12,615 research outputs found
Hatching Strategies in Monogenean (Platyhelminth) Parasites that Facilitate Host Infection
In parasites, environmental cues may influence hatching of eggs and enhance the success of infections. The two major endoparasitic groups of parasitic platyhelminths, cestodes (tapeworms) and digeneans (flukes), typically have high fecundity, infect more than one host species, and transmit trophically. Monogeneans are parasitic flatworms that are among the most host specific of all parasites. Most are ectoparasites with relatively low fecundity and direct life cycles tied to water. They infect a single host species, usually a fish, although some are endoparasites of amphibians and aquatic chelonian reptiles. Monogenean eggs have strong shells and mostly release ciliated larvae, which, against all odds, must find, identify, and infect a suitable specific host. Some monogeneans increase their chances of finding a host by greatly extending the hatching period (possible bet-hedging). Others respond to cues for hatching such as shadows, chemicals, mechanical disturbance, and osmotic changes, most of which may be generated by the host. Hatching may be rhythmical, larvae emerging at times when the host is more vulnerable to invasion, and this may be combined with responses to other environmental cues. Different monogenean species that infect the same host species may adopt different strategies of hatching, indicating that tactics may be more complex than first thought. Control of egg assembly and egg-laying, possibly by host hormones, has permitted colonization of frogs and toads by polystomatid monogeneans. Some monogeneans further improve the chances of infection by attaching eggs to the host or by retaining eggs on, or in, the body of the parasite. The latter adaptation has led ultimately to viviparity in gyrodactylid monogeneans
Parafermions, parabosons and representations of so(\infty) and osp(1|\infty)
The goal of this paper is to give an explicit construction of the Fock spaces
of the parafermion and the paraboson algebra, for an infinite set of
generators. This is equivalent to constructing certain unitary irreducible
lowest weight representations of the (infinite rank) Lie algebra so(\infty) and
of the Lie superalgebra osp(1|\infty). A complete solution to the problem is
presented, in which the Fock spaces have basis vectors labelled by certain
infinite but stable Gelfand-Zetlin patterns, and the transformation of the
basis is given explicitly. We also present expressions for the character of the
Fock space representations
Some Properties of the Calogero-Sutherland Model with Reflections
We prove that the Calogero-Sutherland Model with reflections (the BC_N model)
possesses a property of duality relating the eigenfunctions of two Hamiltonians
with different coupling constants. We obtain a generating function for their
polynomial eigenfunctions, the generalized Jacobi polynomials. The symmetry of
the wave-functions for certain particular cases (associated to the root systems
of the classical Lie groups B_N, C_N and D_N) is also discussed.Comment: 16 pages, harvmac.te
Interval structure of the Pieri formula for Grothendieck polynomials
We give a combinatorial interpretation of a Pieri formula for double
Grothendieck polynomials in terms of an interval of the Bruhat order. Another
description had been given by Lenart and Postnikov in terms of chain
enumerations. We use Lascoux's interpretation of a product of Grothendieck
polynomials as a product of two kinds of generators of the 0-Hecke algebra, or
sorting operators. In this way we obtain a direct proof of the result of Lenart
and Postnikov and then prove that the set of permutations occuring in the
result is actually an interval of the Bruhat order.Comment: 27 page
Fabrication and properties of gallium phosphide variable colour displays
The unique properties of single-junction gallium phosphide devices incorporating both red and green radiative recombination centers were investigated in application to the fabrication of monolithic 5 x 7 displays capable of displaying symbolic and alphanumeric information in a multicolor format. A number of potentially suitable material preparation techniques were evaluated in terms of both material properties and device performance. Optimum results were obtained for double liquid-phase-epitaxial process in which an open-tube dipping technique was used for n-layer growth and a sealed tipping procedure for subsequent p-layer growth. It was demonstrated that to prepare devices exhibiting a satisfactory range of dominant wavelengths which can be perceived as distinct emission colors extending from the red through green region of the visible spectrum involves a compromise between the material properties necessary for efficient red emission and those considered optimum for efficient green emission
Bilinear identities on Schur symmetric functions
A series of bilinear identities on the Schur symmetric functions is obtained
with the use of Pluecker relations.Comment: Accepted to Journal of Nonlinear Mathematical Physics. A reference to
a connected result is adde
Integrity bases for local invariants of composite quantum systems
Unitary group branchings appropriate to the calculation of local invariants
of density matrices of composite quantum systems are formulated using the
method of -function plethysms. From this, the generating function for the
number of invariants at each degree in the density matrix can be computed. For
the case of two two-level systems the generating function is . Factorisation of such series leads
in principle to the identification of an integrity basis of algebraically
independent invariants. This note replaces Appendix B of our paper\cite{us} J
Phys {\bf A33} (2000) 1895-1914 (\texttt{quant-ph/0001076}) which is incorrect.Comment: Latex, 4 pages, correcting Appendix B of quant-ph/0001076 Error in
corrected and conclusions modified accordingl
Gel'fand-Zetlin Basis and Clebsch-Gordan Coefficients for Covariant Representations of the Lie superalgebra gl(m|n)
A Gel'fand-Zetlin basis is introduced for the irreducible covariant tensor
representations of the Lie superalgebra gl(m|n). Explicit expressions for the
generators of the Lie superalgebra acting on this basis are determined.
Furthermore, Clebsch-Gordan coefficients corresponding to the tensor product of
any covariant tensor representation of gl(m|n) with the natural representation
V ([1,0,...,0]) of gl(m|n) with highest weight (1,0,. . . ,0) are computed.
Both results are steps for the explicit construction of the parastatistics Fock
space.Comment: 16 page
Description of Pairing correlation in Many-Body finite systems with density functional theory
Different steps leading to the new functional for pairing based on natural
orbitals and occupancies proposed in ref. [D. Lacroix and G. Hupin,
arXiv:1003.2860] are carefully analyzed. Properties of quasi-particle states
projected onto good particle number are first reviewed. These properties are
used (i) to prove the existence of such a functional (ii) to provide an
explicit functional through a 1/N expansion starting from the BCS approach
(iii) to give a compact form of the functional summing up all orders in the
expansion. The functional is benchmarked in the case of the picked fence
pairing Hamiltonian where even and odd systems, using blocking technique are
studied, at various particle number and coupling strength, with uniform and
random single-particle level spacing. In all cases, a very good agreement is
found with a deviation inferior to 1% compared to the exact energy.Comment: 14 pages, 9 figure
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