Hidden Symmetries of the Principal Chiral Model Unveiled

By relating the two-dimensional U(N) Principal Chiral Model to a simple linear system we obtain a free-field parametrisation of solutions. Obvious symmetry transformations on the free-field data give symmetries of the model. In this way all known `hidden symmetries' and B\"acklund transformations, as well as a host of new symmetries, arise.Comment: 21 pages, Latex. A sentence and citation adde

Aerodynamic characteristics of the standard dynamics model in coning motion at Mach 0.6

A wind tunnel test was conducted on the Standard Dynamics Model (a simplified generic fighter aircraft shape) undergoing coning motion at Mach 0.6. Six component force and moment data are presented for a range of angle of attack, sideslip, and coning rates. At the relatively low non-dimensional coning rate employed (omega b/2V less than or equal to 0.04), the lateral aerodynamic characteristics generally show a linear variation with coning rate

Remittance stability, cyclicality and stabilizing impact in developing countries

That remittances are a stable source of external finance seems to have become the received wisdom. In addition, many studies have found remittances to behave counter-cyclically, increasing during crises and times of hardship for the recipient countries. Are remittances reliable macroeconomic stabilizers? To answer this question, the present study examines the stability, cyclicality, and stabilizing impact of remittances in comparison with the same three features for other foreign-exchange inflows, namely foreign direct investment and official development aid. The analysis is performed at the country and regional levels rather than at the aggregate or global level (on which much of the received wisdom rests), because policymakers are concerned with the impact of remittances in their country rather than at the global level. The main findings for 1980-2007 are that in a majority of countries: i) official development aid is more stable than remittances, and remittances are more stable than foreign direct investment; ii) official development aid is counter-cyclical, while remittances are pro-cyclical, although less so than foreign direct investment; and iii) official development aid is stabilizing and remittances are destabilizing, although less so than foreign direct investment. The paper suggests that it is necessary to examine counter-cyclicality separately from the stabilizing impact, as the former does not seem to always imply the latter.Economic Conditions and Volatility,Remittances,Debt Markets,Economic Theory&Research,Emerging Markets

Advances in breast cancer treatment and prevention: preclinical studies on aromatase inhibitors and new selective estrogen receptor modulators (SERMs).

Intensive basic and clinical research over the past 20 years has yielded crucial molecular understanding into how estrogen and the estrogen receptor act to regulate breast cancer and has led to the development of more effective, less toxic, and safer hormonal therapy agents for breast cancer management and prevention. Selective potent aromatase inhibitors are now challenging the hitherto gold standard of hormonal therapy, the selective estrogen-receptor modulator tamoxifen. Furthermore, new selective estrogen-receptor modulators such as arzoxifene, currently under clinical development, offer the possibility of selecting one with a more ideal pharmacological profile for treatment and prevention of breast cancer. Two recent studies in preclinical model systems that evaluate mechanisms of action of these new drugs and suggestions about their optimal clinical use are discussed

Examining the Contributions of Glacial Till Water to Storm Runoff using Two- and Three-Component Hydrograph Separations

Two- and three-component hydrograph separations based on 18O and dissolved silica are used to investigate the contributions of glacial till water to the storm runoff of a headwater stream on the Canadian Shield. Two-component isotopic hydrograph separations based on 18O indicate that the volume and flux of event water could be accounted for by direct precipitation onto saturated areas. Three-component hydrograph separations distinguish between event water, preevent soil water, and preevent till water. These results show that groundwater flow through coarse-textured glacial tills can make a significant contribution to stream discharge during runoff events (29 and 62% in this study) despite the lower hydraulic conductivities of the tills compared to the overlying soils. The three-component hydrograph separations also demonstrate that the relative contributions of preevent soil water and preevent till water changed during one runoff event such that the average water chemistry of the preevent component varied during the event. Two-component hydrograph separations using dissolved silica indicate that seasonal changes in the till water contributions also occur and are related to groundwater levels. Measurements of vertical hydraulic gradients during runoff events indicate that the increase in flow from the tills to the soils is minimal and cannot account for the large and rapid increase in till water flow into the stream. Till water that has discharged to the soils prior to the event is probably being flushed from the soils into the stream during events

Gauge invariance and non-constant gauge couplings

It is shown that space-time dependent gauge couplings do not completely break gauge invariance. We demonstrate this in various gauge theories.Comment: 18 page