21,669 research outputs found
Size, sounds, and sex: interactions between body size and harmonic convergence signals determine mating success in Aedes aegypti
Background: Several new mosquito control strategies will involve the release of laboratory reared males which will be required to compete with wild males for mates. Currently, the determinants of male mating success remain unclear. The presence of convergence between male and female harmonic flight tone frequencies during a mating attempt have been found to increase male mating success in the yellow fever mosquito, Aedes aegypti. Size has also been implicated as a factor in male mating success. Here we investigated the relationships between body size, harmonic convergence signalling, and mating success. We predicted that harmonic convergence would be an important determinant of mating success and that large individuals would be more likely to converge. Methods: We used diet to manipulate male and female body size and then measured acoustic interactions during mating attempts between pairs of different body sizes. Additionally, we used playback experiments to measure the direct effect of size on signalling performance. Results: In live pair interactions, harmonic convergence was again found to be a significant predictor of copula formation. However, we additionally found interactions between harmonic convergence behaviour and body size. The probability that a given male successfully formed a copula was a consequence of his size, the size of the female encountered, and whether or not they converged. While convergence appears to be predictive of mating success regardless of size, the positive effect of convergence was modulated by size combinations. In playbacks, adult body size did not affect the probability of harmonic convergence responses. Conclusions: Both body size and harmonic convergence signalling were found to be determinants of male mating success. Our results suggest that in addition to measuring convergence ability of mass release lines that the size distribution of released males may need to be adjusted to complement the size distribution of females. We also found that diet amount alone cannot be used to increase male mating success or convergence probability. A clearer understanding of convergence behaviours, their relationship to mating success, and factors influencing convergence ability would provide the groundwork for improving the mating performance of laboratory reared lines
Axial light emission and Ar metastable densities in a parallel plate dc micro discharge in steady state and transient regimes
Axial emission profiles in a parallel plate dc micro discharge (feedgas:
argon; discharge gap d=1mm; pressure p=10Torr) were studied by means of time
resolved imaging with a fast ICCD camera. Additionally, volt-ampere (V-A)
characteristics were recorded and Ar* metastable densities were measured by
tunable diode laser absorption spectroscopy (TDLAS). Axial emission profiles in
the steady state regime are similar to corresponding profiles in standard size
discharges (d=1cm, p=1Torr). For some discharge conditions relaxation
oscillations are present when the micro discharge switches periodically between
low current Townsend-like mode and normal glow. At the same time the axial
emission profile shows transient behavior, starting with peak distribution at
the anode, which gradually moves towards the cathode during the normal glow.
The development of argon metastable densities highly correlates with the
oscillating discharge current. Gas temperatures in the low current
Townsend-like mode (T= 320-400K) and the high current glow mode (T=469-526K)
were determined by the broadening of the recorded spectral profiles as a
function of the discharge current.Comment: submitted to Plasma Sources Sci. Techno
Dynamic polarization of graphene by moving external charges: random phase approximation
We evaluate the stopping and image forces on a charged particle moving
parallel to a doped sheet of graphene by using the dielectric response
formalism for graphene's -electron bands in the random phase approximation
(RPA). The forces are presented as functions of the particle speed and the
particle distance for a broad range of charge-carrier densities in graphene. A
detailed comparison with the results from a kinetic equation model reveal the
importance of inter-band single-particle excitations in the RPA model for high
particle speeds. We also consider the effects of a finite gap between graphene
and a supporting substrate, as well as the effects of a finite damping rate
that is included through the use of Mermin's procedure. The damping rate is
estimated from a tentative comparison of the Mermin loss function with a HREELS
experiment. In the limit of low particle speeds, several analytical results are
obtained for the friction coefficient that show an intricate relationship
between the charge-carrier density, the damping rate, and the particle
distance, which may be relevant to surface processes and electrochemistry
involving graphene.Comment: 14 pages, 10 figures, accepted for publication in Phys. Rev.
