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Sample records for chondrichthyan hoxa clusters

  1. Comparative genomics of chondrichthyan Hoxa clusters

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    Zhong Ying-Fu

    2009-09-01

    Full Text Available Abstract Background The chondrichthyan or cartilaginous fish (chimeras, sharks, skates and rays occupy an important phylogenetic position as the sister group to all other jawed vertebrates and as an early lineage to diverge from the vertebrate lineage following two whole genome duplication events in vertebrate evolution. There have been few comparative genomic analyses incorporating data from chondrichthyan fish and none comparing genomic information from within the group. We have sequenced the complete Hoxa cluster of the Little Skate (Leucoraja erinacea and compared to the published Hoxa cluster of the Horn Shark (Heterodontus francisci and to available data from the Elephant Shark (Callorhinchus milii genome project. Results A BAC clone containing the full Little Skate Hoxa cluster was fully sequenced and assembled. Analyses of coding sequences and conserved non-coding elements reveal a strikingly high level of conservation across the cartilaginous fish, with twenty ultraconserved elements (100%,100 bp found between Skate and Horn Shark, compared to three between human and marsupials. We have also identified novel potential non-coding RNAs in the Skate BAC clone, some of which are conserved to other species. Conclusion We find that the Little Skate Hoxa cluster is remarkably similar to the previously published Horn Shark Hoxa cluster with respect to sequence identity, gene size and intergenic distance despite over 180 million years of separation between the two lineages. We suggest that the genomes of cartilaginous fish are more highly conserved than those of tetrapods or teleost fish and so are more likely to have retained ancestral non-coding elements. While useful for isolating homologous DNA, this complicates bioinformatic approaches to identify chondrichthyan-specific non-coding DNA elements

  2. Clustering of tissue-specific sub-TADs accompanies the regulation of HoxA genes in developing limbs.

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    Soizik Berlivet

    Full Text Available HoxA genes exhibit central roles during development and causal mutations have been found in several human syndromes including limb malformation. Despite their importance, information on how these genes are regulated is lacking. Here, we report on the first identification of bona fide transcriptional enhancers controlling HoxA genes in developing limbs and show that these enhancers are grouped into distinct topological domains at the sub-megabase scale (sub-TADs. We provide evidence that target genes and regulatory elements physically interact with each other through contacts between sub-TADs rather than by the formation of discreet "DNA loops". Interestingly, there is no obvious relationship between the functional domains of the enhancers within the limb and how they are partitioned among the topological domains, suggesting that sub-TAD formation does not rely on enhancer activity. Moreover, we show that suppressing the transcriptional activity of enhancers does not abrogate their contacts with HoxA genes. Based on these data, we propose a model whereby chromatin architecture defines the functional landscapes of enhancers. From an evolutionary standpoint, our data points to the convergent evolution of HoxA and HoxD regulation in the fin-to-limb transition, one of the major morphological innovations in vertebrates.

  3. Biology of deep-water chondrichthyans: Introduction

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    Cotton, C. F.; Grubbs, R. D.

    2015-05-01

    Approximately half of the known chondrichthyans (sharks, skates, rays, and chimaeras), 575 of 1207 species (47.6%, Table 1), live in the deep ocean (below 200 m), yet little is known of the biology or life histories of most of these fishes (Kyne and Simpfendorfer, 2007). The limited information available for deep-water chondrichthyans is compounded by their rarity, as well as the prevalent uncertainty in the alpha taxonomy of deep-water species. Many species are known only from the type materials, which are generally limited to nondestructive sampling, e.g., morphometrics, imaging (X-ray, MRI, CT scanning). Thus, research has been hindered by a lack of specimens available for investigation that requires destructive sampling or live specimens (e.g., life history, diet, telemetry). The need for more research and dissemination of information about deep-water chondrichthyans has become imperative as fisheries worldwide continue to expand into deeper waters and exploit deep-water stocks, usually in the absence of data required for appropriate management (Morato et al., 2006; Kyne and Simpfendorfer, 2010).

  4. Effect of intramural myomectomy on endometrial HOXA10 and HOXA11 mRNA expression at the time of implantation window

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    Zohreh Alizadeh; Shamila Faramarzi; Massoud Saidijam; Tahereh Alizamir; Farzaneh Esna-Ashari; Nooshin Shabab; Marzieh Farimani Sanoee

    2014-01-01

    Background: HOXA11 and HOXA10 are expressed in endometrium throughout the menstrual cycle and show a dramatic increase during the mid-luteal phase at the time of implantation. The expression of these genes is decreased in women with myomas. Objective: To determine whether myomectomy would reverse HOXA11 and HOXA10 expression, we evaluated the transcript levels of these genes in the endometria of patients before and after myomectomy. Materials and Methods: Expression of HOXA11 and HOXA10 were ...

  5. The oldest articulated chondrichthyan from the Early Devonian period.

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    Miller, Randall F; Cloutier, Richard; Turner, Susan

    2003-10-01

    Chondrichthyans (including living sharks, skates, rays and chimaeras) have a fossil record of scales and dermal denticles perhaps dating back to the Late Ordovician period, about 455 million years ago. Their fossil tooth record extends to the earliest Devonian period, almost 418 million years ago, whereas the oldest known articulated shark remains date from the Early Devonian period, about 394 million years ago. Here we report the discovery of an articulated shark that is almost 409 million years old from the Early Devonian (early Emsian) period of New Brunswick, Canada. The specimen, identified as Doliodus problematicus (Woodward), sheds light on the earliest chondrichthyans and their interrelationships with basal jawed vertebrates. This species has been truly problematic. Previously known only from isolated teeth, it has been identified as an acanthodian and a chondrichthyan. This specimen is the oldest shark showing the tooth families in situ, and preserves one of the oldest chondrichthyan braincases. More notably, it shows the presence of paired pectoral fin-spines, previously unknown in cartilaginous fishes.

  6. Bathymetric limits of chondrichthyans in the deep sea: A re-evaluation

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    Musick, J. A.; Cotton, C. F.

    2015-05-01

    Chondrichthyans are largely absent in abyssal (>3000 m) habitats in most regions of the world ocean and are uncommon below 2000 m. The deeper-living chondrichthyans include certain rajids, squaliforms and holocephalans. Several hypotheses have been erected to explain the absence of chondrichthyans from the abyss. These are mostly based on energetics: deep-sea food webs are impoverished due to their distance from primary production, and chondrichthyans, occupying the highest trophic levels, cannot be supported due to entropy among trophic levels. We examined this hypothesis by comparing trophic levels, calculated from dietary data, of deep-sea chondrichthyans with those of deep-sea teleosts. Chondrichthyans were mostly above trophic level 4, whereas all the teleosts examined were below that level. Both small and medium squaloids, as well as sharks and skates of large size, feed on fishes, cephalopods and scavenged prey, and thus occupy the highest trophic levels in bathydemersal fish communities. In addition, whereas teleosts and chondrichthyans both store lipids in their livers to support long periods of fasting, chondrichthyans must devote much of their liver lipids to maintain neutral buoyancy. Consequently teleosts with swim bladders are better adapted to survive in the abyss where food sources are sparse and unpredictable. The potential prey field for both chondrichthyans and teleosts declines in biomass and diversity with depth, but teleosts have more flexibility in their feeding mechanisms and food habits, and occupy abyssal trophic guilds for which chondrichthyans are ill adapted.

  7. Detection of Hoxa1 Expression in Human Breast Cancer

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    Chariot, Alain; Castronovo, Vincenzo

    1996-01-01

    Homeodomain-containing proteins are transcription factors that regulate the coordinated expression of multiple genes involved in development, differentiation and malignant transformation. To better understand the role played by these proteins in breast cancer cells, we demonstrate, using semi-quantitative RT-PCR experiments, that progestin induces HOXA1 mRNAs in MCF7 cells. This is the first evidence of regulation of a HOX gene by steroids. Moreover, we detected HOXA1 expression in a variety ...

  8. Effect of intramural myomectomy on endometrial HOXA10 and HOXA11 mRNA expression at the time of implantation window

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    Alizadeh, Zohreh; Faramarzi, Shamila; Saidijam, Massoud; Alizamir, Tahereh; Esna-Ashari, Farzaneh; Shabab, Nooshin; Farimani Sanoee, Marzieh

    2013-01-01

    Background: HOXA11 and HOXA10 are expressed in endometrium throughout the menstrual cycle and show a dramatic increase during the mid-luteal phase at the time of implantation. The expression of these genes is decreased in women with myomas. Objective: To determine whether myomectomy would reverse HOXA11 and HOXA10 expression, we evaluated the transcript levels of these genes in the endometria of patients before and after myomectomy. Materials and Methods: Expression of HOXA11 and HOXA10 were examined prospectively during the midluteal phase in endometrium obtained from infertile women (n=12) with myoma before and three months after myomectomy. Endometrial HOXA11 and HOXA10 expression were evaluated using quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Results: Endometrial HOXA11 and HOXA10 mRNAs expression levels (normalized to 18SrRNA) were increased insignificantly in endometrium of patients after myomectomy (p=0.7 and p=0.15 respectively). Conclusion: The results suggest that the alteration in expression pattern of these genes could not account for some aspects of fertility after myomectomy. This article extracted from M.Sc. thesis. (Shamila Faramarzi) PMID:24639724

  9. Chondrichthyans from the Pennsylvanian (Desmoinesian) Naco Formation of central Arizona

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    Elliott, D.K.; Irmis, R.B.; Hansen, M.C.; Olson, T.J.

    2004-01-01

    Teeth, spines, and dermal denticles of chondrichthyans are reported from the Middle Pennsylvanian (Desmoinesian) Naco Formation of central Arizona. The most common elements are crushing teeth of the cochliodont Deltodus angularis, less common are teeth of D. sublaevis, Venustodus leidyi, Lagarodus angustus, "Cladodus" occidentalis, Petalodus ohioensis, Orodus sp., and Hybodontoidea. Fin spines of Acondylacanthus sp., Amelacanthus sp., and Physonemus sp., and the dermal denticle Petrodus patelliformis are also present. The material of Venustodus leidyi shows for the first time that this animal was heterodont, having arched anterior teeth with a v-shaped profile grading posteriorly into lower crescentic, and finally flattened teeth. Lagarodus angustus is shown to have at least three tooth morphotypes, and a new tooth arrangement is proposed in which small anterior teeth are replaced posteriorly by large crushing teeth arranged in whorls. This fauna is similar to others in New Mexico, Colorado, and Ohio and constitutes a western extension of such faunas in North America. In addition, the presence of Deltodus sublaevis and Lagarodus angustus documents a range extension from a known European distribution, reinforcing the cosmopolitan nature of chondrichthyan faunas at this time. ?? 2004 by the Society of Vertebrate Paleontology.

  10. Phylogenetic consistencies among chondrichthyan and teleost fishes in their bioaccumulation of multiple trace elements from seawater

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    Jeffree, Ross A., E-mail: R.Jeffree@iaea.org [IAEA Marine Environment Laboratories, 4, Quai Antoine 1er, MC 98000 (Monaco); Oberhansli, Francois; Teyssie, Jean-Louis [IAEA Marine Environment Laboratories, 4, Quai Antoine 1er, MC 98000 (Monaco)

    2010-07-15

    Multi-tracer experiments determined the accumulation from seawater of selected radioactive trace elements (Mn-54, Co-60, Zn-65, Cs-134, Am-241, Cd-109, Ag-110m, Se-75 and Cr-51) by three teleost and three chondrichthyan fish species to test the hypothesis that these phylogenetic groups have different bioaccumulation characteristics, based on previously established contrasts between the carcharhiniform chondrichthyan Scyliorhinus canicula (dogfish) and the pleuronectiform teleost Psetta maxima (turbot). Discriminant function analysis on whole body: water concentration factors (CFs) separated dogfish and turbot in two independent experiments. Classification functions grouped the perciform teleosts, seabream (Sparus aurata) and seabass (Dicentrarchus labrax), with turbot and grouped the chondrichthyans, undulate ray (Raja undulata; Rajiformes) and spotted torpedo (Torpedo marmorata; Torpediniformes), with dogfish, thus supporting our hypothesis. Hierarchical classificatory, multi-dimensional scaling and similarity analyses based on the CFs for the nine radiotracers, also separated all three teleosts (that aggregated lower in the hierarchy) from the three chondrichthyan species. The three chondrichthyans were also more diverse amongst themselves compared to the three teleosts. Particular trace elements that were more important in separating teleosts and chondrichthyans were Cs-134 that was elevated in teleosts and Zn-65 that was elevated in chondrichthyans, these differences being due to their differential rates of uptake rather than loss. Chondrichthyans were also higher in Cr-51, Co-60, Ag-110m and Am-241, whereas teleosts were higher only in Mn-54. These contrasts in bioaccumulation patterns between teleosts and chondrichthyans are interpreted in the context of both proximate causes of underlying differences in physiology and anatomy, as well as the ultimate cause of their evolutionary divergence over more than 500 million years before present (MyBP). Our results

  11. Chondrichthyan egg cases from the south-west Atlantic Ocean.

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    Mabragaña, E; Figueroa, D E; Scenna, L B; Díaz de Astarloa, J M; Colonello, J H; Delpiani, G

    2011-11-01

    Egg cases of 21 oviparous chondrichthyan species from the south-west Atlantic Ocean are described and compared. The catshark Schroederichthys bivius has a cigar-shaped egg case with curled tendrils only at the posterior end. Egg cases of the elephant fish Callorhinchus callorynchus are spindle-shaped with anterior and posterior tubular extensions and lateral flanges. The skate Amblyraja doellojuradoi presents medium-sized egg cases (71 mm in length) with a lateral keel extending to the first portion of the horns. The endemic skate species of the genus Atlantoraja have medium to large egg cases (69-104 mm in length) and present relatively large posterior horns. Egg cases of the genus Bathyraja have a medium size, 75-98 mm in length, and are characterized by a very similar morphology, a relatively smooth to rough surface case and posterior horns strongly curved inwards. Egg cases of the genera Dipturus and Zearaja are very large, 115-230 mm in length, and have a well-developed posterior apron. Despite the problematical identification of skates at species level, the egg capsules of the endemic genus Psammobatis are easily diagnosed; the capsules are small (25-53 mm in length), those of Psammobatis rutrum being the smallest known to date in the world. Egg cases of Rioraja agassizi have a medium size, 61-68 mm in length, relatively straight sides, a smooth surface and silky attachment fibres placed in the lateral keel next to each horn. Those of the genus Sympterygia are small to medium sized, 51-86 mm in length, and display the thickest lateral keel and the longest posterior horns among the skates of the world. Egg cases can be a useful tool for identifying species and egg-laying areas; therefore, a provisional key for the south-west Atlantic Ocean chondrichthyan capsules is presented. PMID:22026605

  12. Does the physiology of chondrichthyan fishes constrain their distribution in the deep sea?

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    Treberg, Jason R; Speers-Roesch, Ben

    2016-03-01

    The deep sea is the largest ecosystem on Earth but organisms living there must contend with high pressure, low temperature, darkness and scarce food. Chondrichthyan fishes (sharks and their relatives) are important consumers in most marine ecosystems but are uncommon deeper than 3000 m and exceedingly rare, or quite possibly absent, from the vast abyss (depths >4000 m). By contrast, teleost (bony) fishes are commonly found to depths of ∼ 8400 m. Why chondrichthyans are scarce at abyssal depths is a major biogeographical puzzle. Here, after outlining the depth-related physiological trends among chondrichthyans, we discuss several existing and new hypotheses that implicate unique physiological and biochemical characteristics of chondrichthyans as potential constraints on their depth distribution. We highlight three major, and not mutually exclusive, working hypotheses: (1) the urea-based osmoregulatory strategy of chondrichthyans might conflict with the interactive effects of low temperature and high pressure on protein and membrane function at great depth; (2) the reliance on lipid accumulation for buoyancy in chondrichthyans has a unique energetic cost, which might increasingly limit growth and reproductive output as food availability decreases with depth; (3) their osmoregulatory strategy may make chondrichthyans unusually nitrogen limited, a potential liability in the food-poor abyss. These hypotheses acting in concert could help to explain the scarcity of chondrichthyans at great depths: the mechanisms of the first hypothesis may place an absolute, pressure-related depth limit on physiological function, while the mechanisms of the second and third hypotheses may limit depth distribution by constraining performance in the oligotrophic abyss, in ways that preclude the establishment of viable populations or lead to competitive exclusion by teleosts. PMID:26936637

  13. Feeding ecology and trophic position of three sympatric demersal chondrichthyans in the northwestern Mediterranean

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    Albo-Puigserver, M.; Navarro, J.; Coll, Marta; Aguzzi, J.; Cardona, L.; Saez-Liante, R.

    2015-01-01

    Understanding how marine predators interact is a scientific challenge. In marine ecosystems, segregation in feeding habits has been largely described as a common mechanism to allow the coexistence of several competing marine predators. However, little is known about the feeding ecology of most species of chondrichthyans, which play a pivotal role in the structure of marine food webs worldwide. In this study, we examined the trophic ecology of 3 relatively abundant chondrichthyans coexisting i...

  14. Dissection of the transformation of primary human hematopoietic cells by the oncogene NUP98-HOXA9.

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    Enas R Yassin

    Full Text Available NUP98-HOXA9 is the prototype of a group of oncoproteins associated with acute myeloid leukemia. It consists of an N-terminal portion of NUP98 fused to the homeodomain of HOXA9 and is believed to act as an aberrant transcription factor that binds DNA through the homeodomain. Here we show that NUP98-HOXA9 can regulate transcription without binding to DNA. In order to determine the relative contributions of the NUP98 and HOXA9 portions to the transforming ability of NUP98-HOXA9, the effects of NUP98-HOXA9 on primary human CD34+ cells were dissected and compared to those of wild-type HOXA9. In contrast to previous findings in mouse cells, HOXA9 had only mild effects on the differentiation and proliferation of primary human hematopoietic cells. The ability of NUP98-HOXA9 to disrupt the differentiation of primary human CD34+ cells was found to depend primarily on the NUP98 portion, whereas induction of long-term proliferation required both the NUP98 moiety and an intact homeodomain. Using oligonucleotide microarrays in primary human CD34+ cells, a group of genes was identified whose dysregulation by NUP98-HOXA9 is attributable primarily to the NUP98 portion. These include RAP1A, HEY1, and PTGS2 (COX-2. Their functions may reflect the contribution of the NUP98 moiety of NUP98-HOXA9 to leukemic transformation. Taken together, these results suggest that the effects of NUP98-HOXA9 on gene transcription and cell transformation are mediated by at least two distinct mechanisms: one that involves promoter binding through the homeodomain with direct transcriptional activation, and another that depends predominantly on the NUP98 moiety and does not involve direct DNA binding.

  15. HoxA Genes and the Fin-to-Limb Transition in Vertebrates

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    João Leite-Castro

    2016-02-01

    Full Text Available HoxA genes encode for important DNA-binding transcription factors that act during limb development, regulating primarily gene expression and, consequently, morphogenesis and skeletal differentiation. Within these genes, HoxA11 and HoxA13 were proposed to have played an essential role in the enigmatic evolutionary transition from fish fins to tetrapod limbs. Indeed, comparative gene expression analyses led to the suggestion that changes in their regulation might have been essential for the diversification of vertebrates’ appendages. In this review, we highlight three potential modifications in the regulation and function of these genes that may have boosted appendage evolution: (1 the expansion of polyalanine repeats in the HoxA11 and HoxA13 proteins; (2 the origin of +a novel long-non-coding RNA with a possible inhibitory function on HoxA11; and (3 the acquisition of cis-regulatory elements modulating 5’ HoxA transcription. We discuss the relevance of these mechanisms for appendage diversification reviewing the current state of the art and performing additional comparative analyses to characterize, in a phylogenetic framework, HoxA11 and HoxA13 expression, alanine composition within the encoded proteins, long-non-coding RNAs and cis-regulatory elements.

  16. Late Viséan pelagic chondrichthyans from northern Europe

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    Michał Ginter

    2015-12-01

    Full Text Available The relatively rich assemblages of shark teeth from pelagic limestone (Mississippian, late Viséan, late Asbian–middle Brigantian of three northern European regions: the Rhenish Mountains (Westenfeld Quarry, Germany, the Holy Cross Mountains (Todowa Grząba at the edge of Ostrówka Quarry, Poland, and Derbyshire (Cawdor Quarry, Matlock, England, UK display certain similarities, with the absolute predominance of the teeth of Falcatidae (small Symmoriiformes and the constant presence of Thrinacodus spp. The largest and most diverse assemblage from Todowa Grząba contains at least three species of a falcatid Denaea, a xenacanthimorph Bransonella nebraskensis, a newly described phoebodontid Thrinacodus dziki sp. nov., a few ctenacanthiform and euselachian teeth, and two abraded euchondrocephalan dental elements. Anachronistidae, common in the most of late Viséan pelagic faunas, are absent from Todowa Grząba and Westenfeld. The material under study differs from the shallow-water chondrichthyan fauna, hitherto described from the Mississippian carbonate platform facies, by its taxonomic content (particularly almost total absence of Euchondrocephali, generally lower diversity, and higher frequency of small teeth.

  17. Human HOXA5 homeodomain enhances protein transduction and its application to vascular inflammation

    International Nuclear Information System (INIS)

    Highlights: → We have developed an E. coli protein expression vector including human specific gene sequences for protein cellular delivery. → The plasmid was generated by ligation the nucleotides 770-817 of the homeobox A5 mRNA sequence. → HOXA5-APE1/Ref-1 inhibited TNF-alpha-induced monocyte adhesion to endothelial cells. → Human HOXA5-PTD vector provides a powerful research tools for uncovering cellular functions of proteins or for the generation of human PTD-containing proteins. -- Abstract: Cellular protein delivery is an emerging technique by which exogenous recombinant proteins are delivered into mammalian cells across the membrane. We have developed an Escherichia coli expression vector including human specific gene sequences for protein cellular delivery. The plasmid was generated by ligation the nucleotides 770-817 of the homeobox A5 mRNA sequence which was matched with protein transduction domain (PTD) of homeodomain protein A5 (HOXA5) into pET expression vector. The cellular uptake of HOXA5-PTD-EGFP was detected in 1 min and its transduction reached a maximum at 1 h within cell lysates. The cellular uptake of HOXA5-EGFP at 37 oC was greater than in 4 oC. For study for the functional role of human HOXA5-PTD, we purified HOXA5-APE1/Ref-1 and applied it on monocyte adhesion. Pretreatment with HOXA5-APE1/Ref-1 (100 nM) inhibited TNF-α-induced monocyte adhesion to endothelial cells, compared with HOXA5-EGFP. Taken together, our data suggested that human HOXA5-PTD vector provides a powerful research tools for uncovering cellular functions of proteins or for the generation of human PTD-containing proteins.

  18. A new paleozoic Symmoriiformes (Chondrichthyes from the late Carboniferous of Kansas (USA and cladistic analysis of early chondrichthyans.

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    Alan Pradel

    Full Text Available BACKGROUND: The relationships of cartilaginous fishes are discussed in the light of well preserved three-dimensional Paleozoic specimens. There is no consensus to date on the interrelationship of Paleozoic chondrichthyans, although three main phylogenetic hypotheses exist in the current literature: 1. the Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are grouped along with the modern sharks (neoselachians into a clade which is sister group of holocephalans; 2. the Symmoriiformes are related to holocephalans, whereas the other Paleozoic shark-like chondrichthyans are related to neoselachians; 3. many Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are stem chondrichthyans, whereas stem and crown holocephalans are sister group to the stem and crown neoselachians in a crown-chondrichthyan clade. This third hypothesis was proposed recently, based mainly on dental characters. METHODOLOGY/PRINCIPAL FINDINGS: On the basis of two well preserved chondrichthyan neurocrania from the Late Carboniferous of Kansas, USA, we describe here a new species of Symmoriiformes, Kawichthys moodiei gen. et sp. nov., which was investigated by means of computerized X-ray synchrotron microtomography. We present a new phylogenetic analysis based on neurocranial characters, which supports the third hypothesis and corroborates the hypothesis that crown-group chondrichthyans (Holocephali+Neoselachii form a tightly-knit group within the chondrichthyan total group, by providing additional, non dental characters. CONCLUSIONS/SIGNIFICANCE: Our results highlight the importance of new well preserved Paleozoic fossils and new techniques of observation, and suggest that a new look at the synapomorphies of the crown-group chondrichthyans would be worthwhile in terms of understanding the adaptive significance of phylogenetically important characters.

  19. The loss of Hoxa5 function promotes Notch-dependent goblet cell metaplasia in lung airways

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    Olivier Boucherat

    2012-05-01

    Hox genes encode transcription factors controlling complex developmental processes in various organs. Little is known, however, about how HOX proteins control cell fate. Herein, we demonstrate that the goblet cell metaplasia observed in lung airways from Hoxa5−/− mice originates from the transdifferentiation of Clara cells. Reduced CC10 expression in Hoxa5−/− embryos indicates that altered cell specification occurs prior to birth. The loss of Hoxa5 function does not preclude airway repair after naphthalene exposure, but the regenerated epithelium presents goblet cell metaplasia and less CC10-positive cells, demonstrating the essential role of Hoxa5 for correct differentiation. Goblet cell metaplasia in Hoxa5−/− mice is a FOXA2-independent process. However, it is associated with increased Notch signaling activity. Consistent with these findings, expression levels of activated NOTCH1 and the effector gene HEY2 are enhanced in patients with chronic obstructive pulmonary disease. In vivo administration of a γ-secretase inhibitor attenuates goblet cell metaplasia in Hoxa5−/− mice, highlighting the contribution of Notch signaling to the phenotype and suggesting a potential therapeutic strategy to inhibit goblet cell differentiation and mucus overproduction in airway diseases. In summary, the loss of Hoxa5 function in lung mesenchyme impacts on epithelial cell fate by modulating Notch signaling.

  20. Deepwater Chondrichthyan Bycatch of the Eastern King Prawn Fishery in the Southern Great Barrier Reef, Australia.

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    Rigby, Cassandra L; White, William T; Simpfendorfer, Colin A

    2016-01-01

    The deepwater chondrichthyan fauna of the Great Barrier Reef is poorly known and life history information is required to enable their effective management as they are inherently vulnerable to exploitation. The chondrichthyan bycatch from the deepwater eastern king prawn fishery at the Swain Reefs in the southern Great Barrier Reef was examined to determine the species present and provide information on their life histories. In all, 1533 individuals were collected from 11 deepwater chondrichthyan species, with the Argus skate Dipturus polyommata, piked spurdog Squalus megalops and pale spotted catshark Asymbolus pallidus the most commonly caught. All but one species is endemic to Australia with five species restricted to waters offshore from Queensland. The extent of life history information available for each species varied but the life history traits across all species were characteristic of deep water chondrichthyans with relatively large length at maturity, small litters and low ovarian fecundity; all indicative of low biological productivity. However, variability among these traits and spatial and bathymetric distributions of the species suggests differing degrees of resilience to fishing pressure. To ensure the sustainability of these bycatch species, monitoring of their catches in the deepwater eastern king prawn fishery is recommended.

  1. HOXA1 mutations are not a common cause of Möbius syndrome.

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    Rankin, Jessica K; Andrews, Caroline; Chan, Wai-Man; Engle, Elizabeth C

    2010-02-01

    The HOXA1-related syndromes result from autosomal-recessive truncating mutations in the homeobox transcription factor, HOXA1. Limited horizontal gaze and sensorineural deafness are the most common features; affected individuals can also have facial weakness, mental retardation, autism, motor disabilities, central hypoventilation, carotid artery, and/or conotruncal heart defects. Möbius syndrome is also phenotypically heterogeneous, with minimal diagnostic criteria of nonprogressive facial weakness and impaired ocular abduction; mental retardation, autism, motor disabilities, additional eye movements restrictions, hearing loss, hypoventilation, and craniofacial, lingual, and limb abnormalities also occur. We asked, given the phenotypic overlap between these syndromes and the variable expressivity of both disorders, whether individuals with Möbius syndrome might harbor mutations in HOXA1. Our results suggest that HOXA1 mutations are not a common cause of sporadic Möbius syndrome in the general population. PMID:20227628

  2. Study of HOXA-10、 HOXA-11、 Esr2、 Pgr expression in endometrium during the peri-implatation period after controlled ovarian hyperstimulation on mice%HOXA-10、 HOXA-11、 Esr2、 Pgr在控制性超排卵小鼠围着床期子宫内膜表达的研究

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    付正英; 卢建荣; 苏晓华

    2012-01-01

    目的:检测同源框基因HOXA-10、HOXA-11以及雌激素受体Esr2、孕激素受体Pgr在控制性超排卵(COH)小鼠围着床期子宫内膜中的表达,探讨COH对子宫内膜容受性的影响.方法:将30只SPF级雌性昆明小鼠随机分为模型组(GnRH-a+HMG+HCG)和对照组(生理盐水),每组15只,造模成功后,计算子宫脏器指数,光学显微镜观察子宫内膜组织学变化;应用RT-PCR和Real-time PCR方法检测小鼠子宫内膜中HOXA-10、HOXA-11、Esr2、Pgr mRNA的表达.结果:模型组围着床期小鼠子宫脏器指数较对照组显著降低(P<0.05),子宫内膜发育延迟,子宫内膜成熟度及厚度降低;模型组小鼠HOXA-10、HOXA-11、Pgr mRNA表达较对照组显著下降(P<0.05),而Esr2 mRNA表达显著升高(P<0.05).结论:COH引起HOXA-10、HOXA-11、Pgr mRNA表达下降,Esr2 mR-NA表达升高,致使围着床期内膜准备不足,子宫内膜容受性下降.%Objective:To study the expressions of HOXA-10,HOXA-11 ,Esr2 and Pgr in endometrium during the peri-implatation period after controlled ovarian hyperstimulation on mice. To explore the influence of COH to endometrial receptivity. Methods: Thirty female mice were randomized into the treatment group ( GnRH-a + HMG + HCG ) and the control group (0.9% NS) ,15 cases in every group. After successful modeling,calculate the uterus index,ob-served the endometrial histology with Optical Microscope. Detection of HOXA-10、HOXA-11、 Esr2、Pgr mRNA expression in endometrial with Polymerase Chain Reaction and Real-time Poly-merase Chain Reaction. Results;The uterus index were decreased significantly and development delay in endometrium,maturity and thickness decreased,HOXA-10、HOXA-11 and Pgr mRNA expressions were decreased, but Esr2 mRNA expression was higher, in treatment group of COH mice(P<0. 05). There were significantly differences compared with the control group (P< 0.05). Conclusion: COH lead to HOXA-10、HOXA-1 l、Pgr mRNA expressions decreased

  3. HOXA1 mutations are not a common cause of Möbius syndrome

    OpenAIRE

    Rankin, Jessica K.; Andrews, Caroline; Chan, Wai-man; Engle, Elizabeth C

    2010-01-01

    The HOXA1-related syndromes result from autosomal recessive truncating mutations in the homeobox transcription factor, HOXA1. Limited horizontal gaze and sensorineural deafness are the most common features; affected individuals can also have facial weakness, mental retardation, autism, motor disabilities, central hypoventilation, carotid artery and/or conotruncal heart defects. Möbius syndrome is also phenotypically heterogeneous, with minimal diagnostic criteria of nonprogressive facial weak...

  4. A shared role for sonic hedgehog signalling in patterning chondrichthyan gill arch appendages and tetrapod limbs.

    Science.gov (United States)

    Gillis, J Andrew; Hall, Brian K

    2016-04-15

    Chondrichthyans (sharks, skates, rays and holocephalans) possess paired appendages that project laterally from their gill arches, known as branchial rays. This led Carl Gegenbaur to propose that paired fins (and hence tetrapod limbs) originally evolved via transformation of gill arches. Tetrapod limbs are patterned by asonic hedgehog(Shh)-expressing signalling centre known as the zone of polarising activity, which establishes the anteroposterior axis of the limb bud and maintains proliferative expansion of limb endoskeletal progenitors. Here, we use loss-of-function, label-retention and fate-mapping approaches in the little skate to demonstrate that Shh secretion from a signalling centre in the developing gill arches establishes gill arch anteroposterior polarity and maintains the proliferative expansion of branchial ray endoskeletal progenitor cells. These findings highlight striking parallels in the axial patterning mechanisms employed by chondrichthyan branchial rays and paired fins/limbs, and provide mechanistic insight into the anatomical foundation of Gegenbaur's gill arch hypothesis. PMID:27095494

  5. Chondrichthyan Fauna from the Pirabas Formation, Miocene of Northern Brazil, with Comments on Paleobiogeography

    Directory of Open Access Journals (Sweden)

    Márcia Aparecida Fernandes dos Reis

    2005-09-01

    Full Text Available The chondrichthyan fauna from the Pirabas Formation is redescribed. Only thirteen nominal taxa are considered valid. From these taxa, ten were reassigned to extant taxa (Carcharhinus sorrah, Carcharhinus perezii, Galeocerdo cuvier, Rhizoprionodon lalandii, Sphyrna sp., Hemipristis elongatus, Carcharodon carcharias, Isurus oxyrinchus, Nebrius ferrugineus, and indeterminate Myliobatidae, confirming the Neogene age of this formation. This elasmofauna is compared with other Caribbean and African Tertiary faunas.

  6. miRNA-135a promotes breast cancer cell migration and invasion by targeting HOXA10

    International Nuclear Information System (INIS)

    miRNAs are a group of small RNA molecules regulating target genes by inducing mRNA degradation or translational repression. Aberrant expression of miRNAs correlates with various cancers. Although miR-135a has been implicated in several other cancers, its role in breast cancer is unknown. HOXA10 however, is associated with multiple cancer types and was recently shown to induce p53 expression in breast cancer cells and reduce their invasive ability. Because HOXA10 is a confirmed miR-135a target in more than one tissue, we examined miR-135a levels in relation to breast cancer phenotypes to determine if miR-135a plays role in this cancer type. Expression levels of miR-135a in tissues and cells were determined by poly (A)-RT PCR. The effect of miR-135a on proliferation was evaluated by CCK8 assay, cell migration and invasion were evaluated by transwell migration and invasion assays, and target protein expression was determined by western blotting. GFP and luciferase reporter plasmids were constructed to confirm the action of miR-135a on downstream target genes including HOXA10. Results are reported as means ± S.D. and differences were tested for significance using 2-sided Student's t-test. Here we report that miR-135a was highly expressed in metastatic breast tumors. We found that the expression of miR-135a was required for the migration and invasion of breast cancer cells, but not their proliferation. HOXA10, which encodes a transcription factor required for embryonic development and is a metastasis suppressor in breast cancer, was shown to be a direct target of miR-135a in breast cancer cells. Our analysis showed that miR-135a suppressed the expression of HOXA10 both at the mRNA and protein level, and its ability to promote cellular migration and invasion was partially reversed by overexpression of HOXA10. In summary, our results indicate that miR-135a is an onco-miRNA that can promote breast cancer cell migration and invasion. HOXA10 is a target gene for mi

  7. The status of chondrichthyan conservation in the Indo-Australasian region.

    Science.gov (United States)

    White, W T; Kyne, P M

    2010-06-01

    The status of chondrichthyan (sharks, batoids and chimaeras) conservation in the Indo-Australasian region is examined, and issues relevant to the conservation of this fauna at the subregional level [Australia, Indonesia (excluding West Papua), New Guinea (West Papua and Papua New Guinea), New Caledonia and New Zealand] are discussed. According to the 2009 IUCN Red List of Threatened Species, c. 21% of Indo-Australasian chondrichthyans are classified as threatened (critically endangered, endangered and vulnerable) and c. 40% are of conservation concern (threatened and near threatened). The proportion of threatened species is highest in New Guinea (c. 39%) and Indonesia (c. 35%) and least in New Zealand (c. 11%). In New Guinea, three quarters of the species are of conservation concern; in Indonesia, nearly two thirds are of conservation concern. Within the region, the proportion of threatened batoids (c. 29%) is higher than threatened sharks (c. 17%), while there are no threatened chimaeras. Conservation status is discussed at the order (for sharks), suborder (for batoids) and family level. Issues relating to the conservation status of chondrichthyans vary greatly between each subregion, but they mostly relate to targeted or incidental capture in fisheries. A handful of sharks and batoids are protected within Australian waters, while one species is protected in New Zealand. Both Australia and New Zealand have developed National Plans of Action for the Conservation and Management of Sharks (NPOA-Sharks), but these are lacking elsewhere. Development and implementation of NPOA-Sharks are a priority in order to drive the conservation of the regional fauna. Sustainable fisheries management (including by-catch), confronting the challenge of illegal, unreported and unregulated fishing, species protection where appropriate and marine protected areas (MPA) are all likely to prove vital in ensuring the long-term conservation of Indo-Australasian sharks, batoids and chimaeras.

  8. Regulatory Effect of Estrogen, Progestin and HB-EGF on the Expression of HOXA10 Gene in Ishikawa Cells

    Institute of Scientific and Technical Information of China (English)

    LIU Xuemei; ZHU Guijin; ZHONG Gang

    2007-01-01

    HOXA10 gene plays an essential role in differentiation of the endometrium and in human reproduction. The aim of this study was to investigate the regulatory effect of sex steroids and HB-EGF on HOXA10 gene in Ishikawa cells. Ishikawa cells were incubated with 17-beta estradiol (10-8 mol/L), medroxyprogesterone acetate (MPA) (10-6 mol/L), RU486 (10-5 mol/L) or HB-EGF (10 ng/mL) for 48 h respectively. The expression of HOXA10 gene was detected by immunofluorescence,reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. Our results showed that either estrogen alone, progestin alone or progestin combined with estrogen could significantly increase the expression of HOXA10 gene 48 h after the treatment (P<0.05). But estrogen combined with progestin and RU486 could inhibit the up-regulation by estrogen and progestin. HB-EGF could elevate the expression of HOXA10 gene 48 h after the treatment (P<0.05). It is concluded that both estrogen and progestin can up-regulate the expression of HOXA10 gene in Ishikawa cells, but RU486 can inhibit the effect and HB-EGF can elevate the expression level of HOXA10 gene.

  9. Adaptation of ovarian cancer cells to the peritoneal environment: Multiple mechanisms of the developmental patterning gene HOXA9

    Science.gov (United States)

    Ko, Song Yi; Naora, Honami

    2015-01-01

    The lethality of ovarian cancer stems from its propensity to involve the peritoneal cavity. However, the mechanisms that enable ovarian cancer cells to readily adapt to the peritoneal environment are not well understood. Here, we describe our recent studies in which we identified the mechanisms by which the transcription factor encoded by the patterning gene HOXA9 promotes the aggressive behavior of ovarian cancer. Firstly, we identified that HOXA9 promotes ovarian tumor growth and angiogenesis by activating the gene encoding transforming growth factor-β2 (TGF-β2), which in turn stimulates peritoneal fibroblasts and mesenchymal stem cells to acquire features of cancer-associated fibroblasts. Secondly, by inducing TGF-β2 and chemokine (C-C motif) ligand 2, HOXA9 stimulates peritoneal macrophages to acquire an immunosuppressive phenotype. Thirdly, HOXA9 stimulates attachment of ovarian cancer cells to peritoneal mesothelial cells by inducing expression of P-cadherin. By inducing P-cadherin, HOXA9 also enables floating cancer cells in the peritoneal cavity to form aggregates and escape anoikis. Together, our studies demonstrate that HOXA9 enables ovarian cancer cells to adapt to the peritoneal environment and ‘educates’ different types of stromal cells to become permissive for tumor growth. Our studies provide new insights into the regulation of tumor-stroma interactions in ovarian cancer and implicate several key effector molecules as candidate therapeutic targets. PMID:26000332

  10. A review of the taxonomy of chondrichthyan fishes: a modern perspective.

    Science.gov (United States)

    White, W T; Last, P R

    2012-04-01

    Taxonomic clarity is a fundamental requirement as it forms the foundation of all other life sciences. In the last decade, chondrichthyan taxonomy has undergone a scientific renaissance with >180 new species formally described. This effort encompasses c. 15% of the global chondrichthyan fauna, which consists of 1185 currently recognized species. The important role of chondrichthyan taxonomy for conservation management has been highlighted in recent years with new species descriptions or taxonomic resolution of a number of threatened species. These include Australian gulper (genus Centrophorus) and speartooth sharks (genus Glyphis) in coastal waters of Australia and Borneo. Closer examination of other wide-ranging species, for which the taxonomy was thought to be stable, has shown that they consist of species complexes, e.g. manta rays (Manta spp.) and spotted eagle rays (the Aetobatus narinari complex), and highlights the need for critical re-examination of other wide-ranging species. Molecular methods have provided another useful tool to taxonomists and they have proven to assist greatly with identifying cryptic species and species complexes. The limitations of particular molecular methods being used need, however, to be carefully considered and there are some concerns about how these are being integrated with classical taxonomy. The fundamental importance of taxonomic nomenclature to life sciences is often poorly understood but striving for nomenclatural stability is a critical component of taxonomy. Similarly, biological collections are an extremely vital asset to both taxonomists and the broader scientific community. These collections are becoming increasingly important due in part to molecular species identification initiatives such as the Barcode of Life which has resulted in a large number of voucher specimens linked to tissue samples being deposited. Biological collections are also proving to be imperative in biodiversity studies as they contain a 'gold mine

  11. A review of the taxonomy of chondrichthyan fishes: a modern perspective.

    Science.gov (United States)

    White, W T; Last, P R

    2012-04-01

    Taxonomic clarity is a fundamental requirement as it forms the foundation of all other life sciences. In the last decade, chondrichthyan taxonomy has undergone a scientific renaissance with >180 new species formally described. This effort encompasses c. 15% of the global chondrichthyan fauna, which consists of 1185 currently recognized species. The important role of chondrichthyan taxonomy for conservation management has been highlighted in recent years with new species descriptions or taxonomic resolution of a number of threatened species. These include Australian gulper (genus Centrophorus) and speartooth sharks (genus Glyphis) in coastal waters of Australia and Borneo. Closer examination of other wide-ranging species, for which the taxonomy was thought to be stable, has shown that they consist of species complexes, e.g. manta rays (Manta spp.) and spotted eagle rays (the Aetobatus narinari complex), and highlights the need for critical re-examination of other wide-ranging species. Molecular methods have provided another useful tool to taxonomists and they have proven to assist greatly with identifying cryptic species and species complexes. The limitations of particular molecular methods being used need, however, to be carefully considered and there are some concerns about how these are being integrated with classical taxonomy. The fundamental importance of taxonomic nomenclature to life sciences is often poorly understood but striving for nomenclatural stability is a critical component of taxonomy. Similarly, biological collections are an extremely vital asset to both taxonomists and the broader scientific community. These collections are becoming increasingly important due in part to molecular species identification initiatives such as the Barcode of Life which has resulted in a large number of voucher specimens linked to tissue samples being deposited. Biological collections are also proving to be imperative in biodiversity studies as they contain a 'gold mine

  12. HOXA10在肺腺癌中的过表达及其临床意义%Over-expression and clinical significance of HOXA10 in human lung adenocarcinoma

    Institute of Scientific and Technical Information of China (English)

    张雪淋; 原薇薇; 傅华; 刘小军; 胡义德

    2013-01-01

    Objective To determine the expression of homeobox 10 (HOXA10) in lung adenocarcinoma and lung adenocarcinoma cell lines and to observe its clinical significance in lung adenocarcinoma. Meth-OdS Immunohistochemical staining was applied to detect the HOXA10 expression in lung tissue samples from 75 cases of lung adenocarcinoma and corresponding normal lung tissues. The correlation between the expression and the clinical feature or 5-year survival rate in these patients was analyzed. RT-PCR, Western blot analysis and immunofluorescence assay were used to detect the expression of HOXA10 in H322, H1650 A549 and H1975 lung adenocarcinoma cell lines and HBE human bronchial epithelial cell line. Results In 75 cases of lung adenocarcinoma, the expression of HOXA10, which was in the cytoplasm, was significantly higher than that in normal lung tissues (P 0. 05 ). In addition, the expression of HOXA10 at mRNA and protein levels was very strong in lung adenocarcinoma cell lines, and significantly higher than in human bronchial epithelial cells. Conclusion HOXA10 is strongly expressed in lung adenocarcinoma and lung adenocarcinoma cell lines, and may be involved in the invasion and lymphatic metastasis degrees of lung adenocarcinoma.%目的 研究肺腺癌组织和细胞系中HOXA10的表达及其临床意义.方法 运用免疫组织化学方法检测75例肺腺癌及其癌旁组织中HOXA10的表达情况,并分析HOXA10的表达与患者的临床特征及5年生存率的相关性.此外利用反转录PCR、Western blot及免疫荧光染色检测正常肺支气管上皮细胞系HBE以及4种肺腺癌细胞系H322、H1650、A549、H1975中HOXA10的表达情况.结果 HOXA10主要表达于胞浆中,且于75例肺腺癌组织中的表达明显高于癌旁组织(P<0.01),并与肿瘤的浸润深度(P<0.05)及淋巴结转移(P<0.01)有关.而HOXA10高表达与低表达的肺腺癌患者的5年生存率没有显著差异(P>0.05).反转录PCR、Western blot及免疫荧光染色的结果显示HOXA

  13. Molecular development of chondrichthyan claspers and the evolution of copulatory organs.

    Science.gov (United States)

    O'Shaughnessy, Katherine L; Dahn, Randall D; Cohn, Martin J

    2015-04-14

    The earliest known vertebrate copulatory organs are claspers, paired penis-like structures that are associated with evolution of internal fertilization and viviparity in Devonian placoderms. Today, only male chondrichthyans possess claspers, which extend from posterior pelvic fins and function as intromittent organs. Here we report that clasper development from pelvic fins of male skates is controlled by hormonal regulation of the Sonic hedgehog (Shh) pathway. We show that Shh signalling is necessary for male clasper development and is sufficient to induce clasper cartilages in females. Androgen receptor (AR) controls the male-specific pattern of Shh in pelvic fins by regulation of Hand2. We identify an androgen response element (ARE) in the Hand2 locus and present biochemical evidence that AR can directly bind the Hand2 ARE. Together, our results suggest that the genetic circuit for appendage development evolved an androgen regulatory input, which prolonged signalling activity and drove clasper skeletogenesis in male fins.

  14. Homozygous HOXA1 mutations disrupt human brainstem, inner ear, cardiovascular and cognitive development.

    Science.gov (United States)

    Tischfield, Max A; Bosley, Thomas M; Salih, Mustafa A M; Alorainy, Ibrahim A; Sener, Emin C; Nester, Michael J; Oystreck, Darren T; Chan, Wai-Man; Andrews, Caroline; Erickson, Robert P; Engle, Elizabeth C

    2005-10-01

    We identified homozygous truncating mutations in HOXA1 in three genetically isolated human populations. The resulting phenotype includes horizontal gaze abnormalities, deafness, facial weakness, hypoventilation, vascular malformations of the internal carotid arteries and cardiac outflow tract, mental retardation and autism spectrum disorder. This is the first report to our knowledge of viable homozygous truncating mutations in any human HOX gene and of a mendelian disorder resulting from mutations in a human HOX gene critical for development of the central nervous system. PMID:16155570

  15. Mutational Analysis of TCOF1, GSC, and HOXA2 in Patients With Treacher Collins Syndrome.

    Science.gov (United States)

    Hao, Shaojuan; Jin, Lei; Wang, Huijun; Li, Chenlong; Zheng, Fengyun; Ma, Duan; Zhang, Tianyu

    2016-09-01

    Treacher Collins syndrome is an autosomal dominant craniofacial malformation mainly caused by mutations in the TCOF1 gene. Few cases have been observed in the Chinese population. Herein, the authors report the mutational analysis of TCOF1, GSC, and HOXA2 to determine the mutational features of the 3 genes in Chinese patients with Treacher Collins syndrome. Genomic DNA of the patients and their parents was extracted from peripheral blood following a standard protocol. DNA sequencing analysis was performed on all exons and the exon-intron borders of TCOF1, GSC, and HOXA2 in addition to the 1200-bp upstream of TCOF1. Four novel single nucleotide polymorphisms were detected in TCOF1, one of which was in the promoter region. Mutations in GSC and HOXA2 were not found in the 3 patients. Our results suggest the possibility of genetic heterogeneity or different mechanisms leading to the disease. Further functional study of the alteration is necessary to obtain more definitive information.

  16. Study on the correlation between HOXA11 and polycystic ovary syndrome%HOXA11与多囊卵巢综合征的相关性研究

    Institute of Scientific and Technical Information of China (English)

    杨意; 钟刚

    2012-01-01

    目的:探讨HOXA11基因在卵巢颗粒细胞内的异常表达与PCOS的相关性.方法:采用免疫荧光法、RT-PCR法、Western - blot法检测颗粒细胞中HOXA11的表达水平.结果:①在PCOS组中,镜下细胞内见明显的红色荧光主要定位于细胞核,细胞液中可见少许微弱红色荧光;对照组中,细胞核和细胞液中可见更强的红色荧光.PCOS组与对照组比较,细胞核和细胞液中HOXA11的表达都明显减少(P<0.05).②PCOS组HOXA11 mRNA的表达水平较对照组低(P<0.05).③Westernblot结果显示,PCOS组与对照组的颗粒细胞中均有HOXA11蛋白表达.PCOS组表达较弱,对照组表达较强(P<0.05).免疫荧光、RT - PCR、Western - blot均提示PCOS组颗粒细胞中HOXA11表达水平较对照组低(P<0.05).结论:HOXA11在PCOS组的颗粒细胞中表达降低,提示其可能在PCOS发生发展过程中起着重要作用.%Objective: To explore the correlation between abnormal expression of HOXA11 gene in ovarian granulosa cells and polycystic ovary syndrome (PCOS) . Methods: Immurinfluorescence method, RT -PCR, and Western blot were used to detect the expression level of HOXA11 gene in ovarian granulosa cells. Results: In PCOS group, obvious red fluorescence mainly located in cell nucleus, there was a little weak fluorescence in cytoplasm; in control group, stronger red fluorescence could be observed in cell nucleus and cytoplasm. The expression levels of HOXA11 in cell nucleus and cytoplasm decreased significantly in PCOS group and control group (P < 0. 05) . The expression level of HOXA11 mRNA in PCOS group was significantly lower than that in control group ( P < 0.05) . The results of western blot showed that HOXA11 protein expressed in granulosa cells of PCOS group and control group, the expression in PCOS group was weaker than that in control group (P<0.05) . The results of immunofluorescence method, RT-PCR, and Western blot indicated that the expression level of H0XA11 in granulosa

  17. HoxA-11 and FOXO1A cooperate to regulate decidual prolactin expression: towards inferring the core transcriptional regulators of decidual genes.

