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1

Prevention of aflatoxicosis in farm animals by Means of hydrated sodium calcium aluminosilicate addition to feedstuffs: a review  

Microsoft Academic Search

Mycotoxins are a wide group of fungal toxins that have been associated with severe toxic effects in man and animals. Aflatoxins are the most dangerous of these fungal secondary metabolites. Because there is no definitive way in which complete detoxification of food and feed contaminated with mycotoxins can be achieved, new methods to eliminate mycotoxicosis are sought.Hydrated sodium calcium aluminosilicate

A. J. Ramos; E. Hernández

1997-01-01

2

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

SciTech Connect

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

Hill, J. [UK Nirex Limited, Curie Avenue, Harwell, Didcot Oxfordshire, OX11 0RH (United Kingdom)]. E-mail: joanne.hill@nirex.co.uk; Harris, A.W. [UK Nirex Limited, Curie Avenue, Harwell, Didcot Oxfordshire, OX11 0RH (United Kingdom); Manning, M. [Formerly AEA Technology, Building 220, Harwell, Didcot Oxfordshire, OX11 0RA (United Kingdom); Chambers, A. [Serco Assurance, Building 150, Harwell International Business Centre, Didcot, Oxfordshire, OX11 0RA (United Kingdom); Swanton, S.W. [Serco Assurance, Building 150, Harwell International Business Centre, Didcot, Oxfordshire, OX11 0RA (United Kingdom)

2006-07-01

3

Hydration of calcium sulfoaluminate cements - Experimental findings and thermodynamic modelling  

SciTech Connect

Calcium sulfoaluminate cements (CSA) are a promising low-CO{sub 2} alternative to ordinary Portland cements and are as well of interest concerning their use as binder for waste encapsulation. In this study, the hydration of two CSA cements has been investigated experimentally and by thermodynamic modelling between 1 h and 28 days at w/c ratios of 0.72 and 0.80, respectively. The main hydration product of CSA is ettringite, which precipitates together with amorphous Al(OH){sub 3} until the calcium sulfate is consumed after around 1-2 days of hydration. Afterwards, monosulfate is formed. In the presence of belite, straetlingite occurs as an additional hydration product. The pore solution analysis reveals that straetlingite can bind a part of the potassium ions, which are released by the clinker minerals. The microstructure of both cements is quite dense even after 16 h of hydration, with not much pore space available at a sample age of 28 days. The pore solution of both cements is dominated during the first hours of hydration by potassium, sodium, calcium, aluminium and sulfate; the pH is around 10-11. When the calcium sulfate is depleted, the sulfate concentration drops by a factor of 10. This increases pH to around 12.5-12.8. Based on the experimental data, a thermodynamic hydration model for CSA cements based on cement composition, hydration kinetics of clinker phases and calculations of thermodynamic equilibria by geochemical speciation has been established. The modelled phase development with ongoing hydration agrees well with the experimental findings.

Winnefeld, Frank, E-mail: Frank.Winnefeld@empa.c [Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Concrete and Construction Chemistry, Duebendorf (Switzerland); Lothenbach, Barbara [Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Concrete and Construction Chemistry, Duebendorf (Switzerland)

2010-08-15

4

Nanostructure of Calcium Silicate Hydrates in Cements  

NASA Astrophysics Data System (ADS)

Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure.

Skinner, L. B.; Chae, S. R.; Benmore, C. J.; Wenk, H. R.; Monteiro, P. J. M.

2010-05-01

5

Nanostructure of calcium silicate hydrates in cements.  

PubMed

Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. PMID:20866975

Skinner, L B; Chae, S R; Benmore, C J; Wenk, H R; Monteiro, P J M

2010-05-14

6

75 FR 39025 - Determination That ACTONEL (Risendronate Sodium) Tablets, 75 Milligrams, and ACTONEL WITH CALCIUM...  

Federal Register 2010, 2011, 2012, 2013

...CALCIUM (Risendronate Sodium and Calcium Carbonate (Copackaged)) Tablets, 35...CALCIUM (risendronate sodium and calcium carbonate (copackaged)) Tablets, 35...CALCIUM (risendronate sodium and calcium carbonate (copackaged)) Tablets,...

2010-07-07

7

Sodium p-toluenesulfinate tetra-hydrate  

PubMed Central

The title compound, Na+·C7H7O2S?·4H2O, is the hydrate of the sodium salt of para-toluene­sulfinic acid. The mol­ecular geometry around the sulfur atom is tetra­hedral with X–S–Y angles spanning a range of 102.23?(6)–110.04?(6)°. In the crystal, the water mol­ecules connect the sodium cations into chains along the b axis via O—H?O hydrogen bonds. An inter­molecular O—H?? inter­action is also observed. PMID:21836887

Betz, Richard; Gerber, Thomas

2011-01-01

8

Influence of the calcium sulphate source on the hydration mechanism of Portland cement–calcium sulphoaluminate clinker–calcium sulphate binders  

Microsoft Academic Search

Two different binders composed of Portland cement, calcium sulphoaluminate clinker and calcium sulphate were studied from early hydration to 28days, one containing gypsum and one containing anhydrite at equimolar CaSO4 amount. Sodium gluconate was used as retarder to obtain a sufficient fluidity to cast the samples. Solids were analyzed by X-ray diffraction, scanning electron microscopy and thermogravimetric analysis and quantified

Laure Pelletier-Chaignat; Frank Winnefeld; Barbara Lothenbach; Gwenn Le Saout; Christian Jörg Müller; Charlotte Famy

2011-01-01

9

Hydration of Portland cement with additions of calcium sulfoaluminates  

SciTech Connect

The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C-S-H has a similar composition as in OPC with no additional Al to Si substitution. As in CSA-OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems.

Le Saout, Gwenn, E-mail: gwenn.le-saout@mines-ales.fr [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Lothenbach, Barbara [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland)] [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Hori, Akihiro [DENKA Chemicals GmbH, Wehrhahn-Center, Cantadorstr. 3, D-40211 Duesseldorf (Germany)] [DENKA Chemicals GmbH, Wehrhahn-Center, Cantadorstr. 3, D-40211 Duesseldorf (Germany); Higuchi, Takayuki [Denki Kagaku Kogyo Kabushiki Kaisha (DENKA), Omi, Itoigawa, Niigata, 949-0393 (Japan)] [Denki Kagaku Kogyo Kabushiki Kaisha (DENKA), Omi, Itoigawa, Niigata, 949-0393 (Japan); Winnefeld, Frank [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland)] [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland)

2013-01-15

10

The hydration of interstitial Portland cement phases in sodium hydroxide and magnesium sulfate solutions  

NASA Astrophysics Data System (ADS)

Formation of sulfoaluminate compounds was investigated by isothermal calorimetry and X-ray diffraction (XRD). Tricalcium aluminate/gypsum mixtures with a molar ratio of 1:1 sulfate-to-aluminate were hydrated at constant temperatures from 30 to 90°C; in de-ionized water, in 200mM and in 500mM sodium hydroxide (NaOH) solutions. Hydration in de-ionized water produced ettringite and monosulfate as the dominant crystalline phases, regardless of temperature. Complex assemblages of phases formed in 200mM and 500mM sodium hydroxide including ettringite, monosulfate and U-phase, at all temperatures. Hydration of monosulfate and gypsum was also carried out at constant temperatures from 30° to 80°C using de-ionized water and 0.2M, 0.5M, and 1.0M sodium hydroxide (NaOH) solutions. Ettringite was found to be the dominant crystalline phase over the entire temperature range and at all sodium hydroxide concentrations. A sodium-substituted monosulfate phase was formed as a hydration product in the 1.0M sodium hydroxide solution regardless of temperature. Sulfoaluminate compounds formed by tricalcium aluminate hydration in magnesium sulfate solution were investigated by isothermal calorimetry, XRD, and scanning electron microscopy (SEM). Hydration was carried out in 0.5, 1.0 and 3.0M magnesium sulfate solutions and isothermally at temperatures from 30 to 80°C. Monosulfate, ettringite, gypsum and a hydrogarnet phase (Ca3Al2O6·6H2O) were all observed as hydration products. Monosulfate and hydrogarnet were the only phases observed for hydration in 0.5 and 1.0M magnesium sulfate solutions. Ettringite was the dominant crystalline phase after hydration in 3.0M solution, regardless of temperature. To investigate the rate of hydration, reactions at 60°C in 3.0M magnesium sulfate solution were quenched after 26 minutes, 73 minutes, 2.5 hours and 12 hours to establish the evolution of hydrated phases. Depending on hydration times ettringite, monosulfate, gypsum, hydrogarnet and residual tricalcium aluminate were observed. No crystalline magnesium-rich phases were detected by XRD. The products formed by hydration of tetracalcium aluminoferrite (Ca 2AlFeO5) and magnesium sulfate solutions were investigated by isothermal calorimetry, XRD and SEM analyses. Hydration reactions were carried out isothermally at temperatures from 25 to 80°C in 0.25M, 0.5M, 1.0M, 2.0M, and 3.0M magnesium sulfate solutions. Gypsum was the initial hydration product in all magnesium sulfate concentrations and was the only crystalline hydration product in 2.0M and 3.0M magnesium sulfate solutions. Monosulfate was the dominant crystalline phase produced over the entire temperature range when hydration was carried out in magnesium sulfate concentrations between 0.25M and 1.0M. No crystalline phases incorporating iron were observed regardless of magnesium sulfate concentration or temperature. Hydration in 1.0M MgSO 4 solution was more extensively investigated at 50°C. SEM observations indicated gypsum formed initially, consisting of fine particles (<5 mum). Complex phase assemblages including gypsum, ettringite, and monosulfate were present at intermediate times. Monosulfate was the final crystalline hydration product. Amorphous solids produced include a calcium/iron-rich gel and a magnesium/aluminum/sulfate-rich phase. The calcium/iron-rich gel is the only iron-rich phase observed in the hydrated phase assemblage.

Clark, Boyd Arthur

11

Sodium-calcium interactions under salinity stress 205 SODIUM-CALCIUM INTERACTIONS UNDER SALINITY STRESS  

E-print Network

USA cramer@unr.edu Abstract There are a wide range of responses of plants to salinity which involve of Salinity Salinity affects plant growth through ionic and osmotic effects. Sometimes these effectsSodium-calcium interactions under salinity stress 205 CHAPTER 10 SODIUM-CALCIUM INTERACTIONS UNDER

Cramer, Grant R.

12

The nanostructure of calcium silicate hydrate  

NASA Astrophysics Data System (ADS)

The nanostructure of C-S-H, the principle binding phase of hydrated cements in concrete, is examined through classical and spectroscopic methods such as solubility, 29Si MAS NMR, inelastic neutron scattering (INS), and small-angle neutron scattering (SANS). A more comprehensive understanding of the nanostructure is proposed. The central finding of this thesis is that variations in Ca/Si ratio, silicate structure, and Ca-OH content of C-S-H are systematically related to previously undiscovered variations in solubility in the CaO-SiO2-H 2O system at room temperature. These relationships show how C-S-H resembles disordered forms of the calcium silicate hydrate minerals 1.4-nm tobermorite [Ca5Si6O16(OH)2·8H 2O] and jennite [Ca9(Si6O18)(OH) 6·8H2O]. For example, in solids lacking Ca-OH groups, the structure resembles a purely tobermorite-like structure, which, when equilibrated in aqueous solutions saturated in Ca(OH)2, has a Ca/Si ratio of 1.5 and a minimum mean silicate chain length of 2; with increasing Ca-OH contents, the structure becomes increasingly jennite-like while showing higher Ca/Si ratios and higher mean chain lengths at saturation in Ca(OH)2. These relationships appear to reconcile the broad variations in the literature. 29Si NMR on concrete specimens aged 43--96 years show that the mean silicate chain length of C-S-H gel ultimately converges to a value of 5. With supporting evidence from chemical analysis and from high Ca-OH contents measured by INS, it is concluded that C-S-H gel formed in Ca3SiO5 pastes eventually equilibrates to a purely jennite-like structure. A Ca/Si ratio of 1.2 in C-S-H gel marks the composition at which Ca-OH groups are eliminated (or introduced) and below which spontaneous silicate polymerization occurs. Leaching studies on cement pastes show that when C-S-H is decalcified below Ca/Si ˜ 1.2, the induced silicate polymerization occurring in situ leads to macroscopic polymerization shrinkage. Cement pastes blended with high contents of mineral additions may be more susceptible to this mechanism. SANS measurements on leached Ca3SiO5 and cement pastes show dramatic variations in surface area with Ca/Si ratio. These variations are attributed to transformations between low- and high-density morphologies of C-S-H.

Chen, Jeffrey J.

13

Hydration of a Portland cement blended with calcium carbonate  

Microsoft Academic Search

The hydration of a commercial Portland cement blended with calcium carbonate was studied by thermal analysis. TG, DTA and DTG analyses were performed on pastes prepared with a water to cement weight ratio of 0.5, after different setting times during the first 28 days of hydration. The analyses were run from 28°C to 1000°C with a 10°C\\/min heating rate and

Jo Dweck; Pedro Mauricio Buchler; Antonio Carlos Vieira Coelho; Frank K Cartledge

2000-01-01

14

Effect of sodium gluconate on the solubility of calcium lactate  

Microsoft Academic Search

Calcium and lactate are present in excess of their solubility in Cheddar cheese. Consequently, calcium lactate crystals (CLC) are a common defect in Cheddar cheese. A novel approach for preventing CLC is the addition of sodium gluconate. Sodium gluconate has the potential to increase the solubility of calcium and lactate by forming soluble complexes with calcium and lactate ions, and

C. Phadungath; L. E. Metzger

2011-01-01

15

Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.  

ERIC Educational Resources Information Center

The gravimetric determination of calcium as calcium carbonate is described. This experiment is suitable for undergraduate quantitative analysis laboratories. It is less expensive than determination of chloride as silver chloride. (BB)

Henrickson, Charles H.; Robinson, Paul R.

1979-01-01

16

Intrinsic elastic properties of Calcium Silicate Hydrates by nanoindentation  

E-print Network

1 Intrinsic elastic properties of Calcium Silicate Hydrates by nanoindentation C. Plassard, E-S-H in the direction perpendicular to the plane of the silicate layers. This has been carried out by nanoindentation to quantitatively predict elastic moduli of cement pastes. Lots of works report results on nanoindentation

Paris-Sud XI, Université de

17

Thermokineticanalysis of the hydration process of calcium phosphate cement  

Microsoft Academic Search

A microcalorimeter (Setaram c-80) was used\\u000a to study the thermokinetics of the hydration process of calcium phosphate\\u000a cement (CPC), a biocompatible biomaterial used in bone repair. The hydration\\u000a enthalpy was determined to be 35.8 J g–1\\u000a at 37.0°C when up to 80 mg CPC was dissolved in 2 mL of citric buffer.\\u000a In the present study, parameters related to time

W. Y. Gao; Y. W. Wang; L. M. Dong

2006-01-01

18

Modulation of L-type calcium channels by sodium ions.  

PubMed Central

It is universally believed that the removal of external sodium ions is without effect on calcium current. We now report that in enzymatically isolated guinea pig ventricular cells, the replacement of external sodium ions with certain other cations causes a 3- to 6-fold increase in peak L-type calcium current. The increase in current is reversibly blocked by L-type calcium-channel antagonists, not mediated by changes in internal calcium, and is inhibited by intracellular 5'-adenylyl imidodiphosphate, a nonhydrolyzable ATP analogue. The effects of sodium removal (and isoproterenol) were almost completely blocked by intracellular application of a specific (peptide) inhibitor of cAMP-dependent protein kinase. These experiments demonstrate a previously unknown effect of sodium ions to modulate calcium-channel phosphorylation via cAMP-dependent protein kinase. PMID:1374902

Balke, C W; Wier, W G

1992-01-01

19

Uptake of chloride and carbonate ions by calcium monosulfoaluminate hydrate  

SciTech Connect

Decommissioning of old nuclear reactors may produce waste streams containing chlorides and carbonates, including radioactive {sup 36}Cl{sup -} and {sup 14}CO{sub 3}{sup 2-}. Their insolubilization by calcium monosulfoaluminate hydrate was investigated. Carbonates were readily depleted from the solution, giving at thermodynamic equilibrium monocarboaluminate, monocarboaluminate + calcite, or calcite only, depending on the initial ratio between the anion and calcium monosulfoaluminate hydrate. Chloride ions reacted more slowly and were precipitated as Kuzel's salt, Kuzel's and Friedel's salts, or Friedel's salt only. Rietveld refinement of X-Ray powder diffraction patterns was successfully used to quantify the phase distributions, which were compared to thermodynamic calculations. Moreover, analysing the lattice parameters of Kuzel's salt as a function of its chloride content showed the occurrence of a restricted solid solution towards the sulfate side with general formula 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}xCaCl{sub 2}{center_dot}(1 - x)CaSO{sub 4}{center_dot}(12 - 2x){center_dot}H{sub 2}O (0.36 {<=} x {<=} 0.50).

Mesbah, Adel [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); Cau-dit-Coumes, Celine, E-mail: celine.cau-dit-coumes@cea.fr [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Renaudin, Guillaume [Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere (France); Frizon, Fabien [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Leroux, Fabrice [Clermont Universite, Universite Blaise Pascal, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere (France)

2012-08-15

20

Monte Carlo Simulations of Calcium and Sodium Channels  

NASA Astrophysics Data System (ADS)

Channels are relatively simple biological proteins with a hole that permit the passage of selected ions through otherwise impermeable membranes and that play a central role in many biological processes. Calcium and sodium channels, which favor the passage of calcium and sodium ions, respectively, are similar in structure, containing four amino acid side chains. In the calcium channel, these side chains are four glutamate residues (EEEE locus) whereas in the sodium channel they are aspartate, glutamate, lysine, and alanine (DEKA locus). In this study, the channel is modeled as a cylinder that penetrates a hard surface, that models the membrane, the residues are modeled as hard spheres with an appropriate charge, and the electolyte in contact with the membrane is modeled by the primitive model, charged hard sphere ions in a dielectric continuum. The selectivity of this model channel is examined by means of a Monte Carlo simulation; these model channels are found to be calcium and sodium selective.

Henderson, Douglas

2003-03-01

21

Sodium-calcium exchange and calcium-calcium exchange in internally dialyzed squid giant axons  

Microsoft Academic Search

Summary The influx and efflux of calcium (as45Ca) and influx of sodium (as24Na) were studied in internally dialyzed squid giant axons. The axons were poisoned with cyanide and ATP was omitted from the dialysis fluid. The internal ionized Ca2+ concentration ([Ca2+]i) was controlled with Ca-EGTA buffers. With [Ca2+]i>0.5 µm,45Ca efflux was largely dependent upon external Na and Ca. The Na0-dependent

M. P. Blaustein; J. M. Russell

1975-01-01

22

Characterization of white Portland cement hydration and the CSH structure in the presence of sodium aluminate by 27Al and 29Si MAS NMR spectroscopy  

Microsoft Academic Search

The effects of hydrating a white Portland cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO2) at 5 and 20 °C are investigated by 27Al and 29Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO2 accelerates the hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO4\\/AlO4

Morten Daugaard Andersen; Hans J. Jakobsen; Joergen Skibsted

2004-01-01

23

Diffusion motions in hydrated sodium alginate by QENS  

NASA Astrophysics Data System (ADS)

QENS experiments are very suitable for the study of water-polysaccharides systems both for slow polymer chains dynamics as well as for faster solvent molecules dynamics. By a suitable choice of experimental conditions as well as a properly data processing we can get information about the motion modes of various molecular groups of polymer chains in aqueous solutions presumes. Virtually we can distinguish the polymer protons motions at nanosecond time scale by choosing a narrow energy resolution window. The present work presents the QENS measurements performed at LLB, MIBEMOL neutron spectrometer on sodium alginate hydrated samples. The experimental spectra were fitted using one lorentzian fit. At high polymer concentration the quasielastic part of the line is given by the translational-rotational diffusion performed by heavy water molecules in confined spaces created by the polymer coils. The experimental data are well described by Chudley Elliot and Hall-Ross models.

Tripadus, V.; Zanotti, J. M.; Statescu, M.; Mitra, S.; Aranghel, D.; Gugiu, M.; Petre, M.; Precup, I.

2010-01-01

24

Effect of sodium gluconate on the solubility of calcium lactate.  

PubMed

Calcium and lactate are present in excess of their solubility in Cheddar cheese. Consequently, calcium lactate crystals (CLC) are a common defect in Cheddar cheese. A novel approach for preventing CLC is the addition of sodium gluconate. Sodium gluconate has the potential to increase the solubility of calcium and lactate by forming soluble complexes with calcium and lactate ions, and preventing them from being available for the formation of CLC. The objective of this study was to determine if sodium gluconate could increase the solubility of calcium lactate (CaL(2)). Seven CaL(2) solutions (5.31% wt/wt) with 7 levels of sodium gluconate (0, 0.5, 1, 1.5, 2, 3, and 4% wt/wt) were made in triplicate. Solutions were stored at 7 °C for 21 d, and were visually inspected for CLC formation. Subsequently, they were filtered to remove CLC and the supernatant was analyzed for lactic acid and gluconic acid by HPLC and for calcium by atomic absorption spectroscopy. The visual inspection demonstrated that CLC were formed in the solution with 0% gluconate after the first day of storage and CLC continued to accumulate over time. A minute amount of CLC was also visible in the solution with 0.5% gluconate after 21 d of storage, whereas CLC were not visible in the other solutions. The HPLC results indicated a higher concentration of calcium and lactic acid in the filtrate from the solutions containing added gluconate. Thus, sodium gluconate can increase the solubility of CaL(2). PMID:21943735

Phadungath, C; Metzger, L E

2011-10-01

25

Electrochemical characteristics of uranium ions in calcium chloride hydrate melts  

NASA Astrophysics Data System (ADS)

Redox reactions of tetravalent uranium ion in calcium chloride hexahydrate CaCl2·6H2O melt ([CaCl2] = 6.9 M) were studied electrochemically and spectrophotometrically. Cyclic voltammograms in CaCl2·6H2O melt containing UCl4 were measured with a pyro-graphite carbon working electrode. A cathodic peak corresponding to the reduction of U4+ to U3+ was observed, and it was found to be controlled by the diffusion of U4+ in the melt. Although the concentration of H+ in the melt was negligible, the redox reaction of U4+ was observed without the disturbance of hydrolysis. The formal potential of the U4+|U3+ couple was determined to be -0.483 ± 0.005 V vs. NHE. The diffusion coefficient of U4+ in CaCl2·6H2O melt was determined to be 1.5 × 10-7 cm2 s-1 at 300 K. The anodic peak in the voltammogram was attributable to the oxidation of U4+ to UO22+, which was identified by using a technique based on the combination of electrolysis and spectrophotometry. Influences of the water content on chemical status of uranium ions in CaCl2 hydrate melts were studied.

Uehara, A.; Fujii, T.; Nagai, T.; Shirai, O.; Sato, N.; Yamana, H.

2010-03-01

26

Pressure induced reactions amongst calcium aluminate hydrate phases  

SciTech Connect

The compressibilities of two AFm phases (straetlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5 GPa by using synchrotron high-pressure X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt volume contraction regardless of the molecular size of the pressure-transmitting media. This volume discontinuity could be associated to a structural transition or to the movement of the weakly bound interlayer water molecules in the AFm structure. The experimental results seem to indicate that the pressure-induced dehydration is the dominant mechanism especially with hygroscopic pressure medium. The Birch-Murnaghan equation of state was used to compute the bulk modulus of the minerals. Due to the discontinuity in the pressure-volume diagram, a two stage bulk modulus of each AFm phase was calculated. The abnormal volume compressibility for the AFm phases caused a significant change to their bulk modulus. The reliability of this experiment is verified by comparing the bulk modulus of hydrogarnet with previous studies.

Moon, Ju-hyuk [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States); Oh, Jae Eun [School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Ulsan Metropolitan City, 689-798 (Korea, Republic of); Balonis, Magdalena; Glasser, Fredrik P. [Department of Chemistry, Meston Building, University of Aberdeen, Aberdeen, AB24 3UE Scotland (United Kingdom); Clark, Simon M. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA20015 (United States); Department of Earth and Planetary Sciences, University of California, Berkeley, CA94720 (United States); Monteiro, Paulo J.M., E-mail: monteiro@berkeley.ed [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)

2011-06-15

27

Synthesis and single crystal structure refinement of the one-layer hydrate of sodium brittle mica  

SciTech Connect

A sodium brittle mica with the ideal composition [Na{sub 4}]{sup inter}[Mg{sub 6}]{sup oct}[Si{sub 4}Al{sub 4}]{sup tet}O{sub 20}F{sub 4} was synthesized via melt synthesis in a gas tight crucible. This mica is unusual inasmuch as the known mica structure holds only room for two interlayer cations per unit cell and inasmuch as it readily hydrates despite the high layer charge while ordinary micas and brittle micas are non-swelling. The crystal structure of one-layer hydrate sodium brittle mica was determined and refined from single crystal X-ray data. Interlayer cations reside at the center of the distorted hexagonal cavities and are coordinated by the three inner basal oxygen atoms. The coordination of the interlayer cation is completed by three interlayer water molecules residing at the center of the interlayer region. The relative position of adjacent 2:1-layers thus is fixed by these octahedrally coordinated interlayer cations. Pseudo-symmetry leads to extensive twinning. In total five twin operations generate the same environment for the interlayer species and are energetically degenerate. - Graphical abstract: The sodium brittle mica has been successfully synthesized by melt synthesis and the crystal structure of the one-layer hydrate of sodium brittle mica was determined from single crystal X-ray diffraction data. Highlights: Black-Right-Pointing-Pointer Melt synthesis yielded coarse grained sodium brittle mica which showed little disorder. Black-Right-Pointing-Pointer Sodium brittle mica hydrated completely to the state of one-layer hydrate. Black-Right-Pointing-Pointer Structure of one-layer hydrate of sodium brittle mica could therefore be determined and refined. Black-Right-Pointing-Pointer Arrangement of upper and lower tetrahedral sheet encompassing interlayer cation were clarified.

Kalo, Hussein; Milius, Wolfgang [Lehrstuhl fuer Anorganische Chemie I, University of Bayreuth, D-95440 Bayreuth (Germany)] [Lehrstuhl fuer Anorganische Chemie I, University of Bayreuth, D-95440 Bayreuth (Germany); Braeu, Michael [BASF Construction Chemicals GmbH, 83308 Trostberg (Germany)] [BASF Construction Chemicals GmbH, 83308 Trostberg (Germany); Breu, Josef, E-mail: Josef.Breu@uni-bayreuth.de [Lehrstuhl fuer Anorganische Chemie I, University of Bayreuth, D-95440 Bayreuth (Germany)] [Lehrstuhl fuer Anorganische Chemie I, University of Bayreuth, D-95440 Bayreuth (Germany)

2013-02-15

28

Enhanced growth of methane-propane clathrate hydrate crystals with sodium dodecyl sulfate, sodium tetradecyl sulfate, and sodium hexadecyl sulfate surfactants  

NASA Astrophysics Data System (ADS)

In the present study the effect of three commercially available anionic surfactants on the hydrate growth from a gas mixture of 90.5 mol% methane/9.5 mol% propane mixture was investigated. The surfactants used were sodium dodecyl sulfate (SDS), sodium tetradecyl sulfate (STS), and sodium hexadecyl sulfate (SHS). The morphology of the growing crystals and the gas consumption were observed during the experiments. The results showed that in the presence of surfactants, branches of porous fibre-like crystals were formed instead of dendritic crystals formed in the absence of any additive. In addition, extensive hydrate crystal growth on the crystallizer walls and a "mushy" hydrate layer instead of a thin crystal film appeared at the gas/water interface. Finally, the addition of SDS with concentration range between 242 and 2200 ppm (? T=13.1 K) was found to increase the mole consumption for hydrate formation by approximately 14 times compared to pure water. This increase is related to the change in hydrate morphology, whereby a more porous hydrate forms with enhanced water/gas contacts.

Yoslim, Jeffry; Linga, Praveen; Englezos, Peter

2010-12-01

29

Accelerated growth of calcium silicate hydrates: Experiments and simulations  

SciTech Connect

Despite the usefulness of isothermal calorimetry in cement analytics, without any further computations this brings only little information on the nucleation and growth of hydrates. A model originally developed by Garrault et al. is used in this study in order to simulate hydration curves of cement obtained by calorimetry with different known hardening accelerators. The limited basis set of parameters used in this model, having a physical or chemical significance, is valuable for a better understanding of mechanisms underlying in the acceleration of C-S-H precipitation. Alite hydration in presence of four different types of hardening accelerators was investigated. It is evidenced that each accelerator type plays a specific role on one or several growth parameters and that the model may support the development of new accelerators. Those simulations supported by experimental observations enable us to follow the formation of the C-S-H layer around grains and to extract interesting information on its apparent permeability.

Nicoleau, Luc, E-mail: luc.nicoleau@basf.com

2011-12-15

30

Hydration of calcium oxide surface predicted by reactive force field molecular dynamics.  

PubMed

In this work, we present the parametrization of Ca-O/H interactions within the reactive force field ReaxFF, and its application to study the hydration of calcium oxide surface. The force field has been fitted using density functional theory calculations on gas phase calcium-water clusters, calcium oxide bulk and surface properties, calcium hydroxide, bcc and fcc Ca, and proton transfer reactions in the presence of calcium. Then, the reactive force field has been used to study the hydration of the calcium oxide {001} surface with different water contents. Calcium oxide is used as a catalyzer in many applications such as CO(2) sequestration and biodiesel production, and the degree of surface hydroxylation is a key factor in its catalytic performance. The results show that the water dissociates very fast on CaO {001} bare surfaces without any defect or vacancy. The surface structure is maintained up to a certain amount of water, after which the surface undergoes a structural rearrangement, becoming a disordered calcium hydroxyl layer. This transformation is the most probable reason for the CaO catalytic activity decrease. PMID:22316164

Manzano, Hegoi; Pellenq, Roland J M; Ulm, Franz-Josef; Buehler, Markus J; van Duin, Adri C T

2012-03-01

31

Progress in understanding the structure and thermodynamics of calcium silicate hydrates  

SciTech Connect

A program has been designed to support the prediction of cement degradation and the chemistry of water in contact with cement, over extended periods of time (e.g., 10,000 y). This multidisciplinary experimental and computer modeling investigation is intended to characterize the structural and thermodynamic properties of crystalline phases found in cement at elevated temperature. Many of these crystalline phases my be hydrated. The hydration state of these phases must be known to the interpret experimentally obtained thermodynamic data, to evaluate the stability of hydrated phases and to estimate long-term water availability, such as would be required for prediction of the radioactive-waste repository`s lifetime. The parts of the program associated with assessing and predicting dehydration/ rehydration behavior are described in this paper. (1) identification of phases present in standardized grout mixtures exposed to elevated temperatures; (2) mechanistic and thermodynamic analysis of the hydration/ dehydration behavior of hydrated calcium silicates as a function of temperature, pressure, and relative humidity; and (3) measurements of thermodynamic data for hydrated calcium silicates.

Meike, A.; Bruton, C.J.; Viani, B.E. [Lawrence Livermore National Lab., CA (United States); Onofrei, M. [Atomic Energy of Canada Ltd., Pinawa, MB (Canada). Whiteshell Nuclear Research Establishment

1994-02-01

32

Early C3A hydration in the presence of different kinds of calcium1 S. Pourcheta*  

E-print Network

manuscript, published in "Cement and Concrete Research 39 (2009) 989-996" DOI : 10.1016/j.cemconres.2009 present in43 Portland clinker. Its early hydration leads to the formation of calcium44 hydroaluminate (3Ca phase composition in this system is at early ages usually saturated or49 supersaturated with respect

Paris-Sud XI, Université de

33

Hydrated sites in biogenic amorphous calcium phosphates: An infrared, Raman, and inelastic neutron scattering study  

Microsoft Academic Search

Amorphous minerals are widely distributed in biology, and occur as carbonates, phosphates, and silica. Calcium and magnesium are the major cations in the phosphate deposits, but in addition, there is usually an organic component, and the minerals are hydrated with up to 20% water. Such deposits are found as intracellular granules in a variety of invertebrates such as the shore

P. C. H. Mitchell; S. F. Parker; J. Simkiss; Jane Simmons; Marina G. Taylor

1996-01-01

34

Chemical and morphological changes of porous hydrated calcium silicate in paddy soil  

Microsoft Academic Search

The chemical and morphological changes of porous hydrated calcium silicate material (PS) during the dissolution process in paddy soil were investigated by using both a scanning electron microscope (SEM) and an energy dispersive X-ray (EDX) analysis. The results showed that original PS consisted of agglomerate of various sizes with almost the same elemental composition. The SEM images at a high

Akiko Yamamoto; Masahiko Saigusa; Masami Nanzyo

2000-01-01

35

Synaptosomal calcium influx is activated by sodium fluoride  

SciTech Connect

Neuronal calcium channels can be modulated by changes in membrane potential or by activation of channel-associated receptors. The latter may be modulated by guanine nucleotide binding proteins. NaF, which activates guanine nucleotide binding proteins, caused a large stimulation of /sup 45/Ca/sup 2 +/ uptake by synaptosomes prepared from rat brain. Stimulation of /sup 45/Ca/sup 2 +/ influx by NaF (i) was apparent in media containing either 5 mM-K+ or 50 mM-K+, (ii) was slower than the fast-phase of voltage-dependent /sup 45/Ca/sup 2 +/ influx but continued for a longer period of time than did depolarization-induced /sup 45/Ca/sup 2 +/ influx, and (iii) was not mimicked or modified by a number of drugs, including ouabain, dinitrophenol, sodium azide or sodium vanadate. These results are consistent with the hypothesis that NaF activates a guanine nucleotide binding protein associated with receptor-coupled calcium channels, resulting in stimulation of calcium influx.

Jope, R.S.; Lally, K.M.

1988-03-15

36

Solid-state characterization and transformation of various creatine phosphate sodium hydrates.  

PubMed

Creatine phosphate sodium (CPS) salt is a first-line cardiovascular drug for severe diastolic heart failure. The drug exists in different hydrate forms. The marketed drug form was determined as CPS·4.5H2 O (H1); however, the reference standard was supplied as CPS·6H2 O (H2). In this work, we present two newly identified hydrate forms: a thermodynamically stable low hydrate form, CPS·1.5H2 O (H3), and a pressure-sensitive transit form, CPS·7H2 O (H4). The hydrate forms were discovered through a comprehensive solid-state screening experiment and fully characterized using a range of analytical techniques including X-ray powder diffraction (XRPD), FTIR, Raman spectroscopy, hot-stage microscopy (HSM), thermogravimetric analysis, and differential scanning calorimetry. Stability tests revealed that H3 was the most stable hydrate under thermal stimulation. H4 is a pressure-sensitive hydrate and easily transforms to H2 and then H1 upon grinding. The form transformation process was closely monitored using the HSM, variable-temperature XRPD (VT-XRPD), and VT-Raman spectroscopy techniques. Specifically, the transformation of H4 to H1 is characterized in a single-crystal-to-single-crystal transformation process. The newly discovered hydrate form H3 has superior physicochemical properties than the marketed forms and is worthy of further development. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3688-3695, 2014. PMID:25223726

Xu, Yun; Jiang, Linglei; Huang, Ying; Wang, Jian-Rong; Mei, Xuefeng

2014-11-01

37

Hydration and strength development of binder based on high-calcium oil shale fly ash  

SciTech Connect

The properties of high-calcium oil shale fly ash and low-calcium coal fly ash, which are produced in Israeli power stations, were investigated. High-calcium oil shale fly ash was found to contain a great amount of CaO{sub free} and SO{sub 3} in the form of lime and anhydrite. Mixtures of high-calcium oil shale fly ash and low-calcium coal fly ash, termed fly ash binder, were shown to cure and have improved strength. The influence of the composition and curing conditions on the compressive strength of fly ash binders was examined. The microstructure and the composition of fly ash binder after curing and long-term exposure in moist air, water and open air conditions were studied. It was determined that ettringite is the main variable in the strength and durability of cured systems. The positive effect of calcium silicate hydrates, CSH, which are formed by interaction of high-calcium oil shale fly ash and low-calcium coal fly ash components, on the carbonation and dehydration resistance of fly ash binder in open air is pronounced. It was concluded that high-calcium oil shale fly ash with high CaO{sub free} and SO{sub 3} content can be used as a binder for building products.

Freidin, C. [Ben-Gurion Univ. of the Negev, Sede-Boqer (Israel)] [Ben-Gurion Univ. of the Negev, Sede-Boqer (Israel)

1998-06-01

38

Accepted by the Journal of Building Physics (2007) Microstructure and Thermal Conductivity of Hydrated Calcium Silicate Board Materials  

E-print Network

of Hydrated Calcium Silicate Board Materials Chi T. Do, Dale P. Bentz1 , and Paul E. Stutzman Building be addressed, (301)975-5865, Fax: (301)990-6891, dale.bentz@nist.gov #12;Experimental Density Measurements

Bentz, Dale P.

39

INDUCTION OF CRYSTALLIZATION OF SPECIFIC CALCIUM OXALATE HYDRATES IN MICELLAR SOLUTIONS OF SURFACTANTS  

Microsoft Academic Search

The influence of octaethylene glycol mono-n-hexadecyl ether (C16EO8) and sodium dodecyl sulphate (SDS) on the crystallization of calcium oxalate from 0.3 mol dm sodium chloride solutions has been investigated. The critical micellar concentration (CMC) of C16EO8 in water and 0.3 mol dm NaCl was determined by surface tension measurements (CMCH2O=CMCNaCl = 7.2.10 mol dm). The kinetics of precipitation of calcium oxalate was followed

H. Füredi-Milhofer; R. Bloch; D. Skrtic; N. Filipovic-Vincekovic; N. Garti

1993-01-01

40

A model for two types of calcium silicate hydrate in the microstructure of Portland cement pastes  

Microsoft Academic Search

A new physical basis for a previously published model for the structure of calcium silicate hydrate (C-S-H) as measured by nitrogen sorption is described. This refined model provides a method of predicting the density, the nitrogen accessible gel porosity, and associated surface area of C-S-H in Portland cement pastes. The basis for the model is that C-S-H forms as one

Paul D Tennis; Hamlin M Jennings

2000-01-01

41

Electronic structure of sodium cobalt oxide: Comparing mono- and bilayer hydrate  

NASA Astrophysics Data System (ADS)

To shed light on the mechanism of superconductivity in sodium cobalt oxide bilayer-hydrate (BLH), we perform a density functional calculation with full structure optimization for BLH and its related nonsuperconducting phase, monolayer hydrate (MLH). We find that these hydrates have similar band structures, but a notable difference can be seen in the a1g band around the Fermi level. While its dispersion in the z direction is negligibly small for BLH, it is of the order of 0.1eV for MLH. This result implies that the three-dimensional feature of the a1g band may be the origin for the absence of superconductivity in MLH.

Arita, Ryotaro

2005-04-01

42

Calcium absorption by fish intestine: The involvement of ATP-and sodium-dependent calcium extrusion mechanisms  

Microsoft Academic Search

Summary Measurements of unidirectional calcium fluxes in stripped intestinal epithelium of the tilapia,Oreochromis mossambicus, in the presence of ouabain or in the absence of sodium indicated that calcium absorption via the fish intestine is sodium dependent. Active Ca2+ transport mechanisms in the enterocyte plasma membrane were analyzed. The maximum capacity of the ATP-dependent Ca2+ pump (Vm:0.63 nmol·min-1 mg-1,Km: 27nm Ca2+)

Gert Flik; Theo J. M. Schoenmakers; Jack A. Groot; Carel H. van Os; Sjoerd E. Wendelaar Bonga

1990-01-01

43

Persistent sodium and calcium currents in rat hypoglossal motoneurons.  

PubMed

Voltage-dependent persistent inward currents are thought to make an important contribution to the input-output properties of alpha-motoneurons, influencing both the transfer of synaptic current to the soma and the effects of that current on repetitive discharge. Recent studies have paid particular attention to the contribution of L-type calcium channels, which are thought to be widely distributed on both the somatic and the dendritic membrane. However, the relative contribution of different channel subtypes as well as their somatodendritic distribution may vary among motoneurons of different species, developmental stages, and motoneuron pools. In this study, we have characterized persistent inward currents in juvenile (10- to 24-day-old) rat hypoglossal (HG) motoneurons. Whole-cell, voltage-clamp recordings were made from the somata of visualized rat HG motoneurons in 300-microm brain stem slices. Slow (10 s), triangular voltage-clamp commands from a holding potential of -70 to 0 mV and back elicited whole-cell currents that were dominated by outward, potassium currents, but often showed a region of negative slope resistance on the rising phase of the command. In the presence of potassium channel blockers (internal cesium and external 4-aminopyridine and tetraethylammonium), net inward currents were present on both the rising and falling phases of the voltage-clamp command. A portion of the inward current present on the ascending phase of the command was mediated by TTX-sensitive sodium channels, whereas calcium channels mediated the remainder of the current. We found roughly the same relative contributions of P-, N-, and L-type channels to the calcium currents recorded at the soma that had previously been found in neonatal rat HG motoneurons. In most cells, the somatic voltage thresholds for calcium current onset and offset were similar and the peak current was largest on the ascending phase of the clamp command. However, about one-third of the cells exhibited a substantial clockwise current hysteresis, i.e., inward currents were present at lower voltages on the descending phase of the clamp command. In the same cells, 1-s depolarizing voltage-clamp commands were followed by prolonged tail currents, consistent with a prominent contribution from dendritic channels. In contrast to previous reports on turtle and mouse motoneurons, blocking L-type calcium channels did not eliminate these presumed dendritic currents. PMID:12522206

Powers, Randall K; Binder, Marc D

2003-01-01

44

Characterization of Calcium Aluminate Hydrates and Related Hydrates of Cement Pastes by (27)Al MQ-MAS NMR.  

PubMed

27Al multi quantum (MQ) MAS NMR spectroscopy was used for the first time to characterize calcium aluminate hydrates, which are of importance in the chemistry of high alumina and Portland cements. Substitution sites of silicon by aluminum in the calcium silicate hydrates (C-S-H) which are the main component of Portland cement paste were studied too. Synthetic samples of Ca(3)Al(OH)(12), [CaAl(OH)(4)][OH(H(2)O)(1.5)], [Ca(2)Al(OH)(6)](OH).3H(2)O, [Ca(2)Al(OH)(6)](2)(CO(3)).5H(2)O, [Mg(2)Al(OH)(6)](CO(3))(0.5).3H(2)O, Al(OH)(3), and C-S-H substituted by aluminum were prepared. In most of the samples, the two dimension 3Q-MAS NMR spectra allow one, more easily than the MAS-only NMR spectra, to obtain the chemical shift, delta(iso), and the quadrupolar parameters nu(Q) and eta, which label each site and bring information on its symmetry and environment. The distributions of the aluminum environments were observed for each site. In [Ca(2)Al(OH)](6)(OH).3H(2)O, (27)Al MAS spectrum demonstrates the presence of two octahedral aluminum sites. In the C-S-H substituted with Al, tetrahedral aluminum is observed, in bridging and nonbridging sites of the silicate chains, mostly in the bridging sites for the sample investigated. PMID:11670472

Faucon, P.; Charpentier, T.; Bertrandie, D.; Nonat, A.; Virlet, J.; Petit, J. C.

1998-07-27

45

Dynamic behavior of hydration water in calcium-silicate-hydrate gel: a quasielastic neutron scattering spectroscopy investigation.  

PubMed

The translational dynamics of hydration water confined in calcium-silicate-hydrate (C-S-H) gel was studied by quasielastic neutron scattering spectroscopy in the temperature range from 280 to 230 K. The stretch exponent ?, the self-diffusion constant D, the average translational relaxation time {?}, and the temperature dependence of confinement radius ? extracted from the elastic fraction of immobile water molecules p(Q) were obtained from the analyses of the low-Q spectra according to the relaxing cage model. Measurements were made using C-S-H of three different water contents, 10%, 17%, and 30%. Among the three samples of C-S-H gel with different water contents, the values of ? decrease with increasing water contents, while ? increases. The values of D and {?} are insensitive to temperature for the two lower water contents, as opposed to the 30% case where a slight variation is observed. The trend for violation of the Stokes-Einstein relation is only visible in the case of 30% water content. PMID:23367956

Li, Hua; Fratini, Emiliano; Chiang, Wei-Shan; Baglioni, Piero; Mamontov, Eugene; Chen, Sow-Hsin

2012-12-01

46

Type IIc sodium-dependent phosphate transporter regulates calcium metabolism.  

PubMed

Primary renal inorganic phosphate (Pi) wasting leads to hypophosphatemia, which is associated with skeletal mineralization defects. In humans, mutations in the gene encoding the type IIc sodium-dependent phosphate transporter lead to hereditary hypophophatemic rickets with hypercalciuria, but whether Pi wasting directly causes the bone disorder is unknown. Here, we generated Npt2c-null mice to define the contribution of Npt2c to Pi homeostasis and to bone abnormalities. Homozygous mutants (Npt2c(-/-)) exhibited hypercalcemia, hypercalciuria, and elevated plasma 1,25-dihydroxyvitamin D(3) levels, but they did not develop hypophosphatemia, hyperphosphaturia, renal calcification, rickets, or osteomalacia. The increased levels of 1,25-dihydroxyvitamin D(3) in Npt2c(-/-) mice compared with age-matched Npt2c(+/+) mice may be the result of reduced catabolism, because we observed significantly reduced expression of renal 25-hydroxyvitamin D-24-hydroxylase mRNA but no change in 1alpha-hydroxylase mRNA levels. Enhanced intestinal absorption of calcium (Ca) contributed to the hypercalcemia and increased urinary Ca excretion. Furthermore, plasma levels of the phosphaturic protein fibroblast growth factor 23 were significantly decreased in Npt2c(-/-) mice. Sodium-dependent Pi co-transport at the renal brush border membrane, however, was not different among Npt2c(+/+), Npt2c(+/-), and Npt2c(-/-) mice. In summary, these data suggest that Npt2c maintains normal Ca metabolism, in part by modulating the vitamin D/fibroblast growth factor 23 axis. PMID:19056871

Segawa, Hiroko; Onitsuka, Akemi; Kuwahata, Masashi; Hanabusa, Etsuyo; Furutani, Junya; Kaneko, Ichiro; Tomoe, Yuka; Aranami, Fumito; Matsumoto, Natsuki; Ito, Mikiko; Matsumoto, Mitsuru; Li, Minqi; Amizuka, Norio; Miyamoto, Ken-Ichi

2009-01-01

47

Composition and density of nanoscale calcium-silicate-hydrate in cement  

NASA Astrophysics Data System (ADS)

Although Portland cement concrete is the world's most widely used manufactured material, basic questions persist regarding its internal structure and water content, and their effect on concrete behaviour. Here, for the first time without recourse to drying methods, we measure the composition and solid density of the principal binding reaction product of cement hydration, calcium-silicate-hydrate (C-S-H) gel, one of the most complex of all gels. We also quantify a nanoscale calcium hydroxide phase that coexists with C-S-H gel. By combining small-angle neutron and X-ray scattering data, and by exploiting the hydrogen/deuterium neutron isotope effect both in water and methanol, we determine the mean formula and mass density of the nanoscale C-S-H gel particles in hydrating cement. We show that the formula, (CaO)1.7(SiO2)(H2O)1.80, and density, 2.604Mgm-3, differ from previous values for C-S-H gel, associated with specific drying conditions. Whereas previous studies have classified water within C-S-H gel by how tightly it is bound, in this study we classify water by its location-with implications for defining the chemically active (C-S-H) surface area within cement, and for predicting concrete properties.

Allen, Andrew J.; Thomas, Jeffrey J.; Jennings, Hamlin M.

2007-04-01

48

Hydration kinetics of modified calcium sulphoaluminate oxides studied by aluminum — 27 NMR spectroscopy and proton magnetic relaxation: Experimental data  

Microsoft Academic Search

Hydration kinetics of Na2O-, MgO-, BaO- and TiO2- doped calcium sulphoaluminate oxides, has been followed using 27Al NMR and proton magnetic relaxation measurements. Aluminum — 27 NMR spectra of hydrated pastes show a narrow peak at 80 ppm corresponding to the hydroxy-aluminate ions in a liquid phase. According to the changes of intensity of this lines during the induction period

A. B. Kudryavtsev; T. V. Kouznetsova

1997-01-01

49

Calcium Transient and Sodium-Calcium Exchange Current in Human versus Rabbit Sinoatrial Node Pacemaker Cells  

PubMed Central

There is an ongoing debate on the mechanism underlying the pacemaker activity of sinoatrial node (SAN) cells, focusing on the relative importance of the “membrane clock” and the “Ca2+ clock” in the generation of the small net membrane current that depolarizes the cell towards the action potential threshold. Specifically, the debate centers around the question whether the membrane clock-driven hyperpolarization-activated current, I f, which is also known as the “funny current” or “pacemaker current,” or the Ca2+ clock-driven sodium-calcium exchange current, I NaCa, is the main contributor to diastolic depolarization. In our contribution to this journal's “Special Issue on Cardiac Electrophysiology,” we present a numerical reconstruction of I f and I NaCa in isolated rabbit and human SAN pacemaker cells based on experimental data on action potentials, I f, and intracellular calcium concentration ([Ca2+]i) that we have acquired from these cells. The human SAN pacemaker cells have a smaller I f, a weaker [Ca2+]i transient, and a smaller I NaCa than the rabbit cells. However, when compared to the diastolic net membrane current, I NaCa is of similar size in human and rabbit SAN pacemaker cells, whereas I f is smaller in human than in rabbit cells. PMID:23606816

Verkerk, Arie O.

2013-01-01

50

Structure of the calcium pyrophosphate monohydrate phase (Ca2P2O7·H2O): towards understanding the dehydration process in calcium pyrophosphate hydrates.  

PubMed

Calcium pyrophosphate hydrate (CPP, Ca(2)P(2)O(7) · nH2O) and calcium orthophosphate compounds (including apatite, octacalcium phosphate etc.) are among the most prevalent pathological calcifications in joints. Even though only two dihydrated forms of CPP (CPPD) have been detected in vivo (monoclinic and triclinic CPPD), investigations of other hydrated forms such as tetrahydrated or amorphous CPP are relevant to a further understanding of the physicochemistry of those phases of biological interest. The synthesis of single crystals of calcium pyrophosphate monohydrate (CPPM; Ca(2)P(2)O(7) · H2O) by diffusion in silica gel at ambient temperature and the structural analysis of this phase are reported in this paper. Complementarily, data from synchrotron X-ray diffraction on a CPPM powder sample have been fitted to the crystal parameters. Finally, the relationship between the resolved structure for the CPPM phase and the structure of the tetrahydrated calcium pyrophosphate ? phase (CPPT-?) is discussed. PMID:25186358

Gras, Pierre; Ratel-Ramond, Nicolas; Teychéné, Sébastien; Rey, Christian; Elkaim, Erik; Biscans, Béatrice; Sarda, Stéphanie; Combes, Christèle

2014-09-15

51

Formation of Hydroxyl Groups at Calcium-Silicate-Hydrate (C-S-H): Coexistence of Ca-OH and Si-OH on Wollastonite(001)  

E-print Network

are the basic building blocks of ordinary Portland cement.1,2 In general, the microstructure of hydrated cement understanding of the concrete interface formed with water is essential. Calcium-silicate-hydrate (C-S-H) phases network is the space in the cement paste not filled with hydration products, called the capillary pore

Schmidt, Wolf Gero

52

Equilibrium hydrate formation conditions for hydrogen sulfide, carbon dioxide, and ethane in aqueous solutions of ethylene glycol and sodium chloride  

SciTech Connect

Natural gas components such as hydrogen sulfide, carbon dioxide, and ethane form gas hydrates of structure I under suitable temperature and pressure conditions. Information on such conditions is vital to the oil and gas industry in order to design and operate processing equipment and pipelines so that hydrate formation is avoided. Incipient equilibrium hydrate formation conditions for hydrogen sulfide, carbon dioxide, and ethane in aqueous solutions of ethylene glycol and sodium chloride were experimentally obtained in the temperature range 264--290 K and the pressure range 0.23--3.18 MPa. A variable-volume sapphire cell was used for the measurements.

