2,266 research outputs found
Asymmetric magnetic reconnection with a flow shear and applications to the magnetopause
We perform a theoretical and numerical study of anti-parallel 2D magnetic
reconnection with asymmetries in the density and reconnecting magnetic field
strength in addition to a bulk flow shear across the reconnection site in the
plane of the reconnecting fields, which commonly occurs at planetary
magnetospheres. We predict the speed at which an isolated X-line is convected
by the flow, the reconnection rate, and the critical flow speed at which
reconnection no longer takes place for arbitrary reconnecting magnetic field
strengths, densities, and upstream flow speeds, and confirm the results with
two-fluid numerical simulations. The predictions and simulation results counter
the prevailing model of reconnection at Earth's dayside magnetopause which says
reconnection occurs with a stationary X-line for sub-Alfvenic magnetosheath
flow, reconnection occurs but the X-line convects for magnetosheath flows
between the Alfven speed and double the Alfven speed, and reconnection does not
occur for magnetosheath flows greater than double the Alfven speed. We find
that X-line motion is governed by momentum conservation from the upstream
flows, which are weighted differently in asymmetric systems, so the X-line
convects for generic conditions including sub-Alfvenic upstream speeds. For the
reconnection rate, while the cutoff condition for symmetric reconnection is
that the difference in flows on the two sides of the reconnection site is twice
the Alfven speed, we find asymmetries cause the cutoff speed for asymmetric
reconnection to be higher than twice the asymmetric form of the Alfven speed.
The results compare favorably with an observation of reconnection at Earth's
polar cusps during a period of northward interplanetary magnetic field, where
reconnection occurs despite the magnetosheath flow speed being more than twice
the magnetosheath Alfven speed, the previously proposed suppression condition.Comment: 46 pages, 7 figures, abstract abridged here, accepted to Journal of
Geophysical Research - Space Physic
Phytochemical Study of Cell Culture Jatropha Curcas
Jatropha curcas belongs to the Euphorbiaceae family which has potential economically. This plant has been reported to contain toxic compounds such as curcin and phorbol ester and its derivatives. These compounds may become a problem if J. curcas will be explored as a source of biofuel. In order to provide safety plants, the research on the study of phytochemical and initiation of cell and organ culture have been carried out. J curcas which has been collected from different regions in Indonesia showed to contain relatively the same profile of chemical contents. Dominant compounds that were detected by GCMS are hidrocarbon such as 2-heptenal, decadienal, hexsadecane, pentadecane, cyclooctane etc, fatty acid such as oktadecanoate acid, etthyl linoleate, ethyl stearate, heksadecanoate acid and steroid such as stigmasterol, fucosterol, sitosterol. No phorbol ester and its derivatives have been detected yet by the GCMS method. Callus and suspension cultures of J. curcas have been established to be used for further investigation
Symmetry, singularities and integrability in complex dynamics III: approximate symmetries and invariants
The different natures of approximate symmetries and their corresponding first
integrals/invariants are delineated in the contexts of both Lie symmetries of
ordinary differential equations and Noether symmetries of the Action Integral.
Particular note is taken of the effect of taking higher orders of the
perturbation parameter. Approximate symmetries of approximate first
integrals/invariants and the problems of calculating them using the Lie method
are considered
Gravitational multi-NUT solitons, Komar masses and charges
Generalising expressions given by Komar, we give precise definitions of
gravitational mass and solitonic NUT charge and we apply these to the
description of a class of Minkowski-signature multi-Taub-NUT solutions without
rod singularities. A Wick rotation then yields the corresponding class of
Euclidean-signature gravitational multi-instantons.Comment: Some references adde
Active tuning of high-Q dielectric metasurfaces
We demonstrate the active tuning of all-dielectric metasurfaces exhibiting
high-quality factor (high-Q) resonances. The active control is provided by
embedding the asymmetric silicon meta-atoms with liquid crystals, which allows
the relative index of refraction to be controlled through heating. It is found
that high quality factor resonances () can be tuned over more than
three resonance widths. Our results demonstrate the feasibility of using
all-dielectric metasurfaces to construct tunable narrow-band filters.Comment: 4 pages, 6 figure
Desain Dan Uji Prototipe Alat Pasteurisasi Susu Berbasis Teknologi Irradiasi Ultraviolet (Kajian Dosis Uv)
The process of milk pasteurization generally use thermal method. The method can cause microorganisms inactive on the other side, the method result in the degradation of quality food. An alternative method that can be used is by using technology of ultraviolet irradiation. Ultraviolet light has short wavelength with a very strong antimicrobacterialenergy.The mechanism of its wor is by absorbing the energy by nucleid acid without causing damaged on the surface of cel. The absorbed energy will cause the bonding of tymine (dimer tymine) so that the function of nucleic acid is disturbed and it cause the dead of microorganism (Lay and of Hastowo, 1992). The devices used in this research are ultraviolet lamp type C, spiral hose, supporting frame, materials containers and the devices for measuring the amount of microbes, fat, specific gravity and colour. Materials used in this research is fresh milk that obtained from KUD DAU Malang. The result are pasteurization process with UV irradiation decrease microorganisms and fat in milk
Consequences of a covariant Description of Heavy Ion Reactions at intermediate Energies
Heavy ion collisions at intermediate energies are studied by using a new RQMD
code, which is a covariant generalization of the QMD approach. We show that
this new implementation is able to produce the same results in the
nonrelativistic limit (i.e. 50MeV/nucl.) as the non-covariant QMD. Such a
comparison is not available in the literature. At higher energies (i.e. 1.5
GeV/nucl. and 2 GeV/nucl.) RQMD and QMD give different results in respect to
the time evolution of the phase space, for example for the directed transverse
flow. These differences show that consequences of a covariant description of
heavy ion reactions within the framework of RQMD are existing even at
intermediate energies.Comment: LaTex-file, 28 pages, 8 figures (available upon request), accepted
for publication in Physical Review
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