    Directory of Open Access Journals (Sweden)

    Vincent J Lynch

    Full Text Available BACKGROUND: During the menstrual cycle, the ovarian steroid hormones estrogen and progesterone control a dramatic transcriptional reprogramming of endometrial stromal cells (ESCs leading to a receptive state for blastocyst implantation and the establishment of pregnancy. A key marker gene of this decidualization process is the prolactin gene. Several transcriptional regulators have been identified that are essential for decidualization of ESCs, including the Hox genes HoxA-10 and HoxA-11, and the forkhead box gene FOXO1A. While previous studies have identified downstream target genes for HoxA-10 and FOXO1A, the role of HoxA-11 in decidualization has not been investigated. Here, we show that HoxA-11 is required for prolactin expression in decidualized ESC. While HoxA-11 alone is a repressor on the decidual prolactin promoter, it turns into an activator when combined with FOXO1A. Conversely, HoxA-10, which has been previously shown to associate with FOXO1A to upregulate decidual IGFBP-1 expression, is unable to upregulate PRL expression when co-expressed with FOXO1A. By co-immunoprecipitation and chromatin immunoprecipitation, we demonstrate physical association of HoxA-11 and FOXO1A, and binding of both factors to an enhancer region (-395 to -148 relative to the PRL transcriptional start site of the decidual prolactin promoter. Because FOXO1A is induced upon decidualization, it serves to assemble a decidual-specific transcriptional complex including HoxA-11. These data highlight cooperativity between numerous transcription factors to upregulate PRL in differentiating ESC, and suggest that this core set of transcription factors physically and functionally interact to drive the expression of a gene battery upregulated in differentiated ESC. In addition, the functional non-equivalence of HoxA-11 and HoxA-10 with respect to PRL regulation suggests that these transcription factors regulate distinct sets of target genes during decidualization.

  18. Investigation of HOXA9 promoter methylation as a biomarker to distinguish oral cancer patients at low risk of neck metastasis

    International Nuclear Information System (INIS)

    Metastasis to the cervical (neck) lymph nodes is one of the most significant clinical factors responsible for death from oral squamous cell carcinoma (SCC). Therefore, the lymph nodes are frequently removed when the tumor is excised (neck dissection), even though the majority of patients will not benefit from the extra surgery. Two subtypes of oral SCC distinguished by the presence of tumor genomic aberrations +3q, -8p, +8q and/or +20 differ in risk for metastasis – high for the 3q8pq20 subtype, harboring one or more of the aberrations and low for the non-3q8pq20 subtype, lacking these alterations. A prior analysis of the literature suggested genes differentially methylated in the two subtypes. Therefore, the goal of this study was to further investigate the methylation status of candidate biomarkers of the non-3q8pq20 subtype, and evaluate their utility for identifying patients at low risk for metastasis. Methylation status of genes in a cohort of 52 oral SCC patients with at least five year follow up was determined by pyrosequencing. Gene expression levels were determined by quantitative RT-PCR. Growth following re-expression of HOXA9 in cultured oral SCC cells was assessed by proliferation and colony formation assays. A pilot study evaluating methylation levels of HOXA9, MT1A and HOXA11 promoters in DNA from 12 tumors (six each of the 3q8pq20 and non-3q8pq20 subtypes) revealed that only HOXA9 was differentially methylated. Significant differences in methylation levels of HOXA9 were observed amongst the 52 oral SCCs with respect to genomic subtype and nodal status (p = 0.014, and p = 0.024, respectively, Wilcoxon rank sum test). High levels of HOXA9 methylation and low levels of expression in oral SCC cell lines were observed compared to HaCaT, a non-tumorigenic keratinocyte cell line. Re-expression of HOXA9 in the SCC4 oral cancer cell line resulted in diminished proliferation and colony formation. HOXA9 methylation is frequent in oral cancers and levels are

  19. Molecular evolution of HoxA13 and the multiple origins of limbless morphologies in amphibians and reptiles

    Science.gov (United States)

    Singarete, Marina E.; Grizante, Mariana B.; Milograna, Sarah R.; Nery, Mariana F.; Kin, Koryu; Wagner, Günter P.; Kohlsdorf, Tiana

    2015-01-01

    Developmental processes and their results, morphological characters, are inherited through transmission of genes regulating development. While there is ample evidence that cis-regulatory elements tend to be modular, with sequence segments dedicated to different roles, the situation for proteins is less clear, being particularly complex for transcription factors with multiple functions. Some motifs mediating protein-protein interactions may be exclusive to particular developmental roles, but it is also possible that motifs are mostly shared among different processes. Here we focus on HoxA13, a protein essential for limb development. We asked whether the HoxA13 amino acid sequence evolved similarly in three limbless clades: Gymnophiona, Amphisbaenia and Serpentes. We explored variation in ω (dN/dS) using a maximum-likelihood framework and HoxA13sequences from 47 species. Comparisons of evolutionary models provided low ω global values and no evidence that HoxA13 experienced relaxed selection in limbless clades. Branch-site models failed to detect evidence for positive selection acting on any site along branches of Amphisbaena and Gymnophiona, while three sites were identified in Serpentes. Examination of alignments did not reveal consistent sequence differences between limbed and limbless species. We conclude that HoxA13 has no modules exclusive to limb development, which may be explained by its involvement in multiple developmental processes. PMID:26500429

  20. Knockdown of HOXA10 reverses the multidrug resistance of human chronic mylogenous leukemia K562/ADM cells by downregulating P-gp and MRP-1.

    Science.gov (United States)

    Yi, Ying-Jie; Jia, Xiu-Hong; Wang, Jian-Yong; Li, You-Jie; Wang, Hong; Xie, Shu-Yang

    2016-05-01

    Multidrug resistance (MDR) of leukemia cells is a major obstacle in chemotherapeutic treatment. The high expression and constitutive activation of P-glycoprotein (P-gp) and multidrug resistance protein-1 (MRP-1) have been reported to play a vital role in enhancing cell resistance to anticancer drugs in many tumors. The present study aimed to investigate the reversal of MDR by silencing homeobox A10 (HOXA10) in adriamycin (ADR)-resistant human chronic myelogenous leukemia (CML) K562/ADM cells by modulating the expression of P-gp and MRP-1. K562/ADM cells were stably transfected with HOXA10-targeted short hairpin RNA (shRNA). The results of reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis showed that the mRNA and protein expression of HOXA10 was markedly suppressed following transfection with a shRNA-containing vector. The sensitivity of the K562/ADM cells to ADR was enhanced by the silencing of HOXA10, due to the increased intracellular accumulation of ADR. The accumulation of ADR induced by the silencing of HOXA10 may be due to the downregulation of P-gp and MRP-1. Western blot analysis revealed that downregulating HOXA10 inhibited the protein expression of P-gp and MRP-1. Taken together, these results suggest that knockdown of HOXA10 combats resistance and that HOXA10 is a potential target for resistant human CML. PMID:27035504

  1. HOXA13 exerts a beneficial effect in albumin-induced epithelial-mesenchymal transition via the glucocorticoid receptor signaling pathway in human renal tubular epithelial cells.

    Science.gov (United States)

    Peng, Li; He, Qingnan; Li, Xiaoyan; Shuai, Lanjun; Chen, Haixia; Li, Yongzhen; Yi, Zhuwen

    2016-07-01

    Previous studies have suggested that albumin-induced renal tubular epithelial cell injury contributes to renal interstitial fibrosis. Epithelial-mesenchymal transition (EMT) is known to be a key mechanism in the pathogenesis and progression of renal interstitial fibrosis. Homeobox protein HOX‑A13 (HOXA13) is a nuclear transcriptional factor that has been reported to be involved in renal fibrosis. However, the mechanism underlying the effect of HOXA13 in human serum albumin (HSA)‑induced EMT in HKC renal tubular epithelial cells remains to be elucidated. Thus, the aim of the present study was to investigate the role of HOXA13 in HSA‑induced EMT in HKC cells and the potential mechanism of the glucocorticoid receptor (GR) signaling pathway. The protein and mRNA expression levels of HOXA13, cytokeratin, and vimentin were determined by western blot analysis and reverse transcription‑quantitative polymerase chain reaction in HKC cells, which were co‑incubated with HSA at different concentrations or for different time periods. The results demonstrated that HOXA13 mRNA and protein expression decreased in a dose‑ and time‑dependent manner when induced by HSA in HCK cells. The liposomal transfection experiment suggested that overexpression of HOXA13 activated the GR signal, which inhibits HSA-induced EMT. HOXA13 is involved in HSA‑induced EMT in HKC cells and upregulation of HOXA13 exerts a beneficial effect in EMT, which may be associated with the GR signaling pathway. PMID:27176855

  2. HOXA9 is Underexpressed in Cervical Cancer Cells and its Restoration Decreases Proliferation, Migration and Expression of Epithelial-to-Mesenchymal Transition Genes.

    Science.gov (United States)

    Alvarado-Ruiz, Liliana; Martinez-Silva, Maria Guadalupe; Torres-Reyes, Luis Alberto; Pina-Sanchez, Patricia; Ortiz-Lazareno, Pablo; Bravo-Cuellar, Alejandro; Aguilar-Lemarroy, Adriana; Jave-Suarez, Luis Felipe

    2016-01-01

    HOX transcription factors are evolutionarily conserved in many different species and are involved in important cellular processes such as morphogenesis, differentiation, and proliferation. They have also recently been implicated in carcinogenesis, but their precise role in cancer, especially in cervical cancer (CC), remains unclear. In this work, using microarray assays followed by the quantitative polymerase chain reaction (qPCR), we found that the expression of 25 HOX genes was downregulated in CC derived cell lines compared with nontumorigenic keratinocytes. In particular, the expression of HOXA9 was observed as down-modulated in CCderived cell lines. The expression of HOXA9 has not been previously reported in CC, or in normal keratinocytes of the cervix. We found that normal CC from women without cervical lesions express HOXA9; in contrast, CC cell lines and samples of biopsies from women with CC showed significantly diminished HOXA9 expression. Furthermore, we found that methylation at the first exon of HOXA9 could play an important role in modulating the expression of this gene. Exogenous restoration of HOXA9 expression in CC cell lines decreased cell proliferation and migration, and induced an epithelial-like phenotype. Interestingly, the silencing of human papilloma virus (HPV) E6 and E7 oncogenes induced expression of HOXA9. In conclusion, controlling HOXA9 expression appears to be a necessary step during CC development. Further studies are needed to delineate the role of HOXA9 during malignant progression and to afford more insights into the relationship between downmodulation of HOXA9 and viral HPV oncoprotein expression during cercical cancer development. PMID:27039722

  3. miR-1271 promotes non-small-cell lung cancer cell proliferation and invasion via targeting HOXA5

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yongfang; Xu, Lianhong; Jiang, Lixin, E-mail: jianglx66766@163.com

    2015-03-13

    MicroRNAs (miRNAs) are short, non-coding RNAs (∼22 nt) that play important roles in the pathogenesis of human diseases by negatively regulating numerous target genes at posttranscriptional level. However, the role of microRNAs in lung cancer, particularly non-small-cell lung cancer (NSCLC), has remained elusive. In this study, two microRNAs, miR-1271 and miR-628, and their predicted target genes were identified differentially expressed in NSCLC by analyzing the miRNA and mRNA expression data from NSCLC tissues and their matching normal controls. miR-1271 and its target gene HOXA5 were selected for further investigation. CCK-8 proliferation assay showed that the cell proliferation was promoted by miR-1271 in NSCLC cells, while miR-1271 inhibitor could significantly inhibited the proliferation of NSCLC cells. Interestingly, migration and invasion assay indicated that overexpression of miR-1271 could significantly promoted the migration and invasion of NSCLC cells, whereas miR-1271 inhibitor could inhibited both cell migration and invasion of NSCLC cells. Western blot showed that miR-1271 suppressed the protein level of HOXA5, and luciferase assays confirmed that miR-1271 directly bound to the 3'untranslated region of HOXA5. This study indicated indicate that miR-1271 regulates NSCLC cell proliferation and invasion, via the down-regulation of HOXA5. Thus, miR-1271 may represent a potential therapeutic target for NSCLC intervention. - Highlights: • Overexpression of miR-1271 promoted proliferation and invasion of NSCLC cells. • miR-1271 inhibitor inhibited the proliferation and invasion of NSCLC cells. • miR-1271 targets 3′ UTR of HOXA5 in NSCLC cells. • miR-1271 negatively regulates HOXA5 in NSCLC cells.

  4. miR-1271 promotes non-small-cell lung cancer cell proliferation and invasion via targeting HOXA5

    International Nuclear Information System (INIS)

    MicroRNAs (miRNAs) are short, non-coding RNAs (∼22 nt) that play important roles in the pathogenesis of human diseases by negatively regulating numerous target genes at posttranscriptional level. However, the role of microRNAs in lung cancer, particularly non-small-cell lung cancer (NSCLC), has remained elusive. In this study, two microRNAs, miR-1271 and miR-628, and their predicted target genes were identified differentially expressed in NSCLC by analyzing the miRNA and mRNA expression data from NSCLC tissues and their matching normal controls. miR-1271 and its target gene HOXA5 were selected for further investigation. CCK-8 proliferation assay showed that the cell proliferation was promoted by miR-1271 in NSCLC cells, while miR-1271 inhibitor could significantly inhibited the proliferation of NSCLC cells. Interestingly, migration and invasion assay indicated that overexpression of miR-1271 could significantly promoted the migration and invasion of NSCLC cells, whereas miR-1271 inhibitor could inhibited both cell migration and invasion of NSCLC cells. Western blot showed that miR-1271 suppressed the protein level of HOXA5, and luciferase assays confirmed that miR-1271 directly bound to the 3'untranslated region of HOXA5. This study indicated indicate that miR-1271 regulates NSCLC cell proliferation and invasion, via the down-regulation of HOXA5. Thus, miR-1271 may represent a potential therapeutic target for NSCLC intervention. - Highlights: • Overexpression of miR-1271 promoted proliferation and invasion of NSCLC cells. • miR-1271 inhibitor inhibited the proliferation and invasion of NSCLC cells. • miR-1271 targets 3′ UTR of HOXA5 in NSCLC cells. • miR-1271 negatively regulates HOXA5 in NSCLC cells

  5. Clustering

    Directory of Open Access Journals (Sweden)

    Jinfei Liu

    2013-04-01

    Full Text Available DBSCAN is a well-known density-based clustering algorithm which offers advantages for finding clusters of arbitrary shapes compared to partitioning and hierarchical clustering methods. However, there are few papers studying the DBSCAN algorithm under the privacy preserving distributed data mining model, in which the data is distributed between two or more parties, and the parties cooperate to obtain the clustering results without revealing the data at the individual parties. In this paper, we address the problem of two-party privacy preserving DBSCAN clustering. We first propose two protocols for privacy preserving DBSCAN clustering over horizontally and vertically partitioned data respectively and then extend them to arbitrarily partitioned data. We also provide performance analysis and privacy proof of our solution..

  6. Understanding the molecular mechanisms of human microtia via a pig model of HOXA1 syndrome

    Directory of Open Access Journals (Sweden)

    Ruimin Qiao

    2015-06-01

    Full Text Available Microtia is a congenital malformation of the outer ears. Although both genetic and environmental components have been implicated in microtia, the genetic causes of this innate disorder are poorly understood. Pigs have naturally occurring diseases comparable to those in humans, providing exceptional opportunity to dissect the molecular mechanism of human inherited diseases. Here we first demonstrated that a truncating mutation in HOXA1 causes a monogenic disorder of microtia in pigs. We further performed RNA sequencing (RNA-Seq analysis on affected and healthy pig embryos (day 14.25. We identified a list of 337 differentially expressed genes (DEGs between the normal and mutant samples, shedding light on the transcriptional network involving HOXA1. The DEGs are enriched in biological processes related to cardiovascular system and embryonic development, and neurological, renal and urological diseases. Aberrant expressions of many DEGs have been implicated in human innate deformities corresponding to microtia-associated syndromes. After applying three prioritizing algorithms, we highlighted appealing candidate genes for human microtia from the 337 DEGs. We searched for coding variants of functional significance within six candidate genes in 147 microtia-affected individuals. Of note, we identified one EVC2 non-synonymous mutation (p.Asp1174Asn as a potential disease-implicating variant for a human microtia-associated syndrome. The findings advance our understanding of the molecular mechanisms underlying human microtia, and provide an interesting example of the characterization of human disease-predisposing variants using pig models.

  7. Similarity between Spatial-temporal Expression Patterning of HOXA11 and Progesterone Receptor in Human Endometrium

    Institute of Scientific and Technical Information of China (English)

    Li-fen WANG; Hong-zhi LUO; Zheng-mei ZHU; Jie-dong WANG

    2003-01-01

    Objective To study HOXAll expression and its correlation with that of the progesterone receptor(PR) gene in human endometriumMethods In situ hybridization and semi-quantitative RT-PCR were used.Results HOXA l l mRNA was detected in both stromal and glandular cells of normal endometrium bv in situ hybridization. But the expression levels in the glandular cells had a dramatic decline or even disappearance at mid-secretory stage.Semi-quantitative RT-PCR analysis, however, demonstrated that the total expression levels of HOXAll mRNA were markedly increased in the mid-secretory endometrium, which suggested that there was an increased expression in stromal cells. Similar results were obtained for PR gene expression in human endometrium by in situ hybridization and semi-quantitative RT-PCR analysis.Conclusion HOXAll gene spatial and temporal expression patterns were similar to that of PR gene in endometrium across menstrual cycle, and HOXA l l was closely related to the endometrial proltferation and differentiation during menstrual cycle, especially the establishment of receptive status in implantation.

  8. Enforced Expression of Hoxa3 Inhibits Classical and Promotes Alternative Activation of Macrophages In Vitro and In Vivo

    Science.gov (United States)

    Al Sadoun, Hadeel; Burgess, Matthew; Hentges, Kathryn E.

    2016-01-01

    The regulated differentiation of macrophages (mφs) and their subsequent activation into proinflammatory or prohealing subtypes is critical for efficient wound healing. Chronic wounds such as diabetic (db) ulcers are associated with dysregulation of macrophage function. Whereas non-db mφs polarize to an M2-like, prohealing phenotype during the late stages of healing, db-derived mφs continue to display an M1-like, proinflammatory, or a mixed M1-like/M2-like phenotype. We have previously shown that sustained expression of Hoxa3 reduces the excessive number of leukocytes within the db wound; however, the effect of Hoxa3 on mφ polarization was unknown. In this study, we show that Hoxa3 protein transduction of mφs in vitro enhances macrophage maturation, inhibits M1 polarization, and promotes M2 polarization, in part via regulation of Pu.1/Spi1 and Stat6. Sustained expression of Hoxa3 in vivo in db wounds reduces the number of Nos2+ (M1-like) mφs, increases the number of Arg1+ and VEGF+ (M2-like) mφs, and accelerates healing in a DNA-binding independent manner. Our findings suggest a role for Hox protein activity in promoting M1-to-M2-like phenotypic switching via interactions with myeloid transcription factors and provide insight into mechanisms regulating this process in db wound healing. PMID:27342843

  9. Temporal dynamics of demersal chondrichthyan species in the central western Mediterranean

    Directory of Open Access Journals (Sweden)

    Antonello Mulas

    2015-11-01

    Full Text Available The rapid expansion of fisheries and globalized trade are emerging as the principal drivers of coastal and ocean threat. Considering the important role of Chondrichthyes as predators at the top of food chain in marine ecosystems, knowledge on their biology remains scarce in the Mediterranean. In this regard, our objective is to give information on their spatial distribution, abundance and population structure. Data were collected for 25 demersal species, including batoid species, sharks and holocephalans from 1994 to 2013 during scientific bottom trawl surveys (MEDITS project carried out around the Sardinian seas. The total frequency of occurrence (f%, the Biomass Index (BI, kg/km2, and the Density Index (DI, N/km2 were estimated for the continental shelf (10-200 m, slope (200-800 m, and overall (10-800 m depth strata. Size trends were also calculated for the most abundant species considering all depth strata. The correlation among MEDITS figures (f%, BI, DI, size structure and years were assessed by species computing the Pearson linear coefficient. From f% and abundance indexes investigation, only the small spotted catshark Scyliorhinus canicula and the thornback ray Raja clavata were ubiquitous in all strata investigated, instead, all the other species showed a preferential distribution for the shelf or the slope. In general, the temporal trends of BI and DI were stable or positive for both macro-strata, except for the longnose spurdog Squalus blainville which seemed to show a statistically significant decreasing trend. All analyzed species displayed temporal stable trends in size structure analysis, apart from Raja brachyura and Dipturus oxyrinchus that showed a statistically significant increase. Despite the time series analysis revealed stable or positive trends, it appears clear the need of urgent management measures to protect the demersal chondrichthyan species extending the monitoring over time and implementing the data collected by

  10. MicroRNA-196a promotes non-small cell lung cancer cell proliferation and invasion through targeting HOXA5

    International Nuclear Information System (INIS)

    MicroRNAs (miRNAs) are short, non-coding RNAs (~22 nt) that play important roles in the pathogenesis of human diseases by negatively regulating gene expression. Although miR-196a has been implicated in several other cancers, its role in non-small cell lung cancer (NSCLC) is unknown. The aim of the present study was to examine the expression pattern of miR-196a in NSCLC and its clinical significance, as well as its biological role in tumor progression. Expression of miR-196a was analyzed in 34 NSCLC tissues and five NSCLC cell lines by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The effect of DNA methylation on miR-196a expression was investigated by 5-aza-2-deoxy-cytidine treatment and bisulfite sequencing. The effect of miR-196a on proliferation was evaluated by MTT and colony formation assays, and cell migration and invasion were evaluated by transwell assays. Analysis of target protein expression was determined by western blotting. Luciferase reporter plasmids were constructed to confirm the action of miR-196a on downstream target genes, including HOXA5. Differences between the results were tested for significance using Student’s t-test (two-tailed). miR-196a was highly expressed both in NSCLC samples and cell lines compared with their corresponding normal counterparts, and the expression of miR-196a may be affected by DNA demethylation. Higher expression of miR-196a in NSCLC tissues was associated with a higher clinical stage, and also correlated with NSCLC lymph-node metastasis. In vitro functional assays demonstrated that modulation of miR-196a expression affected NSCLC cell proliferation, migration and invasion. Our analysis showed that miR-196a suppressed the expression of HOXA5 both at the mRNA and protein levels, and luciferase assays confirmed that miR-196a directly bound to the 3’untranslated region of HOXA5. Knockdown of HOXA5 expression in A549 cells using RNAi was shown to promote NSCLC cell proliferation, migration

  11. Effect of methoxychlor on implantation in mice exposed to HOXA-10 gene expression%甲氧滴滴涕染毒对小鼠着床期HOXA-10基因表达的影响

    Institute of Scientific and Technical Information of China (English)

    翟青枝; 张建芳; 马佳佳; 马向东; 王德堂; 陈必良

    2009-01-01

    目的:观察甲氧滴滴涕慢性染毒对雌鼠HOXA-10基因表达的影响.方法:使用5 wk龄雌性昆明小鼠作为实验动物,按体质量随机分为4组,每组10只,经2 wk适应性饲养后腹腔注射染毒,染毒剂量分别为0(对照)、16(低剂量)、32(中剂量)、64(高剂量)mg/(kg·d),对照组给予等剂量芝麻油,连续15 d后合笼,继续给药4 d,于孕5 d处死.结果:①染毒后小鼠一般情况未见明显异常;②免疫荧光显示:对照组荧光明显亮于染毒组;③实时荧光PCR测得的HOXA-10 mRNA表达:与对照组比较,中、高剂量组均显著降低HOXA-10mRNA的表达水平(P<0.05).结论:MXC染毒可降低孕鼠子宫组织中HOXA-10基因的表达从而影响胚胎着床.

  12. Long none coding RNA HOTTIP/HOXA13 act as synergistic role by decreasing cell migration and proliferation in Hirschsprung disease

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Hua; Zhu, Dongmei; Xu, Cao; Zhu, Hairong; Chen, Pingfa; Li, Hongxing [Department of Pediatric Surgery, State Key Laboratory of Reproductive Medicine, Nanjing Children' s Hospital Affiliated Nanjing Medical University, Nanjing 210008 (China); Key Laboratory of Modern Toxicology (Nanjing Medical University), Institute of Toxicology, School of Public Health, Nanjing Medical University, Ministry of Education, Nanjing 211166 (China); Liu, Xiang [Department of Pediatric Surgery, Anhui Provincial Children' s Hospital, Anhui 230000 (China); Xia, Yankai [Department of Pediatric Surgery, State Key Laboratory of Reproductive Medicine, Nanjing Children' s Hospital Affiliated Nanjing Medical University, Nanjing 210008 (China); Key Laboratory of Modern Toxicology (Nanjing Medical University), Institute of Toxicology, School of Public Health, Nanjing Medical University, Ministry of Education, Nanjing 211166 (China); Tang, Weibing, E-mail: twbcn@njmu.com [Department of Pediatric Surgery, State Key Laboratory of Reproductive Medicine, Nanjing Children' s Hospital Affiliated Nanjing Medical University, Nanjing 210008 (China); Key Laboratory of Modern Toxicology (Nanjing Medical University), Institute of Toxicology, School of Public Health, Nanjing Medical University, Ministry of Education, Nanjing 211166 (China)

    2015-08-07

    Long noncoding RNAs (lncRNAs) have been confirmed to be associated with various human diseases. However, whether they are associated with Hirschsprung disease (HSCR) progression remains unclear. In this study, we designed the experiment to explore the relationship between lncRNA HOTTIP and HOXA13, and their pathogenicity to HSCR. Quantitative real-time PCR and Western blot were performed to detect the levels of lncRNA, mRNAs, and proteins in colon tissues from 79 patients with HSCR and 79 controls. Small RNA interference transfection was used to study the function experiments in human 293T and SK-N-BE cell lines. The cell viability and activities were detected by the transwell assays, CCK8 assay, and flow cytometry, respectively. LncRNA HOTTIP and HOXA13 were significantly down-regulated in HSCR compared to the controls. Meanwhile, the declined extent of their expression levels makes sense between two main phenotype of HSCR. SiRNA-mediated knock-down of HOTTIP or HOXA13 correlated with decreased levels of each other and both reduced the cell migration and proliferation without affecting cell apoptosis or cell cycle. Our study demonstrates that aberrant reduction of HOTTIP and HOXA13, which have a bidirectional regulatory loop, may play an important role in the pathogenesis of HSCR. - Highlights: • LncRNA HOTTIP and HOXA13 are both down-regulated in HSCR. • HOTTIP and HOXA13 can regulate each other in 293T and SK-N-BE(2) cell lines. • Both HOTTIP and HOXA13 can decrease cell migration and proliferation.

  13. Distinct roles of Hoxa2 and Krox20 in the development of rhythmic neural networks controlling inspiratory depth, respiratory frequency, and jaw opening

    Directory of Open Access Journals (Sweden)

    Taillebourg Emmanuel

    2007-09-01

    Full Text Available Abstract Background Little is known about the involvement of molecular determinants of segmental patterning of rhombomeres (r in the development of rhythmic neural networks in the mouse hindbrain. Here, we compare the phenotypes of mice carrying targeted inactivations of Hoxa2, the only Hox gene expressed up to r2, and of Krox20, expressed in r3 and r5. We investigated the impact of such mutations on the neural circuits controlling jaw opening and breathing in newborn mice, compatible with Hoxa2-dependent trigeminal defects and direct regulation of Hoxa2 by Krox20 in r3. Results We found that Hoxa2 mutants displayed an impaired oro-buccal reflex, similarly to Krox20 mutants. In contrast, while Krox20 is required for the development of the rhythm-promoting parafacial respiratory group (pFRG modulating respiratory frequency, Hoxa2 inactivation did not affect neonatal breathing frequency. Instead, we found that Hoxa2-/- but not Krox20-/- mutation leads to the elimination of a transient control of the inspiratory amplitude normally occurring during the first hours following birth. Tracing of r2-specific progenies of Hoxa2 expressing cells indicated that the control of inspiratory activity resides in rostral pontine areas and required an intact r2-derived territory. Conclusion Thus, inspiratory shaping and respiratory frequency are under the control of distinct Hox-dependent segmental cues in the mammalian brain. Moreover, these data point to the importance of rhombomere-specific genetic control in the development of modular neural networks in the mammalian hindbrain.

  14. Long none coding RNA HOTTIP/HOXA13 act as synergistic role by decreasing cell migration and proliferation in Hirschsprung disease

    International Nuclear Information System (INIS)

    Long noncoding RNAs (lncRNAs) have been confirmed to be associated with various human diseases. However, whether they are associated with Hirschsprung disease (HSCR) progression remains unclear. In this study, we designed the experiment to explore the relationship between lncRNA HOTTIP and HOXA13, and their pathogenicity to HSCR. Quantitative real-time PCR and Western blot were performed to detect the levels of lncRNA, mRNAs, and proteins in colon tissues from 79 patients with HSCR and 79 controls. Small RNA interference transfection was used to study the function experiments in human 293T and SK-N-BE cell lines. The cell viability and activities were detected by the transwell assays, CCK8 assay, and flow cytometry, respectively. LncRNA HOTTIP and HOXA13 were significantly down-regulated in HSCR compared to the controls. Meanwhile, the declined extent of their expression levels makes sense between two main phenotype of HSCR. SiRNA-mediated knock-down of HOTTIP or HOXA13 correlated with decreased levels of each other and both reduced the cell migration and proliferation without affecting cell apoptosis or cell cycle. Our study demonstrates that aberrant reduction of HOTTIP and HOXA13, which have a bidirectional regulatory loop, may play an important role in the pathogenesis of HSCR. - Highlights: • LncRNA HOTTIP and HOXA13 are both down-regulated in HSCR. • HOTTIP and HOXA13 can regulate each other in 293T and SK-N-BE(2) cell lines. • Both HOTTIP and HOXA13 can decrease cell migration and proliferation

  15. SkateBase, an elasmobranch genome project and collection of molecular resources for chondrichthyan fishes [v1; ref status: indexed, http://f1000r.es/445

    Directory of Open Access Journals (Sweden)

    Jennifer Wyffels

    2014-08-01

    Full Text Available Chondrichthyan fishes are a diverse class of gnathostomes that provide a valuable perspective on fundamental characteristics shared by all jawed and limbed vertebrates. Studies of phylogeny, species diversity, population structure, conservation, and physiology are accelerated by genomic, transcriptomic and protein sequence data. These data are widely available for many sarcopterygii (coelacanth, lungfish and tetrapods and actinoptergii (ray-finned fish including teleosts taxa, but limited for chondrichthyan fishes.  In this study, we summarize available data for chondrichthyes and describe resources for one of the largest projects to characterize one of these fish, Leucoraja erinacea, the little skate.  SkateBase (http://skatebase.org serves as the skate genome project portal linking data, research tools, and teaching resources.

  16. NID2 and HOXA9 promoter hypermethylation as biomarkers for prevention and early detection in Oral Cavity Squamous Cell Carcinoma tissues and saliva

    Science.gov (United States)

    Guerrero-Preston, R; Soudry, E; Acero, J; Orera, M; Moreno-López, L; Macía-Colón, Germán; Jaffe, A; Berdasco, M; Ili-Gangas, C; Brebi-Mieville, P; Fu, Y; Engstrom, C; Irizarry, R; Esteller, M; Westra, W; Koch, W; Califano, J; Sidransky, D

    2011-01-01

    Differentially methylated oral squamous cell carcinoma (OSCC) biomarkers, identified in-vitro and validated in well-characterized surgical specimens, have shown poor clinical correlation in cohorts with different risk profiles. To overcome this lack of relevance we used the HumanMethylation27 BeadChip, publicly available methylation and expression array data, and Quantitative Methylation Specific PCR to uncover differential methylation in OSCC clinical samples with heterogeneous risk profiles. A two stage-design consisting of Discovery and Prevalence screens was used to identify differential promoter methylation and deregulated pathways in patients diagnosed with OSCC and head and neck squamous cell carcinoma. Promoter methylation of KIF1A (κ = 0.64), HOXA9 (κ = 0.60), NID2 (κ = 0.60), and EDNRB (κ = 0.60) had a moderate to substantial agreement with clinical diagnosis in the Discovery screen. HOXA9 had 68% sensitivity, 100% specificity and a 0.81 AUC. NID2 had 71% sensitivity, 100% specificity and a 0.79 AUC. In the Prevalence screen HOXA9 (κ = 0.82) and NID2 (κ = 0.80) had an almost perfect agreement with histologic diagnosis. HOXA9 had 85% sensitivity, 97% specificity and a 0.95 AUC. NID2 had 87% sensitivity, 95% specificity and a 0.91 AUC. A HOXA9 and NID2 gene panel had 94% sensitivity, 97% specificity and a 0.97 AUC. In saliva from OSCC cases and controls HOXA9 had 75% sensitivity, 53% specificity and a 0.75 AUC. NID2 had 87% sensitivity, 21% specificity and a 0.73 AUC. This Phase I Biomarker Development Trial identified a panel of differentially methylated genes in normal and OSCC clinical samples from patients with heterogeneous risk profiles. This panel may be useful for early detection and cancer prevention studies. PMID:21558411

  17. Chondrichthyans of the San Matías Gulf, Patagonia, Argentina Los condrictios del Golfo San Matías, Patagonia, Argentina

    Directory of Open Access Journals (Sweden)

    María R PERIER

    2011-12-01

    Full Text Available The San Matías Gulf (SMG; 41°- 42° S; 64°- 65° W is the largest gulf in Northern Patagonia, Argentina. Up to date, the chondrichthyan fauna of this area has not been reported. Therefore, the aim of this work is to provide a list with species presence and biological characteristics of the chondrichthyans recorded in SMG during the last 30 years. A total of 13 sharks distributed in 11 families, 19 skates and rays distributed in six families, and one holocephalan have been so far recorded in SMG. From the zoogeographical point of view, this chondrichthyan fauna is a mixed assemblage of species typically found in the Argentinean and Magellanean Provinces. The holocephalan Callorhinchus callorynchus is the most landed chondricthyan of the local fishery. With it, five sharks and seven skates are also exploited.El Golfo San Matías (SMG; 41°- 42° S - 64°-65° O se encuentra ubicado en el norte de la Patagonia, Argentina. Hasta la fecha no se cuentan con reportes de la fauna de condrictios de esta zona. Por lo tanto, el objetivo de este trabajo es proporcionar una lista de la presencia y las características biológicas de los condrictios registrados en el SMG durante los últimos 30 años. Un total de 13 tiburones distribuidos en 11 familias, 19 batoideos distribuidos en seis familias y un holocefalo han sido reportados para la zona. Desde el punto de vista zoogeográfico, el SMG presenta un ensamble de especies pertenecientes a las Provincias Magallánica y Argentina. El holocefalo Callorhinchus callorynchus es el condrictio más desembarcado de la pesquería local. Con menor importancia son explotadas comercialmente, cinco especies de tiburones y siete de rayas.

  18. The discovery of Foxl2 paralogs in chondrichthyan, coelacanth and tetrapod genomes reveals an ancient duplication in vertebrates.

    Science.gov (United States)

    Geraldo, M T; Valente, G T; Braz, A S K; Martins, C

    2013-07-01

    The Foxl2 (forkhead box L2) gene is an important member of the forkhead domain family, primarily responsible for the development of ovaries during female sex differentiation. The evolutionary studies conducted previously considered the presence of paralog Foxl2 copies only in teleosts. However, to search for possible paralog copies in other groups of vertebrates and ensure that all predicted copies were homolog to the Foxl2 gene, a broad evolutionary analysis was performed, based on the forkhead domain family. A total of 2464 sequences for the forkhead domain were recovered, and subsequently, 64 representative sequences for Foxl2 were used in the evolutionary analysis of this gene. The most important contribution of this study was the discovery of a new subgroup of Foxl2 copies (ortholog to Foxl2B) present in the chondrichthyan Callorhinchus milii, in the coelacanth Latimeria chalumnae, in the avian Taeniopygia guttata and in the marsupial Monodelphis domestica. This new scenario indicates a gene duplication event in an ancestor of gnathostomes. Furthermore, based on the analysis of the syntenic regions of both Foxl2 copies, the duplication event was not exclusive to Foxl2. Moreover, the duplicated copy distribution was shown to be complex across vertebrates, especially in tetrapods, and the results strongly support a loss of this copy in eutherian species. Finally, the scenario observed in this study suggests an update for Foxl2 gene nomenclature, extending the actual suggested teleost naming of Foxl2A and Foxl2B to all vertebrate sequences and contributing to the establishment of a new evolutionary context for the Foxl2 gene.

  19. Stable isotope study of a new chondrichthyan fauna (Kimmeridgian, Porrentruy, Swiss Jura): an unusual freshwater-influenced isotopic composition for the hybodont shark Asteracanthus

    Science.gov (United States)

    Leuzinger, L.; Kocsis, L.; Billon-Bruyat, J.-P.; Spezzaferri, S.; Vennemann, T.

    2015-12-01

    Chondrichthyan teeth (sharks, rays, and chimaeras) are mineralized in isotopic equilibrium with the surrounding water, and parameters such as water temperature and salinity can be inferred from the oxygen isotopic composition (δ18Op) of their bioapatite. We analysed a new chondrichthyan assemblage, as well as teeth from bony fish (Pycnodontiformes). All specimens are from Kimmeridgian coastal marine deposits of the Swiss Jura (vicinity of Porrentruy, Ajoie district, NW Switzerland). While the overall faunal composition and the isotopic composition of bony fish are generally consistent with marine conditions, unusually low δ18Op values were measured for the hybodont shark Asteracanthus. These values are also lower compared to previously published data from older European Jurassic localities. Additional analyses on material from Solothurn (Kimmeridgian, NW Switzerland) also have comparable, low-18O isotopic compositions for Asteracanthus. The data are hence interpreted to represent a so far unique, freshwater-influenced isotopic composition for this shark that is classically considered a marine genus. While reproduction in freshwater or brackish realms is established for other hybodonts, a similar behaviour for Asteracanthus is proposed here. Regular excursions into lower salinity waters can be linked to the age of the deposits and correspond to an ecological adaptation, most likely driven by the Kimmeridgian transgression and by the competition of the hybodont shark Asteracanthus with the rapidly diversifying neoselachians (modern sharks).

  20. Stable isotope study of a new chondrichthyan fauna (Kimmeridgian, Porrentruy, Swiss Jura: an unusual freshwater-influenced isotopic composition for the hybodont shark Asteracanthus

    Directory of Open Access Journals (Sweden)

    L. Leuzinger

    2015-08-01

    Full Text Available Chondrichthyan teeth (sharks, rays and chimaeras are mineralised in isotopic equilibrium with the surrounding water, and parameters such as water temperature and salinity can be inferred from the oxygen isotopic composition (δ18Op of their bioapatite. We analysed a new chondrichthyan assemblage, as well as teeth from bony fish (Pycnodontiformes. All specimens are from Kimmeridgian coastal marine deposits of the Swiss Jura (vicinity of Porrentruy, Ajoie district, NW Switzerland. While the overall faunal composition and the isotopic composition of bony fish are consistent with marine conditions, unusually low δ18Op values were measured for the hybodont shark Asteracanthus. These values are also lower compared to previously published data from older European Jurassic localities. Additional analyses on material from Solothurn (Kimmeridgian, NW Switzerland also have comparable, low-18O isotopic compositions for Asteracanthus. The data are hence interpreted to represent a so far unique, freshwater-influenced isotopic composition for this shark that is classically considered as a marine genus. While reproduction in freshwater or brackish realms is established for other hybodonts, a similar behaviour for Asteracanthus is proposed here. Regular excursions into lower salinity waters can be linked to the age of the deposits and correspond to an ecological adaptation, most likely driven by the Kimmeridgian transgression and by the competition of the primitive shark Asteracanthus with the rapidly diversifying neoselachians (modern sharks.

  1. Low expression of miR-196b enhances the expression of BCR-ABL1 and HOXA9 oncogenes in chronic myeloid leukemogenesis.

    Directory of Open Access Journals (Sweden)

    Yue Liu

    Full Text Available MicroRNAs (miRNAs can function as tumor suppressors or oncogene promoters during tumor development. In this study, low levels of expression of miR-196b were detected in patients with chronic myeloid leukemia. Bisulfite genomic sequencing PCR and methylation-specific PCR were used to examine the methylation status of the CpG islands in the miR-196b promoter in K562 cells, patients with leukemia and healthy individuals. The CpG islands showed more methylation in patients with chronic myeloid leukemia compared with healthy individuals (P<0.05, which indicated that low expression of miR-196b may be associated with an increase in the methylation of CpG islands. The dual-luciferase reporter assay system demonstrated that BCR-ABL1 and HOXA9 are the target genes of miR-196b, which was consistent with predictions from bioinformatics software analyses. Further examination of cell function indicated that miR-196b acts to reduce BCR-ABL1 and HOXA9 protein levels, decrease cell proliferation rate and retard the cell cycle. A low level of expression of miR-196b can cause up-regulation of BCR-ABL1 and HOXA9 expression, which leads to the development of chronic myeloid leukemia. MiR-196b may represent an effective target for chronic myeloid leukemia therapy.

  2. DNA methylation profiling of ovarian carcinomas and their in vitro models identifies HOXA9, HOXB5, SCGB3A1, and CRABP1 as novel targets

    Directory of Open Access Journals (Sweden)

    Tropé Claes G

    2007-07-01

    Full Text Available Abstract Background The epigenetics of ovarian carcinogenesis remains poorly described. We have in the present study investigated the promoter methylation status of 13 genes in primary ovarian carcinomas (n = 52 and their in vitro models (n = 4; ES-2, OV-90, OVCAR-3, and SKOV-3 by methylation-specific polymerase chain reaction (MSP. Direct bisulphite sequencing analysis was used to confirm the methylation status of individual genes. The MSP results were compared with clinico- pathological features. Results Eight out of the 13 genes were hypermethylated among the ovarian carcinomas, and altogether 40 of 52 tumours were methylated in one or more genes. Promoter hypermethylation of HOXA9, RASSF1A, APC, CDH13, HOXB5, SCGB3A1 (HIN-1, CRABP1, and MLH1 was found in 51% (26/51, 49% (23/47, 24% (12/51, 20% (10/51, 12% (6/52, 10% (5/52, 4% (2/48, and 2% (1/51 of the carcinomas, respectively, whereas ADAMTS1, MGMT, NR3C1, p14ARF, and p16INK4a were unmethylated in all samples. The methylation frequencies of HOXA9 and SCGB3A1 were higher among relatively early-stage carcinomas (FIGO I-II than among carcinomas of later stages (FIGO III-IV; P = 0.002, P = 0.020, respectively. The majority of the early-stage carcinomas were of the endometrioid histotype. Additionally, HOXA9 hypermethylation was more common in tumours from patients older than 60 years of age (15/21 than among those of younger age (11/30; P = 0.023. Finally, there was a significant difference in HOXA9 methylation frequency among the histological types (P = 0.007. Conclusion DNA hypermethylation of tumour suppressor genes seems to play an important role in ovarian carcinogenesis and HOXA9, HOXB5, SCGB3A1, and CRABP1 are identified as novel hypermethylated target genes in this tumour type.

  3. GnRH-a控制性超促排卵(COH)对小鼠着床期Hoxa-10基因表达的影响%Effect of GnRH-a Controlled Ovarian Hyperstimulation (COH) on Homeobox a10 (Hoxa-10) Gene Expression in Mouse Peri-implantation

    Institute of Scientific and Technical Information of China (English)

    付正英; 卢建荣; 苏晓华

    2012-01-01

    Objective: To research the impact of long GnRH-a protocol controlled ovarian hyperstimulation (COH) on mouse pregnancy rate, embryo nidation rate, mRNA and protein expression of Hoxa-10 in peri-implantation, and to discuss the possible mechanisms of COH influencing on embryo nidation. Methods: Mice were randomly divided into treatment group (GnRH-a +hMG+hCG) and control group (9 g/L, NaCl), female and male mice were copulated, the situation of vaginal plug, pregnancy and embryo nidation were observed. RT-PCR, Real-time PCR were used to detect the concentration of Hoxa-l0mRNA and immunohistochemical method was used to detect the concentration of HOXA-10 protein expression in the uterine tissue in peri-implantation. Results: The vaginal plug rate and pregnancy rate in treatment group were significantiy lower than those in the control (p<0.01), the number of the embryo nidation was larger in treatment group than that in the control (P<0.01), but the implantation rate of embyro was significantly lower in in treatment group than that in the control (p<0.05). Both PCR and immunohistochemical method showed that the expressions of HOXA10 mRNA and protein in treatment group were significantly lower than those in the control. Conclusion: The GnRH-a COH can decrease the expression of Hoxa-10, it disturbs the endometrial receptivity and window phase of normal uterus, thus lower the rate of pregnancy and embryo nidation.%目的:研究GnRH-a长方案控制性超促排卵(COH)对小鼠妊娠率、胚胎着床率及着床期HOXA-10基因表达的影响,探讨COH影响胚胎着床的机制.方法:实验动物随机分为实验组(GnRH-a +hMG+hCG)和对照组(生理盐水),雌、雄合笼后观察小鼠阴栓率,于着床期取小鼠子宫,观察妊娠率及胚胎着床数,计算着床率;应用RT-PCR、Real-time PCR方法及免疫组织化学法分别检测小鼠着床期子宫内膜Hoxa-10 mRNA及蛋白的表达.结果:实验组小鼠阴栓率及妊娠

  4. 产前应用维生素A对先天性膈疝大鼠模型胎肺晚期发育及Hoxa5表达的影响%Effects of prenatal administration of vitamin A on late fetal lung development and expression of Hoxa5 in experimental congenital diaphragmatic hernia

    Institute of Scientific and Technical Information of China (English)

    何秋明; 肖尚杰; 刘芬; 朱士博; 田松; 钟微; 夏慧敏

    2015-01-01

    目的 产前应用维生素A(VitA)对除草醚(Nitrofen)诱导的先天性膈疝(congenital diaphragmatic hernia,CDH)大鼠模型中胎肺晚期发育及胎肺中Hoxa5表达的影响,探讨VitA改善CDH肺发育不良的可能作用机制.方法 12只孕鼠按随机数字表法随机分为Nitrofen诱导CDH肺发育不良组(CDH组),于大鼠孕第9.5天经胃管注入溶于1 ml橄榄油的Nitrofen 100 mg/只;对照组,于孕第9.5天仅注入橄榄油1 ml/只;维生素A产前干预组(CDH+ VitA组),于孕第9.5天注入Ni-trofen 100 mg/只后,再于孕第10.5天经胃管注入VitA 15 000 IU/只.各组均于孕21.5天行剖腹产,取胎肺样本;组织学检查方法分析各组胎肺的发育情况,实时荧光定量PCR(QPCR)、免疫蛋白印迹(Western blot,WB)方法检测各组胎肺中Hoxa5表达水平的变化.结果 CDH组膈疝发生率为50.0% (24/48),CDH+ VitA组膈疝发生率明显下降为28.3% (13/46),差异有统计学意义(P<0.05).组织学分析结果显示,CDH组、对照组、CDH+ VitA组的平均肺泡面积分别为(332.83±72.19)μm2、(1 443.37±285.94) μm2和(907.07±54.78) μm2,平均肺泡间隔厚度分别为(9.72±2.18)μm、(6.17±1.54) μm和(7.26±1.52) μm,肺血管数/HP分别为(3.68±1.03)个、(7.20±0.91)个和(6.24±0.88)个,管腔面积占血管总面积比分别(15.76±4.87)%、(38.74±4.94)%和(30.18±7.03)%.与CDH组比较,CDH+ VitA组胎肺的平均肺泡面积增大、平均肺泡间隔厚度减小、肺血管数/HP增加、管腔增大,且差异均有统计学意义(均P<0.05),肺发育不良明显改善.以对照组胎肺样本作为参照,CDH组、CDH+ VitA组的Hoxa5 mRNA相对表达量分别为1.76±0.23、0.92±0.16;Hoxa5蛋白相对表达量分别为2.95±0.12、1.36±0.07.CDH+ VitA组胎肺的Hoxa5表达水平较CDH组明显降低,差异有统计学意义(P<0.05).结论 产前应用VitA可明显改善CDH模型胎肺发育不良,并下调胎肺中Hoxa5的表达水平,推测调控Hoxa5的表达可

  5. Evolutionary conservation of regulatory elements in vertebrate HOX gene clusters

    Energy Technology Data Exchange (ETDEWEB)

    Santini, Simona; Boore, Jeffrey L.; Meyer, Axel

    2003-12-31

    Due to their high degree of conservation, comparisons of DNA sequences among evolutionarily distantly-related genomes permit to identify functional regions in noncoding DNA. Hox genes are optimal candidate sequences for comparative genome analyses, because they are extremely conserved in vertebrates and occur in clusters. We aligned (Pipmaker) the nucleotide sequences of HoxA clusters of tilapia, pufferfish, striped bass, zebrafish, horn shark, human and mouse (over 500 million years of evolutionary distance). We identified several highly conserved intergenic sequences, likely to be important in gene regulation. Only a few of these putative regulatory elements have been previously described as being involved in the regulation of Hox genes, while several others are new elements that might have regulatory functions. The majority of these newly identified putative regulatory elements contain short fragments that are almost completely conserved and are identical to known binding sites for regulatory proteins (Transfac). The conserved intergenic regions located between the most rostrally expressed genes in the developing embryo are longer and better retained through evolution. We document that presumed regulatory sequences are retained differentially in either A or A clusters resulting from a genome duplication in the fish lineage. This observation supports both the hypothesis that the conserved elements are involved in gene regulation and the Duplication-Deletion-Complementation model.

