in alfalfa seedling roots by the regulation of heme oxygenase-1 (HO-1) gene expression. In this report, we further test whether CDH exhibited the hormonal-like response. The application of CDH and an inducer of HO-1, hemin, were able to induce the up-regulation of cucumber HO-1 gene (CsHO1) expression and thereafter the promotion of adventitious rooting in cucumber explants. The effect is specific for HO-1 since the potent HO-1 inhibitor zinc protoporphyrin IX (ZnPP) blocked the above responses triggered by CDH, and the inhibitory effects were reversed further when 30% saturation of CO aqueous solution was added together. Further, molecular evidence showed that CDH triggered the increases of the HO-1-mediated target genes responsible for adventitious rooting, including one DnaJ-like gene (CsDNAJ-1) and two calcium-dependent protein kinase (CDPK) genes (CsCDPK1 and CsCDPK5), and were inhibited by ZnPP and reversed by CO. The calcium (Ca2+) chelator ethylene glycol-bis (2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) and the Ca2+ channel blocker lanthanum chloride (LaCl3) not only compromised the induction of adventitious rooting induced by CDH but also decreased the transcripts of above three target genes. However, the application of ascorbic acid (AsA), a well-known antioxidant in plants, failed to exhibit similar inducible effect on adventitious root formation. In short, above results illustrated that the response of CDH in the induction of cucumber adventitious rooting might be through HO-1-dependent mechanism and calcium signaling. Physiological, pharmacological and molecular evidence showed that β-cyclodextrin-hemin complex (CDH) was able to induce cucumber adventitious rooting through heme oxygenase-1 (HO-1)-dependent mechanism and calcium signaling.

Strontium-doped calcium silicate bioceramic with enhanced in vitro osteogenic properties.

PubMed

No, Young Jung; Roohaniesfahani, Seyediman; Lu, Zufu; Shi, Jeffrey; Zreiqat, Hala

2017-06-05

Gehlenite (GLN, Ca 2 SiAl 2 O 7 ) is a bioceramic that has been recently shown to possess excellent mechanical strength and in vitro osteogenic properties for bone regeneration. Substitutional incorporation of strontium in place of calcium is an effective way to further enhance biological properties of calcium-based bioceramics and glasses. However, such strategy has the potential to affect other important physicochemical parameters such as strength and degradation due to differences in the ionic radius of strontium and calcium. This study is the first to investigate the effect of a range of concentrations of strontium substitution of calcium at 1, 2, 5, 10 mol% (S1-GLN, S2-GLN, S5-GLN and S10-GLN) on the physicochemical and biological properties of GLN. We showed that up to 2 mol% strontium ion substitution retains the monophasic GLN structure when sintered at 1450 °C, whereas higher concentrations resulted in presence of calcium silicate impurities. Increased strontium incorporation resulted in changes in grain morphology and reduced densification when the ceramics were sintered at 1450 °C. Porous GLN, S1-GLN and S2-GLN scaffolds (∼80% porosity) showed compressive strengths of 2.05 ± 0.46 MPa, 1.76 ± 0.79 MPa and 1.57 ± 0.52 MPa respectively. S1-GLN and S2-GLN immersed in simulated body fluid showed increased strontium ion release but reduced calcium and silicon ion release compared to GLN without affecting overall weight loss and pH over a 21 d period. The bioactivity of the S2-GLN ceramics was significantly improved as reflected in the significant upregulation of HOB proliferation and differentiation compared to GLN. Overall, these results suggest that increased incorporation of strontium presents a trade-off between bioactivity and mechanical strength for GLN bioceramics. This is an important consideration in the development of strontium-doped bioceramics.

In vitro cytotoxicity of calcium silicate-containing endodontic sealers.

PubMed

Zhou, Hui-min; Du, Tian-feng; Shen, Ya; Wang, Zhe-jun; Zheng, Yu-feng; Haapasalo, Markus

2015-01-01

The cytotoxicity of 2 novel calcium silicate-containing endodontic sealers to human gingival fibroblasts was studied. EndoSequence BC (Brasseler, Savannah, GA), MTA Fillapex (Angelus Indústria de Produtos Odontológicos S/A, Londrina, PR, Brazil) and a control sealer (AH Plus; Dentsply DeTrey GmbH, Konstanz, Germany) were evaluated. Human gingival fibroblasts were incubated for 3 days both with the extracts from fresh and set materials in culture medium and cultured on the surface of the set materials in Dulbecco-modified Eagle medium. Fibroblasts cultured in Dulbecco-modified Eagle medium were used as a control group. Cytotoxicity was evaluated by flow cytometry, and the adhesion of the fibroblasts to the surface of the set materials was assessed using scanning electron microscopy. The data of cell cytotoxicity were analyzed statistically using a 1-way analysis of variance test at a significance level of P < .05. Cells incubated with extracts from BC Sealer showed higher viabilities at all extract concentrations than cells incubated with extracts from freshly mixed AH Plus and fresh and set MTA Fillapex, esspecially for the high extract concentrations (1:2 and 1:8 dilutions). Extracts from set MTA Fillapex of 2 weeks and older were more cytotoxic than extracts from freshly mixed and 1-week-old cement. With extract concentrations of 1:32 and lower, MTA Fillapex was no longer cytotoxic. After setting, AH Plus was no longer cytotoxic, and the fibroblast cells grew on set AH Plus equally as well as on BC Sealer. BC Sealer and MTA Fillapex, the 2 calcium silicate-containing endodontic sealers, exhibited different cytotoxicity to human gingival fibroblasts. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Na, Mg, Ni and Cs distribution and speciation after long-term alteration of a simulated nuclear waste glass: A micro-XAS/XRF/XRD and wet chemical study

NASA Astrophysics Data System (ADS)

Curti, Enzo; Dähn, Rainer; Farges, François; Vespa, Marika

2009-04-01

Microscopic distribution and speciation of Na, Mg, Ni and Cs in a simulated (inactive) nuclear waste glass were studied using micro X-ray fluorescence (μ-XRF) and micro X-ray absorption spectroscopy (μ-XAS), after aqueous leaching during 12 years at 90 °C. Na and Mg are major constituents of the glass that can be used to determine the progress of the glass corrosion process and the nature of secondary alteration phases. Ni and Cs represent dose determining long-lived radionuclides ( 59Ni, 135Cs) in vitrified nuclear waste. The Na-Mg μ-XRF maps revealed that the core regions of the glass fragments are apparently unaltered and compositionally homogeneous, whereas rims and interstitial spaces are enriched with Mg-rich smectite formed during the leaching process. The micro X-ray absorption near edge structure (μ-XANES) spectra collected at the Mg K-edge in the altered zones show three sharp resonances typical for crystalline Mg-silicates. These resonances are distinctive of Mg occupying undistorted octahedral positions. In contrast, the μ-XANES spectra collected in the core zones of the glass fragments lack this resonance pattern and are identical to the spectra measured on the pristine (unleached) MW glass. Micro extended X-ray absorption fine structure (μ-EXAFS) and μ-XANES analyses at the Ni K-edge revealed three distinct Ni(II) species: (a) Ni uniformly distributed in the glass matrix, (b) micro-inclusions with high Ni concentrations and (c) Ni associated to the Mg-clay. The comparison with reference spectra of unleached MW and other Ni-bearing silicate glasses indicated that species (a) represents the original coordinative environment of Ni in the glass. The μ-EXAFS analyses revealed that species (b) is structural Ni in trevorite (NiFe 2O 4), which probably formed through unmixing processes during the cooling of the glass melt. The μ-EXAFS of species (c) could be successfully modeled assuming specific adsorption or incorporation of Ni into the lattice of trioctahedral Mg-clay minerals. Alternative models assuming other elements (Ni, Al, Fe) in addition to Mg in the second shell could not be fitted successfully. Aqueous concentration data were used to calculate the speciation of the leaching solutions. Saturation index (SI) calculations indicate undersaturation with respect to NiCO 3 and NiSO 4·7H 2O, but oversaturation with respect to β-Ni(OH) 2. The latter result is probably due to the omission of Ni borate and Ni silicate complexes in the speciation calculations, for which formation constants are not available. With the help of estimation techniques, we could infer that such complexes would dominate the Ni speciation and consequently reduce the SI below the saturation of β-Ni(OH) 2. The μ-XRF maps show that Cs is uniformly distributed in the MW glass, since no region with high Cs concentration could be detected. The Cs L III-edge μ-XAS spectra were all very similar independently of the degree of alteration, indicating similar coordination environments of Cs in the core regions of the glass as well as in the secondary clays. These spectra largely differ from that measured for pollucite (a potential secondary Cs-phase in altered glasses) implying that the coordination environments of Cs in the MW glass and in pollucite are fundamentally different. The present study shows that μ-XRF and μ-XAS are essential tools in determining the fate and the retention mechanisms of radionuclides released from nuclear waste during aqueous alteration. Our spectroscopic analyses allowed us to exclude formation of specific Ni and Cs secondary solids (e.g. nepouite, β-Ni(OH) 2, pollucite) during the aqueous alteration. Ni and Cs are instead distributed as trace elements in the alteration phases formed by major elements during the leaching process. Our results imply that solid solution and/or adsorption equilibria, rather than pure phase solubility equilibria, are the adequate chemical models to determine Ni and Cs aqueous concentrations in performance assessments for radioactive waste repositories.

METHOD OF PURIFYING RADIOACTIVE WATER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acfi, D.; Schmitt, M.; Neveu, M.

The utilization of lithothamnium calcareum as an ion exchanger for the decontamination of radioactive water is described. In order to retain cobalt and strontium the ion exchanger is mixed with calcium silicate or borate; alternatively sodium phosphate is added to the water prior to the purification process. (NPO)

Double cross-polarization MAS NMR in the assignment of abundant-spin resonances: ¹⁹F-{²⁹Si}-¹⁹F FBCP/MAS NMR of fluoride ions incorporated in calcium silicate hydrate (C-S-H) phases.

PubMed

Tran, Thuan T; Bildsøe, Henrik; Jakobsen, Hans J; Skibsted, Jørgen

2012-08-01

A new version of the double cross-polarization MAS NMR experiment, which transfers polarization Forth and Back (FBCP) between high- and low-γ spin nuclei, is presented. The pulse sequence is demonstrated by ¹⁹F-{²⁹Si}-¹⁹F and ¹⁹F-{¹³C}-¹⁹F FBCP NMR spectra of a mixture of cuspidine (Ca₄Si₂O₇F₂) and Teflon (-CF₂-)(n). The experiment is useful for assignment of the high-γ spin resonances, as demonstrated by ¹⁹F-{²⁹Si}-¹⁹F FBCP NMR of a fluoride-containing calcium-silicate-hydrate (C-S-H) phase, where the ¹⁹F resonance from fluoride ions incorporated in the interlayer structure of the C-S-H phase is identified. Copyright © 2012 Elsevier Inc. All rights reserved.

Solubility of a new calcium silicate-based root-end filling material

PubMed Central

Singh, Shishir; Podar, Rajesh; Dadu, Shifali; Kulkarni, Gaurav; Purba, Rucheet

2015-01-01

Introduction: The purpose of this study was to compare solubility of a new calcium silicate-based cement, Biodentine with three commonly used root-end filling materials viz. glass-ionomer cement (GIC), intermediate restorative material (IRM), and mineral trioxide aggregate (MTA). Materials and Methods: Twenty stainless steel ring molds were filled with cements corresponding to four groups (n = 5). The weight of 20 dried glass bottles was recorded. Samples were transferred to bottles containing 5 ml of distilled water and stored for 24 h. The bottles were dried at 105΀C and weighed. This procedure was repeated for 3, 10, 30, and 60 days. Data was analyzed with one-way analysis of variance (ANOVA) test (P < 0.05). Results: Biodentine demonstrated significantly higher solubility than MTA for 30- and 60-day immersion periods. Statistical difference was noted between the solubility values of Biodentine samples amongst each of the five time intervals. Conclusions: Biodentine exhibited higher solubility in comparison with all other cements. PMID:25829696

Mesocrystalline calcium silicate hydrate: A bioinspired route toward elastic concrete materials

PubMed Central

Picker, Andreas; Nicoleau, Luc; Burghard, Zaklina; Bill, Joachim; Zlotnikov, Igor; Labbez, Christophe; Nonat, André; Cölfen, Helmut

2017-01-01

Calcium silicate hydrate (C-S-H) is the binder in concrete, the most used synthetic material in the world. The main weakness of concrete is the lack of elasticity and poor flexural strength considerably limiting its potential, making reinforcing steel constructions necessary. Although the properties of C-S-H could be significantly improved in organic hybrids, the full potential of this approach could not be reached because of the random C-S-H nanoplatelet structure. Taking inspiration from a sea urchin spine with highly ordered nanoparticles in the biomineral mesocrystal, we report a bioinspired route toward a C-S-H mesocrystal with highly aligned C-S-H nanoplatelets interspaced with a polymeric binder. A material with a bending strength similar to nacre is obtained, outperforming all C-S-H–based materials known to date. This strategy could greatly benefit future construction processes because fracture toughness and elasticity of brittle cementitious materials can be largely enhanced on the nanoscale. PMID:29209660

Hydration reactivity of crystalline and vitrified diopside under hydrothermal conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grzeszczyk, S.; Szuba, J.

1990-07-01

Hydration reactivity of diopside in both the crystalline and amorphous (glassy) phase was studied under hydrothermal conditions. Samples were treated in an autoclave at 200{degrees}C in saturated vapor for 24 and 72 h. The progress of hydration was determined by X-ray powder diffractometry and IR spectroscopy. Results indicate that crystalline diopside possessed poor hydraulic activity. However, once vitrified it proved to be much more reactive. The principal hydration products found for the glassy diopside after 24 and 72 h of treatment were calcium silicate hydrate (xonotlite) and magnesium silicate hydrates (chrysotile and tremolite).

First investigations on the quaternary system Na2O-K2O-CaO-SiO2: synthesis and crystal structure of the mixed alkali calcium silicate K1.08Na0.92Ca6Si4O15

NASA Astrophysics Data System (ADS)

Kahlenberg, Volker; Mayerl, Michael Jean-Philippe; Schmidmair, Daniela; Krüger, Hannes; Tribus, Martina

2018-04-01

In the course of an exploratory study on the quaternary system Na2O-K2O-CaO-SiO2 single crystals of the first anhydrous sodium potassium calcium silicate have been obtained from slow cooling of a melt in the range between 1250 and 1050 °C. Electron probe micro analysis suggested the following idealized molar ratios of the oxides for the novel compound: K2O:Na2O:CaO:SiO2 = 1:1:12:8 (or KNaCa6Si4O15). Single-crystal diffraction measurements on a crystal with chemical composition K1.08Na0.92Ca6Si4O15 resulted in the following basic crystallographic data: monoclinic symmetry, space group P 21/ c, a = 8.9618(9) Å, b = 7.3594(6) Å, c = 11.2453(11) Å, β= 107.54(1)°, V = 707.2(1) Å3, Z = 2. Structure solution was performed using direct methods. The final least-squares refinement converged at a residual of R(|F|) = 0.0346 for 1288 independent reflections and 125 parameters. From a structural point of view, K1.08Na0.92Ca6Si4O15 belongs to the group of mixed-anion silicates containing [Si2O7]- and [SiO4]-units in the ratio 1:2. The mono- and divalent cations occupy a total of four crystallographically independent positions located in voids between the tetrahedra. Three of these sites are exclusively occupied by calcium. The fourth site is occupied by 54(1)% K and 46%(1) Na, respectively. Alternatively, the structure can be described as a heteropolyhedral framework based on corner-sharing silicate tetrahedra and [CaO6]-octahedra. The network can build up from kröhnkite-like [Ca(SiO4)2O2]-chains running along [001]. A detailed comparison with other A2B6Si4O15-compounds including topological and group-theoretical aspects is presented.

Insights into the interfacial strengthening mechanisms of calcium-silicate-hydrate/polymer nanocomposites.

PubMed

Zhou, Yang; Hou, Dongshuai; Geng, Guoqing; Feng, Pan; Yu, Jiao; Jiang, Jinyang

2018-03-28

The mechanical properties of organic/inorganic composites can be highly dependent on the interfacial interactions. In this work, with organic polymers intercalated into the interlayer of inorganic calcium silicate hydrate (C-S-H), the primary binding phase of Portland cement, great ductility improvement is obtained for the nanocomposites. Employing reactive molecular dynamics, the simulation results indicate that strong interfacial interactions between the polymers and the substrate contribute greatly to strengthening the materials, when C-S-H/poly ethylene glycol (PEG), C-S-H/poly acrylic acid (PAA), and C-S-H/poly vinyl alcohol (PVA) were subject to uniaxial tension along different lattice directions. In the x and z direction tensile processes, the Si-OCa bonds of the C-S-H gel, which were elongated and broken to form Si-OH and Ca-OH, play a critical role in loading resistance, while the incorporation of polymers bridged the neighboring silicate sheets, and activated more the hydrolytic reactions at the interfaces to avoid strain localization, thus increasing the tensile strength and postponing the fracture. On the other hand, Si-O-Si bonds of C-S-H mainly take the load when tension was applied along the y direction. During the post-yield stage, rearrangements of silicate tetrahedra occurred to prevent rapid damage. The polymer intercalation further elongates this post-yield period by forming interfacial Si-O-C bonds, which promote rearrangements and improve the connectivity of the defective silicate morphology, significantly improving the ductility. Among the polymers, PEG exhibits the strongest interaction with C-S-H, and thus C-S-H/PEG possesses the highest ductility. We expect that the molecular-scale mechanisms interpreted here will shed new light on the stress-activated chemical interactions at the organic/inorganic interfaces, and help eliminate the brittleness of cement-based materials on a genetic level.

Three novel B-type mannose-specific lectins of Cynoglossus semilaevis possess varied antibacterial activities against Gram-negative and Gram-positive bacteria.

PubMed

Sun, Yuan-yuan; Liu, Li; Li, Jun; Sun, Li

2016-02-01

Lectins are a group of sugar-binding proteins that are important factors of the innate immune system. In this study, we examined, in a comparative manner, the expression and function of three Bulb-type (B-type) mannose-specific lectins (named CsBML1, CsBML2, and CsBML3) from tongue sole. All three lectins possess three repeats of the conserved mannose binding motif QXDXNXVXY. Expression of CsBML1, CsBML2, and CsBML3 was most abundant in liver and upregulated by bacterial infection. Recombinant (r) CsBML1, CsBML2, and CsBML3 bound to a wide arrange of bacteria in a dose-dependent manner and with different affinities. All three lectins displayed mannose-specific and calcium-dependent agglutinating capacities but differed in agglutinating profiles. rCsBML1 and rCsBML2, but not rCsBML3, killed target bacteria in vitro and inhibited bacterial dissemination in fish tissues in vivo. These results indicate for the first time that in teleost, different members of B-type mannose-specific lectins likely play different roles in antibacterial immunity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Antagonist effects of calcium on borosilicate glass alteration

NASA Astrophysics Data System (ADS)

Mercado-Depierre, S.; Angeli, F.; Frizon, F.; Gin, S.

2013-10-01

Numerous studies have been conducted on glass and cement durability in contact with water, but very little work to date has focused directly on interactions between the two materials. These interactions are mostly controlled by silicon-calcium reactivity. However, the physical and chemical processes involved remain insufficiently understood to predict the evolution of coupled glass-cement systems used in several industrial applications. Results are reported from borosilicate glass alteration in calcium-rich solutions. Our data show that four distinct behaviors can be expected according to the relative importance of three key parameters: the pH, the reaction progress (short- or long-term alteration) and the calcium concentration. Glass alteration is thus controlled by specific mechanisms depending on the solution chemistry: calcium complexation at the glass surface, precipitation of calcium silicate hydrates (C-S-H) or calcium incorporation in the altered layer. These findings highlight the impact of silicon-calcium interactions on glass durability and open the way for a better understanding of glass-cement mixing in civil engineering applications as well as in nuclear waste storage.

A review of the bioactivity of hydraulic calcium silicate cements

PubMed Central

Niu, Li-na; Jiao, Kai; Wang, Tian-da; Zhang, Wei; Camilleri, Josette; Bergeron, Brian E.; Feng, Hai-lan; Mao, Jing; Chen, Ji-hua; Pashley, David H.; Tay, Franklin R.

2014-01-01

Objectives In tissue regeneration research, the term “bioactivity” was initially used to describe the resistance to removal of a biomaterial from host tissues after intraosseous implantation. Hydraulic calcium silicate cements (HCSCs) are putatively accepted as bioactive materials, as exemplified by the increasing number of publications reporting that these cements produce an apatite-rich surface layer after they contact simulated body fluids. Methods In this review, the same definitions employed for establishing in vitro and in vivo bioactivity in glass–ceramics, and the proposed mechanisms involved in these phenomena are used as blueprints for investigating whether HCSCs are bioactive. Results The literature abounds with evidence that HCSCs exhibit in vitro bioactivity; however, there is a general lack of stringent methodologies for characterizing the calcium phosphate phases precipitated on HCSCs. Although in vivo bioactivity has been demonstrated for some HCSCs, a fibrous connective tissue layer is frequently identified along the bone–cement interface that is reminiscent of the responses observed in bioinert materials, without accompanying clarifications to account for such observations. Conclusions As bone-bonding is not predictably achieved, there is insufficient scientific evidence to substantiate that HCSCs are indeed bioactive. Objective appraisal criteria should be developed for more accurately defining the bioactivity profiles of HCSCs designed for clinical use. PMID:24440449

Cell adhesion to borate glasses by colloidal probe microscopy.

PubMed

Wiederhorn, Sheldon M; Chae, Young-Hun; Simon, Carl G; Cahn, Jackson; Deng, Yan; Day, Delbert

2011-05-01

The adhesion of osteoblast-like cells to silicate and borate glasses was measured in cell growth medium using colloidal probe microscopy. The probes consisted of silicate and borate glass spheres, 25-50 μm in diameter, attached to atomic force microscope cantilevers. Variables of the study included glass composition and time of contact of the cell to the glasses. Increasing the time of contact from 15 to 900 s increased the force of adhesion. The data could be plotted linearly on a log-log plot of adhesive force versus time. Of the seven glasses tested, five had slopes close to 0.5, suggesting a square root dependence of the adhesive force on the contact time. Such behavior can be interpreted as a diffusion limited process occurring during the early stages of cell attachment. We suggest that the rate limiting step in the adhesion process is the diffusion of integrins resident in the cell membrane to the area of cell attachment. Data presented in this paper support the hypothesis of Hench et al. that strong adhesion depends on the formation of a calcium phosphate reaction layer on the surfaces of the glass. Glasses that did not form a calcium phosphate layer exhibited a weaker adhesive force relative to those glasses that did form a calcium phosphate layer. Published by Elsevier Ltd.

Atherosclerotic Plaque in Patients with Zero Calcium Score at Coronary Computed Tomography Angiography.

PubMed

Gabriel, Fabíola Santos; Gonçalves, Luiz Flávio Galvão; Melo, Enaldo Vieira de; Sousa, Antônio Carlos Sobral; Pinto, Ibraim Masciarelli Francisco; Santana, Sara Melo Macedo; Matos, Carlos José Oliveira de; Souto, Maria Júlia Silveira; Conceição, Flávio Mateus do Sacramento; Oliveira, Joselina Luzia Menezes

2018-05-03

In view of the high mortality for cardiovascular diseases, it has become necessary to stratify the main risk factors and to choose the correct diagnostic modality. Studies have demonstrated that a zero calcium score (CS) is characteristic of a low risk for cardiovascular events. However, the prevalence of individuals with coronary atherosclerotic plaques and zero CS is conflicting in the specialized literature. To evaluate the frequency of patients with coronary atherosclerotic plaques, their degree of obstruction and associated factors in patients with zero CS and indication for coronary computed tomography angiography (CCTA). This is a cross-sectional, prospective study with 367 volunteers with zero CS at CCTA in four diagnostic imaging centers in the period from 2011 to 2016. A significance level of 5% and 95% confidence interval were adopted. The frequency of atherosclerotic plaque in the coronary arteries in 367 patients with zero CS was 9.3% (34 individuals). In this subgroup, mean age was 52 ± 10 years, 18 (52.9%) were women and 16 (47%) had significant coronary obstructions (> 50%), with involvement of two or more segments in 4 (25%) patients. The frequency of non-obese individuals (90.6% vs 73.9%, p = 0.037) and alcohol drinkers (55.9% vs 34.8%, p = 0.015) was significantly higher in patients with atherosclerotic plaques, with an odds ratio of 3.4 for each of this variable. The frequency of atherosclerotic plaque with zero CS was relatively high, indicating that the absence of calcification does not exclude the presence of plaques, many of which obstructive, especially in non-obese subjects and alcohol drinkers.

Evaluation of a bioceramic-based nanocomposite material for controlled delivery of a non-steroidal anti-inflammatory drug.

PubMed

Hesaraki, S; Moztarzadeh, F; Nezafati, N

2009-12-01

In this study, nanocomposite of 50wt% calcium sulfate and 50wt% nanocrystalline apatite was produced and its biocompatibility, physical and structural properties were compared with pure calcium sulfate (CS) cement. Indomethacin (IM), a non-steroidal anti-inflammatory drug, was also loaded on both CS and nanocomposite cements and its in vitro release was evaluated over a period of time. The effect of the loaded IM on basic properties of the cements was also investigated. Biocompatibility tests showed a partial cytotoxicity in CS cement due to the reduced number of viable mouse fibroblast L929 cells in contact with the samples as well as spherical morphologies of the cells. However, no cytotoxic effect was observed for nanocomposite cement and no significant difference was found between the number of the cells seeded in contact with this specimens and culture plate as control. Other results showed that the setting time and injectability of the nanocomposite cement was much higher than those of CS cement, whereas reverse result obtained for compressive strength. In addition, incorporation of IM into compositions slightly increased the initial setting time and injectability of the cements and did not change their compressive strength. While a fast IM release was observed from CS cement in which about 97% of the loaded drug was released during 48h, nanocomposite cement showed a sustained release behavior in which 80% of the loaded IM was liberated after 144h. Thus, the nanocomposite can be a more appropriate carrier than CS for controlled release of IM in bone defect treatments.

Oxalate secretion by ectomycorrhizal Paxillus involutus is mineral-specific and controls calcium weathering from minerals

PubMed Central

Schmalenberger, A.; Duran, A. L.; Bray, A. W.; Bridge, J.; Bonneville, S.; Benning, L. G.; Romero-Gonzalez, M. E.; Leake, J. R.; Banwart, S. A.

2015-01-01

Trees and their associated rhizosphere organisms play a major role in mineral weathering driving calcium fluxes from the continents to the oceans that ultimately control long-term atmospheric CO2 and climate through the geochemical carbon cycle. Photosynthate allocation to tree roots and their mycorrhizal fungi is hypothesized to fuel the active secretion of protons and organic chelators that enhance calcium dissolution at fungal-mineral interfaces. This was tested using 14CO2 supplied to shoots of Pinus sylvestris ectomycorrhizal with the widespread fungus Paxillus involutus in monoxenic microcosms, revealing preferential allocation by the fungus of plant photoassimilate to weather grains of limestone and silicates each with a combined calcium and magnesium content of over 10 wt.%. Hyphae had acidic surfaces and linear accumulation of weathered calcium with secreted oxalate, increasing significantly in sequence: quartz, granite < basalt, olivine, limestone < gabbro. These findings confirmed the role of mineral-specific oxalate exudation in ectomycorrhizal weathering to dissolve calcium bearing minerals, thus contributing to the geochemical carbon cycle. PMID:26197714

Oxalate secretion by ectomycorrhizal Paxillus involutus is mineral-specific and controls calcium weathering from minerals

NASA Astrophysics Data System (ADS)

Schmalenberger, A.; Duran, A. L.; Bray, A. W.; Bridge, J.; Bonneville, S.; Benning, L. G.; Romero-Gonzalez, M. E.; Leake, J. R.; Banwart, S. A.

2015-07-01

Trees and their associated rhizosphere organisms play a major role in mineral weathering driving calcium fluxes from the continents to the oceans that ultimately control long-term atmospheric CO2 and climate through the geochemical carbon cycle. Photosynthate allocation to tree roots and their mycorrhizal fungi is hypothesized to fuel the active secretion of protons and organic chelators that enhance calcium dissolution at fungal-mineral interfaces. This was tested using 14CO2 supplied to shoots of Pinus sylvestris ectomycorrhizal with the widespread fungus Paxillus involutus in monoxenic microcosms, revealing preferential allocation by the fungus of plant photoassimilate to weather grains of limestone and silicates each with a combined calcium and magnesium content of over 10 wt.%. Hyphae had acidic surfaces and linear accumulation of weathered calcium with secreted oxalate, increasing significantly in sequence: quartz, granite < basalt, olivine, limestone < gabbro. These findings confirmed the role of mineral-specific oxalate exudation in ectomycorrhizal weathering to dissolve calcium bearing minerals, thus contributing to the geochemical carbon cycle.

Drying-induced atomic structural rearrangements in sodium-based calcium-alumino-silicate-hydrate gel and the mitigating effects of ZrO2 nanoparticles

NASA Astrophysics Data System (ADS)

Yang, Kengran; Özçelik, V. Ongun; Garg, Nishant; Gong, Kai; White, Claire E.

Conventional drying of colloidal materials and gels (including cement) can lead to detrimental effects due to the buildup of internal stresses as water evaporates from the nano/microscopic pores. However, the underlying nanoscopic alterations in these gel materials that are, in part, responsible for macroscopically-measured strain values, especially at low relative humidity, remain a topic of open debate in the literature. In this study, sodium-based calcium-alumino-silicate-hydrate (C-(N)-A-S-H) gel, the major binding phase of silicate-activated blast furnace slag (one type of low-CO$_2$ cement), is investigated from a drying perspective, since it is known to suffer extensively from drying-induced microcracking. By employing in situ synchrotron X-ray total scattering measurements and pair distribution function (PDF) analysis we show that the significant contributing factor to the strain development in this material at extremely low relative humidity (0%) is the local atomic structural rearrangement of the C-(N)-A-S-H gel, including collapse of interlayer spacing and slight disintegration of the gel. Moreover, analysis of the medium range (1.0 - 2.2 nm) ordering in the PDF data reveals that the PDF-derived strain values are in much closer agreement (same order of magnitude) with the macroscopically measured strain data, compared to previous results based on reciprocal space X-ray diffraction data. From a mitigation standpoint, we show that small amounts of ZrO$_2$ nanoparticles are able to actively reinforce the structure of silicate-activated slag during drying, preventing atomic level strains from developing. Mechanistically, these nanoparticles induce growth of a silica-rich gel during drying, which, via density functional theory calculations, we show is attributed to the high surface reactivity of tetragonal ZrO$_2$.

Investigations on the crystal-structure and non-ambient behaviour of K2Ca2Si8O19 - a new potassium calcium silicate

NASA Astrophysics Data System (ADS)

Schmidmair, Daniela; Kahlenberg, Volker; Praxmarer, Alessandra; Perfler, Lukas; Mair, Philipp

2017-09-01

Within the context of a systematic re-investigation of phase relationships between compounds of the ternary system K2O-CaO-SiO2 a new potassium calcium silicate with the chemical formula K2Ca2Si8O19 was synthesized via solid state reactions as well as the flux method using KCl as a solvent. Its crystal structure was determined from single-crystal X-ray diffraction data by applying direct methods. The new compound crystallizes in the triclinic space group P 1 bar . Unit cell dimensions are a = 7.4231(7) Å, b = 10.7649(10) Å, c = 12.1252(10) Å, α = 70.193(8)°, β = 83.914(7)° and γ = 88.683(7)°. K2Ca2Si8O19 is built up of corner-connected, slightly distorted [SiO4]-tetrahedra forming double-sheets, which are linked by double-chains of edge-sharing [CaO6]-octahedra. Electroneutrality of the material is provided by additional potassium atoms that are located within the voids of the silicate layers and between adjacent [Ca2O6]-double-chains. Further characterization of the compound was performed by Raman spectroscopy and differential thermal analysis. The behaviour of K2Ca2Si8O19 under high-temperature and high-pressure was investigated by in-situ high-temperature powder X-ray diffraction up to a maximum temperature of 1125 °C and a piston cylinder experiment at 1.5 GPa and 1100 °C. Additionally an overview of known double-layer silicates is given as well as a comparison of K2Ca2Si8O19 to closely related structures.

Mapping the Mineral Resource Base for Mineral Carbon-Dioxide Sequestration in the Conterminous United States

USGS Publications Warehouse

Krevor, S.C.; Graves, C.R.; Van Gosen, B. S.; McCafferty, A.E.

2009-01-01

This database provides information on the occurrence of ultramafic rocks in the conterminous United States that are suitable for sequestering captured carbon dioxide in mineral form, also known as mineral carbon-dioxide sequestration. Mineral carbon-dioxide sequestration is a proposed greenhouse gas mitigation technology whereby carbon dioxide (CO2) is disposed of by reacting it with calcium or magnesium silicate minerals to form a solid magnesium or calcium carbonate product. The technology offers a large capacity to permanently store CO2 in an environmentally benign form via a process that takes little effort to verify or monitor after disposal. These characteristics are unique among its peers in greenhouse gas disposal technologies. The 2005 Intergovernmental Panel on Climate Change report on Carbon Dioxide Capture and Storage suggested that a major gap in mineral CO2 sequestration is locating the magnesium-silicate bedrock available to sequester the carbon dioxide. It is generally known that silicate minerals with high concentrations of magnesium are suitable for mineral carbonation. However, no assessment has been made in the United States that details their geographical distribution and extent, nor has anyone evaluated their potential for use in mineral carbonation. Researchers at Columbia University and the U.S. Geological Survey have developed a digital geologic database of ultramafic rocks in the conterminous United States. Data were compiled from varied-scale geologic maps of magnesium-silicate ultramafic rocks. The focus of our national-scale map is entirely on ultramafic rock types, which typically consist primarily of olivine- and serpentine-rich rocks. These rock types are potentially suitable as source material for mineral CO2 sequestration.

Simultaneous alloy-silicate fractionation of carbon, nitrogen, and sulfur at high pressures and temperatures: Implications for establishing the volatile budget of the Earth

NASA Astrophysics Data System (ADS)

Grewal, D. S.; Dasgupta, R.; Sun, C.; Tsuno, K.

2017-12-01

Constraining the origin, distribution and evolution of volatiles such as carbon (C), nitrogen (N) and sulfur (S) in terrestrial planets is essential to understand planetary differentiation, habitability and comparative planetology [1]. C/N ratio of Bulk Silicate Earth (BSE) is superchondritic (40 ± 8), while C/S ratio is nearly chondritic (0.49 ± 0.14) [2]. Accretion, core formation, and magma ocean (MO) crystallization are the key processes that could have set the relative budgets of C, N and S in different planetary reservoirs [3]. However, experiments using either C-N or C-S-bearing systems have shown that C is more siderophile than N and S, consequently core formation would have left behind subchondritic C/N and C/S ratios in BSE [4-6]. Accretion of extremely C-rich bodies during core formation or/and as a late veneer along with an early atmospheric blow-off are amongst the scenarios that have been suggested to explain C/N ratio while the addition of a differentiated body with a C-rich mantle has been suggested to explain C/S ratio in BSE [4-6]. However, no internally consistent explanations exist on the origin of all the volatile elements. We performed piston cylinder and multi-anvil experiments, using Fe-Ni-N-C±S alloy with variable amounts of S and mafic-ultramafic silicate mixtures in graphite saturated conditions at 1-7 GPa, 1600-1800 °C, and fO2 ranging from ΔIW of -1.1 to -0.3. EPMA and SIMS were used to determine major elements and volatile abundances in the coexisting alloy and silicate melt phases, while the speciation of the volatiles was determined using Raman spectroscopy. Our experimental data reveals that C becomes less siderophile in the presence of N and S during core-mantle differentiation involving an S-rich alloy. Using a set of inverse Monte-Carlo simulations, we propose that a disequilibrium merger of a Mars-sized planetary embryo with a C-saturated, S-rich core to a volatile-depleted proto-Earth during the main stage of accretion could have simultaneously satisfied C-N-S abundances and ratios in BSE along with setting up the stage of for the presence of NH3 and HCN in the Earth's early atmosphere via MO degassing. [1] Zahnle et al. (2007) Space Sci. Rev. [2] Marty (2012) EPSL. [3] Dasgupta et al. (2013) GCA. [4] Hirschmann (2016) AM. [5] Dalou et al. (2017) EPSL. [6] Li et al. (2016) Nat. Geosci.

