1,721,014 research outputs found
Generalized Dilaton Couplings to Dark Matter
No full textInspired by recent models of inflation within the Jordan-Brans-Dicke theory, namely the ``generalized extended inflation'' models (see Holman, Kolb, Vadas and Wang [Phys. Lett. B 250 (1990) 24; Phys. Rev. D 43 (1991) 995]), we propose generalized couplings of a dark matter component to the Jordan-Brans-Dicke, or dilaton, field. Assuming the dark matter component to be dominant today we use observational data on the rate of change of Newton's constant, as well as on its value during primordial nucleosynthesis, on the age of the Universe and on the present value of the Hubble constant to put limits on these couplings. Our results extended previous ones by Damour, Gibbons and Gundlach [Phys. Rev. Lett. 64 (1990) 123]. Unlike all previously considered models, the Newton constant would change with time even if the universe were dominated by an invisible radiation-like component (i.e., whose energy-momentum tensor has vanishing trace). Using a lagrangian approach we propose a natural coupling of the dilaton field to a perfect fluid dark matter component
Service-oriented modeling for e-business applications components
No full textThe emerging trends for e-business engineering revolve
around specialisation and cooperation. Successful
companies focus on their core competences, and rely on a
network of business partners for the support services
required to compose a comprehensive offer for their
customers. Modulariy is crucial for a flexible e-business
infrastructure, but related requirements seldom reflect on
the design and operational models of business
information systems.
Software components are widely used for the
implementation of e-business applications, with proved
benefits in terms of system development and maintenance.
We propose a service-oriented componentisation of ebusiness
systems as a way to close the gap with the
business models they support. Blurring the distinction
between external services and internal capabilities, we
propose a homogeneous model for the definition of ebusiness
applications components. After a brief
discussion on the foundational aspects of the approach,
we present the process-based technique we adopted for
component modelling. We then present an infrastructure
compliant with the model proposed that we built on top of
an EJB (Enterprise Java Beans) platform
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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