  6. Hox gene clusters in the Indonesian coelacanth, Latimeria menadoensis.

    Science.gov (United States)

    Koh, Esther G L; Lam, Kevin; Christoffels, Alan; Erdmann, Mark V; Brenner, Sydney; Venkatesh, Byrappa

    2003-02-01

    The Hox genes encode transcription factors that play a key role in specifying body plans of metazoans. They are organized into clusters that contain up to 13 paralogue group members. The complex morphology of vertebrates has been attributed to the duplication of Hox clusters during vertebrate evolution. In contrast to the single Hox cluster in the amphioxus (Branchiostoma floridae), an invertebrate-chordate, mammals have four clusters containing 39 Hox genes. Ray-finned fishes (Actinopterygii) such as zebrafish and fugu possess more than four Hox clusters. The coelacanth occupies a basal phylogenetic position among lobe-finned fishes (Sarcopterygii), which gave rise to the tetrapod lineage. The lobe fins of sarcopterygians are considered to be the evolutionary precursors of tetrapod limbs. Thus, the characterization of Hox genes in the coelacanth should provide insights into the origin of tetrapod limbs. We have cloned the complete second exon of 33 Hox genes from the Indonesian coelacanth, Latimeria menadoensis, by extensive PCR survey and genome walking. Phylogenetic analysis shows that 32 of these genes have orthologs in the four mammalian HOX clusters, including three genes (HoxA6, D1, and D8) that are absent in ray-finned fishes. The remaining coelacanth gene is an ortholog of hoxc1 found in zebrafish but absent in mammals. Our results suggest that coelacanths have four Hox clusters bearing a gene complement more similar to mammals than to ray-finned fishes, but with an additional gene, HoxC1, which has been lost during the evolution of mammals from lobe-finned fishes.

  7. New specimens and records of chondrichthyan fishes (Vertebrata: Chondrichthyes off the Mexican Pacific coast Nuevos ejemplares y nuevos registros de peces cartilaginosos (Vertebrata: Chondrichthyes de la costa del Pacífico mexicano

    Directory of Open Access Journals (Sweden)

    Gorgonio Ruiz-Campos

    2010-08-01

    Full Text Available New specimens and new records of occurrence for 10 species of chondrichthyan (elasmobranch and chimaeroid fishes previously unknown or little documented for the continental shelf of the Mexican Pacific are reported. This contribution provides the first record of Centroscyllium nigrum, Isurus paucus, and Bathyraja trachura for the Mexican Pacific, as well as new specimens of Hydrolagus colliei, Hexanchus griseus, Echinorhinus cookei, Pseudocarcharias kamoharai, and Raja velezi for the western coast of the Baja California Peninsula, including the intermediate record within the known distribution range for Apristurus kampae, and the southernmost record for Raja inornata.Se reportan nuevos ejemplares y nuevos registros de concurrencia para 10 especies de elasmobranquios previamente desconocidos o con muy poca documentación en aguas del Pacífico mexicano. Esta contribución ofrece el primer registro de Centroscyllium nigrum, Isurus paucus, y Bathyraja trachura en el Pacífico mexicano; así como nuevos ejemplares de Hydrolagus colliei, Hexanchus griseus, Echinorhinus cookei, Pseudocarcharias kamoharai y Raja velezi en la costa occidental de la península de Baja California, con la inclusión del registro intermedio en el ámbito de distribución conocida para Apristurus kampae, y el registro más meridional para Raja inornata.

  8. Weighted Clustering

    DEFF Research Database (Denmark)

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina;

    2012-01-01

    We investigate a natural generalization of the classical clustering problem, considering clustering tasks in which different instances may have different weights.We conduct the first extensive theoretical analysis on the influence of weighted data on standard clustering algorithms in both the...... partitional and hierarchical settings, characterizing the conditions under which algorithms react to weights. Extending a recent framework for clustering algorithm selection, we propose intuitive properties that would allow users to choose between clustering algorithms in the weighted setting and classify...

  9. Isotopic clusters

    International Nuclear Information System (INIS)

    Spectra of isotopically mixed clusters (dimers of SF6) are calculated as well as transition frequencies. The result leads to speculations about the suitability of the laser-cluster fragmentation process for isotope separation. (Auth.)

  10. Meaningful Clusters

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Data Clustering

    Science.gov (United States)

    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

  12. Cluster Chemistry

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Cansisting of eight scientists from the State Key Laboratory of Physical Chemistry of Solid Surfaces and Xiamen University, this creative research group is devoted to the research of cluster chemistry and creation of nanomaterials.After three-year hard work, the group scored a series of encouraging progresses in synthesis of clusters with special structures, including novel fullerenes, fullerene-like metal cluster compounds as well as other related nanomaterials, and their properties study.

  13. Fuzzy Clustering

    DEFF Research Database (Denmark)

    Berks, G.; Keyserlingk, Diedrich Graf von; Jantzen, Jan;

    2000-01-01

    -mean clustering is an easy and well improved tool, which has been applied in many medical fields. We used c-mean fuzzy clustering after feature extraction from an aphasia database. Factor analysis was applied on a correlation matrix of 26 symptoms of language disorders and led to five factors. The factors...

  14. Weighted Clustering

    CERN Document Server

    Ackerman, Margareta; Branzei, Simina; Loker, David

    2011-01-01

    In this paper we investigate clustering in the weighted setting, in which every data point is assigned a real valued weight. We conduct a theoretical analysis on the influence of weighted data on standard clustering algorithms in each of the partitional and hierarchical settings, characterising the precise conditions under which such algorithms react to weights, and classifying clustering methods into three broad categories: weight-responsive, weight-considering, and weight-robust. Our analysis raises several interesting questions and can be directly mapped to the classical unweighted setting.

  15. Cluster analysis

    CERN Document Server

    Everitt, Brian S; Leese, Morven; Stahl, Daniel

    2011-01-01

    Cluster analysis comprises a range of methods for classifying multivariate data into subgroups. By organizing multivariate data into such subgroups, clustering can help reveal the characteristics of any structure or patterns present. These techniques have proven useful in a wide range of areas such as medicine, psychology, market research and bioinformatics.This fifth edition of the highly successful Cluster Analysis includes coverage of the latest developments in the field and a new chapter dealing with finite mixture models for structured data.Real life examples are used throughout to demons

  16. Cluster editing

    DEFF Research Database (Denmark)

    Böcker, S.; Baumbach, Jan

    2013-01-01

    The Cluster Editing problem asks to transform a graph into a disjoint union of cliques using a minimum number of edge modifications. Although the problem has been proven NP-complete several times, it has nevertheless attracted much research both from the theoretical and the applied side. The...... algorithms for biological problems. © 2013 Springer-Verlag....... problem has been the inspiration for numerous algorithms in bioinformatics, aiming at clustering entities such as genes, proteins, phenotypes, or patients. In this paper, we review exact and heuristic methods that have been proposed for the Cluster Editing problem, and also applications of these...

  17. Cluster headache

    Science.gov (United States)

    Doctors do not know exactly what causes cluster headaches. They seem to be related to the body's sudden release of histamine (chemical in the body released during an allergic response) or serotonin (chemical made by nerve cells). A problem in a small area at ...

  18. Regional Innovation Clusters

    Data.gov (United States)

    Small Business Administration — The Regional Innovation Clusters serve a diverse group of sectors and geographies. Three of the initial pilot clusters, termed Advanced Defense Technology clusters,...

  19. Cluster forcing

    DEFF Research Database (Denmark)

    Christensen, Thomas Budde

    The cluster theory attributed to Michael Porter has significantly influenced industrial policies in countries across Europe and North America since the beginning of the 1990s. Institutions such as the EU, OECD and the World Bank and governments in countries such as the UK, France, The Netherlands......, Portugal and New Zealand have adopted the concept. Public sector interventions that aim to support cluster development in industries most often focus upon economic policy goals such as enhanced employment and improved productivity, but rarely emphasise broader societal policy goals relating to e...... a difference in terms of enhancing regional development but the paper also concludes that the interventions tend to follow the development path of the established industry and thus tend to neglect long term sustainable development issues while failing to escape the traditional confines of regional industrial...

  20. Clustering experiments

    CERN Document Server

    Wang, Zhengwei; Tan, Ken; Di, Zengru; Roehner, Bertrand M

    2011-01-01

    It is well known that bees cluster together in cold weather, in the process of swarming (when the ``old'' queen leaves with part of the colony) or absconding (when the queen leaves with all the colony) and in defense against intruders such as wasps or hornets. In this paper we describe a fairly different clustering process which occurs at any temperature and independently of any special stimulus or circumstance. As a matter of fact, this process is about four times faster at 28 degree Celsius than at 15 degrees. Because of its simplicity and low level of ``noise'' we think that this phenomenon can provide a means for exploring the strength of inter-individual attraction between bees or other living organisms. For instance, and at first sight fairly surprisingly, our observations showed that this attraction does also exist between bees belonging to different colonies. As this study is aimed at providing a comparative perspective, we also describe a similar clustering experiment for red fire ants.

  1. Globular Cluster Formation in the Virgo Cluster

    CERN Document Server

    Moran, C Corbett; Lake, G

    2014-01-01

    Metal poor globular clusters (MPGCs) are a unique probe of the early universe, in particular the reionization era. Systems of globular clusters in galaxy clusters are particularly interesting as it is in the progenitors of galaxy clusters that the earliest reionizing sources first formed. Although the exact physical origin of globular clusters is still debated, it is generally admitted that globular clusters form in early, rare dark matter peaks (Moore et al. 2006; Boley et al. 2009). We provide a fully numerical analysis of the Virgo cluster globular cluster system by identifying the present day globular cluster system with exactly such early, rare dark matter peaks. A popular hypothesis is that that the observed truncation of blue metal poor globular cluster formation is due to reionization (Spitler et al. 2012; Boley et al. 2009; Brodie & Strader 2006); adopting this view, constraining the formation epoch of MPGCs provides a complementary constraint on the epoch of reionization. By analyzing both the l...

  2. Cluster Decline and Resilience

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark, 1963...... in new resources to the cluster but being quick to withdraw in times of crisis....

  3. Partitional clustering algorithms

    CERN Document Server

    2015-01-01

    This book summarizes the state-of-the-art in partitional clustering. Clustering, the unsupervised classification of patterns into groups, is one of the most important tasks in exploratory data analysis. Primary goals of clustering include gaining insight into, classifying, and compressing data. Clustering has a long and rich history that spans a variety of scientific disciplines including anthropology, biology, medicine, psychology, statistics, mathematics, engineering, and computer science. As a result, numerous clustering algorithms have been proposed since the early 1950s. Among these algorithms, partitional (nonhierarchical) ones have found many applications, especially in engineering and computer science. This book provides coverage of consensus clustering, constrained clustering, large scale and/or high dimensional clustering, cluster validity, cluster visualization, and applications of clustering. Examines clustering as it applies to large and/or high-dimensional data sets commonly encountered in reali...

  4. Modernization typologies industrial clusters

    Directory of Open Access Journals (Sweden)

    Karapetian, Eduard

    2011-11-01

    Full Text Available Generalized theoretical approach to the criteria of industrial clusters. On this basis, a detailed typology of industrial cluster structures, which takes into account the peculiarities of the functioning of clusters in the domestic economy.

  5. Factorial PD-Clustering

    CERN Document Server

    Tortora, Cristina; Summa, Mireille Gettler

    2011-01-01

    Factorial clustering methods have been developed in recent years thanks to the improving of computational power. These methods perform a linear transformation of data and a clustering on transformed data optimizing a common criterion. Factorial PD-clustering is based on Probabilistic Distance clustering (PD-clustering). PD-clustering is an iterative, distribution free, probabilistic, clustering method. Factorial PD-clustering make a linear transformation of original variables into a reduced number of orthogonal ones using a common criterion with PD-Clustering. It is demonstrated that Tucker 3 decomposition allows to obtain this transformation. Factorial PD-clustering makes alternatively a Tucker 3 decomposition and a PD-clustering on transformed data until convergence. This method could significantly improve the algorithm performance and allows to work with large dataset, to improve the stability and the robustness of the method.

  6. Possibilistic Exponential Fuzzy Clustering

    Institute of Scientific and Technical Information of China (English)

    Kiatichai Treerattanapitak; Chuleerat Jaruskulchai

    2013-01-01

    Generally,abnormal points (noise and outliers) cause cluster analysis to produce low accuracy especially in fuzzy clustering.These data not only stay in clusters but also deviate the centroids from their true positions.Traditional fuzzy clustering like Fuzzy C-Means (FCM) always assigns data to all clusters which is not reasonable in some circumstances.By reformulating objective function in exponential equation,the algorithm aggressively selects data into the clusters.However noisy data and outliers cannot be properly handled by clustering process therefore they are forced to be included in a cluster because of a general probabilistic constraint that the sum of the membership degrees across all clusters is one.In order to improve this weakness,possibilistic approach relaxes this condition to improve membership assignment.Nevertheless,possibilistic clustering algorithms generally suffer from coincident clusters because their membership equations ignore the distance to other clusters.Although there are some possibilistic clustering approaches that do not generate coincident clusters,most of them require the right combination of multiple parameters for the algorithms to work.In this paper,we theoretically study Possibilistic Exponential Fuzzy Clustering (PXFCM) that integrates possibilistic approach with exponential fuzzy clustering.PXFCM has only one parameter and not only partitions the data but also filters noisy data or detects them as outliers.The comprehensive experiments show that PXFCM produces high accuracy in both clustering results and outlier detection without generating coincident problems.

  7. Management of cluster headache

    DEFF Research Database (Denmark)

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-01-01

    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...

  8. Structures of Mn clusters

    Indian Academy of Sciences (India)

    Tina M Briere; Marcel H F Sluiter; Vijay Kumar; Yoshiyuki Kawazoe

    2003-01-01

    The geometries of several Mn clusters in the size range Mn13–Mn23 are studied via the generalized gradient approximation to density functional theory. For the 13- and 19-atom clusters, the icosahedral structures are found to be most stable, while for the 15-atom cluster, the bcc structure is more favoured. The clusters show ferrimagnetic spin configurations.

  9. Graded cluster algebras

    OpenAIRE

    Grabowski, Jan

    2015-01-01

    In the cluster algebra literature, the notion of a graded cluster algebra has been implicit since the origin of the subject. In this work, we wish to bring this aspect of cluster algebra theory to the foreground and promote its study. We transfer a definition of Gekhtman, Shapiro and Vainshtein to the algebraic setting, yielding the notion of a multi-graded cluster algebra. We then study gradings for finite type cluster algebras without coefficients, giving a full classification. Translating ...

  10. What Makes Clusters Decline?

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    2015-01-01

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark....... The longitudinal study on the high-tech cluster reveals that technological lock-in and exit of key firms have contributed to decline. Entrepreneurship has a positive effect on the cluster’s adaptive capabilities, while multinational companies have contradicting effects by bringing in new resources to the cluster...

  11. Star clusters and associations

    International Nuclear Information System (INIS)

    All 33 papers presented at the symposium were inputted to INIS. They dealt with open clusters, globular clusters, stellar associations and moving groups, and local kinematics and galactic structures. (E.S.)

  12. Quantum Annealing for Clustering

    OpenAIRE

    Kurihara, Kenichi; Tanaka, Shu; Miyashita, Seiji

    2014-01-01

    This paper studies quantum annealing (QA) for clustering, which can be seen as an extension of simulated annealing (SA). We derive a QA algorithm for clustering and propose an annealing schedule, which is crucial in practice. Experiments show the proposed QA algorithm finds better clustering assignments than SA. Furthermore, QA is as easy as SA to implement.

  13. Emergence of regional clusters

    DEFF Research Database (Denmark)

    Dahl, Michael S.; Østergaard, Christian Richter; Dalum, Bent

    2010-01-01

    approach to analyse how successful early firms can lead to formation of clusters. Three key determinants are identified: (1) the geographical dimension of entrepreneurial activity, (2) spinoffs from successful firms and (3) new market opportunities. The chapter studies in great detail the evolution...... of the wireless communications cluster in Northern Denmark and compare it with the evolution of other clusters....

  14. The Durban Auto Cluster

    DEFF Research Database (Denmark)

    Lorentzen, Jochen; Robbins, Glen; Barnes, Justin

    2004-01-01

    The paper describes the formation of the Durban Auto Cluster in the context of trade liberalization. It argues that the improvement of operational competitiveness of firms in the cluster is prominently due to joint action. It tests this proposition by comparing the gains from cluster activities i...

  15. Cluster Physics with Merging Galaxy Clusters

    Directory of Open Access Journals (Sweden)

    Sandor M. Molnar

    2016-02-01

    Full Text Available Collisions between galaxy clusters provide a unique opportunity to study matter in a parameter space which cannot be explored in our laboratories on Earth. In the standard LCDM model, where the total density is dominated by the cosmological constant ($Lambda$ and the matter density by cold dark matter (CDM, structure formation is hierarchical, and clusters grow mostly by merging.Mergers of two massive clusters are the most energetic events in the universe after the Big Bang,hence they provide a unique laboratory to study cluster physics.The two main mass components in clusters behave differently during collisions:the dark matter is nearly collisionless, responding only to gravity, while the gas is subject to pressure forces and dissipation, and shocks and turbulenceare developed during collisions. In the present contribution we review the different methods used to derive the physical properties of merging clusters. Different physical processes leave their signatures on different wavelengths, thusour review is based on a multifrequency analysis. In principle, the best way to analyze multifrequency observations of merging clustersis to model them using N-body/HYDRO numerical simulations. We discuss the results of such detailed analyses.New high spatial and spectral resolution ground and space based telescopeswill come online in the near future. Motivated by these new opportunities,we briefly discuss methods which will be feasible in the near future in studying merging clusters.

  16. Cluster beam sources. Part 1. Methods of cluster beams generation

    Directory of Open Access Journals (Sweden)

    A.Ju. Karpenko

    2012-10-01

    Full Text Available The short review on cluster beams generation is proposed. The basic types of cluster sources are considered and the processes leading to cluster formation are analyzed. The parameters, that affects the work of cluster sources are presented.

  17. Cluster analysis for applications

    CERN Document Server

    Anderberg, Michael R

    1973-01-01

    Cluster Analysis for Applications deals with methods and various applications of cluster analysis. Topics covered range from variables and scales to measures of association among variables and among data units. Conceptual problems in cluster analysis are discussed, along with hierarchical and non-hierarchical clustering methods. The necessary elements of data analysis, statistics, cluster analysis, and computer implementation are integrated vertically to cover the complete path from raw data to a finished analysis.Comprised of 10 chapters, this book begins with an introduction to the subject o

  18. Clusters in nuclei

    CERN Document Server

    Beck, Christian

    Following the pioneering discovery of alpha clustering and of molecular resonances, the field of nuclear clustering is today one of those domains of heavy-ion nuclear physics that faces the greatest challenges, yet also contains the greatest opportunities. After many summer schools and workshops, in particular over the last decade, the community of nuclear molecular physicists has decided to collaborate in producing a comprehensive collection of lectures and tutorial reviews covering the field. This third volume follows the successful Lect. Notes Phys. 818 (Vol. 1) and 848 (Vol. 2), and comprises six extensive lectures covering the following topics:  - Gamma Rays and Molecular Structure - Faddeev Equation Approach for Three Cluster Nuclear Reactions - Tomography of the Cluster Structure of Light Nuclei Via Relativistic Dissociation - Clustering Effects Within the Dinuclear Model : From Light to Hyper-heavy Molecules in Dynamical Mean-field Approach - Clusterization in Ternary Fission - Clusters in Light N...

  19. Unconventional methods for clustering

    Science.gov (United States)

    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.

  20. Spatial cluster modelling

    CERN Document Server

    Lawson, Andrew B

    2002-01-01

    Research has generated a number of advances in methods for spatial cluster modelling in recent years, particularly in the area of Bayesian cluster modelling. Along with these advances has come an explosion of interest in the potential applications of this work, especially in epidemiology and genome research. In one integrated volume, this book reviews the state-of-the-art in spatial clustering and spatial cluster modelling, bringing together research and applications previously scattered throughout the literature. It begins with an overview of the field, then presents a series of chapters that illuminate the nature and purpose of cluster modelling within different application areas, including astrophysics, epidemiology, ecology, and imaging. The focus then shifts to methods, with discussions on point and object process modelling, perfect sampling of cluster processes, partitioning in space and space-time, spatial and spatio-temporal process modelling, nonparametric methods for clustering, and spatio-temporal ...

  1. Survey on Text Document Clustering

    OpenAIRE

    M.Thangamani; Dr.P.Thangaraj

    2010-01-01

    Document clustering is also referred as text clustering, and its concept is merely equal to data clustering. It is hardly difficult to find the selective information from an ‘N’number of series information, so that document clustering came into picture. Basically cluster means a group of similar data, document clustering means segregating the data into different groups of similar data. Clustering can be of mathematical, statistical or numerical domain. Clustering is a fundamental data analysi...

  2. Agricultural Clusters in the Netherlands

    NARCIS (Netherlands)

    Schouten, M.A.; Heijman, W.J.M.

    2012-01-01

    Michael Porter was the first to use the term cluster in an economic context. He introduced the term in The Competitive Advantage of Nations (1990). The term cluster is also known as business cluster, industry cluster, competitive cluster or Porterian cluster. This article aims at determining and mea

  3. Clustering Categorical Data:A Cluster Ensemble Approach

    Institute of Scientific and Technical Information of China (English)

    He Zengyou(何增友); Xu Xiaofei; Deng Shengchun

    2003-01-01

    Clustering categorical data, an integral part of data mining,has attracted much attention recently. In this paper, the authors formally define the categorical data clustering problem as an optimization problem from the viewpoint of cluster ensemble, and apply cluster ensemble approach for clustering categorical data. Experimental results on real datasets show that better clustering accuracy can be obtained by comparing with existing categorical data clustering algorithms.

  4. Spatial Scan Statistic: Selecting clusters and generating elliptic clusters

    DEFF Research Database (Denmark)

    Christiansen, Lasse Engbo; Andersen, Jens Strodl

    2004-01-01

    The spatial scan statistic is widely used to search for clusters. This paper shows that the usually applied elimination of overlapping clusters to find secondary clusters is sensitive to smooth changes in the shape of the clusters. We present an algorithm for generation of set of confocal elliptic...... clusters. In addition, we propose a new way to present the information in a given set of clusters based on the significance of the clusters....

  5. Cosmology with cluster surveys

    Indian Academy of Sciences (India)

    Subhabrata Majumdar

    2004-10-01

    Surveys of clusters of galaxies provide us with a powerful probe of the density and nature of the dark energy. The red-shift distribution of detected clusters is highly sensitive to the dark energy equation of state parameter . Upcoming Sunyaev–Zel'dovich (SZ) surveys would provide us large yields of clusters to very high red-shifts. Self-calibration of cluster scaling relations, possible for such a huge sample, would be able to constrain systematic biases on mass estimators. Combining cluster red-shift abundance with limited mass follow-up and cluster mass power spectrum can then give constraints on , as well as on 8 and to a few per cents.

  6. CSR in Industrial Clusters

    DEFF Research Database (Denmark)

    Lund-Thomsen, Peter; Pillay, Renginee G.

    2012-01-01

    Purpose – The paper seeks to review the literature on CSR in industrial clusters in developing countries, identifying the main strengths, weaknesses, and gaps in this literature, pointing to future research directions and policy implications in the area of CSR and industrial cluster development...... in this field and their comments incorporated in the final version submitted to Corporate Governance. Findings – The article traces the origins of the debate on industrial clusters and CSR in developing countries back to the early 1990s when clusters began to be seen as an important vehicle for local economic...... development in the South. At the turn of the millennium the industrial cluster debate expanded as clusters were perceived as a potential source of poverty reduction, while their role in promoting CSR among small and medium-sized enterprises began to take shape from 2006 onwards. At present, there is still...

  7. Melting of sodium clusters

    CERN Document Server

    Reyes-Nava, J A; Beltran, M R; Michaelian, K

    2002-01-01

    Thermal stability properties and the melting-like transition of Na_n, n=13-147, clusters are studied through microcanonical molecular dynamics simulations. The metallic bonding in the sodium clusters is mimicked by a many-body Gupta potential based on the second moment approximation of a tight-binding Hamiltonian. The characteristics of the solid-to-liquid transition in the sodium clusters are analyzed by calculating physical quantities like caloric curves, heat capacities, and root-mean-square bond length fluctuations using simulation times of several nanoseconds. Distinct melting mechanisms are obtained for the sodium clusters in the size range investigated. The calculated melting temperatures show an irregular variation with the cluster size, in qualitative agreement with recent experimental results. However, the calculated melting point for the Na_55 cluster is about 40 % lower than the experimental value.

  8. Structures in Galaxy Clusters

    CERN Document Server

    Escalera, E; Girardi, M; Giuricin, G; Mardirossian, F; Mazure, A; Mezzetti, M

    1993-01-01

    The analysis of the presence of substructures in 16 well-sampled clusters of galaxies suggests a stimulating hypothesis: Clusters could be classified as unimodal or bimodal, on the basis of to the sub-clump distribution in the {\\em 3-D} space of positions and velocities. The dynamic study of these clusters shows that their fundamental characteristics, in particular the virial masses, are not severely biased by the presence of subclustering if the system considered is bound.

  9. Cluster Symmetries and Dynamics

    Directory of Open Access Journals (Sweden)

    Freer Martin

    2016-01-01

    Full Text Available Many light nuclei display behaviour that indicates that rather than behaving as an A-body systems, the protons and neutrons condense into clusters. The α-particle is the most obvious example of such clustering. This contribution examines the role of such α-clustering on the structure, symmetries and dynamics of the nuclei 8Be, 12C and 16O, recent experimental measurements and future perspectives.

  10. Clustering Techniques in Bioinformatics

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Masood

    2015-01-01

    Full Text Available Dealing with data means to group information into a set of categories either in order to learn new artifacts or understand new domains. For this purpose researchers have always looked for the hidden patterns in data that can be defined and compared with other known notions based on the similarity or dissimilarity of their attributes according to well-defined rules. Data mining, having the tools of data classification and data clustering, is one of the most powerful techniques to deal with data in such a manner that it can help researchers identify the required information. As a step forward to address this challenge, experts have utilized clustering techniques as a mean of exploring hidden structure and patterns in underlying data. Improved stability, robustness and accuracy of unsupervised data classification in many fields including pattern recognition, machine learning, information retrieval, image analysis and bioinformatics, clustering has proven itself as a reliable tool. To identify the clusters in datasets algorithm are utilized to partition data set into several groups based on the similarity within a group. There is no specific clustering algorithm, but various algorithms are utilized based on domain of data that constitutes a cluster and the level of efficiency required. Clustering techniques are categorized based upon different approaches. This paper is a survey of few clustering techniques out of many in data mining. For the purpose five of the most common clustering techniques out of many have been discussed. The clustering techniques which have been surveyed are: K-medoids, K-means, Fuzzy C-means, Density-Based Spatial Clustering of Applications with Noise (DBSCAN and Self-Organizing Map (SOM clustering.

  11. 15th Cluster workshop

    CERN Document Server

    Laakso, Harri; Escoubet, C. Philippe; The Cluster Active Archive : Studying the Earth’s Space Plasma Environment

    2010-01-01

    Since the year 2000 the ESA Cluster mission has been investigating the small-scale structures and processes 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. This book contains presentations made at the 15th Cluster workshop held in March 2008. It also presents several articles about the Cluster Active Archive and its datasets, a few overview papers on the Cluster mission, and articles reporting on scientific findings on the solar wind, the magnetosheath, the magnetopause and the magnetotail.

  12. Galaxy Clusters with Chandra

    CERN Document Server

    Forman, W; Markevitch, M L; Vikhlinin, A A; Churazov, E

    2002-01-01

    We discuss Chandra results related to 1) cluster mergers and cold fronts and 2) interactions between relativistic plasma and hot cluster atmospheres. We describe the properties of cold fronts using NGC1404 in the Fornax cluster and A3667 as examples. We discuss multiple surface brightness discontinuities in the cooling flow cluster ZW3146. We review the supersonic merger underway in CL0657. Finally, we summarize the interaction between plasma bubbles produced by AGN and hot gas using M87 and NGC507 as examples.

  13. Management of cluster headache.

    Science.gov (United States)

    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

  14. Document Clustering Based on Semi-Supervised Term Clustering

    Directory of Open Access Journals (Sweden)

    Hamid Mahmoodi

    2012-05-01

    Full Text Available The study is conducted to propose a multi-step feature (term selection process and in semi-supervised fashion, provide initial centers for term clusters. Then utilize the fuzzy c-means (FCM clustering algorithm for clustering terms. Finally assign each of documents to closest associated term clusters. While most text clustering algorithms directly use documents for clustering, we propose to first group the terms using FCM algorithm and then cluster documents based on terms clusters. We evaluate effectiveness of our technique on several standard text collections and compare our results with the some classical text clustering algorithms.

  15. From collisions to clusters

    DEFF Research Database (Denmark)

    Loukonen, Ville; Bork, Nicolai; Vehkamaki, Hanna

    2014-01-01

    to overcome the possible initial non-optimal collision orientations. No post-collisional cluster break up is observed. The reasons for the efficient clustering are (i) the proton transfer reaction which takes place in each of the collision simulations and (ii) the subsequent competition over the proton...

  16. Cost-Effective Clustering

    CERN Document Server

    Gottlieb, S

    2001-01-01

    Small Beowulf clusters can effectively serve as personal or group supercomputers. In such an environment, a cluster can be optimally designed for a specific problem (or a small set of codes). We discuss how theoretical analysis of the code and benchmarking on similar hardware lead to optimal systems.

  17. Coma cluster of galaxies

    Science.gov (United States)

    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).

  18. Clustering Text Data Streams

    Institute of Scientific and Technical Information of China (English)

    Yu-Bao Liu; Jia-Rong Cai; Jian Yin; Ada Wai-Chee Fu

    2008-01-01

    Clustering text data streams is an important issue in data mining community and has a number of applications such as news group filtering, text crawling, document organization and topic detection and tracing etc. However, most methods are similarity-based approaches and only use the TF*IDF scheme to represent the semantics of text data and often lead to poor clustering quality. Recently, researchers argue that semantic smoothing model is more efficient than the existing TF.IDF scheme for improving text clustering quality. However, the existing semantic smoothing model is not suitable for dynamic text data context. In this paper, we extend the semantic smoothing model into text data streams context firstly. Based on the extended model, we then present two online clustering algorithms OCTS and OCTSM for the clustering of massive text data streams. In both algorithms, we also present a new cluster statistics structure named cluster profile which can capture the semantics of text data streams dynamically and at the same time speed up the clustering process. Some efficient implementations for our algorithms are also given. Finally, we present a series of experimental results illustrating the effectiveness of our technique.

  19. Brightest Cluster Galaxy Identification

    Science.gov (United States)

    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.

  20. Blue emitting undecaplatinum clusters

    Science.gov (United States)

    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

  1. Investigation of Cluster and Cluster Queuing System

    OpenAIRE

    Halifu, Saerda

    2008-01-01

    Cluster became main platform as parallel and distributed computing structure for high performance computing. Following the development of high performance computer architecture more and more different branches of natural science benefit fromhuge and efficient computational power. For instance bio-informatics, climate science, computational physics, computational chemistry, marine science, etc. Efficient and reliable computing powermay not only expending demand of existing high performance com...

  2. The Cluster Substructure - Alignment Connection

    CERN Document Server

    Plionis, M

    2002-01-01

    Using the APM cluster data we investigate whether the dynamical status of clusters is related to the large-scale structure of the Universe. We find that cluster substructure is strongly correlated with the tendency of clusters to be aligned with their nearest neighbour and in general with the nearby clusters that belong to the same supercluster. Furthermore, dynamically young clusters are more clustered than the overall cluster population. These are strong indications that cluster develop in a hierarchical fashion by anisotropy merging along the large-scale filamentary superclusters within which they are embedded.

  3. Job Oriented Monitoring Clusters

    Directory of Open Access Journals (Sweden)

    Vijayalaxmi Cigala,

    2011-03-01

    Full Text Available There has been a lot of development in the field of clusters and grids. Recently, the use of clusters has been on rise in every possible field. This paper proposes a system that monitors jobs onlarge computational clusters. Monitoring jobs is essential to understand how jobs are being executed. This helps us in understanding the complete life cycle of the jobs being executed on large clusters. Also, this paper describes how the information obtained by monitoring the jobs would help in increasing the overall throughput of clusters. Heuristics help in efficient job distribution among the computational nodes, thereby accomplishing fair job distribution policy. The proposed system would be capable of loadbalancing among the computational nodes, detecting failures, taking corrective actions after failure detection, job monitoring, system resource monitoring, etc.

  4. Pulsars in Globular Clusters

    CERN Document Server

    Camilo, F; Camilo, Fernando; Rasio, Frederic A.

    2005-01-01

    More than 100 radio pulsars have been detected in 24 globular clusters. The largest observed samples are in Terzan 5 and 47 Tucanae, which together contain 45 pulsars. Accurate timing solutions, including positions in the cluster, are known for many of these pulsars. Here we provide an observational overview of some properties of pulsars in globular clusters, as well as properties of the globular clusters with detected pulsars. The many recent detections also provide a new opportunity to re-examine theoretically the formation and evolution of recycled pulsars in globular clusters. Our brief review considers the most important dynamical interaction and binary evolution processes: collisions, exchange interactions, mass transfer, and common-envelope phases.

  5. Mathematical classification and clustering

    CERN Document Server

    Mirkin, Boris

    1996-01-01

    I am very happy to have this opportunity to present the work of Boris Mirkin, a distinguished Russian scholar in the areas of data analysis and decision making methodologies. The monograph is devoted entirely to clustering, a discipline dispersed through many theoretical and application areas, from mathematical statistics and combina­ torial optimization to biology, sociology and organizational structures. It compiles an immense amount of research done to date, including many original Russian de­ velopments never presented to the international community before (for instance, cluster-by-cluster versions of the K-Means method in Chapter 4 or uniform par­ titioning in Chapter 5). The author's approach, approximation clustering, allows him both to systematize a great part of the discipline and to develop many in­ novative methods in the framework of optimization problems. The optimization methods considered are proved to be meaningful in the contexts of data analysis and clustering. The material presented in ...

  6. On TPC cluster reconstruction

    CERN Document Server

    Dydak, F; Nefedov, Y; Wotschack, J; Zhemchugov, A

    2004-01-01

    For a bias-free momentum measurement of TPC tracks, the correct determination of cluster positions is mandatory. We argue in particular that (i) the reconstruction of the entire longitudinal signal shape in view of longitudinal diffusion, electronic pulse shaping, and track inclination is important both for the polar angle reconstruction and for optimum r phi resolution; and that (ii) self-crosstalk of pad signals calls for special measures for the reconstruction of the z coordinate. The problem of 'shadow clusters' is resolved. Algorithms are presented for accepting clusters as 'good' clusters, and for the reconstruction of the r phi and z cluster coordinates, including provisions for 'bad' pads and pads next to sector boundaries, respectively.

  7. Cool Cluster Correctly Correlated

    Energy Technology Data Exchange (ETDEWEB)

    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

  8. Cluster ion beam evaporation

    International Nuclear Information System (INIS)

    Cluster ions can be made by the supercooling due to adiabatic expansion of substances to be vaporized which are ejected from a nozzle. This paper is described on the recent progress of studies concerning the cluster beam. The technique of cluster ion beam has been applied for the studies of thermonuclear plasma, the fabrication of thin films, crystal growth and electronic devices. The density of cluster ion beam is larger than that of atomic ion beam, and the formation of thin films can be easily done in high vacuum. This method is also useful for epitaxial growth. Metallic vapour cluster beam was made by the help of jetting rare gas beam. Various beam sources were developed. The characteristics of these sources were measured and analyzed. (Kato, T.)

  9. Textile Industrial Clusters in China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    "National Textile Industry Cluster Development Seminar" convened, held by China National Textile and Apparel Council, 23 cities and towns were awarded as China’s Textile Industry Cluster Pilot District. By far, China’s textile industrial clusters have grown

  10. Spanning Tree Based Attribute Clustering

    DEFF Research Database (Denmark)

    Zeng, Yifeng; Jorge, Cordero Hernandez

    2009-01-01

    inconsistent edges from a maximum spanning tree by starting appropriate initial modes, therefore generating stable clusters. It discovers sound clusters through simple graph operations and achieves significant computational savings. We compare the Star Discovery algorithm against earlier attribute clustering...

  11. Cluster knockout reactions

    Indian Academy of Sciences (India)

    Arun K Jain; B N Joshi

    2014-04-01

    Cluster knockout reactions are expected to reveal the amount of clustering (such as that of , d and even of heavier clusters such as 12C, 16O etc.) in the target nucleus. In simple terms, incident medium high-energy nuclear projectile interacts strongly with the cluster (present in the target nucleus) as if it were existing as a free entity. Theoretically, the relatively softer interactions of the two outgoing particles with the residual nucleus lead to optical distortions and are treated in terms of distorted wave (DW) formalism. The long-range projectile–cluster interaction is accounted for, in terms of the finite range (FR) direct reaction formalism, as against the more commonly adopted zero-range (ZR) distorted wave impulse approximation (DWIA) formalism. Comparison of the DWIA calculations with the observed data provide information about the momentum distribution and the clustering spectroscopic factor of the target nucleus. Interesting results and some recent advancements in the area of (, 2) reactions and heavy cluster knockout reactions are discussed. Importance of the finite-range vertex and the final-state interactions are brought out.

  12. Software-Defined Cluster

    Institute of Scientific and Technical Information of China (English)

    聂华; 杨晓君; 刘淘英

    2015-01-01

    The cluster architecture has played an important role in high-end computing for the past 20 years. With the advent of Internet services, big data, and cloud computing, traditional clusters face three challenges: 1) providing flexible system balance among computing, memory, and I/O capabilities;2) reducing resource pooling overheads;and 3) addressing low performance-power efficiency. This position paper proposes a software-defined cluster (SDC) architecture to deal with these challenges. The SDC architecture inherits two features of traditional cluster: its architecture is multicomputer and it has loosely-coupled interconnect. SDC provides two new mechanisms: global I/O space (GIO) and hardware-supported native access (HNA) to remote devices. Application software can define a virtual cluster best suited to its needs from resources pools provided by a physical cluster, and traditional cluster ecosystems need no modification. We also discuss a prototype design and implementation of a 32-processor cloud server utilizing the SDC architecture.

  13. Extending Beowulf Clusters

    Science.gov (United States)

    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.

  14. Cluster Management Institutionalization

    DEFF Research Database (Denmark)

    Normann, Leo; Agger Nielsen, Jeppe

    2015-01-01

    institutionalism together with a longitudinal case-based inquiry into how cluster management has entered and penetrated the management practices of day care in Denmark. We demonstrate how cluster management became widely adopted in the day care field not only because of its intrinsic properties but also because...... legitimized at the field level, then spread, and finally translated into action in the adopting organizations. Instead, we observed entangled field and organizational-level processes. Accordingly, we argue that cluster management institutionalization is most readily understood by simultaneously investigating...

  15. Introduction to cluster dynamics

    CERN Document Server

    Reinhard, Paul-Gerhard

    2008-01-01

    Clusters as mesoscopic particles represent an intermediate state of matter between single atoms and solid material. The tendency to miniaturise technical objects requires knowledge about systems which contain a ""small"" number of atoms or molecules only. This is all the more true for dynamical aspects, particularly in relation to the qick development of laser technology and femtosecond spectroscopy. Here, for the first time is a highly qualitative introduction to cluster physics. With its emphasis on cluster dynamics, this will be vital to everyone involved in this interdisciplinary subje

  16. Dwarfs in Coma Cluster

    Science.gov (United States)

    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.

  17. Raspberry Pi super cluster

    CERN Document Server

    Dennis, Andrew K

    2013-01-01

    This book follows a step-by-step, tutorial-based approach which will teach you how to develop your own super cluster using Raspberry Pi computers quickly and efficiently.Raspberry Pi Super Cluster is an introductory guide for those interested in experimenting with parallel computing at home. Aimed at Raspberry Pi enthusiasts, this book is a primer for getting your first cluster up and running.Basic knowledge of C or Java would be helpful but no prior knowledge of parallel computing is necessary.

  18. Partially supervised speaker clustering.

    Science.gov (United States)

    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

  19. Clustering in nuclear environment

    International Nuclear Information System (INIS)

    The properties of few-body clusters (mass number A ≤ 4) are modified if they are immersed in a nuclear medium. In particular, Pauli blocking that reflects the antisymmetrization of the many-body wave function is responsible for the medium modification of light clusters and the dissolution with increasing density. A more consistent description is given with takes also the contribution of correlations in the continuum into account. The relation between cluster formation in warm dense matter and in nuclear structure is discussed

  20. Combining cluster number counts and galaxy clustering

    Science.gov (United States)

    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.

  1. Evolution of clustered storage

    CERN Document Server

    CERN. Geneva; Van de Vyvre, Pierre

    2007-01-01

    The session actually featured two presentations: * Evolution of clustered storage by Lance Hukill, Quantum Corporation * ALICE DAQ - Usage of a Cluster-File System: Quantum StorNext by Pierre Vande Vyvre, CERN-PH the second one prepared at short notice by Pierre (thanks!) to present how the Quantum technologies are being used in the ALICE experiment. The abstract to Mr Hukill's follows. Clustered Storage is a technology that is driven by business and mission applications. The evolution of Clustered Storage solutions starts first at the alignment between End-users needs and Industry trends: * Push-and-Pull between managing for today versus planning for tomorrow * Breaking down the real business problems to the core applications * Commoditization of clients, servers, and target devices * Interchangeability, Interoperability, Remote Access, Centralized control * Oh, and yes, there is a budget and the "real world" to deal with This presentation will talk through these needs and trends, and then ask the question, ...

  2. Dynamic Bayesian clustering.

    Science.gov (United States)

    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

  3. Internal Cluster Structure

    CERN Document Server

    Bartelmann, Matthias; Meneghetti, Massimo; Schmidt, Robert

    2013-01-01

    The core structure of galaxy clusters is fundamentally important. Even though self-gravitating systems have no stable equilibrium state due to their negative heat capacity, numerical simulations find density profiles which are universal in the sense that they are fairly flat within a scale radius and gradually steepen farther outward, asymptotically approaching a logarithmic slope of $\\approx-3$ near the virial radius. We argue that the reason for the formation of this profile is not satisfactorily understood. The ratio between the virial radius and the scale radius, the so-called concentration, is found in simulations to be closely related to the mass and the redshift and low for cluster-sized haloes, but observed to be substantially higher at least in a subset of observed clusters. Haloes formed from cold dark matter should furthermore be richly substructured. We review theoretical and observational aspects of cluster cores here, discuss modifications by baryonic physics and observables that can provide bet...

  4. Finnish Mobile Gaming Cluster

    OpenAIRE

    Masira, Elijah; Chowdhury, Nafis Ahmed

    2014-01-01

    Abstract The Finnish mobile gaming cluster is one of the most promising industries that have been growing significantly in the past few years to become a substantial cultural export product / service of Finland. The main objective of this research was to gain a persuasive understanding about the emergence of the mobile gaming cluster in Finland and explore the factors behind its success. The literature review centers on M. E Porter’s publications on competitiveness and other publication...

  5. Clustering audiology data

    OpenAIRE

    Anwar, Naveed; Oakes, Michael; Wermter, Stefan; Heinrich, Stefan

    2010-01-01

    In this paper we describe new results of statistical and neural data mining of audiology patient records, with the ultimate aim of looking for factors influencing which patients would most benefit from being fitted with a hearing aid. We describe how a combination of neural and statistical techniques can usefully subdivide a set of patients into clusters, based on their hearing thresholds at six different frequencies, and then label the clusters with meaningful text labels. In our first exper...

  6. Industry clusters and SMEs

    OpenAIRE

    Arnoud Muizer; Gert Jan Hospers

    1999-01-01

    Studie naar de rol van clusters van bedrijven in de economie. Clusters van bedrijven krijgen een groeiende aandacht op alle bestuurlijke niveaus. De achterliggende gedachte is dat samenwerking tussen bedrijven op technologisch gebied leidt tot de creatie van extra toegevoegde waarde, niet alleen voor de samenwerkingspartners zelf, maar ook voor de lokale, regionale en nationale economie. In de studie wordt een clusterdefinitie gepresenteerd en een raamwerk dat als basis kan dienen voor nader ...

  7. Centroid Based Text Clustering

    Directory of Open Access Journals (Sweden)

    Priti Maheshwari

    2010-09-01

    Full Text Available Web mining is a burgeoning new field that attempts to glean meaningful information from natural language text. Web mining refers generally to the process of extracting interesting information and knowledge from unstructured text. Text clustering is one of the important Web mining functionalities. Text clustering is the task in which texts are classified into groups of similar objects based on their contents. Current research in the area of Web mining is tacklesproblems of text data representation, classification, clustering, information extraction or the search for and modeling of hidden patterns. In this paper we propose for mining large document collections it is necessary to pre-process the web documents and store the information in a data structure, which is more appropriate for further processing than a plain web file. In this paper we developed a php-mySql based utility to convert unstructured web documents into structured tabular representation by preprocessing, indexing .We apply centroid based web clustering method on preprocessed data. We apply three methods for clustering. Finally we proposed a method that can increase accuracy based on clustering ofdocuments.

  8. Galaxy cluster's rotation

    CERN Document Server

    Manolopoulou, Maria

    2016-01-01

    We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their...

  9. Cluster bomb ocular injuries

    Directory of Open Access Journals (Sweden)

    Ahmad M Mansour

    2012-01-01

    Full Text Available Purpose: To present the visual outcomes and ocular sequelae of victims of cluster bombs. Materials and Methods: This retrospective, multicenter case series of ocular injury due to cluster bombs was conducted for 3 years after the war in South Lebanon (July 2006. Data were gathered from the reports to the Information Management System for Mine Action. Results: There were 308 victims of clusters bombs; 36 individuals were killed, of which 2 received ocular lacerations and; 272 individuals were injured with 18 receiving ocular injury. These 18 surviving individuals were assessed by the authors. Ocular injury occurred in 6.5% (20/308 of cluster bomb victims. Trauma to multiple organs occurred in 12 of 18 cases (67% with ocular injury. Ocular findings included corneal or scleral lacerations (16 eyes, corneal foreign bodies (9 eyes, corneal decompensation (2 eyes, ruptured cataract (6 eyes, and intravitreal foreign bodies (10 eyes. The corneas of one patient had extreme attenuation of the endothelium. Conclusions: Ocular injury occurred in 6.5% of cluster bomb victims and 67% of the patients with ocular injury sustained trauma to multiple organs. Visual morbidity in civilians is an additional reason for a global ban on the use of cluster bombs.

  10. Cluster fusion algorithm: application to Lennard-Jones clusters

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2008-01-01

    paths up to the cluster size of 150 atoms. We demonstrate that in this way all known global minima structures of the Lennard-Jones clusters can be found. Our method provides an efficient tool for the calculation and analysis of atomic cluster structure. With its use we justify the magic number sequence......We present a new general theoretical framework for modelling the cluster structure and apply it to description of the Lennard-Jones clusters. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system and absorbing its energy at each step, we find cluster growing...... for the clusters of noble gas atoms and compare it with experimental observations. We report the striking correspondence of the peaks in the dependence of the second derivative of the binding energy per atom on cluster size calculated for the chain of the Lennard-Jones clusters based on the icosahedral symmetry...

  11. Cluster fusion algorithm: application to Lennard-Jones clusters

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2006-01-01

    paths up to the cluster size of 150 atoms. We demonstrate that in this way all known global minima structures of the Lennard-Jones clusters can be found. Our method provides an efficient tool for the calculation and analysis of atomic cluster structure. With its use we justify the magic number sequence......We present a new general theoretical framework for modelling the cluster structure and apply it to description of the Lennard-Jones clusters. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system and absorbing its energy at each step, we find cluster growing...... for the clusters of noble gas atoms and compare it with experimental observations. We report the striking correspondence of the peaks in the dependence of the second derivative of the binding energy per atom on cluster size calculated for the chain of the Lennard-Jones clusters based on the icosahedral symmetry...

  12. The rotation of Galaxy Clusters

    OpenAIRE

    Tovmassian, Hrant M.

    2015-01-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher of 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 in which does not differ significantly from the cluste...

  13. Stellar populations in star clusters

    CERN Document Server

    Li, Chengyuan; Deng, Licai

    2016-01-01

    Stellar populations contain the most important information about star clus- ter formation and evolution. Until several decades ago, star clusters were believed to be ideal laboratories for studies of simple stellar populations (SSPs). However, discoveries of multiple stellar populations in Galactic globular clusters have expanded our view on stellar populations in star clusters. They have simultaneously generated a number of controversies, particularly as to whether young star clusters may have the same origin as old globular clusters. In addition, extensive studies have revealed that the SSP scenario does not seem to hold for some intermediate-age and young star clusters either, thus making the origin of multiple stellar populations in star clusters even more complicated. Stellar population anomalies in numerous star clusters are well-documented, implying that the notion of star clusters as true SSPs faces serious challenges. In this review, we focus on stellar populations in massive clusters with different ...

  14. Clustering by Pattern Similarity

    Institute of Scientific and Technical Information of China (English)

    Hai-xun Wang; Jian Pei

    2008-01-01

    The task of clustering is to identify classes of similar objects among a set of objects. The definition of similarity varies from one clustering model to another. However, in most of these models the concept of similarity is often based on such metrics as Manhattan distance, Euclidean distance or other Lp distances. In other words, similar objects must have close values in at least a set of dimensions. In this paper, we explore a more general type of similarity. Under the pCluster model we proposed, two objects are similar if they exhibit a coherent pattern on a subset of dimensions. The new similarity concept models a wide range of applications. For instance, in DNA microarray analysis, the expression levels of two genes may rise and fall synchronously in response to a set of environmental stimuli. Although the magnitude of their expression levels may not be close, the patterns they exhibit can be very much alike. Discovery of such clusters of genes is essential in revealing significant connections in gene regulatory networks. E-commerce applications, such as collaborative filtering, can also benefit from the new model, because it is able to capture not only the closeness of values of certain leading indicators but also the closeness of (purchasing, browsing, etc.) patterns exhibited by the customers. In addition to the novel similarity model, this paper also introduces an effective and efficient algorithm to detect such clusters, and we perform tests on several real and synthetic data sets to show its performance.

  15. Clustering in bubbly liquids

    Science.gov (United States)

    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.

