Binary clusters

The final methodological chapter (Chapter 6) is devoted to cluster analysis. Besides a general treatment of different clustering approaches, also more specific problems in chemometrics are included, like clustering binary vectors indicating presence or absence of certain substructures. 

Minimum total reflux (lbs or mols/hr) corresponding to given total feed will be greater than if only the actual total mols of heavy and light key components were present. Reflux need will be less than if the actual total mols of feed were present, but composed only of light and heavy keys. The more closely non-keyed components are clustered to volatilities of the keys, the nearer are reflux needs to that calculated for the binary and total feed volume. 

Figure 25.11 Metal frameworks of some high-nuclearity binary carbonyl and carbonylate clusters of osmium (a) Os5(CO)i6 (trigonal bipyramid) (b) Os6(CO)ig (bicapped tetrahedron, or capped trigonal bipyramid) (c) [Os6(CO)ig] (octahedron) (d) Os7(CO)2i (capped octahedron) (e) [Osg(CO)22] (bicapped octahedron) (f) [Osi7(CO)36] (3 shaded atoms cap an Osu trigonal bipyramid).

The quantity b has the dimension of a volume and is known as the excluded volume or the binary cluster integral. The mean force potential is a function of temperature (principally as a result of the soft interactions). For a given solvent or mixture of solvents, there exists a temperature (called the 0-temperature or Te) where the solvent is just poor enough so that the polymer feels an effective repulsion toward the solvent molecules and yet, good enough to balance the expansion of the coil caused by the excluded volume of the polymer chain. Under this condition of perfect balance, all the binary cluster integrals are equal to zero and the chain behaves like an ideal chain. 

Of course, the chemistry of zirconium cluster phases has been well described and reviewed in the literature [1-4]. Apart from a very few examples, mostly in the binary halides, almost all reduced zirconium halides contain octahedra of zirconium atoms centred on an interstitial atom Z. Several possible and experimentally realized Z include H, Be-N, K, Al-P, and the transition metals Mn-Ni. All these compounds have the general formula Ax"[(Zr6Z)Xi2X[J], with a " = alkali or alkaline earth metal cation, X=C1 Br or I, X =inner edge-bridging halide [5], X =outer exo-bonded halide, and 0[Pg.61]

Adsorption phenomena from solutions onto sohd surfaces have been one of the important subjects in colloid and surface chemistry. Sophisticated application of adsorption has been demonstrated recently in the formation of self-assembhng monolayers and multilayers on various substrates [4,7], However, only a limited number of researchers have been devoted to the study of adsorption in binary hquid systems. The adsorption isotherm and colloidal stabihty measmement have been the main tools for these studies. The molecular level of characterization is needed to elucidate the phenomenon. We have employed the combination of smface forces measmement and Fomier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR) to study the preferential (selective) adsorption of alcohol (methanol, ethanol, and propanol) onto glass surfaces from their binary mixtures with cyclohexane. Om studies have demonstrated the cluster formation of alcohol adsorbed on the surfaces and the long-range attraction associated with such adsorption. We may call these clusters macroclusters, because the thickness of the adsorbed alcohol layer is about 15 mn, which is quite large compared to the size of the alcohol. The following describes the results for the ethanol-cycohexane mixtures [10],... 

Binary systems of ruthenium sulfide or selenide nanoparticles (RujcSy, RujcSey) are considered as the state-of-the-art ORR electrocatalysts in the class of non-Chevrel amorphous transition metal chalcogenides. Notably, in contrast to pyrite-type MS2 varieties (typically RUS2) utilized in industrial catalysis as effective cathodes for the molecular oxygen reduction in acid medium, these Ru-based cluster materials exhibit a fairly robust activity even in high methanol content environments of fuel cells. 

In the present study, we synthesized in zeolite cavities Co-Mo binary sulfide clusters by using Co and Mo carbonyls and characterized the clusters by extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and high resolution electron microscopy (HREM). The mechanism of catalytic synergy generation in HDS is discussed. 

Taking into consideration the preparation procedures, the Mo content of 2.1Mo/SC, and the Co/Mo atomic ratio of ca. unity at the maximum HDS activity, highly dispersed Co-Mo binary sulfide clusters, possibly COjMOjSx, in the supercage of the NaY zeolite are suggested for catalytically active species. The HDS activity of the CoSx-MoSx/NaY was not changed even after a 20-h treatment at 673 K in a stream of HjS/H (Fig.3), demonstrating a high thermal stability of the active species. 

As an example of binary clusters for magnetic applications, we present the study performed on Ni-Co alloy [78]. The Co-Ni phase diagram was investigated by performing sequential ion implantation in silica of Co and Ni at the same energy of ISOkeV (Rp 150nm) but with different fluences in order to have a constant total Co+Ni fluence (15 x lO ions/cm or 30 x 10 ions/cm ). For the 1 1 Co Ni ratio, we also performed sequential implants at... 

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