Dynamic Panel Probit Models for Current Account Reversals and their Efficient Estimation

We use panel probit models with unobserved heterogeneity and serially correlated errors in order to analyze the determinants and the dynamics of current-account reversals for a panel of developing and emerging countries. The likelihood evaluation of these models requires high-dimensional integration for which we use a generic procedure known as Efficient Importance Sampling (EIS). Our empirical results suggest that current account balance, terms of trades, foreign reserves and concessional debt are important determinants of the probability of current-account reversal. Furthermore we find under all specifications evidence for serially correlated error components and weak evidence for state dependence. --Panel data,Dynamic discrete choice,Current account reversals,Importance Sampling,Monte Carlo integration,State dependence

Determinants and dynamics of current account reversals: an empirical analysis

We use panel probit models with unobserved heterogeneity, state-dependence and serially correlated errors in order to analyze the determinants and the dynamics of current-account reversals for a panel of developing and emerging countries. The likelihood-based inference of these models requires high-dimensional integration for which we use Efficient Importance Sampling (EIS). Our results suggest that current account balance, terms of trades, foreign reserves and concessional debt are important determinants of current-account reversal. Furthermore, we find strong evidence for serial dependence in the occurrence of reversals. While the likelihood criterion suggest that state-dependence and serially correlated errors are essentially observationally equivalent, measures of predictive performance provide support for the hypothesis that the serial dependence is mainly due to serially correlated country-specific shocks related to local political or macroeconomic events. --Panel data,dynamic discrete choice,importance sampling,Monte Carlo integration,state dependence,spillover effects

U.S. Agriculture, 1960-96 A Multilateral Comparison of Total Factor Productivity

This study provides estimates of the growth and relative levels of agricultural productivity for the 48 contiguous States for the period 1960 to 1996. For the full 1960-96 period, every State exhibits a positive and generally substantial average annual rate of productivity growth. There is considerable variance, however. The wide disparity in growth rates resulted in substantial changes in the ranking order of States by productivity. For each year, we calculate the coefficient of variation of productivity levels. We use these coefficients to show that the range of levels of productivity has narrowed over time, although the pattern of convergence was far from uniform. The fact that in some States, productivity grew faster than others and yet the cross-section dispersion decreased, implies that the States whose productivity grew most rapidly were those with lower initial levels of productivity. This result is consistent with Gerschenkron's notion of the advantage of relative backwardness. The States that were particularly far behind the productivity leaders had the most to gain from the diffusion of technical knowledge and proceeded to grow most rapidly. We also observe a positive relation between capital accumulation and productivity growth, implying embodiment of technology in capital.production accounts, multilateral index numbers, total factor productivity, Productivity Analysis,

Spin observables and spin structure functions: inequalities and dynamics

Model-independent identities and inequalities relating the various spin observables of a reaction are reviewed in a unified formalism, together with their implications for dynamical models, their physical interpretation, and the quantum aspects of the information carried by spins, in particular entanglement. These constraints between observables can be obtained from the explicit expression of the observables in terms of a set of amplitudes, a non-trivial algebraic exercise which can be preceded by numerical simulation with randomly chosen amplitudes, from anticommutation relations, or from the requirement that any polarisation vector is less than unity. The most powerful tool is the positivity of the density matrices describing the reaction or its crossed channels, with a projection to single out correlations between two or three observables. For the exclusive reactions, the cases of the strangeness-exchange proton-antiproton scattering and the photoproduction of pseudoscalar mesons are treated in some detail: all triples of observables are constrained, and new results are presented for the allowed domains. The positivity constraints for total cross-sections and single-particle inclusive reactions are reviewed, with application to spin-dependent structure functions and parton distributions. The corresponding inequalities are shown to be preserved by the evolution equations of QCD.Comment: 135 pages, 37 figures, pdflatex, to appear in Physics Reports, new subsections added, typos corrected, references adde

Efficient likelihood evaluation of state-space representations

We develop a numerical procedure that facilitates efficient likelihood evaluation in applications involving non-linear and non-Gaussian state-space models. The procedure approximates necessary integrals using continuous approximations of target densities. Construction is achieved via efficient importance sampling, and approximating densities are adapted to fully incorporate current information. We illustrate our procedure in applications to dynamic stochastic general equilibrium models. --particle filter,adaption,efficient importance sampling,kernel density approximation,dynamic stochastic general equilibrium model

