91 research outputs found
Hybrids between Schistosoma mansoni and S. rodhaini : characterization by isoelectric focusing of six enzymes
Une étude par isoélectrofocalisation sur gels polyacrulamides à partir d'extraits de #S. mansoni (Guadeloupe) et #S. rodhaini (Burundi) et de leurs hybrides expérimentaux (première et deuxième générations) a été entreprise sur 6 systèmes enzymatiques (LDH, MDH, G6PD, AcP, PGM et GPI). Il a été mis en évidence un polymorphisme avec MDH (locus MDH-1 et MDH-2) et une hérédité liée au sexe avec GPI. Une interprétation génétique est proposée pour expliquer ces résultats et une comparaison est faite avec les résultats obtenus par électrophorèse pour #S. mansoni$ et #S. rodhaini
Kinetic Inductance of Josephson Junction Arrays: Dynamic and Equilibrium Calculations
We show analytically that the inverse kinetic inductance of an
overdamped junction array at low frequencies is proportional to the admittance
of an inhomogeneous equivalent impedance network. The bond in this
equivalent network has an inverse inductance
, where is the Josephson
coupling energy of the bond, is the ground-state phase
of the grain , and is the usual magnetic phase factor. We use this
theorem to calculate for square arrays as large as .
The calculated is in very good agreement with the low-temperature
limit of the helicity modulus calculated by conventional equilibrium
Monte Carlo techniques. However, the finite temperature structure of ,
as a function of magnetic field, is \underline{sharper} than the
zero-temperature , which shows surprisingly weak structure. In
triangular arrays, the equilibrium calculation of yields a series of
peaks at frustrations , where is an integer , consistent with experiment.Comment: 14 pages + 6 postscript figures, 3.0 REVTe
Fine structure of the male genital systems, spermatophores and unusual sperm cells of saxidromidae (Acari, Actinotrichida)
The early derivative actinedid Saxidromidae, Saxidromus delamarei, Bovidromus roussouwi, and Rhinodromus lootsi perform indirect spermatophore transfer by means of a peculiar mating behaviour. The anatomy and fine structure of the male genital systems are described and are shown to exhibit the organisation considered to be fundamental in Actinotrichida: paired testes with germinal and glandular parts, paired vasa deferentia, unpaired ejaculatory duct, progenital chamber containing genital papillae. The genital system is located ventral of the digestive tract. The testes produce relatively few or even very few aflagellate sperm cells, which represent synspermia consisting of likely four undivided sperm cell equivalents in a common cytoplasm. Whereas S. delamarei produces a rather large stalked spermatophore containing many synspermia, both the other species produce very tiny stalked spermatophores with a spherical head representing only one synspermium. Thus, in these latter species only one synspermium is transferred to the female at atime, but the male can convey several (possibly five or more) spermatophores to the female during the mating session. A scenario is suggested which could describe the evolution of this remarkable mating system and behaviour.Fil: Alberti, Gerd. ERNST MORITZ ARNDT UNIVERSITÄT GREIFSWALD (UG);Fil: Coineau, Yves. Muséum National d'Histoire Naturelle; FranciaFil: Fernández, Néstor Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Théron, Pieter D.. North-West University; Sudáfric
Magnetoinductance of Josephson junction array with frozen vortex diffusion
The dependence of sheet impedance of a Josephson junction array on the
applied magnetic field is investigated in the regime when vortex diffusion
between array plaquettes is effectively frozen due to low enough temperature.
