3,232 research outputs found

    Non-Market Valuation of Open Space and Other Amenities Associated with Retention of Lands in Agricultural Use

    Get PDF
    The most productive farmland in southcentral Alaska is currently under intense development pressure due to rapid population increases and consequential increases in demand for suburban housing. This study utilizes a contingent valuation iterative bidding game to estimate the willingness of Matanuska-Susitna Borough residents to pay to preserve open space and other historical/environmental amenities associated with farming activities. Determinants of consumer behavior are addressed as well as total benefits and costs of various posited development scenarios. This information may be useful to policymakers assessing actions designed to purchase development rights from Matanuska-Susitna farmers

    Preparation and properties of amorphous MgB2_2/MgO superstructures: A new model disordered superconductor

    Get PDF
    In this paper we introduce a novel method for fabricating MgB2_2/MgO multilayers and demonstrate the potential for using them as a new model for disordered superconductors. In this approach we control the annealing of the MgB2_2 to yield an interesting new class of disordered (amorphous) superconductors with relatively high transition temperatures. The multilayers appear to exhibit quasi-two-dimensional superconductivity with controlled anisotropy. We discuss the properties of the multilayers as the thickness of the components of the bilayers vary.Comment: 7 pages, 8 figure

    Dual giant gravitons in AdSm_m ×\times Yn^n (Sasaki-Einstein)

    Full text link
    We consider BPS motion of dual giant gravitons on AdS5×Y5S_5\times Y^5 where Y5Y^5 represents a five-dimensional Sasaki-Einstein manifold. We find that the phase space for the BPS dual giant gravitons is symplectically isomorphic to the Calabi-Yau cone over Y5Y^5, with the K\"{a}hler form identified with the symplectic form. The quantization of the dual giants therefore coincides with the K\"{a}hler quantization of the cone which leads to an explicit correspondence between holomorphic wavefunctions of dual giants and gauge-invariant operators of the boundary theory. We extend the discussion to dual giants in AdS4×Y7AdS_4 \times Y^7 where Y7Y^7 is a seven-dimensional Sasaki-Einstein manifold; for special motions the phase space of the dual giants is symplectically isomorphic to the eight-dimensional Calabi-Yau cone.Comment: 14 pages. (v2) typo's corrected; factors of AdS radius reinstated for clarity; remarks about dual giant wavefunctions in T^{1,1} expanded and put in a new subsectio

    Measurement of the Parallax of PSR B0950+08 Using the VLBA

    Full text link
    A new technique has been developed to remove the ionosphere's distorting effects from low frequency VLBI data. By fitting dispersive and non-dispersive components to the phases of multi-frequency data, the ionosphere can be effectively removed from the data without the use of {\em a priori} calibration information. This technique, along with the new gating capability of the VLBA correlator, was used to perform accurate astrometry on pulsar B0950+08, resulting in a much improved measurement of this pulsar's proper motion (μα=1.6±0.4\mu_{\alpha} = -1.6 \pm 0.4 mas/yr, μδ=29.5±0.5\mu_{\delta} = 29.5 \pm 0.5 mas/yr) and parallax (π=3.6±0.3\pi = 3.6 \pm 0.3 mas). This puts the pulsar at a distance of 280±25280 \pm 25 parsecs, about twice as far as previous estimates, but in good agreement with models of the electron density in the local bubble.Comment: 5 pages, Latex with AASTEX. Accepted for publication in Ap

    The two-echelon capacitated vehicle routing problem: models and math-based heuristics

    Get PDF
    Multiechelon distribution systems are quite common in supply-chain and logistics. They are used by public administrations in their transportation and traffic planning strategies, as well as by companies, to model own distribution systems. In the literature, most of the studies address issues relating to the movement of flows throughout the system from their origins to their final destinations. Another recent trend is to focus on the management of the vehicle fleets required to provide transportation among different echelons. The aim of this paper is twofold. First, it introduces the family of two-echelon vehicle routing problems (VRPs), a term that broadly covers such settings, where the delivery from one or more depots to customers is managed by routing and consolidating freight through intermediate depots. Second, it considers in detail the basic version of two-echelon VRPs, the two-echelon capacitated VRP, which is an extension of the classical VRP in which the delivery is compulsorily delivered through intermediate depots, named satellites. A mathematical model for two-echelon capacitated VRP, some valid inequalities, and two math-heuristics based on the model are presented. Computational results of up to 50 customers and four satellites show the effectiveness of the methods developed

    Embedding Fractional Quantum Hall Solitons in M-theory Compactifications

    Full text link
    We engineer U(1)^n Chern-Simons type theories describing fractional quantum Hall solitons (QHS) in 1+2 dimensions from M-theory compactified on eight dimensional hyper-K\"{a}hler manifolds as target space of N=4 sigma model. Based on M-theory/Type IIA duality, the systems can be modeled by considering D6-branes wrapping intersecting Hirzebruch surfaces F_0's arranged as ADE Dynkin Diagrams and interacting with higher dimensional R-R gauge fields. In the case of finite Dynkin quivers, we recover well known values of the filling factor observed experimentally including Laughlin, Haldane and Jain series.Comment: Latex, 14 pages. Modified version, to appear in IJGMM

    Radio Emission from the Exoplanetary System ε Eridani

    Get PDF
    As part of a wider search for radio emission from nearby systems known or suspected to contain extrasolar planets, ε Eridani was observed by the Jansky Very Large Array (VLA) in the 2–4 GHz and 4–8 GHz frequency bands. In addition, as part of a separate survey of thermal emission from solar-like stars, ε Eri was observed in the 8–12 GHz and the 12–18 GHz bands of the VLA. Quasi-steady continuum radio emission from ε Eri was detected in the three high-frequency bands at levels ranging from 67 to 83 μJy. No significant variability is seen in the quasi-steady emission. The emission in the 2–4 GHz emission, however, is shown to be the result of a circularly polarized (up to 50%) radio pulse or flare of a few minutes in duration that occurred at the beginning of the observation. We consider the astrometric position of the radio source in each frequency band relative to the expected position of the K2V star and the purported planet. The quasi-steady radio emission at frequencies ≥8 GHz is consistent with a stellar origin. The quality of the 4–8 GHz astrometry provides no meaningful constraint on the origin of the emission. The location of the 2–4 GHz radio pulse is >2.5σ from the star; however, based on the ephemeris of Benedict et al., it is not consistent with the expected location of the planet either. If the radio pulse has a planetary origin, then either the planetary ephemeris is incorrect or the emission originates from another planet

    Electronic properties of buried hetero-interfaces of LaAlO3 on SrTiO3

    Get PDF
    We have made very thin films of LaAlO3 on TiO2 terminated SrTiO3 and have measured the properties of the resulting interface in various ways. Transport measurements show a maximum sheet carrier density of 1016 cm-2 and a mobility around 104 cm2 V-1 s-1. In situ ultraviolet photoelectron spectroscopy (UPS) indicates that for these samples a finite density of states exists at the Fermi level. From the oxygen pressure dependence measured in both transport as well as the UPS, we detail, as reported previously by us, that oxygen vacancies play an important role in the creation of the charge carriers and that these vacancies are introduced by the pulsed laser deposition process used to make the heterointerfaces. Under the conditions studied the effect of LaAlO3 on the carrier density is found to be minimal.Comment: 19 pages, 6 figure
    corecore