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Sample records for chromium 54

  1. Chromium

    Science.gov (United States)

    ... Intern Med 1991;115:917-24. Abraham AS, Brooks BA, Eylath U. The effects of chromium supplementation on serum glucose and lipids in patients with and without non-insulin-dependent diabetes. Metabolism 1992;41:768-71. Hermann J, Arquitt A. ...

  2. Chromium in diet

    Science.gov (United States)

    The best source of chromium is brewer's yeast. However, many people do not use brewer's yeast because it causes bloating ( abdominal distention ) and nausea . Other good sources of chromium include ...

  3. Heterogeneous chromium catalysts

    NARCIS (Netherlands)

    2005-01-01

    The present invention relates to a heterogeneous chromium catalyst system for the polymerisation of ethylene and/or alpha olefins prepared by the steps of: (a) providing a silica-containing support, (b) treating the silica-containing support with a chromium compound to form a chromium-based silica-c

  4. Peat and coconut fiber as biofilters for chromium adsorption from contaminated wastewaters

    OpenAIRE

    2015-01-01

    Batch adsorption experiments were performed for the removal of chromium (III) and chromium (VI) ions from aqueous solutions using Canadian peat and coconut fiber. The Langmuir model was used to describe the adsorption isotherm. The maximum adsorption for peat reached 18.75 mg/g for Cr(III) and 8.02 mg/g for Cr(VI), whereas the value for fiber was slightly higher and reached 19.21 mg/g for Cr(III) and 9.54 mg/g for Cr(VI). Both chromium forms could be easily eluted from the materials. The adso...

  5. Groundwater contaminant by hexavalent chromium

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, C. [Univ. of Texas, Austin, TX (United States)

    1995-11-01

    Oxidation of trivalent chromium to hexavalent chromium has been investigated as a function of total manganese in soils as well as various incubation conditions. Chromium and manganese contents were analyzed by atomic absorption (graphite furnace and flame emission respectively) following acid digestion. Total hexavalent chromium generation capacity was determined by addition of 0.001 M CrCL3, incubation, and analysis by s-diphenyl carbazide. Samples were then leached with CaSO{sub 4} and MgSO{sub 4} and incubated in various environments (oven, freeze-drier, field moist, ultrafreeze) to test for geogenic generation of Cr(IV). The degree of geogenic generation of hexavalent chromium was compared with total Mn and Cr content as well as hexavalent generational capacity.

  6. On texture formation of chromium electrodeposits

    DEFF Research Database (Denmark)

    Nielsen, Christian Bergenstof; Leisner, Peter; Horsewell, Andy

    1998-01-01

    The microstructure, texture and hardness of electrodeposited hard, direct current (DC) chromium and pulsed reversed chromium has been investigated. These investigations suggest that the growth and texture of hard chromium is controlled by inhibition processes and reactions. Further, it has been...... established that codeposition of Cr2O3 nanoparticles is a general feature of DC chromium electrodeposition....

  7. CHROMIUM STATUS IN DIABETES MELLITUS

    Directory of Open Access Journals (Sweden)

    Keshavarz

    1996-06-01

    Full Text Available Fasting serum chromium, total cholesterol HDL-cholesterol, LDL-cholesterol, triacytglycerot and blood sugar were determined in fifty two diabetic patients with no other organic diseases anil compared with those obtained from a control group including fourty two healthy volunteers matched for age, sex ami body mass irutex (BMI. Fasting serum chromium and HDL-cholesterol were significantly lower in patients than in controls (p<0.0001 and p<0.001 respectively, but the mean triacytglycerot concentration was significantly higher in patients than in controls (p<002. Mean total cholesterol and LDL-cholesterol values were not significantly different in the two groups. Mean intake of energy, proteins, fats and chromium, estimated by the 24 hr dietary recall method were not significantly different in the two groups. We demonstrated that despite an adequate intake of chromium, the fasting serum chromium was lower in diabetic patients than in control subjects. Chromium deficiency in diabetic patients may act as a contributing factor in aggravating the disease's complications.

  8. Galvanic cells including cobalt-chromium alloys.

    Science.gov (United States)

    Gjerdet, N R

    1980-01-01

    Galvanic cells may be created when dentures made of cobalt-chromium alloys are placed on teeth with metallic restorations. The power of such cells was evaluated in an in vitro galvanic using amalgams, gold alloy, and nickel-chromium alloys. The amalgams and one of the nickel-chromium alloys revealed high corrosion currents when placed in contact with cobalt-chromium alloy, the conventional amalgam showing the highest values. The gold alloy and another nickel-chromium alloy exhibited low corrosion currents and they were noble with respect to cobalt-chromium.

  9. Ferrium M54 Steel

    Science.gov (United States)

    2015-03-18

    Examination ................................................................................................. 2 Zinc - Nickel Alloy Plating...resistance measurements using scans from 100 mV below to 100mV above at a scan rate of 0.167 mV/s. ZINC - NICKEL ALLOY PLATING The Zn-14% Ni alloy...release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Bare and Zn-14% Ni alloy coated Ferrium M54 steels were studied to

  10. Chromium at High Pressure

    Science.gov (United States)

    Jaramillo, Rafael

    2012-02-01

    Chromium has long served as the archetype of spin density wave magnetism. Recently, Jaramillo and collaborators have shown that Cr also serves as an archetype of magnetic quantum criticality. Using a combination of x-ray diffraction and electrical transport measurements at high pressures and cryogenic temperatures in a diamond anvil cell, they have demonstrated that the N'eel transition (TN) can be continuously suppressed to zero, with no sign of a concurrent structural transition. The order parameter undergoes a broad regime of exponential suppression, consistent with the weak coupling paradigm, before deviating from a BCS-like ground state within a narrow but accessible quantum critical regime. The quantum criticality is characterized by mean field scaling of TN and non mean field scaling of the transport coefficients, which points to a fluctuation-induced reconstruction of the critical Fermi surface. A comparison between pressure and chemical doping as means to suppress TN sheds light on different routes to the quantum critical point and the relevance of Fermi surface nesting and disorder at this quantum phase transition. The work by Jaramillo et al. is broadly relevant to the study of magnetic quantum criticality in a physically pure and theoretically tractable system that balances elements of weak and strong coupling. [4pt] [1] R. Jaramillo, Y. Feng, J. Wang & T. F. Rosenbaum. Signatures of quantum criticality in pure Cr at high pressure. Proc. Natl. Acad. Sci. USA 107, 13631 (2010). [0pt] [2] R. Jaramillo, Y. Feng, J. C. Lang, Z. Islam, G. Srajer, P. B. Littlewood, D. B. McWhan & T. F. Rosenbaum. Breakdown of the Bardeen-Cooper-Schrieffer ground state at a quantum phase transition. Nature 459, 405 (2009).

  11. Chromium Salen Mediated Alkene Epoxidation

    DEFF Research Database (Denmark)

    Petersen, Kaare Brandt; Norrby, Per-Ola; Daly, Adrian M.;

    2002-01-01

    The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall......, the studies show that the reactions have many similarities, but also a few critical differences. In agreement with experiment, the chromium system requires a change from low- to high-spin in the catalytic cycle, whereas the manganese system can proceed either with spin inversion or entirely on the high......-spin surface. The low-spin addition of metal oxo species to an alkene leads to an intermediate which forms epoxide either with a barrier on the low-spin surface or without a barrier after spin inversion. Supporting evidence for this intermediate was obtained by using vinylcyclopropane traps. The chromium...

  12. Environmental biochemistry of chromium.

    Science.gov (United States)

    Losi, M E; Amrhein, C; Frankenberger, W T

    1994-01-01

    Chromium is a d-block transitional element with many industrial uses. It occurs naturally in various crustal materials and is discharged to the environment as industrial waste. Although it can occur in a number of oxidation states, only 3+ and 6+ are found in environmental systems. The environmental behavior of Cr is largely a function of its oxidation state. Hexavalent Cr compounds (mainly chromates and dichromates) are considered toxic to a variety of terrestrial and aquatic organisms and are mobile in soil/water systems, much more so than trivalent Cr compounds. This is largely because of differing chemical properties: Hexavalent Cr compounds are strong oxidizers and highly soluble, while trivalent Cr compounds tend to form relatively inert precipitates at near-neutral pH. The trivalent state is generally considered to be the stable form in equilibrium with most soil/water systems. A diagram of the Cr cycle in soils and water is given in Fig. 6 (Bartlett 1991). This illustration provides a summary of environmentally relevant reactions. Beginning with hexavalent Cr that is released into the environment as industrial waste, there are a number of possible fates, including pollution of soil and surface water and leaching into groundwater, where it may remain stable and, in turn, can be taken up by plants or animals, and adsorption/precipitation, involving soil colloids and/or organic matter. Herein lies much of the environmental concern associated with the hexavalent form. A portion of the Cr(VI) will be reduced to the trivalent form by inorganic electron donors, such as Fe2+ and S2-, or by bioprocesses involving organic matter. Following this conversion, Cr3+ can be expected to precipitate as oxides and hydroxides or to form complexes with numerous ligands. This fraction includes a vast majority of global Cr reserves. Soluble Cr3+ complexes, such as those formed with citrate, can undergo oxidation when they come in contact with manganese dioxide, thus reforming

  13. Peat and coconut fiber as biofilters for chromium adsorption from contaminated wastewaters.

    Science.gov (United States)

    Henryk, Kołoczek; Jarosław, Chwastowski; Witold, Żukowski

    2016-01-01

    Batch adsorption experiments were performed for the removal of chromium (III) and chromium (VI) ions from aqueous solutions using Canadian peat and coconut fiber. The Langmuir model was used to describe the adsorption isotherm. The maximum adsorption for peat reached 18.75 mg/g for Cr(III) and 8.02 mg/g for Cr(VI), whereas the value for fiber was slightly higher and reached 19.21 mg/g for Cr(III) and 9.54 mg/g for Cr(VI). Both chromium forms could be easily eluted from the materials. The adsorption of chromium forms to organic matter could be explained in terms of formation of donor-acceptor chemical covalent bound with hydroxyl groups as ligands and chromium as the central atom in the formed complex. The chromate-reducing activities were monitored with the use of electron paramagnetic resonance spectroscopy. The results showed that both adsorption and reduction occurred simultaneously and the maximum adsorption capacity of hexavalent chromium being equal to 95% for fiber and 92% for peat was obtained at pH 1.5. The reduction of Cr(VI) in wastewaters began immediately and disappeared after 20 h. Both materials contained yeast and fungi species which can be responsible for reduction of chromium compounds, due to their enzymatic activity (Chwastowski and Koloczek (Acta Biochim Pol 60: 829-834, 2013)). The reduction of Cr(VI) is a two-phase process, the first phase being rapid and based on chemical reaction and the second phase having biological features. After the recovery step, both types of organic materials can be used again for chromium adsorption without any loss in the metal uptake. Both of the materials could be used as biofilters in the wastewater treatment plants.

  14. The use of trivalent chromium bath to obtain a solar selective black chromium coating

    Science.gov (United States)

    Survilienė, S.; Češūnienė, A.; Juškėnas, R.; Selskienė, A.; Bučinskienė, D.; Kalinauskas, P.; Juškevičius, K.; Jurevičiūtė, I.

    2014-06-01

    Black chromium coatings were electrodeposited from a trivalent chromium bath using a ZnO additive as a second main component. Black chromium was electrodeposited on steel and copper plates and substrates plated with bright nickel prior to black chromium electrodeposition. The black chromium coatings were characterized by XRD and SEM. The XRD data suggest that the phase structure of black chromium may be defined as a zinc solid solution in chromium or a chromium solid solution in zinc depending on the chromium/zinc ratio in the deposit. The role of substrate finish was evaluated through the corrosion resistance and reflectance of black chromium. According to corrosion tests the samples plated with bright nickel prior to black chromium deposition have shown the highest corrosion resistance. The electrodeposited black chromium possesses good optical properties for the absorption of solar energy. The absorption coefficient of black chromium was found to be over 0.99 for the samples obtained without the Ni undercoat and below 0.99 for those obtained with the use of Ni undercoat. However, the use of nickel undercoat before black chromium plating is recommended because it remarkably improves the corrosion resistance of samples.

  15. The effect of chronic chromium exposure on the health of Chinook salmon (Oncorhynchus tshawytscha)

    Energy Technology Data Exchange (ETDEWEB)

    Farag, Aida M. [United States Geological Survey, Columbia Environmental Research Center, Jackson Field Research Station, P.O. Box 1089, Jackson, WY 83001 (United States)]. E-mail: aida_farag@usgs.gov; May, Thomas [United States Geological Survey, Columbia Environmental Research Center, Columbia, MO 65201 (United States); Marty, Gary D. [Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, 1 Shields Ave., Davis, CA 95616-8732 (United States); Easton, Michael [International EcoGen Inc., 2015 McLallen Court, North Vancouver, BC, Canada V7P 3H6 (Canada); Harper, David D. [United States Geological Survey, Columbia Environmental Research Center, Jackson Field Research Station, P.O. Box 1089, Jackson, WY 83001 (United States); Little, Edward E. [United States Geological Survey, Columbia Environmental Research Center, Columbia, MO 65201 (United States); Cleveland, Laverne [United States Geological Survey, Columbia Environmental Research Center, Columbia, MO 65201 (United States)

    2006-03-10

    This study was designed to determine fish health impairment of Chinook salmon (Oncorhynchus tshawytscha) exposed to chromium. Juvenile Chinook salmon were exposed to aqueous chromium concentrations (0-266 {mu}g l{sup -1}) that have been documented in porewater from bottom sediments and in well waters near salmon spawning areas in the Columbia River in the northwestern United States. After Chinook salmon parr were exposed to 24 and 54 {mu}g Cr l{sup -1} for 105 days, neither growth nor survival of parr was affected. On day 105, concentrations were increased from 24 to 120 {mu}g Cr l{sup -1} and from 54 to 266 {mu}g Cr l{sup -1} until the end of the experiment on day 134. Weight of parr was decreased in the 24/120 {mu}g Cr l{sup -1} treatment, and survival was decreased in the 54/266 {mu}g Cr l{sup -1} treatment. Fish health was significantly impaired in both the 24/120 and 54/266 {mu}g Cr l{sup -1} treatments. The kidney is the target organ during chromium exposures through the water column. The kidneys of fish exposed to the greatest concentrations of chromium had gross and microscopic lesions (e.g. necrosis of cells lining kidney tububules) and products of lipid peroxidation were elevated. These changes were associated with elevated concentrations of chromium in the kidney, and reduced growth and survival. Also, variations in DNA in the blood were associated with pathological changes in the kidney and spleen. These changes suggest that chromium accumulates and enters the lipid peroxidation pathway where fatty acid damage and DNA damage (expressed as chromosome changes) occur to cause cell death and tissue damage. While most of the physiological malfunctions occurred following parr exposures to concentrations {>=}120 {mu}g Cr l{sup -1}, nuclear DNA damage followed exposures to 24 {mu}g Cr l{sup -1}, which was the smallest concentration tested. The abnormalities measured during this study are particularly important because they are associated with impaired growth

  16. Study of the thermodynamics of chromium(III) and chromium(VI) binding to iron(II/III)oxide or magnetite or ferrite and magnanese(II) iron (III) oxide or jacobsite or manganese ferrite nanoparticles.

    Science.gov (United States)

    Luther, Steven; Brogfeld, Nathan; Kim, Jisoo; Parsons, J G

    2013-06-15

    Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4±0.9 nm (Fe3O4) and 15.5±0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative.

  17. Innovative soil treatment process design for removal of trivalent chromium

    Energy Technology Data Exchange (ETDEWEB)

    Stallings, J.H. [Air Force, Wright-Patterson AFB, OH (United States). Aeronautical Systems Center; Durkin, M.E. [Hughes Missile Systems Co., Tucson, AZ (United States)

    1997-12-31

    A soil treatment process has been developed as part of a US Air Force environmental compliance project at Air Force Plant 44, Tucson, AZ for treating soil contaminated with heavy metals including trivalent chromium, cadmium, copper, and nickel. The process was designed to treat a total of 133,000 tons of soil in a 400 ton per day facility. Features of the soil treatment process include physical treatment and separation, and a chemical treatment process of the remaining fines using a hypochlorite leach allowing chromium to be solubilized at a high pH. After treating, fines are washed in three stage countercurrent thickeners and chromium hydroxide cake is recovered as a final produce from the leach solution. Treatability studies were conducted, laboratory and a pilot plant was built. Process design criteria and flow sheet, material balances, as well as preliminary equipment selection and sizing for the facility have been completed. Facility was designed for the removal of Cr at a concentration of an average of 1230 mg/kg from the soil and meeting a risk based clean-closure limit of 400 mg/kg of Cr. Capital costs for the 400 tpd plant were estimated at 9.6 million with an operating and maintenance cost of $54 per ton As process is most economic for large quantities of soil with relatively low concentrations of contaminants, it was not used in final closure when the estimated volume of contaminated soil removed dropped to 65,000 tons and concentration of chromium increased up to 4000 mg/kg. However, the process could have application in situations where economics and location warrant.

  18. Simultaneous determination of chromium(III) and chromium(VI) in aqueous solutions by ion chromatography and chemiluminescence detection

    DEFF Research Database (Denmark)

    Gammelgaard, Bente; Jøns, O; Nielsen, B

    1992-01-01

    A method for the simultaneous determination of chromium(iii) and chromium(vi) in a flow system based on chemiluminescence was developed. A Dionex cation-exchange guard column was used to separate chromium(iii) from chromium(vi), and chromium(vi) was reduced by potassium sulfite, whereupon both...

  19. Sonoassisted microbial reduction of chromium.

    Science.gov (United States)

    Kathiravan, Mathur Nadarajan; Karthick, Ramalingam; Muthu, Naggapan; Muthukumar, Karuppan; Velan, Manickam

    2010-04-01

    This study presents sonoassisted microbial reduction of hexavalent chromium (Cr(VI)) using Bacillus sp. isolated from tannery effluent contaminated site. The experiments were carried out with free cells in the presence and absence of ultrasound. The optimum pH and temperature for the reduction of Cr(VI) by Bacillus sp. were found to be 7.0 and 37 degrees C, respectively. The Cr(VI) reduction was significantly influenced by the electron donors and among the various electron donors studied, glucose offered maximum reduction. The ultrasound-irradiated reduction of Cr(VI) with Bacillus sp. showed efficient Cr(VI) reduction. The percent reduction was found to increase with an increase in biomass concentration and decrease with an increase in initial concentration. The changes in the functional groups of Bacillus sp., before and after chromium reduction were observed with FTIR spectra. Microbial growth was described with Monod and Andrews model and best fit was observed with Andrews model.

  20. Inoculation of chromium white cast iron

    Directory of Open Access Journals (Sweden)

    D. Kopyciński

    2009-01-01

    Full Text Available It has been proved that an addition of boron carbide introduced as an inoculant to the chromium white cast iron changes the structureof castings. Castings after inoculation revealed a different structure with numerous grains. Primary precipitates of chromium carbide also appeared, reducing the mechanical properties of as-cast parts. Properly established heat treatment regime makes chromium iron castings regain their, originally high, mechanical properties.

  1. Spatial distribution of chromium in soils contaminated by chromium-containing slag

    Institute of Scientific and Technical Information of China (English)

    HUANG Shun-hong; PENG Bing; YANG Zhi-hui; CHAI Li-yuan; XU You-ze; SU Chang-qing

    2009-01-01

    To evaluate the metal chromium (Cr) contamination of soil at a chromium-containing slag site by ferrochromium production, the contaminated sites, under slag heap, in the vicinity of slag heap and arable soils near the outlet of sewer channel, and unpolluted site 5 km away from one ferroalloy plant in Hunan Province, China, were selected. The concentrations of total Cr and water soluble Cr in bulk soil samples and profile depth samples were determined. The results show that the soils in the vicinity of slag heap have the highest total Cr content followed by the soils under the slag heap and near the outlet of sewer channel of the factory. The mean concentrations of total Cr in the top soils at above three contaminated locations exceed the critical level of Secondary Environmental Quality Standard for Soil in China by 3.5, 5.4 and 1.8 times. In most Cr polluted soils, total Cr has a relative accumulation in soil depth of 40-60 cm, but this trend is not found in unpolluted soils. The average concentrations of water soluble Cr (Ⅵ) in top soils under slag heap and in the vicinity of slag heap are 176.9 times and 52.7 times higher than that in the uncontaminated soils, respectively. However, water soluble Cr (Ⅵ) contents in soils near sewer channel are all low and the values are close to that in the uncontaminated soils. Although water soluble Cr (Ⅵ) content in soil profiles decreases with soil depths, it in soils under slag heap maintains a high level even at a depth of 100-150 cm. The results imply that the transportation of Cr (Ⅵ) can result in a potential risk of groundwater system in this area.

  2. Electrodeposition of chromium from trivalent chromium urea bath containing sulfate and chloride

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The reduction of Cr( Ⅲ) to Cr( Ⅱ ) on copper electrode in trivalent chromium urea bath containing chromium sulfate and chromium chloride as chromium source has been investigated by potentiodynamic sweep. The transfer coefficient α for reduction of Cr( Ⅲ ) to Cr( Ⅱ ) on copper electrode was calculated as 0.46. The reduction is a quasi-reversible process. J-t responses at different potential steps showed that the generation and adsorption characteristics of carboxylate bridged oligomer are relevant to cathode potential. The interface behavior between electrode and solution for Cr( Ⅲ ) complex is a critical factor influencing sustained electrode position of chromium. The hypotheses of the electro-inducing polymerization of Cr( Ⅲ ) was proposed. The potential scope in which sustained chromium deposits can be prepared is from- 1.3 V to- 1.7 V (vs SCE) in the urea bath. Bright chromium deposits with thickness of 30 μm can be prepared in the bath.

  3. 29 CFR 1915.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... system dysfunction; any history of asthma, dermatitis, skin ulceration, or nasal septum perforation; and... is present or is likely to be present from skin or eye contact with chromium (VI), the employer shall... cleaned in a manner that minimizes skin or eye contact with chromium (VI) and effectively prevents...

  4. 29 CFR 1926.1126 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... system dysfunction; any history of asthma, dermatitis, skin ulceration, or nasal septum perforation; and... is present or is likely to be present from skin or eye contact with chromium (VI), the employer shall... cleaned in a manner that minimizes skin or eye contact with chromium (VI) and effectively prevents...

  5. 29 CFR 1910.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... activity involving chromium cannot release dusts, fumes, or mists of chromium (VI) in concentrations at or... currents that prevent the LEVs from performing efficiently. The use of fans has a similar effect. Industry... and positioning of cross drafts, fans, doors, windows, partitions and process equipment that...

  6. [Bioremediation of chromium (VI) contaminated site by reduction and microbial stabilization of chromium].

    Science.gov (United States)

    Zheng, Jia-Chuan; Zhang, Jian-Rong; Liu, Xi-Wen; Xu, Qian; Shi, Wei-Lin

    2014-10-01

    Chromium (VI) contaminated soil samples were collected from a chemical plant in Suzhou. Firstly, the reduced soil was prepared by adding reagent (Stone-sulfure reagent) into polluted soil to transfer most chromium (VI) into chromium (III), then a nutrient solution was introduced into the reduced soil, and the stabilized soil was obtained after 60 days culturing. The chromium (VI) content of the three kinds of soil was analyzed. The results showed that the chromium (VI) content in toxicity characteristic leaching liquid (TCLL) dropped by 96. 8% (from 8.26 mg · L(-1) to 0.26 mg · L(-1)), and the total chromium content dropped by 95.7% (from 14.66 mg · L(-1) to 0.63 mg · L(-1)) after bioremediation in 5% nutrient solution. Additionally, the durability of chromium stabilization was tested by potassium permanganate oxidation and sterilization of microbe-treated soil. After oxidation, the chromium (VI) content in TCLL of the reduced soil was increased from 8.26 mg · L(-1) to 14.68 mg · L(-1). However, the content after bioremediation was decreased to 2.68 mg · L(-1). The results of sterilization demonstrated that the death of microbe had no significant effect on the stabilization of chromium. Consequently, the research in this paper demonstrated the feasibility of bioremediation of chromium (VI) polluted soil through reduction followed by stabilization/soilidification, and provided a technique with low cost but high efficiency.

  7. Low-chromium reduced-activation chromium-tungsten steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Bainitic microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of non-classical bainite were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was found to be considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2 1/4Cr-2W and 2 1/4Cr-2WV steel compositions to increase their hardenability, and the microstructures and mechanical properties were examined.

  8. Synthesis of Chromium (Ⅲ) 5-aminosalicylate

    Institute of Scientific and Technical Information of China (English)

    LI Wei; HAO Er-jun; JIANG Yu-qin

    2004-01-01

    As we all known that diabetes is a chronic disease with major health consequences.Research has revealed that the occurrence of diabetes have great thing to do with the chromium deficient. Almost 40 years after the first report of glucose tolerance factor(GTF) [1], no conclusive evidence for an isolable ,biologically active form of chromium exited. Three materials have been proposed to be the biologically active form of chromium: "glucose tolerance factor", chromium Picolinate and low-molecular-weight chromium-binding substance (LWMCr) [2] . So there is potential for the design of new chromium drugs .5-Aminosalicylic acid (5-ASA) is identified as an active component in the therapy of inflammatory bowel disease (IBD) such as Crohn's disease and ulcerative colitis . The therapeutic action of 5-ASA is believed to be coupled to its ability to act as a free radical scavenger [3-4],acting locally on the inflamed colonic mucosa [5-7]. However, the clinical use of 5-ASA is limited, since orally administered 5-ASA is rapidly and completely absorbed from the upper gastrointestinal tract and therefore the local therapeutic effects of 5-ASA in the colon is hardly expected.In this paper, we report the synthesis of chromium(Ⅲ)5-aminosalicylate from 5-ASA and CrCl3. 6H2O.The synthesis route is as follow:The complex has been characterized by elemental analysis, IR spectra, X-ray powder diffractionand TG-DTA . They indicate that the structure is tris(5-ASA) Chromium . Experiments show that thecomplex has a good activity for supplement tiny dietary chromium, lowering blood glucose levels,lowering serum lipid levels and in creasing lean body mass .

  9. Characteristics of chromium-allergic dermatitis patients prior to regulatory intervention for chromium in leather

    DEFF Research Database (Denmark)

    Bregnbak, David; Thyssen, Jacob P; Zachariae, Claus;

    2014-01-01

    BACKGROUND: Chromium-tanned leather articles currently constitute the most important cause of contact allergy to chromium in Denmark. A regulation on the content of hexavalent chromium in leather was adopted in November 2013 by the EU member states. OBJECTIVES: To characterize patients...... with chromium allergy and their disease, to serve as a baseline for future studies on the potential effect of the new regulation on chromium in leather. METHODS: A questionnaire case-control study was performed on 155 dermatitis patients with positive patch test reactions to potassium dichromate and a matched...... control group of 621 dermatitis patients. Comparisons were made by use of a χ(2) -test and the Mann-Whitney U-test. Logistic regression analyses were used to test for associations. RESULTS: Sixty-six per cent of chromium-allergic patients had a positive history of contact dermatitis caused by leather...

  10. Chromium in leather footwear-risk assessment of chromium allergy and dermatitis

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Strandesen, Maria; Poulsen, Pia B;

    2012-01-01

    Background. Chromium-tanned leather footwear, which releases >3 ppm hexavalent Cr(VI), may pose a risk of sensitizing and eliciting allergic dermatitis. Objectives. To determine the content and potential release of chromium in leather footwear and to discuss the prevention of chromium contact...... allergy and dermatitis. Methods. Sixty pairs of leather shoes, sandals and boots (20 children's, 20 men's, and 20 women's) were purchased in Copenhagen and examined with X-ray fluorescence spectroscopy. Chromium was extracted according to the International Standard, ISO 17075. The detection level for Cr......(VI) was 3 ppm. Results. Chromium was identified in 95% of leather footwear products, the median content being 1.7% (range 0-3.3%). No association with store category or footwear category was found. A tendency for there to be a higher chromium content in footwear with high prices was shown (p(trend) = 0...

  11. Leaching of chromium from chromium contaminated soil: Speciation study and geochemical modeling

    Directory of Open Access Journals (Sweden)

    Anđelković Darko H.

    2012-01-01

    Full Text Available Distribution of chromium between soil and leachate was monitored. A natural process of percolating rainwater through the soil was simulated in the laboratory conditions and studied with column leaching extraction. Migration of chromium in the soil is conditioned by the level of chromium soil contamination, the soil organic matter content, and rainwater acidity. Chromium (III and chromium(VI were determined by spectrophotometric method with diphenilcarbazide in acidic media. Comparing the results of chromium speciation in leachate obtained by experimental model systems and geochemical modelling calculations using Visual MINTEQ model, a correlation was observed regarding the influence of the tested parameters. Leachate solutions showed that the concentration of Cr depended on the organic matter content. The influence of pH and soil organic matter content is in compliance after its definition through experimental and theoretical way. The computer model - Stockholm Humic Model used to evaluate the leaching results corresponded rather well with the measured values.

  12. Chromium isotope uptake in carbonates

    DEFF Research Database (Denmark)

    Rodler, Alexandra

    composition of contemporaneous seawater. Marine carbonates are ubiquitous throughout Earth’s rock record rendering them a particularly interesting archive for constraining past changes in ocean chemistry. This thesis includes an investigation of the fractionation behavior of Cr isotopesduring coprecipitation......Chromium (Cr) is a redox sensitive element potentially capable of tracing fine-scale fluctuations of the oxygenation of Earth’s early surface environments and seawater. The Cr isotope composition of carbonates could perhaps be used as paleo-redox proxy to elucidate changes in the geological past...... related to the rise of oxygen and the evolution of the biosphere. However, before the Cr isotopesystem can be applied to faithfully delineate paleo-environmental changes, careful assessment of the signal robustness and a thorough understanding of the Cr cycle in Earth system processes is necessary...

  13. Chromium (VI) adsorption on boehmite

    Energy Technology Data Exchange (ETDEWEB)

    Granados-Correa, F. [Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027 Col., Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)], E-mail: fgc@nuclear.inin.mx; Jimenez-Becerril, J. [Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027 Col., Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)

    2009-03-15

    Boehmite was synthesized and characterized in order to study the adsorption behavior and the removal of Cr(VI) ions from aqueous solutions as a function of contact time, initial pH solution, amount of adsorbent and initial metal ion concentration, using batch technique. Adsorption data of Cr(VI) on the boehmite were analyzed according to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption models. Thermodynamic parameters for the adsorption system were determinated at 293, 303, 313 and 323 K temperatures. The kinetic values and thermodynamic parameters from the adsorption process show that the Cr(VI) ions adsorption on boehmite is an endothermic and spontaneous process. These results show that the boehmite could be considered as a potential adsorbent for chromium ions in aqueous solutions.

  14. Mechanical properties of metal-ceramic systems from nickel-chromium and cobalt-chromium alloys

    Directory of Open Access Journals (Sweden)

    Mirković Nemanja

    2007-01-01

    Full Text Available Background/Aim. Metal-ceramic bond strength and alloys' elastic modulus clearly determine the potential of alloy application, because the ceramic integrity during mastication depends on these two characteristics. The aim of this study was to evaluate metal-ceramic bond strength and elastic modulus of cobalt-chromium alloys in making porcelainfused- to-metal restorations, regarding the application of the most frequent nickel-chromium alloy. Methods. The research was performed as an experimental study. Six metalceramic samples were made from nickel-chromium alloy (Wiron 99 and cobalt-chromium alloy (Wirobond C, according to the manufactures manuals and instructions from ISO 9693: 1996. Three-point bending test was performed up to the ceramic fracture. The fracture load was measured on an universal testing machine (Zwick, type 1464, with cross-head speed of 0,05mm/min. Results. The results of this study confirmed the significant differences between the metal-ceramic bond strength (p < 0.01 and elastic modulus (p < 0.001 of nickel-chromium and cobalt-chromium alloys, where cobalt-chromium alloys showed higher values for both tested parameters. Conclusion. Cobalt-chromium metal-ceramic alloys can successfully replace nickel-chromium alloys, especially for fabrication of long-span metal-ceramic bridges due to the great flexural strength.

  15. AEROSOL BEHAVIOR IN CHROMIUM WASTE INCINERATION

    Institute of Scientific and Technical Information of China (English)

    Suyuan Yu

    2003-01-01

    Cr2O3 is considered as the dominant incineration product during the combustion disposal of chromium waste. A hydrogen/air diffusion flame was employed to simulate the industrial process of incineration. Cr2O3 aerosols were generated inside the flame by the gas phase reaction of chromium and oxygen. Chromium came from the rapid decomposition of chromium hexacarbonyl (Cr(CO)6) at room temperature and was carried into the combustion chamber by hydrogen. Aerosol and clusters can then be easily formed in the flame by nucleation and coagulation. A two dimensional Discrete-Sectional Model (DSM) was adopted to calculate the Cr2O3 aerosol behavior. The experimental measurement method was Dynamic Light Scattering. The numerically predicted results agreed well with those of the experimental measurement. Both results show that the Cr2O3 aerosol size reached about 70 nanometers at the flame top.

  16. Localized Corrosion of Chromium Coated Steel

    NARCIS (Netherlands)

    Zhang, X.; Beentjes, P.; Mol, A.; Terryn, H.

    2006-01-01

    In this paper, we report on the studies of the local corrosion behaviour of chromium-coated ultra low carbon steel in NaCl solution using polarization, electrochemical impedance spectroscopy (EIS) and SVET.

  17. CHROMIUM CONCENTRATION IN TEHRAN ELECTROPLATING PLANTS

    Directory of Open Access Journals (Sweden)

    M. Ghiasseddin

    1988-12-01

    Full Text Available Hazards of soluable hexa and trivalent chromium have been documented by many investigators. But there was no information regarding safety of about 5000 workers at exposure risk to chromium in 600 primitive electroplating work shops of Tehran. During this study more than 70% of work shops were inactive due to some of their own problems. Out of active plants those that were relatively more cooperative 43 manual and 3 semi automatic were investigated for chromium concentration both by personal and environmental Sampling. The Samples were analyzed by AAS and cholormetry. In 30% of personal and 40% of environmental samples both total and Cr+6 were higher than ACGIH’S TLV. In one of semiautomatic plant Cr=6 was as high as 0.71 mg/m.3.Regarding injuries, following observations were made: Nasal wound 85%, skin irritation 73% , Dermatitis 35% and some other chromium related injuries including 2 cases of Septum perforations.

  18. Potentiometry: A Chromium (III) -- EDTA Complex

    Science.gov (United States)

    Hoppe, J. I.; Howell, P. J.

    1975-01-01

    Describes an experiment that involves the preparation of a chromium (III)-EDTA compound, a study of its infrared spectrum, and the potentiometric determination of two successive acid dissociation constants. (Author/GS)

  19. The structures of complexes of Chromium(III with cystine and ethylglycine

    Directory of Open Access Journals (Sweden)

    Lina A. Chernushenko

    2014-03-01

    Full Text Available It has been investigated the electronic spectra of complex compounds of chromium(III with amino acids as bidentate coordinated in compound (I and as monodentate coordinated in compound (II in solution. Three-ethyl glycinate and three-cystinate have the octahedral structure. Two bands of transition were observed in the visible part of the spectrum 4Т1g¬4A2g  and 4Т2g¬4A2g, one band of transition was observed in UV- spectrum, 4Т1g(Р¬4A2g. It was submitted the results of calculations of crystal field parameters: Dq = 1790 cm-1, В = 560.57 cm-1 and b = 0.54 for compound (I, Dq = 1786 cm-1, В = 504.53sm-1 and b = 0.49 for compound (II. The computer three-dimensional models of structure of such chromium(III complexes as three-cystinate chromium (III and three-chromium glycinate were created. Quantum-chemical modeling programs Chemcraft and WinGAMESS were used. Angles and bond lengths were calculated.

  20. Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, Low-Carbon Nickel-Chromium-Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Tungsten, and Low-Carbon Nickel-Molybdenum-Chromium Alloy Plate, Sheet, and Strip

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, Low-Carbon Nickel-Chromium-Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Tungsten, and Low-Carbon Nickel-Molybdenum-Chromium Alloy Plate, Sheet, and Strip

  1. Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Molybdenum-Chromium, Low-Carbon Nickel-Molybdenum-Chromium-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, and Low-Carbon Nickel-Chromium-Molybdenum-Tungsten Alloy Rod

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Molybdenum-Chromium, Low-Carbon Nickel-Molybdenum-Chromium-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, and Low-Carbon Nickel-Chromium-Molybdenum-Tungsten Alloy Rod

  2. STS-54 Physics of Toys

    Science.gov (United States)

    1993-01-01

    Greg Vogt, NASA Headquarters Education Specialist, and Carolyn Sumners, Houston Museum of Natural Science, give an overview of the spaceborne experiments that will take place on the STS-54 Endeavour mission. Mr. Vogt discusses the objectives and procedures of the experiments, which are structured around using toys to show the effects of microgravity. Mr. Vogt and Ms. Sumners then answer questions from the press.

  3. Permeation of chromium salts through human skin in vitro

    DEFF Research Database (Denmark)

    Gammelgaard, Bente; Fullerton, A; Avnstorp, C

    1992-01-01

    Chromium permeation studies were performed on full thickness human skin in diffusion cells. All samples were analysed for the total chromium content by graphite furnace Zeeman-corrected atomic absorption spectrometry. Some samples were analysed by an ion chromatographic method permitting...... the simultaneous determination of Cr(VI) and Cr(III) as well. The amounts of chromium found in all skin layers were significantly higher when potassium dichromate was applied to the skin compared with chromium chloride or chromium nitrate. Chromium could only be detected in the recipient phase after application...... of the dichromate solution. Chromium skin levels increased with increasing concentrations of applied chromium salts up to 0.034 M Cr. The amount of chromium in recipient phase and skin layers increased with increasing pH when the applied solution contained potassium dichromate. This was ascribed to a decreased skin...

  4. Direct access to macroporous chromium nitride and chromium titanium nitride with inverse opal structure.

    Science.gov (United States)

    Zhao, Weitian; DiSalvo, Francis J

    2015-03-21

    We report a facile synthesis of single-phase, nanocrystalline macroporous chromium nitride and chromium titanium nitride with an inverse opal morphology. The material is characterized using XRD, SEM, HR-TEM/STEM, TGA and XPS. Interconversion of macroporous CrN to Cr2O3 and back to CrN while retaining the inverse opal morphology is also demonstrated.

  5. The Key Technique of Manufacture of Dense Chromium Sesquioxide Refractories

    Institute of Scientific and Technical Information of China (English)

    LIMaoqiang; ZHANGShuying; 等

    1998-01-01

    Dense chromium sesquioxide refractories have widely been used in the kilns for making alkai-free and anti-alkali glass fibers due to their excellent re-sistance to molten glasses.Densifications of chromium sesquioxide during sintering can be blocked by evaporation of chromium trioxide derived from oxidation at high temperature,In this paper the mech-anism of sintering chromium oxide and the process-ing technique for making dense chromium sesquiox-ide refractories are discussed .A process in laboratory scale for making dense chromium sesquioxide bricks is demonstrated.

  6. Inverse Association of Plasma Chromium Levels with Newly Diagnosed Type 2 Diabetes: A Case-Control Study

    Directory of Open Access Journals (Sweden)

    Sijing Chen

    2017-03-01

    Full Text Available Chromium has long been known as an enhancer of insulin action. However, the role of chromium in the development of type 2 diabetes mellitus (T2DM in humans remains controversial. The current study aimed to examine the associations of plasma chromium levels with T2DM and pre-diabetes mellitus (pre-DM. We conducted a case-control study involving 1471 patients with newly diagnosed T2DM, 682 individuals with newly diagnosed pre-DM, and 2290 individuals with normal glucose tolerance in a Chinese population from 2009 to 2014. Plasma chromium was measured by inductively coupled plasma mass spectrometry. Plasma chromium levels were lower in the T2DM and pre-DM groups than in the control group (median: 3.68 μg/L, 3.61 μg/L, 3.97 μg/L, respectively, p < 0.001. After adjustment for potential confounding factors, the odds ratios (95% confidence interval for T2DM across increasing quartiles of plasma chromium levels were 1 (referent, 0.67 (0.55–0.83, 0.64 (0.51–0.79, and 0.58 (0.46–0.73, respectively (p for trend <0.001. The corresponding odds ratios (95% confidence interval for pre-DM were 1 (referent, 0.70 (0.54–0.91, 0.67 (0.52–0.88, and 0.58 (0.43–0.78, respectively (p for trend < 0.001. Our results indicated that plasma chromium concentrations were inversely associated with T2DM and pre-DM in Chinese adults.

  7. Inverse Association of Plasma Chromium Levels with Newly Diagnosed Type 2 Diabetes: A Case-Control Study

    Science.gov (United States)

    Chen, Sijing; Jin, Xiaoling; Shan, Zhilei; Li, Shuzhen; Yin, Jiawei; Sun, Taoping; Luo, Cheng; Yang, Wei; Yao, Ping; Yu, Kaifeng; Zhang, Yan; Cheng, Qian; Cheng, Jinquan; Bao, Wei; Liu, Liegang

    2017-01-01

    Chromium has long been known as an enhancer of insulin action. However, the role of chromium in the development of type 2 diabetes mellitus (T2DM) in humans remains controversial. The current study aimed to examine the associations of plasma chromium levels with T2DM and pre-diabetes mellitus (pre-DM). We conducted a case-control study involving 1471 patients with newly diagnosed T2DM, 682 individuals with newly diagnosed pre-DM, and 2290 individuals with normal glucose tolerance in a Chinese population from 2009 to 2014. Plasma chromium was measured by inductively coupled plasma mass spectrometry. Plasma chromium levels were lower in the T2DM and pre-DM groups than in the control group (median: 3.68 μg/L, 3.61 μg/L, 3.97 μg/L, respectively, p < 0.001). After adjustment for potential confounding factors, the odds ratios (95% confidence interval) for T2DM across increasing quartiles of plasma chromium levels were 1 (referent), 0.67 (0.55–0.83), 0.64 (0.51–0.79), and 0.58 (0.46–0.73), respectively (p for trend <0.001). The corresponding odds ratios (95% confidence interval) for pre-DM were 1 (referent), 0.70 (0.54–0.91), 0.67 (0.52–0.88), and 0.58 (0.43–0.78), respectively (p for trend < 0.001). Our results indicated that plasma chromium concentrations were inversely associated with T2DM and pre-DM in Chinese adults. PMID:28304331

  8. Synthesis of a new complex Chromium (Ⅲ) 2-mercaptonicotinate

    Institute of Scientific and Technical Information of China (English)

    LI Wei; HAO Er-jun; JIANG Yu-qin

    2004-01-01

    Chromium is an essential trace element for mammals[1-3].Diabetes is a chronic disease with major health consequence. Studies show that the occurrence of diabetes have great thing to do with the chromium deficient. Almost 40 years after the first report of glucose tolerance factor(GTF)[4]no conclusive evidence for an isolable ,biologically active form of chromium exited. Three materials have been proposed to be the biologically active form of chromium: "glucose tolerance factor", chromium Picolinate and low-molecular-weight chromium-binding substance (LWMCr)[5]So there is potential for the design of new chromium drugs[6].Chromium compounds have been used in medicine for centuries and there is potential for the design of new chromium drugs.2-Mercaptonicotinic acid(MN) displays the interesting biological activity. Chromium( Ⅲ )2-mercaptonicotinate is a common and effective biologically active form of Chromium. The test of biological activity indicated that may be useful in treating of diabetes. In this paper, we reported the The synthesis route is as follow:The structure of the complex has been characterized by IR, elemental analysis, MS,atomic absorption spectroscopy, X-ray powder diffraction and TG-DTA analysis.They indicate that the structure of Chromium 2-mercaptonicotinate.HPLC is used for determination of the purity. Studies show that the complex has a good biological activity for supplement tiny dietary chromium,lowering blood glucose levels, lowering serum lipid levels and increasing lean body mass.

  9. M 54 + Sagittarius = omega Centauri

    CERN Document Server

    Carretta, E; Gratton, R G; Lucatello, S; Bellazzini, M; Catanzaro, G; Leone, F; Momany, Y; Piotto, G; D'Orazi, V

    2010-01-01

    We derive homogeneous abundances of Fe, O, Na and alpha-elements from high resolution FLAMES spectra for 76 red giant stars in NGC 6715 (M 54) and for 25 red giants in the surrounding nucleus of the Sagittarius (Sgr) dwarf galaxy. Our main findings are that: (i) we confirm that M 54 shows intrinsic metallicity dispersion, ~0.19 dex r.m.s.; (ii) when the stars of the Sgr nucleus are included, the metallicity distribution strongly resembles that in omega Cen; the relative contribution of the most metal-rich stars is however different in these two objects; (iii) in both GCs there is a very extended Na-O anticorrelation, signature of different stellar generations born within the cluster, and (iv) the metal-poor and metal-rich components in M 54 (and omega Cen) show clearly distinct extension of the Na-O anticorrelation, the most heavily polluted stars being those of the metal-rich component. We propose a tentative scenario for cluster formation that could explain these features. Finally, similarities and differen...

  10. Evaluation of Beryllium, Total Chromium and Nickel in the Surface Contaminant Layer Available for Dermal Exposure After Abrasive Blasting in a Shipyard

    Science.gov (United States)

    2013-04-24

    8217f Ar~ Z.01 3 L TC Christopher Gellasch DEPARTMENT OF PREVENTfVE MEDICINE AND BIOMETRICS Committee Member Eleanor S. Metcalf. Ph.D., Associate...54 34. Lim JH, Kim HS, Park YM, Lee JY, Kim HO. 2010. A Case of Chromium Contact Dermatitis due to Exposure from a Golf Glove. Annals of

  11. Serum chromium levels in gestational diabetes mellitus

    Directory of Open Access Journals (Sweden)

    P G Sundararaman

    2012-01-01

    Full Text Available Objective: To measure serum chromium level in women with gestational diabetes mellitus (GDM from Chennai, South India. Materials and Methods: Thirty women with gestational diabetes, 60 age matched controls. Inclusion criteria: Gestational age 22-28 weeks, age group 20-35 years. Exclusion Criteria: Gestational age beyond 28 weeks, malnutrition or presence of infection. Serum chromium was measured using inductive couple plasma emission spectrometer. Results: Serum chromium levels of women with GDM, 1.59+/-0.02 ng/ml (range: 0.16-4.0 ng/ml were lower than in controls (4.58+/-0.62 ng/ml; range 0.82-5.33 ng/ml (P < 0.001. However, there were no significant differences among cases and controls when subdivided by parity. Conclusions: Women with GDM from a South Indian city had lower levels of serum chromium compared to pregnant women without GDM. Studies may be done whether chromium supplementation is useful in this group of women.

  12. Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Wachs, I.E.; Schoonheydt, R.A.

    1996-01-01

    Focuses on the surface chemistry and spectroscopy of chromium in inorganic oxides. Characterization of the molecular structures of chromium; Mechanics of hydrogenation-dehydrogenation reactions; Mobility and reactivity on oxidic surfaces.

  13. Residual Chromium in Leather by Instrumental Neutron Activation Analysis

    OpenAIRE

    S. Okoh; I. O. Okunade; D. J. Adeyemo; Ahmed, Y A; A. A. Audu; E. Amali

    2012-01-01

    Problem statement: Most tanning processes employ the use of chromium sulphate. For chromium tanned leather, finished products may contain high amount of residual chromium. This may pose some health hazards, since chromium is known to be toxic at elevated concentration. This justifies the need for the study. Approach: Various samples of leather were collected from a tannery, a leather crafts market, a leather dump site and from local tanners all in Kano, Nigeria in 2009. The samples were irrad...

  14. Hexavalent and trivalent chromium in leather: What should be done?

    Science.gov (United States)

    Moretto, Angelo

    2015-11-01

    Trivalent chromium compounds are used for leather tanning, and chromium may be released during use of leather goods. In certain instances, small amounts of hexavalent chromium can be formed and released. Both trivalent and hexavalent chromium can elicit allergic skin reaction in chromium sensitised subjects, the latter being significantly more potent. Induction of sensitisation only occurs after exposure to hexavalent chromium. A minority of subjects are sensitised to chromium, and in a fraction of these subjects allergic skin reaction have been described after wearing leather shoes or, less frequently, other leather goods. The evidence that in all these cases the reaction is related to hexavalent chromium is not always strong. The content of hexavalent chromium in leather is regulated in European Union, but rate of release rather than content is relevant for allergic skin reaction. The role of trivalent chromium appear much less relevant if at all. Modern tanning procedure do not pose significant risk due to either hexavalent or trivalent chromium. Dismissing bad quality and worn-off leather goods is relevant in reducing or eliminating the skin reaction. It should also be pointed out that shoe components or substances other than chromium in leather may cause allergic/irritative skin reactions.

  15. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  16. Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625), Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219), and Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N06650) Rod and Bar

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2014-01-01

    Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625), Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219), and Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N06650) Rod and Bar

  17. Studying chromium biosorption using arabica coffee leaves

    Directory of Open Access Journals (Sweden)

    Luis Carlos Florez García

    2010-05-01

    Full Text Available This work was aimed at providing an alternative for removing heavy metals such as chromium from waste water (effluent from the leather industry and galvanoplasty (coating with a thin layer of metal by electrochemical means, using coffee leaves as bio- mass. Using arabica coffee (Castle variety leaves led to 82% chromium removal efficiency for 1,000 mg/L synthetic dissolutions in 4 pH dissolution operating conditions, 0 rpm agitation, 0.149 mm diameter biomass particle size and 0.85 g/ml biomass / dissolution volume ratio.

  18. New mixed aluminium–chromium diarsenate

    Directory of Open Access Journals (Sweden)

    Mohamad Alem Bouhassine

    2017-03-01

    Full Text Available Potassium chromium aluminium diarsenate, KCr1/4Al3/4As2O7, was prepared by solid-state reaction. The structure consists of (Cr1/4/Al3/4O6 octahedra and As2O7 diarsenate groups sharing corners to build up a three-dimensional anionic framework. The potassium cations are located in wide channels running along the c-axis direction. The crystal structure is isostructural with the triclinic AIMIIIX2O7 (AI = alkali metal; MIII = Al, Cr, Fe; X = As, P compounds. However, the MIII octahedrally coordinated site is 25% partially occupied by chromium and 75% by aluminium.

  19. Strategies for chromium bioremediation of tannery effluent.

    Science.gov (United States)

    Garg, Satyendra Kumar; Tripathi, Manikant; Srinath, Thiruneelakantan

    2012-01-01

    Bioremediation offers the possibility of using living organisms (bacteria, fungi, algae,or plants), but primarily microorganisms, to degrade or remove environmental contaminants, and transform them into nontoxic or less-toxic forms. The major advantages of bioremediation over conventional physicochemical and biological treatment methods include low cost, good efficiency, minimization of chemicals, reduced quantity of secondary sludge, regeneration of cell biomass, and the possibility of recover-ing pollutant metals. Leather industries, which extensively employ chromium compounds in the tanning process, discharge spent-chromium-laden effluent into nearby water bodies. Worldwide, chromium is known to be one of the most common inorganic contaminants of groundwater at pollutant hazardous sites. Hexavalent chromium poses a health risk to all forms of life. Bioremediation of chromium extant in tannery waste involves different strategies that include biosorption, bioaccumulation,bioreduction, and immobilization of biomaterial(s). Biosorption is a nondirected physiochemical interaction that occurs between metal species and the cellular components of biological species. It is metabolism-dependent when living biomass is employed, and metabolism-independent in dead cell biomass. Dead cell biomass is much more effective than living cell biomass at biosorping heavy metals, including chromium. Bioaccumulation is a metabolically active process in living organisms that works through adsorption, intracellular accumulation, and bioprecipitation mechanisms. In bioreduction processes, microorganisms alter the oxidation/reduction state of toxic metals through direct or indirect biological and chemical process(es).Bioreduction of Cr6+ to Cr3+ not only decreases the chromium toxicity to living organisms, but also helps precipitate chromium at a neutral pH for further physical removal,thus offering promise as a bioremediation strategy. However, biosorption, bioaccumulation, and

  20. Chromium allergy and dermatitis: prevalence and main findings

    DEFF Research Database (Denmark)

    Bregnbak, David; Johansen, Jeanne D.; Jellesen, Morten Stendahl;

    2015-01-01

    The history of chromium as an allergen goes back more than a century, and includesan interventional success with national legislation that led to significant changes inthe epidemiology of chromium allergy in construction workers. The 2015 EU Leather Regulation once again put a focus on chromium...... allergy, emphasizing that the investigation of chromium allergy is still far from complete. Our review article on chromium focuses on the allergen’s chemical properties, its potential exposure sources, and the allergen’s interaction with the skin, and also provides an overview of the regulations...

  1. Pharmacokinetic Modeling of Trivalent and Hexavalent Chromium Based on Ingestion and Inhalation of Soluble Chromium Compounds.

    Science.gov (United States)

    1991-12-01

    be largely Cr(III) although some Cr(VI) exposure probably also occurs. Stainless-steel welders are exposed to nickel as well as to chromium compounds...welders are equivocal with respect to involvement of chromium, particularly since nickel in some chemical forms is an established lung carcinogen (Stern...microglobulin (Lindberg and Vesterberg, 1983), retinol-binding protein (Franchini and Mutti , 1988), B-glucuronidase ( Mutti et al., 1979), and kidney brush border

  2. Biological groundwater treatment for chromium removal at low hexavalent chromium concentrations.

    Science.gov (United States)

    Mamais, Daniel; Noutsopoulos, Constantinos; Kavallari, Ioanna; Nyktari, Eleni; Kaldis, Apostolos; Panousi, Eleni; Nikitopoulos, George; Antoniou, Kornilia; Nasioka, Maria

    2016-06-01

    The objective of this work is to develop and evaluate biological groundwater treatment systems that will achieve hexavalent chromium reduction and total chromium removal from groundwater at hexavalent chromium (Cr(VI)) groundwater concentrations in the 0-200 μg/L range. Three lab-scale units operated, as sequencing batch reactors (SBR) under aerobic, anaerobic and anaerobic-aerobic conditions. All systems received groundwater with a Cr(VI) content of 200 μg/L. In order to support biological growth, groundwater was supplemented with milk, liquid cheese whey or a mixture of sugar and milk to achieve a COD concentration of 200 mg/L. The results demonstrate that a fully anaerobic system or an anaerobic-aerobic system dosed with simple or complex external organic carbon sources can lead to practically complete Cr(VI) reduction to Cr(III). The temperature dependency of maximum Cr(VI) removal rates can be described by the Arrhenius relationship. Total chromium removal in the biological treatment systems was not complete because a significant portion of Cr(III) remained in solution. An integrated system comprising of an anaerobic SBR followed by a sand filter achieved more than 95% total chromium removal thus resulting in average effluent total and dissolved chromium concentrations of 7 μg/L and 3 μg/L, respectively.

  3. The electronic structure of antiferromagnetic chromium

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt

    1981-01-01

    The author has used the local spin density formalism to perform self-consistent calculations of the electronic structure of chromium in the non-magnetic and commensurate antiferromagnetic phases, as a function of the lattice parameter. A change of a few per cent in the atomic radius brings...

  4. A Kinetic Model of Chromium in a Flame

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Chromium has been identified as a carcinogenic metal.Incineration is the useful method for disposal of toxic chromium hazard waste and a chromium kinetic model in a flame is very important to study chromium oxidation.Chromium chemical kinetics over a range of temperatures of a hydrogen/air flame is proposed.Nine chromium compounds and fifty-eight reversible chemical reactions were considered The forward reaction rates are calculated based on the molecular collision approach for unknown ones and Arrhenius's Law for known ones.The backward reaction rates were calculated according to forward reaction rates, the equilibrium constants and chemical thermodynamics.It is verified by several equilibrium cases and is tested by a hydrogen/air diffusion flame.The results show that the kinetic model could be used in cases in which the chromium kinetics play an important role in a flame

  5. 7 CFR 906.54 - Effective time.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Effective time. 906.54 Section 906.54 Agriculture... RIO GRANDE VALLEY IN TEXAS Order Regulating Handling Miscellaneous Provisions § 906.54 Effective time. The provisions of this subpart, or any amendment thereto, shall become effective at such time as...

  6. 28 CFR 54.410 - Comparable facilities.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Comparable facilities. 54.410 Section 54... in Education Programs or Activities Prohibited § 54.410 Comparable facilities. A recipient may provide separate toilet, locker room, and shower facilities on the basis of sex, but such...