Majumdar, A.; Mahmoodaghdam, E.; Bishnoi, P.R.

2000-02-01

53

Intake of protein, calcium and sodium in public child day care centers  

PubMed Central

OBJECTIVE: To assess calcium, protein and sodium intake, of children that attend public day-care centers and to compare it with the recommended one. METHODS: Cross-sectional descriptive study in seven public day care centers of São Paulo city, Southeast Brazil, which enrolled 366 children between 12 and 36 months of age. The data collection occurred between September and December 2010. Each day care center was evaluated for three non-consecutive days, totaling 42 days and 210 meals. Dietary intake was assessed by a direct food weighing method. For the nutritional calculation, DietWin(r) Profissional 2.0 was used, and the adequacy was calculated according to the recommendations of the National School Feeding Program for energy, protein, calcium and sodium. The calcium/protein relation was also calculated, as well as calcium density (mg/1,000kcal). RESULTS: The energy (406.4kcal), protein (18.2g) and calcium (207.6mg) consumption did not reach the recommended values ??in all the evaluated day care centers. Sodium intake exceeded up to three times the recommendation. The calcium/protein ratio of 11.7mg/g was less than the adequate one (20mg/g). CONCLUSIONS: There was inadequacy of calcium, protein and sodium dietary intake, in children attending public day-care centers. PMID:25119750

Longo-Silva, Giovana; Toloni, Maysa Helena de A.; de Menezes, Risia Cristina E.; Temteo, Tatiane Leocadio; Oliveira, Maria Alice A.; Asakura, Leiko; Costa, Emilia Chagas; Taddei, Jose Augusto de A. C.

2014-01-01

54

Characterization of white Portland cement hydration and the C-S-H structure in the presence of sodium aluminate by {sup 27}Al and {sup 29}Si MAS NMR spectroscopy  

SciTech Connect

The effects of hydrating a white Portland cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO{sub 2}) at 5 and 20 deg. C are investigated by {sup 27}Al and {sup 29}Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO{sub 2} accelerates the hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO{sub 4}/AlO{sub 4} tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the hydration (6 h to 2 years) but increases for higher concentration of the NaAlO{sub 2} solution. The average chain lengths of 'pure' silicate and SiO{sub 4}/AlO{sub 4} tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO{sub 2} reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.

Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Joergen

2004-05-01

55

Selective removal of radio-sodium from neutron-activated materials by retention on hydrated antimony pentoxide  

Microsoft Academic Search

A new method is presented to remove sodium interferences from neutron-activated materials. The method is based on passage\\u000a of the samples, dissolved in a concentrated acid solution on a column of hydrated antimony pentoxide (HAP). The retention\\u000a is quantitative with a maximum capacity of 31 mg Na\\/g HAP. Only tantalum, in addition to sodium, was retained by HAP out of

F. Girardi; E. Sabbioni

1968-01-01

56

[Monitoring of formation of diclofenac sodium salt hydrates and their influence on the drug dissolution from prepared tablets].  

PubMed

NIR spectroscopy together with multivariate data analysis were used to analyze the hydrates of diclofenac sodium prepared from the non-aqueous solvents tetrahydrofuran and methanol under standard laboratory conditions at 20 °C and relative humidity less than 60%. It was confirmed that the developed PLS regression model can monitor the process of formation of hydrates. It was also found that the hydrated form of diclofenac sodium arises during the preparation of the dosage form the using technology of impregnating the solid carrier by non-aqueous solvents, which resulted in reducing of the drug release rate from prepared tablets up to twice. NIR spectroscopy was confirmed as one of the effective PAT (Process Analytical Technology) methods. PMID:24393114

Doležel, Petr; Muselík, Jan; Králová, Michaela; Vetchý, David

2013-12-01

57

A Fourier transform infrared spectroscopic investigation of the early hydration of Portland cement and the influence of sodium lignosulfonate  

Microsoft Academic Search

The early stages of hydration of Portland cement Type I in the presence and absence of sodium lignosulfonate (a superplasticizer) have been investigated by Fourier transform infrared spectroscopic technique. Sequential experiments were performed at various times ranging from 2 min to 24 h. A number of discrete OH bands in the water stretching region and the dynamics of changes in

M. Y. A. Mollah; Wenhong Yu; Robert Schennach; David L. Cocke

2000-01-01

58

Wycheproofite: A New Hydrated Sodium Aluminium Zirconium Phosphate from Wycheproof, Victoria, Australia, and a New Occurrence Of Kosnarite  

Microsoft Academic Search

Wycheproofite is a new hydrated sodium aluminium zirconium phosphate from a pegmatite vein in granite at Wycheproof, in northwestern Victoria, Australia. The mineral occurs as compact, finely fibrous masses in small cavities in the quartzjfeldsparjmuscovitejschorl-bearing pegmatite. The fibrous crystals are between 5 and 10 11mwide and up to several rom long. Accompanying minerals include two other zirconium phosphates - kosnarite

William D. Birch; ALLAN PRING; D. J. M. BEVAN

1994-01-01

59

Phosphoprotein staining for sodium dodecyl sulfate-polyacrylamide gel electrophoresis using fluorescent reagent morin hydrate.  

PubMed

A fluorescence-based stain with 3,5,7,2',4'-pentahydroxyflavone (morin hydrate, MH) was designed to stain phosphoproteins in one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Al(3+) was applied as a "fixed bridge," providing an efficient energy transfer channel between phosphoprotein and MH, to produce a strong fluorescent complex for the determination of phosphoprotein. As little as 62.5ng of ?-casein (7 or 8 phosphates) and ?-casein (5 phosphates), 125ng of ovalbumin (2 phosphates), and ?-casein (1 phosphate) could be visualized with a wide linear dynamic range. In comparison with conventional methods, MH stain is a time-saving method that takes just 90min. It also has good compatibility with routine protein stainings such as Coomassie Brilliant Blue R (CBBR) and SYPRO Ruby for total protein analysis. PMID:23274386

Wang, Xu; Hwang, Sun-Young; Cong, Wei-Tao; Jin, Li-Tai; Choi, Jung-Kap

2013-04-01

60

Hydration kinetics of CA{sub 2} and CA-Investigations performed on a synthetic calcium aluminate cement  

SciTech Connect

Much is already known about the hydration of monocalcium aluminate (CA) in calcium aluminate cements (CACs). CA{sub 2} is known to be weakly hydraulic. Therefore, the hydration kinetics of CA{sub 2} were not of as great interest as those of the hydration of CAC. We were able to show that the hydration of CA{sub 2} begins as soon as the hydration rate of CA has reached its maximum and the first precipitation of C{sub 2}AH{sub 8} has started. The hydration of different CA/CA{sub 2} ratios was analyzed by the G-factor quantification. The individual contributions of the phases CA and CA{sub 2} to the heat flow were calculated based on the amounts dissolved by applying thermodynamic data. The heat flow as calculated from XRD data was then compared with the measured heat flow. It obtained a good consistency between the two. The very pronounced influence of CA{sub 2} during hydration of CAC can be clearly demonstrated.

Klaus, S.R., E-mail: klaus@geol.uni-erlangen.de; Neubauer, J., E-mail: juergen.neubauer@gzn.uni-erlangen.de; Goetz-Neunhoeffer, F., E-mail: friedlinde.goetz@gzn.uni-erlangen.de

2013-01-15

61

Incorporation of aluminum in the calcium silicate hydrate (C-S-H) of hydrated portland cements: a high-field 27Al and 29Si MAS NMR investigation.  

PubMed

The calcium silicate hydrate (C-S-H) phase resulting from hydration of a white Portland cement (wPc) in water and in a 0.3 M NaAlO(2) solution has been investigated at 14 and 11 hydration times, respectively, ranging from 6 h to 1 year by (27)Al and (29)Si MAS NMR spectroscopy. (27)Al MAS NMR spectra recorded at 7.05, 9.39, 14.09, and 21.15 T have allowed a determination of the (27)Al isotropic chemical shift (delta(iso)) and quadrupolar product parameter (P(Q) = C(Q)) for tetrahedrally coordinated Al incorporated in the C-S-H phase and for a pentacoordinated Al site. The latter site may originate from Al(3+) substituting for Ca(2+) ions situated in the interlayers of the C-S-H structure. The spectral region for octahedrally coordinated Al displays resonances from ettringite, monosulfate, and a third aluminate hydrate phase (delta(iso) = 5.0 ppm and P(Q) = 1.20 MHz). The latter phase is tentatively ascribed to a less-crystalline aluminate gel or calcium aluminate hydrate. The tetrahedral Al incorporated in the C-S-H phase has been quantitatively determined from (27)Al MAS spectra at 14.09 T and indirectly observed quantitatively in (29)Si MAS NMR spectra by the Q(2)(1Al) resonance at -81.0 ppm. A linear correlation is observed between the (29)Si MAS NMR intensity for the Q(2)(1Al) resonance and the quantity of Al incorporated in the C-S-H phase from (27)Al MAS NMR for the different samples of hydrated wPc. This correlation supports the assignment of the resonance at delta(iso)((29)Si) = -81.0 ppm to a Q(2)(1Al) site in the C-S-H phase and the assignment of the (27)Al resonance at delta(iso)((27)Al) = 74.6 ppm, characterized by P(Q)((27)Al) = 4.5 MHz, to tetrahedrally coordinated Al in the C-S-H. Finally, it is shown that hydration of wPc in a NaAlO(2) solution results in a C-S-H phase with a longer mean chain length of SiO(4) tetrahedra and an increased quantity of Al incorporated in the chain structure as compared to the C-S-H phase resulting from hydration of wPc in water. PMID:12665361

Andersen, Morten Daugaard; Jakobsen, Hans J; Skibsted, Jørgen

2003-04-01

62

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

63

Distribution of magnesium, calcium, sodium and potassium in tissues of the hip joint.  

PubMed

The aim of this study was to determine the distribution of magnesium, calcium, sodium and potassium in tissues of the hip joint and to look for any correlations between these minerals. The study was performed using hip joint samples taken from people living in the Upper Silesian Industrial Region in Poland. Ninety one subjects, 66 women and 25 men, were included in this study. The samples were obtained intra-operatively during hip joint replacement procedures. The concentrations of magnesium, calcium, sodium and potassium were measured by atomic absorption spectrophotometry (AAS). Our results showed that these minerals are most abundant in the cancellous bone of the hip joint. They were found next more abundantly in the cortical bone and the cancellous bone from the intertrochanteric area. Levels of magnesium, potassium and calcium were lower in articular cartilage compared with other parts of the hip joint; however, sodium levels were at their highest in this tissue. The lowest levels of these minerals were found in the articular capsule. Those patients with fractures of the femoral neck had lower levels of magnesium, potassium, and calcium, but higher levels of sodium compared with the group with degenerative changes. We can also confirm that in the population studied, calcium levels in cancellous bone of the head of the femur decreased with age. PMID:24153328

Brodziak-Dopiera?a, Barbara; Kwapuli?ski, Jerzy; Sobczyk, Krzysztof; Wiechu?a, Danuta

2013-01-01

64

Formation of hydroxyapatite in soils using calcium citrate and sodium phosphate for control of strontium migration.  

SciTech Connect

{sup 90}Sr contamination is a major problem at several U.S. sites. At some sites, {sup 90}Sr has migrated deep underground making site remediation difficult. In this paper, we describe a novel method for precipitation of hydroxyapatite, a strong sorbent for {sup 90}Sr, in soil. The method is based on mixing a solution of calcium citrate and sodium phosphate in soil. As the indigenous soil microorganisms mineralize the citrate, the calcium is released and forms hydroxyapatite. Soil, taken from the Albuquerque desert, was treated with a sodium phosphate solution or a sodium phosphate/calcium citrate solution. TEM and EDS were used to identify hydroxyapatite with CO{sub 3}{sup 2-} substitutions, with a formula of (Ca{sub 4.8}Na{sub 0.2})[(PO{sub 4}){sub 2.8}(CO{sub 3}){sub 0.2}](OH), in the soil treated with the sodium phosphate/calcium citrate solution. Untreated and treated soils were used in batch sorption experiments for Sr uptake. Average Sr uptake was 19.5, 77.0 and 94.7% for the untreated soil, soil treated with sodium phosphate, and soil with apatite, respectively. In desorption experiments, the untreated soil, phosphate treated soil and apatite treated soil released an average of 34.2, 28.8 and 4.8% respectively. The results indicate the potential of forming apatite in soil using soluble reagents for retardation of radionuclide migration.

Moore, Robert Charles; Hasan, Ahmed Ali Mohamed; Sanchez, Charles Anthony (University of Arizona, Yuma, AZ); Zhao, Hongting; Salas, Fred Manuel; Hasan, Mahmoud A. (Egyptian Atomic Energy Authority, Cairo, Egypt); Holt, Kathleen Caroline

2003-08-01

65

Dietary Sodium Effects on Bone Loss and Calcium Metabolism During Bed Rest  

NASA Technical Reports Server (NTRS)

The acceleration of age-related bone loss is one of the most detrimental effects of space flight. The ability to understand and counteract this loss will be critical for crew health and safety during and after long-duration missions. Studies in healthy ambulatory individuals have linked high salt (sodium) diets, hypercalciuria, and increased renal stone risk. Dietary salt may modulate bone loss through changes in calcium metabolism and the calcium endocrine system. The research proposed here will determine the role of dietary salt in the loss of bone during simulated space flight. Calcium metabolism will be determined through calcium kinetics studies, endocrine and biochemical measurements; and estimates of the mass, distribution and mechanical properties of bone, in subjects fed low (100 mmol sodium/day) or high (250 mmol sodium/day) levels of dietary salt during 28 days of headdown tilt bedrest. This research addresses the role of dietary salt in the loss of bone and calcium in space flight, and integrates the changes in calcium metabolism with those occurring in other physiologic systems. These data will be critical for both countermeasure development, and in determination of nutritional requirements for extended-duration space flight. The potential countermeasures resulting from this research will reduce health risks due to acceleration of age-related osteoporosis and increased risk of renal stone formation..

Smith, Scott M.; Arnaud, Sara B.; Abrams, Steven A.; Paloski, W. H. (Technical Monitor)

2000-01-01

66

Molecular model for sodium conductance and calcium transport in the squid axon.  

PubMed

A molecular and biochemically plausible model for the excitation process of the sodium pore is suggested. From basic arguments it is concluded that the sodium pore exists in at least three states: the resting state, the sodium conducting state, and the refractory state. They are connected to form a cyclic process. A specification of the different states is given. It is suggested that inactivation of the sodium pore results from a conformational change, which is caused by the transport of a calcium ion through the membrane. The transport carrier is the sodium pore. This assumption can explain the observed calcium influx during stimulation, and the effect of Ca on the rate of inactivation and on the rate, at which sodium conductance shuts off upon repolarization. It cannot give a quantitative explanation for the effect of Ca on the rate of rise, peak sodium conductance, and steady state inactivation. These asects are successfully described by the surface potential hypothesis, which has been published recently. It is concluded, that a combination of both theories gives a rather complete description of the sodium pore. The Ca transport model is discussed quantitatively and in great detail. PMID:731135

Siep, E

1978-03-01

67

Vapour pressure of water over saturated solutions of tartaric acid, sodium hydrogen tartrate, sodium tartrate, potassium tartrate, calcium tartrate, barium tartrate, citric acid, disodium hydrogen citrate, sodium citrate, and potassium citrate at temperatures from 277 K to 317 K  

Microsoft Academic Search

Vapour pressures of saturated aqueous solutions of tartaric acid, sodium hydrogen tartrate, sodium tartrate, potassium tartrate, calcium tartrate, barium tartrate, citric acid, disodium hydrogen citrate, sodium citrate, and potassium citrate were determined in the temperature range (277 to 317)K using an electronic hygrometer. Only for tartaric acid, sodium tartrate, potassium tartrate and citric acid was it possible to compare the

Emanuel Manzurola; Alexander Apelblat

2003-01-01

68

Effect of Sodium Fluoride on Calcium Metabolism of Human Beings  

Microsoft Academic Search

ALTHOUGH bones of human subjects become abnormally dense after several years of industrial exposure to fluorides1,2, no work on the effect of fluoride on calcium balance of human beings has been carried out. Roholm1 and others2 have shown that the severity of skeletal changes is correlated approximately with the extent and duration of exposure to fluoride : moderate exposure resulting

Clayton Rich; John Ensinck

1961-01-01

69

Ion-exchange characteristics of sodium-calcium-silicate glass: Calculation from mode spectra  

NASA Astrophysics Data System (ADS)

The characteristics of silver-sodium ion exchange in standard commercial sodium-calcium-silicate glass are investigated using mode spectroscopy. The activation energy of the process, the silver-sodium interdiffusion coefficient, and the dependence of the maximal modulation of the refractive index on the silver nitrate concentration in the experimental salt bath are determined. The data set presented here makes it possible to specify the conditions for the formation of ion-exchange optical structures with preset parameters based on the glasses studied here.

Zhurikhina, V. V.; Petrov, M. I.; Sokolov, K. S.; Shustova, O. V.

2010-10-01

70

Calcium phosphate-containing precipitate and the carcinogenicity of sodium salts in rats.  

PubMed

Sodium saccharin, ascorbate and other sodium salts fed at high doses to rats produce urinary bladder urothelial cytotoxicity with consequent regenerative hyperplasia. For sodium salts that have been tested, tumor activity is enhanced when administered either alone or after a brief exposure to a known genotoxic bladder carcinogen. These sodium salts alter urinary composition of rats resulting in formation of an amorphous precipitate. We examined the precipitate to ascertain its composition and further delineate the basis for its formation in rat urine. Using scanning electron microscopy with attached X-ray energy dispersive spectroscopy, the principal elements present were calcium, phosphorus, minor amounts of silicon and sulfur. Smaller elements are not detectable by this method. Infrared analyses demonstrated that calcium phosphate was in the tribasic form and silicon was most likely in the form of silica. Small amounts of saccharin were present in the precipitate from rats fed sodium saccharin (<5%), but ascorbate was not detectable in the precipitate from rats fed similar doses of sodium ascorbate. Large amounts of urea and mucopolysaccharide, apparently chondroitin sulfate, were detected in the precipitate by infrared analysis. Chemical analyses confirmed the presence of large amounts of calcium phosphate with variably small amounts of magnesium, possibly present as magnesium ammonium phosphate crystals, present in urine even in controls. Small amounts of protein, including albumin and alpha(2u)-globulin, were also detected (<5% of the precipitate). Calcium phosphate is an essential ingredient of the medium for tissue culture of epithelial cells, but when present at high concentrations (>5 mM) it precipitates and becomes cytotoxic. The nature of the precipitate reflects the unique composition of rat urine and helps to explain the basis for the species specificity of the cytotoxic and proliferative effects of high doses of these sodium salts. PMID:10753216

Cohen, S M; Arnold, L L; Cano, M; Ito, M; Garland, E M; Shaw, R A

2000-04-01

71

27Al and 29Si solid-state NMR characterization of calcium-aluminosilicate-hydrate.  

PubMed

Calcium silicate hydrate (C-S-H) is the main constituent of hydrated cement paste and determines its cohesive properties. Because of the environmental impact of cement industry, it is more and more common to replace a part of the clinker in cement by secondary cementitious materials (SCMs). These SCMs are generally alumina-rich and as a consequence some aluminum is incorporated into the C-S-H. This may have consequences on the cohesion and durability of the material, and it is thus of importance to know the amount and the location of Al in C-S-H and what the parameters are that control these features. The present paper reports the (29)Si and (27)Al MAS NMR analyses of well-characterized C-A-S-H samples (C-S-H containing Al). These samples were synthesized using an original procedure that successfully leads to pure C-A-S-H of controlled compositions in equilibrium with well-characterized solutions. The (27)Al MAS NMR spectra were quantitatively interpreted assuming a tobermorite-like structure for C-A-S-H to determine the aluminum location in this structure. For this purpose, an in-house written software was used which allows decomposing several spectra simultaneously using the same constrained spectral parameters for each resonance but with variable intensities. The hypothesis on the aluminum location in the C-A-S-H structure determines the proportion of each silicon site. Therefore, from the (27)Al NMR quantitative results and the chemical composition of each sample, the intensity of each resonance line in the (29)Si spectra was set. The agreement between the experimental and calculated (29)Si MAS NMR spectra corroborates the assumed C-A-S-H structure and the proposed Al incorporation mechanism. The consistency between the results obtained for all compositions provides another means to assess the assumptions on the C-A-S-H structure. It is found that Al substitutes Si mainly in bridging positions and moderately in pairing positions in some conditions. Al in pairing site is observed only for Ca/(Si+Al) ratios greater than 0.95 (equivalent to 4 mmol.L(-1) of calcium hydroxide). Finally, the results suggest that penta and hexa-coordinated aluminum are adsorbed on the sides of the C-A-S-H particles. PMID:22277014

Pardal, Xiaolin; Brunet, Francine; Charpentier, Thibault; Pochard, Isabelle; Nonat, André

2012-02-01

72

Synaptosomal calcium influx is activated by sodium fluoride  

Microsoft Academic Search

Neuronal calcium channels can be modulated by changes in membrane potential or by activation of channel-associated receptors. The latter may be modulated by guanine nucleotide binding proteins. NaF, which activates guanine nucleotide binding proteins, caused a large stimulation of ⁴⁵Ca\\/sup 2 +\\/ uptake by synaptosomes prepared from rat brain. Stimulation of ⁴⁵Ca\\/sup 2 +\\/ influx by NaF (i) was apparent

R. S. Jope; K. M. Lally

1988-01-01

73

Relevance of rheological properties of sodium alginate in solution to calcium alginate gel properties.  

PubMed

The purpose of this study is to determine whether sodium alginate solutions' rheological parameters are meaningful relative to sodium alginate's use in the formulation of calcium alginate gels. Calcium alginate gels were prepared from six different grades of sodium alginate (FMC Biopolymer), one of which was available in ten batches. Cylindrical gel samples were prepared from each of the gels and subjected to compression to fracture on an Instron Universal Testing Machine, equipped with a 1-kN load cell, at a cross-head speed of 120 mm/min. Among the grades with similar % G, (grades 1, 3, and 4), there is a significant correlation between deformation work (L(E)) and apparent viscosity (?(app)). However, the results for the partial correlation analysis for all six grades of sodium alginate show that L(E) is significantly correlated with % G, but not with the rheological properties of the sodium alginate solutions. Studies of the ten batches of one grade of sodium alginate show that ?(app) of their solutions did not correlate with L(E) while tan ? was significantly, but minimally, correlated to L(E). These results suggest that other factors--polydispersity and the randomness of guluronic acid sequencing--are likely to influence the mechanical properties of the resultant gels. In summary, the rheological properties of solutions for different grades of sodium alginate are not indicative of the resultant gel properties. Inter-batch differences in the rheological behavior for one specific grade of sodium alginate were insufficient to predict the corresponding calcium alginate gel's mechanical properties. PMID:21437788

Fu, Shao; Thacker, Ankur; Sperger, Diana M; Boni, Riccardo L; Buckner, Ira S; Velankar, Sachin; Munson, Eric J; Block, Lawrence H

2011-06-01

74

Calcium-aluminum-silicate-hydrate "cement" phases and rare Ca-zeolite association at Colle Fabbri, Central Italy  

NASA Astrophysics Data System (ADS)

Very high temperature, Ca-rich alkaline magma intruded an argillite formation at Colle Fabbri, Central Italy, producing cordierite-tridymite metamorphism in the country rocks. An intense Ba-rich sulphate-carbonate-alkaline hydrothermal plume produced a zone of mineralization several meters thick around the igneous body. Reaction of hydrothermal fluids with country rocks formed calcium-silicate-hydrate (CSH), i.e., tobermorite-afwillite-jennite; calcium-aluminum-silicate-hydrate (CASH) — "cement" phases - i.e., thaumasite, strätlingite and an ettringite-like phase and several different species of zeolites: chabazite-Ca, willhendersonite, gismon-dine, three phases bearing Ca with the same or perhaps lower symmetry of phillipsite-Ca, levyne-Ca and the Ca-rich analogue of merlinoite. In addition, apophyllite-(KF) and/or apophyllite-(KOH), Ca-Ba-carbonates, portlandite and sulphates were present. A new polymorph from the pyrrhotite group, containing three layers of sphalerite-type structure in the unit cell, is reported for the first time. Such a complex association is unique. Most of these minerals are specifically related to hydration processes of: (1) pyrometamorphic metacarbonate/metapelitic rocks (natural analogues of cement clinkers); (2) mineralization between intrusive stocks and slates; and (3) high-calcium, alkaline igneous rocks such as melilitites and foidites as well as carbonatites. The Colle Fabbri outcrop offers an opportunity to study in situ complex crystalline overgrowth and specific crystal chemistry in mineral phases formed in igneous to hydrothermal conditions.

Stoppa, F.; Scordari, F.; Mesto, E.; Sharygin, V. V.; Bortolozzi, G.

2010-06-01

75

A clinical study of the effect of calcium sodium phosphosilicate on dentin hypersensitivity  

PubMed Central

Objective: Dentinal hypersensitivity is a commonly encountered problem with varied treatment options for its management. A large number of home use products have been tested and used for the management of dentinal hypersensitivity. This 8 week clinical trial investigates the temporal efficacy of commercially available calcium sodium phosphosilicate containing toothpaste in comparison to a potassium nitrate containing toothpaste. Methods: A total 20 subjects between the ages of 18 to 65 years were screened for a visual analogue score (VAS) for sensitivity of 5 or more by testing with a cold stimulus and randomly divided into test and positive control groups. Baseline sensitivity VAS scores to air evaporative stimulus were recorded for minimum two teeth. The subjects were prescribed respective dentifrices and revaluated for sensitivity scores at 2, 4 and 8 weeks. Results:The study demonstrated reduction in symptoms for all treatment groups from baseline to 2, 4 and 8 weeks. The calcium sodium phosphosilicate group showed a higher degree of effectiveness at reducing hypersensitivity to air evaporative stimulus at 2 weeks, than commercially available potassium nitrate. However, there was no significant difference in scores of subjects using the calcium sodium phosphosilicate toothpaste as compared to potassium nitrate at 4 weeks and 8 weeks. Conclusion: Calcium sodium phosphosilicate showed greater reduction in sensitivity compared to potassium nitrate at an earlier stage which is of high clinical value. However, based on the findings of the present study long term effects of calcium sodium phosphosilicate seem to be less promising than previously claimed. Key words:Dentinal desensitizing agents, dentinal hypersensitivity, toothpaste, pain measurement. PMID:24455046

Surve, Sai M.; Thakur, Srinath L.

2013-01-01

76

Structural basis for the transformation pathways of the sodium naproxen anhydrate-hydrate system  

PubMed Central

Crystal structures are presented for two dihydrate polymorphs (DH-I and DH-II) of the non-steroidal anti-inflammatory drug sodium (S)-naproxen. The structure of DH-I is determined from twinned single crystals obtained by solution crystallization. DH-II is obtained by solid-state routes, and its structure is derived using powder X-ray diffraction, solid-state 13C and 23Na MAS NMR, and molecular modelling. The validity of both structures is supported by dispersion-corrected density functional theory (DFT-D) calculations. The structures of DH-I and DH-II, and in particular their relationships to the monohydrate (MH) and anhydrate (AH) structures, provide a basis to rationalize the observed transformation pathways in the sodium (S)-naproxen anhydrate–hydrate system. All structures contain Na+/carboxylate/H2O sections, alternating with sections containing the naproxen molecules. The structure of DH-I is essentially identical to MH in the naproxen region, containing face-to-face arrangements of the naphthalene rings, whereas the structure of DH-II is comparable to AH in the naproxen region, containing edge-to-face arrangements of the naphthalene rings. This structural similarity permits topotactic transformation between AH and DH-II, and between MH and DH-I, but requires re-organization of the naproxen molecules for transformation between any other pair of structures. The topotactic pathways dominate at room temperature or below, while the non-topotactic pathways become active at higher temperatures. Thermochemical data for the dehydration processes are rationalized in the light of this new structural information. PMID:25295174

Bond, Andrew D.; Cornett, Claus; Larsen, Flemming H.; Qu, Haiyan; Raijada, Dhara; Rantanen, Jukka

2014-01-01

77

Structural basis for the transformation pathways of the sodium naproxen anhydrate-hydrate system.  

PubMed

Crystal structures are presented for two dihydrate polymorphs (DH-I and DH-II) of the non-steroidal anti-inflammatory drug sodium (S)-naproxen. The structure of DH-I is determined from twinned single crystals obtained by solution crystallization. DH-II is obtained by solid-state routes, and its structure is derived using powder X-ray diffraction, solid-state (13)C and (23)Na MAS NMR, and molecular modelling. The validity of both structures is supported by dispersion-corrected density functional theory (DFT-D) calculations. The structures of DH-I and DH-II, and in particular their relationships to the monohydrate (MH) and anhydrate (AH) structures, provide a basis to rationalize the observed transformation pathways in the sodium (S)-naproxen anhydrate-hydrate system. All structures contain Na(+)/carboxylate/H2O sections, alternating with sections containing the naproxen molecules. The structure of DH-I is essentially identical to MH in the naproxen region, containing face-to-face arrangements of the naphthalene rings, whereas the structure of DH-II is comparable to AH in the naproxen region, containing edge-to-face arrangements of the naphthalene rings. This structural similarity permits topotactic transformation between AH and DH-II, and between MH and DH-I, but requires re-organization of the naproxen molecules for transformation between any other pair of structures. The topotactic pathways dominate at room temperature or below, while the non-topotactic pathways become active at higher temperatures. Thermochemical data for the dehydration processes are rationalized in the light of this new structural information. PMID:25295174

Bond, Andrew D; Cornett, Claus; Larsen, Flemming H; Qu, Haiyan; Raijada, Dhara; Rantanen, Jukka

2014-09-01

78

Hydrothermal Formation Of Hemi-hydrate Calcium Sulfate Whiskers In The Presence Of Additives  

SciTech Connect

The influence of addictives on the hydrothermal formation of hemi-hydrate calcium sulfate (CaSO{sub 4{center_dot}}0.5H{sub 2}O) whiskers were discussed in this paper, using CaCl{sub 2} and Na{sub 2}SO{sub 4} as the reactants. The presence of NaCl, CaCl{sub 2} or Na{sub 2}SO{sub 4} increased the concentrations of Ca{sup 2+} and SO{sub 4}{sup 2-}, leading to the formation of CaSO{sub 4{center_dot}}0.5H{sub 2}O whiskers with aspect ratio lower than 50. The one dimensional growth of CaSO{sub 4{center_dot}}0.5H{sub 2}O whiskers was enhanced in water with no additives owing to the low super-saturation, leading to the formation of uniform whiskers with a length of 200-2000 {mu}m and an aspect ratio higher than 100.

Luo, K. B. [Department of Chemical Engineering, Kunming University of Science and Technology, Kunming 650224 (China); Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China); Li, C. M.; Li, H. P.; Ning, P. [Department of Chemical Engineering, Kunming University of Science and Technology, Kunming 650224 (China); Xiang, L. [Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China)

2010-11-24

79

Non-ideal solid solution aqueous solution modeling of synthetic calcium silicate hydrate  

SciTech Connect

New data relevant to calcium silicate hydrate (C-S-H) gels prepared at room temperature have been obtained over a time period of up to 112 weeks. X-ray diffraction (XRD) indicates equilibrium was attained after 64 weeks. Coupled with fourier transform infrared (FT-IR) spectroscopy, a phase change in C-S-H gel at Ca/Si {approx} 1.0 was identified and the occurrence of portlandite as a distinct phase for Ca/Si > 1.64. The incongruent dissolution of C-S-H gel was modeled as a non-ideal solid solution aqueous solution (SSAS) between the end-member components CaH{sub 2}SiO{sub 4} (CSH) and Ca(OH){sub 2} (CH) using equations defining the solidus and solutus curves on a Lippmann phase diagram. Despite being semi-empirical, the model provides a reasonable and consistent fit to the solubility data and can therefore be used to describe the incongruent dissolution of C-S-H gels with compositions Ca/Si {>=} 1.0.

Walker, Colin S. [Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ (United Kingdom)]. E-mail: c.walker@nhm.ac.uk; Savage, David [Quintessa Limited, Dalton House, Newtown Road, Henley-on-Thames, RG9 1HG (United Kingdom); Tyrer, Mark [Department of Materials, Imperial College, South Kensington, London, SW7 2AZ (United Kingdom); Ragnarsdottir, K. Vala [Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ (United Kingdom)

2007-04-15

80

Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: cement hydration, strength development and volume stability.  

PubMed

The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5 mol/L ZnCl(2) mixing solution was characterized over one year as a function of the gypsum content of the binder and the thermal history of the material. Blending the CSA clinker with 20% gypsum enabled its rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrates assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, strätlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the gypsum content of the binder), and possibly C-(A)-S-H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes. PMID:21889260

Berger, Stéphane; Cau Dit Coumes, Céline; Le Bescop, Patrick; Damidot, Denis

2011-10-30

81

Effect of Sodium Chloride on Hydration Structures of PMEA and P(MPC-r-BMA).  

PubMed

The hydration structures of two different types of biomaterials, i.e., poly(2-methoxyethyl acrylate) (PMEA) and a random copolymer of 2-methacryloyloxyethyl phosphorylcholine and n-butyl methacrylate (P(MPC-r-BMA)), were investigated by means of attenuated total reflection infrared (ATR-IR) spectroscopy. The effects of the addition of sodium chloride to liquid water in contact with the surfaces of the polymer films were examined. The neutral polymer of PMEA was easily dehydrated by NaCl addition, whereas the zwitterionic polymer of P(MPC-r-BMA) was hardly dehydrated. More specifically, nonfreezing water having a strong interaction with the PMEA chain and freezing bound water having an intermediate interaction were hardly dehydrated by contacting with normal saline solution, whereas freezing water having a weak interaction with the PMEA chain was readily dehydrated. In contrast, freezing water in P(MPC-r-BMA) is exchanged for the saline solution contacting with the material surface without dehydration. PMID:25133748

Morita, Shigeaki; Tanaka, Masaru

2014-09-01

82

Effect of potassium sodium tartrate and sodium citrate on the preparation of -calcium sulfate hemihydrate from flue gas desulfurization gypsum in a concentrated electrolyte solution  

Microsoft Academic Search

Flue gas desulfurization (FGD) gypsum mainly composed of calcium sulfate dihydrate (DH) was used as a raw material to obtain alpha-calcium sulfate hemihydrate (-HH) through dehydration in a Ca-Mg-K-Cl-solution medium at 95{sup o}C under atmospheric pressure. The effects of potassium sodium tartrate and sodium citrate on the preparation of alpha-HH in the electrolyte solution were investigated. The results revealed that

Zhuoxian Shen; Baohong Guan; Hailu Fu; Liuchun Yang

2009-01-01

83

NALCN Ion Channels Have Alternative Selectivity Filters Resembling Calcium Channels or Sodium Channels  

PubMed Central

NALCN is a member of the family of ion channels with four homologous, repeat domains that include voltage-gated calcium and sodium channels. NALCN is a highly conserved gene from simple, extant multicellular organisms without nervous systems such as sponges and placozoans and mostly remains a single gene compared to the calcium and sodium channels which diversified into twenty genes in humans. The single NALCN gene has alternatively-spliced exons at exons 15 or exon 31 that splices in novel selectivity filter residues that resemble calcium channels (EEEE) or sodium channels (EKEE or EEKE). NALCN channels with alternative calcium, (EEEE) and sodium, (EKEE or EEKE) -selective pores are conserved in simple bilaterally symmetrical animals like flatworms to non-chordate deuterostomes. The single NALCN gene is limited as a sodium channel with a lysine (K)-containing pore in vertebrates, but originally NALCN was a calcium-like channel, and evolved to operate as both a calcium channel and sodium channel for different roles in many invertebrates. Expression patterns of NALCN-EKEE in pond snail, Lymnaea stagnalis suggest roles for NALCN in secretion, with an abundant expression in brain, and an up-regulation in secretory organs of sexually-mature adults such as albumen gland and prostate. NALCN-EEEE is equally abundant as NALCN-EKEE in snails, but is greater expressed in heart and other muscle tissue, and 50% less expressed in the brain than NALCN-EKEE. Transfected snail NALCN-EEEE and NALCN-EKEE channel isoforms express in HEK-293T cells. We were not able to distinguish potential NALCN currents from background, non-selective leak conductances in HEK293T cells. Native leak currents without expressing NALCN genes in HEK-293T cells are NMDG+ impermeant and blockable with 10 µM Gd3+ ions and are indistinguishable from the hallmark currents ascribed to mammalian NALCN currents expressed in vitro by Lu et al. in Cell. 2007 Apr 20;129(2):371-83. PMID:23383067

Senatore, Adriano; Monteil, Arnaud; van Minnen, Jan; Smit, August B.; Spafford, J. David

2013-01-01

84

NALCN ion channels have alternative selectivity filters resembling calcium channels or sodium channels.  

PubMed

NALCN is a member of the family of ion channels with four homologous, repeat domains that include voltage-gated calcium and sodium channels. NALCN is a highly conserved gene from simple, extant multicellular organisms without nervous systems such as sponges and placozoans and mostly remains a single gene compared to the calcium and sodium channels which diversified into twenty genes in humans. The single NALCN gene has alternatively-spliced exons at exons 15 or exon 31 that splices in novel selectivity filter residues that resemble calcium channels (EEEE) or sodium channels (EKEE or EEKE). NALCN channels with alternative calcium, (EEEE) and sodium, (EKEE or EEKE) -selective pores are conserved in simple bilaterally symmetrical animals like flatworms to non-chordate deuterostomes. The single NALCN gene is limited as a sodium channel with a lysine (K)-containing pore in vertebrates, but originally NALCN was a calcium-like channel, and evolved to operate as both a calcium channel and sodium channel for different roles in many invertebrates. Expression patterns of NALCN-EKEE in pond snail, Lymnaea stagnalis suggest roles for NALCN in secretion, with an abundant expression in brain, and an up-regulation in secretory organs of sexually-mature adults such as albumen gland and prostate. NALCN-EEEE is equally abundant as NALCN-EKEE in snails, but is greater expressed in heart and other muscle tissue, and 50% less expressed in the brain than NALCN-EKEE. Transfected snail NALCN-EEEE and NALCN-EKEE channel isoforms express in HEK-293T cells. We were not able to distinguish potential NALCN currents from background, non-selective leak conductances in HEK293T cells. Native leak currents without expressing NALCN genes in HEK-293T cells are NMDG(+) impermeant and blockable with 10 µM Gd(3+) ions and are indistinguishable from the hallmark currents ascribed to mammalian NALCN currents expressed in vitro by Lu et al. in Cell. 2007 Apr 20;129(2):371-83. PMID:23383067

Senatore, Adriano; Monteil, Arnaud; van Minnen, Jan; Smit, August B; Spafford, J David

2013-01-01

85

EFFECTS OF SODIUM AND CALCIUM IN LIGNITE ON THE PERFORMANCE OF ACTIVATED CARBON PRODUCTS  

SciTech Connect

Powdered activated carbon (PAC) has traditionally been used by the water treatment industry for the removal of compounds contributing to taste and odor problems. PAC also has the potential to remove naturally occurring organic matter (NOM) from raw waters prior to disinfection, thus controlling the formation of regulated disinfection by-products (DBPs). Many small water systems are currently using PAC for taste and odor control and have the potential to use PAC for controlling DBPs. The Energy & Environmental Research Center has been working on the development of a PAC product to remove NOM from surface water supplies to prevent the formation of carcinogenic DBPs during chlorination. During previous studies, the sodium and calcium content of the lignites showed a significant effect on the sorption capacity of the activated carbon product. As much as a 130% increase in the humic acid sorption capacity of a PAC produced from a high-sodium-content lignite was observed. During this study, activated carbons were prepared from three coals representing high-sodium, low-sodium--low-calcium, and high-calcium compositions in two steps, an initial char formation followed by mild activation with steam to avoid excessive burnout. This set of carbons was characterized with respect to physical and chemical properties. The BET (Brunauer-Emmett-Teller) nitrogen adsorption isotherms gave relatively low surface areas (ranging from 245 to 370 m{sup 2}/g). The lowest-BET area was obtained for the high-sodium carbon, which can be attributed to enlargement of micropores as a result of sodium-catalyzed gasification reaction of the carbon structure. This hypothesis is consistent with the scanning electron microscopy microprobe analyses, which show that in both the coal and the activated carbon from this coal, the sodium is distributed over both the carbon structure and the mineral particles. Thus it is initially associated with carboxylate groups on the coal and then as sodium oxide or other active form in close proximity to the carbon and is, therefore, readily available for catalysis of gasification. Humate adsorption isotherms for the high-sodium carbon gave superior results as defined by very high intercepts in modified Freundlich plots. Thus the high-sodium carbon will be considerably more effective in reducing the humate concentration for a given carbon dosage. Analysis of adsorption isotherms indicated the results were consistent with the hypothesis that only the larger pores are effective for binding the large humate molecules, and that the larger pores developed during activation of the high-sodium char give the appropriate macropore structure for humate binding. Toluene adsorption isotherms indicated that the high-calcium carbon and the low-calcium, low-sodium carbon were superior to the high-sodium carbon for small molecules in aqueous solution, but not as effective as a Calgon F-400 commercial activated carbon. This is consistent with the low-BET surface areas observed for the lignite-derived carbons, and thus there are a lower number of sites for binding the smaller toluene molecule in these carbons.

Edwin S. Olson; Kurt E. Eylands; Daniel J. Stepan

2001-12-01

86

Amorphous calcium silicate hydrate/block copolymer hybrid nanoparticles: synthesis and application as drug carriers.  

PubMed

Amorphous calcium silicate hydrate (CSH)/block copolymer monomethoxy(polyethyleneglycol)-block-poly(lactide-co-glycolide) (mPEG-PLGA) (CSHP) hybrid nanoparticles have been prepared in aqueous solution via a facile coprecipitation route at room temperature. The block copolymer mPEG-PLGA micelles in aqueous solution serve as the templates, and the CSH links to the micelles by hydrogen bonding between the silanol groups and the hydrophilic mPEG segments. The obtained core/shell hybrid nanoparticles can be transformed to solid hybrid nanoparticles by washing with water. The drug ibuprofen (IBU) loading capacity of the CSHP hybrid nanoparticles is ultrahigh (~1.9 g drug per g carrier), and the IBU loading efficiency can reach as high as ~100%. The drug release of loaded IBU in the CSHP hybrid nanoparticles has been investigated in simulated body fluid (SBF). The loaded IBU drug in CSHP hybrid nanoparticles can release in SBF for a long period of time (about 300 h), during which the CSHP nanocarrier is completely transformed to hydroxyapatite, exhibiting a good bioactivity. The IBU drug release profile can be interpreted by the Higuchi model. The loading capacity for the anticancer drug docetaxel (DTX) in the CSHP hybrid nanoparticles is about 82 mg g(-1). More importantly, the release of the loaded DTX in phosphate buffer saline (PBS) at pH 5.5 is obviously faster than that at pH 7.4, which is promising for the application in cancer therapy. Human gastric carcinoma (SGC-7901) cells can be effectively killed in the presence of the DTX-loaded CSHP hybrid nanoparticles at appropriate concentrations. Thus, the CSHP hybrid nanoparticles are promising nanocarriers in drug delivery. Furthermore, the hemoglobin (Hb) loading capacity of CSHP hybrid nanoparticles can achieve an utrahigh value of 995 mg g(-1), suggesting that the as-prepared CSHP hybrid nanoparticles are excellent protein adsorbents. PMID:23511873

Wu, Jin; Zhu, Ying-Jie; Chen, Feng; Zhao, Xin-Yu; Zhao, Jing; Qi, Chao

2013-05-21

87

Hydration and strength development of binder based on high-calcium oil shale fly ash  

Microsoft Academic Search

The properties of high-calcium oil shale fly ash and low-calcium coal fly ash, which are produced in Israeli power stations, were investigated. High-calcium oil shale fly ash was found to contain a great amount of CaOfree and SO3 in the form of lime and anhydrite. Mixtures of high-calcium oil shale fly ash and low-calcium coal fly ash, termed fly ash

C Freidin

1998-01-01

88

Calcium channel characteristics conferred on the sodium channel by single mutations  

Microsoft Academic Search

THE sodium channel, one of the family of structurally homologous voltage-gated ion channels1, differs from other members, such as the calcium and the potassium channels, in its high selectivity for Na+. This selectivity presumably reflects a distinct structure of its ion-conducting pore. We have recently identified two clusters of predominantly negatively charged amino-acid residues, located at equivalent positions in the

Stefan H. Heinemann; Heinrich Terlau; Walter Stühmer; Keiji Imoto; Shosaku Numa

1992-01-01

89

Kinetics of HCl reactions with calcium and sodium sorbents for IGCC fuel gas cleaning  

Microsoft Academic Search

Experiments for HCl sorption by calcium and sodium sorbents have been carried out with simulated gases of compositions typical for “air-blown” and “oxygen-blown” IGCC fuel gases. The concentration of CO2 affects the behaviour of HCl sorption by Ca-sorbents but does not influence the performance of Na-sorbents in the temperature range 300–600°C. The sorbent particle size has a slight effect on

J. H. A. Kiel; A. Bos; H. Den Uil

1996-01-01

90

DIFFERENTIAL MEMBRANOLYTIC EFFECTS OF MICROCRYSTALLINE SODIUM URATE AND CALCIUM PYROPHOSPHATE DIHYDRATE  

PubMed Central

Microcrystals of sodium urate produced direct lysis of erythrocyte membranes, as had been described previously for silica. Calcium pyrophosphate crystals induced modest erythrocyte hemolysis, also, and time-course experiments showed a markedly different reaction curve from those produced by silica and urate. Polyvinylpyridine-N-oxide, a strong hydrogen acceptor, was bound from solution to urate and silica, but not to calcium pyrophosphate crystals; this compound effectively blocked urate and silica, but not calcium pyrophosphate or control hemolysis. Dextran and heparin inhibited urate-but not silica-induced hemolysis. If erythrocyte and lysosome membranes react similarly to these particles, then the absence of phagosomes in gouty synovial fluid leukocytes, and the presence of these structures in pseudogout, may be explained. PMID:4321912

Wallingford, Walter R.; McCarty, Daniel J.

1971-01-01

91

Hydration sequence of swelling clays: evolutions of specific surface area and hydration energy.  

PubMed

In order to identify the key steps and the driving force for the hydration process of swelling clays, the water adsorption isotherms and enthalpies were measured on monoionic montmorillonite samples saturated with alkali or calcium ions, and on bi-ionic samples saturated with a sodium-calcium mixture. The specific surface area evolution along the hydration process was determined using a recent interpretation of the experimental adsorption isotherms of swelling solids. Results are interpreted in structural terms. Compared with additional data from sample-controlled thermal analysis (SCTA), the results confirm experimentally that the hydration of Li- and Na-montmorillonite is mainly a cation-controlled process, in contrast with the hydration of Cs samples in which the cation contribution to hydration is negligible, as we have already demonstrated using electrostatic calculations or conductivity measurements. PMID:19303602

Salles, Fabrice; Douillard, Jean-Marc; Denoyel, Renaud; Bildstein, Olivier; Jullien, Michel; Beurroies, Isabelle; Van Damme, Henri

2009-05-15

92

Comparative analysis of calcium gluconate and sodium gluconate techniques for the production of gluconic acid by Aspergillus niger  

Microsoft Academic Search

Sodium gluconate and calcium gluconate methods are important techniques available for gluconic acid fermentation. The comparative analysis of these fermentations has been addressed using Aspergillus niger. The techniques are equally influenced by the spores age in slant growth, inoculum level in germination and production media, different levels of Fe, Cu, Zn and Mn. Sodium gluconate method is promising with respect

D. Subba Rao; T. Panda

1993-01-01

93

The characterization of hardened alkali-activated blast-furnace slag pastes and the nature of the calcium silicate hydrate (CSH) phase  

Microsoft Academic Search

Calcium silicate hydrate (C-S-H) gel is the principal binding phase in hardened OPC pastes and concretes, and also when the OPC has been partially replaced by pozzolanic by-products such as ground granulated blast-furnace slag (GGBFS) and pulverized fuel ash. The C-S-H gels present in commercial blast-furnace slag and synthetic-slag glass pastes produced by hydrating with 5M KOH solution have been

I. G. Richardson; A. R. Brough; G. W. Groves; C. M. Dobson

1994-01-01

94

Energetics of discrete selectivity bands and mutation-induced transitions in the calcium-sodium ion channels family.  

PubMed

We use Brownian dynamics (BD) simulations to study the ionic conduction and valence selectivity of a generic electrostatic model of a biological ion channel as functions of the fixed charge Q(f) at its selectivity filter. We are thus able to reconcile the discrete calcium conduction bands recently revealed in our BD simulations, M0 (Q(f)=1e), M1 (3e), M2 (5e), with a set of sodium conduction bands L0 (0.5e), L1 (1.5e), thereby obtaining a completed pattern of conduction and selectivity bands vs Q(f) for the sodium-calcium channels family. An increase of Q(f) leads to an increase of calcium selectivity: L0 (sodium-selective, nonblocking channel) ? M0 (nonselective channel) ? L1 (sodium-selective channel with divalent block) ? M1 (calcium-selective channel exhibiting the anomalous mole fraction effect). We create a consistent identification scheme where the L0 band is putatively identified with the eukaryotic sodium channel The scheme created is able to account for the experimentally observed mutation-induced transformations between nonselective channels, sodium-selective channels, and calcium-selective channels, which we interpret as transitions between different rows of the identification table. By considering the potential energy changes during permeation, we show explicitly that the multi-ion conduction bands of calcium and sodium channels arise as the result of resonant barrierless conduction. The pattern of periodic conduction bands is explained on the basis of sequential neutralization taking account of self-energy, as Q(f)(z,i)=ze(1/2+i), where i is the order of the band and z is the valence of the ion. Our results confirm the crucial influence of electrostatic interactions on conduction and on the Ca(2+)/Na(+) valence selectivity of calcium and sodium ion channels. The model and results could be also applicable to biomimetic nanopores with charged walls. PMID:24329301

Kaufman, I; Luchinsky, D G; Tindjong, R; McClintock, P V E; Eisenberg, R S

2013-11-01

95

Human water, sodium, and calcium regulation during space flight and exercise  

NASA Astrophysics Data System (ADS)

When one is exposed to microgravity, fluid which is normally pooled in the lower extremities is redistributed headward and weight bearing bones begin to demineralize due to reduced mechanical stresses. The kidney, which is the primary regulator of body fluid volume and composition, responds to the fluid shift and bone demineralization by increasing the urinary output of water, sodium, and calcium. This research involves developing a mathematical description of how water and electrolytes are internally redistributed and exchanged with the environment during space flight. This model consequently involves kidney function and the associated endocrine system. The model agrees well with actual data, including that a low sodium diet can prevent bone demineralization. Therefore, assumptions made to develop the model are most likely valid. Additionally, various levels of activity are also considered in the model since exercise may help to eliminate some of the undesired effects of space flight such as muscle atrophy and bone demineralization.

Doty, S. E.; Seagrave, R. C.

96

Human water, sodium, and calcium regulation during space flight and exercise  

NASA Astrophysics Data System (ADS)

When one is exposed to microgravity, fluid which is normally pooled in the lower extremities is redistributed headward and weight bearing bones begin to demineralize due to reduced mechanical stresses. The kidney, which is the primary regulator of body fluid volume and composition, responds to the fluid shift and bone demineralization by increasing the urinary output of water, sodium, and calcium. This research involves developing a mathematical description of how water and electrolytes are internally redistributed and exchanged with the environment during space flight. This model consequently involves kidney function and the associated endocrine system. The model agrees well with actual data, including that a low sodium diet can prevent bone demineralization. Therefore, assumptions made to develop the model are most likely valid. Additionally, various levels of activity are also considered in the model since exercise may help to eliminate some of the undesired effects of space flight such as muscle atrophy and bone demineralization.

Doty, S. E.; Seagrave, R. C.