  16. Clusters in Light Nuclei

    CERN Document Server

    Beck, C; Zafra, A Sanchez i; Thummerer, S; Azaiez, F; Bednarczyk, P; Courtin, S; Curien, D; Dorvaux, O; Goasduff, A; ~Lebhertz, D; Nourreddine, A; ~Rousseau, M; Salsac, M -D; von Oertzen, W; Gebauer, B; Wheldon, C; Kokalova, Tz; Efimov, G; Zherebchevsky, V; Schulz, Ch; Bohlen, H G; Kamanin, D; de Angelis, G; Gadea, A; Lenzi, S; Napoli, D R; Szilner, S; Milin, M; Catford, W N; Jenkins, D G; Royer, G

    2010-01-01

    A great deal of research work has been undertaken in the alpha-clustering study since the pioneering discovery, half a century ago, of 12C+12C molecular resonances. Our knowledge of the field of the physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. In this work, the occurence of "exotic" shapes in light N=Z alpha-like nuclei is investigated. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Results on clustering aspects are also discussed for light neutron-rich Oxygen isotopes.

  17. Vanadogermanate cluster anions.

    Science.gov (United States)

    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

  18. Refractory chronic cluster headache

    DEFF Research Database (Denmark)

    Mitsikostas, Dimos D; Edvinsson, Lars; Jensen, Rigmor H;

    2014-01-01

    for clinical and research use. The preparation of the final consensus followed three stages. Internal between authors, a larger between all European Headache Federation members and finally an international one among all investigators that have published clinical studies on cluster headache the last five years......Chronic cluster headache (CCH) often resists to prophylactic pharmaceutical treatments resulting in patients' life damage. In this rare but pragmatic situation escalation to invasive management is needed but framing criteria are lacking. We aimed to reach a consensus for refractory CCH definition...

  19. Kinematics of Clustering

    CERN Document Server

    Wang, Steven; Metcalfe, Guy; Wu, Jie

    2014-01-01

    The dynamical system for inertial particles in fluid flow has both attracting and repelling regions, the interplay of which can localize particles. In laminar flow experiments we find that particles, initially moving throughout the fluid domain, can undergo an instability and cluster into subdomains of the fluid when the flow Reynolds number exceeds a critical value that depends on particle and fluid inertia. We derive an expression for the instability boundary and for a universal curve that describes the clustering rate for all particles.

  20. South Asian Cluster

    Directory of Open Access Journals (Sweden)

    Ionel Sergiu Pirju

    2014-12-01

    Full Text Available This article aims at presenting the South Asian cluster composed of India, Indonesia, Iran and Malaysia, the intercultural values that characterizes it, the supported leadership style and tracing the main macroeconomic considerations which characterizes them. The research is synchronic, analysing the contemporary situation of these countries without reference to their evolution in time, by using the positivist paradigm that explains the reality at one point. It will be analysed the overall cluster with the existing interactions between the countries that composes it, while the article being one of information will avoid building recommendation, or new theories.

  1. Cluster's last stand?

    OpenAIRE

    Lockwood, Mike

    1997-01-01

    On 4 June last year the first attempt to make three-dimensional measurements in space was lost when the Ariane 5 rocket veered off course and self-destructed, 39 s into its maiden flight. On board were four identical spacecraft which made up Cluster,a mission that the European Space Agency called a “cornerstone” of its Horizon 2000 scientific programme. A full description of the Cluster satellites is given in a special issue of Space Science Reviews (Escoubet et al. 1997). Their loss de...

  2. Clustering Game Behavior Data

    DEFF Research Database (Denmark)

    Bauckhage, C.; Drachen, Anders; Sifa, Rafet

    2015-01-01

    and other techniques for player profiling and play style analysis have, therefore, become popular in the nascent field of game analytics. However, the proper use of clustering techniques requires expertise and an understanding of games is essential to evaluate results. With this paper, we address game data...... scientists and present a review and tutorial focusing on the application of clustering techniques to mine behavioral game data. Several algorithms are reviewed and examples of their application shown. Key topics such as feature normalization are discussed and open problems in the context of game analytics...

  3. An Emerge Approach in Inter Cluster Similarity for Quality Clusters

    Directory of Open Access Journals (Sweden)

    H. Venkateswara Reddy

    2013-04-01

    Full Text Available Relationship between the datasets is one most important issue in recent years. The recent methods are based mostly on the numerical data, but these methods are not suitable for real time data such as web pages, business transactions etc., which are known as Categorical data. It is difficult to find relationship in categorical data. In this paper, a new approach is proposed for finding the relationshipbetween the categorical data, hence to find relationship between the clusters. The main aim is to identify the quality clusters based on the relationship between clusters. If there is no relationship between clusters then those clusters are treated as quality clusters.

  4. Combining cluster number counts and galaxy clustering

    CERN Document Server

    Lacasa, Fabien

    2016-01-01

    We present a detailed modelling of the joint covariance matrix between cluster number counts and the galaxy angular power spectrum. To this end, we use a Halo Model framework complemented by a Halo Occupation Distribution model (HOD), and we work in full-sky. We demonstrate the importance of accounting for non-Gaussianity to produce accurate covariance predictions, as the Gaussian part of the covariance can in fact become subdominant in certain configurations. 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, and demonstrating interesting mathematical properties. 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 noticeable better constraints, in particular because the cross-covariance introduces a synergy between the probes on small scales....

  5. Localized attack on clustering networks

    CERN Document Server

    Dong, Gaogao; Du, Ruijin; Shao, Shuai; Stanley, H Eugene; Shlomo, Havlin

    2016-01-01

    Clustering network is one of which complex network attracting plenty of scholars to discuss and study the structures and cascading process. We primarily analyzed the effect of clustering coefficient to other various of the single clustering network under localized attack. These network models including double clustering network and star-like NON with clustering and random regular (RR) NON of ER networks with clustering are made up of at least two networks among which exist interdependent relation among whose degree of dependence is measured by coupling strength. We show both analytically and numerically, how the coupling strength and clustering coefficient effect the percolation threshold, size of giant component, critical coupling point where the behavior of phase transition changes from second order to first order with the increase of coupling strength between the networks. Last, we study the two types of clustering network: one type is same with double clustering network in which each subnetwork satisfies ...

  6. Projection effects in cluster catalogues

    CERN Document Server

    Van Haarlem, M P; White, S D M

    1997-01-01

    We investigate the importance of projection effects in the identification of galaxy clusters in 2D galaxy maps and their effect on the estimation of cluster velocity dispersions. A volume limited galaxy catalogue that was derived from a Standard CDM N-body simulation was used. We select clusters using criteria that match those employed in the construction of real cluster catalogues and find that our mock Abell cluster catalogues are heavily contaminated and incomplete. Over one third (34 per cent) of clusters of richness class R>=1 are miclassifications arising from the projection of one or more clumps onto an intrinsically poor cluster. Conversely, 32 per cent of intrinsically rich clusters are missed from the R>=1 catalogues, mostly because of statistical fluctuations in the background count. Selection by X-ray luminosity rather than optical richness reduces, but does not completely eliminate, these problems. Contamination by unvirialised sub-clumps near a cluster leads to a considerable overestimation of t...

  7. Clustering of resting state networks.

    Directory of Open Access Journals (Sweden)

    Megan H Lee

    Full Text Available 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.

  8. PVM Support for Clusters

    Science.gov (United States)

    Springer, P.

    2000-01-01

    The latest version of PVM (3.4.3) now contains support for a PC cluster running Linux, also known as a Beowulf system. A PVM user of a computer outside the Beowulf system can add the Beowulf as a single machine.

  9. Evolution of Galaxy Clustering

    OpenAIRE

    Bagla, J. S.

    1997-01-01

    We show that the galaxy correlation function does not evolve in proportion with the correlation function of the underlying mass distribution. Earliest galaxies cluster very strongly and the amplitude of the galaxy correlation function decreases from this large value. This continues till the average peaks have collapsed, after which, the galaxy correlation function does not evolve very strongly.

  10. Fuzzy clustering of mechanisms

    Indian Academy of Sciences (India)

    Amitabha Ghosh; Dilip Kumar Pratihar; M V V Amarnath; Guenter Dittrich; Jorg Mueller

    2012-10-01

    During the course of development of Mechanical Engineering, a large number of mechanisms (that is, linkages to perform various types of tasks) have been conceived and developed. Quite a few atlases and catalogues were prepared by the designers of machines and mechanical systems. However, often it is felt that a clustering technique for handling the list of large number of mechanisms can be very useful,if it is developed based on a scientific principle. In this paper, it has been shown that the concept of fuzzy sets can be conveniently used for this purpose, if an adequate number of properly chosen attributes (also called characteristics) are identified. Using two clustering techniques, the mechanisms have been classified in the present work and in future, it may be extended to develop an expert system, which can automate type synthesis phase of mechanical design. To the best of the authors’ knowledge, this type of clustering of mechanisms has not been attempted before. Thus, this is the first attempt to cluster the mechanisms based on some quantitative measures. It may help the engineers to carry out type synthesis of the mechanisms.

  11. Clustering under Perturbation Resilience

    CERN Document Server

    Balcan, Maria Florina

    2011-01-01

    Recently, Bilu and Linial \\cite{BL} formalized an implicit assumption often made when choosing a clustering objective: that the optimum clustering to the objective should be preserved under small multiplicative perturbations to distances between points. They showed that for max-cut clustering it is possible to circumvent NP-hardness and obtain polynomial-time algorithms for instances resilient to large (factor $O(\\sqrt{n})$) perturbations, and subsequently Awasthi et al. \\cite{ABS10} considered center-based objectives, giving algorithms for instances resilient to O(1) factor perturbations. In this paper, we greatly advance this line of work. For the $k$-median objective, we present an algorithm that can optimally cluster instances resilient to $(1 + \\sqrt{2})$-factor perturbations, solving an open problem of Awasthi et al.\\cite{ABS10}. We additionally give algorithms for a more relaxed assumption in which we allow the optimal solution to change in a small $\\epsilon$ fraction of the points after perturbation. ...

  12. Clustering high dimensional data

    DEFF Research Database (Denmark)

    Assent, Ira

    2012-01-01

    High-dimensional data, i.e., data described by a large number of attributes, pose specific challenges to clustering. The so-called ‘curse of dimensionality’, coined originally to describe the general increase in complexity of various computational problems as dimensionality increases, is known to...

  13. Detecting alternative graph clusterings.

    Science.gov (United States)

    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.

  14. Galactic Open Clusters

    CERN Document Server

    Von Hippel, T

    2005-01-01

    The study of open clusters has a classic feel to it since the subject predates anyone alive today. Despite the age of this topic, I show via an ADS search that its relevance and importance in astronomy has grown faster in the last few decades than astronomy in general. This is surely due to both technical reasons and the interconnection of the field of stellar evolution to many branches of astronomy. In this review, I outline what we know today about open clusters and what they have taught us about a range of topics from stellar evolution to Galactic structure to stellar disk dissipation timescales. I argue that the most important astrophysics we have learned from open clusters is stellar evolution and that its most important product has been reasonably precise stellar ages. I discuss where open cluster research is likely to go in the next few years, as well as in the era of 20m telescopes, SIM, and GAIA. Age will continue to be of wide relevance in astronomy, from cosmology to planet formation timescales, an...

  15. Disentangling Porterian Clusters

    DEFF Research Database (Denmark)

    Jagtfelt, Tue

    intertwined and that Porter’s consciously paradigmatic textbook very likely gained worldwide influence due to two interrelated factors. The first factor is the deliberately holistic gestalt figure propounded in Nations, which prompted scientific communities to pursue cluster research; the second factor...

  16. Curriculum Guide Construction Cluster.

    Science.gov (United States)

    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…

  17. Data clustering algorithms and applications

    CERN Document Server

    Aggarwal, Charu C

    2013-01-01

    Research on the problem of clustering tends to be fragmented across the pattern recognition, database, data mining, and machine learning communities. Addressing this problem in a unified way, Data Clustering: Algorithms and Applications provides complete coverage of the entire area of clustering, from basic methods to more refined and complex data clustering approaches. It pays special attention to recent issues in graphs, social networks, and other domains.The book focuses on three primary aspects of data clustering: Methods, describing key techniques commonly used for clustering, such as fea

  18. Quartile Clustering: A quartile based technique for Generating Meaningful Clusters

    CERN Document Server

    Goswami, Saptarsi

    2012-01-01

    Clustering is one of the main tasks in exploratory data analysis and descriptive statistics where the main objective is partitioning observations in groups. Clustering has a broad range of application in varied domains like climate, business, information retrieval, biology, psychology, to name a few. A variety of methods and algorithms have been developed for clustering tasks in the last few decades. We observe that most of these algorithms define a cluster in terms of value of the attributes, density, distance etc. However these definitions fail to attach a clear meaning/semantics to the generated clusters. We argue that clusters having understandable and distinct semantics defined in terms of quartiles/halves are more appealing to business analysts than the clusters defined by data boundaries or prototypes. On the samepremise, we propose our new algorithm named as quartile clustering technique. Through a series of experiments we establish efficacy of this algorithm. We demonstrate that the quartile clusteri...

  19. The Rotation of Galaxy Clusters

    Science.gov (United States)

    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. The rotation of Galaxy Clusters

    CERN Document Server

    Tovmassian, Hrant M

    2015-01-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher of 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 in 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 have merging with other clusters and groups of galaxies, in the result of which the rotation has been prevented.

  1. Single-cluster dynamics for the random-cluster model

    NARCIS (Netherlands)

    Deng, Y.; Qian, X.; Blöte, H.W.J.

    2009-01-01

    We formulate a single-cluster Monte Carlo algorithm for the simulation of the random-cluster model. This algorithm is a generalization of the Wolff single-cluster method for the q-state Potts model to noninteger values q>1. Its results for static quantities are in a satisfactory agreement with those

  2. Eclipsing binaries in open clusters

    DEFF Research Database (Denmark)

    Southworth, John; Clausen, J.V.

    2006-01-01

    Stars: fundamental parameters - Stars : binaries : eclipsing - Stars: Binaries: spectroscopic - Open clusters and ass. : general Udgivelsesdato: 5 August......Stars: fundamental parameters - Stars : binaries : eclipsing - Stars: Binaries: spectroscopic - Open clusters and ass. : general Udgivelsesdato: 5 August...

  3. Radio observations of Planck clusters

    CERN Document Server

    Kale, Ruta

    2012-01-01

    Recently, a number of new galaxy clusters have been detected by the ESA-Planck satellite, the South Pole Telescope and the Atacama Cosmology Telescope using the Sunyaev-Zeldovich effect. Several of the newly detected clusters are massive, merging systems with disturbed morphology in the X-ray surface brightness. Diffuse radio sources in clusters, called giant radio halos and relics, are direct probes of cosmic rays and magnetic fields in the intra-cluster medium. These radio sources are found to occur mainly in massive merging clusters. Thus, the new SZ-discovered clusters are good candidates to search for new radio halos and relics. We have initiated radio observations of the clusters detected by Planck with the Giant Metrewave Radio Telescope. These observations have already led to the detection of a radio halo in PLCKG171.9-40.7, the first giant halo discovered in one of the new Planck clusters.

  4. The Evolution of Cluster Substructure

    CERN Document Server

    Jeltema, T E; Bautz, M W; Buote, D A; Jeltema, Tesla E.; Canizares, Claude R.; Bautz, Mark W.; Buote, David A.

    2003-01-01

    Using Chandra archival data, we have begun a study to quantify the evolution of cluster morphology with redshift. To quantify cluster morphology, we use the power ratio method developed by Buote and Tsai (1995). Power ratios are constructed from moments of the two-dimensional gravitational potential and are, therefore, related to a cluster's dynamical state. Our sample will include around 50 clusters from the Chandra archive with redshifts between 0.11 and 1.1. These clusters were selected from two fairly complete flux-limited X-ray surveys (the ROSAT Bright Cluster Sample and the Einstein Medium Sensitivity Survey), and additional high-redshift clusters were selected from recent ROSAT flux-limited surveys. Here we present preliminary results from the first 15 clusters in this sample. Of these, eight have redshifts below 0.5, and seven have redshifts above 0.5.

  5. Textile Industrial Clusters in China

    Institute of Scientific and Technical Information of China (English)

    Nie Ting

    2010-01-01

    @@ "National Textile Industry Cluster Development Seminar" convened,held by China National Textile and Apparel Council,23 cities and towns were awarded as China's Textile Industry Cluster Pilot District.By far,China's textile industrial clusters have grown to 164,which indicate a quick and gorgeous development.These textile industrial clusters have a great impact on the local economy and even the whole national textile industry's development.

  6. [Cluster analysis in biomedical researches].

    Science.gov (United States)

    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

  7. Clustering analysis using Swarm Intelligence

    OpenAIRE

    Farmani, Mohammad Reza

    2016-01-01

    This thesis is concerned with the application of the swarm intelligence methods in clustering analysis of datasets. The main objectives of the thesis are ∙ Take the advantage of a novel evolutionary algorithm, called artificial bee colony, to improve the capability of K-means in finding global optimum clusters in nonlinear partitional clustering problems. ∙ Consider partitional clustering as an optimization problem and an improved antbased algorithm, named Opposition-Based A...

  8. Defining Clusters of Related Industries

    OpenAIRE

    Mercedes Delgado; Porter, Michael E.; Scott Stern

    2014-01-01

    Clusters are geographic concentrations of industries related by knowledge, skills, inputs, demand, and/or other linkages. A growing body of empirical literature has shown the positive impact of clusters on regional and industry performance, including job creation, patenting, and new business formation. There is an increasing need for cluster-based data to support research, facilitate comparisons of clusters across regions, and support policymakers and practitioners in defining regional strate...

  9. Practical Introduction to Clustering Data

    CERN Document Server

    Hartmann, Alexander K

    2016-01-01

    Data clustering is an approach to seek for structure in sets of complex data, i.e., sets of "objects". The main objective is to identify groups of objects which are similar to each other, e.g., for classification. Here, an introduction to clustering is given and three basic approaches are introduced: the k-means algorithm, neighbour-based clustering, and an agglomerative clustering method. For all cases, C source code examples are given, allowing for an easy implementation.

  10. The Assembly of Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Massive star clusters in galaxies

    CERN Document Server

    Harris, William E

    2009-01-01

    The ensemble of all star clusters in a galaxy constitutes its star cluster system. In this review, the focus of the discussion is on the ability of star clusters, particularly the systems of old massive globular clusters (GCSs), to mark the early evolutionary history of galaxies. I review current themes and key findings in GCS research, and highlight some of the outstanding questions that are emerging from recent work.

  12. On clusters and clustering from atoms to fractals

    CERN Document Server

    Reynolds, PJ

    1993-01-01

    This book attempts to answer why there is so much interest in clusters. Clusters occur on all length scales, and as a result occur in a variety of fields. Clusters are interesting scientifically, but they also have important consequences technologically. The division of the book into three parts roughly separates the field into small, intermediate, and large-scale clusters. Small clusters are the regime of atomic and molecular physics and chemistry. The intermediate regime is the transitional regime, with its characteristics including the onset of bulk-like behavior, growth and aggregation, a

  13. Recovery Rate of Clustering Algorithms

    NARCIS (Netherlands)

    Li, Fajie; Klette, Reinhard; Wada, T; Huang, F; Lin, S

    2009-01-01

    This article provides a simple and general way for defining the recovery rate of clustering algorithms using a given family of old clusters for evaluating the performance of the algorithm when calculating a family of new clusters. Under the assumption of dealing with simulated data (i.e., known old

  14. Analytical Approximations to Galaxy Clustering

    OpenAIRE

    Mo, H. J.

    1997-01-01

    We discuss some recent progress in constructing analytic approximations to the galaxy clustering. We show that successful models can be constructed for the clustering of both dark matter and dark matter haloes. Our understanding of galaxy clustering and galaxy biasing can be greatly enhanced by these models.

  15. Geographic Projection of Cluster Composites

    NARCIS (Netherlands)

    Nerbonne, J.; Bosveld-de Smet, L.M.; Kleiweg, P.; Blackwell, A.; Marriott, K.; Shimojima, A.

    2004-01-01

    A composite cluster map displays a fuzzy categorisation of geographic areas. It combines information from several sources to provide a visualisation of the significance of cluster borders. The basic technique renders the chance that two neighbouring locations are members of different clusters as the

  16. Programming with MPI on clusters

    International Nuclear Information System (INIS)

    The authors discuss the current state of development for the key aspects of MPI programming on clusters. These aspects are the evolution of the MPI Standard itself, developments in cluster hardware and system software that directly affect MPI implementations, and supporting software that facilitates the use of MPI on scalable clusters. In each case we give a brief background and summarize the current status

  17. Adaptive Clustering of Hypermedia Documents.

    Science.gov (United States)

    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…

  18. Binaries in globular clusters

    Science.gov (United States)

    Hut, Piet; Mcmillan, Steve; Goodman, Jeremy; Mateo, Mario; Phinney, E. S.; Pryor, Carlton; Richer, Harvey B.; Verbunt, Frank; Weinberg, Martin

    1992-01-01

    Recent observations have shown that globular clusters contain a substantial number of binaries most of which are believed to be primordial. We discuss different successful optical search techniques, based on radial-velocity variables, photometric variables, and the positions of stars in the color-magnitude diagram. In addition, we review searches in other wavelengths, which have turned up low-mass X-ray binaries and more recently a variety of radio pulsars. On the theoretical side, we give an overview of the different physical mechanisms through which individual binaries evolve. We discuss the various simulation techniques which recently have been employed to study the effects of a primordial binary population, and the fascinating interplay between stellar evolution and stellar dynamics which drives globular-cluster evolution.

  19. Di - lambpha cluster states

    International Nuclear Information System (INIS)

    The lightest (p, n, Λ) closed-shell hypernucleus sub(ΛΛ) sup(6)He can be considered as a most likely candidate for the unit of hypernuclear cluster structure. First the internal structure of lambpha, α sub(Λ) = sub(ΛΛ) sup(6)He, is investigated by solving the α + Λ + Λ three-body problem microscopically. The compact h. o. wave function (0 s)6 is found to be a good description for α sub(Λ). Secondly, by using the fully microscopic GCM, we have demonstrated that di - α sub(Λ) cluster states constitute a characteristic rotational band of J = 0+ -- 6+. The E2 transition rate from particle - stable 2+ to 0+ states is predicted to be 2 - order faster than the weak decay rate of this system. (author)

  20. Outskirts of Galaxy Clusters

    CERN Document Server

    Reiprich, Thomas H; Ettori, Stefano; Israel, Holger; Lovisari, Lorenzo; Molendi, Silvano; Pointecouteau, Etienne; Roncarelli, Mauro

    2013-01-01

    Until recently, only about 10% of the total intracluster gas volume had been studied with high accuracy, leaving a vast region essentially unexplored. This is now changing and a wide area of hot gas physics and chemistry awaits discovery in galaxy cluster outskirts. Also, robust large-scale total mass profiles and maps are within reach. First observational and theoretical results in this emerging field have been achieved in recent years with sometimes surprising findings. Here, we summarize and illustrate the relevant underlying physical and chemical processes and review the recent progress in X-ray, Sunyaev--Zel'dovich, and weak gravitational lensing observations of cluster outskirts, including also brief discussions of technical challenges and possible future improvements.

  1. Are megaquakes clustered?

    CERN Document Server

    Daub, Eric G; Guyer, Robert A; Johnson, Paul A

    2012-01-01

    We study statistical properties of the number of large earthquakes over the past century. We analyze the cumulative distribution of the number of earthquakes with magnitude larger than threshold M in time interval T, and quantify the statistical significance of these results by simulating a large number of synthetic random catalogs. We find that in general, the earthquake record cannot be distinguished from a process that is random in time. This conclusion holds whether aftershocks are removed or not, except at magnitudes below M = 7.3. At long time intervals (T = 2-5 years), we find that statistically significant clustering is present in the catalog for lower magnitude thresholds (M = 7-7.2). However, this clustering is due to a large number of earthquakes on record in the early part of the 20th century, when magnitudes are less certain.

  2. Tailoring and Scaling Energetic Aluminum Clusters into Cluster Assembled Materials

    Science.gov (United States)

    Smith, Jordan Cesar

    As matter decreases in size the importance of a single atom increases exponentially. The properties of clusters, molecules with less than 100 atoms, will change drastically with the addition or removal of a single atom. Clusters have been shown to have properties that mimic other elements and properties that are completely unique. Cluster assemblies could enable the tailoring of precise properties in materials, providing cheap replacements for expensive elements, or novel materials for new applications. Aluminum clusters show great potential use in many applications including energy and catalysis. This work is focused on gaining a better understanding of how geometry and electronic structure affect aluminum cluster reactivity and how useful clusters might be successfully assembled into materials. The effects of doping aluminum cluster ions with boron atoms are reported and show that the addition of a single boron atom usually stabilizes the cluster while adding more boron atoms results in a breaking of symmetry and destabilization. A new analytical technique, matrix isolation cavity ring-down spectroscopy (MICRDS) was developed to help bridge the gap between gas phase cluster studies and condensed phase cluster materials. Molecules are trapped in an inert matrix and studied using cavity ring-down spectroscopy. MICRDS has the potential to also combine clusters into small stable units that would maintain their advantageous gas phase properties.

  3. Clusters and entrepreneurship

    OpenAIRE

    Delgado, Mercedes; Porter, Michael E.; Stern, Scott, 1969-

    2010-01-01

    This article examines the role of regional clusters in regional entrepreneurship. We focus on the distinct influences of convergence and agglomeration on growth in the number of start-up firms as well as in employment in these new firms in a given region-industry. While reversion to the mean and diminishing returns to entrepreneurship at the region-industry level can result in a convergence effect, the presence of complementary economic activity creates externalities that enhance incentives a...

  4. Clusters, Governance and Sustainability

    OpenAIRE

    Neto, Paulo; Serrano, Maria Manuel

    2010-01-01

    One of the most important aspects of current economical and social reality of each local and regional territory, and very much determinative for its economic development potential, is the nature of its territorial organization of the productive processes, as well as, the characteristics, and sophistication level, of the enterprise strategies that are functioning in it. This paper seeks to contribute to the ongoing discussion on the role of clusters as engines of economic and social developmen...

  5. Astrophysics of galaxy clusters

    Science.gov (United States)

    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.

  6. Support Policies in Clusters: Prioritization of Support Needs by Cluster Members According to Cluster Life Cycle

    Directory of Open Access Journals (Sweden)

    Gulcin Salıngan

    2012-07-01

    Full Text Available Economic development has always been a moving target. Both the national and local governments have been facing the challenge of implementing the effective and efficient economic policy and program in order to best utilize their limited resources. One of the recent approaches in this area is called cluster-based economic analysis and strategy development. This study reviews key literature and some of the cluster based economic policies adopted by different governments. Based on this review, it proposes “the cluster life cycle” as a determining factor to identify the support requirements of clusters. A survey, designed based on literature review of International Cluster support programs, was conducted with 30 participants from 3 clusters with different maturity stage. This paper discusses the results of this study conducted among the cluster members in Eskişehir- Bilecik-Kütahya Region in Turkey on the requirement of the support to foster the development of related clusters.

  7. Cluster headache after orbital exenteration.

    Science.gov (United States)

    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

  8. Cluster Based Text Classification Model

    DEFF Research Database (Denmark)

    Nizamani, Sarwat; Memon, Nasrullah; Wiil, Uffe Kock

    2011-01-01

    We propose a cluster based classification model for suspicious email detection and other text classification tasks. The text classification tasks comprise many training examples that require a complex classification model. Using clusters for classification makes the model simpler and increases......, the classifier is trained on each cluster having reduced dimensionality and less number of examples. The experimental results show that the proposed model outperforms the existing classification models for the task of suspicious email detection and topic categorization on the Reuters-21578 and 20 Newsgroups...... datasets. Our model also outperforms A Decision Cluster Classification (ADCC) and the Decision Cluster Forest Classification (DCFC) models on the Reuters-21578 dataset....

  9. Multiscale hierarchical support vector clustering

    Science.gov (United States)

    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.

  10. Silicon clusters: Chemistry and structure

    Energy Technology Data Exchange (ETDEWEB)

    Jarrold, M.F.; Ray, U.; Ijiri, Y. (AT and T Bell Labs., Murray Hill, NJ (USA))

    1991-01-01

    The chemical reactions of size selected silicon cluster ions (containing up to 70 atoms) have been studied with a number of different reagents using injected ion drift tube techniques. Both kinetic and equilibrium measurements have been performed as a function of temperature, and the influence of cluster annealing on chemical reactivity explored. Unlike metal clusters, where bulk behavior appears to be approached with around 30 atoms, large silicon clusters (n up to 70) are much less reactive than bulk silicon surfaces. These results suggest that the clusters in the size range examined here are not small crystals of bulk silicon, but have compact, high coordination number structures with few dangling bonds. (orig.).

  11. Clustering Methodologies for Software Engineering

    Directory of Open Access Journals (Sweden)

    Mark Shtern

    2012-01-01

    Full Text Available The size and complexity of industrial strength software systems are constantly increasing. This means that the task of managing a large software project is becoming even more challenging, especially in light of high turnover of experienced personnel. Software clustering approaches can help with the task of understanding large, complex software systems by automatically decomposing them into smaller, easier-to-manage subsystems. The main objective of this paper is to identify important research directions in the area of software clustering that require further attention in order to develop more effective and efficient clustering methodologies for software engineering. To that end, we first present the state of the art in software clustering research. We discuss the clustering methods that have received the most attention from the research community and outline their strengths and weaknesses. Our paper describes each phase of a clustering algorithm separately. We also present the most important approaches for evaluating the effectiveness of software clustering.

  12. Statistics of sunspot group clusters

    Directory of Open Access Journals (Sweden)

    Getko Ryszarda

    2013-03-01

    Full Text Available The Zubrzycki method is utilized to find all sunspot groups which are close to each other during each Carrington rotation. The sunspot group areas and their positions for the years 1874–2008 are used. The descending, the ascending and the maximum phases of solar cycles for each solar hemisphere are considered separately. To establish the size of the region D where the clusters are searched, the correlation function dependent on the distance between two groups is applied. The method estimates the weighted area of each cluster. The weights dependent on the correlation function of distances between sunspot groups created each cluster. For each cluster the weighted position is also evaluated. The weights dependent on the areas of sunspot groups created a given cluster. The number distribution of the sunspot groups created each cluster and the cluster statistics within different phases of the 11-year cycle and within all considered solar cycles are also presented.

  13. Convex clustering: an attractive alternative to hierarchical clustering.

    Directory of Open Access Journals (Sweden)

    Gary K Chen

    2015-05-01

    Full Text Available 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/.

  14. Web Fuzzy Clustering and a Case Study

    Institute of Scientific and Technical Information of China (English)

    LIU Mao-fu; HE Jing; HE Yan-xiang; HU Hui-jun

    2004-01-01

    We combine the web usage mining and fuzzy clustering and give the concept of web fuzzy clustering, and then put forward the web fuzzy clustering processing model which is discussed in detail. Web fuzzy clustering can be used in the web users clustering and web pages clustering. In the end, a case study is given and the result has proved the feasibility of using web fuzzy clustering in web pages clustering.

  15. Hadoop cluster deployment

    CERN Document Server

    Zburivsky, Danil

    2013-01-01

    This book is a step-by-step tutorial filled with practical examples which will show you how to build and manage a Hadoop cluster along with its intricacies.This book is ideal for database administrators, data engineers, and system administrators, and it will act as an invaluable reference if you are planning to use the Hadoop platform in your organization. It is expected that you have basic Linux skills since all the examples in this book use this operating system. It is also useful if you have access to test hardware or virtual machines to be able to follow the examples in the book.

  16. Convex Decomposition Based Cluster Labeling Method for Support Vector Clustering

    Institute of Scientific and Technical Information of China (English)

    Yuan Ping; Ying-Jie Tian; Ya-Jian Zhou; Yi-Xian Yang

    2012-01-01

    Support vector clustering (SVC) is an important boundary-based clustering algorithm in multiple applications for its capability of handling arbitrary cluster shapes. However,SVC's popularity is degraded by its highly intensive time complexity and poor label performance.To overcome such problems,we present a novel efficient and robust convex decomposition based cluster labeling (CDCL) method based on the topological property of dataset.The CDCL decomposes the implicit cluster into convex hulls and each one is comprised by a subset of support vectors (SVs).According to a robust algorithm applied in the nearest neighboring convex hulls,the adjacency matrix of convex hulls is built up for finding the connected components; and the remaining data points would be assigned the label of the nearest convex hull appropriately.The approach's validation is guaranteed by geometric proofs.Time complexity analysis and comparative experiments suggest that CDCL improves both the efficiency and clustering quality significantly.

  17. Clustering and Classification via Cluster-Weighted Factor Analyzers

    OpenAIRE

    Subedi, Sanjeena; PUNZO, ANTONIO; Ingrassia, Salvatore; McNicholas, Paul D.

    2012-01-01

    In model-based clustering and classification, the cluster-weighted model constitutes a convenient approach when the random vector of interest constitutes a response variable Y and a set p of explanatory variables X. However, its applicability may be limited when p is high. To overcome this problem, this paper assumes a latent factor structure for X in each mixture component. This leads to the cluster-weighted factor analyzers (CWFA) model. By imposing constraints on the variance of Y and the ...

  18. Brightest Cluster Galaxies and Core Gas Density in REXCESS Clusters

    CERN Document Server

    Haarsma, D B; Donahue, M; Bruch, S; Boehringer, H; Croston, J H; Pratt, G W; Voit, G M; Arnaud, M; Pierini, D

    2009-01-01

    We investigate the relationship between brightest cluster galaxies (BCGs) and their host clusters using a sample of nearby galaxy clusters from the Representative XMM-Newton Cluster Structure Survey (REXCESS). The sample was imaged with the Southern Observatory for Astrophysical Research (SOAR) in R band to investigate the mass of the old stellar population. Using a metric radius of 12h^-1 kpc, we find that the BCG luminosity depends weakly on overall cluster mass as L_BCG \\propto M_cl^0.18+-0.07, consistent with previous work. We found that 90% of the BCGs are located within 0.035 R_500 of the peak of the X-ray emission, including all of the cool core (CC) clusters. We also found an unexpected correlation between the BCG metric luminosity and the core gas density for non-cool core (non-CC) clusters, following a power law of n_e \\propto L_BCG^2.7+-0.4 (where n_e is measured at 0.008 R_500). The correlation is not easily explained by star formation (which is weak in non-CC clusters) or overall cluster mass (wh...

  19. Query Results Clustering by Extending SPARQL with CLUSTER BY

    Science.gov (United States)

    Ławrynowicz, Agnieszka

    The task of dynamic clustering of the search results proved to be useful in the Web context, where the user often does not know the granularity of the search results in advance. The goal of this paper is to provide a declarative way for invoking dynamic clustering of the results of queries submitted over Semantic Web data. To achieve this goal the paper proposes an approach that extends SPARQL by clustering abilities. The approach introduces a new statement, CLUSTER BY, into the SPARQL grammar and proposes semantics for such extension.

  20. Decaying neutrinos in galaxy clusters

    Science.gov (United States)

    Melott, Adrian L.; Splinter, Randall J.; Persic, Massimo; Salucci, Paolo

    1994-01-01

    Davidsen et al. (1991) have argued that the failure to detect UV photons from the dark matter (DM) in cluster A665 excludes the decaying neutrino hypothesis. Sciama et al. (1993) argued that because of high central concentration the DM in that cluster must be baryonic. We study the DM profile in clusters of galaxies simulated using the Harrison-Zel'dovich spectrum of density fluctuations, and an amplitude previously derived from numerical simulations (Melott 1984b; Anninos et al. 1991) and in agreement with microwave background fluctuations (Smoot et al. 1992). We find that with this amplitude normalization cluster neutrino DM densities are comparable to observed cluster DM values. We conclude that given this normalization, the cluster DM should be at least largely composed of neutrinos. The constraint of Davidsen et al. can be somewhat weakened by the presence of baryonic DM; but it cannot be eliminated given our assumptions.

  1. Graph partitioning advance clustering technique

    CERN Document Server

    Madhulatha, T Soni

    2012-01-01

    Clustering is a common technique for statistical data analysis, Clustering is the process of grouping the data into classes or clusters so that objects within a cluster have high similarity in comparison to one another, but are very dissimilar to objects in other clusters. Dissimilarities are assessed based on the attribute values describing the objects. Often, distance measures are used. Clustering is an unsupervised learning technique, where interesting patterns and structures can be found directly from very large data sets with little or none of the background knowledge. This paper also considers the partitioning of m-dimensional lattice graphs using Fiedler's approach, which requires the determination of the eigenvector belonging to the second smallest Eigenvalue of the Laplacian with K-means partitioning algorithm.

  2. Cosmology with clusters of galaxies

    CERN Document Server

    Bahcall, Neta A

    1995-01-01

    Rich clusters of galaxies, the largest virialized systems known, provide a powerful tool for the study of cosmology. Some of the fundamental questions that can be addressed with clusters of galaxies include: how did galaxies and large-scale structure form and evolve? What is the amount, composition and distribution of matter in the universe? I review some of the studies utilizing clusters of galaxies to investigare, among others: - The dark matter on clusters scale and the mean mass-density of the universe; - The large-scale structure of the universe; - The peculiar velocity field on large scales; - The mass-function of groups and clusters of galaxies; - The constraints placed on specific cosmological models using the cluster data.

  3. Cluster synchronization in oscillatory networks

    Science.gov (United States)

    Belykh, Vladimir N.; Osipov, Grigory V.; Petrov, Valentin S.; Suykens, Johan A. K.; Vandewalle, Joos

    2008-09-01

    Synchronous behavior in networks of coupled oscillators is a commonly observed phenomenon attracting a growing interest in physics, biology, communication, and other fields of science and technology. Besides global synchronization, one can also observe splitting of the full network into several clusters of mutually synchronized oscillators. In this paper, we study the conditions for such cluster partitioning into ensembles for the case of identical chaotic systems. We focus mainly on the existence and the stability of unique unconditional clusters whose rise does not depend on the origin of the other clusters. Also, conditional clusters in arrays of globally nonsymmetrically coupled identical chaotic oscillators are investigated. The design problem of organizing clusters into a given configuration is discussed.

  4. Active matter clusters at interfaces

    CERN Document Server

    Copenhagen, Katherine

    2016-01-01

    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), wher...

  5. Connecting Remote Clusters with ATM

    Energy Technology Data Exchange (ETDEWEB)

    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. Relativistic Effect in Galaxy Clustering

    OpenAIRE

    Yoo, Jaiyul

    2014-01-01

    The general relativistic description of galaxy clustering provides a complete and unified treatment of all the effects in galaxy clustering such as the redshift-space distortion, gravitational lensing, Sachs-Wolfe effects, and their relativistic effects. In particular, the relativistic description resolves the gauge issues in the standard Newtonian description of galaxy clustering by providing the gauge-invariant expression for the observed galaxy number density. The relativistic effect in ga...

  7. Light cluster production at NICA

    CERN Document Server

    Bastian, N -U; Blaschke, D; Danielewicz, P; Ivanov, Yu B; Karpenko, Iu; Röpke, G; Rogachevsky, O; Wolter, H H

    2016-01-01

    Light cluster production at the NICA accelerator complex offers unique possibilities to use these states as "rare probes" of in-medium characteristics such as phase space occupation and early flow. In order to explain this statement, in this contribution theoretical considerations from the nuclear statistical equilibrium model and from a quantum statistical model of cluster production are supplemented with a discussion of a transport model for light cluster formation and with results from hydrodynamic simulations combined with the coalescence model.

  8. Cluster banding heat source model

    Institute of Scientific and Technical Information of China (English)

    Zhang Liguo; Ji Shude; Yang Jianguo; Fang Hongyuan; Li Yafan

    2006-01-01

    Concept of cluster banding heat source model is put forward for the problem of overmany increment steps in the process of numerical simulation of large welding structures, and expression of cluster banding heat source model is deduced based on energy conservation law.Because the expression of cluster banding heat source model deduced is suitable for random weld width, quantitative analysis of welding stress field for large welding structures which have regular welds can be made quickly.

  9. Synchronization in complex clustered networks

    Institute of Scientific and Technical Information of China (English)

    HUANG Liang; LAI Ying-Cheng; Kwangho PARK; WANG Xingang; LAI Choy Heng; Robert A. GATENBY

    2007-01-01

    Synchronization in complex networks has been an active area of research in recent years. While much effort has been devoted to networks with the small-world and scale-free topology, structurally they are often assumed to have a single, densely connected component. Recently it has also become apparent that many networks in social, biological, and tech-nological systems are clustered, as characterized by a number (or a hierarchy) of sparsely linked clusters, each with dense and complex internal connections. Synchronization is funda-mental to the dynamics and functions of complex clustered networks, but this problem has just begun to be addressed. This paper reviews some progress in this direction by focus-ing on the interplay between the clustered topology and net-work synchronizability. In particular, there are two parame-ters characterizing a clustered network: the intra-cluster and the inter-cluster link density. Our goal is to clarify the roles of these parameters in shaping network synchronizability. By using theoretical analysis and direct numerical simulations of oscillator networks, it is demonstrated that clustered net-works with random inter-cluster links are more synchroniz-able, and synchronization can be optimized when inter-cluster and intra-cluster links match. The latter result has one coun-terintuitive implication: more links, if placed improperly, can actually lead to destruction of synchronization, even though such links tend to decrease the average network distance. It is hoped that this review will help attract attention to the fun-damental problem of clustered structures/synchronization in network science.

  10. Cluster headache and intracranial aneurysm

    OpenAIRE

    Valença, Marcelo Moraes; Andrade-Valença, Luciana P. A.; Martins, Carolina; de Aragão, Maria Fátima Vasco; Batista, Laécio Leitão; Peres, Mario Fernando Prieto; da Silva, Wilson Farias

    2007-01-01

    In the present study we describe the cases of two patients with cluster-like headache related to intracranial carotid artery aneurysm. One of these patients responded to verapamil prescription with headache resolution. In both cases the surgical clipping of the aneurysm resolved the cluster pain. These findings strongly suggest a pathophysiological link between the two conditions. The authors discuss the potential pathophysiological mechanisms underlying cluster-like headache due to intracran...

  11. Collective thermoregulation in bee clusters

    OpenAIRE

    Ocko, Samuel A; Mahadevan, L.

    2014-01-01

    Swarming is an essential part of honeybee behaviour, wherein thousands of bees cling onto each other to form a dense cluster that may be exposed to the environment for several days. This cluster has the ability to maintain its core temperature actively without a central controller, and raises the question of how this is achieved. We suggest that the swarm cluster is akin to an active porous structure whose functional requirement is to adjust to outside conditions by varying its porosity to co...

  12. Knowledge Evolution in Industrial Clusters

    OpenAIRE

    Langfeng Wang; Qunhong Shen

    2009-01-01

    Character of knowledge management conducted in industrial clusters is different from entity of enterpresis and socail public deparment because of distinction in management objection. Many scholars was attracted to reseach knowledge management for enterprises, knowledge management in industrial clusters lack durable study in depth. This paper seeks to lay out an organizational foundation to a theory of industrial clusters and present the necessary, factors, process and characters of knowledge ...

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

    Science.gov (United States)

    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

  14. Brightest Cluster Galaxies and Core Gas Density in REXCESS Clusters

    Science.gov (United States)

    Haarsma, Deborah B.; Leisman, Luke; Donahue, Megan; Bruch, Seth; Böhringer, Hans; Croston, Judith H.; Pratt, Gabriel W.; Voit, G. Mark; Arnaud, Monique; Pierini, Daniele

    2010-04-01

    We investigate the relationship between brightest cluster galaxies (BCGs) and their host clusters using a sample of nearby galaxy clusters from the Representative XMM-Newton Cluster Structure Survey. The sample was imaged with the Southern Observatory for Astrophysical Research in R band to investigate the mass of the old stellar population. Using a metric radius of 12 h -1 kpc, we found that the BCG luminosity depends weakly on overall cluster mass as L BCG vprop M 0.18±0.07 cl, consistent with previous work. We found that 90% of the BCGs are located within 0.035 r 500 of the peak of the X-ray emission, including all of the cool core (CC) clusters. We also found an unexpected correlation between the BCG metric luminosity and the core gas density for non-cool-core (non-CC) clusters, following a power law of ne vprop L 2.7±0.4 BCG (where ne is measured at 0.008 r 500). The correlation is not easily explained by star formation (which is weak in non-CC clusters) or overall cluster mass (which is not correlated with core gas density). The trend persists even when the BCG is not located near the peak of the X-ray emission, so proximity is not necessary. We suggest that, for non-CC clusters, this correlation implies that the same process that sets the central entropy of the cluster gas also determines the central stellar density of the BCG, and that this underlying physical process is likely to be mergers.

  15. Active matter clusters at interfaces.

    Science.gov (United States)

    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.

  16. Relativistic Binaries in Globular Clusters

    Directory of Open Access Journals (Sweden)

    Benacquista Matthew J.

    2006-02-01

    Full Text Available The galactic population of globular clusters are old, dense star systems, with a typical cluster containing 10^4 - 10^7 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss the theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution which lead to relativistic binaries, and current and possible future observational evidence for this population. Globular cluster evolution will focus on the properties that boost the production of hard binary systems and on the tidal interactions of the galaxy with the cluster, which tend to alter the structure of the globular cluster with time. The interaction of the components of hard binary systems alters the evolution of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker-Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.

  17. Mechanical Resonance of embedded cluster

    CERN Document Server

    Wen, Z; Wen, Zhenying; Zhao, Hong

    2004-01-01

    Embedded clusters, which are embedded in bulk materials and different from the surroundings in structures, should be common in materials. This paper studies resonance of such clusters. This work is stimulated by a recent experimental observation that some localized clusters behavior like fluid at the mesoscopic scale in many solid materials [Science in China(Series B). 46, 176 (2003)]. We argue that the phenomenon is just a vivid illustration of resonance of embedded clusters, driven by ubiquitous microwaves. Because the underlying mechanism is fundamental and embedded structures are usual, the phenomenon would have great significance in material physics.

  18. Optical properties of cluster plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kishimoto, Yasuaki; Tajima, Toshiki [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment; Downer, M.C.

    1998-03-01

    It is shown that unlike a gas plasma or an electron plasma in a metal, an ionized clustered material (`cluster plasma`) permits propagation below the plasma cut-off of electromagnetic (EM) waves whose phase velocity is close to but below the speed of light. This results from the excitation of a plasma oscillation mode (and/or polarization mode) through the cluster surface which does not exist in usual gaseous plasma. The existence of this new optical mode, cluster mode, is confirmed via numerical simulation. (author)

  19. Privacy-preserving distributed clustering

    DEFF Research Database (Denmark)

    Erkin, Zekeriya; Veugen, Thijs; Toft, Tomas;

    2013-01-01

    Clustering is a very important tool in data mining and is widely used in on-line services for medical, financial and social environments. The main goal in clustering is to create sets of similar objects in a data set. The data set to be used for clustering can be owned by a single entity, or in s...... provider with computations. Experimental results clearly indicate that the work we present is an efficient way of deploying a privacy-preserving clustering algorithm in a distributed manner....

  20. Active matter clusters at interfaces.

    Directory of Open Access Journals (Sweden)

    Katherine eCopenhagen

    2016-03-01

    Full Text Available 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.

  1. Integrative cluster analysis in bioinformatics

    CERN Document Server

    Abu-Jamous, Basel; Nandi, Asoke K

    2015-01-01

    Clustering techniques are increasingly being put to use in the analysis of high-throughput biological datasets. Novel computational techniques to analyse high throughput data in the form of sequences, gene and protein expressions, pathways, and images are becoming vital for understanding diseases and future drug discovery. This book details the complete pathway of cluster analysis, from the basics of molecular biology to the generation of biological knowledge. The book also presents the latest clustering methods and clustering validation, thereby offering the reader a comprehensive review o

  2. The Confucian Asian cluster

    Directory of Open Access Journals (Sweden)

    Ionel Sergiu Pirju

    2013-11-01

    Full Text Available The Confucian Asian cluster consists of China, Hong Kong, Japan, Singapore, South Korea, and Taiwan. Confucian tradition countries were defined by achieving a consistent performance in the global economy, they still representing the major competitors in the EU and North American countries. Their progress is defined by a great national management that was able to influence beneficial management systems applied in organizations, these rules characterized by authority; aims to ensure the confidence in business. This article will present the intercultural values characterizing it, the leadership style and also tracing major macroeconomic considerations. The research is synchronic, analysing the contemporary situation of these countries, and the analysis will be interdisciplinary exploratory, identifying specific regional cultural elements.

  3. Herd Clustering: A synergistic data clustering approach using collective intelligence

    KAUST Repository

    Wong, Kachun

    2014-10-01

    Traditional data mining methods emphasize on analytical abilities to decipher data, assuming that data are static during a mining process. We challenge this assumption, arguing that we can improve the analysis by vitalizing data. In this paper, this principle is used to develop a new clustering algorithm. Inspired by herd behavior, the clustering method is a synergistic approach using collective intelligence called Herd Clustering (HC). The novel part is laid in its first stage where data instances are represented by moving particles. Particles attract each other locally and form clusters by themselves as shown in the case studies reported. To demonstrate its effectiveness, the performance of HC is compared to other state-of-the art clustering methods on more than thirty datasets using four performance metrics. An application for DNA motif discovery is also conducted. The results support the effectiveness of HC and thus the underlying philosophy. © 2014 Elsevier B.V.

  4. Meaningful Clustered Forest: an Automatic and Robust Clustering Algorithm

    CERN Document Server

    Tepper, Mariano; Almansa, Andrés

    2011-01-01

    We propose a new clustering method that can be regarded as a numerical method to compute the proximity gestalt. The method analyzes edge length statistics in the MST of the dataset and provides an a contrario cluster detection criterion. The approach is fully parametric on the chosen distance and can detect arbitrarily shaped clusters. The method is also automatic, in the sense that only a single parameter is left to the user. This parameter has an intuitive interpretation as it controls the expected number of false detections. We show that the iterative application of our method can (1) provide robustness to noise and (2) solve a masking phenomenon in which a highly populated and salient cluster dominates the scene and inhibits the detection of less-populated, but still salient, clusters.

  5. Tune Your Brown Clustering, Please

    DEFF Research Database (Denmark)

    Derczynski, Leon; Chester, Sean; Bøgh, Kenneth Sejdenfaden

    2015-01-01

    unexplored. Accordingly, we present information for practitioners on the behaviour of Brown clustering in order to assist hyper-parametre tuning, in the form of a theoretical model of Brown clustering utility. This model is then evaluated empirically in two sequence labelling tasks over two text types. We...