Cross sections and transport properties of negative ions in rare gases
We have used a combination of a simple semi-analytic theory - Momentum Transfer Theory (MTT) and exact Monte Carlo (MC) simulations to develop momentum transfer cross sections of negative ions in collisions with noble gases based on the available data for reduced mobility at 300K as a function of E/N. At very low energies, we extrapolated obtained cross sections using Langevin's cross section and supplemented it by the total detachment cross section that was used from the threshold around 6 eV up to 100 eV. Other possible reactive processes have not been taken into account. A good agreement for the mean energy and diffusion coefficients is an independent proof of the validity of the cross sections that were derived for the negative ion mobility data
Hydrostatic pressure induced Dirac semimetal in black phosphorus
Motivated by recent experimental observation of an hydrostatic pressure
induced transition from semiconductor to semimetal in black phosphorus [Chen et
al. in arXiv:1504.00125], we present the first principles calculation on the
pressure effect of the electronic structures of black phosphorus. It is found
that the band crossover and reversal at the Z point occur around the critical
pressure Pc1=1.23 Gpa, and the band inversion evolves into 4 twofold-degenerate
Dirac cones around the Z point, suggesting a 3D Dirac semimetal. With further
increasing pressure the Dirac cones in the Gamma-Z line move toward the Gamma
point and evolve into two hole-type Fermi pockets, and those in the Z-M lines
move toward the M point and evolve into 2 hole-type Fermi pockets up to P=4.0
Gpa. It demonstrates clearly that the Lifshitz transition occurs at
from semiconductor to 3D Dirac semimetal protected by the nonsymmorphic space
symmetry of bulk. This suggests the bright perspective of black phosphorus for
optoelectronic and electronic devices due to its easy modulation by pressure.Comment: 7 pages, 9 figures, and 2 table
Level-Based Analysis of the Population-Based Incremental Learning Algorithm
The Population-Based Incremental Learning (PBIL) algorithm uses a convex
combination of the current model and the empirical model to construct the next
model, which is then sampled to generate offspring. The Univariate Marginal
Distribution Algorithm (UMDA) is a special case of the PBIL, where the current
model is ignored. Dang and Lehre (GECCO 2015) showed that UMDA can optimise
LeadingOnes efficiently. The question still remained open if the PBIL performs
equally well. Here, by applying the level-based theorem in addition to
Dvoretzky--Kiefer--Wolfowitz inequality, we show that the PBIL optimises
function LeadingOnes in expected time for a population size , which matches the bound
of the UMDA. Finally, we show that the result carries over to BinVal, giving
the fist runtime result for the PBIL on the BinVal problem.Comment: To appea
A Monte Carlo simulation of ion transport at finite temperatures
We have developed a Monte Carlo simulation for ion transport in hot
background gases, which is an alternative way of solving the corresponding
Boltzmann equation that determines the distribution function of ions. We
consider the limit of low ion densities when the distribution function of the
background gas remains unchanged due to collision with ions. A special
attention has been paid to properly treat the thermal motion of the host gas
particles and their influence on ions, which is very important at low electric
fields, when the mean ion energy is comparable to the thermal energy of the
host gas. We found the conditional probability distribution of gas velocities
that correspond to an ion of specific velocity which collides with a gas
particle. Also, we have derived exact analytical formulas for piecewise
calculation of the collision frequency integrals. We address the cases when the
background gas is monocomponent and when it is a mixture of different gases.
The developed techniques described here are required for Monte Carlo
simulations of ion transport and for hybrid models of non-equilibrium plasmas.
The range of energies where it is necessary to apply the technique has been
defined. The results we obtained are in excellent agreement with the existing
ones obtained by complementary methods. Having verified our algorithm, we were
able to produce calculations for Ar ions in Ar and propose them as a new
benchmark for thermal effects. The developed method is widely applicable for
solving the Boltzmann equation that appears in many different contexts in
physics.Comment: 14 page
Coexistence of pseudospin- and valley-Hall-like edge states in a photonic crystal with C3v symmetry
We demonstrate the coexistence of pseudospin- and valley-Hall-like edge states in a photonic crystal with
C
3
v
symmetry, which is composed of three interlacing triangular sublattices with the same lattice constants. By tuning the geometry of the sublattices, three complete photonic band gaps with nontrivial topology can be created, one of which is due to the band inversion associated with the pseudospin degree of freedom at the
Γ
point and the other two due to the gapping out of Dirac cones associated with the valley degree of freedom at the
K
,
K
′
points. The system can support triband pseudospin- and valley-momentum locking edge states at properly designed domain-wall interfaces. Furthermore, to demonstrate the novel interplay of the two kinds of edge states in a single configuration, we design a four-channel system, where the unidirectional routing of electromagnetic waves against sharp bends between two routes can be selectively controlled by the pseudospin and valley degrees of freedom. Our work combines the pseudospin and valley degrees of freedom in a single configuration and may provide more flexibility in manipulating electromagnetic waves with promising potential for multiband and multifunctional applications
The last of the simple remainders
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