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  • American Institute of Physics (AIP)  (6)
  • Springer  (5)
  • 1995-1999  (7)
  • 1990-1994  (4)
  • 1
    Electronic Resource
    Electronic Resource
    The ground and excited states of C60M and C60M+ (M=O, F, K, Ca, Mn, Cs, Ba, La, Eu, U) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5004-5010 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Restricted Hartree–Fock ab initio calculations using relativistic core potentials were performed on C60M (M=O, F, K, Ca, Mn, Cs, Ba, La, Eu, U) complexes with M as the central atom in the C60 truncated icosahedron. The icosahedral symmetry was used to great advantage in the calculations. The ground and excited states of both neutral complexes and their positive ions were studied, and the population analyses for the ground states of the complexes were obtained. The C60 cage accepts one or two electrons from electropositive elements in a formal sense, but the actual charge is usually less. Electrons in large-radius s orbitals on the central atom tend to move outward to the carbon cage or inward to smaller-radius d orbitals on the central atom. For the larger central atoms, ionization occurs from a cage orbital so that the ionization potentials of these complexes are almost constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460535
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  • 2
    Electronic Resource
    Electronic Resource
    On the viscous boundary layer near the center of the resistive reconnection region (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 3249-3256 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper studies the behavior of the magnetic field near the center of the reconnection layer in the framework of two-dimensional incompressible resistive magnetohydrodynamics with uniform resistivity in a steady state. Priest and Cowley [J. Plasma Phys. 14, 271 (1975)] have presented an argument showing that when the viscosity ν is zero, the magnetic separatrices do not cross at a finite angle but osculate at the X-point. In the present paper it is shown that this conclusion is in fact not correct. First, some results of numerical simulations of the reconnection layer are presented. These results contradict the conclusions of Priest and Cowley. To explain this contradiction, an analytical theory for the neighborhood of the X-point is developed. When viscosity ν is small, a narrow boundary layer develops near the neutral point. Some of the higher derivatives of the stream function Φ become very large near the X-point, leading to a nonzero angle between the separatrices. As ν→0, the boundary layer shrinks and nonanalytic logarithmic terms emerge in the expansion of Φ in the outer region. This makes the Taylor expansion of Priest and Cowley invalid in the case ν=0. The results of our boundary layer analysis are in good agreement with the numerical simulations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872992
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical analysis of driven magnetic reconnection experiments (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1220-1233 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we present a theoretical framework for the Magnetic Reconnection Experiment (MRX) [M. Yamada et al., Bull. Am. Phys. Soc. 40, 1877 (1995)] in order to understand the basic physics of the experiment, including the effect of the external driving force, and the difference between co- and counterhelicity cases of the experiment. The problem is reduced to a one-dimensional (1-D) resistive magnetohydrodynamic (MHD) model. A special class of holonomic boundary conditions is defined, under which a unique sequence of global equilibria can be obtained, independent of the rate of reconnection. This enables one to break the whole problem into two parts: a global problem for the ideal region, and a local problem for the resistive reconnection layer. The calculations are then carried out and the global solution for the ideal region is obtained in one particular case of holonomic constraints, the so called "constant force'' regime, for both the co- and counterhelicity cases. After the sequence of equilibria in the ideal region is found, the problem of the rate of reconnection in the resistive reconnection region is considered. This rate tells how fast the plasma proceeds through the sequence of global equilibria but does not affect the sequence itself. Based on a modified Sweet–Parker model for the reconnection layer, the reconnection rate is calculated, and the difference between the co- and counterhelicity cases, as well as the role of the external forces is demonstrated. The results from the present analysis are qualitatively consistent with the experimental data, predicting faster reconnection rate for the counterhelicity merging and yielding a positive correlation with external forcing. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871746
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  • 4
    Electronic Resource
    Electronic Resource
    Important plasma problems in astrophysics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1735-1745 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In astrophysics, plasmas occur under very extreme conditions. For example, there are ultrastrong magnetic fields in neutron stars, relativistic plasmas around black holes and in jets, extremely energetic particles such as cosmic rays in the interstellar medium, extremely dense plasmas in accretion disks, and extremely large magnetic Reynolds numbers in the interstellar medium. These extreme limits for astrophysical plasmas make plasma phenomena much simpler to analyze in astrophysics than in the laboratory. An understanding of such phenomena often results in an interesting way, by simply taking the extreme limiting case of a known plasma theory. The author will describe one of the more exciting examples and will attempt to convey the excitement he felt when he was first exposed to it. However, not all plasma astrophysical phenomena are so simple. There are certain important plasma phenomena in astrophysics that have not been so easily resolved. In fact, a resolution of them is blocking significant progress in astrophysical research. They have not yet yielded to attacks by theoretical astrophysicists nor to extensive numerical simulation. The author will attempt to describe one of the more important of these plasma–astrophysical problems, and discuss why its resolution is so important to astrophysics. This significant example is fast, magnetic reconnection. Another significant example is the large-magnetic-Reynolds number magnetohydrodynamics (MHD) dynamos. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871321
