What determines bilateral trade flows?

This paper undertakes an exhaustive search for robust determinants of international trade, where "robustness" is tested using three popular empirical methods. The paper is frankly atheoretical: our goal is solely to establish statistically robust relationships. Along the way, however, we relate our results to the empirical results obtained by prior researchers and to the received theory of international trade. We find that robust variables include a measure of the scale of factor endowments; fixed exchange rates; the level of development; and current account restrictions. Variables that are robust under certain methods and sample periods include exchange rate volatility, an index of sectoral similarity, and currency union. However, the estimated coefficient on currency union is much smaller than estimates obtained by prior researchers.Business cycles ; Trade

Determinants of business cycle comovement: a robust analysis

This paper investigates the determinants of business cycle comovement between countries. Our dataset includes over 100 countries, both developed and developing. We search for variables that are “robust” in explaining comovement, using the approach of Leamer (1983). Variables considered are (i) bilateral trade between countries; (ii) total trade in each country; (iii) sectoral structure; (iv) similarity in export and import baskets; (v) factor endowments; and (vi) gravity variables. We find that bilateral trade is robust. However, two variables that the literature has argued are important for business cycles - industrial structure and currency unions - are found not to be robust.Business cycles ; Trade

Trade structure, industrial structure, and international business cycles

This paper examines the extent to which the composition of a country's production and trade differs among its trade partners. For example, does the US export the same bundle of goods to the UK as it does to Japan? If we find high dispersion in a country's export and import bundles with its various trading partners, can this be linked to identifiable country characteristics? These findings are important for two reasons. First, they enrich our empirical understanding of the nature of trade. Second, they will stand as a guide for further development of economic theories of the international transmission of business cycles.Trade ; Industrial organization (Economic theory) ; Business cycles

Determinants of Business Cycle Comovement: A Robust Analysis

This paper investigates the determinants of business cycle comovement between countries. Our dataset includes over 100 countries, both developed and developing. We search for variables that are robust' in explaining comovement, using the approach of Leamer (1983). Variables considered are (i) bilateral trade between countries; (ii) total trade in each country; (iii) sectoral structure; (iv) similarity in export and import baskets; (v) factor endowments; and (vi) gravity variables. We find that bilateral trade is robust. However, two variables that the literature has argued are important for business cycles industrial structure and currency unions are found not to be robust.

Time-resolved protein dynamics using x-ray crystallography and optical spectroscopy

Reversibly switchable fluorescent proteins (RSFPs) switch between a highly and weakly fluorescent state upon photoexcitation. This switching is known to be driven by reversible photoisomerisation and a change in protonation state of the chromophore. However, the exact sequence of events after optical excitation is unclear. In this thesis, time-resolved crystallography and vibrational spectroscopy are used to study the ultrafast dynamics of a new RSFP.  Time-resolved serial femtosecond crystallography (TR-SFX) is used to probe the trans/cis reaction and reveals ultrafast sub-Angstrom motions of the chromophore and surrounding hydrogen bonding network. The addition of a stokes pulse (shown to dump the excited state population) increases these displacements and allows assignment of the light-induced signals to a vibrationally excited electronic ground state structure instead of an excited state structure. Temperature analysis of the steady-state switching rates resolves an intermediate ground-state structure using conventional crystallography which supports the TR-SFX assignments. Ultrafast pump-probe vibrational spectroscopy confirms that excited state photoisomerisation occurs (~70 ps), proceeded by rearrangement of a nearby arginine residue (~7 ps) with deprotonation (trans-neutral/cis-anion) occurring between 2 ns - 1 ms. An additional dump pulse is then shown to repress product formation and reforms the ground state, further supporting the structural observations of the pump-dump-probe crystallography measurements. These results improve our understanding of photoswitching in RSFPs and have important implications for structural assignments in future TR-SFX experiments. Time-resolved serial synchrotron crystallography (TR-SSX) is an accessible and emerging technique for studying protein dynamics on millisecond timescales. Here, the trans/cis isomerisation of an RSFP is probed at 10 ms with a range of pump intensities to demonstrate precise control of the cis-state formation yields. The population transfer is resolved crystallographically using quantitative analysis of the occupancy, showing excellent agreement with optical flash-photolysis measurements. The issue of X-ray induced heating, which leads to partial thermal recovery, is also addressed. A temperature increase of 82-112 K is extracted for the fixed-target sample delivery used, which should be accounted for in all future TR-SSX experiments. Finally, the effect of pH on the protonation step is investigated by studying a RSFP mutant with a destabilised ground state conformation. Structural and spectroscopic evidence is presented for a new class of reaction at low pH, involving a cis-neutral/trans-cation isomerisation, in contrasts to the typical cis-anion/trans-neutral reaction at neutral pH. These steady-state observations expand our understanding of acid/base equilibria in the photoreactions of RSFPs.Open Acces

Mechanisms of kinetic trapping in self-assembly and phase transformation

In self-assembly processes, kinetic trapping effects often hinder the formation of thermodynamically stable ordered states. In a model of viral capsid assembly and in the phase transformation of a lattice gas, we show how simulations in a self-assembling steady state can be used to identify two distinct mechanisms of kinetic trapping. We argue that one of these mechanisms can be adequately captured by kinetic rate equations, while the other involves a breakdown of theories that rely on cluster size as a reaction coordinate. We discuss how these observations might be useful in designing and optimising self-assembly reactions

What Causes Fluctuations in the Terms of Trade?

This paper investigates the sources of terms of trade volatility, specifically addressing the relative importance of goods-price effects vs. country-price effects. For fuel exporters, most of the terms of trade variation stems from goods-price effects, as one would have expected, a priori. For commodity exporters, there is great dispersion in the importance of goods price effects vs. country price effects, and no overall generalization is possible. Exporters of manufactured goods face terms of trade variation that appears to be about equally due to goods-price effects and country-price effects.