2000-05-01

97

Alginate-based pellets prepared by extrusion\\/spheronization: Effect of the amount and type of sodium alginate and calcium salts  

Microsoft Academic Search

Pellets containing microcrystalline cellulose (MCC), a model drug (theophylline) and a range of levels of sodium alginate (i.e., 10–50% w\\/w) were prepared by extrusion\\/spheronization. Two types of sodium alginate were evaluated with and without the addition of either calcium acetate or calcium carbonate (0, 0.3, 3 and 10% w\\/w). The effects of amount and type of sodium alginate and calcium

Pornsak Sriamornsak; Jurairat Nunthanid; Manee Luangtana-anan; Yossanun Weerapol; Satit Puttipipatkhachorn

2008-01-01

98

The Mechanism of Vapor Phase Hydration of Calcium Oxide: Implications for CO2 capture.  

PubMed

Lime-based sorbents are used for fuel- and flue-gas capture, thereby representing an economic and effective way to reduce CO2 emissions. Their use involves cyclic carbonation/calcination which results in a significant conversion reduction with increasing number of cycles. To reactivate spent CaO, vapor phase hydration is typically performed. However, little is known about the ultimate mechanism of such a hydration process. Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic process, which progresses via an intermediate disordered phase prior to the final formation of oriented Ca(OH)2 nanocrystals. The strong structural control during this solid-state phase transition implies that the microstructural features of the CaO parent phase predetermine the final structural and physicochemical (reactivity and attrition) features of the product hydroxide. The higher molar volume of the product can create an impervious shell around unreacted CaO, thereby limiting the efficiency of the reactivation process. However, in the case of compact, sintered CaO structures, volume expansion cannot be accommodated in the reduced pore volume, and stress generation leads to pervasive cracking. This favors complete hydration but also detrimental attrition. Implications of these results in carbon capture and storage (CCS) are discussed. PMID:25233236

Kud?acz, Krzysztof; Rodriguez-Navarro, Carlos

2014-10-21

99

Mineral content of infant formula after treatment with sodium polystyrene sulfonate or calcium polystyrene sulfonate.  

PubMed

Options for the management of infants with hyperkalemia secondary to renal insufficiency are limited for infants not maintained on dialysis. Precipitation of potassium (K+) from infant formula with sodium polystyrene sulfonate (KX) prior to feeding has been reported. However, its effect on calcium (Ca2+) and sodium (Na+) has not been quantitatively defined. The purpose of this study was to examine the effects of two K+ exchange resins: KX and calcium polystyrene sulfonate (RC) on Na+, K+, and Ca2+. Infant formula powder (Similac PM 60/40, Ross Laboratories, Columbus, OH, USA) was prepared with deionized water (DW) and KX or RC (1 g/mEq of K+) was added. The formula was decanted after 50 minutes and Na+, K+, and Ca2+ were assayed in the supernatant. Na+ and K+ were also assayed in ready-to-feed PM 60/40 (RTF). KX decreased the K+ concentration by 4.5 fold (P < 0.001) and increased the Na+ content by 3.8 fold (P < 0.001). In RC there was a 1.6-fold increase in Ca2+ content (P < 0.001), and a 13% decrease in K+ concentrations (P < 0.05). Preparation of the formula with DW reduced the K+ concentration by 30% compared to ready-to-feed formula (P < 0.001). We conclude that, although KX significantly reduces the K+ content of formulas, DW may be a more practical and convenient method of preparing formula for the hyperkalemic infant. PMID:10649740

Fassinger, N; Dabbagh, S; Mukhopadhyay, S; Lee, D Y

1998-01-01

100

The effect of calcium on gill potentials and on sodium and chloride fluxes in the goldfish, Carassius auratus  

Microsoft Academic Search

Measurements of electric potential and of sodium and chloride effluxes were carried out on a freshwater fish, the goldfishCarassius auratus. The potential was affected by a number of inorganic ion species but that with the most significant influence on transepithelial potential was calcium. The potential was about 10 mV negative in the absence of calcium and about 10 mV positive

F. B. Eddy

1975-01-01

101

A study of the effects of nickel chloride and calcium chloride on hydration of Portland cement  

SciTech Connect

Portland cement samples containing amounts of CaCl[sub 2] and NiCl[sub 2] ranging from approximately 1% to 20% by weight have been examined by [sup 29]Si and [sup 27]Al solid-state MAS NMR as a function of time, and some of the mature pastes have been characterized by X-ray diffraction. Changes in physical properties that had been previously observed as a function of amounts of salt added are clearly traceable to differences in the silicate matrices. Low concentrations of both salts promote Q[sup 1] formation, but high concentrations result in formation of much more Q[sup 2] at the expense of Q[sup 1]. Both salts accelerate both aluminate and silicate hydration, and the effects appear to be almost entirely due to chloride. Minor variations in hydration rates at high Ni concentrations may be the result of nickel salt precipitation.

Akhter, H.; Cartledge, F.K.; Roy, A.; Tittlebaum, M.E. (Louisiana State Univ., Baton Rouge (United States). Department of Chemistry and Institute for Recyclable Materials)

1993-07-01

102

Alendronate sodium hydrate (oral jelly) for the treatment of osteoporosis: review of a novel, easy to swallow formulation  

PubMed Central

Osteoporosis is a skeletal disorder characterized by loss of bone mass, decreased bone strength, and an increased risk of bone fracture. The disease progresses with age, especially in postmenopausal women. Japan is one of the most rapidly aging societies worldwide. Japanese individuals over 65 years of age constituted 23.0% of the population in 2010 and 25.1% to 25.2% as of 2013. The estimated number of people with osteoporosis in Japan is currently 13 million. Bisphosphonates increase bone mineral density by inhibiting osteoclast-mediated bone resorption, thereby reducing the risk of fractures. Alendronate sodium hydrate (alendronate) is a bisphosphonate that potently inhibits bone resorption and is used to treat osteoporosis. Sufficient water is required to take an alendronate oral tablet; insufficient water could result in digestive system diseases, such as esophageal ulceration. Elderly patients with swallowing difficulty may choke on the tablet. Taking a tablet with oral jelly is a method to prevent digestive system disease and reduce the choking hazard. Once-weekly alendronate oral jelly was approved in 2012 by the Ministry of Health, Labour, and Welfare of Japan as the world’s first drug for osteoporosis in a jelly formulation. It consists of a jelly portion and an air portion. The jelly formulation is smoothly discharged by pushing the air portion. Therefore, elderly patients with physical disabilities are able to easily take all of the jelly formulation from the package. In this review, this new formulation of alendronate sodium hydrate (oral jelly) is introduced and discussed in terms of osteoporosis treatment. This new formulation provides an alternative so that patients may select a method of dosing tailored to their preferences. Management of osteoporosis involves assessing fracture risk and preventing fractures. Higher adherence to the treatment of patients with osteoporosis and prevention of osteoporotic fractures are issues to be resolved. PMID:23766643

Imai, Kazuhiro

2013-01-01

103

Hydration products of FBC wastes as SO 2 sorbents: comparison between ettringite and calcium hydroxide  

Microsoft Academic Search

Fluidized bed combustion (FBC) enables the in situ capture of SO2, but generates large amounts of wastes whose composition and physico-chemical properties make both landfilling and reuse in traditional fields of application (e.g., cement and concrete industries) problematic. Reactivation by water hydration of the desulphurizing ability of these residues is considered a viable mean for their recycling: besides Ca(OH)2, this

Fabio Montagnaro; Marianna Nobili; Piero Salatino; Antonio Telesca; Gian Lorenzo Valenti

2008-01-01

104

Sodium-calcium exchange during the action potential in guinea-pig ventricular cells.  

PubMed Central

1. Slow inward tail currents attributable to electrogenic sodium-calcium exchange can be recorded by imposing hyperpolarizing voltage clamp pulses during the normal action potential of isolated guinea-pig ventricular cells. The hyperpolarizations return the membrane to the resting potential (between -65 and -88 m V) allowing an inward current to be recorded. This current usually has peak amplitude when repolarization is imposed during the first 50 ms after the action potential upstroke, but becomes negligible once the final phase of repolarization is reached. The envelope of peak current tail amplitudes strongly resembles that of the intracellular calcium transient recorded in other studies. 2. Repetitive stimulation producing normal action potentials at a frequency of 2 Hz progressively augments the tail current recorded immediately after the stimulus train. Conversely, if each action potential is prematurely terminated at 0.1 Hz, repetitive stimulation produces a tail current much smaller than the control value. The control amplitude of inward current is only maintained if interrupted action potentials are separated by at least one full 'repriming' action potential. These effects mimic those on cell contraction (Arlock & Wohlfart, 1986) and suggest that progressive changes in tail current are controlled by variations in the amplitude and time course of the intracellular calcium transient. 3. When intracellular calcium is buffered sufficiently to abolish contraction, the tail current is abolished. Substitution of calcium with strontium greatly reduces the tail current. 4. The inward tail current can also be recorded at more positive membrane potentials using standard voltage clamp pulse protocols. In this way it was found that temperature has a large effect on the tail current, which can change from net inward at 22 degrees C to net outward at 37 degrees C. The largest inward currents are usually recorded at about 30 degrees C. It is shown that this effect is attributable predominantly to the temperature sensitivity of activation of the delayed potassium current, iK, whose decay can then mask the slow tail current at high temperatures. 5. Studies of the relationship between the tail current and the membrane calcium current, iCa, have been performed using a method of drug application which is capable of perturbing iCa in a very rapid and highly reversible manner. Partial block of iCa with cadmium does not initially alter the size of the associated inward current tail. When iCa is increased by applying isoprenaline, the percentage augmentation of the associated tail current is much greater but occurs more slowly.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2482358

Egan, T M; Noble, D; Noble, S J; Powell, T; Spindler, A J; Twist, V W

1989-01-01

105

Cation Hydration Constants by Proton NMR: A Physical Chemistry Experiment.  

ERIC Educational Resources Information Center

Studies the polarization effect on water by cations and anions. Describes an experiment to illustrate the polarization effect of sodium, lithium, calcium, and strontium ions on the water molecule in the hydration spheres of the ions. Analysis is performed by proton NMR. (MVL)

Smith, Robert L.; And Others

1988-01-01

106

Calcium  

MedlinePLUS

... when taken with food. Some over-the-counter antacid products, such as Tums® and Rolaids®, contain calcium ... calcium excretion and thereby lower blood calcium levels. Antacids containing aluminum or magnesium increase calcium loss in ...

107

Calcium  

MedlinePLUS

... lead levels. Calcium carbonate is used as an antacid for “heartburn.” Calcium carbonate and calcium acetate are ... when given intravenously (by IV). Use as an antacid as calcium carbonate. Reducing phosphate levels in people ...

108

Effect of potassium sodium tartrate and sodium citrate on the preparation of {alpha}-calcium sulfate hemihydrate from flue gas desulfurization gypsum in a concentrated electrolyte solution  

SciTech Connect

Flue gas desulfurization (FGD) gypsum mainly composed of calcium sulfate dihydrate (DH) was used as a raw material to obtain alpha-calcium sulfate hemihydrate ({alpha}-HH) through dehydration in a Ca-Mg-K-Cl-solution medium at 95{sup o}C under atmospheric pressure. The effects of potassium sodium tartrate and sodium citrate on the preparation of alpha-HH in the electrolyte solution were investigated. The results revealed that the addition of potassium sodium tartrate (1.0 x 10{sup -2} - 2.5 x 10{sup -2}M) decreased the dehydration rate of FGD gypsum and increased the length/width (l/w) ratio of {alpha}-HH crystals, which could yield unfavorable strength properties. Addition of sodium citrate (1.0 x 10{sup -5} - 2.0 x 10{sup -5}M) slightly increased the dehydration rate of FGD gypsum and decreased the l/w ratio of {alpha}-HH crystals, which could be beneficial to increase strength. However, it also led to a partial formation of anhydrite (AH) crystals. AH was also the only dehydration product when the concentration of sodium citrate increased to 1.0 x 10{sup -4}M. Therefore, sodium citrate rather than potassium sodium tartrate could be used as an additive in Ca-Mg-K-Cl electrolyte solutions if alpha-HH with a shorter l/w ratio is the desired product from FGD gypsum dehydration. The concentration of sodium citrate should be properly controlled to reduce the formation of AH.

Shen, Z.X.; Guan, B.H.; Fu, H.L.; Yang, L.C. [Zhejiang University, Hangzhou (China). Dept. of Environmental Engineering

2009-12-15

109

Sodium selenite penta­hydrate, Na2SeO3·5H2O  

PubMed Central

In the crystal structure of Na2SeO3·5H2O [disodium selen­ate(IV) penta­hydrate], two Se, two selenite O atoms and one water O atom are located on a mirror plane, and one water O atom is located on a twofold rotation axis. The coordination of one Na+ cation is distorted trigonal bipyramidal, formed by three equatorial H2O ligands and two axial selenite O atoms. The other Na+ cation has an octa­hedral coordination by six water mol­ecules. The two independent SeO3 groups form almost undistorted trigonal pyramids, with Se—O bond lengths in the range 1.6856?(7)–1.7202?(10)?Å and O—Se—O angles in the range 101.98?(3)–103.11?(5)°, and both are ?2-O:O-bonded to a pair of Na+ cations. Hydrogen bonds involving all water molecules and selenite O atoms consolidate the crystal packing. Although anhydrous Na2SeO3 and Na2TeO3 are isotypic, the title compound is surprisingly not isotypic with Na2TeO3·5H2O. In the tellurite hydrate, all Na+ cations have an octa­hedral coordination and the TeO3 groups are bonded to Na+ only via one of their three O atoms. PMID:24454013

Mereiter, Kurt

2013-01-01

110

Sodium selenite penta-hydrate, Na2SeO3·5H2O.  

PubMed

In the crystal structure of Na2SeO3·5H2O [disodium selen-ate(IV) penta-hydrate], two Se, two selenite O atoms and one water O atom are located on a mirror plane, and one water O atom is located on a twofold rotation axis. The coordination of one Na(+) cation is distorted trigonal bipyramidal, formed by three equatorial H2O ligands and two axial selenite O atoms. The other Na(+) cation has an octa-hedral coordination by six water mol-ecules. The two independent SeO3 groups form almost undistorted trigonal pyramids, with Se-O bond lengths in the range 1.6856?(7)-1.7202?(10)?Å and O-Se-O angles in the range 101.98?(3)-103.11?(5)°, and both are ?2-O:O-bonded to a pair of Na(+) cations. Hydrogen bonds involving all water molecules and selenite O atoms consolidate the crystal packing. Although anhydrous Na2SeO3 and Na2TeO3 are isotypic, the title compound is surprisingly not isotypic with Na2TeO3·5H2O. In the tellurite hydrate, all Na(+) cations have an octa-hedral coordination and the TeO3 groups are bonded to Na(+) only via one of their three O atoms. PMID:24454013

Mereiter, Kurt

2013-10-23

111

Cardiac Sodium-Calcium Exchange and Efficient Excitation-Contraction Coupling: Implications for Heart Disease  

PubMed Central

Cardiovascular disease is a leading cause of death worldwide, with ischemic heart disease alone accounting for >12% of all deaths; more than HIV/AIDS, tuberculosis, lung and breast cancer combined. Heart disease has been the leading cause of death in the United States for the past 85 years, and is a major cause of disability and health-care expenditures. The cardiac conditions most likely to result in death include heart failure and arrhythmias, both a consequence of ischemic coronary disease and myocardial infarction, though chronic hypertension and valvular diseases are also important causes of heart failure. Sodium-calcium exchange (NCX) is the dominant calcium (Ca) efflux mechanism in cardiac cells. Using ventricular-specific NCX knockout mice, we have found that NCX is also an essential regulator of cardiac contractility independent of sarcoplasmic reticulum Ca load. During the upstroke of the action potential, sodium (Na) ions enter the diadic cleft space between the sarcolemma and the sarcoplasmic reticulum. The rise in cleft Na, in conjunction with depolarization, causes NCX to transiently reverse. Ca entry by this mechanism then “primes” the diadic cleft so that subsequent Ca entry through Ca channels can more efficiently trigger Ca release from the sarcoplasmic reticulum. In NCX knockout mice, this mechanism is inoperative (Na current has no effect on the Ca transient), and excitation-contraction coupling relies upon the elevated diadic cleft Ca that arises from the slow extrusion of cytoplasmic Ca by the ATP-dependent sarcolemmal Ca pump. Thus our data support the conclusion that NCX is an important regulator of cardiac contractility. These findings suggest that manipulation of NCX may be beneficial in the treatment of heart failure. PMID:23224894

Goldhaber, Joshua I.; Philipson, Kenneth D.

2014-01-01

112

Chemical composition studies on some aquatic macrophytes in three scottish lochs. II. Potassium, sodium, calcium, magnesium and iron  

Microsoft Academic Search

The potassium, sodium, calcium, magnesium and iron levels in seven species of freshwater macrophytes (Juncus effusus L., Iris pseudacorus L., Carex rostrata Stokes, Glyceria maxima (Hartm.) Holmberg, Nuphar lutea (L.) Sm., Polygonum amphibium L. and Schoenoplectus lacustris (L.) Pallas) in three Scottish lochs of different trophic levels were studied during 1975 and the results obtained were compared with similar studies

Y. B. Ho

1979-01-01

113

The effect of cellulose on crystal formation in the kidneys of guinea pigs fed diet rich in calcium and sodium  

Microsoft Academic Search

Our earlier report showed that diet rich in calcium and sodium fed to guinea pigs can be urolithogenic. In this study, we investigated the effect of adding 3% or 15% cellulose as a source of fiber into similar diet to asses the formation of kidney calculus. From the result, animals fed diet with 3% cellulose showed a relatively high concentration

Syed Shamsuddin; Syed Hussain; Tan Kah Ooi; Mohd Azman; Abu Bakar

114

Calmodulin and calcium differentially regulate the neuronal Nav1.1 voltage-dependent sodium channel  

SciTech Connect

Highlights: {yields} Both Ca{sup ++}-Calmodulin (CaM) and Ca{sup ++}-free CaM bind to the C-terminal region of Nav1.1. {yields} Ca{sup ++} and CaM have both opposite and convergent effects on I{sub Nav1.1}. {yields} Ca{sup ++}-CaM modulates I{sub Nav1.1} amplitude. {yields} CaM hyperpolarizes the voltage-dependence of activation, and increases the inactivation rate. {yields} Ca{sup ++} alone antagonizes CaM for both effects, and depolarizes the voltage-dependence of inactivation. -- Abstract: Mutations in the neuronal Nav1.1 voltage-gated sodium channel are responsible for mild to severe epileptic syndromes. The ubiquitous calcium sensor calmodulin (CaM) bound to rat brain Nav1.1 and to the human Nav1.1 channel expressed by a stably transfected HEK-293 cell line. The C-terminal region of the channel, as a fusion protein or in the yeast two-hybrid system, interacted with CaM via a consensus C-terminal motif, the IQ domain. Patch clamp experiments on HEK1.1 cells showed that CaM overexpression increased peak current in a calcium-dependent way. CaM had no effect on the voltage-dependence of fast inactivation, and accelerated the inactivation kinetics. Elevating Ca{sup ++} depolarized the voltage-dependence of fast inactivation and slowed down the fast inactivation kinetics, and for high concentrations this effect competed with the acceleration induced by CaM alone. Similarly, the depolarizing action of calcium antagonized the hyperpolarizing shift of the voltage-dependence of activation due to CaM overexpression. Fluorescence spectroscopy measurements suggested that Ca{sup ++} could bind the Nav1.1 C-terminal region with micromolar affinity.

Gaudioso, Christelle; Carlier, Edmond; Youssouf, Fahamoe [INSERM U641, Institut Jean Roche, Marseille F-13344 (France) [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France); Clare, Jeffrey J. [Eaton Pharma Consulting, Eaton Socon, Cambridgeshire PE19 8EF (United Kingdom)] [Eaton Pharma Consulting, Eaton Socon, Cambridgeshire PE19 8EF (United Kingdom); Debanne, Dominique [INSERM U641, Institut Jean Roche, Marseille F-13344 (France) [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France); Alcaraz, Gisele, E-mail: gisele.alcaraz@univmed.fr [INSERM U641, Institut Jean Roche, Marseille F-13344 (France) [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France)

2011-07-29

115

Crystallization kinetics of calcium oxalate hydrates studied by scanning confocal interference microscopy  

NASA Astrophysics Data System (ADS)

Scanning confocal interference microscopy (SCIM) is an optical technique that allows the visualization of structures below the limits of classical optical microscopy (?250 nm). This study represents the first use of SCIM to analyze the formation of calcium oxalate crystals, the major constituent of kidney stones. Crystals were nucleated and grown on the glass bottom of Petri dishes in the presence and absence of the polyelectrolyte inhibitor poly- L-aspartic acid (poly-asp). In the absence of poly-asp, monoclinic calcium oxalate monohydrate (COM) nucleated from {1 0 0} or {0 1 0} faces. The first observed particles were 70-120 nm in diameter and grew by a step-like progression in the [0 0 1] and [0 1 0] directions. Addition of poly-asp had several effects on calcium oxalate formation. First, the number of particles was increased, but their sizes were decreased. Second, the rate of COM growth in the [0 0 1] direction was decreased to a greater extent than the rate along [0 1 0]. Third, the formation of tetragonal calcium oxalate dihydrate (COD) crystals was favored. Fourth, the rates of COD growth along <1 1 0> and allied directions were decreased, whereas that parallel to <0 0 1> is increased. Sequences of highly resolved growth fronts show step displacement for COM and moving crystal edges for COD. Analysis of image sequences suggested that growth is strongly affected by competing and alternating processes, in which diffusion processes are rate-limiting and induce nonlinear growth. This study shows that SCIM is a powerful technique for the quantitative analysis of crystallization processes and for determining the mode of action of inhibitors.

Grohe, Bernd; Rogers, Kem A.; Goldberg, Harvey A.; Hunter, Graeme K.

2006-10-01

116

X-ray diffraction: a powerful tool to probe and understand the structure of nanocrystalline calcium silicate hydrates.  

PubMed

X-ray diffraction (XRD) patterns were calculated and compared to literature data with the aim of investigating the crystal structure of nanocrystalline calcium silicate hydrates (C-S-H), the main binding phase in hydrated Portland cement pastes. Published XRD patterns from C-S-H of Ca/Si ratios ranging from ~ 0.6 to ~ 1.7 are fully compatible with nanocrystalline and turbostratic tobermorite. Even at a ratio close or slightly higher than that of jennite (Ca/Si = 1.5) this latter mineral, which is required in some models to describe the structure of C-S-H, is not detected in the experimental XRD patterns. The 001 basal reflection from C-S-H, positioned at ~ 13.5 Å when the C-S-H structural Ca/Si ratio is low (< 0.9), shifts towards smaller d values and sharpens with increasing Ca/Si ratio, to reach ~ 11.2 Å when the Ca/Si ratio is higher than 1.5. Calculations indicate that the sharpening of the 001 reflection may be related to a crystallite size along c* (i.e. a mean number of stacked layers) increasing with the C-S-H Ca/Si ratio. Such an increase would contribute to the observed shift of the 001 reflection, but fails to quantitatively explain it. It is proposed that the observed shift could result from interstratification of at least two tobermorite-like layers, one having a high and the other a low Ca/Si ratio with a basal spacing of 11.3 and 14 Å, respectively. PMID:24056355

Grangeon, Sylvain; Claret, Francis; Linard, Yannick; Chiaberge, Christophe

2013-10-01

117

EFFECTS OF SODIUM AND CALCIUM IN LIGNITE ON THE PERFORMANCE OF ACTIVATED CARBON PRODUCTS  

SciTech Connect

New federal drinking water regulations have been promulgated to restrict the levels of disinfection by-products (DBPs) in finished public water supplies. DBPs are suspected carcinogens and are formed when organic material is partially oxidized by disinfectants commonly used in the water treatment industry. Additional federal mandates are expected in the near future that will also affect public water suppliers with respect to DBPs. These new federal drinking water regulations may require public water suppliers to adjust treatment practices or incorporate additional treatment operations into their existing treatment trains. Many options have been identified, including membrane processes, granular activated carbon, powered activated carbon (PAC), enhanced coagulation and/or softening, and alternative disinfectants (e.g., chlorine dioxide, ozone, and chloramines). Of the processes being considered, PAC appears to offer an attractive benefit-to-cost advantage for many water treatment plants, particularly small systems (those serving fewer than 10,000 customers). PAC has traditionally been used by the water treatment industry for the removal of compounds contributing to taste and odor problems. PAC also has the potential to remove naturally occurring organic matter (NOM) from raw waters prior to disinfection, thus controlling the formation of regulated DBPs. Many small water systems are currently using PAC for taste and odor control and have the potential to use PAC for controlling DBPs. Activated carbons can be produced from a variety of raw materials, including wood, peat, coconut husks, and numerous types of coal. The Energy & Environmental Research Center (EERC) has been working on the development of a PAC product to remove NOM from surface water supplies to prevent the formation of carcinogenic DBPs during chlorination. During that study, the sodium and calcium content of the lignites showed a significant effect on the sorption capacity of the activated carbon product. As much as a 130% increase in the humic acid sorption capacity of a PAC produced from a high-sodium-content lignite was observed. We hypothesize that the sodium and calcium content of the coal plays a significant role in the development of pore structures and pore-size distribution, ultimately producing activated carbon products that have greater sorption capacity for specific contaminants, depending on molecular size.

Edwin S. Olson; Kurt E. Eylands; Daniel J. Stepan

2001-12-01

118

Bones and Crohn's: No benefit of adding sodium fluoride or ibandronate to calcium and vitamin D  

PubMed Central

AIM: To compare the effect of calcium and cholecalciferol alone and along with additional sodium fluoride or ibandronate on bone mineral density (BMD) and fractures in patients with Crohn’s disease (CD). METHODS: Patients (n =148) with reduced BMD (T-score < -1) were randomized to receive cholecalciferol (1000 IU) and calcium citrate (800 mg) daily alone(group A, n = 32) or along with additional sodium fluoride (25 mg bid) (group B, n = 62) or additional ibandronate (1 mg iv/3-monthly) (group C, n = 54). Dual energy X-ray absorptiometry of the lumbar spine (L1-L4) and proximal right femur and X-rays of the spine were performed at baseline and after 1.0, 2.25 and 3.5 years. Fracture-assessment included visual reading of X-rays and quantitative morphometry of vertebral bodies (T4-L4). RESULTS: One hundred and twenty three (83.1%) patients completed the first year for intention-to-treat (ITT) analysis. Ninety two (62.2%) patients completed the second year and 71 (47.8%) the third year available for per-protocol (PP) analysis. With a significant increase in T-score of the lumbar spine by +0.28 ± 0.35 [95% confidence interval (CI): 0.162-0.460, P < 0.01], +0.33 ± 0.49 (95% CI: 0.109-0.558, P < 0.01), +0.43 ± 0.47 (95% CI: 0.147-0.708, P < 0.01) in group A, +0.22 ± 0.33 (95% CI: 0.125-0.321, P < 0.01); +0.47 ± 0.60 (95% CI: 0.262-0.676, P < 0.01), +0.51 ± 0.44 (95% CI: 0.338-0.682, P < 0.01) in group B and +0.22 ± 0.38 (95% CI: 0.111-0.329, P < 0.01), +0.36 ± 0.53 (95% CI: 0.147-0.578, P < 0.01), +0.41 ± 0.48 (95% CI: 0.238-0.576, P < 0.01) in group C, respectively, during the 1.0, 2.25 and 3.5 year periods (PP analysis), no treatment regimen was superior in any in- or between-group analyses. In the ITT analysis, similar results in all in- and between-group analyses with a significant in-group but non-significant between-group increase in T-score of the lumbar spine by 0.38 ± 0.46 (group A, P < 0.01), 0.37 ± 0.50 (group B, P < 0.01) and 0.35 ± 0.49 (group C, P < 0.01) was observed. Follow-up in ITT analysis was still 2.65 years. One vertebral fracture in the sodium fluoride group was detected. Study medication was safe and well tolerated. CONCLUSION: Additional sodium fluoride or ibandronate had no benefit over calcium and cholecalciferol alone in managing reduced BMD in CD. PMID:21253392

Klaus, Jochen; Reinshagen, Max; Herdt, Katharina; Schroter, Christoph; Adler, Guido; von Boyen, Georg BT; von Tirpitz, Christian

2011-01-01

119

Belite cements: modifications of calcium silicate hydrate (C-S-H) gel by alkaline hydrothermal activation  

SciTech Connect

The C-S-H gel of two types of fly ash belite cements (FABC) are studied at a nanoscale (1 to 100 nm (39.4 to 3940 nin.)) by means of the specific surface area and pore-size distribution, which were measured by the sorption isotherms of nitrogen gas and the BET method. The two belite cements were fabricated by the hydro-thermal-calcination route of Class C fly ash in NaOH 1M solution (FABC-2-N) and demineralized water (FABC-2-W). Two differentiated zones in the pore-size distribution of the C-S-H gel at similar to 12 and similar to 3 nm (similar to 473 and similar to 118 nin.) with different influences in the mechanical strength were produced. The proportion of both zones depends on the age of hydration and type of belite cement. At early ages, the C-S-H gel of FABC-2-N develops both zones in a greater proportion than those of FABC-2-W. At later ages, the behavior is opposite: the C-S-H gel of FABC-2-W develops high proportion of pores of 3 nin (118 nm.) of diameter. Important quantitative correlations were found among these nanostructure characteristics of the C-S-H gel and macrostructural engineering property.

Guerrero, A.; Goni, S.; Dolado, J.S. [CSIC, Eduardo Torroja Inst. Construct. Sci., Madrid (Spain)

2009-03-15

120

Final Report On the Safety Assessment of Glycolic Acid, Ammonium, Calcium, Potassium, and Sodium Glycolates, Methyl, Ethyl, Propyl, and Butyl Glycolates, and Lactic Acid, Ammonium, Calcium, Potassium, Sodium, and Tea-Lactates, Methyl, Ethyl, Isopropyl, and Butyl Lactates, and Lauryl, Myristyl, and Cetyl Lactates  

Microsoft Academic Search

This report provides a review of the safety of Glycolic Acid, Ammonium, Calcium, Potassium, and Sodium Glycolates, Methyl, Ethyl, Propyl, and Butyl Glycolates, Lactic Acid, Ammonium, Calcium, Potassium, Sodium, and TEA-Lactates, and Lauryl, Myristyl, and Cetyl Lactates. These ingredients belong to a group known as alpha-hydroxy acids (AHAs). Products containing these ingredients may be for consumer use, salon use, or

F. A. Andersen

1998-01-01

121

Calcium-Mediated Regulation of Proton-Coupled Sodium Transport - Final Report  

SciTech Connect

The long-term goal of our experiments was to understand mechanisms that regulate energy coupling by ion currents in plants. Activities of living organisms require chemical, mechanical, osmotic or electrical work, the energy for which is supplied by metabolism. Adenosine triphosphate (ATP) has long been recognized as the universal energy currency, with metabolism supporting the synthesis of ATP and the hydrolysis of ATP being used for the subsequent work. However, ATP is not the only energy currency in living organisms. A second and very different energy currency links metabolism to work by the movement of ions passing from one side of a membrane to the other. These ion currents play a major role in energy capture and they support a range of physiological processes from the active transport of nutrients to the spatial control of growth and development. In Arabidopsis thaliana (Arabidopsis), the activity of a plasma membrane Na+/H+ exchanger, SALT OVERLY SENSITIVE1 (SOS1), is essential for regulation of sodium ion homeostasis during plant growth in saline conditions. Mutations in SOS1 result in severely reduced seedling growth in the presence of salt compared to the growth of wild type. SOS1 is a secondary active transporter coupling movement of sodium ions out of the cell using energy stored in the transplasma membrane proton gradient, thereby preventing the build-up of toxic levels of sodium in the cytosol. SOS1 is regulated by complexes containing the SOS2 and CALCINEURIN B-LIKE10 (CBL10) or SOS3 proteins. CBL10 and SOS3 (also identified as CBL4) encode EF-hand calcium sensors that interact physically with and activate SOS2, a serine/threonine protein kinase. The CBL10/SOS2 or SOS3/SOS2 complexes then activate SOS1 Na+/H+ exchange activity. We completed our studies to understand how SOS1 activity is regulated. Specifically, we asked: (1) how does CBL10 regulate SOS1 activity? (2) What role do two putative CBL10-interacting proteins play in SOS1 regulation? (3) Are there differences in the regulation and/or activity of SOS1 in plants differing in their adaptation to salinity?

Schumaker, Karen S [Professor] [Professor

2013-10-24

122

Calcium, magnesium, potassium and sodium intakes in Japanese children aged 3 to 5 years.  

PubMed

The present study aimed to evaluate in preschool children the intakes of Ca, Mg that possibly affect health and tooth formation and the intakes of K and Na that may affect lifestyle-related diseases. Information on dietary intake was collected from 90 preschool children (15 boys and 15 girls each in the 3-, 4- and 5-year old groups) on 3 separate days in the school fiscal year 1999 (April 1999 to March 2000) by the duplicate-diet technique. The Ca, Mg, K, and Na concentrations were determined by atomic absorption spectrometry using wet-ashed samples. The medians of mean daily intakes of Ca, Mg, K and Na in 3- to 5-year-old children were 432 mg, 110 mg, 1.18 g and 1.60 g, respectively, and no significant differences with regard to gender were observed. Seasonal varia-tion of intake was seen for each mineral. Calcium intake in most preschool children did not meet adequate intake (AI), probably due to low intakes of milk and dairy products in Japan. Magnesium intake was below the estimated average requirement (EAR) in 13.3% of the subjects, while the K intake met the AI. Sodium intake in a quarter of preschool children exceeded the tentative dietary goal. We concluded that in Japanese children aged 3-5 years; Ca intake is low, Na intake is high, and K intake is adequate, but some children could be at risk for Mg deficiency. PMID:18818164

Shibata, Tomiko; Murakami, Taeko; Nakagaki, Haruo; Narita, Naoki; Goshima, Miho; Sugiyama, Tomoko; Nishimuta, Mamoru

2008-01-01

123

Transuranium removal from Hanford high level waste simulants using sodium permanganate and calcium  

NASA Astrophysics Data System (ADS)

Plutonium and americium are present in the Hanford high level liquid waste complexant concentrate (CC) due to the presence of complexing agents including di-(2-ethylhexyl) phosphoric acid (D2EHPA), tributylphosphate (TBP), hydroxyethylene diamine triacetic acid (HEDTA), ethylene diamine tetraacetic acid (EDTA), citric acid, glycolic acid, and sodium gluconate. The transuranic concentrations approach 600 nCi/g and require processing prior to encapsulation into low activity glass. BNFL's (British Nuclear Fuels Limited's) original process was a ferric co-precipitation method based on earlier investigations by Herting and Orth, et al. Furthermore, flocculation and precipitation are widely used for clarification in municipal water treatment. Co-precipitation of Np, Am, and Pu with ferric hydroxide is also used within an analytical method for the sum of those analytes. Tests to evaluate BNFL's original precipitation process indicated the measured decontamination factors (DFs) and filter fluxes were too low. Therefore, an evaluation of alternative precipitation agents to replace ferric ion was undertaken. Agents tested included various transition metals, lanthanide elements, uranium species, calcium, strontium, and permanganate.

Wilmarth, W. R.; Rosencrance, S. W.; Nash, C. A.; Fonduer, F. F.; DiPrete, D. P.; DiPrete, C. C.

2000-07-01

124

Dual inhibition of sodium-mediated proton and calcium efflux triggers non-apoptotic cell death in malignant gliomas  

PubMed Central

Malignant glioma cells maintain an elevated intracellular pH (pHi) within hypoxic-ischemic tumor microenvironments through persistent activation of sodium-proton transport (McLean et al., 2000). Amiloride has been reported to selectively kill human malignant glioma cell lines but not primary astrocytes (Hegde et al., 2004). While amiloride reduces pHi of malignant gliomas by inhibiting isoform 1 of sodium-proton exchange (NHE1), direct acidification was shown to be cytostatic rather than cytotoxic. At cytotoxic concentrations, amiloride has multiple drug targets including inhibition of NHE1 and sodium calcium exchange. Amiloride's glioma cytotoxicity can be explained, at least in part, by dual inhibition of NHE1 and of Na+-dependent calcium efflux by isoform 1.1 of the sodium calcium exchanger (NCX1.1) , which increases [Ca2+]i and initiates glioma cell demise. As a result of persistent NHE1 activity, cytosolic free levels of sodium ([Na+]i) in U87 and C6 glioma cells are elevated 3-fold, as compared with normal astrocytes. Basal cytosolic free calcium levels ([Ca2+]i) also are increased 5-fold. 2?, 4?-dichlorobenzamil (DCB) inhibits the sodium-dependent calcium transporter (NCX1.1) much more potently than NHE1. DCB was employed in a concentration-dependent fashion in glioma cells to selectively inhibit the forward mode of NCX1.1 at ?1uM, while dually inhibiting both NHE1 and NCX1.1 at ?20uM. DCB (1uM) was not cytotoxic to glioma cells, while DCB (20?M) further increased basal elevated levels of [Ca2+]i in glioma cells that was followed by cell demise. Cariporide and SEA0400 are more specific inhibitors of NHE1 and NCX1.1 than amiloride or DCB, respectively. Individually, Cariporide and SEA0400 are not cytotoxic, but in combination induced glioma cell death. Like amiloride, the combination of Cariporide and SEA0400 produced glioma cell death in the absence of demonstrable caspase-activation. PMID:20869350

Harley, William; Floyd, Candace; Dunn, Tamara; Zhang, Xiao-Dong; Chen, Tsung-Yu; Hegde, Manu; Palandoken, Hasan; Nantz, Michael H.; Leon, Leonardo; Carraway, K L; Lyeth, Bruce; Gorin, Fredric A.

2010-01-01

125

Quantitative determination of inorganic minor cations in sodium-, calcium-, magnesium-matrix simulated samples by capillary electrophoresis  

Microsoft Academic Search

The analysis of ammonium, alkali and alkaline-earth trace cations (0.5 ppm) in samples with a calcium, sodium or magnesium matrix (500 ppm) has been achieved using 10 mM imidazole (pH 4.5) electrolyte to which a complexing agent (15-crown-5, oxalic acid or dipicolinic acid) has been specifically added in order to decrease the electrophoretic mobility of the matrix cation and thus

X Cahours; Ph Morin; M Dreux

1998-01-01

126

Effect of phenytoin on sodium and calcium currents in hippocampal CA1 neurons of phenytoin-resistant kindled rats.  

PubMed

About 20-30% of patients with epilepsy continue to have seizures despite carefully monitored treatment with antiepileptic drugs. The mechanisms explaining why some patients' respond and others prove resistant to antiepileptic drugs are poorly understood. It has been proposed that pharmacoresistance is related to reduced sensitivity of sodium channels in hippocampal neurons to antiepileptic drugs such as carbamazepine or phenytoin. In line with this proposal, a reduced effect of carbamazepine on sodium currents in hippocampal CA1 neurons was found in the rat kindling model of temporal lobe epilepsy (TLE), i.e. a form of epilepsy with the poorest prognosis of all epilepsy types in adult patients. To address directly the possibility that neuronal sodium currents in the hippocampus play a crucial role in the pharmacoresistance of TLE, we selected amygdala-kindled rats with respect to their in vivo anticonvulsant response to phenytoin into responders and nonresponders and then compared phenytoin's effect on voltage-activated sodium currents in CA1 neurons. Furthermore, in view of the potential role of calcium current modulation in the anticonvulsant action of phenytoin, the effect of phenytoin on high-voltage-activated calcium currents was studied in CA1 neurons. Electrode-implanted but not kindled rats were used as sham controls for comparison with the kindled rats. In all experiments, the interval between last kindled seizure and ion channel measurements was at least 5 weeks. In kindled rats with in vivo resistance to the anticonvulsant effect of phenytoin (phenytoin nonresponders), in vitro modulation of sodium and calcium currents by phenytoin in hippocampal CA1 neurons did not significantly differ from respective data obtained in phenytoin responders, i.e. phenytoin resistance was not associated with a changed modulation of the sodium or calcium currents by this drug. Compared to sham controls, phenytoin's inhibitory effect on sodium currents was significantly reduced by kindling without difference between the responder and nonresponder subgroups. Further studies in phenytoin-resistant kindled rats may help to elucidate the mechanisms that can explain therapy resistance. PMID:11750920

Jeub, M; Beck, H; Siep, E; Rüschenschmidt, C; Speckmann, E-J; Ebert, U; Potschka, H; Freichel, C; Reissmüller, E; Löscher, W

2002-01-01

127

Evaluation of the Health Aspects of Citric Acid, Sodium Citrate, Potassium Citrate, Calcium Citrate, Ammonium Citrate, Triethyl Citrate, Isopropyl Citrate, and Stearyl Citrate as Food Ingredients.  

National Technical Information Service (NTIS)

The report, by a group of qualified scientists designated the Select Committee on GRAS Substances (SCOGS), provides an independent evaluation of the safety of citric acid, sodium citrate, potassium citrate, calcium citrate, ammonium citrate, triethyl citr...

1977-01-01

128

Simultaneous measurements of magnesium, calcium and sodium influxes in perfused squid giant axons under membrane potential control.  

PubMed Central

1. Giant axons from the squids Dosidicus gigas, Loligo forbesi and Loligo vulgaris were internally perfused with 550 or 275 mM KF plus sucrose and bathed in artificial sea water containing 45Ca, 28Mg or mixtures of 45Ca-28Mg or 45Ca-22Na. Resting influxes and extra influxes during voltage-clamp pulses were measured by collecting and counting the internal perfusate. 2. For Dosidicus axons in 10 mM-CaCl2 the resting influx of calcium was 0-016 +/- 0-007 p-mole/cm2 sec and a linear function of external concentration. For two experiments in 10 and 84-7 mM-CaCl2, 100 nM tetrodotoxin had no effect. Resting calcium influx in 10 mM-CaCl2 was 0-017 +/- 0-013 p-mole/cm2 sec for Loligo axons. 3. With 55 mM-MgCl2 outside the average resting magnesium influx was 0-124 +/- 0-080 p-mole/cm2 sec for Loligo axons. Discarding one aberrant point the value is 0-105 +/- 0-046 which is not significantly different from the resting calcium influx for Dosidicus fibres in 55 mM-CaCl2, given as 0-094 p-mole/cm2 sec by the regression line shown in Fig. 1. In two experiments 150 nM tetrodotoxin had no effect. 4. With 430 mM-NaCl outside 100 nM tetrodotoxin reduced the average resting influx of sodium in Dosidicus axon from 27-7 +/- 4-5 to 25-1 +/- 6-2 p-mole/cm2 sec and for Loligo fibres in 460 mM-NaCl from 50-5 +/- 4 to 20 +/- 8 p-mole/cm2 sec. 5. Using depolarizing pulses of various durations, the extra calcium influx occurred in two phases. The early phase was eliminated by external application of tetrodotoxin. The results of analysis are consistent with, but do not rigorously demonstrate, the conclusion that the tetrodotoxin sensitive calcium entry is flowing through the normal sodium channels (cf. Baker, Hodgkin & Ridgway, 1971). 6. Measurements of extra influxes using 22Na and 45Ca simultaneously indicate that the time courses of tetrodotoxin sensitive calcium and sodium entry are similar but not necessarily identical. It is very doubtful that any significant calcium entry occurs before the sodium or is involved in the activation of the sodium system. 7. These measurements confirm for Loligo, as previously shown for Dosidicus axons, that the magnitude and time course of the sodium entry during a depolarizing pulse deduced from electrical measurements is the same as that measured with 22Na. 8. Using 28Mg, or mixtures of 45Ca and 28Mg, we observed a single phase of magnesium entry which was insensitive to external tetrodotoxin or internal tetraethyl ammonium. The magnitude of the magnesium influx was considerably greater than the calcium extra entry and large enough to have been detected in the experiments of Meves & Vogel (1973) if it represented current. 9. We suggest the possibility that the calcium and magnesium extra influxes, after external treatment with tetrodotoxin, during a depolarizing pulse, do not contribute to the measured current. PMID:1202193

Rojas, E; Taylor, R E

1975-01-01

129

Simultaneous measurements of magnesium, calcium and sodium influxes in perfused squid giant axons under membrane potential control.  

PubMed

1. Giant axons from the squids Dosidicus gigas, Loligo forbesi and Loligo vulgaris were internally perfused with 550 or 275 mM KF plus sucrose and bathed in artificial sea water containing 45Ca, 28Mg or mixtures of 45Ca-28Mg or 45Ca-22Na. Resting influxes and extra influxes during voltage-clamp pulses were measured by collecting and counting the internal perfusate. 2. For Dosidicus axons in 10 mM-CaCl2 the resting influx of calcium was 0-016 +/- 0-007 p-mole/cm2 sec and a linear function of external concentration. For two experiments in 10 and 84-7 mM-CaCl2, 100 nM tetrodotoxin had no effect. Resting calcium influx in 10 mM-CaCl2 was 0-017 +/- 0-013 p-mole/cm2 sec for Loligo axons. 3. With 55 mM-MgCl2 outside the average resting magnesium influx was 0-124 +/- 0-080 p-mole/cm2 sec for Loligo axons. Discarding one aberrant point the value is 0-105 +/- 0-046 which is not significantly different from the resting calcium influx for Dosidicus fibres in 55 mM-CaCl2, given as 0-094 p-mole/cm2 sec by the regression line shown in Fig. 1. In two experiments 150 nM tetrodotoxin had no effect. 4. With 430 mM-NaCl outside 100 nM tetrodotoxin reduced the average resting influx of sodium in Dosidicus axon from 27-7 +/- 4-5 to 25-1 +/- 6-2 p-mole/cm2 sec and for Loligo fibres in 460 mM-NaCl from 50-5 +/- 4 to 20 +/- 8 p-mole/cm2 sec. 5. Using depolarizing pulses of various durations, the extra calcium influx occurred in two phases. The early phase was eliminated by external application of tetrodotoxin. The results of analysis are consistent with, but do not rigorously demonstrate, the conclusion that the tetrodotoxin sensitive calcium entry is flowing through the normal sodium channels (cf. Baker, Hodgkin & Ridgway, 1971). 6. Measurements of extra influxes using 22Na and 45Ca simultaneously indicate that the time courses of tetrodotoxin sensitive calcium and sodium entry are similar but not necessarily identical. It is very doubtful that any significant calcium entry occurs before the sodium or is involved in the activation of the sodium system. 7. These measurements confirm for Loligo, as previously shown for Dosidicus axons, that the magnitude and time course of the sodium entry during a depolarizing pulse deduced from electrical measurements is the same as that measured with 22Na. 8. Using 28Mg, or mixtures of 45Ca and 28Mg, we observed a single phase of magnesium entry which was insensitive to external tetrodotoxin or internal tetraethyl ammonium. The magnitude of the magnesium influx was considerably greater than the calcium extra entry and large enough to have been detected in the experiments of Meves & Vogel (1973) if it represented current. 9. We suggest the possibility that the calcium and magnesium extra influxes, after external treatment with tetrodotoxin, during a depolarizing pulse, do not contribute to the measured current. PMID:1202193

Rojas, E; Taylor, R E

1975-10-01

130

Transformation of meta-stable calcium silicate hydrates to tobermorite: reaction kinetics and molecular structure from XRD and NMR spectroscopy.  

PubMed

Understanding the integrity of well-bore systems that are lined with Portland-based cements is critical to the successful storage of sequestered CO2 in gas and oil reservoirs. As a first step, we investigate reaction rates and mechanistic pathways for cement mineral growth in the absence of CO2 by coupling water chemistry with XRD and NMR spectroscopic data. We find that semi-crystalline calcium (alumino-)silicate hydrate (Al-CSH) forms as a precursor solid to the cement mineral tobermorite. Rate constants for tobermorite growth were found to be k = 0.6 (+/- 0.1) x 10(-5) s(-1) for a solution:solid of 10:1 and 1.6 (+/- 0.8) x 10(-4) s(-1) for a solution:solid of 5:1 (batch mode; T = 150 degrees C). This data indicates that reaction rates for tobermorite growth are faster when the solution volume is reduced by half, suggesting that rates are dependent on solution saturation and that the Gibbs free energy is the reaction driver. However, calculated solution saturation indexes for Al-CSH and tobermorite differ by less than one log unit, which is within the measured uncertainty. Based on this data, we consider both heterogeneous nucleation as the thermodynamic driver and internal restructuring as possible mechanistic pathways for growth. We also use NMR spectroscopy to characterize the site symmetry and bonding environment of Al and Si in a reacted tobermorite sample. We find two [4]Al coordination structures at delta iso = 59.9 ppm and 66.3 ppm with quadrupolar product parameters (PQ) of 0.21 MHz and 0.10 MHz (+/- 0.08) from 27Al 3Q-MAS NMR and speculate on the Al occupancy of framework sites by probing the protonation environment of Al metal centers using 27Al{1H}CP-MAS NMR. PMID:19144195

Houston, Jacqueline R; Maxwell, Robert S; Carroll, Susan A

2009-01-01

131

Continuous infusion of sivelestat sodium hydrate prevents lipopolysaccharide-induced intestinal paralysis and hypotension in conscious guinea-pigs.  

PubMed

1. Sivelestat sodium hydrate (sivelestat), a neutrophil elastase inhibitor, is used to treat acute lung injury associated with systemic inflammatory response syndrome, but its effects have not been described for endotoxaemia. In the present study, we examined the effects of a continuous infusion of sivelestat on intestinal mechanical activity and blood pressure using an endotoxaemic model in conscious, unrestrained guinea-pigs. 2. Guinea-pigs underwent laparotomy while anaesthetized and were implanted with a force transducer sutured onto the taenia caecum. With this transducer, changes in tension in the intestinal longitudinal muscle were measured continuously via telemetry. Catheters were inserted into the carotid artery and jugular vein, were tunnelled subcutaneously and were accessed from the back of the neck. These catheters were connected to a cannula swivel and were used to monitor arterial pressure as well as to administer drugs i.v. in conscious, unrestrained guinea-pigs. Twenty hours after surgery, guinea-pigs received a single dose of lipopolysaccharide (LPS; 0.3 mg/kg, i.p.) 10 min after the start of a continuous 2 h i.v. infusion of sivelestat (30 mg/kg per h) or vehicle (saline). Elastase activity before and after sivelestat or vehicle administration was measured spectrometrically using a specific synthetic substrate. 3. We confirmed that intestinal longitudinal muscle tension decreased 2-3 h after LPS administration in the control group, with a concurrent decline in blood pressure. In guinea-pigs treated with sivelestat, the LPS-induced decreases in muscle tension and blood pressure were significantly reduced. In LPS-treated control guinea-pigs, serum elastase activity was elevated and this increase was significantly attenuated by administration of sivelestat. 4. The findings from the present study suggest that sivelstat can effectively reduce intestinal dysfunction and attenuate LPS-induced decreases in blood pressure in endotoxaemia. PMID:18346172

Hara, Shunsuke; Nemoto, Kayo; Ninomiya, Norifumi; Kubota, Minoru; Kuno, Masamune; Yamamoto, Yasuhiro

2008-07-01

132

Study on coordination characteristics of neptunium and uranium ions in calcium nitrate hydrate melt by Raman spectrometry and UV/Vis/NIR spectrometry  

NASA Astrophysics Data System (ADS)

Extraction behavior of neptunium (Np) by tri-n-butyl phosphate from calcium nitrate hydrate melt was investigated. Distribution ratio of Np was found to increase with the decrease of water content. Adding nitric acid into the system resulted in an increase of the distribution ratio. In order to understand the extraction trends, Np species in the hydrate melt were analyzed by Raman spectrometry and UV/Vis/NIR spectrometry. Major fraction was assigned to be NpO22+ of Np(VI) and small fraction to be NpO2+ of Np(V). A shift of the v1 symmetric vibrational frequency of NpO22+ in nitrate media was found in Raman spectra. This suggests a coordination circumstance change of NpO22+.

Fujii, T.; Okude, G.; Uehara, A.; Yamana, H.

