9,339 research outputs found

    A critique of monetary protectionism

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    An argument against attempts to achieve current-account objectives through monetary manipulation of nominal exchange rates, with an explanation of why such tampering--which for various reasons might appear politically attractive--ultimately harms economic welfare.Foreign exchange - Law and legislation ; Monetary policy

    Regional Integration in Asia and Its Effects on the EU and North America

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    Consequences of free trade agreements (FTAs) among the ASEAN+3 countries and ASEAN+6 countries are explored using a dynamic computable general equilibrium (CGE) model. Quantitative assessments of intra and extra-regional effects on welfare, trade and output are offered. When both trade facilitation and endogenously determined productivity are included in the FTA scenarios, Singapore, other ASEAN countries and China would be able to realize relatively large welfare gains, while the welfare effects on the EU and North America are negligible. The trade and output effects on the latter two regions are also relatively small, with the notable exception of crops, other than rice, in North America.Regional integration, FTA, East Asia, welfare effects, CGE model

    Observations on the Physical Properties of Sea-Ice at Hopedale, Labrador

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    Preliminary results are reported of field studies 1955-56 by the U.S. Air Force Cambridge Research Center, the Hydrographic Office and SIPRE on the general physical properties of sea ice; methods of measurement are described. Characteristics of sea water during the freezing period are outlined: formation, structure, and salinity of the initial ice cover, formation and characteristics of infiltrated snow-ice, growth of the ice and influencing factors, density of the ice at various periods, and crack formation are discussed. Data on the salinity of sea ice formed during during wave action and that of sheet-ice, hourly averages of air and ice temperatures at various levels, snow and slush density and thickness, observed slush levels and theoretical water levels are shown. Salinity of ice before and after the slush layer froze, and that of deteriorating ice , salinity of ice vs. ice thickness, thickness of ice versus degree-days, the density of the ice, and measured ice densities vs. theoretical density of air-free sea ice at -15 C are figured and discussed. The orientation of sea ice c-axes and of infiltrated snow-ice c-axes are diagrammed.--From SIPRE

    Gravitational Radiation Instability in Hot Young Neutron Stars

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    We show that gravitational radiation drives an instability in hot young rapidly rotating neutron stars. This instability occurs primarily in the l=2 r-mode and will carry away most of the angular momentum of a rapidly rotating star by gravitational radiation. On the timescale needed to cool a young neutron star to about T=10^9 K (about one year) this instability can reduce the rotation rate of a rapidly rotating star to about 0.076\Omega_K, where \Omega_K is the Keplerian angular velocity where mass shedding occurs. In older colder neutron stars this instability is suppressed by viscous effects, allowing older stars to be spun up by accretion to larger angular velocities.Comment: 4 Pages, 2 Figure

    Second-order rotational effects on the r-modes of neutron stars

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    Techniques are developed here for evaluating the r-modes of rotating neutron stars through second order in the angular velocity of the star. Second-order corrections to the frequencies and eigenfunctions for these modes are evaluated for neutron star models. The second-order eigenfunctions for these modes are determined here by solving an unusual inhomogeneous hyperbolic boundary-value problem. The numerical techniques developed to solve this unusual problem are somewhat non-standard and may well be of interest beyond the particular application here. The bulk-viscosity coupling to the r-modes, which appears first at second order, is evaluated. The bulk-viscosity timescales are found here to be longer than previous estimates for normal neutron stars, but shorter than previous estimates for strange stars. These new timescales do not substantially affect the current picture of the gravitational radiation driven instability of the r-modes either for neutron stars or for strange stars.Comment: 13 pages, 5 figures, revte

    Historical (1850-2000) gridded anthropogenic and biomass burning emissions of reactive gases and aerosols: Methodology and application

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    We present and discuss a new dataset of gridded emissions covering the historical period (1850-2000) in decadal increments at a horizontal resolution of 0.5 degrees in latitude and longitude. The primary purpose of this inventory is to provide consistent gridded emissions of reactive gases and aerosols for use in chemistry model simulations needed by climate models for the Climate Model Intercomparison Program #5 (CMIP5) in support of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5). Our best estimate for the year 2000 inventory represents a combination of existing regional and global inventories to capture the best information available at this point; 40 regions and 12 sectors are used to combine the various sources. The historical reconstruction of each emitted compound, for each region and sector, is then forced to agree with our 2000 estimate, ensuring continuity between past and 2000 emissions. Simulations from two chemistry-climate models is used to test the ability of the emission dataset described here to capture long-term changes in atmospheric ozone, carbon monoxide and aerosol distributions. The simulated long-term change in the Northern mid-latitudes surface and mid-troposphere ozone is not quite as rapid as observed. However, stations outside this latitude band show much better agreement in both present-day and long-term trend. The model simulations indicate that the concentration of carbon monoxide is underestimated at the Mace Head station; however, the long-term trend over the limited observational period seems to be reasonably well captured. The simulated sulfate and black carbon deposition over Greenland is in very good agreement with the ice-core observations spanning the simulation period. Finally, aerosol optical depth and additional aerosol diagnostics are shown to be in good agreement with previously published estimates and observations

    Stability of the r-modes in white dwarf stars

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    Stability of the r-modes in rapidly rotating white dwarf stars is investigated. Improved estimates of the growth times of the gravitational-radiation driven instability in the r-modes of the observed DQ Her objects are found to be longer (probably considerably longer) than 6x10^9y. This rules out the possibility that the r-modes in these objects are emitting gravitational radiation at levels that could be detectable by LISA. More generally it is shown that the r-mode instability can only be excited in a very small subset of very hot (T>10^6K), rather massive (M>0.9M_sun) and very rapidly rotating (P_min<P<1.2P_min) white dwarf stars. Further, the growth times of this instability are so long that these conditions must persist for a very long time (t>10^9y) to allow the amplitude to grow to a dynamically significant level. This makes it extremely unlikely that the r-mode instability plays a significant role in any real white dwarf stars.Comment: 5 Pages, 5 Figures, revte

    R-Modes in Superfluid Neutron Stars

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    The analogs of r-modes in superfluid neutron stars are studied here. These modes, which are governed primarily by the Coriolis force, are identical to their ordinary-fluid counterparts at the lowest order in the small angular-velocity expansion used here. The equations that determine the next order terms are derived and solved numerically for fairly realistic superfluid neutron-star models. The damping of these modes by superfluid ``mutual friction'' (which vanishes at the lowest order in this expansion) is found to have a characteristic time-scale of about 10^4 s for the m=2 r-mode in a ``typical'' superfluid neutron-star model. This time-scale is far too long to allow mutual friction to suppress the recently discovered gravitational radiation driven instability in the r-modes. However, the strength of the mutual friction damping depends very sensitively on the details of the neutron-star core superfluid. A small fraction of the presently acceptable range of superfluid models have characteristic mutual friction damping times that are short enough (i.e. shorter than about 5 s) to suppress the gravitational radiation driven instability completely.Comment: 15 pages, 8 figure

    Quantum random walks with history dependence

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    We introduce a multi-coin discrete quantum random walk where the amplitude for a coin flip depends upon previous tosses. Although the corresponding classical random walk is unbiased, a bias can be introduced into the quantum walk by varying the history dependence. By mixing the biased random walk with an unbiased one, the direction of the bias can be reversed leading to a new quantum version of Parrondo's paradox.Comment: 8 pages, 6 figures, RevTe
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