1,402 research outputs found
The Supernova Remnant G11.2-0.3 and its central Pulsar
The plerion inside the composite Supernova Remnant G11.2-0.3 appears to be
dominated by the magnetic field to an extent unprecedented among well known
cases. We discuss its evolution as determined by a central pulsar and the
interaction with the surrounding thermal remnant, which in turn interacts with
the ambient medium. We find that a plausible scenario exists, where all the
observations can be reproduced with rather typical values for the parameters of
the system; we also obtain the most likely period for the still undetected
pulsar.Comment: 10 pages, to be published on ApJ Letters. Formatted using AASTe
The physics and kinematics of the evolved, interacting planetary nebula PN G342.0-01.7
Here we aim to study the physical and kinematical characteristics of the
unstudied old planetary nebula (PN) PN G342.0-01.7, which shows evidence of
interaction with its surrounding interstellar medium. We used Integral Field
Spectra from the Wide Field Spectrograph on the ANU 2.3 m telescope to provide
spectroscopy across the whole object covering the spectral range 3400-7000
{\AA}. We formed narrow-band images to investigate the excitation structure.
The spectral analysis shows that the object is a distant Peimbert Type I PN of
low excitation, formally of excitation class of 0.5. The low electron density,
high dynamical age, and low surface brightness of the object confirm that it is
observed fairly late in its evolution. It shows clear evidence for dredge-up of
CN-processed material characteristic of its class. In addition, the low
peculiar velocity of 7 km s shows it to be a member of the young disk
component of our Galaxy. We built a self-consistent photoionisation model for
the PNe matching the observed spectrum, the H luminosity, and the
diameter. On the basis of this we derive an effective temperature and luminosity . The temperature is much
higher than might have been expected using the excitation class, proving that
this can be misleading in classifying evolved PNe. PN G342.0-01.7 is in
interaction with its surrounding interstellar medium through which the object
is moving in the south-west direction. This interaction drives a slow shock
into the outer PN ejecta. A shock model suggests that it only accounts for
about 10\% of the total luminosity, but has an important effect on the global
spectrum of the PN.Comment: 15 pages, 6 figures, A&A accepted 201
An attempt to identify the extended synchrotron structure associated with the micro-quasar GRS 1915+105
The energy ejected from the galaxy micro-quasar GRS1915+105 in the form of
jets is expected to lead to formation of an extended double lobe/hot-spot
structure with the energy content comparable to an average supernova remnant.
We used the Effelsberg 100m telescope at 10.45 GHz in attempt to identify such
structures. For this distant galactic plane source any definite identification
was not possible due to high confusion by numerous background sources, however,
a few suspect structures were pointed out.Comment: LaTeX uses a new 2001 A&A macro, 4 pages, 2 figures, A&A accepte
Galaxy emission line classification using 3D line ratio diagrams
Two-dimensional (2D) line ratio diagnostic diagrams have become a key tool in
understanding the excitation mechanisms of galaxies. The curves used to
separate the different regions - HII-like or else excited by an active galactic
nucleus (AGN) - have been refined over time but the core technique has not
evolved significantly. However, the classification of galaxies based on their
emission line ratios really is a multi-dimensional problem. Here we exploit
recent software developments to explore the potential of three-dimensional (3D)
line ratio diagnostic diagrams. We introduce a specific set of 3D diagrams, the
ZQE diagrams, which separate the oxygen abundance and the ionisation parameter
of HII region-like spectra, and which also enable us to probe the excitation
mechanism of the gas. By examining these new 3D spaces interactively, we define
a new set of 2D diagnostics, the ZE diagnostics, which can provide the
metallicity of objects excited by hot young stars, and which cleanly separate
HII region-like objects from the different classes of AGNs. We show that these
ZE diagnostics are consistent with the key log[NII]/H vs.
log[OIII]/H diagnostic currently used by the community. They also have
the advantage of attaching a probability that a given object belongs to one
class or to the other. Finally, we discuss briefly why ZQE diagrams can provide
a new way to differentiate and study the different classes of AGNs in
anticipation of a dedicated follow-up study.Comment: 21 pages, 15 figures, accepted for publication in ApJ. Due to size
limitations, the supplementary STL file for the 3D-printable diagram is
available here: http://www.mso.anu.edu.au/~fvogt/online_material.htm
Propositional calculus for adjointness lattices
Recently, Morsi has developed a complete syntax for the class of all
adjointness algebras . There, is a partially ordered set with top element , is a
conjunction on for which is a left identity
element, and the two implication-like binary operations and on
are adjoints of .
In this paper, we extend that formal system to one for the class of
all 9-tuples , called \emph{%
adjointness lattices}; in each of which is a bounded lattice, and is an
adjointness algebra. We call it \emph{Propositional Calculus for Adjointness
Lattices}, abbreviated . Our axiom scheme for features four
inference rules and thirteen axioms. We deduce enough theorems and
inferences in to establish its completeness for ; by means of
a quotient-algebra structure (a Lindenbaum type of algebra). We study two
negation-like unary operations in an adjointness lattice, defined by means
of together with and . We end by developing complete syntax for
all adjointness lattices whose implications are -type implications
Geological and groundwater potential studies of El Ismailiya master plan study area
There are no author-identified significant results in this report
Call Blocking Probabilities Reduction of Channel Assignment in Mobile Communication Systems
In wireless mobile communication systems, the radio spectrum is limited resource. However, efficient use of such limited spectrum becomes more important when the two, three or more cells in the network become hot - spot. The use of available channels has been shown to improve the system capacity. The role of channel assignment scheme is to allocate channels to cells in such way as to minimize call-blocking probability or call dropping probability and also maximize the quality of service. Different channel allocation schemes are in use for mobile communication systems, of which the Hybrid channel allocation (HCA) a combination of Fixed and Dynamic channel allocation schemes (FCA and DCA respectively) was effective. In this paper, the performance of three different channel allocation schemes FCA, DCA and HCA will be analytically compared and the results are presented
Mouse cytoplasmic dynein intermediate chains: identification of new isoforms, alternative splicing and tissue distribution of transcripts
BACKGROUND: Intracellular transport of cargoes including organelles, vesicles, signalling molecules, protein complexes, and RNAs, is essential for normal function of eukaryotic cells. The cytoplasmic dynein complex is an important motor that moves cargos along microtubule tracks within the cell. In mammals this multiprotein complex includes dynein intermediate chains 1 and 2 which are encoded by two genes, Dync1i1 and Dync1i2. These proteins are involved in dynein cargo binding and dynein complexes with different intermediate chains bind to specific cargoes, although the mechanisms to achieve this are not known. The DYNC1I1 and DYNC1I2 proteins are translated from different splice isoforms, and specific forms of each protein are essential for the function of different dynein complexes in neurons. METHODOLOGY/PRINCIPAL FINDINGS: Here we have undertaken a systematic survey of the dynein intermediate chain splice isoforms in mouse, basing our study on mRNA expression patterns in a range of tissues, and on bioinformatics analysis of mouse, rat and human genomic and cDNA sequences. We found a complex pattern of alternative splicing of both dynein intermediate chain genes, with maximum complexity in the embryonic and adult nervous system. We have found novel transcripts, including some with orthologues in human and rat, and a new promoter and alternative non-coding exon 1 for Dync1i2. CONCLUSIONS/SIGNIFICANCE: These data, including the cloned isoforms will be essential for understanding the role of intermediate chains in the cytoplasmic dynein complex, particularly their role in cargo binding within individual tissues including different brain regions
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