2010-03-01

133

Myocardial Function with Reduced Expression of the Sodium-Calcium Exchanger  

PubMed Central

Background The complete removal of the cardiac sodium-calcium exchanger (NCX1) is associated with embryonic lethality while its overexpression is linked to heart failure. To determine whether or not a reduced expression of NCX1 is compatible with normal heart structure and function, we studied two knockout mouse models with reduced levels of NCX1: a heterozygous global knockout (HG-KO) with a 50% level of NCX1 expression in all myocytes, and a ventricular specific KO (V-KO) with NCX1 expression in only 10-20% of the myocytes. Methods and Results Both groups of mice were evaluated at baseline, after trans-aortic constriction (TAC), and after acute or chronic beta-adrenergic stimulation. At baseline, the HG-KO mice had smaller hearts and the V-KO mice had larger hearts than their wild-type (WT) controls (P<0.05). The HG-KO and their control WT mice had normal responses to TAC and beta-adrenergic stimulation. However, the V-KO group was intolerant to TAC and had a significantly (P<0.05) blunted response to beta-adrenergic stimulation as compared to the HG-KO mice and WT controls. Unlike the HG-KO mice, the V-KO mice did not tolerate chronic isoproterenol infusion. Telemetric analysis of the ECG, body temperature and activity revealed a normal diurnal rhythm in all groups of mice, but confirmed shorter QT intervals along with increased arrhythmias and reduced R/P amplitude ratios in the V-KO mice. Conclusions Though NCX1 can be reduced by ½ in all myocytes without significant functional alterations, it must be expressed in more than 20% of the myocytes to prevent severe remodeling and heart failure in mouse heart. PMID:20797603

Jordan, Maria C.; Henderson, Scott. A.; Han, Tieyan; Fishbein, Michael C.; Philipson, Kenneth D.; Roos, Kenneth P.

2010-01-01

134

Investigation of the physico-chemical properties of calcium borophosphate glasses. Effect of the substitution of sodium for calcium  

Microsoft Academic Search

Calcium borophosphate glasses have been prepared by quenching melted mixtures of Ca(PO3)2 and B2O3. Their physical and chemical properties, such as glass transition and crystallization temperatures, density, microhardness, solubility in water and UV edge absorption, are studied as a function of the molar fraction B\\/B+P. The interpretation of the results are based on the presence of BO4 units and B–O–P

N Hadj Youssef; M. S Belkhiria; J. J Videau; M Ben Amara

2000-01-01

135

Surfactant effects on gas hydrate formation  

Microsoft Academic Search

Micellar solutions were found to increase gas hydrate formation rate and alter formation mechanism for ethane and natural gas hydrates. A critical micellar concentration (CMC) of sodium dodecyl sulfate water solution was found to be 242 ppm at hydrate-forming conditions, where CMC was best determined by hydrate induction time. At surfactant concentrations above the CMC, hydrate formation rates in a

Y. Zhong; R. E. Rogers

2000-01-01

136

Axonal protection achieved by blockade of sodium/calcium exchange in a new model of ischemia in vivo  

PubMed Central

Ischemic white matter injury has been relatively little studied despite its importance to the outcome of stroke. To aid such research a new rat model has been developed in vivo and used to assess whether blockade of the sodium/calcium exchanger is effective in protecting central axons from ischemic injury. Vasoconstrictive agent endothelin-1 was injected into the rat spinal cord to induce ischemia. KB-R7943 or SEA0400 was administered systemically to block the operation of the sodium/calcium exchanger. Endothelin-1 caused profound reduction of local blood perfusion and resulted in a prompt loss of axonal conduction. Whereas recovery of conduction following vehicle administration was only to 10.5 ± 9% of baseline (n = 8) 4.5 h after endothelin-1 injection, recovery following KB-R7943 (30 mg/kg, i.a.) administration was increased to 35 ± 9% of baseline (n = 6; P < 0.001). SEA0400 (30 mg/kg, i.a.) was also protective (33.2 ± 6% of baseline, n = 4; P < 0.001). Neither drug improved conduction by diminishing the severity of the ischemia. The protective effect of KB-R7943 persisted for at least 3 days after ischemia, as it improved axonal conduction (76.3 ± 11% for KB-R7943 vs. 51.0 ± 19% for vehicle; P < 0.01) and reduced lesion area (55.6 ± 15% for KB-R7943 vs. 77.9 ± 9% for vehicle; P < 0.01) at this time. In conclusion, a new model of white matter ischemia has been introduced suitable for both structural and functional studies in vivo. Blocking the sodium/calcium exchanger protects central axons from ischemic injury in vivo. PMID:22564441

Bei, Fengfeng; Smith, Kenneth J.

2012-01-01

137

Tolperisone-type drugs inhibit spinal reflexes via blockade of voltage-gated sodium and calcium channels.  

PubMed

The spinal reflex depressant mechanism of tolperisone and some of its structural analogs with central muscle relaxant action was investigated. Tolperisone (50-400 microM), eperisone, lanperisone, inaperisone, and silperisone (25-200 microM) dose dependently depressed the ventral root potential of isolated hemisected spinal cord of 6-day-old rats. The local anesthetic lidocaine (100-800 microM) produced qualitatively similar depression of spinal functions in the hemicord preparation, whereas its blocking effect on afferent nerve conduction was clearly stronger. In vivo, tolperisone and silperisone as well as lidocaine (10 mg/kg intravenously) depressed ventral root reflexes and excitability of motoneurons. However, in contrast with lidocaine, the muscle relaxant drugs seemed to have a more pronounced action on the synaptic responses than on the excitability of motoneurons. Whole-cell measurements in dorsal root ganglion cells revealed that tolperisone and silperisone depressed voltage-gated sodium channel conductance at concentrations that inhibited spinal reflexes. Results obtained with tolperisone and its analogs in the [3H]batrachotoxinin A 20-alpha-benzoate binding in cortical neurons and in a fluorimetric membrane potential assay in cerebellar neurons further supported the view that blockade of sodium channels may be a major component of the action of tolperisone-type centrally acting muscle relaxant drugs. Furthermore, tolperisone, eperisone, and especially silperisone had a marked effect on voltage-gated calcium channels, whereas calcium currents were hardly influenced by lidocaine. These data suggest that tolperisone-type muscle relaxants exert their spinal reflex inhibitory action predominantly via a presynaptic inhibition of the transmitter release from the primary afferent endings via a combined action on voltage-gated sodium and calcium channels. PMID:16126840

Kocsis, Pál; Farkas, Sándor; Fodor, László; Bielik, Norbert; Thán, Márta; Kolok, Sándor; Gere, Anikó; Csejtei, Mónika; Tarnawa, István

2005-12-01

138

The substitution of sodium for calcium in the mineral nutrition of cotton  

E-print Network

and partly by allowing the more efficient usage of potas- sium for specific essential functions when potassium is deficient. However, at two locations sodium nitrate significantly increased the yield of seed cotton over an ammonium nitrate-lime combination.... However, sodium increased yields at all levels of potas- sium, and consistently increased the carbohydrate content of the plants by about seven per cent. Various sodium and potassium treatments were also employed in field trials with red beets. Yield...

Whitenberg, David Calvin

2012-06-07

139

Comparative evaluation of a dentifrice containing calcium sodium phosphosilicate to a dentifrice containing potassium nitrate for dentinal hypersensitivity: A clinical study  

PubMed Central

Background: Calcium sodium phosphosilicate is a recently introduced desensitizing agent which acts by occluding the dentinal tubules and also resists acid decalcification. This study was designed to assess the efficacy of a new toothpaste containing 5% calcium sodium phosphosilicate for the treatment of dentinal hypersensitivity and also compare it with 5% potassium nitrate. Materials and Methods: Sixty patients with the chief complaint of dentinal hypersensitivity were enrolled and randomly divided into two groups. The visual analog scale (VAS) scores were taken for water and air stimuli at baseline, 3 weeks after usage of the respective toothpaste, and 3 weeks after discontinuation of the respective toothpaste. Results: Both the groups showed reduction in hypersensitivity scores at 3 weeks and 6 weeks for air stimulus and cold water. The calcium sodium phosphosilicate group, however, showed significantly reduction in hypersensitivity compared to the potassium nitrate group at any time point for both measures of hypersensitivity. Conclusion: The 5% calcium sodium phosphosilicate group showed immense reduction in dentinal hypersensitivity symptoms. The 5% calcium sodium phosphosilicate showed prolonged effects even after discontinuation as compared to 5% potassium nitrate, due to its dentinal tubular occlusion property. PMID:25425819

Satyapal, Tanya; Mali, Rohini; Mali, Amita; Patil, Vishakha

2014-01-01

140

The arrhythmogenic current ITI in the absence of electrogenic sodium-calcium exchange in sheep cardiac Purkinje fibres.  

PubMed Central

Sheep cardiac Purkinje fibres were voltage clamped with a two-microelectrode technique. Under conditions that are known to elevate intracellular calcium (0 mM-external potassium), membrane currents were examined. In the above conditions, a brief depolarizing pulse leads to an oscillatory inward current (ITI) which peaks at about 300 ms after the repolarization. An after-contraction is also observed, the peak of which occurs about 80 ms after the peak of ITI. This result is in accord with the results of Kass, Lederer, Tsien & Weingart (1978a). We replaced external sodium with an isotonic CaCl2 solution to remove the sodium-calcium exchange mechanism as a possible current carrier for ITI. In the steady state under these conditions an oscillatory membrane current and after-contraction are seen following repolarization. This current was identified as ITI on the basis of its temporal relation to both the repolarization step and the after-contraction. In isotonic CaCl2, ITI has a reversal potential of -37 mV. Because of this fact ITI cannot be explained by an electrogenic sodium-calcium exchange mechanism alone. The reversal potential suggests that ITI arises from a channel which is permeable to both potassium and calcium. Fluctuations of membrane current and of tension were recorded in the steady state at different holding potentials. Power spectral analysis showed that the current fluctuations were at a minimum at a holding potential of -37 mV. Tension fluctuations were, however, relatively constant over the range of membrane potentials examined (-17 to -70 mV). The peak power of the current fluctuations occurred at about 1.5 Hz (at a holding potential of -70 mV). This peak shifted towards higher frequencies with increasing depolarization. A similar shift in frequency was observed for the tension fluctuations. Cross-correlations between membrane current and tension were calculated for various steady membrane potentials. This analysis shows that the current fluctuations are associated with the tension fluctuations, each with a principal period of about 0.5 s. This analysis also shows that at potentials more negative than the reversal potential of ITI, increasing tension is associated with increasing inward current and that the tension fluctuations follow current fluctuations by about 70 ms. At potentials positive to the reversal potential of ITI, increasing tension was associated with increasing outward current. This analysis therefore indicates that the fluctuations in membrane current reverse at a potential similar to the reversal potential of ITI.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3746687

Cannell, M B; Lederer, W J

1986-01-01

141

Calcium  

MedlinePLUS

... it from: Dairy products. Low-fat milk, yogurt, cheese, and cottage cheese are good sources of calcium. Veggies. You'll ... burritos or wraps. Fill them with eggs and cheese for breakfast; turkey, cheese, lettuce, tomato, and light ...

142

Influence of Pyrethroid Insecticides on Sodium and Calcium Influx in Neocortical Neurons  

EPA Science Inventory

Pyrethroid insecticides bind to voltage-gated sodium channels and modify their gating kinetics, thereby disrupting neuronal function. Using murine neocortical neurons in primary culture, we have compared the ability of 11 structurally diverse pyrethroid insecticides to evoke Na+ ...

143

Intraoral evaluation of mineralization of cosmetic defects by a toothpaste containing calcium, fluoride, and sodium bicarbonate.  

PubMed

New dual-phase fluoride toothpastes that contain soluble calcium, phosphate, and baking soda have recently been introduced into the market. These toothpastes are designed to fill in small surface defects in tooth enamel and thereby enhance tooth esthetics such as gloss. This two-part study was designed to assess these superficial mineralizing effects from using one of these products compared with an experimental calcium-containing, bicarbonate-free formulation and a conventional fluoride toothpaste using an intraoral model. Enamel specimens with 4 types of defects were mounted into an intraoral appliance and placed in the mouths of volunteers for 1 month. The four types of defects were whitening toothpaste abrasion, coarse abrasion, natural dimpling, and acid etching. Before and after intraoral exposure, scanning electron microscope photographs of the specimens were made. The surface microhardness of the acid-etched specimens also was determined. The volunteers brushed their specimens twice daily with one of three randomly assigned toothpastes. The toothpastes were a two-phase, calcium-containing, bicarbonate-based toothpaste; an experimental, two-phase, calcium-containing, bicarbonate-free toothpaste; and a conventional toothpaste. Only the calcium-containing toothpastes showed unequivocal signs of mineral deposition into surface defects, leading to smoothing of the enamel. All three products significantly increased the hardness of the etched enamel, presumably because of fluoride. However, only the two calcium-containing toothpastes gave significantly greater hardness increases than the conventional toothpaste; the specimens treated with a conventional toothpaste were indistinguishable from those treated with saliva. PMID:15645904

Litkowski, Leonard J; Quinlan, Kathleen B; Ross, David R; Ghassemi, Annahita; Winston, Anthony; Charig, Andrew; Flickinger, Mark; Vorwerk, Linda

2004-09-01

144

Molecular dynamics modeling of the interface between surface functionalized graphitic structures and calcium-silicate-hydrate: interaction energies, structure, and dynamics.  

PubMed

Molecular dynamics simulations were performed to study the molecular-scale energetic, structural, and dynamic properties of the interface between surface functionalized graphitic structures and calcium-silicate-hydrate (C-S-H). The 9 A tobermorite structure was used as a model for C-S-H, the main building block ("the glue") that hold a cementitious matrix together. Six types of carbon surface structures were investigated: a pristine graphite plane and five graphite planes functionalized with hydroxyl (OH), carboxyl (COOH), carboxylate (COO(-), deprotonated carboxyl), carbonyl (CO), and amine (NH(2)) groups. Results demonstrated the dominant role of electrostatic forces in the interfacial interactions and indicated that the polarity of the functional group can be used as an indicator of affinity to C-S-H. MD simulations revealed that an optimal number of polar oxygen containing groups may exist for efficient graphitic structure/cement interaction and emphasized the mediating role of Ca(2+) counterions in the interfacial interactions. PMID:18486142

Sanchez, F; Zhang, L

2008-07-15

145

Morphological and phase changes in calcium oxalate crystals grown in the presence of sodium diisooctyl sulfosuccinate  

Microsoft Academic Search

Calcium oxalate was crystallized in the presence of the anionic surfactant dioctyl sulphosuccinate, AOT, and the phase composition of the precipitates (by X-ray diffraction powder patterns and thermal analysis) and their crystal growth morphology (by scanning electron microscopy and electron diffraction) were determined. In the control systems and in the presence of low concentrations of AOT (below the critical micellar

L. Tunik; L. Addadi; N. Garti; H. Füredi-Milhofer

1996-01-01

146

Glass powder blended cement hydration modelling  

NASA Astrophysics Data System (ADS)

The use of waste materials in construction is among the most attractive options to consume these materials without affecting the environment. Glass is among these types of potential waste materials. In this research, waste glass in powder form, i.e. glass powder (GP) is examined for potential use in enhancing the characteristics of concrete on the basis that it is a pozzolanic material. The experimental and the theoretical components of the work are carried out primarily to prove that glass powder belongs to the "family" of the pozzolanic materials. The chemical and physical properties of the hydrated activated glass powder and the hydrated glass powder cement on the microstructure level have been studied experimentally and theoretically. The work presented in this thesis consists of two main phases. The first phase contains experimental investigations of the reaction of glass powder with calcium hydroxide (CH) and water. In addition, it includes experiments that are aimed at determining the consumption of water and CH with time. The reactivity, degree of hydration, and nature of the pore solution of the glass powder-blended cement pastes and the effect of adding different ratios of glass powder on cement hydration is also investigated. The experiments proved that glass powder has a pozzolanic effect on cement hydration; hence it enhances the chemical and physical properties of cement paste. Based on the experimental test results, it is recommended to use a glass powder-to-cement ratio (GP/C) of 10% as an optimum ratio to achieve the best hydration and best properties of the paste. Two different chemical formulas for the produced GP C-S-H gel due to the pure GP and GP-CH pozzolanic reaction hydration are proposed. For the pure GP hydration, the produced GP C-S-H gel has a calcium-to-silica ratio (C/S) of 0.164, water-to-silica ratio (H/S) of 1.3 and sodium/silica ratio (N/S) of 0.18. However, for the GP-CH hydration, the produced GP C-S-H gel has a C/S ratio of 1.17, H/S ratio of 2.5 and N/S ratio of 0.18. In the second phase of this research, theoretical models are built using a modified version of an existing cement hydration modelling code, "CEMHYD3D", to simulate the chemical reaction of the activated glass powder hydration and glass powder in cement. The modified model, which is referred to as the "MOD-model" is further used to predict the types, compositions and quantities of reaction products. Furthermore, the glass powder hydration data, which is obtained experimentally, is incorporated into the MOD-model to determine the effect of adding glass powder to the paste on the process of cement hydration and resulting paste properties. Comparisons between theoretical and experimental results are made to evaluate the developed models. The MOD-model predictions have been validated using the experimental results, and were further used to investigate various properties of the hydrated glass powder cement paste. These properties include, for example, CH content of the paste, porosity, hydration degree of the glass powder and conventional C-S-H and GP CS-H contents. The results show that the MOD-model is capable of accurately simulating the hydration process of glass powder-blended cement paste and can be used to predict various properties of the hydrating paste.

Saeed, Huda

147

Sodium nitrate particles: physical and chemical properties during hydration and dehydration, and implications for aged sea salt aerosols  

Microsoft Academic Search

Experiments probing the phase and behavior of NaNO3 particles at different relative humidities, important for elucidating the role these particles play in the chemistry and radiative properties of marine regions, are presented. Changes in NaNO3 particles during hydration were studied using environmental scanning electron microscopy (ESEM) and conventional SEM coupled with energy dispersive X-ray analysis (SEM\\/EDX). Mixtures of NaNO3 and

Rachel C. Hoffman; Alexander Laskin; Barbara J. Finlayson-Pitts

2004-01-01

148

Interactions of Organic Additives with Ionic Crystal Hydrates  

NASA Astrophysics Data System (ADS)

The interactions of two groups of hydrated model crystals, calcium hydrogenphosphate dihydrate (DCPD) vs. octacalcium phosphate (OCP) and calcium oxalate monohydrate (COM) vs. calcium oxalate dihydrate (COD) with different organic additives are considered. DCPD precipitates as platelet-like crystals with the dominant faces shielded by hydrated layers and charged lateral faces. In the second system COM has charged surfaces, while all faces of COD are covered with layers containing water molecules. The organic molecules tested include negatively charged, flexible and rigid small and macromolecules (glutamic and aspartic acid, citrate, hexaammonium polyphosphate, phytate and polyaspartate) and anionic surfactants (sodium dodecyl sulphate, SDS, sodium diisooctyl sulfosuccinate, AOT, sodium cholate NaC and disodium oleoamido PEG-2 sulfosuccinate, PEG). Two types of effects have been demonstrated: (1) Effect on crystal growth morphology: Flexible organic molecules with high charge density and anionic surfactants affected the growth morphology of DCPD and COM by selectively interacting with the charged lateral faces while rigid molecules (phytate, polyaspartate) specifically recognized the dominant (010) face of DCPD due to structural and stereochemical compatibility. (2) Effect on phase composition: Anionic surfactants at concentrations above the cmc promoted growth of OCP and COD respectively by selectively adsorbing at, and inhibiting growth oif nuclei of DCPD and/or COM, which were dominant in the respective control systems. The effect was especially pronounced in the calcium oxalate precipitation system, where in some cases complete reversal of the phase composition occurred. The important role of the hydrated layer, as part of the structure of the investigated crystal hydrates, in the above crystal additive interactions is discussed.

Füredi-Milhofer, H.; Sikiri?, M.; Tunik, L.; Filipovi?-Vincekovi?, N.; Garti, N.

149

Sodium helps our body balance fluid levels and maintain hydration. Each person's sodium requirement varies but one thing we do know is that Americans are consuming  

E-print Network

of Agriculture, and County Boards of Chosen Freeholders. Rutgers Cooperative Extension, is a unit of the Rutgers be Caused by Lack of Sleep? 2 Oral Health and Nutrition in Older Adults 3 Don't Sabotage Your Healthy of sodium or other names for the #12;Does lack of sleep really lead to unhealthy eating and decreased

Garfunkel, Eric

150

Facile surface modification of nanoprecipitated calcium carbonate by adsorption of sodium stearate in aqueous solution  

Microsoft Academic Search

A simple and solvent free two-step process for nanosized and surface-modified precipitated calcium carbonate (ns-PCC) synthesis has been proposed. Synthesized ns-PCC was thoroughly characterized by infra-red (IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Langmuir adsorption study. Dynamic laser scattering (DLS) results on particle size showed a good correlation with those obtained by the proposed empirical model. Two aspects

Hoang Vinh Tran; Lam Dai Tran; Hoang Dinh Vu; Hoang Thai

2010-01-01

151

Histrionicotoxins: Effects on binding of radioligands for sodium, potassium, and calcium channels in brain membranes  

Microsoft Academic Search

A series of eight histrionicotoxins and two synthetic analogs inhibit binding of [3H]batrachotoxinin B to sites on voltage dependent sodium channels in brain membranes. Perhydrohistrionicotoxin (IC50 0.33 µM) and octahydrohistrionicotoxin (IC50 1.2 µM) are comparable in activities to potent local anesthetics. Histrionicotoxin (IC50 17 µM) and the other histrionicotoxins are much less potent. The histrionicotoxins also inhibit binding of [3H]phencyclidine

T. Lovenberg; J. W. Daly

1986-01-01

152

The growth and chemical composition of soybeans as influenced by varying sulphur applications, varying soluble salts and varying calcium: sodium ratios  

E-print Network

on the Concentration and Total Uptiice of Calcium bv PLants Table 7 ~ Ths Effect of tbe Combinations of Sulphur' Soluble ~ts~ and Calci~Sium Ratio on the Concentration and Total Uptake of Calcium bv Plants MoKe/gmi Total M, E, Sulphur None None None 750 750... with ccrossing soluble salts, Again the greater pox tion of this decrease oan be accounted fox bf decreasing yield (Tables 9 and 11)& A highly' significant decrease in ma~sium co~ation occurred with dscxeaxd. ng ca3. cium sodium ratio (' fable 9 and Pig. 5...

Peters, Doyle Burne

2012-06-07

153

THE EFFECT OF EXTERNAL SODIUM AND CALCIUM CONCENTRATIONS ON SODIUM FLUXES BY SALT-DEPLETED AND NON-DEPLETED MINNOWS, PHOXINUS PHOXINUS (L.)  

Microsoft Academic Search

SUMMARY The relationship between sodium influx and external sodium concentration in Phoxinus is complex and unusual. In non-depleted fish the relationship is approxi- mately that given by the Michaelis—Menten equation of enzyme kinetics. However, the A.\\

W. J. FRAIN

154

Complete Atrial-Specific Knockout of Sodium-Calcium Exchange Eliminates Sinoatrial Node Pacemaker Activity  

PubMed Central

The origin of sinoatrial node (SAN) pacemaker activity in the heart is controversial. The leading candidates are diastolic depolarization by “funny” current (If) through HCN4 channels (the “Membrane Clock“ hypothesis), depolarization by cardiac Na-Ca exchange (NCX1) in response to intracellular Ca cycling (the "Calcium Clock" hypothesis), and a combination of the two (“Coupled Clock”). To address this controversy, we used Cre/loxP technology to generate atrial-specific NCX1 KO mice. NCX1 protein was undetectable in KO atrial tissue, including the SAN. Surface ECG and intracardiac electrograms showed no atrial depolarization and a slow junctional escape rhythm in KO that responded appropriately to ?-adrenergic and muscarinic stimulation. Although KO atria were quiescent they could be stimulated by external pacing suggesting that electrical coupling between cells remained intact. Despite normal electrophysiological properties of If in isolated patch clamped KO SAN cells, pacemaker activity was absent. Recurring Ca sparks were present in all KO SAN cells, suggesting that Ca cycling persists but is uncoupled from the sarcolemma. We conclude that NCX1 is required for normal pacemaker activity in murine SAN. PMID:24278453

Groenke, Sabine; Larson, Eric D.; Alber, Sarah; Zhang, Rui; Lamp, Scott T.; Ren, Xiaoyan; Nakano, Haruko; Jordan, Maria C.; Karagueuzian, Hrayr S.; Roos, Kenneth P.; Nakano, Atsushi; Proenza, Catherine; Philipson, Kenneth D.; Goldhaber, Joshua I.

2013-01-01

155

Ultrathin calcium silicate hydrate nanosheets with large specific surface areas: synthesis, crystallization, layered self-assembly and applications as excellent adsorbents for drug, protein, and metal ions.  

PubMed

A simple and low-cost solution synthesis is reported for low-crystalline 1.4 nm tobermorite-like calcium silicate hydrate (CSH) ultrathin nanosheets with a thickness of ~2.8 nm and with a large specific surface area (SSA), via a reaction-rate-controlled precipitation process. The BET SSA of the CSH ultrathin nanosheets can reach as high as 505 m(2) g(-1) . The CSH ultrathin nanosheets have little cytotoxicity and can be converted to anhydrous calcium silicate (ACS) ultrathin nanosheets with a well preserved morphology via a heat treatment process. The crystallinity of CSH ultrathin nanosheets can be improved by solvothermal treatment in water/ethanol binary solvents or a single solvent of water, producing well-crystalline 1.1 nm tobermorite-like CSH nanobelts or nanosheets. CSH ultrathin nanosheets acting as building blocks can self-assemble into layered nanostructures via three different routes. The CSH ultrathin nanosheets are investigated as promising adsorbents for protein (hemoglobin, Hb), drug (ibuprofen, IBU), and metal ions (Cr(3+) , Ni(2+) , Cu(2+) , Zn(2+) , Cd(2+) , Pb(2+) ). The highest adsorbed percentages of Hb and IBU are found to be 83% and 94%, respectively. The highest adsorption capacities of Hb and IBU are found to be as high as 878 milligram Hb per gram CSH and 2.2 gram IBU per gram CSH, respectively. The ppm level metal ions can be totally adsorbed from aqueous solution in just a few minutes. Thus, the CSH ultrathin nanosheets are a promising candidate as excellent adsorbents in the biomedical field and for waste water treatment. Several empirical laws are summarized based on the adsorption profiles of Hb and IBU using CSH ultrathin nanosheets as the adsorbent. Furthermore, the ACS ultrathin nanosheets as adsorbents for Hb protein and IBU drug are investigated. PMID:23585365

Wu, Jin; Zhu, Ying-Jie; Chen, Feng

2013-09-01

156

Stabilization/solidification of mercury-contaminated waste ash using calcium sodium phosphate (CNP) and magnesium potassium phosphate (MKP) processes.  

PubMed

This study examined the stabilization and solidification (S/S) of mercury (Hg)-contaminated waste ash generated from an industrial waste incinerator using chemically bonded phosphate ceramic (CBPC) technology. A magnesium potassium phosphate (MKP; MgKPO4 · 6H2O) ceramic, fabricated from MgO and KH2PO4, and a calcium sodium phosphate (CNP; CaNaPO4) ceramic, fabricated from CaO and Na2HPO4, were used as solidification binders in the CBPC process, and Na2S or FeS was added to each solidification binder to stabilize the Hg-contaminated waste ash. The S/S processes were conducted under various operating conditions (based on the solidification binder and stabilization reagent, stabilization reagent dosage, and waste loading ratio), and the performance characteristics of the S/S sample under each operating condition were compared, including the Hg leaching value and compressive strength. The Hg leaching value of untreated Hg-contaminated waste ash was 231.3 ?g/L, whereas the S/S samples treated using the MKP and CNP processes exhibited Hg leaching values below the universal treatment standard (UTS) limit (25 ?g/L). Although the compressive strengths of the S/S samples decreased as the sulfide dosage and waste loading ratio were increased, most of the S/S samples fabricated by the MKP and CNP processes exhibited good mechanical properties. PMID:24997263

Cho, Jae Han; Eom, Yujin; Lee, Tai Gyu

2014-08-15

157

Photoresponsive Ion Extraction/Release Systems: Dynamic Ion Optodes for Calcium and Sodium Based on Photochromic Spiropyran  

PubMed Central

Photoresponsive ion extraction/release systems (PRIONERS) represent a highly interesting tool for the localized and time-controlled chemical perturbation of biological materials. We report here on our first results on phototriggered calcium and sodium exchanging materials. Such materials exist in two distinct states (“on” and “off”), depending on the wavelength of illumination. We used a combination of spectroscopic and electrochemical methods to obtain a better understanding of the dynamic processes involved in the triggered ion-exchange reaction upon activation of the photoactive compound. The driving force for the ion exchange is the light-induced acidity change of the chromoionophore. Activation with UV light generates a species in the membrane with an increased pKa. Protons are pulled into the membrane, and at the same time, ions are expelled. The selectivity of the system is determined by the employed ionophore. In contrast to photoresponsive ionophore-based systems, the concept presented here is applicable for virtually any ion of interest for which an ionophore exists. PMID:23387291

2013-01-01

158

Flame photometric and atomic absorption determination of calcium, potassium, and sodium in Ringer's solution and injection and in lactated Ringer's solution.  

PubMed

Authentic and commerical counterparts of Ringer's solution and lactated Ringer's solution were analyzed by 14 collaborators. Calcium, potassium, and sodium were to be determined by any flame emission or atomic absorption instrument operated at prescribed performance levels, and basic procedures for comparing samples and standards were also given. Recoveries of the cations from authentic and commercial solutions were as follows: calcium 95.6-102.1 and 95.6-103.6%, respectively; potassium 97.9-101.7 and 98.7-102.4%; sodium 98.2-103.1 and 97.3-103.7%. The results indicate that the method yields acceptable precision for the determination of the 3 cations in fluid and electrolyte replenishers. The method has been adopted as official first action. PMID:893312

Weeks, J F

1977-07-01

159

Effect of Sodium and Calcium Carbonates on Milk Production and Composition of Milk, Blood, and Rumen Contents of Cows Fed Grain Ad Libitum with Restricted Roughage1  

Microsoft Academic Search

SUMMARY Six cows were used in a Latin square design consisting of three periods of 28 days each and three treatments, grain plus sodium bicarbonate (1 lb\\/day), grain plus calcium carbonate (0.6 lb\\/day), and grain alone. Roughage was restricted to 2 lb hay\\/day and grain was fed ad libitum. Similarly, two groups of five cows each were used in a

R. S. Emery; L. D. Brown; J. W. Thomas

1964-01-01

160

Dietary Intake Ratios of Calcium-to-Phosphorus and Sodium-to-Potassium Are Associated with Serum Lipid Levels in Healthy Korean Adults  

PubMed Central

The purpose of this study was to identify food sources for major minerals such as calcium (Ca), phosphorus (P), sodium (Na) and potassium (K), and to evaluate the relationship between dietary intake of these minerals and serum lipids in healthy Korean adults. A total of 132 healthy men and women completed a physical examination and dietary record and provided blood samples for lipid profile analysis. Results showed the following daily average mineral intakes: 373.4 mg of calcium, 806.0 mg of phosphorous, 3685.8 mg of sodium, and 1938.3 mg of potassium. The calcium-to-phosphorus and sodium-to-potassium ratio was about 0.5 and 2.0, respectively. The primary sources for each mineral were: vegetables (24.9%) and fishes (19.0%) for calcium, grains (31.4%) for phosphorus, seasonings (41.6%) and vegetables (27.0%) for sodium, and vegetables (30.6%) and grains (18.5%) for potassium. The correlation analysis, which has been adjusted for age, gender, total food consumption, and energy intake, showed significantly positive correlations between Ca/P and serum HDL cholesterol levels, between Na intake and the level of serum total cholesterol, and between Na/K and the level of serum cholesterol and LDL cholesterol. Our data indicates that the level of mineral consumption partially contributes to serum lipid profiles and that a diet consisting of a low Ca/P ratio and a high Na/K ratio may have negative impacts on lipid metabolism. PMID:24471069

Bu, So-Young; Kang, Myung-Hwa; Kim, Eun-Jin; Choi, Mi-Kyeong

2012-01-01

161

Characteristics of sodium and calcium conductance changes produced by membrane depolarization in an Aplysia neurone.  

PubMed Central

1. The time course and voltage dependence of Na and Ca conductance changes produced by depolarization of the soma of the neurone R15 in the abdominal ganglion of Aplysia juliana were examined at temperatures of 10--14 degrees C. 2. During a maintained depolarization, Na currents turned on then decayed (inactivated). Inactivation was exponential with time constant tauh. Activation (after correction for inactivation) was reasonably well described by the expression G'Na(t) = G'Na (infinity) (1 - exp [-t/taum])3 over a wide range of potentials. 3. taum and tauh were both voltage dependent. In the range -20 to +40 mV, taum varied from 5 to 0.5 msec and tauh from 25 to 8 msec (13.5 degrees C). Steady-state Na conductance (corrected for inactivation) was voltage dependent also, increasing sigmoidally with depolarization to a maximum of 25--30 muS at +10 to +20 mV. Half-maximal Na conductance occurred at a membrane potential of -8 mV and from -15 to -5 mV, a 5 mV change in membrane potential produced an e-fold change in steady-state Na conductance. 4. Steady-state inactivation of Na conductance (hNa(infinity)) was voltage dependent with half-inactivation occurring at a membrane potential of -32 mV. Recovery from Na inactivation followed an exponential time course with a voltage-dependent time constant. 5. During a maintained depolarization Ca currents activated then decayed (inactivated) more slowly than Na currents. The decay was exponential with time constant tauH. The decay of Ca current was not an artifact porduced by an outward current. The amplitude of calcium tail currents, produced by voltage steps back to epsilonK at different times during the decay of ICa, decayed also with a time constant close to tauH. 6. Ca conductance (after correction for inactivation) could be described approximately by the expression G'Ca(t) = G'Ca(infinity) (1 - exp [-t/tauM])p but it was necessary to vary p from 1 to 2 at different potentials. No value of p gave as good a fit to this model as that obtained for Na currents. 7. taum and tauH were voltage dependent. In the range of potentials from 0 to +60 mV, tauM varied from 9 to 5 msec and tauH from 300 to 50 msec (13.5 degrees C). Steady-state Ca conductance (corrected for inactivation) was voltage dependent also, increasing sigmoidally with depolarization to a maximum of 10--15 muS at +30 to +40 mV. Half-maximal Ca conductance occurred at a membrane potential of +12 mV, and from +10 to +20 mV a 6 mV change in membrane potential produced an e-fold change in Ca conductance. 8. Steady-state inactivation of Ca conductance (hCa(infinity)) varied with holding potential (VH). Half-inactivation occurred with depolarization to -20 mV. At potentials more negative than -40 mV, hCa(infinity) was less than at -40 mV, i.e. hyperpolarization produced Ca 'inactivation'. 9... Images Fig. 1 Fig. 5 Fig. 7 PMID:458645

Adams, D J; Gage, P W

1979-01-01

162

Early age hydration of calcium sulfoaluminate (synthetic ye'elimite, C{sub 4}A{sub 3}S{sup ¯}) in the presence of gypsum and varying amounts of calcium hydroxide  

SciTech Connect

Suspensions of synthetic ye'elimite (C{sub 4}A{sub 3}S{sup ¯}) in a saturated gypsum (CS{sup ¯}H{sub 2}) and calcium hydroxide (CH) solution were examined in-situ in a wet cell by soft X-ray transmission microscopy and ex-situ by scanning electron microscopy. The most voluminous hydration product observed was ettringite. Ettringite commonly displayed acicular, filiform, reticulated, and stellate crystal habits. Additionally, pastes with C{sub 4}A{sub 3}S{sup ¯}, 15% CS{sup ¯}H{sub 2}, and varying amounts of CH were prepared and examined with X-ray diffraction (XRD) and isothermal calorimetry. The XRD experiments showed that increasing CH content caused more solid solution (SO{sub 4}{sup 2?}/OH{sup ?}) AFm phases to form at early ages (< 1 d) and more monosulfate to form at later ages (> 1 d). Calorimetry indicated that the increased production of solid solution AFm was accompanied with an increase in the initial (< 30 min) rate of heat evolution, and increasing CH generally reduced the time till the second maximum rate of heat evolution due to the formation of ettringite and monosulfate.

Hargis, Craig W. [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States)] [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States); Kirchheim, Ana Paula [Department of Civil Engineering, Federal University of Rio Grande do Sul, Porto Alegre, RS (Brazil)] [Department of Civil Engineering, Federal University of Rio Grande do Sul, Porto Alegre, RS (Brazil); Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States); Gartner, Ellis M. [Lafarge Centre de Recherche, St. Quentin Fallavier, Isere (France)] [Lafarge Centre de Recherche, St. Quentin Fallavier, Isere (France)

2013-06-15

163

Voltage-dependent sodium and calcium currents in cultured parasympathetic neurones from rat intracardiac ganglia.  

PubMed Central

1. Depolarization-activated Na+ and Ca2+ currents underlying the rising phase of the action potential in mammalian parasympathetic ganglion cells were investigated in voltage-clamped neurones dissociated from neonatal rat intracardiac ganglia and maintained in tissue culture. 2. A current component isolated by replacing intracellular K+ with Cs+ or arginine and adding 0.1 mM Cd2+ to the external solution was dependent on extracellular [Na+] and reversibly blocked in the presence of 300 nM tetrodotoxin (TTX). Peak amplitudes of Na+ currents elicited by step depolarization from a holding potential of -100 mV were 351 +/- 18 pA/pF (140 mM extracellular Na+). 3. The sodium current-voltage (I-V) curve exhibited a threshold for activation at -40 mV and reached a maximum at -10 mV. The Na+ conductance increased sigmoidally with increasing depolarization reaching half-maximal activation at -25 mV, with a maximum slope corresponding to 7.5 mV per e-fold change in conductance. 4. During a maintained depolarization, Na+ currents turned on and then decayed (inactivated) with an exponential time course. The time constant of inactivation was voltage dependent decreasing from 0.85 ms at -20 mV to 0.3 ms at +60 mV (23 degrees C). The steady-state inactivation of the Na+ conductance was voltage-dependent with half-inactivation occurring at -61 mV and near-complete inactivation at -20 mV. Recovery from inactivation also followed an exponential time course with a time constant that increased at depolarized membrane potentials. 5. A voltage- and Ca(2+)-dependent current was isolated by replacement of intracellular K+ with either Cs+ or arginine and of extracellular Na+ with tetraethylammonium and the addition of TTX. Extracellular Ba2+ or Na+ (in the absence of external divalent cation) could substitute for Ca2+. Peak Ca2+ current increased with increasing extracellular [Ca2+] and above 10 mM (Kd approximately 4 mM) approached saturation. The peak Ca2+ current density was 45 +/- 4 pA/pF (2.5 mM-extracellular Ca2+). 6. The Ca2+ I-V relation exhibited a high threshold for activation (-20 mV) and reached a maximum at +20 mV. Changing the holding potential from -100 to -40 mV did not alter the I-V relationship. Peak Ca2+ conductance increased sigmoidally with increasing depolarization reaching half-maximal activation at -4 mV, with a maximal slope of 4 mV per e-fold change in Ca2+ conductance. 7. The kinetics of activation and inactivation of the Ca2+ current were voltage dependent and the time course of inactivation was fitted by the sum of two exponentials.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1338101

Xu, Z J; Adams, D J

1992-01-01

164

Molecular Dynamics Simulation of the Structure of Calcium Silicate Hydrates. I. Ca 4+ xSi 6O 14+2 x(OH) 4-2 x(H 2O) 2(0 ? x? 1)  

NASA Astrophysics Data System (ADS)

Molecular dynamics has been used to simulate the structure of calcium silicate hydrates (CSH) having Ca/Si ratios of 0.66 and 0.83. In the absence of labile calcium, silicon nuclear magnetic resonance (NMR) shows that the tetrahedral chains move closer together than predicted by the tobermorite model initially adopted. This proximity may lead to bridging between the chains. In the presence of labile calcium, there is a partial rupture of the chains, as seen with NMR. The instability of the bridging tetrahedra in the initial structure causes this rupture. The dissociation of a water molecule releases the oxygen necessary for the reaction. The rupture of the chains creates two new types of tetrahedra in the structure (Q1(2H) and Q1(1H)).

Faucon, P.; Delaye, J. M.; Virlet, J.

1996-11-01

165

Insight into elastic behavior of calcium silicate hydrated oxide (C-S-H) under pressure and composition effect  

SciTech Connect

The present work relates to the study of structural and elastic properties of Tobermorite 11 A as a function of external pressure and composition in terms of calcium to silicon ratio. Basing on the lattice dynamics method, the main aim of this work is precisely to shed light, for the first time, on the high pressure structural phase transition in Tobermorite 11 A and the possible correlation with some elastic quantities. In order to check the transferability of the potentials used we have, additionally, performed a single calculation based on the density functional theory (DFT) for a pressure of 15 GPa in the case of Ca/Si = 1. The variation of the unit cell parameters with pressure indicates that Tobermorite 11 A undergoes a structural instability around 15 GPa along b-axis and around 20 GPa along a-axis which is confirmed from our calculations of X-Rays diffraction patterns at various pressure values. We have also observed the anisotropic character of the Tobermorite structure for both cases (Ca/Si = 1 and Ca/Si = 0.83). Our results show that around 20 GPa an important change appears in the elastic behaviour of Tobermorite. As pressure increases the calculated elastic quantities for Ca/Si = 1 became closer to those evaluated for Ca/Si = 0.83, which may stimulate further experimental and theoretical research on the matter.

Zaoui, Ali, E-mail: azaoui@polytech-lille.fr

2012-02-15

166

Determination of sodium, potassium, calcium, magnesium, zinc, and iron in emulsified egg samples by flame atomic absorption spectrometry.  

PubMed

In this study, oil-in-water formulations were optimized to determine sodium, potassium, calcium, magnesium, zinc, and iron in emulsified egg samples by flame atomic absorption spectrometry (FAAS). This method is simpler and requires fewer reagents when compared with other sample pre-treatment procedures and allows the calibration to be carried out using aqueous standards. Different oily phases such as corn oil, decyl oleate and octyl stearate were tested, as well as Tween 80, Triton X-100 and Triton 114 were analyzed as surfactants. The optimum type and proportion of formulations were determined and their use depended on the element studied. The emulsion preparation was performed by a conventional method that involves mixing both phases at 60 degrees C by magnetic stirring and phase inversion to change the water-to-oil ratio by increasing the volume of the surfactant-water external phase and correspondingly decreasing the volume of internal phase. The accuracy of the method was further confirmed by determining the metals in a whole egg powder CRM and recoveries ranged from 97.5% for Mg to 102.2% for Na, with relative standard deviations lower than 2.3%. The precision of the procedures was determined through repeatability (intra-day precision) and intermediate precision (inter-day). The repeatability presented RSD values lower than 4.2%. The intermediate precision was evaluated using the RSD and F-test. The RSD values to intermediate precision was lower than 5.3% and the computed F-values were lower than tabulated F-values, indicating no significant difference between the results obtained on different days. The proposed method including, sample emulsification for subsequent metal determination for FAAS, has proved to be sensitive, reproducible, simple and economical. PMID:20006088

Ieggli, C V S; Bohrer, D; do Nascimento, P C; de Carvalho, L M; Garcia, S C

2010-01-15

167

High potency inhibition of hERG potassium channels by the sodium-calcium exchange inhibitor KB-R7943  

PubMed Central

BACKGROUND AND PURPOSE KB-R7943 is an isothiourea derivative that is used widely as a pharmacological inhibitor of sodium–calcium exchange (NCX) in experiments on cardiac and other tissue types. This study investigated KB-R7943 inhibition of hERG (human ether-à-go-go-related gene) K+ channels that underpin the cardiac rapid delayed rectifier potassium current, IKr. EXPERIMENTAL APPROACH Whole-cell patch-clamp measurements were made of hERG current (IhERG) carried by wild-type or mutant hERG channels and of native rabbit ventricular IKr. Docking simulations utilized a hERG homology model built on a MthK-based template. KEY RESULTS KB-R7943 inhibited both IhERG and native IKr rapidly on membrane depolarization with IC50 values of ?89 and ?120 nM, respectively, for current tails at ?40 mV following depolarizing voltage commands to +20 mV. Marked IhERG inhibition also occurred under ventricular action potential voltage clamp. IhERG inhibition by KB-R7943 exhibited both time- and voltage-dependence but showed no preference for inactivated over activated channels. Results of alanine mutagenesis and docking simulations indicate that KB-R7943 can bind to a pocket formed of the side chains of aromatic residues Y652 and F656, with the compound's nitrobenzyl group orientated towards the cytoplasmic side of the channel pore. The structurally related NCX inhibitor SN-6 also inhibited IhERG, but with a markedly reduced potency. CONCLUSIONS AND IMPLICATIONS KB-R7943 inhibits IhERG/IKr with a potency that exceeds that reported previously for acute cardiac NCX inhibition. Our results also support the feasibility of benzyloxyphenyl-containing NCX inhibitors with reduced potential, in comparison with KB-R7943, to inhibit hERG. PMID:21950687

Cheng, Hongwei; Zhang, Yihong; Du, Chunyun; Dempsey, Christopher E; Hancox, Jules C

2012-01-01

168

Effects of sodium bicarbonate and 1,25-dihydroxy-cholecalciferol on calcium and phosphorus balances in the rat  

SciTech Connect

Metabolic balance studies were undertaken to determine whether sodium bicarbonate (NaHCO/sub 3/) supplements (4.5 mmol/day) altered 7-day cumulative calcium (Ca) phosphorus (P) balances in growing rats consuming either a basal diet providing 0.6% Ca and 0.3% P, or this diet plus 1,25-dihydroxycholecalciferol (40 ng 1,25(OH)/sub 2/D/sub 3//day). Feeding bicarbonate lowered urinary Ca but raised fecal Ca so that Ca balance became less positive. However, 1,25(OH)/sub 2/D/sub 3/ increased net absorption of Ca and P to the same degree when given to control rats and rats consuming bicarbonate. Nevertheless, bicarbonate-fed rats had lower net Ca absorption than controls, even when treated with high doses of 1,25(OH)/sub 2/D/sub 3/. Changes in net Ca absorption induced by bicarbonate may occur at a point in the gut distal to the duodenum since duodenal /sup 45/Ca absorption was decreased by bicarbonate feeding. The present results show that bicarbonate consumption depressed net Ca absorption in the rat. The effect appears to be independent of changes in 1,25(OH)/sub 2/D/sub 3/ metabolism because it is manifest in animals receiving high doses of 1,25(OH)/sub 2/D/sub 3/, which stimulate alimentary Ca absorption maximally, and because bicarbonate-fed rats are able to respond normally to exogenous 1,25(OH)/sub 2/D/sub 3/ by increasing their net absorption of Ca and P. In view of this demonstration that NaHCO/sub 3/ supplements elevate fecal Ca loss in the rat, it is suggested that studies should be undertaken to determine whether bicarbonate exerts similar adverse effects on Ca balance in humans.

Goulding, A.; McIntosh, J.; Campbell, D.

1984-04-01

169

Uterine expression of sodium/potassium/calcium exchanger 3 and its regulation by sex-steroid hormones during the estrous cycle of rats.  

PubMed

Plasma membrane sodium/calcium exchangers are an important component of intracellular calcium homeostasis and electrical conduction. NCKX3 (gene SLC24A3), a potassium-dependent sodium-/calcium exchanger, plays a critical role in the transport of one intracellular calcium and potassium ion across the cell membrane in exchange for four extracellular sodium ions. NCKX3 transcripts are most abundant in the brain and smooth muscle, but many other tissues, in particular, the uterus, aorta and intestine, also express this gene at lower levels. However, the expression and physiological roles of NCKX3 in the uterus of rats during the estrous cycle are unknown. Thus, we examined the uterine expression of NCKX3 mRNA and protein at different stages of the estrous cycle in mature and immature female rats in the absence or presence of the sex-steroid hormones estrogen (E2) and progesterone (P4). During the estrous cycle, uterine expression of NCKX3 mRNA and protein was enhanced up to 4.0- and 2.5-fold, respectively, at proestrus compared to during estrus and diestrus. To examine the effect of sex steroids on NCKX3 regulation in the uterus, immature female rats were treated with E2 (40?µg/kg body weight; BW), P4 (4?mg/kg BW), or E2 plus P4 for 3 days. The expression of NCKX3 mRNA and protein was induced by E2, whereas P4 antagonized E2-induced NCKX3 expression. Subsequent immunohistochemical analysis revealed that uterine NCKX3 protein was abundantly localized in the cytoplasm of luminal and glandular epithelial cells throughout the estrous cycle. Taken together, these results indicate that uterine NCKX3 is abundantly expressed in the uterus and that its expression is regulated by the steroid hormones, E2 and P4. These findings suggest that NCKX3 may be involved in reproductive function during the estrous cycle in female rats. PMID:21104767

Yang, Hyun; Yoo, Yeong-Min; Jung, Eui-Man; Choi, Kyung-Chul; Jeung, Eui-Bae

2010-11-01

170

Effect of pulverised-fuel ash on the C\\/S molar ratio and alkali content of calcium silicate hydrates in cement  

Microsoft Academic Search

It has been found that for a cement that has been hydrated for 8 days, pulverized-fuel ash (pfa) caused the C\\/S ratio of the hydrates around the grains to be lowered from 1.71 to 1.55. More potassium was found in the lower C\\/S ratio hydrates. It is not clear whether the resulting reduction in available alkali is sufficient to explain

P RAYMENT

1982-01-01

171

Hydration-Coupled Dynamics in Proteins Studied by Neutron Scattering and NMR: The Case of the Typical EF-Hand Calcium-Binding Parvalbumin  

Microsoft Academic Search

The influence of hydration on the internal dynamics of a typical EF-hand calciprotein, parvalbumin, was investigated by incoherent quasi-elastic neutron scattering (IQNS) and solid-state 13C-NMR spectroscopy using the powdered protein at different hydration levels. Both approaches establish an increase in protein dynamics upon progressive hydration above a threshold that only corresponds to partial coverage of the protein surface by the

Jean-Marc Zanotti; Marie-Claire Bellissent-Funel; Joseph Parello

1999-01-01

172

Effect of calcium on immobilization of rice ( Oryza sativa L.) peroxidase for bioassays in sodium alginate and Agarose gel  

Microsoft Academic Search

The direct immobilization of soluble peroxidase isolated and partially purified from shoots of rice seedlings in calcium alginate\\u000a beads and in calcium agarose gel was carried out. Peroxidase was assayed for guaiacol oxidation products in presence of hydrogen\\u000a peroxide. The maximum specific activity and immobilization yield of the calcium agarose immobilized peroxidase reached 2,200\\u000a U mg?1 protein (540 mU cm?3

Sareeta Nahakpam; Puneeta Singh; Kavita Shah

2008-01-01

173

Gas Hydrates  

Microsoft Academic Search

This review states contemporary views about gas hydrates, and also about non-stoichiometric clathrates with the general formula M·nH2O. The known types of the hydrates and their crystal structure are described. The thermodynamics of hydrate formation is considered. Methods of determining the composition of the hydrates are described. Factual information concerning the hydrates of individual gases and organic liquids and mixed

S. Sh Byk; V. I. Fomina

1968-01-01

174

The use of oral pentobarbital sodium (Nembutal) versus oral chloral hydrate in infants undergoing CT and MR imaging – a pilot study  

Microsoft Academic Search

Background. Chloral hydrate, a commonly used oral sedative for infants undergoing imaging examinations, has a bitter taste and requires\\u000a relatively large volume, provoking unpleasant reactions from the infants. Experience with an alternative sedative, oral pentobarbital\\u000a (Nembutal), has not been reported for infants Objective. To compare patient acceptance of oral Nembutal and oral chloral hydrate for sedation of infants up to

Taylor Chung; Fredric A. Hoffer; Linda Connor; David Zurakowski; P. E. Burrows

2000-01-01

175

Populus euphratica Displays Apoplastic Sodium Accumulation, Osmotic Adjustment by Decreases in Calcium and Soluble Carbohydrates, and Develops Leaf Succulence under Salt Stress1[W  

PubMed Central

Populus euphratica Olivier is known to exist in saline and arid environments. In this study we investigated the physiological mechanisms enabling this species to cope with stress caused by salinity. Acclimation to increasing Na+ concentrations required adjustments of the osmotic pressure of leaves, which were achieved by accumulation of Na+ and compensatory decreases in calcium and soluble carbohydrates. The counterbalance of Na+/Ca2+ was also observed in mature leaves from field-grown P. euphratica trees exposed to an environmental gradient of increasing salinity. X-ray microanalysis showed that a primary strategy to protect the cytosol against sodium toxicity was apoplastic but not vacuolar salt accumulation. The ability to cope with salinity also included maintenance of cytosolic potassium concentrations and development of leaf succulence due to an increase in cell number and cell volume leading to sodium dilution. Decreases in apoplastic and vacuolar Ca2+ combined with suppression of calcineurin B-like protein transcripts suggest that Na+ adaptation required suppression of calcium-related signaling pathways. Significant increases in galactinol synthase and alternative oxidase after salt shock and salt adaptation point to shifts in carbohydrate metabolism and suppression of reactive oxygen species in mitochondria under salt stress. PMID:16299175

Ottow, Eric A.; Brinker, Monika; Teichmann, Thomas; Fritz, Eberhard; Kaiser, Werner; Brosche, Mikael; Kangasjarvi, Jaakko; Jiang, Xiangning; Polle, Andrea

2005-01-01

176

Hydration-coupled dynamics in proteins studied by neutron scattering and NMR: the case of the typical EF-hand calcium-binding parvalbumin.  

