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Topic: Cluster (chemistry)

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	Cluster (chemistry) Encyclopedia (Site not responding. Last check: 2007-10-16)
		In chemistry, a cluster is an ensemble of bound atoms intermediate in size between a molecule and a bulk solid.
		Contemporaneously with the development of metal cluster compounds, numerous boron hydrides were discovered by Alfred Stock and his successors who popularized the use of vacuum-lines for the manipulation of volatile, air-sensitive materials.
		Composite clusters of carbon and boron are carboranes.
	www.hallencyclopedia.com /topic/Cluster_(chemistry).html (1333 words)

	Cluster Studies
		The chemical reactions of transition metal clusters are studied as models for heterogeneous catalysis.
		The evidence suggests that it is the electron donating or withdrawing character of the ligand that is the primary influence on the structure of the metal cluster.
		We have recently initiated experimental studies of bimetallic clusters with the aim of determining the locations of the different metal atoms within the cluster structure.
	chemistry.anl.gov /ClusterStudies/ExperimentalCluster.html (849 words)

	The Computational Cluster
		The Boston College Chemistry Department has a computer cluster that can be used for any department research that involves computational intensive calculations.
		The entire cluster is supported by a 6.3 TB Xraid for data storage connected to the head node by a fiber channel.
		Jobs must be submitted to the cluster via a queue system, Platform LSF or LSF for short, on the head node xray.bc.edu.
	www.bc.edu /schools/cas/chemistry/dept/compcluster.html (168 words)

	Cluster Supramolecules
		In the case of the lanthanide cluster species, the stumbling blocks of lability and facile hydrolysis have hindered the development of reliable syntheses, resulting in a large disparity in the understanding of the chemistry of lanthanide clusters relative to their transition metal cousins.
		These cluster derivatives have proven to be very chemically versatile (L may be anything from a halide ion to complex organic ligands) and particularly useful for generating supramolecular species with predictable dimension and architecture.
		The cluster condensation reactions have afforded several novel structural motifs, including discrete molecular squares (for host-guest applications), and star-shaped molecules which are linked by organic chromophores (figure 1).
	quiz2.chem.arizona.edu /zheng/clustersupra.html (833 words)

	duncanlab
		These clusters may consist of only a few atoms of pure metal, mixtures of metals, or metal compounds (carbides, oxides, etc.), or they may be a metal center with one or more molecules attached to it.
		The metal-containing cluster molecules spray out of this (toward the left in this figure) and the center part of this spray goes through the hole in the "skimmer" (the silver cone-shaped device mounted on the left wall).
		Clusters are produced in the source chamber on the right (see expanded photo above) and then they flow through the skimmer into the second chamber at left where the mass spectrometer is loctated.
	www.arches.uga.edu /%7Emaduncan (779 words)

	Mathematical Cluster Chemistry (Site not responding. Last check: 2007-10-16)
		School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
		The application of mathematical methods, such as polyhedral topology, graph theory and group theory, to the study of cluster molecules is reviewed.
		The development of localised orbital and spherical harmonic methods are outlined and there is an introduction to Tensor Surface Harmonic Theory and Group Theory on a Spherical Shell.
	www.tc.bham.ac.uk /~roy/Papers/math.html (91 words)

	Commodity Cluster Computing for Computational Chemistry
		Unfortunately, traditional supercomputers or cluster computing solutions from commercial vendors remain very expensive, even for entry level configurations, and are therefore often beyond the reach of many small to medium-sized research groups and universities.
		Clusters of networked commodity computers provide an alternative computing platform that can offer substantially better price/performance than commercial supercomputers.
		We believe that the Beowulf cluster we have constructed offers the best price/performance ratio for our computational chemistry applications, and that commodity clusters can now provide dedicated supercomputer performance within the budget of most university departments.
	www.beowulf.org /pipermail/test/2000-February/000446.html (321 words)

