Thu, 21 Aug 2008 15:13:19 BST CiteULike: Tag clusters http://www.citeulike.org/tag/clusters CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/zeta101/article/764946 <i>Applied Physics Letters, Vol. 79, No. 20. (2001), pp. 3317-3319.</i><br /><br />We present a pathway for the formation of ordered Ge quantum dots on Si(111)–(7×7) substrate. Self-assembled growth of Ge quantum dots on the Si(111)–(7×7) surface has been investigated using scanning tunneling microscopy. The Ge is grown on the substrate by solid phase epitaxy at room temperature. It has been found that the deposited submonolayer Ge can aggregate and form ordered Ge quantum dots on the surface through controlling the annealing temperature. The formation of ordered Ge quantum dots is due to the preferential adsorption sites of Ge on Si(111)–(7×7). The formed Ge quantum dots may have a great potential in the application of nanodevices. ©2001 American Institute of Physics. Formation of ordered Ge quantum dots on the Si(111)--(7 x 7) surface YP Zhang L Yan SS Xie SJ Pang HJ Gao doi:10.1063/1.1419052 Applied Physics Letters, Vol. 79, No. 20. (2001), pp. 3317-3319. 2006-07-19T17:09:17-00:00 2001 Applied Physics Letters 79 20 3317 3319 AIP clusters si-7x7 http://www.citeulike.org/user/zeta101/article/764934 <i>Surface Science, Vol. 574, No. 2-3. (10 January 2005), pp. L17-L22.</i><br /><br />We observe initial nucleation of Ge clusters and their arrangement on Si(1 1 1)-7 x 7 by ultrahigh-vacuum scanning tunneling microscopy on an atomic scale; germanium amounts of sub-monolayer are slowly deposited at room temperature at a rate of 0.005 ML/min, and post-annealed. The clusters are arranged uncovering the corner holes and dimer rows of 7 x 7 structure, resulting in a regular hexagonal arrangement of Ge clusters with a periodicity of half unit cell of 7 x 7. This presents direct evidence of the self-organized hexagonal arrangement formed on a template of the 7 x 7 periodicity, which has been under debate between Yan et al. [Surf. Sci. 506 (2002) L255] and Ratto and Rosei [Discussion: Surf. Sci. 530 (2003) 221]. Hexagonal arrangement of Ge clusters self-organized on a template of half unit cells of Si(1 1 1)-7 x 7 observed by scanning tunneling microscopy ZA Ansari T Arai M Tomitori doi:10.1016/j.susc.2004.10.051 Surface Science, Vol. 574, No. 2-3. (10 January 2005), pp. L17-L22. 2006-07-19T16:44:10-00:00 2005 Surface Science 574 2-3 L17 L22 clusters si-7x7 http://www.citeulike.org/user/zeta101/article/771147 <i>Surface Science, Vol. 498, No. 1-2. (1 February 2002), pp. 83-88.</i><br /><br />The initial stage of Ge adsorption on Si(1 1 1)-(7×7) surface has been investigated by ultrahigh-vacuum scanning tunneling microscopy at room temperature. We demonstrate that there is a critical nucleus for the adsorbed Ge clusters on Si(1 1 1)-(7×7) surface. Such clusters can behave like quantum dots, which display two states at +1.5 and −1.5 eV with respect to the Fermi level. The formation mechanism of the clusters is discussed. Initial adsorption of Ge on Si(1 1 1)-(7 x 7) surface at room temperature Long Yan Haiqiang Yang Hongjun Gao Sishen Xie Shijin Pang doi:10.1016/S0039-6028(01)01445-5 Surface Science, Vol. 498, No. 1-2. (1 February 2002), pp. 83-88. 2006-07-24T13:30:01-00:00 2002 Surface Science 498 1-2 83 88 clusters si-7x7 http://www.citeulike.org/user/zeta101/article/771141 <i>Surface Science, Vol. 506, No. 1-2. (10 May 2002), pp. L255-L260.</i><br /><br />The adsorption process of sub-monolayer Ge on Si(1 1 1)-(7×7) surface is studied using ultrahigh-vacuum scanning tunneling microscopy. By carefully controlling Ge deposition condition, a unique sixfold symmetry superlattice of Ge clusters is formed. It is found that almost all the Ge clusters observed have similar shapes and uniform sizes, and that they sit on both halves of the (7×7) unit cells. The formation of the ordered structure is attributed to the fact that the characteristic Si(1 1 1)-(7×7) reconstruction controls the nucleation and growth of the Ge clusters. Formation of two dimension Ge cluster superlattice on Si(1 1 1)-(7 x 7) surface Long Yan Yongping Zhang Hongjun Gao Sishen Xie Shijin Pang doi:10.1016/S0039-6028(01)01820-9 Surface Science, Vol. 506, No. 1-2. (10 May 2002), pp. L255-L260. 2006-07-24T13:20:28-00:00 2002 Surface Science 506 1-2 L255 L260 clusters si-7x7 http://www.citeulike.org/user/zeta101/article/716324 <i>Review of Scientific Instruments, Vol. 70, No. 12. (1999), pp. 4497-4501.</i><br /><br />A new mass selection technique has been developed, which allows one to size-select charged particles from atoms to nanoparticles of almost unlimited size. It provides a mass resolution of m/m = 20–50 and a transmission of about 50% for the selected size, both independent of mass. The technique is based on the time-of-flight principle, but differs fundamentally from time-of-flight mass selection normally used. The basic idea is to use time-limited high voltage pulses to displace laterally a preaccelerated ion beam, without changing its direction or shape. As the movement of the ions perpendicular to their original beam direction is independent of their forward velocity, mass resolution and calibration does not depend on the ion beam energy. A mass selector of this type has been implemented successfully into a cluster deposition experiment and has proven to be reliable and simple to operate. ©1999 American Institute of Physics. A new high transmission infinite range mass selector for cluster and nanoparticle beams B von Issendorff RE Palmer doi:10.1063/1.1150102 Review of Scientific Instruments, Vol. 70, No. 12. (1999), pp. 4497-4501. 2006-06-30T00:28:08-00:00 1999 Review of Scientific Instruments 70 12 4497 4501 AIP clusters http://www.citeulike.org/user/zeta101/article/771496 <i>Applied Physics Letters, Vol. 88, No. 17. (2006)</i><br /><br />Small amounts of Ge atoms are deposited on Si(111)-7×7 surfaces at room temperature (RT) and at 100  °C to clarify the initial adsorption sites using scanning tunneling microscopy. At RT Ge atoms are adsorbed at high coordination B2 sites around the rest atoms, as predicted by Cho and Kaxiras [Surf. Sci. 396, L261 (1998)]. On one hand, at 100  °C Ge atoms are adsorbed on corner adatom sites. With increasing Ge coverage the corner sites are gradually occupied, followed by Ge adsorption at center adatom sites, resulting in Ge cluster growth with a size of the half unit cell. ©2006 American Institute of Physics Evidence of temperature dependence of initial adsorption sites of Ge atoms on Si(111)-7 x 7 Zubaida Ansari Masahiko Tomitori Toyoko Arai doi:10.1063/1.2198109 Applied Physics Letters, Vol. 88, No. 17. (2006) 2006-07-24T14:40:03-00:00 2006 Applied Physics Letters 88 17 AIP clusters si-7x7 http://www.citeulike.org/user/zeta101/article/772008 <i>Physical Review B, Vol. 66, No. 16. (23 October 2002), 165412.</i><br /><br />Artificial nanocluster crystals of In; Ga; and Al were fabricated using a technique in which surface mediated magic clustering is used to achieve identical cluster size while the Si(111)-7Ã7 surface is used as a template for ordering the clusters. The atomic structures; formation mechanism and stability of the nanoclusters were studied with in situ scanning tunneling microscopy combined with first-principles total energy calculations. Our study shows that delicate control of growth kinetics is extremely important for cluster crystal fabrication; and there is essentially no limitation to this method. The high thermal stability and unique structure make these artificial nanocluster crystals promising for various applications. Fabrication and structural analysis of Al, Ga, and In nanocluster crystals Jin-Feng Jia Xi Liu Jun-Zhong Wang Jian-Long Li XS Wang Qi-Kun Xue Zhi-Qiang Li Zhenyu Zhang SB Zhang doi:10.1103/PhysRevB.66.165412 Physical Review B, Vol. 66, No. 16. (23 October 2002), 165412. 