Common naturally occurring orthosilicates can be grouped into those in which the major non-tetrahedral cations are (1) FeII and/or Mg, plus or minus Al (olivine, pyralspite garnets, staurolite); (2) Al (Al2SiO5 polymorphs), or (3) Zr. Feand Mg-bearing orthosilicates have the weakest bonds between non-tetrahedral cations and structural oxygen (M-O bonds), and zircon the strongest, with Al-O bond...

background: silica aerogel is the nano-porous form silica which is the lightest synthetic solid material. some specific properties of this material include high surface area (1500 m2.g-1), low density (< 0.03 g.cm-3) and high porosity (%99). in this research, silica aerogel was investigated as an adsorbent of the heavy metal cations in aqueous solutions. methods: the silica aerogel was synthesi...

Inhibition by polyvalent cations is a defining characteristic of voltage-gated proton channels. The mechanism of this inhibition was studied in rat alveolar epithelial cells using tight-seal voltage clamp techniques. Metal concentrations were corrected for measured binding to buffers. Externally applied ZnCl 2 reduced the H 1 current, shifted the voltage-activation curve toward positive potenti...

AB STRACT The effects of external Zn+2 and other divalent cations on K channels in squid giant axons were studied. At low concentration (2 mM) Zn+2 slows opening kinetics without affecting closing kinetics . Higher concentrations (5-40 mM) progressively slow opening and speed channel closing to a lesser degree. In terms of "shifts," opening kinetics are strongly shifted to the right on the volt...

Phosphonium ions are widely used in preparative organic synthesis and catalysis. The provision of new types cations that contain both functional chiral information is a major synthetic challenge can open up horizons asymmetric cation-directed Lewis acid We discovered an efficient methodology towards Si-chiral four-membered CPSSi* heterocyclic cations. Three approaches presented. stereochemical ...

Ionizations of 2-substituted l,l-dimethyl-3,4-methano-1,2,3,4-tetrahydronaphthalen-2-ols (8) (3,3-dimethylbenzobicyclo[4.1 .O]heptan-2-ols) in FS03H/S02CIF at -1 30 O C do not yield the corresponding 2-cations but benzylic (4-) cations 10 as a result of cyclopropylcarbinyl~yclopropylcarbinyl rearrangements. At higher temperatures, 10a and 10b undergo a further series of rearrangements to yield ...

in the present study, micellar-enhanced ultrafiltration (meuf) was used to remove manganese (mn) (ii) from synthetic wastewater. the effects of different operational conditions on the filtration performance of meuf or the membrane were studied. it was found that the transmembrane pressure has a major influence on the permeate flux and an insignificant effect on the rejection coefficient. the pe...