	Cluster Studies
		Identification and analysis of reaction products are used to determine such cluster properties as geometrical structure, the nature and energetics of adsorbate binding sites on cluster surfaces, the saturation of clusters with adsorbate molecules, and the kinetics of cluster-molecule reactions.
		In the case of Ni, for example, saturation by hydrogen converts the cluster from a double icosahedron to an fcc (or bcc) cluster.
		The evidence suggests that it is the electron donating or withdrawing character of the ligand that is the primary influence on the structure of the metal cluster.
	www.chm.anl.gov /ClusterStudies/ExperimentalCluster.html (849 words)

	Clusters of Aluminum Atoms Found to Have Properties of Other Elements Reveal a New Form of Chemistry
		They found that a cluster of 13 aluminum atoms behaves like a single iodine atom, while a cluster of 14 aluminum atoms behaves like an alkaline earth atom.
		When the researchers substituted the iodine atom with the aluminum cluster, Al13, they observed that the entire chemistry of the compound changed--causing the other iodine molecules to break apart and bind individually to the cluster.
		While the clusters resemble atoms of other elements in their interactions, their chemistry is unique, creating stable compounds with bonds that are not identical to those of single atoms.
	innovations-report.com /html/reports/life_sciences/report-38837.html (677 words)

	AMDboard.com - ClusterVision to Install First AMD Opteron Processor Based Supercomputer Cluster
		The cluster will be used by scientists of the department of Chemistry who use supercomputers to simulate chemical reactions and complex molecular systems.
		The cluster will be running the Linux-based ClusterVisionOS cluster operating system and software environment which includes all software required to effectively use and manage the cluster.
		Clusters can therefore match the performance and stability of traditional supercomputers for a fraction of the cost.
	www.amdboard.com /hn07030301.html (502 words)

	Zirconium Cluster Chemistry
		Synthetic exploration of halide clusters from the group IV and V transition metals, namely, Zr, Hf, Nb, and Ta, has lead to many novel materials with rich structural diversity and redox chemistry.
		The cluster motif most commonly observed in these compounds involves a centered metal octahedron with edge-sharing halide atoms and an electron deficient interstitial atom extending over three dimensions.
		The octahedral disposition of the outer coordination on these clusters is analogous to that of an octahedral metal atom and, therefore, lends itself as a good template for supramolecular assemblies.
	www.chem.tamu.edu /rgroup/hughbanks/research/zir.html (582 words)

	Commodity Cluster Computing for Computational Chemistry (Site not responding. Last check: 2007-10-16)
		In recent years computational chemistry, particularly in the area of electronic structure determination, has seen an explosive growth in the number of researchers using theoretical methods to aid both in interpreting experimental results and designing new experimental strategies.
		Clusters are also easier to maintain, at least in terms of hardware, and can be upgraded cheaply and incrementally, since commodity nodes can easily be added or replaced.
		Parallel chemistry programs may use one or the other based on the type of calculation, the number of processors to be used, and the amount of memory available.
	dhpc.adelaide.edu.au /reports/073/html/dhpc-073.html (12445 words)

	Bioinorganic Chemistry Special Feature: Speculative synthetic chemistry and the nitrogenase problem -- Lee and Holm 100 ...
		Synthetic analogue chemistry nevertheless remains an indispensable component in the armamentarium of bioinorganic investigation.
		congruent by EXAFS criterion to that of the biological cluster.
		The implications raised by the new interstitial ligand and the
	www.pnas.org /cgi/content/full/100/7/3595 (3644 words)

	intas 96-1256 (Site not responding. Last check: 2007-10-16)
		The proposal focuses on the chemistry of chalcogenide cluster complexes of transition elements, where the metal-chalcogenide cores are typically coordinated to inorganic acido ligands or ligands used in organometallic chemistry.
		The main goals are the further development of cluster chemistry in terms of chemical synthesis/ design of less studied compounds, the identification of common trends concerning the properties of clusters based on an investigations of structure and chemical reactivity.
		The study of thermo-destruction of clusters shows that they could be unical precursors for preparing of the materials of definite composition.
	www.intas.be /catalog/961-1256.htm (1453 words)

