581 research outputs found
Comparison of the effectiveness and attractiveness of the trap "Sentrap"and two home-made prototypes to "Multilure" (conventional trap) in male anihilation technique Mbaye Ndiaye1* and Fabrice L. R.
The average catches of Bactrocera invadens obtained from home-made open-bottom dry traps of mineral water translucent plastic bottles of 1.5 L, 5 L, and "Sentrap" Open-top Dry local Trap (plastic prototype improved by SENCHIM, an agrochemicals industry based in Senegal) were compared to the conventional trap "Multilure" (Better World Manufacturing, Inc.., Miami, FL). Results show that no significant difference was found when "Multilure" was compared to the 5 L plastic bottle trap. The study of the relationships between catches and type of trap was significant for all of them. Sentrap, "Multilure" and 1.5 L bottle trap exhibited a very high significant dependency relationships (r = -0.969**, r = -0.903** and r = -0.801**; respectively and p< 0.01). And the 5 L bottle trap was significant with r = -0.801* and p< 0.05. Thus, in case of absence of conventional traps, the plastic bottle of 5 L could, therefore, be used as an alternative and its basal part painted in yellow should increase its efficiency. Also, due to simple design and less time needed for servicing "Sentrap", increasing its volume and openings and fixing firmly the upper part with a lid screw might improve its efficiency.Key words: Traps, catches, Bactrocera
A length scale for the superconducting Nernst signal above T in NbSi
We present a study of the Nernst effect in amorphous superconducting thin
films of NbSi. The field dependence of the Nernst coefficient
above T displays two distinct regimes separated by a field scale set by
the Ginzburg-Landau correlation length. A single function , with the
correlation length as its unique argument set either by the zero-field
correlation length (in the low magnetic field limit) or by the magnetic length
(in the opposite limit), describes the Nernst coefficient. We conclude that the
Nernst signal observed on a wide temperature () and field () range is exclusively generated by short-lived Cooper pairs.Comment: 4 pages, 4 figure
Magnetic field-induced quantum superconductor-insulator transition in
A study of magnetic-field tuned superconductor-insulator transitions in
amorphous thin films shows that quantum
superconductor-insulator transitions are characterized by an unambiguous
signature -- a kink in the temperature profile of the critical magnetic field.
Using this criterion, we show that the nature of the magnetic-field tuned
superconductor-insulator transition depends on the orientation of the field
with respect to the film. For perpendicular magnetic field, the transition is
controlled by quantum fluctuations with indications for the existence of a Bose
insulator; while for parallel magnetic field, the transition is classical,
driven by the breaking of Cooper pairs at the temperature dependent critical
field .Comment: 5 pages, 4 figure
Extended paraconductivity regime in underdoped cuprates
We reconsider transport experiments in strongly anisotropic superconducting
cuprates and we find that universal Aslamazov-Larkin (AL) paraconductivity in
two dimensions is surprisingly robust even in the underdoped regime below the
pseudogap crossover temperature T^*. We also establish that the underlying
normal state resistivity in the pseudogap phase is (almost) linear in
temperature, with all the deviations being quantitatively accounted by AL
paraconductivity. The disappearence of paraconductivity is governed by the
disappearence of gaussian pair fluctuations at an energy scale related to T^*.Comment: 5 pages and 2 figure
Non-linear characteristics in two-dimensional superconductors: Berezinskii-Kosterlitz-Thouless physics vs inhomogeneity
One of the hallmarks of the Berezinskii-Kosterlitz-Thouless (BKT) transition
in two-dimensional (2D) superconductors is the universal jump of the superfluid
density, that can be indirectly probed via the non-linear exponent of the
current-voltage characteristics. Here, we compare the experimental
measurements of characteristics in two cases, namely NbN thin films and
SrTiO-based interfaces. While the former display a paradigmatic example of
BKT-like non-linear effects, the latter do not seem to justify a BKT analysis.
Rather, the observed characteristics can be well reproduced theoretically
by modelling the effect of mesoscopic inhomogeneity of the superconducting
state. Our results offer an alternative perspective on the spontaneous
fragmentation of the superconducting background in confined 2D systems.Comment: Final version, as publishe
Influence of ion implantation on the magnetic and transport properties of manganite films
We have used oxygen ions irradiation to generate controlled structural
disorder in thin manganite films. Conductive atomic force microscopy CAFM),
transport and magnetic measurements were performed to analyze the influence of
the implantation process in the physical properties of the films. CAFM images
show regions with different conductivity values, probably due to the random
distribution of point defect or inhomogeneous changes of the local Mn3+/4+
ratio to reduce lattice strains of the irradiated areas. The transport and
magnetic properties of these systems are interpreted in this context.
Metal-insulator transition can be described in the frame of a percolative
model. Disorder increases the distance between conducting regions, lowering the
observed TMI. Point defect disorder increases localization of the carriers due
to increased disorder and locally enhanced strain field. Remarkably, even with
the inhomogeneous nature of the samples, no sign of low field magnetoresistance
was found. Point defect disorder decreases the system magnetization but doesn t
seem to change the magnetic transition temperature. As a consequence, an
important decoupling between the magnetic and the metal-insulator transition is
found for ion irradiated films as opposed to the classical double exchange
model scenario.Comment: 27 pages, 11 Figure
Coulomb Explosion and Thermal Spikes
A fast ion penetrating a solid creates a track of excitations. This can
produce displacements seen as an etched track, a process initially used to
detect energetic particles but now used to alter materials. From the seminal
papers by Fleischer et al. [Phys. Rev. 156, 353 (1967)] to the present [C.
Trautmann, S. Klaumunzer and H. Trinkaus, Phys. Rev. Lett. 85, 3648 (2000)],
`Coulomb explosion' and thermal spike models are treated as conflicting models
for describing ion track effects. Here molecular dynamics simulations of
electronic-sputtering, a surface manifestation of ion track formation, show
that `Coulomb explosion' produces a `heat' spike so that these are early and
late aspects of the same process. Therefore, differences in scaling are due to
the use of incomplete spike models.Comment: Submitted to PRL. 4 pages, 3 figures. For related movies see:
http://dirac.ms.virginia.edu/~emb3t/coulomb/coulomb.html PACS added in new
versio
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