Cytoskeleton reorganization in influenza hemagglutinin-initiated syncytium formation

AbstractLittle is known about the mechanisms of cell–cell fusion in development and diseases and, especially, about fusion stages downstream of an opening of nascent fusion pore(s). Earlier works on different cell–cell fusion reactions have indicated that cytoskeleton plays important role in syncytium formation. However, due to complexity of these reactions and multifaceted contributions of cytoskeleton in cell physiology, it has remained unclear whether cytoskeleton directly drives fusion pore expansion or affects preceding fusion stages. Here we explore cellular reorganization associated with fusion pore expansion in syncytium formation using relatively simple experimental system. Fusion between murine embryonic fibroblasts NIH3T3-based cells is initiated on demand by well-characterized fusogen influenza virus hemagglutinin. We uncouple early fusion stages dependent on protein fusogens from subsequent fusion pore expansion stage and establish that the transition from local fusion to syncytium requires metabolic activity of living cells. Effective syncytium formation for cells with disorganized actin and microtubule cytoskeleton argues against hypothesis that cytoskeleton drives fusion expansion

Real Capital Input in OECD Agriculture: A Multinational Comparison

This paper provides a farm sector comparison of relative levels of capital input for seventeen OECD countries for the period 1973-2011. The starting point for construction of a measure of capital input is the measurement of capital stock. Estimates of depreciable capital are derived by representing capital stock at each point of time as a weighted sum of past investments. The weights correspond to the relative efficiencies of capital goods of different ages, so that the weighted components of capital stock have the same efficiency. The capital stocks of land are measured as implicit quantities derived from balance sheet data. We convert estimates of capital stock into estimates of capital service flows by means of capital rental prices. Implicit rental prices for each asset are based on the correspondence between the purchase price of the asset and the discounted value of future service flows derived from that asset. Finally, comparisons of levels of capital input among countries require data on relative prices of capital input. We obtain relative price levels for capital input via relative investment goods prices, taking into account the flow of capital input per unit of capital stock in each country

About the stability of the dodecatoplet

A new investigation is done of the possibility of binding the "dodecatoplet", a system of six top quarks and six top antiquarks, using the Yukawa potential mediated by Higgs exchange. A simple variational method gives a upper bound close to that recently estimated in a mean-field calculation. It is supplemented by a lower bound provided by identities among the Hamiltonians describing the system and its subsystems.Comment: 5 pages, two figures merged, refs. added, typos correcte

Demonstrating the decoupling regime of the electron-phonon interaction in a quantum dot using chirped optical excitation

Excitation of a semiconductor quantum dot with a chirped laser pulse allows excitons to be created by rapid adiabatic passage. In quantum dots this process can be greatly hindered by the coupling to phonons. Here we add a high chirp rate to ultra-short laser pulses and use these pulses to excite a single quantum dot. We demonstrate that we enter a regime where the exciton-phonon coupling is effective for small pulse areas, while for higher pulse areas a decoupling of the exciton from the phonons occurs. We thus discover a reappearance of rapid adiabatic passage, in analogy to the predicted reappearance of Rabi rotations at high pulse areas. The measured results are in good agreement with theoretical calculations.Comment: Main manuscript 5 pages and 4 figures, Supplementary Information 5 pages and 3 figures, submitted to PR

Resonant driving of a single photon emitter embedded in a mechanical oscillator

Coupling a microscopic mechanical resonator to a nanoscale quantum system enables control of the mechanical resonator via the quantum system and vice-versa. The coupling is usually achieved through functionalization of the mechanical resonator, but this results in additional mass and dissipation channels. An alternative is an intrinsic coupling based on strain. Here we employ a monolithic semiconductor system: the nanoscale quantum system is a semiconductor quantum dot (QD) located inside a nanowire. We demonstrate the resonant optical driving of the QD transition in such a structure. The noise spectrum of the resonance fluorescence signal, recorded in the single-photon counting regime, reveals a coupling to mechanical modes of different types. We measure a sensitivity to displacement of 65 fm/root Hz limited by charge noise in the device. Finally, we use thermal excitation of the different modes to determine the location of the QD within the trumpet, and calculate the contribution of the Brownian motion to the dephasing of the emitter