Influence of excited electron lifetimes on the electronic structure of carbon nanotubes

We have studied the dynamics of electrons in single wall carbon nanotubes using femtosecond time-resolved photoemission. The lifetime of electrons excited to the pi* bands is found to decrease continuously from 130 fs at 0.2 eV down to less than 20 fs at energies above 1.5 eV with respect to the Fermi level. This should lead to a significant lifetime--induced broadening of the characteristic van Hove singularities in the nanotube DOS.Comment: 6 pages, 4 figure

Potential gains from reducing trade barriers in manufacturing, services and agriculture

Trade barriers

Examining Pinterest as a Curriculum Resource for Negative Integers: An Initial Investigation

This paper reports an investigation of mathematical resources available on the social media site Pinterest. Pinterest is an online bulletin board where users create visual bookmarks called pins in order to share digital content (e.g., webpages, images, videos). Although recent surveys have shown that Pinterest is a popular reference for teachers, understanding of the mathematical resources available on the site is lacking. To take initial steps in investigating the curriculum resources provided by Pinterest, we used keyword searches to gather a database of pins related to the topic of negative integers. A content analysis was conducted on the pins with a focus on several characteristics including mathematical operations, mathematical models, use of real-world context, and whether mathematical errors were present in source material. Results show a dominance of addition and subtraction over other operations, use of mathematical models in half of pins, infrequent use of real-world context, and mathematical errors in roughly one-third of pins. We provide a breakdown of these results and discuss implications of the findings for mathematics teacher education and professional development

A GLOBAL PERSPECTIVE ON REGIONAL INTEGRATION IN NORTH AMERICA

International Relations/Trade,

A Survey of Findings on the Poverty Impacts of Agricultural Trade Liberalization

The purpose of this survey is to review the available empirical evidence on the impacts of agricultural trade liberalization on poverty – considering both the impact of domestic and international liberalization. Since trade liberalization is generally an economywide phenomenon, with tariff cuts occurring across a wide range of commodities, we do not restrict ourselves to episodes where only agricultural trade was liberalized, although emphasis in this survey is given to agricultural trade policies. Furthermore, given the difficulty of isolating the effects of trade policies alone, we will also consider the impact of other types of external shocks which have the effect of changing the relative prices of tradeable and non-tradeable goods. By examining the way in which households adjust to such external shocks, we can learn a great deal about how they would respond to sharp reductions in tariffs, or significant changes in a country’s international terms of trade engendered by multilateral trade liberalization.Poverty, rural development, agriculture, Food Security and Poverty, International Relations/Trade,

Not so cheap talk: a model of advice with communication costs

We model a game similar to the interaction between an academic advisor and advisee. Like the classic cheap talk setup, an informed player sends information to an uninformed receiver who is to take an action which affects the payoffs of both sender and receiver. However, unlike the classic cheap talk setup, the preferences regarding the receiver's actions are identical for both sender and receiver. Additionally, the sender incurs a communication cost which is increasing in the complexity of the message sent. We characterize the resulting equilibria. Under an additional out-of-equilibrium condition (Condition L), if preferences for sender and receiver are identical then the only equilibria are the most informative, feasible ones. A similar result appears in Chen, Kartik and Sobel (2008) when their No Incentive to Separate (NITS) condition is applied to the case where communication is costless but preferences diverge. Additionally, we model the competency of the advisee by the probability that the action is selected by mistake. We show that the informativeness of the sender is decreasing in the likelihood of the mistake. When the preferences between players diverge and when there are communication costs, we are not guaranteed uniqueness and we provide an example where an increase in communication costs can improve communication.complexity, communication, cheap talk