The SO(32) Heterotic String on a K3 Surface

The SO(32) heterotic string on a K3 surface is analyzed in terms of the dual theory of a type II string (or F-theory) on an elliptically fibred Calabi-Yau manifold. The results are in beautiful agreement with earlier work by Witten using very different methods. In particular, we find gauge groups of SO(32) x Sp(k) appearing at points in the moduli space identified with point-like instantons and see hypermultiplets in the (32,2k) representation becoming massless at the same time. We also discuss some aspects of the E8 x E8 case.Comment: 12 pages, LaTeX, 1 figure, refs modifie

American Coastwise Trade Law

Federal involvement in the shipping industry dates back to 1789. Since then, governmental efforts to promote the American merchant marine have taken a variety of forms, including the prohibition of foreign shipping from the coastwise trade. To this end, laws have been enacted which deal with specific activities considered to be coastwise trade in nature and which ban the use of foreign-flag and, in some cases, foreign-built ships from those activities. However, the laws are narrowly worded and archaic, and have been unable to adequately address modern trends in coastal commerce. Maritime service industries have emerged in recent years which are associated with such coastal activities as passenger cruises and oil and gas exploration. Because federal law has not dealt with these specific coastal service activities, the coastwise trade laws have not been applied to them, and they may be undertaken by ships of any flag. Without a modern legal framework to govern cabotage activities, much of the recent coastwise trade policy of the United States has been formulated by federal courts and agencies. At present, the U.S. coastwise trade laws are applied to the navigable waters of the United States and, with certain exceptions, its districts, territories and possessions. In addition, the cabotage principle extends to artificial islands on the outer continental shelf which are in place for the purpose of oil and gas exploitation. Moreover, the requirements for participation in this trade stipulate that the vessel be domestically constructed, owned, and documented. Unfortunately, such ships are usually more expensive to operate than foreign ships, and consequently there is an inherent conflict between the users of coastal marine services, who seek them at the lowest possible cost, and the traditional public policy of the United States, which has been to encourage the growth of its own fleet. It is proposed that two changes to the existing policy regarding the coastwise trade be pursued. The first is to include all coastal maritime commercial services within the purview of the U.S. coastwise trade. The second is to remove the U.S. construction requirement from some or all of the ships participating in that trade

Heterotic-Heterotic String Duality and Multiple K3 Fibrations

A type IIA string compactified on a Calabi-Yau manifold which admits a K3 fibration is believed to be equivalent to a heterotic string in four dimensions. We study cases where a Calabi-Yau manifold can have more than one such fibration leading to equivalences between perturbatively inequivalent heterotic strings. This allows an analysis of an example in six dimensions due to Duff, Minasian and Witten and enables us to go some way to prove a conjecture by Kachru and Vafa. The interplay between gauge groups which arise perturbatively and nonperturbatively is seen clearly in this example. As an extreme case we discuss a Calabi-Yau manifold which admits an infinite number of K3 fibrations leading to infinite set of equivalent heterotic strings.Comment: 13 pages, LaTe

"Institutionalized Europhobia: Britain and Monetary Policy Integration"

This paper examines British policy toward European monetary integration. It challenges dominant liberal theories of preference formation, suggesting an alternative intervening variable in the form of the electoral system, which privileges Euro-sceptical opinion in a relative sense. Empirical evidence is presented on both UK economic behavior and the views of domestic economic interests from the decision not to join the Exchange Rate Mechanism in 1978 to the decision not to participate in the first wave of countries joining stage three of Economic and Monetary Union

Temperature response measurements from eucalypts give insight into the impact of Australian isoprene emissions on air quality in 2050

Predicting future air quality in Australian cities dominated by eucalypt emissions requires an understanding of their emission potentials in a warmer climate. Here we measure the temperature response in isoprene emissions from saplings of four different Eucalyptus species grown under current and future average summertime temperature conditions. The future conditions represent a 2050 climate under Representative Concentration Pathway 8.5, with average daytime temperatures of 294.5 K. Ramping the temperature from 293 to 328 K resulted in these eucalypts emitting isoprene at temperatures 4–9 K higher than the default maximum emission temperature in the Model of Emissions of Gases and Aerosols from Nature (MEGAN). New basal emission rate measurements were obtained at the standard conditions of 303 K leaf temperature and 1000 µmol m−2 s−1 photosynthetically active radiation and converted into landscape emission factors. We applied the eucalypt temperature responses and emission factors to Australian trees within MEGAN and ran the CSIRO Chemical Transport Model for three summertime campaigns in Australia. Compared to the default model, the new temperature responses resulted in less isoprene emission in the morning and more during hot afternoons, improving the statistical fit of modelled to observed ambient isoprene. Compared to current conditions, an additional 2 ppb of isoprene is predicted in 2050, causing hourly increases up to 21 ppb of ozone and 24-hourly increases of 0.4 µg m−3 of aerosol in Sydney. A 550 ppm CO2 atmosphere in 2050 mitigates these peak Sydney ozone mixing ratios by 4 ppb. Nevertheless, these forecasted increases in ozone are up to one-fifth of the hourly Australian air quality limit, suggesting that anthropogenic NOx should be further reduced to maintain healthy air quality in future

Aridity drives clinal patterns in leaf traits and responsiveness to precipitation in a broadly distributed Australian tree species

Aridity shapes species distributions and plant growth and function worldwide. Yet, plant traits often show complex relationships with aridity, challenging our understanding of aridity as a driver of evolutionary adaptation. We grew nine genotypes of Eucalyptus camaldulensis subsp. camaldulensis sourced from an aridity gradient together in the field for ~650 days under low and high precipitation treatments. Eucalyptus camaldulesis is considered a phreatophyte (deep-rooted species that utilizes groundwater), so we hypothesized that genotypes from more arid environments would show lower aboveground productivity, higher leaf gas-exchange rates, and greater tolerance/avoidance of dry surface soils (indicated by lower responsiveness) than genotypes from less arid environments. Aridity predicted genotype responses to precipitation, with more arid genotypes showing lower responsiveness to reduced precipitation and dry surface conditions than less arid genotypes. Under low precipitation, genotype net photosynthesis and stomatal conductance increased with home-climate aridity. Across treatments, genotype intrinsic water-use efficiency and osmotic potential declined with increasing aridity while photosynthetic capacity (Rubisco carboxylation and RuBP regeneration) increased with aridity. The observed clinal patterns indicate that E. camaldulensis genotypes from extremely arid environments possess a unique strategy defined by lower responsiveness to dry surface soils, low water-use efficiency, and high photosynthetic capacity. This strategy could be underpinned by deep rooting and could be adaptive under arid conditions where heat avoidance is critical and water demand is high