31,360 research outputs found

    PO and PN in the wind of the oxygen-rich AGB star IK Tau

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    Phosphorus-bearing compounds have only been studied in the circumstellar environments (CSEs) of the asymptotic giant branch (AGB) star IRC +10216 and the protoplanetary nebula CRL 2688, both C-rich objects, and the O-rich red supergiant VY CMa. The current chemical models cannot reproduce the high abundances of PO and PN derived from observations of VY CMa. No observations have been reported of phosphorus in the CSEs of O-rich AGB stars. We aim to set observational constraints on the phosphorous chemistry in the CSEs of O-rich AGB stars, by focussing on the Mira-type variable star IK Tau. Using the IRAM 30m telescope and the Submillimeter Array (SMA), we observed four rotational transitions of PN (J=2-1,3-2,6-5,7-6) and four of PO (J=5/2-3/2,7/2-5/2,13/2-11/2,15/2-13/2). The IRAM 30m observations were dedicated line observations, while the SMA data come from an unbiased spectral survey in the frequency range 279-355 GHz. We present the first detections of PN and PO in an O-rich AGB star and estimate abundances X(PN/H2) of about 3x10^-7 and X(PO/H2) in the range 0.5-6.0x10^-7. This is several orders of magnitude higher than what is found for the C-rich AGB star IRC +10216. The diameter (<=0.7") of the PN and PO emission distributions measured in the interferometric data corresponds to a maximum radial extent of about 40 stellar radii. The abundances and the spatial occurrence of the molecules are in very good agreement with the results reported for VY CMa. We did not detect PS or PH3 in the survey. We suggest that PN and PO are the main carriers of phosphorus in the gas phase, with abundances possibly up to several 10^-7. The current chemical models cannot account for this, underlining the strong need for updated chemical models that include phosphorous compounds.Comment: Accepted for publication in Astronomy & Astrophysics, 10 pages, 8 figure

    Unified Power Flow Controller to Control Reactive Power

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    The developing countries use thyritor, GTO, IGBT, MOSFET, and many other electronic device. These are use for switching devices because its initial cost is low. The switching device are mechanical and then operating signal are sent to circuit where final control action take place, these are the slow process. Another problem are also associated with mechanical switch that it cannot control frequently[2]. To reduced this problem use in FACTS technology. It is developed in 1990. It can also use series and shunt condition. It is power electronic based and static device such as Thyristors, Gate turn offs(GTO), Insulated gate bipolar transistors(IGBT), Insulated Gate Commutated thyristors (IGCT),they can be controlled very fast as well as different control algorithms adapted to various situations[5]. The FACTS technology is use for controlling the both types of powers and enhancing the USAble capacity of present transmission systems[6]. It has increase line capacity .The ability of FACTS controllers to adjust the power system electrical parameters including series and shunt impedances, current, voltage, phase angle, and the damping oscillations etc. The FACTS devices has various power electronics devices [1]

    Power Flow analysis by Unified Power Flow Controller

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    It is very important to control the power flow along the transmission line. Thus to control and improve the performance of ac power systems, we need the various different types compensators Now-a-days the Flexible AC Transmission Systems (FACTS) is very popular and essential device in power systems. After introducing the FACTS technology, power flow along the transmission lines becomes more flexible and controllable. Several FACTS-devices have been introduced for various applications in power system. Among a variety of FACTS controllers, Unified Power Flow Controller (UPFC) is the most powerful and versatile device

    Eikenella Corrodens and Streptococcus anginosus co-infection causing skull base osteomyelitis and internal carotid artery lesion

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    © 2020 The Author(s) A 35-year-old male presented with headaches and fevers. MRI of his head showed skull-based infection of the clivus extended to the right internal carotid artery. Blood and sinus cultures were positive for Eikenella corrodens and Streptococcus anginosus. He had intravenous antibiotics and sinus washout. The patient had full neurological recovery following this

    Experimental observation of extreme multistability in an electronic system of two coupled R\"{o}ssler oscillators

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    We report the first experimental observation of extreme multistability in a controlled laboratory investigation. Extreme multistability arises when infinitely many attractors coexist for the same set of system parameters. The behavior was predicted earlier on theoretical grounds, supported by numerical studies of models of two coupled identical or nearly identical systems. We construct and couple two analog circuits based on a modified coupled R\"{o}ssler system and demonstrate the occurrence of extreme multistability through a controlled switching to different attractor states purely through a change in initial conditions for a fixed set of system parameters. Numerical studies of the coupled model equations are in agreement with our experimental findings.Comment: to be published in Phys. Rev.

    A duality relation for fluid spacetime

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    We consider the electromagnetic resolution of gravitational field. We show that under the duality transformation, in which active and passive electric parts of the Riemann curvature are interchanged, a fluid spacetime in comoving coordinates remains invariant in its character with density and pressure transforming, while energy flux and anisotropic pressure remaining unaltered. Further if fluid admits a barotropic equation of state, p=(γ1)ρp = (\gamma - 1) \rho where 1γ21 \leq \gamma \leq 2, which will transform to p=(2γ3γ21)ρp = (\frac{2 \gamma}{3 \gamma - 2} - 1) \rho. Clearly the stiff fluid and dust are dual to each-other while ρ+3p=0\rho + 3 p =0, will go to flat spacetime. However the n (ρ3p=0)(\rho - 3 p = 0) and the deSitter (ρ+p=0(\rho + p = 0) universes ar e self-dual.Comment: 5 pages, LaTeX version, Accepted in Classical Quantum Gravity as a Lette

    Dust-forming molecules in VY Canis Majoris (and Betelgeuse)

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    The formation of inorganic dust in circumstellar environments of evolved stars is poorly understood. Spectra of molecules thought to be most important for the nucleation, i.e. AlO, TiO, and TiO2, have been recently detected in the red supergiant VY CMa. These molecules are effectively formed in VY CMa and the observations suggest that non-equilibrium chemistry must be involved in their formation and nucleation into dust. In addition to exploring the recent observations of VY CMa, we briefly discuss the possibility of detecting these molecules in the dust-poor circumstellar environment of Betelgeuse.Comment: contribution to Betelgeuse Workshop 2012: "The physics of Red Supergiants: recent advances and open questions", 26-29 Nov 2012 Paris (France
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