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Sample records for sulfur trioxide

  1. An Aerosol Condensation Model for Sulfur Trioxide

    SciTech Connect

    Grant, K E

    2008-02-07

    This document describes a model for condensation of sulfuric acid aerosol given an initial concentration and/or source of gaseous sulfur trioxide (e.g. fuming from oleum). The model includes the thermochemical effects on aerosol condensation and air parcel buoyancy. Condensation is assumed to occur heterogeneously onto a preexisting background aerosol distribution. The model development is both a revisiting of research initially presented at the Fall 2001 American Geophysical Union Meeting [1] and a further extension to provide new capabilities for current atmospheric dispersion modeling efforts [2]. Sulfuric acid is one of the most widely used of all industrial chemicals. In 1992, world consumption of sulfuric acid was 145 million metric tons, with 42.4 Mt (mega-tons) consumed in the United States [10]. In 2001, of 37.5 Mt consumed in the U.S., 74% went into producing phosphate fertilizers [11]. Another significant use is in mining industries. Lawuyi and Fingas [7] estimate that, in 1996, 68% of use was for fertilizers and 5.8% was for mining. They note that H{sub 2}SO{sub 4} use has been and should continue to be very stable. In the United States, the elimination of MTBE (methyl tertiary-butyl ether) and the use of ethanol for gasoline production are further increasing the demand for petroleum alkylate. Alkylate producers have a choice of either a hydrofluoric acid or sulfuric acid process. Both processes are widely used today. Concerns, however, over the safety or potential regulation of hydrofluoric acid are likely to result in most of the growth being for the sulfuric acid process, further increasing demand [11]. The implication of sulfuric acid being a pervasive industrial chemical is that transport is also pervasive. Often, this is in the form of oleum tankers, having around 30% free sulfur trioxide. Although sulfuric acid itself is not a volatile substance, fuming sulfuric acid (referred to as oleum) is [7], the volatile product being sulfur trioxide

  2. Globins Scavenge Sulfur Trioxide Anion Radical*

    PubMed Central

    Gardner, Paul R.; Gardner, Daniel P.; Gardner, Alexander P.

    2015-01-01

    Ferrous myoglobin was oxidized by sulfur trioxide anion radical (STAR) during the free radical chain oxidation of sulfite. Oxidation was inhibited by the STAR scavenger GSH and by the heme ligand CO. Bimolecular rate constants for the reaction of STAR with several ferrous globins and biomolecules were determined by kinetic competition. Reaction rate constants for myoglobin, hemoglobin, neuroglobin, and flavohemoglobin are large at 38, 120, 2,600, and ≥ 7,500 × 106 m−1 s−1, respectively, and correlate with redox potentials. Measured rate constants for O2, GSH, ascorbate, and NAD(P)H are also large at ∼100, 10, 130, and 30 × 106 m−1 s−1, respectively, but nevertheless allow for favorable competition by globins and a capacity for STAR scavenging in vivo. Saccharomyces cerevisiae lacking sulfite oxidase and deleted of flavohemoglobin showed an O2-dependent growth impairment with nonfermentable substrates that was exacerbated by sulfide, a precursor to mitochondrial sulfite formation. Higher O2 exposures inactivated the superoxide-sensitive mitochondrial aconitase in cells, and hypoxia elicited both aconitase and NADP+-isocitrate dehydrogenase activity losses. Roles for STAR-derived peroxysulfate radical, superoxide radical, and sulfo-NAD(P) in the mechanism of STAR toxicity and flavohemoglobin protection in yeast are suggested. PMID:26381408

  3. Globins Scavenge Sulfur Trioxide Anion Radical.

    PubMed

    Gardner, Paul R; Gardner, Daniel P; Gardner, Alexander P

    2015-11-06

    Ferrous myoglobin was oxidized by sulfur trioxide anion radical (STAR) during the free radical chain oxidation of sulfite. Oxidation was inhibited by the STAR scavenger GSH and by the heme ligand CO. Bimolecular rate constants for the reaction of STAR with several ferrous globins and biomolecules were determined by kinetic competition. Reaction rate constants for myoglobin, hemoglobin, neuroglobin, and flavohemoglobin are large at 38, 120, 2,600, and ≥ 7,500 × 10(6) m(-1) s(-1), respectively, and correlate with redox potentials. Measured rate constants for O2, GSH, ascorbate, and NAD(P)H are also large at ∼100, 10, 130, and 30 × 10(6) m(-1) s(-1), respectively, but nevertheless allow for favorable competition by globins and a capacity for STAR scavenging in vivo. Saccharomyces cerevisiae lacking sulfite oxidase and deleted of flavohemoglobin showed an O2-dependent growth impairment with nonfermentable substrates that was exacerbated by sulfide, a precursor to mitochondrial sulfite formation. Higher O2 exposures inactivated the superoxide-sensitive mitochondrial aconitase in cells, and hypoxia elicited both aconitase and NADP(+)-isocitrate dehydrogenase activity losses. Roles for STAR-derived peroxysulfate radical, superoxide radical, and sulfo-NAD(P) in the mechanism of STAR toxicity and flavohemoglobin protection in yeast are suggested.

  4. EMISSIONS OF SULFUR TRIOXIDE FROM COAL-FIRED POWER PLANTS

    EPA Science Inventory

    Emissions of sulfur trioxide (SO3) are a key component of plume opacity and acid deposition. Consequently, these emissions need to be low enough not to cause opacity violations and acid deposition. Generally, a small fraction of sulfur in coal is converted to SO3 in coal-fired co...

  5. Emissions of sulfur trioxide from coal-fired power plants.

    PubMed

    Srivastava, R K; Miller, C A; Erickson, C; Jambhekar, R

    2004-06-01

    Emissions of sulfur trioxide (SO3) are a key component of plume opacity and acid deposition. Consequently, these emissions need to be low enough to not cause opacity violations and acid deposition. Generally, a small fraction of sulfur (S) in coal is converted to SO3 in coal-fired combustion devices such as electric utility boilers. The emissions of SO3 from such a boiler depend on coal S content, combustion conditions, flue gas characteristics, and air pollution devices being used. It is well known that the catalyst used in the selective catalytic reduction (SCR) technology for nitrogen oxides control oxidizes a small fraction of sulfur dioxide in the flue gas to SO3. The extent of this oxidation depends on the catalyst formulation and SCR operating conditions. Gas-phase SO3 and sulfuric acid, on being quenched in plant equipment (e.g., air preheater and wet scrubber), result in fine acidic mist, which can cause increased plume opacity and undesirable emissions. Recently, such effects have been observed at plants firing high-S coal and equipped with SCR systems and wet scrubbers. This paper investigates the factors that affect acidic mist production in coal-fired electric utility boilers and discusses approaches for mitigating emission of this mist.

  6. Photoresist removal using gaseous sulfur trioxide cleaning technology

    NASA Astrophysics Data System (ADS)

    Del Puppo, Helene; Bocian, Paul B.; Waleh, Ahmad

    1999-06-01

    A novel cleaning method for removing photoresists and organic polymers from semiconductor wafers is described. This non-plasma method uses anhydrous sulfur trioxide gas in a two-step process, during which, the substrate is first exposed to SO3 vapor at relatively low temperatures and then is rinsed with de-ionized water. The process is radically different from conventional plasma-ashing methods in that the photoresist is not etched or removed during the exposure to SO3. Rather, the removal of the modified photoresist takes place during the subsequent DI-water rinse step. The SO3 process completely removes photoresist and polymer residues in many post-etch applications. Additional advantages of the process are absence of halogen gases and elimination of the need for other solvents and wet chemicals. The process also enjoys a very low cost of ownership and has minimal environmental impact. The SEM and SIMS surface analysis results are presented to show the effectiveness of gaseous SO3 process after polysilicon, metal an oxide etch applications. The effects of both chlorine- and fluorine-based plasma chemistries on resist removal are described.

  7. PREVENTION REFERENCE MANUAL: CHEMICAL SPECIFIC. VOL. 15: CONTROL OF ACCIDENTAL RELEASES OF SULFUR TRIOXIDE

    EPA Science Inventory

    The report, discussing sulfur trioxide (SO3), is one of a series addressing the prevention of accidental releases of toxic chemicals. SO3, a clear oily liquid or solid at typical ambient conditions, has an Immediately Dangerous to Life and Health (IDLH) concentration of 20 ppm, w...

  8. Mechanism for forming hydrogen chloride and sodium sulfate from sulfur trioxide, water, and sodium chloride

    NASA Technical Reports Server (NTRS)

    Anderson, A. B.

    1984-01-01

    A molecular orbital study of sodium sulfate and hydrogen chloride formation from sulfur trioxide, water, and sodium chloride shows no activation barrier, in agreement with recent experimental work of Kohl, Fielder, and Stearns. Two overall steps are found for the process. First, gas-phase water reacts with sulfur trioxide along a pathway involving a linear O-H-O transition state yielding closely associated hydroxyl and bisulfite which rearrange to become a hydrogen sulfate molecule. Then the hydrogen sulfate molecule transfers a hydrogen atom to a surface chloride in solid sodium chloride while an electron and a sodium cation simultaneously transfer to yield sodium bisulfate and gas-phase hydrogen chloride. This process repeats. Both of these steps represent well-known reactions for which mechanisms have not been previously determined.

  9. PREPARATION OF URANIUM TRIOXIDE

    DOEpatents

    Buckingham, J.S.

    1959-09-01

    The production of uranium trioxide from aqueous solutions of uranyl nitrate is discussed. The uranium trioxide is produced by adding sulfur or a sulfur-containing compound, such as thiourea, sulfamic acid, sulfuric acid, and ammonium sulfate, to the uranyl solution in an amount of about 0.5% by weight of the uranyl nitrate hexahydrate, evaporating the solution to dryness, and calcining the dry residue. The trioxide obtained by this method furnished a dioxide with a considerably higher reactivity with hydrogen fluoride than a trioxide prepared without the sulfur additive.

  10. Studies of the fate of sulfur trioxide in coal-fired utility boilers based on modified selected condensation methods.

    PubMed

    Cao, Yan; Zhou, Hongcang; Jiang, Wu; Chen, Chien-Wei; Pan, Wei-Ping

    2010-05-01

    The formation of sulfur trioxide (SO(3)) in coal-fired utility boilers can have negative effects on boiler performance and operation, such as fouling and corrosion of equipment, efficiency loss in the air preheater (APH), increase in stack opacity, and the formation of PM(2.5). Sulfur trioxide can also compete with mercury when bonding with injected activated carbons. Tests in a lab-scale reactor confirmed there are major interferences between fly ash and SO(3) during SO(3) sampling. A modified SO(3) procedure to maximize the elimination of measurement biases, based on the inertial-filter-sampling and the selective-condensation-collecting of SO(3), was applied in SO(3) tests in three full-scale utility boilers. For the two units burning bituminous coal, SO(3) levels starting at 20 to 25 ppmv at the inlet to the selective catalytic reduction (SCR), increased slightly across the SCR, owing to catalytic conversion of SO(2) to SO(3,) and then declined in other air pollutant control device (APCD) modules downstream to approximately 5 ppmv and 15 ppmv at the two sites, respectively. In the unit burning sub-bituminous coal, the much lower initial concentration of SO(3) estimated to be approximately 1.5 ppmv at the inlet to the SCR was reduced to about 0.8 ppmv across the SCR and to about 0.3 ppmv at the exit of the wet flue gas desulfurization (WFGD). The SO(3) removal efficiency across the WFGD scrubbers at the three sites was generally 35% or less. Reductions in SO(3) across either the APH or the dry electrostatic precipitator (ESP) in units burning high-sulfur bituminous coal were attributed to operating temperatures being below the dew point of SO(3).

  11. Thiocyanate potentiates antimicrobial photodynamic therapy: In situ generation of the sulfur trioxide radical anion by singlet oxygen

    PubMed Central

    St Denis, Tyler G.; Vecchio, Daniela; Zadlo, Andrzej; Rineh, Ardeshir; Sadasivam, Magesh; Avci, Pinar; Huang, Liyi; Kozinska, Anna; Chandran, Rakkiyappan; Sarna, Tadeusz; Hamblin, Michael R.

    2013-01-01

    Antimicrobial photodynamic therapy (PDT) is used for the eradication of pathogenic microbial cells and involves the light excitation of dyes in the presence of O2, yielding reactive oxygen species including the hydroxyl radical (•OH) and singlet oxygen (1O2). In order to chemically enhance PDT by the formation of longer-lived radical species, we asked whether thiocyanate (SCN−) could potentiate the methylene blue (MB) and light-mediated killing of the gram-positive Staphylococcus aureus and the gram-negative Escherichia coli. SCN− enhanced PDT (10 μM MB, 5J/cm2 660 nm hv) killing in a concentration-dependent manner of S. aureus by 2.5 log10 to a maximum of 4.2 log10 at 10 mM (P < 0.001) and increased killing of E. coli by 3.6 log10 to a maximum of 5.0 log10 at 10 mM (P < 0.01). We determined that SCN− rapidly depleted O2 from an irradiated MB system, reacting exclusively with 1O2, without quenching the MB excited triplet state. SCN− reacted with 1O2, producing a sulfur trioxide radical anion (a sulfur-centered radical demonstrated by EPR spin trapping). We found that MB-PDT of SCN− in solution produced both sulfite and cyanide anions, and that addition of each of these salts separately enhanced MB-PDT killing of bacteria. We were unable to detect EPR signals of •OH, which, together with kinetic data, strongly suggests that MB, known to produce •OH and 1O2, may, under the conditions used, preferentially form 1O2. PMID:23969112

  12. The Centrifugally Induced Pure Rotational Spectrum and the Structure of Sulfur Trioxide. A Microwave Fourier Transform Study of a Nonpolar Molecule

    NASA Astrophysics Data System (ADS)

    Meyer, Volker; Sutter, Dieter Hermann; Dreizler, Helmut

    1991-08-01

    The pure rotational spectrum of sulfur trioxide has been observed for the first time. A total of 25 high-J transitions could be assigned. The rotational constants, two quartic centrifugal distortion constants, and three sextic centrifugal distortion constants were determined as: B= 10 449.0667(23) MHz, C = 5216.0330(12) MHz, DJ = 9.2651 (18) kHz, DJK = -16.3922(18) kHz, HJ, = -8.8(34) • 10-3 Hz, HJK= -15.8(73) • 10-3 Hz, and HKJ = 34.2(73) • 10-3 Hz. An r0- and an re -structure are presented: r0= 1.4198(7) Å (calculated from B), r0 = 1.4210(7) Å (calculated from C), and re = 1.4175 Å

  13. Antimony trioxide

    Integrated Risk Information System (IRIS)

    Antimony trioxide ; CASRN 1309 - 64 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogeni

  14. Method for removing sulfur oxide from waste gases and recovering elemental sulfur

    DOEpatents

    Moore, Raymond H.

    1977-01-01

    A continuous catalytic fused salt extraction process is described for removing sulfur oxides from gaseous streams. The gaseous stream is contacted with a molten potassium sulfate salt mixture having a dissolved catalyst to oxidize sulfur dioxide to sulfur trioxide and molten potassium normal sulfate to solvate the sulfur trioxide to remove the sulfur trioxide from the gaseous stream. A portion of the sulfur trioxide loaded salt mixture is then dissociated to produce sulfur trioxide gas and thereby regenerate potassium normal sulfate. The evolved sulfur trioxide is reacted with hydrogen sulfide as in a Claus reactor to produce elemental sulfur. The process may be advantageously used to clean waste stack gas from industrial plants, such as copper smelters, where a supply of hydrogen sulfide is readily available.

  15. Sulfonate activation of the electrophilic reactivity of chlorine and alkyl hypochlorides by the insertion of sulfur trioxide at the C1-C1 and O-C1 bonds. Addition of chlorine chloro- and ethoxysulfate to olefins

    SciTech Connect

    Zefirov, N.S.; Koz'min, A.S.; Sorokin, V.D.; Zhdankin, V.V.

    1986-10-10

    At low temperatures (-40 to -80/sup 0/C) sulfur trioxide enters the chlorine molecule (with the formation of chlorine chlorosulfate) and the ethyl hypochlorite molecule (giving chlorine ethoxysulfate). Both new compounds are highly reactive electrophilic chlorinating reagents and add to ethylene, activated alkenes (1-hexene and cyclohexene), and deactivated olefins (methyl methacrylate, tri- and tetrachloroethylene) in methylene chloride solution at low temperatures. The addition of chlorine chlorosulfate leads to the formation of ..beta..-chloroalkyl chlorosulfates with yields of 24-85%, and the addition of chlorine ethoxysulfate leads to ..beta..-chloroalkyl ethylsulfates with yields of 65-85%. The reactions with unsymmetrical olefins lead to mixtures of the regioisomers with a preference for the products from addition according to the Markovnikov rule; the addition to cyclohexene is trans-stereospecific. The investigated processes represent a new simple approach to the production of sulfate-activated chlorinating reagents and extend the possibilities for functional substitution of olefins.

  16. Arsenic Trioxide Injection

    MedlinePlus

    Arsenic trioxide is used to treat acute promyelocytic leukemia (APL; a type of cancer in which there ... worsened following treatment with other types of chemotherapy. Arsenic trioxide is in a class of medications called ...

  17. Sulfur

    USGS Publications Warehouse

    Apodaca, L.E.

    2012-01-01

    In 2011, elemental sulfur and the byproduct sulfuric acid were produced at 109 operations in 29 states and the U.S. Virgin Islands. Total shipments were valued at about $1.6 billion. Elemental sulfur production was 8.2 Mt (9 million st); Louisiana and Texas accounted for about 53 percent of domestic production.

  18. Sulfur-oxygen processes on Io

    NASA Technical Reports Server (NTRS)

    Nelson, Robert M.; Smythe, William D.

    1987-01-01

    Laboratory studies of irradiated sulfur dioxide frost have found that sulfur trioxide should be formed as a consequence of the irradiation process. The spectral reflectance of solid sulfur trioxide was measured in the laboratory and it was found that the compound has strong absorption features at 3.37 and 3.70 microns. These features are not present in the spectral geometric albedo of Io. This is interpreted as an indication that sulfur trioxide may exist in such limited abundance that it is undetectable in disk averaged spectrophotometry. It is suggested that the Near-Infrared Mapping Spectrometer on the Galileo spacecraft should be able to identify condensed sulfur trioxide on Io particularly in regions bordering the sulfur dioxide deposits. The presence of elemental sulfur on Io's surface has been questioned on several grounds, most notably the suggested production process (quenched molten sulfur extrusions) and the effect of radiation (particularly X-rays) on some of the allotropes. Mixtures of sulfur allotropes were produced in the laboratory by quenching molten sulfur and it was found that the spectra indicate the presence of certain red-colored allotropes which are preserved upon quenching. The color of the sulfur glass produced is redder when the temperature of the original melt is higher. This is consistent with the suggestion that Io's spectral geometric albedo can be partly explained by the presence of quenched sulfur glasses.

  19. SULFUR DIOXIDE - SULFUR TRIOXIDE REGENERATIVE FUEL CELL RESEARCH

    DTIC Science & Technology

    The thermodynamics and electrolytic characteristics are discussed of an SO2-SO3 regenerative, closed-cycle fuel cell , and summarizes the electrolytic...electrochemical, and phase separation research conducted during a study program to determine the practicability of such a fuel cell . The...experimental results obtained were at such wide variance with the theoretical concept that it became apparent that a fuel cell of this type is not feasible. (Author)

  20. Sulphur trioxide absorption apparatus and process

    SciTech Connect

    Cameron, G.M.

    1987-03-31

    This patent describes a contact process for producing a concentrated sulphuric acid from dry sulphur dioxide and oxygen containing mixtures which employs the absorption of sulphur trioxide from a hot, dry gas stream containing sulphur trioxide into at least one sulphuric acid stream. The improvement described here comprises: (a) feeding the gas stream to a lower packed absorption zone contained within an absorption tower; (b) feeding a first sulphuric acid stream to the lower absorption zone to effect absorption of a major portion of the sulphur trioxide from the gas stream into the first sulphuric acid stream to produce a first enriched sulphuric acid stream and a depleted sulphur trioxide gas stream; (c) feeding the depleted sulphur trioxide gas stream to an upper packed absorption zone above the lower absorption zone within the tower; and (d) feeding a second sulphuric acid stream to the upper absorption zone to effect absorption of substantially all of the sulphur trioxide remaining in the depleted sulphur trioxide gas stream to produce a second enriched sulphuric acid stream and a substantially sulphur trioxide-free gas stream.

  1. Processes for preparing carbon fibers using gaseous sulfur trioxide

    SciTech Connect

    Barton, Bryan E.; Lysenko, Zenon; Bernius, Mark T.; Hukkanen, Eric J.

    2016-01-05

    Disclosed herein are processes for preparing carbonized polymers, such as carbon fibers, comprising: sulfonating a polymer with a sulfonating agent that comprises SO.sub.3 gas to form a sulfonated polymer; treating the sulfonated polymer with a heated solvent, wherein the temperature of said solvent is at least 95.degree. C.; and carbonizing the resulting product by heating it to a temperature of 500-3000.degree. C.

  2. Producing bismuth trioxide and its application in fire assaying

    NASA Astrophysics Data System (ADS)

    Kelly, Zack; Ojebuoboh, Funsho

    2002-04-01

    Bismuth trioxide (Bi2O3) is the prevalent commercial oxide of bismuth. A precursor to the preparation of other compounds of bismuth, including the chemical reagents, bismuth trioxide has specialized uses in optical glass, flame-retardant paper, and, increasingly, in glaze formulations where it substitutes for lead oxides. In the last decade, bismuth trioxide has also become a key ingredient in flux formulations used by mineral analysts in fire assaying. The production of bismuth trioxide generally begins with the minor metal bismuth. This paper describes bismuth trioxide production and the properties and basis for its use in environmentally sound fire assaying.

  3. Infrared detection of Criegee intermediates formed during the ozonolysis of β-pinene and their reactivity towards sulfur dioxide.

    PubMed

    Ahrens, Jennifer; Carlsson, Philip T M; Hertl, Nils; Olzmann, Matthias; Pfeifle, Mark; Wolf, J Lennard; Zeuch, Thomas

    2014-01-13

    Recently, direct kinetic experiments have shown that the oxidation of sulfur dioxide to sulfur trioxide by reaction with stabilized Criegee intermediates (CIs) is an important source of sulfuric acid in the atmosphere. So far, only small CIs, generated in photolysis experiments, have been directly detected. Herein, it is shown that large, stabilized CIs can be detected in the gas phase by FTIR spectroscopy during the ozonolysis of β-pinene. Their transient absorption bands between 930 and 830 cm(-1) appear only in the initial phase of the ozonolysis reaction when the scavenging of stabilized CIs by the reaction products is slow. The large CIs react with sulfur dioxide to give sulfur trioxide and nopinone with a yield exceeding 80%. Reactant consumption and product formation in time-resolved β-pinene ozonolysis experiments in the presence of sulfur dioxide have been kinetically modeled. The results suggest a fast reaction of sulfur dioxide with CIs arising from β-pinene ozonolysis.

  4. Sandwich heterostructures of antimony trioxide and bismuth trioxide films: Structural, morphological and optical analysis

    NASA Astrophysics Data System (ADS)

    Condurache-Bota, Simona; Praisler, Mirela; Gavrila, Raluca; Tigau, Nicolae

    2017-01-01

    Thin film heterostructures can be advantageous since they either exhibit novel or a combination of the properties of their components. Here we propose sandwich-type of heterostructures made of antimony trioxide and bismuth trioxide thin films, which were deposited on glass substrates by thermal vacuum deposition at three substrate temperatures, 50° Celsius apart. Their morphology and optical properties are studied as compared to the corresponding monolayers. It was found that even small substrate temperature changes strongly influence their morphology, increasing their roughness, while the optical transmittance shows a slight decrease as compared with the individual layers. The corresponding absorption coefficient exhibits intermediate values as compared to the component oxides, while the energy bandgaps for the indirect allowed transitions move towards the Infrared when overlapping the antimony and bismuth trioxides.

  5. Organic transformations catalyzed by methylrhenium trioxide

    SciTech Connect

    Zhu, Zuolin

    1995-10-06

    Methylrhenium trioxide (MTO), CH3ReO3, was first prepared in 1979. MTO forms stable or unstable adducts with electron-rich ligands, such as amines (quinuclidine, 1,4-diazabicyclo-octane, pyridine, aniline, 2,2'-bipyridine), alkynes, olefins, 1,2-diols, catechols, hydrogen peroxide, water, thiophenols, 1,2-dithiols, triphenylphosphine, 2-aminophenols, 2-aminothiophenols, 8-hydroxyquinoline and halides (Cl-, Br-, I-). After coordination, different further reactions will occur for different reagents. Reactions described in this report include the dehydration of alcohols, direct amination of alcohols, activation of hydrogen peroxide, oxygen transfer, and decomposition of ethyl diazoacetate.

  6. Can MTA be: Miracle trioxide aggregate?

    PubMed Central

    Naik, Reshma M; Pudakalkatti, Pushpa S; Hattarki, Sanjeevini A

    2014-01-01

    Mineral trioxide aggregate (MTA) has been used for more than 10 years in the dental community and has often been thought of as a material of choice for the endodontist. The dental pulp is closely related to periodontal tissues through apical foramina, accessory canals, and dentinal tubules. Due to this interrelationship, pulpal diseases may influence periodontal health and periodontal infections may affect pulpal integrity. It is estimated that pulpal and periodontal problems are responsible for more than 50% of tooth mortality. Thus, these associations recommend an interdisciplinary approach. MTA appears to exhibit significant results even in periodontal procedures as it is the first restorative material that consistently allows for over-growth of cementum and may facilitate periodontal tissue regeneration. Thus, in the present review, an attempt is made to discuss the clinical applications of MTA as an interdisciplinary approach. PMID:24744536

  7. Mineral trioxide aggregate apexification: A novel approach

    PubMed Central

    Purra, Aamir Rashid; Ahangar, Fayaz Ahmed; Chadgal, Sachin; Farooq, Riyaz

    2016-01-01

    The treatment of choice for necrotic teeth with immature root is apexification, which is induction of apical closure to produce more favorable conditions for conventional root canal filling. The most commonly advocated medicament is calcium hydroxide although recently considerable interest has been expressed in the use of mineral trioxide aggregate (MTA). MTA offers the option of a two-visit apexification procedure so that the fragile tooth can be restored immediately. However, difficulty in placing the material in the wide apical area requires the use of an apical matrix. Materials such as collagen, calcium sulfate, and hydroxyapatite have been used for this purpose. This article describes the use of resorbable suture material to form the apical matrix which offers many advantages over the contemporary materials. PMID:27563191

  8. Arsenic Trioxide Negatively Affects Echinococcus granulosus

    PubMed Central

    Wang, Bo; Wang, Zhuo; Li, Fangfang; Xing, Guoqiang; Peng, Xinyu; Zhang, Shijie

    2015-01-01

    Spillage of cyst contents during surgery is the major cause of recurrences of hydatidosis, also called cystic echinococcosis (CE). Currently, many scolicidal agents are used for inactivation of the cyst contents. However, due to complications in the use of those agents, new and more-effective treatment options are urgently needed. The aim of this study was to investigate the in vitro efficacy of arsenic trioxide (ATO) against Echinococcus granulosus protoscolices. Protoscolices of E. granulosus were incubated in vitro with 2, 4, 6, and 8 μmol/liter ATO; viability of protoscolices was assessed daily by microscopic observation of movements and 0.1% eosin staining. A small sample from each culture was processed for scanning and transmission electron microscopy. ATO demonstrated a potent ability to kill protoscolices, suggesting that ATO may represent a new strategy in treating hydatid cyst echinococcosis. However, the in vivo efficacy and possible side effects of ATO need to be explored. PMID:26324279

  9. Sulfur Cycle

    NASA Technical Reports Server (NTRS)

    Hariss, R.; Niki, H.

    1985-01-01

    Among the general categories of tropospheric sulfur sources, anthropogenic sources have been quantified the most accurately. Research on fluxes of sulfur compounds from volcanic sources is now in progress. Natural sources of reduced sulfur compounds are highly variable in both space and time. Variables, such as soil temperature, hydrology (tidal and water table), and organic flux into the soil, all interact to determine microbial production and subsequent emissions of reduced sulfur compounds from anaerobic soils and sediments. Available information on sources of COS, CS2, DMS, and H2S to the troposphere in the following paragraphs are summarized; these are the major biogenic sulfur species with a clearly identified role in tropospheric chemistry. The oxidation of SO2 to H2SO4 can often have a significant impact on the acidity of precipitation. A schematic representation of some important transformations and sinks for selected sulfur species is illustrated.

  10. Sulfur revisited.

    PubMed

    Lin, A N; Reimer, R J; Carter, D M

    1988-03-01

    Sulfur is a time-honored therapeutic agent useful in a variety of dermatologic disorders. Its keratolytic action is due to formation of hydrogen sulfide through a reaction that depends upon direct interaction between sulfur particles and keratinocytes. The smaller the particle size, the greater the degree of such interaction and the greater the therapeutic efficacy. When applied topically, sulfur induces various histologic changes, including hyperkeratosis, acanthosis, and dilatation of dermal vasculature. One study showed that sulfur was comedogenic when applied onto human and rabbit skin, findings that were not reproduced in other studies. About 1% of topically applied sulfur is systemically absorbed. Adverse effects from topically applied sulfur are uncommon and are mainly limited to the skin. In infants, however, fatal outcome after extensive application has been reported.

  11. Arsenic Trioxide – An Old Drug Rediscovered

    PubMed Central

    Emadi, Ashkan; Gore, Steven D.

    2010-01-01

    Over the last 17 years, clinical trials conducted worldwide have demonstrated the efficacy of arsenic trioxide (As2O3) in the treatment of relapsed acute promyelocytic leukemia (APL). Currently, the role of As2O3 in front-line therapy is under investigation. Recent trials in the US have demonstrated that the addition of As2O3 to standard treatment regimens improves survival outcomes in patients with APL and may allow a reduction in cytotoxic chemotherapy exposure. As2O3 has also shown efficacy in other malignancies, particularly multiple myeloma and myelodysplastic syndromes. Therapeutic doses of As2O3 are well tolerated, with no evidence of long-term toxicity. Adverse events include APL differentiation syndrome, electrocardiographic abnormalities, and mild elevations in liver enzymes. This review highlights trials investigating the role of As2O3 in induction and consolidation for newly diagnosed APL, as well as its role in other hematologic malignancies. The chemistry, mechanisms of action, and clinical side effects of As2O3 are also discussed. PMID:20471733

  12. Lunar sulfur

    NASA Technical Reports Server (NTRS)

    Kuck, David L.

    1991-01-01

    Ideas introduced by Vaniman, Pettit and Heiken in their 1988 Uses of Lunar Sulfur are expanded. Particular attention is given to uses of SO2 as a mineral-dressing fluid. Also introduced is the concept of using sulfide-based concrete as an alternative to the sulfur-based concretes proposed by Leonard and Johnson. Sulfur is abundant in high-Ti mare basalts, which range from 0.16 to 0.27 pct. by weight. Terrestrial basalts with 0.15 pct. S are rare. For oxygen recovery, sulfur must be driven off with other volatiles from ilmenite concentrates, before reduction. Troilite (FeS) may be oxidized to magnetite (Fe3O4) and SO2 gas, by burning concentrates in oxygen within a magnetic field, to further oxidize ilmenite before regrinding the magnetic reconcentration. SO2 is liquid at -20 C, the mean temperature underground on the Moon, at a minimum of 0.6 atm pressure. By using liquid SO2 as a mineral dressing fluid, all the techniques of terrestrial mineral separation become available for lunar ores and concentrates. Combination of sulfur and iron in an exothermic reaction, to form iron sulfides, may be used to cement grains of other minerals into an anhydrous iron-sulfide concrete. A sulfur-iron-aggregate mixture may be heated to the ignition temperature of iron with sulfur to make a concrete shape. The best iron, sulfur, and aggregate ratios need to be experimentally established. The iron and sulfur will be by-products of oxygen production from lunar minerals.

  13. Sulfur Earth

    NASA Astrophysics Data System (ADS)

    de Jong, B. H.

    2007-12-01

    Variations in surface tension affect the buoyancy of objects floating in a liquid. Thus an object floating in water will sink deeper in the presence of dishwater fluid. This is a very minor but measurable effect. It causes for instance ducks to drown in aqueous solutions with added surfactant. The surface tension of liquid iron is very strongly affected by the presence of sulfur which acts as a surfactant in this system varying between 1.9 and 0.4 N/m at 10 mass percent Sulfur (Lee & Morita (2002), This last value is inferred to be the maximum value for Sulfur inferred to be present in the liquid outer core. Venting of Sulfur from the liquid core manifests itself on the Earth surface by the 105 to 106 ton of sulfur vented into the atmosphere annually (Wedepohl, 1984). Inspection of surface Sulfur emission indicates that venting is non-homogeneously distributed over the Earth's surface. The implication of such large variation in surface tension in the liquid outer core are that at locally low Sulfur concentration, the liquid outer core does not wet the predominantly MgSiO3 matrix with which it is in contact. However at a local high in Sulfur, the liquid outer core wets this matrix which in the fluid state has a surface tension of 0.4 N/m (Bansal & Doremus, 1986), couples with it, and causes it to sink. This differential and diapiric movement is transmitted through the essentially brittle mantle (1024 Pa.s, Lambeck & Johnson, 1998; the maximum value for ice being about 1030 Pa.s at 0 K, in all likely hood representing an upper bound of viscosity for all materials) and manifests itself on the surface by the roughly 20 km differentiation, about 0.1 % of the total mantle thickness, between topographical heights and lows with concomitant lateral movement in the crust and upper mantle resulting in thin skin tectonics. The brittle nature of the medium though which this movement is transmitted suggests that the extremes in topography of the D" layer are similar in range to

  14. Mineral trioxide aggregate (MTA): its history, composition, and clinical applications.

    PubMed

    Tawil, Peter Z; Duggan, Derek J; Galicia, Johnah C

    2015-04-01

    Mineral trioxide aggregate (MTA) has been a revolutionary material in endodontics. Since its introduction in the 1990s several studies have demonstrated its use in various clinical applications. MTA has been extensively studied and is currently used for perforation repairs, apexifications, regenerative procedures, apexogenesis, pulpotomies, and pulp capping. This article will review the history, composition, research findings, and clinical applications of this versatile endodontic material.

  15. Cellulose acetate-based composites with antimicrobial properties from embedded molybdenum trioxide particles.

    PubMed

    Shafaei, S; Dörrstein, J; Guggenbichler, J P; Zollfrank, C

    2017-01-01

    The objective of this research was to develop novel cellulose acetate (biopolymer) composite materials with an excellent antimicrobial activity by embedding molybdenum trioxide particles with unique high specific surface area. High surface area molybdenum trioxide particles were prepared from freshly precipitated molybdenum trioxide dihydrate (MoO3 ·2H2 O) and subsequent calcination at 340°C under H2 /N2 gas. Microbiological evaluation against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed applying a roll-on test and excellent antimicrobial activities were determined for composites with embedded anhydrous molybdenum trioxide with a high specific surface area. Cellulose acetate composites comprising MoO3 particles can eliminate three harmful bacteria as a result of the release of protons from the material and surface enlargement of the molybdenum trioxide particles. The findings support a proposed antimicrobial mechanism based on local acidity increase due to large specific surface areas.

  16. Uses of lunar sulfur

    NASA Technical Reports Server (NTRS)

    Vaniman, D.; Pettit, D.; Heiken, G.

    1992-01-01

    Sulfur and sulfur compounds have a wide range of applications for their fluid, electrical, chemical, and biochemical properties. Although known abundances on the Moon are limited (approximately 0.1 percent in mare soils), sulfur is relatively extractable by heating. Coproduction of sulfur during oxygen extraction from ilmenite-rich mare soils could yield sulfur in masses up to 10 percent of the mass of oxygen produced. Sulfur deserves serious consideration as a lunar resource.

  17. Uses of lunar sulfur

    SciTech Connect

    Vaniman, D.T.; Pettit, D.R.; Heiken, G.

    1988-01-01

    Sulfur and sulfur compounds have a wide range of applications for their fluid, electrical, chemical and biochemical properties. Although low in abundance on the Moon (/approximately/0.1% in mare soils), sulfur is surface-correlated and relatively extractable. Co-production of sulfur during oxygen extraction from ilmenite-rich soils could yield sulfur in masses up to 10% of the mass of oxygen produced. Sulfur deserves serious consideration as a lunar resource. 29 refs., 3 figs.

  18. Processes for preparing carbon fibers using sulfur trioxide in a halogenated solvent

    SciTech Connect

    Patton, Jasson T.; Barton, Bryan E.; Bernius, Mark T.; Chen, Xiaoyun; Hukkanen, Eric J.; Rhoton, Christina A.; Lysenko, Zenon

    2015-12-29

    Disclosed here are processes for preparing carbonized polymers (preferably carbon fibers), comprising sulfonating a polymer with a sulfonating agent that comprises SO.sub.3 dissolved in a solvent to form a sulfonated polymer; treating the sulfonated polymer with a heated solvent, wherein the temperature of the solvent is at least 95.degree. C.; and carbonizing the resulting product by heating it to a temperature of 500-3000.degree. C. Carbon fibers made according to these methods are also disclosed herein.

  19. Sulfuric acid-sulfur heat storage cycle

    DOEpatents

    Norman, John H.

    1983-12-20

    A method of storing heat is provided utilizing a chemical cycle which interconverts sulfuric acid and sulfur. The method can be used to levelize the energy obtained from intermittent heat sources, such as solar collectors. Dilute sulfuric acid is concentrated by evaporation of water, and the concentrated sulfuric acid is boiled and decomposed using intense heat from the heat source, forming sulfur dioxide and oxygen. The sulfur dioxide is reacted with water in a disproportionation reaction yielding dilute sulfuric acid, which is recycled, and elemental sulfur. The sulfur has substantial potential chemical energy and represents the storage of a significant portion of the energy obtained from the heat source. The sulfur is burned whenever required to release the stored energy. A particularly advantageous use of the heat storage method is in conjunction with a solar-powered facility which uses the Bunsen reaction in a water-splitting process. The energy storage method is used to levelize the availability of solar energy while some of the sulfur dioxide produced in the heat storage reactions is converted to sulfuric acid in the Bunsen reaction.

  20. Properties of Sulfur Concrete.

    DTIC Science & Technology

    1979-07-06

    This report summarizes the state of the art of sulfur concrete . Sulfur concrete is created by mixing molten sulfur with aggregate and allowing the...and many organic compounds. It works well as a rapid runway repair material. Sulfur concrete also has unfavorable properties. It has poor durability

  1. Band gap engineering and optical properties of tungsten trioxide

    NASA Astrophysics Data System (ADS)

    Ping, Yuan; Li, Yan; Rocca, Dario; Gygi, Francois; Galli, Giulia

    2012-02-01

    Tungsten trioxide (WO3) is a good photoanode material for water oxidation but it is not an efficient absorber of sunlight because of its large band gap (2.6 eV). Recently, stable clathrates of WO3 with interstitial N2 molecules were synthesized [1], which are isostructural to monoclinic WO3 but have a substantially smaller bang gap, 1.8 eV. We have studied the structural, electronic, an vibrational properties of N2-WO3 clathrates using ab-initio calculations and analyzed the physical origin of their gap reduction. We also studied the effect of atomic dopants, in particular rare gases. Substantial band gap reduction has been observed, especially in the case of doping with Xe, due to both electronic and structural effects. Absorption spectra have been computed by solving the Bethe-Salpeter Equation [2] to gain a thourough insight into the optical properties of pure and doped tungsten trioxide. [1] Q. Mi, Y. Ping, Y. Li., B.S. Brunschwig, G. Galli, H B. Gray, N S. Lewis (preprint) [2]D. Rocca, D. Lu and G. Galli, J. Chem. Phys. 133, 164109 (2010)

  2. Resveratrol enhances the suppressive effects of arsenic trioxide on primitive leukemic progenitors.

    PubMed

    Wu, Edward J; Goussetis, Dennis J; Beauchamp, Elspeth; Kosciuczuk, Ewa M; Altman, Jessica K; Eklund, Elizabeth A; Platanias, Leonidas C

    2014-04-01

    Efforts to enhance the antileukemic properties of arsenic trioxide are clinically relevant and may lead to the development of new therapeutic approaches for the management of certain hematological malignancies. We provide evidence that concomitant treatment of acute myeloid leukemia (AML) cells or chronic myeloid leukemia (CML) cells with resveratrol potentiates arsenic trioxide-dependent induction of apoptosis. Importantly, clonogenic assays in methylcellulose demonstrate potent suppressive effects of the combination of these agents on primitive leukemic progenitors derived from patients with AML or CML. Taken together, these findings suggest that combinations of arsenic trioxide with resveratrol may provide an approach for targeting of early leukemic precursors and, possibly, leukemia initiating stem cells.

  3. Sulfur metabolism in phototrophic sulfur bacteria.

    PubMed

    Frigaard, Niels-Ulrik; Dahl, Christiane

    2009-01-01

    Phototrophic sulfur bacteria are characterized by oxidizing various inorganic sulfur compounds for use as electron donors in carbon dioxide fixation during anoxygenic photosynthetic growth. These bacteria are divided into the purple sulfur bacteria (PSB) and the green sulfur bacteria (GSB). They utilize various combinations of sulfide, elemental sulfur, and thiosulfate and sometimes also ferrous iron and hydrogen as electron donors. This review focuses on the dissimilatory and assimilatory metabolism of inorganic sulfur compounds in these bacteria and also briefly discusses these metabolisms in other types of anoxygenic phototrophic bacteria. The biochemistry and genetics of sulfur compound oxidation in PSB and GSB are described in detail. A variety of enzymes catalyzing sulfur oxidation reactions have been isolated from GSB and PSB (especially Allochromatium vinosum, a representative of the Chromatiaceae), and many are well characterized also on a molecular genetic level. Complete genome sequence data are currently available for 10 strains of GSB and for one strain of PSB. We present here a genome-based survey of the distribution and phylogenies of genes involved in oxidation of sulfur compounds in these strains. It is evident from biochemical and genetic analyses that the dissimilatory sulfur metabolism of these organisms is very complex and incompletely understood. This metabolism is modular in the sense that individual steps in the metabolism may be performed by different enzymes in different organisms. Despite the distant evolutionary relationship between GSB and PSB, their photosynthetic nature and their dependency on oxidation of sulfur compounds resulted in similar ecological roles in the sulfur cycle as important anaerobic oxidizers of sulfur compounds.

  4. Cardiac conduction block at multiple levels caused by arsenic trioxide therapy.

    PubMed

    Kathirgamanathan, Kala; Angaran, Paul; Lazo-Langner, Alejandro; Gula, Lorne J

    2013-01-01

    We present a rare case of a woman aged 62 years with refractory acute promyelocytic leukemia treated with arsenic trioxide leading to progressive, multilevel cardiac conduction block. After chelation treatment with dimercaprol, there was normalization of conduction.

  5. Antimony Trioxide (ATO) - Summary of External Peer Review and Public Comments and Disposition

    EPA Pesticide Factsheets

    This document summarizes the public and external peer review comments that the EPA’s Office of Pollution Prevention and Toxics (OPPT) received for the draft work plan risk assessment for Antimony Trioxide (ATO).

  6. Solubility of Sulfur Dioxide in Sulfuric Acid

    NASA Technical Reports Server (NTRS)

    Chang, K. K.; Compton, L. E.; Lawson, D. D.

    1982-01-01

    The solubility of sulfur dioxide in 50% (wt./wt.) sulfuric acid was evaluated by regular solution theory, and the results verified by experimental measurements in the temperature range of 25 C to 70 C at pressures of 60 to 200 PSIA. The percent (wt./wt.) of sulfur dioxide in 50% (wt./wt.) sulfuric acid is given by the equation %SO2 = 2.2350 + 0.0903P - 0.00026P 10 to the 2nd power with P in PSIA.

  7. Mineral Trioxide Aggregate and Portland Cement for Direct Pulp Capping in Dog: A Histopathological Evaluation

    PubMed Central

    Bidar, Maryam; Naghavi, Neda; Mohtasham, Nooshin; Sheik-Nezami, Mahshid; Fallahrastegar, Amir; Afkhami, Farzaneh; Attaran Mashhadi, Negin; Nargesi, Iman

    2014-01-01

    Background and aims. Mineral trioxide aggregate and calcium hydroxide are considered the gold standard pulp-capping materials. Recently, Portland cement has been introduced with properties similar to those of mineral trioxide aggregate. Histopathological effects of direct pulp capping using mineral trioxide aggregate and Portland cements on dog dental pulp tissue were evaluated in the present study. Materials and methods. This histopatological study was carried out on 64 dog premolars. First, the pulp was exposed with a sterile bur. Then, the exposed pulp was capped with white or gray mineral trioxide aggregates and white or gray Portland cements in each quadrant and sealed with glass-ionomer. The specimens were evaluated under a light microscope after 6 months. Statistical analysis was carried out using Kruskal-Wallis test. Statistical significance was defined at α=5%. Results. There was no acute inflammation in any of the specimens. Chronic inflammation in white and gray mineral trioxide aggregates and white and gray Portland cements was reported to be 45.5%, 27.3%, 57.1% and 34.1%, respectively. Although the differences were not statistically significant, severe inflammation was observed mostly adjacent to white mineral trioxide aggregate. The largest extent of increased vascularization (45%) and the least increase in fibrous tissue were observed adjacent to white mineral trioxide aggregate, with no significant differences. In addition, the least calcified tissue formed adjacent to white mineral trioxide aggregate, although the difference was not significant. Conclusion. The materials used in this study were equally effective as pulp protection materials following direct pulp capping in dog teeth. PMID:25346831

  8. Dye leakage and modification of fast-setting mineral trioxide aggregate.

    PubMed

    Challenger, Hereward; Lane, Jason; Becker, Ryan; Nassiripour, Sepehr; Torabinejad, Mahmoud

    2015-02-01

    The objective of this investigation was to determine and decrease dye leakage of fast-setting mineral trioxide aggregate (FSMTA). Specimens using differing setting times or concentrations of calcium sulfate modified FSMTA were assessed for dye penetration. Based on the results, no statistical difference was found in the dye leakage of FSMTA compared with regular mineral trioxide aggregate (MTA). The addition of 10 percent calcium sulfate resulted in a statistical reduction in dye leakage compared to both unmodified FSMTA and regular MTA.

  9. Mineral trioxide aggregate and portland cement for direct pulp capping in dog: a histopathological evaluation.

    PubMed

    Bidar, Maryam; Naghavi, Neda; Mohtasham, Nooshin; Sheik-Nezami, Mahshid; Fallahrastegar, Amir; Afkhami, Farzaneh; Attaran Mashhadi, Negin; Nargesi, Iman

    2014-01-01

    Background and aims. Mineral trioxide aggregate and calcium hydroxide are considered the gold standard pulp-capping materials. Recently, Portland cement has been introduced with properties similar to those of mineral trioxide aggregate. Histopathological effects of direct pulp capping using mineral trioxide aggregate and Portland cements on dog dental pulp tissue were evaluated in the present study. Materials and methods. This histopatological study was carried out on 64 dog premolars. First, the pulp was exposed with a sterile bur. Then, the exposed pulp was capped with white or gray mineral trioxide aggregates and white or gray Portland cements in each quadrant and sealed with glass-ionomer. The specimens were evaluated under a light microscope after 6 months. Statistical analysis was carried out using Kruskal-Wallis test. Statistical significance was defined at α=5%. Results. There was no acute inflammation in any of the specimens. Chronic inflammation in white and gray mineral trioxide aggregates and white and gray Portland cements was reported to be 45.5%, 27.3%, 57.1% and 34.1%, respectively. Although the differences were not statistically significant, severe inflammation was observed mostly adjacent to white mineral trioxide aggregate. The largest extent of increased vascularization (45%) and the least increase in fibrous tissue were observed adjacent to white mineral trioxide aggregate, with no significant differences. In addition, the least calcified tissue formed adjacent to white mineral trioxide aggregate, although the difference was not significant. Conclusion. The materials used in this study were equally effective as pulp protection materials following direct pulp capping in dog teeth.

  10. Mineral trioxide aggregate: part 2 - a review of the material aspects.

    PubMed

    Malhotra, Neeraj; Agarwal, Antara; Mala, Kundabala

    2013-03-01

    The purpose of this two-part series is to review the composition, properties, and products of mineral trioxide aggregate (MTA) materials. PubMed and MedLine electronic databases were used to identify scientific papers from January 1991 to May 2010. Based on the selected inclusion criteria, citations were referenced from the scientific peer-reviewed dental literature. Mineral trioxide aggregate is a refined form of the parent compound, Portland cement (PC), and demonstrates a strong biocompatibility due to the high pH level and the material's ability to form hydroxyapatite. Mineral trioxide aggregate materials provide better microleakage protection than traditional endodontic materials as observed in findings from dye-leakage, fluid-filtration, protein-leakage, and bacterial penetration-leakage studies and has been recognized as a bioactive material. Various MTA commercial products are available, including gray mineral trioxide aggregate (GMTA), white mineral trioxide aggregate (WMTA), and mineral trioxide aggregate-Angelus (AMTA). Although these materials are indicated for various dental uses and applications, long-term in-vivo clinical studies are needed. Part 1 of this article highlighted and discussed the composition and characteristics of the material. Part 2 provides an overview of commercially available MTA materials.

  11. Ethanol Reduced Molybdenum Trioxide for Li-ion Capacitors

    DOE PAGES

    Li, Tianqi; Beidaghi, Majid; Xiao, Xu; ...

    2016-05-06

    Orthorhombic molybdenum trioxide (α-MoO3) is a layered oxide with promising performance as electrode material for Li-ion capacitors. In this study, we show that expansion of the interlayer spacing (by ~0.32 Å) of the structure along the b-axis, introduced by partial reduction of α-MoO3 and formation of MoO3-x (x=0.06–0.43), results in enhanced diffusion of Li ions. Binder-free hybrid electrodes made of MoO3-x nanobelts and carbon nanotubes show excellent electrical conductivity. The combination of increased interlayer spacing and enhanced electron transport leads to high gravimetric and volumetric capacitances of about 420 F/g or F/cm3 and excellent cycle life of binder-free MoO3-x electrodes.

  12. Chemical characteristics of mineral trioxide aggregate and its hydration reaction

    PubMed Central

    2012-01-01

    Mineral trioxide aggregate (MTA) was developed in early 1990s and has been successfully used for root perforation repair, root end filling, and one-visit apexification. MTA is composed mainly of tricalcium silicate and dicalcium silicate. When MTA is hydrated, calcium silicate hydrate (CSH) and calcium hydroxide is formed. Formed calcium hydroxide interacts with the phosphate ion in body fluid and form amorphous calcium phosphate (ACP) which finally transforms into calcium deficient hydroxyapatite (CDHA). These mineral precipitate were reported to form the MTA-dentin interfacial layer which enhances the sealing ability of MTA. Clinically, the use of zinc oxide euginol (ZOE) based materials may retard the setting of MTA. Also, the use of acids or contact with excessive blood should be avoided before complete set of MTA, because these conditions could adversely affect the hydration reaction of MTA. Further studies on the chemical nature of MTA hydration reaction are needed. PMID:23429542

  13. Clinical Applications of Mineral Trioxide Aggregate: Report of Four Cases

    PubMed Central

    Battepati, Prashant M

    2010-01-01

    The greatest threats to developing teeth are dental caries and traumatic injuries. The primary goal of all restorative treatment is to maintain pulp vitality so that normal root development or apexogenesis can occur. If pulpal exposure occurs, then a pulpotomy procedure aims to preserve pulp vitality to allow for normal root development. Historically, calcium hydroxide has been the material of choice for pulpotomy procedures. Recently, an alternative material called mineral trioxide aggregate (MTA) has demonstrated the ability to induce hard-tissue formation in pulpal tissue. This article describes the clinical and radiographic outcome of a series of cases involving the use of MTA in pulpotomy, apexogenesis and apexification procedures and root perforations repair. PMID:27625556

  14. Reactions of ethyl diazoacetate catalyzed by methylrhenium trioxide

    SciTech Connect

    Zhu, Z.; Espenson, H.

    1995-11-03

    Methylrhenium trioxide (CH{sub 3}ReO{sub 3} or MTO) has found wise use in catalysis, including the epoxidation and metathesis of olefins, aldehyde olefination, and oxygen transfer. Extensive reports have now appeared in the area of MTO-catalyzed substrate oxidations with hydrogen peroxide. Certain catalytic applications of MTO for organic reactions that do not utilize peroxide have now been realized. In particular, a catalytic amount of MTO with ethyl diazoacetate (EDA) will convert aromatic imines to aziridines and convert aldehydes and ketones to epoxides. The aziridine preparation proceeds in high yields under anaerobic conditions more conveniently than with existing methods. Compounds with a three-membered heterocyclic ring can be obtained with the EDA/MTO catalytic system. Aromatic imines undergo cycloaddition reactions to give aziridines under mild conditions.

  15. Ethanol Reduced Molybdenum Trioxide for Li-ion Capacitors

    SciTech Connect

    Li, Tianqi; Beidaghi, Majid; Xiao, Xu; Huang, Liang; Hu, Zhimi; Sun, Wanmei; Chen, Xun; Gogotsi, Yury G.; Zhou, Jun

    2016-05-06

    Orthorhombic molybdenum trioxide (α-MoO3) is a layered oxide with promising performance as electrode material for Li-ion capacitors. In this study, we show that expansion of the interlayer spacing (by ~0.32 Å) of the structure along the b-axis, introduced by partial reduction of α-MoO3 and formation of MoO3-x (x=0.06–0.43), results in enhanced diffusion of Li ions. Binder-free hybrid electrodes made of MoO3-x nanobelts and carbon nanotubes show excellent electrical conductivity. The combination of increased interlayer spacing and enhanced electron transport leads to high gravimetric and volumetric capacitances of about 420 F/g or F/cm3 and excellent cycle life of binder-free MoO3-x electrodes.

  16. Mineral trioxide aggregate (MTA)-like materials: an update review.

    PubMed

    Mohammadi, Zahed; Shalavi, Sousan; Soltani, Mohammad Karim

    2014-09-01

    Mineral trioxide aggregate (MTA) is a multi-application material used in endodontics. It is a mixture of a refined Portland cement and bismuth oxide and trace amounts of SiO₂, CaO, MgO, K₂SO₄, and Na₂SO₄. MTA powder is mixed with supplied sterile water in a 3:1 powder/liquid. Hydrated MTA has an initial pH of 10.2, which rises to 12.5 three hours after mixing. There are several materials derived from MTA such as Endo-CPM Sealer, Ortho MTA, MTA-Fillapex, DiaRoot BioAggregate, MTA Bio, light-cured MTA, tricalcium silicate, and iRoot SP. The purpose of this article is to review MTA-like materials.

  17. Sulfuric acid poisoning

    MedlinePlus

    Sulfuric acid is a very strong chemical that is corrosive. Corrosive means it can cause severe burns and ... or mucous membranes. This article discusses poisoning from sulfuric acid. This article is for information only. Do NOT ...

  18. The Sulfur Cycle

    ERIC Educational Resources Information Center

    Kellogg, W. W.; And Others

    1972-01-01

    A model estimating the contributions of sulfur compounds by natural and human activities, and the rate of removal of sulfur from the atmosphere, is based on a review of the existing literature. Areas requiring additional research are identified. (AL)

  19. Sulfuric acid on Europa and the radiolytic sulfur cycle

    NASA Technical Reports Server (NTRS)

    Carlson, R. W.; Johnson, R. E.; Anderson, M. S.

    1999-01-01

    A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes.

  20. Sulfuric acid on Europa and the radiolytic sulfur cycle.

    PubMed

    Carlson, R W; Johnson, R E; Anderson, M S

    1999-10-01

    A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes.

  1. Sulfur tolerant anode materials

    SciTech Connect

    Not Available

    1988-02-01

    The goal of this program is the development of a molten carbonate fuel cell (MCFC) anode which is more tolerant of sulfur contaminants in the fuel than the current state-of-the-art nickel-based anode structures. This program addresses two different but related aspects of the sulfur contamination problem. The primary aspect is concerned with the development of a sulfur tolerant electrocatalyst for the fuel oxidation reaction. A secondary issue is the development of a sulfur tolerant water-gas-shift reaction catalyst and an investigation of potential steam reforming catalysts which also have some sulfur tolerant capabilities. These two aspects are being addressed as two separate tasks.

  2. Successful apexification with resolution of the periapical lesion using mineral trioxide aggregate and demineralized freeze-dried bone allograft

    PubMed Central

    Chhabra, Naveen; Singbal, Kiran P; Kamat, Sharad

    2010-01-01

    Immature teeth with necrotic pulp and large periapical lesion are difficult to treat via conventional endodontic therapy. The role of materials such as calcium hydroxide and mineral trioxide aggregate in apexification is indispensable. This case report presents the successful healing and apexification with combined use of white mineral trioxide aggregate and demineralized freeze-dried bone allograft. PMID:20859486

  3. [Mineral trioxide aggregate (MTA) a success story in apical surgery].

    PubMed

    von Arx, Thomas

    2016-01-01

    The objective of apical surgery is to retain teeth with persistent apical pathosis following orthograde root canal treatment if endodontic non-surgical revision is difficult or associated with risks, or is even declined by the patient. Since the most frequent cause of recurrent apical disease is bacterial reinfection from the (remaining) root canal system, the bacteria-tight root-end filling is the most important step in apical surgery. In the early 1990s, mineral trioxide aggregate (MTA) was developed at the Loma Linda University in California/USA. Preclinical studies clearly showed that MTA has a high sealing capability, a good material stability and an excellent biocompatbility. Multiple experimental studies in animals highlighted the mild tissue reactions observed adjacent to this material. Furthermore, histological analysis of the periapical regions demonstrated a frequent deposition of new cementum not only onto the resection plane (cut dentinal surface), but also directly onto MTA. For these reasons, MTA is considered a bioactive material. In 1997 MTA was cleared for clinical use in patients. Multiple prospective clinical and randomized studies have documented high and constant success rates of MTA-treated teeth in apical surgery. A recently published longitudinal study showed that MTA-treated teeth remained stable over five years; hence the high healed rates documented after one year are maintained during long-term observation.

  4. Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films

    SciTech Connect

    Deki, Shigehito; Beleke, Alexis Bienvenu; Kotani, Yuki; Mizuhata, Minoru

    2009-09-15

    Hexagonal molybdenum trioxide thin films with good crystallinity and high purity have been fabricated by the liquid phase deposition (LPD) technique using molybdic acid (H{sub 2}MoO{sub 4}) dissolved in 2.82% hydrofluoric acid (HF) and H{sub 3}BO{sub 3} as precursors. The crystal was found to belong to a hexagonal hydrate system MoO{sub 3}.nH{sub 2}O (napprox0.56). The unit cell lattice parameters are a=10.651 A, c=3.725 A and V=365.997 A{sup 3}. Scanning electron microscope (SEM) images of the as-deposited samples showed well-shaped hexagonal rods nuclei that grew and where the amount increased with increase in reaction time. X-ray photon electron spectroscopy (XPS) spectra showed a Gaussian shape of the doublet of Mo 3d core level, indicating the presence of Mo{sup 6+} oxidation state in the deposited films. The deposited films exhibited an electrochromic behavior by lithium intercalation and deintercalation, which resulted in coloration and bleaching of the film. Upon dehydration at about 450 deg. C, the hexagonal MoO{sub 3}.nH{sub 2}O was transformed into the thermodynamically stable orthorhombic phase. - Abstract: SEM photograph of typical h-MoO{sub 3}.nH{sub 2}O thin film nuclei obtained after 36 h at 40 deg. C by the LPD method. Display Omitted

  5. Uranium trioxide behavior during electron energy loss spectroscopy analysis

    NASA Astrophysics Data System (ADS)

    Degueldre, Claude; Alekseev, Evgeny V.

    2015-03-01

    A sample of uranium trioxide (UO3) was produced by focused ion beam (~10 μm×~10 μm×<0.5 μm) for transmission electron and electron energy loss (EEL) spectroscopy examinations in a transmission electron microscope (TEM). The EEL spectra were recorded as a function of the thickness for the P and O edges in the low energy range 0-350 eV and were compared to spectra of UO3 small grains attached to a TEM grid. The EEL spectrum was studied through a range of thicknesses going from ~60 to ~260 nm. The EEL spectra recorded for UO3 are compared with those recorded for UO2. The reduction of UO3 into U4O9 and/or UO2 is readily observed apparently during the TEM investigations and as confirmed by electron diffraction (eD). This redox effect is similar to that known for other redox sensitive oxides. Recommendations are suggested to avoid sample decomposition.

  6. Kinetics and mechanism of photopromoted oxidative dissolution of antimony trioxide.

    PubMed

    Hu, Xingyun; Kong, Linghao; He, Mengchang

    2014-12-16

    Light (sunlight, ultraviolet, simulated sunlight) irradiation was used to initiate the dissolution of antimony trioxide (Sb2O3). Dissolution rate of Sb2O3 was accelerated and dissolved trivalent antimony (Sb(III)) was oxidized in the irradiation of light. The photopromoted oxidative dissolution mechanism of Sb2O3 was studied through experiments investigating the effects of pH, free radicals scavengers, dissolved oxygen removal and Sb2O3 dosage on the release rate of antimony from Sb2O3 under simulated sunlight irradiation. The key oxidative components were hydroxyl free radicals, photogenerated holes and superoxide free radicals; their contribution ratios were roughly estimated. In addition, a conceptual model of the photocatalytic oxidation dissolution of Sb2O3 was proposed. The overall pH-dependent dissolution rate of Sb2O3 and the oxidation of Sb(III) under light irradiation were expressed by r = 0.08 ·[OH(-)](0.63) and rox = 0.10 ·[OH(-)](0.79). The present study on the mechanism of the photo-oxidation dissolution of Sb2O3 could help clarify the geochemical cycle and fate of Sb in the environment.

  7. Photocatalysis and photoelectrochemical properties of tungsten trioxide nanostructured films.

    PubMed

    Lai, Chin Wei

    2014-01-01

    Tungsten trioxide (WO₃) possesses a small band gap energy of 2.4-2.8 eV and is responsive to both ultraviolet and visible light irradiation including strong absorption of the solar spectrum and stable physicochemical properties. Thus, controlled growth of one-dimensional (1D) WO₃ nanotubular structures with desired length, diameter, and wall thickness has gained significant interest. In the present study, 1D WO₃ nanotubes were successfully synthesized via electrochemical anodization of tungsten (W) foil in an electrolyte composed of 1 M of sodium sulphate (Na₂SO₄) and ammonium fluoride (NH₄F). The influence of NH₄F content on the formation mechanism of anodic WO₃ nanotubular structure was investigated in detail. An optimization of fluoride ions played a critical role in controlling the chemical dissolution reaction in the interface of W/WO₃. Based on the results obtained, a minimum of 0.7 wt% of NH₄F content was required for completing transformation from W foil to WO₃ nanotubular structure with an average diameter of 85 nm and length of 250 nm within 15 min of anodization time. In this case, high aspect ratio of WO₃ nanotubular structure is preferred because larger active surface area will be provided for better photocatalytic and photoelectrochemical (PEC) reactions.

  8. Compressive Strength of Mineral Trioxide Aggregate with Propylene Glycol

    PubMed Central

    Ghasemi, Negin; Rahimi, Saeed; Shahi, Shahriar; Salem Milani, Amin; Rezaei, Yashar; Nobakht, Mahnaz

    2016-01-01

    Introduction: The aim of this study was to evaluate the effect of adding propylene glycol (PG) to mineral trioxide aggregate (MTA) liquid with volume ratio of 20% on the compressive strength (CS) of MTA in two time periods (4 and 21 days) after mixing. Methods and Materials: Four groups of steel cylinders (n=15) with an internal diameter of 3 and a height of 6 mm were prepared and MTA (groups 1 and 2) and MTA+PG (80% MTA liquid+20% PG) (groups 3 and 4) were placed in to the cylinders. In groups 1 and 3 the CS was evaluated after 4 days and in groups 2 and 4 after 21 days. Data were calculated using the two-ways ANOVA. The level of significance was set at 0.05. Results: The highest (52.22±18.92 MPa) and lowest (4.5±0.67 MPa) of CS was obtained in 21-day MTA samples and 4-day MTA+PG specimen, respectively. The effect of time and PG were significant on the CS (P<0.05). Mixing MTA with PG significantly reduced the CS; but passing the time from 4 to 21 days significantly increased the CS. Conclusion: Considering the limitations of this study, PG had a negative effect on CS of MTA. PMID:27790264

  9. The global sulfur cycle

    NASA Technical Reports Server (NTRS)

    Sagan, D. (Editor)

    1985-01-01

    The results of the planetary biology microbial ecology's 1984 Summer Research Program, which examined various aspects of the global sulfur cycle are summarized. Ways in which sulfur flows through the many living and chemical species that inhabit the surface of the Earth were investigated. Major topics studied include: (1) sulfur cycling and metabolism of phototropic and filamentous sulfur bacteria; (2) sulfur reduction in sediments of marine and evaporite environments; (3) recent cyanobacterial mats; (4) microanalysis of community metabolism in proximity to the photic zone in potential stromatolites; and (5) formation and activity of microbial biofilms on metal sulfides and other mineral surfaces. Relationships between the global sulfur cycle and the understanding of the early evolution of the Earth and biosphere and current processes that affect global habitability are stressed.