  6. Bayesian Agglomerative Clustering with Coalescents

    OpenAIRE

    Teh, Yee Whye; Daumé III, Hal; Roy, Daniel

    2009-01-01

    We introduce a new Bayesian model for hierarchical clustering based on a prior over trees called Kingman's coalescent. We develop novel greedy and sequential Monte Carlo inferences which operate in a bottom-up agglomerative fashion. We show experimentally the superiority of our algorithms over others, and demonstrate our approach in document clustering and phylolinguistics.

  7. FunGeneClusterS

    DEFF Research Database (Denmark)

    Vesth, Tammi Camilla; Brandl, Julian; Andersen, Mikael Rørdam

    2016-01-01

    Secondary metabolites of fungi are receiving an increasing amount of interest due to their prolific bioactivities and the fact that fungal biosynthesis of secondary metabolites often occurs from co-regulated and co-located gene clusters. This makes the gene clusters attractive for synthetic biology...

  8. Chemical exposure and leukemia clusters

    International Nuclear Information System (INIS)

    This paper draws attention to the heterogeneous distribution of leukemia in childhood and in adults. The topic of cluster reports and generalized clustering is addressed. These issues are applied to what is known of the risk factor for both adult and childhood leukemia. Finally, the significance of parental occupational exposure and childhood leukemia is covered. (author). 23 refs

  9. The Nordic Mobile Telecommunication Cluster

    DEFF Research Database (Denmark)

    Jørgensen, Ulrik

    2000-01-01

    A study of the historic role of the Nordic mobile telephone and telecommunications cluster and its background in both coordinated innovation policies and societal developments in Scandinavia.......A study of the historic role of the Nordic mobile telephone and telecommunications cluster and its background in both coordinated innovation policies and societal developments in Scandinavia....

  10. Yellow supergiants in open clusters

    International Nuclear Information System (INIS)

    Superluminous giant stars (SLGs) have been reported in young globular clusters in the Large Magellanic Cloud (LMC). These stars appear to be in the post-asymptotic-giant-branch phase of evolution. This program was an investigation of galactic SLG candidates in open clusters, which are more like the LMC young globular clusters. These were chosen because luminosity, mass, and age determinations can be made for members since cluster distances and interstellar reddenings are known. Color magnitude diagrams were searched for candidates, using the same selection criteria as for SLGs in the LMC. Classification spectra were obtained of 115 program stars from McGraw-Hill Observatory and of 68 stars from Cerro Tololo Inter-American Observatory Chile. These stars were visually classified on the MK system using spectral scans of standard stars taken at the respective observations. Published information was combined with this program's data for 83 stars in 30 clusters. Membership probabilities were assigned to these stars, and the clusters were analyzed according to age. It was seen that the intrinsically brightest supergiants are found in the youngest clusters. With increasing cluster age, the absolute luminosities attained by the supergiants decline. Also, it appears that the evolutionary tracks of luminosity class II stars are more similar to those of class I than of class III

  11. Cold fronts in galaxy clusters

    CERN Document Server

    Ghizzardi, Simona; Molendi, Silvano

    2010-01-01

    Cold fronts have been observed in a large number of galaxy clusters. Understanding their nature and origin is of primary importance for the investigation of the internal dynamics of clusters. To gain insight on the nature of these features, we carry out a statistical investigation of their occurrence in a sample of galaxy clusters observed with XMM-Newton and we correlate their presence with different cluster properties. We have selected a sample of 45 clusters starting from the B55 flux limited sample by Edge et al. (1990) and performed a systematic search of cold fronts. We find that a large fraction of clusters host at least one cold front. Cold fronts are easily detected in all systems that are manifestly undergoing a merger event in the plane of the sky while the presence of such features in the remaining clusters is related to the presence of a steep entropy gradient, in agreement with theoretical expectations. Assuming that cold fronts in cool core clusters are triggered by minor merger events, we esti...

  12. An Exact Relaxation of Clustering

    DEFF Research Database (Denmark)

    Mørup, Morten; Hansen, Lars Kai

    2009-01-01

    of clustering problems such as the K-means objective and pairwise clustering as well as graph partition problems, e.g., for community detection in complex networks. In particular we show that a relaxation to the simplex can be given for which the extreme solutions are stable hard assignment solutions and vice......Continuous relaxation of hard assignment clustering problems can lead to better solutions than greedy iterative refinement algorithms. However, the validity of existing relaxations is contingent on problem specific fuzzy parameters that quantify the level of similarity between the original...... versa. Based on the new relaxation we derive the SR-clustering algorithm that has the same complexity as traditional greedy iterative refinement algorithms but leading to significantly better partitions of the data. A Matlab implementation of the SR-clustering algorithm is available for download....

  13. Protonated water clusters in TPC's

    Science.gov (United States)

    Kaya, Yunus; Kalkan, Yalçın; Veenhof, Rob

    2016-07-01

    Water vapour is added to the ALICE TPC gas to enhance its stability. These polar molecules create large protonated water clusters around a H+ core. In this context, the reactions H3O+(H2 O) n - 1 +H2 O →H3O+(H2O)n (n=1-9) were studied in the gas phase. Structures for these clusters are suggested and the most stable structures for each cluster size are shown. The thermodynamic parameters Δ Hn-1,n0, Δ Gn-1,n0, Δ Sn-1,n0 and equilibrium constants K n - 1 , n for the reaction were calculated to determine the size of the water clusters. The results are close to experimental data found in the literature. Protonated water clusters at stp have a size of 6-9 which corresponds to a mass of 127.1 - 181.2 g / mole.

  14. The inner Galactic globular clusters

    Directory of Open Access Journals (Sweden)

    Mateo M.

    2013-03-01

    Full Text Available Galactic globular clusters located towards the inner regions of the Milky Way have been historically neglected, mainly due to the difficulties caused by the presence of an elevated extinction by foreground dust, and high field star densities along the lines of sight where most of them lie. To overcome these difficulties we have developed a new method to map the differential extinction suffered by these clusters, which was successfully applied to a sample of moderately-extincted, luminous, extended, inner Galactic globular clusters observed in the optical, for which we have been able to determine more accurate physical parameters. For the most extincted inner Galactic globular clusters, near-infrared wavelengths provide a more suitable window for their study. The VVV survey, which is currently observing the central regions of the Milky Way at these wavelengths, will provide a comprehensive view, from the inner regions out to their tidal radii and beyond, of most of these globular clusters.

  15. Seven poor clusters of galaxies

    Science.gov (United States)

    Beers, T. C.; Geller, M. J.; Huchra, J. P.; Latham, D. W.; Davis, R. J.

    1984-01-01

    The measurement of 83 new redshifts from galaxies in the region of seven of the poor clusters of galaxies identified by Morgan et al (1975) and Albert et al (1977) has been followed by an estimation of cluster masses through the application of both the virial theorem and the projected mas method. For each system, these two estimates are consistent. For the two clusters with highest X-ray luminosities, the line-of-sight velocity dispersions are about 700 km/sec, while for the five other clusters, the dispersions are of the order of less than about 370 km/sec. The D or cD galaxy in each poor cluster is at the kinematic center of each system.

  16. High Dimensional Data Clustering Using Fast Cluster Based Feature Selection

    Directory of Open Access Journals (Sweden)

    Karthikeyan.P

    2014-03-01

    Full Text Available Feature selection involves identifying a subset of the most useful features that produces compatible results as the original entire set of features. A feature selection algorithm may be evaluated from both the efficiency and effectiveness points of view. While the efficiency concerns the time required to find a subset of features, the effectiveness is related to the quality of the subset of features. Based on these criteria, a fast clustering-based feature selection algorithm (FAST is proposed and experimentally evaluated in this paper. The FAST algorithm works in two steps. In the first step, features are divided into clusters by using graph-theoretic clustering methods. In the second step, the most representative feature that is strongly related to target classes is selected from each cluster to form a subset of features. Features in different clusters are relatively independent; the clustering-based strategy of FAST has a high probability of producing a subset of useful and independent features. To ensure the efficiency of FAST, we adopt the efficient minimum-spanning tree (MST using the Kruskal‟s Algorithm clustering method. The efficiency and effectiveness of the FAST algorithm are evaluated through an empirical study. Index Terms—

  17. Cluster-lensing: A Python Package for Galaxy Clusters & Miscentering

    CERN Document Server

    Ford, Jes

    2016-01-01

    We describe a new open source package for calculating properties of galaxy clusters, including NFW halo profiles with and without the effects of cluster miscentering. This pure-Python package, cluster-lensing, provides well-documented and easy-to-use classes and functions for calculating cluster scaling relations, including mass-richness and mass-concentration relations from the literature, as well as the surface mass density $\\Sigma(R)$ and differential surface mass density $\\Delta\\Sigma(R)$ profiles, probed by weak lensing magnification and shear. Galaxy cluster miscentering is especially a concern for stacked weak lensing shear studies of galaxy clusters, where offsets between the assumed and the true underlying matter distribution can lead to a significant bias in the mass estimates if not accounted for. This software has been developed and released in a public GitHub repository, and is licensed under the permissive MIT license. The cluster-lensing package is archived on Zenodo (Ford 2016). Full documenta...

  18. Radio Bubbles in Clusters

    CERN Document Server

    Dunn, R J H; Taylor, G B

    2005-01-01

    We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with Ghz radio emission, to our sample, and also investigating ``ghost bubbles,'' i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies within the range 1 < k/f < 1000. In the assumption that there is pressure equilibrium between the radio-emitting plasma and the surrounding thermal X-ray gas, none of the radio lobes has equipartition between the relativistic particles and the magnetic field. A Monte-Carlo simulation of the data led to the conclusion that there are not enough bubbles present in the current sample to be able to determine the shape of the population. An analysis of the ghost bubbles in our sample showed that on the whole they have high...

  19. SACS: Spitzer Archival Cluster Survey

    Science.gov (United States)

    Stern, Daniel

    Emerging from the cosmic web, galaxy clusters are the most massive gravitationally bound structures in the universe. Thought to have begun their assembly at z > 2, clusters provide insights into the growth of large-scale structure as well as the physics that drives galaxy evolution. Understanding how and when the most massive galaxies assemble their stellar mass, stop forming stars, and acquire their observed morphologies in these environments remain outstanding questions. The redshift range 1.3 imaging or from X-ray surveys. Mid-infrared (MIR) imaging with the IRAC camera on board of the Spitzer Space Telescope has changed the landscape. High-redshift clusters are easily identified in the MIR due to a combination of the unique colors of distant galaxies and a negative k-correction in the 3-5 μm range which makes such galaxies bright. Even 90-sec observations with Spitzer/IRAC, a depth which essentially all extragalactic observations in the archive achieve, is sufficient to robustly detect overdensities of L* galaxies out to z~2. Here we request funding to embark on a ambitious scientific program, the “SACS: Spitzer Archival Cluster Survey”, a comprehensive search for the most distant galaxy clusters in all Spitzer/IRAC extragalactic pointings available in the archive. With the SACS we aim to discover ~2000 of 1.3 < z < 2.5 clusters, thus provide the ultimate catalog for high-redshift MIR selected clusters: a lasting legacy for Spitzer. The study we propose will increase by more than a factor of 10 the number of high-redshift clusters discovered by all previous surveys combined, providing a high-purity, uniform sample. Matching the Spitzer/IRAC-selected clusters with data at similar and longer wavelengths available in the archive (WISE 3- 5μm, Spitzer/MIPS 24μm or Herschel/SPIRE 250μm data) we will be also able to study the dependence on the environment of star formation and AGN activity out to z~2, and to study the effect of star-forming galaxies and AGNs

  20. THE EXTENDED VIRGO CLUSTER CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Suk; Rey, Soo-Chang; Lee, Youngdae; Chung, Jiwon; Pak, Mina; Yi, Wonhyeong; Lee, Woong [Department of Astronomy and Space Science, Chungnam National University, 99 Daehak-ro, Daejeon 305-764 (Korea, Republic of); Jerjen, Helmut [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Lisker, Thorsten [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg (ZAH), Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Sung, Eon-Chang [Korea Astronomy and Space Science institute, 776 Daedeokdae-ro, Daejeon 305-348 (Korea, Republic of)

    2015-01-01

    We present a new catalog of galaxies in the wider region of the Virgo cluster, based on the Sloan Digital Sky Survey (SDSS) Data Release 7. The Extended Virgo Cluster Catalog (EVCC) covers an area of 725 deg{sup 2} or 60.1 Mpc{sup 2}. It is 5.2 times larger than the footprint of the classical Virgo Cluster Catalog (VCC) and reaches out to 3.5 times the virial radius of the Virgo cluster. We selected 1324 spectroscopically targeted galaxies with radial velocities less than 3000 km s{sup –1}. In addition, 265 galaxies that have been overlooked in the SDSS spectroscopic survey but have available redshifts in the NASA Extragalactic Database are also included. Our selection process secured a total of 1589 galaxies, 676 of which are not included in the VCC. The certain and possible cluster members are defined by means of redshift comparison with a cluster infall model. We employed two independent and complementary galaxy classification schemes: the traditional morphological classification based on the visual inspection of optical images and a characterization of galaxies from their spectroscopic features. SDSS u, g, r, i, and z passband photometry of all EVCC galaxies was performed using Source Extractor. We compare the EVCC galaxies with the VCC in terms of morphology, spatial distribution, and luminosity function. The EVCC defines a comprehensive galaxy sample covering a wider range in galaxy density that is significantly different from the inner region of the Virgo cluster. It will be the foundation for forthcoming galaxy evolution studies in the extended Virgo cluster region, complementing ongoing and planned Virgo cluster surveys at various wavelengths.

  1. Second generation stellar disks in Globular Clusters and cluster ellipticities

    CERN Document Server

    Mastrobuono-Battisti, Alessandra

    2015-01-01

    Globular clusters (GCs) and Nuclear Stellar Clusters (NSCs) are typically composed by several stellar generations, characterized by different ages and chemical compositions. The youngest populations in NSCs appear to reside in disk-like structures, as observed in our Galaxy and in M31. Gas infall followed by formation of second generation (SG) stars in GCs may similarly form disk-like structures in the clusters nuclei. Here we explore this possibility and follow the long term evolution of stellar disks embedded in GCs, and study their affects on the evolution of the clusters. We study disks with different masses by means of detailed N-body simulations and explore their morphological and kinematic signatures on the GC structures. We find that as a second generation disk relaxes, the old, first generation, stellar population flattens and becomes more radially anisotropic, making the GC structure become more elliptical. The second generation stellar population is characterized by a lower velocity dispersion, and...

  2. Herschel photometry of brightest cluster galaxies in cooling flow clusters

    CERN Document Server

    Edge, A C; Mittal, R; Allen, S W; Baum, S A; Boehringer, H; Bregman, J N; Bremer, M N; Combes, F; Crawford, C S; Donahue, M; Egami, E; Fabian, A C; Hamer, S L; Hatch, N A; Jaffe, W; Johnstone, R M; McNamara, B R; O'Dea, C P; Popesso, P; Quillen, A C; Salome, P; Sarazin, C L; Voit, G M; Wilman, R J; Wise, M W

    2010-01-01

    The dust destruction timescales in the cores of clusters of galaxies are relatively short given their high central gas densities. However, substantial mid-infrared and sub-mm emission has been detected in many brightest cluster galaxies. In this letter we present Herschel PACS and SPIRE photometry of the brightest cluster galaxy in three strong cooling flow clusters, A1068, A2597 and Zw3146. This photometry indicates that a substantial mass of cold dust is present (>3 x 10^7 Mo) at temperatures significantly lower (20-28K) than previously thought based on limited MIR and/or sub-mm results. The mass and temperature of the dust appear to match those of the cold gas traced by CO with a gas-to-dust ratio of 80-120.

  3. Fast Online Clustering with Randomized Skeleton Sets

    OpenAIRE

    Choromanski, Krzysztof; Kumar, Sanjiv; Liu, Xiaofeng

    2015-01-01

    We present a new fast online clustering algorithm that reliably recovers arbitrary-shaped data clusters in high throughout data streams. Unlike the existing state-of-the-art online clustering methods based on k-means or k-medoid, it does not make any restrictive generative assumptions. In addition, in contrast to existing nonparametric clustering techniques such as DBScan or DenStream, it gives provable theoretical guarantees. To achieve fast clustering, we propose to represent each cluster b...

  4. Dynamics and Shape of Brightest Cluster Galaxies

    CERN Document Server

    Andernach, H; Coziol, R; Tago, E

    2006-01-01

    We identified Brightest Cluster Members (BCM) on DSS images of 1083 Abell clusters, derived their individual and host cluster redshifts from literature and determined the BCM ellipticity. Half the BCMs move at a speed higher than 37 % of the cluster velocity dispersion sigma_{cl}, suggesting that most BCMs are part of substructures falling into the main cluster. Both, the BCM's velocity offset in units of sigma_{cl}, and BCM ellipticity, weakly decrease with cluster richness.

  5. Dynamical Processes in Globular Clusters

    CERN Document Server

    McMillan, Stephen L W

    2014-01-01

    Globular clusters are among the most congested stellar systems in the Universe. Internal dynamical evolution drives them toward states of high central density, while simultaneously concentrating the most massive stars and binary systems in their cores. As a result, these clusters are expected to be sites of frequent close encounters and physical collisions between stars and binaries, making them efficient factories for the production of interesting and observable astrophysical exotica. I describe some elements of the competition among stellar dynamics, stellar evolution, and other processes that control globular cluster dynamics, with particular emphasis on pathways that may lead to the formation of blue stragglers.

  6. Cluster de ventiladores em Catanduva.

    Directory of Open Access Journals (Sweden)

    Luciana M. Onusic

    2005-04-01

    Full Text Available Este trabalho apresenta os resultados de um levantamento feito na cidade de Catanduva sobre a indústria de ventiladores nela instalada. É, inicialmente, apresentado o conceito de cluster, para, em seguida, serem apresentadas as características do setor de ventiladores de Catanduva, fazendo uma comparação desse setor com o conceito de cluster. Diversos aspectos mostram o interesse em considerar o setor como um cluster e são feitas sugestões para seu aprimoramento.

  7. PHAT Stellar Cluster Survey. II. Andromeda Project Cluster Catalog

    CERN Document Server

    Johnson, L Clifton; Dalcanton, Julianne J; Wallace, Matthew L; Simpson, Robert J; Lintott, Chris J; Kapadia, Amit; Skillman, Evan D; Caldwell, Nelson; Fouesneau, Morgan; Weisz, Daniel R; Williams, Benjamin F; Beerman, Lori C; Gouliermis, Dimitrios A; Sarajedini, Ata

    2015-01-01

    We construct a stellar cluster catalog for the Panchromatic Hubble Andromeda Treasury (PHAT) survey using image classifications collected from the Andromeda Project citizen science website. We identify 2,753 clusters and 2,270 background galaxies within ~0.5 deg$^2$ of PHAT imaging searched, or ~400 kpc$^2$ in deprojected area at the distance of the Andromeda galaxy (M31). These identifications result from 1.82 million classifications of ~20,000 individual images (totaling ~7 gigapixels) by tens of thousands of volunteers. We show that our crowd-sourced approach, which collects >80 classifications per image, provides a robust, repeatable method of cluster identification. The high spatial resolution Hubble Space Telescope images resolve individual stars in each cluster and are instrumental in the factor of ~6 increase in the number of clusters known within the survey footprint. We measure integrated photometry in six filter passbands, ranging from the near-UV to the near-IR. PHAT clusters span a range of ~8 ma...

  8. Survey and Analysis of University Clustering

    Directory of Open Access Journals (Sweden)

    Srinatha Karur

    2013-07-01

    Full Text Available This paper gives on Clustering of Universities in the world with respect to their country policies OR local polices OR continent level polices with sub aims. So clustering method can generally apply when objective is specifically mentioned. For general objectives clusters are available in the form of logical or physical groups without networks. In this paper we emphasis on only University Clusters directly or University Clusters with some other clusters. Data miming methods are used for useful for Sampling Analysis and Clustering of Universities and Colleges with respect to local clusters [1] pp 1.

  9. A Clustering Graph Generator

    Energy Technology Data Exchange (ETDEWEB)

    Winlaw, Manda [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); De Sterck, Hans [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sanders, Geoffrey [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-26

    In very simple terms a network can be de ned as a collection of points joined together by lines. Thus, networks can be used to represent connections between entities in a wide variety of elds including engi- neering, science, medicine, and sociology. Many large real-world networks share a surprising number of properties, leading to a strong interest in model development research and techniques for building synthetic networks have been developed, that capture these similarities and replicate real-world graphs. Modeling these real-world networks serves two purposes. First, building models that mimic the patterns and prop- erties of real networks helps to understand the implications of these patterns and helps determine which patterns are important. If we develop a generative process to synthesize real networks we can also examine which growth processes are plausible and which are not. Secondly, high-quality, large-scale network data is often not available, because of economic, legal, technological, or other obstacles [7]. Thus, there are many instances where the systems of interest cannot be represented by a single exemplar network. As one example, consider the eld of cybersecurity, where systems require testing across diverse threat scenarios and validation across diverse network structures. In these cases, where there is no single exemplar network, the systems must instead be modeled as a collection of networks in which the variation among them may be just as important as their common features. By developing processes to build synthetic models, so-called graph generators, we can build synthetic networks that capture both the essential features of a system and realistic variability. Then we can use such synthetic graphs to perform tasks such as simulations, analysis, and decision making. We can also use synthetic graphs to performance test graph analysis algorithms, including clustering algorithms and anomaly detection algorithms.

  10. Hierarchical clustering for graph visualization

    CERN Document Server

    Clémençon, Stéphan; Rossi, Fabrice; Tran, Viet Chi

    2012-01-01

    This paper describes a graph visualization methodology based on hierarchical maximal modularity clustering, with interactive and significant coarsening and refining possibilities. An application of this method to HIV epidemic analysis in Cuba is outlined.

  11. Magnetic Bubbles in Galaxy Clusters

    OpenAIRE

    McNamara, B. R.

    2003-01-01

    I discuss Chandra X-ray Observatory measurements of cavities in galaxy clusters and their implications for heating the intracluster gas. The emerging paradigm for cooling flows has important implications for understanding self-regulated galaxy formation.

  12. Clustering of financial time series

    Science.gov (United States)

    D'Urso, Pierpaolo; Cappelli, Carmela; Di Lallo, Dario; Massari, Riccardo

    2013-05-01

    This paper addresses the topic of classifying financial time series in a fuzzy framework proposing two fuzzy clustering models both based on GARCH models. In general clustering of financial time series, due to their peculiar features, needs the definition of suitable distance measures. At this aim, the first fuzzy clustering model exploits the autoregressive representation of GARCH models and employs, in the framework of a partitioning around medoids algorithm, the classical autoregressive metric. The second fuzzy clustering model, also based on partitioning around medoids algorithm, uses the Caiado distance, a Mahalanobis-like distance, based on estimated GARCH parameters and covariances that takes into account the information about the volatility structure of time series. In order to illustrate the merits of the proposed fuzzy approaches an application to the problem of classifying 29 time series of Euro exchange rates against international currencies is presented and discussed, also comparing the fuzzy models with their crisp version.

  13. Infrared spectroscopy of ionic clusters

    International Nuclear Information System (INIS)

    This thesis describes new experiments wherein the infrared vibrational predissociation spectra of a number of mass-selected ionic cluster systems have been obtained and analyzed in the 2600 to 4000 cm-1 region. The species studied include: the hydrated hydronium ions, H3O+ (H2O)3-10, ammoniated ammonium ions, NH4+(NH3)1-10 and cluster ions involving both water and ammonia around an ammonium ion core, (mixed clusters) NH4+(NH3)n(H2O)m (n+m=4). In each case, the spectra reveal well resolved structures that can be assigned to transitions arising from the vibrational motions of both the ion core of the clusters and the surrounding neutral solvent molecules. 154 refs., 19 figs., 8 tabs

  14. Star Cluster Formation and Feedback

    CERN Document Server

    Krumholz, Mark R; Arce, Hector G; Dale, James E; Gutermuth, Robert; Klein, Richard I; Li, Zhi-Yun; Nakamura, Fumitaka; Zhang, Qizhou

    2014-01-01

    Stars do not generally form in isolation. Instead, they form in clusters, and in these clustered environments newborn stars can have profound effects on one another and on their parent gas clouds. Feedback from clustered stars is almost certainly responsible for a number of otherwise puzzling facts about star formation: that it is an inefficient process that proceeds slowly when averaged over galactic scales; that most stars disperse from their birth sites and dissolve into the galactic field over timescales $\\ll 1$ Gyr; and that newborn stars follow an initial mass function (IMF) with a distinct peak in the range $0.1 - 1$ $M_\\odot$, rather than an IMF dominated by brown dwarfs. In this review we summarize current observational constraints and theoretical models for the complex interplay between clustered star formation and feedback.

  15. The Clustering of Massive Halos

    CERN Document Server

    Wetzel, A R; White, M; Holz, D E; Warren, M S; Wetzel, Andrew R.; White, Martin; Holz, Daniel E.; Warren, Michael S.

    2006-01-01

    The clustering properties of dark matter halos are a firm prediction of modern theories of structure formation. We use two large volume, high-resolution N-body simulations to study how the correlation function of massive dark matter halos depends upon their mass and formation history. We find that halos with the lowest concentrations are presently more clustered than those of higher concentration, the size of the effect increasing with halo mass; this agrees with trends found in studies of lower mass halos. The clustering dependence on other characterizations of the full mass accretion history appears weaker than the effect with concentration. Using the integrated correlation function, marked correlation functions, and a power-law fit to the correlation function, we find evidence that halos which have recently undergone a major merger or a large mass gain have slightly enhanced clustering relative to a randomly chosen population with the same mass distribution.

  16. Symplectic maps from cluster algebras

    CERN Document Server

    Fordy, Allan

    2011-01-01

    We consider nonlinear recurrences generated from the iteration of maps that arise from cluster algebras. More precisely, starting from a skew-symmetric integer matrix, or its corresponding %associated quiver, one can define a set of mutation operations, as well as a set of associated cluster mutations that are applied to a set of affine coordinates (the cluster variables). Fordy and Marsh recently provided a complete classification of all such quivers that have a certain periodicity property under sequences of mutations. This periodicity implies that a suitable sequence of cluster mutations is precisely equivalent to iteration of a nonlinear recurrence relation. Here we explain briefly how to introduce a % symplectic structure in this setting, which is preserved by a corresponding birational map (possibly on a space of lower dimension). We give examples of both integrable and non-integrable maps that arise from this construction. We use algebraic entropy as an approach to classifying integrable cases. The deg...

  17. Infrared spectroscopy of ionic clusters

    Energy Technology Data Exchange (ETDEWEB)

    Price, J.M. (California Univ., Berkeley, CA (USA). Dept. of Chemistry Lawrence Berkeley Lab., CA (USA))

    1990-11-01

    This thesis describes new experiments wherein the infrared vibrational predissociation spectra of a number of mass-selected ionic cluster systems have been obtained and analyzed in the 2600 to 4000 cm{sup {minus}1} region. The species studied include: the hydrated hydronium ions, H{sub 3}O{sup +} (H{sub 2}O){sub 3 {minus}10}, ammoniated ammonium ions, NH{sub 4}{sup +}(NH{sub 3}){sub 1 {minus}10} and cluster ions involving both water and ammonia around an ammonium ion core, (mixed clusters) NH{sub 4}{sup +}(NH{sub 3}){sub n}(H{sub 2}O){sub m} (n+m=4). In each case, the spectra reveal well resolved structures that can be assigned to transitions arising from the vibrational motions of both the ion core of the clusters and the surrounding neutral solvent molecules. 154 refs., 19 figs., 8 tabs.

  18. Radio Emission from Globular Clusters

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Radio emission of globular clusters is studied by analyzing the VLA radio survey data of the NVSS and FIRST. We find that 13 clusters have radio sources within their half-mass radii of clusters. Sources detected previously in NGC 7078and NGC 6440 are identified. Pulsars in NGC 6121, NGC 6440 and NGC 7078cannot be detected because of the insufficient survey sensitivity and resolution.There may be a pulsar in the core of Terzan 1. The nature of the extended radio source near the core of NGC 6440 remains unclear. In the core of a globular cluster,there may be many neutron stars or an intermediate mass black hole, but this cannot be clarified with the current radio observations.

  19. IRAC imaging of GOGREEN clusters

    Science.gov (United States)

    McGee, Sean; Balogh, Michael; Cooper, Michael; Gilbank, David; Lidman, Chris; Muzzin, Adam; Old, Lyndsay; Rudnick, Greg; Wilson, Gillian; Yee, Howard

    2016-08-01

    We propose deep IRAC imaging of three galaxy clusters drawn from the GOGREEN survey of 21 galaxy clusters in the redshift range 1 Magellan and CFHT imaging and by an ongoing Gemini Large Programme, with which we are obtaining deep spectroscopy of > 1000 member and > 600 field galaxies. With these data and our own lower-redshift descendant data, we will measure 1) the evolution of the quenched fraction and its dependence on distance from the cluster center and 2) the relation between stellar and halo mass and its evolution. This will provide unique constraints to our in-house theoretical models at an epoch where there are currently almost none available. The imaging that we propose will ensure all 21 GOGREEN clusters have deep IRAC data, ensuring the lasting legacy of this benchmark sample.

  20. Gravitational "convergence" and cluster masses

    CERN Document Server

    Broadhurst, T J

    1995-01-01

    Two colour photometry of the cluster A1689 reveals a `relative magnification-bias' between lensed blue and red background galaxies, arising from a dependence of the faint galaxy count-slope on colour. The colour distribution is skewed blueward of the far field, allowing us to measure the cluster magnification and to understand the notorious blueness of large arcs. We show that the magnification information can be combined with the usual image distortion measurements to isolate the local `convergence' component of lensing and hence derive the projected mass. This is achieved through a simple local relation between the convergence and the observables, which can be applied generally over the surface a cluster. In the weak lensing limit, the convergence reduces to a dependence on the magnification alone, so that in the outskirts of clusters the surface-density of matter is obtained directly from the surface-density of background galaxies. Hence, useful lensing work requires colour information but not necessarily ...

  1. Intuitionistic fuzzy hierarchical clustering algorithms

    Institute of Scientific and Technical Information of China (English)

    Xu Zeshui

    2009-01-01

    Intuitionistic fuzzy set (IFS) is a set of 2-tuple arguments, each of which is characterized by a mem-bership degree and a nonmembership degree. The generalized form of IFS is interval-valued intuitionistic fuzzy set (IVIFS), whose components are intervals rather than exact numbers. IFSs and IVIFSs have been found to be very useful to describe vagueness and uncertainty. However, it seems that little attention has been focused on the clus-tering analysis of IFSs and IVIFSs. An intuitionistic fuzzy hierarchical algorithm is introduced for clustering IFSs, which is based on the traditional hierarchical clustering procedure, the intuitionistic fuzzy aggregation operator, and the basic distance measures between IFSs: the Hamming distance, normalized Hamming, weighted Hamming, the Euclidean distance, the normalized Euclidean distance, and the weighted Euclidean distance. Subsequently, the algorithm is extended for clustering IVIFSs. Finally the algorithm and its extended form are applied to the classifications of building materials and enterprises respectively.

  2. Kernel Generalized Noise Clustering Algorithm

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-hong; ZHOU Jian-jiang

    2007-01-01

    To deal with the nonlinear separable problem, the generalized noise clustering (GNC) algorithm is extended to a kernel generalized noise clustering (KGNC) model. Different from the fuzzy c-means (FCM) model and the GNC model which are based on Euclidean distance, the presented model is based on kernel-induced distance by using kernel method. By kernel method the input data are nonlinearly and implicitly mapped into a high-dimensional feature space, where the nonlinear pattern appears linear and the GNC algorithm is performed. It is unnecessary to calculate in high-dimensional feature space because the kernel function can do itjust in input space. The effectiveness of the proposed algorithm is verified by experiments on three data sets. It is concluded that the KGNC algorithm has better clustering accuracy than FCM and GNC in clustering data sets containing noisy data.

  3. Re-shaping colloidal clusters

    Science.gov (United States)

    Kraft, Daniela

    2015-03-01

    Controlling the geometry and yield of anisotropic colloidal particles remains a challenge for hierarchical self-assembly. I will discuss a synthetic strategy for fabricating colloidal clusters by creating order in randomly aggregated polymer spheres using surface tension and geometrical constraints. The technique can be extended to a variety of charge-stabilized polymer spheres and offers control over the cluster size distribution. VENI grant from The Netherlands Organization for Scientific Research (NWO).

  4. Agglomerative Forces and Cluster Shapes

    OpenAIRE

    Kerr,William Robert; Kominers, Scott Duke

    2014-01-01

    We model spatial clusters of similar firms. Our model highlights how agglomerative forces lead to localized, individual connections among firms, while interaction costs generate a defined distance over which attraction forces operate. Overlapping firm interactions yield agglomeration clusters that are much larger than the underlying agglomerative forces themselves. Empirically, we demonstrate that our model’s assumptions are present in the structure of technology and labor flows within Silico...

  5. Clusters, Convergence, and Economic Performance

    OpenAIRE

    Mercedes Delgado; Porter, Michael E.; Scott Stern

    2012-01-01

    This paper evaluates the role of regional cluster composition in the economic performance of industries, clusters and regions. On the one hand, diminishing returns to specialization in a location can result in a convergence effect: the growth rate of an industry within a region may be declining in the level of activity of that industry. At the same time, positive spillovers across complementary economic activities provide an impetus for agglomeration: the growth rate of an industry within a r...

  6. Wild cluster bootstrap confidence intervals

    OpenAIRE

    MacKinnon, James G.

    2014-01-01

    Confidence intervals based on cluster-robust covariance matrices can be constructed in many ways. In addition to conventional intervals obtained by inverting Wald (t) tests, the paper studies intervals obtained by inverting LM tests, studentized bootstrap intervals based on the wild cluster bootstrap, and restricted bootstrap intervals obtained by inverting bootstrap Wald and LM tests. It also studies the choice of an auxiliary distribution for the wild bootstrap, a modified covariance matrix...

  7. IntroductionThe Cluster mission

    Directory of Open Access Journals (Sweden)

    M. Fehringer

    Full Text Available The Cluster mission, ESA’s first cornerstone project, together with the SOHO mission, dating back to the first proposals in 1982, was finally launched in the summer of 2000. On 16 July and 9 August, respectively, two Russian Soyuz rockets blasted off from the Russian cosmodrome in Baikonour to deliver two Cluster spacecraft, each into their proper orbit. By the end of August 2000, the four Cluster satellites had reached their final tetrahedral constellation. The commissioning of 44 instruments, both individually and as an ensemble of complementary tools, was completed five months later to ensure the optimal use of their combined observational potential. On 1 February 2001, the mission was declared operational. The main goal of the Cluster mission is to study the small-scale plasma structures in three dimensions in key plasma regions, such as the solar wind, bow shock, magnetopause, polar cusps, magnetotail and the auroral zones. With its unique capabilities of three-dimensional spatial resolution, Cluster plays a major role in the International Solar Terrestrial Program (ISTP, where Cluster and the Solar and Heliospheric Observatory (SOHO are the European contributions. Cluster’s payload consists of state-of-the-art plasma instrumentation to measure electric and magnetic fields from the quasi-static up to high frequencies, and electron and ion distribution functions from energies of nearly 0 eV to a few MeV. The science operations are coordinated by the Joint Science Operations Centre (JSOC, at the Rutherford Appleton Laboratory (UK, and implemented by the European Space Operations Centre (ESOC, in Darmstadt, Germany. A network of eight national data centres has been set up for raw data processing, for the production of physical parameters, and their distribution to end users all over the world. The latest information on the Cluster mission can be found at http://sci.esa.int/cluster/.

  8. Multicore Processing for Clustering Algorithms

    Directory of Open Access Journals (Sweden)

    RekhanshRao

    2012-03-01

    Full Text Available Data Mining algorithms such as classification and clustering are the future of computation, though multidimensional data-processing is required. People are using multicore processors with GPU’s. Most of the programming languages doesn’t provide multiprocessing facilities and hence wastage of processing resources. Clustering and classification algorithms are more resource consuming. In this paper we have shown strategies to overcome such deficiencies using multicore processing platform OpelCL.

  9. Polarizability effect in metallic clusters

    Indian Academy of Sciences (India)

    Ş Şentürk; K Harigaya; O Özsoy

    2006-03-01

    Langevin approach implemented in the inelastic cross-sections measured for the low-energy electrons colliding with metallic clusters points out that statical form of the polarizability dominate at energies less than 1.25 eV. The dynamical form comes into play at energies around 1.3 eV. The form of the polarizabilities indicates that polarizability of the metallic clusters is energy-dependent.

  10. Cluster algebras and Poisson geometry

    OpenAIRE

    Gekhtman, M.; Shapiro, M.; Vainshtein, A.

    2002-01-01

    We introduce a Poisson variety compatible with a cluster algebra structure and a compatible toric action on this variety. We study Poisson and topological properties of the union of generic orbits of this toric action. In particular, we compute the number of connected components of the union of generic toric orbits for cluster algebras over real numbers. As a corollary we compute the number of connected components of refined open Bruhat cells in Grassmanians G(k,n) over real numbers.

  11. Identification of Urban Leprosy Clusters

    Directory of Open Access Journals (Sweden)

    José Antonio Armani Paschoal

    2013-01-01

    Full Text Available Overpopulation of urban areas results from constant migrations that cause disordered urban growth, constituting clusters defined as sets of people or activities concentrated in relatively small physical spaces that often involve precarious conditions. Aim. Using residential grouping, the aim was to identify possible clusters of individuals in São José do Rio Preto, Sao Paulo, Brazil, who have or have had leprosy. Methods. A population-based, descriptive, ecological study using the MapInfo and CrimeStat techniques, geoprocessing, and space-time analysis evaluated the location of 425 people treated for leprosy between 1998 and 2010. Clusters were defined as concentrations of at least 8 people with leprosy; a distance of up to 300 meters between residences was adopted. Additionally, the year of starting treatment and the clinical forms of the disease were analyzed. Results. Ninety-eight (23.1% of 425 geocoded cases were located within one of ten clusters identified in this study, and 129 cases (30.3% were in the region of a second-order cluster, an area considered of high risk for the disease. Conclusion. This study identified ten clusters of leprosy cases in the city and identified an area of high risk for the appearance of new cases of the disease.

  12. The Arches Cluster Mass Function

    CERN Document Server

    Kim, S S; Kudritzki, R P; Najarro, F; Kim, Sungsoo S.; Figer, Donald F.; Kudritzki, Rolf P.

    2006-01-01

    We have analyzed H and K_s-band images of the Arches cluster obtained using the NIRC2 instrument on Keck with the laser guide star adaptive optics (LGS AO) system. With the help of the LGS AO system, we were able to obtain the deepest ever photometry for this cluster and its neighborhood, and derive the background-subtracted present-day mass function (PDMF) down to 1.3 Msun for the 5 arcsec-9 arcsec annulus of the cluster. We find that the previously reported turnover at 6 Msun is simply due to a local bump in the mass function (MF), and that the MF continues to increase down to our 50 % completeness limit (1.3 Msun) with a power-law exponent of Gamma = -0.91 for the mass range of 1.3 < M/Msun < 50. Our numerical calculations for the evolution of the Arches cluster show that the Gamma values for our annulus increase by 0.1-0.2 during the lifetime of the cluster, and thus suggest that the Arches cluster initially had Gamma of -1.0 ~ -1.1, which is only slightly shallower than the Salpeter value.

  13. Autophagy selectivity through receptor clustering

    Science.gov (United States)

    Rutenberg, Andrew; Brown, Aidan

    Substrate selectivity in autophagy requires an all-or-none cellular response. We focus on peroxisomes, for which autophagy receptor proteins NBR1 and p62 are well characterized. Using computational models, we explore the hypothesis that physical clustering of autophagy receptor proteins on the peroxisome surface provides an appropriate all-or-none response. We find that larger peroxisomes nucleate NBR1 clusters first, and lose them due to competitive coarsening last, resulting in significant size-selectivity. We then consider a secondary hypothesis that p62 inhibits NBR1 cluster formation. We find that p62 inhibition enhances size-selectivity enough that, even if there is no change of the pexophagy rate, the volume of remaining peroxisomes can significantly decrease. We find that enhanced ubiquitin levels suppress size-selectivity, and that this effect is more pronounced for individual peroxisomes. Sufficient ubiquitin allows receptor clusters to form on even the smallest peroxisomes. We conclude that NBR1 cluster formation provides a viable physical mechanism for all-or-none substrate selectivity in pexophagy. We predict that cluster formation is associated with significant size-selectivity. Now at Simon Fraser University.

  14. Collective thermoregulation in bee clusters.

    Science.gov (United States)

    Ocko, Samuel A; Mahadevan, L

    2014-02-01

    Swarming is an essential part of honeybee behaviour, wherein thousands of bees cling onto each other to form a dense cluster that may be exposed to the environment for several days. This cluster has the ability to maintain its core temperature actively without a central controller. We suggest that the swarm cluster is akin to an active porous structure whose functional requirement is to adjust to outside conditions by varying its porosity to control its core temperature. Using a continuum model that takes the form of a set of advection-diffusion equations for heat transfer in a mobile porous medium, we show that the equalization of an effective 'behavioural pressure', which propagates information about the ambient temperature through variations in density, leads to effective thermoregulation. Our model extends and generalizes previous models by focusing the question of mechanism on the form and role of the behavioural pressure, and allows us to explain the vertical asymmetry of the cluster (as a consequence of buoyancy-driven flows), the ability of the cluster to overpack at low ambient temperatures without breaking up at high ambient temperatures, and the relative insensitivity to large variations in the ambient temperature. Our theory also makes testable hypotheses for the response of the cluster to external temperature inhomogeneities and suggests strategies for biomimetic thermoregulation. PMID:24335563

  15. The Extended Virgo Cluster Catalog

    CERN Document Server

    Kim, Suk; Jerjen, Helmut; Lisker, Thorsten; Sung, Eon-Chang; Lee, Youngdae; Chung, Jiwon; Pak, Mina; Yi, Wonhyeong; Lee, Woong

    2014-01-01

    We present a new catalog of galaxies in the wider region of the Virgo cluster, based on the Sloan Digital Sky Survey (SDSS) Data Release 7. The Extended Virgo Cluster Catalog (EVCC) covers an area of 725 deg^2 or 60.1 Mpc^2. It is 5.2 times larger than the footprint of the classical Virgo Cluster Catalog (VCC) and reaches out to 3.5 times the virial radius of the Virgo cluster. We selected 1324 spectroscopically targeted galaxies with radial velocities less than 3000 kms^-1. In addition, 265 galaxies that have been missed in the SDSS spectroscopic survey but have available redshifts in the NASA Extragalactic Database are also included. Our selection process secured a total of 1589 galaxies of which 676 galaxies are not included in the VCC. The certain and possible cluster members are defined by means of redshift comparison with a cluster infall model. We employed two independent and complementary galaxy classification schemes: the traditional morphological classification based on the visual inspection of opti...

  16. Relativistic Binaries in Globular Clusters

    Directory of Open Access Journals (Sweden)

    Matthew J. Benacquista

    2013-03-01

    Full Text Available Galactic globular clusters are old, dense star systems typically containing 10^4 – 10^6 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of tight binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker–Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.

  17. UCDs in the Coma Cluster

    CERN Document Server

    Chiboucas, Kristin; Marzke, Ronald O; Phillipps, Steven; Price, James; Peng, Eric W; Trentham, Neil; Carter, David; Hammer, Derek

    2010-01-01

    As part of the HST/ACS Coma Cluster Treasury Survey, we have undertaken a Keck/LRIS spectroscopic campaign to determine membership for faint dwarf galaxies. In the process, we discovered a population of Ultra Compact Dwarf galaxies (UCDs) in the core region of the Coma cluster. At the distance of Coma, UCDs are expected to have angular sizes 0.01 < R_e < 0.2 arcsec. With ACS imaging, we can resolve all but the smallest ones with careful fitting. Candidate UCDs were chosen based on magnitude, color, and degree of resolution. We spectroscopically confirm 27 objects as bona fide UCD members of the Coma cluster, a 60% success rate for objects targeted with M_R < -12. We attribute the high success rate in part to the high resolution of HST data and to an apparent large population of UCDs in Coma. We find that the UCDs tend to be strongly clustered around giant galaxies, at least in the core region of the cluster, and have a distribution and colors that are similar to globular clusters. These findings sugg...

  18. Identification of urban leprosy clusters.

    Science.gov (United States)

    Paschoal, José Antonio Armani; Paschoal, Vania Del'Arco; Nardi, Susilene Maria Tonelli; Rosa, Patrícia Sammarco; Ismael, Manuela Gallo y Sanches; Sichieri, Eduvaldo Paulo

    2013-01-01

    Overpopulation of urban areas results from constant migrations that cause disordered urban growth, constituting clusters defined as sets of people or activities concentrated in relatively small physical spaces that often involve precarious conditions. Aim. Using residential grouping, the aim was to identify possible clusters of individuals in São José do Rio Preto, Sao Paulo, Brazil, who have or have had leprosy. Methods. A population-based, descriptive, ecological study using the MapInfo and CrimeStat techniques, geoprocessing, and space-time analysis evaluated the location of 425 people treated for leprosy between 1998 and 2010. Clusters were defined as concentrations of at least 8 people with leprosy; a distance of up to 300 meters between residences was adopted. Additionally, the year of starting treatment and the clinical forms of the disease were analyzed. Results. Ninety-eight (23.1%) of 425 geocoded cases were located within one of ten clusters identified in this study, and 129 cases (30.3%) were in the region of a second-order cluster, an area considered of high risk for the disease. Conclusion. This study identified ten clusters of leprosy cases in the city and identified an area of high risk for the appearance of new cases of the disease.

  19. Defense Industry Clusters in Turkey

    Directory of Open Access Journals (Sweden)

    Kadir Alpaslan Demir

    2016-06-01

    Full Text Available All countries strive for a capable national defense supported by a strong national defense industry. Supporting national defense with imported defense systems has many limitations and risks because the terms of arms trade agreements between countries may easily be influenced by the political climate of the signatories. As a result, establishing an independent national defense requires a strong national defense industry. Furthermore, exporting defense systems may be an important source of national income. National defense industries mostly consist of large-scale defense firms that have the resources required for big defense contracts. However, small to medium enterprises (SMEs do not have the necessary resources, therefore they are at a disadvantage. To overcome this handicap and be part of the business, defense industry clusters mostly consisting of SMEs are being established. Provided that there is good national planning and support in this area, defense clusters consisting of SMEs may play a significant role in industry. SMEs have a chance to offer specialized services, special or customized products when needed. As a result, large defense firms subcontract certain portions of defense projects to SMEs. Since 2010, Turkey has shown signs of continuous improvement in defense industry clustering. In parallel with these developments, this study discusses the importance of clustering in the defense industry, briefly presents the state of the Turkish defense industry as highlighted by national statistics, and presents the current status of defense clusters in Turkey. The novelty of this article consists in its assessment of Turkish defense clusters.

  20. A revised moving cluster distance to the Pleiades open cluster

    CERN Document Server

    Galli, P A B; Bouy, H; Bouvier, J; Olivares, J; Teixeira, R

    2016-01-01

    Aims: We provide a new distance estimate for the Pleiades based on the moving cluster method, which will be useful to further discuss the so-called Pleiades distance controversy and compare it with the very precise parallaxes from the Gaia space mission. Methods: We apply a refurbished implementation of the convergent point search method to an updated census of Pleiades stars to calculate the convergent point position of the cluster from stellar proper motions. Then, we derive individual parallaxes for 64 cluster members using radial velocities compiled from the literature, and approximate parallaxes for another 1146 stars based on the spatial velocity of the cluster. This represents the largest sample of Pleiades stars with individual distances to date. Results: The parallaxes derived in this work are in good agreement with previous results obtained in different studies (excluding Hipparcos) for individual stars in the cluster. We report a mean parallax of $7.44\\pm 0.08$~mas and distance of $134.4^{+2.9}_{-2...

  1. Properties of Star Clusters - II: Scale Height Evolution of Clusters

    CERN Document Server

    Buckner, Anne S M

    2014-01-01

    Until now it has been impossible to observationally measure how star cluster scale height evolves beyond 1Gyr as only small samples have been available. Here we establish a novel method to determine the scale height of a cluster sample using modelled distributions and Kolmogorov-Smirnov tests. This allows us to determine the scale height with a 25% accuracy for samples of 38 clusters or more. We apply our method to investigate the temporal evolution of cluster scale height, using homogeneously selected sub-samples of Kharchenko et al. (MWSC), Dias et al. (DAML02), WEBDA, and Froebrich et al. (FSR). We identify a linear relationship between scale height and log(age/yr) of clusters, considerably different from field stars. The scale height increases from about 40pc at 1Myr to 75pc at 1Gyr, most likely due to internal evolution and external scattering events. After 1Gyr, there is a marked change of the behaviour, with the scale height linearly increasing with log(age/yr) to about 550pc at 3.5Gyr. The most likely...

  2. The Finnish solar cluster

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-07-01

    There are numerous drivers behind the increasing utilization of solar energy. Currently solar energy is a relatively small market in Finland but there are many visible signs of increasing interest towards solar technologies and solar energy. There are already some Finnish companies offering their products and services for the global solar market. Considering the high Finnish competence in various fields of technology, there should be no reason why more companies would not follow in the future. This report drafts the Finnish solar cluster in its current form, including both those companies that operate in and along the solar value chain as well as those who have the opportunity to promote solar implementation and utilization. Further, this report brings up existing solar-related strengths of Finnish companies and research including inverters and material technology as well as the identified main obstacles for large-scale solar expansion in Finland. In addition, this report will also list some key barriers for solar implementation identified during the study. The report will also look solar from an urban planning perspective and discuss about implementing solar into new and existing built environments, which extends the study further beyond the traditional solar value chain. In order to get insights into urban solar development in Finland, we have interviewed the following exerts for this work: Robert Eriksson from City of Espoo; Alpo Tani from City of Helsinki, Pauli Valimaki and Elina Seppanen from City of Tampere; Mika Pekkinen from Tampereen Saehkoelaitos; Maarit Tuomainen and Kimmo Ruokoniemi from SATO, Kaisa Kekki and Pellervo Matilainen from Skanska; Eero Vartiainen from Fortum; Jari Suominen from ST1 and Karin Wikman from Tekes. We would like to express our sincere thanks to the persons we interviewed for their support and ideas regarding the subject. This report relates to the Solar Energy Forum organized by the Finnish Funding Agency for Technology and

  3. Novel Cluster Validity Index for FCM Algorithm

    Institute of Scientific and Technical Information of China (English)

    Jian Yu; Cui-Xia Li

    2006-01-01

    How to determine an appropriate number of clusters is very important when implementing a specific clustering algorithm, like c-means, fuzzy c-means (FCM). In the literature, most cluster validity indices are originated from partition or geometrical property of the data set. In this paper, the authors developed a novel cluster validity index for FCM, based on the optimality test of FCM. Unlike the previous cluster validity indices, this novel cluster validity index is inherent in FCM itself. Comparison experiments show that the stability index can be used as cluster validity index for the fuzzy c-means.