Effect of irrigation and silicon fertilizer on total rice grain arsenic content and yield

USDA-ARS?s Scientific Manuscript database

Field tests were conducted for two years with rice grown with different irrigation systems and rates of calcium silicate fertilizer to determine the effects on brown rice arsenic (As) levels and rough rice yields. Irrigation systems were sprinkler irrigation using a center pivot system, intermitten...

Investigation and Development of Methods to Increase the Dispersibility of Aluminum Metal Power

DTIC Science & Technology

1977-01-01

Tullanox-500 remain intact. A fourth material investigated as a possible deagglomerating agent was Micro- Cel ( Johns - Manville , Inc. ). This material is...20 percent Johns - Manville Micro-Cel (calcium silicate), (3) 20 percent Baker & Adamson, Code 1551, activated carbon, (4) 2 percent Cabot Cab-O-Sil

Relation of an Echocardiographic-Based Cardiac Calcium Score to Mitral Stenosis Severity and Coronary Artery Disease in Patients with Severe Aortic Stenosis.

PubMed

Sheng, Siyuan P; Howell, Lucius A; Caughey, Melissa C; Yeung, Michael; Vavalle, John P

2018-01-15

Patients with calcific aortic stenosis (AS) often have diffuse cardiac calcification involving the mitral valve apparatus and coronary arteries. We examined the association between global cardiac calcification quantified by a previously validated echocardiographic calcium score (eCS) with the severity of mitral stenosis (MS) and coronary artery disease (CAD) in patients with a clinical diagnosis of severe calcific AS. In this sample of 147 patients (mean age 81 ± 9 years, 50% male), 81 patients (55%) were determined by echocardiography to have some degree of MS. Higher mean eCS was observed in patients with more severe MS (r = 0.54, p < 0.0001). Higher eCS was also inversely associated with mitral valve area (r = -0.31, p = 0.001) and positively associated with mitral valve mean pressure gradient (r = 0.46, p < 0.0001) and mitral valve peak flow velocity (r = 0.55, p < 0.0001). The area under the receiver operating characteristic curve for using eCS to predict the presence of MS was 0.76. An eCS ≥ 8 predicted MS with a sensitivity of 68%, specificity of 76%, positive predictive value of 77%, and negative predictive value of 66%. High eCS, relative to low eCS, was associated with 2.70 times the adjusted odds of CAD (odds ratio = 2.70, 95% confidence interval 1.02 to 7.17). In conclusion, global cardiac calcification is associated with MS and CAD in patients with severe calcific AS, and eCS shows ability to predict the presence of MS. This study suggests that a simple eCS may be used as part of a risk-stratification tool in patients with severe calcific aortic valve stenosis. Copyright © 2017 Elsevier Inc. All rights reserved.

Bioactive calcium phosphate-based glasses and ceramics and their biomedical applications: A review.

PubMed

Islam, Md Towhidul; Felfel, Reda M; Abou Neel, Ensanya A; Grant, David M; Ahmed, Ifty; Hossain, Kazi M Zakir

2017-01-01

An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented.

Calcium leaching behavior of cementitious materials in hydrochloric acid solution.

PubMed

Yang, Huashan; Che, Yujun; Leng, Faguang

2018-06-11

The calcium leaching behavior of cement paste and silica fume modified calcium hydroxide paste, exposed to hydrochloric acid solution, is reported in this paper. The kinetic of degradation was assessed by the changes of pH of hydrochloric acid solution with time. The changes of compressive strength of specimens in hydrochloric acid with time were tested. Hydration products of leached specimens were also analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG), and atomic force microscope (AFM). Tests results show that there is a dynamic equilibrium in the supply and consumption of calcium hydroxide in hydrochloric acid solution, which govern the stability of hydration products such as calcium silicate hydrate (C-S-H). The decrease of compressive strength indicates that C-S-H are decomposed due to the lower concentration of calcium hydroxide in the pore solution than the equilibrium concentration of the hydration products. Furthermore, the hydration of unhydrated clinker delayed the decomposition of C-S-H in hydrochloric acid solution due to the increase of calcium hydroxide in pore solution of cementitious materials.

Clinical and histologic outcomes of calcium sulfate in the treatment of postextraction sockets.

PubMed

Ruga, Emanuele; Gallesio, Cesare; Chiusa, Luigi; Boffano, Paolo

2011-03-01

The aim of this prospective study was to assess the clinical and histologic outcomes obtained with calcium sulfate (CS) used as a filler material in fresh premolar and molar postextraction sockets. Sixty premolar or molar postextraction sockets were filled with CS. Among the 60 grafted sockets, after 3 months, 50 underwent implant placement and clinical assessment. The removal of a sample core of newly generated intrasocket tissue was performed in 19 sockets. Collected samples were sent for histologic examination. The percentage of vital bone, nonvital bone, residual CS, amorphous material, and connective areas in every sample was calculated and recorded. Fifty postextraction regenerated sockets that underwent implant placement 3 months after tooth removal were included in this study.A partial postoperative exposition of the graft was observed in 12 of 50 sockets. At the surgical reentry, the augmented extraction sockets were completely filled by a hard material with an adequate alveolar crest in 41 cases. Histologic examination of the cores revealed that 63.16% of the intrasocket tissue was new vital bone, 2.1% was nonvital bone, 4.74% was fibrous tissue, and 30% was amorphous material. No residual CS was identified in bone cores. This study confirmed that CS is an ideal grafting material. The clinical adequacy aspect of filled sockets at surgical reentry seemed to be indicative of a qualitatively better bone regeneration. Postoperative exposition of graft material after a first intervention seemed to constitute an important risk factor for a worse bone regeneration.

Prognostic Analysis for Cardiogenic Shock in Patients with Acute Myocardial Infarction Receiving Percutaneous Coronary Intervention

PubMed Central

Lin, Mao-Jen; Chen, Chun-Yu; Lin, Hau-De

2017-01-01

Cardiogenic shock (CS) is uncommon in patients suffering from acute myocardial infarction (AMI). Long-term outcome and adverse predictors for outcomes in AMI patients with CS receiving percutaneous coronary interventions (PCI) are unclear. A total of 482 AMI patients who received PCI were collected, including 53 CS and 429 non-CS. Predictors for AMI patients with CS including recurrent MI, cardiovascular (CV) mortality, all-cause mortality, and repeated-PCI were analyzed. The CS group had a lower central systolic pressure and central diastolic pressure (both P < 0.001). AMI patients with hypertension history were less prone to develop CS (P < 0.001). Calcium channel blockers and statins were less frequently used by the CS group than the non-CS group (both P < 0.05) after discharge. Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery (SYNTAX) score, CV mortality, and all-cause mortality were higher in the CS group than the non-CS group (all P < 0.005). For patients with CS, stroke history was a predictor of recurrent MI (P = 0.036). CS, age, SYNTAX score, and diabetes were predictors of CV mortality (all P < 0.05). CS, age, SYNTAX score, and stroke history were predictors for all-cause mortality (all P < 0.05). CS, age, and current smoking were predictors for repeated-PCI (all P < 0.05). PMID:28251160

[Effects of various adsorbants on coagulation factors (author's transl)].

PubMed

Soulier, J P; Prou-Wartelle, O

1975-01-01

Adsorption of clotting factors by various adsorbants is studied (tricalcium phosphate, baryum sulfate or carbonate or citrate, calcium oxalate, aluminium hydroxyde and several silicate such as: kaolin, celite, bentonite, attapulgite, beidellite, asbestos). The main properties of each adsorbant are listed as well as several applications such as: selective adsorption of fibrinogen, separation between fibrinogen and factor VIII, separation of factor II from the other components of the prothrombin complex. Activation of factors XII and XI by the various silicates, as well as the activation of factor V by attapulgite are studied. Finally, the action of such adsorbants on the fibrinolytic system is summarized.

Atherosclerotic Plaque in Patients with Zero Calcium Score at Coronary Computed Tomography Angiography

PubMed Central

Gabriel, Fabíola Santos; Gonçalves, Luiz Flávio Galvão; de Melo, Enaldo Vieira; Sousa, Antônio Carlos Sobral; Pinto, Ibraim Masciarelli Francisco; Santana, Sara Melo Macedo; de Matos, Carlos José Oliveira; Souto, Maria Júlia Silveira; Conceição, Flávio Mateus do Sacramento; Oliveira, Joselina Luzia Menezes

2018-01-01

Background In view of the high mortality for cardiovascular diseases, it has become necessary to stratify the main risk factors and to choose the correct diagnostic modality. Studies have demonstrated that a zero calcium score (CS) is characteristic of a low risk for cardiovascular events. However, the prevalence of individuals with coronary atherosclerotic plaques and zero CS is conflicting in the specialized literature. Objective To evaluate the frequency of patients with coronary atherosclerotic plaques, their degree of obstruction and associated factors in patients with zero CS and indication for coronary computed tomography angiography (CCTA). Methods This is a cross-sectional, prospective study with 367 volunteers with zero CS at CCTA in four diagnostic imaging centers in the period from 2011 to 2016. A significance level of 5% and 95% confidence interval were adopted. Results The frequency of atherosclerotic plaque in the coronary arteries in 367 patients with zero CS was 9.3% (34 individuals). In this subgroup, mean age was 52 ± 10 years, 18 (52.9%) were women and 16 (47%) had significant coronary obstructions (> 50%), with involvement of two or more segments in 4 (25%) patients. The frequency of non-obese individuals (90.6% vs 73.9%, p = 0.037) and alcohol drinkers (55.9% vs 34.8%, p = 0.015) was significantly higher in patients with atherosclerotic plaques, with an odds ratio of 3.4 for each of this variable. Conclusions The frequency of atherosclerotic plaque with zero CS was relatively high, indicating that the absence of calcification does not exclude the presence of plaques, many of which obstructive, especially in non-obese subjects and alcohol drinkers. PMID:29723329

Scanning electron microscope view of iron crystal growing on pyroxene crystal

NASA Technical Reports Server (NTRS)

1972-01-01

A scanning electron microscope photograph of a four-micron size iron crystal growing on a pyroxene crystal (calcium-magnesium-iron silicate) from the Apollo 15 Hadley-Apennino lunar landing site. The well developed crystal faces indicate that the crystal was formed from a hot vapor as the rock was cooling.

Evaluation of Military Field-Water Quality. Volume 3. Opportunity Poisons

DTIC Science & Technology

1987-12-01

Acidic chemical cleaners fluoric acid, nitric acid, perchloric Spent acid acid, sulfuric acid Alkalies Miscellaneous caustic products Ammonia, lime...calcium oxide), potassium Alkaline battery fluid hydroxide, sodium hydroxide, sodium Caustic wastewater silicate Cleaning solutions Lye Nonhalogenated...Laboratory chemicals chloride, polychlorinated biphenyls, zinc Paint and varnish removers naphthenate , copper naphthenate , dichloro- Capacitors and

The Effects of Minor Constituents in Calcium Silicate Insulation on the Corrosion of Underground Heat Distribution Systems.

DTIC Science & Technology

1984-05-01

distribution systems were ob- ride content per unit weight of insulation was deter- tained from Johns - Manville , Pabco, and Owens- mined as the ratio...either adding more distilled-deionized water to the Aecomecial oraoh milly ana-yzedias-received samples of Johns - Manville . Owens-Corning, suspension, or

ToF-SIMS images and spectra of biomimetic calcium silicate-based cements after storage in solutions simulating the effects of human biological fluids

NASA Astrophysics Data System (ADS)

Torrisi, A.; Torrisi, V.; Tuccitto, N.; Gandolfi, M. G.; Prati, C.; Licciardello, A.

2010-01-01

ToF-SIMS images were obtained from a section of a tooth, obturated by means of a new calcium-silicate based cement (wTCF) after storage for 1 month in a saline solutions (DPBS), in order to simulate the body fluid effects on the obturation. Afterwards, ToF-SIMS spectra were obtained from model samples, prepared by using the same cement paste, after storage for 1 month and 8 months in two different saline solutions (DPBS and HBSS). ToF-SIMS spectra were also obtained from fluorine-free cement (wTC) samples after storage in HBSS for 1 month and 8 months and used for comparison. It was found that the composition of both the saline solution and the cement influenced the composition of the surface of disks and that longer is the storage greater are the differences. Segregation phenomena occur both on the cement obturation of the tooth and on the surface of the disks prepared by using the same cement. Indirect evidences of formation of new crystalline phases are supplied.

Mechanochemical Synthesis of Hydroxyapatite and Its Modifications: Composition, Structure, and Properties

NASA Astrophysics Data System (ADS)

Chaikina, M. V.; Bulina, N. V.; Ishchenko, A. V.; Prosanov, I. Yu.

2014-02-01

The mechanochemical method is used to synthesize samples of hydroxyapatite (HA) with substitution of the phosphate ion by silicate and zirconate ions, and substitution of calcium ions by copper ions. In the process of mechanochemical synthesis, carbonate ions and water molecules are incorporated into the structure of HA due to interaction of components of the reaction mixture with air. Intrusion of carbonate into the structure of HA is a competing process with modification of apatite by silicate and zirconate anions; therefore, the composition of the product during synthesis differs from the prescribed one. After annealing of the samples, the composition of the anion-modified HA can be described by the formula Са10(РО4)6- х (АО4) х (ОН)2- х , where (АО4)4- is the modifying anion. Substitution of calcium by copper ions localized at the Са1 position has been detected. Silver ions are not incorporated into the structure of HA, but are distributed in the apatite matrix in the form of nanocrystals of metallic silver.

Production of geopolymers using glass produced from DC plasma treatment of air pollution control (APC) residues.

PubMed

Kourti, Ioanna; Rani, D Amutha; Deegan, D; Boccaccini, A R; Cheeseman, C R

2010-04-15

Air pollution control (APC) residues are the hazardous waste produced from cleaning gaseous emissions at energy-from-waste (EfW) facilities processing municipal solid waste (MSW). APC residues have been blended with glass-forming additives and treated using DC plasma technology to produce a high calcium alumino-silicate glass. This research has investigated the optimisation and properties of geopolymers prepared from this glass. Work has shown that high strength geopolymers can be formed and that the NaOH concentration of the activating solution significantly affects the properties. The broad particle size distribution of the APC residue glass used in these experiments results in a microstructure that contains unreacted glass particles included within a geopolymer binder phase. The high calcium content of APC residues may cause the formation of some amorphous calcium silicate hydrate (C-S-H) gel. A mix prepared with S/L=3.4, Si/Al=2.6 and [NaOH]=6M in the activating solution, produced high strength geopolymers with compressive strengths of approximately 130 MPa. This material had high density (2070 kg/m(3)) and low porosity. The research demonstrates for the first time that glass derived from DC plasma treatment of APC residues can be used to form high strength geopolymer-glass composites that have potential for use in a range of applications. 2009 Elsevier B.V. All rights reserved.

Bioactive calcium phosphate–based glasses and ceramics and their biomedical applications: A review

PubMed Central

Islam, Md Towhidul; Felfel, Reda M; Abou Neel, Ensanya A; Grant, David M; Ahmed, Ifty; Hossain, Kazi M Zakir

2017-01-01

An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented. PMID:28794848

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cantrill, E.R.; Ray, A.; Stevens, M.G.

The interfacial bond between fiber and matrix is one of the most important factors influencing fiber-reinforced composites. This is particularly apparent in cellulose wood pulp reinforced cement/quartz composites cured by autoclaving under saturated steam at 180 C. Scanning electron microscopy (SEM) studies have shown that there is little modification of the surface of the hydrated calcium silicate matrix immediately adjacent to the cellulose fiber surface, provided the cellulose fiber is relatively free from lignin, hemicelluloses, or chemicals from the pulping process. Coutts & Campbell (1979) in their investigation of water cured cement composites, applied several commercial coupling agents to cellulosemore » fibres and established that two of these agents significantly increased the strength of the interfacial bond. In this paper, the surface of cellulose fibres was modified by sodium silicate, CTBN [carboxy terminated butadiene nitrile] and ATBN [amino terminated butadiene nitrile] in order to enhance the interfacial bond, and also to increase the resistance of the cellulose to oxidation, alkaline or thermal degradation, and algal attack. Algal attack can occur as the calcium silicate matrix is neutralized by atmospheric carbonation, especially in external wall board applications of the sheet composite. In addition, suitable coatings will protect the cellulose fiber from degradation arising from the presence of elevated temperature and alkaline solutions during the autoclaving process. Cellulose reinforced composites with substandard strengths, due to inhibited autoclave reactions, cannot be reautoclaved as the resultant material is too brittle due, in part, to the degradation of the cellulose fiber.« less

Quantification of epicardial adipose tissue in coronary calcium score and CT coronary angiography image data sets: comparison of attenuation values, thickness and volumes.

PubMed

La Grutta, Ludovico; Toia, Patrizia; Farruggia, Alfonso; Albano, Domenico; Grassedonio, Emanuele; Palmeri, Antonella; Maffei, Erica; Galia, Massimo; Vitabile, Salvatore; Cademartiri, Filippo; Midiri, Massimo

2016-06-01

The aim of the study was to compare epicardial adipose tissue (EAT) characteristics assessed with coronary calcium score (CS) and CT coronary angiography (CTCA) image data sets. In 76 patients (mean age 59 ± 13 years) who underwent CS and CTCA owing to suspected coronary artery disease (CAD), EAT was quantified in terms of density (Hounsfield units), thickness and volume. The EAT volume was extracted with a semi-automatic software. A moderate correlation was found between EAT density in CS and CTCA image data sets (-100 ± 19 HU vs -70 ± 24 HU; p < 0.05, r = 0.55). The distribution of EAT was not symmetrical with a maximal thickness at the right atrioventricular groove (14.2 ± 5.3 mm in CS, 15.7 ± 5 mm in CTCA; p > 0.05, r = 0.76). The EAT volume resulted as 122 ± 50 cm(3) in CS and 86 ± 40 cm(3) in CTCA (Δ = 30%, p < 0.05, r = 0.92). After adjustment for post-contrast EAT attenuation difference (Δ = 30 HU), the volume was 101 ± 47 cm(3) (Δ = 17%, p < 0.05, r = 0.92). Based on EAT volume median values, no differences were found between groups with smaller and larger volumes in terms of Agatston score and CAD severity. CS and CTCA image data sets may be equally employed for EAT assessment; however, an underestimation of volume is found with the latter acquisition even after post-contrast attenuation adjustment. EAT may be measured by processing either the CS or CTCA image data sets.

Reuse of residual sludge from stone-processing: differences and similarities between sludge coming from carbonate and silicate stones

NASA Astrophysics Data System (ADS)

Careddu, Nicola; Antonella Dino, Giovanna

2015-04-01

Residual sludge coming from dimension stone working activities represents a serious environmental and economic problem both for Stone Industry and citizens. Indeed, most of time, residual sludge is landfilled because of the difficulties to recover it; such difficulties are mainly connected to local legislation and a lack of proper protocols. In general, it is possible to individuate two different categories of sludge: residual sludge coming from carbonate rocks (CS) and those coming from silicate rocks (SS). Both of them are characterised by a very fine size distribution. CS is composed mainly by the same compounds of the processed stones (marble, limestone, travertine). The reason of this is related to the very slow wear of diamond tools during processing which entails a negligible content of heavy metals. CS becomes very interesting, from an economic point of view, when it has a CaCO3 grade > 95 %. On the contrary, SS is characterised by high heavy metal and TPH content. Residual sludge from the processing of silicate rocks can be split in three different sub-categories, depending on the way they are produced, and in particular: sludge from gangsaw using abrasive steel shot (GSS), sludge from multi diamond-saw block cutter (DBC), and mixed sludge (MS) from gangsaw and block cutter. These three sub-categories show different problems connected to heavy metal content, indeed on the one hand GSS is characterised by a high percentage of Ni, Cr, Cu, etc., on the other hand DBC is characterised by Co and Cu high content. In general, sludge, management of which in Italy is administered in accordance with the Italian Legislative Decree 152/06, can be used as waste from for environmental restoration or for cement plants. Several researches investigate the possible reuse of these materials but, at present time, there is no evidence of its systematic recovery as "recycled product" or "by-product". On the basis of the results of these researches it is possible to highlight its recovery, after a proper treatment, mainly as: landfill waterproofing material; filler material for civil works; artificial soil for land rehabilitation and high value added products from carbonate rocks. Such "new products", obtained from the treatment of residual sludge, have to be certified not only on the basis of their technical and physical characteristics but also by means of appropriate chemical analyses to guarantee that the products are not polluted. The research will show a comparison between the characteristics of the two main sludge categories (similarities and differences), the environmental problems connected to sludge management, the potential applications for both the categories (CS and SS), highlighting the most promising ones (e.g., SS: artificial soil for land rehabilitation and filler material for civil works; CS: filler in high value added products as paper, rubber and paints), the problems connected to "new products" certification and selling, and some suggestions for executive protocols to boost their systematic recovery.

Calcium-based biomaterials for diagnosis, treatment, and theranostics.

PubMed

Qi, Chao; Lin, Jing; Fu, Lian-Hua; Huang, Peng

2018-01-22

Calcium-based (CaXs) biomaterials including calcium phosphates, calcium carbonates, calcium silicate and calcium fluoride have been widely utilized in the biomedical field owing to their excellent biocompatibility and biodegradability. In recent years, CaXs biomaterials have been strategically integrated with imaging contrast agents and therapeutic agents for various molecular imaging modalities including fluorescence imaging, magnetic resonance imaging, ultrasound imaging or multimodal imaging, as well as for various therapeutic approaches including chemotherapy, gene therapy, hyperthermia therapy, photodynamic therapy, radiation therapy, or combination therapy, even imaging-guided therapy. Compared with other inorganic biomaterials such as silica-, carbon-, and gold-based biomaterials, CaXs biomaterials can dissolve into nontoxic ions and participate in the normal metabolism of organisms. Thus, they offer safer clinical solutions for disease theranostics. This review focuses on the state-of-the-art progress in CaXs biomaterials, which covers from their categories, characteristics and preparation methods to their bioapplications including diagnosis, treatment, and theranostics. Moreover, the current trends and key problems as well as the future prospects and challenges of CaXs biomaterials are also discussed at the end.

Evidence for the presence of carbonate melt during the formation of cumulates in the Colli Albani Volcanic District, Italy

NASA Astrophysics Data System (ADS)

Shaw, Cliff S. J.

2018-06-01

Fergusite and syenite xenoliths and mafic lapilli from two locations in the Villa Senni ignimbrite of the Colli Albani Volcanic District show evidence for fractionation of a silicate magma that led to exsolution of an immiscible carbonate melt. The fergusite xenoliths are divided into two groups on the basis of their clinopyroxene compositions. Group 1 clinopyroxene records the crystallisation of a silicate melt and enrichment of the melt in Al, Ti and Mn and depletion in Si as well as enrichment in incompatible trace elements. The second group of clinopyroxene compositions (group 2) comes mainly from Ba-F-phlogopite- and Ti-andradite-bearing fergusites. They have significantly higher Si and lower Al and Ti and, like the coexisting phlogopite and garnet are strongly enriched in Mn. The minerals in the fergusites containing group 2 clinopyroxene are enriched in Ba, Sr, Cs, V and Li all of which are expected to partition strongly into a carbonate melt phase relative to the coexisting silicate melt. The compositional data suggest that the group 1 fergusites record sidewall crystallisation of CO2-rich silicate melt and that once the melt reached a critical degree of fractionation, carbonate melt exsolved. The group 2 fergusites record continued crystallisation in this heterogeneous silicate - carbonate melt system. Composite xenoliths of fergusite and thermometamorphic skarn record contact times of hundreds to a few thousand years indicating that fractionation and assimilation was relatively rapid.

Prognostic value of calcium score and coronary flow velocity reserve in asymptomatic diabetic patients.

PubMed

Dikic, Miodrag; Tesic, Milorad; Markovic, Zeljko; Giga, Vojislav; Djordjevic-Dikic, Ana; Stepanovic, Jelena; Beleslin, Branko; Jovanovic, Ivana; Mladenovic, Ana; Seferovic, Jelena; Ostojic, Miodrag; Arandjelovic, Aleksandra

2015-09-04

The risk stratification of patients with diabetes mellitus (DM) is a major objective for the clinicians, and it can be achieved by coronary flow velocity reserve (CFVR) or with coronary artery calcium score (CS). CS evaluates underlying coronary atherosclerotic plaque burden and CFVR estimates both presence of coronary artery stenosis and microvascular function. Consequently, CFVR may provide unique risk information beyond the extent of coronary atherosclerosis. Our aim is to assess joint prognostic value of CFVR and CS in asymptomatic DM patients. We prospectively included 200 asymptomatic patients (45,5 % male, mean age 57,35 ± 11,25), out of which, there were 101 asymptomatic patients with DM and 99 asymptomatic patients without DM, but with one or more conventionally risk factors for coronary artery disease. We analyzed clinical, biochemical, metabolic, inflammatory parameters, CS by Agatston method, transthoracic Doppler echocardiography CFVR of left anterior descending artery and echocardiographic parameters. Total CS and CS LAD were significantly higher, while mean CFVR was lower in diabetics compared to the nondiabetics. During 1 year follow-up, 24 patients experienced cardio-vascular events (one cardiovascular death, two strokes, three myocardial infarctions, nine new onsets of unstable angina and nine myocardial revascularizations): 19 patients with DM and five non DM patients, (p = 0,003). Overall event free survival was significantly higher in non DM group, compared to the DM group (94,9 % vs. 81,2 %, p = 0,002 respectively), while the patients with CS ≥200 and CFVR <2 had the worst outcome during 1 year follow up in the whole study population as well as in the DM group. At multivariable analysis CFVR on LAD (HR 12.918, 95 % CI 3.865-43.177, p < 0.001) and total CS (HR 13.393, 95 % CI 1.675-107.119, p = 0.014) were independent prognostic predictors of adverse events in DM group of patients. Both CS and CFVR provide independent and complementary prognostic information in asymptomatic DM patients. When two parameters are analyzed together, the risk stratification ability improves, even when DM patients are analyzed together with non DM patients. As a result, DM patients with CS ≥200 and CFVR <2 had the worst outcome. Consequently, the use of two tests identified subset of patients who can derive the most benefit from the intensive prevention measures.

Overview of insoluble radioactive cesium particles emitted from the Fukushima Dai-ichi Nuclear Power Station

NASA Astrophysics Data System (ADS)

Satou, Yukihiko

2017-04-01

In the early stage of the Fukushima Dai-ichi Nuclear Power Station (F1NPS) accident, number of spot type contamination has been observed in computed autoradiography (Kashimura 2013, Shibata 2013, Satou 2014). It's means presence of radioactive particles, however, insoluble cesium particle was overlooked because cesium, which is dominant radioactive element in the accident, becomes ionized in the environment. Adachi et al. (2013) showed presence of cesium (Cs)-bearing particles within air dust sample collected at Tsukuba, 170 km south from the Fukushima site, in midnight of 14 to morning of 15 March 2011. These particles were micrometer order small particles and Cs was could be detectable as element using an energy dispersive X-ray spectroscopy (EDX). However, other radioactive elements such as Co-60, Ru-103 and uranium, which were dominant element of radioactive particles delivered from Chernobyl accident, could not detected. Abe et al. (2014) employed a synchrotron radiation (SR)-micro(μ)-X-ray analysis to the Cs-bearing particles, and they were concluded that (1) contained elements derived from nuclear fission processes and from nuclear reactor and fuel materials; (2) were amorphous; (3) were highly oxidized; and (4) consisted of glassy spherules formed from a molten mixture of nuclear fuel and reactor material. In addition, Satou et al. (2016) and Yamaguchi et al. (2016) disclosed that silicate is main component of Cs-bearing particles. Satou et al. (2015) discovered two types of radioactive particles from soil samples collected in the vicinity of the F1NPS. These particles were remained in the natural environment more than four years, silicate is main component in common of each group particles. Group A particles were very similar to Cs-bearing particles reported by Adachi et al. except particle shape. On the other hand, group B is big particles found in north area from the F1NPS, and the strongest particles contained 20 kBq of Cs-137 within a particle. Radioactive ratio of Cs-134/Cs-137 of group A and B is completely different. Group B particles shown 0.92 (mean value) of Cs ratio, and specific radioactivity are much lowers than group A particles. In contrast, activity ratio in group A particles shown 1.0 (mean value), and it was consistent with previous studies by Adachi (2013). The location of soil samples, which was containing group B particles, has been contaminated with radioactive materials from Unit 1 with hydrogen explosion on 12 March (Satou et al. 2014, Chino et al. 2016). More than 300 um of diameter particles has been transported from the Unit 1 of F1NPS. This result shown that the insoluble radioactive cesium particles are emitted from not only Units 2 and/or 3 on 15 March but also Unit 1 on 12 March. The insoluble radioactive Cs particles were spread widely, and it is require to evaluation for particulate percentage of contribution in total emitted radioactive cesium, and long term monitoring of these behaviors.

Bioactive calcium silicate ceramics and coatings.

PubMed

Liu, Xuanyong; Morra, Marco; Carpi, Angelo; Li, Baoe

2008-10-01

CaO-SiO2 based ceramics have been regarded as potential candidates for artificial bone due to their excellent bone bioactivity and biocompatibility. However, they cannot be used as implants under a heavy load because of their poor mechanical properties, in particular low fracture toughness. Plasma spraying CaO-SiO2 based ceramic coatings onto titanium alloys can expand their application to the hard tissue replacement under a heavy load. Plasma sprayed wollastonite, dicalcium silicate and diopside coatings have excellent bone bioactivity and high bonding strength to titanium alloys. It is possible that these plasma sprayed CaO-SiO2 based ceramic coatings will be applied in clinic after they are widely and systematically researched.

Assessment of Dephosphorization During Vanadium Extraction Process in Converter

NASA Astrophysics Data System (ADS)

Chen, Lian; Diao, Jiang; Wang, Guang; Xie, Bing

2018-06-01

Dephosphorization during the vanadium extraction process in the converter was studied. The effects of the slag basicity and FeO content on the dephosphorization and the mineral phases in the phosphorus-containing vanadium slag are discussed. The results show that removal of phosphorus from the hot metal during the vanadium extraction process can be achieved by adding lime into the vanadium extraction converter. The highest dephosphorization rate was obtained at slag basicity of 1.93. The phosphorus distribution ratio increased with increasing FeO content up to 16-18% but decreased thereafter. Vanadium was present in the slag only as spinels rather than calcium vanadate. Phosphorus was still present in the form of calcium phosphate eutectic in calcium silicate. The present work proves that the vanadium extraction and dephosphorization processes are nonconflicting reactions.

Three-dimensional culture of dental pulp stem cells in direct contact to tricalcium silicate cements.

PubMed

Widbiller, M; Lindner, S R; Buchalla, W; Eidt, A; Hiller, K-A; Schmalz, G; Galler, K M

2016-03-01

Calcium silicate cements are biocompatible dental materials applicable in contact with vital tissue. The novel tricalcium silicate cement Biodentine™ offers properties superior to commonly used mineral trioxide aggregate (MTA). Objective of this study was to evaluate its cytocompatibility and ability to induce differentiation and mineralization in three-dimensional cultures of dental pulp stem cells after direct contact with the material. Test materials included a new tricalcium silicate (Biodentine™, Septodont, Saint-Maur-des-Fossés, France), MTA (ProRoot® MTA, DENSPLY Tulsa Dental Specialities, Johnson City, TN, USA), glass ionomer (Ketac™ Molar Aplicap™, 3M ESPE, Seefeld, Germany), human dentin disks and polystyrene. Magnetic activated cell sorting for to the surface antigen STRO-1 was performed to gain a fraction enriched with mesenchymal stem cells. Samples were allowed to set and dental pulp stem cells in collagen carriers were placed on top. Scanning electron microscopy of tricalcium silicate cement surfaces with and without cells was conducted. Cell viability was measured for 14 days by MTT assay. Alkaline phosphatase activity was evaluated (days 3, 7, and 14) and expression of mineralization-associated genes (COL1A1, ALP, DSPP, and RUNX2) was quantified by real-time quantitative PCR. Nonparametric statistical analysis for cell viability and alkaline phosphatase data was performed to compare different materials as well as time points (Mann-Whitney U test, α = 0.05). Cell viability was highest on tricalcium silicate cement, followed by MTA. Viability on glass ionomer cement and dentin disks was significantly lower. Alkaline phosphatase activity was lower in cells on new tricalcium silicate cement compared to MTA, whereas expression patterns of marker genes were alike. Increased cell viability and similar levels of mineralization-associated gene expression in three-dimensional cell cultures on the novel tricalcium silicate cement and mineral trioxide aggregate indicate that the material is cytocompatible and bioactive. The tested new tricalcium silicate cement confirms its suitability as an alternative to MTA in vital pulp therapy.

Reply to Smith and Shortle: Lacking evidence of hydraulic efficiency changes

Treesearch

Mark B. Green; Amey S. Bailey; Scott W. Bailey; John J. Battles; John L. Campbell; Charles T. Driscoll; Timothy J. Fahey; Lucie C. Lepine; Gene E. Likens; Scott V. Ollinger; Paul G. Schaberg

2013-01-01

After calcium silicate amendment to an entire watershed at the Hubbard Brook Experimental Forest, evapotranspiration (ET) increased by ~20% for 2 y, broadly attributed to a fertilization of tree physiology (1). We suggested that the increase in ET most likely arose from enhanced transpiration due to increased stomatal conductance (gs) associated with increased...

Environmental Assessment of Selected Cone Penetrometer Grouts and a Tracer

DTIC Science & Technology

1993-08-01

Bentonite Clay ............ ...................... A2 Attapulgite Clay ................................... A22 Microfine Portland Cement...and the tracer are a. Bentonite clay. b. Attapulgite clay. c. Microfine portland cement. d. Joosten grout (calcium silicate grout). e. Urethane grout. f...Inc., on an attapulgite clay product (trade name: Zeogel). " Microfine portland cement. Information was obtained for two micro- fine portland cements

Prognostic Impact of Calcium Score after Transcatheter Aortic Valve Implantation Performed With New Generation Prosthesis.

PubMed

Akodad, Mariama; Lattuca, Benoit; Agullo, Audrey; Macia, Jean-Christophe; Gandet, Thomas; Marin, Grégory; Iemmi, Anaïs; Vernhet, Hélène; Schmutz, Laurent; Nagot, Nicolas; Albat, Bernard; Cayla, Guillaume; Leclercq, Florence

2018-05-15

Calcium score (CS) is a well-known prognostic factor after transcatheter aortic valve implantation (TAVI) performed with first generation prosthesis but few data are available concerning new generation valves. The aim of this study was to evaluate if CS remains a prognostic factor after Sapien 3 and Evolut R valves implantation. Agatston CS was evaluated on multislice computed tomography before TAVI in 346 patients implanted with Sapien XT (n = 61), CoreValve (n = 57) devices, (group 1, n = 118), and with new generation Sapien 3 (n = 147), Evolut R (n = 81) prosthesis, (group 2, n = 228). Major adverse cardiovascular events and aortic regurgitation (AR) were evaluated at 1 month. The 2 groups were similar at baseline except for logistic Euroscore (20.1% in group 1 vs 15.0 % in group 2; p = 0.001), chronic renal failure (44.1% vs 37.2% respectively, p = 0.007) and preprocedural CS (4,092 ± 2,176 vs 3,682 ± 2,109 respectively, p = 0.022). In group 1, 28 patients (23.7%) had adverse clinical events vs 21 (9.2%) in group 2 (p <0.01). In multivariate analysis, a higher CS was predictive of adverse events in group 1 (5,785 ± 3,285 vs 3,565 ± 1,331 p <0.0001) but not in group 2 (p = 0.28). A higher CS was associated with AR in group 1 (6,234 ± 2711 vs 3,429 ± 1,505; p <0.001) and in patients implanted with an Evolut R device from group 2 (4,085 ± 3,645 vs 2,551 ± 1,356; p = 0.01). In conclusion, CS appears as an important prognostic factor of major events after TAVI with first generation valves but not with new generation devices. CS remains associated with AR only with new generation self-expandable Evolut R devices. Copyright © 2018 Elsevier Inc. All rights reserved.

