Science.gov

Sample records for re4q4x124 cluster complexes

  1. Cluster algorithms and computational complexity

    NASA Astrophysics Data System (ADS)

    Li, Xuenan

    Cluster algorithms for the 2D Ising model with a staggered field have been studied and a new cluster algorithm for path sampling has been worked out. The complexity properties of Bak-Seppen model and the Growing network model have been studied by using the Computational Complexity Theory. The dynamic critical behavior of the two-replica cluster algorithm is studied. Several versions of the algorithm are applied to the two-dimensional, square lattice Ising model with a staggered field. The dynamic exponent for the full algorithm is found to be less than 0.5. It is found that odd translations of one replica with respect to the other together with global flips are essential for obtaining a small value of the dynamic exponent. The path sampling problem for the 1D Ising model is studied using both a local algorithm and a novel cluster algorithm. The local algorithm is extremely inefficient at low temperature, where the integrated autocorrelation time is found to be proportional to the fourth power of correlation length. The dynamic exponent of the cluster algorithm is found to be zero and therefore proved to be much more efficient than the local algorithm. The parallel computational complexity of the Bak-Sneppen evolution model is studied. It is shown that Bak-Sneppen histories can be generated by a massively parallel computer in a time that is polylog in the length of the history, which means that the logical depth of producing a Bak-Sneppen history is exponentially less than the length of the history. The parallel dynamics for generating Bak-Sneppen histories is contrasted to standard Bak-Sneppen dynamics. The parallel computational complexity of the Growing Network model is studied. The growth of the network with linear kernels is shown to be not complex and an algorithm with polylog parallel running time is found. The growth of the network with gamma ≥ 2 super-linear kernels can be realized by a randomized parallel algorithm with polylog expected running time.

  2. CLUSTERED K+ CHANNEL COMPLEXES IN AXONS

    PubMed Central

    Rasband, Matthew N.

    2010-01-01

    Voltage-gated K+ (Kv) channels regulate diverse neuronal properties including action potential threshold, amplitude, and duration, frequency of firing, neurotransmitter release, and resting membrane potential. In axons, Kv channels are clustered at a variety of functionally important sites including axon initial segments, juxtaparanodes of myelinated axons, nodes of Ranvier, and cerebellar basket cell terminals. These channels are part of larger protein complexes that include cell adhesion molecules and scaffolding proteins. These interacting proteins play important roles in recruiting K+ channels to distinct axonal domains. Here, I review the composition, functions, and mechanism of localization of these K+ channel complexes in axons. PMID:20816921

  3. Detecting complex network modularity by dynamical clustering

    NASA Astrophysics Data System (ADS)

    Boccaletti, S.; Ivanchenko, M.; Latora, V.; Pluchino, A.; Rapisarda, A.

    2007-04-01

    Based on cluster desynchronization properties of phase oscillators, we introduce an efficient method for the detection and identification of modules in complex networks. The performance of the algorithm is tested on computer generated and real-world networks whose modular structure is already known or has been studied by means of other methods. The algorithm attains a high level of precision, especially when the modular units are very mixed and hardly detectable by the other methods, with a computational effort O(KN) on a generic graph with N nodes and K links.

  4. X-RAY STAR CLUSTERS IN THE CARINA COMPLEX

    SciTech Connect

    Feigelson, Eric D.; Getman, Konstantin V.; Townsley, Leisa K.; Broos, Patrick S.; Povich, Matthew S.; Garmire, Gordon P.; King, Robert R.; Montmerle, Thierry; Preibisch, Thomas; Smith, Nathan; Stassun, Keivan G.; Wang Junfeng; Wolk, Scott; Zinnecker, Hans

    2011-05-01

    The distribution of young stars found in the Chandra Carina Complex Project (CCCP) is examined for clustering structure. X-ray surveys are advantageous for identifying young stellar populations compared to optical and infrared surveys in suffering less contamination from nebular emission and Galactic field stars. The analysis is based on smoothed maps of a spatially complete subsample of {approx}3000 brighter X-ray sources classified as Carina members and {approx}10,000 stars from the full CCCP sample. The principal known clusters are recovered, and some additional smaller groups are identified. No rich embedded clusters are present, although a number of sparse groups are found. The CCCP reveals considerable complexity in clustering properties. The Trumpler 14 and 15 clusters have rich stellar populations in unimodal, centrally concentrated structures several parsecs across. Non-spherical internal structure is seen, and large-scale low surface density distributions surround these rich clusters. Trumpler 16, in contrast, is comprised of several smaller clusters within a circular boundary. Collinder 228 is a third type of cluster which extends over tens of parsecs with many sparse compact groups likely arising from triggered star formation processes. A widely dispersed, but highly populous, distribution of X-ray stars across the {approx}50 pc CCCP mosaic supports a model of past generations of star formation in the region. Collinder 234, a group of massive stars without an associated cluster of pre-main-sequence stars, may be part of this dispersed population.

  5. X-ray Star Clusters in the Carina Complex

    NASA Astrophysics Data System (ADS)

    Feigelson, Eric D.; Getman, Konstantin V.; Townsley, Leisa K.; Broos, Patrick S.; Povich, Matthew S.; Garmire, Gordon P.; King, Robert R.; Montmerle, Thierry; Preibisch, Thomas; Smith, Nathan; Stassun, Keivan G.; Wang, Junfeng; Wolk, Scott; Zinnecker, Hans

    2011-05-01

    The distribution of young stars found in the Chandra Carina Complex Project (CCCP) is examined for clustering structure. X-ray surveys are advantageous for identifying young stellar populations compared to optical and infrared surveys in suffering less contamination from nebular emission and Galactic field stars. The analysis is based on smoothed maps of a spatially complete subsample of ~3000 brighter X-ray sources classified as Carina members and ~10,000 stars from the full CCCP sample. The principal known clusters are recovered, and some additional smaller groups are identified. No rich embedded clusters are present, although a number of sparse groups are found. The CCCP reveals considerable complexity in clustering properties. The Trumpler 14 and 15 clusters have rich stellar populations in unimodal, centrally concentrated structures several parsecs across. Non-spherical internal structure is seen, and large-scale low surface density distributions surround these rich clusters. Trumpler 16, in contrast, is comprised of several smaller clusters within a circular boundary. Collinder 228 is a third type of cluster which extends over tens of parsecs with many sparse compact groups likely arising from triggered star formation processes. A widely dispersed, but highly populous, distribution of X-ray stars across the ~50 pc CCCP mosaic supports a model of past generations of star formation in the region. Collinder 234, a group of massive stars without an associated cluster of pre-main-sequence stars, may be part of this dispersed population.

  6. Symmetries, Cluster Synchronization, and Isolated Desynchronization in Complex Networks

    NASA Astrophysics Data System (ADS)

    Pecora, Louis

    2015-03-01

    Many networks are observed to produce patterns of synchronized clusters, but it has been difficult to predict these clusters in general or understand the conditions for their formation. We show the intimate connection between network symmetry and cluster synchronization. We apply computational group theory to reveal the clusters and determine their stability. In complex networks the symmetries can number in the millions, billions, and more. The connection between symmetry and cluster synchronization is experimentally explored using an electro-optic network. We observe and explain a surprising and common phenomenon (isolated desynchronization) in which some clusters lose synchrony while leaving others connected to them synchronized. We show the isolated desynchronization is intimately related to the decomposition of the group of symmetries into subgroups. The results could guide the design of new power grid systems or lead to new understanding of the dynamical behavior of networks ranging from neural to social.

  7. Multiscale ensemble clustering for finding modules in complex networks

    NASA Astrophysics Data System (ADS)

    Kim, Eun-Youn; Hwang, Dong-Uk; Ko, Tae-Wook

    2012-02-01

    The identification of modules in complex networks is important for the understanding of systems. Here, we propose an ensemble clustering method incorporating node groupings in various sizes and the sequential removal of weak ties between nodes which are rarely grouped together. This method successfully detects modules in various networks, such as hierarchical random networks and the American college football network, with known modular structures. Some of the results are compared with those obtained by modularity optimization and K-means clustering.

  8. Water clusters in mixed ionic complexes with metal dipicolinate anions

    NASA Astrophysics Data System (ADS)

    Das, Babulal; Baruah, Jubaraj B.

    2013-02-01

    Formations of three different types of hydrogen-bonded water clusters in the interstices of mixed ionic complexes with metal dipicolinate anions are reported. In the complex [Co(phen)2(H2O)2][Zn(dpa)2]ṡ7H2O (1) (where phen = 1,10-phenanthroline, dpa = dipicolinate), both the cation and anion is hydrophilic in nature, exhibits an unusual 2D infinite cyclic water decamers (H2O)10 stabilized by four identical zinc dipicolinato complex anions. Modulating the cationic unit to a hydrophobic environment by replacing the aqua ligand with 2,2'-bipyridine ligand the water cluster can be modified. The complex [Ni(phen)2ṡbpy][Co(dpa)2]ṡ8H2O (2) (where bpy = 2,2'-bipyridine) has unprecedented discrete hydrogen bonded hexadecameric (H2O)16 water clusters encapsulated between eight anionic units. A rare wavelike infinite water chain (H2O)n is observed in complex [Co(phen)3][Mn(dpa)2]ṡ12H2O (3), in this case the water chain fills the interstitial space created by packing of large hydrophilic anionic units and hydrophobic cationic units. The reported clusters are indefinitely stable in their respective complex at ambient temperature, but the water loss is irreversible when thermally decomposed.

  9. Mathematical modelling of complex contagion on clustered networks

    NASA Astrophysics Data System (ADS)

    O'sullivan, David J.; O'Keeffe, Gary; Fennell, Peter; Gleeson, James

    2015-09-01

    The spreading of behavior, such as the adoption of a new innovation, is influenced bythe structure of social networks that interconnect the population. In the experiments of Centola (Science, 2010), adoption of new behavior was shown to spread further and faster across clustered-lattice networks than across corresponding random networks. This implies that the “complex contagion” effects of social reinforcement are important in such diffusion, in contrast to “simple” contagion models of disease-spread which predict that epidemics would grow more efficiently on random networks than on clustered networks. To accurately model complex contagion on clustered networks remains a challenge because the usual assumptions (e.g. of mean-field theory) regarding tree-like networks are invalidated by the presence of triangles in the network; the triangles are, however, crucial to the social reinforcement mechanism, which posits an increased probability of a person adopting behavior that has been adopted by two or more neighbors. In this paper we modify the analytical approach that was introduced by Hebert-Dufresne et al. (Phys. Rev. E, 2010), to study disease-spread on clustered networks. We show how the approximation method can be adapted to a complex contagion model, and confirm the accuracy of the method with numerical simulations. The analytical results of the model enable us to quantify the level of social reinforcement that is required to observe—as in Centola’s experiments—faster diffusion on clustered topologies than on random networks.

  10. Deciphering the global organization of clustering in real complex networks

    PubMed Central

    Colomer-de-Simón, Pol; Serrano, M. Ángeles; Beiró, Mariano G.; Alvarez-Hamelin, J. Ignacio; Boguñá, Marián

    2013-01-01

    We uncover the global organization of clustering in real complex networks. To this end, we ask whether triangles in real networks organize as in maximally random graphs with given degree and clustering distributions, or as in maximally ordered graph models where triangles are forced into modules. The answer comes by way of exploring m-core landscapes, where the m-core is defined, akin to the k-core, as the maximal subgraph with edges participating in at least m triangles. This property defines a set of nested subgraphs that, contrarily to k-cores, is able to distinguish between hierarchical and modular architectures. We find that the clustering organization in real networks is neither completely random nor ordered although, surprisingly, it is more random than modular. This supports the idea that the structure of real networks may in fact be the outcome of self-organized processes based on local optimization rules, in contrast to global optimization principles. PMID:23982757

  11. Stellar Clusters in the NGC 6334 Star-Forming Complex

    NASA Astrophysics Data System (ADS)

    Feigelson, Eric D.; Martin, Amanda L.; McNeill, Collin J.; Broos, Patrick S.; Garmire, Gordon P.

    2009-07-01

    The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, has not been well sampled in past studies. We analyze here a mosaic of two Chandra X-ray Observatory images of the region using sensitive data analysis methods, giving a list of 1607 faint X-ray sources with arcsecond positions and approximate line-of-sight absorption. About 95% of these are expected to be cluster members, most lower mass pre-main-sequence stars. Extrapolating to low X-ray levels, the total stellar population is estimated to be 20,000-30,000 pre-main-sequence stars. The X-ray sources show a complicated spatial pattern with ~10 distinct star clusters. The heavily obscured clusters are mostly associated with previously known far-infrared sources and radio H II regions. The lightly obscured clusters are mostly newly identified in the X-ray images. Dozens of likely OB stars are found, both in clusters and dispersed throughout the region, suggesting that star formation in the complex has proceeded over millions of years. A number of extraordinarily heavily absorbed X-ray sources are associated with the active regions of star formation.

  12. STELLAR CLUSTERS IN THE NGC 6334 STAR-FORMING COMPLEX

    SciTech Connect

    Feigelson, Eric D.; Martin, Amanda L.; McNeill, Collin J.; Broos, Patrick S.; Garmire, Gordon P.

    2009-07-15

    The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, has not been well sampled in past studies. We analyze here a mosaic of two Chandra X-ray Observatory images of the region using sensitive data analysis methods, giving a list of 1607 faint X-ray sources with arcsecond positions and approximate line-of-sight absorption. About 95% of these are expected to be cluster members, most lower mass pre-main-sequence stars. Extrapolating to low X-ray levels, the total stellar population is estimated to be 20,000-30,000 pre-main-sequence stars. The X-ray sources show a complicated spatial pattern with {approx}10 distinct star clusters. The heavily obscured clusters are mostly associated with previously known far-infrared sources and radio H II regions. The lightly obscured clusters are mostly newly identified in the X-ray images. Dozens of likely OB stars are found, both in clusters and dispersed throughout the region, suggesting that star formation in the complex has proceeded over millions of years. A number of extraordinarily heavily absorbed X-ray sources are associated with the active regions of star formation.

  13. UV and VUV Ionization of Organic Molecules, Clusters, and Complexes

    NASA Astrophysics Data System (ADS)

    Marksteiner, Markus; Haslinger, Philipp; Sclafani, Michele; Ulbricht, Hendrik; Arndt, Markus

    2009-08-01

    The generation of organic particle beams is studied in combination with photoionization using UV radiation at 266 nm and vacuum ultraviolet (VUV) light at 157 nm. Single-photon ionization with pulsed VUV light turns out to be sensitive enough to detect various large neutral biomolecular complexes ranging from metal-amino acid complexes to nucleotide clusters and aggregates of polypeptides. Different biomolecular clusters are shown to exhibit rather specific binding characteristics with regard to the various metals that are codesorbed in the source. We also find that the ion signal of gramicidin can be increased by a factor of 15 when the photon energy is increased from 4.66 to 7.9 eV.

  14. Cage Opening of a Carborane Ligand by Metal Cluster Complexes.

    PubMed

    Adams, Richard D; Kiprotich, Joseph; Peryshkov, Dmitry V; Wong, Yuen Onn

    2016-05-01

    The reaction of Os3 (CO)10 (NCMe)2 with closo-o-C2 B10 H10 has yielded two interconvertible isomers Os3 (CO)9 (μ3 -4,5,9-C2 B10 H8 )(μ-H)2 (1 a) and Os3 (CO)9 (μ3 -3,4,8-C2 B10 H8 )(μ-H)2 (1 b) formed by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster. Two BH bonds of the o-C2 B10 H10 were activated in its addition to the osmium cluster. A second triosmium cluster was added to the 1 a/1 b mixture to yield the complex Os3 (CO)9 (μ-H)2 (μ3 -4,5,9-μ3 -7,11,12-C2 B10 H7 )Os3 (CO)9 (μ-H)3 (2) that contains two triosmium triangles attached to the same carborane cage. When heated, 2 was transformed to the complex Os3 (CO)9 (μ-H)(μ3 -3,4,8-μ3 -7,11,12-C2 B10 H8 )Os3 (CO)9 (μ-H) (3) by a novel opening of the carborane cage with loss of H2 . PMID:26971388

  15. The globular cluster system of NGC 1316. III. Kinematic complexity

    NASA Astrophysics Data System (ADS)

    Richtler, T.; Hilker, M.; Kumar, B.; Bassino, L. P.; Gómez, M.; Dirsch, B.

    2014-09-01

    discernable out to 3' radius. The kinematic major axis of NGC 1316 is misaligned by about 10° with the photometric major axis, which might indicate a triaxial symmetry. A simple spherical model like that suggested by dynamical analyses of planetary nebulae also reproduces the velocity dispersions of the faint globular clusters. Conclusions: The central dark matter density of the present model resembles a giant elliptical galaxy. This contradicts population properties which indicate spiral galaxies as pre-merger components. Modified Newtonian dynamics (MOND) would provide a solution, but the kinematical complexity of NGC 1316 does not allow a really firm conclusion. However, NGC 1316 might anyway be a problem for a cold dark matter scenario, if the high dark matter density in the inner region is confirmed in future studies. Based on observations obtained with the VLT at ESO, Cerro Paranal, Chile under the programme 078.B-0856.Appendices are available in electronic form at http://www.aanda.org

  16. Knockout driven reactions in complex molecules and their clusters

    NASA Astrophysics Data System (ADS)

    Gatchell, Michael; Zettergren, Henning

    2016-08-01

    Energetic ions lose some of their kinetic energy when interacting with electrons or nuclei in matter. Here, we discuss combined experimental and theoretical studies on such impulse driven reactions in polycyclic aromatic hydrocarbons (PAHs), fullerenes, and pure or mixed clusters of these molecules. These studies show that the nature of excitation is important for how complex molecular systems respond to ion/atom impact. Rutherford-like nuclear scattering processes may lead to prompt atom knockout and formation of highly reactive fragments, while heating of the molecular electron clouds in general lead to formation of more stable and less reactive fragments. In this topical review, we focus on recent studies of knockout driven reactions, and present new calculations of the angular dependent threshold (displacement) energies for such processes in PAHs. The so-formed fragments may efficiently form covalent bonds with neighboring molecules in clusters. These unique molecular growth processes may be important in astrophysical environments such as low velocity shock waves.

  17. Adaptive clustering algorithm for community detection in complex networks.

    PubMed

    Ye, Zhenqing; Hu, Songnian; Yu, Jun

    2008-10-01

    Community structure is common in various real-world networks; methods or algorithms for detecting such communities in complex networks have attracted great attention in recent years. We introduced a different adaptive clustering algorithm capable of extracting modules from complex networks with considerable accuracy and robustness. In this approach, each node in a network acts as an autonomous agent demonstrating flocking behavior where vertices always travel toward their preferable neighboring groups. An optimal modular structure can emerge from a collection of these active nodes during a self-organization process where vertices constantly regroup. In addition, we show that our algorithm appears advantageous over other competing methods (e.g., the Newman-fast algorithm) through intensive evaluation. The applications in three real-world networks demonstrate the superiority of our algorithm to find communities that are parallel with the appropriate organization in reality. PMID:18999501

  18. Petaflop hydrokinetic simulations of complex flows on massive GPU clusters

    NASA Astrophysics Data System (ADS)

    Bernaschi, M.; Bisson, M.; Fatica, M.; Melchionna, S.; Succi, S.

    2013-02-01

    We present recent extensions of the MUPHY computational framework for multi-scale simulation of complex bio-fluidic phenomena in real-life geometries. The new framework, which builds on concurrent advances of the computational modeling and parallelization techniques, is able to simulate suspensions with several hundreds of millions of finite-size bodies, interacting with each other and with the surrounding fluid, in geometries of realistic anatomic complexity. Blood flow through the human coronary arteries, at physiological hematocrit values, is simulated with a spatial resolution of 10 micrometers, comparable with the size of red blood cells. The simulation exhibits excellent parallel scalability on a cluster of 4000 M2050 Nvidia GPUs, with an aggregate performance close to 1 Petaflop/s.

  19. Radical AdoMet enzymes in complex metal cluster biosynthesis.

    PubMed

    Duffus, Benjamin R; Hamilton, Trinity L; Shepard, Eric M; Boyd, Eric S; Peters, John W; Broderick, Joan B

    2012-11-01

    Radical S-adenosylmethionine (AdoMet) enzymes comprise a large superfamily of proteins that engage in a diverse series of biochemical transformations through generation of the highly reactive 5'-deoxyadenosyl radical intermediate. Recent advances into the biosynthesis of unique iron-sulfur (FeS)-containing cofactors such as the H-cluster in [FeFe]-hydrogenase, the FeMo-co in nitrogenase, as well as the iron-guanylylpyridinol (FeGP) cofactor in [Fe]-hydrogenase have implicated new roles for radical AdoMet enzymes in the biosynthesis of complex inorganic cofactors. Radical AdoMet enzymes in conjunction with scaffold proteins engage in modifying ubiquitous FeS precursors into unique clusters, through novel amino acid decomposition and sulfur insertion reactions. The ability of radical AdoMet enzymes to modify common metal centers to unusual metal cofactors may provide important clues into the stepwise evolution of these and other complex bioinorganic catalysts. This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology. PMID:22269887

  20. Synthesis of supramolecular iron (III) complexes by cluster aggregation

    NASA Astrophysics Data System (ADS)

    Seddon, Elisa Joy

    2000-12-01

    Biologically, iron is a ubiquitous and versatile metal, found in the active sites of proteins responsible for both oxygen and electron transport. Multinuclear iron-oxo proteins are either dinuclear, or contain many iron atoms; the [Fe2O] unit occurs in hemerythrin (Hr), ribonucleotide reductase, purple acid phosphatase (POP) and methane monooxygenase (MMO), whereas ferritin (Ft) can store up to 4500 iron atoms. Iron storage and transport are essential for protecting biological organisms from free iron, since free Fe(II) ions, will react with dioxygen to form destructive organic radicals, and free Fe(III) ions form insoluble iron hydroxide aggregates under physiological conditions. The tendency of iron to form molecular aggregates in systems containing water or alcohol, together with the fact that each iron atom possesses a large number of unpaired electrons (5 for high-spin FeIII) often results in products possessing large spin ground states (S). The current record-holder for iron is a Fe19 complex, with at least 33 unpaired electrons in the ground state (S = 33/2). Hence, iron is also important in the rapidly developing field of molecular magnetic materials. For these two reasons, the preparation of iron clusters with new topologies and properties has become a major goal of many synthetic inorganic groups, including our own. In this thesis work, synthetic and spectroscopic methods of inorganic coordination chemistry were used to achieve two different goals: firstly, to synthesize dinuclear iron complexes with the use of tetradentate ligands in order to study the magnetic interactions between the two metal centers; and secondly, to identify reactions and characterize the products whereby pre-formed iron oxide clusters undergo aggregation reactions to produce higher nuclearity products. The tetradentate ligands investigated were a bis-(beta-diketone) ligand L and a bis-bpy ligand L'. The reactions involving L and Fe(III) reagents produced complexes with a triple

  1. Unsaturated platinum-rhenium cluster complexes. Synthesis, structures and reactivity.

    PubMed

    Adams, Richard D; Captain, Burjor; Smith, Mark D; Beddie, Chad; Hall, Michael B

    2007-05-01

    Two new compounds PtRe3(CO)12(PBut3)(micro-H)3, 9, and PtRe2(CO)9(PBut3)(micro-H)2, 10, were obtained from the reaction of Pt(PBut3)2 with Re3(CO)12(micro-H3), 8, at room temperature. Compound 9 contains a butterfly cluster of four metals formed by the insertion of the platinum atom from a Pt(PBut3) group into one of the hydride-bridged metal-metal bonds of 8. The three hydrido ligands are bridging ligands across each of three new Pt-Re bonds. Compound 10 contains a triangular PtRe2 cluster with two hydrido ligands; one bridges a Pt-Re bond, and the other bridges the Re-Re bond. The new compound Pt2Re2(CO)7(PBut3)2(micro-H)2, 11, was obtained from the reaction of 8 with Pt(PBut3)2 in hexane at reflux. Compound 11 was also obtained from 10 by reaction with an additional quantity of Pt(PBut3)2. Compound 11 contains a tetrahedral cluster of four metal atoms with two dynamically active hydrido ligands. A CO ligand on one of the two platinum atoms also exchanges between the two platinum atoms rapidly on the NMR time scale. Compound 11 is electronically unsaturated and was found to add hydrogen at room temperature to form the tetrahydrido cluster complex, Pt2Re2(CO)7(PBut3)2(micro-H)4, 12. Compound 12 has a structure similar to 11 but contains one triply bridging hydrido ligand, two edge bridging hydrido ligands, and one terminal hydrido ligand on one of the two platinum atoms. A kinetic isotope effect D/H of 1.5(1) was determined for the addition of H2 to 11. Hydrogen can be eliminated from 12 by heating to 97 degrees C or by the application of UV-vis irradiation at room temperature. Compound 12 adds CO at room temperature to yield the complex Pt2Re2(CO)8(PBut3)2(micro-H)4, 13, which contains a planar cluster of four metal atoms with a Pt-Pt bond and four edge bridging hydrido ligands. Compounds 11 and 12 react with Pt(PBut3)2 to yield the known five metal cluster complexes Pt3Re2(CO)6(PBut3)3(micro-H)2, 14, and Pt3Re2(CO)6(PBut3)3(micro-H)4, 15, respectively. Density

  2. Mono- and Dinuclear Macrocyclic Calcium Complexes as Platforms for Mixed-Metal Complexes and Clusters.

    PubMed

    Connolly, Emma A; Leeland, James W; Love, Jason B

    2016-01-19

    Mono- and dinuclear calcium complexes of the Schiff-base macrocycles H4L have been prepared and characterized spectroscopically and crystallographically. In the formation of Ca(THF)2(H2L(1)), Ca2(THF)2(μ-THF)(L(1)), and Ca2(THF)4(L(2)), the ligand framework adopts a bowl-shaped conformation instead of the conventional wedge, Pacman-shaped structure as seen with the anthracenyl-hinged complex Ca2(py)5(L(3)). The mononuclear calcium complex Ca(THF)2(H2L(1)) reacts with various equivalents of LiN(SiMe3)2 to form calcium/alkali metal clusters and dinuclear transition metal complexes when reacted subsequently with transition metal salts. The dinuclear calcium complex Ca2(THF)2(μ-THF)(L(1)), when reacted with various equivalents of NaOH, is shown to act as a platform for the formation of calcium/alkali metal hydroxide clusters, displaying alternate wedged and bowl-shaped conformations. PMID:26709870

  3. Synthesis and characterization of reduced tungsten sulfide cluster complexes

    SciTech Connect

    Zhang, Xiang.

    1991-06-27

    Reduction of tungsten(IV) chloride with metals was studied in order to find a high-yield and convenient preparation of {alpha}-tungsten (II) chloride. The reduction of tungsten(IV) chloride with iron metal proved to be the most convenient and reliable synthesis, with a good yield of 60%. The reactions between {alpha}-tungsten(II) chloride and sodium hydrosulfide were investigated. Complete substitution of sulfide for chloride in W{sub 6}Cl{sub 8}{sup 4+} was achieved in the presence of sodium n-butoxide in pyridine solution. Single crystals were grown at elevated temperature (200{degrees}C) in pyridine, and the structure of W{sub 6}S{sub 8}(py){sub 6} was determined by single crystal x-ray techniques. The triethylphosphine (PEt{sub 3}) and tetrahydrothiophene (THT) complexes of W{sub 6}S{sub 8} were established by ligand displacement of pyridine in W{sub 6}S{sub 8}(py){sub 6}. Structures for both W{sub 6}S{sub 8}(PEt{sub 3}){sub 6}. 1.44CH{sub 2}Cl{sub 2} and W{sub 6}S{sub 8}(THT){sub 6} were determined by single crystal x-ray diffraction. These molecular complexes of the W{sub 6}S{sub 8} cluster were also characterized by infrared spectroscopy. 86 refs., 19 figs., 22 tabs.

  4. ClusterViSu, a method for clustering of protein complexes by Voronoi tessellation in super-resolution microscopy

    PubMed Central

    Andronov, Leonid; Orlov, Igor; Lutz, Yves; Vonesch, Jean-Luc; Klaholz, Bruno P.

    2016-01-01

    Super-resolution microscopy (PALM, STORM etc.) provides a plethora of fluorescent signals in dense cellular environments which can be difficult to interpret. Here we describe ClusterViSu, a method for image reconstruction, visualization and quantification of labelled protein clusters, based on Voronoi tessellation of the individual fluorescence events. The general applicability of this clustering approach for the segmentation of super-resolution microscopy data, including for co-localization, is illustrated on a series of important biological objects such as chromatin complexes, RNA polymerase, nuclear pore complexes and microtubules. PMID:27068792

  5. FAINT FUZZY STAR CLUSTERS IN NGC 1023 AS REMNANTS OF MERGED STAR CLUSTER COMPLEXES

    SciTech Connect

    Bruens, R. C.; Kroupa, P.; Fellhauer, M. E-mail: pavel@astro.uni-bonn.de

    2009-09-10

    In the lenticular galaxy NGC 1023 a third population of globular clusters (GCs), called faint fuzzies (FFs), was discovered next to the blue and red GC populations by Larsen and Brodie. While these FFs have colors comparable to the red population, the new population is fainter, larger (R{sub eff}>7 pc) and, most importantly, shows clear signs of corotation with the galactic disk of NGC 1023. We present N-body simulations verifying the hypothesis that these disk-associated FFs are related to the young massive cluster complexes (CCs) observed by Bastian et al. in M51, who discovered a mass-radius relation for these CCs. Our models have an initial configuration based on the observations from M51 and are placed on various orbits in a galactic potential derived for NGC 1023. All computations end up with a stable object containing 10%-60% of the initial CC mass after an integration time of 5 Gyr. A conversion to visual magnitudes demonstrates that the resulting objects cover exactly the observed range for FFs. Moreover, the simulated objects show projected half-mass radii between 3.6 and 13.4 pc, in good agreement with the observed FF sizes. We conclude that objects like the young massive CCs in M51 are likely progenitors of the FFs observed in NGC 1023.

  6. Complexes and clusters of water relevant to atmospheric chemistry: H2O complexes with oxidants.

    PubMed

    Sennikov, Petr G; Ignatov, Stanislav K; Schrems, Otto

    2005-03-01

    Experimental observations and data from quantum chemical calculations on complexes between water molecules and small, oxygen-containing inorganic species that play an important role as oxidants in the atmosphere (O(1D), O(3P), O2(X3sigmag), O2(b1sigmag+), O3, HO, HOO, HOOO, and H2O2) are reviewed, with emphasis on their structure, hydrogen bonding, interaction energies, thermodynamic parameters, and infrared spectra. In recent years, weakly bound complexes containing water have increasingly attracted scientific attention. Water in all its phases is a major player in the absorption of solar and terrestrial radiation. Thus, complexes between water and other atmospheric species may have a perceivable influence on the radiative balance and contribute to the greenhouse effect, even though their concentrations are low. In addition, they can play an important role in the chemistry of the Earth's atmosphere, particularly in the oxidation of trace gases. Apart from gas-phase complexes, the interactions of oxidants with ice surfaces have also received considerable advertency lately due to their importance in the chemistry of snow, ice clouds, and ice surfaces (e.g., ice shields in polar regions). In paleoclimate--respectively paleoenvironmental--studies, it is essential to understand the transfer processes from the atmosphere to the ice surface. Consequently, special attention is being paid here to the intercomparison of the properties of binary complexes and the complexes and clusters of more complicated compositions, including oxidants adsorbed on ice surfaces, where ice is considered a kind of large water cluster. Various facts concerning the chemistry of the Earth's atmosphere (concentration profiles and possible influence on radical reactions in the atmosphere) are discussed. PMID:15799459

  7. On the complexity of some quadratic Euclidean 2-clustering problems

    NASA Astrophysics Data System (ADS)

    Kel'manov, A. V.; Pyatkin, A. V.

    2016-03-01

    Some problems of partitioning a finite set of points of Euclidean space into two clusters are considered. In these problems, the following criteria are minimized: (1) the sum over both clusters of the sums of squared pairwise distances between the elements of the cluster and (2) the sum of the (multiplied by the cardinalities of the clusters) sums of squared distances from the elements of the cluster to its geometric center, where the geometric center (or centroid) of a cluster is defined as the mean value of the elements in that cluster. Additionally, another problem close to (2) is considered, where the desired center of one of the clusters is given as input, while the center of the other cluster is unknown (is the variable to be optimized) as in problem (2). Two variants of the problems are analyzed, in which the cardinalities of the clusters are (1) parts of the input or (2) optimization variables. It is proved that all the considered problems are strongly NP-hard and that, in general, there is no fully polynomial-time approximation scheme for them (unless P = NP).

  8. Effect of mitochondrial complex I inhibition on Fe-S cluster protein activity

    SciTech Connect

    Mena, Natalia P.; Bulteau, Anne Laure; Salazar, Julio; Hirsch, Etienne C.; Nunez, Marco T.

    2011-06-03

    Highlights: {yields} Mitochondrial complex I inhibition resulted in decreased activity of Fe-S containing enzymes mitochondrial aconitase and cytoplasmic aconitase and xanthine oxidase. {yields} Complex I inhibition resulted in the loss of Fe-S clusters in cytoplasmic aconitase and of glutamine phosphoribosyl pyrophosphate amidotransferase. {yields} Consistent with loss of cytoplasmic aconitase activity, an increase in iron regulatory protein 1 activity was found. {yields} Complex I inhibition resulted in an increase in the labile cytoplasmic iron pool. -- Abstract: Iron-sulfur (Fe-S) clusters are small inorganic cofactors formed by tetrahedral coordination of iron atoms with sulfur groups. Present in numerous proteins, these clusters are involved in key biological processes such as electron transfer, metabolic and regulatory processes, DNA synthesis and repair and protein structure stabilization. Fe-S clusters are synthesized mainly in the mitochondrion, where they are directly incorporated into mitochondrial Fe-S cluster-containing proteins or exported for cytoplasmic and nuclear cluster-protein assembly. In this study, we tested the hypothesis that inhibition of mitochondrial complex I by rotenone decreases Fe-S cluster synthesis and cluster content and activity of Fe-S cluster-containing enzymes. Inhibition of complex I resulted in decreased activity of three Fe-S cluster-containing enzymes: mitochondrial and cytosolic aconitases and xanthine oxidase. In addition, the Fe-S cluster content of glutamine phosphoribosyl pyrophosphate amidotransferase and mitochondrial aconitase was dramatically decreased. The reduction in cytosolic aconitase activity was associated with an increase in iron regulatory protein (IRP) mRNA binding activity and with an increase in the cytoplasmic labile iron pool. Since IRP activity post-transcriptionally regulates the expression of iron import proteins, Fe-S cluster inhibition may result in a false iron deficiency signal. Given that

  9. Complex dynamics of synergistic coinfections on realistically clustered networks

    PubMed Central

    Hébert-Dufresne, Laurent; Althouse, Benjamin M.

    2015-01-01

    We investigate the impact of contact structure clustering on the dynamics of multiple diseases interacting through coinfection of a single individual, two problems typically studied independently. We highlight how clustering, which is well known to hinder propagation of diseases, can actually speed up epidemic propagation in the context of synergistic coinfections if the strength of the coupling matches that of the clustering. We also show that such dynamics lead to a first-order transition in endemic states, where small changes in transmissibility of the diseases can lead to explosive outbreaks and regions where these explosive outbreaks can only happen on clustered networks. We develop a mean-field model of coinfection of two diseases following susceptible-infectious-susceptible dynamics, which is allowed to interact on a general class of modular networks. We also introduce a criterion based on tertiary infections that yields precise analytical estimates of when clustering will lead to faster propagation than nonclustered networks. Our results carry importance for epidemiology, mathematical modeling, and the propagation of interacting phenomena in general. We make a call for more detailed epidemiological data of interacting coinfections. PMID:26195773

  10. Carbon-vacancy complexes as traps for self-interstitial clusters in Fe-C alloys

    NASA Astrophysics Data System (ADS)

    Anento, N.; Serra, A.

    2013-09-01

    Self-interstitial loops in irradiated Fe-C alloys are formed by the growth of small self-interstitial atom clusters created directly in cascades. For these clusters to grow up to visible sizes they should be stopped by traps otherwise they would disappear in sinks due to their high one dimensional mobility. The well-known affinity of carbon with vacancies in α-Fe leads to the formation of carbon-vacancy (C-V) complexes that are potential candidates as traps for SIA loops. Applying molecular static simulations we have studied the interaction between the most abundant C-V complexes and SIA clusters using a metallic covalent interatomic model for the Fe-C system. The complexes studied, {Cn-Vm}, are C-V, C-V2 and C2-V. The maximum binding energies obtained for the interaction with a 1/2 <1 1 1> 61SIA cluster are 0.75 eV for the C-V, 1.4 eV for the C-V2 and 1.5 eV for C2-V. Finally, additional MD simulations were used to check the stability of the traps at high temperature. C-V} complexes have higher binding energies than single C atoms and their interaction depends strongly on their position relative to the SIA cluster. The vacancies of the complexes only recombine with the interstitials when they are at the edge of the cluster. The C-V2 complex located in the central region of the cluster has a binding energy of 1.4 eV which results in a good trap for the cluster. In this case the efficiency of a di-vacancy to stop the movement of the cluster is enhanced by the C atom that contributes to the binding energy and inhibits the vacancies to migrate to the cluster edge. C2-V extends to high temperatures the effectiveness of C-V2 as a trap at low temperatures. For this complex the higher interaction occurs at the periphery of the cluster when the vacancy recombination leaves two C atoms strongly tight with a binding energy up to 1.5 eV. Both linear and adjacent configurations are stable and should coexist. Since their binding energies with the cluster are comparable, the

  11. Intrafamilial cluster of pulmonary tuberculosis due to Mycobacterium bovis of the African 1 clonal complex.

    PubMed

    Godreuil, S; Jeziorski, E; Bañuls, A L; Fraisse, T; Van de Perre, P; Boschiroli, M L

    2010-12-01

    A new clonal complex of Mycobacterium bovis present at high frequency in cattle from west central African countries has been described as the African 1 (Af1) clonal complex. Here, the first intrafamilial cluster of human tuberculosis cases due to M. bovis Af1 clonal complex strains is reported. We discuss hypotheses regarding modes of transmission. PMID:20980573

  12. Reconstructing Histories of Complex Gene Clusters on a Phylogeny

    NASA Astrophysics Data System (ADS)

    Vinař, Tomáš; Brejová, Broňa; Song, Giltae; Siepel, Adam

    Clusters of genes that have evolved by repeated segmental duplication present difficult challenges throughout genomic analysis, from sequence assembly to functional analysis. These clusters are one of the major sources of evolutionary innovation, and they are linked to multiple diseases, including HIV and a variety of cancers. Understanding their evolutionary histories is a key to the application of comparative genomics methods in these regions of the genome. We propose a probabilistic model of gene cluster evolution on a phylogeny, and an MCMC algorithm for reconstruction of duplication histories from genomic sequences in multiple species. Several projects are underway to obtain high quality BAC-based assemblies of duplicated clusters in multiple species, and we anticipate use of our methods in their analysis. Supplementary materials are located at http://compbio.fmph.uniba.sk/suppl/09recombcg/

  13. Dynamic Expression of DNA Complexation with Self-assembled Biomolecular Clusters.

    PubMed

    Bartolami, Eline; Bessin, Yannick; Gervais, Virginie; Dumy, Pascal; Ulrich, Sébastien

    2015-08-24

    We report herein the implementation of a dynamic covalent chemistry approach to the generation of multivalent clusters for DNA recognition. We show that biomolecular clusters can be expressed in situ by a programmed self-assembly process using chemoselective ligations. The cationic clusters are shown, by fluorescence displacement assay, gel electrophoresis and isothermal titration calorimetry, to effectively complex DNA through multivalent interactions. The reversibility of the ligation was exploited to demonstrate that template effects occur, whereby DNA imposes component selection in order to favor the most active DNA-binding clusters. Furthermore, we show that a chemical effector can be used to trigger DNA release through component exchange reactions. PMID:26177835

  14. Frataxin Accelerates [2Fe-2S] Cluster Formation on the Human Fe–S Assembly Complex

    PubMed Central

    Fox, Nicholas G.; Das, Deepika; Chakrabarti, Mrinmoy; Lindahl, Paul A.; Barondeau, David P.

    2015-01-01

    Iron–sulfur (Fe–S) clusters function as protein cofactors for a wide variety of critical cellular reactions. In human mitochondria, a core Fe–S assembly complex [called SDUF and composed of NFS1, ISD11, ISCU2, and frataxin (FXN) proteins] synthesizes Fe–S clusters from iron, cysteine sulfur, and reducing equivalents and then transfers these intact clusters to target proteins. In vitro assays have relied on reducing the complexity of this complicated Fe–S assembly process by using surrogate electron donor molecules and monitoring simplified reactions. Recent studies have concluded that FXN promotes the synthesis of [4Fe-4S] clusters on the mammalian Fe–S assembly complex. Here the kinetics of Fe–S synthesis reactions were determined using different electron donation systems and by monitoring the products with circular dichroism and absorbance spectroscopies. We discovered that common surrogate electron donor molecules intercepted Fe–S cluster intermediates and formed high-molecular weight species (HMWS). The HMWS are associated with iron, sulfide, and thiol-containing proteins and have properties of a heterogeneous solubilized mineral with spectroscopic properties remarkably reminiscent of those of [4Fe-4S] clusters. In contrast, reactions using physiological reagents revealed that FXN accelerates the formation of [2Fe-2S] clusters rather than [4Fe-4S] clusters as previously reported. In the preceding paper [Fox, N. G., et al. (2015) Biochemistry 54, DOI: 10.1021/bi5014485], [2Fe-2S] intermediates on the SDUF complex were shown to readily transfer to uncomplexed ISCU2 or apo acceptor proteins, depending on the reaction conditions. Our results indicate that FXN accelerates a rate-limiting sulfur transfer step in the synthesis of [2Fe-2S] clusters on the human Fe–S assembly complex. PMID:26016518

  15. The multitude of iron-sulfur clusters in respiratory complex I.

    PubMed

    Gnandt, Emmanuel; Dörner, Katerina; Strampraad, Marc F J; de Vries, Simon; Friedrich, Thorsten

    2016-08-01

    Respiratory complex I couples the electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. Complex I contains one non-covalently bound flavin mononucleotide and, depending on the species, up to ten iron-sulfur (Fe/S) clusters as cofactors. The reason for the presence of the multitude of Fe/S clusters in complex I remained enigmatic for a long time. The question was partly answered by investigations on the evolution of the complex revealing the stepwise construction of the electron transfer domain from several modules. Extension of the ancestral to the modern electron input domain was associated with the acquisition of several Fe/S-proteins. The X-ray structure of the complex showed that the NADH oxidation-site is connected with the quinone-reduction site by a chain of seven Fe/S-clusters. Fast enzyme kinetics revealed that this chain of Fe/S-clusters is used to regulate electron-tunneling rates within the complex. A possible function of the off-pathway cluster N1a is discussed. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi. PMID:26944855

  16. A HIERARCHY OF ANKYRIN/SPECTRIN COMPLEXES CLUSTERS SODIUM CHANNELS AT NODES OF RANVIER

    PubMed Central

    Ho, Tammy Szu-Yu; Zollinger, Daniel R.; Chang, Kae-Jiun; Xu, Mingxuan; Cooper, Edward C.; Stankewich, Michael C.; Bennett, Vann; Rasband, Matthew N.

    2014-01-01

    SUMMARY The scaffolding protein ankyrinG is required for Na+ channel clustering at axon initial segments. It is also considered essential for Na+ channel clustering at nodes of Ranvier to facilitate fast and efficient action potential propagation. However, in contrast to these widely accepted roles, we show here that ankyrinG is dispensable for nodal Na+ channel clustering in vivo. Surprisingly, without ankyrinG, erythrocyte ankyrin (ankyrinR) and its binding partner βI spectrin substitute and rescue nodal Na+ channel clustering. In addition, channel clustering is also rescued after loss of nodal βIV spectrin by βI spectrin and ankyrinR. In mice lacking both ankyrinG and ankyrinR, Na+ channels fail to cluster at nodes. Thus, ankyrinR/βI spectrin protein complexes function as secondary reserve Na+ channel clustering machinery, and two independent ankyrin/spectrin protein complexes exist in myelinated axons to cluster Na+ channels at nodes of Ranvier. PMID:25362473

  17. Link-Prediction Enhanced Consensus Clustering for Complex Networks

    PubMed Central

    Burgess, Matthew; Adar, Eytan; Cafarella, Michael

    2016-01-01

    Many real networks that are collected or inferred from data are incomplete due to missing edges. Missing edges can be inherent to the dataset (Facebook friend links will never be complete) or the result of sampling (one may only have access to a portion of the data). The consequence is that downstream analyses that “consume” the network will often yield less accurate results than if the edges were complete. Community detection algorithms, in particular, often suffer when critical intra-community edges are missing. We propose a novel consensus clustering algorithm to enhance community detection on incomplete networks. Our framework utilizes existing community detection algorithms that process networks imputed by our link prediction based sampling algorithm and merges their multiple partitions into a final consensus output. On average our method boosts performance of existing algorithms by 7% on artificial data and 17% on ego networks collected from Facebook. PMID:27203750

  18. Applying Clustering Techniques to Reduce Complexity in Automated Planning Domains

    NASA Astrophysics Data System (ADS)

    Dicken, Luke; Levine, John

    Automated Planning is a very active area of research within Artificial Intelligence. Broadly this discipline deals with the methods by which an agent can independently determine the action sequence required to successfully achieve a set of objectives. In this paper, we will present initial work outlining a new approach to planning based on Clustering techniques, in order to group states of the world together and use the fundamental structure of the world to lift out more abstract representations. We will show that this approach can limit the combinatorial explosion of a typical planning problem in a way that is much more intuitive and reusable than has previously been possible, and outline ways that this approach can be developed further.

  19. Clustering of complex shaped data sets via Kohonen maps and mathematical morphology

    NASA Astrophysics Data System (ADS)

    Ferreira Costa, Jose A.; de Andrade Netto, Marcio L.

    2001-03-01

    Clustering is the process of discovering groups within the data, based on similarities, with a minimal, if any, knowledge of their structure. The self-organizing (or Kohonen) map (SOM) is one of the best known neural network algorithms. It has been widely studied as a software tool for visualization of high-dimensional data. Important features include information compression while preserving topological and metric relationship of the primary data items. Although Kohonen maps had been applied for clustering data, usually the researcher sets the number of neurons equal to the expected number of clusters, or manually segments a two-dimensional map using some a-priori knowledge of the data. This paper proposes techniques for automatic partitioning and labeling SOM networks in clusters of neurons that may be used to represent the data clusters. Mathematical morphology operations, such as watershed, are performed on the U-matrix, which is a neuron-distance image. The direct application of watershed leads to an oversegmented image. It is used markers to identify significant clusters and homotopy modification to suppress the others. Markers are automatically found by performing a multilevel scan of connected regions of the U-matrix. Each cluster of neurons is a sub-graph that defines, in the input space, complex and non-parametric geometries which approximately describes the shape of the clusters. The process of map partitioning is extended recursively. Each cluster of neurons gives rise to a new map, which are trained with the subset of data that were classified to it. The algorithm produces dynamically a hierarchical tree of maps, which explains the cluster's structure in levels of granularity. The distributed and multiple prototypes cluster representation enables the discoveries of clusters even in the case when we have two or more non-separable pattern classes.

  20. Conditional pseudolikelihood methods for clustered ordinal, multinomial, or count outcomes with complex survey data.

    PubMed

    Brumback, Babette A; Cai, Zhuangyu; He, Zhulin; Zheng, Hao W; Dailey, Amy B

    2013-04-15

    In order to adjust individual-level covariate effects for confounding due to unmeasured neighborhood characteristics, we have recently developed conditional pseudolikelihood methods to estimate the parameters of a proportional odds model for clustered ordinal outcomes with complex survey data. The methods require sampling design joint probabilities for each within-neighborhood pair. In the present article, we develop a similar methodology for a baseline category logit model for clustered multinomial outcomes and for a loglinear model for clustered count outcomes. All of the estimators and asymptotic sampling distributions we present can be conveniently computed using standard logistic regression software for complex survey data, such as sas proc surveylogistic. We demonstrate validity of the methods theoretically and also empirically by using simulations. We apply the new method for clustered multinomial outcomes to data from the 2008 Florida Behavioral Risk Factor Surveillance System survey in order to investigate disparities in frequency of dental cleaning both unadjusted and adjusted for confounding by neighborhood. PMID:22976045

  1. Colorimetric recognition of different enzymology-concerning transition metals based on a hybrid cluster complex.

    PubMed

    Li, Shun-Hua; Yuan, Wen-Tao; Zheng, Hong; Xu, Jin-Gou

    2004-07-01

    A hybrid cluster complex, formed by chelating a chromogenic ligand to a [2Fe-2S] cluster, sensitively exhibited differential colorimetric responses towards Hg2+, Cd2+, Cr3+, Pb2, Sn2+, Cu2+, Zn2+, Fe3+ and Co2+ in water at physiological pH. Speciation of some of these metal elements, such as Cr(III) and Sn(IV), was also studied by UV/Vis absorption. PMID:15293390

  2. Diffuse radio emission in the complex merging galaxy cluster Abell2069

    NASA Astrophysics Data System (ADS)

    Drabent, A.; Hoeft, M.; Pizzo, R. F.; Bonafede, A.; van Weeren, R. J.; Klein, U.

    2015-03-01

    Context. Galaxy clusters with signs of a recent merger in many cases show extended diffuse radio features. This emission originates from relativistic electrons that suffer synchrotron losses due to the intracluster magnetic field. The mechanisms of particle acceleration and the properties of the magnetic field are still poorly understood. Aims: We search for diffuse radio emission in galaxy clusters. Here, we study the complex galaxy cluster Abell 2069, for which X-ray observations indicate a recent merger. Methods: We investigate the cluster's radio continuum emission by deep Westerbork Synthesis Radio Telescope (WSRT) observations at 346 MHz and Giant Metrewave Radio Telescope (GMRT) observations at 322 MHz. Results: We find an extended diffuse radio feature roughly coinciding with the main component of the cluster. We classify this emission as a radio halo and estimate its lower limit flux density at 25 ± 9 mJy. Moreover, we find a second extended diffuse source located at the cluster's companion and estimate its flux density at 15 ± 2 mJy. We speculate that this is a small halo or a mini-halo. If true, this cluster is the first example of a double-halo in a single galaxy cluster.

  3. Cluster formation by allelomimesis in real-world complex adaptive systems

    NASA Astrophysics Data System (ADS)

    Juanico, Dranreb Earl; Monterola, Christopher; Saloma, Caesar

    2005-04-01

    Animal and human clusters are complex adaptive systems and many organize in cluster sizes s that obey the frequency distribution D(s)∝s-τ . The exponent τ describes the relative abundance of the cluster sizes in a given system. Data analyses reveal that real-world clusters exhibit a broad spectrum of τ values, 0.7 (tuna fish schools) ⩽τ⩽4.61 (T4 bacteriophage gene family sizes). Allelomimesis is proposed as an underlying mechanism for adaptation that explains the observed broad τ spectrum. Allelomimesis is the tendency of an individual to imitate the actions of others and two cluster systems have different τ values when their component agents display unequal degrees of allelomimetic tendencies. Cluster formation by allelomimesis is shown to be of three general types: namely, blind copying, information-use copying, and noncopying. Allelomimetic adaptation also reveals that the most stable cluster size is formed by three strongly allelomimetic individuals. Our finding is consistent with available field data taken from killer whales and marmots.

  4. Defect clustering in simple and complex oxides. Progress report, June 1, 1992--May 31, 1993

    SciTech Connect

    Cohen, J.B.; Ellis, D.E.; Mason, T.O.

    1992-10-01

    Vacancy:interstitial clusters in Fe{sub 1{minus}x}O were surveyed theoretically, and the 7:2 cluster is predicted to be the most stable, followed by 4:1. In Mn{sub 1{minus}x}O, the 2:1 cluster is predicted to be the most stable, followed by 6:2. The Co{sub 1{minus}x}O is still unresolved, although the 2:1 cluster should be the most stable. Work on complex oxides is also reported, including REAECuO (RE=rare earth, AE=alkaline earth), NdCeCuO, LaCuO-based cuprates, and doped sapphire.

  5. Complexities in complex posttraumatic stress disorder in inpatient women: evidence from cluster analysis of MCMI-III Personality Disorder Scales.

    PubMed

    Allen, J G; Huntoon, J; Evans, R B

    1999-12-01

    Herman's (1992a) clinical formulation of complex posttraumatic stress disorder (PTSD) captures the extensive diagnostic comorbidity seen in patients with a history of repeated interpersonal trauma and severe psychiatric disorders. Yet the sheer breadth of symptoms and personality disturbance encompassed by complex PTSD limits its descriptive usefulness. This study employed cluster analysis of the MCMI-III (Millon, 1994) personality disorder scales to determine whether there is meaningful heterogeneity within a group of 227 severely traumatized women who were treated in a specialized inpatient program. The analysis distinguishes 5 clinically meaningful clusters, which we label alienated, withdrawn, aggressive, suffering, and adaptive. The study examined differences among these 5 personality disorder clusters on the MCMI-III clinical syndrome scales, as well as on the Brief Symptom Inventory (Derogatis, 1993), Dissociative Experiences Scale (E. M. Bernstein & Putnam, 1986), Adult Attachment Scale (Collins & Read, 1990), and Childhood Trauma Questionnaire (D.P. Bernstein, 1995). We present a classification-tree method for determining the cluster membership of new cases and discuss the implications of the findings for diagnostic assessment, treatment, and research. PMID:10689654

  6. Ant colony clustering with fitness perception and pheromone diffusion for community detection in complex networks

    NASA Astrophysics Data System (ADS)

    Ji, Junzhong; Song, Xiangjing; Liu, Chunnian; Zhang, Xiuzhen

    2013-08-01

    Community structure detection in complex networks has been intensively investigated in recent years. In this paper, we propose an adaptive approach based on ant colony clustering to discover communities in a complex network. The focus of the method is the clustering process of an ant colony in a virtual grid, where each ant represents a node in the complex network. During the ant colony search, the method uses a new fitness function to percept local environment and employs a pheromone diffusion model as a global information feedback mechanism to realize information exchange among ants. A significant advantage of our method is that the locations in the grid environment and the connections of the complex network structure are simultaneously taken into account in ants moving. Experimental results on computer-generated and real-world networks show the capability of our method to successfully detect community structures.

  7. Investigating the function of [2Fe–2S] cluster N1a, the off-pathway cluster in complex I, by manipulating its reduction potential

    PubMed Central

    Birrell, James A.; Morina, Klaudia; Bridges, Hannah R.; Friedrich, Thorsten; Hirst, Judy

    2013-01-01

    NADH:quinone oxidoreductase (complex I) couples NADH oxidation and quinone reduction to proton translocation across an energy-transducing membrane. All complexes I contain a flavin to oxidize NADH, seven iron–sulfur clusters to transfer electrons from the flavin to quinone and an eighth cluster (N1a) on the opposite side of the flavin. The role of cluster N1a is unknown, but Escherichia coli complex I has an unusually high-potential cluster N1a and its reduced flavin produces H2O2, not superoxide, suggesting that cluster N1a may affect reactive oxygen species production. In the present study, we combine protein film voltammetry with mutagenesis in overproduced N1a-binding subunits to identify two residues that switch N1a between its high- (E. coli, valine and asparagine) and low- (Bos taurus and Yarrowia lipolytica, proline and methionine) potential forms. The mutations were incorporated into E. coli complex I: cluster N1a could no longer be reduced by NADH, but H2O2 and superoxide production were unaffected. The reverse mutations (that increase the potential by ~0.16 V) were incorporated into Y. lipolytica complex I, but N1a was still not reduced by NADH. We conclude that cluster N1a does not affect reactive oxygen species production by the complex I flavin; it is probably required for enzyme assembly or stability. PMID:23980528

  8. Adult Speakers' Tongue-Palate Contact Patterns for Bilabial Stops within Complex Clusters

    ERIC Educational Resources Information Center

    Zharkova, Natalia; Schaeffler, Sonja; Gibbon, Fiona E.

    2009-01-01

    Previous studies using Electropalatography (EPG) have shown that individuals with speech disorders sometimes produce articulation errors that affect bilabial targets, but currently there is limited normative data available. In this study, EPG and acoustic data were recorded during complex word final sps clusters spoken by 20 normal adults. A total…

  9. COMPLEX DIFFUSE RADIO EMISSION IN THE MERGING PLANCK ESZ CLUSTER A3411

    SciTech Connect

    Van Weeren, R. J.; Fogarty, K.; Jones, C.; Forman, W. R.; Kraft, R. P.; Murray, S. S.; Clarke, T. E.; Brueggen, M.; Lal, D. V.; Roettgering, H. J. A.

    2013-06-01

    We present Very Large Array (VLA) radio and Chandra X-ray observations of the merging galaxy cluster A3411. For the cluster, we find an overall temperature of 6.4{sup +0.6}{sub -1.0} keV and an X-ray luminosity of 2.8 {+-} 0.1 Multiplication-Sign 10{sup 44} erg s{sup -1} between 0.5 and 2.0 keV. The Chandra observation reveals the cluster to be undergoing a merger event. The VLA observations show the presence of large-scale diffuse emission in the central region of the cluster, which we classify as a 0.9 Mpc size radio halo. In addition, a complex region of diffuse, polarized emission is found in the southeastern outskirts of the cluster along the projected merger axis of the system. We classify this region of diffuse emission as a radio relic. The total extent of this radio relic is 1.9 Mpc. For the combined emission in the cluster region, we find a radio spectral index of -1.0 {+-} 0.1 between 74 MHz and 1.4 GHz. The morphology of the radio relic is peculiar, as the relic is broken up into five fragments. This suggests that the shock responsible for the relic has been broken up due to interaction with a large-scale galaxy filament connected to the cluster or other substructures in the intracluster medium. Alternatively, the complex morphology reflects the presence of electrons in fossil radio bubbles that are re-accelerated by a shock.

  10. Adaptive fuzzy leader clustering of complex data sets in pattern recognition

    NASA Technical Reports Server (NTRS)

    Newton, Scott C.; Pemmaraju, Surya; Mitra, Sunanda

    1992-01-01

    A modular, unsupervised neural network architecture for clustering and classification of complex data sets is presented. The adaptive fuzzy leader clustering (AFLC) architecture is a hybrid neural-fuzzy system that learns on-line in a stable and efficient manner. The initial classification is performed in two stages: a simple competitive stage and a distance metric comparison stage. The cluster prototypes are then incrementally updated by relocating the centroid positions from fuzzy C-means system equations for the centroids and the membership values. The AFLC algorithm is applied to the Anderson Iris data and laser-luminescent fingerprint image data. It is concluded that the AFLC algorithm successfully classifies features extracted from real data, discrete or continuous.

  11. Complex nanoscale cage clusters built from uranyl polyhedra and phosphate tetrahedra

    SciTech Connect

    Unruh, Daniel K.; Ling, Jie; Qiu, Jie; Pressprich, Laura; Baranay, Melissa; Ward, Matthew; Burns, Peter C.

    2011-06-20

    Five cage clusters that self-assemble in alkaline aqueous solution have been isolated and characterized. Each is built from uranyl hexagonal bipyramids with two or three equatorial edges occupied by peroxide, and three also contain phosphate tetrahedra. These clusters contain 30 uranyl polyhedra; 30 uranyl polyhedra and six pyrophosphate groups; 30 uranyl polyhedra, 12 pyrophosphate groups, and one phosphate tetrahedron; 42 uranyl polyhedra; and 40 uranyl polyhedra and three pyrophosphate groups. These clusters present complex topologies as well as a range of compositions, sizes, and charges. Two adopt fullerene topologies, and the others contain combinations of topological squares, pentagons, and hexagons. An analysis of possible topologies further indicates that higher-symmetry topologies are favored.

  12. Opening of Carborane Cages by Metal Cluster Complexes: The Reaction of a Thiolate-Substituted Carborane with Triosmium Carbonyl Cluster Complexes.

    PubMed

    Adams, Richard D; Kiprotich, Joseph; Peryshkov, Dmitry V; Wong, Yuen Onn

    2016-08-15

    The reaction of Os3(CO)10(NCMe)2 with closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)9[μ3-η(3)-C2B10H9(SCH3)](μ-H)2, 1, by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster and the coordination of the sulfur atom and the activation of two B-H bonds with transfer of the hydrogen atoms to the cluster. Reaction of 1 with a second equivalent of Os3(CO)10(NCMe)2 yielded the complex Os3(CO)9(μ-H)[(μ3-η(3)-1,4,5-μ3-η(3)-6,10,11-C2B10H8S(CH3)]Os3(CO)9(μ-H)2, 2, that contains two triosmium triangles attached to the same carborane cage. The carborane cage was opened by cleavage of two B-C bonds and one B-B bond. The B-H group that was pulled out of the cage became a triply bridging group on one of the Os3 triangles but remains bonded to the cage by two B-B bonds. When heated to 150 °C, 2 was transformed into the complex Os3(CO)9(μ-H)[(μ3-η(3)-μ3-η(3)-C2B10H7S(CH3)]Os3(CO)9(μ-H), 3, by the loss of two hydrogen atoms and a rearrangement that led to further opening of the carborane cage. Reaction of 1 with a second equivalent of closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)6)(μ3-η(3)-C2B10H9-R-SCH3) (μ3-η(3)-C2B10H10-S-SCH3)(μ-H)3, 4a, containing two carborane cages coordinated to one Os3 cluster. Compound 4a was isomerized to the compound Os3(CO)6(μ3-η(3)-C2B10H9-R-SCH3)(μ3-η(3)-C2B10H10-R-SCH3)(μ-H)3, 4b, by an inversion of stereochemistry at one of the sulfur atoms by heating to 174 °C. PMID:27487332

  13. Studying the Effect of a Composition of the Cluster Core in High-Radiopacity Cluster Complexes of Rhenium on Their Acute Toxicity In Vivo.

    PubMed

    Pozmogova, T N; Krasil'nikova, A A; Ivanov, A A; Shestopalov, M A; Gyrylova, S N; Shestopalova, L V; Shestopaloiv, A M; Shkurupy, V A

    2016-05-01

    An in vivo study was performed to evaluate the dependence of acute toxicity of high-radiopacity and luminescent octahedral cluster complexes of rhenium after intravenous injection on a composition of the cluster core. Changes in mouse body weight, water and food consumption, degree of intoxication, and morphological changes in the visceral organs were studied after intravenous injection of the following cluster complexes with various internal ligands (S, Se, or Te): Na4[{Re 6 Te 8 }(CN)6], Na4[{Re 6 Se 8 }(CN)6], and Na4[{Re 6 S 8 }(CN)6]. The Na4[{Re 6 S 8 } (CN)6] cluster complex was shown to be the safest for animals. PMID:27270936

  14. Complete characterization of the stability of cluster synchronization in complex dynamical networks.

    PubMed

    Sorrentino, Francesco; Pecora, Louis M; Hagerstrom, Aaron M; Murphy, Thomas E; Roy, Rajarshi

    2016-04-01

    Synchronization is an important and prevalent phenomenon in natural and engineered systems. In many dynamical networks, the coupling is balanced or adjusted to admit global synchronization, a condition called Laplacian coupling. Many networks exhibit incomplete synchronization, where two or more clusters of synchronization persist, and computational group theory has recently proved to be valuable in discovering these cluster states based on the topology of the network. In the important case of Laplacian coupling, additional synchronization patterns can exist that would not be predicted from the group theory analysis alone. Understanding how and when clusters form, merge, and persist is essential for understanding collective dynamics, synchronization, and failure mechanisms of complex networks such as electric power grids, distributed control networks, and autonomous swarming vehicles. We describe a method to find and analyze all of the possible cluster synchronization patterns in a Laplacian-coupled network, by applying methods of computational group theory to dynamically equivalent networks. We present a general technique to evaluate the stability of each of the dynamically valid cluster synchronization patterns. Our results are validated in an optoelectronic experiment on a five-node network that confirms the synchronization patterns predicted by the theory. PMID:27152349

  15. Complete characterization of the stability of cluster synchronization in complex dynamical networks

    PubMed Central

    Sorrentino, Francesco; Pecora, Louis M.; Hagerstrom, Aaron M.; Murphy, Thomas E.; Roy, Rajarshi

    2016-01-01

    Synchronization is an important and prevalent phenomenon in natural and engineered systems. In many dynamical networks, the coupling is balanced or adjusted to admit global synchronization, a condition called Laplacian coupling. Many networks exhibit incomplete synchronization, where two or more clusters of synchronization persist, and computational group theory has recently proved to be valuable in discovering these cluster states based on the topology of the network. In the important case of Laplacian coupling, additional synchronization patterns can exist that would not be predicted from the group theory analysis alone. Understanding how and when clusters form, merge, and persist is essential for understanding collective dynamics, synchronization, and failure mechanisms of complex networks such as electric power grids, distributed control networks, and autonomous swarming vehicles. We describe a method to find and analyze all of the possible cluster synchronization patterns in a Laplacian-coupled network, by applying methods of computational group theory to dynamically equivalent networks. We present a general technique to evaluate the stability of each of the dynamically valid cluster synchronization patterns. Our results are validated in an optoelectronic experiment on a five-node network that confirms the synchronization patterns predicted by the theory. PMID:27152349

  16. Clustering of protein families into functional subtypes using Relative Complexity Measure with reduced amino acid alphabets

    PubMed Central

    2010-01-01

    Background Phylogenetic analysis can be used to divide a protein family into subfamilies in the absence of experimental information. Most phylogenetic analysis methods utilize multiple alignment of sequences and are based on an evolutionary model. However, multiple alignment is not an automated procedure and requires human intervention to maintain alignment integrity and to produce phylogenies consistent with the functional splits in underlying sequences. To address this problem, we propose to use the alignment-free Relative Complexity Measure (RCM) combined with reduced amino acid alphabets to cluster protein families into functional subtypes purely on sequence criteria. Comparison with an alignment-based approach was also carried out to test the quality of the clustering. Results We demonstrate the robustness of RCM with reduced alphabets in clustering of protein sequences into families in a simulated dataset and seven well-characterized protein datasets. On protein datasets, crotonases, mandelate racemases, nucleotidyl cyclases and glycoside hydrolase family 2 were clustered into subfamilies with 100% accuracy whereas acyl transferase domains, haloacid dehalogenases, and vicinal oxygen chelates could be assigned to subfamilies with 97.2%, 96.9% and 92.2% accuracies, respectively. Conclusions The overall combination of methods in this paper is useful for clustering protein families into subtypes based on solely protein sequence information. The method is also flexible and computationally fast because it does not require multiple alignment of sequences. PMID:20718947

  17. A Transition Metal Complex (Venus Flytrap Cluster) for Radioimmunodetection and Radioimmunotherapy

    NASA Astrophysics Data System (ADS)

    Paxton, Raymond J.; Beatty, Barbara G.; Hawthorne, M. Frederick; Varadarajan, Aravamuthan; Williams, Lawrence E.; Curtis, Frederick L.; Knobler, Carolyn B.; Beatty, J. David; Shiveley, John E.

    1991-04-01

    A novel transition metal complex, Venus flytrap cluster (VFC), is described for the preparation of radiolabeled antibodies. VFC contained 57Co, which was held tightly between the faces of two covalently bridged carborane ligands by cluster bonding of the metal with appropriate ligand orbitals. Anti-carcinoembryonic antigen monoclonal antibody T84.66 was conjugated to 57Co-VFC with full retention of immunological activity. Biodistribution studies in nude mice bearing carcinoembryonic antigen-producing tumors showed excellent tumor localization of 57Co-VFC-T84.66. The accumulation of radionuclide in normal liver was low and independent of dose, which may reflect the stability of the radionuclide complex. These results presage the use of VFC systems for binding transition metals that are clinically useful for radio-immunodiagnosis and radioimmunotherapy.

  18. A transition metal complex (Venus flytrap cluster) for radioimmunodetection and radioimmunotherapy

    SciTech Connect

    Paxton, R.J.; Curtis, F.L.; Shively, J.E. ); Beatty, B.G.; Williams, L.E.; Beatty, J.D. ); Hawthorne, M.F.; Varadarajan, A.; Knobler, C.B. )

    1991-04-15

    A novel transition metal complex, Venus flytrap cluster (VFC), is described for the preparation of radiolabeled antibodies. VFC contained {sup 57}Co, which was held tightly between the faces of two covalently bridged carborane ligands by cluster bonding of the metal with appropriate ligand orbitals. Anti-carcinoembryonic antigen monoclonal antibody T84,66 was conjugated to {sup 57}Co-VFC with full retention of immunological activity. Biodistribution studies in nude mice bearing carcinoembryonic antigen-producing tumors showed excellent tumor localization of {sup 57}Co-VFC-T84.66. The accumulation of radionuclide in normal liver was low and independent of dose, which may reflect the stability of the radionuclide complex. These results presage the use of VFC systems for binding transition metals that are clinically useful for radioimmunodiagnosis and radioimmunotherapy.

  19. Molecular orbital calculations of octahedral molybdenum cluster complexes with the DV-X{alpha} method

    SciTech Connect

    Imoto, Hideo; Saito, Taro; Adachi, Hirohiko

    1995-04-26

    Discrete variational-{Chi}{alpha} molecular orbital methods were applied to octahedral cluster complexes, [Mo{sub 6}X{sub 8}-(PH{sub 3}){sub 6}](X = S and Se). This structure is of interest due to its role in superconductivity of Chevrel plates. Level energies are discussed and factors contributing to their separations are categorized. Agreement with empirical XPS data is excellent.

  20. Detecting overlapping protein complexes by rough-fuzzy clustering in protein-protein interaction networks.

    PubMed

    Wu, Hao; Gao, Lin; Dong, Jihua; Yang, Xiaofei

    2014-01-01

    In this paper, we present a novel rough-fuzzy clustering (RFC) method to detect overlapping protein complexes in protein-protein interaction (PPI) networks. RFC focuses on fuzzy relation model rather than graph model by integrating fuzzy sets and rough sets, employs the upper and lower approximations of rough sets to deal with overlapping complexes, and calculates the number of complexes automatically. Fuzzy relation between proteins is established and then transformed into fuzzy equivalence relation. Non-overlapping complexes correspond to equivalence classes satisfying certain equivalence relation. To obtain overlapping complexes, we calculate the similarity between one protein and each complex, and then determine whether the protein belongs to one or multiple complexes by computing the ratio of each similarity to maximum similarity. To validate RFC quantitatively, we test it in Gavin, Collins, Krogan and BioGRID datasets. Experiment results show that there is a good correspondence to reference complexes in MIPS and SGD databases. Then we compare RFC with several previous methods, including ClusterONE, CMC, MCL, GCE, OSLOM and CFinder. Results show the precision, sensitivity and separation are 32.4%, 42.9% and 81.9% higher than mean of the five methods in four weighted networks, and are 0.5%, 11.2% and 66.1% higher than mean of the six methods in five unweighted networks. Our method RFC works well for protein complexes detection and provides a new insight of network division, and it can also be applied to identify overlapping community structure in social networks and LFR benchmark networks. PMID:24642838

  1. Detecting Overlapping Protein Complexes by Rough-Fuzzy Clustering in Protein-Protein Interaction Networks

    PubMed Central

    Wu, Hao; Gao, Lin; Dong, Jihua; Yang, Xiaofei

    2014-01-01

    In this paper, we present a novel rough-fuzzy clustering (RFC) method to detect overlapping protein complexes in protein-protein interaction (PPI) networks. RFC focuses on fuzzy relation model rather than graph model by integrating fuzzy sets and rough sets, employs the upper and lower approximations of rough sets to deal with overlapping complexes, and calculates the number of complexes automatically. Fuzzy relation between proteins is established and then transformed into fuzzy equivalence relation. Non-overlapping complexes correspond to equivalence classes satisfying certain equivalence relation. To obtain overlapping complexes, we calculate the similarity between one protein and each complex, and then determine whether the protein belongs to one or multiple complexes by computing the ratio of each similarity to maximum similarity. To validate RFC quantitatively, we test it in Gavin, Collins, Krogan and BioGRID datasets. Experiment results show that there is a good correspondence to reference complexes in MIPS and SGD databases. Then we compare RFC with several previous methods, including ClusterONE, CMC, MCL, GCE, OSLOM and CFinder. Results show the precision, sensitivity and separation are 32.4%, 42.9% and 81.9% higher than mean of the five methods in four weighted networks, and are 0.5%, 11.2% and 66.1% higher than mean of the six methods in five unweighted networks. Our method RFC works well for protein complexes detection and provides a new insight of network division, and it can also be applied to identify overlapping community structure in social networks and LFR benchmark networks. PMID:24642838

  2. The G305 star-forming complex: the central star clusters Danks 1 and Danks 2

    NASA Astrophysics Data System (ADS)

    Davies, Ben; Clark, J. S.; Trombley, Christine; Figer, Donald F.; Najarro, Francisco; Crowther, Paul A.; Kudritzki, Rolf-Peter; Thompson, Mark; Urquhart, James S.; Hindson, Luke

    2012-01-01

    The G305 H II complex (G305.4+0.1) is one of the most massive star-forming structures yet identified within the Galaxy. It is host to many massive stars at all stages of formation and evolution, from embedded molecular cores to post-main-sequence stars. Here, we present a detailed near-infrared analysis of the two central star clusters Danks 1 and Danks 2, using Hubble Space Telescope+NICMOS imaging and Very Large Telescope+ISAAC spectroscopy. We find that the spectrophotometric distance to the clusters is consistent with the kinematic distance to the G305 complex, an average of all measurements giving a distance of 3.8 ± 0.6 kpc. From analysis of the stellar populations and the pre-main-sequence stars, we find that Danks 2 is the elder of the two clusters, with an age of 3+3- 1 Myr. Danks 1 is clearly younger with an age of 1.5+1.5- 0.5 Myr, and is dominated by three very luminous H-rich Wolf-Rayet stars which may have masses ≳100 M⊙. The two clusters have mass functions consistent with the Salpeter slope, and total cluster masses of 8000 ± 1500 and 3000 ± 800 M⊙ for Danks 1 and Danks 2, respectively. Danks 1 is significantly the more compact cluster of the two, and is one of the densest clusters in the Galaxy with log (ρ/M⊙ pc-3) = 5.5+0.5- 0.4. In addition to the clusters, there is a population of apparently isolated Wolf-Rayet stars within the molecular cloud's cavity. Our results suggest that the star-forming history of G305 began with the formation of Danks 2, and subsequently Danks 1, with the origin of the diffuse evolved population currently uncertain. Together, the massive stars at the centre of the G305 region appear to be clearing away what is left of the natal cloud, triggering a further generation of star formation at the cloud's periphery.

  3. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion.

    PubMed

    Zarkesh, Ryan A; Ichimura, Andrew S; Monson, Todd C; Tomson, Neil C; Anstey, Mitchell R

    2016-06-14

    The redox-active bis(imino)acenapthene (BIAN) ligand was used to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events. PMID:26998892

  4. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion

    DOE PAGESBeta

    Zarkesh, Ryan A.; Ichimura, Andrew S.; Monson, Todd C.; Tomson, Neil C.; Anstey, Mitchell R.

    2016-02-01

    We used the redox-active bis(imino)acenapthene (BIAN) ligand to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Ultimately, complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  5. The Fas-FADD Death Domain Complex Structure Unravels Signalling by Receptor Clustering

    SciTech Connect

    Scott, F.; Stec, B; Pop, C; Dobaczewska, M; Lee, J; Monosov, E; Robinson, H; Salvesen, G; Schwarzenbacher, R; Riedl, S

    2009-01-01

    The death inducing signalling complex (DISC) formed by Fas receptor, FADD (Fas-associated death domain protein) and caspase 8 is a pivotal trigger of apoptosis1, 2, 3. The Fas-FADD DISC represents a receptor platform, which once assembled initiates the induction of programmed cell death. A highly oligomeric network of homotypic protein interactions comprised of the death domains of Fas and FADD is at the centre of DISC formation4, 5. Thus, characterizing the mechanistic basis for the Fas-FADD interaction is crucial for understanding DISC signalling but has remained unclear largely because of a lack of structural data. We have successfully formed and isolated the human Fas-FADD death domain complex and report the 2.7 A crystal structure. The complex shows a tetrameric arrangement of four FADD death domains bound to four Fas death domains. We show that an opening of the Fas death domain exposes the FADD binding site and simultaneously generates a Fas-Fas bridge. The result is a regulatory Fas-FADD complex bridge governed by weak protein-protein interactions revealing a model where the complex itself functions as a mechanistic switch. This switch prevents accidental DISC assembly, yet allows for highly processive DISC formation and clustering upon a sufficient stimulus. In addition to depicting a previously unknown mode of death domain interactions, these results further uncover a mechanism for receptor signalling solely by oligomerization and clustering events.