  4. Nonlocalized cluster dynamics and container picture

    International Nuclear Information System (INIS)

    A container picture is proposed for understanding cluster dynamics where the clusters make nonlocalized motion occupying the lowest orbit of the cluster mean-field potential characterized by the size parameter ''B'' in the THSR (Tohsaki-Horiuchi-Schuck-Röpke) wave function. The nonlocalized cluster aspects of the inversion-doublet bands in 20Ne which have been considered as a typical manifestation of localized clustering are discussed. In the α+16O system, localization is entirely of kinematical origin, that is, due to the inter-cluster Pauli repulsion. It is concluded that this feature is general for nuclear cluster states

  5. STAR CLUSTERS IN M31: OLD CLUSTERS WITH BAR KINEMATICS

    International Nuclear Information System (INIS)

    We analyze our accurate kinematical data for the old clusters in the inner regions of M31. These velocities are based on high signal-to-noise Hectospec data. The data are well suited for analysis of M31's inner regions because we took particular care to correct for contamination by unresolved field stars from the disk and bulge in the fibers. The metal-poor clusters show kinematics that are compatible with a pressure-supported spheroid. The kinematics of metal-rich clusters, however, argue for a disk population. In particular the innermost region (inside 2 kpc) shows the kinematics of the x2 family of bar periodic orbits, arguing for the existence of an inner Lindblad resonance in M31.

  6. Young star clusters in starburst environments

    CERN Document Server

    Ho, L C

    1996-01-01

    Recent high-resolution observations with the Hubble Space Telescope (HST) reveal that young star clusters of extraordinary luminosity and compactness ("super star clusters") are commonly found in starburst systems. Cluster formation appears to be a dominant mode of star formation in starbursts. The principal properties of the young clusters are summarized. A new ultraviolet HST imaging survey of the central regions of nearby galaxies indicates that young clusters form in a wide range of environments. Circumnuclear star-forming rings, in particular, are richly populated with clusters, and several examples from recent imaging studies are discussed. There has been much speculation that super star clusters represent present-day analogs of young globular clusters. I will present evidence suggesting that at least some super star clusters indeed have masses and mass densities comparable to those of evolved globular clusters in the Milky Way.

  7. A Nonparametric Bayesian Model for Nested Clustering.

    Science.gov (United States)

    Lee, Juhee; Müller, Peter; Zhu, Yitan; Ji, Yuan

    2016-01-01

    We propose a nonparametric Bayesian model for clustering where clusters of experimental units are determined by a shared pattern of clustering another set of experimental units. The proposed model is motivated by the analysis of protein activation data, where we cluster proteins such that all proteins in one cluster give rise to the same clustering of patients. That is, we define clusters of proteins by the way that patients group with respect to the corresponding protein activations. This is in contrast to (almost) all currently available models that use shared parameters in the sampling model to define clusters. This includes in particular model based clustering, Dirichlet process mixtures, product partition models, and more. We show results for two typical biostatistical inference problems that give rise to clustering. PMID:26519174

  8. Quantum Monte Carlo methods and lithium cluster properties. [Atomic clusters

    Energy Technology Data Exchange (ETDEWEB)

    Owen, R.K.

    1990-12-01

    Properties of small lithium clusters with sizes ranging from n = 1 to 5 atoms were investigated using quantum Monte Carlo (QMC) methods. Cluster geometries were found from complete active space self consistent field (CASSCF) calculations. A detailed development of the QMC method leading to the variational QMC (V-QMC) and diffusion QMC (D-QMC) methods is shown. The many-body aspect of electron correlation is introduced into the QMC importance sampling electron-electron correlation functions by using density dependent parameters, and are shown to increase the amount of correlation energy obtained in V-QMC calculations. A detailed analysis of D-QMC time-step bias is made and is found to be at least linear with respect to the time-step. The D-QMC calculations determined the lithium cluster ionization potentials to be 0.1982(14) (0.1981), 0.1895(9) (0.1874(4)), 0.1530(34) (0.1599(73)), 0.1664(37) (0.1724(110)), 0.1613(43) (0.1675(110)) Hartrees for lithium clusters n = 1 through 5, respectively; in good agreement with experimental results shown in the brackets. Also, the binding energies per atom was computed to be 0.0177(8) (0.0203(12)), 0.0188(10) (0.0220(21)), 0.0247(8) (0.0310(12)), 0.0253(8) (0.0351(8)) Hartrees for lithium clusters n = 2 through 5, respectively. The lithium cluster one-electron density is shown to have charge concentrations corresponding to nonnuclear attractors. The overall shape of the electronic charge density also bears a remarkable similarity with the anisotropic harmonic oscillator model shape for the given number of valence electrons.

  9. 3D simulation of the Cluster-Cluster Aggregation model

    Science.gov (United States)

    Li, Chao; Xiong, Hailing

    2014-12-01

    We write a program to implement the Cluster-Cluster Aggregation (CCA) model with java programming language. By using the simulation program, the fractal aggregation growth process can be displayed dynamically in the form of a three-dimensional (3D) figure. Meanwhile, the related kinetics data of aggregation simulation can be also recorded dynamically. Compared to the traditional programs, the program has better real-time performance and is more helpful to observe the fractal growth process, which contributes to the scientific study in fractal aggregation. Besides, because of adopting java programming language, the program has very good cross-platform performance.

  10. Large scale cluster computing workshop

    Energy Technology Data Exchange (ETDEWEB)

    Dane Skow; Alan Silverman

    2002-12-23

    Recent revolutions in computer hardware and software technologies have paved the way for the large-scale deployment of clusters of commodity computers to address problems heretofore the domain of tightly coupled SMP processors. Near term projects within High Energy Physics and other computing communities will deploy clusters of scale 1000s of processors and be used by 100s to 1000s of independent users. This will expand the reach in both dimensions by an order of magnitude from the current successful production facilities. The goals of this workshop were: (1) to determine what tools exist which can scale up to the cluster sizes foreseen for the next generation of HENP experiments (several thousand nodes) and by implication to identify areas where some investment of money or effort is likely to be needed. (2) To compare and record experimences gained with such tools. (3) To produce a practical guide to all stages of planning, installing, building and operating a large computing cluster in HENP. (4) To identify and connect groups with similar interest within HENP and the larger clustering community.

  11. Clusters - Territorial Networks. Where to?

    Directory of Open Access Journals (Sweden)

    Luiza Nicoleta Radu

    2013-08-01

    Full Text Available Globalization has led to an increased international trade relations between organizations spatially separated. This determined a greater spatial differentiation influenced by local and regional competition production systems. Territoriality has been considered as the main cause for the development of active areas, explaining also the success of certain local systems of production that became competitive on a global scale. The new school of regional competitiveness promoted by Porter (2003 identifies the cluster industry as a source of competitive advantages, supporting the identification and cluster setting – up as an objective of the public policy. In the last few years, clusters became an important basis for the new policies promoted at the level of the European Union. The challenges established through the Lisbon Strategy, respectively “to make the Europe the most competitive and dynamic based knowledge economy”, determinate a new approach of the economic policy in order to increase competitiveness. For the regional economy, the cluster has the aim to develop new strategies focused on the economic sectors of the regional development, by taking into account sectoral advantages. However, in terms of economic activities promoted at regional level, the spatial development is an essential component for increasing EU competitiveness in terms of economic globalization trends, regional networks being considered the most advanced form of cluster in the economic sector.

  12. Learning regularized LDA by clustering.

    Science.gov (United States)

    Pang, Yanwei; Wang, Shuang; Yuan, Yuan

    2014-12-01

    As a supervised dimensionality reduction technique, linear discriminant analysis has a serious overfitting problem when the number of training samples per class is small. The main reason is that the between- and within-class scatter matrices computed from the limited number of training samples deviate greatly from the underlying ones. To overcome the problem without increasing the number of training samples, we propose making use of the structure of the given training data to regularize the between- and within-class scatter matrices by between- and within-cluster scatter matrices, respectively, and simultaneously. The within- and between-cluster matrices are computed from unsupervised clustered data. The within-cluster scatter matrix contributes to encoding the possible variations in intraclasses and the between-cluster scatter matrix is useful for separating extra classes. The contributions are inversely proportional to the number of training samples per class. The advantages of the proposed method become more remarkable as the number of training samples per class decreases. Experimental results on the AR and Feret face databases demonstrate the effectiveness of the proposed method.

  13. Scalable Density-Based Subspace Clustering

    DEFF Research Database (Denmark)

    Müller, Emmanuel; Assent, Ira; Günnemann, Stephan;

    2011-01-01

    For knowledge discovery in high dimensional databases, subspace clustering detects clusters in arbitrary subspace projections. Scalability is a crucial issue, as the number of possible projections is exponential in the number of dimensions. We propose a scalable density-based subspace clustering...... synthetic databases show that steering is efficient and scalable, with high quality results. For future work, our steering paradigm for density-based subspace clustering opens research potential for speeding up other subspace clustering approaches as well....

  14. Inflammatory breast cancer clusters: A hypothesis

    OpenAIRE

    Levine, Paul H; Hashmi, Salman; Minaei, Ashley A; Veneroso, Carmela

    2014-01-01

    Cancer clusters have long been a focus of interest because of the possibility of identifying etiologic agents. Only on rare occasions, however, have such cluster investigations been successful. One major difficulty in cluster investigations, particularly in the area of breast cancer, is the long latent period. There have been a number of publications providing a discouraging picture regarding cancer cluster investigations. The possibility of learning from a cluster investigation, however, is ...

  15. Simulated Versus Observed Cluster Eccentricity Evolution

    OpenAIRE

    Floor, Stephen; Melott, Adrian; Motl, and Patrick

    2003-01-01

    The rate of galaxy cluster eccentricity evolution is useful in understanding large scale structure. Rapid evolution for $z < $ 0.13 has been found in two different observed cluster samples. We present an analysis of projections of 41 clusters produced in hydrodynamic simulations augmented with radiative cooling and 43 clusters from adiabatic simulations. This new, larger set of simulated clusters strengthens the claims of previous eccentricity studies. We find very slow evolution in simulated...

  16. Investigating Bimodal Clustering in Human Mobility

    CERN Document Server

    Bagrow, James P; 10.1109/CSE.2009.283

    2009-01-01

    We apply a simple clustering algorithm to a large dataset of cellular telecommunication records, reducing the complexity of mobile phone users' full trajectories and allowing for simple statistics to characterize their properties. For the case of two clusters, we quantify how clustered human mobility is, how much of a user's spatial dispersion is due to motion between clusters, and how spatially and temporally separated clusters are from one another.

  17. Towards a policy to promote tourism clusters

    OpenAIRE

    Benner, Maximilian

    2013-01-01

    When thinking about clusters, primarily agglomerations of manufacturing and related service industries come into mind. Yet, clustering in tourism is as salient as in few other industries. Tourism clusters are an empirical fact. Considering the high relevance of tourism to many regions and nations, linking cluster and tourism policy seems worth considering. For this, a special theory of tourism cluster policy is needed, as tourism offers some particular characteristics that set it apart from ...

  18. The HST/ACS Coma Cluster Survey IV. Intergalactic Globular Clusters and the Massive Globular Cluster System at the Core of the Coma Galaxy Cluster

    OpenAIRE

    Peng, Eric W.; Ferguson, Henry C.; Goudfrooij, Paul; Hammer, Derek; Lucey, John R.; Marzke, ; Ronald O.; Puzia, Thomas H.; Carter, David; Balcells, Marc; Bridges, Terry; Chiboucas, Kristin; del Burgo, Carlos; Graham, Alister W.; Guzman, Rafael; Hudson, Michael J.

    2011-01-01

    Intracluster stellar populations are a natural result of tidal interactions in galaxy clusters. Measuring these populations is difficult, but important for understanding the assembly of the most massive galaxies. The Coma cluster is one of the nearest truly massive galaxy clusters, and is host to a correspondingly large system of globular clusters (GCs). We use imaging from the HST/ACS Coma Cluster Survey to present the first definitive detection of a large population of intracluster GCs (IGC...

  19. Cluster Beams Sources. Part 2. The Formation of Cluster Beams in Nozzle Sources

    Directory of Open Access Journals (Sweden)

    A.Ju. Karpenko

    2012-12-01

    Full Text Available The article briefly examines the processes occurring during the formation of cluster beams in sources of clusters, using the expansion of the gas mixture through a nozzle. The basic parameters of the gas cluster flow at the outlet nozzle, leading to the formation of clusters are analyzed. Some aspects of the formation of cluster beams from aerodynamic flows are discussed.

  20. Author Clustering on Large Bibliographies

    CERN Document Server

    Sterz, Christoph

    2014-01-01

    We analyze and design an algorithm for clustering large sets of authors in Bibliographies. Not considering a distance function for a mutual comparison, but transforming the data into a multidimensional metric space, the algorithm described is similar to locally sensitive hashing. The task lies in the field of Record-Linkage. The algorithm was designed and performed based on the data of the CERN Document Server, consisting out of more than 1.7 million metadata entries and is part of the digital assets-managing-software invenio. Meant as a prototype, the algorithm performs efficiently, clustering all authors on CDS in under 30 minutes. We will discuss extensions improving the recall rate, wich still remains inferior to the currently used clustering-approach.

  1. Nuclear Star Clusters and Bulges

    CERN Document Server

    Cole, David R

    2015-01-01

    Nuclear star clusters are among the densest stellar systems known and are common in both early- and late-type galaxies. They exhibit scaling relations with their host galaxy which may be related to those of supermassive black holes. These may therefore help us to unravel the complex physical processes occurring at the centres of galaxies. The properties of nuclear stellar systems suggest that their formation requires both dissipational and dissipationless processes. They have stellar populations of different ages, from stars as old as their host galaxy to young stars formed in the last 100 Myr. Therefore star formation must be happening either directly in the nuclear star cluster or in its vicinity. The secular processes that fuel the formation of pseudobulges very likely also contributes to nuclear star cluster growth.

  2. Amphoteric Aqueous Hafnium Cluster Chemistry.

    Science.gov (United States)

    Goberna-Ferrón, Sara; Park, Deok-Hie; Amador, Jenn M; Keszler, Douglas A; Nyman, May

    2016-05-17

    Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxide enables extreme UV lithographic patterning of sub-10 nm HfO2 structures. Hafnium speciation under these basic conditions (pH>10), however, is unknown, as studies of hafnium aqueous chemistry have been limited to acid. Here, we report synthesis, crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA]6 [Hf6 (μ-O2 )6 (μ-OH)6 (OH)12 ]⋅38 H2 O. The solution behavior of the cluster, including supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens a new chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing a critical process in single-digit-nm lithography. PMID:27094575

  3. Pair-Wise Cluster Analysis

    CERN Document Server

    Hardoon, David R

    2010-01-01

    This paper studies the problem of learning clusters which are consistently present in different (continuously valued) representations of observed data. Our setup differs slightly from the standard approach of (co-) clustering as we use the fact that some form of `labeling' becomes available in this setup: a cluster is only interesting if it has a counterpart in the alternative representation. The contribution of this paper is twofold: (i) the problem setting is explored and an analysis in terms of the PAC-Bayesian theorem is presented, (ii) a practical kernel-based algorithm is derived exploiting the inherent relation to Canonical Correlation Analysis (CCA), as well as its extension to multiple views. A content based information retrieval (CBIR) case study is presented on the multi-lingual aligned Europal document dataset which supports the above findings.

  4. Seismic constraints on open clusters

    CERN Document Server

    Piau, L; Turck-Chièze, S

    2005-01-01

    We derive knowledge on the global and structural parameters of low-mass stars using asteroseismology and taking advantage of the stellar collective behavior within open clusters. We build stellar models and compute the seismic signal expected from main sequence objects in the 0.8-1.6 Msun range. We first evaluate apparent magnitudes and oscillations-induced luminosity fluctuations expected in the Hyades, the Pleiades and the alpha Persei clusters. The closest cluster presents a feasible challenge to observational asteroseismology in the present and near future. We combine seismological and classical computations to address three questions: what can be inferred about 1) mass, 2) composition and 3) extension of outer convection zones of solar analogs in the Hyades. The first issue relies on the strong sensitivity of the large separation to mass. Then large separations and second differences are used to respectively constrain metal and helium fractions in the Hyades.When plotted for several masses, the relation ...

  5. Spherical k-Means Clustering

    Directory of Open Access Journals (Sweden)

    Kurt Hornik

    2012-09-01

    Full Text Available Clustering text documents is a fundamental task in modern data analysis, requiring approaches which perform well both in terms of solution quality and computational efficiency. Spherical k-means clustering is one approach to address both issues, employing cosine dissimilarities to perform prototype-based partitioning of term weight representations of the documents.This paper presents the theory underlying the standard spherical k-means problem and suitable extensions, and introduces the R extension package skmeans which provides a computational environment for spherical k-means clustering featuring several solvers: a fixed-point and genetic algorithm, and interfaces to two external solvers (CLUTO and Gmeans. Performance of these solvers is investigated by means of a large scale benchmark experiment.

  6. Consensus clustering in complex networks

    CERN Document Server

    Lancichinetti, Andrea; 10.1038/srep00336

    2012-01-01

    The community structure of complex networks reveals both their organization and hidden relationships among their constituents. Most community detection methods currently available are not deterministic, and their results typically depend on the specific random seeds, initial conditions and tie-break rules adopted for their execution. Consensus clustering is used in data analysis to generate stable results out of a set of partitions delivered by stochastic methods. Here we show that consensus clustering can be combined with any existing method in a self-consistent way, enhancing considerably both the stability and the accuracy of the resulting partitions. This framework is also particularly suitable to monitor the evolution of community structure in temporal networks. An application of consensus clustering to a large citation network of physics papers demonstrates its capability to keep track of the birth, death and diversification of topics.

  7. The state and creative clusters

    DEFF Research Database (Denmark)

    Vang, Jan; Jakobsen, Hannes

    2013-01-01

    , neglected paying attention to the role of the state in general but more importantly in facilitating the emergence of a film cluster from scratch in the context of global Hollywood dominance. This is a problem as the state plays a central role in constructing catching up oriented competitiveness in many...... creative industries, especially film industries outside Hollywood. Based on an original empirical study of the Danish film cluster we show how it has emerged almost from scratch and positioned itself as a noteworthy player on the global scene industry during the last 20 years. Special attention is paid...

  8. Communication Optimization for SMP Clusters

    Institute of Scientific and Technical Information of China (English)

    林伟坚; 李志光; 陈文光; 郑纬民

    2001-01-01

    Shared Memory Processors (SMP) workstation clusters are becomingmore and more popular. To optimize communication between the workstations, a new graph partition problem was developed to schedule tasks in SMP clusters. The problem is NP-complete and a heuristic algorithm was developed based on Lee, Kim and Park's algorithm. Experimental results indicate that our algorithm outperforms theirs, especially when the number of partitions is large. This algorithm can be integrated in a parallelizing compiler as a back end optimizer for the distributed code generator.

  9. Clustering of Sun Exposure Measurements

    DEFF Research Database (Denmark)

    Have, Anna Szynkowiak; Larsen, Jan; Hansen, Lars Kai;

    2002-01-01

    In a medically motivated Sun-exposure study, questionnaires concerning Sun-habits were collected from a number of subjects together with UV radiation measurements. This paper focuses on identifying clusters in the heterogeneous set of data for the purpose of understanding possible relations between...... Sun-habits exposure and eventually assessing the risk of skin cancer. A general probabilistic framework originally developed for text and Web mining is demonstrated to be useful for clustering of behavioral data. The framework combines principal component subspace projection with probabilistic...

  10. IPO Price Clustering and Discreetness

    OpenAIRE

    Bristow, Duke K.

    1998-01-01

    Price clustering in initial public offerings (IPOs) is extreme, pervasive, and long-lived. In a 25 year sample of 7,805 IPOs, offering prices range form one tenth cent to $5,000 per share. However, the price frequency distribution yields a clear triple peak with three discrete values, $5, 10, and $15 per share, accounting for 21.5% of all IPO prices. Clustering pervades every one of the top 20 two-digit SIC code groupings and every year from 1970 through 1994. Firms, underwriters and inve...

  11. The IMF of Globular Clusters

    Science.gov (United States)

    De Marchi, G.; Paresce, F.

    1999-12-01

    Accurate luminosity functions (LF) for a dozen globular clusters have now been measured at or just beyond their half-light radius using HST. They span almost the entire cluster main sequence below 0.75 MO. All these clusters exhibit LF that rise continuously from an absolute I magnitude MI 6 to a peak at MI 8.5-9 and then drop with increasing MI. Transformation of the LF into mass functions (MF) by means of the most recent mass luminosity relations that are consistent with all presently available data on the physical properties of low mass, low metallicity stars shows that all the LF observed so far can be obtained from MF having the shape of a log-normal distribution with characteristic mass mc=0.33 +/- 0.03 MO and standard deviation sigma =1.81 +/- 0.19. In particular, the LF of the four clusters in the sample that extend well beyond the peak luminosity down to close to the Hydrogen burning limit (NGC6341, NGC6397, NGC6752, and NGC6809) can only be reproduced by such distributions and not by a single power-law in the 0.1 - 0.6 MO range. After correction for the effects of mass segregation, the variation of the ratio of the number of higher to lower mass stars with cluster mass or any simple orbital parameter or the expected time to disruption recently computed for these clusters shows no statistically significant trend over a range of this last parameter of more than a factor of 100. We conclude that the global MF of these clusters have not been measurably modified by evaporation and tidal interactions with the Galaxy and, thus, should reflect the initial distribution of stellar masses. Since the log-normal function that we find is also very similar to the one obtained independently for much younger clusters and to the form expected theoretically, the implication seems to be unavoidable that it represents the true stellar IMF for this type of stars in this mass range.

  12. Fission approach to cluster radioactivity

    Indian Academy of Sciences (India)

    D N Poenaru; R A Gherghescu

    2015-09-01

    Fission theory is used to explain decay. Also, the analytical superasymmetric fission (ASAF) model is successfully employed to make a systematic search and to predict, with other models, cluster radioactivity. The macroscopic–microscopic method is illustrated for the superheavy nucleus 286Fl. Then a few results of the theoretical approach of decay (ASAF, UNIV and semFIS models), cluster decay (ASAF and UNIV) and spontaneous fission dynamics are described with Werner–Wheeler and cranking inertia. UNIV denotes universal curve and semFIS the fission-based semiempirical formula.

  13. Nonlinear analysis of EAS clusters

    CERN Document Server

    Zotov, M Yu; Fomin, Y A; Fomin, Yu. A.

    2002-01-01

    We apply certain methods of nonlinear time series analysis to the extensive air shower clusters found earlier in the data set obtained with the EAS-1000 Prototype array. In particular, we use the Grassberger-Procaccia algorithm to compute the correlation dimension of samples in the vicinity of the clusters. The validity of the results is checked by surrogate data tests and some additional quantities. We compare our conclusions with the results of similar investigations performed by the EAS-TOP and LAAS groups.

  14. Collaborative Clustering for Sensor Networks

    Science.gov (United States)

    Wagstaff. Loro :/; Green Jillian; Lane, Terran

    2011-01-01

    Traditionally, nodes in a sensor network simply collect data and then pass it on to a centralized node that archives, distributes, and possibly analyzes the data. However, analysis at the individual nodes could enable faster detection of anomalies or other interesting events, as well as faster responses such as sending out alerts or increasing the data collection rate. There is an additional opportunity for increased performance if individual nodes can communicate directly with their neighbors. Previously, a method was developed by which machine learning classification algorithms could collaborate to achieve high performance autonomously (without requiring human intervention). This method worked for supervised learning algorithms, in which labeled data is used to train models. The learners collaborated by exchanging labels describing the data. The new advance enables clustering algorithms, which do not use labeled data, to also collaborate. This is achieved by defining a new language for collaboration that uses pair-wise constraints to encode useful information for other learners. These constraints specify that two items must, or cannot, be placed into the same cluster. Previous work has shown that clustering with these constraints (in isolation) already improves performance. In the problem formulation, each learner resides at a different node in the sensor network and makes observations (collects data) independently of the other learners. Each learner clusters its data and then selects a pair of items about which it is uncertain and uses them to query its neighbors. The resulting feedback (a must and cannot constraint from each neighbor) is combined by the learner into a consensus constraint, and it then reclusters its data while incorporating the new constraint. A strategy was also proposed for cleaning the resulting constraint sets, which may contain conflicting constraints; this improves performance significantly. This approach has been applied to collaborative

  15. Intra Cluster Globular Clusters around NGC 1399 in Fornax?

    CERN Document Server

    Schuberth, Y; Bassino, L; Hilker, M

    2007-01-01

    We investigate whether the globular clusters (GCs) in the recently published sample of GCs in the Fornax cluster by Bergond and coworkers are indeed intra-cluster objects. We combine the catalogue of radial velocity measurements by Bergond et al. with our CTIO MOSAIC photometry in the Washington system and analyse the relation of metal-poor and metal-rich GCs with their host galaxies. The metal-rich GCs appear to be kinematically associated with their respective host galaxies. The vast majority of the metal-poor GCs found in between the galaxies of the Fornax cluster have velocities which are consistent with them being members of the very extended NGC 1399 GC system. We find that when the sample is restricted to the most accurate velocity measurements, the GC velocity dispersion profile can be described with a mass model derived for the NGC 1399 GC system within 80 kpc. We identify one ``vagrant'' GC whose radial velocity suggests that it is not bound to any galaxy unless its orbit has a very large apogalacti...

  16. Globular Cluster Systems in Brightest Cluster Galaxies. II: NGC 6166

    CERN Document Server

    Harris, William E; Whitmore, Bradley C; Gnedin, Oleg Y; Geisler, Douglas; Rothberg, Barry

    2015-01-01

    We present new deep photometry of the globular cluster system (GCS) around NGC 6166, the central supergiant galaxy in Abell 2199. HST data from the ACS and WFC3 cameras in F475W, F814W are used to determine the spatial distribution of the GCS, its metallicity distribution function (MDF), and the dependence of the MDF on galactocentric radius and on GC luminosity. The MDF is extremely broad, with the classic red and blue subpopulations heavily overlapped, but a double-Gaussian model can still formally match the MDF closely. The spatial distribution follows a Sersic-like profile detectably to a projected radius of at least $R_{gc} = 250$ kpc. To that radius, the total number of clusters in the system is N_{GC} = 39000 +- 2000, the global specific frequency is S_N = 11.2 +- 0.6, and 57\\% of the total are blue, metal-poor clusters. The GCS may fade smoothly into the Intra-Cluster Medium of A2199; we see no clear transition from the core of the galaxy to the cD halo or the ICM. The radial distribution, projected e...

  17. Clusters galore: insights about environmental clusters from probability theory.

    Science.gov (United States)

    Neutra, R; Swan, S; Mack, T

    1992-12-15

    The posterior probability of a causal explanation given that an environmental cancer cluster is statistically significant depends on the prior probability of an environmentally caused cluster, the sensitivity of the statistical test and its specificity. The prior probability is low, because it is rare to have enough carcinogen in the general environment to cause a relative risk of cancer high enough to achieve statistical significance in a small geographic area. The sensitivity and specificity are not great. The likelihood that a census tract escapes statistically significant elevations in all 80 types of cancer can be calculated. Many of the thousands of census tracts will, by chance alone, have at least one type of cancer whose elevation is statistically significant. Actual observation from a large cancer registry confirms this probabilistic prediction. Applying the principles of Bayes' Theorem would suggest that most statistically significant environmental cancer clusters are not due to environmental carcinogens. One would have to investigate hundreds of environmental cancer clusters to find one with a true environmental cause.

  18. Brightest Cluster Galaxies in the Extended GMRT radio halo cluster sample. Radio properties and cluster dynamics

    CERN Document Server

    Kale, Ruta; Cassano, Rossella; Giacintucci, Simona; Bardelli, sandro; Dallacasa, Daniele; Zucca, Elena

    2015-01-01

    Brightest Cluster Galaxies (BCGs) show exceptional properties over the whole electromagnetic spectrum. Their special location at the centres of galaxy clusters raises the question of the role of the environment on their radio properties. To decouple the effect of the galaxy mass and of the environment in their statistical radio properties, we investigate the possible dependence of the occurrence of radio loudness and of the fractional radio luminosity function on the dynamical state of the hosting cluster. We studied the radio properties of the BCGs in the Extended GMRT Radio Halo Survey (EGRHS). We obtained a statistical sample of 59 BCGs, which was divided into two classes, depending on the dynamical state of the host cluster, i.e. merging (M) and relaxed (R). Among the 59 BCGs, 28 are radio-loud, and 31 are radio--quiet. The radio-loud sources are located favourably located in relaxed clusters (71\\%), while the reverse is true for the radio-quiet BCGs, mostly located in merging systems (81\\%). The fraction...

  19. Innovation performance and clusters : a dynamic capability perspective on regional technology clusters

    NARCIS (Netherlands)

    Röttmer, Nicole

    2009-01-01

    This research provides a novel, empirically tested, actionable theory of cluster innovativeness. Cluster innovativeness has for long been subject of research and resulting policy efforts. The cluster's endowment with assets, such as specialized labor, firms, research institutes, existing regional ne

  20. LITERATURE SURVEY ON ENHANCING CLUSTER QUALITY

    Directory of Open Access Journals (Sweden)

    Mrs.S.THILAGAMANI

    2010-09-01

    Full Text Available In this paper, we extensively study about the important aspect of various Clustering techniques, the cluster quality. The goodness of clustering is measured in terms of cluster validity indices wherethe results of clustering are validated every time to give the maximum efficiency. The quality of clusters is measured in a decision-theoretic rough set oriented approach rather than the traditional geometry-based measures. Experiments are carried out with synthetic,standard and real world data for evaluating rough and crisp clustering. Also a new advancement in estimating the number of clusters in the analysis of gene expression data is studied. Here we follow a scheme called System Evolution to estimate the number of clusters based on Partitioning around medoids algorithm.

  1. Chaos theory perspective for industry clusters development

    Science.gov (United States)

    Yu, Haiying; Jiang, Minghui; Li, Chengzhang

    2016-03-01

    Industry clusters have outperformed in economic development in most developing countries. The contributions of industrial clusters have been recognized as promotion of regional business and the alleviation of economic and social costs. It is no doubt globalization is rendering clusters in accelerating the competitiveness of economic activities. In accordance, many ideas and concepts involve in illustrating evolution tendency, stimulating the clusters development, meanwhile, avoiding industrial clusters recession. The term chaos theory is introduced to explain inherent relationship of features within industry clusters. A preferred life cycle approach is proposed for industrial cluster recessive theory analysis. Lyapunov exponents and Wolf model are presented for chaotic identification and examination. A case study of Tianjin, China has verified the model effectiveness. The investigations indicate that the approaches outperform in explaining chaos properties in industrial clusters, which demonstrates industrial clusters evolution, solves empirical issues and generates corresponding strategies.

  2. An Improved Cluster Richness Estimator

    Energy Technology Data Exchange (ETDEWEB)

    Rozo, Eduardo; /Ohio State U.; Rykoff, Eli S.; /UC, Santa Barbara; Koester, Benjamin P.; /Chicago U. /KICP, Chicago; McKay, Timothy; /Michigan U.; Hao, Jiangang; /Michigan U.; Evrard, August; /Michigan U.; Wechsler, Risa H.; /SLAC; Hansen, Sarah; /Chicago U. /KICP, Chicago; Sheldon, Erin; /New York U.; Johnston, David; /Houston U.; Becker, Matthew R.; /Chicago U. /KICP, Chicago; Annis, James T.; /Fermilab; Bleem, Lindsey; /Chicago U.; Scranton, Ryan; /Pittsburgh U.

    2009-08-03

    Minimizing the scatter between cluster mass and accessible observables is an important goal for cluster cosmology. In this work, we introduce a new matched filter richness estimator, and test its performance using the maxBCG cluster catalog. Our new estimator significantly reduces the variance in the L{sub X}-richness relation, from {sigma}{sub lnL{sub X}}{sup 2} = (0.86 {+-} 0.02){sup 2} to {sigma}{sub lnL{sub X}}{sup 2} = (0.69 {+-} 0.02){sup 2}. Relative to the maxBCG richness estimate, it also removes the strong redshift dependence of the richness scaling relations, and is significantly more robust to photometric and redshift errors. These improvements are largely due to our more sophisticated treatment of galaxy color data. We also demonstrate the scatter in the L{sub X}-richness relation depends on the aperture used to estimate cluster richness, and introduce a novel approach for optimizing said aperture which can be easily generalized to other mass tracers.

  3. Clustering problems for geochemical data

    International Nuclear Information System (INIS)

    The Union Carbide Corporation, Nuclear Division, Uranium Resource Evaluation Project uses a two-stage sampling program to identify potential uranium districts. Cluster analysis techniques are used in locating high density sampling areas as well as in identifying potential uranium districts. Problems are considered involving the analysis of multivariate censored data, laboratory measurement error, and data standardization

  4. Binaries and Globular Cluster Dynamics

    CERN Document Server

    Rasio, F A; Joshi, K J; Rasio, Frederic A.; Fregeau, John M.; Joshi, Kriten J.

    2001-01-01

    We summarize the results of recent theoretical work on the dynamical evolution of globular clusters containing primordial binaries. Even a very small initial binary fraction (e.g., 10%) can play a key role in supporting a cluster against gravothermal collapse for many relaxation times. Inelastic encounters between binaries and single stars or other binaries provide a very significant energy source for the cluster. These dynamical interactions also lead to the production of large numbers of exotic systems such as ultracompact X-ray binaries, recycled radio pulsars, double degenerate systems, and blue stragglers. Our work is based on a new parallel supercomputer code implementing Henon's Monte Carlo method for simulating the dynamical evolution of dense stellar systems in the Fokker-Planck approximation. This new code allows us to calculate very accurately the evolution of a cluster containing a realistic number of stars (N ~ 10^5 - 10^6) in typically a few hours to a few days of computing time. The discrete, s...

  5. Polymer modification via. cluster formation

    International Nuclear Information System (INIS)

    Ion beam treatment studies have been carried out to investigate the potential for improvements in conductivity properties of the polymers. Change in polymer stoichiometry were characterised by investigating into the carbon clusters formed along the latent tracks of energetic ions in polymers. Here we present some new results which have been derived from UV-Vis spectroscopic examinations. (author)

  6. Cold Fronts in CDM clusters

    CERN Document Server

    Nagai, D; Nagai, Daisuke; Kravtsov, Andrey V.

    2003-01-01

    Recently, high-resolution Chandra observations revealed the existence of very sharp features in the X-ray surface brightness and temperature maps of several clusters (Vikhlinin et. al., 2001). These features, called ``cold fronts'', are characterized by an increase in surface brightness by a factor >2 over 10-50 kpc, accompanied by a drop in temperature of a similar magnitude. The existence of such sharp gradients can be used to put interesting constraints on the physics of the intracluster medium (ICM), if their mechanism and longevity are well understood. Here, we present results of a search for cold fronts in high-resolution simulations of galaxy clusters in cold dark matter (CDM) models. We show that sharp gradients with properties similar to those of observed cold fronts naturally arise in cluster mergers when the shocks heat gas surrounding the merging sub-cluster, while its dense core remains relatively cold. The compression induced by supersonic motions and shock heating during the merger enhance the ...

  7. Innovation clusters in sound progress

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ The achievements of S&T innovation clusters,a CAS drive to set up an S&T network for sharing knowledge,information and resources in order to deal with major S&T problems.were applauded by a high-caliber panel of S&T experts.

  8. Automated Clustering of Similar Amendments

    CERN Document Server

    CERN. Geneva

    2016-01-01

    The Italian Senate is clogged by computer-generated amendments. This talk will describe a simple strategy to cluster them in an automated fashion, so that the appropriate Senate procedures can be used to get rid of them in one sweep.

  9. Thermodynamics of confined gallium clusters

    International Nuclear Information System (INIS)

    We report the results of ab initio molecular dynamics simulations of Ga13 and Ga17 clusters confined inside carbon nanotubes with different diameters. The cluster-tube interaction is simulated by the Lennard–Jones (LJ) potential. We discuss the geometries, the nature of the bonding and the thermodynamics under confinement. The geometries as well as the isomer spectra of both the clusters are significantly affected. The degree of confinement decides the dimensionality of the clusters. We observe that a number of low-energy isomers appear under moderate confinement while some isomers seen in the free space disappear. Our finite-temperature simulations bring out interesting aspects, namely that the heat capacity curve is flat, even though the ground state is symmetric. Such a flat nature indicates that the phase change is continuous. This effect is due to the restricted phase space available to the system. These observations are supported by the mean square displacement of individual atoms, which are significantly smaller than in free space. The nature of the bonding is found to be approximately jellium-like. Finally we note the relevance of the work to the problem of single file diffusion for the case of the highest confinement. (paper)

  10. Cluster radioactivity - status and developments

    International Nuclear Information System (INIS)

    Cluster radioactivities are intermediate phenomena between fission and alpha decay. The spontaneously emitted light fragment is a small cluster heavier then α particle, by lighter than the lightest fission fragment. Our works unifying the theory of the cold fission, cluster radioactivities, and α decay, as well as other theoretical models and the experimental results have been recently reviewed. Some of the cluster decay modes, like 14 C, 20 O, 23 F, 24,25 Ne, 28-30 Mg, and 32,34 Si, in a region of trans-francium parent nuclei, leading to daughters around 208 Pb, have half-live in good agreement with our predictions within the analytical superasymmetric model. The superconducting spectrometer SOLENO at I.P.N. Orsay has been employed to detect and identify 14 C radioactivity. Its good energy resolution allowed to discover 'fine structure' in the kinetic energy spectrum of 14 C emitted by 223 Ra. It was shown that the transition towards the first excited state of the daughter nucleus is stronger than that to the ground state. The interpretation given by Sheline and Ragnarsson according to which the main spherical component of the deformed parent wave function has a i11/2 character, has been confirmed. An explanation based on the Landau-Zener effect has been recently proposed by Mirea

  11. Clusters, Innovation and Tertiary Education

    Science.gov (United States)

    Madgett, Paul; Belanger, Charles H.; Mount, Joan

    2005-01-01

    The purpose of this paper is to investigate the integration between research findings produced at the University and Community College levels and local SMEs (small and medium enterprises) as it impacts regional innovation systems and in particular the prospect of cluster formation. The paper explores certain factors that have been identified in…

  12. Neutrinos as cluster dark matter

    NARCIS (Netherlands)

    Sanders, R. H.

    2007-01-01

    The dynamical mass of clusters of galaxies, calculated in terms of MOdified Newtonian Dynamics (MOND), is a factor of 2 or 3 times smaller than the Newtonian dynamical mass but remains significantly larger than the observed baryonic mass in the form of hot gas and stars in galaxies. Here I consider

  13. Innovation, learning and cluster dynamics

    NARCIS (Netherlands)

    B. Nooteboom (Bart)

    2004-01-01

    textabstractThis chapter offers a theory and method for the analysis of the dynamics, i.e. the development, of clusters for innovation. It employs an analysis of three types of embedding: institutional embedding, which is often localized, structural embedding (network structure), and relational embe

  14. Epistemic communities and cluster dynamics

    DEFF Research Database (Denmark)

    Håkanson, Lars

    2003-01-01

    This paper questions the prevailing notions that firms within industrial clusters have privi-leged access to `tacit knowledge' that is unavailable - or available only at high cost - to firms located elsewhere, and that such access provides competitive advantages that help to explain the growth...

  15. Fuzzy clustering with Minkowski distance

    NARCIS (Netherlands)

    P.J.F. Groenen (Patrick); U. Kaymak (Uzay); J.M. van Rosmalen (Joost)

    2006-01-01

    textabstractDistances in the well known fuzzy c-means algorithm of Bezdek (1973) are measured by the squared Euclidean distance. Other distances have been used as well in fuzzy clustering. For example, Jajuga (1991) proposed to use the L_1-distance and Bobrowski and Bezdek (1991) also used the L_inf

  16. Thermodynamic basis for cluster kinetics

    DEFF Research Database (Denmark)

    Hu, Lina; Bian, Xiufang; Qin, Xubo;

    2006-01-01

    Due to the inaccessibility of the supercooled region of marginal metallic glasses (MMGs) within the experimental time window, we study the cluster kinetics above the liquidus temperature, Tl, to acquire information on the fragility of the MMG systems. Thermodynamic basis for the stability...

  17. Cluster Analysis of Adolescent Blogs

    Science.gov (United States)

    Liu, Eric Zhi-Feng; Lin, Chun-Hung; Chen, Feng-Yi; Peng, Ping-Chuan

    2012-01-01

    Emerging web applications and networking systems such as blogs have become popular, and they offer unique opportunities and environments for learners, especially for adolescent learners. This study attempts to explore the writing styles and genres used by adolescents in their blogs by employing content, factor, and cluster analyses. Factor…

  18. Progressive Exponential Clustering-Based Steganography

    Directory of Open Access Journals (Sweden)

    Li Yue

    2010-01-01

    Full Text Available Cluster indexing-based steganography is an important branch of data-hiding techniques. Such schemes normally achieve good balance between high embedding capacity and low embedding distortion. However, most cluster indexing-based steganographic schemes utilise less efficient clustering algorithms for embedding data, which causes redundancy and leaves room for increasing the embedding capacity further. In this paper, a new clustering algorithm, called progressive exponential clustering (PEC, is applied to increase the embedding capacity by avoiding redundancy. Meanwhile, a cluster expansion algorithm is also developed in order to further increase the capacity without sacrificing imperceptibility.

  19. CLOC: Cluster Luminosity Order-Statistic Code

    Science.gov (United States)

    Da Silva, Robert L.; Krumholz, Mark R.; Fumagalli, Michele; Fall, S. Michael

    2016-02-01

    CLOC computes cluster order statistics, i.e. the luminosity distribution of the Nth most luminous cluster in a population. It is flexible and requires few assumptions, allowing for parametrized variations in the initial cluster mass function and its upper and lower cutoffs, variations in the cluster age distribution, stellar evolution and dust extinction, as well as observational uncertainties in both the properties of star clusters and their underlying host galaxies. It uses Markov chain Monte Carlo methods to search parameter space to find best-fitting values for the parameters describing cluster formation and disruption, and to obtain rigorous confidence intervals on the inferred values.

  20. Co-clustering models, algorithms and applications

    CERN Document Server

    Govaert, Gérard

    2013-01-01

    Cluster or co-cluster analyses are important tools in a variety of scientific areas. The introduction of this book presents a state of the art of already well-established, as well as more recent methods of co-clustering. The authors mainly deal with the two-mode partitioning under different approaches, but pay particular attention to a probabilistic approach. Chapter 1 concerns clustering in general and the model-based clustering in particular. The authors briefly review the classical clustering methods and focus on the mixture model. They present and discuss the use of different mixture

  1. Ionization of Water Clusters is Mediated by Exciton Energy Transfer from Argon Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Golan, Amir; Ahmed, Musahid

    2012-01-25

    The exciton energy deposited in an argon cluster, (Arn ,< n=20>) using VUV radiation is transferred to softly ionize doped water clusters, ((H2O)n, n=1-9) leading to the formation of non-fragmented clusters. Following the initial excitation, electronic energy is channeled to ionize the doped water cluster while evaporating the Ar shell, allowing identification of fragmented and complete water cluster ions. Examination of the photoionization efficiency curve shows that cluster evaporation from excitons located above 12.6 eV are not enough to cool the energized water cluster ion, and leads to their dissociation to (H2O)n-2H+ (protonated) clusters.

  2. An extended EM algorithm for subspace clustering

    Institute of Scientific and Technical Information of China (English)

    Lifei CHEN; Qingshan JIANG

    2008-01-01

    Clustering high dimensional data has become a challenge in data mining due to the curse of dimension-ality. To solve this problem, subspace clustering has been defined as an extension of traditional clustering that seeks to find clusters in subspaces spanned by different combinations of dimensions within a dataset. This paper presents a new subspace clustering algorithm that calcu-lates the local feature weights automatically in an EM-based clustering process. In the algorithm, the features are locally weighted by using a new unsupervised weight-ing method, as a means to minimize a proposed cluster-ing criterion that takes into account both the average intra-clusters compactness and the average inter-clusters separation for subspace clustering. For the purposes of capturing accurate subspace information, an additional outlier detection process is presented to identify the pos-sible local outliers of subspace clusters, and is embedded between the E-step and M-step of the algorithm. The method has been evaluated in clustering real-world gene expression data and high dimensional artificial data with outliers, and the experimental results have shown its effectiveness.

  3. A Fault Tolerant Trajectory Clustering (FTTC) for selecting cluster heads inWireless Sensor Networks

    CERN Document Server

    Munaga, Hazarath; Venkateswarlu, N B

    2011-01-01

    Wireless sensor networks (WSNs) suffers from the hot spot problem where the sensor nodes closest to the base station are need to relay more packet than the nodes farther away from the base station. Thus, lifetime of sensory network depends on these closest nodes. Clustering methods are used to extend the lifetime of a wireless sensor network. However, current clustering algorithms usually utilize two techniques; selecting cluster heads with more residual energy, and rotating cluster heads periodically to distribute the energy consumption among nodes in each cluster and lengthen the network lifetime. Most of the algorithms use random selection for selecting the cluster heads. Here, we propose a Fault Tolerant Trajectory Clustering (FTTC) technique for selecting the cluster heads in WSNs. Our algorithm selects the cluster heads based on traffic and rotates periodically. It provides the first Fault Tolerant Trajectory based clustering technique for selecting the cluster heads and to extenuate the hot spot proble...

  4. Comparative Studies of Various Clustering Techniques and Its Characteristics

    Directory of Open Access Journals (Sweden)

    M.Sathya Deepa

    2014-05-01

    Full Text Available Discovering knowledge from the mass database is the main objective of the Data Mining. Clustering is the key technique in data mining. A cluster is made up of a number of similar objects grouped together. The clustering is an unsupervised learning. There are many methods to form clusters. The four important methods of clustering are Partitional Clustering, Hierarchical Clustering, Density-Based Clustering and Grid-Based Clustering. In this paper, we discussed these four methods in detail.

  5. Clustering by Fuzzy Neural Gas and Evaluation of Fuzzy Clusters

    OpenAIRE

    Tina Geweniger; Lydia Fischer; Marika Kaden; Mandy Lange; Thomas Villmann

    2013-01-01

    We consider some modifications of the neural gas algorithm. First, fuzzy assignments as known from fuzzy c-means and neighborhood cooperativeness as known from self-organizing maps and neural gas are combined to obtain a basic Fuzzy Neural Gas. Further, a kernel variant and a simulated annealing approach are derived. Finally, we introduce a fuzzy extension of the ConnIndex to obtain an evaluation measure for clusterings based on fuzzy vector quantization.

  6. Dynamics of rich clusters of galaxies. I. The Coma cluster

    International Nuclear Information System (INIS)

    The structure and dynamics of the Coma cluster are analyzed using self-consistent equilibrium dynamical models. Observational material for Coma is culled from a variety of sources. Projected surface, density, and velocity-dispersion profiles are derived extending out to a radius of 30 from the cluster center, which are essentially free from field contamination. Segregation of galaxies by luminosity and morphology are discussed and a quantitative estimate of the latter is made. The method of constructing self-consistent dynamical models is discussed. Four different forms of the distribution function are analyzed allowing for different possible dependences of f on energy and angular momentum. Properties of typical models that might resemble actual clusters are presented, and the importance of having velocity-dispersion information is empha sized. The effect of a central massive object such as a cD galaxy on the core structure is illustrated. A comparison of these models with Coma reveals that only models with a distribution function in which the ratio of tangential to radial velocity dispersions is everywhere constant give acceptable fits. In particular, it is possible to rule out models that have isotropic motions in the core and predominantly radial motions in the halo. For H0 = 50, the best-fitting models give a total projected mass inside 30 of 2.9 x 1015 M/sub sun/ , a core radius of 340--400 kpc (8.5'--10'), an upper limit to any central massive object of approx.1013 M/sub sun/ , and a mass-to-blue-light ratio of M/L = 181. From cosmological considerations the cluster ''edge'' is determined to lie at rapprox.50--60. The possible distribution of ''dark matter'' in Coma is discussed and it is argued that this distribution cannot be significantly different from that of the galaxies. The dynamics of morphological segregation are examined quantitatively, and are explained at least qualitatively

  7. Frequent Pattern Mining Algorithms for Data Clustering

    DEFF Research Database (Denmark)

    Zimek, Arthur; Assent, Ira; Vreeken, Jilles

    2014-01-01

    that frequent pattern mining was at the cradle of subspace clustering—yet, it quickly developed into an independent research field. In this chapter, we discuss how frequent pattern mining algorithms have been extended and generalized towards the discovery of local clusters in high-dimensional data......Discovering clusters in subspaces, or subspace clustering and related clustering paradigms, is a research field where we find many frequent pattern mining related influences. In fact, as the first algorithms for subspace clustering were based on frequent pattern mining algorithms, it is fair to say....... In particular, we discuss several example algorithms for subspace clustering or projected clustering as well as point out recent research questions and open topics in this area relevant to researchers in either clustering or pattern mining...

  8. Simulated Versus Observed Cluster Eccentricity Evolution

    CERN Document Server

    Floor, S; Motl, P M; Floor, Stephen; Melott, Adrian; Motl, and Patrick

    2003-01-01

    The rate of galaxy cluster eccentricity evolution is useful in understanding large scale structure. Rapid evolution for $z < $ 0.13 has been found in observed clusters. We present an analysis of projections of 41 clusters produced in hydrodynamic simulations augmented with radiative cooling and 43 clusters from adiabatic simulations. This new, larger set of simulated clusters strengthens the claims of previous eccentricity studies. We find very slow evolution in simulated clusters, significantly different from the reported rates of observational eccentricity evolution. We estimate the rate of change of eccentricity with redshift and compare the rates between simulated and observed clusters. We also use a variable aperture radius to compute the eccentricity, r$_{200}$. This method is much more robust than the fixed aperture radius used in previous studies. Apparently, radiative cooling does not change cluster morphology on scales large enough to alter eccentricity. The discrepancy between simulated and obse...