2006-07-25T09:06:24-00:00 2002 Physical Review B 66 16 165412 American Physical Society clusters si-7x7 http://www.citeulike.org/user/zeta101/article/821193 <i>Review of Scientific Instruments, Vol. 76, No. 2. (2005)</i><br /><br />A pulsed source for production of metal atoms and their oxide compounds in a supersonic expansion is described. The design utilizes a simple pulsed valve and produces a concentration of 106–107  atoms  per  cm–3 of the desired metal atoms in a molecular beam. Depending on the carrier gas used, metal compounds at similar concentration levels can also be produced. ©2005 American Institute of Physics Pulsed source of metal atoms and their compounds DA Chestakov A Zawadzka DH Parker KV Vidma AV Baklanov SA Kochubei doi:10.1063/1.1841952 Review of Scientific Instruments, Vol. 76, No. 2. (2005) 2006-08-29T15:43:14-00:00 2005 Review of Scientific Instruments 76 2 AIP clusters pulsed-valve http://www.citeulike.org/user/zeta101/article/772003 <i>Physical Review Letters, Vol. 88, No. 6. (25 January 2002), 066101.</i><br /><br />A method; by which periodic two-dimensional arrays of identical metal clusters of nanometer size and spacing could be spontaneously obtained by taking advantage of surface mediated clustering; is reported. The versatility of the method is demonstrated for a broad range of metals on Si(111)-(7Ã7) substrates. In situ scanning tunneling microscopy analysis of In clusters; combined with first-principles total energy calculations; unveils unique initial-stage atomic structures of the surface-supported clusters and the vital steps that lead to the success of this method. A strong interaction between the clusters and the surface holds the key to the observed cluster sizes. Spontaneous Assembly of Perfectly Ordered Identical-Size Nanocluster Arrays Jian-Long Li Jin-Feng Jia Xue-Jin Liang Xi Liu Jun-Zhong Wang Qi-Kun Xue Zhi-Qiang Li John Tse Zhenyu Zhang SB Zhang doi:10.1103/PhysRevLett.88.066101 Physical Review Letters, Vol. 88, No. 6. (25 January 2002), 066101. 2006-07-25T08:54:03-00:00 2002 Physical Review Letters 88 6 066101 American Physical Society clusters si-7x7 http://www.citeulike.org/user/zeta101/article/772002 <i>Physical Review B, Vol. 64, No. 24. (3 December 2001), 241404.</i><br /><br />Under certain deposition conditions; gallium induces almost exclusive formation of a type of especially stable clustersâmagic clusters; on the 7Ã7-reconstructed silicon(111) surface. The cluster has a triangular closed-shell structure and resides on the center of a 7Ã7 half unit-cell. As the gallium coverage is increased; the cluster density increases proportionally; leading essentially to the complete filling of the 7Ã7 half unit-cells and the creation of an unprecedented two-dimensional lattice of magic clusters. A structure model employing three silicon atoms to link six gallium atoms into a configuration with satisfied bonding is proposed to qualitatively account for the clusterâs stability. Self-organized two-dimensional lattice of magic clusters MY Lai YL Wang doi:10.1103/PhysRevB.64.241404 Physical Review B, Vol. 64, No. 24. (3 December 2001), 241404. 2006-07-25T08:49:08-00:00 2001 Physical Review B 64 24 241404 American Physical Society clusters si-7x7 http://www.citeulike.org/user/zeta101/article/843404 <i>New Journal of Physics, Vol. 4 (2002)</i><br /><br />We investigate the optical properties of spherical gold and silver clusters with diameters of 20~nm and larger. The light scattering spectra of individual clusters are measured using dark-field microscopy, thus avoiding inhomogeneous broadening effects. The dipolar plasmon resonances of the clusters are found to have nearly Lorentzian line shapes. With increasing size we observe polaritonic red-shifts of the plasmon line and increased radiation damping for both gold and silver clusters. Apart from some cluster-to-cluster variations of the plasmon lines, agreement with Mie theory is reasonably good for the gold clusters. However, it is less satisfactory for the silver clusters, possibly due to cluster faceting or chemical effects. Plasmon resonances in large noble-metal clusters C Sönnichsen T Franzl T Wilk G von Plessen J Feldmann doi:10.1088/1367-2630/4/1/393 New Journal of Physics, Vol. 4 (2002) 2006-09-14T10:29:27-00:00 2002 New Journal of Physics 4 clusters plasmons http://www.citeulike.org/user/zeta101/article/778195 <i>Surface Science, Vol. 600, No. 9. (1 May 2006), pp. 1936-1941.</i><br /><br />Using scanning tunneling microscopy, ordered magic nanoclustering in the submonolayer Tl/Si(1 1 1)7 x 7 system has been studied. In contrast to the other known metal/silicon systems where ordered magic nanoclustering takes place, the Tl/Si(1 1 1) system has been found to be the only one to exhibit the diverse magic clustering. In the present study, occurrence of, at least, three distinct types of the well-defined Tl/Si(1 1 1) magic clusters has been detected. Diverse magic nanoclustering in submonolayer Tl/Si(1 1 1) system AV Zotov AA Saranin VG Kotlyar OA Utas YL Wang doi:10.1016/j.susc.2006.02.023 Surface Science, Vol. 600, No. 9. (1 May 2006), pp. 1936-1941. 2006-07-28T16:04:18-00:00 2006 Surface Science 600 9 1936 1941 clusters si-7x7 http://www.citeulike.org/user/zeta101/article/771037 <i>Surface Science, Vol. 546, No. 2-3. (1 December 2003), pp. L803-L807.</i><br /><br />Size selectable Ge nanoclusters are formed on Si using a buffer layer-assisted growth method. A condensed inert gas layer of xenon, with low surface free energy, was used as a buffer to prevent direct interactions of deposited Ge atoms with Si substrates during Ge nanocluster growth. The scanning tunneling microscope studies indicate absence of a strained wetting layer between Ge nanoclusters. These nanoclusters are substantially smaller and denser than the Ge hut clusters that are formed with the normal Stranski-Krastanov growth mode. The morphology of the nanoclusters can be tuned over a wide range, which is very desirable for studying the three-dimensional confinement effect. Fabrication of Ge nanoclusters on Si with a buffer layer-assisted growth method K Yoo Li Zhenyu Zhang HH Weitering F Flack MG Lagally JF Wendelken doi:10.1016/j.susc.2003.09.029 Surface Science, Vol. 546, No. 2-3. (1 December 2003), pp. L803-L807. 2006-07-24T10:52:58-00:00 2003 Surface Science 546 2-3 L803 L807 clusters http://www.citeulike.org/user/zeta101/article/778020 <i>Physical Review B (Condensed Matter and Materials Physics), Vol. 73, No. 19. (2006)</i><br /><br />The electronic structure of cobalt-induced magic clusters grown on Si(111)-(7×7) is investigated by scanning tunneling microscopy, scanning tunneling spectroscopy, and real-space multiple-scattering calculations. Topographical images of a half unit cell of Si(111)-(7×7) with the cluster acquired at low bias voltages of ±0.4  V show greatly reduced cluster heights; however, the heights of the corner adatoms are unchanged, indicative of the highly localized nature of the charge distribution. Spectroscopic studies of the clusters indicate a band gap of ~0.8  eV, suggesting localized nonmetallic behavior. The opening of such a band gap is suggested to be a stabilizing factor for the observed magic clusters. A 65-atom Co-Si cluster is constructed to calculate the momentum- and element-projected density of states. The calculated result identifies that the intense state below the Fermi level at –1.75  V in the experimental spectroscopic curve is primarily due to localized 3d orbitals of Co atoms in the magic clusters. Electronic structure of Co-induced magic clusters grown on Si(111)-(7 x 7): Scanning tunneling microscopy and spectroscopy and real-space multiple-scattering calculations MAK Zilani H Xu T Liu YY Sun YP Feng XS Wang ATS Wee doi:10.1103/PhysRevB.73.195415 Physical Review B (Condensed Matter and Materials Physics), Vol. 73, No. 19. (2006) 2006-07-28T15:08:30-00:00 2006 Physical Review B (Condensed Matter and Materials Physics) 73 19 APS clusters si-7x7 http://www.citeulike.org/user/zeta101/article/777361 <i>Surface Science, Vol. 366, No. 1. (10 October 1996), pp. 51-59.</i><br /><br />At the initial stages of room-temperature deposition we have observed the preferential adsorption of the individual Sn atoms on the Si center-adatom (T1) sites on Si(111)-(7 x 7) using scanning tunneling microscopy. A spectroscopic analysis of changes in the energy spectrum of surface states around the Fermi level (Ef) suggests that covalent bonding occurs between individual Sn and Si adatoms. This results in a surface metal-insulator transition due to the removal of Si adatom surface states at Ef while preserving the (7 x 7) sub-lattice. An energy-level scheme is proposed to explain this behavior. Interaction of Sn atoms with the intrinsic dangling-bond states of Si(111)-(7 x 7) XF Lin I Chizhov HA Mai RF Willis doi:10.1016/0039-6028(96)00799-6 Surface Science, Vol. 366, No. 1. (10 October 1996), pp. 51-59. 