  6. Oligomeric rare-earth metal cluster complexes with endohedral transition metal atoms

    SciTech Connect

    Steinberg, Simon; Zimmermann, Sina; Brühmann, Matthias; Meyer, Eva; Rustige, Christian; Wolberg, Marike; Daub, Kathrin; Bell, Thomas; Meyer, Gerd

    2014-11-15

    Comproportionation reactions of rare-earth metal trihalides (RX{sub 3}) with the respective rare-earth metals (R) and transition metals (T) led to the formation of 22 oligomeric R cluster halides encapsulating T, in 19 cases for the first time. The structures of these compounds were determined by single-crystal X-ray diffraction and are composed of trimers ((T{sub 3}R{sub 11})X{sub 15}-type, P6{sub 3}/m), tetramers ((T{sub 4}R{sub 16})X{sub 28}(R{sub 4}) (P-43m), (T{sub 4}R{sub 16})X{sub 20} (P4{sub 2}/nnm), (T{sub 4}R{sub 16})X{sub 24}(RX{sub 3}){sub 4} (I4{sub 1}/a) and (T{sub 4}R{sub 16})X{sub 23} (C2/m) types of structure) and pentamers ((Ru{sub 5}La{sub 14}){sub 2}Br{sub 39}, Cc) of (TR{sub r}){sub n} (n=2–5) clusters. These oligomers are further enveloped by inner (X{sup i}) as well as outer (X{sup a}) halido ligands, which possess diverse functionalities and interconnect like oligomers through i–i, i–a and/or a–i bridges. The general features of the crystal structures for these new compounds are discussed and compared to literature entries as well as different structure types with oligomeric T centered R clusters. Dimers and tetramers originating from the aggregation of (TR{sub 6}) octahedra via common edges are more frequent than trimers and pentamers, in which the (TR{sub r}) clusters share common faces. - Graphical abstract: Rare earth-metal cluster complexes with endohedral transition metal atoms (TR{sub 6}) may connect via common edges or faces to form dimers, trimers, tetramers and pentamers of which the tetramers are the most prolific. Packing effects and electron counts play an important role. - Highlights: • Rare-earth metal cluster complexes encapsulate transition metal atoms. • Oligomers are built via connection of octahedral clusters via common edges or faces. • Dimers through pentamers with closed structures are known. • Tetramers including a tetrahedron of endohedral atoms are the most prolific.

  7. The impact of polyploidy on the evolution of a complex NB-LRR resistance gene cluster in soybean

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A comparative genomics approach was used to investigate the evolution of a complex NB-LRR gene cluster found in soybean (Glycine max), common bean (Phaseolus vulgaris), and other legumes. In soybean, the cluster is associated with several disease resistance (R) genes of known function including Rpg1...

  8. High resolution Raman spectroscopy of complexes and clusters in molecular beams

    SciTech Connect

    Felker, P.M.

    1991-01-01

    The DOE-sponsored project in this laboratory has two facets. The first is the development of methods of nonlinear Raman spectroscopy for application in studies of sparse samples. The second is the application of such methods to structural and dynamical studies of species in supersonic molecular beams. The progress we have made in both of these areas is described in this paper. The report is divided into five remaining sections. The first pertains to theoretical and experimental developments in Fourier transform stimulated emission spectroscopy and Fourier transform hole-burning spectroscopy. The second deals with progress in the development of ionization-detected stimulated Raman spectroscopies (IDSRS). The third describes results from the application of IDSRS methods to studies of jet-cooled benzene clusters. The fourth describes IDSRS results from studies of hydrogen-bonded complexes containing phenols. The fifth relates to studies of carbazole-(Ar){sub n} clusters.

  9. Depth resolution improvement in secondary ion mass spectrometry analysis using metal cluster complex ion bombardment

    SciTech Connect

    Tomita, M.; Kinno, T.; Koike, M.; Tanaka, H.; Takeno, S.; Fujiwara, Y.; Kondou, K.; Teranishi, Y.; Nonaka, H.; Fujimoto, T.; Kurokawa, A.; Ichimura, S.

    2006-07-31

    Secondary ion mass spectrometry analyses were carried out using a metal cluster complex ion of Ir{sub 4}(CO){sub 7}{sup +} as a primary ion beam. Depth resolution was evaluated as a function of primary ion species, energy, and incident angle. The depth resolution obtained using cluster ion bombardment was considerably better than that obtained by oxygen ion bombardment under the same experimental condition due to reduction of atomic mixing in the depth. The authors obtained a depth resolution of {approx}1 nm under 5 keV, 45 deg. condition. Depth resolution was degraded by ion-bombardment-induced surface roughness at 5 keV with higher incident angles.

  10. High resolution Raman spectroscopy of complexes and clusters in molecular beams. Performance report

    SciTech Connect

    Felker, P.M.

    1991-12-31

    The DOE-sponsored project in this laboratory has two facets. The first is the development of methods of nonlinear Raman spectroscopy for application in studies of sparse samples. The second is the application of such methods to structural and dynamical studies of species in supersonic molecular beams. The progress we have made in both of these areas is described in this paper. The report is divided into five remaining sections. The first pertains to theoretical and experimental developments in Fourier transform stimulated emission spectroscopy and Fourier transform hole-burning spectroscopy. The second deals with progress in the development of ionization-detected stimulated Raman spectroscopies (IDSRS). The third describes results from the application of IDSRS methods to studies of jet-cooled benzene clusters. The fourth describes IDSRS results from studies of hydrogen-bonded complexes containing phenols. The fifth relates to studies of carbazole-(Ar){sub n} clusters.

  11. Amprenavir complexes with HIV-1 protease and its drug-resistant mutants altering hydrophobic clusters

    SciTech Connect

    Shen, Chen-Hsiang; Wang, Yuan-Fang; Kovalevsky, Andrey Y.; Harrison, Robert W.; Weber, Irene T.

    2010-10-22

    The structural and kinetic effects of amprenavir (APV), a clinical HIV protease (PR) inhibitor, were analyzed with wild-type enzyme and mutants with single substitutions of V32I, I50V, I54V, I54M, I84V and L90M that are common in drug resistance. Crystal structures of the APV complexes at resolutions of 1.02-1.85 {angstrom} reveal the structural changes due to the mutations. Substitution of the larger side chains in PR{sub V32I}, PR{sub I54M} and PR{sub L90M} resulted in the formation of new hydrophobic contacts with flap residues, residues 79 and 80, and Asp25, respectively. Mutation to smaller side chains eliminated hydrophobic interactions in the PR{sub I50V} and PR{sub I54V} structures. The PR{sub I84V}-APV complex had lost hydrophobic contacts with APV, the PR{sub V32I}-APV complex showed increased hydrophobic contacts within the hydrophobic cluster and the PR{sub I50V} complex had weaker polar and hydrophobic interactions with APV. The observed structural changes in PR{sub I84V}-APV, PR{sub V32I}-APV and PR{sub I50V}-APV were related to their reduced inhibition by APV of six-, 10- and 30-fold, respectively, relative to wild-type PR. The APV complexes were compared with the corresponding saquinavir complexes. The PR dimers had distinct rearrangements of the flaps and 80's loops that adapt to the different P1{prime} groups of the inhibitors, while maintaining contacts within the hydrophobic cluster. These small changes in the loops and weak internal interactions produce the different patterns of resistant mutations for the two drugs.

  12. Energy transfer and clustering of photosynthetic light-harvesting complexes in reconstituted lipid membranes

    NASA Astrophysics Data System (ADS)

    Dewa, Takehisa; Sumino, Ayumi; Watanabe, Natsuko; Noji, Tomoyasu; Nango, Mamoru

    2013-06-01

    In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting/reaction centre core complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. We addressed this issue by evaluating the energy transfer in reconstituted photosynthetic protein complexes LH2 and LH1-RC and studying the structures and the membrane environment of the LH2/LH1-RC assemblies, which had been embedded into various lipid bilayers. Thus, LH2 and LH1-RC from Rhodopseudomonas palustris 2.1.6 were reconstituted in phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Efficient energy transfer from LH2 to LH1-RC was observed in the PC and PE/PG/CL membranes. Atomic force microscopy revealed that LH2 and LH1-RC were heterogeneously distributed to form clusters in the PC and PE/PG/CL membranes. The results indicated that the phospholipid species influenced the cluster formation of LH2 and LH1-RC as well as the energy transfer efficiency.

  13. The Talin Head Domain Reinforces Integrin-Mediated Adhesion by Promoting Adhesion Complex Stability and Clustering

    PubMed Central

    Ellis, Stephanie J.; Lostchuck, Emily; Goult, Benjamin T.; Bouaouina, Mohamed; Fairchild, Michael J.; López-Ceballos, Pablo; Calderwood, David A.; Tanentzapf, Guy

    2014-01-01

    Talin serves an essential function during integrin-mediated adhesion in linking integrins to actin via the intracellular adhesion complex. In addition, the N-terminal head domain of talin regulates the affinity of integrins for their ECM-ligands, a process known as inside-out activation. We previously showed that in Drosophila, mutating the integrin binding site in the talin head domain resulted in weakened adhesion to the ECM. Intriguingly, subsequent studies showed that canonical inside-out activation of integrin might not take place in flies. Consistent with this, a mutation in talin that specifically blocks its ability to activate mammalian integrins does not significantly impinge on talin function during fly development. Here, we describe results suggesting that the talin head domain reinforces and stabilizes the integrin adhesion complex by promoting integrin clustering distinct from its ability to support inside-out activation. Specifically, we show that an allele of talin containing a mutation that disrupts intramolecular interactions within the talin head attenuates the assembly and reinforcement of the integrin adhesion complex. Importantly, we provide evidence that this mutation blocks integrin clustering in vivo. We propose that the talin head domain is essential for regulating integrin avidity in Drosophila and that this is crucial for integrin-mediated adhesion during animal development. PMID:25393120

  14. Identifying driving gene clusters in complex diseases through critical transition theory

    NASA Astrophysics Data System (ADS)

    Wolanyk, Nathaniel; Wang, Xujing; Hessner, Martin; Gao, Shouguo; Chen, Ye; Jia, Shuang

    A novel approach of looking at the human body using critical transition theory has yielded positive results: clusters of genes that act in tandem to drive complex disease progression. This cluster of genes can be thought of as the first part of a large genetic force that pushes the body from a curable, but sick, point to an incurable diseased point through a catastrophic bifurcation. The data analyzed is time course microarray blood assay data of 7 high risk individuals for Type 1 Diabetes who progressed into a clinical onset, with an additional larger study requested to be presented at the conference. The normalized data is 25,000 genes strong, which were narrowed down based on statistical metrics, and finally a machine learning algorithm using critical transition metrics found the driving network. This approach was created to be repeatable across multiple complex diseases with only progression time course data needed so that it would be applicable to identifying when an individual is at risk of developing a complex disease. Thusly, preventative measures can be enacted, and in the longer term, offers a possible solution to prevent all Type 1 Diabetes.

  15. Low temperature pathways to Chevrel phases via reduced molybdenum sulfide cluster complexes

    NASA Astrophysics Data System (ADS)

    Shane, H.

    1993-03-01

    The initial cluster compound, Na(2y)Mo(6)S(8+y) py(sub x), was discovered by reacting Mo(6)Cl(12) with higher stoichiometries of sodium hydrosulfide and sodium butoxide in butanol/pyridine. This compound can subsequently undergo ligand exchange reactions to form a variety of cluster complexes. Single-crystal structure determinations are reported for the pyridine (py), piperidine (pip), and pyrrolidine (pyrr) complexes: triclinic Mo(6)S(8)(PY)(6) (center dot) 1.65py, cubic Mo(6)S(8)(py)(6) (center dot) 2py, Mo(6)S(8)(pip)(6) (center dot) 7pip, and Mo(6)S(8) (pyrr)(6) (center dot) 1pyrr. Delegation of the cluster complexes was explored. Direct heating under dynamic vacuum led to incomplete delegation. Reactions with tin and lead resulted in formation of corresponding Chevrel phase compounds along with MoS(2). Thermolysis reactions in the presence of flowing ammonia gas resulted in further delegation than was evidenced for reactions explored in vacuo. Solution reactions with strong acids were studied in an attempt to protonate the ligands and thus make them better leaving groups only limited success was achieved. A new preparative route was developed for ternary molybdenum sulfides. Cation exchange reactions with Na(2y)Mo(6)S(8+y)(MeOH)(x) were used to form the cobalt, tin, lead, and holmium compounds. Preliminary hydrodesulfurization studies on the sodium and cobalt compounds showed that they possess larger surface areas and thiophene conversion percentages than Chevrel phases, but a lower HDS rate.

  16. The young open cluster NGC 3293 and its relation to Car OB1 and the Carina Nebula complex

    NASA Technical Reports Server (NTRS)

    Turner, D. G.; Grieve, G. R.; Herbst, W.; Harris, W. E.

    1980-01-01

    On the basis of visible evidence, NGC 3293 appears to be associated with a number of objects in the Carina Nebula complex. UBVRI photoelectric photometry and MK-spectral specifications are presented for a large number of stars in this cluster and its surroundings (Car OB1). Over 70 cluster members with spectral types earlier than B9 are identified. Star counts indicate that the expected number of members brighter than V = 18 is 297 plus or minus 9. The cluster appears to be situated just in front of a dense dust lane, which itself appears to be part of the dust complex emanating from the center of the Carina Nebula.

  17. Capillary Liquid Chromatography Mass Spectrometry Analysis of Intact Monolayer-Protected Gold Clusters in Complex Mixtures.

    PubMed

    Black, David M; Bach, Stephan B H; Whetten, Robert L

    2016-06-01

    In some respects, large noble-metal clusters protected by thiolate ligands behave as giant molecules of definite composition and structure; however, their rigorous analysis continues to be quite challenging. Analysis of complex mixtures of intact monolayer-protected clusters (MPCs) by liquid chromatography mass spectrometry (LC-MS) could provide quantitative identification of the various components present. This advance is critical for biomedical and toxicological research, as well as in fundamental studies that rely on the identification of selected compositions. This work expands upon the separate LC and MS results previously achieved, by interfacing the capillary liquid chromatograph directly to the electrospray source of the mass spectrometer, in order to provide an extremely sensitive, quantitative, and rapid means to characterize MPCs and their derivatives far beyond that of earlier reports. Here, we show that nonaqueous reversed-phase chromatography can be coupled to mass-spectrometry detection to resolve complex mixtures in minute (∼100 ng) samples of gold MPCs, of molecular masses up to ∼40 kDa, and with single-species sensitivity easily demonstrated for components on the level of sub-10 ng or picomole (1 pmol). PMID:27216373

  18. The Intrinsic Properties of the Stellar Clusters in the M82 Starburst Complex: Propagating Star Formation?

    NASA Astrophysics Data System (ADS)

    Satyapal, S.; Watson, Dan M.; Pipher, J. L.; Forrest, W. J.; Greenhouse, M. A.; Smith, H. A.; Fischer, J.; Woodward, Charles E.

    1997-07-01

    Near-Infrared spectroscopy combined with high spatial resolution imaging have been used in this work to probe the central 500 pc of M82. Imaging observations in the 2.36 μm CO band head are added to our previously published near-infrared hydrogen recombination line imaging, near-infrared broadband imaging, and 3.29 μm dust feature imaging observations, in order to study the nature of the starburst stellar population. A starburst model is constructed and compared with the observations of the stellar clusters in the starburst complex. Our analysis implies that the typical age for the starburst clusters is 107 yr. In addition, our high spatial resolution observations indicate that there is an age dispersion within the starburst complex that is correlated with projected distance from the center of the galaxy. The inferred age dispersion is 6 × 106 yr. If the starburst in M82 is propagating outward from the center, this age dispersion corresponds to a velocity of propagation, originating in the center, of ~50 km s-1. Our quantitative analysis also reveals that a Salpeter initial mass function, extending from 0.1 to 100 M⊙, can fit the observed properties of M82 without using up more than 30% of the total dynamical mass in the starburst.

  19. Lipoprotein insertion into membranes of various complexity: lipid sorting, interfacial adsorption and protein clustering.

    PubMed

    Erwin, Nelli; Sperlich, Benjamin; Garivet, Guillaume; Waldmann, Herbert; Weise, Katrin; Winter, Roland

    2016-04-01

    In a combined chemical-biological and biophysical approach we explored the membrane partitioning of the lipidated signaling proteins N-Ras and K-Ras4B into membrane systems of different complexity, ranging from one-component lipid bilayers and anionic binary and ternary heterogeneous membrane systems even up to partitioning studies on protein-free and protein-containing giant plasma membrane vesicles (GPMVs). To yield a pictorial view of the localization process, imaging using confocal laser scanning and atomic force microscopy was performed. The results reveal pronounced isoform-specific differences regarding the lateral distribution and formation of protein-rich membrane domains. Line tension is one of the key parameters controlling not only the size and dynamic properties of segregated lipid domains but also the partitioning process of N-Ras that acts as a lineactant. The formation of N-Ras protein clusters is even recorded for almost vanishing hydrophobic mismatch. Conversely, for K-Ras4B, selective localization and clustering are electrostatically mediated by its polybasic farnesylated C-terminus. The formation of K-Ras4B clusters is also observed for the multi-component GPMV membrane, i.e., it seems to be a general phenomenon, largely independent of the details of the membrane composition, including the anionic charge density of lipid headgroups. Our data indicate that unspecific and entropy-driven membrane-mediated interactions play a major role in the partitioning behavior, thus relaxing the need for a multitude of fine-tuned interactions. Such a scenario seems also to be reasonable recalling the high dynamic nature of cellular membranes. Finally, we note that even relatively simple models of heterogeneous membranes are able to reproduce many of the properties of much more complex biological membranes. PMID:26960984

  20. STAR CLUSTER COMPLEXES AND THE HOST GALAXY IN THREE H II GALAXIES: Mrk 36, UM 408, AND UM 461

    SciTech Connect

    Lagos, P.; Telles, E.; Nigoche-Netro, A.

    2011-11-15

    We present a stellar population study of three H II galaxies (Mrk 36, UM 408, and UM 461) based on the analysis of new ground-based high-resolution near-infrared J, H, and K{sub p} broadband and Br{gamma} narrowband images obtained with Gemini/NIRI. We identify and determine the relative ages and masses of the elementary star clusters and/or star cluster complexes of the starburst regions in each of these galaxies by comparing the colors with evolutionary synthesis models that include the contribution of stellar continuum, nebular continuum, and emission lines. We found that the current star cluster formation efficiency in our sample of low-luminosity H II galaxies is {approx}10%. Therefore, most of the recent star formation is not in massive clusters. Our findings seem to indicate that the star formation mode in our sample of galaxies is clumpy, and that these complexes are formed by a few massive star clusters with masses {approx}>10{sup 4} M{sub Sun }. The age distribution of these star cluster complexes shows that the current burst started recently and likely simultaneously over short timescales in their host galaxies, triggered by some internal mechanism. Finally, the fraction of the total cluster mass with respect to the low surface brightness (or host galaxy) mass, considering our complete range in ages, is less than 1%.

  1. Spatiotemporal Clustering of Mycobacterium tuberculosis Complex Genotypes in Florida: Genetic Diversity Segregated by Country of Birth

    PubMed Central

    Séraphin, Marie Nancy; Lauzardo, Michael; Morris, J. Glenn; Blackburn, Jason K.

    2016-01-01

    Background Tuberculosis (TB) is caused by members of the Mycobacterium tuberculosis complex (MTBC). Although the MTBC is highly clonal, between-strain genetic diversity has been observed. In low TB incidence settings, immigration may facilitate the importation of MTBC strains with a potential to complicate TB control efforts. Methods We investigated the genetic diversity and spatiotemporal clustering of 2,510 MTBC strains isolated in Florida, United States, between 2009 and 2013 and genotyped using spoligotyping and 24-locus MIRU-VNTR. We mapped the genetic diversity to the centroid of patient residential zip codes using a geographic information system (GIS). We assessed transmission dynamics and the influence of immigration on genotype clustering using space-time permutation models adjusted for foreign-born population density and county-level HIV risk and multinomial models stratified by country of birth and timing of immigration in SaTScan. Principal Findings Among the 2,510 strains, 1,245 were reported among foreign-born persons; including 408 recent immigrants (<5 years). Strain allelic diversity (h) ranged from low to medium in most locations and was most diverse in urban centers where foreign-born population density was also high. Overall, 21.5% of cases among U.S.-born persons and 4.6% among foreign-born persons clustered genotypically and spatiotemporally and involved strains of the Haarlem family. One Haarlem space-time cluster identified in the mostly rural northern region of Florida included US/Canada-born individuals incarcerated at the time of diagnosis; two clusters in the mostly urban southern region of Florida were composed predominantly of foreign-born persons. Both groups had HIV prevalence above twenty percent. Conclusions/Significance Almost five percent of TB cases reported in Florida during 2009–2013 were potentially due to recent transmission. Improvements to TB screening practices among the prison population and recent immigrants are

  2. Creation of cosmic structure in the complex galaxy cluster merger Abell 2744

    NASA Astrophysics Data System (ADS)

    Merten, J.; Coe, D.; Dupke, R.; Massey, R.; Zitrin, A.; Cypriano, E. S.; Okabe, N.; Frye, B.; Braglia, F. G.; Jiménez-Teja, Y.; Benítez, N.; Broadhurst, T.; Rhodes, J.; Meneghetti, M.; Moustakas, L. A.; Sodré, L., Jr.; Krick, J.; Bregman, J. N.

    2011-10-01

    We present a detailed strong-lensing, weak-lensing and X-ray analysis of Abell 2744 (z= 0.308), one of the most actively merging galaxy clusters known. It appears to have unleashed 'dark', 'ghost', 'bullet' and 'stripped' substructures, each ˜1014 M⊙. The phenomenology is complex and will present a challenge for numerical simulations to reproduce. With new, multiband Hubble Space Telescope (HST) imaging, we identify 34 strongly lensed images of 11 galaxies around the massive Southern 'core'. Combining this with weak-lensing data from HST, VLT and Subaru, we produce the most detailed mass map of this cluster to date. We also perform an independent analysis of archival Chandra X-ray imaging. Our analyses support a recent claim that the Southern core and Northwestern substructure are post-merger and exhibit morphology similar to the Bullet Cluster viewed from an angle. From the separation between X-ray emitting gas and lensing mass in the Southern core, we derive a new and independent constraint on the self-interaction cross-section of dark matter particles σ/m < 3 ± 1 cm2 g-1. In the Northwestern substructure, the gas, dark matter and galaxy components have become separated by much larger distances. Most curiously, the 'ghost' clump (primarily gas) leads the 'dark' clump (primarily dark matter) by more than 150 kpc. We propose an enhanced 'ram-pressure slingshot' scenario which may have yielded this reversal of components with such a large separation, but needs further confirmation by follow-up observations and numerical simulations. A secondary merger involves a second 'bullet' clump in the North and an extremely 'stripped' clump to the West. The latter appears to exhibit the largest separation between dark matter and X-ray emitting baryons detected to date in our sky.

  3. Predicting Water Activity for Complex Wastes with Solvation Cluster Equilibria (SCE) - 12042

    SciTech Connect

    Agnew, S.F.; Reynolds, J.G.; Johnston, C.T.

    2012-07-01

    Predicting an electrolyte mixture's water activity, i.e. the ratio of water vapor pressure over a solution with that of pure water, in principle reveals both boiling point and solubilities for that mixture. Better predictions of these properties helps support the ongoing missions to concentrate complex nuclear waste mixtures in order to conserve tank space and improved predictions of water activity will help. A new approach for predicting water activity, the solvation cluster equilibria (SCE) model, uses pure electrolyte water activities to predict water activity for a complex mixture of those electrolytes. An SCE function based on electrolyte hydration free energy and a standard Debye- Hueckel (DH) charge compression fits each pure electrolyte's water activity with three parameters. Given these pure electrolyte water activities, the SCE predicts any mixture water activity over a large range of concentration with an additional parameter for each mixture vector, the multinarity. In contrast to ionic strength, which scales with concentration, multinarity is related to the relative proportion of electrolytes in a mixture and can either increase or decrease the water activity prediction over a broad range of concentration for that mixture. The SCE model predicts water activity for complex electrolyte mixtures based on the water activities of pure electrolytes. Three parameter SCE functions fit the water activities of pure electrolytes and along with a single multinarity parameter for each mixture vector then predict the mixture water activity. Predictions of water activity can in principle predict solution electrolyte activity and this relationship will be explored in the future. Predicting electrolyte activities for complex mixtures provides a means of determining solubilities for each electrolyte. Although there are a number of reports [9, 10, 11] of water activity models for pure and binary mixtures of electrolytes, none of them compare measured versus calculated

  4. Communication: A reduced-space algorithm for the solution of the complex linear response equations used in coupled cluster damped response theory

    NASA Astrophysics Data System (ADS)

    Kauczor, Joanna; Norman, Patrick; Christiansen, Ove; Coriani, Sonia

    2013-12-01

    We present a reduced-space algorithm for solving the complex (damped) linear response equations required to compute the complex linear response function for the hierarchy of methods: coupled cluster singles, coupled cluster singles and iterative approximate doubles, and coupled cluster singles and doubles. The solver is the keystone element for the development of damped coupled cluster response methods for linear and nonlinear effects in resonant frequency regions.

  5. Ring opening of strained-ring heterocycles containing nitrogen by an osmium cluster complex

    SciTech Connect

    Adams, R.D.; Chen, Gong

    1992-11-01

    The osmium cluster complex Os{sub 3}(CO){sub 10}({mu}-NCH{sub 2}CH{sub 2}CH{sub 2})({mu}-H) (1) was obtained in 34% yield from the reaction of Os{sub 3}(CO){sub 10}(NCMe){sub 2} with azetidine. Complex 1 was characterized crystallographically and shown to contain a four-membered NCH{sub 2}CH{sub 2}CH{sub 2} ring bridging two of the metal atoms via the nitrogen atom. When heated to 125{degrees}C, 1 was transformed to the new complex Os{sub 3}(CO){sub 10}[{mu}-N=C(H)Et]({mu}-H) (2; 27% yield) by an opening of the four-membered ring and a hydrogen shift. Crystal data: for 1, space group P2{sub 1}/c, a = 8.793 (2) A, b = 16.265 (2) A, c = 13.766 (4) A, {Beta} = 110.56 (1){degrees}, Z = 4, 1872 reflections, R = 0.039; for 2, space group P1, a = 92.73 (2){degrees}, {Beta} = 99.03 (2){degrees}, {gamma} = 81.52 (2){degrees}, Z = 6, 4862 reflections, R = 0.024. 16 refs. 2 figs.

  6. Clustering of time-evolving scaling dynamics in a complex signal.

    PubMed

    Saghir, Hamidreza; Chau, Tom; Kushki, Azadeh

    2016-07-01

    Complex time series are widespread in physics and physiology. Multifractal analysis provides a tool to study the scaling dynamics of such time series. However, the temporal evolution of scaling dynamics has been ignored by traditional tools such as the multifractal spectrum. We present scaling maps that add the time dimension to the study of scaling dynamics. This is particularly important in cases in which the dynamics of the underlying processes change in time or in applications that necessitate real-time detection of scaling dynamics. In addition, we present a methodology for automatic clustering of existing scaling regimes in a signal. We demonstrate the methodology on time-evolving correlated and uncorrelated noise and the output of a physiological control system (i.e., cardiac interbeat intervals) in healthy and pathological states. PMID:27575136

  7. Clustering of time-evolving scaling dynamics in a complex signal

    NASA Astrophysics Data System (ADS)

    Saghir, Hamidreza; Chau, Tom; Kushki, Azadeh

    2016-07-01

    Complex time series are widespread in physics and physiology. Multifractal analysis provides a tool to study the scaling dynamics of such time series. However, the temporal evolution of scaling dynamics has been ignored by traditional tools such as the multifractal spectrum. We present scaling maps that add the time dimension to the study of scaling dynamics. This is particularly important in cases in which the dynamics of the underlying processes change in time or in applications that necessitate real-time detection of scaling dynamics. In addition, we present a methodology for automatic clustering of existing scaling regimes in a signal. We demonstrate the methodology on time-evolving correlated and uncorrelated noise and the output of a physiological control system (i.e., cardiac interbeat intervals) in healthy and pathological states.

  8. CHIMERA: Top-down model for hierarchical, overlapping and directed cluster structures in directed and weighted complex networks

    NASA Astrophysics Data System (ADS)

    Franke, R.

    2016-11-01

    In many networks discovered in biology, medicine, neuroscience and other disciplines special properties like a certain degree distribution and hierarchical cluster structure (also called communities) can be observed as general organizing principles. Detecting the cluster structure of an unknown network promises to identify functional subdivisions, hierarchy and interactions on a mesoscale. It is not trivial choosing an appropriate detection algorithm because there are multiple network, cluster and algorithmic properties to be considered. Edges can be weighted and/or directed, clusters overlap or build a hierarchy in several ways. Algorithms differ not only in runtime, memory requirements but also in allowed network and cluster properties. They are based on a specific definition of what a cluster is, too. On the one hand, a comprehensive network creation model is needed to build a large variety of benchmark networks with different reasonable structures to compare algorithms. On the other hand, if a cluster structure is already known, it is desirable to separate effects of this structure from other network properties. This can be done with null model networks that mimic an observed cluster structure to improve statistics on other network features. A third important application is the general study of properties in networks with different cluster structures, possibly evolving over time. Currently there are good benchmark and creation models available. But what is left is a precise sandbox model to build hierarchical, overlapping and directed clusters for undirected or directed, binary or weighted complex random networks on basis of a sophisticated blueprint. This gap shall be closed by the model CHIMERA (Cluster Hierarchy Interconnection Model for Evaluation, Research and Analysis) which will be introduced and described here for the first time.

  9. Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

    SciTech Connect

    Liang, W.

    1994-11-01

    X-ray absorption spectroscopy (XAS) was performed on Photosystem II (PSII)-enriched membranes prepared from spinach to explore: (1) the correlation between structure and magnetic spin state of the Mn cluster in the oxygen evolving complex (OEC) in the S{sub 2} state; and (2) the oxidation state changes of the Mn cluster in the flash-induced S-states. The structure of the Mn cluster in the S{sub 2} state with the g{approx}4 electron paramagnetic resonance (EPR) signal (S{sub 2}-g4 state) was compared with that in the S{sub 2} state with multiline signal (S{sub 2}-MLS state) and the S{sub 1} state. The S{sub 2}-g4 state has a higher XAS inflection point energy than that of the S{sub 1} state, indicating the oxidation of Mn in the advance from the S{sub 1} to the S{sub 2}-g4 state. Differences in the edge shape and in the extended X-ray absorption fine structure (EXAFS) show that the structure of the Mn cluster in the S{sub 2}-g4 state is different from that in the S{sub 2}-MLS or the S{sub 1} state. In the S{sub 2}-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 {angstrom} and 2.85 {angstrom}. Very little distance disorder exists in the second shell of the S{sub 1} or S{sub 2}-MLS states. The third shell of the S{sub 2}-g4 state at about 3.3 {angstrom} also contains increased heterogeneity relative to that of the S{sub 2}-MLS or the S{sub 1} state. Various S-states were prepared at room-temperature by saturating, single-turnover flashes. The flash-dependent oscillation in the amplitude of the MLS was used to characterize the S-state composition and to construct {open_quotes}pure{close_quotes} S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S{sub 1} {yields} S{sub 2} transition.

  10. A CEP215-HSET complex links centrosomes with spindle poles and drives centrosome clustering in cancer.

    PubMed

    Chavali, Pavithra L; Chandrasekaran, Gayathri; Barr, Alexis R; Tátrai, Péter; Taylor, Chris; Papachristou, Evaggelia K; Woods, C Geoffrey; Chavali, Sreenivas; Gergely, Fanni

    2016-01-01

    Numerical centrosome aberrations underlie certain developmental abnormalities and may promote cancer. A cell maintains normal centrosome numbers by coupling centrosome duplication with segregation, which is achieved through sustained association of each centrosome with a mitotic spindle pole. Although the microcephaly- and primordial dwarfism-linked centrosomal protein CEP215 has been implicated in this process, the molecular mechanism responsible remains unclear. Here, using proteomic profiling, we identify the minus end-directed microtubule motor protein HSET as a direct binding partner of CEP215. Targeted deletion of the HSET-binding domain of CEP215 in vertebrate cells causes centrosome detachment and results in HSET depletion at centrosomes, a phenotype also observed in CEP215-deficient patient-derived cells. Moreover, in cancer cells with centrosome amplification, the CEP215-HSET complex promotes the clustering of extra centrosomes into pseudo-bipolar spindles, thereby ensuring viable cell division. Therefore, stabilization of the centrosome-spindle pole interface by the CEP215-HSET complex could promote survival of cancer cells containing supernumerary centrosomes. PMID:26987684

  11. Electrostatic complexation of polyelectrolyte and magnetic nanoparticles: from wild clustering to controllable magnetic wires

    NASA Astrophysics Data System (ADS)

    Yan, Minhao; Qu, Li; Fan, Jiangxia; Ren, Yong

    2014-05-01

    We present the electrostatic complexation between polyelectrolytes and charged nanoparticles. The nanoparticles in solution are γ-Fe2O3 (maghemite) spheres with 8.3 nm diameter and anionic surface charges. The complexation was monitored using three different formulation pathways such as direct mixing, dilution, and dialysis. In the first process, the hybrids were obtained by mixing stock solutions of polymers and nanoparticles. A `destabilization state' with sharp and intense maximum aggregation was found at charges stoichiometry (isoelectric point). While on the two sides of the isoelectric point, `long-lived stable clusters state' (arrested states) were observed. Dilution and dialysis processes were based on controlled desalting kinetics according to methods developed in molecular biology. Under an external magnetic field ( B = 0.3 T), from dialysis at isoelectric point and at arrested states, cationic polyelectrolytes can `paste' these magnetic nanoparticles (NPs) together to yield irregular aggregates (size of 100 μm) and regular rod-like aggregates, respectively. These straight magnetic wires were fabricated with diameters around 200 nm and lengths comprised between 1 μm and 0.5 mm. The wires can have either positive or negative charges on their surface. After analyzing their orientational behavior under an external rotating field, we also showed that the wires made from different polyelectrolytes have the same magnetic property. The recipe used a wide range of polyelectrolytes thereby enhancing the versatility and applied potentialities of the method. This simple and general approach presents significant perspective for the fabrication of hybrid functional materials.

  12. The Raman and vibronic activity of intermolecular vibrations in aromatic-containing complexes and clusters

    SciTech Connect

    Maxton, P.M.; Schaeffer, M.W.; Ohline, S.M.; Kim, W.; Venturo, V.A.; Felker, P.M. )

    1994-11-15

    Theoretical and experimental results pertaining to the excitation of intermolecular vibrations in the Raman and vibronic spectra of aromatic-containing, weakly bound complexes and clusters are reported. The theoretical analysis of intermolecular Raman activity is based on the assumption that the polarizability tensor of a weakly bound species is given by the sum of the polarizability tensors of its constituent monomers. The analysis shows that the van der Waals bending fundamentals in aromatic--rare gas complexes may be expected to be strongly Raman active. More generally, it predicts strong Raman activity for intermolecular vibrations that involve the libration or internal rotation of monomer moieties having appreciable permanent polarizability anisotropies. The vibronic activity of intermolecular vibrations in aromatic-rare gas complexes is analyzed under the assumption that every vibronic band gains its strength from an aromatic-localized transition. It is found that intermolecular vibrational excitations can accompany aromatic-localized vibronic excitations by the usual Franck--Condon mechanism or by a mechanism dependent on the librational amplitude of the aromatic moiety during the course of the pertinent intermolecular vibration. The latter mechanism can impart appreciable intensity to bands that are forbidden by rigid-molecule symmetry selection rules. The applicability of such rules is therefore called into question. Finally, experimental spectra of intermolecular transitions, obtained by mass-selective, ionization-detected stimulated Raman spectroscopies, are reported for benzene--X (X=Ar, --Ar[sub 2], N[sub 2], HCl, CO[sub 2], and --fluorene), fluorobenzene--Ar and --Kr, aniline--Ar, and fluorene--Ar and --Ar[sub 2]. The results support the conclusions of the theoretical analyses and provide further evidence for the value of Raman methods in characterizing intermolecular vibrational level structures.

  13. VizieR Online Data Catalog: Galaxies in the UMa cluster complex (Karachentsev+, 2013)

    NASA Astrophysics Data System (ADS)

    Karachentsev, I. D.; Nasonova, O. G.; Courtois, H. M.

    2015-04-01

    A nearby friable cloud in Ursa Majoris contains 270 galaxies with radial velocities 500complex. According to Makarov & Karachentsev (2011MNRAS.412.2498M, Cat. J/MNRAS/412/2498), most of the UMa galaxies belong to seven bound groups, which have the following median parameters: velocity dispersion of 58k/s, harmonic projected radius of 300kpc, virial mass of 2x1012M⊙ and virial mass-to-K-band luminosity ratio of 27M⊙/L⊙. Almost a half of the UMa cloud population are gas-rich dwarfs (Ir, Im, BCD) with active star formation seen in the GALEX UV-survey. The UMa groups reside within 15-19Mpc from us, being just at the same distance as the Virgo cluster. The total virial mass of the UMa groups is 4x1013M⊙, yielding the average density of dark matter in the UMa cloud to be Ωm=0.08, i.e. a factor of 3 lower than the cosmic average. This is despite the fact that the UMa cloud resides in a region of the Universe that is an apparent overdensity. A possible explanation for this is that most mass in the Universe lies in the empty space between clusters. Herewith, the mean distances and velocities of the UMa groups follow nearly undisturbed Hubble flow without a sign of the 'Z-wave' effect caused by infall towards a massive attractor. This constrains the total amount of dark matter between the UMa groups within the cloud volume. (1 data file).

  14. Nucleophilic ring opening of bridging thietanes in open triosmium cluster complexes

    SciTech Connect

    Adams, R.D.; Belinski, J.A.

    1992-07-01

    The complexes Os{sub 3}(CO){sub 9}({mu}{sub 3}-S)[{mu}-SCH{sub 2}CMe{sub 2}CMe{sub 2}CH{sub 2}] (1) and Os{sub 3}(CO){sub 9}({mu}{sub 3}-S)[{mu}-SCH{sub 2}CH{sub 2}CH{sub 2}] (2) were obtained from the reactions of Os{sub 3}(CO){sub 10}({mu}{sub 3}-S) with 3,3-dimethylthietane (DMT) and thietane, respectively, at -42 {degree}C in the presence of Me{sub 3}NO. Compound 1 was characterized by a single-crystal X-ray diffraction analysis and was found to contain a DMT group bridging two of the nonbonded metal atoms in the open cluster of three metal atoms by using both lone pairs of electrons on the sulfur atom. Compound 1 reacted with bis(triphenylphosphine)nitrogen(1+) chloride ([PPN]Cl) at 25 {degrees}C to yield the salt [PPN][Os{sub 3}-(CO){sub 9}({mu}-SCH{sub 2}CMe{sub 2}CH{sub 2}Cl)({mu}{sub 3}-S)] (3; 76%), in which the chloride ion was added to one of the methylene groups of the DMT ring in a process that caused the ring to open by cleavage of one of the carbon-sulfur bonds. A 4-chloro-3,3-dimethylpropanethiolate ligand bridges the open edge of the anionic triosmium cluster. Compound 3 was converted to the neutral complex Os{sub 3}(CO){sub 9}[{mu}-SCH{sub 2}CMe{sub 2}CMe{sub 2}CH{sub 2}Cl]({mu}{sub 3}-S)({mu}-H) (4) by reaction with HCl at 25 {degrees}C. Compound 4 is structurally similar to 3, except that is contains a hydride ligand bridging one of the two metal-metal bonds. Compounds 1 and 2 react with HCl in CH{sub 2}Cl{sub 2} solvent to yield the neutral compounds 4 and Os{sub 3}(CO){sub 9}[{mu}-SCH{sub 2}CH{sub 2}CH{sub 2}Cl]({mu}{sub 3}-S)({mu}-H) (5) in 89% and 90% yields, respectively, in one step. 11 refs., 3 figs., 10 tabs.

  15. Nucleophilic ring opening of bridging thietane ligands in trirhenium carbonyl cluster complexes

    SciTech Connect

    Adams, R.D.; Cortopassi, J.E.; Falloon, S.B.

    1992-11-01

    The reactions of 3,3-dimethylthietane, SCH{sub 2}CMe{sub 2}CH{sub 2} (3,3-DMT), and thietane, SCH{sub 2}CH{sub 2}CH{sub 2}, with Re{sub 3}(CO){sub 10}[{mu}-SCH{sub 2}CH{sub 2}CH{sub 2}]({mu}-H){sub 3}, 2b. Compound 2a was characterized crystallographically and was found to consist of a trirhenium cluster with three bridging hydride ligands and a bridging thietane ligand coordinated through its sulfur atom. 2a and 2b react with halide ions by ring-opening additions to the 3,3-DMT ligand to yield the complex anions [Re{sub 3}(CO){sub 10}({mu}-SCH{sub 2}CMe{sub 2}CH{sub 2}x)({mu}-h){sub 3}]{sup -} 3A-6A, X = F (71%), Cl(71%), Br(84%), I(87%) and [Re{sub 3}(CO){sub 10}({mu}-SCH{sub 2}CH{sub 2}CH{sub 2}Cl)({mu}-H){sub 3}]{sup -}, 4b (67%). Similarly, addition of NMe{sub 3} to 2a and 2b yielded the ring-opened zwitterions Re{sub 3}(CO){sub 10}({mu}-SCH{sub 2}CMe{sub 2}CH{sub 2}NMe{sub 3})({mu}-H){sub 3}, 7 a crystographically. They are zwitterions positively charged at the nitrogen atoms and negatively charged on the trirhenium clusters. Complex 7b was also obtained in a 48% yield from the reaction of Re{sub 3}(C){sub 12}({mu}-H){sub 3} with Me{sub 3}NO in the presence of thietane, but the corresponding reaction using 3,3-DMT yielded only 2a and Re{sub 3}(CO){sub 11}(SCH{sub 2}CMe{sub 2}CH{sub 2})({mu}-H){sub 3}, 8. Attempts to obtain a ring-opening addition to 2a by reaction with PMe{sub 2}Ph yielded only Re{sub 3}(CO){sub 10}(PMe{sub 2}PH){sub 2}({mu}-H){sub 3} by ligand substitution. Attempts to obtain ring opening addition to 8 by reaction with I{sup -} yielded only [Re{sub 3}(CO){sub 11}I({mu}-H){sub 3}]{sup -} by ligand substitution. 20 refs., 3 figs., 10 tabs.

  16. Non-traditional spectral clustering algorithms for the detection of community structure in complex networks: a comparative analysis

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoke; Gao, Lin

    2011-05-01

    The detection of community structure in complex networks is crucial since it provides insight into the substructures of the whole network. Spectral clustering algorithms that employ the eigenvalues and eigenvectors of an appropriate input matrix have been successfully applied in this field. Despite its empirical success in community detection, spectral clustering has been criticized for its inefficiency when dealing with large scale data sets. This is confirmed by the fact that the time complexity for spectral clustering is cubic with respect to the number of instances; even the memory efficient iterative eigensolvers, such as the power method, may converge slowly to the desired solutions. In efforts to improve the complexity and performance, many non-traditional spectral clustering algorithms have been proposed. Rather than using the real eigenvalues and eigenvectors as in the traditional methods, the non-traditional clusterings employ additional topological structure information characterized by the spectrum of a matrix associated with the network involved, such as the complex eigenvalues and their corresponding complex eigenvectors, eigenspaces and semi-supervised labels. However, to the best of our knowledge, no work has been devoted to comparison among these newly developed approaches. This is the main goal of this paper, through evaluating the effectiveness of these spectral algorithms against some benchmark networks. The experimental results demonstrate that the spectral algorithm based on the eigenspaces achieves the best performance but is the slowest algorithm; the semi-supervised spectral algorithm is the fastest but its performance largely depends on the prior knowledge; and the spectral method based on the complement network shows similar performance to the conventional ones.

  17. Carbonyl substitution chemistry of some trimetallic transition metal cluster complexes with polyfunctional ligands

    SciTech Connect

    Byrne, Lindsay T.; Hondow, Nicole S.; Koutsantonis, George A.; Skelton, Brian W.; Torabi, A. Asgar; White, Allan H.; Wild, S. Bruce

    2008-11-03

    The trimetallic clusters [Ru{sub 3}(CO){sub 10}(dppm)], [Ru{sub 3}(CO){sub 12}] and [RuCo{sub 2}(CO){sub 11}] react with a number of multifunctional secondary phosphine and tertiary arsine ligands to give products consequent on carbonyl substitution and, in the case of the secondary phosphines, PH activation. The reaction with the unresolved mixed P/S donor, 1-phenylphosphino-2-thio(ethane), HSCH{sub 2}CH{sub 2}PHPh ({double_bond}LH{sub 2}), gave two products under various conditions which have been characterized by spectroscopic and crystallographic means. These two complexes [Ru{sub 3}({mu}dppm)(H)(CO){sub 7}(LH)] and [Ru{sub 3}({mu}-dppm)(H)(CO){sub 8}(LH)Ru{sub 3}({mu}-dppm)(CO){sub 9}], show the versatility of the ligand, with it chelating in the former and bridging two Ru{sub 3} units in the latter. The stereogenic centres in the molecules gave rise to complicated spectroscopic data which are consistent with the presence of diastereoisomers. In the case of [Ru{sub 3}(CO){sub 12}] the reaction with LH{sub 2} gave a poor yield of a tetranuclear butterfly cluster, [Ru{sub 4}(CO){sub 10}(L){sub 2}], in which two of the ligands bridge opposite hinge wingtip bonds of the cluster. A related ligand, HSCH{sub 2}CH{sub 2}AsMe(C{sub 6}H{sub 4}CH{sub 2}OMe), reacted with [RuCo{sub 2}(CO){sub 11}] to give a low yield of the heterobimetallic Ru-Co adduct, [RuCo(CO){sub 6}(SCH{sub 2}CH{sub 2}AsMe(C{sub 6}H{sub 4}CH{sub 2}OMe))], which appears to be the only one of its type so far structurally characterized. The secondary phosphine, HPMe(C{sub 6}H{sub 4}(CH{sub 2}OMe)) and its oxide HP(O)Me(C{sub 6}H{sub 4}(CH{sub 2}OMe)) also react with the cluster [Ru{sub 3}(CO){sub 10}(dppm)] to give carbonyl substitution products, [Ru{sub 3}(CO){sub 5}(dppm)({mu}{sub 2}-PMe(C{sub 6}H{sub 4}CH{sub 2}OMe)){sub 4}], and [Ru{sub 3}H(CO){sub 7}(dppm)({mu}{sub 2},{eta}{sup 1}P({double_bond}O)Me(C{sub 6}H{sub 4}CH{sub 2}OMe))]. The former consists of an open Ru{sub 3} triangle with four

  18. Ca cofactor of the water-oxidation complex: Evidence for a Mn/Ca heteronuclear cluster

    SciTech Connect

    Cinco, Roehl M.; Robblee, John H.; Messinger, Johannes; Fernandez, Carmen; McFarlane, Karen L.; Pizarro, Shelly A.; Sauer, Ken; Yachandra, Vittal K.

    2001-07-25

    Calcium and chloride are necessary cofactors for the proper function of the oxygen-evolving complex (OEC) of Photosystem II (PS II). Located in the thylakoid membranes of green plants, cyanobacteria and algae, PS II and the OEC catalyze the light-driven oxidation of water into dioxygen (released into the biosphere), protons and electrons for carbon fixation. The actual chemistry of water oxidation is performed by a cluster of four manganese atoms, along with the requisite cofactors Ca{sup 2+} and Cl{sup -}. While the Mn complex has been extensively studied by X-ray absorption techniques, comparatively less is known about the Ca{sup 2+} cofactor. The fewer number of studies on the Ca{sup 2+} cofactor have sometimes relied on substituting the native cofactor with strontium or other metals, and have stirred some debate about the structure of the binding site. past efforts using Mn EXAFS on Sr-substituted PSII are suggestive of a close link between the Mn cluster and Sr, within 3.5 {angstrom}. The most recent published study using Sr EXAFS on similar samples confirms this finding of a 3.5 {angstrom} distance between Mn and Sr. This finding was base3d on a second Fourier peak (R {approx} 3 {angstrom}) in the Sr EXAFS from functional samples, but is absent from inactive, hydroxylamine-treated PS II. This Fourier peak II was found to fit best to two Mn at 3.5 {angstrom} rather than lighter atoms (carbon). Nevertheless, other experiments have given contrary results. They wanted to extend the technique by using polarized Sr EXAFS on layered Sr-substituted samples, to provide important angle information. Polarized EXAFS involves collecting spectra for different incident angles ({theta}) between the membrane normal of the layered sample and the X-ray electric field vector. Dichroism in the EXAFS can occur, depending on how the particular absorber-backscatterer (A-B) vector is aligned with the electric field. Through analysis of the dichroism, they extract the average number

  19. X-ray observations of complex temperature structure in the cool-core cluster A85

    SciTech Connect

    Schenck, David E.; Datta, Abhirup; Burns, Jack O.; Skillman, Sam

    2014-07-01

    X-ray observations were used to examine the complex temperature structure of A85, a cool-core galaxy cluster. Temperature features can provide evidence of merging events which shock heat the intracluster gas. Temperature maps were made from both Chandra and XMM-Newton observations. The combination of a new, long-exposure XMM observation and an improved temperature map binning technique produced the highest fidelity temperature maps of A85 to date. Hot regions were detected near the subclusters to the south and southwest in both the Chandra and XMM temperature maps. The presence of these structures implies A85 is not relaxed. The hot regions may indicate the presence of shocks. The Mach numbers were estimated to be ∼1.9 at the locations of the hot spots. Observational effects will tend to systematically reduce temperature jumps, so the measured Mach numbers are likely underestimated. Neither temperature map showed evidence for a shock in the vicinity of the presumed radio relic near the southwest subcluster. However, the presence of a weak shock cannot be ruled out. There was tension between the temperatures measured by the two instruments.

  20. Tribological coatings for complex mechanical elements produced by supersonic cluster beam deposition of metal dichalcogenide nanoparticles

    NASA Astrophysics Data System (ADS)

    Piazzoni, C.; Buttery, M.; Hampson, M. R.; Roberts, E. W.; Ducati, C.; Lenardi, C.; Cavaliere, F.; Piseri, P.; Milani, P.

    2015-07-01

    Fullerene-like MoS2 and WS2 nanoparticles can be used as building blocks for the fabrication of fluid and solid lubricants. Metal dichalcogenide films have a very low friction coefficient in vacuum, therefore they have mostly been used as solid lubricants in space and vacuum applications. Unfortunately, their use is significantly hampered by the fact that in the presence of humidity, oxygen and moisture, the low-friction properties of these materials rapidly degrade due to oxidation. The use of closed-cage MoS2 and WS2 nanoparticles may eliminate this problem, although the fabrication of lubricant thin films starting from dichalcogenide nanoparticles is, to date, a difficult task. Here we demonstrate the use of supersonic cluster beam deposition for the coating of complex mechanical elements (angular contact ball bearings) with nanostructured MoS2 and WS2 thin films. We report structural and tribological characterization of the coatings in view of the optimization of tribological performances for aerospace applications.

  1. Frontier Fields Clusters: Deep Chandra Observations of the Complex Merger MACS~J1149.6+2223

    NASA Astrophysics Data System (ADS)

    Ogrean, G. A.; van Weeren, R. J.; Jones, C.; Forman, W.; Dawson, W. A.; Golovich, N.; Andrade-Santos, F.; Murray, S. S.; Nulsen, P.; Roediger, E.; Zitrin, A.; Bulbul, E.; Kraft, R.; Goulding, A.; Umetsu, K.; Mroczkowski, T.; Bonafede, A.; Randall, S.; Sayers, J.; Churazov, E.; David, L.; Merten, J.; Donahue, M.; Mason, B.; Rosati, P.; Vikhlinin, A.; Ebeling, H.

    2016-03-01

    The Hubble Space Telescope Frontier Fields cluster MACS J1149.6+2223 is one of the most complex merging clusters, believed to consist of four dark matter halos. We present results from deep (365 ks) Chandra observations of the cluster, which reveal the most distant cold front (z = 0.544) discovered to date. In the cluster outskirts, we also detect hints of a surface brightness edge that could be the bow shock preceding the cold front. The substructure analysis of the cluster identified several components with large relative radial velocities, thus indicating that at least some collisions occur almost along the line of sight. The inclination of the mergers with respect to the plane of the sky poses significant observational challenges at X-ray wavelengths. MACS J1149.6+2223 possibly hosts a steep-spectrum radio halo. If the steepness of the radio halo is confirmed, then the radio spectrum, combined with the relatively regular ICM morphology, could indicate that MACS J1149.6+2223 is an old merging cluster.

  2. Organizational and mutational analysis of a complete FR-008/candicidin gene cluster encoding a structurally related polyene complex.

    PubMed

    Chen, Shi; Huang, Xi; Zhou, Xiufen; Bai, Linquan; He, Jing; Jeong, Ki Jun; Lee, Sang Yup; Deng, Zixin

    2003-11-01

    The complete gene cluster for biosynthesis of a polyene complex, FR-008, spans 137.2 kb of the genome of Streptomyces sp. FR-008 consisting of six genes for a modular PKS and 15 additional genes. The extensive similarity to the partially characterized candicidin gene cluster in Streptomyces griseus IMRU3570, especially for genes involved in mycosamine biosynthesis, prompted us to compare the compounds produced by Streptomyces sp. FR-008 and Streptomyces griseus IMRU3570, and we found that FR-008 and candicidin complex are identical. A model for biosynthesis of a set of four structurally related FR-008/candicidin compounds was proposed. Deletion of the putative regulatory genes abolished antibiotic production, while disruption of putative glycosyltransferase and GDP-ketosugar aminotransferase functionalities led to the productions of a set of nonmycosaminated aglycones and a novel polyene complex with attachment of altered sugar moiety, respectively. PMID:14652074

  3. The properties of clusters in the gas phase. IV - Complexes of H2O and HNOx clustering on NOx/-/

    NASA Technical Reports Server (NTRS)

    Lee, N.; Castleman, A. W., Jr.; Keesee, R. G.

    1980-01-01

    Thermodynamic quantities for the gas-phase clustering equilibria of NO2(-) and NO3(-) were determined with high-pressure mass spectrometry. A comparison of values of the free energy of hydration derived from the data shows good agreement with formerly reported values at 296 K. New data for larger NO2(-) and NO3(-) hydrates as well as NO2(-)(HNO2)n were obtained in this study. To aid in understanding the bonding and stability of the hydrates of nitrite and nitrate ions, CNDO/2 calculations were performed, and the results are discussed. A correlation between the aqueous-phase total hydration enthalpy of a single ion and its gas-phase hydration enthalpy was obtained. Atmospheric implications of the data are also briefly discussed.

  4. Ring opening and carbonylation of 3,3-dimethylthietane ligands in ruthenium carbonyl cluster complexes

    SciTech Connect

    Adams, R.D.; Belinski, J.A.; Yamamoto, J.H.

    1992-10-01

    When heated to 97{degrees}C, the complex Ru{sub 4}(CO){sub 12}[{mu}-SCH{sub 2}CMe{sub 2}CH{sub 2}]2 (1) was transformed into two new hexaruthenium cluster complexes, Ru{sub 6}(CO){sub 13}({mu}{sub 3}-SCH{sub 2}CMe{sub 2}CH{sub 2}){sub 4} (2) and Ru{sub 6}(CO){sub 12}({mu}-SCH{sub 2}CMe{sub 2}CH{sub 2})({mu}{sub 3}-SCH{sub 2}CMe{sub 2}CH{sub 2}){sub 3}[{mu}{sub 3}-SCH{sub 2}C(Me)(CH{sub 2})CH{sub 2}] ({mu}-H) (3), that contain four and five ring-opened 3,3-dimethylthietane (3,3-DMT) ligands, respectively. In compound 3 one of the ring-opened DMT ligands has also undergone a CH activation on one of the methyl groups. Compound 2 reacts with additional 3,3-DMT at 97{degrees}C to form 3 in 18% yield. When treated with CO at 95{degrees}C (500 psi), compound 2 yielded 4,4-dimethylthiobutyrolactone and Ru{sub 3}(CO){sub 12}. It was also found that the complex Os{sub 3}(CO){sub 11-}(SCH{sub 2}CMe{sub 2}CH{sub 2}C{double_bond}O) (4) yields 4,4-dimethylthiobutyrolactone when treated with CO at 120{degrees}C (1200 psi). Crystal data for 2: space group P2{sub 1}/n, {alpha} = 22.652 (7) A, {beta} = 11.712 (2) A, c = 19.965 (6) A, {Beta} = 115.75 (2){degrees} Z = 4, 3665 reflections, R = 0.021. Crystal data for 3: space group P2{sub 1}/c, {alpha} = 17.332 (8) A, {Beta} = 14.668 (9) A, c = 19.823 (9) A, {Beta} = 91.27 (4){degrees}, Z = 4, 1875 reflections, R = 0.050. 13 refs., 2 figs., 13 refs.

  5. Assessment of the CCSD and CCSD(T) Coupled-Cluster Methods in Calculating Heats of Formation for Zn Complexes

    NASA Astrophysics Data System (ADS)

    Weaver, Michael N.; Yang, Yue; Merz, Kenneth M.

    2009-08-01

    Heats of formation were calculated using coupled-cluster methods for a series of zinc complexes. The calculated values were evaluated against previously conducted computational studies using density functional methods as well as experimental values. Heats of formation for nine neutral ZnXn complexes [X = -Zn, -H, -O, -F2, -S, -Cl, -Cl2, -CH3, (-CH3)2] were determined at the CCSD and CCSD(T) levels using the 6-31G** and TZVP basis sets as well as the LANL2DZ-6-31G** (LACVP**) and LANL2DZ-TZVP hybrid basis sets. The CCSD(T)/6-31G** level of theory was found to predict the heat of formation for the nonalkyl Zn complexes most accurately. The alkyl Zn species were problematic in that none of the methods that were tested accurately predicted the heat of formation for these complexes. In instances where experimental geometric parameters were available, these were most accurately predicted by the CCSD/6-31G** level of theory; going to CCSD(T) did not improve agreement with the experimental values. Coupled-cluster methods did not offer a systemic improvement over DFT calculations for a given functional/basis set combination. With the exceptions of ZnH and ZnF2, there are multiple density functionals that outperform coupled-cluster calculations with the 6-31G** basis set.

  6. Analysis of the Tribolium homeotic complex: insights into mechanisms constraining insect Hox clusters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The remarkable conservation of Hox clusters is an accepted but little understood principle of biology. Some organizational constraints have been identified for vertebrate Hox clusters, but most of these are thought to be recent innovations that may not apply to other organisms. Ironically, many mode...

  7. Probing the Dragonfish star-forming complex: the ionizing population of the young massive cluster Mercer 30

    NASA Astrophysics Data System (ADS)

    de la Fuente, D.; Najarro, F.; Borissova, J.; Ramírez Alegría, S.; Hanson, M. M.; Trombley, C.; Figer, D. F.; Davies, B.; Garcia, M.; Kurtev, R.; Urbaneja, M. A.; Smith, L. C.; Lucas, P. W.; Herrero, A.

    2016-05-01

    It has recently been claimed that the nebula, Dragonfish, is powered by a superluminous but elusive OB association. However, systematic searches in near-infrared photometric surveys have found many other cluster candidates in this region of the sky. Among these, the first confirmed young massive cluster was Mercer 30, where Wolf-Rayet stars were found.We perform a new characterization of Mercer 30 with unprecedented accuracy, combining NICMOS/HST and VVV photometric data with multi-epoch ISAAC/VLT H- and K-band spectra. Stellar parameters for most of spectroscopically observed cluster members are found through precise non-LTE atmosphere modeling with the CMFGEN code. Our spectrophotometric study for this cluster yields a new, revised distance of d = (12.4 ± 1.7) kpc and a total of QHMc30 ≈ 6.70 × 1050 s-1 Lyman ionizing photons. A cluster age of (4.0 ± 0.8) Myr is found through isochrone fitting, and a total mass of (1.6 ± 0.6) × 104M⊙ is estimated, thanks to our extensive knowledge of the post-main-sequence population. As a consequence, membership of Mercer 30 to the Dragonfish star-forming complex is confirmed, allowing us to use this cluster as a probe for the whole complex, which turns out to be extremely large (~400 pc across) and located at the outer edge of the Sagittarius-Carina spiral arm (~11 kpc from the Galactic center). The Dragonfish complex hosts 19 young clusters or cluster candidates (including Mercer 30 and a new candidate presented in this work) and an estimated minimum of nine field Wolf-Rayet stars. All these contributions account for, at least 73% of the ionization of the Dragonfish nebula and leaves little or no room for the alleged superluminous OB association; alternative explanations are discussed. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under programs IDs 179.B-2002, 081.D-0471, 083.D-0765, 087.D-0957, and 089.D-0989.

  8. Probing the Dragonfish star-forming complex: the ionizing population of the young massive cluster Mercer 30

    NASA Astrophysics Data System (ADS)

    de la Fuente, D.; Najarro, F.; Borissova, J.; Ramírez Alegría, S.; Hanson, M. M.; Trombley, C.; Figer, D. F.; Davies, B.; Garcia, M.; Kurtev, R.; Urbaneja, M. A.; Smith, L. C.; Lucas, P. W.; Herrero, A.

    2016-04-01

    It has recently been claimed that the nebula, Dragonfish, is powered by a superluminous but elusive OB association. However, systematic searches in near-infrared photometric surveys have found many other cluster candidates in this region of the sky. Among these, the first confirmed young massive cluster was Mercer 30, where Wolf-Rayet stars were found.We perform a new characterization of Mercer 30 with unprecedented accuracy, combining NICMOS/HST and VVV photometric data with multi-epoch ISAAC/VLT H- and K-band spectra. Stellar parameters for most of spectroscopically observed cluster members are found through precise non-LTE atmosphere modeling with the CMFGEN code. Our spectrophotometric study for this cluster yields a new, revised distance of d = (12.4 ± 1.7) kpc and a total of QHMc30 ≈ 6.70 × 1050 s-1 Lyman ionizing photons. A cluster age of (4.0 ± 0.8) Myr is found through isochrone fitting, and a total mass of (1.6 ± 0.6) × 104M⊙ is estimated, thanks to our extensive knowledge of the post-main-sequence population. As a consequence, membership of Mercer 30 to the Dragonfish star-forming complex is confirmed, allowing us to use this cluster as a probe for the whole complex, which turns out to be extremely large (~400 pc across) and located at the outer edge of the Sagittarius-Carina spiral arm (~11 kpc from the Galactic center). The Dragonfish complex hosts 19 young clusters or cluster candidates (including Mercer 30 and a new candidate presented in this work) and an estimated minimum of nine field Wolf-Rayet stars. All these contributions account for, at least 73% of the ionization of the Dragonfish nebula and leaves little or no room for the alleged superluminous OB association; alternative explanations are discussed. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under programs IDs 179.B-2002, 081.D-0471, 083.D-0765, 087.D-0957, and 089.D-0989.

  9. Cluster synchronization of complex networks via event-triggered strategy under stochastic sampling

    NASA Astrophysics Data System (ADS)

    Hu, Aihua; Cao, Jinde; Hu, Manfeng; Guo, Liuxiao

    2015-09-01

    This paper is concerned with the issue of mean square cluster synchronization of non-identical nodes connected by a directed network. Suppose that the nodes possess nonlinear dynamics and split into several clusters, then an event-triggered control scheme is proposed for synchronization based on the information from stochastic sampling. Meanwhile, an equilibrium is considered to be the synchronization state or the virtual leader for each cluster, which can apply pinning control to the following nodes. Assume that a spanning tree exists in the subgraph consisting of the nodes belonging to the same cluster and the corresponding virtual leader, and the instants for updating controllers are determined by the given event-triggered strategy, then some sufficient conditions for cluster synchronization are presented according to the Lyapunov stability theory and linear matrix inequality technique. Finally, a specific numerical example is shown to demonstrate the effectiveness of the theoretical results.

  10. The Complexities of Implementing Cluster Supply Chain - Case Study of JCH

    NASA Astrophysics Data System (ADS)

    Xue, Xiao; Zhang, Jibiao; Wang, Yang

    As a new type of management pattern, "cluster supply chain" (CSC) can help SMEs to face the global challenges through all kinds of collaboration. However, a major challenge in implementing CSC is the gap between theory and practice in the field. In an effort to provide a better understanding of this emerging phenomenon, this paper presents the implementation process of CSC in the context of JingCheng Mechanical & Electrical Holding co., ltd.(JCH) as a case study. The cast study of JCH suggests that the key problems in the practice of cluster supply chain: How do small firms use cluster supply chain? Only after we clarify the problem, the actual construction and operation of cluster supply chain does show successful results as it should be.

  11. Scaling, cluster dynamics and complex oscillations in a multispecies Lattice Lotka-Volterra Model

    NASA Astrophysics Data System (ADS)

    Shabunin, A. V.; Efimov, A.; Tsekouras, G. A.; Provata, A.

    2005-03-01

    The cluster formation in the cyclic (4+1)-Lattice Lotka-Volterra Model is studied by Kinetic Monte Carlo simulations on a square lattice support. At the Mean Field level this model demonstrates conservative four-dimensional oscillations which, depending on the parameters, can be chaotic or quasi-periodic. When the system is realized on a square lattice substrate the various species organize in domains (clusters) with fractal boundaries and this is consistent with dissipative dynamics. For small lattice sizes, the entire lattice oscillates in phase and the size distribution of the clusters follows a pure power law distribution. When the system size is large many independently oscillating regions are formed and as a result the cluster size distribution in addition to the power law, acquires a exponential decay dependence. This combination of power law and exponential decay of distributions and correlations is indicative, in this case, of mixing and superposition of regions oscillating asynchronously.

  12. The complex stellar populations in the background of open clusters in the third Galactic quadrant

    NASA Astrophysics Data System (ADS)

    Carraro, Giovanni; Seleznev, Anton F.; Baume, Gustavo; Turner, David. G.

    2016-02-01

    Multicolour photometry of the stellar populations in five fields in the third Galactic quadrant centred on the clusters NGC 2215, NGC 2354, Haffner 22, Ruprecht 11, and ESO489 SC01 is interpreted in terms of a warped and flared Galactic disc, without resort to an external entity such as the popular Monoceros or Canis Major overdensities. Except for NGC 2215, the clusters are poorly or unstudied previously. The data generate basic parameters for each cluster, including the distribution of stars along the line of sight. We use star counts and photometric analysis, without recourse to Galactic-model-based predictions or interpretations, and confirms earlier results for NGC 2215 and NGC 2354. ESO489 SC01 is not a real cluster, while Haffner 22 is an overlooked cluster aged ˜2.5 Gyr. Conclusions for Ruprecht 11 are preliminary, evidence for a cluster being marginal. Fields surrounding the clusters show signatures of young and intermediate-age stellar populations. The young population background to NGC 2354 and Ruprecht 11 lies ˜8-9 kpc from the Sun and ˜1 kpc below the formal Galactic plane, tracing a portion of the Norma-Cygnus arm, challenging Galactic models that adopt a sharp cut-off of the disc 12-14 kpc from the Galactic Centre. The old population is metal-poor with an age of ˜2-3 Gyr, resembling star clusters like Tombaugh 2 or NGC 2158. It has a large colour spread and is difficult to locate precisely. Young and old populations follow a pattern that depends critically on the vertical location of the thin and/or thick disc, and whether or not a particular line of sight intersects one, both, or none.

  13. Electronic Structure of Transition Metal Clusters, Actinide Complexes and Their Reactivities

    SciTech Connect

    Krishnan Balasubramanian

    2009-07-18

    methods with all-electron Douglas-Kroll relativistic methods. We have the capabilities for computing full CI extrapolations including spin-orbit effects and several one-electron properties and electron density maps including spin-orbit effects. We are continuously collaborating with several experimental groups around the country and at National Labs to carry out computational studies on the DOE-BES funded projects. The past work in the last 3 years was primarily motivated and driven by the concurrent or recent experimental studies on these systems. We were thus significantly benefited by coordinating our computational efforts with experimental studies. The interaction between theory and experiment has resulted in some unique and exciting opportunities. For example, for the very first time ever, the upper spin-orbit component of a heavy trimer such as Au{sub 3} was experimentally observed as a result of our accurate computational study on the upper electronic states of gold trimer. Likewise for the first time AuH{sub 2} could be observed and interpreted clearly due to our computed potential energy surfaces that revealed the existence of a large barrier to convert the isolated AuH{sub 2} back to Au and H{sub 2}. We have also worked on yet to be observed systems and have made predictions for future experiments. We have computed the spectroscopic and thermodynamic properties of transition metal carbides transition metal clusters and compared our electronic states to the anion photodetachment spectra of Lai Sheng Wang. Prof Mike Morse and coworkers(funded also by DOE-BES) and Prof Stimle and coworkers(also funded by DOE-BES) are working on the spectroscopic properties of transition metal carbides and nitrides. Our predictions on the excited states of transition metal clusters such as Hf{sub 3}, Nb{sub 2}{sup +} etc., have been confirmed experimentally by Prof. Lombardi and coworkers using resonance Raman spectroscopy. We have also been studying larger complexes critical to the

  14. Cationic cluster formation versus disproportionation of low-valent indium and gallium complexes of 2,2'-bipyridine

    PubMed Central

    Lichtenthaler, Martin R.; Stahl, Florian; Kratzert, Daniel; Heidinger, Lorenz; Schleicher, Erik; Hamann, Julian; Himmel, Daniel; Weber, Stefan; Krossing, Ingo

    2015-01-01

    Group 13 MI compounds often disproportionate into M0 and MIII. Here, however, we show that the reaction of the MI salt of the weakly coordinating alkoxyaluminate [GaI(C6H5F)2]+[Al(ORF)4]− (RF=C(CF3)3) with 2,2'-bipyridine (bipy) yields the paramagnetic and distorted octahedral [Ga(bipy)3]2+•{[Al(ORF)4]−}2 complex salt. While the latter appears to be a GaII compound, both, EPR and DFT investigations assign a ligand-centred [GaIII{(bipy)3}•]2+ radical dication. Surprisingly, the application of the heavier homologue [InI(C6H5F)2]+[Al(ORF)4]− leads to aggregation and formation of the homonuclear cationic triangular and rhombic [In3(bipy)6]3+, [In3(bipy)5]3+ and [In4(bipy)6]4+ metal atom clusters. Typically, such clusters are formed under strongly reductive conditions. Analysing the unexpected redox-neutral cationic cluster formation, DFT studies suggest a stepwise formation of the clusters, possibly via their triplet state and further investigations attribute the overall driving force of the reactions to the strong In−In bonds and the high lattice enthalpies of the resultant ligand stabilized [M3]3+{[Al(ORF)4]−}3 and [M4]4+{[Al(ORF)4]−}4 salts. PMID:26478464

  15. X-ray spectroscopy of the Mn4Ca cluster in the water-oxidation complex of Photosystem II

    PubMed Central

    Sauer, Kenneth; Yano, Junko; Yachandra, Vittal K.

    2014-01-01

    The water-oxidation complex of Photosystem II (PS II) contains a heteronuclear cluster of 4 Mn atoms and a Ca atom. Ligands to the metal cluster involve bridging O atoms, and O and N atoms from amino acid side-chains of the D1 polypeptide of PS II, with likely additional contributions from water and CP43. Although moderate resolution X-ray diffraction-based structures of PS II have been reported recently, and the location of the Mn4Ca cluster has been identified, the structures are not resolved at the atomic level. X-ray absorption (XAS), emission (XES), resonant inelastic X-ray scattering (RIXS) and extended X-ray absorption fine structure (EXAFS) provide independent and potentially highly accurate sources of structural and oxidation-state information. When combined with polarized X-ray studies of oriented membranes or single-crystals of PS II, a more detailed picture of the cluster and its disposition in PS II is obtained. PMID:15977060

  16. The Human Iron–Sulfur Assembly Complex Catalyzes the Synthesis of [2Fe-2S] Clusters on ISCU2 That Can Be Transferred to Acceptor Molecules

    PubMed Central

    Fox, Nicholas G.; Chakrabarti, Mrinmoy; McCormick, Sean P.; Lindahl, Paul A.; Barondeau, David P.

    2015-01-01

    Iron–sulfur (Fe–S) clusters are essential protein cofactors for most life forms. In human mitochondria, the core Fe–S biosynthetic enzymatic complex (called SDUF) consists of NFS1, ISD11, ISCU2, and frataxin (FXN) protein components. Few mechanistic details about how this complex synthesizes Fe–S clusters and how these clusters are delivered to targets are known. Here circular dichroism and Mössbauer spectroscopies were used to reveal details of the Fe–S cluster assembly reaction on the SDUF complex. SDUF reactions generated [2Fe-2S] cluster intermediates that readily converted to stable [2Fe-2S] clusters bound to uncomplexed ISCU2. Similar reactions that included the apo Fe–S acceptor protein human ferredoxin (FDX1) resulted in formation of [2Fe-2S]-ISCU2 rather than [2Fe-2S]-FDX1. Subsequent addition of dithiothreitol (DTT) induced transfer of the cluster from ISCU2 to FDX1, suggesting that [2Fe-2S]-ISCU2 is an intermediate. Reactions that initially included DTT rapidly generated [2Fe-2S]-FDX1 and bypassed formation of [2Fe-2S]-ISCU2. In the absence of apo-FDX1, incubation of [2Fe-2S]-ISCU2 with DTT generated [4Fe-4S]-ISCU2 species. Together, these results conflict with a recent report of stable [4Fe-4S] cluster formation on the SDUF complex. Rather, they support a model in which SDUF builds transient [2Fe-2S] cluster intermediates that generate clusters on sulfur-containing molecules, including uncomplexed ISCU2. Additional small molecule or protein factors are required for the transfer of these clusters to Fe–S acceptor proteins or the synthesis of [4Fe-4S] clusters. PMID:26016389

  17. High-throughput sequencing and graph-based cluster analysis facilitate microsatellite development from a highly complex genome.

    PubMed

    Shah, Abhijeet B; Schielzeth, Holger; Albersmeier, Andreas; Kalinowski, Joern; Hoffman, Joseph I

    2016-08-01

    Despite recent advances in high-throughput sequencing, difficulties are often encountered when developing microsatellites for species with large and complex genomes. This probably reflects the close association in many species of microsatellites with cryptic repetitive elements. We therefore developed a novel approach for isolating polymorphic microsatellites from the club-legged grasshopper (Gomphocerus sibiricus), an emerging quantitative genetic and behavioral model system. Whole genome shotgun Illumina MiSeq sequencing was used to generate over three million 300 bp paired-end reads, of which 67.75% were grouped into 40,548 clusters within RepeatExplorer. Annotations of the top 468 clusters, which represent 60.5% of the reads, revealed homology to satellite DNA and a variety of transposable elements. Evaluating 96 primer pairs in eight wild-caught individuals, we found that primers mined from singleton reads were six times more likely to amplify a single polymorphic microsatellite locus than primers mined from clusters. Our study provides experimental evidence in support of the notion that microsatellites associated with repetitive elements are less likely to successfully amplify. It also reveals how advances in high-throughput sequencing and graph-based repetitive DNA analysis can be leveraged to isolate polymorphic microsatellites from complex genomes. PMID:27547349

  18. Experiments in clustered neuronal networks: A paradigm for complex modular dynamics

    NASA Astrophysics Data System (ADS)

    Teller, Sara; Soriano, Jordi

    2016-06-01

    Uncovering the interplay activity-connectivity is one of the major challenges in neuroscience. To deepen in the understanding of how a neuronal circuit shapes network dynamics, neuronal cultures have emerged as remarkable systems given their accessibility and easy manipulation. An attractive configuration of these in vitro systems consists in an ensemble of interconnected clusters of neurons. Using calcium fluorescence imaging to monitor spontaneous activity in these clustered neuronal networks, we were able to draw functional maps and reveal their topological features. We also observed that these networks exhibit a hierarchical modular dynamics, in which clusters fire in small groups that shape characteristic communities in the network. The structure and stability of these communities is sensitive to chemical or physical action, and therefore their analysis may serve as a proxy for network health. Indeed, the combination of all these approaches is helping to develop models to quantify damage upon network degradation, with promising applications for the study of neurological disorders in vitro.

