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  • 1
    Electronic Resource
    Electronic Resource
    Formation of massive black holes through runaway collisions in dense young star clusters (2004)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 428 (2004), S. 724-726 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A luminous X-ray source is associated with MGG 11—a cluster of young stars ∼200 pc from the centre of the starburst galaxy M 82 (refs 1, 2). The properties of this source are best explained by invoking a black hole with a mass of at least 350 solar masses ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02448
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  • 2
    Electronic Resource
    Electronic Resource
    The formation of Kuiper-belt binaries through exchange reactions (2004)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 427 (2004), S. 518-520 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Recent observations have revealed that an unexpectedly high fraction—a few per cent—of the trans-Neptunian objects (TNOs) that inhabit the Kuiper belt are binaries. The components have roughly equal masses, with very eccentric orbits that are wider than a hundred times the radius of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02323
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  • 3
    Electronic Resource
    Electronic Resource
    Modelling the evolution of globular star clusters (1988)
    [s.l.] : Nature Publishing Group
    Nature 336 (1988), S. 31-35 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Globular star clusters provide a unique laboratory. In astronomy they present an opportunity to study dense stellar systems that are more accessible than galactic nuclei. In statistical mechanics, concepts of negative heat capacity and resulting gravothermal instabilities challenge the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/336031a0
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  • 4
    Electronic Resource
    Electronic Resource
    A special-purpose computer for gravitational many-body problems (1990)
    [s.l.] : Nature Publishing Group
    Nature 345 (1990), S. 33-35 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A processor has been constructed using a 'pipeline' architecture to simulate many-body systems with long-range forces. It has a speed equivalent to 120 megaflops, and the architecture can be readily parallelized to make teraflop machines a feasible possibility. The machine can be adapted to study ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/345033a0
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  • 5
    Electronic Resource
    Electronic Resource
    Galaxies in the connection machine (1988)
    Springer
    Celestial mechanics and dynamical astronomy 45 (1988), S. 141-147 
    Details
    ISSN: 1572-9478
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Many problems in galactic dynamics require computer speeds orders of magnitude larger than what can be achieved on current single-processor machines. In the near future such speeds are likely to become available through computer architectures based on large-scale, fine-grained parallelism. An example of a highly parallel computer is the Connection Machine, with up to 65,636 processors. We have benchmarked gravitationalN-body algorithms on the Connection Machine, and compared those with similar benchmarks which we have obtained on more traditional vector supercomputers. Our conclusions are: (1) The direct summation algorithm, with of orderN 2 interactions forN particles, can be made to run with high efficiency on either type of computer. As a result, the Connection Machine clearly wins in speed over all supercomuters tested, with the exception of an 8-processor ETA, which shows a comparable performance. (2) A more efficient tree algorithm reduces the growth of the number of interactions fromN 2 toN logN. However, the greater complexity of this algorithm causes a considerable degradation of efficiency, by a factor which is larger on the Connection Machine than on vector supercomputers. As a result, out tree code runs at comparable speeds on both types of machines, with the notable exception of the 8-processor ETA, which has an extrapolated speed for running our tree code which is higher than any of the other machines we have tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01228995
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  • 6
    Electronic Resource
    Electronic Resource
    Merger of binary globular clusters: Case of unequal masses (1991)
    Springer
    Astrophysics and space science 185 (1991), S. 63-78 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Merger process of binary globular cluster is discussed for a pair of unequal-mass components. We calculated the case of mass ratio 1∶0.5 by means of anN-body code with 6144 particles in total. We have found the followings. The mass exchange between the components takes place through the Roche-lobe overflow. In the early stages, however, the dynamical evolution is mainly governed by escape of particles from the system. As the particles escape carrying angular momentum with them, the separation between the component cluster shrinks. The time-scale of this shrinkage depends upon the size of the clusters. When a critical separation is reached, the orbital angular momentum is transferred unstably to the spins of the component clusters. This is the process of the synchronization instability which was found in a previous study on binary cluster of equal masses. As a result the component clusters merge into a single cluster. The structures of the mergers are quite similar among different cases except for the central cores which retain their initial central concentrations. In particular, the ellipticity and the rotation curve are quite close each other among models of different initial radii and of different mass ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00642706
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  • 7
    Electronic Resource
    Electronic Resource
    Productivity of research groups-relation between citation analysis and reputation within research communities (1998)
    Springer
    Scientometrics 43 (1998), S. 87-93 
    Details
    ISSN: 1588-2861
    Source: Springer Online Journal Archives 1860-2000
    Topics: Information Science and Librarianship , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Abstract In this paper I discuss the relation between widely used “Scientometric” measures and “reputation” of research groups within the scientific community. To this goal, I present the result of the detailed comparison of two research groups of theoretical astrophysics in post-world-war-2nd Japan. Though one of the two groups gained much higher reputation within the research community, we could not find much difference in the macroscopic indices such as the number of publications or the average citation index. The two groups showed similar scores for these macroscopic indices. This result suggests that widely used quantitative measures of the productivity do not give meaningful measure for the actual contribution of a research group to science.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02458398
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  • 8
    Electronic Resource
    Electronic Resource
    Application of a high-performance, special-purpose computer, GRAPE-2A, to molecular dynamics (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 1372-1376 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The special-purpose computer GRAPE-2A accelerates the calculation of pairwise interactions in many-body systems. This computer is a back-end processor connected to a host computer through a Versa Module Europe (VME) bus. GRAPE-2A receives coordinates and other physical data for particles from the host and then calculates the pairwise interactions. The host then integrates an equation of motion by using these interactions. We did molecular dynamics simulations for two systems of liquid water: System 1 (1000 molecules), and System 2 (1728 molecules). The time spent for one step of molecular dynamics was 3.9 s (System l), and 10.2 s (System 2). The larger the molecular system, the higher the performance. The speed of GRAPE-2A did not depend on the formula describing the pairwise interaction. The cost performance was about 20 times better than that of the fastest workstations available today, and GRAPE-2A cost only $22,000. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540151207
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  • 9
    Electronic Resource
    Electronic Resource
    A special-purpose computer for molecular dynamics: GRAPE-2A (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 139-148 
    Details
    ISSN: 0887-3585
    Keywords: hardware ; molecular dynamics ; simulation ; special-purpose computer ; supercomputing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Molecular dynamics simulations have been extensively used in research of proteins. Since these simulations are quite computer intensive, their acceleration is of main interest of the research. In molecular dynamics simulations, almost all computing time is consumed in calculating the forces between particles, e.g., Coulomb and van der Waals forces. We have designed and built GRAPE-2A (GRAvity PipE 2A), a special-purpose computer for use in simulations of classical many-body systems. GRAPE-2A calculates forces exerted on a particle from the other particles. GRAPE-2A can calculate force of an arbitrary functional form of a central force. The host computer, which is connected to GRAPE-2A through the VME bus, performs other calculations such as time integration. The peak speed of GRAPE-2A is 180 Mflops. We can also stimulate systems with periodic boundary conditions by the Ewald method, using GRAPE-2A and another special-purpose computer, WINE (Wave space INtegrator for the Ewald method). © 1994 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340200204
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