3,903 research outputs found
Aphid parasitoids from Malta (Hymenoptera, Braconidae, Aphidiinae)
Six aphid parasitoids are listed including three species which are
recorded for the fi rst time from the Maltese islands, namely Aphidius funebris,
Ephedrus persicae and Lysiphlebus confusus. Aphidius colemani, a species which
was introduced for the control of greenhouse aphids, was also found for the fi rst time
in the open.peer-reviewe
Pauesia silana Tremblay, 1969 a parasitoid of Cinara-aphids on Conifers in Malta (Hymenoptera: Braconidae: Aphidiinae)
Pauesia silana is recorded for the first time from Malta and the Lefkada
and Meganissi islands in Greece. From Malta, the species was reared from Cinara
palaestinensis on Pinus halepensis from material collected from Buskett. From the
Greek islands, the species was collected on Cinara sp. on the same mentioned hostplant.
The new record contributes to the information on its distribution, hosts and
plant associations in the Mediterranean area.peer-reviewe
Lipolexis gracilis Förster, 1862 - new record of an aphid parasitoid from Malta (Hymenoptera, Braconidae, Aphidiinae)
Lipolexis gracilis, an aphid parasitoid reared from a species of Aphis associated with Papaver is newly recorded from Malta. A check-list of the Aphidiinae known from Malta is given.peer-reviewe
Fast-slow asymptotics for a Markov chain model of fast sodium current
We explore the feasibility of using fast-slow asymptotic to eliminate the
computational stiffness of the discrete-state, continuous-time deterministic
Markov chain models of ionic channels underlying cardiac excitability. We focus
on a Markov chain model of the fast sodium current, and investigate its
asymptotic behaviour with respect to small parameters identified in different
ways.Comment: 16 pages, 6 figures, as accepted to Chaos 2017/09/0
Exponential integrators for a Markov chain model of the fast sodium channel of cardiomyocytes
The modern Markov chain models of ionic channels in excitable membranes are
numerically stiff. The popular numerical methods for these models require very
small time steps to ensure stability. Our objective is to formulate and test
two methods addressing this issue, so that the timestep can be chosen based on
accuracy rather than stability.
Both proposed methods extend Rush-Larsen technique, which was originally
developed to Hogdkin-Huxley type gate models. One method, "Matrix Rush-Larsen"
(MRL) uses a matrix reformulation of the Rush-Larsen scheme, where the matrix
exponentials are calculated using precomputed tables of eigenvalues and
eigenvectors. The other, "hybrid operator splitting" (HOS) method exploits
asymptotic properties of a particular Markov chain model, allowing explicit
analytical expressions for the substeps.
We test both methods on the Clancy and Rudy (2002) INa Markov chain model.
With precomputed tables for functions of the transmembrane voltage, both
methods are comparable to the forward Euler method in accuracy and
computational cost, but allow longer time steps without numerical instability.
We conclude that both methods are of practical interest. MRL requires more
computations than HOS, but is formulated in general terms which can be readily
extended to other Markov Chain channel models, whereas the utility of HOS
depends on the asymptotic properties of a particular model.
The significance of the methods is that they allow a considerable speed-up of
large-scale computations of cardiac excitation models by increasing the time
step, while maintaining acceptable accuracy and preserving numerical stability.Comment: 9 pages, 5 figures main text + 14 pages, 1 figure appendix, as
submitted in final form to IEEE TBME 2014/11/11. Copyright IEEE (2014
Further contributions to the tritrophic plant-aphid-parasitoid associations in Malta with special reference to Aphis nerii (Hemiptera, Aphidoidea) as a prevalent refugium of Aphidiinae (Hymenoptera, Braconidae)
Four species of aphid parasitoids, namely Aphidius colemani, Binodoxys angelicae, Lysiphlebus fabarum and Lysiphlebus testaceipes were reared from Aphis nerii on Nerium oleander and/or Stephanotis floribunda in Malta. Aphidius colemani was the most abundant, occurring in different habitat types. Binodoxys angelicae represents a confirmation of a doubtful past record, while Lysiphlebus testaceipes is a new record for Malta. Aphis nerii is evaluated as a refugium of several aphid parasitoids in Malta. Praon yomenae, another new record for Malta is also included in the present work.peer-reviewe
Aphids and their parasitoids on the Canary grass, Phalaris canariensis in Malta (Hymenoptera, Braconidae, Aphidiinae)
Adialytus ambiguus and Diaeretiella rapae were reared from Rhopalosiphum padi on the Canary grass, Phalaris canariensis in Malta. The identity to species level of the Adialytus required confirmation via DNA analysis of the respective species group. Some ecosystem interrelationships derived from the determined food webs are discussed.peer-reviewe
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