  19. Three complexes of Cu(I) cluster with flexible and rigid ligands: Synthesis, characterization and photoluminescent properties

    SciTech Connect

    Sun, Shu; Liu, Li-Juan; Ma, Wang-Yang; Zhou, Wei-Xia; Li, Jun; Zhang, Feng-Xing

    2015-05-15

    Three new Cu(I) cluster complexes, viz. [(Cu{sub 4}I{sub 4})(Cu{sub 2}I{sub 2})(dimb){sub 3}]{sub n} (1; dimb=1,4-diimidazol-1-ylbutane), [(Cu{sub 3}I{sub 2})(dimb)(dmtz)]{sub n} (2; dmtz=3,5-dimethyl-1,2,4-triazole), and [Cu{sub 6}(mbt){sub 6}] (3; mbt=2-mercaptobenzothiazole), have been solvothermally synthesized and structurally characterized. In 1, a Cu{sub 4}I{sub 4} cubane core as a 4-connecting node, connects the neighboring nodes either through single dimb or μ{sub 2}-[(Cu{sub 2}I{sub 2})(dimb){sub 2}] linkers, affording an undulated 2D (4,4) net. Parallel interpenetration occurs between the adjacent nets and thus the overall 2D→3D network is formed. Complex 2 is constructed by 2D (4,4) topological plane grid layers of AB stacking. The core, a distorted triangular bipyramidal Cu{sub 3}I{sub 2} cluster, is acted as a 4-connecting node and connected with dimb and μ{sub 3}-dmtz to form the layer. Complex 3 contains a (Cu{sub 6}S{sub 6}) core in discrete paddle-wheel molecule, which serves as a 4-connecting node to link equivalent ones via π···π interaction, forming 2D (4,4) layers. Solid-state luminescence properties and thermogravimetric analyses of 1, 2 and 3 were investigated. - Graphical abstract: Complexes based on Cu(I) clusters possess two-fold 2D→3D parallel interpenetrating (1), triple emissions (2) and near-infrared emission (3). - Highlights: • Complex 1 represents two-fold 2D→3D parallel interpenetrating framework. • Complex 2 shows triple emissions. • Complex 3 displays a quite intense near-infrared (NIR) emission. • These complexes have good thermal stability.

  20. Calcium EXAFS establishes the Mn-Ca cluster in the oxygen-evolving complex of Photosystem II

    SciTech Connect

    Cinco, Roehl M.; McFarlane Holman, Karen L.; Robblee, John H.; Yano, Junko; Pizarro, Shelly A.; Bellacchio, Emanuele; Sauer, Kenneth; Yachandra, Vittal K.

    2002-08-02

    The proximity of Ca to the Mn cluster of the photosynthetic water-oxidation complex is demonstrated by X-ray absorption spectroscopy. We have collected EXAFS data at the Ca K-edge using active PS II membrane samples that contain approximately 2 Ca per 4 Mn. These samples are much less perturbed than previously investigated Sr-substituted samples, which were prepared subsequent to Ca depletion. The new Ca EXAFS clearly shows backscattering from Mn at 3.4 angstroms, a distance that agrees with that surmised from previously recorded Mn EXAFS. This result is also consistent with earlier related experiments at the Sr K-edge, using samples that contained functional Sr, that show Mn is {approx}; 3.5 angstroms distant from Sr. The totality of the evidence clearly advances the notion that the catalytic center of oxygen evolution is a Mn-Ca heteronuclear cluster.

  1. Multilevel Hierarchical Kernel Spectral Clustering for Real-Life Large Scale Complex Networks

    PubMed Central

    Mall, Raghvendra; Langone, Rocco; Suykens, Johan A. K.

    2014-01-01

    Kernel spectral clustering corresponds to a weighted kernel principal component analysis problem in a constrained optimization framework. The primal formulation leads to an eigen-decomposition of a centered Laplacian matrix at the dual level. The dual formulation allows to build a model on a representative subgraph of the large scale network in the training phase and the model parameters are estimated in the validation stage. The KSC model has a powerful out-of-sample extension property which allows cluster affiliation for the unseen nodes of the big data network. In this paper we exploit the structure of the projections in the eigenspace during the validation stage to automatically determine a set of increasing distance thresholds. We use these distance thresholds in the test phase to obtain multiple levels of hierarchy for the large scale network. The hierarchical structure in the network is determined in a bottom-up fashion. We empirically showcase that real-world networks have multilevel hierarchical organization which cannot be detected efficiently by several state-of-the-art large scale hierarchical community detection techniques like the Louvain, OSLOM and Infomap methods. We show that a major advantage of our proposed approach is the ability to locate good quality clusters at both the finer and coarser levels of hierarchy using internal cluster quality metrics on 7 real-life networks. PMID:24949877

  2. Multilevel hierarchical kernel spectral clustering for real-life large scale complex networks.

    PubMed

    Mall, Raghvendra; Langone, Rocco; Suykens, Johan A K

    2014-01-01

    Kernel spectral clustering corresponds to a weighted kernel principal component analysis problem in a constrained optimization framework. The primal formulation leads to an eigen-decomposition of a centered Laplacian matrix at the dual level. The dual formulation allows to build a model on a representative subgraph of the large scale network in the training phase and the model parameters are estimated in the validation stage. The KSC model has a powerful out-of-sample extension property which allows cluster affiliation for the unseen nodes of the big data network. In this paper we exploit the structure of the projections in the eigenspace during the validation stage to automatically determine a set of increasing distance thresholds. We use these distance thresholds in the test phase to obtain multiple levels of hierarchy for the large scale network. The hierarchical structure in the network is determined in a bottom-up fashion. We empirically showcase that real-world networks have multilevel hierarchical organization which cannot be detected efficiently by several state-of-the-art large scale hierarchical community detection techniques like the Louvain, OSLOM and Infomap methods. We show that a major advantage of our proposed approach is the ability to locate good quality clusters at both the finer and coarser levels of hierarchy using internal cluster quality metrics on 7 real-life networks. PMID:24949877

  3. COMPLEX SCATTERED RADIATION FIELDS AND MULTIPLE MAGNETIC FIELDS IN THE PROTOSTELLAR CLUSTER IN NGC 2264

    SciTech Connect

    Kwon, Jungmi; Tamura, Motohide; Kandori, Ryo; Kusakabe, Nobuhiko; Hashimoto, Jun; Nakajima, Yasushi; Nakamura, Fumitaka; Nagayama, Takahiro; Nagata, Tetsuya; Hough, James H.; Werner, Michael W.; Teixeira, Paula S.

    2011-11-01

    Near-infrared imaging polarimetry in the J, H, and K{sub s} bands has been carried out for the protostellar cluster region around NGC 2264 IRS 2 in the Monoceros OB1 molecular cloud. Various infrared reflection nebula clusters (IRNCs) associated with NGC 2264 IRS 2 and the IRAS 12 S1 core, as well as local infrared reflection nebulae (IRNe), were detected. The illuminating sources of the IRNe were identified with known or new near- and mid-infrared sources. In addition, 314 point-like sources were detected in all three bands and their aperture polarimetry was studied. Using a color-color diagram, reddened field stars and diskless pre-main-sequence stars were selected to trace the magnetic field (MF) structure of the molecular cloud. The mean polarization position angle of the point-like sources is 81 Degree-Sign {+-} 29 Degree-Sign in the cluster core, and 58 Degree-Sign {+-} 24 Degree-Sign in the perimeter of the cluster core, which is interpreted as the projected direction on the sky of the MF in the observed region of the cloud. The Chandrasekhar-Fermi method gives a rough estimate of the MF strength to be about 100 {mu}G. A comparison with recent numerical simulations of the cluster formation implies that the cloud dynamics is controlled by the relatively strong MF. The local MF direction is well associated with that of CO outflow for IRAS 12 S1 and consistent with that inferred from submillimeter polarimetry. In contrast, the local MF direction runs roughly perpendicular to the Galactic MF direction.

  4. Three complexes of Cu(I) cluster with flexible and rigid ligands: Synthesis, characterization and photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Sun, Shu; Liu, Li-Juan; Ma, Wang-Yang; Zhou, Wei-Xia; Li, Jun; Zhang, Feng-Xing

    2015-05-01

    Three new Cu(I) cluster complexes, viz. [(Cu4I4)(Cu2I2)(dimb)3]n (1; dimb=1,4-diimidazol-1-ylbutane), [(Cu3I2)(dimb)(dmtz)]n (2; dmtz=3,5-dimethyl-1,2,4-triazole), and [Cu6(mbt)6] (3; mbt=2-mercaptobenzothiazole), have been solvothermally synthesized and structurally characterized. In 1, a Cu4I4 cubane core as a 4-connecting node, connects the neighboring nodes either through single dimb or μ2-[(Cu2I2)(dimb)2] linkers, affording an undulated 2D (4,4) net. Parallel interpenetration occurs between the adjacent nets and thus the overall 2D→3D network is formed. Complex 2 is constructed by 2D (4,4) topological plane grid layers of AB stacking. The core, a distorted triangular bipyramidal Cu3I2 cluster, is acted as a 4-connecting node and connected with dimb and μ3-dmtz to form the layer. Complex 3 contains a (Cu6S6) core in discrete paddle-wheel molecule, which serves as a 4-connecting node to link equivalent ones via π···π interaction, forming 2D (4,4) layers. Solid-state luminescence properties and thermogravimetric analyses of 1, 2 and 3 were investigated.

  5. {sup 35}Mn ESE-ENDOR of a mixed valence Mn(III)Mn(IV) complex: Comparison with the Mn cluster of the photosynthetic oxygen-evolving complex

    SciTech Connect

    Randall, D.W.; Sturgeon, B.E.; Ball, J.A.; Lorigan, G.A.; Chan, M.K.; Britt, R.D.; Klein, M.P. |; Armstrong, W.H.

    1995-11-29

    Analysis of {sup 55}Mn electron spin echo-electron nuclear double resonance (ESE-ENDOR) spectra obtained on a dinuclear mixed valence Mn(III)Mn(IV) complex [di-{mu}-oxotetrakis(2, 2`-bipyridine)dimanganese(III,IV)] (1) reveals the hyperfine and nuclear quadrupolar parameters for the spin I=5/2 {sup 55}Mn nucleus of both Mn(III) and Mn(IV) ions. The {sup 55}Mn ESE-ENDOR data obtained on the g = 2 Mn multiline EPR signal of the S{sub 2} state of the photosystem II oxygen-evolving complex demonstrate that this EPR signal cannot arise from a dinuclear Mn(III)-Mn(IV) center. The ENDOR spectra are consistent with a tetranuclear Mn cluster origin for the photosystem II multiline EPR signal. 75 refs., 7 figs., 2 tabs.

  6. Quantitative Z-Contrast Imaging of Supported Metal Complexes and Clusters - A Gateway to Understanding Catalysis on the Atomic Scale

    SciTech Connect

    Browning, Nigel D.; Aydin, C.; Lu, Jing; Kulkarni, Apoorva; Okamoto, Norihiko L.; Ortalan, V.; Reed, Bryan W.; Uzun, Alper; Gates, Bruce C.

    2013-09-01

    Z-contrast imaging in an aberration-corrected scanning transmission electron microscope can be used to observe and quantify the sizes, shapes, and compositions of the metal frames in supported mono-, bi-, and multimetallic metal clusters and can even detect the metal atoms in single-metal-atom complexes, as well as providing direct structural information characterizing the metal-support interface. Herein, we assess the major experimental challenges associated with obtaining atomic resolution Z-contrast images of the materials that are highly beam-sensitive, that is, the clusters readily migrate and sinter on support surfaces, and the support itself can drastically change in structure if the experiment is not properly controlled. Calibrated and quantified Z-contrast images are used in conjunction with exsitu analytical measurements and larger-scale characterization methods such as extended X-ray absorption fine structure spectroscopy to generate an atomic-scale understanding of supported catalysts and their function. Examples of the application of these methods include the characterization of a wide range of sizes and compositions of supported clusters, primarily those incorporating Ir, Os, and Au, on highly crystalline supports (zeolites and MgO).

  7. Light-harvesting Complexes (LHCs) Cluster Spontaneously in Membrane Environment Leading to Shortening of Their Excited State Lifetimes.

    PubMed

    Natali, Alberto; Gruber, J Michael; Dietzel, Lars; Stuart, Marc C A; van Grondelle, Rienk; Croce, Roberta

    2016-08-01

    The light reactions of photosynthesis, which include light-harvesting and charge separation, take place in the amphiphilic environment of the thylakoid membrane. The light-harvesting complex II (LHCII) is the main responsible for light absorption in plants and green algae and is involved in photoprotective mechanisms that regulate the amount of excited states in the membrane. The dual function of LHCII has been extensively studied in detergent micelles, but recent results have indicated that the properties of this complex differ in a lipid environment. In this work we checked these suggestions by studying LHCII in liposomes. By combining bulk and single molecule measurements, we monitored the fluorescence characteristics of liposomes containing single complexes up to densely packed proteoliposomes. We show that the natural lipid environment per se does not alter the properties of LHCII, which for single complexes remain very similar to that in detergent. However, we show that LHCII has the strong tendency to cluster in the membrane and that protein interactions and the extent of crowding modulate the lifetimes of the excited state in the membrane. Finally, the presence of LHCII monomers at low concentrations of complexes per liposome is discussed. PMID:27252376

  8. Evolutionary origins of the placental expression of Chromosome 19 cluster galectins and their complex dysregulation in preeclampsia

    PubMed Central

    Than, Nandor Gabor; Xu, Yi; Erez, Offer; Xu, Zhonghui; Bhatti, Gaurav; Leavitt, Ron; Chung, Tzu Hung; El-Azzamy, Haidy; LaJeunesse, Christopher; Wang, Bing; Balogh, Andrea; Szalai, Gabor; Land, Susan; Dong, Zhong; Hassan, Sonia S.; Chaiworapongsa, Tinnakorn; Krispin, Manuel; Kim, Chong Jai; Tarca, Adi L.; Papp, Zoltan; Bohn, Hans

    2014-01-01

    . Conclusions These findings reveal the evolutionary origins of the placental expression of Chr19 cluster galectins. The complex dysregulation of these genes in preeclampsia may alter immune tolerance mechanisms at the maternal-fetal interface. PMID:25266889

  9. Toward accurate molecular identification of species in complex environmental samples: testing the performance of sequence filtering and clustering methods

    PubMed Central

    Flynn, Jullien M; Brown, Emily A; Chain, Frédéric J J; MacIsaac, Hugh J; Cristescu, Melania E

    2015-01-01

    Metabarcoding has the potential to become a rapid, sensitive, and effective approach for identifying species in complex environmental samples. Accurate molecular identification of species depends on the ability to generate operational taxonomic units (OTUs) that correspond to biological species. Due to the sometimes enormous estimates of biodiversity using this method, there is a great need to test the efficacy of data analysis methods used to derive OTUs. Here, we evaluate the performance of various methods for clustering length variable 18S amplicons from complex samples into OTUs using a mock community and a natural community of zooplankton species. We compare analytic procedures consisting of a combination of (1) stringent and relaxed data filtering, (2) singleton sequences included and removed, (3) three commonly used clustering algorithms (mothur, UCLUST, and UPARSE), and (4) three methods of treating alignment gaps when calculating sequence divergence. Depending on the combination of methods used, the number of OTUs varied by nearly two orders of magnitude for the mock community (60–5068 OTUs) and three orders of magnitude for the natural community (22–22191 OTUs). The use of relaxed filtering and the inclusion of singletons greatly inflated OTU numbers without increasing the ability to recover species. Our results also suggest that the method used to treat gaps when calculating sequence divergence can have a great impact on the number of OTUs. Our findings are particularly relevant to studies that cover taxonomically diverse species and employ markers such as rRNA genes in which length variation is extensive. PMID:26078860

  10. UV Insights into the Complex Populations of M87 Globular Clusters

    NASA Astrophysics Data System (ADS)

    Bellini, A.; Renzini, A.; Anderson, J.; Bedin, L. R.; Piotto, G.; Soto, M.; Brown, T. M.; Milone, A. P.; Sohn, S. T.; Sweigart, A. V.

    2015-06-01

    We have imaged with Hubble Space Telescope WFC3/UVIS the central 2\\buildrel{ \\prime}\\over{.} 7× 2\\buildrel{ \\prime}\\over{.} 7 region of the giant elliptical galaxy M87, using the ultraviolet filter F275W. In combination with archival ACS/WFC data taken through the F606W and F814W filters, covering the same field, we have constructed integrated-light UV-optical colors and magnitudes for 1460 objects, most of which are believed to be globular clusters (GCs) belonging to M87. The purpose was to ascertain whether the multiple-populations syndrome, ubiquitous among Galactic GCs, also exists among the M87 family of clusters. To achieve this goal, we sought those GCs with exceptionally blue UV-to-optical colors because helium-enriched sub-populations produce a horizontal-branch morphology that is well populated at high effective temperature. For comparison, integrated, synthetic UV-optical and purely optical colors and magnitudes have been constructed for 45 Galactic GCs, starting from individual-star photometry obtained with the same instruments and the same filters. We identify a small group of M87 clusters exhibiting a radial UV-optical color gradient, representing our best candidate GCs hosting multiple populations with extreme helium content. We also find that the central spatial distribution of the bluer GCs is flattened in a direction parallel to the jet, while the distribution of redder GCs is more spherical. We release to the astronomical community our photometric catalog in F275W, F606W, and F814W bands and the high-quality image stacks in the same bands. Based on proprietary and archival observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  11. Complex Stellar System ESO65SC03: Open Cluster or Remnant?

    NASA Astrophysics Data System (ADS)

    Joshi, Gireesh C.; Joshi, Y. C.; Joshi, S.; Chowdhury, S.; Tyagi, R. K.

    2015-06-01

    We present a complete spatial and dynamical study of the poorly populated stellar system ESO65SC03. The radial distribution of the system gives a core and cluster radii of 1.10±0.63 and 5.36±0.24 arcmin, respectively. The SNDP does not show any clear enhancement of the surface stellar number density between the stars of the system and the field regions. We derive the optimum isochrone solution for a particular grid size in the CMD using the statistical cleaning procedure. Using the statistically cleaned CMDs, we find the distance modulus, (m - M)0, and reddening, E(B - V), of the system to be 11.8±0.2 and 0.45 mag, respectively. The mean proper motion of this system is - 5.37±0.81 mas yr-1 and 0.31±0.40 in RA and DEC directions, respectively. The mean proper motion of this system is found to be almost similar to the field region. The mass function for the brighter stars is found to be too high for the system to be an open cluster. These combined results place constraints on whether stellar system ESO65SC03 is a POCR or an Asterism. Our understanding is that the ESO65SC03 is in a stage of POCR by losing their main-sequence stars in the dynamic evolution processes.

  12. Properties of clusters in the gas phase. V - Complexes of neutral molecules onto negative ions

    NASA Technical Reports Server (NTRS)

    Keesee, R. G.; Lee, N.; Castleman, A. W., Jr.

    1980-01-01

    Ion-molecules association reactions of the form A(-)(B)n-1 + B = A(-)(B)n were studied over a range of temperatures in the gas phase using high pressure mass spectrometry. Enthalpy and entropy changes were determined for the stepwise clustering reactions of (1) sulfur dioxide onto Cl(-), I(-), and NO2(-) with n ranging from one to three or four, and onto SO2(-) and SO3(-) with n equal to one; and (2) carbon dioxide onto Cl(-), I(-), NO2(-), CO3(-), and SO3(-) with n equal to one. From these data and earlier hydration results, the order of the magnitude of the enthalpy changes on the association of the first neutral for a series of negative ions was found to parallel the gas-phase basicity of those anions.

  13. Cluster analysis in soft x-ray spectromicroscopy : finding the patterns in complex specimens.

    SciTech Connect

    Lerotic, M.; Jacobsen, C.; Gillow, J. B.; Wirick, S.; Vogt, S.; Maser, J.; Experimental Facilities Division; State Univ. of New York at Stony Brook; BNL

    2005-06-01

    Soft X-ray spectromicroscopy provides spectral data on the chemical speciation of light elements at sub-100 nanometer spatial resolution. If all chemical species in a specimen are known and separately characterized, existing approaches can be used to measure the concentration of each component at each pixel. In other situations such as in biology or environmental science, this approach may not be possible. We have previously described the use of principle component analysis (PCA) to orthogonalize and noise-filter spectromicroscopy data, and cluster analysis (CA) to classify the analyzed data and obtain thickness maps of representative spectra. We describe here an extension of that work employing an angle distance measure; this measure provides better classification based on spectral signatures alone in specimens with significant thickness variations. The method is illustrated using simulated data, and also to examine sporulation in the bacterium Clostridium sp.

  14. Communication: Relativistic Fock-space coupled cluster study of small building blocks of larger uranium complexes

    SciTech Connect

    Tecmer, Paweł Visscher, Lucas; Severo Pereira Gomes, André; Knecht, Stefan

    2014-07-28

    We present a study of the electronic structure of the [UO{sub 2}]{sup +}, [UO{sub 2}]{sup 2} {sup +}, [UO{sub 2}]{sup 3} {sup +}, NUO, [NUO]{sup +}, [NUO]{sup 2} {sup +}, [NUN]{sup −}, NUN, and [NUN]{sup +} molecules with the intermediate Hamiltonian Fock-space coupled cluster method. The accuracy of mean-field approaches based on the eXact-2-Component Hamiltonian to incorporate spin–orbit coupling and Gaunt interactions are compared to results obtained with the Dirac–Coulomb Hamiltonian. Furthermore, we assess the reliability of calculations employing approximate density functionals in describing electronic spectra and quantities useful in rationalizing Uranium (VI) species reactivity (hardness, electronegativity, and electrophilicity)

  15. Synthesis of self-assembled large area films of complex hierarchical PZT clusters

    NASA Astrophysics Data System (ADS)

    Pratap Chaudhary, Raghvendra; Saxena, Sumit; Kmar, Amit; Bharadwaj, Rajesh; Shukla, Shobha

    2016-02-01

    The ability to bridge nano-micro interface for applications in functional miniaturized devices is of fundamental interest. We have synthesized novel large area films of complex hierarchical micro-flower morphologies of piezo-ceramics using hydrothermal reactions. The overall size of the samples produced is ∼cm2. The growth morphologies are found to be dependent on concentration and pressure inside the reaction chamber. This can be used to deterministically grow these complex multi-scaled microstructures over a large area. These results outline a strategy for growth of omni-directional microstructures by utilizing self assembly processes.

  16. Iridium Complexes and Clusters in Dealuminated Zeolite HY: Distribution between Crystalline and Impurity Amorphous Regions

    SciTech Connect

    Martinez-Macias, Claudia; Xu, Pinghong; Hwang, Son-Jong; Lu, Jing; Chen, Cong-Yan; Browning, Nigel D.; Gates, Bruce C.

    2014-07-08

    Dealuminated zeolite HY was used to support Ir(CO)2 complexes formed from Ir(CO)2(C5H7O2). Infrared and X-ray absorption spectra and atomic-resolution electron microscopy images identify these complexes, and the images and 27Al NMR spectra identify impurity amorphous regions in the zeolite where the iridium is more susceptible to aggregation than in the crystalline regions. The results indicate a significant stability limitation of metal in amorphous impurity regions of zeolites.

  17. Characterization of Toxin Complex Gene Clusters and Insect Toxicity of Bacteria Representing Four Subgroups of Pseudomonas fluorescens.

    PubMed

    Rangel, Lorena I; Henkels, Marcella D; Shaffer, Brenda T; Walker, Francesca L; Davis, Edward W; Stockwell, Virginia O; Bruck, Denny; Taylor, Barbara J; Loper, Joyce E

    2016-01-01

    Ten strains representing four lineages of the Pseudomonas fluorescens group (P. chlororaphis, P. corrugata, P. koreensis, and P. fluorescens subgroups) were evaluated for toxicity to the tobacco hornworm Manduca sexta and the common fruit fly Drosophila melanogaster. The three strains within the P. chlororaphis subgroup exhibited both oral and injectable toxicity to the lepidopteran M. sexta. All three strains have the gene cluster encoding the FitD insect toxin and a ΔfitD mutant of P. protegens strain Pf-5 exhibited diminished oral toxicity compared to the wildtype strain. Only one of the three strains, P. protegens Pf-5, exhibited substantial levels of oral toxicity against the dipteran D. melanogaster. Three strains in the P. fluorescens subgroup, which lack fitD, consistently showed significant levels of injectable toxicity against M. sexta. In contrast, the oral toxicity of these strains against D. melanogaster was variable between experiments, with only one strain, Pseudomonas sp. BG33R, causing significant levels of mortality in repeated experiments. Toxin complex (Tc) gene clusters, which encode insecticidal properties in Photorhabdus luminescens, were identified in the genomes of seven of the ten strains evaluated in this study. Within those seven genomes, six types of Tc gene clusters were identified, distinguished by gene content, organization and genomic location, but no correlation was observed between the presence of Tc genes and insect toxicity of the evaluated strains. Our results demonstrate that members of the P. fluorescens group have the capacity to kill insects by both FitD-dependent and independent mechanisms. PMID:27580176

  18. A critical look at the merger scenario to explain multiple populations and rotation in iron-complex globular clusters

    NASA Astrophysics Data System (ADS)

    Gavagnin, Elena; Mapelli, Michela; Lake, George

    2016-09-01

    Merging has been proposed to explain multiple populations in globular clusters (GCs) where there is a spread in iron abundance (hereafter, iron-complex GCs). By means of N-body simulations, we investigate if merging is consistent with the observations of subpopulations and rotation in iron-complex GCs. The key parameters are the initial mass and density ratios of the progenitors. When densities are similar, the more massive progenitor dominates the central part of the merger remnant and the less massive progenitor forms an extended rotating population. The low-mass progenitor can become the majority population in the central regions of the merger remnant only if its initial density is higher by roughly the mass ratio. To match the radial distribution of multiple populations in two iron-complex GCs (ω Cen and NGC 1851), the less massive progenitor needs to be four times as dense as the larger one. Our merger remnants show solid-body rotation in the inner parts, becoming differential in the outer parts. Rotation velocity V and ellipticity ɛ are in agreement with models for oblate rotators with isotropic dispersion. We discuss several kinematic signatures of a merger with a denser lower mass progenitor that can be tested with future observations.

  19. Photo-induced transformation process at gold clusters-semiconductor interface: Implications for the complexity of gold clusters-based photocatalysis

    PubMed Central

    Liu, Siqi; Xu, Yi-Jun

    2016-01-01

    The recent thrust in utilizing atomically precise organic ligands protected gold clusters (Au clusters) as photosensitizer coupled with semiconductors for nano-catalysts has led to the claims of improved efficiency in photocatalysis. Nonetheless, the influence of photo-stability of organic ligands protected-Au clusters at the Au/semiconductor interface on the photocatalytic properties remains rather elusive. Taking Au clusters–TiO2 composites as a prototype, we for the first time demonstrate the photo-induced transformation of small molecular-like Au clusters to larger metallic Au nanoparticles under different illumination conditions, which leads to the diverse photocatalytic reaction mechanism. This transformation process undergoes a diffusion/aggregation mechanism accompanied with the onslaught of Au clusters by active oxygen species and holes resulting from photo-excited TiO2 and Au clusters. However, such Au clusters aggregation can be efficiently inhibited by tuning reaction conditions. This work would trigger rational structural design and fine condition control of organic ligands protected-metal clusters-semiconductor composites for diverse photocatalytic applications with long-term photo-stability. PMID:26947754

  20. Photo-induced transformation process at gold clusters-semiconductor interface: Implications for the complexity of gold clusters-based photocatalysis

    NASA Astrophysics Data System (ADS)

    Liu, Siqi; Xu, Yi-Jun

    2016-03-01

    The recent thrust in utilizing atomically precise organic ligands protected gold clusters (Au clusters) as photosensitizer coupled with semiconductors for nano-catalysts has led to the claims of improved efficiency in photocatalysis. Nonetheless, the influence of photo-stability of organic ligands protected-Au clusters at the Au/semiconductor interface on the photocatalytic properties remains rather elusive. Taking Au clusters–TiO2 composites as a prototype, we for the first time demonstrate the photo-induced transformation of small molecular-like Au clusters to larger metallic Au nanoparticles under different illumination conditions, which leads to the diverse photocatalytic reaction mechanism. This transformation process undergoes a diffusion/aggregation mechanism accompanied with the onslaught of Au clusters by active oxygen species and holes resulting from photo-excited TiO2 and Au clusters. However, such Au clusters aggregation can be efficiently inhibited by tuning reaction conditions. This work would trigger rational structural design and fine condition control of organic ligands protected-metal clusters-semiconductor composites for diverse photocatalytic applications with long-term photo-stability.

  1. Quick detection of QRS complexes and R-waves using a wavelet transform and K-means clustering.

    PubMed

    Xia, Yong; Han, Junze; Wang, Kuanquan

    2015-01-01

    Based on the idea of telemedicine, 24-hour uninterrupted monitoring on electrocardiograms (ECG) has started to be implemented. To create an intelligent ECG monitoring system, an efficient and quick detection algorithm for the characteristic waveforms is needed. This paper aims to give a quick and effective method for detecting QRS-complexes and R-waves in ECGs. The real ECG signal from the MIT-BIH Arrhythmia Database is used for the performance evaluation. The method proposed combined a wavelet transform and the K-means clustering algorithm. A wavelet transform is adopted in the data analysis and preprocessing. Then, based on the slope information of the filtered data, a segmented K-means clustering method is adopted to detect the QRS region. Detection of the R-peak is based on comparing the local amplitudes in each QRS region, which is different from other approaches, and the time cost of R-wave detection is reduced. Of the tested 8 records (total 18201 beats) from the MIT-BIH Arrhythmia Database, an average R-peak detection sensitivity of 99.72 and a positive predictive value of 99.80% are gained; the average time consumed detecting a 30-min original signal is 5.78s, which is competitive with other methods. PMID:26405862

  2. Theoretical prediction of new Kubas four centre H2 complexes involving dimolybdate clusters

    NASA Astrophysics Data System (ADS)

    Simandiras, Emmanuel D.; Liakos, Dimitrios G.

    2013-09-01

    A new type of Kubas nonclassical molecular hydrogen complex involving two metallic centers is predicted by extensive DFT calculations, using five accurate functionals. The interaction consists of a four centre bond involving two metal atoms and the H2 molecule, the latter retaining a significant part of its molecular nature. [Mo2Cl8(μ-H2)]2- and [Mo2(CO)8(μ-H2)] are two examples that are found to be stable.

  3. Two hybrid compounds constructed from Ni-tris(imidazolyl) complexes and Keggin clusters: Syntheses, structures and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuanfang; Sun, Xiaojun; Ma, Huiyuan; Pang, Haijun; Li, Shaobin; Zhao, Chunyan

    2016-07-01

    By introducing different polyoxotungstates into the Ni-tib (tib = 1, 3, 5-tris (1-imidazolyl)benzene) system, two new polyoxometalate-based inorganic-organic hybrids with distinct architectures, [Ni(Htib)4][PW12O40]2 (1) and [Nitib]2(H2O)4](GeW12O40)·2H2O (2) have been synthesized under the same hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD) patterns and thermogravimetic (TG) analyses. Structural analyses show that compound 1 is a dimer, in which two neighboring mono-connected [PW12O40]3- (PW12) clusters are linked together by a [Ni(Htib)4] complex cation. In contrast to compound 1, compound 2 presents a 2D grid layer formed by bi-connected [GeW12O40]4- (GeW12) clusters and [Ni2(H2O)4(tib)2] complex cations, and the adjacent layers are further linked together by the hydrogen bondings to form a highly opened 3D framework. The distinct structural features of two hybrids suggest that the charge of the Keggin anions should play a key role in the process of assembly. Additionally, the electrochemical properties of compounds 1 and 2 have been investigated, and the results indicated that 1 and 2 have good electrocatalytic activities towards reduction of nitrite and oxidation of ascorbic acid.

  4. Two hybrid compounds constructed from Ni-tris(imidazolyl) complexes and Keggin clusters: Syntheses, structures and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuanfang; Sun, Xiaojun; Ma, Huiyuan; Pang, Haijun; Li, Shaobin; Zhao, Chunyan

    2016-07-01

    By introducing different polyoxotungstates into the Ni-tib (tib = 1, 3, 5-tris (1-imidazolyl)benzene) system, two new polyoxometalate-based inorganic-organic hybrids with distinct architectures, [Ni(Htib)4][PW12O40]2 (1) and [Nitib]2(H2O)4](GeW12O40)·2H2O (2) have been synthesized under the same hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD) patterns and thermogravimetic (TG) analyses. Structural analyses show that compound 1 is a dimer, in which two neighboring mono-connected [PW12O40]3- (PW12) clusters are linked together by a [Ni(Htib)4] complex cation. In contrast to compound 1, compound 2 presents a 2D grid layer formed by bi-connected [GeW12O40]4- (GeW12) clusters and [Ni2(H2O)4(tib)2] complex cations, and the adjacent layers are further linked together by the hydrogen bondings to form a highly opened 3D framework. The distinct structural features of two hybrids suggest that the charge of the Keggin anions should play a key role in the process of assembly. Additionally, the electrochemical properties of compounds 1 and 2 have been investigated, and the results indicated that 1 and 2 have good electrocatalytic activities towards reduction of nitrite and oxidation of ascorbic acid.

  5. The connection between prestellar cores and filaments in cluster-forming clumps of the Aquila Rift complex

    NASA Astrophysics Data System (ADS)

    Könyves, Vera; André, Philippe; Maury, Anaëlle

    2015-08-01

    One of the main goals of the Herschel Gould Belt survey (André et al. 2010) is to elucidate the physicalmechanisms responsible for the formation and evolution of prestellar cores in molecular clouds. In theAquila cloud complex imaged with Herschel/SPIRE-PACS between 70-500 μm, we have recently identifieda complete sample of 651 starless cores, 446 of them are gravitationally-bound prestellar cores, likelyforming stars in the future. We also detected 58 protostellar cores (Könyves et al. 2010 and 2015, subm.- see http://gouldbelt-herschel.cea.fr/archives). This region is dominated by two (proto)clusters which arecurrently active sites of clustered star formation (SF): the filamentary Serpens South cloud and the W40HII region. The latter is powered by massive young stars, and a 2nd-generation SF can be witnessed inthe surroundings (Maury et al. 2011).Our Herschel observations also provide an unprecedented census of filaments in Aquila and suggest aclose connection between them and the formation process of prestellar cores, where both structures arehighly concentrated around the protoclusters. About 10-20% of the gas mass is in the form of filamentsbelow Av~7, while ~50-75% of the dense gas mass above Av~7-10 is in filamentary structures.Furthermore, ~90% of our prestellar cores are located above a background column density correspondingto Av~7, and ~75% of them lie within the densest filamentary structures with supercritical masses per unitlength >16 M⊙/pc. Indeed, a strong correlation is found between the spatial distribution of prestellar coresand the densest filaments.Comparing the statistics of cores and filaments with the number of young stellar objects found by Spitzerin the same complex, we also infer a typical timescale ~1 Myr for the formation and evolution of bothprestellar cores and filaments.In summary, our Herschel findings in Aquila support a filamentary paradigm for the early stages of SF,where the cores result from the gravitational fragmentation

  6. Dissection of Two Complex Clusters of Resistance Genes in Lettuce (Lactuca sativa).

    PubMed

    Christopoulou, Marilena; McHale, Leah K; Kozik, Alex; Reyes-Chin Wo, Sebastian; Wroblewski, Tadeusz; Michelmore, Richard W

    2015-07-01

    Of the over 50 phenotypic resistance genes mapped in lettuce, 25 colocalize to three major resistance clusters (MRC) on chromosomes 1, 2, and 4. Similarly, the majority of candidate resistance genes encoding nucleotide binding-leucine rich repeat (NLR) proteins genetically colocalize with phenotypic resistance loci. MRC1 and MRC4 span over 66 and 63 Mb containing 84 and 21 NLR-encoding genes, respectively, as well as 765 and 627 genes that are not related to NLR genes. Forward and reverse genetic approaches were applied to dissect MRC1 and MRC4. Transgenic lines exhibiting silencing were selected using silencing of β-glucuronidase as a reporter. Silencing of two of five NLR-encoding gene families resulted in abrogation of nine of 14 tested resistance phenotypes mapping to these two regions. At MRC1, members of the coiled coil-NLR-encoding RGC1 gene family were implicated in host and nonhost resistance through requirement for Dm5/8- and Dm45-mediated resistance to downy mildew caused by Bremia lactucae as well as the hypersensitive response to effectors AvrB, AvrRpm1, and AvrRpt2 of the nonpathogen Pseudomonas syringae. At MRC4, RGC12 family members, which encode toll interleukin receptor-NLR proteins, were implicated in Dm4-, Dm7-, Dm11-, and Dm44-mediated resistance to B. lactucae. Lesions were identified in the sequence of a candidate gene within dm7 loss-of-resistance mutant lines, confirming that RGC12G confers Dm7. PMID:25650829

  7. The formation of complex acetylcholine receptor clusters requires MuSK kinase activity and structural information from the MuSK extracellular domain

    PubMed Central

    Mazhar, Sania; Herbst, Ruth

    2012-01-01

    Efficient synaptic transmission at the neuromuscular junction (NMJ) requires the topological maturation of the postsynaptic apparatus from an oval acetylcholine receptor (AChR)-rich plaque into a complex pretzel-shaped array of branches. However, compared to NMJ formation very little is known about the mechanisms that regulate NMJ maturation. Recently the process of in vivo transformation from plaque into pretzel has been reproduced in vitro by culturing myotubes aneurally on laminin-coated substrate. It was proposed that the formation of complex AChR clusters is regulated by a MuSK-dependent muscle intrinsic program. To elucidate the structure–function role of MuSK in the aneural maturation of AChR pretzels, we used muscle cell lines expressing MuSK mutant and chimeric proteins. Here we report, that besides its role during agrin-induced AChR clustering, MuSK kinase activity is also necessary for substrate-dependent cluster formation. Constitutive-active MuSK induces larger AChR clusters, a faster cluster maturation on laminin and increases the anchorage of AChRs to the cytoskeleton compared to MuSK wild-type. In addition, we find that the juxtamembrane region of MuSK, which has previously been shown to regulate agrin-induced AChR clustering, is unable to induce complex AChR clusters on laminin substrate. Most interestingly, MuSK kinase activity is not sufficient for laminin-dependent AChR cluster formation since the MuSK ectodomain is also required suggesting a so far undiscovered instructive role for the extracellular domain of MuSK. PMID:22210232

  8. Mutations in LYRM4, encoding iron–sulfur cluster biogenesis factor ISD11, cause deficiency of multiple respiratory chain complexes

    PubMed Central

    Lim, Sze Chern; Friemel, Martin; Marum, Justine E.; Tucker, Elena J.; Bruno, Damien L.; Riley, Lisa G.; Christodoulou, John; Kirk, Edwin P.; Boneh, Avihu; DeGennaro, Christine M.; Springer, Michael; Mootha, Vamsi K.; Rouault, Tracey A.; Leimkühler, Silke; Thorburn, David R.; Compton, Alison G.

    2013-01-01

    Iron–sulfur clusters (ISCs) are important prosthetic groups that define the functions of many proteins. Proteins with ISCs (called iron–sulfur or Fe–S proteins) are present in mitochondria, the cytosol, the endoplasmic reticulum and the nucleus. They participate in various biological pathways including oxidative phosphorylation (OXPHOS), the citric acid cycle, iron homeostasis, heme biosynthesis and DNA repair. Here, we report a homozygous mutation in LYRM4 in two patients with combined OXPHOS deficiency. LYRM4 encodes the ISD11 protein, which forms a complex with, and stabilizes, the sulfur donor NFS1. The homozygous mutation (c.203G>T, p.R68L) was identified via massively parallel sequencing of >1000 mitochondrial genes (MitoExome sequencing) in a patient with deficiency of complexes I, II and III in muscle and liver. These three complexes contain ISCs. Sanger sequencing identified the same mutation in his similarly affected cousin, who had a more severe phenotype and died while a neonate. Complex IV was also deficient in her skeletal muscle. Several other Fe–S proteins were also affected in both patients, including the aconitases and ferrochelatase. Mutant ISD11 only partially complemented for an ISD11 deletion in yeast. Our in vitro studies showed that the l-cysteine desulfurase activity of NFS1 was barely present when co-expressed with mutant ISD11. Our findings are consistent with a defect in the early step of ISC assembly affecting a broad variety of Fe–S proteins. The differences in biochemical and clinical features between the two patients may relate to limited availability of cysteine in the newborn period and suggest a potential approach to therapy. PMID:23814038

  9. Mixed-Valent Heptairon Complex with a Ground-State Spin Value of S=12/2 Constructed from a Triiron Cluster Ligand.

    PubMed

    Kajiwara; Ito

    2000-01-01

    The anionic triiron(III) cluster ligand [Fe(III)(3)(µ(3)-O)(bpca)(2)Cl(4)(EtO)(2)](-) (1; Hbpca=bis(2-pyridylcarbonyl)amine) was prepared as a building block for constructing larger metal assemblies. This "metal cluster complex ligand" was used in the synthesis of the mixed-valent heptairon complex [Fe(II)(1)(2)(EtOH)(2)], which has a ground-state spin value of S=12/2. PMID:10649385

  10. The resistance of electron-transport chain Fe-S clusters to oxidative damage during the reaction of peroxynitrite with mitochondrial complex II and rat-heart pericardium.

    PubMed

    Pearce, Linda L; Martinez-Bosch, Sandra; Manzano, Elisenda Lopez; Winnica, Daniel E; Epperly, Michael W; Peterson, Jim

    2009-05-01

    The effects of peroxynitrite and nitric oxide on the iron-sulfur clusters in complex II (succinate dehydrogenase) isolated from bovine heart have been studied primarily by EPR spectroscopy and no measurable damage to the constitutive 2Fe-2S, 3Fe-4S, or 4Fe-4S clusters was observed. The enzyme can be repeatedly oxidized with a slight excess of peroxynitrite and then quantitatively re-reduced with succinate. When added in large excess, peroxynitrite reacted with at least one tyrosine in each subunit of complex II to form 3-nitrotyrosines, but activity was barely compromised. Examination of rat-heart pericardium subjected to conditions leading to peroxynitrite production showed a small inhibition of complex II (16%) and a greater inhibition of aconitase (77%). In addition, experiments performed with excesses of sodium citrate and sodium succinate on rat-heart pericardium indicated that the "g approximately 2.01" EPR signal observed immediately following the beginning of conditions modeling oxidative/nitrosative stress, could be a consequence of both reversible oxidation of the constitutive 3Fe-4S cluster in complex II and degradation of the 4Fe-4S cluster in aconitase. However, the net signal envelope, which becomes apparent in less than 1min following the start of oxidative/nitrosative conditions, is dominated by the component arising from complex II. Taking into account the findings of a previous study concerning complexes I and III (L.L. Pearce, A.J. Kanai, M.W. Epperly, J. Peterson, Nitrosative stress results in irreversible inhibition of purified mitochondrial complexes I and III without modification of cofactors, Nitric Oxide 13 (2005) 254-263) it is now apparent that, with the exception of the cofactor in aconitase, mammalian (mitochondrial) iron-sulfur clusters are surprisingly resistant to degradation stemming from oxidative/nitrosative stress. PMID:19118636

  11. Synaptonemal complex extension from clustered telomeres mediates full-length chromosome pairing in Schmidtea mediterranea

    PubMed Central

    Xiang, Youbin; Miller, Danny E.; Ross, Eric J.; Sánchez Alvarado, Alejandro; Hawley, R. Scott

    2014-01-01

    In the 1920s, József Gelei proposed that chromosome pairing in flatworms resulted from the formation of a telomere bouquet followed by the extension of synapsis from telomeres at the base of the bouquet, thus facilitating homolog pairing in a processive manner. A modern interpretation of Gelei’s model postulates that the synaptonemal complex (SC) is nucleated close to the telomeres and then extends progressively along the full length of chromosome arms. We used the easily visible meiotic chromosomes, a well-characterized genome, and RNAi in the sexual biotype of the planarian Schmidtea mediterranea to test that hypothesis. By identifying and characterizing S. mediterranea homologs of genes encoding synaptonemal complex protein 1 (SYCP1), the topoisomerase-like protein SPO11, and RAD51, a key player in homologous recombination, we confirmed that SC formation begins near the telomeres and progresses along chromosome arms during zygotene. Although distal regions pair at the time of bouquet formation, pairing of a unique interstitial locus is not observed until the formation of full-length SC at pachytene. Moreover, neither full extension of the SC nor homologous pairing is dependent on the formation of double-strand breaks. These findings validate Gelei’s speculation that full-length pairing of homologous chromosomes is mediated by the extension of the SC formed near the telomeres. S. mediterranea thus becomes the first organism described (to our knowledge) that forms a canonical telomere bouquet but does not require double-strand breaks for synapsis between homologous chromosomes. However, the initiation of SC formation at the base of the telomere bouquet, which then is followed by full-length homologous pairing in planarian spermatocytes, is not observed in other species and may not be conserved. PMID:25404302

  12. Synthesis and structure of electron rich ruthenium polyhydride complexes and clusters containing AlCp* and GaCp*.

    PubMed

    Cadenbach, Thomas; Bollermann, Timo; Gemel, Christian; Fischer, Roland A

    2009-01-14

    The reactions of the ruthenium hydride complexes [{Ru(COD)(H)(NH2NMe2)3}{BArF}] (BArF=B{C6H3(CF3)2}4), [{Cp*Ru}2(micro-H)4] and [{Cp*Ru}3(micro-H)3(micro3-H)2] with GaCp* and AlCp* are investigated. The reaction of [{Ru(COD)(H)(NH2NMe2)3}{BArF}] with GaCp* leads to substitution of the hydrazine ligands by GaCp* and the formation of [{Ru(COD)(H)(GaCp*)3}{BArF}] (), while the reactions of [{Cp*Ru}2(micro-H)4] and [{Cp*Ru}3(micro-H)3(micro3-H)2] with ECp* (E=Al, Ga) results in the formation of the polyhydride clusters [{Cp*Ru(micro-H)(H)(micro-ECp*)}2] (, E=Ga; , E=Al) and [{Cp*Ru}3(micro-H)5(micro3-ECp*)] (, E=Al; , E=Ga). All Ru complexes react upon coordination of the group 13 ligand without loss of H2 or reductive elimination of Cp*H and without insertion into the Ru-H bonds; some of the products, however, showing Ru-H-E bridging motifs. All compounds were characterized by NMR spectroscopy, elemental analysis and single crystal X-ray diffraction studies. PMID:19089014

  13. Association between GABAA Receptor Subunit Gene Cluster and Zolpidem-Induced Complex Sleep Behaviors in Han Chinese

    PubMed Central

    Tsai, Jui-Hsiu; Yang, Pinchen; Lin, Hung-Hsun; Cheng, Kuang-hung; Yang, Yi-Hsin; Wu, Ming-Tsang; Chen, Cheng-Chung

    2013-01-01

    Study Objectives: To investigate and elucidate the role of GABAA receptor subunits, specifically the 2 genetic markers at the GABAA α1 and GABAA α6 receptors, in zolpidem-induced complex sleep behaviors (CSBs). Design: Genetic association study. Setting: Kaohsiung Medical University-affiliated hospitals, Kaohsiung, Taiwan. Patients: 30 zolpidem-induced CSB subjects and 37 controls. Interventions: N/A. Measurements and Results: The χ2 test demonstrated an association between the A15G variant at the GABAA α1 receptor subunit gene and zolpidem-induced CSBs (P = 0.007). The adjusted odds ratio of the GABAA α1 receptor subunit genotype for the risk of zolpidem-induced CSBs was approximately 10 (OR = 9.99, 95% CI = 1.82, 74.87; P = 0.013). Conclusions: The finding reveals that the A15G variant at the GABAA α1 receptor subunit gene confers a high risk of zolpidem-induced CSBs and may be considered in clinical services. Citation: Tsai JH; Yang P; Lin HH; Cheng Kh; Yang YH; Wu MT; Chen CC. Association between GABAA receptor subunit gene cluster and zolpidem-induced complex sleep behaviors in Han Chinese. SLEEP 2013;36(2):197–202. PMID:23372267

  14. Explicitly correlated coupled cluster calculations for the benzenium ion (C6H7(+)) and its complexes with Ne and Ar.

    PubMed

    Botschwina, Peter; Oswald, Rainer

    2011-11-24

    Explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level (Adler, T. B.; Knizia, G.; Werner, H.-J. J. Chem. Phys. 2007, 127, 221106) has been employed in a study of the benzenium ion (C6H7(+)) and its complexes with a neon or an argon atom. The ground-state rotational constants of C6H7(+) are predicted to be A0 = 5445 MHz, B0 = 5313 MHz, and C0 = 2731 MHz. Anharmonic vibrational wavenumbers of this cation were obtained by combination of harmonic CCSD(T*)-F12a values with anharmonic contributions calculated by double-hybrid density functional theory at the B2PLYP-D level. For the complexes of C6H7(+) with Ne or Ar, the lowest energy minimum is of π-bonded structure. The corresponding dissociation energies D0 are estimated to be 160 and 550 cm(-1), respectively. There is no indication of H-bonds to the aromatic or aliphatic hydrogen atoms. Instead, three nonequivalent local energy minima were found for nuclear configurations where the rare-gas atom lies in the ring-plane and approximatly points to the center of one of the six CC bonds. PMID:21981720

  15. A CEP215–HSET complex links centrosomes with spindle poles and drives centrosome clustering in cancer

    PubMed Central

    Chavali, Pavithra L.; Chandrasekaran, Gayathri; Barr, Alexis R.; Tátrai, Péter; Taylor, Chris; Papachristou, Evaggelia K.; Woods, C. Geoffrey; Chavali, Sreenivas; Gergely, Fanni

    2016-01-01

    Numerical centrosome aberrations underlie certain developmental abnormalities and may promote cancer. A cell maintains normal centrosome numbers by coupling centrosome duplication with segregation, which is achieved through sustained association of each centrosome with a mitotic spindle pole. Although the microcephaly- and primordial dwarfism-linked centrosomal protein CEP215 has been implicated in this process, the molecular mechanism responsible remains unclear. Here, using proteomic profiling, we identify the minus end-directed microtubule motor protein HSET as a direct binding partner of CEP215. Targeted deletion of the HSET-binding domain of CEP215 in vertebrate cells causes centrosome detachment and results in HSET depletion at centrosomes, a phenotype also observed in CEP215-deficient patient-derived cells. Moreover, in cancer cells with centrosome amplification, the CEP215–HSET complex promotes the clustering of extra centrosomes into pseudo-bipolar spindles, thereby ensuring viable cell division. Therefore, stabilization of the centrosome–spindle pole interface by the CEP215–HSET complex could promote survival of cancer cells containing supernumerary centrosomes. PMID:26987684

  16. Clustering of OB-fold domains of the partner protease complexed with trimeric stomatin from Thermococcales.

    PubMed

    Yokoyama, Hideshi; Matsui, Eriko; Hiramoto, Kana; Forterre, Patrick; Matsui, Ikuo

    2013-07-01

    The C-terminal soluble domain of stomatin operon partner protein (STOPP) of the hyperthermophilic archaeon Pyrococcus horikoshii has an oligonucleotide binding-fold (OB-fold). STOPP lacks the conserved surface residues necessary for binding to DNA/RNA. A tryptophan (W) residue is conserved instead at the molecular surface. Solvent-accessible W residues are often found at interfaces of protein-protein complexes, which suggested the possibility of self-assembling of STOPP. Protein-protein interactions among the C-terminal soluble domains of STOPP PH1510 (1510-C) were then analyzed by chemical linking and blue native polyacrylamide gel electrophoresis (BN-PAGE) methods. These results suggest that the soluble domains of STOPP could assemble into homo-oligomers. Since hexameric subcomplex I from archaeal proteasome consists of coiled-coil segments and OB-fold domains, molecular modeling of 1510-C was performed using hexameric subcomplex I as a template. Although 1510-C is a comparatively small polypeptide consisting of approximately 60 residues, numerous salt bridges and hydrophobic interactions were observed in the predicted hexamer of 1510-C, suggesting the stability of the homo-oligomeric structure. This oligomeric property of STOPP may be favorable for triplicate proteolysis of the trimer of prokaryotic stomatin. PMID:23587725

  17. Star formation in the filament of S254-S258 OB complex: a cluster in the process of being created

    NASA Astrophysics Data System (ADS)

    Samal, M. R.; Ojha, D. K.; Jose, J.; Zavagno, A.; Takahashi, S.; Neichel, B.; Kim, J. S.; Chauhan, N.; Pandey, A. K.; Zinchenko, I.; Tamura, M.; Ghosh, S. K.

    2015-09-01

    Infrared dark clouds are ideal laboratories for studying the initial processes of high-mass star and star-cluster formation. We investigated the star formation activity of an unexplored filamentary dark cloud (size ~5.7 pc × 1.9 pc), which itself is part of a large filament (~20 pc) located in the S254-S258 OB complex at a distance of 2.5 kpc. Using Multi-band Imaging Photometer (MIPS) Spitzer 24 μm data, we uncovered 49 sources with signal-to-noise ratios greater than 5. We identified 45 sources as candidate young stellar objects (YSOs) of Class I, flat-spectrum, and Class II natures. Additional 17 candidate YSOs (9 Class I and 8 Class II) are also identified using JHK and Wide-field Infrared Survey Explorer (WISE) photometry. We find that the protostar-to-Class II sources ratio (~2) and the protostar fraction (~70%) of the region are high. Comparison of the protostar fraction to other young clusters suggests that the star formation in the dark cloud possibly started only 1 Myr ago. Combining the near-infrared photometry of the YSO candidates with the theoretical evolutionary models, we infer that most of the candidate YSOs formed in the dark cloud are low-mass (<2 M⊙). We examine the spatial distribution of the YSOs and find that majority of them are linearly aligned along the highest column density line (N(H2)~1 × 1022 cm-2) of the dark cloud along its long axis at the mean nearest-neighbour separation of ~0.2 pc. Using the observed properties of the YSOs, physical conditions of the cloud and a simple cylindrical model, we explore the possible star formation process of this filamentary dark cloud and suggest that gravitational fragmentation within the filament should have played a dominant role in the formation of the YSOs. From the total mass of the YSOs, the gaseous mass associated with the dark cloud, and the surrounding environment, we infer that the region is presently forming stars at an efficiency of ~3% and a rate ~30 M⊙ Myr-1, and it may emerge

  18. Three tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole and different aromatic carboxylates: Assembly, structures, electrochemical and magnetic properties

    SciTech Connect

    Wang, Xiu-Li; Zhao, Wei; Zhang, Ju-Wen; Lu, Qi-Lin

    2013-02-15

    Three new tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole (atrz) and three types of aromatic carboxylates, [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(DNBA){sub 6}] (1), [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(1,3-BDC){sub 3}]{center_dot}2H{sub 2}O (2) and [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(SIP){sub 2}]{center_dot}4H{sub 2}O (3) (HDNBA=3,5-dinitrobenzoic acid, 1,3-H{sub 2}BDC=1,3-benzenedicarboxylic acid and NaH{sub 2}SIP=sodium 5-sulfoisophthalate), have been hydrothermally synthesized and structurally characterized. Complex 1 displays a single-molecular Cu{sup II}{sub 4} cluster structure, which is further connected by the intermolecular hydrogen-bonding interactions to form a 2D supramolecular layer. In 2, there also exist tetranuclear Cu{sup II}{sub 4} clusters, which are linked by the 1,3-BDC anions to give a 3D NaCl-type framework. In 3, the Cu{sup II}{sub 4} clusters are connected by the carboxyl and sulfo groups of SIP anions to generate 3D (4,8)-connected framework with a (4{sup 10}{center_dot}6{sup 14}{center_dot}8{sup 4})(4{sup 5}{center_dot}6){sub 2} topology. The atrz ligand conduces to the construction of tetranuclear copper(II) clusters and the carboxylates with different non-carboxyl substituent show important effects on the final structures of the title complexes. The electrochemical and magnetic properties of 1-3 have been investigated. - Graphical abstract: Three tetranuclear copper(II) cluster-based complexes based on different carboxylates have been synthesized under hydrothermal conditions. The carboxylate anions play a key role in the formation of three different structures. Highlights: Black-Right-Pointing-Pointer Three new tetranuclear copper(II) cluster-based complexes have been obtained. Black-Right-Pointing-Pointer The atrz conduces to the construction of tetranuclear copper(II) clusters. Black-Right-Pointing-Pointer Carboxylates show important effect on the structures of

  19. Detecting hidden spatial and spatio-temporal structures in glasses and complex physical systems by multiresolution network clustering.

    PubMed

    Ronhovde, P; Chakrabarty, S; Hu, D; Sahu, M; Sahu, K K; Kelton, K F; Mauro, N A; Nussinov, Z

    2011-09-01

    We elaborate on a general method that we recently introduced for characterizing the "natural" structures in complex physical systems via multi-scale network analysis. The method is based on "community detection" wherein interacting particles are partitioned into an "ideal gas" of optimally decoupled groups of particles. Specifically, we construct a set of network representations ("replicas") of the physical system based on interatomic potentials and apply a multiscale clustering ("multiresolution community detection") analysis using information-based correlations among the replicas. Replicas may i) be different representations of an identical static system, ii) embody dynamics by considering replicas to be time separated snapshots of the system (with a tunable time separation), or iii) encode general correlations when different replicas correspond to different representations of the entire history of the system as it evolves in space-time. Inputs for our method are the inter-particle potentials or experimentally measured two (or higher order) particle correlations. We apply our method to computer simulations of a binary Kob-Andersen Lennard-Jones system in a mixture ratio of A(80)B(20) , a ternary model system with components "A", "B", and "C" in ratios of A(88)B(7)C(5) (as in Al(88)Y(7)Fe(5) , and to atomic coordinates in a Zr(80)Pt(20) system as gleaned by reverse Monte Carlo analysis of experimentally determined structure factors. We identify the dominant structures (disjoint or overlapping) and general length scales by analyzing extrema of the information theory measures. We speculate on possible links between i) physical transitions or crossovers and ii) changes in structures found by this method as well as phase transitions associated with the computational complexity of the community detection problem. We also briefly consider continuum approaches and discuss rigidity and the shear penetration depth in amorphous systems; this latter length scale increases as

  20. Theoretical differential Raman scattering cross-sections of totally-symmetric vibrational modes of free pyridine and pyridine-metal cluster complexes

    NASA Astrophysics Data System (ADS)

    Wu, D. Y.; Hayashi, M.; Lin, S. H.; Tian, Z. Q.

    2004-01-01

    The differential Raman scattering cross-sections of totally-symmetric vibrational modes for pyridine and pyridine-metal clusters have been calculated by using ab initio and density functional methods. The results are compared with experimental data and a good agreement is obtained. In particular, we can theoretically reproduce the significant changes in the relative Raman intensities of the ν12 mode in pyridine-metal cluster complexes. We focus on two mechanisms for these Raman intensities changes: (1) the chemical interaction between the pyridine and the metal clusters; and (2) the charge transfer mechanism. For the pyridine-silver cluster complexes, we find that due to the weak bonding, the chemical interaction does not influence the relative intensities of the Raman peaks of the ν1 and ν12 modes. However, in the case where the copper or the gold clusters are attached to pyridine, the intensity of the band of the ν12 mode is weakened significantly. We also find that the charge transfer mechanism increases the asymmetry of the bands of the ν1 and ν12 modes on all three metals.

  1. Methane activation by cobalt cluster cations, Con+ (n=2-16): Reaction mechanisms and thermochemistry of cluster-CHx (x=0-3) complexes

    NASA Astrophysics Data System (ADS)

    Citir, Murat; Liu, Fuyi; Armentrout, P. B.

    2009-02-01

    The kinetic energy dependences of the reactions of Con+ (n =2-16) with CD4 are studied in a guided ion beam tandem mass spectrometer over the energy range of 0-10 eV. The main products are hydride formation, ConD+, dehydrogenation to form ConCD2+, and double dehydrogenation yielding ConC+. These primary products decompose to form secondary and higher order products, ConCD+, Con-1D+, Con-1C+, Con-1CD+, and Con-1CD2+ at higher energies. Adduct formation of ConCD4+ is also observed for the largest cluster cations, n ≥10. In general, the efficiencies of the single and double dehydrogenation processes increase with cluster size, although the hexamer cation shows a reduced reactivity compared to its neighbors. All reactions exhibit thresholds, and cross sections for the various primary and secondary reactions are analyzed to yield reaction thresholds from which bond energies for cobalt cluster cations to D, C, CD, CD2, and CD3 are determined. The relative magnitudes of these bond energies are consistent with simple bond order considerations. Bond energies for larger clusters rapidly reach relatively constant values, which are used to estimate the chemisorption energies of the C, CD, CD2, and CD3 molecular fragments to cobalt surfaces.

  2. Functional characterization of diverse ring-hydroxylating oxygenases and induction of complex aromatic catabolic gene clusters in Sphingobium sp. PNB

    PubMed Central

    Khara, Pratick; Roy, Madhumita; Chakraborty, Joydeep; Ghosal, Debajyoti; Dutta, Tapan K.

    2014-01-01

    Sphingobium sp. PNB, like other sphingomonads, has multiple ring-hydroxylating oxygenase (RHO) genes. Three different fosmid clones have been sequenced to identify the putative genes responsible for the degradation of various aromatics in this bacterial strain. Comparison of the map of the catabolic genes with that of different sphingomonads revealed a similar arrangement of gene clusters that harbors seven sets of RHO terminal components and a sole set of electron transport (ET) proteins. The presence of distinctly conserved amino acid residues in ferredoxin and in silico molecular docking analyses of ferredoxin with the well characterized terminal oxygenase components indicated the structural uniqueness of the ET component in sphingomonads. The predicted substrate specificities, derived from the phylogenetic relationship of each of the RHOs, were examined based on transformation of putative substrates and their structural homologs by the recombinant strains expressing each of the oxygenases and the sole set of available ET proteins. The RHO AhdA1bA2b was functionally characterized for the first time and was found to be capable of transforming ethylbenzene, propylbenzene, cumene, p-cymene and biphenyl, in addition to a number of polycyclic aromatic hydrocarbons. Overexpression of aromatic catabolic genes in strain PNB, revealed by real-time PCR analyses, is a way forward to understand the complex regulation of degradative genes in sphingomonads. PMID:24918041

  3. Deficiency of the iron-sulfur clusters of mitochondrial reduced nicotinamide-adenine dinucleotide-ubiquinone oxidoreductase (complex I) in an infant with congenital lactic acidosis.

    PubMed

    Moreadith, R W; Batshaw, M L; Ohnishi, T; Kerr, D; Knox, B; Jackson, D; Hruban, R; Olson, J; Reynafarje, B; Lehninger, A L

    1984-09-01

    We report the case of an infant with hypoglycemia, progressive lactic acidosis, an increased serum lactate/pyruvate ratio, and elevated plasma alanine, who had a moderate to profound decrease in the ability of mitochondria from four organs to oxidize pyruvate, malate plus glutamate, citrate, and other NAD+-linked respiratory substrates. The capacity to oxidize the flavin adenine dinucleotide-linked substrate, succinate, was normal. The most pronounced deficiency was in skeletal muscle, the least in kidney mitochondria. Enzymatic assays on isolated mitochondria ruled out defects in complexes II, III, and IV of the respiratory chain. Further studies showed that the defect was localized in the inner membrane mitochondrial NADH-ubiquinone oxidoreductase (complex I). When ferricyanide was used as an artificial electron acceptor, complex I activity was normal, indicating that electrons from NADH could reduce the flavin mononucleotide cofactor. However, electron paramagnetic resonance spectroscopy performed on liver submitochondrial particles showed an almost total loss of the iron-sulfur clusters characteristic of complex I, whereas normal signals were noted for other mitochondrial iron-sulfur clusters. This infant is presented as the first reported case of congenital lactic acidosis caused by a deficiency of the iron-sulfur clusters of complex I of the mitochondrial electron transport chain. PMID:6432847

  4. Complex trend of magnetic order in Fe clusters on 4d transition-metal surfaces. I. Experimental evidence and Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Sessi, V.; Otte, F.; Krotzky, S.; Tieg, C.; Wasniowska, M.; Ferriani, P.; Heinze, S.; Honolka, J.; Kern, K.

    2014-05-01

    We demonstrate the occurrence of compensated spin configurations in Fe clusters and monolayers on Ru(0001) and Rh(111) by a combination of x-ray magnetic circular dichroism experiments, first-principles calculations, and Monte Carlo simulations. Our results reveal complex intracluster exchange interactions which depend strongly on the substrate 4d-band filling, the cluster geometry, as well as lateral and vertical structural relaxations. The importance of substrate 4d-band filling manifests itself also in small nearest-neighbor exchange interactions in Fe dimers and in a nearly inverted trend of the Ruderman-Kittel-Kasuya-Yosida coupling constants for Fe adatoms on the Ru and Rh surface.

  5. The Yeast Iron Regulatory Proteins Grx3/4 and Fra2 Form Heterodimeric Complexes Containing a [2Fe-2S] Cluster with Cysteinyl and Histidyl Ligation†

    PubMed Central

    Li, Haoran; Mapolelo, Daphne T.; Dingra, Nin N.; Naik, Sunil G.; Lees, Nicolas S.; Hoffman, Brian M.; Riggs-Gelasco, Pamela J.; Huynh, Boi Hanh; Johnson, Michael K.; Outten, Caryn E.

    2009-01-01

    The transcription of iron uptake and storage genes in S. cerevisiae is primarily regulated by the transcription factor Aft1. Nucleocytoplasmic shuttling of Aft1 is dependent upon mitochondrial Fe-S cluster biosynthesis via a signaling pathway that includes the cytosolic monothiol glutaredoxins (Grx3 and Grx4) and the BolA homologue Fra2. However the interactions between these proteins and the iron-dependent mechanism by which they control Aft1 localization are unclear. To reconstitute and characterize components of this signaling pathway in vitro, we have overexpressed yeast Fra2 and Grx3/4 in E. coli. We have shown that co-expression of recombinant Fra2 with Grx3 or Grx4 allows purification of a stable [2Fe-2S]2+ cluster-containing Fra2-Grx3 or Fra2-Grx4 heterodimeric complex. Reconstitution of a [2Fe-2S] cluster on Grx3 or Grx4 without Fra2 produces a [2Fe-2S]-bridged homodimer. UV-visible absorption and CD, resonance Raman, EPR, ENDOR, Mössbauer, and EXAFS studies of [2Fe-2S] Grx3/4 homodimers and the [2Fe-2S] Fra2-Grx3/4 heterodimers indicate that inclusion of Fra2 in the Grx3/4 Fe-S complex causes a change in the cluster stability and coordination environment. Taken together, our analytical, spectroscopic, and mutagenesis data indicate that Grx3/4 and Fra2 form a Fe-S-bridged heterodimeric complex with Fe ligands provided by the active site cysteine of Grx3/4, glutathione, and a histidine residue. Overall, these results suggest that the ability of the Fra2-Grx3/4 complex to assemble a [2Fe-2S] cluster may act as a signal to control the iron regulon in response to cellular iron status in yeast. PMID:19715344

  6. Crystal Structures of the Iron-Sulfur Cluster-Dependent Quinolinate Synthase in Complex with Dihydroxyacetone Phosphate, Iminoaspartate Analogues, and Quinolinate.

    PubMed

    Fenwick, Michael K; Ealick, Steven E

    2016-08-01

    The quinolinate synthase of prokaryotes and photosynthetic eukaryotes, NadA, contains a [4Fe-4S] cluster with unknown function. We report crystal structures of Pyrococcus horikoshii NadA in complex with dihydroxyacetone phosphate (DHAP), iminoaspartate analogues, and quinolinate. DHAP adopts a nearly planar conformation and chelates the [4Fe-4S] cluster via its keto and hydroxyl groups. The active site architecture suggests that the cluster acts as a Lewis acid in enediolate formation, like zinc in class II aldolases. The DHAP and putative iminoaspartate structures suggest a model for a condensed intermediate. The ensemble of structures suggests a two-state system, which may be exploited in early steps. PMID:27404889

  7. A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters

    NASA Astrophysics Data System (ADS)

    De La Cruz, Carlos; Sheppard, Norman

    2011-01-01

    The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(σ-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M 2(μ 2-NO)]; (c) threefold nitrosyl bridges, [M 3(μ 3-NO)]; (d) σ/π-dihaptonitrosyls or " side-on" nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls). Typical ranges for the values of internuclear N-O and M-N bond-distances and M-N-O bond-angles for linear nitrosyls are: 1.14-1.20 Å/1.60-1.90 Å/180-160° and for bent nitrosyls are 1.16-1.22 Å/1.80-2.00 Å/140-110°. The [M 2(μ 2-NO)] bridges have been divided into those that contain one or several metal-metal bonds and those without a formal metal/metal bond (M⋯M). Typical ranges for the M-M, N-O, M-N bond distances and M-N-M bond angles for the normal twofold NO bridges are: 2.30-3.00 Å/1.18-1.22 Å/1.80-2.00 Å/90-70°, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 Å/1.20-1.24 Å/1.90-2.10 Å/130-110°. In both situations the N-O vector is approximately at right angle to the M-M (or M⋯M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M 3-plane of a cluster compound. Characteristic values for the N-O and M-N bond-distances of these NO bridges are: 1.24-1.28 Å/1.80-1.90 Å, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis. The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the

  8. A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters.

    PubMed

    De La Cruz, Carlos; Sheppard, Norman

    2011-01-01

    The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(σ-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M2(μ2-NO)]; (c) threefold nitrosyl bridges, [M3(μ3-NO)]; (d) σ/π-dihaptonitrosyls or "side-on" nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls). Typical ranges for the values of internuclear N-O and M-N bond-distances and M-N-O bond-angles for linear nitrosyls are: 1.14-1.20 Å/1.60-1.90 Å/180-160° and for bent nitrosyls are 1.16-1.22 Å/1.80-2.00 Å/140-110°. The [M2(μ2-NO)] bridges have been divided into those that contain one or several metal-metal bonds and those without a formal metal/metal bond (M⋯M). Typical ranges for the M-M, N-O, M-N bond distances and M-N-M bond angles for the normal twofold NO bridges are: 2.30-3.00 Å/1.18-1.22 Å/1.80-2.00 Å/90-70°, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 Å/1.20-1.24 Å/1.90-2.10 Å/130-110°. In both situations the N-O vector is approximately at right angle to the M-M (or M⋯M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M3-plane of a cluster compound. Characteristic values for the N-O and M-N bond-distances of these NO bridges are: 1.24-1.28 Å/1.80-1.90 Å, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis. The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the

  9. Exome sequencing identifies NFS1 deficiency in a novel Fe-S cluster disease, infantile mitochondrial complex II/III deficiency.

    PubMed

    Farhan, Sali M K; Wang, Jian; Robinson, John F; Lahiry, Piya; Siu, Victoria M; Prasad, Chitra; Kronick, Jonathan B; Ramsay, David A; Rupar, C Anthony; Hegele, Robert A

    2014-01-01

    Iron-sulfur (Fe-S) clusters are a class of highly conserved and ubiquitous prosthetic groups with unique chemical properties that allow the proteins that contain them, Fe-S proteins, to assist in various key biochemical pathways. Mutations in Fe-S proteins often disrupt Fe-S cluster assembly leading to a spectrum of severe disorders such as Friedreich's ataxia or iron-sulfur cluster assembly enzyme (ISCU) myopathy. Herein, we describe infantile mitochondrial complex II/III deficiency, a novel autosomal recessive mitochondrial disease characterized by lactic acidemia, hypotonia, respiratory chain complex II and III deficiency, multisystem organ failure and abnormal mitochondria. Through autozygosity mapping, exome sequencing, in silico analyses, population studies and functional tests, we identified c.215G>A, p.Arg72Gln in NFS1 as the likely causative mutation. We describe the first disease in man likely caused by deficiency in NFS1, a cysteine desulfurase that is implicated in respiratory chain function and iron maintenance by initiating Fe-S cluster biosynthesis. Our results further demonstrate the importance of sufficient NFS1 expression in human physiology. PMID:24498631

  10. Friedreich's Ataxia Variants I154F and W155R Diminish Frataxin-Based Activation of the Iron-Sulfur Cluster Assembly Complex

    SciTech Connect

    Tsai, Chi-Lin; Bridwell-Rabb, Jennifer; Barondeau, David P

    2011-11-07

    Friedreich's ataxia (FRDA) is a progressive neurodegenerative disease that has been linked to defects in the protein frataxin (Fxn). Most FRDA patients have a GAA expansion in the first intron of their Fxn gene that decreases protein expression. Some FRDA patients have a GAA expansion on one allele and a missense mutation on the other allele. Few functional details are known for the ~15 different missense mutations identified in FRDA patients. Here in vitro evidence is presented that indicates the FRDA I154F and W155R variants bind more weakly to the complex of Nfs1, Isd11, and Isu2 and thereby are defective in forming the four-component SDUF complex that constitutes the core of the Fe-S cluster assembly machine. The binding affinities follow the trend Fxn ~ I154F > W155F > W155A ~ W155R. The Fxn variants also have diminished ability to function as part of the SDUF complex to stimulate the cysteine desulfurase reaction and facilitate Fe-S cluster assembly. Four crystal structures, including the first for a FRDA variant, reveal specific rearrangements associated with the loss of function and lead to a model for Fxn-based activation of the Fe-S cluster assembly complex. Importantly, the weaker binding and lower activity for FRDA variants correlate with the severity of disease progression. Together, these results suggest that Fxn facilitates sulfur transfer from Nfs1 to Isu2 and that these in vitro assays are sensitive and appropriate for deciphering functional defects and mechanistic details for human Fe-S cluster biosynthesis.

  11. A possible evolutionary origin for the Mn4 cluster of the photosynthetic water oxidation complex from natural MnO2 precipitates in the early ocean

    SciTech Connect

    Sauer, Kenneth; Yachandra, Vittal K.

    2002-04-30

    The photosynthetic water oxidation complex consists of a cluster of 4 Mn atoms bridged by O atoms, associated with Ca2+ and Cl- and incorporated into protein. The structure is similar in higher plants and algae, as well as in cyanobacteria of more ancient lineage, dating back more than 2.5 Ga on Earth. It has been proposed that the proto-enzyme derived from a component of a natural early marine manganese precipitate that contained a CaMn4O9 cluster. A variety of MnO2 minerals is found in nature. Three major classes are spinels, sheet-like layered structures and 3-dimensional networks that contain parallel tunnels. These relatively open structures readily incorporate cations (Na+, Li+, Mg2+, Ca2+, Ba2+, H+ and even Mn2+) and water. The minerals have different ratios of Mn(III) and Mn(IV) octahedrally coordinated to oxygens. Using X-ray spectroscopy we compare the chemical structures of Mn in the minerals with what is known about the arrangement in the water-oxidation complex to define the parameters of a structural model for the photosynthetic catalytic site. This comparison provides for the structural model a set of candidate Mn4 clusters -- some previously proposed and considered and others entirely novel.