The physical properties and ion release of CPP-ACP-modified calcium silicate-based cements.

PubMed

Dawood, A E; Manton, D J; Parashos, P; Wong, Rhk; Palamara, Jea; Stanton, D P; Reynolds, E C

2015-12-01

This study investigated the physical properties and ion release of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP)-modified calcium silicate-based cements (CSCs) and compared the properties of a trial mineral trioxide aggregate (MTA) with two commercially available CSCs, Biodentine(™) and Angelus(®) MTA. The setting time, solubility, compressive strength and Vickers surface microhardness of the three CSCs incorporated with 0%, 0.5%, 1.0%, 2.0% and 3.0% (w/w) CPP-ACP were investigated. Release of calcium (Ca(2+) ), phosphate ions (Pi ) and pH of the test cements were measured after 24, 72, 168 and 336 h of storage. The addition of up to 1.0% CPP-ACP into Biodentine(™) and 0.5% into the other cements did not adversely affect their physical properties except for the setting time. The addition of 0.5% CPP-ACP increased Ca(2+) released from Biodentine(™) (after 168 and 336 h), Angelus(®) MTA (after 168 h) and the trial MTA (after 72 h). The addition of 1.0-3.0% CPP-ACP increased Ca(2+) and Pi released from all the cements. Biodentine(™) released more Ca(2+) particularly in the early stages and showed shorter setting time and higher mechanical properties than the other cements. The mechanical properties of Angelus(®) MTA and the trial MTA were similar. All the cements produced highly alkaline storage solutions. Up to 1.0% CPP-ACP in Biodentine(™) improves Ca(2+) and Pi release and 0.5% CPP-ACP in Angelus(®) MTA and the trial MTA improves Ca(2+) release without altering the mechanical properties and solubility. The addition of CPP-ACP into CSCs prolonged the setting time. © 2015 Australian Dental Association.

Particulate systems based on pectin/chitosan association for the delivery of manuka honey components and platelet lysate in chronic skin ulcers.

PubMed

Tenci, Marika; Rossi, Silvia; Bonferoni, Maria Cristina; Sandri, Giuseppina; Boselli, Cinzia; Di Lorenzo, Arianna; Daglia, Maria; Icaro Cornaglia, Antonia; Gioglio, Luciana; Perotti, Cesare; Caramella, Carla; Ferrari, Franca

2016-07-25

The aim of the present work was the development of a powder formulation for the delivery of manuka honey (MH) bioactive components and platelet lysate (PL) in chronic skin ulcers. In particular pectin (PEC)/chitosan (CS) particles were prepared by ionotropic gelation in the presence of calcium chloride and subsequently characterized for particle size, hydration properties and mechanical resistance. Different experimental conditions (calcium chloride and CS concentrations; rest time in the cationic solution) were considered in order to obtain particles characterized by optimal size, hydration properties and mechanical resistance. Two different fractions of MH were examined: one (Fr1), rich in methylglyoxal and the other (Fr2), rich in polyphenols. Particles were loaded with Fr1, fraction able to enhance in vitro proliferation of human fibroblasts, and with PL. The presence of CS in Fr1-loaded particles produced an improvement in cell proliferation. Moreover, PL loading into particles did not affect the biological activity of the hemoderivative. In vivo efficacy of PL- and Fr1-loaded particles was evaluated on a rat wound model. Both treatments markedly increased wound healing to the same extent. Copyright © 2016 Elsevier B.V. All rights reserved.

Octopamine and Dopamine differentially modulate the nicotine-induced calcium response in Drosophila Mushroom Body Kenyon Cells.

PubMed

Leyton, V; Goles, N I; Fuenzalida-Uribe, N; Campusano, J M

2014-02-07

In Drosophila associative olfactory learning, an odor, the conditioned stimulus (CS), is paired to an unconditioned stimulus (US). The CS and US information arrive at the Mushroom Bodies (MB), a Drosophila brain region that processes the information to generate new memories. It has been shown that olfactory information is conveyed through cholinergic inputs that activate nicotinic acetylcholine receptors (nAChRs) in the MB, while the US is coded by biogenic amine (BA) systems that innervate the MB. In this regard, the MB acts as a coincidence detector. A better understanding of the properties of the responses gated by nicotinic and BA receptors is required to get insights on the cellular and molecular mechanisms responsible for memory formation. In recent years, information has become available on the properties of the responses induced by nAChR activation in Kenyon Cells (KCs), the main neuronal MB population. However, very little information exists on the responses induced by aminergic systems in fly MB. Here we have evaluated some of the properties of the calcium responses gated by Dopamine (DA) and Octopamine (Oct) in identified KCs in culture. We report that exposure to BAs induces a fast but rather modest increase in intracellular calcium levels in cultured KCs. The responses to Oct and DA are fully blocked by a VGCC blocker, while they are differentially modulated by cAMP. Moreover, co-application of BAs and nicotine has different effects on intracellular calcium levels: while DA and nicotine effects are additive, Oct and nicotine induce a synergistic increase in calcium levels. These results suggest that a differential modulation of nicotine-induced calcium increase by DA and Oct could contribute to the events leading to learning and memory in flies. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Chitosan-rectorite nanospheres immobilized on polystyrene fibrous mats via alternate electrospinning/electrospraying techniques for copper ions adsorption

NASA Astrophysics Data System (ADS)

Tu, Hu; Huang, Mengtian; Yi, Yang; Li, Zhenshun; Zhan, Yingfei; Chen, Jiajia; Wu, Yang; Shi, Xiaowen; Deng, Hongbing; Du, Yumin

2017-12-01

Chitosan (CS), as a kind of well characterized biopolymer, has been used for heavy metal adsorption due to its low cost and high efficacy. However, when used directly, chitosan particles had small surface area and weak mechanical strength which is unfavorable to metal adsorption and reused. Besides, it cannot be easily recycled that may cause a secondary pollution. In this paper, CS and layered silicate rectorite (REC) were fully mixed and the mixtures were subsequently electrosprayed nano-sized spheres, which were immobilized on the surface of electrospun polystyrene (PS) mats for metal adsorption. The morphology analysis taken from SEM confirmed that CS-REC nanospheres were loaded on the surface of PS fibrous mats. Small Angle X-ray diffraction patterns showed that the interlayer distance of REC in composite mats was enlarged by the intercalation of CS chains; such structure meant bigger surface area which was helpful for metal adsorption. The data of contact angle implied that PS mats coated with CS-REC nanospheres exhibited better hydrophilicity than PS mats, which was conductive to adsorption rate. Besides, the copper ions adsorption of composite mats was tested at different conditions including the adsorption time, the initial pH and the initial concentration of copper ion. The results demonstrated that PS mats coated with CS-REC nanospheres had the adsorption capacity up to 134 mg/g. In addition, the addition of REC containing Ca2+ could also improve the metal adsorption because of cation exchange. The desorption assay indicated that PS mats immobilized with CS and CS-REC still kept high adsorption ability which retained 74% and 78% after three adsorption-desorption cycles.

Solubility of copper in silicate melts as function of oxygen and sulfur fugacities, temperature, and silicate composition

NASA Astrophysics Data System (ADS)

Holzheid, A.; Lodders, K.

2001-06-01

The solubility of Cu in silicate melts coexisting with liquid Cu(Fe) metal and liquid Cu(Fe) sulfide was determined experimentally at oxygen fugacities ranging from 10 -9.1 to 10 -13.6 bar and sulfur fugacities ranging from 10 -2.5 to 10 -6.3 bar at 1300°C. An iron oxide-free silicate of anorthite-diopside eutectic composition and a synthetic MgO-rich basaltic silicate (FeO-bearing) were used in the partitioning experiments. In S-containing systems, some of the metal reacted to metal sulfide. The silicates in the four systems investigated (Fe-free and S-free; Fe-containing and S-free; Fe-free and S-containing; Fe-containing and S-containing) had different colors depending on the dissolved Cu species and the presence of iron and/or sulfur. Irrespective of the presence of sulfur, the solubility of Cu in the silicate increases with increasing oxygen fugacity and metal/silicate partition coefficients for Cu decrease. Increasing the temperature from 1300°C to 1514°C increases the Cu solubility (decreases the metal/silicate partition coefficient) at an oxygen fugacity 0.5 log units below the iron-wüstite (IW) equilibrium in the Fe-free, S-free and Fe-containing, S-free systems. We infer the presence of monovalent Cu + ("CuO 0.5") in the silicate melt on the basis of the solubility of Cu as function of oxygen fugacity. Experiments containing iron yield a formal valence of ˜0.5 for Cu at very low oxygen fugacities, which is not observed in Fe-free systems. The low formal valence is explained by redox reactions between iron and copper in the silicate melts. There is no evidence for sulfidic dissolution of Cu in the silicates but sulfur has indirect effects on Cu partitioning. Iron metal/silicate partition coefficients depend on oxygen fugacity and on sulfur fugacity. Sulfidic dissolution of iron and oxide-sulfide exchange reactions with Cu cause a small increase in Cu metal/silicate partition coefficients. We derive an activity coefficient (γ CuO 0.5) of 10 ± 1 for liquid CuO 0.5 at 1300°C for the silicate melts used here. A comparison with literature data shows that log γ CuO 0.5 increases in proportion to the mass percentages [CaO +(Al 2O 3)/2] in silicate melts. We recommend the following equations for Cu metal/silicate and sulfide/silicate partitioning for geochemical and cosmochemical modeling if silicate composition and the activity of Cu in the metal or sulfide is known: log D met/sil = -0.48 - 0.25 · log fO 2 - log γ Cu metal + 0.02 · [CaO + (Al 2O 3)/2; wt%] silicate logD sul/sil=+0.76-0.25 · logfO 2+0.25logfS 2-logγ CS 0.5,sulfide +0.02 · [CaO+Al 2O 3/2;wt%] silicate. The derived Cu metal/silicate and metal/sulfide partition coefficients are applied to core formation in the Earth and Mars. The observed Cu abundances in the Earth cannot be easily explained by simple core-mantle equilibrium, but the observed Cu abundances for Mars are consistent with core-mantle equilibrium at low pressure and temperatures.

EXTINCTION LAWS TOWARD STELLAR SOURCES WITHIN A DUSTY CIRCUMSTELLAR MEDIUM AND IMPLICATIONS FOR TYPE IA SUPERNOVAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagao, Takashi; Maeda, Keiichi; Nozawa, Takaya, E-mail: nagao@kusastro.kyoto-u.ac.jp

Many astronomical objects are surrounded by dusty environments. In such dusty objects, multiple scattering processes of photons by circumstellar (CS) dust grains can effectively alter extinction properties. In this paper, we systematically investigate the effects of multiple scattering on extinction laws for steady-emission sources surrounded by the dusty CS medium using a radiation transfer simulation based on the Monte Carlo technique. In particular, we focus on whether and how the extinction properties are affected by properties of CS dust grains by adopting various dust grain models. We confirm that behaviors of the (effective) extinction laws are highly dependent on themore » properties of CS grains, especially the total-to-selective extinction ratio R{sub V}, which characterizes the extinction law and can be either increased or decreased and compared with the case without multiple scattering. We find that the criterion for this behavior is given by a ratio of albedos in the B and V bands. We also find that either small silicate grains or polycyclic aromatic hydrocarbons are necessary for realizing a low value of R{sub V} as often measured toward SNe Ia if the multiple scattering by CS dust is responsible for their non-standard extinction laws. Using the derived relations between the properties of dust grains and the resulting effective extinction laws, we propose that the extinction laws toward dusty objects could be used to constrain the properties of dust grains in CS environments.« less

Effects of anticaking agents and relative humidity on the physical and chemical stability of powdered vitamin C.

PubMed

Lipasek, Rebecca A; Taylor, Lynne S; Mauer, Lisa J

2011-09-01

Vitamin C is an essential nutrient that is widely used by the food industry in the powder form for both its nutritional and functional properties. However, vitamin C is deliquescent, and deliquescence has been linked to physical and chemical instabilities. Anticaking agents are often added to powder systems to delay or prevent caking, but little is known about their effect on the chemical stability of powders. In this study, various anticaking agents (calcium phosphate, calcium silicate, calcium stearate, corn starch, and silicon dioxide) were combined with sodium ascorbate at 2% and 50% w/w ratios and stored at various relative humidities (23%, 43%, 64%, 75%, 85%, and 98% RHs). Chemical and physical stability and moisture sorption were monitored over time. Additionally, saturated solution samples were stored at various pHs to determine the effect of surface pH and dissolution on the vitamin degradation rate. Storage RH, time, and anticaking agent type and ratio all significantly affected (P < 0.05) moisture sorption and vitamin C stability. Silicon dioxide and calcium silicate (50% w/w) and calcium stearate (at both ratios) were the only anticaking agents to improve the physical stability of powdered sodium ascorbate while none of the anticaking agents improved its chemical stability. However, corn starch and calcium stearate had the least adverse effect on chemical stability. Dissolution rate and pH were also important factors affecting the chemical and physical stability of the powders. Therefore, monitoring storage environmental conditions and anticaking agent usage are important for understanding the stability of vitamin C. Anticaking agent type and ratio significantly affected the physical and chemical stability of vitamin C over time and over a range of RHs. No anticaking agent improved the chemical stability of the vitamin, and most caused an increase in chemical degradation even if physical stability was improved. It is possible that anticaking agents would greatly affect other chemically labile deliquescent ingredients, and therefore, anticaking agent usage and storage conditions should be monitored in blended powder systems. © 2011 Institute of Food Technologists®

In Situ Soft X-ray Spectromicroscopy of Early Tricalcium Silicate Hydration

DOE PAGES

Bae, Sungchul; Kanematsu, Manabu; Hernandez-Cruz, Daniel; ...

2016-12-01

The understanding and control of early hydration of tricalcium silicate (C 3S) is of great importance to cement science and concrete technology. However, traditional characterization methods are incapable of providing morphological and spectroscopic information about in situ hydration at the nanoscale. Using soft X-ray spectromicroscopy, we report the changes in morphology and molecular structure of C 3S at an early stage of hydration. In situ C 3S hydration in a wet cell, beginning with induction (~1 h) and acceleration (~4 h) periods of up to ~8 h, was studied and compared with ex situ measurements in the deceleration period aftermore » 15 h of curing. Analysis of the near-edge X-ray absorption fine structure showed that the Ca binding energy and energy splitting of C 3S changed rapidly in the early age of hydration and exhibited values similar to calcium silicate hydrate (C–S–H). The formation of C–S–H nanoseeds in the C 3S solution and the development of a fibrillar C–S–H morphology on the C 3S surface were visualized. Following this, silicate polymerization accompanied by C–S–H precipitation produced chemical shifts in the peaks of the main Si K edge and in multiple scattering. However, the silicate polymerization process did not significantly affect the Ca binding energy of C–S–H.« less

In Situ Soft X-ray Spectromicroscopy of Early Tricalcium Silicate Hydration

PubMed Central

Bae, Sungchul; Kanematsu, Manabu; Hernández-Cruz, Daniel; Moon, Juhyuk; Kilcoyne, David; Monteiro, Paulo J. M.

2016-01-01

The understanding and control of early hydration of tricalcium silicate (C3S) is of great importance to cement science and concrete technology. However, traditional characterization methods are incapable of providing morphological and spectroscopic information about in situ hydration at the nanoscale. Using soft X-ray spectromicroscopy, we report the changes in morphology and molecular structure of C3S at an early stage of hydration. In situ C3S hydration in a wet cell, beginning with induction (~1 h) and acceleration (~4 h) periods of up to ~8 h, was studied and compared with ex situ measurements in the deceleration period after 15 h of curing. Analysis of the near-edge X-ray absorption fine structure showed that the Ca binding energy and energy splitting of C3S changed rapidly in the early age of hydration and exhibited values similar to calcium silicate hydrate (C–S–H). The formation of C–S–H nanoseeds in the C3S solution and the development of a fibrillar C–S–H morphology on the C3S surface were visualized. Following this, silicate polymerization accompanied by C–S–H precipitation produced chemical shifts in the peaks of the main Si K edge and in multiple scattering. However, the silicate polymerization process did not significantly affect the Ca binding energy of C–S–H. PMID:28774096

Influence of man-made aluminosilicate raw materials on physical and mechanical properties of building materials.

NASA Astrophysics Data System (ADS)

Volodchenko, A. A.; Lesovik, V. S.; Stoletov, A. A.; Glagolev, E. S.; Volodchenko, A. N.; Magomedov, Z. G.

2018-03-01

It has been identified that man-made aluminosilicate raw materials represented by clay rock of varied genesis can be used as energy-efficient raw materials to obtain efficient highly-hollow non-autoclaved silicate materials. A technique of structure formation in the conditions of pressureless steam treatment has been offered. Cementing compounds of non- autoclaved silicate materials based on man-made aluminosilicate raw materials possess hydraulic properties that are conditioned by the process of further formation and recrystallization of calcium silicate hydrates, which optimizes the ratio between gellike and crystalline components and densifies the cementing compound structure, which leads to improvement of performance characteristics. Increasing the performance characteristics of the obtained products is possible by changing the molding conditions. For this reason, in order to create high-density material packaging and, as a result, to increase the strength properties of the products, it is reasonable to use higher pressure, under which raw brick is formed, which will facilitate the increase of quality of highly-hollow products.

Raloxifene analog (LY117018 HCL) ameliorates cyclosporin A-induced osteopenia in oophorectomized rats.

PubMed

Bowman, A R; Sass, D A; Marshall, I; Ma, Y F; Liang, H; Jee, W S; Epstein, S

1996-08-01

Cyclosporin A (CsA) administered to the oophorectomized (Ox) rat exacerbates the high turnover osteopenia associated with estrogen deficiency. 17 beta-estradiol replacement therapy prevent this bone loss. The aim of this study was to see whether an estrogen-like compound, Raloxifene analog (LY117018 HCL, Ral) could likewise ameliorate CsA-induced osteopenia in the Ox rat. Sixty 6-month-old Sprague-Dawley rats, divided into five groups, underwent oophorectomy. One group acted as a basal group and the others received either vehicle (group B), CsA 15 mg/kg/day (group C), Ral 3 mg/kg/day (group D), or CsA 15 mg/kg/day and Ral 3 mg/kg/day (group E) for 28 days by gavage. A sixth sham operated group of 12 rats received vehicle only (group A). Rats were weighed and bled on days 0, 14, and 28 for measurement of ionized calcium, glucose, osteocalcin (BGP), 17 beta-estradiol, and 1,25-dihydroxyvitamin D3 (1,25[OH]2D3). Tibiae were removed on day 28 for bone histomorphometry after double tetracycline and calcein labeling. Oophorectomy caused a significant gain in weight in groups B and C which was prevented by Ral in groups D and E. Randomized blood glucose levels and 1,25(OH)2D3 levels were elevated in both CsA-treated groups. Blood ionized calcium levels were lower in vehicle (group B) compared with sham (group A) on day 28. Ox (group B) had significantly higher serum BGP levels compared with sham-operated rats. Serum BGP levels were further elevated in group C compared with vehicle and were lowered in both Ral-treated groups to vehicle levels by day 28. Bone histomorphometry revealed a high turnover osteopenia with increased parameters of bone formation and resorption and loss of cancellous bone volume postoophorectomy (group B). CsA (group C) exacerbated the effects of oophorectomy. Ral (group D) completely prevented the high turnover osteopenia caused by oophorectomy and was able to attenuate substantially the effects of CsA in the Ox rat (group E). Ral therapy ameliorated CsA-induced osteopenia in the Ox rat and might prove a useful agent in preventing bone loss in postmenopausal women receiving CsA.

Chronic stress and calcium oxalate stone disease: influence on blood cortisol and urine composition.

PubMed

Arzoz-Fàbregas, Montserrat; Ibarz-Servio, Luis; Fernández-Castro, Jordi; Valiente-Malmagro, Manuel; Roca-Antonio, Josep; Edo-Izquierdo, Sílvia; Buisan-Rueda, Oscar

2013-12-01

To evaluate the influence of chronic stress (CS) on urine composition of calcium oxalate (CaOx) stone patients and controls. This case-control study enrolled 128 patients during a period of 20 months. The cases were CaOx stone formers with a recent stone episode. Controls were matched by sex and age. Dimensions of CS were evaluated in cases and controls by validated self-report questionnaires measuring stressful life events, perceived stress, anxiety, depression, burnout, and satisfaction with life. Blood and urine samples were collected to determine cortisol levels and urinary composition. More relations between CS dimensions and blood and urine parameters were observed in cases than in controls. In cases, the blood cortisol level was related positively with the number of stressful life events (P = .03), intensity of these events (P = .04), and anxiety (P = .04). In addition, urinary magnesium (P = .03) and pyrophosphate (P = .05) levels were positively related with satisfaction with life and burnout, respectively. In contrast, urinary magnesium levels were negatively related with perceived stress (P = .01), anxiety (P = .016), and depression (P = .03). In controls, the number of stressful life events and the intensity of stressful life events was related positively with magnesium (P = .06, P = .02) levels and negatively with blood cortisol levels (P = .03, P = .004). Based on the variation between cases and controls in relations between CS dimensions and biochemical parameters, we hypothesize that CS may trigger a differential biological response in CaOx stone formers and controls, which in turn may promote or protect against CaOx stone formation. Copyright © 2013 Elsevier Inc. All rights reserved.

Antibiotic loaded calcium sulfate bead and pulse lavage eradicates biofilms on metal implant materials in vitro.

PubMed

Knecht, Cory S; Moley, James P; McGrath, Mary S; Granger, Jeffrey F; Stoodley, Paul; Dusane, Devendra H

2018-03-30

Pulse lavage (PL) debridement and antibiotic loaded calcium sulfate beads (CS-B) are both used for the treatment of biofilm related periprosthetic joint infection (PJI). However, the efficacy of these alone and in combination for eradicating biofilm from orthopaedic metal implant surfaces is unclear. The purpose of the study was to understand the efficacy of PL and antibiotic loaded CS-B in eradicating bacterial biofilms on 316L stainless steel (SS) alone and in combination in vitro. Biofilms of bioluminescent strains of Pseudomonas aeruginosa Xen41 and a USA300 MRSA Staphylococcus aureus SAP231 were grown on SS coupons for 3 days. The coupons were either, (i) debrided for 3 s with PL, (ii) exposed to tobramycin (TOB) and vancomycin (VAN) loaded CS-B for 24 h, or (iii) exposed to both. An untreated biofilm served as a control. The amount of biofilm was measured by bioluminescence, viable plate count and confocal microscopy using live/dead staining. PL alone reduced the CFU count of both strains of biofilms by approximately 2 orders of magnitude, from an initial cell count on metal surface of approximately 10 9 CFU/cm 2 . The antibiotic loaded CS-B caused an approximate six log reduction and the combination completely eradicated viable biofilm bacteria. Bioluminescence and confocal imaging corroborated the CFU data. While PL and antibiotic loaded CS-B both significantly reduced biofilm, the combination of two was more effective than alone in removing biofilms from SS implant surfaces. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:1-6, 2018. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Characteristics of solidified products containing radioactive molten salt waste.

PubMed

Park, Hwan-Seo; Kim, In-Tae; Cho, Yong-Zun; Eun, Hee-Chul; Kim, Joon-Hyung

2007-11-01

The molten salt waste from a pyroprocess to recover uranium and transuranic elements is one of the problematic radioactive wastes to be solidified into a durable wasteform for its final disposal. By using a novel method, named as the GRSS (gel-route stabilization/solidification) method, a molten salt waste was treated to produce a unique wasteform. A borosilicate glass as a chemical binder dissolves the silicate compounds in the gel products to produce one amorphous phase while most of the phosphates are encapsulated by the vitrified phase. Also, Cs in the gel product is preferentially situated in the silicate phase, and it is vitrified into a glassy phase after a heat treatment. The Sr-containing phase is mainly phosphate compounds and encapsulated by the glassy phase. These phenomena could be identified by the static and dynamic leaching test that revealed a high leach resistance of radionuclides. The leach rates were about 10(-3) - 10(-2) g/m2 x day for Cs and 10(-4) - 10(-3) g/m2 x day for Sr, and the leached fractions of them were predicted to be 0.89% and 0.39% at 900 days, respectively. This paper describes the characteristics of a unique wasteform containing a molten salt waste and provides important information on a newly developed immobilization technology for salt wastes, the GRSS method.

Effect of chemical admixtures on properties of high-calcium fly ash geopolymer

NASA Astrophysics Data System (ADS)

Rattanasak, Ubolluk; Pankhet, Kanokwan; Chindaprasirt, Prinya

2011-06-01

Owing to the high viscosity of sodium silicate solution, fly ash geopolymer has the problems of low workability and rapid setting time. Therefore, the effect of chemical admixtures on the properties of fly ash geopolymer was studied to overcome the rapid set of the geopolymer in this paper. High-calcium fly ash and alkaline solution were used as starting materials to synthesize the geopolymer. Calcium chloride, calcium sulfate, sodium sulfate, and sucrose at dosages of 1wt% and 2wt% of fly ash were selected as admixtures based on concrete knowledge to improve the properties of the geopolymer. The setting time, compressive strength, and degree of reaction were recorded, and the microstructure was examined. The results show that calcium chloride significantly shortens both the initial and final setting times of the geopolymer paste. In addition, sucrose also delays the final setting time significantly. The degrees of reaction of fly ash in the geopolymer paste with the admixtures are all higher than those of the control paste. This contributes to the obvious increases in compressive strength.

Biomimetic Mineralization on a Macroporous Cellulose-Based Matrix for Bone Regeneration

PubMed Central

Petrauskaite, Odeta; Gomes, Pedro de Sousa; Fernandes, Maria Helena; Juodzbalys, Gintaras; Maminskas, Julius

2013-01-01

The aim of this study is to investigate the biomimetic mineralization on a cellulose-based porous matrix with an improved biological profile. The cellulose matrix was precalcified using three methods: (i) cellulose samples were treated with a solution of calcium chloride and diammonium hydrogen phosphate; (ii) the carboxymethylated cellulose matrix was stored in a saturated calcium hydroxide solution; (iii) the cellulose matrix was mixed with a calcium silicate solution in order to introduce silanol groups and to combine them with calcium ions. All the methods resulted in a mineralization of the cellulose surfaces after immersion in a simulated body fluid solution. Over a period of 14 days, the matrix was completely covered with hydroxyapatite crystals. Hydroxyapatite formation depended on functional groups on the matrix surface as well as on the precalcification method. The largest hydroxyapatite crystals were obtained on the carboxymethylated cellulose matrix treated with calcium hydroxide solution. The porous cellulose matrix was not cytotoxic, allowing the adhesion and proliferation of human osteoblastic cells. Comparatively, improved cell adhesion and growth rate were achieved on the mineralized cellulose matrices. PMID:24163816

Influence of synthetic calcium silicates on the strength properties of fine-grained concrete

NASA Astrophysics Data System (ADS)

Yarusova, S. B.; Gordienko, P. S.; Kozin, A. V.; Zhevtun, I. G.; Perfilev, A. V.

2018-04-01

The effect of additives based on acicular calcium hydrosilicates (xonotlite and tobermorite) and wollastonite, obtained from boric acid production waste in autoclave synthesis at a temperature of 220 °C, on the strength of fine-grained concrete, has been studied in this paper. It was shown that when the calcium hydrosilicates and wollastonite are introduced, an increase in the strength characteristics of concrete is observed. After heat and moisture treatment, the maximum increase in strength is observed with the addition of 4% of mass content of calcium hydrosilicates and 6% of mass content of wollastonite. After 28 days of hardening under normal conditions, the maximum increase in strength of concrete is observed with the addition of 4% of mass content of both types of additives. It was shown that the water absorption of concrete decreases with a maximum when 4% of mass content is added, as in the case of the introduction of calcium hydrosilicates, and wollastonite. With a further increase in the number of additives, the amount of water absorption increases, but these values remain below the values for the control sample without additives.

Nanostructured calcium silicate hydrate seeds accelerate concrete hardening: a combined assessment of benefits and risks.

PubMed

Bräu, Michael; Ma-Hock, Lan; Hesse, Christoph; Nicoleau, Luc; Strauss, Volker; Treumann, Silke; Wiench, Karin; Landsiedel, Robert; Wohlleben, Wendel

2012-07-01

Nanotechnology creates new possibilities to control and improve material properties for civil infrastructure. Special focus in this area is put on Portland cement and gypsum. Together their annual production is by far larger than for any other material worldwide. Nanomodification of these materials can be done during the few hours between dissolution and hardening, especially by nucleation of the re-crystallization with suitable colloids. Here we report first results in homogeneous seeding of the precipitation of calcium silicate hydrates within a real Portland cement composition. The occupational safety during the production phase and during mixing of concrete paste is addressed in detail by in vivo testing. We perform 5-day inhalation with 21-day recovery in rats and analyze organ-specific toxicity and 71 endpoints from bronchoalveolar lavage (BALF) and blood. In BALF parameters, no test-related changes were observed, indicating the generally low toxicity of the test material. Some mild lesions were observed in larynx level. In the lungs, all animals of the 50 mg/m³ concentration group revealed a minimal to mild increase in alveolar macrophages, which recovered back to control level.

Electrophoretic deposition of porous CaO-MgO-SiO2 glass-ceramic coatings with B2O3 as additive on Ti-6Al-4V alloy.

PubMed

Zhang, Wei; Chen, Xianchun; Liao, Xiaoming; Huang, Zhongbing; Dan, Xiuli; Yin, Guangfu

2011-10-01

The sub-micron glass-ceramic powders in CaO-MgO-SiO(2) system with 10 wt% B(2)O(3) additive were synthesized by sol-gel process. Then bioactive porous CaO-MgO-SiO(2) glass-ceramic coatings on Ti-6Al-4V alloy substrates were fabricated using electrophoretic deposition (EPD) technique. After being calcined at 850°C, the above coatings with thickness of 10-150 μm were uniform and crack-free, possessing porous structure with sub-micron and micron size connected pores. Ethanol was employed as the most suitable solvent to prepare the suspension for EPD. The coating porous appearance and porosity distribution could be controlled by adjusting the suspension concentration, applied voltage and deposition time. The heat-treated coatings possessed high crystalline and was mainly composed of diopside, akermanite, merwinite, calcium silicate and calcium borate silicate. Bonelike apatite was formed on the coatings after 7 days of soaking in simulated body fluid (SBF). The bonding strength of the coatings was needed to be further improved.

Resistance to fracture of roots filled with different sealers.

PubMed

Sağsen, Burak; Ustün, Yakup; Pala, Kanşad; Demırbuğa, Sezer

2012-01-01

The aim of this study was to compare the fracture resistance of roots filled with gutta percha (GP) and different root canal sealers.Fifty-five human maxillary central incisors were selected and randomly divided into three experimental groups (Groups 1-3) and two control groups (Groups 4 and 5). They were Group 1-15 root canals filled with an epoxy resin-based sealer (AH Plus) and GP, Group 2 -15 root canals filled with a calcium silicate-based sealer (iRoot SP) and GP, Group 3: 15 root canals filled with another calcium silicate-based sealer (MTA Fillapex) and GP, Group 4: five roots were instrumented but not filled, and Group 5: five roots were neither instrumented nor filled. Compressive loading was carried out using a universal testing machine until fracture occurred. Force applied at time of fracture was recorded as fracture strength of specimen in Newtons. There were no significant differences in fracture strength among the three experimental groups (p>0.05), whose results were significantly superior to that of Group 4 (p<0.05). In conclusion, all the root canal sealers used in the present study increased the fracture resistance of instrumented root canals.

Clinical and radiographic comparison of indirect pulp treatment using light-cured calcium silicate and mineral trioxide aggregate in primary molars: A randomized clinical trial.

PubMed

Menon, Navya P; Varma, Balagopal R; Janardhanan, Sureshkumar; Kumaran, Parvathy; Xavier, Arun Mamachan; Govinda, Bhat Sangeetha

2016-01-01

To clinically and radiographically evaluate the reparative dentin formation in indirect pulp treatment (IPT) using mineral trioxide aggregate (MTA) and light cured calcium silicate (TheraCal) in primary molars over a period of 6 months. A clinical trial on IPT on 43 primary molars in 21 patients between the age of 4-7 years, divided into two groups: 22 teeth in MTA group and 21 in TheraCal group. Measurement of the variation in dentin thickness was done on the digitalized radiograph at baseline, 3 months and 6 months using CorelDRAW X3 software. Statistical analysis using an independent t -test for intragroup and intergroup comparison showed a significant increase in dentin thickness in both the MTA and TheraCal group (intragroup comparison [ P < 0.05]). However, intergroup comparison between MTA and TheraCal showed no statistical difference in reparative dentin formation ( P > 0.05). Clinically and radiographically, both MTA and TheraCal are good IPT materials. The better handling characteristics and comparable reparative dentin-forming ability of TheraCal make this material an alternative to MTA in pediatric restorative procedures.

The Impact of Thermocycling Process on the Dislodgement Force of Different Endodontic Cements

PubMed Central

Saghiri, Mohammad Ali; Asatourian, Armen; Garcia-Godoy, Franklin; Gutmann, James L.; Sheibani, Nader

2013-01-01

To evaluate the effects of thermocycling (500 cycles, 5°C/55°C) on the push-out bond strength of calcium silicate based cements including WMTA, Nano-WMTA, and Bioaggregate to root dentin. Forty-eight dentin slices were prepared and divided into 3 groups (n = 16) and filled with Angelus WMTA, Nano-WMTA, or Bioaggregate. After incubation, half of the samples were thermocycled while the other half remained untreated. Push-out bond strength was calculated, and the modes of the bond failures were determined by SEM. The highest bond strength was seen in nonthermocycled Nano-WMTA samples and the lowest in thermocycled Bioaggregate samples. The significant differences between nonthermocycled and thermocycled samples were only noticed in WMTA and Nano-WMTA groups (P < 0.001). The mode of failure for thermocycled samples of all three cements was mostly cohesive. Thermocycling process can drastically affect the push-out bond strength of calcium silicate based cements. The intrastructural damages occurred due to the thermal stresses, causing cohesive failures in set materials. Sealing property of endodontic cements which have experienced the thermal stresses can be jeopardized due to occlusal forces happening in furcation cites. PMID:24063004

Nanoscale Charge Balancing Mechanism in Calcium-Silicate-Hydrate Gels: Novel Complex Disordered Materials from First-principles

NASA Astrophysics Data System (ADS)

Ozcelik, Ongun; White, Claire

Alkali-activated materials which have augmented chemical compositions as compared to ordinary Portland cement are sustainable technologies that have the potential to lower CO2 emissions associated with the construction industry. In particular, calcium-silicate-hydrate (C-S-H) gel is altered at the atomic scale due to changes in its chemical composition. Here, based on first-principles calculations, we predict a charge balancing mechanism at the molecular level in C-S-H gels when alkali atoms are introduced into their structure. This charge balancing process is responsible for the formation of novel structures which possess superior mechanical properties compared to their charge unbalanced counterparts. Different structural representations are obtained depending on the level of substitution and the degree of charge balancing incorporated in the structures. The impact of these charge balancing effects on the structures is assessed by analyzing their formation energies, local bonding environments, diffusion barriers and mechanical properties. These results provide information on the phase stability of alkali/aluminum containing C-S-H gels, shedding light on the fundamental mechanisms that play a crucial role in these complex disordered materials. We acknowledge funding from the Princeton Center for Complex Materials, a MRSEC supported by NSF.

Effect of root canal obturation with calcium silicate materials on pH change in simulated root resorption defects.