PubMed Central

The influence of hydration on the internal dynamics of a typical EF-hand calciprotein, parvalbumin, was investigated by incoherent quasi-elastic neutron scattering (IQNS) and solid-state 13C-NMR spectroscopy using the powdered protein at different hydration levels. Both approaches establish an increase in protein dynamics upon progressive hydration above a threshold that only corresponds to partial coverage of the protein surface by the water molecules. Selective motions are apparent by NMR in the 10-ns time scale at the level of the polar lysyl side chains (externally located), as well as of more internally located side chains (from Ala and Ile), whereas IQNS monitors diffusive motions of hydrogen atoms in the protein at time scales up to 20 ps. Hydration-induced dynamics at the level of the abundant lysyl residues mainly involve the ammonium extremity of the side chain, as shown by NMR. The combined results suggest that peripheral water-protein interactions influence the protein dynamics in a global manner. There is a progressive induction of mobility at increasing hydration from the periphery toward the protein interior. This study gives a microscopic view of the structural and dynamic events following the hydration of a globular protein. PMID:10233057

Zanotti, J M; Bellissent-Funel, M C; Parello, J

1999-01-01

177

Sodium/calcium exchanger is upregulated by sulfide signaling, forms complex with the ?1 and ?3 but not ?2 adrenergic receptors, and induces apoptosis.  

PubMed

Hydrogen sulfide (H2S) as a novel gasotransmitter regulates variety of processes, including calcium transport systems. Sodium calcium exchanger (NCX) is one of the key players in a regulation calcium homeostasis. Thus, the aims of our work were to determine effect of sulfide signaling on the NCX type 1 (NCX1) expression and function in HeLa cells, to investigate the relationship of ?-adrenergic receptors with the NCX1 in the presence and/or absence of H2S, and to determine physiological importance of this potential communication. As a H2S donor, we used morpholin-4-ium-4-methoxyphenyl(morpholino) phosphinodithioate-GYY4137. We observed increased levels of the NCX1 mRNA, protein, and activity after 24 h of GYY4137 treatment. This increase was accompanied by elevated cAMP due to the GYY4137 treatment, which was completely abolished, when NCX1 was silenced. Increased cAMP levels would point to upregulation of ?-adrenergic receptors. Indeed, GYY4137 increased expression of ?1 and ?3 (but not ?2) adrenergic receptors. These receptors co-precipitated, co-localized with the NCX1, and induced apoptosis in the presence of H2S. Our results suggest that sulfide signaling plays a role in regulation of the NCX1, ?1 and ?3 adrenergic receptors, their co-localization, and stimulation of apoptosis, which might be of a potential importance in cancer treatment. PMID:24114174

Markova, Jana; Hudecova, Sona; Soltysova, Andrea; Sirova, Marta; Csaderova, Lucia; Lencesova, Lubomira; Ondrias, Karol; Krizanova, Olga

2014-07-01

178

The hydration number n of calcium dipicolinate trihydrate, CaDP center dot nH(2)O, and its effect on the IR spectra of sporulated Bacillus bacteria  

SciTech Connect

Previous results have shown a unique "quartet" of peaks in the infrared spectra of the sporulated phase of Bacillus bacteria, the four peaks being observed reproducibly for many different species of Bacillus endospores. We consistently observe peaks at 766, 725, 701, and 659 cm-1 and with the same relative amplitudes, as well as other spore peaks at 1441, 1277, 1015 cm-1. We have previously suggested that the peaks arise from calcium dipicolinate, not the conjugate acid. In this paper we conduct a theoretical and experimental study to show that the IR peaks not only arise from the calcium dipicolinate, a known spore component, but specifically the trihydrate salt, CaDP•3H2O. This is shown by calculating the absolute IR intensities of the lone dipicolinate dianion, the calcium salt, as well as the mono-, di- and tri-hydrate salts of calcium dipicolinate. The quartet peaks arise from the crystalline trihydrate salt as we verify both experimentally as well as using quantum chemistry methods. Using a method whereby the calculated intensities are not normalized, only the trihydrate spectrum shows low frequency modes (below 1000 cm-1, including the quartet) having intensities comparable to those of the pyridine ring. The vibrational modes in this part of the spectrum are associated with many internal coordinate motions including contributions from the Ca2+ counterion and the three waters including Ca-O-H bends, H2O-Ca-O torsions and O-C-O bends. Index Headings: Infrared, calcium dipicolinate, Bacillus, Bacteria, Endospores

Johnson, Timothy J.; Williams, Stephen D.; Valentine, Nancy B.; Su, Yin-Fong

2010-05-26

179

A realistic molecular model of cement hydrates  

E-print Network

Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially unexplored. Together these ...

Ulm, Franz-Josef

180

Effect of phenytoin on sodium and calcium currents in hippocampal CA1 neurons of phenytoin-resistant kindled rats  

Microsoft Academic Search

About 20–30% of patients with epilepsy continue to have seizures despite carefully monitored treatment with antiepileptic drugs. The mechanisms explaining why some patients' respond and others prove resistant to antiepileptic drugs are poorly understood. It has been proposed that pharmacoresistance is related to reduced sensitivity of sodium channels in hippocampal neurons to antiepileptic drugs such as carbamazepine or phenytoin. In

M. Jeub; H. Beck; E. Siep; C. Rüschenschmidt; E.-J. Speckmann; U. Ebert; H. Potschka; C. Freichel; E. Reissmüller; W. Löscher

2002-01-01

181

Histamine Release by Calcium from Sodium Fluoride-Activated Rat Mast Cells. Further Evidence for a Secretory Process  

Microsoft Academic Search

Histamine release induced by calcium (step 2) from fluoride-activated (step 1) rat mast cells was found to be dependent on temperature and pH. Whereas the influence of temperature was different on the two steps, the pH effects were similar. The activation of the cells by fluoride occurred faster at low pH. Agents considered to influence cyclic nucleotide content of the

S. A. Patkar; W. Kazimierczak; B. Diamant

1978-01-01

182

21 CFR 73.2125 - Potassium sodium copper chlorophyllin (chlorophyllin-copper complex).  

Code of Federal Regulations, 2012 CFR

...Sodium carboxymethylcellulose. Tetrasodium pyrophosphate. Sorbitol. Magnesium phosphate, tribasic. Calcium carbonate. Calcium phosphate, dibasic. Sodium N -lauroyl sarcosinate. Artificial sweeteners that are generally...

2012-04-01

183

21 CFR 73.2125 - Potassium sodium copper chlorophyllin (chlorophyllin-copper complex).  

...Sodium carboxymethylcellulose. Tetrasodium pyrophosphate. Sorbitol. Magnesium phosphate, tribasic. Calcium carbonate. Calcium phosphate, dibasic. Sodium N -lauroyl sarcosinate. Artificial sweeteners that are generally...

2014-04-01

184

21 CFR 73.2125 - Potassium sodium copper chlorophyllin (chlorophyllin-copper complex).  

Code of Federal Regulations, 2011 CFR

...Sodium carboxymethylcellulose. Tetrasodium pyrophosphate. Sorbitol. Magnesium phosphate, tribasic. Calcium carbonate. Calcium phosphate, dibasic. Sodium N -lauroyl sarcosinate. Artificial sweeteners that are generally...

2011-04-01

185

21 CFR 73.2125 - Potassium sodium copper chlorophyllin (chlorophyllin-copper complex).  

Code of Federal Regulations, 2010 CFR

...Sodium carboxymethylcellulose. Tetrasodium pyrophosphate. Sorbitol. Magnesium phosphate, tribasic. Calcium carbonate. Calcium phosphate, dibasic. Sodium N -lauroyl sarcosinate. Artificial sweeteners that are generally...

2010-04-01

186

21 CFR 73.2125 - Potassium sodium copper chlorophyllin (chlorophyllin-copper complex).  

Code of Federal Regulations, 2013 CFR

...Sodium carboxymethylcellulose. Tetrasodium pyrophosphate. Sorbitol. Magnesium phosphate, tribasic. Calcium carbonate. Calcium phosphate, dibasic. Sodium N -lauroyl sarcosinate. Artificial sweeteners that are generally...

2013-04-01

187

Modulating drug release and matrix erosion of alginate matrix capsules by microenvironmental interaction with calcium ion.  

PubMed

Effect of calcium gluconate (CG) content on release of dextromethorphan hydrobromide (DMP), model drug, from capsules containing low and medium viscosity grades of sodium alginate (SA) was investigated in different dissolution media. Matrix erosion of the SA matrix capsules in distilled water and pH 7.4 phosphate buffer was compared. Molecular interaction of SA with calcium ion in surface gel layer of the SA matrix capsules was examined using Fourier transform infrared spectroscopy and differential scanning calorimetry. In distilled water and pH 7.4 phosphate buffer, DMP release rate depended on the viscosity grade of SA, whereas a comparable DMP release rate was found in 0.1N HCl. Incorporation of CG into the SA matrix capsules caused a faster drug release in acidic medium because CG acted as a channeling agent in the hydrated insoluble gel matrix of alginic acid. Interaction of calcium ions with carboxyl groups of SA could be formed in surface gel layer of hydrated matrix capsules in distilled water. This led to a more rigid matrix gel structure that caused a slower drug release and matrix erosion. In contrast, the extent of this interaction in pH 7.4 phosphate buffer was less than that in distilled water because the common ion effect and high concentration of sodium ion retarded the hydration of SA and the binding of calcium ions with carboxyl groups of SA. Thus, a small change in drug release and matrix erosion was observed. This finding suggests that microenvironmental interaction between hydrated SA and calcium ion in distilled water could be created in the formulations prepared using low compression force. Moreover, incorporation of CG could moderate drug release and matrix erosion of the SA matrix capsules. PMID:17270407

Pongjanyakul, Thaned; Puttipipatkhachorn, Satit

2007-08-01

188

Investigations on interactions of sodium dodecyl sulfate and polyacryloamide molecules on calcium carbonate surface using radiotracer technique  

SciTech Connect

From the studies of sodium dodecyl sulfate (SDS) adsorption on nonflocculated and flocculated CaCO/sub 3/ precipitate it was found that on a CaCO/sub 3/ surface on which a polymer (polyacryloamide (PAA)) was previously adsorbed PAA and SDS complexes were formed. Studies of adsorption carried out on the function of the surface charge, SDS concentration, as well as flocculant concentration allowed a probable mechanism of SDS binding on flocculated CaCO/sub 3/ precipitate to be defined. In these studies a radiotracer technique was applied using SDS labeled with radioactive /sup 35/S for measurements of adsorption. 19 references.

Chibowski, S.

1980-08-01

189

21 CFR 184.1205 - Calcium hydroxide.  

Code of Federal Regulations, 2010 CFR

...hydroxide. (a) Calcium hydroxide (Ca(OH)2 , CAS Reg. No. 1305-62-0) is also known as slaked lime or calcium hydrate. It is produced by the hydration of lime. (b) The ingredient meets the specifications of the Food Chemicals...

2010-04-01

190

Separation of sodium-22 from irradiated targets  

DOEpatents

A process for selective separation of sodium-22 from an irradiated target including dissolving an irradiated target to form a first solution, contacting the first solution with hydrated antimony pentoxide to selectively separate sodium-22 from the first solution, separating the hydrated antimony pentoxide including the separated sodium-22 from the first solution, dissolving the hydrated antimony pentoxide including the separated sodium-22 in a mineral acid to form a second solution, and, separating the antimony from the sodium-22 in the second solution.

Taylor, Wayne A. (Los Alamos, NM); Jamriska, David (Los Alamos, NM)

1996-01-01

191

Solvent effects on squid sodium channels are attributable to movements of a flexible protein structure in gating currents and to hydration in a pore  

PubMed Central

Solvent effects on the time course of gating and sodium currents were analysed in squid sodium channels using four non-electrolytes of different size, glycerol, erythritol, glucose and sucrose, to separate effects of viscosity from those of osmolarity and to obtain viscosity and osmolarity parameters that were independent of molecular size. The gating and sodium currents were reversibly slowed in a voltage-independent manner as the non-electrolyte concentration increased. Solvent effects were analysed using a model in which the percentage change in time constant was expressed by an equation involving the viscosity parameter ? and the osmolarity parameter ?: t/t0 =?((?/?0) – 1 + 100??1)exp(???), where ?/?0 is solution viscosity and ?? is increase in osmolarity. Since the solution viscosity was found experimentally to be a function of the solution osmolarity, solvent effects are described by an equation with one independent variable ?/?0 or ??. Voltage sensor movement, reflected in gating currents, was primarily sensitive to viscosity, as its decay time constant was a function of ?/?0, with only a minor sensitivity to osmolarity (? was 2–3 water molecules). For sodium currents, ? was equal to that of gating currents but ? was 2–3 times greater, suggesting that the final channel opening was primarily sensitive to osmolarity (?? was 5 water molecules). The relative ineffectiveness of the largest non-electrolyte, sucrose, suggested that this osmolarity-sensitive step in channel opening occurred in the narrow pore region. Sodium channel inactivation was primarily sensitive to osmolarity (?? was 8–12 water molecules). The observed viscosity dependence of the sodium current activation and inactivation processes was attributable to the viscosity-dependent process accompanying the gating current. This model explains why non-electrolytes slow sodium currents while electrolytes do not. Viscosity effects on gating currents can be explained by a process in which non-electrolytes interact with the flexible hydrophilic parts of sodium channel proteins, but osmolarity effects on the final step need to be explained by a local interaction of several water molecules with fluctuating protein segments in the pore. PMID:10713962

Kukita, Fumio

2000-01-01

192

21 CFR 184.1721 - Sodium acetate.  

Code of Federal Regulations, 2013 CFR

...anhydrous or trihydrated form. It is produced synthetically by the neutralization of acetic acid with sodium carbonate or by treating calcium acetate with sodium sulfate and sodium bicarbonate. (b) The ingredient meets the...

2013-04-01

193

21 CFR 184.1721 - Sodium acetate.  

...anhydrous or trihydrated form. It is produced synthetically by the neutralization of acetic acid with sodium carbonate or by treating calcium acetate with sodium sulfate and sodium bicarbonate. (b) The ingredient meets the...

2014-04-01

194

21 CFR 184.1721 - Sodium acetate.  

Code of Federal Regulations, 2012 CFR

...anhydrous or trihydrated form. It is produced synthetically by the neutralization of acetic acid with sodium carbonate or by treating calcium acetate with sodium sulfate and sodium bicarbonate. (b) The ingredient meets the...

2012-04-01

195

21 CFR 184.1721 - Sodium acetate.  

Code of Federal Regulations, 2011 CFR

...anhydrous or trihydrated form. It is produced synthetically by the neutralization of acetic acid with sodium carbonate or by treating calcium acetate with sodium sulfate and sodium bicarbonate. (b) The ingredient meets the...

2011-04-01

196

21 CFR 184.1721 - Sodium acetate.  

Code of Federal Regulations, 2010 CFR

...anhydrous or trihydrated form. It is produced synthetically by the neutralization of acetic acid with sodium carbonate or by treating calcium acetate with sodium sulfate and sodium bicarbonate. (b) The ingredient meets the...

2010-04-01

197

Measurement and prediction of gas hydrate and hydrated salt equilibria in aqueous ethylene glycol and electrolyte solutions  

Microsoft Academic Search

A recently developed method in modelling electrolyte solutions is extended to include phase behaviour of aqueous solutions containing hydrated salts (e.g., calcium chloride) and organic hydrate inhibitors (e.g., ethylene glycol). A novel salt precipitation model applicable to various hydrated salts is presented. The precipitation model takes into account various precipitates of hydrated salts over a wide range of temperature (i.e.,

Rahim Masoudi; Bahman Tohidi; Ali Danesh; Adrian C. Todd; Ross Anderson; Rod W. Burgass; Jinhai Yang

2005-01-01

198

Simultaneous determination of timolol maleate, rosuvastatin calcium and diclofenac sodium in pharmaceuticals and physiological fluids using HPLC-UV.  

PubMed

A novel HPLC-UV method was developed for the simultaneous determination of timolol (TM), rosuvastatin (RST), and diclofenac sodium (DS) in pharmaceuticals, human plasma and aqueous humor using naproxen sodium as internal standard (IS). The target compounds were analyzed on Hypersil BDS C(18) column (250 mm × 4.6 mm, 5 ?m), applying 0.2% triethylamine (TEA) and acetonitrile (ACN) (40:60, v/v), in isocratic mode as mobile phase, pH 2.75 adjusted with 85% phosphoric acid at a flow rate of 1 ml/min. The column oven temperature was kept at 45°C and the peak response was monitored at 284 nm after injecting a 50 ?l sample into HPLC system. The direct liquid-liquid extraction procedure was applied to human plasma and bovine aqueous humor samples using mobile phase as an extraction solvent after deproteination with methanol. The different HPLC experimental parameters were optimized and the method was validated according to standard guidelines. The recoveries of the suggested method in human plasma were 98.72, 96.04, and 95.14%, for TM, RST, and DS, while in aqueous humor were 94.99, and 98.23%, for TM, and DS, respectively. The LOD values were found to be 0.800, 0.500, and 0.250 ng/ml, for TM, RST, and DS, respectively, while their respective LOQ values were 2.00, 1.50, and 1.00 ng/ml. The co-efficient of variation (CV) were in the range of 0.1492-1.1729% and 1.0516-4.0104%, for intra-day and inter-day studies, respectively. The method was found accurate in human plasma and bovine aqueous humor and will be applied for the quantification of these compounds in plasma, and aqueous humor samples using animal models and in pharmaceuticals. PMID:21963479

Nasir, Fazli; Iqbal, Zafar; Khan, Abad; Ahmad, Lateef; Shah, Yasar; Khan, Amir Zada; Khan, Jamshaid Ali; Khan, Salimullah

2011-11-15

199

Comparison of a dual-phase fluoride toothpaste containing calcium, phosphate, and sodium bicarbonate with a regular fluoride toothpaste on calculus formation.  

PubMed

This clinical study compared the effect on dental calculus formation of a dual-phase fluoride dentifrice containing sodium bicarbonate, calcium, and phosphate with that of a regular dentifrice using a short-term clinical model in which calculus formation was facilitated. A total of 87 adult volunteers completed this study, which was a double-blind, parallel-group design, consisting of 2-week pretrial and trial periods separated by a washout period. A partial-mouth technique was used wherein the lower anterior teeth were protected from brushing by a custom-fitted toothshield, which doubled as an applicator for an undiluted dentifrice, twice daily. Calculus was measured on the labial/lingual surfaces of six lower anterior teeth by the Volpe-Manhold Index (V-MI). Subjects used a non-tartar-control dentifrice during the pretrial period to determine calculus formation rates, and these V-MI scores were used as baseline data for random allocation to either a control or test product for the trial period. Subjects who were accepted into the study, based on existing tartar deposits, readily formed calculus during the pretrial period using the toothshield method. During the trial period, subjects who were assigned the test dentifrice had comparable amounts of calculus accumulation to those who used the control dentifrice. However, subjects in the test dentifrice group had significantly lower (16%) calculus scores on lingual surfaces than those in the control group. Intragroup comparisons of V-MI data from the pretrial period with those from the trial period provided similar overall results to the comparisons between groups. This study demonstrated that a dual-phase baking soda dentifrice containing calcium and phosphate did not increase calculus accumulation relative to a regular dentifrice when used by adults with a propensity for developing calculus. PMID:15645907

Putt, Mark S; Milleman, Kimberly R; Milleman, Jeffery L; Ghassemi, Annahita

2004-09-01

200

Comparative efficacy of dentifrice containing sodium monofluorophosphate + calcium glycerophosphate and non-fluoridated dentifrice: A randomized, double-blind, prospective study  

PubMed Central

Background: The efficacy of fluoridated dentifrices in caries prevention has been well documented and research into various formulations continues for a more effective dentifrice. This study evaluated the anti-caries and anti-plaque efficacy of a dentifrice containing sodium monofluorophosphate (1000 ppm) and calcium glycerophosphate, and compared it with a non-fluoridated dentifrice. Materials and Methods: A total of 595 school children (12–15 years) were divided into test (302 children) and control (293 children) groups. The test group used the dentifrice containing sodium monofluorophosphate (1000 ppm) and calcium glycerophosphate, whereas the control group was given a placebo dentifrice. Oral examination for dental caries and plaque assessment was carried out at the start of the study and the children were followed up semiannually up to 18 months. Data were analyzed using repeated-measure analysis of variance (ANOVA) followed by one-way ANOVA. Results: The values for decayed missing filled teeth (DMFT) increased from baseline to 18 month examination from 4.43±2.03 and 4.67±2.25 (P=0.175) to 5.84±2.29 and 5.13±2.30 (P=0.001) for control and test groups, respectively. Similarly, the increase in decayed missing filled surface (DMFS) values were from 6.42±4.10 and 7.06±4.77 (P=0.082) to 8.64±4.51 and 7.92±5.07 (P=0.095) for test and control groups, respectively. The mean DMFT and DMFS values increased for both the groups; however, the increase was less in test group as compared to control group. The baseline plaque score reduced from 2.94±0.72 and 2.91±0.72 (P=0.679), respectively, for control and test groups to 1.33±0.46 and 0.91±0.38 (P<0.001), respectively, at 18 month examination. Conclusion: Results revealed that the test dentifrice was effective in inhibiting the progression of plaque and control of dental caries as compared to the placebo dentifrice. PMID:22363366

Damle, Satyawan G.; Deoyani, D; Bhattal, Hiteshwar; Yadav, Renu; Lomba, Ashish

2012-01-01

201

Requirement for store-operated calcium entry in sodium butyrate-induced apoptosis in human colon cancer cells.  

PubMed

The SOCE (store-operated Ca2+ entry) pathway plays a key role in both normal cells and cancerous cells. However, its molecular mechanism remains a long-lasting puzzle of Ca2+ signalling. In this paper, we provide evidence that butyric acid, a dietary fibre-derived short-chain fatty acid, induces apoptosis of colon cancer cells via SOCE signalling networks. We found that sodium butyrate (NaB) induces Ca2+ release from endoplasmic reticulum, which in turn causes extracellular Ca2+ influx in HCT-116 cells. The Ca2+ release and influx are important, because the addition of chelators, EGTA or BAPTA/AM [1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid tetrakis(acetoxymethyl ester)] respectively blocked NaB-induced apoptosis. Furthermore, down-regulation of STIM1 (stromal interaction molecule 1) by RNA interference or pharmacological blockade of the SOCC (store-operated Ca2+ channel) by 2-APB (2-aminoethoxydiphenyl borate) or SKF-96365 inhibited NaB-induced extracellular Ca2+ influx and apoptosis in HCT-116 cells. Thus we conclude that NaB triggers colon cancer cell apoptosis in an SOCE-dependent manner. This finding provides new insights into how butyric acid suppresses colon carcinogenesis. PMID:21699495

Sun, Suxia; Li, Wenjun; Zhang, He; Zha, Longying; Xue, Yong; Wu, Xianbo; Zou, Fei

2012-02-01

202

Determination of calcium, magnesium, sodium, and potassium in foodstuffs by using a microsampling flame atomic absorption spectrometric method after closed-vessel microwave digestion: method validation.  

PubMed

This paper describes a validation process in compliance with the NFIEN ISO/IEC 17025 standard for the determination of the macrominerals calcium, magnesium, sodium, and potassium in foodstuffs by microsampling with flame atomic absorption spectrometry after closed-vessel microwave digestion. The French Standards Commission (Agence Francaise de Normalisation) standards NF V03-110, NF EN V03-115, and XP T-90-210 were used to evaluate this method. The method was validated in the context of an analysis of the 1322 food samples of the second French Total Diet Study (TDS). Several performance criteria (linearity, LOQ, specificity, trueness, precision under repeatability conditions, and intermediate precision reproducibility) were evaluated. Furthermore, the method was monitored by several internal quality controls. The LOQ values obtained (25, 5, 8.3, and 8.3 mg/kg for Ca, Mg, Na, and K, respectively) were in compliance with the needs of the TDS. The method provided accurate results as demonstrated by a repeatability CV (CVr) of < 7% and a reproducibility CV (CVR) of < 12% for all the elements. Therefore, the results indicated that this method could be used in the laboratory for the routine determination of these four elements in foodstuffs with acceptable analytical performance. PMID:21313817

Chekri, Rachida; Noël, Laurent; Vastel, Christelle; Millour, Sandrine; Kadar, Ali; Guérin, Thierry

2010-01-01

203

Tunable color temperature solid state white light source using flux grown phosphor crystals of Eu3+, Dy3+ and Tb3+ activated calcium sodium molybdenum oxide  

NASA Astrophysics Data System (ADS)

Solid state light sources with dynamically tunable color temperature in the range of 3000-6000 K with chromaticity coordinates lying on the Planckian black body curve has been designed using mixtures of narrow emissions at 615 nm, 575 nm and 550 nm. These respective emissions lines were generated by individual phosphor crystals of trivalent rare earth (RE3+) species, europium (Eu3+), dysprosium (Dy3+) and terbium (Tb3+) activated calcium sodium molybdenum oxide (Ca1-2xNaxMoO4:RE3+x), when excited by near-ultra-violet (NUV) light emitting diode (LED) with emission wavelength of 380 nm. Highly luminescent crystals of these compounds have been grown from molten solutions (flux) of molybdenum (VI) oxide. The flux grown crystals exhibit emission intensity 2-4 times more than phosphor powders of the same compounds synthesized by traditional solid-state reactions. An optimum flux to solute ratio of 2.5 and solute dissolution temperature of 1100 °C resulted in the largest size crystals.

Khanna, A.; Dutta, P. S.

2014-11-01

204

Hydrothermal treatment of naturally contaminated maize in the presence of sodium metabisulfite, methylamine and calcium hydroxide; effects on the concentration of zearalenone and deoxynivalenol.  

PubMed

Fusarium toxin-contaminated ground maize was hydrothermally treated in the presence of different combinations of chemicals in order to simultaneously reduce zearalenone (ZEA) and deoxynivalenol (DON) concentrations. Treatments were carried out in a laboratory conditioner at 80 °C and 17 % moisture. Six different treatments were performed, consisting of 3 doses of methylamine (MMA; 2.5, 5 and 10 g/kg maize) at a constant dose of 5 g sodium metabisulfite (SBS)/kg, either with or without the addition of 20 g calcium hydroxide (Ca(OH)2)/kg. The used maize was contaminated with approximately 45.99 mg DON/kg and 3.46 mg ZEA/kg. Without the addition of Ca(OH)2, DON reductions reached approximately 82% after 1-min treatment and the toxin disappeared nearly completely after 10 min when 2.5 or 5 g MMA were applied. ZEA concentrations were only marginally affected. In the presence of Ca(OH)2, reductions in DON concentrations were lower, but were enhanced by increasing doses of MMA. ZEA concentrations were reduced by 72, 85 and 95% within the first 5 min of the treatment at MMA dosages of 2.5, 5 and 10 g/kg maize, respectively. The application of SBS in combination with a strong alkaline during hydrothermal treatment seems to be a promising approach to simultaneously decontaminate even high amounts of DON and ZEA in ground maize and may contribute to reduce the toxin load of diets. PMID:23536360

Rempe, Inga; Kersten, Susanne; Valenta, Hana; Dänicke, Sven

2013-08-01

205

Emissions of alkaline elements calcium, magnesium, potassium, and sodium from open sources in the contiguous United States  

SciTech Connect

Models of dust emissions by wind erosion (including winds associated with regional activity as well as dust devils) and vehicular disturbances of unpaved roads were developed, calibrated, and used to estimate alkaline dust emissions from elemental soil and road composition data. Emissions from tillage of soils were estimated form the work of previous researchers. The area of maximum dust production by all of those sources is the area of the old Dust Bowl' of the 1930s (the panhandles of Texas and Oklahoma, eastern New Mexico and Colorado, and western Kansas). The areas of maximum alkaline dust production are the arid southwest, the Dust Bowl,' and the midwestern-mideastern states from Iowa to Pennsylvania. Our calculations show that calcium is the dominant alkaline element produced by open sources' (sources too great in extent to be controlled by enclosure or ducting). Although the largest dust mass source is wind erosion (by winds associated with regional activity and convective activity), the largest producer of the alkaline component is road dust because the abundance of alkaline materials in road coverings (which include crushed limestone) is significantly higher than for soils. Comparing the above estimated sources of alkaline material with inventories of SO[sub 2] and NO[sub x] emissions by previous investigators gives the rough approximation that alkaline emission rates are of the order of the SO[sub 2] + NO[sub x] emissions in the western United States and that they are much smaller than SO[sub 2] + NO[sub x] in the eastern United States. This approximation is substantiated by data on Ca/(SO[sub 4] + NO[sub 3]) for wet deposition for National Atmospheric Deposition Program sites. 53 refs., 9 figs., 2 tabs.

Gillette, D.A. (National Oceanic and Atmospheric Administration, Boulder, CO (United States)); Stensland, G.J.; Williams, A.L.; Barnard, W.; Gatz, D. (Illinois State Water Survey, Champaign, IL (United States)); Sinclair, P.C. (Colorado State Univ., Fort Collins (United States)); Johnson, T.C. (Univ. of Colorado, Boulder (United States))

1992-12-01

206

Influence of finely ground limestone on cement hydration  

Microsoft Academic Search

Some work has been carried out on the effect of calcium carbonate on cement paste, but there is no general agreement on the relative effects of different amounts of calcium carbonate on cement paste properties. The objective of the present work is to assess the effect of various amounts of calcium carbonate on the hydration of tricalcium silicate in order

Jean Péra; Sophie Husson; Bernard Guilhot

1999-01-01

207

Effect of metal ion hydration on the interaction between sodium carboxylates and aluminum(III) or chromium(III) ions in aqueous solution.  

PubMed

The interaction between sodium octanoate, decanoate, and dodecanoate and aluminum(III) and chromium(III) has been studied in water at natural pH values, starting well below the surfactant critical micelle concentration, using electrical conductivity, turbidity, and potentiometric measurements. With decanoate or dodecanoate, maximum interaction occurs at 3:1 stoichiometry, corresponding to charge neutralization. Although the solutions become turbid with both metal ions, indicating phase separation, differences are observed and attributed to the fact that aluminum(III) is relatively labile to substitution and rapidly replaces its water ligands, whereas chromium(III) is substitution inert. This shows up in well-defined floc formation with Al(3+), whereas Cr(3+) suspensions do not precipitate, probably because that replacement of coordinated water by carboxylate ligands is impeded. This can be overcome by increasing temperature, and differences in the thermal behavior with Al(3+) and Cr(3+) are suggested to be due to increased involvement of substitution reactions in the latter case. The effect of octanoate on the trivalent metal ions is less clear, and with Cr(3+) interaction only occurs when the carboxylate is in excess. Hydrophobic interactions between alkyl chains play a major role in driving phase separation. At high surfactant concentrations, the solid phases do not dissolve, in contrast to what is observed with the corresponding alkylsulfates. This has implications for use of these systems in metal separation through froth flotation. The concentration of metal ions in supernatant solution has been determined for sodium dodecanoate and sodium dodecylsulfate with Al(3+) and Cr(3+) over the whole surfactant concentration range by inductively coupled plasma-mass spectrometry (ICP-MS). From this, association constants have been determined and are found to be larger for the carboxylate than the alkylsulfate, in agreement with the greater Lewis basicity of the -CO(2)(-) group. PMID:22107111

Pereira, Rui F P; Tapia, Maria J; Valente, Artur J M; Burrows, Hugh D

2012-01-10

208

Fluid and salt supplementation effect on body hydration and electrolyte homeostasis during bed rest and ambulation  

NASA Astrophysics Data System (ADS)

Bed rest (BR) induces significant urinary and blood electrolyte changes, but little is known about the effect of fluid and salt supplements (FSS) on catabolism, hydration and electrolytes. The aim was to measure the effect of FSS on catabolism, body hydration and electrolytes during BR. Studies were done during 7 days of a pre-bed rest period and during 30 days of a rigorous bed rest period. Thirty male athletes aged, 24.6±7.6 years were chosen as subjects. They were divided into three groups: unsupplemented ambulatory control subjects (UACS), unsupplemented bed rested subjects (UBRS) and supplemented bed rested subjects (SBRS). The UBRS and SBRS groups were kept under a rigorous bed rest regime for 30 days. The SBRS daily took 30 ml water per kg body weight and 0.1 sodium chloride per kg body weight. Plasma sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg) levels, urinary Na, K, Ca and Mg excretion, plasma osmolality, plasma protein level, whole blood hemoglobin (Hb) and hematocrit (Hct) level increased significantly ( p?0.05), while plasma volume (PV), body weight, body fat, peak oxygen uptake, food and fluid intake decreased significantly ( p?0.05) in the UBRS group when compared with the SBRS and UACS groups. In contrast, plasma and urinary electrolytes, osmolality, protein level, whole blood Hct and Hb level decreased significantly ( p?0.05), while PV, fluid intake, body weight and peak oxygen uptake increased significantly ( p?0.05) in the SBRS group when compared with the UBRS group. The measured parameters did not change significantly in the UACS group when compared with their baseline control values. The data indicate that FSS stabilizes electrolytes and body hydration during BR, while BR alone induces significant changes in electrolytes and body hydration. We conclude that FSS may be used to prevent catabolism and normalize body hydration status and electrolyte values during BR.

Zorbas, Yan G.; Kakurin, Vassily J.; Kuznetsov, Nikolai A.; Yarullin, Vladimir L.

2002-06-01

209

Effects of a Fusarium toxin-contaminated maize treated with sodium metabisulphite, methylamine and calcium hydroxide in diets for female piglets.  

PubMed

Deoxynivalenol (DON) and zearalenone (ZEN) contaminated maize was hydrothermally treated in the presence of sodium metabisulphite (SBS), methylamine and calcium hydroxide (Ca(OH)2) and included into diets for female piglets to evaluate effects on performance, organ weights, development of hyperestrogenism, serum biochemical parameters, stimulation of peripheral blood mononuclear cells and toxin residues in serum. For this purpose, both uncontaminated maize (CON) and Fusarium toxin-contaminated maize (FUS) were included into diets either untreated (-) or treated (+) according to a 2 by 2-factorial design. One-hundred female weaned piglets were assigned to one of the four treatment groups (n = 25) CON-, CON+, FUS- and FUS+ with DON/ZEN concentrations of 0.43/0.03, 0.04/0.0, 3.67/0.32 and 0.36/0.08 mg per kg diet, respectively. After a feeding period of 27 days, 20 piglets (n = 5) were slaughtered. Performance parameters such as feed intake, live weight gain and feed-to-gain ratio remained unaffected by the treatments. Uterus weights were significantly reduced in group FUS+ compared to FUS- (p = 0.028), while visceral organ weights were not influenced. Vulva width in relation to body weight was highest in group FUS- at the end of the trial, while hydrothermal treatment significantly reduced the parameter (p < 0.01). The highest toxin and toxin metabolite concentrations in serum were detected in group FUS-, whereas ingestion of diet FUS+ reduced the concentrations to the level of the control groups. Serum biochemical and haematological parameters were mainly within the given reference ranges and showed no treatment-related alterations. Stimulation of peripheral blood mononuclear cells was not affected. An effective detoxification of maize by hydrothermal treatment in the presence of SBS, methylamine and Ca(OH)2 could be demonstrated by means of serum toxin analyses. No undesired side effects of the treated-feed stuff or the chemicals themselves on the health of piglets were detected. PMID:23859352

Rempe, Inga; Brezina, Ulrike; Kersten, Susanne; Dänicke, Sven

2013-08-01

210

Activation of sodium-dependent glutamate transporters regulates the morphological aspects of oligodendrocyte maturation via signaling through calcium/calmodulin-dependent kinase II?'s actin-binding/-stabilizing domain.  

PubMed

Signaling via the major excitatory amino acid glutamate has been implicated in the regulation of various aspects of the biology of oligodendrocytes, the myelinating cells of the central nervous system (CNS). In this respect, cells of the oligodendrocyte lineage have been described to express a variety of glutamate-responsive transmembrane proteins including sodium-dependent glutamate transporters. The latter have been well characterized to mediate glutamate clearance from the extracellular space. However, there is increasing evidence that they also mediate glutamate-induced intracellular signaling events. Our data presented here show that the activation of oligodendrocyte expressed sodium-dependent glutamate transporters, in particular GLT-1 and GLAST, promotes the morphological aspects of oligodendrocyte maturation. This effect was found to be associated with a transient increase in intracellular calcium levels and a transient phosphorylation event at the serine (S)(371) site of the calcium sensor calcium/calmodulin-dependent kinase type II? (CaMKII?). The potential regulatory S(371) site is located within CaMKII?'s previously defined actin-binding/-stabilizing domain, and phosphorylation events within this domain were identified in our studies as a requirement for sodium-dependent glutamate transporter-mediated promotion of oligodendrocyte maturation. Furthermore, our data provide good evidence for a role of these phosphorylation events in mediating detachment of CaMKII? from filamentous (F)-actin, and hence allowing a remodeling of the oligodendrocyte's actin cytoskeleton. Taken together with our recent findings, which demonstrated a crucial role of CaMKII? in regulating CNS myelination in vivo, our data strongly suggest that a sodium-dependent glutamate transporter-CaMKII?-actin cytoskeleton axis plays an important role in the regulation of oligodendrocyte maturation and CNS myelination. PMID:24866099

Martinez-Lozada, Zila; Waggener, Christopher T; Kim, Karam; Zou, Shiping; Knapp, Pamela E; Hayashi, Yasunori; Ortega, Arturo; Fuss, Babette

2014-09-01

211

ESP (electrostatic precipitator) tests at Toronto: Test results: Part 3. [Hydrate Addition at Low Temperature for the removal of SOâ  

Microsoft Academic Search

''Hydrate Addition at Low Temperature'' or HALT is a dry calcium-based hydrate injection process for the removal of SOâ from flue gases off a sulfur bearing fuel. In this process the hydrate is pneumatically conveyed and injected into the flue gas stream as a dry particulate. The flue gas is cooled downstream of the hydrate injection location by spraying the

J. Gooch; R. Beittel; J. DuBard; G. Jr. Marchant

1988-01-01

212

Normal pregnancy: mechanisms underlying the paradox of a ouabain-resistant state with elevated endogenous ouabain, suppressed arterial sodium calcium exchange, and low blood pressure  

PubMed Central

Endogenous cardiotonic steroids (CTS) raise blood pressure (BP) via vascular sodium calcium exchange (NCX1.3) and transient receptor-operated channels (TRPCs). Circulating CTS are superelevated in pregnancy-induced hypertension and preeclampsia. However, their significance in normal pregnancy, where BP is low, is paradoxical. Here we test the hypothesis that vascular resistance to endogenous ouabain (EO) develops in normal pregnancy and is mediated by reduced expression of NCX1.3 and TRPCs. We determined plasma and adrenal levels of EO and the impact of exogenous ouabain in pregnancy on arterial expression of Na+ pumps, NCX1.3, TRPC3, and TRPC6 and BP. Pregnant (embryonic day 4) and nonpregnant rats received infusions of ouabain or vehicle. At 14–16 days, tissues and plasma were collected for blotting and EO assay by radioimmunoassay (RIA), liquid chromatography (LC)-RIA, and LC-multidimensional mass spectrometry (MS3). BP (?8 mmHg; P < 0.05) and NCX1.3 expression fell (aorta ?60% and mesenteric artery ?30%; P < 0.001) in pregnancy while TRPC expression was unchanged. Circulating EO increased (1.14 ± 0.13 nM) vs. nonpregnant (0.6 ± 0.08 nM; P < 0.05) and was confirmed by LC-MS3 and LC-RIA. LC-MS3 revealed two previously unknown isomers of EO; one increased ?90-fold in pregnancy. Adrenal EO but not isomers were increased in pregnancy. In nonpregnant rats, similar infusions of ouabain raised BP (+24 ± 3 mmHg; P < 0.001). In ouabain-infused rats, impaired fetal and placental growth occurred with no BP increase. In summary, normal pregnancy is an ouabain-resistant state associated with low BP, elevated circulating levels of EO, two novel steroidal EO isomers, and increased adrenal mass and EO content. Ouabain raises BP only in nonpregnant animals. Vascular resistance to the chronic pressor activity of endogenous and exogenous ouabain is mediated by suppressed NCX1.3 and reduced sensitivity of events downstream of Ca2+ entry. The mechanisms of EO resistance and the impaired fetal and placental growth due to elevated ouabain may be important in pregnancy-induced hypertension (PIH) and preeclampsia (PE). PMID:22245773

Jacobs, Brandiese E.; Liu, Yong; Pulina, Maria V.; Golovina, Vera A.

2012-01-01

213

A new aluminium-hydrate species in hydrated Portland cements characterized by 27Al and 29Si MAS NMR spectroscopy  

Microsoft Academic Search

Recent 27Al MAS NMR studies of hydrated Portland cements and calcium-silicate-hydrate (C-S-H) phases have shown a resonance from Al in octahedral coordination, which cannot be assigned to the well-known aluminate species in hydrated Portland cements. This resonance, which exhibits the isotropic chemical shift ?iso=5.0 ppm and the quadrupole product parameter PQ=1.2 MHz, has been characterized in detail by 27Al MAS

Morten Daugaard Andersen; Hans J. Jakobsen; Jørgen Skibsted

2006-01-01

214

XPS of fast-frozen hematite colloids in NaCl aqueous solutions: I. Evidence for the formation of multiple layers of hydrated sodium and chloride ions induced by the {001} basal plane  

SciTech Connect

The influence of the {001} basal plane of hematite on the composition of fast-frozen centrifuged wet pastes of hematite prepared at pH 4 and 9 and at ionic strengths of 0, 10 and 100 mM NaCl was investigated by x-ray photoelectron spectroscopy. Two hematite preparations consisted of micrometer-sized platelets with 42% (HEM-1) and 95% (HEM-8) of the surface terminated by the {001} basal plane. A third preparation of spherical shape with no recognizable crystal plane (HEM-control) was used as a control to these experiments. All hematite samples responded to changes in pH and ionic strength, showing that acid/base reactions of surface hydroxyl groups control the composition of the paste. The HEM-1 and HEM-8 sample exhibited divergent properties at the highest ionic strength (100 mM) with energy loss features in the Na 1s and Cl 2p spectra and an important water content. As the spectra were typical of hydrated Na+ and Cl- ions and that the surface concentrations were unusually large, the HEM-1 and HEM-8 samples are proposed to induce the formation of a three-dimensional distribution of these ions in the paste. The sodium, chloride and water content was also correlated to the fraction of the {001} basal plane present in the sample and provided evidence for an approximate stochiometric Na:Cl:H2O ratio of 1:1:2. The {001} basal plane of hematite is consequently proposeD to be the cause of this feature.

Shchukarev, Andrei; Boily, Jean F.; Felmy, Andrew R.

2007-12-13

215

21 CFR 172.715 - Calcium lignosulfonate.  

Code of Federal Regulations, 2010 CFR

...safely used in or on food, subject to the provisions of this section. (a) Calcium lignosulfonate consists of sulfonated lignin, primarily as calcium and sodium salts. (b) It is used in an amount not to exceed that reasonably required to...

2010-04-01

216

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2012 CFR

...hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The ingredient meets the specifications of the Food Chemicals Codex, 3d Ed....

2012-04-01

217

21 CFR 184.1763 - Sodium hydroxide.  

...hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The ingredient meets the specifications of the Food Chemicals Codex, 3d Ed....

2014-04-01

218

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2010 CFR

...hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The ingredient meets the specifications of the Food Chemicals Codex, 3d Ed....

2010-04-01

219

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2011 CFR

...hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The ingredient meets the specifications of the Food Chemicals Codex, 3d Ed....

2011-04-01

220

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2013 CFR

...hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The ingredient meets the specifications of the Food Chemicals Codex, 3d Ed....

2013-04-01

221

Gas hydrate growth morphology outside of horizontal heat transfer tube  

Microsoft Academic Search

Visual observation of HCFC141b gas hydrate growth process outside of a horizontal heat transfer tube was done on a visual apparatus of gas hydrate reaction system. Growth processes of two situations (with, or without sodium dodecyl sulfate (SDS)) were observed, their growth morphology were compared and explained with the theory of surface free energy. During the experiment process, phenomenon of

Yingming Xie; Kaihua Guo; Deqing Liang; Shuanshi Fan; Jianming Gu

2005-01-01

222

Separation and Purification of Methane from coal-Bed Methane via the Hydrate Technology  

Microsoft Academic Search

The separation of methane from coal-bed methane (CBM) via hydrate process using tetrahydrofuran (THF) + sodium dodecyl sulfate (SDS) as additives was investigated in this work. The effect of additives, the concentration of the additives and hydrate memory effect on the hydrate-based separation process were examined at various concentrations of THF + SDS solutions. The results indicate that THF +

Cai Jing; Chen Zhaoyang; Li Xiaosen; Xu Chungang

2010-01-01

223

The role of CSH microstructure and calcium hydroxide on creep and shrinkage of hardened portland cement paste  

Microsoft Academic Search

The thesis provides new research related to the mechanisms of creep and shrinkage of hardened Portland cement paste. The emphasis is put on the role of calcium silicate hydrate (C-S-H) microstructure and calcium hydroxide the most important phases in hydrated Portland cement paste. Specially designed specimens were used for creep and shrinkage measurements. These were well hydrated and very thin

Basile-Honore Tamtsia Tamboue

2001-01-01

224

Identifying inhibitors of hydrate formation rate with viscometric experiments  

SciTech Connect

Inhibiting the rate of hydrate formation with low concentration additives is an economically and environmentally attractive alternative to prevention of hydrates with large doses of methanol. Here, a method for screening possible rate inhibitors is described. In the method, a viscometer is used to follow the development of hydrate formation for water-THF solutions and for water-gas solutions at conditions favoring hydrate formation. The method was applied to about 30 different chemicals, plus binary combinations of many of these chemicals. The best chemical additives included BASF F-127, Mirawet ASC, Surfynol-465, sodium dodecyl sulfate(SDS), Mirataine CBS with polyvinylpyrrolidone(PVP), and SDS with PVP.

Kalbus, J.S.; Christiansen, R.L.; Sloan, D. Jr.

1995-12-31

225

Effects of Chemomechanical Preparation With 2.5% Sodium Hypochlorite and Intracanal Medication With Calcium Hydroxide on Cultivable Bacteria in Infected Root Canals  

Microsoft Academic Search

This clinical study was conducted to assess the bacterial reduction after chemomechanical preparation with 2.5% NaOCl as an irrigant and the additive antibacte- rial effect of intracanal dressing with calcium hydrox- ide. According to stringent inclusion criteria, 11 teeth with primary intraradicular infections and chronic apical periodontitis were selected and monitored in the study. Bacterial samples were taken at the

José F. Siqueira Jr; Tatiana Guimarães-Pinto; Isabela N. Rôças

2007-01-01

226

Calcium supplements  

MedlinePLUS

... The two main forms of calcium pills are: Calcium carbonate: Over-the-counter antacid products, such as Tums and Rolaids contain calcium carbonate. These sources of calcium carbonate do not cost ...

227

Combinatorial molecular optimization of cement hydrates  

NASA Astrophysics Data System (ADS)

Despite its ubiquitous presence in the built environment, concrete’s molecular-level properties are only recently being explored using experimental and simulation studies. Increasing societal concerns about concrete’s environmental footprint have provided strong motivation to develop new concrete with greater specific stiffness or strength (for structures with less material). Herein, a combinatorial approach is described to optimize properties of cement hydrates. The method entails screening a computationally generated database of atomic structures of calcium-silicate-hydrate, the binding phase of concrete, against a set of three defect attributes: calcium-to-silicon ratio as compositional index and two correlation distances describing medium-range silicon-oxygen and calcium-oxygen environments. Although structural and mechanical properties correlate well with calcium-to-silicon ratio, the cross-correlation between all three defect attributes reveals an indentation modulus-to-hardness ratio extremum, analogous to identifying optimum network connectivity in glass rheology. We also comment on implications of the present findings for a novel route to optimize the nanoscale mechanical properties of cement hydrate.

Abdolhosseini Qomi, M. J.; Krakowiak, K. J.; Bauchy, M.; Stewart, K. L.; Shahsavari, R.; Jagannathan, D.; Brommer, D. B.; Baronnet, A.; Buehler, M. J.; Yip, S.; Ulm, F.-J.; van Vliet, K. J.; Pellenq, R. J.-. M.

2014-09-01

228

Combinatorial molecular optimization of cement hydrates.  

PubMed

Despite its ubiquitous presence in the built environment, concrete's molecular-level properties are only recently being explored using experimental and simulation studies. Increasing societal concerns about concrete's environmental footprint have provided strong motivation to develop new concrete with greater specific stiffness or strength (for structures with less material). Herein, a combinatorial approach is described to optimize properties of cement hydrates. The method entails screening a computationally generated database of atomic structures of calcium-silicate-hydrate, the binding phase of concrete, against a set of three defect attributes: calcium-to-silicon ratio as compositional index and two correlation distances describing medium-range silicon-oxygen and calcium-oxygen environments. Although structural and mechanical properties correlate well with calcium-to-silicon ratio, the cross-correlation between all three defect attributes reveals an indentation modulus-to-hardness ratio extremum, analogous to identifying optimum network connectivity in glass rheology. We also comment on implications of the present findings for a novel route to optimize the nanoscale mechanical properties of cement hydrate. PMID:25248305

Abdolhosseini Qomi, M J; Krakowiak, K J; Bauchy, M; Stewart, K L; Shahsavari, R; Jagannathan, D; Brommer, D B; Baronnet, A; Buehler, M J; Yip, S; Ulm, F-J; Van Vliet, K J; Pellenq, R J-M

2014-01-01

229

Combinatorial molecular optimization of cement hydrates  

PubMed Central

Despite its ubiquitous presence in the built environment, concrete’s molecular-level properties are only recently being explored using experimental and simulation studies. Increasing societal concerns about concrete’s environmental footprint have provided strong motivation to develop new concrete with greater specific stiffness or strength (for structures with less material). Herein, a combinatorial approach is described to optimize properties of cement hydrates. The method entails screening a computationally generated database of atomic structures of calcium-silicate-hydrate, the binding phase of concrete, against a set of three defect attributes: calcium-to-silicon ratio as compositional index and two correlation distances describing medium-range silicon-oxygen and calcium-oxygen environments. Although structural and mechanical properties correlate well with calcium-to-silicon ratio, the cross-correlation between all three defect attributes reveals an indentation modulus-to-hardness ratio extremum, analogous to identifying optimum network connectivity in glass rheology. We also comment on implications of the present findings for a novel route to optimize the nanoscale mechanical properties of cement hydrate. PMID:25248305

Abdolhosseini Qomi, M.J.; Krakowiak, K.J.; Bauchy, M.; Stewart, K.L.; Shahsavari, R.; Jagannathan, D.; Brommer, D.B.; Baronnet, A.; Buehler, M.J.; Yip, S.; Ulm, F.-J; Van Vliet, K.J.; Pellenq, R.J-.M.

2014-01-01

230

Changes in calcium dynamics following the reversal of the sodium-calcium exchanger have a key role in AMPA receptor-mediated neurodegeneration via calpain activation in hippocampal neurons.  