  12. Mixed-metal chloro sulfido cluster complex of molybdenum and platinum, (Mo sub 3 Pt sub 2 S sub 4 Cl sub 4 (PEt sub 3 ) sub 6 )

    SciTech Connect

    Saito, Taro; Tsuboi, Toshio; Kajitani, Yoshimichi; Yamagata, Tsuneaki; Imoto, Hideo )

    1991-09-04

    In the authors recent publication, syntheses of mixed-metal chloro sulfido and chloro selenido complexes of molybdenum and nickel were reported. They were prepared by the reaction of (Mo{sub 3}X{sub 4}Cl{sub 4}(PEt{sub 3}){sub 3}(MeOH){sub 2}) (X = S, Se){sup 2} with Ni(cod){sub 2} (cod = 1,5-cyclooctadiene). In the present study, another excellent building block compound, Pt(cot){sub 2}, was reacted with the same trinuclear molybdenum complex, and the mixed-metal cluster complex (Mo{sub 3}Pt{sub 2}S{sub 4}Cl{sub 4}(PEt{sub 3}){sub 6}) (1) with an unexpected structure was obtained.

  13. Malfunctioning of the Iron–Sulfur Cluster Assembly Machinery in Saccharomyces cerevisiae Produces Oxidative Stress via an Iron-Dependent Mechanism, Causing Dysfunction in Respiratory Complexes

    PubMed Central

    Gomez, Mauricio; Pérez-Gallardo, Rocío V.; Sánchez, Luis A.; Díaz-Pérez, Alma L.; Cortés-Rojo, Christian; Meza Carmen, Victor; Saavedra-Molina, Alfredo; Lara-Romero, Javier; Jiménez-Sandoval, Sergio; Rodríguez, Francisco; Rodríguez-Zavala, José S.; Campos-García, Jesús

    2014-01-01

    Biogenesis and recycling of iron–sulfur (Fe–S) clusters play important roles in the iron homeostasis mechanisms involved in mitochondrial function. In Saccharomyces cerevisiae, the Fe–S clusters are assembled into apoproteins by the iron–sulfur cluster machinery (ISC). The aim of the present study was to determine the effects of ISC gene deletion and consequent iron release under oxidative stress conditions on mitochondrial functionality in S. cerevisiae. Reactive oxygen species (ROS) generation, caused by H2O2, menadione, or ethanol, was associated with a loss of iron homeostasis and exacerbated by ISC system dysfunction. ISC mutants showed increased free Fe2+ content, exacerbated by ROS-inducers, causing an increase in ROS, which was decreased by the addition of an iron chelator. Our study suggests that the increment in free Fe2+ associated with ROS generation may have originated from mitochondria, probably Fe–S cluster proteins, under both normal and oxidative stress conditions, suggesting that Fe–S cluster anabolism is affected. Raman spectroscopy analysis and immunoblotting indicated that in mitochondria from SSQ1 and ISA1 mutants, the content of [Fe–S] centers was decreased, as was formation of Rieske protein-dependent supercomplex III2IV2, but this was not observed in the iron-deficient ATX1 and MRS4 mutants. In addition, the activity of complexes II and IV from the electron transport chain (ETC) was impaired or totally abolished in SSQ1 and ISA1 mutants. These results confirm that the ISC system plays important roles in iron homeostasis, ROS stress, and in assembly of supercomplexes III2IV2 and III2IV1, thus affecting the functionality of the respiratory chain. PMID:25356756

  14. Complex-to-Predict Generational Shift between Nested and Clustered Organization of Individual Prey Networks in Digger Wasps

    PubMed Central

    Ballesteros, Yolanda; Polidori, Carlo; Tormos, José; Baños-Picón, Laura; Asís, Josep Daniel

    2014-01-01

    Although diet has traditionally been considered to be a property of the species or populations as a whole, there is nowadays extensive knowledge that individual specialization is widespread among animal populations. Nevertheless, the factors determining the shape of interactions within food webs remain largely undiscovered, especially in predatory insects. We used an aggregation of the digger wasp Bembix merceti to 1) analyse patterns of individual prey use across three flying seasons in a network–based context; and 2) test the effect of four potential factors that might explain network topologies (wasp mass, nest spatial distribution, simultaneous nest-provisioning, prey availability). Inter-individual diet variation was found in all three years, under different predator-prey network topologies: Individuals arranged in dietary clusters and displayed a checkerboard pattern in 2009, but showed nestedness in 2008 and 2010. Network topologies were not fully explained by the tested factors. Larger females consumed a higher proportion of the total number of prey species captured by the population as a whole, in such a way that nested patterns may arise from mass-dependent prey spectrum width. Conversely, individuals with similar body mass didn’t form clusters. Nested patterns seemed to be associated with a greater availability of the main prey species (a proxy for reduced intra-specific competition). Thus, according with theory, clusters seemed to appear when competition increased. On the other hand, the nests of the individuals belonging to a given cluster were not more closely located, and neither did individuals within a cluster provision their nests simultaneously. Thus, a female-female copying behaviour during foraging was unlikely. In conclusion, wasp populations can maintain a considerable individual variation across years under different food web organizations. The tested factors only partially accounted for the shift in network properties, and new analyses

  15. Interaction between Nbp35 and Cfd1 Proteins of Cytosolic Fe-S Cluster Assembly Reveals a Stable Complex Formation in Entamoeba histolytica

    PubMed Central

    Anwar, Shadab; Dikhit, Manas Ranjan; Singh, Krishn Pratap; Kar, Rajiv Kumar; Zaidi, Amir; Sahoo, Ganesh Chandra; Roy, Awadh Kishore; Nozaki, Tomoyoshi; Das, Pradeep; Ali, Vahab

    2014-01-01

    Iron-Sulfur (Fe-S) proteins are involved in many biological functions such as electron transport, photosynthesis, regulation of gene expression and enzymatic activities. Biosynthesis and transfer of Fe-S clusters depend on Fe-S clusters assembly processes such as ISC, SUF, NIF, and CIA systems. Unlike other eukaryotes which possess ISC and CIA systems, amitochondriate Entamoeba histolytica has retained NIF & CIA systems for Fe-S cluster assembly in the cytosol. In the present study, we have elucidated interaction between two proteins of E. histolytica CIA system, Cytosolic Fe-S cluster deficient 1 (Cfd1) protein and Nucleotide binding protein 35 (Nbp35). In-silico analysis showed that structural regions ranging from amino acid residues (P33-K35, G131-V135 and I147-E151) of Nbp35 and (G5-V6, M34-D39 and G46-A52) of Cfd1 are involved in the formation of protein-protein complex. Furthermore, Molecular dynamic (MD) simulations study suggested that hydrophobic forces surpass over hydrophilic forces between Nbp35 and Cfd1 and Van-der-Waal interaction plays crucial role in the formation of stable complex. Both proteins were separately cloned, expressed as recombinant fusion proteins in E. coli and purified to homogeneity by affinity column chromatography. Physical interaction between Nbp35 and Cfd1 proteins was confirmed in vitro by co-purification of recombinant Nbp35 with thrombin digested Cfd1 and in vivo by pull down assay and immunoprecipitation. The insilico, in vitro as well as in vivo results prove a stable interaction between these two proteins, supporting the possibility of its involvement in Fe-S cluster transfer to target apo-proteins through CIA machinery in E. histolytica. Our study indicates that initial synthesis of a Fe-S precursor in mitochondria is not necessary for the formation of Cfd1-Nbp35 complex. Thus, Cfd1 and Nbp35 with the help of cytosolic NifS and NifU proteins can participate in the maturation of non-mitosomal Fe-S proteins without any

  16. High-Resolution Mn EXAFS of the Oxygen-Evolving Complex inPhotosystem II: Structural Implications for the Mn4Ca Cluster

    SciTech Connect

    Yano, Junko; Pushkar, Yulia; Glatzel, Pieter; Lewis, Azul; Sauer,Kenneth; Messinger, Johannes; Bergmann, Uwe; Yachandra, Vittal

    2005-09-06

    The biological generation of oxygen by the oxygen-evolving complex in photosystem II (PS II) is one of natures most important reactions. The recent X-ray crystal structures, while limited by resolutions of 3.2 to 3.5 A, have located the electron density associated with the Mn4Ca complex within the multi-protein PS II complex. Detailed structures critically depend on input from spectroscopic techniques such as EXAFS and EPR/ENDOR, as the XRD resolution does not allow for accurate determination of the position of Mn/Ca or the bridging and terminal ligand atoms. The number and distances of Mn-Mn/Ca/ligand interactions determined from EXAFS provide important constraints for the structure of the Mn cluster. Here we present data from a high-resolution EXAFS method using a novel multi-crystal monochromator that show three short Mn-Mn distances between 2.7 and 2.8 A and hence the presence of three di-mu-oxobridged units in the Mn4Ca cluster. This result imposes clear limitations on the proposed structures based on spectroscopic and diffraction data and provides input for refining such structures.

  17. Oxide- and zeolite-supported molecular metal complexes and clusters: physical characterization and determination of structure, bonding, and metal oxidation state.

    PubMed

    Fierro-Gonzalez, Juan C; Kuba, Stefan; Hao, Yalin; Gates, Bruce C

    2006-07-13

    This article is a review of the physical characterization of well-defined site-isolated molecular metal complexes and metal clusters supported on metal oxides and zeolites. These surface species are of interest primarily as catalysts; as a consequence of their relatively uniform structures, they can be characterized much more precisely than traditional supported catalysts. The properties discussed in this review include metal nuclearity, oxidation state, and ligand environment, as well as metal-support interactions. These properties are determined by complementary techniques, including transmission electron microscopy; X-ray absorption, infrared, Raman, and NMR spectroscopies; and density functional theory. The strengths and limitations of these techniques are assessed in the context of results characterizing samples that have been investigated thoroughly and with multiple techniques. The depth of understanding of well-defined metal complexes and metal clusters on supports is approaching that attainable for molecular analogues in solution. The results provide a foundation for understanding the more complex materials that are typical of industrial catalysts. PMID:16821852

  18. Synthesis, structures, and fluorescence properties of two d-d heterometallic cluster-based complexes constructed by N-(phosphonomethyl) iminodiacetic acid

    NASA Astrophysics Data System (ADS)

    Li, Sa-Ying

    2016-12-01

    Two novel d-d heterometallic cluster-based complexes constructed by N-(Phosphonomethyl)imino-diacetic acid (H4PMIDA) multifunctional ligand, [Cu2Zn2(PMIDA)2(H2O)3]·3H2O(1), [ZnNi14(PMIDA)6(H2O)18]·(NO3)6·15H2O(2), have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR spectra, thermal analyses, and single-crystal X-ray diffraction. The complex 1 is one-dimensional heteronuclear molecular chain, which is further extends into a 3D supramolecular network through very extensive Osbnd H⋯O hydrogen bonds. The compound 2 is a rare novel zero-dimensional heteronuclear molecular cluster, which is further extends into a 3D supramolecular network through very extensive Osbnd H⋯O hydrogen bonds. Moreover, the solid-state fluorescence properties of the two complexes have also been investigated at room temperature.

  19. Identifying structural building blocks in CuO 6 clusters: CuO 2 complexes vs CuO 3 ozonides

    NASA Astrophysics Data System (ADS)

    Pouillon, Y.; Massobrio, C.

    2002-04-01

    Structural minima of neutral and negatively charged CuO 6 clusters have been investigated within density functional theory and a plane-wave approach. Among the lower energy structures, three isomers made of CuO 2 complexes and two isomers featuring a double ozonide Cu(O 3) unit lie within a few hundredths of eV. Isomers containing CuOOO chains are higher in energy. Formation of Cu(O 3) units is accompanied by hybridization between O 2p- and Cu 3d-like states. We highlight analogies and differences between our results and the structural identification proposed in the framework of photoelectron spectroscopy experiments.

  20. Crystal Structure of Human Arginase l Complexed with Thiosemicarbazide Reveals an Unusual Thiocarbonly u-Sulfide Ligand in the Binuclear Manganese Cluster

    SciTech Connect

    Di Costanzo,L.; Pique, M.; Christianson, D.

    2007-01-01

    The crystal structure of the human arginase I-thiosemicarbazide complex reveals an unusual thiocarbonyl {mu}-sulfide ligand in the binuclear manganese cluster. The CS moiety of thiosemicarbazide bridges Mn2+A and Mn2+B with coordination distances of 2.6 and 2.4 Angstroms, respectively. Otherwise, the binding of thiosemicarbazide to human arginase I does not cause any significant structural changes in the active site. The crystal structure of the unliganded enzyme reveals a hydrogen-bonded water molecule that could support proton transfer between a {mu}-water molecule and H141 to regenerate the nucleophilic {mu}-hydroxide ion in the final step of catalysis.

  1. Synthetic Tuning of Redox, Spectroscopic, and Photophysical Properties of {Mo6I8}(4+) Core Cluster Complexes by Terminal Carboxylate Ligands.

    PubMed

    Mikhailov, Maxim A; Brylev, Konstantin A; Abramov, Pavel A; Sakuda, Eri; Akagi, Soichiro; Ito, Akitaka; Kitamura, Noboru; Sokolov, Maxim N

    2016-09-01

    The reactions between the tetra-n-butylammonium salt of [{Mo6I8}I6](2-) and silver carboxylates RCOOAg (R = CH3 (1), C(CH3)3 (2), α-C4H3O (3), C6H5 (4), α-C10H7 (5), or C2F5 (6)) in CH2Cl2 afforded new carboxylate complexes [{Mo6I8}(RCOO)6](2-). The complexes were characterized by X-ray single-crystal diffraction and elemental analysis, cyclic/differential pulse voltammetry, and IR, NMR, and UV-visible spectroscopies. The emission properties of the complexes 1-6, and those of the earlier reported complexes with R = CF3 (7) and n-C3F7 (8), were studied both in acetonitrile solution and in the solid state. In deaerated CH3CN at 298 K, all of the complexes 1-8 exhibit intense and long-lived emission with the quantum yield and lifetime being 0.48-0.73 and 283-359 μs, respectively. The oxidation (Eox)/reduction (Ered) potentials of the complexes correlate linearly with the pKa value of the terminal carboxylate ligands L = RCOO (pKa(L)). Reflecting the pKa(L) dependences of Eox/Ered, the emission energy (νem) of the complexes was also shown to correlate with pKa(L). The present study successfully demonstrates synthetic tuning of the redox, spectroscopic, and photophysical characteristics of a {Mo6I8}(4+)-based cluster complex with pKa(L). PMID:27505303

  2. Effect of the Keggin anions on assembly of Cu{sup I}-bis(tetrazole) thioether complexes containing multinuclear Cu{sup I}-cluster

    SciTech Connect

    Wang Xiuli; Gao Qiang; Tian Aixiang; Hu Hailiang; Liu Guocheng

    2012-03-15

    In order to investigate the effect of polyoxometalate (POM) on the assembly of transition metal-bis(tetrazole) thioether complexes, three new complexes based on different Keggin anions and multinuclear Cu{sup I}-cluster [Cu{sup I}{sub 12}(bmtr){sub 9}(HSiMo{sub 12}O{sub 40}){sub 4}] (1), [Cu{sup I}{sub 3}(bmtr){sub 3}(PM{sub 12}O{sub 40})] (M=W for 2; Mo for 3) (bmtr=1,3-bis(1-methyl-5-mercapto-1,2,3,4-tetrazole)propane), have been hydrothermally synthesized and characterized by routine physical methods and single crystal X-ray diffraction. In compound 1, two kinds of nanometer-scale tetranuclear subunits linked by [SiMo{sub 12}O{sub 40}]{sup 4-} polyanions assemble a (3, 4)-connected three-dimensional (3D) self-penetrating framework. Compounds 2 and 3 are isostructural, exhibiting a 1D chain with [PW{sub 12}O{sub 40}]{sup 3-}/[PMo{sub 12}O{sub 40}]{sup 3-} polyanions and trinuclear clusters arranging alternately. The distinct structural differences between these POM-based Cu{sup I}-bmtr complexes of 1 and 2/3 maybe rest on the contrast of Keggin-type polyoxometalate with different central heteroatoms, which have been discussed in detail. In addition, the electrochemical properties of the title complexes have been investigated. - Graphical abstract: Three new complexes based on different Keggin anions and multinuclear Cu{sup I}-cluster have been synthesized under hydrothermal conditions. The Keggin polyanions with different central heteroatoms play a key role. Highlights: Black-Right-Pointing-Pointer The flexible bis(tetrazole)-based thioether ligand with some advantages have been used. Black-Right-Pointing-Pointer The effect of Keggin anions with different central heteroatoms has been discussed in detail. Black-Right-Pointing-Pointer The electrochemical behaviors and electrocatalysis property have been investigated.

  3. Organotin-oxido cluster-based multiferrocenyl complexes obtained by hydrolysis of ferrocenyl-functionalized organotin chlorides.

    PubMed

    You, Zhiliang; Möckel, Robert; Bergunde, Jakob; Dehnen, Stefanie

    2014-10-13

    Three organotin-oxido clusters were formed by hydrolysis of ferrocenyl-functionalized organotin chloride precursors in the presence of NaEPh (E=S, Se). [R(Fc) SnCl3 ⋅HCl] (C; R(Fc) = CMe2 CH2 C(Me)=N-N=C(Me)Fc) and [SnCl6 ](2-) formed {(R(Fc) SnCl2 )3 [Sn(OH)6 ]}[SnCl3 ] (3 a) and {(R(Fc) SnCl2 )3 [Sn(OH)6 ]}[PhSeO3 ] (3 b), bearing an unprecedented [Sn4 O6 ] unit, in a one-pot synthesis or stepwise through [(R(Fc) SnCl2 )2 Se] (1) plus [(R(Fc) SnCl2 )SePh] (2). A one-pot reaction starting out from FcSnCl3 gave [(FcSn)9 (OH)6 O8 Cl5 ] (4), which represents the largest Fc-decorated Sn/O cluster reported to date. PMID:25164865

  4. Titanium oxo-clusters derivatized from the Ti10O12(cat)8(py)8 complex: structural investigation and spectroscopic studies of light absorption.

    PubMed

    Chaumont, Clément; Chaumont, Alain; Kyritsakas, Nathalie; Mobian, Pierre; Henry, Marc

    2016-06-01

    A series of deep-red colored nano-sized titanium oxo-clusters bearing catecholato ligands is reported. These architectures are produced via post-synthetic modification of the Ti10O12(cat)8(py)8 (cat = catecholato, py = pyridine) complex through quantitative substitution of labile pyridine ligands by three substituted pyridines (pico, 4-Phpy and pyrald). The crystal structure analysis reveals a common Ti10O12(cat)8 backbone for the three isolated molecular architectures. Partial charge analysis indicates two types of titanium atoms within these complexes with one resembling titanium(iv) found in TiO2. These complexes strongly absorb visible light in solution (λmax = 411 nm, ε = 10 800 for Ti10O12(cat)8(py)8 in CHCl3) and in the solid-state. The band gaps estimated from the reflectance spectra are between 1.85 eV and 1.97 eV. The present work also details the HOMO and LUMO representations obtained via DFT calculation for Ti10O12(cat)8(py)8 and a virtual Ti10O12(cat)8 complex as well as the DOS (density of states) plots calculated for those structures. This computational study highlights an impact of the pyridine ligand on the DOS plots. PMID:27142485

  5. A structural snapshot of CYP2B4 in complex with paroxetine provides insights into ligand binding and clusters of conformational states.

    PubMed

    Shah, Manish B; Kufareva, Irina; Pascual, Jaime; Zhang, Qinghai; Stout, C David; Halpert, James R

    2013-07-01

    An X-ray crystal structure of CYP2B4 in complex with the drug paroxetine [(3S,4R)-3-[(2H-1,3-benzodioxol-5-yloxy)methyl]-4-(4-fluorophenyl)piperidine] was solved at 2.14 Å resolution. The structure revealed a conformation intermediate to that of the recently solved complex with amlodipine and that of the more compact complex with 4-(4-chlorophenyl)imidazole in terms of the placement of the F-G cassette. Moreover, comparison of the new structure with 15 previously solved structures of CYP2B4 revealed some new insights into the determinants of active-site size and shape. The 2B4-paroxetine structure is nearly superimposable on a previously solved closed structure in a ligand-free state. Despite the overall conformational similarity among multiple closed structures, the active-site cavity volume of the paroxetine complex is enlarged. Further analysis of the accessible space and binding pocket near the heme reveals a new subchamber that resulted from the movement of secondary structural elements and rearrangements of active-site side chains. Overall, the results from the comparison of all 16 structures of CYP2B4 demonstrate a cluster of protein conformations that were observed in the presence or absence of various ligands. PMID:23633618

  6. Edge-bridging and face-capping coordination of alkenyl ligands in triruthenium carbonyl cluster complexes derived from hydrazines: synthetic, structural, theoretical, and kinetic studies.

    PubMed

    Cabeza, Javier A; del Río, Ignacio; Fernández-Colinas, José M; García-Granda, Santiago; Martínez-Méndez, Lorena; Pérez-Carreño, Enrique

    2004-12-01

    The reactions of the triruthenium cluster complex [Ru3(mu-H)(mu3-eta2-HNNMe2)(CO)9] (1; H2NNMe2=1,1-dimethylhydrazine) with alkynes (PhC triple bond CPh, HC triple bond CH, MeO2CC triple bond CCO2Me, PhC triple bond CH, MeO2CC triple bond CH, HOMe2CC triple bond CH, 2-pyC triple bond CH) give trinuclear complexes containing edge-bridging and/or face-capping alkenyl ligands. Whereas the edge-bridged products are closed triangular species (three Ru-Ru bonds), the face-capped products are open derivatives (two Ru-Ru bonds). For terminal alkynes, products containing gem (RCCH2) and/or trans (RHCCH) alkenyl ligands have been identified in both edge-bridging and face-capping positions, except for the complex [Ru3(mu3-eta2-HNNMe2)(mu3-eta3-HCCH-2-py)(mu-CO)(CO)7], which has the two alkenyl H atoms in a cis arrangement. Under comparable reaction conditions (1:1 molar ratio, THF at reflux, time required for the consumption of complex 1), some reactions give a single product, but most give mixtures of isomers (not all the possible ones), which were separated. To determine the effect of the hydrazido ligand, the reactions of [Ru3(mu-H)(mu3-eta2-MeNNHMe)(CO)9] (2; HMeNNHMe=1,2-dimethylhydrazine) with PhC triple bond CPh, PhC triple bond CH, and HC triple bond CH were also studied. For edge-bridged alkenyl complexes, the Ru--Ru edge that is spanned by the alkenyl ligand depends on the position of the methyl groups on the hydrazido ligand. For face-capped alkenyl complexes, the relative orientation of the hydrazido and alkenyl ligands also depends on the position of the methyl groups on the hydrazido ligand. A kinetic analysis of the reaction of 1 with PhC[triple chemical bond]CPh revealed that the reaction follows an associative mechanism, which implies that incorporation of the alkyne in the cluster is rate-limiting and precedes the release of a CO ligand. X-ray diffraction, IR and NMR spectroscopy, and calculations of minimum-energy structures by DFT methods were used to

  7. Complexation of the vulcanization accelerator tetramethylthiuram disulfide and related molecules with zinc compounds including zinc oxide clusters (Zn4O4).

    PubMed

    Steudel, Ralf; Steudel, Yana; Wong, Ming Wah

    2008-01-01

    Zinc chemicals are used as activators in the vulcanization of organic polymers with sulfur to produce elastic rubbers. In this work, the reactions of Zn(2+), ZnMe(2), Zn(OMe)(2), Zn(OOCMe)(2), and the heterocubane cluster Zn(4)O(4) with the vulcanization accelerator tetramethylthiuram disulfide (TMTD) and with the related radicals and anions Me(2)NCS(2)(*), Me(2)NCS(3)(*), Me(2)NCS(2)(-), and Me(2)NCS(3)(-) have been studied by quantum chemical methods at the MP2/6-31+G(2df,p)//B3LYP/6-31+G* level of theory. More than 35 zinc complexes have been structurally characterized and the energies of formation from their components calculated for the first time. The binding energy of TMTD as a bidendate ligand increases in the order ZnMe(2)complexes with the radicals Me(2)NCS(2)(*) and Me(2)NCS(3)(*). Dissociation of the TMTD molecule at the S-S bond on reaction with the Zn(4)O(4) cluster is predicted to be strongly exothermic, in sharp contrast to the endothermic S-S bond dissociation of the free molecule. The same holds for tetramethylthiuram trisulfide (TMTT). Surprisingly, the resulting complexes contain Zn-S as well as S-O bonds. The Zn(4)O(4) nanocluster serves here as a model for bulk zinc oxide used as an activator in rubber vulcanization by sulfur. The further uptake of sulfur atoms by the various complexes from S(8) or TMTD with formation of species derived from the radical Me(2)NCS(3)(*) or the trithiocarbamate anion Me(2)NCS(3)(-) is endothermic for mono- and dinuclear zinc dithiocarbamate (dtc) complexes such as [Zn(dtc)(2)] and [Zn(2)(dtc)(4)], but exothermic in the case of polynuclear zinc oxide species containing bridging ligands as in [Zn(4)O(4)(mu-S(2)CNMe(2))] and [Zn(4)O(4)(mu-dtc)]. Therefore, zinc oxide as a polynuclear species is predicted to promote the formation of trisulfido complexes, which are generally assumed to serve as catalysts for the transfer of

  8. The use of phosphonates for constructing 3d-4f clusters at high oxidation states: synthesis and characterization of two unusual heterometallic CeMn complexes.

    PubMed

    Wang, Mei; Yuan, Da-Qiang; Ma, Cheng-Bing; Yuan, Ming-Jian; Hu, Ming-Qiang; Li, Na; Chen, Hui; Chen, Chang-Neng; Liu, Qiu-Tian

    2010-08-21

    The use of phosphonic acids in the synthesis of mixed-metal CeMn complexes has led to the formation of two phosphonate complexes with unusual topologies: [Ce(2)Mn(6)O(6)(OH)(5)(t-BuPO(3))(6)(O(2)CMe)(3)] x 53 H(2)O (1 x 53 H(2)O) and [Ce(22)Mn(12)O(34)(MePO(3))(12)(O(2)CMe)(33)(OMe)(6)(NO(3))(H(2)O)(12)](n) (2). The two mixed-metal CeMn complexes were both prepared from a reaction system containing Mn(O(2)CMe)(2) and (NH(4))(2)[Ce(NO(3))(6)] with similar procedures except for using different phosphonic acids (tert-butylphosphonic acid and methylphosphonic acid, respectively) as coligands. Both complexes possess rare topology of triangular type, with compound 1 being a 0D discrete cluster, whereas, compound 2 is a 1D polymer. The octanuclear core of complex 1 is composed of three symmetry equivalent distorted cubanes {Ce(IV)(2)Mn(IV)(2)O(2)(OH)(2)} sharing a trigonal-bipyramidal unit {Ce(IV)(2)(OH)(3)} in the centre. Compound 2 is a one-dimensional chain polymer of identical Ce(22)Mn(12)O(34) units linked together by NO(3)(-) and MeCO(2)(-) groups, while the Ce(22)Mn(12)O(34) unit is constituted by two centrosymmetric Ce(9)(IV)Ce(2)(III)Mn(IV)(6)O(17) subunits, which features three identical distorted cubanes {Ce(IV)(2)Mn(IV)(2)O(4)} connecting to a central trigonal-bipyramidal unit {Ce(IV)(3)O(2)}, and two additional Ce(III) ions capping the top and bottom of the central trigonal bipyramid by six MePO(3)(2-) ligands. Complexes 1 and 2 are the first high-nuclearity Mn/Ln aggregates reported to date using phosphonates as ligands. Magnetic susceptibility measurements reveal that compound 1 displays dominant ferromagnetic interactions between the adjacent metal ions with the best fit parameters for the exchanges are J(1) = 6.186 cm(-1), J(2) = 4.172 cm(-1), and with a result of S = 9 ground state confirmed by the M versus HT(-1) data, which indicates the spins of all the six Mn(IV) ions in the cluster are parallel to each other. In contrast, the data for 2 reveals

  9. σ-Aromatic cyclic M3(+) (M = Cu, Ag, Au) clusters and their complexation with dimethyl imidazol-2-ylidene, pyridine, isoxazole, furan, noble gases and carbon monoxide.

    PubMed

    Pan, Sudip; Saha, Ranajit; Mandal, Subhajit; Chattaraj, Pratim K

    2016-04-28

    The σ-aromaticity of M3(+) (M = Cu, Ag, Au) is analyzed and compared with that of Li3(+) and a prototype σ-aromatic system, H3(+). Ligands (L) like dimethyl imidazol-2-ylidene, pyridine, isoxazole and furan are employed to stabilize these monocationic M3(+) clusters. They all bind M3(+) with favorable interaction energy. Dimethyl imidazol-2-ylidene forms the strongest bond with M3(+) followed by pyridine, isoxazole and furan. Electrostatic contribution is considerably more than that of orbital contribution in these M-L bonds. The orbital interaction arises from both L → M σ donation and L ← M back donation. M3(+) clusters also bind noble gas atoms and carbon monoxide effectively. In general, among the studied systems Au3(+) binds a given L most strongly followed by Cu3(+) and Ag3(+). Computation of the nucleus-independent chemical shift (NICS) and its different extensions like the NICS-rate and NICS in-plane component vs. NICS out-of-plane component shows that the σ-aromaticity in L bound M3(+) increases compared to that of bare clusters. The aromaticity in pyridine, isoxazole and furan bound Au3(+) complexes is quite comparable with that in the recently synthesized Zn3(C5(CH3)5)3(+). The energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital also increases upon binding with L. The blue-shift and red-shift in the C-O stretching frequency of M3(CO)3(+) and M3(OC)3(+), respectively, are analyzed through reverse polarization of the σ- and π-orbitals of CO as well as the relative amount of OC → M σ donation and M → CO π back donation. The electron density analysis is also performed to gain further insight into the nature of interaction. PMID:26624276

  10. Complex-scaled equation-of-motion coupled-cluster method with single and double substitutions for autoionizing excited states: Theory, implementation, and examples

    SciTech Connect

    Bravaya, Ksenia B.; Zuev, Dmitry; Epifanovsky, Evgeny; Krylov, Anna I.

    2013-03-28

    Theory and implementation of complex-scaled variant of equation-of-motion coupled-cluster method for excitation energies with single and double substitutions (EOM-EE-CCSD) is presented. The complex-scaling formalism extends the EOM-EE-CCSD model to resonance states, i.e., excited states that are metastable with respect to electron ejection. The method is applied to Feshbach resonances in atomic systems (He, H{sup -}, and Be). The dependence of the results on one-electron basis set is quantified and analyzed. Energy decomposition and wave function analysis reveal that the origin of the dependence is in electron correlation, which is essential for the lifetime of Feshbach resonances. It is found that one-electron basis should be sufficiently flexible to describe radial and angular electron correlation in a balanced fashion and at different values of the scaling parameter, {theta}. Standard basis sets that are optimized for not-complex-scaled calculations ({theta} = 0) are not sufficiently flexible to describe the {theta}-dependence of the wave functions even when heavily augmented by additional sets.

  11. Influence of Single Skimmer Versus Dual Funnel Transfer on the Appearance of ESI-Generated LiCl Cluster/ß-Cyclodextrin Inclusion Complexes.

    PubMed

    Kellner, Ina D; Drewello, Thomas

    2015-08-01

    Singly and doubly charged adducts of LiCl with β-cyclodextrin (βCD) of the type (βCD)(LiCl)(n)Li(+) and (βCD)2(LiCl)(p)Li2(2+) were studied using electrospray ionization mass spectrometry (ESI-MS). Insight into their structural composition was gained by analysis of their collision-induced dissociation (CID) mass spectra. The conditions the ions experience in the transfer region interfacing the ESI source and the mass analyzer were found to have a marked influence on the nature of the detected ions. In one instrument incorporating a single skimmer, individually attached LiCl ion pairs were observed, whereas the dual funnel ion guides of the second instrument allow the detection of previously unknown labile inclusion complexes of (LiCl)n clusters in βCD. PMID:25895893

  12. Influence of Single Skimmer Versus Dual Funnel Transfer on the Appearance of ESI-Generated LiCl Cluster/ß-Cyclodextrin Inclusion Complexes

    NASA Astrophysics Data System (ADS)

    Kellner, Ina D.; Drewello, Thomas

    2015-08-01

    Singly and doubly charged adducts of LiCl with β-cyclodextrin (βCD) of the type (βCD)(LiCl)nLi+ and (βCD)2(LiCl)pLi2 2+ were studied using electrospray ionization mass spectrometry (ESI-MS). Insight into their structural composition was gained by analysis of their collision-induced dissociation (CID) mass spectra. The conditions the ions experience in the transfer region interfacing the ESI source and the mass analyzer were found to have a marked influence on the nature of the detected ions. In one instrument incorporating a single skimmer, individually attached LiCl ion pairs were observed, whereas the dual funnel ion guides of the second instrument allow the detection of previously unknown labile inclusion complexes of (LiCl)n clusters in βCD.

  13. A new algorithm for essential proteins identification based on the integration of protein complex co-expression information and edge clustering coefficient.

    PubMed

    Luo, Jiawei; Wu, Juan

    2015-01-01

    Essential proteins provide valuable information for the development of biology and medical research from the system level. The accuracy of topological centrality only based methods is deeply affected by noise in the network. Therefore, exploring efficient methods for identifying essential proteins would be of great value. Using biological features to identify essential proteins is efficient in reducing the noise in PPI network. In this paper, based on the consideration that essential proteins evolve slowly and play a central role within a network, a new algorithm, named CED, is proposed. CED mainly employs gene expression level, protein complex information and edge clustering coefficient to predict essential proteins. The performance of CED is validated based on the yeast Protein-Protein Interaction (PPI) network obtained from DIP database and BioGRID database. The prediction accuracy of CED outperforms other seven algorithms when applied to the two databases. PMID:26510286

  14. Complex absorbing potential based equation-of-motion coupled cluster method for the potential energy curve of CO{sub 2}{sup −} anion

    SciTech Connect

    Ghosh, Aryya; Vaval, Nayana; Pal, Sourav; Bartlett, Rodney J.

    2014-10-28

    The equation-of-motion coupled cluster method employing the complex absorbing potential has been used to investigate the low energy electron scattering by CO{sub 2}. We have studied the potential energy curve for the {sup 2}Π{sub u} resonance states of CO{sub 2}{sup −} upon bending as well as symmetric and asymmetric stretching of the molecule. Specifically, we have stretched the C−O bond length from 1.1 Å to 1.5 Å and the bending angles are changed between 180° and 132°. Upon bending, the low energy {sup 2}Π{sub u} resonance state is split into two components, i.e., {sup 2}A{sub 1}, {sup 2}B{sub 1} due to the Renner-Teller effect, which behave differently as the molecule is bent.

  15. Crystal structure of human arginase I complexed with thiosemicarbazide reveals an unusual thiocarbonyl μ-sulfide ligand in the binuclear manganese cluster

    PubMed Central

    Di Costanzo, Luigi; Pique, Michael E.; Christianson, David W.

    2008-01-01

    The crystal structure of the human arginase I-thiosemicarbazide complex reveals an unusual thiocarbonyl μ-sulfide ligand in the binuclear manganese cluster. The C=S moiety of thiosemicarbazide bridges Mn2+A and Mn2+B with coordination distances of 2.6 Å and 2.4 Å, respectively. Otherwise, the binding of thiosemicarbazide to human arginase I does not cause any significant structural changes in the active site. The crystal structure of the unliganded enzyme reveals a hydrogen bonded water molecule that could support proton transfer between a μ-water molecule and H141 to regenerate the nucleophilic μ-hydroxide ion in the final step of catalysis. PMID:17469833

  16. First principles calculations in iron: structure and mobility of defect clusters and defect complexes for kinetic modelling

    NASA Astrophysics Data System (ADS)

    Fu, Chu Chun; Willaime, F.

    2008-04-01

    Predictive simulations of the defect population evolution in materials under or after irradiation can be performed in a multi-scale approach, where the atomistic properties of defects are determined by electronic structure calculations based on the Density Functional Theory and used as input for kinetic simulations covering macroscopic time and length scales. Recent advances obtained in iron are presented. The determination of the 3D migration of self-interstitial atoms instead of a fast one-dimensional glide induced an overall revision of the widely accepted picture of radiation damage predicted by previously existing empirical potentials. A coupled ab initio and mesoscopic kinetic Monte Carlo simulation provided strong evidence to clarify controversial interpretations of electrical resistivity recovery experiments concerning the mobility of vacancies, self-interstitial atoms, and their clusters. The results on the dissolution and migration properties of helium in α-Fe were used to parameterize Rate Theory models and new inter-atomic potentials, which improved the understanding of fusion reactor materials behavior. Finally, the effects of carbon, present in all steels as the principal hardening element, are also shown. To cite this article: C.C. Fu, F. Willaime, C. R. Physique 9 (2008).

  17. High-nuclearity ruthenium carbonyl cluster complexes derived from 2-amino-6-methylpyridine: synthesis of nonanuclear derivatives containing mu4- and mu5-oxo ligands.

    PubMed

    Cabeza, Javier A; del Río, Ignacio; García-Alvarez, Pablo; Miguel, Daniel

    2006-07-24

    Nonanuclear cluster complexes [Ru9(mu3-H)2(mu-H)(mu5-O)(mu4-ampy)(mu3-Hampy)(CO)21] (4) (H2ampy = 2-amino-6-methylpyridine), [Ru9(mu5-O)2(mu4-ampy)(mu3-Hampy)2(mu-CO)(CO)20] (5), [Ru9(mu5-O)2(mu4-ampy)(mu3-Hampy)2(mu-CO)2(CO)19] (6), and [Ru9(mu4-O)(mu5-O)(mu4-ampy)(mu3-Hampy)(mu-Hampy)(mu-CO)(CO)19] (7), together with the known hexanuclear [Ru6(mu3-H)2(mu5-ampy)(mu-CO)2(CO)14] (2) and the novel pentanuclear [Ru5(mu4-ampy)(2)(mu-CO)(CO)12] (3) complexes, are products of the thermolysis of [Ru3(mu-H)(mu3-Hampy)(CO)9] (1) in decane at 150 degrees C. Two different and very unusual quadruply bridging coordination modes have been observed for the ampy ligand. Compounds 4-7 also feature one (4) or two (5-7) bridging oxo ligands. With the exception of one of the oxo ligands of 7, which is in a distorted tetrahedral environment, the remaining oxo ligands of 4-7 are surrounded by five metal atoms. In carbonyl metal clusters, quadruply bridging oxo ligands are very unusual, whereas quintuply bridging oxo ligands are unprecedented. By using 18O-labeled water, we have unambiguously established that these oxo ligands arise from water. PMID:16842009

  18. FT-IR spectroscopic characterization of NADH:ubiquinone oxidoreductase (complex I) from Escherichia coli: oxidation of FeS cluster N2 is coupled with the protonation of an aspartate or glutamate side chain.

    PubMed

    Hellwig, P; Scheide, D; Bungert, S; Mäntele, W; Friedrich, T

    2000-09-01

    The proton-pumping NADH:ubiquinone oxidoreductase, also called complex I, is the first energy-transducing complex of many respiratory chains. It couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. One FMN and up to nine iron-sulfur (FeS) clusters participate in the redox reaction. So far, complex I has been described mainly by means of EPR- and UV-vis spectroscopy. Here, we report for the first time an infrared spectroscopic characterization of complex I. Electrochemically induced FT-IR difference spectra of complex I from Escherichia coli and of the NADH dehydrogenase fragment of this complex were obtained for critical potential steps. The spectral contributions of the FMN in both preparations were derived from a comparison using model compounds and turned out to be unexpectedly small. Furthermore, the FT-IR difference spectra reveal that the redox transitions of the FMN and of the FeS clusters induce strong reorganizations of the polypeptide backbone. Additional signals in the spectra of complex I reflect contributions induced by the redox transition of the high-potential FeS cluster N2 which is not present in the NADH dehydrogenase fragment. Part of these signals are attributed to the reorganization of protonated/deprotonated Asp or Glu side chains. On the basis of these data we discuss the role of N2 for proton translocation of complex I. PMID:10978175

  19. A novel octanuclear vanadium(V) oxide cluster complex having an unprecedented neutral V8O20 core functionalized with 4,4'-di-tert-butyl-2,2'-bipyridine.

    PubMed

    Kodama, Shintaro; Taya, Nobuto; Ishii, Youichi

    2014-03-17

    A novel octanuclear vanadium(V) oxide cluster complex, [V8O20(4,4'-(t)Bubpy)4] (1), was synthesized and characterized by single-crystal X-ray structure analysis to reveal that 1 has an unprecedented neutral V8O20 core. An unexpected interconversion between 1 and the methoxo(oxo)vanadium(V) cluster complex, [V4O8(OMe)4(4,4'-(t)Bubpy)2] (2), was observed upon changes in the solvent systems. PMID:24559114

  20. Histidine 103 in Fra2 Is an Iron-Sulfur Cluster Ligand in the [2Fe-2S] Fra2-Grx3 Complex and Is Required for in Vivo Iron Signaling in Yeast*

    PubMed Central

    Li, Haoran; Mapolelo, Daphne T.; Dingra, Nin N.; Keller, Greg; Riggs-Gelasco, Pamela J.; Winge, Dennis R.; Johnson, Michael K.; Outten, Caryn E.

    2011-01-01

    The BolA homologue Fra2 and the cytosolic monothiol glutaredoxins Grx3 and Grx4 together play a key role in regulating iron homeostasis in Saccharomyces cerevisiae. Genetic studies indicate that Grx3/4 and Fra2 regulate activity of the iron-responsive transcription factors Aft1 and Aft2 in response to mitochondrial Fe-S cluster biosynthesis. We have previously shown that Fra2 and Grx3/4 form a [2Fe-2S]2+-bridged heterodimeric complex with iron ligands provided by the active site cysteine of Grx3/4, glutathione, and a histidine residue. To further characterize this unusual Fe-S-binding complex, site-directed mutagenesis was used to identify specific residues in Fra2 that influence Fe-S cluster binding and regulation of Aft1 activity in vivo. Here, we present spectroscopic evidence that His-103 in Fra2 is an Fe-S cluster ligand in the Fra2-Grx3 complex. Replacement of this residue does not abolish Fe-S cluster binding, but it does lead to a change in cluster coordination and destabilization of the [2Fe-2S] cluster. In vivo genetic studies further confirm that Fra2 His-103 is critical for control of Aft1 activity in response to the cellular iron status. Using CD spectroscopy, we find that ∼1 mol eq of apo-Fra2 binds tightly to the [2Fe-2S] Grx3 homodimer to form the [2Fe-2S] Fra2-Grx3 heterodimer, suggesting a mechanism for formation of the [2Fe-2S] Fra2-Grx3 heterodimer in vivo. Taken together, these results demonstrate that the histidine coordination and stability of the [2Fe-2S] cluster in the Fra2-Grx3 complex are essential for iron regulation in yeast. PMID:20978135

  1. A review of immune amplification via ligand clustering by self-assembled liquid-crystalline DNA complexes.

    PubMed

    Lee, Ernest Y; Lee, Calvin K; Schmidt, Nathan W; Jin, Fan; Lande, Roberto; Curk, Tine; Frenkel, Daan; Dobnikar, Jure; Gilliet, Michel; Wong, Gerard C L

    2016-06-01

    We examine how the interferon production of plasmacytoid dendritic cells is amplified by the self-assembly of liquid-crystalline antimicrobial peptide/DNA complexes. These specialized dendritic cells are important for host defense because they quickly release large quantities of type I interferons in response to infection. However, their aberrant activation is also correlated with autoimmune diseases such as psoriasis and lupus. In this review, we will describe how polyelectrolyte self-assembly and the statistical mechanics of multivalent interactions contribute to this process. In a more general compass, we provide an interesting conceptual corrective to the common notion in molecular biology of a dichotomy between specific interactions and non-specific interactions, and show examples where one can construct exquisitely specific interactions using non-specific interactions. PMID:26956527

  2. Electronic Structure of the Mn[subscript 4]Ca Cluster in the Oxygen-Evolving Complex of Photosystem II Studied by Resonant Inelastic X-Ray Scattering

    SciTech Connect

    Yano, Junko; Pushkar, Yulia; Messinger, Johannes; Bergmann, Uwe; Glatzel, Pieter; Yachandra, Vittal K.

    2007-11-12

    Oxygen-evolving complex (Mn{sub 4}Ca cluster) of Photosystem II cycles through five intermediate states (S{sub i}-states, i = 0-4) before a molecule of dioxygen is released. During the S-state transitions, electrons are extracted from the OEC, either from Mn or alternatively from a Mn ligand. The oxidation state of Mn is widely accepted as Mn{sub 4}(III{sub 2},IV{sub 2}) and Mn{sub 4}(III,IV{sub 3}) for S{sub 1} and S{sub 2} states, while it is still controversial for the S{sub 0} and S{sub 3} states. We used resonant inelastic X-ray scattering (RIXS) to study the electronic structure of Mn{sub 4}Ca complex in the OEC. The RIXS data yield two-dimensional plots that provide a significant advantage by obtaining both K-edge pre-edge and L-edge-like spectra simultaneously. The second energy dimension separates the pre-edge (1s to 3d) transitions from the main K-edge (1s to 4p), and thus more precise analysis is possible. The 1s2p RIXS final state electron configuration along the energy transfer axis is identical to conventional L-edge absorption spectroscopy and the RIXS spectra are therefore sensitive to the metal spin state. We have collected data from PS II samples in the each of the S-states and compared them with data from various inorganic Mn complexes. The spectral changes in the Mn 1s2p{sub 3/2} RIXS spectra between the S-states are small compared to those of the oxides of Mn and coordination complexes. The results indicate strong covalency for the electronic configuration in the OEC, and we conclude that the electron is transferred from a strongly delocalized orbital, compared to those in Mn oxides or coordination complexes. The magnitude for the S{sub 0} to S{sub 1}, and S{sub 1} to S{sub 2} transitions is twice as large as that during the S{sub 2} to S{sub 3} transition, indicating that the electron for this transition is extracted from a highly delocalized orbital with little change in charge density at the Mn atoms. The RIXS spectra of S{sub 0} and S{sub 3

  3. Employment of 2,6-diacetylpyridine dioxime as a new route to high nuclearity metal clusters: Mn6 and Mn8 complexes.

    PubMed

    Stamatatos, Theocharis C; Luisi, Brian S; Moulton, Brian; Christou, George

    2008-02-01

    The employment of the anion of 2,6-diacetylpyridine dioxime (dapdoH2) as a pentadentate chelate in transition metal cluster chemistry is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn6O2(OMe)2(dapdo)2(dapdoH)4](ClO4)2 (1), [Mn6O2(OMe)2(dapdo)2(dapdoH)4][Ca(NO3)4] (2), and [Mn8O4(OH)4(OMe)2(N3)2(dapdo)2(dapdoH)2(H2O)2] (3). The reaction of [Mn3O(O2CMe)6(py)3](ClO4) with 3 equiv of dapdoH2 (with or without 2 equiv of NEt3) in MeOH gave 1. The same cation, but with a [Ca(NO3)4]2- anion, was found in complex 2, which was obtained from the reaction in MeOH between Mn(NO3)2, Ca(NO3)2, and dapdoH2 in the presence of NEt3. In contrast, addition of NaN3 to several reactions comprising MnCl2, dapdoH2, and NEt3 in MeOH gave the octanuclear complex 3. Complexes 1-3 all possess rare topologies and are mixed-valence: 2MnII, 4MnIII for 1 and 2, and 2MnII, 6MnIII for 3. The core of the cation of 1 and 2 consists of two edge-sharing Mn4 tetrahedra at the center of each of which is a micro4-O2- ion. Peripheral ligation is provided by two micro-OMe-, four micro-dapdoH-, and two micro3-dapdo2- groups. The core of 3 consists of two [MnIIMnIII3(micro3-O)2]7+ "butterfly" units linked together by one of the micro3-O2- ions, which thus becomes micro4. Peripheral ligation is provided by four micro-OMe-, two micro-OH-, two micro-dapdoH-, and two micro4-dapdo2- groups. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1-3 in the 5.0-300 K range; the data for 1 and 2 are identical. Fitting of the obtained magnetization versus field (H) and temperature (T) data by matrix diagonalization and including only axial anisotropy (zero-field splitting, D) established that 1 possesses an S=5 ground state with D=-0.24 cm(-1). For 3, low-lying excited states precluded obtaining a good fit from the magnetization data, and the ground state was instead determined from the ac data, which indicated an S=1

  4. Effectiveness of a complex intervention in reducing the prevalence of smoking among adolescents: study design of a cluster-randomized controlled trial

    PubMed Central

    2014-01-01

    Background The likelihood of an adolescent taking up smoking may be influenced by his or her society, school and family. Thus, changes in the immediate environment may alter a young person’s perception of smoking. Methods/Design The proposed multi-center, cluster-randomized controlled trial will be stratified by the baseline prevalence of smoking in schools. Municipalities with fewer than 100,000 inhabitants will be randomly assigned to a control or intervention group. One secondary school will be randomly selected from each municipality. These schools will be randomized to two groups: the students of one will receive any existing educational course regarding smoking, while those of the other school will receive a four-year, class-based curriculum intervention (22 classroom lessons) aimed at reinforcing a smoke-free school policy and encouraging smoking cessation in parents, pupils, and teachers. The intervention will also include annual meetings with parents and efforts to empower adolescents to change the smoking-related attitudes and behaviors in their homes, classrooms and communities. We will enroll children aged 12-13 years as they enter secondary school during two consecutive school years (to obtain sufficient enrolled subjects). We will follow them for five years, until two years after they leave secondary school. All external evaluators and analysts will be blinded to school allocation. The aim of this study is to analyze the effectiveness of a complex intervention in reducing the prevalence of smoking in the third year of compulsory secondary education (ESO) and two years after secondary school, when the participants are 14-15 and 17-18 years old, respectively. Discussion Most interventions aimed at preventing smoking among adolescents yield little to no positive long-term effects. This clinical trial will analyze the effectiveness of a complex intervention aimed at reducing the incidence and prevalence of smoking in this vulnerable age group. Trial

  5. Pharmacokinetics of an anti-carcinoembryonic antigen monoclonal antibody conjugated to a bifunctional transition metal carborane complex (venus flytrap cluster) in tumor-bearing mice.

    PubMed

    Beatty, B G; Paxton, R J; Hawthorne, M F; Williams, L E; Rickard-Dickson, K J; Do, T; Shively, J E; Beatty, J D

    1993-08-01

    An anticarcinoembryonic antigen (CEA) monoclonal antibody, T84.66, has been conjugated to a metallocarborane complex (Venus flytrap cluster, VFC) containing 57Co. This radioimmunoconjugate, 57Co-VFC-T84.66, retained > 90% immunoreactivity, was stable in serum (7 days) and demonstrated good localization in LS174T tumor xenografts. Pharmacokinetics of 57Co-VFC-T84.66 in tumor-bearing mice were compared to T84.66 Mab conjugated with either DTPA or its benzylisothiocyanate derivative (BzDTPA) labeled with 111In. Whole-body half-life for VFC-T84.66 was less (t1/2 = 62 hr) than that for either DTPA-T84.66 (t1/2 = 157 hr) or BzDTPA-T84.66 (t1/2 = 167 hr). Blood clearance was similar for all three radioimmunoconjugates (t1/2 = 22 hr). Hepatic uptake of the radiolabel was rapid and remained constant for 7 days for both DTPA radioimmunoconjugates (DTPA radioimmunoconjugate = 13.7 +/- 1.5 %ID/g; BzDTPA radioimmunoconjugate = 10.4 +/- 1.7%ID/g). For VFC, however, liver radioactivity decreased from 19.1 +/- 0.6%ID/g at 1 hr to 0.9 +/- 0.1 %ID/g 7 days postinjection, suggesting a possible role for VFC radioimmunoconjugate in the imaging and therapy of liver metastases. PMID:8326387

  6. Human Lin28 Forms a High-Affinity 1:1 Complex with the 106~363 Cluster miRNA miR-363.

    PubMed

    Peters, Daniel T; Fung, Herman K H; Levdikov, Vladimir M; Irmscher, Tobias; Warrander, Fiona C; Greive, Sandra J; Kovalevskiy, Oleg; Isaacs, Harry V; Coles, Mark; Antson, Alfred A

    2016-09-13

    Lin28A is a post-transcriptional regulator of gene expression that interacts with and negatively regulates the biogenesis of let-7 family miRNAs. Recent data suggested that Lin28A also binds the putative tumor suppressor miR-363, a member of the 106~363 cluster of miRNAs. Affinity for this miRNA and the stoichiometry of the protein-RNA complex are unknown. Characterization of human Lin28's interaction with RNA has been complicated by difficulties in producing stable RNA-free protein. We have engineered a maltose binding protein fusion with Lin28, which binds let-7 miRNA with a Kd of 54.1 ± 4.2 nM, in agreement with previous data on a murine homologue. We show that human Lin28A binds miR-363 with a 1:1 stoichiometry and with a similar, if not higher, affinity (Kd = 16.6 ± 1.9 nM). Further analysis suggests that the interaction of the N-terminal cold shock domain of Lin28A with RNA is salt-dependent, supporting a model in which the cold shock domain allows the protein to sample RNA substrates through transient electrostatic interactions. PMID:27559824

  7. CLUSTER CHEMISTRY

    SciTech Connect

    Muetterties, Earl L.

    1980-05-01

    Metal cluster chemistry is one of the most rapidly developing areas of inorganic and organometallic chemistry. Prior to 1960 only a few metal clusters were well characterized. However, shortly after the early development of boron cluster chemistry, the field of metal cluster chemistry began to grow at a very rapid rate and a structural and a qualitative theoretical understanding of clusters came quickly. Analyzed here is the chemistry and the general significance of clusters with particular emphasis on the cluster research within my group. The importance of coordinately unsaturated, very reactive metal clusters is the major subject of discussion.

  8. High-nuclearity homometallic iron and nickel clusters: Fe22 and Ni24 complexes from the use of N-methyldiethanolamine.

    PubMed

    Foguet-Albiol, Dolos; Abboud, Khalil A; Christou, George

    2005-09-14

    The use of N-methyldiethanolamine (mdaH2) in reactions with Fe(III) and Ni(II) sources has led to Fe22 and Ni24 products; the clusters are the highest and second-highest, respectively, homometallic clusters for these metals to date, and possess S = 0 and S = 6 ground states, respectively. PMID:16113722

  9. Complexes of type C6H7+.L (L = N2 and CO2) studied by explicitly correlated coupled cluster theory

    NASA Astrophysics Data System (ADS)

    Botschwina, Peter; Oswald, Rainer

    2012-05-01

    Complexes of the benzenium ion (C_6 H_7^ +) with N2 or CO2 have been studied by explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level [T. B. Adler et al., J. Chem. Phys. 127, 221106 (2007), 10.1063/1.2817618] and the double-hybrid density functional B2PLYP-D [T. Schwabe and S. Grimme, Phys. Chem. Chem. Phys. 9, 3397 (2007), 10.1039/b704725h]. Improved harmonic vibrational wavenumbers for C_6 H_7^ + have been obtained by CCSD(T*)-F12a calculations with the VTZ-F12 basis set. Combining them with previous B2PLYP-D anharmonic contributions we arrive at anharmonic wavenumbers which are in excellent agreement with recent experimental data from p-H2 matrix isolation IR spectroscopy [M. Bahou et al., J. Chem. Phys. 136, 154304 (2012), 10.1063/1.3703502]. The energetically most favourable conformer of C_6 H_7^ +.N2 shows a π-bonded structure similar to C_6 H_7^ +.Rg (Rg = Ne, Ar) [P. Botschwina and R. Oswald, J. Phys. Chem. A 115, 13664 (2011), 10.1021/jp207905t] with De ≈ 870 cm-1. For C_6 H_7^ +.CO2, a slightly lower energy is calculated for a conformer with the CO2 ligand lying in the ring-plane of the C_6 H_7^ + moiety (De ≈ 1508 cm-1). It may be discriminated from other conformers through a strong band predicted at 1218 cm-1, red-shifted by 21 cm-1 from the corresponding band of free C_6 H_7^ +.

  10. Complexes of type C6H7(+)·L (L = N2 and CO2) studied by explicitly correlated coupled cluster theory.

    PubMed

    Botschwina, Peter; Oswald, Rainer

    2012-05-28

    Complexes of the benzenium ion (C(6)H(7)(+)) with N(2) or CO(2) have been studied by explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level [T. B. Adler et al., J. Chem. Phys. 127, 221106 (2007)] and the double-hybrid density functional B2PLYP-D [T. Schwabe and S. Grimme, Phys. Chem. Chem. Phys. 9, 3397 (2007)]. Improved harmonic vibrational wavenumbers for C(6)H(7)(+) have been obtained by CCSD(T∗)-F12a calculations with the VTZ-F12 basis set. Combining them with previous B2PLYP-D anharmonic contributions we arrive at anharmonic wavenumbers which are in excellent agreement with recent experimental data from p-H(2) matrix isolation IR spectroscopy [M. Bahou et al., J. Chem. Phys. 136, 154304 (2012)]. The energetically most favourable conformer of C(6)H(7)(+)·N(2) shows a π-bonded structure similar to C(6)H(7)(+)·Rg (Rg = Ne, Ar) [P. Botschwina and R. Oswald, J. Phys. Chem. A 115, 13664 (2011)] with D(e) ≈ 870 cm(-1). For C(6)H(7)(+)·CO(2), a slightly lower energy is calculated for a conformer with the CO(2) ligand lying in the ring-plane of the C(6)H(7)(+) moiety (D(e) ≈ 1508 cm(-1)). It may be discriminated from other conformers through a strong band predicted at 1218 cm(-1), red-shifted by 21 cm(-1) from the corresponding band of free C(6)H(7)(+). PMID:22667554

  11. Architecture of the Yeast Mitochondrial Iron-Sulfur Cluster Assembly Machinery: THE SUB-COMPLEX FORMED BY THE IRON DONOR, Yfh1 PROTEIN, AND THE SCAFFOLD, Isu1 PROTEIN.

    PubMed

    Ranatunga, Wasantha; Gakh, Oleksandr; Galeano, Belinda K; Smith, Douglas Y; Söderberg, Christopher A G; Al-Karadaghi, Salam; Thompson, James R; Isaya, Grazia

    2016-05-01

    The biosynthesis of Fe-S clusters is a vital process involving the delivery of elemental iron and sulfur to scaffold proteins via molecular interactions that are still poorly defined. We reconstituted a stable, functional complex consisting of the iron donor, Yfh1 (yeast frataxin homologue 1), and the Fe-S cluster scaffold, Isu1, with 1:1 stoichiometry, [Yfh1]24·[Isu1]24 Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional reconstruction of this complex at a resolution of ∼17 Å. In addition, via chemical cross-linking, limited proteolysis, and mass spectrometry, we identified protein-protein interaction surfaces within the complex. The data together reveal that [Yfh1]24·[Isu1]24 is a roughly cubic macromolecule consisting of one symmetric Isu1 trimer binding on top of one symmetric Yfh1 trimer at each of its eight vertices. Furthermore, molecular modeling suggests that two subunits of the cysteine desulfurase, Nfs1, may bind symmetrically on top of two adjacent Isu1 trimers in a manner that creates two putative [2Fe-2S] cluster assembly centers. In each center, conserved amino acids known to be involved in sulfur and iron donation by Nfs1 and Yfh1, respectively, are in close proximity to the Fe-S cluster-coordinating residues of Isu1. We suggest that this architecture is suitable to ensure concerted and protected transfer of potentially toxic iron and sulfur atoms to Isu1 during Fe-S cluster assembly. PMID:26941001

  12. The food choice at work study: effectiveness of complex workplace dietary interventions on dietary behaviours and diet-related disease risk - study protocol for a clustered controlled trial

    PubMed Central

    2013-01-01

    Background Dietary behaviour interventions have the potential to reduce diet-related disease. Ample opportunity exists to implement these interventions in the workplace. The overall aim is to assess the effectiveness and cost-effectiveness of complex dietary interventions focused on environmental dietary modification alone or in combination with nutrition education in large manufacturing workplace settings. Methods/design A clustered controlled trial involving four large multinational manufacturing workplaces in Cork will be conducted. The complex intervention design has been developed using the Medical Research Council’s framework and the National Institute for Health and Clinical Excellence (NICE) guidelines and will be reported using the TREND statement for the transparent reporting of evaluations with non-randomized designs. It will draw on a soft paternalistic “nudge” theoretical perspective. Nutrition education will include three elements: group presentations, individual nutrition consultations and detailed nutrition information. Environmental dietary modification will consist of five elements: (a) restriction of fat, saturated fat, sugar and salt, (b) increase in fibre, fruit and vegetables, (c) price discounts for whole fresh fruit, (d) strategic positioning of healthier alternatives and (e) portion size control. No intervention will be offered in workplace A (control). Workplace B will receive nutrition education. Workplace C will receive nutrition education and environmental dietary modification. Workplace D will receive environmental dietary modification alone. A total of 448 participants aged 18 to 64 years will be selected randomly. All permanent, full-time employees, purchasing at least one main meal in the workplace daily, will be eligible. Changes in dietary behaviours, nutrition knowledge, health status with measurements obtained at baseline and at intervals of 3 to 4 months, 7 to 9 months and 13 to 16 months will be recorded. A process

  13. Increasing chlamydia screening tests in general practice: a modified Zelen prospective Cluster Randomised Controlled Trial evaluating a complex intervention based on the Theory of Planned Behaviour

    PubMed Central

    McNulty, Cliodna A M; Hogan, Angela H; Ricketts, Ellie J; Wallace, Louise; Oliver, Isabel; Campbell, Rona; Kalwij, Sebastian; O'Connell, Elaine; Charlett, Andre

    2014-01-01

    Objective To determine if a structured complex intervention increases opportunistic chlamydia screening testing of patients aged 15–24 years attending English general practitioner (GP) practices. Methods A prospective, Cluster Randomised Controlled Trial with a modified Zelen design involving 160 practices in South West England in 2010. The intervention was based on the Theory of Planned Behaviour (TPB). It comprised of practice-based education with up to two additional contacts to increase the importance of screening to GP staff and their confidence to offer tests through skill development (including videos). Practical resources (targets, posters, invitation cards, computer reminders, newsletters including feedback) aimed to actively influence social cognitions of staff, increasing their testing intention. Results Data from 76 intervention and 81 control practices were analysed. In intervention practices, chlamydia screening test rates were 2.43/100 15–24-year-olds registered preintervention, 4.34 during intervention and 3.46 postintervention; controls testing rates were 2.61/100 registered patients prior intervention, 3.0 during intervention and 2.82 postintervention. During the intervention period, testing in intervention practices was 1.76 times as great (CI 1.24 to 2.48) as controls; this persisted for 9 months postintervention (1.57 times as great, CI 1.27 to 2.30). Chlamydia infections detected increased in intervention practices from 2.1/1000 registered 15–24-year-olds prior intervention to 2.5 during the intervention compared with 2.0 and 2.3/1000 in controls (Estimated Rate Ratio intervention versus controls 1.4 (CI 1.01 to 1.93). Conclusions This complex intervention doubled chlamydia screening tests in fully engaged practices. The modified Zelen design gave realistic measures of practice full engagement (63%) and efficacy of this educational intervention in general practice; it should be used more often. Trial registration The trial was

  14. Effectiveness of a primary care based complex intervention to promote self-management in patients presenting psychiatric symptoms: study protocol of a cluster-randomized controlled trial

    PubMed Central

    2014-01-01

    Background Anxiety, Depression and Somatoform (ADSom) disorders are highly prevalent in primary care. Managing these disorders is time-consuming and requires strong commitment on behalf of the General Practitioners (GPs). Furthermore, the management of these patients is restricted by the high patient turnover rates in primary care practices, especially in the German health care system. In order to address this problem, we implement a complex, low-threshold intervention by an Advanced Practice Nurse (APN) using a mixture of case management and counseling techniques to promote self-management in these patients. Here we present the protocol of the “Self-Management Support for Anxiety, Depression and Somatoform Disorders in Primary Care” (SMADS)-Study. Methods/Design The study is designed as a cluster-randomized controlled trial, comparing an intervention and a control group of 10 primary care practices in each case. We will compare the effectiveness of the intervention applied by an APN with usual GP-care. A total of 340 participants will be enrolled in the study, 170 in either arm. We use the Patient Health Questionnaire-German version (PHQ-D) as a screening tool for psychiatric symptoms, including patients with a score above 5 on any of the three symptom scales. The primary outcome is self-efficacy, measured by the General Self-Efficacy Scale (GSE), here used as a proxy for self-management. As secondary outcomes we include the PHQ-D symptom load and questionnaires regarding coping with illness and health related quality of life. Outcome assessments will be applied 8 weeks and 12 months after the baseline assessment. Discussion The SMADS-study evaluates a complex, low threshold intervention for ambulatory patients presenting ADSom-symptoms, empowering them to better manage their condition, as well as improving their motivation to engage in self-help and health-seeking behaviour. The benefit of the intervention will be substantiated, when patients can enhance

  15. A Cluster of Four Homologous Small RNAs Modulates C1 Metabolism and the Pyruvate Dehydrogenase Complex in Rhodobacter sphaeroides under Various Stress Conditions

    PubMed Central

    Billenkamp, Fabian; Peng, Tao; Berghoff, Bork A.

    2015-01-01

    ABSTRACT In bacteria, regulatory RNAs play an important role in the regulation and balancing of many cellular processes and stress responses. Among these regulatory RNAs, trans-encoded small RNAs (sRNAs) are of particular interest since one sRNA can lead to the regulation of multiple target mRNAs. In the purple bacterium Rhodobacter sphaeroides, several sRNAs are induced by oxidative stress. In this study, we focused on the functional characterization of four homologous sRNAs that are cotranscribed with the gene for the conserved hypothetical protein RSP_6037, a genetic arrangement described for only a few sRNAs until now. Each of the four sRNAs is characterized by two stem-loops that carry CCUCCUCCC motifs in their loops. They are induced under oxidative stress, as well as by various other stress conditions, and were therefore renamed here sRNAs CcsR1 to CcsR4 (CcsR1–4) for conserved CCUCCUCCC motif stress-induced RNAs 1 to 4. Increased CcsR1–4 expression decreases the expression of genes involved in C1 metabolism or encoding components of the pyruvate dehydrogenase complex either directly by binding to their target mRNAs or indirectly. One of the CcsR1–4 target mRNAs encodes the transcriptional regulator FlhR, an activator of glutathione-dependent methanol/formaldehyde metabolism. Downregulation of this glutathione-dependent pathway increases the pool of glutathione, which helps to counteract oxidative stress. The FlhR-dependent downregulation of the pyruvate dehydrogenase complex reduces a primary target of reactive oxygen species and reduces aerobic electron transport, a main source of reactive oxygen species. Our findings reveal a previously unknown strategy used by bacteria to counteract oxidative stress. IMPORTANCE Phototrophic organisms have to cope with photo-oxidative stress due to the function of chlorophylls as photosensitizers for the formation of singlet oxygen. Our study assigns an important role in photo-oxidative stress resistance to a

  16. Rhenium Complexes and Clusters Supported on c-Al2O3: Effects of Rhenium Oxidation State and Rhenium Cluster Size on Catalytic Activity for n-butane Hydrogenolysis

    SciTech Connect

    Lobo Lapidus, R.; Gates, B

    2009-01-01

    Supported metals prepared from H{sub 3}Re{sub 3}(CO){sub 12} on {gamma}-Al{sub 2}O{sub 3} were treated under conditions that led to various rhenium structures on the support and were tested as catalysts for n-butane conversion in the presence of H{sub 2} in a flow reactor at 533 K and 1 atm. After use, two samples were characterized by X-ray absorption edge positions of approximately 5.6 eV (relative to rhenium metal), indicating that the rhenium was cationic and essentially in the same average oxidation state in each. But the Re-Re coordination numbers found by extended X-ray absorption fine structure spectroscopy (2.2 and 5.1) show that the clusters in the two samples were significantly different in average nuclearity despite their indistinguishable rhenium oxidation states. Spectra of a third sample after catalysis indicate approximately Re{sub 3} clusters, on average, and an edge position of 4.5 eV. Thus, two samples contained clusters approximated as Re{sub 3} (on the basis of the Re-Re coordination number), on average, with different average rhenium oxidation states. The data allow resolution of the effects of rhenium oxidation state and cluster size, both of which affect the catalytic activity; larger clusters and a greater degree of reduction lead to increased activity.

  17. HUBBLE SPACE TELESCOPE DISCOVERY OF A z = 3.9 MULTIPLY IMAGED GALAXY BEHIND THE COMPLEX CLUSTER LENS WARPS J1415.1+36 AT z = 1.026

    SciTech Connect

    Huang, X.; Fakhouri, H. K.; Barbary, K.; Goldhaber, G.; Hennawi, J. F.; Morokuma, T.; Aldering, G.; Faccioli, L.; Amanullah, R.; Brodwin, M.; Connolly, N. V.; Dawson, K. S.; Doi, M.; Ihara, Y.; Fadeyev, V.; Fruchter, A. S.; Gladders, M. D.; Jee, M. J.; Kowalski, M.; Konishi, K.

    2009-12-10

    We report the discovery of a multiply lensed Lyalpha emitter at z = 3.90 behind the massive cluster WARPS J1415.1+3612 at z = 1.026. Images taken by the Hubble Space Telescope using the Advanced Camera for Surveys reveal a complex lensing system that produces a prominent, highly magnified arc and a triplet of smaller arcs grouped tightly around a spectroscopically confirmed cluster member. Spectroscopic observations using the Faint Object Camera and Spectrograph on Subaru confirm strong Lyalpha emission in the source galaxy and provide the redshifts for more than 21 cluster members with a velocity dispersion of 807 +- 185 km s{sup -1}. Assuming a singular isothermal sphere profile, the mass within the Einstein ring (7.13 +- 0.''38) corresponds to a central velocity dispersion of 686{sup +15} {sub -19} km s{sup -1} for the cluster, consistent with the value estimated from cluster member redshifts. Our mass profile estimate from combining strong lensing and dynamical analyses is in good agreement with both X-ray and weak lensing results.

  18. Cyclostomes Lack Clustered Protocadherins.

    PubMed

    Ravi, Vydianathan; Yu, Wei-Ping; Pillai, Nisha E; Lian, Michelle M; Tay, Boon-Hui; Tohari, Sumanty; Brenner, Sydney; Venkatesh, Byrappa

    2016-02-01

    The brain, comprising billions of neurons and intricate neural networks, is arguably the most complex organ in vertebrates. The diversity of individual neurons is fundamental to the neuronal network complexity and the overall function of the vertebrate brain. In jawed vertebrates, clustered protocadherins provide the molecular basis for this neuronal diversity, through stochastic and combinatorial expression of their various isoforms in individual neurons. Based on analyses of transcriptomes from the Japanese lamprey brain and sea lamprey embryos, genome assemblies of the two lampreys, and brain expressed sequence tags of the inshore hagfish, we show that extant jawless vertebrates (cyclostomes) lack the clustered protocadherins. Our findings indicate that the clustered protocadherins originated from a nonclustered protocadherin in the jawed vertebrate ancestor, after the two rounds of whole-genome duplication. In the absence of clustered protocadherins, cyclostomes might have evolved novel molecules or mechanisms for generating neuronal diversity which remains to be discovered. PMID:26545918

  19. The mitochondrial Hsp70 chaperone Ssq1 facilitates Fe/S cluster transfer from Isu1 to Grx5 by complex formation

    PubMed Central

    Uzarska, Marta A.; Dutkiewicz, Rafal; Freibert, Sven-Andreas; Lill, Roland; Mühlenhoff, Ulrich

    2013-01-01

    The mitochondrial Hsp70 chaperone Ssq1 plays a dedicated role in the maturation of iron–sulfur (Fe/S) proteins, an essential process of mitochondria. Similar to its bacterial orthologue HscA, Ssq1 binds to the scaffold protein Isu1, thereby facilitating dissociation of the newly synthesized Fe/S cluster on Isu1 and its transfer to target apoproteins. Here we use in vivo and in vitro approaches to show that Ssq1 also interacts with the monothiol glutaredoxin 5 (Grx5) at a binding site different from that of Isu1. Grx5 binding does not stimulate the ATPase activity of Ssq1 and is most pronounced for the ADP-bound form of Ssq1, which interacts with Isu1 most tightly. The vicinity of Isu1 and Grx5 on the Hsp70 chaperone facilitates rapid Fe/S cluster transfer from Isu1 to Grx5. Grx5 and its bound Fe/S cluster are required for maturation of all cellular Fe/S proteins, regardless of the type of bound Fe/S cofactor and subcellular localization. Hence Grx5 functions as a late-acting component of the core Fe/S cluster (ISC) assembly machinery linking the Fe/S cluster synthesis reaction on Isu1 with late assembly steps involving Fe/S cluster targeting to dedicated apoproteins. PMID:23615440

  20. Stormy weather in galaxy clusters

    PubMed

    Burns

    1998-04-17

    Recent x-ray, optical, and radio observations coupled with particle and gas dynamics numerical simulations reveal an unexpectedly complex environment within clusters of galaxies, driven by ongoing accretion of matter from large-scale supercluster filaments. Mergers between clusters and continuous infall of dark matter and baryons from the cluster periphery produce long-lived "stormy weather" within the gaseous cluster atmosphere-shocks, turbulence, and winds of more than 1000 kilometers per second. This weather may be responsible for shaping a rich variety of extended radio sources, which in turn act as "barometers" and "anemometers" of cluster weather. PMID:9545210

  1. Application of Balanced Scorecard in the Evaluation of a Complex Health System Intervention: 12 Months Post Intervention Findings from the BHOMA Intervention: A Cluster Randomised Trial in Zambia

    PubMed Central

    Mutale, Wilbroad; Stringer, Jeffrey; Chintu, Namwinga; Chilengi, Roma; Mwanamwenge, Margaret Tembo; Kasese, Nkatya; Balabanova, Dina; Spicer, Neil; Lewis, James; Ayles, Helen

    2014-01-01

    Introduction In many low income countries, the delivery of quality health services is hampered by health system-wide barriers which are often interlinked, however empirical evidence on how to assess the level and scope of these barriers is scarce. A balanced scorecard is a tool that allows for wider analysis of domains that are deemed important in achieving the overall vision of the health system. We present the quantitative results of the 12 months follow-up study applying the balanced scorecard approach in the BHOMA intervention with the aim of demonstrating the utility of the balanced scorecard in evaluating multiple building blocks in a trial setting. Methods The BHOMA is a cluster randomised trial that aims to strengthen the health system in three rural districts in Zambia. The intervention aims to improve clinical care quality by implementing practical tools that establish clear clinical care standards through intensive clinic implementations. This paper reports the findings of the follow-up health facility survey that was conducted after 12 months of intervention implementation. Comparisons were made between those facilities in the intervention and control sites. STATA version 12 was used for analysis. Results The study found significant mean differences between intervention(I) and control (C) sites in the following domains: Training domain (Mean I:C; 87.5.vs 61.1, mean difference 23.3, p = 0.031), adult clinical observation domain (mean I:C; 73.3 vs.58.0, mean difference 10.9, p = 0.02 ) and health information domain (mean I:C; 63.6 vs.56.1, mean difference 6.8, p = 0.01. There was no gender differences in adult service satisfaction. Governance and motivation scores did not differ between control and intervention sites. Conclusion This study demonstrates the utility of the balanced scorecard in assessing multiple elements of the health system. Using system wide approaches and triangulating data collection methods seems to be key to successful

  2. Meaningful Clusters

    SciTech Connect

    Sanfilippo, Antonio P.; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2004-05-26

    We present an approach to the disambiguation of cluster labels that capitalizes on the notion of semantic similarity to assign WordNet senses to cluster labels. The approach provides interesting insights on how document clustering can provide the basis for developing a novel approach to word sense disambiguation.

  3. Genesis of a Cerium Oxide-Supported Gold Catalyst for CO Oxidation: Transformation of Mononuclear Gold Complexes into Clusters as Characterized by X-Ray Absorption Spectroscopy

    SciTech Connect

    Aguilar-Guerrero, V.; Lobo-Lapidus, R; Gates, B

    2009-01-01

    CeO{sub 2}-supported mononuclear gold species synthesized from Au(CH{sub 3}){sub 2}(acac) catalyzed CO oxidation at 353 K, with a turnover frequency of 6.5 x 10{sup -3} molecules of CO (Au atom s){sup -1} at CO and O{sub 2} partial pressures of 1.0 and 0.5 kPa, respectively. As the catalyst functioned in a flow reactor, the activity increased markedly so that within about 10 h the conversion of CO had increased from about 1% to almost 100%. Activated catalyst samples were characterized by X-ray absorption spectroscopy and found to incorporate clusters of gold, which increased in size, undergoing reduction, with increasing time of operation. The X-ray absorption near-edge structure spectrum of the catalyst used for the longest period was indistinguishable from that characterizing gold foil. Extended X-ray absorption fine structure data characterizing the catalyst after the longest period of operation indicated the presence of clusters of approximately 30 Au atoms each, on average. The evidence that the catalytic activity increased as the clusters grew is contrasted with earlier reports pointing to increasing activity of supported gold clusters as they were made smallerin a cluster size range largely exceeding ours.