PubMed

Aggarwal, Vivek; Singla, Mamta; Miglani, Sanjay; Sharma, Ritu

2018-01-01

This study evaluated the effect of 3 commercially available calcium silicate materials (CSMs) on pH changes in simulated root resorption defects. Simulated root resorption defects were prepared on the facial root surface of 40 mandibular premolars. The depth of each defect was individually calculated to standardize the remaining dentin thickness to 1 mm. Prepared canals were obturated with the 3 CSMs. Ten specimens were kept as controls, filled with unbuffered normal saline. The pH measurements were taken at 1 hour, 6 hours, 1 day, 1 week, 2 weeks, 3 weeks, 1 month, and 2 months. All CSM groups exhibited an initial alkaline pH of 9.0-9.7. The pH decreased to 8.0-8.5 after 2 months of storage. There were no significant differences between pH measurements at other time intervals. The CSM groups exhibited higher pH levels than the control group. The results showed that intracanal placement of the CSMs maintained initial pH levels of 9.0-9.7 inside the simulated resorption defects; these measurements gradually decreased to 8.0-8.5 over the span of 2 months.

Scaffolds containing chitosan/carboxymethyl cellulose/mesoporous wollastonite for bone tissue engineering.

PubMed

Sainitya, R; Sriram, M; Kalyanaraman, V; Dhivya, S; Saravanan, S; Vairamani, M; Sastry, T P; Selvamurugan, N

2015-09-01

Scaffold based bone tissue engineering utilizes a variety of biopolymers in different combinations aiming to deliver optimal properties required for bone regeneration. In the current study, we fabricated bio-composite scaffolds containing chitosan (CS), carboxymethylcellulose (CMC) with varied concentrations of mesoporous wollastonite (m-WS) particles by the freeze drying method. The CS/CMC/m-WS scaffolds were characterized by the SEM, EDS and FT-IR studies. Addition of m-WS particles had no effect on altering the porosity of the scaffolds. m-WS particles at 0.5% concentration in the CS/CMC scaffolds showed significant improvement in the bio-mineralization and protein adsorption properties. Addition of m-WS particles in the CS/CMC scaffolds significantly reduced their swelling and degradation properties. The CS/CMC/m-WS scaffolds also showed cyto-friendly nature to human osteoblastic cells. The osteogenic potential of CS/CMC/m-WS scaffolds was confirmed by calcium deposition and expression of an osteoblast specific microRNA, pre-mir-15b. Thus, the current investigations support the use of CS/CMC/m-WS scaffolds for bone tissue engineering applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Impact of co-pretreatment of calcium hydroxide and steam explosion on anaerobic digestion efficiency with corn stover.

PubMed

Ji, Jinli; Zhang, Jiyu; Yang, Liutianyi; He, Yanfeng; Zhang, Ruihong; Liu, Guangqing; Chen, Chang

2017-06-01

Anaerobic digestion (AD) is an effective way to utilize the abundant resource of corn stover (CS). In this light, Ca(OH) 2 pretreatment alone, steam explosion (SE) pretreatment alone, and co-pretreatment of Ca(OH) 2 and SE were applied to improve the digestion efficiency of CS. Results showed that AD of co-pretreated CS with 1.0% Ca(OH) 2 and SE at 1.5 MPa achieved the highest cumulative methane yield of [Formula: see text], which was 61.54% significantly higher (p < .01) than untreated CS. The biodegradability value of CS after co-pretreatment enhanced from 43.03% to 69.52%. Methane yield could be well fitted by the first-order model and the modified Gompertz model. In addition, composition and structural changes of CS after pretreatment were analyzed by a fiber analyzer, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The validated results indicated that co-pretreatment of Ca(OH) 2 and SE was efficient to improve the digestion performance of CS and might be a suitable method for agricultural waste pretreatment in the future AD industry.

Properties of ambient cured blended alkali activated cement concrete

NASA Astrophysics Data System (ADS)

Talha Junaid, M.

2017-11-01

This paper presents results of the development and strength properties of ambient-cured alkali activated geopolymer concrete (GPC). The study looks at the strength properties, such as compressive strength, splitting tensile strength, and elastic modulus of such concretes and its dependency on various parameters. The parameters studied in this work are the type and proportions of pre-cursor materials, type of activator and their respective ratios and the curing time. Two types of pre-cursor material; low calcium fly ash (FA) and ground granulated blast furnace slag (GGBFS) were activated using different proportions of sodium silicate and sodium hydroxide solutions. The results indicate that ambient cured geopolymer concrete can be manufactured to match strength properties of ordinary Portland cement concrete (OPC). The strength properties of GPC are dependent on the type and ratio of activator and the proportion of GGBFS used. Increasing the percentage of GGBFS increased the compressive and tensile strengths, while reducing the setting time of the mix. The effect of GGBFS on strength was more pronounced in mixes that contained sodium silicate as activator solution. Unlike OPC, ambient-cured GPC containing sodium silicate gain most of their strength in the first 7 days and there is no change in strength thereafter. However, GPC mixes not containing sodium silicate only achieve a fraction of their strength at 7 days and extended curing is required for such concretes to gain full strength. The results also indicate that the elastic modulus values of GPC mixes without sodium silicate are comparable to OPC while mixes with sodium silicate have elastic modulus values much lower than ordinary concrete.

Process for removing sulfur from sulfur-containing gases: high calcium fly-ash

DOEpatents

Rochelle, Gary T.; Chang, John C. S.

1991-01-01

The present disclosure relates to improved processes for treating hot sulfur-containing flue gas to remove sulfur therefrom. Processes in accordance with the present invention include preparing an aqueous slurry composed of a calcium alkali source and a source of reactive silica and/or alumina, heating the slurry to above-ambient temperatures for a period of time in order to facilitate the formation of sulfur-absorbing calcium silicates or aluminates, and treating the gas with the heat-treated slurry components. Examples disclosed herein demonstrate the utility of these processes in achieving improved sulfur-absorbing capabilities. Additionally, disclosure is provided which illustrates preferred configurations for employing the present processes both as a dry sorbent injection and for use in conjunction with a spray dryer and/or bagfilter. Retrofit application to existing systems is also addressed.

Magnesium-enriched hydroxyapatite compared to calcium sulfate in the healing of human extraction sockets: radiographic and histomorphometric evaluation at 3 months.

PubMed

Crespi, Roberto; Capparè, Paolo; Gherlone, Enrico

2009-02-01

Reduction of alveolar height and width after tooth extraction may present problems for implant placement, especially in the anterior maxilla where bone volume is important for biologic and esthetic reasons. Different graft materials have been proposed to minimize the reduction in ridge volume. The aim of this study was to compare radiographic and histomorphometric results of magnesium-enriched hydroxyapatite (MHA) and calcium sulfate (CS) grafts in fresh sockets after tooth extractions. Forty-five fresh extraction sockets with three bone walls were selected in 15 patients. A split-mouth design was used: 15 sockets on the right side of the jaw received MHA, 15 sockets on the left side received CS, and 15 random unfilled sockets were considered the control (C) group. Intraoral digital radiographs were taken at baseline and at 3 months after graft material placement. At 3 months, cylinder bone samples were obtained for histology and histomorphometry analysis. The difference in mean radiographic vertical bone level from baseline to 3 months was -2.48 +/- 0.65 mm in the CS group, -0.48 +/- 0.21 mm in the MHA group, and -3.75 +/- 0.63 mm in the unfilled C group. Statistically significant differences (P <0.05) were found between CS and MHA groups and between MHA and C groups. Histologic examination revealed bone formation in all treated sites; trabecular bone assessment did not differ among apical, mesial, and coronal portions of the specimens. Mean vital bone measurements for CS, MHA, and C groups were 45.0% +/- 6.5%, 40.0% +/- 2.7%, and 32.8% +/- 5.8%, respectively. Statistically significant differences (P <0.05) were found among all groups. Connective tissue percentages averaged 41.5% +/- 6.7% for the CS group, 41.3% +/- 1.3% for the MHA group, and 64.6% +/- 6.8% for the C group. Statistically significant differences (P <0.05) were found between CS and C groups and between MHA and C groups. The CS-grafted sockets showed 13.9% +/- 3.4% residual implant material, whereas the MHA-treated sockets showed 20.2% +/- 3.2% residual material. The difference between the groups was statistically significant (P <0.05). Radiographs revealed a greater reduction of alveolar ridge in the CS group than in the MHA group. Histologic examination showed more bone formation and faster resorption in the CS group and more residual implant material in the MHA group.

90Sr and 137Cs in environmental samples from Dolon near the Semipalatinsk Nuclear Test Site.

PubMed

Gastberger, M; Steinhäusler, F; Gerzabek, M H; Hubmer, A; Lettner, H

2000-09-01

The (90)Sr and (137)Cs activities of soil, plant, and milk samples from the village of Dolon, located close to the Semipalatinsk Nuclear Test Site in Kazakhstan, were determined. The areal deposition at the nine sampling sites is in the range of <500 to 6,100 Bq m(-2) and 300 to 7,900 Bq m-2 for (90)Sr and (137)Cs, respectively. Similar values have been reported in the literature. At some of the sites both nuclides mainly have remained in the top 6 cm of the soil profiles; at others they were partly transported into deeper soil layers since the deposition. For most of the samples the (90)Sr yield after destruction of the soil matrix is significantly higher than after extracting with 6 M HCl indicating that (90)Sr is partly associated with fused silicates. The low mean (90)Sr activity concentrations of vegetation samples (14 Bq kg(-1) dw) and milk samples (0.05 Bq kg(-1) fw) suggest that this has favorable consequences in terms of limiting its bioavailability.

Vitamin D metabolism impairment in the rat's offspring following maternal exposure to 137cesium.

PubMed

Tissandie, E; Guéguen, Y; Lobaccaro, J M A; Grandcolas, L; Grison, S; Aigueperse, J; Souidi, M

2009-04-01

Previous works clearly showed that chronic contamination by 137cesium alters vitamin D metabolism. Since children are known to be a high-risk group for vitamin D metabolism disorders, effects of 137Cs on vitamin D biosynthetic pathway were investigated in newborn rats. The experiments were performed in 21-day-old male offspring of dams exposed to 137Cs in their drinking water at a dose of 6,500 Bq/l (150 Bq/rat/day) during the lactation period. Significant modifications of blood calcium (-7%, P < 0.05), phosphate (+80%, P < 0.01) and osteocalcin (-25%, P < 0.05) levels were observed in contaminated offspring, associated with an increase of blood vitamin D3 (+25%, P < 0.01). Besides, decreased expression levels of cyp2r1 and cyp27b1 (-26 and -39%, respectively, P < 0.01) were measured in liver and kidney suggesting a physiological adaptation in response to the rise in vitamin D level. Expressions of vdr, ecac1, cabp-d28k, ecac2 and cabp-9k involved in renal and intestinal calcium transport were unaffected. Altogether, these data show that early exposure to post-accidental doses of 137Cs induces the alteration of vitamin D metabolism, associated with a dysregulation of mineral homeostasis.

Elevation dependent sensitivity of northern hardwoods to Ca addition at Hubbard Brook Experimental Forest, NH USA

Treesearch

Rakesh Minocha; Stephanie Long; Palaniswamy Thangavel; Subhash C. Minocha; Christopher Eagar; Charles T. Driscoll

2010-01-01

Acidic deposition has caused a depletion of calcium (Ca) in the northeastern forest soils. Wollastonite (Ca silicate) was added to watershed 1 (WS1) at the Hubbard Brook Experimental Forest (HBEF) in 1999 to evaluate its effects on various functions of the HBEF ecosystem. The effects of Ca addition on foliar soluble (extractable in 5% HClO4) ions...

Effects of Different Calcium Compounds on the Corrosion Resistance of Andalusite-Based Low-Cement Castables in Contact with Molten Al-Alloy

NASA Astrophysics Data System (ADS)

Adabifiroozjaei, Esmaeil; Saidi, Ali; Monshi, Ahmad; Koshy, Pramod

2011-04-01

Andalusite containing low-cement castables (LCCs) have been used in aluminum casthouses for several decades. CaF2 is commonly added to the refractory to improve its corrosion resistance mainly because of its role in the formation of anorthite (CaAl2Si2O8); the latter has been reported to decrease the penetration of molten aluminum alloys into refractories. This article investigates the effect of the addition of different calcium containing compounds (CaO, CaCO3, CaSO4, CaF2, Clinker white cement, calcia feldspar, wollastonite, and Ca3(PO4)2) on reactions with the refractory constituents to form anorthite as well as the effect of the additives on both the subsequent physical properties and the corrosion resistance of andalusite LCC refractories. Corrosion tests using the Alcoa cup test at temperatures (1123 K [850 °C] for 150 hours and 1433 K [1160 °C] for 72 hours) were conducted to determine the extent of penetration, whereas immersion tests in boiling water were conducted to determine the extent of open porosity in the material. Scanning electron microscopy coupled with energy dispersive spectrometer, optical microscopy, and X-ray diffraction techniques were employed to characterize the phase formations in the materials after the tests. The study demonstrated that both calcia feldspar and clinker white cement had the potential to be used as new additives for decreasing the penetration of molten Al-alloy into the refractory materials. Anorthite formation (in the refractory matrix), along with the absence of glassy phases, were responsible for the improvement in the corrosion resistance of the castables containing calcia feldspar. However, in the sample containing cement, the presence of calcium silicate phases were observed to resist reactions with molten aluminum. The observed results were validated using thermodynamic calculations, which indicated that tricalcium silicates (3CaO.SiO2) and dicalcium silicate (2CaO.SiO2) phases were more resistant than wollastonite (CaSiO3) for applications involving contact with molten aluminum.

SPECT myocardial perfusion imaging as an adjunct to coronary calcium score for the detection of hemodynamically significant coronary artery stenosis

PubMed Central

2012-01-01

Background Coronary artery calcifications (CAC) are markers of coronary atherosclerosis, but do not correlate well with stenosis severity. This study intended to evaluate clinical situations where a combined approach of coronary calcium scoring (CS) and nuclear stress test (SPECT-MPI) is useful for the detection of relevant CAD. Methods Patients with clinical indication for invasive coronary angiography (ICA) were included into our study during 08/2005-09/2008. At first all patients underwent CS procedure as part of the study protocol performed by either using a multidetector computed tomography (CT) scanner or a dual-source CT imager. CAC were automatically defined by dedicated software and the Agatston score was semi-automatically calculated. A stress-rest SPECT-MPI study was performed afterwards and scintigraphic images were evaluated quantitatively. Then all patients underwent ICA. Thereby significant CAD was defined as luminal stenosis ≥75% in quantitative coronary analysis (QCA) in ≥1 epicardial vessel. To compare data lacking Gaussian distribution an unpaired Wilcoxon-Test (Mann–Whitney) was used. Otherwise a Students t-test for unpaired samples was applied. Calculations were considered to be significant at a p-value of <0.05. Results We consecutively included 351 symptomatic patients (mean age: 61.2±12.3 years; range: 18–94 years; male: n=240) with a mean Agatston score of 258.5±512.2 (range: 0–4214). ICA verified exclusion of significant CAD in 66/67 (98.5%) patients without CAC. CAC was detected in remaining 284 patients. In 132/284 patients (46.5%) with CS>0 significant CAD was confirmed by ICA, and excluded in 152/284 (53.5%) patients. Sensitivity for CAD detection by CS alone was calculated as 99.2%, specificity was 30.3%, and negative predictive value was 98.5%. An additional SPECT in patients with CS>0 increased specificity to 80.9% while reducing sensitivity to 87.9%. Diagnostic accuracy was 84.2%. Conclusions In patients without CS=0 significant CAD can be excluded with a high negative predictive value by CS alone. An additional SPECT-MPI in those patients with CS>0 leads to a high diagnostic accuracy for the detection of CAD while reducing the number of patients needing invasive diagnostic procedure. PMID:23206557

Silicate Weathering and Pervasive Authigenic Carbonate Precipitation Coupled to Methanogenesis in the Krishna-Godavari Basin, Offshore India

NASA Astrophysics Data System (ADS)

Solomon, E. A.; Spivack, A. J.; Kastner, M.; Torres, M. E.

2014-12-01

The cycling of methane in marine sediments has been actively studied for the past several decades, but less attention has been paid to the cycling of CO2 produced in methanogenic sediments. The National Gas Hydrate Program Expedition 01 cored 10 sites with the Joides Resolution drillship in the Krishna-Godavari basin, located on the southeastern margin of India. A comprehensive suite of pore water solute concentrations and isotope ratios were analyzed to investigate the distribution and concentration of gas hydrate along the margin, in situ diagenetic and metabolic reactions, fluid migration and flow pathways, and fluid and gas sources. This represents one of the most comprehensive pore water geochemical datasets collected at a continental margin to date, and provides the necessary tracers to better understand the processes and sinks controlling CO2 in margin sediments. Our results show that the CO2 produced through net microbial methanogenesis is effectively neutralized through silicate weathering throughout the sediment column drilled at each site (~100-300 m), buffering the pH of the sedimentary pore water and generating excess alkalinity through the same reaction sequence as continental silicate weathering. Most of the excess alkalinity produced through silicate weathering in the Krishna-Godavari basin is sequestered in Ca- and Fe-carbonates as a result of ubiquitous calcium release from weathering detrital silicates and Fe-reduction within the methanogenic sediments. Formation of secondary hydrous silicates (e.g. smectite) related to incongruent primary silicate dissolution acts as a significant sink for pore water Mg, K, Li, Rb, and B. The consumption of methane through anaerobic oxidation of methane, sequestration of methane in gas hydrate, and sequestration of dissolved inorganic carbon in authigenic carbonates keeps methanogenesis as a thermodynamically feasible catabolic pathway. Our results combined with previous indications of silicate weathering in anoxic sediments in the Sea of Okhotsk, suggest that silicate weathering coupled to microbial methanogenesis should be occurring in continental margins worldwide, providing a net sink of atmospheric CO2 over geologic timescales.

Stable thermosensitive in situ gel-forming systems based on the lyophilizate of chitosan/α,β-glycerophosphate salts.

PubMed

Wu, Guanghao; Yuan, Yuan; He, Jintian; Li, Ying; Dai, Xiaojing; Zhao, Baohua

2016-09-10

In the present study, lyophilization was attempted to improve the long-term storage of CS/GP thermogelling systems for biopharmaceutical applications. After lyophilization, CS/α,β-GP lyophilizate could not be dissolved in water, but some metal salts, such as NaCl, CaCl2, and MgCl2 surprisingly facilitated its dissolution. X-ray powder diffraction analysis suggested that calcium ions might preferentially form salts with α,β-GP, inhibit the transfer of protons from CS to α,β-GP, and then inhibit the aggregation of CS molecules during lyophilization. Comparison of the freshly prepared CS/α,β-GP/salt solutions and the reconstituted solutions from lyophilizates showed that lyophilization clearly influenced the properties of reconstituted CS/α,β-GP/salt solutions such as gelation time, viscosity, and pH. Furthermore, the reconstituted CS/α,β-GP/CaCl2 solutions maintained thermogelling properties and formed hydrogels at 37°C within approximately 5min, but did not form hydrogels at 20°C and 4°C over 2 weeks. The model protein bovine serum albumin (BSA) was further incorporated into the CS/α,β-GP/CaCl2 system. In vitro release experiments showed the sustained release of BSA from CS/α,β-GP/CaCl2 hydrogels in a pH-sensitive manner, demonstrating that CS/α,β-GP/CaCl2 may be useful as an in situ gel-forming system. Copyright © 2016 Elsevier B.V. All rights reserved.

Suitability assessment of grey water quality treated with an upflow-downflow siliceous sand/marble waste filtration system for agricultural and industrial purposes.

PubMed

Chaabane, Safa; Riahi, Khalifa; Hamrouni, Hédi; Thayer, Béchir Ben

2017-04-01

The present study examines the suitability assessment of an upflow-downflow siliceous sand/marble waste filtration system for treatment and reuse of grey water collected from bathrooms of the student residential complex at the Higher Institute of Engineering Medjez El Bab (Tunisia). Once the optimization of grey water pre-treatment system has been determined, the filtration system was operated at different hydraulic loading rate and media filter proportions in order to assess the suitability of treated grey water for irrigational purpose according to salinity hazard, sodium hazard, magnesium hazard, permeability index, water infiltration rate, and widely used graphical methods. Suitability of the treated grey water for industrial purpose was evaluated in terms of foaming, corrosion, and scaling. Under optimal operational conditions, results reveals that treated grey water samples with an upflow-downflow siliceous sand/marble waste filtration system may be considered as a good and an excellent water quality suitable for irrigation purpose. However, treated grey water was found not appropriate for industrial purpose due to high concentrations of calcium and sodium that can generate foaming and scaling harm to boilers. These results suggest that treated grey water with an upflow-downflow siliceous sand/marble waste filtration system would support production when used as irrigation water.

Alkali-activated complex binders from class C fly ash and Ca-containing admixtures.

PubMed

Guo, Xiaolu; Shi, Huisheng; Chen, Liming; Dick, Warren A

2010-01-15

Processes that maximize utilization of industrial solid wastes are greatly needed. Sodium hydroxide and sodium silicate solution were used to create alkali-activated complex binders (AACBs) from class C fly ash (CFA) and other Ca-containing admixtures including Portland cement (PC), flue gas desulfurization gypsum (FGDG), and water treatment residual (WTR). Specimens made only from CFA (CFA100), or the same fly ash mixed with 40 wt% PC (CFA60-PC40), with 10 wt% FGDG (CFA90-FGDG10), or with 10 wt% WTR (CFA90-WTR10) had better mechanical performance compared to binders using other mix ratios. The maximum compressive strength of specimens reached 80.0 MPa. Geopolymeric gel, sodium polysilicate zeolite, and hydrated products coexist when AACB reactions occur. Ca from CFA, PC, and WTR precipitated as Ca(OH)(2), bonded in geopolymers to obtain charge balance, or reacted with dissolved silicate and aluminate species to form calcium silicate hydrate (C-S-H) gel. However, Ca from FGDG probably reacted with dissolved silicate and aluminate species to form ettringite. Utilization of CFA and Ca-containing admixtures in AACB is feasible. These binders may be widely utilized in various applications such as in building materials and for solidification/stabilization of other wastes, thus making the wastes more environmentally benign.

Amorphization of itraconazole by inorganic pharmaceutical excipients: comparison of excipients and processing methods.

PubMed

Grobelny, Pawel; Kazakevich, Irina; Zhang, Dan; Bogner, Robin

2015-01-01

The aim of this study was to investigate the effects of solid carriers and processing routes on the properties of amorphous solid dispersions of itraconazole. Three solid carriers with a range of surface properties were studied, (1) a mesoporous silicate, magnesium aluminum silicate (Neusilin US2), (2) a nonporous silicate of corresponding composition (Veegum) and (3) a non-silicate, inorganic excipient, calcium phosphate dibasic anhydrous (A-TAB). The drug was incorporated via either solvent-deposition or ball milling. Both the maximum drug deposited by solvent-based method that produced an amorphous composite and the time for complete amorphization by co-milling was determined by X-ray powder diffraction (XRPD). Changes in the drug and excipients were monitored by nitrogen adsorption and wettability of the powder. The ability of the excipients to amorphize the drug and enhance its dissolution was related to the powder characteristics. Neusilin provided the fastest amorphization time in the mill and highest drug loading by solvent-deposition, compared with the other two excipients. Solvent-deposition provided greater dissolution enhancement than milling, due to the reduction in Neusilin porosity during high energy milling.This study confirms that substrates as well as the processing routes have notable influence on the drug deposition, amorphization, physical stability and drug in vitro release.

Porous silicon confers bioactivity to polycaprolactone composites in vitro.

PubMed

Henstock, J R; Ruktanonchai, U R; Canham, L T; Anderson, S I

2014-04-01

Silicon is an essential element for healthy bone development and supplementation with its bioavailable form (silicic acid) leads to enhancement of osteogenesis both in vivo and in vitro. Porous silicon (pSi) is a novel material with emerging applications in opto-electronics and drug delivery which dissolves to yield silicic acid as the sole degradation product, allowing the specific importance of soluble silicates for biomaterials to be investigated in isolation without the elution of other ionic species. Using polycaprolactone as a bioresorbable carrier for porous silicon microparticles, we found that composites containing pSi yielded more than twice the amount of bioavailable silicic acid than composites containing the same mass of 45S5 Bioglass. When incubated in a simulated body fluid, the addition of pSi to polycaprolactone significantly increased the deposition of calcium phosphate. Interestingly, the apatites formed had a Ca:P ratio directly proportional to the silicic acid concentration, indicating that silicon-substituted hydroxyapatites were being spontaneously formed as a first order reaction. Primary human osteoblasts cultured on the surface of the composite exhibited peak alkaline phosphatase activity at day 14, with a proportional relationship between pSi content and both osteoblast proliferation and collagen production over 4 weeks. Culturing the composite with J744A.1 murine macrophages demonstrated that porous silicon does not elicit an immune response and may even inhibit it. Porous silicon may therefore be an important next generation biomaterial with unique properties for applications in orthopaedic tissue engineering.

Cardiac computed tomography in patients with symptomatic new-onset atrial fibrillation, rule-out acute coronary syndrome, but with intermediate pretest probability for coronary artery disease admitted to a chest pain unit.

PubMed

Koopmann, Matthias; Hinrichs, Liane; Olligs, Jan; Lichtenberg, Michael; Eckardt, Lars; Böse, Dirk; Möhlenkamp, Stefan; Waltenberger, Johannes; Breuckmann, Frank

2018-01-24

Atrial fibrillation (AF) and coronary artery disease (CAD) may be encountered coincidently in a large portion of patients. However, data on coronary artery calcium burden in such patients are lacking. Thus, we sought to determine the value of cardiac computed tomography (CCT) in patients presenting with new-onset AF associated with an intermediate pretest probability for CAD admitted to a chest pain unit (CPU). Calcium scores (CS) of 73 new-onset, symptomatic AF subjects without typical clinical, electrocardiographic, or laboratory signs of acute coronary syndrome (ACS) admitted to our CPU were analyzed. In addition, results from computed tomography angiography (CTA) were related to coronary angiography findings whenever available. Calcium scores of zero were found in 25%. Median Agatston score was 77 (interquartile range: 1-270) with gender- and territory-specific dispersal. CS scores above average were present in about 50%, high (> 400)-to-very high (> 1000) CS scores were found in 22%. Overall percentile ranking showed a relative accordance to the reference percentile distribution. Additional CTA was performed in 47%, revealing stenoses in 12%. Coronary angiography was performed in 22% and resulted in coronary intervention or surgical revascularization in 7%. On univariate analysis, CS > 50th percentile failed to serve as an independent determinant of significant stenosis during catheterization. Within a CPU setting, relevant CAD was excluded or confirmed in almost 50%, the latter with a high proportion of coronary angiographies and subsequent coronary interventions, underlining the diagnostic value of CCT in symptomatic, non-ACS, new-onset AF patients when admitted to a CPU.

Biocalcite, a multifunctional inorganic polymer: Building block for calcareous sponge spicules and bioseed for the synthesis of calcium phosphate-based bone

PubMed Central

Schröder, Heinz C; Müller, Werner E G

2014-01-01

Summary Calcium carbonate is the material that builds up the spicules of the calcareous sponges. Recent results revealed that the calcium carbonate/biocalcite-based spicular skeleton of these animals is formed through an enzymatic mechanism, such as the skeleton of the siliceous sponges, evolutionarily the oldest animals that consist of biosilica. The enzyme that mediates the calcium carbonate deposition has been identified as a carbonic anhydrase (CA) and has been cloned from the calcareous sponge species Sycon raphanus. Calcium carbonate deposits are also found in vertebrate bones besides the main constituent, calcium phosphate/hydroxyapatite (HA). Evidence has been presented that during the initial phase of HA synthesis poorly crystalline carbonated apatite is deposited. Recent data summarized here indicate that during early bone formation calcium carbonate deposits enzymatically formed by CA, act as potential bioseeds for the precipitation of calcium phosphate mineral onto bone-forming osteoblasts. Two different calcium carbonate phases have been found during CA-driven enzymatic calcium carbonate deposition in in vitro assays: calcite crystals and round-shaped vaterite deposits. The CA provides a new target of potential anabolic agents for treatment of bone diseases; a first CA activator stimulating the CA-driven calcium carbonate deposition has been identified. In addition, the CA-driven calcium carbonate crystal formation can be frozen at the vaterite state in the presence of silintaphin-2, an aspartic acid/glutamic acid-rich sponge-specific protein. The discovery that calcium carbonate crystals act as bioseeds in human bone formation may allow the development of novel biomimetic scaffolds for bone tissue engineering. Na-alginate hydrogels, enriched with biosilica, have recently been demonstrated as a suitable matrix to embed bone forming cells for rapid prototyping bioprinting/3D cell printing applications. PMID:24991497

Biocalcite, a multifunctional inorganic polymer: Building block for calcareous sponge spicules and bioseed for the synthesis of calcium phosphate-based bone.

PubMed

Wang, Xiaohong; Schröder, Heinz C; Müller, Werner E G

2014-01-01

Calcium carbonate is the material that builds up the spicules of the calcareous sponges. Recent results revealed that the calcium carbonate/biocalcite-based spicular skeleton of these animals is formed through an enzymatic mechanism, such as the skeleton of the siliceous sponges, evolutionarily the oldest animals that consist of biosilica. The enzyme that mediates the calcium carbonate deposition has been identified as a carbonic anhydrase (CA) and has been cloned from the calcareous sponge species Sycon raphanus. Calcium carbonate deposits are also found in vertebrate bones besides the main constituent, calcium phosphate/hydroxyapatite (HA). Evidence has been presented that during the initial phase of HA synthesis poorly crystalline carbonated apatite is deposited. Recent data summarized here indicate that during early bone formation calcium carbonate deposits enzymatically formed by CA, act as potential bioseeds for the precipitation of calcium phosphate mineral onto bone-forming osteoblasts. Two different calcium carbonate phases have been found during CA-driven enzymatic calcium carbonate deposition in in vitro assays: calcite crystals and round-shaped vaterite deposits. The CA provides a new target of potential anabolic agents for treatment of bone diseases; a first CA activator stimulating the CA-driven calcium carbonate deposition has been identified. In addition, the CA-driven calcium carbonate crystal formation can be frozen at the vaterite state in the presence of silintaphin-2, an aspartic acid/glutamic acid-rich sponge-specific protein. The discovery that calcium carbonate crystals act as bioseeds in human bone formation may allow the development of novel biomimetic scaffolds for bone tissue engineering. Na-alginate hydrogels, enriched with biosilica, have recently been demonstrated as a suitable matrix to embed bone forming cells for rapid prototyping bioprinting/3D cell printing applications.

Comparison of osteoblast-like cell responses to calcium silicate and tricalcium phosphate ceramics in vitro.

PubMed

Ni, Siyu; Chang, Jiang; Chou, Lee; Zhai, Wanyin

2007-01-01

Calcium silicate ceramics have been proposed as new bone repair biomaterials, since they have proved to be bioactive, degradable, and biocompatible. Beta-tricalcium phosphate ceramic is a well-known degradable material for bone repair. This study compared the effects of CaSiO3 (alpha-, and beta-CaSiO3) and beta-Ca3(PO4)2 (beta-TCP) ceramics on the early stages of rat osteoblast-like cell attachment, proliferation, and differentiation. Osteoblast-like cells were cultured directly on CaSiO3 (alpha-, and beta-CaSiO3) and beta-TCP ceramics. Attachment of a greater number of cells was observed on CaSiO3 (alpha-, and beta-CaSiO3) ceramics compared with beta-TCP ceramics after incubation for 6 h. SEM observations showed an intimate contact between cells and the substrates, significant cells adhesion, and that the cells spread and grew on the surfaces of all the materials. In addition, the proliferation rate and alkaline phosphatase (ALP) activity of the cells on the CaSiO3 (alpha-, and beta-CaSiO3) ceramics were improved when compared with the beta-TCP ceramics. In the presence of CaSiO3, elevated levels of calcium and silicon in the culture medium were observed throughout the 7-day culture period. In conclusion, the results of the present study revealed that CaSiO3 ceramics showed greater ability to support cell attachment, proliferation, and differentiation than beta-TCP ceramic. 2006 Wiley Periodicals, Inc.

Investigating permeability and carbonation behavior of sustainable cements

NASA Astrophysics Data System (ADS)

White, C.; Blyth, A.; Scherer, G. W.; Morandeau, A. E.

2015-12-01

The durability of new sustainable cementitious materials is intimately linked with the ability for these materials to prevent the ingress of aggressive ions through their percolated pore networks. However, it is also important to be able to control and limit the detrimental chemical degradation mechanisms that occur to the cement binder once the ions have diffused through the pore network. Here, alkali-activated materials will be discussed, and recent research on measuring the permeability of this class of cements using the beam-bending method will be presented. It will be shown that the permeability can be controlled by tailoring the activator chemistry, and that the addition of free silica in the activator has a strong (favorable) influence on the resulting percolated pore network. Carbonation is one type of chemical degradation process that is known to severely shorten the service life of concrete, especially in environments containing elevated CO­2 levels. However, the exact atomic structural changes that occur to the main binder phase (calcium-silicate-hydrate gel) during carbonation remain largely unknown. Here, X-ray pair distribution function analysis is used to elucidate the local atomic structural changes that occur during carbonation of calcium-silicate-hydrate gel and calcium-aluminosilicate-hydrate gel (alkali-activated slag binder), where distinct differences in the extent of gel decalcification are measured according to the chemistry of the starting precursor material. The results will be discussed in the context of limiting the extent of carbonation in cementitious materials, with potential applications of alkali-activated materials in geological storage of CO2 due to their increased resistance to carbonation.

Residual stresses and phase transformations in Ytterbium silicate environmental barrier coatings

NASA Astrophysics Data System (ADS)

Stolzenburg, Fabian

Due to their high melting temperature, low density, and good thermomechanical stability, silicon-based ceramics (SiC, Si3N4) are some of the most promising materials systems for high temperature structural applications in gas turbine engines. However, their silica surface layer reacts with water vapor contained in combustion environments. The resulting hydroxide layer volatilizes, leading to component recession. Environmental barrier coatings (EBCs) have been developed to shield the substrate from degradation. Next generation coatings for silicon-based ceramics based on ytterbium silicates have shown a promising combination of very low and good thermomechanical properties. The focus of this thesis is threefold: In the first part, phase transformations in plasma sprayed ytterbium silicates were investigated. Plasma sprayed materials are known to contain large amounts of amorphous material. Phase changes during the conversion from amorphous to crystalline materials were investigated as they have been known to lead to failure in many coatings. The second part of this work focused on measuring residual stresses in multilayer EBCs using synchrotron X-ray diffraction (XRD). Strains were resolved spatially, with probe sizes as small as 20 um. Stresses were calculated using mechanical properties of ytterbium silicates, determined with in-situ loading and heating experiments. In-situ and ex-situ heating experiments allowed for the study of changes in stress states that occur in these EBC materials during heating and cooling cycles. Lastly, the interaction of ytterbium silicates with low-melting environmental calcium-magnesium-aluminosilicate (CMAS) glasses was studied. Synchrotron XRD was used to study the influence of CMAS on the stress state in the coating, X-ray computed tomography was used to provide 3D images of coatings, and EDS and TEM analysis were used to study the interactions at the CMAS/ytterbium silicate interface in detail.

The chemistry of Saudi Arabian sand: A deposition problem on helicopter turbine airfoils

NASA Technical Reports Server (NTRS)

Smialek, James L.

1991-01-01

Recent operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz (Ca,Mg) CO3 dolomite, CaCO3 calcite, and occasionally CaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 0.25 in. thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of GaSO4.

The chemistry of Saudi Arabian sand - A deposition problem on helicopter turbine airfoils

NASA Astrophysics Data System (ADS)

Smialek, James L.; Archer, Frances A.; Garlick, Ralph G.

Operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz, (Ca,Mg)CO3 dolomite, CaCO3 calcite, and occasionally NaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 5 mm thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of CaSO4.

The Chemistry of Saudi Arabian Sand - A Deposition Problem on Helicopter Turbine Airfoils

NASA Technical Reports Server (NTRS)

Smialek, James L.; Archer, Frances A.; Garlick, Ralph G.

1992-01-01

Operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz, (Ca,Mg)CO3 dolomite, CaCO3 calcite, and occasionally NaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 5 mm thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of CaSO4.

The calcineruin inhibitor cyclosporine a synergistically enhances the susceptibility of Candida albicans biofilms to fluconazole by multiple mechanisms.