2006-07-28T07:54:07-00:00 1996 Surface Science 366 1 51 59 clusters si-7x7 http://www.citeulike.org/user/zeta101/article/773223 <i>Physical Review Letters, Vol. 92, No. 6. (2004)</i><br /><br />The structure of a type of surface magic cluster is determined by a combination of scanning tunneling microscopy, density-functional calculations, and dynamical low energy electron diffraction. The diffraction method is applicable because these clusters created through hierarchical self-organization of Ga deposited onto a Si(111)–7×7 surface have identical size and structure and form an ordered array with exact translational symmetry. The unprecedented detailed structure information provided by the diffraction measurement is consistent with direct microscopic imaging and theoretical calculations. Structure Determination of Surface Magic Clusters HH Chang MY Lai JH Wei CM Wei YL Wang doi:10.1103/PhysRevLett.92.066103 Physical Review Letters, Vol. 92, No. 6. (2004) 2006-07-25T13:13:24-00:00 2004 Physical Review Letters 92 6 APS clusters si-7x7 http://www.citeulike.org/user/zeta101/article/771629 <i>Physical Review B (Condensed Matter and Materials Physics), Vol. 73, No. 3. (2006)</i><br /><br />Atomic structures of Ga nanoclusters formed on the Si(111)-(7×7) surface have been studied. Combination of scanning tunneling microscopy and rocking-curve analysis of reflection high-energy electron diffraction enables us to study detailed structure of the Ga-adsorbed surface. Highly ordered arrays of nanoclusters, consisting of six Ga and three Si atoms, have been confirmed, in good agreement with the previous studies. We found that the formation of Ga nanoclusters is accompanied by the partial (~40%) substitution of the Si adatoms, surrounding the nanoclusters, by the deposited Ga atoms. Atomic structure of the Ga nanoclusters on Si(111)-(7 x 7) Akihiro Ohtake doi:10.1103/PhysRevB.73.033301 Physical Review B (Condensed Matter and Materials Physics), Vol. 73, No. 3. (2006) 2006-07-24T16:42:03-00:00 2006 Physical Review B (Condensed Matter and Materials Physics) 73 3 APS clusters si-7x7 http://www.citeulike.org/user/zeta101/article/737005 <i>Advanced Materials, Vol. 17, No. 6. (2005), pp. 731-734.</i><br /><br />No abstract. High-Temperature Stability of Size-Selected Gold Nanoclusters Pinned on Graphite F Yin C Xirouchaki Q Guo R E Palmer doi:10.1002/adma.200401095 Advanced Materials, Vol. 17, No. 6. (2005), pp. 731-734. 2006-07-04T08:41:48-00:00 2005 Advanced Materials 17 6 731 734 clusters http://www.citeulike.org/user/zeta101/article/771603 <i>Physical Review Letters, Vol. 96, No. 19. (2006)</i><br /><br />The evolution of the plasmon spectrum of the Si(111) (7×7)-Cs surface has been studied by energy loss spectroscopy individually resolved in energy and momentum during the transition from substrate to Cs overlayer metallization. The multipole plasmon is identified by an extremely narrow angular distribution of the inelastic electron scattering, unaccounted for by standard dipole scattering theory. A crossover between multipole and monopole surface plasmon is observed at finite surface wave vectors q||, depending on Cs coverage, and reveals a high sensitivity of the short-wavelength multipole components on surface morphology. Crossover between Monopole and Multipole Plasmon of Cs Monolayers on Si(111) Individually Resolved in Energy and Momentum Volkmar Zielasek Neele Ronitz Martin Henzler Herbert Pfnur doi:10.1103/PhysRevLett.96.196801 Physical Review Letters, Vol. 96, No. 19. (2006) 2006-07-24T16:18:18-00:00 2006 Physical Review Letters 96 19 APS clusters eels si-7x7 http://www.citeulike.org/user/zeta101/article/762936 <i>Surface Science, Vol. 493, No. 1-3. (1 November 2001), pp. 49-55.</i><br /><br />Electron energy loss and Auger electron spectra have been obtained for Si(1 1 1) covered with 0.02 bilayer Ge with a scanning tunneling microscope (STM) combined with an electron energy analyzer. The Ge islands with 5×5 and 7×7 reconstructions grown on the step and the domain boundaries of the Si(1 1 1)7×7 substrate are imaged with the STM. After STM imaging, the STM tip is retracted and the primary electron beam for these spectroscopies is field emitted from the tip of build-up [1 1 1]-oriented W, which has the most protruding point of the [1 1 1] apex. Several energy peaks are found, which are probably attributed to plasmon and to Auger electrons of Si LVV and Ge MVV. The origin of anomalous peak shift with decreasing separation between tip and sample is discussed. An applicability of scanning tunneling microscopy for surface electron spectroscopy M Tomitori M Hirade Y Suganuma T Arai doi:10.1016/S0039-6028(01)01188-8 Surface Science, Vol. 493, No. 1-3. (1 November 2001), pp. 49-55. 2006-07-18T10:58:44-00:00 2001 Surface Science 493 1-3 49 55 clusters si-7x7 spels http://www.citeulike.org/user/suze/article/7357 <i>Transport Policy, Vol. 10, No. 4. (October 2003), pp. 299-306.</i> Scatters and clusters in time and space: implications for delivering integrated and inclusive transport J Hine M Grieco doi:10.1016/S0967-070X(03)00055-6 Transport Policy, Vol. 10, No. 4. (October 2003), pp. 299-306. 2004-12-28T15:35:58-00:00 2003 Transport Policy 0967-070X 10 4 299 306 Elsevier Science clusters inclusive space space-time time transport http://www.citeulike.org/user/slaanco/article/3116701 <i>(2 Sep 2002)</i><br /><br />Considerable progress has been made over the last decade in the study of the evolutionary trends of the population of galaxy clusters in the Universe. In this review we focus on observations in the X-ray band. X-ray surveys with the ROSAT satellite, supplemented by follow-up studies with ASCA and Beppo-SAX, have allowed an assessment of the evolution of the space density of clusters out to z~1, and the evolution of the physical properties of the intra-cluster medium out to z~0.5. With the advent of Chandra and Newton-XMM, and their unprecedented sensitivity and angular resolution, these studies have been extended beyond redshift unity and have revealed the complexity of the thermodynamical structure of clusters. The properties of the intra-cluster gas are significantly affected by non-gravitational processes including star formation and Active Galactic Nucleus (AGN) activity. Convincing evidence has emerged for modest evolution of both the bulk of the X-ray cluster population and their thermodynamical properties since redshift unity. Such an observational scenario is consistent with hierarchical models of structure formation in a flat low density universe with Omega_m=0.3 and sigma_8=0.7-0.8 for the normalization of the power spectrum. Basic methodologies for construction of X-ray-selected cluster samples are reviewed and implications of cluster evolution for cosmological models are discussed. The Evolution of X-ray Clusters of Galaxies Piero Rosati Stefano Borgani Colin Norman (2 Sep 2002) 2008-08-14T07:20:12-00:00 2002 clusters review http://www.citeulike.org/user/slaanco/article/3139719 <i>(14 Jul 2008)</i><br /><br />We explore the role of the group environment in the evolution of AGN at the redshift interval 0.7<z<1.4, by combining deep Chandra observations with extensive optical spectroscopy from the All-wavelength Extended Groth strip International Survey (AEGIS). The sample consists of 3902 optical sources and 71 X-ray AGN. Compared to the overall optically selected galaxy population, X-ray AGN are more frequently found in groups at the 99% confidence level. This is partly because AGN are hosted by red luminous galaxies, which are known to reside, on average, in dense environments. Relative to these sources, the excess of X-ray AGN in groups is significant at the 91% level only. Restricting the sample to 0.7<z<0.9 and M_B<-20mag in order to control systematics we find that X-ray AGN represent (4.7±1.6) and (4.5±1.0)% of the optical galaxy population in groups and in the field respectively. These numbers are consistent with the AGN fraction in low redshift clusters, groups and the field. The results above, although affected by small number statistics, suggest that X-ray AGN are spread over