  4. Methane activation by cobalt cluster cations, Co{sub n}{sup +} (n=2-16): Reaction mechanisms and thermochemistry of cluster-CH{sub x} (x=0-3) complexes

    SciTech Connect

    Citir, Murat; Liu Fuyi; Armentrout, P. B.

    2009-02-07

    The kinetic energy dependences of the reactions of Co{sub n}{sup +} (n=2-16) with CD{sub 4} are studied in a guided ion beam tandem mass spectrometer over the energy range of 0-10 eV. The main products are hydride formation, Co{sub n}D{sup +}, dehydrogenation to form Co{sub n}CD{sub 2}{sup +}, and double dehydrogenation yielding Co{sub n}C{sup +}. These primary products decompose to form secondary and higher order products, Co{sub n}CD{sup +}, Co{sub n-1}D{sup +}, Co{sub n-1}C{sup +}, Co{sub n-1}CD{sup +}, and Co{sub n-1}CD{sub 2}{sup +} at higher energies. Adduct formation of Co{sub n}CD{sub 4}{sup +} is also observed for the largest cluster cations, n{>=}10. In general, the efficiencies of the single and double dehydrogenation processes increase with cluster size, although the hexamer cation shows a reduced reactivity compared to its neighbors. All reactions exhibit thresholds, and cross sections for the various primary and secondary reactions are analyzed to yield reaction thresholds from which bond energies for cobalt cluster cations to D, C, CD, CD{sub 2}, and CD{sub 3} are determined. The relative magnitudes of these bond energies are consistent with simple bond order considerations. Bond energies for larger clusters rapidly reach relatively constant values, which are used to estimate the chemisorption energies of the C, CD, CD{sub 2}, and CD{sub 3} molecular fragments to cobalt surfaces.

  5. Two EPR-detectable [4Fe-4S] clusters, N2a and N2b, are bound to the NuoI (TYKY) subunit of NADH:ubiquinone oxidoreductase (Complex I) from Rhodobacter capsulatus.

    PubMed

    Chevallet, Mireille; Dupuis, Alain; Issartel, Jean-Paul; Lunardi, Joël; van Belzen, Ronald; Albracht, Simon P J

    2003-03-01

    NADH:ubiquinone oxidoreductases (Complex I) contain a subunit, TYKY in the bovine enzyme and NuoI in the enzyme from Rhodobacter capsulatus, which is assumed to bind two [4Fe-4S] clusters because it contains two sets of conserved cysteine motifs similar to those found in the 2[4Fe-4S] ferredoxins. It was recently shown that the TYKY subunit is not an ordinary 2[4Fe-4S] ferredoxin, but has a unique amino acid sequence, which is only found in NAD(P)H:quinone oxidoreductases and certain membrane-bound [NiFe]-hydrogenases expected to be involved in redox-linked proton translocation [FEBS Lett. 485 (2000) 1]. We have generated a set of R. capsulatus mutants in which five out of the eight conserved cysteine residues in NuoI were replaced by other amino acids. The resulting mutants fell into three categories with virtually no, intermediate or quite normal Complex I activities. EPR-spectroscopic analysis of the membranes of the C67S and C106S mutants, two mutants belonging to the second and third group, respectively, showed a specific 50% decrease of the EPR signal attributed to cluster N2. It is concluded that the NuoI (TYKY) subunit binds two clusters N2, called N2a and N2b, which exhibit very similar spectral features when analyzed by X-band EPR spectroscopy. PMID:12615348

  6. A family of octahedral rhenium cluster complexes [Re6Q8(H2O)n(OH)6-n]n-4 (Q=S, Se; n=0-6): structural and pH-dependent spectroscopic studies.

    PubMed

    Brylev, Konstantin A; Mironov, Yuri V; Yarovoi, Spartak S; Naumov, Nikolai G; Fedorov, Vladimir E; Kim, Sung-Jin; Kitamura, Noboru; Kuwahara, Yusuke; Yamada, Konatsu; Ishizaka, Shoji; Sasaki, Yoichi

    2007-09-01

    The conversions of hexahydroxo rhenium cluster complexes [Re6Q8(OH)6]4- (Q=S, Se) in aqueous solutions in a wide pH range were investigated by chemical methods and spectroscopic measurements. Dependences of the spectroscopic and excited-state properties of the solutions on pH have been studied in detail. It has been found that a pH decrease of aqueous solutions of the potassium salts K4[Re6Q8(OH)6].8H2O (Q=S, Se) results in the formation of aquahydroxo and hexaaqua cluster complexes with the general formula [Re6Q8(H2O)n(OH)6-n]n-4 that could be considered as a result of the protonation of the terminal OH- ligands in the hexahydroxo complexes. The compounds K2[Re6S8(H2O)2(OH)4].2H2O (1), [Re6S8(H2O)4(OH)2].12H2O (2), [Re6S8(H2O)6][Re6S6Br8].10H2O (3), and [Re6Se8(H2O)4(OH)2] (4) have been isolated and characterized by X-ray single-crystal diffraction and elemental analyses and infrared (IR) spectroscopy. In crystal structures of the aquahydroxo complexes, the cluster units are connected to each other by an extensive system of very strong hydrogen bonds between terminal ligands. PMID:17676730

  7. Initial use of dioximate ligands in 3d/4f cluster chemistry: synthesis, structure, and magnetic studies of an unusual [Gd(III)2Mn(IV)O]8+ complex.

    PubMed

    Lampropoulos, Christos; Stamatatos, Theocharis C; Abboud, Khalil A; Christou, George

    2009-01-19

    An unusual [Mn(IV)Gd(III)(2)(mu(3)-O(2-))](8+) triangular complex has been prepared from the initial use of 2,6-diacetylpyridine dioxime (dapdoH(2)) in 3d/4f cluster chemistry. The complex has an S = (13)/(2) ground state, with exchange parameters J = +0.49 cm(-1) and J' = -0.12 cm(-1) [H = -2J(S(i) x S(j)) convention] for the Gd(III)...Mn(IV) and Gd(III)...Gd(III) interactions, respectively. The origin of this ground state has been rationalized by consideration of the spin frustration occurring within the complex as a function of the relative magnitude of the competing interactions. PMID:19072591

  8. Dynamic Bayesian clustering.

    PubMed

    Fowler, Anna; Menon, Vilas; Heard, Nicholas A

    2013-10-01

    Clusters of time series data may change location and memberships over time; in gene expression data, this occurs as groups of genes or samples respond differently to stimuli or experimental conditions at different times. In order to uncover this underlying temporal structure, we consider dynamic clusters with time-dependent parameters which split and merge over time, enabling cluster memberships to change. These interesting time-dependent structures are useful in understanding the development of organisms or complex organs, and could not be identified using traditional clustering methods. In cell cycle data, these time-dependent structure may provide links between genes and stages of the cell cycle, whilst in developmental data sets they may highlight key developmental transitions. PMID:24131050

  9. Ferredoxin, in conjunction with NADPH and ferredoxin-NADP reductase, transfers electrons to the IscS/IscU complex to promote iron-sulfur cluster assembly.

    PubMed

    Yan, Robert; Adinolfi, Salvatore; Pastore, Annalisa

    2015-09-01

    Fe-S cluster biogenesis is an essential pathway coordinated by a network of protein-protein interactions whose functions include desulfurase activity, substrate delivery, electron transfer and product transfer. In an effort to understand the intricacies of the pathway, we have developed an in vitro assay to follow the ferredoxin role in electron transfer during Fe-S cluster assembly. Previously, assays have relied upon the non-physiological reducing agents dithionite and dithiothreitol to assess function. We have addressed this shortcoming by using electron transfer between NADPH and ferredoxin-NADP-reductase to reduce ferredoxin. Our results show that this trio of electron transfer partners are sufficient to sustain the reaction in in vitro studies, albeit with a rate slower compared with DTT-mediated cluster assembly. We also show that, despite overlapping with the CyaY protein in binding to IscS, Fdx does not interfere with the inhibitory activity of this protein. We suggest explanations for these observations which have important consequences for understanding the mechanism of cluster formation. Cofactor-dependent proteins: evolution, chemical diversity and bio-applications. PMID:25688831

  10. Cool Cluster Correctly Correlated

    SciTech Connect

    Sergey Aleksandrovich Varganov

    2005-12-17

    Atomic clusters are unique objects, which occupy an intermediate position between atoms and condensed matter systems. For a long time it was thought that physical and chemical properties of atomic dusters monotonically change with increasing size of the cluster from a single atom to a condensed matter system. However, recently it has become clear that many properties of atomic clusters can change drastically with the size of the clusters. Because physical and chemical properties of clusters can be adjusted simply by changing the cluster's size, different applications of atomic clusters were proposed. One example is the catalytic activity of clusters of specific sizes in different chemical reactions. Another example is a potential application of atomic clusters in microelectronics, where their band gaps can be adjusted by simply changing cluster sizes. In recent years significant advances in experimental techniques allow one to synthesize and study atomic clusters of specified sizes. However, the interpretation of the results is often difficult. The theoretical methods are frequently used to help in interpretation of complex experimental data. Most of the theoretical approaches have been based on empirical or semiempirical methods. These methods allow one to study large and small dusters using the same approximations. However, since empirical and semiempirical methods rely on simple models with many parameters, it is often difficult to estimate the quantitative and even qualitative accuracy of the results. On the other hand, because of significant advances in quantum chemical methods and computer capabilities, it is now possible to do high quality ab-initio calculations not only on systems of few atoms but on clusters of practical interest as well. In addition to accurate results for specific clusters, such methods can be used for benchmarking of different empirical and semiempirical approaches. The atomic clusters studied in this work contain from a few atoms to

  11. Embedded Clusters in Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Lada, Charles J.; Lada, Elizabeth A.

    Stellar clusters are born embedded within giant molecular clouds (GMCs) and during their formation and early evolution are often only visible at infrared wavelengths, being heavily obscured by dust. Over the past 15 years advances in infrared detection capabilities have enabled the first systematic studies of embedded clusters in galactic molecular clouds. In this article we review the current state of empirical knowledge concerning these extremely young protocluster systems. From a survey of the literature we compile the first extensive catalog of galactic embedded clusters. We use the catalog to construct the mass function and estimate the birthrate for embedded clusters within 2 kpc of the sun. We find that the embedded cluster birthrate exceeds that of visible open clusters by an order of magnitude or more indicating a high infant mortality rate for protocluster systems. Less than 4-7% of embedded clusters survive emergence from molecular clouds to become bound clusters of Pleiades age. The vast majority (90%) of stars that form in embedded clusters form in rich clusters of 100 or more members with masses in excess of 50 M⊙. Moreover, observations of nearby cloud complexes indicate that embedded clusters account for a significant (70-90%) fraction of all stars formed in GMCs. We review the role of embedded clusters in investigating the nature of the initial mass function (IMF) that, in one nearby example, has been measured over the entire range of stellar and substellar mass, from OB stars to substellar objects near the deuterium burning limit. We also review the role embedded clusters play in the investigation of circumstellar disk evolution and the important constraints they provide for understanding the origin of planetary systems. Finally, we discuss current ideas concerning the origin and dynamical evolution of embedded clusters and the implications for the formation of bound open clusters.

  12. Temperature-controlled formation of olygomeric and polymeric compounds based on [Re4Te4(CN)12]4- cluster anions and Tm3+/1,10-phen complex cations

    NASA Astrophysics Data System (ADS)

    Litvinova, Yulia M.; Gayfulin, Yakov M.; Samsonenko, Denis G.; Piryazev, Dmitry A.; Mironov, Yuri V.

    2016-03-01

    Self-assembly reaction of [Re4Te4(CN)12]4- tetrahedral rhenium chalcocyanide cluster anions, Tm3+ cations and 1,10-phenanthroline in an H2O/EtOH medium was investigated at different temperatures. Slow mixing of reagent solutions at the room temperature lead to formation of cluster compound (1) containing unique trimeric anionic fragment [{Tm(phen) (H2O)4}{Tm(phen)2(H2O)3}{Tm(phen)2(H2O)2}{Re4Te4(CN)12}3]3- (A1, phen = 1,10-phenanthroline). Oligomeric anion A1 shows an unusual U-shaped structure build from three cluster anions and three {Tm(phen)n(H2O)m}3+ (n = 1, 2; m = 2-4) complex cations linked to each other by sbnd Ctbnd Nsbnd Tmsbnd Ntbnd Csbnd covalent bonds and two couples of short OH…N hydrogen bonds. At the elevated (80-100 °C) temperatures the initial reaction products were dissolved, however, further increase of temperature up to 150 °C resulted in formation of layered (2D) coordination polymer K[{Tm(phen) (H2O)3}{Re4Te4(CN)12}]·0.5H2O (2). In addition to the experimental and X-Ray structural analysis data, thermal decomposition of compounds is also discussed.

  13. Oxidative group transfer to a trimanganese complex to form Mn6(μ6-E) (E = O, N) clusters featuring interstitial oxide and nitride functionalities

    PubMed Central

    Fout, Alison R.; Zhao, Qinliang; Xiao, Dianne J.

    2011-01-01

    Utilizing a hexadentate ligand platform, a trinuclear manganese complex of the type (HL)Mn3(thf)3 was synthesized and characterized ([HL]6− = [MeC(CH2N(C6H4-o-NH))3]6−). The pale orange, formally divalent trimanganese complex rapidly reacts with O-atom transfer reagents to afford the μ6-oxo complex (HL)2Mn6(μ6-O)(NCMe)4, where two trinuclear subunits bind the central O-atom and the (HL) ligands cooperatively bind both trinuclear subunits. The trimanganese complex (HL)Mn3(thf)3 rapidly consumes inorganic azide ([N3]NBu4) to afford a dianionic hexanuclear nitride complex [(HL)2Mn6(μ6-N)](NBu4)2, which subsequently can be oxidized with elemental iodine to (HL)2Mn6(μ6-N)(NCMe)4. EPR and alkylation of the interstitial light atom substituent were used to distinguish the nitride from the oxo complex. The oxo and oxidized nitride complexes gives rise to well-defined Mn(II) and Mn(III) sites, determined by bond-valence summation, while the dianionic nitride shows a more symmetric complex, giving rise to indistinguishable ion oxidation states based on crystal structure bond metrics. PMID:21942370

  14. X-ray Absorption and Emission Spectroscopic Studies of [L2Fe2S2](n) Model Complexes: Implications for the Experimental Evaluation of Redox States in Iron-Sulfur Clusters.

    PubMed

    Kowalska, Joanna K; Hahn, Anselm W; Albers, Antonia; Schiewer, Christine E; Bjornsson, Ragnar; Lima, Frederico A; Meyer, Franc; DeBeer, Serena

    2016-05-01

    Herein, a systematic study of [L2Fe2S2](n) model complexes (where L = bis(benzimidazolato) and n = 2-, 3-, 4-) has been carried out using iron and sulfur K-edge X-ray absorption (XAS) and iron Kβ and valence-to-core X-ray emission spectroscopies (XES). These data are used as a test set to evaluate the relative strengths and weaknesses of X-ray core level spectroscopies in assessing redox changes in iron-sulfur clusters. The results are correlated to density functional theory (DFT) calculations of the spectra in order to further support the quantitative information that can be extracted from the experimental data. It is demonstrated that due to canceling effects of covalency and spin state, the information that can be extracted from Fe Kβ XES mainlines is limited. However, a careful analysis of the Fe K-edge XAS data shows that localized valence vs delocalized valence species may be differentiated on the basis of the pre-edge and K-edge energies. These findings are then applied to existing literature Fe K-edge XAS data on the iron protein, P-cluster, and FeMoco sites of nitrogenase. The ability to assess the extent of delocalization in the iron protein vs the P-cluster is highlighted. In addition, possible charge states for FeMoco on the basis of Fe K-edge XAS data are discussed. This study provides an important reference for future X-ray spectroscopic studies of iron-sulfur clusters. PMID:27097289

  15. Systolic architecture for heirarchical clustering

    SciTech Connect

    Ku, L.C.

    1984-01-01

    Several hierarchical clustering methods (including single-linkage complete-linkage, centroid, and absolute overlap methods) are reviewed. The absolute overlap clustering method is selected for the design of systolic architecture mainly due to its simplicity. Two versions of systolic architectures for the absolute overlap hierarchical clustering algorithm are proposed: one-dimensional version that leads to the development of a two dimensional version which fully takes advantage of the underlying data structure of the problems. The two dimensional systolic architecture can achieve a time complexity of O(m + n) in comparison with the conventional computer implementation of a time complexity of O(m/sup 2*/n).

  16. A Complex of Cas Proteins 5, 6, and 7 Is Required for the Biogenesis and Stability of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-derived RNAs (crRNAs) in Haloferax volcanii*

    PubMed Central

    Brendel, Jutta; Stoll, Britta; Lange, Sita J.; Sharma, Kundan; Lenz, Christof; Stachler, Aris-Edda; Maier, Lisa-Katharina; Richter, Hagen; Nickel, Lisa; Schmitz, Ruth A.; Randau, Lennart; Allers, Thorsten; Urlaub, Henning; Backofen, Rolf; Marchfelder, Anita

    2014-01-01

    The clustered regularly interspaced short palindromic repeats/CRISPR-associated (CRISPR-Cas) system is a prokaryotic defense mechanism against foreign genetic elements. A plethora of CRISPR-Cas versions exist, with more than 40 different Cas protein families and several different molecular approaches to fight the invading DNA. One of the key players in the system is the CRISPR-derived RNA (crRNA), which directs the invader-degrading Cas protein complex to the invader. The CRISPR-Cas types I and III use the Cas6 protein to generate mature crRNAs. Here, we show that the Cas6 protein is necessary for crRNA production but that additional Cas proteins that form a CRISPR-associated complex for antiviral defense (Cascade)-like complex are needed for crRNA stability in the CRISPR-Cas type I-B system in Haloferax volcanii in vivo. Deletion of the cas6 gene results in the loss of mature crRNAs and interference. However, cells that have the complete cas gene cluster (cas1–8b) removed and are transformed with the cas6 gene are not able to produce and stably maintain mature crRNAs. crRNA production and stability is rescued only if cas5, -6, and -7 are present. Mutational analysis of the cas6 gene reveals three amino acids (His-41, Gly-256, and Gly-258) that are essential for pre-crRNA cleavage, whereas the mutation of two amino acids (Ser-115 and Ser-224) leads to an increase of crRNA amounts. This is the first systematic in vivo analysis of Cas6 protein variants. In addition, we show that the H. volcanii I-B system contains a Cascade-like complex with a Cas7, Cas5, and Cas6 core that protects the crRNA. PMID:24459147

  17. On the accuracy of explicitly correlated methods to generate potential energy surfaces for scattering calculations and clustering: application to the HCl-He complex.

    PubMed

    Ajili, Yosra; Hammami, Kamel; Jaidane, Nejm Eddine; Lanza, Mathieu; Kalugina, Yulia N; Lique, François; Hochlaf, Majdi

    2013-07-01

    We closely compare the accuracy of multidimensional potential energy surfaces (PESs) generated by the recently developed explicitly correlated coupled cluster (CCSD(T)-F12) methods in connection with the cc-pVXZ-F12 (X = D, T) and aug-cc-pVTZ basis sets and those deduced using the well-established orbital-based coupled cluster techniques employing correlation consistent atomic basis sets (aug-cc-pVXZ, X = T, Q, 5) and extrapolated to the complete basis set (CBS) limit. This work is performed on the benchmark rare gas-hydrogen halide interaction (HCl-He) system. These PESs are then incorporated into quantum close-coupling scattering dynamical calculations in order to check the impact of the accuracy of the PES on the scattering calculations. For this system, we deduced inelastic collisional data including (de-)excitation collisional and pressure broadening cross sections. Our work shows that the CCSD(T)-F12/aug-cc-pVTZ PES describes correctly the repulsive wall, the van der Waals minimum and long range internuclear distances whereas cc-pVXZ-F12 (X = D,T) basis sets are not diffuse enough for that purposes. Interestingly, the collision cross sections deduced from the CCSD(T)-F12/aug-cc-pVTZ PES are in excellent agreement with those obtained with CCSD(T)/CBS methodology. The position of the resonances and the general shape of these cross sections almost coincide. Since the cost of the electronic structure computations is reduced by several orders of magnitude when using CCSD(T)-F12/aug-cc-pVTZ compared to CCSD(T)/CBS methodology, this approach can be recommended as an alternative for generation of PESs of molecular clusters and for the interpretation of accurate scattering experiments as well as for a wide production of collisional data to be included in astrophysical and atmospherical models. PMID:23443908

  18. Quintuplet Cluster

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Penetrating 25,000 light-years of obscuring dust and myriad stars, NASA's Hubble Space Telescope has provided the clearest view yet of one of the largest young clusters of stars inside our Milky Way galaxy, located less than 100 light-years from the very center of the Galaxy. Having the equivalent mass greater than 10,000 stars like our sun, the monster cluster is ten times larger than typical young star clusters scattered throughout our Milky Way. It is destined to be ripped apart in just a few million years by gravitational tidal forces in the galaxy's core. But in its brief lifetime it shines more brightly than any other star cluster in the Galaxy. Quintuplet Cluster is 4 million years old. It has stars on the verge of blowing up as supernovae. It is the home of the brightest star seen in the galaxy, called the Pistol star. This image was taken in infrared light by Hubble's NICMOS camera in September 1997. The false colors correspond to infrared wavelengths. The galactic center stars are white, the red stars are enshrouded in dust or behind dust, and the blue stars are foreground stars between us and the Milky Way's center. The cluster is hidden from direct view behind black dust clouds in the constellation Sagittarius. If the cluster could be seen from earth it would appear to the naked eye as a 3rd magnitude star, 1/6th of a full moon's diameter apart.

  19. First principle-based AKMC modelling of the formation and medium-term evolution of point defect and solute-rich clusters in a neutron irradiated complex Fe-CuMnNiSiP alloy representative of reactor pressure vessel steels

    NASA Astrophysics Data System (ADS)

    Ngayam-Happy, R.; Becquart, C. S.; Domain, C.

    2013-09-01

    The formation and medium-term evolution of point defect and solute-rich clusters under neutron irradiation have been modelled in a complex Fe-CuMnNiSiP alloy representative of RPV steels, by means of first principle-based atomistic kinetic Monte Carlo simulations. The results obtained reproduce most features observed in available experimental studies, highlighting the very good agreement between both series. According to simulation, solute-rich clusters form and develop via an induced segregation mechanism on either the vacancy or interstitial clusters, and these point defect clusters are efficiently generated only in cascade debris and not Frenkel pair flux. The results have revealed the existence of two distinct populations of clusters with different characteristic features. Solute-rich clusters in the first group are bound essentially to interstitial clusters and they are enriched in Mn mostly, but also Ni to a lesser extent. Over the low dose regime, their density increases in the alloy as a result of the accumulation of highly stable interstitial clusters. In the second group, the solute-rich clusters are merged with vacancy clusters, and they contain mostly Cu and Si, but also substantial amount of Mn and Ni. The formation of a sub-population of pure solute clusters has been observed, which results from annihilation of the low stable vacancy clusters on sinks. The results indicate finally that the Mn content in clusters is up to 50%, Cu, Si, and Ni sharing the other half in more or less equivalent amounts. This composition has not demonstrated any noticeable modification with increasing dose over irradiation.

  20. Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Miller, Christopher J. Miller

    2012-03-01

    There are many examples of clustering in astronomy. Stars in our own galaxy are often seen as being gravitationally bound into tight globular or open clusters. The Solar System's Trojan asteroids cluster at the gravitational Langrangian in front of Jupiter’s orbit. On the largest of scales, we find gravitationally bound clusters of galaxies, the Virgo cluster (in the constellation of Virgo at a distance of ˜50 million light years) being a prime nearby example. The Virgo cluster subtends an angle of nearly 8◦ on the sky and is known to contain over a thousand member galaxies. Galaxy clusters play an important role in our understanding of theUniverse. Clusters exist at peaks in the three-dimensional large-scale matter density field. Their sky (2D) locations are easy to detect in astronomical imaging data and their mean galaxy redshifts (redshift is related to the third spatial dimension: distance) are often better (spectroscopically) and cheaper (photometrically) when compared with the entire galaxy population in large sky surveys. Photometric redshift (z) [Photometric techniques use the broad band filter magnitudes of a galaxy to estimate the redshift. Spectroscopic techniques use the galaxy spectra and emission/absorption line features to measure the redshift] determinations of galaxies within clusters are accurate to better than delta_z = 0.05 [7] and when studied as a cluster population, the central galaxies form a line in color-magnitude space (called the the E/S0 ridgeline and visible in Figure 16.3) that contains galaxies with similar stellar populations [15]. The shape of this E/S0 ridgeline enables astronomers to measure the cluster redshift to within delta_z = 0.01 [23]. The most accurate cluster redshift determinations come from spectroscopy of the member galaxies, where only a fraction of the members need to be spectroscopically observed [25,42] to get an accurate redshift to the whole system. If light traces mass in the Universe, then the locations

  1. Respiratory chain complex I is essential for sexual development in neurospora and binding of iron sulfur clusters are required for enzyme assembly.

    PubMed Central

    Duarte, M; Videira, A

    2000-01-01

    We have cloned and disrupted in vivo, by repeat-induced point mutations, the nuclear gene coding for an iron sulfur subunit of complex I from Neurospora crassa, homologue of the mammalian TYKY protein. Analysis of the obtained mutant nuo21.3c revealed that complex I fails to assemble. The peripheral arm of the enzyme is disrupted while its membrane arm accumulates. Furthermore, mutated 21.3c-kD proteins, in which selected cysteine residues were substituted with alanines or serines, were expressed in mutant nuo21. 3c. The phenotypes of these strains regarding the formation of complex I are similar to that of the original mutant, indicating that binding of iron sulfur centers to protein subunits is a prerequisite for complex I assembly. Homozygous crosses of nuo21.3c strain, and of other complex I mutants, are unable to complete sexual development. The crosses are blocked at an early developmental stage, before fusion of the nuclei of opposite mating types. This phenotype can be rescued only by transformation with the intact gene. Our results suggest that this might be due to the compromised capacity of complex I-defective strains in energy production. PMID:11014810

  2. Occupational Clusters.

    ERIC Educational Resources Information Center

    Pottawattamie County School System, Council Bluffs, IA.

    The 15 occupational clusters (transportation, fine arts and humanities, communications and media, personal service occupations, construction, hospitality and recreation, health occupations, marine science occupations, consumer and homemaking-related occupations, agribusiness and natural resources, environment, public service, business and office…

  3. Data Clustering

    NASA Astrophysics Data System (ADS)

    Wagstaff, Kiri L.

    2012-03-01

    On obtaining a new data set, the researcher is immediately faced with the challenge of obtaining a high-level understanding from the observations. What does a typical item look like? What are the dominant trends? How many distinct groups are included in the data set, and how is each one characterized? Which observable values are common, and which rarely occur? Which items stand out as anomalies or outliers from the rest of the data? This challenge is exacerbated by the steady growth in data set size [11] as new instruments push into new frontiers of parameter space, via improvements in temporal, spatial, and spectral resolution, or by the desire to "fuse" observations from different modalities and instruments into a larger-picture understanding of the same underlying phenomenon. Data clustering algorithms provide a variety of solutions for this task. They can generate summaries, locate outliers, compress data, identify dense or sparse regions of feature space, and build data models. It is useful to note up front that "clusters" in this context refer to groups of items within some descriptive feature space, not (necessarily) to "galaxy clusters" which are dense regions in physical space. The goal of this chapter is to survey a variety of data clustering methods, with an eye toward their applicability to astronomical data analysis. In addition to improving the individual researcher’s understanding of a given data set, clustering has led directly to scientific advances, such as the discovery of new subclasses of stars [14] and gamma-ray bursts (GRBs) [38]. All clustering algorithms seek to identify groups within a data set that reflect some observed, quantifiable structure. Clustering is traditionally an unsupervised approach to data analysis, in the sense that it operates without any direct guidance about which items should be assigned to which clusters. There has been a recent trend in the clustering literature toward supporting semisupervised or constrained

  4. Cluster generator

    DOEpatents

    Donchev, Todor I.; Petrov, Ivan G.

    2011-05-31

    Described herein is an apparatus and a method for producing atom clusters based on a gas discharge within a hollow cathode. The hollow cathode includes one or more walls. The one or more walls define a sputtering chamber within the hollow cathode and include a material to be sputtered. A hollow anode is positioned at an end of the sputtering chamber, and atom clusters are formed when a gas discharge is generated between the hollow anode and the hollow cathode.

  5. A novel anagostic C sbnd H⋯Cu interaction and clustered water molecules in copper(II)-pyridine-2,5-dicarboxylate complex

    NASA Astrophysics Data System (ADS)

    Çolak, Alper Tolga; Yeşilel, Okan Zafer; Büyükgüngör, Orhan

    2011-04-01

    In this study, a new mononuclear Cu(II)-pyridine-2,5-dicarboxylate complex with N,N-diethylethylenediamine (deen), [Cu(pydc)(deen)(H 2O)]·2H 2O ( 1) (pydc = pyridine-2,5-dicarboxylic acid or isocinchomeronic acid), has been synthesized. Elemental, thermal analysis and IR spectroscopic study have been performed to characterize the complex. The molecular structure of the complex has been determined by single crystal X-ray diffraction. In 1, the Cu(II) ion is coordinated by pyridine nitrogen and carboxylate oxygen atoms from pydc. The square pyramidal geometry around Cu(II) is completed by two N atoms from deen and aqua ligands. One of the interesting structural features of 1 is the presence of obvious C sbnd H⋯M anagostic interactions between the Cu(II) ion and the H atom of ethyl group.

  6. Detecting alternative graph clusterings.

    PubMed

    Mandala, Supreet; Kumara, Soundar; Yao, Tao

    2012-07-01

    The problem of graph clustering or community detection has enjoyed a lot of attention in complex networks literature. A quality function, modularity, quantifies the strength of clustering and on maximization yields sensible partitions. However, in most real world networks, there are an exponentially large number of near-optimal partitions with some being very different from each other. Therefore, picking an optimal clustering among the alternatives does not provide complete information about network topology. To tackle this problem, we propose a graph perturbation scheme which can be used to identify an ensemble of near-optimal and diverse clusterings. We establish analytical properties of modularity function under the perturbation which ensures diversity. Our approach is algorithm independent and therefore can leverage any of the existing modularity maximizing algorithms. We numerically show that our methodology can systematically identify very different partitions on several existing data sets. The knowledge of diverse partitions sheds more light into the topological organization and helps gain a more complete understanding of the underlying complex network. PMID:23005495

  7. Detecting alternative graph clusterings

    NASA Astrophysics Data System (ADS)

    Mandala, Supreet; Kumara, Soundar; Yao, Tao

    2012-07-01

    The problem of graph clustering or community detection has enjoyed a lot of attention in complex networks literature. A quality function, modularity, quantifies the strength of clustering and on maximization yields sensible partitions. However, in most real world networks, there are an exponentially large number of near-optimal partitions with some being very different from each other. Therefore, picking an optimal clustering among the alternatives does not provide complete information about network topology. To tackle this problem, we propose a graph perturbation scheme which can be used to identify an ensemble of near-optimal and diverse clusterings. We establish analytical properties of modularity function under the perturbation which ensures diversity. Our approach is algorithm independent and therefore can leverage any of the existing modularity maximizing algorithms. We numerically show that our methodology can systematically identify very different partitions on several existing data sets. The knowledge of diverse partitions sheds more light into the topological organization and helps gain a more complete understanding of the underlying complex network.

  8. ROTATING GLOBULAR CLUSTERS

    SciTech Connect

    Bianchini, P.; Varri, A. L.; Bertin, G.; Zocchi, A.

    2013-07-20

    Internal rotation is thought to play a major role in the dynamics of some globular clusters. However, in only a few cases has internal rotation been studied by the quantitative application of realistic and physically justified global models. Here, we present a dynamical analysis of the photometry and three-dimensional kinematics of {omega} Cen, 47 Tuc, and M15, by means of a recently introduced family of self-consistent axisymmetric rotating models. The three clusters, characterized by different relaxation conditions, show evidence of differential rotation and deviations from sphericity. The combination of line-of-sight velocities and proper motions allows us to determine their internal dynamics, predict their morphology, and estimate their dynamical distance. The well-relaxed cluster 47 Tuc is interpreted very well by our model; internal rotation is found to explain the observed morphology. For M15, we provide a global model in good agreement with the data, including the central behavior of the rotation profile and the shape of the ellipticity profile. For the partially relaxed cluster {omega} Cen, the selected model reproduces the complex three-dimensional kinematics; in particular, the observed anisotropy profile, characterized by a transition from isotropy to weakly radial anisotropy and then to tangential anisotropy in the outer parts. The discrepancy found for the steep central gradient in the observed line-of-sight velocity dispersion profile and for the ellipticity profile is ascribed to the condition of only partial relaxation of this cluster and the interplay between rotation and radial anisotropy.

  9. Active matter clusters at interfaces.

    NASA Astrophysics Data System (ADS)

    Copenhagen, Katherine; Gopinathan, Ajay

    2016-03-01

    Collective and directed motility or swarming is an emergent phenomenon displayed by many self-organized assemblies of active biological matter such as clusters of embryonic cells during tissue development, cancerous cells during tumor formation and metastasis, colonies of bacteria in a biofilm, or even flocks of birds and schools of fish at the macro-scale. Such clusters typically encounter very heterogeneous environments. What happens when a cluster encounters an interface between two different environments has implications for its function and fate. Here we study this problem by using a mathematical model of a cluster that treats it as a single cohesive unit that moves in two dimensions by exerting a force/torque per unit area whose magnitude depends on the nature of the local environment. We find that low speed (overdamped) clusters encountering an interface with a moderate difference in properties can lead to refraction or even total internal reflection of the cluster. For large speeds (underdamped), where inertia dominates, the clusters show more complex behaviors crossing the interface multiple times and deviating from the predictable refraction and reflection for the low velocity clusters. We then present an extreme limit of the model in the absence of rotational damping where clusters can become stuck spiraling along the interface or move in large circular trajectories after leaving the interface. Our results show a wide range of behaviors that occur when collectively moving active biological matter moves across interfaces and these insights can be used to control motion by patterning environments.

  10. The SMART CLUSTER METHOD - adaptive earthquake cluster analysis and declustering

    NASA Astrophysics Data System (ADS)

    Schaefer, Andreas; Daniell, James; Wenzel, Friedemann

    2016-04-01

    Earthquake declustering is an essential part of almost any statistical analysis of spatial and temporal properties of seismic activity with usual applications comprising of probabilistic seismic hazard assessments (PSHAs) and earthquake prediction methods. The nature of earthquake clusters and subsequent declustering of earthquake catalogues plays a crucial role in determining the magnitude-dependent earthquake return period and its respective spatial variation. Various methods have been developed to address this issue from other researchers. These have differing ranges of complexity ranging from rather simple statistical window methods to complex epidemic models. This study introduces the smart cluster method (SCM), a new methodology to identify earthquake clusters, which uses an adaptive point process for spatio-temporal identification. Hereby, an adaptive search algorithm for data point clusters is adopted. It uses the earthquake density in the spatio-temporal neighbourhood of each event to adjust the search properties. The identified clusters are subsequently analysed to determine directional anisotropy, focussing on a strong correlation along the rupture plane and adjusts its search space with respect to directional properties. In the case of rapid subsequent ruptures like the 1992 Landers sequence or the 2010/2011 Darfield-Christchurch events, an adaptive classification procedure is applied to disassemble subsequent ruptures which may have been grouped into an individual cluster using near-field searches, support vector machines and temporal splitting. The steering parameters of the search behaviour are linked to local earthquake properties like magnitude of completeness, earthquake density and Gutenberg-Richter parameters. The method is capable of identifying and classifying earthquake clusters in space and time. It is tested and validated using earthquake data from California and New Zealand. As a result of the cluster identification process, each event in

  11. Symmetry Based Automatic Evolution of Clusters: A New Approach to Data Clustering

    PubMed Central

    Vijendra, Singh; Laxman, Sahoo

    2015-01-01

    We present a multiobjective genetic clustering approach, in which data points are assigned to clusters based on new line symmetry distance. The proposed algorithm is called multiobjective line symmetry based genetic clustering (MOLGC). Two objective functions, first the Davies-Bouldin (DB) index and second the line symmetry distance based objective functions, are used. The proposed algorithm evolves near-optimal clustering solutions using multiple clustering criteria, without a priori knowledge of the actual number of clusters. The multiple randomized K dimensional (Kd) trees based nearest neighbor search is used to reduce the complexity of finding the closest symmetric points. Experimental results based on several artificial and real data sets show that proposed clustering algorithm can obtain optimal clustering solutions in terms of different cluster quality measures in comparison to existing SBKM and MOCK clustering algorithms. PMID:26339233

  12. Self-Assembled Multimetallic/Peptide Complexes: Structures and Unimolecular Reactions of [Mn (GlyGly-H)2n-1 ](+) and Mn+1 (GlyGly-H2n ](2+) Clusters in the Gas Phase.

    PubMed

    Moghaddam, Maryam B; Jami-Alahmadi, Yasaman; Fridgen, Travis D

    2015-10-26

    The unimolecular chemistry and structures of self-assembled complexes containing multiple alkaline-earth-metal dications and deprotonated GlyGly ligands are investigated. Singly and doubly charged ions [Mn (GlyGly-H)n-1 ](+) (n=2-4), [Mn+1 (GlyGly-H)2n ](2+) (n=2,4,6), and [M(GlyGly-H)GlyGly](+) were observed. The losses of 132 Da (GlyGly) and 57 Da (determined to be aminoketene) were the major dissociation pathways for singly charged ions. Doubly charged Mg(2+) clusters mainly lost GlyGly, whereas those containing Ca(2+) or Sr(2+) also underwent charge separation. Except for charge separation, no loss of metal cations was observed. Infrared multiple photon dissociation spectra were the most consistent with the computed IR spectra for the lowest energy structures, in which deprotonation occurs at the carboxyl acid groups and all amide and carboxylate oxygen atoms are complexed to the metal cations. The N-H stretch band, observed at 3350 cm(-1) , is indicative of hydrogen bonding between the amine nitrogen atoms and the amide hydrogen atom. This study represents the first into large self-assembled multimetallic complexes bound by peptide ligands. PMID:26279054

  13. First solid-state NMR analysis of uniformly ¹³C-enriched major light-harvesting complexes from Chlamydomonas reinhardtii and identification of protein and cofactor spin clusters.

    PubMed

    Pandit, Anjali; Morosinotto, Tomas; Reus, Michael; Holzwarth, Alfred R; Bassi, Roberto; de Groot, Huub J M

    2011-04-01

    The light-harvesting complex II (LHCII) is the main component of the antenna system of plants and green algae and plays a major role in the capture of sun light for photosynthesis. The LHCII complexes have also been proposed to play a key role in the optimization of photosynthetic efficiency through the process of state 1-state 2 transitions and are involved in down-regulation of photosynthesis under excess light by energy dissipation through non-photochemical quenching (NPQ). We present here the first solid-state magic-angle spinning (MAS) NMR data of the major light-harvesting complex (LHCII) of Chlamydomonas reinhardtii, a eukaryotic green alga. We are able to identify nuclear spin clusters of the protein and of its associated chlorophyll pigments in ¹³C-¹³C dipolar homonuclear correlation spectra on a uniformly ¹³C-labeled sample. In particular, we were able to resolve several chlorophyll 13¹ carbon resonances that are sensitive to hydrogen bonding to the 13¹-keto carbonyl group. The data show that ¹³C NMR signals of the pigments and protein sites are well resolved, thus paving the way to study possible structural reorganization processes involved in light-harvesting regulation through MAS solid-state NMR. PMID:21276419

  14. High-resolution neutron and X-ray diffraction room-temperature studies of an H-FABP-oleic acid complex: study of the internal water cluster and ligand binding by a transferred multipolar electron-density distribution.

    PubMed

    Howard, E I; Guillot, B; Blakeley, M P; Haertlein, M; Moulin, M; Mitschler, A; Cousido-Siah, A; Fadel, F; Valsecchi, W M; Tomizaki, Takashi; Petrova, T; Claudot, J; Podjarny, A

    2016-03-01

    Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader's quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H⋯H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface. PMID:27006775

  15. On the guiding principles for lucid understanding of the damage-free S1 structure of the CaMn4O5 cluster in the oxygen evolving complex of photosystem II

    NASA Astrophysics Data System (ADS)

    Shoji, Mitsuo; Isobe, Hiroshi; Yamanaka, Shusuke; Suga, Michihiro; Akita, Fusamichi; Shen, Jian-Ren; Yamaguchi, Kizashi

    2015-05-01

    Several key concepts and geometrical rules for the Mn-Mn and Mn-O distances of the CaMn4O5 cluster in the oxygen evolving complex (OEC) of photosystem II (PSII) by previous and present theoretical calculations were examined for a clear understanding of the damage-free S1 structure revealed by X-ray free electron laser (XFEL). A simple equation to estimate the Mna-Mnb distance in relation to the Mna-O(5) distance was derived taking into consideration the Jahn-Teller (JT) effects for Mn centers, indicating that the XFEL structure is regarded as a slightly right-elongated quasi-central structure in contradiction to a right-opened structure proposed by the EXAFS measurements.

  16. H-D exchange in metal carbene complexes: Structure of cluster (μ-H)(μ-OCD3)Os3(CO)9{:C(CD3)NC2H8O}

    NASA Astrophysics Data System (ADS)

    Savkov, Boris; Maksakov, Vladimir; Kuratieva, Natalia

    2015-10-01

    X-ray and spectroscopic data for the new complex (μ-H)(μ-OCH3)Os3(CO)9{:C(CD3)NC2H8O} (2) obtained in the reaction of the (μ-H)(μ-Cl)Os3(CO)9{:C(CH3)NC2H8O} (1) with NaOCD3 in CD3OD solution are reported. It is shown that cluster 1 has the property of CH-acidity inherent of Fisher type carbenes. This had demonstrated using hydrogen deuterium exchange reaction in the presence of a strong base. Bridging chlorine to metoxide ligand substitution takes place during the reaction. The molecular structure of 2 is compared with known analogues.

  17. Large-scale QM/MM calculations of the CaMn4O5 cluster in the oxygen-evolving complex of photosystem II: Comparisons with EXAFS structures

    NASA Astrophysics Data System (ADS)

    Shoji, Mitsuo; Isobe, Hiroshi; Nakajima, Takahito; Yamaguchi, Kizashi

    2016-08-01

    Large-scale QM/MM calculations including hydrogen-bonding networks in the oxygen evolving complex (OEC) of photosystem II (PSII) were performed to elucidate the geometric structures of the CaMn4O5 cluster in the key catalytic states (Si (i = 0-3)). The optimized Mn-Mn, Ca-Mn and Mn-O distances by the large-scale QM/MM starting from the high-resolution XRD structure were consistent with those of the EXAFS experiments in the dark stable S1 state by the Berkeley and Berlin groups. The optimized geometrical parameters for other Si (i = 0, 2, 3) states were also consistent with those of EXAFS, indicating the importance of the large-scale QM/MM calculations for the PSII-OEC.

  18. A geological explanation for intraplate earthquake clustering complexity: The zeolite-bearing fault/fracture networks in the Adamello Massif (Southern Italian Alps)

    NASA Astrophysics Data System (ADS)

    Dempsey, E. D.; Holdsworth, R. E.; Imber, J.; Bistacchi, A.; Di Toro, G.

    2014-09-01

    Interconnected networks of faults and veins filled with hydrothermal minerals such as zeolite are widespread in many orogenic terrains. These fractures commonly form at relatively low temperatures (e.g. <200 °C) late in the tectonic history and represent significant phases of fluid flow and mineralisation during exhumation. Zeolite-bearing fractures spatially associated with the Gole Larghe Fault Zone in the Southern Italian Alps are preserved along an interconnected network of variably orientated pre-existing structures. They show evidence of repeated episodes of hydraulic tensile fracturing and small magnitude (total offsets <5 m) shear displacements. We use geological observations and Coulomb stress modelling to propose that repeated seismogenic rupturing of larger offset faults led to local stress transfer and reactivation of widely distributed smaller pre-existing structures in the wall rocks. The differing orientations of the pre-existing features within what is assumed to have been a single regional stress field led to the simultaneous development of reverse, strike-slip and extensional faults. The kinematic diversity and cyclic nature of the hydraulically-assisted deformation suggest that the mineralised fracture systems represent a geological manifestation of intraplate micro-earthquake clusters associated with fluid migration episodes in the upper crust. Our observations highlight the role of crustal fluids and structural reactivation during earthquakes.

  19. Assembly of juxtaparanodes in myelinating DRG culture: Differential clustering of the Kv1/Caspr2 complex and scaffolding protein 4.1B.

    PubMed

    Hivert, Bruno; Pinatel, Delphine; Labasque, Marilyne; Tricaud, Nicolas; Goutebroze, Laurence; Faivre-Sarrailh, Catherine

    2016-05-01

    The precise distribution of ion channels at the nodes of Ranvier is essential for the efficient propagation of action potentials along myelinated axons. The voltage-gated potassium channels Kv1.1/1.2 are clustered at the juxtaparanodes in association with the cell adhesion molecules, Caspr2 and TAG-1 and the scaffolding protein 4.1B. In the present study, we set up myelinating cultures of DRG neurons and Schwann cells to look through the formation of juxtaparanodes in vitro. We showed that the Kv1.1/Kv1.2 channels were first enriched at paranodes before being restricted to distal paranodes and juxtaparanodes. In addition, the Kv1 channels displayed an asymmetric expression enriched at the distal juxtaparanodes. Caspr2 was strongly co-localized with Kv1.2 whereas the scaffolding protein 4.1B was preferentially recruited at paranodes while being present at juxtaparanodes too. Kv1.2/Caspr2 but not 4.1B, also transiently accumulated within the nodal region both in myelinated cultures and developing sciatic nerves. Studying cultures and sciatic nerves from 4.1B KO mice, we further showed that 4.1B is required for the proper targeting of Caspr2 early during myelination. Moreover, using adenoviral-mediated expression of Caspr-GFP and photobleaching experiments, we analyzed the stability of paranodal junctions and showed that the lateral stability of paranodal Caspr was not altered in 4.1B KO mice indicating that 4.1B is not required for the assembly and stability of the paranodal junctions. Thus, developing an adapted culture paradigm, we provide new insights into the dynamic and differential distribution of Kv1 channels and associated proteins during myelination. GLIA 2016;64:840-852. PMID:26840208

  20. How often are interventions in cluster-randomised controlled trials of complex interventions in general practices effective and reasons for potential shortcomings? Protocol and results of a feasibility project for a systematic review

    PubMed Central

    Siebenhofer, Andrea; Erckenbrecht, Stefanie; Pregartner, Gudrun; Berghold, Andrea; Muth, Christiane

    2016-01-01

    Introduction Most studies conducted at general practices investigate complex interventions and increasingly use cluster-randomised controlled trail (c-RCT) designs to do so. Our primary objective is to evaluate how frequently complex interventions are shown to be more, equally or less effective than routine care in c-RCTs with a superior design. The secondary aim is to discover whether the quality of a c-RCT determines the likelihood of the complex intervention being effective. Methods and analysis All c-RCTs of any design that have a patient-relevant primary outcome and with a duration of at least 1 year will be included. The search will be performed in three electronic databases (MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews (CDSR)). The screening process, data collection, quality assessment and statistical data analyses (if suitably similar and of adequate quality) will be performed in accordance with requirements of the Cochrane Handbook for Systematic Reviews of Interventions. A feasibility project was carried out that was restricted to a search in MEDLINE and the CCTR for c-RCTs published in 1 of the 8 journals that are most relevant to general practice. The process from trial selection to data collection, assessment and results presentation was piloted. Of the 512 abstracts identified during the feasibility search, 21 studies examined complex interventions in a general practice setting. Extrapolating the preliminary search to include all relevant c-RCTs in three databases, about 5000 abstracts and 150 primary studies are expected to be identified in the main study. 14 studies included in the feasibility project (67%) did not show a positive effect on a primary patient-relevant end point. Ethics and dissemination Ethical approval is not being sought for this review. Findings will be disseminated via peer-reviewed journals that frequently publish articles on the results of c-RCTs and through presentations at international conferences. Trial

  1. SVM clustering

    PubMed Central

    Winters-Hilt, Stephen; Merat, Sam

    2007-01-01

    Background Support Vector Machines (SVMs) provide a powerful method for classification (supervised learning). Use of SVMs for clustering (unsupervised learning) is now being considered in a number of different ways. Results An SVM-based clustering algorithm is introduced that clusters data with no a priori knowledge of input classes. The algorithm initializes by first running a binary SVM classifier against a data set with each vector in the set randomly labelled, this is repeated until an initial convergence occurs. Once this initialization step is complete, the SVM confidence parameters for classification on each of the training instances can be accessed. The lowest confidence data (e.g., the worst of the mislabelled data) then has its' labels switched to the other class label. The SVM is then re-run on the data set (with partly re-labelled data) and is guaranteed to converge in this situation since it converged previously, and now it has fewer data points to carry with mislabelling penalties. This approach appears to limit exposure to the local minima traps that can occur with other approaches. Thus, the algorithm then improves on its weakly convergent result by SVM re-training after each re-labeling on the worst of the misclassified vectors – i.e., those feature vectors with confidence factor values beyond some threshold. The repetition of the above process improves the accuracy, here a measure of separability, until there are no misclassifications. Variations on this type of clustering approach are shown. Conclusion Non-parametric SVM-based clustering methods may allow for much improved performance over parametric approaches, particularly if they can be designed to inherit the strengths of their supervised SVM counterparts. PMID:18047717

  2. A Robust Open Framework Formed by Decavanadate Clusters and Copper(II) Complexes of Macrocyclic Polyamines: Permanent Microporosity and Catalytic Oxidation of Cycloalkanes.

    PubMed

    Martín-Caballero, Jagoba; San José Wéry, Ana; Reinoso, Santiago; Artetxe, Beñat; San Felices, Leire; El Bakkali, Bouchra; Trautwein, Guido; Alcañiz-Monge, Juan; Vilas, José Luis; Gutiérrez-Zorrilla, Juan M

    2016-05-16

    The first decavanadate-based microporous hybrid, namely, [Cu(cyclam)][{Cu(cyclam)}2(V10O28)]·10H2O (1, cyclam = 1,4,8,11-tetraazacyclotetradecane) was prepared by reaction of (VO3)(-) anions and {Cu(cyclam)}(2+) complexes in NaCl (aq) at pH 4.6-4.7 and characterized by elemental analyses, thermogravimetry, and X-ray diffraction (powder, single-crystal) techniques. Compound 1 exhibits a POMOF-like supramolecular open-framework built of covalent decavanadate/metalorganic layers with square-like voids, the stacking of which is aided by interlamellar cementing complexes and generates water-filled channels with approximate cross sections of 10.4 × 8.8 Å(2). The framework is robust enough to remain virtually unaltered upon thermal evacuation of all water molecules of hydration, as demonstrated through single-crystal X-ray diffraction studies on the anhydrous phase 1a. This permanent microporosity renders interesting functionality to 1, such as selective adsorption of CO2 over N2 and remarkable activity as heterogeneous catalyst toward the H2O2-based oxidation of the highly-stable, tricyclic alkane adamantane. PMID:27111578

  3. Active matter clusters at interfaces

    NASA Astrophysics Data System (ADS)

    Copenhagen, Katherine; Gopinathan, Ajay

    Collective and directed motility or swarming is an emergent phenomenon displayed by many self-organized assemblies of active biological matter such as clusters of embryonic cells during tissue development and flocks of birds. Such clusters typically encounter very heterogeneous environments. What happens when a cluster encounters an interface between two different environments has implications for its function and fate. Here we study this problem by using a mathematical model of a cluster that treats it as a single cohesive unit whose movement depends on the nature of the local environment. We find that low speed clusters which exert forces but no active torques, encountering an interface with a moderate difference in properties can lead to refraction or even total internal reflection of the cluster. For large speeds and clusters with active torques, they show more complex behaviors crossing the interface multiple times, becoming trapped at the interface and deviating from the predictable refraction and reflection of the low velocity clusters. Our results show a wide range of behaviors that occur when collectively moving active biological matter moves across interfaces and these insights can be used to control motion by patterning environments.

  4. On the equilibrium structures of the complexes H2C3H+ · Ar and c-C3H3(+) · Ar: results of explicitly correlated coupled cluster calculations.

    PubMed

    Botschwina, Peter; Oswald, Rainer

    2011-01-28

    Explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level [T. B. Adler et al., J. Chem. Phys. 127, 221106 (2007)] has been employed in a study of the potential energy surfaces for the complexes H(2)C(3)H(+) · Ar and c-C(3)H(3)(+) · Ar. For the former complex, a pronounced minimum with C(s) symmetry was found (D(e) ≈ 780 cm(-1)), well below the local "H-bound" minimum with C(2v) symmetry (D(e) ≈ 585 cm(-1)). The absorption at 3238 cm(-1) found in the recent infrared photodissociation spectra [A. M. Ricks et al., J. Chem. Phys. 132, 051101 (2010)] is, thus, interpreted as an essentially free acetylenic CH stretching vibration of the propargyl cation. A global minimum of C(s) symmetry was also obtained for c-C(3)H(3)(+) (D(e) ≈ 580 cm(-1)), but the energy difference with respect to the local C(2v) minimum is only 54 cm(-1). PMID:21280723

  5. High-resolution neutron and X-ray diffraction room-temperature studies of an H-FABP–oleic acid complex: study of the internal water cluster and ligand binding by a transferred multipolar electron-density distribution

    PubMed Central

    Howard, E. I.; Guillot, B.; Blakeley, M. P.; Haertlein, M.; Moulin, M.; Mitschler, A.; Cousido-Siah, A.; Fadel, F.; Valsecchi, W. M.; Tomizaki, Takashi; Petrova, T.; Claudot, J.; Podjarny, A.

    2016-01-01

    Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader’s quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H⋯H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface. PMID:27006775

  6. Thermal and electrochemically assisted Pd-Cl bond cleavage in the d9-d9 Pd2dppm2Cl2 complex by Pd3 dppm3COn+ clusters (n = 2, 1, 0).

    PubMed

    Cugnet, Cyril; Mugnier, Yves; Dal Molin, Sophie; Brevet, David; Lucas, Dominique; Harvey, Pierre D

    2007-04-16

    A new aspect of reactivity of the cluster [Pd3(dppm)3(micro3-CO)]n+, ([Pd3]n+, n = 2, 1, 0) with the low-valent metal-metal-bonded Pd2(dppm)2Cl2 dimer (Pd2Cl2) was observed using electrochemical techniques. The direct reaction between [Pd3]2+ and Pd2Cl2 in THF at room temperature leads to the known [Pd3(dppm)3(micro3-CO)(Cl)]+ ([Pd3(Cl)]+) adduct and the monocationic species Pd2(dppm)2Cl+ (very likely as Pd2(dppm)2(Cl)(THF)+, [Pd2Cl]+) as unambiguously demonstrated by UV-vis and 31P NMR spectroscopy. In this case, [Pd3]2+ acts as a strong Lewis acid toward the labile Cl- ion, which weakly dissociates from Pd2Cl2 (i.e., dissociative mechanism). Host-guest interactions between [Pd3]2+ and Pd2Cl2 seem unlikely on the basis of computer modeling because of the strong screening of the Pd-Cl fragment by the Ph-dppm groups in Pd2Cl2. The electrogenerated clusters [Pd3]+ and [Pd3]0 also react with Pd2Cl2 to unexpectedly form the same oxidized adduct, [Pd3(Cl)]+, despite the known very low affinity of [Pd3]+ and [Pd3]0 toward Cl- ions. The reduced biproduct in this case is the highly reactive zerovalent species "Pd2(dppm)2" or "Pd(dppm)" as demonstrated by quenching with CDCl3 (forming the well-known complex Pd(dppm)Cl2) or in presence of dppm (forming the known Pd2(dppm)3 d10-d10 dimer). To bring these halide-electron exchange reactions to completion for [Pd3]+ and [Pd3]0, 0.5 and 1.0 equiv of Pd2Cl2 are necessary, respectively, accounting perfectly for the number of exchanged electrons. The presence of a partial dissociation of Pd2Cl2 into the Cl- ion and the monocation [Pd2Cl]+, which is easier to reduce than Pd2Cl2, is suggested to explain the overall electrochemical results. It is possible to regulate the nature of the species formed from Pd2Cl2 by changing the state of charge of the title cluster. PMID:17371010

  7. Architecture of Eph receptor clusters

    SciTech Connect

    Himanen, Juha P.; Yermekbayeva, Laila; Janes, Peter W.; Walker, John R.; Xu, Kai; Atapattu, Lakmali; Rajashankar, Kanagalaghatta R.; Mensinga, Anneloes; Lackmann, Martin; Nikolov, Dimitar B.; Dhe-Paganon, Sirano

    2010-10-04

    Eph receptor tyrosine kinases and their ephrin ligands regulate cell navigation during normal and oncogenic development. Signaling of Ephs is initiated in a multistep process leading to the assembly of higher-order signaling clusters that set off bidirectional signaling in interacting cells. However, the structural and mechanistic details of this assembly remained undefined. Here we present high-resolution structures of the complete EphA2 ectodomain and complexes with ephrin-A1 and A5 as the base unit of an Eph cluster. The structures reveal an elongated architecture with novel Eph/Eph interactions, both within and outside of the Eph ligand-binding domain, that suggest the molecular mechanism underlying Eph/ephrin clustering. Structure-function analysis, by using site-directed mutagenesis and cell-based signaling assays, confirms the importance of the identified oligomerization interfaces for Eph clustering.

  8. Chemical evolution of star clusters.

    PubMed

    van Loon, Jacco Th

    2010-02-28

    I discuss the chemical evolution of star clusters, with emphasis on old Galactic globular clusters (GCs), in relation to their formation histories. GCs are clearly formed in a complex fashion, under markedly different conditions from any younger clusters presently known. Those special conditions must be linked to the early formation epoch of the Galaxy and must not have occurred since. While a link to the formation of GCs in dwarf galaxies has been suggested, present-day dwarf galaxies are not representative of the gravitational potential wells within which the GCs formed. Instead, a formation deep within the proto-Galaxy or within dark-matter mini-haloes might be favoured. Not all GCs may have formed and evolved similarly. In particular, we may need to distinguish Galactic Halo from Galactic Bulge clusters. PMID:20083507

  9. ClusterViz: A Cytoscape APP for Cluster Analysis of Biological Network.

    PubMed

    Wang, Jianxin; Zhong, Jiancheng; Chen, Gang; Li, Min; Wu, Fang-xiang; Pan, Yi

    2015-01-01

    Cluster analysis of biological networks is one of the most important approaches for identifying functional modules and predicting protein functions. Furthermore, visualization of clustering results is crucial to uncover the structure of biological networks. In this paper, ClusterViz, an APP of Cytoscape 3 for cluster analysis and visualization, has been developed. In order to reduce complexity and enable extendibility for ClusterViz, we designed the architecture of ClusterViz based on the framework of Open Services Gateway Initiative. According to the architecture, the implementation of ClusterViz is partitioned into three modules including interface of ClusterViz, clustering algorithms and visualization and export. ClusterViz fascinates the comparison of the results of different algorithms to do further related analysis. Three commonly used clustering algorithms, FAG-EC, EAGLE and MCODE, are included in the current version. Due to adopting the abstract interface of algorithms in module of the clustering algorithms, more clustering algorithms can be included for the future use. To illustrate usability of ClusterViz, we provided three examples with detailed steps from the important scientific articles, which show that our tool has helped several research teams do their research work on the mechanism of the biological networks. PMID:26357321

  10. Poxvirus Orthologous Clusters (POCs).

    PubMed

    Ehlers, Angelika; Osborne, John; Slack, Stephanie; Roper, Rachel L; Upton, Chris

    2002-11-01

    Poxvirus Orthologous Clusters (POCs) is a JAVA client-server application which accesses an updated database containing all complete poxvirus genomes; it automatically groups orthologous genes into families based on BLASTP scores for assessment by a human database curator. POCs has a user-friendly interface permitting complex SQL queries to retrieve interesting groups of DNA and protein sequences as well as gene families for subsequent interrogation by a variety of integrated tools: BLASTP, BLASTX, TBLASTN, Jalview (multiple alignment), Dotlet (Dotplot), Laj (local alignment), and NAP (nucleotide to amino acid alignment). PMID:12424130

  11. Self-assembly of mixed-valence Co(II/III) and Ni(II) clusters: azide-bridged 1D single chain coordination polymers comprised of tetranuclear units, tetranuclear Co(II/III) complexes, ferromagnetically coupled azide-bridged tetranuclear, and hexanuclear Ni(II) complexes: synthesis, structural, and magnetic properties.

    PubMed

    Tandon, Santokh S; Bunge, Scott D; Rakosi, Robert; Xu, Zhiqiang; Thompson, Laurence K

    2009-09-01

    One-pot reactions between 2,6-diformyl-4-methylphenol (DFMP) and 2-aminoethanol (AE) in the presence of cobalt(II) salts [Co(ClO4)2, CoCl2, Co(CH3CO2)2, Co(NO3)2] and sodium azide result in the self-assembly of novel one-dimensional single chain mixed-valence cobalt coordination polymers {[Co2(II)Co2(III) (HL)2(OCH3)2(N3)3]ClO(4).5H2O.CH3OH}n (1), {[Co2(II)Co2(III) (HL)2(OCH3)2(N3)3]Cl.H2O}n (2) in which tetra-cobalt cationic units are bridged by symmetrical 1,3-azides, forming single chains; mixed valence neutral tetranuclear clusters [Co2(II)Co2(III) (HL)2(OCH3)2(N3)4]CH3OH.2H2O (3), [Co2(II)Co2(III)(HL)2(OCH3)2(N3)2(CH3CO2)2].2CH3OH.2H2O (4), and the cationic cluster [Co2(II) Co2(III) (HL)2(OCH3)2(CH3OH)2(N3)2](NO3)2 (5). In all these reactions, H3L, the potentially pentadentate (N2O3), trianionic double Schiff base ligand 2,6-bis[(2-hydroxy-ethylimino)-methyl]-4-methylphenol is formed. The reaction between DFMP and AE in the presence of nickel(ii) salts and sodium azide in methanol-water mixture results in the self-assembly of ferromagnetically coupled hexanuclear complexes [Ni6(H2L)2(HL-1)2(H2O)2(N3)6](ClO4)(2).2CH3OH (6), and [Ni6(H2L)2(HL-1)2(CH3OH)2(N3)6](BF4)2 (7), involving double (H3L) and single (H2L-1) Schiff base ligands, and a neutral tetranuclear complex [Ni4(H2L)2(OCH3)2(CH3CO2)2(N3)2] (8) with only double Schiff-base (H3L). In these complexes, the nature of the anion and the reaction conditions seem to play an important role in directing the formation of tetranuclear, hexanuclear or polymeric clusters. All complexes involve divacant double cubane-type cores containing three to four different types of bridging ligands (phenoxy, azido, methoxy/alkoxy, and acetate). Variable temperature magnetic properties of these spin coupled clusters have been investigated and magneto-structural correlations have been established. PMID:19672499

  12. CARTILAGE CELL CLUSTERS

    PubMed Central

    Lotz, Martin K.; Otsuki, Shuhei; Grogan, Shawn P.; Sah, Robert; Terkeltaub, Robert; D’Lima, Darryl

    2010-01-01

    The formation of new cell clusters is a histological hallmark of arthritic cartilage but the biology of clusters and their role in disease are poorly understood. This is the first comprehensive review of clinical and experimental conditions associated with cluster formation. Genes and proteins that are expressed in cluster cells, the cellular origin of the clusters, mechanisms that lead to cluster formation and the role of cluster cells in pathogenesis are discussed. PMID:20506158

  13. Astrophysics of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Ettori, Stefano

    2016-07-01

    As the nodes of the cosmic web, clusters of galaxies trace the large-scale distribution of matter in the Universe. They are thus privileged sites in which to investigate the complex physics of structure formation. However, the complete story of how these structures grow, and how they dissipate the gravitational and non-thermal components of their energy budget over cosmic time, is still beyond our grasp. Most of the baryons gravitationally bound to the cluster's halo is in the form of a diffuse, hot, metal-enriched plasma that radiates primarily in the X-ray band. X-ray observations of the evolving cluster population provide a unique opportunity to address such fundamental open questions as: How do hot diffuse baryons accrete and dynamically evolve in dark matter potentials? How and when was the energy that we observe in the ICM generated and distributed? Where and when are heavy elements produced and how are they circulated? We will present the ongoing activities to define the strategy on how an X-ray observatory with large collecting area and an unprecedented combination of high spectral and angular resolution, such as Athena, can address these questions.

  14. Coordination chemistry of bis(delta-camphorquinone dioximato)nickel(II) and -palladium(II). Reactions and structural studies of some M/sub 3/Ag/sub 3/ cluster complexes of camphorquinone dioxime

    SciTech Connect

    Ma, M.S.; Angelici, R.J.; Powell, D.; Jacobson, R.A.

    1980-01-01

    Reactions of AgNO/sub 3/ with Ni(delta-HCQD)/sub 2/ or Pd(delta-HCQD)/sub 2/, where delta-HCQD/sup -/ is delta-camphorquinone dioximato, yielded the hexanuclear metal cluster complexes (Ni(delta-HCQD)/sub 2/Ag)/sub 3/ x 2.5CHCl/sub 3/, Ni-Ag, and (Pd(delta-HCQD)/sub 2/Ag)/sub 3/ x 2CHCl/sub 3/, Pd-Ag, respectively. X-ray crystallographic studies performed on both complexes showed them to belong to space group P2/sub 1/2/sub 1/2/sub 1/. The unit cell dimensions of Ni-Ag are a = 15.990 (5) A, b = 38.44 (1) A, c = 13.437 (5) A, V = 8260.97 A/sup 3/, and Z = 4 while those of Pd-Ag are a = 16.110 (6), b = 38.92 (1), c = 13.393 (3) A, V = 8395.55 A/sup 3/, and Z = 4. Block-diagonal least-squares refinement of 3021 observed reflections for Ni-Ag and 6112 for Pd-Ag converged to R/sub F/ = 10.7 and 11.4 (R/sub w/ = 12.7 and 15.0) for the Ni-Ag and Pd-Ag structures, respectively. Their structures indicate that each hexanuclear molecule consists of three individual M(delta-HCQD)/sub 2//sup -/ units which act as multidentate ligands coordinating to a linear chain of three silver atoms. The coordination geometry around each M ion in the M(delta-HCQD)/sub 2//sup -/ units is square planar, and the delta-HCQD/sup -/ ligands are coordinated to M via N and O atoms. The Ag in the center of the molecule is coordinated to six O atoms with average Ag-O distances of 2.49 (3) and 2.45 (2) A for Ni-Ag and Pg-Ag, respectively. The two silver atoms at the ends of the chain are each coordinated to three nitrogen atoms from the M(delta-HCQD)/sub 2//sup -/ units with average Ag-N distances of 2.20 (4) and 2.27 (3) A, respectively. The Ag-Ag distances, 3.059 (5) and 3.052 (5) A in Ni-Ag and 3.173 (3) and 3.179 (3) A in Pd-Ag, are somewhat longer than those (2.89 A) in Ag metal and indicate that there are Ag-Ag interactions along the linear chains. The bis(pyridine) adduct of Ni(delta-HCQD)/sub 2/ was also prepared. A proposed structure for this complex is based on the similarity of its ir

  15. Uranyl peroxide closed clusters containing topological squares

    SciTech Connect

    Unruh, Daniel K.; Burtner, Alicia; Pressprich, Laura; Sigmon, Ginger E.; Burns, Peter C

    2010-01-01

    Four self-assembling clusters of uranyl peroxide polyhedra have been formed in alkaline aqueous solutions and structurally characterized. These clusters consist of 28, 30, 36 and 44 uranyl polyhedra and exhibit complex new topologies. Each has a structure that contains topological squares, pentagons and hexagons. Analysis of possible topologies within boundary constraints indicates a tendency for adoption of higher symmetry topologies in these cases. Small angle X-ray scattering data demonstrated that crystals of one of these clusters can be dissolved in ultrapure water and that the clusters remain intact for at least several days.

  16. An analysis of hospital brand mark clusters.

    PubMed

    Vollmers, Stacy M; Miller, Darryl W; Kilic, Ozcan

    2010-07-01

    This study analyzed brand mark clusters (i.e., various types of brand marks displayed in combination) used by hospitals in the United States. The brand marks were assessed against several normative criteria for creating brand marks that are memorable and that elicit positive affect. Overall, results show a reasonably high level of adherence to many of these normative criteria. Many of the clusters exhibited pictorial elements that reflected benefits and that were conceptually consistent with the verbal content of the cluster. Also, many clusters featured icons that were balanced and moderately complex. However, only a few contained interactive imagery or taglines communicating benefits. PMID:20582849

  17. A uniform catalog of candidate IR-excess and optically variable Young Stellar Objects (YSOs) across the full Orion complex: Aiding target selection for the APOGEE-2 Young Cluster Program

    NASA Astrophysics Data System (ADS)

    Cottle, J'Neil; Covey, Kevin R.; Ford Schlafly, Edward; Arce, Hector G.; Borissova, Jura; Downes, Juan Jose; Feigelson, Eric; Getman, Konstantin V.; Kim, Jinyoung Serena; Roman-Lopes, Alexandre; Roman-Zuniga, Carlos G.; Stringfellow, Guy S.; Ybarra, Jason E.; Chojnowski, S. Drew; Frinchaboy, Peter M.; Hearty, Fred R.; Majewski, Steven R.; Skrutskie, Michael F.; Stassun, Keivan; Wilson, John C.; Zasowski, Gail

    2016-01-01

    Precise measurements of the intrinsic (e.g., T_eff & log g) and dynamical (e.g, radial velocity & v sin i) properties of young stars provide important constraints for models of star formation and early stellar evolution. The APOGEE-2 YSO Young Cluster Program aims to measure the dynamics and star formation history uniformly across the full extent of the Orion star forming complex, based on thousands of high-resolution H-band spectra that APOGEE-2 will obtain of candidate Orion members. We utilize data from wide-field photometric surveys to select candidate YSOs throughout Orion via two complementary techniques. We follow the Koenig et al. (2014) criteria by using WISE+2MASS data to identify YSOs with IR excesses due to warm circumstellar dust; we also use multi-epoch optical PanSTARRS photometry to identify variable YSOs both with and without circumstellar disks (or circumstellar materials). The IR excess technique identifies 1729 candidates brighter than H=12.8 mag, a limit selected to ensure a minimum S/N > 50 for a typical 3-hour APOGEE exposure. selecting sources which display significant variability in at least 3 PanSTARRS bands similarly produces a preliminary sample of 1500 candidates with H<12.8 mag. In total, we identify nearly 2700 YSO candidates, 450 of which were identified via both selection methods. The resulting catalog exhibits clear spatial over-densities associated with known sub-regions of Orion such as the ONC, sigma Ori and L1641, and provides a uniform catalog for spectroscopic targeting over Orion's full 250+ sq. degree footprint.

  18. Coordination chemistry of bis(delta-camphorquinone dioximato)nickel(II) and -palladium(II). Reactions and structural studies of some M/sub 3/Ag/sub 3/ cluster complexes of camphorquinone dioxime

    SciTech Connect

    Ma, M.S.; Angelici, R.J.; Powell, D.; Jacobson, R.A.

    1980-10-01

    Reactions of AgNO/sub 3/ with Ni(delta-HCQD)/sub 2/ or Pd(delta-HCQD)/sub 2/, where delta-HCQD/sup -/ is delta-camphorquinone dioximato, yielded the hexanuclear metal cluster complexes (Ni(delta-HCQD)/sub 2/Ag)/sub 3/.2.5CHCl/sub 3/, Ni-Ag, and (Pd(delta-HCQD)/sub 2/Ag)/sub 3/.2CHCl/sub 3/, Pd-Ag, respectively. X-ray crystallographic studies performed on both complexes showed them to belong to space group P2/sub 1/2/sub 1/2/sub 1/. The unit cell dimensions of Ni-Ag are a = 15.990 (5) A, B = 38.44 (1) A, c = 13.437 (5) A, V = 8260.97 A/sup 3/, and Z = 4 while those of Pd-Ag are a = 16.110 (6), b = 38.92 (1), c = 13.393 (3) A, V = 8395.55 A/sup 3/, and Z = 4. Block-diagonal least-squares refinement of 3021 observed reflections for Ni-Ag and 6112 for Pd-Ag converged to R/sub F/ = 10.7 and 11.4 (R/sub w/ = 12.7 and 15.0) for the Ni-Ag and Pd-Ag structures, respectively. Their structures indicate that each hexanuclear molecule consists of three individual M(delta-HCQD)/sub 2//sup -/units which act as multidentate ligands coordinating to a linear chain of three silver atoms. The coordination geometry around each M ion in the M(delta-HCQD)/sub 2//sup -/units is square planar, and the delta-HCQD/sup -/ligands are coordinated to M via N and O atoms. The Ag in the center of the molecule is coordinated to six O atoms with average Ag-O distances of 2.49 (3) and 2.45 (2) A for Ni-Ag and Pd-Ag, respectively. The two silver atoms at the ends of the chain are each coordinated to three nitrogen atoms from the M(delta-HCQD)/sub 2//sup -/ units with average Ag-N distances of 2.20 (4) and 2.27 (3) A, respectively. The Ag-Ag distances, 3.059 (5) and 3.052 (5) A in Ni-Ag and 3.173 (3) and 3.179 (3) A in Pd-Ag, are somewhat longer than those (2.89 A) in Ag metal and indicate that there are Ag-Ag interactions along the linear chains.

  19. Two giant stellar complexes

    NASA Astrophysics Data System (ADS)

    Efremov, Yu. N.; Efremov, E. Yu.

    Common star complexes are huge (0.3-1 kpc in diameter) groups of relatively young stars, associations and clusters. The complexes usually form regular chains along spiral arms of grand design galaxies, being evidently formed and supported by magneto- gravitational instability developing along an arm. Special attention is given to a few large complexes which have signatures of gravitational boundness, such as round shape and high central density. Concentrations of stars and clusters in such a complex in M51 galaxy were found in this paper; we concluded it is possible to suggest that the complex is gravitationally bound. It is also stressed that some properties of the giant complex in NGC 6946 (such as its semicircular and sharp Western edge) are still enigmatic.

