1,402 research outputs found

    The Supernova Remnant G11.2-0.3 and its central Pulsar

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    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

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    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 s1^{-1} 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 Hβ\beta luminosity, and the diameter. On the basis of this we derive an effective temperature logTeff5.05\log T_{\rm eff} \sim 5.05 and luminosity 1.85<logL<2.251.85 < \log L < 2.25. 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

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    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

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    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]/Hα\alpha vs. log[OIII]/Hβ\beta 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

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    Recently, Morsi has developed a complete syntax for the class of all adjointness algebras (L,,A,K,H)\left( L,\leq ,A,K,H\right) . There, (L,)\left( L,\leq \right) is a partially ordered set with top element 11, KK is a conjunction on (L,)\left( L,\leq \right) for which 11 is a left identity element, and the two implication-like binary operations AA and HH on LL are adjoints of KK. In this paper, we extend that formal system to one for the class ADJLADJL of all 9-tuples (L,,1,0,A,K,H,,)\left( L,\leq ,1,0,A,K,H,\wedge ,\vee \right) , called \emph{% adjointness lattices}; in each of which (L,,1,0,,)\left( L,\leq ,1,0,\wedge ,\vee \right) is a bounded lattice, and (L,,A,K,H)\left( L,\leq ,A,K,H\right) is an adjointness algebra. We call it \emph{Propositional Calculus for Adjointness Lattices}, abbreviated AdjLPCAdjLPC. Our axiom scheme for AdjLPCAdjLPC features four inference rules and thirteen axioms. We deduce enough theorems and inferences in AdjLPCAdjLPC to establish its completeness for ADJLADJL; 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 00 together with AA and HH. We end by developing complete syntax for all adjointness lattices whose implications are SS-type implications

    Call Blocking Probabilities Reduction of Channel Assignment in Mobile Communication Systems

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    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

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    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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