a range of environments, from groups to the field, once the properties of their hosts (e.g. colour, luminosity) are accounted for. There is also tentative evidence, significant at the 98% level, that the field produces more X-ray luminous AGN compared to groups, extending similar results at low redshift to z~1. This trend may be because of either cold gas availability or the nature of the interactions occurring in the denser group environment (i.e. prolonged tidal encounters). X-ray selected AGN in groups at redshifts z~1 A Georgakakis Brian Gerke K Nandra ES Laird AL Coil MC Cooper JA Newman (14 Jul 2008) 2008-08-20T11:23:06-00:00 2008 agn clusters read survey http://www.citeulike.org/user/slaanco/article/3107247 <i>(20 Aug 2003)</i><br /><br />Conduction may play an important role in reducing cooling flows in galaxy clusters. We analyse a sample of sixteen objects using Chandra data and find that a balance between conduction and cooling can exist in the hotter clusters (T > 5 keV), provided the plasma conductivity is close to the unhindered Spitzer value. In the absence of any additional heat sources, a reduced mass inflow must develop in the cooler objects in the sample. We fit cooling flow models to deprojected data and compare the spectral mass deposition rates found to the values required to account for the excess luminosity, assuming Spitzer-rate heat transfer over the observed temperature gradients. The mass inflow rates found are lower than is necessary to maintain energy balance in at least five clusters. However, emission from cooling gas may be partially absorbed. We also compute the flux supplied by turbulent heat transport (Cho et al. 2003) and find conductivity profiles which follow a strikingly similar temperature dependence to the conductivity values required to prevent cooling. Finally, we show that the cluster radio luminosities vary by over five orders of magnitude in objects with X-ray luminosities differing by no more than a factor of a few. This suggests that there is unlikely to be a straightforward correlation between the mechanical power provided by the radio lobes and the rate of energy loss in cooling flow clusters. Thermal conduction and reduced cooling flows in galaxy clusters LM Voigt AC Fabian (20 Aug 2003) 2008-08-11T07:46:22-00:00 2003 clusters conduction cooling flow http://www.citeulike.org/user/slaanco/article/3107244 <i>(7 Oct 2004)</i><br /><br />The most successful cosmological models to date envision structure formation as a hierarchical process in which gravity is constantly drawing lumps of matter together to form increasingly larger structures. Clusters of galaxies currently sit atop this hierarchy as the largest objects that have had time to collapse under the influence of their own gravity. Thus, their appearance on the cosmic scene is also relatively recent. Two features of clusters make them uniquely useful tracers of cosmic evolution. First, clusters are the biggest things whose masses we can reliably measure because they are the largest objects to have undergone gravitational relaxation and entered into virial equilibrium. Mass measurements of nearby clusters can therefore be used to determine the amount of structure in the universe on scales of 10^14 to 10^15 solar masses, and comparisons of the present-day cluster mass distribution with the mass distribution at earlier times can be used to measure the rate of structure formation, placing important constraints on cosmological models. Second, clusters are essentially “closed boxes” that retain all their gaseous matter, despite the enormous energy input associated with supernovae and active galactic nuclei, because the gravitational potential wells of clusters are so deep. The baryonic component of clusters therefore contains a wealth of information about the processes associated with galaxy formation, including the efficiency with which baryons are converted into stars and the effects of the resulting feedback processes on galaxy formation. This article reviews our theoretical understanding of both the dark-matter component and the baryonic component of clusters. (Abridged) Tracing cosmic evolution with clusters of galaxies Mark Voit (7 Oct 2004) 2008-08-11T07:45:35-00:00 2004 clusters review http://www.citeulike.org/user/siebertm/article/562794 <i>J Mol Biol, Vol. 316, No. 1. (8 February 2002), pp. 139-154.</i><br /><br />Given the massive increase in the number of new sequences and structures, a critical problem is how to integrate these raw data into meaningful biological information. One approach, the Evolutionary Trace, or ET, uses phylogenetic information to rank the residues in a protein sequence by evolutionary importance and then maps those ranked at the top onto a representative structure. If these residues form structural clusters, they can identify functional surfaces such as those involved in molecular recognition. Now that a number of examples have shown that ET can identify binding sites and focus mutational studies on their relevant functional determinants, we ask whether the method can be improved so as to be applicable on a large scale. To address this question, we introduce a new treatment of gaps resulting from insertions and deletions, which streamlines the selection of sequences used as input. We also introduce objective statistics to assess the significance of the total number of clusters and of the size of the largest one. As a result of the novel treatment of gaps, ET performance improves measurably. We find evolutionarily privileged clusters that are significant at the 5% level in 45 out of 46 (98%) proteins drawn from a variety of structural classes and biological functions. In 37 of the 38 proteins for which a protein-ligand complex is available, the dominant cluster contacts the ligand. We conclude that spatial clustering of evolutionarily important residues is a general phenomenon, consistent with the cooperative nature of residues that determine structure and function. In practice, these results suggest that ET can be applied on a large scale to identify functional sites in a significant fraction of the structures in the protein databank (PDB). This approach to combining raw sequences and structure to obtain detailed insights into the molecular basis of function should prove valuable in the context of the Structural Genomics Initiative. Structural clusters of evolutionary trace residues are statistically significant and common in proteins. S Madabushi H Yao M Marsh DM Kristensen A Philippi ME Sowa O Lichtarge doi:10.1006/jmbi.2001.5327 J Mol Biol, Vol. 316, No. 1. (8 February 2002), pp. 139-154. 2006-03-25T01:01:15-00:00 2002 J Mol Biol 0022-2836 316 1 139 154 clusters evolutionary proteins significance statistical structural trace http://www.citeulike.org/user/Scis0000002/article/1918122 <i>Physica A Statistical Mechanics and its Applications, Vol. 382 (August 2007), pp. 16-21.</i><br /><br /><A HREF="/cgi-bin/nph-data_query?link_type=EJOURNAL&bibcode=2007PhyA..382...16A">Electronic Article Available</A> from <A HREF="http://www.elsevier.com">Elsevier Science.</A> Clusters or networks of economies? A macroeconomy study through Gross Domestic Product M Ausloos R Lambiotte doi:10.1016/j.physa.2007.02.005 Physica A Statistical Mechanics and its Applications, Vol. 382 (August 2007), pp. 16-21. 2007-11-15T00:14:52-00:00 2007 Physica A Statistical Mechanics and its Applications 382 16 21 clusters correlations evolving-networks global-economy heterogeneity hypernetworks interoperability markets modularity networks networks-of-economies time-delay http://www.citeulike.org/user/rodney/article/1145120 <i>New J. Phys., Vol. 4 (2002)</i><br /><br />We investigate the optical properties of spherical gold and silver clusters with diameters of 20 nm and larger. The light scattering spectra of individual clusters are measured using dark-field microscopy, thus avoiding inhomogeneous broadening effects. The dipolar plasmon resonances of the clusters are found to have nearly Lorentzian line shapes. With increasing size we observe polaritonic red-shifts of the plasmon line and increased radiation damping for both gold and silver clusters. Apart from some cluster-to-cluster variations of the plasmon lines, agreement with Mie theory is reasonably good for the gold clusters. However, it is less satisfactory for the silver clusters, possibly due to cluster faceting or chemical effects. Plasmon resonances in large noble-metal clusters C So?nnichsen T Franzl T Wilk G Von Plessen J Feldmann New J. Phys., Vol. 4 (2002) 2007-03-07T04:35:49-00:00 2002 New J. Phys. 4 clusters plasmons http://www.citeulike.org/user/rodney/article/1197157 <i>Appl Phys B, Vol. 71, No. 3. (2000), pp. 381-384.