  20. Avoiding common pitfalls when clustering biological data.

    PubMed

    Ronan, Tom; Qi, Zhijie; Naegle, Kristen M

    2016-01-01

    Clustering is an unsupervised learning method, which groups data points based on similarity, and is used to reveal the underlying structure of data. This computational approach is essential to understanding and visualizing the complex data that are acquired in high-throughput multidimensional biological experiments. Clustering enables researchers to make biological inferences for further experiments. Although a powerful technique, inappropriate application can lead biological researchers to waste resources and time in experimental follow-up. We review common pitfalls identified from the published molecular biology literature and present methods to avoid them. Commonly encountered pitfalls relate to the high-dimensional nature of biological data from high-throughput experiments, the failure to consider more than one clustering method for a given problem, and the difficulty in determining whether clustering has produced meaningful results. We present concrete examples of problems and solutions (clustering results) in the form of toy problems and real biological data for these issues. We also discuss ensemble clustering as an easy-to-implement method that enables the exploration of multiple clustering solutions and improves robustness of clustering solutions. Increased awareness of common clustering pitfalls will help researchers avoid overinterpreting or misinterpreting the results and missing valuable insights when clustering biological data. PMID:27303057

  1. Scientific Cluster Deployment and Recovery - Using puppet to simplify cluster management

    NASA Astrophysics Data System (ADS)

    Hendrix, Val; Benjamin, Doug; Yao, Yushu

    2012-12-01

    Deployment, maintenance and recovery of a scientific cluster, which has complex, specialized services, can be a time consuming task requiring the assistance of Linux system administrators, network engineers as well as domain experts. Universities and small institutions that have a part-time FTE with limited time for and knowledge of the administration of such clusters can be strained by such maintenance tasks. This current work is the result of an effort to maintain a data analysis cluster (DAC) with minimal effort by a local system administrator. The realized benefit is the scientist, who is the local system administrator, is able to focus on the data analysis instead of the intricacies of managing a cluster. Our work provides a cluster deployment and recovery process (CDRP) based on the puppet configuration engine allowing a part-time FTE to easily deploy and recover entire clusters with minimal effort. Puppet is a configuration management system (CMS) used widely in computing centers for the automatic management of resources. Domain experts use Puppet's declarative language to define reusable modules for service configuration and deployment. Our CDRP has three actors: domain experts, a cluster designer and a cluster manager. The domain experts first write the puppet modules for the cluster services. A cluster designer would then define a cluster. This includes the creation of cluster roles, mapping the services to those roles and determining the relationships between the services. Finally, a cluster manager would acquire the resources (machines, networking), enter the cluster input parameters (hostnames, IP addresses) and automatically generate deployment scripts used by puppet to configure it to act as a designated role. In the event of a machine failure, the originally generated deployment scripts along with puppet can be used to easily reconfigure a new machine. The cluster definition produced in our CDRP is an integral part of automating cluster deployment

  2. Personalized PageRank Clustering: A graph clustering algorithm based on random walks

    NASA Astrophysics Data System (ADS)

    A. Tabrizi, Shayan; Shakery, Azadeh; Asadpour, Masoud; Abbasi, Maziar; Tavallaie, Mohammad Ali

    2013-11-01

    Graph clustering has been an essential part in many methods and thus its accuracy has a significant effect on many applications. In addition, exponential growth of real-world graphs such as social networks, biological networks and electrical circuits demands clustering algorithms with nearly-linear time and space complexity. In this paper we propose Personalized PageRank Clustering (PPC) that employs the inherent cluster exploratory property of random walks to reveal the clusters of a given graph. We combine random walks and modularity to precisely and efficiently reveal the clusters of a graph. PPC is a top-down algorithm so it can reveal inherent clusters of a graph more accurately than other nearly-linear approaches that are mainly bottom-up. It also gives a hierarchy of clusters that is useful in many applications. PPC has a linear time and space complexity and has been superior to most of the available clustering algorithms on many datasets. Furthermore, its top-down approach makes it a flexible solution for clustering problems with different requirements.

  3. Kinematics and dynamics of the MKW/AWM poor clusters

    NASA Technical Reports Server (NTRS)

    Beers, Timothy C.; Kriessler, Jeffrey R.; Bird, Christina M.; Huchra, John P.

    1995-01-01

    We report 472 new redshifts for 416 galaxies in the regions of the 23 poor clusters of galaxies originally identified by Morgan, Kayser, and White (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poor clusters now have 10 or more available redshifts within 1.5/h Mpc of the central galaxy; 11 clusters have at least 20 available redshifts. Based on the 21 clusters for which we have sufficient velocity information, the median velocity scale is 336 km/s, a factor of 2 smaller than found for rich clusters. Several of the poor clusters exhibit complex velocity distributions due to the presence of nearby clumps of galaxies. We check on the velocity of the dominant galaxy in each poor cluster relative to the remaining cluster members. Significantly high relative velocities of the dominant galaxy are found in only 4 of 21 poor clusters, 3 of which we suspect are due to contamination of the parent velocity distribution. Several statistical tests indicate that the D/cD galaxies are at the kinematic centers of the parent poor cluster velocity distributions. Mass-to-light ratios for 13 of the 15 poor clusters for which we have the required data are in the range 50 less than or = M/L(sub B(0)) less than or = 200 solar mass/solar luminosity. The complex nature of the regions surrounding many of the poor clusters suggests that these groupings may represent an early epoch of cluster formation. For example, the poor clusters MKW7 and MKWS are shown to be gravitationally bound and likely to merge to form a richer cluster within the next several Gyrs. Eight of the nine other poor clusters for which simple two-body dynamical models can be carried out are consistent with being bound to other clumps in their vicinity. Additional complex systems with more than two gravitationally bound clumps are observed among the poor clusters.

  4. Kinematics and dynamics of the MKW/AWM poor clusters

    NASA Astrophysics Data System (ADS)

    Beers, Timothy C.; Kriessler, Jeffrey R.; Bird, Christina M.; Huchra, John P.

    1995-03-01

    We report 472 new redshifts for 416 galaxies in the regions of the 23 poor clusters of galaxies originally identified by Morgan, Kayser, and White (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poor clusters now have 10 or more available redshifts within 1.5/h Mpc of the central galaxy; 11 clusters have at least 20 available redshifts. Based on the 21 clusters for which we have sufficient velocity information, the median velocity scale is 336 km/s, a factor of 2 smaller than found for rich clusters. Several of the poor clusters exhibit complex velocity distributions due to the presence of nearby clumps of galaxies. We check on the velocity of the dominant galaxy in each poor cluster relative to the remaining cluster members. Significantly high relative velocities of the dominant galaxy are found in only 4 of 21 poor clusters, 3 of which we suspect are due to contamination of the parent velocity distribution. Several statistical tests indicate that the D/cD galaxies are at the kinematic centers of the parent poor cluster velocity distributions. Mass-to-light ratios for 13 of the 15 poor clusters for which we have the required data are in the range 50 less than or = M/LB(0) less than or = 200 solar mass/solar luminosity. The complex nature of the regions surrounding many of the poor clusters suggests that these groupings may represent an early epoch of cluster formation. For example, the poor clusters MKW7 and MKWS are shown to be gravitationally bound and likely to merge to form a richer cluster within the next several Gyrs. Eight of the nine other poor clusters for which simple two-body dynamical models can be carried out are consistent with being bound to other clumps in their vicinity. Additional complex systems with more than two gravitationally bound clumps are observed among the poor clusters.

  5. Clusters of mobile molecules in supercooled water

    NASA Astrophysics Data System (ADS)

    Giovambattista, Nicolas; Buldyrev, Sergey V.; Stanley, H. Eugene; Starr, Francis W.

    2005-07-01

    We study the spatially heterogeneous dynamics in water via molecular dynamics simulations using the extended simple point charge potential. We identify clusters formed by mobile molecules and study their properties. We find that these clusters grow in size and become more compact as temperature decreases. We analyze the probability density function of cluster size, and we study the cluster correlation length. We find that clusters appear to be characterized by a fractal dimension consistent with that of lattice animals. We relate the cluster size and correlation length to the configurational entropy, Sconf . We find that these quantities depend weakly on 1/Sconf . In particular, the linearity found between the cluster mass n* and 1/Sconf suggests that n* may be interpreted as the mass of the cooperatively rearranging regions that form the basis of the Adam-Gibbs approach to the dynamics of supercooled liquids. We study the motion of molecules within a cluster, and find that each molecule preferentially follows a neighboring molecule in the same cluster. Based on this finding we hypothesize that stringlike cooperative motion may be a general mechanism for molecular rearrangement of complex, as well as simple liquids. By mapping each equilibrium configuration onto its corresponding local potential energy minimum or inherent structure (IS), we are able to compare the mobile molecule clusters in the equilibrium system with the molecules forming the clusters identified in the transitions between IS. We find that (i) mobile molecule clusters obtained by comparing different system configurations and (ii) clusters obtained by comparing the corresponding IS are completely different for short time scales, but are the same on the longer time scales of diffusive motion.

  6. Foodservice Occupations Cluster Guide.

    ERIC Educational Resources Information Center

    Oregon State Dept. of Education, Salem.

    Intended to assist vocational teachers in developing and implementing a cluster program in food service occupations, this guide contains sections on cluster organization and implementation and instructional emphasis areas. The cluster organization and implementation section covers goal-based planning and includes a proposed cluster curriculum, a…

  7. Cluster-impact fusion

    SciTech Connect

    Echenique, P.M.; Manson, J.R.; Ritchie, R.H. )

    1990-03-19

    We present a model for the cluster-impact-fusion experiments of Buehler, Friedlander, and Friedman, Calculated fusion rates as a function of bombarding energy for constant cluster size agree well with experiment. The dependence of the fusion rate on cluster size at fixed bombarding energy is explained qualitatively. The role of correlated, coherent collisions in enhanced energy loss by clusters is emphasized.

  8. DNA templates silver clusters with magic sizes and colors for multi-cluster fluorescent assemblies

    NASA Astrophysics Data System (ADS)

    Copp, Stacy

    2015-03-01

    The natural inclusion of information in DNA, a vital part of life's rich complexity, can also be exploited to create diverse structures with multiple scales of complexity. Now emerging in novel photonic applications, DNA-stabilized silver clusters (AgN-DNA) are compelling examples of multi-scale DNA-directed assembly: individual fluorescent clusters, each templated by specific DNA base motifs, can then be arranged together in DNA-mediated multi-cluster assemblies with nanoscale precision. We discuss how DNA imbues AgN-DNA with unique features. Our optical data on pure AgN-DNA show that DNA base-cationic silver ligands impose rod-like shapes for neutral silver clusters, whose length primarily determines fluorescence color. This shape anisotropy leads to the aspherical AgN-DNA magic number cluster sizes and ``magic color'' groupings. We exploit DNA's sequence properties to extract multi-base motifs that select certain magic cluster sizes, using machine learning algorithms applied to large data sets. With these base motifs, we design DNA scaffolds to arrange multiple atomically precise AgN together in nanoscale proximity. We demonstrate that clusters are stable when held at separations below 10 nm, both in bicolor, dual cluster DNA clamp assemblies and in one-dimensional assemblies of atomically precise clusters arrayed on DNA nanotubes. Supported by NSF-CHE-1213895 and NSF-DMR-1309410. SMC acknowledges NSF-DGE-1144085, a NSF GRFP.

  9. Uranium pyrophosphate / methylenediphosphonate polyoxometalate cage clusters

    SciTech Connect

    Ling, Jie; Qiu, Jie; Sigmon, Ginger E.; Ward, Matt; Szymanowski, Jennifer E.S.; Burns, Peter C

    2010-09-29

    Despite potential applications in advanced nuclear energy systems, nanoscale control of uranium materials is in its infancy. In its hexavalent state, U occurs as (UO{sub 2}){sup 2+} uranyl ions that are coordinated by various ligands to give square, pentagonal, or hexagonal bipyramids. Creation and design of nanostructured uranyl materials requires interruption of the tendency of uranyl bipyramids to share equatorial edges to form infinite sheets that occur in extended structures. Where a bidentate peroxide group bridges uranyl bipyramids, the configuration is inherently bent, fostering formation of cage clusters. Here the bent configurations of four- and five-membered rings of uranyl peroxide hexagonal bipyramids are bridged by pyrophosphate or methylenediphosphonate, creating eight chemically complex cage clusters with specific topologies. Chemical complexity in such clusters provides opportunities for the tuning of cage sizes, pore sizes, and properties such as aqueous solubility. Several of these are topological derivatives of simpler clusters that contain only uranyl bipyramids, whereas others exhibit new topologies.

  10. Survey on granularity clustering.

    PubMed

    Ding, Shifei; Du, Mingjing; Zhu, Hong

    2015-12-01

    With the rapid development of uncertain artificial intelligent and the arrival of big data era, conventional clustering analysis and granular computing fail to satisfy the requirements of intelligent information processing in this new case. There is the essential relationship between granular computing and clustering analysis, so some researchers try to combine granular computing with clustering analysis. In the idea of granularity, the researchers expand the researches in clustering analysis and look for the best clustering results with the help of the basic theories and methods of granular computing. Granularity clustering method which is proposed and studied has attracted more and more attention. This paper firstly summarizes the background of granularity clustering and the intrinsic connection between granular computing and clustering analysis, and then mainly reviews the research status and various methods of granularity clustering. Finally, we analyze existing problem and propose further research. PMID:26557926

  11. Dynamic multifactor clustering of financial networks.

    PubMed

    Ross, Gordon J

    2014-02-01

    We investigate the tendency for financial instruments to form clusters when there are multiple factors influencing the correlation structure. Specifically, we consider a stock portfolio which contains companies from different industrial sectors, located in several different countries. Both sector membership and geography combine to create a complex clustering structure where companies seem to first be divided based on sector, with geographical subclusters emerging within each industrial sector. We argue that standard techniques for detecting overlapping clusters and communities are not able to capture this type of structure and show how robust regression techniques can instead be used to remove the influence of both sector and geography from the correlation matrix separately. Our analysis reveals that prior to the 2008 financial crisis, companies did not tend to form clusters based on geography. This changed immediately following the crisis, with geography becoming a more important determinant of clustering structure. PMID:25353536

  12. Dynamic multifactor clustering of financial networks

    NASA Astrophysics Data System (ADS)

    Ross, Gordon J.

    2014-02-01

    We investigate the tendency for financial instruments to form clusters when there are multiple factors influencing the correlation structure. Specifically, we consider a stock portfolio which contains companies from different industrial sectors, located in several different countries. Both sector membership and geography combine to create a complex clustering structure where companies seem to first be divided based on sector, with geographical subclusters emerging within each industrial sector. We argue that standard techniques for detecting overlapping clusters and communities are not able to capture this type of structure and show how robust regression techniques can instead be used to remove the influence of both sector and geography from the correlation matrix separately. Our analysis reveals that prior to the 2008 financial crisis, companies did not tend to form clusters based on geography. This changed immediately following the crisis, with geography becoming a more important determinant of clustering structure.

  13. Swarm Intelligence in Text Document Clustering

    SciTech Connect

    Cui, Xiaohui; Potok, Thomas E

    2008-01-01

    Social animals or insects in nature often exhibit a form of emergent collective behavior. The research field that attempts to design algorithms or distributed problem-solving devices inspired by the collective behavior of social insect colonies is called Swarm Intelligence. Compared to the traditional algorithms, the swarm algorithms are usually flexible, robust, decentralized and self-organized. These characters make the swarm algorithms suitable for solving complex problems, such as document collection clustering. The major challenge of today's information society is being overwhelmed with information on any topic they are searching for. Fast and high-quality document clustering algorithms play an important role in helping users to effectively navigate, summarize, and organize the overwhelmed information. In this chapter, we introduce three nature inspired swarm intelligence clustering approaches for document clustering analysis. These clustering algorithms use stochastic and heuristic principles discovered from observing bird flocks, fish schools and ant food forage.

  14. Numerical Flow Visualization in Basic- and Hyper-Cluster Spheres

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.; Athavale, M. M.; Braun, M. J.; Lattime, S.

    1997-01-01

    Packed spherical particle beds have wide applications throughout the process industry and are usually analyzed using an appropriate combination of laminar and turbulent flows with empirically derived coefficients of which the Ergun (1952) relation is probably the best known. The 3-D complexity of the void distribution within the beds has precluded detailed studies of sphere clusters. Numerical modeling and flow vector visualization for the basic tetra- and hexa-sphere clusters and two hyper-sphere clusters are presented at two Reynolds numbers, 400 and 1200. Cutting planes are used to enable visualization of the complex flows generated within the sphere clusters and are discussed herein. The boundary conditions and flow fields for the simple clusters are also compared to the hyper-clusters with larger variations found for hexa-clusters.

  15. Photodissociation of (SO{sub 2}⋯XH) Van der Waals complexes and clusters (XH = C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, C{sub 2}H{sub 6}) excited at 32 040–32 090 cm{sup −1} with formation of HSO{sub 2} and X

    SciTech Connect

    Makarov, Vladimir I.; Kochubei, Sergei A.; Khmelinskii, Igor

    2014-02-07

    We studied photodecomposition dynamics of (SO{sub 2}⋯XH) Van der Waals’ (VdW) complexes and clusters in gas phase, with X = C{sub 2}H, C{sub 2}H{sub 3}, and C{sub 2}H{sub 5}. SO{sub 2} was excited by frequency-doubled radiation of a tunable dye laser and resonance-enhanced multiphoton ionization was used to detect the C{sub 2}H (m/z 25), C{sub 2}H{sub 3} (m/z 27), and C{sub 2}H{sub 5} (m/z 29) ions by time-of-flight mass spectroscopy. Spectra obtained at higher nozzle pressures (P{sub 0} > 2.5 atm) indicate formation of clusters. Detailed studies of the VdW complex structure were carried out by analyzing the rotational structure of the respective action spectra. We also performed ab initio theoretical analysis of structures of the VdW complexes and transitional states leading to photodecomposition. We find that the structure of the transition state is significantly different as compared to the equilibrium ground-state structure of the respective complex. The photodecomposition mechanism depends on the hydrocarbon molecule bound to SO{sub 2}.

  16. Cluster Morphology Analysis

    PubMed Central

    Jacquez, Geoffrey M.

    2009-01-01

    Most disease clustering methods assume specific shapes and do not evaluate statistical power using the applicable geography, at-risk population, and covariates. Cluster Morphology Analysis (CMA) conducts power analyses of alternative techniques assuming clusters of different relative risks and shapes. Results are ranked by statistical power and false positives, under the rationale that surveillance should (1) find true clusters while (2) avoiding false clusters. CMA then synthesizes results of the most powerful methods. CMA was evaluated in simulation studies and applied to pancreatic cancer mortality in Michigan, and finds clusters of flexible shape while routinely evaluating statistical power. PMID:20234799

  17. Hierarchical link clustering algorithm in networks

    NASA Astrophysics Data System (ADS)

    Bodlaj, Jernej; Batagelj, Vladimir

    2015-06-01

    Hierarchical network clustering is an approach to find tightly and internally connected clusters (groups or communities) of nodes in a network based on its structure. Instead of nodes, it is possible to cluster links of the network. The sets of nodes belonging to clusters of links can overlap. While overlapping clusters of nodes are not always expected, they are natural in many applications. Using appropriate dissimilarity measures, we can complement the clustering strategy to consider, for example, the semantic meaning of links or nodes based on their properties. We propose a new hierarchical link clustering algorithm which in comparison to existing algorithms considers node and/or link properties (descriptions, attributes) of the input network alongside its structure using monotonic dissimilarity measures. The algorithm determines communities that form connected subnetworks (relational constraint) containing locally similar nodes with respect to their description. It is only implicitly based on the corresponding line graph of the input network, thus reducing its space and time complexities. We investigate both complexities analytically and statistically. Using provided dissimilarity measures, our algorithm can, in addition to the general overlapping community structure of input networks, uncover also related subregions inside these communities in a form of hierarchy. We demonstrate this ability on real-world and artificial network examples.

  18. Hierarchical link clustering algorithm in networks.

    PubMed

    Bodlaj, Jernej; Batagelj, Vladimir

    2015-06-01

    Hierarchical network clustering is an approach to find tightly and internally connected clusters (groups or communities) of nodes in a network based on its structure. Instead of nodes, it is possible to cluster links of the network. The sets of nodes belonging to clusters of links can overlap. While overlapping clusters of nodes are not always expected, they are natural in many applications. Using appropriate dissimilarity measures, we can complement the clustering strategy to consider, for example, the semantic meaning of links or nodes based on their properties. We propose a new hierarchical link clustering algorithm which in comparison to existing algorithms considers node and/or link properties (descriptions, attributes) of the input network alongside its structure using monotonic dissimilarity measures. The algorithm determines communities that form connected subnetworks (relational constraint) containing locally similar nodes with respect to their description. It is only implicitly based on the corresponding line graph of the input network, thus reducing its space and time complexities. We investigate both complexities analytically and statistically. Using provided dissimilarity measures, our algorithm can, in addition to the general overlapping community structure of input networks, uncover also related subregions inside these communities in a form of hierarchy. We demonstrate this ability on real-world and artificial network examples. PMID:26172761

  19. Universal Cluster Deposition System

    NASA Astrophysics Data System (ADS)

    Qiang, You; Sun, Zhiguang; Sellmyer, David J.

    2001-03-01

    We have developed a universal cluster deposition system (UCDS), which combines a new kind of sputtering-gas-aggregation (SGA) cluster beam source with two atom beams from magnetron sputtering. A highly intense, very stable beam of nanoclusters (like Co, Fe, Ni, Si, CoSm or CoPt) are produced. A quadrupole and/or a new high transmission infinite range mass selector have been designed for the cluster beam. The size distribution (Δd/d) is between 0.05+/-0.10, measured in situ by TOF. A range of mean cluster size is 2 to 10 nm. Usually the deposition rate is about 5 deg/s. The cluster concentration in the film is adjusted through the ratio of cluster and atomic beam deposition rates, as measured in situ with a rotatable quartz microbalance. The UCDS can be used to prepare coated clusters. After exiting from the cluster source, the clusters can be coated first with an atomic or molecular species in an evaporation chamber, and deposited alone or co-deposited with another material. This system is used to deposit simultaneously or alternately mesoscopic thin films or multilayers, and offers the possibility to control independently the incident cluster size and concentration, and thereby the interaction between clusters and cluster-matrix material which is of interest for fundamental research and industry applications. Magnetic properties of Co cluster-assembled materials will be discussed. * Research supported by NSF, DARPA through ARO, and CMRA

  20. EINSTEIN Cluster Alignments Revisited

    NASA Astrophysics Data System (ADS)

    Chambers, S. W.; Melott, A. L.; Miller, C. J.

    2000-12-01

    We have examined whether the major axes of rich galaxy clusters tend to point (in projection) toward their nearest neighboring cluster. We used the data of Ulmer, McMillan and Kowalski, who used x-ray morphology to define position angles. Our cluster samples, with well measured redshifts and updated positions, were taken from the MX Northern Abell Cluster Survey. The usual Kolmogorov-Smirnov test shows no significant alignment signal for nonrandom angles for all separations less than 100 Mpc/h. Refining the null hypothesis, however, with the Wilcoxon rank-sum test, reveals a high confidence signal for alignment. This confidence is highest when we restrict our sample to small nearest neighbor separations. We conclude that we have identified a more powerful tool for testing cluster-cluster alignments. Moreover, there is a strong signal in the data for alignment, consistent with a picture of hierarchical cluster formation in which matter falls into clusters along large scale filamentary structures.

  1. Matlab Cluster Ensemble Toolbox

    SciTech Connect

    Sapio, Vincent De; Kegelmeyer, Philip

    2009-04-27

    This is a Matlab toolbox for investigating the application of cluster ensembles to data classification, with the objective of improving the accuracy and/or speed of clustering. The toolbox divides the cluster ensemble problem into four areas, providing functionality for each. These include, (1) synthetic data generation, (2) clustering to generate individual data partitions and similarity matrices, (3) consensus function generation and final clustering to generate ensemble data partitioning, and (4) implementation of accuracy metrics. With regard to data generation, Gaussian data of arbitrary dimension can be generated. The kcenters algorithm can then be used to generate individual data partitions by either, (a) subsampling the data and clustering each subsample, or by (b) randomly initializing the algorithm and generating a clustering for each initialization. In either case an overall similarity matrix can be computed using a consensus function operating on the individual similarity matrices. A final clustering can be performed and performance metrics are provided for evaluation purposes.

  2. Star clusters as simple stellar populations.

    PubMed

    Bruzual A, Gustavo

    2010-02-28

    In this paper, I review to what extent we can understand the photometric properties of star clusters, and of low-mass, unresolved galaxies, in terms of population-synthesis models designed to describe 'simple stellar populations' (SSPs), i.e. groups of stars born at the same time, in the same volume of space and from a gas cloud of homogeneous chemical composition. The photometric properties predicted by these models do not readily match the observations of most star clusters, unless we properly take into account the expected variation in the number of stars occupying sparsely populated evolutionary stages, owing to stochastic fluctuations in the stellar initial mass function. In this case, population-synthesis models reproduce remarkably well the full ranges of observed integrated colours and absolute magnitudes of star clusters of various ages and metallicities. The disagreement between the model predictions and observations of cluster colours and magnitudes may indicate problems with or deficiencies in the modelling, and does not necessarily tell us that star clusters do not behave like SSPs. Matching the photometric properties of star clusters using SSP models is a necessary (but not sufficient) condition for clusters to be considered SSPs. Composite models, characterized by complex star-formation histories, also match the observed cluster colours. PMID:20083506

  3. Grid Computing Environment using a Beowulf Cluster

    NASA Astrophysics Data System (ADS)

    Alanis, Fransisco; Mahmood, Akhtar

    2003-10-01

    Custom-made Beowulf clusters using PCs are currently replacing expensive supercomputers to carry out complex scientific computations. At the University of Texas - Pan American, we built a 8 Gflops Beowulf Cluster for doing HEP research using RedHat Linux 7.3 and the LAM-MPI middleware. We will describe how we built and configured our Cluster, which we have named the Sphinx Beowulf Cluster. We will describe the results of our cluster benchmark studies and the run-time plots of several parallel application codes that were compiled in C on the cluster using the LAM-XMPI graphics user environment. We will demonstrate a "simple" prototype grid environment, where we will submit and run parallel jobs remotely across multiple cluster nodes over the internet from the presentation room at Texas Tech. University. The Sphinx Beowulf Cluster will be used for monte-carlo grid test-bed studies for the LHC-ATLAS high energy physics experiment. Grid is a new IT concept for the next generation of the "Super Internet" for high-performance computing. The Grid will allow scientist worldwide to view and analyze huge amounts of data flowing from the large-scale experiments in High Energy Physics. The Grid is expected to bring together geographically and organizationally dispersed computational resources, such as CPUs, storage systems, communication systems, and data sources.

  4. Incremental Clustering Algorithm For Earth Science Data Mining

    SciTech Connect

    Vatsavai, Raju

    2009-01-01

    Remote sensing data plays a key role in understanding the complex geographic phenomena. Clustering is a useful tool in discovering interesting patterns and structures within the multivariate geospatial data. One of the key issues in clustering is the specication of appropriate number of clusters, which is not obvious in many practical situations. In this paper we provide an extension of G-means algorithm which automatically learns the number of clusters present in the data and avoids over estimation of the number of clusters. Experimental evaluation on simulated and remotely sensed image data shows the effectiveness of our algorithm.

  5. [Pathophysiology of cluster headache].

    PubMed

    Donnet, Anne

    2015-11-01

    The aetiology of cluster headache is partially unknown. Three areas are involved in the pathogenesis of cluster headache: the trigeminal nociceptive pathways, the autonomic system and the hypothalamus. The cluster headache attack involves activation of the trigeminal autonomic reflex. A dysfunction located in posterior hypothalamic gray matter is probably pivotal in the process. There is a probable association between smoke exposure, a possible genetic predisposition and the development of cluster headache. PMID:26470883

  6. CLUSTERING OF RARE EVENTS

    EPA Science Inventory

    The clustering of cases of a rare disease is considered. The number of events observed for each unit is assumed to have a Poisson distribution, the mean of which depends upon the population size and the cluster membership of that unit. Here a cluster consists of those units that ...

  7. Improved Ant Colony Clustering Algorithm and Its Performance Study.

    PubMed

    Gao, Wei

    2016-01-01

    Clustering analysis is used in many disciplines and applications; it is an important tool that descriptively identifies homogeneous groups of objects based on attribute values. The ant colony clustering algorithm is a swarm-intelligent method used for clustering problems that is inspired by the behavior of ant colonies that cluster their corpses and sort their larvae. A new abstraction ant colony clustering algorithm using a data combination mechanism is proposed to improve the computational efficiency and accuracy of the ant colony clustering algorithm. The abstraction ant colony clustering algorithm is used to cluster benchmark problems, and its performance is compared with the ant colony clustering algorithm and other methods used in existing literature. Based on similar computational difficulties and complexities, the results show that the abstraction ant colony clustering algorithm produces results that are not only more accurate but also more efficiently determined than the ant colony clustering algorithm and the other methods. Thus, the abstraction ant colony clustering algorithm can be used for efficient multivariate data clustering. PMID:26839533

  8. Improved Ant Colony Clustering Algorithm and Its Performance Study

    PubMed Central

    Gao, Wei

    2016-01-01

    Clustering analysis is used in many disciplines and applications; it is an important tool that descriptively identifies homogeneous groups of objects based on attribute values. The ant colony clustering algorithm is a swarm-intelligent method used for clustering problems that is inspired by the behavior of ant colonies that cluster their corpses and sort their larvae. A new abstraction ant colony clustering algorithm using a data combination mechanism is proposed to improve the computational efficiency and accuracy of the ant colony clustering algorithm. The abstraction ant colony clustering algorithm is used to cluster benchmark problems, and its performance is compared with the ant colony clustering algorithm and other methods used in existing literature. Based on similar computational difficulties and complexities, the results show that the abstraction ant colony clustering algorithm produces results that are not only more accurate but also more efficiently determined than the ant colony clustering algorithm and the other methods. Thus, the abstraction ant colony clustering algorithm can be used for efficient multivariate data clustering. PMID:26839533

  9. The C4 clustering algorithm: Clusters of galaxies in the Sloan Digital Sky Survey

    SciTech Connect

    Miller, Christopher J.; Nichol, Robert; Reichart, Dan; Wechsler, Risa H.; Evrard, August; Annis, James; McKay, Timothy; Bahcall, Neta; Bernardi, Mariangela; Boehringer, Hans; Connolly, Andrew; Goto, Tomo; Kniazev, Alexie; Lamb, Donald; Postman, Marc; Schneider, Donald; Sheth, Ravi; Voges, Wolfgang; /Cerro-Tololo InterAmerican Obs. /Portsmouth U., ICG /North Carolina U. /Chicago U., Astron. Astrophys. Ctr. /Chicago U., EFI /Michigan U. /Fermilab /Princeton U. Observ. /Garching, Max Planck Inst., MPE /Pittsburgh U. /Tokyo U., ICRR /Baltimore, Space Telescope Sci. /Penn State U. /Chicago U. /Stavropol, Astrophys. Observ. /Heidelberg, Max Planck Inst. Astron. /INI, SAO

    2005-03-01

    exclude clusters embedded in complex large-scale environments, we find that the velocity dispersion of the remaining clusters is as good an estimator of M{sub 200} as L{sub r}. The final C4 catalog will contain {approx_equal} 2500 clusters using the full SDSS data set and will represent one of the largest and most homogeneous samples of local clusters.

  10. A new clustering strategy

    NASA Astrophysics Data System (ADS)

    Feng, Jian-xin; Tang, Jia-fu; Wang, Guang-xing

    2007-04-01

    On the basis of the analysis of clustering algorithm that had been proposed for MANET, a novel clustering strategy was proposed in this paper. With the trust defined by statistical hypothesis in probability theory and the cluster head selected by node trust and node mobility, this strategy can realize the function of the malicious nodes detection which was neglected by other clustering algorithms and overcome the deficiency of being incapable of implementing the relative mobility metric of corresponding nodes in the MOBIC algorithm caused by the fact that the receiving power of two consecutive HELLO packet cannot be measured. It's an effective solution to cluster MANET securely.

  11. Unconventional methods for clustering

    NASA Astrophysics Data System (ADS)

    Kotyrba, Martin

    2016-06-01

    Cluster analysis or clustering is a task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to those in other groups (clusters). It is the main task of exploratory data mining and a common technique for statistical data analysis used in many fields, including machine learning, pattern recognition, image analysis, information retrieval, and bioinformatics. The topic of this paper is one of the modern methods of clustering namely SOM (Self Organising Map). The paper describes the theory needed to understand the principle of clustering and descriptions of algorithm used with clustering in our experiments.

  12. Stability of Phosphine-Ligated Gold Cluster Ions toward Dissociation: Effect of Ligand and Cluster Size

    NASA Astrophysics Data System (ADS)

    Laskin, Julia

    2015-03-01

    Precise control of the composition of phosphine-ligated gold clusters is of interest to their applications in catalysis, sensing, and drug delivery. Reduction synthesis in solution typically generates a distribution of ligated clusters containing different number of gold atoms and capping ligands. Ligand binding energy is an important factor determining the kinetics of cluster nucleation and growth in solution and hence the resulting cluster distribution. Phosphines are popular capping ligands with tunable electronic and steric properties that affect their binding to the gold core. We examined the effect of the number of gold atoms in the cluster and the properties of the phosphine ligand on the ligand binding energy to the gold core using surface-induced dissociation (SID) of mass selected cluster cations produced through electrospray ionization. SID of vibrationally excited ions is ideally suited for studying gas-phase fragmentation of complex ions such as ligated gold clusters. The energetics, dynamics, and mechanisms of cluster ion fragmentation in the absence of solvent are determined through RRKM modeling of time and kinetic energy dependent SID spectra. This approach provides quantitative information on the ligand binding energies in phosphine-ligated gold clusters important for understanding their formation in solution. Furthermore, ligand binding energies derived from SID data provide the first benchmark values for comparison with electronic structure calculations. This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences.

  13. Large-Scale Multi-Dimensional Document Clustering on GPU Clusters

    SciTech Connect

    Cui, Xiaohui; Mueller, Frank; Zhang, Yongpeng; Potok, Thomas E

    2010-01-01

    Document clustering plays an important role in data mining systems. Recently, a flocking-based document clustering algorithm has been proposed to solve the problem through simulation resembling the flocking behavior of birds in nature. This method is superior to other clustering algorithms, including k-means, in the sense that the outcome is not sensitive to the initial state. One limitation of this approach is that the algorithmic complexity is inherently quadratic in the number of documents. As a result, execution time becomes a bottleneck with large number of documents. In this paper, we assess the benefits of exploiting the computational power of Beowulf-like clusters equipped with contemporary Graphics Processing Units (GPUs) as a means to significantly reduce the runtime of flocking-based document clustering. Our framework scales up to over one million documents processed simultaneously in a sixteennode GPU cluster. Results are also compared to a four-node cluster with higher-end GPUs. On these clusters, we observe 30X-50X speedups, which demonstrates the potential of GPU clusters to efficiently solve massive data mining problems. Such speedups combined with the scalability potential and accelerator-based parallelization are unique in the domain of document-based data mining, to the best of our knowledge.

  14. Dynamically allocated virtual clustering management system

    NASA Astrophysics Data System (ADS)

    Marcus, Kelvin; Cannata, Jess

    2013-05-01

    The U.S Army Research Laboratory (ARL) has built a "Wireless Emulation Lab" to support research in wireless mobile networks. In our current experimentation environment, our researchers need the capability to run clusters of heterogeneous nodes to model emulated wireless tactical networks where each node could contain a different operating system, application set, and physical hardware. To complicate matters, most experiments require the researcher to have root privileges. Our previous solution of using a single shared cluster of statically deployed virtual machines did not sufficiently separate each user's experiment due to undesirable network crosstalk, thus only one experiment could be run at a time. In addition, the cluster did not make efficient use of our servers and physical networks. To address these concerns, we created the Dynamically Allocated Virtual Clustering management system (DAVC). This system leverages existing open-source software to create private clusters of nodes that are either virtual or physical machines. These clusters can be utilized for software development, experimentation, and integration with existing hardware and software. The system uses the Grid Engine job scheduler to efficiently allocate virtual machines to idle systems and networks. The system deploys stateless nodes via network booting. The system uses 802.1Q Virtual LANs (VLANs) to prevent experimentation crosstalk and to allow for complex, private networks eliminating the need to map each virtual machine to a specific switch port. The system monitors the health of the clusters and the underlying physical servers and it maintains cluster usage statistics for historical trends. Users can start private clusters of heterogeneous nodes with root privileges for the duration of the experiment. Users also control when to shutdown their clusters.

  15. Cluster randomized trials for pharmacy practice research.

    PubMed

    Gums, Tyler; Carter, Barry; Foster, Eric

    2016-06-01

    Introduction Cluster randomized trials (CRTs) are now the gold standard in health services research, including pharmacy-based interventions. Studies of behaviour, epidemiology, lifestyle modifications, educational programs, and health care models are utilizing the strengths of cluster randomized analyses. Methodology The key property of CRTs is the unit of randomization (clusters), which may be different from the unit of analysis (individual). Subject sample size and, ideally, the number of clusters is determined by the relationship of between-cluster and within-cluster variability. The correlation among participants recruited from the same cluster is known as the intraclass correlation coefficient (ICC). Generally, having more clusters with smaller ICC values will lead to smaller sample sizes. When selecting clusters, stratification before randomization may be useful in decreasing imbalances between study arms. Participant recruitment methods can differ from other types of randomized trials, as blinding a behavioural intervention cannot always be done. When to use CRTs can yield results that are relevant for making "real world" decisions. CRTs are often used in non-therapeutic intervention studies (e.g. change in practice guidelines). The advantages of CRT design in pharmacy research have been avoiding contamination and the generalizability of the results. A large CRT that studied physician-pharmacist collaborative management of hypertension is used in this manuscript as a CRT example. The trial, entitled Collaboration Among Pharmacists and physicians To Improve Outcomes Now (CAPTION), was implemented in primary care offices in the United States for hypertensive patients. Limitations CRT design limitations include the need for a large number of clusters, high costs, increased training, increased monitoring, and statistical complexity. PMID:26715549

  16. Modeling Clustered Data with Very Few Clusters.

    PubMed

    McNeish, Daniel; Stapleton, Laura M

    2016-01-01

    Small-sample inference with clustered data has received increased attention recently in the methodological literature, with several simulation studies being presented on the small-sample behavior of many methods. However, nearly all previous studies focus on a single class of methods (e.g., only multilevel models, only corrections to sandwich estimators), and the differential performance of various methods that can be implemented to accommodate clustered data with very few clusters is largely unknown, potentially due to the rigid disciplinary preferences. Furthermore, a majority of these studies focus on scenarios with 15 or more clusters and feature unrealistically simple data-generation models with very few predictors. This article, motivated by an applied educational psychology cluster randomized trial, presents a simulation study that simultaneously addresses the extreme small sample and differential performance (estimation bias, Type I error rates, and relative power) of 12 methods to account for clustered data with a model that features a more realistic number of predictors. The motivating data are then modeled with each method, and results are compared. Results show that generalized estimating equations perform poorly; the choice of Bayesian prior distributions affects performance; and fixed effect models perform quite well. Limitations and implications for applications are also discussed. PMID:27269278

  17. A perfect starburst cluster made in one go: The NGC 3603 young cluster

    SciTech Connect

    Banerjee, Sambaran; Kroupa, Pavel

    2014-06-01

    Understanding how distinct, near-spherical gas-free clusters of very young, massive stars shape out of vast, complex clouds of molecular hydrogen is one of the biggest challenges in astrophysics. A popular thought dictates that a single gas cloud fragments into many newborn stars which, in turn, energize and rapidly expel the residual gas to form a gas-free cluster. This study demonstrates that the above classical paradigm remarkably reproduces the well-observed central, young cluster (HD 97950) of the Galactic NGC 3603 star-forming region, in particular, its shape, internal motion, and mass distribution of stars naturally and consistently follow from a single model calculation. Remarkably, the same parameters (star formation efficiency, gas expulsion timescale, and delay) reproduce HD 97950, as were found to reproduce the Orion Nebula Cluster, Pleiades, and R136. The present results therefore provide intriguing evidence of formation of star clusters through single-starburst events followed by significant residual gas expulsion.

  18. [Clustering of simple obesity].

    PubMed

    Yoshida, K; Matsuda, H; Kurita, M; Umetada, Y

    1988-05-01

    An attempt was made to classify persons with simple obesity from the viewpoint of health education. Subjects of the study were 1,278 male workers in a financing company who underwent health examination. At the time of health examinations, questionnaire survey concerning their life styles was carried out on all the subjects. The obese group consisted of 127 subjects whose obesity indices were over 15% and the control group consisted of 342 subjects whose obesity indices ranged from -5 to 5%. Subjects in the obese group were classified into four clusters based on cluster analysis using five life-style parameters; that is, frequency of taking breakfast, frequency of taking staple food, drinking habits, smoking habits, and frequency of exercise. The first cluster (N = 10) included inactive persons, the second cluster (N = 46) non smokers, the third cluster (N = 39) smokers and heavy drinkers, and the fourth cluster (N = 32) smokers and non-drinkers. Comparison of the four clusters of obese persons with the control group revealed the following findings: 1) All the four clusters had significantly high frequencies of abnormal values of triglyceride (TG) and fasting blood sugar (FBS). 2) The first cluster had significantly high frequencies of abnormal values of glutamic oxalacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT). 3) The second cluster had significantly high frequencies of abnormal values of systolic and diastolic blood pressure, total cholesterol, TG, FBS, uric acid, GOT, GPT and gamma glutamyl transferase (GGT).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3172544

  19. Beyond organic chemistry: aromaticity in atomic clusters.

    PubMed

    Boldyrev, Alexander I; Wang, Lai-Sheng

    2016-04-28

    We describe joint experimental and theoretical studies carried out collaboratively in the authors' labs for understanding the structures and chemical bonding of novel atomic clusters, which exhibit aromaticity. The concept of aromaticity was first discovered to be useful in understanding the square-planar unit of Al4 in a series of MAl4(-) bimetallic clusters that led to discoveries of aromaticity in many metal cluster systems, including transition metals and similar cluster motifs in solid compounds. The concept of aromaticity has been found to be particularly powerful in understanding the stability and bonding in planar boron clusters, many of which have been shown to be analogous to polycyclic aromatic hydrocarbons in their π bonding. Stimulated by the multiple aromaticity in planar boron clusters, a design principle has been proposed for stable metal-cerntered aromatic molecular wheels of the general formula, M@Bn(k-). A series of such borometallic aromatic wheel complexes have been produced in supersonic cluster beams and characterized experimentally and theoretically, including Ta@B10(-) and Nb@B10(-), which exhibit the highest coordination number in two dimensions. PMID:26864511

  20. Multi-level coupled cluster theory

    SciTech Connect

    Myhre, Rolf H.; Koch, Henrik; Sánchez de Merás, Alfredo M. J.

    2014-12-14

    We present a general formalism where different levels of coupled cluster theory can be applied to different parts of the molecular system. The system is partitioned into subsystems by Cholesky decomposition of the one-electron Hartree-Fock density matrix. In this way the system can be divided across chemical bonds without discontinuities arising. The coupled cluster wave function is defined in terms of cluster operators for each part and these are determined from a set of coupled equations. The total wave function fulfills the Pauli-principle across all borders and levels of electron correlation. We develop the associated response theory for this multi-level coupled cluster theory and present proof of principle applications. The formalism is an essential tool in order to obtain size-intensive complexity in the calculation of local molecular properties.

  1. Dust cluster explosion

    SciTech Connect

    Saxena, Vikrant; Avinash, K.; Sen, A.

    2012-09-15

    A model for the dust cluster explosion where micron/sub-micron sized particles are accelerated at the expense of plasma thermal energy, in the afterglow phase of a complex plasma discharge is proposed. The model is tested by molecular dynamics simulations of dust particles in a confining potential. The nature of the explosion (caused by switching off the discharge) and the concomitant dust acceleration is found to depend critically on the pressure of the background neutral gas. At low gas pressure, the explosion is due to unshielded Coulomb repulsion between dust particles and yields maximum acceleration, while in the high pressure regime it is due to shielded Yukawa repulsion and yields much feebler acceleration. These results are in agreement with experimental findings. Our simulations also confirm a recently proposed electrostatic (ES) isothermal scaling relation, P{sub E}{proportional_to}V{sub d}{sup -2} (where P{sub E} is the ES pressure of the dust particles and V{sub d} is the confining volume).

  2. Metal interactions with boron clusters

    SciTech Connect

    Grimes, R.N.

    1982-01-01

    This book presents information on the following topics: the structural and bonding features of metallaboranes and metallacarboranes; transition-metal derivatives of nido-boranes and some related species; interactions of metal groups with the octahydrotriborate (1-) anion, B/sub 3/H/sub 8/; metallaboron cage compounds of the main group metals; closo-carborane-metal complexes containing metal-carbon and metal-boron omega-bonds; electrochemistry of metallaboron cage compounds; and boron clusters with transition metal-hydrogen bonds.

  3. Multi-viewpoint clustering analysis

    NASA Technical Reports Server (NTRS)

    Mehrotra, Mala; Wild, Chris

    1993-01-01

    In this paper, we address the feasibility of partitioning rule-based systems into a number of meaningful units to enhance the comprehensibility, maintainability and reliability of expert systems software. Preliminary results have shown that no single structuring principle or abstraction hierarchy is sufficient to understand complex knowledge bases. We therefore propose the Multi View Point - Clustering Analysis (MVP-CA) methodology to provide multiple views of the same expert system. We present the results of using this approach to partition a deployed knowledge-based system that navigates the Space Shuttle's entry. We also discuss the impact of this approach on verification and validation of knowledge-based systems.

  4. CluMan - Cluster management toolsuit

    NASA Astrophysics Data System (ADS)

    Šiket, Miroslav; Babik, Marián; Lopienski, Sebastian; Borba Manana, Filipe David

    2010-04-01

    LHC computing requirements are such that the number of CPU and storage nodes, and the complexity of the services to be managed are bringing new challenges. Operations like checking configuration consistency, executing actions on nodes, moving them between clusters etc. are very frequent. These scaling challenges are the basis for CluMan, a new cluster management tool being designed and developed at CERN. High-density displays such as heat maps, grids or color maps are more and more commonly used in various applications like data visualization or monitoring systems. They allow humans to see, interpret and understand complex and detailed information at a glance. We propose to present the ideas behind the CluMan project, and to show how high density displays are used to help service managers to understand, manage and control the state and behavior of their clusters.

  5. Radical attached aluminum nanoclusters: an alternative way of cluster stabilization.

    PubMed

    Sengupta, Turbasu; Pal, Sourav

    2016-08-21

    The stability and electronic structure of radical attached aluminum nanoclusters are investigated using density functional theory (DFT). A detailed investigation shows good correlation between the thermodynamic stability of radical attached clusters and the stability of the attached radical anions. All other calculated parameters like HOMO-LUMO gap and charge transfer are also found to be consistent with the observed thermodynamic stabilities of the complexes. Investigation of the electronic structure of radical attached complexes further shows the presence of jellium structures within the core similar to the ligated clusters. Comparison with available experimental and theoretical data also proves the validity of superatomic complex theory for the radical attached clusters as well. Based on the evaluated thermodynamic parameters, selected radical attached clusters are observed to be more thermodynamically stable in comparison with experimentally synthesized ligated clusters. Stabilization of small metal clusters is one of the greatest challenges in current cluster science and the present investigation confirms the fact that radical attached clusters can provide a viable alternative to ligated clusters in the future. PMID:27435912

  6. Electron: Cluster interactions

    SciTech Connect

    Scheidemann, A.A.; Kresin, V.V.; Knight, W.D.

    1994-02-01

    Beam depletion spectroscopy has been used to measure absolute total inelastic electron-sodium cluster collision cross sections in the energy range from E {approximately} 0.1 to E {approximately} 6 eV. The investigation focused on the closed shell clusters Na{sub 8}, Na{sub 20}, Na{sub 40}. The measured cross sections show an increase for the lowest collision energies where electron attachment is the primary scattering channel. The electron attachment cross section can be understood in terms of Langevin scattering, connecting this measurement with the polarizability of the cluster. For energies above the dissociation energy the measured electron-cluster cross section is energy independent, thus defining an electron-cluster interaction range. This interaction range increases with the cluster size.

  7. Information-based clustering

    PubMed Central

    Slonim, Noam; Atwal, Gurinder Singh; Tkačik, Gašper; Bialek, William

    2005-01-01

    In an age of increasingly large data sets, investigators in many different disciplines have turned to clustering as a tool for data analysis and exploration. Existing clustering methods, however, typically depend on several nontrivial assumptions about the structure of data. Here, we reformulate the clustering problem from an information theoretic perspective that avoids many of these assumptions. In particular, our formulation obviates the need for defining a cluster “prototype,” does not require an a priori similarity metric, is invariant to changes in the representation of the data, and naturally captures nonlinear relations. We apply this approach to different domains and find that it consistently produces clusters that are more coherent than those extracted by existing algorithms. Finally, our approach provides a way of clustering based on collective notions of similarity rather than the traditional pairwise measures. PMID:16352721

  8. Spanish Dyslexic Spelling Abilities: The Case of Consonant Clusters

    ERIC Educational Resources Information Center

    Serrano, Francisca; Defior, Sylvia

    2012-01-01

    This paper investigates Spanish dyslexic spelling abilities: specifically, the influence of syllabic linguistic structure (simple vs consonant cluster) on children's spelling performance. Consonant clusters are phonologically complex structures, so it was anticipated that there would be lower spelling performance for these syllabic structures than…

  9. Candidates for Young Super Star Clusters in the Milky Way

    NASA Astrophysics Data System (ADS)

    Rahman, Mubdi; Matzner, C. D.; Moon, D.

    2011-01-01

    Massive Star Clusters (M > 104 M⊙) have been known to exist throughout the local Universe, but few such objects have been found within our own Galaxy. These clusters the majority of the galactic OB star formation, and thus dramatically alter their surroundings through winds, ionizing flux and radiation pressure, and supernovae, eventually destroying their natal clouds and inflating superbubbles which will erupt from the Galactic plane. We search for the young stellar clusters within the star forming complexes identified by Rahman & Murray (2010) using the WMAP free-free and Spitzer GLIMPSE 8 micron observations. Located far across the Galactic plane, these clusters are highly extinguished and crowded by field stars. Using the 2MASS catalogue, we have developed a method of identifying overdensities of sources with colours consistent with the extinguished upper main sequence coincident with the star forming complexes. The difficulty in this method comes from the large number of overlapping foreground sources in comparison to the expected number of cluster sources in any given candidate cluster. We identify a candidate for the most massive young cluster in the Galaxy (M 105 M⊙), which we have dubbed the Dragonfish Cluster. The candidate cluster is at a distance of 9.7 kpc and has a total ionizing luminosity of 7×1051 photons s-1. We identify nearly 400 OB star candidates associated with the cluster, to be confirmed with near-infrared spectroscopy.

  10. Mini-clusters

    NASA Technical Reports Server (NTRS)

    Chinellato, J. A.; Dobrigkeit, C.; Bellandifilho, J.; Lattes, C. M. G.; Menon, M. J.; Navia, C. E.; Pamilaju, A.; Sawayanagi, K.; Shibuya, E. H.; Turtelli, A., Jr.

    1985-01-01

    Experimental results of mini-clusters observed in Chacaltaya emulsion chamber no.19 are summarized. The study was made on 54 single core shower upper and 91 shower clusters of E(gamma) 10 TeV from 30 families which are visible energy greater than 80 TeV and penetrate through both upper and lower detectors of the two-story chamber. The association of hadrons in mini-cluster is made clear from their penetrative nature and microscopic observation of shower continuation in lower chamber. Small P sub t (gamma) of hadrons in mini-clusters remained in puzzle.

  11. Management of cluster headache.

    PubMed

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-07-01

    The prevalence of cluster headache is 0.1% and cluster headache is often not diagnosed or misdiagnosed as migraine or sinusitis. In cluster headache there is often a considerable diagnostic delay - an average of 7 years in a population-based survey. Cluster headache is characterized by very severe or severe orbital or periorbital pain with a duration of 15-180 minutes. The cluster headache attacks are accompanied by characteristic associated unilateral symptoms such as tearing, nasal congestion and/or rhinorrhoea, eyelid oedema, miosis and/or ptosis. In addition, there is a sense of restlessness and agitation. Patients may have up to eight attacks per day. Episodic cluster headache (ECH) occurs in clusters of weeks to months duration, whereas chronic cluster headache (CCH) attacks occur for more than 1 year without remissions. Management of cluster headache is divided into acute attack treatment and prophylactic treatment. In ECH and CCH the attacks can be treated with oxygen (12 L/min) or subcutaneous sumatriptan 6 mg. For both oxygen and sumatriptan there are two randomized, placebo-controlled trials demonstrating efficacy. In both ECH and CCH, verapamil is the prophylactic drug of choice. Verapamil 360 mg/day was found to be superior to placebo in one clinical trial. In clinical practice, daily doses of 480-720 mg are mostly used. Thus, the dose of verapamil used in cluster headache treatment may be double the dose used in cardiology, and with the higher doses the PR interval should be checked with an ECG. At the start of a cluster, transitional preventive treatment such as corticosteroids or greater occipital nerve blockade can be given. In CCH and in long-standing clusters of ECH, lithium, methysergide, topiramate, valproic acid and ergotamine tartrate can be used as add-on prophylactic treatment. In drug-resistant CCH, neuromodulation with either occipital nerve stimulation or deep brain stimulation of the hypothalamus is an alternative treatment strategy

  12. The youngest globular clusters

    NASA Astrophysics Data System (ADS)

    Beck, Sara

    2015-11-01

    It is likely that all stars are born in clusters, but most clusters are not bound and disperse. None of the many protoclusters in our Galaxy are likely to develop into long-lived bound clusters. The super star clusters (SSCs) seen in starburst galaxies are more massive and compact and have better chances of survival. The birth and early development of SSCs takes place deep in molecular clouds, and during this crucial stage the embedded clusters are invisible to optical or UV observations but are studied via the radio-infrared supernebulae (RISN) they excite. We review observations of embedded clusters and identify RISN within 10 Mpc whose exciting clusters have ≈ 106 M⊙ or more in volumes of a few pc3 and which are likely to not only survive as bound clusters, but to evolve into objects as massive and compact as Galactic globulars. These clusters are distinguished by very high star formation efficiency η, at least a factor of 10 higher than the few percent seen in the Galaxy, probably due to the violent disturbances their host galaxies have undergone. We review recent observations of the kinematics of the ionized gas in RISN showing outflows through low-density channels in the ambient molecular cloud; this may protect the cloud from feedback by the embedded H II region.

  13. Clustering versus non-clustering phase synchronizations.

    PubMed

    Liu, Shuai; Zhan, Meng

    2014-03-01

    Clustering phase synchronization (CPS) is a common scenario to the global phase synchronization of coupled dynamical systems. In this work, a novel scenario, the non-clustering phase synchronization (NPS), is reported. It is found that coupled systems do not transit to the global synchronization until a certain sufficiently large coupling is attained, and there is no clustering prior to the global synchronization. To reveal the relationship between CPS and NPS, we further analyze the noise effect on coupled phase oscillators and find that the coupled oscillator system can change from CPS to NPS with the increase of noise intensity or system disorder. These findings are expected to shed light on the mechanism of various intriguing self-organized behaviors in coupled systems. PMID:24697366

  14. Clustering versus non-clustering phase synchronizations

    SciTech Connect

    Liu, Shuai; Zhan, Meng

    2014-03-15

    Clustering phase synchronization (CPS) is a common scenario to the global phase synchronization of coupled dynamical systems. In this work, a novel scenario, the non-clustering phase synchronization (NPS), is reported. It is found that coupled systems do not transit to the global synchronization until a certain sufficiently large coupling is attained, and there is no clustering prior to the global synchronization. To reveal the relationship between CPS and NPS, we further analyze the noise effect on coupled phase oscillators and find that the coupled oscillator system can change from CPS to NPS with the increase of noise intensity or system disorder. These findings are expected to shed light on the mechanism of various intriguing self-organized behaviors in coupled systems.

  15. When galaxy clusters collide: the impact of merger shocks on cluster gas and galaxy evolution

    NASA Astrophysics Data System (ADS)

    Stroe, A.

    2015-09-01

    Galaxy clusters mainly grow through mergers with other clusters and groups. Major mergers give rise to cluster-wide traveling shocks, which can be detected at radio wavelengths as relics: elongated, diffuse synchrotron emitting areas located at the periphery of merging clusters. The 'Sausage' cluster hosts an extraordinary Mpc-wide relic, which enables us to study to study particle acceleration and the effects of shocks on cluster galaxies. We derive shock properties and the magnetic field structure for the relic. Our results indicate that particles are shock-accelerated, but turbulent re-acceleration or unusually efficient transport of particles in the downstream area are important effects. We demonstrate the feasibility of high-frequency observations of radio relics, by presenting a 16 GHz detection of the 'Sausage' relic. Halpha mapping of the cluster provides the first direct test as to whether the shock drives or prohibits star formation. We find numerous galaxies in! close proximity to the radio relic which are extremely massive, metal-rich, star-forming with evidence for gas mass loss though outflows. We speculate that the complex interaction between the merger, the shock wave and gas is a fundamental driver in the evolution of cluster galaxies from gas rich spirals to gas-poor ellipticals.

  16. A nonparametric clustering technique which estimates the number of clusters

    NASA Technical Reports Server (NTRS)

    Ramey, D. B.

    1983-01-01

    In applications of cluster analysis, one usually needs to determine the number of clusters, K, and the assignment of observations to each cluster. A clustering technique based on recursive application of a multivariate test of bimodality which automatically estimates both K and the cluster assignments is presented.

  17. Reactive accelerated cluster erosion (RACE) by ionized cluster beams

    NASA Astrophysics Data System (ADS)

    Gspann, Jürgen

    1996-05-01

    Beams of ionized clusters accelerated up to about 120 keV kinetic energy per cluster are used for cluster impact lithography. Chemical reactions of clusters of CO 2, or of SF 6, respectively, are found to assist the physical erosion by hypervelocity cluster impacts in yielding volatile products. Natural diamond, silicon and Pyrex glass have been microstructured showing very smooth eroded surfaces.

  18. The transformation of organic amines by transition metal cluster compounds. Progress report, 1992--1993

    SciTech Connect

    Adams, R.D.

    1993-01-01

    The paper reports results on the following five studies: (1) The activation of tertiary amines by osmium cluster complexes; (2) Nucleophilic ring opening of thietane ligand in metal carbonyl cluster complexes; (3) Ring opening of a nitrogen containing strained ring heterocycle by an osmium cluster complex; (4) Insertion of an alkynes into a metal-metal bond -- evidence for an intramolecular insertion with a trans-stereochemistry; and (5) Cyclobutyne -- the ligand. Plans for future research are also briefly discussed. Two studies are planned: (1) studies of the synthesis and reactivity of strained ring ligands in metal cluster compounds; and (2) studies of the reactivity of dimetallic complexes with alkynes.

  19. The LLNL Cluster Tool

    SciTech Connect

    Hunter, S L

    2007-03-27

    {lg_bullet} The Cluster Tool -is a set of linked vacuum chambers -can deposit multiple layers of metal and metal oxides {lg_bullet} Each layer can be deposited without breaking vacuum {lg_bullet} Shadow masks can give each layer a different pattern {lg_bullet} The Cluster Tool will be operational in April

  20. Cluster Interest Inventory.

    ERIC Educational Resources Information Center

    Herzog, Douglas

    The Cluster Interest Inventory is designed to familiarize students with representative occupations in 13 career clusters: (1) agribusiness and natural resources, (2) business marketing, and office occupations, (3) communications and media, (4) consumer and homemaker, (5) fine arts and humanities, (6) health, (7) manufacturing and processing, (8)…

  1. Coma cluster of galaxies

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Atlas Image mosaic, covering 34' x 34' on the sky, of the Coma cluster, aka Abell 1656. This is a particularly rich cluster of individual galaxies (over 1000 members), most prominently the two giant ellipticals, NGC 4874 (right) and NGC 4889 (left). The remaining members are mostly smaller ellipticals, but spiral galaxies are also evident in the 2MASS image. The cluster is seen toward the constellation Coma Berenices, but is actually at a distance of about 100 Mpc (330 million light years, or a redshift of 0.023) from us. At this distance, the cluster is in what is known as the 'Hubble flow,' or the overall expansion of the Universe. As such, astronomers can measure the Hubble Constant, or the universal expansion rate, based on the distance to this cluster. Large, rich clusters, such as Coma, allow astronomers to measure the 'missing mass,' i.e., the matter in the cluster that we cannot see, since it gravitationally influences the motions of the member galaxies within the cluster. The near-infrared maps the overall luminous mass content of the member galaxies, since the light at these wavelengths is dominated by the more numerous older stellar populations. Galaxies, as seen by 2MASS, look fairly smooth and homogeneous, as can be seen from the Hubble 'tuning fork' diagram of near-infrared galaxy morphology. Image mosaic by S. Van Dyk (IPAC).

  2. Probability and Cancer Clusters

    ERIC Educational Resources Information Center

    Hamilton-Keene, Rachael; Lenard, Christoper T.; Mills, Terry M.

    2009-01-01

    Recently there have been several news items about possible cancer clusters in the Australian media. The term "cancer cluster" is used when an unusually large number of people in one geographic area, often a workplace, are diagnosed with cancer in a short space of time. In this paper the authors explore this important health issue using probability…

  3. Illinois' Career Cluster Model

    ERIC Educational Resources Information Center

    Jankowski, Natasha A.; Kirby, Catherine L.; Bragg, Debra D.; Taylor, Jason L.; Oertle, Kathleen M.

    2009-01-01

    This booklet provides information to multiple stakeholders on the implementation of career clusters in Illinois. The booklet is an extension of the previous edition titled "An Introduction to Illinois CTE Programs of Study" (2008), and provides a resource for partners to understand Illinois' Career Cluster Model as its own adaptation of the…

  4. Matlab Cluster Ensemble Toolbox

    Energy Science and Technology Software Center (ESTSC)

    2009-04-27

    This is a Matlab toolbox for investigating the application of cluster ensembles to data classification, with the objective of improving the accuracy and/or speed of clustering. The toolbox divides the cluster ensemble problem into four areas, providing functionality for each. These include, (1) synthetic data generation, (2) clustering to generate individual data partitions and similarity matrices, (3) consensus function generation and final clustering to generate ensemble data partitioning, and (4) implementation of accuracy metrics. Withmore » regard to data generation, Gaussian data of arbitrary dimension can be generated. The kcenters algorithm can then be used to generate individual data partitions by either, (a) subsampling the data and clustering each subsample, or by (b) randomly initializing the algorithm and generating a clustering for each initialization. In either case an overall similarity matrix can be computed using a consensus function operating on the individual similarity matrices. A final clustering can be performed and performance metrics are provided for evaluation purposes.« less

  5. Mixed-Initiative Clustering

    ERIC Educational Resources Information Center

    Huang, Yifen

    2010-01-01

    Mixed-initiative clustering is a task where a user and a machine work collaboratively to analyze a large set of documents. We hypothesize that a user and a machine can both learn better clustering models through enriched communication and interactive learning from each other. The first contribution or this thesis is providing a framework of…

  6. Young Massive Star Clusters

    NASA Astrophysics Data System (ADS)

    Portegies Zwart, Simon F.; McMillan, Stephen L. W.; Gieles, Mark

    2010-09-01

    Young massive clusters (YMCs) are dense aggregates of young stars that form the fundamental building blocks of galaxies. Several examples exist in the Milky Way Galaxy and the Local Group, but they are particularly abundant in starburst and interacting galaxies. The few YMCs that are close enough to resolve are of prime interest for studying the stellar mass function and the ecological interplay between stellar evolution and stellar dynamics. The distant unresolved clusters may be effectively used to study the star-cluster mass function, and they provide excellent constraints on the formation mechanisms of young cluster populations. YMCs are expected to be the nurseries for many unusual objects, including a wide range of exotic stars and binaries. So far only a few such objects have been found in YMCs, although their older cousins, the globular clusters, are unusually rich in stellar exotica. In this review, we focus on star clusters younger than ˜100 Myr, more than a few current crossing times old, and more massive than ˜104M⊙; the size of the cluster and its environment are considered less relevant as distinguishing parameters. We describe the global properties of the currently known young massive star clusters in the Local Group and beyond, and discuss the state of the art in observations and dynamical modeling of these systems. In order to make this review readable by observers, theorists, and computational astrophysicists, we also review the cross-disciplinary terminology.

  7. Blue emitting undecaplatinum clusters

    NASA Astrophysics Data System (ADS)

    Chakraborty, Indranath; Bhuin, Radha Gobinda; Bhat, Shridevi; Pradeep, T.

    2014-07-01

    A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents.A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents. Electronic supplementary information (ESI) available: Details of experimental procedures, instrumentation, chromatogram of the crude cluster; SEM/EDAX, DLS, PXRD, TEM, FT-IR, and XPS of the isolated Pt11 cluster; UV/Vis, MALDI MS and SEM/EDAX of isolated 2 and 3; and 195Pt NMR of the K2PtCl6 standard. See DOI: 10.1039/c4nr02778g

  8. Brightest Cluster Galaxy Identification

    NASA Astrophysics Data System (ADS)

    Leisman, Luke; Haarsma, D. B.; Sebald, D. A.; ACCEPT Team

    2011-01-01

    Brightest cluster galaxies (BCGs) play an important role in several fields of astronomical research. The literature includes many different methods and criteria for identifying the BCG in the cluster, such as choosing the brightest galaxy, the galaxy nearest the X-ray peak, or the galaxy with the most extended profile. Here we examine a sample of 75 clusters from the Archive of Chandra Cluster Entropy Profile Tables (ACCEPT) and the Sloan Digital Sky Survey (SDSS), measuring masked magnitudes and profiles for BCG candidates in each cluster. We first identified galaxies by hand; in 15% of clusters at least one team member selected a different galaxy than the others.We also applied 6 other identification methods to the ACCEPT sample; in 30% of clusters at least one of these methods selected a different galaxy than the other methods. We then developed an algorithm that weighs brightness, profile, and proximity to the X-ray peak and centroid. This algorithm incorporates the advantages of by-hand identification (weighing multiple properties) and automated selection (repeatable and consistent). The BCG population chosen by the algorithm is more uniform in its properties than populations selected by other methods, particularly in the relation between absolute magnitude (a proxy for galaxy mass) and average gas temperature (a proxy for cluster mass). This work supported by a Barry M. Goldwater Scholarship and a Sid Jansma Summer Research Fellowship.

  9. Marketing Occupations. Cluster Guide.

    ERIC Educational Resources Information Center

    Oregon State Dept. of Education, Salem.

    This cluster guide, which is designed to show teachers what specific knowledge and skills qualify high school students for entry-level employment (or postsecondary training) in marketing occupations, is organized into three sections: (1) cluster organization and implementation, (2) instructional emphasis areas, and (3) assessment. The first…

  10. Muster: Massively Scalable Clustering

    Energy Science and Technology Software Center (ESTSC)

    2010-05-20

    Muster is a framework for scalable cluster analysis. It includes implementations of classic K-Medoids partitioning algorithms, as well as infrastructure for making these algorithms run scalably on very large systems. In particular, Muster contains algorithms such as CAPEK (described in reference 1) that are capable of clustering highly distributed data sets in-place on a hundred thousand or more processes.

  11. Water Adsorption on Free Cobalt Cluster Cations.

    PubMed

    Kiawi, Denis M; Bakker, Joost M; Oomens, Jos; Buma, Wybren Jan; Jamshidi, Zahra; Visscher, Lucas; Waters, L B F M

    2015-11-01

    Cationic cobalt clusters complexed with water Con(+)-H2O (n = 6-20) are produced through laser ablation and investigated via infrared multiple photon dissociation (IR-MPD) spectroscopy in the 200-1700 cm(-1) spectral range. All spectra exhibit a resonance close to the 1595 cm(-1) frequency of the free water bending vibration, indicating that the water molecule remains intact upon adsorption. For n = 6, the frequency of this band is blue-shifted, but it gradually converges to the free water value with increasing cluster size. In the lower-frequency range (200-650 cm(-1)) the spectra contain several bands which show a very regular frequency evolution, suggesting that the exact cluster geometry has little effect on the water-surface interaction. Density functional theory (DFT) calculations are carried out at the OPBE/TZP level for three representative sizes (n = 6, 9, 13) and indicate that the vibrations responsible for the resonances correspond to bending and torsional modes between the cluster and water moieties. The potential energy surfaces describing these interactions are very shallow, making the calculated harmonic frequencies and IR intensities very sensitive to small geometrical perturbations. We conclude that harmonic frequency calculations on (local) minima structures provide insufficient information for these types of cluster complexes and need to be complemented with calculations that provide a more extensive sampling of the potential energy surface. PMID:26447780

  12. Dynamic clustering of bacterial population

    NASA Astrophysics Data System (ADS)

    Ko, Elizabeth P.; Yomo, Tetsuya; Urabe, Itaru

    1994-08-01

    Bacterial cells having the same genotype were observed to split into a few clusters of phenotypes with various levels of enzyme activity. When the mixture of these phenotypically heterogeneous but genotypically homogeneous cells was cultivated in a liquid medium, the distribution of the population size of each cluster of phenotypes showed various kinds of dynamic oscillations. In addition, when this dynamic behavior was examined for the cells of the single colony, various patterns of shifting of homogeneous to heterogeneous lineage and vice versa were observed in the population. The results imply that differentiation of the cells with the same genotype can occur without spatial information and even under the same environment where the cells interact globally without spatial constrait. This interesting phenomenon totally contradicts the conventional biology that the genotype of a cell uniquely determines the phenotype of the cell and its progeny, but is consistent with the theoretical model of cell differentiation presented in the following paper. The sources of discrepancy between the existing theory in molecular biology and our results were discussed and it is concluded that in understanding a complex living system, a simple model consisting of the essence of the complex system can be constructed justifying the observed properties of the molecules in the system which provide free interactions.

  13. Cosmology with galaxy clusters

    NASA Astrophysics Data System (ADS)

    Sartoris, Barbara

    2015-08-01

    Clusters of galaxies are powerful probes to constrain parameters that describe the cosmological models and to distinguish among different models. Since, the evolution of the cluster mass function and large-scale clustering contain the informations about the linear growth rate of perturbations and the expansion history of the Universe, clusters have played an important role in establishing the current cosmological paradigm. It is crucial to know how to determine the cluster mass from observational quantities when using clusters as cosmological tools. For this, numerical simulations are helpful to define and study robust cluster mass proxies that have minimal and well understood scatter across the mass and redshift ranges of interest. Additionally, the bias in cluster mass determination can be constrained via observations of the strong and weak lensing effect, X-ray emission, the Sunyaev- Zel’dovic effect, and the dynamics of galaxies.A major advantage of X-ray surveys is that the observable-mass relation is tight. Moreover, clusters can be easily identified in X-ray as continuous, extended sources. As of today, interesting cosmological constraints have been obtained from relatively small cluster samples (~102), X-ray selected by the ROSAT satellite over a wide redshift range (0clusters, the ROSAT All-Sky Survey.The next generation of X-ray telescopes will enhance the statistics of detected clusters and enlarge their redshift coverage. In particular, eROSITA will produce a catalog of >105 clusters with photometric redshifts from multi-band optical surveys (e.g. PanSTARRS, DES, and LSST). This will vastly improve upon current cosmological constraints, especially by the synergy with other cluster surveys that

  14. Cluster speckle structures through multiple apertures forming a closed curve

    NASA Astrophysics Data System (ADS)

    Mosso, E.; Tebaldi, M.; Lencina, A.; Bolognini, N.

    2010-04-01

    In this work, cluster-like speckle patterns are analyzed. These patterns are generated when a diffuser illuminated by coherent light is imaged by a lens having a pupil mask with multiple apertures forming a closed curve. We show that the cluster structure results from the complex modulation produced inside each speckle which is generated by multiple interferences of light through the apertures. In particular, when the apertures are uniformly distributed along a closed curve, the resulting image speckle cluster replicates the pupil aperture distribution. Experimental results and theoretical simulations show that cluster features depend on the apertures distribution and the size of the closed curves.

  15. Connections between MWG Star Clusters and Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Venn, Kim A.

    2015-03-01

    It seems that in the past decade, there have been two paradigm shifts regarding star clusters. Firstly, the observational evidence for multiple stellar populations requires more extended and often complex star formation histories in star clusters. Secondly, theoretical models that form globular clusters in dwarf galaxies that are accreted at very early epochs (z > 5) are able to reproduce the age-metallicity relations observed. For the accretion scenario to be viable, globular clusters should also resemble the chemistry of at least some dwarf galaxies.

  16. Hybridization schemes for clusters

    NASA Astrophysics Data System (ADS)

    Wales, David J.

    The concept of an optimum hybridization scheme for cluster compounds is developed with particular reference to electron counting. The prediction of electron counts for clusters and the interpretation of the bonding is shown to depend critically upon the presumed hybridization pattern of the cluster vertex atoms. This fact has not been properly appreciated in previous work, particularly in applications of Stone's tensor surface harmonic (TSH) theory, but is found to be a useful tool when dealt with directly. A quantitative definition is suggested for the optimum cluster hybridization pattern based directly upon the ease of interpretation of the molecular orbitals, and results are given for a range of species. The relationship of this scheme to the detailed cluster geometry is described using Löwdin's partitioned perturbation theory, and the success and range of application of TSH theory are discussed.

  17. Statistical Issues in Galaxy Cluster Cosmology

    NASA Technical Reports Server (NTRS)

    Mantz, Adam

    2013-01-01

    The number and growth of massive galaxy clusters are sensitive probes of cosmological structure formation. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneously constrain scaling relations of observable signals with mass. The problem can be cast as one of regression, in which the data set is truncated, the (cosmology-dependent) underlying population must be modeled, and strong, complex correlations between measurements often exist. Simulations of cosmological structure formation provide a robust prediction for the number of clusters in the Universe as a function of mass and redshift (the mass function), but they cannot reliably predict the observables used to detect clusters in sky surveys (e.g. X-ray luminosity). Consequently, observers must constrain observable-mass scaling relations using additional data, and use the scaling relation model in conjunction with the mass function to predict the number of clusters as a function of redshift and luminosity.

  18. Message Passing Framework for Globally Interconnected Clusters

    NASA Astrophysics Data System (ADS)

    Hafeez, M.; Asghar, S.; Malik, U. A.; Rehman, A.; Riaz, N.

    2011-12-01

    In prevailing technology trends it is apparent that the network requirements and technologies will advance in future. Therefore the need of High Performance Computing (HPC) based implementation for interconnecting clusters is comprehensible for scalability of clusters. Grid computing provides global infrastructure of interconnecting clusters consisting of dispersed computing resources over Internet. On the other hand the leading model for HPC programming is Message Passing Interface (MPI). As compared to Grid computing, MPI is better suited for solving most of the complex computational problems. MPI itself is restricted to a single cluster. It does not support message passing over the internet to use the computing resources of different clusters in an optimal way. We propose a model that provides message passing capabilities between parallel applications over the internet. The proposed model is based on Architecture for Java Universal Message Passing (A-JUMP) framework and Enterprise Service Bus (ESB) named as High Performance Computing Bus. The HPC Bus is built using ActiveMQ. HPC Bus is responsible for communication and message passing in an asynchronous manner. Asynchronous mode of communication offers an assurance for message delivery as well as a fault tolerance mechanism for message passing. The idea presented in this paper effectively utilizes wide-area intercluster networks. It also provides scheduling, dynamic resource discovery and allocation, and sub-clustering of resources for different jobs. Performance analysis and comparison study of the proposed framework with P2P-MPI are also presented in this paper.

  19. Building the World's Fastest Linux Cluster

    SciTech Connect

    Goldstone, R; Seager, M

    2003-10-24

    Imagine having 2,304 Xeon processors running day and night solving complex problems. With a theoretical peak of 11.2 teraflops, that is just what the MCR cluster at Lawrence Livermore National Labs (LLNL) is doing. Over the past several years, Lawrence Livermore National Laboratory has deployed a series of increasingly large and powerful Intel-based Linux clusters. The most significant of these is a cluster known as the MCR (Multiprogrammactic Capability Resource). With 1,152 Intel Xeon (2.4 GHz) dual-processor nodes from Linux NetworX and a high performance interconnect from Quadrics, LTD., the MCR currently ranks third on the 21st Top 500 Supercomputer Sites List and is the fastest Linux cluster in the world. This feat was accomplished with a total system cost (hardware including maintenance, in-reconnect, global file system storage) of under $14 million. Although production clusters like the MCR are still custom built supercomputers that require as much artistry as skill, the experiences of LLNL have helped clear an important path for other clusters to follow.

  20. Structural diversity in Ni(II) cluster chemistry: Ni5, Ni6, and {NiNa2}n complexes bearing the Schiff-base ligand N-naphthalidene-2-amino-5-chlorobenzoic acid.

