16,622 research outputs found
Dissipative solitons which cannot be trapped
In this paper we study the behavior of dissipative solitons in systems with
high order nonlinear dissipation and show how they cannot survive under the
effect of trapping potentials both of rigid wall type or asymptotically
increasing ones. This provides an striking example of a soliton which cannot be
trapped and only survives to the action of a weak potential
Warming up brane-antibrane inflation
We show that, in constructions with additional intersecting D-branes,
brane-antibrane inflation may naturally occur in a warm regime, such that
strong dissipative effects damp the inflaton's motion, greatly alleviating the
associated eta-problem. We illustrate this for D3-antiD3 inflation in flat
space with additional flavor D7-branes, where for both a Coulomb-like or a
quadratic hybrid potential a sufficient number of e-folds may be obtained for
perturbative couplings and O(10-10^4) branes. This is in clear contrast with
the corresponding cold scenarios, thus setting the stage for more realistic
constructions within fully stabilized compactifications. Such models
generically predict a negligible amount of tensor perturbations and
non-gaussianity f_NL \sim O(10).Comment: 8 pages, 2 figures; version to be published in Physical Review
Usability engineering practices in software development organizations: The Greek and the Italian case study
This paper reports the results of a study of software development organizationsâ approach towards usability, conducted on software development organizations in Greece, extending a survey conducted in Southern Italy in 2011. The results show that the organization performing usability evaluation is nearly the same in both countries as well as the key advantages and the problems in performing usability evaluation emphasized by Italian and Greek respondents. A difference in the understanding of usability evaluation concept between the two studies emerged
Application of the S=1 underscreened Anderson lattice model to Kondo uranium and neptunium compounds
Magnetic properties of uranium and neptunium compounds showing the
coexistence of Kondo screening effect and ferromagnetic order are investigated
within the Anderson lattice Hamiltonian with a two-fold degenerate -level in
each site, corresponding to electronic configuration with spins. A
derivation of the Schrieffer-Wolff transformation is presented and the
resulting Hamiltonian has an effective -band term, in addition to the
regular exchange Kondo interaction between the -spins and the
spins of the conduction electrons. The obtained effective Kondo lattice model
can describe both the Kondo regime and a weak delocalization of -electron.
Within this model we compute the Kondo and Curie temperatures as a function of
model parameters, namely the Kondo exchange interaction constant , the
magnetic intersite exchange interaction and the effective -bandwidth.
We deduce, therefore, a phase diagram of the model which yields the coexistence
of Kondo effect and ferromagnetic ordering and also accounts for the pressure
dependence of the Curie temperature of uranium compounds such as UTe.Comment: 9 pages, 4 figure
Scaling of variables and the relation between noncommutative parameters in Noncommutative Quantum Mechanics
We consider Noncommutative Quantum Mechanics with phase space
noncommutativity. In particular, we show that a scaling of variables leaves the
noncommutative algebra invariant, so that only the self-consistent effective
parameters of the model are physically relevant. We also discuss the recently
proposed relation of direct proportionality between the noncommutative
parameters, showing that it has a limited applicability.Comment: Revtex4, 4 pages; version to match the published on
Proteolytic Activity of the Entomopathogenic Fungi (Penicillium SP. ) of Cockroaches (Periplaneta Americana)
Cockroaches (Periplaneta americana) were the insect vectors of disease that caused adverse effects on human health. Control cockroaches\u27 excessive use of insecticides can lead to residue in the environment and resistance cockroach. Therefore it was necessary to use an alternative such as entomopathogenic fungal as biological agents. The entomopathogenic fungi penetrated via the integument of a cockroach to reach the hemocoel. Proteins were the molecules responsible for integument strength in the cockroach, It was synthesis the proteases to degrading proteins. The study begins with the isolation of entomopathogenic fungi using the moist chamber method with the cockroach as insect bait. The fungus that grows on cockroaches are cultured and purified on Potato Dextrose Agar (PDA) medium then identified. Identification was carried out through macroscopic observations including colony color and diameter and microscopic observations including conidia, conidiophores, hyphae, vesicles, fialids, and leg cells. The result of isolation and identification obtained as Penicillium sp. Proteases enzymatic activity tested on PDA with anlene 1%. The clear zone formed is measured to show the activity of proteases produced by Penicillium sp
Novel Sum-of-Sinusoids Simulation Models for Rayleigh and Rician Fading Channels
The statistical properties of Clarke\u27s fading model with a finite number of sinusoids are analyzed, and an improved reference model is proposed for the simulation of Rayleigh fading channels. A novel statistical simulation model for Rician fading channels is examined. The new Rician fading simulation model employs a zero-mean stochastic sinusoid as the specular (line-of-sight) component, in contrast to existing Rician fading simulators that utilize a non-zero deterministic specular component. The statistical properties of the proposed Rician fading simulation model are analyzed in detail. It is shown that the probability density function of the Rician fading phase is not only independent of time but also uniformly distributed over [-pi, pi). This property is different from that of existing Rician fading simulators. The statistical properties of the new simulators are confirmed by extensive simulation results, showing good agreement with theoretical analysis in all cases. An explicit formula for the level-crossing rate is derived for general Rician fading when the specular component has non-zero Doppler frequenc
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