  10. Sulfur removal from coal

    SciTech Connect

    Lompa-Krzymien, L.

    1985-01-01

    Coal is treated to remove both pyritic and organic sulfur by contacting with an aqueous solution comprising cupric ions at temperatures of about 140/sup 0/ C.-200/sup 0/ C. under autogenic pressure, until substantial amounts of the sulfur are solubilized, separating the coal solids, and washing the solids with water to remove soluble forms of sulfur, iron and copper therefrom. The copper can be recovered and recycled as a cupric salt.

  11. The embryotoxic response to maternal chromium trioxide exposure in different strains of hamsters

    SciTech Connect

    Gale, T.F.

    1982-10-01

    This paper compares the chromium trioxide-induced embryotoxic effects among one noninbred (LVG) and five inbred (CB, LHC, LSH, MHA, PD4) strains of hamsters. A single dose of chromium trioxide (8 mg/kg, iv) was injected into pregnant hamsters on the morning of gestation Day 8. Treated and control animals were killed on gestation Day 15 and studied for the types and incidence of external and internal abnormalities, as well as the frequency of resorption sites per uterus. The embryotoxic effects described in this study include significant rates of resorptions, external abnormalities, cleft palate, and hydrocephalus. The results indicate that the MHA, LSH, and LVG strains are susceptible, while the CB, LHC, and PD4 strains are resistant to chromium trioxide-induced embryotoxicity. This study was compared with prior work in which the same hamster strains were treated with either cadmium, lead, or mercury.

  12. Sulfurization of α-MoO{sub 3} nanostructured thin film

    SciTech Connect

    Kumar, Prabhat; Singh, Megha; Sharma, Rabindar K. Reddy, G. B.

    2015-08-28

    In this report, the sulfurization of vertically aligned molybdenum trioxide (α- MoO{sub 3}) nanoflakes (NFs) with high aspect ratio (height/thickness >20) on the nickel coated glass substrates in a mixture of H{sub 2}S and argon gas at atmospheric pressure has been studied. The effect of sulfurization have been investigated to understand the basic reaction mechanism and the morphology, structural properties of grown nanoflakes. XPS and XRD indicate the formation of MoS{sub 2} along with the other intermediate phase such as MoO{sub 2} at temperature 200 °C. The surface morphology of samples have been studied systematically by using scanning electron microscope (SEM). The results demonstrate partial conversion of MoO{sub 3} NFs into MoS{sub 2} along with the change in the morphology of nanoflakes. All the observed results are well in consonance with each other.

  13. Reactions of connective tissue to amalgam, intermediate restorative material, mineral trioxide aggregate, and mineral trioxide aggregate mixed with chlorhexidine.

    PubMed

    Sumer, Mahmut; Muglali, Mehtap; Bodrumlu, Emre; Guvenc, Tolga

    2006-11-01

    The aim of this study was to histopathologically examine the biocompatibility of the high-copper amalgam, intermediate restorative material (IRM), mineral trioxide aggregate (MTA), and MTA mixed with chlorhexidine (CHX). This study was conducted to observe the rat subcutaneous connective tissue reaction to the implanted tubes filled with amalgam, IRM, MTA, and MTA mixed with CHX. The animals were sacrificed 15, 30, and 60 days after the implantation procedure. The implant sites were excised and prepared for histological evaluation. Sections of 5 to 6 microm thickness were cut by a microtome and stained with hemotoxylin eosin and examined under a light microscope. The inflammatory reactions were categorized as weak (none or few inflammatory cells < or =25 cells), moderate (>25 cells), and severe (a lot of inflammatory cells not to be counted, giant cells, and granulation tissue). Thickness of fibrous capsules measured five different areas by the digital imaging and the mean values were scored. Amalgam, IRM, and MTA mixed with CHX caused a weak inflammatory response on days 15, 30, and 60. MTA provoked an initial severe inflammatory response that subsided at the 30 and 60 day study period. A clear fibrous capsule was observed beginning from the 15 days in all of the groups. Within the limits of this study, amalgam, IRM, MTA, and MTA mixed with CHX materials were surrounded by fibrous connective tissue indicated that they were well tolerated by the tissues, therefore, MTA/CHX seemed to be biocompatible.

  14. ADVANCED SULFUR CONTROL CONCEPTS

    SciTech Connect

    Apostolos A. Nikolopoulos; Santosh K. Gangwal; William J. McMichael; Jeffrey W. Portzer

    2003-01-01

    Conventional sulfur removal in integrated gasification combined cycle (IGCC) power plants involves numerous steps: COS (carbonyl sulfide) hydrolysis, amine scrubbing/regeneration, Claus process, and tail-gas treatment. Advanced sulfur removal in IGCC systems involves typically the use of zinc oxide-based sorbents. The sulfides sorbent is regenerated using dilute air to produce a dilute SO{sub 2} (sulfur dioxide) tail gas. Under previous contracts the highly effective first generation Direct Sulfur Recovery Process (DSRP) for catalytic reduction of this SO{sub 2} tail gas to elemental sulfur was developed. This process is currently undergoing field-testing. In this project, advanced concepts were evaluated to reduce the number of unit operations in sulfur removal and recovery. Substantial effort was directed towards developing sorbents that could be directly regenerated to elemental sulfur in an Advanced Hot Gas Process (AHGP). Development of this process has been described in detail in Appendices A-F. RTI began the development of the Single-step Sulfur Recovery Process (SSRP) to eliminate the use of sorbents and multiple reactors in sulfur removal and recovery. This process showed promising preliminary results and thus further process development of AHGP was abandoned in favor of SSRP. The SSRP is a direct Claus process that consists of injecting SO{sub 2} directly into the quenched coal gas from a coal gasifier, and reacting the H{sub 2}S-SO{sub 2} mixture over a selective catalyst to both remove and recover sulfur in a single step. The process is conducted at gasifier pressure and 125 to 160 C. The proposed commercial embodiment of the SSRP involves a liquid phase of molten sulfur with dispersed catalyst in a slurry bubble-column reactor (SBCR).

  15. Advanced sulfur control concepts

    SciTech Connect

    Gangwal, S.K.; Turk, B.S.; Gupta, R.P.

    1995-11-01

    Regenerable metal oxide sorbents, such as zinc titanate, are being developed to efficiently remove hydrogen sulfide (H{sub 2}S) from coal gas in advanced power systems. Dilute air regeneration of the sorbents produces a tailgas containing a few percent sulfur dioxide (SO{sub 2}). Catalytic reduction of the SO{sub 2} to elemental sulfur with a coal gas slipstream using the Direct Sulfur Recovery Process (DSRP) is a leading first-generation technology. Currently the DSRP is undergoing field testing at gasifier sites. The objective of this study is to develop second-generation processes that produce elemental sulfur without coal gas or with limited use. Novel approaches that were evaluated to produce elemental sulfur from sulfided sorbents include (1) sulfur dioxide (SO{sub 2}) regeneration, (2) substoichiometric (partial) oxidation, (3) steam regeneration followed by H{sub 2}S oxidation, and (4) steam-air regeneration. Preliminary assessment of these approaches indicated that developing SO{sub 2} regeneration faced the fewest technical and economic problems among the four process options. Elemental sulfur is the only likely product of SO{sub 2} regeneration and the SO{sub 2} required for the regeneration can be obtained by burning a portion of the sulfur produced. Experimental efforts have thus been concentrated on SO{sub 2}-based regeneration processes. Results from laboratory investigations are presented and discussed.

  16. Sulfur isotopic data

    SciTech Connect

    Rye, R.O.

    1987-01-01

    Preliminary sulfur isotope data have been determined for samples of the Vermillion Creek coal bed and associated rocks in the Vermillion Creek basin and for samples of evaporites collected from Jurassic and Triassic formations that crop out in the nearby Uinta Mountains. The data are inconclusive, but it is likely that the sulfur in the coal was derived from the evaporites.

  17. The Phases of Sulfur.

    ERIC Educational Resources Information Center

    Birdwhistell, Kurt R.

    1995-01-01

    Presents a demonstration that illustrates the dramatic changes that sulfur undergoes upon heating to 200 degrees centigrade and then cooling to room temperature. Supplements the demonstration of the rubberlike properties of catenasulfur made by rapid cooling of the sulfur melt in ice water. (JRH)

  18. Interaction between arsenic trioxide (ATO) and human neutrophils.

    PubMed

    Binet, François; Chiasson, Sonia; Girard, Denis

    2011-05-01

    The cytotoxic effect of arsenic trioxide (ATO) is known to be mediated by its ability to induce cell apoptosis in a variety of cells, including neutrophils. More recently, we demonstrated that ATO induced several parameters involved in endoplasmic reticulum (ER) stress-induced neutrophil apoptosis but that caspase-4 was not involved. The aim of this study was to better understand how neutrophils are activated by ATO and to further demonstrate that ATO is an ER stressor. Human neutrophils were isolated from healthy blood donors and incubated in vitro in the presence or absence of ATO and several parameters were investigated. We found that ATO induced the expression of the proapoptotic GADD153 protein, a key player involved in ER stress-induced apoptosis, activated nuclear nuclear factor κB (NF-κB) DNA binding activities, and increased prostaglandine E2 (PGE2) production. Using an antibody array approach, we found that ATO increased the production of several cytokines, with interleukin 8 (IL-8) being the predominant one. We confirmed that ATO increased the production of IL-8 by enzyme-linked-immunosorbent assay (ELISA). Treatment with a caspase-4 inhibitor did not inhibit IL-8 production. The results of the present study further support the notion that ATO is an ER stressor and that, although its toxic effect is mediated by induction of apoptosis, this chemical also induced, in parallel, NF-κB activation, the production of PGE2 and several cytokines probably involved in other cell functions. Also, we conclude that the production of IL-8 is not induced by a caspase-4-dependent mechanism, suggesting that ATO-induced caspase-4 activation is involved in other as yet unidentified functions in human neutrophils.

  19. Sulfur-rich Sediments

    NASA Astrophysics Data System (ADS)

    Goldhaber, M. B.

    2003-12-01

    Marine sediments with more than a few tenths of a percent of organic carbon, as well as organic-matter-bearing, nonmarine sediments with significant concentrations of sulfate in the depositional waters contain the mineral pyrite (FeS2). Pyrite, along with sulfur-bearing organic compounds, form indirectly through the metabolic activities of sulfate-reducing microorganisms. The geochemical transformations of sulfur in sediments leading to these products significantly impact the pathway of early sedimentary diagenesis, conditions for the localization of mineral deposits (Ohmoto and Goldhaber, 1997), the global cycling of sulfur and carbon, the abundance of oxygen in the Earth's atmosphere, and perhaps even the emergence of life on Earth (e.g., Russell and Hall, 1997). This chapter provides an overview of sedimentary-sulfur geochemistry from its microbial and abiologic pathways to the global consequences of these processes.The geochemistry of sulfur is complicated by its wide range of oxidation states (Table 1). Under oxidizing conditions (e.g., in the presence of atmospheric oxygen) sulfate, with sulfur in the +6 valence state, is the stable form of sulfur. Under reducing conditions (e.g., in the presence of H2), sulfide (S=-2 valent) is the stable oxidation state. However, a range of additional aqueous and solid-phase sulfur species exist with valences between these two end-members. What makes the study of sulfur geochemistry so exciting and challenging is that many of these intermediate-valent forms play key roles in sedimentary-sulfur transformations. Furthermore, many of these reactions are microbially mediated. As detailed below, these complex biogeochemical pathways are now yielding to research whose scope ranges from molecular to global level. Table 1. Forms of sulfur in marine sediments and their oxidation states Aqueous species or mineralFormulaOxidation state(s) of sulfur SulfideH2S(aq), HS-(aq)-2 Iron sulfideaFeS(s)-2 GreigiteFe3S4(s)-2, 0 PyriteFeS2(s)-2

  20. Elemental sulfur recovery process

    DOEpatents

    Flytzani-Stephanopoulos, Maria; Hu, Zhicheng

    1993-01-01

    An improved catalytic reduction process for the direct recovery of elemental sulfur from various SO.sub.2 -containing industrial gas streams. The catalytic process provides combined high activity and selectivity for the reduction of SO.sub.2 to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over certain catalyst formulations based on cerium oxide. The process is a single-stage, catalytic sulfur recovery process in conjunction with regenerators, such as those used in dry, regenerative flue gas desulfurization or other processes, involving direct reduction of the SO.sub.2 in the regenerator off gas stream to elemental sulfur in the presence of a catalyst.

  1. Elemental sulfur recovery process

    DOEpatents

    Flytzani-Stephanopoulos, M.; Zhicheng Hu.

    1993-09-07

    An improved catalytic reduction process for the direct recovery of elemental sulfur from various SO[sub 2]-containing industrial gas streams. The catalytic process provides combined high activity and selectivity for the reduction of SO[sub 2] to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over certain catalyst formulations based on cerium oxide. The process is a single-stage, catalytic sulfur recovery process in conjunction with regenerators, such as those used in dry, regenerative flue gas desulfurization or other processes, involving direct reduction of the SO[sub 2] in the regenerator off gas stream to elemental sulfur in the presence of a catalyst. 4 figures.

  2. Regional river sulfur runoff

    SciTech Connect

    Husar, R.B.; Husar, J.D.

    1985-01-20

    The water and sulfur runoff data for 54 large river basins were assembled, covering 65% of the nondesert land area of the world. The sulfur concentration ranges from 0.5 mg S/L for the West African rivers Niger and Volta to 100 mg S/L in the Colorado River; the world average is 3.2 mg S/L. The concentrations in central and eastern Europe as well as central and eastern North America exceed 8 mg S/L. The sulfur runoff density is also highest in the river basins over these industrialized regions, exceeding 2 g S/m/sup 2//yr. However, high sulfur runoff density in excess of 3 g S/m/sup 2//yr is also measured over the Pacific islands New Zealand and New Guinea and the archipelagos of Indonesia and the Philippines. The natural background sulfur runoff was estimated by assuming that South America, Africa, Australia, and the Pacific Islands are unperturbed by man and that the average river sulfur concentration is in the range 1--3 mg S/L. Taking these background concentration values, the man-induced sulfur runoff for Europe ranges between 2 and 8 times the natural flow, and over North America, man's contribution ranges between 1 and 5 times the natural runoff. The global sulfur flow from nondesert land to the oceans and the Caspian Sea is estimated as 131 Tg S/yr, of which 46--85 Tg S/yr is attributed to natural causes. The regional river sulfur runoff pattern discussed in this paper does not have enough spatial resolution to be directly applicable to studies of the environmental effects of man-induced sulfur flows. However, it points to the continental-size regions where those perturbations are most evident and to the magnitude of the perturbations as expressed in units of the natural flows.

  3. Regional river sulfur runoff

    NASA Astrophysics Data System (ADS)

    Husar, Rudolf B.; Husar, Janja Djukic

    1985-01-01

    The water and sulfur runoff data for 54 large river basins were assembled, covering 65% of the nondesert land area of the world. The sulfur concentration ranges from 0.5 mg S/L for the West African rivers Niger and Volta to 100 mg S/L in the Colorado River; the world average is 3.2 mg S/L. The concentrations in central and eastern Europe as well as central and eastern North America exceed 8 mg S/L. The sulfur runoff density is also highest in the river basins over these industrialized regions, exceeding 2 g S/m2/yr. However, high sulfur runoff density in excess of 3 g S/m2/yr is also measured over the Pacific islands New Zealand and New Guinea and the archipelagos of Indonesia and the Philippines. The natural background sulfur runoff was estimated by assuming that South America, Africa, Australia, and the Pacific Islands are unperturbed by man and that the average river sulfur concentration is in the range 1-3 mg S/L. Taking these background concentration values, the man-induced sulfur runoff for Europe ranges between 2 and 8 times the natural flow, and over North America, man's contribution ranges between 1 and 5 times the natural runoff. The global sulfur flow from nondesert land to the oceans and the Caspian Sea is estimated as 131 Tg S/yr, of which 46-85 Tg S/yr is attributed to natural causes. The regional river sulfur runoff pattern discussed in this paper does not have enough spatial resolution to be directly applicable to studies of the environmental effects of man-induced sulfur flows. However, it points to the continental-size regions where those perturbations are most evident and to the magnitude of the perturbations as expressed in units of the natural flows.

  4. Combination treatment with arsenic trioxide and phytosphingosine enhances apoptotic cell death in arsenic trioxide-resistant cancer cells.

    PubMed

    Park, Moon-Taek; Kang, Young-Hee; Park, In-Chul; Kim, Chun-Ho; Lee, Yun-Sil; Chung, Hee Yong; Lee, Su-Jae

    2007-01-01

    Resistance to anticancer drugs can sometimes be overcome by combination treatment with other therapeutic drugs. Here, we showed that phytosphingosine treatment in combination with arsenic trioxide (As(2)O(3)) enhanced cell death of naturally As(2)O(3)-resistant human myeloid leukemia cells. The combination treatment induced an increase in intracellular reactive oxygen species level, mitochondrial relocalization of Bax, poly(ADP-ribose) polymerase-1 (PARP-1) activation, and cytochrome c release from the mitochondria. N-acetyl-l-cysteine, a thiol-containing antioxidant, completely blocked Bax relocalization, PARP-1 activation, and cytochrome c release. Pretreatment of 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone, a PARP-1 inhibitor, or PARP-1/small interfering RNA partially attenuated cytochrome c release, whereas the same treatment did not affect Bax relocalization. The combination treatment induced selective activation of p38 mitogen-activated protein kinase (MAPK). Inhibition of p38 MAPK by treatment of SB203580 or expression of dominant-negative forms of p38 MAPK suppressed the combination treatment-induced Bax relocalization but did not affect PARP-1 activation. In addition, antioxidant N-acetyl-l-cysteine completely blocked p38 MAPK activation. These results indicate that phytosphingosine in combination with As(2)O(3) induces synergistic apoptosis in As(2)O(3)-resistant leukemia cells through the p38 MAPK-mediated mitochondrial translocation of Bax and the PARP-1 activation, and that p38 MAPK and PARP-1 activations are reactive oxygen species dependent. The molecular mechanism that we elucidated in this study may provide insight into the design of future combination cancer therapies to cells intrinsically less sensitive to As(2)O(3) treatment.

  5. Arsenic trioxide induced indirect and direct inhibition of glutathione reductase leads to apoptosis in rat hepatocytes.

    PubMed

    Ray, Atish; Chatterjee, Sarmishtha; Mukherjee, Sandip; Bhattacharya, Shelley

    2014-06-01

    Glutathione reductase (GR) is an essential enzyme which maintains the reduced state of a cell. Therefore GR malfunction is closely associated with several disorders related to oxidative damage. The present study reports toxic manifestation of arsenic trioxide in respect of GR leading to apoptosis. Isolated rat hepatocytes exposed to arsenic trioxide were analyzed for GR expression and activity. Arsenic resulted in a time dependent inhibition of GR mediated by the superoxide anion. The cellular demand of functional enzyme is achieved by concomitant rise in gene expression. However, direct inhibition of GR by arsenic trioxide was also evident. Furthermore, arsenic induced free radical mediated inhibition of GR was found to be partially uncompetitive and associated with time dependent decrease in the substrate binding rate. Externalization of phosphatidylserine, nuclear degradation, apoptosis inducing factor leakage, apoptosome formation, caspase activation, DNA damage and break down of PARP suggest consequential induction of apoptosis due to inhibition of GR. The implication of GR was further established from the reduced rate of caspase activation in the arsenic trioxide treated cell, supplemented with complete and incomplete enzyme systems.

  6. Relativistic Multireference Quantum Chemical Study of the Electronic Structure of Actinide Trioxide Molecules.

    PubMed

    Kovács, Attila

    2017-03-17

    Actinide trioxide (AnO3, An = U, Np, Pu, Am, Cm) molecules have been investigated by relativistic multireference quantum chemical calculations with the goal to elucidate their electronic structures. The molecular geometries of the ground and selected excited electronic states have been optimized at the spin-orbit-free complete active space second-order perturbation theory (SF-CASPT2) level. The low-lying vertical excitation states have been computed and characterized by CASPT2 calculations taking into account spin-orbit coupling. The reason for the considerable lengthening of the equatorial An-O bond in AmO3 and CmO3 with respect to the other trioxides has been analyzed on the basis of valence molecular orbitals of the SF ground electronic states. For the bond in question a singly occupied π orbital has been identified, this orbital is doubly occupied in the other (An = U, Np, Pu) trioxides. The clarified electronic structures of the investigated AnO3 molecules confirmed the pentavalent character of Am and Cm in their trioxides in contrast to the hexavalent character of U, Np, and Pu.

  7. Contribution to the photometric determination of small amounts of boron trioxide in glasses

    NASA Technical Reports Server (NTRS)

    Markova, D.

    1985-01-01

    The photometric determination for boron trioxide is described in amounts of 0-75 micrograms B2O3 with an azomethin H reagent. The yellow colored complex which occurs in a medium held at a pH of 4.5 was measured in light of a wavelength of 415 nm.

  8. Sulfuric Acid on Europa

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Frozen sulfuric acid on Jupiter's moon Europa is depicted in this image produced from data gathered by NASA's Galileo spacecraft. The brightest areas, where the yellow is most intense, represent regions of high frozen sulfuric acid concentration. Sulfuric acid is found in battery acid and in Earth's acid rain.

    This image is based on data gathered by Galileo's near infrared mapping spectrometer.

    Europa's leading hemisphere is toward the bottom right, and there are enhanced concentrations of sulfuric acid in the trailing side of Europa (the upper left side of the image). This is the face of Europa that is struck by sulfur ions coming from Jupiter's innermost moon, Io. The long, narrow features that crisscross Europa also show sulfuric acid that may be from sulfurous material extruded in cracks.

    Galileo, launched in 1989, has been orbiting Jupiter and its moons since December 1995. JPL manages the Galileo mission for NASA's Office of Space Science, Washington DC. JPL is a division of the California Institute of Technology, Pasadena, CA.

  9. Cytoplasmic sulfur trafficking in sulfur-oxidizing prokaryotes.

    PubMed

    Dahl, Christiane

    2015-04-01

    Persulfide groups are chemically versatile and participate in a wide array of biochemical pathways. Although it is well documented that persulfurated proteins supply a number of important and elaborate biosynthetic pathways with sulfane sulfur, it is far less acknowledged that the enzymatic generation of persulfidic sulfur, the successive transfer of sulfur as a persulfide between multiple proteins, and the oxidation of sulfane sulfur in protein-bound form are also essential steps during dissimilatory sulfur oxidation in bacteria and archaea. Here, the currently available information on sulfur trafficking in sulfur oxidizing prokaryotes is reviewed, and the idea is discussed that sulfur is always presented to cytoplasmic oxidizing enzymes in a protein-bound form, thus preventing the occurrence of free sulfide inside of the prokaryotic cell. Thus, sulfur trafficking emerges as a central element in sulfur-oxidizing pathways, and TusA homologous proteins appear to be central and common elements in these processes.

  10. Electron Irradiation of Carbon Disulfide-Oxygen Ices: Toward the Formation of Sulfur-bearing Molecules in Interstellar Ices

    NASA Astrophysics Data System (ADS)

    Maity, Surajit; Kaiser, Ralf I.

    2013-08-01

    The formation of sulfur-bearing molecules in interstellar ices was investigated during the irradiation of carbon disulfide (CS2)-oxygen (O2) ices with energetic electrons at 12 K. The irradiation-induced chemical processing of these ices was monitored online and in situ via Fourier transform infrared spectroscopy to probe the newly formed products quantitatively. The sulfur-bearing molecules produced during the irradiation were sulfur dioxide (SO2), sulfur trioxide (SO3), and carbonyl sulfide (OCS). Formations of carbon dioxide (CO2), carbon monoxide (CO), and ozone (O3) were observed as well. To fit the temporal evolution of the newly formed products and to elucidate the underlying reaction pathways, kinetic reaction schemes were developed and numerical sets of rate constants were derived. Our studies suggest that carbon disulfide (CS2) can be easily transformed to carbonyl sulfide (OCS) via reactions with suprathermal atomic oxygen (O), which can be released from oxygen-containing precursors such as water (H2O), carbon dioxide (CO2), and/or methanol (CH3OH) upon interaction with ionizing radiation. This investigation corroborates that carbonyl sulfide (OCS) and sulfur dioxide (SO2) are the dominant sulfur-bearing molecules in interstellar ices.

  11. ELECTRON IRRADIATION OF CARBON DISULFIDE-OXYGEN ICES: TOWARD THE FORMATION OF SULFUR-BEARING MOLECULES IN INTERSTELLAR ICES

    SciTech Connect

    Maity, Surajit; Kaiser, Ralf I.

    2013-08-20

    The formation of sulfur-bearing molecules in interstellar ices was investigated during the irradiation of carbon disulfide (CS{sub 2})-oxygen (O{sub 2}) ices with energetic electrons at 12 K. The irradiation-induced chemical processing of these ices was monitored online and in situ via Fourier transform infrared spectroscopy to probe the newly formed products quantitatively. The sulfur-bearing molecules produced during the irradiation were sulfur dioxide (SO{sub 2}), sulfur trioxide (SO{sub 3}), and carbonyl sulfide (OCS). Formations of carbon dioxide (CO{sub 2}), carbon monoxide (CO), and ozone (O{sub 3}) were observed as well. To fit the temporal evolution of the newly formed products and to elucidate the underlying reaction pathways, kinetic reaction schemes were developed and numerical sets of rate constants were derived. Our studies suggest that carbon disulfide (CS{sub 2}) can be easily transformed to carbonyl sulfide (OCS) via reactions with suprathermal atomic oxygen (O), which can be released from oxygen-containing precursors such as water (H{sub 2}O), carbon dioxide (CO{sub 2}), and/or methanol (CH{sub 3}OH) upon interaction with ionizing radiation. This investigation corroborates that carbonyl sulfide (OCS) and sulfur dioxide (SO{sub 2}) are the dominant sulfur-bearing molecules in interstellar ices.

  12. Sulfur Dioxide Designations

    EPA Pesticide Factsheets

    This area provides information on the process EPA, the states, and the tribes follow to designate areas as attainment (meeting) or nonattainment (not meeting) the sulfur dioxide air quality standards.

  13. Sulfur compounds in coal

    NASA Technical Reports Server (NTRS)

    Attar, A.; Corcoran, W. H.

    1977-01-01

    The literature on the chemical structure of the organic sulfur compounds (or functional groups) in coal is reviewed. Four methods were applied in the literature to study the sulfur compounds in coal: direct spectrometric and chemical analysis, depolymerization in drastic conditions, depolymerization in mild conditions, and studies on simulated coal. The data suggest that most of the organic sulfur in coal is in the form of thiophenic structures and aromatic and aliphatic sulfides. The relative abundance of the sulfur groups in bituminous coal is estimated as 50:30:20%, respectively. The ratio changes during processing and during the chemical analysis. The main effects are the transformation during processing of sulfides to the more stable thiophenic compounds and the elimination of hydrogen sulfide.

  14. Sulfur cycling in freshwater sediments

    NASA Technical Reports Server (NTRS)

    Klug, M. J.

    1985-01-01

    Organic sulfur containing compounds represent greater than 80% of the total sulfur in sediments of eutrophic freshwater lakes. Although sedimentary sulfur is predominantly in the form of organic compounds, more sulfur is transformed by sulfate reduction than by any other process. Rates of sulfate reduction in these sediments average 7 mmol/sq m/day. This rate is 19 times greater than the net rate of production of inorganic sulfur from organic compounds on an annual basis.

  15. Separation of sulfur isotopes

    DOEpatents

    DeWitt, Robert; Jepson, Bernhart E.; Schwind, Roger A.

    1976-06-22

    Sulfur isotopes are continuously separated and enriched using a closed loop reflux system wherein sulfur dioxide (SO.sub.2) is reacted with sodium hydroxide (NaOH) or the like to form sodium hydrogen sulfite (NaHSO.sub.3). Heavier sulfur isotopes are preferentially attracted to the NaHSO.sub.3, and subsequently reacted with sulfuric acid (H.sub.2 SO.sub.4) forming sodium hydrogen sulfate (NaHSO.sub.4) and SO.sub.2 gas which contains increased concentrations of the heavier sulfur isotopes. This heavy isotope enriched SO.sub.2 gas is subsequently separated and the NaHSO.sub.4 is reacted with NaOH to form sodium sulfate (Na.sub.2 SO.sub.4) which is subsequently decomposed in an electrodialysis unit to form the NaOH and H.sub.2 SO.sub.4 components which are used in the aforesaid reactions thereby effecting sulfur isotope separation and enrichment without objectionable loss of feed materials.

  16. Nitrogen oxides, sulfur trioxide, and mercury emissions during oxy-fuel fluidized bed combustion of Victorian brown coal.

    PubMed

    Roy, Bithi; Chen, Luguang; Bhattacharya, Sankar

    2014-12-16

    This study investigates, for the first time, the NOx, N2O, SO3, and Hg emissions from combustion of a Victorian brown coal in a 10 kWth fluidized bed unit under oxy-fuel combustion conditions. Compared to air combustion, lower NOx emissions and higher N2O formation were observed in the oxy-fuel atmosphere. These NOx reduction and N2O formations were further enhanced with steam in the combustion environment. The NOx concentration level in the flue gas was within the permissible limit in coal-fired power plants in Victoria. Therefore, an additional NOx removal system will not be required using this coal. In contrast, both SO3 and gaseous mercury concentrations were considerably higher under oxy-fuel combustion compared to that in the air combustion. Around 83% of total gaseous mercury released was Hg(0), with the rest emitted as Hg(2+). Therefore, to control harmful Hg(0), a mercury removal system may need to be considered to avoid corrosion in the boiler and CO2 separation units during the oxy-fuel fluidized-bed combustion using this coal.

  17. Corrosion-resistant sulfur concretes

    NASA Astrophysics Data System (ADS)

    McBee, W. C.; Sullivan, T. A.; Jong, B. W.

    1983-04-01

    Sulfur concretes have been developed by the Bureau of Mines as construction materials with physical and mechanical properties that suit them for use in acid and salt corrosive environments where conventional concretes fail. Mixture design methods were established for preparing sulfur concretes using different types of aggregates and recently developed mixed-modified sulfur cements. Bench-scale testing of the sulfur concretes has shown their potential value. Corrosion resistance, strength, and durability of sulfur concrete are superior to those of conventional materials. Field in situ evaluation tests of the sulfur concretes as replacement for conventional concrete materials are in progress in corrosive areas of 24 commercial chemical, fertilizer, and metallurgical plants.

  18. Sodium sulfur battery seal

    DOEpatents

    Mikkor, Mati

    1981-01-01

    This disclosure is directed to an improvement in a sodium sulfur battery construction in which a seal between various battery compartments is made by a structure in which a soft metal seal member is held in a sealing position by holding structure. A pressure applying structure is used to apply pressure on the soft metal seal member when it is being held in sealing relationship to a surface of a container member of the sodium sulfur battery by the holding structure. The improvement comprises including a thin, well-adhered, soft metal layer on the surface of the container member of the sodium sulfur battery to which the soft metal seal member is to be bonded.

  19. Advanced sulfur control concepts

    SciTech Connect

    Harrison, D.P.; Lopez-Ortiz, A.; White, J.D.; Groves, F.R. Jr.

    1995-11-01

    The primary objective of this study is the direct production of elemental sulfur during the regeneration of high temperature desulfurization sorbents. Three possible regeneration concepts were identified as a result of a literature search. The potential for elemental sulfur production from a number of candidate metal oxide sorbents using each regeneration concept was evaluated on the basis of a thermodynamic analysis. Two candidate sorbents, Fe{sub 2}O{sub 3} and CeO{sub 2} were chosen for experimental testing. The experimental test program using both electrobalance and fixed-bed reactor sis now getting underway. The objective is to determine reaction conditions--temperature, pressure, space velocity, and regeneration feed gas composition--which will maximize the yield of elemental sulfur in the regeneration product gas. Experimental results are to be used to define a conceptual desulfurization-regeneration process and to provide a preliminary economic evaluation.

  20. Summary of the Preliminary Analysis of Savannah River Depleted Uranium Trioxide

    SciTech Connect

    NSTec Environmental Management

    2010-10-13

    This report summarizes a preliminary special analysis of the Savannah River Depleted Uranium Trioxide waste stream (SVRSURANIUM03, Revision 2). The analysis is considered preliminary because a final waste profile has not been submitted for review. The special analysis is performed to determine the acceptability of the waste stream for shallow land burial at the Area 5 Radioactive Waste Management Site (RWMS) at the Nevada National Security Site (NNSS). The Savannah River Depleted Uranium Trioxide waste stream requires a special analysis because the waste stream’s sum of fractions exceeds one. The 99Tc activity concentration is 98 percent of the NNSS Waste Acceptance Criteria and the largest single contributor to the sum of fractions.

  1. Treatment of Internal Resorption with Mineral Trioxide Aggregates: A Case Report

    PubMed Central

    Yadav, Pankaj; Rao, Yogesh; Jain, Anurag; Relhan, Nikhil; Gupta, Sandeep

    2013-01-01

    Tooth resorption is a common sequel which follows injuries or irritation to the periodontal ligament and/or tooth pulp. The course of tooth resorption involves an elaborate interaction among inflammatory cells, resorbing cells, and hard tissue structures. The key cells which are involved in resorption are multi–nucleated giant cells. Internal root resorptions are usually non–symptomatic and they are discovered occasionally through periapical radiographs, which reveal very defined and regular outlines. Many techniques and materials have been used to fill internal resorptive defects. Among them, Mineral Trioxide Aggregates (MTAs) have satisfactory properties, which include: biocompatibility, a favourable sealing ability, mechanical strength and a capacity to promote a periradicular tissue healing. Thus, a Mineral Trioxide Aggregate (MTA) repair of a maxillary left central incisor tooth with an inflammatory resorptive defect, in the middle third of the root canal, has been reported here. PMID:24298543

  2. [Periapical regeneration. About one case of necrotic immature tooth treated with mineral trioxide aggregate (MTA)].

    PubMed

    Dhaimy, S; Lahlou, K; Karami, M; Elmerini, H; Elouazzani, A

    2013-09-01

    Therapeutic of apexification with calcium hydroxide has been extensively used in clinical practice, but this technique has some drawbacks (long duration of treatment, weakening of the radicular walls). Different studies have proposed to close the apex opened with MTA (Mineral trioxide Aggregate) which is biocompatible, bacteriostatic, this material induces regeneration of the periapical region through the formation of cementum, bone and periodontal ligament (1, 2). This case report describes the technique of setting up in a single step of the Mineral trioxide Aggregate as an apical barrier for immature permanent roots. This method has allowed us an immediate apical sealing and a root canal filling and a coronary restore permanently as soon as possible. The radiological control confirmed that this type of apexification could be successful with periapical regeneration ad-integrum.

  3. Catalyst for the reduction of sulfur dioxide to elemental sulfur

    DOEpatents

    Jin, Yun; Yu, Qiquan; Chang, Shih-Ger

    1996-01-01

    The inventive catalysts allow for the reduction of sulfur dioxide to elemental sulfur in smokestack scrubber environments. The catalysts have a very high sulfur yield of over 90% and space velocity of 10,000 h.sup.-1. They also have the capacity to convert waste gases generated during the initial conversion into elemental sulfur. The catalysts have inexpensive components, and are inexpensive to produce. The net impact of the invention is to make this technology practically available to industrial applications.

  4. Comparison of radiation shielding ratios of nano-sized bismuth trioxide and molybdenum

    NASA Astrophysics Data System (ADS)

    Cho, J. H.; Kim, M. S.; Rhim, J. D.

    2015-07-01

    In this study, radiation shielding fibers using non-hazardous nano-sized bismuth trioxide and molybdenum instead of lead were developed and evaluated. Among the elements with high densities and atomic numbers, non-hazardous elements such as bismuth trioxide and molybdenum were chosen as a shielding element. Then, bismuth trioxide (Bi2O3) with average particle size 1-500 µm was ball milled for 10 min to produce a powdered form of nanoparticles with average particle size of 10-100 nm. Bismuth trioxide nanoparticles were dispersed to make a colloidal suspension, followed by spreading and hardening onto one or two sides of fabric, to create the radiation shielding fabric. The thicknesses of the shielding sheets using nano-sized bismuth and molybdenum were 0.4 and 0.7 mm. According to the lead equivalent test of X-ray shielding products suggested by KS, the equivalent dose was measured, followed by calculation of the shielding rate. The shielding rate of bismuth with 0.4 mm thickness and at 50 kVp was 90.5%, which is comparable to lead of 0.082 mm thickness. The shielding rate of molybdenum was 51.89%%, which is comparable to lead of 0.034 mm. At a thickness of 0.7 mm, the shielding rate of bismuth was 98.73%, equivalent to 0.101 mm Pb, whereas the shielding rate of molybdenum was 74.68%, equivalent to 0.045 mm Pb. In conclusion, the radiation shielding fibers using nano-sized bismuth developed in this study are capable of reducing radiation exposure by X-ray and its low-dose scatter ray.

  5. The Charge and Discharge Behavior of Molybdenum Trioxide Electrodes in Lithium Perchlorate-Propylene Carbonate Electrolyte.

    DTIC Science & Technology

    1980-07-01

    AMM/§ Diet. specialAK f* I, THE CHARGE AND DISCHARGE BEHAVIOR OF MOLYBDENUM TRIOXIDE ELECTRODES IN LITHIUM PERCHLORATE-PROPYLENE CARBONATE ELECTROLYTE...SHE). Thus, the propylene carbonate oxidation potential is +3.145 V versus SHE or since the potential of the reversible lithium electrode in propylene... carbonate is -3.265 V versus the SHE potential, the solvent oxidation potential should be +6.4 V versus lithium . Thus, another anodic process must be

  6. Optical characteristics of aerosol trioxide dialuminum at the IR wavelength range

    NASA Astrophysics Data System (ADS)

    Voitsekhovskaya, O. K.; Shefer, O. V.; Kashirskii, D. E.

    2015-11-01

    In this work, a numerical study of the transmission function, extinction coefficient, scattering coefficient, and absorption coefficient of the aerosol generated by the jet engine emissions was performed. Analyzing the calculation results of the IR optical characteristics of anthropogenic emissions containing the dialuminum trioxide was carried out. The spectral features of the optical characteristics of the medium caused by the average size, concentration and complex refractive index of the particles were illustrated.

  7. Method for preventing sulfur emissions from vessels containing molten sulfur

    SciTech Connect

    Hass, R. H.

    1984-10-23

    Emissions from sulfur pits or other vessels containing molten sulfur are prevented or minimized by use of an air purge drawn into the vessel from the atmosphere and subsequently utilized as a portion of the oxidant required in a process for oxidizing hydrogen sulfide to elemental sulfur.

  8. Effects of arsenic trioxide inhalation exposure on pulmonary antibacterial defenses in mice

    SciTech Connect

    Aranyi, C.; Bradof, J.N.; O'Shea, W.J.; Graham, J.A.; Miller, F.J.

    1985-01-01

    The effects of single and multiple (5 and 20) 3-h inhalation exposures to aerosols of arsenic trioxide on the pulmonary defense system of mice were investigated. Arsenic trioxide mist was generated from an aqueous solution and dried to produce particulate aerosols of 0. 4 micron mass median aerodynamic diameter. Aerosol mass concentration ranged from 125 to 1000 micrograms As/m3. Effects of the exposures were evaluated by determination of changes in susceptibility to experimentally induced streptococcal aerosol infection and in pulmonary bactericidal activity to /sup 35/S-labeled Klebsiella pneumoniae. Significant increases in mortality due to the infectious challenge and decreases in bactericidal activity were seen after single 3-h exposures to 270, 500, and 940 micrograms As/m3. Similarly, 5 or 20 multiple 3-h exposures to 500 micrograms As/m3 produced consistently significant increases in mortality and decreases in pulmonary bactericidal activity. At 125 or 250 micrograms As/m3, a decrease in bactericidal activity was seen only after 20 exposures to 250 micrograms/m3. Results from earlier studies with an arsenic-containing copper smelter dust were compared to these data. The possibility of the development of adaptation during multiple exposures to arsenic trioxide is also considered.

  9. The Effect of Tungsten Trioxide Thin Films at Ferroelectric-Electrode Boundaries on Fatigue Behaviour

    NASA Astrophysics Data System (ADS)

    Baxter, Paul; Bowman, Robert M.; Gregg, J. Marty

    2008-05-01

    A conventional thin film capacitor heterostructure, consisting of sol-gel deposited lead zirconium titanate (PZT) layers with sputtered platinum top and bottom electrodes, was subjected to fatiguing pulses at a variety of frequencies. The fatigue characteristics were compared to those of a similarly processed capacitor in which a ˜20 nm tungsten trioxide layer had been deposited, using pulsed laser deposition, between the ferroelectric and upper electrode. The expectation was that, because of its ability to accommodate considerable oxygen non-stoichiometry, tungsten trioxide (WO3) might act as an efficient sink for any oxygen vacancies flushed to the electrode-ferroelectric boundary layer during repetitive switching, and hence would improve the fatigue characteristics of the thin film capacitor. However, it was found that, in general, the addition of tungsten trioxide actually increases the rate of fatigue. It appears that any potential benefit from the WO3, in terms of absorbing oxygen vacancies, is far outweighed by it causing dramatically increased charge injection in the system.

  10. Efficient photoelectrochemical hydrogen production from bismuth vanadate-decorated tungsten trioxide helix nanostructures.

    PubMed

    Shi, Xinjian; Choi, Il Yong; Zhang, Kan; Kwon, Jeong; Kim, Dong Yeong; Lee, Ja Kyung; Oh, Sang Ho; Kim, Jong Kyu; Park, Jong Hyeok

    2014-09-02

    Tungsten trioxide/bismuth vanadate heterojunction is one of the best pairs for solar water splitting, but its photocurrent densities are insufficient. Here we investigate the advantages of using helical nanostructures in photoelectrochemical solar water splitting. A helical tungsten trioxide array is fabricated on a fluorine-doped tin oxide substrate, followed by subsequent coating with bismuth vanadate/catalyst. A maximum photocurrent density of ~5.35±0.15 mA cm(-2) is achieved at 1.23 V versus the reversible hydrogen electrode, and related hydrogen and oxygen evolution is also observed from this heterojunction. Theoretical simulations and analyses are performed to verify the advantages of this helical structure. The combination of effective light scattering, improved charge separation and transportation, and an enlarged contact surface area with electrolytes due to the use of the bismuth vanadate-decorated tungsten trioxide helical nanostructures leads to the highest reported photocurrent density to date at 1.23 V versus the reversible hydrogen electrode, to the best of our knowledge.

  11. Efficient photoelectrochemical hydrogen production from bismuth vanadate-decorated tungsten trioxide helix nanostructures

    NASA Astrophysics Data System (ADS)

    Shi, Xinjian; Choi, Il Yong; Zhang, Kan; Kwon, Jeong; Kim, Dong Yeong; Lee, Ja Kyung; Oh, Sang Ho; Kim, Jong Kyu; Park, Jong Hyeok

    2014-09-01

    Tungsten trioxide/bismuth vanadate heterojunction is one of the best pairs for solar water splitting, but its photocurrent densities are insufficient. Here we investigate the advantages of using helical nanostructures in photoelectrochemical solar water splitting. A helical tungsten trioxide array is fabricated on a fluorine-doped tin oxide substrate, followed by subsequent coating with bismuth vanadate/catalyst. A maximum photocurrent density of ~5.35±0.15 mA cm-2 is achieved at 1.23 V versus the reversible hydrogen electrode, and related hydrogen and oxygen evolution is also observed from this heterojunction. Theoretical simulations and analyses are performed to verify the advantages of this helical structure. The combination of effective light scattering, improved charge separation and transportation, and an enlarged contact surface area with electrolytes due to the use of the bismuth vanadate-decorated tungsten trioxide helical nanostructures leads to the highest reported photocurrent density to date at 1.23 V versus the reversible hydrogen electrode, to the best of our knowledge.

  12. Electrosprayed molybdenum trioxide aqueous solution and its application in organic photovoltaic cells.

    PubMed

    Suzuki, Katsumi; Fukuda, Takeshi; Liao, Yingjie

    2014-01-01

    A molybdenum trioxide thin film with smooth surface and uniform thickness was successfully achieved by an electrospray deposition method using an aqueous solution with a drastically low concentration of 0.05 wt%. Previous papers demonstrated that an additive solvent technique is useful for depositing the thin film by the electrospray deposition, and the high vapor pressure and a low surface tension of an additive solvent were found to be important factors. As a result, the smooth molybdenum trioxide thin film was obtained when the acetonitrile was used as the additive solvent. Furthermore, the vapor pressure of acetone is much higher than that of aqueous solution, and this indicates that the acetone is easily evaporated after spraying from the glass capillary. By optimizing a concentration of acetone in the molybdenum aqueous solution, a minimum root mean square roughness of the MoO3 thin film became 3.7 nm. In addition, an organic photovoltaic cell was also demonstrated using the molybdenum trioxide as a hole transport layer. Highest photoconversion efficiency was 1.72%, a value comparable to that using conventional thermal evaporation process even though the aqueous solution was used for the solution process. The photovonversion efficiency was not an optimized value, and the higher value can be achieved by optimizing the coating condition of the active layer.

  13. Setting expansion of gray and white mineral trioxide aggregate and Portland cement.

    PubMed

    Storm, Buffy; Eichmiller, Frederick C; Tordik, Patricia A; Goodell, Gary G

    2008-01-01

    One possible reason for the sealing ability of mineral trioxide aggregate (MTA) is its slight expansion upon setting. Both gray mineral trioxide aggregate (GMTA) and white mineral trioxide aggregate (WMTA) are composed of approximately 75% Portland cement (PC). WMTA differs from GMTA in its lower content of tetracalcium aluminoferrite. This difference in composition may affect setting expansion. The purpose of this study was to compare the hydroscopic linear setting expansions of GMTA, WMTA, and PC with a new device. Materials were mixed with water, placed into a cylindrical mold, and covered with sterile water or Hank's balanced salt solution (HBSS). Expansion changes were measured by using a linear variable displacement transformer dilatometer. One-way analysis of variance and post hoc tests (alpha = 0.05) showed the mean expansion at 24 hours was 1.02% for GMTA, 0.29% for PC, and 0.08% for WMTA in water immersion and 0.68% for GMTA and 0.11% for WMTA in HBSS immersion. GMTA expanded significantly more than WMTA in either water or HBSS immersion.

  14. Pyrolysis of waste electrical and electronic equipment: effect of antinomy trioxide on the pyrolysis of styrenic polymers.

    PubMed

    Hall, W J; Bhaskar, T; Merpati, N M M; Muto, A; Sakata, Y; Williams, P T

    2007-09-01

    This work has investigated the effect that antimony trioxide has on the pyrolysis of styrenic polymers and the effect that different types of brominated flame retardants used in plastics have on the composition of the pyrolysis products. Brominated high impact polystyrene (Br-HIPS) which contained either 5% or 0% antimony trioxide and either decabromodiphenyl oxide (DDO) or decabromodiphenyl ethane (DDE) was pyrolysed in a fixed bed reactor at 430 degrees C. Some experiments on the fixed bed reactor involved mixing the Br-HIPS with polystyrene. The gaseous products were analysed by GC-FID and GC-TCD and it was found that antimony trioxide caused an increase in the proportion of ethane and ethene and suppressed the proportion of butane and butene. When DDE was the flame retardant increased proportions of ethane and ethene were found in the pyrolysis gas compared to when DDO used. When polystyrene was mixed with the Br-HIPS it suppressed the trends observed in the gas composition during the pyrolysis of Br-HIPS. The pyrolysis oils were characterised using FT-IR, GC-MS, GC-FID, and GC-ECD. It was found that the plastic which did not contain antimony trioxide pyrolysed to form mainly toluene, ethylbenzene, styrene, cumene, and alpha-methylstyrene. The oils produced from the pyrolysis of the plastic that contained antimony trioxide did not contain any styrene or alpha-methylstyrene, but instead contained greater concentrations of ethylbenzene and cumene. The absence of styrene and alpha-methylstyrene from the pyrolysis oil occurred even when the Br-HIPS was mixed with polystyrene. GC-ECD analysis of the oils showed that the plastics which did not contain antimony trioxide pyrolysed to form (1-bromoethyl)benzene, which was totally absent from the pyrolysis oils when antimony trioxide was present in the plastic.

  15. Zeolites Remove Sulfur From Fuels

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E.; Sharma, Pramod K.

    1991-01-01

    Zeolites remove substantial amounts of sulfur compounds from diesel fuel under relatively mild conditions - atmospheric pressure below 300 degrees C. Extracts up to 60 percent of sulfur content of high-sulfur fuel. Applicable to petroleum refineries, natural-gas processors, electric powerplants, and chemical-processing plants. Method simpler and uses considerably lower pressure than current industrial method, hydro-desulfurization. Yields cleaner emissions from combustion of petroleum fuels, and protects catalysts from poisoning by sulfur.

  16. Process for forming sulfuric acid

    DOEpatents

    Lu, Wen-Tong P.

    1981-01-01

    An improved electrode is disclosed for the anode in a sulfur cycle hydrogen generation process where sulfur dioxie is oxidized to form sulfuric acid at the anode. The active compound in the electrode is palladium, palladium oxide, an alloy of palladium, or a mixture thereof. The active compound may be deposited on a porous, stable, conductive substrate.

  17. Sodium sulfur battery seal

    DOEpatents

    Topouzian, Armenag

    1980-01-01

    This invention is directed to a seal for a sodium sulfur battery in which a flexible diaphragm sealing elements respectively engage opposite sides of a ceramic component of the battery which separates an anode compartment from a cathode compartment of the battery.

  18. Meteoritic Sulfur Isotopic Analysis

    NASA Technical Reports Server (NTRS)

    Thiemens, Mark H.

    1996-01-01

    Funds were requested to continue our program in meteoritic sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta(sup 33), delta(sup 34)S, delta(sup 36)S isotopic analysis were improved. Analysis of sub milligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron meteorites. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.

  19. Sulfur Dioxide Pollution Monitor.

    ERIC Educational Resources Information Center

    National Bureau of Standards (DOC), Washington, DC.

    The sulfur dioxide pollution monitor described in this document is a government-owed invention that is available for licensing. The background of the invention is outlined, and drawings of the monitor together with a detailed description of its function are provided. A sample stream of air, smokestack gas or the like is flowed through a…

  20. SULFUR POLYMER ENCAPSULATION.

    SciTech Connect

    KALB, P.

    2001-08-22

    Sulfur polymer cement (SPC) is a thermoplastic polymer consisting of 95 wt% elemental sulfur and 5 wt% organic modifiers to enhance long-term durability. SPC was originally developed by the U.S. Bureau of Mines as an alternative to hydraulic cement for construction applications. Previous attempts to use elemental sulfur as a construction material in the chemical industry failed due to premature degradation. These failures were caused by the internal stresses that result from changes in crystalline structure upon cooling of the material. By reacting elemental sulfur with organic polymers, the Bureau of Mines developed a product that successfully suppresses the solid phase transition and significantly improves the stability of the product. SPC, originally named modified sulfur cement, is produced from readily available, inexpensive waste sulfur derived from desulfurization of both flue gases and petroleum. The commercial production of SPC is licensed in the United States by Martin Resources (Odessa, Texas) and is marketed under the trade name Chement 2000. It is sold in granular form and is relatively inexpensive ({approx}$0.10 to 0.12/lb). Application of SPC for the treatment of radioactive, hazardous, and mixed wastes was initially developed and patented by Brookhaven National Laboratory (BNL) in the mid-1980s (Kalb and Colombo, 1985; Colombo et al., 1997). The process was subsequently investigated by the Commission of the European Communities (Van Dalen and Rijpkema, 1989), Idaho National Engineering Laboratory (Darnell, 1991), and Oak Ridge National Laboratory (Mattus and Mattus, 1994). SPC has been used primarily in microencapsulation applications but can also be used for macroencapsulation of waste. SPC microencapsulation has been demonstrated to be an effective treatment for a wide variety of wastes, including incinerator hearth and fly ash; aqueous concentrates such as sulfates, borates, and chlorides; blowdown solutions; soils; and sludges. It is not

  1. Hydrate sulfuric acid after sulfur implantation in water ice

    NASA Astrophysics Data System (ADS)

    Strazzulla, G.; Baratta, G. A.; Leto, G.; Gomis, O.

    2007-12-01

    For many years an ongoing research program performed at our laboratory has had the aim to investigate the implantation of reactive ions in ices relevant to planetology by using IR spectroscopy. We present new results obtained by implanting 200 keV sulfur ions into water ice at 80 K. We have looked at the formation of sulfur-bearing molecules such as sulfuric acid, sulfur dioxide and hydrogen sulfide. We find that hydrated sulfuric acid is formed with high yield ( 0.65±0.1 molecules/ion). An upper limit to the production yield of SO 2 ( Y⩽0.025 molecules/ion) has been estimated; no hydrogen sulfide has been detected. The formation of hydrogen peroxide is confirmed. Ozone is not detected. The results are discussed relevant to the inquiry on the radiolytic sulfur cycle considered responsible for the formation of sulfur-bearing molecules on the surfaces of the Galilean satellites. We demonstrate that sulfur implantation efficiently forms hydrated sulfuric acid whose observed abundance is explained as caused by an exogenic process. It is more difficult to say if the observed sulfur dioxide is quantitatively supported by only sulfur implantation; additional experimental studies are necessary along with direct observations, especially at UV wavelengths such as those that could be performed by instruments on board Hubble Space Telescope or by the forthcoming World Space Observatory (WSO/UV).

  2. Inorganic sulfur oxidizing system in green sulfur bacteria.

    PubMed

    Sakurai, Hidehiro; Ogawa, Takuro; Shiga, Michiko; Inoue, Kazuhito

    2010-06-01

    Green sulfur bacteria use various reduced sulfur compounds such as sulfide, elemental sulfur, and thiosulfate as electron donors for photoautotrophic growth. This article briefly summarizes what is known about the inorganic sulfur oxidizing systems of these bacteria with emphasis on the biochemical aspects. Enzymes that oxidize sulfide in green sulfur bacteria are membrane-bound sulfide-quinone oxidoreductase, periplasmic (sometimes membrane-bound) flavocytochrome c sulfide dehydrogenase, and monomeric flavocytochrome c (SoxF). Some green sulfur bacteria oxidize thiosulfate by the multienzyme system called either the TOMES (thiosulfate oxidizing multi-enzyme system) or Sox (sulfur oxidizing system) composed of the three periplasmic proteins: SoxB, SoxYZ, and SoxAXK with a soluble small molecule cytochrome c as the electron acceptor. The oxidation of sulfide and thiosulfate by these enzymes in vitro is assumed to yield two electrons and result in the transfer of a sulfur atom to persulfides, which are subsequently transformed to elemental sulfur. The elemental sulfur is temporarily stored in the form of globules attached to the extracellular surface of the outer membranes. The oxidation pathway of elemental sulfur to sulfate is currently unclear, although the participation of several proteins including those of the dissimilatory sulfite reductase system etc. is suggested from comparative genomic analyses.

  3. Relapsed acute promyelocytic leukemia in a hemodialysis-dependent patient treated with arsenic trioxide: a case report

    PubMed Central

    2012-01-01

    Introduction In the relapsed setting, arsenic trioxide remains the backbone of treatment. Scant literature exists regarding treatment of relapsed acute promyelocytic leukemia in patients with renal failure. To the best of our knowledge we are the first to report a safe and effective means of treatment for relapsed acute promyelocytic leukemia in the setting of advanced renal failure, employing titration of arsenic trioxide based on clinical parameters rather than arsenic trioxide levels. Case presentation A 33-year-old Caucasian man with a history of acute promyelocytic leukemia in remission for 3 years, as well as dialysis-dependent chronic renal failure secondary to a solitary kidney and focal segmental glomerulosclerosis and human immunodeficiency virus infection, receiving highly active antiretroviral therapy presented to our hospital with bone marrow biopsy-confirmed relapsed acute promyelocytic leukemia. Arsenic trioxide was begun at a low dose with dose escalation based only on side effect profile monitoring and not laboratory testing for induction as well as maintenance without undue toxicity. Our patient achieved and remains in complete hematologic and molecular remission as of this writing. Conclusion Arsenic trioxide can be used safely and effectively to treat acute promyelocytic leukemia in patients with advanced renal failure using careful monitoring of side effects rather than blood levels of arsenic to guide therapeutic dosing. PMID:23078653

  4. Sulfur plumes off Namibia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Sulfur plumes rising up from the bottom of the ocean floor produce colorful swirls in the waters off the coast of Namibia in southern Africa. The plumes come from the breakdown of marine plant matter by anaerobic bacteria that do not need oxygen to live. This image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on April 24, 2002 Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  5. Spectrophotometric analysis of tooth discolouration induced by mineral trioxide aggregate after final irrigation with sodium hypochlorite: An in vitro study.

    PubMed

    Voveraityte, Valdone; Gleizniene, Simona; Lodiene, Greta; Grabliauskiene, Zivile; Machiulskiene, Vita

    2016-03-09

    The aim of this study was to evaluate specific chromatic alterations induced by white mineral trioxide aggregate after final irrigation with sodium hypochlorite. Sixty specimens were prepared mechanically and filled with mineral trioxide aggregate after different final irrigation protocols: Group 1 - distilled water, Group 2 - sodium hypochlorite followed by distilled water, Group 3 - sodium hypochlorite, only. Colour changes were recorded with a spectrophotometer at baseline, and then after 1, 2 and 4 months. The Commision Internationale de l'éclairage colour system was used and the total colour changes ΔE were calculated. In groups where sodium hypochlorite was used, parameter L* decreased significantly after the first month (Group 2 (P < 0.006), Group 3 (P < 0.009)). Group 3 demonstrated greater colour change ΔE than Group 1, after the first month (P < 0.02). In conclusion, white mineral trioxide aggregate can lead to tooth discolouration by contact with sodium hypochlorite residues in dentinal tubules.

  6. Advanced Sulfur Control Processing

    SciTech Connect

    Gangwal, S.K.; Portzer, J.W.; Turk, B.S.; Gupta, R.

    1996-12-31

    The primary objective of this project is to determine the feasibility of an alternate concept for the regeneration of high temperature desulfurization sorbents in which elemental sulfur, instead of SO{sub 2}, is produced. If successful, this concept will eliminate or alleviate problems caused by the highly exothermic nature of the regeneration reaction, the tendency for metal sulfate formation, and the need to treat the regeneration off-gas to prevent atmospheric SO{sub 2}, emissions. Iron and cerium-based sorbents were chosen on the basis of thermodynamic analysis to determine the feasibility of elemental sulfur production. The ability of both to remove H{sub 2}S during the sulfidation phase is less than that of zinc-based sorbents, and a two-stage desulfurization process will likely be required. Preliminary experimental work used electrobalance reactors to compare the relative rates of reaction of O{sub 2} and H{sub 2}O with FeS. More detailed studies of the regeneration of FeS as well as the sulfidation of CeO{sub 2} and regeneration of Ce{sub 2}O{sub 2}S are being carried out in a laboratory-scale fixed-bed reactor equipped with a unique analytical system which permits semi-continuous analysis of the distribution of elemental sulfur, H{sub 2}S, and SO{sub 2} in the reaction product gas.

  7. Sulfur oxides scrubbing process

    SciTech Connect

    Reeder, P.E.

    1986-07-15

    A process is described for removing sulfur oxides and solid particulates from a gaseous effluent. The steps of the process consist of: contacting within a venturi structure a gaseous effluent containing sulfur oxides with a liquid scrubbing mixture; passing the admixture of the gaseous effluent and liquid scrubbing mixture through a constricted passage of the venturi structure to increase the velocity thereof; separating the admixture into a liquid portion and a gas portion; delivering the gas portion of the separation step to a packed tower beneath the packed section thereof; contacting the gas portion with liquid scrubbing mixture in the packed section of the tower to form a gaseous overhead effluent substantially free of sulfur oxides and a bottoms liquid; combining the bottom liquid from the packed section of the tower with the liquid portion from the separating step to form a combined liquid bottoms; adjusting the pH of the combined liquid bottoms with a basic solution to form a liquid scrubbing mixture, the basic solution selected from the group consisting of alkali metal hydroxides, ammonium hydroxide, and ammonia; and dividing the liquid scrubbing mixture into a tower bottoms products, a first recycle stream providing the liquid scrubbing mixture to the first contacting step, and a second recycle stream providing the liquid scrubbing mixture to the second contacting step.

  8. Lunar Sulfur Capture System

    NASA Technical Reports Server (NTRS)

    Berggren, Mark; Zubrin, Robert; Bostwick-White, Emily

    2013-01-01

    The Lunar Sulfur Capture System (LSCS) protects in situ resource utilization (ISRU) hardware from corrosion, and reduces contaminant levels in water condensed for electrolysis. The LSCS uses a lunar soil sorbent to trap over 98 percent of sulfur gases and about two-thirds of halide gases evolved during hydrogen reduction of lunar soils. LSCS soil sorbent is based on lunar minerals containing iron and calcium compounds that trap sulfur and halide gas contaminants in a fixed-bed reactor held at temperatures between 250 and 400 C, allowing moisture produced during reduction to pass through in vapor phase. Small amounts of Earth-based polishing sorbents consisting of zinc oxide and sodium aluminate are used to reduce contaminant concentrations to one ppm or less. The preferred LSCS configuration employs lunar soil beneficiation to boost concentrations of reactive sorbent minerals. Lunar soils contain sulfur in concentrations of about 0.1 percent, and halogen compounds including chlorine and fluorine in concentrations of about 0.01 percent. These contaminants are released as gases such as H2S, COS, CS2,HCl, and HF during thermal ISRU processing with hydrogen or other reducing gases. Removal of contaminant gases is required during ISRU processing to prevent hardware corrosion, electrolyzer damage, and catalyst poisoning. The use of Earth-supplied, single-use consumables to entirely remove contaminants at the levels existing in lunar soils would make many ISRU processes unattractive due to the large mass of consumables relative to the mass of oxygen produced. The LSCS concept of using a primary sorbent prepared from lunar soil was identified as a method by which the majority of contaminants could be removed from process gas streams, thereby substantially reducing the required mass of Earth-supplied consumables. The LSCS takes advantage of minerals containing iron and calcium compounds that are present in lunar soil to trap sulfur and halide gases in a fixedbed reactor

  9. Sulfur dioxide oxidation induced mechanistic branching and particle formation during the ozonolysis of β-pinene and 2-butene.

    PubMed

    Carlsson, Philip T M; Keunecke, Claudia; Krüger, Bastian C; Maaß, Mona-C; Zeuch, Thomas

    2012-12-05

    Recent studies have suggested that the reaction of stabilised Criegee Intermediates (CIs) with sulfur dioxide (SO(2)), leading to the formation of a carbonyl compound and sulfur trioxide, is a relevant atmospheric source of sulfuric acid. Here, the significance of this pathway has been examined by studying the formation of gas phase products and aerosol during the ozonolysis of β-pinene and 2-butene in the presence of SO(2) in the pressure range of 10 to 1000 mbar. For β-pinene at atmospheric pressure, the addition of SO(2) suppresses the formation of the secondary ozonide and leads to highly increased nopinone yields. A complete consumption of SO(2) is observed at initial SO(2) concentrations below the yield of stabilised CIs. In experiments using 2-butene a significant consumption of SO(2) and additional formation of acetaldehyde are observed at 1 bar. A consistent kinetic simulation of the experimental findings is possible when a fast CI + SO(2) reaction rate in the range of recent direct measurements [Welz et al., Science, 2012, 335, 204] is used. For 2-butene the addition of SO(2) drastically increases the observed aerosol yields at higher pressures. Below 60 mbar the SO(2) oxidation induced particle formation becomes inefficient pointing to the critical role of collisional stabilisation for sulfuric acid controlled nucleation at low pressures.

  10. Monoblock obturation technique for non-vital immature permanent maxillary incisors using mineral trioxide aggregate: results from case series.

    PubMed

    Iqbal, Zahid; Qureshi, Abdul Hakeem

    2014-01-01

    Ten patients presented with non-vital immature teeth for root canal treatment. In all these cases the pre-operative clinical examination revealed apical periodontitis with a buccal sinus tract of endodontic origin. These cases were treated by a mineral trioxide aggregate (MTA) monoblock obturation technique. Follow-up evaluations were performed at 1 - 2 years after treatment. Eight out of 10 cases were associated with periradicular healing at follow-up evaluation. Mineral trioxide aggregate Monoblock obturation technique appears to be a valid material to obtain periradicular healing in teeth with open apices and necrotic pulps.

  11. Catalyst for the reduction of sulfur dioxide to elemental sulfur

    DOEpatents

    Jin, Y.; Yu, Q.; Chang, S.G.