    PubMed

    Perlepe, Panagiota S; Cunha-Silva, Luís; Bekiari, Vlasoula; Gagnon, Kevin J; Teat, Simon J; Escuer, Albert; Stamatatos, Theocharis C

    2016-06-21

    The employment of the fluorescent bridging and chelating ligand N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2) in Ni(II) cluster chemistry has led to a series of pentanuclear and hexanuclear compounds with different structural motifs, magnetic and optical properties, as well as an interesting 1-D coordination polymer. Synthetic parameters such as the inorganic anion present in the NiX2 starting materials (X = ClO4(-) or Cl(-)), the reaction solvent and the nature of the organic base employed for the deprotonation of nacbH2 were proved to be structure-directing components. Undoubtedly, the reported results demonstrate the rich coordination chemistry of nacbH2 in the presence of Ni(II) metal ions and the ability of this chelate to adopt a variety of different modes, thus fostering the formation of high-nuclearity molecules with many physical properties. PMID:27240998

  1. Document clustering methods, document cluster label disambiguation methods, document clustering apparatuses, and articles of manufacture

    DOEpatents

    Sanfilippo, Antonio; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2009-12-22

    Document clustering methods, document cluster label disambiguation methods, document clustering apparatuses, and articles of manufacture are described. In one aspect, a document clustering method includes providing a document set comprising a plurality of documents, providing a cluster comprising a subset of the documents of the document set, using a plurality of terms of the documents, providing a cluster label indicative of subject matter content of the documents of the cluster, wherein the cluster label comprises a plurality of word senses, and selecting one of the word senses of the cluster label.

  2. Structural changes correlated with magnetic spin state isomorphism in the S2 state of the Mn4CaO5 cluster in the oxygen-evolving complex of photosystem II

    DOE PAGESBeta

    Chatterjee, Ruchira; Han, Guangye; Kern, Jan; Gul, Sheraz; Fuller, Franklin D.; Garachtchenko, Anna; Young, Iris D.; Weng, Tsu -Chien; Nordlund, Dennis; Alonso-Mori, Roberto; et al

    2016-05-09

    The Mn4CaO5 cluster in photosystem II catalyzes the four-electron redox reaction of water oxidation in natural photosynthesis. This catalytic reaction cycles through four intermediate states (Si, i = 0 to 4), involving changes in the redox state of the four Mn atoms in the cluster. Recent studies suggest the presence and importance of isomorphous structures within the same redox/intermediate S-state. It is highly likely that geometric and electronic structural flexibility play a role in the catalytic mechanism. Among the catalytic intermediates that have been identified experimentally thus far, there is clear evidence of such isomorphism in the S2 state, withmore » a high-spin (5/2) (HS) and a low spin (1/2) (LS) form, identified and characterized by their distinct electron paramagnetic resonance (EPR spectroscopy) signals. We studied these two S2 isomers with Mn extended X-ray absorption fine structure (EXAFS) and absorption and emission spectroscopy (XANES/XES) to characterize the structural and electronic structural properties. The geometric and electronic structure of the HS and LS S2 states are different as determined using Mn EXAFS and XANES/XES, respectively. The Mn K-edge XANES and XES for the HS form are different from the LS and indicate a slightly lower positive charge on the Mn atoms compared to the LS form. Based on the EXAFS results which are clearly different, we propose possible structural differences between the two spin states. As a result, such structural and magnetic redox-isomers if present at room temperature, will likely play a role in the mechanism for water-exchange/oxidation in photosynthesis.« less

  3. Prokaryotic Gene Clusters: A Rich Toolbox for Synthetic Biology

    PubMed Central

    Fischbach, Michael; Voigt, Christopher A.

    2014-01-01

    Bacteria construct elaborate nanostructures, obtain nutrients and energy from diverse sources, synthesize complex molecules, and implement signal processing to react to their environment. These complex phenotypes require the coordinated action of multiple genes, which are often encoded in a contiguous region of the genome, referred to as a gene cluster. Gene clusters sometimes contain all of the genes necessary and sufficient for a particular function. As an evolutionary mechanism, gene clusters facilitate the horizontal transfer of the complete function between species. Here, we review recent work on a number of clusters whose functions are relevant to biotechnology. Engineering these clusters has been hindered by their regulatory complexity, the need to balance the expression of many genes, and a lack of tools to design and manipulate DNA at this scale. Advances in synthetic biology will enable the large-scale bottom-up engineering of the clusters to optimize their functions, wake up cryptic clusters, or to transfer them between organisms. Understanding and manipulating gene clusters will move towards an era of genome engineering, where multiple functions can be “mixed-and-matched” to create a designer organism. PMID:21154668

  4. Lipid Bilayers: Clusters, Domains and Phases

    PubMed Central

    Ackerman, David G.; Feigenson, Gerald W.

    2015-01-01

    In this chapter we discuss the complex mixing behavior of plasma membrane lipids. To do so, we first introduce the plasma membrane and membrane mixtures often used to model its complexity. We then discuss the nature of lipid phase behavior in bilayers and the distinction between these phases and other manifestations of nonrandom mixing found in one-phase mixtures, such as clusters, micelles, and microemulsions. Finally, we demonstrate the applicability of Gibbs phase diagrams to the study of increasingly complex model membrane systems, with a focus on phase coexistence, morphology and their implications for the cell plasma membrane. PMID:25658342

  5. Mechanochromic luminescence of copper iodide clusters.

    PubMed

    Benito, Quentin; Maurin, Isabelle; Cheisson, Thibaut; Nocton, Gregory; Fargues, Alexandre; Garcia, Alain; Martineau, Charlotte; Gacoin, Thierry; Boilot, Jean-Pierre; Perruchas, Sandrine

    2015-04-01

    Luminescent mechanochromic materials are particularly appealing for the development of stimuli-responsive materials. Establishing the mechanism responsible for the mechanochromism is always an issue owing to the difficulty in characterizing the ground phase. Herein, the study of real crystalline polymorphs of a mechanochromic and thermochromic luminescent copper iodide cluster permits us to clearly establish the mechanism involved. The local disruption of the crystal packing induces changes in the cluster geometry and in particular the modification of the cuprophilic interactions, which consequently modify the emissive states. This study constitutes a step further toward the understanding of the mechanism involved in the mechanochromic luminescent properties of multimetallic coordination complexes. PMID:25755012

  6. Emergence of clustering: Role of inhibition

    NASA Astrophysics Data System (ADS)

    Dwivedi, Sanjiv K.; Jalan, Sarika

    2014-09-01

    Though biological and artificial complex systems having inhibitory connections exhibit a high degree of clustering in their interaction pattern, the evolutionary origin of clustering in such systems remains a challenging problem. Using genetic algorithm we demonstrate that inhibition is required in the evolution of clique structure from primary random architecture, in which the fitness function is assigned based on the largest eigenvalue. Further, the distribution of triads over nodes of the network evolved from mixed connections reveals a negative correlation with its degree providing insight into origin of this trend observed in real networks.

  7. Challenges in imaging cell surface receptor clusters

    NASA Astrophysics Data System (ADS)

    Medda, Rebecca; Giske, Arnold; Cavalcanti-Adam, Elisabetta Ada

    2016-01-01

    Super-resolution microscopy offers unique tools for visualizing and resolving cellular structures at the molecular level. STED microscopy is a purely optical method where neither complex sample preparation nor mathematical post-processing is required. Here we present the use of STED microscopy for imaging receptor cluster composition. We use two-color STED to further determine the distribution of two different receptor subunits of the family of receptor serine/threonine kinases in the presence or absence of their ligands. The implications of receptor clustering on the downstream signaling are discussed, and future challenges are also presented.

  8. The Isolated Embedded Cluster GM 24

    NASA Astrophysics Data System (ADS)

    Tapia, M.; Persi, P.

    2008-12-01

    GM 24 is a compact nebulous object immersed in the low-brightness HII region RCW 126. It is associated with a warm and dense CO cloud at whose centre a deeply embedded (A_V = 55) massive cluster of more than one hundred members is located. The most luminous young stellar object of the cluster, Irs 3 (= IRAS 17136-3617), radiates most of its energy in the mid- and far-infrared and ionizes a compact HII region. The kinematic distance, derived from the radial velocities of CO and hydrogen recombination lines, is d=2.0 kpc. The physical properties of the complex, derived from the available observations, are presented.

  9. Coevolutionary dynamics with clustering behaviors on cyclic competition

    NASA Astrophysics Data System (ADS)

    Dong, Linrong; Yang, Guangcan

    2012-05-01

    We propose a dynamic model for describing clustering behaviors on a cyclic game, in which the same species form a cluster to compete. The rates of consuming the prey depend not only on the individual competing ability v, but also on the two interacting cluster’s sizes. The fragmentation and coagulation rates of the clusters are related to the cohesive strength among the individuals. A new parameter u is introduced to indicate the uniting degree. We find that the probability distribution of the clustering sizes is almost a power law in a large regime specified by the two parameters, which reflects the scale-free behavior in complex systems. In addition, the exponential magnitudes are mostly in the range of real social systems. Our simulation shows that clustering promotes biodiversity. At steady state, the amounts about the three species evolve tempestuously with asymmetric period; the aggregations about big size’s clusters to compete are obvious and on-off intermittence.

  10. Experimental studies of the chemistry of metal clusters

    SciTech Connect

    Parks, E.K.; Riley, S.J.

    1988-01-01

    The procedures for studying chemical reactions of metal clusters in a continuous-flow reactor are described, and examples of such studies are given. Experiments to be discussed include kinetics and thermodynamics measurements, and determination of the composition of clusters saturated with various adsorbate reagents. Specific systems to be covered include the reaction of iron clusters with ammonia and with hydrogen, the reaction of nickel clusters with hydrogen and with ammonia, and the reaction of platinum clusters with ethylene. The last two reactions are characterized by complex, multi-step processes that lead to adsorbate decomposition and hydrogen desorption from the clusters. Methods for probing these processes will be discussed. 26 refs., 8 figs.

  11. Discriminant non-stationary signal features' clustering using hard and fuzzy cluster labeling

    NASA Astrophysics Data System (ADS)

    Ghoraani, Behnaz; Krishnan, Sridhar

    2012-12-01

    Current approaches to improve the pattern recognition performance mainly focus on either extracting non-stationary and discriminant features of each class, or employing complex and nonlinear feature classifiers. However, little attention has been paid to the integration of these two approaches. Combining non-stationary feature analysis with complex feature classifiers, this article presents a novel direction to enhance the discriminatory power of pattern recognition methods. This approach, which is based on a fusion of non-stationary feature analysis with clustering techniques, proposes an algorithm to adaptively identify the feature vectors according to their importance in representing the patterns of discrimination. Non-stationary feature vectors are extracted using a non-stationary method based on time-frequency distribution and non-negative matrix factorization. The clustering algorithms including the K-means and self-organizing tree maps are utilized as unsupervised clustering methods followed by a supervised labeling. Two labeling methods are introduced: hard and fuzzy labeling. The article covers in detail the formulation of the proposed discriminant feature clustering method. Experiments performed with pathological speech classification, T-wave alternans evaluation from the surface electrocardiogram, audio scene analysis, and telemonitoring of Parkinson's disease problems produced desirable results. The outcome demonstrates the benefits of non-stationary feature fusion with clustering methods for complex data analysis where existing approaches do not exhibit a high performance.

  12. Cluster synthesis. 39. New platinum-ruthenium carbonyl cluster complexes with bridging hydride ligands. Synthesis and structural characterizations of Ru sub 4 Pt(CO) sub 13 (COD)(. mu. -H) sub 2 , Ru sub 3 Pt(CO) sub 9 (. mu. -CO)(COD)(. mu. -H) sub 2 , Ru sub 4 Pt sub 2 (CO) sub 11 (COD) sub 2 (. mu. sub 3 -H) sub 2 , and Ru sub 5 Pt sub 5 (CO) sub 18 (COD) sub 2 (. mu. -H) sub 2 , COD = Cycloocta-1,5-diene

    SciTech Connect

    Adams, R.D.; Zhaoyang Li; Jauching Lii; Wengan Wu )

    1992-08-05

    The reaction of Ru{sub 4}(CO){sub 13}({mu}-H){sub 2} (1) with Pt(COD){sub 2} at 25 C yielded four new platinum-ruthenium carbonyl cluster complexes Ru{sub 4}Pt(CO){sub 13}(COD)({mu}-H){sub 2} (2) (37%), Ru{sub 3}Pt(CO){sub 9}({mu}-CO)(COD)({mu}-H){sub 2} (3) (10%), Ru{sub 4}Pt{sub 2}-(CO){sub 11}(COD){sub 2}({mu}{sub 3}-H){sub 2} (4) (2.5%), and Ru{sub 5}Pt{sub 5}(CO){sub 18}(COD){sub 2}({mu}{sub 3}-H){sub 2} (5) (1%). All compounds were characterized by IR, {sup 1}H NMR, and single-crystal X-ray diffraction analyses. The cluster of compound 2 consists of a butterfly tetrahedron of four ruthenium atoms with one triangular face capped by a Pt(COD) grouping. Compound 3 consists of a cluster of three ruthenium atoms and one platinum atom in a tetrahedral arrangement. Compound 4 consists of a tetrahedral cluster of four ruthenium atoms with two of the triangular faces capped by Pt(COD) groupings. The other two triangular faces have triply bridging hydride ligands. In the cluster of compound 5, the five ruthenium and four of the platinum atoms are arranged in the form of a face-shared bioctahedron. The shared face consists of three of the platinum atoms. The fifth platinum atom is a cap on one of the Ru{sub 2}Pt triangles. Two hydride ligands are believed to bridge metals of the triangular faces on the opposite ends of the bioctahedron.

  13. Statistical properties of convex clustering

    PubMed Central

    Tan, Kean Ming; Witten, Daniela

    2016-01-01

    In this manuscript, we study the statistical properties of convex clustering. We establish that convex clustering is closely related to single linkage hierarchical clustering and k-means clustering. In addition, we derive the range of the tuning parameter for convex clustering that yields a non-trivial solution. We also provide an unbiased estimator of the degrees of freedom, and provide a finite sample bound for the prediction error for convex clustering. We compare convex clustering to some traditional clustering methods in simulation studies.

  14. Partially supervised speaker clustering.

    PubMed

    Tang, Hao; Chu, Stephen Mingyu; Hasegawa-Johnson, Mark; Huang, Thomas S

    2012-05-01

    Content-based multimedia indexing, retrieval, and processing as well as multimedia databases demand the structuring of the media content (image, audio, video, text, etc.), one significant goal being to associate the identity of the content to the individual segments of the signals. In this paper, we specifically address the problem of speaker clustering, the task of assigning every speech utterance in an audio stream to its speaker. We offer a complete treatment to the idea of partially supervised speaker clustering, which refers to the use of our prior knowledge of speakers in general to assist the unsupervised speaker clustering process. By means of an independent training data set, we encode the prior knowledge at the various stages of the speaker clustering pipeline via 1) learning a speaker-discriminative acoustic feature transformation, 2) learning a universal speaker prior model, and 3) learning a discriminative speaker subspace, or equivalently, a speaker-discriminative distance metric. We study the directional scattering property of the Gaussian mixture model (GMM) mean supervector representation of utterances in the high-dimensional space, and advocate exploiting this property by using the cosine distance metric instead of the euclidean distance metric for speaker clustering in the GMM mean supervector space. We propose to perform discriminant analysis based on the cosine distance metric, which leads to a novel distance metric learning algorithm—linear spherical discriminant analysis (LSDA). We show that the proposed LSDA formulation can be systematically solved within the elegant graph embedding general dimensionality reduction framework. Our speaker clustering experiments on the GALE database clearly indicate that 1) our speaker clustering methods based on the GMM mean supervector representation and vector-based distance metrics outperform traditional speaker clustering methods based on the “bag of acoustic features” representation and statistical

  15. Dwarfs in Coma Cluster

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version

    This false-color mosaic of the central region of the Coma cluster combines infrared and visible-light images to reveal thousands of faint objects (green). Follow-up observations showed that many of these objects, which appear here as faint green smudges, are dwarf galaxies belonging to the cluster. Two large elliptical galaxies, NGC 4889 and NGC 4874, dominate the cluster's center. The mosaic combines visible-light data from the Sloan Digital Sky Survey (color coded blue) with long- and short-wavelength infrared views (red and green, respectively) from NASA's Spitzer Space Telescope.

  16. H-cluster stars

    NASA Astrophysics Data System (ADS)

    Lai, X. Y.; Gao, C. Y.; Xu, R. X.

    2013-06-01

    The study of dense matter at ultrahigh density has a very long history, which is meaningful for us to understand not only cosmic events in extreme circumstances but also fundamental laws of physics. It is well known that the state of cold matter at supranuclear density depends on the non-perturbative nature of quantum chromodynamics (QCD) and is essential for modelling pulsars. A so-called H-cluster matter is proposed in this paper as the nature of dense matter in reality. In compact stars at only a few nuclear densities but low temperature, quarks could be interacting strongly with each other there. That might render quarks grouped in clusters, although the hypothetical quark clusters in cold dense matter have not been confirmed due to the lack of both theoretical and experimental evidence. Motivated by recent lattice QCD simulations of the H-dibaryons (with structure uuddss), we therefore consider here a possible kind of quark clusters, H-clusters, that could emerge inside compact stars during their initial cooling as the dominant components inside (the degree of freedom could then be H-clusters there). Taking into account the in-medium stiffening effect, we find that at baryon densities of compact stars H-cluster matter could be more stable than nuclear matter. We also find that for the H-cluster matter with lattice structure, the equation of state could be so stiff that it would seem to be `superluminal' in the most dense region. However, the real sound speed for H-cluster matter is in fact difficult to calculate, so at this stage we do not put constraints on our model from the usual requirement of causality. We study the stars composed of H-clusters, i.e. H-cluster stars, and derive the dependence of their maximum mass on the in-medium stiffening effect, showing that the maximum mass could be well above 2 M⊙ as observed and that the resultant mass-radius relation fits the measurement of the rapid burster under reasonable parameters. Besides a general

  17. Extending Beowulf Clusters

    USGS Publications Warehouse

    Steinwand, Daniel R.; Maddox, Brian; Beckmann, Tim; Hamer, George

    2003-01-01

    Beowulf clusters can provide a cost-effective way to compute numerical models and process large amounts of remote sensing image data. Usually a Beowulf cluster is designed to accomplish a specific set of processing goals, and processing is very efficient when the problem remains inside the constraints of the original design. There are cases, however, when one might wish to compute a problem that is beyond the capacity of the local Beowulf system. In these cases, spreading the problem to multiple clusters or to other machines on the network may provide a cost-effective solution.

  18. The Effect of Cluster Size Variability on Statistical Power in Cluster-Randomized Trials

    PubMed Central

    Lauer, Stephen A.; Kleinman, Ken P.; Reich, Nicholas G.

    2015-01-01

    The frequency of cluster-randomized trials (CRTs) in peer-reviewed literature has increased exponentially over the past two decades. CRTs are a valuable tool for studying interventions that cannot be effectively implemented or randomized at the individual level. However, some aspects of the design and analysis of data from CRTs are more complex than those for individually randomized controlled trials. One of the key components to designing a successful CRT is calculating the proper sample size (i.e. number of clusters) needed to attain an acceptable level of statistical power. In order to do this, a researcher must make assumptions about the value of several variables, including a fixed mean cluster size. In practice, cluster size can often vary dramatically. Few studies account for the effect of cluster size variation when assessing the statistical power for a given trial. We conducted a simulation study to investigate how the statistical power of CRTs changes with variable cluster sizes. In general, we observed that increases in cluster size variability lead to a decrease in power. PMID:25830416

  19. Synthesis, structural characterization, and antiinflammatory activity of triethylphosphinegold(I) sulfanylpropenoates of the type [(AuPEt3)2xspa] [H2xspa = 3-(aryl)-2-sulfanylpropenoic acid]: an (H2O)6 cluster in the lattice of the complexes [(AuPEt3)2xspa] x 3 H2O.

    PubMed

    Barreiro, Elena; Casas, José S; Couce, María D; Gato, Angeles; Sánchez, Agustín; Sordo, José; Varela, José M; Vázquez López, Ezequiel M

    2008-07-21

    Gold complexes of the type [(AuPEt3)2xspa] were prepared by reacting AuPEt3Cl in basic media with the 3-(aryl)-2-sulfanylpropenoic acids H2xspa [x = p, Clp, -o-mp, -p-mp, -o-hp, -p-hp, diBr-o-hp, f, t, -o-py; p = 3-phenyl, Clp = 3-(2-chlorophenyl)-, -o-mp = 3-(2-methoxyphenyl)-, -p-mp = 3-(4-methoxyphenyl)-, -o-hp = 3-(2-hydroxyphenyl)-, -p-hp = 3-(4-hydroxyphenyl)-, diBr-o-hp = 3-(3,5- dibromo-2-hydroxyphenyl)-, f = 3-(2-furyl)-, t = 3-(2-thienyl)-, -o-py = 3-(2-pyridyl); spa = 2-sulfanylpropenoato], and 2-cyclopentylidene-2-sulfanylacetic acid (H2cpa). The complexes were characterized by spectroscopic methods (IR, (1)H, (13)C and (31)P NMR) and mass spectrometry, and the complexes [(AuPEt3)2pspa] x 3 H2O, [(AuPEt3)2-p-hpspa] x 3 H2O, [(AuPEt3)2tspa)] x 3 H2O, and [(AuPEt3)2-o-hpspa] by X-ray diffractometry. The crystals of the first three complexes contain (H2O)6 clusters hydrogen bonded to [(AuPEt3)2xspa]2 dimer units, whereas in the -o-hpspa derivative the hydrogen bonds are between the monomer [(AuPEt3)2-o-hpspa] units. The antiinflammatory activity of the complexes against plantar edema induced by carrageenan in rats is generally significant, with the values for the o-hpspa and tspa derivatives being particularly high. PMID:18563877

  20. Theory-driven group-based complex intervention to support self-management of osteoarthritis and low back pain in primary care physiotherapy: protocol for a cluster randomised controlled feasibility trial (SOLAS)

    PubMed Central

    Hurley, Deirdre A; Hall, Amanda M; Currie-Murphy, Laura; Pincus, Tamar; Kamper, Steve; Maher, Chris; McDonough, Suzanne M; Lonsdale, Chris; Walsh, Nicola E; Guerin, Suzanne; Segurado, Ricardo; Matthews, James

    2016-01-01

    Introduction International clinical guidelines consistently endorse the promotion of self-management (SM), including physical activity for patients with chronic low back pain (CLBP) and osteoarthritis (OA). Patients frequently receive individual treatment and advice to self-manage from physiotherapists in primary care, but the successful implementation of a clinical and cost-effective group SM programme is a key priority for health service managers in Ireland to maximise long-term outcomes and efficient use of limited and costly resources. Methods/analysis This protocol describes an assessor-blinded cluster randomised controlled feasibility trial of a group-based education and exercise intervention underpinned by self-determination theory designed to support an increase in SM behaviour in patients with CLBP and OA in primary care physiotherapy. The primary care clinic will be the unit of randomisation (cluster), with each clinic randomised to 1 of 2 groups providing the Self-management of Osteoarthritis and Low back pain through Activity and Skills (SOLAS) intervention or usual individual physiotherapy. Patients are followed up at 6 weeks, 2 and 6 months. The primary outcomes are the (1) acceptability and demand of the intervention to patients and physiotherapists, (2) feasibility and optimal study design/procedures and sample size for a definitive trial. Secondary outcomes include exploratory analyses of: point estimates, 95% CIs, change scores and effect sizes in physical function, pain and disability outcomes; process of change in target SM behaviours and selected mediators; and the cost of the intervention to inform a definitive trial. Ethics/dissemination This feasibility trial protocol was approved by the UCD Human Research Ethics—Sciences Committee (LS-13-54 Currie-Hurley) and research access has been granted by the Health Services Executive Primary Care Research Committee in January 2014. The study findings will be disseminated to the research

  1. Interlaced coarse-graining for the dynamic cluster approximation

    NASA Astrophysics Data System (ADS)

    Staar, P.; Jiang, M.; Hähner, U. R.; Schulthess, T. C.; Maier, T. A.

    2016-04-01

    The dynamical cluster approximation (DCA) and its DCA+ extension use coarse-graining of the momentum space to reduce the complexity of quantum many-body problems, thereby mapping the bulk lattice to a cluster embedded in a dynamical mean-field host. Here, we introduce a new form of an interlaced coarse-graining and compare it with the traditional coarse-graining. While it gives a more localized self-energy for a given cluster size, we show that it leads to more controlled results with weaker cluster shape and smoother cluster size dependence, which converge to the results obtained from the standard coarse-graining with increasing cluster size. Most importantly, the new coarse-graining reduces the severity of the fermionic sign problem of the underlying quantum Monte Carlo cluster solver and thus allows for calculations on larger clusters. This enables the treatment of correlations longer ranged than those accessible with the standard coarse-graining and thus can allow for the evaluation of the exact infinite cluster size result via finite size scaling. As a demonstration, we study the hole-doped two-dimensional Hubbard model and show that the interlaced coarse-graining in combination with the extended DCA+ algorithm permits the determination of the superconducting Tc on cluster sizes for which the results can be fit with a Kosterlitz-Thouless scaling law.

  2. Kinematics and dynamics of the Morgan poor clusters

    NASA Astrophysics Data System (ADS)

    Bird, Christina M.; Beers, Timothy C.; Kriessler, Jeffrey R.; Huchra, John P.

    1995-07-01

    Eighteen of the 23 MKW and AWM poor clusters now have 10 or more measured redshifts within 1.5h-1 Mpc of the central galaxy; 11 clusters have at least 20 measured redshifts. Based on the 21 clusters for which we have sufficient velocity information, the median velocity scale is 336 km s-1, a factor of two smaller than found for rich clusters. Several of the poor clusters exhibit complex velocity distributions due to the presence of nearby clumps of galaxies. We check on the velocity of the dominant galaxy in each poor cluster relative to the remaining cluster members. Significantly high relative velocities of the dominant galaxy are found in only 4 of 21 poor clusters, 3 of which we suspect are due to contamination of the parent velocity distribution. Several statistical tests indicate that the D/cD galaxies are at the kinematic centers of the parent poor cluster velocity distributions. Mass-to-light ratios for the 13 of the 15 poor clusters for which we have the required data are in the range 50<=M/LB(0)<=200 Msolar/Lsolar.

  3. Combining cluster number counts and galaxy clustering

    NASA Astrophysics Data System (ADS)

    Lacasa, Fabien; Rosenfeld, Rogerio

    2016-08-01

    The abundance of clusters and the clustering of galaxies are two of the important cosmological probes for current and future large scale surveys of galaxies, such as the Dark Energy Survey. In order to combine them one has to account for the fact that they are not independent quantities, since they probe the same density field. It is important to develop a good understanding of their correlation in order to extract parameter constraints. We present a detailed modelling of the joint covariance matrix between cluster number counts and the galaxy angular power spectrum. We employ the framework of the halo model complemented by a Halo Occupation Distribution model (HOD). We demonstrate the importance of accounting for non-Gaussianity to produce accurate covariance predictions. Indeed, we show that the non-Gaussian covariance becomes dominant at small scales, low redshifts or high cluster masses. We discuss in particular the case of the super-sample covariance (SSC), including the effects of galaxy shot-noise, halo second order bias and non-local bias. We demonstrate that the SSC obeys mathematical inequalities and positivity. Using the joint covariance matrix and a Fisher matrix methodology, we examine the prospects of combining these two probes to constrain cosmological and HOD parameters. We find that the combination indeed results in noticeably better constraints, with improvements of order 20% on cosmological parameters compared to the best single probe, and even greater improvement on HOD parameters, with reduction of error bars by a factor 1.4-4.8. This happens in particular because the cross-covariance introduces a synergy between the probes on small scales. We conclude that accounting for non-Gaussian effects is required for the joint analysis of these observables in galaxy surveys.

  4. Towards Semantically Sensitive Text Clustering: A Feature Space Modeling Technology Based on Dimension Extension

    PubMed Central

    Liu, Yuanchao; Liu, Ming; Wang, Xin

    2015-01-01

    The objective of text clustering is to divide document collections into clusters based on the similarity between documents. In this paper, an extension-based feature modeling approach towards semantically sensitive text clustering is proposed along with the corresponding feature space construction and similarity computation method. By combining the similarity in traditional feature space and that in extension space, the adverse effects of the complexity and diversity of natural language can be addressed and clustering semantic sensitivity can be improved correspondingly. The generated clusters can be organized using different granularities. The experimental evaluations on well-known clustering algorithms and datasets have verified the effectiveness of our approach. PMID:25794172

  5. Mantis BT Cluster Support

    Energy Science and Technology Software Center (ESTSC)

    2009-06-05

    The software is a modidication to the Mantis BT V1.5 open source application provided by the mantis BT group to support cluster web servers. It also provides various cosmetic modifications used a LLNL.

  6. Supramolecular assembled of hexameric water clusters into a 1D chain containing (H2O)6 and [(H2O)4O2] stabilized by hydrogen bonding in a copper complex

    PubMed Central

    2012-01-01

    Background Various water clusters including hexamers, heptamers, octamers, decamers and 1D or 2D infinite water chains in a number of organic and inorganic-organic hybrid hosts, have been reported. Results {[Cu(pydc)(amp)].3H2O}n has been hydrothermally synthesized and characterized by elemental analysis and by IR spectroscopy. A wide range of hydrogen bonds (of the O-H...O, N-H...O and N-H...N type) are present in the crystal structure. Hydrogen bond interactions between the co-crystallized water molecules led to formation of six-membered rings with chair conformation. Conclusion In {[Cu(pydc)(amp)].3H2O}n, there are three uncoordinated water molecules. Thermal methods confirm number of co-crystallized water molecules in polymer. Hydrogen bond interactions between the co-crystallized water molecules led to the formation of a six-membered ring with the chair conformation. These rings are part of a 1D chain containing six-membered O6 rings, which are alternately made from (H2O)6 and [(H2O)4O2] rings. [(H2O)4O2] rings are also in chair conformation. PMID:22264401

  7. Reconstructing galaxy histories from globular clusters

    NASA Astrophysics Data System (ADS)

    West, Michael J.; Côté, Patrick; Marzke, Ronald O.; Jordán, Andrés

    2004-01-01

    Nearly a century after the true nature of galaxies as distant `island universes' was established, their origin and evolution remain great unsolved problems of modern astrophysics. One of the most promising ways to investigate galaxy formation is to study the ubiquitous globular star clusters that surround most galaxies. Globular clusters are compact groups of up to a few million stars. They generally formed early in the history of the Universe, but have survived the interactions and mergers that alter substantially their parent galaxies. Recent advances in our understanding of the globular cluster systems of the Milky Way and other galaxies point to a complex picture of galaxy genesis driven by cannibalism, collisions, bursts of star formation and other tumultuous events.

  8. Reconstructing galaxy histories from globular clusters.

    PubMed

    West, Michael J; Côté, Patrick; Marzke, Ronald O; Jordán, Andrés

    2004-01-01

    Nearly a century after the true nature of galaxies as distant 'island universes' was established, their origin and evolution remain great unsolved problems of modern astrophysics. One of the most promising ways to investigate galaxy formation is to study the ubiquitous globular star clusters that surround most galaxies. Globular clusters are compact groups of up to a few million stars. They generally formed early in the history of the Universe, but have survived the interactions and mergers that alter substantially their parent galaxies. Recent advances in our understanding of the globular cluster systems of the Milky Way and other galaxies point to a complex picture of galaxy genesis driven by cannibalism, collisions, bursts of star formation and other tumultuous events. PMID:14702077

  9. [Cluster headache differential diagnosis].

    PubMed

    Guégan-Massardier, Evelyne; Laubier, Cécile

    2015-11-01

    Cluster headache is characterized by disabling stereotyped headache. Early diagnosis allows appropriate treatment, unfortunately diagnostic errors are frequent. The main differential diagnoses are other primary or essential headaches. Migraine, more frequent and whose diagnosis is carried by excess, trigeminal neuralgia or other trigemino-autonomic cephalgia. Vascular or tumoral underlying condition can mimic cluster headache, neck and brain imaging is recommended, ideally MRI. PMID:26549687

  10. Wild Duck Cluster

    NASA Technical Reports Server (NTRS)

    2005-01-01

    On April 7, 2005, the Deep Impact spacecraft's Impactor Target Sensor camera recorded this image of M11, the Wild Duck cluster, a galactic open cluster located 6 thousand light years away. The camera is located on the impactor spacecraft, which will image comet Tempel 1 beginning 22 hours before impact until about 2 seconds before impact. Impact with comet Tempel 1 is planned for July 4, 2005.

  11. Cluster functional renormalization group

    NASA Astrophysics Data System (ADS)

    Reuther, Johannes; Thomale, Ronny

    2014-01-01

    Functional renormalization group (FRG) has become a diverse and powerful tool to derive effective low-energy scattering vertices of interacting many-body systems. Starting from a free expansion point of the action, the flow of the RG parameter Λ allows us to trace the evolution of the effective one- and two-particle vertices towards low energies by taking into account the vertex corrections between all parquet channels in an unbiased fashion. In this work, we generalize the expansion point at which the diagrammatic resummation procedure is initiated from a free UV limit to a cluster product state. We formulate a cluster FRG scheme where the noninteracting building blocks (i.e., decoupled spin clusters) are treated exactly, and the intercluster couplings are addressed via RG. As a benchmark study, we apply our cluster FRG scheme to the spin-1/2 bilayer Heisenberg model (BHM) on a square lattice where the neighboring sites in the two layers form the individual two-site clusters. Comparing with existing numerical evidence for the BHM, we obtain reasonable findings for the spin susceptibility, the spin-triplet excitation energy, and quasiparticle weight even in coupling regimes close to antiferromagnetic order. The concept of cluster FRG promises applications to a large class of interacting electron systems.

  12. CHANDRA Observation of Galaxy Cluster A2069 - Implication for Hierarchical Mergers

    NASA Astrophysics Data System (ADS)

    Murray, Steven

    2003-09-01

    We propose a 60 ks CHANDRA observation of the irregular cluster A2069. The purpose of this proposal is twofold. EINSTEIN IPC reveals significant substructures in this cluster with at least five gas condensations. It is a good target to test the cool core merging scenario proposed by Motl et al. 2003. The complex morphology of A2069 also enables us to study rich gas dynamics phenomena inside the cluster, and shed light on cluster formation and large-scale structure.

  13. Communication: The cluster vapor to cluster solid transition

    NASA Astrophysics Data System (ADS)

    Sweatman, Martin B.; Lue, Leo

    2016-05-01

    Until now, depletion induced transitions have been the hallmark of multicomponent systems only. Monte Carlo simulations reveal a depletion-induced phase transition from cluster vapor to cluster solid in a one-component fluid with competing short range and long range interactions. This confirms a prediction made by earlier theoretical work. Analysis of renormalized cluster-cluster and cluster-vapor interactions suggests that a cluster liquid is also expected within a very narrow range of model parameters. These insights could help identify the mechanisms of clustering in experiments and assist the design of colloidal structures through engineered self-assembly.

  14. The Clustering of Young Stellar Cluster Populations in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Grasha, Kathryn; Calzetti, Daniela

    2016-01-01

    We present measurements of clustering among star clusters for several galaxies drawn from the Legacy ExtraGalactic UV Survey (LEGUS), in order to establish whether the clustering strength depends on properties of the cluster population. We use the two point autocorrelation function to study clustering as a function of spatial scale, age, concentration index (CI), and mass. We separate the clusters into different classes, defined by their (a)symmetry and number of peaks, comparing the trends of the autocorrelation functions between all the cluster classes. For one galaxy, NGC 628, we find that younger star clusters are more strongly clustered over small spatial scales and that the clustering disappears rapidly for ages as young as 40 Myr. We present here a similar analysis for the other galaxies. We also measure the power-law slope and amplitude of the autocorrelation functions and discuss the results.

  15. Relation chain based clustering analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng-ning; Zhao, Ming-yang; Luo, Hai-bo

    2011-08-01

    Clustering analysis is currently one of well-developed branches in data mining technology which is supposed to find the hidden structures in the multidimensional space called feature or pattern space. A datum in the space usually possesses a vector form and the elements in the vector represent several specifically selected features. These features are often of efficiency to the problem oriented. Generally, clustering analysis goes into two divisions: one is based on the agglomerative clustering method, and the other one is based on divisive clustering method. The former refers to a bottom-up process which regards each datum as a singleton cluster while the latter refers to a top-down process which regards entire data as a cluster. As the collected literatures, it is noted that the divisive clustering is currently overwhelming both in application and research. Although some famous divisive clustering methods are designed and well developed, clustering problems are still far from being solved. The k - means algorithm is the original divisive clustering method which initially assigns some important index values, such as the clustering number and the initial clustering prototype positions, and that could not be reasonable in some certain occasions. More than the initial problem, the k - means algorithm may also falls into local optimum, clusters in a rigid way and is not available for non-Gaussian distribution. One can see that seeking for a good or natural clustering result, in fact, originates from the one's understanding of the concept of clustering. Thus, the confusion or misunderstanding of the definition of clustering always derives some unsatisfied clustering results. One should consider the definition deeply and seriously. This paper demonstrates the nature of clustering, gives the way of understanding clustering, discusses the methodology of designing a clustering algorithm, and proposes a new clustering method based on relation chains among 2D patterns. In

  16. Hot outflows in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, C. C.; McNamara, B. R.

    2015-10-01

    The gas-phase metallicity distribution has been analysed for the hot atmospheres of 29 galaxy clusters using Chandra X-ray Observatory observations. All host brightest cluster galaxies (BCGs) with X-ray cavity systems produced by radio AGN. We find high elemental abundances projected preferentially along the cavities of 16 clusters. The metal-rich plasma was apparently lifted out of the BCGs with the rising X-ray cavities (bubbles) to altitudes between twenty and several hundred kiloparsecs. A relationship between the maximum projected altitude of the uplifted gas (the `iron radius') and jet power is found with the form R_Fe ∝ P_jet^{0.45}. The estimated outflow rates are typically tens of solar masses per year but exceed 100 M⊙ yr- 1 in the most powerful AGN. The outflow rates are 10-20 per cent of the cooling rates, and thus alone are unable to offset a cooling inflow. Nevertheless, hot outflows effectively redistribute the cooling gas and may play a significant role at regulating star formation and AGN activity in BCGs and presumably in giant elliptical galaxies. The metallicity distribution overall can be complex, perhaps due to metal-rich gas returning in circulation flows or being blown around in the hot atmospheres. Roughly 15 per cent of the work done by the cavities is expended lifting the metal-enriched gas, implying their nuclear black holes have increased in mass by at least ˜107-109 M⊙. Finally, we show that hot outflows can account for the broad, gas-phase metallicity distribution compared to the stellar light profiles of BCGs, and we consider a possible connection between hot outflows and cold molecular gas flows discovered in recent Atacama Large Millimeter Array observations.

  17. The Improving Rural Cancer Outcomes (IRCO) Trial: a factorial cluster-randomised controlled trial of a complex intervention to reduce time to diagnosis in rural patients with cancer in Western Australia: a study protocol

    PubMed Central

    Emery, Jon D; Gray, Victoria; Walter, Fiona M; Cheetham, Shelley; Croager, Emma J; Slevin, Terry; Saunders, Christobel; Threlfall, Tim; Auret, Kirsten; Nowak, Anna K; Geelhoed, Elizabeth; Bulsara, Max; Holman, C D'Arcy J

    2014-01-01

    Introduction While overall survival for most common cancers in Australia is improving, the rural–urban differential has been widening, with significant excess deaths due to lung, colorectal, breast and prostate cancer in regional Australia. Internationally a major focus on understanding variations in cancer outcomes has been later presentation to healthcare and later diagnosis. Approaches to reducing time to diagnosis of symptomatic cancer include public symptom awareness campaigns and interventions in primary care to improve early cancer detection. This paper reports the protocol of a factorial cluster-randomised trial of community and general practice (GP) level interventions to reduce the time to diagnosis of cancer in rural Western Australia (WA). Methods and analysis The community intervention is a symptom awareness campaign tailored for rural Australians delivered through a community engagement model. The GP intervention includes a resource card with symptom risk assessment charts and local referral pathways implemented through multiple academic detailing visits and case studies. Participants are eligible if recently diagnosed with breast, colorectal, lung or prostate cancer who reside in specific regions of rural WA with a planned sample size of 1350. The primary outcome is the Total Diagnostic Interval, defined as the duration from first symptom (or date of cancer screening test) to cancer diagnosis. Secondary outcomes include cancer stage, healthcare utilisation, disease-free status, survival at 2 and 5 years and cost-effectiveness. Ethics and dissemination Ethics approval has been granted by the University of Western Australia and from all relevant hospital recruitment sites in WA. Results Results of this trial will be reported in peer-reviewed publications and in conference presentations. Trial registration number Australian New Zealand Clinical Trials Registry (ANZCTR). ACTRN12610000872033. PMID:25231496

  18. Novel decavanadate cluster complexes [H2V10O28][LH]4·nH2O (L = Imidazole, n = 2 or 2-methylimidazole, n = 0): Preparation, characterization and genotoxic studies

    NASA Astrophysics Data System (ADS)

    Siddiqi, Zafar A.; Anjuli; Sharma, Prashant K.; Shahid, M.; Khalid, Mohd.; Siddique, Armeen; Kumar, Sarvendra

    2012-12-01

    The title complexes were obtained from the reaction of VOSO4 with imidazole or 2-methyl imidazole in presence of adipic acid/iminodiacetic acid. X-ray crystallographic investigations on [H2V10O28](2-MeImzH)4 (2) revealed a strong interaction between decavanadate anion and the protonated ligand moieties as counter cations to stabilize the crystal motif resulting in a high symmetry 2D sheet network. The cyclic voltammetry of (2) suggested formation of a quasi-reversible redox (VV/IV) couple in the solution. The genotoxic studies employing single cell gel electrophoresis (comet assay) confirmed the non-toxic nature of the compounds.

  19. Clustering of gene ontology terms in genomes.

    PubMed

    Tiirikka, Timo; Siermala, Markku; Vihinen, Mauno

    2014-10-25

    Although protein coding genes occupy only a small fraction of genomes in higher species, they are not randomly distributed within or between chromosomes. Clustering of genes with related function(s) and/or characteristics has been evident at several different levels. To study how common the clustering of functionally related genes is and what kind of functions the end products of these genes are involved, we collected gene ontology (GO) terms for complete genomes and developed a method to detect previously undefined gene clustering. Exhaustive analysis was performed for seven widely studied species ranging from human to Escherichia coli. To overcome problems related to varying gene lengths and densities, a novel method was developed and a fixed number of genes were analyzed irrespective of the genome span covered. Statistically very significant GO term clustering was apparent in all the investigated genomes. The analysis window, which ranged from 5 to 50 consecutive genes, revealed extensive GO term clusters for genes with widely varying functions. Here, the most interesting and significant results are discussed and the complete dataset for each analyzed species is available at the GOme database at http://bioinf.uta.fi/GOme. The results indicated that clusters of genes with related functions are very common, not only in bacteria, in which operons are frequent, but also in all the studied species irrespective of how complex they are. There are some differences between species but in all of them GO term clusters are common and of widely differing sizes. The presented method can be applied to analyze any genome or part of a genome for which descriptive features are available, and thus is not restricted to ontology terms. This method can also be applied to investigate gene and protein expression patterns. The results pave a way for further studies of mechanisms that shape genome structure and evolutionary forces related to them. PMID:24995610

  20. Peeking Network States with Clustered Patterns

    SciTech Connect

    Kim, Jinoh; Sim, Alex

    2015-10-20

    Network traffic monitoring has long been a core element for effec- tive network management and security. However, it is still a chal- lenging task with a high degree of complexity for comprehensive analysis when considering multiple variables and ever-increasing traffic volumes to monitor. For example, one of the widely con- sidered approaches is to scrutinize probabilistic distributions, but it poses a scalability concern and multivariate analysis is not gen- erally supported due to the exponential increase of the complexity. In this work, we propose a novel method for network traffic moni- toring based on clustering, one of the powerful deep-learning tech- niques. We show that the new approach enables us to recognize clustered results as patterns representing the network states, which can then be utilized to evaluate “similarity” of network states over time. In addition, we define a new quantitative measure for the similarity between two compared network states observed in dif- ferent time windows, as a supportive means for intuitive analysis. Finally, we demonstrate the clustering-based network monitoring with public traffic traces, and show that the proposed approach us- ing the clustering method has a great opportunity for feasible, cost- effective network monitoring.

  1. The cluster of galaxies Abell 2670

    NASA Astrophysics Data System (ADS)

    Shambrook, Anouk Aimee

    2001-10-01

    to understanding the complex interplay of various aspects of the cluster (the cold gas from which stars eventually are formed, the current population of stars, their formation history, and the intracluster medium which is formed in part by material ejected by stars out of galaxies).

  2. The binuclear nickel center in the A-cluster of acetyl-CoA synthase (ACS) and two biomimetic dinickel complexes studied by X-ray absorption and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Schrapers, P.; Mebs, S.; Ilina, Y.; Warner, D. S.; Wörmann, C.; Schuth, N.; Kositzki, R.; Dau, H.; Limberg, C.; Dobbek, H.; Haumann, M.

    2016-05-01

    Acetyl-CoA synthase (ACS) is involved in the bacterial carbon oxide conversion pathway. The binuclear nickel sites in ACS enzyme and two biomimetic synthetic compounds containing a Ni(II)Ni(II) unit (1 and 2) were compared using XAS/XES. EXAFS analysis of ACS proteins revealed similar Ni-N/O/S bond lengths and Ni-Ni/Fe distances as in the crystal structure in oxidized ACS, but elongated Ni-ligand bonds in reduced ACS, suggesting more reduced nickel species. The XANES spectra of ACS and the dinickel complexes showed overall similar shapes, but less resolved pre-edge and edge features in ACS, attributed to more distorted square-planar nickel sites in particular in reduced ACS. DFT calculation of pre-edge absorption and Kβ2,5 emission features reproduced the experimental spectra of the synthetic complexes, was sensitive even to the small geometry differences in 1 and 2, and indicated low-spin Ni(II) sites. Comparison of nickel sites in proteins and biomimetic compounds is valuable for deducing structural and electronic differences in response to ligation and redox changes.

  3. Globular Clusters and Spur Clusters in NGC 4921, the Brightest Spiral Galaxy in the Coma Cluster

    NASA Astrophysics Data System (ADS)

    Lee, Myung Gyoon; Jang, In Sung

    2016-03-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 105 M⊙. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 < (V - I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting MI (max) = -8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H0 = 77.9 ± 3.6 km s-1 Mpc-1. We estimate the GC specific frequency of NGC 4921 to be SN = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.

  4. Hexaruthenium carbonyl cluster complexes with basal edge-bridged square pyramidal metallic skeleton: efficient synthesis of 2-imidopyridine derivatives and determination of their reactive sites in carbonyl substitution reactions.

    PubMed

    Cabeza, Javier A; del Río, Ignacio; García-Alvarez, Pablo; Miguel, Daniel; Riera, Víctor

    2004-08-23

    The reactions of [Ru(3)(CO)(12)] with half equivalent of 2-amino-6-methylpyridine (H(2)ampy) or 2-aminopyridine (H(2)apy) in refluxing xylene give the hexanuclear products [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-L)(mu-CO)(2)(CO)(14)] (L = ampy, 1; apy, 2). These reactions represent the first high-yield syntheses of hexanuclear complexes with a basal edge-bridged square pyramidal metallic skeleton. Five metal atoms of these complexes are bridged by the N-donor ligand in such a way that the edge-bridging metal atom is attached to the pyridine nitrogen, while the basal atoms of the square pyramid are capped by an imido fragment that arises from the activation of both N-H bonds of the NH(2) group. The reactive sites of these complexes in CO substitution reactions have been determined by studying the reactivity of 1 with triphenylphosphine. Two kinetically controlled monosubstitutions take place on the edge-bridging metal atom in positions cis to the pyridine nitrogen, leading to a mixture of two isomers of formula [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-ampy)(mu-CO)(2)(CO)(13)(PPh(3))] (3 and 4). On heating at 80 degrees C, these monosubstituted isomers are transformed, via a dissociative pathway, into the product of thermodynamic control (5), which has the PPh(3) ligand on the apical Ru atom. The di- and trisubstituted derivatives [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-ampy)(mu-CO)(2)(CO)(12)(PPh(3))(2)] (6) and [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-ampy)(mu-CO)(2)(CO)(11)(PPh(3))(3)] (7) are stepwise formed from 3-5 and PPh(3). Compound 6 has the PPh(3) ligands on the edge-bridging and apical Ru atoms, and compound 7 has an additional PPh(3) ligand on an unbridged basal Ru atom. The compound [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-ampy)(mu-CO)(2)(CO)(12)(mu-dppm)] (8), in which a basal and the apical Ru atoms are spanned by the dppm ligand, has been isolated from the reaction of 1 with bis(diphenylphosphino)methane. PMID:15310227

  5. The growth of structures - Building clusters

    NASA Astrophysics Data System (ADS)

    Arnaud, M.

    Clusters of galaxies are the largest and most massive collapsed objects in the Universe. In the standard cosmological scenario, they form from the collapse of initial density fluctuations that grow under the influence of gravity, following recurrent merging events. Clusters of galaxies are still forming at the present epoch and the observation of this evolving population provides unique constraints on the physics that governs large scale structure formation and evolution. The presence of substructure in present epoch clusters give clear support to the hierarchical scenario. More recently, detailed gas temperature maps obtained with XMM and Chandra, and the discovery of cold fronts, provide unambiguous evidence of ongoing mergers. The substructures in clusters contain of fossil record of the merger history. Thus, statistical studies of the cluster morphology can provide important test of cosmological models of structure formation. However, data from a single epoch cannot unambiguously disentangle the merging history of clusters. The available data clearly show that the physics of merger events is a particularly complex process, which remains poorly understood, in particular the survival time of merger substructures. In the hierarchical merging scenario, clusters are expected to constitute a homologous family. We do see regularity in the local cluster population - strong correlations between the various properties, like the luminosity, mass, temperature, velocity dispersion, evidence for universal density and temperature profile for hot clusters. However, it is now well established that a purely gravitational scenario fails to explain all the observed properties of clusters. For instance, the luminosity-temperature relation is steeper than expected and an entropy excess is observed in the core of cool systems. Recent XMM data suggest that this entropy floor has been established at high redshift. However, the physical origin of this break of self-similarity remains

  6. Clustering in bubbly liquids

    NASA Astrophysics Data System (ADS)

    Figueroa, Bernardo; Zenit, Roberto

    2004-11-01

    We are conducting experiments to determine the amount of clustering that occurs when small gas bubbles ascend in clean water. In particular, we are interested in flows for which the liquid motion around the bubbles can be described, with a certain degree of accuracy, using potential flow theory. This model is applicable for the case of bubbly liquids in which the Reynolds number is large and the Weber number is small. To clearly observe the formation of bubble clusters we propose the use of a Hele-Shaw-type channel. In this thin channel the bubbles cannot overlap in the depth direction, therefore the identification of bubble clusters cannot be misinterpreted. Direct video image analysis is performed to calculate the velocity and size of the bubbles, as well as the formation of clusters. Although the walls do affect the motion of the bubbles, the clustering phenomena does occur and has the same qualitative behavior as in fully three-dimensional flows. A series of preliminary measurements are presented. A brief discussion of our plans to perform PIV measurements to obtain the liquid velocity fields is also presented.

  7. HST Cluster Supernova Survey

    NASA Astrophysics Data System (ADS)

    Suzuki, Nao; Aldering, G.; Amanullah, R.; Barbary, K.; Barrientos, L.; Brodwin, M.; Connolly, N.; Dawson, K.; de Jong, R.; Dey, A.; Doi, M.; Donahue, M.; Eisenhardt, P.; Ellingson, E.; Faccioli, L.; Fadeyev, V.; Fakhouri, H.; Fruchter, A.; Gilbank, D.; Gladders, M.; Goldhaber, G.; Gonzalez, A.; Goobar, A.; Gude, A.; Hennawi, J.; Hoekstra, H.; Hsiao, E.; Huang, X.; Ihara, Y.; Jannuzi, B.; Jee, M. J.; Koester, B.; Kowalski, M.; Lidman, C.; Linder, E.; Lubin, L.; Morokuma, T.; Perlmutter, S.; Postman, M.; Rhodes, J.; Rosati, P.; Ripoche, P.; Rubin, D.; Schlegel, D.; Spadafora, A.; Stanford, A.; Stern, D.; Yasuda, N.; Yee, H.; Cosmology Project, Supernova

    2010-01-01

    We report results from the Hubble Space Telescope (HST) Cluster Supernova Survey with the Advanced Camera for Surveys (ACS) (PI: Perlmutter; see Dawson et al. AJ, 2009). We have introduced a novel approach to discover and follow Type Ia supernovae (SNeIa). With HST, we monitored 25 massive clusters (0.9 < z < 1.4) found by the RCS, XMM, IRAC, and RDCS surveys and conducted spectroscopic observations with the Keck, Subaru, and VLT telescopes. Sixteen SNe were discovered at 0.95 < z < 1.41, nine of which were in galaxy clusters (for a discussion of the rates, see K. Barbary, oral presentation at this meeting). The SNe in galaxy clusters are found primarily in early type galaxies in the cluster red-sequence that have been shown to be nearly dust-free and uniform populations (see poster presentation by Meyers et al.). The reduction and control of systematic error is an urgent task for the study of dark energy today (see Rubin et al. poster presentation), and we discuss how this unique SNe Ia data set reduces both statistical and more importantly systematic uncertainty at the highest redshifts. This work has been supported by the Office of Science, U.S. Department of Energy, through contract DE-AC02-05CH11231 and in part by NASA through grants associated with HST-GO-10496.

  8. Mental health clustering and diagnosis in psychiatric in-patients.

    PubMed

    Trevithick, Liam; Painter, Jon; Keown, Patrick

    2015-06-01

    Aims and method This paper investigates the relationship between cluster (Mental Health Clustering Tool, MHCT) and diagnosis in an in-patient population. We analysed the diagnostic make-up of each cluster and the clinical utility of the diagnostic advice in the Department of Health's Mental Health Clustering Booklet. In-patients discharged from working-age adult and older people's services of a National Health Service trust over 1 year were included. Cluster on admission was compared with primary diagnosis on discharge. Results Organic, schizophreniform, anxiety disorder and personality disorders aligned to one superclass cluster. Alcohol and substance misuse, and mood disorders distributed evenly across psychosis and non-psychosis superclass clusters. Two-thirds of diagnoses fell within the MHCT 'likely' group and a tenth into the 'unlikely' group. Clinical implications Cluster and diagnosis are best viewed as complimentary systems to describe an individual's needs. Improvements are suggested to the MHCT diagnostic advice in in-patient settings. Substance misuse and affective disorders have a more complex distribution between superclass clusters than all other broad diagnostic groups. PMID:26191449

  9. Infrared Multiple Photon Dissociation Spectroscopy Of Metal Cluster-Adducts

    NASA Astrophysics Data System (ADS)

    Cox, D. M.; Kaldor, A.; Zakin, M. R.

    1987-01-01

    Recent development of the laser vaporization technique combined with mass-selective detection has made possible new studies of the fundamental chemical and physical properties of unsupported transition metal clusters as a function of the number of constituent atoms. A variety of experimental techniques have been developed in our laboratory to measure ionization threshold energies, magnetic moments, and gas phase reactivity of clusters. However, studies have so far been unable to determine the cluster structure or the chemical state of chemisorbed species on gas phase clusters. The application of infrared multiple photon dissociation IRMPD to obtain the IR absorption properties of metal cluster-adsorbate species in a molecular beam is described here. Specifically using a high power, pulsed CO2 laser as the infrared source, the IRMPD spectrum for methanol chemisorbed on small iron clusters is measured as a function of the number of both iron atoms and methanols in the complex for different methanol isotopes. Both the feasibility and potential utility of IRMPD for characterizing metal cluster-adsorbate interactions are demonstrated. The method is generally applicable to any cluster or cluster-adsorbate system dependent only upon the availability of appropriate high power infrared sources.

  10. Star Cluster Buzzing With Pulsars

    NASA Astrophysics Data System (ADS)

    2005-01-01

    left after a massive star explodes as a supernova at the end of its life. The pulsars in Terzan 5 are the product of a complex history. The stars in the cluster formed about 10 billion years ago, the astronomers say. Some of the most massive stars in the cluster exploded and left the neutron stars as their remnants after only a few million years. Normally, these neutron stars would no longer be seen as swiftly-rotating pulsars: their spin would have slowed because of the "drag" of their intense magnetic fields until the "lighthouse" effect is no longer observable. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF (Click on image for GBT gallery) However, the dense concentration of stars in the cluster gave new life to the pulsars. In the core of a globular cluster, as many as a million stars may be packed into a volume that would fit easily between the Sun and our nearest neighbor star. In such close quarters, stars can pass near enough to form new binary pairs, split apart such pairs, and binary systems even can trade partners, like an elaborate cosmic square dance. When a neutron star pairs up with a "normal" companion star, its strong gravitational pull can draw material off the companion onto the neutron star. This also transfers some of the companion's spin, or angular momentum, to the neutron star, thereby "recycling" the neutron star into a rapidly-rotating millisecond pulsar. In Terzan 5, all the pulsars discovered are rotating rapidly as a result of this process. Astronomers previously had discovered three pulsars in Terzan 5, some 28,000 light-years distant in the constellation Sagittarius, but suspected there were more. On July 17, 2004, Ransom and his colleagues used the GBT, and, in a 6-hour observation, found 14 new pulsars, the most ever found in a single observation. "This was possible because of the great sensitivity of the GBT and the new capabilities of our backend processor," said Ingrid Stairs, a professor at the

  11. Ru{sub 3}(CO){sub 9}({mu}{sub 3}-{eta}{sup 2},{eta}{sup 2},{eta}{sup 2}-C{sub 60}): A cluster face-capping, arene-like complex of C{sub 60}

    SciTech Connect

    Hsu, H.F.; Shapely, J.R.

    1996-09-25

    We report the synthesis and first structural characterization of a hexahapto C{sub 60} complex, in which C{sub 60} displays arene-like coordination to the open face of a triruthenium cluster. The bonding of C{sub 60} to a single transition metal center has been analyzed in terms of the familiar Dewar-Chatt-Duncanson donation/back-donation model, with a `double bond` donor orbital largely generated from the HOMO (h{sub u}) and the corresponding acceptor orbital formed from the LUMO (t{sub 1u}). Because of the relatively low energies of the C{sub 60} orbitals (high electron affinity), there is strong charge transfer (back-donation) from the metal center to coordinated C{sub 60}, consistent with experimental data on stable compounds. A qualitatively similar bonding model, in terms of donor/acceptor interactions of C{sub 60} with the Ru{sub 3}(CO){sub 9} fragment, is likely for 1; theoretical studies of the bonding in the benzene complexes 2 and 3 provide analogies. However. the relative contribution of back-donation to bonding with the metal triangle should be higher for C{sub 60} than for benzene, which is consistent with both the higher v{sub CO} values and the shorter Ru-C distances seen for 1 compared with those of 2. 21 refs., 1 fig.

  12. Vanadogermanate cluster anions.

    PubMed

    Whitfield, T; Wang, X; Jacobson, A J

    2003-06-16

    Three novel vanadogermanate cluster anions have been synthesized by hydrothermal reactions. The cluster anions are derived from the (V(18)O(42)) Keggin cluster shell by substitution of V=O(2+) "caps" by Ge(2)O(OH)(2)(4+) species. In Cs(8)[Ge(4)V(16)O(42)(OH)(4)].4.7H(2)O, 1, (monoclinic, space group C2/c (No. 15), Z = 8, a = 44.513(2) A, b = 12.7632(7) A, c = 22.923(1) A, beta = 101.376(1) degrees ) and (pipH(2))(4)(pipH)(4)[Ge(8)V(14)O(50).(H(2)O)] (pip = C(4)N(2)H(10)), 2 (tetragonal, space group P4(2)/nnm (No. 134), Z = 2, a = 14.9950(7) A, c = 18.408(1) A), two and four VO(2+) caps are replaced, respectively, and each cluster anion encapsulates a water molecule. In K(5)H(8)Ge(8)V(12)SO(52).10H(2)O, 3, (tetragonal, space group I4/m (No. 87), Z = 2, a = 15.573(1) A, c = 10.963(1) A), four VO(2+) caps are replaced by Ge(2)O(OH)(2)(4+) species, and an additional two are omitted. The cluster ion in 3 contains a sulfate anion disordered over two positions. The cluster anions are analogous to the vanadoarsenate anions [V(18)(-)(n)()As(2)(n)()O(42)(X)](m)(-) (X = SO(3), SO(4), Cl; n = 3, 4) previously reported. PMID:12793808

  13. Clusters in storage rings

    SciTech Connect

    Hvelplund, P.; Andersen, J. U.; Hansen, K.

    1999-01-15

    Anions of fullerenes and small metal clusters have been stored in the storage rings ASTRID and ELISA. Decays on a millisecond time scale are due to electron emission from metastable excited states. For the fullerenes the decay curves have been interpreted in terms of thermionic emission quenched by radiative cooling. The stored clusters were heated by a Nd:YAG laser resulting in increased emission rates. With an OPO laser this effect was used to study the wavelength dependence of the absorption of light in hot C{sub 60}{sup -} ion molecules.

  14. Linked supramolecular building blocks for enhanced cluster formation

    DOE PAGESBeta

    McLellan, Ross; Palacios, Maria A.; Beavers, Christine M.; Teat, Simon J.; Piligkos, Stergios; Brechin, Euan K.; Dalgarno, Scott J.

    2015-01-09

    Methylene-bridged calix[4]arenes have emerged as extremely versatile ligand supports in the formation of new polymetallic clusters possessing fascinating magnetic properties. Metal ion binding rules established for this building block allow one to partially rationalise the complex assembly process. The ability to covalently link calix[4]arenes at the methylene bridge provides significantly improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis-calix[4]arenes and transition metal ions or 3d-4f combinations display characteristic features of the analogous calix[4]arene supported clusters, thereby demonstrating an enhanced and rational approach towards the targeted synthesis of complex and challenging structures.

  15. Linked supramolecular building blocks for enhanced cluster formation

    SciTech Connect

    McLellan, Ross; Palacios, Maria A.; Beavers, Christine M.; Teat, Simon J.; Piligkos, Stergios; Brechin, Euan K.; Dalgarno, Scott J.

    2015-01-09

    Methylene-bridged calix[4]arenes have emerged as extremely versatile ligand supports in the formation of new polymetallic clusters possessing fascinating magnetic properties. Metal ion binding rules established for this building block allow one to partially rationalise the complex assembly process. The ability to covalently link calix[4]arenes at the methylene bridge provides significantly improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis-calix[4]arenes and transition metal ions or 3d-4f combinations display characteristic features of the analogous calix[4]arene supported clusters, thereby demonstrating an enhanced and rational approach towards the targeted synthesis of complex and challenging structures.

  16. Linked Supramolecular Building Blocks for Enhanced Cluster Formation

    PubMed Central

    McLellan, Ross; Palacios, Maria A; Beavers, Christine M; Teat, Simon J; Piligkos, Stergios; Brechin, Euan K; Dalgarno, Scott J

    2015-01-01

    Methylene-bridged calix[4]arenes have emerged as extremely versatile ligand supports in the formation of new polymetallic clusters possessing fascinating magnetic properties. Metal ion binding rules established for this building block allow one to partially rationalise the complex assembly process. The ability to covalently link calix[4]arenes at the methylene bridge provides significantly improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis-calix[4]arenes and transition metal ions or 3d-4f combinations display characteristic features of the analogous calix[4]arene supported clusters, thereby demonstrating an enhanced and rational approach towards the targeted synthesis of complex and challenging structures. PMID:25641542

  17. Phase behavior of the 38-atom Lennard-Jones cluster

    SciTech Connect

    Sehgal, Ray M.; Maroudas, Dimitrios E-mail: ford@ecs.umass.edu; Ford, David M. E-mail: ford@ecs.umass.edu

    2014-03-14

    We have developed a coarse-grained description of the phase behavior of the isolated 38-atom Lennard-Jones cluster (LJ{sub 38}). The model captures both the solid-solid polymorphic transitions at low temperatures and the complex cluster breakup and melting transitions at higher temperatures. For this coarse model development, we employ the manifold learning technique of diffusion mapping. The outcome of the diffusion mapping analysis over a broad temperature range indicates that two order parameters are sufficient to describe the cluster's phase behavior; we have chosen two such appropriate order parameters that are metrics of condensation and overall crystallinity. In this well-justified coarse-variable space, we calculate the cluster's free energy landscape (FEL) as a function of temperature, employing Monte Carlo umbrella sampling. These FELs are used to quantify the phase behavior and onsets of phase transitions of the LJ{sub 38} cluster.

  18. Clustering algorithms for Stokes space modulation format recognition.

    PubMed

    Boada, Ricard; Borkowski, Robert; Monroy, Idelfonso Tafur

    2015-06-15

    Stokes space modulation format recognition (Stokes MFR) is a blind method enabling digital coherent receivers to infer modulation format information directly from a received polarization-division-multiplexed signal. A crucial part of the Stokes MFR is a clustering algorithm, which largely influences the performance of the detection process, particularly at low signal-to-noise ratios. This paper reports on an extensive study of six different clustering algorithms: k-means, expectation maximization, density-based DBSCAN and OPTICS, spectral clustering and maximum likelihood clustering, used for discriminating between dual polarization: BPSK, QPSK, 8-PSK, 8-QAM, and 16-QAM. We determine essential performance metrics for each clustering algorithm and modulation format under test: minimum required signal-to-noise ratio, detection accuracy and algorithm complexity. PMID:26193532

  19. Clustering of Resting State Networks

    PubMed Central

    Lee, Megan H.; Hacker, Carl D.; Snyder, Abraham Z.; Corbetta, Maurizio; Zhang, Dongyang; Leuthardt, Eric C.; Shimony, Joshua S.

    2012-01-01

    Background The goal of the study was to demonstrate a hierarchical structure of resting state activity in the healthy brain using a data-driven clustering algorithm. Methodology/Principal Findings The fuzzy-c-means clustering algorithm was applied to resting state fMRI data in cortical and subcortical gray matter from two groups acquired separately, one of 17 healthy individuals and the second of 21 healthy individuals. Different numbers of clusters and different starting conditions were used. A cluster dispersion measure determined the optimal numbers of clusters. An inner product metric provided a measure of similarity between different clusters. The two cluster result found the task-negative and task-positive systems. The cluster dispersion measure was minimized with seven and eleven clusters. Each of the clusters in the seven and eleven cluster result was associated with either the task-negative or task-positive system. Applying the algorithm to find seven clusters recovered previously described resting state networks, including the default mode network, frontoparietal control network, ventral and dorsal attention networks, somatomotor, visual, and language networks. The language and ventral attention networks had significant subcortical involvement. This parcellation was consistently found in a large majority of algorithm runs under different conditions and was robust to different methods of initialization. Conclusions/Significance The clustering of resting state activity using different optimal numbers of clusters identified resting state networks comparable to previously obtained results. This work reinforces the observation that resting state networks are hierarchically organized. PMID:22792291

  20. Precision Photometric Redshifts Of Clusters

    NASA Astrophysics Data System (ADS)

    Holden, L.; Annis, J.

    2006-06-01

    Clusters of galaxies provide a means to achieve more precise photometric redshifts than achievable using individual galaxies simply because of the numbers of galaxies available in clusters. Here we examine the expectation that one can achieve root-N improvement using the N galaxies in a cluster. We extracted from a maxBCG SDSS cluster catalog 28,000 clusters and used SDSS DR4 spectra to find spectroscopic redshifts for the cluster. We examined both using the brightest cluster galaxy redshift as the proxy for the cluster and using the mean of a collection of galaxies within a given angular diameter and redshift (about the cluster photo-z) range. We find that the BCG provides a better estimate of the cluster redshift, to be understood in the context of a handful of spectra in the neighborhood of the cluster. We find that the cluster photo-z has an approximate root-N scaling behavior with the normalization for maxBCG techniques being 0.07. We predict what ``afterburner photo-z'' techniques, which use individual galaxy photo-z's good to 0.03-0.05, can achieve for cluster catalogs and for cluster cosmology.

  1. Detecting Non-Uniform Clusters in Large-Scale Interaction Graphs

    PubMed Central

    Levtov, Nissan; Amberkar, Sandeep; Kaderali, Lars; Volkovich, Zeev

    2014-01-01

    Abstract Graph clustering becomes difficult as the graph size and complexity increase. In particular, in interaction graphs, the clusters are small and the data on the underlying interaction are not only complex, but also noisy due to the lack of information and experimental errors. The graphs representing such data consist of (possibly overlapping) clusters of non-uniform size with some false positive and false negative links. In this article, we propose a new approach, assuming that clusters in the graphs of protein–protein interaction (PPI) networks resemble corrupted cliques. Therefore, the problem can be reduced to looking for clusters only among nodes of approximately similar degrees. This idea was implemented using a soft version of the Farthest-Point-First (FPF) clustering algorithm with the Jaccard distance function modified to perform on slightly overlapping clusters. The StripClust program developed by us was tested on a synthetic network and on the yeast PPI network. PMID:24050498

  2. SAR image change detection using watershed and spectral clustering

    NASA Astrophysics Data System (ADS)

    Niu, Ruican; Jiao, L. C.; Wang, Guiting; Feng, Jie

    2011-12-01

    A new method of change detection in SAR images based on spectral clustering is presented in this paper. Spectral clustering is employed to extract change information from a pair images acquired on the same geographical area at different time. Watershed transform is applied to initially segment the big image into non-overlapped local regions, leading to reduce the complexity. Experiments results and system analysis confirm the effectiveness of the proposed algorithm.

  3. Countdown for the Cluster quartet

    NASA Astrophysics Data System (ADS)

    2000-07-01

    the first pair of Clusters on 15 July will be covered live also on the Internet by ESA at http://clusterlaunch.esa.int and also by Spaceflight Now at http://spaceflightnow.com Note for editors. ESA's Cluster II mission will study the complex interaction between the Sun and Earth in unprecedented detail. For the first time, four satellites will fly in close formation above the Earth's poles, studying the magnetic field around our planet and its continual battle with the energetic particles of the solar wind. This groundbreaking mission to explore the magnetosphere and provide the first small-scale, three-dimensional 'map' of near-Earth space is one of the key Cornerstones in ESA's Horizons 2000 long term science programme. For more information on the winning entries, visit the ESA Science Website at: http://sci.esa.int/cluster/competition For interviews with the winners up to 10 July, 2000, please contact: Martine Caparros, tel:+31 71 565 3183, fax: +31 71 565 4101, E-mail: mcaparro@estec.esa.nl Further information on the Cluster II mission - including regular updates from Baikonur - can be found on the Internet at: http://sci.esa.int/cluster/ ESA Communication Department, Media Relations Office Tel: +33(0)1. 53.69.7155 Fax: +33(0)1.53.69 7690 Further information on ESA at http://www.esa.int

  4. Construction Cluster Skills Standards.

    ERIC Educational Resources Information Center

    DePaul Univ., Chicago, IL. Built Environment Partnership.

    Twelve construction cluster skill standards and associated benchmarks were developed as part of a federally funded school-to-work initiative that included the following parties: the Chicago Public Schools; City Colleges of Chicago; and business, labor, and community organizations. The standards, which include core academic, generic workplace…

  5. Clustered for Success

    ERIC Educational Resources Information Center

    Brulles, Dina; Winebrenner, Susan

    2012-01-01

    Schools need to address the needs of their students with high ability. Not only does this raise achievement levels schoolwide, it also attracts students from surrounding districts and recaptures advanced learners who left the school because their needs weren't being met. One practical intervention--cluster grouping--provides an inclusive…

  6. Nuclear Cluster Physics

    SciTech Connect

    Kamimura, Masayasu

    2011-05-06

    Predictive power of theory needs good models and accurate calculation methods to solve the Schroedinger equations of the systems concerned. We present some examples of successful predictions based on the nuclear cluster models of light nuclei and hypernuclei and on the calculation methods that have been developed by Kyushu group.

  7. The Cluster Active Archive

    NASA Astrophysics Data System (ADS)

    Laakso, H.; Perry, C. H.; Escoubet, C. P.; McCaffrey, S.; Herment, D.; Esson, S.; Bowen, H.; Buggy, O.; Taylor, M. G.

    2008-05-01

    The four-satellite Cluster mission investigates small-scale structures (in three dimensions) of the Earth's plasma environment, such as those involved in the interaction between the solar wind and the magnetospheric plasma, in global magnetotail dynamics, in cross-tail currents, and in the formation and dynamics of the neutral line and of plasmoids. The Cluster Active Archive CAA (http://caa.estec.esa.int/) will contain the entire set of Cluster high resolution data and other allied products in a standard format and with a complete set of metadata in machine readable form. The data archived are (1) publicly accessible, (2) of the best quality achievable with the given resources, and (3) suitable for science use and publication by both the Cluster and broader scientific community. The CAA to provide user friendly services for searching and accessing these data, e.g. users can save and restore their selections speeding up similar requests. The CAA is continuing to extend and improve the online capabilities of the system, e.g., the CAA products can be downloaded either via a web interface or a machine accessible interface.

  8. Health Occupations Cluster.

    ERIC Educational Resources Information Center

    Walraven, Catherine; And Others

    These instructional materials consist of a series of curriculum worksheets that cover tasks to be mastered by students in health occupations cluster programs. Covered in the curriculum worksheets are diagnostic procedures; observing/recording/reporting/planning; safety; nutrition/elimination; hygiene/personal care/comfort;…

  9. FUEL ROD CLUSTERS

    DOEpatents

    Schultz, A.B.

    1959-08-01

    A cluster of nuclear fuel rods and a tubular casing therefor through which a coolant flows in heat-exchange contact with the fuel rods is described. The fuel rcds are held in the casing by virtue of the compressive force exerted between longitudinal ribs of the fuel rcds and internal ribs of the casing or the internal surfaces thereof.

  10. Clustering in Bubble Suspensions

    NASA Astrophysics Data System (ADS)

    Zenit, Roberto

    2000-11-01

    A monidisperse bubble suspension is studied experimentally for the limit in which the Weber number is small and the Reynolds number is large. For this regime the suspension can be modeled using potential flow theory to describe the dynamics of the interstitial fluid. Complete theoretical descriptions have been composed (Spelt and Sangani, 1998) to model the behavior of these suspensions. Bubble clustering is a natural instability that arises from the potential flow considerations, in which bubbles tend to align in horizontal rafts as they move upwards. The appearance of bubble clusters was recently corroborated experimentally by Zenit et al. (2000), who found that although clusters did appear, their strength was not as strong as the predictions. Experiments involving gravity driven shear flows are used to explain the nature of the clustering observed in these type of flows. Balances of the bubble phase pressure (in terms of a calculated diffusion coefficient) and the Maxwell pressure (from the potential flow description) are presented to predict the stability of the bubble suspension. The predictions are compared with experimental results.

  11. Buckets, Clusters and Dienst

    NASA Technical Reports Server (NTRS)

    Nelson, Michael L.; Maly, Kurt; Shen, Stewart N. T.

    1997-01-01

    In this paper we describe NCSTRL+, a unified, canonical digital library for scientific and technical information (STI). NCSTRL+ is based on the Networked Computer Science Technical Report Library (NCSTRL), a World Wide Web (WWW) accessible digital library (DL) that provides access to over 80 university departments and laboratories. NCSTRL+ implements two new technologies: cluster functionality and publishing "buckets." We have extended the Dienst protocol, the protocol underlying NCSTRL, to provide the ability to "cluster" independent collections into a logically centralized digital library based upon subject category classification, type of organization, and genres of material. The concept of "buckets" provides a mechanism for publishing and managing logically linked entities with multiple data formats. The NCSTRL+ prototype DL contains the holdings of NCSTRL and the NASA Technical Report Server (NTRS). The prototype demonstrates the feasibility of publishing into a multi-cluster DL, searching across clusters, and storing and presenting buckets of information. We show that the overhead for these additional capabilities is minimal to both the author and the user when compared to the equivalent process within NCSTRL.

  12. Curriculum Guide Construction Cluster.

    ERIC Educational Resources Information Center

    Kline, Ken

    As part of a model construction cluster curriculum development project, this guide was developed and implemented in the Beaverton (Oregon) School District. The curriculum guide contains 16 units covering the following topics: introduction to construction jobs; safety and first aid; blueprint readings; basic mathematics; site work; framing; roofing…

  13. Health Occupations Cluster Guide.

    ERIC Educational Resources Information Center

    Oregon State Dept. of Education, Salem.