PubMed

Jia, Wei; Zhang, Haiyun; Li, Caiyun; Li, Gang; Liu, Xiaoming; Wei, Jun

2016-06-18

Biofilms produced by Candida albicans (C. albicans) are intrinsically resistant to fungicidal agents, which are a main cause of the pathogenesis of catheter infections. Several lines of evidence have demonstrated that calcineurin inhibitor FK506 or cyclosporine A (CsA) can remarkably enhance the antifungal activity of fluconazole (FLC) against biofilm-producing C. albicans strain infections. The aim of present study is thus to interrogate the mechanism underpinning the synergistic effect of FLC and calcineurin inhibitors. Twenty four clinical C. albicans strains isolated from bloodstream showed a distinct capacity of biofilm formation. A combination of calcineurin inhibitor CsA and FLC exhibited a dose-dependent synergistic antifungal effect on the growth and biofilm formation of C. albicans isolates as determined by a XTT assay and fluorescent microscopy assay. The synergistic effect was accompanied with a significantly down-regulated expression of adhesion-related genes ALS3, hypha-related genes HWP1, ABC transporter drug-resistant genes CDR1 and MDR1, and FLC targeting gene, encoding sterol 14alpha-demethylase (ERG11) in clinical C. albicans isolates. Furthermore, an addition of CsA significantly reduced the cellular surface hydrophobicity but increased intracellular calcium concentration as determined by a flow cytometry assay (p < 0.05). The results presented in this report demonstrated that the synergistic effect of CsA and FLC on inhibited C. albicans biofilm formation and enhanced susceptibility to FLC was in part through a mechanism involved in suppressing the expression of biofilm related and drug-resistant genes, and reducing cellular surface hydrophobicity, as well as evoking intracellular calcium concentration.

Overexpression of a calpastatin transgene in mdx muscle reduces dystrophic pathology.

PubMed

Spencer, Melissa J; Mellgren, Ronald L

2002-10-01

Reduced sarcolemmal integrity in dystrophin-deficient muscles of mdx mice and Duchenne muscular dystrophy (DMD) patients has been reported to result in altered calcium homeostasis. Previous studies have shown a correlative relationship between calcium-dependent protease (calpain) activity in dystrophic muscle and muscle necrosis, but have not tested whether calpain activation precedes cell death or is a consequence of it. To test a causal relationship between calpain activation and muscle cell death in dystrophin deficiency, mdx mice were generated that overexpress a calpastatin transgene in muscle. Calpastatin (CS) is a specific, endogenous inhibitor of m- and micro -calpains that does not inhibit calpain 3 (p94). CS overexpression on a C57/BL 10 background produced no phenotype. Transgenic (Tg) mice crossed with mdx mice were tested for pathological indicators of necrosis, regeneration and membrane damage. Two lines of mice were examined, with different levels of CS overexpression. Both lines of Tg/mdx mice showed reductions in muscle necrosis at 4 weeks of age. These mice had fewer as well as smaller lesions. In addition, one line of mice had significantly less regeneration, indicating a reduction in previous necrosis. The extent of improvement correlated with the level of CS protein expression. Membrane damage, as assessed by procion orange and creatine kinase assays, was unchanged, supporting the idea that calpains act downstream of the primary muscle defect. These data suggest that calpains play an active role in necrotic processes in dystrophic muscle and that inhibition of calpains might provide a good therapeutic option for treatment of DMD.

The effect of geothermal fluid composition in lime-pozzolan reactions on elastic and transport properties.

NASA Astrophysics Data System (ADS)

MacFarlane, J.; Vanorio, T.

2016-12-01

Calcium-Silicate-Hydrates (C-S-H) are a complex family of hydrates known to form within hyper-alkaline geothermal systems as well as concrete. Within both environments the formation of C-S-H can be linked to the lime-pozzolan reaction. Pozzolan's defined as a siliceous or alumino-siliceous material, which in itself possesses little or no cementing property, but in the presence of moisture chemically reacts with calcium hydroxide at ordinary temperatures to form cementitious compounds. C-S-H fibers have been discovered in a low permeability, caprock layer beneath the Campi Flegrei caldera, as well as within ancient Roman concrete made using volcanic ash and fluids from the Campi Flegrei region over 2000 years ago. By replicating the recipe for Roman concrete, fibrous minerals have been formed in laboratory experiments and imaged using a scanning electron microscope. The formation of C-S-H within concrete has been shown to depend on the mineral ions present, among other factors. Here, we report on how the geothermal fluid composition effects the elastic and transport properties of laboratory samples. Samples were made using the same volcanic ash as the Romans, called Pozzolana, slaked lime and geothermal fluid. Two geothermal fluids from the Campi Flegrei region were compared, as well as deionized water as a control. Preliminary results have shown changes in both the elastic and transport properties between sample sets made with geothermal fluid and the control. These changes are attributed to the structure of the C-S-H that forms in the lime-pozzolan reaction. Understanding how the geothermal fluid composition controls the properties of this reaction has implications for the understanding of both geothermal systems and concrete engineering.

NASA's Advanced Environmental Barrier Coatings Development for SiC/SiC Ceramic Matrix Composites: Understanding Calcium Magnesium Alumino-Silicate (CMAS) Degradations and Resistance

NASA Technical Reports Server (NTRS)

Zhu, Dongming

2014-01-01

Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is essential to the viability and reliability of the envisioned CMC engine component applications, ensuring integrated EBC-CMC system durability and designs are achievable for successful applications of the game-changing component technologies and lifing methodologies.This paper will emphasize recent NASA environmental barrier coating developments for SiCSiC turbine airfoil components, utilizing advanced coating compositions, state-of-the-art processing methods, and combined mechanical and environment testing and durability evaluations. The coating-CMC degradations in the engine fatigue-creep and operating environments are particularly complex; one of the important coating development aspects is to better understand engine environmental interactions and coating life debits, and we have particularly addressed the effect of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the durability of the environmental barrier coating systems, and how the temperature capability, stability and cyclic life of the candidate rare earth oxide and silicate coating systems will be impacted in the presence of the CMAS at high temperatures and under simulated heat flux conditions. Advanced environmental barrier coating systems, including HfO2-Si with rare earth dopant based bond coat systems, will be discussed for the performance improvements to achieve better temperature capability and CMAS resistance for future engine operating conditions.

Enhancing proliferation and osteogenic differentiation of HMSCs on casein/chitosan multilayer films.

PubMed

Li, Yan; Zheng, Zebin; Cao, Zhinan; Zhuang, Liangting; Xu, Yong; Liu, Xiaozhen; Xu, Yue; Gong, Yihong

2016-05-01

Creating a bioactive surface is important in tissue engineering. Inspired by the natural calcium binding property of casein (CA), multilayer films ((CA/CS)n) with chitosan (CS) as polycation were fabricated to enhance biomineralization, cell adhesion and differentiation. LBL self-assembly technique was used and the assembly process was intensively studied based on changes of UV absorbance, zeta potential and water contact angle. The increasing content of chitosan and casein with bilayers was further confirmed with XPS and TOF-SIMS analysis. To improve the biocompatibility, gelatin was surface grafted. In vitro mineralization test demonstrated that multilayer films had more hydroxyapatite crystal deposition. Human mesenchymal stem cells (HMSCs) were seeded onto these films. According to fluorescein diacetate (FDA) and cell cytoskeleton staining, MTT assay, expression of osteogenic marker genes, ALP activity, and calcium deposition quantification, it was found that these multilayer films significantly promoted HMSCs attachment, proliferation and osteogenic differentiation than TCPS control. Copyright © 2016. Published by Elsevier B.V.

Early age hydration of calcium sulfoaluminate (synthetic ye'elimite, C{sub 4}A{sub 3}S{sup ¯}) in the presence of gypsum and varying amounts of calcium hydroxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hargis, Craig W.; Kirchheim, Ana Paula; Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu

Suspensions of synthetic ye'elimite (C{sub 4}A{sub 3}S{sup ¯}) in a saturated gypsum (CS{sup ¯}H{sub 2}) and calcium hydroxide (CH) solution were examined in-situ in a wet cell by soft X-ray transmission microscopy and ex-situ by scanning electron microscopy. The most voluminous hydration product observed was ettringite. Ettringite commonly displayed acicular, filiform, reticulated, and stellate crystal habits. Additionally, pastes with C{sub 4}A{sub 3}S{sup ¯}, 15% CS{sup ¯}H{sub 2}, and varying amounts of CH were prepared and examined with X-ray diffraction (XRD) and isothermal calorimetry. The XRD experiments showed that increasing CH content caused more solid solution (SO{sub 4}{sup 2−}/OH{sup −}) AFmmore » phases to form at early ages (< 1 d) and more monosulfate to form at later ages (> 1 d). Calorimetry indicated that the increased production of solid solution AFm was accompanied with an increase in the initial (< 30 min) rate of heat evolution, and increasing CH generally reduced the time till the second maximum rate of heat evolution due to the formation of ettringite and monosulfate.« less

Effect of additives on mineral trioxide aggregate setting reaction product formation.

PubMed

Zapf, Angela M; Chedella, Sharath C V; Berzins, David W

2015-01-01

Mineral trioxide aggregate (MTA) sets via hydration of calcium silicates to yield calcium silicate hydrates and calcium hydroxide (Ca[OH]2). However, a drawback of MTA is its long setting time. Therefore, many additives have been suggested to reduce the setting time. The effect those additives have on setting reaction product formation has been ignored. The objective was to examine the effect additives have on MTA's setting time and setting reaction using differential scanning calorimetry (DSC). MTA powder was prepared with distilled water (control), phosphate buffered saline, 5% calcium chloride (CaCl2), 3% sodium hypochlorite (NaOCl), or lidocaine in a 3:1 mixture and placed in crucibles for DSC evaluation. The setting exothermic reactions were evaluated at 37°C for 8 hours to determine the setting time. Separate samples were stored and evaluated using dynamic DSC scans (37°C→640°C at10°C/min) at 1 day, 1 week, 1 month, and 3 months (n = 9/group/time). Dynamic DSC quantifies the reaction product formed from the amount of heat required to decompose it. Thermographic peaks were integrated to determine enthalpy, which was analyzed with analysis of variance/Tukey test (α = 0.05). Isothermal DSC identified 2 main exothermal peaks occurring at 44 ± 12 and 343 ± 57 minutes for the control. Only the CaCl2 additive was an accelerant, which was observed by a greater exothermic peak at 101 ± 11 minutes, indicating a decreased setting time. The dynamic DSC scans produced an endothermic peak around 450°C-550°C attributed to Ca(OH)2 decomposition. The use of a few additives (NaOCl and lidocaine) resulted in significantly less Ca(OH)2 product formation. DSC was used to discriminate calcium hydroxide formation in MTA mixed with various additives and showed NaOCl and lidocaine are detrimental to MTA reaction product formation, whereas CaCl2 accelerated the reaction. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Preparation and Physicochemical Evaluation of Controlled-release Carbon Source Tablet for Groundwater in situ Denitrification

NASA Astrophysics Data System (ADS)

Kim, Y.; Kang, J. H.; Yeum, Y.; Han, K. J.; Kim, D. W.; Park, C. W.

2015-12-01

Nitric nitrogen could be the one of typical pollution source such asNO3-through domestic sewage, livestock and agricultural wastewater. Resident microflorain aquifer has known to remove the nitric nitrogen spontaneously following the denitration process with the carbon source (CS) as reactant. However, it could be reacted very slowly with the rack of CS and there have been some studies for controlled addition of CS (Ref #1-3). The aim of this study was to prepare the controlled-release carbon source (CR-CS) tablet and to evaluate in vitro release profile for groundwater in situ denitrification. CR-CS tablet could be manufactured by direct compression method using hydraulic laboratory press (Caver® 3850) with 8 mm rounded concave punch/ die.Seven kinds of CR-CS tablet were prepared to determine the nature of the additives and their ratio such as sodium silicate, dicalcium phosphate, bentonite and sand#8.For each formulation, the LOD% and flowability of pre-mixed powders and the hardness of compressed tablets were analyzed. In vitro release study was performed to confirm the dissolution profiles following the USP Apparatus 2 method with Distilled water of 900mL, 20 °C. As a result, for each lubricated powders, they were compared in terms of ability to give an acceptable dry pre-mixed powder for tableting process. The hardness of the compressed tablets is acceptable whatever the formulations tested. After in vitro release study, it could confirm that the different formulations of CR-CS tablet have a various release rate patterns, which could release 100% at 3 hrs, 6 hrs and 12 hrs. The in vitro dissolution profiles were in good correlation of Higuchi release kinetic model. In conclusion, this study could be used as a background for development and evaluation of the controlled-release carbon source (CR-CS) tablet for the purification of groundwater following the in situ denitrification.

Plaque triclosan concentration and antimicrobial efficacy of a new calcium carbonate toothpaste with 0.3% triclosan compared to a marketed 0.3% triclosan toothpaste.

PubMed

Srinivasan, Shashank; Chandrasekhar, Sembian; Shashikumar, K V; Payne, David; Maclure, Robert; Kapadiya, Bhavin; Schäfer, Fred; Adams, Suzi

2013-01-01

To compare the delivery and retention of triclosan in dental plaque, and to compare the antibacterial efficacy of a newly developed toothpaste to a marketed calcium carbonate toothpaste. Two clinical delivery/retention studies were carried out to determine the concentration of triclosan in plaque 10 minutes, and two and four hours after brushing with a new triclosan-containing toothpaste with magnesium aluminium silicate or a marketed triclosan-containing toothpaste. Both studies had a double-blind, randomized, complete cross-over design. Supragingival plaque samples (minimum 2 microg) were taken from smooth surfaces of all teeth (1-7) in all four quadrants for the 10-minute plaque measurements and in two randomly allocated quadrants at the two- and four-hour time points. Triclosan concentration was measured by HPLC. Antibacterial efficacy was evaluated in vitro using a biofilm formation approach. Three replicate experiments were carried out to check for repeatability and consistency of the assay. Toothpaste slurries were prepared by stirring one part by weight of each toothpaste with two parts by weight of deionized water. An overnight culture suspension of Streptococcus mutans (ATCC 25175) was prepared and then adjusted to give a bacterial count of approximately 10(7) CFU/ml. Sterile HAP discs were used as substrate and treated with the toothpaste slurry before inoculation with the standardized culture suspension of S. mutans. Following incubation in brain heart infusion (BHI) broth containing 2% sucrose for four hours, standard Total Viable Count (TVC) procedures were carried out and colonies counted (log10 values). Brushing with the new calcium carbonate/triclosan toothpaste resulted in a higher triclosan concentration in plaque after 10 minutes, and two and four hours compared to a marketed triclosan toothpaste. The increase ranged from 14% to 35% and was statistically significant (p < 0.05). The antibacterial efficacy of the new calcium carbonate/triclosan toothpaste, measured four hours after application, was greater than that of a marketed toothpaste with 0.3% triclosan. The difference was statistically significant (p < 0.05). The new calcium carbonate toothpaste with 0.3% triclosan and magnesium aluminium silicate demonstrated significantly greater efficacy four hours post-brushing both in terms of in vivo delivery and in vitro antibacterial action compared to a marketed calcium carbonate toothpaste with 0.3% triclosan.

Biological Assessment of a Calcium Silicate Incorporated Hydroxyapatite-Gelatin Nanocomposite: A Comparison to Decellularized Bone Matrix

PubMed Central

Lee, Dong Joon; Padilla, Ricardo; Zhang, He; Hu, Wei-Shou; Ko, Ching-Chang

2014-01-01

Our laboratory utilized biomimicry to develop a synthetic bone scaffold based on hydroxyapatite-gelatin-calcium silicate (HGCS). Here, we evaluated the potential of HGCS scaffold in bone formation in vivo using the rat calvarial critical-sized defect (CSD). Twelve Sprague-Dawley rats were randomized to four groups: control (defect only), decellularized bone matrix (DECBM), and HGCS with and without multipotent adult progenitor cells (MAPCs). DECBM was prepared by removing all the cells using SDS and NH4OH. After 12 weeks, the CSD specimens were harvested to evaluate radiographical, histological, and histomorphometrical outcomes. The in vitro osteogenic effects of the materials were studied by focal adhesion, MTS, and alizarin red. Micro-CT analysis indicated that the DECBM and the HGCS scaffold groups developed greater radiopaque areas than the other groups. Bone regeneration, assessed using histological analysis and fluorochrome labeling, was the highest in the HGCS scaffold seeded with MAPCs. The DECBM group showed limited osteoinductivity, causing a gap between the implant and host tissue. The group grafted with HGCS+MAPCs resulting in twice as much new bone formation seems to indicate a role for effective bone regeneration. In conclusion, the novel HGCS scaffold could improve bone regeneration and is a promising carrier for stem cell-mediated bone regeneration. PMID:25054149

Bond strength and interfacial morphology of orthodontic brackets bonded to eroded enamel treated with calcium silicate-sodium phosphate salts or resin infiltration.

PubMed

Costenoble, Aline; Vennat, Elsa; Attal, Jean-Pierre; Dursun, Elisabeth

2016-11-01

 To investigate the shear bond strength (SBS) of orthodontic brackets bonded to eroded enamel treated with preventive approaches and to examine the enamel/bracket interfaces.  Ninety-one brackets were bonded to seven groups of enamel samples: sound; eroded; eroded+treated with calcium silicate-sodium phosphate salts (CSP); eroded+infiltrated by ICON ® ; eroded+infiltrated by ICON ® and brackets bonded with 1-month delay; eroded+infiltrated by an experimental resin; and eroded+infiltrated by an experimental resin and brackets bonded with 1-month delay. For each group, 12 samples were tested in SBS and bond failure was assessed with the adhesive remnant index (ARI); one sample was examined using scanning electron microscopy (SEM).  Samples treated with CSP or infiltration showed no significant differences in SBS values with sound samples. Infiltrated samples followed by a delayed bonding showed lower SBS values. All of the values remained acceptable. The ARI scores were significantly higher for sound enamel, eroded, and treated with CSP groups than for all infiltrated samples. SEM examinations corroborated the findings.  Using CSP or resin infiltration before orthodontic bonding does not jeopardize the bonding quality. The orthodontic bonding should be performed shortly after the resin infiltration.

A cohesive-frictional force field (CFFF) for colloidal calcium-silicate-hydrates

NASA Astrophysics Data System (ADS)

Palkovic, Steven D.; Yip, Sidney; Büyüköztürk, Oral

2017-12-01

Calcium-silicate-hydrate (C-S-H) gel is a cohesive-frictional material that exhibits strength asymmetry in compression and tension and normal-stress dependency of the maximum shear strength. Experiments suggest the basic structural component of C-S-H is a colloidal particle with an internal layered structure. These colloids form heterogeneous assemblies with a complex pore network at the mesoscale. We propose a cohesive-frictional force field (CFFF) to describe the interactions in colloidal C-S-H materials that incorporates the strength anisotropy fundamental to the C-S-H molecular structure that has been omitted from recent mesoscale models. We parameterize the CFFF from reactive force field simulations of an internal interface that controls mechanical performance, describing the behavior of thousands of atoms through a single effective pair interaction. We apply the CFFF to study the mesoscale elastic and Mohr-Coulomb strength properties of C-S-H with varying polydispersity and packing density. Our results show that the consideration of cohesive-frictional interactions lead to an increase in stiffness, shear strength, and normal-stress dependency, while also changing the nature of local deformation processes. The CFFF and our coarse-graining approach provide an essential connection between nanoscale molecular interactions and macroscale continuum behavior for hydrated cementitious materials.

In vivo evaluation of the effects of hydraulic calcium silicate dental cements on plasma and liver aluminium levels in rats.

PubMed

Demirkaya, Kadriye; Can Demirdöğen, Birsen; Öncel Torun, Zeynep; Erdem, Onur; Çetinkaya, Serdar; Akay, Cemal

2016-02-01

Our aim was to test whether the presence of three hydraulic calcium silicate dental cements--MTA Angelus, MTA Fillapex, and Theracal LC--in the dental extraction socket of an in vivo model, would affect the levels of aluminium (Al) in the plasma and liver. Following anesthesia, the right upper incisor of each male Wistar albino rat was extracted and polyethylene tubes filled with MTA Angelus, MTA Fillapex, or Theracal LC were inserted into the depth of the extraction socket and gingival tissue was sutured. The rats were killed 7, 30, or 60 d after the operation. Blood and liver samples were obtained from the rats before they were killed, and the levels of Al were measured by atomic absorption spectrometry. Plasma Al levels were higher in the rats in which the mineral trioxide aggregate (MTA) cements were implanted, especially MTA Angelus and MTA Fillapex, compared with control rats. In liver samples, however, the differences in Al level were not statistically significant. Our results show that Al might have been released into the circulation from the three dental cements tested, especially MTA Angelus and MTA Fillapex. Further research should be carried out on the possible biological effects of Al liberated from dental cements. © 2015 Eur J Oral Sci.

Rapid Removal of Atmospheric CO2 by Urban Soils.

PubMed

Washbourne, Carla-Leanne; Lopez-Capel, Elisa; Renforth, Phil; Ascough, Philippa L; Manning, David A C

2015-05-05

The measured calcium carbonate content of soils to a depth of 100 mm at a large urban development site has increased over 18 months at a rate that corresponds to the sequestration of 85 t of CO2/ha (8.5 kg of CO2 m(-2)) annually. This is a consequence of rapid weathering of calcium silicate and hydroxide minerals derived from the demolition of concrete structures, which releases Ca that combines with CO2 ultimately derived from the atmosphere, precipitating as calcite. Stable isotope data confirm an atmospheric origin for carbonate carbon, and 14C dating indicates the predominance of modern carbon in the pedogenic calcite. Trial pits show that carbonation extends to depths of ≥1 m. Work at other sites shows that the occurrence of pedogenic carbonates is widespread in artificially created urban soils containing Ca and Mg silicate minerals. Appropriate management of fewer than 12000 ha of urban land to maximize calcite precipitation has the potential to remove 1 million t of CO2 from the atmosphere annually. The maximal global potential is estimated to be approximately 700-1200 Mt of CO2 per year (representing 2.0-3.7% of total emissions from fossil fuel combustion) based on current rates of production of industry-derived Ca- and Mg-bearing materials.

Deposition velocities and impact of physical properties on ozone removal for building materials

NASA Astrophysics Data System (ADS)

Lin, Chi-Chi; Hsu, Shu-Chen

2015-01-01

This study aims to estimate the ozone deposition velocities of eight commonly used building materials (BMs) which include calcium silicate board (CSB), green calcium silicate board (GCSB), mineral fiber ceiling (MFC), green mineral fiber ceiling (GMFC), gypsum board (GB), green gypsum board (GGB), wooden flooring (WF) and green wooden flooring (GWF). In addition, the impact of physical properties (specific surface area and total pore volume of BM) on ozone removal ability was also explored and discussed. Studies were conducted in a small-scale environmental stainless steel chamber. CSB and GCSB showed the highest ozone deposition velocities, while WF and GWF showed the lowest ozone deposition velocities among test BMs materials. All reaction probabilities were estimated to fall within the order of magnitude of 10-6. Green BMs showed lower reaction probabilities with ozone comparing with non-green BMs except for GGB. Consistent with the trends for deposition velocity, fleecy and porous materials exhibit higher reaction probabilities than smooth, non-porous surfaces. Specific surface area of BM is more closely related to ozone removal than total pore volume of BM with R2 of 0.93 vs. R2 of 0.84. Discussion of Thiele modulus for all test BMs indicates surface reactions are occurring quickly relative to internal diffusion and ozone removal is internal diffusion-limited.

Impact de la pollution industrielle sur la zone côtière du Jorf Lasar (océan Atlantique marocain): la moule comme indicateur de la contamination métallique

NASA Astrophysics Data System (ADS)

Kaimoussi, Aziz; Chafik, Abdelghani; Mouzdahir, Abdelkrim; Bakkas, Salem

2001-09-01

The present study characterizes the effluents of the 'Maroc Phosphore' factories III and IV (of Jorf Lasfar coastal zone). The results show that the effluent (Cs/l) is very acid, very phosphate-rich, high in suspended matter and calcium-rich. Hydrological parameters indicate an important content of phosphates, especially in the stations located in the South of Cs/l. Tissues of mussel Mytilus galloprovincialis from the Jorf Lasfar zone present high concentrations of Cd and Cu.

Cigarette smoke directly impairs skeletal muscle function through capillary regression and altered myofibre calcium kinetics in mice.

PubMed

Nogueira, Leonardo; Trisko, Breanna M; Lima-Rosa, Frederico L; Jackson, Jason; Lund-Palau, Helena; Yamaguchi, Masahiro; Breen, Ellen C

2018-05-23

Cigarette smoke components directly alter muscle fatigue resistance and intracellular muscle fibre Ca 2+ handling independent of a change in lung structure. Changes in muscle vascular structure are associated with a depletion of satellite cells. Sarcoplasmic reticulum Ca 2+ uptake is substantially impaired in myofibres during fatiguing contractions in mice treated with cigarette smoke extract. Cigarette smokers exhibit exercise intolerance before a decline in respiratory function. In the present study, the direct effects of cigarette smoke on limb muscle function were tested by comparing cigarette smoke delivered to mice by weekly injections of cigarette smoke extract (CSE), or nose-only exposure (CS) 5 days each week, for 8 weeks. Cigarette smoke delivered by either route did not alter pulmonary airspace size. Muscle fatigue measured in situ was 50% lower in the CSE and CS groups than in control. This was accompanied by 34% and 22% decreases in soleus capillary-to-fibre ratio of the CSE and CS groups, respectively, and a trend for fewer skeletal muscle actin-positive arterioles (P = 0.07). In addition, fewer quiescent satellite cells (Nes+Pax7+) were associated with soleus fibres in mice with skeletal myofibre VEGF gene deletion (decreased 47%) and CS exposed (decreased 73%) than with control fibres. Contractile properties of isolated extensor digitorum longus and soleus muscles were impaired. In flexor digitorum brevis myofibres isolated from CSE mice, fatigue resistance was diminished by 43% compared to control and CS myofibres, and this was accompanied by a pronounced slowing in relaxation, an increase in intracellular Ca 2+ accumulation, and a slowing in sarcoplasmic reticulum Ca 2+ uptake. These data suggest that cigarette smoke components may impair hindlimb muscle vascular structure, fatigue resistance and myofibre calcium handling, and these changes ultimately affect contractile efficiency of locomotor muscles independent of a change in lung function. © 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.

Evaluating vertical concentration profile of carbon source released from slow-releasing carbon source tablets and in situ biological nitrate denitrification activity

NASA Astrophysics Data System (ADS)

Yeum, Y.; HAN, K.; Yoon, J.; Lee, J. H.; Song, K.; Kang, J. H.; Park, C. W.; Kwon, S.; Kim, Y.

2017-12-01

Slow-releasing carbon source tablets were manufactured during the design of a small-scale in situ biological denitrification system to reduce high-strength nitrate (> 30 mg N/L) from a point source such as livestock complexes. Two types of slow-releasing tablets, precipitating tablet (PT, apparent density of 2.0 g/mL) and floating tablet (FT), were prepared to achieve a vertically even distribution of carbon source (CS) in a well and an aquifer. Hydroxypropyl methylcellulose (HPMC) was used to control the release rate, and microcrystalline cellulose pH 101 (MCC 101) was added as a binder. The #8 sand was used as a precipitation agent for the PTs, and the floating agents for the FTs were calcium carbonate and citric acid. FTs floated within 30 min. and remained in water because of the buoyance from carbon dioxide, which formed during the acid-base reaction between citric acid and calcium carbonate. The longevities of PTs with 300 mg of HPMC and FTs with 400 mg of HPMC were 25.4 days and 37.3 days, respectively. We assessed vertical CS profile in a continuous flowing physical aquifer model (release test, RT) and its efficiency on biological nitrate denitrification (denitrification test, DT). During the RT, PTs, FTs and a tracer (as 1 mg rhodamine B/L) were initially injected into a well of physical aquifer model (PAM). Concentrations of CS and the tracer were monitored along the streamline in the PAM to evaluate vertical profile of CS. During the DT, the same experiment was performed as RT, except continuous injection of solution containing 30 mg N/L into the PAM to evaluate biological denitrification activity. As a result of RT, temporal profiles of CS were similar at 3 different depths of monitoring wells. These results suggest that simultaneous addition of PT and FT be suitable for achieving a vertically even distribution of the CS in the injection well and an aquifer. In DT, similar profile of CS was detected in the injection well, and nitrate was biologically denitrified at downstream of the injection well. In conclusion, addition of PT and FT into a well under natural gradient condition may be an effective means for remediating high-strength nitrate in groundwater.

Trends in Effective Diffusion Coefficients for Ion-exchange Strengthening of Soda Lime Silicate Glasses

NASA Astrophysics Data System (ADS)

Karlsson, Stefan; Wondraczek, Lothar; Ali, Sharafat; Jonson, Bo

2017-04-01

Monovalent cations enable efficient ion exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda lime silicates (SLS) such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+ and Cs+) by drawing relations to physico-chemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion exchange rate.

Densification of the interlayer spacing governs the nanomechanical properties of calcium-silicate-hydrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geng, Guoqing; Myers, Rupert J.; Qomi, Mohammad Javad Abdolhosseini

Calciuam-silicate-hydrate (C-S-H) is the principal binding phase in modern concrete. Molecular simulations imply that its nanoscale stiffness is 'defect-driven', i.e., dominated by crystallographic defects such as bridging site vacancies in its silicate chains. However, experimental validation of this result is difficult due to the hierarchically porous nature of C-S-H down to nanometers. Here in this paper, we integrate high pressure X-ray diffraction and atomistic simulations to correlate the anisotropic deformation of nanocrystalline C-S-H to its atomic-scale structure, which is changed by varying the Ca-To-Si molar ratio. Contrary to the 'defect-driven' hypothesis, we clearly observe stiffening of C-S-H with increasing Ca/Simore » in the range 0.8 ≤ Ca/Si ≤ 1.3, despite increasing numbers of vacancies in its silicate chains. The deformation of these chains along the b-Axis occurs mainly through tilting of the Si-O-Si dihedral angle rather than shortening of the Si-O bond, and consequently there is no correlation between the incompressibilities of the a-and b-Axes and the Ca/Si. On the contrary, the intrinsic stiffness of C-S-H solid is inversely correlated with the thickness of its interlayer space. This work provides direct experimental evidence to conduct more realistic modelling of C-S-H-based cementitious material.« less

Densification of the interlayer spacing governs the nanomechanical properties of calcium-silicate-hydrate

DOE PAGES

Geng, Guoqing; Myers, Rupert J.; Qomi, Mohammad Javad Abdolhosseini; ...

2017-09-08

Calciuam-silicate-hydrate (C-S-H) is the principal binding phase in modern concrete. Molecular simulations imply that its nanoscale stiffness is 'defect-driven', i.e., dominated by crystallographic defects such as bridging site vacancies in its silicate chains. However, experimental validation of this result is difficult due to the hierarchically porous nature of C-S-H down to nanometers. Here in this paper, we integrate high pressure X-ray diffraction and atomistic simulations to correlate the anisotropic deformation of nanocrystalline C-S-H to its atomic-scale structure, which is changed by varying the Ca-To-Si molar ratio. Contrary to the 'defect-driven' hypothesis, we clearly observe stiffening of C-S-H with increasing Ca/Simore » in the range 0.8 ≤ Ca/Si ≤ 1.3, despite increasing numbers of vacancies in its silicate chains. The deformation of these chains along the b-Axis occurs mainly through tilting of the Si-O-Si dihedral angle rather than shortening of the Si-O bond, and consequently there is no correlation between the incompressibilities of the a-and b-Axes and the Ca/Si. On the contrary, the intrinsic stiffness of C-S-H solid is inversely correlated with the thickness of its interlayer space. This work provides direct experimental evidence to conduct more realistic modelling of C-S-H-based cementitious material.« less

Densification of the interlayer spacing governs the nanomechanical properties of calcium-silicate-hydrate.

PubMed

Geng, Guoqing; Myers, Rupert J; Qomi, Mohammad Javad Abdolhosseini; Monteiro, Paulo J M

2017-09-08

Calciuam-silicate-hydrate (C-S-H) is the principal binding phase in modern concrete. Molecular simulations imply that its nanoscale stiffness is 'defect-driven', i.e., dominated by crystallographic defects such as bridging site vacancies in its silicate chains. However, experimental validation of this result is difficult due to the hierarchically porous nature of C-S-H down to nanometers. Here, we integrate high pressure X-ray diffraction and atomistic simulations to correlate the anisotropic deformation of nanocrystalline C-S-H to its atomic-scale structure, which is changed by varying the Ca-to-Si molar ratio. Contrary to the 'defect-driven' hypothesis, we clearly observe stiffening of C-S-H with increasing Ca/Si in the range 0.8 ≤ Ca/Si ≤ 1.3, despite increasing numbers of vacancies in its silicate chains. The deformation of these chains along the b-axis occurs mainly through tilting of the Si-O-Si dihedral angle rather than shortening of the Si-O bond, and consequently there is no correlation between the incompressibilities of the a- and b-axes and the Ca/Si. On the contrary, the intrinsic stiffness of C-S-H solid is inversely correlated with the thickness of its interlayer space. This work provides direct experimental evidence to conduct more realistic modelling of C-S-H-based cementitious material.

Pegmatite/wallrock interactions, Black Hills, South Dakota: Progressive boron metasomatism adjacent to the Tip Top pegmatite

NASA Astrophysics Data System (ADS)

Shearer, C. K.; Papike, J. J.; Simon, S. B.; Laul, J. C.; Christian, R. P.

1984-12-01

Interaction between country rock and fluids derived from the Tip Top pegmatite has resulted in a series of boron enriched assemblages. Between unaltered quartz-mica schist to the pegmatite contact is a succession of four mineral assemblages: (1) Quartz-Biotite-Potassium Feldspar assemblage (Q-B-K), which consists essentially of the original metamorphic silicate assemblage plus anomalously high amounts of modal tourmaline (2) Quartz-Biotite-Tourmaline assemblage (Q-B-T) (3) Tourmaline-Quartz-Muscovite assemblage (T-Q-M) (4) Tourmaline-Quartz assemblage (T-Q). Alkali elements (Cs, Rb, K, Li), SiO 2, and Ba show a decrease from the Q-B-K assemblage to the T-Q assemblage. A1 2O 3, Ga, B, total Fe and Zn increase moderately from the Q-B-K assemblage to the T-Q assemblage. The mineral chemistries also change considerably. The Mg/(Mg + Fe 2+) ratios in biotites range from 0.54 to 0.50 in samples from the Q-B-K assemblage to 0.39 in the (Q-B-T) assemblage. The range in tourmaline end-member components from the Q-B-K assemblage to the T-Q assemblage is as follows: Q-B-K: Dravite .63 Schorl .23 Elbaite .05 Buergerite .09 T-Q: Dravite .23 Schorl .37 Elbaite .17 Buergerite .23. Observed variations in mineral assemblage and whole rock chemistry within the alteration zone appear to a first approximation to be a function of μB2O3 (boron metasomatism) and μK2O (alkali leaching). The breakdown of feldspar and biotite may be approximated by reactions: 2HCl + 2(K, Na)AlSi 3O 8 /ai 2(K, Na)Cl + Al 2SiO 5 + 5SiO 2 + H 2O and 2 Annite + SiO 2 + 5Al 2SiO 5 + 2NaCl + 6H 3BO 3 /ai 2 Tourmaline + 2KCl + 7H 2O. The alteration zone may represent either a single episode (B-, Cs-, Li-, Rb-enriched fluid) or multiple episodes (B, Zn, Mn fluid and Cs, Li, Rb fluid) of pegmatite fluid-schist interactions. In both situations, B in the aqueous fluid from the pegmatite reacts with the schist breaking down sheet silicate "traps" for Cs, Rb, Li, and K and forming tourmaline-rich assemblages.

Pegmatite/wallrock interactions, Black Hills, South Dakota: Progressive boron metasomatism adjacent to the Tip Top pegmatite

USGS Publications Warehouse

Shearer, C.K.; Papike, J.J.; Simon, S.B.; Laul, J.C.; Christian, R.P.