PubMed

Proteolytic cleavage of the Na(+)/Ca(2+) exchanger (NCX) by calpains impairs calcium homeostasis, leading to a delayed calcium overload and excitotoxic cell death. However, it is not known whether reversal of the exchanger contributes to activate calpains and trigger neuronal death. We investigated the role of the reversal of the NCX in Ca(2+) dynamics, calpain activation and cell viability, in alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor-stimulated hippocampal neurons. Selective overactivation of AMPA receptors caused the reversal of the NCX, which accounted for approximately 30% of the rise in intracellular free calcium concentration ([Ca(2+)](i)). The NCX reverse-mode inhibitor, 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea (KB-R7943), partially inhibited the initial increase in [Ca(2+)](i), and prevented a delayed increase in [Ca(2+)](i). In parallel, overactivation of AMPA receptors strongly activated calpains and led to the proteolysis of NCX3. KB-R7943 prevented calpain activation, cleavage of NCX3 and was neuroprotective. Silencing of NCX3 reduced Ca(2+) uptake, calpain activation and was neuroprotective. Our data show for the first time that NCX reversal is an early event following AMPA receptor stimulation and is linked to the activation of calpains. Since calpain activation subsequently inactivates NCX, causing a secondary Ca(2+) entry, NCX may be viewed as a new suicide substrate operating in a Ca(2+)-dependent loop that triggers cell death and as a target for neuroprotection. PMID:17585341

Araújo, I M; Carreira, B P; Pereira, T; Santos, P F; Soulet, D; Inácio, A; Bahr, B A; Carvalho, A P; Ambrósio, A F; Carvalho, C M

2007-09-01

231

Effect of intravenous hydration in patients receiving bisphosphonate therapy.  

PubMed

Background Patients with advanced cancers are at high risk for bone metastases, which accelerate bone resorption and skeletal complications. Therefore, bisphosphonates, which are strong inhibitors of bone resorption, are widely used to prevent pathological fractures, pain and tumour-induced hypercalcaemia. Intravenous infusion of bisphosphonate is associated with dose- and infusion rate-dependent adverse renal effects. Objective The present study investigated the effect of hydration on bisphosphonate efficacy and safety. Settings The 600-bed CHOV Hospital (Neufchâteau, France) and the Université de Lorraine (Nancy, France). Methods Patients who received pamidronate or zoledronic acid treatments were identified: 50 patients [16 of whom were hydrated and 34 of whom were non-hydrated]. Data on serum calcium levels, creatinine clearance and clinical tolerance were collected. Main outcome measure The impact of hydration on these parameters was analysed between day 1 and day 7. Results Bisphosphonate normalized calcaemia and hydration did not induce further reduction of calcium levels. Patient kidneys were significantly preserved by hydration in both groups (median clearance: +6.2 %), whereas dehydrated patients had lower creatinine clearance (median clearance: -1.1 %). Hydration did not influence other clinical or biological parameters tested. Conclusion Hydration plays an important role in the treatment of hypercalcaemia by pamidronate and zoledronic acid: it enhances kidney protection (i.e., creatinine clearance). PMID:25208980

Attivi, David; Kosmalski, Gaétan; Zeghmouli, Claire; Gibaud, Stéphane

2014-12-01

232

Counterion-assisted cation transport in a biological calcium channel.  

PubMed

How ions pass through the lumen of an ion channel is a key question underlying cellular communication. The effects of water and pore-lining residues (channel design) have been extensively explored. However, the role of counterions is less well understood. The pore subunit of the calcium release-activated calcium channel, Orai, provides a useful model to explore the effect of anions on the permeation of cations. Herein, we employ computer simulations molecular dynamics (MD) to explore ion permeation through the V174A Orai mutant, a constitutively open pore, in a phospholipid membrane hydrated by a 150 mM NaCl solution. When an external voltage is applied in the MD simulations, it induces only a moderate conformational change to the channel, which facilitates the passage of ions. Infrequent sodium permeation is observed on the microsecond time scale, which is consistent with experiment. In contrast, the chloride counterions exhibit higher mobility in the channel and are actively involved in sodium transport. The anion-assisted cation permeation identified here likely highlights a more general functional role for counterions, especially in ion channels with medium pore-size. Experiments with a variety of counterions might further illuminate the nature of their active role. PMID:25068680

Dong, Hao; Klein, Michael L; Fiorin, Giacomo

2014-08-14

233

IQENS from hydrated lysozyme  

NASA Astrophysics Data System (ADS)

We present quasi-elastic incoherent neutron scattering data on wet lysozyme powders at water contents (grams of water/grams of protein) of h=0.20 and 0.45, corresponding to hydration levels below and above the full monolayer coverage of the protein surface. The data were collected under H2O and D2O hydration condition; using the IRIS spectrometer with a resolution of 11 ?eV (full-width). From spectra for the D2O hydrated sample we obtain information on the protein dynamics. These spectra are used to separate from the H2O hydrated sample the contribution due to the hydration water. We show that at low hydration the dynamics of water is very slow and on the same time scale as that of the protein dynamics, while at higher hydration the water molecules show a faster dynamics. The results support the idea that there are clusters of hydration water.

Wanderlingh, U. N.; Giordano, R.; Kagunya, W. W.

1998-04-01

234

Hydrate-phobic surfaces  

E-print Network

Clathrate hydrate formation and subsequent plugging of deep-sea oil and gas pipelines represent a significant bottleneck for ultra deep-sea production. Current methods for hydrate mitigation focus on injecting thermodynamic ...

Smith, Jonathan David, S.M. Massachusetts Institute of Technology

2011-01-01

235

A new aluminium-hydrate species in hydrated Portland cements characterized by ²⁷Al and ²⁹Si MAS NMR spectroscopy  

Microsoft Academic Search

Recent ²⁷Al MAS NMR studies of hydrated Portland cements and calcium-silicate-hydrate (C-S-H) phases have shown a resonance from Al in octahedral coordination, which cannot be assigned to the well-known aluminate species in hydrated Portland cements. This resonance, which exhibits the isotropic chemical shift δ {sub iso} = 5.0 ppm and the quadrupole product parameter P {sub Q} = 1.2 MHz,

Morten Daugaard Andersen; Hans J. Jakobsen; Jorgen. Skibsted

2006-01-01

236

Nucleation of gas hydrates  

Microsoft Academic Search

The kinetics of nucleation of one-component gas hydrates in aqueous solutions are analyzed. The size of the hydrate nucleus and the work for nucleus formation are determined as functions of the supersaturation ??. Expressions for the stationary rate J of hydrate nucleation are derived. These expressions describe the J(??) dependence for homogeneous nucleation and for heterogeneous nucleation at the solution\\/gas

Dimo Kashchiev; Abbas Firoozabadi

2002-01-01

237

Tungsten mine waste geopolymeric binder: Preliminary hydration products investigations  

Microsoft Academic Search

Geopolymeric mine waste mud (GMWM) binders are obtained from dehydroxylated waste powder mixed with minor quantities of calcium hydroxide, activated with NaOH and waterglass solutions. In this work recent investigations of GMWM binders hydration products have been carried out. The hydration products have been investigated by means of X-ray diffraction (XRD) and scanning electron microscopy\\/energy dispersive spectroscopy (SEM\\/EDS).Results indicate that

Fernando Pacheco-Torgal; João Castro-Gomes; Said Jalali

2009-01-01

238

Hydrate characterization research overview  

SciTech Connect

Gas hydrate research has been focused primarily on the development of a basic understanding of hydrate formation and dissociation in the laboratory, as well as in the field. Laboratory research on gas hydrates characterized the physical system, which focused on creating methane hydrates samples, tetrahydrofuran (THF) hydrate samples, consolidated rock samples, frost base mixtures, water/ice-base mixtures, and water-base mixtures. Laboratory work produced measurements of sonic velocity and electrical resistivity of hydrates. As work progressed, areas, such as the Gulf of Mexico and the Guatemala Trench, where gas hydrates are likely to occur were identified, and specific high potential areas were targeted for detailed investigation. The testing of samples and recovered cores from such areas provided information for detection of hydrate formations in the natural environment. Natural gas hydrate samples have been tested for thermal properties, dissociation properties, fracture mechanics, and optical properties. Acoustical properties were investigated both in the laboratory and, as possible, in the field. Sonic velocity and electrical resistivity measurements will continue to be obtained. These activities have been undertaken in hydrate deposits on Alaska`s North Slope, the Gulf of Mexico and the US East coast offshore, as well as other gas hydrate target areas.

Malone, R.D.

1993-06-01

239

Thermodynamic modelling of the hydration of Portland cement  

SciTech Connect

A thermodynamic model is developed and applied to calculate the composition of the pore solution and the hydrate assemblage during the hydration of an OPC. The calculated hydration rates of the individual clinker phases are used as time dependent input. The modelled data compare well with the measured composition of pore solutions gained from OPC as well as with TGA and semi-quantitative XRD data. The thermodynamic calculations indicate that in the presence of small amounts of calcite typically included in OPC cements, C-S-H, portlandite, ettringite and calcium monocarbonates are the main hydration products. The thermodynamic model presented in this paper helps to understand the interactions between the different components and the environment and to predict the influence of changes in cement composition on the hydrate assemblage.

Lothenbach, Barbara [Empa, Laboratory for Concrete and Construction Chemistry, Uberlandstrasse 129, 8600 Duebendorf (Switzerland)]. E-mail: barbara.lothenbach@empa.ch; Winnefeld, Frank [Empa, Laboratory for Concrete and Construction Chemistry, Uberlandstrasse 129, 8600 Duebendorf (Switzerland)

2006-02-15

240

Modeling and simulation of cement hydration kinetics and microstructure development  

SciTech Connect

Efforts to model and simulate the highly complex cement hydration process over the past 40 years are reviewed, covering different modeling approaches such as single particle models, mathematical nucleation and growth models, and vector and lattice-based approaches to simulating microstructure development. Particular attention is given to promising developments that have taken place in the past few years. Recent applications of molecular-scale simulation methods to understanding the structure and formation of calcium-silicate-hydrate phases, and to understanding the process of dissolution of cement minerals in water are also discussed, as these topics are highly relevant to the future development of more complete and fundamental hydration models.

Thomas, Jeffrey J., E-mail: jthomas39@slb.com [Schlumberger-Doll Research, Cambridge, MA 02139 (United States); Biernacki, Joseph J. [Department of Chemical Engineering, Tennessee Tech University, Cookeville, TN (United States); Bullard, Jeffrey W. [Materials and Construction Research Division, National Institute of Standards and Technology, Gaithersburg, MD (United States); Bishnoi, Shashank [Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi (India); Dolado, Jorge S. [Center for Nanomaterials Application in Construction, LABEIN-Tecnalia, Bilbao (Spain); Scherer, George W. [Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ (United States); Luttge, Andreas [Department of Chemistry, Rice University, Houston, TX (United States)

2011-12-15

241

Calcium and Cancer Prevention: Strengths and Limits of the Evidence  

MedlinePLUS

... is high in calcium) and some types of antacids, especially antacids containing calcium carbonate or sodium bicarbonate (baking soda), ... LP. Life-threatening milk-alkali syndrome resulting from antacid ingestion during pregnancy. Medical Journal of Australia 2005; ...

242

Long-term behaviour of hydraulic binders based on calcium sulfoaluminate and calcium sulfosilicate  

Microsoft Academic Search

Hydration, physico-mechanical and carbonation studies have been carried out on the ternary system of calcium sulfoaluminate (C4A3S?), calcium sulfosilicate (C5S2S?) and anhydrite (CS?), synthesised by single firing at 1200 °C. The raw materials used were natural materials, viz. limestone, bauxite and clay, and also industrial process; wastes and by-products, viz. phosphogypsum, fly ash and blast furnace slag.These clinkers containing calcium

N. Sherman; J. Beretka; L. Santoro; G. L. Valenti

1995-01-01

243

Methane Hydrate Field Program  

SciTech Connect

This final report document summarizes the activities undertaken and the output from three primary deliverables generated during this project. This fifteen month effort comprised numerous key steps including the creation of an international methane hydrate science team, determining and reporting the current state of marine methane hydrate research, convening an international workshop to collect the ideas needed to write a comprehensive Marine Methane Hydrate Field Research Plan and the development and publication of that plan. The following documents represent the primary deliverables of this project and are discussed in summary level detail in this final report. • Historical Methane Hydrate Project Review Report • Methane Hydrate Workshop Report • Topical Report: Marine Methane Hydrate Field Research Plan • Final Scientific/Technical Report

None

2013-12-31

244

[Calcium--essential for everybody].  

PubMed

Calcium regulates majority of metabolic processes within human organism and its optimal intake decreases risk of metabolic illnesses conditioned by diet. Deficiency of calcium results in higher body max index, increase risk of insulin resistance, diabetes type 2 and osteoporosis. Diet delivering full calcium load diminished impendency of hypertension; calcium regulates tension of smooth muscles of blood vessels, limits neurotransmitters activity and also diminish hazardous activity of sodium chloride. Anticancerogenic activity of calcium results from formation insoluble bile acids and fat acids salts, and most of all, from inhibition of intestine mucosa cells hyper proliferation. Due to presence of vitamin D3, CLA, proteins and bioactive peptides emerging from them, milk is more efficient in prophylaxis of diet conditioned illnesses than calcium supplements. Efficiency of milk and dairy products in treatment of obesity, sclerosis and hypertension has been proved by DASH diet. PMID:25095643

Cichosz, Grazyna; Czeczot, Hanna

2014-06-01

245

Nucleation of gas hydrates  

NASA Astrophysics Data System (ADS)

The kinetics of nucleation of one-component gas hydrates in aqueous solutions are analyzed. The size of the hydrate nucleus and the work for nucleus formation are determined as functions of the supersaturation ? ?. Expressions for the stationary rate J of hydrate nucleation are derived. These expressions describe the J(? ?) dependence for homogeneous nucleation and for heterogeneous nucleation at the solution/gas interface or on solid substrates and nucleation-active microparticles in the solution. The results are applied to nucleation of methane hydrate in solutions containing additives that may act as kinetic inhibitors of the process.

Kashchiev, Dimo; Firoozabadi, Abbas

2002-09-01

246

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

SciTech Connect

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

Grant, Steven A. [U.S. Army Engineer Research and Development Center, Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755-1290 (United States)]. E-mail: steven.a.grant@usace.army.mil; Boitnott, Ginger E. [U.S. Army Engineer Research and Development Center, Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755-1290 (United States); Korhonen, Charles J. [U.S. Army Engineer Research and Development Center, Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755-1290 (United States); Sletten, Ronald S. [Quaternary Research Center, University of Washington, Seattle (United States)

2006-04-15

247

Determination of calcium, copper, iron, magnesium, manganese, potassium, phosphorus, sodium, and zinc in fortified food products by microwave digestion and inductively coupled plasma-optical emission spectrometry: single-laboratory validation and ring trial.  

PubMed

A single-laboratory validation (SLV) and a ring trial (RT) were undertaken to determine nine nutritional elements in food products by inductively coupled plasma-optical emission spectrometry in order to modernize AOAC Official Method 984.27. The improvements involved extension of the scope to all food matrixes (including infant formula), optimized microwave digestion, selected analytical lines, internal standardization, and ion buffering. Simultaneous determination of nine elements (calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, and zinc) was made in food products. Sample digestion was performed through wet digestion of food samples by microwave technology with either closed- or open-vessel systems. Validation was performed to characterize the method for selectivity, sensitivity, linearity, accuracy, precision, recovery, ruggedness, and uncertainty. The robustness and efficiency of this method was proven through a successful RT using experienced independent food industry laboratories. Performance characteristics are reported for 13 certified and in-house reference materials, populating the AOAC triangle food sectors, which fulfilled AOAC criteria and recommendations for accuracy (trueness, recovery, and z-scores) and precision (repeatability and reproducibility RSD, and HorRat values) regarding SLVs and RTs. This multielemental method is cost-efficient, time-saving, accurate, and fit-for-purpose according to ISO 17025 Norm and AOAC acceptability criteria, and is proposed as an extended updated version of AOAC Official Method 984.27 for fortified food products, including infant formula. PMID:22468357

Poitevin, Eric

2012-01-01

248

The Effect of Modified Atmosphere Packaging and Addition of Rosemary Extract, Sodium Acetate and Calcium Lactate Mixture on the Quality of Pre-cooked Hamburger Patties during Refrigerated Storage  

PubMed Central

The effect of modified atmosphere packaging (MAP; 30% CO2+70% N2 or 100% N2) and an additive mixture (500 ppm rosemary extract, 3,000 ppm sodium acetate and 1,500 ppm calcium lactate) on the quality of pre-cooked hamburger patties during storage at 5°C for 14 d was evaluated. The addition of the additive mixture reduced aerobic and anaerobic bacteria counts in both 30% CO2-MAP (30% CO2+70% N2) and 100% N2-MAP (p<0.05). The 30% CO2-MAP was more effective to suppress the microbial growth than 100% N2-MAP, moreover the 30% CO2-MAP combined with additive mixture resulted in the lowest bacterial counts. The hamburger patties with additive mixture showed lower CIE L* and CIE a*, and higher CIE b* than those with no additive mixture. The 30% CO2-MAP tended to decrease the TBARS during storage regardless of the addition of additives. The use of 30% CO2-MAP in combination with additives mixture was effective for maintaining the quality and extending the shelf-life of pre-cooked hamburger patties. PMID:25049716

Muhlisin; Kang, Sun Moon; Choi, Won Hee; Lee, Keun Taik; Cheong, Sung Hee; Lee, Sung Ki

2013-01-01

249

Class H cement hydration at 180 °C and high pressure in the presence of added silica  

SciTech Connect

Under deep oil-well conditions of elevated temperature and pressure, crystalline calcium silicate hydrates are formed during Portland cement hydration. The use of silica rich mineral additives leads to the formation of crystalline hydrates with better mechanical properties than those formed without the additive. The effects of silica flour, silica fume (amorphous silica), and a natural zeolite mixture on the hydration of Class H cement slurries at 180 C under externally applied pressures of 7 and 52 MPa are examined in real time using in-situ synchrotron X-ray diffraction. For some compositions examined, but not all, pressure was found to have a large effect on the kinetics of crystalline hydrate formation. The use of silica fume delayed both C{sub 3}S hydration and the formation of crystalline silicate hydrates compared to what was seen with other silica sources.

Jupe, Andrew C.; Wilkinson, Angus P.; Luke, Karen; Funkhouser, Gary P. (Halliburton); (GIT)

2008-10-06

250

Experimental study on a small scale of gas hydrate cold storage apparatus  

Microsoft Academic Search

To have an overall investigation of cold storage characteristics to help to promote the application, a novel small scale of gas hydrate cold storage apparatus was designed. The amount of cold energy, growth rate, Hydrate Packed Factor (HPF) and overall heat transfer coefficient during the cold storage process were calculated and analyzed under different heat exchangers, sodium dodecyl benzene sulfonate

Yingming Xie; Gang Li; Daoping Liu; Ni Liu; Yingxia Qi; Deqing Liang; Kaihua Guo; Shuanshi Fan

2010-01-01

251

Gas hydrate inhibition  

Microsoft Academic Search

This patent describes a process for inhibiting gas hydrate formation in the production fluid of a well, connected facilities and pipelines of the well comprising injecting into the well inhibitor comprising a carrier and a polycyclicpolyetherpolyol. This patent also describes a process for shutting-in a well having a fluid therein which is susceptible to the formation of gas hydrates. It

A. H. Hale; A. K. R. Dewan; G. C. Blytas

1991-01-01

252

Gas hydrate inhibition  

SciTech Connect

This patent describes a process for inhibiting gas hydrate formation in the production fluid of a well, connected facilities and pipelines of the well comprising injecting into the well inhibitor comprising a carrier and a polycyclicpolyetherpolyol. This patent also describes a process for shutting-in a well having a fluid therein which is susceptible to the formation of gas hydrates. It comprises preparing a gas hydrate inhibitor by admixing an alcohol with a carrier, the carrier and the alcohol and the quantities thereof being selected to be compatible with the well and effective to prevent the formation of gas hydrates in the well fluid; selecting an appropriate location, depending upon the type of well being shut-in, and injecting the gas hydrate inhibitor into the well at the location; and shutting-in the well.

Hale, A.H.; Dewan, A.K.R.; Blytas, G.C.

1991-12-31

253

Calcium Carbonate  

MedlinePLUS

... heart. Calcium carbonate also is used as an antacid to relieve heartburn, acid indigestion, and upset stomach. ... use.Do not take calcium carbonate as an antacid for more than 2 weeks unless your doctor ...

254

The influence of additives and metal rods on the nucleation and growth of gas hydrates.  

PubMed

A major technical issue in industrial applications of the gas hydrate storage process is to develop a practical means for rapid hydrate formation. In this paper, the formation processes of HCFC141b (CH(3)CCl(2)F) gas hydrate in a column of water with additives and with an iron rod that was placed in the center of the column have been studied to reveal the influence of the additives and the iron rod on the nucleation and growth of the gas hydrate. The water solution column, in a cylindrical glass container, was placed in a thermostatic bath at 274.15-280.15 K and under atmospheric pressure. The experimental results show that, compared to the pure water and the HCFC141b system, the properly placed iron rod combined with proper concentrations of lauryl sodium sulfonate, lauryl sodium sulfate, and sodium dodecylbenzenesulfonate-6 considerably reduces the hydrate nucleation time and promotes formation speed. The formation rate of HCFC141b gas hydrate increases with increasing concentration of sodium dodecylbenzenesulfonate-6 in the water solution, while the addition of potassium oxalate monohydrate in water has shown no effect on the nucleation and growth of HCFC141b gas hydrate. Under the experimental conditions, both the anion surfactants and the iron rod strongly induce the first nucleation of HCFC141b gas hydrate, while the following growth of the HCFC141b gas hydrate is primarily influenced by the anion surfactant. This experiment suggests a new way of fast formation of clathrate hydrate, which may be much easier for practical application of the gas hydrate for cold storage in air conditioning systems. PMID:15694442

Li, Jinping; Liang, Deqing; Guo, Kaihua; Wang, Ruzhu

2005-03-01

255

21 CFR 201.70 - Calcium labeling.  

Code of Federal Regulations, 2010 CFR

...bullet] 1 kidney stones [bullet] a calcium-restricted diet”. The warnings in §§ 201.64(c), 201.70(c...alphabetical order, e.g., a calcium or sodium restricted diet. 1 See § 201.66(b)(4) of this chapter for...

2010-04-01

256

Adsorption of Gemini surfactants onto clathrate hydrates.  

PubMed

This work addresses the adsorption of two Gemini surfactants at the cyclopentane (CP) hydrate-water interface. The Gemini surfactants investigated here are Dowfax C6L and Dowfax 2A1 that have two anionic head groups and one hydrophobic tail group. The adsorption of these surfactants was quantified using adsorption isotherms and the adsorption isotherms were determined using liquid-liquid titrations. Even if the Gemini surfactant adsorption isotherms show multi-layer adsorption, they possess the first Langmuir layer with the second adsorption layer only evident in the 2A1 adsorption isotherm. Zeta potentials of CP hydrate particles in the surfactant solution of various concentrations of Dowfax C6L and Dowfax 2A1 were measured to further explain their adsorption behavior at the CP hydrate-water interface. Zeta potentials of alumina particles as a model particle system in different concentrations of sodium dodecyl sulfate (SDS), Dowfax C6L and Dowfax 2A1 were also measured to confirm the configuration of all the surfactants at the interface. The determination of the isotherms and zeta-potentials provides an understanding framework for the adsorption behavior of the two Gemini surfactants at the hydrate-water interface. PMID:24144366

Salako, O; Lo, C; Couzis, A; Somasundaran, P; Lee, J W

2013-12-15

257

Here's butane hydrates equilibria  

SciTech Connect

In 1961 McLeod and Campbell studied hydrates formation for binary mixtures of methane with ethane through butane at pressures up to 10,000 psia. Their data showed that butane lowered the pressure of hydrate formation for methane up to pressures ranging from 1,500 to 2,000 psia. At pressures above this range methane-n-butane mixtures generally followed the curve for pure methane or were slightly above it. McLeod and Campbell conclude that the crystal lattice is deformed at higher pressures (above 6,000 psia) and that hydrate composition on a water-free basis is the same as the gas.

Peettman, F.H.

1984-06-01

258

Methane Hydrates: Chapter 8  

USGS Publications Warehouse

Gas hydrate is a solid, naturally occurring substance consisting predominantly of methane gas and water. Recent scientific drilling programs in Japan, Canada, the United States, Korea and India have demonstrated that gas hydrate occurs broadly and in a variety of forms in shallow sediments of the outer continental shelves and in Arctic regions. Field, laboratory and numerical modelling studies conducted to date indicate that gas can be extracted from gas hydrates with existing production technologies, particularly for those deposits in which the gas hydrate exists as pore-filling grains at high saturation in sand-rich reservoirs. A series of regional resource assessments indicate that substantial volumes of gas hydrate likely exist in sand-rich deposits. Recent field programs in Japan, Canada and in the United States have demonstrated the technical viability of methane extraction from gas-hydrate-bearing sand reservoirs and have investigated a range of potential production scenarios. At present, basic reservoir depressurisation shows the greatest promise and can be conducted using primarily standard industry equipment and procedures. Depressurisation is expected to be the foundation of future production systems; additional processes, such as thermal stimulation, mechanical stimulation and chemical injection, will likely also be integrated as dictated by local geological and other conditions. An innovative carbon dioxide and methane swapping technology is also being studied as a method to produce gas from select gas hydrate deposits. In addition, substantial additional volumes of gas hydrate have been found in dense arrays of grain-displacing veins and nodules in fine-grained, clay-dominated sediments; however, to date, no field tests, and very limited numerical modelling, have been conducted with regard to the production potential of such accumulations. Work remains to further refine: (1) the marine resource volumes within potential accumulations that can be produced through exploratory drilling programs; (2) the tools for gas hydrate detection and characterisation from remote sensing data; (3) the details of gas hydrate reservoir production behaviour through additional, well-monitored and longer duration field tests and (4) the understanding of the potential environmental impacts of gas hydrate resource development. The results of future production tests, in the context of varying market and energy supply conditions around the globe, will be the key to determine the ultimate timing and scale of the commercial production of natural gas from gas hydrates.

Boswell, Ray; Yamamoto, Koji;Lee, Sung-Rock; Collett, Timothy S.; Kumar, Pushpendra; Dallimore, Scott

2008-01-01

259

21 CFR 201.64 - Sodium labeling.  

Code of Federal Regulations, 2010 CFR

...you have [in bold type] [bullet] 1 a sodium-restricted diet”. The warnings in §§ 201.64(c), 201.70(c...in alphabetical order, e g., a calcium or sodium restricted diet. 1 See § 201 .66(b)(4) of this chapter for...

2010-04-01

260

Hydrate adhesive and tensile strengths  

NASA Astrophysics Data System (ADS)

The physical properties of hydrate-bearing sediments depend on the interaction between hydrates and minerals. In particular, hydrates prefer to nucleate on mineral surfaces, therefore, the hydrate-mineral adhesive strength and the tensile strength of the hydrate mass itself affect the mechanical response of hydrate-bearing sediments. In this study, ice and hydrates made with various guest molecules (CO2, CH4, and THF) are formed between mica and calcite substrates. Adhesive and tensile strengths are measured by applying an external pull-out force. Results show that tensile failure occurs in CO2 and CH4 hydrates when calcite is the substrate, while ice and all hydrates exhibit adhesive failure on mica. The debonding strength is higher when calcite substrates are involved rather than mica substrates. A nominal pull-out strength of 0.15 ± 0.03 MPa can be adopted for mechanical analyses of hydrate-bearing sediments.

Jung, J. W.; Santamarina, J. Carlos

2011-08-01

261

Hydrate morphology: Physical properties of sands with patchy hydrate saturation  

USGS Publications Warehouse

The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate-bearing sediments, including the coarse-grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate-bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore-space hydrate saturation are embedded in hydrate-free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate-bearing sands and captures observed physical-property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate-patch size itself impacts the physical properties of hydrate-bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate-saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate-saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross-section of the specimen.

Dai, S.; Santamarina, J. C.; Waite, William F.; Kneafsey, T. J.

2012-01-01

262

[Disorders in sodium-water balance.  

PubMed

Water balance control is aimed at normalizing cellular hydration, and sodium balance control at normalizing extracellular volume. Water balance control is based on the regulation of body fluid tonicity, while the control of sodium balance is based on the regulation of effective arterial volume. Disorders of water balance act on cellular hydration: primary disorders induce a proportional change in tonicity; secondary disorders are induced by a change in tonicity or effective arterial volume. Disorders of sodium balance act on extracellular volume: primary disorders of sodium balance induce a change in effective arterial volume; secondary disorders are induced by a change in effective arterial volume. Physical examination of the patient allows assessing the extracellular volume and the severity of the sodium balance disorder. Natremia - that generally reflects tonicity - allows to assess cellular hydration and to determine the type of water balance disorder. In the case of natremia disturbance, the assessment of both the tonicity and the extracellular volume allows the determination of the type of water and/or sodium balance disorder that is necessary for prescribing the adequate therapy. PMID:23177272

Petitclerc, Thierry

2012-11-21

263

Ris-R-1143(EN) Modelling Calcium Carbonate Deposition  

E-print Network

Risø-R-1143(EN) CRACK2 - Modelling Calcium Carbonate Deposition from Bicarbonate Solution in Cracks: The numerical CRACK2 model simulates precipitation of calcite from calcium bi- carbo-nate solution (e is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide dissolved in the pore

264

The role of silica fume in the kinetics and mechanisms during the early stage of cement hydration  

Microsoft Academic Search

The role of silica fume in the reaction kinetics and mechanisms of the early stage hydration of Portland-slag cement–silica fume pastes (W\\/S=0.5 at 20°C) has been studied. Using differential scanning calorimetry (DSC), the rate of calcium hydroxide (CH) formed during hydration has been determined quantitatively and the percentage of reaction of hydration has been calculated. The kinetic analysis was used

J Zeli?; D Ruši?; D Ve; R Krstulovi?

2000-01-01

265

Relative bioavailability of calcium from calcium formate, calcium citrate, and calcium carbonate  

E-print Network

of calcium from calcium formate, a new experimental dietary calcium supplement, to that of calcium citrate and calcium carbonate. In a four-way crossover study, either a placebo or 1200 mg of calcium as calcium carbonate, calcium citrate, or calcium formate...

Hanzlik, Robert P.; Fowler, S. C.; Fisher, D. H.

2005-06-01

266

NCLX: The Mitochondrial Sodium Calcium Exchanger  

PubMed Central

The free Ca2+ concentration within the mitochondrial matrix ([Ca2+]m) regulates the rate of ATP production and other [Ca2+]m sensitive processes. It is set by the balance between total Ca2+ influx (through the mitochondrial Ca2+ uniporter (MCU) and any other influx pathways) and the total Ca2+ efflux (by the mitochondrial Na+/Ca2+ exchanger and any other efflux pathways). Here we review and analyze the experimental evidence reported over the past 40 years which suggest that in the heart and many other mammalian tissues a putative Na+/Ca2+ exchanger is the major pathway for Ca2+ efflux from the mitochondrial matrix. We discuss those reports with respect to a recent discovery that the protein product of the human FLJ22233 gene mediates such Na+/Ca2+ exchange across the mitochondrial inner membrane. Among its many functional similarities to other Na+/Ca2+ exchanger proteins is a unique feature: it efficiently mediates Li+/Ca2+ exchange (as well as Na+/Ca2+ exchange) and was therefore named NCLX. The discovery of NCLX provides both the identity of a novel protein and new molecular means of studying various unresolved quantitative aspects of mitochondrial Ca2+ movement out of the matrix. Quantitative and qualitative features of NCLX are discussed as is the controversy regarding the stoichiometry of the NCLX Na+/Ca2+ exchange, the electrogenicity of NCLX, the [Na+]i dependency of NCLX and the magnitude of NCLX Ca2+ efflux. Metabolic features attributable to NCLX and the physiological implication of the Ca2+ efflux rate via NCLX during systole and diastole are also briefly discussed. PMID:23538132

Boyman, Liron; Williams, George S. B.; Khananshvili, Daniel; Sekler, Israel; Lederer, W. J.

2013-01-01

267

Class H cement hydration at 180 deg. C and high pressure in the presence of added silica  

SciTech Connect

Under deep oil-well conditions of elevated temperature and pressure, crystalline calcium silicate hydrates are formed during Portland cement hydration. The use of silica rich mineral additives leads to the formation of crystalline hydrates with better mechanical properties than those formed without the additive. The effects of silica flour, silica fume (amorphous silica), and a natural zeolite mixture on the hydration of Class H cement slurries at 180 deg. C under externally applied pressures of 7 and 52 MPa are examined in real time using in-situ synchrotron X-ray diffraction. For some compositions examined, but not all, pressure was found to have a large effect on the kinetics of crystalline hydrate formation. The use of silica fume delayed both C{sub 3}S hydration and the formation of crystalline silicate hydrates compared to what was seen with other silica sources.

Jupe, Andrew C. [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States); Wilkinson, Angus P. [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States)], E-mail: angus.wilkinson@chemistry.gatech.edu; Luke, Karen [Formerly with Halliburton, now with Trican Well Services Ltd. R and D Centre, 11979-40th Street S.E., Calgary, AB T2Z 4M3 (Canada); Funkhouser, Gary P. [Halliburton, Duncan Technology Center, 2600 South 2nd Street, Duncan, OK 73536-0470 (United States)

2008-05-15

268

Potential of gas hydrates outlined  

SciTech Connect

This paper reports on large volumes of natural gas, composed mainly of methane, which can occur in sediments as gas hydrates. These substances are solids, composed of rigid cages of water molecules that trap molecules of gas. At standard conditions (STP), 1 cu ft of methane hydrate will contain as much as 180 cu ft of methane; because of this large gas storage capacity, gas hydrates may represent an important source of natural gas. Cold surface temperatures at high latitudes are conducive to the development of onshore permafrost and gas hydrate in the subsurface. The combined information from Arctic gas hydrate studies shows that in permafrost regions gas hydrates may exist at subsurface depths ranging from about 130-2,000 m. The amount of gas sequestered in gas hydrates is probably enormous, but estimates are highly speculative. For example, worldwide estimates of the amount of gas within continental gas hydrates range from 500 trillion to 1,200,000 trillion cu ft.

Collett, T.S. (Geological Survey, Lakewood, CO (United States))

1992-06-22

269

Gas Hydrates: It's A Gas!  

NSDL National Science Digital Library

In this activity, students will investigate the occurrence of gas hydrates on the ocean floor. They will discover the importance of carbon, where carbon is stored on Earth, and that the largest reservoir of carbon is gas hydrates. Students will discover that Earth's climate changes, and how the greenhouse effect works. They will also learn about the potential of hydrates as a major new energy resource and explore the conditions under which hydrates form.

270

Ethyl-enedi-ammonium sodium tetra-kis-[bis-(ethyl-enedi-amine-?2 N,N?)(oxalato-?2 O 1,O 2)cobalt(III)] [penta-hydrogen di(phosphato-octa-deca-tungstate)] tetra-deca-hydrate  

PubMed Central

The title compound, Na(C2H10N2)[Co(C2O4)(C2H8N2)2]4[H5(P2W18O62)2]·14H2O, prepared under hydro­thermal conditions, consists of two Dawson-type [P2W18O62]6? anions, four isolated [Co(en)2(ox)]+ cations (en = ethyl­enedi­amine and ox = oxalate), one Na+ cation, one [H2en]2+ cation, and a number of ordered (14) and disordered solvent water mol­ecules. The [P2W18O62]6? polyoxidometalate anion has site symmetry 1 and contains two structurally distinct types of W atoms: viz. six W atoms on vertical pseudo-mirror planes grouped in two sets of three, and 12 equatorial W atoms that do not lie in the pseudo-mirror planes grouped in two sets of six. In each [Co(en)2(ox)]+ cation, the CoIII ion is coordinated by four N atoms from two en ligands and two O atoms from the ox ligands, completing a distorted octa­hedral structure. The sodium cation lies on an inversion centre and additionally links the complex cations and anions. In the crystal, the various units are linked by N—H?O and O—H?O hydrogen bonds, which together with C—H?O hydrogen bonds form a three-dimensional structure. The contribution of a region of disordered electron density, possibly highly disordered solvent water mol­ecules, to the scattering was removed with the SQUEEZE option of PLATON [Spek (2009 ?). Acta Cryst. D65, 148–155]. To equilibrate the charges five H+ ions have been added to the polyoxidometalate. These H+ ions and the disordered solvent contribution were not included in the reported mol­ecular weight and density. PMID:24454036

Zhang, Shuzhuo; Wang, Jing; Xu, Yun

2013-01-01

271

Hydration reactions of cement combinations containing vitrified incinerator fly ash  

SciTech Connect

One treatment option for municipal solid waste incinerator fly ash (IFA) is vitrification. The process yields a material containing reduced levels of trace metals relative to the original ash. The material is glassy and potentially suitable as a cement component in concrete. This paper examines the vitrification of an IFA and studies the hydration reactions of combinations of this vitrified material and Portland cement (PC). Isothermal conduction calorimetry, powder X-ray diffraction (XRD), thermogravimetry (TG) and scanning electron microscopy were employed to study the hydration reactions. As the levels of vitrified ash increase, the quantities of AFt phase produced decrease, whilst quantities of AFm phase increase, due to the reduced levels of sulfate in the vitrified ash. The levels of calcium silicate hydrate (CSH) gel (inferred from estimates of quantities of gel-bound water) remain constant at 28 days regardless of vitrified ash content, indicating that the material is contributing toward the formation of this product.

Dyer, Thomas D.; Dhir, Ravindra K

2004-05-01

272

Impact of admixtures on the hydration kinetics of Portland cement  

SciTech Connect

Most concrete produced today includes either chemical additions to the cement, chemical admixtures in the concrete, or both. These chemicals alter a number of properties of cementitious systems, including hydration behavior, and it has been long understood by practitioners that these systems can differ widely in response to such chemicals. In this paper the impact on hydration of several classes of chemicals is reviewed with an emphasis on the current understanding of interactions with cement chemistry. These include setting retarders, accelerators, and water reducing dispersants. The ability of the chemicals to alter the aluminate-sulfate balance of cementitious systems is discussed with a focus on the impact on silicate hydration. As a key example of this complex interaction, unusual behavior sometimes observed in systems containing high calcium fly ash is highlighted.

Cheung, J., E-mail: Josephine.H.Cheung@grace.com [W.R. Grace, 62 Whittemore Avenue, Cambridge MA 02140 (United States); Jeknavorian, A. [W.R. Grace, 62 Whittemore Avenue, Cambridge MA 02140 (United States); Roberts, L. [Roberts Consulting Group LLC, 44 Windsor Avenue, Acton MA 01720 (United States); Silva, D. [W.R. Grace, 62 Whittemore Avenue, Cambridge MA 02140 (United States)

2011-12-15

273

Initial hydration reactions and mechanisms of delayed ettringite formation in Portland cements  

Microsoft Academic Search

The aluminate hydration reactions in Portland cements were followed by X-ray diffraction. Using a computerized focusing Huber-Guinier diffractometer, the patterns were obtained from the pastes directly, without preliminary drying or grinding. It is shown that the widely accepted theories on the hydration of C3A in the presence of calcium sulfate cannot be applied generally to commercial Portland cements. Only in

H.-J. Kuzel

1996-01-01

274

Characterization of high-calcium fly ash and its influence on ettringite formation in portland cement pastes  

Microsoft Academic Search

High-calcium Class C fly ashes derived from Powder River Basin coal are currently used as supplementary cementing materials in portland cement concrete. These fly ashes tend to contain significant amounts of sulfur, calcium, and aluminum, thus they are potential sources of ettringite. Characterization of six high-calcium fly ashes originating from Powder River Basin coal have been carried out. The hydration

Jody Kathleen Tishmack

1999-01-01

275

A study on high strength concrete prepared with large volumes of low calcium fly ash  

Microsoft Academic Search

This paper presents the results of a laboratory study on high strength concrete prepared with large volumes of low calcium fly ash. The parameters studied included compressive strength, heat of hydration, chloride diffusivity, degree of hydration, and pore structures of fly ash\\/cement concrete and corresponding pastes. The experimental results showed that concrete with a 28-day compressive strength of 80 MPa

C. S. Poon; L. Lam; Y. L. Wong

2000-01-01

276

Aluminum Sulfate 18 Hydrate  

ERIC Educational Resources Information Center

A chemical laboratory information profile (CLIP) of the chemical, aluminum sulfate 18 hydrate, is presented. The profile lists physical and harmful properties, exposure limits, reactivity risks, and symptoms of major exposure for the benefit of teachers and students using the chemical in the laboratory.

Young, Jay A.

2004-01-01

277

Dalteparin sodium.  

PubMed

Dalteparin sodium (Fragmin, Pharmacia Corporation) is a low molecular weight heparin (LMWH) with a mean molecular weight of approximately 5000 Da. As with the other LMWHs, dalteparin sodium has certain advantages over unfractionated heparin (UFH), most important of which are improved bio-availability by sc. injection, a prolonged antithrombotic activity which is highly correlated with body weight permitting the o.d. administration of the drug. Dalteparin sodium has been subjected to a large number of well-designed randomised clinical trials for the prevention and treatment of thrombotic disorders. Based on data from the randomised clinical trials, dalteparin sodium has been approved internationally for a wide spectrum of clinical indications (e.g., prevention of thromboembolic events after surgery). Dalteparin sodium has also been studied in randomised controlled trials in the maintenance of graft patentcy following peripheral vascular surgery, in place of warfarin for the long-term treatment of patients presenting with deep vein thrombosis (DVT), in the prevention of upper extremity thrombosis in patients with indwelling portacath devices and in pregnant patients with a history of previous venous thromboembolism with or without thrombophilia. Dalteparin sodium has been compared with heparin for the prevention of thrombotic complications during haemodyalisis and haemofiltration. These studies have shown promising results but further work is required before dalteparin sodium can be recommended for these indications. PMID:11585001

Pineo, G F; Hull, R D

2001-08-01

278

Structure of hydrated layers on silicate electrode glasses.  

PubMed

The structural changes of the silicate framework in hydrated layers of silicate electrode glasses compared with untreated glasses as well as the quality and quantity of water and its ionic species stored in the layer have been investigated by high-resolution solid-state nuclear magnetic resonance (NMR) techniques [29Si magic-angle spinning (MAS), 29Si cross-polarization (CP) MAS, 1H high-speed MAS, 1H CRAMPS and 1H Echo NMR]. To support the results, infrared (IR) spectroscopy, thermal analysis and sodium ion concentration analyses were used. It was found that at least two different water species exist in the hydrated layer: SiOH groups and not very mobile hydrogen-bonded molecular water. Concerning the framework modified, Q3 groups [(SiO)3SiOH] were formed in the hydrated glass. During the swelling process a condensation of silanol groups formed took place to a great extent. PMID:7827973

Herzog, K; Scholz, K; Thomas, B

1994-02-01

279

Calcium orthophosphates  

PubMed Central

The present overview is intended to point the readers’ attention to the important subject of calcium orthophosphates. This type of materials is of special significance for human beings, because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with calcium orthophosphates, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenphosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of calcium orthophosphates. Similarly, dental caries and osteoporosis might be considered an in vivo dissolution of calcium orthophosphates. Thus, calcium orthophosphates hold a great significance for humankind, and in this paper, an overview on the current knowledge on this subject is provided. PMID:23507744

Dorozhkin, Sergey V.

2011-01-01

280

A thermodynamic approach to the hydration of sulphate-resisting Portland cement.  

PubMed

A thermodynamic approach is used to model changes in the hydrate assemblage and the composition of the pore solution during the hydration of calcite-free and calcite-containing sulphate-resisting Portland cement CEM I 52.5 N HTS. Modelling is based on thermodynamic data for the hydration products and calculated hydration rates for the individual clinker phases, which are used as time-dependent input parameters. Model predictions compare well with the composition of the hydrate assemblage as observed by TGA and semi-quantitative XRD and with the experimentally determined compositions of the pore solutions. The calculations show that in the presence of small amounts of calcite typically associated with Portland cement, C-S-H, portlandite, ettringite and calcium monocarbonate are the main hydration products. In the absence of calcite in the cement, however, siliceous hydrogarnet instead of calcium monocarbonate is observed to precipitate. The use of a higher water-to-cement ratio for the preparation of a calcite-containing cement paste has a minor effect on the composition of the hydrate assemblage, while it significantly changes the composition of the pore solution. In particular, lower pH value and higher Ca concentrations appear that could potentially influence the solubility and uptake of heavy metals and anions by cementitious materials. PMID:16529919

Lothenbach, Barbara; Wieland, Erich

2006-01-01

281

Sodium Phosphate  

MedlinePLUS

... at other times before, during, and after your treatment with sodium phosphate. Clear liquids are liquids that can be seen through such as water, flavored water, lemonade without pulp, apple juice, and ginger ale. Do not drink ...

282

Sodium Oxybate  

MedlinePLUS

... attacks of cataplexy (episodes of muscle weakness that begin suddenly and last for a short time) and ... go to sleep for the night. Sodium oxybate begins to work very quickly. Place your second dose ...

283

Nutrition, Hydration & Health  

NSDL National Science Digital Library

The following resource is a NFL sponsored, National Science Foundation funded program intended to teach students about scientific concepts by using the popular sport of Football. Each lesson is accompanied by an informative and fast paced video. In this lesson, athletic trainers from the Pittsburgh Steelers explain what NFL players must do to stay hydrated and replenish the essential nutrients needed to maintain good health during rigorous practices.

2010-01-01

284

Gel time of calcium acrylate grouting material.  

PubMed

Calcium acrylate is a polymerized grout, and can polymerize in an aqueous solution. The polymerization reaction utilizes ammonium persulfate as a catalyst and sodium thiosulfate as the activator. Based on the theory of reaction kinetics, this study on the relation between gel time and concentration of activator and catalyst showed that gel time of calcium acrylate is inversely proportional to activator and catalyst concentration. A formula of gel time is proposed, and an example is provided to verify the proposed formula. PMID:15236477

Han, Tong-Chun

2004-08-01

285

Late PleistoceneHolocene sedimentation surrounding an active seafloor gas-hydrate and cold-seep field on the Northern Gulf of Mexico Slope  

E-print Network

biogenic calcium and siliciclastic titanium sediment inputs, and provide a means to correlate sediments as a greenhouse gas, and the potential for destabilization of large hydrate deposits (e.g., Dickens et al., 1997; Katz et al., 1999; Kennett et al., 2000, 2003). In addition, gas- hydrate deposits and natural

Meyers, Stephen R.

286

Hydration-dependent dynamic crossover phenomenon in protein hydration water  

NASA Astrophysics Data System (ADS)

The characteristic relaxation time ? of protein hydration water exhibits a strong hydration level h dependence. The dynamic crossover is observed when h is higher than the monolayer hydration level hc=0.2-0.25 and becomes more visible as h increases. When h is lower than hc, ? only exhibits Arrhenius behavior in the measured temperature range. The activation energy of the Arrhenius behavior is insensitive to h, indicating a local-like motion. Moreover, the h dependence of the crossover temperature shows that the protein dynamic transition is not directly or solely induced by the dynamic crossover in the hydration water.

Wang, Zhe; Fratini, Emiliano; Li, Mingda; Le, Peisi; Mamontov, Eugene; Baglioni, Piero; Chen, Sow-Hsin

2014-10-01

287

Rapid gas hydrate formation process  

DOEpatents

The disclosure provides a method and apparatus for forming gas hydrates from a two-phase mixture of water and a hydrate forming gas. The two-phase mixture is created in a mixing zone which may be wholly included within the body of a spray nozzle. The two-phase mixture is subsequently sprayed into a reaction zone, where the reaction zone is under pressure and temperature conditions suitable for formation of the gas hydrate. The reaction zone pressure is less than the mixing zone pressure so that expansion of the hydrate-forming gas in the mixture provides a degree of cooling by the Joule-Thompson effect and provides more intimate mixing between the water and the hydrate-forming gas. The result of the process is the formation of gas hydrates continuously and with a greatly reduced induction time. An apparatus for conduct of the method is further provided.

Brown, Thomas D.; Taylor, Charles E.; Unione, Alfred J.

2013-01-15

288

Textural profiling and statistical optimization of crosslinked calcium-alginate-pectinate-cellulose acetophthalate gelisphere matrices.  

PubMed

A 2(5) factorial design was employed to statistically evaluate the textural properties of a crosslinked calcium-alginate-pectinate-cellulose acetophthalate gelisphere system. In accordance with the factorial matrix, gelispheres were formulated by titrating a combination polymeric solution comprised of sodium alginate, pectin and/or cellulose acetophthalate into an inducer solution (crosslinking agent) consisting of calcium and/or acetate ions. A Texture Analyzer was used to profile the gelisphere matrices for their resilience in the unhydrated and hydrated states, the fracture energy involved in matrix rupture, and the matrix hardness achieved with different levels of crosslinking. Significantly different textural properties were found among the crosslinked formulations. In particular, the unhydrated matrix resilience was selected as a parameter for optimization of the gelisphere formulation because of its large impact on drug release modulation, matrix integrity, and sensitivity to the crosslinking process. Resilience increased with increasing polymer concentration, irrespective of the polymer combination. Furthermore, resilience was not significantly influenced by the concentration of the crosslinking agents, but rather by the application of a higher polymer concentration in the crosslinking reaction; again irrespective of the polymer combination. In addition to the use of a factorial design, artificial neural modeling was employed to predict the textural properties based on the factorial matrix as a statistically suitable data source. Neural networks appeared to be a strong competitor of factorial regression for the prediction of textural data. PMID:12434399

Pillay, Viness; Danckwerts, Michael P

2002-12-01

289

A new aluminium-hydrate species in hydrated Portland cements characterized by {sup 27}Al and {sup 29}Si MAS NMR spectroscopy  

SciTech Connect

Recent {sup 27}Al MAS NMR studies of hydrated Portland cements and calcium-silicate-hydrate (C-S-H) phases have shown a resonance from Al in octahedral coordination, which cannot be assigned to the well-known aluminate species in hydrated Portland cements. This resonance, which exhibits the isotropic chemical shift {delta} {sub iso} = 5.0 ppm and the quadrupole product parameter P {sub Q} = 1.2 MHz, has been characterized in detail by {sup 27}Al MAS and {sup 27}Al{l_brace}{sup 1}H{r_brace} CP/MAS NMR for different hydrated white Portland cements and C-S-H phases. These experiments demonstrate that the resonance originates from an amorphous or disordered aluminate hydrate which contains Al(OH){sub 6} {sup 3-} or O {sub x}Al(OH){sub 6-x} {sup (3+x)-} units. The formation of the new aluminate hydrate is related to the formation of C-S-H at ambient temperatures, however, it decomposes by thermal treatment at temperatures of 70-90 {sup o}C. From the experiments in this work it is proposed that the new aluminate hydrate is either an amorphous/disordered aluminate hydroxide or a calcium aluminate hydrate, produced as a separate phase or as a nanostructured surface precipitate on the C-S-H phase. Finally, the possibilities of Al{sup 3+} for Ca{sup 2+} substitution in the principal layers and interlayers of the C-S-H structure are discussed.

Andersen, Morten Daugaard [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry, University of Aarhus, DK-8000 Aarhus C (Denmark); Jakobsen, Hans J. [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry, University of Aarhus, DK-8000 Aarhus C (Denmark); Skibsted, Jorgen [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry, University of Aarhus, DK-8000 Aarhus C (Denmark)]. E-mail: jskib@chem.au.dk

2006-01-15

290

Adsorption and heterocoagulation of nonionic surfactants and latex particles on cement hydrates.  