    Intended to assist the vocational teacher in designing and implementing a cluster program in health occupations, this guide suggests ideas for teaching the specific knowledge and skills that qualify students for entry-level employment in the health occupations field. The knowledge and skills are applicable to 12 occupations: dental assistant;…

  14. Globular Cluster Streams as Galactic High-Precision Scales

    NASA Astrophysics Data System (ADS)

    Küpper, Andreas H. W.; Balbinot, Eduardo; Bonaca, Ana; Johnston, Kathryn V.; Hogg, David W.; Kroupa, Pavel; Santiago, Basilio X.

    2016-08-01

    Tidal streams of globular clusters are ideal tracers of the Galactic gravitational potential. Compared to the few known, complex and diffuse dwarf-galaxy streams, they are kinematically cold, have thin morphologies and are abundant in the halo of the Milky Way. Their coldness and thinness in combination with potential epicyclic substructure in the vicinity of the stream progenitor turns them into high-precision scales. With the example of Palomar 5, we demonstrate how modeling of a globular cluster stream allows us to simultaneously measure the properties of the disrupting globular cluster, its orbital motion, and the gravitational potential of the Milky Way.

  15. Electron transfer between [4Fe-4S] clusters

    NASA Astrophysics Data System (ADS)

    Voityuk, Alexander A.

    2010-07-01

    Iron-sulfur clusters [4Fe-4S] are major components in biological electron transport (ET). Using the DFT/B3LYP method, we calculate electronic coupling for low- and high-potential ET between [4Fe-4S] clusters and explore its sensitivity to structural parameters of the system and external electric field. As an example, we consider a model of the bacterial respiratory complex I and estimate the role of neighboring amino acids in facilitating the ET process between the clusters. Our results suggest that the superexchange mechanism rather than hole hopping should be operative in ET between [4Fe-4S] redox centers.

  16. Ultra-small rhenium clusters supported on graphene

    PubMed Central

    Miramontes, Orlando; Bonafé, Franco; Santiago, Ulises; Larios-Rodriguez, Eduardo; Velázquez-Salazar, Jesús J.; Mariscal, Marcelo M.; Yacaman, Miguel José

    2015-01-01

    The adsorption of very small rhenium clusters (2 – 13 atoms) supported on graphene was studied with high annular dark field - scanning transmission electron microscopy (HAADF-STEM). The atomic structure of the clusters was fully resolved with the aid of density functional calculations and STEM simulations. It was found that octahedral and tetrahedral structures work as seeds to obtain more complex morphologies. Finally, a detailed analysis of the electronic structure suggested that a higher catalytic effect can be expected in Re clusters when adsorbed on graphene than in isolated ones. PMID:25721176

  17. moCluster: Identifying Joint Patterns Across Multiple Omics Data Sets.

    PubMed

    Meng, Chen; Helm, Dominic; Frejno, Martin; Kuster, Bernhard

    2016-03-01

    Increasingly, multiple omics approaches are being applied to understand the complexity of biological systems. Yet, computational approaches that enable the efficient integration of such data are not well developed. Here, we describe a novel algorithm, termed moCluster, which discovers joint patterns among multiple omics data. The method first employs a multiblock multivariate analysis to define a set of latent variables representing joint patterns across input data sets, which is further passed to an ordinary clustering algorithm in order to discover joint clusters. Using simulated data, we show that moCluster's performance is not compromised by issues present in iCluster/iCluster+ (notably, the nondeterministic solution) and that it operates 100× to 1000× faster than iCluster/iCluster+. We used moCluster to cluster proteomic and transcriptomic data from the NCI-60 cell line panel. The resulting cluster model revealed different phenotypes across cellular subtypes, such as doubling time and drug response. Applying moCluster to methylation, mRNA, and protein data from a large study on colorectal cancer patients identified four molecular subtypes, including one characterized by microsatellite instability and high expression of genes/proteins involved in immunity, such as PDL1, a target of multiple drugs currently in development. The other three subtypes have not been discovered before using single data sets, which clearly illustrates the molecular complexity of oncogenesis and the need for holistic, multidata analysis strategies. PMID:26653205

  18. PDMS embedded Ag clusters: Coalescence and cluster-matrix interaction

    NASA Astrophysics Data System (ADS)

    Roese, S.; Engemann, D.; Hoffmann, S.; Latussek, K.; Sternemann, C.; Hövel, H.

    2016-05-01

    Polydimethylsiloxane (PDMS) has proven to be a suitable embedding medium for silver clusters to prevent aggregation. In order to investigate the influence of the PDMS on the electronic and local atomic structure of the clusters the measurement of x-ray absorption near edge structure (XANES) spectra for different coverages of silver clusters in PDMS and calculations of corresponding XANES spectra have been performed. The coalescence process and the cluster-PDMS interaction were investigated with XANES.

  19. The Rotation of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Tovmassian, H. M.

    2015-09-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher than the cluster mean velocity over the cluster image is proposed. The search for rotation is made for flat clusters with a/b > 1.8 and BMI type clusters which are expected to be rotating. For comparison there were studied also round clusters and clusters of NBMI type, the second by brightness galaxy, which does not differ significantly from the cluster cD galaxy. Seventeen out of studied 65 clusters are found to be rotating. It was found that the detection rate is sufficiently high for flat clusters, over 60%, and clusters of BMI type with dominant cD galaxy, ≈ 35% . The obtained results show that clusters were formed from the huge primordial gas clouds and preserved the rotation of the primordial clouds, unless they did not experience mergings with other clusters and groups of galaxies, as a result of which the rotation was prevented.

  20. Femtosecond dynamics of cluster expansion

    NASA Astrophysics Data System (ADS)

    Gao, Xiaohui; Wang, Xiaoming; Shim, Bonggu; Arefiev, Alexey; Tushentsov, Mikhail; Breizman, Boris; Downer, Mike

    2010-03-01

    Noble gas clusters irradiated by intense ultrafast laser expand quickly and become typical plasma in picosecond time scale. During the expansion, the clustered plasma demonstrates unique optical properties such as strong absorption and positive contribution to the refractive index. Here we studied cluster expansion dynamics by fs-time-resolved refractive index and absorption measurements in cluster gas jets after ionization and heating by an intense pump pulse. The refractive index measured by frequency domain interferometry (FDI) shows the transient positive peak of refractive index due to clustered plasma. By separating it from the negative contribution of the monomer plasma, we are able to determine the cluster fraction. The absorption measured by a delayed probe shows the contribution from clusters of various sizes. The plasma resonances in the cluster explain the enhancement of the absorption in our isothermal expanding cluster model. The cluster size distribution can be determined. A complete understanding of the femtosecond dynamics of cluster expansion is essential in the accurate interpretation and control of laser-cluster experiments such as phase-matched harmonic generation in cluster medium.

  1. [Complex posttraumatic stress disorder].

    PubMed

    Green, Tamar; Kotler, Moshe

    2007-11-01

    The characteristic symptoms resulting from exposure to an extreme trauma include three clusters of symptoms: persistent experience of the traumatic event, persistent avoidance of stimuli associated with the trauma and persistent symptoms of increased arousal. Beyond the accepted clusters of symptoms for posttraumatic stress disorder exists a formation of symptoms related to exposure to extreme or prolonged stress e.g. childhood abuse, physical violence, rape, and confinement within a concentration camp. With accumulated evidence of the existence of these symptoms began a trail to classify a more complex syndrome, which included, but was not confined to the symptoms of posttraumatic stress disorder. This review addresses several subjects for study in complex posttraumatic stress disorder, which is a complicated and controversial topic. Firstly, the concept of complex posttraumatic stress disorder is presented. Secondly, the professional literature relevant to this disturbance is reviewed and finally, the authors present the polemic being conducted between the researchers of posttraumatic disturbances regarding validity, reliability and the need for separate diagnosis for these symptoms. PMID:18087837

  2. Interglacial complex and solcomplex

    NASA Astrophysics Data System (ADS)

    Schirmer, Wolfgang

    2010-03-01

    All younger Pleistocene interglacials form interglacial complexes. The term interglacial complex is a short term for a tight complex of interglacials, interstadials and breviglacials, separating a complex of warm periods from the long glacial periods (euglacials). In the terrestric environment the interglacial complexes are represented by soil clusters (solcomplexes). Therein which occur interglacial and interstadial soils of different types in the loess environment separated by thin beds of loess or loess derivates (breviglacials). This article considers the mutilation and simulation of solcomplexes. Frequently, fossil solcomplexes present themselves as diminished to a few soils or to one single soil. This mutilation of solcomplexes can be due to soil convergence (soils of different warm periods — interglacials, interstadials — merge to form optically one soil), syn-solcomplex erosion or post-solcomplex erosion and sometimes to soil disguise. Conversely solcomplexes may be simulated by narrowing of soils which belong to different interglacial complexes and moreover by soil divergence (splitting of a soil of one single warm period by an interlayer of rock) or by reworked soil sediment.

  3. Cluster Active Archive: Overview

    NASA Astrophysics Data System (ADS)

    Laakso, H.; Perry, C.; McCaffrey, S.; Herment, D.; Allen, A. J.; Harvey, C. C.; Escoubet, C. P.; Gruenberger, C.; Taylor, M. G. G. T.; Turner, R.

    The four-satellite Cluster mission investigates the small-scale structures and physical processes related to interaction between the solar wind and the magnetospheric plasma. The Cluster Active Archive (CAA) (URL: http://caa.estec.esa.int) will contain the entire set of Cluster high-resolution data and other allied products in a standard format and with a complete set of metadata in machine readable format. The total amount of the data files in compressed format is expected to exceed 50 TB. The data archive is publicly accessible and suitable for science use and publication by the world-wide scientific community. The CAA aims to provide user-friendly services for searching and accessing these data and ancillary products. The CAA became operational in February 2006 and as of Summer 2008 has data from most of the Cluster instruments for at least the first 5 years of operations (2001-2005). The coverage and range of products are being continually improved with more than 200 datasets available from each spacecraft, including high-resolution magnetic and electric DC fields and wave spectra; full three-dimensional electron and ion distribution functions from a few eV to hundreds of keV; and various ancillary and browse products to help with spacecraft and event location. The CAA is continuing to extend and improve the online capabilities of the system and the quality of the existing data. It will add new data files for years 2006-2009 and is preparing for the long-term archive with complete coverage after the completion of the Cluster mission.

  4. Clustered DNA damages induced in human hematopoietic cells by low doses of ionizing radiation

    NASA Technical Reports Server (NTRS)

    Sutherland, Betsy M.; Bennett, Paula V.; Cintron-Torres, Nela; Hada, Megumi; Trunk, John; Monteleone, Denise; Sutherland, John C.; Laval, Jacques; Stanislaus, Marisha; Gewirtz, Alan

    2002-01-01

    Ionizing radiation induces clusters of DNA damages--oxidized bases, abasic sites and strand breaks--on opposing strands within a few helical turns. Such damages have been postulated to be difficult to repair, as are double strand breaks (one type of cluster). We have shown that low doses of low and high linear energy transfer (LET) radiation induce such damage clusters in human cells. In human cells, DSB are about 30% of the total of complex damages, and the levels of DSBs and oxidized pyrimidine clusters are similar. The dose responses for cluster induction in cells can be described by a linear relationship, implying that even low doses of ionizing radiation can produce clustered damages. Studies are in progress to determine whether clusters can be produced by mechanisms other than ionizing radiation, as well as the levels of various cluster types formed by low and high LET radiation.

  5. Choosing the Number of Clusters in K-Means Clustering

    ERIC Educational Resources Information Center

    Steinley, Douglas; Brusco, Michael J.

    2011-01-01

    Steinley (2007) provided a lower bound for the sum-of-squares error criterion function used in K-means clustering. In this article, on the basis of the lower bound, the authors propose a method to distinguish between 1 cluster (i.e., a single distribution) versus more than 1 cluster. Additionally, conditional on indicating there are multiple…

  6. The next generation Virgo cluster survey. VIII. The spatial distribution of globular clusters in the Virgo cluster

    SciTech Connect

    Durrell, Patrick R.; Accetta, Katharine; Côté, Patrick; Blakeslee, John P.; Ferrarese, Laura; McConnachie, Alan; Gwyn, Stephen; Peng, Eric W.; Zhang, Hongxin; Mihos, J. Christopher; Puzia, Thomas H.; Jordán, Andrés; Lançon, Ariane; Liu, Chengze; Cuillandre, Jean-Charles; Boissier, Samuel; Boselli, Alessandro; Courteau, Stéphane; Duc, Pierre-Alain; and others

    2014-10-20

    slightly lower than but consistent with those derived for individual galactic halos. Taken as a whole, our results show that the production of the complex structures in the unrelaxed Virgo cluster core (including the production of the diffuse intracluster light) is an ongoing and continuing process.

  7. Iron-sulfur cluster biogenesis in mammalian cells: new insights into the molecular mechanisms of cluster delivery

    PubMed Central

    Maio, Nunziata; Rouault, Tracey. A.

    2014-01-01

    Iron-sulfur (Fe-S) clusters are ancient, ubiquitous cofactors composed of iron and inorganic sulfur. The combination of the chemical reactivity of iron and sulfur, together with many variations of cluster composition, oxidation states and protein environments, enables Fe-S clusters to participate in numerous biological processes. Fe-S clusters are essential to redox catalysis in nitrogen fixation, mitochondrial respiration and photosynthesis, to regulatory sensing in key metabolic pathways (i. e. cellular iron homeostasis and oxidative stress response), and to the replication and maintenance of the nuclear genome. Fe-S cluster biogenesis is a multistep process that involves a complex sequence of catalyzed protein- protein interactions and coupled conformational changes between the components of several dedicated multimeric complexes. Intensive studies of the assembly process have clarified key points in the biogenesis of Fe-S proteins. However several critical questions still remain, such as: what is the role of frataxin? Why do some defects of Fe-S cluster biogenesis cause mitochondrial iron overload? How are specific Fe-S recipient proteins recognized in the process of Fe-S transfer? This review focuses on the basic steps of Fe-S cluster biogenesis, drawing attention to recent advances achieved on the identification of molecular features that guide selection of specific subsets of nascent Fe-S recipients by the cochaperone HSC20. Additionally, it outlines the distinctive phenotypes of human diseases due to mutations in the components of the basic pathway. PMID:25245479

  8. Exploring Function Prediction in Protein Interaction Networks via Clustering Methods

    PubMed Central

    Trivodaliev, Kire; Bogojeska, Aleksandra; Kocarev, Ljupco

    2014-01-01

    Complex networks have recently become the focus of research in many fields. Their structure reveals crucial information for the nodes, how they connect and share information. In our work we analyze protein interaction networks as complex networks for their functional modular structure and later use that information in the functional annotation of proteins within the network. We propose several graph representations for the protein interaction network, each having different level of complexity and inclusion of the annotation information within the graph. We aim to explore what the benefits and the drawbacks of these proposed graphs are, when they are used in the function prediction process via clustering methods. For making this cluster based prediction, we adopt well established approaches for cluster detection in complex networks using most recent representative algorithms that have been proven as efficient in the task at hand. The experiments are performed using a purified and reliable Saccharomyces cerevisiae protein interaction network, which is then used to generate the different graph representations. Each of the graph representations is later analysed in combination with each of the clustering algorithms, which have been possibly modified and implemented to fit the specific graph. We evaluate results in regards of biological validity and function prediction performance. Our results indicate that the novel ways of presenting the complex graph improve the prediction process, although the computational complexity should be taken into account when deciding on a particular approach. PMID:24972109

  9. Animation of the Phoenix Cluster

    NASA Video Gallery

    This animation shows how large numbers of stars form in the Phoenix Cluster. It begins by showing several galaxies in the cluster and hot gas (in red). This hot gas contains more normal matter than...

  10. Validating clustering of molecular dynamics simulations using polymer models

    PubMed Central

    2011-01-01

    Background Molecular dynamics (MD) simulation is a powerful technique for sampling the meta-stable and transitional conformations of proteins and other biomolecules. Computational data clustering has emerged as a useful, automated technique for extracting conformational states from MD simulation data. Despite extensive application, relatively little work has been done to determine if the clustering algorithms are actually extracting useful information. A primary goal of this paper therefore is to provide such an understanding through a detailed analysis of data clustering applied to a series of increasingly complex biopolymer models. Results We develop a novel series of models using basic polymer theory that have intuitive, clearly-defined dynamics and exhibit the essential properties that we are seeking to identify in MD simulations of real biomolecules. We then apply spectral clustering, an algorithm particularly well-suited for clustering polymer structures, to our models and MD simulations of several intrinsically disordered proteins. Clustering results for the polymer models provide clear evidence that the meta-stable and transitional conformations are detected by the algorithm. The results for the polymer models also help guide the analysis of the disordered protein simulations by comparing and contrasting the statistical properties of the extracted clusters. Conclusions We have developed a framework for validating the performance and utility of clustering algorithms for studying molecular biopolymer simulations that utilizes several analytic and dynamic polymer models which exhibit well-behaved dynamics including: meta-stable states, transition states, helical structures, and stochastic dynamics. We show that spectral clustering is robust to anomalies introduced by structural alignment and that different structural classes of intrinsically disordered proteins can be reliably discriminated from the clustering results. To our knowledge, our framework is the

  11. Joint clustering of protein interaction networks through Markov random walk

    PubMed Central

    2014-01-01

    Biological networks obtained by high-throughput profiling or human curation are typically noisy. For functional module identification, single network clustering algorithms may not yield accurate and robust results. In order to borrow information across multiple sources to alleviate such problems due to data quality, we propose a new joint network clustering algorithm ASModel in this paper. We construct an integrated network to combine network topological information based on protein-protein interaction (PPI) datasets and homological information introduced by constituent similarity between proteins across networks. A novel random walk strategy on the integrated network is developed for joint network clustering and an optimization problem is formulated by searching for low conductance sets defined on the derived transition matrix of the random walk, which fuses both topology and homology information. The optimization problem of joint clustering is solved by a derived spectral clustering algorithm. Network clustering using several state-of-the-art algorithms has been implemented to both PPI networks within the same species (two yeast PPI networks and two human PPI networks) and those from different species (a yeast PPI network and a human PPI network). Experimental results demonstrate that ASModel outperforms the existing single network clustering algorithms as well as another recent joint clustering algorithm in terms of complex prediction and Gene Ontology (GO) enrichment analysis. PMID:24565376

  12. Clustering phenomena of implants in tungsten observed with THDS

    NASA Astrophysics Data System (ADS)

    van der Kolk, G. J.; van Veen, A.; de Hosson, J. Th. M.; Caspers, L. M.

    1985-02-01

    A W(100) single crystal was irradiated with 5-10 keV of different metallic species (Ag, Cu, Cr, Mn, Al and In). Subsequently the crystal was annealed at temperatures ranging from room temperature to 2400 K. Thermal helium desorption spectrometry (THDS) was applied to monitor the dissociation and clustering reactions of defect complexes either formed at room temperature during implantation or during partial annealing at a higher temperature. Strong evidence is found for clustering of Ag if implantation doses of Ag exceed 6 × 10 12 Ag + cm -2. For the implants Al, Cr, Cu and Mn, substantial clustering was not detected. For In, a conclusion could not be made concerning clustering since He does not bind to In in W at room temperature. Atomistic calculations are presented which indicate that clustering of the implants other than Ag would certainly be detected if the impurity atoms in the cluster all occupy lattice positions. Therefore we believe that thermally activated radiation enhanced diffusion is much more efficient for Ag than for Cu and Mn in W. For Cr and Al we cannot exclude enhanced diffusion, since the binding energies of Cr and Al to Cr- and Al-clusters in W, respectively, will be rather small. Of the implants Cu, Mn and Ag, the latter is the only one being oversized. A rather strong binding of vacancies to Ag is envisaged, which enables transport of the Ag atom, being part of a moving vacancy cluster.

  13. Joint clustering of protein interaction networks through Markov random walk.

    PubMed

    Wang, Yijie; Qian, Xiaoning

    2014-01-01

    Biological networks obtained by high-throughput profiling or human curation are typically noisy. For functional module identification, single network clustering algorithms may not yield accurate and robust results. In order to borrow information across multiple sources to alleviate such problems due to data quality, we propose a new joint network clustering algorithm ASModel in this paper. We construct an integrated network to combine network topological information based on protein-protein interaction (PPI) datasets and homological information introduced by constituent similarity between proteins across networks. A novel random walk strategy on the integrated network is developed for joint network clustering and an optimization problem is formulated by searching for low conductance sets defined on the derived transition matrix of the random walk, which fuses both topology and homology information. The optimization problem of joint clustering is solved by a derived spectral clustering algorithm. Network clustering using several state-of-the-art algorithms has been implemented to both PPI networks within the same species (two yeast PPI networks and two human PPI networks) and those from different species (a yeast PPI network and a human PPI network). Experimental results demonstrate that ASModel outperforms the existing single network clustering algorithms as well as another recent joint clustering algorithm in terms of complex prediction and Gene Ontology (GO) enrichment analysis. PMID:24565376

  14. The Influence of Cluster Mergers on Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Rawle, T. D.; Altieri, B.; Bouy, H.; Egami, E.; Pérez-González, P. G.; Richard, J.; Valtchanov, I.; Walth, G.

    2016-06-01

    The rich environment of galaxy clusters is understood to have a profound effect on the evolution of constituent galaxies. However, even clusters of a similar mass and at fixed redshift are not homogeneous, displaying a range in structural complexity. Here we concentrate on the effect of cluster merging, the most massive dynamic process in the Universe. Two spectacular cluster mergers at z~0.3 are explored: the archetypal Bullet cluster (1E0657-558; Rawle et al. 2012), and the HST Frontier Field, Pandora's cluster (Abell 2744; Rawle et al. 2014, 2016). We present detailed analysis of their total star formation, derived from multi-wavelength observations of both dusty and unobscured activity from Herschel, Spitzer, WISE and GALEX. Examination of the morphologies of individual cluster galaxies reveals striking evidence for transformation and enhanced star formation, triggered by the merger-induced shock front. This includes several galaxies identified as having "jellyfish" morphologies caused by the passing shock. We discuss the implications, and preview future work exploring a large sample of clusters covering a range of dynamic states and redshifts.

  15. Progeny Clustering: A Method to Identify Biological Phenotypes.

    PubMed

    Hu, Chenyue W; Kornblau, Steven M; Slater, John H; Qutub, Amina A

    2015-01-01

    Estimating the optimal number of clusters is a major challenge in applying cluster analysis to any type of dataset, especially to biomedical datasets, which are high-dimensional and complex. Here, we introduce an improved method, Progeny Clustering, which is stability-based and exceptionally efficient in computing, to find the ideal number of clusters. The algorithm employs a novel Progeny Sampling method to reconstruct cluster identity, a co-occurrence probability matrix to assess the clustering stability, and a set of reference datasets to overcome inherent biases in the algorithm and data space. Our method was shown successful and robust when applied to two synthetic datasets (datasets of two-dimensions and ten-dimensions containing eight dimensions of pure noise), two standard biological datasets (the Iris dataset and Rat CNS dataset) and two biological datasets (a cell phenotype dataset and an acute myeloid leukemia (AML) reverse phase protein array (RPPA) dataset). Progeny Clustering outperformed some popular clustering evaluation methods in the ten-dimensional synthetic dataset as well as in the cell phenotype dataset, and it was the only method that successfully discovered clinically meaningful patient groupings in the AML RPPA dataset. PMID:26267476

  16. Clusters and the new economics of competition.

    PubMed

    Porter, M E

    1998-01-01

    Economic geography in an era of global competition poses a paradox. In theory, location should no longer be a source of competitive advantage. Open global markets, rapid transportation, and high-speed communications should allow any company to source any thing from any place at any time. But in practice, Michael Porter demonstrates, location remains central to competition. Today's economic map of the world is characterized by what Porter calls clusters: critical masses in one place of linked industries and institutions--from suppliers to universities to government agencies--that enjoy unusual competitive success in a particular field. The most famous example are found in Silicon Valley and Hollywood, but clusters dot the world's landscape. Porter explains how clusters affect competition in three broad ways: first, by increasing the productivity of companies based in the area; second, by driving the direction and pace of innovation; and third, by stimulating the formation of new businesses within the cluster. Geographic, cultural, and institutional proximity provides companies with special access, closer relationships, better information, powerful incentives, and other advantages that are difficult to tap from a distance. The more complex, knowledge-based, and dynamic the world economy becomes, the more this is true. Competitive advantage lies increasingly in local things--knowledge, relationships, and motivation--that distant rivals cannot replicate. Porter challenges the conventional wisdom about how companies should be configured, how institutions such as universities can contribute to competitive success, and how governments can promote economic development and prosperity. PMID:10187248

  17. Mixed-Monolayer-Protected Au25 Clusters with Bulky Calix[4]arene Functionalities.

    PubMed

    Hassinen, Jukka; Pulkkinen, Petri; Kalenius, Elina; Pradeep, Thalappil; Tenhu, Heikki; Häkkinen, Hannu; Ras, Robin H A

    2014-02-01

    Although various complex, bulky ligands have been used to functionalize plasmonic gold nanoparticles, introducing them to small, atomically precise gold clusters is not trivial. Here, we demonstrate a simple one-pot procedure to synthesize fluorescent magic number Au25 clusters carrying controlled amounts of bulky calix[4]arene functionalities. These clusters are obtained from a synthesis feed containing binary mixtures of tetrathiolated calix[4]arene and 1-butanethiol. By systematic variation of the molar ratio of ligands, clusters carrying one to eight calixarene moieties were obtained. Structural characterization reveals unexpected binding of the calix[4]arenes to the Au25 cluster surface with two or four thiolates per moiety. PMID:26276613

  18. The Assembly of Galaxy Clusters

    SciTech Connect

    Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.

    2008-05-16

    We study the formation of fifty-three galaxy cluster-size dark matter halos (M = 10{sup 14.0-14.76} M{sub {circle_dot}}) formed within a pair of cosmological {Lambda}CDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host {approx} 0.1L{sub *} galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'pre-processing' in the group environment prior to their accretion into the cluster. On average, {approx} 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; and less than {approx} 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past ({approx}< 6 Gyr) than a field halo of the same mass. These results suggest that local, cluster processes like ram-pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass; and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with {approx} 20% incorporated into the cluster halo more than 7 Gyr ago and {approx} 20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate time-scale for late-type to early-type transformation within the cluster environment to be {approx} 6 Gyr.

  19. [Cluster analysis in biomedical researches].

    PubMed

    Akopov, A S; Moskovtsev, A A; Dolenko, S A; Savina, G D

    2013-01-01

    Cluster analysis is one of the most popular methods for the analysis of multi-parameter data. The cluster analysis reveals the internal structure of the data, group the separate observations on the degree of their similarity. The review provides a definition of the basic concepts of cluster analysis, and discusses the most popular clustering algorithms: k-means, hierarchical algorithms, Kohonen networks algorithms. Examples are the use of these algorithms in biomedical research. PMID:24640781

  20. The Orion nebula star cluster

    NASA Technical Reports Server (NTRS)

    Panek, R. J.

    1982-01-01

    Photography through filters which suppress nebular light reveal a clustering of faint red stars centered on the Trapezium, this evidences a distinct cluster within the larger OB1 association. Stars within about 20 ft of trapezium comprise the Orion Nebula star cluster are considered. Topics discussed re: (1) extinction by dust grains; (2) photometric peculiarities; (3) spectroscopic peculiarities; (4) young variables; (5) the distribution and motion of gas within the cluster.

  1. Clustering signatures classify directed networks

    NASA Astrophysics Data System (ADS)

    Ahnert, S. E.; Fink, T. M. A.

    2008-09-01

    We use a clustering signature, based on a recently introduced generalization of the clustering coefficient to directed networks, to analyze 16 directed real-world networks of five different types: social networks, genetic transcription networks, word adjacency networks, food webs, and electric circuits. We show that these five classes of networks are cleanly separated in the space of clustering signatures due to the statistical properties of their local neighborhoods, demonstrating the usefulness of clustering signatures as a classifier of directed networks.

  2. Observations of Distant Clusters

    NASA Technical Reports Server (NTRS)

    Donahue, Megan

    2004-01-01

    The is the proceedings and papers supported by the LTSA grant: Homer, D. J.\\& Donahue, M. 2003, in "The Emergence of Cosmic Structure": 13'h Astrophysics Conference Proceedings, Vol. 666,3 1 1-3 14, (AIP). Baumgartner, W. H., Loewenstein, M., Horner, D. J., Mushotzky, R. F. 2003, HEAD- AAS, 35.3503. Homer, D. J. , Donahue, M., Voit G. M. 2003, HEAD-AAS, 35.1309. Nowak, M. A., Smith, B., Donahue, M., Stocke, J. 2003, HEAD-AAS, 35.1316. Scott, D., Borys, C., Chapman, S. C., Donahue, M., Fahlman, G. G., Halpem, M. Newbury, P. 2002, AAS, 128.01. Jones, L. R. et al. 2002, A new era in cosmology, ASP Conference Proceedings, Vol. 283, p. 223 Donahue, M., Daly, R. A., Homer, D. J. 2003, ApJ, 584, 643, Constraints on the Cluster Environments and Hotspot magnetic field strengths for radio sources 3280 and 3254. Donahue, M., et al. 2003, ApJ, 598, 190. The mass, baryonic fraction, and x-ray temperature of the luminous, high-redshift cluster of galaxies MS045 1.6-0305 Perlman, E. S. et al. 2002, ApJS, 140, 256. Smith, B. J., Nowak, M., Donahue, M., Stocke, J. 2003, AJ, 126, 1763. Chandra Observations of the Interacting NGC44 10 Group of Galaxies. Postman, M., Lauer, T. R., Oegerle, W., Donahue, M. 2002, ApJ, 579, 93. The KPNO/deep-range cluster survey I. The catalog and space density of intermediate-redshift clusters. Molnar, S. M., Hughes, J. P., Donahue, M., Joy, M. 2002, ApJ, 573, L91, Chandra Observations of Unresolved X-Ray Sources around Two Clusters of Galaxies. Donahue, M., Mack, J., 2002 NewAR, 46, 155, HST NIcmos and WFPC2 observations of molecular hydrogen and dust around cooling flows. Koekemoer, A. M. et al. 2002 NewAR, 46, 149, Interactions between the A2597 central radio source and dense gas host galaxy. Donahue, M. et al. 2002 ApJ, 569,689, Distant cluster hunting II.

  3. Derivatized gold clusters and antibody-gold cluster conjugates

    DOEpatents

    Hainfeld, James F.; Furuya, Frederic R.

    1994-11-01

    Antibody- or antibody fragment-gold cluster conjugates are shown wherein the conjugate size can be as small as 5.0 nm. Methods and reagents are disclosed in which antibodies, Fab' or F(ab').sub.2 fragments thereof are covalently bound to a stable cluster of gold atoms. The gold clusters may contain 6, 8, 9, 11, 13, 55 or 67 gold atoms in their inner core. The clusters may also contain radioactive gold. The antibody-cluster conjugates are useful in electron microscopy applications as well as in clinical applications that include imaging, diagnosis and therapy.

  4. Derivatized gold clusters and antibody-gold cluster conjugates

    DOEpatents

    Hainfeld, J.F.; Furuya, F.R.

    1994-11-01

    Antibody- or antibody fragment-gold cluster conjugates are shown wherein the conjugate size can be as small as 5.0 nm. Methods and reagents are disclosed in which antibodies, Fab' or F(ab')[sub 2] fragments are covalently bound to a stable cluster of gold atoms. The gold clusters may contain 6, 8, 9, 11, 13, 55 or 67 gold atoms in their inner core. The clusters may also contain radioactive gold. The antibody-cluster conjugates are useful in electron microscopy applications as well as in clinical applications that include imaging, diagnosis and therapy. 7 figs.

  5. Connecting Remote Clusters with ATM

    SciTech Connect

    Hu, T.C.; Wyckoff, P.S.

    1998-10-01

    Sandia's entry into utilizing clusters of networked workstations is called Computational Plant or CPlant for short. The design of CPlant uses Ethernet to boot the individual nodes, Myrinet to communicate within a node cluster, and ATM to connect between remote clusters. This SAND document covers the work done to enable the use of ATM on the CPlant nodes in the Fall of 1997.

  6. Adaptive Clustering of Hypermedia Documents.

    ERIC Educational Resources Information Center

    Johnson, Andrew; Fotouhi, Farshad

    1996-01-01

    Discussion of hypermedia systems focuses on a comparison of two types of adaptive algorithm (genetic algorithm and neural network) in clustering hypermedia documents. These clusters allow the user to index into the nodes to find needed information more quickly, since clustering is "personalized" based on the user's paths rather than representing…

  7. Coupled Cluster Evaluation of the Stability of Atmospheric Acid-Base Clusters with up to 10 Molecules.

    PubMed

    Myllys, Nanna; Elm, Jonas; Halonen, Roope; Kurtén, Theo; Vehkamäki, Hanna

    2016-02-01

    We investigate the utilization of the domain local pair natural orbital coupled cluster (DLPNO-CCSD(T)) method for calculating binding energies of atmospherical molecular clusters. Applied to small complexes of atmospherical relevance we find that the DLPNO method significantly reduces the scatter in the binding energy, which is commonly present in DFT calculations. For medium sized clusters consisting of sulfuric acid and bases the DLPNO method yields a systematic underestimation of the binding energy compared to canonical coupled cluster results. The errors in the DFT binding energies appear to be more random, while the systematic nature of the DLPNO results allows the establishment of a scaling factor, to better mimic the canonical coupled cluster calculations. Based on the trends identified for the small and medium sized systems, we further extend the application of the DLPNO method to large acid - base clusters consisting of up to 10 molecules, which have previously been out of reach with accurate coupled cluster methods. Using the Atmospheric Cluster Dynamics Code (ACDC) we compare the sulfuric acid dimer formation based on the new DLPNO binding energies with previously published RI-CC2/aug-cc-pV(T+d)Z results. We also compare the simulated sulfuric acid dimer concentration as a function of the base concentration with measurement data from the CLOUD chamber and flow tube experiments. The DLPNO method, even after scaling, underpredicts the dimer concentration significantly. Reasons for this are discussed. PMID:26771121

  8. Gas deficiency in cluster galaxies - A comparison of nine clusters

    NASA Technical Reports Server (NTRS)

    Giovanelli, R.; Haynes, M. P.

    1985-01-01

    The available 21 cm line data in the literature for galaxies in nine clusters is combined with new high-sensitivity observations of 51 galaxies in five of the nine clusters in order to test for discriminating circumstances between those clusters which show H I deficiency among their spiral population and those which do not. An H I deficiency for the complete cluster sample is derived employing a comparison sample of galaxies chosen from the Catalog of Isolated Galaxies. The deficiency and its radial dependence is summarized for each cluster and a composite. A comparison of the environments in different clusters leads to the conclusion that the occurrence of H I deficiency is correlated with the presence of a hot X-ray intracluster medium, and that an ongoing interaction process is active through the cores of X-ray clusters.

  9. Cluster synthesis. 38. Formation of high-nuclearity platinum-osmium cluster complexes. Synthesis, structural characterizations, and interrelationships of Pt[sub 4]Os[sub 6](CO)[sub 22](COD), Pt[sub 5]Os[sub 6](CO)[sub 21](COD)[sub 2], Pt[sub 4]Os[sub 6](CO)[sub 19](COD)[sub 2], and Pt[sub 7]Os[sub 6](CO)[sub 21](COD)[sub 2] (COD = cycloocta-1,5-diene)

    SciTech Connect

    Adams, R.D.; Jauching Lii; Wengan Wu )

    1992-06-10

    The chemistry of heteronuclear cluster complexes containing Pt has attracted a great deal of interest becasue of the importance of Pt alloys to the process of catalytic petroleum reforming. Three new high-nuclearity Pt-Os carbonyl cluster complexes Pt[sub 4]Os[sub 6](CO)[sub 22](COD) (2), Pt[sub 5]Os[sub 6](CO)[sub 21](COD)[sub 2] (3), and Pt[sub 4]Os[sub 6](CO)[sub 19](COD)[sub 2] (4) were obtained in 17%, 13%, and 9% yields, respectively, from the pyrolysis of Pt[sub 2]Os[sub 3](CO)[sub 10](COD)[sub 2] (1) under a CO atmosphere at 128C. Compounds 2-4 were characterized by IR, [sup 1]H NMR, and single-crystal X-ray diffraction analyses. Compound 2 consists of two Pt[sub 3]Os[sub 3] octahedra sharing a Pt[sub 3] triangular face. A Pt(COD) group caps one of the Os[sub 3] triangular faces. Compound 3 is structurally similar to compound 2 but has an additional Pt(COD) group capping one of the PtOs[sub 2] triangular faces. The cluster of compound 4 can be viewed as a meta-bicapped Pt[sub 2]Os[sub 4] octahedron with an additional Pt(COD) group capping a PtOs[sub 2] traingle to one of the capping groups on the octahedron and a Pt(COD) group bridging the Pt-Pt edge of the octahedron. Compound 2 was converted to 4 in 65% yield, when it was irradiated in the presence of COD. When compound 2 was treated with 1 equiv of trimethylamine N-oxide and 2 equiv of Pt(COD)[sub 2], compound 3 and a new higher nuclearity platinum-osmium carbonyl complex Pt[sub 7]Os[sub 6](CO)[sub 21](COD)[sub 2] (5; 8% yeild) were obtained. Compound 5 was characterized by a single-crystal X-ray diffraction analysis. It was formed by the loss of one CO from 2 and the addition of three Pt atoms and one COD ligand. Compound 2 was converted to the known compound Pt[sub 4]Os[sub 6](CO)[sub 21](COD)([mu]-H)[sub 2] in good yield (79%) by reacting with trimethylamine N-oxide and hydrogen.

  10. Clusterization in Ternary Fission

    NASA Astrophysics Data System (ADS)

    Kamanin, D. V.; Pyatkov, Y. V.

    This lecture notes are devoted to the new kind of ternary decay of low excited heavy nuclei called by us "collinear cluster tri-partition" (CCT) due to the features of the effect observed, namely, decay partners fly away almost collinearly and at least one of them has magic nucleon composition. At the early stage of our work the process of "true ternary fission" (fission of the nucleus into three fragments of comparable masses) was considered to be undiscovered for low excited heavy nuclei. Another possible prototype—three body cluster radioactivity—was also unknown. The most close to the CCT phenomenon, at least cinematically, stands so called "polar emission", but only very light ions (up to isotopes of Be) were observed so far.

  11. Swirling granular solidlike clusters

    NASA Astrophysics Data System (ADS)

    Scherer, Michael A.; Kötter, Karsten; Markus, Mario; Goles, Eric; Rehberg, Ingo

    2000-04-01

    Experiments and three-dimensional numerical simulations are presented to elucidate the dynamics of granular material in a cylindrical dish driven by a horizontal, periodic motion. The following phenomena are obtained both in the experiments and in the simulations: First, for large particle numbers N the particles describe hypocycloidal trajectories. In this state the particles are embedded in a solidlike cluster (``pancake'') which counter-rotates with respect to the external driving (reptation). Self-organization within the cluster occurs such that the probability distribution of the particles consists of concentric rings. Second, the system undergoes phase transitions. These can be identified by changes of the quantity dEkin/dN (Ekin is the mean kinetic energy) between zero (rotation), positive (reptation), and negative values (appearance of the totality of concentric rings).

  12. Massive cold cloud clusters

    NASA Astrophysics Data System (ADS)

    Toth, L. Viktor; Marton, Gabor; Zahorecz, Sarolta

    2015-08-01

    The all-sky Planck catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015) allows an almost unbiased study of the early phases of star-formation in our Galaxy. Several thousand of the clumps have also distance estimates allowing a mass, and density determination. The nature of Planck clumps varies from IRDCs to tiny nearby cold clouds with masses ranging from one to several tens of thousands solar masses. Some of the clumps are embedded in GMCs, others are isolated. Some are close or even very close to OB associations, while others lay far from any UV luminous objects.The small scale clustering of these objects was studied with the improved Minimum Spanning Tree method of Cartwright & Whitworth identifying groups in 3D space. As a result also massive cold cloud clusters were identified. We analyse the MST structures, and discuss their relation to ongoing and future massive star formation.

  13. Fractal polyzirconosiloxane cluster coatings

    SciTech Connect

    Sugama, T.

    1992-08-01

    Fractal polyzirconosiloxane (PZS) cluster films were prepared through the hydrolysis-polycondensation-pyrolysis synthesis of two-step HCl acid-NaOH base catalyzed sol precursors consisting of N-[3-(triethoxysilyl)propyl]-4,5-dihydroimidazole, Zr(OC{sub 3}H{sub 7}){sub 4}, methanol, and water. When amorphous PZSs were applied to aluminum as protective coatings against NaCl-induced corrosion, the effective film was that derived from the sol having a pH near the isoelectric point in the positive zeta potential region. The following four factors played an important role in assembling the protective PZS coating films: (1) a proper rate of condensation, (2) a moderate ratio of Si-O-Si to Si-O-Zr linkages formed in the PZS network, (3) hydrophobic characteristics, and (4) a specific microstructural geometry, in which large fractal clusters were linked together.

  14. Fractal polyzirconosiloxane cluster coatings

    SciTech Connect

    Sugama, T.

    1992-01-01

    Fractal polyzirconosiloxane (PZS) cluster films were prepared through the hydrolysis-polycondensation-pyrolysis synthesis of two-step HCl acid-NaOH base catalyzed sol precursors consisting of N-(3-(triethoxysilyl)propyl)-4,5-dihydroimidazole, Zr(OC{sub 3}H{sub 7}){sub 4}, methanol, and water. When amorphous PZSs were applied to aluminum as protective coatings against NaCl-induced corrosion, the effective film was that derived from the sol having a pH near the isoelectric point in the positive zeta potential region. The following four factors played an important role in assembling the protective PZS coating films: (1) a proper rate of condensation, (2) a moderate ratio of Si-O-Si to Si-O-Zr linkages formed in the PZS network, (3) hydrophobic characteristics, and (4) a specific microstructural geometry, in which large fractal clusters were linked together.

  15. Hydrated hydride anion clusters

    NASA Astrophysics Data System (ADS)

    Lee, Han Myoung; Kim, Dongwook; Singh, N. Jiten; Kołaski, Maciej; Kim, Kwang S.

    2007-10-01

    On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed.

  16. Layers in Crater Cluster

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-431, 24 July 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a cluster of old, small impact craters near 36.3oN, 281.9oW. The group of craters was probably formed by secondary impacts following a much larger impact that occurred some distance away; the material that created these craters would have been the ejecta from the larger crater, rather than meteoroids from outer space. The craters cluster is considered to be relatively old because none of the craters have ejecta blankets any more, and each was filled, or partially filled, with layered material that was later eroded to form the terraced mounds found in their floors. This picture is illuminated from the lower left.

  17. High resolution electron attachment to CO₂ clusters.

    PubMed

    Denifl, Stephan; Vizcaino, Violaine; Märk, Tilmann D; Illenberger, Eugen; Scheier, Paul

    2010-01-01

    Electron attachment to CO₂ clusters performed at high energy resolution (0.1 eV) is studied for the first time in the extended electron energy range from threshold (0 eV) to about 10 eV. Dissociative electron attachment (DEA) to single molecules yields O(-) as the only fragment ion arising from the well known (2)Π(u) shape resonance (ion yield centered at 4.4 eV) and a core excited resonance (at 8.2 eV). On proceeding to CO₂ clusters, non-dissociated complexes of the form (CO₂)(n)(-) including the monomer CO₂(-) are generated as well as solvated fragment ions of the form (CO₂)(n)O(-). The non-decomposed complexes appear already within a resonant feature near threshold (0 eV) and also within a broad contribution between 1 and 4 eV which is composed of two resonances observed for example for (CO₂)(4)(-) at 2.2 eV and 3.1 eV (peak maxima). While the complexes observed around 3.1 eV are generated via the (2)Π(u) resonance as precursor with subsequent intracluster relaxation, the contribution around 2.2 eV can be associated with a resonant scattering feature, recently discovered in single CO₂ in the selective excitation of the higher energy member of the well known Fermi dyad [M. Allan, Phys. Rev. Lett., 2001, 87, 0332012]. Formation of (CO₂)(n)(-) in the threshold region involves vibrational Feshbach resonances (VFRs) as previously discovered via an ultrahigh resolution (1 meV) laser photoelectron attachment method [E. Leber, S. Barsotti, I. I. Fabrikant, J. M. Weber, M.-W. Ruf and H. Hotop, Eur. Phys. J. D, 2000, 12, 125]. The complexes (CO₂)(n)O(-) clearly arise from DEA at an individual molecule within the cluster involving both the (2)Π(u) and the core excited resonance. PMID:21491691

  18. Ground and excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters: Insight into the electronic structure of the [Fe(H2O)6]2+ – [Fe(H2O)6]3+ complex

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2015-04-14

    We report the ground and low lying electronically excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters using multi-configuration electronic structure theory. In particular, we have constructed the Potential Energy Curves (PECs) with respect to the iron-oxygen distance when removing all water ligands at the same time from the cluster minima and established their correlation to the long range dissociation channels. Due to the fact that both the second and third ionization potentials of iron are larger than the one for water, the ground state products asymptotically correlate with dissociation channels that are repulsive in nature at large separations as they contain at least one H2O+ fragment and a positive metal center. The most stable equilibrium structures emanate – via intersections and/or avoided crossings – from the channels consisting of the lowest electronic states of Fe2+(5D; 3d6) or Fe3+(6S; 3d5) and six neutral water molecules. Upon hydration, the ground state of Fe2+(H2O)6 is a triply (5Tg) degenerate one with the doubly (5Eg) degenerate state lying slightly higher in energy. Similarly, Fe3+(H2O)6 has a ground state of 6Ag symmetry under Th symmetry. We furthermore examine a multitude of electronically excited states of many possible spin multiplicities, and report the optimized geometries for several selected states. The PECs for those cases are characterized by a high density of states. Focusing on the ground and the first few excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters, we studied their mutual interaction in the gas phase. We obtained the optimal geometries of the Fe2+(H2O)6 – Fe3+(H2O)6 gas phase complex for different Fe–Fe distances. For distances shorter than 6.0 Å, the water molecules in the respective first solvation shells located between the two metal centers were found to interact via weak hydrogen bonds. We examined a total of ten electronic states for this complex, including those corresponding to the

  19. Cosmology, Clusters and Calorimeters

    NASA Technical Reports Server (NTRS)

    Figueroa-Feliciano, Enectali

    2005-01-01

    I will review the current state of Cosmology with Clusters and discuss the application of microcalorimeter arrays to this field. With the launch of Astro-E2 this summer and a slew of new missions being developed, microcalorimeters are the next big thing in x-ray astronomy. I will cover the basics and not-so-basic concepts of microcalorimeter designs and look at the future to see where this technology will go.

  20. Cluster galaxies die hard

    NASA Astrophysics Data System (ADS)

    Weinmann, Simone M.; Kauffmann, Guinevere; von der Linden, Anja; De Lucia, Gabriella

    2010-08-01

    We investigate how the specific star formation rates of galaxies of different masses depend on cluster-centric radius and on the central/satellite dichotomy in both field and cluster environments. Recent data from a variety of sources, including the cluster catalogue of von der Linden et al., are compared to the semi-analytic models of De Lucia & Blaizot. We find that these models predict too many passive satellite galaxies in clusters, too few passive central galaxies with low stellar masses and too many passive central galaxies with high masses. We then outline a series of modifications to the model necessary to solve these problems: (a) instead of instantaneous stripping of the external gas reservoir after a galaxy becomes a satellite, the gas supply is assumed to decrease at the same rate that the surrounding halo loses mass due to tidal stripping and (b) the active galactic nuclei (AGN) feedback efficiency is lowered to bring the fraction of massive passive centrals in better agreement with the data. We also allow for radio mode AGN feedback in satellite galaxies. (c) We assume that satellite galaxies residing in host haloes with masses below 1012h-1Msolar do not undergo any stripping. We highlight the fact that in low-mass galaxies, the external reservoir is composed primarily of gas that has been expelled from the galactic disc by supernovae-driven winds. This gas must remain available as a future reservoir for star formation, even in satellite galaxies. Finally, we present a simple recipe for the stripping of gas and dark matter in satellites that can be used in models where subhalo evolution is not followed in detail.

  1. Cluster headache after orbital exenteration.

    PubMed

    Evers, S; Sörös, P; Brilla, R; Gerding, H; Husstedt, I W

    1997-10-01

    A 37-year-old man developed an ipsilateral headache which fulfilled the criteria for cluster headache after orbital extenteration because of a traumatic lesion of the bulb. The headache could be treated successfully by drugs usually applied in the therapy of cluster headache. Six similar cases of cluster headache after orbital exenteration could be identified in the literature suggesting that the eye itself is not necessarily part of the pathogenesis of cluster headache. We hypothesize that orbital exenteration can cause cluster headache by lesions of sympathetic structures. Possibly, these mechanisms are similar to those of sympathetic reflex dystrophy (Sudeck-Leriche syndrome) causing pain of the limbs. PMID:9350391

  2. Multiscale hierarchical support vector clustering

    NASA Astrophysics Data System (ADS)

    Hansen, Michael Saas; Holm, David Alberg; Sjöstrand, Karl; Ley, Carsten Dan; Rowland, Ian John; Larsen, Rasmus

    2008-03-01

    Clustering is the preferred choice of method in many applications, and support vector clustering (SVC) has proven efficient for clustering noisy and high-dimensional data sets. A method for multiscale support vector clustering is demonstrated, using the recently emerged method for fast calculation of the entire regularization path of the support vector domain description. The method is illustrated on artificially generated examples, and applied for detecting blood vessels from high resolution time series of magnetic resonance imaging data. The obtained results are robust while the need for parameter estimation is reduced, compared to support vector clustering.

  3. Complexity Survey.

    ERIC Educational Resources Information Center

    Gordon, Sandra L.; Anderson, Beth C.

    To determine whether consensus existed among teachers about the complexity of common classroom materials, a survey was administered to 66 pre-service and in-service kindergarten and prekindergarten teachers. Participants were asked to rate 14 common classroom materials as simple, complex, or super-complex. Simple materials have one obvious part,…

  4. Stellar Snowflake Cluster

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1 Stellar Snowflake Cluster Combined Image [figure removed for brevity, see original site] Figure 2 Infrared Array CameraFigure 3 Multiband Imaging Photometer

    Newborn stars, hidden behind thick dust, are revealed in this image of a section of the Christmas Tree cluster from NASA's Spitzer Space Telescope, created in joint effort between Spitzer's infrared array camera and multiband imaging photometer instruments.

    The newly revealed infant stars appear as pink and red specks toward the center of the combined image (fig. 1). The stars appear to have formed in regularly spaced intervals along linear structures in a configuration that resembles the spokes of a wheel or the pattern of a snowflake. Hence, astronomers have nicknamed this the 'Snowflake' cluster.

    Star-forming clouds like this one are dynamic and evolving structures. Since the stars trace the straight line pattern of spokes of a wheel, scientists believe that these are newborn stars, or 'protostars.' At a mere 100,000 years old, these infant structures have yet to 'crawl' away from their location of birth. Over time, the natural drifting motions of each star will break this order, and the snowflake design will be no more.

    While most of the visible-light stars that give the Christmas Tree cluster its name and triangular shape do not shine brightly in Spitzer's infrared eyes, all of the stars forming from this dusty cloud are considered part of the cluster.

    Like a dusty cosmic finger pointing up to the newborn clusters, Spitzer also illuminates the optically dark and dense Cone nebula, the tip of which can be seen towards the bottom left corner of each image.

    This combined image shows the presence of organic molecules mixed with dust as wisps of green, which have been illuminated by nearby star formation. The larger yellowish dots neighboring the baby red stars in the Snowflake Cluster are massive stellar infants forming

  5. Communication complexity and information complexity

    NASA Astrophysics Data System (ADS)

    Pankratov, Denis

    Information complexity enables the use of information-theoretic tools in communication complexity theory. Prior to the results presented in this thesis, information complexity was mainly used for proving lower bounds and direct-sum theorems in the setting of communication complexity. We present three results that demonstrate new connections between information complexity and communication complexity. In the first contribution we thoroughly study the information complexity of the smallest nontrivial two-party function: the AND function. While computing the communication complexity of AND is trivial, computing its exact information complexity presents a major technical challenge. In overcoming this challenge, we reveal that information complexity gives rise to rich geometrical structures. Our analysis of information complexity relies on new analytic techniques and new characterizations of communication protocols. We also uncover a connection of information complexity to the theory of elliptic partial differential equations. Once we compute the exact information complexity of AND, we can compute exact communication complexity of several related functions on n-bit inputs with some additional technical work. Previous combinatorial and algebraic techniques could only prove bounds of the form theta( n). Interestingly, this level of precision is typical in the area of information theory, so our result demonstrates that this meta-property of precise bounds carries over to information complexity and in certain cases even to communication complexity. Our result does not only strengthen the lower bound on communication complexity of disjointness by making it more exact, but it also shows that information complexity provides the exact upper bound on communication complexity. In fact, this result is more general and applies to a whole class of communication problems. In the second contribution, we use self-reduction methods to prove strong lower bounds on the information

  6. PLIC: protein-ligand interaction clusters.

    PubMed

    Anand, Praveen; Nagarajan, Deepesh; Mukherjee, Sumanta; Chandra, Nagasuma

    2014-01-01

    Most of the biological processes are governed through specific protein-ligand interactions. Discerning different components that contribute toward a favorable protein- ligand interaction could contribute significantly toward better understanding protein function, rationalizing drug design and obtaining design principles for protein engineering. The Protein Data Bank (PDB) currently hosts the structure of ∼68 000 protein-ligand complexes. Although several databases exist that classify proteins according to sequence and structure, a mere handful of them annotate and classify protein-ligand interactions and provide information on different attributes of molecular recognition. In this study, an exhaustive comparison of all the biologically relevant ligand-binding sites (84 846 sites) has been conducted using PocketMatch: a rapid, parallel, in-house algorithm. PocketMatch quantifies the similarity between binding sites based on structural descriptors and residue attributes. A similarity network was constructed using binding sites whose PocketMatch scores exceeded a high similarity threshold (0.80). The binding site similarity network was clustered into discrete sets of similar sites using the Markov clustering (MCL) algorithm. Furthermore, various computational tools have been used to study different attributes of interactions within the individual clusters. The attributes can be roughly divided into (i) binding site characteristics including pocket shape, nature of residues and interaction profiles with different kinds of atomic probes, (ii) atomic contacts consisting of various types of polar, hydrophobic and aromatic contacts along with binding site water molecules that could play crucial roles in protein-ligand interactions and (iii) binding energetics involved in interactions derived from scoring functions developed for docking. For each ligand-binding site in each protein in the PDB, site similarity information, clusters they belong to and description of

  7. Monothiol glutaredoxins and A-type proteins: partners in Fe-S cluster trafficking.

    PubMed

    Mapolelo, Daphne T; Zhang, Bo; Randeniya, Sajini; Albetel, Angela-Nadia; Li, Haoran; Couturier, Jérémy; Outten, Caryn E; Rouhier, Nicolas; Johnson, Michael K

    2013-03-01

    Monothiol glutaredoxins (Grxs) are proposed to function in Fe-S cluster storage and delivery, based on their ability to exist as apo monomeric forms and dimeric forms containing a subunit-bridging [Fe(2)S(2)](2+) cluster, and to accept [Fe(2)S(2)](2+) clusters from primary scaffold proteins. In addition yeast cytosolic monothiol Grxs interact with Fra2 (Fe repressor of activation-2), to form a heterodimeric complex with a bound [Fe(2)S(2)](2+) cluster that plays a key role in iron sensing and regulation of iron homeostasis. In this work, we report on in vitro UV-visible CD studies of cluster transfer between homodimeric monothiol Grxs and members of the ubiquitous A-type class of Fe-S cluster carrier proteins ((Nif)IscA and SufA). The results reveal rapid, unidirectional, intact and quantitative cluster transfer from the [Fe(2)S(2)](2+) cluster-bound forms of A. thaliana GrxS14, S. cerevisiae Grx3, and A. vinelandii Grx-nif homodimers to A. vinelandii(Nif)IscA and from A. thaliana GrxS14 to A. thaliana SufA1. Coupled with in vivo evidence for interaction between monothiol Grxs and A-type Fe-S cluster carrier proteins, the results indicate that these two classes of proteins work together in cellular Fe-S cluster trafficking. However, cluster transfer is reversed in the presence of Fra2, since the [Fe(2)S(2)](2+) cluster-bound heterodimeric Grx3-Fra2 complex can be formed by intact [Fe(2)S(2)](2+) cluster transfer from (Nif)IscA. The significance of these results for Fe-S cluster biogenesis or repair and the cellular regulation of the Fe-S cluster status are discussed. PMID:23292141

  8. Convex Clustering: An Attractive Alternative to Hierarchical Clustering

    PubMed Central

    Chen, Gary K.; Chi, Eric C.; Ranola, John Michael O.; Lange, Kenneth

    2015-01-01

    The primary goal in cluster analysis is to discover natural groupings of objects. The field of cluster analysis is crowded with diverse methods that make special assumptions about data and address different scientific aims. Despite its shortcomings in accuracy, hierarchical clustering is the dominant clustering method in bioinformatics. Biologists find the trees constructed by hierarchical clustering visually appealing and in tune with their evolutionary perspective. Hierarchical clustering operates on multiple scales simultaneously. This is essential, for instance, in transcriptome data, where one may be interested in making qualitative inferences about how lower-order relationships like gene modules lead to higher-order relationships like pathways or biological processes. The recently developed method of convex clustering preserves the visual appeal of hierarchical clustering while ameliorating its propensity to make false inferences in the presence of outliers and noise. The solution paths generated by convex clustering reveal relationships between clusters that are hidden by static methods such as k-means clustering. The current paper derives and tests a novel proximal distance algorithm for minimizing the objective function of convex clustering. The algorithm separates parameters, accommodates missing data, and supports prior information on relationships. Our program CONVEXCLUSTER incorporating the algorithm is implemented on ATI and nVidia graphics processing units (GPUs) for maximal speed. Several biological examples illustrate the strengths of convex clustering and the ability of the proximal distance algorithm to handle high-dimensional problems. CONVEXCLUSTER can be freely downloaded from the UCLA Human Genetics web site at http://www.genetics.ucla.edu/software/ PMID:25965340

  9. Formation of Cool Cores in Galaxy Clusters via Hierarchical Mergers

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Burns, Jack O.; Loken, Chris; Norman, Michael L.; Bryan, Greg

    2004-05-01

    We present a new scenario for the formation of cool cores in rich galaxy clusters, based on results from recent high spatial dynamic range, adaptive mesh Eulerian hydrodynamic simulations of large-scale structure formation. We find that cores of cool gas, material that would be identified as a classical cooling flow on the basis of its X-ray luminosity excess and temperature profile, are built from the accretion of discrete stable subclusters. Any ``cooling flow'' present is overwhelmed by the velocity field within the cluster; the bulk flow of gas through the cluster typically has speeds up to about 2000 km s-1, and significant rotation is frequently present in the cluster core. The inclusion of consistent initial cosmological conditions for the cluster within its surrounding supercluster environment is crucial when the evolution of cool cores in rich galaxy clusters is simulated. This new model for the hierarchical assembly of cool gas naturally explains the high frequency of cool cores in rich galaxy clusters, despite the fact that a majority of these clusters show evidence of substructure that is believed to arise from recent merger activity. Furthermore, our simulations generate complex cluster cores in concordance with recent X-ray observations of cool fronts, cool ``bullets,'' and filaments in a number of galaxy clusters. Our simulations were computed with a coupled N-body, Eulerian, adaptive mesh refinement, hydrodynamics cosmology code that properly treats the effects of shocks and radiative cooling by the gas. We employ up to seven levels of refinement to attain a peak resolution of 15.6 kpc within a volume 256 Mpc on a side and assume a standard ΛCDM cosmology.

  10. HUBBLE SNAPS PICTURE OF REMARKABLE DOUBLE CLUSTER

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The double cluster NGC 1850, found in one of our neighboring galaxies, the Large Magellanic Cloud, is an eye-catching object. It is a young, 'globular-like' star cluster -- a type of object unknown in our own Milky Way Galaxy. Moreover, NGC 1850 is surrounded by a filigree pattern of diffuse gas, which scientists believe was created by the explosion of massive stars. NGC 1850, imaged here with the NASA Hubble Space Telescope, is an unusual double cluster that lies in the bar of the Large Magellanic Cloud, a satellite galaxy of our own Milky Way. After the 30 Doradus complex, NGC 1850 is the brightest star cluster in the Large Magellanic Cloud. It is representative of a special class of objects -- young, globular-like star clusters -- that have no counterpart in our galaxy. The two components of the cluster are both relatively young and consist of a main, globular-like cluster in the center and an even younger, smaller cluster, seen below and to the right, composed of extremely hot, blue stars and, fainter red T-Tauri stars. The main cluster is about 50 million years old; the smaller cluster is only 4 million years old. One of Hubble's main contributions to the study of NGC 1850 is in the investigation of star formation at both ends of the stellar mass scale -- the low-mass T-Tauri stars and the high-mass OB stars. T-Tauri stars are young, solar-class stars that are still forming, so young that they may have not started converting hydrogen to helium, which is how our Sun produces its energy. Instead they radiate energy released by their own gravitational contraction. By investigating these stars astronomers learn about the births and lives of low-mass stars. T-Tauri stars tend to occur in crowded environments, but are themselves faint, making them difficult to distinguish with ground-based telescopes. However, Hubble's fine angular resolution can pick out these stars, even in galaxies other than our own. Hubble also has advantages when studying very massive stars

  11. Enantiospecific adsorption of cysteine on a chiral Au34 cluster

    NASA Astrophysics Data System (ADS)

    Pelayo, José de Jesús; Valencia, Israel; Díaz, Gabriela; López-Lozano, Xóchitl; Garzón, Ignacio L.

    2015-12-01

    The interaction of biological molecules like chiral amino acids with chiral metal clusters is becoming an interesting and active field of research because of its potential impact in, for example, chiral molecular recognition phenomena. In particular, the enantiospecific adsorption (EA) of cysteine (Cys) on a chiral Au55 cluster was theoretically predicted a few years ago. In this work, we present theoretical results, based on density functional theory, of the EA of non-zwitterionic cysteine interacting with the C3-Au34 chiral cluster, which has been experimentally detected in gas phase, using trapped ion electron diffraction. Our results show that, indeed, the adsorption energy of the amino acid depends on which enantiomers participate in the formation Cys-Au34 chiral complex. EA was obtained in the adsorption modes where both the thiol, and the thiol-amino functional groups of Cys are adsorbed on low-coordinated sites of the metal cluster surface. Similarly to what was obtained for the Cys-Au55 chiral complex, in the present work, it is found that the EA is originated from the different strength and location of the bond between the COOH functional group and surface Au atoms of the Au34 chiral cluster. Calculations of the vibrational spectrum for the different Cys-Au34 diastereomeric complexes predict the existence of a vibro-enantiospecific effect, indicating that the vibrational frequencies of the adsorbed amino acid depend on its handedness.

  12. Measuring Cluster Relaxedness

    SciTech Connect

    Moreland, Blythe; /Michigan U. /SLAC

    2012-08-24

    When is a dark matter halo 'relaxed'? In our efforts to understand the structure of the universe, dark matter simulations have provided essential grounds for theoretical predictions. These simulations provide a wealth of ways of parameterizing and measuring the features of astronomical objects. It is these measurements on which we base comparisons of our world and our attempts to re-create it. One of the essential questions dark matter simulations help address is how dark matter halos evolve. How does one characterize different states of that evolution? The focus of this project is identifying cluster relaxedness and how it relates to the internal structure of the halo. A dark matter simulation consists of an N-body simulation which takes an initial set of positions and velocities of the dark matter particles and evolves them under the influence of gravity [6]. Though scientists have so far not been able to detect dark matter particles, the information from these simulations is still valuable especially given the relationship between dark matter halos and galaxy clusters. Galaxies sit within dark matter halos and recent evidence points to filaments of dark matter forming the framework on which galaxy clusters grow [7]. A dark matter halo is a collapsed group of gravitationally bound dark matter particles. Subsets of bound particles form subhalos or substructures. The dark matter simulation is carried out over time - with decreasing redshift (z) or increasing scale factor (a = 1/1+z ). (Thus, z = 0 or a = 1.0 is present-day.) The merger history of a halo can be represented pictorally by a merger tree. A major merger event occurs when a structure joins the main halo with the mass ratio between it and the main halo being above a certain threshold. These events mark important points in the halo's evolution. And it is at these events that one hopes, and perhaps is more likely, to relate measures of relaxedness to this mass accretion. Cluster relaxedness is not a well

  13. Role of Anions Associated with the Formation and Properties of Silver Clusters.

    PubMed

    Wang, Quan-Ming; Lin, Yu-Mei; Liu, Kuan-Guan

    2015-06-16

    Metal clusters have been very attractive due to their aesthetic structures and fascinating properties. Different from nanoparticles, each cluster of a macroscopic sample has a well-defined structure with identical composition, size, and shape. As the disadvantages of polydispersity are ruled out, informative structure-property relationships of metal clusters can be established. The formation of a high-nuclearity metal cluster involves the organization of metal ions into a complex entity in an ordered way. To achieve controllable preparation of metal clusters, it is helpful to introduce a directing agent in the formation process of a cluster. To this end, anion templates have been used to direct the formation of high nuclearity clusters. In this Account, the role of anions played in the formation of a variety of silver clusters has been reviewed. Silver ions are positively charged, so anionic species could be utilized to control the formation of silver clusters on the basis of electrostatic interactions, and the size and shape of the resulted clusters can be dictated by the templating anions. In addition, since the anion is an integral component in the silver clusters described, the physical properties of the clusters can be modulated by functional anions. The templating effects of simple inorganic anions and polyoxometales are shown in silver alkynyl clusters and silver thiolate clusters. Intercluster compounds are also described regarding the importance of anions in determining the packing of the ion pairs and making contribution to electron communications between the positive and negative counterparts. The role of the anions is threefold: (a) an anion is advantageous in stabilizing a cluster via balancing local positive charges of the metal cations; (b) an anion template could help control the size and shape of a cluster product; (c) an anion can be a key factor in influencing the function of a cluster through bringing in its intrinsic properties. Properties

  14. Clustering siRNA conjugates for MMP-responsive therapeutics in chronic wounds of diabetic animals

    NASA Astrophysics Data System (ADS)

    Kim, Hye Sung; Son, Young Ju; Yoo, Hyuk Sang

    2016-07-01

    The MMP-responsive breakdown of siRNA clusters was translated to site-specific gene transfection and enhanced wound healing in diabetic ulcers. MMP-2 siRNA was chemically tethered to the end of multi-armed PEG via MMP-cleavable linkers (4PEG-siRNA) and subsequently clustered into submicron particles complexed with LPEI. 4PEG-siRNA was more tightly complexed with LPEI and the associated cluster showed higher resistance against RNase attack, in comparison to naked siRNA. Because the size of the clusters increased depending on the increase in charge ratio of LPEI to siRNA, cellular uptake of the 4PEG-siRNA/LPEI cluster was significantly attenuated due to the huge size of the cluster. However, upon MMP treatment, the cluster dissociated into smaller particles and was efficiently endocytosed by cells. An in vivo fluorescence resonance energy transfer (FRET) study also revealed that the clusters were effectively dissociated in MMP-rich environments of dorsal wounds in diabetic animals. In addition, diabetic ulcers treated with the clusters showed a faster wound closure rate and the recovered tissue expressed a larger amount of cytokeratin along with a lower expression level of MMP-2 compared to the other groups.The MMP-responsive breakdown of siRNA clusters was translated to site-specific gene transfection and enhanced wound healing in diabetic ulcers. MMP-2 siRNA was chemically tethered to the end of multi-armed PEG via MMP-cleavable linkers (4PEG-siRNA) and subsequently clustered into submicron particles complexed with LPEI. 4PEG-siRNA was more tightly complexed with LPEI and the associated cluster showed higher resistance against RNase attack, in comparison to naked siRNA. Because the size of the clusters increased depending on the increase in charge ratio of LPEI to siRNA, cellular uptake of the 4PEG-siRNA/LPEI cluster was significantly attenuated due to the huge size of the cluster. However, upon MMP treatment, the cluster dissociated into smaller particles and was

  15. The Ages of Globular Clusters

    NASA Astrophysics Data System (ADS)

    McNamara, D. H.

    2001-03-01

    We examine the luminosity levels of the main-sequence turnoffs, MTOv, and horizontal branches, Mv(HB), in 16 globular clusters. An entirely new approach of inferring the luminosity levels by utilizing high-amplitude δ Scuti variables (HADS) is introduced. When the MTOv values are compared with theoretical values inferred from models, we find all 16 clusters (metal-strong to metal-poor) are coeval with an average age of ~11.3 Gyr. A considerable scatter of Mv(HB) values of clusters at similar [Fe/H] values is found. A trend for clusters with blue horizontal branches to have brighter Mv(HB) than clusters with blue-red horizontal branches is suggested by the data. The Mv(HB) values appear to depend on another or other parameters in addition to the [Fe/H] values. In spite of this problem, we derive an equation relating Mv(HB) values of globular clusters to their [Fe/H] values. We also derive an equation relating the MTOv values of clusters to their [Fe/H] values. Both of these equations can be utilized to find cluster distances. The distance modulus of the LMC is found to be 18.66 from the VTO values of three LMC globular clusters; RR Lyrae stars in seven globular clusters yield 18.61, and RR Lyrae stars in the LMC bar yield 18.64.

  16. GPU-based Multilevel Clustering.

    PubMed

    Chiosa, Iurie; Kolb, Andreas

    2010-04-01

    The processing power of parallel co-processors like the Graphics Processing Unit (GPU) are dramatically increasing. However, up until now only a few approaches have been presented to utilize this kind of hardware for mesh clustering purposes. In this paper we introduce a Multilevel clustering technique designed as a parallel algorithm and solely implemented on the GPU. Our formulation uses the spatial coherence present in the cluster optimization and hierarchical cluster merging to significantly reduce the number of comparisons in both parts . Our approach provides a fast, high quality and complete clustering analysis. Furthermore, based on the original concept we present a generalization of the method to data clustering. All advantages of the meshbased techniques smoothly carry over to the generalized clustering approach. Additionally, this approach solves the problem of the missing topological information inherent to general data clustering and leads to a Local Neighbors k-means algorithm. We evaluate both techniques by applying them to Centroidal Voronoi Diagram (CVD) based clustering. Compared to classical approaches, our techniques generate results with at least the same clustering quality. Our technique proves to scale very well, currently being limited only by the available amount of graphics memory. PMID:20421676

  17. Visual cluster analysis in support of clinical decision intelligence.

    PubMed

    Gotz, David; Sun, Jimeng; Cao, Nan; Ebadollahi, Shahram

    2011-01-01

    Electronic health records (EHRs) contain a wealth of information about patients. In addition to providing efficient and accurate records for individual patients, large databases of EHRs contain valuable information about overall patient populations. While statistical insights describing an overall population are beneficial, they are often not specific enough to use as the basis for individualized patient-centric decisions. To address this challenge, we describe an approach based on patient similarity which analyzes an EHR database to extract a cohort of patient records most similar to a specific target patient. Clusters of similar patients are then visualized to allow interactive visual refinement by human experts. Statistics are then extracted from the refined patient clusters and displayed to users. The statistical insights taken from these refined clusters provide personalized guidance for complex decisions. This paper focuses on the cluster refinement stage where an expert user must interactively (a) judge the quality and contents of automatically generated similar patient clusters, and (b) refine the clusters based on his/her expertise. We describe the DICON visualization tool which allows users to interactively view and refine multidimensional similar patient clusters. We also present results from a preliminary evaluation where two medical doctors provided feedback on our approach. PMID:22195102

  18. Visual Cluster Analysis in Support of Clinical Decision Intelligence

    PubMed Central

    Gotz, David; Sun, Jimeng; Cao, Nan; Ebadollahi, Shahram

    2011-01-01

    Electronic health records (EHRs) contain a wealth of information about patients. In addition to providing efficient and accurate records for individual patients, large databases of EHRs contain valuable information about overall patient populations. While statistical insights describing an overall population are beneficial, they are often not specific enough to use as the basis for individualized patient-centric decisions. To address this challenge, we describe an approach based on patient similarity which analyzes an EHR database to extract a cohort of patient records most similar to a specific target patient. Clusters of similar patients are then visualized to allow interactive visual refinement by human experts. Statistics are then extracted from the refined patient clusters and displayed to users. The statistical insights taken from these refined clusters provide personalized guidance for complex decisions. This paper focuses on the cluster refinement stage where an expert user must interactively (a) judge the quality and contents of automatically generated similar patient clusters, and (b) refine the clusters based on his/her expertise. We describe the DICON visualization tool which allows users to interactively view and refine multidimensional similar patient clusters. We also present results from a preliminary evaluation where two medical doctors provided feedback on our approach. PMID:22195102

  19. Extensive Polycistronism and Antisense Transcription in the Mammalian Hox Clusters

    PubMed Central

    Mainguy, Gaëll; Koster, Jan; Woltering, Joost; Jansen, Hans; Durston, Antony

    2007-01-01

    The Hox clusters play a crucial role in body patterning during animal development. They encode both Hox transcription factor and micro-RNA genes that are activated in a precise temporal and spatial sequence that follows their chromosomal order. These remarkable collinear properties confer functional unit status for Hox clusters. We developed the TranscriptView platform to establish high resolution transcriptional profiling and report here that transcription in the Hox clusters is far more complex than previously described in both human and mouse. Unannotated transcripts can represent up to 60% of the total transcriptional output of a cluster. In particular, we identified 14 non-coding Transcriptional Units antisense to Hox genes, 10 of which (70%) have a detectable mouse homolog. Most of these Transcriptional Units in both human and mouse present conserved sizeable sequences (>40 bp) overlapping Hox transcripts, suggesting that these Hox antisense transcripts are functional. Hox clusters also display at least seven polycistronic clusters, i.e., different genes being co-transcribed on long isoforms (up to 30 kb). This work provides a reevaluated framework for understanding Hox gene function and dys-function. Such extensive transcriptions may provide a structural explanation for Hox clustering. PMID:17406680

  20. THE NEXT GENERATION VIRGO CLUSTER SURVEY. IV. NGC 4216: A BOMBARDED SPIRAL IN THE VIRGO CLUSTER

    SciTech Connect

    Paudel, Sanjaya; Duc, Pierre-Alain; Ferriere, Etienne; Cuillandre, Jean-Charles; Mihos, J. Christopher; Vollmer, Bernd; Balogh, Michael L.; Carlberg, Ray G.; Boissier, Samuel; Boselli, Alessandro; Durrell, Patrick R.; Emsellem, Eric; Michel-Dansac, Leo; Mei, Simona; Van Driel, Wim

    2013-04-20

    The final stages of mass assembly of present-day massive galaxies are expected to occur through the accretion of multiple satellites. Cosmological simulations thus predict a high frequency of stellar streams resulting from this mass accretion around the massive galaxies in the Local Volume. Such tidal streams are difficult to observe, especially in dense cluster environments, where they are readily destroyed. We present an investigation into the origins of a series of interlaced narrow filamentary stellar structures, loops and plumes in the vicinity of the Virgo Cluster, edge-on spiral galaxy, NGC 4216 that were previously identified by the Blackbird telescope. Using the deeper, higher-resolution, and precisely calibrated optical CFHT/MegaCam images obtained as part of the Next Generation Virgo Cluster Survey (NGVS), we confirm the previously identified features and identify a few additional structures. The NGVS data allowed us to make a physical study of these low surface brightness features and investigate their origin. The likely progenitors of the structures were identified as either already cataloged Virgo Cluster Catalog dwarfs or newly discovered satellites caught in the act of being destroyed. They have the same g - i color index and likely contain similar stellar populations. The alignment of three dwarfs along an apparently single stream is intriguing, and we cannot totally exclude that these are second-generation dwarf galaxies being born inside the filament from the debris of an original dwarf. The observed complex structures, including in particular a stream apparently emanating from a satellite of a satellite, point to a high rate of ongoing dwarf destruction/accretion in the region of the Virgo Cluster where NGC 4216 is located. We discuss the age of the interactions and whether they occurred in a group that is just falling into the cluster and shows signs of the so-called pre-processing before it gets affected by the cluster environment, or in a