1984-01-01

Interaction between country rock and fluids derived from the Tip Top pegmatite has resulted in a series of boron enriched assemblages. Between unaltered quartz-mica schist to the pegmatite contact is a succession of four mineral assemblages: 1. (1) Quartz-Biotite-Potassium Feldspar assemblage (Q-B-K), which consists essentially of the original metamorphic silicate assemblage plus anomalously high amounts of modal tourmaline 2. (2) Quartz-Biotite-Tourmaline assemblage (Q-B-T) 3. (3) Tourmaline-Quartz-Muscovite assemblage (T-Q-M) 4. (4) Tourmaline-Quartz assemblage (T-Q). Alkali elements (Cs, Rb, K, Li), SiO2, and Ba show a decrease from the Q-B-K assemblage to the T-Q assemblage. A12O3, Ga, B, total Fe and Zn increase moderately from the Q-B-K assemblage to the T-Q assemblage. The mineral chemistries also change considerably. The Mg/(Mg + Fe2+) ratios in biotites range from 0.54 to 0.50 in samples from the Q-B-K assemblage to 0.39 in the (Q-B-T) assemblage. The range in tourmaline end-member components from the Q-B-K assemblage to the T-Q assemblage is as follows: Q-B-K: Dravite.63 Schorl.23 Elbaite.05 Buergerite.09 T-Q: Dravite.23 Schorl.37 Elbaite.17 Buergerite.23. Observed variations in mineral assemblage and whole rock chemistry within the alteration zone appear to a first approximation to be a function of ??B2O3 (boron metasomatism) and ??K2O (alkali leaching). The breakdown of feldspar and biotite may be approximated by reactions: 2HCl + 2(K, Na)AlSi3O8 /ai 2(K, Na)Cl + Al2SiO5 + 5SiO2 + H2O and 2 Annite + SiO2 + 5Al2SiO5 + 2NaCl + 6H3BO3 /ai 2 Tourmaline + 2KCl + 7H2O. The alteration zone may represent either a single episode (B-, Cs-, Li-, Rb-enriched fluid) or multiple episodes (B, Zn, Mn fluid and Cs, Li, Rb fluid) of pegmatite fluid-schist interactions. In both situations, B in the aqueous fluid from the pegmatite reacts with the schist breaking down sheet silicate "traps" for Cs, Rb, Li, and K and forming tourmaline-rich assemblages. ?? 1984.

Chitosan inhibits platelet-mediated clot retraction, increases platelet-derived growth factor release, and increases residence time and bioactivity of platelet-rich plasma in vivo.

PubMed

Deprés-Tremblay, Gabrielle; Chevrier, Anik; Tran-Khanh, Nicolas; Nelea, Monica; Buschmann, Michael D

2017-11-10

Platelet-rich plasma (PRP) has been used to treat different orthopedic conditions, however, the clinical benefits of using PRP remain uncertain. Chitosan (CS)-PRP implants have been shown to improve meniscus, rotator cuff and cartilage repair in pre-clinical models. The purpose of this current study was to investigate in vitro and in vivo mechanisms of action of CS-PRP implants. Freeze-dried formulations containing 1% (w/v) CS (80% degree of deacetylation and number average molar mass 38 kDa), 1% (w/v) trehalose as a lyoprotectant and 42.2 mM calcium chloride as a clot activator were solubilized in PRP. Gravimetric measurements and molecular/cellular imaging studies revealed that clot retraction is inhibited in CS-PRP hybrid clots through physical coating of platelets, blood cells and fibrin strands by chitosan, which interferes with platelet aggregation and platelet-mediated clot retraction. Flow cytometry and ELISA assays revealed that platelets are activated and granules secreted in CS-PRP hybrid clots and that cumulative release of platelet-derived growth factor (PDGF-AB) and epidermal growth factor is higher from CS-PRP hybrid clots compared to PRP clots in vitro. Finally, CS-PRP implants resided for up to 6 weeks in a subcutaneous implantation model and induced cell recruitment and granulation tissue synthesis, confirming greater residency and bioactivity compared to PRP in vivo.

Coronary artery calcification and large artery stiffness in renal transplant recipients.

PubMed

Stróżecki, Paweł; Serafin, Zbigniew; Adamowicz, Andrzej; Flisiński, Mariusz; Włodarczyk, Zbigniew; Manitius, Jacek

2015-09-01

Coronary artery calcification (CAC) is an independent predictor of cardiovascular (CV) events in renal transplant recipients (RTR). Carotid-femoral pulse wave velocity (PWV), a non-invasive measure of large artery stiffness, also predicts CV events in RTR. The study investigated the relationship between CAC and PWV in RTR and assessed the performance of PWV measurement in predicting CAC. The study was performed as cross-sectional analysis in 104 RTR. CAC was determined as total calcium score (CS) and calcium mass (CM). Carotid-femoral PWV was also measured. Sensitivity, specificity and receiver operating characteristic (ROC) curve were used to assess the performance of PWV as diagnostic test for presence of CAC. CAC was found in 69% of participants. PWV was higher in RTR with CAC than in RTR without CAC (10.2±2.2 vs. 8.6±15; p<0.001). In univariate analysis CS was significantly correlated with age, duration of hypertension, waist circumference, PWV, hemoglobin concentration, and serum glucose. In multiple linear regression analysis CS was independently associated with age only, but not with PWV. Sensitivity and specificity of PWV>7.6m/s as cut-off for detecting CAC>0 was 0.889 and 0.406, respectively. Sensitivity and specificity of PWV>10.2m/s as cut-off for detecting severe CAC (CS>400) was 0.319 and 0.969, respectively. The study confirmed high prevalence of coronary artery calcification in renal transplant recipients. The study does not support the hypothesis that aortic stiffness is independently associated with coronary artery calcification in RTR. PWV measurement may be useful in excluding severe CAC in RTR. Copyright © 2015 Medical University of Bialystok. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Testing of DentStat (trademark) and Competing Dental Materials

DTIC Science & Technology

2014-06-13

NAVAL MEDICAL RESEARCH UNIT SAN ANTONIO TESTING OF DENTST AT™ AND COMPETING DENTAL MATERIALS Y OON HWANG PHD, JONATHAN STAHL DDS PHD, WAYNE M. D...LtCOL Wen Lien of the US Air Force Dental Evaluation and Consultation Service for assistance with the strength testing. 1 Reviewed and Approved by...direct dental repair materials. They are made of calcium or strontium aluminofluoro-silicate glass powder (base) combined with a water-soluble polymer

Soil bacterial communities of a calcium-supplemented and a reference watershed at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA

Treesearch

Ganapathi Sridevi; Rakesh Minocha; Swathi A. Turlapati; Katherine C. Goldfarb; Eoin L. Brodie; Louis S. Tisa; Subhash C. Minocha

2012-01-01

Soil Ca depletion because of acidic deposition-related soil chemistry changes has led to the decline of forest productivity and carbon sequestration in the northeastern USA. In 1999, acidic watershed (WS) 1 at the Hubbard Brook Experimental Forest (HBEF), NH, USA was amended with Ca silicate to restore soil Ca pools. In 2006, soil samples were collected from the Ca-...

A method for estimating radioactive cesium concentrations in cattle blood using urine samples.

PubMed

Sato, Itaru; Yamagishi, Ryoma; Sasaki, Jun; Satoh, Hiroshi; Miura, Kiyoshi; Kikuchi, Kaoru; Otani, Kumiko; Okada, Keiji

2017-12-01

In the region contaminated by the Fukushima nuclear accident, radioactive contamination of live cattle should be checked before slaughter. In this study, we establish a precise method for estimating radioactive cesium concentrations in cattle blood using urine samples. Blood and urine samples were collected from a total of 71 cattle on two farms in the 'difficult-to-return zone'. Urine 137 Cs, specific gravity, electrical conductivity, pH, sodium, potassium, calcium, and creatinine were measured and various estimation methods for blood 137 Cs were tested. The average error rate of the estimation was 54.2% without correction. Correcting for urine creatinine, specific gravity, electrical conductivity, or potassium improved the precision of the estimation. Correcting for specific gravity using the following formula gave the most precise estimate (average error rate = 16.9%): [blood 137 Cs] = [urinary 137 Cs]/([specific gravity] - 1)/329. Urine samples are faster to measure than blood samples because urine can be obtained in larger quantities and has a higher 137 Cs concentration than blood. These advantages of urine and the estimation precision demonstrated in our study, indicate that estimation of blood 137 Cs using urine samples is a practical means of monitoring radioactive contamination in live cattle. © 2017 Japanese Society of Animal Science.

A proposition for the classification of carbonaceous chondritic micrometeorites

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.

1994-01-01

Classification of interplanetary dust particles (IDP's) should be unambiguous and, if possible, provide an opportunity to interrelate these ultrafine IDP's with the matrices of undifferentiated meteorites. I prefer a scheme of chemical groupings and petrologic classes that is based on primary IDP properties that can be determined without prejudice by individual investigators. For IDP's of 2-50 microns these properties are bulk elemental chemistry, morphology, shape, and optical properties. The two major chemical groups are readily determined by energy dispersive spectroscopic analysis using the scanning or analytical electron microscope. Refinement of chondritic IDP classification is possible using the dominant mineral species, e.g. olivine, pyroxene, and layer silicates, and is readily inferred from FTIR, and automated chemical analysis. Petrographic analysis of phyllosilicate-rich IDP's will identify smectite-rich and serpentine-rich particles. Chondritic IDP's are also classified according to morphology, viz., CP and CF IDP's are aggregate particles that differ significantly in porosity, while the dense CS IDP's have a smooth surface. The CP IDP's are characterized by an anhydrous silicate mineralogy, but small amounts of layer silicates may be present. Distinction between the CP and CF IDP's is somewhat ambiguous, but the unique CP IDP's are fluffy, or porous, ultrafine-grained aggregates. The CP IDP's, which may contain silicate whiskers, are the most carbon-rich extraterrestrial material presently known. The CF IDP's are much less porous that CP IDP's. Using particle type definitions, CP IDP's in the NASA JSC Cosmic Dust Catalogs are approx. 15 percent of all IDP's that include nonchondritic spheres. Most aggregate particles are of the CF type.

First physical volcanological description of a Miocene, silicic, phreatomagmatic fall complex in the Carpatho-Pannonian Region (CPR)

NASA Astrophysics Data System (ADS)

Biró, Tamás; Hencz, Mátyás; Karátson, Dávid; Márton, Emő; Bradák-Hayashi, Balázs; Szalai, Zoltán

2017-04-01

The study reports the basic physical volcanological and stratigraphical features of a hitherto unrecognized silicic phreatomagmatic fall succession from the Bükk Foreland Volcanic Area (Hungary), known as part of the extensive Miocene ignimbrite volcanism of the northern CPR. The complex have been identified at two sites, in the vicinity of Bogács and Tibolddaróc villages. Tens of mm to several dm thick layers make up the 20 m thick entire succession. The complex could be subdivided into three eruption cycles by two, intercalated well-developed paleosoil horizons, which indicate longer repose periods. The eruption cycles consist of several individual eruptive events. The volcano-sedimentological field approach was completed by granulometrical and low field anisotropy of magnetic susceptibility (AMS) studies. Combined dry sieving and laser diffraction particle size analysis were performed to get information on median grain size (MdΦ) and sorting (σΦ) of friable layers. AMS was used to infer the emplacement processes. Based on the following features the succession is proposed to record a large-scale, silicic, phreatomagmatic fall activity: i) Presence of very fine ash and abundant ash aggregates, ii) General poor sorting, and often bimodal grain-size distributions; ii) Extremely weak magnetic fabric compared to dilute, thin pyroclastic density current deposits. On the basis of comparison of the recorded grain size characteristics with data from other silicic phretomagmatic fall deposits worldwide, several units in the succession can be considered as phreatoplinian fall deposit (sensu lato), described for the first time in the CPR.

Caesium and strontium accumulation in shoots of Arabidopsis thaliana: genetic and physiological aspects

PubMed Central

Kanter, Ulrike; Hauser, Andreas; Michalke, Bernhard; Dräxl, Stephan; Schäffner, Anton R.

2010-01-01

Due to the physico-chemical similarities of caesium (Cs+) to potassium (K+) on the one hand and strontium (Sr2+) to calcium (Ca2+) on the other hand, both elements can easily be taken up by plants and thus enter the food chain. This could be detrimental when radionuclides such as 137Cs and 90Sr are involved. In this study, both genetic and physiological aspects of Cs+ and Sr2+ accumulation in Arabidopsis thaliana were investigated using 86 Arabidopsis accessions and a segregating F2 population of the low Cs+ accumulating Sq-1 (Ascot, UK) crossed with the high uptaking Sorbo (Khurmatov, Tajikistan). Hydroponically grown plants were exposed to subtoxic levels of Cs+ and Sr2+ using radioactive isotopes as tracers. In the natural accessions shoot concentration of Cs+ as well as Sr2+ varied about 2-fold, whereas its heritability ranged for both ions between 0.60 and 0.73. Shoot accumulation of Cs+ and Sr2+ could be compromised by increasing concentrations of their essential analogues K+ and Ca2+, respectively, causing a reduction of up to 80%. In the case of the segregating F2/F3 population Sq-1×Sorbo, this study identified several QTL for the trait Cs+ and Sr2+ accumulation, with main QTL on chromosomes 1 and 5. According to the correlation and discrimination surveys combined with QTL-analysis Cs+ and Sr2+ uptake seemed to be mediated mostly via non-selective cation channels. A polymorphism, affecting amino acids close to the K+-pore of one candidate, CYCLIC-NUCLEOTIDE-GATED CHANNEL 1 (CNGC1), was identified in Sorbo and associated with high Cs+ concentrating accessions. PMID:20624763

Cyclosporine A normalizes mitochondrial coupling, reactive oxygen species production, and inflammation and partially restores skeletal muscle maximal oxidative capacity in experimental aortic cross-clamping.

PubMed

Pottecher, Julien; Guillot, Max; Belaidi, Elise; Charles, Anne-Laure; Lejay, Anne; Gharib, Abdallah; Diemunsch, Pierre; Geny, Bernard

2013-04-01

By binding to cyclophilin D, cyclosporine A (CsA) inhibits mitochondrial permeability transition pore (mPTP) opening and prevents mitochondrial dysfunction and ultimately cell death after ischemia-reperfusion (IR) injury in cardiac muscle. This study tested whether CsA would decrease skeletal muscle oxidative stress and mitochondrial dysfunctions after aortic cross-clamping related IR. Forty-five Wistar rats were investigated. The sham group (n = 8) had aortic exposure but no ischemia, the IR group (n = 10) had aortic cross-clamping for 3 hours followed by 2 hours of reperfusion, and the IR+CsA group (n = 9) had two intraperitoneal injections of 10 mg of CsA at 90 and 150 minutes of ischemia before reperfusion. Mitochondrial coupling (acceptor control ratio) and mitochondrial respiratory chain complexes' activities were measured. Reactive oxygen species (ROS) production, cyclophilin D expression, and muscle inflammation were determined using dihydroethidium staining, Western blot, and immunohistochemistry, respectively. An additional 18 sham rats were investigated to determine CsA blood levels and the effects of CsA on mitochondrial respiration and calcium retention capacity, a marker of mPTP opening, both in myocardium and gastrocnemius with and without CsA. Compared with sham, IR decreased mitochondrial coupling (1.38 ± 0.06 vs 1.98 ± 0.20; P = .0092), increased ROS production (3992 ± 706 arbitrary units [AU] vs 1812 ± 322 AU; P = .033), was associated with macrophage infiltration, and decreased maximal oxidative capacity (V(max): 4.08 ± 0.38 μmol O(2)/min/g vs 5.98 ± 0.56 μmol O(2)/min/g; P = .015). Despite IR, CsA treatment totally restored mitochondrial coupling (1.93 ± 0.12; P = .023 vs IR), normalized ROS (1569 ± 348 AU; P = .0098 vs IR), and decreased inflammation. The V(max) was slightly enhanced (5.02 ± 0.39 μmol O(2)/min/g; P = .33 vs IR; P = .35 vs sham). Compared with myocardium, gastrocnemius muscle was characterized by a decreased cyclophilin D content (-50%) associated with an earlier opening of mPTP (calcium retention capacity increased from 10.85 ± 1.35 μM/mg dry weight [DW] to 12.11 ± 2.77 μM/mg DW; P = .65; and from 11.07 ± 1.67 to 37.65 ± 11.41 μM/mg DW; P = .0098 in gastrocnemius and heart, respectively). Cyclosporine A normalized ROS production, decreased inflammation, and restored mitochondrial coupling during aortic cross-clamping. Incomplete Vmax protection might be due to low cyclophilin D expression in gastrocnemius, preventing CsA from blocking mPTP opening. Copyright © 2013 Society for Vascular Surgery. Published by Mosby, Inc. All rights reserved.

Evaluation of the filling ability of artificial lateral canals using calcium silicate-based and epoxy resin-based endodontic sealers and two gutta-percha filling techniques.

PubMed

Fernández, R; Restrepo, J S; Aristizábal, D C; Álvarez, L G

2016-04-01

To evaluate the ability of a calcium silicate-based sealer (iRoot SP) and an epoxy resin-based sealer (Topseal) using two gutta-percha filling techniques to fill artificial lateral canals (ALCs). Seventy single-rooted human teeth were selected. Ten of these were used to obtain pilot data. Three ALCs were produced on mesial and distal surfaces of each root, one in each third, using size 10 engine reamers. The roots were randomly assigned to four experimental groups according to the filling technique and sealer used: 1, cold gutta-percha (single-point technique) with iRoot SP (SP-iR); 2, cold gutta-percha (single-point technique) with Topseal (SP-T); 3, continuous wave of condensation technique with iRoot SP (CWC-iR); and 4, continuous wave of condensation technique with Topseal (CWC-T). Digital periapical radiographs were taken. After the sealer had set, the roots were demineralized, cleared in methyl-salicylate and examined under a stereomicroscope. The depth of penetration of sealer and/or gutta-percha into the ALC was scored using a 5-point system, conducting an analysis on four surfaces. Filling scores of 0-1 were considered not acceptable, whilst scores of 2-4 were considered acceptable. Pearson's chi-square test was used to compare the experimental groups (P < 0.05). CWC-T was associated with the highest acceptable filling (57.8%), followed by CWC-iR (53.3%), SP-T (48.9%) and SP-iR (36.7%). Only when SP-iR was compared to the other groups, was the difference significant (P < 0.05). The apical third was associated with the lowest acceptable filling (37.5%). It was followed, in ascending order, by the middle (51.6%) and coronal thirds (58.3%). These differences were significant only when the apical thirds were compared to the other root thirds (P < 0.05). The calcium silicate-based sealer with continuous wave of condensation was more effective in artificial filling lateral canals than the single-point technique. The epoxy resin-based sealer with both filling techniques was effective in artificial filling lateral canals. © 2015 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Effects of industrial and agricultural waste amendment on soil greenhouse gas production in a paddy field in Southeastern China

NASA Astrophysics Data System (ADS)

Wang, Weiqi; Neogi, Suvadip; Lai, Derrick Y. F.; Zeng, Congsheng; Wang, Chun; Zeng, Dongping

2017-09-01

Controlling the production and subsequent emissions of greenhouse gases (GHGs) from paddy fields is crucial to minimize the climatic impacts arising from crop production. The application of chemical or biological amendments is one possible way to limit the production of GHGs in paddy soils. Yet, few existing studies have examined the impacts of applying fertilizers originated from industrial and agricultural wastes on soil GHG production and its governing factors in subtropical paddy fields. In this study, we examined the effects of various agricultural and industrial amendments, including biochar, steel slag, shell slag, gypsum slag, and slag-derived silicate and calcium fertilizers, on the production potential of GHGs in an early paddy field in southeast China. The mean CO2 production rates from soils amended with steel slag as well as silicate and calcium fertilizers were significantly higher than those of the controls by 13.4% and 18.6%, respectively (P < 0.05). Mean soil CH4 production rates from the plots amended with steel slag, biochar, shell slag, and gypsum slag were significantly lower than those of the controls by 42.5%, 36.1%, 60.8%, and 61.8%, respectively (P < 0.05). Meanwhile, we found no significant difference in mean soil N2O production rates between the control and any of the treatments (P > 0.05). Overall, the soil production rate of CO2 was positively correlated with that of CH4 (P < 0.05), but negatively correlated with that of N2O (P < 0.05). When compared to the controls, the ratio of soil CO2:CH4 production increased significantly in the plots receiving biochar, and silicate and calcium fertilizer amendments (P < 0.05), while that of CO2:N2O production increased significantly only in the biochar-amended plots. Soil CH4:N2O production ratio decreased significantly in the plots amended with steel slag and gypsum slag, as compared to the controls (P < 0.05). Our results suggest that the application of biochar, shell slag and gypsum slag would help reduce greenhouse gas production and mitigate climate change impacts of rice cultivation, largely attributable to the reduction in methanogenesis.

X-ray analysis of aerosol samples from a therapeutic cave

NASA Astrophysics Data System (ADS)

Alföldy, B.; Török, Sz.; Kocsonya, A.; Szőkefalvi-Nagy, Z.; Balla, Md. I.

2001-04-01

Cave therapy is an efficient therapeutic method to cure asthma, the exact healing effect, however, is not clarified, yet. This study is motivated by the basic assumption that aerosols do play the key role in the cave therapy. This study is based on measurements of single aerosol particles originating from a therapeutic cave of Budapest, Hungary (Szemlőhegyi cave). Aerosol particles have been collected in the regions arranged for the therapeutic treatment. Samples were further analysed for chemical and morphological aspects, determining the particle size distribution and classifying them according to elemental composition. Three particle classes have been detected based on major element concentration: alumino-silicate, quartz and calcium carbonate. Calcium ions have well-known physiological influence: anti-spastic, anti-inflammation and excretion reducing effects. Inflammation, accompanying spasm and extreme excretion production cause the smothering stigma, the so-called asthma. Therefore it could be assumed that calcium ions present in high concentration in the cave's atmosphere is the major cause of the healing effect.

Calcium titanium silicate based glass-ceramic for nuclear waste immobilisation

NASA Astrophysics Data System (ADS)

Sharma, K.; Srivastav, A. P.; Goswami, M.; Krishnan, Madangopal

2018-04-01

Titanate based ceramics (synroc) have been studied for immobilisation of nuclear wastes due to their high radiation and thermal stability. The aim of this study is to synthesis glass-ceramic with stable phases from alumino silicate glass composition and study the loading behavior of actinides in glass-ceramics. The effects of CaO and TiO2 addition on phase evolution and structural properties of alumino silicate based glasses with nominal composition x(10CaO-9TiO2)-y(10Na2O-5 Al2O3-56SiO2-10B2O3); where z = x/y = 1.4-1.8 are reported. The glasses are prepared by melt-quench technique and characterized for thermal and structural properties using DTA and Raman Spectroscopy. Glass transition and peak crystallization temperatures decrease with increase of CaO and TiO2 content, which implies the weakening of glass network and increased tendency of glasses towards crystallization. Sphene (CaTiSiO5) and perovskite (CaTiO3) crystalline phases are confirmed from XRD which are well known stable phase for conditioning of actinides. The microsturcture and elemental analysis indicate the presence of actinide in stable crystalline phases.

Producing Durable Continuously Reinforced Concrete Pavement using Glass-ceramic Coated Reinforcing Steel

DTIC Science & Technology

2010-02-01

reinforcement if the enamel is broken  Embedded cement grains hydrate if enamel is cracked to self-heal with the formation of calcium silicate hydrate Goal...Reinforced Concrete Pavement The 600% volume change in the iron to iron oxide formation put the concrete in tension and it cracks an spalls BUILDING...corrodes prematurely and delaminates the pavement  Moisture and chlorides can move through the natural porosity of concrete and the cracks in the

Fabrication and characterization of a novel carbon fiber-reinforced calcium phosphate silicate bone cement with potential osteo-inductivity.

PubMed

Zheng, Jiangjiang; Xiao, Yu; Gong, Tianxing; Zhou, Shuxin; Troczynski, Tom; Yang, Quanzu; Bao, Chongyun; Xu, Xiaoming

2015-12-23

The repair of bone defects is still a pressing challenge in clinics. Injectable bone cement is regarded as a promising material to solve this problem because of its special self-setting property. Unfortunately, its poor mechanical conformability, unfavorable osteo-genesis ability and insufficient osteo-inductivity seriously limit its clinical application. In this study, novel experimental calcium phosphate silicate bone cement reinforced by carbon fibers (CCPSC) was fabricated and characterized. First, a compressive strength test and cell culture study were carried out. Then, the material was implanted into the femoral epiphysis of beagle dogs to further assess its osteo-conductivity using a micro-computed tomography scan and histological analysis. In addition, we implanted CCPSC into the beagles' intramuscular pouches to perform an elementary investigation of its osteo-inductivity. The results showed that incorporation of carbon fibers significantly improved its mechanical properties. Meanwhile, CCPSC had better biocompatibility to activate cell adhesion as well as proliferation than poly-methyl methacrylate bone cement based on the cell culture study. Moreover, pronounced biodegradability and improved osteo-conductivity of CCPSC could be observed through the in vivo animal study. Finally, a small amount of osteoid was found at the heterotopic site one month after implantation which indicated potential osteo-inductivity of CCPSC. In conclusion, the novel CCPSC shows promise as a bioactive bone substitute in certain load-bearing circumstances.

Self-repairing properties of OPC clinker/natural zeolite blend in water and alkali carbonate environments at 270°C

DOE PAGES

Pyatina, Tatiana; Sugama, Toshifumi; Ronne, Arthur; ...

2018-01-01

The 10 d recoveries of the mechanical properties and crack sealing of an ordinary Portland cement (OPC) clinker/natural zeolite (ferrierite (Fer)) blend modified or unmodified with silica were tested at 270°C in water and alkali carbonate environments. The recoveries of the samples depended on their modification with silica and the curing environment, but were more than 100% after repeated damage under some test conditions. The mechanical properties and phase compositions of recovered samples were evaluated by compressive strength measurements and x-ray diffraction, differential thermogravimetric analyses, Fourier transform infrared analyses and scanning electron microscopy coupled with energy dispersive x-ray spectroscopy. Themore » sealing of 0·25 mm wide and ~2 mm deep cracks was visualised with a three-dimensional optical microscope. Fer decomposed under high-temperature alkaline conditions with the release of hydrolysates that, along with the hydrating clinker, participated in the formation of new phases contributing to strength recoveries. Here, these phases included crystalline magnesium and aluminium-containing silicates, calcium and carbonated calcium silicates and amorphous hydrates. Crack sealing was complete for the silica-modified samples and partial for unmodified ones cured in carbonate environments. The sealing was very poor for samples cured in water. Lastly, the main sealing phases included crystalline and amorphous silica, high-temperature-stable zeolites and talc mineral.« less

Self-repairing properties of OPC clinker/natural zeolite blend in water and alkali carbonate environments at 270°C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyatina, Tatiana; Sugama, Toshifumi; Ronne, Arthur

The 10 d recoveries of the mechanical properties and crack sealing of an ordinary Portland cement (OPC) clinker/natural zeolite (ferrierite (Fer)) blend modified or unmodified with silica were tested at 270°C in water and alkali carbonate environments. The recoveries of the samples depended on their modification with silica and the curing environment, but were more than 100% after repeated damage under some test conditions. The mechanical properties and phase compositions of recovered samples were evaluated by compressive strength measurements and x-ray diffraction, differential thermogravimetric analyses, Fourier transform infrared analyses and scanning electron microscopy coupled with energy dispersive x-ray spectroscopy. Themore » sealing of 0·25 mm wide and ~2 mm deep cracks was visualised with a three-dimensional optical microscope. Fer decomposed under high-temperature alkaline conditions with the release of hydrolysates that, along with the hydrating clinker, participated in the formation of new phases contributing to strength recoveries. Here, these phases included crystalline magnesium and aluminium-containing silicates, calcium and carbonated calcium silicates and amorphous hydrates. Crack sealing was complete for the silica-modified samples and partial for unmodified ones cured in carbonate environments. The sealing was very poor for samples cured in water. Lastly, the main sealing phases included crystalline and amorphous silica, high-temperature-stable zeolites and talc mineral.« less

Investigation on the thermo-chemical reaction mechanism between yttria-stabilized zirconia (YSZ) and calcium-magnesium-alumino-silicate (CMAS)

NASA Astrophysics Data System (ADS)

Zhang, Dong-Bo; Wang, Bin-Yi; Cao, Jian; Song, Guan-Yu; Liu, Juan-Bo

2015-03-01

Thermal barrier coatings (TBCs) with Y2O3-stabilized ZrO2 (YSZ) top coat play a very important role in advanced turbine blades by considerably increasing the engine efficiency and improving the performance of highly loaded blades. However, at high temperatures, environment factors result in the failure of TBCs. The influence of calcium-magnesium-alumino-silicate (CMAS) is one of environment factors. Although thermo-physical effect is being paid attention to, the thermo-chemical reaction becomes the hot-spot in the research area of TBCs affected by CMAS. In this paper, traditional twolayered structured TBCs were prepared by electron beam physical vapor deposition (EBPVD) as the object of study. TBCs coated with CMAS were heated at 1240°C for 3 h. Additionally, 15 wt.% simulated molten CMAS powder and YSZ powder were mixed and heated at 1240°C or 1350°C for 48 h. SEM and EDS were adopted to detect morphology and elements distribution. According to XRD and TEM results, it was revealed that CMAS react with YSZ at high temperature and form ZrSiO4, Ca0.2Zr0.8O1.8 and Ca0.15Zr0.85O1.85 after reaction, as a result, leading to the failure of TBCs and decreasing the TBC lifetime.

A food-grade process for isolation and partial purification of bacteriocins of lactic acid bacteria that uses diatomite calcium silicate.

PubMed Central

Coventry, M J; Gordon, J B; Alexander, M; Hickey, M W; Wan, J

1996-01-01

Bacteriocins, including nisin, pediocin PO2, brevicin 286, and piscicolin 126, were extracted from fermentation media by adsorption onto Micro-Cel (a food-grade diatomite calcium silicate anticaking agent) and subsequent desorption. The optimal conditions for desorption of piscicolin 126 were determined and applied to other bacteriocins, and the relative purities of the desorbed preparations were compared. Piscicolin was not successfully desorbed from Micro-Cel at pH 1.0 to 12.0, with organic solvents, or by increase of ionic strength up to 1 M NaCl. However, 25 and 75% of the bacteriocin activity was desorbed by using 1% sodium deoxycholate and 1% sodium dodecyl sulfate (SDS), respectively. Higher levels (up to 100%) of desorption were achieved by repeated elution or by an increase in surfactant concentration. Desorption of piscicolin with 1/10 volume of SDS solution resulted in a preparation with 10 times concentration in activity, equivalent to that of ammonium sulfate preparations (409,600 to 819,200 activity units/ml). Determination of organic nitrogen (N) content revealed that the desorbed piscicolin preparations were substantially free of proteinaceous substances (approximately 92 to 99%) compared with original culture supernatants and ammonium sulfate preparations. Nisin, pediocin, and brevicin were also desorbed with 1% SDS with a similar level of purification. PMID:8633875

Nanoscale Charge-Balancing Mechanism in Alkali-Substituted Calcium-Silicate-Hydrate Gels.

PubMed

Özçelik, V Ongun; White, Claire E

2016-12-15

Alkali-activated materials and related alternative cementitious systems are sustainable technologies that have the potential to substantially lower the CO 2 emissions associated with the construction industry. However, these systems have augmented chemical compositions as compared to ordinary Portland cement (OPC), which may impact the evolution of the hydrate phases. In particular, calcium-silicate-hydrate (C-S-H) gel, the main hydrate phase in OPC, is likely to be altered at the atomic scale due to changes in the bulk chemical composition, specifically via the addition of alkalis (i.e., Na or K) and aluminum. Here, via density functional theory calculations, we reveal the presence of a charge balancing mechanism at the molecular level in C-S-H gel (as modeled using crystalline 14 Å tobermorite) when alkalis and aluminum atoms are introduced into the structure. Different structural representations are obtained depending on the level of substitution and the degree of charge balancing incorporated in the structures. The impact of these substitutional and charge balancing effects on the structures is assessed by analyzing the formation energies, local bonding environments, diffusion barriers and mechanical properties. The results of this computational study provide information on the phase stability of alkali/aluminum containing C-S-H gels, shedding light on the fundamental atomic level mechanisms that play a crucial role in these complex disordered materials.

Impedance methodology: A new way to characterize the setting reaction of dental cements.

PubMed

Villat, Cyril; Tran, Xuan-Vinh; Tran, V X; Pradelle-Plasse, Nelly; Ponthiaux, Pierre; Wenger, François; Grosgogeat, Brigitte; Colon, Pierre

2010-12-01

Impedance spectroscopy is a non-destructive, quantitative method, commonly used nowadays for industrial research on cement and concrete. The aim of this study is to investigate the interest of impedance spectroscopy in the characterization of setting process of dental cements. Two types of dental cements are used in this experiment: a new Calcium Silicate cement Biodentine™ (Septodont, Saint Maur-des Fossés, France) and a glass ionomer cement resin modified or not (Fuji II(®) LC Improved Capsules and Fuji IX(®) GP Fast set Capsules, GC Corp., Tokyo, Japan). The conductivity of the dental cements was determined by impedance spectroscopy measurements carried out on dental cement samples immersed in a 0.1M potassium chloride solution (KCl) in a "like-permeation" cell connected to a potentiostat and a Frequency Response Analyzer. The temperature of the solution is 37°C. From the moment of mixing of powder and liquid, the experiments lasted 2 weeks. The results obtained for each material are relevant of the setting process. For GIC, impedance values are stabilized after 5 days while at least 14 days are necessary for the calcium silicate based cement. In accordance with the literature regarding studies of cements and concrete, impedance spectroscopy can characterize ion mobility, porosity and hardening process of dental hydrogel materials. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Preparation of Cotton-Wool-Like Poly(lactic acid)-Based Composites Consisting of Core-Shell-Type Fibers

PubMed Central

Wang, Jian; Zhou, Pin; Obata, Akiko; Jones, Julian R.; Kasuga, Toshihiro

2015-01-01

In previous works, we reported the fabrication of cotton-wool-like composites consisting of siloxane-doped vaterite and poly(l-lactic acid) (SiVPCs). Various irregularly shaped bone voids can be filled with the composite, which effectively supplies calcium and silicate ions, enhancing the bone formation by stimulating the cells. The composites, however, were brittle and showed an initial burst release of ions. In the present work, to improve the mechanical flexibility and ion release, the composite fiber was coated with a soft, thin layer consisting of poly(d,l-lactic-co-glycolic acid) (PLGA). A coaxial electrospinning technique was used to prepare a cotton-wool-like material comprising “core-shell”-type fibers with a diameter of ~12 µm. The fibers, which consisted of SiVPC coated with a ~2-µm-thick PLGA layer, were mechanically flexible; even under a uniaxial compressive load of 1.5 kPa, the cotton-wool-like material did not exhibit fracture of the fibers and, after removing the load, showed a ~60% recovery. In Tris buffer solution, the initial burst release of calcium and silicate ions from the “core-shell”-type fibers was effectively controlled, and the ions were slowly released after one day. Thus, the mechanical flexibility and ion-release behavior of the composites were drastically improved by the thin PLGA coating. PMID:28793691

Intrinsic Size Effect in Scaffolded Porous Calcium Silicate Particles and Mechanical Behavior of Their Self-Assembled Ensembles.

PubMed

Hwang, Sung Hoon; Shahsavari, Rouzbeh

2018-01-10

Scaffolded porous submicron particles with well-defined diameter, shape, and pore size have profound impacts on drug delivery, bone-tissue replacement, catalysis, sensors, photonic crystals, and self-healing materials. However, understanding the interplay between pore size, particle size, and mechanical properties of such ultrafine particles, especially at the level of individual particles and their ensemble states, is a challenge. Herein, we focus on porous calcium-silicate submicron particles with various diameters-as a model system-and perform extensive 900+ nanoindentations to completely map out their mechanical properties at three distinct structural forms from individual submicron particles to self-assembled ensembles to pressure-induced assembled arrays. Our results demonstrate a notable "intrinsic size effect" for individual porous submicron particles around ∼200-500 nm, induced by the ratio of particle characteristic diameter to pore characteristic size distribution. Increasing this ratio results in a brittle-to-ductile transition where the toughness of the submicron particles increases by 120%. This size effect becomes negligible as the porous particles form superstructures. Nevertheless, the self-assembled arrays collectively exhibit increasing elastic modulus as a function of applied forces, while pressure-induced compacted arrays exhibit no size effect. This study will impact tuning properties of individual scaffolded porous particles and can have implications on self-assembled superstructures exploiting porosity and particle size to impart new functionalities.