</i><br /><br />We investigate non-equilibrium relaxation processes in optically excited large gold and silver clusters. Time-resolved pump-probe experiments and model calculations show that optical excitation of the clusters by femtosecond laser pulses results in a heating of the electron system, which is followed by electron cooling via phonon emission. The electron heating leads to an enhanced damping of the surface-plasmon resonance in the clusters. This enhanced damping is caused by an enhancement of the Landau damping and electron scattering rates at high electron temperatures. Furthermore, we find that the rate of electron cooling in the clusters changes with electron temperature; this is a consequence of the temperature-dependent specific heat of the conduction electrons. Finally, pump-probe experiments on ellipsoidal silver clusters show that the thermal expansion of the heated clusters triggers mechanical vibrations at the acoustic eigenfrequencies of the clusters. Ultrafast relaxation dynamics of electronic excitations in noble-metal clusters G Von Plessen M Perner J Feldmann Appl Phys B, Vol. 71, No. 3. (2000), pp. 381-384. 2007-03-30T05:22:46-00:00 2000 Appl Phys B 71 3 381 384 clusters metal noble relaxation ultrafast http://www.citeulike.org/user/rodney/article/880171 <i>Nanotechnology, Vol. 17, No. 20. (28 October 2006), pp. 5167-5179.</i> Optical amplification of photothermal therapy with gold nanoparticles and nanoclusters Khlebtsov Boris Zharov Vladimir Melnikov Andrei Tuchin Valery Khlebtsov Nikolai doi:10.1088/0957-4484/17/20/022 Nanotechnology, Vol. 17, No. 20. (28 October 2006), pp. 5167-5179. 2006-10-01T05:07:35-00:00 2006 Nanotechnology 0957-4484 17 20 5167 5179 Institute of Physics Publishing bubble clusters inter-nanoparticle nanoparticle review http://www.citeulike.org/user/rodney/article/1145034 <i>Chin. Chem. Lett., Vol. 14, No. 11. (2003), pp. 1163-1166.</i><br /><br />A simple method to prepare the non-spherical gold particles was developed. The result solution included trigonal, truncated trigonal, hexagonal layers, and a pseudo-pentagonal shaped gold nanocrystals. The key factor is to control the relative rates of nucleation and cluster growth in this method. These attributes make seeding growth method as a useful tool in the fabrication of colloidal metal materials. A longitudinal plasmon resonance of 866 nm was observed, which is in the near-IR spectral regions (600-1000 nm). The excellent optical properties as near-IR labels are used to develop highly sensitive analysis method. A Simple Approach to Control the Growth of Non-spherical Gold Nanoparticles H Yuan RX Cai DW Pang Chin. Chem. Lett., Vol. 14, No. 11. (2003), pp. 1163-1166. 2007-03-07T03:10:48-00:00 2003 Chin. Chem. Lett. 14 11 1163 1166 aspherical clusters gold growth nanoparticles nir http://www.citeulike.org/user/rodney/article/1145033 <i>Progr. Biomed. Opt. Imaging Proc. SPIE, Vol. 5695, pp. 43-50.</i><br /><br />Background and Objective: The application of nanotechnology for laser thermal-based killing of abnormal cells (e.g. cancer cells) targeted with absorbing nanoparticles (e.g. gold solid nanospheres, nanoshells, or rod) is becoming an extensive area of research. We develop an approach to enhance the efficiency of selective nanophotothermolysis of cancer cells through laser-induced synergistic effects around gold nanoparticles aggregated in nanoclusters on cell membrane. Study Design/Materials and Methods: A concept of selective target damage by laser-induced synergistic interaction of optical, thermal, and acoustic fields around clustered nanoparticles is presented with focus on overlapping bubbles from nanoparticles aggregated on cell's membrane. The experimental verification of this concept in vitro was performed by the use a tunable laser pulses (420-570 nm, 8-12 ns, 0.1-300 ?J, laser flux of 0.1-10 J/cm2) for irradiation of MDA-MB-231 breast cancer cells targeted with primary antibodies to which selectively 40-nm gold nanoparticles were attached by the means of secondary antibodies. The photothermal, electron and atomic force microscopes in combination with viability test (Annexin -V-Propidium iodide) were employed to study the nanoparticle's spatial organization, the dynamics of microbubble formations around the particle's clusters, and cells damage. Results: An aggregation of nanoparticles on cell membrane was observed with simultaneous increase bubble formation phenomena, and red-shifted absorption due to plasmon-plasmon resonances into nanoclusters. It led to a significant enhancement, at least two orders of magnitude, of the efficiency of selectively killing cancer cells with nanosecond laser pulses. Conclusion: Described approach allows using relatively small nanoparticles which would be easier delivery to target site with further creation of nanoclusters with larger sizes which provide more profound thermal and related phenomena leading to more efficient laser killing of cancer cells. This nanocluster model might be promising also for treatment or modification different targets (e.g. bacteria, virus, vascular lesions, fat, etc.) as well as the use different type energy deposition (focused ultrasound, microwave, magnetic field, etc.). Sponsors: SPIE Laser-induced synergistic effects around absorbing nanoclusters in live cells VP Zharov RR Letfullin E Galitovskay SL Jacques WP Roach doi:10.1117/12.598776 Progr. Biomed. Opt. Imaging Proc. SPIE, Vol. 5695, pp. 43-50. 2007-03-07T03:08:20-00:00 Progr. Biomed. Opt. Imaging Proc. SPIE 5695 43 50 absorption clusters inter-nanoparticle nanoparticles http://www.citeulike.org/user/rodney/article/1844115 <i>C. R. Phys., Vol. 3, No. 3. (2002), pp. 365-380.</i><br /><br />The recent extension of time-resolved femtosecond optical techniques to the investigation of the ultrafast electron scattering processes in metal clusters offers the unique possibility to follow their evolution from a bulk to a confined metal. The size dependent results obtained in model materials, the noble metals, are presented, focusing on the impact of the confinement on energy redistribution processes (electron-electron and electron-phonon coupling). Their application to the investigation of the acoustic vibration property of cluster and to the cluster-surrounding matrix energy transfers are also discussed.© 2002 Acade?mie des sciences/E?ditions scientifiques et me?dicales Elsevier SAS. Ultrafast electron interactions in metal clusters N Del Fatti F Valle?e doi:10.1016/S1631-0705(02)01317-8 C. R. Phys., Vol. 3, No. 3. (2002), pp. 365-380. 2007-10-31T00:55:59-00:00 2002 C. R. Phys. 3 3 365 380 clusters electron interactions metal ultrafast http://www.citeulike.org/user/rodney/article/1186359 <i>Colloid Journal, Vol. 62, No. 6. (1 November 2000), pp. 765-779.</i> Light Absorption by the Clusters of Colloidal Gold and Silver Particles Formed During Slow and Fast Aggregation NG Khlebtsov LA Dykman Ya AG Mel'nikov doi:10.1023/A:1026643111821 Colloid Journal, Vol. 62, No. 6. (1 November 2000), pp. 765-779. 2007-03-25T20:43:48-00:00 2000 Colloid Journal 62 6 765 779 absorption aggregates clusters colloidal gold nanoparticles silver http://www.citeulike.org/user/rodney/article/1186350 <i>Lasers in Surgery and Medicine, Vol. 37, No. 3. (2005), pp. 219-226.