The field dependent contribution to sheet inductance is found to be
proportional to f*ln(1/f), where f<<1 is the magnitude of the field expressed
in terms of flux quanta per plaquette.Comment: 5 pages, no figure
A near-field scanning microwave microscope in a scanning electron microscope: design and challenges
International audienc
Multiport Vector Network Analyzer Configured in RF Interferometric Mode for Reference Impedance Renormalization
International audienceA novel active microwave interferometric technique is implemented on a multiport vector network analyzer for renormalizing the reference impedance 50 Ohms into any desired complex impedance. The resulting measured reflection coefficient around the new reference impedance is around zero, resulting in high measurement sensitivity. The method proposed avoids any external component commonly found in interferometric setups. In addition, a zeroing process including vector calibration is developed for broad frequency range and requires only a software procedure to be implemented in the system framework
Interactions between Natural Populations of Human and Rodent Schistosomes in the Lake Victoria Region of Kenya: A Molecular Epidemiological Approach
One of the world's most prevalent neglected diseases is schistosomiasis, which infects approximately 200 million people worldwide. Schistosoma mansoni is transmitted to humans by skin penetration by free-living larvae that develop in freshwater snails. The origin of this species is East Africa, where it coexists with its sister species, S. rodhaini. Interactions between these species potentially influence their epidemiology, ecology, and evolutionary biology, because they infect the same species of hosts and can hybridize. Over two years, we examined their distribution in Kenya to determine their degree of overlap geographically, within snail hosts, and in the water column as infective stages. Both species were spatially and temporally patchy, although S. mansoni was eight times more common than S. rodhaini. Both species overlap in the time of day they were present in the water column, which increases the potential for the species to coinfect the same host and interbreed. Peak infective time for S. mansoni was midday and dawn and dusk for S. rodhaini. Three snails were coinfected, which was more common than expected by chance. These findings indicate a lack of obvious isolating mechanisms to prevent hybridization, raising the intriguing question of how the two species retain separate identities
Vortex dynamics for two-dimensional XY models
Two-dimensional XY models with resistively shunted junction (RSJ) dynamics
and time dependent Ginzburg-Landau (TDGL) dynamics are simulated and it is
verified that the vortex response is well described by the Minnhagen
phenomenology for both types of dynamics. Evidence is presented supporting that
the dynamical critical exponent in the low-temperature phase is given by
the scaling prediction (expressed in terms of the Coulomb gas temperature
and the vortex renormalization given by the dielectric constant
) both for RSJ and TDGL
and that the nonlinear IV exponent a is given by a=z+1 in the low-temperature
phase. The results are discussed and compared with the results of other recent
papers and the importance of the boundary conditions is emphasized.Comment: 21 pages including 15 figures, final versio
Dynamic scaling for 2D superconductors, Josephson junction arrays and superfluids
The value of the dynamic critical exponent is studied for two-dimensional
superconducting, superfluid, and Josephson Junction array systems in zero
magnetic field via the Fisher-Fisher-Huse dynamic scaling. We find
, a relatively large value indicative of non-diffusive
dynamics. Universality of the scaling function is tested and confirmed for the
thinnest samples. We discuss the validity of the dynamic scaling analysis as
well as the previous studies of the Kosterlitz-Thouless-Berezinskii transition
in these systems, the results of which seem to be consistent with simple
diffusion (). Further studies are discussed and encouraged.Comment: 19 pages in two-column RevTex, 8 embedded EPS figure
Vortex Lattice Melting in 2D Superconducting Networks and Films
We carry out MC studies of 2D superconducting networks, in an applied
magnetic field, for square and honeycomb geometries. We consider both dilute
systems (f=1/q) and systems near full frustration (f=1/2-1/q). For the dilute
case (which models a film as q->infinity), we find two transitions: at
T_c(f)~1/q there is a depinning transition from a pinned to a floating vortex
lattice; at T_m(f)~constant the floating vortex lattice melts into an isotropic
liquid. We analyze this melting according to the Kosterlitz- Thouless theory of
dislocation mediated melting, and find that the melting is weakly first order.
For the case near full frustration, the system can be described in terms of the
density of defects in an otherwise fully frustrated vortex pattern. We find
pinned solid, floating solid, and liquid defect phases, as well as a higher
sharp transition corresponding to the disordering of the fully frustrated
background.Comment: 55 pages, RevTex3.0, 25 figures (available by mail by contacting
[email protected]
- …