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic reconnection in a magnetohydrodynamic plasma : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1599-1606 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic reconnection is important because of its connection with the topology of field lines. In general, a change in topology means a change of equilibrium, and a release of energy, such as occurs in solar flares. In the context of the solar flare two models for magnetic reconnection, the Sweet–Parker and the Petschek mechanism are presented. The pros and cons of these two models are presented. The role of anomalous resistivity in the Sweet–Parker model is discussed. The bearing of a laboratory experiment and a boundary layer analysis of the problem are described. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872827
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  • 6
    Electronic Resource
    Electronic Resource
    Cusp and Y-type magnetic structures and velocity fields at the endpoint of the reconnection layer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3960-3973 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The two-dimensional global scale magnetic field structure for a system of two merging cylindrical plasmas in a steady state is studied. In the limit of very large magnetic Reynolds numbers the reconnection process is slow, and the plasma almost everywhere finds itself in magnetostatic equilibrium. It is shown that under certain conditions the classical Syrovatskii-type Y-point configuration, with surface current concentrated only in the reconnection layer, is not possible. Instead, a cusp configuration is formed, with finite surface current in the separatrix. The equilibrium condition, together with constraints on the volume per flux, enables one to determine the shape of the separatrix and the magnetic field in the vicinity of the cusp point. The solution is characterized by a singular power law dependence of current density on the flux coordinate Ψ near the separatrix: j(Ψ)∼|Ψ|−1/2. This solution gives the boundary conditions that are needed to find the flow in the reconnection and the separatrix regions. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872538
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  • 7
    Electronic Resource
    Electronic Resource
    Subcellular location of the tetrapyrrole synthesis enzyme porphobilinogen deaminase in higher plants: an immunological investigation (1996)
    Springer
    Planta 199 (1996), S. 557-564 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Chlorophyll biosynthesis ; Plastid ; Porphobilinogen deaminase (purification, subcellular location)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A recombinant plasmid, pArab8, harbouring the cDNA encoding the mature form of the tetrapyrrole synthesis enzyme porphobilinogen deaminase (EC 4.3.1.8; also known as hydroxymethylbilane synthase) from Arabidopsis thaliana (L.) Heynh. has been constructed, and used to transform Escherichia coli. The porphobilinogen deaminase protein from Arabidopsis was overexpressed in this strain, and purified to homogeneity (3000-fold) with a yield of 20%. Antibodies were raised against the purified plant enzyme, and used in Western blot analysis, immunoprecipitation of enzyme activity and immuno-gold electron microscopy. The results indicate that the enzyme is confined to plastids in both leaves and roots. The implications of this finding for plant tetrapyrrole synthesis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195187
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  • 8
    Electronic Resource
    Electronic Resource
    Need for well-balanced education in software engineering measurement (1992)
    Springer
    Software quality journal 1 (1992), S. 81-100 
    Details
    ISSN: 1573-1367
    Keywords: education ; measurement ; metrics ; models ; goal oriented approach ; data collection ; data analysis ; measurement programme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper deals with a perceived need for a well-balanced education (or in some cases re-education) in the subject of software engineering measurement, more commonly although less accurately known as software metrics. This need was confirmed by a major survey of both industry and academia conducted in 1989. Software metrics have received a lot of bad press in the past, mainly due to some much criticized early work in so-called complexity metrics. A result of this has been scepticism or lack of interest in other areas of the wider subject of software engineering measurement, which covers not only models and measures applicable to software products, but also those applicable to the processes and resources involved in software production. The ideas and work described in this paper have arisen out of the ESPRIT project ‘METKIT’, which has produced educational material about software engineering measurement for use in both industry and academia. This paper also describes the material designed for academia, most of which has now been tested in 12 European academic institutions. The material concentrates on principles and examples rather than prescribing the use of particular models and measures. This material has been widely publicized; the response to it has been encouraging so far and it appears that the material will have a significant impact towards getting the subject taught much more widely, and in a more balanced way.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01845741
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  • 9
    Electronic Resource
    Electronic Resource
    Cache coherence requirements for interprocess rendezvous (1990)
    Springer
    International journal of parallel programming 19 (1990), S. 31-51 
    Details
    ISSN: 1573-7640
    Keywords: Cache coherence ; rendezvous ; run-time systems ; process migration ; concurrent programming languages
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Multiprocessors in which a shared bus is used by the processor to communicate with common memory are an emerging class of machines where there is a need to support parallel programming languages. A language construct that is found in a number of parallel programming languages to support synchronization and communication in the interprocess rendezvous. Shared-bus multiprocessor require a protocol to keep the date in their caches coherent. There are two major categories of these protocols: invalidation and write-boadcast. This paper examines the requirements for cache coherence protocols to support efficient interprocessor rendezvous. The approach taken is to examine the memory referencing patterns to the run-time data structures during rendezvous execution. The appropriate coherence protocol is shown to be a function of the processor scheduling strategy used by the run-time system at synchronzation points during the rendezvous. When processes migrate freely as a result of the scheduling strategy, invalidation protocols are found to be more efficient. When migration is restricted by the scheduler, write-broadcast protocols are more efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01407863
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  • 10
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    Coinjection strategy for visual identification of transgenic mice (1991)
    Springer
    Details
    Publication Date: 1991-12-01
    Print ISSN: 0962-8819
    Electronic ISSN: 1573-9368
    Topics: Biology
    Published by Springer
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