	Department of Syntheses
		Associated with this chemistry is also the area of related metallacarba/heteroborane chemistry, with emphasis on monoanionic cluster ligands analogous to cyclopentadienyl anion.
		The observed 9®10 rearrangement of the substituted cluster carbon is quite unexpected and is supposed to result from higher thermodynamic stabilities of the 10-substituted isomers.
		The structures of all compounds of type 3 were established by high-field NMR spectroscopy and mass spectrometry, and that of 3d was determined by an X-ray diffraction study.
	www.iic.cas.cz /boron.htm (1388 words)

	Journal of Cluster Science - Catalysis Journals, Books & Online Media \| Springer
		Journal of Cluster Science covers a broad range of topics in basic and applied cluster science in all phases - gas, solution, and crystalline or amorphous solids - including:
		New Wider Scope - To better meet the needs of researchers from every corner of the cluster science community, the editors have expanded the journal's scope to include nanomaterials, complementing its traditional focus on chemistry.
		As a truly interdisciplinary journal, contributions from the fields of chemistry, physics, biology, mathematics, and statistics are most welcome.
	www.springer.com /west/home?SGWID=4-102-70-35540218-0&changeHeader=true&referer=www.wkap.nl&SHORTCUT=www.springer.com/prod/j/1040-7278 (205 words)

	W0220: Design, Synthesis and Structural Studies of Open-Framework Materials in Niobium Oxohalide Cluster Chemistry (Site not responding. Last check: 2007-10-16)
		The most common structural building unit in reduced niobium halides (Cl or Br) and oxides is the Nb -type cluster based on an octahedral Nb core surrounded by two sets of ligands: 12 inner ligands that bridge two Nb atoms; and 6 outer ligands, each bonded to one Nb.
		cluster as our starting motif, we designed new cluster units in which we substituted some inner chlorines with oxide ligands.
		The layers in the novel framework of (I) are built-up from clusters connected to each other through outer-outer chlorine bridges to form large hexagonal voids where the potassium cations are located.
	www.hwi.buffalo.edu /ACA/ACA98/abstracts/text/W0220.html (248 words)

	research-interests (Site not responding. Last check: 2007-10-16)
		Cluster ions can be viewed as an intermediate state of matter between the dilute gas-phase and solution.
		Of particular interest to our group is the chemistry of cluster ions related to atmospheric systems.
		The presence of isomerisation reactions in cluster chemistry may have implications for the environmental models developed in atmospheric science.
	www.science.uottawa.ca /~pmayer/research-interests.html (989 words)

	PCI, Uni Hannover, Prof. Becker
		The clusters are prepared by laser-ablation in a helium flow, isolated in a molecular beam, and optionally trapped in a rare gas matrix.
		The characterisation of clusters in matrices utilizes fourier transform spectroscopy in spectral regions from UV to far-IR as well as Raman spectroscopy.
		Combinatorial chemistry (CC) and high troughput experimentation (HTE) can accelerate the pace od new materials discovery and enable a rapid exploration of a wide range of materials characteristics in parallel and on a miniaturized scale.
	www.pci.uni-hannover.de /~lgpca/clusterchemistry/index.html.en (536 words)

	Department of Chemistry: Seminar (Site not responding. Last check: 2007-10-16)
		Fast-flow reactor studies of the kinetics of transition metal cluster reactions with hydrocarbons have revealed several new insights into cluster chemistry.
		Our earlier work on isobutane reactions with niobium clusters has underscored the importance of a local reaction site model for C-H bond cleavage, that is, one which does not require consideration of the cluster geometry in detail.
		Such effects are expected to be of general importance in the early stages of cluster-molecule reactions, but may not be manifest in the reaction kinetics, depending upon the nature of the transition state and its position in energy with respect to the separated reactants.
	www.chemistry.mcmaster.ca /seminars/9798/chem.980212.html (191 words)

	Water cluster quackery
		The clusters are somehow immune to the ravages of the thermal jostlings to which water molecules are normally subject, and are able to remain intact for weeks or years.
		The clusters are claimed to be essential for transporting water and wastes across cell membranes and for maintaining the structural integrity of proteins, DNA and other biomolecules.
		This is similar to the pseudoscientific concept of homeopathic remedies, except in the latter the imprinting substances are supposed to be those that produce symptoms of the malady to be corrected.
	www.chem1.com /CQ/clusqk.html (10335 words)