  7. 47 CFR 54.508 - Technology plans.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Technology plans. 54.508 Section 54.508... SERVICE Universal Service Support for Schools and Libraries § 54.508 Technology plans. (a) Contents. The technology plans referred to in this subpart must include the following five elements: (1) A clear...

  8. 31 CFR 103.54 - Disclosure.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Disclosure. 103.54 Section 103.54 Money and Finance: Treasury Regulations Relating to Money and Finance FINANCIAL RECORDKEEPING AND REPORTING OF CURRENCY AND FOREIGN TRANSACTIONS General Provisions § 103.54 Disclosure. All reports...

  9. 42 CFR 54.10 - Fiscal accountability.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Fiscal accountability. 54.10 Section 54.10 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS CHARITABLE CHOICE... PROJECTS FOR ASSISTANCE IN TRANSITION FROM HOMELESSNESS GRANTS § 54.10 Fiscal accountability. (a)...

  10. 42 CFR 54a.10 - Fiscal accountability.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Fiscal accountability. 54a.10 Section 54a.10 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS CHARITABLE CHOICE... PREVENTION AND TREATMENT SERVICES § 54a.10 Fiscal accountability. (a) Religious organizations that...

  11. 28 CFR 345.54 - Overtime compensation.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Overtime compensation. 345.54 Section 345.54 Judicial Administration FEDERAL PRISON INDUSTRIES, INC., DEPARTMENT OF JUSTICE FEDERAL PRISON INDUSTRIES (FPI) INMATE WORK PROGRAMS Inmate Pay and Benefits § 345.54 Overtime compensation. An...

  12. 45 CFR 86.54 - Compensation.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 1 2010-10-01 2010-10-01 false Compensation. 86.54 Section 86.54 Public Welfare... in Employment in Education Programs or Activities Prohibited § 86.54 Compensation. A recipient shall... of pay or other compensation; (b) Results in the payment of wages to employees of one sex at a...

  13. 7 CFR 15a.54 - Compensation.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 1 2010-01-01 2010-01-01 false Compensation. 15a.54 Section 15a.54 Agriculture Office... Activities Prohibited § 15a.54 Compensation. A recipient shall not make or enforce any policy or practice which, on the basis of sex: (a) Makes distinctions in rates of pay or other compensation; (b) Results...

  14. 45 CFR 1801.54 - Annual report.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Annual report. 1801.54 Section 1801.54 Public.... TRUMAN SCHOLARSHIP PROGRAM Payment Conditions and Procedures § 1801.54 Annual report. (a) Scholars with remaining eligibility for scholarship stipends must submit no later than July 15 an annual report to...

  15. 42 CFR 21.54 - Students.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Students. 21.54 Section 21.54 Public Health PUBLIC....54 Students. A potential candidate for appointment in the Regular Corps who is pursuing a course of... training for periods not to exceed 120 days during any fiscal year, and (b) those students who...

  16. 46 CFR 54.30-3 - Introduction.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Introduction. 54.30-3 Section 54.30-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS Mechanical Stress Relief § 54.30-3 Introduction. (a) Large conventional pressure vessels used to transport...

  17. 46 CFR 503.54 - Original classification.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 9 2010-10-01 2010-10-01 false Original classification. 503.54 Section 503.54 Shipping... Program § 503.54 Original classification. (a) No Commission Member or employee has the authority to... require classification, or receives any foreign government information as defined in section 1.1(d)...

  18. 40 CFR 30.54 - Quality assurance.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 1 2010-07-01 2010-07-01 false Quality assurance. 30.54 Section 30.54... NON-PROFIT ORGANIZATIONS Post-Award Requirements Reports and Records § 30.54 Quality assurance. If the... data generation, the grantee shall develop and implement quality assurance practices consisting...

  19. 32 CFR 54.5 - Responsibilities.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 1 2010-07-01 2010-07-01 false Responsibilities. 54.5 Section 54.5 National Defense Department of Defense OFFICE OF THE SECRETARY OF DEFENSE PERSONNEL, MILITARY AND CIVILIAN ALLOTMENTS FOR CHILD AND SPOUSAL SUPPORT § 54.5 Responsibilities. (a) The Assistant Secretary of...

  20. 7 CFR 1700.54 - Electric Program.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Electric Program. 1700.54 Section 1700.54 Agriculture... GENERAL INFORMATION Loan and Grant Approval Authorities § 1700.54 Electric Program. (a) Administrator: The... Administrator, Electric Program, has the authority to approve the following loans, loan guarantees, and...

  1. 7 CFR 54.1033 - Confidential treatment.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Confidential treatment. 54.1033 Section 54.1033 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... and Poultry Products § 54.1033 Confidential treatment. Every design review specialist...

  2. 7 CFR 989.54 - Marketing policy.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Marketing policy. 989.54 Section 989.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... CALIFORNIA Order Regulating Handling Marketing Policy § 989.54 Marketing policy. (a) Trade demand. On...

  3. 29 CFR 1918.54 - Rigging gear.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 7 2010-07-01 2010-07-01 false Rigging gear. 1918.54 Section 1918.54 Labor Regulations...) SAFETY AND HEALTH REGULATIONS FOR LONGSHORING Vessel's Cargo Handling Gear § 1918.54 Rigging gear. (a... other alternate device shall be provided to allow trimming of the gear and to prevent employees...

  4. 47 CFR 54.207 - Service areas.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Service areas. 54.207 Section 54.207... SERVICE Carriers Eligible for Universal Service Support § 54.207 Service areas. (a) The term service area means a geographic area established by a state commission for the purpose of determining...

  5. 27 CFR 7.54 - Prohibited statements.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Prohibited statements. 7.54 Section 7.54 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU... § 7.54 Prohibited statements. (a) General prohibition. An advertisement of malt beverages must...

  6. 41 CFR 105-54.301 - Meetings.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Meetings. 105-54.301... COMMITTEE MANAGEMENT 54.3-Advisory Committee Procedures § 105-54.301 Meetings. (a) Each GSA advisory committee meeting is open to the public unless the Administrator decides otherwise; (b) Each meeting is...

  7. 40 CFR 205.54 - Test procedures.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Test procedures. 205.54 Section 205.54 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) NOISE ABATEMENT PROGRAMS TRANSPORTATION EQUIPMENT NOISE EMISSION CONTROLS Medium and Heavy Trucks § 205.54 Test procedures. The procedures...

  8. 7 CFR 51.54 - Plant survey.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Plant survey. 51.54 Section 51.54 Agriculture... Requirements for Plants Operating Under Continuous Inspection on A Contract Basis § 51.54 Plant survey. Prior..., the Administrator will make or cause to be made a survey and inspection where such service is to...

  9. 28 CFR 54.540 - Advertising.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Advertising. 54.540 Section 54.540... in Employment in Education Programs or Activities Prohibited § 54.540 Advertising. A recipient shall not in any advertising related to employment indicate preference, limitation, specification,...

  10. 40 CFR 68.54 - Training.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 15 2010-07-01 2010-07-01 false Training. 68.54 Section 68.54... ACCIDENT PREVENTION PROVISIONS Program 2 Prevention Program § 68.54 Training. (a) The owner or operator... covered process have been trained or tested competent in the operating procedures provided in § 68.52...

  11. 77 FR 6627 - National Emission Standards for Hazardous Air Pollutant Emissions: Hard and Decorative Chromium...

    Science.gov (United States)

    2012-02-08

    ... aluminum to provide resistance to corrosion. The chromium anodizing process is used to coat aircraft parts... Hazardous Air Pollutant Emissions: Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks... Pollutant Emissions: Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks; and...

  12. CHROMIUM INDUCED CYTOTOXICITY IN BLACKGRAM (VIGNA MUNGO L.

    Directory of Open Access Journals (Sweden)

    A. Chidambaram ، P. Sundaramoorthy ، A. Murugan ، K. Sankar Ganesh ، L. Baskaran

    2009-01-01

    Full Text Available Chromium is known to be highly toxic to biological systems. This study was designed to determine the mutagenic effects of different concentrations (0, 10, 25, 50, 100 and 200 mg/L of hexavalent chromium on root tip cells of blackgram (Vigna mungo L. Hepper. The blackgram seeds were equi-spacially arranged in sterilized petriplates lined with filter paper and they were treated with different concentrations of chromium solution. In germination studies, the morphological growth parameters such as germination percentage, root length, shoot length fresh weight and dry weight of blackgram seedlings were decreased with increasing dose of chromium concentrations. No germination of blackgram seeds was recorded at 300mg/l chromium concentration. Chromosome aberration assay was used to determine the mitotic indices and rate of chromosome aberration in blackgram root tip cells due to chromium treatment. The results showed that the mitotic indices were complicated due to different concentrations of chromium. However, the increase in chromium concentration has led to a gradual increase in the percentage of chromosomal aberration and mitotic index. The chromosome length, absolute chromosome length and average chromosome lengths were gradually found to decrease. There was no considerable change in 2n number of chromosome with the increase in chromium concentrations. It is concluded that the hexavalent chromium has significant mutagenic effect on the root tip cells of blackgram.

  13. Femtosecond laser surface structuring and oxidation of chromium thin coatings: Black chromium

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Mthunzi, P. [National Laser Centre, Council for Scientific and Industrial Research, 0001 Pretoria (South Africa); Muller, T.F.G. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Julies, B. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Manikandan, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Ramponi, R. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa)

    2014-12-01

    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr{sub 2}O{sub 3} layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr{sub 2}O{sub 3} layer. The α-Cr{sub 2}O{sub 3} layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%.

  14. Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather.

    Science.gov (United States)

    Dettmer, Aline; Nunes, Keila Guerra Pacheco; Gutterres, Mariliz; Marcílio, Nilson Romeu

    2010-04-15

    Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept.

  15. Interactions of chromium with microorganisms and plants.

    Science.gov (United States)

    Cervantes, C; Campos-García, J; Devars, S; Gutiérrez-Corona, F; Loza-Tavera, H; Torres-Guzmán, J C; Moreno-Sánchez, R

    2001-05-01

    Chromium is a highly toxic non-essential metal for microorganisms and plants. Due to its widespread industrial use, chromium (Cr) has become a serious pollutant in diverse environmental settings. The hexavalent form of the metal, Cr(VI), is considered a more toxic species than the relatively innocuous and less mobile Cr(III) form. The presence of Cr in the environment has selected microbial and plant variants able to tolerate high levels of Cr compounds. The diverse Cr-resistance mechanisms displayed by microorganisms, and probably by plants, include biosorption, diminished accumulation, precipitation, reduction of Cr(VI) to Cr(III), and chromate efflux. Some of these systems have been proposed as potential biotechnological tools for the bioremediation of Cr pollution. In this review we summarize the interactions of bacteria, algae, fungi and plants with Cr and its compounds.

  16. Effect of polyethylene glycol on electrochemically deposited trivalent chromium layers

    Institute of Scientific and Technical Information of China (English)

    Joo-Yul LEE; Man KIM; Sik-Chol KWON

    2009-01-01

    The structural characteristics of the trivalent chromium deposits and their interfacial behavior in the plating solution with and without polyethylene glycol molecules were observed by using various electrochemical methods such as cyclic voltammetry, open circuit potential transition, electrochemical impedance spectroscopy, scanning electron microscopy and X-ray photoelectron spectrometry. It is shown that the polyethylene glycol molecules make the reductive current density lower in the trivalent chromium plating system and promote a hydrogen evolution reaction through their adsorption on the electrode surface. And the trivalent chromium layer formed from the polyethylene glycol-containing solution has somewhat higher density of cracks on its surface and results in a lower film resistance, lower polarization resistance, and higher capacitance in a corrosive atmosphere. It is also revealed that the formation of chromium carbide layer is facilitated in the presence of polyethylene glycol, which means easier electrochemical codeposition of chromium and carbon, not single chromium deposition.

  17. Speciation and recovery of chromium from chromite ore processing residues.

    Science.gov (United States)

    Sreeram, K J; Ramasami, T

    2001-10-01

    The processing of chromite ore is associated with the generation of large quantities of solid wastes containing chromium, which have been disposed of as landfill for many years. The mobilization and operational speciation of chromium contained in soils contaminated with metal salts are important in terms of the environment. Several methods have been employed for the extraction and recovery of solid wastes. Chromium contained in contaminated soils and solid wastes can be categorized as exchangeable, oxidizable, carbonate-bound, reducible and residual. The results from this study indicate a need for efficient leaching methodologies in chromite ore processing plants to decrease the non-detrital fractions of chromium in the residue. Aggressive methodologies are required to recover chromium from the detrital fractions. The potential benefits of employing sodium peroxide for the complete recovery of chromium from chromite residue have been demonstrated, and the need to ensure the safety of the process has been emphasized.

  18. Chromium Toxicity: Reductive Enzymes in Humans.

    Science.gov (United States)

    2007-11-02

    internal organs (e.g. lungs, liver, kidneys) [24,27,64], pulmonary fibrosis and chronic bronchitis [2], skin ulcers and allergic dermatitis [2], and...cross the skin [2] and are readily transported across cell membranes [18] via an anion carrier [6]. Cr compounds are also mutagenic [67], and the bulk of...reduced nicotinamide adenine dinucleotide phosphate-cytochrome P450 oxidoreductase- dependent chromium(VI) reduction. Analyst 120:935-938. 42. Miura, A

  19. Dimensionally Controlled Lithiation of Chromium Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Fister, Tim T. [Argonne National Lab. (ANL), Argonne, IL (United States); Hu, Xianyi [Northwestern Univ., Evanston, IL (United States); Esbenshade, Jennifer [Univ. of Illinois, Urbana-Champaign, IL (United States); Chen, Xiao [Northwestern Univ., Evanston, IL (United States); Wu, Jinsong [Northwestern Univ., Evanston, IL (United States); Dravid, Vinayak [Northwestern Univ., Evanston, IL (United States); Bedzyk, Michael [Northwestern Univ., Evanston, IL (United States); Long, Brandon [Argonne National Lab. (ANL), Argonne, IL (United States); Gewirth, Andrew A. [Univ. of Illinois, Urbana-Champaign, IL (United States); Shi, Bing [Argonne National Lab. (ANL), Argonne, IL (United States); Schlepütz, Christian M. [Argonne National Lab. (ANL), Argonne, IL (United States); Fenter, Paul [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-01-12

    Oxide conversion reactions are an alternative approach for high capacity lithium ion batteries but are known to suffer from structural irreversibility associated with the phase separation and reconstitution of reduced metal species and Li2O. In particular, the morphology of the reduced metal species is thought to play a critical role in the electrochemical properties of a conversion material. Here we use a model electrode with alternating layers of chromium and chromium oxide to better understand and control these phase changes in real-time and at molecular length scales. Despite lacking crystallinity at the atomic scale, this superstructure is observed (with X-ray reflectivity, XR) to lithiate and delithiate in a purely one-dimensional manner, preserving the layered structure. The XR data show that the metal layers act as nucleation sites for the reduction of chromium in the conversion reaction. Irreversibility during delithiation is due to the formation of a ternary phase, LiCrO2, which can be further delithiated at higher potentials. The results reveal that the combination of confining lithiation to nanoscale sheets of Li2O and the availability of reaction sites in the metal layers in the layered structure is a strategy for improving the reversibility and mass transport properties that can be used in a wide range of conversion materials.

  20. Processes affecting the remediation of chromium-contaminated sites.

    OpenAIRE

    Palmer, C.D.; Wittbrodt, P R

    1991-01-01

    The remediation of chromium-contaminated sites requires knowledge of the processes that control the migration and transformation of chromium. Advection, dispersion, and diffusion are physical processes affecting the rate at which contaminants can migrate in the subsurface. Heterogeneity is an important factor that affects the contribution of each of these mechanisms to the migration of chromium-laden waters. Redox reactions, chemical speciation, adsorption/desorption phenomena, and precipitat...

  1. New technology for comprehensive utilization of aluminum-chromium residue from chromium salts production

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-bin; QI Tian-gui; JIANG Xin-min; ZHOU Qiu-sheng; LIU Gui-hua; PENG Zhi-hong; HAN Deng-lun; ZHANG Zhong-yuan; YANG Kun-shan

    2008-01-01

    Colloidal aluminum-chromium residue(ACR) was mass-produced in chromate production process, and the large energy consumption and high recovery cost existed in traditional methods of utilizing such ACR. To overcome those problems, a new comprehensive method was proposed to deal with the ACR, and was proven valid in industry. In the new process, the chromate was separated firstly from the colloidal ACR by ripening and washing with additives, by which more than 95% hexavalent chromium was recovered. The chromium-free aluminum residue(CFAR), after properly dispersed, was digested at 120-130 ℃ and more than 90% alumina can be recovered. And then the pregnant aluminate solution obtained from digestion was seeded to precipitate aluminum hydroxide. This new method can successfully recover both alumina and sodium chromate, and thus realize the comprehensive utilization of ACR from chromate industry.

  2. Stabilization and solidification of chromium-contaminated soil

    Energy Technology Data Exchange (ETDEWEB)

    Cherne, C.A.; Thomson, B.M. [Univ. of New Mexico, Albuquerque, NM (United States). Civil Engineering Dept.; Conway, R. [Sandia National Labs., Albuquerque, NM (United States)

    1997-11-01

    Chromium-contaminated soil is a common environmental problem in the United States as a result of numerous industrial processes involving chromium. Hexavalent chromium [Cr(VI)] is the species of most concern because of its toxicity and mobility in groundwater. One method of diminishing the environmental impact of chromium is to reduce it to a trivalent oxidation state [Cr(III)], in which it is relatively insoluble and nontoxic. This study investigated a stabilization and solidification process to minimize the chromium concentration in the Toxicity Characteristic Leaching Procedure (TCLP) extract and to produce a solidified waste form with a compressive strength in the range of 150 to 300 pounds per square inch (psi). To minimize the chromium in the TCLP extract, the chromium had to be reduced to the trivalent oxidation state. The average used in this study was an alluvium contaminated with chromic and sulfuric acid solutions. The chromium concentration in the in the in situ soil was 1212 milligrams per kilogram (mg/kg) total chromium and 275 mg/kg Cr(VI). The effectiveness of iron, ferrous sulfate to reduce Cr(VI) was tested in batch experiments.

  3. Tribological Characteristics of Chromium-active Carbon Electroplated Composite Coatings

    Institute of Scientific and Technical Information of China (English)

    GUKa-fi; HUAMeng; Yi-min

    2004-01-01

    A process of chromium electroplating using a standard bath with additives and active carbon particles was reported, and the tribological behaviors of the composite coatings using the pin-on-disk tester and the table wear tester were i nvestig(aed. Experimental results indicate that the electroplated chromium-active carbon composite coatings exhibited the low friction coefficient anti excellent anti-wear properties whets coffered with the normal chromium electroplated ones. The formation of active carbon particles within the chromium matrices can be explained by SEM analysis and the mechanis of wear resistance of the composite coatings were studied.

  4. REINFORCEMENT OF NICKEL CHROMIUM ALLOYS WITH SAPPHIRE WHISKERS.

    Science.gov (United States)

    SAPPHIRE, COMPOSITE MATERIALS, CERAMIC FIBERS , CERAMIC FIBERS , TITANIUM COMPOUNDS, ZIRCONIUM COMPOUNDS, HYDRIDES, ADDITIVES, CHROMIUM ALLOYS, FIBER METALLURGY, IRON COMPOUNDS, ENCAPSULATION, DENSITY, SURFACE TENSION.

  5. Chromium recycling of tannery waste through microbial fermentation.

    Science.gov (United States)

    Katsifas, E A; Giannoutsou, E; Lambraki, M; Barla, M; Karagouni, A D

    2004-02-01

    An Aspergillus carbonarius isolate, selected from an established microbial culture collection, was used to study the biodegradation of chromium shavings in solid-state fermentation experiments. Approximately 97% liquefaction of the tannery waste was achieved and the liquid obtained from long-term experiments was used to recover chromium. The resulting alkaline chromium sulfate solution was useful in tanning procedures. A proteinaceous liquid was also obtained which has potential applications as a fertilizer or animal feed additive and has several other industrial uses. The A. carbonarius strain proved to be a very useful tool in tannery waste-treatment processes and chromium recovery in the tanning industries.

  6. Influence of Chelating Agents on Chromium Fate in Sediment

    Institute of Scientific and Technical Information of China (English)

    WANGXIAOCHANG; SUNJINHE; 等

    1996-01-01

    A laboratory investigation on reaction between chelating agents and chromium was conducted to evaluate the effect of chelating agents on the adsorption and desorption of chromium in sediment.The amount of adsorbed chromium(VI) in sediment decreased slightly by 5%-10% because of addition of chelating agents.Chelating agents inhibited the removal of Cr(Ⅲ)by sediment from solutions and the inhibiting effect was in the order:citric acid>tartaric acid>EDTA,Salicylic acid.No effect of chelating agents on desorption of chromium in sediment was observed.

  7. 38 CFR 3.54 - Marriage dates.

    Science.gov (United States)

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Marriage dates. 3.54..., Compensation, and Dependency and Indemnity Compensation Relationship § 3.54 Marriage dates. A surviving spouse may qualify for pension, compensation, or dependency and indemnity compensation if the marriage to...

  8. 7 CFR 932.54 - Transfers.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Transfers. 932.54 Section 932.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... § 932.51(a)(3) may be transferred along with the olives, in which event the receiving handler...

  9. 34 CFR 106.54 - Compensation.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Compensation. 106.54 Section 106.54 Education... Compensation. A recipient shall not make or enforce any policy or practice which, on the basis of sex: (a) Makes distinctions in rates of pay or other compensation; (b) Results in the payment of wages...

  10. 40 CFR 61.54 - Sludge sampling.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 8 2010-07-01 2010-07-01 false Sludge sampling. 61.54 Section 61.54... sampling. (a) As an alternative means for demonstrating compliance with § 61.52(b), an owner or operator... days prior to a sludge sampling test, so that he may at his option observe the test. (c) Sludge...

  11. 28 CFR 54.500 - Employment.

    Science.gov (United States)

    2010-07-01

    ... in Employment in Education Programs or Activities Prohibited § 54.500 Employment. (a) General. (1) No... Federal financial assistance. (2) A recipient shall make all employment decisions in any education program... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Employment. 54.500 Section...

  12. 28 CFR 54.505 - Employment criteria.

    Science.gov (United States)

    2010-07-01

    ... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Discrimination on the Basis of Sex in Employment in Education Programs or Activities Prohibited § 54.505 Employment criteria. A... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Employment criteria. 54.505 Section...

  13. 28 CFR 54.525 - Fringe benefits.

    Science.gov (United States)

    2010-07-01

    ... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Discrimination on the Basis of Sex in Employment in Education Programs or Activities Prohibited § 54.525 Fringe benefits. (a) “Fringe..., leave, and any other benefit or service of employment not subject to the provision of § 54.515....

  14. 32 CFR 651.54 - Introduction.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 4 2010-07-01 2010-07-01 true Introduction. 651.54 Section 651.54 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY (CONTINUED) ENVIRONMENTAL QUALITY... Introduction. (a) Protection of the environment is an Army priority, no matter where the Army actions...

  15. 15 CFR 923.54 - Mediation.

    Science.gov (United States)

    2010-01-01

    ... 15 Commerce and Foreign Trade 3 2010-01-01 2010-01-01 false Mediation. 923.54 Section 923.54... Mediation. (a) Section 307(h) of the Act provides for mediation of serious disagreement between any Federal... cases, mediation by the Secretary, with the assistance of the Executive Office of the President, may...

  16. 9 CFR 3.54 - Feeding.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Feeding. 3.54 Section 3.54 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE ANIMAL WELFARE STANDARDS Specifications for the Humane Handling, Care, Treatment and Transportation of Rabbits...

  17. Diffusion of hexavalent chromium in chromium-containing slag as affected by microbial detoxification.

    Science.gov (United States)

    Wang, Yunyan; Yang, Zhihui; Chai, Liyuan; Zhao, Kun

    2009-09-30

    An electrochemical method was used to determine the diffusion coefficient of chromium(VI) in chromium-containing slag. A slag plate was prepared from the original slag or the detoxified slag by Achromobacter sp. CH-1. The results revealed that the apparent diffusion coefficient of Cr(VI) was 4.4 x 10(-9)m(2)s(-1) in original slag and 2.62 x 10(-8)m(2)s(-1) in detoxified slag. The results implied that detoxification of chromium-containing slag by Achromobacter sp. CH-1 could enhance Cr(VI) release. Meanwhile, the results of laboratory experiment showed that the residual total Cr(VI) in slag decreased from an initial value of 6.8 mg g(-1) to 0.338 mg g(-1) at the end of the detoxification process. The Cr(VI) released from slag was also reduced by Achromobacter sp. CH-1 strain since water soluble Cr(VI) in the leachate was not detected after 4 days. Therefore, Achromobacter sp. CH-1 has potential application for the bio-detoxification of chromium-containing slag.

  18. ALUMINUM AND CHROMIUM LEACHING WORKSHOP WHITEPAPER

    Energy Technology Data Exchange (ETDEWEB)

    McCabe, D; Jeff Pike, J; Bill Wilmarth, B

    2007-04-25

    A workshop was held on January 23-24, 2007 to discuss the status of processes to leach constituents from High Level Waste (HLW) sludges at the Hanford and Savannah River Sites. The objective of the workshop was to examine the needs and requirements for the HLW flowsheet for each site, discuss the status of knowledge of the leaching processes, communicate the research plans, and identify opportunities for synergy to address knowledge gaps. The purpose of leaching of non-radioactive constituents from the sludge waste is to reduce the burden of material that must be vitrified in the HLW melter systems, resulting in reduced HLW glass waste volume, reduced disposal costs, shorter process schedules, and higher facility throughput rates. The leaching process is estimated to reduce the operating life cycle of SRS by seven years and decrease the number of HLW canisters to be disposed in the Repository by 1000 [Gillam et al., 2006]. Comparably at Hanford, the aluminum and chromium leaching processes are estimated to reduce the operating life cycle of the Waste Treatment Plant by 20 years and decrease the number of canisters to the Repository by 15,000-30,000 [Gilbert, 2007]. These leaching processes will save the Department of Energy (DOE) billions of dollars in clean up and disposal costs. The primary constituents targeted for removal by leaching are aluminum and chromium. It is desirable to have some aluminum in glass to improve its durability; however, too much aluminum can increase the sludge viscosity, glass viscosity, and reduce overall process throughput. Chromium leaching is necessary to prevent formation of crystalline compounds in the glass, but is only needed at Hanford because of differences in the sludge waste chemistry at the two sites. Improving glass formulations to increase tolerance of aluminum and chromium is another approach to decrease HLW glass volume. It is likely that an optimum condition can be found by both performing leaching and improving

  19. Safety, absorption, and antioxidant effects of chromium histidine

    Science.gov (United States)

    Supplemental chromium has been shown to be involved in the alleviation of the metabolic syndrome, glucose intolerance, polycystic ovary syndrome, depression, excess body fat, and gestational, steroid-induced, and type 2 diabetes. Chromium amino acid complexes that contained histidine displayed cons...

  20. Mechanisms of bacterial resistance to chromium compounds.

    Science.gov (United States)

    Ramírez-Díaz, Martha I; Díaz-Pérez, César; Vargas, Eréndira; Riveros-Rosas, Héctor; Campos-García, Jesús; Cervantes, Carlos

    2008-06-01

    Chromium is a non-essential and well-known toxic metal for microorganisms and plants. The widespread industrial use of this heavy metal has caused it to be considered as a serious environmental pollutant. Chromium exists in nature as two main species, the trivalent form, Cr(III), which is relatively innocuous, and the hexavalent form, Cr(VI), considered a more toxic species. At the intracellular level, however, Cr(III) seems to be responsible for most toxic effects of chromium. Cr(VI) is usually present as the oxyanion chromate. Inhibition of sulfate membrane transport and oxidative damage to biomolecules are associated with the toxic effects of chromate in bacteria. Several bacterial mechanisms of resistance to chromate have been reported. The best characterized mechanisms comprise efflux of chromate ions from the cell cytoplasm and reduction of Cr(VI) to Cr(III). Chromate efflux by the ChrA transporter has been established in Pseudomonas aeruginosa and Cupriavidus metallidurans (formerly Alcaligenes eutrophus) and consists of an energy-dependent process driven by the membrane potential. The CHR protein family, which includes putative ChrA orthologs, currently contains about 135 sequences from all three domains of life. Chromate reduction is carried out by chromate reductases from diverse bacterial species generating Cr(III) that may be detoxified by other mechanisms. Most characterized enzymes belong to the widespread NAD(P)H-dependent flavoprotein family of reductases. Several examples of bacterial systems protecting from the oxidative stress caused by chromate have been described. Other mechanisms of bacterial resistance to chromate involve the expression of components of the machinery for repair of DNA damage, and systems related to the homeostasis of iron and sulfur.

  1. Observational Approach to Chromium Site Remediation - 13266

    Energy Technology Data Exchange (ETDEWEB)

    Scott Myers, R. [Washington Closure Hanford, 2620 Fermi, Richland, Washington 99354 (United States)

    2013-07-01

    Production reactors at the U.S. Department of Energy's (DOE) Hanford Site in Richland, Washington, required massive quantities of water for reactor cooling and material processing. To reduce corrosion and the build-up of scale in pipelines and cooling systems, sodium dichromate was added to the water feedstock. Spills and other releases at the makeup facilities, as well as leaks from miles of pipelines, have led to numerous areas with chromium-contaminated soil and groundwater, threatening fish populations in the nearby Columbia River. Pump-and-treat systems have been installed to remove chromium from the groundwater, but significant contamination remain in the soil column and poses a continuing threat to groundwater and the Columbia River. Washington Closure Hanford, DOE, and regulators are working on a team approach that implements the observational approach, a strategy for effectively dealing with the uncertainties inherent in subsurface conditions. Remediation of large, complex waste sites at a federal facility is a daunting effort. It is particularly difficult to perform the work in an environment of rapid response to changing field and contamination conditions. The observational approach, developed by geotechnical engineers to accommodate the inherent uncertainties in subsurface conditions, is a powerful and appropriate method for site remediation. It offers a structured means of quickly moving into full remediation and responding to the variations and changing conditions inherent in waste site cleanups. A number of significant factors, however, complicate the application of the observational approach for chromium site remediation. Conceptual models of contamination and site conditions are difficult to establish and get consensus on. Mid-stream revisions to the design of large excavations are time-consuming and costly. And regulatory constraints and contract performance incentives can be impediments to the flexible responses required under the

  2. Atom Lithography with a Chromium Atomic Beam

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wen-Tao; LI Tong-Bao

    2006-01-01

    @@ Direct write atom lithography is a new technique in which resonant light is used to pattern an atomic beam and the nanostructures are formed when the atoms deposit on the substrate. We design an experiment setup to fabricate chromium nanolines by depositing an atomic beam of 52 Cr through an off-resonant laser standing wave with the wavelength of 425.55 nm onto a silicon substrate. The resulting nanolines exhibit a period of 215 ± 3 nm with height of 1 nm.

  3. The fate of chromium during tropical weathering

    DEFF Research Database (Denmark)

    Berger, Alfons; Frei, Robert

    2014-01-01

    We performed a mineral, geochemical and Cr–Sr–Pb isotope study on a laterite profile developed on ca. 540 Ma old tonalitic bedrock in Madagascar with special emphasis on the behavior of chromium during tropical weathering. The observed strong depletions of Ca, Si, and P, and enrichment of Fe and Al......, in the soil, relative to bedrock and underlying saprolite, are the characteristic features pertinent to laterites. The enrichment of Fe in topsoil horizon can be correlated with enrichment of P, and the redox sensitive elements Mn and Cr, and indicates redistribution of these elements related to oxidation...

  4. Bioleaching of chromium from tannery sludge by indigenous Acidithiobacillus thiooxidans.

    Science.gov (United States)

    Wang, Yuan-Shan; Pan, Zhi-Yan; Lang, Jian-Min; Xu, Jian-Miao; Zheng, Yu-Guo

    2007-08-17

    Chromium in tannery sludge will cause serious environmental problems and is toxic to organisms. The acidophilic sulfur-oxidizing Acidithiobacillus thiooxidans can leach heavy metals form urban and industrial wastes. This study examined the ability of an indigenous sulfur-oxidizing A. thiooxidans to leach chromium from tannery sludge. The results showed that the pH of sludge mixture inoculated with the indigenous A. thiooxidans decreased to around 2.0 after 4 days. After 6 days incubation in shaking flasks at 30 degrees C and 160 rpm, up to 99% of chromium was solubilized from tannery sludge. When treated in a 2-l bubble column bioreactor for 5 days at 30 degrees C and aeration of 0.5 vvm, 99.7% of chromium was leached from tannery sludge. The results demonstrated that chromium in tannery sludge can be efficiently leached by the indigenous A. thiooxidans.

  5. The Theory for the Mechanism of Chromium Plating: The Theory for the Physical Characteristics of Chromium Plate

    Science.gov (United States)

    1947-01-01

    deposits arc pro- duced as the coll potential is successively raised. The sulfato ion "hus has an extremely important effect in the chromium plating...and sulfato iDU in the bath wore then used in an attempt to obtain more satisfactory hexagonal chromium deposits. The data obtained are summarUod

  6. Dissolution of chromium in sulfuric acid

    Directory of Open Access Journals (Sweden)

    J. P. POPIC

    2002-11-01

    Full Text Available By combining electrochemical corrosion rate measurements and spectrophotometric analysis of the electrolyte it was shown that at room temperature chromium dissolves in deaerated 0.1 M Na2SO4 + H2SO4 (pH 1 solution as Cr(II and Cr(III ions in he ratio Cr(II : Cr(III @ 7 : 1. This process was stable over 4 h without any detectable change. The total corrosion rate of chromium calculated from the analytical data is about 12 times higher, than that determined electrochemically by cathodic Tafel line extrapolation to the corrosion potential. This finding was confirmed by applying the weight-loss method for the determination of the corrosion rate. This enormous difference between these experimentally determined corrosion rates can be explained by the rather fast, “anomalous” dissolution process proposed by Kolotyrkin and coworkers (chemical reaction of Cr with H2O molecules occurring simultaneously with the electrochemical corrosion process.

  7. 28 CFR 54.515 - Compensation.

    Science.gov (United States)

    2010-07-01

    ... EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Discrimination on the Basis of Sex in Employment in Education Programs or Activities Prohibited § 54.515 Compensation. A recipient...

  8. 47 CFR 54.516 - Auditing.

    Science.gov (United States)

    2010-10-01

    ... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) UNIVERSAL SERVICE Universal Service Support for Schools and Libraries § 54.516 Auditing. (a) Recordkeeping..., state or federal agency with jurisdiction over the entity. (c) Audits. Schools, libraries, and...

  9. Electrochemical modification of chromium surfaces using 4-nitro- and4-fluorobenzenediazonium salts

    DEFF Research Database (Denmark)

    Hinge, Mogens; Cecatto, Marcel; Kingshott, Peter;

    2009-01-01

    Chromium surfaces can be electrografted with organic surface films using 4-nitro- or 4-fluorobenzenediazonium salts, despite the fact that the surfaces are covered with a protective chromium oxide layer......Chromium surfaces can be electrografted with organic surface films using 4-nitro- or 4-fluorobenzenediazonium salts, despite the fact that the surfaces are covered with a protective chromium oxide layer...

  10. Standard Specification for Pressure Consolidated Powder Metallurgy Iron-Nickel-Chromium-Molybdenum (UNS N08367), Nickel-Chromium-Molybdenum-Columbium (Nb) (UNS N06625), Nickel-Chromium-Iron Alloys (UNS N06600 and N06690), and Nickel-Chromium-Iron-Columbium-Molybdenum (UNS N07718) Alloy Pipe Flanges, Fittings, Valves, and Parts

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Pressure Consolidated Powder Metallurgy Iron-Nickel-Chromium-Molybdenum (UNS N08367), Nickel-Chromium-Molybdenum-Columbium (Nb) (UNS N06625), Nickel-Chromium-Iron Alloys (UNS N06600 and N06690), and Nickel-Chromium-Iron-Columbium-Molybdenum (UNS N07718) Alloy Pipe Flanges, Fittings, Valves, and Parts

  11. Workshop on effects of chromium coating on Nb{sub 3}Sn superconductor strand: Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    1994-04-12

    This report discusses the following topics: Chromium coating on superconductor strand -- an overview; technology of chromium plating; comparison of wires plated by different platers; search for chromium in copper; strand manufactures` presentations; chromium plating at the Lawrence Livermore National Laboratory; a first look at a chromium plating process development project tailored for T.P.X. and I.T.E.R. strand; and influence of chromium diffusion and related phenomena on the reference ratios of bare and chromium plated Nb{sub 3}Sn strand.

  12. Bioavailability of a potato chromium complex to the laboratory rat

    Energy Technology Data Exchange (ETDEWEB)

    Gilbert, H.K.

    1985-01-01

    Research objectives were to study the effect of food source, preparation method and chemical form on bioavailability of chromium. Chromium concentration in potatoes was determined and tubers labeled either intrinsically or extrinsically with radioactive chromate. A labeled chromium complexes was isolated from preparations of raw, baked or fried potatoes and chromatographed on gel permeation media. Availability of the potato chromium complex to the rat was examined in three feeding studies. Animals were dosed with radioactive extrinsically or intrinsically labeled potato extract or with chromate. A labeled chromium complex was isolated from gastrointestinal contents of rats and chromatographed. Potato pulp and peel contained 1.63 and 2.70 ..mu..g Cr/g tissue respectively. True and apparent absorption from extrinsically labeled feedings were 33.4 +/- 4.7 and 29.8 +/- 11.2% respectively, and no differences existed between absorption from raw and cooked potatoes. Absorption from the extrinsic labeled potatoes differed significantly from absorption of inorganic chromatium. Apparent absorption of raw (11.1 +/- 7.9%) and cooked (-0.7 +/- 2.8%) intrinsically labeled feedings differed significantly. Absorption of inorganic chromium was 17.8% (true) and 11.5% (apparent). Examination of the chromium complex isolated from gastrointestinal tract contents showed enlargement of the complex in the stomach after consumption.

  13. Chromium Content in the Human Hip Joint Tissues

    Institute of Scientific and Technical Information of China (English)

    Barbara Brodziak-Dopiera; Jerzy Kwapuliski; Krzysztof Sobczyk; Danuta Wiechua

    2015-01-01

    Objective Chromium has many important functions in the human body. For the osseous tissue, its role has not been clearly defined. This study was aimed at determining chromium content in hip joint tissues. Methods A total of 91 hip joint samples were taken in this study, including 66 from females and 25 from males. The sample tissues were separated according to their anatomical parts. The chromium content was determined by the AAS method. The statistical analysis was performed with U Mann-Whitney's non-parametric test, P≤0.05. Results The overall chromium content in tissues of the hip joint in the study subjects was as follows:5.73 µg/g in the articular cartilage, 5.33 µg/g in the cortical bone, 17.86 µg/g in the cancellous bone, 5.95 µg/g in the fragment of the cancellous bone from the intertrochanteric region, and 1.28 µg/g in the joint capsule. The chromium contents were observed in 2 group patients, it was 7.04 µg/g in people with osteoarthritis and 12.59 µg/g in people with fractures. Conclusion The observed chromium content was highest in the cancellous bone and the lowest in the joint capsule. Chromium content was significantly different between the people with hip joint osteoarthritis and the people with femoral neck fractures.

  14. Mode of occurrence of chromium in four US coals

    Science.gov (United States)

    Huggins, Frank E.; Shah, N.; Huffman, G.P.; Kolker, A.; Crowley, S.; Palmer, C.A.; Finkelman, R.B.

    2000-01-01

    The mode of occurrence of chromium in three US bituminous coals and one US subbituminous has been examined using both X-ray absorption fine structure (XAFS) spectroscopy and a selective leaching protocol supplemented by scanning electron microscopy (SEM) and electron microprobe measurements. A synthesis of results from both methods indicates that chromium occurs principally in two forms in the bituminous coals: the major occurrence of chromium is associated with the macerals and is not readily leached by any reagent, whereas a second, lesser occurrence, which is leachable in hydrofluoric acid (HF), is associated with the clay mineral, illite. The former occurrence is believed to be a small particle oxyhydroxide phase (CrO(OH)). One coal also contained a small fraction (<5%) of the chromium in the form of a chromian magnetite, and the leaching protocol indicated the possibility of a similar small fraction of chromium in sulfide form in all three coals. There was little agreement between the two techniques on the mode of occurrence of chromium in the subbituminous coal; however, only a limited number of subbituminous coals have been analyzed by either technique. The chromium in all four coals was trivalent as no evidence was found for the Cr6+ oxidation state in any coal.

  15. Removal of chromium from tannery effluents by adsorption.

    Science.gov (United States)

    Fadali, O A; Magdy, Y H; Daifullah, A A M; Ebrahiem, E E; Nassar, M M

    2004-01-01

    Tannery effluent is characterized not only by heavy loads but also with toxic heavy metals especially chromium ions. Chromium is considered an important source of contamination due to large volume of exhaust liquid discharged and solid sludge produced. Details on adsorption studies were carried out using synthetic chromium salts (chromium chloride) as adsorbate, and cement kiln dust (a waste from white cement industry) as adsorbent. Equilibrium isotherms have been determined for the adsorption of chromium ions on cement kiln dust. Kinetic study provided that the adsorption process is diffusion controlled. The experimental results have been fitted using Freundlich, Langmuir, and Redlich Peterson isotherms. The maximum adsorption capacity of cement kiln dust was found to be 33 mg/g. Industrial tannery effluent (22-mg/L chromium and COD 952 mg/L) was also treated by cement dust. The treated effluent (using 20 g cement dust per 1 L) contains only 0.6 mg/L chromium and COD 200 mg/L.

  16. Chromium-induced membrane damage: protective role of ascorbic acid

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Importance of chromium as environmental toxicant is largely due to impact on the body to produce cellular toxicity. The impact of chromium and their supplementation with ascorbic acid was studied on plasma membrane of liver and kidney in male Wistar rats (80 - 100gbody weight). It has been observed that the intoxication with chromium ( i. p. ) at the dose of 0.8 mg/100g body weight per day for a period of 28 days causes significant increase in the level of cholesterol and decrease in the level of phospbolipid of both liver and kidney. The alkaline pbosphatase, total ATPase and Na + -K + -ATPase activities were significantly decreased in both liver and kidney after chromium treatment,except total ATPase activity of kidney. It is suggested that chromium exposure at the present dose and duration induce for the alterations of structure and function of both liver and kidney plasma membrane. Ascorbic acid ( i.p. at the dose of 0.5 mg,/100g body weight per day for period of 28 days) supplementation can reduce these structural changes in the plasma membrane of liver and kidney. But the functional changes can not be completely replenished by the ascorbic acid supplementation in response to chromium exposure. So it is also suggested that ascorbic acid (nutritional antioxidant) is useful free radical scavenger to restrain the chromium-induced membrane damage.

  17. Stabilization of chromium salt in ordinary portland cement

    Indian Academy of Sciences (India)

    Damir Barbir; Pero Dabić; Petar Krolo

    2012-12-01

    Ordinary Portland cement (OPC) samples containing the chromium salt have been investigated using differential microcalorimetry, conductometry and Fourier transform infrared spectroscopic analysis. The effect of chromium on OPC hydration was evaluated by continuous observing of early hydration. The microcalorimetrical results show that with increasing the share of chromium salt, heat maximums assume lower values and the occurrence of the maximum registered in the earlier hydration times. Conductometrical measurements show that with increasing addition of chromium salt, curve did not show any specific shape, immediate drop in specific conductivity is noticed and the maximum is reached earlier. This coincides with microcalorimetrical results. It can be concluded that the addition of chromium does not affect the mechanism of the hydration process, but it does affect the kinetic parameters and dynamics of the cement hydration process. It was found that chromium salt addition to the cement–water system is acceptable up to 2 wt.%. According to standard EN 196-3 for OPC, the beginning of binding time should occur after 60 minutes. Increased amount of chromium over 2 wt.% significantly accelerate the beginning of binding time and for the system it is not acceptable.

  18. Spectroscopic analysis of chromium bioremediation products

    Science.gov (United States)

    Varadharajan, C.; Nico, P. S.; Yang, L.; Marcus, M. A.; Steefel, C.; Larsen, J. T.; Beller, H. R.; Brodie, E. L.

    2010-12-01

    Remediation of chromium contamination frequently involves reducing the toxic and soluble hexavalent form, Cr(VI), to the relatively harmless and mostly immobile trivalent state, Cr(III). The objective of this study is to identify the biogeochemical reactions that control in situ chromium reduction in the presence of different dominant electron acceptors, i.e., NO3-, Fe(III), and SO42-. It was hypothesized that indirect, abiotic reduction of Cr(VI) by reduced metabolic products [Fe(II) and sulfides] would dominate over direct enzymatic reduction by denitrifying, iron-reducing, or sulfate-reducing bacteria. It is further hypothesized that the enzymatic reduction of Cr(VI) would produce relatively pure chromium hydroxide precipitates, whereas indirect reduction would result in mixed Cr-Fe hydroxide solid phases. Flow-through columns containing homogenized sediments from the 100H site at Hanford, WA were subjected to nitrate-, sulfate- or iron-reducing conditions in the presence of 5 µM Cr(VI) and 5 mM lactate. Cr(VI) was depleted in the effluent solutions from the nitrate- and sulfate-reducing columns; however only a small amount of Cr(VI) was removed under iron-reducing conditions. Preliminary analysis of micro X-ray absorption spectra indicate that the untreated and iron-reducing column sediments contained pre-existing Cr in the form of primary minerals, e.g. chromite and/or Cr-bearing micas. However, there was an increase in the relative abundance of mixed-phase Cr-Fe hydroxides, i.e., Cr1-xFex(OH)3 in the nitrate- and sulfate-treated columns. A possible explanation for the observations is that the production of Fe(II) was enhanced under the nitrate- and sulfate- reducing conditions, and was most likely sulfide-driven in the latter case. The Fe(II) was subsequently available for reduction of Cr(VI) resulting in the mixed-phase precipitates. The results from the spectroscopic analysis support the hypothesis that Fe(II)-mediated Cr reduction prevails over direct

  19. Analytical investigation of chromium and zinc in sweet, sour and bitter tasting fruits, vegetables and medicinal plants

    Directory of Open Access Journals (Sweden)

    Syed Ahmad Tirmizi

    2007-01-01

    Full Text Available Sweet, sour and bitter tasting fruits, vegetables and medicinal plants are an important component of human diet. The role of chromium and zinc in carbohydrate metabolism for control of diabetes is highlighted in selected commodities. Average levels of chromium and zinc in sweet taste were 0.69 ± 0.48 mg kg-1 and 4.81 ± 4.31 mg kg-1 respectively with correlation of 0.545, while in sour taste the values were 22.5 ± 22.0 mg kg-1 and 24.5 ± 11.8 mg kg-1 respectively with the correlation of 0.239 and in bitter taste, 0.61 ± 0.33 mg kg-1 and 4.70 ± 3.54 mg kg-1 respectively with correlation of 0.343. Overall, sour tasting commodities were found higher in levels of chromium and zinc and are recommended as food supplement for diabeties. None of these species contain metals above the toxic level.

  20. Mutagenic and carcinogenic actions of chromium and its compounds.

    Science.gov (United States)

    Mamyrbaev, Arstan Abdramanovich; Dzharkenov, Timur Agataevich; Imangazina, Zina Amangalievna; Satybaldieva, Umit Abulkhairovna

    2015-05-01

    Numerous experimental observations have been made on microorganisms and culture of the cells of mammals as well as the accounting of the chromosomal aberrations in the bone marrow cells of the mammals and of human cells displayed that the chromium and its compounds possess a pronounced mutagenic effect. Translocation test, induction record of DNA damage and repair systems in the mammalian and human cells with greater precision proves the presence of the mutagenic effect of the chromium and its compounds, which in turn is dependent on dose and time of this metal intoxication. Chromium and its compounds have pronounced mutagenic effect, on increased admission to organism of mammals and protozoa.

  1. Microbial biotechnology for remediation of aquatic habitats polluted with chromium

    OpenAIRE

    Viorica Coşier; I. Valentin Petrescu-Mag

    2008-01-01

    Chromium may occur in nine different forms of oxidation ranging from ?II to +VI, with forms II, III and VI as the most commonly encountered. In Cluj county, chromium pollution dates well back in time and has caused important dysfunction to the mechanical-biological wastewater purification station of the city of Cluj (Coşier & Diţă 1996). The purpose of this study was to develop one microbial method able to reduce hexavalent chromium (mobile, permeable to cell membrane, carcinogenic and mutage...

  2. Microbial Diversity of Chromium-Contaminated Soils and Characterization of Six Chromium-Removing Bacteria

    Science.gov (United States)

    He, Zhiguo; Hu, Yuting; Yin, Zhen; Hu, Yuehua; Zhong, Hui

    2016-06-01

    Three soil samples obtained from different sites adjacent to a chromium slag heap in a steel alloy factory were taken to examine the effect of chromium contamination on soil bacterial diversity as determined by construction of 16S rDNA clone libraries and sequencing of selected clones based on restriction fragment length polymorphism (RFLP) analysis. Results revealed that Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Alphaproteobacteria occurred in all three soil samples, although the three samples differed in their total diversity. Sample 1 had the highest microbial diversity covering 12 different classes, while Sample 3 had the lowest microbial diversity. Strains of six different species were successfully isolated, one of which was identified as Zobellella denitrificans. To our knowledge, this is the first report of a strain belonging to the genus Zobellella able to resist and reduce chromium. Among all isolates studied, Bacillus odysseyi YH2 exhibited the highest Cr(VI)-reducing capability, with a total removal of 23.5 % of an initial Cr(VI) concentration of 350 mg L-1.

  3. [Blood and urine chromium: compared values between chromium exposed workers and common people].

    Science.gov (United States)

    Provenzani, A; Verso, M G; Picciotto, D

    2008-01-01

    Aim of present study is the valutation and quantification of chromium in blood and urine. We compared 3 groups of persons formed by building workers, in particular masons, because cement contains potassium chromate that is dangerous for health, and by common people: urban population and outside the town population. In fact, exposure to CrVI risk is high for people who live near chromate industries. We maked a medical examination, blood and instrumental tests, chromium measuring in blood (recent exposure indicator) and urine (recent and previous indicator). Then we used statistical methods to estimate obtained values of blood and urine chromium among professional exposed people and common people. At the end we think that preventive measures in working environment reduced exposure to CrVI but environmental exposure (for example road dust from catalytic converter erosion, from brake lining erosion, cement dust and tobacco smoke), in the last years, has increased. So there are no difference between urban population and outside the town population and there are also no difference with professional exposed people for work prevention according to law in force, that let down professional risk using safe limits.

  4. Chromium accumulation, microorganism population and enzyme activities in soils around chromium-containing slag heap of steel alloy factory

    Institute of Scientific and Technical Information of China (English)

    HUANG Shun-hong; PENG Bing; YANG Zhi-hui; CHAI Li-yuan; ZHOU Li-cheng

    2009-01-01

    The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by chromium. 45 soil samples obtained from different places of the slag heap in a steel alloy factory were analyzed for chromium contamination level and its effect on soil microorganisms and enzyme activities. The results show that the average concentrations of total Cr in the soil under the slag heap, adjacent to the slag heap and outside the factory exceed the threshold of Secondary Environmental Quality Standard for Soil in China by 354%, 540% and 184%, respectively, and are 15, 21 and 9 times higher than the local background value, respectively. Elevated chromium loadings result in changes in the activity of the soil microbe, as indicated by the negative correlations between soil microbial population and chromium contents. Dehydrogenase activity is greatly depressed by chromium in the soil. The results imply that dehydrogenase activity can be used as an indicator for the chromium pollution level in the area of the steel alloy factory.

  5. Possible adverse effect of chromium in occupational exposure of tannery workers.

    Science.gov (United States)

    Kornhauser, Carlos; Wróbel, Katarzyna; Wróbel, Kazimierz; Malacara, Juan Manuel; Nava, Laura Eugenia; Gómez, Leobardo; González, Rita

    2002-04-01

    Our aim was to investigate the adverse effects of occupational exposure to trivalent chromium. We measured chromium and iron levels in serum and urine and hemoglobin levels in tannery workers and unexposed persons. We studied three groups of subjects. Group 1 included 15 non-smoking male tannery workers highly exposed to chromium from tanning and retanning departments. Group 2 included 14 non-smoking male tannery workers with moderate chromium exposure from dying, drying and finishing departments. Group 3 included 11 healthy, non-smoking male subjects without direct chromium exposure. Higher serum chromium levels were observed in groups 1 and 2 with respect to group 3 (mean values respectively: 0.43; 0.25 and 0.13 microg x l(-1)). Urine chromium levels in group 1 were higher than those in controls (mean values: 1.78 and 1.35 microg x l(-1)). In group 1 an inverse association was found between serum chromium and urine iron (-0.524), urine chromium and hemoglobin (-0.594) and between the urine chromium to iron ratio and hemoglobin (-0.693, p<0.05). The results suggest a chromium adverse effect on iron metabolism, possibly associated with excessive body chromium accumulation. In conclusion, chromium urine test could be recommended for diagnosis of chromium adverse effect on iron metabolism. Further studies are needed to quantify the relationship between urine chromium and hemoglobin metabolism.

  6. Scientific Opinion on ChromoPrecise® cellular bound chromium yeast added for nutritional purposes as a source of chromium in food supplements and the bioavailability of chromium from this source

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS

    2012-11-01

    Full Text Available The Panel on Food Additives and Nutrient Sources added to Food (ANS provides a scientific opinion re-evaluating the safety of ChromoPrecise® cellular bound chromium yeast added for nutritional purposes as a source of chromium in food supplements and the bioavailability of chromium from this source. ChromoPrecise® is a yeast preparation with an enriched trivalent chromium content, obtained by culture of Saccharomyces cerevisiae in the presence of chromium chloride. A daily intake of 100 µg chromium(III. There are limited data on the nature and identity of the organic chromium(III compounds contained in chromium-enriched yeast and on their toxicokinetic and toxicodynamic behaviour in the body. Overall, the Panel concluded that the bioavailability in man of chromium from chromium-enriched yeast is potentially up to approximately ten times higher than that of chromium from chromium chloride. A NOAEL of 2500 mg/kg bw/day ChromoPrecise® was identified in a 90-day feeding study in rats; no evidence of adverse effects of chromium yeasts were reported in other animal studies investigating the effects of dietary supplementation with chromium yeast. ChromoPrecise® chromium yeast was non-genotoxic in a range of in vitro genotoxicity studies. Although no information was available on the chronic toxicity, carcinogenicity or reproductive toxicity of ChromoPrecise® chromium yeast, the ANS Panel has previously concluded that trivalent chromium is not carcinogenic, and limited data on other chromium yeasts provide no evidence of an effect on reproductive endpoints. No adverse effects have been reported in clinical efficacy trials with chromium yeasts. The Panel concluded that the use of ChromoPrecise® chromium yeast in food supplements is not of concern, despite the lack of data on the nature and identity of the organic chromium(III compounds contained in the product, provided that the intake does not exceed 250 μg/day, as recommended by the WHO.

  7. 41 CFR 105-54.304 - Cost guidelines.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Cost guidelines. 105-54.304 Section 105-54.304 Public Contracts and Property Management Federal Property Management... Administration 54-ADVISORY COMMITTEE MANAGEMENT 54.3-Advisory Committee Procedures § 105-54.304 Cost...

  8. Thermodynamic Equilibrium Diagrams of Sulphur-Chromium System

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The chemical and electrochemical equilibria in the presence of gaseous phase were investigated. Many substances, which consisted of sulphur and chromium, were considered. Various thermodynamic equilibria were calculated in different pressures. Calculation results were shown as log p―1/T and E―T diagrams. These diagrams may be used to study the corrosion of chromium in sulphur-containing circumstances. The diagrams are also used to thermodynami-cally determine the existence area of various substances and so on.

