11,968 research outputs found

    Star Formation Rate from Dust Infrared Emission

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    We examine what types of galaxies the conversion formula from dust infrared (IR) luminosity into the star formation rate (SFR) derived by Kennicutt (1998) is applicable to. The ratio of the observed IR luminosity, LIRL_{\rm IR}, to the intrinsic bolometric luminosity of the newly (\la 10 Myr) formed stars, LSFL_{\rm SF}, of a galaxy can be determined by a mean dust opacity in the interstellar medium and the activity of the current star formation. We find that these parameters area being 0.5LIR/LSF2.00.5 \le L_{\rm IR}/L_{\rm SF} \le 2.0 is very large, and many nearby normal and active star-forming galaxies really fall in this area. It results from offsetting two effects of a small dust opacity and a large cirrus contribution of normal galaxies relative to starburst galaxies on the conversion of the stellar emission into the dust IR emission. In conclusion, the SFR determined from the IR luminosity under the assumption of LIR=LSFL_{\rm IR}=L_{\rm SF} like Kennicutt (1998) is reliable within a factor of 2 for all galaxies except for dust rich but quiescent galaxies and extremely dust poor galaxies.Comment: Accepted by ApJL: 6 pages (emulateapj5), 2 figures (one is an extra figure not appeared in ApJL

    Perturbation theory for localized solutions of sine-Gordon equation: decay of a breather and pinning by microresistor

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    We develop a perturbation theory that describes bound states of solitons localized in a confined area. External forces and influence of inhomogeneities are taken into account as perturbations to exact solutions of the sine-Gordon equation. We have investigated two special cases of fluxon trapped by a microresistor and decay of a breather under dissipation. Also, we have carried out numerical simulations with dissipative sine-Gordon equation and made comparison with the McLaughlin-Scott theory. Significant distinction between the McLaughlin-Scott calculation for a breather decay and our numerical result indicates that the history dependence of the breather evolution can not be neglected even for small damping parameter

    Magnetic moments of S-shell pentaquarks in the constituent quark model

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    We discuss the magnetic moments of the recently discovered exotic baryons Theta(+) and Xi(--) and their multiplet partners in the framework of a naive additive quark model. These baryons are set up as pentaquark states where four quarks and a single antiquark are located in their ground state orbit. The pentaquark states are classified as members of the flavor SU(3) octet and antidecuplet with spin-parity J^P = (1/2)^- and (3/2)^-, where we determine the magnetic moments of these pentaquark states.Comment: 13 pages, 2 figures, elsart; publication version, 8 pages, 1 figure, ptptex; upload miss correcte

    Constraints to achieving the MDGs through domestic resource mobilization

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    The present paper focuses on the role of domestic resource mobilization for financing poverty reduction strategies. Policy makers should be aware of important macroeconomic trade-offs associated with MDG strategies financed from tax increases or domestic borrowing. The trade-offs are largely intertemporal: can poor and middle-income countries absorb the initial financing costs in order to achieve expected gains in productivity and human development over time? This calls for a dynamic economy-wide framework to identify the importance of such trade-offs. The paper presents such a framework and illustrates its usefulness in applications for Costa Rica and Ecuador.computable general equilibrium models; distribution; welfare and poverty; foreign aid; macroeconomic analyses of economic development.

    One-way electromagnetic Tamm states in magnetophotonic structures

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    We study surface Tamm states in magnetophotonic structures magnetized in the Cotton–Mouton (Voigt) geometry. We demonstrate that the periodicity violation due to the structure truncation together with the violation of the time reversal symmetry due to the presence of magneto-optical materials gives rise to nonreciprocality of the surface modes. Dispersion of forward and backward modes splits and becomes magnetization dependent. This results in the magnetization-induced transitions between bulk and surface modes and unidirectional propagation of surface waves.We thank the Australian Research Council for a financial support and S. Fan for useful discussions. This work was supported in part by the Super Optical Information Memory Project from the Ministry of Education, Culture, Sports, Science and Technology of Japan MEXT, and Grant-in-Aid for Scientific Research S Grant No. 17106004 from Japan Society for the Promotion of Science JSPS

    Non-equilibrium spin accumulation in ferromagnetic single-electron transistors

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    We study transport in ferromagnetic single-electron transistors. The non- equilibrium spin accumulation on the island caused by a finite current through the system is described by a generalized theory of the Coulomb blockade. It enhances the tunnel magnetoresistance and has a drastic effect on the time- dependent transport properties. A transient decay of the spin accumulation may reverse the electric current on time scales of the order of the spin-flip relaxation time. This can be used as an experimental signature of the non- equilibrium spin accumulation.Comment: 9 postscript figures, to appear in The European Physical Journal

    Comparison of theory with experiment for positron production from high-energy electrons moving along crystal axes

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    Various positron distributions are obtained using an approach developed earlier for the description of electron-photon showers in axially aligned single crystals. Based on these distributions, characteristics of the positron yield measured in recent experiments are calculated. Theoretical estimations display a rather good agreement with experimental results obtained using 3 to 10 GeV electrons aligned to the - axis of the tungsten crystals.Comment: 10 pages, 6 Postscript figure
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