The structure of zeolite clinoptilolite and the coordination of extraframework cations (Ca, Ba, Na and K) by framework oxygen atoms are examined by density functional theory (DFT) using two methods: the ONIOM two-layer model (DFT/MM) and periodic DFT. Both ONIOM and periodic model calculations predict correctly the clinoptilolite structure and find configurations with Al ? Si substitution at th...

The presence of potentially toxic cations and anions in the environment has become a global problem, mainly due to their high toxicity ability bioaccumulate/biomagnify. Although elements considered may occur naturally, human activities contribute significantly increasing concentration these substances ecosystems. In this context, review addresses details disposition mercury (Hg), lead (Pb), cad...

The passive binding of cations to submitochondrial fragments prepared by sonic oscillation of bovine heart mitochondria has been examined. At least two different types of binding sites can be distinguished. The first site appears to be phospholipid in nature and binds the following cations in the sequence indicated: La3+ > Ca2+ > Mg2+ > K+ and Na+. Each of these cations inhibits the binding of ...

In this paper, polyacrylamide/chromium acetate gel polymer system was prepared as water shut-off system to control water production in one of the Iranian oil reservoirs condition. Effect of various parameters such as temperature (90 °C) and water formation from view point of salinity and divalent cations, was evaluated on the gelation kinetic and gel strength using bottle testing method. Th...

The title compound, sodium potassium trialuminium tetra-kis-(orthoarsenate), was prepared by solid-state reactions. The anionic framework consists of corrugated layers parallel to (010) and is made up of corner-sharing AlO6 octa-hedra (site symmetries .2. and 2/m..) that are connected to isolated AsO4 tetra-hedra (site symmetries .2. and m..) through edge- and corner-sharing. The alkali cations...

The crystal structure of the title compound, [Rb(C18H36N2O6)]3RbSn9, consists of deltahedral [Sn9]4- cluster anions, Rb+ cations and cryptand mol-ecules, which partially sequester the cations. Those cations, which are not coordinated by cryptand mol-ecules, are neighboured directly to the [Sn9]4- clusters and inter-connect them to form ∞1[RbSn9]3- chains. These chains extend parallel to [001] a...

This paper presents an algorithm for executing formal speci cations, and a proof of the soundness of that algorithm. The algorithm executes speci cations written in the model-based speci cation language SPECS-C++ by transforming such speci cations to constraint programs. The generated programs use constraint satisfaction techniques to execute speci cations written at a high level of abstraction...