  9. Spatial clustering with Density-Ordered tree

    Science.gov (United States)

    Cheng, Qing; Lu, Xin; Liu, Zhong; Huang, Jincai; Cheng, Guangquan

    2016-10-01

    Clustering has emerged as an active research direction for knowledge discovery in spatial databases. Most spatial clustering methods become ineffective when inappropriate parameters are given or when datasets of diverse shapes and densities are provided. To address this issue, we propose a novel clustering method, called SCDOT (Spatial Clustering with Density-Ordered Tree). By projecting a dataset to a Density-Ordered Tree, SCDOT partitions the data into several relatively small sub-clusters with a box-plot method. A heuristic method is proposed to find the genuine clusters by repeatedly merging sub-clusters and an iteration strategy is utilized to automatically determine input parameters. Moreover, we also provide an innovative way to identify cluster center and noise. Extensive experiments on both synthetic and real-world datasets demonstrate the superior performance of SCDOT over the baseline methods.

  10. Cluster-like headache aura status

    NARCIS (Netherlands)

    Langedijk, M; van der Naalt, J; Luijckx, GJ; De Keyser, J

    2005-01-01

    We describe a patient with successive attacks (40 to 90 minutes) of cluster-like headache associated with aphasia, and contralateral hemihypesthesia and hemiplegia. The condition can best be described as cluster-like headache aura status.

  11. Kernel method-based fuzzy clustering algorithm

    Institute of Scientific and Technical Information of China (English)

    Wu Zhongdong; Gao Xinbo; Xie Weixin; Yu Jianping

    2005-01-01

    The fuzzy C-means clustering algorithm(FCM) to the fuzzy kernel C-means clustering algorithm(FKCM) to effectively perform cluster analysis on the diversiform structures are extended, such as non-hyperspherical data, data with noise, data with mixture of heterogeneous cluster prototypes, asymmetric data, etc. Based on the Mercer kernel, FKCM clustering algorithm is derived from FCM algorithm united with kernel method. The results of experiments with the synthetic and real data show that the FKCM clustering algorithm is universality and can effectively unsupervised analyze datasets with variform structures in contrast to FCM algorithm. It is can be imagined that kernel-based clustering algorithm is one of important research direction of fuzzy clustering analysis.

  12. Star Cluster Dissolution in Arp 284

    CERN Document Server

    Peterson, Bradley W; Smith, Beverly J; Hancock, Mark

    2009-01-01

    We present results from a study of proto-globular cluster candidates in the interacting galaxy system Arp 284 (NGC 7714/5). Studies of the Antennae and M51 have suggested that the majority of these star clusters dissolve within 20 Myr due to mass loss. We obtain cluster colors using archival \\emph{HST} data, and estimate ages and extinctions for over 150 clusters using evolutionary synthesis models. We find that clusters in NGC 7714 are generally less than 20 Myr old, while the data in the bridge is too limited to allow good estimates for individual clusters. We also examine {H {\\sc ii}} region complexes with lower-resolution \\emph{GALEX} and ground-based H$\\alpha$ images. Several of these regions appear to be much older than the detected clusters within them, which may indicate the presence of an older, unresolved population of low mass or dispersed clusters.

  13. Modeling the Metallicity Distribution of Globular Clusters

    CERN Document Server

    Muratov, Alexander L

    2010-01-01

    Observed metallicities of globular clusters reflect physical conditions in the interstellar medium of their high-redshift host galaxies. Globular cluster systems in most large galaxies display bimodal color and metallicity distributions, which are often interpreted as indicating two distinct modes of cluster formation. The metal-rich and metal-poor clusters have systematically different locations and kinematics in their host galaxies. However, the red and blue clusters have similar internal properties, such as the masses, sizes, and ages. It is therefore interesting to explore whether both metal-rich and metal-poor clusters could form by a common mechanism and still be consistent with the bimodal distribution. We present such a model, which prescribes the formation of globular clusters semi-analytically using galaxy assembly history from cosmological simulations coupled with observed scaling relations for the amount and metallicity of cold gas available for star formation. We assume that massive star clusters...

  14. Discovery of eight lensing clusters of galaxies

    CERN Document Server

    Liang, S M; Han, J L; Jiang, Y Y

    2013-01-01

    Clusters of galaxies have a huge mass which can act as gravitational lenses. Galaxies behind clusters can be distorted to form arcs in images by the lenses. Herein a search was done for giant lensed arcs by galaxy clusters using the SDSS data. By visually inspecting SDSS images of newly identified clusters in the SDSS DR8 and Stripe 82 data, we discover 8 strong lensing clusters together with additional 3 probable and 6 possible cases. The lensed arcs show bluer colors than the member galaxies of clusters. The masses and optical luminosities of galaxy clusters interior to the arcs are calculated, and the mass-to-light ratios are found to be in the range of a few tens of M_Solar/L_Solar, consistent with the distribution of previously known lensing clusters.

  15. The Evolution of Cluster Substructure with Redshift

    CERN Document Server

    Jeltema, T E; Bautz, M W; Buote, D A; Jeltema, Tesla E.; Canizares, Claude R.; Bautz, Mark W.; Buote, David A.

    2003-01-01

    Using Chandra archival data, we quantify the evolution of cluster morphology with redshift. To quantify cluster morphology, we use the power ratio method developed by Buote and Tsai (1995). Power ratios are constructed from moments of the two-dimensional gravitational potential and are, therefore, related to a cluster's dynamical state. Our sample will include 40 clusters from the Chandra archive with redshifts between 0.11 and 0.89. These clusters were selected from two fairly complete flux-limited X-ray surveys (the ROSAT Bright Cluster Sample and the Einstein Medium Sensitivity Survey), and additional high-redshift clusters were selected from recent ROSAT flux-limited surveys. Here we present preliminary results from the first 28 clusters in this sample. Of these, 16 have redshifts below 0.5, and 12 have redshifts above 0.5.

  16. Top-down induction of clustering trees

    OpenAIRE

    Blockeel, Hendrik; De Raedt, Luc; Ramon, Jan

    2000-01-01

    An approach to clustering is presented that adapts the basic top-down induction of decision trees method towards clustering. To this aim, it employs the principles of instance based learning. The resulting methodology is implemented in the TIC (Top down Induction of Clustering trees) system for first order clustering. The TIC system employs the first order logical decision tree representation of the inductive logic programming system Tilde. Various experiments with TIC are presented, in both ...

  17. Hybrid Self Organizing Map for Overlapping Clusters

    OpenAIRE

    M.N.M. Sap; Ehsan Mohebi

    2008-01-01

    The Kohonen self organizing map is an excellent tool in exploratoryphase of data mining and pattern recognition. The SOM is a popular tool that maps high dimensional space into a small number of dimensions by placing similar elements close together, forming clusters. Recently researchers found that to capture the uncertainty involved in cluster analysis, it is not necessary to have crisp boundaries in some clustering operations. In this paper to overcomethe uncertainty, a two-level clustering...

  18. Cluster Dynamics in a Circulating Fluidized Bed

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, C.P.; Breault, R.W.

    2006-11-01

    A common hydrodynamic feature in industrial scale circulating fluidized beds is the presence of clusters. The continuous formation and destruction of clusters strongly influences particle hold-up, pressure drop, heat transfer at the wall, and mixing. In this paper fiber optic data is analyzed using discrete wavelet analysis to characterize the dynamic behavior of clusters. Five radial positions at three different axial locations under five different operating were analyzed using discrete wavelets. Results are summarized with respect to cluster size and frequency.

  19. Diffuse radio emission in the Coma cluster

    OpenAIRE

    Feretti, L.; Giovannini, G.

    1997-01-01

    The Coma cluster is peculiar in the radio domain owing to the presence of cluster-wide diffuse sources: the radio halo Coma C, the relic source 1253+275, and the bridge between them. Diffuse radio sources in clusters are a rare and poorly understood phenomenon. We summarize here the properties of the diffuse radio sources in Coma and their relation to other cluster properties.

  20. Coordination in humanitarian logistics through clusters

    OpenAIRE

    Jahre, Marianne; Jensen, Leif-Magnus

    2010-01-01

    Purpose – In the field of humanitarianism, cluster thinking has been suggested as a solution to the lack of coordinated disaster response. Clusters for diverse functions, including sheltering, logistics and water and sanitation, can be viewed as an effort to achieve functional coordination. The purpose of this paper is to contribute to a greater understanding of the potential of cluster concepts using supply chain coordination and inter‐cluster coordination. The focus is on the conceptual lev...

  1. Watching the Birth of Super Star Clusters

    CERN Document Server

    Turner, J L; Turner, Jean L.; Beck, Sara C.

    2003-01-01

    Subarcsecond infrared and radio observations yield important information about the formation of super star clusters from their surrounding gas. We discuss the general properties of ionized and molecular gas near young, forming SSCs, as illustrated by the prototypical young forming super star cluster nebula in the dwarf galaxy, NGC 5253. This super star cluster appears to have a gravitationally bound nebula. The lack of molecular gas suggests a very high star formation efficiency, consistent with the formation of a large, bound star cluster.

  2. Radio Relics in Clusters of Galaxies

    CERN Document Server

    Giovannini, G

    2004-01-01

    In this paper we review the observational results on Relic radio sources in clusters of galaxies. We discuss their observational properties, structures and radio spectra. We will show that Relics can be divided according to their size, morphology, and location in the galaxy cluster. These differences could be related to physical properties of Relic sources. The comparison with cluster conditions suggests that Relics could be related to shock waves originated by cluster mergers.

  3. The BMW X-ray Cluster Survey

    OpenAIRE

    Moretti, Alberto; Guzzo, Luigi; Campana, Sergio; Covino, Stefano; Lazzati, Davide; Longhetti, Marcella; Molinari, Emilio; Panzera, Maria Rosa; Tagliaferri, Gianpiero; Dell'Antonio, Ian

    2001-01-01

    We describe the main features of the BMW survey of serendipitous X-ray clusters, based on the still unexploited ROSAT-HRI archival observations. The sky coverage, surface density and first deep optical CCD images of the candidates indicate that this sample can represent an excellent complement to the existing PSPC deep cluster surveys and will provide us with a fully independent probe of the evolution of the cluster abundance, in addition to significantly increasing the number of clusters kno...

  4. Comparing Clusters and Supercomputers for Lattice QCD

    CERN Document Server

    Gottlieb, S

    2001-01-01

    Since the development of the Beowulf project to build a parallel computer from commodity PC components, there have been many such clusters built. The MILC QCD code has been run on a variety of clusters and supercomputers. Key design features are identified, and the cost effectiveness of clusters and supercomputers are compared.

  5. Structural Trends of Small Silicon Clusters

    Science.gov (United States)

    Ho, K. M.; Pan, B. C.; Wacker, J. G.; Wang, C. Z.; Turner, D. E.; Deaven, D.

    1997-03-01

    We have performed a systematic search for the low energy structures of silicon clusters in the range from Si_10 to Si_20 using a recently developed genetic algorithm. Our results revealed the structural motif for the elongated clusters observed in mobility experiments. We also observe the beginning of another competing family for clusters larger than Si_17.

  6. Optical response of small magnesium clusters

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2004-01-01

    We predict strong enhancement in the photoabsorption of small Mg clusters in the region of 4–5 eV due to the resonant excitation of the plasmon oscillations of cluster electrons. Photoabsorption spectra for neutral Mg clusters consisting of up to N = 11 atoms have been calculated using an ab initio...

  7. Photoabsorption of small sodium and magnesium clusters

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2004-01-01

    We predict the strong enhancement in the photoabsorption of small Mg clusters in the region of 4-5 eV due to the resonant excitation of the plasmon oscillations of cluster electrons. The photoabsorption spectra for neutral Mg clusters consisting of up to N=11 atoms have been calculated using it a...

  8. Cost functions for pairwise data clustering

    Science.gov (United States)

    Angelini, L.; Nitti, L.; Pellicoro, M.; Stramaglia, S.

    2001-07-01

    Cost functions for non-hierarchical pairwise clustering are introduced, in the probabilistic autoencoder framework, by the request of maximal average similarity between input and the output of the autoencoder. Clustering is thus formulated as the problem of finding the ground state of Potts spins Hamiltonians. The partition, provided by this procedure, identifies clusters with dense connected regions in the data space.

  9. Cost functions for pairwise data clustering

    OpenAIRE

    Angelini, L.; Nitti, L.; M. Pellicoro; Stramaglia, S.

    2001-01-01

    Cost functions for non-hierarchical pairwise clustering are introduced, in the probabilistic autoencoder framework, by the request of maximal average similarity between the input and the output of the autoencoder. The partition provided by these cost functions identifies clusters with dense connected regions in data space; differences and similarities with respect to a well known cost function for pairwise clustering are outlined.

  10. Graph coarsening and clustering on the GPU

    NARCIS (Netherlands)

    Fagginger Auer, B.O.; Bisseling, R.H.

    2013-01-01

    Agglomerative clustering is an effective greedy way to quickly generate graph clusterings of high modularity in a small amount of time. In an effort to use the power offered by multi-core CPU and GPU hardware to solve the clustering problem, we introduce a fine-grained sharedmemory parallel graph co

  11. The Design of Cluster Randomized Crossover Trials

    Science.gov (United States)

    Rietbergen, Charlotte; Moerbeek, Mirjam

    2011-01-01

    The inefficiency induced by between-cluster variation in cluster randomized (CR) trials can be reduced by implementing a crossover (CO) design. In a simple CO trial, each subject receives each treatment in random order. A powerful characteristic of this design is that each subject serves as its own control. In a CR CO trial, clusters of subjects…

  12. Hierarchical word clustering - automatic thesaurus generation

    OpenAIRE

    Hodge, V.J.; Austin, J.

    2002-01-01

    In this paper, we propose a hierarchical, lexical clustering neural network algorithm that automatically generates a thesaurus (synonym abstraction) using purely stochastic information derived from unstructured text corpora and requiring no prior word classifications. The lexical hierarchy overcomes the Vocabulary Problem by accommodating paraphrasing through using synonym clusters and overcomes Information Overload by focusing search within cohesive clusters. We describe existing word catego...

  13. Cosmology and cluster halo scaling relations

    NARCIS (Netherlands)

    Araya-Melo, Pablo A.; van de Weygaert, Rien; Jones, Bernard J. T.

    2009-01-01

    We explore the effects of dark matter and dark energy on the dynamical scaling properties of galaxy clusters. We investigate the cluster Faber-Jackson (FJ), Kormendy and Fundamental Plane (FP) relations between the mass, radius and velocity dispersion of cluster-sized haloes in cosmological N-body s

  14. Consequences of Violating Randomization in Cluster Sampling

    OpenAIRE

    Parrott Jason; Sawilowsky Shlomo

    2014-01-01

    Although not as efficient as simple random sampling, cluster sampling has been regarded as a valid sampling technique when the researcher is attempting to save cost. In order to do so, it is necessary that random selection occurs in all stages of sampling. This simulation study examines purposeful selection of cluster sampling in the second stage of a two stage cluster design.

  15. Surface decorated platinum carbonyl clusters

    Science.gov (United States)

    Ciabatti, Iacopo; Femoni, Cristina; Iapalucci, Maria Carmela; Longoni, Giuliano; Zacchini, Stefano; Zarra, Salvatore

    2012-06-01

    Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters.Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters. CCDC 867747 and 867748. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30400g

  16. Planetary systems in star clusters

    CERN Document Server

    Kouwenhoven, M B N; Cai, Maxwell Xu; Spurzem, Rainer

    2016-01-01

    Thousands of confirmed and candidate exoplanets have been identified in recent years. Consequently, theoretical research on the formation and dynamical evolution of planetary systems has seen a boost, and the processes of planet-planet scattering, secular evolution, and interaction between planets and gas/debris disks have been well-studied. Almost all of this work has focused on the formation and evolution of isolated planetary systems, and neglect the effect of external influences, such as the gravitational interaction with neighbouring stars. Most stars, however, form in clustered environments that either quickly disperse, or evolve into open clusters. Under these conditions, young planetary systems experience frequent close encounters with other stars, at least during the first 1-10 Myr, which affects planets orbiting at any period range, as well as their debris structures.

  17. Clusters of Pneumocystis carinii pneumonia

    DEFF Research Database (Denmark)

    Helweg-Larsen, J; Tsolaki, A G; Miller, Raymonde;

    1998-01-01

    Genotyping at the internal transcribed spacer (ITS) regions of the nuclear rRNA operon was performed on isolates of P. carinii sp. f. hominis from three clusters of P. carinii pneumonia among eight patients with haematological malignancies and six with HIV infection. Nine different ITS sequence...... types of P. carinii sp. f. hominis were identified in the samples from the patients with haematological malignancies, suggesting that this cluster of cases of P. carinii pneumonia was unlikely to have resulted from nosocomial transmission. A common ITS sequence type was observed in two of the patients...... with haematological malignancies who shared a hospital room, and also in two of the patients with HIV infection who had prolonged close contact on the ward. In contrast, different ITS sequence types were detected in samples from an HIV-infected homosexual couple who shared the same household. These data suggest...

  18. Ontology Partitioning: Clustering Based Approach

    Directory of Open Access Journals (Sweden)

    Soraya Setti Ahmed

    2015-05-01

    Full Text Available The semantic web goal is to share and integrate data across different domains and organizations. The knowledge representations of semantic data are made possible by ontology. As the usage of semantic web increases, construction of the semantic web ontologies is also increased. Moreover, due to the monolithic nature of the ontology various semantic web operations like query answering, data sharing, data matching, data reuse and data integration become more complicated as the size of ontology increases. Partitioning the ontology is the key solution to handle this scalability issue. In this work, we propose a revision and an enhancement of K-means clustering algorithm based on a new semantic similarity measure for partitioning given ontology into high quality modules. The results show that our approach produces meaningful clusters than the traditional algorithm of K-means.

  19. Clustering Implies Geometry in Networks

    Science.gov (United States)

    Krioukov, Dmitri

    2016-05-01

    Network models with latent geometry have been used successfully in many applications in network science and other disciplines, yet it is usually impossible to tell if a given real network is geometric, meaning if it is a typical element in an ensemble of random geometric graphs. Here we identify structural properties of networks that guarantee that random graphs having these properties are geometric. Specifically we show that random graphs in which expected degree and clustering of every node are fixed to some constants are equivalent to random geometric graphs on the real line, if clustering is sufficiently strong. Large numbers of triangles, homogeneously distributed across all nodes as in real networks, are thus a consequence of network geometricity. The methods we use to prove this are quite general and applicable to other network ensembles, geometric or not, and to certain problems in quantum gravity.

  20. Clustering Implies Geometry in Networks.

    Science.gov (United States)

    Krioukov, Dmitri

    2016-05-20

    Network models with latent geometry have been used successfully in many applications in network science and other disciplines, yet it is usually impossible to tell if a given real network is geometric, meaning if it is a typical element in an ensemble of random geometric graphs. Here we identify structural properties of networks that guarantee that random graphs having these properties are geometric. Specifically we show that random graphs in which expected degree and clustering of every node are fixed to some constants are equivalent to random geometric graphs on the real line, if clustering is sufficiently strong. Large numbers of triangles, homogeneously distributed across all nodes as in real networks, are thus a consequence of network geometricity. The methods we use to prove this are quite general and applicable to other network ensembles, geometric or not, and to certain problems in quantum gravity. PMID:27258887

  1. Tuning Properties in Silver Clusters

    KAUST Repository

    Joshi, Chakra P

    2015-07-09

    The properties of Ag nanoclusters are not as well understood as those of their more precious Au cousins. However, a recent surge in the exploration of strategies to tune the physicochemical characteristics of Ag clusters addresses this imbalance, leading to new insights into their optical, luminescence, crystal habit, metal-core, ligand-shell and environmental properties. In this Perspective, we provide an overview of the latest strategies along with a brief introduction of the theoretical framework necessary to understand the properties of silver nanoclusters and the basis for their tuning. The advances in cluster research and the future prospects presented in this Perspective will eventually guide the next large systematic study of nanoclusters, resulting in a single collection of data similar to the periodic table of elements.

  2. Clustering Coefficients in Multiplex Networks

    CERN Document Server

    Cozzo, Emanuele; De Domenico, Manlio; Solé, Albert; Arenas, Alex; Gómez, Sergio; Porter, Mason A; Moreno, Yamir

    2013-01-01

    Recent advances in the study of complex networked systems has highlighted that our interconnected world is made of networks that are coupled together through different layers that each stand for one type of interaction or system. Despite this situation, it is traditional to aggregate multiplex data into a single weighted network in order take advantage of existing tools. This is admittedly convenient, but it is also extremely problematic. In this paper, we generalize the concept of clustering coefficients for multiplex networks. We show how the layered structure of multiplex networks introduces a new degree of freedom that has a fundamental effect on transitivity. We compute our new multiplex clustering coefficients for several real multiplex networks and illustrate why generalizing monoplex concepts to multiplex networks must be done with great care.

  3. Customer Behavior Clustering Using SVM

    Science.gov (United States)

    Yang, Zhongying; Su, Xiaolong

    In order to supply better service for network customers, deeply analyzing customers' behavior is required. This paper extracts three features from customers' network behavior which is divided into different categories, such as browsing news, downloading shared resources and real-time communications etc. Support vector machine is used to perform clustering, thanks to its fast and valid executing, especially in the situation of small datasets. Using the analysis results, we can make our applications and services more personalized and easier to be used.

  4. The entrepreneur in the cluster

    OpenAIRE

    Kronholm, Thomas; Vidhall, Martin

    2008-01-01

    Abstract Entrepreneurship has become an important issue in the modern society where the business landscape consists of many small and medium sized firms. These firms have all been started by an entrepreneur who has identified and business idea and developed that idea into a new venture. We therefore see the idea identification and idea development process as a central part of the creation of a new firm. A concept that has become popular in the discussion about entrepreneurship is the cluster ...

  5. Extreme quadrupole deformation and clusterization

    Directory of Open Access Journals (Sweden)

    Antonenko N.

    2012-12-01

    Full Text Available We discuss a simple symmetry-adapted method for the determination of the shape isomers, and for the study of their possible fragmentation. In other words the connection between the quadrupole (collective and dipole (cluster degrees of freedom is considered in terms of an easily applicable, yet microscopic method. The energetics is taken into account by the double-folding method. Special attention is focused on those cases in which the theoretical predictions have a direct comparison with experimental observation.

  6. The Cluster as Market Organization

    DEFF Research Database (Denmark)

    Maskell, Peter; Lorenzen, Mark

    2003-01-01

    information as they arecommonly conceived in mainstream economics. One of the original attractions of Neoclassicalprice theory was precisely that it promised a way of analysing the economy in general andmarket exchange in particular independently of specific institutional settings.However, introducing...... organization or market form. The cluster is one suchspecific market organization that is structured along territorial lines because this enables thebuilding of a set of institutions that are helpful in conducting certain kinds of economicactivities....

  7. Intuitionistic fuzzy aggregation and clustering

    CERN Document Server

    Xu, Zeshui

    2012-01-01

    This book offers a systematic introduction to the clustering algorithms for intuitionistic fuzzy values, the latest research results in intuitionistic fuzzy aggregation techniques, the extended results in interval-valued intuitionistic fuzzy environments, and their applications in multi-attribute decision making, such as supply chain management, military system performance evaluation, project management, venture capital, information system selection, building materials classification, and operational plan assessment, etc.

  8. Cluster models and other topics

    CERN Document Server

    Akaishi, Yoshinori; Horiuchi, Hisashi; Ikeda, Kiyomi

    1986-01-01

    This volume consists of contributions from some of Japan's most eminent nuclear theorists. The cluster model of the nucleus is discussed pedagogically and the current status of the field is surveyed. A contribution on Monte Carlo Methods and Lattice Gauge Theories gives nuclear theorists a glimpse of related developments in QCD and Gauge Theories. Few Body Systems are reviewed by Y Akaishi, paying special attention to the ATMS Multiple Scattering Method.

  9. Clusters, Governance and Business Intelligence

    OpenAIRE

    Neto, Paulo; Serrano, Maria Manuel

    2010-01-01

    One of the most important aspects of current economical and social reality of each local and regional territory, and very much determinative for its economic development potential, is the nature of its territorial organization of the productive processes, as well as, the characteristics, and sophistication level of the enterprise strategies that are functioning in it. This article seeks to contribute to the ongoing discussion on the role of clusters as engines of economic and social developme...

  10. Motivic amplitudes and cluster coordinates

    OpenAIRE

    J.K. Golden; Goncharov, A. B.; M. Spradlin; C. Vergu; Volovich, A.

    2014-01-01

    In this paper we study motivic amplitudes--objects which contain all of the essential mathematical content of scattering amplitudes in planar SYM theory in a completely canonical way, free from the ambiguities inherent in any attempt to choose particular functional representatives. We find that the cluster structure on the kinematic configuration space Conf_n(P^3) underlies the structure of motivic amplitudes. Specifically, we compute explicitly the coproduct of the two-loop seven-particle MH...

  11. CLUSTER INITIATIVES IN EU POLICY

    OpenAIRE

    Piotr Pachura

    2008-01-01

    According to the results of literary research it is possible to univocally state thatthe geographical proximity between enterprises of a similar profile of activity facilitates theachievement of a higher level of productivity and innovativenesss. The clusters covering thespatial sphere of its location: producers, suppliers, service providers, research units,educational institutions and other units supporting a given sector became an important factorin the economic development of regions. The ...

  12. cluster-lensing: Tools for calculating properties and weak lensing profiles of galaxy clusters

    Science.gov (United States)

    Ford, Jes

    2016-05-01

    The cluster-lensing package calculates properties and weak lensing profiles of galaxy clusters. Implemented in Python, it includes cluster mass-richness and mass-concentration scaling relations, and NFW halo profiles for weak lensing shear, the differential surface mass density ΔΣ(r), and for magnification, Σ(r). Optionally the calculation will include the effects of cluster miscentering offsets.

  13. Applications of Cluster Analysis to the Creation of Perfectionism Profiles: A Comparison of two Clustering Approaches

    Directory of Open Access Journals (Sweden)

    Jocelyn H Bolin

    2014-04-01

    Full Text Available Although traditional clustering methods (e.g., K-means have been shown to be useful in the social sciences it is often difficult for such methods to handle situations where clusters in the population overlap or are ambiguous. Fuzzy clustering, a method already recognized in many disciplines, provides a more flexible alternative to these traditional clustering methods. Fuzzy clustering differs from other traditional clustering methods in that it allows for a case to belong to multiple clusters simultaneously. Unfortunately, fuzzy clustering techniques remain relatively unused in the social and behavioral sciences. The purpose of this paper is to introduce fuzzy clustering to these audiences who are currently relatively unfamiliar with the technique. In order to demonstrate the advantages associated with this method, cluster solutions of a common perfectionism measure were created using both fuzzy clustering and K-means clustering, and the results compared. Results of these analyses reveal that different cluster solutions are found by the two methods, and the similarity between the different clustering solutions depends on the amount of cluster overlap allowed for in fuzzy clustering.

  14. When galaxy clusters collide : the impact of merger shocks on cluster gas and galaxy evolution

    NARCIS (Netherlands)

    Stroe, Andra

    2015-01-01

    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' cluste

  15. Niching method using clustering crowding

    Institute of Scientific and Technical Information of China (English)

    GUO Guan-qi; GUI Wei-hua; WU Min; YU Shou-yi

    2005-01-01

    This study analyzes drift phenomena of deterministic crowding and probabilistic crowding by using equivalence class model and expectation proportion equations. It is proved that the replacement errors of deterministic crowding cause the population converging to a single individual, thus resulting in premature stagnation or losing optional optima. And probabilistic crowding can maintain equilibrium multiple subpopulations as the population size is adequate large. An improved niching method using clustering crowding is proposed. By analyzing topology of fitness landscape using hill valley function and extending the search space for similarity analysis, clustering crowding determines the locality of search space more accurately, thus greatly decreasing replacement errors of crowding. The integration of deterministic and probabilistic replacement increases the capacity of both parallel local hill climbing and maintaining multiple subpopulations. The experimental results optimizing various multimodal functions show that,the performances of clustering crowding, such as the number of effective peaks maintained, average peak ratio and global optimum ratio are uniformly superior to those of the evolutionary algorithms using fitness sharing, simple deterministic crowding and probabilistic crowding.

  16. STAR FORMATION IN DENSE CLUSTERS

    International Nuclear Information System (INIS)

    A model of core-clump accretion with equally likely stopping describes star formation in the dense parts of clusters, where models of isolated collapsing cores may not apply. Each core accretes at a constant rate onto its protostar, while the surrounding clump gas accretes as a power of protostar mass. Short accretion flows resemble Shu accretion and make low-mass stars. Long flows resemble reduced Bondi accretion and make massive stars. Accretion stops due to environmental processes of dynamical ejection, gravitational competition, and gas dispersal by stellar feedback, independent of initial core structure. The model matches the field star initial mass function (IMF) from 0.01 to more than 10 solar masses. The core accretion rate and the mean accretion duration set the peak of the IMF, independent of the local Jeans mass. Massive protostars require the longest accretion durations, up to 0.5 Myr. The maximum protostar luminosity in a cluster indicates the mass and age of its oldest protostar. The distribution of protostar luminosities matches those in active star-forming regions if protostars have a constant birthrate but not if their births are coeval. For constant birthrate, the ratio of young stellar objects to protostars indicates the star-forming age of a cluster, typically ∼1 Myr. The protostar accretion luminosity is typically less than its steady spherical value by a factor of ∼2, consistent with models of episodic disk accretion.

  17. Extinction in young massive clusters

    Science.gov (United States)

    De Marchi, Guido; Panagia, Nino

    2016-01-01

    Up to ages of ~100 Myr, massive clusters are still swamped in large amounts of gas and dust, causing considerable and uneven levels of extinction. At the same time, large grains (ices?) produced by type II supernovae profoundly alter the interstellar medium (ISM), thus resulting in extinction properties very different from those of the diffuse ISM. To obtain physically meaningful parameters of stars (luminosities, effective temperatures, masses, ages, etc.) we must understand and measure the local extinction law. We have developed a powerful method to unambiguously determine the extinction law everywhere across a cluster field, using multi-band photometry of red giant stars belonging to the red clump (RC) and are applying it to young massive clusters in the Local Group. In the Large Magellanic Cloud, with about 20 RC stars per arcmin2, for each field we can easily derive an accurate extinction curve over the entire wavelength range of the photometry. As an example, we present the extinction law of the Tarantula nebula (30 Dor) based on thousands of stars observed as part of the Hubble Tarantula Treasury Project. We discuss how the incautious adoption of the Milky Way extinction law in the analysis of massive star forming regions may lead to serious underestimates of the fluxes and of the star formation rates by factors of 2 or more.

  18. Pair extended coupled cluster doubles

    CERN Document Server

    Henderson, Thomas M; Scuseria, Gustavo E

    2015-01-01

    The accurate and efficient description of strongly correlated systems remains an important challenge for computational methods. Doubly occupied configuration interaction (DOCI), in which all electrons are paired and no correlations which break these pairs are permitted, can in many cases provide an accurate account of strong correlations, albeit at combinatorial computational cost. Recently, there has been significant interest in a method we refer to as pair coupled cluster doubles (pCCD), a variant of coupled cluster doubles in which the electrons are paired. This is simply because pCCD provides energies nearly identical to those of DOCI, but at mean-field computational cost (disregarding the cost of the two-electron integral transformation). Here, we introduce the more complete pair extended coupled cluster doubles (pECCD) approach which, like pCCD, has mean-field cost and reproduces DOCI energetically. We show that unlike pCCD, pECCD also reproduces the DOCI wave function with high accuracy. Moreoever, pEC...

  19. Hot Outflows in Galaxy Clusters

    CERN Document Server

    Kirkpatrick, C C

    2015-01-01

    The gas-phase metallicity distribution has been analyzed for the hot atmospheres of 29 galaxy clusters using {\\it 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 $R_{\\rm Fe} \\propto P_{\\rm jet}^{0.45}$. The estimated outflow rates are typically tens of solar masses per year but exceed $100 ~\\rm M_\\odot ~yr^{-1}$ in the most powerful AGN. The outflow rates are 10% to 20% 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 ...

  20. A GMBCG galaxy cluster catalog of 55,880 rich clusters from SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Jiangang; McKay, Timothy A.; Koester, Benjamin P.; Rykoff, Eli S.; Rozo, Eduardo; Annis, James; Wechsler, Risa H.; Evrard, August; Siegel, Seth R.; Becker, Matthew; Busha, Michael; /Fermilab /Michigan U. /Chicago U., Astron. Astrophys. Ctr. /UC, Santa Barbara /KICP, Chicago /KIPAC, Menlo Park /SLAC /Caltech /Brookhaven

    2010-08-01

    We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.

  1. A GMBCG Galaxy Cluster Catalog of 55,424 Rich Clusters from SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Jiangang; /Fermilab; McKay, Timothy A.; /Michigan U.; Koester, Benjamin P.; /Chicago U.; Rykoff, Eli S.; /UC, Santa Barbara /LBL, Berkeley; Rozo, Eduardo; /Chicago U.; Annis, James; /Fermilab; Wechsler, Risa H.; /SLAC; Evrard, August; /Michigan U.; Siegel, Seth R.; /Michigan U.; Becker, Matthew; /Chicago U.; Busha, Michael; /SLAC; Gerdes, David; /Michigan U.; Johnston, David E.; /Fermilab; Sheldon, Erin; /Brookhaven

    2011-08-22

    We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.

  2. Cluster algorithms and computational complexity

    Science.gov (United States)

    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.

  3. Rearrangement of cluster structure during fission processes

    DEFF Research Database (Denmark)

    Lyalin, Andrey G.; Obolensky, Oleg I.; Solov'yov, Andrey V.;

    2004-01-01

    groups of atoms from the parent cluster is largely independent of the isomer form of the parent cluster. The importance of rearrangement of the cluster structure during the fission process is elucidated. This rearrangement may include transition to another isomer state of the parent cluster before actual......Results of molecular dynamics simulations of fission reactions $Na_10^2+ -->Na_7^++ Na_3^+ and Na_18^2+--> 2Na_9^+ are presented. The dependence of the fission barriers on the isomer structure of the parent cluster is analysed. It is demonstrated that the energy necessary for removing homothetic...

  4. A Novel Research on Rough Clustering Algorithm

    Directory of Open Access Journals (Sweden)

    Tao Qu

    2014-01-01

    Full Text Available The aim of this study is focusing the issue of traditional clustering algorithm subjects to data space distribution influence, a novel clustering algortihm combined with rough set theory is employed to the normal clustering. The proposed rough clustering algorithm takes the condition attributes and decision attributes displayed in the information table as the consistency principle, meanwhile it takes the data supercubic and information entropy to realize data attribute shortcutting and discretizing. Based on above discussion, by applying assemble feature vector addition principle computiation only one scanning information table can realize clustering for the data subject. Experiments reveal that the proposed algorithm is efficient and feasible.

  5. Likelihood Functions for Galaxy Cluster Surveys

    CERN Document Server

    Holder, G

    2006-01-01

    Galaxy cluster surveys offer great promise for measuring cosmological parameters, but survey analysis methods have not been widely studied. Using methods developed decades ago for galaxy clustering studies, it is shown that nearly exact likelihood functions can be written down for galaxy cluster surveys. The sparse sampling of the density field by galaxy clusters allows simplifications that are not possible for galaxy surveys. An application to counts in cells is explicitly tested using cluster catalogs from numerical simulations and it is found that the calculated probability distributions are very accurate at masses above several times 10^{14}h^{-1} solar masses at z=0 and lower masses at higher redshift.

  6. What Qualifies as a Cluster Theory?

    DEFF Research Database (Denmark)

    Maskell, Peter; Kebir, Leïla

    2005-01-01

    on the cluster concept. The paper considers approaches based on the idea of externalities (illustrated by the Marshall's work on `Industrial district'); oncompetitiveness issue (illustrated by Michael Porter's theory of cluster growth); on a territorial perspective (illustrated by the GREMI approach......This paper investigates the theoretical backgrounds of the `cluster' and proposes a framework aiming at drawing the contour of cluster theory.The profundity of the notion of `clusters' is arguably conditional on the coherence of four fundamental issues associated with the concept: 1) the economic...

  7. Witnessing galaxy clusters: from maturity to childhood

    CERN Document Server

    Ascaso, Begoña

    2012-01-01

    Galaxy clusters are the largest structures in Universe. They are very important as both cosmological probes and astrophysical laboratories. Several methods have been developed to detect galaxy clusters with different techniques (optical, X-rays, Weak Lensing and Sunyaev-Zeldovich effect) providing cluster samples with a well-characterized purity and completeness rates up to moderate redshift (z$$1.5-2) ever detected. In this talk, I introduce these techniques and review some of the cluster samples obtained including particular striking cases. I discuss their relevance in terms of cosmological and galaxy evolution constraints and finally, I briefly refer to the cluster science predictions for the next generation surveys.

  8. AMiBA, XMM, and Cluster Surveys

    CERN Document Server

    Liang, H

    2001-01-01

    The Array for Microwave Background Anisotropy (AMiBA) is an interferometric array of 19 dishes co-mounted on a steerable platform and operating at 95GHz. One of the main scientific aims of AMiBA is to conduct cluster surveys using the Sunyaev-Zel'dovich (SZ) effect. Here we explore the potential of AMiBA as a tailor-made SZ instrument for the study of cluster physics and cosmology via cluster surveys out to the epoch of cluster formation. In particular, we explore the potential of combining AMiBA cluster surveys with the XMM-LSS (Large Scale Structure) survey.

  9. A copper cluster protected with phenylethanethiol

    Energy Technology Data Exchange (ETDEWEB)

    Ganguly, Anindya; Chakraborty, Indranath; Udayabhaskararao, Thumu; Pradeep, Thalappil, E-mail: pradeep@iitm.ac.in [Indian Institute of Technology Madras, DST Unit of Nanoscience (DST UNS), Department of Chemistry (India)

    2013-04-15

    A copper cluster protected with 2-phenylethanethiol (PET) exhibiting distinct optical features in UV/Vis spectroscopy is reported. Matrix-assisted laser desorption ionisation mass spectrometry of the cluster shows a well-defined molecular ion peak at m/z 5,800, assigned to {approx}Cu{sub 38}(PET){sub 25}. Fragmented ions from the cluster show the expected isotope patterns in electrospray ionisation mass spectrometry. The as-synthesized cluster was well-characterised using other tools as well. Clusters undergo decomposition in about 2 h after synthesis as a metallic few-atom core of copper is highly unstable. The products of decomposition were also characterised.

  10. MVClustViz: A Novice Yet Simple Multivariate Cluster Visualization Technique for Centroid-based Clusters

    OpenAIRE

    Sagar S. De; Minati Mishra; Satchidananda Dehuri

    2013-01-01

    In the visual data mining, visualization of clusters is a challenging task. Although lots of techniques already have been developed, the challenges still remain to represent large volume of data with multiple dimension and overlapped clusters. In this paper, a multivariate clusters visualization technique (MVClustViz) has been presented to visualize the centroid-based clusters. The geographic projection technique supports multi-dimension, large volume, and both crisp and fuzzy clusters visual...

  11. A Survey on Various Clustering Techniques with K-means Clustering Algorithm in Detail

    OpenAIRE

    Supreet Kaur; Usvir Kaur

    2013-01-01

    Clustering is the division of data into groups of similar objects. In clustering, some details aredisregarded in exchange for data simplification. Clustering can be viewed as a data modeling technique thatprovides for concise summaries of the data. Clustering is therefore related to many disciplines and plays animportant role in a broad range of applications. The applications of clustering usually deal with largedatasets and data with many attributes. Exploration of such data is a subject of ...

  12. The construction of Pauli-correct separable cluster-cluster potentials

    International Nuclear Information System (INIS)

    We construct effective cluster-cluster potentials from microscopic point of view so that we analyze the three-cluster model of the light nucleus by the three-body Faddeev equations. Our potentials are based on the resonating group method (RGM) by which a lot of works in the cluster physics have been carried out. Pauli-correct separable potentials between two-clusters such as α, 3He, t, d, n and p are presented in the momentum space representation. (author)

  13. Efficient clustering aggregation based on data fragments.

    Science.gov (United States)

    Wu, Ou; Hu, Weiming; Maybank, Stephen J; Zhu, Mingliang; Li, Bing

    2012-06-01

    Clustering aggregation, known as clustering ensembles, has emerged as a powerful technique for combining different clustering results to obtain a single better clustering. Existing clustering aggregation algorithms are applied directly to data points, in what is referred to as the point-based approach. The algorithms are inefficient if the number of data points is large. We define an efficient approach for clustering aggregation based on data fragments. In this fragment-based approach, a data fragment is any subset of the data that is not split by any of the clustering results. To establish the theoretical bases of the proposed approach, we prove that clustering aggregation can be performed directly on data fragments under two widely used goodness measures for clustering aggregation taken from the literature. Three new clustering aggregation algorithms are described. The experimental results obtained using several public data sets show that the new algorithms have lower computational complexity than three well-known existing point-based clustering aggregation algorithms (Agglomerative, Furthest, and LocalSearch); nevertheless, the new algorithms do not sacrifice the accuracy. PMID:22334025

  14. Multilevel Techniques for the Clustering Problem

    Directory of Open Access Journals (Sweden)

    Noureddine Bouhmala

    2014-02-01

    Full Text Available Data Mining is concerned with the discovery of int eresting patterns and knowledge in data repositories. Cluster Analysis which belongs to the core methods of data mining is the process of discovering homogeneous groups called clusters. Given a data-set and some measure of similarity between data objects, the goal in most c lustering algorithms is maximizing both the homogeneity within each cluster and the heterogene ity between different clusters. In this work, two multilevel algorithms for the clustering problem are introduced. The multilevel paradigm suggests looking at the clustering proble m as a hierarchical optimization process going through different levels evolving from a coar se grain to fine grain strategy. The clustering problem is solved by first reducing the problem level by level to a coarser problem where an initial clustering is computed. The clustering of the coarser problem is mapped back level-by- level to obtain a better clustering of the original problem by refining the intermediate different clustering obtained at various levels. A benchmark using a number of data sets collected from a variety of domains is used to compare the effective ness of the hierarchical approach against its single-level counterpart.

  15. Optical Substructures in 48 Galaxy Clusters

    CERN Document Server

    Girardi, M; Fadda, D; Giuricin, G; Mardirossian, F; Mezzetti, M

    1996-01-01

    We analyze the presence of substructures in a set of 48 galaxy clusters, by using galaxy positions and redshifts. We use a multi-scale analysis which couples kinematical estimators with the wavelet transform. 14% of our clusters are strongly substructured (i.e. they are bimodal or complex) and 24% of the remaining unimodal clusters contain substructures at small scales. Thus, in substantial agreement with previous studies, about one third of clusters show substructures. In unimodal clusters the presence of substructures does not affect the estimates of both virial masses and velocity dispersions, which are generally in good agreement with the X-ray temperatures. Thus, unimodal clusters are not too far from a status of dynamical equilibrium. On the contrary, velocity dispersions and masses for some bimodal or complex clusters strongly depend on whether they are treated as single systems or as sums of different clumps and X-ray temperatures and velocity dispersions may be very different.

  16. Clustering: Applied to Data Structuring and Retrieval

    Directory of Open Access Journals (Sweden)

    Ogechukwu N. Iloanusi

    2011-11-01

    Full Text Available Clustering is a very useful scheme for data structuring and retrieval behuhcause it can handle large volumes of multi-dimensional data and employs a very fast algorithm. Other forms of data structuring techniques include hashing and binary tree structures. However, clustering has the advantage of employing little computational storage requirements and a fast speed algorithm. In this paper, clustering, k-means clustering and the approaches to effective clustering are extensively discussed. Clustering was employed as a data grouping and retrieval strategy in the filtering of fingerprints in the Fingerprint Verification Competition 2000 database 4(a. An average penetration of 7.41% obtained from the experiment shows clearly that the clustering scheme is an effective retrieval strategy for the filtering of fingerprints.

  17. Node clustering for wireless sensor networks

    International Nuclear Information System (INIS)

    Recent years have witnessed considerable growth in the development and deployment of clustering methods which are not only used to maintain network resources but also increases the reliability of the WSNs (Wireless Sensor Network) and the facts manifest by the wide range of clustering solutions. Node clustering by selecting key parameters to tackle the dynamic behaviour of resource constraint WSN is a challenging issue. This paper highlights the recent progress which has been carried out pertaining to the development of clustering solutions for the WSNs. The paper presents classification of node clustering methods and their comparison based on the objectives, clustering criteria and methodology. In addition, the potential open issues which need to be considered for future work are high lighted. Keywords: Clustering, Sensor Network, Static, Dynamic

  18. Cosine-Based Clustering Algorithm Approach

    Directory of Open Access Journals (Sweden)

    Mohammed A. H. Lubbad

    2012-02-01

    Full Text Available Due to many applications need the management of spatial data; clustering large spatial databases is an important problem which tries to find the densely populated regions in the feature space to be used in data mining, knowledge discovery, or efficient information retrieval. A good clustering approach should be efficient and detect clusters of arbitrary shapes. It must be insensitive to the outliers (noise and the order of input data. In this paper Cosine Cluster is proposed based on cosine transformation, which satisfies all the above requirements. Using multi-resolution property of cosine transforms, arbitrary shape clusters can be effectively identified at different degrees of accuracy. Cosine Cluster is also approved to be highly efficient in terms of time complexity. Experimental results on very large data sets are presented, which show the efficiency and effectiveness of the proposed approach compared to other recent clustering methods.

  19. Formation and stability of sputtered clusters

    International Nuclear Information System (INIS)

    Current theory for the formation of sputtered clusters states that either atoms are sputtered individually and aggregate after having left the surface or they are sputtered as complete clusters. There is no totally sharp boundary between the two interpretations, but experimental evidence is mainly thought to favour the latter model. Both theories demand a criterion for the stability of the clusters. In computer simulations of sputtering, the idea has been to use the same interaction potential as in the lattice computations to judge the stability. More qualitatively, simple geometrical shapes have also been looked for. It is found here, that evidence for 'magic numbers' and electron parity effects in clusters have existed in the sputtering literature for a long time, making more sophisticated stability criteria necessary. The breakdown of originally sputtered metastable clusters into stable clusters gives strong support to the 'sputtered as clusters' hypothesis. (author)

  20. Stellar Encounter Rate in Galactic Globular Clusters

    CERN Document Server

    Bahramian, Arash; Sivakoff, Gregory R; Gladstone, Jeanette C

    2013-01-01

    The high stellar densities in the cores of globular clusters cause significant stellar interactions. These stellar interactions can produce close binary mass-transferring systems involving compact objects and their progeny, such as X-ray binaries and radio millisecond pulsars. Comparing the numbers of these systems and interaction rates in different clusters drives our understanding of how cluster parameters affect the production of close binaries. In this paper we estimate stellar encounter rates (Gamma) for 124 Galactic globular clusters based on observational data as opposed to the methods previously employed, which assumed "King-model" profiles for all clusters. By deprojecting cluster surface brightness profiles to estimate luminosity density profiles, we treat "King-model" and "core-collapsed" clusters in the same way. In addition, we use Monte-Carlo simulations to investigate the effects of uncertainties in various observational parameters (distance, reddening, surface brightness) on Gamma, producing t...

  1. Validity Index and number of clusters

    Directory of Open Access Journals (Sweden)

    Mohamed Fadhel Saad

    2012-01-01

    Full Text Available Clustering (or cluster analysis has been used widely in pattern recognition, image processing, and data analysis. It aims to organize a collection of data items into c clusters, such that items within a cluster are more similar to each other than they are items in the other clusters. The number of clusters c is the most important parameter, in the sense that the remaining parameters have less influence on the resulting partition. To determine the best number of classes several methods were made, and are called validity index. This paper presents a new validity index for fuzzy clustering called a Modified Partition Coefficient And Exponential Separation (MPCAES index. The efficiency of the proposed MPCAES index is compared with several popular validity indexes. More information about these indexes is acquired in series of numerical comparisons and also real data Iris.

  2. Energy Balance in Clusters of Galaxies

    Science.gov (United States)

    Motl, P. M.; Burns, J. M.

    2005-04-01

    We review different physical mechanisms that are likely to play a significant role in determining the detailed thermal state of gas in clusters of galaxies. Mergers are the dominant process impacting clusters and these collisions significantly perturb the cluster state. The continual loss of energy from the gas to radiation must also be accounted for and cooling gas can drive several positive feedback mechanisms. From simple energy arguments, AGN are likely to make a significant contribution to balance the energy lost from cluster cores. We also explore additional positive feedback mechanisms including supernovae feedback and thermal conduction. If AGN are the sole feedback mechanism, what are to be made of clusters that lack evidence for AGN activity yet have canonical cool cores? As cluster samples with high-resolution X-ray data grow larger, it is likely to be the properties of relaxed, cool-core clusters that will be the best guides to numerical simulations.

  3. Hesitant fuzzy agglomerative hierarchical clustering algorithms

    Science.gov (United States)

    Zhang, Xiaolu; Xu, Zeshui

    2015-02-01

    Recently, hesitant fuzzy sets (HFSs) have been studied by many researchers as a powerful tool to describe and deal with uncertain data, but relatively, very few studies focus on the clustering analysis of HFSs. In this paper, we propose a novel hesitant fuzzy agglomerative hierarchical clustering algorithm for HFSs. The algorithm considers each of the given HFSs as a unique cluster in the first stage, and then compares each pair of the HFSs by utilising the weighted Hamming distance or the weighted Euclidean distance. The two clusters with smaller distance are jointed. The procedure is then repeated time and again until the desirable number of clusters is achieved. Moreover, we extend the algorithm to cluster the interval-valued hesitant fuzzy sets, and finally illustrate the effectiveness of our clustering algorithms by experimental results.