</i><br /><br />We developed a new approach that enhances selective photothermolysis of tumor through laser activation of synergistic phenomena around nanoclusters, which are self-assembled into cancer cells.In vitro verification of this approach was performed by laser pulse irradiation (420-570 nm and 1064 nm; 8-12 nanosecond; 0.1-10 J/cm2) of MDA-MB-231 breast cancer cells targeted with primary antibodies to which 40-nm gold nanoparticles were selectively attached by means of secondary antibodies. Photothermal (PT) radiometry, thermolens techniques, electron microscopy, atomic force microscopy, silver and gold enhancing kits, and viability test (Annexin V-propidium iodide) were employed to study nanoparticle spatial organization, the dynamics of microbubble formation, and cell damage.The assembly of gold nanoclusters on the cell membrane was accompanied by increased local absorption and red-shifting as compared to cells that did not have nanoclusters. These effects were amplified by a silver-enhancing kit and pre-irradiation of cells with low laser-pulse energy. Finally, a significant increase in laser-induced bubble formation and cancer cell killing was observed using near-IR lasers (1064 nm). A cancer cell antigens was used to provide target specificity for nanoclusters formation making the cancer cells sensitive to laser activation.The described approach uses relatively small and simple gold nanoparticles offering more effective delivery to target. In addition, the further self-assembling of these nanoparticles into nanoclusters on live cells provides significant enhancement of laser-induced cell damage. These nanoclusters (gold ?nanobombs?) can be activated in cancer cells only by confining near-IR laser pulse energy within the critical mass of the nanoparticles in the nanoclusters. Lasers Surg. Med. 37:219-226, 2005. © 2005 Wiley-Liss, Inc. Synergistic enhancement of selective nanophotothermolysis with gold nanoclusters: Potential for cancer therapy Vladimir Zharov Elena Galitovskaya Carl Johnson Thomas Kelly doi:10.1002/lsm.20223 Lasers in Surgery and Medicine, Vol. 37, No. 3. (2005), pp. 219-226. 2007-03-25T20:24:33-00:00 2005 Lasers in Surgery and Medicine 37 3 219 226 cancer clusters enhancement gold inter-nanoparticle photothermolysis synergy therapy http://www.citeulike.org/user/rodney/article/1176801 <i>Langmuir, Vol. 18, No. 6. (2002), pp. 2436-2437.</i><br /><br />The optical properties of small clusters of silver and gold atoms were discussed. The properties of metals involved both interactions of light with the free electrons and electron transitions from one band to another. It was found that as the particle size of metallic clusters decreases, the mean free path of the free electrons in the clusters reduces, and the optical properties of the metal in the clusters change. Optical properties of small clusters of silver and gold atoms RH Doremus doi:10.1021/la011350h Langmuir, Vol. 18, No. 6. (2002), pp. 2436-2437. 2007-03-20T01:44:31-00:00 2002 Langmuir 18 6 2436 2437 atoms clusters gold optical silver http://www.citeulike.org/user/Rigas/article/80507 <i>Regional Studies: The Journal of the Regional Studies Association, Vol. 39, No. 1. (February 2005), 129.</i> Creating a Cluster While Building a Firm: Entrepreneurs and the Formation of Industrial Clusters Maryann Feldman Johanna Francis Janet Bercovitz doi:10.1080/0034340052000320888 Regional Studies: The Journal of the Regional Studies Association, Vol. 39, No. 1. (February 2005), 129. 2005-01-19T21:05:53-00:00 2005 Regional Studies: The Journal of the Regional Studies Association 0034-3404 39 1 129 Carfax Publishing, part of the Taylor & Francis Group apprentissage clusters competences economie entreprises learning sociology http://www.citeulike.org/user/Rigas/article/37692 <i>Journal of Business Venturing, Vol. 19, No. 1. (January 2004), pp. 153-167.</i> Regional transformation through technological entrepreneurship S Venkataraman doi:10.1016/j.jbusvent.2003.04.001 Journal of Business Venturing, Vol. 19, No. 1. (January 2004), pp. 153-167. 2004-12-28T17:05:57-00:00 2004 Journal of Business Venturing 0883-9026 19 1 153 167 Elsevier Science apprentissage clusters development entreprises industrie innovation technologie http://www.citeulike.org/user/Rigas/article/375063 <i></i><br /><br /> This paper surveys some of the current methodologies employed to analyse cluster development, as well as some of the key themes emerging from both the analytical and prescriptive literature noted above. It uses this survey as the context in which to present a synthesis of the initial findings of the current national study of industrial clusters in Canada, conducted by the Innovation Systems Research Network. The national study comprises 26 cases which aim to identify the presence of significant concentrations of firms in the local economy and to understand the process by which these regional-industrial concentrations of economic activity are managing the transition to more knowledge-intensive forms of production. The central questions in each case are: What role do local institutions and actors play in fostering this transition? How important is interaction with non-local actors in this process? How dependent are local firms on unique local knowledge assets and what is the relative importance of local versus non-local knowledge flows between economic actors? How did each local industrial concentration evolve over time to reach its present state and what key events and decisions shaped its path? And, finally, to what extent do these processes, relationships and local capabilities constitute a true cluster? Ultimately, what are the key relationships, linkages and processes that ground the cluster in its existing location? Clusters from the inside and out: local dynamics and global linkages D Wolfe M Gertler doi:10.1080/00420980410001675832 2005-11-01T14:08:28-00:00 0042-0980 canada clusters entreprises industrie innovation http://www.citeulike.org/user/Rigas/article/117476 <i>Small Business Economics, Vol. 23, No. 5. (December 2004), pp. 363-400.</i> Entrepreneurship and Development: The Role of Clusters Rocha Hector doi:10.1007/s11187-004-3991-8 Small Business Economics, Vol. 23, No. 5. (December 2004), pp. 363-400. 2005-03-08T16:08:35-00:00 2004 Small Business Economics 0921-898X 23 5 363 400 Kluwer Academic Publishers clusters entrepreunariat entreprises industrie http://www.citeulike.org/user/rickl/article/3102961 <i>International Journal of Applied Linguistics, Vol. 18, No. 1. (2008), pp. 41-62.</i><br /><br />An important component of fluent linguistic production is control of the multi-word expressions referred to as "clusters", "chunks" or "bundles". These are extended collocations which appear more frequently than expected by chance, helping to shape meanings and contributing to our sense of coherence in a text. Clusters seem to present considerable challenges to student writers struggling to make their texts both fluent and assured to readers in their new communities. This paper explores the forms, structures and functions of 4-word clusters in a corpus of research articles, doctoral dissertations and master's theses of 3.5 million words to show not only that clusters are central to academic discourse but that they offer an important means of differentiating genres, with implications for more evidence-based instructional practices in advanced writing contexts. Componente essenziale di una produzione linguistica scorrevole è la padronanza di espressioni multilessicali comunemente denominate clusters, chunks o bundles. Tali espressioni si presentano come collocazioni estese che ricorrono con frequenza superiore alla casualità, contribuendo alla formazione del significato e alla nostra percezione della coerenza testuale. I clusters appaiono un'area particolarmente problematica per chi, nel processo di acquisizione di una specifica scrittura disciplinare, necessita di rivolgersi alla nuova comunità scientifica con testi a un tempo scorrevoli e sicuri. Questo articolo esplora forma, struttura e funzioni dei clusters di quattro parole in un corpus di articoli di ricerca, tesi di dottorato e tesi di master (3.5 milioni di parole) e si propone di mostrare che i clusters non solo sono un elemento centrale nel discorso accademico, ma offrono un importante strumento di differenziazione dei generi, con una ricaduta verso pratiche di formazione alla scrittura avanzata sempre più basate su dati autentici.1 Academic clusters: text patterning in published and postgraduate writing Ken Hyland doi:10.1111/j.1473-4192.2008.00178.x International Journal of Applied Linguistics, Vol. 18, No. 1. (2008), pp. 41-62. 2008-08-09T01:50:58-00:00 2008 International Journal of Applied Linguistics 18 1 41 62 bundles chunks clusters coherence corpora discourse eap fluency http://www.citeulike.org/user/RebeccaHamer/article/1279024 <i>Proc Natl Acad Sci U S A, Vol. 103, No. 21. (23 May 2006), pp. 8209-8214.