  9. Stereology of carbide phase in modified hypereutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2010-04-01

    Full Text Available In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and rare-earth (RE. The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  10. SCIENCE AND TECHNOLOGY ACTIVITIES FOR CHROMIUM IN THE 100 AREAS

    Energy Technology Data Exchange (ETDEWEB)

    PETERSEN SW

    2009-07-02

    {sm_bullet} Primary Objective: Protect the Columbia River - Focus is control and treatment of contamination at or near the shoreline, which is influenced by bank storage {sm_bullet} Secondary Objective: Reduce hexavalent chromium to <48 parts per billion (ppb) in aquifer (drinking water standard) - Large plumes with isolated areas of high chromium concentrations (> 40,000 ppb), - Unknown source location(s); probably originating in reactor operation areas

  11. Chromium Ions Improve Moisure Resistance of Epoxy Resins

    Science.gov (United States)

    St. Clair, A. K.; St. Clair, T. L.; Stoakley, D. M.; Singh, J. J.; Sprinkle, D. R.

    1986-01-01

    Broad spectrum of thermosetting epoxy resins used on commercial and military aircraft, primarily as composite matrices and adhesives. In new technique, chromium-ion containing epoxy with improved resistance to moisture produced where chromium ions believed to prevent absorption of water molecules by coordinating themselves to hydroxyl groups on epoxy chain. Anticipated that improved epoxy formulation useful as composite matrix resin, adhesive, or casting resin for applications on commercial and advanced aircraft. Improvement made without sacrifice in mechanical properties of polymer.

  12. Performance of chromium nitride based coatings under plastic processing conditions

    OpenAIRE

    Cunha, l.; Andritschky, M.; Pischow, K.; Wang, Z.(Institute of High Energy Physics, Beijing, China); Zarychta, A.; Miranda, A. S.; A.M. Cunha

    2000-01-01

    Chromium nitride based coatings were produced in the form of monolithic and multilayer coatings, by DC and RF reactive magnetron sputtering. These coatings were deposited onto stainless steel and tool steel substrates. Chromium nitride coatings have;proved to be wear and corrosion resistant. The combination of these characteristics was necessary to protect surfaces during plastic processing. In order to select the best coatings, some mechanical and tribological tests were performed. Har...

  13. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces XII Appendix XII to Part 266... FACILITIES Pt. 266, App. XII Appendix XII to Part 266—Nickel or Chromium-Bearing Materials that may...

  14. Lime enhanced chromium removal in advanced integrated wastewater pond system.

    Science.gov (United States)

    Tadesse, I; Isoaho, S A; Green, F B; Puhakka, J A

    2006-03-01

    The removal of trivalent chromium from a combined tannery effluent in horizontal settling tanks and subsequent Advanced Integrated Wastewater Pond System (AIWPS) reactors was investigated. The raw combined effluent from Modjo tannery had pH in the range of 11.2-12. At this pH, a trivalent chromium removal of 46-72% was obtained in the horizontal settling tanks after a one-day detention time. Trivalent chromium precipitated as chromium hydroxide, Cr(OH)3. 58-95% Cr(III) was removed in the advanced facultative pond (AFP) where the water column pH of 7.2-8.4 was close to pH 8, which is the optimum precipitation pH for trivalent chromium. Chromium removals in the secondary facultative pond (SFP) and maturation pond (MP) were 30-50% and 6-16%, respectively. With Cr(III) concentration of 0.2-0.8 mg/l in the final treated effluent, the AIWPS preceded by horizontal settling tanks produced effluent that could easily meet most of the current Cr(III) discharge limits to receive water bodies.

  15. Experimental skin deposition of chromium on the hands following handling of samples of leather and metal

    DEFF Research Database (Denmark)

    Bregnbak, David; Thyssen, Jacob P.; Jellesen, Morten Stendahl;

    2016-01-01

    Background: Chromium is an important skin sensitizer. Exposure to it has been regulated in cement, and recently in leather. Studies on the deposition of chromium ions on the skin as a result of handling different chromium-containing materials are sparse, but could improve the risk assessment...... of contact sensitization and allergic contact dermatitis caused by chromium. Objectives: To determine whether the handling of chromium-containing samples of leather and metal results in the deposition of chromium onto the skin. Methods: Five healthy volunteers participated. For 30 min, they handled samples...... of leather and metal known to contain and release chromium. Skin deposition of chromium was assessed with the acid wipe sampling technique. Results: Acid wipe sampling of the participants' fingers showed chromium deposition on the skin in all participants who had been exposed to leather (range 0.01–0.20 µg...

  16. 12 CFR 5.4 - Filing required.

    Science.gov (United States)

    2010-01-01

    ... CORPORATE ACTIVITIES Rules of General Applicability § 5.4 Filing required. (a) Filing. A depository institution shall file an application or notice with the OCC to engage in corporate activities and... advise an applicant through a pre-filing communication to send the filing or submission directly to...

  17. 47 CFR 54.401 - Lifeline defined.

    Science.gov (United States)

    2010-10-01

    ... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) UNIVERSAL SERVICE Universal Service Support for Low-Income Consumers § 54.401 Lifeline defined. (a) As used in this... assistance. Eligible telecommunications carriers not subject to state commission jurisdiction also shall...

  18. 21 CFR 54.1 - Purpose.

    Science.gov (United States)

    2010-04-01

    ... applications and reclassification petitions for medical devices. (b) The agency reviews data generated in these... DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL FINANCIAL DISCLOSURE BY CLINICAL INVESTIGATORS § 54.1 Purpose. (a) The Food and Drug Administration (FDA) evaluates clinical studies submitted...

  19. 47 CFR 54.615 - Obtaining services.

    Science.gov (United States)

    2010-10-01

    ... non-profit entity that falls within one of the seven categories set forth in the definition of health... provided under § 54.621, that the requester cannot obtain toll-free access to an Internet service provider... thing of value; (6) If the service or services are being purchased as part of an aggregated...

  20. 28 CFR 54.230 - Transition plans.

    Science.gov (United States)

    2010-07-01

    ... Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) NONDISCRIMINATION ON THE BASIS OF SEX IN EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Coverage § 54.230 Transition plans... one administratively separate unit may submit either a single transition plan applicable to all...

  1. 9 CFR 54.20 - Administration.

    Science.gov (United States)

    2010-01-01

    ... COOPERATIVE CONTROL AND ERADICATION OF LIVESTOCK OR POULTRY DISEASES CONTROL OF SCRAPIE Scrapie Flock Certification Program § 54.20 Administration. The Scrapie Flock Certification Program is a cooperative effort... governments. APHIS coordinates with State scrapie certification boards and State animal health agencies...

  2. 9 CFR 54.21 - Participation.

    Science.gov (United States)

    2010-01-01

    ... COOPERATIVE CONTROL AND ERADICATION OF LIVESTOCK OR POULTRY DISEASES CONTROL OF SCRAPIE Scrapie Flock Certification Program § 54.21 Participation. Any owner of a sheep or goat flock may apply to enter the Scrapie Flock Certification Program by sending a written request to a State scrapie certification board or...

  3. [Chromium content in foods and dietary intake estimation in the Northwest of Mexico].

    Science.gov (United States)

    Grijalva Haro, M I; Ballesteros Vázquez, M N; Cabrera Pacheco, R M

    2001-03-01

    Chromium is an indispensable nutrient for the carbohydrates and lipids metabolism. In this study the chromium content in the twenty main foods of the diet from Northwestern Mexico was determined, as well as the daily mean intake which was estimated based on the food intake basket of this region. Chromium content was analyzed by atomic absorption spectrophotometry using the graphite furnace technique and previous digestion of foods in microwave oven. The chromium mean intake was estimated considering the chromium daily mean intake for person per day and the chromium content of the foods analyzed in this study. The range chromium content in the foods analyzed was between 0.0004 and 0.1641 microgram/g dry weight. White cheese showed the highest chromium content followed by pasta soup, wheat tortilla, bread and meat. The main foods chromium contributors in the diet were: wheat tortilla (20%), white cheese (11%), corn tortilla (11%), pasta soup (10%), milk (10%), meat (9%) and white bread (8%). The daily chromium intake was 30.43 +/- 1.6 micrograms/d. Chromium values obtained in the food analyzed are considered low. Moreover, chromium intake obtained from the diet is not enough to meet the safety and adequate daily chromium intake. Therefore, the population from the Northwestern Mexico has a suboptimal dietary chromium intake.

  4. Chromium-chromium interaction in a binuclear mixed-valent Cr(I)-Cr(II) complex.

    Science.gov (United States)

    Alzamly, Ahmed; Gorelsky, Serge I; Gambarotta, Sandro; Korobkov, Ilia; Le Roy, Jennifer; Murugesu, Muralee

    2014-11-03

    A mixed-valent Cr(I)-Cr(II) binuclear complex, {κ(1),κ(2),κ(3)-N,P,P-cyclo[(Ph)PCH2N(CH2Ph)CH2]}2(CrCl2)[Cr(μ-Cl)(AlClMe2)]·4toluene (1), of a P2N2 cyclic ligand was obtained upon treatment of the chromium precursor with alkylaluminum. Complex 1 was accessible from either its trivalent or divalent precursors, and density functional theory calculations revealed the presence of only σ- and π-orbital interactions in the Cr-Cr bond.

  5. CALVES GROWTH INFANT OF BREED NELLORE SUPPLEMENTED WITH CHROMIUM

    Directory of Open Access Journals (Sweden)

    C. C. Lima

    2016-11-01

    Full Text Available The present study evaluated the growth of nursling Nelore calves supplemented with chromium during creep feeding. The study was conducted using 131 Nelore calves with an average age of 60 days and average adjusted initial weight of 75 kg; considering that all calves were accompanied by their mothers. Therefore, the experimental groups were defined as T1: 35 males supplemented with chromium; T2: 34 males without chromium, T3: 30 females supplemented with chromium and T4: 32 females supplemented without chromium. The experimental period lasted from 60 days of age to 210 days (weaning, the animals were kept in two pickets of Panicum maximum cv. Mombasa provided with troughs for the creep feeding system, which permitted calves exclusive access to the concentrate formula based on 75% of TDN and 20% of crude protein, with 35% of soybean meal, 63% of corn and 2% of mineral nucleus containing 10 mg of chromium chelate for each kg of the product. The data were subjected to the analysis of variance, using the software R (R Development Core Team, 2013. In the evaluation of the live weight at 150 days of age, no significant difference was found in the use of chromium in males and females (regardless of sex. However, in the analysis between sexes, females’ live weights were lower than males’ live weight (p = 0.04, being 131.1 kg and 138.1 kg respectively. In the evaluation of live weight at 210 days there was no significant difference between males and females (p = 0.07, but there was a difference (p = 0.03 in the use of chrome in the evaluated treatments. So, it could be concluded that the creep feeding system with chrome chelate supplementation promoted an improvement in male and females calves’ growth for average daily weight gain and weaning weight, with a positive influence on the weight of cows.

  6. Nitridation of chromium powder in ammonia atmosphere

    Institute of Scientific and Technical Information of China (English)

    Ling Li; Qiang Zhen; Rong Li

    2015-01-01

    CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr−N−O predominance diagrams were constructed for different tempera-tures. Chromium nitride formed at 700−1200°C under relatively higher nitrogen and lower oxygen partial pressures. Phases in the products were then investigated using X-ray diffraction (XRD), and the Cr2N content varied with reaction temperature and holding time. The results indicate that the Cr metal powder nitridation process can be explained by a diffusion model. Further, Cr2N formed as an intermediate product because of an incomplete reaction, which was observed by high-resolution transmission electron microscopy (HRTEM). After nitriding at 1000°C for 20 h, CrN powder with an average grain size of 63 nm was obtained, and the obtained sample was analyzed by using a scanning electron microscope (SEM).

  7. Chromium increases pancreatic metallothionein in the rat.

    Science.gov (United States)

    Solis-Heredia, M J; Quintanilla-Vega, B; Sierra-Santoyo, A; Hernández, J M; Brambila, E; Cebrián, M E; Albores, A

    2000-01-03

    The ability of chromium (Cr) salts to increase metallothionein (MT) levels in rat liver, kidney and pancreas, and its relationship with the presence of toxic effects are reported here. Rats were injected subcutaneously with 0, 10, 20, 30, 40, or 50 mg K2Cr2O7/kg and sacrificed 24 h later. Total Cr accumulation followed a dose-dependent pattern, levels in kidney being higher than those in liver or pancreas, suggesting different tissue bioavailabilities and accumulation patterns. Cr(IV) administration resulted in a tissue-specific MT induction: pancreas and liver showed five- and 3.5-fold MT increases, respectively; no increase was observed in the kidney. A positive correlation was observed between zinc and MT concentrations in liver, and between total Cr and MT concentrations in pancreas. Serum alpha-amylase activity showed a dose-dependent increase starting from 20 mg/kg, whereas serum glucose levels increased at doses higher than 30 mg/kg. Serum aspartate aminotransferase and alanine aminotransferase activities were increased in a dose-dependent manner, from 20 and 30 mg/kg, respectively. Our results showed that treatment with Cr(VI) can induce MT synthesis in pancreas and suggests a subsequent binding of Cr to MT. Also, pancreas is a target organ for Cr toxicity, and the usefulness of alpha-amylase activity as a sensitive biomarker of Cr toxicity in human exposed populations merits further study.

  8. Can elevated chromium induce somatopsychic responses?

    Science.gov (United States)

    Lovrincevic, I; Leung, F Y; Alfieri, M A; Grace, D M

    1996-01-01

    The possible somatopsychological effects of chromium (Cr) was investigated in a population of patients, from a surgical ward of our hospital, who required total parenteral nutrition (TPN) solutions, and who became exposed to various amounts of this metal from this treatment. The study involved a questionnaire as well as biochemical tests which included serum Cr and other selected trace metals. The renal status for all eligible patients was within normal parameters. The patient population varied in age, pathology, surgical treatment, and duration on TPN. The results showed that every patient who received TPN had an increased serum Cr level; some increases were up to 50-fold above the normal reference level for serum Cr. Although statistical analysis failed to show any significant statistical relationship between an increased serum Cr and the investigated somatopsychological disturbances, this effect cannot be ruled out since one case did show all the dream disturbances. Considering these cases, the action of sedative medications that may suppress the effects of Cr, cannot be ruled out. As Cr(III) may be potentially genotoxic at high concentrations, infusion of this metal over long time periods should be avoided. Supplementation of Cr in TPN solutions appears to be unnecessary for short-term TPN because this metal is a known contaminant of these solutions. Efforts are required to find TPN nutrients with low or no Cr contamination.

  9. Hexavalent Chromium Reduction and Its Distribution in the Cell and Medium by Chromium Resistant Fusarium solani

    Directory of Open Access Journals (Sweden)

    Mousumi Sen

    2013-01-01

    Full Text Available In the present work, batch biosorption of Cr(VI was studied using the fungal strain isolated from soil. The fungal strain was characterized as Fusarium solani. The total Cr distribution in the biomass (fungus and in the media obtained from the experiment conducted at 500 mg l -1 initial Cr(VI concentration and pH 5.0. The results indicated both intracellular and extracellular accumulation and enzymatic reduction of Cr(VI and this was supported by the Transmission Electron Microscopic (TEM observation at the same Cr(VI concentration and pH value. Chromium elution from Fusarium solani containing Cr was then tried out using a number of chromium eluting reagents and a maximum Cr could be eluted using 0.5N sodium hydroxide solution without destructing the biomass structure. The total Cr was recovered by pH adjustment from both biomass and media was found to be 44% of the initial Cr(VI concentration (500 mg l-1.

  10. Spectroscopic study for a chromium-adsorbed montmorillonite

    Science.gov (United States)

    Nurtay, Maidina ·; Tuersun, Maierdan ·; Cai, Yuanfeng; Açıkgöz, Muhammed; Wang, Hongtao; Pan, Yuguan; Zhang, Xiaoke; Ma, Xiaomei

    2017-02-01

    Samples of purified montmorillonite with trace amounts of quartz were subjected to different concentrations of chromium sulphate solutions for one week to allow cation exchange. The chromium-bearing montmorillonites were verified and tested using powder X-ray diffractometry (XRD), X-ray fluorescence spectrometry, electron spin resonance (ESR) spectrometry and Fourier transformation infrared (FTIR) spectroscopy to explore the occupation sites of the chromium. The ESR spectra recorded before and after the chromium exchange show clear differences: a strong and broad resonance with two shoulders at the lower magnetic field side was present to start, and its intensity as well as that of the ferric iron resonance, increased with the concentration of added chromium. The signals introduced by the chromium, for example at g = 1.975 and 2.510 etc., suggested that the chromium had several occupational sites. The ESR peak with g = 2.510 in the second derivative spectrum suggested that Cr3+ was weakly bounded to TOT with the form of [Cr(H2O)3]3+ in hexagonal cavities. This was verified by comparing the FTIR spectra of the pure and modified montmorillonite. The main resonance centred at g = 1.975 indicated that the majority of Cr3+ occupied the interlayer region as [Cr(H2O)6]3+. The substitution of Ca2 + by Cr3+ also greatly affected the vibration of the hydrogens associate to water, ranged from 3500 to 2600 cm-1 in FTIR. Furthermore, the presence of two diffraction lines in the XRD results (specifically those with d-values of 1.5171 and 1.2673 nm) and the calculations of the size of the interlayer space suggested the presence of two types of montmorillonite with different hydration cations in the sample exposed to 0.2 M chromium sulphate. The two diffraction lines were assigned to [Cr(H2O)6]3+ and [Cr(H2O)3O3]3+, respectively. This also suggested that the species of hydration cation was constrained by the concentration of the chromium solution.

  11. A possible role for chromium(III) in genotoxicity

    Energy Technology Data Exchange (ETDEWEB)

    Snow, E.T. (New York Univ. Medical Center, Tuxedo (United States))

    1991-05-01

    Chromium is found in the environment in two major forms: reduced Cr{sup III} and Cr{sup VI}, or chromate. Chromate, the most biologically active species, is readily taken up by living cells and reduced intracellularly, via reactive intermediates, to stable Cr{sup III} species. Cr{sup III}, the most abundant form of chromium in the environment, does not readily cross cell membranes and is relatively inactive in vivo. However, intracellular Cr{sup III} can react slowly with both nucleic acids and proteins and can be genotoxic. The authors have investigated the genotoxicity of Cr{sup III} in vitro using a DNA replication assay and in vivo by CaCl{sub 2}-mediated transfection of chromium-treated DNA into Escherichia coli. These results suggest that Cr{sup III} alters the interaction between the DNA template and the polymerase such that the binding strength of the DNA polymerase is increased and the fidelity of DNA replication is decreased. These interactions may contribute to the mutagenicity of chromium ions in vivo and suggest that Cr{sup III} can contribute to chromium-mediated carcinogenesis.

  12. Low-chromium reduced-activation ferritic steels for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Kenik, E.A. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    Development of reduced-activation ferritic steels has concentrated on high-chromium (8-10 wt% Cr) steels. However, there are advantages for a low-chromium steel, and initial ORNL studies on reduced-activation steels were on compositions with 2.25 to 12% Cr. Those studies showed an Fe-2.25Cr-2W-0.25V-0.1C (2 1/4Cr-2WV) steel to have the highest strenglth of the steels studied. Although this steel had the best strength, Charpy impact properties were inferior to those of an Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) and an Fe-2.25Cr-2W-0.1C (2 1/4Cr-2W) steel. Therefore, further development of the low-chromium Cr-W steels was required. These results indicate that it is possible to develop low-chromium reduced-activation ferritic steels that have tensile and impact properties as good or better than those of high-chromium (7-9% Cr) steels. Further improvement of properties should be possible by optimizing the composition.

  13. Enhancement of chromium uptake in tanning using oxazolidine.

    Science.gov (United States)

    Sundarapandiyan, S; Brutto, Patrick E; Siddhartha, G; Ramesh, R; Ramanaiah, B; Saravanan, P; Mandal, A B

    2011-06-15

    Monocyclic and bicyclic oxazolidines were offered at three different junctures of chrome tanning process viz. prior to BCS offer, along with BCS and after basification. It was found that oxazolidine when offered after basification brought about better chromium uptake and reduction of chromium load in the wastewater. Offer of oxazolidine was also varied. Increase in offer of oxazolidine from 0.25% to 1% was found to enhance the chromium uptake and decrease the chromium load in wastewater. But the increase in uptake was not proportionate to the increase in oxazolidine offer more than 0.75%. Offer of 1% Zoldine ZA 78 (monocyclic oxazolidine) and Zoldine ZE (bicyclic oxazolidine) after basification brought about 63.4% and 73.1% enhancement in chrome content in leather compared to control where oxazolidine was not offered. The tone of the wetblue was found to be altered moderately. However this did not call for any process adjustments in wet-finishing. The oxazolidine treated leathers were found to be immensely fuller and tighter. It was found experimentally that offer of 1% of oxazolidine facilitated reduction in the offer of syntans administered for filling and grain tightening by around 46%. Oxazolidine could bring about significant reduction in cost of chemicals apart from resulting environmental benefits due to enhancement of chromium uptake during tanning.

  14. Bioaccumulation and biosorption of chromium by Aspergillus niger MTCC 2594.

    Science.gov (United States)

    Sandana Mala, John Geraldine; Unni Nair, Balachandran; Puvanakrishnan, Rengarajulu

    2006-06-01

    Chromium toxicity is of prime concern due to chrome tanning processes in the leather sector. Chrome tanning results in the discharge of toxic levels of chromium causing pollution hazards. Chromium levels of Cr(III) and Cr(VI) were high above permissible limits in chrome samples after chrome tanning. The potential of Aspergillus niger MTCC 2594 to accumulate chromium as well as its biosorption capacity is investigated in this study. Bioaccumulation of Cr(III) and Cr(VI) in the spent chrome liquor has resulted in a 75-78% reduction of the initial Cr content in 24-36 h. A. niger biomass is found to be very effective in the biosorption of Cr(III) and Cr(VI) in spent chrome liquor. Maximum adsorption of 83% for biosorption of Cr(III) at 48 h and 79% of Cr(VI) at 36 h in spent chrome liquor is observed. The biosorption characteristics fit well with Langmuir and Freundlich isotherms and the adsorption parameters are evaluated. The biosorption of Cr also follows Lagergren kinetics. A. niger biomass is effectively used for the biosorption of chromium with 79-83% Cr removal in 36-48 h.

  15. Microbial exudate promoted dissolution and transformation of chromium containing minerals

    Science.gov (United States)

    Saad, E. M.; Sun, J.; Tang, Y.

    2015-12-01

    Because of its utility in many industrial processes, chromium has become the second most common metal contaminant in the United States. The two most common oxidation states of chromium in nature are Cr(III), which is highly immobile, and Cr(VI), which is highly mobile and toxic. In both natural and engineered environments, the most common remediation of Cr(VI) is through reduction, which results in chromium sequestration in the low solubility mixed Cr(III)-Fe(III) (oxy)hydroxide phases. Consequently, the stability of these minerals must be examined to assess the fate of chromium in the subsurface. We examined the dissolution of mixed Cr(III)-Fe(III) (oxy)hydroxides in the presence of common microbial exudates, including the siderophore desferrioxamine B (DFOB; a common organic ligand secreted by most microbes with high affinity for ferric iron and other trivalent metal ions) and oxalate (a common organic acid produced by microbes). The solids exhibited incongruent dissolution with preferential leaching of Fe from the solid phase. Over time, this leads to a more Cr rich mineral, which is known to be more soluble than the corresponding mixed mineral phase. We are currently investigating the structure of the reacted mineral phases and soluble Cr(III) species, as well as the potential oxidation and remobilization of the soluble Cr species. Results from this study will provide insights regarding the long term transport and fate of chromium in the natural environment in the presence of microbial activities.

  16. Effective bioleaching of chromium in tannery sludge with an enriched sulfur-oxidizing bacterial community.

    Science.gov (United States)

    Zeng, Jing; Gou, Min; Tang, Yue-Qin; Li, Guo-Ying; Sun, Zhao-Yong; Kida, Kenji

    2016-10-01

    In this study, a sulfur-oxidizing community was enriched from activated sludge generated in tannery wastewater treatment plants. Bioleaching of tannery sludge containing 0.9-1.2% chromium was investigated to evaluate the effectiveness of the enriched community, the effect of chromium binding forms on bioleaching efficiency, and the dominant microbes contributing to chromium bioleaching. Sludge samples inoculated with the enriched community presented 79.9-96.8% of chromium leaching efficiencies, much higher than those without the enriched community. High bioleaching efficiencies of over 95% were achieved for chromium in reducible fraction, while 60.9-97.9% were observed for chromium in oxidizable and residual fractions. Acidithiobacillus thiooxidans, the predominant bacteria in the enriched community, played an important role in bioleaching, whereas some indigenous heterotrophic species in sludge might have had a supporting role. The results indicated that A. thiooxidans-dominant enriched microbial community had high chromium bioleaching efficiency, and chromium binding forms affected the bioleaching performance.

  17. Development of a coprecipitation system for the speciation/preconcentration of chromium in tap waters

    Energy Technology Data Exchange (ETDEWEB)

    Karatepe, Aslihan, E-mail: karatepea@gmail.com [Nevsehir University, Faculty of Science and Arts, Department of Chemistry, 50000 Nevsehir (Turkey); Korkmaz, Esra [Bozok University, Faculty of Science and Arts, Department of Chemistry, Yozgat (Turkey); Soylak, Mustafa [Erciyes University, Faculty of Science and Arts, Chemistry Department, 38039 Kayseri (Turkey); Elci, Latif [Pamukkale University, Faculty of Science and Arts, Department of Chemistry, 20020 Denizli (Turkey)

    2010-01-15

    A method for the speciation of chromium(III), chromium(VI) and determination of total chromium based on coprecipitation of chromium(III) with dysprosium hydroxide has been investigated and applied to tap water samples. Chromium(III) was quantitatively recovered by the presented method, while the recovery values for chromium(VI) was below 10%. The influences of analytical parameters including amount of dysprosium(III), pH, centrifugation speed and sample volume for the quantitative precipitation were examined. No interferic effects were observed from alkali, earth alkali and some transition metals for the analyte ions. The detection limits (k = 3, N = 15) were 0.65 {mu}g/L for chromium(III) and 0.78 {mu}g/L for chromium(VI). The validation of the presented method was checked by the analysis of certified reference materials.

  18. Process for improving moisture resistance of epoxy resins by addition of chromium ions

    Science.gov (United States)

    St.clair, A. K.; Stoakley, D. M.; St.clair, T. L.; Singh, J. J. (Inventor)

    1985-01-01

    A process for improving the moisture resistance properties of epoxidized TGMDA and DGEBA resin system by chemically incorporating chromium ions is described. The addition of chromium ions is believed to prevent the absorption of water molecules.

  19. CHROMIUM ELECTROANALYSIS AT SCREEN PRINTED ELECTRODE MODIFIED BY THIN FILMS OF NICKEL

    Science.gov (United States)

    A rapid and potentially cost-effective electrochemical method is reported for analysis of chromium (VI) and Chromium(III) using a nickel modified screen printed carbon ink electrode. Electrochemical characteristics of nickel modified electrode as well voltammetric behavior f...

  20. 46 CFR 54.01-35 - Corrosion (modifies UG- 25).

    Science.gov (United States)

    2010-10-01

    ... (incorporated by reference; see 46 CFR 54.01-1) except as noted otherwise in this section. (b) The pressure... 46 Shipping 2 2010-10-01 2010-10-01 false Corrosion (modifies UG- 25). 54.01-35 Section 54.01-35... General Requirements § 54.01-35 Corrosion (modifies UG- 25). (a) Vessels or portions of vessels subject...

  1. 46 CFR 54.25-5 - Corrosion allowance.

    Science.gov (United States)

    2010-10-01

    ... Construction With Carbon, Alloy, and Heat Treated Steels § 54.25-5 Corrosion allowance. The corrosion allowance must be as required in 46 CFR 54.01-35. ... 46 Shipping 2 2010-10-01 2010-10-01 false Corrosion allowance. 54.25-5 Section 54.25-5...

  2. Reduction of chromium oxide from slags

    Directory of Open Access Journals (Sweden)

    Gutiérrez-Paredes, J.

    2005-12-01

    Full Text Available Experimental and theoretical work were performed to estimate the effect of slag basicity and amount of reducing agents on the reduction of chromium oxide from the slag which interacted with molten steel at 1,600 °C. The slag system contained CaO, MgO, SiO2, CaF2 and Cr2O3 together with Fe-alloys (Fe-Si and Fe-Si-Mg. The CaF2 and MgO contents in the slags were 10 mass % each; Cr2O3 was 25%. The amount of the ferroalloys ranged from 12.5 to 50 g per 100 g of slag. The (CaO+MgO/SiO2 ratio was held at 1 and 2. The Cr yield was determined using both Fe-alloys as reducing agents. Some estimations were made to determine the theoretical effect of temperature, slag basicity, (CaO+MgO/SiO2, and amount of reducing agents in the slag on the chromium recovery. The FACT (Facility for the Analysis of Chemical Thermodynamics computational package is used to determine the equilibrium between the slag and molten steel.

    En el presente trabajo se realiza un estudio teórico y experimental para determinar el efecto de la basicidad de la escoria y la cantidad de agentes reductores sobre la reducción de óxidos de cromo contenidos en la escoria, la cual está en contacto con acero líquido a 1.600 °C. La escoria se prepara con los reactivos CaO, MgO, SiO2, CaF2 y ferroaleaciones (Fe-Si y Fe-Si-Mg. Los contenidos de CaF2 y MgO en la escoria son de 10 %, cada uno, y el de Cr2O3 es 25 %. La cantidad de la ferroaleación varía de 12,5 a 50 g por cada 100 g de escoria. La relación (CaO+MgO/SiO2 tiene los valores de 1 y 2. Se determina la eficiencia de recuperación de cromo empleando los dos tipos de ferroaleaciones. Se realizaron cálculos para determinar el efecto teórico de la temperatura, la basicidad de la escoria, (CaO+MgO/SiO2, y la cantidad de agentes reductores sobre la reducci

  3. Effects of irradiation on chromium's behavior in ferritic/martensitic FeCr alloy

    Institute of Scientific and Technical Information of China (English)

    Xinfu HE; Wen YANG; Zhehao QU; Sheng FAN

    2009-01-01

    The effects of irradiation on chromium performance under different temperatures in Fe-20at%Cr were modeled by modified Marlowe code. Chromium precipitation was observed in FeCr alloy after irradiation; interstitial Chromium atoms are the preferred formation of mixed FeCr dumbbells in the direction ofand; interstitial chromium atoms congregated on {111} and {110} plane. The results are compared with experiment observations and are useful to understanding the irradiation performances of FeCr alloy.

  4. A study of the process of desorption of hexavalent chromium

    Directory of Open Access Journals (Sweden)

    W.B. Amorim

    2003-09-01

    Full Text Available In this work the process of desorption of hexavalent chromium, a toxic metal ion, from the marine algae Sargassum sp, following biosorption experiments 2³ factorial design was studied. A technique was applied to three eluents: HCl, H2SO4 and EDTA. Three factors of importance were evaluated: concentration of eluent, the ratio between mass of biosorbent and volume of eluent (S/L and process time. A statistical analysis of the experimental results showed that the three variables evaluated are significant for all three eluents. The models for chromium desorption were validated, as the results agreed well with the observed values. Through use of the response surface methodology, a factorial design based optimization technique; it was possible to identify the most suitable eluent and the interval of values for the process variables that resulted in the most significant desorption of chromium, which is relevant information for work aiming at process optimization.

  5. Bioabsorption of chromium from retan chrome liquor by cyanobacteria.

    Science.gov (United States)

    Pandi, M; Shashirekha, V; Swamy, Mahadeswara

    2009-01-01

    The bioaccumulation of chromium from retan chrome liquor by Spirulina fusiformis was investigated under laboratory as well as field conditions. At the optimal conditions, metal ion uptake increased with initial metal ion concentration up to 300mg/l. The effect on various physico-chemical parameters like total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), chlorides, sulphates, phenols, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) and biochemical studies related to biomass, chlorophyll-a and protein were also carried out. The present study indicates that S. fusiformis is very effective in removal of chromium (93-99%) besides removing other toxicants from retan chrome liquor. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and FTIR studies indicate the interaction/complexation between Cr and alga. The mechanism involved in bioaccumulation of chromium is also discussed. The process when upgraded can be applied for detoxification of tannery effluents.

  6. Extraction of Chromium from Carbon Ferrochromium Residual Wastes

    Science.gov (United States)

    Lazarevskiy, P. P.; Gizatulin, R. A.; Romanenko, Yu E.; Valuev, D. V.; Valueva, A. V.; Serikbol, A.

    2015-09-01

    This work reports the problem of processing residual wastes after producing carbon ferrochrome by recycling dust using a hydrometallurgical method with the purpose of extracting the basic component - chromium, The X-ray diffraction analysis results, chemical and granulometric compositions of dust from the carbon ferrochrome production are given, The method for the production of chemical-enrichment concentrate (CEC) by processing ferrous dust is described, with obtaining a middling product - sodium mono-chromate with its further reduction to chromium hydroxide, followed by autoclave leaching, and resulting in the production of chemically enriched chrome concentrate, The plant used for autoclave leaching and filtering is schematically depicted, The smelting process of metallic chromium using the ladle aluminothermic method is described,

  7. Studies of removal of chromium by model constructed wetland

    Directory of Open Access Journals (Sweden)

    C. Mant

    2005-09-01

    Full Text Available Chromium is a pollutant present in tannery wastewater, its removal is necessary for protection of the environment. Penisetum purpureum, Brancharia decumbens and Phragmites australis were grown hydroponically in experimental gravel beds to determine their potential for the phytoremediation of solutions containing 10 and 20 mg Cr dm-3. These concentrations, similar to tannery wastewater after initial physico-chemical treatment were used with the aim of developing an economic secondary treatment to protect the environment. All the systems achieved removal efficiencies of 97 - 99.6% within 24 hours. P. purpureum and B. decumbens removed 78.1% and 68.5% respectively within the first hour. Both P. purpureum and B. decumbens were tolerant of the concentrations of chromium applied, but P. purpureum showed the greatest potential because its faster growth and larger biomass achieved a much greater chromium removal over the whole length of time of the experiment.

  8. Electron magnetic resonance investigation of chromium diffusion in yttria powders

    Energy Technology Data Exchange (ETDEWEB)

    Biasi, R.S. de, E-mail: rsbiasi@ime.eb.b [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, Pr. General Tiburcio, 80, 22290-270 Rio de Janeiro, RJ (Brazil); Grillo, M.L.N., E-mail: mluciag@uerj.b [Instituto de Fisica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil)

    2010-03-01

    The electron magnetic resonance (EMR) technique was used to investigate the diffusion of chromium in yttria (Y{sub 2}O{sub 3}) powders. The EMR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323 and 1373 K. The activation temperature for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be E{sub A}=342+-5 kJ mol{sup -1}. This value is larger than the activation energy for the diffusion of chromium in rutile (TiO{sub 2}), periclase (MgO) and cobalt monoxide (CoO) and smaller than the activation energy for the diffusion of chromium in chrysoberyl (BeAl{sub 2}O{sub 4}).

  9. Chromium Resistant Bacteria: Impact on Plant Growth in Soil Microcosm

    Directory of Open Access Journals (Sweden)

    Sayel Hanane

    2014-07-01

    Full Text Available Three chromium resistant bacterial strains, Pseudomonas fluorescens PF28, Enterobacter amnigenus EA31 and Enterococcus gallinarum S34 isolated from tannery waste contaminated soil were used in this study. All strains could resist a high concentration of K2Cr2O7 that is up to 300 mg/L. The effect of these strains on clover plants (Trifolium campestre in the presence of two chromium salts CrCl3 and K2Cr2O7 was studied in soil microcosm. Application of chromium salts adversely affected seed germination, root and shoot length. Bacterial inoculation improved the growth parameters under chromate stress when compared with non inoculated respective controls. There was observed more than 50% reduction of Cr(VI in inoculated soil microcosms, as compared to the uninoculated soil under the same conditions. The results obtained in this study are significant for the bioremediation of chromate pollution.

  10. Improvement on simultaneous determination of chromium species in aqueous solution by ion chromatography and chemiluminescence detection

    DEFF Research Database (Denmark)

    Gammelgaard, Bente; Liao, Y.P.; Jons, O.

    1997-01-01

    A sensitive method for the simultaneous determination of chromium(III) and chromium(VI) was chromatography and chemiluminescence detection. Two Dionex ion-exchange guard columns in series, CG5 and AG7, were used to separate chromium(III) from chromium(VI). Chromium(VI) was reduced by potassium......, the stabilities of reductant and luminol solutions were studied. The linear range of the calibration curve for chromium(III) and chromium(VI) was 1-400 mu g l(-1). The detection limit was 0.12 mu g l(-1) for chromium(III) and 0.09 mu g l(-1) for chromium(VI), respectively. The precision at the 20 mu g l(-1) level...... was 1.4% for chromium(III) and 2.5% for chromium(VI), respectively. The accuracy of the chromium(III) determination was determined by analysis of the NIST standard reference material 1643c, Trace elements in water with the result 19.1 +/- 1.0 mu g Cr(III) l(-1) (certified value 19.0 +/- 0.6 mu g Cr...

  11. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  12. Experimental study on 830 MPa grade pipeline steel containing chromium

    Institute of Scientific and Technical Information of China (English)

    Yi Ren; Shuai Zhang; Shuang Wang; Wen-yue Liu

    2009-01-01

    The diversity of microstructure and properties of 830 Mpa grade pipeline steel containing chromium was investigated by optical microscope and transmission electron microscopy. The main microstructures were multiple configurations, containing lath bainite and granule bainite. Mechanical properties test results showed that the yield strength and tensile strength improved with in-creasing chromium content. The toughness and elongation decreased at the same time, so temper process was introduced. Appling proper temper parameters, the values of toughness and elongation were improved dramatically, and the strength decreased slightly.

  13. Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes;

    2015-01-01

    Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track paleoenviro......Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track...

  14. Use of chitosan for chromium removal from exhausted tanning baths.

    Science.gov (United States)

    Cesaro, Raffaele; Fabbricino, Massimiliano; Lanzetta, Rosa; Mancino, Anna; Naviglio, Biagio; Parrilli, Michelangelo; Sartorio, Roberto; Tomaselli, Michele; Tortora, Gelsomina

    2008-01-01

    A novel approach, based on chitosan heavy-metal sequestrating ability, is proposed for chromium(III) removal from spent tanning liquor. Experimental results, obtained at lab-scale using real wastewater, are presented and discussed. Resulting efficiencies are extremely high, and strongly dependent on chitosan dose and pH value. Comparative analyses with other polysaccharides is also carried out showing that amine groups are more efficient than carboxyl and sulphate ones. Chromium recovery from sorption complexes and chitosan regeneration is finally proposed to optimize the whole process.

  15. Primary and secondary crystallization of modified hypoeutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2010-04-01

    Full Text Available The paper presents investigations of crystallization of modified hypoeutectic wear resistant chromium cast iron which contains carbon about 2% and chromium on three levels (12%, 18% and 25%. Three substances were applied to the modification ( boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and mischmetal (RE. The investigations of crystallization were conducted the DTA method in DTA-C and DTA-Is testers. The influence on the course of the process of primary and secondary crystallization was observed.

  16. Urinary levels of nickel and chromium associated with dental restoration by nickel-chromium based alloys.

    Science.gov (United States)

    Chen, Bo; Xia, Gang; Cao, Xin-Ming; Wang, Jue; Xu, Bi-Yao; Huang, Pu; Chen, Yue; Jiang, Qing-Wu

    2013-03-01

    This paper aims to investigate if the dental restoration of nickel-chromium based alloy (Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of dental restoration. Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.

  17. Fertilizers and Mixed Crop Cultivation of Chromium Tolerant and Sensitive Plants under Chromium Toxicity

    Directory of Open Access Journals (Sweden)

    B. Dheeba

    2015-01-01

    Full Text Available Zea mays (maize and Vigna radiata (green gram are found to be the chromium (Cr tolerant and sensitive plants, respectively. In the present paper, we investigate the reduction of the toxicity of Cr in the sensitive plants by the mixed crop cultivation in the field using various amendments. Further, the potassium dichromate was used as the source of hexavalent Cr. The results indicated that Cr adversely affects both the growth and yield of plants. The soil properties vary with Cr and different fertilizer amendments and the yield of both plants were affected by Cr. We conclude that metal accumulation of seeds of green gram was higher than corn and the application of single fertilizer either farm yard manure (FYM or nitrogen, phosphorous, and potassium (NPK enhances the growth and yield of both the tolerant and sensitive plants in the mixed crop cultivations.

  18. The role of Candida albicans homologous recombination factors Rad54 and Rdh54 in DNA damage sensitivity

    Directory of Open Access Journals (Sweden)

    White Theodore C

    2011-09-01

    Full Text Available Abstract Background The fungal pathogen Candida albicans is frequently seen in immune suppressed patients, and resistance to one of the most widely used antifungals, fluconazole (FLC, can evolve rapidly. In recent years it has become clear that plasticity of the Candida albicans genome contributes to drug resistance through loss of heterozygosity (LOH at resistance genes and gross chromosomal rearrangements that amplify gene copy number of resistance associated genes. This study addresses the role of the homologous recombination factors Rad54 and Rdh54 in cell growth, DNA damage and FLC resistance in Candida albicans. Results The data presented here support a role for homologous recombination in cell growth and DNA damage sensitivity, as Candida albicans rad54Δ/rad54Δ mutants were hypersensitive to MMS and menadione, and had an aberrant cell and nuclear morphology. The Candida albicans rad54Δ/rad54Δ mutant was defective in invasion of Spider agar, presumably due to the altered cellular morphology. In contrast, mutation of the related gene RDH54 did not contribute significantly to DNA damage resistance and cell growth, and deletion of either Candida albicans RAD54 or Candida albicans RDH54 did not alter FLC susceptibility. Conclusions Together, these results support a role for homologous recombination in genome stability under nondamaging conditions. The nuclear morphology defects in the rad54Δ/rad54Δ mutants show that Rad54 performs an essential role during mitotic growth and that in its absence, cells arrest in G2. The viability of the single mutant rad54Δ/rad54Δ and the inability to construct the double mutant rad54Δ/rad54Δ rdh54Δ/rdh54Δ suggests that Rdh54 can partially compensate for Rad54 during mitotic growth.

  19. Physiological, biochemical and histometric responses of Nile tilapia (Oreochromis niloticus L.) by dietary organic chromium (chromium picolinate) supplementation

    OpenAIRE

    2014-01-01

    Chromium has been recognized as a new and important micro-nutrient, essential for both human and animal nutrition. This study was conducted to evaluate the appropriateness and/or the use of safety level of dietary chromium picolinate (Cr-Pic), and its effects on the physiological responses, the histometric characteristics, and the chemical analysis of dorsal muscles of mono-sex Nile tilapia, Oreochromis niloticus. A total of 420 fingerlings (28.00 ± 0.96 g) were randomly distributed into 21 f...

  20. Chromium(VI) release from leather and metals can be detected with a diphenylcarbazide spot test

    DEFF Research Database (Denmark)

    Bregnbak, David; Johansen, Jeanne D.; Jellesen, Morten Stendahl

    2015-01-01

    Along with chromium, nickel and cobalt are the clinically most important metal allergens. However, unlike for nickel and cobalt, there is no validated colorimetric spot test that detects chromium. Such a test could help both clinicians and their patients with chromium dermatitis to identify culprit...... at 0.5 ppm without interference from other pure metals, alloys, or leather. A market survey using the test showed no chromium(VI) release from work tools (0/100). However, chromium(VI) release from metal screws (7/60), one earring (1/50), leather shoes (4/100) and leather gloves (6/11) was observed. We...

  1. Reactor target from metal chromium for "pure" high-intensive artificial neutrino source

    Science.gov (United States)

    Gavrin, V. N.; Kozlova, Yu. P.; Veretenkin, E. P.; Logachev, A. V.; Logacheva, A. I.; Lednev, I. S.; Okunkova, A. A.

    2017-01-01

    The paper presents the first results of development of manufacturing technology of metallic chromium targets from highly enriched isotope 50Cr for irradiation in a high flux nuclear reactor to obtain a compact high intensity neutrino source with low content of radionuclide impurities and minimum losses of enriched isotope. The main technological stages are the hydrolysis of chromyl fluoride, the electrochemical reduction of metallic chromium, the hot isostatic pressing of chromium powder and the electrical discharge machining of chromium bars. The technological stages of hot isostatic pressing of chromium powder and of electrical discharge machining of Cr rods have been tested.

  2. The oxidation and reduction of chromium of stainless steels in an eletric arc furnace

    Directory of Open Access Journals (Sweden)

    B. Arh

    2011-07-01

    Full Text Available The oxidation of chromium during the elaboration of stainless steels occurs with oxygen in solution blown inthe melt and with oxides in the slag. A higher content of silicon in the furnace charge decreases the extent of oxidation of chromium, however, the efficient reduction of chromium from the slag is of essential importance for a minimal loss of chromium. In this survey, the theory of the oxidation of chromium, its reduction from the slag and the conditions for the formation of foaming slag are discussed.

  3. Chromium(VI) transport and fate in unsaturated zone and aquifer: 3D Sandbox results.

    Science.gov (United States)

    Zhao, Xingmin; Sobecky, Patricia A; Zhao, Lanpo; Crawford, Patrice; Li, Mingtang

    2016-04-01

    The simulation of Cr(VI) behavior in an unsaturated zone and aquifer, using a 3D experimental set-up were performed to illustrate the distribution, transport and transformation of Cr(VI), and further to reveal the potential harm of Cr(VI) after entering the groundwater. The result indicated that chromium(VI) was transported in the vertical direction, meanwhile, was transported in the horizontal direction under the influence of groundwater flow. The direction and distance away from the pollution source zone had great effect on the chromium(VI) concentration. At the sampling sites near the pollution source zone, there was a sudden increase of chromium(VI) concentration. The concentration of chromium(III) concentration in some random effluent samples was not detected. Chromium had not only transported but also had fraction and specie transformation in the unsaturated zone and aquifer. The relative concentration of residue fraction chromium was decreased with time. The content of Fe-Mn oxide fraction chromium was increased with time. The relative content of exchangeable and carbonate-bound fraction chromium was lower and the content variations were not obvious. Chromium(VI) (91-98%) was first reduced to chromium(III) rapidly. The oxidation reaction occurred later and the relative content of chromium(VI) was increased again. The presence of manganese oxides under favorable soil conditions can promote the reoxidation of Cr(III) to Cr(VI).

  4. 75 FR 67100 - Superalloy Degassed Chromium From Japan

    Science.gov (United States)

    2010-11-01

    ... superalloy degassed chromium from Japan (70 FR 76030). The Commission is conducting a review to determine..., subparts A, D, E, and F (19 CFR part 207), as most recently amended at 74 FR 2847 (January 16, 2009). \\1... rule 201.15(b)(19 CFR 201.15(b)), 73 FR 24609 (May 5, 2008). This advice was developed in...

  5. 76 FR 8773 - Superalloy Degassed Chromium From Japan

    Science.gov (United States)

    2011-02-15

    ... applicable deadline.'' (75 FR 80457). Accordingly, pursuant to section 751(c) of the Tariff Act of 1930 (19 U... COMMISSION Superalloy Degassed Chromium From Japan AGENCY: United States International Trade Commission... Japan would be likely to lead to continuation or recurrence of material injury. On December 22,...

  6. Effects of chromium picolinate supplementation in type 2 diabetic patients

    Directory of Open Access Journals (Sweden)

    Niladê Rosinski Rocha

    2014-10-01

    Full Text Available The effects of chromium picolinate in Type 2 diabetic patients are investigated.  Seventeen Type 2 diabetic patients were randomly divided into two groups. The experimental group received fiber-rich hypocaloric diet and chromium picolinate whereas the control group received fiber-rich hypocaloric diet and placebo. The chromium picolinate was offered twice a day at the dose of 100 μg. Anthropometric data such as blood pressure, fasting glycemia and glycated hemoglobin (HbA1c were measured and these parameters were evaluated again after 90 days. No difference was reported in rates of body weight, waist, hip, body mass index, blood pressure and fasting glycemia (Control vs. Experimental groups after treatment. However, a decrease (p = 0.0405 of HbA1c occurred in the experimental group when the pre- and post-treatment rates were compared. HbA1c data showed that chromium picolinate improved the glycemic control in Type 2 diabetes.

  7. Cobalt chromium stents versus stainless steel stents in diabetic patients

    Directory of Open Access Journals (Sweden)

    Mahmoud Ahmed Tantawy

    2014-03-01

    Conclusions: We concluded that no significant statistical difference was found between the two stents (cobalt-chromium alloy bare metal stent versus conventional bare metal stainless steel stent in diabetic patients regarding (initial procedural success, in-hospital complications, the incidence of ISR at follow up, event-free survival at follow up.

  8. Intestinal absorption of chromium as affected by wheat bran

    Energy Technology Data Exchange (ETDEWEB)

    Keim, K.S.; Holloway, C.L.; Hegsted, M.

    1986-03-01

    This study was designed to investigate the influence of dietary fiber, as found in wheat bran, on the absorption of chromium. Twenty male Sprague-Dawley rats were divided into two groups of 10. The control was fed a semi-purified diet containing casein, methionine, cornstarch, sucrose, corn oil, mineral and vitamin mix, and choline bitartrate. The experimental group was fed the same diet but with soft red winter wheat bran added to a level of 35% of the diet at the expense of sucrose. To determine chromium absorption and uptake by selected tissues, rats were fasted for 24 hr, fed 5 g of the respective diet, 2 hr later intubated with 100..mu..Ci of Cr-51of sacrificed 24 hr later. The rats wee housed in metabolic cages after the Cr-51 intubation. The addition of wheat brand to the diet did not significantly affect chromium absorption as measured by percent dose of Cr-51 in the 24 hr urine. The percent dose in the control group was 0.68 +/- 0.20% (mean +/- SEM) and in the experimental group 0.63 +/- 0.24% (mean +/-SEM) (N.S.). The cr-51 uptake of liver, spleen, jejunum, and blood was not statistically different between groups. These results indicate that dietary fiber as found in wheat bran does not impair intestinal absorption of chromium.

  9. Domestic Production Issues in Chromium and Platinum-Group Metals

    Science.gov (United States)

    1988-09-01

    Protection Agency. OPA 87-005. Washington: Government Printing Office, May 1987. 16. Foley, Jeffrey Y. and James C. Barker . Chromite Deposits Along...Mining, Metallurgical, and Petroleum Engineers, 1976. 52. Stowe, Clive W. Evolution of Chromium Ore Fields. New York: Van Nostrand Reinhold Company

  10. Spin-wave and critical neutron scattering from chromium

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Axe, J.D.; Shirane, G.

    1971-01-01

    Chromium and its dilute alloys are unique examples of magnetism caused by itinerant electrons. The magnetic excitations have been studied by inelastic neutron scattering using a high-resolution triple-axis spectrometer. Spin-wave peaks in q scans at constant energy transfer ℏω could, in general, ...

  11. New alloys to conserve critical elements. [replacing chromium in steels

    Science.gov (United States)

    Stephens, J. R.

    1978-01-01

    Previous studies and surveys on availability of domestic reserves have shown that chromium is a most critical element within the U.S. metal industry. More precisely, the bulk of chromium is consumed in the production of stainless steels, specifically Type 304 stainless steel (304SS) which contains 18% Cr. The present paper deals with means of reducing chromium in commercial stainless steels by substituting more abundant or less expensive elements with the intent of maintaining the properties of 304SS. The discussion focuses on some of the oxidation and corrosion properties of new substitute stainless steels with only 12% Cr, which represents a potential saving of 33% of the chromium consumed in the production of 304SS. The alloying elements substituted for Cr in 304SS are selected according to their potential for protective oxide formation during high-temperature oxidation; these are Al, Si, Ti, Y, and misch metal which is 99.7% rare-earth metals containing 50 to 55% cerium. Other alloying elements to impart corrosion resistance are Mn, Mo, and V.

  12. Microbial biotechnology for remediation of aquatic habitats polluted with chromium

    Directory of Open Access Journals (Sweden)

    Viorica Coşier

    2008-12-01

    Full Text Available Chromium may occur in nine different forms of oxidation ranging from ?II to +VI, with forms II, III and VI as the most commonly encountered. In Cluj county, chromium pollution dates well back in time and has caused important dysfunction to the mechanical-biological wastewater purification station of the city of Cluj (Coşier & Diţă 1996. The purpose of this study was to develop one microbial method able to reduce hexavalent chromium (mobile, permeable to cell membrane, carcinogenic and mutagenic (Ishikawa et al 1994 to the trivalent form (insoluble and an essential element for humans (Song et al 2006. Different sources of chromium-reducing bacteria and many sources of carbon and energy added to the Kvasnikov mineral basal medium (Komori et al 1990 with increasing amount of chromate (200- 1000 mg/l were tested. Two bacterial strains, able to reduce even 1000 mg chromate/l, were isolated in pure culture. For one of these bacterial strains, we determined the optimum conditions for the reduction of Cr (VI.

  13. Oxidation resistant, thoria-dispersed nickel-chromium-aluminum alloy

    Science.gov (United States)

    Baranow, S.; Klingler, L. J.

    1973-01-01

    Modified thoria-dispersed nickel-chromium alloy has been developed that exhibits greatly improved resistance to high-temperature oxidation. Additions of aluminum have been made to change nature of protective oxide scale entirely and to essentially inhibit oxidation at temperatures up to 1260 C.

  14. DANGER OF HEXAVALENT CHROMIUM AND STRATEGY FOR THE REMEDITATION

    Directory of Open Access Journals (Sweden)

    Aniruddha Roy

    2013-02-01

    Full Text Available Some metals as micronutrients have a major role in the life and growth process of plants and animals. However, certain forms of some metals may also act as toxic material even in relatively small quantities. Chromium is such a metal, whose concentration above a certain limit may cause a serious problem to the health of living organisms. Chromium (Cr may occur in several chemical forms in organic and inorganic systems. In biological systems only Cr (III and Cr (VI are significant. Among these two states, trivalent chromium (Cr-III is considered as an essential component, while hexavalent Chromium (Cr-VI in biological system has been detected as responsible for so many diseases, even some specific forms of cancer. This paper intends to present the adverse effect of Cr(VI on environment as well as on human beings and also try to find a way out to dissolve the problem by a newly developed efficient and cost effective technique.

  15. FEATURES OF CHROMIUM DOPING OF WEAR-RESISTANT CAST IRON

    Directory of Open Access Journals (Sweden)

    V. V. Netrebko

    2013-01-01

    Full Text Available The aim of this work analysis of the influence of chromium on the process of carbide formation, changes in chemical composition of the metal substrate in the areas adjacent to the carbides and at the hardness of iron while economy nickel and manganesealloying.

  16. Structure and morphology studies of chromium film at elevated temperature in hypersonic environment

    Indian Academy of Sciences (India)

    G M Hegde; V Kulkarni; M Nagaboopathy; K P J Reddy

    2012-06-01

    This paper presents the after shock heated structural and morphological studies of chromium film coated on hypersonic test model as a passive drag reduction element. The structural changes and the composition of phases of chromium due to shock heating (2850 K) are characterized using X-ray diffraction studies. Surface morphology changes of chromium coating have been studied using scanning electron microscopy (SEM) before and after shock heating. Significant amount of chromium ablation and sublimation from the model surface is noticed from SEM micrographs. Traces of randomly oriented chromium oxides formed along the coated surface confirm surface reaction of chromium with oxygen present behind the shock. Large traces of amorphous chromium oxide phases are also observed.

  17. Preparation and Characterization of Plasma-Sprayed Ultrafine Chromium Oxide Coatings

    Institute of Scientific and Technical Information of China (English)

    LIN Feng; JIANG Xianliang; YU Yueguang; ZENG Keli; REN Xianjing; LI Zhenduo

    2007-01-01

    Ultrafine chromium oxide coatings were prepared by plasma spraying with ultrafine feedstock. Processing parameters of plasma spraying were optimized. Optical microscope (OM) was used to observe the microstructure of the ultrafine chromium oxide coatings. Scanning electron microscopy (SEM) was used to observe the morphology and particle size of ultrafine powder feedstock as well as to examine the microstructure of the chromium oxide coating. In addition, hardness and bonding strength of the ultrafine chromium oxide coatings were measured.The results showed that the optimized plasma spraying parameters were suitable for ultrafine chromium oxide coating and the properties and microstructure of the optimized ultrafine chromium oxide coating were superior compared to conventional chromium oxide wear resistant coatings.

