The Economics of Small Worlds

We examine a simple economic model of network formation where agents benefit from indirect relationships. We show that small-world features—short path lengths between nodes together with highly clustered link structures—necessarily emerge for a wide set of parameters

Leishmania manipulation of sand fly feeding behavior results in enhanced transmission.

In nature the prevalence of Leishmania infection in whole sand fly populations can be very low (<0.1%), even in areas of endemicity and high transmission. It has long since been assumed that the protozoan parasite Leishmania can manipulate the feeding behavior of its sand fly vector, thus enhancing transmission efficiency, but neither the way in which it does so nor the mechanisms behind such manipulation have been described. A key feature of parasite development in the sand fly gut is the secretion of a gel-like plug composed of filamentous proteophosphoglycan. Using both experimental and natural parasite-sand fly combinations we show that secretion of this gel is accompanied by differentiation of mammal-infective transmission stages. Further, Leishmania infection specifically causes an increase in vector biting persistence on mice (re-feeding after interruption) and also promotes feeding on multiple hosts. Both of these aspects of vector behavior were found to be finely tuned to the differentiation of parasite transmission stages in the sand fly gut. By experimentally accelerating the development rate of the parasites, we showed that Leishmania can optimize its transmission by inducing increased biting persistence only when infective stages are present. This crucial adaptive manipulation resulted in enhanced infection of experimental hosts. Thus, we demonstrate that behavioral manipulation of the infected vector provides a selective advantage to the parasite by significantly increasing transmission

The Economics of Small Worlds

We examine a simple economic model of network formation where agents benefit from indirect relationships. We show that small-world features - -- short path lengths between nodes together with highly clustered link structures --- necessarily emerge for a wide set of parameters.networks, small worlds

Heat in the Heartland: Climate Change and Economic Risk in the Midwest

This report offers a first step toward defining the range of potential economic consequences to the Midwest if we continue on our current greenhouse gas emissions pathway. The research combines state-of-the-art climate science projections through the year 2100 (and beyond in some cases) with empirically-derived estimates of the impact of projected changes in temperature and precipitation on the Midwest economy. The authors analyze not only those outcomes most likely to occur, but also lower-probability, higher-cost climate futures. These are the "tail risks," most often expressed here as the 1-in-20 chance something will occur. Unlike any other study to date, this report looks at climate impacts at a very geographically granular level, in some cases providing county-level results

THE PACIFIC DECADAL PRECESSION AND ITS RELATIONSHIP TO TROPICAL PACIFIC DECADAL VARIABILITY IN CMIP6 MODELS

Persistent, multi-year shifts in atmospheric circulations and their associated influence on regional climates can have profound impacts on physical, biological, and socioeconomic systems. The Pacific Decadal Precession (PDP), a quasi-decadal mode of variability in the North Pacific, describes a series of such shifts in atmospheric circulations. Unlike previously established modes of quasi-decadal variability, the PDP is characterized by the cyclonic progression of an atmospheric pressure anomaly dipole around the North Pacific and has been connected to climate variations across North America. The north-south (N-S) oriented phase of the PDP (i.e., when the pressure dipole is oriented meridionally) has been hypothesized to be partially driven by decadal variability in central Pacific (CP) sea surface temperatures given its similarities to the North Pacific Oscillation (NPO). This thesis investigates this hypothesis by identifying connections between the N-S phase of the PDP, the NPO, and tropical Pacific decadal variability (PDV), in both reanalysis and select models from the Coupled Model Intercomparison Project phase 6 (CMIP6) archive. The analyses here show that the N-S phase of the PDP is indeed related to the NPO, as the quasi-decadal temporal evolution of the NPO tracks the PDP well. However, there is a considerable portion of variability in the PDP that is not explained by the NPO which is likely due to the NPO not explaining variability associated with the east-west orientation of the PDP. This thesis also shows that the emergence of the N-S phase is both related to and influenced by tropical Pacific decadal sea surface temperature variability, specifically variability associated with CP El Niño-Southern Oscillation (ENSO) events. The link between the N-S phase of the PDP and CP ENSO events is demonstrated by the similarity in sea surface temperature anomaly patterns associated with both the emergence of the N-S phase of the PDP and the structure of CP ENSO events, and highly significant temporal correlations between the two patterns. In contrast to reanalysis, current climate models struggle with simulating the evolution of the PDP, and in general do not capture the observed relationships between the PDP, the NPO, and tropical PDV. Potential reasons for models not capturing the relationships between the PDP, NPO, and tropical PDV are discussed briefly to motivate future research. While this thesis finds evidence supporting connections between the PDP and other modes of Pacific variability, more understanding of the dynamics of the PDP and how current models simulate it is needed. Establishing a better understanding of the dynamics of the PDP and further assessment of these dynamics in models will aid in improving current prediction capabilities of the PDP and PDP-related regional climate impacts