PubMed

The adsorption of nonionic surfactants of the alkyl-phenol-poly(ethylene oxide) family and of acrylic latex particles on several anhydrous (but hydrating) or fully hydrated mineral phases of Portland cement was studied. No or negligible adsorption of the surfactant was observed. This was assigned to the ionized character of the surface silanol groups in calcium-silicate-hydrates and to the strongly ionic character of the OH groups in calcium hydroxide and in the calcium-sulfoaluminate-hydrates, which prevents the formation of surface-ethoxy hydrogen bonds. In contrast, provided they are properly stabilized by the surfactant, the latex particles form a loose monolayer on the surface of hydrating tricalcium silicate particles. The attractive interaction between the positive mineral surface and the negative latex surface appears to be the driving force for adsorption. In line with this, adsorption is reduced by sulfate anions, which adsorb specifically onto the silicate surface. Compared to tricalcium silicate, portlandite and gypsum interact only marginally with the latex particles. Our results show that the stability of the nonionic surfactant/latex/cement systems is essentially controlled by the latex colloidal stability and the latex-cement interactions, the surfactant having little direct interaction, if any, with the mineral surfaces. PMID:15567373

Merlin, Fabrice; Guitouni, Hicham; Mouhoubi, Hayette; Mariot, Sandrine; Vallée, Franck; Van Damme, Henri

2005-01-01

291

Project Calcium  

SciTech Connect

Fouling problems in utility boilers have been classified into two principal types: high-temperature and low-temperature fouling. A multiclient-sponsored program was initiated at the Energy and Environmental Research Center (EERC) to better understand the causes of low-temperature fouling when burning high-calcium western US coals. The goals of Project Calcium were to define the low-temperature deposition problem, identify the calcium-based components that are responsible for the formation of the deposits, develop ways to predict their formation, and identify possible methods to mitigate the formation of these deposits. To achieve the goals of Project Calcium, detailed sampling of utility boilers and laboratory-scale studies coupled with state-of-the-art methods to determine the inorganic components in coals and coal ash-derived materials were conducted. Boiler Sampling was also performed. The work involved sampling coal, entrained ash, deposits and slags from five full-scale utility boilers combined with detailed advanced characterization of the materials. The results of this work aided in identifying the key phenomena to focus the laboratory studies and in model verification. Field testing was conducted at three utilities.

Hurley, J.P.; Benson, S.A.; Erickson, T.A.; Allan, S.E.; Bieber, J.

1992-09-01

292

Rosuvastatin calcium  

Microsoft Academic Search

Rosuvastatin calcium (Crestor; AstraZeneca), the seventh drug in the statin class, was approved by the US FDA in August 2003 for the reduction of cholesterol levels in patients with hypercholesterolaemia. Billed as the most potent statin available, can it overcome initial setbacks and make a significant impact in the multi-billion-dollar market for cholesterol-lowering drugs?

Mark Thornton; Peter Kirkpatrick; Jeremy Quirk

2003-01-01

293

The influence of magnetic fields on calcium carbonate precipitation  

Microsoft Academic Search

Laboratory experiments were undertaken to assess the effects of magnetic treatment on calcium carbonate precipitate. Static test solutions of calcium chloride, calcium sulphate and sodium carbonate were placed in a magnetic field. After magnetic treatment the solutions CaCl2\\/Na2CO3 and CaSO4\\/Na2CO3 were mixed and changes in precipitation recorded and compared with non-magnetised solutions. The results of this study support earlier work

Rebecca A Barrett; Simon A Parsons

1998-01-01

294

Evolution of Iron speciation during hydration of C4AF. , A. Bnard2,3  

E-print Network

phases are good candidates for metal retention in real cement, the role of the calcium-ferric aluminate showed a strong affinity for the hydration products of C4AF. The C4AF content in Portland cement is 2- 7 proportion of the trace metals in an actual cement will be associated with Fe phases. However, the metal

Paris-Sud XI, Université de

295

Atomic Transition Probabilities of Sodium and Magnesium. A Critical Compilation  

E-print Network

Atomic Transition Probabilities of Sodium and Magnesium. A Critical Compilation D. E. Kellehera Transition Probabilities, Vol. II: Sodium through Calcium, NSRDS-NBS Vol. 2 U.S. GPO, Washington, D.C., 1969 . Atomic transition probabilities have been critically evaluated and compiled for about 11 400 spectral

Magee, Joseph W.

296

Preparation and evaluation of sodium diclofenac controlled-release tablets  

Microsoft Academic Search

The dissolution behaviour of a direct compression compact prepared with sodium diclofenac and dibasic calcium phosphate (DCP) in different weight ratios with or without Biosoluble polymer® (acrylic-based resin) was investigated in distilled water and in a medium with changing pH. The results indicate that the amount of sodium diclofenac released from the compact was dependent on the amount of drug

Shan-Yang Lin; Ching-Li Cheng; Pei-Chin Lin

1995-01-01

297

A combined QXRD/TG method to quantify the phase composition of hydrated Portland cements  

SciTech Connect

A new method is reported for quantifying the mineral phases in hydrated cement pastes that is based on a combination of quantitative X-ray diffractometry (QXRD) and thermogravimetry (TG). It differs from previous methods in that it gives a precise measure of the amorphous phase content without relying on an assumed stoichiometric relationship between the principal hydration products, calcium hydroxide (CH) and calcium silicate hydrate (C–S–H). The method was successfully applied to gray and white ordinary Portland cements (GOPC and WOPC, respectively) that were cured for up to 56 days. Phase distributions determined by QXRD/TG closely matched those from gray-level analysis of backscattered scanning electron microscope (BSEM) images, whereas elemental compositions obtained for the amorphous phase by QXRD/TG agreed well with those measured by quantitative energy dispersive X-ray spectroscopy (EDS)

Soin, Alexander V.; Catalan, Lionel J.J. [Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1 (Canada)] [Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1 (Canada); Kinrade, Stephen D., E-mail: stephen.kinrade@lakeheadu.ca [Department of Chemistry, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1 (Canada)

2013-06-15

298

Formation of submarine gas hydrates  

Microsoft Academic Search

and bottom sampling in many offshore regions. This paper reports on expeditions carried out in the Black, Caspian and Okhotsk Seas. Gas hydrate accumulations were discovered and investigated in all these areas. The data and an analysis of the results of the deep-sea drilling programme suggest that the infiltration of gas-bearing fluids is a necessary condition for gas hydrate accumulation.

V. SOLOVIEV; G. D. GINSBURG

299

Ductile flow of methane hydrate  

USGS Publications Warehouse

Compressional creep tests (i.e., constant applied stress) conducted on pure, polycrystalline methane hydrate over the temperature range 260-287 K and confining pressures of 50-100 MPa show this material to be extraordinarily strong compared to other icy compounds. The contrast with hexagonal water ice, sometimes used as a proxy for gas hydrate properties, is impressive: over the thermal range where both are solid, methane hydrate is as much as 40 times stronger than ice at a given strain rate. The specific mechanical response of naturally occurring methane hydrate in sediments to environmental changes is expected to be dependent on the distribution of the hydrate phase within the formation - whether arranged structurally between and (or) cementing sediments grains versus passively in pore space within a sediment framework. If hydrate is in the former mode, the very high strength of methane hydrate implies a significantly greater strain-energy release upon decomposition and subsequent failure of hydrate-cemented formations than previously expected.

Durham, W.B.; Stern, L.A.; Kirby, S.H.

2003-01-01

300

Effect of Calcium Content on Soil Stabilisation with Alkaline Activation  

Microsoft Academic Search

This paper in concerned with the role of calcium content in fly ash used to stabilise soft soils through alkaline activation with sodium-based alkaline activators. A 10 molal sodium hydroxide solution was used to activate fly ash at solution: ash ratios of 2: 1 and 4: 1, and at a solution: (soil + ash) ratio of 0.40. Fly ash type

Nuno Cristelo; Stephanie Glendinning; Lisete Fernandes; Amândio Teixeira Pinto

301

Hydration and physical performance.  

PubMed

There is a rich scientific literature regarding hydration status and physical function that began in the late 1800s, although the relationship was likely apparent centuries before that. A decrease in body water from normal levels (often referred to as dehydration or hypohydration) provokes changes in cardiovascular, thermoregulatory, metabolic, and central nervous function that become increasingly greater as dehydration worsens. Similarly, performance impairment often reported with modest dehydration (e.g., -2% body mass) is also exacerbated by greater fluid loss. Dehydration during physical activity in the heat provokes greater performance decrements than similar activity in cooler conditions, a difference thought to be due, at least in part, to greater cardiovascular and thermoregulatory strain associated with heat exposure. There is little doubt that performance during prolonged, continuous exercise in the heat is impaired by levels of dehydration >or= -2% body mass, and there is some evidence that lower levels of dehydration can also impair performance even during relatively short-duration, intermittent exercise. Although additional research is needed to more fully understand low-level dehydration's effects on physical performance, one can generalize that when performance is at stake, it is better to be well-hydrated than dehydrated. This generalization holds true in the occupational, military, and sports settings. PMID:17921463

Murray, Bob

2007-10-01

302

Development of tungsten oxide hydrate phases during precipitation, room temperature ripening and hydrothermal treatment  

Microsoft Academic Search

Morphology and structure transformation of tungstic acid hydrate, H2WO4·nH2O precipitates, have been studied in aqueous phase with various levels of residual [Na+]s at room temperature and at 120 °C in autoclave. Spindle-shaped morphology is characteristic for the washing product of the freshly prepared precipitates. Residual sodium is a persistent contaminant in H2WO4·H2O. Sodium ion content in the solid phase has

Csaba Balázsi; Judit Pfeifer

2002-01-01

303

Sulfate resistance of high calcium fly ash concrete  

NASA Astrophysics Data System (ADS)

Sulfate attack is one of the mechanisms which can cause deterioration of concrete. In general, Class C fly ash mixtures are reported to provide poor sulfate resistance. Fly ashes, mainly those belonging to the Class C, were tested as per the ASTM C 1012 procedure to evaluate chemical sulfate resistance. Overall the Class C fly ashes showed poor resistance in the sulfate environment. Different strategies were used in this research work to improve the sulfate resistance of Class C fly ash mixes. The study revealed that some of the strategies such as use of low W/CM (water to cementing materials by mass ratio), silica fume or ultra fine fly ash, high volumes of fly ash and, ternary or quaternary mixes with suitable supplementary cementing materials, can successfully improve the sulfate resistance of the Class C fly ash mixes. Combined sulfate attack, involving physical and chemical action, was studied using sodium sulfate and calcium sulfate solutions. The specimens were subjected to wetting-drying cycles and temperature changes. These conditions were found to accelerate the rate of degradation of concrete placed in a sodium sulfate environment. W/CM was found to be the main governing factor in providing sulfate resistance to mixes. Calcium sulfate did not reveal damage as a result of mainly physical action. Characterization of the selected fly ashes was undertaken by using SEM, XRD and the Rietveld analysis techniques, to determine the relation between the composition of fly ashes and resistance to sulfate attack. The chemical composition of glass represented on the ternary diagram was the main factor which had a significant influence on the sulfate resistance of fly ash mixtures. Mixes prepared with fly ashes containing significant amounts of vulnerable crystalline phases offered poor sulfate resistance. Comparatively, fly ash mixes containing inert crystalline phases such as quartz, mullite and hematite offered good sulfate resistance. The analysis of hydrated lime-fly ash pastes confirmed that fly ash mortar or concrete mixes forming more monosulfate than ettringite before exposure to sulfates would offer poor sulfate resistance and vice versa. During quantitative Rietveld analysis carried out for determining ettringite, monosulfate and gypsum formed in the fly ash pastes, it was observed that fly ash mixtures showing more ettringite after exposures to sulfates, give poor sulfate resistance. A good relationship between the amounts of ettringite formed and expansions of mortar specimens in the ASTM C 1012 test was found.

Dhole, Rajaram

304

Study of the relation between hydrated Portland cement composition and leaching resistance  

SciTech Connect

The present paper addresses cement compositions that have an optimal resistance against acid attack and hence, low leaching rates and optimal waste containment. To this end a shrinking core leaching model is used that describes the leaching of metals from a cement sample. This process is directly related to the calcium hydroxide removal from the sample by the acidified leachant. Effective diffusion coefficients in this so-called leached shell were calculated using the equations derived from a cement hydration model. This results in equations in which leaching rates were dependent on cement composition, especially the calcium hydroxide fraction. Optimizing the calcium hydroxide fraction yields cement compositions possessing the optimal leaching resistance as a function of the water porosity or as a function of the hydration degree and water to cement ratio used. The results were also used for the determination of optimal amounts of silica fume and fly ash. A comparison with experimental and practical data reported in literature yields good agreement.

Eijk, R.J. van; Brouwers, H.J.H. [Univ. of Twente, Enschede (Netherlands). Dept. of Civil Engineering and Management] [Univ. of Twente, Enschede (Netherlands). Dept. of Civil Engineering and Management

1998-06-01

305

Water, Hydration and Health  

PubMed Central

This review attempts to provide some sense of our current knowledge of water including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, the effects of variation in water intake on health and energy intake, weight, and human performance and functioning. Water represents a critical nutrient whose absence will be lethal within days. Water’s importance for prevention of nutrition-related noncommunicable diseases has emerged more recently because of the shift toward large proportions of fluids coming from caloric beverages. Nevertheless, there are major gaps in knowledge related to measurement of total fluid intake, hydration status at the population level, and few longer-term systematic interventions and no published random-controlled longer-term trials. We suggest some ways to examine water requirements as a means to encouraging more dialogue on this important topic. PMID:20646222

Popkin, Barry M.; D'Anci, Kristen E.; Rosenberg, Irwin H.

2010-01-01

306

Gas hydrate on the continental margin  

Microsoft Academic Search

Because the stability of gas hydrate is constrained mainly by the temperature and pressure condition, gas hydrate on the continental margins had dissociated in response to the global climate changes during the earth's history. Marine gas hydrate hosts isotopically light carbon as gas (mostly methane) and heavy oxygen as water, dissociation of gas hydrate liberates these isotopes into the environment,

Hitoshi Tomaru

307

Effective kinetic inhibitors for natural gas hydrates  

Microsoft Academic Search

Kinetic inhibition is a new means of preventing flow channel blockage by natural gas hydrates. In kinetic inhibition the system is allowed to exist within the hydrate thermodynamic stability zone, so that small crystals are stabilized without agglomerating to larger hydrate masses which plug pipelines. A hydrate formation mechanism is reviewed to suggest the new inhibition method. Macroscopic experiments on

J. P. Lederhos; J. P. Long; A. Sum; R. L. Christiansen; E. D. Sloan

1996-01-01

308

Induction time in crystallization of gas hydrates  

Microsoft Academic Search

The kinetics of the initial stage of crystallization of one-component gas hydrates in aqueous solutions are analyzed. The temporal evolution of the volume of hydrate crystallized and the moles of gas consumed are determined. Expressions are derived for the supersaturation dependence of the hydrate crystallite growth rate and the induction time in hydrate crystallization. These expressions are used for revealing

Dimo Kashchiev; Abbas Firoozabadi

2003-01-01

309

Natural gas hydrates: problem or opportunity  

Microsoft Academic Search

Natural gas hydrates, once viewed solely as a nuisance by the gas processing industry, are rapidly gaining favorable status as an unconventional natural gas resource. Hydrates are solids which form when gas is contacted with water, both above and below 273 Kelvin. Conditions are favorable for hydrate formation in permafrost regions and in many oceans. Natural gas hydrates are solid

1981-01-01

310

Gas Hydrates: It's a Gas  

NSDL National Science Digital Library

In this activity, students will discover the importance of carbon, where carbon is stored on Earth, and that the largest reservoir of carbon is in the form of gas hydrates where methane and other hydrocarbon gases are trapped in a lattice of water molecules in deep sea sediments. Students will learn how climate change is related to the greenhouse effect. They will also learn about the potential of hydrates as a major new energy resource, and explore the conditions under which hydrates form. In addition, students will understand the use of acoustics for mapping the sea floor and sub-sea floor.

311

Calcium and osteoporosis  

Microsoft Academic Search

Calcium is an essential nutrient that is involved in most metabolic processes and the phosphate salts of which provide mechanical rigidity to the bones and teeth, where 99% of the body's calcium resides. The calcium in the skeleton has the additional role of acting as a reserve supply of calcium to meet the body's metabolic needs in states of calcium

B. E. Christopher Nordin

1997-01-01

312

Novel hydrated brittle mica: Synthesis, characterization and cation exchange selectivity  

NASA Astrophysics Data System (ADS)

Na-4-mica, a novel hydrated brittle mica with theoretical chemical formula of Nasb4Sisb4Alsb4Mgsb6Osb2OFsb4. XHsb2O, with a layer charge of -4 per unit cell, and with an unusually high number (four) of interlayer sodium ions was synthesized from metakaolinite + MgO and magnesium aluminosilicate gel powder at different temperatures and durations in a sodium fluoride melt. Highly crystalline and phase pure Na-4-mica with uniform charge distribution and particle size ranging from 2-5 mum could be economically synthesized from metakaolinite route at 890sp°C with reaction times varying from 6-24 hours. Almost all the aluminum was present in the tetrahedral sheets leading to a very high layer charge. Unlike the naturally occurring micas, this mica can undergo hydration readily under ambient conditions. Due to the presence of unusually high number (4) of interlayer cations the adjacent layers undergo displacement such that each hexagonal ring acts as an individual cavity enclosing the sodium ion. This interlayer arrangement leads to hydration of the sodium ions upon exposure to air. Sodium ions once hydrated can be readily exchanged with the surrounding ions. The selective cation exchange behavior of this material was evaluated by carrying out a series of experiments. Selective strontium exchange kinetics showed the uptake was slow because of a restricted interlayer spacing as well as somewhat large particle size. Ion exchange isotherms for Cusp{2+},\\ Znsp{2+},\\ Cosp{2+},\\ and\\ Nisp{2+} were obtained and the standard free energy change for the ion exchange equilibria calculated. The selectivity sequence of the above transition metal ions on Na-4-mica was found to be as follows: Cusp{2+}>Znsp{2+}>Cosp{2+}>Nisp{2+}. These selectivity studies suggest that Na-4-mica can have several commercial applications. It can be used in the selective removal of radioactive strontium and divalent heavy metal ions from nuclear waste solutions, and industrial effluents and can also participate in the recovery of metals by their selective uptake from mixed cationic solutions. It can also be used as a barrier to prevent migration of hazardous ions into drinking water.

Pidugu, Rajyalakshmi

313

Calcium Collage  

NSDL National Science Digital Library

In this activity (on pages 11-14 of PDF), learners cut out pictures from magazines of foods that help make bones strong and glue the pictures to a paper bone. The lesson plan includes information about various activities - including physical exercise as well as diet - that lead to healthy bones. It also includes a list of foods that provide calcium to strengthen bones, including dairy products, spinach, and tofu. The paper bones can be cut out of construction paper prior to the activity.

Omsi

2004-01-01

314

Kinetic hydrate inhibitor provides treatment alternative  

SciTech Connect

An inherent problem with natural gas production or transmission is the formation of gas hydrates. Historically, methanol has been injected into the gas stream to combat hydrate formation. Unichem, a division of B.J. Services Co., has developed a hydrate inhibitor that is a safe, effective, competitively priced alternative method of preventing hydrate formation. The paper briefly describes hydrate formation, the alternative inhibitor, and a successful trial.

NONE

1996-12-01

315

Herbal extracts of Tribulus terrestris and Bergenia ligulata inhibit growth of calcium oxalate monohydrate crystals in vitro  

NASA Astrophysics Data System (ADS)

A large number of people in this world are suffering from urinary stone problem. Calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) containing stones (calculi) are commonly found. In the present study, COM crystals were grown by a double diffusion gel growth technique using U-tubes. The gel was prepared from hydrated sodium metasilicate solution. The gel framework acts like a three-dimensional crucible in which the crystal nuclei are delicately held in the position of their formation, and nutrients are supplied for the growth. This technique can be utilized as a simplified screening static model to study the growth, inhibition and dissolution of urinary stones in vitro. The action of putative litholytic medicinal plants, Tribulus terrestris Linn. ( T.t) and Bergenia ligulata Linn. ( B.l.), has been studied in the growth of COM crystals. Tribulus terrestris and Bergenia ligulata are commonly used as herbal medicines for urinary calculi in India. To verify the inhibitive effect, aqueous extracts of Tribulus terrestris and Bergenia ligulata were added along with the supernatant solutions. The growth was measured and compared, with and without the aqueous extracts. Inhibition of COM crystal growth was observed in the herbal extracts. Maximum inhibition was observed in Bergenia ligulata followed by Tribulus terrestris. The results are discussed.

Joshi, V. S.; Parekh, B. B.; Joshi, M. J.; Vaidya, A. B.

2005-02-01

316

Calcium source (image)  

MedlinePLUS

... kidney stones, for avoiding calcium-rich food sources. Calcium deficiency also effects the heart and circulatory system, as well as the secretion of essential hormones. There are many ways to supplement calcium, including a growing number of fortified foods.

317

Ion Permeation, Divalent Ion Block, and Chemical Modification of Single Sodium Channels Description by Single and Double-occupancy Rate-Theory Models  

Microsoft Academic Search

Calcium ions, applied internally, externally, or symmetrically, have been used in conjunction with rate-theory modeling to explore the energy profile of the ion-conducting pore of sodium channels. The block, by extracellular and\\/or intracellular calcium, of sodium ion conduction through single, batrachotoxin- activated sodium channels from rat brain was studied in planar lipid bilayers. Extracellular calcium caused a reduction of inward

ROBERT J. FRENCH; JENNINGS F. WORLEY; WILLIAM F. WONDERLIN; A. SHAVANTHA KULARATNA; BRUCE K. KRUEGER

318

Hydrate control in deepwater drilling  

SciTech Connect

Gas-hydrate formation during deepwater offshore drilling and production is a well-recognized operational hazard. In water depths greater than 1,000 ft, seabed conditions of pressure and temperature become conducive to gas-hydrate formation. In a well-control situation, although the kick fluid leaves the formation at a high temperature, it can cool to seabed temperature with an extended shut-in period. With high enough hydrostatic pressure at the mudline, hydrates could form in the blowout-preventer (BOP) stack and choke and kill lines, as has been observed in field operations. The current practice in deepwater drilling is to suppress the hydrate-formation temperature by use of highly saline drilling fluids formulated from NaCl or other salts. This solution is applicable for the Gulf of Mexico but insufficient for the conditions encountered in Norwegian deep waters. At extreme water depths or extremely low mudline temperatures, this thermodynamic inhibition alone may not be sufficient to prevent hydrate formation. Instead, the use of kinetic inhibitors or crystal modifiers, in conjunction with thermodynamic inhibitors, may allow successful operations in such an environment. The definition of kinetic inhibitors (to distinguish them from the classic thermodynamic inhibitors, such as polar compounds and electrolytes) comes from the effect of the chemicals on the nucleation and growth of natural gas hydrates, both of which are time-dependent, stochastic processes. The paper describes deepwater drilling fluids, polar and surface-active additives, kinetic inhibition and crystal modifiers, laboratory measurements, and test results.

NONE

1997-09-01

319

A Sodium-Pump-Mediated Afterhyperpolarization in Pyramidal Neurons  

PubMed Central

The sodium-potassium ATPase (i.e., the “sodium pump”) plays a central role in maintaining ionic homeostasis in all cells. Although the sodium pump is intrinsically electrogenic and responsive to dynamic changes in intracellular sodium concentration, its role in regulating neuronal excitability remains unclear. Here we describe a physiological role for the sodium pump in regulating the excitability of mouse neocortical layer 5 and hippocampal CA1 pyramidal neurons. Trains of action potentials produced long-lasting (?20 s) afterhyperpolarizations (AHPs) that were insensitive to blockade of voltage-gated calcium channels or chelation of intracellular calcium, but were blocked by tetrodotoxin, ouabain, or the removal of extracellular potassium. Correspondingly, the AHP time course was similar to the decay of activity-induced increases in intracellular sodium, whereas intracellular calcium decayed at much faster rates. To determine whether physiological patterns of activity engage the sodium pump, we replayed in vitro a place-specific burst of 15 action potentials recorded originally in vivo in a CA1 “place cell” as the animal traversed the associated place field. In both layer 5 and CA1 pyramidal neurons, this “place cell train” generated small, long-lasting AHPs capable of reducing neuronal excitability for many seconds. Place-cell-train-induced AHPs were blocked by ouabain or removal of extracellular potassium, but not by intracellular calcium chelation. Finally, we found calcium contributions to the AHP to be temperature dependent: prominent at room temperature, but largely absent at 35°C. Our results demonstrate a previously unappreciated role for the sodium-potassium ATPase in regulating the excitability of neocortical and hippocampal pyramidal neurons. PMID:23926257

Dasari, Sameera; Onoue, Keita; Stephens, Emily K.; Hasse, J. Michael; Avesar, Daniel

2013-01-01

320

A sodium-pump-mediated afterhyperpolarization in pyramidal neurons.  

PubMed

The sodium-potassium ATPase (i.e., the "sodium pump") plays a central role in maintaining ionic homeostasis in all cells. Although the sodium pump is intrinsically electrogenic and responsive to dynamic changes in intracellular sodium concentration, its role in regulating neuronal excitability remains unclear. Here we describe a physiological role for the sodium pump in regulating the excitability of mouse neocortical layer 5 and hippocampal CA1 pyramidal neurons. Trains of action potentials produced long-lasting (?20 s) afterhyperpolarizations (AHPs) that were insensitive to blockade of voltage-gated calcium channels or chelation of intracellular calcium, but were blocked by tetrodotoxin, ouabain, or the removal of extracellular potassium. Correspondingly, the AHP time course was similar to the decay of activity-induced increases in intracellular sodium, whereas intracellular calcium decayed at much faster rates. To determine whether physiological patterns of activity engage the sodium pump, we replayed in vitro a place-specific burst of 15 action potentials recorded originally in vivo in a CA1 "place cell" as the animal traversed the associated place field. In both layer 5 and CA1 pyramidal neurons, this "place cell train" generated small, long-lasting AHPs capable of reducing neuronal excitability for many seconds. Place-cell-train-induced AHPs were blocked by ouabain or removal of extracellular potassium, but not by intracellular calcium chelation. Finally, we found calcium contributions to the AHP to be temperature dependent: prominent at room temperature, but largely absent at 35°C. Our results demonstrate a previously unappreciated role for the sodium-potassium ATPase in regulating the excitability of neocortical and hippocampal pyramidal neurons. PMID:23926257

Gulledge, Allan T; Dasari, Sameera; Onoue, Keita; Stephens, Emily K; Hasse, J Michael; Avesar, Daniel

2013-08-01

321

Induction time in crystallization of gas hydrates  

NASA Astrophysics Data System (ADS)

The kinetics of the initial stage of crystallization of one-component gas hydrates in aqueous solutions are analyzed. The temporal evolution of the volume of hydrate crystallized and the moles of gas consumed are determined. Expressions are derived for the supersaturation dependence of the hydrate crystallite growth rate and the induction time in hydrate crystallization. These expressions are used for revealing how additives in the solution that act as kinetic inhibitors of hydrate crystallization can affect the induction time of the process. The results obtained are applied to crystallization of methane, ethane and cyclopropane hydrates.

Kashchiev, Dimo; Firoozabadi, Abbas

2003-04-01

322

Sodium content (image)  

MedlinePLUS

... contribute to high blood pressure. When watching the intake of sodium, read labels carefully to determine the total sodium content. Canned, packaged, and frozen foods can be particularly high in sodium.

323

Calcium and aluminium-based fillers as flame-retardant additives in silicone matrices. I. Blend preparation and thermal properties  

Microsoft Academic Search

This series investigates silicone composites with enhanced thermal behaviour for cable applications. Calcium and aluminium-based fillers introduced into silicone formulations were classified according to three categories: non-hydrated fillers such as CaCO3 (precipitated calcium carbonate and natural calcite) and wollastonite, water-releasing fillers such as calcium hydroxide, ATH, boehmite, and hydroxyl-functionalized fillers including alumina and mica. The fillers were first characterized in

Siska Hamdani; Claire Longuet; José-Marie Lopez-Cuesta; François Ganachaud

2010-01-01

324

Ground-Based Detection of Exoatmospheric Calcium  

NASA Astrophysics Data System (ADS)

Data acquired with HDS@Subaru for HD209458b is re-analyzed. A new pipeline performs an automated search for the exoatmospheric presence of several elements without any a-priori assumptions on its existence or strength. We analyzed thousands of lines in the full spectral range of this optical echelle spectrograph using a robust method to correct for the telluric contamination. We recover previous detections of Sodium and Halpha, and present the first strong detection of Calcium in an Extrasolar Atmosphere as well as the tentative detection of other elements. The Calcium detection is in disagreement with theoretical thermal-equilibrium models.

Rojo, Patricio M.; Astudillo-Defru, Nicola

2014-11-01

325

A realistic molecular model of cement hydrates  

PubMed Central

Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially unexplored. Together these characteristics of C-S-H define and modulate the physical and mechanical properties of this “liquid stone” gel phase. With the recent determination of the calcium/silicon (C/S = 1.7) ratio and the density of the C-S-H particle (2.6 g/cm3) by neutron scattering measurements, there is new urgency to the challenge of explaining these essential properties. Here we propose a molecular model of C-S-H based on a bottom-up atomistic simulation approach that considers only the chemical specificity of the system as the overriding constraint. By allowing for short silica chains distributed as monomers, dimers, and pentamers, this C-S-H archetype of a molecular description of interacting CaO, SiO2, and H2O units provides not only realistic values of the C/S ratio and the density computed by grand canonical Monte Carlo simulation of water adsorption at 300 K. The model, with a chemical composition of (CaO)1.65(SiO2)(H2O)1.75, also predicts other essential structural features and fundamental physical properties amenable to experimental validation, which suggest that the C-S-H gel structure includes both glass-like short-range order and crystalline features of the mineral tobermorite. Additionally, we probe the mechanical stiffness, strength, and hydrolytic shear response of our molecular model, as compared to experimentally measured properties of C-S-H. The latter results illustrate the prospect of treating cement on equal footing with metals and ceramics in the current application of mechanism-based models and multiscale simulations to study inelastic deformation and cracking. PMID:19805265

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

2009-01-01

326

Sodium nitroprusside suppresses male fertility in vitro.  

PubMed

Sodium nitroprusside is a nitric oxide donor involved in the regulation of the motility, hyperactivation, capacitation, and acrosome reaction (AR) of spermatozoa. However, the molecular mechanism underlying this regulation has not yet been elucidated. Therefore, this study was designed to evaluate the molecular basis for the effects of sodium nitroprusside on different processes in spermatozoa and its consequences on subsequent oocyte fertilization and embryo development. In this in vitro study, mouse spermatozoa were incubated with various concentrations of sodium nitroprusside (1, 10, and 100 ?m) for 90 min. Our results showed that sodium nitroprusside inhibited sperm motility and motion kinematics in a dose-dependent manner by significantly enhancing intracellular iron and reactive oxygen species (ROS), and decreasing Ca(2+) , and adenosine triphosphate levels in spermatozoa. Moreover, short-term exposure of spermatozoa to sodium nitroprusside increased the tyrosine phosphorylation of sperm proteins involved in PKA-dependent regulation of intracellular calcium levels, which induced a robust AR. Finally, sodium nitroprusside significantly decreased the rates of fertilization and blastocyst formation during embryo development. Based on these results, we propose that sodium nitroprusside increases ROS production and precocious AR may alter overall sperm physiology, leading to poor fertilization and compromised embryonic development. PMID:25180787

Rahman, M S; Kwon, W-S; Lee, J-S; Kim, J; Yoon, S-J; Park, Y-J; You, Y-A; Hwang, S; Pang, M-G

2014-11-01

327

Hydrophobic hydration of amphipathic peptides.  

PubMed Central

Biomolecular surfaces and interfaces are commonly found with apolar character. The hydrophobic effect thus plays a crucial role in processes involving association with biomolecular surfaces in the cellular environment. By computer simulation, we compared the hydrogen bonding structures and energetics of the proximal hydration shells of the monomer and dimer from a recent study of an extrinsic membrane peptide, melittin. The two peptides were studied in their amphipathic alpha-helical forms, which possess extended hydrophobic surfaces characterized by different topography. The topography of the peptide-water interface was found to be critical in determining the enthalpic nature of hydrophobic hydration. This topographical dependence has far-reaching implications in the regulation of bioactivities in the presence of amphipathicity. This result also engenders reconsideration of the validity of using free energy parameters that depend solely on the chemical nature of constituent moieties in characterizing hydrophobic hydration of proteins and biomolecules in general. PMID:10096874

Cheng, Y K; Sheu, W S; Rossky, P J

1999-01-01

328

Gas Hydrate and Pore Pressure  

NASA Astrophysics Data System (ADS)

Many efforts have been devoted to quantify excess pore pressures related to gas hydrate dissociation in marine sediments below the BSR using several approaches. Dissociation of gas hydrates in proximity of the BSR, in response to a change in the physical environment (i.e., temperature and/or pressure regime), can liberate excess gas incrising the local pore fluid pressure in the sediment, so decreasing the effective normal stress. So, gas hydrate dissociation may lead to excess pore pressure resulting in sediment deformation or failure, such as submarine landslides, sediment slumping, pockmarks and mud volcanoes, soft-sediment deformation and giant hummocks. Moreover, excess pore pressure may be the result of gas hydrate dissociation due to continuous sedimentation, tectonic uplift, sea level fall, heating or inhibitor injection. In order to detect the presence of the overpressure below the BSR, we propose two approachs. The fist approach models the BSR depth versus pore pressure; in fact, if the free gas below the BSR is in overpressure condition, the base of the gas hydrate stability is deeper with respect to the hydrostatic case. This effect causes a discrepancy between seismic and theoretical BSR depths. The second approach models the velocities versus gas hydrate and free gas concentrations and pore pressure, considering the approximation of the Biot theory in case of low frequency, i.e. seismic frequency. Knowing the P and S seismic velocity from seismic data analysis, it is possibile to jointly estimate the gas hydrate and free gas concentrations and the pore pressure regime. Alternatively, if the S-wave velocity is not availbale (due to lack of OBS/OBC data), an AVO analysis can be performed in order to extract information about Poisson ratio. Our modeling suggests that the areas characterized by shallow waters (i.e., areas in which human infrastructures, such as pipelines, are present) are significantly affected by the presence of overpressure condition. Moreover, the knoweledge of seismic velocities can be considered an powerful tool to detect the overpressure in case that the pore pressure is equal to the hydrostatic pressure plus the 50% of the difference between the lithostatic and the hydrostatic pressure. In conclusions, an accurate analysis of the BSR nature and the pore pressure are required to improve the reliability of the gas-phase estimation for different target, such as gas hydrate and free gas exploitations and environmental studies.

Tinivella, Umberta; Giustiniani, Michela

2014-05-01

329

Electron microscopy of frozen hydrated biological specimens  

Microsoft Academic Search

The use of frozen hydrated specimens for molecular structure determination is limited primarily by radiation damage. The radiation damage effect in frozen hydrated catalase crystals has been measured in terms of the loss of electron diffraction. The results show an improvement for this type of specimen relative to wet hydrated or glucose embedded catalase crystals at room temperature. Bright field

K. A. Taylor; R. M. Glaeser

1976-01-01

330

Multipole Electrostatics in Hydration Free Energy Calculations  

E-print Network

Multipole Electrostatics in Hydration Free Energy Calculations YUE SHI,1 CHUANJIE WU,2 JAY W and biochemical processes. The ability to accu- rately calculate the hydration free energy (HFE) is critical: Hydration free energy (HFE) is generally used for evaluating molecular solubility, which is an important

Ponder, Jay

331

Mechanisms of gas hydrate formation and inhibition  

Microsoft Academic Search

The formation of gas hydrates in gas and oil subsea pipelines often results in blockage and shutdown of these pipelines. Modern control methods depend on understanding the mechanisms through which gas hydrates form. This paper reviews our recent studies of clathrate hydrate formation and inhibition mechanisms using neutron diffraction, differential scanning calorimetry (DSC) and a multiple cell photo-sensing instrument. The

C. A. Koh; R. E. Westacott; W. Zhang; K. Hirachand; J. L. Creek; A. K. Soper

2002-01-01

332

Inhibition of Gas Hydrates in Deepwater Drilling  

Microsoft Academic Search

With the movement of offshore rigs into deep water, the problem of gas hydrates has become an important issue in drilling. If a kick is taken, gas hydrates can form in the blowout preventer (BOP) or chokelines while the kick is circulated out. The water-based pill presented here significantly improves gas-hydrate inhibition. This pill, which can be spotted in the

Arthur Hale; Ashok Dewan

1990-01-01

333

A new high performance gas hydrate inhibitor  

Microsoft Academic Search

In petroleum exploration and production operations, gas hydrates pose serious flow assurance, economic and safety concerns. Thermodynamic inhibitors are widely used to reduce the risks associated with gas hydrate formation. In the present study, systematic laboratory work was undertaken to determine synergistic effects between methanol and a Poly Vinyl Methyl Ether as Low Dosage Hydrate Inhibitors (LDHIs). A valuable effect

Ehsan Heidaryan; Amir Salarabadi; Jamshid Moghadasi; Alireza Dourbash

2010-01-01

334

Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum  

E-print Network

Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum Silicate, Magnesium Silicate, Magnesium Trisilicate, Sodium Magnesium Silicate, Zirconium Silicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Lithium Magnesium Silicate, Lithium Magnesium

Ahmad, Sajjad

335

PYRETHROID INDUCED ALTERATIONS IN TRANSCRIPTION OF CALCIUM RESPONSIVE AND IMMEDIATE EARLY GENES IN VIVO.  

EPA Science Inventory

Multiple molecular targets for pyrethroid insecticides have been evaluated in in vitro preparations, including but not limited to voltage-sensitive sodium channels (VSSCs), voltage-sensitive calcium channels (VSCCs), GABAergic receptors, ATPases and mitochondrial respiratory chai...

336

Sodium valproate induced gingival enlargement in 22 months old child  

PubMed Central

Gingival enlargement is a common clinical feature seen in patients suffering from gingival and periodontal diseases and is a common side-effect of drugs such as anti-convulsants, calcium channel blockers and immunosuppresants. This is a case report of 22 months old child suffering from gingival enlargement following intake of sodium valproate. Among the anti-convulsants phenytoin is commonly associated with gingival enlargement; however, there are not many cases reported on sodium valproate induced gingival enlargement.

Dhalkari, Chandulal Digambarrao; Ganatra, Pallav Virendra

2014-01-01

337

The Fractal Ratio as a Metric of Nanostructure Development in Hydrating Cement Paste  

Microsoft Academic Search

It is necessary to have appropriate metrics to quantify the development of the nanostructure in Portland cement paste. The\\u000a fractal ratio, calculated from Small Angle Neutron Scattering (SANS) data, serves as such a metric. It expresses the proportion\\u000a of the volume-fractal surface area of calcium-silicate-hydrate gel (C-S-H) to the surface-fractal surface area. The volume\\u000a fractal develops in the scale range

R. A. Livingston; W. Bumrongjaroen; A. J. Allen

338

Microstructure and hydration characteristics of artificial pozzolana-cement pastes containing burnt kaolinite clay  

SciTech Connect

The reaction of pozzolana with the lime liberated during the hydration process of Portland cement modifies some properties of cement and resulting concrete. This study aimed to investigate experimentally the change occurring in the phase composition and microstructure of pozzolanic cement pastes containing activated kaolinite clay. The artificial pozzolana (burnt kaolinite clay) were thermally activated by firing at 850 C for two hours. The ordinary Portland cement (OPC) was partially replaced by different amounts of activated kaolinite clay by weight. The changes in the electrical conductivity were reported during setting and hardening processes after gauging with water. The change occurring in the phase composition and microstructure of cement pastes were investigated by differential thermal analysis and scanning electron microscopy. The results of this investigation show that, the thermal activated kaolinite clay prolonged the initial and final setting times and reduced the porosity, it also improved the microstructure of the formed hydrates by recrystallization of hydrated calcium silicates (mainly as CSH-(I)) together with the formation of hexagonal calcium aluminate hydrate (mainly as C{sub 4}AH{sub 13}).

Morsy, M.S.; Hanna, G.B. [Building Research Center, Cairo (Egypt)] [Building Research Center, Cairo (Egypt); El-Enein, S.A.A. [Ain Shams Univ., Cairo (Egypt). Faculty of Science] [Ain Shams Univ., Cairo (Egypt). Faculty of Science

1997-09-01

339

Effect of oral calcium and calcium + fluoride treatments on mouse bone properties during suspension  

NASA Technical Reports Server (NTRS)

The bone effects of oral dosages of calcium chloride with or without supplementary sodium fluoride were assessed in antiorthostatically suspended mice. Two calcium dosages were used to replace half (3.1 mM) or all(6.3 mM) of the dietary calcium lost due to reduced food intake by the suspended mice. Two groups of 6.3 mM CaCl2-treated mice were additionally treated with 0.25 or 2.5 mM NaF. The results indicate that supplementation of the mouse drinking water with calcium salts prevents bone changes induced by short-term suspension, while calcium salts in combination with fluoride are less effective as fluoride dosage increases. However, the calcium supplements change the relationship between the femur mechanical properties and the mineral composition of the bone. Because of this, it appears that oral calcium supplements are effective through a mechanism other than simple dietary supplementation and may indicate a dependence of bone consistency on systemic and local fluid conditions.

Simske, S. J.; Luttges, M. W.; Allen, K. A.; Spooner, B. S. (Principal Investigator)

1992-01-01

340

Gas hydrate reservoir characteristics and economics  

SciTech Connect

The primary objective of the DOE-funded USGS Gas Hydrate Program is to assess the production characteristics and economic potential of gas hydrates in northern Alaska. The objectives of this project for FY-1992 will include the following: (1) Utilize industry seismic data to assess the distribution of gas hydrates within the nearshore Alaskan continental shelf between Harrison Bay and Prudhoe Bay; (2) Further characterize and quantify the well-log characteristics of gas hydrates; and (3) Establish gas monitoring stations over the Eileen fault zone in northern Alaska, which will be used to measure gas flux from destabilized hydrates.

Collett, T.S.; Bird, K.J.; Burruss, R.C.; Lee, Myung W.

1992-06-01

341

Theoretical study of the dimerization of calcium carbonate in aqueous solution under natural water conditions  

NASA Astrophysics Data System (ADS)

First principles calculations have been used to investigate the condensation reactions of hydrated calcium bicarbonate monomers in a simulated aqueous environment. The reaction pathway for the calcium bicarbonate dimerization process has been computed at the density functional theory-PBE level with the COSMO dielectric continuum model to simulate the hydrated environment. The results indicate that calcium bicarbonate dimers form via an associative mechanism: the first step involves a sevenfold calcium bicarbonate intermediate followed by the loss of one water molecule from the first coordination shell of calcium. Both steps are characterised by a low energy barrier of approximately 2 kcal mol -1, suggesting that the dimerization process is not kinetically hindered in aqueous solution. However, the Gibbs free energies for the condensation reactions to form the calcium bicarbonate dimers and the species Ca(HCO 3) 2(H 2O) 4, Ca(HCO 3) 3(H 2O) 3- and Ca 2(HCO 3)(H 2O) 103+, computed using the PBE and mPW1B95 density functional theory levels for the gas-phase component and the UAHF-CPCM solvation model for the hydration contribution, are all positive, which indicates that the formation of these early calcium bicarbonate clusters is thermodynamically unfavourable in aqueous solutions. Our calculations therefore suggest that the oligomerization of calcium carbonate is not spontaneous in water, at the conditions considered in our simulations, i.e. T = 298 K and neutral pH, which indicates that the nucleation of calcium carbonate cannot occur through a homogeneous process when calcium-bicarbonate ion pairs are the major source of CaCO 3 in the aqueous environment.

Di Tommaso, Devis; de Leeuw, Nora H.

2009-09-01

342

Workability and strength of coarse high calcium fly ash geopolymer  

Microsoft Academic Search

In this paper, the basic properties viz., workability and strength of geopolymer mortar made from coarse lignite high calcium fly ash were investigated. The geopolymer was activated with sodium hydroxide (NaOH), sodium silicate and heat. The results revealed that the workable flow of geopolymer mortar was in the range of 110±5%–135±5% and was dependent on the ratio by mass of

P. Chindaprasirt; T. Chareerat; V. Sirivivatnanon

2007-01-01

343

Handbook of gas hydrate properties and occurrence  

SciTech Connect

This handbook provides data on the resource potential of naturally occurring hydrates, the properties that are needed to evaluate their recovery, and their production potential. The first two chapters give data on the naturally occurring hydrate potential by reviewing published resource estimates and the known and inferred occurrences. The third and fourth chapters review the physical and thermodynamic properties of hydrates, respectively. The thermodynamic properties of hydrates that are discussed include dissociation energies and a simplified method to calculate them; phase diagrams for simple and multi-component gases; the thermal conductivity; and the kinetics of hydrate dissociation. The final chapter evaluates the net energy balance of recovering hydrates and shows that a substantial positive energy balance can theoretically be achieved. The Appendices of the Handbook summarize physical and thermodynamic properties of gases, liquids and solids that can be used in designing and evaluating recovery processes of hydrates. 158 references, 67 figures, 47 tables.

Kuustraa, V.A.; Hammershaimb, E.C.

1983-12-01

344

Pockmark formation and evolution in deep water Nigeria: Rapid hydrate growth versus slow hydrate dissolution  

NASA Astrophysics Data System (ADS)

previous works, it has been suggested that dissolution of gas hydrate can be responsible for pockmark formation and evolution in deep water Nigeria. It was shown that those pockmarks which are at different stages of maturation are characterized by a common internal architecture associated to gas hydrate dynamics. New results obtained by drilling into gas hydrate-bearing sediments with the MeBo seafloor drill rig in concert with geotechnical in situ measurements and pore water analyses indicate that pockmark formation and evolution in the study area are mainly controlled by rapid hydrate growth opposed to slow hydrate dissolution. On one hand, positive temperature anomalies, free gas trapped in shallow microfractures near the seafloor and coexistence of free gas and gas hydrate indicate rapid hydrate growth. On the other hand, slow hydrate dissolution is evident by low methane concentrations and almost constant sulfate values 2 m above the Gas Hydrate Occurrence Zone.

Sultan, N.; Bohrmann, G.; Ruffine, L.; Pape, T.; Riboulot, V.; Colliat, J.-L.; De Prunelé, A.; Dennielou, B.; Garziglia, S.; Himmler, T.; Marsset, T.; Peters, C. A.; Rabiu, A.; Wei, J.

2014-04-01

345

SLAM: a sodium-limestone concrete ablation model  

SciTech Connect

SLAM is a three-region model, containing a pool (sodium and reaction debris) region, a dry (boundary layer and dehydrated concrete) region, and a wet (hydrated concrete) region. The model includes a solution to the mass, momentum, and energy equations in each region. A chemical kinetics model is included to provide heat sources due to chemical reactions between the sodium and the concrete. Both isolated model as well as integrated whole code evaluations have been made with good results. The chemical kinetics and water migration models were evaluated separately, with good results. Several small and large-scale sodium limestone concrete experiments were simulated with reasonable agreement between SLAM and the experimental results. The SLAM code was applied to investigate the effects of mixing, pool temperature, pool depth and fluidization. All these phenomena were found to be of significance in the predicted response of the sodium concrete interaction. Pool fluidization is predicted to be the most important variable in large scale interactions.

Suo-Anttila, A.J.

1983-12-01

346

Calcium carbonate overdose  

MedlinePLUS

... is an ingredient that is commonly found in antacids (for heartburn) and some dietary supplements. Calcium carbonate ... Products containing calcium carbonate, including Certain antacids ... mineral supplements Note: This list may not be all-inclusive.

347

Antagonist effects of calcium on borosilicate glass alteration  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

348

Calcium absorption and achlorhydria  

Microsoft Academic Search

Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium

Robert R. Recker

1985-01-01

349

Calcium and Mitosis  

NASA Technical Reports Server (NTRS)

Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

Hepler, P.

1983-01-01

350

Hydrated calcareous oil-shale ash as potential filter media for phosphorus removal in constructed wetlands.  

PubMed

The P-retention in hydrated calcareous ash sediment from oil-shale burning thermal power plants in Estonia was studied. Batch experiments indicate good (up to 65 mg P g(-1)) P-binding capacity of the hydrated oil-shale ash sediment, with a removal effectiveness of 67-85%. The high phosphorus sorption potential of hydrated oil-shale ash is considered to be due to the high content of reactive Ca-minerals, of which ettringite Ca6Al2(SO4)3(OH)12.26H2O and portlandite Ca(OH)2 are the most important. The equilibrium dissolution of ettringite provides free calcium ions that act as stable nuclei for phosphate precipitation. The precipitation mechanism of phosphorus removal in hydrated ash plateau sediment is suggested by Ca-phosphate formation in batch experiments at different P-loadings. Treatment with a P-containing solution causes partial-to-complete dissolution of ettringite and portlandite, and precipitation of Ca-carbonate and Ca-phosphate phases, which was confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM)-EDS studies. Thus, the hydrated oil-shale ash sediment can be considered as a potential filtration material for P removal in constructed wetlands for wastewater treatment. PMID:17959214

Kaasik, Ago; Vohla, Christina; Mõtlep, Riho; Mander, Ulo; Kirsimäe, Kalle

2008-02-01

351

Hyperuricosuric calcium oxalate nephrolithiasis  

Microsoft Academic Search

Many investigators have observed that renal calcium stones may be associated with uric acid disorders. Prien and Prien [1] noted that patients with gout who had stone disease frequently passed stones which contained or were composed of calcium oxalate. Gutman [2] also observed a high frequency of calcium oxalate stones in patients who had gout; and he called attention to

Fredric L Coe

1978-01-01

352

Adenine Dinucleotide Second Messengers and T-lymphocyte Calcium Signaling  

PubMed Central

Calcium signaling is a universal signal transduction mechanism in animal and plant cells. In mammalian T-lymphocytes calcium signaling is essential for activation and re-activation and thus important for a functional immune response. Since many years it has been known that both calcium release from intracellular stores and calcium entry via plasma membrane calcium channels are involved in shaping spatio-temporal calcium signals. Second messengers derived from the adenine dinucleotides NAD and NADP have been implicated in T cell calcium signaling. Nicotinic acid adenine dinucleotide phosphate (NAADP) acts as a very early second messenger upon T cell receptor/CD3 engagement, while cyclic ADP-ribose (cADPR) is mainly involved in sustained partial depletion of the endoplasmic reticulum by stimulating calcium release via ryanodine receptors. Finally, adenosine diphosphoribose (ADPR) a breakdown product of both NAD and cADPR activates a plasma membrane cation channel termed TRPM2 thereby facilitating calcium (and sodium) entry into T cells. Receptor-mediated formation, metabolism, and mode of action of these novel second messengers in T-lymphocytes will be reviewed. PMID:24009611

Ernst, Insa M. A.; Fliegert, Ralf; Guse, Andreas H.

2013-01-01

353

National workshop on gas hydrates  

NASA Astrophysics Data System (ADS)

The range of present knowledge on the subject of gas hydrates and related federal research programs was the topic of discussion at the National Workshop on Gas Hydrates, April 23-24. The intention of the meeting was to provide the impetus for an expanded and broader-based national research program in both academia and government. Held at the U.S. Geological Survey National Center, Reston, Va., the workshop was organized by Michael D. Max, Naval Research Laboratory, Washington, D.C.; William P. Dillon, USGS, Woods Hole, Mass.; and Rodney D. Malone, U.S. Department of Energy, Morgantown Energy Technology Center, Morgantown, W.Va. The 33 attendees represented academia (33%), federal agencies (58%), and industry (9%).

Max, Michael D.; Dillon, William P.; Malone, Rodney D.; Kvenvolden, Keith A.

354

Keeping nursing home residents hydrated.  