  18. Investigations on the fracture toughness of austempered ductile iron alloyed with chromium

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P. Prasad; Putatunda, Susil K

    2003-04-15

    An investigation was carried out to examine the influence of chromium content on the plane strain fracture toughness of austempered ductile iron (ADI). ADIs containing 0, 0.3 and 0.5 wt.% chromium were austempered over a range of temperatures to produce different microstructures. The microstructures were characterized by optical microscopy and X-ray diffraction. Plane strain fracture toughness of all these materials was determined and correlated with microstructure and chromium content. The chromium content was found to influence the fracture toughness through its influence on the processing window. Since the chromium addition shifts the processing window to shorter durations, the higher chromium alloys at higher austempering temperatures tend to fall outside of the processing window, resulting in less than optimum microstructure and inferior fracture toughness. A small chromium addition of 0.3 wt.% was found to be beneficial for the fracture toughness of ADI.

  19. Ailanthus Altissima and Phragmites Australis for chromium removal from a contaminated soil.

    Science.gov (United States)

    Ranieri, Ezio; Fratino, Umberto; Petrella, Andrea; Torretta, Vincenzo; Rada, Elena Cristina

    2016-08-01

    The comparative effectiveness for hexavalent chromium removal from irrigation water, using two selected plant species (Phragmites australis and Ailanthus altissima) planted in soil contaminated with hexavalent chromium, has been studied in the present work. Total chromium removal from water was ranging from 55 % (Phragmites) to 61 % (Ailanthus). After 360 days, the contaminated soil dropped from 70 (initial) to 36 and 41 mg Cr/kg (dry soil), for Phragmites and Ailanthus, respectively. Phragmites accumulated the highest amount of chromium in the roots (1910 mg Cr/kg(dry tissue)), compared with 358 mg Cr/kg(dry tissue) for Ailanthus roots. Most of chromium was found in trivalent form in all plant tissues. Ailanthus had the lowest affinity for Cr(VI) reduction in the root tissues. Phragmites indicated the highest chromium translocation potential, from roots to stems. Both plant species showed good potentialities to be used in phytoremediation installations for chromium removal.

  20. 47 CFR 54.519 - State telecommunications networks.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false State telecommunications networks. 54.519 Section 54.519 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES... telecommunications networks. (a) Telecommunications services. State telecommunications networks may secure...

  1. Laboratory scale studies on removal of chromium from industrial wastes

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Chromium being one of the major toxic pollutants is discharged from electroplating and chrome tanning processes and is also found in the effluents of dyes, paint pigments, manufacturing units etc. Chromium exists in aqueous systems in both trivalent (Cr 3+) and hexavalent (Cr 6+) forms. The hexavalent form is carcinogenic and toxic to aquatic life, whereas Cr3+ is however comparatively less toxic. This study was undertaken to investigate the total chromium removal from industrial effluents by chemical means in order to achieve the Pakistan NEQS level of 1 mg/L by the methods of reduction and precipitation. The study was conducted in four phases.In phase I, the optimum pH and cost effective reducing agent among the four popular commercial chemicals was selected. As a result, pH of 2 was found to be most suitable and sodium meta bisulfate was found to be the most cost effective reducing agent respectively. Phase II showed that lower dose of sodium meta bisulfate was sufficient to obtain 100 % efficiency in reducing Cr6+ to Cr3+, and it was noted that reaction time had no significance in the whole process. A design curve for reduction process was established which can act as a tool for treatment of industrial effluents.Phase III studies indicated the best pH was 8.5 for precipitation of Cr 3+ to chromium hydroxide by using lime. An efficiency of 100 % was achievable and a settling time of 30 minutes produced clear effluent. Finally in Phase IV actual waste samples from chrome tanning and electroplating industries, when precipitated at pH of 12 gave 100 % efficiency at a settling time of 30 minutes and confirmed that chemical means of reduction and precipitation is a feasible and viable solution for treating chromium wastes from industries.

  2. Arsenic and chromium topsoil levels and cancer mortality in Spain.

    Science.gov (United States)

    Núñez, Olivier; Fernández-Navarro, Pablo; Martín-Méndez, Iván; Bel-Lan, Alejandro; Locutura, Juan F; López-Abente, Gonzalo

    2016-09-01

    Spatio-temporal cancer mortality studies in Spain have revealed patterns for some tumours which display a distribution that is similar across the sexes and persists over time. Such characteristics would be common to tumours that shared risk factors, including the chemical soil composition. The objective of the present study is to assess the association between levels of chromium and arsenic in soil and the cancer mortality. This is an ecological cancer mortality study at municipal level, covering 861,440 cancer deaths in 7917 Spanish mainland towns from 1999 to 2008. Chromium and arsenic topsoil levels (partial extraction) were determined by ICP-MS at 13,317 sampling points. To estimate the effect of these concentrations on mortality, we fitted Besag, York and Mollié models, which included, as explanatory variables, each town's chromium and arsenic soil levels, estimated by kriging. In addition, we also fitted geostatistical-spatial models including sample locations and town centroids (non-aligned data), using the integrated nested Laplace approximation (INLA) and stochastic partial differential equations (SPDE). All results were adjusted for socio-demographic variables and proximity to industrial emissions. The results showed a statistical association in men and women alike, between arsenic soil levels and mortality due to cancers of the stomach, pancreas, lung and brain and non-Hodgkin's lymphomas (NHL). Among men, an association was observed with cancers of the prostate, buccal cavity and pharynx, oesophagus, colorectal and kidney. Chromium topsoil levels were associated with mortality among women alone, in cancers of the upper gastrointestinal tract, breast and NHL. Our results suggest that chronic exposure arising from low levels of arsenic and chromium in topsoil could be a potential risk factor for developing cancer.

  3. Activated carbon adsorption for chromium treatment and recovery; Adsorbimento di cromo su carboni attivi a scopo di recupero e decontaminazione

    Energy Technology Data Exchange (ETDEWEB)

    Baroncelli, F.; Castelli, S.; De Francesco, M. [ENEA, Casaccia (Italy). Area Energia e Innovazione

    1994-05-01

    The capability of actived carbon systems to adsorb chromium from wastewater of galvanic industry is valued. Batch tests and column tests are carried out with good results. An activated carbon with acidic surface oxides can adsorb both chromate and chromium (III); chromate is reduced in situ and then adsorbed as chromium (III). Chromium can be desorbed from carbon by an acid or basic treatment obtaining respectively chromium (III) or chromate solutions. Carbon can be regenerated many times without evident signs of deterioration.

  4. Reduction of hexavalent chromium by ferrous iron: A process of chromium isotope fractionation and its relevance to natural environments

    DEFF Research Database (Denmark)

    Døssing, Lasse Nørbye; Dideriksen, Knud; Stipp, Susan Louise Svane;

    2011-01-01

    Stable chromium (Cr) isotopes can be used as a tracer for changing redox conditions in modern marine systems and in the geological record. We have investigated isotope fractionation during reduction of Cr(VI)aq by Fe(II)aq. Reduction of Cr(VI)aq by Fe(II)aq in batch experiments leads to significant...

  5. Raman spectroscopy of supported chromium oxide catalysts : determination of chromium-oxygen bond distances and bond orders

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Wachs, I.E.

    1996-01-01

    An empirical correlation is described for relating Raman stretching frequencies of chromium—oxygen (Cr—O) bonds to their bond lengths in chromium oxide reference compounds. An exponential fit of crystallographically determined Cr—O bond lengths to Cr—O Raman symmetric stretching frequencies (800–130

  6. 26 CFR 54.4980B-4 - Qualifying events.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 17 2010-04-01 2010-04-01 false Qualifying events. 54.4980B-4 Section 54.4980B... EXCISE TAXES (CONTINUED) PENSION EXCISE TAXES § 54.4980B-4 Qualifying events. The determination of what constitutes a qualifying event is addressed in the following questions and answers: Q-1: What is a...

  7. 36 CFR 7.54 - Theodore Roosevelt National Park.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Theodore Roosevelt National Park. 7.54 Section 7.54 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.54 Theodore Roosevelt National Park....

  8. 19 CFR 151.54 - Testing by Customs laboratory.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Testing by Customs laboratory. 151.54 Section 151.54 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF... Other Metal-Bearing Materials § 151.54 Testing by Customs laboratory. Samples taken in accordance...

  9. 49 CFR 386.54 - Administrative Law Judge.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 5 2010-10-01 2010-10-01 false Administrative Law Judge. 386.54 Section 386.54... General Rules and Hearings § 386.54 Administrative Law Judge. (a) Powers of an Administrative Law Judge. The Administrative Law Judge may take any action and may prescribe all necessary rules and...

  10. 7 CFR 54.1 - Meaning of words.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Meaning of words. 54.1 Section 54.1 Agriculture... MEAT PRODUCTS (GRADING, CERTIFICATION, AND STANDARDS) Regulations Definitions § 54.1 Meaning of words. Words used in this subpart in the singular form shall be deemed to import the plural, and vice versa,...

  11. 7 CFR 54.1001 - Meaning of words.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Meaning of words. 54.1001 Section 54.1001 Agriculture... and Poultry Products § 54.1001 Meaning of words. For the purposes of the regulations in this subpart, words in the singular form shall be deemed to impart the plural and vice versa, as the case may demand....

  12. 46 CFR 111.54-3 - Remote control.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Remote control. 111.54-3 Section 111.54-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Circuit Breakers § 111.54-3 Remote control. Remotely controlled circuit breakers must have...

  13. 46 CFR 111.54-1 - Circuit breakers.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Circuit breakers. 111.54-1 Section 111.54-1 Shipping... REQUIREMENTS Circuit Breakers § 111.54-1 Circuit breakers. (a) Each Circuit breaker must— (1) Meet the general... circuit breaker frame. (e) Each circuit breaker located in an engineroom, boilerroom, or machinery......

  14. 9 CFR 54.3 - Animals eligible for indemnity payments.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Animals eligible for indemnity payments. 54.3 Section 54.3 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE... SCRAPIE Scrapie Indemnification Program § 54.3 Animals eligible for indemnity payments. (a) Indemnity...

  15. 9 CFR 54.10 - Tests for scrapie.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Tests for scrapie. 54.10 Section 54.10... COOPERATIVE CONTROL AND ERADICATION OF LIVESTOCK OR POULTRY DISEASES CONTROL OF SCRAPIE Scrapie Indemnification Program § 54.10 Tests for scrapie. (a) The Administrator may approve new tests for the...

  16. 40 CFR 205.54-2 - Sound data acquisition system.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Sound data acquisition system. 205.54-2 Section 205.54-2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) NOISE ABATEMENT PROGRAMS TRANSPORTATION EQUIPMENT NOISE EMISSION CONTROLS Medium and Heavy Trucks § 205.54-2...

  17. 40 CFR 424.54-424.56 - [Reserved

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 28 2010-07-01 2010-07-01 true 424.54-424.56 Section 424.54-424.56 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS FERROALLOY MANUFACTURING POINT SOURCE CATEGORY Other Calcium Carbide Furnaces Subcategory §§ 424.54-424.56...

  18. 7 CFR 201.54 - Number of seeds for germination.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Number of seeds for germination. 201.54 Section 201.54... REGULATIONS Germination Tests in the Administration of the Act § 201.54 Number of seeds for germination. At least 400 seeds shall be tested for germination; except that in mixtures, 200 seeds of each of...

  19. Chromium, chromium isotopes and selected trace elements, western Mojave Desert, USA

    Energy Technology Data Exchange (ETDEWEB)

    Izbicki, John A. [U.S. Geological Survey, 4165 Spruance Road, Suite O, San Diego, CA 92123 (United States)], E-mail: jaizbick@usgs.gov; Ball, James W. [U.S. Geological Survey, 3215 Marine Street, Boulder, Colorado, CO 80303 (United States); Bullen, Thomas D. [U.S. Geological Survey, 345 Middlefield Road, Building 15, McKelvey Building, MS-420, Menlo Park, CA 94025 (United States); Sutley, Stephen J. [Denver Federal Center, P.O. Box 25046, MS-964, Denver, CO 80225-0046 (United States)

    2008-05-15

    Chromium(VI) concentrations in excess of the California Maximum Contaminant Level (MCL) of 50 {mu}g/L occur naturally in alkaline, oxic ground-water in alluvial aquifers in the western Mojave Desert, southern California. The highest concentrations were measured in aquifers eroded from mafic rock, but Cr(VI) as high as 27 {mu}g/L was measured in aquifers eroded from granitic rock. Chromium(VI) concentrations did not exceed 5 {mu}g/L at pH < 7.5 regardless of geology. {delta}{sup 53}Cr values in native ground-water ranged from 0.7 to 5.1 per mille and values were fractionated relative to the average {delta}{sup 53}Cr composition of 0 per mille in the earth's crust. Positive {delta}{sup 53}Cr values of 1.2 and 2.3 per mille were measured in ground-water recharge areas having low Cr concentrations, consistent with the addition of Cr(VI) that was fractionated on mineral surfaces prior to entering solution. {delta}{sup 53}Cr values, although variable, did not consistently increase or decrease with increasing Cr concentrations as ground-water flowed down gradient through more oxic portions of the aquifer. However, increasing {delta}{sup 53}Cr values were observed as dissolved O{sub 2} concentrations decreased, and Cr(VI) was reduced to Cr(III), and subsequently removed from solution. As a result, the highest {delta}{sup 53}Cr values were measured in water from deep wells, and wells in discharge areas near dry lakes at the downgradient end of long flow paths through alluvial aquifers. {delta}{sup 53}Cr values at an industrial site overlying mafic alluvium having high natural background Cr(VI) concentrations ranged from -0.1 to 3.2 per mille . Near zero {delta}{sup 53}Cr values at the site were the result of anthropogenic Cr. However, mixing with native ground-water and fractionation of Cr within the plume increased {delta}{sup 53}Cr values at the site. Although {delta}{sup 53}Cr was not necessarily diagnostic of anthropogenic Cr, it was possible to identify the extent

  20. Resultados da microcirurgia em 54 aneurismas intracranianos

    Directory of Open Access Journals (Sweden)

    Paulo Niemeyer

    1974-09-01

    Full Text Available O autor apresenta sua experiência em 54 aneurismas arteriais intracranianos operados com técnica microcirúrgica, no período de janeiro de 1971 a março de 1974. Em 40 doentes classificados nos grupos I, II e III, não houve mortalidade. Incluindo 8 doentes do grupo IV, onde ocorreram 3 óbitos, a mortalidade foi de 6,2%. Nos doentes do grupo V, a mortalidade continua proibitiva, seja qual for a técnica usada. Os doentes foram operados com microscópio cirúrgico de fabricação brasileira, sendo usados clips de Yasargil, Scoville, Mayfield e de modelo do autor. Comparando os resultados atuais de microcirurgia (1971-1974, com a experiência anterior, baseada em cerca de 400 casos, no período de 1949 a 1970, o autor conclui que a cirurgia dos aneurismas com auxílio do microscópio é benigna e sem mortalidade nos doentes de bom risco cirúrgico. Considera a existência de espasmo o maior problema e julga que o momento mais oportuno de operar é quando surgem as melhoras clínicas, coincidindo com o desaparecimento do espasmo, entre o 7º e 10º dia, geralmente.

  1. Analysis list: lin-54 [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available lin-54 Larvae + ce10 http://dbarchive.biosciencedbc.jp/kyushu-u/ce10/target/lin-54....1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/ce10/target/lin-54.5.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/ce10/target/li...n-54.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/ce10/colo/lin-54.Larvae.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/ce10/colo/Larvae.gml ...

  2. A computational investigation of boron-doped chromium and chromium clusters by density functional theory

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The geometries,stabilities and electronic properties of Crn and CrnB(n=2-9) clusters have been systematically investigated by density functional theory.The results suggest that the lowest energy structures for CrnB clusters can be obtained by substituting one Cr atom in Crn+1 clusters with B atom.The geometries of CrnB clusters are similar to that of Crn+1 clusters except for local structural distortion.The second-order difference and fragmentation energy show Cr4,Cr6,Cr8,Cr3B,Cr5B and Cr8B cluster are the most stable among these studied clusters.The impurity B increases the stabilities of chromium cluster.When B is doped on the Crn clusters,cluster geometry does dominate positive role in enhancing their stability.The doped B atom does not change the coupling way of the Cr site in Crn clusters,but breaks the symmetry and the Cr atoms are no longer equivalent.The doped B atom increases the total magnetic moments of Crn in most cases.

  3. Urinary levels of nickel and chromium associated with dental restoration by nickel-chromium based alloys

    Institute of Scientific and Technical Information of China (English)

    Bo Chen; Gang Xia; Xin-Ming Cao; Jue Wang; Bi-Yao Xu; Pu Huang; Yue Chen; Qing-Wu Jiang

    2013-01-01

    This paper aims to investigate if the dental restoration of nickel-chromium based alloy (Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of 〈 1 month of the restoration duration, among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain. Urinary levels of Cr were significantly higher in the three patient groups of 〈1, 1 to 〈3 and 3 to 〈6 months, especially in those with a higher metal crown exposure index. Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups. Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration. Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.

  4. A metastable chromium carbide powder obtained by carburization of a metastable chromium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Loubiere, S. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Laurent, C. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Bonino, J.P. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Rousset, A. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique

    1996-10-15

    A metastable Cr{sub 3}C{sub 2-x} carbide powder is prepared by carburization of a metastable chromium oxide in H{sub 2}-CH{sub 4} atmosphere under the appropriate conditions (temperature, dwell time and CH{sub 4} content). A very high specific surface area (greater than 210 m{sup 2} g{sup -1}) of the starting oxide is necessary to avoid the formation of the sole stable Cr{sub 3}C{sub 2} phase. The transformation from the stable Cr{sub 3}C{sub 2} to the metastable Cr{sub 3}C{sub 2-x} is observed for the first time. The driving force could be an epitaxial effect between Cr{sub 3}C{sub 2-x} and the surrounding graphite layer. This is consistent with the observation that the formation of graphite layers by CH{sub 4} cracking is easier in the Cr{sub 3}C{sub 2-x}-containing powders. (orig.)

  5. Chromium(VI) but not chromium(III) species decrease mitoxantrone affinity to DNA.

    Science.gov (United States)

    Nowicka, Anna M; Stojek, Zbigniew; Hepel, Maria

    2013-01-31

    Binding of mitoxantrone (MXT) to double-stranded DNA has been investigated as a model drug-DNA binding system to evaluate the effects of various forms of chromium on the binding properties. We have found that Cr(III), which binds strongly to DNA, does not affect the MXT affinity to DNA. In contrast, Cr(VI), in the form of chromate ions CrO(4)(2-), decreases the MXT affinity to DNA despite electrostatic repulsions with phosphate-deoxyribose chains of DNA. The MXT-DNA binding constant was found to decrease from (1.96 ± 0.005) × 10(5) to (0.77 ± 0.018) × 10(5) M(-1) for Cr(VI) concentration changing from 0 to 30 μM. The influence of Cr(VI) on MXT-DNA binding has been attributed to the oxidation of guanine residue, thus interrupting the intercalation of MXT into the DNA double helix at the preferential CpG intercalation site. This supposition is corroborated by the observed increase in the MXT binding site size from 2 bp (base pairs) to 4-6 bp in the presence of Cr(VI). The measurements of the MXT-DNA binding constant and the MXT binding site size on a DNA molecule have been carried out using spectroscopic, voltammetric, and nanogravimetric techniques, providing useful information on the mechanism of the interactions.

  6. Maximum availability and mineralogical control of chromium released from AOD slag.

    Science.gov (United States)

    Li, Junguo; Liu, Bao; Zeng, Yanan; Wang, Ziming; Gao, Zhiyuan

    2017-03-01

    AOD (argon oxygen decarburization) slag is the by-product in the stainless steel refining process. Chromium existing in AOD slag can leach out and probably poses a serious threat to the environment. To assess the leaching toxicity of chromium released from AOD slag, the temperature-dependent maximum availability leaching test was performed. To determine the controlling mineralogical phases of chromium released from AOD slag, a Visual MINTEQ simulation was established based on Vminteq30 and the FactSage 7.0 database. The leaching tests indicated that the leaching availability of chromium was slight and mainly consisted of trivalent chromium. Aging of AOD slag under the atmosphere can oxidize trivalent chromium to hexavalent chromium, which could be leached out by rainwater. According to the simulation, the chromium concentration in leachates was controlled by the freely soluble pseudo-binary phases in the pH = 7.0 leaching process and controlled by the Cr2O3 phase in the pH = 4.0 leaching process. Chromium concentrations were underestimated when the controlling phases were determined to be FeCr2O4 and MgCr2O4. Facilitating the generation of the insoluble spinel-like phases during the cooling and disposal process of the molten slag could be an effective approach to decreasing the leaching concentration of chromium and its environmental risk.

  7. Finished leather waste chromium acid extraction and anaerobic biodegradation of the products.

    Science.gov (United States)

    Ferreira, Maria J; Almeida, Manuel F; Pinho, Sílvia C; Santos, Isabel C

    2010-06-01

    Due to the amounts of chromium in the leachate resulting from leather leaching tests, chromium sulfate tanned leather wastes are very often considered hazardous wastes. To overcome this problem, one option could be recovering the chromium and, consequently, lowering its content in the leather scrap. With this objective, chromium leather scrap was leached with sulfuric acid solutions at low temperature also aiming at maximizing chromium removal with minimum attack of the leather matrix. The effects of leather scrap dimension, sulfuric acid and sodium sulfate concentration in the solutions, as well as extraction time and temperature on chromium recovery were studied, and, additionally, organic matrix degradation was evaluated. The best conditions found for chromium recovery were leather scrap conditioning using 25mL of concentrated H(2)SO(4)/L solution at 293 or 313K during 3 or 6days. Under such conditions, 30-60+/-5% of chromium was recovered and as low as 3-6+/-1% of the leather total organic carbon (TOC) was dissolved. Using such treatment, the leather scrap area and volume are reduced and the residue is a more brittle material showing enhanced anaerobic biodegradability. Although good recovery results were achieved, due to the fact that the amount of chromium in eluate exceeded the threshold value this waste was still hazardous. Thus, it needs to be methodically washed in order to remove all the chromium de-linked from collagen.

  8. Black and green pigments based on chromium-cobalt spinels

    Energy Technology Data Exchange (ETDEWEB)

    Eliziario, Sayonara A., E-mail: sayonaraea@iq.unesp.br [Departamento de Fisico-Quimica, Instituto de Quimica, UNESP - Univ Estadual Paulista, Araraquara, SP (Brazil); Departamento de Quimica, CCEN, Universidade Federal da Paraiba, Campus I, Joao Pessoa, PB (Brazil); Andrade, Jeferson M. de [Departamento de Quimica, CCEN, Universidade Federal da Paraiba, Campus I, Joao Pessoa, PB (Brazil); Lima, Severino J.G. [Departamento de Engenharia Mecanica, CT, Universidade Federal da Paraiba, Campus I, Joao Pessoa, PB (Brazil); Paskocimas, Carlos A. [Universidade Federal do Rio Grande do Norte, CT, Natal, RN (Brazil); Soledade, Luiz E.B. [Departamento de Quimica, CCEN, Universidade Federal da Paraiba, Campus I, Joao Pessoa, PB (Brazil); Hammer, P.; Longo, E. [Departamento de Fisico-Quimica, Instituto de Quimica, UNESP - Univ Estadual Paulista, Araraquara, SP (Brazil); Souza, Antonio G.; Santos, Ieda M.G. [Departamento de Quimica, CCEN, Universidade Federal da Paraiba, Campus I, Joao Pessoa, PB (Brazil)

    2011-09-15

    Highlights: {yields} Co(Co{sub 2-x}Cr{sub x})O{sub 4} powders with different chromium concentrations (x = 0, 0.25 and 1) were prepared by the polymeric precursor method. {yields} Co(CoCr)O{sub 4} and Co(Co{sub 1.75}Cr{sub 0.25})O{sub 4} displayed a dark color and CoCr{sub 2}O{sub 4} was green. {yields} The colors were related to the different oxidation states of Cr and Co. {yields} Cobalt enrichment result in an increasing presence of Co(III) and a decrease amount of Cr(VI). - Abstract: Chromium and cobalt oxides are widely used in the manufacture of industrial pigments. In this work, the Co(Co{sub 2-x}Cr{sub x})O{sub 4} powders with different chromium concentrations (x = 0, 0.25 and 1) were synthesized by the polymeric precursor method, heat treatment between 600 and 1000 deg. C. These powders were characterized by X-ray diffraction, infrared spectroscopy, colorimetry, UV-vis absorption and X-ray photoelectron spectroscopies. Even with the addition of chromium, the XRD patterns revealed that all powders crystallize in a single spinel cubic structure. The spinels with higher cobalt amount, Co(CoCr)O{sub 4} and Co(Co{sub 1.75}Cr{sub 0.25})O{sub 4}, displayed a dark color, without the Co{sup 3+} reduction observed in Co{sub 3}O{sub 4} between 900 and 950 deg. C. The spinel with higher chromium amount, CoCr{sub 2}O{sub 4}, was green. The colors were directly related to the occupation of tetrahedral and octahedral sites by the chromophores, as well as to the different oxidation states of chromium and cobalt. The different optical band gap values estimated from UV-vis spectra suggested the existence of intermediary energy levels within the band gap. X-ray photoelectron spectroscopy confirmed an increasing presence of Co(III) and a decreasing amount of Cr(VI) with cobalt enrichment.

  9. STS-54 Space Shuttle mission report

    Science.gov (United States)

    Fricke, Robert W., Jr.

    1993-03-01

    The STS-54 Space Shuttle Program Mission Report is a summary of the Orbiter, External Tank (ET), Solid Rocket Booster/Redesigned Solid Rocket Motor (SRB/RSRM), and the Space Shuttle Main Engine (SSME) subsystems performance during this fifty-third flight of the Space Shuttle Program, and the third flight of the Orbiter vehicle Endeavour (OV-105). In addition to the Orbiter, the flight vehicle consisted of an ET, which was designated ET-51; three SSME's, which were serial numbers 2019, 2033, and 2018 in positions 1, 2, and 3, respectively; and two retrievable and reusable SRB's which were designated BI-056. The lightweight RSRM's that were installed in each SRB were designated 360L029A for the left SRB, and 360L029B for the right SRB. The primary objectives of this flight were to perform the operations to deploy the Tracking and Data Relay Satellite-F/Inertial Upper Stage payload and to fulfill the requirements of the Diffuse X-Ray Spectrometer (DXS) payload. The secondary objective was to fly the Chromosome and Plant Cell Division in Space (CHROMEX), Commercial Generic Bioprocessing Apparatus (CGBA), Physiological and Anatomical Rodent Experiment (PARE), and the Solid Surface Combustion Experiment (SSCE). In addition to presenting a summary of subsystem performance, this report also discusses each Orbiter, ET, SSME, SRB, and RSRM in-flight anomaly in the applicable section of the report. The official tracking number for each in-flight anomaly, assigned by the cognizant project, is also shown. All times are given in Greenwich mean time (G.m.t.) and mission elapsed time (MET).

  10. Removal of Chromium with The Complexing Agents from Industrial Effluents

    Directory of Open Access Journals (Sweden)

    J. L. Prameena Sheeja

    2016-08-01

    Full Text Available Human activities and consequent developments have brought about the spectre of an overwhelming degradation of all facets of the natural environment-physical, chemical, biological and social. Environmental pollution, especially by chemicals, is one of the most significant factors in the degradation of the biosphere components. Among all chemical contaminants, heavy metals are believed to be of special ecological, biological and health significance. Unlike organic pollutants, the majority of which are susceptible to biological degradation, metal ions do not degrade into harmless end products. Chemical precipitation is a simple and economical method, and hence, has been widely used. The reduction of chromium (VI to chromium (III can be done with the help of ferrous sulphate. The precipitation was carried out in the presence and absence of complexing agents such as ammonium chloride, tartrate and citrate.

  11. Internal Friction In The PFN Ceramics With Chromium Dopand

    OpenAIRE

    Zachariasz R.; Bochenek D.; Bruś B.

    2015-01-01

    An aim of this work was to determine an influence of an admixture, the chromium (for x from 0.01 to 0.06), on the mechanical properties of the PFN ceramics. The ceramics with chemical composition Pb(Fe0.5−xCrxNb0.5)O3 was synthesized in two steps from simple oxides PbO, Fe2O3, Nb2O5, Cr2O3. The first stage was based on obtaining the FeNbO4 from the Fe2O3 and Nb2O5 simple oxides. At this stage an admixture in a form the Cr2O3 chromium oxide was added to the solution. In the second stage the Pb...

  12. Preparation of Silica Modified with 2-Mercaptoimidazole and its SorptionProperties of Chromium(III

    Directory of Open Access Journals (Sweden)

    Harry Budiman

    2009-01-01

    Full Text Available Modified silica gel was prepared to remove the heavy metal of chromium(III from water sample. Silica gel was used as supporting material and the 2-mercaptoimidazole was immobilized onto surface silica so that the silica would have selective properties to adsorb the heavy metal chromium(III through the formation of coordination compound between the 2-mercaptoimidazole and chromium(III. The characterization of modified silica gel was carried out by analyzing the Fourier Transform Infrared Spectrum of this material in order to ensure the immobilization of 2-mercaptoimidazole onto the surface. The effect of pH solution, initial concentration of chromium(III, and interaction time were investigated in batch mode to find the adsorption properties of chromium(III onto modified silica. The condition optimum of these parameters was applied to determine the removal percentage of chromium(III in water sample using the modified silica gel

  13. Determination of Chromium(III) Picolinate Using High Performance Liquid Chromatography-Ultraviolet Spectrophotometry

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Il; Woo, Dong Jin; Kang, Dae Kyung [EASY BIO System, Inc, Chonan (Korea, Republic of); Lee, Myung Hee [Pollin, Inc, Seoul (Korea, Republic of); Woo, Gun Jo [Korea Food and Drug Administration, Seoul (Korea, Republic of); Cha, Ki Won [Inha University, Incheon (Korea, Republic of)

    2003-10-15

    Cr-(pic){sub 3} has been widely used as food additives, drugs, and feed additives. Accordingly, its determination method should be established. In the present paper, we have studied the determination method of chromium(III) picolinate accurately using ESI-MS on-lined with HPLC. Chromium(III) picolinate in feed products was determined successfully. Chromium(III) is very well known as an essential mineral. It is suggested as a cofactor in the maintenance of both normal lipid and carbohydrate metabolism by assisting the action of insulin on a cell membrane. According to the National Research Council, the daily recommended intake of chromium(III) is 50-200 μg. Several organic chromium(III) complexes have been reported to have significantly higher absorption and tissue incorporation activity than inorganic salts such as chromium(III) chloride.

  14. Biological monitoring of occupational exposure to different chromium compounds at various valency states

    Energy Technology Data Exchange (ETDEWEB)

    Mutti, A.; Pedroni, C.; Arfini, G.; Franchini, I.; Minoia, C.; Micoli, G.; Baldi, C.

    1984-01-01

    Chromium concentrations in the air were measured in seven different workroom environments, where exposure to water soluble hexavalent or trivalent compounds was expected. Urinary excretion of chromium was measured before and after the same arbitrarily chosen working day. End-of-shift urinary chromium and its increase above pre-exposure levels were closely related to the concentration of water soluble chromium (VI) in the air. The values corresponding to 50 micrograms m-3 in the air, which is the current threshold limit value in most countries, were 29.8 and 12.2 micrograms g-1 of creatinine, respectively. Urinary chromium in workers exposed to water insoluble chromates or to water soluble chromic (III) sulphate was definitely higher than that observed in subjects not occupationally exposed to chromium compounds, but it cannot be recommended as short-term exposure test for evaluation of the job-related hazard.

  15. Bioconcentration of chromium in edible mushrooms: influence of environmental and genetic factors.

    Science.gov (United States)

    García, M A; Alonso, J; Melgar, M J

    2013-08-01

    Chromium concentrations were determined in 167 samples of wild edible mushrooms, collected from three different sites (urban, traffic and pastureland areas) in Lugo (NW Spain). The hymenophore (H) and the rest of the fruiting body (RFB) were analysed separately. The analyses were performed using inductively coupled plasma optical emission spectrometry (ICP-OES). The highest mean chromium levels (mg/kg dry weight) of 3.5 and 8.0, 4.5 and 6.2, and 6.2 and 4.3 were found in Lycoperdon utriforme, Coprinus comatus and Agaricus campestris in H and RFB, respectively. The highest concentrations of chromium were observed in terrestrial saprophytic species in relation to mycorrhizal species. With respect to the underlying substrates, chromium concentration was lowest in the pastureland area (24.6 mg/kg dw). All mushroom species were bioexclusors of chromium (BCFmushrooms harvested from the areas investigated poses no toxicological risk to human health due to chromium.

  16. Chromium speciation in solid matrices and regulation: a review

    Energy Technology Data Exchange (ETDEWEB)

    Unceta, N. [University of the Basque Country, Department of Analytical Chemistry, Faculty of Pharmacy, Vitoria-Gasteiz (Spain); Seby, F. [Ultra Traces Analyses Aquitaine (UT2A), Helioparc Pau-Pyrenees, Pau (France); Malherbe, J.; Donard, O.F.X. [Universite de Pau et des Pays de l' Adour, Helioparc Pau-Pyrenees, Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, IPREM, UMR CNRS 5254, Pau (France)

    2010-06-15

    In recent years, the extensive use of chromium in industrial processes has led to the promotion of several directives and recommendations by the European Union, that try to limit and regulate the presence of Cr(VI) in the environment and to protect industrial workers using chromium and end-users of manufactured products. As a consequence, new standard methods and analytical procedures have been published at the EU level for Cr(VI) determination in soil, sludge, sediment, and similar waste materials, workplace atmospheres, cement, packaging materials, industrially produced samples, and corrosion-protection layers on some components of vehicles and electrical and electronic equipment. The objective of this article is to summarize the different directives and recommendations and to critically review the currently existing standard methods and the methods published in the literature for chromium speciation in the above mentioned solid matrices, putting the emphasis on the different extraction procedures which have been developed for each matrix. Particular attention has been paid to Cr(III) and Cr(VI) inter-conversions that can occur during extraction and efforts to minimize these unwanted reactions. Although the use of NaOH-Na{sub 2}CO{sub 3} solutions with hot plate extraction seems to be the more widespread procedure, species transformation can still occur and several studies suggest that speciated isotope-dilution mass spectrometry (SIDMS) could be a suitable tool for correction of these interconversions. Besides, recent studies have proved the role of Cr(III) in chromium toxicology. As a consequence, the authors suggest an update of standard methods in the near future. (orig.)

  17. Technology Demonstration of the Zero Emissions Chromium Electroplating System

    Science.gov (United States)

    2008-02-01

    blanket technology for electroplating tanks. When no liquid blanket is used, evaporation of water, especially during warm weather conditions, requires...0.007 0.004 0.002 Tank 12A had noticeable blobs floating on the surface and also at the interfacial layer of PRD fluid and the chromium acid solution...Tank 12B did not have any such blobs . All the parts removed after plating looked fairly good. There were no visible streaks, water breaks, etc. The

  18. Recovery of Chromium from Waste Taning Liquors by Magnesium Oxide

    Directory of Open Access Journals (Sweden)

    Mahmood M. Barbooti

    2010-10-01

    Full Text Available This is a case study of AL-Za’afaraniya tanning factory, 15 km to the south of Baghdad, to spot light on simple chemical treatment of the discharged water to solve the environmental problems associated with its chromium content management. The treatment was extended to the recovery and reuse of chromium. Chromium was precipitated by the addition of magnesium oxide which also aid as a neutralizer for the acidic effluent. The laboratory treatment was carried out to find the optimum conditions. The wastewater samples were taken from the outline area of the tannery. Box-Wilson method was adopted to find useful relationships between the operating variables (temperature, mixing period and magnesium oxide dose and the pH and chromium content of effluent. The experimental data were successfully fitted to second order polynomial mathematical models for the treatment. The most favorable operating conditions for the treatment were: temperature, 30 ºC; mixing period, 50 min and magnesium oxide concentration, 3000 mg/L. On using the optimum conditions a mathematical model simulating the operation for the treatment was obtained as follows:Cr = 6.0848 – 0.001839 X11 – 0.105334 X12 – 0.041038 X13pH = 10.29086 – 0.001223 X11 – 0.140043 X12 – 0.00953 X13Experimentally Cr concentration was decreased to about (0.5 mg/L in wastewater after raising the pH value to (7.35 by adding magnesium oxide.

  19. THE WEAR RESISTANCE INCREASE OF CHROMIUM CAST IRON

    Directory of Open Access Journals (Sweden)

    V. M. Ilyushenko

    2016-01-01

    Full Text Available The article presents the results of the tests on the wear resistance of chromium cast irons of different compositions obtained in sand forms. It has been shown that increase of the wear resistance and mechanical properties of the cast iron is possible to obtain using the casting in metal molds. A further increase in wear resistance of parts produced in metal molds is possible by changing the technological parameters of casting and alloying by titanium.

  20. Evidence of weak ferromagnetism in chromium(III) oxide particles

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez-Vazquez, Carlos E-mail: qfmatcvv@usc.es; Banobre-Lopez, Manuel; Lopez-Quintela, M.A.; Hueso, L.E.; Rivas, J

    2004-05-01

    The low temperature (4chromium(III) oxide particles have been studied. A clear evidence of the presence of weak ferromagnetism is observed below 250 K. The magnetisation curves as a function of the applied field show coercive fields due to the canted antiferromagnetism of the particles. Around 55 K a maximum is observed in the zero-field-cooled curves; this maximum can be assumed as a blocking temperature, similarly to ultrafine ferromagnetic particles.

  1. Chromium related degradation of solid oxide fuel cells; Chrom-bezogene Degradation von Festoxid-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Anita

    2011-05-04

    Solid Oxide Fuel Cells (SOFCs) offer a high potential for application as an auxiliary power unit (APU) for heavy goods vehicles as well as combined heat and power (CHP) systems. SOFCs are especially attractive due to their high efficiencies and the use of different fuel types. However, optimization in terms of long term stability and costs are still necessary. This work characterized the degradation of SOFCs with lanthanum strontium manganite (LSM) cathodes under chromium influence. Galvanostatic cell tests were carried out at 800 C with operation times from 250 - 3000 h and variation of the chromium source and current density. The current densities of j = 0 (A)/(cm{sup 2}), j = 0,3 (A)/(cm{sup 2}) and j = 0,5 (A)/(cm{sup 2}) were applied. The high temperature ferritic alloy Crofer22APU was used as a chromium source. Variation of the chromium source was realized by coating the Crofer22APU insert with the chromium retention layer Mn{sub 3}O{sub 4} and the cathode contact layer LCC10. Cell degradation was analyzed with regard to cell voltage, current density and area specific resistance (ASR). Microstructural alterations of the cathode as well as chromium content and distribution across the cell were investigated after completion of the cell tests. For cells with a chromium source present and operation with a nonzero current density, the course of cell degradation was divided into three phases: a run-in, weak linear degradation and strong linear degradation. A decrease of the chromium release rate by means of different coatings stretched the course of degradation along the timescale. Strong degradation, which is characterized by a significant increase in ASR as well as a decrease of current density at the operating point, was only observed when a chromium source in the setup was comb ined with operation of the cell with a non-zero current density. Operation of the cell with a chromium source but no current density caused a degradation of current density at the

  2. Study on anaerobic treatment of wastewater containing hexavalent chromium

    Institute of Scientific and Technical Information of China (English)

    XU Yan-bin; XIAO Hua-hua; SUN Shui-yu

    2005-01-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and CODCr ofwastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L,the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear superiority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microorganisms.

  3. Adsorptive stripping voltammetric determination of chromium in gallium.

    Science.gov (United States)

    Palrecha, M M; Mathur, P K

    1997-12-19

    The electroanalytical chemistry of trace metals has progressed strongly with the development of cathodic stripping voltammetry (CSV) preceded by adsorption collection of organic metal complexes. A sensitive method for the determination of trace amount of chromium in gallium is described. Gallium is dissolved in sodium hydroxide containing hydrogen peroxide. The method is based on the catalytic activity of nitrate ions on the reduction of Cr(III)TTHA (triethylene tetramine-N,N,N',N'',N''',N'''-hexaacetic acid) complex. The sensitivity of this method is further improved by adsorption preconcentration of Cr(III)TTHA complex at a hanging mercury drop electrode (HMDE). The Cr(III) formed at the electrode surface by the reduction of Cr(VI), which is present in the bulk solution, is immediately complexed by TTHA. The adsorbed complex is then reduced at a peak potential of - 1.26 V, and the peak height of Cr(III) reduction is measured. The determination limit was restricted by the amount of chromium present in the reagent blank solution. The method is suitable for the determination of chromium at level as low as 0.2 mug g(-1) (with about 50 mg of sample) and a relative standard deviation of 15%.

  4. The chromium site in doped glassy lithium tetraborate

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, T.D. [Department of Engineering Physics, Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, OH 45433 (United States); Echeverria, E.; Beniwal, Sumit [Department of Physics and Astronomy, 855 North 16th Street, Theodore Jorgensen Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0299 (United States); Adamiv, V.T.; Burak, Ya. V.; Enders, Axel [Institute of Physical Optics, 23 Dragomanov Street, Lviv 79005 (Ukraine); Petrosky, J.C.; McClory, J.W. [Department of Engineering Physics, Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, OH 45433 (United States); Dowben, P.A., E-mail: pdowben1@unl.edu [Department of Physics and Astronomy, 855 North 16th Street, Theodore Jorgensen Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0299 (United States)

    2014-10-15

    Using extended X-ray absorption fine structure (EXAFS) spectroscopy, we find that Cr substitutes primarily in the Li{sup +} site as a dopant in lithium tetraborate Li{sub 2}B{sub 4}O{sub 7} glasses, in this case 98.4Li{sub 2}B{sub 4}O{sub 7}–1.6Cr{sub 2}O{sub 3} or nominally Li{sub 1.98}Cr{sub 0.025}B{sub 4}O{sub 7}. This strong preference for a single site is nonetheless accompanied by site distortions and some site disorder, helping explain the optical properties of chromium doped Li{sub 2}B{sub 4}O{sub 7} glasses. The resulting O coordination shell has a contraction of the Cr–O bond lengths as compared to the Li–O bond lengths. There is also an increase in the O coordination number. - Graphical abstract: Lithium tetraborate: labeled are the B1 and B2 sites, where the latter correspond to BO{sub 3} and BO{sub 4} structures respectively. - Highlights: • Adoption of the Li + site for chromium dopants in lithium tetraborate identified. • Increased oxygen coordination for glass over the crystalline lithium tetraborate. • Distortions about the doping chromium characterized. • Local bond order is preserved in spite of the glassy nature.

  5. Study on anaerobic treatment of wastewater containing hexavalent chromium.

    Science.gov (United States)

    Xu, Yan-bin; Xiao, Hua-hua; Sun, Shui-yu

    2005-06-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and COD(Cr) of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear superiority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microorganisms.

  6. Study on anaerobic treatment of wastewater containing hexavalent chromium*

    Science.gov (United States)

    Xu, Yan-bin; Xiao, Hua-hua; Sun, Shui-yu

    2005-01-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and CODCr of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear superiority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microorganisms. PMID:15909347

  7. Chromium and manganese interactions in streptozocin-diabetic rats

    Energy Technology Data Exchange (ETDEWEB)

    Davis, M.L.; Jarrett, C.R.; Adeleye, B.O.; Stoecker, B.J. (Oklahoma State Univ., Stillwater (United States))

    1991-03-15

    Weanling male rats were fed casein-based diets low in chromium and manganese ({minus}Cr-MN) or supplemented with 1 ppm chromium as chromium chloride (+Cr) and/or 55 ppm manganese as manganous carbonate in a factorial design. After 7 weeks on the experimental diets, half of the rats in each group were injected on 2 consecutive days with 55 mg/kg streptozocin (STZ) in citrate buffer pH 4. Four weeks after injection, serum glucose in the diabetic group supplement with both Cr and Mn was not different from non-diabetic animals; however, diabetic animals in {minus}Cr groups or in the +Cr-Mn group had significantly elevated serum glucose. Serum insulin was reduced by STZ. A significant interaction between Mn and diabetes affected serum cortisol concentrations. More new tissue was formed on a polyvinyl sponge inserted under the skin in +Mn animals. In this study, the STZ animals were more sensitive than the control animals to dietary Cr and Mn concentrations.

  8. Magnesium, zinc, and chromium nutriture and physical activity.

    Science.gov (United States)

    Lukaski, H C

    2000-08-01

    Magnesium, zinc, and chromium are mineral elements required in modest amounts to maintain health and optimal physiologic function. For physically active persons, adequate amounts of these micronutrients are needed in the diet to ensure the capacity for increased energy expenditure and work performance. Most physically active individuals consume diets that provide amounts of magnesium and zinc sufficient to meet population standards. Women tend to consume less of these minerals than is recommended, in part because they eat less food than men. Inadequate intakes of magnesium and zinc have been reported for participants in activities requiring restriction of body weight. Dietary chromium is difficult to estimate because of a lack of appropriate reference databases. Acute, intense activity results in short-term increases in both urine and sweat losses of minerals that apparently diminish during recovery in the days after exercise. Supplemental magnesium and zinc apparently improve strength and muscle metabolism. However, evidence is lacking as to whether these observations relate to impaired nutritional status or a pharmacologic effect. Chromium supplementation of young men and women does not promote muscle accretion, fat loss, or gains in strength. Physically active individuals with concerns about meeting guidelines for nutrient intake should be counseled to select and consume foods with high nutrient densities rather than to rely on nutritional supplements. The indiscriminate use of mineral supplements can adversely affect physiologic function and impair health.

  9. Fabrication of chitosan-magnetite nanocomposite strip for chromium removal

    Science.gov (United States)

    Sureshkumar, Vaishnavi; Kiruba Daniel, S. C. G.; Ruckmani, K.; Sivakumar, M.

    2016-02-01

    Environmental pollution caused by heavy metals is a serious threat. In the present work, removal of chromium was carried out using chitosan-magnetite nanocomposite strip. Magnetite nanoparticles (Fe3O4) were synthesized using chemical co-precipitation method at 80 °C. The nanoparticles were characterized using UV-visible spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction spectrometer, atomic force microscope, dynamic light scattering and vibrating sample magnetometer, which confirm the size, shape, crystalline nature and magnetic behaviour of nanoparticles. Atomic force microscope revealed that the particle size was 15-30 nm and spherical in shape. The magnetite nanoparticles were mixed with chitosan solution to form hybrid nanocomposite. Chitosan strip was casted with and without nanoparticle. The affinity of hybrid nanocomposite for chromium was studied using K2Cr2O7 (potassium dichromate) solution as the heavy metal solution containing Cr(VI) ions. Adsorption tests were carried out using chitosan strip and hybrid nanocomposite strip at different time intervals. Amount of chromium adsorbed by chitosan strip and chitosan-magnetite nanocomposite strip from aqueous solution was evaluated using UV-visible spectroscopy. The results confirm that the heavy metal removal efficiency of chitosan-magnetite nanocomposite strip is 92.33 %, which is higher when compared to chitosan strip, which is 29.39 %.

  10. Foam separation of chromium (Ⅵ) from aqueous solution

    Institute of Scientific and Technical Information of China (English)

    JIAO Cai-shan; DING Yan

    2009-01-01

    Removal of chromium (Ⅵ) dissolved in water by intermittent foam separation was implemented with cetyl trimethy-ammonium bromide as surfactant. The influence of various factors on removal efficiency was systematically studied. The removal efficiency has a maximum value near pH 4.0; thus, most experiments were carried out at pH 4.0. The orthogonal experiment was conducted to confirm the optimal operating parameters. The orthogonal experimental results show that when the liquid feed concentration is 10 mg/L, the pH value of feed solution is 4.00, air flow rates 0.9 L/min, surfactant dosage is 300 mg/L, the maximum removal efficiency of chromium (Ⅵ) reaches 97.80%, and condense multiple reaches 1711. The kinetic test indicates that the foam separation of chromium is a first-order process. The equivalent rate constant calculated from the slope is 0.406 4, and the equivalent rate equation is obtained.

  11. Fabrication of Carbon Nanotube - Chromium Carbide Composite Through Laser Sintering

    Science.gov (United States)

    Liu, Ze; Gao, Yibo; Liang, Fei; Wu, Benxin; Gou, Jihua; Detrois, Martin; Tin, Sammy; Yin, Ming; Nash, Philip; Tang, Xiaoduan; Wang, Xinwei

    2016-03-01

    Ceramics often have high hardness and strength, and good wear and corrosion resistance, and hence have many important applications, which, however, are often limited by their poor fracture toughness. Carbon nanotubes (CNTs) may enhance ceramic fracture toughness, but hot pressing (which is one typical approach of fabricating CNT-ceramic composites) is difficult to apply for applications that require localized heat input, such as fabricating composites as surface coatings. Laser beam may realize localized material sintering with little thermal effect on the surrounding regions. However, for the typical ceramics for hard coating applications (as listed in Ref.[1]), previous work on laser sintering of CNT-ceramic composites with mechanical property characterizations has been very limited. In this paper, research work has been reported on the fabrication and characterization of CNT-ceramic composites through laser sintering of mixtures of CNTs and chromium carbide powders. Under the studied conditions, it has been found that laser-sintered composites have a much higher hardness than that for plasma-sprayed composites reported in the literature. It has also been found that the composites obtained by laser sintering of CNTs and chromium carbide powder mixtures have a fracture toughness that is ~23 % higher than the material obtained by laser sintering of chromium carbide powders without CNTs.

  12. Response of soil catalase activity to chromium contamination

    Institute of Scientific and Technical Information of China (English)

    Zofia St(e)pniewska; Agnieszka Woli(n)ska; Joanna Ziomek

    2009-01-01

    The impact of chromium (III) and (VI) forms on soil catalase activity is presented.The Orthic Podzol, Haplic Phaeozem and Mollic Gleysol from different depths were used in the experiment.The soil samples were amended with solution of Cr(III) using CrCl3, and with Cr(VI) using K2Cr2O7 in the concentration range from 0 to 20 mg/kg, whereas the samples without the addition of chromium served as control.Catalase activity was assayed by one of the commonly used spectrophotometric methods.As it is demonstrated in the experiment, both Cr(III) and Cr(VI) forms have ability to reduce soil catalase activity.A chromium dose of 20 mg/kg caused the inhibition of catalase activity and the corresponding contamination levels ranged from 75% to 92% for Cr(III) and 68% to 76% for Cr(VI), with relation to the control.Catalase activity reached maximum in the soil material from surface layers (0-25 cm), typically characterized by the highest content of organic matter creating favorable conditions for microorganisms.

  13. Achieving Zero Stress in Iridium, Chromium, and Nickle Thin Films

    Science.gov (United States)

    Broadway, David M.; Weimer, Jeffrey; Gurgew, Danielle; Lis, Tomasz; Ramsey, Brian D.; O'Dell, Stephen L.; Ames, A.; Bruni, R.

    2015-01-01

    We examine a method for achieving zero intrinsic stress in thin films of iridium, chromium, and nickel deposited by magnetron sputter deposition. The examination of the stress in these materials is motivated by efforts to advance the optical performance of light-weight x-ray space telescopes into the regime of sub-arc second resolution that rely on control of the film stress to values within 10-100 MPa. A characteristic feature of the intrinsic stress behavior in chromium and nickel is their sensitivity to the magnitude and sign of the intrinsic stress with argon gas pressure, including the existence of a critical pressure that results in zero film stress. This critical pressure scales linearly with the film's density. While the effect of stress reversal with argon pressure has been previously reported by Hoffman and others for nickel and chromium, we have discovered a similar behavior for iridium. Additionally, we have identified zero stress in iridium shortly after island coalescence. This feature of film growth is used for achieving a total internal stress of -2.89 MPa for a 15.8 nm thick iridium film. The surface roughness of this low-stress film was examined using scanning probe microscopy (SPM) and x-ray reflectivity (XRR) at CuKa and these results presented and discussed.

  14. Simultaneously Recovering High-Purity Chromium and Removing Organic Pollutants from Tannery Effluent

    OpenAIRE

    Jie Zong; Yan-Chun Li; Kang Hu

    2016-01-01

    Chromium pollution is a serious issue because of carcinogenic toxicities of the pollutants and low recovery rate of chromium because of the presence of organic, such as protein and fat. In this work, high recovery rate and high purity of the chromium ion were successfully prepared by the way of acid enzyme, flocculant, and Fenton oxidation. The experiments were characterized by TG, TOC, UV-VIS, and SEM. In the work, the tannery waste chrome liquor was used as experimental material. The result...

  15. Adsorption of Chromium(VI) from Aqueous Solutions by Coffee Polyphenol-Formaldehyde/Acetaldehyde Resins

    OpenAIRE

    2013-01-01

    Removal of chromium(VI) from wastewater is essential as it is toxic. Thus, removal of chromium(VI) was performed using coffee polyphenol-formaldehyde/acetaldehyde resins as adsorbents. Adsorbent resins were prepared by condensation of decaffeinated coffee powder with formaldehyde/acetaldehyde and used for the removal of Cr(VI) ions from aqueous solutions. A simple and sensitive solid phase extraction procedure was applied for the determination of chromium at trace levels by spectroscopic meth...

  16. Caracterización Fitoquímica y Efecto Hipoglucemiante de Tecoma stans y su Relación con la Presencia del Cromo como Factor de Tolerancia a la Glucosa Phytochemical Characterization and Hypoglycemic Effect of the Tecoma stans and its Relationship to the Presence of Chromium as a Factor for Glucose Tolerance

    Directory of Open Access Journals (Sweden)

    Ma. de J Ibarra

    2009-01-01

    Full Text Available Se realizó la caracterización fitoquímica y la determinación del cromo en hojas de Tecoma stans, observando su efecto hipoglucemiante en animales con diabetes mellitus inducida en forma experimental. Como hiperglucemiante se utilizó estreptozotocina en ratas machos Sprague-Dawley a una dosis de 45 mg/kg de peso. Los tratamientos experimentales, todos por vía oral, fueron los siguientes para grupos diabéticos y grupos no diabéticos: agua, infusión de la planta, picolinato de cromo, e infusión combinada con picolinato de cromo. Se encontró cromo en T. stans (54 µg/100g, la hiperglucemia disminuyó hasta 33.5 % con T. stans, 10.1% con picolinato de cromo y 32.3% con la combinación de T. stans y picolinato de cromo, en 45 días. Con este estudio se confirma el efecto hipoglucemiante de T. stans.Phytochemical characterization of Tecoma stans leaves, determination of chromium and their hypoglucemiant action in experimental animals with induced diabetes was done. The hyperglucemiant streptozotocin was employed in Sprague Dawley male rats at a dose of 45 mg/kg. The experimental treatments, all orally delivered, were the following for both diabetic and non diabetic groups: water, infusion of the plant, chromium picolinate and infusion combined with chromium picolinato. Chromium was found in T. stans (54 µg/100g, glucose levels decreased up to 33, 5 % with T. stans, 10, 1% with chromium picolinate and 32, 3% with the combination of T. stans and chromium picolinate, in 45 days. The hypoglucemiant effect of T. stans was confirmed with this study.

  17. Reductive activation with cysteine represents a chromium(III)-dependent pathway in the induction of genotoxicity by carcinogenic chromium(VI).

    Science.gov (United States)

    Zhitkovich, Anatoly; Quievryn, George; Messer, Joseph; Motylevich, Zhanna

    2002-10-01

    Induction of DNA damage by carcinogenic hexavalent chromium compounds [Cr(VI)] results from its reduction to lower oxidation states. Reductive metabolism of Cr(VI) generates intermediate Cr(V/IV)species, organic radicals, and finally Cr(III), which forms stable complexes with many biological ligands, including DNA. To determine the biological significance of different reaction products, we examined genotoxic responses and the formation of DNA damage during reduction of Cr(VI) by its biological reducer, cysteine. We have found that cysteine-dependent activation of Cr(VI) led to the formation of Cr-DNA and cysteine-Cr-DNA adducts as well as interstrand DNA cross-links. The yield of binary and ternary DNA adducts was relatively constant at different concentrations of Cr(VI) and averaged approximately 54 and 45%, respectively. Interstrand DNA cross-links accounted on average for 1% of adducts, and their yield was even less significant at low Cr(VI) concentrations. Reduction of Cr(VI) in several commonly used buffers did not induce detectable damage to the sugar-phosphate backbone of DNA. Replication of Cr(VI)-modified plasmids in intact human fibroblasts has shown that cysteine-dependent metabolism of Cr(VI) resulted in the formation of mutagenic and replication-blocking DNA lesions. Selective elimination of Cr-DNA adducts from Cr(VI)-treated plasmids abolished all genotoxic responses, indicating that nonoxidative, Cr(III)-dependent reactions were responsible for the induction of both mutagenicity and replication blockage by Cr(VI). The demonstration of the mutagenic potential of Cr-DNA adducts suggests that these lesions can be explored in the development of specific and mechanistically important biomarkers of exposure to toxic forms of Cr.

