Exchangers discovery

Sodium-Calcium Exchangers Discovery, Distribution, and Properties 129... 

SODIUM-CALCIUM EXCHANGERS DISCOVERY, DISTRIBUTION, AND PROPERTIES... 

Quinoa, E. and Crews, P, Phenohc constituents of Psammaplysilla, Tetrahedron Lett., 28,3229, 1987. Nicolaou, K.C. et al, Combinatorial synthesis through disulfide exchange discovery of potent psam-maplin A type antibacterial agents active against methiciUin-resistant Staphylococcus aureus (MRSA), Chem. Eur. J., 7, 4280, 2001. 

The cost of dysprosium metal has dropped in recent years since the development of ion-exchange and solvent extraction techniques, and the discovery of large ore bodies. The metal costs about 300/kg in purities of 99+%. 

To foster a close relationship with the chemical, petroleum, gas, and energy industries and governmental agencies for the exchange of information and knowledge and to ensure that research results and discoveries of significance will be effectively exploited... 

Ion exchange (qv see also Chromatography) is an important procedure for the separation and chemical identification of curium and higher elements. This technique is selective and rapid and has been the key to the discovery of the transcurium elements, in that the elution order and approximate peak position for the undiscovered elements were predicted with considerable confidence (9). Thus the first experimental observation of the chemical behavior of a new actinide element has often been its ion-exchange behavior—an observation coincident with its identification. Further exploration of the chemistry of the element often depended on the production of larger amounts by this method. Solvent extraction is another useful method for separating and purifying actinide elements. 

Cobalt exists in the +2 or +3 valence states for the majority of its compounds and complexes. A multitude of complexes of the cobalt(III) ion [22541-63-5] exist, but few stable simple salts are known (2). Werner s discovery and detailed studies of the cobalt(III) ammine complexes contributed gready to modem coordination chemistry and understanding of ligand exchange (3). Octahedral stereochemistries are the most common for the cobalt(II) ion [22541-53-3] as well as for cobalt(III). Cobalt(II) forms numerous simple compounds and complexes, most of which are octahedral or tetrahedral in nature cobalt(II) forms more tetrahedral complexes than other transition-metal ions. Because of the small stabiUty difference between octahedral and tetrahedral complexes of cobalt(II), both can be found in equiUbrium for a number of complexes. Typically, octahedral cobalt(II) salts and complexes are pink to brownish red most of the tetrahedral Co(II) species are blue (see Coordination compounds). 

The production of tritium-labelled organic compounds was enormously facilitated by K. E. Wilz-bach s discovery in 1956 that tritium could be introduced merely by storing a compound under tritium gas for a few days or weeks the radiation induces exchange reactions between the hydrogen atoms in the compound and the tritium gas. The excess of gas is recovered for further use and the tritiated compound is purified chro-matographically. Another widely used method of... 

In addition to providing some control of price risk, futures and options markets are also very useful mechanisms for price discovery and for gauging market sentiment. There is a world-wide need for accurate, real-time information about the prices established through futures and options trading, that is, a need for price transparency. Exchange prices are simultaneously transmitted around the world via a network of information vendors terminal seiwices directly to clients, thereby allowing users to follow the market in real time wherever they may be. Energy futures prices are also widely reported in the financial press. These markets thus enable an open, equitable and competitive environment. 

It was a characteristic feature of Bohr s classical quantum mechanics that it could never be generalized to give good quantitative results for systems containing more than one electron. The extension from N = 1 to N = 2, 3,. . . came first with modern wave mechanics and Heisenberg s discovery in 1926 of the exchange phenomenon in the He-atom, which, with the identity... 

Even more exciting was the discovery of bands at higher frequency (430-1600 cm ). Exchanging the sample in H2 0 resulted in a shift to lower frequency. A shift to lower frequency was also observed when the protein was enriched in Fe or Fe (Fig. 6). These data indicated the presence of an iron-oxo species. It was argued that this functionality may be related to the physiological function. 

The several polymeric metal carbonyls studied have led to some surprisingly high yields [e.g., Fe3(CO),2 and Ruj(CO)j2 in Table IV] but to no substantiated mechanisms. The 17% yield of Fe3(CO),2 in neutron-irradiated Fe(CO)j was interpreted as a reaction of Fe(CO)4 with the Fe(CO)5, but no further evidence is available. The study of Mn2(CO),o has been fruitful (44, 46). The insensitivity of the parent yield MnMn(CO),o to heat indicates that the molecule is formed by a reaction quite early in the sequence, perhaps epithermal. The discovery (46) of a species which reacts rapidly with I2 and exchanges with IMn(CO)5 led to the conclusion that the Mn(CO)5 radical is produced prominently (4.5%) by nuclear reactions in the solid decacarbonyl. The availability of this labeled Mn(CO)5 has made possible several interesting observations about the exchange properties of this radical in the solid (45) and in solution (42). 

This discovery was quite unexpected, since iron oxide has been never reported as an active catalyst in either partial or full oxidation. The studies of two simplest reactions, i.e. O2 isotopic exchange and N2O decomposition, revealed a dramatic change of Fe properties in the ZSM-5 matrix compared to Fe203 [4]. Fe atoms lose their ability to activate O2 but gain remarkably in their ability to activate N2O. It gives rise to a great effect of the oxidant nature in the reaction of benzene oxidation over the FeZSM-5 zeolite (Table 1). Thus, in the presence of N2O benzene conversion is 27% at 623 K, while in the presence of O2 it is only 0.3% at 773 K. And what is more, there is a perfect change of the reaction route. Instead of selective phenol formation with... 

The search for models of biological membranes led to the formation of a separate branch of electrochemistry, i.e. membrane electrochemistry. The most important results obtained in this field include the theory and application of ion-exchanger membranes and the discovery of ion-selective electrodes (including glass electrodes) and bilayer lipid membranes. 

The incorporation of 14C into compounds at a suitable site often requires extensive and complicated syntheses, and thus a relatively long time. This usually means that 14C-labeled compounds are unsuitable for studies to be carried out during discovery. There are however, very rapid methods for incorporating 3 H into compounds. The newer methods, generally involving metal-catalyzed exchange reactions [15-18], in our experience, mean that suitable labels can often be prepared in 2 or 3 weeks. These time scales make the approach viable for discovery support. Additionally, and importantly, these methods can lead to specific incorporation of tritium. 

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