    1996-02-27

    The inventive catalysts allow for the reduction of sulfur dioxide to elemental sulfur in smokestack scrubber environments. The catalysts have a very high sulfur yield of over 90% and space velocity of 10,000 h{sup {minus}1}. They also have the capacity to convert waste gases generated during the initial conversion into elemental sulfur. The catalysts have inexpensive components, and are inexpensive to produce. The net impact of the invention is to make this technology practically available to industrial applications. 21 figs.

  12. Utilization of 'elemental' sulfur by different phototrophic sulfur bacteria (Chromatiaceae, Ectothiorhodospiraceae): A sulfur K-edge XANES spectroscopy study

    NASA Astrophysics Data System (ADS)

    Franz, B.; Lichtenberg, H.; Dahl, C.; Hormes, J.; Prange, A.

    2009-11-01

    Phototrophic sulfur bacteria are generally able to use elemental sulfur as an electron donor for anoxygenic photosynthesis. Elemental sulfur is mainly a mixture of cyclo-octasulfur and polymeric sulfur. The purple sulfur bacterium Allochromatium vinosum strongly prefers the polymeric sulfur fraction showing that sulfur speciation has a strong influence on availability of elemental sulfur. X-ray absorption near edge structure (XANES) spectroscopy was used to investigate whether polymeric sulfur is also the preferred sulfur species in other purple sulfur bacteria belonging to the families Chromatiaceae and Ecothiorodospiraceae. The cultures were fed with 50 mM of elemental sulfur consisting of 68% polymeric sulfur and 30% cyclo-octasulfur. In all cultures, elemental sulfur was converted into intra- or extracellular sulfur globules, respectively, and further oxidized to sulfate. Sulfate concentrations were determined by HPLC and turbidometric assays, respectively. However, the added elemental sulfur was only partly used by the bacteria, one part of the 'elemental sulfur' remained in the cultures and was not taken up. XANES spectroscopy revealed that only the polymeric sulfur fraction was taken up by all cultures investigated. This strongly indicates that polymeric 'chain-like' sulfur is the form preferably used by phototrophic sulfur bacteria.

  13. Photoelectrochemical water splitting at titanium dioxide nanotubes coated with tungsten trioxide

    NASA Astrophysics Data System (ADS)

    Park, Jong Hyeok; Park, O. Ok; Kim, Sungwook

    2006-10-01

    The photocatalytic splitting of water into hydrogen and oxygen using solar light is a potentially clean and renewable source for hydrogen fuel. Titanium oxide nanotubes coated with tungsten oxide were prepared to harvest more solar light for the first time and characterized their water splitting efficiency. The tungsten trioxide coatings significantly enhanced the visible spectrum absorption of the titanium dioxide nanotube array, as well as their solar-spectrum induced photocurrents. For the sample, upon white light illumination at 150mW/cm2, hydrogen gas generated at the overall conversion efficiency of 0.87%.

  14. A patient with progressive multiple myeloma treated successfully with arsenic trioxide after allogeneic bone marrow transplantation.

    PubMed

    Gesundheit, B; Shapira, M Y; Ackerstein, A; Resnik, I B; Bitan, M; Or, R

    2007-01-01

    Multiple myeloma (MM) is an incurable progressive disease. Many therapeutic options are available to delay progression, including autologous and allogeneic bone marrow transplantation. At advanced stages, MM is often refractory to treatment. We report a heavily pretreated patient with graft-versus-host disease after bone marrow transplantations, treated at a terminal stage with a modified protocol for arsenic trioxide (ATO). This patient with poor clinical status tolerated the treatment very well. He had a remarkable clinical response and achieved complete remission. The mechanisms of ATO are presented and the potential role of ATO for MM is discussed.

  15. Mineral trioxide aggregate (MTA) apexification: a novel approach for traumatised young immature permanent teeth

    PubMed Central

    Vijayran, Manisha; Chaudhary, Seema; Manuja, Naveen; Kulkarni, Adwait Uday

    2013-01-01

    Here, we report a case of 9-year-old boy who came with a chief complaint of pain and fractured upper front teeth. Significant history of trauma was revealed 6 months before reporting, during playing at his school time. Proper diagnosis was made with the help of radiological investigations. The available treatment options were discussed with the patient's parents and root canal therapy, using mineral trioxide aggregate, as an apical barrier was carried out in his upper right front teeth. However, later on, the boy was aesthetically rehabilitated in relation to his fractured upper front teeth with the help of post and core and acrylic crown. PMID:23314456

  16. Enthalpies of the formation and decomposition of hydrogen trioxide HOOOH in an aqueous solution

    NASA Astrophysics Data System (ADS)

    Levanov, A. V.; Isaikina, O. Ya.; Lunin, V. V.

    2016-11-01

    The enthalpies of the formation and decomposition of hydrogen trioxide are estimated from the heating curves of peroxide-radical condensates synthesized from gaseous O2 + H2 mixtures. Enthalpy of decomposition H2O3(aq.) → H2O(liq.) + O2(gas) is -31.2 ± 1.5 kcal/mol, and enthalpy of formation Δf H(H2O3, aq.) =-37.5 ± 1.6 kcal/mol. Both values correspond to the temperature range of 240-265 K.

  17. Rethinking the Ancient Sulfur Cycle

    NASA Astrophysics Data System (ADS)

    Fike, David A.; Bradley, Alexander S.; Rose, Catherine V.

    2015-05-01

    The sulfur biogeochemical cycle integrates the metabolic activity of multiple microbial pathways (e.g., sulfate reduction, disproportionation, and sulfide oxidation) along with abiotic reactions and geological processes that cycle sulfur through various reservoirs. The sulfur cycle impacts the global carbon cycle and climate primarily through the remineralization of organic carbon. Over geological timescales, cycling of sulfur is closely tied to the redox state of Earth's exosphere through the burial of oxidized (sulfate) and reduced (sulfide) sulfur species in marine sediments. Biological sulfur cycling is associated with isotopic fractionations that can be used to trace the fluxes through various metabolic pathways. The resulting isotopic data provide insights into sulfur cycling in both modern and ancient environments via isotopic signatures in sedimentary sulfate and sulfide phases. Here, we review the deep-time δ34S record of marine sulfates and sulfides in light of recent advances in understanding how isotopic signatures are generated by microbial activity, how these signatures are encoded in marine sediments, and how they may be altered following deposition. The resulting picture shows a sulfur cycle intimately coupled to ambient carbon cycling, where sulfur isotopic records preserved in sedimentary rocks are critically dependent on sedimentological and geochemical conditions (e.g., iron availability) during deposition.

  18. Method of removing and recovering elemental sulfur from highly reducing gas streams containing sulfur gases

    DOEpatents

    Gangwal, Santosh K.; Nikolopoulos, Apostolos A.; Dorchak, Thomas P.; Dorchak, Mary Anne

    2005-11-08

    A method is provided for removal of sulfur gases and recovery of elemental sulfur from sulfur gas containing supply streams, such as syngas or coal gas, by contacting the supply stream with a catalyst, that is either an activated carbon or an oxide based catalyst, and an oxidant, such as sulfur dioxide, in a reaction medium such as molten sulfur, to convert the sulfur gases in the supply stream to elemental sulfur, and recovering the elemental sulfur by separation from the reaction medium.

  19. Impact of free calcium oxide content of fly ash on dust and sulfur dioxide emissions in a lignite-fired power plant

    SciTech Connect

    Dimitrios Sotiropoulos; Andreas Georgakopoulos; Nestoras Kolovos

    2005-07-01

    Emitted pollutants from the Agios Dimitrios lignite-fired power plant in northern Greece show a very strong linear correlation with the free calcium oxide content of the lignite ash. Dust (fly ash) emissions are positively correlated to free calcium oxide content, whereas sulfur dioxide (SO{sub 2}) emissions are negatively correlated. As a result, at present, the Agios Dimitrios Power Plant operates very strictly within the legislative limits on atmospheric particulate emission. In the study reported, the factors to be considered in assessing the impact of lignite combustion on the environment are presented and evaluated statistically. The ash appears to have a remarkable SO{sub 2} natural dry scrubbing capability when the free calcium oxide content ranges between 4 and 7%. Precipitator operating problems attributable to high ash resistivity can be overcome by injecting sulfur trioxide to reduce the ash resistivity, with, of course, a probable increase in operating costs. 27 refs., 7 figs., 1 tab.

  20. JWA is required for arsenic trioxide induced apoptosis in HeLa and MCF-7 cells via reactive oxygen species and mitochondria linked signal pathway

    SciTech Connect

    Zhou Jinhong; Ye Jian; Zhao Xiaojia; Li Aiping; Zhou Jianwei

    2008-07-01

    Arsenic trioxide, emerging as a standard therapy for refractory acute promyelocytic leukemia, induces apoptosis in a variety of malignant cell lines. JWA, a novel retinoic acid-inducible gene, is known to be involved in apoptosis induced by various agents, for example, 12-O-tetradecanoylphorbol 13-acetate, N-4-hydroxy-phenyl-retinamide and arsenic trioxide. However, the molecular mechanisms underlying how JWA gene is functionally involved in apoptosis remain largely unknown. Herein, our studies demonstrated that treatment of arsenic trioxide produced apoptosis in HeLa and MCF-7 cells in a dose-dependent manner and paralleled with increased JWA expression. JWA expression was dependent upon generation of intracellular reactive oxygen species induced by arsenic trioxide. Knockdown of JWA attenuated arsenic trioxide induced apoptosis, and was accompanied by significantly reduced activity of caspase-9, enhanced Bad phosphorylation and inhibited MEK1/2, ERK1/2 and JNK phosphorylations. Arsenic trioxide induced loss of mitochondrial transmembrane potential was JWA-dependent. These findings suggest that JWA may serve as a pro-apoptotic molecule to mediate arsenic trioxide triggered apoptosis via a reactive oxygen species and mitochondria-associated signal pathway.

  1. 40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level...). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference...

  2. 40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level...). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference...

  3. 40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level...). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference...

  4. 40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level...). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference...

  5. Sulfuric acid as autocatalyst in the formation of sulfuric acid.

    PubMed

    Torrent-Sucarrat, Miquel; Francisco, Joseph S; Anglada, Josep M

    2012-12-26

    Sulfuric acid can act as a catalyst of its own formation. We have carried out a computational investigation on the gas-phase formation of H(2)SO(4) by hydrolysis of SO(3) involving one and two water molecules, and also in the presence of sulfuric acid and its complexes with one and two water molecules. The hydrolysis of SO(3) requires the concurrence of two water molecules, one of them acting as a catalyzer, and our results predict an important catalytic effect, ranging between 3 and 11 kcal·mol(-1) when the catalytic water molecule is substituted by a sulfuric acid molecule or one of its hydrates. In these cases, the reaction products are either bare sulfuric acid dimer or sulfuric acid dimer complexed with a water molecule. There are broad implications from these new findings. The results of the present investigation show that the catalytic effect of sulfuric acid in the SO(3) hydrolysis can be important in the Earth's stratosphere, in the heterogeneous formation of sulfuric acid and in the formation of aerosols, in H(2)SO(4) formation by aircraft engines, and also in understanding the formation of sulfuric acid in the atmosphere of Venus.

  6. Process for removing sulfur from sulfur-containing gases

    DOEpatents

    Rochelle, Gary T.; Jozewicz, Wojciech

    1989-01-01

    The present disclosure relates to improved processes for treating hot sulfur-containing flue gas to remove sulfur therefrom. Processes in accorda The government may own certain rights in the present invention pursuant to EPA Cooperative Agreement CR 81-1531.

  7. Direct Hydrothermal Precipitation of Pyrochlore-Type Tungsten Trioxide Hemihydrate from Alkaline Sodium Tungstate Solution

    NASA Astrophysics Data System (ADS)

    Li, Xiaobin; Li, Jianpu; Zhou, Qiusheng; Peng, Zhihong; Liu, Guihua; Qi, Tiangui

    2012-04-01

    Pyrochlore-type tungsten trioxide hemihydrate (WO3·0.5H2O) powder with the average particle size of 0.5 μm was prepared successfully from the weak alkaline sodium tungstate solution by using organic substances of sucrose or cisbutenedioic acid as the acidification agent. The influences of solution pH and acidification agents on the precipitation process were investigated. The results showed that organic acidification agents such as sucrose and cisbutenedioic acid could improve the precipitation of pyrochlore WO3·0.5H2O greatly from sodium tungstate solution compared with the traditional acidification agent of hydrochloric acid. In addition, the pH value of the hydrothermal system played a critical role in the precipitation process of WO3·0.5H2O, and WO3·0.5H2O precipitation mainly occured in the pH range of 7.0 to 8.5. The precipitation rate of tungsten species in the sodium tungstate solution could reach up to 98 pct under the optimized hydrothermal conditions. This article proposed also the hydrothermal precipitation mechanism of WO3·0.5H2O from the weak alkaline sodium tungstate solution. The novel method reported in this study has a great potential to improve the efficiency of advanced tungsten trioxide-based functional material preparation, as well as for the pollution-reducing and energy-saving tungsten extractive metallurgy.

  8. Capping a Pulpotomy with Calcium Aluminosilicate Cement: Comparison to Mineral Trioxide Aggregates

    PubMed Central

    Kramer, Phillip R.; Woodmansey, Karl F.; White, Robert; Primus, Carolyn M.; Opperman, Lynne A.

    2014-01-01

    Introduction Calcium aluminate cements have shown little affinity for bacterial growth, low toxicity, and immunogenicity when used as a restoration material, but calcium aluminate cements have not been tested in vivo in pulpotomy procedures. Methods To address this question, a calcium aluminate cement (Quick-Set) was tested along with 2 mineral trioxide aggregates, ProRoot MTA and MTA Plus. These cements were used as a capping agent after pulpotomy. Control rats had no pulpotomy, or the pulpotomy was not capped. Proinflammatory cytokines interleukin (IL)-1β and IL-1α were measured, and histology was performed at 30 and 60 days after capping. The nociceptive response was determined by measuring the lengthening of the rat's meal duration. Results and Conclusions: IL-1β and IL-1α concentrations were reduced in the capped teeth, but no differences were observed among the 3 cements. Dentinal bridging could be detected at both 30 and 60 days with each of the 3 cements, and the pulps were still vital 60 days after capping. Meal duration significantly shortened after placement of the 3 different cements, indicating a nociceptive response, but there were no differences among the materials. Calcium aluminate cements had similar properties to mineral trioxide aggregates and is a viable option for pulpotomy procedures. PMID:25146026

  9. Use of Mineral Trioxide Aggregate in Surgical and Conventional Endodontics: A Report of Five Cases

    PubMed Central

    Goswami, Mridula

    2013-01-01

    ABSTRACT Facial trauma that results in fractured, displaced or lost teeth can have significant negative functional, esthetic and psychological effects on children. An acute dental trauma may imply impact to the hard dental tissues and damage to the pulp and periodontium, ultimately leading to partial or total pulp necrosis and/or root resorption. Apexification is a commonly used procedure for treating and preserving immature permanent teeth that have lost pulp vitality. Immature teeth undergoing apexification were earlier filled with calcium hydroxide paste for the purpose of disinfection and induction of an apical calcific barrier. However, certain drawbacks led to the use of mineral trioxide aggregate (MTA) to fill the apical end without the need for calcific barrier formation. This article demonstrates the use of MTA as an apical barrier material for root-end closure in the permanent teeth of five patients. How to cite this article: Gupta S, Goswami M. Use of Mineral Trioxide Aggregate in Surgical and Conventional Endodontics: A Report of Five Cases. Int J Clin Pediatr Dent 2013;6(2): 134-139. PMID:25206209

  10. Sulfur in Cometary Dust

    NASA Technical Reports Server (NTRS)

    Fomenkova, M. N.

    1997-01-01

    The computer-intensive project consisted of the analysis and synthesis of existing data on composition of comet Halley dust particles. The main objective was to obtain a complete inventory of sulfur containing compounds in the comet Halley dust by building upon the existing classification of organic and inorganic compounds and applying a variety of statistical techniques for cluster and cross-correlational analyses. A student hired for this project wrote and tested the software to perform cluster analysis. The following tasks were carried out: (1) selecting the data from existing database for the proposed project; (2) finding access to a standard library of statistical routines for cluster analysis; (3) reformatting the data as necessary for input into the library routines; (4) performing cluster analysis and constructing hierarchical cluster trees using three methods to define the proximity of clusters; (5) presenting the output results in different formats to facilitate the interpretation of the obtained cluster trees; (6) selecting groups of data points common for all three trees as stable clusters. We have also considered the chemistry of sulfur in inorganic compounds.

  11. The charge and discharge behavior of molybdenum trioxide electrodes in lithium perchlorate-propylene carbonate electrolyte. Technical report

    SciTech Connect

    Hunger, H.F.; Ellison, J.E.

    1980-07-01

    The anodic and cathodic behavior of molybdenum trioxide electrodes in various states of lithiation was investigated in 1M LiClO/sub 4/-PC electrolytes at room temperature. A comparison was made between the anodic and cathodic rate capabilities of the electrodes. From cycling experiments at various depths of discharge, cycle life data were obtained. Problems observed after deep discharges are discussed.

  12. Volume efficient sodium sulfur battery

    DOEpatents

    Mikkor, Mati

    1980-01-01

    In accordance with the teachings of this specification, a sodium sulfur battery is formed as follows. A plurality of box shaped sulfur electrodes are provided, the outer surfaces of which are defined by an electrolyte material. Each of the electrodes have length and width dimensions substantially greater than the thicknesses thereof as well as upwardly facing surface and a downwardly facing surface. An electrode structure is contained in each of the sulfur electrodes. A holding structure is provided for holding the plurality of sulfur electrodes in a stacked condition with the upwardly facing surface of one sulfur electrode in facing relationship to the downwardly facing surface of another sulfur electrode thereabove. A small thickness dimension separates each of the stacked electrodes thereby defining between each pair of sulfur electrodes a volume which receives the sodium reactant. A reservoir is provided for containing sodium. A manifold structure interconnects the volumes between the sulfur electrodes and the reservoir. A metering structure controls the flow of sodium between the reservoir and the manifold structure.

  13. Demonstrating Allotropic Modifications of Sulfur.

    ERIC Educational Resources Information Center

    McCarty, Jillian L.; Dragojlovic, Veljko

    2002-01-01

    Shows how a common demonstration that consists of slowly heating sulfur powder in a test tube to illustrate sulfur's allotropic modifications can convince students of conclusions about the moon Io which they often find surprising. Describes the demonstration in full. (Author/MM)

  14. Improve operations and enhance refinery sulfur recovery

    SciTech Connect

    Bourdon, J.C.

    1997-04-01

    Sulfur is a common contaminant in fossil fuels, released when these fuels are combusted. It causes acid rain and other environmental problems. Sulfur emissions have gained worldwide attention, resulting in tighter requirements for sulfur recovery facilities. New technologies and enhancements to existing technologies have emerged as a result. This overview presents many technologies used for sulfur recovery. It is organized around the unit operations of gas and liquid sweetening, sour water stripping, sulfur recovery, sulfur degassing and solidification, tail gas treating, and incineration. New technical and equipment innovations have resulted in sulfur recovery facilities that are more reliable, recover more sulfur, are easier to operate, and reduce capital and operating costs.

  15. In vitro arsenic trioxide induces apoptosis in T cells of asthmatic patients by a Bcl-2 related mechanism.

    PubMed

    Qin, Dong-Yun; Huang, Ren; Wu, Tie

    2008-01-01

    This study examined the effects of arsenic trioxide on apoptosis and interleukin-4 release in T cells of asthmatic patients in vitro and investigated the role of Bcl-2 in the active mechanism. T cells were isolated from asthmatic patients (n = 21) and healthy controls (n = 20), and then treated with arsenic trioxide and dexamethasone. Cell apoptosis was measured using fluorescence microscopy, flow cytometry and a cytochrome c ELISA kit. Interleukin-4 levels in the serum and in supernatants from T cells were quantified by ELISA. Flow cytometric analysis and immunofluorescence studies were performed to determine Bcl-2 expression. T cells of the asthmatic patients (i. e. without treatment) exhibited decelerated spontaneous apoptosis after 24 h incubation in vitro when compared to T cells of the healthy controls. With dexamethasone treatment, an increase in apoptosis of T cells was not significantly different between both groups, irrespective of the method used. Arsenic trioxide treatment, however, significantly increased the apoptosis of T cells of the asthmatic group and showed a slight effect on the control group. In asthmatic patients, elevated levels of interleukin-4 and up-regulated Bcl-2 expression were detected. Moreover, in vitro, T cells of asthmatic patients spontaneously released more interleukin-4 and exhibited more Bcl-2 expression than T cells from the control group. Arsenic trioxide treatment significantly decreased interleukin-4 release and down-regulated Bcl-2 expression in asthmatic patients, while it only slightly affected healthy controls. Dexamethasone treatment decreased interleukin-4 release in both groups examined. It did not significantly influence Bcl-2 expression. These results suggest that arsenic trioxide induces T cell apoptosis and decreases interleukin-4 release in T cells of asthmatic patients in vitro and that down-regulation of Bcl-2 expression may be an important mechanism.

  16. Effects of Combined Treatment With Arsenic Trioxide and Itraconazole in Patients With Refractory Metastatic Basal Cell Carcinoma

    PubMed Central

    Ally, Mina S.; Ransohoff, Katherine; Sarin, Kavita; Atwood, Scott X.; Rezaee, Melika; Bailey-Healy, Irene; Kim, Jynho; Beachy, Philip A.; Chang, Anne Lynn S.; Oro, Anthony; Tang, Jean Y.; Colevas, A. Dimitrios

    2016-01-01

    IMPORTANCE Tumor resistance is an emerging problem for Smoothened (SMO) inhibitor–treated metastatic basal cell carcinoma (BCC). Arsenic trioxide and itraconazole antagonize the hedgehog (HH) pathway at sites distinct from those treated by SMO inhibitors. OBJECTIVE To determine whether administration of intravenous arsenic trioxide and oral itraconazole in patients with metastatic BCC is associated with a reduction in GLI1 messenger RNA expression in tumor and/or normal skin biopsy samples. DESIGN, SETTING, AND PARTICIPANTS Five men with metastatic BCC who experienced relapse after SMO inhibitor treatment underwent intravenous arsenic trioxide treatment for 5 days, every 28 days, and oral itraconazole treatment on days 6 to 28. Data were collected from April 10 to November 14, 2013. Follow-up was completed on October 3, 2015, and data were analyzed from June 5 to October 6, 2015. MAIN OUTCOMES AND MEASURES The primary outcome was the change in messenger RNA levels of the GLI family zinc finger 1 (GLI1) gene (HH-pathway target gene) in biopsy specimens of normal skin or BCC before and after treatment. Secondary objectives were evaluation of tumor response and tolerability. RESULTS Of the 5 patients (mean [SD] age, 52 [9] years; age range, 43-62 years), 3 completed 3 cycles of treatment and 2 discontinued treatment early owing to disease progression or adverse events. Adverse effects included grade 2 transaminitis and grade 4 leukopenia with a grade 3 infection. Overall, arsenic trioxide and itraconazole reduced GLI1 messenger RNA levels by 75% from baseline (P < .001). The best overall response after 3 treatment cycles was stable disease in 3 patients. CONCLUSIONS AND RELEVANCE Targeting the HH pathway with sequential arsenic trioxide and itraconazole treatment is a feasible treatment for metastatic BCC. Although some patients experienced stable disease for 3 months, none had tumor shrinkage, which may be owing to transient GLI1 suppression with sequential dosing

  17. Fossilization of melanosomes via sulfurization.

    PubMed

    McNamara, Maria E; van Dongen, Bart E; Lockyer, Nick P; Bull, Ian D; Orr, Patrick J

    2016-05-01

    Fossil melanin granules (melanosomes) are an important resource for inferring the evolutionary history of colour and its functions in animals. The taphonomy of melanin and melanosomes, however, is incompletely understood. In particular, the chemical processes responsible for melanosome preservation have not been investigated. As a result, the origins of sulfur-bearing compounds in fossil melanosomes are difficult to resolve. This has implications for interpretations of original colour in fossils based on potential sulfur-rich phaeomelanosomes. Here we use pyrolysis gas chromatography mass spectrometry (Py-GCMS), fourier transform infrared spectroscopy (FTIR) and time of flight secondary ion mass spectrometry (ToF-SIMS) to assess the mode of preservation of fossil microstructures, confirmed as melanosomes based on the presence of melanin, preserved in frogs from the Late Miocene Libros biota (NE Spain). Our results reveal a high abundance of organosulfur compounds and non-sulfurized fatty acid methyl esters in both the fossil tissues and host sediment; chemical signatures in the fossil tissues are inconsistent with preservation of phaeomelanin. Our results reflect preservation via the diagenetic incorporation of sulfur, i.e. sulfurization (natural vulcanization), and other polymerization processes. Organosulfur compounds and/or elevated concentrations of sulfur have been reported from melanosomes preserved in various invertebrate and vertebrate fossils and depositional settings, suggesting that preservation through sulfurization is likely to be widespread. Future studies of sulfur-rich fossil melanosomes require that the geochemistry of the host sediment is tested for evidence of sulfurization in order to constrain interpretations of potential phaeomelanosomes and thus of original integumentary colour in fossils.

  18. Analysis of six heavy metals in Ortho mineral trioxide aggregate and ProRoot mineral trioxide aggregate by inductively coupled plasma-optical emission spectrometry.

    PubMed

    Kum, Kee-Yeon; Zhu, Qiang; Safavi, Kamran; Gu, Yu; Bae, Kwang-Shik; Chang, Seok Woo

    2013-12-01

    Ortho mineral trioxide aggregate (MTA) is a mineral aggregate newly developed for perforation repair, root end filling and pulp capping. The aim of this study was to investigate the levels of cadmium (Cd), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni) and zinc (Zn) in Ortho MTA and ProRoot MTA. A total of 0.2 g of each MTA was digested using a mixture of hydrochloric and nitric acids and filtered. Six heavy metals in the resulting filtrates were analyzed by inductively coupled plasma-optical emission spectrometry (n = 5). The results were statistically analyzed using the Mann-Whitney U-test. The concentrations of Cd, Cu, Fe, Mn, Ni and Zn in Ortho MTA were 0.10, 7.73, 49.51, 2.58, 0.82 and 10.09 p.p.m., respectively. The concentrations of Cd, Cu, Fe, Mn, Ni and Zn in ProRoot MTA were 0.16, 9.38, 1438.11, 74.51, 18.98 and 4.05 p.p.m., respectively. In conclusion, Ortho MTA had lower levels of Cd, Cu, Fe, Mn and Ni than ProRoot MTA.

  19. Sulfur cycling and metabolism of phototrophic and filamentous sulfur bacteria

    NASA Technical Reports Server (NTRS)

    Guerrero, R.; Brune, D.; Poplawski, R.; Schmidt, T. M.

    1985-01-01

    Phototrophic sulfur bacteria taken from different habitate (Alum Rock State Park, Palo Alto salt marsh, and Big Soda Lake) were grown on selective media, characterized by morphological and pigment analysis, and compared with bacteria maintained in pure culture. A study was made of the anaerobic reduction of intracellular sulfur globules by a phototrophic sulfur bacterium (Chromatium vinosum) and a filamentous aerobic sulfur bacterium (Beggiatoa alba). Buoyant densities of different bacteria were measured in Percoll gradients. This method was also used to separate different chlorobia in mixed cultures and to assess the relative homogeneity of cultures taken directly or enriched from natural samples (including the purple bacterial layer found at a depth of 20 meters at Big Soda Lake.) Interactions between sulfide oxidizing bacteria were studied.

  20. Inorganic arsenic trioxide induces gap junction loss in association with the downregulation of connexin43 and E-cadherin in rat hepatic "stem-like" cells.

    PubMed

    Hsiao, Pi-Jung; Jao, Jo-Chi; Tsai, Jin-Lian; Chang, Wen-Tsan; Jeng, Kuo-Shyang; Kuo, Kung-Kai

    2014-02-01

    Chronic exposure to inorganic arsenic trioxide causes tumors of the skin, urinary bladder, lung, and liver. Several cancer initiators and promoters have been shown to alter cell-cell signaling by interference with gap junction intercellular communication (GJIC) and/or modulation of cell adhesion molecules, such as connexin43 (Cx43), E-cadherin, and β-catenin. The aim of this study was to determine whether the disruption of cell-cell interactions occurs in liver epithelial cells after exposure to arsenic trioxide. WB-F344 cells were treated with arsenic trioxide (6.25-50 μM) for up to 8 hours, and gap junction function was analyzed using the scrape-load/dye transfer assay. In addition, the changes in mRNA and protein levels of Cx43, E-cadherin, and β-catenin were determined. A significant dose- and time-dependent decrease in GJIC was observed when WB-F344 cells were exposed to arsenic trioxide (p < 0.05). Consistent with the inhibition of GJIC, cells' exposure to arsenic trioxide resulted in dose- and time-dependent decreases in Cx43 and E-cadherin mRNA expression and protein levels. However, arsenic trioxide did not alter the mRNA or protein levels of β-catenin. In an immunofluorescence study, nuclei were heavily stained with anti-β-catenin antibody, indicating significant nuclear translocation. In this study, we also demonstrated that arsenic trioxide-induced GJIC loss was a reversible process. Taken together, these data support the hypothesis that disruption of cell-cell communication may contribute to the tumor-promoting effect of inorganic arsenic trioxide.

  1. Arsenic trioxide as a radiation sensitizer for 131I-metaiodobenzylguanidine therapy: Results of a phase II study

    PubMed Central

    Modak, Shakeel; Zanzonico, Pat; Carrasquillo, Jorge A.; Kushner, Brian H.; Kramer, Kim; Cheung, Nai-Kong V.; Larson, Steven M.; Pandit-Taskar, Neeta

    2016-01-01

    Arsenic trioxide has in vitro and in vivo radiosensitizing properties. We hypothesized that Arsenic trioxide would enhance the efficacy of the targeted radiotherapeutic agent 131I-metaiodobenzylguanidine (131I-MIBG), and tested the combination in a phase II clinical trial. Methods Patients with recurrent or refractory stage 4 neuroblastoma or metastatic paraganglioma/pheochromocytoma (MP) were treated on an institutional review board-approved protocol (Clinicaltrials.gov identifier NCT00107289). Planned treatment was 131I-MIBG (444 or 666MBq/kg) intravenously on day 1 plus arsenic trioxide (0.15 or 0.25mg/m2) intravenously on days 6–10 and 13–17. Toxicity was evaluated using National Cancer Institute Common Toxicity Criteria version 3.0. Response was assessed by International NB response criteria or (for MP) by changes in 123I-MIBG or PET scans. Results Twenty-one patients were treated: 19 with neuroblastoma and 2 with MP. Fourteen patients received 131I-MIBG and AT both at maximal dosages, 2 patients received a 444MBq/kg dose of 131I-MIBG plus a 0.15mg/kg/dose dose of arsenic trioxide; and 3 patients received a 666MBq/kg dose of 131I-MIBG plus a 0.15mg/kg/dose dose of arsenic trioxide. One did not receive arsenic trioxide because of transient central line-induced cardiac arrhythmia and another received only 6 of 10 planned doses of arsenic trioxide because of grade 3 diarrhea and vomiting with concurrent grade 3 hypokalemia and hyponatremia. Nineteen patients experienced myelosuppression higher than grade 2, most frequently, thrombocytopenia (n=18), though none required autologous stem cell rescue. 12 of 13 evaluable patients experienced hyperamylasemia higher than grade 2 from transient sialoadenitis. By International Neuroblastoma Response Criteria, 12 NB patients had no response and 7 had progressive disease, including 6 of 8 entering the study with progressive disease. Objective improvements in semiquantitative 131I-MIBG scores were observed in 6 patients

  2. Production of sulfur from sulfur dioxide obtained from flue gas

    SciTech Connect

    Miller, R.

    1989-06-06

    This patent describes a regenerable process for recovery of elemental sulfur from a gas containing sulfur dioxide comprising the steps of: contacting the gas with an aqueous, alkaline reaction medium containing sodium sulfite in concentration sufficient so that a slurry containing solid sodium sulfide is formed to react sulfur dioxide with sodium sulfite to form a solution containing dissolved sodium pyrosulfite and sodium sulfite; separating sulfur dioxide from the solution produced to leave a residual mixture containing water, sodium sulfite and a sodium pyrosulfite, the amount of sulfur dioxide separated being equal to about one-third the amount of sulfur dioxide which reacted with sodium sulfite; adding, in substantial absence of air, sufficient water and sodium bicarbonate to the residual mixture to react with the dissolved sodium pyrsulfide and form a slurry of solid sodium sulfite suspended in the resulting aqueous, alkaline reaction medium and gaseous carbon dioxide; separating the gaseous carbon dioxide; separating the solid sodium sulfite from the aqueous alkaline reaction medium and recycling the separated reaction medium; reducing the separated sodium sulfite to sodium sulfide; adding the sodium sulfide to an aqueous reaction medium containing sodium bicarbonate and, in the substantial absence of air, carbonating the resulting mixture with the gaseous carbon dioxide to form a slurry of solid particles of sodium bicarbonate dispersed in an aqueous reactor medium containing sodium bicarbonate, along with a gas composed primarily of hydrogen sulfide.

  3. Deep sulfur cycle

    NASA Astrophysics Data System (ADS)

    Shimizu, N.; Mandeville, C. W.

    2009-12-01

    Geochemical cycle of sulfur in near-surface reservoirs has been a subject of intense studies for decades. It has been shown that sulfur isotopic compositions of sedimentary sulfides and sulfates record interactions of the atmosphere, hydrosphere, biosphere and lithosphere, with δ34S of sedimentary sulfides continuously decreasing from 0‰ toward present-day values of ~-30 to -40‰ over the Phanerozoic (e.g., Canfield, 2004). It has also been shown that microbial reduction of the present-day seawater sulfate (δ34S=+21‰) results in large shifts in isotopic compositions of secondary pyrites in altered oceanic crust (to δ34S=-70‰: Rouxel et al., 2009). How much of these near surface isotopic variations survive during deep geochemical cycle of sulfur interacting with the mantle infinite reservoir with δ34S=0‰? Could extent of their survival be used as a tracer of processes and dynamics involved in deep geochemical cycle? As a first step toward answering these questions, δ34S was determined in-situ using a Cameca IMS 1280 ion microprobe at Woods Hole Oceanographic Institution in materials representing various domains of deep geochemical cycle. They include pyrites in altered MORB as potential subducting materials and pyrites in UHP eclogites as samples that have experienced subduction zone processes, and mantle-derived melts are represented by olivine-hosted melt inclusions in MORB and those in IAB, and undegassed submarine OIB glasses. Salient features of the results include: (1) pyrites in altered MORB (with O. Rouxel; from ODP site 801 and ODP Hole 1301B) range from -70 to +19‰, (2) pyrites in UHP eclogites from the Western Gneiss Region, Norway (with B. Hacker and A. Kylander-Clark) show a limited overall range from -3.4 to + 2.8‰ among five samples, with one of them covering almost the entire range, indicating limited scale lengths of isotopic equilibration during subduction, (3) olivine-hosted melt inclusions in arc basalts from Galunggung (-2

  4. Sulfuric Acid in the Venus Clouds

    NASA Technical Reports Server (NTRS)

    Sill, G. T.

    1972-01-01

    The visible and ultraviolet transmission features of a thin layer of elemental bromine and hydrobromic acid dissolved in sulfuric acid somewhat resemble the Venus spectrum, up to 14 microns. The chemical process postulated for forming sulfuric acid involves the oxidation of sulfur and its compounds to sulfuric acid through the agency of elemental bromine, produced by the photolytic decomposition of hydrogen bromide.

  5. Mineral resource of the month: sulfur

    USGS Publications Warehouse

    ,

    2010-01-01

    The article presents information on sulfur. Sulfur is said to be among the few solid elements found in elemental form in nature and has industrial uses. Changes in the sulfur production process over the years are discussed as well as the mining process developed by German engineer Herman Frasch that involves melting the sulfur underground and pumping it to the surface.

  6. 46 CFR 148.04-20 - Sulfur.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Sulfur. 148.04-20 Section 148.04-20 Shipping COAST GUARD... Special Additional Requirements for Certain Material § 148.04-20 Sulfur. (a) When sulfur is loaded in a deep hold with general cargo in the 'tween deck hold above the sulfur, a dust proof wooden...

  7. Method of preparing graphene-sulfur nanocomposites for rechargeable lithium-sulfur battery electrodes

    DOEpatents

    Liu, Jun; Lemmon, John P; Yang, Zhenguo; Cao, Yuliang; Li, Xiaolin

    2015-04-07

    A method of preparing a graphene-sulfur nanocomposite for a cathode in a rechargeable lithium-sulfur battery comprising thermally expanding graphite oxide to yield graphene layers, mixing the graphene layers with a first solution comprising sulfur and carbon disulfide, evaporating the carbon disulfide to yield a solid nanocomposite, and grinding the solid nanocomposite to yield the graphene-sulfur nanocomposite. Rechargeable-lithium-sulfur batteries having a cathode that includes a graphene-sulfur nanocomposite can exhibit improved characteristics. The graphene-sulfur nanocomposite can be characterized by graphene sheets with particles of sulfur adsorbed to the graphene sheets. The sulfur particles have an average diameter of less than 50 nm.

  8. Mineral trioxide aggregate as a pulpotomy agent in immature teeth: Long-term case report

    PubMed Central

    Subay, Rustem Kemal; Ilhan, Banu; Ulukapi, Hasmet

    2013-01-01

    This case report aimed to present the long-term clinical performance of mineral trioxide aggregate (MTA) pulpotomies in immature permanent teeth. Four patients with complicated crown fractures of five maxillary immature central incisor teeth were treated with pulpotomy using gray MTA. An immature mandibular first molar showing signs of reversible pulpitis that was exposed mechanically during cavity preparation was also treated with MTA pulpotomy. Four of the 6 immature teeth were diagnosed vitally with complete root maturation and with the presence of dentin bridges after 55 months (mean time of follow-ups). MTA pulpotomy was assessed unsuccessfully in two fractured central incisors. Severe discoloration in the crowns was present in all 6 cases. MTA may induce pulp healing with dentin bridge formation and prevent necrosis at long-term periods in most of the pulpotomy cases. However, discoloration following MTA pulpotomy is a significant clinical complication. PMID:23408174

  9. Effect of Dentin Bonding Agent on the Prevention of Tooth Discoloration Produced by Mineral Trioxide Aggregate

    PubMed Central

    Akbari, Majid; Rouhani, Armita; Samiee, Sadeq; Jafarzadeh, Hamid

    2012-01-01

    Objective. Determination of the effect of dentin bonding agent (DBA) on the prevention of tooth discoloration produced by mineral trioxide aggregate (MTA). Methods. 50 teeth were endodontically treated and after removal of 3 mm of obturating materials were divided into five groups. In white MTA (WMTA) and grey MTA (GMTA) groups, these materials were placed in root canal below the orifice. In DBA + WMTA and DBA + GMTA groups, DBAs were applied in the access cavity. Then, 3 mm of WMTA and GMTA was placed. The last 10 teeth served as control. All of teeth were restored and color measurement was recorded for each specimen at this time and 6 months later. Results. The mean tooth discoloration in WMTA and GMTA groups was significantly more than DBA + WMTA and DBA + GMTA groups, respectively. There was no significant difference between DBA + WMTA and DBA + GMTA groups and control group. Conclusion. Application of DBA before MTA may prevent tooth discoloration. PMID:22114601

  10. Evaluation of genetic damage in human peripheral lymphocytes exposed to mineral trioxide aggregate and Portland cements.

    PubMed

    Braz, M G; Camargo, E A; Salvadori, D M F; Marques, M E A; Ribeiro, D A

    2006-03-01

    summary Mineral trioxide aggregate (MTA) and Portland cement are being used in dentistry as root-end-filling material for periapical surgery and for the sealing of communications between the root canal system and the surrounding tissues. However, genotoxicity tests for complete risk assessment of these compounds have not been conducted up to now. In the present study, the genotoxic effects of MTA and Portland cements were evaluated in peripheral lymphocytes from 10 volunteers by the alkaline single cell gel (comet) assay. The results pointed out that the single cell gel (comet) assay failed to detect the presence of DNA damage after a treatment of peripheral lymphocytes by MTA and Portland cements for concentrations up to 1000 mug mL(-1). In summary, our results indicate that exposure to MTA or Portland cements may not be a factor that increases the level of DNA lesions in human peripheral lymphocytes as detected by single cell gel (comet) assay.

  11. Histology of Irreversible pulpitis premolars treated with mineral trioxide aggregate pulpotomy.

    PubMed

    Chueh, Ling-Huey; Chiang, Chun-Pun

    2010-01-01

    Studies show that human permanent teeth with carious pulpal exposures can result in a high clinical success rate when treated with pulpotomy and direct pulp capping with mineral trioxide aggregate (MTA pulpotomy). In this case report, a 19-year-old female patient with a second premolar with irreversible pulpitis and symptomatic apical periodontitis was treated with MTA pulpotomy. Follow-up electric pulp tests showed viability of the tooth at three and 10 months. Ten months after the initial treatment, the tooth was extracted for orthodontic reasons and processed for histological examination. Microscopically, the pulpal wound treated with MTA was free from inflammation and covered with a thin layer of reparative dentin. The authors conclude that, when caries and bacterial contamination can be removed from the dentin-pulp complex, the inflamed but vital pulp of a permanent tooth may have a chance to return to a healthy, functional status after MTA pulpotomy.

  12. Mineral trioxide aggregate as pulp capping agent for primary teeth pulpotomy: 2 year follow up study.

    PubMed

    Subramaniam, Priya; Konde, Sapna; Mathew, Somy; Sugnani, Sony

    2009-01-01

    The aim of the present study was to clinically and radiographically evaluate Mineral Trioxide Aggregate (MTA) as an agent for pulpotomy in primary teeth and to compare it with that of formocresol (FC) pulpotomy. Nineteen children between the ages of 6 to 8 years with 40 carious primary molars were treated with pulpotomy using either FC or MTA. All the molars were evaluated clinically and radiographically at regular intervals over a twenty four month period. The observations were tabulated and statistically analyzed. Eighty five percent success was observed with FC pulpotomy whereas MTA showed 95% success. MTA showed a higher clinical and radiographic success rate than FC. MTA may be a favorable material for pulpotomy in primary teeth whose pulps have been compromised by a carious or mechanical pulp exposure.

  13. Conservative Management of Unset Mineral Trioxide Aggregate Root-End Filling: A Case Report

    PubMed Central

    Parirokh, Masoud; Farzaneh, Sedigheh; Hallajmofrad, Ali Reza

    2016-01-01

    This case report presents conservative management of unset mineral trioxide aggregate (MTA) after being placed as a root-end filling material following periapical surgery. Periapical surgery was indicated for a maxillary lateral incisor of a 15-year-old male due to persistent exudate and a large periapical lesion. During surgery Angelus MTA was placed as root-end filling. The next session it was noticed that MTA had failed to completely set. In an orthograde approach, calcium-enriched mixture (CEM) cement was used to obturate the root canal space. The patient was followed up for 27 months and did not exhibit any clinical signs and symptoms. Radiographic images showed complete healing of the lesion. PMID:27471540

  14. Enhancement of the antimicrobial properties of orthorhombic molybdenum trioxide by thermal induced fracturing of the hydrates.

    PubMed

    Shafaei, Shahram; Van Opdenbosch, Daniel; Fey, Tobias; Koch, Marcus; Kraus, Tobias; Guggenbichler, Josef Peter; Zollfrank, Cordt

    2016-01-01

    The oxides of the transition metal molybdenum exhibit excellent antimicrobial properties. We present the preparation of molybdenum trioxide dihydrate (MoO3 × 2H2O) by an acidification method and demonstrate the thermal phase development and morphological evolution during and after calcination from 25 °C to 600 °C. The thermal dehydration of the material was found to proceed in two steps. Microbiological roll-on tests using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed and exceptional antimicrobial activities were determined for anhydrous samples with orthorhombic lattice symmetry and a large specific surface area. The increase in the specific surface area is due to crack formation and to the loss of the hydrate water after calcination at 300 °C. The results support the proposed antimicrobial mechanism for transition metal oxides, which based on a local acidity increase as a consequence of the augmented specific surface area.

  15. Signal transduction pathways and transcription factors triggered by arsenic trioxide in leukemia cells

    SciTech Connect

    Sumi, Daigo; Shinkai, Yasuhiro; Kumagai, Yoshito

    2010-05-01

    Arsenic trioxide (As{sub 2}O{sub 3}) is widely used to treat acute promyelocytic leukemia (APL). Several lines of evidence have indicated that As{sub 2}O{sub 3} affects signal transduction and transactivation of transcription factors, resulting in the stimulation of apoptosis in leukemia cells, because some transcription factors are reported to associate with the redox condition of the cells, and arsenicals cause oxidative stress. Thus, the disturbance and activation of the cellular signaling pathway and transcription factors due to reactive oxygen species (ROS) generation during arsenic exposure may explain the ability of As{sub 2}O{sub 3} to induce a complete remission in relapsed APL patients. In this report, we review recent findings on ROS generation and alterations in signal transduction and in transactivation of transcription factors during As{sub 2}O{sub 3} exposure in leukemia cells.

  16. The effect of using propylene glycol as a vehicle on the microhardness of mineral trioxide aggregate.

    PubMed

    Salem Milani, Amin; Banifatemeh, Alireza; Rahimi, Saeed; Jafarabadi, Mohammad Asghari

    2015-01-01

    While it has been proven that the handling properties of mineral trioxide aggregate (MTA) are improved upon mixing it with propylene glycol (PG), this study sought to evaluate how PG affects the microhardness of MTA in terms of setting quality. MTA was mixed with different proportions of distilled water (DW) and PG to prepare 5 groups (n = 30). The DW/PG percent proportions used in Groups 1-5 were 100/0, 80/20, 50/50, 20/80, and 0/100, respectively. The mixed MTA was condensed into acrylic molds. Half of the samples of each group were evaluated on Day 4, the other half on Day 28. The results indicated that PG reduces the microhardness of MTA, thus adversely affecting its setting process. Group 2 (80% DW/20% PG) best improved the handling of MTA without a significant reduction in setting quality.

  17. The use of mineral trioxide aggregate to achieve root end closure: three case reports.

    PubMed

    Albadri, Sondos; Chau, Yang See; Jarad, Fadi

    2013-12-01

    The use of mineral trioxide aggregate (MTA) to achieve root end closure has many advantages over the traditional calcium hydroxide (Ca(OH)2) technique including the reduced number of visits and the reduced mechanical damage to dentine. Limited studies have reported the outcome of using MTA as an apexification material and a one-stage obturation technique in non-vital immature teeth. This article illustrates three successful clinical cases where MTA was used as an apexification material. In case study one: Type 1 Dens Invaginatus tooth with incomplete root formation, case study two: an immature tooth that suffered pulp necrosis following an enamel and dentine fracture trauma and case study three: a non-vital tooth following an apical root fracture.

  18. Mineral trioxide aggregate repair of a perforating internal resorption in a mandibular molar.

    PubMed

    Meire, Maarten; De Moor, Roeland

    2008-02-01

    Internal resorption is a rare condition in permanent teeth that poses difficulties for treatment. The challenge is complicated further if the resorption extends beyond the confines of the root. This article describes treatment of a perforating internal resorption in the mesial root of a second lower molar, with adjacent destruction of the alveolar bone. After cleaning the root canal space and the resorption lacuna by mechanical instrumentation, irrigation, and interim calcium hydroxide dressing, the defect was filled with mineral trioxide aggregate, and the canals were obturated conventionally with gutta percha and epoxy resin sealer. At a 2-year follow-up examination, no clinical abnormalities were found, and complete resolution of the alveolar bone lesion and establishment of a new periodontal ligament were observed.

  19. Graphene-sulfur nanocomposites for rechargeable lithium-sulfur battery electrodes

    DOEpatents

    Liu, Jun; Lemmon, John P; Yang, Zhenguo; Cao, Yuiliang; Li, Xiaolin

    2014-06-17

    Rechargeable lithium-sulfur batteries having a cathode that includes a graphene-sulfur nanocomposite can exhibit improved characteristics. The graphene-sulfur nanocomposite can be characterized by graphene sheets with particles of sulfur adsorbed to the graphene sheets. The sulfur particles have an average diameter less than 50 nm..

  20. 40 CFR 50.5 - National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... standard for sulfur oxides (sulfur dioxide). 50.5 Section 50.5 Protection of Environment ENVIRONMENTAL....5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level... than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as...

  1. 40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75...

  2. 40 CFR 50.5 - National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... standard for sulfur oxides (sulfur dioxide). 50.5 Section 50.5 Protection of Environment ENVIRONMENTAL....5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level... than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as...

  3. 40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75...

  4. 40 CFR 50.5 - National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... standard for sulfur oxides (sulfur dioxide). 50.5 Section 50.5 Protection of Environment ENVIRONMENTAL....5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level... than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as...

  5. 40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). Link to an... to or greater than 0.005 ppm shall be rounded up). (c) Sulfur oxides shall be measured in the...

  6. 40 CFR 50.5 - National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... standard for sulfur oxides (sulfur dioxide). 50.5 Section 50.5 Protection of Environment ENVIRONMENTAL....5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level... than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as...

  7. 40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75...

  8. 40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75...

  9. 40 CFR 50.5 - National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... standard for sulfur oxides (sulfur dioxide). 50.5 Section 50.5 Protection of Environment ENVIRONMENTAL....5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level... than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as...

  10. 40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75...

  11. Toxicology of sulfur in ruminants: review

    SciTech Connect

    Kandylis, K.

    1984-10-01

    This review deals with the toxicology of sulfur in ruminants including toxicity, neurotoxic effects, and mechanism of toxic action of hydrogen sulfide, clinical signs, and treatment. It will report effects of excessive intake of sulfur by ruminants on feed intake, animal performance, ruminal digestion and motility, rumination, and other physiological functions. Poisoning of animals with sulfur from industrial emissions (sulfur dioxide) also is discussed. Excessive quantities of dietary sulfur (above .3 to .4%) as sulfate or elemental sulfur may cause toxic effects and in extreme cases can be fatal. The means is discussed whereby consumption of excessive amounts of sulfur leads to toxic effects. 53 references, 1 table.

  12. Sulfur diagenesis in marine sediments

    NASA Technical Reports Server (NTRS)

    Goldhaber, M.

    1985-01-01

    Bacterial sulfate reduction occurs in all marine sediments that contain organic matter. Aqueous sulfide (HS-, H2S), one of the initial products of bacterial sulfide reduction, is extremely reactive with iron bearing minerals: sulfur is fixed into sediments as iron sulfide (first FeS and then Fe2S2). A working definition is given of sulfur diagenesis in marine sediments. Controls and consequences of sulfate reduction rates in marine sediments are examined.

  13. Alkali metal/sulfur battery

    DOEpatents

    Anand, Joginder N.

    1978-01-01

    Alkali metal/sulfur batteries in which the electrolyte-separator is a relatively fragile membrane are improved by providing means for separating the molten sulfur/sulfide catholyte from contact with the membrane prior to cooling the cell to temperatures at which the catholyte will solidify. If the catholyte is permitted to solidify while in contact with the membrane, the latter may be damaged. The improvement permits such batteries to be prefilled with catholyte and shipped, at ordinary temperatures.

  14. Flexible neutron shielding composite material of EPDM rubber with boron trioxide: Mechanical, thermal investigations and neutron shielding tests

    NASA Astrophysics Data System (ADS)

    Özdemir, T.; Güngör, A.; Reyhancan, İ. A.

    2017-02-01

    In this study, EPDM and boron trioxide composite was produced and mechanical, thermal and neutron shielding tests were performed. EPDM rubber (Ethylene Propylene Diene Monomer) having a considerably high hydrogen content is an effective neutron shielding material. On the other hand, the materials containing boron components have effective thermal neutron absorption crossection. The composite of EPDM and boron trioxide would be an effective solution for both respects of flexibility and effectiveness for developing a neutron shielding material. Flexible nature of EPDM would be a great asset for the shielding purpose in case of intervention action to a radiation accident. The theoretical calculations and experimental neutron absorption tests have shown that the results were in parallel and an effective neutron shielding has been achieved with the use of the developed composite material.

  15. Optimizing stratospheric sulfur geoengineering by seasonally changing sulfur injections

    NASA Astrophysics Data System (ADS)

    Laakso, Anton; Partanen, Antti-Ilari; Kokkola, Harri; Lehtinen, Kari; Korhonen, Hannele

    2015-04-01

    Solar radiation management (SRM) by stratospheric sulfur injection has been shown to have potential in counteracting global warming if reducing of greenhouse gases has not been achieved fast enough and if climate warming will continue. Injecting large amounts of sulfate particles to the stratosphere would increase the reflectivity of the atmosphere and less sunlight would reach the surface. However, the effectivity (per injected sulphur mass unit) of this kind of geoengineering would decrease when amount of injected sulfur is increased. When sulfur concentration increases, stratospheric particles would grow to larger sizes which have larger gravitational settling velocity and which do not reflect radiation as efficiently as smaller particles. In many previous studies, sulfur has been assumed to be injected along the equator where yearly mean solar intensity is the highest and from where sulfur is spread equally to both hemispheres. However, the solar intensity will change locally during the year and sulfate has been assumed to be injected and spread to the hemisphere also during winter time, when the solar intensity is low. Thus sulfate injection could be expected to be more effective, if sulfur injection area is changed seasonally. Here we study effects of the different SRM injection scenarios by using two versions of the MPI climate models. First, aerosol spatial and temporal distributions as well as the resulting radiative properties from the SRM are defined by using the global aerosol-climate model ECHAM6.1-HAM2.2-SALSA. After that, the global and regional climate effects from different injection scenarios are predicted by using the Max Planck Institute's Earth System Model (MPI-ESM). We carried out simulations, where 8 Tg of sulfur is injected as SO2 to the stratosphere at height of 20-22 km in an area ranging over a 20 degree wide latitude band. Results show that changing the sulfur injection area seasonally would lead to similar global mean shortwave

  16. An ex-vivo comparative study of root-end marginal adaptation using grey mineral trioxide aggregate, white mineral trioxide aggregate, and Portland cement under scanning electron microscopy

    PubMed Central

    Baranwal, Akash Kumar; Paul, Mohan L.; Mazumdar, Dibyendu; Adhikari, Haridas Das; Vyavahare, Nishant K.; Jhajharia, Kapil

    2015-01-01

    Context: Where nonsurgical endodontic intervention is not possible, or it will not solve the problem, surgical endodontic treatment must be considered. A major cause of surgical endodontic failures is an inadequate apical seal, so the use of the suitable substance as root-end filling material that prevents egress of potential contaminants into periapical tissue is very critical. Aims: The aim of the present ex-vivo study was to compare and evaluate the three root-end filling materials of mineral trioxide aggregate (MTA) family (white MTA [WMTA], grey MTA [GMTA] and Portland cement [PC]) for their marginal adaptation at the root-end dentinal wall using scanning electron microscopy (SEM). Materials and Methods: Sixty human single-rooted teeth were decoronated, instrumented, and obturated with Gutta-percha. After the root-end resection and apical cavity preparation, the teeth were randomly divided into three-experimental groups (each containing 20 teeth) and each group was filled with their respective experimental materials. After longitudinal sectioning of root, SEM examination was done to determine the overall gap between retrograde materials and cavity walls in terms of length and width of the gap (maximum) at the interface. Descriptive statistical analysis was performed to calculate the means with corresponding standard errors, median and ranges along with an analysis of variance and Tukey's test. Results: The least overall gap was observed in GMTA followed by PC and WMTA. While after statistically analyzing the various data obtained from different groups, there was no significant difference among these three groups in terms of marginal adaptation. Conclusion: GMTA showed the best overall adaptation to root dentinal wall compared to PC and WMTA. Being biocompatible and cheaper, the PC may be an alternative but not a substitute for MTA. PMID:26430305

  17. Arsenic trioxide prevents nitric oxide production in lipopolysaccharide -stimulated RAW 264.7 by inhibiting a TRIF-dependent pathway.

    PubMed

    Takahashi, Miyuki; Ota, Akinobu; Karnan, Sivasundaram; Hossain, Ekhtear; Konishi, Yuko; Damdindorj, Lkhagvasuren; Konishi, Hiroyuki; Yokochi, Takashi; Nitta, Masakazu; Hosokawa, Yoshitaka

    2013-02-01

    Arsenic trioxide (ATO) is one of the most potent drugs in cancer chemotherapy, and is highly effective in treating both newly diagnosed and relapse patients with acute promyelocytic leukemia (APL). Despite a number of reports regarding the molecular mechanisms by which ATO promotes anti-tumor or pro-apoptotic activity in hematological and other solid malignancies, the effects of ATO on immune responses remain poorly understood. To further understand and clarify the effects of ATO on immune responses, we sought to examine whether ATO affects the production of nitric oxide (NO) in a lipopolysaccharide (LPS)-stimulated mouse macrophage cell line, RAW 264.7. Arsenic trioxide was found to prevent NO production in a dose-dependent manner. Arsenic trioxide significantly inhibited the increase in inducible nitric oxide synthase (iNOS) at both the mRNA and protein levels. Furthermore, our analyses revealed that the inhibitory effect of ATO on iNOS expression was ascribed to the prevention of IRF3 phosphorylation, interferon (IFN)-β expression, and STAT1 phosphorylation, but not the prevention of the MyD88-dependent pathway. Taken together, our results indicate that ATO prevents NO production by inhibiting the TIR-domain-containing adaptor protein inducing IFN-β (TRIF)-dependent pathway, thus highlighting an anti-inflammatory property of ATO in innate immunity.

  18. Sulfur-doped ordered mesoporous carbons: A stability-improving sulfur host for lithium-sulfur battery cathodes

    NASA Astrophysics Data System (ADS)

    Nitze, Florian; Fossum, Kjell; Xiong, Shizhao; Matic, Aleksandar; Palmqvist, Anders E. C.

    2016-06-01

    We report on sulfur-functionalized ordered mesoporous carbons aimed for lithium-sulfur battery electrode applications with improved charge capacity retention. The carbons were obtained by a hard-template strategy using a mixture of furfuryl alcohol and furfuryl mercaptan. For the application as electrode material in lithium-sulfur batteries, the carbons were additionally loaded with sulfur following a traditional melt-diffusion approach. It was found that the sulfur interacts stronger with the sulfur-functionalized carbon matrix than with the non-functionalized material. Electrodes showed very high capacity in the second discharge-charge cycle amounting to approximately 1500, 1200 and 1400 mAh/g (sulfur) for carbon materials with no, medium and high degrees of sulfur functionalization, respectively. More importantly, the sulfur-functionalization of the carbon was found to increase the capacity retention after 50 discharge-charge cycles by 8 and 5% for the carbons with medium and high degrees of sulfur-functionalization, respectively, compared to carbon with no sulfur-functionalization. We attribute this significant improvement to the presence of covalently bound sulfur groups at the internal surface of the functionalized carbon providing efficient anchoring sites for catenation to the sulfur loaded into the pores of the carbons and provide experimental support for this in the form of results from cyclic voltammetry and X-ray photoelectron spectroscopy.

  19. Biochemistry of Dissimilatory Sulfur Oxidation

    SciTech Connect

    Blake II, R.

    2003-05-30

    The long term goals of this research were to define the substrate oxidation pathways, the electron transport mechanisms, and the modes of energy conservation employed during the dissimilatory oxidation of sulfur practiced by various species of the thiobacilli. Specific adhesion of the thiobacilli to elemental sulfur was studied by electrical impedance, dynamic light scattering, laser Doppler velocimetry, and optical trapping methods. The conclusion is that the thiobacilli appear to express specific receptors that enable the bacteria to recognize and adhere to insoluble sulfur. The enzyme tetrathionate oxidase was purified from two species of the thiobacilli. Extensive structural and functional studies were conducted on adenosine 5'-phosphosulfate reductase purified from cell-free extracts of Thiobacillus denitrificans. The kinetic mechanism of rhodanese was studied.

  20. Effect of temperature on the setting time of Mineral Trioxide Aggregate (MTA)

    PubMed Central

    Sharifi, R; Araghid, A; Ghanem, S; Fatahi, A

    2015-01-01

    Introduction: Mineral trioxide aggregate (MTA) has numerous applications in dentistry due to various advantages. However, its long setting time has still remained a problem. The current study was conducted to investigate the effect of temperature (ambient and distilled water temperature) on the setting time of mineral trioxide aggregate (MTA). Materials and methods: This experimental study comprised of two parts. In the first part, MTA and distilled water samples were kept at ambient temperature for 24 hours (before mixing: effect of distilled water temperature on the setting time of MTA and after mixing: effect of distilled water and ambient temperature on the setting time of MTA), and analyzed and divided into three groups: group 1 (4°C), group 2 (37°C) and group 3 (90°C). The mixed samples were placed in the glass cylinders with an internal diameter of 8 mm and a height of 10 mm, and kept at 37°C temperature and 100% humidity. In the second part, the samples were prepared the same as those of the first part and divided into three groups according to the terms of maintenance: group 1 (4°C), group 2 (37°C) and group 3 (75°C). The mixed samples were then put in glass cylinders with an internal diameter of 8 mm and a height of 10 mm and the samples of groups 1, 2 and 3 were kept at 4, 37 and 75 °C, respectively. At the end of each part, the primary and final setting times were measured by Gilmore needle. Data were analyzed by SPSS using Kruskal-Wallis test (p<0.05). Results: The findings of this study showed a significant reduction of the primary and final setting time of MTA for the samples of both parts of the study with an increase in ambient temperature (p<0.05). Conclusion: This study indicated that increased ambient temperature caused a reduction in the setting time of MTA. PMID:28255404

  1. Low dose of arsenic trioxide triggers oxidative stress in zebrafish brain: expression of antioxidant genes.

    PubMed

    Sarkar, Shuvasree; Mukherjee, Sandip; Chattopadhyay, Ansuman; Bhattacharya, Shelley

    2014-09-01

    Occurrence of arsenic in the aquatic environment of West Bengal (India), Bangladesh and other countries are of immediate environmental concern. In the present study, zebrafish (Danio rerio) was used as a model to investigate oxidative stress related enzyme activities and expression of antioxidant genes in the brain to 50µg/L arsenic trioxide for 90 days. In treated fish, generation of reactive oxygen species (ROS), malondialdehyde (MDA) and conjugated diene (CD) showed a triphasic response attaining a peak at the end of the exposure. In addition, a gradual increase in GSH level was noted until 60 days and at 90 days, a sudden fall was recorded which heightened arsenic toxicity. However, GSH level does not correlate well with the glutathione reductase (GR) activity. Generation of ROS in zebrafish brain due to As2O3 exposure was further evidenced by significant alteration of glutathione peroxidase (GPx) and catalase (CAT) activity, which converts H2O2 to water and helps in detoxication. Moreover, enhanced mRNA level of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in As2O3 exposed zebrafish indicates a protective role of Nrf2. kelch-like ECH-associated protein 1 (Keap1), a negative regulator of Nrf2, inversely correlates with the mRNA expression of Nrf2. As2O3 induced toxicity was also validated by the alteration in NRF2 and NRF2 dependent expression of proteins such as heme oxygenase1 (HO1) and NAD(P)H dehydrogenase quinone1 (NQO1). The mRNA expression of glutathione peroxidase (Gpx1), catalase (Cat), manganese superoxide dismutase (Mn-Sod), copper/zinc superoxide dismutase (Cu/Zn Sod) and cytochrome c oxidase1 (Cox1) were also up regulated. The expression of uncoupling protein 2 (Ucp2), an important mitochondrial enzyme was also subdued in arsenic exposed zebrafish. The oxidative stress induced by arsenic also cause reduced mRNA expression of B-cell lymphoma 2 (Bcl2) present in the inner mitochondrial membrane and thereby indicating onset of apoptosis in

  2. Effect of temperature on the setting time of Mineral Trioxide Aggregate (MTA).

    PubMed

    Sharifi, R; Araghid, A; Ghanem, S; Fatahi, A

    2015-01-01

    Introduction: Mineral trioxide aggregate (MTA) has numerous applications in dentistry due to various advantages. However, its long setting time has still remained a problem. The current study was conducted to investigate the effect of temperature (ambient and distilled water temperature) on the setting time of mineral trioxide aggregate (MTA). Materials and methods: This experimental study comprised of two parts. In the first part, MTA and distilled water samples were kept at ambient temperature for 24 hours (before mixing: effect of distilled water temperature on the setting time of MTA and after mixing: effect of distilled water and ambient temperature on the setting time of MTA), and analyzed and divided into three groups: group 1 (4°C), group 2 (37°C) and group 3 (90°C). The mixed samples were placed in the glass cylinders with an internal diameter of 8 mm and a height of 10 mm, and kept at 37°C temperature and 100% humidity. In the second part, the samples were prepared the same as those of the first part and divided into three groups according to the terms of maintenance: group 1 (4°C), group 2 (37°C) and group 3 (75°C). The mixed samples were then put in glass cylinders with an internal diameter of 8 mm and a height of 10 mm and the samples of groups 1, 2 and 3 were kept at 4, 37 and 75 °C, respectively. At the end of each part, the primary and final setting times were measured by Gilmore needle. Data were analyzed by SPSS using Kruskal-Wallis test (p<0.05). Results: The findings of this study showed a significant reduction of the primary and final setting time of MTA for the samples of both parts of the study with an increase in ambient temperature (p<0.05). Conclusion: This study indicated that increased ambient temperature caused a reduction in the setting time of MTA.

