3,676 research outputs found
Endurant Types in Ontology-Driven Conceptual Modeling: Towards OntoUML 2.0
For over a decade now, a community of researchers has contributed
to the development of the Unified Foundational Ontology (UFO)
- aimed at providing foundations for all major conceptual modeling constructs.
This ontology has led to the development of an Ontology-Driven
Conceptual Modeling language dubbed OntoUML, reflecting the ontological
micro-theories comprising UFO. Over the years, UFO and OntoUML
have been successfully employed in a number of academic, industrial and
governmental settings to create conceptual models in a variety of different
domains. These experiences have pointed out to opportunities of
improvement not only to the language itself but also to its underlying
theory. In this paper, we take the first step in that direction by revising
the theory of types in UFO in response to empirical evidence. The
new version of this theory shows that many of the meta-types present
in OntoUML (differentiating Kinds, Roles, Phases, Mixins, etc.) should
be considered not as restricted to Substantial types but instead should
be applied to model Endurant Types in general, including Relator types,
Quality types and Mode types. We also contribute a formal characterization
of this fragment of the theory, which is then used to advance a
metamodel for OntoUML 2.0. Finally, we propose a computational support
tool implementing this updated metamodel
Precise determination of muon and electromagnetic shower contents from shower universality property
We consider two new aspects of Extensive Air Shower development universality
allowing to make accurate estimation of muon and electromagnetic (EM) shower
contents in two independent ways. In the first case, to get muon (or EM) signal
in water Cherenkov tanks or in scintillator detectors it is enough to know the
vertical depth of shower maximum and the total signal in the ground detector.
In the second case, the EM signal can be calculated from the primary particle
energy and the zenith angle. In both cases the parametrizations of muon and EM
signals are almost independent on primary particle nature, energy and zenith
angle. Implications of the considered properties for mass composition and
hadronic interaction studies are briefly discussed. The present study is
performed on 28000 of proton, oxygen and iron showers, generated with CORSIKA
6.735 for spectrum in the energy range log(E/eV)=18.5-20.0 and
uniformly distributed in cos^2(theta) in zenith angle interval theta=0-65
degrees for QGSJET II/Fluka interaction models.Comment: Submitted to Phys. Rev.
A new multiparametric topological method for determining the primary cosmic ray mass composition in the knee energy region
The determination of the primary cosmic ray mass composition from the
characteristics of extensive air showers (EAS), obtained at an observation
level in the lower half of the atmosphere, is still an open problem. In this
work we propose a new method of the Multiparametric Topological Analysis and
show its applicability for the determination of the mass composition of the
primary cosmic rays at the PeV energy region.Comment: 8 pages, 4 figures, talk given at Vulcano 2004 Workshop 'Frontier
Objects in Physics and Astrophysics', Vulcano, Italy, 24-29.05.04, to be
published in the Proceedings of the Worksho
A simplified thermal analysis approach for power transistor rating in PWM-controlled DC/AC converters
A simplified dynamic thermal analysis approach is proposed for the estimation of the peak junction temperature in power IGBT transistors operating in pulse-width modulation (PWM) controlled DC/AC converters. This approach can be used for the rating of electron devices or heatsink systems in power circuit design, as it provides a direct analytical link, in terms of electrical and thermal device parameters and converter operating conditions between the case and the peak junction temperatures. In this way, by imposing a given upper limit on the junction temperature, indirect constraints on device size or load current or heatsink efficiency can easily be obtained. The approach is based on mild, pessimistic approximations on both the spectrum of dissipated power and on the dynamic thermal behavior of the device. The validity of such approximations has been verified by comparison with the results of accurate numerical simulations carried out by using measurement-based loss models. Possible ways of using this approach in a converter rating context are outlined in the paper, by considering different design scenario
Dissecting the Extracellular Complexity of Neuromuscular Junction Organizers
Synapse formation is a very elaborate process dependent upon accurate coordination of pre and post-synaptic specialization, requiring multiple steps and a variety of receptors and signaling molecules. Due to its relative structural simplicity and the ease in manipulation and observation, the neuromuscular synapse or neuromuscular junction (NMJ)—the connection between motor neurons and skeletal muscle—represents the archetype junction system for studying synapse formation and conservation. This junction is essential for survival, as it controls our ability to move and breath. NMJ formation requires coordinated interactions between motor neurons and muscle fibers, which ultimately result in the formation of a highly specialized post-synaptic architecture and a highly differentiated nerve terminal. Furthermore, to ensure a fast and reliable synaptic transmission following neurotransmitter release, ligand-gated channels (acetylcholine receptors, AChRs) are clustered on the post-synaptic muscle cell at high concentrations in sites opposite the presynaptic active zone, supporting a direct role for nerves in the organization of the post-synaptic membrane architecture. This organized clustering process, essential for NMJ formation and for life, relies on key signaling molecules and receptors and is regulated by soluble extracellular molecules localized within the synaptic cleft. Notably, several mutations as well as auto-antibodies against components of these signaling complexes have been related to neuromuscular disorders. The recent years have witnessed strong progress in the understanding of molecular identities, architectures, and functions of NMJ macromolecules. Among these, prominent roles have been proposed for neural variants of the proteoglycan agrin, its receptor at NMJs composed of the lipoprotein receptor-related protein 4 (LRP4) and the muscle-specific kinase (MuSK), as well as the regulatory soluble synapse-specific protease Neurotrypsin. In this review we summarize the current state of the art regarding molecular structures and (agrin-dependent) canonical, as well as (agrin-independent) non-canonical, MuSK signaling mechanisms that underscore the formation of neuromuscular junctions, with the aim of providing a broad perspective to further stimulate molecular, cellular and tissue biology investigations on this fundamental intercellular contact
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