  18. USE OF TWO DIGESTION METHODS IN THE EVALUATION OF CHROMIUM CONTENT IN CATTLE'S MEAT SUPPLEMENTED WITH CHROMIUM CHELATES

    Directory of Open Access Journals (Sweden)

    R. L. T. de Andrade

    2015-06-01

    Full Text Available The present study aimed to analyze the chromium content in beef using two digestion methods. There were used samples from 24 18-month-old male cattle, and twelve of them were supplemented and twelve were not supplemented with chromium chelate. These samples were evaluated by atomic absorption spectroscopy, previously submitted to digestion method using nitric acid (65% with hydrogen peroxide (35% and to digestion method, using solution of nitric perchloric acid in the proportion 3:1. Immediately after the slaughter, the carcasses were sent to sanitary maturation. After 24 hours, samples between 12th and 13th rib in the muscle Longissimus Thoracis were taken. For evaluation, it was used completely randomized design (Die and analysis of variance (ANOVA at 5% of significance level. The results didn't evidenced any significant difference (p>0,05 between the (cromo content, regardless the supplementation. The same happened with the digestion methods used.

  19. Advantages and Disadvantages of Chromium Salt%铬盐功过论(续)

    Institute of Scientific and Technical Information of China (English)

    王全杰

    2012-01-01

    对铬及其对人类的利害关系进行了详细的论述,包括铬与人体健康,铬在畜禽业中的应用,富铬农副产品的应用,铬鞣剂的不可取代性等。%Chromium as well as its advantages and disadvantages were introduced in detail,including chromium and human health,application in Livestock and Poultry Industry,Rich chromium agricultural and sideline products,Irreplaceable performance of chromium tanning agent,etc.

  20. Advantages and Disadvantages of Chromium Salt%铬盐功过论

    Institute of Scientific and Technical Information of China (English)

    王全杰

    2012-01-01

    Chromium as well as its advantages and disadvantages were introduced in detail, including chromium and human health, application in Livestock and Poultry Industry, Rich chromium agricultural and sideline products, Irreplaceable performance of chromium tanning agent, etc.%对铬及其对人类的利害关系进行了详细的论述,包括铬与人体健康,铬在畜禽业中的应用,富铬农副产品的应用,铬鞣剂的不可取代性等。

  1. Determination of total chromium in tanned leather samples used in car industry.

    Science.gov (United States)

    Zeiner, Michaela; Rezić, Iva; Ujević, Darko; Steffan, Ilse

    2011-03-01

    Despite the high competition of synthetic fibers leather is nowadays still widely used for many applications. In order to ensure a sufficient stability of the skin matrix against many factors, such as microbial degradation, heat and sweat, a tanning process is indispensable. Using chromium (III) for this purpose offers a multitude of advantages, thus this way of tanning is widely applied. During the use of chromium tanned leather as clothing material as well as for decoration/covering purposes, chromium is extracted from the leather and may then cause nocuous effects to human skin, e.g. allergic reactions. Thus the knowledge of the total chromium content of leather samples expected to come into prolonged touch with human skin is very important. In car industry leather is used as cover for seats, steering wheel and gearshift lever The chromium contents often chromium tanned leather samples used in car industry were determined. First all samples were dried at 65 degrees C overnight and then cut in small pieces using a ceramic knife, weighed and analyzed by inductively coupled plasma--optical emission spectrometry (ICP-OES) after acidic microwave assisted digestion. The total chromium amounts found were in the range from 19 mg/g up to 32 mg/g. The extraction yield of chromium from leather samples in sweat is approximately 2-7%. Thus especially during long journeys in summer chromium can be extracted in amounts which may cause nocuous effects for example on the palm of the hands or on the back.

  2. The regeneration and recycle of chromium etching solutions using concentrator cell membrane technology.

    Science.gov (United States)

    Chaudhary, Abdul J; Ganguli, Bijita; Grimes, Susan M

    2006-02-01

    The regeneration of chromium (VI) and the recovery of etched copper from chromium etching solutions by electrodialysis is improved by the addition of a concentrator cell in the catholyte chamber. The concentrator media used are ion-exchange resins or activated carbon cloth. The maximum percentages for the regeneration of chromium and recovery of copper in these systems is however less than 80% and 90% respectively because of the competition between the processes of oxidation of Cr(III) and electrodeposition of copper. A novel combination of electrolysis with electrodialysis and concentrator cell technology is developed that achieves 92% chromium regeneration and 90% copper recovery.

  3. Chromium status and glucose tolerance in Saudi men with and without coronary artery disease.

    Science.gov (United States)

    Alissa, Eman M; Bahjri, Suhad M; Ahmed, Waqar H; Al-Ama, Nabeel; Ferns, Gordon A A

    2009-12-01

    Chromium deficiency is associated with impaired glucose tolerance (IGT) and dyslipidemia. Hence, the objective of the current study was to investigate chromium status among Saudi men with and without established cardiovascular disease (CVD) and its relationship to glucose tolerance, lipid profile and other established CVD risk factors. We measured serum and urine chromium concentrations, fasted lipid profile, plasma glucose, and serum lipid peroxide in 130 Saudi men with an established history of myocardial infarction and 130 age-matched controls without established CVD. Patients with established CVD had higher serum triglycerides (p < 0.05) and plasma glucose (p < 0.0001) and lower serum and urinary chromium concentrations (p < 0.0001) than controls. Serum chromium was inversely correlated with plasma glucose among cases and controls (r = -0.189, p < 0.05 and r = -0.354, p < 0.00001, respectively). Plasma glucose (OR 1.127, CI 1.0-1.269, p < 0.05), serum chromium (OR 0.99, CI 0.985-0.995, p < 0.0001), and urinary chromium (OR 0.988, CI 0.981-0.995, p < 0.001) were independently associated with the presence of established coronary disease applying this model. While chromium metabolism appears to be altered in individuals with CVD, it is unclear whether chromium supplementation would be effective in CVD prevention among patients with IGT. This would need to be tested in long-term outcome trials.

  4. The risk implications of the distribution of chromium forms in environmental media

    Energy Technology Data Exchange (ETDEWEB)

    Mahoney, L.A.; Petroff, D.M.; Batey, J.C. [Eckenfelder Inc., Nashville, TN (United States)

    1996-12-31

    Chromium exhibits multiple oxidation (valence) states, ranging from ({minus}2) to (+6). Under natural conditions, however, chromium typically exists in the Cr(III) (trivalent) and/or Cr(VI) (hexavalent) form, with the hexavalent form exhibiting higher solubility and much greater toxicity than the trivalent form. Due to the large differences in toxicity, the distribution of chromium oxidation states (Cr(III) and Cr(VI)) in site media is potentially of great importance to the calculation of site risk levels, and thus ultimately to cleanup activities. Despite its importance, chromium oxidation states are often not available for media samples collected at waste sites. Typical assumptions regarding the chromium distribution in site media are presented. Actual chromium distribution data from media from baseline investigations of several waste sites are also presented for groundwater, surface water, and soil and compared in terms of background chromium levels and the nature of site wastes. The differences in toxicity of Cr(III) and Cr(VI) are briefly discussed. Risk estimates and risk-based cleanup levels generated using different assumptions for the distribution of chromium in site media for a selected example site are then given. These risk-based cleanup levels are compared to various state regulatory limits, MCLs, and Practical Quantitation Limits (PQLs) for chromium.

  5. The prevalence of chromium allergy in Denmark is currently increasing as a result of leather exposure

    DEFF Research Database (Denmark)

    Thyssen, J P; Jensen, P; Carlsen, B C;

    2009-01-01

    previously been demonstrated among Danish construction workers. OBJECTIVES: To investigate the development of chromium allergy among patients with dermatitis tested between 1985 and 2007 in Denmark. Furthermore, to determine causative exposures in patients with chromium allergy. PATIENTS AND METHODS......: A retrospective analysis of patch test data was performed (n = 16,228) and charts from patients with chromium allergy were reviewed. Comparisons were made using a chi(2) test. Logistic regression analyses were used to test for associations. RESULTS: The prevalence of chromium allergy decreased significantly from...

  6. 45 CFR 1309.54 - Davis-Bacon Act.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Davis-Bacon Act. 1309.54 Section 1309.54 Public... Renovation § 1309.54 Davis-Bacon Act. Construction and renovation projects and subcontracts financed with funds awarded under the Head Start program are subject to the Davis-Bacon Act (40 U.S.C. 276a et...

  7. Chromium Isotopes in Marine Carbonates - an Indicator for Climatic Change?

    Science.gov (United States)

    Frei, R.; Gaucher, C.

    2010-12-01

    Chromium (Cr) stable isotopes experience an increased interest as a tracer of Cr (VI) reduction in groundwater and thus showed their potential as a monitor of remediation of anthropogenic and natural contamination in water (Berna et al., 2009; Izbicki et al., 2008). Chromium stable isotopes in Fe-rich chemical sediments (BIFs and Fe-cherts) have recently also been used as a tracer for Earth's atmospheric oxygenation through time (Frei et al., 2009). We have applied the Cr isotope system to organic-rich carbonates from a late Ediacaran succession in Uruguay (Polanco Formation), from which we have previously analyzed BIFs with extremely fractionated (δ53Cr up to 5.0 ‰) Cr isotope signatures that are part of an underlying deep water clastic sediment (shale-dominated) sequence (Yerbal Formation) deposited in a glacio-marine environment (Gaucher et al.,2004). δ53Cr values of organic rich carbonates correlate with positive and negative carbon isotope excursions (δ13C PDB between -3 and +3 ‰) and with systematic changes in strontium isotope compositions, commonly interpreted as to reflect fluctuations in organic (photosynthetic algae) production related to fluctuations in atmospheric oxygen and weathering intensities, respectively. Slightly positively fractioned δ53Cr values (up to +0.25‰), paralleling positive (δ13C PDB and 87Sr/86Sr ratio excursions would thereby trace elevated atmospheric oxygen levels/pulses possibly related to glacier retreat/melting stages that caused bioproductivity to increase. While the causal link between these multiple isotopic tracers and the mechanisms of Cr stripping into carbonates has to be further investigated in detail, the first indications from this study point to a potentially promising use of stable Cr isotopes in organic-rich carbonates to monitor fluctuations of atmospheric oxygen, particularly over the Neoproterozoic and Phanerozoic ice age periods. E.C. Berna et al. (2010) Cr stable isotopes as indicators of Cr

  8. Magnetic face-to-face interaction and electrocommunication in chromium sandwich compounds.

    Science.gov (United States)

    Elschenbroich, Christoph; Kanellakopulos, Basil; Köhler, Frank H; Metz, Bernhard; Lescouëzec, Rodrigue; Mitzel, Norbert W; Strauss, Werner

    2007-01-01

    The reaction of [{(C5Me5)CrCl2}2] with [2.2](1,4)cyclophane gave [(C5Me5)Cr{[2.2](1,4)cyclophane}] (1) and [(C5Me5)Cr{[2.2](1,4)cyclophane}Cr(C5Me5)] (2), depending on the reaction conditions. X-ray structure analysis showed 2 to be a ministack which in turn is stacked in the lattice. The chromium atoms are 6.035 A apart, and the distortion of the benzene rings to boat-shaped moieties is less pronounced than in parent [2.2](1,4)cyclophane. The NMR and EPR spectra were consistent with a S=1/2 ground state for 1 and with two interacting S=1/2 centers in 2. Spin density was found in the ligand pi systems, where its sign was negative when the pi system was adjacent to chromium, while on the nonbonded benzene moiety of 1 it was positive. Cyclic voltammograms showed reductions to 1- and 2(2-), as well as oxidations to 1+, 2+, and 2(2+) which were quasireversible, whereas oxidations to 1(2+) and 2(3+) were irreversible. Interaction between the metal ions was revealed by a 260 mV separation of the redox waves belonging to 2+, and 2(2+). Both cations were isolated as [B(C6H5)4]- salts, which in solution decomposed to [2.2](1,4)cyclophane and [(C5Me5)Cr{(eta6-C6H5)B(C6H5)3}] (3). The 1H and 13C NMR spectra of 3 were in accordance with an S=1 ground state. Solid-state magnetic measurements of the dimetallic compounds showed antiferromagnetic interaction with J=-122 cm-1 for 2, J=-31 cm-1 for 2+ (ground state S=1/2), and J=-23.5 cm-1 for 2(2+) (with H=-JS1S2). The decrease of J in the series 2, 2+, and 2(2+) was traced to the number of unpaired electrons and, for the mixed-valent cation 2+, to additional double exchange.

  9. THE INFLUENCE OF CHEMICAL COMPOSITION OF HIGH-CHROMIUM CAST IRONS ON THE MACHINABILITY

    Directory of Open Access Journals (Sweden)

    V. V. Netrebko

    2016-02-01

    Full Text Available Purpose. This research is aimed to obtain the regression dependence of the machinability on the chemical composition of pig iron (C, Cr, Mn and Ni in cast state. Methodology. The method of active experiment planning was used to build a mathematical model. Cast irons of composition 1.09…3.91 % С; 11.43…25.57 % Cr; 0.6…5.4 % Mn; 0.19…3.01 % Ni were studied. Cutting tools with plates 10х10 mm out of ВК8 according to State Standard 19051-80 were used for turning. Cutting modes: cutting depth – 0.8 mm, longitudinal feed – 0.15 mm/rot., spindle’s rotation frequency during turning – 200…360 rot./min. Lubricating and cooling liquids were not applied. Evaluation of iron workability was produced by determining the linear tool flank wear per unit length of the cutting path. Findings. Mathematically probabilistic equation of the regression dependence of the cutting tool’s wear on the C, Cr, Mn and Ni content in the machined cast iron were obtained. It was established that with the increase of Cr content in the cast iron to 14.8 % the cutting tool’s wear decreased as a result of formation of carbide eutectic which destroyed the doped ledeburite continuous frame. Further increase of chromium content promoted appearing of chromic carbides with high microhardness which considerably increased the tool’s wear. The conducted research shown that the minimum cutting tool’s wear 0,18 mkm/m was observed during the machining of cast iron containing: 1.09 % C, 14.8 % Cr, 2.3 % Mn and 1.2 % Ni; and the maximum wear is 48,96 mkm/m – when the content was: 3.91 % C, 11.43 % Cr, 5.4 % Mn and 0.19 % Ni. The tool’s wear reached 47.61 mkm/m during the treatment of cast iron containing 3.91 % C, 25.57 % Cr, 5.4 % Mn and 0.19 % Ni. Originality. Mathematically probabilistic model of the dependence of the cutting tool’s wear on the C, Cr, Mn and Ni content in the machined cast iron has been elaborated by the author. Practical value. The model

  10. Iron-rich Oklahoma clays as a natural source of chromium in monitoring wells.

    Science.gov (United States)

    Scott, Dane; Apblett, Allen; Materer, Nicholas F

    2011-12-01

    Water samples, drawn from groundwater monitoring wells located southeast of Oklahoma City, OK, were found to contain elevated concentrations of total chromium with an apparent source localized to the area surrounding each well. Since these monitoring wells are located in areas with no historic chromium usage, industrial sources of chromium were ruled out. Water testing was performed on twelve monitoring wells in the area that historically had elevated total chromium concentrations ranging from 10-4900 micrograms per litre. Filtered water samples were found to be free of chromium contamination, indicating that the source of the chromium is the suspended solids. Analysis of these solids by acid digestion and a sequential extraction technique revealed that the chromium was primarily associated with iron-containing solids. X-ray diffraction identified goethite, an iron oxide hydroxide, as the dominant iron-containing phase in the suspended solids. The mineralogy in this region is dominated by interbedded red-bed sandstone and mudstone whose mineral content includes mixed-layer illite-smectite, hematite, goethite, gypsum and dolomite. Elemental analysis of soil samples collected as a function of depth in the locale of the monitoring wells indicated that the iron rich clays contain a natural source of chromium. The elevated levels of total chromium are most likely due to the dissolution of silica and alumina from the chromium containing iron clays in the basic well water, resulting in the release of fine suspended solids that naturally have high chromium concentrations. These results should be applicable to other areas containing iron-rich clays.

  11. 22 CFR 96.54 - Placement standards in outgoing cases.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Placement standards in outgoing cases. 96.54 Section 96.54 Foreign Relations DEPARTMENT OF STATE LEGAL AND RELATED SERVICES ACCREDITATION OF AGENCIES... print, media, and internet resources designed to communicate with potential prospective adoptive...

  12. 47 CFR 17.54 - Rated lamp voltage.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Rated lamp voltage. 17.54 Section 17.54... voltage. To insure the necessary lumen output by obstruction lights, the rated voltage of incandescent lamps used shall correspond to be within 3 percent higher than the voltage across the lamp socket...

  13. 28 CFR 54.520 - Job classification and structure.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Job classification and structure. 54.520 Section 54.520 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) NONDISCRIMINATION ON THE BASIS OF... and structure. A recipient shall not: (a) Classify a job as being for males or for females;...

  14. 33 CFR 401.54 - Interference with navigation aids.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Interference with navigation aids. 401.54 Section 401.54 Navigation and Navigable Waters SAINT LAWRENCE SEAWAY DEVELOPMENT CORPORATION... with navigation aids. (a) Aids to navigation shall not be interfered with or used as moorings. (b)...

  15. 41 CFR 105-54.203-2 - Active charters file.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Active charters file. 105-54.203-2 Section 105-54.203-2 Public Contracts and Property Management Federal Property Management... charters file. The GSA Committee Management Officer retains each original signed charter in a file...

  16. 19 CFR 134.54 - Articles released from Customs custody.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Articles released from Customs custody. 134.54 Section 134.54 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY... released from Customs custody. (a) Demand for liquidated damages. If within 30 days from the date of...

  17. 20 CFR 901.54 - Petition for reinstatement.

    Science.gov (United States)

    2010-04-01

    ... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Petition for reinstatement. 901.54 Section 901.54 Employees' Benefits JOINT BOARD FOR THE ENROLLMENT OF ACTUARIES REGULATIONS GOVERNING THE PERFORMANCE OF ACTUARIAL SERVICES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 Suspension...

  18. 28 CFR 54.545 - Pre-employment inquiries.

    Science.gov (United States)

    2010-07-01

    ... SEX IN EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Discrimination on the Basis of Sex in Employment in Education Programs or Activities Prohibited § 54.545 Pre-employment... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Pre-employment inquiries. 54.545...

  19. 28 CFR 54.435 - Employment assistance to students.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Employment assistance to students. 54.435... Basis of Sex in Education Programs or Activities Prohibited § 54.435 Employment assistance to students... agency, organization, or person in making employment available to any of its students: (1) Shall...

  20. The sigma(54) regulon (sigmulon) of Pseudomonas putida

    DEFF Research Database (Denmark)

    Cases, I.; Ussery, David; de Lorenzo, V.

    2003-01-01

    , the sigma(54) regulon has been studied both in Escherichia coli, Salmonella typhimurium and several species of the Rhizobiaceae. Here we present the analysis of the sigma(54) regulon (sigmulon) in the complete genome of Pseudomonas putida KT2440. We have developed an improved method for the prediction...

  1. 27 CFR 21.54 - Formula No. 27-B.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Formula No. 27-B. 21.54 Section 21.54 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT... gallon of lavender oil, N.F., and 100 pounds of green soap, U.S.P. Note. The requirements of this...

  2. 7 CFR 550.54 - Invention disclosure and utilization reporting.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 6 2010-01-01 2010-01-01 false Invention disclosure and utilization reporting. 550.54... Management of Agreements Reports and Records § 550.54 Invention disclosure and utilization reporting. (a) The Cooperator shall report Invention Disclosures and Utilization information electronically via i-Edison...

  3. 47 CFR 54.702 - Administrator's functions and responsibilities.

    Science.gov (United States)

    2010-10-01

    .... 54.702 Section 54.702 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER... schools and libraries support mechanism, the rural health care support mechanism, the high cost support mechanism, the low income support mechanism, the interstate access universal service support...

  4. 9 CFR 145.54 - Terminology and classification; States.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Terminology and classification; States. 145.54 Section 145.54 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE... Terminology and classification; States. (a) U.S. Pullorum-Typhoid Clean State. (1) A State will be declared...

  5. 9 CFR 54.22 - State scrapie certification boards.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false State scrapie certification boards. 54... SCRAPIE Scrapie Flock Certification Program § 54.22 State scrapie certification boards. An area... a State scrapie certification board for the purpose of coordinating activities for the Scrapie...

  6. 10 CFR 50.54 - Conditions of licenses.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Conditions of licenses. 50.54 Section 50.54 Energy NUCLEAR...)(1) Each nuclear power plant or fuel reprocessing plant licensee subject to the quality assurance... governmental entities in the United States that are wholly or partially within a plume exposure pathway EPZ,...

  7. 7 CFR 905.54 - Marketing, research and development.

    Science.gov (United States)

    2010-01-01

    ... development projects, and marketing promotion including paid advertising, designed to assist, improve, or... 7 Agriculture 8 2010-01-01 2010-01-01 false Marketing, research and development. 905.54 Section 905.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL...

  8. 42 CFR 71.54 - Etiological agents, hosts, and vectors.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Etiological agents, hosts, and vectors. 71.54..., INSPECTION, LICENSING FOREIGN QUARANTINE Importations § 71.54 Etiological agents, hosts, and vectors. (a) A... any arthropod or other animal host or vector of human disease, or any exotic living arthropod or...

  9. 26 CFR 54.4980G-4 - Calculating comparable contributions.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 17 2010-04-01 2010-04-01 false Calculating comparable contributions. 54.4980G-4 Section 54.4980G-4 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY... calendar year. (c) Model notice. Employers may use the following sample language as a basis in...

  10. 32 CFR 516.54 - Witnesses for the United States.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Witnesses for the United States. 516.54 Section 516.54 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY AID OF CIVIL AUTHORITIES AND PUBLIC RELATIONS LITIGATION Release of Information and Appearance of Witnesses Scope Status, Travel, and Expenses of Witnesses §...

  11. 47 CFR 54.502 - Supported telecommunications services.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Supported telecommunications services. 54.502 Section 54.502 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES... telecommunications services. For purposes of this subpart, supported telecommunications services provided...

  12. 7 CFR 54.1016 - Advance information concerning service rendered.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Advance information concerning service rendered. 54..., Processing, and Packaging of Livestock and Poultry Products § 54.1016 Advance information concerning service... MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE...

  13. 7 CFR 54.15 - Advance information concerning service rendered.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Advance information concerning service rendered. 54.15... Service § 54.15 Advance information concerning service rendered. Upon request of any applicant, all or any... SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED)...

  14. The sigma54 regulon (sigmulon) of Pseudomonas putida.

    Science.gov (United States)

    Cases, Ildefonso; Ussery, David W; de Lorenzo, Víctor

    2003-12-01

    sigma54 is unique among the bacterial sigma factors. Besides not being related in sequence with the rest of such factors, its mechanism of transcription initiation is completely different and requires the participation of a transcription activator. In addition, whereas the rest of the alternative sigma factors use to be involved in transcription of somehow related biological functions, this is not the case for sigma54 and many different and unrelated genes have been shown to be transcribed from sigma54-dependent promoters, ranging from flagellation, to utilization of several different carbon and nitrogen sources, or alginate biosynthesis. These genes have been characterized in many different bacterial species and, only until recently with the arrival of complete genome sequences, we have been able to look at the sigma54 functional role from a genomic perspective. Aided by computational methods, the sigma54 regulon has been studied both in Escherichia coli, Salmonella typhimurium and several species of the Rhizobiaceae. Here we present the analysis of the sigma54 regulon (sigmulon) in the complete genome of Pseudomonas putida KT2440. We have developed an improved method for the prediction of sigma54-dependent promoters which combines the scores of sigma54-RNAP target sequences and those of activator binding sites. In combination with other evidence obtained from the chromosomal context and the similarity with closely related bacteria, we have been able to predict more than 80% of the sigma54-dependent promoters of P. putida with high confidence. Our analysis has revealed new functions for sigma54 and, by means of comparative analysis with the previous studies, we have drawn a potential mechanism for the evolution of this regulatory system.

  15. High temperature oxidation of iron-chromium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mikkelsen, Lars

    2003-06-15

    The high temperature oxidation of the ferritic alloy Fe78Cr22 has been investigated in the present work. The effect of small alloying additions of cerium and/or silicon was also investigated. The alloys were oxidized at 973, 1173 and 1373 K in either air or a hydrogen/argon mixture. The various reaction atmospheres contained between 0.02 and 50% water vapour. The oxide scales formed on the various alloys at 973 K consisted of thin chromia layers. The oxide scales grown on the alloys at 1173 K also consisted of a chromia layer. The microstructure of the chromia scales was found to depend on the reaction atmosphere. The chromia scales grown in hydrogen/argon atmospheres formed oxide whiskers and oxide ridges at the surface of the scales, while the chromia scales grown in air formed larger oxide grains near the surface. This difference in oxide microstructure was due to the vaporization of chromium species from the chromia scales grown in air. Two different growth mechanisms are proposed for the growth of oxide whiskers. The growth rate of the chromia scales was independent of the oxygen activity. This is explained by a growth mechanism of the chromia scales, where the growth is governed by the diffusion of interstitial chromium. The addition of silicon to the iron-chromium alloy resulted in the formation of silica particles beneath the chromia scale. The presence of silicon in the alloy was found to decrease the growth rate of the chromia scale. This is explained by a blocking mechanism, where the silica particles beneath the chromia scale partly block the outwards diffusion of chromium from the alloy to the chromia scale. The addition of cerium to the iron-chromium alloy improved the adhesion of the chromia scale to the alloy and decreased the growth rate of chromia. It was observed that the minimum concentration of cerium in the alloy should be 0.3 at.% in order to observe an effect of the cerium addition. The effect of cerium is explained by the &apos

  16. Noncarcinogenic effects of chromium: Update to health-assessment document. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Victery, W.; Lee, S.D.; Mushak, P.; Piscator, M.

    1990-04-01

    The document updates the 1984 Health Assessment Document for Chromium by addressing issues regarding noncarcinogenic health effects of chromium: oxidation states and persistence of these states in the environment, sampling and analytical methodology to differentiate these oxidation states and amounts at submicrogram ambient air levels, the degree of human exposure to chromium in the environment, both short-term and long-term, in vivo reduction of Cr (VI) to Cr (III), and effects from environmentally relevant levels on pulmonary function and renal function. Trivalent chromium is chemically stable; Cr (VI) is readily reduced to Cr (III). Oxidation state of chromium in ambient air depends on proximity to sources emitting one form over the other. Reliable monitoring methods to speciate oxidation states at ambient air levels below 1 microgram/cu m are not available. Ambient levels of total chromium (obtained from EPA's National Air Data Branch) range from a high of 0.6 microgram/cu m to below the detection limit of 0.005 microgram/cu m. Reduction of hexavalent chromium in vivo occurs in several organ systems and therefore, small amounts of inhaled Cr (VI) will be reduced before systemic absorption can occur. Trivalent chromium is an essential trace metal which potentiates actions of insulin-mediated glucose transport.

  17. Measuring cytotoxicity by bioluminescence imaging outperforms the standard chromium-51 release assay.

    Directory of Open Access Journals (Sweden)

    Mobin A Karimi

    Full Text Available The chromium-release assay developed in 1968 is still the most commonly used method to measure cytotoxicity by T cells and by natural killer cells. Target cells are loaded in vitro with radioactive chromium and lysis is determined by measuring chromium in the supernatant released by dying cells. Since then, alternative methods have been developed using different markers of target cell viability that do not involve radioactivity. Here, we compared and contrasted a bioluminescence (BLI-based cytotoxicity assay to the standard radioactive chromium-release assay using an identical set of effector cells and tumor target cells. For this, we stably transduced several human and murine tumor cell lines to express luciferase. When co-cultured with cytotoxic effector cells, highly reproducible decreases in BLI were seen in an effector to target cell dose-dependent manner. When compared to results obtained from the chromium release assay, the performance of the BLI-based assay was superior, because of its robustness, increased signal-to-noise ratio, and faster kinetics. The reduced/delayed detection of cytotoxicity by the chromium release method was attributable to the association of chromium with structural components of the cell, which are released quickly by detergent solubilization but not by hypotonic lysis. We conclude that the (BLI-based measurement of cytotoxicity offers a superior non-radioactive alternative to the chromium-release assay that is more robust and quicker to perform.

  18. The temperature gradient on section of casting in process of primary crystallization of chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2008-08-01

    Full Text Available The methodology of defining in article was introduced the temperature gradient in process of primary crystallization during cooling the casting from chromium cast iron on basis of measurements of thermal field in test DTA-K3. Insert also the preliminary results of investigations of influence temperature gradient on structure of studied wear resistance chromium cast iron.

  19. Hexavalent chromium removal from wastewater using aniline formaldehyde condensate coated silica gel.

    Science.gov (United States)

    Kumar, P Albino; Ray, Manabendra; Chakraborty, Saswati

    2007-05-08

    A resinous polymer, aniline formaldehyde condensate (AFC) coated on silica gel was used as an adsorbent in batch system for removal of hexavalent chromium from aqueous solution by considering the effects of various parameters like reaction pH, dose of AFC coated silica gel, initial Cr(VI) concentration and aniline to formaldehyde ratio in AFC synthesis. The optimum pH for total chromium [Cr(VI) and Cr(III)] adsorption was observed as 3. Total chromium adsorption was second order and equilibrium was achieved within 90-120 min. Aniline to formaldehyde ratio of 1.6:1 during AFC synthesis was ideal for chromium removal. Total chromium adsorption followed Freundlich's isotherm with adsorption capacity of 65 mg/g at initial Cr(VI) 200mg/L. Total chromium removal was explained as combinations of electrostatic attraction of acid chromate ion by protonated AFC, reduction of Cr(VI) to Cr(III) and bond formation of Cr(III) with nitrogen atom of AFC. Almost 40-84% of adsorbed chromium was recovered during desorption by NaOH, EDTA and mineral acids. AFC coated silica gel can be effectively used for treatment of chromium containing wastewaters as an alternative.

  20. Environmental optimization of chromium recovery from tannery sludge using a life cycle assessment approach.

    Science.gov (United States)

    Kiliç, Eylem; Puig, Rita; Baquero, Grau; Font, Joaquim; Colak, Selime; Gürler, Deniz

    2011-08-15

    Life cycle assessment (LCA) was used to evaluate the environmental impact of an oxidative chromium recovery method from tannery sludge, in comparison with the usual landfilling process. Three improvement options (water reduction, byproduct use and anaerobic sludge digestion) were considered. The results showed that the proposed chromium recovery process would be better environmentally than conventional landfilling in all the evaluated impact categories if the amount of chromium recovered was 43 kg per ton of sludge. This amount could be recovered if the chromium concentration was about 20 times higher than that considered in this study. Alternatively, a lower chromium concentration would produce a better result if the recovery method was optimized and implemented at industrial rather than laboratory scale, and if more accurate data were provided on environmental credits for avoiding the chromium production process. Thus, the recovery method is environmentally beneficial when tannery sludge contains a chromium concentration of about 100,000 ppm. According to the literature, such concentrations are not unusual. The results could serve as the basis for further environmental improvements in chromium recovery and tannery sludge management and should be used in decision-making processes, especially for end-of-pipe treatments.

  1. The temperature gradient on section of casting in process of primary crystallization of chromium cast iron

    OpenAIRE

    2008-01-01

    The methodology of defining in article was introduced the temperature gradient in process of primary crystallization during cooling the casting from chromium cast iron on basis of measurements of thermal field in test DTA-K3. Insert also the preliminary results of investigations of influence temperature gradient on structure of studied wear resistance chromium cast iron.

  2. Tribological properties of the two-step thermally deposited chromium films

    NARCIS (Netherlands)

    Lazauskas, A.; Baltrusaitis, J.; Grigaliunas, V.; Baltusnikas, A.; Abakeviciene, B.; Polcar, T.

    2013-01-01

    Chromium thin films were prepared on glass substrate via a two-step thermal deposition and their structural, chemical and tribological properties were determined. The X-ray diffraction pattern of the two-step thermally deposited chromium film showed the presence of well-defined body-centered cubic C

  3. Suppression of interference in the AAS determination of chromium by use of ammonium bifluoride.

    Science.gov (United States)

    Purushottam, A; Naidu, P P; Lal, S S

    1973-07-01

    Addition of 1% of ammonium bifluoride successfully suppresses interference by diverse ions in the atomic-absorption determination of chromium(VI). If the sample solutions also contain chromium(III) addition of 1% of ammonium bifluoride and 0.2% of sodium sulphate is recommended for the suppression.

  4. Leaching behavior of chromium in chrome shaving generated in tanning process and its stabilization.

    Science.gov (United States)

    Erdem, Mehmet; Ozverdi, Arzu

    2008-08-15

    In this study, leaching properties and pollution potential of chromium in chrome shaving (CS), which is a solid residue of leather industry, containing 2.27% Cr were investigated and thermal stabilization procedure was applied to the CS for chromium immobilization. For this purpose, firstly, effects of the liquid/solid ratio, contact time, pH and sequential extraction on the leaching behavior of chromium in the CS were studied. It was determined that the CS-caused chromium pollution is a hazardous material for environment. Thermal stabilization procedure was applied to the CS in the temperature range of 250-500 degrees C for the chromium immobilization. Effective stabilization of chromium in the CS was achieved by heating of CS at 350 degrees C under CO(2) atmosphere. Leaching experiments were also carried out with the samples obtained from the stabilization process and the results compared with that of the CS. Also, TCLP test method was applied to the samples to determine pollution potentials and discharge situations of the CS and its stabilization products. While the chromium concentrations in the test solutions of all samples stabilized thermally at above 350 degrees C were below the USEPA regulatory limit of 5 mg/l, the concentration of chromium leached out from the CS was 30-fold bigger than the USEPA regulatory limit.

  5. Reduction of tetravalent chromium induced optical loss in Nd:Cr:GSGG

    Energy Technology Data Exchange (ETDEWEB)

    Pertica, A.J.; Marion, J.E.; Stokowski, S.E. (Lawrence Livermore National Laboratory, Livermore, CA 94550 (US))

    1989-10-20

    We report on methods for eliminating of optical absorption in neodymium, chromium doped gadolinium scandium gallium garnet (Nd;Cr:GSGG) due to tetravalent chromium at the laser wavelength. These methods include doping of the crystal melt with specific additive as well as post growth heat treatments.

  6. Kinetics of chromium ion absorption by cross-linked polyacrylate films

    Science.gov (United States)

    May, C. E.

    1984-01-01

    Three cross-linked ion exchange membranes were studied as to their ability to absorb chromium ion from aqueous chromium III nitrate solutions. Attention was given to the mechanism of absorption, composition of the absorbed product, and the chemical bonding. The membranes were: calcium polyacrylate, polyacrylic acid, and a copolymer of acrylic acid and vinyl alcohol. For the calcium polyacrylate and the copolymer, parabolic kinetics were observed, indicating the formation of a chromium polyacrylate phase as a coating on the membrane. The rate of absorption is controlled by the diffusion of the chromium ion through this coating. The product formed in the copolymer involves the formation of a coordination complex of a chromium ion with 6 carboxylic acid groups from the same molecule. The absorption of the chromium ion by the polyacrylic acid membranes appears to be more complicated, involving cross-linking. This is due to the coordination of the chromium ion with carboxylic acid groups from more than one polymer molecule. The absorption rate of the chromium ion by the calcium salt membrane was found to be more rapid than that by the free polyacrylic acid membrane.

  7. Redox Equilibria of Chromium in Calcium Silicate Base Melts

    Science.gov (United States)

    Mirzayousef-Jadid, A.-M.; Schwerdtfeger, Klaus

    2009-08-01

    The oxidation state of chromium has been determined at 1600 °C in CaO-SiO2-CrO x melts with CaO/SiO2 ratios (mass pct) of 0.66, 0.93, and 1.10, and 0.15 to 3.00 pct Cr2O3 (initial). A few experiments were also carried out with CaO-SiO2-Al2O3-CrO x melts at 1430 °C. The slag samples were equilibrated with gas phases of controlled oxygen pressure. Two techniques were applied to determine the oxidation state: thermogravimetry and quenching of the samples with subsequent wet chemical analysis. In the low-oxygen pressure range, the chromium is mainly divalent. In the high-oxygen pressure range, it is trivalent and hexavalent. It was found that the Cr3+/Cr2+ and Cr6+/Cr3+ ratios depend on oxygen pressure at a constant CaO/SiO2 ratio and a constant content of total chromium, according to the ideal law of mass action. According to the respective chemical reactions, these ratios change proportional to p_{{{text{O}}2 }}{}^{1/4} or p_{{{text{O}}_{ 2} }}{}^{3/4}, respectively. They also increase with increasing basicity. The data are used to compute the fractions of the different ions in the melt. There is a certain range of oxygen pressure in which all three valence states, Cr2+, Cr3+, and Cr6+, coexist. The color of the solidified slag samples is described and is explained with the help of transmission spectra.

  8. Chromium speciation in coal and biomass co-combustion products.

    Science.gov (United States)

    Stam, Arthur F; Meij, Ruud; Te Winkel, Henk; Eijk, Ronald J van; Huggins, Frank E; Brem, Gerrit

    2011-03-15

    Chromium speciation is vital for the toxicity of products resulting from co-combustion of coal and biomass. Therefore, understanding of formation processes has been studied using a combination of X-ray absorption fine structure (XAFS) spectroscopy and thermodynamic equilibrium calculations. The influence of cofiring on Cr speciation is very dependent on the type of fuel. Cr(VI) contents in the investigated fly ash samples from coal and cofiring average around 7% of the total chromium. An exception is cofiring 7-28% wood for which ashes exhibited Cr(VI) concentrations of 12-16% of the total chromium. Measurements are in line with thermodynamic predictions: RE factors of Cr around 1 are in line with volatile Cr only above 1400 °C; lower Cr(VI) concentrations with lower oxygen content and Cr(III) dissolved in aluminosilicate glass. Stability of Cr(VI) below 700 °C does not correlate with Cr(VI) concentrations found in the combustion products. It is indicated that Cr(VI) formation is a high-temperature process dependent on Cr evaporation (mode of occurrence in fuel, promoted by organic association), oxidation (local oxygen content), and formation of solid chromates (promoted by presence of free lime (CaO) in the ash). CaCrO(4)(s) is a probable chemical form but, given different leachable fractions (varying from 25 to 100%), different forms of Cr(VI) must be present. Clay-bound Cr is likely to dissolve in the aluminosilicate glass phase during melting of the clay.

  9. Chromium(III) complexes of naturally occurring ligands

    Science.gov (United States)

    El-Shahawi, M. S.

    1995-02-01

    Chromium(III) complexes prepared from CrCl 3Py 3 and anhydrous CrCl 3 with L(-)-threonine, nicotinic acid, glycine, D(-)-penicillamine, L(-)-cysteine and L(-)-cystine have been characterized. The magnetic moments (3.4-4.05 B.M.) are close to the spin only value for a d3 chromium(III) ion in octahedral or pseudo octahedral symmetry. In the electronic spectra two sharp peaks are observed at (15.9-19.8) × 10 3 and (22.0-26.7) × 10 3 cm -1 and are assigned to d-d transitions in the pseudo octahedral configuration. The parameters ( Dq, B, β35) and the interelectronic repulsion parameter with the ionic charge, Z∗, are calculated and place the ligand in the middle of the spectrochemical series. In the circular dichroism spectra three Cotton effects are observed in the forbidden band of the optically active chelates and are assigned to the 2E( 2Eg), 2A 2( 2T 1g) and2E( 2T 1g) while that in the spin allowed band are a result of the splitting of the 4A 2g( 4T 2g) to 4A 1( 4T 2g) and4E( 4T 2g) transitions. The structure of threonine, cystine and cysteine chelates are likely to be fac since strong and well defined Cotton effects are observed. The Cotton effects of penicillamine chelates are weak suggesting formation of the mer structure. Prolonged heating or bubbling air through the solution of CrCl 3Py 3 containing L(-)-threonine, glycine or nicotinic acid for several hours enhances chromium(VI) formation.

  10. Chromium Isotopes Record Fluctuations in Precambrian Biospheric Oxygenation

    Science.gov (United States)

    Frei, R.; Gaucher, C.; Poulton, S. W.; Canfield, D. E.

    2009-12-01

    There is a direct relationship between life, oxygen, and the surface chemistry of the Earth. Geochemical data suggest that oxygenation of the Earth's atmosphere occurred in two broad steps, near the beginning and the end of the Proterozoic Eon (2500 to 542 million years ago), but the details of this history are unclear. The geochemical behaviour of chromium (Cr) is highly sensitive to the redox state of the surface environment as oxidative weathering processes produce the oxidised hexavalent [Cr(VI)] form. Oxidation of reduced trivaltent [Cr(III)] chromium on land is accompanied by an isotopic fractionation, leading to enrichment of the mobile hexavalent form in the heavier isotope. The fractionated Cr isotope signature is then tranfered by riverine transport to the sea. Here, we use Cr stable isotopes from banded iron formations (BIFs) to track the presence of Cr(VI) in Precambrian oceans, providing a time-resolved picture of the oxygenation history of Earth’s atmosphere-hydrosphere system. Fractionated Cr isotopes indicate the accumulation of Cr(VI) in ocean surface waters ~2.8 to 2.6 billion years (Gyr) ago and a likely transient elevation in atmospheric and surface ocean oxygen prior to the first great rise of oxygen 2.45-2.2 Gyr ago (the Great Oxidation Event; GOE). In contrast, Cr isotopes in ~1.88 Gyr old BIFs are not fractionated, indicating a major decline in atmospheric oxygen and demonstrating that the GOE did not lead to a unidirectional stepwise increase in atmospheric oxygen. In the late Neoproterozoic, ~800 to 542 million years (Myr) ago, we observe strong positive fractionations in Cr isotopes (δ53Cr up to +4.9 ‰) providing independent support for increased surface oxygenation at this time. This may have stimulated rapid evolution of macroscopic multicellular life. Our chromium isotope data thus provide new insights into the oxygenation history of the Earth, and highlight its use as a powerful redox tracer in aquatic systems.

  11. Chromium removal from electroplating wastewater by coir pith.

    Science.gov (United States)

    Suksabye, Parinda; Thiravetyan, Paitip; Nakbanpote, Woranan; Chayabutra, Supanee

    2007-03-22

    Coir pith is a by-product from padding used in mattress factories. It contains a high amount of lignin. Therefore, this study investigated the use of coir pith in the removal of hexavalent chromium from electroplating wastewater by varying the parameters, such as the system pH, contact time, adsorbent dosage, and temperature. The maximum removal (99.99%) was obtained at 2% (w/v) dosage, particle size <75microm, at initial Cr(VI) 1647mgl(-1), system pH 2, and an equilibrium time of 18h. The adsorption isotherm of coir pith fitted reasonably well with the Langmuir model. The maximum Cr(VI) adsorption capacity of coir pith at 15, 30, 45 and 60 degrees C was 138.04, 197.23, 262.89 and 317.65mgCr(VI)g(-1) coir pith, respectively. Thermodynamic parameters indicated an endothermic process and the adsorption process was favored at high temperature. Desorption studies of Cr(VI) on coir pith and X-ray absorption near edge structure (XANES) suggested that most of the chromium bound on the coir pith was in Cr(III) form due to the fact that the toxic Cr(VI) adsorbed on the coir pith by electrostatic attraction was easily reduced to less toxic Cr(III). Fourier transform infrared (FT-IR) spectrometry analysis indicated that the carbonyl (CO) groups and methoxy (O-CH(3)) groups from the lignin structure in coir pith may be involved in the mechanism of chromium adsorption. The reduced Cr(III) on the coir pith surface may be bound with CO groups and O-CH(3) groups through coordinate covalent bonding in which a lone pair of electrons in the oxygen atoms of the methoxy and carbonyl groups can be donated to form a shared bond with Cr(III).

  12. Chromium removal from electroplating wastewater by coir pith

    Energy Technology Data Exchange (ETDEWEB)

    Suksabye, Parinda [The Joint School of Energy and Environment, King Mongkut' s University of Technology Thonburi, 91 Pracha-Utit Road, Bangmod, Thungkru, Bangkok 10140 (Thailand); Thiravetyan, Paitip [Division of Biotechnology, School of Bioresources and Technology, King Mongkut' s University of Technology Thonburi, 83 Moo. 8 Thakham, Bangkhuntien, Bangkok 10150 (Thailand)]. E-mail: paitip.thi@kmutt.ac.th; Nakbanpote, Woranan [Pilot Plant Development and Training Institute, King Mongkut' s University of Technology Thonburi, 83 Moo. 8 Thakham, Bangkhuntien, Bangkok 10150 (Thailand); Chayabutra, Supanee [Department of Chemistry, Faculty of Science, Silpaorn University, 6 Rajamankhanai Road, Amphoe Muang, Nakorn Pathom Province, Bangkok 73000 (Thailand)

    2007-03-22

    Coir pith is a by-product from padding used in mattress factories. It contains a high amount of lignin. Therefore, this study investigated the use of coir pith in the removal of hexavalent chromium from electroplating wastewater by varying the parameters, such as the system pH, contact time, adsorbent dosage, and temperature. The maximum removal (99.99%) was obtained at 2% (w/v) dosage, particle size <75 {mu}m, at initial Cr(VI) 1647 mg l{sup -1}, system pH 2, and an equilibrium time of 18 h. The adsorption isotherm of coir pith fitted reasonably well with the Langmuir model. The maximum Cr(VI) adsorption capacity of coir pith at 15, 30, 45 and 60 deg. C was 138.04, 197.23, 262.89 and 317.65 mg Cr(VI) g{sup -1} coir pith, respectively. Thermodynamic parameters indicated an endothermic process and the adsorption process was favored at high temperature. Desorption studies of Cr(VI) on coir pith and X-ray absorption near edge structure (XANES) suggested that most of the chromium bound on the coir pith was in Cr(III) form due to the fact that the toxic Cr(VI) adsorbed on the coir pith by electrostatic attraction was easily reduced to less toxic Cr(III). Fourier transform infrared (FT-IR) spectrometry analysis indicated that the carbonyl (C=O) groups and methoxy (O-CH{sub 3}) groups from the lignin structure in coir pith may be involved in the mechanism of chromium adsorption. The reduced Cr(III) on the coir pith surface may be bound with C=O groups and O-CH{sub 3} groups through coordinate covalent bonding in which a lone pair of electrons in the oxygen atoms of the methoxy and carbonyl groups can be donated to form a shared bond with Cr(III)

  13. MICROSTRUCTURE AND CORROSION RESISTANCE OF CHROMIUM NITRIDES OBTAINED BY VACUUM GAS NITRIDING OF ELECTROLYTIC CHROMIUM DEPOSITED ON AISI H13 STEEL

    Directory of Open Access Journals (Sweden)

    H. Cifuentes

    2013-06-01

    Full Text Available In this scientific research paper, the microstructure and corrosion resistance of chromium nitrides obtained from a duplex treatment consisting of an electroplated hard chromium coating applied on a steel AISI H13 follow by a thermochemical treatment in vacuum using NH3 as precursor gas of nitrogen, is evaluated. This type of duplex treatments combine the benefits of each individual treatment in order to obtain, with this synergic effect, compounds type CrxN more economic than those obtained by other kind of treatments e.g. physical vapor deposition (PVD. The results obtained by X-Ray Diffraction (XRD indicate the surface and subsurface transformation of the electrolytic hard chromium coating by formation of CrN and Cr2N phases. Likewise, potentiodynamic polarization tests indicate an increase in corrosion resistance of such kind of compounds in comparison with the obtained results with electroplated hard chromium.

  14. Chromium removal by zeolite-rich materials obtained from an exhausted FCC catalyst: Influence of chromium incorporation on the sorbent structure.

    Science.gov (United States)

    Gonzalez, Maximiliano R; Pereyra, Andrea M; Torres Sánchez, Rosa M; Basaldella, Elena I

    2013-10-15

    A spent FCC catalyst was converted into a zeolitic mixture, and the product obtained was afterward used as trapping material for Cr(III) species frequently found in aqueous solutions. Eventual changes in the sorbent structure produced by Cr incorporation were studied by different characterization techniques such as point of zero charge determinations (PZC), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and infrared absorption (FTIR). The XRD and FTIR analyses indicated that chromium incorporation produces an amorphization of the material, and PZC measurements show no surface adsorption of charged chromium species. SEM and EDX analyses clearly show that after chromium sorption, the initial microspheroidal catalyst morphology was maintained, and the presence of chromium species was mainly detected in the outer microsphere surface, where the zeolite crystals were hydrothermally grown.

  15. Type 2 diabetic rats on diet supplemented with chromium malate show improved glycometabolism, glycometabolism-related enzyme levels and lipid metabolism.

    Directory of Open Access Journals (Sweden)

    Weiwei Feng

    Full Text Available Our previous study showed that chromium malate improved the regulation of blood glucose in mice with alloxan-induced diabetes. The present study was designed to evaluate the effect of chromium malate on glycometabolism, glycometabolism-related enzymes and lipid metabolism in type 2 diabetic rats. Our results showed that fasting blood glucose, serum insulin level, insulin resistance index and C-peptide level in the high dose group had a significant downward trend when compared with the model group, chromium picolinate group and chromium trichloride group. The hepatic glycogen, glucose-6-phosphate dehydrogenase, glucokinase, Glut4, phosphor-AMPKβ1 and Akt levels in the high dose group were significantly higher than those of the model, chromium picolinate and chromium trichloride groups. Chromium malate in a high dose group can significantly increase high density lipoprotein cholesterol level while decreasing the total cholesterol, low density lipoprotein cholesterol and triglyceride levels when compared with chromium picolinate and chromium trichloride. The serum chromium content in chromium malate and chromium picolinate group is significantly higher than that of the chromium trichloride group. The results indicated that the curative effects of chromium malate on glycometabolism, glycometabolism-related enzymes and lipid metabolism changes are better than those of chromium picolinate and chromium trichloride. Chromium malate contributes to glucose uptake and transport in order to improved glycometabolism and glycometabolism-related enzymes.

  16. Chromium Renderserver: Scalable and Open Source Remote RenderingInfrastructure

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Brian; Ahern, Sean; Bethel, E. Wes; Brugger, Eric; Cook,Rich; Daniel, Jamison; Lewis, Ken; Owen, Jens; Southard, Dale

    2007-12-01

    Chromium Renderserver (CRRS) is software infrastructure thatprovides the ability for one or more users to run and view image outputfrom unmodified, interactive OpenGL and X11 applications on a remote,parallel computational platform equipped with graphics hardwareaccelerators via industry-standard Layer 7 network protocolsand clientviewers. The new contributions of this work include a solution to theproblem of synchronizing X11 and OpenGL command streams, remote deliveryof parallel hardware-accelerated rendering, and a performance analysis ofseveral different optimizations that are generally applicable to avariety of rendering architectures. CRRSis fully operational, Open Sourcesoftware.

  17. Evaluating Foraminifera as an Archive for Seawater Chromium Isotopic Composition

    Science.gov (United States)

    Wang, X.; Planavsky, N.; Hull, P. M.; Tripati, A.; Reinhard, C.; Zou, H.; Elder, L. E.; Henehan, M. J.

    2015-12-01

    In recent years there has been growing interest in using chromium isotopes (δ53Cr) as a proxy to investigate the redox evolution of Earth's ocean-atmosphere system throughout geological history. Potential archives for seawater δ53Cr that have been identified to date include iron formations and organic-rich siliciclastic sediments. However, these types of sediments are not common and they are discontinuous over geologic time. As a result, alternative types of archives are needed. Here we evaluate the utility of foraminifera tests as a recorder of seawater δ53Cr. Core-tops used were from different ocean basins. Mono-specific samples of Globigerinoides sacculifer, Orbulina universa, Pulleniatina obliquiloculata, Globoratalia crassula-crassaformis, Globoratalia truncatulinoides, and Globigerinella siphonifera were isolated to investigate inter-species isotope fractionation. Chromium concentrations were measured by isotope dilution method to be 0.1-0.3 μg/g. The δ53Cr values of these species range from 0.2‰ to 2.4‰, with an analytical uncertainty of 0.3‰ (95% confidence). Despite the high analytical uncertainty due to the extremely low levels of Cr present, there is still large detectable variation in foraminiferal δ53Cr values, which overlap presently available seawater values (Bonnand et al., 2013; Scheiderich et al., 2015). Possible explanations for such variations in foraminiferal δ53Cr values include heterogeneity of seawater δ53Cr in the modern oceans, and/or photobiochemical redox cycling of Cr in the surface oceans. Therefore, care should be taken when using foraminifera to reconstruct past seawater δ53Cr values. ReferencesBonnand, P., James, R., Parkinson, I., Connelly, D., Fairchild, I., 2013. The chromium isotopic composition of seawater and marine carbonates. Earth and Planetary Science Letters, 382: 10-20. Scheiderich, K., Amini, M., Holmden, C., Francois, R., 2015. Global variability of chromium isotopes in seawater demonstrated by Pacific

  18. Adsorption of chromium ion (VI) by acid activated carbon

    OpenAIRE

    A. A. Attia; Khedr,S. A.; Elkholy,S. A.

    2010-01-01

    The activated carbon produced from olive stones was chemically activated using sulfuric acid, (OS-S), and utilized as an adsorbent for the removal of Cr(VI) from aqueous solution in the concentration range 4-50 mg/L. Adsorption experiments were carried out in a batch process and various experimental parameters such as effect of contact time, initial chromium ion concentration, carbon dosage, and pH on percentage removal have been studied. Adsorption results obtained for activated carbon (OS-S...

  19. Study on anaerobic treatment of wastewater containing hexavalent chromium*

    OpenAIRE

    Xu, Yan-Bin; Xiao, Hua-hua; Sun, Shui-yu

    2005-01-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and CODCr of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment ...

  20. Structural, morphological and optical properties of chromium oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Babukutty, Blessy; Parakkal, Fasalurahman; Nair, Swapna S., E-mail: swapna.s.nair@gmail.com [School of Mathematical and Physical Sciences, Department of Physics, Central University of Kerala, Kasaragod 671314 (India); Bhalero, G. M. [UGC-DAE, IGCAR, Kalpakkam, TamilNadu (India); Aravind, P. B. [Cochin University of Science and Technology(CUSAT), Cochin (India)

    2015-06-24

    Chromium oxide nanoparticles are synthesized by reduction route from chloride precursors with surfactant, trioctylphosphine oxide (TOPO). Structural and morphological characterization are analyzed using X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Transmission Electron micrographs show that the average grain size lies in the range 5nm to 10nm. Optical characterization has been done by UV-VIS spectrophotometer. Distinct optical absorptions of Cr{sup 3+} ions show hinting towards the presence of Cr{sub 2}O{sub 3}. Presence of oxygen is also confirmed from Electron Energy Loss Spectroscopy (EELS) studies.

  1. Isocyanide and Phosphine Oxide Coordination in Binuclear Chromium Pacman Complexes.

    Science.gov (United States)

    Stevens, Charlotte J; Nichol, Gary S; Arnold, Polly L; Love, Jason B

    2013-12-01

    The new binuclear chromium Pacman complex [Cr2(L)] of the Schiff base pyrrole macrocycle H4L has been synthesized and structurally characterized. Addition of isocyanide, C≡NR (R = xylyl, (t)Bu), or triphenylphosphine oxide donors to [Cr2(L)] gives contrasting chemistry with the formation of the new coordination compounds [Cr2(μ-CNR)(L)], in which the isocyanides bridge the two Cr(II) centers, and [Cr2(OPPh3)2(L)], a Cr(II) phosphine oxide adduct with the ligands exogenous to the cleft.

  2. MODELING THE RATE-CONTROLLED SORPTION OF HEXAVALENT CHROMIUM.

    Science.gov (United States)

    Grove, D.B.; Stollenwerk, K.G.

    1985-01-01

    Sorption of chromium VI on the iron-oxide- and hydroxide-coated surface of alluvial material was numerically simulated with rate-controlled reactions. Reaction kinetics and diffusional processes, in the form of film, pore, and particle diffusion, were simulated and compared with experimental results. The use of empirically calculated rate coefficients for diffusion through the reacting surface was found to simulate experimental data; pore or particle diffusion is believed to be a possible rate-controlling mechanism. The use of rate equations to predict conservative transport and rate- and local-equilibrium-controlled reactions was shown to be feasible.