  3. [Mechanism of apoptosis of NB4 cells induced by arsenic trioxide and cyclooxygenase-2 expression].

    PubMed

    Qin, Da-Bing; Chen, Jie-Ping; Wang, Sheng-Qi

    2011-06-01

    Objective of this study was to investigate the changes of cyclooxygenase-2 expression and mitochondrial membrane potential in apoptotic NB4 cells induced by arsenic trioxide (As(2)O(3)). The morphological changes in apoptosis process of NB4 cells treated by arsenic trioxide were observed under immunofluorescence microscope and DNA electrophoresis method, and the apoptosis rate of NB4 cells and the variations of mitochondrial membrane potential were detected by flow cytometry. Furthermore, the variations of expression level of cyclooxygenase-2 protein were analyzed by using Western blot method. The results indicated that after NB4 cells were treated with 2 µmol/L As(2)O(3) for 48 hours, some variations of NB4 cells were observed, such as pyknosis, chromatin segmentation, even fragmentation. Meanwhile, the typical DNA Ladder phenomenon was observed. The apoptosis rate of NB4 cells treated with 3 µmol/L As(2)O(3) for 48 hours was 33.34%, Furthermore the apoptosis rate of NB4 cells was enhanced along with the increase of concentration of As(2)O(3). After NB4 cells were treated with 0.5, 1, 2, 4 and 8 µmol/L As(2)O(3) for 48 hours, the mitochondrial membrane potential decreased by 12.8%, 21.6%, 66.9%, 83.7% and 83.8% respectively. The Western blot detection results showed that the expression level of cyclooxygenase-2 protein in NB4 cells was lower than that in control cells and decreased along with the rise of As(2)O(3) concentration, then the negative dose-dependent manner was observed between these 2 groups. It is concluded that As(2)O(3) can effectively induce NB4 cell apoptosis, and the dose-dependent manner existed in certain extent of concentrations. The decrease of mitochondrial membrane potential may be related with NB4 cell apoptosis induced by As(2)O(3). Cyclooxygenase-2 participates in the process of NB4 cell apoptosis induced by As(2)O(3).

  4. Effect of Mineral Trioxide Aggregate, Calcium-Enriched Mixture Cement and Mineral Trioxide Aggregate with Disodium Hydrogen Phosphate on BMP-2 Production

    PubMed Central

    Ghasemi, Negin; Rahimi, Saeed; Lotfi, Mehrdad; Solaimanirad, Jafar; Shahi, Shahriar; Shafaie, Hajar; Salem Milani, Amin; Shakuie, Sahar; Zand, Vahid; Abdolrahimi, Majid

    2014-01-01

    Introduction: One of the hypotheses regarding the calcification induction by mineral trioxide aggregate (MTA) is the involvement of transforming growth factor-Beta (TGF-β) super family. Calcium-enriched mixture (CEM) cement is one of the endodontic biomaterials with clinical applications similar to MTA. The aim of the present in vitro study was to compare the induction of bone morphogenic protein-2 (BMP-2) by a combination of disodium hydrogen phosphate (DSHP) and tooth colored ProRoot MTA (WMTA), to that of CEM cement and WMTA. Methods and Materials: Human gingival fibroblasts (HGFs) were obtained from the attached gingiva of human premolars. HGFs were cultured in Dulbecco’s Modified Eagle’s medium, supplemented with 10% fetal calf serum, penicillin, and streptomycin. Cells in groups 1, 2 and 3 were exposed to WMTA, CEM and WMTA+DSHP discs, respectively. The fourth group served as the control. After 72 h of exposure, HGF viability was determined by Mosmann’s tetrazolium toxicity (MTT) assay. BMP-2 levels in cell-free culture media were determined by enzyme-linked immunosorbent assay (ELISA). Statistical analysis was performed using the one-way ANOVA, followed by the post hoc Games-Howell test for BMP-2 and post hoc Tukey’s test for the results of MTT assay. Results: Cellular viability was significantly higher in group 3 compared to the other groups (P<0.05); however, CEM and WMTA did not exhibit significant differences (P=0.08). The control group exhibited significantly higher cellular viability in comparison to the other groups of the study (P<0.05). The highest and lowest protein production rates were observed in the WMTA (3167±274.46 pg/mL) and WMTA+DSHP (1796±839.49 pg/mL) groups, respectively. There were no significant differences between the control, WMTA and CEM groups (P>0.05). Conclusion: WMTA and CEM did not exhibit any significant differences in terms of inducing BMP-2 production; however, incorporation of DSHP into WMTA resulted in a

  5. Behavior of sulfur during coal pyrolysis

    USGS Publications Warehouse

    Shao, D.; Hutchinson, E.J.; Heidbrink, J.; Pan, W.-P.; Chou, C.-L.

    1994-01-01

    The behavior of sulfur in Illinois coals during pyrolysis was evaluated by thermogravimetry/ Fourier transform-infrared spectroscopy (TG/FT-IR) techniques. SO2, COS, and H2S were major gaseous sulfur-containing products observed during coal pyrolysis. The release rates of the gaseous sulfur species showed several peaks within the temperature ranges, which were due to the emission of different forms of sulfur in coal. ?? 1994.

  6. Absorbable Suture as an Apical Matrix in Single Visit Apexification with Mineral Trioxide Aggregate

    PubMed Central

    Jha, Padmanabh

    2016-01-01

    Several procedures have been recommended to induce the root end barrier formation in teeth with open apices. Conventional treatment for such cases will require many appointments with an average duration of 12.9 months. During this period, the root canal is susceptible to reinfection from around the provisional restoration, which may promote apical periodontitis and arrest of apical repair. Mineral trioxide aggregate (MTA) has been successfully used for one visit apexification wherein the root canal can be obturated within 24 hours after placement of MTA. Using a matrix prior to the placement of MTA avoids its extrusion, reduces leakage in the sealing material, and allows favorable response of the periapical tissues. This report presents a case of apexification where an absorbable suture was used as an apical matrix. Use of an absorbable suture circumvents all the problems associated with other conventional materials. Conclusion. Placement of the matrix made from the suture material is predictable and is easily positioned at the apex and the length can be adjusted as required. 10-month follow-up of the case shows resorbed matrix and bone healing in the periapical region. The patient was asymptomatic during the whole follow-up period and tooth exhibited mobility within physiologic limits and was functioning normally. PMID:28058120

  7. Density-functional studies of tungsten trioxide, tungsten bronzes, and related systems

    NASA Astrophysics Data System (ADS)

    Ingham, B.; Hendy, S. C.; Chong, S. V.; Tallon, J. L.

    2005-08-01

    Tungsten trioxide adopts a variety of structures which can be intercalated with charged species to alter the electronic properties, thus forming “tungsten bronzes.” Similar effects are observed upon removing oxygen from WO3 . We present a computational study of cubic and hexagonal alkali bronzes and examine the effects on cell size and band structure as the size of the intercalated ion is increased. With the exception of hydrogen (which is predicted to be unstable as an intercalate), the behavior of the bronzes are relatively consistent. NaWO3 is the most stable of the cubic systems, although in the hexagonal system the larger ions are more stable. The band structures are identical, with the intercalated atom donating its single electron to the tungsten 5d valence band. A study of fractional doping in the NaxWO3 system (0⩽x⩽1) showed a linear variation in cell parameter and a systematic shift in the Fermi level into the conduction band. In the oxygen-deficient WO3-x system the Fermi level undergoes a sudden jump into the conduction band at around x=0.2 . Lastly, three compounds of a layered WO4•α,ω -diaminoalkane hybrid series were studied and found to be insulating, with features in the band structure similar to those of the parent WO3 compound that relate well to experimental UV-visible spectroscopy results.

  8. Comparing Gray Mineral Trioxide Aggregate and Diluted Formocresol in Pulpotomized Human Primary Molars

    PubMed Central

    Zealand, Cameron M.; Briskie, Daniel M.; Botero, Tatiana M.; Boynton, James R.; Hu, Jan C.C.

    2016-01-01

    Purpose The purpose of this multisite, multioperator, prospective, randomized, controlled clinical trial was to evaluate the 6-month outcomes of diluted formocresol (DFC) compared to gray mineral trioxide aggregate (GMTA) as pulpotomy medicament. Methods Determined by a power analysis, 252 molars of 152 children were recruited. The teeth were randomly assigned to receive GMTA or DFC. At the 6-month follow-up, 118 children with 203 treated teeth were evaluated. Results Four blinded and calibrated evaluators scored each radiograph for pathologies. Clinical success was similar for DFC (97%) and GMTA (100%), (P<.09). Radiographic success differed significantly (P<.04) for DFC (86%) and GMTA (95%). Pulp canal obliteration was radiographically observed in 25% of the DFC group and in 37% of the GMTA group (P=.07). Dentin bridging was observed in 22% of the GMTA group but was not found in the DFC group (P<.01). Conclusion Teeth treated with GMTA showed more favorable radiographic outcomes than DFC at 6 months post-treatment. PMID:21070705

  9. Sealing ability of mineral trioxide aggregate (MTA) combined with distilled water, chlorhexidine, and doxycycline.

    PubMed

    Arruda, Roberta A A; Cunha, Rodrigo S; Miguita, Kenner B; Silveira, Cláudia F M; De Martin, Alexandre S; Pinheiro, Sérgio L; Rocha, Daniel G P; Bueno, Carlos E S

    2012-09-01

    The aim of this study was to evaluate the sealing ability of mineral trioxide aggregate (MTA Bio) combined with different mixing agents (distilled water, chlorhexidine, doxycycline), used as an apical root-end filling material. Forty-two extracted human teeth were divided into three groups (n = 12); six teeth were used as controls. Root-ends were resected at 90 degrees, 3 mm from the apex. Root-end cavities were prepared using ultrasonic tips and filled with MTA Bio plus distilled water, 2% chlorhexidine solution, or 10% doxycycline solution. Apical sealing was assessed by microleakage of 50% silver nitrate solution. Roots were longitudinally sectioned in a buccolingual plane and analyzed using an operating microscope (20× magnification). Depth of dye leakage into the dentinal walls was measured in millimeters. Results were analyzed using ANOVA and Tukey's test (P = 0.05). MTA Bio plus distilled water showed significantly higher mean leakage results (1.06 mm) when compared with MTA Bio plus doxycycline (0.61 mm), and higher, although not significant, results when compared with MTA Bio plus chlorhexidine (0.79 mm). In conclusion, replacing distilled water with two biologically active mixing agents (doxycycline and chlorhexidine) did not alter the sealing properties of MTABio. The antimicrobial properties of these combinations should be further investigated.

  10. Pulpotomy of Symptomatic Permanent Teeth with Carious Exposure Using Mineral Trioxide Aggregate

    PubMed Central

    Barngkgei, Imad Hassan; Halboub, Esam Saleh; Alboni, Roula Safouh

    2013-01-01

    Introduction To evaluate the clinical and radiographic outcomes of pulpotomy treatment with mineral trioxide aggregate (MTA) in symptomatic mature permanent teeth with carious exposure. Materials and Methods Ten patients aged 27-54 years presented with 11 symptomatic permanent teeth (n=11). Each offending carious tooth was clinically and radiographically determined. We removed caries as conservatively as possible; however pulp exposure was inevitable. ProRoot MTA pulpotomy was performed on these teeth. The patients were followed-up clinically and radiographically for 24-42 months. Results Immediate relief of patients` symptoms occurred. Moreover, teeth responses to the electric pulp tester were within normal range on follow-up appointment and the radiographs did not reveal any abnormality/lesion in the periapical areas. Conclusion Pulpotomy using MTA could be a good alternative for root canal therapy (RCT) for managing symptomatic mature permanent teeth with carious exposure, however further large-scale multicenter clinical trials are highly encouraged to confirm this hypothesis. PMID:23717332

  11. Mineral trioxide aggregate as a root canal filling material in reimplanted teeth. Microscopic analysis in monkeys.

    PubMed

    Panzarini, Sônia Regina; Holland, Roberto; de Souza, Valdir; Poi, Wilson Roberto; Sonoda, Celso Koogi; Pedrini, Denise

    2007-10-01

    This study analyzed mineral trioxide aggregate (MTA) as a root canal filling material for the immediate reimplantation of monkey teeth. Four adult capuchin monkeys Cebus apella were used, which had their maxillary and mandibular lateral incisors on both sides extracted and reimplanted after 15 min. During the extra-alveolar period, the teeth were kept in saline solution and after reimplantation retention was performed with a stainless steel wire and composite resin for 14 days. After 7 days, the reimplanted teeth were submitted to endodontic treatment with biomechanics up to file n. 30 and irrigation with a saturated solution of calcium hydroxide [Ca(OH)(2)], and then divided into two study groups: group I - root canal filled with a Ca(OH)(2) paste, and group II - root canal filled with MTA. Radiographic follow up was performed at 30, 60 and 90 days postoperatively, and after 180 days the animals were killed and specimens were processed for histomorphological analysis. The results revealed that most specimens of both groups presented organized periodontal ligament with no inflammation. The resorptions observed were surface resorptions and were repaired by cementum. Both MTA and Ca(OH)(2) were good root canal filling materials for immediately reimplanted teeth, providing good repair and also allowing biological sealing of some lateral canals. There was no significant difference between the study groups (alpha = 29.60%).

  12. Dose Response of MTLn3 Cells to Serial Dilutions of Arsenic Trioxide and Ionizing Radiation.

    PubMed

    Raja, Waseem Khan; Satti, Jahangir; Liu, Gang; Castracane, James

    2013-01-01

    MTLn3 cells derived from mouse mammary epithelium are known to be highly malignant and are resistant to both radio- and chemo-therapy. We exposed MTLn3 cells to various doses of inorganic Arsenic trioxide (As2O3) in combination with ionizing radiation. Cells were treated with a series of As2O3 concentrations ranging from 20 μM to 1.22 nM for 8 hour, 24 hour and 48 hour periods. Post-treated cell proliferation was quantified by measuring mitochondrial activity and DNA analysis. Cells exposed to radiation and As2O3 at concentration greater than 1.25 μM showed apoptosis and radiations alone treated cells were statistically not different from the control. Hormesis was observed for As2O3 concentrations in the range of 0.078 μM to 0.625 μM while the combined chemo and radiation treatments of the cells did not affect the hormetic effect. We have demonstrated that As2O3 (in the presence and absence of ionizing radiation) in specific low concentrations induced apoptosis in the otherwise chemoresistant cancer cells. This low concentration-mediated cell death is immediately followed by a surge in cell survival. Low dosing dosimetry is highly desirable in metronomic therapy however, it has a narrow window since necrosis, hormesis, apoptosis and other dose-dependent biological processes take place in this region. Further quantifiable dosimetry is highly desired for routine clinical practice.

  13. Tissue Reaction and Biocompatibility of Implanted Mineral Trioxide Aggregate with Silver Nanoparticles in a Rat Model

    PubMed Central

    Zand, Vahid; Lotfi, Mehrdad; Aghbali, Amirala; Mesgariabbasi, Mehran; Janani, Maryam; Mokhtari, Hadi; Tehranchi, Pardis; Pakdel, Seyyed Mahdi Vahid

    2016-01-01

    Introduction: Biocompatibility and antimicrobial activity of endodontic materials are of utmost importance. Considering the extensive applications of mineral trioxide aggregate (MTA) in dentistry and antimicrobial properties of silver nanoparticles, this study aimed to evaluate the subcutaneous inflammatory reaction of rat connective tissues to white MTA with and without nanosilver (NS) particles. Methods and Materials: Polyethylene tubes (1.1×8 mm) containing experimental materials (MTA and MTA+NS and empty control tubes) were implanted in subcutaneous tissues of seventy-five male rats. Animals were divided into five groups (n=15) according to the time of evaluation: group 1; after 7 days, group 2; after 15 days, group 3; after 30 days, group 4; after 60 days and group 5; after 90 days. The inflammatory reaction was graded and data was analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Statistical significance was defined at 0.05. Results: Comparison of cumulative inflammatory reaction at all intervals revealed that the mean grade of inflammatory reaction to MTA, MTA+NS and control samples were 3, 2 and 2, respectively. According to the Mann-Whitney analysis there were no significant differences between MTA+NS and MTA (P=0.42). Conclusion: Incorporation of 1% nanosilver to MTA does not affect the inflammatory reaction of subcutaneous tissue in rat models. PMID:26843871

  14. Arsenic trioxide targets MTHFD1 and SUMO-dependent nuclear de novo thymidylate biosynthesis.

    PubMed

    Kamynina, Elena; Lachenauer, Erica R; DiRisio, Aislyn C; Liebenthal, Rebecca P; Field, Martha S; Stover, Patrick J

    2017-03-06

    Arsenic exposure increases risk for cancers and is teratogenic in animal models. Here we demonstrate that small ubiquitin-like modifier (SUMO)- and folate-dependent nuclear de novo thymidylate (dTMP) biosynthesis is a sensitive target of arsenic trioxide (As2O3), leading to uracil misincorporation into DNA and genome instability. Methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) and serine hydroxymethyltransferase (SHMT) generate 5,10-methylenetetrahydrofolate for de novo dTMP biosynthesis and translocate to the nucleus during S-phase, where they form a multienzyme complex with thymidylate synthase (TYMS) and dihydrofolate reductase (DHFR), as well as the components of the DNA replication machinery. As2O3 exposure increased MTHFD1 SUMOylation in cultured cells and in in vitro SUMOylation reactions, and increased MTHFD1 ubiquitination and MTHFD1 and SHMT1 degradation. As2O3 inhibited de novo dTMP biosynthesis in a dose-dependent manner, increased uracil levels in nuclear DNA, and increased genome instability. These results demonstrate that MTHFD1 and SHMT1, which are key enzymes providing one-carbon units for dTMP biosynthesis in the form of 5,10-methylenetetrahydrofolate, are direct targets of As2O3-induced proteolytic degradation, providing a mechanism for arsenic in the etiology of cancer and developmental anomalies.

  15. Targeting catalase but not peroxiredoxins enhances arsenic trioxide-induced apoptosis in K562 cells.

    PubMed

    Song, Li-Li; Tu, Yao-Yao; Xia, Li; Wang, Wei-Wei; Wei, Wei; Ma, Chun-Min; Wen, Dong-Hua; Lei, Hu; Xu, Han-Zhang; Wu, Ying-Li

    2014-01-01

    Despite considerable efficacy of arsenic trioxide (As2O3) in acute promyelocytic leukemia (APL) treatment, other non-APL leukemias, such as chronic myeloid leukemia (CML), are less sensitive to As2O3 treatment. However, the underlying mechanism is not well understood. Here we show that relative As2O3-resistant K562 cells have significantly lower ROS levels than As2O3-sensitive NB4 cells. We compared the expression of several antioxidant enzymes in these two cell lines and found that peroxiredoxin 1/2/6 and catalase are expressed at high levels in K562 cells. We further investigated the possible role of peroxirdoxin 1/2/6 and catalase in determining the cellular sensitivity to As2O3. Interestingly, knockdown of peroxiredoxin 1/2/6 did not increase the susceptibility of K562 cells to As2O3. On the contrary, knockdown of catalase markedly enhanced As2O3-induced apoptosis. In addition, we provide evidence that overexpression of BCR/ABL cannot increase the expression of PRDX 1/2/6 and catalase. The current study reveals that the functional role of antioxidant enzymes is cellular context and treatment agents dependent; targeting catalase may represent a novel strategy to improve the efficacy of As2O3 in CML treatment.

  16. Bacterial entombment by intratubular mineralization following orthograde mineral trioxide aggregate obturation: a scanning electron microscopy study

    PubMed Central

    Yoo, Jun Sang; Chang, Seok-Woo; Oh, So Ram; Perinpanayagam, Hiran; Lim, Sang-Min; Yoo, Yeon-Jee; Oh, Yeo-Rok; Woo, Sang-Bin; Han, Seung-Hyun; Zhu, Qiang; Kum, Kee-Yeon

    2014-01-01

    The time domain entombment of bacteria by intratubular mineralization following orthograde canal obturation with mineral trioxide aggregate (MTA) was studied by scanning electron microscopy (SEM). Single-rooted human premolars (n=60) were instrumented to an apical size #50/0.06 using ProFile and treated as follows: Group 1 (n=10) was filled with phosphate buffered saline (PBS); Group 2 (n=10) was incubated with Enterococcus faecalis for 3 weeks, and then filled with PBS; Group 3 (n=20) was obturated orthograde with a paste of OrthoMTA (BioMTA, Seoul, Korea) and PBS; and Group 4 (n=20) was incubated with E. faecalis for 3 weeks and then obturated with OrthoMTA–PBS paste. Following their treatments, the coronal openings were sealed with PBS-soaked cotton and intermediate restorative material (IRM), and the roots were then stored in PBS for 1, 2, 4, 8 or 16 weeks. After each incubation period, the roots were split and their dentin/MTA interfaces examined in both longitudinal and horizontal directions by SEM. There appeared to be an increase in intratubular mineralization over time in the OrthoMTA-filled roots (Groups 3 and 4). Furthermore, there was a gradual entombment of bacteria within the dentinal tubules in the E. faecalis inoculated MTA-filled roots (Group 4). Therefore, the orthograde obturation of root canals with OrthoMTA mixed with PBS may create a favorable environment for bacterial entombment by intratubular mineralization. PMID:25012869

  17. Properties of Hydrogen Sulfide Sensors Based on Thin Films of Tin Dioxide and Tungsten Trioxide

    NASA Astrophysics Data System (ADS)

    Sevastianov, E. Yu.; Maksimova, N. K.; Chernikov, E. V.; Sergeichenko, N. V.; Rudov, F. V.

    2016-12-01

    The effect of hydrogen sulfide in the concentration range of 0-100 ppm on the characteristics of thin films of tin dioxide and tungsten trioxide obtained by the methods of magnetron deposition and modified with gold in the bulk and on the surface is studied. The impurities of antimony and nickel have been additionally introduced into the SnO2 bulk. An optimal operating temperature of sensors 350°C was determined, at which there is a satisfactory correlation between the values of the response to H2S and the response time. Degradation of the sensor characteristics is investigated in the long-term ( 0.5-1.5 years) tests at operating temperature and periodic exposure to hydrogen sulfide, as well as after conservation of samples in the laboratory air. It is shown that for the fabrication of H2S sensors, the most promising are thin nanocrystalline Au/WO3:Au films characterized by a linear concentration dependence of the response and high stability of parameters during exploitation.

  18. Use of Arsenic Trioxide as an Antivascular and Thermosensitizing Agent in Solid Tumors1

    PubMed Central

    Griffin, Robert J; Lee, Sang H; Rood, Kelly L; Stewart, Michael J; Lyons, John C; Lew, Young S; Park, Heonjoo; Song, Chang W

    2000-01-01

    Abstract Arsenic trioxide, As2O3 (ATO), has been found to be an effective chemotherapy drug for acute promyelocytic leukemia but its effect on solid tumors has not been fully explored. In the present report, we describe our observation that ATO is a potent antivascular agent and that it markedly enhances the effect of hyperthermia on tumors. The tumor blood perfusion in SCK tumors of A/J mice and FSall tumors of C3H mice was significantly suppressed for up to 24 hours after an i.p. injection of 8 mg/kg ATO. ATO was also found to be able to increase the thermosensitivity of tumor cells in vitro. As a probable consequence of these effects, ATO treatment markedly increased the tumor growth delay caused by hyperthermia at 41.5–42.5°C. Immunohistochemical staining of tumor tissue revealed that the expression levels of several adhesion molecules and TNFα are noticeably increased in tumors 2–6 hours after systemic ATO treatment. It is concluded that ATO is potentially useful to enhance the effect of hyperthermia on tumors at a clinically relevant temperature. PMID:11228548

  19. Effect of methods of evaluation on sealing ability of mineral trioxide aggregate apical plug

    PubMed Central

    Nikhil, Vineeta; Jha, Padmanabh; Suri, Navleen Kaur

    2016-01-01

    Aim: The purpose of the study was to evaluate and compare the sealing ability of mineral trioxide aggregate (MTA) with three different methods. Materials and Methods: Forty single canal teeth were decoronated, and root canals were enlarged to simulate immature apex. The samples were randomly divided into Group MD = MTA-angelus mixed with distilled water and Group MC = MTA-angelus mixed with 2% chlorhexidine, and apical seal was recorded with glucose penetration method, fluid filtration method, and dye penetration methods and compared. Results: The three methods of evaluation resulted differently. The glucose penetration method showed that MD sealed better than MC, but difference was statistically insignificant (P > 0.05). The fluid filtration method resulted that Group MC was statistically insignificant superior to Group MD (P > 0.05). The dye penetration method showed that Group MC sealed statistically better than Group MD. Conclusion: No correlation was found among the results obtained with the three methods of evaluation. Addition of chlorhexidine enhanced the sealing ability of MTA according to the fluid filtration test and dye leakage while according to the glucose penetration test, chlorhexidine did not enhance the sealing ability of MTA. This study showed that relying on the results of apical sealing by only method can be misleading. PMID:27217635

  20. Immediate and delayed solubility of mineral trioxide aggregate and Portland cement.

    PubMed

    Bodanezi, Augusto; Carvalho, Nara; Silva, Daniela; Bernardineli, Norberti; Bramante, Clovis Monteiro; Garcia, Roberto Brandão; de Moraes, Ivaldo Gomes

    2008-01-01

    This study investigated the solubility of mineral trioxide aggregate (MTA) and Portland cement since its mixture until 672 hours, by means of two complimentary methods. Metal ring molds filled with the cements were covered with distilled water and, at each experimental time (3, 24, 72, 168, 336 and 672 hours), were weighed as soon as the plates in which the samples have been placed. Empty rings served as the control group (n=8). Mean weight gain and loss was determined and analyzed statistically by two-way ANOVA and Tukey's test for all pairwise comparisons. Only Portland cement showed less than 3% weight loss through 24 hours. Detached MTA residues were heavier than those of Portland cement over the 3 to 168 hours. The weight of MTA rings increased more than that of Portland rings within 672 hours (p=0.05). The findings of the present study indicate that, in an aqueous environment MTA is more soluble than Portland cement and exceeds the maximum weight loss considered acceptable by ISO 6876 standard (2001).

  1. Bacterial entombment by intratubular mineralization following orthograde mineral trioxide aggregate obturation: a scanning electron microscopy study.

    PubMed

    Yoo, Jun Sang; Chang, Seok-Woo; Oh, So Ram; Perinpanayagam, Hiran; Lim, Sang-Min; Yoo, Yeon-Jee; Oh, Yeo-Rok; Woo, Sang-Bin; Han, Seung-Hyun; Zhu, Qiang; Kum, Kee-Yeon

    2014-12-01

    The time domain entombment of bacteria by intratubular mineralization following orthograde canal obturation with mineral trioxide aggregate (MTA) was studied by scanning electron microscopy (SEM). Single-rooted human premolars (n=60) were instrumented to an apical size #50/0.06 using ProFile and treated as follows: Group 1 (n=10) was filled with phosphate buffered saline (PBS); Group 2 (n=10) was incubated with Enterococcus faecalis for 3 weeks, and then filled with PBS; Group 3 (n=20) was obturated orthograde with a paste of OrthoMTA (BioMTA, Seoul, Korea) and PBS; and Group 4 (n=20) was incubated with E. faecalis for 3 weeks and then obturated with OrthoMTA-PBS paste. Following their treatments, the coronal openings were sealed with PBS-soaked cotton and intermediate restorative material (IRM), and the roots were then stored in PBS for 1, 2, 4, 8 or 16 weeks. After each incubation period, the roots were split and their dentin/MTA interfaces examined in both longitudinal and horizontal directions by SEM. There appeared to be an increase in intratubular mineralization over time in the OrthoMTA-filled roots (Groups 3 and 4). Furthermore, there was a gradual entombment of bacteria within the dentinal tubules in the E. faecalis inoculated MTA-filled roots (Group 4). Therefore, the orthograde obturation of root canals with OrthoMTA mixed with PBS may create a favorable environment for bacterial entombment by intratubular mineralization.

  2. Cytotoxicity of calcium enriched mixture cement compared with mineral trioxide aggregate and intermediate restorative material.

    PubMed

    Mozayeni, Mohammad A; Milani, Amin S; Marvasti, Laleh A; Asgary, Saeed

    2012-08-01

    Calcium enriched mixture (CEM) cement has been recently invented by the last author. It is composed of calcium oxide, calcium phosphate, calcium silicate and calcium sulphate; however, it has a different chemical composition to mineral trioxide aggregate (MTA). The purpose of this ex vivo study was to investigate the cytotoxicity of CEM cement, and compare it with intermediate restorative material (IRM) and MTA. The materials were tested in fresh and set states on L929 fibroblasts to assess their cytotoxicity. The cell viability responses were evaluated with methyl-tetrazolium bromide assay and Elisa reader at 1, 24 and 168 h (7 days). The tested materials were eluted with L929 culture medium according to international standard organisation 109935 standard. Distilled water and culture medium served as positive and negative controls, respectively. Differences in cytotoxicity were evaluated by one-way anova and t-tests. The cytotoxicity of the materials was statistically different at the three time intervals (P < 0.01). The lowest cytotoxic values recorded were expressed by MTA subgroups followed by CEM cement; IRM subgroups were the most cytotoxic root-end/dental material (P < 0.001). CEM cement and MTA are reasonable alternatives to IRM because of lower cytotoxicity. CEM cement also has good biocompatibility as well as lower estimated cost to MTA and seems to be a promising dental material.

  3. Remineralization of artificial dentinal caries lesions by biomimetically modified Mineral Trioxide Aggregate

    PubMed Central

    Qi, Yi-pin; Li, Nan; Niu, Li-na; Primus, Carolyn M.; Ling, Jun-Qi; Pashley, David H.; Tay, Franklin R.

    2011-01-01

    Fluoride-releasing restorative materials are available for remineralization of enamel and root caries. However, dentin remineralization is more difficult than enamel remineralization due to the paucity of apatite seed crystallites along the lesion surface for heterogeneous crystal growth. Extracellular matrix proteins play critical roles in controlling apatite nucleation/growth in collagenous tissues. This study examined the remineralization efficacy of mineral trioxide aggregate (MTA) in phosphate-containing simulated body fluid (SBF) by incorporating polyacrylic acid and sodium tripolyphosphate as biomimetic analogs of matrix proteins for remineralizing caries-like dentin. Artificial caries-like dentin lesions incubated in SBF were remineralized over a 6-week period using MTA or MTA containing biomimetic analogs in the absence or presence of dentin adhesive application. Lesion depths and integrated mineral loss were monitored with micro-computed tomography. Ultrastructure of baseline and remineralized lesions were examined by transmission electron microscopy. Dentin remineralization was best achieved using MTA containing biomimetic analogs regardless of whether an adhesive was applied; dentinal tubules within the remineralized dentin were occluded by apatite. It is concluded that the MTA version employed in the study may be doped with biomimetic analogs for remineralization of unbonded and bonded artificial caries-like lesions in the presence of SBF. PMID:22085925

  4. Pulp Revascularization in Immature Permanent Tooth with Apical Periodontitis Using Mineral Trioxide Aggregate

    PubMed Central

    Saeki, Katsura; Shiono, Yasuhiro; Maki, Kenshi

    2014-01-01

    Mineral trioxide aggregate (MTA) is a material that has been used worldwide in several clinical applications, such as apical barriers in teeth with immature apices, repair of root perforations, root-end filling, pulp capping, and pulpotomy. The purpose of this case report was to describe successful revascularization treatment of an immature mandibular right second premolar with apical periodontitis in a 9-year-old female patient. After preparing an access cavity without anesthesia, the tooth was isolated using a rubber dam and accessed. The canal was gently debrided using 5% sodium hypochlorite (NaOCl) and 3% hydrogen peroxide irrigant. And then MTA was packed into the canal. X-ray photographic examination showed the dentin bridge 5 months after the revascularization procedure. Thickening of the canal wall and complete apical closure were confirmed 10 months after the treatment. In this case, MTA showed clinical and radiographic success at revascularization treatment in immature permanent tooth. The successful outcome of this case suggests that MTA is reliable and effective for endodontic treatment in the pediatric dentistry. PMID:24959181

  5. Organic reactions catalyzed by methylrhenium trioxide: Reactions of ethyl diazoacetate and organic azides

    SciTech Connect

    Zhu, Z.; Espenson, J.H. |

    1996-10-16

    Methylrhenium trioxide (CH{sub 3}ReO{sub 3} or MTO) catalyzes several classes of reactions of ethyl diazoacetate, EDA. It is the first high valent oxo complex for carbene transfer. Under mild conditions and in the absence of other substrates, EDA was converted to a 9:1 mixture of diethyl maleate and diethyl fumarate. In the presence of alcohols, {alpha}-alkoxy ethyl acetates were obtained in good yield. The yields dropped for the larger and more branched alcohols, the balance of material being diethyl maleate and fumarate. An electron-donating group in the para position of phenols favors the formation of {alpha}-phenoxy ethyl acetates. The use of EDA to form {alpha}-thio ethyl acetates and N-substituted glycine ethyl esters, on the other hand, is hardly affected by the size or structure of the parent thiol or amine, with all of these reactions proceeding in high yield. MTO-catalyzed cycloaddition reactions occur between EDA and aromatic imines, olefins, and carbonyl compounds. Three-membered ring products are formed: aziridines, cyclopropanes, and epoxides, respectively. The reactions favor the formation of trans products, and provide a convenient route for the preparation of aziridines. Intermediate carbenoid and nitrenoid species have been proposed. In the presence of an oxygen source such as an epoxide, ethyl diazoacetate and azibenzil are converted to an oxalic acid monoethyl ester and to benzil; at the same time the epoxide was converted to an olefin. 75 refs., 1 fig., 7 tabs.

  6. Morphological and chemical analysis of different precipitates on mineral trioxide aggregate immersed in different fluids.

    PubMed

    Han, Linlin; Okiji, Takashi; Okawa, Seigo

    2010-10-01

    The purpose of this study was to analyze the ultrastructures and chemical compositions of precipitates formed on mineral trioxide aggregate (MTA; White ProRoot MTA) immersed in distilled water (DW) or phosphate buffered saline (PBS), based on the attribution that MTA's bioactivity and sealing ability are influenced by its interaction with the external fluid environment. After 1 and 14 days of immersion, precipitates formed on MTA disks were analyzed using wavelength-dispersive X-ray spectroscopy electron probe microanalyzer with image observation function (SEM-EPMA; EPMA1601, Shimadzu, Kyoto, Japan), and Fourier transform-infrared (FT-IR) spectroscopy. On DW specimens, cubic-like crystals containing Ca, O, and C (17, 66, and 17 at% respectively) were produced. State analysis of calcium k(β)spectrum also revealed calcium hydroxide. On PBS specimens, acicular-spherical and lath-like crystals with Ca/P molar ratios of 1.42 and 1.58 respectively were produced. In conclusion, the precipitates formed on DW specimens were identified as calcium carbonate and calcium hydroxide primarily, whereas the precipitates on PBS specimens were inferred to be amorphous calcium phosphate.

  7. Effects of EDTA on the hydration mechanism of mineral trioxide aggregate.

    PubMed

    Lee, Y-L; Lin, F-H; Wang, W-H; Ritchie, H H; Lan, W-H; Lin, C-P

    2007-06-01

    Ethylenediaminetetraacetic acid (EDTA) is commonly used during the preparation of obstructed root canals that face a high risk of root perforation. Such perforations may be repaired with mineral trioxide aggregate (MTA). Due to EDTA's ability to chelate calcium ions, we hypothesized that EDTA may disrupt the hydration of MTA. Using scanning electron microscopy and energy-dispersive x-ray spectroscopy, we found that MTA specimens stored in an EDTA solution had no crystalline structure and a Ca/Si molar ratio considerably lower than those obtained for specimens stored in distilled water and normal saline. Poor cell adhesion in EDTA-treated MTA was also noted. X-ray diffraction indicated that the peak corresponding to portlandite, which is normally present in hydrated MTA, was not shown in the EDTA group. The microhardness of EDTA-treated specimens was also significantly reduced (p < 0.0001). These findings suggest that EDTA interferes with the hydration of MTA, resulting in decreased hardness and poor biocompatibility.

  8. Bortezomib and Arsenic Trioxide Activity on a Myelodysplastic Cell Line (P39): A Gene Expression Study

    PubMed Central

    Savlı, Hakan; Galimberti, Sara; Sünnetçi, Deniz; Canestraro, Martina; Palumbo, Giuseppe; Nagy, Balint; Raimondo, Francesco Di; Petrini, Mario

    2015-01-01

    Objective: We aimed to understand the molecular pathways affected by bortezomib and arsenic trioxide treatment on myelomonocytoid cell line P39. Materials and Methods: Oligonucleotide microarray platforms were used for gene expression and pathway analysis. Confirmation studies were performed using quantitative real time PCR. Results: Bortezomib treatment has shown upregulated DIABLO and NF-κBIB (a NF-κB inhibitor) and downregulated NF-κB1, NF-κB2, and BIRC1 gene expressions. Combination treatment of the two compounds showed gene expression deregulations in concordance by the results of single bortezomib treatment. Especially, P53 was a pathway more significantly modified and a gene network centralized around the beta estradiol gene. Beta estradiol, BRCA2, and FOXA1 genes were remarkable deregulations in our findings. Conclusion: Results support the suggestions about possible use of proteasome inhibitors in the treatment of high-risk myelodysplastic syndrome (MDS). NF-κB was observed as an important modulator in leukemic transformation of MDS. PMID:25913414

  9. Cytotoxic effects of mineral trioxide aggregate, calcium enrichedmixture cement, Biodentine and octacalcium pohosphate onhuman gingival fibroblasts

    PubMed Central

    A. Saberi, Eshagh; Farhadmollashahi, Narges; Ghotbi, Faroogh; Karkeabadi, Hamed; Havaei, Roholla

    2016-01-01

    Background. This in vitro study compared the effects of mineral trioxide aggregate (MTA), calcium enriched mixture(CEM) cement, Biodentine (BD) and octacalcium phosphate (OCP) on the viability of human gingival fibroblasts (HGFs). Methods. After completion of the setting time of the materials under study, fibroblasts were placed in 24-well insert platesand 1 mg of each material was added to the respective wells. The plates were then incubated at 37°C. The inserts were removedat 24, 48 and 168 hours and 2,5-diphenyltetrazolium bromide was added to assess cytotoxicity via the MTT colorimetricassay. Data were analyzed at different time intervals using repeated-measures ANOVA, followed by the Bonferronitest at three levels of significance of P < 0.05, P < 0.01 and P < 0.001. Results. Cytotoxicity of the materials under study was not significantly different at 24 and 48 hours compared to the controlgroup. However, at 168 hours, a significant difference was noted between MTA (P < 0.05) and Biodentine (P < 0.01)and the control group. Conclusion. Cytotoxicity of MTA, CEM, Biodentine and OCP against HGFs was similar to that of the control group at 24and 48 hours. Over time, MTA and Biodentine exhibited less cytotoxicity than other materials. PMID:27429722

  10. Treatment of pulp floor and stripping perforation by mineral trioxide aggregate.

    PubMed

    Tsai, Yi-Ling; Lan, Wan-Hong; Jeng, Jiiang-Huei

    2006-06-01

    Mineral trioxide aggregate (MTA) has been widely used to repair various kinds of tooth perforations, but its use for obturation of the entire root canal has not been reported. We report two cases of tooth perforation successfully repaired with MTA. The first patient was a 78-year-old male with calcified canal and pulp floor perforation in the left maxillary first premolar. After bypass of the calcified palatal canal, both buccal and palatal canals were filled with gutta percha, and the pulp floor perforation was repaired with MTA. Clinical success with no evident radicular lesion was found at the 18-month follow-up. The second patient was a 51-year-old female with a stripping perforation in a C-shaped root canal of the right mandibular second molar detected after removal of a post. Following root canal debridement and calcium hydroxide therapy to control inflammation at the stripping perforation site, apical and furcation bone healing were observed by radiographic examination. The stripping perforation was repaired by obturation of the entire C-shaped root canal with MTA. Observation at the 9-month follow-up revealed bone healing without any clinical symptoms and signs. These cases suggest that MTA is an alternative root canal obturation material for treatment of stripping perforation in a C-shaped root canal and for repair of pulp floor perforation.

  11. Performances and mechanistic investigations of a triphosphine trioxide/ionic liquid system for rare earth extraction.

    PubMed

    Turgis, R; Arrachart, G; Dubois, V; Dourdain, S; Virieux, D; Michel, S; Legeai, S; Lejeune, M; Draye, M; Pellet-Rostaing, S

    2016-01-21

    The extraction of rare earth elements (REEs) from nitric acid solution with a triphosphine trioxide (TPO) is presented. Performances of such a ligand in ionic liquids vs. a classical solvent (benzyl ether) are compared. TPO seems to be 10 to 100 times more efficient when it is dissolved in ionic media whatever the concentration of nitric acid involved. Mechanistic investigations reveal that cation exchange classically observed in ionic liquids is not consistent with the experimental data. Moreover, clear differences in the TPO/Ln complexes between classical and ionic media are highlighted. A stable complex of 1 lanthanide for 3 TPO is formed in an ionic liquid whereas a complex of 1 lanthanide for 6 to 9 TPO is formed in benzyl ether. Back extraction is also studied and good recovery of REEs could be obtained. The TPO/ionic liquid system shows remarkable performances i.e. efficiency and selectivity towards lanthanides in a simulated leaching solution of a Nd/Fe/B/Dy magnet.

  12. Electron Transfer Governed Crystal Transformation of Tungsten Trioxide upon Li Ions Intercalation

    SciTech Connect

    Wang, Zhiguo; He, Yang; Gu, Meng; Du, Yingge; Mao, Scott X.; Wang, Chongmin

    2016-09-21

    Reversible insertion/extraction of ions into a host lattice constitutes the fundamental operating principle of rechargeable battery and electrochromic materials. It is far more commonly observed that insertion of ions into a host lattice can lead to structural evolution of the host lattice, and for the most cases such a lattice evolution is subtle. However, it has never been clear as what kind of factors to control such a lattice structural evolution. Based on tungsten trioxide (WO3) model crystal, we use in situ transmission electron microscopy (TEM) and first principles calculation to explore the nature of Li ions intercalation induced crystal symmetry evolution of WO3. We discovered that Li insertion into the octahedral cavity of WO3 lattice will lead to a low to high symmetry transition, featuring a sequential monoclinic→tetragonal→cubic phase transition. The first principle calculation reveals that the phase transition is essentially governed by the electron transfer from Li to the WO6 octahedrons, which effectively leads to the weakening the W-O bond and modifying system band structure, resulting in an insulator to metal transition. The observation of the electronic effect on crystal symmetry and conductivity is significant, providing deep insights on the intercalation reactions in secondary rechargeable ion batteries and the approach for tailoring the functionalities of material based on insertion of ions in the lattice.

  13. Cytotoxicity of two available mineral trioxide aggregate cements and a new formulation on human gingival fibroblasts

    PubMed Central

    Torshabi, Maryam; Amid, Reza; Kadkhodazadeh, Mahdi; Shahrbabaki, Sara Eslami; Tabatabaei, Fahimeh S.

    2016-01-01

    Aim: The purpose of this study was to investigate the cytotoxicity of nanohybrid mineral trioxide aggregate (MTA) in comparison with calcium-enriched mixture (CEM) cement and MTA-Angelus, using human gingival fibroblasts (HGFs). Materials and Methods: Nine disc-shaped specimens of each material (in 2 set stat: A, set for 24 h; B, set for 30 min; and C, fresh stat) were prepared. HGFs were exposed to tested materials’ extracts or control media. Cytotoxicity testing was performed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assay in two time intervals. Statistical Analysis: Results were evaluated by one-way ANOVA and t-test. Statistical significance was set at P < 0.05. Results: CEM cement demonstrated favorable cell viability values when completely set (24 h set MTA = 24 h set CEM) at both time intervals. Interestingly, 24 h after incubation, CEM in Groups B and C demonstrated higher cell viability values than MTA (P < 0.05). However, after 72 h of incubation, these groups of CEM and MTA showed equal cell viability. All samples of nanohybrid MTA had slight cytotoxic effects after 24 h of incubation, and moderate cytotoxic effects after 72 h of incubation. Conclusion: Set CEM and set MTA-Angelus exerted similar, favorable effects on cell viability. However, within the limitations of this in vitro study, the results suggest that nanohybrid MTA could not be recommended as a material of choice for cervical root resorption. PMID:27994312

  14. Blockage of JNK pathway enhances arsenic trioxide-induced apoptosis in human keratinocytes

    SciTech Connect

    Huang, H.-S.; Liu, Z.-M.; Hong, D.-Y.

    2010-04-15

    Arsenic is well known as a carcinogen predisposing humans to some severe diseases and also as an effective medicine for treating acute promyelocytic leukemia, syphilis, and psoriasis. Multiple active mechanisms, including cell cycle arrest and apoptosis, have been proposed in therapy; however, the opposing effects of arsenic remain controversial. Our previous study found that arsenic trioxide (ATO)-induced activation of p21{sup WAF1/CIP1} (p21) led to A431 cell death through the antagonistic effects of the signaling of ERK1/2 and JNK1. In the current study, the inhibitory effects of JNK1 on ATO-induced p21 expression were explored. Over-expression of JNK1 in A431 cells could inhibit p21 expression, which was associated with HDAC1 and TGIF. Using the GST pull-down assay and fluorescence resonance energy transfer analysis, N-terminal domain (amino acids 1-108) of TGIF, critical to its binding with c-Jun, was found. Using reporter assays, requirement of the C-terminal domain (amino acids 138-272) of TGIF to suppress ATO-induced p21 expression was observed. Thus, the domains of TGIF that carried out its inhibitory effects on p21 were identified. Finally, treatment with JNK inhibitor SP600125 could enhance ATO-induced apoptosis of HaCaT keratinocytes by using flow cytometry.

  15. Endothelial to mesenchymal transition contributes to arsenic-trioxide-induced cardiac fibrosis

    PubMed Central

    Zhang, Yong; Wu, Xianxian; Li, Yang; Zhang, Haiying; Li, Zhange; Zhang, Ying; Zhang, Longyin; Ju, Jiaming; Liu, Xin; Chen, Xiaohui; Glybochko, Peter V.; Nikolenko, Vladimir; Kopylov, Philipp; Xu, Chaoqian; Yang, Baofeng

    2016-01-01

    Emerging evidence has suggested the critical role of endothelial to mesenchymal transition (EndMT) in fibrotic diseases. The present study was designed to examine whether EndMT is involved in arsenic trioxide (As2O3)-induced cardiac fibrosis and to explore the underlying mechanisms. Cardiac dysfunction was observed in rats after exposure to As2O3 for 15 days using echocardiography, and the deposition of collagen was detected by Masson’s trichrome staining and electron microscope. EndMT was indicated by the loss of endothelial cell markers (VE-cadherin and CD31) and the acquisition of mesenchymal cell markers (α-SMA and FSP1) determined by RT-PCR at the mRNA level and Western blot and immunofluorescence analysis at the protein level. In the in-vitro experiments, endothelial cells acquired a spindle-shaped morphology accompanying downregulation of the endothelial cell markers and upregulation of the mesenchymal cell markers when exposed to As2O3. As2O3 activated the AKT/GSK-3β/Snail signaling pathway, and blocking this pathway with PI3K inhibitor (LY294002) abolished EndMT in As2O3-treated endothelial cells. Our results highlight that As2O3 is an EndMT-promoting factor during cardiac fibrosis, suggesting that targeting EndMT is beneficial for preventing As2O3-induced cardiac toxicity. PMID:27671604

  16. Identifying arsenic trioxide (ATO) functions in leukemia cells by using time series gene expression profiles.

    PubMed

    Yang, Hong; Lin, Shan; Cui, Jingru

    2014-02-10

    Arsenic trioxide (ATO) is presently the most active single agent in the treatment of acute promyelocytic leukemia (APL). In order to explore the molecular mechanism of ATO in leukemia cells with time series, we adopted bioinformatics strategy to analyze expression changing patterns and changes in transcription regulation modules of time series genes filtered from Gene Expression Omnibus database (GSE24946). We totally screened out 1847 time series genes for subsequent analysis. The KEGG (Kyoto encyclopedia of genes and genomes) pathways enrichment analysis of these genes showed that oxidative phosphorylation and ribosome were the top 2 significantly enriched pathways. STEM software was employed to compare changing patterns of gene expression with assigned 50 expression patterns. We screened out 7 significantly enriched patterns and 4 tendency charts of time series genes. The result of Gene Ontology showed that functions of times series genes mainly distributed in profiles 41, 40, 39 and 38. Seven genes with positive regulation of cell adhesion function were enriched in profile 40, and presented the same first increased model then decreased model as profile 40. The transcription module analysis showed that they mainly involved in oxidative phosphorylation pathway and ribosome pathway. Overall, our data summarized the gene expression changes in ATO treated K562-r cell lines with time and suggested that time series genes mainly regulated cell adhesive. Furthermore, our result may provide theoretical basis of molecular biology in treating acute promyelocytic leukemia.

  17. The status of mineral trioxide aggregate in endodontics education in dental schools in Turkey.

    PubMed

    Tanalp, Jale; Karapinar-Kazandag, Meriç; Ersev, Handan; Bayirli, Gündüz

    2012-06-01

    The aim of this study was to assess the current status of mineral trioxide aggregate (MTA) as an educational material in dental schools in Turkey. A survey was sent to senior members of the endodontic departments of seventeen dental schools; fourteen responded. All respondents reported that they used MTA in their clinical practice, with apexification, perforations, retrograde fillings, and root resorptions being the most frequently occurring treatment procedures. All reported that information was given to students regarding MTA mainly as part of the curriculum. The third and fourth years were the periods when MTA was introduced to students in most of the schools. Twelve schools reported that students had the opportunity to observe procedures in which MTA was used, but students had the chance to use the material in a very minor proportion of the schools, mainly under the supervision of clinical instructors. Ten schools agreed that MTA should be included in the regular endodontic curriculum. Financial constraints seemed to be the predominant reason for those who answered this question negatively, followed by difficult handling properties and low radiopacity of the material. Within the limitations of this study, it can be concluded that ways should be sought to prevent financial difficulties from depriving dental students of the opportunity to receive information about contemporary methodologies such as MTA utilization.

  18. Tooth discoloration induced by a novel mineral trioxide aggregate-based root canal sealer

    PubMed Central

    Lee, Dae-Sung; Lim, Myung-Jin; Choi, Yoorina; Rosa, Vinicius; Hong, Chan-Ui; Min, Kyung-San

    2016-01-01

    Objectives: The aim of this study was to evaluate tooth discoloration caused by contact with a novel injectable mineral trioxide aggregate (MTA)-based root canal sealer (Endoseal; Maruchi, Wonju, Korea) compared with a widely used resin-based root canal sealer (AHplus; Dentsply De Trey, Konstanz, Germany) and conventional MTA (ProRoot; Dentsply, Tulsa, OK, USA). Materials and Methods: Forty standardized bovine tooth samples were instrumented and divided into three experimental groups and one control group (n = 10/group). Each material was inserted into the cavity, and all specimens were sealed with a self-adhesive resin. Based on CIE Lab system, brightness change (ΔL) and total color change (ΔE) of each specimen between baseline and 1, 2, 4, and 8 weeks were obtained. Results: At all time points, Endoseal showed no significant difference in ΔL and ΔE compared to AHplus and control group (P > 0.05), whereas the ProRoot group showed significantly higher ΔL and ΔE values than the Endoseal group at 2, 4, and 8 weeks (P < 0.05). Therefore, Endoseal showed less discoloration than conventional MTA and a similar color change to AHplus. Conclusions: Within the limitations of this study, our data indicate that the MTA-based sealer produces a similar amount of tooth discoloration as AHplus which is considered to be acceptable. PMID:27403062

  19. A Histological Comparison of a New Pulp Capping Material and Mineral Trioxide Aggregate in Rat Molars

    PubMed Central

    Moazzami, Fariborz; Ghahramani, Yasmin; Tamaddon, Ali Mohammad; Dehghani Nazhavani, Ali; Adl, Alireza

    2014-01-01

    Introduction: Recent investigations have attempted to improve regenerative endodontics with the help of stem cell therapy. In vitro studies have shown the ability of different agents to stimulate the differentiation of dental pulp stem cells (DPSC) into odontoblast-like cells. A combination of dexamethasone, β-glycerophosphate and Vitamin D has been proven to induce a successful differentiation. The aim of this animal study was to evaluate the effect of this combination, named odontoblastic differentiating material (ODM), on pulp tissue when used as a capping material. Materials and Methods: Sixty maxillary right and left molars of 30 Sprague-dawley rats were selected for this study. The teeth were exposed under sterile condition. Half of the teeth were capped with mineral trioxide aggregate (MTA) and the other half with ODM. All cavities were restored with glass ionomer. The rats were sacrificed at post-operative intervals of 2 weeks and 2 months. Samples were histologically evaluated for the degree of inflammation and reparative dentin formation. Finally the data was analyzed with Mann-Whitney and Chi-Square tests. Results: Reparative dentin formed in all groups within both time periods and there was no statistically significant difference between the groups in the mentioned time periods. The MTA group, however, showed a statistically significant reduction in inflammation at both time intervals (P<0.05). Compared to MTA, ODM samples showed a greater amount of inflammation in the pulp tissue. Conclusion: ODM, as a pulp capping material, can induce dentinal bridge formation. PMID:24396376

  20. Morphine Attenuated the Cytotoxicity Induced by Arsenic Trioxide in H9c2 Cardiomyocytes.

    PubMed

    Amini-Khoei, Hossein; Hosseini, Mir-Jamal; Momeny, Majid; Rahimi-Balaei, Maryam; Amiri, Shayan; Haj-Mirzaian, Arya; Khedri, Mostafa; Jahanabadi, Samane; Mohammadi-Asl, Ali; Mehr, Shahram Ejtemaie; Dehpour, Ahmad Reza

    2016-09-01

    Arsenic trioxide (ATO) is an efficient drug for the treatment of the patients with acute promyelocytic leukemia (APL). Inhibition of proliferation as well as apoptosis, attenuation of migration, and induction of differentiation in tumor cells are the main mechanisms through which ATO acts against APL. Despite advantages of ATO in treatment of some malignancies, certain harmful side effects, such as cardiotoxicity, have been reported. It has been well documented that morphine has antioxidant, anti-apoptotic, and cytoprotective properties and is able to attenuate cytotoxicity. Therefore, in this study, we aimed to investigate the protective effects of morphine against ATO toxicity in H9c2 myocytes using multi-parametric assay including thiazolyl blue tetrazolium bromide (MTT) assay, reactive oxygen species (ROS) generation, caspase 3 activity, nuclear factor kappa B (NF-κB) phosphorylation assay, and expression of apoptotic markers. Our results showed that morphine (1 μM) attenuated cytotoxicity induced by ATO in H9c2 cells. Results of this study suggest that morphine may have protective properties in management of cardiac toxicity in patients who receive ATO as an anti-cancer treatment.

  1. Heat shock protein inhibitors, 17-DMAG and KNK437, enhance arsenic trioxide-induced mitotic apoptosis

    SciTech Connect

    Wu Yichen; Yen Wenyen; Lee, T.-C. Yih, L.-H.

    2009-04-15

    Arsenic trioxide (ATO) has recently emerged as a promising therapeutic agent in leukemia because of its ability to induce apoptosis. However, there is no sufficient evidence to support its therapeutic use for other types of cancers. In this study, we investigated if, and how, 17-dimethylaminoethylamino-17-demethoxy-geldanamycin (17-DMAG), an antagonist of heat shock protein 90 (HSP90), and KNK437, a HSP synthesis inhibitor, potentiated the cytotoxic effect of ATO. Our results showed that cotreatment with ATO and either 17-DMAG or KNK437 significantly increased ATO-induced cell death and apoptosis. siRNA-mediated attenuation of the expression of the inducible isoform of HSP70 (HSP70i) or HSP90{alpha}/{beta} also enhanced ATO-induced apoptosis. In addition, cotreatment with ATO and 17-DMAG or KNK437 significantly increased ATO-induced mitotic arrest and ATO-induced BUBR1 phosphorylation and PDS1 accumulation. Cotreatment also significantly increased the percentage of mitotic cells with abnormal mitotic spindles and promoted metaphase arrest as compared to ATO treatment alone. These results indicated that 17-DMAG or KNK437 may enhance ATO cytotoxicity by potentiating mitotic arrest and mitotic apoptosis possibly through increased activation of the spindle checkpoint.

  2. Tungsten trioxide as a visible light photocatalyst for volatile organic carbon removal.

    PubMed

    Wicaksana, Yossy; Liu, Sanly; Scott, Jason; Amal, Rose

    2014-10-31

    Tungsten trioxide (WO3) has been demonstrated to possess visible light photoactivity and presents a means of overcoming the UV-light dependence of photocatalysts, such as titanium dioxide. In this study, WO3 nanostructures have been synthesised by a hydrothermal method using sodium tungstate (Na2WO4·2H2O), sulphate precursors and pH as structure-directing agents and parameters, respectively. By altering the concentration of the sulphate precursors and pH, it was shown that different morphologies and phases of WO3 can be achieved. The effect of the morphology of the final WO3 product on the visible light photoactivity of ethylene degradation in the gas phase was investigated. In addition, platinum (Pt) was photodeposited on the WO3 structures with various morphologies to enhance the photocatalytic properties. It was found that the photocatalytic properties of the WO3 samples greatly depend on their morphology, chemical composition and surface modification. WO3 with a cuboid morphology exhibited the highest visible light photoactivity compared to other morphologies, while adding Pt to the surface improved the performance of certain WO3 structures.

  3. Arsenic trioxide alters the differentiation of mouse embryonic stem cell into cardiomyocytes

    PubMed Central

    Rebuzzini, Paola; Cebral, Elisa; Fassina, Lorenzo; Alberto Redi, Carlo; Zuccotti, Maurizio; Garagna, Silvia

    2015-01-01

    Chronic arsenic exposure is associated with increased morbidity and mortality for cardiovascular diseases. Arsenic increases myocardial infarction mortality in young adulthood, suggesting that exposure during foetal life correlates with cardiac alterations emerging later. Here, we investigated the mechanisms of arsenic trioxide (ATO) cardiomyocytes disruption during their differentiation from mouse embryonic stem cells. Throughout 15 days of differentiation in the presence of ATO (0.1, 0.5, 1.0 μM) we analysed: the expression of i) marker genes of mesoderm (day 4), myofibrillogenic commitment (day 7) and post-natal-like cardiomyocytes (day 15); ii) sarcomeric proteins and their organisation; iii) Connexin 43 and iv) the kinematics contractile properties of syncytia. The higher the dose used, the earlier the stage of differentiation affected (mesoderm commitment, 1.0 μM). At 0.5 or 1.0 μM the expression of cardiomyocyte marker genes is altered. Even at 0.1 μM, ATO leads to reduction and skewed ratio of sarcomeric proteins and to a rarefied distribution of Connexin 43 cardiac junctions. These alterations contribute to the dysruption of the sarcomere and syncytium organisation and to the impairment of kinematic parameters of cardiomyocyte function. This study contributes insights into the mechanistic comprehension of cardiac diseases caused by in utero arsenic exposure. PMID:26447599

  4. Arsenic trioxide alters the differentiation of mouse embryonic stem cell into cardiomyocytes.

    PubMed

    Rebuzzini, Paola; Cebral, Elisa; Fassina, Lorenzo; Alberto Redi, Carlo; Zuccotti, Maurizio; Garagna, Silvia

    2015-10-08

    Chronic arsenic exposure is associated with increased morbidity and mortality for cardiovascular diseases. Arsenic increases myocardial infarction mortality in young adulthood, suggesting that exposure during foetal life correlates with cardiac alterations emerging later. Here, we investigated the mechanisms of arsenic trioxide (ATO) cardiomyocytes disruption during their differentiation from mouse embryonic stem cells. Throughout 15 days of differentiation in the presence of ATO (0.1, 0.5, 1.0 μM) we analysed: the expression of i) marker genes of mesoderm (day 4), myofibrillogenic commitment (day 7) and post-natal-like cardiomyocytes (day 15); ii) sarcomeric proteins and their organisation; iii) Connexin 43 and iv) the kinematics contractile properties of syncytia. The higher the dose used, the earlier the stage of differentiation affected (mesoderm commitment, 1.0 μM). At 0.5 or 1.0 μM the expression of cardiomyocyte marker genes is altered. Even at 0.1 μM, ATO leads to reduction and skewed ratio of sarcomeric proteins and to a rarefied distribution of Connexin 43 cardiac junctions. These alterations contribute to the dysruption of the sarcomere and syncytium organisation and to the impairment of kinematic parameters of cardiomyocyte function. This study contributes insights into the mechanistic comprehension of cardiac diseases caused by in utero arsenic exposure.

  5. Evaluation of mineral trioxide aggregate as root canal sealer: A clinical study

    PubMed Central

    Thakur, Sophia; Emil, Jonathan; Paulaian, Benin

    2013-01-01

    Aim: The aim of this study was to compare the clinical and radiological outcome of mineral trioxide aggregate (MTA) or epoxy resin as a root canal sealer compared with zinc oxide eugenol sealer. Materials and Methods: 45 single rooted teeth with periapical index Score 2 or more were allotted to three groups with 15 teeth in each group. Root canal treatment was performed in two visits and obturated with Gutta-percha as obturating material and zinc oxide eugenol as sealer in Group 1, epoxy resin as sealer in Group 2 and MTA mixed with propylene glycol as sealer in Group 3. Visual analog scale, periapical index and VixWin digital Pro image analysis software were used for evaluation. The quantitative data was analyzed by t-test and analysis of variance. Ordinal data was analyzed by Wilcoxon's signed rank test, Mann-Whitney and Kruskall-Wallis test. Results: Results suggested that there exists no statistically significant difference in clinical or radiological outcome of root canal therapy with three different types of sealers used in this study. Conclusions: MTA could be used as a root canal sealer with equal effectiveness compared with epoxy resin and zinc oxide eugenol sealers. Further long-term studies should be carried out to prove the effectiveness. PMID:24347880

  6. Optimization of combination therapy of arsenic trioxide and fractionated radiotherapy for malignant glioma

    SciTech Connect

    Ning Shoucheng; Knox, Susan J. . E-mail: sknox@stanford.edu

    2006-06-01

    Purpose: The primary objective was to optimize the combined treatment regimen using arsenic trioxide (ATO) and fractionated radiotherapy for the treatment of malignant glioma. Methods and Materials: Nude mice with human glioma xenograft tumors were treated with fractionated local tumor radiation of 250 cGy/fraction/day and 5 mg/kg ATO for 5-10 days. Results: Time course experiments demonstrated that maximal tumor growth delay occurred when ATO was administered between 0 and 4 h after radiation. The combination treatment of ATO and radiation synergistically inhibited tumor growth and produced a tumor growth delay time of 13.2 days, compared with 1.4 days and 6.5 days for ATO and radiation alone (p < 0.01), respectively. The use of concurrent therapy of radiation and ATO initially, followed by ATO as maintenance therapy, was superior to the use of preloading with ATO before combined therapy and produced a tumor growth delay time of 22.7 days as compared with 11.7 days for the ATO preloading regimen (p < 0.01). The maintenance dose of ATO after concurrent therapy was effective and important for continued inhibition of tumor growth. Conclusions: The combined use of fractionated radiation and ATO is effective for the treatment of glioma xenograft tumors. ATO was most effective when administered 0-4 h after radiation without pretreatment with ATO. These results have important implications for the optimization of treatment regimen using ATO and fractionated radiotherapy for the treatment of brain tumors.

  7. Grape seed and skin extract protects against arsenic trioxide induced oxidative stress in rat heart.

    PubMed

    Sfaxi, Ichraf; Charradi, Kamel; Limam, Ferid; El May, Michèle Veronique; Aouani, Ezzedine

    2015-07-29

    Arsenic is a metalloid found in water, soil, and air from natural and anthropogenic sources, and is commonly found in inorganic as well as organic forms. The clinical use of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL) is limited by its cardiotoxic side effects. Grape seed and skin extract (GSSE) is a polyphenolic mixture with antioxidant properties. This study aimed to evaluate the protective effect of GSSE on arsenic-induced cardiac oxidative stress and injury. Animals exposed to 2.5 mg/kg As2O3 for 21 days exhibited a relevant increase in heart lipoperoxidation, protein carbonylation, and inflammation, as well as a drop in the activity of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx). In addition, As2O3 disturbed heart lipidemia and lipase activity, transition metals distribution and the associated enzymes, intracellular mediators such as calcium and the associated calpain activity, as well as myocardial architecture. Treatment with 4 g/kg GSSE protected against most of the deleterious effects provoked by As2O3. Our data suggest that GSSE has the potential to protect against As2O3-induced cardiotoxicity.

