26 research outputs found
Entanglement of two delocalised electrons
Several convenient formulae for the entanglement of two indistinguishable
delocalised spin-1/2 particles are introduced. This generalizes the standard
formula for concurrence, valid only in the limit of localised or
distinguishable particles. Several illustrative examples are given.Comment: 4 page
Spatial Structure of Spin Polarons in the t-J Model
The deformation of the quantum Neel state induced by a spin polaron is
analyzed in a slave fermion approach. Our method is based on the selfconsistent
Born approximation for Green's and the wave function for the quasiparticle. The
results of various spin-correlation functions relative to the position of the
moving hole are discussed and shown to agree with those available from small
cluster calculations. Antiferromagnetic correlations in the direct neighborhood
of the hole are reduced, but they remain antiferromagnetic even for J as small
as 0.1 t. These correlation functions exhibit dipolar distortions in the spin
structure, which sensitively depend on the momentum of the quasiparticle. Their
asymptotic decay with the distance from the hole is governed by power laws, yet
the spectral weight of the quasiparticles does not vanish.Comment: 12 pages, 2 postscipt files with figures; uses REVTeX, to be
published in Phys. Rev. B, Feb. 199
Coulomb Blockade Resonances in Quantum Wires
The conductance through a quantum wire of cylindrical cross section and a
weak bulge is solved exactly for two electrons within the Landauer-Buettiker
formalism. We show that this 'open' quantum dot exhibits spin-dependent Coulomb
blockade resonances resulting in two anomalous structure on the rising edge to
the first conductance plateau, one near 0.25(2e^2/h), related to a singlet
resonance, and one near 0.7(2e^2/h), related to a triplet resonance. These
resonances are generic and robust, occurring for other types of quantum wire
and surviving to temperatures of a few degrees.Comment: 5 pages, 3 postscript files with figures; uses REVTe
Finite volume simulation of 2-D steady square lid driven cavity flow at high reynolds numbers
In this work, computer simulation results of steady incompressible flow in a 2-D square lid-driven cavity up to Reynolds number (Re) 65000 are presented and compared with those of earlier studies. The governing flow equations are solved by using the finite volume approach. Quadratic upstream interpolation for convective kinematics (QUICK) is used for the approximation of the convective terms in the flow equations. In the implementation of QUICK, the deferred correction technique is adopted. A non-uniform staggered grid arrangement of 768x768 is employed to discretize the flow geometry. Algebraic forms of the coupled flow equations are then solved through the iterative SIMPLE (Semi-Implicit Method for Pressure-Linked Equation) algorithm. The outlined computational methodology allows one to meet the main objective of this work, which is to address the computational convergence and wiggled flow problems encountered at high Reynolds and Peclet (Pe) numbers. Furthermore, after Re > 25000 additional vortexes appear at the bottom left and right corners that have not been observed in earlier studies
Maristem—Stem Cells of Marine/Aquatic Invertebrates: From Basic Research to Innovative Applications
The “stem cells” discipline represents one of the most dynamic areas in biomedicine. While adult marine/aquatic invertebrate stem cell (MISC) biology is of prime research and medical interest, studies on stem cells from organisms outside the classical vertebrate (e.g., human, mouse, and zebrafish) and invertebrate (e.g., Drosophila, Caenorhabditis) models have not been pursued vigorously. Marine/aquatic invertebrates constitute the largest biodiversity and the widest phylogenetic radiation on Earth, from morphologically simple organisms (e.g., sponges, cnidarians), to the more complex mollusks, crustaceans, echinoderms, and protochordates. These organisms contain a kaleidoscope of MISC-types that allow the production of a large number of novel bioactive-molecules, many of which are of significant potential interest for human health. MISCs further participate in aging and regeneration phenomena, including whole-body regeneration. For years, the European MISC-community has been highly fragmented and has established scarce ties with biomedical industries in an attempt to harness MISCs for human welfare. Thus, it is important to (i) consolidate the European community of researchers working on MISCs; (ii) promote and coordinate European research on MISC biology; (iii) stimulate young researchers to embark on research in MISC-biology; (iv) develop, validate, and share novel MISC tools and methodologies; (v) establish the MISC discipline as a forefront interest of biomedical disciplines, including nanobiomedicine; and (vi) establish collaborations with industries to exploit MISCs as sources of bioactive molecules. In order to fill the recognized gaps, the EC-COST Action 16203 “MARISTEM” has recently been launched. At its initial stage, the consortium unites 26 scientists from EC countries, Cooperating countries, and Near Neighbor Countries.This study is supported by the European Cooperation in Science & Technology program (EUCOST).Grant title: “Stem cells of marine/aquatic invertebrates: from basic research to innovative applications” (MARISTEM). The project idea developed as a direct outcome of a EuroMarine (European Marine Research Network) working group meeting held in Padua on 9–10 March 2016.info:eu-repo/semantics/publishedVersio
Carriers binding to excitons: Crystal-field excitations in doped Mott-Hubbard insulators
Where are the polyps? Molecular identification, distribution and population differentiation of Aurelia aurita jellyfish polyps in the southern North Sea area
Redescription of Pelagia benovici into a new jellyfish genus, Mawia, gen. nov., and its phylogenetic position within Pelagiidae (Cnidaria : Scyphozoa : Semaeostomeae)
This study provides new and additional data on morphology and a phylogenetic analysis of the recently described species Pelagia benovici Piraino, Aglieri, Scorrano & Boero, 2014 from the Northern Adriatic (Mediterranean Sea). Comprehensive morphological analyses of diagnostic characters, of which the most significant are marginal tentacles anatomy, basal pillars, gonad pattern, subgenital ostia and exumbrellar sensory pits, revealed significant differences from the currently known genera Sanderia, Chrysaora and Pelagia in the family Pelagiidae. A phylogenetic analysis of mitochondrial genes (COI, 16S rRNA, 12S rRNA) and nuclear ribosomal genes (28S rRNA, ITS1/ITS2 regions), together with cladistic analysis of morphological characters, positioned Pelagia benovici as a sister taxon with Sanderia malayensis, and both share a common ancestor with Chrysaora hysoscella. Pelagia benovici does not share a direct common ancestor with the genus Pelagia, and thus we propose it should not belong to this genus. Therefore, a new genus Mawia, gen. nov. (Semaeostomeae : Pelagiidae) is described, and Pelagia benovici is renamed as Mawia benovici, comb, nov