Exports and international logistics

Do better international logistics reduce trade costs, raising a developing country's exports? Yes, but the magnitude of the effect depends on the country's size. The authors apply a gravity model that accounts for firm heterogeneity and multilateral resistance to a comprehensive new international logistics index. A one-standard deviation improvement in logistics is equivalent to a 14 percent reduction in distance. An average-sized developing country would raise exports by about 36 percent. Most countries are much smaller than average however, so the typical effect is 8 percent. This difference is chiefly due to multilateral resistance: it is bilateral trade costs relative to multilateral trade costs that matter for bilateral exports, and multilateral resistance is more important for small countries.Economic Theory&Research,Free Trade,Trade Policy,Common Carriers Industry,Trade Law

Terahertz generation by beamlet superposition

We analytically show how a superposition of beamlets produces terahertz radiation with greater spatial homogeneity and efficiency compared to tilted-pulse-fronts generated by diffraction gratings. The advantages are particularly notable for large pump bandwiths and beam sizes, alluding to better performance in the presence of cascading effects and higher energy pumping. A theory of terahertz generation using a superposition of beamlets is developed. It is shown how such an arrangement produces a distortion free tilted-pulse-front. Closed form expressions for terahertz spectra and transients in three spatial dimensions are derived. Conditions for obtaining performance parity and bounds for optimal parameters are furnished

THz generation using a reflective stair-step echelon

We present a novel method for THz generation in lithium niobate using a reflective stair-step echelon structure. The echelon produces a discretely tilted pulse front with less angular dispersion compared to a high groove-density grating. The THz output was characterized using both a 1-lens and 3-lens imaging system to set the tilt angle at room and cryogenic temperatures. Using broadband 800 nm pulses with a pulse energy of 0.95 mJ and a pulse duration of 70 fs (24 nm FWHM bandwidth, 39 fs transform limited width), we produced THz pulses with field strengths as high as 500 kV/cm and pulse energies as high as 3.1 $\mu$J. The highest conversion efficiency we obtained was 0.33%. In addition, we find that the echelon is easily implemented into an experimental setup for quick alignment and optimization.Comment: 19 pages, 4 figure

Las Mujeres De Oro

De un plato simple de bellotas durante una cena con algunos cabreros, el protagonista don Quijote se hace sentimental y filosfico y, a causa de esto, empieza a alabar poeticamente la Edad de Oro. Durante su discurso, este caballero pinta con sus palabras una utopia en que la humanidad vivia en armonia perfecta con la naturaleza fertil. Continuando con su descripci6n, comenta tambien sobre la relaci6n entre los hombres y las mujeres

Opaque assets and rollover risk

We model the asset-opacity choice of an intermediary subject to rollover risk in wholesale funding markets. Greater opacity means investors form more dispersed beliefs about an intermediary's profitability. The endogenous benefit of opacity is lower fragility when profitability is expected to be high. However, the endogenous cost of opacity is a "partial run," whereby some investors receive bad private signals about profitability and run, even though the intermediary is solvent. We find that intermediaries choose to be transparent (opaque) when expected profitability is low (high). Intermediaries with lessvolatile profitability are also more likely to choose to be opaque

Decoherence of one-dimensional flying qubits due to their cross-talk and imperfections

We study decoherence of propagating spin-1/2 excitations in generic (non-integrable and/or disordered) spin chains. We find the relevant decoherence times to be shorter in both the near-critical and diffusive regimes (if any), which fact might have important implications for the recently proposed spin chain-based implementations of quantum information processing.Comment: Latex, 5 pages, no figure

Systematic Mischaracterization of Exoplanetary System Dynamical Histories from a Model Degeneracy near Mean-motion Resonance

There is a degeneracy in the radial velocity exoplanet signal between a single planet on an eccentric orbit and a two-planet system with a period ratio of 2:1. This degeneracy could lead to misunderstandings of the dynamical histories of planetary systems as well as measurements of planetary abundances if the correct architecture is not established. We constrain the rate of mischaracterization by analysing a sample of 60 non-transiting, radial velocity systems orbiting main-sequence stars from the NASA Exoplanet Archive (NASA Archive) using a new Bayesian model comparison pipeline. We find that 15 systems (25 per cent of our sample) show compelling evidence for the two-planet case with a confidence level of 95 per cent