  3. CHROMIUM EXTRACTION BY MICROEMULSIONS IN TWO- AND THREE-PHASE SYSTEMS

    Directory of Open Access Journals (Sweden)

    K. R. O. Melo

    2015-12-01

    Full Text Available Abstract Microemulsion systems were used to remove chromium from an aqueous solution obtained from acid digestion of tannery sludge. The systems were composed by: coconut oil soap as surfactant, 1-butanol as cosurfactant, kerosene as the oil phase, and chromium solution as the aqueous phase. Two- and three-phase microemulsion extraction methods were investigated in the experiments. Viscosity, effective diameter of the droplets, and extraction and re-extraction efficiencies were evaluated for each system. Two- and three-phase systems showed small variations in droplet diameter, which can be attributed to the formation of micellar structures. Chromium recovery efficiencies for the studied systems were over 96%. The re-extraction step showed that the stripping solution used can release more than 96% of the chromium from the microemulsion phase. Experimental results confirm that chromium can be recovered efficiently using microemulsion systems.

  4. Detergents and bleaches are sources of chromium contact dermatitis in Israel

    DEFF Research Database (Denmark)

    Ingber, A; Gammelgaard, Bente; David, M

    1998-01-01

    Total chromium levels were determined in 38 detergents and 12 bleaches on the market in Israel (45 locally produced, 5 imported). The samples were analyzed by Zeeman-corrected graphite furnace atomic absorption spectrophotometry. Chromium levels were higher than 5 ppm in 28 (56%) of the 50 products......, from 1 to 5 ppm in 16 (32%), and lower than 1 ppm in only 6 (12%). Among the 5 imported products, only 1 had a chromium level below 1 ppm and the other 4 (1 from Germany, 3 from the USA) had high levels. Since a most 90% of the detergents and bleaches examined contained chromium levels higher than 1...... ppm, it is concluded that these consumer products may be the cause of the high incidence of chromium sensitivity in Israel....

  5. Development of Alkaline Oxidative Dissolution Methods for Chromium (III) Compounds Present in Hanford Site Tank Sludges

    Energy Technology Data Exchange (ETDEWEB)

    NN Krot; VP Shilov; AM Fedoseev; NA Budantseva; MV Nikonov; AB Yusov; AYu Garnov; IA Charushnikova; VP Perminov; LN Astafurova; TS Lapitskaya; VI Makarenkov

    1999-07-02

    The high-level radioactive waste sludge in the underground storage tanks at the Hanford Site contains various chromium(III)solid phases. Dissolution and removal of chromium from tank waste sludges is desirable prior to high-level waste vitrification because increased volume is required to incorporate the residual chromium. Unfortunately, dissolution of chromium from the sludge to form Cr(OH){sub 4}{sup {minus}} through treatment with heated NaOH solution (also used to dissolve aluminum phases and metathesize phosphates to sodium salts) generally has been unsuccessful in tests with both simulated and genuine Hanford waste sludges. Oxidative dissolution of the Cr(III) compounds to form soluble chromate has been proposed as an alternative chromium solid phase dissolution method and results of limited prior testing have been reported.

  6. Bioremediation of the soils contaminated with cadmium and chromium, by the earthworm Eisenia fetida.

    Directory of Open Access Journals (Sweden)

    E Aseman

    2016-01-01

    Results: There was a significant correlation between the reduction of chromium and cadmium metals in the soils and the accumulation of chromium and cadmium metals in the worm’s body. A significant decline of chromium levels of the soil was observed in the days 21 and 42 during the study compared to the initial amount of 0.1 mg/g. On the other hand, chromium concentration of the soil decreased from 0.14 to 0.1 mg/g after 42 days. Conclusion: said the research indicated that increased mortality of worms in the soil at a concentration of 0.08 mg/g of chromium, using the worms for bioremediation is not recommended. Although, this method is effective to remove cadmium from the soils having cadmium with concentrations of 0.04 and 0.08 mg/g but it needs further investigation.

  7. Chromium related degradation of solid oxide fuel cells; Chrom-bezogene Degradation von Festoxid-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Anita

    2011-05-04

    Solid Oxide Fuel Cells (SOFCs) offer a high potential for application as an auxiliary power unit (APU) for heavy goods vehicles as well as combined heat and power (CHP) systems. SOFCs are especially attractive due to their high efficiencies and the use of different fuel types. However, optimization in terms of long term stability and costs are still necessary. This work characterized the degradation of SOFCs with lanthanum strontium manganite (LSM) cathodes under chromium influence. Galvanostatic cell tests were carried out at 800 C with operation times from 250 - 3000 h and variation of the chromium source and current density. The current densities of j = 0 (A)/(cm{sup 2}), j = 0,3 (A)/(cm{sup 2}) and j = 0,5 (A)/(cm{sup 2}) were applied. The high temperature ferritic alloy Crofer22APU was used as a chromium source. Variation of the chromium source was realized by coating the Crofer22APU insert with the chromium retention layer Mn{sub 3}O{sub 4} and the cathode contact layer LCC10. Cell degradation was analyzed with regard to cell voltage, current density and area specific resistance (ASR). Microstructural alterations of the cathode as well as chromium content and distribution across the cell were investigated after completion of the cell tests. For cells with a chromium source present and operation with a nonzero current density, the course of cell degradation was divided into three phases: a run-in, weak linear degradation and strong linear degradation. A decrease of the chromium release rate by means of different coatings stretched the course of degradation along the timescale. Strong degradation, which is characterized by a significant increase in ASR as well as a decrease of current density at the operating point, was only observed when a chromium source in the setup was comb ined with operation of the cell with a non-zero current density. Operation of the cell with a chromium source but no current density caused a degradation of current density at the

  8. Investigate of atmospheric arsenic, cadmium, chromium, lead, and mercury levels in moss species found around Zilkale, by EDXRF Spectrometry

    Science.gov (United States)

    Akçay, Nilay; Batan, Nevzat; Ćinar, Yunus

    2016-04-01

    Zilkale is a castle located in Fırtına Valley and it is one of the most important historical structures in Çamlihemşin district of Rize Province in the Black Sea Region of Turkey. The castle surrounded by very high mountains that poke up into the clouds, and it rains here all year round. Tourism businesses or industrial plants are not so much there yet. In recent years, Zilkale region has begun the attract tourist, people on treaking holidays in the Kaçkar. But many domestic and foreign tourists come to this region by own car or tour buses. The aim of this study is to investigate the atmospheric concentrations of arsenic, cadmium, chromium, lead, and mercury levels in five different moss species collected around Zilkale by using Energy Dispersive X-ray Fluorescence (EDXRF) Spectrometry. The average concentrations of heavy metals in moss samples ranged from 0.79-4.63 ppm for arsenic, 54.47-143.39 ppm for chromium, 39.97-81.03 ppm for lead. The values of cadmium and mercury were found below the detection limit. This study has shown that Hypnum cupressiforme, Abietinella abietina, Rhytidium rugosum, Plagiomnium undulate, and Thuidium tamariscinum samples collected around Zilkale were used to assess the potential contamination of atmospheric As, Cd, Cr, Pb, Hg contamination in the region and made important contributions toward the understanding of atmospheric As, Cd, Cr, Pb, Hg baseline data can be used for identification of changes in the levels of these heavy metals in the studied area.

  9. Chromium Isotopic Fractionation During Biogeochemical Cr (IV) Reduction in Hanford Sediment Column Experiments with Native Aquifer Microbial Communities

    Science.gov (United States)

    Qin, L.; Christensen, J. N.; Brown, S. T.; Yang, L.; Conrad, M. E.; Sonnenthal, E. L.; Beller, H. R.

    2010-12-01

    Hexavalent Chromium contamination in groundwater within the DOE complex, including the Hanford 100D and 100H sites has been a long-standing issue. It has been established that certain bacteria (including denitrifying and sulfate-reducing bacteria) harbor enzymes that catalyze Cr(VI) reduction to relatively nontoxic Cr(III). Microbial reduction of Cr(VI) also occurs indirectly by products of microbial respiration, such as sulfide and Fe(II). Chromium isotopes can be fractionated during Cr(VI) reduction and provides a potential basis for characterizing and discriminating between different microbial metabolic and geochemical pathways associated with Cr(VI) reductive immobilization. Addition of electron donor to contaminated groundwater systems to create conditions favorable for reductive metal immobilization has become a widely utilized remediation practice. We conducted a series of small-scale column experiments with homogenized material from the Hanford 100H aquifer to examine the effects of differing electron acceptors on local microbial communities. All columns have a continuous inflow of solutions with constant concentrations of Cr(VI), lactate (electron donor), and the appropriate electron acceptor (e.g. nitrate or sulfate). The Cr isotopic composition in the effluent was measured using a 50-54 double-spike technique and a Triton TIMS. Cr concentration measurements showed that the greatest Cr(VI) reduction occurred in the sulfate columns. Our preliminary Cr isotopic data show that under these conditions the delta 53Cr value increased from close to 0 to 4 per mil while the Cr concentration decreased from 260 ppb to 30 ppb in the effluent. This yields an apparent fractionation factor of 0.9979 (2.1 per mil). A decrease in Cr concentration from 260 ppb to 190 ppb in a nitrate-reducing column was accompanied by an increase of 1 per mil in delta 53Cr. Further Cr isotopic data will be presented and the effects of differing flow rates and electron acceptors will be

  10. Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

  11. Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nikel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) seamless pipe and tube

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nikel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) seamless pipe and tube

  12. Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) rod, bar, and wire

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) rod, bar, and wire

  13. Chromium isotope anomaly in an impactite sample from the El'gygytgyn structure, Russia: Evidence for a ureilite projectile?

    Science.gov (United States)

    Foriel, Julien; Moynier, Frederic; Schulz, Toni; Koeberl, Christian

    2013-07-01

    The 3.6 Ma, 18-km-diameter El'gygytgyn impact structure (Arctic Russia) is unique among the currently known terrestrial impact craters in that it is the only one that was formed in acid volcanic rocks. Previous analyses of impactites from El'gygytgyn showed minor enrichments of the siderophile elements, including Ir, which, together with distinct Cr enrichments, gave rise to speculation that an achondritic projectile was involved. We studied the major and trace element composition in samples from the new ICDP drill core obtained near the center of the structure, as well as the chromium isotopic composition of an impact glass sample collected on the surface. Several suevitic breccias from the upper part of the suevite sequence in the drill core show higher Cr and Ni contents compared with felsic volcanic rocks in the lower part of the core and from surface samples. However, it is difficult to unambiguously establish a meteoritic component from trace element data, as input from (rare) mafic target rocks is a possibility. In contrast, the Cr isotopic composition of the impact glass sample yielded a nonterrestrial ɛ54Cr value of -0.72 ± 0.31 (2 std. err.). This negative ɛ54Cr is different from known carbonaceous chondrite values (ɛ54Cr of +0.95 to +1.65), but is nearly identical to reported values for ureilites (approximately -0.77). The value is, however, also within analytical error of eucrites (approximately -0.38) and ordinary chondrites (approximately -0.42). Given the chemical signatures found in previous analyses of El'gytgytgyn impactites and the similarity of our Cr isotopic data to ureilites, we suggest that the impacting asteroid could have been an F-type asteroid of mixed composition, similar to the recent Almahata Sitta fall in Sudan.

  14. Speciation of chromium in bread and breakfast cereals.

    Science.gov (United States)

    Mathebula, Mpho Wendy; Mandiwana, Khakhathi; Panichev, Nikolas

    2017-02-15

    Bread and breakfast cereals are a major constituents of the human diet, yet their Cr(VI) content is not known. Chromium(VI) was determined in these products by high resolution continuum source atomic absorption spectrometer (HR-CS AAS) after leaching Cr(VI) with 0.10molL(-1) Na2CO3. The results showed that 33-73% of total Cr (58.17±5.12μgkg(-1)-156.1±6.66μgkg(-1)) in bread exist as Cr(VI) and the highest total Cr content was found in brown bread. It was shown that Cr(III) is oxidized to Cr(VI) during toasting of bread. Chromium(VI) content in breakfast cereals ranged between 20.4±4μgkg(-1) and 470.4±68μgkg(-1). Therefore, it can be concluded that bread and breakfast cereals contains Cr(VI) which does not exceed maximum acceptable concentration (MAC) of 0.003mgkg(-1)bw(-1)day(-1) through daily consumption of half a bowl (65g) of breakfast cereal and four slices of toasted (122g) or untoasted bread (160g).

  15. Biosorption of aqueous chromium(VI) by Tamarindus indica seeds.

    Science.gov (United States)

    Agarwal, G S; Bhuptawat, Hitendra Kumar; Chaudhari, Sanjeev

    2006-05-01

    The effectiveness of low cost agro-based materials namely, Tamarindus indica seed (TS), crushed coconut shell (CS), almond shell (AS), ground nut shell (GS) and walnut shell (WS) were evaluated for Cr(VI) removal. Batch test indicated that hexavalent chromium sorption capacity (q(e)) followed the sequence q(e)(TS) > q(e)(WS) > q(e)(AS) > q(e)(GS) > q(e)(CS). Due to high sorptive capacity, tamarind seed was selected for detailed sorption studies. Sorption kinetic data followed first order reversible kinetic fit model for all the sorbents. The equilibrium conditions were achieved within 150 min under the mixing conditions employed. Sorption equilibria exhibited better fit to Freundlich isotherms (R>0.92) than Langmuir isotherm (R approximately = 0.87). Hexavalent chromium sorption by TS decreased with increase in pH, and slightly reduced with increase in ionic strength. Cr(VI) removal by TS seems to be mainly by chemisorption. Desorption of Cr(VI) from Cr(VI) laden TS was quite less by distilled water and HCl. Whereas with NaOH, maximum desorption achieved was about 15.3%. When TS was used in downflow column mode, Cr(VI) removal was quite good but head loss increased as the run progressed and was stopped after 200 h.

  16. Structural effects of metallic chromium on its electrochemical behavior

    Directory of Open Access Journals (Sweden)

    VELIMIR RADMILOVIC

    2007-06-01

    Full Text Available Chromium dissolution in aqueous sulfuric acid solution of pH 1 was studied electrochemically on chromium electrodes with different crystallographic structures. A slow potentiodynamic method was used for the electrochemical measurements in deaerated solutions (purgedwith nitrogen,while the Cr(III ions in the solution after the corrosion were determined by atomic absorption spectrometry. Three electrode materials with a very dominant crystallite orientation resembling single crystal structures (i.e., 111 and 110 confirmed by the electron backscattering diffraction (EBSD, were used in the experiments. The (111 structures were somewhat more active electrochemically (both anodic and cathodic than the (110 structure. However, Cr electrochemically deposited in standard plating bath, assumed from literature data to has also the (111 structure, was more than 4 times active for anodic dissolution and, by the same number, less active for cathodic hydrogen evolution. The concentrations of Cr(III ions determined in the solution after definite times of corrosion of all the materials showed almost two times larger dissolution rates than observed electrochemically by three different electrochemical methods (Wagner–Traud, Stern–Geary, electrochemical impedance spectroscopy. This is explained by the simultaneous occurrence of potential independent chemical dissolution of Cr, by a direct reaction of metallic Cr with H2O molecules, proposed a long time ago by Kolotyrkin and coworkers.

  17. Pseudo-Stem Banana Fibers: Characterization and Chromium Removal

    Directory of Open Access Journals (Sweden)

    Helena Becker

    2013-11-01

    Full Text Available In this work, pseudo-stems of the banana tree were collected, characterized and used as adsorbent materials for the removal of the chromium ions from aqueous solution. The characterization of pseudo-stems by FTIR suggests the presence of cellulose, hemicellulose and lignin. The predominant groups were carbonyls (0.312 ± 0.010 mmol g–1 adsorbent, phenols (0.237 ± 0.021 mmol g–1 adsorbent, lactones (0.041 ± 0.003 mmol g–1 adsorbent and basic groups (0.096 ± 0.006 mmol g–1 adsorbent. The textural propriety of the adsorbent, surface area, pore volume and pore diameter were found to be 0.383 m2 g–1, 0.003525 cm3 g–1 and 368.3 Å, respectively. The pHpzc value was found 7.5 and so the adsorption assays of chromium removal from solution were more efficiently at acidic pH values. The experiments show that approximately 95% and 78% of the Cr (VI was removed from solution by untreated and treated fiber, respectively, in 300 minutes of the contact time.

  18. Internal Friction In The PFN Ceramics With Chromium Dopand

    Directory of Open Access Journals (Sweden)

    Zachariasz R.

    2015-09-01

    Full Text Available An aim of this work was to determine an influence of an admixture, the chromium (for x from 0.01 to 0.06, on the mechanical properties of the PFN ceramics. The ceramics with chemical composition Pb(Fe0.5−xCrxNb0.5O3 was synthesized in two steps from simple oxides PbO, Fe2O3, Nb2O5, Cr2O3. The first stage was based on obtaining the FeNbO4 from the Fe2O3 and Nb2O5 simple oxides. At this stage an admixture in a form the Cr2O3 chromium oxide was added to the solution. In the second stage the PbO lead oxide and the doped FeNbO4 (obtained earlier were synthetized. The sintering of ceramic samples PFCN type was carried out by free sintering method. Temperature measurements of the internal friction were conducted on a computer-controlled automatic resonant mechanical spectrometer (heating cycle with 3 deg/min.

  19. Study of effect of chromium on titanium dioxide phase transformation

    Indian Academy of Sciences (India)

    A Bellifa; L Pirault-Roy; C Kappenstein; A Choukchou-Braham

    2014-05-01

    MTi samples with different atomic chromium percentages were synthesized by sol–gel method and calcined at 400 °C under air. The effects of Cr and temperature on titanium dioxide phase transition were studied. In situ measurement showed the presence of anatase phase for all samples at temperature < 500 °C. Without Cr content, the anatase–rutile transition takes place at 600 °C and the rutile fraction increases with increase of temperature. In the presence of Cr content, rutile phase appeared at 700 °C. Cr2O3 phase was shown only in the case of CrTi20 content at 800 °C which indicates that the segregation remains modest. We have also studied the anatase–rutile transition kinetics by using in situ X-ray measurements. It was found that the anatase phase stability increases as the chromium content increases. Results confirm that the transformation of anatase–rutile is of first order.

  20. The complexes structures of chromium(III with ethylglycine and alanine

    Directory of Open Access Journals (Sweden)

    Line A. Chernushenko

    2016-12-01

    Full Text Available The reaction of chromium(III chloride with the amino acid ethylglycine in a 1:1 molar ratio of metal to ligand has been performed. The complex with monodentate coordinated ethylglycine [Cr(CH3СН2CH(NH3COO(H2O3Cl2]Cl∙3H2O (І has been synthesized. Interaction of compound (І with the α-аlanine results in formation of different-ligand complex [Cr(CH3СН2CH(NH3COO(СН3CH(NH3COO(H2O3Cl]Cl2 (ІІ. The complexes I and II have been analyzed by IR and UV/Vis spectroscopy. Significant difference in wave numbers of carboxylic group valence vibritations (nas(COO––νs(COO–=220 cm–1 for (I and nas(COO––ν s(COO–=244 cm–1 for (IIconfirms that both amino aсids are coordinated to Cr3+ by oxygen of carboxyl group. Compounds (І–ІІ have the octahedral structure. Two bands of transition (4Т1g¬4A2g and4Т2g¬4A2g have been observed in the visible part of the spectrum and one band of transition (4Т1g(Р¬4A2g in UV region. The parameters of crystal field of complexes have been calculated (Dq = 1640 cm–1, В= 627 cm–1 and b = 0.61 for (I and Dq = 1700 cm–1 В= 553 cm–1 and b = 0.54 for (IІ. The computer three-dimension models of complexes (II has been created. Geometrical parameters of complexes have been calculated at HF/6-31G(D level of theory.

  1. Hexavalent chromium is cytotoxic and genotoxic to hawksbill sea turtle cells.

    Science.gov (United States)

    Wise, Sandra S; Xie, Hong; Fukuda, Tomokazu; Douglas Thompson, W; Wise, John Pierce

    2014-09-01

    Sea turtles are a charismatic and ancient ocean species and can serve as key indicators for ocean ecosystems, including coral reefs and sea grass beds as well as coastal beaches. Genotoxicity studies in the species are absent, limiting our understanding of the impact of environmental toxicants on sea turtles. Hexavalent chromium (Cr(VI)) is a ubiquitous environmental problem worldwide, and recent studies show it is a global marine pollutant of concern. Thus, we evaluated the cytotoxicity and genotoxicity of soluble and particulate Cr(VI) in hawksbill sea turtle cells. Particulate Cr(VI) was both cytotoxic and genotoxic to sea turtle cells. Concentrations of 0.1, 0.5, 1, and 5μg/cm(2) lead chromate induced 108, 79, 54, and 7% relative survival, respectively. Additionally, concentrations of 0, 0.1, 0.5, 1, and 5μg/cm(2) lead chromate induced damage in 4, 10, 15, 26, and 36% of cells and caused 4, 11, 17, 30, and 56 chromosome aberrations in 100 metaphases, respectively. For soluble Cr, concentrations of 0.25, 0.5, 1, 2.5, and 5μM sodium chromate induced 84, 69, 46, 25, and 3% relative survival, respectively. Sodium chromate induced 3, 9, 9, 14, 21, and 29% of metaphases with damage, and caused 3, 10, 10, 16, 26, and 39 damaged chromosomes in 100 metaphases at concentrations of 0, 0.25, 0.5, 1, 2.5, and 5μM sodium chromate, respectively. These data suggest that Cr(VI) may be a concern for hawksbill sea turtles and sea turtles in general.

  2. Hexavalent chromium is cytotoxic and genotoxic to hawksbill sea turtle cells

    Energy Technology Data Exchange (ETDEWEB)

    Wise, Sandra S., E-mail: sandra.wise@maine.edu [Wise Laboratory of Environmental and Genetic Toxicology, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Maine Center for Toxicology and Environmental Health, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Xie, Hong, E-mail: hongxie@usm.maine.edu [Wise Laboratory of Environmental and Genetic Toxicology, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Maine Center for Toxicology and Environmental Health, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Fukuda, Tomokazu, E-mail: tomofukuda009@gmail.com [Graduate School of Agricultural Sciences, Tohoku University, Laboratory of Animal Breeding and Genetics, Second Research Building, Rm 112, 1-1 Amamiyamachi, Aoba-ku, Sendai 981-8555 (Japan); Douglas Thompson, W., E-mail: dougt@usm.maine.edu [Maine Center for Toxicology and Environmental Health, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); and others

    2014-09-01

    Sea turtles are a charismatic and ancient ocean species and can serve as key indicators for ocean ecosystems, including coral reefs and sea grass beds as well as coastal beaches. Genotoxicity studies in the species are absent, limiting our understanding of the impact of environmental toxicants on sea turtles. Hexavalent chromium (Cr(VI)) is a ubiquitous environmental problem worldwide, and recent studies show it is a global marine pollutant of concern. Thus, we evaluated the cytotoxicity and genotoxicity of soluble and particulate Cr(VI) in hawksbill sea turtle cells. Particulate Cr(VI) was both cytotoxic and genotoxic to sea turtle cells. Concentrations of 0.1, 0.5, 1, and 5 μg/cm{sup 2} lead chromate induced 108, 79, 54, and 7% relative survival, respectively. Additionally, concentrations of 0, 0.1, 0.5, 1, and 5 μg/cm{sup 2} lead chromate induced damage in 4, 10, 15, 26, and 36% of cells and caused 4, 11, 17, 30, and 56 chromosome aberrations in 100 metaphases, respectively. For soluble Cr, concentrations of 0.25, 0.5, 1, 2.5, and 5 μM sodium chromate induced 84, 69, 46, 25, and 3% relative survival, respectively. Sodium chromate induced 3, 9, 9, 14, 21, and 29% of metaphases with damage, and caused 3, 10, 10, 16, 26, and 39 damaged chromosomes in 100 metaphases at concentrations of 0, 0.25, 0.5, 1, 2.5, and 5 μM sodium chromate, respectively. These data suggest that Cr(VI) may be a concern for hawksbill sea turtles and sea turtles in general. - Highlights: • Particulate Cr(VI) is cytotoxic and clastogenic to hawksbill sea turtle cells. • Soluble Cr(VI) is cytotoxic and clastogenic to hawksbill sea turtle cells. • Cr(VI) may be a risk factor for hawksbill sea turtle health.

  3. Scintillation Velocity of PSR B0329+54

    Indian Academy of Sciences (India)

    R. X. Zhou; N. Wang; Z. Y. Liu; X. Liu

    2011-03-01

    We monitored PSR B0329+54 for one year using the Nanshan 25-m radio telescope, the scintillation velocity VISS shows evidence of systematic variation with the day of the year. States of interstellar medium (ISM) are discussed.

  4. Resolving the shocked gas in HH54 with Herschel

    DEFF Research Database (Denmark)

    Bjerkeli, P.; Liseau, R.; Brinch, C.

    2014-01-01

    Context. The HH 54 shock is a Herbig-Haro object, located in the nearby Chamaeleon II cloud. Observed CO line profiles are due to a complex distribution in density, temperature, velocity, and geometry. Aims. Resolving the HH 54 shock wave in the far-infrared (FIR) cooling lines of CO constrain...... the kinematics, morphology, and physical conditions of the shocked region. Methods. We used the PACS and SPIRE instruments on board the Herschel space observatory to map the full FIR spectrum in a region covering the HH 54 shock wave. Complementary Herschel-HIFI, APEX, and Spitzer data are used in the analysis...... as well. The observed features in the line profiles are reproduced using a 3D radiative transfer model of a bow-shock, constructed with the Line Modeling Engine code (LIME). Results. The FIR emission is confined to the HH 54 region and a coherent displacement of the location of the emission maximum of CO...

  5. Bioinformatics Analysis of the Duck Enteritis Virus UL54 Gene

    Directory of Open Access Journals (Sweden)

    Chaoyue Liu

    2014-04-01

    Full Text Available In this study, we analyze the Duck Enteritis Virus (DEV UL54 gene, which has been isolated and identified in our lab (GenBank accession NO EU071033, to help deeply research on DEV. DNA sequence analysis showed that the identified ORF which composed of 1377 bp nucleotides encoded 458 amino acids with a predicted Mr. of 51.75 kDa. Multiple sequence alignment suggested that the UL54 gene was highly conserved in Alphaherpesvirinae and was similar to the other herpesviral UL54 gene. Phylogenetic analysis of the DEV UL54 gene revealed that DEV had a close evolutionary relationship with Gallid, Herpesvirus 2 (GaHV-2, Gallid Herpesvirus 3 (GaHV-3, Meleagrid Herpesvirus1 (MeHV-1 and should belong to a single cluster within the Alphaherpesvirinae subfamily.

  6. 7 CFR 916.54 - Special purpose shipments.

    Science.gov (United States)

    2010-01-01

    ... Order Regulating Handling Regulations § 916.54 Special purpose shipments. (a) Except as otherwise... State of California; or (2) for such specified purposes (including shipments to facilitate the...

  7. 7 CFR 924.54 - Special purpose shipments.

    Science.gov (United States)

    2010-01-01

    ... COUNTIES IN WASHINGTON AND IN UMATILLA COUNTY, OREGON Order Regulating Handling Regulations § 924.54... shipments to facilitate the conduct of marketing research and development projects established pursuant...

  8. 7 CFR 946.54 - Shipments for specified purposes.

    Science.gov (United States)

    2010-01-01

    ... POTATOES GROWN IN WASHINGTON Order Regulating Handling Regulation § 946.54 Shipments for specified purposes... part in order to facilitate shipments of potatoes for the following purposes: (1) Livestock feed;...

  9. 7 CFR 923.54 - Special purpose shipments.

    Science.gov (United States)

    2010-01-01

    ... DESIGNATED COUNTIES IN WASHINGTON Order Regulating Handling Regulations § 923.54 Special purpose shipments... grading or packing to specified locations outside the production area and shipments to facilitate...

  10. 7 CFR 922.54 - Special purpose shipments.

    Science.gov (United States)

    2010-01-01

    ... COUNTIES IN WASHINGTON Order Regulating Handling Regulations § 922.54 Special purpose shipments. (a) Except... quantities, or types of shipments, or for such specified purposes (including shipments to facilitate...

  11. 7 CFR 966.54 - Shipments for special purposes.

    Science.gov (United States)

    2010-01-01

    ... Regulating Handling Regulation § 966.54 Shipments for special purposes. Upon the basis of recommendations and... facilitate handling of tomatoes for the following purposes: (a) For export; (b) For relief or for charity;...

  12. Chromium behavior during cement-production processes: A clinkerization, hydration, and leaching study

    Energy Technology Data Exchange (ETDEWEB)

    Sinyoung, Suthatip [Department of Environmental Engineering, Faculty of Engineering, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); Songsiriritthigul, Prayoon [Synchrotron Light Research Institute, PO Box 93 Nakhon Ratchasima, 30000 (Thailand); School of Physics, Suranaree University of Technology, Nakhon Ratchasima, 30000 (Thailand); Asavapisit, Suwimol, E-mail: suwimol_s@hotmail.com [Environmental Technology, School of Energy and Materials, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); National Center of Excellence for Environmental and Hazardous Waste Management, Faculty of Engineering, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); Kajitvichyanukul, Puangrat, E-mail: puangratk@nu.ac.th [National Center of Excellence for Environmental and Hazardous Waste Management, Faculty of Engineering, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); Department of Civil Engineering, Faculty of Engineering, Naresuan University, Phitsanulok, 65000 (Thailand)

    2011-07-15

    Highlights: {yields} Behavior of chromium during cement-production processes. {yields} Formation of new chromium compounds in clinker with chromium oxidation states of +3, +4.6, +5, and +6. {yields} Addition of chromium altered the composition of the clinker phases, setting time, and compressive strength of hydrated mixes. {yields} Cr{sup 3+} and Cr{sup 6} were leached during leaching tests, whereas other species remained in the mortar. - Abstract: The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM/EDS, and TG/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca{sub 6}Al{sub 4}Cr{sub 2}O{sub 15}, Ca{sub 5}Cr{sub 3}O{sub 12}, Ca{sub 5}Cr{sub 2}SiO{sub 12}, and CaCr{sub 2}O{sub 7}, with chromium oxidation states of +3, +4.6, +5, and +6, respectively, was detected. After the hydration process, additional chromium compounds were identified in the mortar matrix, including Ca{sub 5}(CrO{sub 4}){sub 3}OH, CaCrO{sub 4}.2H{sub 2}O, and Al{sub 2}(OH){sub 4}CrO{sub 4}, with chromium oxidation states of +4.6, +6, and +6, respectively. Additionally, some species of chromium, such as Cr{sup 3+} from Ca{sub 6}Al{sub 4}Cr{sub 2}O{sub 15} and Cr{sup 6+} from CaCr{sub 2}O{sub 7}, CaCrO{sub 4}.2H{sub 2}O, and Al{sub 2}(OH){sub 4}CrO{sub 4}, were leached during leaching tests, whereas other species remained in the mortar. The concentrations of chromium that leached from the mortar following U.S. EPA Method 1311 and EA NEN 7375:2004 leaching tests were higher than limits set by the U.S. EPA and the Environment Agency of England and Wales related to hazardous waste disposal in landfills. Thus, waste containing chromium should not be allowed to mix with raw materials in the cement manufacturing process.

  13. Compact potentiostat for cellular electrochemical imaging with 54 parallel channels

    DEFF Research Database (Denmark)

    Vergani, Marco; Carminati, M.; Ferrari, G.

    2012-01-01

    A novel potentiostat containing 54 current amplifiers matched to an array of custom-fabricated 5μm microelectrodes for electrochemical imaging of released neurotransmitters is presented. The board is integrated with a programmable microfluidic cell culture system and the whole assembly is thin...... characterization of the system are reported together with its functionality, certified by a 54-pixel electrochemical imaging of the diffusion of a 10μl droplet of a target analyte inside the cell culture chamber....

  14. Chromium treatment has no effect in patients with type 2 diabetes in a Western population : a randomized, double-blind, placebo-controlled trial

    NARCIS (Netherlands)

    Kleefstra, N.; Houweling, S.T.; Bakker, S.J.; Gans, R.O.; Meyboom-de Jong, B.; Bilo, H.J.

    2007-01-01

    OBJECTIVE: Chromium treatment has been reported to improve glycemic control in patients with type 2 diabetes. However, concern exists about the possible toxic effects of chromium picolinate. The aim of this study was to determine the effect of chromium treatment in the form of chromium yeast on glyc

  15. Chromium treatment has no effect in patients with type 2 diabetes in a western population - A randomized, double-blind, placebo-controlled trial

    NARCIS (Netherlands)

    Kleefstra, Nanne; Gans, Rijk O. B.; Houweling, Sebastiaan T.; Meyboom-de Jong, Betty; Bakker, Stephan J. L.; Bilo, Henk J. G.; Verhoeven, Simon

    2007-01-01

    OBJECTIVE - Chromium treatment has been reported to improve glycemic control in patients with type 2 diabetes. However, concern exists about the possible toxic effects of chromium picolinate. The aim of this study was to determine the effect of chromium treatment in the form of chromium yeast on gly

  16. Investigation of total and hexavalent chromium in filtered and unfiltered groundwater samples at the Tucson International Airport Superfund Site

    Science.gov (United States)

    Tillman, Fred; McCleskey, R. Blaine; Hermosillo, Edyth

    2016-01-01

    Potential health effects from hexavalent chromium in groundwater have recently become a concern to regulators at the Tucson International Airport Area Superfund site. In 2016, the U.S. Geological Survey sampled 46 wells in the area to characterize the nature and extent of chromium in groundwater, to understand what proportion of total chromium is in the hexavalent state, and to determine if substantial differences are present between filtered and unfiltered chromium concentrations. Results indicate detectable chromium concentrations in all wells, over 75 % of total chromium is in the hexavalent state in a majority of wells, and filtered and unfiltered results differ substantially in only a few high-turbidity total chromium samples.

  17. Solid waste removes toxic liquid waste: adsorption of chromium(VI) by iron complexed protein waste.

    Science.gov (United States)

    Fathima, Nishtar Nishad; Aravindhan, Rathinam; Rao, Jonnalagadda Raghava; Nair, Balachandran Unni

    2005-04-15

    The leather processing industry generates huge amounts of wastes, both in solid and liquid form. Fleshing from animal hides/skins is one such waste that is high in protein content. In this study, raw fleshing has been complexed with iron and is used for removal of chromium(VI). The effect of pH and the initial concentration of chromium(VI) on the removal of Cr(IV) by iron treated fleshing is presented. Iron treatment is shown to greatly improve adsorption of the fleshing for hexavalent chromium. The ultimate adsorption capacity of iron treated fleshing is 51 mg of chromium(VI) per gram of fleshing. That of untreated fleshing is 9 mg/g such that iron treatment increases the adsorption capacity of fleshing by 10-fold. The measured adsorption kinetics is well described by a pseudo-second-order kinetic model. The uptake of chromium(VI) by fleshing is best described by the Langmuir adsorption isotherm model. X-ray photoelectron spectroscopic (XPS) studies show that the iron is incorporated into the protein matrix. Shifts in XPS spectra suggest that dichromate binding occurs with iron at active adsorption sites and that iron treated fleshing removes chromium(VI) without reducing it to chromium(III).

  18. Removal of chromium(VI) from aqueous solutions by polymer inclusion membranes.

    Science.gov (United States)

    Kozlowski, Cezary A; Walkowiak, Wladyslaw

    2002-11-01

    The transport through polymer inclusion membranes (PIMs) was found as the effective and selective method of chromium(VI) anions removal from chloride acidic aqueous solutions. The optimal PIMs content was as follows: 41 wt% of cellulose triacetate as the support, 23 wt% of tri-n-octylamine as the ionic carrier, and 36 wt% of o-nitrophenyl pentyl ether as the plasticizer. The results obtained show a linear decrease of permeability coefficient and initial flux values with source phase pH increase. Also linear decrease of initial flux in log-log scale with chromium(VI) concentration increase was observed. Value of slope of this relationship was found to be 0.96 which indicates a first order of chromium(VI) reaction with tri-n-octylamine at membrane/aqueous source interface. Transport of chromium(VI) through PIMs reduces the concentration of chromium(VI) in source aqueous phase from 1.0 to 0.0028 ppm, which is below permissible limit in drinking water in Poland. Competitive transport of chromium(VI), cadmium(II), zinc(II), and iron(III) from acidic aqueous solution across PIMs was found to be efficient for chromium(VI) (99%), and cadmium(II) (99%).

  19. Reduction of chromium (VI by the indirect action of Thiobacillus thioparus

    Directory of Open Access Journals (Sweden)

    E. Donati

    2003-03-01

    Full Text Available The microbial reduction of chromium(VI to chromium(III has been one of the most widely studied forms of metal bioremediation. Recently, we have found that Thiobacillus ferrooxidans and Thiobacillus thiooxidans, growing on elemental sulphur, can indirectly promote chromium(VI reduction by producing reducing agents such as sulphite and thiosulphate, which abiotically reduce chromium(VI. Those species of Thiobacillus are acidophilic bacteria which grow optimally at pH values lower than 4. However, most of those reducing agents are stabilised at higher pH values. Thus, the present paper reports on the ability to reduce chromium(VI using another specie of Thiobacilli, Thiobacillus thioparus, which is able to grow at pH close to 7.0. T. thioparus cultures were carried out in a fermentation vessel containing medium and sulphur as the sole energy source and maintained at 30ºC and 400 rpm. The pH was adjusted to 6.0, 7.0 or 8.0 and maintained with the automatic addition of KOH. Our results show high chromium (VI reduction values (close to 100% at the end of bacterial growth at the three pH values. The results of these experiments are very promising for development of a microbiological process to be used in the detoxification of chromium(VI-polluted effluents.

  20. [In vitro percutaneous absorption of chromium powder and the effect of skin cleanser].

    Science.gov (United States)

    D'Agostin, F; Crosera, M; Adami, G; Malvestio, A; Rosani, R; Bovenzi, M; Maina, G; Filon, F Larese

    2007-01-01

    Occupational chromium dermatitis occurs frequently among cement and metal workers, workers dealing with leather tanning and employees in the ceramic industry. The present study, using an in-vitro system, evaluated percutaneous absorption of chromium powder and the effect of rapid skin decontamination with a common detergent. Experiments were performed using the Franz diffusion cell method with human skin. Physiological solution was used as receiving phase and a suspension of chromium powder in synthetic sweat was used as donor phase. The tests were performed without or with decontamination using the cleanser 30 minutes after the start of exposure. The amount of chromium permeated through the skin was analysed by Inductively Coupled Plasma Atomic Emission Spectroscopy and Electro Thermal Atomic Absorption Spectroscopy. Speciation analysis and measurements of chromium skin content were also performed. We calculated a permeation flux of 0.843 +/- 0.25 ng cm(-2) h(-1) and a lag time of 1.1 +/- 0.7 h. The cleaning procedure significantly increased chromium skin content, whereas skin passage was not increased. These results showed that chromium powder can pass through the skin and that skin decontamination did not decrease skin absorption. Therefore, it is necessary to prevent skin contamination when using toxic agents.

  1. Efficiency of Removing Chromium from Plating Industry Wastewater using the Electrocoagulation Method

    Directory of Open Access Journals (Sweden)

    Borghe-ei S.M.1 PhD,

    2015-06-01

    Full Text Available Aims Chromium is one of the most important metallic pollutants in plating industry wastewater. This toxic metal is a serious threat to human health and to the environment due to its cumulative effects and non-degradability. This research intended to study the effects of pH, contact time, and voltage on the degree of chromium removal from wastewater of plating industry by using the electrocoagulation method. Materials & Methods This laboratory research conducted from late May to late November 2012. A 1000cc reactor at laboratory scale was used that included 4 aluminum electrodes of 90% purity, dimensions of 5 by 10cm, and thickness of 1mm, with parallel arrangement. Synthetic chromium-bearing wastewater was prepared at the initial concentration of 50mg/l. The process is done at pH values of 3, 7, and 9, electric potentials of 20, 30, and 40 volts contact durations of 20, 40, 60, and 80 minutes. Findings The degree of chromium reduction did not change linearly with time in the solution and strongly depended on the pH. The efficiency of chromium removal in the samples had an ascending trend with increases in voltage from 20 to 30 and 40 volts. The degree of chromium removal increased at longer contact times. Conclusion Lower pH, more contact time and higher voltages are effective factors in the chromium removal from wastewater by coagulation method.

  2. Chromium in water, suspended particles, sediments and biota in the Iraja River estuary

    Energy Technology Data Exchange (ETDEWEB)

    Pfeiffer, W.C.; Fiszman, M.; de Lacerda, L.D.; van Weerfelt, M.; Carbonell, N.

    1982-11-01

    Analyses of chromium concentrations in waters, suspended particles, bottom sediments, fish (Poecilia reticulata), plants (Paspalum vaginatum, Sesuvium portulacastrum, Philoxeros vermicularis), soils and barnacles (Balanus sp.) were performed from August 1976 to September 1980 in samples collected from the Iraja River and inside its estuary in Guanabara Bay (Rio de Janeiro, Brazil). Sediments and water from the Iraja River showed chromium concentrations of 17536 and 23.39 ppm--a thousand times higher than the published data for freshwater systems. Chromium removed from solution by bottom sediments reaches Guanabara Bay linked to particulate matter. Fish and emergent grass inside the river concentrate chromium from water and/or sediment, returning the metal to the system as detritus. Soil and plants inside the estuary concentrate chromium thirty and ten times higher than in the control area. The vegetal community exhibits a concentration factor smaller than that related to soil and prevents the return of chromium to the estuarine waters. Inside the Guanabara Bay, Balanus sp. appears to be an effective biological monitor as it concentrates chromium in soft tissues 10/sup 3/ times higher than values found in suspended particles (0.012 ..mu..g ml/sup -1/).

  3. High Chromium Tolerant Bacterial Strains from Palar River Basin: Impact of Tannery Pollution

    Directory of Open Access Journals (Sweden)

    K. Sundar

    2010-04-01

    Full Text Available The basic survey study on tanneries and its pollution in the Palar river basin of Vellore District showed that it has been contaminated with heavy metals especially chromium and salts. This study is to improve our understanding to find the Cr contamination level and the ecology of heavy metal tolerance of the native bacterial flora of our study area. Chromium tolerant strains were isolated from contaminated sediments, water and effluents of various tanneries. The minimum and maximum concentration of chromium sediments was in the range of 47.4 and 682.4 mg/L, with an average of 306.285 mg/L in the study area. Sixty-eight chromium resistant bacterial strains were isolated and Maximum Tolerance Concentration (MTC studies have indicated that the tolerance concentrations of the isolates were in the range of 100-3300 mg/L. These bacterial isolates were also checked for their resistance to other heavy metals like Ni, Pb, Zn, Fe and Cd. Eighty percent of the isolates showed resistance to Ni, Pb, Zn, Fe at 100 ppm level and 45% had shown resistance to Cd. The isolates also had shown tolerance to salt (NaCl up to 9%. Significant note was found in the concentration of chromium and in the chromium tolerance ability of the bacteria in the study area and these chromium tolerance bacteria can be used as the indicator for the Cr contamination.

  4. Determination of Chromium(III), Chromium(VI), and Chromium(III) acetylacetonate in water by ion-exchange disk extraction/metal furnace atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Kamakura, Nao, E-mail: minnie04_tb@yahoo.co.jp; Inui, Tetsuo; Kitano, Masaru; Nakamura, Toshihiro

    2014-03-01

    A new method for the separate determination of Chromium(III) (Cr(III)), Chromium(VI) (Cr(VI)), and Cr(III) acetylacetonate (Cr(acac){sub 3}) in water was developed using a cation-exchange extraction disk (CED) and an anion-exchange extraction disk (AED) combined with metal furnace atomic absorption spectrometry (MFAAS). A 100-mL water sample was adjusted to pH 5.6 and passed through the CED placed on the AED. Cr(acac){sub 3} and Cr(III) were adsorbed on the CED, and Cr(VI) was adsorbed on the AED. The adsorbed Cr(acac){sub 3} was eluted with 50 mL of carbon tetrachloride, followed by the elution of Cr(III) with 50 mL of 3 mol L{sup −1} nitric acid. Cr(VI) was eluted with 50 mL of 3 mol L{sup −1} nitric acid. The chemical species of Cr eluted from the CED with carbon tetrachloride was identified as Cr(acac){sub 3} using infrared spectroscopy. The eluate of Cr(acac){sub 3} was diluted to 100 mL with carbon tetrachloride, and those of Cr(III) and Cr(VI) were diluted to 100 mL with deionized water. All of the solutions were subsequently analyzed by MFAAS. The calibration curve for the Cr(acac){sub 3} aqueous solutions exhibited good linearity in the range of 0.1 to 1 ng. The detection limit of Cr, which corresponded to three times the standard deviation (n = 10) of the blank values, was 20 pg. The recovery test for Cr(III), Cr(VI), and Cr(acac){sub 3} exhibited desirable results (96.0%–107%) when 5 μg of each species (50 μg L{sup −1}) was added to 100 mL water samples (i.e., tap water, rainwater, and bottled drinking water). In a humic acid solution, Cr(acac){sub 3} was quantitatively recovered (103%), but Cr(III) and Cr(VI) exhibited poor recoveries (i.e., 84.8% and 78.4%, respectively). - Highlights: • A determination method of Cr(III), Cr(VI), and Cr(III) acetylacetonate in water was developed. • The combination of ion-exchange resin disks with metal furnace AAS was used. • No effect of humic acid on the recovery of Cr(III) acetylacetonate was

  5. Chromium behavior during cement-production processes: a clinkerization, hydration, and leaching study.

    Science.gov (United States)

    Sinyoung, Suthatip; Songsiriritthigul, Prayoon; Asavapisit, Suwimol; Kajitvichyanukul, Puangrat

    2011-07-15

    The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM/EDS, and TG/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca(6)Al(4)Cr(2)O(15), Ca(5)Cr(3)O(12), Ca(5)Cr(2)SiO(12), and CaCr(2)O(7), with chromium oxidation states of +3, +4.6, +5, and +6, respectively, was detected. After the hydration process, additional chromium compounds were identified in the mortar matrix, including Ca(5)(CrO(4))(3)OH, CaCrO(4)·2H(2)O, and Al(2)(OH)(4)CrO(4), with chromium oxidation states of +4.6, +6, and +6, respectively. Additionally, some species of chromium, such as Cr(3+) from Ca(6)Al(4)Cr(2)O(15) and Cr(6+) from CaCr(2)O(7), CaCrO(4)·2H(2)O, and Al(2)(OH)(4)CrO(4), were leached during leaching tests, whereas other species remained in the mortar. The concentrations of chromium that leached from the mortar following U.S. EPA Method 1311 and EA NEN 7375:2004 leaching tests were higher than limits set by the U.S. EPA and the Environment Agency of England and Wales related to hazardous waste disposal in landfills. Thus, waste containing chromium should not be allowed to mix with raw materials in the cement manufacturing process.

  6. Portable x-ray fluorescence for the analysis of chromium in nail and nail clippings.

    Science.gov (United States)

    Fleming, David E B; Ware, Chris S

    2017-03-01

    Assessment of chromium content in human nail or nail clippings could serve as an effective biomarker of chromium status. The feasibility of a new portable x-ray fluorescence (XRF) approach to chromium measurement was investigated through analysis of nail and nail clipping phantoms. Five measurements of 180s (real time) duration were first performed on six whole nail phantoms having chromium concentrations of 0, 2, 5, 10, 15, and 20µg/g. Using nail clippers, these phantoms were then converted to nail clippings, and assembled into different mass groups of 20, 40, 60, 80, and 100mg for additional measurements. The amplitude of the chromium Kα characteristic x-ray energy peak was examined as a function of phantom concentration for all measurement conditions to create a series of calibration lines. The minimum detection limit (MDL) for chromium was also calculated for each case. The chromium MDL determined from the whole nail intact phantoms was 0.88±0.03µg/g. For the clipping phantoms, the MDL ranged from 1.2 to 3.3µg/g, depending on the mass group analyzed. For the 40mg clipping group, the MDL was 1.2±0.1µg/g, and higher mass collections did not improve upon this result. This MDL is comparable to chromium concentration levels seen in various studies involving human nail clippings. Further improvements to the portable XRF technique would be required to detect chromium levels expected from the lower end of a typical population.

  7. Technological progress on detoxification and comprehensive utilization of chromium-containing slag

    Institute of Scientific and Technical Information of China (English)

    柴立元; 何德文; 于霞; 刘恢; 闵小波; 陈为亮

    2002-01-01

    Chromium salt is an important industrial material, but vast waste slag containing chrome(Ⅵ) is brought out in the process of its production. The slag is seriously harmful to environments and human health. The technologies on detoxification and comprehensive utilization of chromium-containing slag were summarized abroad and at home. And various methods were also described for the detoxification mechanism, technology process, and practical application effects in detail. A new concept for detoxification of chromium-containing slag, furthermore, was put forward by using microorganism.

  8. Analysis of Nanometer Structure for Chromium Atoms in Gauss Standing Laser Wave

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wen-Tao; ZHU Bao-Hua; XIONG Xian-Ming

    2010-01-01

    @@ The equation of motion of two-level chromium atoms in Gauss standing laser wave is discussed and the distribution of chromium atoms is given under different transverse velocity conditions.The results show that the focusing position of atoms will be affected by the transverse velocity of atoms.Based on the four-order Runge-Kutta method,the locus of chromium atoms in Gauss standing laser wave is simulated.The three-dimensional characteristics of nanometer structures are stimulated under perfect and emanative conditions.

  9. STUDY ON MORPHOLOGY OF CHROMIUM IN CHILLED Cu-0.14%-2.0%Cr ALLOYS

    Institute of Scientific and Technical Information of China (English)

    H.W.Yang; Z.K.Fan

    2004-01-01

    The morphology of chromium in chilled Cu-Cr alloys with 0.14%-2.0% Cr has been studied. The results showed that eutectic Cr phase takes a fibrous shape, and pre-eutectic Cr is dendritic in the studied chilled Cu-Cr alloy. During solute treatment of the eutectic and super-eutectic Cu-Cr alloys, only part of chromium particles dissolved in copper phase,some fiber and dendritic chromium still remained. Forging before solute treatment can reduce the size of primary Cr particles, which benefits the aging structure.

  10. Growth of magnetic cobalt/chromium nano-arrays by atom-optical lithography

    Energy Technology Data Exchange (ETDEWEB)

    Atoneche, F; Malik, D; Kirilyuk, A; Toonen, A J; Etteger, A F van; Rasing, Th, E-mail: f.atoneche@science.ru.nl [Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ, Nijmegen (Netherlands)

    2011-07-06

    Arrays of magnetic cobalt/chromium (Co-Cr) nanolines are grown by depositing an atomic beam of Co-Cr alloy through a laser standing wave (SW) at {lambda}/2 = 212.8 nm onto a substrate. During deposition, only the chromium atoms are resonantly affected by the optical potential created by the SW, causing a periodic modulation of the chromium concentration and consequently of the magnetic properties. Magnetic force microscopy and magneto-optical Kerr effect studies reveal a patterned magnetic structure on the substrate surface.

  11. Growth of magnetic cobalt/chromium nano-arrays by atom-optical lithography

    Science.gov (United States)

    Atoneche, F.; Malik, D.; Kirilyuk, A.; Toonen, A. J.; van Etteger, A. F.; Rasing, Th

    2011-07-01

    Arrays of magnetic cobalt/chromium (Co-Cr) nanolines are grown by depositing an atomic beam of Co-Cr alloy through a laser standing wave (SW) at λ/2 = 212.8 nm onto a substrate. During deposition, only the chromium atoms are resonantly affected by the optical potential created by the SW, causing a periodic modulation of the chromium concentration and consequently of the magnetic properties. Magnetic force microscopy and magneto-optical Kerr effect studies reveal a patterned magnetic structure on the substrate surface.

  12. Proposed adsorption-diffusion model for characterizing chromium(VI) removal using dried water hyacinth roots

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Debasish; Mukherjee, Paramartha; Bandyopadhyay, Amitava [Department of Chemical Engineering, University of Calcutta, Kolkata (India); Das, Sudip Kumar [Department of Chemical Technology, University of Calcutta, Kolkata (India)

    2010-08-15

    Experiments have been carried out to characterize the adsorption of chromium(VI) in the aqueous phase onto dried roots of water hyacinth. Results revealed a very high degree of removal efficiency ({proportional_to}100%). Theoretical analyzes are also made for describing the sorption and diffusion processes. The effective pore diffusivity of chromium(VI) in the water hyacinth roots is determined by a suitable global optimization technique. The depth of penetration, on the other hand, has been estimated for various initial concentrations of chromium(VI). Theoretically predicted concentration profiles are in excellent agreement with the experimental values. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  13. Menstrual cyclic change of metastin/GPR54 in endometrium.

    Science.gov (United States)

    Baba, Tsukasa; Kang, Hyun Sook; Hosoe, Yuko; Kharma, Budiman; Abiko, Kaoru; Matsumura, Noriomi; Hamanishi, Junzo; Yamaguchi, Ken; Yoshioka, Yumiko; Koshiyama, Masafumi; Mandai, Masaki; Murphy, Susan K; Konishi, Ikuo

    2015-06-01

    Metastin/kisspeptin is encoded by KISS1 and functions as an endogenous ligand of GPR54. Interaction of metastin with GPR54 suppresses metastasis and also regulates release of gonadotropin-releasing hormone, which promotes secretion of estradiol (E2) and progesterone (P4). We have previously demonstrated epigenetic regulation of GPR54 in endometrial cancer and the potent role of metastin peptides in inhibiting metastasis in endometrial cancer. However, little is known about how the metastin-GPR54 axis is regulated in the endometrium, the precursor tissue of endometrial cancer. Endometrial stromal cells (ESCs) and endometrial glandular cells (EGCs) within the endometrium show morphological changes when exposed to E2 and P4. In this study, we show that metastin expression is induced in ESCs through decidualization, but is repressed in glandular components of atypical endometrial hyperplasia (AEH) and endometrial cancer relative to EGCs. The promoter of GPR54 is unmethylated in normal endometrium and in AEH. These results indicate metastin may function in decidualized endometrium to prepare for adequate placentation but this autocrine secretion of metastin is deregulated during oncogenesis to enable tumor cells to spread.

  14. Electrochemical reduction of hexavalent chromium in ground water

    Energy Technology Data Exchange (ETDEWEB)

    Bansal, S. [Lawrence Livermore National Lab., CA (United States)

    1994-12-01

    Electrochemical reduction of hexavalent chromium (Cr{sup +6}) to its trivalent state (Cr{sup +3}) is showing promising results in treating ground water at Lawrence Livermore National Laboratory`s (LLNL`s) Main Site. An electrolytic cell using stainless-steel and brass electrodes has been found to offer the most efficient reduction while yielding the least amount of precipitate. Trials have successfully lowered concentrations of Cr{sup +6} to below 11 parts per billion (micrograms/liter), the California state standard. We ran several trials to determine optimal voltage for running the cell; each trial consisted of applying a voltage between 6V and 48V for ten minutes through samples obtained at Treatment Facility C(TFC). No conclusive data has been obtained yet.

  15. Fracture and Delamination of Chromium Thin Films on Polymer Substrates

    Science.gov (United States)

    Cordill, M. J.; Taylor, A.; Schalko, J.; Dehm, G.

    2010-04-01

    New emerging technologies in the field of flexible electronic devices require that metal films adhere well and flex with polymer substrates. Common thin film materials used for these applications include copper (Cu) with an adhesion interlayer of chromium (Cr). Copper can be quite ductile and easily move with the polymer substrate. However, Cr is more brittle and fractures at lower strains than Cu. This study aims to examine the fracture and subsequent buckling and delamination of strained Cr films on polyimide (PI). In-situ scanning electron microscope (SEM) straining is used to systematically study the influence of film thickness on fracture and buckling strains. Film fracture and delamination depend on film thickness, and increases in crack and buckle density with decreasing thickness are explored by a shear lag model.

  16. Hexavalent Chromium Removal by Litchi chinensis Sonn Peel

    Directory of Open Access Journals (Sweden)

    Ismael Acosta-Rodriguez

    2012-01-01

    Full Text Available Problem statement: We studied the Chromium (VI removal capacity in aqueous solution by the litchi peel. Approach: We use the diphenylcarbazide method to evaluate the metal concentration. Results: The highest biosorption of the metal (50 mg L-1 occurs within 6 min, at pH of 1 and 28°C. According to temperature, the highest removal was observed at 40 and 50°C, in 45 min, when the metal (1 g L-1 was completely adsorbed. At the analyzed concentrations of Cr (VI, litchi peel, showed excellent removal capacity, besides it removes efficiently the metal in situ (100% removal, 5 days of incubation, 5 and 10 g of biomass. After 1 h of incubation the studied biomass reduces 1.0 g of Cr (VI with the simultaneous production of Cr (III. Conclusion: The shell can be used to eliminate it from industrial wastewater."

  17. Investigation of hexavalent chromium sorption in serpentine sediments

    Science.gov (United States)

    Mpouras, Thanasis; Chrysochoou, Maria; Dermatas, Dimitris

    2017-02-01

    In this study the removal of hexavalent chromium (Cr6 +) by serpentine sediments was investigated in order to delineate Cr6 + sorption behavior in aquifers with ultramafic geologic background. Batch experiments were conducted in order to determine the influence of several parameters on Cr6 + removal, including the pH of the sediment solution, mineralogy, sediment's particle size and Cr6 + initial concentration. The results showed that Cr6 + removal was due to both adsorption and reduction phenomena. Reduction was attributed to the presence of a magnetic fraction in the sediment, mostly related to magnetite, which contributed almost 50% of the total removal in the pH range 3-7. Adsorption behavior was dominated by the finer sediment fraction (d transport modeling.

  18. Polyaniline coating with various substrates for hexavalent chromium removal

    Science.gov (United States)

    Qiu, Bin; Xu, Cuixia; Sun, Dezhi; Wang, Qiang; Gu, Hongbo; Zhang, Xin; Weeks, Brandon L.; Hopper, Jack; Ho, Thomas C.; Guo, Zhanhu; Wei, Suying

    2015-04-01

    Hexavalent chromium (Cr(VI)) contamination is increasingly serious in surface water and groundwater, therefore, its removal attracts increasing attention due to its highly toxic to human health. The cost effective and sustainable adsorbents are urgently needed for the remediation of Cr(VI) pollution. Polyanline (PANI), a conductive polymer, has demonstrated a great performance on Cr(VI) removal. But the recycling is the challenge for its application due to its small size. The PANI coating with various substrates is an effective approach to solve this problem. The synthesis methods and applications of the PANI coated magnetic Fe3O4, carbon fabric and cellulose composites for the Cr(VI) removal were reviewed. Finally, this review analyzed the Cr(VI) removal mechanisms by the PANI composites considering the substrate and the PANI coating.

  19. Chromium Renderserver: scalable and open remote rendering infrastructure.

    Science.gov (United States)

    Paul, Brian; Ahern, Sean; Bethel, E Wes; Brugger, Eric; Cook, Rich; Daniel, Jamison; Lewis, Ken; Owen, Jens; Southard, Dale

    2008-01-01

    Chromium Renderserver (CRRS) is software infrastructure that provides the ability for one or more users to run and view image output from unmodified, interactive OpenGL and X11 applications on a remote, parallel computational platform equipped with graphics hardware accelerators via industry-standard Layer 7 network protocols and client viewers. The new contributions of this work include a solution to the problem of synchronizing X11 and OpenGL command streams, remote delivery of parallel hardware accelerated rendering, and a performance analysis of several different optimizations that are generally applicable to a variety of rendering architectures. CRRS is fully operational, Open Source software. imagery and sending it to a remote viewer.

  20. Tuning ferromagnetism in zinc oxide nanoparticles by chromium doping

    Science.gov (United States)

    Kaur, Palvinder; Pandey, S. K.; Kumar, Sanjeev; Negi, N. S.; Chen, C. L.; Rao, S. M.; Wu, M. K.

    2015-11-01

    Zn1- x Cr x O nanoparticles with x = 0.0, 0.01, 0.03 and 0.05 were synthesized by the sol-gel technique. Powder X-ray diffraction (XRD) studies reveal that chromium (Cr) incorporates into the ZnO crystal lattice without disturbing the parent hexagonal (wurtzite) structure. Transmission electron microscopy (TEM) measurements show that the average size of these nanoparticles is in the range 15-25 nm. Optical absorption studies show that the band gap of ZnO nanoparticles varies with Cr doping. Photoluminescence (PL) studies depict the presence of defects in Cr-doped nanoparticles. Undoped ZnO exhibits diamagnetic behavior while Cr-doped ZnO samples exhibit weak ferromagnetism to anti-ferromagnetism depending on the Cr content.

  1. Nanotwin hardening in a cubic chromium oxide thin film

    Directory of Open Access Journals (Sweden)

    Kazuma Suzuki

    2015-09-01

    Full Text Available NaCl-type (B1 chromium oxide (CrO has been expected to have a high hardness value and does not exist as an equilibrium phase. We report a B1-based Cr0.67O thin film with a thickness of 144 nm prepared by pulsed laser deposition as an epitaxial thin film on a MgO single crystal. The thin film contained a number of stacking faults and had a nanotwinned structure composed of B1 with disordered vacancies and corundum structures. The Cr0.67O thin film had a high indentation hardness value of 44 GPa, making it the hardest oxide thin film reported to date.

  2. Identification Trial of Crystallization Parameters of Modified Chromium Cast Iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2007-07-01

    Full Text Available In the paper results of researches of abrasion-resisting chromium cast iron inoculated with boron carbide B4C primary crystallization are presented. The main aim of work was make an attempt to identification of crystallization parameters that changed in reason of inoculation. Essential primary crystallization parameters, with the help of which, will be possible to evaluate the inoculation capacity were searched. It was found that in the result of inoculant actions characteristic temperatures were changed and time of primary crystallization was decreased. For tests the new broadened Derivative Thermal Analysis method, in which three samples with different solidification module were applied, was used. Thanks to this inoculation capacity in casts with significant diversified self-cooling ranges was possible to observe.

  3. Tetravalent chromium doped laser materials and NIR tunable lasers

    Science.gov (United States)

    Alfano, Robert R. (Inventor); Petricevic, Vladimir (Inventor); Bykov, Alexey (Inventor)

    2008-01-01

    A method is described to improve and produce purer Cr.sup.4+-doped laser materials and lasers with reduced co-incorporation of chromium in any other valence states, such as Cr.sup.3+, Cr.sup.2+, Cr.sup.5+, and Cr.sup.6+. The method includes: 1) certain crystals of olivine structure with large cation (Ca) in octahedral sites such as Cr.sup.4+:Ca.sub.2GeO.sub.4, Cr.sup.4+:Ca.sub.2SiO.sub.4, Cr.sup.4+:Ca.sub.2Ge.sub.xSi.sub.1-xO.sub.4 (where 0NIR laser applications.

  4. Semisolid Slurry Preparation of Die Steel with High Chromium Content

    Institute of Scientific and Technical Information of China (English)

    MAO Wei-min; ZHAO Ai-min; ZHANG Li-juan; ZHONG Xue-you

    2004-01-01

    The semisolid slurry preparation of die steels Cr12 and Cr12MoV with high chromium content was studied. The results show that the semisolid slurry of both steels with solid of 40 %-60 % can be made by electromagnetic stirring method and is easy to be discharged from the bottom little hole of the stirring chamber. The sizes of the spherical primary austenite in the slurry of die steels Cr12 and Cr12MoV are 50-100 μm and 80-150 μm, respectively. The homogeneous temperature field and solute field for both steel melts are obtained. The strong temperature fluctuation in the melt with many fine primary austenite grains occurs and the remelting of the secondary arm roots at the same time is accelerated because of the electromagnetic stirring. These are the most important reasons for deposition of spherical primary austenite grains.

  5. Characterization of electrocoagulation for removal of chromium and arsenic

    Energy Technology Data Exchange (ETDEWEB)

    Parga, J.R.; Valverde, V. [Institute of Technology of Saltillo, Dept. of Metallurgy and Materials Science, V. Carranza 2400, Saltillo Coah., C.P. 25280 (Mexico); Cocke, D.L.; Gomes, J.A.G.; Kesmez, M.; Moreno, H. [Lamar University, Gill Chair of Chemistry and Chemical Engineering, Beaumont, TX 77710 (United States); Weir, M.; Mencer, D. [Wilkes University, Dept. of Chemistry, Wilkes-Barre, PA 18766 (United States)

    2005-05-01

    Protection of the global environment and, in particular, providing a sustainable source of clean water is a necessity for human survival. The wide use of heavy metals by modern industries has generated by-products containing heavy metals. Specifically, large quantities of chromium and arsenic containing compounds are being discharged into the environment. This study has been conducted to determine the feasibility of an electrocoagulation (EC) process using air injection to remove these inorganic elements with iron electrodes. Powder X-ray diffraction, scanning electron microscopy, and transmission Moessbauer spectroscopy were used to characterize the solid products formed at iron electrodes during EC. The results of this study suggest that magnetite particles and amorphous iron oxyhydroxides are present in the examined EC products. The field pilot-scale study demonstrated the removal of Cr(VI)/Cr(III) and As(III)/As(V) with an efficiency of more than 99 % from both wastewater and wells. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  6. Adsorption of hexavalent chromium by graphite–chitosan binary composite

    Indian Academy of Sciences (India)

    RAJENDRA S DONGRE

    2016-06-01

    Graphite chitosan binary (GCB) composite was prepared for hexavalent chromium adsorption from studied water. GCB was characterized by TGA, FTIR, SEM and X-ray diffraction techniques.Wide porous sorptive surface of 3.89 m$^2$ g$^{−1}$ and absorptive functionalities of GCB was due to 20% (w/w) graphite support on chitosan evidenced from FTIR and SEM that impart maximum adsorption at pH 4, agitation with 200 rpm for 180 min. Adsorption studies revealed intraparticle diffusion models and best-fitted kinetics was pseudo 2nd order one. A wellfitted Langmuir isotherm model suggested monolayer adsorption with an adsorption capacity ($q_m$) of 105.6 mg g$^{−1}$ and $R^2 = 0.945$. Sorption mechanisms based on metal ionic interactions, intrusion/diffusion and chemisorptions onto composite. This graphite chitosan binary composite improve sorbent capacity for Cr(VI).

  7. Microbial reduction of hexavalent chromium by landfill leachate.

    Science.gov (United States)

    Li, Yarong; Low, Gary K-C; Scott, Jason A; Amal, Rose

    2007-04-02

    The reduction of hexavalent chromium (Cr(VI)) in municipal landfill leachates (MLL) and a non-putrescible landfill leachate (NPLL) was investigated. Complete Cr(VI) reduction was achieved within 17 days in a MLL when spiked with 100 mg l(-1) Cr(VI) or less. In the same period, negligible Cr(VI) reduction was observed in NPLL. In MLL, Cr(VI) reduction was demonstrated to be a function of initial Cr(VI) concentration and bacterial biomass and organic matter concentrations. The bacteria were observed to tolerate 250 mg l(-1) Cr(VI) in MLL and had an optimal growth activity at pH 7.4 in a growth medium. The MLL also possessed an ability to sequentially reduce Cr(VI) over three consecutive spiking cycles.

  8. Chromium as resonant donor impurity in PbTe

    Science.gov (United States)

    Nielsen, M. D.; Levin, E. M.; Jaworski, C. M.; Schmidt-Rohr, K.; Heremans, J. P.

    2012-01-01

    We synthesize and perform structural, thermoelectric, magnetic, and 125Te NMR characterization measurements on chromium-doped PbTe. 125Te NMR and magnetic measurements show that Pb1-xCrxTe is a solid solution up to x = 0.4 at.% and forms an n-type dilute paramagnetic semiconductor. The Cr level is resonant and pins the Fermi level about 100 meV into the conduction band at liquid nitrogen temperatures and below, but it moves into the gap as the temperature increases to 300 K. 125Te NMR spectra exhibit a Knight shift that correlates well with Hall effect measurements and resolve peaks of Te near Cr. Magnetic behavior indicates that Cr exists mainly as Cr2+. No departure from the Pisarenko relation for PbTe is observed. Secondary Cr2Te3 and Cr3+δTe4 phases are present in samples with x > 0.4%.

  9. Chromium as Resonant Donor Impurity in PbTe

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, M.D.; Levin, Evgenii; Jaworski, C.M.; Schmidt-Rohr, Klaus; Heremans, J.P.

    2012-01-25

    We synthesize and perform structural, thermoelectric, magnetic, and 125Te NMR characterization measurements on chromium-doped PbTe. 125Te NMR and magnetic measurements show that Pb1−xCrxTe is a solid solution up to x = 0.4 at.% and forms an n-type dilute paramagnetic semiconductor. The Cr level is resonant and pins the Fermi level about 100 meV into the conduction band at liquid nitrogen temperatures and below, but it moves into the gap as the temperature increases to 300 K. 125Te NMR spectra exhibit a Knight shift that correlates well with Hall effect measurements and resolve peaks of Te near Cr. Magnetic behavior indicates that Cr exists mainly as Cr2+. No departure from the Pisarenko relation for PbTe is observed. Secondary Cr2Te3 and Cr3+δTe4 phases are present in samples with x > 0.4%.

  10. Ab initio calculation of chromium oxide containing Ti dopant

    Energy Technology Data Exchange (ETDEWEB)

    Maldonado, Frank [Grupo de Fisicoquimica de Materiales, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador); Novillo, Corina [Escuela de Ingenieria Quimica, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador); Stashans, Arvids, E-mail: arvids@utpl.edu.ec [Grupo de Fisicoquimica de Materiales, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)

    2012-01-17

    Highlights: Black-Right-Pointing-Pointer Microstructure changes in chromium oxide due to the Ti doping. Black-Right-Pointing-Pointer Discovery of magnetism in Ti-doped {alpha}-Cr{sub 2}O{sub 3} crystal. Black-Right-Pointing-Pointer Explanation of the origin of n-type electrical conductivity. Black-Right-Pointing-Pointer Detailed analysis of electronic properties and density of states. Black-Right-Pointing-Pointer As to authors' knowledge, Ti-doped crystal is studied for the first time by the DFT. - Abstract: First-principles computations based on the density functional theory within the generalised gradient approximation and introduced intra-atomic interaction term for strongly correlated electrons (DFT + U method) has been used in this work. Ti impurity doping in the {alpha}-Cr{sub 2}O{sub 3} crystal has been carried out considering single defect model within the periodic crystalline structure. Atomic displacements, Bader charges on atoms have been computed showing that Ti dopant converts the chemical bonding in its neighbourhood into more ionic one. The defect-local microstructure is such as there exist general tendency of atomic rearrangements away with respect to the Ti imperfection. It is found that defect incorporation produces some local changes upon the band structure of the material and also induces a metallic state. That implies n-type electrical conductivity in the Ti-doped {alpha}-Cr{sub 2}O{sub 3} crystals and relates our work directly to a number of experimental studies in this area. Our results provide evidence over change in magnetic moments in the vicinity of defect, which means that the chromium oxide doped with Ti impurity might not act as an antiferromagnetic substance.

  11. Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes

    Science.gov (United States)

    Frei, Robert; Gaucher, Claudio; Poulton, Simon W.; Canfield, Don E.

    2009-09-01

    Geochemical data suggest that oxygenation of the Earth's atmosphere occurred in two broad steps. The first rise in atmospheric oxygen is thought to have occurred between ~2.45 and 2.2Gyr ago, leading to a significant increase in atmospheric oxygen concentrations and concomitant oxygenation of the shallow surface ocean. The second increase in atmospheric oxygen appears to have taken place in distinct stages during the late Neoproterozoic era (~800-542Myr ago), ultimately leading to oxygenation of the deep ocean ~580Myr ago, but details of the evolution of atmospheric oxygenation remain uncertain. Here we use chromium (Cr) stable isotopes from banded iron formations (BIFs) to track the presence of Cr(VI) in Precambrian oceans, providing a time-resolved picture of the oxygenation history of the Earth's atmosphere-hydrosphere system. The geochemical behaviour of Cr is highly sensitive to the redox state of the surface environment because oxidative weathering processes produce the oxidized hexavalent [Cr(VI)] form. Oxidation of reduced trivalent [Cr(III)] chromium on land is accompanied by an isotopic fractionation, leading to enrichment of the mobile hexavalent form in the heavier isotope. Our fractionated Cr isotope data indicate the accumulation of Cr(VI) in ocean surface waters ~2.8 to 2.6Gyr ago and a likely transient elevation in atmospheric and surface ocean oxygenation before the first great rise of oxygen 2.45-2.2Gyr ago (the Great Oxidation Event). In ~1.88-Gyr-old BIFs we find that Cr isotopes are not fractionated, indicating a decline in atmospheric oxygen. Our findings suggest that the Great Oxidation Event did not lead to a unidirectional stepwise increase in atmospheric oxygen. In the late Neoproterozoic, we observe strong positive fractionations in Cr isotopes (δ53Cr up to +4.9‰), providing independent support for increased surface oxygenation at that time, which may have stimulated rapid evolution of macroscopic multicellular life.

  12. Probing neutrino nature at Borexino detector with chromium neutrino source

    Energy Technology Data Exchange (ETDEWEB)

    Sobkow, W.; Blaut, A. [University of Wroclaw, Institute of Theoretical Physics, Wroclaw (Poland)

    2016-10-15

    In this paper, we indicate a possibility of utilizing the intense chromium source (∝370 PBq) in probing the neutrino nature in low energy neutrino experiments with the ultra-low threshold and background real-time Borexino detector located near the source (∝8 m). We analyse the elastic scattering of electron neutrinos (Dirac or Majorana, respectively) on the unpolarised electrons in the relativistic neutrino limit. We assume that the incoming neutrino beam is the superposition of left-right chiral states produced by the chromium source. Left chiral neutrinos may be detected by the standard V - A and non-standard scalar S{sub L}, pseudoscalar P{sub L}, tensor T{sub L} interactions, while right chiral ones partake only in the exotic V + A and S{sub R}, P{sub R}, T{sub R} interactions. Our model-independent study is carried out for the flavour (current) neutrino eigenstates. We compute the expected event number for the standard V - A interaction of the left chiral neutrinos using the current experimental values of standard couplings and in the case of left-right chiral superposition. We show that the significant decrement in the event number due to the interference terms between the standard and exotic interactions for the Majorana neutrinos may appear. We also demonstrate how the presence of the exotic couplings affects the energy spectrum of outgoing electrons, both for the Dirac and Majorana cases. The 90 % C.L. sensitivity contours in the planes of corresponding exotic couplings are found. The presence of interferences in the Majorana case gives the stronger constraints than for the Dirac neutrinos, even if the neutrino source is placed outside the detector. (orig.)

  13. High-valent imido complexes of manganese and chromium corroles.

    Science.gov (United States)

    Edwards, Nicola Y; Eikey, Rebecca A; Loring, Megan I; Abu-Omar, Mahdi M

    2005-05-16

    The oxidation reaction of M(tpfc) [M = Mn or Cr and tpfc = tris(pentafluorophenyl)corrole] with aryl azides under photolytic or thermal conditions gives the first examples of mononuclear imido complexes of manganese(V) and chromium(V). These complexes have been characterized by NMR, mass spectrometry, UV-vis, EPR, elemental analysis, and cyclic voltammetry. Two X-ray structures have been obtained for Mn(tpfc)(NMes) and Cr(tpfc)(NMes) [Mes = 2,4,6-(CH(3))(3)C(6)H(2)]. Short metal-imido bonds (1.610 and 1.635 Angstroms) as well as nearly linear M-N-C angles are consistent with triple M triple-bond NR bond formation. The kinetics of nitrene [NR] group transfer from manganese(V) corroles to various organic phosphines have been defined. Reduction of the manganese(V) corrolato complex affords phosphine imine and Mn(III) with reaction rates that are sensitive to steric and electronic elements of the phosphine substrate. An analogous manganese complex with a variant corrole ligand containing bromine atoms in the beta-pyrrole positions, Mn(Br(8)tpfc)(NAr), has been prepared and studied. Its reaction with PEt(3) is 250x faster than that of the parent tpfc complex, and its Mn(V/IV) couple is shifted by 370 mV to a more positive potential. The EPR spectra of chromium(V) imido corroles reveal a rich signal at ambient temperature consistent with Cr(V) triple-bond NR (d(1), S = 1/2) containing a localized spin density in the d(xy) orbital, and an anisotropic signal at liquid nitrogen temperature. Our results demonstrate the synthetic utility of organic aryl azides in the preparation of mononuclear metal imido complexes previously considered elusive, and suggest strong sigma-donation as the underlying factor in stabilizing high-valent metals by corrole ligands.

  14. 40 CFR 749.68 - Hexavalent chromium-based water treatment chemicals in cooling systems.

    Science.gov (United States)

    2010-07-01

    ... proprietorship, association, or any other business entity; any State or political subdivision thereof; any municipality; any interstate body; and any department, agency, or instrumentality of the Federal Government... the following language: WARNING: This product contains hexavalent chromium. Inhalation of...

  15. RESEARCH AND APPLICATION OF AS-CAST WEAR RESISTANCE HIGH CHROMIUM CAST IRON

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The influence of alloy elements, such as boron and silicon, on the microstructure and properties of as-cast high chromium cast iron is studied. The results show that boron and silicon have a great effect on the mechanical properties and the wear resistance. Through proper addition of boron and silicon, the properties of as-cast high chromium cast iron can be improved effectively. Through analyzing the distribution of elements by scanning electron microscope, it has been shown that the addition of boron and silicon lowers the mass fraction of chromium saturated in as-cast austenite, and makes it unstable and liable to be transformed into martensite. The as-cast high chromium cast iron with proper content of boron and silicon is suitable for the manufacture of lining for asphalt concrete mixer and its wear resistance is 14 times that of lining made of low alloy white cast iron.

  16. Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds

    Science.gov (United States)

    This document summarizes the approaches and rationale for the technical and scientific considerations used to derive inhalation cancer risks for emissions of chromium and nickel compounds from electric utility steam generating units.

  17. Preconcentration and Determination of Chromium Species Using Octadecyl Silica Membrane Disks and Flame Atomic Absorption Spectrometry

    Institute of Scientific and Technical Information of China (English)

    MOGHIMI Ali; SABER-TEHRANI Mohammad; WAQIF-HUSAIN Syed; MOHAMMADHOSSEINI Majid

    2007-01-01

    A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed.The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(Ⅱ) as an enhancement agent of chromium signals followed by elutionwith organic eluents and determination by atomic flame absorption spectrometry.The maximum capacity of the employed disks was found to be (3964±3) μg and (376±2) μg for Cr(Ⅲ) and Cr(Ⅵ),respectively.The detection limit of the proposed method is 49 and 43 ng·L-1 for Cr(Ⅲ) and Cr(Ⅵ),respectively.The proposed method was successfully applied for determination of chromium species Cr(Ⅲ) and Cr(Ⅵ) in different water samples.

  18. EXPERIMENTAL INVESTIGATION ON CHROMIUM(VI REMOVAL FROM AQUEOUS SOLUTION USING ACTIVATED CARBON RESORCINOL FORMALDEHYDE XEROGELS

    Directory of Open Access Journals (Sweden)

    Eghe A. Oyedoh

    2016-10-01

    Full Text Available The adsorption of chromium(VI metal ion in aqueous solutions by activated carbon resorcinol formaldehyde xerogels (ACRF was investigated. The results showed that pore structure, surface area and the adsorbent surface chemistry are important factors in the control of the adsorption of chromium(VI metal ions. The isotherm parameters were obtained from plots of the isotherms and from the application of Langmuir and Freundlich Isotherms. Based on regression analysis, the Langmuir isotherm model was the best fit. The maximum adsorption capacity of ACRF for chromium (VI was 241.9 mg/g. The pseudo-second-order kinetic model was the best fit to the experimental data for the adsorption of chromium metal ions by activated carbon resorcinol formaldehyde xerogels. The thermodynamics of Cr(VI ions adsorption onto ACRF was a spontaneous and endothermic process.

  19. Remediation of Nitrate and ChromiumContaminated Groundwater by Zero-valent IronPRB

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    Through continuous flow experimentation, the reactivity characteristics of zero-valent iron (Fe0)-PRB with ground watercontaminated by nitrate, chromium and the combination of nitrate and chromium were investigated. The results showed thatnitrate could be effectively deoxidized by zero-valent iron. NO2- -N was the transitional deoxidization product, while NH4+-Nwas the main final product in the effluent. Chromium could be deoxidized by zero-valent iron more effectively for the chromiumcontaminated ground water which was treated by PRB. The redox products such as Fe3+ and Cr(III) precipitated on the packingmedia during the process. For the treatment of ground water contaminated by both nitrate and chromium, the results showed thatthe Cr(VI) removal efficiency by the zero-valent iron was not affected by the co-existence of NO3- -N, while the NO3- -N removalefficiency decreased with the existence of Cr(VI).

  20. THE INVESTIGATION ON PLASMA ARC TREATMENT OF CHROMIUM PLATED ALLOY STRUCTURE STEEL

    Institute of Scientific and Technical Information of China (English)

    X.M. Fan; J.W. Huang; K.H. Wang; Q. Liu

    2005-01-01

    The technology of plasma arc was used to modify the interface adhesion between chromium coating and steel substrate. The interface microstructure was studied as a function of plasma arc processing parameters. Microstructure analysis was performed by optical microscopy,scanning electron microscopy and electron probe. The microhardness distribution along the depth of a cross-section of the chromium coating and the substrate was measured. The results show the energy density of transferred plasma arc is obviously higher than plasma non-transferred arc. The molten interface was obtained by plasma transferred arc. Interfaces between chromium coating and steel substrate can be divided by plasma non-transferred arc into three classes: non-molten, a little molten and molten. Good interface bonding was obtained by proper process parameters. The microhardness of chromium coating decreases with increasing energy density of plasma arc.

  1. Reduction of chromium oxides with calcium carbide during thestainless steelmaking process

    Directory of Open Access Journals (Sweden)

    B. Arh

    2015-04-01

    Full Text Available An efficient reduction of chromium from slag requires an appropriate reduction agent for the given steelmaking technology. The usual slag reduction praxis consists of carbon injections and additions of ferrosilicon and aluminum.Reduction of chromium containing slags with calcium carbide is an appealing alternative. Calcium carbide is a strong reduction agent that unlike ferrosilicon and aluminum also provides the possibility of foaming slag formation.Experimental work regarding chromium slag reduction with calcium carbide towards usual slag reduction praxis is described in this work. The results show that higher reduction rates in the stage of refining period of the melt and higher level of overall chromium reduction from slag can be reached with the blowing of CaC2.

  2. Mechanoactivation of chromium silicide formation in the SiC-Cr-Si system

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2002-01-01

    Full Text Available The processes of simultaneous grinding of the components of a SiC-Cr-Si mixture and further temperature treatment in the temperature range 1073-1793 K were studied by X-ray phase analysis, IR spectroscopy, electron microscopy, and X-ray microanalysis. It was established that, during grinding of the mixture, chromium silicides form. A temperature treatment completes the process. Silicide formation proceeds within the framework of the diffusion of silicon into chromium. In the presence of SiO2 in the mixture, silicide formation occurs also as a result of the reduction of silica by silicon and silicon carbide. The sintering of synthesized composite SiC-chromium silicides powders at a high temperature under a high pressure (T = 2073 K, P = 5 GPa is accompanied by the destruction of cc-SiC particles, the cc/3 transition in silicon carbide and deformation distortions of the lattices of chromium silicides.

  3. Removal of chromium from electroplating industry effluents by ion exchange resins.

    Science.gov (United States)

    Cavaco, Sofia A; Fernandes, Sandra; Quina, Margarida M; Ferreira, Licínio M

    2007-06-18

    Effluent discharged from the chromium electroplating industry contains a large number of metals, including chromium, copper, nickel, zinc, manganese and lead. The ion exchange process is an alternative technique for application in the treatment of industrial wastewater containing heavy metals and indeed it has proven to be very promising in the removal and recovery of valuable species. The main objective of the present work is to evaluate the performance of commercial ion exchange resins for removing chromium trivalent from industrial effluents, and for this purpose two resins were tested: a chelating exchange resin (Diaion CR11) and a weak cationic resin (Amberlite IRC86). In order to evaluate the sorption capacity of the resins some equilibrium experiments were carried out, being the temperature and pH the main variables considered. The chromium solutions employed in the experiments were synthetic solutions and industrial effluents. In addition, a transient test was also performed as an attempt to understand the kinetic behaviour of the process.

  4. Ecotoxicological tests with cadmium and chromium using postlarvae of silverside Odontesthes (Austromenidia regia regia Hildebrand

    Directory of Open Access Journals (Sweden)

    Giovana Vera

    2014-06-01

    Full Text Available In the present paper, the mean effective concentrations (EC50% of cadmium (Cd+2 and chromium (Cr+6 using postlarvae of the silverside fish Odontesthes (Austromenidia regia regia were determined. The postlarvae were exposed to different concentrations of the metals, between 0,142 and 1,208 mg.L–1 of cadmium and between 0,53 and 33,74 mg.L–1 of chromium. The mean effective concentrations (EC50% obtained were 0,648 mg.L–1 of cadmium (at 96 h and 2,68 mg.L–1 of chromium (at 96 h. Comparatively, cadmium is more toxic than chromium, and silverside is more tolerant than other organisms.

  5. Precise measurement of chromium isotopes by MC-ICPMS

    DEFF Research Database (Denmark)

    Schiller, Martin; Van Kooten, Elishevah; Holst, Jesper Christian

    2014-01-01

    of the neutron-rich isotope 54Cr. Because nitride and oxide interferences are a major obstacle to precise and accurate 54Cr measurements by MC-ICPMS, our approach is designed to minimize these interferences. Based on repeat measurements of standards, we show that the mass-independent 53Cr and 54Cr compositions......We report novel analytical procedures allowing for the concurrent determination of the stable and mass-independent Cr isotopic composition of silicate materials by multiple collector inductively coupled mass spectrometry (MC-ICPMS). In particular, we focus on improved precision of the measurement...... by equilibrium processes during production of the synthetic standards. The stable isotope data concurrently obtained have a precision of 0.05‰ Da-1, which is comparable to earlier studies. Comparison of the measured isotopic composition of four meteorites with published data indicates that Cr isotope data...

  6. Intracellular chromium localization and cell physiological response in the unicellular alga Micrasterias

    Energy Technology Data Exchange (ETDEWEB)

    Volland, Stefanie, E-mail: Stefanie.Volland@stud.sbg.ac.at [Plant Physiology Division, Cell Biology Department, University of Salzburg, Hellbrunnerstr 34, 5020 Salzburg (Austria); Luetz, Cornelius, E-mail: cornelius.luetz@uibk.ac.at [Institute of Botany, University of Innsbruck, Sternwartestrasse 15, 6020 Innsbruck (Austria); Michalke, Bernhard, E-mail: bernhard.michalke@helmholtz-muenchen.de [Helmholtz Zentrum Muenchen, German Research Centre for Environmental Health, Institute of Ecological Chemistry, Ingolstaedter Landstrasse 1, 85764 Neuherberg (Germany); Luetz-Meindl, Ursula, E-mail: ursula.luetz-meindl@sbg.ac.at [Plant Physiology Division, Cell Biology Department, University of Salzburg, Hellbrunnerstr 34, 5020 Salzburg (Austria)

    2012-03-15

    Various contaminants like metals and heavy metals are constantly released into the environment by anthropogenic activities. The heavy metal chromium has a wide industrial use and exists in two stable oxidation states: trivalent and hexavalent. Chromium can cause harm to cell metabolism and development, when it is taken up by plants instead of necessary micronutrients such as for example iron. The uptake of Cr VI into plant cells has been reported to be an active process via carriers of essential anions, while the cation Cr III seems to be taken up inactively. Micrasterias denticulata, an unicellular green alga of the family Desmidiaceae is a well-studied cell biological model organism. Cr III and VI had inhibiting effects on its cell development, while cell division rates were only impaired by Cr VI. Transmission electron microscopy (TEM) revealed ultrastructural changes such as increased vacuolization, condensed cytoplasm and dark precipitations in the cell wall after 3 weeks of Cr VI treatment. Electron energy loss spectroscopy (EELS) and electron spectroscopic imaging (ESI) were applied to measure intracellular chromium distribution. Chromium was only detected after 3 weeks of 10 {mu}M Cr VI treatment in electron dense precipitations found in bag-like structures along the inner side of the cell walls together with iron and elevated levels of oxygen, pointing toward an accumulation respectively extrusion of chromium in form of an iron-oxygen compound. Atomic emission spectroscopy (EMS) revealed that Micrasterias cells are able to accumulate considerable amounts of chromium and iron. During chromium treatment the Cr:Fe ratio shifted in favor of chromium, which implied that chromium may be taken up instead of iron. Significant and rapid increase of ROS production within the first 5 min of treatment confirms an active Cr VI uptake. SOD and CAT activity after Cr VI treatment did not show a response, while the glutathione pool determined by immuno-TEM decreased

  7. Bioremediation of the Soils Contaminated with Cadmium and Chromium, by the Earthworm Eisenia fetida

    Directory of Open Access Journals (Sweden)

    Elham Aseman- Bashiz1

    2014-07-01

    Full Text Available One of the most important environmental problems in the world is the soils contamination by heavy metals in the industrial areas, and especially the contamination of the agricultural lands. The use of earthworms to bioremediate the soils results in reducing the pollutants concentration through a bioaccumulation mechanism on the contaminants in the earthworm's body. Hence, the present study aimed to prove the biological effectiveness of Eisenia fetida earthworms in bioremediation the soils contaminated with chromium and cadmium. Concentration of chromium and cadmium pollution in soil was determined to be 0.04 mg/g and 0.08 mg/g respectively. 30 worms were added to 500 g soil samples. Chromium and cadmium concentration in soil and in the body of worms was measured at two time periods of 21 and 42 days. To measure the concentration of chromium and cadmium we used ICP spectrometry. Software in usage was SPSS version 17. There was a significant correlation between the reduction of chromium and cadmium metals in the soils and the accumulation of chromium and cadmium metals in the worm’s body. A significant decline of chromium levels of the soil was observed in the days 21 and 42 during the study compared to initial amount of 0.1 mg/g. on the other hand chromium concentration of the soil decreased from 0.14 mg/g to 0.1 mg/g after 42 days. Comparison of mortality in two different time periods showed that by passing the time and by increase in soil chromium and cadmium concentrations the death toll of worms rises. The increased mortality of worms in the soil at a concentration of 0.08 mg/g of chromium, say that using the worms for bioremediation is not recommended at such concentration of chromium but using the worms for the removal of cadmium at concentrations of 0.04 mg/g and 0.08 mg/g in the soil is recommended.

  8. Physiological, biochemical and histometric responses of Nile tilapia (Oreochromis niloticus L.) by dietary organic chromium (chromium picolinate) supplementation.

    Science.gov (United States)

    Mehrim, Ahmed I

    2014-05-01

    Chromium has been recognized as a new and important micro-nutrient, essential for both human and animal nutrition. This study was conducted to evaluate the appropriateness and/or the use of safety level of dietary chromium picolinate (Cr-Pic), and its effects on the physiological responses, the histometric characteristics, and the chemical analysis of dorsal muscles of mono-sex Nile tilapia, Oreochromis niloticus. A total of 420 fingerlings (28.00 ± 0.96 g) were randomly distributed into 21 fiberglass tanks representing seven treatments at a rate of 20 fish m(-3). The control fish group (T1) was fed a Cr-Pic free basal diet. Other fish groups were fed the basal diet supplemented with 200 (T2), 400 (T3), 600 (T4), 800 (T5), 1000 (T6) and 1200 μg Cr-Pic kg(-1) diet (T7). Diets were offered to fish at a feeding rate of 3% of life body weight for 12 weeks. Results revealed that blood hematological parameters (hemoglobin, red blood cells, packed cell volume, mean corpuscular hemoglobin concentration, blood platelets, and white blood cells lymphocytes); serum biochemical measurements (total testosterone, high density lipoprotein, total protein, albumin, and globulin); and the dry matter and crude protein of the fish dorsal muscles all have significantly increased (P ⩽ 0.05) in the T3 treatment compared with the other treatments. Meanwhile, no significant differences were found among all treatments with regard to the histometric characteristics. It can be concluded that Cr-Pic at 400 μg kg(-1) diet (T3) seems to be the most appropriate level for O. niloticus fingerlings.

  9. Physiological, biochemical and histometric responses of Nile tilapia (Oreochromis niloticus L. by dietary organic chromium (chromium picolinate supplementation

    Directory of Open Access Journals (Sweden)

    Ahmed I. Mehrim

    2014-05-01

    Full Text Available Chromium has been recognized as a new and important micro-nutrient, essential for both human and animal nutrition. This study was conducted to evaluate the appropriateness and/or the use of safety level of dietary chromium picolinate (Cr-Pic, and its effects on the physiological responses, the histometric characteristics, and the chemical analysis of dorsal muscles of mono-sex Nile tilapia, Oreochromis niloticus. A total of 420 fingerlings (28.00 ± 0.96 g were randomly distributed into 21 fiberglass tanks representing seven treatments at a rate of 20 fish m−3. The control fish group (T1 was fed a Cr-Pic free basal diet. Other fish groups were fed the basal diet supplemented with 200 (T2, 400 (T3, 600 (T4, 800 (T5, 1000 (T6 and 1200 μg Cr-Pic kg−1 diet (T7. Diets were offered to fish at a feeding rate of 3% of life body weight for 12 weeks. Results revealed that blood hematological parameters (hemoglobin, red blood cells, packed cell volume, mean corpuscular hemoglobin concentration, blood platelets, and white blood cells lymphocytes; serum biochemical measurements (total testosterone, high density lipoprotein, total protein, albumin, and globulin; and the dry matter and crude protein of the fish dorsal muscles all have significantly increased (P ⩽ 0.05 in the T3 treatment compared with the other treatments. Meanwhile, no significant differences were found among all treatments with regard to the histometric characteristics. It can be concluded that Cr-Pic at 400 μg kg−1 diet (T3 seems to be the most appropriate level for O. niloticus fingerlings.

  10. Microcalorimetric Study on Effect of Chromium(Ⅲ) and Chromium(Ⅵ) Species on the Growth of Escherichia coli

    Institute of Scientific and Technical Information of China (English)

    YAO,Jun; WANG,Yan-Xin; TIAN,Lin; WANG,Fei; CHEN,Hui-Lun; XU,Chao-Qian; SU,Chun-Li; CAI,Ming-Fa; MASKOW,Thomas; ZARAY,Gyula

    2008-01-01

    The effects of Cr(Ⅲ) and Cr(Ⅵ) species ( Cr2O2-7, CrO2-4 and Cr3+) on the growth of Escherichia coli (E.coli) have been investigated in detail by microcalorimetry at 37 ℃. Parameters including the growth rate constant (k),inhibitory ratio (Ⅰ), half-inhibitory concentration (IC50), total heat output (Qtotal), time of the maximum heat production (tlog) in the log phase have been obtained. The results showed that Cr(Ⅵ) and Cr(Ⅲ) had the inhibition effect on the growth of E. coli in aquatic environment; however, the inhibitory ratio of Cr(Ⅲ) to E. coli was smaller than that of Cr(Ⅵ). The k values of E. coli in the presence of Cr(Ⅵ) and at high concentrations of Cr(Ⅲ) were decreased with increasing the concentrations of these chromium species. Among the three chromium species investigated,Cr2O2-7 was found to be the most poisonous species against E. coli with an IC50 value of 35.52 μg·mL-1. CrO42- exhibited moderate toxicity on E. coli with an IC50 of 50.24 μg·mL-1, and Cr3+ had the lowest toxicity with an IC50 of 84.30 μg·mL-1. Microcalorimetry can provide a convenient, sensitive and reliable method to study the effect of various metal species on the growth of bacteria or other microorganisms.

  11. Differential contributions of mammalian Rad54 paralogs to recombination, DNA damage repair, and meiosis.

    NARCIS (Netherlands)

    J. Wesoly (Joanna); S. Agarwal (Sheba); S. Sigurdsson (Stefan); W. Bussen (Wendy); S. Komen (Stephen); J. Qin (Jian); H. van Steeg (Harry); J. van Benthem (Jan); E. Wassenaar (Evelyne); W.M. Baarends (Willy); M. Ghazvini (Mehrnaz); A. Tafel (Agnieszka); H. Heath (Helen); N.J. Galjart (Niels); J. Essers (Jeroen); J.A. Grootegoed (Anton); N. Arnheim (Norman); O.Y. Bezzubova (Olga); J-M. Buerstedde; P. Sung (Patrick); R. Kanaar (Roland)

    2006-01-01

    textabstractHomologous recombination is a versatile DNA damage repair pathway requiring Rad51 and Rad54. Here we show that a mammalian Rad54 paralog, Rad54B, displays physical and functional interactions with Rad51 and DNA that are similar to those of Rad54. While ablation of Rad54 in mouse embryoni

  12. Mechanical Property of Low Chromium Semi-Steel Grinding Ball Prepared by Cross Rolling

    Institute of Scientific and Technical Information of China (English)

    CHANG Li-min; MENG De-liang; NIE Pu-lin; LIU Jian-hua

    2004-01-01

    The preparing method, rolling technology and mechanical properties of low chromium semi-steel grinding ball by cross rolling were studied. The results show that when the low chromium semi-steel bar is forged from 55 mm to 50 mm, cross-rolled into grinding ball at 1 000-1 050 ℃, air cooled and tempered at 550 ℃ for 2 h, the best mechanical properties, especially the abrasive resistance under the action of hard abrasive, can be obtained.

  13. Microstructure and Property of High Carbonic-Chromium Cast Steel with Different Hot Deformation Ratio

    Institute of Scientific and Technical Information of China (English)

    XU Tao; WANG Jiu-liang; ZHANG Run-jun; CHAO Guo-hua; LIU Jian-hua

    2004-01-01

    The microstructure and properties of high carbonic-chromium cast steel subjected to different hot deformation ratios were studied. The experimental results show that the microstructure and properties of high carbonic-chromium cast steel are obviously improved after hot deformation, and the best mechanical properties of the cast steel can be obtained under hot deformation ratio of 40 %-50 %, which leads to the morphology change of eutectic carbide and the precipitation of granular carbides.

  14. Biodegradation of nickel and chromium from space maintainers: An in vitro study

    OpenAIRE

    Bhaskar V; Subba Reddy V

    2010-01-01

    Band materials are often used in the practice of pediatric dentistry. Nickel and Chromium are the main ingredients of these materials. The potential health hazards of nickel and chromium and their compounds have been the focus of attention for more than 100 years. It has established that these metals could cause hypersensitivity. The study was undertaken to analyze in vitro biodegradation of space maintainers made out of stainless steel band materials from manufacturers Dentaurum and Unitek. ...

  15. Characterization of the chromium retention potential of non polluted aquifer solids in an industrial site

    OpenAIRE

    Reynal, Caroline; Kedziorek, Monika A.M.; Rollin, Claire; Bourg, Alain.C.M.

    2003-01-01

    National audience; A hydrogeochemical study of an industrial site where sulfuric acid and copper sulfate ("bouillie bordelaise") are manufactured showed that the phreatic aquifer is contaminated by copper, sulfate, chromium, arsenic and has an acid pH Field observations and laboratory experiments, both necessary if we are to understand the processes controlling tranfers at the solid-liquid interface, were used to investigate the behaviour of chromium. In the field, monitoring the mixing of po...

  16. Self-focusing in chromium-doped potassium niobate single ceramic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Castillo T, J.; Gonzalez M, S.; Aguirre L, A.; Hernandez, M.B.; Aguilar M, J.A. [Instituto de Fisica y Matematicas, Universidad Tecnologica de la Mixteca, 69000, Huajuapan de Leon, Oaxaca (Mexico); Hernandez A, J. [lFUNAM, PO Box 20-364, 01000 Mexico, DF (Mexico)]. e-mail: jaimec@mixteco.utm.mx

    2006-07-01

    The self-focusing and nonlinear optical absorption in a chromium-doped potassium niobate single ceramic crystal have been investigated. The third-order electric susceptibility X{sup (3)} at continuous 532 nm radiation is estimated based on a band transport model describing photo refractive properties for this electro-optic material. An anisotropic behavior on its nonlinear optical absorption properties has also been observed due to the presence of chromium ions. (Author)

  17. The influence of solidification speed during heating on allotropic transformations of chromium cast iron casting

    Directory of Open Access Journals (Sweden)

    M. Przybył

    2008-08-01

    Full Text Available The unique stand to founding dilatometric samples ("on ready” which solidify with different cooling speeds was presented. The dilatometric investigations, X-ray, metallographic they disclosed the occurrence in matrix of chromium cast iron of considerable quantity of austenite in dependence from concentration of chromium (18% and 23% and the speed of solidification. Castings these despite large part of austenite mark with high hardness in raw state.

  18. Effect of Chromium(VI Toxicity on Enzymes of Nitrogen Metabolism in Clusterbean (Cyamopsis tetragonoloba L.

    Directory of Open Access Journals (Sweden)

    Punesh Sangwan

    2014-01-01

    Full Text Available Heavy metals are the intrinsic component of the environment with both essential and nonessential types. Their excessive levels pose a threat to plant growth and yield. Also, some heavy metals are toxic to plants even at very low concentrations. The present investigation (a pot experiment was conducted to determine the affects of varying chromium(VI levels (0.0, 0.5, 1.0, 2.0, and 4.0 mg chromium(VI kg−1 soil in the form of potassium dichromate on the key enzymes of nitrogen metabolism in clusterbean. Chromium treatment adversely affect nitrogenase, nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate dehydrogenase in various plant organs at different growth stages as specific enzyme activity of these enzymes decreased with an increase in chromium(VI levels from 0 to 2.0 mg chromium(VI kg−1 soil and 4.0 mg chromium(VI kg−1 soil was found to be lethal to clusterbean plants. In general, the enzyme activity increased with advancement of growth to reach maximum at flowering stage and thereafter decreased at grain filling stage.

  19. The influence of substrate temperature on the tribo- mechanical properties of chromium nitride thin films

    Science.gov (United States)

    Merie, V. V.; Negrea, G.; Modi, E.

    2016-08-01

    Different nitrides such as titanium nitride, chromium nitride and so on are used in a widespread range of applications such as cutting tools, medical implants, and microelectromechanical devices and all that due to their mechanical, physical and chemical properties. The aim of this study is to obtain chromium nitride thin films and to characterize them by atomic force microscopy investigations. The chromium nitride thin films were deposited by reactive magnetron sputtering on silicon substrates. During the deposition process, the discharge current, the argon and nitrogen flows, the pressure inside the chamber and the deposition time were kept constant. A chromium target with a purity of 99.95 % was used. Some of the films were deposited after a chromium buffer layer was previously deposited on the silicon substrate. The deposition was carried out when substrate temperature was at room temperature, at 300 and 500°C respectively. Once the films were deposited, atomic force microscopy investigations were performed in order to emphasize the influence of the substrate temperature on the topographical, mechanical and tribological characteristics. The results pointed out an important influence of the substrate temperature on topographical, mechanical and tribological properties of the investigated chromium nitride thin films.

  20. Fabrication of Unique Magnetic Bionanocomposite for Highly Efficient Removal of Hexavalent Chromium from Water

    Science.gov (United States)

    Zhong, Yunlei; Qiu, Xun; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-08-01

    Biotreatment of hexavalent chromium has attracted widespread interest due to its cost effective and environmental friendliness. However, the difficult separation of biomass from aqueous solution and the slow hexavalent chromium bioreduction rate are bottlenecks for biotechnology application. In this approach, a core-shell structured functional polymer coated magnetic nanocomposite was prepared for enriching the hexavalent chromium. Then the nanocomposite was connected to the bacteria via amines on bacterial (Bacillus subtilis ATCC-6633) surface. Under optimal conditions, a series of experiments were launched to degrade hexavalent chromium from the aqueous solution using the as-prepared bionanocomposite. Results showed that B. subtilis@Fe3O4@mSiO2@MANHE (BFSM) can degrade hexavalent chromium from the water more effectively (a respectable degradation efficiency of about 94%) when compared with pristine B. subtilis and Fe3O4@mSiO2@MANHE (FSM). Moreover, the BFSM could be separated from the wastewater by magnetic separation technology conveniently due to the Fe3O4 core of FSM. These results indicate that the application of BFSM is a promising strategy for effective treating wastewater containing hexavalent chromium.

  1. Chromium (III Removal and Recovery from Tannery Wastewater by Precipitation Process

    Directory of Open Access Journals (Sweden)

    Abass Esmaeili

    2005-01-01

    Full Text Available Chromium (III salts are the most widely used chemicals for tanning processes, but 60-70% of total chromium salts reacts with the hides. In the other word, about 30-40% of the chromium amount remains in the solids and liquid wastes (especially spent tanning solutions. Therefore, the removal and recovery of the chromium content of these wastewaters are necessary for environmental protection and economic reasons. Removal and recovery of chromium were carried out by using precipitation process. For this purpose, three precipitating agents calcium hydroxide, sodium hydroxide and magnesium oxide were used. The effects of pH, stirring time, settling rate and sludge volume were studied in batch experiments. Results show that the optimum pH is 8-9 and the good sludge with high settling rate and lower volume obtain by the MgO precipitating agent. Hence the MgO is a good precipitating agent for removal and recovery of chromium from tanning wastewater.

  2. Chromium redistribution in thermally aged and irradiated ferritic-martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Camus, E.; Wanderka, N.; Welzel, S.; Wollenberger, H. [Hahn-Meitner-Institut Berlin GmbH (Germany); Materna-Morris, E. [Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe (Germany)

    1998-07-15

    Ferritic-martensitic steels containing 8-12 at.% chromium are considered as structural materials for spallation sources and fusion reactors. Materials will be subjected to intense damage rates, e.g. 50-100 dpa per year at full power. Therefore, the behavior under irradiation of these steels must be investigated. Our earlier dual-beam irradiation results on the DIN 1.4914 steel showed a decomposition into chromium-enriched and chromium-depleted regions. The mean concentration of the chromium-depleted regions was found to be 5.19{+-}0.32 at.% after irradiation at 500 C to a fluence of 50 dpa, as measured by atom probe field-ion microscopy. The chromium distribution in the matrix of the DIN 1.4914 steel after thermal ageing at temperatures between 400 and 600 C has been investigated for times up to 17000 h. The carbides were characterized by means of transmission electron microscopy and extraction replicas. The concentrations of the constituents of the matrix were measured by means of atom probe. The mean chromium concentrations in the matrix are found to be 8.66{+-}0.32, 4.5{+-}0.3, and 7.2{+-}0.4 at.%, after ageing at 400, 500, and 600 C, respectively. The matrix contains virtually no carbon. The results are discussed in terms of phase decomposition and species segregation. (orig.) 15 refs.

  3. Alpha -tocopherol supplementation on chromium toxicity : a study on rat liver and kidney cell membrane

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Membrane damage is one of the important consequence of chromium, an environmental toxicant, to produce cytotoxicity. α-tocopherol, a membrane protectant can be used to reduce the chromium-induced membrane damage. In the present study, the impact of chromium in presence and absence of α-tocopherol was studied on plasma membrane of liver and kidney in male Wistar rats (80 - 100g body weight). Significant increase in membrane cholesterol level as well as significant decrease in membrane phospholipid level in chromium exposed ( 0.8 mg /100g body weight/d, i.p., for 4 weeks) animals suggest structural alteration of both liver and kidney plasma memebrane. The alkaline phosphatase, total ATPase and Na+-K+-ATPase activities of plasma membrane were significantly decreased in both liver and kidney after chromium treatment. However, α-tocopherol (30 mg / 100g diet) supplementation can restrict the changes in these membrane-bound enzyme activities. Thus, the usefulness of dietary supplementation of α-tocopherol to restrain the chromium-induced membrane damage is suggested.

  4. Influence of dietary supplementation of chromium on the carcass traits of crossbred pigs

    Directory of Open Access Journals (Sweden)

    Guikinglung Pamei

    2014-09-01

    Full Text Available This study was conducted to assess the influence of chromium on the carcass traits in crossbred (Large White Yorkshire X Landrace pigs fed with swill feeding for a period of 5 months. Early-weaned crossbred piglets (n=24 were selected for this study, and the piglets were randomly divided into three equal groups; Group I, II, and III. The piglets were reared by following standard health coverage protocols. The feeds of Group I and II were supplemented with chromium in the form of chromium tripicolinate at 0.1 and 0.2 mg/kg of swill feed respectively, and Group III was kept as control. Carcass weight, carcass length, and bone percentage showed no significant difference among the three groups. However, better dressing percentage was observed in Group I (p<0.05. Liver and kidney weights were reduced in chromium supplemented groups (p<0.05. Chromium supplemented groups showed lower backfat thickness and fat percentage (p<0.01; whereas, loin eye areas and muscle percentage were increased as compared to the control group. Thus, it was concluded that chromium supplementation in feed of crossbred piglets influenced positively in their carcass traits.

  5. Ability of Bacillus mucilaginosus GY03 Strain to Adsorb Chromium Ions

    Institute of Scientific and Technical Information of China (English)

    CHEN Ye; LIAN Bin

    2005-01-01

    A research with Bacillus mucilaginosus cultured in nitrogen-free medium for forming a flocculant material to adsorb Cr+6 was conducted to determine the effects of different pH, volume, treatment time, and chromium (Ⅵ) concentrations on chromium (Ⅵ) adsorption by microbial flocculant (MBF), which was produced from the B. mucilaginosus GY03 strain. The results showed that MBF had outstanding flocculation on chromium (Ⅵ). Based on the results of a oneway experiment and actual wastewater treatment conditions, the optimum conditions, obtained by using orthogonal experiments, for chromium (Ⅵ) adsorption by MBF were: Cr6+ solution pH of 9, flocculant material volume of 15 mL,treatment time of 12 h and chromium ion concentration of 30 mg L-1. The results demonstrated that the MBF produced from GY03 could be used in the chromium-containing wastewater treatment. Meanwhile, after extraction and analysis of the MBF polysaccharides, it was found that MBF was mainly composed of glycoprotein. Analysis on constituents of monosaccharide showed that polysaccharides of B. mucilaginosus were composed of rhamnose, glucose etc. Thus, because it was applied over a wide range of pH, in small amounts and had a rapid flocculation speed the flocculant used in this experiment had a vast field of application potential.

  6. Immobilization in cement mortar of chromium removed from water using titania nanoparticles.

    Science.gov (United States)

    Husnain, Ahmed; Qazi, Ishtiaq Ahmed; Khaliq, Wasim; Arshad, Muhammad

    2016-05-01

    Because of the high toxicity of chromium, particularly as Cr (VI), it is removed from industrial effluents before their discharge into water bodies by a variety of techniques, including adsorption. Ultimate disposal of the sludge or the adsorbate, however, is a serious problem. While titania, in nanoparticle form, serves as a very good adsorbent for chromium, as an additive, it also helps to increase the compressive strength of mortar and concrete. Combining these two properties of the material, titania nanoparticles were used to adsorb chromium and then added to mortar up to a concentration of 20% by weight. The compressive strength of the resulting mortar specimens that replaced 15% of cement with chromium laden titania showed an improved strength than that without titania, thus confirming that this material had positive effect on the mortar strength. Leachate tests using the Toxicity Characteristics Leaching Procedure (TCLP) confirmed that the mortar sample chromium leachate was well within the permissible limits. The proposed technique thus offers a safe and viable method for the ultimate disposal of toxic metal wastes, in general, and those laden waste chromium, in particular.

  7. Photocatalysis with chromium-doped TiO2: bulk and surface doping.

    Science.gov (United States)

    Ould-Chikh, Samy; Proux, Olivier; Afanasiev, Pavel; Khrouz, Lhoussain; Hedhili, Mohamed N; Anjum, Dalaver H; Harb, Moussab; Geantet, Christophe; Basset, Jean-Marie; Puzenat, Eric

    2014-05-01

    The photocatalytic properties of TiO2 modified by chromium are usually found to depend strongly on the preparation method. To clarify this problem, two series of chromium-doped titania with a chromium content of up to 1.56 wt % have been prepared under hydrothermal conditions: the first series (Cr:TiO2) is intended to dope the bulk of TiO2, whereas the second series (Cr/TiO2) is intended to load the surface of TiO2 with Cr. The catalytic properties have been compared in the photocatalytic oxidation of formic acid. Characterization data provides evidence that in the Cr/TiO2 catalysts chromium is located on the surface of TiO2 as amorphous CrOOH clusters. In contrast, in the Cr:TiO2 series, chromium is mostly dissolved in the titania lattice, although a minor part is still present on the surface. Photocatalytic tests show that both series of chromium-doped titania demonstrate visible-light-driven photo-oxidation activity. Surface-doped Cr/TiO2 solids appear to be more efficient photocatalysts than the bulk-doped Cr:TiO2 counterparts.