PubMed

The purpose of this research is to ascertain nursing home (NH) staffs' perspectives of the problem of dehydration in NHs (skilled nursing facilities) and have them identify clinically practical interventions to ensure that NH residents consistently take adequate fluids. Four focus groups with 28 NH staff members in attendance are held in three NHs in metropolitan Los Angeles. The majority of participants are certified nursing assistants; however, licensed vocational nurses, registered nurses, and other NH staff also attend the groups. Content analytic techniques are used to analyze the data. Three themes emerge focusing on residents' reasons for not drinking, signs and symptoms of dehydration, and strategies for improving hydration in NH residents. NH staff members identify the complexity of providing adequate hydration that was influenced by the resident's relationship with family and NH staff and communication between staff members. PMID:16672630

Mentes, Janet C; Chang, Betty L; Morris, Joseph

2006-06-01

355

Chemistry of Petroleum Crude Oil Deposits: Sodium Naphthenates 2009 NHMFL Science Highlight for NSF  

E-print Network

Chemistry of Petroleum Crude Oil Deposits: Sodium Naphthenates 2009 NHMFL Science Highlight for NSF DMR-Award 0654118 Ion Cyclotron Resonance User Program Solid deposits and emulsions from crude oil can form by the interaction of naphthenic acids with divalent (calcium; magnesium) or monovalent (sodium

Weston, Ken

356

Dielectric response of hydrated proteins  

NASA Astrophysics Data System (ADS)

We study dipolar susceptibility of hydrated proteins, representing the average dipole moment induced at the hydrated protein by a uniform external field. This parameter shows remarkable variation among proteins. We find a negative value of the dipolar susceptibility for some proteins, which implies a dia-electric dipolar response and negative dielectrophoresis. Such proteins, even though carrying significant permanent dipole moments, repel from the electric field. This outcome is the result of a negative cross-correlation between the protein and water dipoles, compensating for the positive variance of the intrinsic protein dipole in the overall dipolar susceptibility. We therefore suggest that the dipolar response of proteins in solution is strongly affected by the coupling of the protein surface charge to the hydration water. The protein-water dipolar cross-correlations are long-ranged, extending approximately 2 nm from the protein surface into the bulk. A similar correlation length of about 1 nm is found for the electrostatic potential. The model is applied to the analysis of light absorption by protein solutions in the THz window of radiation. Here we also find significant deviations of the absorption coefficient from the predictions of traditional theories.

Matyushov, Dmitry

2013-03-01

357

Sodium Polystyrene Sulfonate  

MedlinePLUS

Sodium polystyrene sulfonate is used to treat increased amounts of potassium in the body. ... Sodium polystyrene sulfonate comes as a powder and suspension to take by mouth. It may also be used as ...

358

Diclofenac sodium overdose  

MedlinePLUS

Diclofenac sodium is a prescription medicine used to relieve pain and swelling. It is a nonsteroidal anti-inflammatory drug (NSAID). Diclofenac sodium overdose occurs when someone accidentally or intentionally ...

359

Alterations in renal tubular sodium and water reabsorption in chronic renal disease in man  

Microsoft Academic Search

Alterations in renal tubular sodium and water reabsorption in chronic renal disease in man. Clearance studies were performed on subjects with GFR from 4 to 127 ml\\/min under conditions of maximal hydration and hypotonic mannitol loading. Nonelectrolyte solute excretion per GFR (UNESV\\/GFR) was calculated as [UOsm-2(UNa + UK)] V\\/GFR. Fractional sodium excretion (CNa\\/GFR) per level of UNESV\\/GFR in the low

Thomas Kahn; Ghani Mohammad; Richard M Stein

1972-01-01

360

Investigations of surfactant effects on gas hydrate formation via infrared spectroscopy.  

PubMed

This infrared (IR) spectroscopic study addresses surfactant effects on cyclopentane (CP) hydrate-water interfaces by observing both ice-like (3100 cm(-1)) and water-like (3400 cm(-1)) bands in the bonded OH region together with free OH bands. IR spectroscopy of hydrates has not been actively employed due to the overwhelming signal saturation of the OH bonding. However, this work is able to utilize this large signal of the OH bonding to understand the water structure changes upon adding sodium dodecyl sulfate (SDS) to CP hydrate-water interfaces. The spectral data suggest a change to more ice like (3100 cm(-1)) features starting from 100 ppm to 750 ppm SDS, indicating favorable nucleation. At the same instance, water like (3400 cm(-1)) features are also shown in this range of SDS concentration, which suggests looser hydrogen bonding that is an indicator for facilitating hydrate growth. Additionally, this ATR-IR study firstly identifies both symmetric and anti-symmetric free OH bands of the hydrogen bond (HB) acceptors in the clathrate hydrate system. Relative area ratios of free and bonded OH bands provide important information about spatial arrangements of adsorbed SDS monomers. PMID:22465735

Lo, Chi; Zhang, Junshe; Somasundaran, Ponisseril; Lee, Jae W

2012-06-15

361

Development of Alaskan gas hydrate resources  

SciTech Connect

The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

Kamath, V.A.; Sharma, G.D.; Patil, S.L.

1991-06-01

362

Hydrate-phobic surfaces: fundamental studies in clathrate hydrate adhesion reduction  

E-print Network

Clathrate hydrate formation and subsequent plugging of deep-sea oil and gas pipelines represent a significant bottleneck for deep-sea oil and gas operations. Current methods for hydrate mitigation are expensive and energy ...

Smith, J. David

363

SEMIMICRO DETERMINATION OF STRONTIUM AND CALCIUM IN MIXTURES  

Microsoft Academic Search

A method is described for the quantitative separation and determination ; of about 5 mg of strontium and 0.5--5 mg of calcium, by precipitation of ; strontium at pH~ 6 with sodium rhodizonate, and determination of both ions by ; complexometric titrations. (auth);

C. Heitner-Wirguin; A. Albu

1962-01-01

364

Computer Simulation of Cosolvent Effects on Hydrophobic Hydration Paul E. Smith*  

E-print Network

for helium, neon, argon, and methane solutes in solutions of sodium chloride, ammonium sulfate, calcium chloride, ammonium acetate, tetramethylammonium chloride, guanidinium chloride, urea, and TFE. The effects of varying the cosolvent concentration was also investigated for guanidinium chloride, urea, and TFE

Smith, Paul E.

365

JOURNAL DE PHYSIQUE Colloque C7, supplkment au no 12, Tome 37, Dtcembre 1976,page C7-331 POINT DEFECT PARAMETERS FOR CALCIUM FLUORIDE  

E-print Network

DEFECT PARAMETERS FOR CALCIUM FLUORIDE FROM IONIC CONDUCTIVITY MEASUREMENTS AT LOW TEMPERATURES P. W. M and sodium doped calcium fluoride crystals has been measured at temperatures up to 1 125K, avoiding chemical reaction of the calcium fluoride with residual water vapour or oxygen. The data have been analyzed using

Boyer, Edmond

366

Simulation of silica fume blended cement hydration  

Microsoft Academic Search

A model is proposed in this paper to simulate silica fume (SF) blended cement hydration based on the kinetics, stoichiometry\\u000a and physical chemistry of cement hydration and pozzolanic reaction. The pozzolanic reaction degree, volume fraction of hydration\\u000a products, capillary porosity and gel porosity can be obtained from model simulation. By using proper amount of silica fume\\u000a replacement, the microstructure of

J. Yajun; J. H. Cahyadi

2004-01-01

367

Inhibition of gas hydrates by methanol  

Microsoft Academic Search

A molecular-thermodynamic correlation has been developed for calculating the inhibition effect of methanol on the formation of hydrates in moist gas mixtures. Six phases are potentially present in these mixtures: gas, aqueous liquid, hydrocarbon liquid, ice, and hydrate structures I and II. For a given temperature and system composition, the molecular-thermodynamic method described allows computation of the hydrate-point pressure as

F. E. Anderson; J. M. Prausnitz

1986-01-01

368

Potential geologic hazards of Arctic gas hydrates  

SciTech Connect

Sediments of the Arctic region may contain enormous quantities of natural gas in the form of gas hydrates, which are crystalline substances composed of water and mostly methane gas. These ice-like substances are generally found in two distinct environments: (1) offshore in sediments of outer continental margins and (2) nearshore and onshore in areas associated with the occurrence of permafrost. Recently, US, Canadian, and Soviet researchers have described numerous drilling and production problems attributed to the presence of gas hydrates, including uncontrolled gas releases during drilling, collapsed casings, and gas leakage to the surface. When the drill bit penetrates a gas hydrate, the drilling mud, unless cooled significantly by the operator, will become highly gasified as the hydrate decomposes. The hydrate adjacent to the well bore will continue to decompose and gasify the drilling mud as long as drilling and/or production introduces heat into the hydrate-bearing interval. The production of hot fluids from depth through the permafrost and gas hydrate-bearing intervals adversely raises formation temperatures, thus decomposing the gas hydrates. If the disassociated, free gas is trapped behind the casing, reservoir pressures may substantially increase and cause the casing to collapse. In several wells in northern Alaska, the disassociated free gas has leaked to the surface outside the conductor casing. An additional drilling hazard associated with gas hydrates results from the sealing attributes of hydrates, which may trap large volumes of over pressured free gas at shallow depths. Even though documented problems attributed to the presence of gas hydrates have been relatively few, it is likely that as exploration and development activity moves farther offshore into deeper water (>300 m) and to higher latitudes in the Arctic, the frequency of gas hydrate-related problems will increase.

Collett, T.S. (Geological Survey, Menlo Park, CA (USA))

1990-05-01

369

Why not use methanol for hydrate control  

SciTech Connect

Methanol, instead of solid bed dehydration, is suggested to avoid hydrate formation in turboexpander plants. Hydrates (crystals resembling wet snow) plug pipeworks and valves. Methanol used as an antifreeze to depress the freezing point of the water is studied. Alcohol to depress the formation temperature of hydrate in a gas is also studied. Confusion between the two methods is clarified. Comparison between methanol injection and solid bed dehydration is made; methanol has lower costs.

Nielsen, R.B.; Bucklin, R.W.

1983-04-01

370

Natural gas hydrates: problem or opportunity  

SciTech Connect

Natural gas hydrates, once viewed solely as a nuisance by the gas processing industry, are rapidly gaining favorable status as an unconventional natural gas resource. Hydrates are solids which form when gas is contacted with water, both above and below 273 Kelvin. Conditions are favorable for hydrate formation in permafrost regions and in many oceans. Natural gas hydrates are solid crystalline compounds composed of cavities, formed by water molecules, which contain a natural gas guest. Hydrates are more properly called clathrates, after a general class of inclusion compounds, because they do not contain the fixed chemical formula characteristics of normal hydrates. These compounds represent a condensed form of natural gas, and each volume of the solid may contain as much as 170 volumes of gas at standard conditions. During the last decade, significant amounts of in situ hydrates have been found in permafrost regions of the earth and in deep oceans in warmer climates. Of the mechanisms proposed for recovery of gas from hydrates, all involve at least one of four principles: (1) pressure reduction; (2) thermal injection; (3) reservoir fracture; or (4) inhibitor injection, to break the hydrogen bonds of the water in the hydrate. Calculations by researchers in the United States indicate that thermal stimulation with a hot fluid, perhaps combined with reservoir fracture is energy efficient when the reservoir contains excess free gas. The question of definite reserve identification and commercialization of gas recovery is still a major challenge for this unconventional natural gas resource.

Sloan, E.D.

1981-11-01

371

The growth kinetics of hydrate film on the surface of gas bubble suspended in water or aqueous surfactant solution  

NASA Astrophysics Data System (ADS)

A novel experimental method to study the hydrate formation kinetics on the gas/water interface was presented and, using this method, the two-dimensional growth kinetic data of hydrate film on the surface of quiescent methane gas bubble suspended in pure water, natural water and natural water added with different contents of sodium dodecyl sulfate (SDS) were measured and compared. The experimental results showed that the presence of the low dose of ions in natural water appreciably inhibited the hydrate formation; the presence of SDS promoted the hydrate growth when its concentration was lower than 1000 mg/L while it inhibited the hydrate formation beyond this region, the concentration of SDS corresponding to the most efficient promotion was determined to be 500 mg/L or so; the presence of low-dose ions in the natural water has little negative influence upon the promotion efficiency of SDS. A two-parameter kinetic model was developed to correlate the growth rates of hydrate films in different aqueous solutions consistently, where the dimensionless Gibbs free energy difference of hydrate formation reaction was chosen as driving force. Good agreement between calculated results and experimental data was achieved and only one parameter was found to be SDS concentration dependent. The mechanism that the presence of SDS affects the hydrate formation rate was discussed based on the experimental and theoretical results with some new insights. Additionally, the three-dimensional growth of hydrate shell covering the gas bubble was studied morphologically and a series of interesting phenomena were observed and discussed.

Sun, Chang-Yu; Chen, Guang-Jin; Ma, Chang-Feng; Huang, Qiang; Luo, Hu; Li, Qing-Ping

2007-08-01

372

Distribution of hydrate on Europa: Further evidence for sulfuric acid hydrate  

Microsoft Academic Search

Sulfuric acid hydrate has been proposed as an important species on Europa's surface, the acid being produced by radiolysis of surficial sulfur compounds. We investigated the spectral properties of disordered and crystalline forms of sulfuric acid and suggest that the hydration properties of Europa's hypothesized sulfuric acid lie between two end members: liquid sulfuric acid and its higher crystalline hydrates.

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

2005-01-01

373

Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments  

USGS Publications Warehouse

The interaction among water molecules, guest gas molecules, salts, and mineral particles determines the nucleation and growth behavior of gas hydrates in natural sediments. Hydrate of tetrahydrofuran (THF) has long been used for laboratory studies of gas hydrate-bearing sediments to provide close control on hydrate concentrations and to overcome the long formation history of methane hydrate from aqueous phase methane in sediments. Yet differences in the polarizability of THF (polar molecule) compared to methane (nonpolar molecule) raise questions about the suitability of THF as a proxy for methane in the study of hydrate-bearing sediments. From existing data and simple macroscale experiments, we show that despite its polar nature, THF's large molecular size results in low permittivity, prevents it from dissolving precipitated salts, and hinders the solvation of ions on dry mineral surfaces. In addition, the interfacial tension between water and THF hydrate is similar to that between water and methane hydrate. The processes that researchers choose for forming hydrate in sediments in laboratory settings (e.g., from gas, liquid, or ice) and the pore-scale distribution of the hydrate that is produced by each of these processes likely have a more pronounced effect on the measured macroscale properties of hydrate-bearing sediments than do differences between THF and methane hydrates themselves.

Lee, J.Y.; Yun, T.S.; Santamarina, J.C.; Ruppel, C.

2007-01-01

374

Microbial Community Structure and Diversity in Hydrate Ridge Gas Hydrates (Cascadia Margin)  

Microsoft Academic Search

Here, we present the first quantitative study investigating microorganisms physically associated with Hydrate Ridge gas hydrates. Previous studies have shown that the anaerobic oxidation of methane (AOM) in methane enriched surface sediments of Hydrate Ridge is apparently mediated by highly structured microbial consortia (Boetius et al., 2000). These AOM consortia consist of an inner core of methane-oxidizing archaea (ANME2-group) and

T. Lösekann; K. Knittel; A. Boetius; R. Amann

2003-01-01

375

Methane hydrates as potential energy resource: Part 2 – Methane production processes from gas hydrates  

Microsoft Academic Search

Three processes have been proposed for dissociation of methane hydrates: thermal stimulation, depressurization, and inhibitor injection. The obvious production approaches involve depressurization, heating and their combinations. The depressurization method is lowering the pressure inside the well and encouraging the methane hydrate to dissociate. Its objective is to lower the pressure in the free-gas zone immediately beneath the hydrate stability zone,

Ayhan Demirbas

2010-01-01

376

Sodium and cardiovascular disease.  

PubMed

To the Editor: In 2013, I served on an Institute of Medicine (IOM) panel whose members concluded that data published through 2012 relating cardiovascular outcomes to a sodium intake below 2300 mg per day were inconsistent and insufficient.(1) The article by O'Donnell and colleagues (Aug. 14 issue),(2) which presents data from the Prospective Urban Rural Epidemiology (PURE) study, only adds to the confusion. A single morning urine sample is an inaccurate measure of usual sodium intake, ignoring day-to-day variability in sodium intake, diurnal variation in sodium excretion, and the effects of medication.(3) The Kawasaki formula also overestimates sodium exposure in . . . PMID:25427119

Batuman, Vecihi

2014-11-27

377

Sodium and cardiovascular disease.  

PubMed

To the Editor: In 2013, I served on an Institute of Medicine (IOM) panel whose members concluded that data published through 2012 relating cardiovascular outcomes to a sodium intake below 2300 mg per day were inconsistent and insufficient.(1) The article by O'Donnell and colleagues (Aug. 14 issue),(2) which presents data from the Prospective Urban Rural Epidemiology (PURE) study, only adds to the confusion. A single morning urine sample is an inaccurate measure of usual sodium intake, ignoring day-to-day variability in sodium intake, diurnal variation in sodium excretion, and the effects of medication.(3) The Kawasaki formula also overestimates sodium exposure in . . . PMID:25427122

Alderman, Michael H

2014-11-27

378

Sodium and cardiovascular disease.  

PubMed

To the Editor: In 2013, I served on an Institute of Medicine (IOM) panel whose members concluded that data published through 2012 relating cardiovascular outcomes to a sodium intake below 2300 mg per day were inconsistent and insufficient.(1) The article by O'Donnell and colleagues (Aug. 14 issue),(2) which presents data from the Prospective Urban Rural Epidemiology (PURE) study, only adds to the confusion. A single morning urine sample is an inaccurate measure of usual sodium intake, ignoring day-to-day variability in sodium intake, diurnal variation in sodium excretion, and the effects of medication.(3) The Kawasaki formula also overestimates sodium exposure in . . . PMID:25427121

Graudal, Niels

2014-11-27

379

Sodium and cardiovascular disease.  

PubMed

To the Editor: In 2013, I served on an Institute of Medicine (IOM) panel whose members concluded that data published through 2012 relating cardiovascular outcomes to a sodium intake below 2300 mg per day were inconsistent and insufficient.(1) The article by O'Donnell and colleagues (Aug. 14 issue),(2) which presents data from the Prospective Urban Rural Epidemiology (PURE) study, only adds to the confusion. A single morning urine sample is an inaccurate measure of usual sodium intake, ignoring day-to-day variability in sodium intake, diurnal variation in sodium excretion, and the effects of medication.(3) The Kawasaki formula also overestimates sodium exposure in . . . PMID:25427120

Saulnier, Pierre-Jean; Gand, Elise; Hadjadj, Samy

2014-11-27

380

Sodium and cardiovascular disease.  

PubMed

To the Editor: In 2013, I served on an Institute of Medicine (IOM) panel whose members concluded that data published through 2012 relating cardiovascular outcomes to a sodium intake below 2300 mg per day were inconsistent and insufficient.(1) The article by O'Donnell and colleagues (Aug. 14 issue),(2) which presents data from the Prospective Urban Rural Epidemiology (PURE) study, only adds to the confusion. A single morning urine sample is an inaccurate measure of usual sodium intake, ignoring day-to-day variability in sodium intake, diurnal variation in sodium excretion, and the effects of medication.(3) The Kawasaki formula also overestimates sodium exposure in . . . PMID:25427117

2014-11-27

381

Sodium and cardiovascular disease.  

PubMed

To the Editor: In 2013, I served on an Institute of Medicine (IOM) panel whose members concluded that data published through 2012 relating cardiovascular outcomes to a sodium intake below 2300 mg per day were inconsistent and insufficient.(1) The article by O'Donnell and colleagues (Aug. 14 issue),(2) which presents data from the Prospective Urban Rural Epidemiology (PURE) study, only adds to the confusion. A single morning urine sample is an inaccurate measure of usual sodium intake, ignoring day-to-day variability in sodium intake, diurnal variation in sodium excretion, and the effects of medication.(3) The Kawasaki formula also overestimates sodium exposure in . . . PMID:25427118

Cook, Nancy R

2014-11-27

382

Physicochemical properties of common and waxy corn starches oxidized by different levels of sodium hypochlorite  

Microsoft Academic Search

Structure and physicochemical properties of oxidized common and waxy corn starches by different levels of sodium hypochlorite (0.25–3.0% active chlorine based on dry starch weight) were studied. The oxidized common corn starch generally had a higher carboxyl content but a similar carbonyl content compared with the oxidized waxy corn starch. The introduction of carboxyl and carbonyl groups promoted starch hydration

Ya-Jane Wang; Linfeng Wang

2003-01-01

383

Sodium-sulfur thermal battery  

Microsoft Academic Search

This paper discusses a sodium-sulfur thermal battery for generating electrical energy at temperatures above the melting point of sodium metal and sulfur. It comprises a sodium electrode comprising sodium metal; a sulfur electrode comprising sulfur; and a separator located between the sodium and sulfur electrodes. The separator having sufficient porosity to allow preliminary migration of fluid sodium metal and fluid

Ludwig

1990-01-01

384

Discovery of calcium in Mercury's atmosphere.  

PubMed

The composition and evolutionary history of Mercury's crust are not well determined. The planet as a whole has been predicted to have a refractory, anhydrous composition: rich in Ca, Al, Mg and Fe, but poor in Na, K, OH, and S. Its atmosphere is believed to be derived in large part from the surface materials. A combination of effects that include impact vaporization (from infalling material), volatile evaporation, photon-stimulated desorption and sputtering releases material from the surface to form the atmosphere. Sodium and potassium have already been observed in Mercury's atmosphere, with abundances that require a volatile-rich crust. The sodium probably results from photon-stimulated desorption, and has a temperature of 1,500 K (ref. 10). Here we report the discovery of calcium in the atmosphere near Mercury's poles. The column density is very low and the temperature is apparently very high (12,000 K). The localized distribution and high temperature, if confirmed, suggest that the atmospheric calcium may arise from surface sputtering by ions, which enter Mercury's auroral zone. The low abundance of atmospheric Ca may indicate that the regolith is rarefied in calcium. PMID:10724161

Bida, T A; Killen, R M; Morgan, T H

2000-03-01

385

Original article Availability of calcium from skim milk, calcium sulfate  

E-print Network

Original article Availability of calcium from skim milk, calcium sulfate and calcium carbonate that the calcium in milk was more efficiently used than that from any other source. Carbonate, gluconate, citrate; accepted 19 November 1999) Abstract --Dairy products provide abundant, accessible calcium for humans, while

Paris-Sud XI, Université de

386

Calcium is incorporated into the calcium carbonate matrix of otoliths  

E-print Network

118 Calcium is incorporated into the calcium carbonate matrix of otoliths and into the calcium). In addition to calcium, trace elements, such as strontium, are also incorporated into the calcified components valence) allow strontium ions to act as replace- ments for calcium during the pro- cess of calcification

387

Aluminum Citrate Prevents Renal Injury from Calcium Oxalate Crystal Deposition  

PubMed Central

Calcium oxalate monohydrate crystals are responsible for the kidney injury associated with exposure to ethylene glycol or severe hyperoxaluria. Current treatment strategies target the formation of calcium oxalate but not its interaction with kidney tissue. Because aluminum citrate blocks calcium oxalate binding and toxicity in human kidney cells, it may provide a different therapeutic approach to calcium oxalate-induced injury. Here, we tested the effects of aluminum citrate and sodium citrate in a Wistar rat model of acute high-dose ethylene glycol exposure. Aluminum citrate, but not sodium citrate, attenuated increases in urea nitrogen, creatinine, and the ratio of kidney to body weight in ethylene glycol–treated rats. Compared with ethylene glycol alone, the addition of aluminum citrate significantly increased the urinary excretion of both crystalline calcium and crystalline oxalate and decreased the deposition of crystals in renal tissue. In vitro, aluminum citrate interacted directly with oxalate crystals to inhibit their uptake by proximal tubule cells. These results suggest that treating with aluminum citrate attenuates renal injury in rats with severe ethylene glycol toxicity, apparently by inhibiting calcium oxalate’s interaction with, and retention by, the kidney epithelium. PMID:23138489

Besenhofer, Lauren M.; Cain, Marie C.; Dunning, Cody

2012-01-01

388

Hydration recommendations for sport 2008.  

PubMed

Fluid replacement remains an important strategy for preserving exercise performance as dehydration in excess of 2% of body weight consistently impairs aerobic exercise performance. Too much of a good thing, however, can have negative health consequences as persistent drinking in excess of sweating rate can induce symptomatic exercise associated hyponatremia. This short review highlights new position stands and/or policy statements regarding fluid replacement for sport, evidence that laboratory findings translate to team sport performance, and current hydration practices of athletes. It is culminated with practical strategies for drinking appropriately during physical activity. PMID:18607219

Montain, Scott J

2008-01-01

389

Deliquescence of calcium perchlorate: A route to liquid water on Mars and other possibly habitable planets  

NASA Astrophysics Data System (ADS)

The Wet Chemistry Laboratory (WCL) aboard the Phoenix Mars Lander identified the presence of 0.5% perchlorate (ClO4-). Reanalysis of the Viking gas chromatography-mass spectrometry results also suggests perchlorate was present in the soil and the Mars Science Laboratory (MSL) rover has potentially found perchlorate as well. Perchlorate salts are known to readily absorb water vapor from the atmosphere and deliquesce into an aqueous solution. We have previously performed laboratory studies to better understand the deliquescence (crystalline solid to aqueous salt) and also efflorescence (aqueous salt to crystalline solid) of several perchlorate salts at low temperatures. We found that NaClO4 and Mg(ClO4)2 are highly deliquescent, forming aqueous solutions at humidity values as low as 40% RH and at temperatures as low as 223 K. We also observed a significant hysteresis that occurs during efflorescence of these salt solutions, expected due to the kinetic inhibition of crystal nucleation. The efflorescence relative humidity values of sodium and magnesium perchlorate solutions are 13% RH and 19% RH, respectively, indicating that perchlorate salts could exist as stable or metastable aqueous solutions over a wide range of Martian RH and temperature conditions. Although the low temperature deliquescence of several perchlorate salts is now well characterized, instruments onboard Phoenix and MSL have identified calcium perchlorate (Ca(ClO4)2) as the likely parent salt. Calcium perchlorate is known for its highly deliquescent properties and low eutectic point; however, the deliquescence and efflorescence of this salt have not yet been quantified as a function of temperature. We have used Raman microscopy to examine the deliquescence and efflorescence of Ca(ClO4)2 under relevant Martian temperatures. A extremely low DRH of ~1% for the anhydrous Ca(ClO4)2 at 273 K was observed, which could allow for formation of aqueous solutions under very low RH environmental conditions. Hydrated calcium perchlorate deliquesces at higher RHs from 25-45%RH. In all cases studied, however, the aqueous solutions remain liquid until the RH decreases to a much lower value where the particle eventually effloresces. At 273 K, the ERH is less than 1% RH and on average, less than 15% RH for all temperatures studied. Understanding RH phase transition range for Ca(ClO4)2 aqueous solutions, or any briny mixture, is important for characterizing the present-day water on Mars and has implications for the availability of liquid water and the habitability of other similar planets.

Tolbert, M.; Nuding, D.; Gough, R. V.

2013-05-01

390

Dissolution of various calcium fluoride preparations in inorganic solutions and in stimulated human saliva.  

PubMed

The aim of the present study was to examine the dissolution of various preparations of calcium fluoride in inorganic solutions and in human saliva. Calcium fluoride was prepared by mixing either 0.25 or 0.02 mol/l calcium chloride with 0.5 or 0.04 mol/l sodium fluoride. After preparation, the salts were washed in 1 mmol/l calcium chloride solution and in distilled water. A commercial product, calcium fluoride Suprapur (Merck), was used for comparison. The solubility of the salts was examined in distilled water, in a 2-mmol/l sodium phosphate solution, and in whole human saliva, produced by chewing paraffin. It was found that the calcium fluoride ion product after suspension for 1-3 h in distilled water ranged closely around 10(-10.7) for all salts. In the phosphate solution, the commercial product dissolved slowly, the ratio between dissolved fluoride and calcium ranged from 4 to 7, in buffered solutions approaching 2. The supernatant was not saturated by the salt. Our two calcium fluoride salts dissolved quickly and made the phosphate-containing solutions supersaturated with respect to fluorapatite, leading to fluorapatite formation, and because of compensating calcium fluoride dissolution, this led to increasing fluoride concentrations in saliva of up to around 85-95 ppm. The results of this study indicate that calcium fluoride of less than Suprapur standard may dissolve quickly in saliva, unless the dissolution is retarded by a physical barrier, like a forming pellicle. PMID:7850849

Larsen, M J; Ravnholt, G

1994-01-01

391

Signaling complexes of voltage-gated sodium and calcium channels.  

PubMed

Membrane depolarization and intracellular Ca(2+) transients generated by activation of voltage-gated Na+ and Ca(2+) channels are local signals, which initiate physiological processes such as action potential conduction, synaptic transmission, and excitation-contraction coupling. Targeting of effector proteins and regulatory proteins to ion channels is an important mechanism to ensure speed, specificity, and precise regulation of signaling events in response to local stimuli. This article reviews experimental results showing that Na+ and Ca(2+) channels form local signaling complexes, in which effector proteins, anchoring proteins, and regulatory proteins interact directly with ion channels. The intracellular domains of these channels serve as signaling platforms, mediating their participation in intracellular signaling processes. These protein-protein interactions are important for regulation of cellular plasticity through modulation of Na+ channel function in brain neurons, for short-term synaptic plasticity through modulation of presynaptic Ca(V)2 channels, and for the fight-or-flight response through regulation of postsynaptic Ca(V)1 channels in skeletal and cardiac muscle. These localized signaling complexes are essential for normal function and regulation of electrical excitability, synaptic transmission, and excitation-contraction coupling. PMID:20816922

Catterall, William A

2010-12-10

392

Natural gas hydrates: myths, facts and issues  

Microsoft Academic Search

Gas hydrates are solid-like substances naturally occurring beneath the oceans and in polar regions. They contain vast, and potentially unstable, reserves of methane and other natural gases. Many believe that, if released in the environment, the methane from hydrates would be a considerable hazard to marine ecosystems, coastal populations and infrastructures, or worse, that it would dangerously contribute to global

2004-01-01

393

Well log evaluation of natural gas hydrates.  

National Technical Information Service (NTIS)

Gas hydrates are crystalline substances composed of water and gas, in which a solid-water-lattice accommodates gas molecules in a cage-like structure. Gas hydrates are globally widespread in permafrost regions and beneath the sea in sediment of outer cont...

T. S. Collett

1992-01-01

394

Hydrate Inhibition Design for Deepwater Completions  

Microsoft Academic Search

This paper will review the design considerations for gas hydrate prevention in deepwater well completions. The influence of seafloor temperature, wellbore pressure, water production rate and composition of gas on hydrate inhibition system design will be discussed. The impact of various inhibitors will be discussed in relationship to the design of the system and potential handling problems. Examples will review

Janardhan Davalath; J. W. Barker

1995-01-01

395

Effect of massive gas hydrate formation on the water isotopic fractionation of the gas hydrate system at Hydrate Ridge, Cascadia margin, offshore Oregon  

Microsoft Academic Search

Because gas hydrate is preferentially enriched in the heavy water isotopes, the ?18O and ?D values of pore waters collected from gas hydrate–bearing sediment can provide information on the abundance and mechanisms of gas hydrate formation. Pore waters sampled from deep-seated (40 to 125 mbsf) gas hydrate deposits in Hydrate Ridge during ODP Leg 204 show depletion in dissolved Cl?

Hitoshi Tomaru; Marta E. Torres; Ryo Matsumoto; Walter S. Borowski

2006-01-01

396

Inhibition of gas hydrates in deepwater drilling  

SciTech Connect

With the movement of offshore rigs into deep water, the problem of gas hydrates has become an important issue in drilling. If a kick is taken, gas hydrates can form in the blowout preventer (BOP) or chokelines while the kick is circulated out. The water-based pill presented here significantly improves gas-hydrate inhibition. This pill, which can be spotted in the BOP and weighted up, is environmentally safe and easily adaptable to offshore operations. Compatible with commonly used drilling fluids, the pill can be mixed directly into the mud system without any adverse effects after the danger of hydrate formation diminishes. This technology is an important safety consideration for deepwater drilling well control and hydrate-free operations above the mudline.

Hale, A.H.; Dewan, A.K.R. (Shell Development Co., Houston, TX (USA))

1990-06-01

397

METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST  

SciTech Connect

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope drilled and cored a well The HOT ICE No.1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report.

Thomas E. Williams; Keith Millheim; Buddy King

2004-06-01

398

METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST  

SciTech Connect

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Oil-field engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in Arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrates agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored the HOT ICE No. 1 on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was designed, constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. Unfortunately, no gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in the project reports.

Thomas E. Williams; Keith Millheim; Bill Liddell

2005-03-01

399

Ground-based Detection of Exoatmospheric Calcium  

NASA Astrophysics Data System (ADS)

Data acquired with HDS@Subaru for HD209458b is re-analyzed. A new pipeline performs an automated search for the exoatmospheric presence of several elements without any a-priori assumptions on its existence or strength. We analyzed thousands of lines in the full spectral range of this optical echelle spectrograph using a robust method to correct for the telluric contamination. We recover previous detections of Sodium and Halpha, and present the first strong detection of Calcium in an Extrasolar Atmosphere as well as the tentative detection of other elements. The Calcium detection is in disagreement with theoretical thermal-equilibrium models. Results published in Astudillo-Defru and Rojo (2013, A&A 557, 56)

Rojo, P.; Astudillo-Defru, N.

2014-03-01

400

Solubilities of sodium nitrate, sodium nitrite, and sodium aluminate in simulated nuclear waste  

SciTech Connect

Solubilities were determined for sodium nitrate, sodium nitrite, and sodium aluminate in synthetic nuclear waste liquor. Solubilities were determined as a function of temperature and solution composition (concentrations of sodium hydroxide, sodium nitrate, sodium nitrite, and sodium aluminate). Temperature had the greatest effect on the solubilities of sodium nitrate and sodium nitrite and a somewhat lesser effect on sodium aluminate solubility. Hydroxide had a great effect on the solubilities of all three salts. Other solution components had minor effects. 2 references, 8 figures, 11 tables.

Reynolds, D.A.; Herting, D.L.

1984-09-01

401

Sodium fill of FFTF  

SciTech Connect

With construction of the Fast Flux Test Facility (FFTF) completed, the first major objective in the startup program was to fill the sodium systems. A sodium fill sequence was developed to match construction completion, and as systems became available, they were inerted, preheated, and filled with sodium. The secondary sodium systems were filled first while dry refueling system testing was in progress in the reactor vessel. The reactor vessel and the primary loops were filled last. This paper describes the methods used and some of the key results achieved for this major FFTF objective.

Waldo, J.B.; Greenwell, R.K.; Keasling, T.A.; Collins, J.R.; Klos, D.B.

1980-02-01

402

Effects of elevated intracellular calcium on the osmotic fragility of human red blood cells.  

PubMed

High throughput methodologies that measure the distribution of osmotic fragilities in red blood cell populations have enabled the investigation of dynamic changes in red cell homeostasis and membrane permeability in health and disease. The common assumption in the interpretation of dynamic changes in osmotic fragility curves is that left or right shifts reflect a decreased or increased hydration state of the cells, respectively, allowing direct inferences on membrane transport from osmotic fragility measurements. However, the assumed correlation between shifts in osmotic fragility and hydration state has never been directly explored, and may prove invalid in certain conditions. We investigated here whether this correlation holds for red cells exposed to elevated intracellular calcium. The results showed that elevated cell calcium causes a progressive increase in osmotic fragility with minimal contribution from cell hydration (<8%). Loss of membrane area by the release of 160+/-40nm diameter (mean+/-SD) vesicles is shown to be a major contributor, but may not account for the full non-hydration component. The rest must reflect a specific calcium-induced lytic vulnerability of the membrane causing rupture before the cells attain their maximal spherical volumes. The implications of these findings are discussed. PMID:19954845

Cueff, Anne; Seear, Rachel; Dyrda, Agnieszka; Bouyer, Guillaume; Egée, Stéphane; Esposito, Alessandro; Skepper, Jeremy; Tiffert, Teresa; Lew, Virgilio L; Thomas, Serge L Y

2010-01-01

403

The Fractal Ratio as a Metric of Nanostructure Development in Hydrating Cement Paste  

NASA Astrophysics Data System (ADS)

It is necessary to have appropriate metrics to quantify the development of the nanostructure in Portland cement paste. The fractal ratio, calculated from Small Angle Neutron Scattering (SANS) data, serves as such a metric. It expresses the proportion of the volume-fractal surface area of calcium-silicate-hydrate gel (C-S-H) to the surface-fractal surface area. The volume fractal develops in the scale range from ? 5 nm to ? 100 nm, and it is associated with the formation of outer product in the capillary pore space by the through-solution mechanism. The surface fractal is attributed to the surface structure formed by colloidal particles on solid substrates such as the Portland cement grains and fly ash particles. The evolution of this ratio over time provides insight into which types of hydration processes are dominant. Applied to study of the hydration of fly ash/Portland cement mixes at later ages, the fractal ratio method showed that in every case, except two, there was a reduced hydration rate due to the dilution effect. The two exceptions involved fly ash fractions with sufficient CaO to generate significant C-S-H gel by the alkali-activated reaction. In all cases the fractal ratio increased with time, indicating the production of additional C-S-H through the topochemical reaction.

Livingston, R. A.; Bumrongjaroen, W.; Allen, A. J.

404

The effects of source and level of calcium on the performance and shell quality of laying hens  

E-print Network

-488. Balloun, S. L. and W. W. Marion, 1962. Relative efficiency of calcium lactate and calcium carbonate in promoting sound egg shells. Poultry Sci. 41: 1625. Davidson, J. and A. W. Boyne, 1970. The calcium and phosphorous requirements of laying hens. British.... The effect of high levels of calcium, fish pro- ducts and sodium carbonate on egg shell quality. Poultry Sci. 47:224-229. Pepper, W. F. , C. M. Winget and S. K. Slinger, 1961. influence of calcium and ascorbic acid on egg quality. Poultry Sci. 40...

Lockamy, Terry Allan

2012-06-07

405

Micro Determination of Calcium  

Microsoft Academic Search

Hildebrand and Reilly1 have recently described a complexometric titration method for the determination of calcium: the indicator used, `Calcon', is superior to `Solochrome' black in that calcium can be determined independently of magnesium, and, unlike the murexide method, a sharp end-point is obtained. All three methods employ ethylenediamine tetraacetic acid. The purpose of the present communication is to direct attention

A. B. Gilbert

1959-01-01

406

Methane Recovery from Hydrate-bearing Sediments  

SciTech Connect

Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with emphasis; (6) detailed study of CH4-CO2 exchange as a unique alternative to recover CH4 gas while sequestering CO2; (7) the relevance of fines in otherwise clean sand sediments on gas recovery and related phenomena such as fines migration and clogging, vuggy structure formation, and gas-driven fracture formation during gas production by depressurization.

J. Carlos Santamarina; Costas Tsouris

2011-04-30

407

Mass fractionation of noble gases in synthetic methane hydrate: Implications for naturally occurring gas hydrate dissociation  

USGS Publications Warehouse

As a consequence of contemporary or longer term (since 15 ka) climate warming, gas hydrates in some settings may presently be dissociating and releasing methane and other gases to the ocean-atmosphere system. A key challenge in assessing the impact of dissociating gas hydrates on global atmospheric methane is the lack of a technique able to distinguish between methane recently released from gas hydrates and methane emitted from leaky thermogenic reservoirs, shallow sediments (some newly thawed), coal beds, and other sources. Carbon and deuterium stable isotopic fractionation during methane formation provides a first-order constraint on the processes (microbial or thermogenic) of methane generation. However, because gas hydrate formation and dissociation do not cause significant isotopic fractionation, a stable isotope-based hydrate-source determination is not possible. Here, we investigate patterns of mass-dependent noble gas fractionation within the gas hydrate lattice to fingerprint methane released from gas hydrates. Starting with synthetic gas hydrate formed under laboratory conditions, we document complex noble gas fractionation patterns in the gases liberated during dissociation and explore the effects of aging and storage (e.g., in liquid nitrogen), as well as sampling and preservation procedures. The laboratory results confirm a unique noble gas fractionation pattern for gas hydrates, one that shows promise in evaluating modern natural gas seeps for a signature associated with gas hydrate dissociation.

Hunt, Andrew G.; Stern, Laura; Pohlman, John W.; Ruppel, Carolyn; Moscati, Richard J.; Landis, Gary P.

2013-01-01

408

Use of sodium polyaspartate for the removal of hydroxyapatite/brushite deposits from stainless steel tubing  

SciTech Connect

This research investigates the use of sodium polyaspartate, a nontoxic, biodegradable polycarboxylic sequestrant, for removing calcium phosphate deposit consisting of hydroxyapatite (HAP) and brushite or dicalcium phosphate dihydrate (DCPD) from stainless steel surfaces. Cleaning studies show that the use of sodium polyaspartate under alkaline conditions significantly enhances the removal rates when compared to deionized water. In acidic solutions, sodium polyaspartate concentrations below 300 ppm inhibit removal of HAP/DCPD deposits whereas higher concentrations increase the removal rate. Comparative cleaning studies at alkaline pHs show that sodium polyaspartate cleans the surface at a rate comparable to sodium citrate but slower than in ethylenediaminetetraacetic acid. Supplementary dissolution experiments show that sodium polyaspartate enhances the HAP/DCPD dissolution rate while inhibiting the release of Ca{sup 2+}. On the basis of these findings, the authors have concluded that sodium polyaspartate improves the HAP/DCPD dissolution and cleaning rates by Ca{sup 2+} sequestration.

Littlejohn, F.; Saez, A.E.; Grant, C.S. [North Carolina State Univ., Raleigh, NC (United States). Dept. of Chemical Engineering] [North Carolina State Univ., Raleigh, NC (United States). Dept. of Chemical Engineering

1998-07-01

409

Multiphasic finite element modeling of concrete hydration  

SciTech Connect

This paper presents a model predicting the development of hydration and its consequences on temperature and water content. As it considers the effects of climatic conditions, the proposed model is a promising tool to evaluate the temperature, hydric and hydration fields of structures in situ. The hydration model predicts the hydration evolution of several main species (not only clinker but also mineral additions like fly ash or silica fume for instance). For each component, the modeling considers hydration development and chemical interaction between reactions. It also takes into account temperature and water content effects on reaction kinetics through thermal and hydric activation. Hydration development in turn modifies the thermal and hydric states of material. The result is a numerical model coupling hydration, and the thermal and hydric states of cement-based material. The model was tested on a 27 m{sup 3} concrete block in situ equipped with temperature sensors situated in the core and close to the face exposed to solar radiation.

Buffo-Lacarriere, L. [VINCI Construction Grands Projets, 5 cours Ferdinand de Lesseps, F-92851 Rueil-Malmaison Cedex (France); Laboratoire Materiaux et Durabilite des Constructions, INSA-UPS, 135 avenue de Rangueil, F-31077 Toulouse Cedex 4 (France); Sellier, A. [Laboratoire Materiaux et Durabilite des Constructions, INSA-UPS, 135 avenue de Rangueil, F-31077 Toulouse Cedex 4 (France)]. E-mail: alain.sellier@insa-toulouse.fr; Escadeillas, G. [Laboratoire Materiaux et Durabilite des Constructions, INSA-UPS, 135 avenue de Rangueil, F-31077 Toulouse Cedex 4 (France); Turatsinze, A. [Laboratoire Materiaux et Durabilite des Constructions, INSA-UPS, 135 avenue de Rangueil, F-31077 Toulouse Cedex 4 (France)

2007-02-15

410

Gas Hydrates Research Programs: An International Review  

SciTech Connect

Gas hydrates sediments have the potential of providing a huge amount of natural gas for human use. Hydrate sediments have been found in many different regions where the required temperature and pressure conditions have been satisfied. Resource exploitation is related to the safe dissociation of the gas hydrate sediments. Basic depressurization techniques and thermal stimulation processes have been tried in pilot efforts to exploit the resource. There is a growing interest in gas hydrates all over the world due to the inevitable decline of oil and gas reserves. Many different countries are interested in this valuable resource. Unsurprisingly, developed countries with limited energy resources have taken the lead in worldwide gas hydrates research and exploration. The goal of this research project is to collect information in order to record and evaluate the relative strengths and goals of the different gas hydrates programs throughout the world. A thorough literature search about gas hydrates research activities has been conducted. The main participants in the research effort have been identified and summaries of their past and present activities reported. An evaluation section discussing present and future research activities has also been included.

Jorge Gabitto; Maria Barrufet

2009-12-09

411

Changes in calcium and bone metabolism during treatment with low dose prednisone in young, healthy, male volunteers  

Microsoft Academic Search

Summary The effect of low dose prednisone on calcium and bone metabolism was evaluated in 8 healthy, young, male volunteers. Sodium and calcium intake were kept stable during the whole study period of 7 weeks. Week 0 was the baseline period; during week 1, 3 and 5 prednisone (10 mg\\/day) was given, during week 3 together with 500 mg elementary

W. F. Lems; J. W. G. Jacobs; H. J. M. VAN RIJN; J. W. J. Bijlsma

1995-01-01

412

Opacity reduction using hydrated lime injection  

SciTech Connect

The purpose of this investigation is to study the effects of injecting dry hydrated lime into flue gas to reduce sulfur trioxide (SO{sub 3}) concentrations and consequently stack opacity at the University of Missouri, Columbia power plant. Burning of high sulfur coal (approx. 4% by weight) at the power plant resulted in opacity violations. The opacity problem was due to sulfuric acid mist (H{sub 2}SO{sub 4}) forming at the stack from high SO{sub 3} concentrations. As a result of light scattering by the mist, a visible plume leaves the stack. Therefore, reducing high concentrations of SO{sub 3} reduces the sulfuric acid mist and consequently the opacity problem. The current hydrated lime injection system has reduced the opacity to acceptable limits. To reduce SO{sub 3} concentrations, dry hydrated lime is injected into the flue gas upstream of a particulate collection device (baghouse) and downstream of the induced draft fan. The lime is periodically injected into the flue via a pneumatic piping system. The hydrated lime is transported down the flue and deposited on the filter bags in the baghouse. As the hydrated lime is deposited on the bags a filter cake is established. The reaction between the SO{sub 3} and the hydrated lime takes place on the filter bags. The hydrated lime injection system has resulted in at least 95% reduction in the SO{sub 3} concentration. Low capital equipment requirements and operating cost coupled with easy installation and maintenance makes the system very attractive to industries with similar problems. This paper documents the hydrated lime injection system and tests the effectiveness of the system on SO{sub 3} removal and subsequent opacity reduction. Measurements Of SO{sub 3} concentrations, flue gas velocities, and temperatures have been performed at the duct work and baghouse. A complete analysis of the hydrated lime injection system is provided.

Wolf, D.E.; Seaba, J.P. [Univ. of Missouri, Columbia, MO (United States)

1993-12-31

413

METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST  

SciTech Connect

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the second year of a three-year endeavor being sponsored by Maurer Technology, Noble, and Anadarko Petroleum, in partnership with the DOE. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition. We plan to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. We also plan to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope is to drill and core a well on Anadarko leases in FY 2003 and 2004. We are also using an on-site core analysis laboratory to determine some of the physical characteristics of the hydrates and surrounding rock. The well is being drilled from a new Anadarko Arctic Platform that will have minimal footprint and environmental impact. We hope to correlate geology, geophysics, logs, and drilling and production data to allow reservoir models to be calibrated. Ultimately, our goal is to form an objective technical and economic evaluation of reservoir potential in Alaska.

Thomas E. Williams; Keith Millheim; Buddy King

2004-03-01

414

METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST  

SciTech Connect

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the US have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the second year of a three-year endeavor being sponsored by maurer Technology, noble, and Anadarko Petroleum, in partnership with the DOE. The purpose of the project is to build on previous and ongoing R and D in the area of onshore hydrate deposition. They plan to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. They also plan to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope is to drill and core a well on Anadarko leases in FY 2003 and 2004. They are also using an on-site core analysis laboratory to determine some of the physical characteristics of the hydrates and surrounding rock. The well is being drilled from a new Anadarko Arctic Platform that will have minimal footprint and environmental impact. They hope to correlate geology, geophysics, logs, and drilling and production data to allow reservoir models to be calibrated. Ultimately, the goal is to form an objective technical and economic evaluation of reservoir potential in Alaska.

Thomas E. Williams; Keith Millheim; Buddy King

2003-12-01

415

Structure of the hydration shell of the Na+ ion in a planar nanopore with hydrophobic walls  

NASA Astrophysics Data System (ADS)

The effect of steric hindrances in extremely narrow planar pores on the structure of the hydration shell of the single-charged sodium cation in water vapors at room temperature was studied by computer simulation. The deficiency of empty space for the motion in the slit-like pore was shown to slightly affect the radial distribution of molecules around the ion. The integrated (over the directions) numbers of ion-oxygen atom bonds of molecules in the ion's hydration shell did not change despite the change in the shape of the hydration cluster from three- to two-dimensional. It was concluded that the changes in the positions of molecules relative to the ion were mainly reduced to azimuthal displacements; as a result, the local bulk density of molecules in the pore was higher than at the same distances outside the pore for the same total number of molecules. The distribution of molecules over layers inside the pore demonstrates the effect of molecules spread over the walls. The effect of ion displacement from its own hydration shell found earlier for the free chloride ion is steadily reproduced under the pore conditions. An alternative explanation to this effect was proposed that does not suggest high ion polarizability.

Shevkunov, S. V.

2014-10-01

416

Rotifers colonising sediments with shallow gas hydrates.  

PubMed

Rotifers, one of the smallest metazoans, are only seldom found in marine environments. Surprisingly, we discovered high abundances of at least two new species of rotifers settling in anoxic and highly sulphidic sediments associated with shallow gas hydrates (GH) at the southern crest of Hydrate Ridge off Oregon, NE Pacific, in a water depth of about 780 m. At basins adjacent to Hydrate Ridge, 1,285-2,304 m deep, we found rotifers co-occurring with the sulphide-oxidising bacteria Thioploca sp. PMID:12835839

Sommer, Stefan; Gutzmann, Erik; Ahlrichs, Wilko; Pfannkuche, Olaf

2003-06-01

417

Carbon dioxide hydrate and floods on Mars  

NASA Technical Reports Server (NTRS)

Ground ice on Mars probably consists largely of carbon dioxide hydrate. This hydrate dissociates upon release of pressure at temperatures between 0 and 10 C. The heat capacity of the ground would be sufficient to produce up to 4% (by volume) of water at a rate equal to that at which it can be drained away. Catastrophic dissociation of carbon dioxide hydrate during some past epoch when the near-surface temperature was in this range would have produced chaotic terrain and flood channels.

Milton, D. J.

1974-01-01

418

Clathrate hydrates in cometary nuclei and porosity  

NASA Technical Reports Server (NTRS)

Possible mechanisms of formation and decomposition of CO2-clathrate hydrate in cometary nuclei are discussed. As far as it is known, this is the only clathrate hydrate which is unstable at low temperatures. Calculation shows that, in accord with other evidence, neither volume nor grain boundary diffusion in the clathrate lattice can be responsible for the rate of these reactions and that a surface mechanism with the attendant sensitivity to pressure must play a crucial role. Density changes accompanying CO2-clathrate decomposition and formation can lead to microporosity and enhanced brittleness or even to fracture of cometary nuclei at low temperatures. Other clathrate hydrates and mixed clathrates are also discussed.

Smoluchowski, R.

1988-01-01

419

Inhibition of gas hydrates by methanol  

SciTech Connect

A molecular-thermodynamic correlation has been developed for calculating the inhibition effect of methanol on the formation of hydrates in moist gas mixtures. Six phases are potentially present in these mixtures: gas, aqueous liquid, hydrocarbon liquid, ice, and hydrate structures I and II. For a given temperature and system composition, the molecular-thermodynamic method described allows computation of the hydrate-point pressure as well as relative amounts and compositions of all coexisting phases. Good agreement is obtained when calculated results are compared with diverse experimental data reported in the literature. The correlation given here may be useful for computer-aided design for gas processing and transportation.

Anderson, F.E.; Prausnitz, J.M.

1986-08-01

420

Effects of inhibitors on hydrate formation  

SciTech Connect

This method for predicting the effect of inhibitors on natural gas hydrate-formation conditions appears to be more accurate than that currently used for injecting inhibitor into a natural gas stream. Incorporating existing hydrate parameters and data from the literature, analysts can predict the effects of KCl, CaCl/sub 2/, CH/sub 3/OH, and C/sub 2/H/sub 5/OH inhibition of pure gas hydrates. The extension to other inhibitors and gas mixtures is straightforward. Work is proceeding to extend the measurements to simulated natural gases with methanol and glycol inhibitors.

Menten, P.D.; Parrish, W.R.; Sloan, E.D.

1981-04-01