  8. Arsenic trioxide inhibits cell proliferation and human papillomavirus oncogene expression in cervical cancer cells.

    PubMed

    Wang, Hongtao; Gao, Peng; Zheng, Jie

    2014-09-05

    Arsenic trioxide (As2O3) has shown therapeutic effects in some leukemias and solid cancers. However, the molecular mechanisms of its anticancer efficacy have not been clearly elucidated, particularly in solid cancers. Our previous data showed that As2O3 induced apoptosis of human papillomavirus (HPV) 16 DNA-immortalized human cervical epithelial cells and cervical cancer cells and inhibited the expression of HPV oncogenes in these cells. In the present study, we systemically examined the effects of As2O3 on five human cervical cancer cell lines and explored the possible molecular mechanisms. MTT assay showed that HPV-negative C33A cells were more sensitive to growth inhibition induced by As2O3 than HPV-positive cervical cancer cells, and HPV 18-positive HeLa and C4-I cells were more sensitive to As2O3 than HPV 16-positive CaSki and SiHa cells. After As2O3 treatment, both mRNA and protein levels of HPV E6 and E7 obviously decreased in all HPV positive cell lines. In contrast, p53 and Rb protein levels increased in all tested cell lines. Transcription factor AP-1 protein expression decreased significantly in HeLa, CaSki and C33A cells with ELISA method. These results suggest that As2O3 is a potential anticancer drug for cervical cancer.

  9. Antimicrobial Efficacy of Mineral Trioxide Aggregate with and without Silver Nanoparticles

    PubMed Central

    Samiei, Mohammad; Aghazadeh, Mohammad; Lotfi, Mehrdad; Shakoei, Sahar; Aghazadeh, Zahra; Vahid Pakdel, Seyyed Mahdi

    2013-01-01

    Introduction Most current root-end filling materials do not provide a perfect seal. Thus, a microscopic space is likely to exist in the interface between walls of the root-end cavity and filling material, which allows microorganisms and their products to penetrate. In addition to good sealing ability and biocompatibility, root-end filling materials should ideally have some antimicrobial activity. Therefore, this in vitro study aimed to evaluate the antimicrobial properties of Angelus white mineral trioxide aggregate (MTA) and the mixture of MTA with silver nanoparticles (1% weight; MTA/SN). Materials and Methods Antimicrobial properties of MTA and MTA/SN were tested by agar diffusion technique against Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans. The microbial inhibition zones around the materials were measured by a caliper with 0.1-mm accuracy. Student’s t-test was used for comparison between the two groups in normal data distribution and Man-Whitney U test for non-normal distribution. Results Student’s t-test revealed that for E. faecalis, C. albicans, and P. aeruginosa, microbial inhibition zone of MTA/SN was significantly greater than that of MTA (P = 0.000). Mann-Whitney U test indicated no significant difference between the effect of MTA and MTA/SN on S. aureus (P > 0.05). Conclusion Based on the results of this study, adding silver nanoparticles to MTA improved its antimicrobial efficacy. PMID:24171023

  10. In vitro investigations into the etiology of mineral trioxide tooth staining

    PubMed Central

    Berger, Todd; Baratz, Adam Z.; Gutmann, James L.

    2014-01-01

    Aim: To investigate the role of bismuth oxide, a constituent of contemporary mineral trioxide aggregate (MTA) materials, and its response to various solutions that may contribute to the potential discoloration that occurs following MTA applications within the scope of endodontics. Setting and Design: Laboratory assessment of chemical reactions with white ProRoot® MTA and white Portland cement (WPC). Materials and Methods: Set specimens and freshly mixed specimens of white ProRoot® MTA and white ProRoot® MTA powder, along with specimens of WPC were exposed to distilled water, phosphate buffered saline (PBS), 10% formalin, hydroxyethylmethacrylate (HEMA), sodium hypochlorite, sodium hydroxide (NaOH) base, and hydrochloric acid (HCl) acid. Specimens were visually inspected periodically for color changes. Results: All forms of ProRoot MTA showed discoloration when exposed to 10% formalin within 30 min, as opposed to WPC, and were completely blackened at 4 days. Bismuth oxide alone and with calcium oxide also turned black within 30 min after exposure to 10% formalin. No discoloration was seen when exposed to the other solutions. Conclusions: Exposing MTA in various forms to a variety of liquids has determined that bismuth oxidein combination with other chemical moieties is the prime cause of staining observed by clinicians. PMID:25506138

  11. Microleakage of accelerated mineral trioxide aggregate and Portland cement in an in vitro apexification model.

    PubMed

    Hong, Seong-Tae; Bae, Kwang-Shik; Baek, Seung-Ho; Kum, Kee-Yeon; Lee, WooCheol

    2008-01-01

    The purpose of this study was to evaluate the microleakage of accelerated mineral trioxide aggregate (MTA) and Portland cement by flow porometry analysis in an in vitro apexification model. Sixty-four single-rooted, extracted teeth were divided into 4 groups (group 1, MTA; group 2, MTA with accelerator; group 3, Portland cement; and group 4, Portland cement with accelerator). In an in vitro apexification model, MTA or Portland cement mixed with or without 10% CaCl2 was condensed to 2-mm thickness. The negative control group (n = 4) had the apical foramen sealed with epoxy resin. The maximum and mean flow pore diameters of the samples were tested by capillary flow porometry at 90 minutes and 48 hours after obturation. The addition of accelerator significantly reduced the maximum pore diameters of MTA and Portland cement at the initial setting phase. After 48 hours of obturation, the maximum and mean flow pore diameters of the accelerated samples were significantly reduced compared with the normal samples. There was no statistically significant difference in the maximum pore diameter of MTA and Portland cement between the measurements at 90 minutes and 48 hours. The results imply that the addition of accelerator into MTA or Portland cement can be useful in a one-visit apexification by reducing microleakage even in an early setting time.

  12. Arsenic trioxide induces endoplasmic reticulum stress-related events in neutrophils.

    PubMed

    Binet, François; Chiasson, Sonia; Girard, Denis

    2010-04-01

    We recently reported that the endoplasmic reticulum (ER)-induced cell pathway of apoptosis is operational in human neutrophils and that some ER stressors can accelerate this process. Recent data suggest that arsenic trioxide (As(2)O(3) or ATO), may also act as an ER stressor. The aims of the present study were to elucidate if other ER stress-related events occur in ATO-induced neutrophils, and to determine the role of caspase-4 in the proapoptotic activity of ATO. We found that ATO induced ubiquitination of proteins, and increased calcium concentration and gene expression of calcineurin in neutrophils. In addition to caspase-4, activities of caspase-3, -8 and -9 were increased by ATO. The processing of caspase-4 was reversed by a caspase-8 inhibitor, indicating that caspase-4 activation requires the action of upstream initiator components, questioning on the role of caspase-4 in ATO-induced ER stress-mediated cell apoptosis. Using caspase-4 deficient THP-1 cells, we demonstrated that the proapoptotic effect of ATO was similar to that of control caspase-4-positive cells. We conclude that ATO is an ER stressor that can induce cell apoptosis by a mechanism which does not require caspase-4. In addition, we conclude that caspase-4 activation in ATO-induced neutrophils could be involved in functions other than apoptosis.

  13. Interaction between arsenic trioxide and human primary cells: emphasis on human cells of myeloid origin.

    PubMed

    Binet, François; Antoine, Francis; Girard, Denis

    2009-03-01

    Arsenic trioxide (As(2)O(3); ATO) is considered to be one of the most potent drugs in cancer chemotherapy and is highly effective in the treatment of acute promyelocytic leukemia (APL). It is well established that treatment of APL patients with ATO is associated with the disappearance of the PML-RARalpha fusion transcript, the characteristic APL gene product of the chromosomal translocation t(15;17). Although its mode of action is still not fully understood, ATO is known to induce cell apoptosis via generation of reactive oxygen species and activation of caspases. Several reports have indicated that ATO acts principally by inducing cell apoptosis not only in APL, but in a variety of non-APL cells including myeloma cells, chronic myeloid leukemia cells and cells of immune origin, including B or T lymphocytes, macrophages and, more recently, neutrophils. There is an increasing amount of data, including some from our laboratory, concerning the interaction between ATO and human primary cells. The focus of this review will be to cover the role of ATO in human immune primary cells with special emphasis on cells of myeloid origin.

  14. Placement in an acidic environment increase the solubility of white mineral trioxide aggregate

    PubMed Central

    Yavari, Hamid Reza; Borna, Zahra; Rahimi, Saeed; Shahi, Shahriar; Valizadeh, Hadi; Ghojazadeh, Morteza

    2013-01-01

    Aims: The aim of the present study was to evaluate solubility of white mineral trioxide aggregate (WMTA) in an acidic environment. Materials and Methods: Twenty-four metal rings were prepared, filled with WMTA and randomly divided into two groups. The samples in groups 1 and 2 were set in synthetic tissue fluid with pH values of 7.4 and 4.4, respectively and then were transferred to beakers containing synthetic tissue fluid with pH values of 7.7 and 4.4. Solubility of WMTA samples were calculated at the 9 experimental intervals. Data was analyzed with two-factor ANOVA and Bonferroni test (P < 0.03). Results: The total solubility of WMTA in groups 1 and 2 were −9.1796 ± 1.9158% and −1.1192 ± 2.6236%, (P = 0.028) with weight changes of 9.1574 ± 2.1432% and 7.3276 ± 1.5823%, respectively (P = 0.002). Statistical analysis revealed significant differences between the two groups. Conclusions: It was concluded that solubility of WMTA increases in acidic environments and additional therapeutic precautions should be taken to decrease inflammation in endodontic treatment. PMID:23833462

  15. Two stage sorption of sulfur compounds

    DOEpatents

    Moore, William E.

    1992-01-01

    A two stage method for reducing the sulfur content of exhaust gases is disclosed. Alkali- or alkaline-earth-based sorbent is totally or partially vaporized and introduced into a sulfur-containing gas stream. The activated sorbent can be introduced in the reaction zone or the exhaust gases of a combustor or a gasifier. High efficiencies of sulfur removal can be achieved.

  16. 21 CFR 582.1095 - Sulfuric acid.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Sulfuric acid. 582.1095 Section 582.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS....1095 Sulfuric acid. (a) Product. Sulfuric acid. (b) Conditions of use. This substance is...

  17. 21 CFR 582.1095 - Sulfuric acid.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Sulfuric acid. 582.1095 Section 582.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS....1095 Sulfuric acid. (a) Product. Sulfuric acid. (b) Conditions of use. This substance is...

  18. 46 CFR 153.1046 - Sulfuric acid.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Sulfuric acid. 153.1046 Section 153.1046 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK....1046 Sulfuric acid. No person may liquefy frozen or congealed sulfuric acid other than by external...

  19. 46 CFR 153.1046 - Sulfuric acid.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Sulfuric acid. 153.1046 Section 153.1046 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK....1046 Sulfuric acid. No person may liquefy frozen or congealed sulfuric acid other than by external...

  20. 21 CFR 184.1095 - Sulfuric acid.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sulfuric acid. 184.1095 Section 184.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1095 Sulfuric acid. (a) Sulfuric acid (H2SO4, CAS Reg. No. 7664-93-9),...

  1. 46 CFR 153.1046 - Sulfuric acid.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Sulfuric acid. 153.1046 Section 153.1046 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK....1046 Sulfuric acid. No person may liquefy frozen or congealed sulfuric acid other than by external...

  2. 21 CFR 184.1095 - Sulfuric acid.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sulfuric acid. 184.1095 Section 184.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1095 Sulfuric acid. (a) Sulfuric acid (H2SO4, CAS Reg. No. 7664-93-9),...

  3. 21 CFR 582.1095 - Sulfuric acid.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Sulfuric acid. 582.1095 Section 582.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS....1095 Sulfuric acid. (a) Product. Sulfuric acid. (b) Conditions of use. This substance is...

  4. 21 CFR 184.1095 - Sulfuric acid.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sulfuric acid. 184.1095 Section 184.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1095 Sulfuric acid. (a) Sulfuric acid (H2SO4, CAS Reg. No. 7664-93-9),...

  5. 21 CFR 184.1095 - Sulfuric acid.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sulfuric acid. 184.1095 Section 184.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1095 Sulfuric acid. (a) Sulfuric acid (H2SO4, CAS Reg. No. 7664-93-9),...

  6. 21 CFR 582.1095 - Sulfuric acid.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Sulfuric acid. 582.1095 Section 582.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS....1095 Sulfuric acid. (a) Product. Sulfuric acid. (b) Conditions of use. This substance is...

  7. 21 CFR 184.1095 - Sulfuric acid.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sulfuric acid. 184.1095 Section 184.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD....1095 Sulfuric acid. (a) Sulfuric acid (H2SO4, CAS Reg. No. 7664-93-9), also known as oil of vitriol,...

  8. 46 CFR 153.1046 - Sulfuric acid.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Sulfuric acid. 153.1046 Section 153.1046 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK....1046 Sulfuric acid. No person may liquefy frozen or congealed sulfuric acid other than by external...

  9. 21 CFR 582.1095 - Sulfuric acid.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Sulfuric acid. 582.1095 Section 582.1095 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS....1095 Sulfuric acid. (a) Product. Sulfuric acid. (b) Conditions of use. This substance is...

  10. 46 CFR 153.1046 - Sulfuric acid.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Sulfuric acid. 153.1046 Section 153.1046 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK....1046 Sulfuric acid. No person may liquefy frozen or congealed sulfuric acid other than by external...

  11. 46 CFR 148.315 - Sulfur.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Sulfur. 148.315 Section 148.315 Shipping COAST GUARD... SPECIAL HANDLING Special Requirements for Certain Materials § 148.315 Sulfur. (a) This part applies to lump or coarse grain powder sulfur only. Fine-grained powder (“flowers of sulfur”) may not...

  12. 21 CFR 182.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sulfur dioxide. 182.3862 Section 182.3862 Food and... CONSUMPTION (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives § 182.3862 Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation. This substance...

  13. 21 CFR 182.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sulfur dioxide. 182.3862 Section 182.3862 Food and... CONSUMPTION (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives § 182.3862 Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation. This substance...

  14. 21 CFR 582.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Sulfur dioxide. 582.3862 Section 582.3862 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation....

  15. 21 CFR 582.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Sulfur dioxide. 582.3862 Section 582.3862 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation....

  16. 21 CFR 582.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Sulfur dioxide. 582.3862 Section 582.3862 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation....

  17. 46 CFR 148.315 - Sulfur.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Sulfur. 148.315 Section 148.315 Shipping COAST GUARD... SPECIAL HANDLING Special Requirements for Certain Materials § 148.315 Sulfur. (a) This part applies to lump or coarse grain powder sulfur only. Fine-grained powder (“flowers of sulfur”) may not...

  18. 46 CFR 148.315 - Sulfur.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Sulfur. 148.315 Section 148.315 Shipping COAST GUARD... SPECIAL HANDLING Special Requirements for Certain Materials § 148.315 Sulfur. (a) This part applies to lump or coarse grain powder sulfur only. Fine-grained powder (“flowers of sulfur”) may not...

  19. 21 CFR 582.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Sulfur dioxide. 582.3862 Section 582.3862 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation....

  20. 21 CFR 582.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Sulfur dioxide. 582.3862 Section 582.3862 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation....

  1. 21 CFR 182.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sulfur dioxide. 182.3862 Section 182.3862 Food and... CONSUMPTION (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives § 182.3862 Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation. This substance...

  2. 46 CFR 148.315 - Sulfur.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Sulfur. 148.315 Section 148.315 Shipping COAST GUARD... SPECIAL HANDLING Special Requirements for Certain Materials § 148.315 Sulfur. (a) This part applies to lump or coarse grain powder sulfur only. Fine-grained powder (“flowers of sulfur”) may not...

  3. Air Quality Criteria for Sulfur Oxides.

    ERIC Educational Resources Information Center

    National Air Pollution Control Administration (DHEW), Washington, DC.

    Included is a literature review which comprehensively discusses knowledge of the sulfur oxides commonly found in the atmosphere. The subject content is represented by the 10 chapter titles: Physical and Chemical Properties and the Atmospheric Reactions of the Oxides of Sulfur; Sources and Methods of Measurements of Sulfur Oxides in the Atmosphere;…

  4. 21 CFR 182.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sulfur dioxide. 182.3862 Section 182.3862 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives § 182.3862 Sulfur dioxide. (a) Product. Sulfur...

  5. 21 CFR 182.3862 - Sulfur dioxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sulfur dioxide. 182.3862 Section 182.3862 Food and... CONSUMPTION (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives § 182.3862 Sulfur dioxide. (a) Product. Sulfur dioxide. (b) (c) Limitations, restrictions, or explanation. This substance...

  6. Seal for sodium sulfur battery

    DOEpatents

    Topouzian, Armenag; Minck, Robert W.; Williams, William J.

    1980-01-01

    This invention is directed to a seal for a sodium sulfur battery in which the sealing is accomplished by a radial compression seal made on a ceramic component of the battery which separates an anode compartment from a cathode compartment of the battery.

  7. TRENDS IN RURAL SULFUR CONCENTRATIONS

    EPA Science Inventory

    This paper presents an analysis of regional trends in atmospheric concentrations in sulfur dioxide (502) and particulate sulfate (50~- ) at rural monitoring sites in the Clean Air Act Status and Trends Monitoring Network (CAsTNet) from 1990 to 1999. A two-stage approach is used t...

  8. Sulfur monochloride in organic synthesis

    NASA Astrophysics Data System (ADS)

    Konstantinova, L. S.; Rakitin, O. A.

    2014-03-01

    The data on the reactivity of sulfur monochloride published in the past 15 years have been reviewed and systematized. The review focuses on the synthesis of acyclic and heterocyclic compounds with the use of S2Cl2. The bibliography includes 154 references.

  9. Sulfur Dioxide and Material Damage

    ERIC Educational Resources Information Center

    Gillette, Donald G.

    1975-01-01

    This study relates sulfur dioxide levels with material damage in heavily populated or polluted areas. Estimates of loss were determined from increased maintenance and replacement costs. The data indicate a decrease in losses during the past five years probably due to decline in pollution levels established by air quality standards. (MR)

  10. Sulfur isotope distribution in solfataras, yellowstone national park.

    PubMed

    Schoen, R; Rye, R O

    1970-12-04

    Sulfur isotope data on hydrogen sulfide, native sulfur, and sulfates from acid hot-spring areas at Yellowstone National Park suggest that hydrogen sulfide oxidizes to sulfur abiologically, whereas sulfur undergoes biological oxidation to sulfuric acid. An exception occurs at Mammoth Hot Springs where hydrogen sulfide apparently undergoes biochemical oxidation to sulfur.

  11. Sulfur isotope distribution in solfatares, Yellowstone National Park

    USGS Publications Warehouse

    Schoen, R.; Rye, R.O.

    1970-01-01

    Sulfur isotope data on hydrogen sulfide, native sulfur, and sulfates from acid hot-spring areas at Yellowstone National Park suggest that hydrogen sulfide oxidizes to sulfur analogically, whereas sulfur undergoes biological oxidation to sulfuric acid. An exception occurs at Mammoth Hot Springs where hydrogen sulfide apparently undergoes biochemical oxidation to sulfur.

  12. Wet Chemistry Synthesis of Multidimensional Nanocarbon-Sulfur Hybrid Materials with Ultrahigh Sulfur Loading for Lithium-Sulfur Batteries.

    PubMed

    Du, Wen-Cheng; Yin, Ya-Xia; Zeng, Xian-Xiang; Shi, Ji-Lei; Zhang, Shuai-Feng; Wan, Li-Jun; Guo, Yu-Guo

    2016-02-17

    An optimized nanocarbon-sulfur cathode material with ultrahigh sulfur loading of up to 90 wt % is realized in the form of sulfur nanolayer-coated three-dimensional (3D) conducting network. This 3D nanocarbon-sulfur network combines three different nanocarbons, as follows: zero-dimensional carbon nanoparticle, one-dimensional carbon nanotube, and two-dimensional graphene. This 3D nanocarbon-sulfur network is synthesized by using a method based on soluble chemistry of elemental sulfur and three types of nanocarbons in well-chosen solvents. The resultant sulfur-carbon material shows a high specific capacity of 1115 mA h g(-1) at 0.02C and good rate performance of 551 mA h g(-1) at 1C based on the mass of sulfur-carbon composite. Good battery performance can be attributed to the homogeneous compositing of sulfur with the 3D hierarchical hybrid nanocarbon networks at nanometer scale, which provides efficient multidimensional transport pathways for electrons and ions. Wet chemical method developed here provides an easy and cost-effective way to prepare sulfur-carbon cathode materials with high sulfur loading for application in high-energy Li-S batteries.

  13. Unexpected extracellular and intracellular sulfur species during growth of Allochromatium vinosum with reduced sulfur compounds.

    PubMed

    Franz, Bettina; Gehrke, Thomas; Lichtenberg, Henning; Hormes, Josef; Dahl, Christiane; Prange, Alexander

    2009-08-01

    Before its uptake and oxidation by purple sulfur bacteria, elemental sulfur probably first has to be mobilized. To obtain more insight into this mobilization process in the phototrophic purple sulfur bacterium Allochromatium vinosum, we used HPLC analysis and X-ray absorption near-edge structure (XANES) spectroscopy for the detection and identification of sulfur compounds in culture supernatants and bacterial cells. We intended to identify soluble sulfur compounds that specifically occur during growth on elemental sulfur, and therefore compared spectra of cultures grown on sulfur with those of cultures grown on sulfide or thiosulfate. While various unexpected oxidized organic sulfur species (sulfones, C-SO(2)-C, and sulfonates, C-SO(3)(-)) were observed via XANES spectroscopy in the supernatants, we obtained evidence for the presence of monosulfane sulfonic acids inside the bacterial cells by HPLC analysis. The concentrations of the latter compounds showed a tight correlation with the content of intracellular sulfur, reaching their maximum when sulfur began to be oxidized. None of the detected sulfur compounds appeared to be a specific soluble intermediate or product of elemental sulfur mobilization. It therefore seems unlikely that mobilization of elemental sulfur by purple sulfur bacteria involves excretion of soluble sulfur-containing substances that would be able to act on substrate distant from the cells.

  14. Rhodanese functions as sulfur supplier for key enzymes in sulfur energy metabolism.

    PubMed

    Aussignargues, Clément; Giuliani, Marie-Cécile; Infossi, Pascale; Lojou, Elisabeth; Guiral, Marianne; Giudici-Orticoni, Marie-Thérèse; Ilbert, Marianne

    2012-06-08

    How microorganisms obtain energy is a challenging topic, and there have been numerous studies on the mechanisms involved. Here, we focus on the energy substrate traffic in the hyperthermophilic bacterium Aquifex aeolicus. This bacterium can use insoluble sulfur as an energy substrate and has an intricate sulfur energy metabolism involving several sulfur-reducing and -oxidizing supercomplexes and enzymes. We demonstrate that the cytoplasmic rhodanese SbdP participates in this sulfur energy metabolism. Rhodaneses are a widespread family of proteins known to transfer sulfur atoms. We show that SbdP has also some unusual characteristics compared with other rhodaneses; it can load a long sulfur chain, and it can interact with more than one partner. Its partners (sulfur reductase and sulfur oxygenase reductase) are key enzymes of the sulfur energy metabolism of A. aeolicus and share the capacity to use long sulfur chains as substrate. We demonstrate a positive effect of SbdP, once loaded with sulfur chains, on sulfur reductase activity, most likely by optimizing substrate uptake. Taken together, these results lead us to propose a physiological role for SbdP as a carrier and sulfur chain donor to these key enzymes, therefore enabling channeling of sulfur substrate in the cell as well as greater efficiency of the sulfur energy metabolism of A. aeolicus.

  15. Process for reducing sulfur in coal char

    DOEpatents

    Gasior, Stanley J.; Forney, Albert J.; Haynes, William P.; Kenny, Richard F.

    1976-07-20

    Coal is gasified in the presence of a small but effective amount of alkaline earth oxide, hydroxide or carbonate to yield a char fraction depleted in sulfur. Gases produced during the reaction are enriched in sulfur compounds and the alkaline earth compound remains in the char fraction as an alkaline earth oxide. The char is suitable for fuel use, as in a power plant, and during combustion of the char the alkaline earth oxide reacts with at least a portion of the sulfur oxides produced from the residual sulfur contained in the char to further lower the sulfur content of the combustion gases.

  16. The NRF2-mediated oxidative stress response pathway is associated with tumor cell resistance to arsenic trioxide across the NCI-60 panel

    PubMed Central

    2010-01-01

    Background Drinking water contaminated with inorganic arsenic is associated with increased risk for different types of cancer. Paradoxically, arsenic trioxide can also be used to induce remission in patients with acute promyelocytic leukemia (APL) with a success rate of approximately 80%. A comprehensive study examining the mechanisms and potential signaling pathways contributing to the anti-tumor properties of arsenic trioxide has not been carried out. Methods Here we applied a systems biology approach to identify gene biomarkers that underlie tumor cell responses to arsenic-induced cytotoxicity. The baseline gene expression levels of 14,500 well characterized human genes were associated with the GI50 data of the NCI-60 tumor cell line panel from the developmental therapeutics program (DTP) database. Selected biomarkers were tested in vitro for the ability to influence tumor susceptibility to arsenic trioxide. Results A significant association was found between the baseline expression levels of 209 human genes and the sensitivity of the tumor cell line panel upon exposure to arsenic trioxide. These genes were overlayed onto protein-protein network maps to identify transcriptional networks that modulate tumor cell responses to arsenic trioxide. The analysis revealed a significant enrichment for the oxidative stress response pathway mediated by nuclear factor erythroid 2-related factor 2 (NRF2) with high expression in arsenic resistant tumor cell lines. The role of the NRF2 pathway in protecting cells against arsenic-induced cell killing was validated in tumor cells using shRNA-mediated knock-down. Conclusions In this study, we show that the expression level of genes in the NRF2 pathway serve as potential gene biomarkers of tumor cell responses to arsenic trioxide. Importantly, we demonstrate that tumor cells that are deficient for NRF2 display increased sensitivity to arsenic trioxide. The results of our study will be useful in understanding the mechanism of

  17. Healing process of dog dental pulp after pulpotomy and pulp covering with mineral trioxide aggregate or Portland cement.

    PubMed

    Holland, R; de Souza, V; Murata, S S; Nery, M J; Bernabé, P F; Otoboni Filho, J A; Dezan Júnior, E

    2001-01-01

    Considering several reports about the similarity between the chemical compositions of the mineral trioxide aggregate (MTA) and Portland cement (PC), the subject of this investigation was to analyze the behavior of dog dental pulp after pulpotomy and direct pulp protection with these materials. After pulpotomy, the pulp stumps of 26 roots of dog teeth were protected with MTA or PC. Sixty days after treatment, the animal was sacrificed and the specimens removed and prepared for histomorphological analysis. There was a complete tubular hard tissue bridge in almost all specimens. In conclusion, MTA and PC show similar comparative results when used in direct pulp protection after pulpotomy.

  18. Facile synthesis of single crystalline rhenium (VI) trioxide nanocubes with high catalytic efficiency for photodegradation of methyl orange.

    PubMed

    Chong, Yuan Yi; Fan, Wai Yip

    2013-05-01

    Single-crystalline rhenium trioxide (ReO3) nanocubes have been prepared for the first time without the need of surfactants via controlled reduction of rhenium (VII) oxide (Re2O7), sandwiched between silicon wafers at 250°C. The metallic ReO3 nanocubes are magnetic and possess surface plasmon resonance (SPR) bands down to the NIR region. The nanocubes also show very high catalytic activity toward the photodegradation of methyl orange (MO) under ambient conditions. A mechanism has been proposed to account for the photodegradation process.

  19. Clinical manipulation of mineral trioxide aggregate: lessons from the construction industry and their relevance to clinical practice.

    PubMed

    Ha, William N; Kahler, Bill; Walsh, Laurence J

    2015-01-01

    Mineral trioxide aggregate (MTA) is based on ordinary Portland cement (with added radiopaque agents) and, thus, shares many of its features. Although MTA is reported to be difficult to handle clinically, concrete materials made using Portland cement are the foundation of the construction industry. In this paper, we summarize important lessons from the construction literature that are relevant to the successful use of MTA in clinical practice, including behaviour during storage, susceptibility to acidic environments, the effects of exposure of the setting material to moisture and interactions with substances that may interfere with the speed of setting and the quality of the end product.

  20. Improving chemical vapor deposition graphene conductivity using molybdenum trioxide: An in-situ field effect transistor study

    SciTech Connect

    Han, Cheng; Lin, Jiadan; Xiang, Du; Wang, Chaocheng; Wang, Li; Chen, Wei

    2013-12-23

    By using in situ field effect transistor characterization integrated with molecular beam epitaxy technique, we demonstrate the strong surface transfer p-type doping effect of single layer chemical vapor deposition (CVD) graphene, through the surface functionalization of molybdenum trioxide (MoO{sub 3}) layer. After doping, both the hole and electron mobility of CVD graphene are nearly retained, resulting in significant enhancement of graphene conductivity. With coating of 10 nm MoO{sub 3}, the conductivity of CVD graphene can be increased by about 7 times, showing promising application for graphene based electronics and transparent, conducting, and flexible electrodes.

  1. Transporters in plant sulfur metabolism

    PubMed Central

    Gigolashvili, Tamara; Kopriva, Stanislav

    2014-01-01

    Sulfur is an essential nutrient, necessary for synthesis of many metabolites. The uptake of sulfate, primary and secondary assimilation, the biosynthesis, storage, and final utilization of sulfur (S) containing compounds requires a lot of movement between organs, cells, and organelles. Efficient transport systems of S-containing compounds across the internal barriers or the plasma membrane and organellar membranes are therefore required. Here, we review a current state of knowledge of the transport of a range of S-containing metabolites within and between the cells as well as of their long distance transport. An improved understanding of mechanisms and regulation of transport will facilitate successful engineering of the respective pathways, to improve the plant yield, biotic interaction and nutritional properties of crops. PMID:25250037

  2. Sodium Sulfur Technology Program Nastec

    NASA Technical Reports Server (NTRS)

    Highley, Bob; Somerville, W. Andrew

    1992-01-01

    The NaSTEC program focuses on developing currently available sodium sulfur cells for use in space applications and investigating the operational parameters of the cells. The specific goals of the program are to determine the operational parameters and verify safety limits of Na/S technology battery cells; test long term zero-g operation; and create a life test database. The program approach and ground and flight test objectives are described in textual and graphic form.

  3. [Sulfur isotopic ratios indicating sulfur cycling in slope soils of karst areas].

    PubMed

    Zhang, Wei; Liu, Cong-qiang; Li, Xiao-dong; Liu, Tao-ze; Zhang, Li-li

    2010-02-01

    Sequential extraction methods for soil sulfur were used to determine delta34 S ratios and sulfur contents of total sulfur, organic sulfur, SO4(21) and FeS2 in slope soils of karst areas. In general, FeS2 has the lowest delta34 S ratios, ranging from -6.86% per hundred to -4.229% per hundred, followed in ascending order by SO4(2-) (-2.64% per hundred - -1.34% per hundred), total sulfur (-3.25% per hundred - -1.03% per hundred) and organic sulfur (-1.63% per hundred -0.50% per hundred) in surface soils of profiles, and delta34 S ratios in different sulfur forms all show increasing trend with profiles deepening. Covariations of delta34 S ratios of SO4(2-) and FeS2 with increasing depth are related to SO4(2-) dissimilatory reduction, while the increase in parallel of delta34 S ratios of total sulfur and organic sulfur could be resulted from organic sulfur cycling. delta34 S ratios have been extensively used to indicate sulfur sources, moreover, SO4(2-) dissimilatory reduction and organic sulfur mineralization result in significant sulfur isotopic fractionation, and sulfides oxidation and SO4(2-) assimilation have no isotopic fractionation occurred, the vertical variations of delta34 S ratios in different sulfur forms can therefore be good records for depth-dependant sulfur cycling processes. Furthermore, by comparing depth distributions of sulfur contents and delta34 S ratios in different sulfur forms, it is easily to discuss the migration of SO4(-1) and organic sulfur fractions in soil profiles.

  4. Comparison of Tooth Discoloration Induced by Calcium-Enriched Mixture and Mineral Trioxide Aggregate

    PubMed Central

    Rouhani, Armita; Akbari, Majid; Farhadi-faz, Aida

    2016-01-01

    Introduction: The aim of this in vitro study was to evaluate the tooth discoloration induced by calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA). Methods and Materials: Forty five endodontically treated human maxillary central incisors were selected and divided into three groups (n=15) after removing the coronal 3 mm of the obturating materials. In the MTA group, white MTA plug was placed in pulp chamber and coronal zone of the root canal. In CEM cement group, CEM plug was placed in the tooth in the same manner. In both groups, a wet cotton pellet was placed in the access cavity and the teeth were temporarily sealed. After 24 h the teeth were restored with resin composite. In the negative control group the teeth were also restored with resin composite. The color change in the cervical third of teeth was measured with a colorimeter and was repeated 3 times for each specimen. The teeth were kept in artificial saliva for 6 months. After this period, the color change was measured again. Data were collected by Commission International de I'Eclairage's L*a*b color values, and corresponding ΔE values were calculated. The results were analyzed using the one-way ANOVA and post-hoc Tukey’s test with the significance level defined as 0.05. Results: There was no significant differences between CEM group and control group in mean discoloration. The mean tooth discoloration in MTA group was significantly greater than CEM and control groups (P<0.05). Conclusion: According to the result of the present study CEM cement did not induce tooth discoloration after six months. Therefore it can be used in vital pulp therapy of esthetically sensitive teeth. PMID:27471526

  5. Twenty Years of Research on Mineral Trioxide Aggregate: A Scientometric Report

    PubMed Central

    Asgary, Saeed; Motazedian, Hamid Reza; Parirokh, Masoud; Eghbal, Mohammad Jafar; Kheirieh, Sanam

    2013-01-01

    Introduction Mineral trioxide aggregate (MTA) has been suggested for root-end filling, vital pulp therapy, apical plug, perforations repair, and root canal filling. Since the introduction of MTA in 1993, many studies about this material have been published. The aim of this survey was to illustrate statistical information about published articles in PubMed-index journals vis-à-vis the various aspects of this biomaterial. Material and Methods A PubMed search was performed to retrieve the relative articles from 1993 to August 2012. The data of each article including publication year, journal name, number of authors, first author name, affiliations and study design were recorded. Citation of each article till 2009 was obtained from Scopus and Google scholar databases. Data were analyzed to determine the related scientometric indicators. Results In total, 1027 articles were found in PubMed-indexed journals which show considerable increase from 2 papers in 1993 to 139 in 2011. While ~62% of articles had no level of evidence, only ~5% could be classified as having the highest level of evidence (LOE1); however, the majority of LOE1 articles originated from Iran (~1%: n=10). Journal of Endodontics, as the top rank journal, published 31.7% of MTA related articles. The majority of articles were four-authored (19.6%). Most of the articles originated from USA (21.9%), Brazil (18.5%) and Iran (8.76%). The average number of citation for the top ten articles from Scopus was 231. Conclusion This data demonstrates that during the past two decades, research on this novel endodontic biomaterial had a rapid positive trend especially during the last 5 years. Further high-level evidence articles for the various clinical applications of MTA would result in superior clinical decision making and stronger scientific-based endodontic practice. PMID:23411944

  6. Retinoic acid and arsenic trioxide in the treatment of acute promyelocytic leukemia: current perspectives

    PubMed Central

    McCulloch, Derek; Brown, Christina; Iland, Harry

    2017-01-01

    Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML) with a unique morphological appearance, associated coagulopathy and canonical balanced translocation of genetic material between chromosomes 15 and 17. APL was first described as a distinct subtype of AML in 1957 by Dr Leif Hillestad who recognized the pattern of an acute leukemia associated with fibrinolysis, hypofibrinogenemia and catastrophic hemorrhage. In the intervening years, the characteristic morphology of APL has been described fully with both classical hypergranular and variant microgranular forms. Both are characterized by a balanced translocation between the long arms of chromosomes 15 and 17, [t(15;17)(q24;q21)], giving rise to a unique fusion gene PML-RARA and an abnormal chimeric transcription factor (PML-RARA), which disrupts normal myeloid differentiation programs. The success of current treatments for APL is in marked contrast to the vast majority of patients with non-promyelocytic AML. The overall prognosis in non-promyelocytic AML is poor, and although there has been an improvement in overall survival in patients aged <60 years, only 30%–40% of younger patients are still alive 5 years after diagnosis. APL therapy has diverged from standard AML therapy through the empirical discovery of two agents that directly target the molecular basis of the disease. The evolution of treatment over the last 4 decades to include all-trans retinoic acid and arsenic trioxide, with chemotherapy limited to patients with high-risk disease, has led to complete remission in 90%–100% of patients in trials and rates of overall survival between 86% and 97%. PMID:28352191

  7. Unfolded protein response (UPR) signaling regulates arsenic trioxide-mediated macrophage innate immune function disruption

    SciTech Connect

    Srivastava, Ritesh K.; Li, Changzhao; Chaudhary, Sandeep C.; Ballestas, Mary E.; Elmets, Craig A.; Robbins, David J.; Matalon, Sadis; Deshane, Jessy S.; Afaq, Farrukh; Bickers, David R.; Athar, Mohammad

    2013-11-01

    Arsenic exposure is known to disrupt innate immune functions in humans and in experimental animals. In this study, we provide a mechanism by which arsenic trioxide (ATO) disrupts macrophage functions. ATO treatment of murine macrophage cells diminished internalization of FITC-labeled latex beads, impaired clearance of phagocytosed fluorescent bacteria and reduced secretion of pro-inflammatory cytokines. These impairments in macrophage functions are associated with ATO-induced unfolded protein response (UPR) signaling pathway characterized by the enhancement in proteins such as GRP78, p-PERK, p-eIF2α, ATF4 and CHOP. The expression of these proteins is altered both at transcriptional and translational levels. Pretreatment with chemical chaperon, 4-phenylbutyric acid (PBA) attenuated the ATO-induced activation in UPR signaling and afforded protection against ATO-induced disruption of macrophage functions. This treatment also reduced ATO-mediated reactive oxygen species (ROS) generation. Interestingly, treatment with antioxidant N-acetylcysteine (NAC) prior to ATO exposure, not only reduced ROS production and UPR signaling but also improved macrophage functions. These data demonstrate that UPR signaling and ROS generation are interdependent and are involved in the arsenic-induced pathobiology of macrophage. These data also provide a novel strategy to block the ATO-dependent impairment in innate immune responses. - Highlights: • Inorganic arsenic to humans and experimental animals disrupt innate immune responses. • The mechanism underlying arsenic impaired macrophage functions involves UPR signaling. • Chemical chaperon attenuates arsenic-mediated macrophage function impairment. • Antioxidant, NAC blocks impairment in arsenic-treated macrophage functions.

  8. Using mineral trioxide aggregate powder as an apical barrier: a bacterial leakage study.

    PubMed

    Milani, Amin Salem; Jafarabadi, Mohammad Asghari; Pakdel, Mahdi Vahid

    2014-01-01

    Mineral trioxide aggregate (MTA) has been used successfully for the treatment of necrotic immature teeth as part of a 2-step apical barrier. Recently, some researchers have used MTA powder instead of wet-mix MTA. It has also been used in a single-step approach in order to decrease the number of patient appointments. The aim of this study was to evaluate the bacterial microleakage of MTA powder in comparison with wet-mix MTA, in single or 2-step barrier approaches. This ex vivo study was carried out on 70 extracted single-rooted teeth. The canals were enlarged to simulate immature teeth. The prepared specimens were assigned to 4 experimental (n = 15) and 2 control (n = 5) groups. In Group 1, a wet paper point was placed in the canal following placement of wet-mix MTA. In Group 2, a dry paper point was placed on wet-mix MTA. In Group 3, the samples were treated similar to Group 1, but MTA powder was used instead of wet-mix MTA. In Group 4, the same procedures were followed as Group 3 except that a dry paper point was used. Microleakage of the samples was compared using a 2-chamber bacterial leakage apparatus. Results showed that there were no significant differences in the number of leaked samples or rate of leakage over time (P > 0.05) among the experimental groups. It can be concluded that MTA used in a single step approach has the same resistance against bacterial penetration as in a 2-step approach, and MTA powder provides the same sealing ability as wet-mix MTA.

  9. The Effect of Different Concentrations of Chlorhexidine Gluconate on the Compressive Strength of Mineral Trioxide Aggregate

    PubMed Central

    Bidar, Maryam; Eslami, Neda; Naghavi, Neda; Fasihi, Zohreh; Attaran Mashhadi, Negin

    2015-01-01

    Background and aims. Substituting chlorhexidine (CHX) for water has been shown to enhance antimicrobial activity of mineral trioxide aggregate (MTA). The purpose of this study was to compare the compressive strength of MTA mixed with distilled water, 0.12% and 0.2% chlorhexidine. Materials and methods. MTA was mixed according to manufacturer's instructions in group I (n = 20). In groups II & III, 0.12% and 0.2% CHX liquid was substituted for water, respectively. Samples were condensed with moderate force into 20 tubes with 1.5×5 mm dimensions and were allowed to set for 72 hours at 37°C in 100% humidity. After being removed from the molds, their compressive strength was determined using Instron testing machine. Each group was divided into two subgroups according to the time of testing (at 72 hours, and one week). Fractured surfaces of 4 specimens in each group were then evaluated under Scanning Electron Microscope (SEM) to determine their microstructure. One-way ANOVA, Tukey, and paired sample t-test was used for statistical analysis. P < 0.05 was set as significant. Results. There was no significant difference between three groups in terms of their compressive strength after 72 hours. However, the compressive strength of group II was significantly higher than group I (P = 0.034) and group III (P = 0.021) after one week. Crystalline microstructure was similar in all groups. Conclusion. Substitution of 0.012% chlorhexidine for water significantly increased the compressive strength of MTA at 1 week without significant change in crystalline structure. PMID:25973146

  10. Dynamic intratubular biomineralization following root canal obturation with pozzolan‐based mineral trioxide aggregate sealer cement

    PubMed Central

    Yoo, Yeon‐Jee; Baek, Seung‐Ho; Kum, Kee‐Yeon; Shon, Won‐Jun; Woo, Kyung‐Mi

    2015-01-01

    Summary The application of mineral trioxide aggregates (MTA) cement during the root canal obturation is gaining concern due to its bioactive characteristic to form an apatite in dentinal tubules. In this regard, this study was to assess the biomineralization of dentinal tubules following root canal obturation by using pozzolan‐based (Pz‐) MTA sealer cement (EndoSeal MTA, Maruchi). Sixty curved roots (mesiobuccal, distobuccal) from human maxillary molars were instrumented and prepared for root canal obturation. The canals were obturated with gutta‐percha (GP) and Pz‐MTA sealer by using continuous wave of condensation technique. Canals obturated solely with ProRoot MTA (Dentsply Tulsa Dental) or Pz‐MTA sealer were used for comparison. In order to evaluate the biomineralization ability under different conditions, the PBS pretreatment before the root canal obturation was performed in each additional samples. At dentin‐material interfaces, the extension of intratubular biomineralization was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. When the root canal was obturated with GP and Pz‐MTA sealer, enhanced biomineralization of the dentinal tubules beyond the penetrated sealer tag was confirmed under the SEM observation (p < 0.05). Mineralized apatite structures (calcium/phosphorous ratio, 1.45–1.89) connecting its way through the dentinal tubules were detected at 350–400 μm from the tubule orifice, and the pre‐crystallization seeds were also observed along the intra‐ and/or inter‐tubular collagen fiber. Intratubular biomineralization depth was significantly enhanced in all PBS pretreated canals (p < 0.05). Pz‐MTA cement can be used as a promising bioactive root canal sealer to enhance biomineralization of dentinal tubules under controlled environment. SCANNING 38:50–56, 2016. © 2015 The Authors. Scanning Published by Wiley Periodicals, Inc. PMID:26179659

  11. Preferential action of arsenic trioxide in solid-tumor microenvironment enhances radiation therapy

    SciTech Connect

    Griffin, Robert J. . E-mail: griff007@umn.edu; Williams, Brent W.; Park, Heon Joo; Song, Chang W.

    2005-04-01

    Purpose: To investigate the effect of arsenic trioxide, Trisenox (TNX), on primary cultures of endothelial cells and tumor tissue under varying pH and pO{sub 2} environments and the effects of combined TNX and radiation therapy on experimental tumors. Methods and Materials: Human dermal microvascular endothelial cells were cultured in vitro and exposed to TNX under various combinations of aerobic, hypoxic, neutral, or acidic conditions, and levels of activated JNK MAP kinase were assessed by Western blotting. FSaII fibrosarcoma cells grown in the hind limb of female C3H mice were used to study the effect of TNX on tumor blood perfusion and oxygenation. The tumor-growth delay after a single or fractionated irradiation with or without TNX treatment was assessed. Results: A single intraperitoneal injection of 8 mg/kg TNX reduced the blood perfusion in FSaII tumors by 53% at 2 hours after injection. To increase the oxygenation of the tumor vasculature during TNX treatment, some animals were allowed to breathe carbogen (95% O{sub 2}/5% CO{sub 2}). Carbogen breathing alone for 2 hours reduced tumor perfusion by 33%. When carbogen breathing was begun immediately after TNX injection, no further reduction occurred in tumor blood perfusion at 2 hours after injection. In vitro, TNX exposure increased activity JNK MAP kinase preferentially in endothelial cells cultured in an acidic or hypoxic environment. In vivo, the median oxygenation in FSaII tumors measured at 3 or 5 days after TNX injection was found to be significantly elevated compared with control tumors. Subsequently, radiation-induced tumor-growth delay was synergistically increased when radiation and TNX injection were fractionated at 3-day or 5-day intervals. Conclusions: Trisenox has novel vascular-damaging properties, preferentially against endothelium in regions of low pH or pO{sub 2}, which leads to tumor cell death and enhancement of the response of tumors to radiotherapy.

  12. In vitro chemical and cellular tests applied to uranium trioxide with different hydration states.

    PubMed Central

    Ansoborlo, E; Chalabreysse, J; Hengé-Napoli, M H; Pujol, E

    1992-01-01

    A simple and rapid in vitro chemical solubility test applicable to industrial uranium trioxide (UO3) was developed together with two in vitro cellular tests using rat alveolar macrophages maintained either in gas phase or in alginate beads at 37 degrees C. Industrial UO3 was characterized by particle size, X-ray, and IR spectra, and chemical transformation (e.g., aging and hydration of the dust) was also studied. Solvents used for the in vitro chemical solubility study included carbonates, citrates, phosphates, water, Eagle's basal medium, and Gamble's solution (simulated lung fluid), alone, with oxygen, or with superoxide ions. Results, expressed in terms of the half-time of dissolution, according to International Commission on Radiological Protection (ICRP) classification (D,W,Y), varied for different hydration states of UO3, showing a lower solubility of hydrated UO3 in solvents compared to basic UO3 or UO3 heated at 450 degrees C. Two in vitro cellular tests on cultured rat alveolar macrophages (cells maintained in gas phase and cells immobilized in alginate beads) were used on the same UO3 samples and generally showed a lower solution transfer rate in the presence of macrophages than in the culture medium alone. The results of in vitro chemical and cellular tests were compared, with four main conclusions: a good reproducibility of the three tests in Eagle's basal medium the effect of hydration state on solubility, the classification of UO3 in terms of ICRP solubility criteria, and the ability of macrophages to decrease uranium solubility in medium. PMID:1396449

  13. Mineral Trioxide Aggregate vs. Calcium Hydroxide in Primary Molar Pulpotomy: A Systematic Review

    PubMed Central

    Shirvani, Armin; Hassanizadeh, Raheleh; Asgary, Saeed

    2014-01-01

    Introduction: The aim of this quantitative systematic review/meta-analysis was to compare the treatment outcomes of mineral trioxide aggregate (MTA) and calcium hydroxide (CH) in pulpotomy of human primary molars. The focused PICO question was “in case of pulp exposure in vital primary molars, how does MTA pulpotomy compare to CH in terms of clinical/radiographic success?” Methods and Materials: We retrieved published randomized clinical trials (RCTs) of at least 6-month duration; our search included articles published up to March 2013 in five following databases: PubMed (Medline), Cochrane database of systematic reviews, Science Citation Index, EMBASE, and Google Scholar. Mantel Haenszel and Inverse Variance-weighted methods were applied by STATA; the relative risk (RR) was calculated with 95% confidence intervals (CI). Results: A total of 282 English articles were collected. Two authors independently screened the articles and five RCTs were selected; data extraction and quality assessment were then carried out. Four RCTs were appropriate for meta-analysis according to their follow-up times by Mantel Haenszel method. Statistically significant difference was found between success rate of MTA compared to CH, with RR=0.08 (95% CI, 0.02-0.39), RR=0.19 (95% CI, 0.08-0.46), and RR=0.38 (95% CI, 0.21-0.68) for 6-, 12-, and 24-month follow-ups, respectively. A significant difference was also observed for all included RCTs after analyses using the Inverse Variance-weighted method (RR=0.44; 95% CI, 0.27-0.72). Conclusions: Systematic review/meta-analysis of included RCTs revealed that for pulpotomy of vital primary molars, MTA has better treatment outcomes compared to CH. PMID:24688575

  14. Therapeutic Potential of Delivering Arsenic Trioxide into HPV-Infected Cervical Cancer Cells Using Liposomal Nanotechnology

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyan; Li, Dong; Ghali, Lucy; Xia, Ruidong; Munoz, Leonardo P.; Garelick, Hemda; Bell, Celia; Wen, Xuesong

    2016-02-01

    Arsenic trioxide (ATO) has been used successfully to treat acute promyelocytic leukaemia, and since this discovery, it has also been researched as a possible treatment for other haematological and solid cancers. Even though many positive results have been found in the laboratory, wider clinical use of ATO has been compromised by its toxicity at higher concentrations. The aim of this study was to explore an improved method for delivering ATO using liposomal nanotechnology to evaluate whether this could reduce drug toxicity and improve the efficacy of ATO in treating human papillomavirus (HPV)-associated cancers. HeLa, C33a, and human keratinocytes were exposed to 5 μm of ATO in both free and liposomal forms for 48 h. The stability of the prepared samples was tested using inductively coupled plasma optical emission spectrometer (ICP-OES) to measure the intracellular arsenic concentrations after treatment. Fluorescent double-immunocytochemical staining was carried out to evaluate the protein expression levels of HPV-E6 oncogene and caspase-3. Cell apoptosis was analysed by flow cytometry. Results showed that liposomal ATO was more effective than free ATO in reducing protein levels of HPV-E6 and inducing cell apoptosis in HeLa cells. Moreover, lower toxicity was observed when liposomal-delivered ATO was used. This could be explained by lower intracellular concentrations of arsenic. The slowly accumulated intracellular ATO through liposomal delivery might act as a reservoir which releases ATO gradually to maintain its anti-HPV effects. To conclude, liposome-delivered ATO could protect cells from the direct toxic effects induced by higher concentrations of intracellular ATO. Different pathways may be involved in this process, depending on local architecture of the tissues and HPV status.

  15. Dissolution of a mineral trioxide aggregate sealer in endodontic solvents compared to conventional sealers.

    PubMed

    Alzraikat, Hanan; Taha, Nessrin Ahmad; Hassouneh, Layla

    2016-01-01

    The aim of this study is to evaluate the solubility of a Mineral Trioxide Aggregate sealer (MTA-Fillapex) compared with five other sealers, calcium hydroxide (Sealapex), resin (Realseal), zinc oxide-eugenol (Tubli-Seal), and two epoxy resins (AH-26 and AH-Plus), in chloroform and eucalyptoil in static and ultrasonic environments. Samples of each sealer were prepared (n = 180) and then divided into 12 groups that were immersed in solvents for 5 and 10 min in static and ultrasonic environments. The mean weight loss was determined, and the values were compared using Student's t-test, One-way ANOVA, and Tukey's HSD post-hoc test (p < 0.05). In chloroform, MTA-Fillapex, AH-26, and Sealapex displayed moderate solubility with no significant difference in dissolution (p = 0.125); however, their dissolution was significantly lower than that of AH-Plus (p < 0.001), which was almost fully dissolved after 10 minutes. Realseal was significantly less soluble than all sealers (p < 0.001). In eucalyptoil, MTA-Fillapex showed low solubility, as all of the sealers did, but Tubli-Seal was significantly more soluble than other sealers (p < 0.001). Using ultrasonic activation resulted in a significantly higher dissolution rate in chloroform for all sealers except MTA-Fillapex after 10 min (p = 0.226). In eucalyptoil, ultrasonic activation significantly increased the dissolution rate of all sealers except MTA-Fillapex after 5 and 10 min, Sealapex at 10 min, and AH-Plus at 5 min (p > 0.05). In conclusion, MTA-Fillapex was not sufficiently dissolved in either solvent. Ultrasonic activation had limited effectiveness on MTA-Fillapex dissolution, whereas it significantly increased the efficiency of solvents in dissolving a number of endodontic sealers.

  16. Fracture resistance of immature teeth filled with mineral trioxide aggregate, bioaggregate, and biodentine

    PubMed Central

    Bayram, Emre; Bayram, Huda Melike

    2016-01-01

    Objective: The purpose of this study was to evaluate fracture resistance of teeth with immature apices treated with coronal placement of mineral trioxide aggregate (MTA), bioaggregate (BA), and Biodentine. Materials and Methods: Forty-one freshly extracted, single-rooted human premolar teeth were used for the study. At first, the root length was standardized to 9 mm. The crown-down technique was used for the preparation of the root canals using the rotary ProTaper system (Dentsply Maillefer, Ballaigues, Switzerland) of F3 (30). Peeso reamer no. 6 was stepped out from the apex to simulate an incompletely formed root. The prepared roots were randomly assigned to one control (n = 5) and three experimental (n = 12) groups, as described below. Group 1: White MTA (Angelus, Londrina, Brazil) was prepared as per the manufacturer's instructions and compacted into the root canal using MAP system (Dentsply Maillefer, Ballaigues, Switzerland) and condensed by pluggers (Angelus, Londrina, Brazil). Group 2: The canals were filled with DiaRoot-BA (DiaDent Group International, Canada). Group 3: Biodentine (Septodont, Saint Maur des Fosses, France) solution was mixed with the capsule powder and condensed using pluggers. Instron was used to determine the maximum horizontal load to fracture the tooth, placing the tip 3 mm incisal to the cementoenamel junction. Mean values of the fracture strength were compared by ANOVA followed by a post hoc test. P < 0.05 was considered statistically significant. Results: No significant difference was observed among the MTA, BA, and biodentine experimental groups. Conclusion: All the three materials tested, may be used as effective strengthening agents for immature teeth. PMID:27095900

  17. The cytotoxic evaluation of mineral trioxide aggregate and bioaggregate in the subcutaneous connective tissue of rats

    PubMed Central

    Acar, Gözde; Yalcin, Yagmur; Dindar, Seckin; Sancakli, Hande; Erdemir, Ugur

    2013-01-01

    Objectives: The purpose of this study was to evaluate and compare the cytotoxic effects of ProRoot MTA and DiaRoot BA, a bioceramic nanoparticulate cement, on subcutaneous rat tissue. Study Design: Fifty Sprouge Dawley rats were used in this study. Polyethylene tubes filled with ProRoot MTA and DiaRoot BioAggregate, along with a control group of empty, were implanted into dorsal connective tissue of rats for 7, 15, 30, 60, and 90 days. After estimated time intervals the rats were sacrificed. The specimens were fixed, stained with hematoxylin and eosin, and then evaluated under a light microscope for inflammatory reactions and mineralization. Results: All groups evoked a severe to moderate chronic inflammatory reaction at 7 and 15 days, which decreased with time. Both the MTA and BioAggregate groups showed similar inflammatory reactions, except at 90 days when MTA showed statistically significant greater inflammation (p>0.05). The MTA group showed foreign body reaction at all times. Compared to BioAggregate, MTA showed significantly more foreign body reaction at 60 and 90 days (p<0.0001). After 30 days foreign body reaction of BioAggregate decreased significantly. Both MTA and BioAggregate groups showed similar necrosis at 7 and 15 days (p=0.094 and p=0.186 respectively). No necrosis was observed after 15 days. Similarly there was no fibrosis after 30 days for both MTA and BioAggregate groups (p>0.05). Conclusions: Since DiaRoot BioAggregate showed significantly better results than MTA, we can conclude that it is more biocompatible. However, further studies are required to confirm this result. Key words:Biocompatibility, mineral trioxide aggregate, bioAggregate. PMID:23722144

  18. Marginal Adaptation of New Bioceramic Materials and Mineral Trioxide Aggregate: A Scanning Electron Microscopy Study

    PubMed Central

    Shokouhinejad, Noushin; Nekoofar, Mohmmad Hossein; Ashoftehyazdi, Kazem; Zahraee, Shohreh; Khoshkhounejad, Mehrfam

    2014-01-01

    Introduction: This study aimed to compare the marginal adaptation of new bioceramic materials, EndoSequence Root Repair Material (ERRM putty and ERRM paste), to that of mineral trioxide aggregate (MTA) as root-end filling materials. Materials and Methods: Thirty-six extracted human single-rooted teeth were prepared and obturated with gutta-percha and AH-26 sealer. The roots were resected 3 mm from the apex. Root-end cavities were then prepared with an ultrasonic retrotip. The specimens were divided into three groups (n=12) and filled with MTA, ERRM putty or ERRM paste. Epoxy resin replicas from the resected root-end surfaces and longitudinally sectioned roots were fabricated. The gaps at the material/dentin interface were measured using scanning electron microscope (SEM). Transversal, longitudinal, and overall gap sizes were measured for each specimen. The data were analyzed using the Kruskal-Wallis test. Results: In transversal sections, no significant difference was found between MTA, ERRM putty and ERRM paste (P=0.31). However, in longitudinal sections, larger gaps were evident between ERRM paste and dentinal walls compared to MTA and ERRM putty (P=0.002 and P=0.033, respectively). Considering the overall gap size values, the difference between three tested materials was not statistically significant (P=0.17). Conclusion: Within the limits of this study, the marginal adaptation of ERRM paste and putty was comparable to that of MTA. However, ERRM putty might be more suitable for filling the root-end cavities because of its superior adaptation compared to ERRM paste in longitudinal sections. PMID:24688585

  19. Biocompatibility of mineral trioxide aggregate and three new endodontic cements: An animal study

    PubMed Central

    Aminozarbian, Mohammad-Ghasem; Barati, Masoud; Salehi, Iman; Mousavi, Seyed Behrouz

    2012-01-01

    Background: Introducing new endodontic cements should await comprehensive investigations and new formulations have to be tested in vivo before applying in human beings. So, the purpose of this study was to compare the biocompatibility of new endodontic cements, calcium aluminate α-aluminate cement (CAAC), calcium aluminate α-aluminate plus cement (CAAC plus), and a mixture of wollastonite and CAAC cement (WOLCA) and mineral trioxide aggregate (MTA), in subcutaneous connective tissue of rats. Materials and Methods: Twenty-seven Wistar rats were divided into three groups of 7, 14, and 30 experimental days. Sterile polyethylene tubes were filled with MTA, CAAC, CAAC Plus, and WOLCA cement and implanted subcutaneously. Empty tubes were implanted as negative control. After the experimental periods, animals were sacrificed by anesthetic overdosing. The occurrence of inflammatory responses was scored according to the previously established scores. Data were statistically analyzed using Friedman, Wilcoxon, Kruskal-Wallis, and Mann-Whitney tests. The level of significance was 5% (P<0.05). Results: There was a statistically significant difference between experimental and negative control sites in each group (P<0.05). CAAC Plus showed the highest mean scores of inflammation, compared with MTA, CAAC, and WOLCA cement sits at the end of all periods (P<0.05). There were no statistically significant differences between inflammatory scores of each site in different experimental groups, except CAAC plus sites, in which inflammation increased significantly with time (P<0.05). Conclusion: According to the results of the current study, biocompatibility of CAAC and WOLCA cement were comparable with that of MTA, but CAAC Plus induced an inflammatory response higher than MTA, therefore is not biocompatible. PMID:22363364

  20. Biocompatibility of Mineral Trioxide Aggregate with TiO2 Nanoparticles on Human Gingival Fibroblasts

    PubMed Central

    Samiei, Mohammad; Aghazadeh, Marzieh; Divband, Baharak; Akbarzadeh, Farzaneh

    2017-01-01

    Background The New compositions of white mineral trioxide aggregate (WMTA) or use of various additives like nanoparticles might affect MTA’s ideal characteristics This study was performed to evaluate the cytotoxicity of WMTA and WMTA with Titanium dioxide (TiO2) nanoparticles (1% weight ratio) at different storage times after mixing on human gingival fibroblasts (HGFs). Material and Methods HGFs were obtained from the attached gingiva of human premolars. HGFs were cultured in Dulbecco’s Modified Eagle medium, supplemented with 10% fetal calf serum, penicillin and streptomycin. The cells were exposed to WMTA (groups 1 and 2) and WMTA+TiO2 (groups 3 and 4). The fifth and sixth groups served as controls. Each group contained 15 wells. After 24h (groups 1, 3 and 5) and 48 h (groups 2, 4 and 6) of exposure, HGF viability was determined by Mosmann’s tetrazolium toxicity (MTT) assay. Statistical analysis of the data was performed by using one-way analysis of variance and Tukey post hoc test, with significance of p < 0.05. Results With both materials, the viability of HGFs significantly decrased with increasing the incubation time from 24h to 48 h (P<0.05). There was no significant difference between the materials regarding HGF viability (P>0.05). Conclusions Under the limitations of the present study, incorporation of TiO2 nanoparticles into MTA at 1 wt% had no negative effect on its biocompatibility. Key words:Cytotoxicity, fibroblast, MTA, MTT assay, nanoparticle, TiO2. PMID:28210432

  1. Omega-3 Fatty Acid Protects Against Arsenic Trioxide-Induced Cardiotoxicity In Vitro and In Vivo.

    PubMed

    Varghese, Mathews V; Abhilash, M; Paul, M V Sauganth; Alex, Manju; Nair, R Harikumaran

    2017-04-01

    Arsenic trioxide (As2O3) is a highly effective therapeutic against acute promyelocytic leukaemia, but its clinical efficacy is burdened by serious cardiac toxicity. The present study was performed to evaluate the effect of omega (ω)-3 fatty acid on As2O3-induced cardiac toxicity in in vivo and in vitro settings. In in vivo experiments, male Wistar rats were orally administered with As2O3 4 mg/kg body weight for a period of 45 days and cardiotoxicity was assessed. As2O3 significantly increased the tissue arsenic deposition, micronuclei frequency and creatine kinase (CK)-MB activity. There were a rise in lipid peroxidation and a decline in reduced glutathione, glutathione peroxidase, glutathione-S-transferase, superoxide dismutase and catalase in heart tissue of arsenic-administered rats. The cardioprotective role of ω-3 fatty acid was assessed by combination treatment with As2O3. ω-3 fatty acid co-administration with As2O3 significantly alleviated these changes. In in vitro study using H9c2 cardiomyocytes, As2O3 treatment induced alterations in cell viability, lactate dehydrogenase (LDH) release, lipid peroxidation, cellular calcium levels and mitochondrial membrane potential (∆Ψm). ω-3 fatty acid co-treatment significantly increased cardiomyocyte viability, reduced LDH release, lipid peroxidation and intracellular calcium concentration and improved the ∆Ψm. These findings suggested that the ω-3 fatty acid has the potential to protect against As2O3-induced cardiotoxicity.

  2. Biocompatibility of Accelerated Mineral Trioxide Aggregate on Stem Cells Derived from Human Dental Pulp.

    PubMed

    Kulan, Pinar; Karabiyik, Ozge; Kose, Gamze T; Kargul, Betul

    2016-02-01

    The aim of this study was to evaluate the effects of several additives on the setting time and cytotoxicity of accelerated-set mineral trioxide aggregate (MTA) on stem cells of human dental pulp. ProRoot white MTA (WMTA) (Dentsply Tulsa Dental, Johnson City, TN) was mixed with various additives including distilled water, 2.5% disodium hydrogen phosphate (Na2HPO4) (Merck, Darmstadt, Germany), K-Y Jelly (Johnson & Johnson, Markham, ON, Canada), and 5% and 10% calcium chloride (CaCl2) (Merck). The setting times were evaluated using a Vicat apparatus (Alsa Lab, Istanbul, Turkey). Human dental pulp stem cells were isolated and seeded into 48-well plates at 2 × 10(3) cells per well and incubated with MTA samples for 24 hours, 3 days, and 7 days. Cell viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. MTA mixed with 10% CaCl2 showed the lowest setting time (P < .05). According to the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium results on the 1st, 3rd, and 7th days, a statistically significant difference was found (P < .05) between MTA groups and the control group. MTA mixed with K-Y Jelly in all groups showed the lowest cell viability at all time points (P < .05). The cell viability of MTA mixed with distilled water, 5% CaCl2, 10% CaCl2, and Na2HPO4 increased significantly through time (P < .05). This in vitro study found MTA mixed with 5% and 10% CaCl2 and Na2HPO4 is biocompatible with dental pulp stem cells in terms of cell viability. Further in vitro and in vivo investigations are required to prove the clinical applications of MTA mixed with various additives.

  3. A New Simulated Plasma for Assessing the Solubility of Mineral Trioxide Aggregate

    PubMed Central

    Samiei, Mohammad; Shahi, Shahriar; Aslaminabadi, Naser; Valizadeh, Hadi; Aghazadeh, Zahra; Pakdel, Seyyed Mahdi Vahid

    2015-01-01

    Introduction: Solubility of mineral trioxide aggregate (MTA) is an important characteristic that affects other properties such as microleakage and biocompatibility. Distilled water (DW) has previously been used for solubility tests. This experimental study compared the solubility of MTA in DW, synthetic tissue fluid (STF) and new simulated plasma (SP). Methods and Materials: In this study, 36 samples of tooth-colored ProRoot MTA were prepared and divided into three groups (n=12) to be immersed in three different solutions (DW, STF, and SP). Solubility tests were conducted at 2, 5, 9, 14, 21, 30, 50, and 78-day intervals. The unequal variance F-test (Welch test) was utilized to determine the effect of solubility media and Games-Howell analysis was used for pairwise comparisons. The repeated-measures ANOVA was used to assess the importance of immersion duration. Results: Welch test showed significant differences in solubility rates of samples between all the different solubility media at all the study intervals (P<0.05) except for the 14-day interval (P=0.094). The mixed repeated-measures ANOVA revealed a significant difference in solubility rate of MTA in three different solutions at all time-intervals (P=0.000). Games-Howell post-hoc test revealed that all pairwise comparisons were statistically significant at all time-intervals (P=0.000). Conclusion: Based on the findings of this study, the long-term solubility of MTA in simulated plasma was less than that in synthetic tissue fluid and distilled water. PMID:25598806

  4. Utilization of solid "elemental" sulfur by the phototrophic purple sulfur bacterium Allochromatium vinosum: a sulfur K-edge X-ray absorption spectroscopy study.

    PubMed

    Franz, Bettina; Lichtenberg, Henning; Hormes, Josef; Modrow, Hartwig; Dahl, Christiane; Prange, Alexander

    2007-04-01

    The purple sulfur bacterium Allochromatium vinosum can use elemental sulfur as an electron donor for anoxygenic photosynthesis. The elemental sulfur is taken up, transformed into intracellular sulfur globules and oxidized to sulfate. Commercially available "elemental" sulfur usually consists of the two species cyclo-octasulfur and polymeric sulfur. The authors investigated whether only one sulfur species is used or at least preferred when Alc. vinosum takes up elemental sulfur and forms globules. To this end, Alc. vinosum was cultivated photolithoautotrophically with two types of elemental sulfur that differed in their cyclo-octasulfur : polymeric sulfur ratio, as well as with pure polymeric sulfur. Sulfur speciation was analysed using X-ray absorption spectroscopy, and sulfate contents were determined by HPLC to quantify the amount of elemental sulfur being taken up and oxidized by Alc. vinosum. The results show that Alc. vinosum uses only the polymeric sulfur (sulfur chain) fraction of elemental sulfur and is probably unable to take up and form sulfur globules from cyclo-octasulfur. Furthermore, direct cell-sulfur contact appears to be necessary for uptake of elemental sulfur by Alc. vinosum.

  5. Incorporating Sulfur Inside the Pores of Carbons for Advanced Lithium-Sulfur Batteries: An Electrolysis Approach.

    PubMed

    He, Bin; Li, Wen-Cui; Yang, Chao; Wang, Si-Qiong; Lu, An-Hui

    2016-01-26

    We have developed an electrolysis approach that allows effective and uniform incorporation of sulfur inside the micropores of carbon nanosheets for advanced lithium-sulfur batteries. The sulfur-carbon hybrid can be prepared with a 70 wt % sulfur loading, in which no nonconductive sulfur agglomerations are formed. Because the incorporated sulfur is electrically connected to the carbon matrix in nature, the hybrid cathode shows excellent electrochemical performance, including a high reversible capacity, good rate capability, and good cycling stability, as compared to one prepared using the popular melt-diffusion method.

  6. Reduction mechanism of sulfur in lithium-sulfur battery: From elemental sulfur to polysulfide

    DOE PAGES

    Zheng, Dong; Yang, Xuran; Zhang, Xiaoqing; ...

    2015-10-30

    In this study, the polysulfide ions formed during the first reduction wave of sulfur in Li–S battery were determined through both in-situ and ex-situ derivatization of polysulfides. By comparing the cyclic voltammetric results with and without the derivatization reagent (methyl triflate) as well as the in-situ and ex-situ derivatization results under potentiostatic condition, in-situ derivatization was found to be more appropriate than its ex-situ counterpart, since subsequent fast chemical reactions between the polysulfides and sulfur may occur during the timeframe of ex-situ procedures. It was found that the major polysulfide ions formed at the first reduction wave of elemental sulfurmore » were the S42– and S52– species, while the widely accepted reduction products of S82– and S62– for the first reduction wave were in low abundance.« less

  7. Radiolysis of Sulfuric Acid, Sulfuric Acid Monohydrate, and Sulfuric Acid Tetrahydrate and Its Relevance to Europa

    NASA Technical Reports Server (NTRS)

    Loeffler, M. J.; Hudson, R. L.; Moore, M. H.; Carlson, R. W.

    2011-01-01

    We report laboratory studies on the 0.8 MeV proton irradiation of ices composed of sulfuric acid (H2SO4), sulfuric acid monohydrate (H2SO4 H2O), and sulfuric acid tetrahydrate (H2SO4 4H2O) between 10 and 180 K. Using infrared spectroscopy, we identify the main radiation products as H2O, SO2, (S2O3)x, H3O+, HSO4(exp -), and SO4(exp 2-). At high radiation doses, we find that H2SO4 molecules are destroyed completely and that H2SO4 H2O is formed on subsequent warming. This hydrate is significantly more stable to radiolytic destruction than pure H2SO4, falling to an equilibrium relative abundance of 50% of its original value on prolonged irradiation. Unlike either pure H2SO4 or H2SO4 H2O, the loss of H2SO4 4H2O exhibits a strong temperature dependence, as the tetrahydrate is essentially unchanged at the highest irradiation temperatures and completely destroyed at the lowest ones, which we speculate is due to a combination of radiolytic destruction and amorphization. Furthermore, at the lower temperatures it is clear that irradiation causes the tetrahydrate spectrum to transition to one that closely resembles the monohydrate spectrum. Extrapolating our results to Europa s surface, we speculate that the variations in SO2 concentrations observed in the chaotic terrains are a result of radiation processing of lower hydration states of sulfuric acid and that the monohydrate will remain stable on the surface over geological times, while the tetrahydrate will remain stable in the warmer regions but be destroyed in the colder regions, unless it can be reformed by other processes, such as thermal reactions induced by diurnal cycling.

  8. Reduction mechanism of sulfur in lithium-sulfur battery: From elemental sulfur to polysulfide

    SciTech Connect

    Zheng, Dong; Yang, Xuran; Zhang, Xiaoqing; Wang, Jiankun; Qu, Deyu; Qu, Deyang

    2015-10-30

    In this study, the polysulfide ions formed during the first reduction wave of sulfur in Li–S battery were determined through both in-situ and ex-situ derivatization of polysulfides. By comparing the cyclic voltammetric results with and without the derivatization reagent (methyl triflate) as well as the in-situ and ex-situ derivatization results under potentiostatic condition, in-situ derivatization was found to be more appropriate than its ex-situ counterpart, since subsequent fast chemical reactions between the polysulfides and sulfur may occur during the timeframe of ex-situ procedures. It was found that the major polysulfide ions formed at the first reduction wave of elemental sulfur were the S42– and S52– species, while the widely accepted reduction products of S82– and S62– for the first reduction wave were in low abundance.

  9. Chemokine induction by all-trans retinoic acid and arsenic trioxide in acute promyelocytic leukemia: triggering the differentiation syndrome.

    PubMed

    Luesink, Maaike; Pennings, Jeroen L A; Wissink, Willemijn M; Linssen, Peter C M; Muus, Petra; Pfundt, Rolph; de Witte, Theo J M; van der Reijden, Bert A; Jansen, Joop H

    2009-12-24

    In acute promyelocytic leukemia (APL), differentiation therapy with all-trans retinoic acid (ATRA) and/or arsenic trioxide can induce a differentiation syndrome (DS) with massive pulmonary infiltration of differentiating leukemic cells. Because chemokines are implicated in migration and extravasation of leukemic cells, chemokines might play a role in DS. ATRA stimulation of the APL cell line NB4 induced expression of multiple CC-chemokines (CCLs) and their receptors (> 19-fold), resulting in increased chemokine levels and chemotaxis. Induction of CCL2 and CCL24 was directly mediated by ligand-activated retinoic acid receptors. In primary leukemia cells derived from APL patients at diagnosis, ATRA induced chemokine production as well. Furthermore, in plasma of an APL patient with DS, we observed chemokine induction, suggesting that chemokines might be important in DS. Dexamethasone, which efficiently reduces pulmonary chemokine production, did not inhibit chemokine induction in APL cells. Finally, chemokine production was also induced by arsenic trioxide as single agent or in combination with ATRA. We propose that differentiation therapy may induce chemokine production in the lung and in APL cells, which both trigger migration of leukemic cells. Because dexamethasone does not efficiently reduce leukemic chemokine production, pulmonary infiltration of leukemic cells may induce an uncontrollable hyperinflammatory reaction in the lung.

  10. Effect of the TiO2 nanoparticles on the selected physical properties of mineral trioxide aggregate

    PubMed Central

    Samiei, Mohammad; Janani, Maryam; Asl-Aminabadi, Naser; Divband, Baharak; Shirazi, Sajjad; Kafili, Kayvan

    2017-01-01

    Background Some of the efforts to improve the properties of Mineral Trioxide Aggregate (MTA) include incorporation of some nanoparticles such as Titanium dioxide (TiO2). The aim of this study was to evaluate the effect of TiO2 nanoparticles on the setting time, working time, push-out bond strength and compressive strength of MTA. Material and Methods The physical properties to be evaluated were determined using the ISO 6786:2001 and 9917 specifications. Fifteen samples of each material (MTA or MTA with 1% weight ratio of TiO2 Nanoparticles) were prepared for any evaluated physical property. Data were analyzed using descriptive statistics and T-test. Statistical significance was set at P<0.05. Results There was the significant effect of the material type (presence and absence of TiO2 nanoparticles) on the push-out bond strength, compressive strength, working time and setting time, with significantly higher values achieved in the group with TiO2 nanoparticles than the group without these particles (P=0.01 for the setting time and compressive strength, P=0.03 for the working time and P=0.001 for the bond strength). Conclusions Based on the findings of this in vitro study, incorporation of the TiO2 nanoparticles with weight ratio of 1% increased the setting time, working time, compressive strength and push out bond strength of MTA. Key words:Mineral trioxide aggregate, nanoparticles, physical properties, titanium dioxide. PMID:28210434

  11. Have all-trans retinoic acid and arsenic trioxide replaced all-trans retinoic acid and anthracyclines in APL as standard of care.

    PubMed

    Iland, Harry J; Wei, Andrew; Seymour, John F

    2014-03-01

    Until recently, the standard of care in the treatment of APL has involved the combination of all-trans retinoic acid with anthracycline-based chemotherapy during both induction and consolidation. Additionally, the intensity of consolidation chemotherapy has evolved according to a universally accepted relapse-risk stratification algorithm based on the white cell and platelet counts at presentation. That standard of care is being challenged by the increasing incorporation of arsenic trioxide into front-line treatment protocols, based on two complementary observations. The first is the undoubted anti-leukaemic activity of arsenic trioxide as shown in the relapsed and refractory setting, and in the initial management of low- and intermediate-risk patients. The second is an improved understanding of the action of both all-trans retinoic acid and arsenic trioxide in mediating APL cell eradication, with increasing recognition that PML-RARA fusion protein degradation rather than direct induction of terminal differentiation is the primary mechanism for their ability to eliminate leukaemia initiating cells. As a result, we believe the standard of care for initial therapy in APL is shifting towards an all-trans retinoic acid plus arsenic trioxide-based approach, with additional chemotherapy reserved for patients with high-risk disease.

  12. Cytochromes and iron sulfur proteins in sulfur metabolism of phototrophic bacteria

    NASA Technical Reports Server (NTRS)

    Fischer, U.

    1985-01-01

    Dissimilatory sulfur metabolism in phototrophic sulfur bacteria provides the bacteria with electrons for photosynthetic electron transport chain and, with energy. Assimilatory sulfate reduction is necessary for the biosynthesis of sulfur-containing cell components. Sulfide, thiosulfate, and elemental sulfur are the sulfur compounds most commonly used by phototrophic bacteria as electron donors for anoxygenic photosynthesis. Cytochromes or other electron transfer proteins, like high-potential-iron-sulfur protein (HIPIP) function as electron acceptors or donors for most enzymatic steps during the oxidation pathways of sulfide or thiosulfate. Yet, heme- or siroheme-containing proteins themselves undergo enzymatic activities in sulfur metabolism. Sirohemes comprise a porphyrin-like prosthetic group of sulfate reductase. eenzymatic reactions involve electron transfer. Electron donors or acceptors are necessary for each reaction. Cytochromes and iron sulfur problems, are able to transfer electrons.

  13. Thiophenic Sulfur Compounds Released During Coal Pyrolysis.

    PubMed

    Xing, Mengwen; Kong, Jiao; Dong, Jie; Jiao, Haili; Li, Fan

    2013-06-01

    Thiophenic sulfur compounds are released during coal gasification, carbonization, and combustion. Previous studies indicate that thiophenic sulfur compounds degrade very slowly in the environment, and are more carcinogenic than polycyclic aromatic hydrocarbons and nitrogenous compounds. Therefore, it is very important to study the principle of thiophenic sulfur compounds during coal conversion, in order to control their emission and promote clean coal utilization. To realize this goal and understand the formation mechanism of thiophenic sulfur compounds, this study focused on the release behavior of thiophenic sulfur compounds during coal pyrolysis, which is an important phase for all coal thermal conversion processes. The pyrolyzer (CDS-5250) and gas chromatography-mass spectrometry (Focus GC-DSQII) were used to analyze thiophenic sulfur compounds in situ. Several coals with different coal ranks and sulfur contents were chosen as experimental samples, and thiophenic sulfur compounds of the gas produced during pyrolysis under different temperatures and heating rates were investigated. Levels of benzothiophene and dibenzothiophene were obtained during pyrolysis at temperatures ranging from 200°C to 1300°C, and heating rates ranging from 6°C/ms to 14°C/ms and 6°C/s to 14°C/s. Moreover, the relationship between the total amount of benzothiophene and dibenzothiophene released during coal pyrolysis and the organic sulfur content in coal was also discussed. This study is beneficial for understanding the formation and control of thiophenic sulfur compounds, since it provides a series of significant results that show the impact that operation conditions and organic sulfur content in coal have on the amount and species of thiophenic sulfur compounds produced during coal pyrolysis.

  14. HYDROCARBON AND SULFUR SENSORS FOR SOFC SYSTEMS

    SciTech Connect

    A.M. Azad; Chris Holt; Todd Lesousky; Scott Swartz

    2003-11-01

    The following report summarizes work conducted during the Phase I program Hydrocarbon and Sulfur Sensors for SOFC Systems under contract No. DE-FC26-02NT41576. For the SOFC application, sensors are required to monitor hydrocarbons and sulfur in order to increase the operation life of SOFC components. This report discusses the development of two such sensors, one based on thick film approach for sulfur monitoring and the second galvanic based for hydrocarbon monitoring.

  15. Thiophenic Sulfur Compounds Released During Coal Pyrolysis

    PubMed Central

    Xing, Mengwen; Kong, Jiao; Dong, Jie; Jiao, Haili; Li, Fan

    2013-01-01

    Abstract Thiophenic sulfur compounds are released during coal gasification, carbonization, and combustion. Previous studies indicate that thiophenic sulfur compounds degrade very slowly in the environment, and are more carcinogenic than polycyclic aromatic hydrocarbons and nitrogenous compounds. Therefore, it is very important to study the principle of thiophenic sulfur compounds during coal conversion, in order to control their emission and promote clean coal utilization. To realize this goal and understand the formation mechanism of thiophenic sulfur compounds, this study focused on the release behavior of thiophenic sulfur compounds during coal pyrolysis, which is an important phase for all coal thermal conversion processes. The pyrolyzer (CDS-5250) and gas chromatography–mass spectrometry (Focus GC-DSQII) were used to analyze thiophenic sulfur compounds in situ. Several coals with different coal ranks and sulfur contents were chosen as experimental samples, and thiophenic sulfur compounds of the gas produced during pyrolysis under different temperatures and heating rates were investigated. Levels of benzothiophene and dibenzothiophene were obtained during pyrolysis at temperatures ranging from 200°C to 1300°C, and heating rates ranging from 6°C/ms to 14°C/ms and 6°C/s to 14°C/s. Moreover, the relationship between the total amount of benzothiophene and dibenzothiophene released during coal pyrolysis and the organic sulfur content in coal was also discussed. This study is beneficial for understanding the formation and control of thiophenic sulfur compounds, since it provides a series of significant results that show the impact that operation conditions and organic sulfur content in coal have on the amount and species of thiophenic sulfur compounds produced during coal pyrolysis. PMID:23781126

  16. Active microbial sulfur disproportionation in the Mesoproterozoic.

    PubMed

    Johnston, David T; Wing, Boswell A; Farquhar, James; Kaufman, Alan J; Strauss, Harald; Lyons, Timothy W; Kah, Linda C; Canfield, Donald E

    2005-12-02

    The environmental expression of sulfur compound disproportionation has been placed between 640 and 1050 million years ago (Ma) and linked to increases in atmospheric oxygen. These arguments have their basis in temporal changes in the magnitude of 34S/32S fractionations between sulfate and sulfide. Here, we present a Proterozoic seawater sulfate isotope record that includes the less abundant sulfur isotope 33S. These measurements imply that sulfur compound disproportionation was an active part of the sulfur cycle by 1300 Ma and that progressive Earth surface oxygenation may have characterized the Mesoproterozoic.

  17. Charles H. Winston and Confederate Sulfuric Acid

    NASA Astrophysics Data System (ADS)

    Reithmiller, Steven

    1995-07-01

    Sulfuric acid turned out to be one of the critical chemicals made in the South during the Civil War. It was necessary for the manufacture of mercury fulminate which was used in the production of percussion caps and sulfuric acid was used in the Daniells cell to produce electricity. Charles H. Winston, president of the Richmond Female Institute and later professor at the University of Richmond (VA) was instrumental in the establishment of a plant to manufacture sulfuric acid in Charlotte, North Carolina. His patent and method of manufacture plus the uses of sulfuric acid during the Civil War are discussed.

  18. Elemental sulfur in Eddy County, New Mexico

    USGS Publications Warehouse

    Hinds, Jim S.; Cunningham, Richard R.

    1970-01-01

    Sulfur has been reported in Eddy County, N. Mex., in rocks ranging from Silurian to Holocene in age at depths of 0-15,020 feet. Targets of present exploration are Permian formations in the Delaware Basin and northwest shelf areas at depths of less than 4,000 feet. Most of the reported sulfur occurrences in the shelf area are in the 'Abo' (as used by some subsurface geologists), Yeso, and San Andres Formations and the Artesia Group. Sulfur deposition in the dense dolomites of the 'Abo,' Yeso, and San Andres Formations is attributed to the reduction of ionic sulfate by hydrogen sulfide in formation waters in zones of preexisting porosity and permeability. A similar origin accounts for most of the sulfur deposits in the formations of the Artesia Group, but some of the sulfur in these formations may have originated in place through the alteration of anhydrite to carbonate and sulfur by the metabolic processes of bacteria in the presence of hydrocarbons. Exploration in the Delaware Basin area is directed primarily toward the Castile Formation. Sulfur deposits in the Castile Formation are found in irregular masses of cavernous brecciated secondary carbonate rock enveloped by impermeable anhydrite. The carbonate masses, or 'castiles,' probably originated as collapse features resulting from subsurface solution and upward stopping. Formation of carbonate rock and sulfur in the castiles is attributed to the reduction of brecciated anhydrite by bacteria and hydrocarbons in the same process ascribed to the formation of carbonate and sulfur in the caprocks of salt domes.

  19. Are the clouds of Venus sulfuric acid.

    NASA Technical Reports Server (NTRS)

    Young, A. T.

    1973-01-01

    It is shown that strong aqueous sulfuric acid solutions have the right refractive index and freeze at Venusian cloud temperature, explain the dryness of the Venusian stratosphere, are consistent with some features of the Venusian IR spectrum, and do not absorb in highly reflecting areas of Venus. It is also indicated that such solutions should be produced by reactions between known atmospheric constituents and most sulfur-bearing rock at the Venusian surface temperature, and require only small amounts of sulfur consistent with its cosmic abundance and with the amounts of other volatile elements present in the atmosphere. It is believed therefore that the clouds of Venus consist of sulfuric acid solutions.

  20. Improved sulfur removal processes evaluated for IGCC

    SciTech Connect

    Not Available

    1986-12-01

    An inherent advantage of Integrated Coal Gasification Combined Cycle (IGCC) electric power generation is the ability to easily remove and recover sulfur. During the last several years, a number of new, improved sulfur removal and recovery processes have been commercialized. An assessment is given of alternative sulfur removal processes for IGCC based on the Texaco coal gasifier. The Selexol acid gas removal system, Claus sulfur recovery, and SCOT tail gas treating are currently used in Texaco-based IGCC. Other processes considered are: Purisol, Sulfinol-M, Selefning, 50% MDEA, Sulften, and LO-CAT. 2 tables.

  1. Characterization of Sulfur Compounds in Coffee Beans by Sulfur K-XANES Spectroscopy

    SciTech Connect

    Lichtenberg, H.; Hormes, J.; Prange, A.; Modrow, H.

    2007-02-02

    In this 'feasibility study' the influence of roasting on the sulfur speciation in Mexican coffee beans was investigated by sulfur K-XANES Spectroscopy. Spectra of green and slightly roasted beans could be fitted to a linear combination of 'standard' reference spectra for biological samples, whereas longer roasting obviously involves formation of additional sulfur compounds in considerable amounts.

  2. Characterization of Sulfur and Nanostructured Sulfur Battery Cathodes in Electron Microscopy Without Sublimation Artifacts.

    PubMed

    Levin, Barnaby D A; Zachman, Michael J; Werner, Jörg G; Sahore, Ritu; Nguyen, Kayla X; Han, Yimo; Xie, Baoquan; Ma, Lin; Archer, Lynden A; Giannelis, Emmanuel P; Wiesner, Ulrich; Kourkoutis, Lena F; Muller, David A

    2017-02-01

    Lithium sulfur (Li-S) batteries have the potential to provide higher energy storage density at lower cost than conventional lithium ion batteries. A key challenge for Li-S batteries is the loss of sulfur to the electrolyte during cycling. This loss can be mitigated by sequestering the sulfur in nanostructured carbon-sulfur composites. The nanoscale characterization of the sulfur distribution within these complex nanostructured electrodes is normally performed by electron microscopy, but sulfur sublimates and redistributes in the high-vacuum conditions of conventional electron microscopes. The resulting sublimation artifacts render characterization of sulfur in conventional electron microscopes problematic and unreliable. Here, we demonstrate two techniques, cryogenic transmission electron microscopy (cryo-TEM) and scanning electron microscopy in air (airSEM), that enable the reliable characterization of sulfur across multiple length scales by suppressing sulfur sublimation. We use cryo-TEM and airSEM to examine carbon-sulfur composites synthesized for use as Li-S battery cathodes, noting several cases where the commonly employed sulfur melt infusion method is highly inefficient at infiltrating sulfur into porous carbon hosts.

  3. Synergistic inhibition of colon carcinoma cell growth by Hedgehog-Gli1 inhibitor arsenic trioxide and phosphoinositide 3-kinase inhibitor LY294002.

    PubMed

    Cai, Xinyi; Yu, Kun; Zhang, Lijuan; Li, Yunfeng; Li, Qiang; Yang, Zhibin; Shen, Tao; Duan, Lincan; Xiong, Wei; Wang, Weiya

    2015-01-01

    The Hedgehog (Hh) signaling pathway not only plays important roles in embryogenesis and adult tissue homeostasis, but also in tumorigenesis. Aberrant Hh pathway activation has been reported in a variety of malignant tumors including colon carcinoma. Here, we sought to investigate the regulation of the Hh pathway transcription factor Gli1 by arsenic trioxide and phosphoinositide 3-kinase (PI3K) inhibitor LY294002 in colon carcinoma cells. We transfected cells with siGli1 and observed a significant reduction of Gli1 expression in HCT116 and HT29 cells, which was confirmed by quantitative real-time polymerase chain reaction and Western blots. Knocking down endogenous Gli1 reduced colon carcinoma cell viability through inducing cell apoptosis. Similarly, knocking down Gli2 using short interfering RNA impaired colon carcinoma cell growth in vitro. To elucidate the regulation of Gli1 expression, we found that both Gli inhibitor arsenic trioxide and PI3K inhibitor LY294002 significantly reduced Gli1 protein expression and colon carcinoma cell proliferation. Arsenic trioxide treatment also reduced Gli1 downstream target gene expression, such as Bcl2 and CCND1. More importantly, the inhibition of Hedgehog-Gli1 by arsenic trioxide showed synergistic anticancer effect with the PI3K inhibitor LY294002 in colon carcinoma cells. Our findings suggest that the Hh pathway transcription factor Gli1 is involved in the regulation of colon carcinoma cell viability. Inhibition of Hedgehog-Gli1 expression by arsenic trioxide and PI3K inhibitor synergistically reduces colon cancer cell proliferation, indicating that they could be used as an effective anti-colon cancer combination therapy.

  4. Arsenic trioxide treatment of rabbit liver VX-2 carcinoma via hepatic arterial cannulation-induced apoptosis and decreased levels of survivin in the tumor tissue

    PubMed Central

    Li, Hong; Gong, Jian; Jiang, Xuyuan; Shao, Haibo

    2013-01-01

    Aim To investigate the role of tumor apoptosis-inhibitory protein survivin in arsenic trioxide-induced apoptosis in VX-2 carcinoma in the rabbit liver by means of transcatheter arterial chemoembolization. Methods Sixteen rabbits with 32 implanted hepatic VX-2 tumors were randomly divided into two groups. The experimental group received 2 mg of arsenic trioxide and 1 mL of ultra-fluid lipiodol co-injected via hepatic arterial cannulation and the control group received only 1 mL of lipiodol. Animals were sacrificed 3 weeks after trans-catheterial arterial chemoembolization. Tumor tissue and tumor-peripheral tissue were collected for analysis. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling staining was used to assess tumor cells apoptosis. Immunohistochemistry was used to assess the presence of survivin protein. Reverse transcription polymerase chain reaction was used to determine the expression of survivin gene. Results The number of apoptotic cells significantly increased in the tumor tissue (5.20 ± 0.60%) compared to tumor-peripheral tissue (1.29 ± 0.42%) of the arsenic trioxide-treated group. Survivin expression levels in the tumor tissue were significantly reduced in arsenic trioxide-treated group (7.68 ± 0.65) compared to the control group (35.30 ± 4.63). Conclusion Transcatheter arterial chemoembolization with arsenic trioxide induced apoptosis of VX-2 carcinoma, in which tumor apoptosis-inhibitory protein survivin may have played a role. PMID:23444241

  5. Arsenic trioxide inhibits cell proliferation and human papillomavirus oncogene expression in cervical cancer cells

    SciTech Connect

    Wang, Hongtao; Gao, Peng; Zheng, Jie

    2014-09-05

    Highlights: • As{sub 2}O{sub 3} inhibits growth of cervical cancer cells and expression of HPV oncogenes in these cells. • HPV-negative cervical cancer cells are more sensitive to As{sub 2}O{sub 3} than HPV-positive cervical cancer cells. • HPV-18 positive cervical cancer cells are more sensitive to As{sub 2}O{sub 3} than HPV-16 positive cancer cells. • Down-regulation of HPV oncogenes by As{sub 2}O{sub 3} is partially due to the diminished AP-1 binding. - Abstract: Arsenic trioxide (As{sub 2}O{sub 3}) has shown therapeutic effects in some leukemias and solid cancers. However, the molecular mechanisms of its anticancer efficacy have not been clearly elucidated, particularly in solid cancers. Our previous data showed that As{sub 2}O{sub 3} induced apoptosis of human papillomavirus (HPV) 16 DNA-immortalized human cervical epithelial cells and cervical cancer cells and inhibited the expression of HPV oncogenes in these cells. In the present study, we systemically examined the effects of As{sub 2}O{sub 3} on five human cervical cancer cell lines and explored the possible molecular mechanisms. MTT assay showed that HPV-negative C33A cells were more sensitive to growth inhibition induced by As{sub 2}O{sub 3} than HPV-positive cervical cancer cells, and HPV 18-positive HeLa and C4-I cells were more sensitive to As{sub 2}O{sub 3} than HPV 16-positive CaSki and SiHa cells. After As{sub 2}O{sub 3} treatment, both mRNA and protein levels of HPV E6 and E7 obviously decreased in all HPV positive cell lines. In contrast, p53 and Rb protein levels increased in all tested cell lines. Transcription factor AP-1 protein expression decreased significantly in HeLa, CaSki and C33A cells with ELISA method. These results suggest that As{sub 2}O{sub 3} is a potential anticancer drug for cervical cancer.

  6. Reactive oxygen species are involved in arsenic trioxide inhibition of pyruvate dehydrogenase activity.

    PubMed

    Samikkannu, Thangavel; Chen, Chien-Hung; Yih, Ling-Huei; Wang, Alexander S S; Lin, Shu-Yu; Chen, Tsen-Chien; Jan, Kun-Yan

    2003-03-01

    Arsenite was shown to inhibit pyruvate dehydrogenase (PDH) activity through binding to vicinal dithiols in pure enzyme and tissue extract. However, no data are available on how arsenite inhibits PDH activity in human cells. The IC(50) values for arsenic trioxide (As(2)O(3)) to inhibit the PDH activity in porcine heart pure enzyme preparation and in human leukemia cell line HL60 cells were estimated to be 182 and 2 microM, respectively. Thus, As(2)O(3) inactivation of PDH activity was about 90 times more potent in HL60 cells than in purified enzyme preparation. The IC(50) values for As(2)O(3) and phenylarsine oxide to reduce the vicinal thiol content in HL60 cells were estimated to be 81.7 and 1.9 microM, respectively. Thus, As(2)O(3) is a potent PDH inhibitor but a weak vicinal thiol reacting agent in HL60 cells. Antioxidants but not dithiol compounds suppressed As(2)O(3) inhibition of PDH activity in HL60 cells. Conversely, dithiol compounds but not antioxidants suppressed the inhibition of PDH activity by phenylarsine oxide. As(2)O(3) increased H(2)O(2) level in HL60 cells, but this was not observed for phenylarsine oxide. Mitochondrial respiration inhibitors suppressed the As(2)O(3)-induced H(2)O(2) production and As(2)O(3) inhibition of PDH activity. Moreover, metal chelators ameliorated whereas Fenton metals aggravated As(2)O(3) inhibition of PDH activity. Treatment with H(2)O(2) plus Fenton metals also decreased the PDH activity in HL60 cells. Therefore, it seems that As(2)O(3) elevates H(2)O(2) production in mitochondria and this may produce hydroxyl through the Fenton reaction and result in oxidative damage to the protein of PDH. The present results suggest that arsenite may cause protein oxidation to inactivate an enzyme and this can occur at a much lower concentration than arsenite binding directly to the critical thiols.

  7. Activity of Nanobins Loaded with Cisplatin and Arsenic Trioxide in Primary and Metastatic Breast Cancer

    NASA Astrophysics Data System (ADS)

    Swindell, Elden Peter, III

    Despite recent advances in breast cancer screening and detection, the disease is still a leading cause of death for women of all ages. Young, African-American women are disproportionally affected with a type of breast cancer, triple-negative breast cancer, which is particularly difficult to treat and has the worst prognosis of any breast cancer subtype. These tumors often spread to the lungs, liver, bones and brains of patients, which is ultimately fatal. This dissertation presents results from a series of in vivo and in vitro experiments that investigate the clinical utility of a novel nanoparticulate formulation of cisplatin and arsenic trioxide, NB(Pt,As) for treating primary and metastatic triple-negative breast cancer. These nanobins consist of a solid, crystalline metal nanoparticle surrounded by a lipid bilayer with 80-90 nm diameter. This drug payload is extremely stable, and so NB(Pt,As) is extremely well tolerated in mice. Furthermore, NB(Pt,As) is effective in two different mouse models of breast cancer, one of primary tumor growth an another of lung metastases. A discovery presented here, that thiol containing compounds are required for drug release, may explain these seemingly incongruous results. The large amount of intracellular thiol can trigger drug release, while the low concentration of free thiols in blood is insufficient to cause drug release. To improve the treatment of brain tumors with this unique drug, we added transferrin to the surface of the nanobin using copper-catalyzed "click" chemistry, which preserves protein activity. The addition of transferrin to the nanobins enables 10 fold greater uptake in the brains of mice treated with the transferrin-targeted nanobins Tf-NB(Pt,A) compared to NB(Pt,As). By penetrating the blood brain barrier, the Tf-NB(Pt,As) was able to reduce breast cancer metastases in the brains of mice, whereas NB(Pt,As) had no effect. Taken together, these results demonstrate the intricate balance of drug release

  8. Heat Shock Protein Alteration in the Gastrointestinal Tract Tissues of Chickens Exposed to Arsenic Trioxide.

    PubMed

    Zhao, Panpan; Zhang, Kexin; Guo, Guangyang; Sun, Xiao; Chai, Hongliang; Zhang, Wen; Xing, Mingwei

    2016-03-01

    Arsenic (As) is widely distributed in our living environment and is useful for industry, agriculture, medical treatment, and other fields. Arsenic trioxide (As2O3) is an existing form of As. Exposure to As2O3 has a toxic effect on humans and animals. It not only leads to skin cancer, peripheral vascular disease, hyperkeratosis, etc. but also interferes with the functioning of the gastrointestinal tract. The gastrointestinal tract is an important organ for animals to transform the food they eat into the nutrients their body needs for maintenance and growth. Heat shock proteins (Hsps) exist in the non-stress normal cells and their expression increases under stimuli. Therefore, we wonder whether the "stimulus" of As2O3 could change the messenger RNA (mRNA) abundance and expression level of Hsps in the gastrointestinal tract of birds. To investigate the relation between arseniasis and Hsp alterations in the chicken's gastrointestinal tract induced by an As2O3-supplemented diet, we selected 72 one-day-old male Hy-line chickens and randomly divided them into four groups. They were fed either a commercial diet or an As2O3-supplemented diet containing 7.5, 15, and 30 mg/kg As2O3. The experiment lasted for 90 days, and gastrointestinal tract tissue samples (gizzard, glandular stomach, duodenum, jejunum, ileum, cecum, and rectum) were collected at 30, 60, and 90 days. The mRNA contents of Hsps (including Hsp27, Hsp40, Hsp60, Hsp70, and Hsp90) were examined by real-time PCR (RT-PCR). The correlation between As2O3 and Hsp genes was assessed. In addition, the protein expression levels of Hsp60 and Hsp70 in the gastrointestinal tract tissue samples were measured by western blot. The results indicated that the mRNA expression levels and the Hsp expression levels in the gastrointestinal tract tissues of chickens with As2O3 supplementation increased at different time points in a dose-dependent manner (p < 0.05 or p < 0.01). These data suggested that arseniasis influenced the

  9. Graphene-wrapped sulfur nanospheres with ultra-high sulfur loading for high energy density lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Liu, Ya; Guo, Jinxin; Zhang, Jun; Su, Qingmei; Du, Gaohui

    2015-01-01

    Lithium-sulfur (Li-S) battery with high theoretical energy density is one of the most promising energy storage systems for electric vehicles and intermittent renewable energy. However, due to the poor conductivity of the active material, considerable weight of the electrode is occupied by the conductive additives. Here we report a graphene-wrapped sulfur nanospheres composite (S-nanosphere@G) with sulfur content up to 91 wt% as the high energy density cathode material for Li-S battery. The sulfur nanospheres with diameter of 400-500 nm are synthesized through a solution-based approach with the existence of polyvinylpyrrolidone (PVP). Then the sulfur nanospheres are uniformly wrapped by conductive graphene sheets through the electrostatic interaction between graphene oxide and PVP, followed by reducing of graphene oxide with hydrazine. The design of graphene wrapped sulfur nanoarchitecture provides flexible conductive graphene coating with void space to accommodate the volume expansion of sulfur and to minimize polysulfide dissolution. As a result, the S-nanosphere@G nanocomposite with 91 wt% sulfur shows a reversible initial capacity of 970 mA h g-1 and an average columbic efficiency > 96% over 100 cycles at a rate of 0.2 C. Taking the total mass of electrode into account, the S-nanosphere@G composite is a promising cathode material for high energy density Li-S batteries.

  10. Sulfur-carbon nanocomposites and their application as cathode materials in lithium-sulfur batteries

    DOEpatents

    Liang, Chengdu; Dudney, Nancy J; Howe, Jane Y

    2015-05-05

    The invention is directed in a first aspect to a sulfur-carbon composite material comprising: (i) a bimodal porous carbon component containing therein a first mode of pores which are mesopores, and a second mode of pores which are micropores; and (ii) elemental sulfur contained in at least a portion of said micropores. The invention is also directed to the aforesaid sulfur-carbon composite as a layer on a current collector material; a lithium ion battery containing the sulfur-carbon composite in a cathode therein; as well as a method for preparing the sulfur-composite material.

  11. Kinetics and mechanism of the oxidation of alkenes and silanes by hydrogen peroxide catalyzed by methylrhenium trioxide (MTO) and a novel application of electrospray mass spectrometry to study the hydrolysis of MTO

    SciTech Connect

    Tan, Haisong

    1999-11-08

    Conjugated dienes were oxidized by hydrogen peroxide with methylrhenium trioxide (MTO) as catalyst. Methylrhenium bis-peroxide was the major reactive catalyst present. Hydroxyalkenes and trisubstituted silane were also tested. Mechanisms for each of these reactions are presented.

  12. Structural, electronic and magnetic properties of 3d metal trioxide clusters-doped monolayer graphene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Rafique, Muhammad; Shuai, Yong; Tan, He-Ping; Hassan, Muhammad

    2017-03-01

    We present first-principles density-functional calculations for the structural, electronic and magnetic properties of monolayer graphene doped with 3d (Ti, V, Cr, Fe, Co, Mn and Ni) metal trioxide TMO3 halogen clusters. In this paper we used two approaches for 3d metal trioxide clusters (i) TMO3 halogen cluster was embedded in monolayer graphene substituting four carbon (C) atoms (ii) three C atoms were substituted by three oxygen (O) atoms in one graphene ring and TM atom was adsorbed at the hollow site of O atoms substituted graphene ring. All the impurities were tightly bonded in the graphene ring. In first case of TMO3 doped graphene layer, the bond length between Csbnd O atom was reduced and bond length between TM-O atom was increased. In case of Cr, Fe, Co and Ni atoms substitution in between the O atoms, leads to Fermi level shifting to conduction band thereby causing the Dirac cone to move into valence band, however a band gap appears at high symmetric K-point. In case of TiO3 and VO3 substitution, system exhibits semiconductor properties. Interestingly, TiO3-substituted system shows dilute magnetic semiconductor behavior with 2.00 μB magnetic moment. On the other hand, the substitution of CoO3, CrO3, FeO3 and MnO3 induced 1.015 μB, 2.347 μB, 2.084 μB and 3.584 μB magnetic moment, respectively. In second case of O atoms doped in graphene and TM atoms adsorbed at the hollow site, the O atom bulges out of graphene plane and bond length between TM-O atom is increased. After TM atoms adsorption at the O substituted graphene ring the Fermi level (EF) shifts into conduction band. In case of Cr and Ni adsorption, system displays indirect band gap semiconductor properties with 0.0 μB magnetic moment. Co adsorption exhibits dilute magnetic semiconductor behavior producing 0.916 μB magnetic moment. Fe, Mn, Ti and V adsorption introduces band gap at high symmetric K-point also inducing 1.54 μB, 0.9909 μB, 1.912 μB, and 0.98 μB magnetic moments, respectively

  13. Ambient Air Monitoring for Sulfur Compounds

    ERIC Educational Resources Information Center

    Forrest, Joseph; Newman, Leonard

    1973-01-01

    A literature review of analytical techniques available for the study of compounds at low concentrations points up some of the areas where further research is needed. Compounds reviewed are sulfur dioxide, sulfuric acid, ammonium sulfate and bisulfate, metal sulfates, hydrogen sulfide, and organic sulfides. (BL)

  14. Pyrolysis of high sulfur Indian coals

    SciTech Connect

    B.P. Baruah; Puja Khare

    2007-12-15

    Pyrolysis experiments under laboratory conditions for five numbers of high sulfur coal samples from the states of Meghalaya and Nagaland, India, were carried out at temperatures of 450, 600, 850, and 1000{sup o}C, respectively. The yield of products and thermal release of sulfur from these coals are investigated. The distribution of sulfur in the pyrolyzed products, i.e., char/coke, gas, and tar, is also reported. Hydrocarbon and sulfurous gases released at different temperatures were analyzed by a gas chromatograph (GC) with an FID (flame ionized detector) and an FPD (flame photometric detector), respectively. H{sub 2}S evolution during coal pyrolysis was found to be a function of temperature up to 850{sup o}C. The low concentration of SO{sub 2} detected for some of the samples is due to decomposition of inorganic sulphates present. Evolution of methane for the coals tested increases with the increase of temperature. Maximum sulfur release was found in the range of 600-850{sup o}C and has a decreasing tendency from 850-1000{sup o}C, which might be due to the incorporation of sulfur released into the coal matrix. Activation energies for sulfur release were found in the range of 38-228 kJ mol{sup -1}, which were higher than the reported activation energies for lignites and bituminous coals mainly due to highly stable organic sulfur functionalities. 52 refs., 9 figs., 6 tabs.

  15. Sulfuric Acid and Water: Paradoxes of Dilution

    ERIC Educational Resources Information Center

    Leenson, I. A.

    2004-01-01

    On equilibrium properties of aqueous solutions of sulfuric acid, Julius Thomsen has marked that the heat evolved on diluting liquid sulfuric acid with water is a continuous function of the water used, and excluded absolutely the acceptance of definite hydrates as existing in the solution. Information about thermochemical measurement, a discussion…

  16. Stabilized sulfur binding using activated fillers

    DOEpatents

    Kalb, Paul D.; Vagin, Vyacheslav P.; Vagin, Sergey P.

    2015-07-21

    A method of making a stable, sulfur binding composite comprising impregnating a solid aggregate with an organic modifier comprising unsaturated hydrocarbons with at least one double or triple covalent bond between adjacent carbon atoms to create a modifier-impregnated aggregate; heating and drying the modifier-impregnated aggregate to activate the surface of the modifier-impregnated aggregate for reaction with sulfur.

  17. Sulfur in Distillers Grains for Dairy Cattle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sulfur is an essential element needed by animals for many functions. About 0.15% of the body weight is sulfur. It is found in the amino acids methionine, cysteine, cystine, homocysteine, and taurine; in chondroitin sulfate of cartilage; and in the B-vitamins, thiamin and biotin. Methionine, thiam...

  18. Heterogeneous photocatalytic reactions of sulfur aromatic compounds.

    PubMed

    Samokhvalov, Alexander

    2011-11-18

    Sulfur aromatic compounds, such as mono-, di-, tri-, and tetraalkyl-substituted thiophene, benzothiophenes, dibenzothiophenes, are the molecular components of many fossils (petroleum, oil shale, tar sands, bitumen). Structural units of natural, cross-linked heteroaromatic polymers present in brown coals, turf, and soil are similar to those of sulfur aromatic compounds. Many sulfur aromatic compounds are found in the streams of petroleum refining and upgrading (naphthas, gas oils) and in the consumer products (gasoline, diesel, jet fuels, heating fuels). Besides fossils, the structural fragments of sulfur aromatic compounds are present in molecules of certain organic semiconductors, pesticides, small molecule drugs, and in certain biomolecules present in human body (pheomelanin pigments). Photocatalysis is the frontier area of physical chemistry that studies chemical reactions initiated by absorption of photons by photocatalysts, that is, upon electronic rather than thermal activation, under "green" ambient conditions. This review provides systematization and critical review of the fundamental chemical and physicochemical information on heterogeneous photocatalysis of sulfur aromatic compounds accumulated in the last 20-30 years. Specifically, the following topics are covered: physicochemical properties of sulfur aromatic compounds, major classes of heterogeneous photocatalysts, mechanisms and reactive intermediates of photocatalytic reactions of sulfur aromatic compounds, and the selectivity of these reactions. Quantum chemical calculations of properties and structures of sulfur aromatic compounds, their reactive intermediates, and the structure of adsorption complexes formed on the surface of the photocatalysts are also discussed.

  19. Sulfur oxide adsorbents and emissions control

    DOEpatents

    Li, Liyu; King, David L.

    2006-12-26

    High capacity sulfur oxide absorbents utilizing manganese-based octahedral molecular sieve (Mn--OMS) materials are disclosed. An emissions reduction system for a combustion exhaust includes a scrubber 24 containing these high capacity sulfur oxide absorbents located upstream from a NOX filter 26 or particulate trap.

  20. Sulfur Chemistry in Bacterial Leaching of Pyrite

    PubMed Central

    Schippers, A.; Jozsa, P.; Sand, W.

    1996-01-01

    In the case of pyrite bioleaching by Leptospirillum ferrooxidans, an organism without sulfur-oxidizing capacity, besides the production of tetra- and pentathionate, a considerable accumulation of elemental sulfur occurred. A similar result was obtained for chemical oxidation assays with acidic, sterile iron(III) ion-containing solutions. In the case of Thiobacillus ferrooxidans, only slight amounts of elemental sulfur were detectable because of the organism's capacity to oxidize sulfur compounds. In the course of oxidative, chemical pyrite degradation under alkaline conditions, the accumulation of tetrathionate, trithionate, and thiosulfate occurred. The data indicate that thiosulfate, trithionate, tetrathionate, and disulfane-monosulfonic acid are key intermediate sulfur compounds in oxidative pyrite degradation. A novel (cyclic) leaching mechanism is proposed which basically is indirect. PMID:16535406

  1. Sulfur's price collapse to force market changes

    SciTech Connect

    Not Available

    1993-09-13

    Price drops for sulfur over the past 2 years of 50-66% at most major consuming locations are prompting a major industry restructuring, according to Fertecon, a U.K.-based research organization that follows worldwide sulfur production for the fertilizer industry. A recently completed Fertecon study of the cost of producing and marketing sulfur indicates that the attrition in worldwide sulfur-mining capacity has now mostly run its course. Moreover, the burden of balancing the market will fall firmly on major producers of sulfur in the sour-gas industry, especially Canada. The paper discusses supply and demand realities, regional analysis, the role of sour gas, and the outlook for the future.

  2. Drug Targets in Mycobacterial Sulfur Metabolism

    PubMed Central

    Bhave, Devayani P.; Muse, Wilson B.; Carroll, Kate S.

    2011-01-01

    The identification of new antibacterial targets is urgently needed to address multidrug resistant and latent tuberculosis infection. Sulfur metabolic pathways are essential for survival and the expression of virulence in many pathogenic bacteria, including Mycobacterium tuberculosis. In addition, microbial sulfur metabolic pathways are largely absent in humans and therefore, represent unique targets for therapeutic intervention. In this review, we summarize our current understanding of the enzymes associated with the production of sulfated and reduced sulfur-containing metabolites in Mycobacteria. Small molecule inhibitors of these catalysts represent valuable chemical tools that can be used to investigate the role of sulfur metabolism throughout the Mycobacterial lifecycle and may also represent new leads for drug development. In this light, we also summarize recent progress in the development of inhibitors of sulfur metabolism enzymes. PMID:17970225

  3. Mineral trioxide aggregate pulpotomy in autotransplanted immature mandibular third molar with a 4-year follow-up

    PubMed Central

    Dharmani, Umesh; Jadhav, Ganesh Ranganath; Kaur Dharmani, Charan Kamal; Devi, Takhellambam Premlata

    2016-01-01

    Autotransplantation is the surgical transposition of a tooth from its original site to another, replacing a lost or a compromised tooth by another tooth, usually the third molar in the same individual. This technique is considered a viable method due to its high success rate, well-grounded treatment option, provided the case selection and the procedure followed is within the acceptable limits. Autotransplantation is considered as an alternative approach of oral rehabilitations in a conservative manner mainly in young patients with compromised financial conditions to perform a high cost treatment. It is a fast way to recover function and aesthetic properties without interfering with the orofacial growth. This report describes a successful 4-year follow-up of a case of immediately performed mineral trioxide aggregate (MTA) pulpotomy in autotransplantated mandibular left immature third molar to replace the mandibular left first molar that was extracted due to extensive carious lesion. PMID:27217648

  4. Histological evaluation of the effect of three medicaments; trichloracetic acid, formocresol and mineral trioxide aggregate on pulpotomised teeth of dogs.

    PubMed

    Karami, Babak; Khayat, Akbar; Moazami, Fariborz; Pardis, Soheil; Abbott, Paul

    2009-04-01

    The aim of this study was to use clinical, radiographic and histological examinations to compare the dental pulp response in 162 premolar roots of eight dogs when trichloracetic acid (TCA), formocresol, mineral trioxide aggregate (MTA) and zinc oxide eugenol were used as pulpotomy agents. The teeth were divided into four groups. Following pulpotomy, the teeth were restored with amalgam. The animals were sacrificed at 48 h, 2, 4 and 8 weeks (two dogs at each interval). Histological evaluation indicated no cases with necrosis. After 8 weeks follow up, dentine bridge formation was evident in 20%, 50% and 91.7% of formocresol, TCA and MTA cases respectively. The first signs of bridge formation were seen for MTA at 2 weeks and for TCA at 4 weeks. MTA was superior to formocresol and TCA in treating pulps in dogs. However, bridge formation was seen in 50% of TCA cases after 8 weeks which is a desirable finding in pulpotomy procedures.

  5. Efficient degradation of methylene blue dye over tungsten trioxide/multi-walled carbon nanotube system as a novel photocatalyst

    NASA Astrophysics Data System (ADS)

    Dinari, Mohammad; Momeni, Mohamad Mohsen; Ahangarpour, Marzieh

    2016-10-01

    Combination of acid-functionalized multi-walled carbon nanotube/tungsten trioxide (MWCNT/WO3) with different MWCNT's weight percentages as visible light-induced photocatalysts for photodegradation of methylene blue (MB) dye was synthesized. These photocatalysts were characterized by Fourier transform infrared, X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, field emission scanning electron microscopy and transmission electron microscopy techniques. Their photocatalytic activities were tested by using MB as a model compound. The results show that the MWCNT/WO3 hybrid nanostructures exhibit higher photocatalytic activity than pure WO3 or MWCNTs due to their higher absorption enhancement in visible light region and effective separation of electrons and holes. The stability of the hybrid was characterized through cyclic photocatalytic test.

  6. Long-term observation of the mineral trioxide aggregate extrusion into the periapical lesion: a case series.

    PubMed

    Chang, Seok-Woo; Oh, Tae-Seok; Lee, WooCheol; Cheung, Gary Shun-Pan; Kim, Hyeon-Cheol

    2013-03-01

    One-step apexification using mineral trioxide aggregate (MTA) has been reported as an alternative treatment modality with more benefits than the use of long-term calcium hydroxide for teeth with open apex. However, orthograde placement of MTA is a challenging procedure in terms of length control. This case series describes the sequence of events following apical extrusion of MTA into the periapical area during a one-step apexification procedure for maxillary central incisor with an infected immature apex. Detailed long-term observation revealed complete resolution of the periapical radiolucent lesion around the extruded MTA. These cases revealed that direct contact with MTA had no negative effects on healing of the periapical tissues. However, intentional MTA overfilling into the periapical lesion is not to be recommended.

  7. Effect of Oral Administration of Tungsten Trioxide (WO3) Particles on Hispathological Feature of liver and kidney in Rat

    NASA Astrophysics Data System (ADS)

    Munawaroh, H. S. H.; Nandiyanto, A. B. D.; Gumilar, G. G.; Widi, A.; Subangkit, M.

    2017-03-01

    This study aims to investigate the toxicity and histopathology of tungsten trioxide (WO3) administration on rat’s liver and kidney. The LD50 of WO3 was determined and the sub acute toxicity was evaluated by orally administration of 5000 mg kg-1 of WO3 to rat for 14 consecutive days. Parameter of blood cells, ALT, creatinine, and BUN were experimentally measured. The toxicological evaluation showed that WO3 is a non toxic compound with the LD50 higher that 5000 mg kg-1. No biochemical change was observed for creatinine and Blood Urea Nitrogen parameter. In contrast, ALT parameter shows higher value in the experiment than that in the control group. Histopathological changes on rat’s liver and kidney were also studied. Small defects in rat’s liver and kidney were found, which may interfere the functional of related enzymes.

  8. Zeolite-silver-zinc nanoparticles: Biocompatibility and their effect on the compressive strength of mineral trioxide aggregate

    PubMed Central

    Samiei, Mohammad; Ghasemi, Negin; Asl-Aminabadi, Naser; Divband, Baharak; Golparvar-Dashti, Yasamin

    2017-01-01

    Background This study was carried out to evaluate the biocompatibility of zeolite-silver-zinc (Ze-Ag-Zn) nanoparticles and their effect on the compressive strength of Mineral Trioxide Aggregate (MTA). Material and Methods Biocompatibility was evaluated by an MTT assay on the pulmonary adenocarcinoma cells with 0.05, 0.1, 0.25, 0.5, 1 and 5 mg/mL concentrations of Ze-Ag-Zn. For compressive strength test, four groups containing 15 stainless-steel cylinders with an internal diameter of 4 and a height of 6 mm were prepared and MTA (groups 1 and 2) or MTA + 2% Ze-Ag-Zn (groups 3 and 4) were placed in the cylinders. The compressive strength was evaluated using a universal testing machine 4 days after mixing in groups 1 and 3, and 21 days after mixing in groups 2 and 4. Results There was no significant difference between cytotoxicity of different concentrations. The highest (52.22±18.92 MPa) and lowest (19.57±5.76 MPa) compressive strength were observed in MTA group after 21 days and in MTA + 2% Ze-Ag-Zn group after four days, respectively. The effect of time and 2% Ze-Ag-Zn on the compressive strength were significant (P<0.05). Mixing MTA with Ze-Ag-Zn significantly reduced and passage of time from day four to 21 significantly increased the compressive strength. Conclusions Mixing MTA with 2% Ze-Ag-Zn had an adverse effect on the compressive strength of MTA, but this combination had no cytotoxic effects. Key words:Compressive strength, Cytotoxicity, Mineral Trioxide Aggregate, Nanoparticle, Zeolite-Silver-Zinc. PMID:28298974

  9. Sulfur nanocrystals anchored graphene composite with highly improved electrochemical performance for lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Dong, Zimin; Wang, Xiuli; Zhao, Xuyang; Tu, Jiangping; Su, Qingmei; Du, Gaohui

    2014-12-01

    Two kinds of graphene-sulfur composites with 50 wt% of sulfur are prepared using hydrothermal method and thermal mixing, respectively. Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectra mapping show that sulfur nanocrystals with size of ∼5 nm dispersed on graphene sheets homogeneously for the sample prepared by hydrothermal method (NanoS@G). While for the thermal mixed graphene-sulfur composite (S-G mixture), sulfur shows larger and uneven size (50-200 nm). X-ray Photoelectron Spectra (XPS) reveals the strong chemical bonding between the sulfur nanocrystals and graphene. Comparing with the S-G mixture, the NanoS@G composite shows highly improved electrochemical performance as cathode for lithium-sulfur (Li-S) battery. The NanoS@G composite delivers an initial capacity of 1400 mAh g-1 with the sulfur utilization of 83.7% at a current density of 335 mA g-1. The capacity keeps above 720 mAh g-1 over 100 cycles. The strong adherence of the sulfur nanocrystals on graphene immobilizes sulfur and polysulfides species and suppressed the "shuttle effect", resulting higher coulombic efficiency and better capacity retention. Electrochemical impedance also suggests that the strong bonding enabled rapid electronic/ionic transport and improved electrochemical kinetics, therefore good rate capability is obtained. These results demonstrate that the NanoS@G composite is a very promising candidate for high-performance Li-S batteries.

  10. A mesoporous carbon–sulfur composite as cathode material for high rate lithium sulfur batteries

    SciTech Connect

    Choi, Hyunji; Zhao, Xiaohui; Kim, Dul-Sun; Ahn, Hyo-Jun; Kim, Ki-Won; Cho, Kwon-Koo; Ahn, Jou-Hyeon

    2014-10-15

    Highlights: • CMK-3 mesoporous carbon was synthesized as conducting reservoir for housing sulfur. • Sulfur/CMK-3 composites were prepared by two-stage thermal treatment. • The composite at 300 °C for 20 h shows improved electrochemical properties. - Abstract: Sulfur composite was prepared by encapsulating sulfur into CMK-3 mesoporous carbon with different heating times and then used as the cathode material for lithium sulfur batteries. Thermal treatment at 300 °C plays an important role in the sulfur encapsulation process. With 20 h of heating time, a portion of sulfur remained on the surface of carbon, whereas with 60 h of heating time, sulfur is confined deeply in the small pores of carbon that cannot be fully exploited in the redox reaction, thus causing low capacity. The S/CMK-3 composite with thermal treatment for 40 h at 300 °C contained 51.3 wt.% sulfur and delivered a high initial capacity of 1375 mA h g{sup −1} at 0.1 C. Moreover, it showed good capacity retention of 704 mA h g{sup −1} at 0.1 C and 578 mA h g{sup −1} at 2 C even after 100 cycles, which proves its potential as a cathode material for high capability lithium sulfur batteries.

  11. Sodium sulfur battery flight experiment definition study

    NASA Technical Reports Server (NTRS)

    Chang, Rebecca R.; Minck, Robert

    1989-01-01

    Sodium-sulfur batteries were identified as the most likely successor to nickel-hydrogen batteries for space applications. One advantage of the Na/S battery system is that the usable specific energy is two to three times that of nickel-hydrogen batteries. This represents a significant launch cost savings or increased payload mass capabilities. Sodium-sulfur batteries support NASA OAST's proposed Civil Space Technology Initiative goal of a factor of two improvement in spacecraft power system performance, as well as the proposed Spacecraft 2000 initiative. The sodium-sulfur battery operates at between 300 and 400 C, using liquid sodium and sulfur/polysulfide electrodes and solid ceramic electrolyte. The transport of the electrode materials to the surface of the electrolyte is through wicking/capillary forces. These critical transport functions must be demonstrated under actual microgravity conditions before sodium-sulfur batteries can be confidently utilized in space. Ford Aerospace Corporation, under contract to NASA Lewis Research Center, is currently working on the sodium-sulfur battery space flight experiment definition study. The objective is to design the experiment that will demonstrate operation of the sodium-sulfur battery/cell in the space environment with particular emphasis on evaluation of microgravity effects. Experimental payload definitions were completed and preliminary designs of the experiment were defined.

  12. Phanerozoic cycles of sedimentary carbon and sulfur.

    PubMed

    Garrels, R M; Lerman, A

    1981-08-01

    A reservoir model of a Recent steady-state sedimentary system in which the reduced sulfur and oxidized sulfur reservoirs were coupled with the oxidized carbon and reduced carbon reservoirs was constructed. The time curve of the sulfur isotope ratios of the sedimentary sulfate reservoir was used to drive the model back to the beginning of Cambrian time (600 million years ago), producing the reservoir sizes and isotope values and material fluxes of the carbon-sulfur system. The predicted values of carbon isotope ratios of the carbonate reservoir agree well with observed values, showing that the model is basically sound. Some general conclusions from this success are (i) material flux rates in the carbon-oxygen-sulfur system of the geologic past (averaged over tens of millions of years) lie within about a factor of 2 of Recent rates. (ii) The oxidation-reduction balances of Phanerozoic time were dominated by reciprocal relationships between carbon and sulfur compounds. (iii) The rate of production of atmospheric oxygen by storage in sediments of organic carbon of photosynthetic origin increased from the Cambrian Period to the Permian Period and declined somewhat from the Permian Period to the Present. (iv) The storage of oxygen in oxidized sulfur compounds kept pace (within the limits of the data) with oxygen production. (v) Transfer of oxygen from CO(2) to SO(4) from the Cambrian to the Permian Period was several times the Recent free oxygen content of the atmosphere.

  13. Reformer operation improved by feed sulfur removal

    SciTech Connect

    Mc Clung, R.G. )

    1990-10-08

    This paper reports how reduction of sulfur in catalytic reforming feeds below that typically obtainable with naphtha hydrotreating improves the reformer operation significantly. In evaluations of pilot-plant and commercial operations, high-rhenium content reforming catalysts have been used with low-sulfur naphtha feeds and have been shown to dramatically affect catalyst cycle length, gasoline yield, and stability. The consequences of insufficient removal of sulfur include shorter cycle length, more rapid reactor temperature rise to maintain octane, and as a result of that increase, more rapid catalyst deactivation.

  14. Catalyst for elemental sulfur recovery process

    DOEpatents

    Flytzani-Stephanopoulos, M.; Liu, W.

    1995-01-24

    A catalytic reduction process is described for the direct recovery of elemental sulfur from various SO[sub 2]-containing industrial gas streams. The catalytic process provides high activity and selectivity, as well as stability in the reaction atmosphere, for the reduction of SO[sub 2] to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over a metal oxide composite catalyst having one of the following empirical formulas: [(FO[sub 2])[sub 1[minus]n](RO)[sub n

  15. Organic Sulfur Gas Production in Sulfidic Caves

    NASA Astrophysics Data System (ADS)

    Stern, L. A.; Engel, A. S.; Bennett, P. C.

    2001-12-01

    Lower Kane Cave, Big Horn Basin, WY, permits access to an environment where anaerobic sulfide-rich groundwater meets the aerobic vadose zone. At this interface microorganisms thrive on diverse metabolic pathways including autotrophic sulfur oxidation, sulfate reduction, and aerobic heterotrophy. Springs introduce groundwater rich in H2S to the cave where it both degasses into the cave atmosphere and is used by chemautotrophic sulfur oxidizing bacteria in the cave spring and stream habitat. The cave atmosphere in the immediate vicinity of the springs has elevated levels of CO2, H2S and methane, mirroring the higher concentration of H2S and methane in the spring water. The high CO2 concentrations are attenuated toward the two main sources of fresh air, the cave entrance and breathing holes at the rear of the cave. Conventional toxic gas monitors permit estimations of H2S concentrations, but they have severe cross sensitivity with other reduced sulfur gases, and thus are inadequate for characterization of sulfur cave gases. However employment of a field-based GC revealed elevated concentrations of carbonyl sulfide in cave atmosphere. Cultures of microorganisms collected from the cave optimized for enriching fermenters and autotrophic and heterophic sulfate reducing bacteria each produced carbonyl sulfide suggesting a biogenic in origin of the COS in addition to H2S. Enrichment cultures also produced methanethiol (methyl mercaptan) and an additional as yet undetermined volatile organic sulfur compound. In culture, the organo-sulfur compounds were less abundant than H2S, whereas in the cave atmosphere the organo-sulfur compounds were the dominant sulfur gases. Thus, these organo-sulfur gases may prove to be important sources of both reduced sulfur and organic carbon to microorganisms living on the cave wall in a subaerial habitat. Moreover groundwater has not yet been recognized as a source of sulfur gases to the atmosphere, but with the abundance of sulfidic

  16. A Carbon-Sulfur Hybrid with Pomegranate-like Structure for Lithium-Sulfur Batteries.

    PubMed

    Shi, Yanting; Lv, Wei; Niu, Shuzhang; He, Yanbing; Zhou, Guangmin; Chen, Guohua; Li, Baohua; Yang, Quan-Hong; Kang, Feiyu

    2016-05-06

    A carbon-sulfur hybrid with pomegranate-like core-shell structure, which demonstrates a high rate performance and relatively high cyclic stability, is obtained through carbonization of a carbon precursor in the presence of a sulfur precursor (FeS2 ) and a following oxidation of FeS2 to sulfur by HNO3 . Such a structure effectively protects the sulfur and leaves enough buffer space after Fe(3+) removal and, at the same time, has an interconnected conductive network. The capacity of the obtained hybrid is 450 mA h g(-1) under the current density of 5 C. This work provides a simple strategy to design and prepare various high-performance carbon-sulfur hybrids for lithium-sulfur batteries.

  17. Amylopectin wrapped graphene oxide/sulfur for improved cyclability of lithium-sulfur battery.

    PubMed

    Zhou, Weidong; Chen, Hao; Yu, Yingchao; Wang, Deli; Cui, Zhiming; Disalvo, Francis J; Abruña, Héctor D

    2013-10-22

    An amylopectin wrapped graphene oxide-sulfur composite was prepared to construct a 3-dimensionally cross-linked structure through the interaction between amylopectin and graphene oxide, for stabilizing lithium sulfur batteries. With the help of this cross-linked structure, the sulfur particles could be confined much better among the layers of graphene oxide and exhibited significantly improved cyclability, compared with the unwrapped graphene oxide-sulfur composite. The effect of the electrode mass loading on electrochemical performance was investigated as well. In the lower sulfur mass loading cells, such as 2 mg cm(-2), both the capacity and the efficiency were obviously better than those of the higher sulfur mass loading cells, such as 6 mg cm(-2).

