On the Identification of Agents in the Design of Production Control Systems

This paper describes a methodology that is being developed for designing and building agent-based systems for the domain of production control. In particular, this paper deals with the steps that are involved in identifying the agents and in specifying their responsibilities. The methodology aims to be usable by engineers who have a background in production control but who have no prior experience in agent technology. For this reason, the methodology needs to be very prescriptive with respect to the agent-related aspects of design

Oxygen-isotope effect on the superconducting gap in the cuprate superconductor Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta}

The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the zero-temperature superconducting energy gap \Delta_0 was studied for a series of Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta} samples (0.0\leq x\leq0.45). The OIE on \Delta_0 was found to scale with the one on the superconducting transition temperature. These experimental results are in quantitative agreement with predictions from a polaronic model for cuprate high-temperature superconductors and rule out approaches based on purely electronic mechanisms.Comment: 5 pages, 3 figure

A Detailed Gravitational Lens Model Based on Submillimeter Array and Keck Adaptive Optics Imaging of a Herschel-ATLAS Submillimeter Galaxy at z = 4.243

We present high-spatial resolution imaging obtained with the Submillimeter Array (SMA) at 880 μm and the Keck adaptive optics (AO) system at the KS-band of a gravitationally lensed submillimeter galaxy (SMG) at z = 4.243 discovered in the Herschel Astrophysical Terahertz Large Area Survey. The SMA data (angular resolution ≈0". 6) resolve the dust emission into multiple lensed images, while the Keck AO K_S-band data (angular resolution ≈0". 1) resolve the lens into a pair of galaxies separated by 0". 3. We present an optical spectrum of the foreground lens obtained with the Gemini-South telescope that provides a lens redshift of z_(lens) = 0.595 ± 0.005. We develop and apply a new lens modeling technique in the visibility plane that shows that the SMG is magnified by a factor of μ = 4.1 ± 0.2 and has an intrinsic infrared (IR) luminosity of L_(IR) = (2.1 ± 0.2) × 10_(13) L_☉. We measure a half-light radius of the background source of r_s = 4.4 ± 0.5 kpc which implies an IR luminosity surface density of Σ_(IR) = (3.4 ± 0.9) × 10^(11) L_☉ kpc^(−2), a value that is typical of z > 2 SMGs but significantly lower than IR luminous galaxies at z ∼ 0. The two lens galaxies are compact (r_(lens) ≈ 0.9 kpc) early-types with Einstein radii of θ_(E1) = 0.57 ± 0.01 and θ_(E2) = 0.40 ± 0.01 that imply masses of M_(lens1) = (7.4 ± 0.5) × 10^(10)M_☉ and M_(lens2) = (3.7 ± 0.3) × 10^(10) M_☉. The two lensing galaxies are likely about to undergo a dissipationless merger, and the mass and size of the resultant system should be similar to other early-type galaxies at z ∼ 0.6. This work highlights the importance of high spatial resolution imaging in developing models of strongly lensed galaxies discovered by Herschel

On the Superconductivity in the Induced Pairing Model

The two component model of coexisting local electron pairs and itinerant fermions coupled via charge exchange mechanism, which mutually induces superconductivity in both subsystems, is discussed. The cases of isotropic s-wave and anisotropic pairing of extended s and d_{x^2-y^2} -wave symmetries are analyzed for a 2D square lattice within the BCS-mean field approximation and the Kosterlitz-Thouless theory. We determined the phase diagrams and superconducting characteristics as a function of the position of the local pair (LP) level and the total electron concentration. The model exhibits several types of interesting crossovers from BCS like behavior to that of LP's. Some of our results are discussed in connection with a two-component scenario of preformed pairs and unpaired electrons for exotic superconductors.Comment: Proceedings of the 3rd Polish-US Workshop on Magnetism and Superconductivity of Advanced Materials, July 14-19, 2002, Ladek Zdroj (Poland) to appear in Physica

Hybrid paramagnon phonon modes at elevated temperatures in EuTiO3

EuTiO3 (ETO) has recently experienced an enormous revival of interest because of its possible multiferroic properties which are currently in the focus of research. Unfortunately ETO is an unlikely candidate for enlarged multifunctionality since the mode softening - typical for ferroelectrics - remains incomplete, and the antiferromagnetic properties appear at 5.5K only. However, a strong coupling between lattice and Eu spins exists and leads to the appearance of a magnon-phonon-hybrid mode at elevated temperatures as evidenced by electron paramagnetic resonance (EPR), muon spin rotation ({\mu}SR) experiments and model predictions based on a coupled spin-polarizability Hamiltonian. This novel finding supports the notion of strong magneto-dielectric (MD) effects being realized in ETO and opens new strategies in material design and technological applications.Comment: 9 pages, 4 figure

