EXAFS and MAS NMR studies of sodium molybdophosphate and sodium tungstophosphate glasses

he local order around molybdenum and tungsten atoms in various sodium molybdophosphate and sodium tungstophosphate glasses has been investigated using extended X-ray absorption fine structure (EXAFS). Both molybdenum and tungsten atoms are present in six-coordinated environment in these glasses. Magic angle spinning nuclear magnetic resonance (MAS NMR) of P-31 suggests that metaphosphate or neutral [POO3/2] groups are present in these glasses.

Xenon in sodium Y zeolite. 2. Arrhenius relation, mechanism, and barrier height distribution for cage-to-cage diffusion

Various geometrical and energetic distribution functions and other properties connected with the cage-to-cage diffusion of xenon in sodium Y zeolite have been obtained from long molecular dynamics calculations. Analysis of diffusion pathways reveals two interesting mechanisms-surface-mediated and centralized modes for cage-to-cage diffusion. The surface-mediated mode of diffusion exhibits a small positive barrier, while the centralized diffusion exhibits a negative barrier for the sorbate to diffuse across the 12-ring window. In both modes, however, the sorbate has to be activated from the adsorption site to enable it to gain mobility. The centralized diffusion additionally requires the sorbate to be free of the influence of the surface of the cage as well. The overall rate for cage-to-cage diffusion shows an Arrhenius temperature dependence with E(a) = 3 kJ/mol. It is found that the decay in the dynamical correction factor occurs on a time scale comparable to the cage residence time. The distributions of barrier heights have been calculated. Functions reflecting the distribution of the sorbate-zeolite interaction at the window and the variations of the distance between the sorbate and the centers of the parent and daughter cages are presented.

High level stable expression of rat brain type IIA sodium channel ?-subunit in CHO cells

The neuronal sodium channels are responsible for the rising phase of action potential and are composed of three subunits, of which the alpha-subunit has been shown to be adequate for most of its functional properties. We have stably expressed the rat brain type IIA sodium channel alpha-subunit in CHO cell tine using a CMV promoter-based vector. The expression was confirmed by detecting a 6.5 kb RNA corresponding to sodium channel alpha-subunit using Northern hybridization. The cells stably expressing the alpha-subunit, yield isolated sodium currents of amplitudes greater than 4nA when studied in whole-cell configuration of the patch-clamp technique. The sodium currents are characterized by activation and inactivation properties similar to neuronal sodium channels, and are blocked by the voltage gated sodium channel blocker tetrodotoxin (TTX).

ChemInform Abstract: Sodium Perborate/Acetic Anhydride: A Convenient Reagent for the Conversion of Cyclic Acetals to Esters

A facile oxidative cleavage of cyclic acetals to their respective esters using an inexpensive reagent system, sodium perborate/acetic anhydride is described.

Investigations on sodium tin phosphate and tin pyrophosphate glasses

Glasses of the alkali tin phosphate system have been investigated. The infrared absorption and fluorescence spectra of the glasses have been examined. It is found that tin is present in both + 2 and + 4 oxidation states. Also tin ions occupy four- or six-coordinated sites in the glass.

Laboratory studies on the volume change characteristics of kaolinite contaminated with sodium phosphate/sulfate

Reported distress to an industrial structure from phosphate/sulfate contamination of kaolinitic foundation soil at an industrial location in Southern India prompted this laboratory study. The study examines the short-term effect of sodium sulfate/phosphate contamination on the swell/compression characteristics of a commercial kaolinite. Experimental results showed that the unsaturated contaminated kaolinite specimens exhibited slightly higher swell potentials and lower compressions than the unsaturated uncontaminated kaolinite specimens. It is suggested that the larger double layer promoted by the increased exchangeable sodium ion concentration is responsible for the slightly higher swell potentials and lower compressions of the unsaturated contaminated kaolinite specimens.

Nonlinear optical activity of anhydrous and hydrated sodium p-nitrophenolate

Differently hydrated sodium p-nitrophenolate (NPNa) crystals were obtained while growing them from different solvents such as methanol and water. Thermal analysis and powder X-ray diffraction studies were carried out on these crystals. Kurtz powder SHG technique was used for qualitative assessment of their nonlinear optical (NLO) activity. From the detailed single-crystal X-ray diffraction studies it is established that NPNa has three different forms, of which only one is found to possess NLO activity. Additionally, a new NLO active crystal was also found to grow from aqueous solution. (C) 1999 Elsevier Science B.V. All rights reserved.

Bubble size measurement in a gas-liquid ejector for a sodium chloride-air system

A high speed photographic technique has been employed to measure the Sauter mean diameter of bubbles experimentally in a gas liquid ejector using a sodium chloride-air system. The measured values are compared with the theoretically predicted maximum bubble size diameter using Sprow's correlation. Bubble size as a function of the liquid flow rate and also of its distance from the throat of the ejector has been reported in this paper. The results obtained for this non-reactive system are also compared with those obtained earlier for the air-water system.

Swelling pressure of sodium montmorillonites

Determination of the swelling pressure of montmorillonitic clays is required in many situations concerned with stability problems of foundations, retaining walls, slope stability of embankments and excavations in expansive soils. Recently expansive soils such as bentonite have been used as a mixture backfill material, for example as backfill material for nuclear waste disposal systems, for which a knowledge of the swelling pressure is desirable. This is the pressure required to keep the clay-water system at the required void ratio when it is allowed to absorb water or electrolyte. If the pressure is less than the swelling pressure, volume expansion occurs; if the pressure is more than the swelling pressure, volume compression occurs. Because of isomorphous substitutions in the crystal lattice, in general the clay particles carry negative charges at the surfaces of the platelets. Exchangeable cations in the clay media are attracted to these negative charges, but this attraction is opposed by the tendency of ions to be distributed. As a result, an electric diffuse double layer is formed (Gouy, 1910).

Manipulation of the Hydration Levels in Minerals of Sodium Cadmium Bisulfate toward the Design of Functional Materials

Several variants of hydrated sodium cadmium bisulfate, Na(2)Cd(2)(SO(4))(3) center dot 3H(2)O, Na(2)Cd(SO(4))(2) center dot 2H(2)O, and Na(2)Cd(SO(4))(2) center dot 4H(2)O have been synthesized, and their thermal properties followed by phase transitions have been invesigated. The formation of these phases depends on the stochiometry and the time taken for crystallization from water. Na(2)Cd(2)(SO(4))(3)center dot 3H(2)O, which crystallizes in the trigonal system, space group P3c, is grown from the aqueous solution in about four weeks. The krohnkite type mineral Na(2)Cd(SO(4))(2) center dot 2H(2)O and the mineral astrakhanite, also known as blodite, Na(2)Cd (SO(4))(2)center dot 4H(2)O, crystallize concomittantly in about 24 weeks. Both these minerals belong to the monoclinic system(space group P2(1)/c). Na(2)Cd(2)(SO(4))(3)center dot 3H(2)O loses water completely when heated to 250 degrees C and transforms to a dehydrated phase (cubic system, space group I (4) over bar 3d) whose structure has been established using ab initio powder diffration techniques. Na(2)Cd(SO(4))(2)center dot 2H(2)O transforms to alpha-Na(2)Cd(SO(4))(2) (space group C2/c) on heating to 150 degrees C which is a known high ionic conductor and remains intact over prolonged periods of exposure to moisture (over six months). However, when alpha-Na(2)Cd(SO(4))(2) is heated to 570 degrees C followed by sudden quenching in liquid nitrogen beta-Na(2)Cd(SO(4))(2) (P2(1)/c) is formed. beta-Na(2)Cd(SO(4))(2) takes up water from the atmosphere and gets converted completely to the krohnkite type mineral in about four weeks. Further, beta-Na(2)Cd(SO(4))(2) has a conductivity behavior comparable to the a-form up to 280 degrees C, the temperature required for the transformation of the beta- to alpha-form. These experiments demonstrate the possibility of utilizing the abundantly available mineral sources as precursors to design materials with special properties.

Efficient syntheses of benzothiazepines as antagonists for the mitochondrial sodium-calcium exchanger: Potential therapeutics for type II diabetes

Type II diabetes mellitus is a chronic metabolic disorder that can lead to serious cardiovascular, renal, neurologic, and retinal complications. While several drugs are currently prescribed to treat type II diabetes, their efficacy is limited by mechanism-related side effects (weight gain, hypoglycemia, gastrointestinal distress), inadequate efficacy for use as monotherapy, and the development of tolerance to the agents. Consequently, combination therapies are frequently employed to effectively regulate blood glucose levels. We have focused on the mitochondrial sodium-calcium exchanger (mNCE) as a novel target for diabetes drug discovery. We have proposed that inhibition of the mNCE can be used to regulate calcium flux across the mitochondrial membrane, thereby enhancing mitochondrial oxidative metabolism, which in turn enhances glucose-stimulated insulin secretion (GSIS) in the pancreatic beta-cell. In this paper, we report the facile synthesis of benzothiazepines and derivatives by S-alkylation using 2-aminobenzhydrols. The syntheses of other bicyclic analogues based on benzothiazepine, benzothiazecine, benzodiazecine, and benzodiazepine templates are also described. These compounds have been evaluated for their inhibition of mNCE activity, and the results from the structure-activity relationship (SAR) studies are discussed.

