Impact experimentation and the microgravity environment: An overview

Impact is an ubiguitous physical process in the solar system. It occurs on all solid bodies and operates over a spectrum of scales. Understanding impact phenomena is therefore paramount in constraining and underpinning a large number of research efforts into fundamental problems in planetary geology. Gravity is an important parameter in impact processes. The advantages of microgravity experimentation are discussed

Solitons, Links and Knots

Using numerical simulations of the full nonlinear equations of motion we investigate topological solitons of a modified O(3) sigma model in three space dimensions, in which the solitons are stabilized by the Hopf charge. We find that for solitons up to charge five the solutions have the structure of closed strings, which become increasingly twisted as the charge increases. However, for higher charge the solutions are more exotic and comprise linked loops and knots. We discuss the structure and formation of these solitons and demonstrate that the key property responsible for producing such a rich variety of solitons is that of string reconnection.Comment: 24 pages plus 14 figures in GIF forma

Variations in mid-ocean ridge CO2 emissions driven by glacial cycles

The geological record shows links between glacial cycles and volcanic productivity, both subaerially and at mid-ocean ridges. Sea-level-driven pressure changes could also affect chemical properties of mid-ocean ridge volcanism. We consider how changing sea-level could alter the CO2 emissions rate from mid-ocean ridges, on both the segment and global scale. We develop a simplified transport model for a highly incompatible element through a homogenous mantle; variations in the melt concentration the emission rate of the element are created by changes in the depth of first silicate melting. The model predicts an average global mid-ocean ridge CO2 emissions-rate of 53 Mt/yr, in line with other estimates. We show that falling sea level would cause an increase in ridge CO2 emissions with a lag of about 100 kyrs after the causative sea level change. The lag and amplitude of the response are sensitive to mantle permeability and plate spreading rate. For a reconstructed sea-level time series of the past million years, we predict variations of up to 12% (7 Mt/yr) in global mid-ocean ridge CO2 emissions. The magnitude and timing of the predicted variations in CO2 emissions suggests a potential role for ridge carbon emissions in glacial cycles

U.S. Beer Flows & the Impact of NAFTA

After World War II and up until the 1980’s, the liberalization of trade was realized on a multilateral basis. World trade grew at twice the pace of GDP growth (Krueger, 1999). However, starting in the mid 1980’s, preferential trading arrangements (PTAs) increased in numbers. Perhaps the most influential PTA ever to be signed could be the North America Free Trade Agreement, or simply NAFTA, which came into effect January 1, 1994. The agreement established a free-trade area between its member countries- US, Canada and Mexico- in which all tariffs would be phased out between them, but each country would maintain its separate national barriers against the rest of the world. A lot of attention has been paid to the impact of NAFTA on the welfare of its member countries and on the rest of the world. This paper will focus on the impact of the agreement on the US’s beer trade flows by analyzing annual import and export data using several methods. To our knowledge there is no precedent for such research. Section II provides a brief review of the conclusions and methodology of existing works on NAFTA trade issues, as well as some important aspects of the agreement. Section III provides an overview of the world beer industry, and the NAFTA member countries beer markets. Section IV provides in great detail the methodology that we will employ. The focus of Section V is to explain the results obtained. Section VI provides conclusions and implications for further research on this subject. References and other sources can be found in Section VII.beer trade on US market, NAFTA