23,247 research outputs found
Invalidation of the Kelvin Force in Ferrofluids
Direct and unambiguous experimental evidence for the magnetic force density
being of the form in a certain geometry - rather than being the
Kelvin force - is provided for the first time. (M is the
magnetization, H the field, and B the flux density.)Comment: 4 pages, 4 figure
Matter wave quantum dots (anti-dots) in ultracold atomic Bose-Fermi mixtures
The properties of ultracold atomic Bose-Fermi mixtures in external potentials
are investigated and the existence of gap solitons of Bose-Fermi mixtures in
optical lattices demonstrated. Using a self-consistent approach we compute the
energy spectrum and show that gap solitons can be viewed as matter wave
realizations of quantum dots (anti-dots) with the bosonic density playing the
role of trapping (expulsive) potential for the fermions. The fermionic states
trapped in the condensate are shown to be at the bottom of the Fermi sea and
therefore well protected from thermal decoherence. Energy levels, filling
factors and parameters dependence of gap soliton quantum dots are also
calculated both numerically and analytically.Comment: Extended version of talk given at the SOLIBEC conference, Almagro,
Spain, 8-12 February 2005. To be published on Phys.Rev.
Electromagnetic Force in Dispersive and Transparent Media
A hydrodynamic-type, macroscopic theory was set up recently to simultaneously
account for dissipation and dispersion of electromagnetic field, in
nonstationary condensed systems of nonlinear constitutive relations~\cite{JL}.
Since it was published in the letter format, some algebra and the more subtle
reasonings had to be left out. Two of the missing parts are presented in this
paper: How algebraically the new results reduce to the known old ones; and more
thoughts on the range of validity of the new theory, especially concerning the
treatment of dissipation.Comment: 10 pages, 0 figur
Environmental accounting for ecosystem conservation: Linking societal and ecosystem metabolisms
This paper proposes an approach to environmental accounting useful for
studying the feasibility of socio-economic systems in relation to the external
constraints posed by ecological compatibility. The approach is based on a
multi-scale analysis of the metabolic pattern of ecosystems and societies and
it provides an integrated characterization of the resulting interaction. The
text starts with a theoretical part explaining (i) the implicit epistemological
revolution implied by the notion of ecosystem metabolism and the fund-flow
model developed by Georgescu-Roegen applied to environmental accounting, and
(ii) the potentials of this approach to create indicators to assess ecological
integrity and environmental impacts. This revolution also makes it possible to
carry out a multi-scale integrated assessment of ecosystem and societal
metabolisms at the territorial level. In the second part, two applications of
this approach using an indicator of the negentropic cost show the possibility
to characterize in quantitative and qualitative terms degrees of alteration
(crop cultivation, tree plantations)for different biomes (tropical and boreal
forests). Also, a case study for land use scenarios has been included. The
proposed approach represents an integrated multi-scale tool for the analysis of
nature conservation scenarios and strategies.Comment: 29 pages including 6 figure
Synchronization in random networks with given expected degree sequences
Synchronization in random networks with given expected degree sequences is studied. We also investigate in details the synchronization in networks whose topology is described by classical random graphs, power-law random graphs and hybrid graphs when N goes to infinity. In particular, we show that random graphs almost surely synchronize. We also show that adding small number of global edges to a local graph makes the corresponding hybrid graph to synchroniz
Possible multiple evolution of indirect telencephalo-cerebellar pathways in teleosts: studies in Carassius auratus and Pantodon buchholzi
Among vertebrates, telencephalo-pontine systems exist only in birds and mammals. However, three nuclei in the diencephalon and mesencephalon of teleost fishes have been indicated — analogous to the pons — to represent relay stations between telencephalon and cerebellum. Since two of these nuclei (dorsal preglomerular nucleus, dorsal tegmental nucleus) have only been described in the highly derived, electrosensory mormyrids, we investigated telencephalic connections in two nonelectrosensory teleosts, the goldfish Carassius auratus and the freshwater butterflyfish Pantodon buchholzi, and cerebellar connections only in the latter species, since for C. auratus these connections are already established. Horseradish peroxidase tracing reveals that C. auratus has a dorsal tegmental nucleus and a paracommissural nucleus both of which are telencephalo-recipient and project to the cerebellum, and that P. buchholzi has a dorsal preglomerular nucleus with such connections. These results extend our knowlegde of the distribution and, therefore, the phylogeny of telencephalo-cerebellar systems in teleosts. Similar to tetrapods, teleosts appear to have developed telencephalo-cerebellar systems several times independently
A Fast BCS/FCS Algorithm for Image Segmentation
A fast and efficient segmentation algorithm based on the Boundary Contour System/Feature Contour System (BCS/FCS) of Grossberg and Mingolla [3] is presented. This implementation is based on the FFT algorithm and the parallelism of the system.Consejo Nacional de Ciencia y Tecnología (63l462); Defense Advanced Research Projects Agency (AFOSR 90-0083); Office of Naval Research (N00014-92-J-l309
Phylogeny of putative cholinergic visual pathways through the pretectum to the hypothalamus in teleost fish
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