</i><br /><br />Cell division is a carefully orchestrated procedure. Bacterial cells have intricate mechanisms to ensure that genetic material is copied, proofread, and accurately partitioned into daughter cells. Partitioning now appears to also occur for some cytoplasmic proteins. Previously, using chromosomal fluorescent protein fusions, we demonstrated that a subset of Rhodobacter sphaeroides chemotaxis proteins colocalize to a discrete region within the bacterial cytoplasm. Using TlpT-yellow fluorescent protein as a marker for the position of the cytoplasmic protein clusters, we show most cells contain either one cluster localized at mid-cell or two clusters at the one-fourth and three-fourths positions of cell length. The number and positioning of these protein clusters depend on a previously unrecognized bacterial protein positioning factor, PpfA, which has homology to bacterial type I DNA partitioning factors. These data suggest that there is a mechanism involved in partitioning some cytoplasmic proteins upon cell division that is analogous to a mechanism seen for plasmid and chromosomal DNA. The positioning of cytoplasmic protein clusters in bacteria. SR Thompson GH Wadhams JP Armitage doi:10.1073/pnas.0600919103 Proc Natl Acad Sci U S A, Vol. 103, No. 21. (23 May 2006), pp. 8209-8214. 2007-05-05T12:24:59-00:00 2006 Proc Natl Acad Sci U S A 0027-8424 103 21 8209 8214 clusters localization http://www.citeulike.org/user/ptak/article/3134815 <i>(18 Aug 2008)</i><br /><br />Temperature, density and abundance profiles of the hot intracluster medium (ICM) are important diagnostics of the complex interactions of gravitational and feedback processes in the cores of galaxy clusters. Deprojection of X-ray data by methods such as projct, which are model dependent, can produce large and unphysical oscillating temperature profiles. Here we validate a deprojection routine, Direct Spectral Deprojection (DSDeproj; Sanders & Fabian 2007), showing that it solves some of the issues inherent to model-dependent deprojection routines. DSDeproj is a model-independent approach, assuming only spherical symmetry, which subtracts projected spectra from each successive annulus to produce a set of deprojected spectra. Direct X-ray Spectral Deprojection of Galaxy Clusters HR Russell JS Sanders AC Fabian (18 Aug 2008) 2008-08-19T02:24:49-00:00 2008 clusters methodology x-ray http://www.citeulike.org/user/petzlux/article/375054 <i>Urban Studies, Vol. 41, No. 5/6. (2004), pp. 1025-1044.</i><br /><br />This article explores a prominent cluster in the Swedish capital Stockholm and its surrounding region: the ICT (information and communications technology) cluster. In particular, the article focuses on the issue of the extent to which labour market and labour mobility are the most likely channels for local and extra-local sources of knowledge and ideas. Thus the article positions itself against a growing literature that focuses on rather diffuse and vague notions that knowledge and innovation reside 'in the air' or in the 'buzz' of urban life. Instead, the underlying hypothesis is that in many sectors and industries such things as a cosmopolitan street life or accidental face-to-face encounters play relatively little part in the flow of experiences, knowledge and innovation. Rather, it is in the workplace that these exchanges and flows are located and it is thus through labour mobility that intracluster exchanges occur. The article tests such ideas in relation to the ICT cluster and the Stockholm region using a uniquely detailed time-series data-set. The data-set used is based on official taxation and civil registration records and contains complete details on everything from education to career changes to income levels for every individual resident in Sweden. The detail of the individual records and the complete nature of the data-set mean that it offers a unique possibility to examine, on a large scale, the micro dynamics of individuals in the labour market and in clusters. The data are used to examine whether there have existed over time higher levels of labour market mobility in clusters as opposed to the rest of the urban economy. The article empirically verifies the idea that labour market mobility is significantly higher in the cluster than in the rest of the urban economy. Working through knowledge pools: labour market dynamics, the transference of knowledge and ideas, and industrial clusters D Power M Lundmark doi:10.1080/00420980410001675850 Urban Studies, Vol. 41, No. 5/6. (2004), pp. 1025-1044. 2005-11-01T13:38:23-00:00 2004 Urban Studies 0042-0980 41 5/6 1025 1044 clusters development industrial innovation knowledge labour-market http://www.citeulike.org/user/petzlux/article/423355 <i>Regional Studies, Vol. 37, No. 6&7. (August 2003), 549-578.</i><br /><br />PORTER M. E. (2003) The economic performance of regions, Reg. Studies 37, 549-578. This paper examines the basic facts about the regional economic performance, the composition of regional economies and the role of clusters in the US economy over period of 1990 to 2000. The performance of regional economies varies markedly in terms of wage, wage growth, employment growth and patenting rate. Based on the distribution of economic activity across geography, we classify US industries into traded, local and resource-dependent. Traded industries account for only about one-third of employment but register much higher wages, far higher rates of innovation and influence local wages. We delineate clusters of traded industries using co-location patterns across US regions. The mix of clusters differs markedly across regions. The performance of regional economies is strongly influenced by the strength of local clusters and the vitality and plurality of innovation. Regional wage differences are dominated by the relative performance of the region in the clusters in which it has positions, with the particular mix of clusters secondary. A series of regional policy implications emerge from the findings.PORTER M. E. (2003) La performance économique des regions, Reg. Studies 37, 549-578. Cet article cherche à examiner les principes fondamentaux de la performance économique régionale, de la structure des économies régionales, et du rôle des groupements dans l'économie des Etats-Unis de 1990 à 2000. La performance des économies régionales varie sensiblement du point de vue des salaires, de la croissance des salaires, de la hausse de l'emploi, et du nombre des brevets. A partir de la répartition de l'activité économique géographique, on classe les entreprises industrielles aux Etats-Unis sous les rubriques commerciale, locale, et dépendante des ressources. Les entreprises industrielles à vocation commerciale n'expliquent qu'un tiers de l' emploi mais laissent voir des salaires nettement plus élevés, des taux d'innovation bien plus importants, et influent sur les salaires locaux. Employant des distributions de localisations partagées à travers les Etats-Unis, on délimite des groupements d'entreprises industrielles à vocation commerciale. La structure des groupements varie sensiblement suivant la région. La performance des économies régionales est fortement influencé par la force des groupements locaux et par la vitalité et par la pluralité de l'innovation. Les écarts des salaires réels s'expliquent primordialement par la performance relative de la région quant aux groupements où elle est pré sente, la structure particulière des groupements n'étant que d'une importance secondaire. Il en résulte toute une série d'implications pour la politique.PORTER M. E. (2000) Die wirtschaftliche Leistungskraft von Regionen, Reg. Studies 37, 549-578. Dieser Beitrag analysiert Kerndaten regionaler Wirtschaftsräume in den Vereinigten Staaten, insbesondere ihre wirtschaftliche Leistungskraft, ihre Zusammensetzung und die Rolle regionaler Cluster. Die Regionen der Vereinigten Staaten unterschieden sich in den Jahren 1990 bis 2000 deutlich in ihrer wirtschaftlichen Leistungskraft gemessen an Lohnniveau und - wachstum, Beschäftigungsentwicklung, und Patentrate. Basierend auf der geographischen Konzentration öknomischer Aktitivtät klassifizieren wir Industriezweige als überregional ("traded'), lokal oder abhängig von der Präsenz von Naturschä tzen. Cluster überregionaler Industrien beschäftigen nur circa ein Drittel aller Erwerbstätigen, verzeichnen aber überdurchschnittliche Lö hne und signifikant höhere Innovationsraten als die Gesamtwirtschaft. Die relative Bedeutung einzelner Cluster innerhalb der Gruppe überregionaler Industrien unterscheidet sich deutlich im regionalen Vergleich. Der wirtschaftliche Erfolg einer Region wird stark von der relative Leistungskraft und Innovationsstärke der dort angesiedelten überregionalen Cluster beeinflusst. So hat das relative Lohnniveau in den überregionalen Clustern in einer Region einen dominanten Einfluss auf das regionale Lohnniveau, während die spezifische Identität dieser Cluster nur eine sekundäre Rolle spielt. Der Beitrag entwickelt aus dieser Analyse eine Reihe von Implikationen für die Wirtschaftspolitik. The Economic Performance of Regions Michael Porter doi:10.1080/0034340032000108688 Regional Studies, Vol. 37, No. 6&7. (August 2003), 549-578. 