  18. One-step apexification in immature tooth using grey mineral trioxide aggregate as an apical barrier and autologus platelet rich fibrin membrane as an internal matrix

    PubMed Central

    Rudagi, Kavitarani B; Rudagi, BM

    2012-01-01

    Immature teeth with necrotic pulp and periapical lesion are difficult to treat via conventional endodontic therapy. Numerous procedures and materials have been utilized to induce root-end barrier formation. Traditionally, calcium hydroxide has been the material of choice for the apexification of immature permanent teeth; however, Mineral Trioxide Aggregate holds significant promise as an alternative to multiple treatments with calcium hydroxide. One of the technical problems associated with the placement of the restorative materials used as artificial barrier is to prevent overfill and underfill. Using a matrix avoids the extrusion of the material into the periodontal tissues. This case report presents the successful healing and apexification with combined use of Mineral Trioxide Aggregate as an apical barrier, and autologus platelet rich fibrin membrane as an internal matrix. PMID:22557824

  19. 46 CFR 151.50-21 - Sulfuric acid.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Sulfuric acid. 151.50-21 Section 151.50-21 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-21 Sulfuric acid. (a) How sulfuric acid may be carried. (1) Sulfuric acid of concentration of 77.5 percent (1.7019 specific gravity)...

  20. 46 CFR 151.50-21 - Sulfuric acid.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Sulfuric acid. 151.50-21 Section 151.50-21 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-21 Sulfuric acid. (a) How sulfuric acid may be carried. (1) Sulfuric acid of concentration of 77.5 percent (1.7019 specific gravity)...

  1. 46 CFR 151.50-21 - Sulfuric acid.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Sulfuric acid. 151.50-21 Section 151.50-21 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-21 Sulfuric acid. (a) How sulfuric acid may be carried. (1) Sulfuric acid of concentration of 77.5 percent (1.7019 specific gravity)...

  2. 46 CFR 151.50-21 - Sulfuric acid.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Sulfuric acid. 151.50-21 Section 151.50-21 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-21 Sulfuric acid. (a) How sulfuric acid may be carried. (1) Sulfuric acid of concentration of 77.5 percent (1.7019 specific gravity)...

  3. 46 CFR 151.50-21 - Sulfuric acid.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Sulfuric acid. 151.50-21 Section 151.50-21 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-21 Sulfuric acid. (a) How sulfuric acid may be carried. (1) Sulfuric acid of concentration of 77.5 percent (1.7019 specific gravity)...

  4. 46 CFR 151.50-84 - Sulfur dioxide.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Sulfur dioxide. 151.50-84 Section 151.50-84 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-84 Sulfur dioxide. (a) Sulfur... respiratory protective device that protects the wearer against sulfur dioxide vapors and provides...

  5. 46 CFR 151.50-84 - Sulfur dioxide.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Sulfur dioxide. 151.50-84 Section 151.50-84 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-84 Sulfur dioxide. (a) Sulfur... respiratory protective device that protects the wearer against sulfur dioxide vapors and provides...

  6. 46 CFR 151.50-84 - Sulfur dioxide.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Sulfur dioxide. 151.50-84 Section 151.50-84 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-84 Sulfur dioxide. (a) Sulfur... respiratory protective device that protects the wearer against sulfur dioxide vapors and provides...

  7. 46 CFR 151.50-84 - Sulfur dioxide.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Sulfur dioxide. 151.50-84 Section 151.50-84 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-84 Sulfur dioxide. (a) Sulfur... respiratory protective device that protects the wearer against sulfur dioxide vapors and provides...

  8. 46 CFR 151.50-84 - Sulfur dioxide.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Sulfur dioxide. 151.50-84 Section 151.50-84 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-84 Sulfur dioxide. (a) Sulfur... respiratory protective device that protects the wearer against sulfur dioxide vapors and provides...

  9. Cyclic process for the removal of sulfur dioxide and the recovery of sulfur from gases

    SciTech Connect

    Lo, C.L.

    1991-11-19

    This patent describes a process for the removal of sulfur dioxide from a gas containing sulfur dioxide. It comprises contacting a gas containing sulfur dioxide with an aqueous solution comprising water, ferric chloride and a salt selected from the group consisting of barium chloride and calcium chloride to form ferrous chloride, hydrochloric acid and a precipitate selected from the group consisting of barium sulfate and calcium sulfate; and treating the aqueous solution with an oxidizing agent to convert ferrous chloride to ferric chloride.

  10. Mass-independent sulfur of inclusions in diamond and sulfur recycling on early Earth.

    PubMed

    Farquhar, J; Wing, B A; McKeegan, K D; Harris, J W; Cartigny, P; Thiemens, M H

    2002-12-20

    Populations of sulfide inclusions in diamonds from the Orapa kimberlite pipe in the Kaapvaal-Zimbabwe craton, Botswana, preserve mass-independent sulfur isotope fractionations. The data indicate that material was transferred from the atmosphere to the mantle in the Archean. The data also imply that sulfur is not well mixed in the diamond source regions, allowing for reconstruction of the Archean sulfur cycle and possibly offering insight into the nature of mantle convection through time.

  11. Probing single cells of purple sulfur bacteria with Raman spectroscopy: carotenoids and elemental sulfur.

    PubMed

    Oren, Aharon; Mana, Lily; Jehlička, Jan

    2015-03-01

    We explored the use of Raman spectroscopy to simultaneously monitor the presence of different biomarkers (carotenoids, elemental sulfur) within single cells of the purple sulfur photosynthetic bacteria Allochromatium vinosum and A. warmingii. Raman microspectrometry using excitation at 532 nm allowed the detection of different carotenoids. Raman signals of elemental sulfur appeared soon after feeding starved cells with sulfide. Raman spectroscopy is thus a convenient and sensitive technique to qualitatively and semiquantitatively assess the presence of different compounds of interest within single bacterial cells.

  12. Inspection, testing, and operating requiremens for the packaging and shipping of uranium trioxide in 55-gallon Department of Transportation (DOT) Specification 6M shipping packagings

    SciTech Connect

    Toomer, D.V.

    1991-06-01

    This document identifies the inspection, testing and operating requirements for the packaging, loading, and shipping of uranium trioxide (UO{sub 3}) in 55-gallon DOT Specification 6M shipping packagings from the Idaho Chemical Processing Plant (ICPP). Compliance with this document assures established controls for the purchasing, packaging, loading, and shipping of DOT Specification 6M shipping packagings are maintained in strict accordance with applicable Code of Federal Regulations (CFRs) and Department of Energy (DOE) Orders. 7 refs., 3 figs., 1 tab.

  13. Reaction of stabilized Criegee intermediates from ozonolysis of limonene with sulfur dioxide: ab initio and DFT study.

    PubMed

    Jiang, Lei; Xu, Yi-sheng; Ding, Ai-zhong

    2010-12-02

    The mechanism of the reaction of the sulfur dioxide (SO(2)) with four stabilized Criegee intermediates (stabCI-CH(3)-OO, stabCI-OO, stabCIx-OO, and stabCH(2)OO) produced via the ozonolysis of limonene have been investigated using ab initio and DFT (density functional theory) methods. It has been shown that the intermediate adduct formed by the initiation of these reactions may be followed by two different reaction pathways such as H migration reaction to form carboxylic acids and rearrangement of oxygen to produce the sulfur trioxide (SO(3)) from the terminal oxygen of the COO group and SO(2). We found that the reaction of stabCI-OO and stabCH(2)OO with SO(2) can occur via both the aforementioned scenarios, whereas that of stabCI-CH(3)-OO and stabCIx-OO with SO(2) is limited to the second pathway only due to the absence of migrating H atoms. It has been shown that at the CCSD(T)/6-31G(d) + CF level of theory the activation energies of six reaction pathways are in the range of 14.18-22.59 kcal mol(-1), with the reaction between stabCIx-OO and SO(2) as the most favorable pathway of 14.18 kcal mol(-1) activation energy and that the reaction of stabCI-OO and stabCH(2)OO with SO(2) occurs mainly via the second reaction path. The thermochemical analysis of the reaction between SO(2) and stabilized Criegee intermediates indicates that the reaction of SO(2) and stabilized Criegee intermediates formed from the exocyclic primary ozonide decomposition is the main pathway of the SO(3) formation. This is likely to explain the large (~100%) difference in the production rate in the favor of the exocyclic compounds observed in recent experiments on the formation of H(2)SO(4) from exocyclic and endocyclic compounds.

  14. The sulfur thermochemical cycle for hydrogen production

    NASA Astrophysics Data System (ADS)

    Dokiya, M.

    1981-07-01

    Results of research on sulfur-cycle hydrogen production are presented. An H2S cycle using MoS2 as a catalyst is mentioned as showing promise for thermochemical water splitting, with an equilibrium reaction yield of 7%. Use of I or Pt as catalysts raised efficiencies to 16 and 12%, respectively, and further studies employing hybrid cycles with CO2-S and noble metals are reviewed. Thermal decomposition reactions with sulfuric acid are examined, noting a potential 30% thermal efficiency, and sulfur cycle research being undertaken at various industrial laboratories is outlined. It is noted that experiments with sulfuric acid salts for water electrolysis at Los Alamos will probably use solar collectors as a heat source.

  15. Environmental behavior and analysis of agricultural sulfur.

    PubMed

    Griffith, Corey M; Woodrow, James E; Seiber, James N

    2015-11-01

    Sulfur has been widely used for centuries as a staple for pest and disease management in agriculture. Presently, it is the largest-volume pesticide in use worldwide. This review describes the sources and recovery methods for sulfur, its allotropic forms and properties and its agricultural uses, including development and potential advantages of nanosulfur as a fungicide. Chemical and microbial reactivity, interactions in soil and water and analytical methods for determination in environmental samples and foodstuffs, including inexpensive analytical methods for sulfur residues in wine, beer and other food/beverage substrates, will be reviewed. The toxicology of sulfur towards humans and agriculturally important fungi is included, with some restrictions on use to promote safety. The review concludes with areas for which more research is warranted.

  16. Ceres: Sulfur deposits and graphitized carbon

    NASA Astrophysics Data System (ADS)

    Hendrix, Amanda R.; Vilas, Faith; Li, Jian-Yang

    2016-09-01

    We report new results from observations of the dwarf planet Ceres using the Hubble Space Telescope in the spectral range 1160-5700 Å. Comparisons between Ceres' UV-visible spectra and laboratory measurements indicate that both sulfur species and graphitized carbon are important on Ceres' surface. We find a latitudinal gradient in UV absorption, with northern latitudes being more UV absorbing than southern latitudes, a trend that can be explained by increasing abundances of sulfur and SO2 toward northern latitudes. The presence of graphitized carbon is consistent with the surface of this airless body being carbonized in response to processes such as charged particle bombardment. The presence of volatile sulfur species is consistent with the idea that Ceres exhibits geothermal activity. Spectral differences with previous UV observations are likely due to the changing sulfurous and carbonaceous surface of Ceres.

  17. Molecular Strategies Against Sulfur Mustard Toxicity

    DTIC Science & Technology

    2010-04-01

    meiosis . Our current understanding of epigenetic regulation of gene expression involves basically two classes of molecular mechanisms: histone...Molecular Strategies Against Sulfur Mustard Toxicity 30 - 4 RTO-MP-HFM-182 meiosis . Our current understanding of epigenetic gene regulation

  18. Ultra-Low Sulfur Gasoline Emissions Study

    EPA Pesticide Factsheets

    Understanding the effects of gasoline sulfur level on the in-use fleet is important for assessing emissions inventories and impacts of future policy decisions. Test fuels were two non-ethanol gasolines with properties typical of certification fuel.

  19. Primary Sulfur Dioxide NAAQS Implementation Schedule

    EPA Pesticide Factsheets

    The effective date for the primary sulfur dioxide (SO2) National Ambient Air Quality Standard (NAAQS) established in 2012, is followed by designations of nonattainment areas and subsequently required state implementation plans (SIPs).

  20. Mesoporous hollow carbon spheres for lithium–sulfur batteries: distribution of sulfur and electrochemical performance

    PubMed Central

    Juhl, Anika C; Schneider, Artur; Ufer, Boris; Brezesinski, Torsten

    2016-01-01

    Summary Hollow carbon spheres (HCS) with a nanoporous shell are promising for the use in lithium–sulfur batteries because of the large internal void offering space for sulfur and polysulfide storage and confinement. However, there is an ongoing discussion whether the cavity is accessible for sulfur. Yet no valid proof of cavity filling has been presented, mostly due to application of unsuitable high-vacuum methods for the analysis of sulfur distribution. Here we describe the distribution of sulfur in hollow carbon spheres by powder X-ray diffraction and Raman spectroscopy along with results from scanning electron microscopy and nitrogen physisorption. The results of these methods lead to the conclusion that the cavity is not accessible for sulfur infiltration. Nevertheless, HCS/sulfur composite cathodes with areal sulfur loadings of 2.0 mg·cm−2 were investigated electrochemically, showing stable cycling performance with specific capacities of about 500 mAh·g−1 based on the mass of sulfur over 500 cycles. PMID:27826497

  1. Mesoporous hollow carbon spheres for lithium-sulfur batteries: distribution of sulfur and electrochemical performance.

    PubMed

    Juhl, Anika C; Schneider, Artur; Ufer, Boris; Brezesinski, Torsten; Janek, Jürgen; Fröba, Michael

    2016-01-01

    Hollow carbon spheres (HCS) with a nanoporous shell are promising for the use in lithium-sulfur batteries because of the large internal void offering space for sulfur and polysulfide storage and confinement. However, there is an ongoing discussion whether the cavity is accessible for sulfur. Yet no valid proof of cavity filling has been presented, mostly due to application of unsuitable high-vacuum methods for the analysis of sulfur distribution. Here we describe the distribution of sulfur in hollow carbon spheres by powder X-ray diffraction and Raman spectroscopy along with results from scanning electron microscopy and nitrogen physisorption. The results of these methods lead to the conclusion that the cavity is not accessible for sulfur infiltration. Nevertheless, HCS/sulfur composite cathodes with areal sulfur loadings of 2.0 mg·cm(-2) were investigated electrochemically, showing stable cycling performance with specific capacities of about 500 mAh·g(-1) based on the mass of sulfur over 500 cycles.

  2. Dual protection of sulfur by carbon nanospheres and graphene sheets for lithium-sulfur batteries.

    PubMed

    Wang, Bei; Wen, Yanfen; Ye, Delai; Yu, Hua; Sun, Bing; Wang, Guoxiu; Hulicova-Jurcakova, Denisa; Wang, Lianzhou

    2014-04-25

    Well-confined elemental sulfur was implanted into a stacked block of carbon nanospheres and graphene sheets through a simple solution process to create a new type of composite cathode material for lithium-sulfur batteries. Transmission electron microscopy and elemental mapping analysis confirm that the as-prepared composite material consists of graphene-wrapped carbon nanospheres with sulfur uniformly distributed in between, where the carbon nanospheres act as the sulfur carriers. With this structural design, the graphene contributes to direct coverage of sulfur to inhibit the mobility of polysulfides, whereas the carbon nanospheres undertake the role of carrying the sulfur into the carbon network. This composite achieves a high loading of sulfur (64.2 wt %) and gives a stable electrochemical performance with a maximum discharge capacity of 1394 mAh g(-1) at a current rate of 0.1 C as well as excellent rate capability at 1 C and 2 C. The improved electrochemical properties of this composite material are attributed to the dual functions of the carbon components, which effectively restrain the sulfur inside the carbon nano-network for use in lithium-sulfur rechargeable batteries.

  3. Method for reducing the sulfur content of a sulfur-containing hydrocarbon stream

    DOEpatents

    Mahajan, Devinder

    2004-12-28

    The sulfur content of a liquid hydrocarbon stream is reduced under mild conditions by contracting a sulfur-containing liquid hydrocarbon stream with transition metal particles containing the transition metal in a zero oxidation state under conditions sufficient to provide a hydrocarbon product having a reduced sulfur content and metal sulfide particles. The transition metal particles can be produced in situ by adding a transition metal precursor, e.g., a transition metal carbonyl compound, to the sulfur-containing liquid feed stream and sonicating the feed steam/transition metal precursor combination under conditions sufficient to produce the transition metal particles.

  4. Definition of Non-Conventional Sulfur Utilization in Western Kazakhstan for Sulfur Concrete (Phase 1)

    SciTech Connect

    Kalb, Paul

    2007-05-31

    Battelle received a contract from Agip-KCO, on behalf a consortium of international oil and gas companies with exploration rights in the North Caspian Sea, Kazakhstan. The objective of the work was to identify and help develop new techniques for sulfur concrete products from waste, by-product sulfur that will be generated in large quantitites as drilling operations begin in the near future. BNL has significant expertise in the development and use of sulfur concrete products and has direct experience collaborating with the Russian and Kazakh partners that participated. Feasibility testing was successfully conducted for a new process to produce cost-effective sulfur polymer cement that has broad commerical applications.

  5. Protected Sulfur Cathode with Mixed Conductive Coating Layer for Lithium Sulfur Battery

    NASA Astrophysics Data System (ADS)

    Jin, Jun; Wen, Zhaoyin; Wang, Qingsong; Gu, Sui; Huang, Xiao; Chen, Chunhua

    2016-10-01

    A mixed conductive coating layer composed of lithium ion conductive ceramic powder, carbon and binder was introduced on the surface of a sulfur electrode. This coating layer is designed to suppress the migration of lithium polysulfides from the sulfur electrode, and improve the cycling capacity of a lithium sulfur battery. The protected sulfur cathode with a mixed conductive coating layer delivered an initial specific capacity of 1236 mAh g-1 at 0.5C and maintained a capacity of 842 mAh g-1 after 100 cycles. In particular, a soft package battery with protected cathode exhibits improved cycling capacity and excellent rate performance.

  6. Effects of variation of dietary sulfur on movement of sulfur in sheep rumen

    SciTech Connect

    Kandylis, K.; Bray, A.C.

    1987-01-01

    Effects of variations in dietary sulfur on rumen sulfur dynamics were studied under steady state conditions. In the first experimental period, three sheep were given 33.3 g of a pelleted diet hourly containing 1.59 g sulfur/kg (low) and in the second period the sulfur content was increased to 3.21 g/kg (high) by the addition of sodium sulfate. The daily sulfur intake was 1.158 g on the low sulfur diet and .545 g of this passed from the rumen in protein, .614 g was calculated to be absorbed from the rumen as sulfide, and .052 g was estimated to be recycled to the rumen. For sheep with daily intakes of 2.317 g sulfur, 1.212 g passed from the rumen in protein, 1.078 g was absorbed from the rumen, and .093 g was estimated to be recycled. It was estimated that 127 and 165 g microbial protein were synthesized/kg organic matter truly digested in the rumen for low and high sulfur diets, respectively. A simple model using simultaneous equations was proposed to describe rumen sulfur metabolism.

  7. The Biogeochemistry of Sulfur in Hydrothermal Systems

    NASA Technical Reports Server (NTRS)

    Schulte, Mitchell; Rogers, K. L.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    The incorporation of sulfur into many biomolecules likely dates back to the development of the earliest metabolic strategies. Sulfur is common in enzymes and co-enzymes and is an indispensable structural component in many peptides and proteins. Early metabolism may have been heavily influenced by the abundance of sulfide minerals in hydrothermal systems. The incorporation of sulfur into many biomolecules likely dates back to the development of the earliest metabolic strategies. Sulfur is common in enzymes and co-enzymes and is an indispensable structural component in many peptides and proteins. Early metabolism may have been heavily influenced by the abundance of sulfide minerals in hydrothermal systems. Understanding how sulfur became prevalent in biochemical processes and many biomolecules requires knowledge of the reaction properties of sulfur-bearing compounds. We have previously estimated thermodynamic data for thiols, the simplest organic sulfur compounds, at elevated temperatures and pressures. If life began in hydrothermal environments, it is especially important to understand reactions at elevated temperatures among sulfur-bearing compounds and other organic molecules essential for the origin and persistence of life. Here we examine reactions that may have formed amino acids with thiols as reaction intermediates in hypothetical early Earth hydrothermal environments. (There are two amino acids, cysteine and methionine, that contain sulfur.) Our calculations suggest that significant amounts of some amino acids were produced in early Earth hydrothermal fluids, given reasonable concentrations H2, NH3, H2S and CO. For example, preliminary results indicate that glycine activities as high as 1 mmol can be reached in these systems at 100 C. Alanine formation from propanethiol is also a favorable reaction. On the other hand, the calculated equilibrium log activities of cysteine and serine from propanethiol are -21 and -19, respectively, at 100 C. These results

  8. Transfer of sulfur: from simple to diverse.

    PubMed

    Liu, Hui; Jiang, Xuefeng

    2013-11-01

    The introduction of sulfur atoms onto target molecules is an important area in organic synthesis, in particular in the synthesis of pharmaceutical compounds, and a wide variety of sulfuration agents have been developed for thionation reactions over the past few decades. In this Focus Review, we collect and summarize the C-S bond-formation reactions that have been used to construct C-S bonds in natural products and pharmaceutical compounds.

  9. Copper mercaptides as sulfur dioxide indicators

    DOEpatents

    Eller, Phillip G.; Kubas, Gregory J.

    1979-01-01

    Organophosphine copper(I) mercaptide complexes are useful as convenient and semiquantitative visual sulfur dioxide gas indicators. The air-stable complexes form 1:1 adducts in the presence of low concentrations of sulfur dioxide gas, with an associated color change from nearly colorless to yellow-orange. The mercaptides are made by mixing stoichiometric amounts of the appropriate copper(I) mercaptide and phosphine in an inert organic solvent.

  10. Process for removing sulfur from coal

    DOEpatents

    Aida, T.; Squires, T.G.; Venier, C.G.

    1983-08-11

    A process is disclosed for the removal of divalent organic and inorganic sulfur compounds from coal and other carbonaceous material. A slurry of pulverized carbonaceous material is contacted with an electrophilic oxidant which selectively oxidizes the divalent organic and inorganic compounds to trivalent and tetravalent compounds. The carbonaceous material is then contacted with a molten caustic which dissolves the oxidized sulfur compounds away from the hydrocarbon matrix.

  11. Sulfuric Acid Regeneration Waste Disposal Technology.

    DTIC Science & Technology

    1986-11-01

    46 2 4 H2 3 4 4 2 Phosphate Sulfuric Water Phosphoric Hydro- Phosphogypsum Rock Acid Acid fluoric Acid For our purposes the process could be viewed as...one where sulfuric acid is neutralized using phosphate rock rather than lime. Although the resulting calcium sulfate (referred to as phosphogypsum ...spearhead research in this country on uses for waste gypsum or phosphogypsum . They have published a recent review of historic and current work on

  12. Process for removing sulfur from coal

    DOEpatents

    Aida, Tetsuo; Squires, Thomas G.; Venier, Clifford G.

    1985-02-05

    A process for the removal of divalent organic and inorganic sulfur compounds from coal and other carbonaceous material. A slurry of pulverized carbonaceous material is contacted with an electrophilic oxidant which selectively oxidizes the divalent organic and inorganic compounds to trivalent and tetravalent compounds. The carbonaceous material is then contacted with a molten caustic which dissolves the oxidized sulfur compounds away from the hydrocarbon matrix.

  13. A Cable-Shaped Lithium Sulfur Battery.

    PubMed

    Fang, Xin; Weng, Wei; Ren, Jing; Peng, Huisheng

    2016-01-20

    A carbon nanostructured hybrid fiber is developed by integrating mesoporous carbon and graphene oxide into aligned carbon nanotubes. This hybrid fiber is used as a 1D cathode to fabricate a new cable-shaped lithium-sulfur battery. The fiber cathode exhibits a decent specific capacity and lifespan, which makes the cable-shaped lithium-sulfur battery rank far ahead of other fiber-shaped batteries.

  14. Sulfur nutrition of deciduous trees

    NASA Astrophysics Data System (ADS)

    Herschbach, Cornelia; Rennenberg, Heinz

    2001-01-01

    Sulfur in its reduced form (-II) is an essential nutrient for growth and development, but is mainly available to plants in its oxidised form as sulfate. Deciduous trees take up sulfate by the roots from the soil solution and reduce sulfate to sulfide via assimilatory sulfate reduction in both roots and leaves. For reduction in the leaves, sulfate is loaded into the xylem and transported to the shoot. The surplus of sulfate not reduced in the chloroplast or stored in the vacuole and the surplus of reduced S not used for protein synthesis in the leaves is loaded into the phloem and transported back to the roots. Along the transport path, sulfate and glutathione (GSH) is unloaded from the phloem for storage in xylem and phloem parenchyma as well as in pit and ray cells. Re-mobilised S from storage tissues is loaded into the xylem during spring, but a phloem to xylem exchange does not appear to exist later in the season. As a consequence, a cycling pool of S was only found during the change of the seasons. The sulfate:glutathione ratio in the phloem seems to be involved in the regulation of S nutrition. This picture of S nutrition is discussed in relation to the different growth patterns of deciduous trees from the temperate climate zone, i.e. (1) terminated, (2) periodic and (3) indeterminate growth patterns, and in relation to environmental changes.

  15. Theoretical studies of the marine sulfur cycle

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Kasting, James B.; Liu, May S.

    1985-01-01

    Several reduced sulfur compounds are produced by marine organisms and then enter the atmosphere, where they are oxidized and ultimately returned to the ocean or the land. The oceanic dimethyl sulfide (DMS) flux, in particular, represents a significant fraction of the annual global sulfur input to the atmosphere. In the atmosphere, this gas is converted to sulfur dioxide (SO2), methane sulfonic acid, and other organic acids which are relatively stable and about which little is known. SO2 is a short lived gas which, in turn, is converted to sulfuric acid and other sulfate compounds which contribute significantly to acid rain. Because of the complexity of the sulfur system, it is not well understood even in the unperturbed atmosphere. However, a number of new observations and experiments have led to a significant increase in the understanding of this system. A number of one dimensional model experiments were conducted on the gas phase part of the marine sulfur cycle. The results indicate the measured concentration of DMS and the amplitude of its diurnal cycle are in agreement with estimates of its global flux. It was also found that DMS can make a large contribution to the background SO2 concentration in the free troposphere. Estimates of CS2 concentrations in the atmosphere are inconsistent with estimated fluxes; however, measured reaction rates are consistent with the observed steep tropospheric gradient in CS2. Observations of CS2 are extremely sparse. Further study is planned.

  16. The biology of reactive sulfur species (RSS).

    PubMed

    Gruhlke, Martin C H; Slusarenko, Alan J

    2012-10-01

    Sulfur is an essential and quantitatively important element for living organisms. Plants contain on average approximately 1 g S kg⁻¹ dry weight (for comparison plants contain approximately 15 g N kg⁻¹ dry weight). Sulfur is a constituent of many organic molecules, for example amino acids such as cysteine and methionine and the small tripeptide glutathione, but sulfur is also essential in the form of Fe-S clusters for the activity of many enzymes, particularly those involved in redox reactions. Sulfur chemistry is therefore important. In particular, sulfur in the form of thiol groups is central to manifold aspects of metabolism. Because thiol groups are oxidized and reduced easily and reversibly, the redox control of cellular metabolism has become an increasing focus of research. In the same way that oxygen and nitrogen have reactive species (ROS and RNS), sulfur too can form reactive molecular species (RSS), for example when a -SH group is oxidized. Indeed, several redox reactions occur via RSS intermediates. Several naturally occurring S-containing molecules are themselves RSS and because they are physiologically active they make up part of the intrinsic plant defence repertoire against herbivore and pathogen attack. Furthermore, RSS can also be used as redox-active pharmacological tools to study cell metabolism. The aim of this review is to familiarize the general reader with some of the chemical concepts, terminology and biology of selected RSS.

  17. Sulfur "Concrete" for Lunar Applications - Sublimation Concerns

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Toutanji, Houssam

    2006-01-01

    Melting sulfur and mixing it with an aggregate to form "concrete" is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO2 powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.

  18. Improved Chromatographic Techniques for Sulfur Pollutants

    NASA Technical Reports Server (NTRS)

    Hartmann, C. H.

    1971-01-01

    This paper describes several improvements in instrumental techniques for the analysis of low ppb concentrations of sulfur gases using gas chromatography (G.C.). This work has focused on the analytical problem of ambient air monitoring of the two main sulfur gas pollutants, hydrogen sulfide and sulfur dioxide. The most significant technical improvement that will be reported here is the newly developed silica gel column for ppb concentrations of the light sulfur gases (COS, H2S, CS2, SO2, CH3SH). A simplified inlet system will be described which improves reliability of the GC system. The flame photometric detector is used as the means of selectively and sensitively detecting the low concentrations of sulfur gases. Improvements will be described which have yielded better performance than previously reported for this application of the detector. Also included in this paper will be a report of field monitoring using this improved GC system. Reliability and repeatability of performance at the low ppb concentrations of sulfur gases will be demonstrated.

  19. Differential accumulation of transcripts encoding sulfur assimilation enzymes upon sulfur and/or nitrogen deprivation in Arabidopsis thaliana.

    PubMed

    Yamaguchi, Y; Nakamura, T; Harada, E; Koizumi, N; Sano, H

    1999-04-01

    Expression of nine genes encoding enzymes involved in the sulfur assimilation pathway was examined by RNA blot hybridization. Significantly increased levels of transcripts encoding ATP sulfurylase and APS reductase were apparent under sulfur deprivation. However, in the absence of nitrogen, their responsiveness to sulfur deprivation was markedly reduced. Results suggest that the sulfur assimilation pathway is regulated at the transcriptional level by both nitrogen and sulfur sources.

  20. Acidithiobacillus caldus Sulfur Oxidation Model Based on Transcriptome Analysis between the Wild Type and Sulfur Oxygenase Reductase Defective Mutant

    PubMed Central

    Chen, Linxu; Ren, Yilin; Lin, Jianqun; Liu, Xiangmei; Pang, Xin; Lin, Jianqiang

    2012-01-01

    Background Acidithiobacillus caldus (A. caldus) is widely used in bio-leaching. It gains energy and electrons from oxidation of elemental sulfur and reduced inorganic sulfur compounds (RISCs) for carbon dioxide fixation and growth. Genomic analyses suggest that its sulfur oxidation system involves a truncated sulfur oxidation (Sox) system (omitting SoxCD), non-Sox sulfur oxidation system similar to the sulfur oxidation in A. ferrooxidans, and sulfur oxygenase reductase (SOR). The complexity of the sulfur oxidation system of A. caldus generates a big obstacle on the research of its sulfur oxidation mechanism. However, the development of genetic manipulation method for A. caldus in recent years provides powerful tools for constructing genetic mutants to study the sulfur oxidation system. Results An A. caldus mutant lacking the sulfur oxygenase reductase gene (sor) was created and its growth abilities were measured in media using elemental sulfur (S0) and tetrathionate (K2S4O6) as the substrates, respectively. Then, comparative transcriptome analysis (microarrays and real-time quantitative PCR) of the wild type and the Δsor mutant in S0 and K2S4O6 media were employed to detect the differentially expressed genes involved in sulfur oxidation. SOR was concluded to oxidize the cytoplasmic elemental sulfur, but could not couple the sulfur oxidation with the electron transfer chain or substrate-level phosphorylation. Other elemental sulfur oxidation pathways including sulfur diooxygenase (SDO) and heterodisulfide reductase (HDR), the truncated Sox pathway, and the S4I pathway for hydrolysis of tetrathionate and oxidation of thiosulfate in A. caldus are proposed according to expression patterns of sulfur oxidation genes and growth abilities of the wild type and the mutant in different substrates media. Conclusion An integrated sulfur oxidation model with various sulfur oxidation pathways of A. caldus is proposed and the features of this model are summarized. PMID:22984393

  1. 40 CFR Appendix T to Part 50 - Interpretation of the Primary National Ambient Air Quality Standards for Oxides of Sulfur (Sulfur...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) T Appendix T to Part 50 Protection of... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) 1. General (a) This appendix explains... ambient air quality standards for Oxides of Sulfur as measured by Sulfur Dioxide (“SO2 NAAQS”)...

  2. 40 CFR Appendix T to Part 50 - Interpretation of the Primary National Ambient Air Quality Standards for Oxides of Sulfur (Sulfur...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) T Appendix T to Part 50 Protection of... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) 1. General (a) This appendix explains... ambient air quality standards for Oxides of Sulfur as measured by Sulfur Dioxide (“SO2 NAAQS”)...

  3. 40 CFR Appendix T to Part 50 - Interpretation of the Primary National Ambient Air Quality Standards for Oxides of Sulfur (Sulfur...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) T Appendix T to Part 50 Protection of... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) 1. General (a) This appendix explains... ambient air quality standards for Oxides of Sulfur as measured by Sulfur Dioxide (“SO2 NAAQS”)...

  4. 40 CFR Appendix T to Part 50 - Interpretation of the Primary National Ambient Air Quality Standards for Oxides of Sulfur (Sulfur...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) T Appendix T to Part 50 Protection of... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) 1. General (a) This appendix explains... ambient air quality standards for Oxides of Sulfur as measured by Sulfur Dioxide (“SO2 NAAQS”)...

  5. 40 CFR Appendix T to Part 50 - Interpretation of the Primary National Ambient Air Quality Standards for Oxides of Sulfur (Sulfur...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) T Appendix T to Part 50 Protection of... Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) 1. General (a) This appendix explains... ambient air quality standards for Oxides of Sulfur as measured by Sulfur Dioxide (“SO2 NAAQS”)...

  6. A facile route to core-shell nanoparticulate formation of arsenic trioxide for effective solid tumor treatment

    NASA Astrophysics Data System (ADS)

    Zhang, Zongjun; Liu, Hanyu; Zhou, Hualu; Zhu, Xianglong; Zhao, Zhenghuan; Chi, Xiaoqin; Shan, Hong; Gao, Jinhao

    2016-02-01

    Arsenic trioxide has achieved great clinical success in the treatment of acute promyelocytic leukemia (APL). However, it is difficult to replicate the success in other cancers, such as solid tumors, in part because of the rapid renal clearance and dose-limiting toxicity. Nanotechnology is expected to overcome these disadvantages through altering its pharmacokinetics and concentrating the drug at the desired sites. Herein, we report a ``one-pot'' method to develop arsenic-based nanodrugs by in situ coating the as-prepared arsenic nanocomplexes with porous silica shells. This process can be easily reproduced and scaled up because no complicated synthesis and purification steps are involved. This core-shell embedding method endows nanodrugs with high loading capacity (57.9 wt%) and a prolonged pH-responsive releasing profile, which is crucial to increase the drug concentration at tumor sites and improve the drug efficacy. Based on these unique features, the nanodrugs significantly inhibit the growth of solid tumors without adverse side effects. Therefore, we anticipate that the arsenic-based nanodrugs generated by this facile synthetic route may be a powerful and alternative strategy for solid tumor therapy.Arsenic trioxide has achieved great clinical success in the treatment of acute promyelocytic leukemia (APL). However, it is difficult to replicate the success in other cancers, such as solid tumors, in part because of the rapid renal clearance and dose-limiting toxicity. Nanotechnology is expected to overcome these disadvantages through altering its pharmacokinetics and concentrating the drug at the desired sites. Herein, we report a ``one-pot'' method to develop arsenic-based nanodrugs by in situ coating the as-prepared arsenic nanocomplexes with porous silica shells. This process can be easily reproduced and scaled up because no complicated synthesis and purification steps are involved. This core-shell embedding method endows nanodrugs with high loading capacity

  7. COULOMETRIC DETERMINATION OF TOTAL SULFUR AND REDUCED INORGANIC SULFUR FRACTIONS IN ENVIRONMENTAL SAMPLES

    EPA Science Inventory

    Evaluation of the solid-phase partitioning of sulfur is frequently an important analytical component of risk assessments at hazardous waste sites because minerals containing reduced-sulfur can significantly affect the transport and fate of organic and inorganic contaminants in na...

  8. Airborne sulfur trace species intercomparison campaign: Sulfur dioxide, dimethylsulfide, hydrogen sulfide, carbon disulfide, and carbonyl sulfide

    NASA Technical Reports Server (NTRS)

    Gregory, Gerald L.; Hoell, James M., Jr.; Davis, Douglas D.

    1991-01-01

    Results from an airborne intercomparison of techniques to measure tropospheric levels of sulfur trace gases are presented. The intercomparison was part of the NASA Global Tropospheric Experiment (GTE) and was conducted during the summer of 1989. The intercomparisons were conducted on the Wallops Electra aircraft during flights from Wallops Island, Virginia, and Natal, Brazil. Sulfur measurements intercompared included sulfur dioxide (SO2), dimethylsulfide (DMS), hydrogen sulfide (H2S), carbon disulfide (CS2), and carbonyl sulfide (OCS). Measurement techniques ranged from filter collection systems with post-flight analyses to mass spectrometer and gas chromatograph systems employing various methods for measuring and identifying the sulfur gases during flight. Sampling schedules for the techniques ranged from integrated collections over periods as long as 50 minutes to one- to three-minute samples every ten or fifteen minutes. Several of the techniques provided measurements of more than one sulfur gas. Instruments employing different detection principles were involved in each of the sulfur intercomparisons. Also included in the intercomparison measurement scenario were a host of supporting measurements (i.e., ozone, nitrogen oxides, carbon monoxide, total sulfur, aerosols, etc.) for purposes of: (1) interpreting results (i.e., correlation of any noted instrument disagreement with the chemical composition of the measurement environment); and (2) providing supporting chemical data to meet CITE-3 science objectives of studying ozone/sulfur photochemistry, diurnal cycles, etc. The results of the intercomparison study are briefly discussed.

  9. Inverse Vulcanization of Sulfur using Natural Dienes as Sustainable Materials for Lithium-Sulfur Batteries.

    PubMed

    Gomez, Iñaki; Leonet, Olatz; Blazquez, J Alberto; Mecerreyes, David

    2016-12-20

    Lithium-sulfur batteries are among the most promising next-generation battery systems due to the high capacity of sulfur as cathodic material. Beyond its interesting intrinsic properties, sulfur possesses a very low conductivity and complex electrochemistry, which involves the high solubility of the lithium sulfides in the electrolyte. These two characteristics are at the core of a series of limitations of its performance as active cathode material, which leads to batteries with low cyclability. Recently, inverse vulcanized sulfur was shown to retain capacity far better than elemental sulfur, leading to batteries with excellent cyclability. Nevertheless, the diene co-monomers used so far in the inverse vulcanization process are man-made molecules. Herein, a tentative work on exploring inverse vulcanization using two naturally available monomers, diallyl sulfide and myrcene, is presented. The inverse vulcanization of sulfur was successfully completed, and the resulting polymers were characterized by FTIR, NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Afterwards these polymers were tested as cathodic materials in lithium-sulfur cells. The sulfur-natural dienes materials exhibited high capacity at different C rates and high lifetime over 200 cycles with very high capacity retention at a moderate C rate of C/5. Altogether, these materials made from inexpensive and abundant chemicals are an excellent option as sustainable materials for electrochemical energy storage.

  10. Fibrous hybrid of graphene and sulfur nanocrystals for high-performance lithium-sulfur batteries.

    PubMed

    Zhou, Guangmin; Yin, Li-Chang; Wang, Da-Wei; Li, Lu; Pei, Songfeng; Gentle, Ian Ross; Li, Feng; Cheng, Hui-Ming

    2013-06-25

    Graphene-sulfur (G-S) hybrid materials with sulfur nanocrystals anchored on interconnected fibrous graphene are obtained by a facile one-pot strategy using a sulfur/carbon disulfide/alcohol mixed solution. The reduction of graphene oxide and the formation/binding of sulfur nanocrystals were integrated. The G-S hybrids exhibit a highly porous network structure constructed by fibrous graphene, many electrically conducting pathways, and easily tunable sulfur content, which can be cut and pressed into pellets to be directly used as lithium-sulfur battery cathodes without using a metal current-collector, binder, and conductive additive. The porous network and sulfur nanocrystals enable rapid ion transport and short Li(+) diffusion distance, the interconnected fibrous graphene provides highly conductive electron transport pathways, and the oxygen-containing (mainly hydroxyl/epoxide) groups show strong binding with polysulfides, preventing their dissolution into the electrolyte based on first-principles calculations. As a result, the G-S hybrids show a high capacity, an excellent high-rate performance, and a long life over 100 cycles. These results demonstrate the great potential of this unique hybrid structure as cathodes for high-performance lithium-sulfur batteries.

  11. [Purple sulfur bacteria isolated from reservoirs of the Yavoriv sulfur deposit].

    PubMed

    Kim, L Ia; Hudz', S P

    2007-01-01

    Three pure cultures of purple sulfur bacteria were isolated from reservoirs of the Yavoriv sulfur deposit. The studying of their morphology, cytology and physiology has confirmed the belonging of these bacteria to Chromatiaceae family and has allowed identifying them as Thiocapsa sp., Lamprocystis sp. and Chromatium sp.

  12. Sulfur-Immobilized, Activated Porous Carbon Nanotube Composite Based Cathodes for Lithium-Sulfur Batteries.

    PubMed

    Lee, Jun Seop; Jun, Jaemoon; Jang, Jyongsik; Manthiram, Arumugam

    2017-03-01

    Activated highly porous carbon nanotubes are synthesized with a facile dual-nozzle co-electrospinning and a redox process to apply the framework of a sulfur-immobilized composite as a high-performance cathode in lithium-sulfur batteries.

  13. Infiltrating sulfur into a highly porous carbon sphere as cathode material for lithium–sulfur batteries

    SciTech Connect

    Zhao, Xiaohui; Kim, Dul-Sun; Ahn, Hyo-Jun; Kim, Ki-Won; Cho, Kwon-Koo; Ahn, Jou-Hyeon

    2014-10-15

    Highlights: • A highly porous carbon (HPC) with regular spherical morphology was synthesized. • Sulfur/HPC composites were prepared by melt–diffusion method. • Sulfur/HPC composites showed improved cyclablity and long-term cycle life. - Abstract: Sulfur composite material with a highly porous carbon sphere as the conducting container was prepared. The highly porous carbon sphere was easily synthesized with resorcinol–formaldehyde precursor as the carbon source. The morphology of the carbon was observed with field emission scanning electron microscope and transmission electron microscope, which showed a well-defined spherical shape. Brunauer–Emmett–Teller analysis indicated that it possesses a high specific surface area of 1563 m{sup 2} g{sup −1} and a total pore volume of 2.66 cm{sup 3} g{sup −1} with a bimodal pore size distribution, which allow high sulfur loading and easy transportation of lithium ions. Sulfur carbon composites with varied sulfur contents were prepared by melt–diffusion method and lithium sulfur cells with the sulfur composites showed improved cyclablity and long-term cycle life.

  14. Direct Observation of Sulfur Radicals as Reaction Media in Lithium Sulfur Batteries

    SciTech Connect

    Wang, Qiang; Zheng, Jianming; Walter, Eric; Pan, Huilin; Lv, Dongping; Zuo, Pengjian; Chen, Honghao; Deng, Z. D.; Liaw, Bor Y.; Yu, Xiqian; Yang, Xiao-Qing; Zhang, Ji-Guang; Liu, Jun; Xiao, Jie

    2015-01-09

    Lithium sulfur (Li-S) battery has been regaining tremendous interest in recent years because of its attractive attributes such as high gravimetric energy, low cost and environmental benignity. However, it is still not conclusively known how polysulfide ring/chain participates in the whole cycling and whether the discharge and charge processes follow the same pathway. Herein, we demonstrate the direct observation of sulfur radicals by using in situ electron paramagnetic resonance (EPR) technique. Based on the concentration changes of sulfur radicals at different potentials and the electrochemical characteristics of the cell, it is revealed that the chemical and electrochemical reactions in Li-S cell are driving each other to proceed through sulfur radicals, leading to two completely different reaction pathways during discharge and charge. The proposed radical mechanism may provide new perspectives to investigate the interactions between sulfur species and the electrolyte, inspiring novel strategies to develop Li-S battery technology.

  15. Direct Observation of Sulfur Radicals as Reaction Media in Lithium Sulfur Batteries

    DOE PAGES

    Wang, Qiang; Zheng, Jianming; Walter, Eric; ...

    2015-01-09

    Lithium sulfur (Li-S) battery has been regaining tremendous interest in recent years because of its attractive attributes such as high gravimetric energy, low cost and environmental benignity. However, it is still not conclusively known how polysulfide ring/chain participates in the whole cycling and whether the discharge and charge processes follow the same pathway. Herein, we demonstrate the direct observation of sulfur radicals by using in situ electron paramagnetic resonance (EPR) technique. Based on the concentration changes of sulfur radicals at different potentials and the electrochemical characteristics of the cell, it is revealed that the chemical and electrochemical reactions in Li-Smore » cell are driving each other to proceed through sulfur radicals, leading to two completely different reaction pathways during discharge and charge. The proposed radical mechanism may provide new perspectives to investigate the interactions between sulfur species and the electrolyte, inspiring novel strategies to develop Li-S battery technology.« less

  16. Direct Observation of Sulfur Radicals as Reaction Media in lithium Sulfur Batteries

    SciTech Connect

    Wang, Qiang; Zheng, Jianming; Walter, Eric D.; Pan, Huilin; Lu, Dongping; Zuo, Pengjian; Chen, Honghao; Deng, Zhiqun; Liaw, Bor Yann; Yu, Xiqian; Yang, Xiaoning; Zhang, Jiguang; Liu, Jun; Xiao, Jie

    2014-12-09

    Lithium sulfur (Li-S) battery has been regaining tremendous interest in recent years because of its attractive attributes such as high gravimetric energy, low cost and environmental benignity. However, it is still not conclusively known how polysulfide ring/chain participates in the whole cycling and whether the discharge and charge process follow the same pathway. Herein, we demonstrate the direct observation of sulfur radicals by using in situ electron paramagnetic resonance (EPR) technique. Based on the concentration changes of sulfur radicals at different potentials, it is revealed that the chemical and electrochemical reactions in Li-S cell are driven each other to proceed through sulfur radicals, leading to two completely different reaction pathways during discharge and charge. The proposed radical mechanism may provide new insights to investigate the interactions between sulfur species and the electrolyte, inspiring novel strategies to develop Li-S battery technology.

  17. Electrostatic self-assembly of graphene oxide wrapped sulfur particles for lithium–sulfur batteries

    SciTech Connect

    Wu, Haiwei; Huang, Ying Zong, Meng; Ding, Xiao; Ding, Juan; Sun, Xu

    2015-04-15

    Highlights: • Researched graphene oxide wrapped sulfur particles for lithium–sulfur batteries. • New approach for core–shell GO/S composites by electrostatic self-assembly method. • Both core–shell structure and the GO support help to retard the diffusion of polysulfides during the electrochemical cycling process of GO/S cathode. - Abstract: A novel graphene oxide (GO)/sulfur (S) composite is developed by electrostatic self-assembly method. Remarkably, the core–shell structure of the composite and the GO support helps to retard the diffusion of polysulfides during the electrochemical cycling process. The GO/sulfur cathode presents enhanced cycling ability. Specific discharge capacities up to 494.7 mAh g{sup −1} over 200 cycles at 0.1 C is achieved with enhanced columbic efficiency around 95%, representing a good cathode material for lithium–sulfur batteries.

  18. Activated porous carbon wrapped sulfur sub-microparticles as cathode materials for lithium sulfur batteries

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Yan, Y. L.; Ren, B.; Yang, R.; Zhang, W.; Xu, Y. H.

    2017-03-01

    The lithium-sulfur batteries holds a high theoretical capacity and specific energy, which is 4-5 times larger than that of today’s lithium-ion batteries, yet the low sulfur loading and large particles in the cathode greatly offset its advantage in high energy density. In the present paper, a liquid phase deposition method was introduced to synthesize sub-micro sulfur particles, which utilized as cathode materials after composed with activated porous carbon. Compared with common sublimed sulfur cathodes, as-obtained composite cathode shows an enhanced initial discharge capacity from 840.7 mAh/g to 1093 mAh/g at C/10. The reversible specific capacity after 50 cycles increased from 383 mAh/g to 504 mAh/g. The developed method has the advantages of simple process, convenient operation and low cost, and is suitable for the industrial preparation of lithium/sulfur batteries.

  19. Effect of sulfur content in a sulfur-activated carbon composite on the electrochemical properties of a lithium/sulfur battery

    SciTech Connect

    Park, Jin-Woo; Kim, Changhyeon; Ryu, Ho-Suk; Cho, Gyu-Bong; Cho, Kwon-Koo; Kim, Ki-Won; Ahn, Jou-Hyeon; Wang, Guoxiu; Ahn, Jae-Pyeung; Ahn, Hyo-Jun

    2015-09-15

    Highlights: • The content of sulfur in activated carbon was controlled by solution process. • The sulfur electrode with low sulfur content shows the best performance. • The Li/S battery has capacity of 1360 mAh/g at 1 C and 702 mAh/g at 10 C. - Abstract: The content of sulfur in sulfur/activated carbon composite is controlled from 32.37 wt.% to 55.33 wt.% by a one-step solution-based process. When the sulfur content is limited to 41.21 wt.%, it can be loaded into the pores of an activated carbon matrix in a highly dispersed state. On the contrary, when the sulfur content is 55.33 wt.%, crystalline sulfur can be detected on the surface of the activated carbon matrix. The best electrochemical performance can be obtained for a sulfur electrode with the lowest sulfur content. The sulfur/activated carbon composite with 32.37 wt.% sulfur afforded the highest first discharge capacity of 1360 mAh g{sup −1} at 1 C rate and a large reversible capacity of 702 mAh g{sup −1} at 10 C (16.75 A/g)

  20. The effecting factors of sulfur evolution during coal combustion

    SciTech Connect

    Liu Zechang; Yu Hongguan; Wang Li

    1997-12-31

    Three kinds of bituminous coal and one kind of anthracite have been used to investigate the factors affecting sulfur evolution during coal combustion by means of improved automatic sulfur analyzer. In this paper the sulfur evolution index, that is, the relative quantity of sulfur evolution (Vs), the final quantity of sulfur evolution (Va), the rate of sulfur evolution and delay time, are selected to describe the sulfur evolution. The results show that the rate and quantity of sulfur evolution is affected by the temperature, retention time, type of coal, sulfur forms, calcium-based content in coal, oxygen concentration and flow velocity of air. The study can provide some knowledge for selecting sorbent for coal combustion.

  1. A primer on sulfur for the planetary geologist

    NASA Technical Reports Server (NTRS)

    Theilig, E.

    1982-01-01

    Sulfur has been proposed as the dominant composition for the volcanic material on Io. Sulfur is a complex element which forms many intramolecular and intermolecular allotropes exhibiting a variety of physical properties. Cyclo-S8 sulfur is the most abundant and stable molecular form. The important molecular species within liquid sulfur change in concentration with temperature. Concentrations of the allotropes control the physical properties of the melt. Discontinuities in density, viscosity, and thermal properties reflect the polymerization process within liquid sulfur. Variations in the melting point are related to autodissociation of the liquid. Many solids forms of sulfur have been identified but only orthorhombic alpha and monoclinic beta sulfur, both composed of cyclo-S8 sulfur, are stable under terrestrial conditions. Physical properties of solid sulfur are dependent on the allotrope and, in some cases, the thermal history. Three natural terrestrial sulfur flows are described: (1) Siretoko-Iosan, Japan; (2) Volcan Azufre, Galapagos Islands; and (3) Mauna Loa, Hawaii. All of the flows are associated with fumarolic areas and are considered to have formed by the melting and mobilization of sulfur deposits. Surface textures of the flows indicate a behavior of molten sulfur similar to that of silicate lava. Channels, rivulets, and lobate edges were described for the flows. The solidification of man-made sulfur flows formed as part of the Frasch mining process by which sulfur is removed from the subsurface in a liquid state is described.

  2. Sulfur vesicles from Thermococcales: A possible role in sulfur detoxifying mechanisms.

    PubMed

    Gorlas, A; Marguet, E; Gill, S; Geslin, C; Guigner, J-M; Guyot, F; Forterre, P

    2015-11-01

    The euryarchaeon Thermococcus prieurii inhabits deep-sea hydrothermal vents, one of the most extreme environments on Earth, which is reduced and enriched with heavy metals. Transmission electron microscopy and cryo-electron microscopy imaging of T. prieurii revealed the production of a plethora of diverse membrane vesicles (MVs) (from 50 nm to 400 nm), as is the case for other Thermococcales. T. prieurii also produces particularly long nanopods/nanotubes, some of them containing more than 35 vesicles encased in a S-layer coat. Notably, cryo-electron microscopy of T. prieurii cells revealed the presence of numerous intracellular dark vesicles that bud from the host cells via interaction with the cytoplasmic membrane. These dark vesicles are exclusively found in conjunction with T. prieurii cells and never observed in the purified membrane vesicles preparations. Energy-Dispersive-X-Ray analyses revealed that these dark vesicles are filled with sulfur. Furthermore, the presence of these sulfur vesicles (SVs) is exclusively observed when elemental sulfur was added into the growth medium. In this report, we suggest that these atypical vesicles sequester the excess sulfur not used for growth, thus preventing the accumulation of toxic levels of sulfur in the host's cytoplasm. These SVs transport elemental sulfur out of the cell where they are rapidly degraded. Intriguingly, closely related archaeal species, Thermococcus nautili and Thermococcus kodakaraensis, show some differences about the production of sulfur vesicles. Whereas T. kodakaraensis produces less sulfur vesicles than T. prieurii, T. nautili does not produce such sulfur vesicles, suggesting that Thermococcales species exhibit significant differences in their sulfur metabolic pathways.

  3. Self-assembled peptides for coating of active sulfur nanoparticles in lithium-sulfur battery

    NASA Astrophysics Data System (ADS)

    Jewel, Yead; Yoo, Kisoo; Liu, Jin; Dutta, Prashanta

    2016-03-01

    Development of lithium-sulfur (Li-S) battery is hindered by poor cyclability due to the loss of sulfur, although Li-S battery can provide high energy density. Coating of sulfur nanoparticles can help maintain active sulfur in the cathode of Li-S battery, and hence increase the cyclability. Among myriad of coating materials, synthetic peptides are very attractive because of their spontaneous self-assembly as well as electrical conductive characteristics. In this study, we explored the use of various synthetic peptides as a coating material for sulfur nanoparticles. Atomistic simulations were carried out to identify optimal peptide structure and density for coating sulfur nanoparticles. Three different peptide models, poly-proline, poly(leucine-lysine) and poly-histidine, are selected for this study based on their peptide-peptide and peptide-sulfur interactions. Simulation results show that both poly-proline and poly(leucine-lysine) can form self-assembled coating on sulfur nanoparticles (2-20 nm) in pyrrolidinone, a commonly used solvent for cathode slurry. We also studied the structural integrity of these synthetic peptides in organic [dioxolane (DOL) and dimethoxyethane (DME)] electrolyte used in Li-S battery. Both peptides show stable structures in organic electrolyte (DOL/DME) used in Li-S battery. Furthermore, the dissolution of sulfur molecules in organic electrolyte is investigated in the absence and presence of these peptide coatings. It was found that only poly(leucine-lysine)-based peptide can most effectively suppress the sulfur loss in electrolyte, suggesting its potential applications in Li-S battery as a coating material.

  4. Sulfur copolymers for infrared optical imaging

    NASA Astrophysics Data System (ADS)

    Namnabat, S.; Gabriel, J. J.; Pyun, J.; Norwood, R. A.; Dereniak, E. L.; van der Laan, J.

    2014-06-01

    The development of organic polymers with low infrared absorption has been investigated as a possible alternative to inorganic metal oxide, semiconductor, or chalcogenide-based materials for a variety of optical devices and components, such as lenses, goggles, thermal imaging cameras and optical fibers. In principle, organic-based polymers are attractive for these applications because of their low weight, ease of processing, mechanical toughness, and facile chemical variation using commercially available precursors. Herein we report on the optical characterization of a new class of sulfur copolymers that are readily moldable, transparent above 500 nm, possess high refractive index (n > 1.8) and take advantage of the low infrared absorption of S-S bonds for potential use in the mid-infrared at 3-5 microns. These materials are largely made from elemental sulfur by an inverse vulcanization process; in the current study we focus on the properties of a chemically stable, branched copolymer of poly(sulfur-random-1,3-diisopropenylbenzene) (poly(S-r- DIB). Copolymers with elemental sulfur content ranging from 50% to 80% by weight were studied by UV-VIS spectroscopy, FTIR, and prism coupling for refractive index measurement. Clear correlation between material composition and the optical properties was established, confirming that the high polarizability of the sulfur atom leads to high refractive index while also maintaining low optical loss in the infrared.

  5. Methane activation and oxidation in sulfuric acid.

    PubMed

    Goeppert, Alain; Dinér, Peter; Ahlberg, Per; Sommer, Jean

    2002-07-15

    The H/D exchange observed when methane is contacted with D(2)SO(4) at 270-330 degrees C shows that the alkane behaves as a sigma base and undergoes rapid and reversible protonation at this temperature. DFT studies of the hydrogen exchange between a monomer and a dimer of sulfuric acid and methane show that the transition states involved in the exchange are bifunctional, that is one hydrogen atom is transferred from a hydroxy group in sulfuric acid to methane, while one hydrogen atom is abstracted from methane by a non-hydroxy oxygen atom in sulfuric acid. All the transition states include a CH(5) moiety, which shows similarities to the methanium ion CH(5) (+). The calculated potential activation energy of the hydrogen exchange for the monomer is 174 kJ mol(-1), which is close to the experimental value (176 kJ mol(-1)). Solvation of the monomer and the transition state of the monomer with an extra sulfuric acid molecule, decrease the potential activation energy by 6 kJ mol(-1). The acid-base process is in competition, however, with an oxidative process involving methane and sulfuric acid which leads to CO(2), SO(2), and water, and thus to a decrease of acidity and loss of reactivity of the medium.

  6. LIVER INJURY, LIVER PROTECTION, AND SULFUR METABOLISM

    PubMed Central

    Miller, L. L.; Whipple, G. H.

    1942-01-01

    Protein-depleted dogs are very susceptible to injurious agents—in particular, chloroform. Methionine given shortly before chloroform anesthesia will give complete protection against chloroform. Methionine (or cysteine plus choline) given 3 or 4 hours after chloroform anesthesia will give significant protection against the liver injury of chloroform anesthesia. Methionine given more than 4 hours after chloroform anesthesia gives no protection against liver injury. Choline alone given before chloroform gives no protection against liver injury. The protein-depleted dogs have livers which are deficient in both nitrogen and sulfur, but sulfur is depleted more than is the nitrogen. The N/S ratio therefore rises. Methionine or cystine feeding promptly makes up this liver sulfur deficit. Viable liver cells are necessary for this uptake of sulfur. Livers of fetuses in utero or of newborn pups tolerate a chloroform anesthesia which will cause fatal liver injury in adults. The nitrogen and sulfur values of these fetus or pup livers are within the high normal values for adults. Blood-forming cells are present in the fetus or pup livers during this period. When these blood islands are eliminated during the 3rd or 4th week of life, the liver then becomes normally susceptible to chloroform liver injury. Methionine or methionine-rich protein digests (e.g. casein) or various proteins by mouth or by vein should prove useful to protect the liver against certain types of injury and to aid in organ repair. PMID:19871248

  7. Metabolic Reactions among Organic Sulfur Compounds

    NASA Technical Reports Server (NTRS)

    Schulte, M.; Rogers, K.

    2005-01-01

    Sulfur is central to the metabolisms of many organisms that inhabit extreme environments. Numerous authors have addressed the energy available from a variety of inorganic sulfur redox pairs. Less attention has been paid, however, to the energy required or gained from metabolic reactions among organic sulfur compounds. Work in this area has focused on the oxidation of alkyl sulfide or disulfide to thiol and formaldehyde, e.g. (CH3)2S + H2O yields CH3SH + HCHO + H2, eventually resulting in the formation of CO2 and SO4(-2). It is also found that reactions among thiols and disulfides may help control redox disequilibria between the cytoplasm and the periplasm. Building on our earlier efforts for thiols, we have compiled and estimated thermodynamic properties for alkyl sulfides. We are investigating metabolic reactions among various sulfur compounds in a variety of extreme environments, ranging from sea floor hydrothermal systems to organic-rich sludge. Using thermodynamic data and the revised HKF equation of state, along with constraints imposed by the geochemical environments sulfur-metabolizing organisms inhabit, we are able to calculate the amount of energy available to these organisms.

  8. Sulfuric acid in the Venus clouds.

    NASA Technical Reports Server (NTRS)

    Sill, G. T.

    1972-01-01

    The extremely dry nature of the Venus upper atmosphere appears to demand the presence of an efficient desiccating agent as the chief constituent of the clouds of Venus. On the basis of polarization measures it is to be expected that this substance is present as spherical droplets, 1 to 2 microns in diameter, with a refractive index n of 1.46 plus or minus 0.02 at 3500A in the observed region of the atmosphere, with T about equal to 235 K. This substance must have ultraviolet, visible, and infrared reflection properties not inconsistent with the observed spectrum of Venus. Sulfuric acid, of about 86% by weight composition, roughly fulfills the first of these properties. The visible and ultraviolet transmission features of a thin layer of elemental bromine and hydrobromic acid dissolved in sulfuric acid somewhat resemble the Venus spectrum, up to 14 microns. The chemical process postulated for forming sulfuric acid involves the oxidation of sulfur and its compounds to sulfuric acid through the agency of elemental bromine produced by the photolytic decomposition of hydrogen bromide.

  9. Development of enhanced sulfur rejection processes

    SciTech Connect

    Yoon, R.H.; Luttrell, G.; Adel, G.; Richardson, P.E.

    1993-03-23

    Research at Virginia Tech led to two complementary concepts for improving the removal of inorganic sulfur from much of the Eastern US coals. One controls the surface properties of coal pyrite (FeS[sub 2]) by electrochemical-.potential control, referred to as the Electrochemically Enhanced Sulfur Rejection (EESR) Process: The second controls the flotation of middlings, i.e., particles composed of pyrite with coal inclusions by using polymeric reagents to react with pyrite and convert the middlings to hydrophilic particles, and is termed the Polymer Enhanced Sulfur Rejection (PESR) Process. These new concepts are based on recent research establishing the two main reasons why flotation fails to remove more than about 50% of the pyritic sulfur from coal: superficial oxidization of liberated pyrite to form polysulfide oxidation products so that a part of the liberated pyrite floats with the coal; and hydrophobic coal inclusions in the middlings dominating their flotation so that the middlings also float with the coal. These new pyritic-sulfur rejection processes do not require significant modifications of existing coal preparation facilities, enhancing their adoptability by the coal industry. It is believed that they can be used simultaneously to achieve both free pyrite and locked pyrite rejection.

  10. Sulfur 'Concrete' for Lunar Applications - Environmental Considerations

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.

    2008-01-01

    Commercial use of sulfur concrete on Earth is well established, particularly in corrosive, e.g., acid and salt, environments. Having found troilite (FeS) on the Moon raises the question of using extracted sulfur as a lunar construction material, an attractive alternative to conventional concrete as it does not require water. For the purpose of this Technical Memorandum, it is assumed that lunar ore is mined, refined, and the raw sulfur processed with appropriate lunar regolith to form, for example, bricks. With this stipulation, it is then noted that the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. The work presented here evaluates two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar simulant as an aggregate addition. One set was subjected to extended periods in high vacuum to evaluate sublimation issues, and the other was cycled between room and liquid nitrogen temperatures to investigate their subsequent mechanical integrity. Results are presented from both investigations, discussed, and put into the context of the lunar environment.

  11. Emissions of sulfur gases from wetlands

    NASA Technical Reports Server (NTRS)

    Hines, Mark E.

    1992-01-01

    Data on the emissions of sulfur gases from marine and freshwater wetlands are summarized with respect to wetland vegetation type and possible formation mechanisms. The current data base is largest for salt marshes inhabited by Spartina alterniflora. Both dimethyl sulfide (DMS) and hydrogen sulfide (H2S) dominate emissions from salt marshes, with lesser quantities of methyl mercaptan (MeSH), carbonyl sulfide (COS), carbon disulfide (CS2) and dimethyl disulfide (DMDS) being emitted. High emission rates of DMS are associated with vegetation that produces the DMS precursor dimethylsulfonionpropionate (DMSP). Although large quantities of H2S are produced in marshes, only a small percentage escapes to the atmosphere. High latitude marshes emit less sulfur gases than temperate ones, but DMS still dominates. Mangrove-inhabited wetlands also emit less sulfur than temperate S. alterniflora marshes. Few data are available on sulfur gas emissions from freshwater wetlands. In most instances, sulfur emissions from temperate freshwater sites are low. However, some temperate and subtropical freshwater sites are similar in magnitude to those from marine wetlands which do not contain vegetation that produces DMSP. Emissions are low in Alaskan tundra but may be considerably higher in some bogs and fens.

  12. Rapid sulfur capture studies at high temperatures

    SciTech Connect

    Richards, G.A.; Lawson, W.F.; Maloney, D.J.; Shaw, D.W.