  8. 27 CFR 6.54 - Advertising in retailer publications.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Advertising in retailer..., DEPARTMENT OF THE TREASURY LIQUORS âTIED-HOUSEâ Unlawful Inducements Paying for Advertising, Display Or Distribution Service § 6.54 Advertising in retailer publications. The purchase, by an industry member,...

  9. 28 CFR 79.54 - Proof of primary lung cancer.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Proof of primary lung cancer. 79.54... cancer. (a) In determining whether a claimant developed primary lung cancer following pertinent... conclusion that a claimant developed primary lung cancer must be supported by medical documentation. To...

  10. 7 CFR 250.54 - Recordkeeping and reviews.

    Science.gov (United States)

    2010-01-01

    ... AGRICULTURE GENERAL REGULATIONS AND POLICIES-FOOD DISTRIBUTION DONATION OF FOODS FOR USE IN THE UNITED STATES... Service Management Companies § 250.54 Recordkeeping and reviews. (a) Recordkeeping requirements for the... foods in its contract with the food service management company: (1) The donated foods and processed...

  11. 10 CFR 51.54 - Environmental report-manufacturing license.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 2 2010-01-01 2010-01-01 false Environmental report-manufacturing license. 51.54 Section... report—manufacturing license. (a) Each applicant for a manufacturing license under subpart F of part 52... Environmental Report—Manufacturing License.” The environmental report must address the costs and benefits...

  12. 47 CFR 54.717 - Audits of the Administrator.

    Science.gov (United States)

    2010-10-01

    ... report to the Office of Inspector General Audit Staff. (g) The Office of Inspector General shall review... General. The Administrator shall provide the independent auditor time to perform additional audit work... 47 Telecommunication 3 2010-10-01 2010-10-01 false Audits of the Administrator. 54.717 Section...

  13. 7 CFR 54.20 - Request for appeal service.

    Science.gov (United States)

    2010-01-01

    ... writing. Requests for appeal service received through an official grader or an office of grading shall be... MEAT PRODUCTS (GRADING, CERTIFICATION, AND STANDARDS) Regulations Appeal Service § 54.20 Request for... who performed the original service or the official in charge of the office of grading to which...

  14. 47 CFR 54.715 - Administrative expenses of the Administrator.

    Science.gov (United States)

    2010-10-01

    ... support mechanism, the low income support mechanism, the interstate access universal service support... SERVICES (CONTINUED) UNIVERSAL SERVICE Administration § 54.715 Administrative expenses of the Administrator... an amount not to exceed the rate of basic pay in effect for Level I of the Executive Schedule under...

  15. 47 CFR 54.403 - Lifeline support amount.

    Science.gov (United States)

    2010-10-01

    ... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) UNIVERSAL SERVICE Universal Service Support for Low-Income Consumers § 54.403 Lifeline support amount. (a) The...-discretionary charges associated with basic residential service) below $1 per month per qualifying...

  16. 47 CFR 54.619 - Audits and recordkeeping.

    Science.gov (United States)

    2010-10-01

    ... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) UNIVERSAL SERVICE Universal Service Support for Health Care Providers § 54.619 Audits and recordkeeping. (a) Health... Administrator or any other state or federal agency with jurisdiction. (c) Random audits. Health care...

  17. 40 CFR 258.54 - Detection monitoring program.

    Science.gov (United States)

    2010-07-01

    ... FOR MUNICIPAL SOLID WASTE LANDFILLS Ground-Water Monitoring and Corrective Action § 258.54 Detection monitoring program. (a) Detection monitoring is required at MSWLF units at all ground-water monitoring wells... from the MSWLF unit to the ground water. In determining alternative parameters, the Director...

  18. 47 CFR 54.711 - Contributor reporting requirements.

    Science.gov (United States)

    2010-10-01

    ... administrators of the North American Numbering Plan administration cost recovery (See 47 CFR 52.16 of this chapter), the local number portability cost recovery (See 47 CFR 52.32 of this chapter), and the TRS Fund... (CONTINUED) UNIVERSAL SERVICE Administration § 54.711 Contributor reporting requirements. (a)...

  19. 47 CFR 54.603 - Competitive bid requirements.

    Science.gov (United States)

    2010-10-01

    ... categories set forth in the definition of health care provider, listed in § 54.601(a); (ii) The requester is... requester cannot obtain toll-free access to an Internet service provider; (iv) The requested service or... be sold, resold or transferred in consideration of money or any other thing of value; and (vi) If...

  20. 28 CFR 54.415 - Access to course offerings.

    Science.gov (United States)

    2010-07-01

    ... SEX IN EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Discrimination on the Basis of Sex in Education Programs or Activities Prohibited § 54.415 Access to course offerings. (a) A...) Where use of a single standard of measuring skill or progress in a physical education class has...

  1. 47 CFR 54.509 - Adjustments to the discount matrix.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Adjustments to the discount matrix. 54.509... discount matrix. (a) Estimating future spending requests. When submitting their requests for specific... matrices, the Administrator shall consult with the Commission to establish the best way to distribute...

  2. 47 CFR 73.54 - Antenna resistance and reactance measurements.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna resistance and reactance measurements... SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.54 Antenna resistance and reactance measurements. (a) The resistance of an omnidirectional series fed antenna is measured at either the base of...

  3. 28 CFR 54.400 - Education programs or activities.

    Science.gov (United States)

    2010-07-01

    ... SEX IN EDUCATION PROGRAMS OR ACTIVITIES RECEIVING FEDERAL FINANCIAL ASSISTANCE Discrimination on the Basis of Sex in Education Programs or Activities Prohibited § 54.400 Education programs or activities... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Education programs or activities....

  4. Commissioning of the LEIR electron cooler with Pb$^{+54}$ ions

    CERN Document Server

    Tranquille, G; Carly, Ch; Prieto, V; Sautier, R; Bubley, A; Parkhomchuk, V; Reva, V; Brizgunov, M; Vedenev, M; Panasyuk, V

    2006-01-01

    The new LEIR cooler with a variable profile of the electron beam and electrostatic bending was commissioned in 2005-2006. In this paper we present our experience with the commissioning of the new device as well as the first results of the ion beam Pb +54 cooling with a high-intensity variable-density electron beam.

  5. Effect of some non functional surfactants and electrolytes on the hexavalent chromium reduction by glycerol. A mechanistic study

    Energy Technology Data Exchange (ETDEWEB)

    Basu, A.; Ghosh, S.K.; Saha, R.; Nandi, R.; Saha, B. [Burdwan Univ., WB (India). Dept. of Chemistry; Gosh, T. [A.B.N. Seal College, Coochbehar, WB (India). Dept. of Chemistry

    2011-11-15

    Hexavalent chromium is a widespread environmental contaminant and a known human carcinogen. Kinetics of reduction of hexavalent chromium by bio-molecule glycerol in micellar media have been studied spectrophotometrically. The cytoplasmic reduction of hexavalent chromium to trivalent chromium occurs in micro-heterogeneous systems. In vitro, the micelles are considered to mimic the cellular membranes. The electron transfer processes occurring in the micellar systems is considered as model to obtain insight into the electron transport process prevailing in biological systems. Micellar media is also a probe to establish the mechanistic paths of reduction of hexavalent chromium to trivalent chromium. Effects of electrolytes common to biological system are studied to establish the proposed reaction mechanism strongly. (orig.)

  6. Genesis and transport of hexavalent chromium in the system ophiolitic rocks - groundwater

    Science.gov (United States)

    Shchegolikhina, Anastasia; Guadagnini, Laura; Guadagnini, Alberto

    2015-04-01

    Our study aims at contributing to the quantification and characterization of chromium transport processes from host rocks and soil matrices to groundwater. We focus on dissolved hexavalent chromium detected in groundwaters of geological regions with ophiolitic rocks (ophiolites and serpentinites) inclusions due to its critical ecological impact. (Oze et al., 2004). Despite the large number of analyses on the occurrence of high concentrations of hazardous hexavalent chromium ions in natural waters, only few studies were performed with the objective of identifying and investigating the geochemical reactions which could occur in the natural system rock - groundwater - dissolved chromium (Fantoni et al., 2002, Stephen and James, 2004, Lelli et al., 2013). In this context, there is a need for integration of results obtained from diverse studies in various regions and settings to improve our knowledge repository. Our theoretical analyses are grounded and driven by practical scenarios detected in subsurface reservoirs exploited for civil and industrial use located in the Emilia-Romagna region (Italy). Available experimental datasets are complemented with data from other international regional-scale settings (Altay mountains region, Russia). Modeling of chromium transformation and migration particularly includes characterization of the multispecies geochemical system. A key aspect of our study is the analysis of the complex competitive sorption processes governing heavy metal evolution in groundwater. The results of the research allow assessing the critical qualitative features of the mechanisms of hexavalent chromium ion mobilization from host rocks and soils and the ensuing transformation and migration to groundwater under the influence of diverse environmental factors. The study is then complemented by the quantification of the main sources of uncertainty associated with prediction of heavy metal contamination levels in the groundwater system explored. Fantoni, D

  7. Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes.

    Science.gov (United States)

    Frei, Robert; Gaucher, Claudio; Poulton, Simon W; Canfield, Don E

    2009-09-10

    Geochemical data suggest that oxygenation of the Earth's atmosphere occurred in two broad steps. The first rise in atmospheric oxygen is thought to have occurred between approximately 2.45 and 2.2 Gyr ago, leading to a significant increase in atmospheric oxygen concentrations and concomitant oxygenation of the shallow surface ocean. The second increase in atmospheric oxygen appears to have taken place in distinct stages during the late Neoproterozoic era ( approximately 800-542 Myr ago), ultimately leading to oxygenation of the deep ocean approximately 580 Myr ago, but details of the evolution of atmospheric oxygenation remain uncertain. Here we use chromium (Cr) stable isotopes from banded iron formations (BIFs) to track the presence of Cr(VI) in Precambrian oceans, providing a time-resolved picture of the oxygenation history of the Earth's atmosphere-hydrosphere system. The geochemical behaviour of Cr is highly sensitive to the redox state of the surface environment because oxidative weathering processes produce the oxidized hexavalent [Cr(VI)] form. Oxidation of reduced trivalent [Cr(III)] chromium on land is accompanied by an isotopic fractionation, leading to enrichment of the mobile hexavalent form in the heavier isotope. Our fractionated Cr isotope data indicate the accumulation of Cr(VI) in ocean surface waters approximately 2.8 to 2.6 Gyr ago and a likely transient elevation in atmospheric and surface ocean oxygenation before the first great rise of oxygen 2.45-2.2 Gyr ago (the Great Oxidation Event). In approximately 1.88-Gyr-old BIFs we find that Cr isotopes are not fractionated, indicating a decline in atmospheric oxygen. Our findings suggest that the Great Oxidation Event did not lead to a unidirectional stepwise increase in atmospheric oxygen. In the late Neoproterozoic, we observe strong positive fractionations in Cr isotopes (delta(53)Cr up to +4.9 per thousand), providing independent support for increased surface oxygenation at that time, which may

  8. Trivalent chromium removal from aqueous solutions by a sol–gel synthesized silica adsorbent functionalized with sulphonic acid groups

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Gonzalez, Sergio Efrain [Departamento de Ingeniería Química, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico); Carbajal-Arizaga, Gregorio Guadalupe [Departamento de Química, CUCEI, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico); Manriquez-Gonzalez, Ricardo [Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Km 15.5, carretera Guadalajara-Nogales, Las Agujas, C.P. 45020 Zapopan, Jalisco (Mexico); De la Cruz-Hernandez, Wencel [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Km 107 carretera Tijuana-Ensenada, C.P. 22830 Ensenada, Baja California (Mexico); Gomez-Salazar, Sergio, E-mail: sergio.gomez@cucei.udg.mx [Departamento de Ingeniería Química, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico)

    2014-11-15

    Highlights: • Corpuscular sulphonic acid-functionalized silica holds improved uptake of chromium. • Mesopores on adsorbent facilitate (CH{sub 3}COO){sub 2}Cr{sup +} ion uptake on sulphonate sites. • Formation of chromium acetate sulphonate complex proposed from XPS results. • Fixed bed chromium uptake results suggest potential industrial use. - Abstract: A high capacity hybrid silica adsorbent was synthesized via sol–gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed to assess the removal of this metal from aqueous solutions. {sup 13}C, {sup 29}Si CPMAS NMR, FTIR, XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching ≤0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (≤0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level.

  9. Study on the Cultivation of Chromium-enriched Yeast%富铬酵母的研制

    Institute of Scientific and Technical Information of China (English)

    王盛良; 黄杰; 黄薇; 孙桂菊

    2001-01-01

    This paper offered a method to get organic chromium nutrient bycultivating chromium-enriched yeast. It was found that the solution of low consistency promoted the growth of yeast, and with increasing the chromium concentration in culture,the chromium content of chromium-enriched yeast would increase. The solution of chromium-enriched and normal brewer' s yeast was measured by ultraviolet spectrometry with in 200~320nm wavelength range. A characteristic ultraviolet absorption peak appeared at 260nm. The organic chromium was about 97.6% of the total chromium in chromium-enriched yeast.%研究了富铬酵母的培养方法,发现培养基中低浓度的铬(<100mg/kg)对酵母生长起促进作用,且随着铬浓度的增加酵母对铬的富集作用亦增加。用200~320nm波长范围对富铬酵母及普通酵母溶液进行紫外扫描,发现在260nm处有一特征的吸收峰。富铬酵母中有机铬占总铬量的97.6%.

  10. Quantification of total and hexavalent chromium in lager beers: variability between styles and estimation of daily intake of chromium from beer.

    Science.gov (United States)

    Vieira, Elsa; Soares, M Elisa; Kozior, Marta; Krejpcio, Zbigniew; Ferreira, Isabel M P L V O; Bastos, M Lourdes

    2014-09-17

    A survey of the presence of total and hexavalent chromium in lager beers was conducted to understand the variability between different styles of lager beer packaged in glass or cans and to estimate daily intake of total Cr and hexavalent chromium from beer. Graphite-furnace atomic absorption spectroscopy using validated methodologies was applied. Selective extraction of hexavalent chromium was performed using a Chromabond NH2/500 mg column and elution with nitric acid. The detection limits were 0.26 and 0.68 μg L(-1) for total Cr and Cr(VI), respectively. The mean content of total Cr ranged between 1.13 μg L(-1) in canned pale lager and 4.32 μg L(-1) in low-alcohol beers, whereas the mean content of Cr(VI) was beer, beer consumption can contribute approximately 2.28-8.64 and 1.6-6.17% of the recommended daily intake of chromium for women and men, respectively.

  11. Beneficial effect of chromium-rich yeast on glucose tolerance and blood lipids in elderly subjects.

    Science.gov (United States)

    Offenbacher, E G; Pi-Sunyer, F X

    1980-11-01

    Twenty-four volunteers, mean age 78, including eight mildly non-insulin-dependent diabetics, were randomly allocated to one of two groups and were fed (daily for 8 wk) 9 g of either chromium-rich brewers' yeast (experimental) or chromium-poor torula yeast (control). Before and after yeast supplementation, the serum glucose and insulin response to 100 g oral glucose was measured at 30 min intervals for 2 h. Fasting serum cholesterol, total lipids, and triglycerides were also determined. In the total experimental group (normals + diabetics) and in both the diabetic and nondiabetic experimental subgroups, glucose tolerance improved significantly and insulin output decreased after supplementation. Cholesterol and total lipids fell significantly after supplementation in the total experimental group. The cholesterol decrease was particularly marked in hypercholesterolemic subjects (cholesterol > 300 mg/dl). In the control group, no significant change in glucose tolerance, insulin, triglycerides, or total lipids was found. Cholesterol was significantly lowered in the nondiabetic but not in the diabetic group. Thus, chromium-rich brewers' yeast improved glucose tolerance and total lipids in elderly subjects, while chromium-poor torula yeast did not. An improvement in insulin sensitivity also occurred with brewers' yeast supplementation. This supports the thesis that elderly people may have a low level of chromium and that an effective source for chromium repletion, such as brewers' yeast, may improve their carbohydrate tolerance and total lipids. The improvement in serum cholesterol in some control subjects, as well as in the total experimental group, also suggests the presence of a hypocholesterolemic factor other than chromium in both brewers' and torula yeast.

  12. Influence of the chromium and ytterbium co-doping on the photoluminescence of zinc selenide crystals

    Institute of Scientific and Technical Information of China (English)

    I Radevici

    2014-01-01

    The luminescent properties of ZnSe, ZnSe:Cr (0.05 at.%Cr), ZnSe:Yb (0.03 at.%Yb) and ZnSe:Cr:Yb (0.05 at.%Cr, 0.05 at.%Yb) crystals, doped during the growth process by the chemical vapor transport method, were studied within the temperature in-terval of 6-300 K. At the 6 K temperature in the visible spectral range 2 bands were observed:a band in the excitonic spectral region and a band of self-activated luminescence. It was shown that co-doping of zinc selenide crystals with the chromium and ytterbium led to the combination of the impurities influence on the photoluminescent properties. At the liquid helium temperature in the middle in-frared range of the spectra of the ytterbium and chromium co-doped crystal a band with the maximum localized at 1.7 µm was ob-served, which was overlapped with a complex band in the middle-IR spectral range, characteristic for the chromium doped ZnSe crys-tals. On the basis of obtained data an interaction mechanism of the chromium and ytterbium co-doping impurities was proposed. Guided by the existent model of the ytterbium ion incorporation in the selenide sublattice of the ZnSe crystals, an assumption about stabilization of single charged chromium ions in the zinc sublattice crystal nodes, by means of formation of the local charge compen-sating clusters, was made. It was assumed that the resonant energy transfer from one chromium ion to another, which led to the con-centration quenching of the IR emission in the ZnSe:Cr PL spectra, would lead to the broadening of the IR emission in the spectra of ytterbium and chromium co-doped zinc selenide crystals.

  13. Photocatalysis with chromium-doped TiO2: Bulk and surface doping

    KAUST Repository

    Ould-Chikh, Samy

    2014-04-15

    The photocatalytic properties of TiO2 modified by chromium are usually found to depend strongly on the preparation method. To clarify this problem, two series of chromium-doped titania with a chromium content of up to 1.56 wt % have been prepared under hydrothermal conditions: the first series (Cr:TiO2) is intended to dope the bulk of TiO2, whereas the second series (Cr/TiO2) is intended to load the surface of TiO2 with Cr. The catalytic properties have been compared in the photocatalytic oxidation of formic acid. Characterization data provides evidence that in the Cr/TiO2 catalysts chromium is located on the surface of TiO2 as amorphous CrOOH clusters. In contrast, in the Cr:TiO 2 series, chromium is mostly dissolved in the titania lattice, although a minor part is still present on the surface. Photocatalytic tests show that both series of chromium-doped titania demonstrate visible-light-driven photo-oxidation activity. Surface-doped Cr/TiO2 solids appear to be more efficient photocatalysts than the bulk-doped Cr:TiO2 counterparts. It\\'s classified! The photocatalytic properties of TiO2 modified by chromium depend strongly on the preparation method. To clarify this problem, two types of modified titania are discussed: one with CrIII doped in the bulk and one with CrOOH clusters on the TiO2 surface (see picture). Both series show visible-light-driven photo-oxidation activity. However, surface modification appears to be a more efficient strategy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Selective and sensitive detection of chromium(VI) in waters using electrospray ionization mass spectrometry.

    Science.gov (United States)

    Weldy, Effie; Wolff, Chloe; Miao, Zhixin; Chen, Hao

    2013-09-01

    From 2000 through 2011, there were 14 criminal cases of violations of the Clean Water Act involving the discharge of chromium, a toxic heavy metal, into drinking and surface water sources. As chromium(VI), a potential carcinogen present in the environment, represents a significant safety concern, it is currently the subject of an EPA health risk assessment. Therefore, sensitive and selective detection of this species is highly desired. This study reports the analysis of chromium(VI) in water samples by electrospray ionization mass spectrometry (ESI-MS) following its reduction and complexation with ammonium pyrrolidinedithiocarbamate (APDC). The reduction and subsequent complexation produce a characteristic [Cr(III)O]-PDC complex which can be detected as a protonated ion of m/z 507 in the positive ion mode. The detection is selective to chromium(VI) under acidic pH, even in the presence of chromium(III) and other metal ions, providing high specificity. Different water samples were examined, including deionized, tap, and river waters, and sensitive detection was achieved. In the case of deionized water, quantification over the concentration range of 3.7 to 148ppb gave an excellent correlation coefficient of 0.9904 using the enhanced MS mode scan. Using the single-reaction monitoring (SRM) mode (monitoring the characteristic fragmentation of m/z 507 to m/z 360), the limit of detection (LOD) was found to be 0.25ppb. The LOD of chromium(VI) for both tap and river water samples was determined to be 2.0ppb. A preconcentration strategy using simple vacuum evaporation of the aqueous sample was shown to further improve the ESI signal by 15 fold. This method, with high sensitivity and selectivity, should provide a timely solution for the real-world analysis of toxic chromium(VI).

  15. Pressure-driven formation and stabilization of superconductive chromium hydrides

    Science.gov (United States)

    Yu, Shuyin; Jia, Xiaojing; Frapper, Gilles; Li, Duan; Oganov, Artem R.; Zeng, Qingfeng; Zhang, Litong

    2015-01-01

    Chromium hydride is a prototype stoichiometric transition metal hydride. The phase diagram of Cr-H system at high pressures remains largely unexplored due to the challenges in dealing with the high activation barriers and complications in handing hydrogen under pressure. We have performed an extensive structural study on Cr-H system at pressure range 0 ∼ 300 GPa using an unbiased structure prediction method based on evolutionary algorithm. Upon compression, a number of hydrides are predicted to become stable in the excess hydrogen environment and these have compositions of Cr2Hn (n = 2–4, 6, 8, 16). Cr2H3, CrH2 and Cr2H5 structures are versions of the perfect anti-NiAs-type CrH with ordered tetrahedral interstitial sites filled by H atoms. CrH3 and CrH4 exhibit host-guest structural characteristics. In CrH8, H2 units are also identified. Our study unravels that CrH is a superconductor at atmospheric pressure with an estimated transition temperature (T c) of 10.6 K, and superconductivity in CrH3 is enhanced by the metallic hydrogen sublattice with T c of 37.1 K at 81 GPa, very similar to the extensively studied MgB2. PMID:26626579

  16. Chromium Extraction from Sewage Sludge Using Polyepoxysuccinic Acid

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li-Hua; ZHU Zhi-Liang

    2012-01-01

    An environmentally benign biodegradable chelant,polyepoxysuccinic acid (PESA),was used to separate heavy metals from sewage sludge from the Shanghai Taopu Wastewater Treatment Plant,China,based on chemical extraction technology.The extraction of chromium (Cr) from sewage sludge with an aqueous solution of PESA was studied under various conditions.It was found that the extraction of Cr using PESA was more efficient than that using ethylenediaminetetraacetic acid (EDTA) and S,S-ethylenediaminedisuccinic acid (EDDS) under similar conditions.PESA was capable of extracting Cr from the sewage sludge,and the extraction efficiency was obviously dependent on both the pH and the concentration of the chelating reagent.The extraction efficiency decreased gradually with increasing pH,and the dependence on pH decreased as the concentration of PESA increased.The extraction efficiency reached 58% under conditions of pH =4 and a ratio of PESA to total heavy metals of 10∶1.The extraction efficiency was maintained above 40% within the pH range from 1 to 7 at the high ratio of PESA to total heavy metals of 10∶1.Comparing the contents of heavy metals in the sewage sludge before and after the extraction,it was found that the extracted Cr came mainly from the reducible and oxidizable fractions.

  17. Inhibition by chromium and cadmium of anaerobic acidogenesis.

    Science.gov (United States)

    Yu, H Q; Fang, H H

    2001-01-01

    The effects of chromium (III) and cadmium on the anaerobic acidogenesis of a simulated dairy waste were examined using serum vials. At Cd dosages less than 20 mg/l, the acidogenesis process was enhanced by the dosage, resulting in a higher degree of acidification, protein conversion, and hydrogen production than the control. At dosages over 20-mg/l, Cd inhibited the acidogenesis. The Cr (III) dosage of 5 mg/l reduced overall volatile fatty acid and alcohol generation, degree of acidification, conversions of lactose, lipid and protein, and total biogas production, with the exception of accumulation of hydrogen and propionate. At dosages exceeding 5 mg/l, Cr (III) had a severe inhibition on the acidogenesis. The Cd concentrations which caused a 50% reduction in total volatile fatty acid and alcohol production, degree of acidification and cumulative gas production were higher than the corresponding values caused by Cr (III), suggesting that Cr (III) was more toxic to acidogenic bacteria than Cd.

  18. Enhanced chromium adsorption capacity via plasma modification of natural zeolites

    Science.gov (United States)

    Cagomoc, Charisse Marie D.; Vasquez, Magdaleno R., Jr.

    2017-01-01

    Natural zeolites such as mordenite are excellent adsorbents for heavy metals. To enhance the adsorption capacity of zeolite, sodium-exchanged samples were irradiated with 13.56 MHz capacitively coupled radio frequency (RF) argon gas discharge. Hexavalent chromium [Cr(VI)] was used as the test heavy metal. Pristine and plasma-treated zeolite samples were soaked in 50 mg/L Cr solution and the amount of adsorbed Cr(VI) on the zeolites was calculated at predetermined time intervals. Compared with untreated zeolite samples, initial Cr(VI) uptake was 70% higher for plasma-treated zeolite granules (50 W 30 min) after 1 h of soaking. After 24 h, all plasma-treated zeolites showed increased Cr(VI) uptake. For a 2- to 4-month period, Cr(VI) uptake increased about 130% compared with untreated zeolite granules. X-ray diffraction analyses between untreated and treated zeolite samples revealed no major difference in terms of its crystal structure. However, for plasma-treated samples, an increase in the number of surface defects was observed from scanning electron microscopy images. This increase in the number of surface defects induced by plasma exposure played a crucial role in increasing the number of active sorption sites on the zeolite surface.

  19. Adsorption of chromium ion (VI by acid activated carbon

    Directory of Open Access Journals (Sweden)

    A. A. Attia

    2010-03-01

    Full Text Available The activated carbon produced from olive stones was chemically activated using sulfuric acid, (OS-S, and utilized as an adsorbent for the removal of Cr(VI from aqueous solution in the concentration range 4-50 mg/L. Adsorption experiments were carried out in a batch process and various experimental parameters such as effect of contact time, initial chromium ion concentration, carbon dosage, and pH on percentage removal have been studied. Adsorption results obtained for activated carbon (OS-S were compared with the acid-treated commercial activated carbon (CAC-S. The optimum efficiency shows that the Cr(VI uptake being attained at pH 1.5. The equilibrium adsorption data was better fitted to the Langmuir adsorption model. The results of kinetic models showed that the pseudo-first-order kinetic model was found to correlate the experimental data well. It was concluded that activated carbon produced from olive stones (OS-S has an efficient adsorption capacity compared to (CAC-S sample.

  20. Microstructure Evolution and Grain Growth Kinetics in Annealed Nanocrystalline Chromium

    Energy Technology Data Exchange (ETDEWEB)

    Chojnowski, Grzegorz [Warsaw University; Przenioslo, Radoslaw [Warsaw University; Sosnowska, Izabela [Warsaw University; Bukowski, Mirko [University of Saarbrucken, Saarbrucken, Germany; Natter, Harald [University of Saarbrucken, Saarbrucken, Germany; Hempelmann, Rolf [University of Saarbrucken, Saarbrucken, Germany; Fitch, Andrew [European Synchrotron Radiation Facility (ESRF); Urban, Volker S [ORNL

    2007-01-01

    The kinetics of thermal evolution of the microstructure of nanocrystalline chromium (nano-Cr) has been studied by time-resolved synchrotron radiation techniques: high-resolution powder diffraction and small-angle X-ray scattering (SAXS). The as-prepared electrodeposited nano-Cr with average grain size of 27 nm shows the same bcc structure as {alpha}-Cr. The nano-Cr cubic lattice parameter thermal expansion is the same as that of reference polycrystalline {alpha}-Cr. Annealing of nano-Cr at temperatures above 400 C leads to a grain growth process with the final grain size not exceeding 125 nm even at a temperature of 700 C. The single power-law behavior is observed by SAXS in as-prepared nano-Cr changes during annealing above 400 C. In nano-Cr samples annealed at temperatures between 400 and 700 C, the low-q part of the SAXS signal shows a Porod-type behavior while the high-q part shows a power-law Q-{alpha} with the exponent {alpha} < 4. This effect is probably due to changes of the grain surface roughness during grain growth.

  1. Elementary surface processes during reactive magnetron sputtering of chromium

    Energy Technology Data Exchange (ETDEWEB)

    Monje, Sascha; Corbella, Carles, E-mail: carles.corbella@rub.de; Keudell, Achim von [Research Group Reactive Plasmas, Ruhr-University Bochum, Universitystr. 150, 44801 Bochum (Germany)

    2015-10-07

    The elementary surface processes occurring on chromium targets exposed to reactive plasmas have been mimicked in beam experiments by using quantified fluxes of Ar ions (400–800 eV) and oxygen atoms and molecules. For this, quartz crystal microbalances were previously coated with Cr thin films by means of high-power pulsed magnetron sputtering. The measured growth and etching rates were fitted by flux balance equations, which provided sputter yields of around 0.05 for the compound phase and a sticking coefficient of O{sub 2} of 0.38 on the bare Cr surface. Further fitted parameters were the oxygen implantation efficiency and the density of oxidation sites at the surface. The increase in site density with a factor 4 at early phases of reactive sputtering is identified as a relevant mechanism of Cr oxidation. This ion-enhanced oxygen uptake can be attributed to Cr surface roughening and knock-on implantation of oxygen atoms deeper into the target. This work, besides providing fundamental data to control oxidation state of Cr targets, shows that the extended Berg's model constitutes a robust set of rate equations suitable to describe reactive magnetron sputtering of metals.

  2. Spectroscopic analysis of the interaction between chromium (III) and apoovotransferrin

    Energy Technology Data Exchange (ETDEWEB)

    Li Yingqi [Department of Chemistry, College of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006 (China); Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Molecular Science, Shanxi University, Taiyuan 030006 (China); Liu Bin [Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Molecular Science, Shanxi University, Taiyuan 030006 (China); Yang Binsheng, E-mail: yangbs@sxu.edu.c [Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Molecular Science, Shanxi University, Taiyuan 030006 (China)

    2010-12-15

    Ovotransferrin (OTf) is a main member of the transferrin family that functions both as an iron transporter and an antibacterial agent. In this study, the thermodynamic property of the interaction between chromium (III) and ovotransferrin was investigated. The conditional binding constants for Cr{sup 3+} binding to the protein were determined by difference UV spectroscopy and were found to be log K{sub C}=13.08{+-}0.24 and log K{sub N}=5.65{+-}0.12. It was found that Cr{sup 3+} preferentially binds to the C-terminal site over the N-terminal site under these experimental conditions. The conformational changes in apoovotransferrin (apoOTf) during Cr{sup 3+} binding were studied by fluorescence spectroscopy using 2-p-toluidinylnaphthalene-6-sulfonate (TNS) as the fluorescence probe and by circular dichroism (CD) spectroscopy. The results show that a large conformational change in apoOTf can be attributed to binding of Cr{sup 3+} to the N-terminal site, instead of the C-terminal site. In addition, the binding of Cr{sup 3+} to apoOTf stabilizes the structure of OTf as determined by guanidine hydrochloride denaturation studies. These findings help advance our understanding of the biological effects of Cr{sup 3+}.

  3. Chromium Diffusion Doping on ZnSe Crystals

    Science.gov (United States)

    Journigan, Troy D.; Chen, K.-T.; Chen, H.; Burger, A.; Schaffers, K.; Page, R. H.; Payne, S. A.

    1997-01-01

    Chromium doped zinc selenide crystal have recently been demonstrated to be a promising material for near-IR room temperature tunable lasers which have an emission range of 2-3 micrometers. In this study a new diffusion doping process has been developed for incorporation of Cr(+2) ion into ZnSe wafers. This process has been successfully performed under isothermal conditions, at temperatures above 800 C. Concentrations in excess of 10(exp 19) Cr(+2) ions/cu cm, an order of magnitude larger than previously reported in melt grown ZnSe material, have been obtained by diffusion doping, as estimated from optical absorption measurements. The diffusivity was estimated to be about 10(exp -8) sq cm/sec using a thin film diffusion model. Resistivity was derived from current-voltage measurements and in the range of 10(exp 13) and 10(exp 16) omega-cm. The emission spectra and temperature dependent lifetime data will also be presented and discussed.

  4. Solution growth of silicon carbide using unary chromium solvent

    Science.gov (United States)

    Miyasaka, Ryo; Kawanishi, Sakiko; Narumi, Taka; Sasaki, Hideaki; Yoshikawa, Takeshi; Maeda, Masafumi

    2017-02-01

    Solution growth of silicon carbide (SiC) using unary chromium (Cr) solvent was studied because the system enables a high solubility difference and a low degree of supersaturation, which would lead to rapid growth with a stabilized growth interface. The liquidus composition at SiC saturation in a quasi-binary Cr-SiC system was studied at 1823-2173 K. The measured carbon (C) contents are in good agreement with the thermodynamic evaluation using the sub-regular solution model. In addition, growth experiments using a unary Cr solvent were performed by the bottom-seeded travelling solvent method. The obtained growth rates at 1803-1923 K with a temperature difference of 15-70 K were proportional to the solubility difference between the seed and source temperatures, indicating that the growth was controlled by the mass transfer of C in the solution. The maximum growth rate of 720 μm/h at 1803 K was much higher than the growth rate by Si-rich solvents, suggesting that the Cr-rich solvent is suitable for the rapid growth at a low temperature.

  5. Extractive removal of chromium (VI) from industrial waste solution.

    Science.gov (United States)

    Agrawal, Archana; Pal, Chandana; Sahu, K K

    2008-11-30

    Extractive removal of Cr (VI) was carried out from chloride solutions using cyanex 923 mixed with kerosene. The efficiency of this extractant was studied under various experimental conditions, such as concentration of different mineral acids in the aqueous phase, concentration of cyanex 923 and Cr (VI) present in the initial aqueous feed, temperature and time of extraction, organic to aqueous (O/A) phase ratio. Percentage Cr (VI) extraction decreases with the increase in temperature at varying concentration of cyanex 923. The interference of the impurities usually associated with Cr (VI) such as Cr (III), Cu, Ni, Fe (II), Zn, Chloride and sulphate, etc., were examined under the optimized conditions and only Zn was found to interfere. Under the optimum experimental conditions 98.6-99.9% of Cr (VI) was extracted in 3-5 min at O/A of 2 with the initial feed concentration of 1g/L of Cr (VI). The extracted Cr (VI) was quantitatively stripped with 1M NaOH and the organic phase obtained after the stripping of Cr (VI) was washed with dilute HCl solution to neutralize any NaOH trapped/adhered to the solvent and then with distilled water. This regenerated solvent was reused in succeeding extraction of chromium (VI). Finally a few experiments were performed with the synthetic effluent from an electroplating industry.

  6. Kinetics of hexavalent chromium reduction by iron metal

    Institute of Scientific and Technical Information of China (English)

    Huijing QIAN; Yanjun WU; Yong LIU; Xinhua XU

    2008-01-01

    The kinetics of Cr(Ⅵ) reduction to Cr(Ⅲ) by metallic iron (Fe0) was studied in batch reactors for a range of reactant concentrations, pH and temperatures. Nearly 86.8% removal efficiency for Cr(Ⅵ) was achieved when Fe0 concentration was 6 g/L (using commercial iron powder (200 mesh) I n 120 min). The reduction ofhexavalent chro-mium took place on the surface of the iron particles following pseudo-first order kinetics. The rate of Cr(Ⅵ) reduction increased with increasing Fe0 addition and temperature but inversely with initial pH. The pseudo-first-order rate coeffi-cients (kobs) were determined as 0.0024, 0.010, 0.0268 and 0.062 8 min-1 when iron powder dosages were 2, 6, 10 and 14 g/L at 25℃ and pH 5.5, respectively. According to the Arrehenius equation, the apparent activation energy of 26.5 kJ/mol and pre-exponential factor of 3 330 min-1 were obtained at the temperature range of 288-308 K. Different Fe0 types were compared in this study. The reactivity was in the order starch-stabilized Fe0 nanoparticlesFe0 nano-particlesFe0 powderFe0 filings. Electrochemical analysis of the reaction process showed that Cr(Ⅲ) and Fe(Ⅲ) hydroxides should be the dominant final products.

  7. Alleviation of chromium toxicity by hydrogen sulfide in barley.

    Science.gov (United States)

    Ali, Shafaqat; Farooq, Muhammad Ahsan; Hussain, Sabir; Yasmeen, Tahira; Abbasi, G H; Zhang, Guoping

    2013-10-01

    A hydroponic experiment was carried out to examine the effect of hydrogen sulfide (H2 S) in alleviating chromium (Cr) stress in barley. A 2-factorial design with 6 replications was selected, including 3 levels of NaHS (0 μM, 100 μM, and 200 μM) and 2 levels of Cr (0 μM and 100 μM) as treatments. The results showed that NaHS addition enhances plant growth and photosynthesis slightly compared with the control. Moreover, NaHS alleviated the inhibition in plant growth and photosynthesis by Cr stress. Higher levels of NaHS exhibited more pronounced effects in reducing Cr concentrations in roots, shoots, and leaves. Ultrastructural examination of plant cells supported the facts by indication of visible alleviation of cell disorders in both root and leaf with exogenous application of NaHS. An increased number of plastoglobuli, disintegration, and disappearance of thylakoid membranes and starch granules were visualized inside the chloroplast of Cr-stressed plants. Starch accumulation in the chloroplasts was also noticed in the Cr-treated cells, with the effect being much less in Cr + NaHS-treated plants. Hence, it is concluded that H2 S produced from NaHS can improve plant tolerance under Cr stress.

  8. Probing neutrino nature at Borexino detector with chromium neutrino source

    CERN Document Server

    Sobków, W

    2016-01-01

    In this paper, we indicate a possibility of utilizing the intense chromium source ($\\sim 370 PBq$) in probing the neutrino nature in low energy neutrino experiments with the ultra-low threshold and background real-time Borexino detector located near the source ($\\sim 8 m$). We analyze the elastic scattering of electron neutrinos (Dirac or Majorana, respectively) on the unpolarized electrons in the relativistic neutrino limit. We assume that the incoming neutrino beam is the superposition of left-right chiral states. Left chiral neutrinos may be detected by the standard $V A$ and non-standard scalar $S_L$, tensor $T_L$ interactions, while right chiral ones partake only in the exotic $V + A$ and $S_R, T_R$ interactions. Our model-independent study is carried out for the flavour (current) neutrino eigenstates. We compute the expected event number for the standard $V-A$ interaction of the left chiral neutrinos using the current experimental values of standard couplings and in the case of left-right chiral superpo...

  9. Distribution of chromium contamination and microbial activity in soil aggregates.

    Science.gov (United States)

    Tokunaga, Tetsu K; Wan, Jiamin; Hazen, Terry C; Schwartz, Egbert; Firestone, Mary K; Sutton, Stephen R; Newville, Matthew; Olson, Keith R; Lanzirotti, Antonio; Rao, William

    2003-01-01

    Biogeochemical transformations of redox-sensitive chemicals in soils can be strongly transport-controlled and localized. This was tested through experiments on chromium diffusion and reduction in soil aggregates that were exposed to chromate solutions. Reduction of soluble Cr(VI) to insoluble Cr(II) occurred only within the surface layer of aggregates with higher available organic carbon and higher microbial respiration. Sharply terminated Cr diffusion fronts develop when the reduction rate increases rapidly with depth. The final state of such aggregates consists of a Cr-contaminated exterior, and an uncontaminated core, each having different microbial community compositions and activity. Microbial activity was significantly higher in the more reducing soils, while total microbial biomass was similar in all of the soils. The small fraction of Cr(VI) remaining unreduced resides along external surfaces of aggregates, leaving it potentially available to future transport down the soil profile. Using the Thiele modulus, Cr(VI) reduction in soil aggregates is shown to be diffusion rate- and reaction rate-limited in anaerobic and aerobic aggregates, respectively. Thus, spatially resolved chemical and microbiological measurements are necessary within anaerobic soil aggregates to characterize and predict the fate of Cr contamination. Typical methods of soil sampling and analyses that average over redox gradients within aggregates can erase important biogeochemical spatial relations necessary for understanding these environments.

  10. 54位高速冗余二进制乘法器的设计%High-Speed 54 × 54-b Redundant Binary Multiplier Design

    Institute of Scientific and Technical Information of China (English)

    崔晓平; 高鹏辉; 尹洁珺; 丁晶; 李启

    2014-01-01

    Redundant binary representation is one of the signed-digit number systems . High modularity and the carry-free feature of RB arithmetic can be used to design high-speed parallel multipliers . In this paper , the algorithm and structure of RB multiplier is systematically studied . The 54-bit RB multiplier is designed by the modified Booth algorithm ,RB partial product accumulator and RB-NB converter .The hybrid parallel-prefix/carry-select adder is used to design optimized RB-NB converter .The multiplier has been realized by Verilog HDL and simulated in the ModelSim platform .Under SMIC 0 .18 mm standard process library ,the synthesis results of this design by Design Compiler show that the delay can be reduced to 3 .97 ns and the area is 409 293 mm2 .%冗余二进制(RB )数是一种有符号数的表示方法,利用冗余二进制算法的进位无关特性和规整的结构,可以设计高速RB并行乘法器.系统地研究了RB乘法器的算法和结构,给出了基于修正Booth算法,RB部分积压缩树和RB-NB转换器的54b乘法器的设计过程,并利用并行前缀/进位选择混合加法器对RB-NB转换器进行优化设计.采用Verilog HDL对乘法器进行描述,并在ModelSim平台上进行仿真验证,在SMIC 0.18 mm标准工艺库下,通过Syn-opsys公司综合工具Design Compiler进行综合,得到54b RB乘法器的延时可达到3.97 ns ,面积是409293 mm2.

  11. Looks: Studio 54 and the Production of Fabulous Nightlife

    Directory of Open Access Journals (Sweden)

    madison alexander moore

    2013-05-01

    Full Text Available 0 0 1 92 528 yale university 4 1 619 14.0 Normal 0 false false false EN-US JA X-NONE This article combines my experience as a party-host and nightlife-creator with a close reading of Studio 54 as a theatrical production. I call for a consideration of how the staging of nightlife functions as an art form, relying on the dual practices of creation and curation. I provide a close reading of the tightly-staged Studio 54 experience, focusing on the club's infamously tight door policy and production of fabulousness to reveal what scholars and ethnographers of nightlife can learn from approaching nightlife as an artistic production. This approach can also inform a nightlife-focused research agenda.  

  12. Internal bremsstrahlung endpoint energy of {sup 54}Mn

    Energy Technology Data Exchange (ETDEWEB)

    Hindi, M. M. [Physics Department, Tennessee Technological University, Cookeville, Tennessee 38505 (United States); Larimer, R.-M. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Norman, E. B. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Rech, G. A. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2000-05-01

    For {sup 54}Mn there is a discrepancy between the Q{sub EC} obtained from the endpoint energy of the internal bremsstrahlung (IB) spectrum which accompanies the electron capture decay (Q{sub EC}=1353{+-}8 keV) and that obtained from the accepted mass differences (Q{sub EC}=1377{+-}1 keV). This Q value is needed to deduce the partial-half life of the astrophysically interesting {beta}{sup -} decay of {sup 54}Mn from the recently measured {beta}{sup +} partial half-life. To resolve this discrepancy, we have remeasured the endpoint energy of the IB spectrum, by recording coincidences between the IB and the 835-keV {gamma} ray, both detected in Compton-suppressed Ge detectors. The Q{sub EC} we deduce is 1379{+-}8 keV, in agreement with the accepted mass differences. (c) 2000 The American Physical Society.

  13. A Teacher Supports Her 54 Students to Realize Their Dreams

    Institute of Scientific and Technical Information of China (English)

    1997-01-01

    "I’VE become a teacher in my dream," Gao Jinying wrote in her composition entitled, "My Dream" when she was a fourth grade student in an elementary school. Now, having been a teacher for 25 years, when she reads her students’ stories about their dreams, she still feels excited. Fifty-Four Dreams There are 54 first year students in Class One at Guangqumen High School.

  14. Effect of recasting on the elastic modulus of metal-ceramic systems from nickel-chromium and cobalt-chromium alloys

    Directory of Open Access Journals (Sweden)

    Mirković Nemanja

    2007-01-01

    Full Text Available Background/Aim. Elastic modulus of metal-ceramic systems determines their flexural strength and prevents damages on ceramics during mastication. Recycling of basic alloys is often a clinical practice, despite the possible effects on the quality of the future metal-ceramic dentures. This research was done to establish recasting effects of nickel-chromium and cobalt-chromium alloys on the elastic modulus of metalceramic systems in making fixed partial dentures. Methods. The research was performed as an experimental study. Six metal-ceramic samples of nickel-chromium alloy (Wiron 99 and cobalt-chromium alloy (Wirobond C were made. Alloy residues were recycled through twelve casting generations with the addition of 50% of new alloy on the occasion of every recasting. Three- point bending test was used to determine elastic modulus, recommended by the standard ISO 9693:1999. Fracture load for damaging ceramic layer was recorded on the universal testing machine (Zwick, type 1464, with the speed of 0,05 mm/min. Results. The results of this research revealed significant differences between elasticity modules of metal-ceramic samples in every examined recycle generation. Recasting had negative effect on the elastic modulus of the examined alloys. This research showed the slight linear reduction of elastic modulus up to the 6th generation of recycling. After the 6th recycling there was a sudden fall of elastic modulus. Conclusion. Recasting of nickelchromium and cobalt-chromium alloys is not recommended because of the reduced elastic modulus of these alloys. Instead of reusing previously recasted alloys, the alloy residues should be returned to the manufacturer. .

  15. Microbeam x-ray absorption spectroscopy study of chromium in large-grain uranium dioxide fuel

    Science.gov (United States)

    Mieszczynski, C.; Kuri, G.; Bertsch, J.; Martin, M.; Borca, C. N.; Delafoy, Ch; Simoni, E.

    2014-09-01

    Synchrotron-based microprobe x-ray absorption spectroscopy (XAS) has been used to study the local atomic structure of chromium in chromia-doped uranium dioxide (UO2) grains. The specimens investigated were a commercial grade chromia-doped UO2 fresh fuel pellet, and materials from a spent fuel pellet of the same batch, irradiated with an average burnup of ~40 MW d kg-1. Uranium L3-edge and chromium K-edge XAS have been measured, and the structural environments of central uranium and chromium atoms have been elucidated. The Fourier transform of uranium L3-edge extended x-ray absorption fine structure shows two well-defined peaks of U-O and U-U bonds at average distances of 2.36 and 3.83 Å. Their coordination numbers are determined as 8 and 11, respectively. The chromium Fourier transform extended x-ray absorption fine structure of the pristine UO2 matrix shows similar structural features with the corresponding spectrum of the irradiated spent fuel, indicative of analogous chromium environments in the two samples studied. From the chromium XAS experimental data, detectable next neighbor atoms are oxygen and uranium of the cation-substituted UO2 lattice, and two distinct subshells of chromium and oxygen neighbors, possibly because of undissolved chromia particles present in the doped fuels. Curve-fitting analyses using theoretical amplitude and phase-shift functions of the closest Cr-O shell and calculations with ab initio computer code FEFF and atomic clusters generated from the chromium-dissolved UO2 structure have been carried out. There is a prominent reduction in the length of the adjacent Cr-O bond of about 0.3 Å in chromia-doped UO2 compared with the ideal U-O bond length in standard UO2 that would be expected because of the change in effective Coulomb interactions resulting from replacing U4+ with Cr3+ and their ionic size differences. The contraction of shortest Cr-U bond is ~0.1 Å relative to the U-U bond length in bulk UO2. The difference in the

  16. Hard Chromium Electroplating and Improvement the Properties by the Thermo Chemical Treatments (Solid Carburizing of Low Carbon Steel

    Directory of Open Access Journals (Sweden)

    Ahmed Salloum Abbas

    2009-01-01

    Full Text Available In this research the hard chromium electroplating process, which is one of the common methods of overlay coating was used, by using chromium acid as source of chromium and sulphuric acid as catalyst since the ratio between chromic acid and sulphuric acid is (100 : 1 consequently. Plating process was made by applying current of density (40 Amp / dm2 and the range of solution temperature was (50 – 55oC with different time periods (1-5 hr. A low carbon steel type (Ck15 was used as substrate for hard chromium electroplating. Solid carburization was carried out for hard chromium plating specimen at temperature (925oC with time duration (2 hr to be followed with quenching and tempering. The phase analysis was conducted by using X– ray diffraction. The examination results show that the chromium carbides in plating layer were (Cr23C6, Cr7C3. The microhardness of hard chromium plating specimen was measured, and the results show that the high hardness was about (907HV. After solid carburization the hardness values increase and the results show that the higher hardness for chromium plating layer on low carbon steel surface was (1276 HV. Wear apparatus type (Pin on Disc was used to study dry sliding wear properties of low carbon steel (As received and hard chromium plating specimens and solid carburized. The effect of applied normal load on wear rate was studied with weighting method using five normal loads (5, 10, 15, 20, 25 N at constant sliding speed (2.198 m / sec. The results reveal that the wear rate increases with the increasing of applied normal load. A good improvement in wear resistance was noticed for hard chromium plating specimens as compared with substrate specimen. It was also seen that, the improvement in wear resistance was (94% as compared with substrate metal when carburizing treatment is carried out on hard chromium plating specimens.

  17. Simultaneously Recovering High-Purity Chromium and Removing Organic Pollutants from Tannery Effluent

    Directory of Open Access Journals (Sweden)

    Jie Zong

    2016-01-01

    Full Text Available Chromium pollution is a serious issue because of carcinogenic toxicities of the pollutants and low recovery rate of chromium because of the presence of organic, such as protein and fat. In this work, high recovery rate and high purity of the chromium ion were successfully prepared by the way of acid enzyme, flocculant, and Fenton oxidation. The experiments were characterized by TG, TOC, UV-VIS, and SEM. In the work, the tannery waste chrome liquor was used as experimental material. The results showed that the percentage of reduction of TOC in the tannery waste chrome liquor by method of Fenton oxidation, acid enzyme, and the flocculant was 71.15%, 65.26%, and 22.05%, respectively. Therefore, the organism content of chrome tanning waste liquid was greatly reduced through the pretreatment. And the application experiment showed that the properties and grain surface and fibers of the tanned leather with commercial chromium powder and chrome tanning agent prepared from the chromium waste liquid treated with Fenton are nearly the same.

  18. Thermodynamics of chromium in UO{sub 2} fuel: A solubility model

    Energy Technology Data Exchange (ETDEWEB)

    Riglet-Martial, Ch., E-mail: chantal.martial@cea.fr [Commissariat à l’Energie Atomique et aux Energies Alternatives, Direction de l’Energie Nucléaire, Département d’Etudes des Combustibles, Centre d’Etudes de Cadarache, 13108 Saint-Paul-lez-Durance Cedex (France); Martin, Ph. [Commissariat à l’Energie Atomique et aux Energies Alternatives, Direction de l’Energie Nucléaire, Département d’Etudes des Combustibles, Centre d’Etudes de Cadarache, 13108 Saint-Paul-lez-Durance Cedex (France); Testemale, D. [Université Grenoble Alpes, Institut NEEL, F-38042 Grenoble (France); CNRS, Institut NEEL, F-38042 Grenoble (France); Sabathier-Devals, C.; Carlot, G.; Matheron, P.; Iltis, X.; Pasquet, U.; Valot, C. [Commissariat à l’Energie Atomique et aux Energies Alternatives, Direction de l’Energie Nucléaire, Département d’Etudes des Combustibles, Centre d’Etudes de Cadarache, 13108 Saint-Paul-lez-Durance Cedex (France); Delafoy, C. [AREVA NP SAS, 10 rue Juliette Recamier, 69456 Lyon Cedex 06 (France); Largenton, R. [EDF R and D, Mechanics and Material Component Department, Avenue des Renardières, 77818 Moret sur Loing Cedex (France)

    2014-04-01

    The solubility and speciation of chromium in doped uranium oxide are measured in carefully controlled temperature and oxygen potential conditions using electron probe microanalysis (EPMA) and scanning electron spectroscopy (SEM). The examination of the samples by X-ray Absorption Spectroscopy (XAS) provides evidence that (i) chromium is soluble in the UO{sub 2} matrix under the +3 oxidation state only regardless of the sintering conditions which is in accordance with a soluble species of type CrO{sub 3/2} and (ii) soluble chromium exhibits octahedral symmetry with 6 atoms of oxygen forming CrO{sub 6} patterns in the UO{sub 2} structure. In consistency with all available experimental information including previously published data, the solubility of chromium in UO{sub 2} corresponding to each two-phase field with either Cr, CrO and Cr{sub 2}O{sub 3} may be described in the ranges 1500 °C < T < 2000 °C and −460 < μ{sub O2} < −360 kJ/mol using the standard thermodynamic equations governing solubility equilibria. The characteristic parameters of the solubility laws in UO{sub 2} for the three chromium phases are derived.

  19. Competition of Chromium on Iron binding sites in the biological system

    Directory of Open Access Journals (Sweden)

    *F. S. Rehmani

    2011-09-01

    Full Text Available Hexavalent chromium is mutagenic and neurotoxic. Trivalent Chromium is involved in the enzymes of glucose metabolism. Chromium is generally found in +3 oxidation state and sometimes it competes for the binding sites of iron in the biological system, when the concentration of chromium exceeds above the normal, it inhibits the absorption of iron and iron deficiency leads diseases such as anemia, tinnitus and depression. Salicylicdhydroxamic acid a hydroxamate type siderophore is used as a drug in the chelation therapy of iron overload patients. The complex formation of Cr(III and Fe(III with salicyclic hydroxamate were studied potentiometrically at different temperatures and data was subjected to computer programs. The stability constant (log beta values and thermodynamic stabilities were calculated. It was found that salicyclic hydroxamate forms 1:1 complex at pH 3 and 1:2 complex at pH 4 with Cr(III and Fe(III, respectively. The stability constant (Log beta and thermodynamic stabilities of Cr(III Salicyclic hydroxamate complexes are close to Fe(III Salicyclic hydroxamate complexes. It was observed from the stability constant values that after chelating therapy the concentration of chromium become low and deficiency symptoms appear resulting diabetes.

  20. REMOVAL OF CHROMIUM FROM AQUEOUS SOLUTION USING LOCALLY AVAILABLE INEXPENSIVE TARO AND WATER HYACINTH AS BIOSORBENT

    Directory of Open Access Journals (Sweden)

    Shahjalal Khandaker

    2016-04-01

    Full Text Available In this investigation, locally available and inexpensive Taro and Water Hyacinth were used as biosorbents to remove chromium from synthetic wastewater. The removal of this metal ion from water in the batch and column method have been studied and discussed. Adsorption kinetics and equilibrium isotherm studies were also carried out. The material exhibits good adsorption capacity and the data follow both Freundlich and Langmuir models. Scanning Electronic Microscopic image was also used to understand the surface characteristics of biosorbent before and after biosorption studies. Effects of various factors such as pH, adsorbent dose, adsorbate initial concentration, particle size etc. were analyzed. The initial concentrations of chromium were considered 5-30mgL-1 in batch method and only 4mgL-1 in column method. The maximum chromium adsorbed was 1.64 mgg-1 and 4.44 mgg-1 in Batch method and 1.15 mgg-1 and 0.75 mgg-1 in Column method. Batch and Column desorption and regeneration studies were conducted. Column desorption studies indicated that both of these biosorbents could be reused for removing heavy metals. Results of the laboratory experiments show that the performance of Taro and Water Hyacinth prove that they can effectively be used as low cost biosorbents for the removal of chromium from wastewater.KEYWORDS:   adsorption; chromium removal; Taro; water hyacinth; batch method; column studies