High calcium fly ash geopolymer stabilized lateritic soil and granulated blast furnace slag blends as a pavement base material.

PubMed

Phummiphan, Itthikorn; Horpibulsuk, Suksun; Rachan, Runglawan; Arulrajah, Arul; Shen, Shui-Long; Chindaprasirt, Prinya

2018-01-05

Granulated Blast Furnace Slag (GBFS) was used as a replacement material in marginal lateritic soil (LS) while class C Fly Ash (FA) was used as a precursor for the geopolymerization process to develop a low-carbon pavement base material at ambient temperature. Unconfined Compression Strength (UCS) tests were performed to investigate the strength development of geopolymer stabilized LS/GBFS blends. Scanning Electron Microscopy and X-ray Diffraction analysis were undertaken to examine the role of the various influencing factors on UCS development. The influencing factors studied included GBFS content, Na 2 SiO 3 :NaOH ratio (NS:NH) and curing time. The 7-day soaked UCS of FA geopolymer stabilized LS/GBFS blends at various NS:NH ratios tested was found to satisfy the specifications of the Thailand national road authorities. The GBFS replacement was found to be insignificant for the improvement of the UCS of FA geopolymer stabilized LS/GBFS blends at low NS:NH ratio of 50:50. Microstructural analysis indicated the coexistence of Calcium Silicate Hydrate (CSH) and Sodium Alumino Silicate Hydrate products in FA geopolymer stabilized LS/GBFS blends. This research enables GBFS, which is traditionally considered as a waste material, to be used as a replacement and partially reactive material in FA geopolymer pavement applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of the Ca ion release, pH and surface apatite formation of a prototype tricalcium silicate cement.

PubMed

Yamamoto, S; Han, L; Noiri, Y; Okiji, T

2017-12-01

To evaluate the Ca 2+ -releasing, alkalizing and apatite-like surface precipitate-forming abilities of a prototype tricalcium silicate cement, which was mainly composed of synthetically prepared tricalcium silicate and zirconium oxide radiopacifier. The prototype tricalcium silicate cement, white ProRoot MTA (WMTA) and TheraCal LC (a light-cured resin-modified calcium silicate-filled material) were examined. The chemical compositions were analysed with a wavelength-dispersive X-ray spectroscopy electron probe microanalyser with an image observation function (SEM-EPMA). The pH and Ca 2+ concentrations of water in which the set materials had been immersed were measured, and the latter was assessed with the EDTA titration method. The surface precipitates formed on the materials immersed in phosphate-buffered saline (PBS) were analysed with SEM-EPMA and X-ray diffraction (XRD). Kruskal-Wallis tests followed by Mann-Whitney U-test with Bonferroni correction were used for statistical analysis (α = 0.05). The prototype cement contained Ca, Si and Zr as major elemental constituents, whereas it did not contain some metal elements that were detected in the other materials. The Ca 2+ concentrations and pH of the immersion water samples exhibited the following order: WMTA = prototype cement > TheraCal LC (P < 0.05). All three materials produced Ca- and P-containing surface precipitates after PBS immersion, and the precipitates produced by TheraCal LC displayed lower Ca/P ratios than those formed by the other materials. XRD peaks corresponding to hydroxyapatite were detected in the precipitates produced by the prototype cement and WMTA. The prototype tricalcium silicate cement exhibited similar Ca 2+ -releasing, alkalizing and apatite-like precipitate-forming abilities to WMTA. The Ca 2+ -releasing, alkalizing and apatite-like precipitate-forming abilities of TheraCal LC were lower than those of the other materials. © 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Experimental determination of activities of FeO and Fe 2O 3 components in hydrous silicic melts under oxidizing conditions

NASA Astrophysics Data System (ADS)

Gaillard, Fabrice; Pichavant, Michel; Scaillet, Bruno

2003-11-01

The critical role of iron on crystal-silicate liquid relationships and melt differentiation is mainly controlled by the redox conditions prevailing in magmas, but the presently available database merely constrains the thermodynamic properties of iron-bearing components in strongly reduced and anhydrous molten silicate where iron is in the ferrous form. This paper provides new standard states for pure ferrous (FeOliq) and ferric (Fe2O3liq) molten iron oxides and extends the experimental database towards oxidizing and water-bearing domains. Iron-iridium, iron-platinum alloys, magnetite or hematite were equilibrated with synthetic silicic liquids at high temperature and high pressure under controlled oxygen fugacity (fO2) to determine activity-composition relationships for FeOliq and Fe2O3liq. Between 1000 and 1300°C, the fO2 ranges from that in air to 3-log units below that of the nickel-nickel oxide buffer (NNO). Experiments were performed on both anhydrous and hydrous melts containing up to 6-wt.% water. Incorporation of water under reducing conditions increases the activity coefficient of FeOliq but has an opposite effect on Fe2O3liq. As calcium is added to system, the effect of water becomes weaker and is inverted for Fe2O3liq. Under oxidizing conditions, water has a negligible effect on both activities of FeOliq and Fe2O3liq. In contrast, changes in redox conditions dominate the activity coefficients of both FeOliq and Fe2O3liq, which increase significantly with increasing fO2. The present results combined with the previous work provide a specific database on the energetics of iron in silicate melts that cover most of the condition prevailing in natural magmas.

The calcium isotope evolution of Lake Lisan, the Dead Sea glacial precursor

NASA Astrophysics Data System (ADS)

Bradbury, H. J.; Turchyn, A. V.; Wong, K.; Torfstein, A.

2016-12-01

Calcium is a stoichiometric component of carbonate minerals whose calcium isotopic composition reflects changes in the calcium isotope composition of the water from which it precipitates as well as the calcium isotope fractionation factor during precipitation. The lacustrine deposits of the last glacial Dead Sea (Lisan Formation) are dominated by carbonate minerals (aragonite) that record the geochemical history of the lake. The sediment sequence comprises alternating laminae of aragonite and clay-rich marls, interspersed with primary gypsum beds and disseminated secondary gypsum crystals. The aragonite precipitated annually during high lake stands associated with wet periods, while the primary gypsum precipitated during low lake conditions (arid periods). We report the calcium isotopic composition (δ44Ca in ‰ relative to bulk silicate earth) of primary aragonite laminae, primary gypsum and secondary gypsum at 1-5kyr resolution throughout the Lisan Formation sampled at the Masada section (70 - 14.5 ka). The δ44Ca of the primary gypsum averages +0.29‰, and displays smaller temporal variations than the aragonite, which averages -0.35‰ but ranges between +0.18‰ and -0.68‰. The aragonite δ44Ca changes temporally in sync with the previously reconstructed lake level suggesting the aragonite δ44Ca reflects changes in the lake calcium balance during lake level changes. The secondary gypsum composition (-0.3‰) corresponds to coeval aragonite samples. For the secondary gypsum to have a similar δ44Ca to the aragonite it is likely that the calcium derived from the aragonite in a near quantitative fashion through recrystallization of the aragonite to gypsum. A numerical box model is used to explore the effect of changing lake water levels on the calcium isotope composition of the aragonite and gypsum over the time interval studied.

Study of a hydraulic DCPA/CaO-based cement for dental applications.

PubMed

El Briak, Hasna; Durand, Denis; Boudeville, Philippe

2008-02-01

A CPC was obtained by mixing calcium hydrogenphosphate (DCPA: CaHPO(4)) and calcium oxide with either water or sodium phosphate (NaP) buffers. Physical and mechanical properties such as compressive strength (CS), initial (I) and final (F) setting times, cohesion time (T(C)), dough time (T(D)), swelling time (T(S)), dimensional and thermal behavior, injectability (t(100%)), antimicrobial properties, setting reaction kinetics, and powder stability over time were investigated by varying different parameters such as liquid-to-powder (L/P) ratio (0.35 to 0.7 mL g(-1)), molar calcium-to-phosphate (Ca/P) ratio (1.67 to 3), the pH (4, 7 or 9) and the concentration (0 to 1 M) of the NaP buffer. The best results were obtained with the pH 7 NaP buffer at a concentration of 0.75 M. With this liquid phase, physical and mechanical properties depended on the Ca/P and L/P ratios, varying from 3 to 11 MPa (CS), 6 to 10 min (I), 11 to 15 min (F), 15 to 45 min (T(S)), 3 to 12 min (t(100%)), 16 min (T(D)). This cement expanded during its setting (2.5-7%), and is thus appropriate for tight filling. Finally the cement has antimicrobial activity from Ca/P = 2 and the whole properties were conserved after 8 months storage. Given the mechanical, rheological and antimicrobial properties of this new DCPA/CaO-based cement, its use as root canal sealing or pulp capping material may be considered as similar to calcium hydroxide or ZnO/eugenol-based pastes, without or with a gutta-percha point.

A pharmacologically-based array to identify targets of cyclosporine A-induced toxicity in cultured renal proximal tubule cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarró, Eduard, E-mail: eduard.sarro@vhir.org; Renal Physiopathology, CIBBIM-Nanomedicine, Vall d'Hebron Research Institute; Jacobs-Cachá, Conxita, E-mail: conxita.jacobs@vhir.org

2012-01-15

Mechanisms of cyclosporine A (CsA)-induced nephrotoxicity were generally thought to be hemodynamic in origin; however, there is now accumulating evidence of a direct tubular effect. Although genomic and proteomic experiments by our group and others provided overall information on genes and proteins up- or down-regulated by CsA in proximal tubule cells (PTC), a comprehensive view of events occurring after CsA exposure remains to be described. For this purpose, we applied a pharmacologic approach based on the use of known activities of a large panel of potentially protective compounds and evaluated their efficacy in preventing CsA toxicity in cultured mouse PTC.more » Our results show that compounds that blocked protein synthesis and apoptosis, together with the CK2 inhibitor DMAT and the PI3K inhibitor apigenin, were the most efficient in preventing CsA toxicity. We also identified GSK3, MMPs and PKC pathways as potential targets to prevent CsA damage. Additionally, heparinase-I and MAPK inhibitors afforded partial but significant protection. Interestingly, antioxidants and calcium metabolism-related compounds were unable to ameliorate CsA-induced cytotoxicity. Subsequent experiments allowed us to clarify the hierarchical relationship of targeted pathways after CsA treatment, with ER stress identified as an early effector of CsA toxicity, which leads to ROS generation, phenotypical changes and cell death. In summary, this work presents a novel experimental approach to characterizing cellular responses to cytotoxics while pointing to new targets to prevent CsA-induced toxicity in proximal tubule cells. Highlights: ► We used a novel pharmacological approach to elucidate cyclosporine (CsA) toxicity. ► The ability of a broad range of compounds to prevent CsA toxicity was evaluated. ► CsA toxicity was monitored using LDH release assay and PARP cleavage. ► Protein synthesis, PI3K, GSK3, MMP, PKC and caspase inhibitors prevented CsA toxicity. ► We also identified ER stress as an early effector of CsA toxicity.« less

Corn silage versus corn silage:alfalfa hay mixtures for dairy cows: effects of dietary potassium, calcium, and cation-anion difference.

PubMed

Erdman, R A; Piperova, L S; Kohn, R A

2011-10-01

Corn silage (CS) has replaced alfalfa hay (AH) and haylage as the major forage fed to lactating dairy cows, yet many dairy producers believe that inclusion of small amounts of alfalfa hay or haylage improves feed intake and milk production. Alfalfa contains greater concentrations of K and Ca than corn silage and has an inherently higher dietary cation-anion difference (DCAD). Supplemental dietary buffers such as NaHCO(3) and K(2)CO(3) increase DCAD and summaries of studies with these buffers showed improved performance in CS-based diets but not in AH-based diets. We speculated that improvements in performance with AH addition to CS-based diets could be due to differences in mineral and DCAD concentrations between the 2 forages. The objective of this experiment was to test the effects of forage (CS vs. AH) and mineral supplementation on production responses using 45 lactating Holstein cows during the first 20 wk postpartum. Dietary treatments included (1) 50:50 mixture of AH and CS as the forage (AHCS); (2) CS as the sole forage; and (3) CS fortified with mineral supplements (CaCO(3) and K(2)CO(3)) to match the Ca and K content of the AHCS diet (CS-DCAD). Feed intake and milk production were equivalent or greater for cows fed the CS and CS-DCAD diets compared with those fed the AHCS diet. Fat percentage was greater in cows fed the CS compared with the AHCS diet. Fat-corrected milk (FCM; 3.5%) tended to be greater in cows fed the CS and CS-DCAD diets compared with the AHCS diet. Feed efficiencies measured as FCM/dry matter intake were 1.76, 1.80, and 1.94 for the AHCS, CS, and CS-DCAD diets, respectively. The combined effects of reduced feed intake and increased FCM contributed to increased feed efficiency with the CS-DCAD diet, which contained 1.41% K compared with 1.18% K in the CS diet, and we speculate that this might be the result of added dietary K and DCAD effects on digestive efficiency. These results indicate no advantage to including AH in CS-based diets, but suggest that improving mineral supplementation in CS-based diets may increase feed efficiency. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Investigation of mechanical and thermal properties of microwave-sintered lunar simulant materials using 2.45 GHz radiation

NASA Technical Reports Server (NTRS)

Meek, T. T.

1990-01-01

The mechanical and thermal properties of lunar simulant material were investigated. An alternative method of examining thermal shock in microwave-sintered lunar samples was researched. A computer code was developed that models how the fracture toughness of a thermally shocked lunar simulant sample is related to the sample hardness as measured by a micro-hardness indentor apparatus. This technique enables much data to be gathered from a few samples. Several samples were sintered at different temperatures and for different times at the temperatures. The melting and recrystallization characteristics of a well-studied binary system were also investigated to see if the thermodynamic barrier for the nucleation of a crystalline phase may be affected by the presence of a microwave field. The system chosen was the albite (sodium alumino silicate) anorthite system (calcium alumino silicate). The results of these investigations are presented.

Preliminary Results from the Viking X-ray Fluorescence Experiment: The First Sample from Chryse Planitia, Mars.

PubMed

Toulmin, P; Clark, B C; Baird, A K; Keil, K; Rose, H J

1976-10-01

Iron, calcium, aluminum, silicon, and sulfur are major elements in the first surface sample of Mars that has been analyzed by the Viking x-ray fluorescence spectrometer. Titanium is present in minor quantities. This is consistent with the sample being a mixture of fine silicate and oxide mineral grains, with a significant proportion of sulfates, possibly hydrated. Ferric oxide is regarded as the red pigmenting agent on the martian surface, but if it coats silicate grains, the coatings must be very thin (

Preliminary results from the Viking X-ray fluorescence experiment - The first sample from Chryse Planitia, Mars

NASA Technical Reports Server (NTRS)

Toulmin, P., III; Rose, H. J., Jr.; Clark, B. C.; Baird, A. K.; Keil, K.

1976-01-01

Iron, calcium, aluminum, silicon, and sulfur are major elements in the first surface sample of Mars that has been analyzed by the Viking X-ray fluorescence spectrometer. Titanium is present in minor quantities. This is consistent with the sample's being a mixture of fine silicate and oxide mineral grains, with a significant proportion of sulfates, possibly hydrated. Ferric oxide is regarded as the red pigmenting agent on the Martian surface, but if it coats silicate grains, the coatings must be very thin or discontinuous. A high abundance of Fe, relatively low abundances of Al, Rb, Sr, and Zr, and a high Ca/K ratio are distinctive features of the spectra. Preliminary determinations indicate the following abundances (as percentages by weight): Fe, 14 plus or minus 2; Ti, less than 1; S, 2 to 5; the Ca/K ratio by weight is greater than 5.

Preliminary results from the viking x-ray fluorescence experiment: The first sample from chryse planitia, Mars

USGS Publications Warehouse

Toulmin, P.; Clark, B. C.; Baird, A.K.; Keil, Klaus; Rose, H.J.

1976-01-01

Iron, calcium, aluminum, silicon, and sulfur are major elements in the first surface sample of Mars that has been analyzed by the Viking x-ray fluorescence spectrometer. Titanium is present in minor quantities. This is consistent with the sample being a mixture of fine silicate and oxide mineral grains, with a significant proportion of sulfates, possibly hydrated. Ferric oxide is regarded as the red pigmenting agent on the martian surface, but if it coats silicate grains, the coatings must be very thin (??? 2 micrometers) or discontinuous. A high abundance of Fe, relatively low abundances of Al, Rb, Sr, and Zr, and a high Ca/K ratio are distinctive features of the spectra. Preliminary determinations indicate the following abundances (as percentages by weight): Fe, 14 ?? 2; Ti < 1; S, 2 to 5; the Ca/K ratio by weight is greater than 5.

Towards Development of a Dermal Pain Model: In Vitro Activation of Rat and Human Transient Receptor Potential Ankyrin Repeat 1 and Safe Dermal Injection of o-Chlorobenzylidene Malononitrile to Rat.

PubMed

Annas, Anita; Berg, Anna-Lena; Nyman, Eva; Meijer, Thomas; Lundgren, Viveka; Franzén, Bo; Ståhle, Lars

2015-12-01

During clinical development of analgesics, it is important to have access to pharmacologically specific human pain models. o-Chlorobenzylidene malononitrile (CS) is a selective and potent agonist of the transient receptor potential ankyrin repeat 1 (TRPA1), which is a transducer molecule in nociceptors sensing reactive chemical species. While CS has been subject to extensive toxicological investigations in animals and human beings, its effects on intradermal or subcutaneous injection have not previously been reported. We have investigated the potential of CS to be used as an agonist on TRPA1 in human experimental pain studies. A calcium influx assay was used to confirm the capacity of CS to activate TRPA1 with >100,000 times the selectivity over the transient receptor potential vanilloid receptor 1. CS dose-dependently (EC50 0.9 μM) released calcitonin gene-related peptide in rat dorsal root ganglion cultures, supporting involvement in pain signalling. In a local tolerance study, injection of a single intradermal dose of 20 mM CS to rats resulted in superficial, circular crusts at the injection sites after approximately 4 days. The histopathology evaluation revealed a mild, acute inflammatory reaction in the epidermis and dermis at the intradermal CS injection site 1 day after administration. After 14 days, the epidermal epithelium was fully restored. The symptoms were not considered to be adverse, and it is suggested that doses up to 20 μL of 20 mM CS can be safely administered to human beings. In conclusion, our data support development of a CS human dermal pain model. © 2015 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Low temperature synthesis of CaO-SiO2 glasses having stable liquid-liquid immiscibility by sol-gel process

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1990-01-01

Calcium silicate glass compositions lying within the liquid-liquid immiscibility dome of the phase diagram, which could not have been prepared by the conventional melting method, were synthesized by the sol-gel process. Hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) solutions containing up to 20 mol percent calcium nitrate resulted in the formation of clear and transparent gels. The gel formation time decreased with increase in water:TEOS mole ratio, calcium content, and the reaction temperature. Smaller values of gel times in the presence of calcium nitrate are probably caused by lowering of the ionic charge on the sol particles by the salt present. The gelation activation energy, E(sub gel), was evaluated from temperature dependence of the gel time. Presence of Ca(2+) ions or the water:TEOS mole ratio did not have an appreciable effect on the value of E(sub gel). Presence of glycerol in the solution helped in the formation of crack-free monolithic gel specimens. Chemical and structural changes occurring in the gels, as a function of the heat treatments, have been monitored using DTA, TGA, IR-spectroscopy, x ray diffraction, surface area and pore size distribution measurements.

Low temperature synthesis of CaO-SiO2 glasses having stable liquid-liquid immiscibility by the sol-gel process

NASA Technical Reports Server (NTRS)

Bansal, N. P.

1992-01-01

Calcium silicate glass compositions lying within the liquid-liquid immiscibility dome of the phase diagram, which could not have been prepared by the conventional melting method, were synthesized by the sol-gel process. Hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) solutions containing up to 20 mol percent calcium nitrate resulted in the formation of clear and transparent gels. The gel formation time decreased with increase in water: TEOS mole ratio, calcium content, and the reaction temperature. Smaller values of gel times in the presence of calcium nitrate are probably caused by lowering of the ionic charge on the sol particles by the salt present. The gelation activation energy, E(sub gel), was evaluated from temperature dependence of the gel time. Presence of Ca(2+) ions or the water:TEOS mole ratio did not have an appreciable effect on the value of E(sub gel). Presence of glycerol in the solution helped in the formation of crack-free monolithic gel specimens. Chemical and structural changes occurring in the gels, as a function of the heat treatments, have been monitored using DTA, TGA, IR-spectroscopy, X-ray diffraction, surface area and pore size distribution measurements.

Intercalated chitosan/hydroxyapatite nanocomposites: Promising materials for bone tissue engineering applications.

PubMed

Nazeer, Muhammad Anwaar; Yilgör, Emel; Yilgör, Iskender

2017-11-01

Preparation and characterization of chitosan/hydroxyapatite (CS/HA) nanocomposites displaying an intercalated structure is reported. Hydroxyapatite was synthesized through sol-gel process. Formic acid was introduced as a new solvent to obtain stable dispersions of nano-sized HA particles in polymer solution. CS/HA dispersions with HA contents of 5, 10 and 20% by weight were prepared. Self-assembling of HA nanoparticles during the drying of the solvent cast films led to the formation of homogeneous CS/HA nanocomposites. Composite films were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-rays (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, X-rays diffraction (XRD) analysis and thermogravimetric analysis (TGA). SEM and AFM confirmed the presence of uniformly distributed HA nanoparticles on the chitosan matrix surface. XRD patterns and cross-sectional SEM images showed the formation of layered nanocomposites. Complete degradation of chitosan matrix in TGA experiments, led to the formation of nanoporous 3D scaffolds containing hydroxyapatite, β-tricalcium phosphate and calcium pyrophosphate. CS/HA composites can be considered as promising materials for bone tissue engineering applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

The effect of human blood on the setting and surface micro-hardness of calcium silicate cements.

PubMed

Song, Minju; Yue, Wonyoung; Kim, Soyeon; Kim, Wooksung; Kim, Yaelim; Kim, Jeong-Woong; Kim, Euiseong

2016-11-01

The purpose of the present study was to evaluate the effects of human blood on the setting and microhardness of calcium silicate cements. Three types of silicate-based cements were used: ProRoot MTA (PMTA), OrthoMTA (OMTA), and RetroMTA (RMTA). Mixed cement was placed into polyethylene molds with lengths of 2 and 4 mm. After storage for 4 days under three different storage conditions, i.e., saline, saline after 5 min of human blood, and human blood, the polyethylene molds were removed. With the specimens set, the surface microhardness was measured using a Vickers microhardness tester, crystalline structure was analyzed with X-ray diffraction (XRD), and the surface characteristics were examined with scanning electron microscopy (SEM). All specimens of 4 mm in length were set with all materials, and the blood groups exhibited lower microhardnesses than did the saline groups (p < 0.05). Among the 2-mm specimens that were stored in blood, the numbers of specimens that set were significantly different across the materials (p < 0.001). Regarding the microhardnesses of the RMTA and OMTA groups, there were no significant differences between storage conditions. For the PMTA group, only one specimen that was set in the blood group exhibited reduced microhardness. XRD showed changes of crystalline structure in the PMTA and OMTA blood group, whereas RMTA did not. SEM analysis revealed more rounded and homogeneous structures and demonstrated a clear lack of acicular or needle-like crystals in the PMTA and OMTA blood groups, while RMTA did not reveal substantial differences between the saline- and blood-stored groups. Blood contamination detrimentally affected the surface microhardnesses of all materials; furthermore, among the 2-mm specimens, blood contamination interfered with normal setting. Therefore, RMTA might be a more suitable choice when blood contamination is unavoidable due to limited depth. Clinical relevance RetroMTA might be a more suitable choice in situations in which blood contamination is unavoidable.

McCrillisite, NaCs(Be,Li)Zr2(PO4)4.1-2H2O, a new mineral species from Mount Mica, Oxford County, Maine, and new data for gainesite

USGS Publications Warehouse

Foord, E.E.; Brownfield, M.E.; Lichte, F.E.; Davis, A.M.; Sutley, S.J.

1994-01-01

McCrillisite, a member of the gainesite group, occurs in the Mount Mica granitic pegmatite, South Paris, Oxford County, Maine. The mineral is a product of late-stage hydrothermal alteration and is associated with approximately 20 other silicate, oxide, carbonate, arsenite and phosphate minerals. Crystals occur in mm- to cm-sized cavities, and individuals are up to 1.2 mm in maximum dimension. The crystallography and mineral chemistry of McCrillisite are described. -from Authors

Geochemistry of the Birch Creek Drainage Basin, Idaho

USGS Publications Warehouse

Swanson, Shawn A.; Rosentreter, Jeffrey J.; Bartholomay, Roy C.; Knobel, LeRoy L.

2003-01-01

The U.S. Survey and Idaho State University, in cooperation with the U.S. Department of Energy, are conducting studies to describe the chemical character of ground water that moves as underflow from drainage basins into the eastern Snake River Plain aquifer (ESRPA) system at and near the Idaho National Engineering and Environmental Laboratory (INEEL) and the effects of these recharge waters on the geochemistry of the ESRPA system. Each of these recharge waters has a hydrochemical character related to geochemical processes, especially water-rock interactions, that occur during migration to the ESRPA. Results of these studies will benefit ongoing and planned geochemical modeling of the ESRPA at the INEEL by providing model input on the hydrochemical character of water from each drainage basin. During 2000, water samples were collected from five wells and one surface-water site in the Birch Creek drainage basin and analyzed for selected inorganic constituents, nutrients, dissolved organic carbon, tritium, measurements of gross alpha and beta radioactivity, and stable isotopes. Four duplicate samples also were collected for quality assurance. Results, which include analyses of samples previously collected from four other sites, in the basin, show that most water from the Birch Creek drainage basin has a calcium-magnesium bicarbonate character. The Birch Creek Valley can be divided roughly into three hydrologic areas. In the northern part, ground water is forced to the surface by a basalt barrier and the sampling sites were either surface water or shallow wells. Water chemistry in this area was characterized by simple evaporation models, simple calcite-carbon dioxide models, or complex models involving carbonate and silicate minerals. The central part of the valley is filled by sedimentary material and the sampling sites were wells that are deeper than those in the northern part. Water chemistry in this area was characterized by simple calcite-dolomite-carbon dioxide models. In the southern part, ground water enters the ESRPA. In this area, the sampling sites were wells with depths and water levels much deeper than those in the northern and central parts of the valley. The calcium and carbon water chemistry in this area was characterized by a simple calcite-carbon dioxide model, but complex calcite-silicate models more accurately accounted for mass transfer in these areas. Throughout the geochemical system, calcite precipitated if it was an active phase in the models. Carbon dioxide either precipitated (outgassed) or dissolved depending on the partial pressure of carbon dioxide in water from the modeled sites. Dolomite was an active phase only in models from the central part of the system. Generally the entire geochemical system could be modeled with either evaporative models, carbonate models, or carbonate-silicate models. In both of the latter types of models, a significant amount of calcite precipitated relative to the mass transfer to and from the other active phases. The amount of calcite precipitated in the more complex models was consistent with the amount of calcite precipitated in the simpler models. This consistency suggests that, although the simpler models can predict calcium and carbon concentrations in Birch Creek Valley ground and surface water, silicate-mineral-based models are required to account for the other constituents. The amount of mass transfer to and from the silicate mineral phases was generally small compared with that in the carbonate phases. It appears that the water chemistry of well USGS 126B represents the chemistry of water recharging the ESRPA by means of underflow from the Birch Creek Valley.

Calcium Isotope Fractionation during Carbonate Weathering in the Northern Guangdong, South China

NASA Astrophysics Data System (ADS)

Liu, F.; Mao, G.; Wei, G.; Zhang, Z.

2017-12-01

CO2 is consumed during the weathering of carbonates, whereas carbonates are precipitated rapidly in the oceans, which are pivotal to modulate atmospheric CO2, oceanic pH and climate. Calcium carbonate in limestone is one of the largest reservoirs of carbon at the Earth's surface, so calcium is an important element that links the lithosphere, hydrosphere, biosphere, and the atmosphere. Compared with silicate rocks, carbonate rocks have more rapid rates of physical and chemical erosions, so the carbonate weathering will respond more quickly to the climatic changes. In the southeast of China, enormous of carbonate rocks are widely distributed. Due to the influence of the subtropical monsoon climate, the rocks experienced strong chemical weathering and pedogenic process, resulting in red weathering crust of carbonate rocks. This type of weathering crust is geochemistry-sensitive and ecology-vulnerable, which can provide important insights into the recycle of supergene geochemistry in the karst areas. In this study, we report calcium isotopic compositions of saprolites from a weathering profile developed on argillaceous carbonate rocks in northern Guangdong, South China. The acid-leachable fraction, which was extracted by 1N hydrochloride acid, showed limited variation of δ44/40Ca(NIST 915a) spanning from 0.55 ± 0.06‰ (2SD) to 0.72 ± 0.05‰ (2SD) despite CaO content ranging from 0.01 wt.% to 45.7 wt.%, implying that Ca isotope didn't fractionate much which may due to the congruent dissolution of limestone minerals. In contrast, radiogenic 87Sr/86Sr ratios of the whole rocks changed with depth from 0.710086 ± 6 (2SE) at the base rock to 0.722164± 8 (2SE) at the top-soil, which are possibly attributed to the mixing effect between carbonate and silicate fractions. Sr is an analogue for Ca due to its similar ionic size and charge; however, these two systems can differ in certain respects. The coupled study of Ca and Sr will be helpful to verify sources of Ca and the global Ca and C cycles.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Masaomi; Nozawa, Takaya; Maeda, Keiichi

Most of the observational studies of supernova (SN) explosions are limited to early phases (100 yr) in our Galaxy or very nearby galaxies. SNe at the epoch between these two, which we call the 'transitional' phase, have not been explored in detail except for several extragalactic SNe including SN 1987A in the Large Magellanic Cloud. We present theoretical predictions for the infrared (IR) dust emissions by several mechanisms; emission from dust formed in the SN ejecta, light echo by circumstellar (CS) and interstellar (IS) dust, and emission from shocked CS dust. We search for IR emission from six core-collapse SNemore » at the transitional phase in the nearby galaxies NGC 1313, NGC 6946, and M101 by using the data taken with the AKARI satellite and Spitzer. Among six targets, we detect the emission from SN 1978K in NGC 1313. SN 1978K is associated with 1.3 Multiplication-Sign 10{sup -3} M{sub Sun} of silicate dust. We show that, among several mechanisms, the shocked CS dust is the most probable emission source to explain the IR emission observed for SN 1978K. IR emission from the other five objects is not detected. Our current observations are sensitive to IR luminosity of >10{sup 38} erg s{sup -1}, and the non-detection of SN 1962M excludes the existence of the shocked CS dust for a high gas mass-loss rate of {approx}10{sup -4} M{sub Sun} yr{sup -1}. Observations of SNe at the transitional phase with future IR satellites will fill the gap of IR observations of SNe with the age of 10-100 yr, and give a new opportunity to study the CS and IS environments of the progenitor, and possibly dust formation in SNe.« less

Preparation of thermally stable microcapsules with a chitosan-silica hybrid.

PubMed

Kang, Hong-Yi; Chen, Hui-Huang

2014-09-01

Addition of microcapsules with a high dielectric constant and low specific heat capacity to a battered layer was designed to create a higher temperature in the crust than in the prefried fish nuggets to prevent the water vapor in the fish nuggets from migrating to the crust during microwave heating. Therefore, chitosan-silica hybrids and soybean oil were utilized to prepare the shell and core of the thermally stable microcapsules (MC(CS)), respectively. The MC(CS) were prepared by sol-gel coacervation from an oil-in-water emulsion. The sodium silicate was hydrolyzed and coacervated through polymerization for 24 h at pH 5. The zeta potential analysis indicated that chitosan with a positive charge and silica with a negative charge interacted through electrostatic attraction to form a hybrid shell. The volume mean particle size and encapsulation efficiency of the MC(CS) were 9.6 ± 0.2 μm and 75.6% ± 1.3%, respectively, when oil/chitosan = 0.2 and chitosan/silica = 0.5 (w/w). In addition to H-bonding and electrostatic attraction, Si-O-N bonds were formed between chitosan and silica. Dehydration of the bound water in the MC(CS) was observed in the range of 25 to 250 °C in the differential scanning calorimetry thermal analysis, with the lack of apparent thermal peaks indicating its high thermal stability. The decrease of force to cut the crust observed by texture analysis as well as the increase of hedonic score by consumer acceptance test revealed the addition of 1% MC(CS) significantly improved the crispness of the crust in the microwave-reheated nuggets. © 2014 Institute of Food Technologists®

Engineering and Development Support of General Decon Technology for the DARCOM Installation Restoration Program. Task 4. General Technology Literature Searches (II) Solidification Techniques for Lagoon Waters

DTIC Science & Technology

1980-12-01

40.8 Sodium 70.1 Zinc 0.01 37 The process includes the following steps (Pichat et al., 1979): - neutralization precipitation (silicates, borates...Compressive Strength of Polyester - Encapsulated Sodium Sulfate Waste Composite ....... .............. 64 9. Deep Chemical Mixer Mounted on a Barge...zinc, copper, lead, manganese and tin; sodium salts of arsenate, borate, phosphate, iodate, and sulfide; and sulfate salts. Sulfate salts form calcium

Determination of the Tribological Fundamentals of Solid Lubricated Ceramics. Volume 3. Appendices P through II

DTIC Science & Technology

1991-09-01

9H and tungsten silicides may also be present in the microstructure. The non-SiC eiemental concentrations for NC-203 would not be expected to exceed...lesser amounts of yttrium silicate and tungsten silicide . Trace amounts of a-Si 3N4 , silicon oxynitride, tungsten-iron- silicide , and yttrium silicon...SiC ESK On this sample, we detect Silicon, Carbon, and also Oxygen and Nitrogen, as well as Calcium and Sodium traces. After ionic etching up to about

Investigation of Tri-Service Heat Distribution Systems (Modernization of Existing Underground Heat Distribution Systems).

DTIC Science & Technology

1984-06-01

carrier pipe is usually insulated with preformed calcium silicate or mineral wool insulation. The preformed insula- tion is secured with stainless steel...glass or mineral wool insula- tion. Each tile is installed in this manner. Repair is difficult, but can be done by local workers with readily available...corrosion S Site I and return lines in of condensate line ( mineral wool insulation). 2. Ft. Campbell, 12 Tile system B No insulation was installed on

Thermal insulation materials for inside applications: Hygric and thermal properties

NASA Astrophysics Data System (ADS)

Jerman, Miloš; Černý, Robert

2017-11-01

Two thermal insulation materials suitable for the application on the interior side of historical building envelopes, namely calcium silicate and polyurethane-based foam are studied. Moisture diffusivity and thermal conductivity of both materials, as fundamental moisture and heat transport parameters, are measured in a dependence on moisture content. The measured data will be used as input parameters in computer simulation studies which will provide moisture and temperature fields necessary for an appropriate design of interior thermal insulation systems.

The Charge-Balancing Role of Calcium and Alkali Ions in Per-Alkaline Aluminosilicate Glasses.

