34,263 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
The Nonlinear Optical Effects of Opening a Gap in Graphene
Graphene possesses remarkable electronic, optical and mechanical properties
that have taken the research of two-dimensional relativistic condensed matter
systems to prolific levels. However, the understanding of how its nonlinear
optical properties are affected by relativistic-like effects has been broadly
uncharted. It has been recently shown that highly-nontrivial currents can be
generated in free-standing samples, notably leading to the generation of even
harmonics. Since graphene monolayers are centrosymmetric media, for which such
harmonic generation is deemed inaccessible, this light-driven phenomenon is
both startling and promising. More realistically, graphene samples are often
deposited on a dielectric substrate, leading to additional intricate
interactions. Here, we present a treatment to study this instance by gapping
the spectrum and we show this leads to the appearance of a Berry phase in the
carrier dynamics. We analyse the role of such a phase in the generated
nonlinear current and conclude that it suppresses odd-harmonic generation. The
pump energy can be tuned to the energy gap to yield interference among odd
harmonics mediated by interband transitions, allowing even harmonics to be
generated. Our results and general methodology pave the way for understanding
the role of gap-opening physical factors in the nonlinear optics of hexagonal
two-dimensional lattices.Comment: 5 figure
Effect of Relative Air Himidity on the Stomatal Functionality in Fully Developed Leaves
Several studies have shown that stomata developed under long-term high relative air humidity (RH =85%) are malfunctional, resulting in a poor control of water loss. Yet, little is known about the dynamics of stomatal adaptation to moderate RH, and the possibilities to improve or reverse the destabilized stomatal responsiveness. In this study, a reciprocal transfer experiment was conducted in climate chambers using Rosa hybrida ‘Prophyta’, grown at moderate RH (60%) or at high RH (90%). The adaptation of fully developed leaves to the new RH environment was assessed at day 0, 4, 8 and 12 after plant transfer by measuring the transpiration rate in detached leaves. Stomata fully developed at high RH had a lower closing capacity in response to a decrease in leaf Relative Water Content (RWC) (i.e. water loss was considerably high at RWC below 20%, whereas in moderate RH stomata the water loss almost ceased at 57% RWC). Furthermore, stomata developed at high RH did not become functional after 12 days of cultivation at moderate RH. Similarly, stomata developed at moderate RH and transferred to high RH for a 12 day period did not loose their ability to close in response to desiccation. This indicates that stomatal functionality is determined during leaf development, while after this period stomata have a limited capacity to adapt to new RH environment. It is concluded that stomata from fully developed rose leaves conserve their behaviour independently of the post-development humidity leve
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