3,219 research outputs found
Classical R-Operators and Integrable Generalizations of Thirring Equations
We construct different integrable generalizations of the massive Thirring
equations corresponding loop algebras in
different gradings and associated ''triangular'' -operators. We consider the
most interesting cases connected with the Coxeter automorphisms, second order
automorphisms and with ''Kostant-Adler-Symes'' -operators. We recover a
known matrix generalization of the complex Thirring equations as a partial case
of our construction.Comment: This is a contribution to the Proc. of the Seventh International
Conference ''Symmetry in Nonlinear Mathematical Physics'' (June 24-30, 2007,
Kyiv, Ukraine), published in SIGMA (Symmetry, Integrability and Geometry:
Methods and Applications) at http://www.emis.de/journals/SIGMA
Stationary and impulsive injection of electron beams in converging magnetic field
In this work we study time-dependent precipitation of an electron beam
injected into a flaring atmosphere with a converging magnetic field by
considering collisional and Ohmic losses with anisotropic scattering and pitch
angle diffusion. Two injection regimes are investigated: short impulse and
stationary injection. The effects of converging magnetic fields with different
spatial profiles are compared and the energy deposition produced by the
precipitating electrons at different depths and regimes is calculated. The time
dependent Fokker-Planck equation for electron distribution in depth, energy and
pitch angle was solved numerically by using the summary approximation method.
It was found that steady state injection is established for beam electrons at
0.07-0.2 seconds after the injection onset depending on the initial beam
parameters. Energy deposition by a stationary beam is strongly dependent on a
self-induced electric field but less on a magnetic field convergence. Energy
depositions by short electron impulses are found to be insensitive to the
self-induced electric field but are strongly affected by a magnetic
convergence. Short beam impulses are shown to produce sharp asymmetric hard
X-ray bursts within a millisecond timescale often observed in solar flares.Comment: 14 pages, 15 figures, Astronomy and Astrophysics (accepted
New Records of Thecacineta cothurnioides and Trematosoma rotunda (Ciliophora, Suctorea) as epibionts on nematodes from the Indian Ocean
This article deals with the report of two suctorian ciliates species viz. Thecacineta
cothurnioides Collin, 1909 and Trematosoma rotunda (Allgén, 1952 ) as epibionts
on Tricoma sp. and Pseudochromadora sp. (Nematoda) respectively from Ratnagiri,
west coast of India, Arabian Sea (Indian Ocean). Redescription of two species with
distribution and nomenclatural notes are given. Both species are recorded here first
time from Indian coast and the Indian Ocean. Genus Tricoma Cobb, 1894 is also
recorded here first time as a host of Th. cothurnioides
An overview of Suctorian ciliates (Ciliophora, Suctorea) as epibionts of halacarid mites (Acari, Halacaridae)
Scant information is available regarding the prevalence and distribution of suctorian ciliates on halacarid mites. However,
using this limited information and data from our laboratory on the systematics, biology, ecology and distribution of
suctorian ciliates that are epibionts of halacarid mites, we redescribed four suctorian species: Limnoricus ceter (Jankowski),
Praethecacineta halacari (Schulz), Thecacineta calix (Schroder) and Acineta sulcata Dons. We also recognized
Lissacineta allgeni Jankowski and Thecacineta allgeni (Jankowski) as synonyms of Praethecacineta halacari (Schluz),
and Thecacineta laophontis Jankowski and Paracineta moebiusi Kahl as synonyms of Thecacineta calix (Schroder).
Many suctorians have been reported, but not properly identified in the halacarid literature. So, we have attempted to
identify those suctorians to species level. Lastly, the interactions between the suctorians and their hosts are also discussed
and Praethecacineta halacari is also reported for the first time from the Indian coast
Horizontal mantle flow controls subduction dynamics
It is generally accepted that subduction is driven by downgoing-plate negative buoyancy. Yet plate age –the main control on buoyancy– exhibits little correlation with most of the present-day subduction velocities and slab dips. “West”-directed subduction zones are on average steeper (~65°) than “East”-directed (~27°). Also, a “westerly”-directed net rotation of the lithosphere relative to the mantle has been detected in the hotspot reference frame. Thus, the existence of an “easterly”-directed horizontal mantle wind could explain this subduction asymmetry, favouring steepening or lifting of slab dip angles. Here we test this hypothesis using high-resolution two-dimensional numerical thermomechanical models of oceanic plate subduction interacting with a mantle flow. Results show that when subduction polarity is opposite to that of the mantle flow, the descending slab dips subvertically and the hinge retreats, thus leading to the development of a back-arc basin. In contrast, concordance between mantle flow and subduction polarity results in shallow dipping subduction, hinge advance and pronounced topography of the overriding plate, regardless of their age-dependent negative buoyancy. Our results are consistent with seismicity data and tomographic images of subduction zones. Thus, our models may explain why subduction asymmetry is a common feature of convergent margins on Earth
Report of epibiont Thecacineta calix (Ciliophora: Suctorea) on deep sea Desmodora (Nematoda) from the Andaman Sea, Indian Ocean
Suctorian epibionts Thecacineta calix attached on the cuticle of nematodes Desmodora sphaerica and
D. pontica are reported here from the deep sea hexactinellid sponge Pheronema sp. from the Andaman
Sea (Indian Ocean). The epibiont T. calix is reported here for first time from the Andaman Sea
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