Theory of Dynamic Stripe Induced Superconductivity

Since the recently reported giant isotope effect on T* [1] could be consistently explained within an anharmonic spin-charge-phonon interaction model, we consider here the role played by stripe formation on the superconducting properties within the same model. This is a two-component scenario and we recast its basic elements into a BCS effective Hamiltonian. We find that the stripe formation is vital to high-Tc superconductivity since it provides the glue between the two components to enhance Tc to the unexpectedly large values observed experimentally.Comment: 7 pages, 2 figure

Field Dependent Superfluid Density in the Optimally Doped SmFeAsO_(1-x)F_y Superconductor

The magnetic field dependence of the in-plane magnetic penetration depth for optimally doped SmFeAsO_(1-x)F_y was investigated by combining torque magnetometry, SQUID magnetometry, and muon-spin rotation. The results obtained from these techniques show all a pronounced decrease of the superfluid density as the field is increased up to 1.4 T. This behavior is analysed within a two-band model with self-consistently derived coupled gaps, where the superfluid density related to the larger gap is field independent and the superfluid density related to the smaller gap is strongly suppressed with increasing field.Comment: 7 pages, 5 figure

The Spectral Energy Distributions and Infrared Luminosities of z \approx 2 Dust Obscured Galaxies from Herschel and Spitzer

Dust-obscured galaxies (DOGs) are a subset of high-redshift (z \approx 2) optically-faint ultra-luminous infrared galaxies (ULIRGs, e.g. L_{IR} > 10^{12} Lsun). We present new far-infrared photometry, at 250, 350, and 500 um (observed-frame), from the Herschel Space Telescope for a large sample of 113 DOGs with spectroscopically measured redshifts. Approximately 60% of the sample are detected in the far-IR, confirming their high IR luminosities, which range from 10^{11.6} Lsun < L_{IR} (8-1000 um) <10^{13.6} Lsun. 90% of the Herschel detected DOGs in this sample are ULIRGs and 30% have L_{IR} > 10^{13} Lsun. The rest-frame near-IR (1 - 3 um) SEDs of the Herschel detected DOGs are predictors of their SEDs at longer wavelengths. DOGs with "power-law" SEDs in the rest-frame near-IR show observed-frame 250/24 um flux density ratios similar to the QSO-like local ULIRG, Mrk 231. DOGs with a stellar "bump" in their rest-frame near-IR show observed-frame 250/24 um flux density ratios similar to local star-bursting ULIRGs like NGC 6240. For the Herschel detected DOGs, accurate estimates (within \approx 25%) of total IR luminosity can be predicted from their rest-frame mid-IR data alone (e.g. from Spitzer observed-frame 24 um luminosities). Herschel detected DOGs tend to have a high ratio of infrared luminosity to rest-frame 8 um luminosity (the IR8= L_{IR}(8-1000 um)/v L_{v}(8 um) parameter of Elbaz et al. 2011). Instead of lying on the z=1-2 "infrared main-sequence" of star forming galaxies (like typical LIRGs and ULIRGs at those epochs) the DOGs, especially large fractions of the bump sources, tend to lie in the starburst sequence. While, Herschel detected DOGs are similar to scaled up versions of local ULIRGs in terms of 250/24 um flux density ratio, and IR8, they tend to have cooler far-IR dust temperatures (20-40 K for DOGs vs. 40-50 K for local ULIRGs). Abridged.Comment: 24 pages, 14 figures, 3 tables, accepted for publication in the Astronomical Journa

Gravitational Lens Models Based on Submillimeter Array Imaging of Herschel-selected Strongly Lensed Sub-millimeter Galaxies at z > 1.5

Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S_(500) > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r_(half)) and far-infrared luminosities (L_(FIR)) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z_(lens) > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 μm flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L_(FIR) (median L_(FIR) = 7.9 × 10^(12) L_☉) and two decades in FIR luminosity surface density (median Σ_(FIR) = 6.0 × 10^(11) L_☉ kpc^(–2)). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift