12,491 research outputs found
Super-energy tensor for space-times with vanishing scalar curvature
A four-index tensor is constructed with terms both quadratic in the Riemann
tensor and linear in its second derivatives, which has zero divergence for
space-times with vanishing scalar curvature. This tensor reduces in vacuum to
the Bel-Robinson tensor. Furthermore, the completely timelike component
referred to any observer is positive, and zero if and only if the space-time is
flat (excluding some unphysical space-times). We also show that this tensor is
the unique that can be constructed with these properties. Such a tensor does
not exist for general gravitational fields. Finally, we study this tensor in
several examples: the Friedmann-Lema\^{\i}tre-Robertson-Walker space-times
filled with radiation, the plane-fronted gravitational waves, and the Vaidya
radiating metric.Comment: 13 pages, LaTeX 2.09. To be published in Journal of Mathematical
Physic
Interface growth in two dimensions: A Loewner-equation approach
The problem of Laplacian growth in two dimensions is considered within the
Loewner-equation framework. Initially the problem of fingered growth recently
discussed by Gubiec and Szymczak [T. Gubiec and P. Szymczak, Phys. Rev. E 77,
041602 (2008)] is revisited and a new exact solution for a three-finger
configuration is reported. Then a general class of growth models for an
interface growing in the upper-half plane is introduced and the corresponding
Loewner equation for the problem is derived. Several examples are given
including interfaces with one or more tips as well as multiple growing
interfaces. A generalization of our interface growth model in terms of
``Loewner domains,'' where the growth rule is specified by a time evolving
measure, is briefly discussed.Comment: To appear in Physical Review
Fintech and the socialization of the financial industry
Fintech have known an incredible exposure over the last years, attracting investments of large billions of dollars. Fintech are the match between finance and technology and they are imposing a new way of thinking in all the branches of the financial industry. After the financial crisis of 2008, people have changed their way of seeing “Finance” and, more particularly, the role of banks, looking for products and services that correspond to their needs. Moreover, the financial crisis has highlighted a relevant number of dysfunctions on the banking sector and on the financial regulation. Regulators have strengthened their requirements for banks, particularly in their relations with clients. These have opened a breach for Fintech companies and they are using it. Fintech companies rely on a different value proposition to clients that is based on a timesaving, fast and clear experience. Indeed, they propose major innovations in products and processes. Fintech companies put the client back at the center of all their attention and clients are now the top priority.info:eu-repo/semantics/publishedVersio
Identification of novel Cu, Ag, and Au ternary oxides from global structural prediction
We use ab initio global structural prediction, and specifically the minima
hopping method, to explore the periodic table in search of novel oxide phases.
In total, we study 183 different compositions of the form MXO2, where M=(Cu,
Ag, Au) and X is an element of the periodic table. This set includes the
well-known Cu delafossite compounds that are, up to now, the best p-type
transparent conductive oxides known to mankind. Our calculations discover 81
stable compositions, out of which only 36 are included in available databases.
Some of these new phases are potentially good candidates for transparent
electrodes. These results demonstrate, on one hand, how incomplete is still our
knowledge of the phase-space of stable ternary materials. On the other hand, we
show that structural prediction combined with high-throughput approaches is a
powerful tool to extend that knowledge, paving the way for the experimental
discovery of new materials on a large scale
The interplay of university and industry through the FP5 network
To improve the quality of life in a modern society it is essential to reduce
the distance between basic research and applications, whose crucial roles in
shaping today's society prompt us to seek their understanding. Existing studies
on this subject, however, have neglected the network character of the
interaction between university and industry. Here we use state-of-the-art
network theory methods to analyze this interplay in the so-called Framework
Programme--an initiative which sets out the priorities for the European Union's
research and technological development. In particular we study in the 5th
Framework Programme (FP5) the role played by companies and scientific
institutions and how they contribute to enhance the relationship between
research and industry. Our approach provides quantitative evidence that while
firms are size hierarchically organized, universities and research
organizations keep the network from falling into pieces, paving the way for an
effective knowledge transfer.Comment: 21 pages (including Appendix), 8 figures. Published online at
http://stacks.iop.org/1367-2630/9/18
Spatiotemporal Chaos, Localized Structures and Synchronization in the Vector Complex Ginzburg-Landau Equation
We study the spatiotemporal dynamics, in one and two spatial dimensions, of
two complex fields which are the two components of a vector field satisfying a
vector form of the complex Ginzburg-Landau equation. We find synchronization
and generalized synchronization of the spatiotemporally chaotic dynamics. The
two kinds of synchronization can coexist simultaneously in different regions of
the space, and they are mediated by localized structures. A quantitative
characterization of the degree of synchronization is given in terms of mutual
information measures.Comment: 6 pages, using bifchaos.sty (included). 7 figures. Related material,
including higher quality figures, could be found at
http://www.imedea.uib.es/PhysDept/publicationsDB/date.html . To appear in
International Journal of Bifurcation and Chaos (1999
Fuzzy logic as a decision-making support system for the indication of bariatric surgery based on an index (OBESINDEX) generated by the association between body fat and body mass index
Background: A Fuzzy Obesity Index (OBESINDEX) for use as an alternative in bariatric surgery indication (BSI) is presented. The search for a more accurate method to evaluate obesity and to indicate a better treatment is important in the world health context. BMI (body mass index) is considered the main criteria for obesity treatment and BSI. Nevertheless, the fat excess related to the percentage of Body Fat (%BF) is actually the principal harmful factor in obesity disease that is usually neglected. This paper presents a new fuzzy mechanism for evaluating obesity by associating BMI with %BF that yields a fuzzy obesity index for obesity evaluation and treatment and allows building up a Fuzzy Decision Support System (FDSS) for BSI.

Methods: Seventy-two patients were evaluated for both BMI and %BF. These data are modified and treated as fuzzy sets. Afterwards, the BMI and %BF classes are aggregated yielding a new index (OBESINDEX) for input linguistic variable are considered the BMI and %BF, and as output linguistic variable is employed the OBESINDEX, an obesity classification with entirely new classes of obesity in the fuzzy context as well is used for BSI.

Results: There is a gradual, smooth obesity classification and BSI when using the proposed fuzzy obesity index when compared with other traditional methods for dealing with obesity.

Conclusion: The BMI is not adequate for surgical indication in all the conditions and fuzzy logic becomes an alternative for decision making in bariatric surgery indication based on the OBESINDEX
Tree-Shaped Fluid Flow and Heat Transfe
This book is an attempt to present a comprehensive overview of the fundamentals
in the area of tree flow networks. Emphasis is placed on the understanding of the design features of these networks and on their significance to the transport
phenomena associated with these systems. It is intended to bring into perspective the relevant research that has been performed, mainly that which provides the reader with a comprehensive overview of the topic
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