PubMed

Thomsen, René M; Skibsted, Jørgen; Yue, Yuanzheng

2018-03-29

The structural arrangement of alkali-modified calcium aluminosilicate glasses has implications for important properties of these glasses in a wide range of industrial applications. The roles of sodium and potassium and their competition with calcium as network modifiers in peralkaline aluminosilicate glasses have been investigated by 27 Al and 29 Si MAS NMR spectroscopy. The 29 Si MAS NMR spectra are simulated using two models for distributing Al in the silicate glass network. One model assumes a hierarchical, quasi-heterogeneous aluminosilicate network, whereas the other is based on differences in relative lattice energies between Si-O-Si, Al-O-Al, and Si-O-Al linkages. A systematic divergence between these simulations and the experimental 29 Si NMR spectra is observed as a function of the sodium content exceeding that required for stoichiometric charge-balancing of the negatively charged AlO 4 tetrahedra. Similar correlations between simulations and experimental 29 Si NMR spectra cannot be made for the excess calcium content. Moreover, systematic variations in the 27 Al isotropic chemical shifts and the second-order quadrupole effect parameters, derived from the 27 Al MAS NMR spectra, are reported as a function of the SiO 2 content. These observations strongly suggest that alkali ions preferentially charge-balance AlO 4 3- as compared to alkaline earth (calcium) ions. In contrast, calcium dominates over the alkali ions in the formation of nonbridging oxygens associated with the SiO 4 tetrahedra.

Effect of particle size on calcium release and elevation of pH of endodontic cements.

PubMed

Saghiri, Mohammad Ali; Asatourian, Armen; Orangi, Jafar; Lotfi, Mehrdad; Soukup, Jason W; Garcia-Godoy, Franklin; Sheibani, Nader

2015-06-01

Elevation of pH and calcium ion release are of great importance in antibacterial activity and the promotion of dental soft and hard tissue healing process. In this study, we evaluated the effect of particle size on the elevation of pH and the calcium ion release from calcium silicate-based dental cements. Twelve plastic tubes were divided into three groups, filled with white mineral trioxide aggregate (WMTA), WMTA plus 1% methylcellulose, and nano-modified WMTA (nano-WMTA), and placed inside flasks containing 10 ml of distilled water. The pH values were measured using a pH sensor 3, 24, 72, and 168 h after setting of the cements. The calcium ion release was measured using an atomic absorption spectrophotometer with same sample preparation method. Data were subjected to two-way analysis of variance (anova) followed by post hoc Tukey tests with significance level of P < 0.05. Nano-WMTA showed significant pH elevation only after 24 h (P < 0.05) compared with WMTA, and after 3, 24, and 72 h compared with WMTA plus 1% methylcellulose (P < 0.05). Nano-WMTA showed significantly higher calcium ion release values compared to the other two groups (P < 0.05). Nano-modification of WMTA remarkably increased the calcium ion release at all time intervals postsetting, which can significantly influence the osteogenic properties of human dental pulp cells and as a consequence enhance mineralized matrix nodule formation to achieve desirable clinical outcomes. However, the increase in pH values mainly occurred during the short time postsetting. Addition of 1% methylcellulose imposed a delay in elevation of pH and calcium ion release by WMTA. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

A structural coarse-grained model for clays using simple iterative Boltzmann inversion

NASA Astrophysics Data System (ADS)

Schaettle, Karl; Ruiz Pestana, Luis; Head-Gordon, Teresa; Lammers, Laura Nielsen

2018-06-01

Cesium-137 is a major byproduct of nuclear energy generation and is environmentally threatening due to its long half-life and affinity for naturally occurring micaceous clays. Recent experimental observations of illite and phlogopite mica indicate that Cs+ is capable of exchanging with K+ bound in the anhydrous interlayers of layered silicates, forming sharp exchange fronts, leading to interstratification of Cs- and K-illite. We present here a coarse-grained (CG) model of the anhydrous illite interlayer developed using iterative Boltzmann inversion that qualitatively and quantitatively reproduces features of a previously proposed feedback mechanism of ion exchange. The CG model represents a 70-fold speedup over all-atom models of clay systems and predicts interlayer expansion for K-illite near ion exchange fronts. Contrary to the longstanding theory that ion exchange in a neighboring layer increases the binding of K in lattice counterion sites leading to interstratification, we find that the presence of neighboring exchanged layers leads to short-range structural relaxations that increase basal spacing and decrease cohesion of the neighboring K-illite layers. We also provide evidence that the formation of alternating Cs- and K-illite interlayers (i.e., ordered interstratification) is both thermodynamically and mechanically favorable compared to exchange in adjacent interlayers.

The remineralisation of enamel: a review of the literature.

PubMed

Li, Xiaoke; Wang, Jinfang; Joiner, Andrew; Chang, Jiang

2014-06-01

The purpose of this paper is to review current knowledge and technologies for tooth remineralisation. The literature was searched using the "Scopus" and "Web of Knowledge" database from the year 1971, with principal key words of *miner*, teeth and enamel. Language was restricted to English. Original studies and reviews were included. Conference papers and posters were excluded. The importance of oral health for patients and consumers has seen a steady increase in the number of tooth remineralisation agents, products and procedures over recent years. Concomitantly, there has been continued publication of both in vivo and in vitro tooth remineralisation and demineralisation studies. It is clear that fluoride treatments are generally effective in helping to protect the dental enamel from demineralisation and enhancing remineralisation. Continued efforts to increase the efficacy of fluoride have been made, in particular, by the addition of calcium salts or calcium containing materials to oral care products which may enhance the delivery and retention of fluoride into the oral cavity. In addition, the calcium salts or materials may act as additional sources of calcium to promote enamel remineralisation or reduce demineralisation processes. Inspired by the concept of bioactive materials for bone repair and regeneration, bioglass and in particular calcium silicate type materials show potential for enamel health benefits and is a growing area of research. © 2014 Elsevier Ltd. All rights reserved.

Modeling cation/anion-water interactions in functional aluminosilicate structures.

PubMed

Richards, A J; Barnes, P; Collins, D R; Christodoulos, F; Clark, S M

1995-02-01

A need for the computer simulation of hydration/dehydration processes in functional aluminosilicate structures has been noted. Full and realistic simulations of these systems can be somewhat ambitious and require the aid of interactive computer graphics to identify key structural/chemical units, both in the devising of suitable water-ion simulation potentials and in the analysis of hydrogen-bonding schemes in the subsequent simulation studies. In this article, the former is demonstrated by the assembling of a range of essential water-ion potentials. These span the range of formal charges from +4e to -2e, and are evaluated in the context of three types of structure: a porous zeolite, calcium silicate cement, and layered clay. As an example of the latter, the computer graphics output from Monte Carlo computer simulation studies of hydration/dehydration in calcium-zeolite A is presented.

Gehlenite and anorthite formation from fluid fly ash

NASA Astrophysics Data System (ADS)

Perná, Ivana; Šupová, Monika; Hanzlíček, Tomáš

2018-04-01

Fluid fly ash could be considered a waste, but, when well treated, it may also become a useful secondary source material. Its rather high content of calcium-containing phases along with thermally treated alumino-silicate residues resulting from coal combustion can lead to the formation of a stable system with newly formatted phases. The high temperature destroys the clay lattice and activates a new configuration of aluminum ions, changing their coordination to oxygen. The effect is accompanied by changes in charge in the surroundings, which are compensated for by calcium ions. The higher the temperature of the fluid ash treatment, the more pronounced the appearance of gehlenite and anorthite in the final mass. Both are natural materials and, together with mullite and anhydrite, they could ensure safety and protection even if exposed to open fire of up to 1150 °C.

Calcium-magnesium Aluminosilicate (CMAS) Interactions with Advanced Environmental Barrier Coating Material

NASA Technical Reports Server (NTRS)

Wiesner, Valerie L.; Bansal, Narottam P.

2015-01-01

Particulates, like sand and volcanic ash, threaten the development of robust environmental barrier coatings (EBCs) that protect next-generation silicon-based ceramic matrix composite (CMC) turbine engine components from harsh combustion environments during service. The siliceous particulates transform into molten glassy deposits of calcium-magnesium aluminosilicate (CMAS) when ingested by an aircraft engine operating at temperatures above 1200C. In this study, a sample of desert sand was melted into CMAS glass to evaluate high-temperature interactions between the sand glass and an advanced EBC material. Desert sand glass was added to the surface of hot-pressed EBC substrates, which were then heated in air at temperatures ranging from 1200C to 1500C. Scanning electron microscopy and X-ray energy-dispersive spectroscopy were used to evaluate microstructure and phase compositions of specimens and the CMASEBC interface after heat treatments.

The Biochemistry of the Muscle Contraction Process: An Undergraduate Laboratory Experiment Using Viscosity to Follow the Progress of a Reaction.

ERIC Educational Resources Information Center

Belliveau, James F.; And Others

1981-01-01

Describes an undergraduate laboratory experiment using viscosity to follow the progress of the contractile process in muscles. This simple, short experiment illustrates the action of ATP as the source of energy in the contractile process and the catalytic effect of calcium ions as a control in the energy producing process. (CS)

Chondroitin Sulfate-E Binds to Both Osteoactivin and Integrin αVβ3 and Inhibits Osteoclast Differentiation.

PubMed

Miyazaki, Tatsuya; Miyauchi, Satoshi; Anada, Takahisa; Tawada, Akira; Suzuki, Osamu

2015-10-01

Integrins and their ligands have been suggested to be associated with osteoclast-mediated bone resorption. The present study was designed to investigate whether chondroitin sulfate E (CS-E), which is one of the sulfated glycosaminoglycans (GAGs), is involved in osteoactivin (OA) activity, and osteoclast differentiation. The binding affinity of sulfated GAGs to integrin and its ligand was measured using biotin-labeled CS-E, and the osteoclast differentiation was evaluated by tartrate-resistant acid phosphatase staining and a pit formation assay. CS-E as well as CS-B, synthetic chondroitin polysulfate, and heparin inhibited osteoclast differentiation of bone marrow-derived macrophages. Pre-coating of OA to synthetic calcium phosphate-coated plates enhanced the osteoclastic differentiation of RAW264 cells, and addition of a neutralizing antibody to OA inhibited its differentiation. CS-E bound not only to OA, fibronectin, and vitronectin, but also to its receptor integrin αVβ3, and inhibited the direct binding of OA to integrin αVβ3. Furthermore, CS-E blocked the binding of OA to cells and inhibited OA-induced osteoclastic differentiation. On the other hand, heparinase treatment of RAW264 cells inhibited osteoclastic differentiation. Since binding of OA to the cells was inhibited by the presence of heparan sulfate or heparinase treatment of cells, heparan sulfate proteoglycan (HSPG) was also considered to be an OA receptor. Taken together, the present results suggest that CS-E is capable of inhibiting OA-induced osteoclast differentiation by blocking the interaction of OA to integrin αVβ3 and HSPG. © 2015 Wiley Periodicals, Inc.

Clouds on Hot Jupiters Illustration

NASA Image and Video Library

2016-10-18

Hot Jupiters are exoplanets that orbit their stars so tightly that their temperatures are extremely high, reaching over 2,400 degrees Fahrenheit (1600 Kelvin). They are also tidally locked, so one side of the planet always faces the sun and the other is in permanent darkness. Research suggests that the "dayside" is largely free of clouds, while the "nightside" is heavily clouded. This illustration represents how hot Jupiters of different temperatures and different cloud compositions might appear to a person flying over the dayside of these planets on a spaceship, based on computer modeling. Cooler planets are entirely cloudy, whereas hotter planets have morning clouds only. Clouds of different composition have different colors, whereas the clear sky is bluer than on Earth. For the hottest planets, the atmosphere is hot enough on the evening side to glow like a charcoal. Figure 1 shows an approximation of what various hot Jupiters might look like based on a combination of computer modeling and data from NASA's Kepler Space Telescope. From left to right it shows: sodium sulfide clouds (1000 to 1200 Kelvin), manganese sulfide clouds (1200 to 1600 Kelvin), magnesium silicate clouds (1600 to 1800 Kelvin), magnesium silicate and aluminum oxide clouds (1800 Kelvin) and clouds composed of magnesium silicate, aluminum oxide, iron and calcium titanate (1900 to 2200 Kelvin). http://photojournal.jpl.nasa.gov/catalog/PIA21074

Revealing the Effect of Irradiation on Cement Hydrates: Evidence of a Topological Self-Organization.

PubMed

Krishnan, N M Anoop; Wang, Bu; Sant, Gaurav; Phillips, James C; Bauchy, Mathieu

2017-09-20

Despite the crucial role of concrete in the construction of nuclear power plants, the effects of radiation exposure (i.e., in the form of neutrons) on the calcium-silicate-hydrate (C-S-H, i.e., the glue of concrete) remain largely unknown. Using molecular dynamics simulations, we systematically investigate the effects of irradiation on the structure of C-S-H across a range of compositions. Expectedly, although C-S-H is more resistant to irradiation than typical crystalline silicates, such as quartz, we observe that radiation exposure affects C-S-H's structural order, silicate mean chain length, and the amount of molecular water that is present in the atomic network. By topological analysis, we show that these "structural effects" arise from a self-organization of the atomic network of C-S-H upon irradiation. This topological self-organization is driven by the (initial) presence of atomic eigenstress in the C-S-H network and is facilitated by the presence of water in the network. Overall, we show that C-S-H exhibits an optimal resistance to radiation damage when its atomic network is isostatic (at Ca/Si = 1.5). Such an improved understanding of the response of C-S-H to irradiation can pave the way to the design of durable concrete for radiation applications.

Validation of an enzyme-linked immunosorbent assay (ELISA) for the measurement of canine S100A12.

PubMed

Heilmann, Romy M; Cranford, Shannon M; Ambrus, Andy; Grützner, Niels; Schellenberg, Stefan; Ruaux, Craig G; Suchodolski, Jan S; Steiner, Jörg M

2016-03-01

Canine S100 calcium-binding protein A12 (cS100A12) shows promise as biomarker of inflammation in dogs. A previously developed cS100A12-radioimmunoassay (RIA) requires radioactive tracers and is not sensitive enough for fecal cS100A12 concentrations in 79% of tested healthy dogs. An ELISA assay may be more sensitive than RIA and does not require radioactive tracers. The purpose of the study was to establish a sandwich ELISA for serum and fecal cS100A12, and to establish reference intervals (RI) for normal healthy canine serum and feces. Polyclonal rabbit anti-cS100A12 antibodies were generated and tested by Western blotting and immunohistochemistry. A sandwich ELISA was developed and validated, including accuracy and precision, and agreement with cS100A12-RIA. The RI, stability, and biologic variation in fecal cS100A12, and the effect of corticosteroids on serum cS100A12 were evaluated. Lower detection limits were 5 μg/L (serum) and 1 ng/g (fecal), respectively. Intra- and inter-assay coefficients of variation were ≤ 4.4% and ≤ 10.9%, respectively. Observed-to-expected ratios for linearity and spiking recovery were 98.2 ± 9.8% (mean ± SD) and 93.0 ± 6.1%, respectively. There was a significant bias between the ELISA and the RIA. The RI was 49-320 μg/L for serum and 2-484 ng/g for fecal cS100A12. Fecal cS100A12 was stable for 7 days at 23, 4, -20, and -80°C; biologic variation was negligible but variation within one fecal sample was significant. Corticosteroid treatment had no clinically significant effect on serum cS100A12 concentrations. The cS100A12-ELISA is a precise and accurate assay for serum and fecal cS100A12 in dogs. © 2016 American Society for Veterinary Clinical Pathology.

Storage Medium Affects the Surface Porosity of Dental Cements.

PubMed

Saghiri, M Ali; Shabani, Asal; Asatourian, Armen; Sheibani, Nader

2017-08-01

Calcium silicate-based cements physical properties is influenced by environmental changes. Here, we intended to evaluate the effect of storage medium on surface porosity of root Mineral Trioxide Aggregate (MTA) and Biodentine cement. A total of 40 polyethylene tubes were selected and divided into two groups: Group A (MTA) and Group B (Biodentine). Each group was subdivided into two subgroups (n=10). In subgroups A1 and B1, tubes were transferred to Distilled Water (DW), while samples of subgroup A2 and B2 were transferred to Synthetic Tissue Fluid (STF) as storage medium and samples were stored for three days. All specimens were then placed in a desiccator for 24 hours and then subject to surface porosity evaluation by Scanning Electron Microscopy (SEM) at ×500, ×1000, ×2000 and ×5000 magnifications. The number and the surface porosities were determined by Image J analysis. Data were analyzed by ANOVA at level of significance of p<0.05. The lowest surface porosity was observed in MTA samples stored in STF and the highest was in Biodentine samples stored in DW. Significant differences were noted between groups and subgroups of each group (p< 0.05). MTA samples stored in DW and STF showed significantly lower surface porosities compared to Biodentine samples (p < 0.05). Storage medium can drastically affect the surface porosity of tested calcium silicate-based cements. However, MTA showed lower surface porosity compared to Biodentine cement, which can result in lower microleakage in applied area.

Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach.

PubMed

Taylor, Lyla L; Banwart, Steve A; Valdes, Paul J; Leake, Jonathan R; Beerling, David J

2012-02-19

Global weathering of calcium and magnesium silicate rocks provides the long-term sink for atmospheric carbon dioxide (CO(2)) on a timescale of millions of years by causing precipitation of calcium carbonates on the seafloor. Catchment-scale field studies consistently indicate that vegetation increases silicate rock weathering, but incorporating the effects of trees and fungal symbionts into geochemical carbon cycle models has relied upon simple empirical scaling functions. Here, we describe the development and application of a process-based approach to deriving quantitative estimates of weathering by plant roots, associated symbiotic mycorrhizal fungi and climate. Our approach accounts for the influence of terrestrial primary productivity via nutrient uptake on soil chemistry and mineral weathering, driven by simulations using a dynamic global vegetation model coupled to an ocean-atmosphere general circulation model of the Earth's climate. The strategy is successfully validated against observations of weathering in watersheds around the world, indicating that it may have some utility when extrapolated into the past. When applied to a suite of six global simulations from 215 to 50 Ma, we find significantly larger effects over the past 220 Myr relative to the present day. Vegetation and mycorrhizal fungi enhanced climate-driven weathering by a factor of up to 2. Overall, we demonstrate a more realistic process-based treatment of plant fungal-geosphere interactions at the global scale, which constitutes a first step towards developing 'next-generation' geochemical models.

Carbon dioxide released from subduction zones by fluid-mediated reactions

NASA Astrophysics Data System (ADS)

Ague, Jay J.; Nicolescu, Stefan

2014-05-01

The balance between the subduction of carbonate mineral-bearing rocks into Earth's mantle and the return of CO2 to the atmosphere by volcanic and metamorphic degassing is critical to the carbon cycle. Carbon is thought to be released from subducted rocks mostly by simple devolatilization reactions. However, these reactions will also retain large amounts of carbon within the subducting slab and have difficulty in accounting for the mass of CO2 emitted from volcanic arcs. Carbon release may therefore occur via fluid-induced dissolution of calcium carbonate. Here we use carbonate δ18O and δ13C systematics, combined with analyses of rock and fluid inclusion mineralogy and geochemistry, to investigate the alteration of the exhumed Eocene Cycladic subduction complex on the Syros and Tinos islands, Greece. We find that in marble rocks adjacent to two fluid conduits that were active during subduction, the abundance of calcium carbonate drastically decreases approaching the conduits, whereas silicate minerals increase. Up to 60-90% of the CO2 was released from the rocks--far greater than expected via simple devolatilization reactions. The δ18O of the carbonate minerals is 5-10 lighter than is typical for metamorphosed carbonate rocks, implying that isotopically light oxygen was transported by fluid infiltration from the surroundings. We suggest that fluid-mediated carbonate mineral removal, accompanied by silicate mineral precipitation, provides a mechanism for the release of enormous amounts of CO2 from subduction zones.

Hydration kinetics and morphology of cement pastes with pozzolanic volcanic ash studied via synchrotron-based techniques

DOE PAGES

Kupwade-Patil, Kunal; Chin, Stephanie; Ilavsky, Jan; ...

2017-10-13

Here, this study investigates the early ages of hydration behavior when basaltic volcanic ash was used as a partial substitute to ordinary Portland cement using ultra-small-angle X-ray scattering and wide-angle X-ray scattering (WAXS). The mix design consisted of 10, 30 and 50% substitution of Portland cement with two different-sized volcanic ashes. The data showed that substitution of volcanic ash above 30% results in excess unreacted volcanic ash, rather than additional pozzolanic reactions along longer length scales. WAXS studies revealed that addition of finely ground volcanic ash facilitated calcium-silicate-hydrate related phases, whereas inclusion of coarser volcanic ash caused domination by calcium-aluminum-silicate-hydratemore » and unreacted MgO phases, suggesting some volcanic ash remained unreacted throughout the hydration process. Addition of more than 30% volcanic ash leads to coarser morphology along with decreased surface area and higher intensity of scattering at early-age hydration. This suggests an abrupt dissolution indicated by changes in surface area due to the retarding gel formation that can have implication on early-age setting influencing the mechanical properties of the resulting cementitious matrix. The findings from this work show that the concentration of volcanic ash influences the specific surface area and morphology of hydration products during the early age of hydration. Therefore, natural pozzolanic volcanic ashes can be a viable substitute to Portland cement by providing environmental benefits in terms of lower-carbon footprint along with long-term durability.« less

Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

PubMed Central

Taylor, Lyla L.; Banwart, Steve A.; Valdes, Paul J.; Leake, Jonathan R.; Beerling, David J.

2012-01-01

Global weathering of calcium and magnesium silicate rocks provides the long-term sink for atmospheric carbon dioxide (CO2) on a timescale of millions of years by causing precipitation of calcium carbonates on the seafloor. Catchment-scale field studies consistently indicate that vegetation increases silicate rock weathering, but incorporating the effects of trees and fungal symbionts into geochemical carbon cycle models has relied upon simple empirical scaling functions. Here, we describe the development and application of a process-based approach to deriving quantitative estimates of weathering by plant roots, associated symbiotic mycorrhizal fungi and climate. Our approach accounts for the influence of terrestrial primary productivity via nutrient uptake on soil chemistry and mineral weathering, driven by simulations using a dynamic global vegetation model coupled to an ocean–atmosphere general circulation model of the Earth's climate. The strategy is successfully validated against observations of weathering in watersheds around the world, indicating that it may have some utility when extrapolated into the past. When applied to a suite of six global simulations from 215 to 50 Ma, we find significantly larger effects over the past 220 Myr relative to the present day. Vegetation and mycorrhizal fungi enhanced climate-driven weathering by a factor of up to 2. Overall, we demonstrate a more realistic process-based treatment of plant fungal–geosphere interactions at the global scale, which constitutes a first step towards developing ‘next-generation’ geochemical models. PMID:22232768

Hydration kinetics and morphology of cement pastes with pozzolanic volcanic ash studied via synchrotron-based techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kupwade-Patil, Kunal; Chin, Stephanie; Ilavsky, Jan

Here, this study investigates the early ages of hydration behavior when basaltic volcanic ash was used as a partial substitute to ordinary Portland cement using ultra-small-angle X-ray scattering and wide-angle X-ray scattering (WAXS). The mix design consisted of 10, 30 and 50% substitution of Portland cement with two different-sized volcanic ashes. The data showed that substitution of volcanic ash above 30% results in excess unreacted volcanic ash, rather than additional pozzolanic reactions along longer length scales. WAXS studies revealed that addition of finely ground volcanic ash facilitated calcium-silicate-hydrate related phases, whereas inclusion of coarser volcanic ash caused domination by calcium-aluminum-silicate-hydratemore » and unreacted MgO phases, suggesting some volcanic ash remained unreacted throughout the hydration process. Addition of more than 30% volcanic ash leads to coarser morphology along with decreased surface area and higher intensity of scattering at early-age hydration. This suggests an abrupt dissolution indicated by changes in surface area due to the retarding gel formation that can have implication on early-age setting influencing the mechanical properties of the resulting cementitious matrix. The findings from this work show that the concentration of volcanic ash influences the specific surface area and morphology of hydration products during the early age of hydration. Therefore, natural pozzolanic volcanic ashes can be a viable substitute to Portland cement by providing environmental benefits in terms of lower-carbon footprint along with long-term durability.« less

Optical and spectroscopic investigation on Calcium Borotellurite glass system

NASA Astrophysics Data System (ADS)

Paz, E. C.; Lodi, T. A.; Gomes, B. R. A.; Melo, G. H. A.; Pedrochi, F.; Steimacher, A.

2016-05-01

In this work, the glass formation in Calcium Borotellurite (CBTx) system and their optical properties were studied. Six glass samples were prepared by melt-quenching technique and the samples obtained are transparent, lightly yellowish, without any visible crystallites. The results showed that TeO2 addition increases the density, the electronic polarizability and, consequently, the refractive index. The increase of electronic polarizability and optical basicity suggest that TeO2 addition increases the non-bridging oxygen (NBO) concentration. The increase of TeO2 shifts the band edge to longer wavelength owing to increase in non-bridging oxygen ions, resulting in a linear decrease of optical energy gap. The addition of TeO2 increases the temperature coefficient of the optical path length (dS/dT) in room temperature, which are comparable to phosphate and lower than Low Silica Calcium Alumino Silicate (LSCAS) glasses. The values of dS/dT present an increase as a function of temperature for all the samples measured. The results suggest that CBTx is a good candidate for rare-earth doping and several optical applications.

Efficacy of Erbium, Chromium-doped:Yttrium, Scandium, Gallium, and Garnet Laser Irradiation Combined with Resin-based Tricalcium Silicate and Calcium Hydroxide on Direct Pulp Capping: A Randomized Clinical Trial.

PubMed

Cengiz, Esra; Yilmaz, Hasan Guney

2016-03-01

The purpose of this randomized clinical study was to evaluate the efficiency of erbium, chromium-doped:yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser irradiation combined with a resin-based tricalcium silicate material and calcium hydroxide in direct pulp capping for a 6-month follow-up period. A total of 60 teeth of 60 patients between the ages of 18 and 41 years were recruited for this study. Sixty permanent vital teeth without symptoms and radiographic changes were randomly assigned to the following 4 groups (n = 15): Gr CH, the exposed area was sealed with calcium hydroxide (CH) paste; Gr laser CH, the treated area was sealed with CH paste after Er,Cr:YSGG laser irradiation at an energy level of 0.5 W without water and with 45% air; Gr TheraCal, TheraCal LC (Bisco, Schaumburg, IL) was applied directly to the exposed pulp; and Gr Laser TheraCal, TheraCal LC was applied after irradiation with an Er,Cr:YSGG laser. At the 1-week and 1-, 3-, and 6-month recall examinations, the loss of vitality, spontaneous pain, reactions to thermal stimuli and percussion, and radiographic changes were considered as failure. The success rates in the CH and TheraCal groups were 73.3% and 66.6%, respectively. These rates did not reveal any significant difference. In both laser groups, success rates were 100%. The Er,Cr:YSGG laser-irradiated TheraCal and Er,Cr:YSGG laser-irradiated CH groups showed statistically higher success rates than the TheraCal and CH groups, respectively. Er,Cr:YSGG laser irradiation at 0.5 W without water combined with pulp capping agents can be recommended for direct pulp therapy. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Biocompatibility Investigation of New Endodontic Materials Based on Nanosynthesized Calcium Silicates Combined with Different Radiopacifiers.

PubMed

Cetenovic, Bojana; Prokic, Bogomir; Vasilijic, Sasa; Dojcinovic, Biljana; Magic, Marko; Jokanovic, Vukoman; Markovic, Dejan

2017-03-01

The aim of this article was to analyze biocompatibility and bioactivity of new endodontic materials on the basis of nanosynthesized calcium silicates (ALBO-MPCA 1 and ALBO-MPCA 2 ) combined with different radiopacifiers in comparison with MTA + . Morphology of the samples was studied by scanning electron microscopy, and the pH and ion release analysis were also assessed. Biocompatibility of materials' eluates (24-hour, 7-day, and 21-day) was conducted by using MTT test. Twelve New Zealand white rabbits were used for intraosseous implantation. Four calvarial defects per animal were created and filled with freshly prepared investigated materials. Samples mostly consisted of agglomerates built up from nanoparticles, preferably spherical and rod-like. There was no significant difference among pH values of materials' eluates after 24 hours (P > .05). The amount of calcium and aluminum ion release decreased, whereas the amount of magnesium and bismuth (ALBO-MPCA 1 , MTA + ) and barium (ALBO-MPCA 2 ) increased during 21-day period. The metabolic activity of cells increased after the extraction time, except in case of undiluted elutes of ALBO-MPCA 2 and ALBO-MPCA 1 (21-day). Histologic analysis of the samples revealed newly formed bone tissue with moderate inflammation for all investigated materials, which subsided during 90-day period to mild. Both MTA + and ALBO-MPCA 1 were in direct contact with the newly formed bone tissue. After 90 days, statistically significant difference in hard tissue formation was observed in comparison of MTA + and ALBO-MPCA 1 with control group (P < .05). Experimental materials ALBO-MPCA 1 and ALBO-MPCA 2 possess both biocompatibility and bioactivity. Because ALBO-MPCA 1 provokes favorable biological response, it is especially good candidate for further clinical investigations. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

The effect of mixing method on tricalcium silicate-based cement.

PubMed

Duque, J A; Fernandes, S L; Bubola, J P; Duarte, M A H; Camilleri, J; Marciano, M A

2018-01-01

To evaluate the effect of three methods of mixing on the physical and chemical properties of tricalcium silicate-based cements. The materials evaluated were MTA Angelus and Portland cement with 20% zirconium oxide (PC-20-Zr). The cements were mixed using a 3 : 1 powder-to-liquid ratio. The mixing methods were manual (m), trituration (tr) and ultrasonic (us) activation. The materials were characterized by means of scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy. Flowability was analysed according to ANSI/ADA 57/2012. Initial and final setting times were assessed following ASTM C266/08. Volume change was evaluated using a micro-CT volumetric method. Solubility was analysed according to ADA 57/2012. pH and calcium ion release were measured after 3, 24, 72 and 168 h. Statistical analysis was performed using two-way analysis of variance. The level of significance was set at P = 0.05. The SEM analysis revealed that ultrasonic activation was associated with a homogeneous distribution of particles. Flowability, volume change and initial setting time were not influenced by the mixing method (P > 0.05). Solubility was influenced by the mixing method (P < 0.05). For pH, at 168 h, significant differences were found between MTA-m and PC-20-Zr-m (P < 0.05). For calcium ion release, PC-20-Zr-tr had higher values than MTA-m at 3 h, and MTA-tr had higher values than PC-20-Zr-m at 168 h (P < 0.05). The ultrasonic and trituration methods led to higher calcium ion release and pH compared with manual mixing for all cements, whilst the ultrasonic method produced smaller particles for the PC-20-Zr cement. Flow, setting times and volume change were not influenced by the mixing method used; however, it did have an impact on solubility. © 2017 International Endodontic Journal. Published by John Wiley & Sons Ltd.

The role of Sr2+ on the structure and reactivity of SrO-CaO-ZnO-SiO2 ionomer glasses.

PubMed

Boyd, Daniel; Towler, Mark R; Watts, Sally; Hill, Robert G; Wren, Anthony W; Clarkin, Owen M

2008-02-01

The suitability of Glass Polyalkenoate Cements (GPCs) for use in orthopaedics is retarded by the presence in the glass phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of GPCs and its absence is likely to hinder cement formation. However, the authors have previously shown that aluminium free GPCs may be formulated based on calcium zinc silicate glasses and these novel materials exhibit significant potential as hard tissue biomaterials. To further improve their potential, and given that Strontium (Sr) based drugs have had success in the treatment of osteoporosis, the authors have substituted Calcium (Ca) with Sr in the glass phase of a series of aluminium free GPCs. However to date little data exists on the effect SrO has on the structure and reactivity of SrO-CaO-ZnO-SiO(2) glasses. The objective of this work was to characterise the effect of the Ca/Sr substitution on the structure of such glasses, and evaluate the subsequent reactivity of these glasses with an aqueous solution of Polyacrylic acid (PAA). To this end (29)Si MAS-NMR, differential scanning calorimetry (DSC), X-ray diffraction, and network connectivity calculations, were used to characterize the structure of four strontium calcium zinc silicate glasses. Following glass characterization, GPCs were produced from each glass using a 40 wt% solution of PAA (powder:liquid = 2:1.5). The working times and setting times of the GPCs were recorded as per International standard ISO9917. The results acquired as part of this research indicate that the substitution of Ca for Sr in the glasses examined did not appear to significantly affect the structure of the glasses investigated. However it was noted that increasing the amount of Ca substituted for Sr did result in a concomitant increase in setting times, a feature that may be attributable to the higher basicity of SrO over CaO.

A sorption model for alkalis in cement-based materials - Correlations with solubility and electrokinetic properties

NASA Astrophysics Data System (ADS)

Henocq, Pierre

2017-06-01

In cement-based materials, radionuclide uptake is mainly controlled by calcium silicate hydrates (C-S-H). This work presents an approach for defining a unique set of parameters of a surface complexation model describing the sorption behavior of alkali ions on the C-S-H surface. Alkali sorption processes are modeled using the CD-MUSIC function integrated in the Phreeqc V.3.0.6 geochemical code. Parameterization of the model was performed based on (1) retention, (2) zeta potential, and (3) solubility experimental data from the literature. This paper shows an application of this model to sodium ions. It was shown that retention, i.e. surface interactions, and solubility are closely related, and a consistent sorption model for radionuclides in cement-based materials requires a coupled surface interaction/chemical equilibrium model. In case of C-S-H with low calcium-to-silicon ratios, sorption of sodium ions on the C-S-H surface strongly influences the chemical equilibrium of the C-S-H + NaCl system by significantly increasing the aqueous calcium concentration. The close relationship between sorption and chemical equilibrium was successfully illustrated by modeling the effect of the solid-to-liquid ratio on the calcium content in solution in the case of C-S-H + NaCl systems.

Radioecological study of the Charophytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marciulioninene, D.P.; Dusauskiene-Duz, R.F.; Cibiraite, N.A.

1976-01-01

The accumulation of Sr/sup 90/, Ce/sup 144/, Cs/sup 137/ and Ru/sup 106/ in Charophyta depends on the species, while accumulation of Sr/sup 90/ and Cs/sup 137/ depends on sampling time and vegetative period. The accumulation and excretion of Sr/sup 90/ and Cs/sup 137/ in Charophyta depend both on the exchangeable calcium and potassium in these algae and on the concentration of these elements in water. The Sr/sup 90/ and Cs/sup 137/ are taken up by the Charophyta during short-term experiments not only via absorption on a cell membrane but also via high-rate ion exchange between the environment and cellular components.more » The Ce/sup 144/ and Ru/sup 106/ uptake by Charophyta cells in short-term experiments occurs via absorption on cellular membrane. The uptake coefficients for aquatic plants notable for high mineralization (Charophyta) appear to be approximately 16 times as high under natural conditions as those under laboratory conditions, while the accumulation factors for Sr/sup 90/ in aquatic plants with fairly low mineralization (phytoplankton, Cladospora, Elodea and duckweed) were the same both under laboratory and natural conditions.« less

Effect of Potassium on Uptake of 137Cs in Food Crops Grown on Coral Soils: Annual Crops at Bikini Atoll

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stone, E R; Robinson, W

2002-02-01

In 1954 a radioactive plume from the thermonuclear device code named BRAVO contaminated the principal residential islands, Eneu and Bikini, of Bikini Atoll (11{sup o} 36 minutes N; 165{sup o} 22 minutes E), now part of the Republic of the Marshall Islands. The resulting soil radioactivity diminished greatly over the three decades before the studies discussed below began. By that time the shorter-lived isotopes had all but disappeared, but strontium-90 ({sup 90}Sr), and cesium-137, ({sup 137}Cs) were reduced by only one half-life. Minute amounts of the long-lived isotopes, plutonium-239+240 ({sup 239+240}Pu) and americium-241 ({sup 241}Am), were present in soil, butmore » were found to be inconsequential in the food chain of humans and land animals. Rather, extensive studies demonstrated that the major concern for human health was {sup 137}Cs in the terrestrial food chain (Robison et al., 1983; Robison et al., 1997). The following papers document results from several studies between 1986 and 1997 aimed at minimizing the {sup 137}Cs content of annual food crops. The existing literature on radiocesium in soils and plant uptake is largely a consequence of two events: the worldwide fallout of 1952-58, and the fallout from Chernobyl. The resulting studies have, for the most part, dealt either with soils containing some amount of silicate clays and often with appreciable K, or with the short-term development of plants in nutrient cultures.« less