  4. Characterizing Galaxy Clusters with Gravitational Potential

    CERN Document Server

    Lau, Erwin Tin-Hay

    2010-01-01

    We propose a simple estimator for the gravitational potential of cluster-size halos using the temperature and density profiles of the intracluster gas based on the assumptions of hydrostatic equilibrium and spherical symmetry. Using high resolution cosmological simulations of galaxy clusters, we show that the scaling relation between this estimator and the gravitational potential has a small intrinsic scatter of about 10%, and it is insensitive to baryon physics outside the cluster core. The slope and the normalization of the scaling relation vary weakly with redshift, and they are relatively independent of the choice of radial range used and the dynamical states of the clusters. The results presented here provide a way for using the cluster potential function as an alternative to the cluster mass function in constraining cosmology using galaxy clusters.

  5. Measurement of cluster-cluster interaction in liquids by deposition and AFM of silicon clusters onto HOPG surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Galinis, Gediminas; Torricelli, Gauthier; Akraiam, Atea; Haeften, Klaus von, E-mail: kvh6@le.ac.uk [University of Leicester, Department of Physics and Astronomy (United Kingdom)

    2012-08-15

    We have investigated the interaction and aggregation of novel fluorescent silicon nanoclusters in liquids by measuring the size distribution of dried clusters on graphite. The clusters were produced by gas aggregation and co-deposition with a beam of water vapour. Drops of the solutions were placed on freshly cleaved highly oriented pyrolitic graphite, subsequently vacuum dried and investigated by atomic force microscopy (AFM) in ultra high vacuum. The AFM images show single clusters and agglomerates. The height distributions are Gaussian-shaped with average heights of 1 nm and widths of 1 nm. The heights never exceed 3 nm. In some regions a second cluster layer is observed. In all samples the separation between first and second layers is larger than the separation between the first layer and the graphite substrate, which we attribute to a stronger interaction between clusters and surface than the cluster self-interaction. We conclude that the separation between first and second layer represents a much better fingerprint of the original size distribution of the clusters in solution than the height of the first layer. The observation of a second cluster layer is important for using silicon clusters as building blocks for cluster-assembled materials.

  6. Countdown for the Cluster quartet

    Science.gov (United States)

    2000-07-01

    Following the successful completion of the Cluster II Flight Readiness Review on 23 June, final launch preparations are progressing smoothly and combined operations with the Soyuz-Fregat launch vehicle are now under way. The dual launches, each involving two Cluster spacecraft built under the prime contractorship of Astrium (former Dornier Satellitensysteme GmbH, Germany), are currently scheduled for 15 July with a launch window opening at 14:40 CEST, 12:40 GMT and lasting 6 minutes, and 9 August from Baikonur Space Centre in Kazakhstan. A number of press events have been organised in various countries to coincide with both launches. The main press centre for the first launch will be located at ESA's European Space Operations Centre (ESOC) at Darmstadt in Germany. Local press centres are also being set up in the other ESA establishments: ESRIN (Italy), ESTEC (The Netherlands), and VILSPA (Spain). See attachment for more detailed information and reply form to register at the various sites. Details of the second launch press event, which will be held in London (UK), will be available at a later date. Cluster II Competition Attracts Record Entries. A highlight of the first launch event at ESOC will be the announcement of the overall winner of ESA's "Name the Cluster quartet" competition and the chosen names of the four Cluster II satellites. Last February, members of the public in all of ESA's 15 member states were asked to suggest the most suitable names for the Cluster II spacecraft. The satellites are currently known as flight models (FM) 5, 6, 7 and 8. Competitors were asked to propose a set of four names (places, people, or things from history, mythology, or fiction, but not living persons) and explain in a few sentences the reasons for their choice. After sifting through more than 5,000 entries from all over Europe and debating at length the merits of the various suggestions, the multinational jury eventually produced a list of 15 national prize winners - one

  7. Star Cluster Buzzing With Pulsars

    Science.gov (United States)

    2005-01-01

    A dense globular star cluster near the center of our Milky Way Galaxy holds a buzzing beehive of rapidly-spinning millisecond pulsars, according to astronomers who discovered 21 new pulsars in the cluster using the National Science Foundation's 100-meter Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The cluster, called Terzan 5, now holds the record for pulsars, with 24, including three known before the GBT observations. Pulsar Diagram Pulsar Diagram: Click on image for more detail. "We hit the jackpot when we looked at this cluster," said Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, VA. "Not only does this cluster have a lot of pulsars -- and we still expect to find more in it -- but the pulsars in it are very interesting. They include at least 13 in binary systems, two of which are eclipsing, and the four fastest-rotating pulsars known in any globular cluster, with the fastest two rotating nearly 600 times per second, roughly as fast as a household blender," Ransom added. Ransom and his colleagues reported their findings to the American Astronomical Society's meeting in San Diego, CA, and in the online journal Science Express. The star cluster's numerous pulsars are expected to yield a bonanza of new information about not only the pulsars themselves, but also about the dense stellar environment in which they reside and probably even about nuclear physics, according to the scientists. For example, preliminary measurements indicate that two of the pulsars are more massive than some theoretical models would allow. "All these exotic pulsars will keep us busy for years to come," said Jason Hessels, a Ph.D student at McGill University in Montreal. Globular clusters are dense agglomerations of up to millions of stars, all of which formed at about the same time. Pulsars are spinning, superdense neutron stars that whirl "lighthouse beams" of radio waves or light around as they spin. A neutron star is what is

  8. All about RIKEN Integrated Cluster of Clusters (RICC

    Directory of Open Access Journals (Sweden)

    Maho Nakata

    2012-07-01

    Full Text Available

    This is an introduction to the RIKEN's supercomputer RIKEN Integrated Cluster of Clusters (RICC, that has been in operation since August 2009. The basic concept of the RICC is to "provide an environment with high power computational resources to facilitate research and development for RIKEN's researchers". Based on this concept, we have been operating the RICC system as a (i data analysis environment for experimental researchers, (ii development environment targeting the next-generation supercomputer; i.e., the "K" computer, and (iii GPU (graphics processing unit computers for exploring challenges in developing a future computer environment. The total performance of RICC is 97.94 TFlops, ranking it as the 125th on the Top500 list in Nov. 2011. We prepared four job class accounts, based on the researchers' proposals prior to evaluation by our Review Committee. We also provided backup services to RIKEN's researchers, such as conducting RICC training classes, software installation services, and speed up and visualization support. To encourage affirmative participation and proactive initiation, all the services were free of charge; however, access to RICC was limited to researchers and collaborators of RIKEN. As a result, RICC has been able to maintain a high activity ratio (> 90% since the beginning of its operation.

  9. DISTANT CLUSTER OF GALAXIES [left

    Science.gov (United States)

    2002-01-01

    One of the deepest images to date of the universe, taken with NASA's Hubble Space Telescope (HST), reveals thousands of faint galaxies at the detection limit of present day telescopes. Peering across a large volume of the observable cosmos, Hubble resolves thousands of galaxies from five to twelve billion light-years away. The light from these remote objects has taken billions of years to cross the expanding universe, making these distant galaxies fossil evidence' of events that happened when the universe was one-third its present age. A fraction of the galaxies in this image belong to a cluster located nine billion light-years away. Though the field of view (at the cluster's distance) is only two million light-years across, it contains a multitude of fragmentary objects. (By comparison, the two million light-years between our Milky Way galaxy and its nearest large companion galaxy, in the constellation Andromeda, is essentially empty space!) Very few of the cluster's members are recognizable as normal spiral galaxies (like our Milky Way), although some elongated members might be edge-on disks. Among this zoo of odd galaxies are ``tadpole-like'' objects, disturbed and apparently merging systems dubbed 'train-wrecks,' and a multitude of faint, tiny shards and fragments, dwarf galaxies or possibly an unknown population of objects. However, the cluster also contains red galaxies that resemble mature examples of today's elliptical galaxies. Their red color comes from older stars that must have formed shortly after the Big Bang. The image is the full field view of the Wide Field and Planetary Camera-2. The picture was taken in intervals between May 11 and June 15, 1994 and required an 18-hour long exposure, over 32 orbits of HST, to reveal objects down to 29th magnitude. [bottom right] A close up view of the peculiar radio galaxy 3C324 used to locate the cluster. The galaxy is nine billion light-years away as measured by its spectral redshift (z=1.2), and located in the

  10. International collaboration clusters in Africa

    CERN Document Server

    Adams, Jonathan; Hook, Daniel; Leydesdorff, Loet

    2013-01-01

    Recent discussion about the increase in international research collaboration suggests a comprehensive global network centred around a group of core countries and driven by generic socio-economic factors where the global system influences all national and institutional outcomes. In counterpoint, we demonstrate that the collaboration pattern for countries in Africa is far from universal. Instead, it exhibits layers of internal clusters and external links that are explained not by monotypic global influences but by regional geography and, perhaps even more strongly, by history, culture and language. Analysis of these bottom-up, subjective, human factors is required in order to provide the fuller explanation useful for policy and management purposes.

  11. Clustering analysis of telecommunication customers

    Institute of Scientific and Technical Information of China (English)

    REN Hong; ZHENG Yan; WU Ye-rong

    2009-01-01

    In this article, a clustering method based on genetic algorithm (GA) for telecommunication customer subdivision is presented. First, the features of telecommunication customers (such as the calling behavior and consuming behavior) are extracted. Second, the similarities between the multidimensional feature vectors of telecommunication customers are computed and mapped as the distance between samples on a two-dimensional plane. Finally, the distances are adjusted to approximate the similarities gradually by GA. One advantage of this method is the independent distribution of the sample space. The experiments demonstrate the feasibility of the proposed method.

  12. Sound oscillation of dropwise cluster

    Science.gov (United States)

    Shavlov, A. V.; Dzhumandzhi, V. A.; Romanyuk, S. N.

    2012-06-01

    There was registered sound oscillation of a dropwise cluster formed over the warmed-up water surface. We have calculated the electrical charge of drops on the basis of experimental data on ion-sound oscillation. It was demonstrated that the charge is proportional to surface area of the drops and does not depend on intensity of their evaporation (condensation) in the range of 60-100 °C. The charge of drops reaches 102-103 units of elementary charge and coincides on magnitude order with the literary value of a charge calculated by another method.

  13. Linked coupled cluster Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Franklin, R. S. T.; Zoccante, A.; Thom, A. J. W. [University Chemical Laboratory, Cambridge University, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Spencer, J. S. [Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)

    2016-01-28

    We consider a new formulation of the stochastic coupled cluster method in terms of the similarity transformed Hamiltonian. We show that improvement in the granularity with which the wavefunction is represented results in a reduction in the critical population required to correctly sample the wavefunction for a range of systems and excitation levels and hence leads to a substantial reduction in the computational cost. This development has the potential to substantially extend the range of the method, enabling it to be used to treat larger systems with excitation levels not easily accessible with conventional deterministic methods.

  14. Cluster identification based on correlations

    Science.gov (United States)

    Schulman, L. S.

    2012-04-01

    The problem addressed is the identification of cooperating agents based on correlations created as a result of the joint action of these and other agents. A systematic method for using correlations beyond second moments is developed. The technique is applied to a didactic example, the identification of alphabet letters based on correlations among the pixels used in an image of the letter. As in this example, agents can belong to more than one cluster. Moreover, the identification scheme does not require that the patterns be known ahead of time.

  15. Parallel algorithms and cluster computing

    CERN Document Server

    Hoffmann, Karl Heinz

    2007-01-01

    This book presents major advances in high performance computing as well as major advances due to high performance computing. It contains a collection of papers in which results achieved in the collaboration of scientists from computer science, mathematics, physics, and mechanical engineering are presented. From the science problems to the mathematical algorithms and on to the effective implementation of these algorithms on massively parallel and cluster computers we present state-of-the-art methods and technology as well as exemplary results in these fields. This book shows that problems which seem superficially distinct become intimately connected on a computational level.

  16. On Charged Insulated Metallic Clusters

    Science.gov (United States)

    Dietrich, K.; Garny, M.; Pomorski, K.

    We determine the wavefunctions and eigen-values of electrons bound to a positively charged mesoscopic metallic cluster covered by an insulating surface layer. The radius of the metal core and the thickness of the insulating surface layer are of the order of a couple of Ångström. We study in particular the electromagnetic decay of externally located electrons into unoccupied internally located states which exhibits a resonance behaviour. This resonance structure has the consequence that the lifetime of the "mesoscopic atoms" may vary by up to 6 orders of magnitude depending on the values of the parameters (from sec to years).

  17. Performance Evaluation of Spectral Clustering Algorithm using Various Clustering Validity Indices

    Directory of Open Access Journals (Sweden)

    M. T. Somashekara

    2014-11-01

    Full Text Available In spite of the popularity of spectral clustering algorithm, the evaluation procedures are still in developmental stage. In this article, we have taken benchmarking IRIS dataset for performing comparative study of twelve indices for evaluating spectral clustering algorithm. The results of the spectral clustering technique were also compared with k-mean algorithm. The validity of the indices was also verified with accuracy and (Normalized Mutual Information NMI score. Spectral clustering algorithm showed better results when compared to k-mean algorithm. All indices showed consistent results with spectral clustering technique. Silhouette Index, Hartigan Index, Davies-Bouldin (DB index and Krzanowski-Lai (KL index failed to evaluate k-mean clustering. Surprisingly, all eleven indices showed acceptable results for spectral clustering algorithm. This article confirms the superiority of spectral clustering algorithm and also confirms that all 12 indices are suitable for evaluating spectral clustering

  18. Fuzzy Logic Method for Enhancement Fault-Tolerant of Cluster Head in Wireless Sensor Networks Clustering

    Directory of Open Access Journals (Sweden)

    Farnaz Pakdeland

    2016-08-01

    Full Text Available Wireless sensor network is comprised of several sensor nodes. The retaining factors influence the network operation. In the clustering structure the cluster head failure can cause loss of information.The aim of this paper is to increase tolerance error in the cluster head node. At first, paying attention to the producing balance in the density of the cluster cause to postpone the death time of the cluster head node and lessen the collision due to the lack of the energy balance in clusters. The innovation in this stage is formed by using two fuzzy logic systems. One in the phase of evaluation of the cluster head chance, and the other in the phase of producing balance and the nodes migration to the qualified clusters to increase balance, Then the focus is on recognizing and repairing the cluster head fault.

  19. Cluster synchronization induced by one-node clusters in networks with asymmetric negative couplings

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jianbao [School of Science, Hangzhou Dianzi University, Hangzhou 310018 (China); Ma, Zhongjun, E-mail: mzj1234402@163.com [School of Mathematics and Computing Science, Guilin University of Electronic Technology, Guilin 541004 (China); Zhang, Gang [College of Mathematics and Information Science, Hebei Normal University, Shijiazhuang 050024 (China)

    2013-12-15

    This paper deals with the problem of cluster synchronization in networks with asymmetric negative couplings. By decomposing the coupling matrix into three matrices, and employing Lyapunov function method, sufficient conditions are derived for cluster synchronization. The conditions show that the couplings of multi-node clusters from one-node clusters have beneficial effects on cluster synchronization. Based on the effects of the one-node clusters, an effective and universal control scheme is put forward for the first time. The obtained results may help us better understand the relation between cluster synchronization and cluster structures of the networks. The validity of the control scheme is confirmed through two numerical simulations, in a network with no cluster structure and in a scale-free network.

  20. Star Clusters in the Magellanic Clouds-1: Parameterisation and Classification of 1072 Clusters in the LMC

    Science.gov (United States)

    Nayak, P. K.; Subramaniam, A.; Choudhury, S.; Indu, G.; Sagar, Ram

    2016-08-01

    We have introduced a semi-automated quantitative method to estimate the age and reddening of 1072 star clusters in the Large Magellanic Cloud (LMC) using the Optical Gravitational Lensing Experiment (OGLE) III survey data. This study brings out 308 newly parameterised clusters. In a first of its kind, the LMC clusters are classified into groups based on richness/mass as very poor, poor, moderate and rich clusters, similar to the classification scheme of open clusters in the Galaxy. A major cluster formation episode is found to happen at 125±25 Myr in the inner LMC. The bar region of the LMC appears prominently in the age range 60 - 250 Myr and is found to have a relatively higher concentration of poor and moderate clusters. The eastern and the western ends of the bar are found to form clusters initially, which later propagates to the central part. We demonstrate that there is a significant difference in the distribution of clusters as a function of mass, using a movie based on the propagation (in space and time) of cluster formation in various groups. The importance of including the low mass clusters in the cluster formation history is demonstrated. The catalog with parameters, classification, and cleaned and isochrone fitted CMDs of 1072 clusters, which are available as online material, can be further used to understand the hierarchical formation of clusters in selected regions of the LMC.

  1. Intelligent Pattern Mining and Data Clustering for Pattern Cluster Analysis using Cancer Data

    Directory of Open Access Journals (Sweden)

    G.Raj Kumar

    2010-12-01

    Full Text Available Data mining techniques are used for the knowledge discovery process under the large data set environment. Clustering techniques are used to group up the relevant data sets. Hierarchical and partitioned clustering techniques are used for the clustering process. The clustering process is the complex task with high process time. The pattern extraction scheme is applied to find frequent item sets. Association rule mining techniques are applied to carry out the pattern extraction process. The pattern extraction scheme and the clustering scheme are integrated in the simultaneous pattern extraction and clustering scheme. The clustering process is improved with pattern comparison and transaction transfer process. The simultaneous clustering scheme is implemented to analyze the cancer patient diagnosis reports. The system is implemented as four major modules data set management, pattern extraction, clustering process and performance analysis. The data sets are preprocessed before the pattern extraction process. The patterns are used in the simultaneous clustering process. The performance analysis is done with the comparison of the data clustering scheme and pattern clustering schemes. The process time and memory factors are used in the performance analysis process. The cluster accuracy is represented using the fitness values. The system is enhanced with the K-means clustering algorithm.

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

    Science.gov (United States)

    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

  3. NEW CLUSTERING SCHEMES FOR WIRELESS SENSOR NETWORKS

    Directory of Open Access Journals (Sweden)

    S. M. Mazinani

    2010-05-01

    Full Text Available In this paper, two clustering algorithms are proposed. In the first one, we investigate a clustering protocol for single hop wireless sensor networks that employs a competitive scheme for cluster head selection. The proposed algorithm is named EECS-M that is a modified version to the well known protocol EECS where some of the nodes become volunteers to be cluster heads with an equal probability.  In the competition phase in contrast to EECS using a fixed competition range for any volunteer node, we assign a variable competition range to it that is related to its distance to base station. The volunteer nodes compete in their competition ranges and every one with more residual energy would become cluster head. In the second one, we develop a clustering protocol for single hop wireless sensor networks. In the proposed algorithm some of the nodes become volunteers to be cluster heads. We develop a time based competitive clustering algorithm that the advertising time is based on the volunteer node’s residual energy. We assign to every volunteer node a competition range that may be fixed or variable as a function of distance to BS. The volunteer nodes compete in their competition ranges and every one with more energy would become cluster head. In both proposed algorithms, our objective is to balance the energy consumption of the cluster heads all over the network. Simulation results show the more balanced energy consumption and longer lifetime.

  4. The Sloan Great Wall. Rich clusters

    CERN Document Server

    Einasto, M; Saar, E; Nurmi, P; Enkvist, I; Einasto, P; Heinamaki, P; Liivamagi, L J; Tempel, E; Einasto, J; Martinez, V J; Vennik, J; Pihajoki, P

    2010-01-01

    We present the results of the study of the substructure and galaxy content of ten rich clusters of galaxies in three different superclusters of the Sloan Great Wall. We determine the substructure in clusters using the 'Mclust' package from the 'R' statistical environment and analyse their galaxy content. We analyse the distribution of the peculiar velocities of galaxies in clusters and calculate the peculiar velocity of the first ranked galaxy. We show that clusters in our sample have more than one component; in some clusters different components also have different galaxy content. We find that in some clusters with substructure the peculiar velocities of the first ranked galaxies are large. All clusters in our sample host luminous red galaxies. They can be found both in the central areas of clusters as well as in the outskirts, some of them have large peculiar velocities. About 1/3 of red galaxies in clusters are spirals. The scatter of colours of red ellipticals is in most clusters larger than that of red s...

  5. Comparative Study of K-means and Robust Clustering

    Directory of Open Access Journals (Sweden)

    Shashi Sharma

    2013-09-01

    Full Text Available Data mining is the mechanism of implementing patterns in large amount of data sets involving methods at the intersection of artificial intelligence, machine learning, statistics, and database systems. Clustering is the very big area in which grouping of same type of objects in data mining. Clustering has divided into different categories – partitioned clustering and hierarchical clustering. In this paper we study two types of clustering first is Kmeans which is part of partitioned clustering. Kmeans clustering generates a specific number of disjoint, flat (non-hierarchical clusters. Second clustering is robust clustering which is part of hierarchical clustering. This clustering uses Jaccard coefficient instead of using the distance measures to find the similarity between the data or documents to classify the clusters. We show comparison between Kmeans clustering and robust clustering which is better for categorical data.

  6. Sound oscillation of dropwise cluster

    International Nuclear Information System (INIS)

    There was registered sound oscillation of a dropwise cluster formed over the warmed-up water surface. We have calculated the electrical charge of drops on the basis of experimental data on ion-sound oscillation. It was demonstrated that the charge is proportional to surface area of the drops and does not depend on intensity of their evaporation (condensation) in the range of 60–100 °C. The charge of drops reaches 102–103 units of elementary charge and coincides on magnitude order with the literary value of a charge calculated by another method. -- Highlights: ► The present investigation registered short-wave sound oscillations of water drops in a dropwise cluster in the range of 60–100 °C. ► We have found autocorrelation functions and Fourier transforms of time series of interdroplet distance; defined oscillation frequencies. ► Calculated electrical charge of drops and specified that the charge is proportional to the drop surface area.

  7. Critical exponents from cluster coefficients

    Science.gov (United States)

    Rotman, Z.; Eisenberg, E.

    2009-09-01

    For a large class of repulsive interaction models, the Mayer cluster integrals can be transformed into a tridiagonal real symmetric matrix Rmn , whose elements converge to two constants. This allows for an effective extrapolation of the equation of state for these models. Due to a nearby (nonphysical) singularity on the negative real z axis, standard methods (e.g., Padé approximants based on the cluster integrals expansion) fail to capture the behavior of these models near the ordering transition, and, in particular, do not detect the critical point. A recent work [E. Eisenberg and A. Baram, Proc. Natl. Acad. Sci. U.S.A. 104, 5755 (2007)] has shown that the critical exponents σ and σ' , characterizing the singularity of the density as a function of the activity, can be exactly calculated if the decay of the R matrix elements to their asymptotic constant follows a 1/n2 law. Here we employ renormalization group (RG) arguments to extend this result and analyze cases for which the asymptotic approach of the R matrix elements toward their limiting value is of a more general form. The relevant asymptotic correction terms (in RG sense) are identified, and we then present a corrected exact formula for the critical exponents. We identify the limits of usage of the formula and demonstrate one physical model, which is beyond its range of validity. The formula is validated numerically and then applied to analyze a number of concrete physical models.

  8. Sound oscillation of dropwise cluster

    Energy Technology Data Exchange (ETDEWEB)

    Shavlov, A.V., E-mail: shavlov@ikz.ru [Institute of the Earth Cryosphere, RAS Siberian Branch, P.O. 1230, 625000 Tyumen (Russian Federation); Dzhumandzhi, V.A.; Romanyuk, S.N. [Institute of the Earth Cryosphere, RAS Siberian Branch, P.O. 1230, 625000 Tyumen (Russian Federation)

    2012-06-04

    There was registered sound oscillation of a dropwise cluster formed over the warmed-up water surface. We have calculated the electrical charge of drops on the basis of experimental data on ion-sound oscillation. It was demonstrated that the charge is proportional to surface area of the drops and does not depend on intensity of their evaporation (condensation) in the range of 60–100 °C. The charge of drops reaches 10{sup 2}–10{sup 3} units of elementary charge and coincides on magnitude order with the literary value of a charge calculated by another method. -- Highlights: ► The present investigation registered short-wave sound oscillations of water drops in a dropwise cluster in the range of 60–100 °C. ► We have found autocorrelation functions and Fourier transforms of time series of interdroplet distance; defined oscillation frequencies. ► Calculated electrical charge of drops and specified that the charge is proportional to the drop surface area.

  9. Doping graphene with BSO clusters

    Science.gov (United States)

    Magaña, Fernando; Vazquez, Gerardo Jorge; Lopez, Julio

    2014-03-01

    Sillenite crystals (Bi12MO20, M = Ge, Si and Ti) present a number of interesting properties, such as photorefractive, piezoelectric, electro-optical, photoinduced absorption, optical activity and photoconductivity. Employing them at the nanoscale in electronic and optoelectronic devices may result in new applications. For example the electronic properties of inherently two-dimensional (2D) materials such as graphene may be change by doping it with Bi12SiO20 (BSO) clusters. BSO is the fastest photorefractive crystal to date. By means of a calculation of first principles using the DFT, the density the levels of energy of molecules of BSO was investigated. The evolution was observed from the levels when going adding more molecules from BSO to the system, obtaining a behavior of the levels that looks like the levels in the bulk. In this work also was studied the effect on electronic properties of graphene when BSO clusters was added to it. We want to thank computing facilities to Supercomputo, UNAM.

  10. Gas clumping in galaxy clusters

    CERN Document Server

    Eckert, D; Molendi, S; Vazza, F; Roncarelli, M; Gastaldello, F; Rossetti, M

    2013-01-01

    The reconstruction of galaxy cluster's gas density profiles is usually performed by assuming spherical symmetry and averaging the observed X-ray emission in circular annuli. In the case of a very inhomogeneous and asymmetric gas distribution, this method has been shown to return biased results in numerical simulations because of the $n^2$ dependence of the X-ray emissivity. We propose a method to recover the true density profiles in the presence of inhomogeneities, based on the derivation of the azimuthal median of the surface brightness in concentric annuli. We demonstrate the performance of this method with numerical simulations, and apply it to a sample of 31 galaxy clusters in the redshift range 0.04-0.2 observed with ROSAT/PSPC. The emissivity biases recovered by comparing the mean and the median are mild and show a slight trend of increasing bias with radius. For $R

  11. Cluster radioactivity from Osmium isotopes

    International Nuclear Information System (INIS)

    The spontaneous emission of fragments heavier than alpha particle and lighter than the lightest fission fragment from a nucleus is called cluster radioactivity. It is a cold nuclear phenomenon predicted based on Quantum Mechanical Fragmentation Theory (QMFT). Cluster radioactivity is studied using Unified Fission Model (UFM). Present study is conducted using proton rich osmium isotopes with mass ranging from 162-190. The interacting potential chosen is the Effective Liquid Drop Model (ELDM). The total potential in one dimensional case is the sum of Coulomb, surface and centrifugal potential. Here centrifugal part is not considered. Barrier penetrability (P) is calculated using one dimensional WKB approximation. The decay constant is obtained as λ = νoP where νo is the assault frequency. From the calculated values we have found that osmium isotopes in the mass range between 162-168 is highly unstable against alpha decay. Mass range of osmium isotopes found favourable to 8Be decay are 162-170, to 12C decay are 162-172, to 16O decay are 162-172, to 20Ne decay are 163-169, and to 24Mg decay are 162-171

  12. Deconstructing the Antlia cluster core

    CERN Document Server

    Caso, J P

    2015-01-01

    The present literature does not give a satisfactory answer to the question about the nature of the "Antlia galaxy cluster". The radial velocities of galaxies found in the region around the giant ellipticals NGC 3258/3268 range from about 1000 km/s to 4000 km/s. We characterise this region and its possible kinematical and population substructure. We have obtained VLT--VIMOS multi-object spectra of the galaxy population in the inner part of the Antlia cluster and measure radial velocities for 45 potential members. We supplement our galaxy sample with literature data, ending up with 105 galaxy velocities. We find a large radial velocity dispersion for the entire sample as reported in previous papers. However, we find three groups at about 1900 km/s, 2800 km/s, and 3700 km/s, which we interpret as differences in the recession velocities rather than peculiar velocities. The high radial velocity dispersion of galaxies in the Antlia region reflects a considerable extension along the line of sight.

  13. A clustering routing algorithm based on improved ant colony clustering for wireless sensor networks

    Science.gov (United States)

    Xiao, Xiaoli; Li, Yang

    Because of real wireless sensor network node distribution uniformity, this paper presents a clustering strategy based on the ant colony clustering algorithm (ACC-C). To reduce the energy consumption of the head near the base station and the whole network, The algorithm uses ant colony clustering on non-uniform clustering. The improve route optimal degree is presented to evaluate the performance of the chosen route. Simulation results show that, compared with other algorithms, like the LEACH algorithm and the improve particle cluster kind of clustering algorithm (PSC - C), the proposed approach is able to keep away from the node with less residual energy, which can improve the life of networks.

  14. Gene expression data clustering using a multiobjective symmetry based clustering technique.

    Science.gov (United States)

    Saha, Sriparna; Ekbal, Asif; Gupta, Kshitija; Bandyopadhyay, Sanghamitra

    2013-11-01

    The invention of microarrays has rapidly changed the state of biological and biomedical research. Clustering algorithms play an important role in clustering microarray data sets where identifying groups of co-expressed genes are a very difficult task. Here we have posed the problem of clustering the microarray data as a multiobjective clustering problem. A new symmetry based fuzzy clustering technique is developed to solve this problem. The effectiveness of the proposed technique is demonstrated on five publicly available benchmark data sets. Results are compared with some widely used microarray clustering techniques. Statistical and biological significance tests have also been carried out. PMID:24209942

  15. Relics as Probes of Galaxy Cluster Mergers

    Indian Academy of Sciences (India)

    R. J. van Weeren; M. Brüggen; H. J. A. Röttgering; M. Hoeft

    2011-12-01

    Galaxy clusters grow by mergers with other clusters and galaxy groups. These mergers create shocks within the intracluster medium (ICM). It is proposed that particles can be accelerated to extreme energies within the shocks. In the presence of a magnetic field these particles should then form large regions emitting synchrotron radiation, creating the so-called radio relics. An example of a cluster with relics is CIZA J2242.8+5301. Here we present hydrodynamical simulations of idealized binary cluster collisions with the aim of constraining the merger scenario for this cluster. We conclude that by using the location, size and width of double radio relics we can set constraints on the mass ratios, impact parameters, time scales, and viewing geometries of binary cluster merger events.

  16. Hybrid Self Organizing Map for Overlapping Clusters

    Directory of Open Access Journals (Sweden)

    M.N.M. Sap

    2008-12-01

    Full Text Available The Kohonen self organizing map is an excellent tool in exploratoryphase of data mining and pattern recognition. The SOM is a popular tool that maps high dimensional space into a small number of dimensions by placing similar elements close together, forming clusters. Recently researchers found that to capture the uncertainty involved in cluster analysis, it is not necessary to have crisp boundaries in some clustering operations. In this paper to overcomethe uncertainty, a two-level clustering algorithm based on SOM which employs the rough set theory is proposed. The two-level stage Rough SOM (first using SOM to produce the prototypes that are then clustered in the second stage is found to perform well and more accurate compared with the proposed crisp clustering method (Incremental SOM and reduces the errors.

  17. Secure Clustering in Vehicular Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Zainab Nayyar

    2015-09-01

    Full Text Available A vehicular Ad-hoc network is composed of moving cars as nodes without any infrastructure. Nodes self-organize to form a network over radio links. Security issues are commonly observed in vehicular ad hoc networks; like authentication and authorization issues. Secure Clustering plays a significant role in VANETs. In recent years, various secure clustering techniques with distinguishing feature have been newly proposed. In order to provide a comprehensive understanding of these techniques are designed for VANETs and pave the way for the further research, a survey of the secure clustering techniques is discussed in detail in this paper. Qualitatively, as a result of highlighting various techniques of secure clustering certain conclusions are drawn which will enhance the availability and security of vehicular ad hoc networks. Nodes present in the clusters will work more efficiently and the message passing within the nodes will also get more authenticated from the cluster heads.

  18. Statistical issues in galaxy cluster cosmology

    DEFF Research Database (Denmark)

    Mantz, Adam; Allen, Steven W.; Rapetti Serra, David Angelo

    2013-01-01

    The number and growth of massive galaxy clusters is a sensitive probe of cosmological structure formation and dark energy. 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 simultaneo......The number and growth of massive galaxy clusters is a sensitive probe of cosmological structure formation and dark energy. 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 in the form of a regression, in which the data set is truncated, the (cosmology-dependent) underlying population must be modeled, and strong, complex correlations between measurements often exist. © Springer...... Science+Business Media New York 2013....

  19. Knowledge Engineering Technique for Cluster Development

    CERN Document Server

    Sureephong, Pradorn; Ouzrout, Yacine; Neubert, Gilles; Bouras, Abdelaziz

    2007-01-01

    After the concept of industry cluster was tangibly applied in many countries, SMEs trended to link to each other to maintain their competitiveness in the market. The major key success factors of the cluster are knowledge sharing and collaboration between partners. This knowledge is collected in form of tacit and explicit knowledge from experts and institutions within the cluster. The objective of this study is about enhancing the industry cluster with knowledge management by using knowledge engineering which is one of the most important method for managing knowledge. This work analyzed three well known knowledge engineering methods, i.e. MOKA, SPEDE and CommonKADS, and compares the capability to be implemented in the cluster context. Then, we selected one method and proposed the adapted methodology. At the end of this paper, we validated and demonstrated the proposed methodology with some primary result by using case study of handicraft cluster in Thailand.

  20. First LOFAR results on galaxy clusters

    CERN Document Server

    Ferrari, C; Bonafede, A; Bîrzan, L; Brüggen, M; Brunetti, G; Cassano, R; Conway, J; De Gasperin, F; Heald, G; Jackson, N; Macario, G; McKean, J; Offringa, A R; Orrù, E; Pizzo, R; Rafferty, D A; Röttgering, H J A; Shulevski, A; Tasse, C; van der Tol, S; van Weeren, R J; Wise, M; van Zwieten, J E

    2012-01-01

    Deep radio observations of galaxy clusters have revealed the existence of diffuse radio sources related to the presence of relativistic electrons and weak magnetic fields in the intracluster volume. The role played by this non-thermal intracluster component on the thermodynamical evolution of galaxy clusters is debated, with important implications for cosmological and astrophysical studies of the largest gravitationally bound structures of the Universe. The low surface brightness and steep spectra of diffuse cluster radio sources make them more easily detectable at low-frequencies. LOFAR is the first instrument able to detect diffuse radio emission in hundreds of massive galaxy clusters up to their formation epoch. We present the first observations of clusters imaged by LOFAR and the huge perspectives opened by this instrument for non-thermal cluster studies.

  1. Web Log Clustering Approaches – A Survey

    Directory of Open Access Journals (Sweden)

    G. Sudhamathy,

    2011-07-01

    Full Text Available As more organization rely on the Internet and the World Wide Web to conduct business, the proposed strategies and techniques for market analysis need to be revisited in this context. We therefore present a survey of the most recent work in the field of Web usage mining, focusing on three different approaches towards web logs clustering. Clustering analysis is a widely used data mining algorithm which is a process of partitioning a set of data objects into a number of object clusters, where each data object shares the high similarity with the other objects within the same cluster but is quite dissimilar to objects in other clusters. In this work we discuss three different approaches on web logs clustering, analyze their benefits and drawbacks. We finally conclude on the most efficient algorithm based on the results of experiments conducted with various web log files.

  2. Proceedings of the symposium on leukemia clustering

    International Nuclear Information System (INIS)

    Clusters of leukemia in populations living in specific locations in various countries have been examined by scientific and medical experts for many years. In general, the reason for the existence of these clusters is unknown. The recent discovery of a small cluster of leukemias among children who were born in the vicinity of a nuclear fuel reprocessing facility in England has stimulated wide interest in the possible occurrence of clusters of leukemia around nuclear facilities. The purpose of this symposium was to present scientific evidence concerning the existence of leukemia clusters in the population, to discuss possible causes for these clusters and to suggest directions for future research. Distinguished speakers from Canada, the United Kingdom, Germany, Italy and the U.S.A. participated in this symposium. (author)

  3. Spectral clustering based on matrix perturbation theory

    Institute of Scientific and Technical Information of China (English)

    TIAN Zheng; LI XiaoBin; JU YanWei

    2007-01-01

    This paper exposes some intrinsic characteristics of the spectral clustering method by using the tools from the matrix perturbation theory. We construct a weight matrix of a graph and study its eigenvalues and eigenvectors. It shows that the number of clusters is equal to the number of eigenvalues that are larger than 1, and the number of points in each of the clusters can be approximated by the associated eigenvalue. It also shows that the eigenvector of the weight matrix can be used directly to perform clustering; that is, the directional angle between the two-row vectors of the matrix derived from the eigenvectors is a suitable distance measure for clustering. As a result, an unsupervised spectral clustering algorithm based on weight matrix (USCAWM) is developed. The experimental results on a number of artificial and real-world data sets show the correctness of the theoretical analysis.

  4. Nature of multiple-nucleus cluster galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Merritt, D.

    1984-05-01

    In models for the evolution of galaxy clusters which include dynamical friction with the dark binding matter, the distribution of galaxies becomes more concentrated to the cluster center with time. In a cluster like Coma, this evolution could increase by a factor of approximately 3 the probability of finding a galaxy very close to the cluster center, without decreasing the typical velocity of such a galaxy significantly below the cluster mean. Such an enhancement is roughly what is needed to explain the large number of first-ranked cluster galaxies which are observed to have extra ''nuclei''; it is also consistent with the high velocities typically measured for these ''nuclei.'' Unlike the cannibalism model, this model predicts that the majority of multiple-nucleus systems are transient phenomena, and not galaxies in the process of merging.

  5. Recent Dynamical Evolution of Galaxy Clusters

    CERN Document Server

    Plionis, M

    2002-01-01

    Evidence is presented for a recent evolution of the relaxation processes in clusters of galaxies, using large optical and X-ray cluster samples. The criteria of the cluster relaxation used are the cluster ellipticity, the ICM temperature and X-ray cluster luminosity. We find evidence of varying strength and significance of all three indicators evolving with redshift for z <0.15. This result supports the view that clusters have mostly stopped undergoing mergers and accreting matter, as expected in a low-Omega_matter Universe, and are now in the process of gravitational relaxation, which reduces their flattening, their ICM temperature (shock heated during the merging phase), and their X-ray luminosity. These results support similar recent claims of Melott, Chambers and Miller (2001).

  6. Structural Parameters of Star Clusters: Stochastic Effects

    CERN Document Server

    Narbutis, D; de Meulenaer, P; Mineikis, T; Vansevičius, V

    2014-01-01

    Stochasticity of bright stars introduces uncertainty and bias into derived structural parameters of star clusters. We have simulated a grid of cluster $V$-band images, observed with Subaru Suprime-Cam with age, mass, and size representing a cluster population in the M31 galaxy and derived their structural parameters by fitting King model to the surface brightness distribution. We have found that clusters less massive than $10^4 M_\\odot$ show significant uncertainty in their core and tidal radii for all ages, while clusters younger than 10 Myr have their sizes systematically underestimated for all masses. This emphasizes the importance of stochastic simulations to asses the true uncertainty of structural parameters in studies of semi-resolved and unresolved clusters.

  7. Clusters and Groups of Galaxies : International Meeting

    CERN Document Server

    Giuricin, G; Mezzetti, M

    1984-01-01

    The large-scale structure of the Universe and systems Clusters, and Groups of galaxies are topics like Superclusters, They fully justify the meeting on "Clusters of great interest. and Groups of Galaxies". The topics covered included the spatial distribution and the clustering of galaxies; the properties of Superclusters, Clusters and Groups of galaxies; radio and X-ray observations; the problem of unseen matter; theories concerning hierarchical clustering, pancakes, cluster and galaxy formation and evolution. The meeting was held at the International Center for Theoretical Physics in Trieste (Italy) from September 13 to September 16, 1983. It was attended by about 150 participants from 22 nations who presented 67 invited lectures (il) and contributed papers (cp), and 45 poster papers (pp). The Scientific Organizing Committee consisted of F. Bertola, P. Biermann, A. Cavaliere, N. Dallaporta, D. Gerba1, M. Hack, J . V . Peach, D. Sciama (Chairman), G. Setti, M. Tarenghi. We are particularly indebted to D. Scia...

  8. Clustering aspects in nuclear structure and collisions

    International Nuclear Information System (INIS)

    Four topics on nuclear clustering are discussed. The first subject is about the cluster formation in dilute matter which we think is now observed in heavy ion collisions at hundreds MeV/nucleon. The second subject is about our new proposal of the existence of alpha condensed states in light nuclei. Two other subjects are both about the clustering in neutron-rich nuclei. One is the cluster structures in neutron-rich Be and B isotopes. In these isotopes, the clustering prevails as fundamental characters of nuclear structure. The other is the report of our recent study about the possible relation of the clustering with the breaking of the neutron magic number N=20 in 32Mg and 30Ne. (author)

  9. Clustering Aspects in Nuclear Structure and Collisions

    Science.gov (United States)

    Horiuchi, H.

    Four topics on nuclear clustering are discussed. The first subject is about the cluster formation in dilute matter which we think is now observed in heavy ion collisions at hundreds MeV/nucleon. The second subject is about our new proposal of the existense of alpha condensed states in light nuclei. Two other subjects are both about the clustering in neutron-rich nuclei. One is the cluster structures in neutron-rich Be and B isotopes. In these isotopes, the clustering prevails as fundamental characters of nuclear structure. The other is the report of our recent study about the possible relation of the clustering with the breaking of the neutron magic number N=20 in 32Mg and 30Ne.

  10. Load Balancing Algorithm for Cache Cluster

    Institute of Scientific and Technical Information of China (English)

    刘美华; 古志民; 曹元大

    2003-01-01

    By the load definition of cluster, the request is regarded as granularity to compute load and implement the load balancing in cache cluster. First, the processing power of cache-node is studied from four aspects: network bandwidth, memory capacity, disk access rate and CPU usage. Then, the weighted load of cache-node is customized. Based on this, a load-balancing algorithm that can be applied to the cache cluster is proposed. Finally, Polygraph is used as a benchmarking tool to test the cache cluster possessing the load-balancing algorithm and the cache cluster with cache array routing protocol respectively. The results show the load-balancing algorithm can improve the performance of the cache cluster.

  11. Node Clustering for Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Sania Bhatti

    2012-01-01

    Full Text Available Recent years have witnessed considerable growth in the development and deployment of clustering methods which are not only used to maintain network resources but also increases the reliability of the WSNs (Wireless Sensor Network and the facts manifest by the wide range of clustering solutions. Node clustering by selecting key parameters to tackle the dynamic behaviour of resource constraint WSN is a challenging issue. This paper highlights the recent progress which has been carried out pertaining to the development of clustering solutions for the WSNs. The paper presents classification of node clustering methods and their comparison based on the objectives, clustering criteria and methodology. In addition, the potential open issues which need to be considered for future work are high lighted.

  12. Catching Dissolving Clusters: a New Approach

    CERN Document Server

    Pellerin, A; Harris, J; Calzetti, D; Pellerin, Anne; Meyer, Martin; Harris, Jason; Calzetti, Daniela

    2006-01-01

    Traditional studies of stellar clusters in external galaxies use surface photometry and therefore focus on systems that are still bright and compact enough to be separated from the stellar background. Consequently, the latter stages of unbound cluster evolution are still poorly understood. This dramatically constrains our knowledge of the dissolution processes of stellar clusters in various physical environments. We present the first results of a new approach to directly detect and quantify the characteristics of evolved stellar clusters. Using the exceptional spatial resolution and sensitivity of HST/ACS images to resolve the stellar content nearby galaxies, we construct colour-magnitude diagrams for the observed fields. This enable us to separate the younger population likely present in young clusters from the older stellar content of the star field background. We utilize a clustering algorithm to assign each star to a group based on its local spatial density. This novel approach makes use of algorithms typ...

  13. Quantum information processing with noisy cluster states

    CERN Document Server

    Tame, M S; Kim, M S; Vedral, V

    2005-01-01

    We provide an analysis of basic quantum information processing protocols under the effect of intrinsic non-idealities in cluster states. These non-idealities are based on the introduction of randomness in the entangling steps that create the cluster state and are motivated by the unavoidable imperfections faced in creating entanglement using condensed-matter systems. Aided by the use of an alternative and very efficient method to construct cluster state configurations, which relies on the concatenation of fundamental cluster structures, we address quantum state transfer and various fundamental gate simulations through noisy cluster states. We find that a winning strategy to limit the effects of noise, is the management of small clusters processed via just a few measurements. Our study also reinforces recent ideas related to the optical implementation of a one-way quantum computer.

  14. A review of subsequence time series clustering.

    Science.gov (United States)

    Zolhavarieh, Seyedjamal; Aghabozorgi, Saeed; Teh, Ying Wah

    2014-01-01

    Clustering of subsequence time series remains an open issue in time series clustering. Subsequence time series clustering is used in different fields, such as e-commerce, outlier detection, speech recognition, biological systems, DNA recognition, and text mining. One of the useful fields in the domain of subsequence time series clustering is pattern recognition. To improve this field, a sequence of time series data is used. This paper reviews some definitions and backgrounds related to subsequence time series clustering. The categorization of the literature reviews is divided into three groups: preproof, interproof, and postproof period. Moreover, various state-of-the-art approaches in performing subsequence time series clustering are discussed under each of the following categories. The strengths and weaknesses of the employed methods are evaluated as potential issues for future studies. PMID:25140332

  15. Data clustering theory, algorithms, and applications

    CERN Document Server

    Gan, Guojun; Wu, Jianhong

    2007-01-01

    Cluster analysis is an unsupervised process that divides a set of objects into homogeneous groups. This book starts with basic information on cluster analysis, including the classification of data and the corresponding similarity measures, followed by the presentation of over 50 clustering algorithms in groups according to some specific baseline methodologies such as hierarchical, center-based, and search-based methods. As a result, readers and users can easily identify an appropriate algorithm for their applications and compare novel ideas with existing results. The book also provides examples of clustering applications to illustrate the advantages and shortcomings of different clustering architectures and algorithms. Application areas include pattern recognition, artificial intelligence, information technology, image processing, biology, psychology, and marketing. Readers also learn how to perform cluster analysis with the C/C++ and MATLAB® programming languages.

  16. Relativistic Particles in Clusters of Galaxies

    CERN Document Server

    Ensslin, T A

    2002-01-01

    A brief overview on the theory and observations of relativistic particle populations in clusters of galaxies is given. The following topics are addressed: (i) the diffuse relativistic electron population within the intra-cluster medium (ICM) as seen in the cluster wide radio halos and possibly also seen in the high energy X-ray and extreme ultraviolet excess emissions of some clusters, (ii) the observed confined relativistic electrons within fresh and old radio plasma and their connection to cluster radio relics at cluster merger shock waves, (iii) the relativistic proton population within the ICM, and its observable consequences (if it exists), and (iv) the confined relativistic proton population (if it exists) within radio plasma. The importance of upcoming, sensitive gamma-ray telescopes for this research area is highlighted.

  17. Globular Clusters in the Galactic Bulge

    Science.gov (United States)

    Bica, E.; Ortolani, S.; Barbuy, B.

    2016-06-01

    A view of the Galactic bulge by means of their globular clusters is fundamental for a deep understanding of its formation and evolution. Connections between the globular cluster and field star properties in terms of kinematics, orbits, chemical abundances, and ages should shed light on different stellar population components. Based on spatial distribution and metallicity, we define a probable best list of bulge clusters, containing 43 entries. Future work on newly discovered objects, mostly from the VVV survey, is suggested. These candidates might alleviate the issue of missing clusters on the far side of the bulge. We discuss the reddening law affecting the cluster distances towards the centre of the Galaxy, and conclude that the most suitable total-to-selective absorption value appears to be R V=3.2, in agreement with recent analyses. An update of elemental abundances for bulge clusters is provided.

  18. Multiple Clustering Views via Constrained Projections

    DEFF Research Database (Denmark)

    Dang, Xuan-Hong; Assent, Ira; Bailey, James

    2012-01-01

    Clustering, the grouping of data based on mutual similarity, is often used as one of principal tools to analyze and understand data. Unfortunately, most conventional techniques aim at finding only a single clustering over the data. For many practical applications, especially those being described...... in high dimensional data, it is common to see that the data can be grouped into different yet meaningful ways. This gives rise to the recently emerging research area of discovering alternative clusterings. In this preliminary work, we propose a novel framework to generate multiple clustering views....... The framework relies on a constrained data projection approach by which we ensure that a novel alternative clustering being found is not only qualitatively strong but also distinctively different from a reference clustering solution. We demonstrate the potential of the proposed framework using both...

  19. Destruction of the galactic globular cluster system

    CERN Document Server

    Gnedin, O Y; Gnedin, Oleg Y; Ostriker, Jeremiah P

    1996-01-01

    We investigate the dynamical evolution of the Galactic Globular Cluster System in considerably greater detail than has been done hitherto, finding that destruction rates are significantly larger than given by previous estimates. More than half of the present clusters (52%-58% for the OC galactic model, and 75%-86% for the BSS model) will be destroyed in the next Hubble time. For the evolution of individual clusters we use a Fokker-Planck code including two-body relaxation, tidal truncation of clusters, compressive gravitational shocks while clusters pass through the Galactic disk, and tidal shocks due to passage close to the bulge. Gravitational shocks are treated comprehensively, using a recent result by Kundic & Ostriker (1995) that the shock-induced relaxation term, driving an additional dispersion of energies, is generally more important than the usual energy shift term. We discuss some implications for a past history of the Globular Cluster System, and the initial distribution of the destruction time...

  20. Chemical Abundances of Giants in Globular Clusters

    Science.gov (United States)

    Gratton, Raffaele G.; Bragaglia, Angela; Carretta, Eugenio; D'Orazi, Valentina; Lucatello, Sara

    A large fraction of stars form in clusters. According to a widespread paradigma, stellar clusters are prototypes of single stellar populations. According to this concept, they formed on a very short time scale, and all their stars share the same chemical composition. Recently it has been understood that massive stellar clusters (the globular clusters) rather host various stellar populations, characterized by different chemical composition: these stellar populations have also slightly different ages, stars of the second generations being formed from the ejecta of part of those of an earlier one. Furthermore, it is becoming clear that the efficiency of the process is quite low: many more stars formed within this process than currently present in the clusters. This implies that a significant, perhaps even dominant fraction of the ancient population of galaxies formed within the episodes that lead to formation the globular clusters.