Novel spin functionalities of C60 based metallo-molecular interfaces

Novel functionalities of C60-based interfaces are investigated with the aim of controlling induced spin-dependent phenomena through electrical and optical charging in photovoltaic devices and the generation of spin-triplet correlations in magneto-molecular/superconductor proximity systems. Low-energy muon spin rotation is used to probe local magnetic field distributions in molecule/metal-oxide heterojunctions. It is shown that the population of interfacial traps after electrical and optical charging produces an induced magnetisation due to the spin-splitting of the interface. This is supported by XAS and XMLD measurements in similar systems. The emergence of a peak at 282 eV, often associated with interfacial hybridisation, after an electrical bias shows a magnetic field dependence in its X-ray linear dichroism. We propose how these effects may be reversibly switched on and off through the tuning of the interfacial chemistry via electromigration of oxygen in the device. In Nb/C60 stacks a superconducting state can be induced in the molecular layer via the proximity effect. The incorporation of weakly magnetic Cu/C60 interfaces leads to the emergence of a paramagnetic spin susceptibility in the superconducting state, as probed by low-energy muon spin rotation. We attribute this effect to the generation of odd-frequency spin-triplet correlations at the spin-split Cu/C60 interface. These studies are a demonstration of novel device architectures available to the field of molecular spintronics. Utilising the unique spin-dependent phenomena observed in hybrid molecular interfaces, systems with new functionalities can be designed

Rethinking 'multi-user': an in-the-wild study of how groups approach a walk-up-and-use tabletop interface

Multi-touch tabletops have been much heralded as an innovative technology that can facilitate new ways of group working. However, there is little evidence of these materialising outside of research lab settings. We present the findings of a 5-week in-the-wild study examining how a shared planning application – designed to run on a walk-up- and-use tabletop – was used when placed in a tourist information centre. We describe how groups approached, congregated and interacted with it and the social interactions that took place – noting how they were quite different from research findings describing the ways groups work around a tabletop in lab settings. We discuss the implications of such situated group work for designing collaborative tabletop applications for use in public settings

Eminent Domain in the Wake of the Kelo Decision

The controversial Supreme Court decision, Kelo v. The City of New London, allowed a local government to utilize eminent domain to transfer land from one private entity to another in order to enhance economic development. In response, state governments rushed to pass legislation in order to curtail the use of eminent domain. State governments, however, struggled to pass meaningful eminent domain legislation, since many powerful forces, such as major corporations, stood in their way. Opponents of eminent domain claim that the politically weakest in our society, namely the poor and racial minorities, are saddled with the resulting hardship emanating from this policy. Meanwhile, supporters argue that eminent domain is vitally necessary in order to rejuvenate those cities which have fallen on hard times. A prime example of the controversy surrounding the use of eminent domain derives from New York City. Columbia University attempted to expand its campus through the use of eminent domain, resulting in intense controversy. Eventually, the New York State Court of Appeals ruled that the project could move forward. This example clearly attests to the passion exhibited on both sides of the very volatile issue of eminent domai