Impact of Sulphate counter ion in the migration of sodium ion through soils

Laboratory advection-diffusion tests are performed on two regional soils-Brown Earth and Red Earth-in order to assess their capacity to control contaminant migration with synthetic contaminant solution of sodium sulphate with sodium concentration of 1000 mg/L. The test was designed to study the transport/attenuation behaviour of sodium in the presence of sulphate. Effective diffusion coefficient (De) that takes into consideration of attenuation processes is used. Cation exchange capacity is an important factor for the attenuation of cationic species. Monovalent sodium ion cannot usually replace other cations and the retention of sodium ion is very less. This is particularly true when chloride is anion is solution. However, sulphate is likely to play a role in the attenuation of sodium. Cation exchange capacity and type of exchangeable ions of soils are likely to play an important role. The effect of sulphate ions on the effective diffusion coefficient of sodium, in two different types of soils, of different cation exchange capacity has been studied. The effective diffusion coefficients of sodium ion for both the soils were calculated using Ogata Bank’s equation. It was shown that effective diffusion coefficient of sodium in the presence of sulphate is lower for Brown Earth than for Red Earth due to exchange of sodium with calcium ions from the exchangeable complex of clay. The soil with the higher cation exchange retained more sodium. Consequently, the breakthrough times and the number of pore volumes of sodium ion increase with the cation exchange capacity of soil.

Reversible Swelling/Deswelling Characteristics of Ethylene Glycol Dimethacrylate Cross-Linked Poly(acrylic acid-co-sodium acrylate-co-acrylamide) Superabsorbents

Poly(acrylic acid-co-sodium acrylate-co-acrylamide) superabsorbent polymers (SAPs) cross-linked with ethylene glycol dimethacrylate (EGDMA) were synthesized by inverse suspension polymerization. The SAPs were swollen in DI water, and it was found that the equilibrium swelling capacities varied with the acrylamide content. The SAPs were subjected to reversible swelling/deswelling cycles in DI water and aqueous NaCl solution, respectively. The effect of the addition of an electrolyte on the swelling of the SAP was explored. The equilibrium swelling capacity of the SAPs was found to decrease with increasing concentration of added electrolyte in the swelling medium. The effect of the particle size of the dry SAPs on the swelling properties was also investigated. A first order model was used to describe the kinetics of swelling/deswelling, and the equilibrium swelling capacity, limiting swelling capacity, and swelling/deswelling rate coefficients were determined.

l-pGlu-(2-propyl)-l-His-l-ProNH2 attenuates 4-aminopyridine-induced epileptiform activity and sodium current: a possible action of new thyrotropin-releasing hormone analog for its anticonvulsant potential

L-PGlu-(2-proPyl)-L-His-L-ProNH(2) (NP-647) is a CNS active thyrotropin-releasing hormone (TRH) analog with potential application in various CNS disorders including seizures. In the present study, mechanism of action for protective effect of NP-647 was explored by studying role of NP-647 on epileptiform activity and sodium channels by using patch-clamp methods. Epileptiform activity was induced in subicular pyramidal neurons of hippocampal slice of rat by perfusing 4-aminopyridine (4-AP) containing Mg(+2)-free normal artificial cerebrospinal fluid (nACSF). Increase in mean firing frequency was observed after perfusion of 4-AP and zero Mg(+2) (2.10+/-0.47 Hz) as compared with nACSF (0.12+/-0.08 Hz). A significant decrease in mean firing frequency (0.61+/-0.22 Hz), mean frequency of epileptiform events (0.03+/-0.02 Hz vs. 0.22+/-0.05 Hz of 4-AP+0 Mg), and average number of action potentials in paroxysmal depolarization shift-burst (2.54+/-1.21 Hz vs. 8.16+/-0.88 Hz of 4-AP +0 Mg) was observed. A significant reduction in peak dV/dt (246+/-19 mV ms(-1) vs. 297 18 mV ms-1 of 4-AP+0 Mg) and increase (1.332+/-0.018 ms vs. 1.292+/-0.019 ms of 4-AP+0 Mg) in time required to reach maximum depolarization were observed indicating role of sodium channels. Concentration-dependent depression of sodium current was observed after exposure to dorsal root ganglion neurons to NP-647. NP-647 at different concentrations (1, 3, and 10 mu M) depressed sodium current (15+/-0.5%, 50+/-2.6%, and 75+/-0.7%, respectively). However, NP-647 did not show change in the peak sodium current in CNa18 cells. Results of present study demonstrated potential of NP-647 in the inhibition of epileptiform activity by inhibiting sodium channels indirectly. (C) 2011 IBRO. Published by Elsevier Ltd. All rights reserved.