	Discovery of organic-metallic multiple-decker sandwich clusters - Opening up cluster chemistry - - MEXT Nanotechnology ...
		As a result, he discovered that sandwich clusters of benzene and a metal could be synthesized with metal atoms belonging to the scandium to chrome groups in the periodic table.
		When the magnetism of vanadium atoms inside the sandwich clusters was measured, their magnetic moment was found to have increased linearly as the number of metal atom is increased.
		These clusters were formed by combining aluminum tridecamer having 39 valence electrons with sodium having a single valence electron, to bring the total amount of valence electrons to the magic number of 40.
	www.nanonet.go.jp /english/mailmag/2004/021a.html (790 words)

	Observations specific to Old Chemistry cluster (Site not responding. Last check: 2007-10-16)
		The Old Chemistry cluster appears to experience periodic high load, with saturation occurring during peak periods of the semester.
		During some periods, the cluster is relatively under-utilized -- situated as it is on the Main West academic quad, it may hold less attraction for residential students than some residential clusters.
		Application usage is typical of a non-residential cluster, with netscape and word still accounting for the majority of use, but with X, Splus, SAS, and minitab making strong showings.
	www.oit.duke.edu /~rob/cluster-usage/1999/pc/oldchem/oldchem.html (91 words)

	Metal Cluster Chemistry: Structure and Stereochemistry in the Polynuclear Rhodium Hybrides HnRhn[P(OR)3]2n -- Brown et ...
		Metal Cluster Chemistry: Structure and Stereochemistry in the Polynuclear Rhodium Hybrides HnRhn[P(OR)3]2n -- Brown et al.
		Metal Cluster Chemistry: Structure and Stereochemistry in the Polynuclear Rhodium Hybrides H
		The significance of this chemistry in the metal clustermetal surface analogy is described.
	www.pnas.org /cgi/content/abstract/76/5/2099 (181 words)

	JCE 2002 (79) 677 [Jun] Transition Metal Carbonyl Cluster Chemistry (by Paul J. Dyson and J. Scott McIndoe) (Site not responding. Last check: 2007-10-16)
		The material will be more familiar to British students, given the past domination of transition metal carbonyl cluster chemistry by Jack Lewis and multiple generations of his subsequent students.
		Chapter 5 is a brief introduction to characterization of transition-metal carbonyl clusters.
		Chapter 10 covers a few of the most famous catalytic reactions in carbonyl cluster chemistry and explains the ideas behind clusters as models for surface reactivity.
	jchemed.chem.wisc.edu /Journal/Issues/2002/Jun/abs677_2.html (750 words)

	[No title]
		The organic chemistry of ruthenium and osmium is an area which has burgeoned during the period since the publication of COMC.
		This is especially true for the cluster chemistry of these elements, which have provided most of the advances in this important field.
		This is because many of the early results in ruthenium and osmium cluster chemistry described in COMC are now much better understood and can thus be placed in a more general context.
	www.shop.com /op/aprod-p20749204 (269 words)

	Site-directed Mutagenesis of the PsaC Subunit of Photosystem I. FB IS THE CLUSTER INTERACTING WITH SOLUBLE FERREDOXIN ... (Site not responding. Last check: 2007-10-16)
		the clusters and the solvent accessibility are important (53-55).
		In each part, the lower cluster lies behind the upper cluster, which means, according to the current structural knowledge of the PSI stromal side, that PsaD and PsaE are lying "behind" and "in front of" the page, respectively (10, 19, 57).
		Fd is most probably binding from the right side as shown (17, 18), and its orientation was chosen with its [2Fe-2S] close to the distal cluster.
	www.jbc.org /cgi/content/full/274/33/23333 (5310 words)

	Computer Systems for Computational Chemistry
		DSB Scientific is now building high-performance workstations designed for use in computational chemistry environments.
		You can configure as a headless cluster (our default configuration) or add keyboard, mouse and monitor(s) to use as simple workstations on an existing network, a network of workstations (with a dedicated back-end communication path) or a workstation cluster.
		Systems are also stress tested for stability using real computational chemistry calculations (not artificial benchmarks).
	www.dsbscience.com /hpc_systems.php (302 words)

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