Showing 731 - 740 of 2040 Items
Polar oceanography: Engendering students with a sense of place and a sense of time
Date: 2016-06-01
Creator: Collin S. Roesler
Access: Open access
The Art Gallery Theorem for Polyominoes
Date: 2012-10-01
Creator: Therese Biedl
Mohammad T. Irfan
Justin Iwerks
Joondong Kim
Joseph S.B., Mitchell
Access: Open access
- We explore the art gallery problem for the special case that the domain (gallery) P is an m-polyomino, a polyform whose cells are m unit squares. We study the combinatorics of guarding polyominoes in terms of the parameter m, in contrast with the traditional parameter n, the number of vertices of P. In particular, we show that ⌊m+1/3⌋ point guards are always sufficient and sometimes necessary to cover an m-polyomino, possibly with holes. When m < 3n/4-4, the sufficiency condition yields a strictly lower guard number than ⌊ n/4⌋, given by the art gallery theorem for orthogonal polygons. © 2012 Springer Science+Business Media, LLC.
The citizens united election? or same as it ever was?
Date: 2010-12-01
Creator: Michael M. Franz
Access: Open access
- In January 2010, the Supreme Court in Citizens United v. FEC overturned long-standing regulations governing the role of unions and corporations in sponsoring pro-candidate advocacy. Many predicted a deleterious effect on the electoral process. In the aftermath of the midterm elections, a number of questions deserve consideration. Was the observed level of outside spending abnormally high in 2010? What can we say about the potential effect of outside spending on the outcomes of House and Senate races? Moreover, what has the decision done to the power of parties and, most especially, their ability to compete with special interests in backing federal candidates? This paper investigates these questions using data from the Wesleyan Media Project, which tracked political ads in 2010. The initial evidence suggests that while interest groups were aggressive players in the air war, their impact may not have been as negative or as large as initially predicted. © 2011 Berkeley Electronic Press.
The H.C. Carey School of U.S. Currency Doctors: A "Subtle Principle" and its Progeny
Date: 2024-02-20
Creator: Stephen Meardon
Access: Open access
- Henry C. Carey led a school of post-Civil War U.S. currency doctors prescribing an “elastic currency,” expanding and contracting according to commercial needs. The problem for the Careyites was reconciling elasticity, which implied inconvertibility with gold, with the related aim of decentralized financial power. Careyite currency doctors included, among others, Wallace P. Groom, editor of the New York Mercantile Journal, and Henry Carey Baird, Carey’s own nephew and inheritor of his mantle. Their prescribed reform of the banking system featured a financial innovation that would remove superfluous currency from circulation while supplying what was needed. The innovation was an “interconvertible bond,” a debt instrument of the U.S. Treasury that was to be issued upon demand and redeemable for currency at the option of the holder. Its function was supposed to be like the mechanical governor of a steam engine, operating by a “subtle principle” that obviated human governing power and discretion. The Carey school’s prescription and its rationale remained salient up to the advent of the Federal Reserve System.
Hedgehog signaling regulates dental papilla formation and tooth size during zebrafish odontogenesis
Date: 2015-04-01
Creator: Jeffrey C. Yu
Zachary D. Fox
James L. Crimp
Hana E. Littleford
Andrea L., Jowdry
William R. Jackman
Access: Open access
- Intercellular communication by the hedgehog cell signaling pathway is necessary for tooth development throughout the vertebrates, but it remains unclear which specific developmental signals control cell behavior at different stages of odontogenesis. To address this issue, we have manipulated hedgehog activity during zebrafish tooth development and visualized the results using confocal microscopy. Results: We first established that reporter lines for dlx2b, fli1, NF-κB, and prdm1a are markers for specific subsets of tooth germ tissues. We then blocked hedgehog signaling with cyclopamine and observed a reduction or elimination of the cranial neural crest derived dental papilla, which normally contains the cells that later give rise to dentin-producing odontoblasts. Upon further investigation, we observed that the dental papilla begins to form and then regresses in the absence of hedgehog signaling, through a mechanism unrelated to cell proliferation or apoptosis. We also found evidence of an isometric reduction in tooth size that correlates with the time of earliest hedgehog inhibition. Conclusions: We hypothesize that these results reveal a previously uncharacterized function of hedgehog signaling during tooth morphogenesis, regulating the number of cells in the dental papilla and thereby controlling tooth size.
Statement by Melinda (Mindy) Kane collected by Rachel George on September 11, 2014
Date: 2014-09-11
Creator: Melinda Kane
Access: Open access
Statement by Wendy Newell Dyer collected by Rachel George on January 12, 2015
Date: 2015-01-12
Creator: Wendy Newell Dyer
Access: Open access
Statement by Andrew Mead collected by Rachel George on August 21, 2014
Date: 2014-08-21
Creator: Andrew Mead
Access: Open access
Vertical Trade, Exchange Rate Pass-Through, and Exchange Rate Regime
Date: 2012-09-01
Creator: Yao Tang
Ke Pang
Access: Open access
- We compare the welfare of different combinations of monetary and currency policies in an open-economy macroeconomic model that incorporates two important features of many small economies: a high level of vertical international trade and a prevalent use of a large trade partner's currency as the invoicing currency for both imports and exports. In this environment, a small economy prefers a fixed exchange rate regime over a flexible regime, while the larger economy prefers a flexible exchange rate regime. There are two main causes underlying our results. First, in the presence of sticky prices, relative prices adjust through changes in the exchange rate. Multiple stages of production and trade make it more difficult for one exchange rate to balance the whole economy by adjusting several relative prices throughout the vertical chain of production and trade. Namely, there is a trade-off between delivering an efficient relative price between home and foreign final goods and delivering an efficient relative price between home and foreign intermediate goods. Second, because the small economy uses the larger economy's currency in trade, it faces a high degree of exchange rate pass-through under a flexible regime and hence suffers from the lack of efficient relative prices in vertical trade. The larger economy, however, does not face this problem because its level of exchange rate pass-through is low.
Learning cognitive maps: Finding useful structure in an uncertain world
Date: 2008-05-22
Creator: Eric Chown
Byron Boots
Access: Open access
- In this chapter we will describe the central mechanisms that influence how people learn about large-scale space. We will focus particularly on how these mechanisms enable people to effectively cope with both the uncertainty inherent in a constantly changing world and also with the high information content of natural environments. The major lessons are that humans get by with a "less is more" approach to building structure, and that they are able to quickly adapt to environmental changes thanks to a range of general purpose mechanisms. By looking at abstract principles, instead of concrete implementation details, it is shown that the study of human learning can provide valuable lessons for robotics. Finally, these issues are discussed in the context of an implementation on a mobile robot. © 2007 Springer-Verlag Berlin Heidelberg.