A comparative study of online news retrieval and presentation strategies

We introduce a news retrieval system on which we evaluated three alternative presentation strategies for online news retrieval. We used a user-oriented and task-oriented evaluation framework. The interfaces studied were Image, giving a grid of thumbnails for each story together with query-based summaries presented as tooltips, Summary, which displayed the summary information alongside each thumbnail, and Cluster, which grouped similar stories together and used the same display format as Image. The evaluation showed that the Summary Interface was preferred to the Image Interface, and that the Cluster Interface was helpful to users with a set task to complete. The implications of this study are also discussed in this paper

Barter Economies and Centralized Merchants

The main goal of this essay is to analyze the emergence of a barter economy, and the rise of centralized merchants and a barter redistribution system out of a primitive barter system. The environment is a spatial general equilibrium model where exchange is costly. Since exchange becomes more complicated as the scope of the economy increases, we prove that, after the economy reaches a critical size, the cost of trade expansion surpasses its benefits. This imposes limitations on the scope of the economy and the production level. To overcome these limitations, rational individuals can develop a more advanced barter system leading to the appearance of centralized merchants. This more sophisticated system is the redistribution system. We also show that under some circumstances, in the presence of transaction costs it may be optimal for individuals to keep using barter instead of adopting a monetary system. This result explains why some primitive economies, like the Incas in Peru and ancient Egypt, did not evolve to a monetary system, and kept barter as their main exchange system.Barter, City, Exchange system, Market center, Merchant, Redistribution system, Transaction cost

The Appearance of Carriers and the Origins of Money

The main goal of this essay is to provide microfoundations in a spatial general equilibrium framework for the fact that individuals use money to make transactions, and hence microfoundations for the cash in advance constraint. We analyze the emergence of a monetary economy out of a redistribution barter system where goods are sent to a central market and then redistributed among individuals. We show that, as the population increases beyond a certain point, the barter exchange system becomes too expensive. To reduce the exchange system cost, and as a result of individuals’ rational behavior, a new specialized merchant, the carrier, appears and causes frictions among traders leading to the appearance of money. There are, however, certain conditions for this process to succeed. These conditions concern the economic characteristics of those goods chosen to act as money, and the level of economic development.Barter, Money, Carrier, Market center, City, Transaction cost

Bulk Fermions in Soft Wall Models

We discuss the implementation of bulk fermions in soft wall models. The introduction of a position dependent bulk mass allows for a well defined Kaluza-Klein expansion for bulk fermions. The realization of flavor and the contribution to electroweak precision observables are shown to be very similar to the hard wall case. The bounds from electroweak precision test are however milder with gauge boson Kaluza-Klein modes as light as $\sim 1.5$ TeV compatible with current experimental bounds.Comment: Based on seminars given by the authors. To appear in the SUSY 09 proceeding