2005-12-06T10:51:46-00:00 2003 Regional Studies 0034-3404 37 6&7 549-578 cities clusters competitiveness economic_growth economy foreign_direct_investment http://www.citeulike.org/user/nuin/article/3063933 <i>Bioinformatics (Oxford, England), Vol. 24, No. 13. (1 July 2008)</i><br /><br />MOTIVATION: The classification of proteins into homologous groups (families) allows their structure and function to be analysed and compared in an evolutionary context. The modular nature of eukaryotic proteins presents a considerable challenge to the delineation of families, as different local regions within a single protein may share common ancestry with distinct, even mutually exclusive, sets of homologs, thereby creating an intricate web of homologous relationships if full-length sequences are taken as the unit of evolution. We attempt to disentangle this web by developing a fully automated pipeline to delineate protein subsequences that represent sensible units for homology inference, and clustering them into putatively homologous families using the Markov clustering algorithm. RESULTS: Using six eukaryotic proteomes as input, we clustered 162,349 protein sequences into 19,697-77,415 subsequence families depending on granularity of clustering. We validated these Markov clusters of homologous subsequences (MACHOS) against the manually curated Pfam domain families, using a quality measure to assess overlap. Our subsequence families correspond well to known domain families and achieve higher quality scores than do groups generated by fully automated domain family classification methods. We illustrate our approach by analysis of a group of proteins that contains the glutamyl/glutaminyl-tRNA synthetase domain, and conclude that our method can produce high-coverage decomposition of protein sequence space into precise homologous families in a way that takes the modularity of eukaryotic proteins into account. This approach allows for a fine-scale examination of evolutionary histories of proteins encoded in eukaryotic genomes. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online. MACHOS for the six proteomes are available as FASTA-formatted files: http://research1t.imb.uq.edu.au/ragan/machos. MACHOS: Markov clusters of homologous subsequences. S Wong MA Ragan doi:10.1093/bioinformatics/btn144 Bioinformatics (Oxford, England), Vol. 24, No. 13. (1 July 2008) 2008-07-30T18:12:31-00:00 2008 Bioinformatics (Oxford, England) 1460-2059 24 13 clusters markov proteins http://www.citeulike.org/user/nuin/article/2931199 <i>Genome Res., Vol. 11, No. 1. (1 January 2001), pp. 112-123.</i><br /><br />Large-scale gene expression studies and genomic sequencing projects are providing vast amounts of information that can be used to identify or predict cellular regulatory processes. Genes can be clustered on the basis of the similarity of their expression profiles or function and these clusters are likely to contain genes that are regulated by the same transcription factors. Searches for cis-regulatory elements can then be undertaken in the noncoding regions of the clustered genes. However, it is necessary to assess the efficiency of both the gene clustering and the postulated regulatory motifs, as there are many difficulties associated with clustering and determining the functional relevance of matches to sequence motifs. We have developed a method to assess the potential functional significance of clusters and motifs based on the probability of finding a certain number of matches to a motif in all of the gene clusters. To avoid problems with threshold scores for a match, the top matches to a motif are taken in several sample sizes. Genes from a sample are then counted by the cluster in which they appear. The probability of observing these counts by chance is calculated using the hypergeometric distribution. Because of the multiple sample sizes, strong and weak matching motifs can be detected and refined and significant matches to motifs across cluster boundaries are observed as all clusters are considered. By applying this method to many motifs and to a cluster set of yeast genes, we detected a similarity between Swi Five Factor and forkhead proteins and suggest that the currently unidentified Swi Five Factor is one of the yeast forkhead proteins. 10.1101/gr.148301 Assessing Clusters and Motifs from Gene Expression Data Lars Jakt Liang Cao Kathryn Cheah David Smith doi:10.1101/gr.148301 Genome Res., Vol. 11, No. 1. (1 January 2001), pp. 112-123. 2008-06-26T14:32:18-00:00 2001 Genome Res. 11 1 112 123 clusters enhancing motifs http://www.citeulike.org/user/mxhf/article/3108225 <i>(7 Aug 2008)</i><br /><br />Studies of nearby galaxies reveal that roughly half of their low mass X-ray binary (LMXB) populations are associated with globular clusters (GCs). We have established that the LMXB hosting frequency is correlated to various GC properties such as mass and metallicity. While the X-ray luminosities of a few of the brightest LMXBs in GCs are consistent with the accreting object being a black hole (BH), the only definitive way to distinguish between a black hole and multiple superposed sources in a GC is to detect variability. We have discovered just such a variable 4x10^39 erg/s black hole X-ray binary in a low metallicity globular cluster in the halo of NGC 4472. The change in the X-ray spectrum between the bright and faint epochs suggests that the luminosity variation is due to eclipsing by a warped accretion disk. The optical spectrum of this source also reveals strong, broad, [O III] lambda 5007 and [O III] lambda 4959 emission. An analysis of the X-ray spectrum suggests that the [O III] lines are produced by the photoionization of a wind driven by a stellar mass black hole accreting mass at or above its Eddington luminosity. As it is dynamically implausible to form an accreting stellar mass BH system in a GC with an intermediate mass BH it appears that this massive globular cluster does not harbor an intermediate mass BH. The inferred mass of this BH falls well below the extrapolation of the well known M_BH-sigma and M_BH-M_Stellar relations to this GC. Therefore our analysis suggests that not all old, metal poor stellar systems form black holes consistent with these relations, which have been established for much more massive stellar systems. Low Mass X-ray Binaries and Black Holes in Globular Clusters Arunav Kundu Thomas Maccarone Stephen Zepf Chun Shih Katherine Rhode (7 Aug 2008) 2008-08-11T12:18:35-00:00 2008 binaries black clusters globular holes xray http://www.citeulike.org/user/mllee/article/2245604 <i>Applied Physics Letters, Vol. 77, No. 23. (2000), pp. 3794-3796.</i><br /><br />  Transport properties of GaAs[sub 1 - x]N[sub x] thin films grown by metalorganic chemical vapor deposition RK Ahrenkiel SW Johnston BM Keyes DJ Friedman SM Vernon Applied Physics Letters, Vol. 77, No. 23. (2000), pp. 3794-3796. 2008-01-17T14:58:06-00:00 2000 Applied Physics Letters 77 23 3794 3796 AIP clusters gaasn http://www.citeulike.org/user/mllee/article/2245588 <i>Applied Physics Letters, Vol. 75, No. 11. (1999), pp. 1538-1540.</i><br /><br />  Excitons bound to nitrogen clusters in GaAsN S Francoeur SA Nikishin C Jin Y Qiu H Temkin Applied Physics Letters, Vol. 75, No. 11. (1999), pp. 1538-1540. 2008-01-17T14:54:03-00:00 1999 Applied Physics Letters 75 11 1538 1540 AIP clusters localization