Clustering, categories

Another catalyst system that could be considered in the bimetallic cluster category is supported platinum-rhenium (5), which represents still another type of system in the sense that a Group VIIA metallic element (rhenium) is incorporated with the Group VIII metal component. Platinum and rhenium have different crystal structures (fee vs. hep) (8) and do not exhibit complete miscibility in the bulk (Ref. 45, p. 820). However, these factors may have limited... 

In this article we have shown that the electronic structures of transition metal compounds based on a cubic architecture can be rationalized, by use of results obtained from molecular orbital calculations, leading to some interesting extensions of the electron-counting PSEP rules. Indeed, the cluster topology of the different cubic cluster categories is highly dependent on several parameters which can be calibrated. 

Clusters Category Antiaromatic Behavior through Minimum ... 

In dissimilarity-based compound selection the required subset of molecules is identified directly, using an appropriate measure of dissimilarity (often taken to be the complement of the similarity). This contrasts with the two-stage procedure in cluster analysis, where it is first necessary to group together the molecules and then decide which to select. Most methods for dissimilarity-based selection fall into one of two categories maximum dissimilarity algorithms and sphere exclusion algorithms [Snarey et al. 1997]. 

Molecular dynamics simulation (MDS) is a powerful tool for the processing mechanism study of silicon surface fabrication. When a particle impacts with a solid surface, what will happen Depending on the interaction between cluster and surface, behaviors of the cluster fall into several categories including implantation [20,21], deposition [22,23], repulsion [24], and emission [25]. Owing to limitations of computer time, the cluster that can be simulated has a diameter of only a few nanometres with a small cohesive energy, which induces the cluster to fragment after collision. 

The premise of this review is that synthetic procedures for very mixed"-metal clusters are comparatively well understood, but that reactivity and physical properties are less well studied. Metal core transformations (modifications of a preexisting cluster) fall into both the synthesis and reactivity categories. A summary is presented here, but as they have been reviewed elsewhere (see Refs. 4, 107-109), the account below is necessarily brief. Section lI.E. 1. considers core transformations where the cluster core nuclearity is pre.served, whereas Section 11.E.2. summarizes reactions involving a change in core size. 

Synthesis methods such as those described earlier for monometallics have been applied with metal carbonyls incorporating two metals. The resultant supported species may be small supported metal clusters [41,42], and, as for monometallics, the usual products are supported species that are nonuniform in both composition and structure [42]. There are several examples of well-defined metal carbonyl clusters in this category but hardly any examples of well-defined decarbonylated bimetalhcs on supports. 

In order to deposit gold on the supports with high dispersion as nanoparticles (NPs) and clusters, there are at least nine techniques which can be classified into five categories well mixed precursors, specific surface interaction, mixing gold colloids [18], physical deposition [19,20], and direct reduction [21]. The former two categories are schematically presented in Figure 3. 

The Cluster Rules reorganized the subcategorization scheme to simplify the categories. Previously, mills were grouped by the types of products manufactured. The Cluster Rules reduced the number of subcategories by grouping mills by similar processes. 

Suppose we have an isolated system with a single unpaired electron and no hyper-fine interaction. Mononuclear low-spin Fe111 and many iron-sulfur clusters fall in this category (cf. Table 4.2). The only relevant interaction is the electronic Zeeman term, so the spin Hamiltonian is... 

Solar-type stars start destroying Li soon after their arrival on the ZAMS. The difference in the average Li between the Pleiades and the 2 Gyr clusters implies depletion timescales of the order of 1 Gyr. After 2 Gyr they become extremely long for part of the stars (Li depletion virtually stops) or very short for another fraction. The Sun belongs to the second category and, as such, it is not representative of all stars with the same mass, age, and metallicity. Li depletion is clearly not a monotonic function of age and at least one additional... 

For each wind energy system category, there is a particular approach of how to apply an electrolyzing hydrogen production unit. The most common application studied currently is the stand-alone wind energy system combined with an electrolyzer. The latter is connected in the place of the battery cluster. The electrolyzer unit can be either a PEM or an alkaline type where there is a constant feed with water. The produced hydrogen is usually stored in a tank at the output pressure of the electrolyzer or compressed at a higher... 

Metalloproteins fall into three main structure categories depending on whether the active site consists of a single coordinated metal atom, a metal-porphyrin unit, or metal atoms in a cluster arrangement. In the context of electron-transfer metalloproteins, the blue Cu proteins, cytochromes, and ferre-doxins respectively are examples of these different structure types. Attention will be confined here mainly to a discussion of the reactivity of the blue Cu protein plastocyanin. Reactions of cytochrome c are also considered, with brief mention of the [2Fe-2S] ferredoxin, and high potential Fe/S protein [HIPIP]. 

When a defect is introduced into a crystalline environment, crystal translational symmetry can no longer be invoked to transform the problem into tractable form as is done in band-structure calculations. Most of the computational treatments of defects in semiconductors rely on approximations to the defect environment that fall into one of three categories cluster, supercell (or cyclic cluster), and Green s function. 

Determination of categories is directly relevant to the determination of syndromes. The DSM has used a syndromal approach to classification that focuses on the identification of clusters of symptoms that are believed to cooccur with enough regularity that we may call them a syndrome. The authors of the DSM believe that identification of syndromes may reflect something important about etiology, course, and treatment. In other words, the DSM taxonomy is based on the idea that syndromes reflect something about their... 

Hierarchical Cluster Analysis (HCA) is a multivariate statistical method that can be used assign groundwater samples or monitoring sites to distinct categories (hydrochemical facies). HCA offers several advantages over other methods of... 

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