    1990-12-01

    Determine conditions that would reproduce optimum sulfur capture ( super-equilibrium'') behavior. No attempt was made to extract kinetic data for calcination or sulfur capture, as might be done in a comprehensive study of sorbent behavior. While some interesting anomalies are present in the calcination data and in the limited surface area data, no attempt was made to pursue those issues. Since little sulfur capture was observed at operating conditions where super-equilibrium'' might be expected to occur, tests were stopped when the wide range of parameters that were studied failed to produce significant sulfur capture via the super-equilibrium mechanism. Considerable space in this report is devoted to a description of the experiment, including details of the GTRC construction. This description is included because we have received requests for a detailed description of the GTRC itself, as well as the pressurized dry powder feed system. In addition, many questions about accurately sampling the sulfur species from a high-temperature, high-pressure reactor were raised during the course of this investigation. A full account of the development of the gas and particulate sampling train in thus provided. 8 refs., 17 figs., 2 tabs.

  13. Effect of pH on sealing ability of white mineral trioxide aggregate as a root-end filling material.

    PubMed

    Saghiri, Mohammad Ali; Lotfi, Mehrdad; Saghiri, Ali Mohammad; Vosoughhosseini, Sepideh; Fatemi, Ali; Shiezadeh, Vahab; Ranjkesh, Bahram

    2008-10-01

    The aim of the present study was to evaluate microleakage of mineral trioxide aggregate (MTA) used as a root-end filling material after its exposure to a range of acidic environments during hydration. Seventy single-rooted teeth were divided into 4 experimental and 2 control groups. All the teeth were instrumented, and their apices were resected. Root-end cavities were filled with white MTA in the experimental groups. In the control groups root-end cavities were not filled. Root-end fillings were exposed to acidic environments with pH values of 4.4, 5.4, 6.4, or 7.4 for 3 days in the experimental groups. Microleakage was evaluated by using bovine serum albumin. The evaluation was conducted at 24-hour intervals for 80 days. Data were analyzed by using one-way analysis of variance and a post hoc Tukey test. The earliest bovine serum albumin microleakage was observed in a pH value of 4.4 followed by pH values of 5.4, 6.4, and 7.4, respectively. There was a significantly longer time necessary for leakage to occur in samples stored in higher pH values (P < .000).

  14. Clinical and radiographical evaluation of mineral trioxide aggregate, biodentine and propolis as pulpotomy medicaments in primary teeth

    PubMed Central

    Rakesh, Kumar; Richa, Khanna

    2015-01-01

    Objectives The purpose of this study was to evaluate the efficacy of mineral trioxide aggregate (MTA), Biodentine and Propolis as pulpotomy medicaments in primary dentition, both clinically and radiographically. Materials and Methods A total of 75 healthy 3 to 10 yr old children each having at least one carious primary molar tooth were selected. Random assignment of the pulpotomy medicaments was done as follows: Group I, MTA; Group II, Biodentine; Group III, Propolis. All the pulpotomized teeth were evaluated at 3, 6, and 9 mon clinically and radiographically, based on the scoring criteria system. Results The clinical success rates were found to be similar among the three groups at 3 and 6 mon where as a significant decrease in success rate was observed in Group III (84%) compared to both Group I (100%) and Group II (100%) at 9 mon. Radiographic success rates over a period of 9 mon in Groups I, II, and III were 92, 80, and 72%, respectively. Conclusions Teeth treated with MTA and Biodentine showed more favorable clinical and radiographic success as compared to Propolis at 9 mon follow-up. PMID:26587413

  15. Microbial degradation of high impact polystyrene (HIPS), an e-plastic with decabromodiphenyl oxide and antimony trioxide.

    PubMed

    Sekhar, Vini C; Nampoothiri, K Madhavan; Mohan, Arya J; Nair, Nimisha R; Bhaskar, Thallada; Pandey, Ashok

    2016-11-15

    Accumulation of electronic waste has increased catastrophically and out of that various plastic resins constitute one of the leading thrown out materials in the electronic machinery. Enrichment medium, containing high impact polystyrene (HIPS) with decabromodiphenyl oxide and antimony trioxide as sole carbon source, was used to isolate microbial cultures. The viability of these cultures in the e-plastic containing mineral medium was further confirmed by triphenyl tetrazolium chloride (TTC) reduction test. Four cultures were identified by 16S rRNA sequencing as Enterobacter sp., Citrobacter sedlakii, Alcaligenes sp. and Brevundimonas diminuta. Biodegradation experiments were carried out in flask level and gelatin supplementation (0.1% w/v) along with HIPS had increased the degradation rate to a maximum of 12.4% (w/w) within 30days. This is the first report for this kind of material. The comparison of FTIR, NMR, and TGA analysis of original and degraded e-plastic films revealed structural changes under microbial treatment. Polystyrene degradation intermediates in the culture supernatant were also detected using HPLC analysis. The gravity of biodegradation was validated by morphological changes under scanning electron microscope. All isolates displayed depolymerase activity to substantiate enzymatic degradation of e-plastic.

  16. The Coadministration of N-Acetylcysteine Ameliorates the Effects of Arsenic Trioxide on the Male Mouse Genital System

    PubMed Central

    da Silva, Raquel Frenedoso; Borges, Cibele dos Santos; Villela e Silva, Patrícia; Kiguti, Luiz Ricardo Almeida; Pupo, André Sampaio; Barbosa Junior, Fernando; Anselmo-Franci, Janete Aparecida; Kempinas, Wilma De Grava

    2016-01-01

    Arsenic trioxide (As2O3) has shown effectiveness in treatment of leukemia but is also associated with reproductive toxicity. Since remediation with N-acetylcysteine (NAC) may mitigate the adverse effects caused by exposure, we assessed the effects of As2O3 and its potential reversibility after exposure cessation or coadministration of NAC. Animals received 0.3 or 3.0 mg/Kg/day of As2O3 subcutaneously and 40 mM of NAC in tap water. As2O3 treatment impaired spermatogenesis and sperm motility and decreased seminal vesicle weight and testosterone serum levels; after suspension of treatment, these parameters remained altered. When NAC was administered, animals showed improvement in sperm parameters and seminal vesicle weight. In vitro epididymal contractility was increased in As2O3-treated animals. We concluded that As2O3 is toxic to the male mouse genital system by compromising sperm quality and quantity; these effects persisted even after suspension of the treatment. However, the coadministration of NAC ameliorates the harmful effects of the drug on the male genital system. PMID:26839632

  17. Partial Pulpotomy of Immature Teeth with Apical Periodontitis using Bioceramics and Mineral Trioxide Aggregate: A Report of Three Cases.

    PubMed

    Jiang, Shan; Wu, Hao; Zhang, Cheng Fei

    2016-06-01

    Pulpal necrosis of an immature permanent tooth with an open apex poses a challenge for the clinician. The conventional apexification technique using calcium hydroxide has yielded short-term success, but this technique has inevitable shortcomings. Hence, this case series aimed to evaluate the effectiveness of using bioceramics (iRoot BP) or mineral trioxide aggregate (MTA) for partial pulpotomies. Three boys aged 9 to 11 years old presented with partial pulp necrosis and symptomatic apical periodontitis of the mandibular right and left second premolar. The involved teeth were treated with a partial pulpotomy using either iRoot BP (case 1 and 2) or MTA (case 3). At the 8-month follow-up, no abnormal clinical signs or symptoms were observed. Periapical radiographs revealed a significant reduction in periapical radiolucency, a marked increase in the root canal wall thickness and ongoing closure of the apical opening. The bioceramic material (iRoot BP) and MTA both produced successful outcomes in the partial pulpotomy of immature teeth with partial pulp necrosis and apical periodontitis. However, iRoot BP was superior in terms of ease of clinical application, and would therefore be a better treatment alternative than MTA.

  18. Histological evaluation of mineral trioxide aggregate and enamel matrix derivative combination in direct pulp capping: An in vivo study

    PubMed Central

    Bollu, Indira Priyadarshini; Velagula, L. Deepa; Bolla, Nagesh; Kumar, K. Kiran; Hari, Archana; Thumu, Jayaprakash

    2016-01-01

    Aim: The aim of this study is to evaluate the response of human pulp tissue to mineral trioxide aggregate (MTA), Emdogain (EMD), and combination of MTA/EMD. Materials and Methods: This study was performed on sixty intact first and second premolars of human maxillary and mandibular teeth. A standard pulpal exposure was done on all the teeth and was divided into three groups of twenty teeth each and was capped with MTA, EMD, and MTA/EMD combination. The final restoration was done with resin-modified glass ionomer cement. The teeth were then extracted on the 15th or 45th day and histological evaluation done. Results: Differences in inflammatory response and thickness of dentin bridge formation of the exposed pulp to the three different groups were statistically evaluated using Chi-square and Mann–Whitney tests and were found to be significant. No significant difference was found between MTA/EMD and MTA in terms of calcified bridge formation and pulp inflammatory response to the capping materials. Conclusions: MTA and MTA/EMD combination produced a better quality hard tissue response compared with the use of EMD. PMID:27994315

  19. Comparison of the sealing ability of mineral trioxide aggregate and Portland cement used as root-end filling materials.

    PubMed

    Shahi, Shahriar; Yavari, Hamid R; Rahimi, Saeed; Eskandarinezhad, Mahsa; Shakouei, Sahar; Unchi, Mahsa

    2011-12-01

    Inadequate apical seal is the major cause of surgical endodontic failure. The root-end filling material used should prevent egress of potential contaminants into periapical tissue. The purpose of this study was to compare the sealing ability of four root-end filling materials: white mineral trioxide aggregate (MTA), gray MTA, white Portland cement (PC) and gray PC by dye leakage test. Ninety-six human single-rooted teeth were instrumented, and obturated with gutta-percha. After resecting the apex, an apical cavity was prepared. The teeth were randomly divided into four experimental groups (A: white MTA, B: gray MTA, C: white PC and D: gray PC; n = 20) and two control groups (positive and negative control groups; n = 8). Root-end cavities in the experimental groups were filled with the experimental materials. The teeth were exposed to Indian ink for 72 hours. The extent of dye penetration was measured with a stereomicroscope at 16× magnification. The negative controls showed no dye penetration and dye penetration was seen in the entire root-end cavity of positive controls. However, there was no statistically significant difference among the four experimental groups (P > 0.05). All retrograde filling materials tested in this study showed the same microleakage in vitro. Given the low cost and apparently similar sealing ability of PC, PC could be considered as a substitute for MTA as a root-end filling material.

  20. Bacterial Leakage of Mineral Trioxide Aggregate, Calcium-Enriched Mixture and Biodentine as Furcation Perforation Repair Materials in Primary Molars

    PubMed Central

    Ramazani, Nahid; Sadeghi, Parisa

    2016-01-01

    Introduction: Adequate seal of iatrogenically perforated area within the root canal system can improve the long term treatment prognosis. This in vitro study evaluated the sealing ability of mineral trioxide aggregate (MTA), calcium-enriched mixture (CEM) cement and Biodentine in repair of furcation perforation in primary molars. Methods and Materials: A total of 61 freshly extracted primary mandibular second molars were randomly divided into three groups (n=17) and 10 teeth were put in negative (without perforation, n=5) and positive (perforated without repair, n=5) control groups. Turbidity was used as the criteria of bacterial leakage, when detected in the model of dual-chamber leakage. Data were analyzed using the Chi-Square and Kaplan-Meier survival analysis in SPSS software. The level of significance was set at 0.05. Results: All positive samples showed turbidity, whereas none of the negative samples allowed bacterial leakage. There was no significant difference between the number of turbidity samples in repaired teeth with all test materials (P=0.13). No significant difference was also detected in the mean survival time (P>0.05). Conclusion: CEM cement and Biodentine showed promising results as perforation repair materials and can be recommended as suitable alternatives of MTA for repair of furcation perforation of primary molars. PMID:27471534

  1. Melatonin enhances arsenic trioxide-induced cell death via sustained upregulation of Redd1 expression in breast cancer cells.

    PubMed

    Yun, Sun-Mi; Woo, Sang Hyeok; Oh, Sang Taek; Hong, Sung-Eun; Choe, Tae-Boo; Ye, Sang-Kyu; Kim, Eun-Kyu; Seong, Min Ki; Kim, Hyun-A; Noh, Woo Chul; Lee, Jin Kyung; Jin, Hyeon-Ok; Lee, Yun-Han; Park, In-Chul

    2016-02-15

    Melatonin is implicated in various physiological functions, including anticancer activity. However, the mechanism(s) of its anticancer activity is not well understood. In the present study, we investigated the combined effects of melatonin and arsenic trioxide (ATO) on cell death in human breast cancer cells. Melatonin enhanced the ATO-induced apoptotic cell death via changes in the protein levels of Survivin, Bcl-2, and Bax, thus affecting cytochrome c release from the mitochondria to the cytosol. Interestingly, we found that the cell death induced by co-treatment with melatonin and ATO was mediated by sustained upregulation of Redd1, which was associated with increased production of reactive oxygen species (ROS). Combined treatment with melatonin and ATO induced the phosphorylation of JNK and p38 MAP kinase downstream from Redd1 expression. Rapamycin and S6K1 siRNA enhanced, while activation of mTORC1 by transfection with TSC2 siRNA suppressed the cell death induced by melatonin and ATO treatment. Taken together, our findings suggest that melatonin enhances ATO-induced apoptotic cell death via sustained upregulation of Redd1 expression and inhibition of mTORC1 upstream of the activation of the p38/JNK pathways in human breast cancer cells.

  2. Comparing Gray and White Mineral Trioxide Aggregate as a Repair Material for Furcation Perforation: An in Vitro Dye Extraction Study

    PubMed Central

    Patel, Kiran; Baba, Suheel Manzoor; Jaiswal, Shikha; Venkataraghavan, Karthik; Jani, Mehul

    2014-01-01

    Introduction: Furcation perforation can have a negative impact on the prognosis of the affected tooth by compromising the attached apparatus. Hence these perforations require immediate repair. A variety of materials have been suggested for repair, of that MTA is the most promising material. The purpose of this study was to compare the ability of Gray and White MTA to seal furcation perforations using a dye extraction method under spectrophotometer. Materials and Methods: A total of 60 permanent mandibular molars were randomly divided into four experimental groups of 15 samples each as follows: Group A: Perforation repaired with White MTA. Group B: Perforation repaired with Gray MTA. Group C: Perforation left unsealed (positive). Group D: without perforation (negative). Dye extraction was performed using full concentration nitric acid. Dye absorbance was measured at 550 nm using spectrophotometer. The data analyzed using one-way-Anova Ratio and Unpaired t-test showing statistically significance difference among the groups. Result: It was seen that Group D samples without perforation showed least absorbance followed by Group A (perforation repaired with White MTA) and Group B (perforation repaired with Gray MTA). Group C (perforation left unsealed) showed highest absorbance. Conclusion: The White and Gray Mineral Trioxide Aggregate performed similarly as a furcation perforation repair material. There was no significant difference between the Gray MTA and White MTA. PMID:25478452

  3. Sealing efficacy of mineral trioxide aggregate with and without nanosilver for root end filling: An in vitro bacterial leakage study

    PubMed Central

    Eskandarinezhad, Mahsa; Sharghi, Reza; Shirazi, Sajjad; Shakouie, Sahar; Milani, Amin-Salem; Balaei, Esrafil

    2017-01-01

    Background Various materials have been added to mineral trioxide aggregate to enhance its properties. This study was aimed to compare the sealing efficacy of MTA with and without nanosilver using bacterial leakage approach. Material and Methods Seventy canine teeth were prepared and obturated. Then, after apical resection, the root-end cavities were prepared by ultrasonic retrotips. Teeth were randomly divided into 4 groups containing two experimental groups (n=30) and two negative and positive controls (n=5). In group 1 and 2, root-end cavities were respectively filled with MTA and MTA with nanosilver (by 1% weight). Leakage assessment was carried out by bacterial leakage apparatus with Enterococcus faecalis species. Leakage comparison between experimental groups was done using Mann-Whitney test by Spss 16 software at significancy level of 0.05. Results The median bacterial leakages for MTA and MTA with nanosilver were 19 and 2, respectively. The mean bacterial leakages for MTA and MTA with nanosilver were 30.06±28.67 and 9.66±14.25, respectively. Mann-Whitney test indicated that there was a significant difference in bacterial leakage day between two experimental groups (P=0.002). Conclusions Based on the findings of this in-vitro bacterial leakage study, adding nanosilver to MTA decreased its sealing ability. Key words:Root canal therapy, root canal obturation, root canal filling materials, nanosilver, MTA. PMID:28149459

  4. Evaluation of pulpal response of deciduous teeth after direct pulp capping with bioactive glass and mineral trioxide aggregate

    PubMed Central

    Haghgoo, Roza; Ahmadvand, Motahare

    2016-01-01

    Aim: The aim of this study was to evaluate the pulpal response of primary teeth after direct pulp capping (DPC) with two biocompatible materials namely mineral trioxide aggregate (MTA) and bioactive glass (BAG). Settings and Design: This study was a randomized clinical trial. Materials and Methods: A total of 22 healthy primary canine teeth scheduled for extraction for orthodontic reasons were selected. The teeth were divided into two groups of 11 and underwent DPC. The exposure sites were randomly capped with MTA or BAG in the two groups. After 2 months, the teeth were extracted and prepared for histopathologic evaluation. Statistical Analysis: The data were analyzed using Fisher's exact test. Results: In the BAG group, inflammation was seen in three patients; internal resorption and abscess were not seen at all. In the MTA group, inflammation was seen in one patient and internal resorption and abscess were not seen in any patient. Fisher's exact test showed no significant difference between the two groups (P > 0.05). Dentinal bridge formation was noted in five patients in the BAG group and six patients in the MTA group. No significant difference was observed between the BAG and MTA groups using Chi-square analysis (P = 0.67). Conclusion: Based on the results of this study, MTA and BAG can be used for DPC of primary teeth. PMID:27630497

  5. Contamination of tooth-colored mineral trioxide aggregate used as a root-end filling material: a bacterial leakage study.

    PubMed

    Montellano, Angela M; Schwartz, Scott A; Beeson, Thomas J

    2006-05-01

    This experiment investigated the ability of tooth-colored mineral trioxide aggregate (MTA) to maintain an apical seal in the presence of bacteria when contaminated with blood, saline or saliva. Ninety extracted human teeth with single canals were randomly placed into six groups of 15. Canals were prepared to size 50. The apical 3 mm of each root was removed and 3 mm root-end preparations were made with a #329 bur. Root-end preparations in groups 1 through 3 were filled with MTA after contamination with blood, saline, or saliva, respectively. In group 4, uncontaminated root-end preparations were filled with MTA. Groups 5 and 6 served as negative and positive controls. A tube/tooth assembly was utilized to suspend each root end in Trypticase Soy Broth (TSB). The access chambers were filled with Staphylococcus epidermidis. Positive growth over thirty days was demonstrated by turbidity of the TSB. Vitek analysis was used to confirm the presence of S. epidermidis in the positive samples. Data evaluation consisted of a chi(2) analysis (p < 0.05). Although all experimental groups demonstrated leakage, tooth-colored MTA contaminated with saliva (group 3) leaked significantly more than the uncontaminated tooth-colored MTA (group 4) (p = 0.028).

  6. Sealing properties of mineral trioxide aggregate orthograde apical plugs and root fillings in an in vitro apexification model.

    PubMed

    Martin, Rebecca L; Monticelli, Francesca; Brackett, William W; Loushine, Robert J; Rockman, Roy A; Ferrari, Marco; Pashley, David H; Tay, Franklin R

    2007-03-01

    One-visit mineral trioxide aggregate (MTA) apexification is gaining in popularity over the use of calcium hydroxide barriers. This study examined the sealing properties of two MTA apexification procedures using an in vitro apexification model. White MTA was introduced into instrumented single-rooted canals with standardized artificially created open apices to form 3- to 5-mm-thick orthograde apical plugs or complete orthograde fillings of the root segments. The remaining canal spaces in the former group were backfilled with thermoplasticized gutta-percha without a sealer. A Flodec fluid filtration device was used to record fluid flow across filled root canals at 48 hours and after 4 weeks of immersion in phosphate-buffered saline (PBS). Although MTA root fillings exhibited a better seal than MTA apical plugs at 48 hours, seals of these two groups were not significantly different after 4 weeks. Interaction of MTA with PBS may result in apatite deposition that improves the seal of MTA apical plugs with time.

  7. The Effect of Mineral Trioxide Aggregate Mixed with Chlorhexidine as Direct Pulp Capping Agent in Dogs Teeth: A Histologic Study

    PubMed Central

    Manochehrifar, Hamed; Parirokh, Masoud; Kakooei, Sina; Oloomi, Mohammad Mehdi; Asgary, Saeed; Eghbal, Mohammad Jafar; Mashhadi Abbas, Fatemeh

    2016-01-01

    Introduction: The aim of the present investigation was to compare the efficacy of mineral trioxide aggregate (MTA) and 0.2% chlorhexidine (CHX) mixture to pure MTA, as a pulp capping material. Methods and Materials: The pulp of 24 lateral incisors and canines from four dogs were exposed and capped either with MTA or MTA+0.2% CHX. After 2 months the animals were sacrificed and the teeth were prepared for histological evaluation in terms of calcified bridge formation, the degree of inflammation and presence of necrosis. The Fisher’s exact test was used for data analysis. Results: The results showed that formation of complete calcified bridge in MTA specimens was significantly more than MTA+CHX (P<0.05). No significant difference was found in the degree of inflammation and necrosis between MTA and MTA+CHX groups (P>0.05). Conclusion: Mixing MTA with CHX as pulp capping agent had a significant negative impact on formation of calcified bridge on directly capped dog’s teeth. PMID:27790263

  8. Reparative Dentinogenesis Induced by Mineral Trioxide Aggregate: A Review from the Biological and Physicochemical Points of View

    PubMed Central

    Okiji, Takashi; Yoshiba, Kunihiko

    2009-01-01

    This paper aims to review the biological and physicochemical properties of mineral trioxide aggregate (MTA) with respect to its ability to induce reparative dentinogenesis, which involves complex cellular and molecular events leading to hard-tissue repair by newly differentiated odontoblast-like cells. Compared with that of calcium hydroxide-based materials, MTA is more efficient at inducing reparative dentinogenesis in vivo. The available literature suggests that the action of MTA is attributable to the natural wound healing process of exposed pulps, although MTA can stimulate hard-tissue-forming cells to induce matrix formation and mineralization in vitro. Physicochemical analyses have revealed that MTA not only acts as a “calcium hydroxide-releasing” material, but also interacts with phosphate-containing fluids to form apatite precipitates. MTA also shows better sealing ability and structural stability, but less potent antimicrobial activity compared with that of calcium hydroxide. The clinical outcome of direct pulp capping and pulpotomy with MTA appears quite favorable, although the number of controled prospective studies is still limited. Attempts are being conducted to improve the properties of MTA by the addition of setting accelerators and the development of new calcium silicate-based materials. PMID:20339574

  9. Arsenic trioxide regulates adipogenic and osteogenic differentiation in bone marrow MSCs of aplastic anemia patients through BMP4 gene.

    PubMed

    Cheng, Huan Chen; Liu, Sheng Wei; Li, Wei; Zhao, Xue Fei; Zhao, Xu; Cheng, Mei; Qiu, Lin; Ma, Jun

    2015-09-01

    The typical pathological feature of aplastic anemia (AA) is the rise in the number of fat cells and the reduction of osteoblasts in bone marrow. However, both fat cells and osteobalsts in bone marrow are derived from the mesenchymal stem cells (MSCs). Generally, the adipogenic and osteogenic differentiation is a dynamic and balanceable process. The imbalance of the adipogenic and osteogenic differentiation may participate in the occurrence and progress of many diseases. Arsenic trioxide (ATO) could induce differentiation and apoptosis in tumor cells. In this study, Oil Red-O and Alizarin red were used to detect the adipogenic and osteogenic differentiation. The ability of adipogenic differentiation is much higher, whereas the osteogenic differentiation is much lower in the MSCs of AA patients compared with healthy controls. ATO inhibits adipogenic differentiation and promotes osteogenic differentiation in the MSC of AA patients. The expression of BMP4 is increased with ATO treatment. The ability of adipogenic differentiation is decreased, whereas the osteogenic differentiation is increased after transfection of BMP4 gene into the MSCs of AA patients. This study shows that ATO regulates the adipogenic and osteogenic differentiation balance of MSCs in AA, which provides a theoretical basis for the adjunctive therapy of ATO on AA. The BMP4 gene is involved in the ATO regulation of adipogenic and osteogenic differentiation balance, which provides a new target for the treatment of AA.

  10. Rationale and efficacy of proteasome inhibitor combined with arsenic trioxide in the treatment of acute promyelocytic leukemia

    PubMed Central

    Ganesan, S; Alex, A A; Chendamarai, E; Balasundaram, N; Palani, H K; David, S; Kulkarni, U; Aiyaz, M; Mugasimangalam, R; Korula, A; Abraham, A; Srivastava, A; Padua, R A; Chomienne, C; George, B; Balasubramanian, P; Mathews, V

    2016-01-01

    Arsenic trioxide (ATO) mediates PML-RARA (promyelocytic leukemia–retinoic acid receptor-α) oncoprotein degradation via the proteasome pathway and this degradation appears to be critical for achieving cure in acute promyeloytic leukemia (APL). We have previously demonstrated significant micro-environment-mediated drug resistance (EMDR) to ATO in APL. Here we demonstrate that this EMDR could be effectively overcome by combining a proteasome inhibitor (bortezomib) with ATO. A synergistic effect on combining these two agents in vitro was noted in both ATO-sensitive and ATO-resistant APL cell lines. The mechanism of this synergy involved downregulation of the nuclear factor-κB pathway, increase in unfolded protein response (UPR) and an increase in reactive oxygen species generation in the malignant cell. We also noted that PML-RARA oncoprotein is effectively cleared with this combination in spite of proteasome inhibition by bortezomib, and that this clearance is mediated through a p62-dependent autophagy pathway. We further demonstrated that proteasome inhibition along with ATO had an additive effect in inducing autophagy. The beneficial effect of this combination was further validated in an animal model and in an on-going clinical trial. This study raises the potential of a non-myelotoxic proteasome inhibitor replacing anthracyclines in the management of high-risk and relapsed APL. PMID:27560113

  11. Comparative investigation of clinical/radiographical signs of mineral trioxide aggregate and formocresol on pulpotomized primary molars.

    PubMed

    Hugar, Shivayogi M; Deshpande, Shobha D

    2010-07-01

    The objectives of this study were (1) to evaluate clinically and radiographically the effects of mineral trioxide aggregate (MTA) as a pulp dressing after coronal pulp amputation (pulpotomy) in primary molars, (2) to compare the effects of MTA and formocresol in pulpotomized primary teeth. Sixty primary mandibular molars of thirty healthy children aged between 5-8 years were treated by conventional pulpotomy technique. The teeth on the right side are assigned to MTA (Group A) and the left side for the Formocresol (Group B). The children were examined clinically and radiographically every 6 months over a period of 36 months. Results of present study revealed that both MTA and Formocresol has the same effect on the first as well as second primary molars, with chi-square value being 1.1483 (P ≥ 0.05). None of the teeth in either group showed any clinical pathology, showing 100% success rate but radiographically formocresol group showed one case of internal resorption that was regarded as failure in the present study. MTA seems to be more promising predictable with positive response in vital pulp therapy in future than formocresol pulpotomy except for the cost factor.

  12. Evaluation of setting properties and retention characteristics of mineral trioxide aggregate when used as a furcation perforation repair material.

    PubMed

    Sluyk, S R; Moon, P C; Hartwell, G R

    1998-11-01

    Furcation perforations were created in 32 extracted maxillary and mandibular molars. The perforations were prepared in the center of the pulp chamber floor parallel to the long axis of each tooth and a saline-moistened Gelfoam matrix was placed below the perforation to simulate a clinical condition. The teeth were randomly divided into four groups, and the perforations were all repaired with mineral trioxide aggregate (MTA) and then covered with either a wet or dry cotton pellet for 24 or 72 h. Instron testing was used to measure the force required to displace the material from the perforation. The force measurements showed that MTA resisted displacement at 72 h to a significantly greater level than at 24 h (p < 0.05). When slight displacement occurred at 24 h the material demonstrated the ability to re-establish resistance to dislodgement from the dentin wall. The presence of some moisture in the perforation during placement was advantageous in aiding adaptation of MTA to the walls of the perforation, but there was no significant difference in MTA retention when a wet or dry cotton pellet was placed in the pulp chamber during the setting time (p > 0.05).

  13. Root reconstructed with mineral trioxide aggregate and guided tissue regeneration in apical surgery: a 5-year follow-up.

    PubMed

    Bernabé, Pedro Felício Estrada; Azuma, Mariane Maffei; Ferreira, Luciana Louzada; Dezan-Júnior, Eloi; Gomes-Filho, João Eduardo; Cintra, Luciano Tavares Angelo

    2013-01-01

    Apical surgery should be considered as the last treatment option and employed when conventional endodontic treatment does not provide the expected result. In teeth undergoing apical surgery, the type of retrograde filling material is one of the factors interfering with the repair of periapical tissues. The material in intimate contact with the periapical tissues plays a fundamental role in the repair process. Several materials have been studied and indicated for use in apical surgery procedures, but the mineral trioxide aggregate (MTA) is still the most frequently used one. Guided tissue regeneration (GTR) techniques have been proposed as an adjunct to apical surgery to enhance bone healing. Here is reported a clinical case in which apical surgery was performed in conjunction with MTA-based root reconstruction of the maxillary right second incisor. After the apical surgery, a root-end cavity was prepared at the vestibular face of the involved tooth and filled with MTA. A bovine bone graft and a cortical collagen membrane were placed on the bone defect. After 5 years, clinical and radiographic assessments showed that the treatment was successful. It may be concluded that MTA presents favorable characteristics in adverse conditions and can be used in conjunction with GTR in cases involving root reconstruction.

  14. Salvianolic Acid B Prevents Arsenic Trioxide-Induced Cardiotoxicity In Vivo and Enhances Its Anticancer Activity In Vitro

    PubMed Central

    Wang, Min; Sun, Guibo; Wu, Ping; Chen, Rongchang; Yao, Fan; Qin, Meng; Luo, Yun; Sun, Hong; Zhang, Qiang; Dong, Xi; Sun, Xiaobo

    2013-01-01

    Clinical attempts to reduce the cardiotoxicity of arsenic trioxide (ATO) without compromising its anticancer activities remain to be an unresolved issue. In this study, we determined whether Sal B can protect against ATO-induced cardiac toxicity in vivo and increase the toxicity of ATO toward cancer cells. Combination treatment of Sal B and ATO was investigated using BALB/c mice and human hepatoma (HepG2) cells and human cervical cancer (HeLa) cells. The results showed that the combination treatment significantly improved the ATO-induced loss of cardiac function, attenuated damage of cardiomyocytic structure, and suppressed the ATO-induced release of cardiac enzymes into serum in BALB/c mouse models. The expression levels of Bcl-2 and p-Akt in the mice treated with ATO alone were reduced, whereas those in the mice given the combination treatment were similar to those in the control mice. Moreover, the combination treatment significantly enhanced the ATO-induced cytotoxicity and apoptosis of HepG2 cells and HeLa cells. Increases in apoptotic marker cleaved poly (ADP-ribose) polymerase and decreases in procaspase-3 expressions were observed through western blot. Taken together, these observations indicate that the combination treatment of Sal B and ATO is potentially applicable for treating cancer with reduced cardiotoxic side effects. PMID:23662152

  15. Comparative evaluation of antimicrobial activity of three cements: new endodontic cement (NEC), mineral trioxide aggregate (MTA) and Portland.

    PubMed

    Hasan Zarrabi, Mohammad; Javidi, Maryam; Naderinasab, Mahboube; Gharechahi, Maryam

    2009-09-01

    Using the agar diffusion method, we conducted an in vitro study to evaluate the antimicrobial activity of mineral trioxide aggregate (MTA), new endodontic cement (NEC) and Portland cement at different concentrations against five different microorganisms. A base layer was made using Muller-Hinton agar for Escherichia coli (ATCC 10538) and Candida (ATCC 10231). For Actinomyces viscosus (ATCC 15987), Enterococcus faecalis (ATCC 10541) and Streptococcus mutans (ATCC 25175) blood agar medium was used. Wells were formed by removing the agar, and the materials were placed in the well immediately after manipulation. The plates were kept at room temperature for 2 h for prediffusion, and then incubated at 37 degrees C for 72 h. The inhibition zones were then measured. The data were analyzed using ANOVA and the Tukey test to compare the differences among the three cements at different concentrations. The positive controls showed bacterial growth, while the negative controls showed no bacterial growth. All materials showed antimicrobial activity against the tested strains except for Enterococcus faecalis. NEC created larger inhibition zones than MTA and Portland cement. This difference was significant for Portland cement (P < 0.05), but not for MTA (P > 0.05). Among the examined microorganisms, the largest inhibition zone was observed for Actinomyces group (P < 0.05). The antimicrobial activity of the materials increased with time and concentration (P < 0.05). It was concluded that NEC is a potent inhibitor of microorganism growth.

  16. Arsenic trioxide enhances the cytotoxic effect of cisplatin in head and neck squamous cell carcinoma cell lines

    PubMed Central

    KOTOWSKI, ULANA; HEIDUSCHKA, GREGOR; BRUNNER, MARKUS; EROVIC, BOBAN M.; MARTINEK, HELGA; THURNHER, DIETMAR

    2012-01-01

    Arsenic trioxide (ATO) has been approved for the treatment of relapsed acute promyelocytic leukaemia. The aim of this study was to determine whether ATO would lead to cell death in head and neck squamous cell carcinoma (HNSCC) cell lines and whether it was able to enhance the cytotoxicity of cisplatin, a standard chemotherapeutic agent. The four HNSCC cell lines SCC9, SCC25, CAL27 and FADU were treated with ATO or cisplatin alone or with ATO and cisplatin in combination. Cytotoxicity assays, immunohistochemistry, western blot analysis and flow cytometry were carried out. Possible interactions between the two drugs were calculated using the Chou-Talalay equation. Ther results demonstrated a synergistic cytotoxic effect of the combination of ATO and cisplatin at high doses. The two agents induced apoptosis in all four HNSCC cell lines. In conclusion, this study showed that ATO is a promising therapeutic drug with cytotoxic effects in HNSCC. We demonstrated a synergistic effect in the combined treatment with cisplatin at high doses. PMID:22783443

  17. BIBR 1532 increases arsenic trioxide-mediated apoptosis in acute promyelocytic leukemia cells: therapeutic potential for APL.

    PubMed

    Bashash, Davood; Ghaffari, Seyed H; Zaker, Farhad; Kazerani, Maryam; Hezave, Kebria; Hassani, Saeed; Rostami, Masomeh; Alimoghaddam, Kamran; Ghavamzadeh, Ardeshir

    2013-09-01

    The current treatment of acute promyelocytic leukemia with arsenic trioxide (ATO) has increased long-lasting complete remissions; however, a proportion of patients continues to die eventually as a result of disease recurrence. In an effort to enhance the effectiveness of the APL treatment, we designed experiments to evaluate the effects of ATO in combination with the lead compound of non-nucleoside inhibitor of telomerase, BIBR 1532. After combined treatments with BIBR 1532 and ATO, decreased cell viability index with a concomitant increase in apoptotic cell death was observed in NB4 leukemic cells. Apoptosis induced by the combined treatments was accompanied by elevated Bax/Bcl-2 molecular ratio and enhanced caspase 3 activation. Our study has also demonstrated that the combined treatment suppressed NB4 cell proliferative capacity and inhibited telomerase activity probably via transcriptional suppression of c-Myc and hTERT. In conclusion, this study may supply insight into the application of this new combination therapy to APL cells intrinsically less sensitive to routine therapies and suggested a novel combination therapy for patients with more aggressive disease; those who may not respond favorably to the arsenic mono-therapy.

  18. Comparison of the antimicrobial activity of direct pulp-capping materials: Mineral trioxide aggregate-Angelus and Biodentine

    PubMed Central

    Özyürek, Taha; Demiryürek, Ebru Özsezer

    2016-01-01

    Purpose: To compare the antimicrobial activity of the tricalcium silicate-based Biodentine (BD) and mineral trioxide aggregate (MTA)-Angelus cement with the aid of agar diffusion test. Materials and Methods: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecium were inoculated in the Brucella liquid medium and were incubated at 37°C for 24 h. Thereafter, 100 >μl of the liquid culture of bacteria inoculated in the Mueller-Hinton agar with spread plate technique. Petri plates were dried in room temperature. For every microorganism, 3 petri plates were prepared (12 in total). In the medium, in every petri plate, 2 holes with 5 mm diameter and 2 mm depth were made. Afterward, BD and MTA-Angelus were filled into these holes under aseptic conditions according to the instructions of the manufacturing company. Then, the plates were kept in the incubator at 37°C for 24 h, and the diameters of the inhibition zones were measured with a digital caliper. Results: Inhibition zones formed by BD against E. coli and S. aureus were significantly larger than the zones formed by MTA-Angelus (P < 0.05). However, the inhibition zones formed by MTA-Angelus against P. aureus and E. faecium were larger than the zones formed by BD (P < 0.05). Conclusion: Within the limits of the present study, tricalcium silicate-based MTA-Angelus and BD have antimicrobial activity against E. coli, S. aureus, P. aureus, and E. faecium. PMID:27994321

  19. Treatment of experimental furcation perforations with mineral trioxide aggregate, platelet rich plasma or platelet rich fibrin in dogs' teeth.

    PubMed

    Tawfik, Hosam E; Abu-Seida, Ashraf M; Hashem, Ahmed A; El-Khawlani, Mohammed M

    2016-06-01

    This work evaluates the effect of mineral trioxide aggregate (MTA), platelet rich plasma (PRP) or platelet rich fibrin (PRF) on healing of non-contaminated and contaminated furcation perforations. A total of 192 teeth of 12 dogs was divided into three equal groups according to evaluation period. Each group was further subdivided into MTA, PRP, PRF, negative and positive control subgroups. Each experimental subgroup was further subdivided according to perforation status into non-contaminated and contaminated subdivisions. Root canal therapy was carried out and furcation perforation was made in all teeth except in negative control subgroup. The furcation perforation was repaired immediately in subdivision (1) and after 4 weeks in subdivision (2). The change in vertical bone loss was measured by radiography. Inflammatory cell count, cemental deposition, new bone formation, bone resorption and epithelial proliferation were assessed. Both PRP and PRF demonstrated statistically significant reduction in vertical bone loss and inflammatory cell count than MTA. No significant difference was found between MTA, PRP and PRF in cemental deposition, new bone formation, bone resorption and epithelial proliferation. The non-contaminated teeth demonstrated better treatment outcomes than the contaminated teeth. In conclusion, PRP and PRF are successful treatment options for repairing of furcation perforation in both non-contaminated and contaminated teeth in dogs with superior outcomes in non contaminated teeth.

  20. Osseous reaction to implantation of two endodontic cements: Mineral trioxide aggregate (MTA) and calcium enriched mixture (CEM)

    PubMed Central

    Rahimi, Saeed; Shahi, Shahriar; Kazemi, Ali; Asgary, Saeed; Eghbal, Mohammad J.; Mesgariabbasi, Mehran; Mohajeri, Daryoush

    2012-01-01

    Aim: The aim of the present in vivo study was to determine bone tissue reaction to calcium enriched mixture (CEM) and mineral trioxide aggregate (MTA) using a rat femur model. Study Design: Sixty-three rats were selected and randomly divided into three groups of 21 each [experimental groups (n=15), control (n=6)]. Implantation cavities were prepared in each femoral bone and randomly filled with the biomaterials only in the experimental groups. The animals in three groups were sacrificed 1, 4, and 8 weeks postoperatively. Histologic evaluations comprising inflammation severity and new bone formation were blindly made on H&E-stained decalcified 6-µm sections. Results: At 1, 4, and 8 weeks after implantation number of inflammatory cells had decreased in the CEM, MTA and control groups, respectively, with no statistically significant differences. Conversely, new bone formation had increased in all the experimental and control groups, without statistically significant differences. Conclusion: The results suggest that biocompatibility of MTA, as gold standard, and CEM cement as a new endodontic biomaterial are comparable Key words:Endodontics, MTA,CEM, osseous reaction. PMID:22549692

  1. Arsenic Trioxide Activate Transcription of Heme Oxygenase-1 by Promoting Nuclear Translocation of NFE2L2.

    PubMed

    Yue, Zhen; Zhong, Lingzhi; Mou, Yan; Wang, Xiaotong; Zhang, Haiying; Wang, Yang; Xia, Jianxin; Li, Ronggui; Wang, Zonggui

    2015-01-01

    In a previous study, we found that induced expression of Heme Oxygenase-1 (HO-1) is responsible for the resistance of human osteosarcoma MG63 cells to the chemotherapeutic agent arsenic trioxide (ATO). The present study was aimed at investigating the molecular mechanisms underlying the induction of HO-1 that occurs after exposure of MG63 cells to ATO. First, using RT-QPCT and Western-blot, we found that ATO strongly induced the expression of heme oxygenase-1 (HO-1) in these human osteosarcoma cells. Then by analyzing HO-1 mRNA of MG63 cells exposed to ATO in the presence and absence of a transcription inhibitor Actinomycin-D (Act-D), we demonstrated that ATO activates HO-1 expression in MG63 cells by regulating the transcription of the gene. Finally, through the analysis of the NFE2L2 protein levels among the total cellular and nuclear proteins by Western-blot and Immunocytochemical staning, we determined that ATO enhanced the nuclear translocation of nuclear factor erythroid 2-like 2 (NFE2L2), also known as Nrf2. From these results we have concluded that transcription activation of HO-1 resulting from the nuclear translocation of NFE2L2 is the underlying molecular mechanism for its high induction, which, in turn, is responsible for the resistance of human osteosarcoma cells to ATO treatment.

  2. Bacterial leakage in root canals filled with resin-based and mineral trioxide aggregate-based sealers

    PubMed Central

    Razavian, Hamid; Barekatain, Behnaz; Shadmehr, Elham; Khatami, Mahdieh; Bagheri, Fahime; Heidari, Fariba

    2014-01-01

    Background: Sealing ability is one of the most important features of endodontic sealers. The purpose of this in vitro study was to compare the sealing ability of a resin-based sealer with a mineral trioxide aggregate-based sealer. Materials and Methods: A total of 60 single-rooted extracted human teeth were randomly divided into two experimental groups (n = 25) and two control groups (n = 5). After canal preparation and smear layer removal, both groups were obturated with gutta-percha and sealer. Resin-based AH26 sealer was used in the first group and Fillapex® sealer in the second group. Two layers of nail varnish were applied on tooth surfaces except for the apical 2 mm. In the negative control group, nail varnish was applied on the entire surface. The teeth were mounted according to Lima et al. study and then sterilized by ethylene oxide gas. The samples were evaluated for bacterial microleakage using Enterococcus faecalis (ATCC 29212) for 90 days. Data were analyzed by survival test (P < 0.05). Results: Control groups had either immediate leakage or no leakage. The Fillapex® showed significantly higher amounts of microleakage compared with AH26 sealer (P < 0.05) and both groups exhibited significant differences in comparison with control groups. Conclusion: Both sealers had bacterial leakage. Sealing ability of AH26 was significantly higher than that of Fillapex®. PMID:25426153

  3. The Effect of Mineral Trioxide Aggregate on the Periapical Tissues after Unintentional Extrusion beyond the Apical Foramen

    PubMed Central

    Nagmode, Pradnya S.; Patel, Ankit V.; Ladhe, Pushpak L.

    2016-01-01

    Introduction. Single-step apexification procedures using mineral trioxide aggregate (MTA) have been reported as favorable treatment options for teeth with an open apex, posing greater benefits compared to the other available medicaments. However, controlled apical placement of MTA is a challenging procedure to perform using orthograde approach. This case series describes the outcome of the unintentional extrusion of MTA into periradicular tissues during apexification, in three separate cases. Methods. Three adult patients reported to the Department of Conservative Dentistry and Endodontics for the management of maxillary incisors with open apices. After isolation, conventional access, and cleaning and shaping procedures, one-step MTA apexification was performed. On subsequent radiographs, a considerable amount of MTA was seen to be extruded in all the three cases. Results. During follow-up examination the teeth were seen to be asymptomatic in all cases and radiographically demonstrated repair of the periapical lesion. Conclusion. The results of these cases suggest that extrusion of MTA into the periapical tissues does not cause any detrimental effect, which could be attributed to the biologic properties of MTA. PMID:27840745

  4. A complementary electrochromic device with highly improved performance based on brick-like hydrated tungsten trioxide film.

    PubMed

    Jiao, Zhihui; Wang, Jinmin; Ke, Lin; Sun, Xiao Wei; Demir, Hilmi Volkan

    2012-05-01

    Uniform and well adhesive nanostructured hydrated tungsten trioxide (3WO3 x H2O) films were grown on fluorine doped tin oxide (FTO) substrate via a facile and template-free crystal-seed-assisted hydrothermal method by addition of ammonium sulfate ((NH4)2SO4) and hydrogen peroxide (H2O2). X-ray diffraction (XRD) studies indicated that the films are of orthorhombic structure. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) analysis showed that the film was composed of brick-like nanostructures with a preferred growing direction along (002). The influence of seed layer, (NH4)2SO4 and H2O2 on the products were also studied. The film showed good cyclic stability, comparable switching speed and coloration efficiency (30.1 cm2 C(-1)). A complementary electrochromic device based on the film and Prussian blue depicted highly improved color contrast, coloration/bleaching response (1.8 and 3.7 s respectively) and coloration efficiency (164.6 cm2 C(-1)).

  5. In Vitro Evaluation of Different Solvents for Retrieval of Mineral Trioxide Aggregate and Calcium-Enriched Mixture

    PubMed Central

    Shojaee, Nooshin Sadat; Adl, Alireza; Sobhnamayan, Fereshte; Khademi, Azam; Hamedi, Mina

    2016-01-01

    Introduction: The purpose of this study was to evaluate the effect of different solvents; carbonic acid (H2CO3), hydrochloric acid (HCl), chlorhexidine (CHX) and sodium hypochlorite (NaOCl) on the surface hardness of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM) cement. Methods and Materials: Plexiglass molds were prepared and filled with Angelus MTA or CEM cement and then exposed to 2% carbonic acid, 37% hydrochloric acid, 2% chlorhexidine, 5.25% sodium hypochlorite and normal saline at intervals of 1 and 21 days, respectively (n=4). Surface microhardness of all specimens was analyzed by a universal testing machine and an electron microscope for some selected samples. Data were analyzed using the three-way ANOVA. Subgroup analysis was performed by Student’s t-test, One-way ANOVA and Tukey’s tests. The level of significance was set at 0.05. Results: On the first day, all solvents and on 21st day HCl, and H2CO3 were more effective in reducing the microhardness of MTA compared to CEM cement (P<0.05). Conclusion: The two experimental cements were differently affected by the solvents at specific time intervals. The solvents were more effective on MTA. PMID:27471536

  6. X-ray Diffraction Analysis of ProRoot Mineral Trioxide Aggregate Hydrated at Different pH Values

    PubMed Central

    Akhavan, Hengameh; Mohebbi, Pooneh; Firouzi, Amir; Noroozi, Mehdi

    2016-01-01

    Introduction: The aim of this study was to compare the chemical compounds of white ProRoot mineral trioxide aggregate (WMTA) hydrated at different pH environments. Methods and Materials: Mixed samples of WMTA were kept in acidic (pH=5.4), neutral (pH=7.4) and alkaline (pH=9.4) environments for 48 h. Then, X-ray diffraction (XRD) analysis was performed for both hydrated and powder forms of WMTA. Portlandite crystalline structures of environments were compared from three aspects: intensity (height of the peak, corresponding to the concentration), crystallinity (peak area/total area) and crystal size (full-width at half-maximum of the peak). Results: After matching the peaks of each sample with those of the International Center for Diffraction Data (ICDD) database, the main constituent of all set cements and powder form was found to be bismuth oxide. Acidic environment exhibited lower intensity and crystallinity of portlandite in comparison with neutral environment. Conclusion: The highest concentration and crystallinity of portlandite were observed in WMTA samples hydrated at neutral pH and the highest crystal size was detected after hydration in alkaline pH. PMID:27141218

  7. Sealing ability of mineral trioxide aggregate and Portland cement for furcal perforation repair: a protein leakage study.

    PubMed

    Shahi, Shahriar; Rahimi, Saeed; Hasan, Maryam; Shiezadeh, Vahab; Abdolrahimi, Majid

    2009-12-01

    The purpose of this study was to compare the sealing ability of gray mineral trioxide aggregate (GMTA), white MTA (WMTA), and both white and gray Portland cement as furcation perforation repair materials. A total of 120 human mandibular first molars were used. After root canal obturation and preparation of furcal perforations the specimens were randomly divided into four groups of 25 teeth each. In groups A, B, C, and D furcation perforations were filled with WMTA, GMTA, white Portland cement, and type II Portland cement, respectively. Ten teeth were used as positive controls with no filling materials in the perforations and 10 teeth with complete coverage with two layers of nail varnish were used as negative controls. A protein leakage model utilizing 22% bovine serum albumin (BSA) was used for evaluation. Leakage was noted when color conversion of the protein reagent was observed. The controls behaved as expected. Leakage was found in the samples from group A (WMTA), group B (GMTA), and in the two other groups (white and gray Portland cement). There were no statistically significant differences between GMTA and WMTA or white and gray Portland cement, but significant differences were observed between the MTA groups and the Portland cement groups. It was concluded that Portland cements have better sealing ability than MTA, and can be recommended for repair of furcation perforation if the present results are supported by other in vivo and in vitro studies.

  8. Comparative evaluation of intracanal sealing ability of mineral trioxide aggregate and glass ionomer cement: An in vitro study

    PubMed Central

    Malik, Gauri; Bogra, Poonam; Singh, Simranjeet; Samra, Rupandeep K

    2013-01-01

    Aims: The purpose of this study was to compare the sealing ability of Mineral Trioxide Aggregate (MTA) and Glass Ionomer Cement (GIC) when used over gutta-percha as intracanal sealing materials. The study also evaluated the sealing ability of Zinc oxide eugenol (ZOE) cement and Acroseal sealer. Materials and Methods: Teeth were obturated with gutta-percha using sealer ZOE (group A, C, D) and Acroseal (group B). The groups were further divided into 2 subgroups (15 premolars each) on the basis of intracanal sealing material used: GIC subgroups (A1, B1) and MTA in subgroups (A2, B2). The clearing technique was used in this study for leakage evaluation. Seventy mandibular premolars were prepared using step-back technique and divided into experimental groups A and B (30 premolars each) and the positive and negative control groups C and D (5 premolars each). Statistical analysis used: Coronal microleakage was determined under stereomicroscope using 15X magnification. Data was statistically analyzed using one-way ANOVA followed by Post-Hoc Multiple comparison (Bonferroni). Results: MTA group leaked significantly less than GIC group (P < 0.05). Acroseal exhibited better sealing ability than ZOE sealer. Teeth with no intracanal barrier showed almost complete leakage. Conclusions: MTA may be preferred over GIC as an intracanal barrier. PMID:24347890

  9. Elemental sulfur aerosol-forming mechanism

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Francisco, Joseph S.

    2017-01-01

    Elemental sulfur aerosols are ubiquitous in the atmospheres of Venus, ancient Earth, and Mars. There is now an evolving body of evidence suggesting that these aerosols have also played a role in the evolution of early life on Earth. However, the exact details of their formation mechanism remain an open question. The present theoretical calculations suggest a chemical mechanism that takes advantage of the interaction between sulfur oxides, SOn (n = 1, 2, 3) and hydrogen sulfide (nH2S), resulting in the efficient formation of a Sn+1 particle. Interestingly, the SOn + nH2S → Sn+1 + nH2O reactions occur via low-energy pathways under water or sulfuric acid catalysis. Once the Sn+1 particles are formed, they may further nucleate to form larger polysulfur aerosols, thus providing a chemical framework for understanding the formation mechanism of S0 aerosols in different environments.

  10. Anthropogenic sulfur dioxide emissions: 1850-2005

    SciTech Connect

    Smith, S. J.; Van Aardenne, J.; Klimont, Z.; Andres, Robert Joseph; Volke, A.; Delgado Arias, S

    2011-01-01

    Sulfur aerosols impact human health, ecosystems, agriculture, and global and regional climate. A new annual estimate of anthropogenic global and regional sulfur dioxide emissions has been constructed spanning the period 1850 2005 using a bottom-up mass balance method, calibrated to country-level inventory data. Global emissions peaked in the early 1970s and decreased until 2000, with an increase in recent years due to increased emissions in China, international shipping, and developing countries in general. An uncertainty analysis was conducted including both random and systemic uncertainties. The overall global uncertainty in sulfur dioxide emissions is relatively small, but regional uncertainties ranged up to 30%. The largest contributors to uncertainty at present are emissions from China and international shipping. Emissions were distributed on a 0.5 grid by sector for use in coordinated climate model experiments.

  11. Spatially Resolved Sulfur Speciation in Urban Soils

    NASA Astrophysics Data System (ADS)

    Brettholle, M.; Gleber, S.-C.; Mekiffer, B.; Legnini, D.; McNulty, I.; Vogt, S.; Wessolek, G.; Thieme, J.

    2011-09-01

    A combination of x-ray microscopy, elemental mapping, and XANES spectroscopy at the K-absorption edge of sulfur was used to analyze the elemental and particulate composition of an urban soil loaded with building rubble from WWII, exemplarily from Berlin, Germany. This combination of element specific high-resolution microscopy with high spectral resolution capabilities allows for the determination of elemental composition as well as chemical speciation and is therefore well suited for the analysis of highly heterogeneous environmental samples. Different soil and debris constituents could be assigned to elemental distribution patterns within collected fluorescence maps, allowing for a detailed analysis of the sulfur pool and release from war debris in subsequent studies. A detailed understanding of this sulfur lixiviation is central to preserve urban water quality.

  12. Anthropogenic Sulfur Dioxide Emissions: 1850-2005

    SciTech Connect

    Smith, Steven J.; van Aardenne, John; Klimont, Z.; Andres, Robert; Volke, April C.; Delgado Arias, Sabrina

    2011-01-02

    Sulfur aerosols impact human health, ecosystems, agriculture, and global and regional climate. A new annual estimate of anthropogenic global and regional sulfur dioxide emissions has been constructed spanning the period 1850 - 2005. A combination of mass balance and best available inventory data was used in order to achieve the most accurate estimate possible. Global emissions peaked in the early 1970s and decreased until 2000, with an increase in recent years due to increased emissions in China, international shipping, and developing countries in general. An uncertainty analysis was conducted including both random and systemic uncertainties. The overall global uncertainty in sulfur dioxide emissions is relatively small, but regional uncertainties of up to 30% were found. The largest contributors to uncertainty at present are emissions from China and international shipping.

  13. Anthropogenic sulfur dioxide emissions: 1850-2005

    NASA Astrophysics Data System (ADS)

    Smith, S. J.; van Aardenne, J.; Klimont, Z.; Andres, R.; Volke, A.; Delgado Arias, S.

    2010-06-01

    Sulfur aerosols impact human health, ecosystems, agriculture, and global and regional climate. A new annual estimate of anthropogenic global and regional sulfur dioxide emissions has been constructed spanning the period 1850-2005 using a bottom-up mass balance method, calibrated to country-level inventory data. Global emissions peaked in the early 1970s and decreased until 2000, with an increase in recent years due to increased emissions in China, international shipping, and developing countries in general. An uncertainty analysis was conducted including both random and systemic uncertainties. The overall global uncertainty in sulfur dioxide emissions is relatively small, but regional uncertainties ranged up to 30%. The largest contributors to uncertainty at present are emissions from China and international shipping. Emissions were distributed on a 0.5° grid by sector for use in coordinated climate model experiments.

  14. Anthropogenic sulfur dioxide emissions: 1850-2005

    NASA Astrophysics Data System (ADS)

    Smith, S. J.; van Aardenne, J.; Klimont, Z.; Andres, R. J.; Volke, A.; Delgado Arias, S.

    2011-02-01

    Sulfur aerosols impact human health, ecosystems, agriculture, and global and regional climate. A new annual estimate of anthropogenic global and regional sulfur dioxide emissions has been constructed spanning the period 1850-2005 using a bottom-up mass balance method, calibrated to country-level inventory data. Global emissions peaked in the early 1970s and decreased until 2000, with an increase in recent years due to increased emissions in China, international shipping, and developing countries in general. An uncertainty analysis was conducted including both random and systemic uncertainties. The overall global uncertainty in sulfur dioxide emissions is relatively small, but regional uncertainties ranged up to 30%. The largest contributors to uncertainty at present are emissions from China and international shipping. Emissions were distributed on a 0.5° grid by sector for use in coordinated climate model experiments.

  15. Atomic-Layer-Deposition Functionalized Carbonized Mesoporous Wood Fiber for High Sulfur Loading Lithium Sulfur Batteries.

    PubMed

    Luo, Chao; Zhu, Hongli; Luo, Wei; Shen, Fei; Fan, Xiulin; Dai, Jiaqi; Liang, Yujia; Wang, Chunsheng; Hu, Liangbing

    2017-04-14

    Lithium-sulfur battery (LSB) as one of the most promising energy storage devices suffers from poor conductivity of sulfur and fast capacity decay triggered by the dissolution of polysulfides. In this work, functionalized carbonized mesoporous wood fiber (f-CMWF) is employed as a host to accommodate sulfur for the first time. Natural wood microfiber has unique hierarchical and mesoporous structure, which is well maintained after carbonization. With such a hierarchical mesoporous structure, a high sulfur loading of 76 wt% is achieved in CMWF electrodes. The pore size of CMWF is tunable by atomic layer deposition (ALD) of 5 nm Al2O3 coating to form the f-CMWF. Such a thin layer coating slightly decreases the sulfur loading to 70%, but remarkably promotes the cyclic stability of sulfur cathode, which delivers an initial capacity of 1115 mAh g-1, and maintains a reversible capacity of 859 mAh g-1 for 450 cycles, corresponding to a slow capacity decay rate of 0.046% per cycle. More importantly, natural wood microfiber is firstly used as a raw material for sulfur encapsulating. This work is also critical for using low cost and mesoporous biomass carbon as bi-functional scaffold for LSB.

  16. Conductive framework of inverse opal structure for sulfur cathode in lithium-sulfur batteries.

    PubMed

    Jin, Lu; Huang, Xiaopeng; Zeng, Guobo; Wu, Hua; Morbidelli, Massimo

    2016-09-07

    As a promising cathode inheritor for lithium-ion batteries, the sulfur cathode exhibits very high theoretical volumetric capacity and energy density. In its practical applications, one has to solve the insulating properties of sulfur and the shuttle effect that deteriorates cycling stability. The state-of-the-art approaches are to confine sulfur in a conductive matrix. In this work, we utilize monodisperse polystyrene nanoparticles as sacrificial templates to build polypyrrole (PPy) framework of an inverse opal structure to accommodate (encapsulate) sulfur through a combined in situ polymerization and melting infiltration approach. In the design, the interconnected conductive PPy provides open channels for sulfur infiltration, improves electrical and ionic conductivity of the embedded sulfur, and reduces polysulfide dissolution in the electrolyte through physical and chemical adsorption. The flexibility of PPy and partial filling of the inverse opal structure endure possible expansion and deformation during long-term cycling. It is found that the long cycling stability of the cells using the prepared material as the cathode can be substantially improved. The result demonstrates the possibility of constructing a pure conductive polymer framework to accommodate insulate sulfur in ion battery applications.

  17. Conductive framework of inverse opal structure for sulfur cathode in lithium-sulfur batteries

    PubMed Central

    Jin, Lu; Huang, Xiaopeng; Zeng, Guobo; Wu, Hua; Morbidelli, Massimo

    2016-01-01

    As a promising cathode inheritor for lithium-ion batteries, the sulfur cathode exhibits very high theoretical volumetric capacity and energy density. In its practical applications, one has to solve the insulating properties of sulfur and the shuttle effect that deteriorates cycling stability. The state-of-the-art approaches are to confine sulfur in a conductive matrix. In this work, we utilize monodisperse polystyrene nanoparticles as sacrificial templates to build polypyrrole (PPy) framework of an inverse opal structure to accommodate (encapsulate) sulfur through a combined in situ polymerization and melting infiltration approach. In the design, the interconnected conductive PPy provides open channels for sulfur infiltration, improves electrical and ionic conductivity of the embedded sulfur, and reduces polysulfide dissolution in the electrolyte through physical and chemical adsorption. The flexibility of PPy and partial filling of the inverse opal structure endure possible expansion and deformation during long-term cycling. It is found that the long cycling stability of the cells using the prepared material as the cathode can be substantially improved. The result demonstrates the possibility of constructing a pure conductive polymer framework to accommodate insulate sulfur in ion battery applications. PMID:27600885

  18. Multiple sulfur isotopes and the evolution of Earth's surface sulfur cycle

    NASA Astrophysics Data System (ADS)

    Johnston, David T.

    2011-05-01

    The distribution of sulfur isotopes in geological materials reveals information about Earth history and biogeochemical processes. Research during the last several decades has used sulfur isotope geochemistry as a tool to better understand microbial processes ( Harrison and Thode, 1958; Kaplan, 1975; Monster et al., 1979; Peck, 1959, 1962; Rees, 1973) and sediment diagenesis ( Berner, 1969, 1982; Canfield et al., 1993b). Earth historians also realized this potential, as there exists a rich record of environmental change within the sedimentary records ( Canfield and Teske, 1996; Claypool et al., 1980; Goodwin et al., 1976; Habicht et al., 2002; Kah et al., 2004; Monster et al., 1979; Shen et al., 2001; Strauss, 1993; Thode and Goodwin, 1983). These applications have championed the use of the two most abundant sulfur isotopes [ 32S and 34S], and provide a rich introduction to what the sulfur isotope record has to offer [see ( Canfield, 2004; Canfield and Raiswell, 1999)]. Within the last decade, this information has been supplemented by new data derived from the less abundant isotopes [ 33S and 36S]. The measurement of all four stable sulfur isotopes - multiple sulfur isotope geochemistry - has expanded our understanding of biological evolution and activity, atmospheric chemistry and transport, crustal recycling, and many more fields related to Earth surface processes [see ( Farquhar and Wing, 2003)]. Here, I present a review of recent works in multiple sulfur isotope geochemistry with a focus on results that inform our understanding of biogeochemical processes and Earth surface evolution.

  19. One-step synthesis of a sulfur-impregnated graphene cathode for lithium-sulfur batteries.

    PubMed

    Park, Min-Sik; Yu, Ji-Sang; Kim, Ki Jae; Jeong, Goojin; Kim, Jae-Hun; Jo, Yong-Nam; Hwang, Uk; Kang, Shin; Woo, Taewoo; Kim, Young-Jun

    2012-05-21

    A practical route is introduced for synthesizing a sulfur-impregnated graphene composite as a promising cathode material for lithium-sulfur batteries. Sulfur particles with a size of a few microns are successfully grown in the interior spaces between randomly dispersed graphene sheets through a heterogeneous crystal growth mechanism. The proposed route not only enables the control of the particle size of active sulfur but also affords quantitative yields of composite powder in large quantities. We investigate the potential use of the sulfur-impregnated graphene composite as a cathode material owing to its advantages of confining active sulfur, preventing the dissolution of soluble polysulfides, and providing sufficient electrical conduction. A high discharge capacity of 1237 mA h g(-1) during the first cycle and a good cyclic retention of 67% after 50 cycles are attained in a voltage range of 1.8-2.6 V vs. Li/Li(+). These results emphasize the importance of tailoring cathode materials for improving the electrochemical properties of lithium-sulfur batteries. Our results provide a basis for further investigations on advanced lithium batteries.

  20. Reinforced Conductive Confinement of Sulfur for Robust and High-Performance Lithium-Sulfur Batteries.

    PubMed

    Lai, Chao; Wu, Zhenzhen; Gu, Xingxing; Wang, Chao; Xi, Kai; Kumar, R Vasant; Zhang, Shanqing

    2015-11-04

    Sulfur is an attractive cathode material in energy storage devices due to its high theoretical capacity of 1672 mAh g(-1). However, practical application of lithium-sulfur (Li-S) batteries can be achieved only when the major barriers, including the shuttling effect of polysulfides (Li2Sx, x = 3-8), significant volume change (∼80%), and the resultant rapid deterioration of electrodes, are tackled. Here, we propose an "inside-out" synthesis strategy by mimicking the structure of the pomegranate fruit to achieve conductive confinement of sulfur to address these issues. In the proposed pomegranate-like structure, sulfur and carbon nanotubes composite is encapsulated by the in situ formed amorphous carbon network, which allows the regeneration of electroactive material sulfur and the confinement of the sulfur as well as the lithium polysulfide within the electrical conductive carbon network. Consequently, a highly robust sulfur cathode is obtained, delivering remarkable performance in a Li-S battery. The obtained composite cathode shows a reversible capacity of 691 mAh g(-1) after 200 cycles with impressive cycle stability at the current density of 1600 mA g(-1).