Anisotropy for spatial summation of elongated patches of grating:A tale of two tails

Studies of spatial summation often use sinusoidal gratings with blurred edges. When the envelope is elongated (i) along the grating stripes and (ii) at right angles to the grating stripes, we refer to the stimuli as skunk-tails and tiger-tails respectively. Previous work [Polat & Tyler, 1999; Vision Research, 39, 887-895.] has found that sensitivity to skunk-tails is greater than for tiger-tails, but there have been several failures to replicate this result within a subset of the conditions. To address this we measured detection thresholds for skunk-tails, tiger-tails and squares of grating with sides matched to the lengths of the tails. For foveal viewing, we found a contrast sensitivity advantage in the order of 2 dB for skunk-tails over tiger-tails, but only for horizontal gratings. For vertical gratings, sensitivity was very similar for both tail-types. When the stimuli were presented parafoveally (upper right visual field), a small advantage was found for skunk-tails over tiger-tails at both orientations, and spatial summation slopes were close to that of the ideal observer. We did not replicate the findings of Polat & Tyler, but our results are consistent with (i) those of Foley et al. [Foley, J. M., Varadharajan, S., Koh, C. C., & Farias, C. Q. (2007) Vision Research, 47, 85-107.] who used only vertical gratings and (ii) those from modelfest, where only horizontal gratings were used. The small effect of tail-type here suggests an anisotropy in the underlying physiology. © 2007 Elsevier Ltd. All rights reserved.

New business formation in a rapidly growing economy: The Irish experience

The extraordinary growth of the Irish economy since the mid-1990s - the 'Celtic Tiger' - has attracted a great deal of interest, commentary and research. Indeed, many countries look to Ireland as an economic development role model, and it has been suggested that Ireland might provide key lessons for other EU members as they seek to achieve the objectives set out in the Lisbon Agenda. Much of the discussion of Ireland's growth has focused on its possible triggers: the long term consequences of the late 1980s fiscal stabilisation; EU structural funds; education; wage moderation; and devaluation of the Irish punt. The industrial policy perspective has highlighted the importance of inflows of foreign direct investment, but a notable absence from the discourse on the 'Celtic Tiger' has been any mention of the role of new business venture creation and entrepreneurship. In this paper we use unpublished Irish VAT data for the years 1988 to 2004 to provide the first detailed look at national trends in business birth and death rates in Ireland over the 'take-off' period. We also use sub-national VAT data to shed light on spatial trends in new venture creation. Our overall conclusions are that new business formation made no detectable contribution to the acceleration of Ireland's growth in the late 1990s, although we do find evidence of spatial convergence in per capita business stocks.

New business formation in a rapidly growing economy:the Irish experience

The extraordinary growth of the Irish economy since the mid-1990s—the ‘Celtic Tiger’—has attracted a great deal of interest, commentary and research. Indeed, many countries look to Ireland as an economic development role model, and it has been suggested that Ireland might provide key lessons for other EU members as they seek to achieve the objectives set out in the Lisbon Agenda. Much of the discussion of Ireland’s growth has focused on its possible triggers: the long-term consequences of the late 1980s fiscal stabilisation, EU structural funds, education, wage moderation and devaluation of the Irish punt. The industrial policy perspective has highlighted the importance of inflows of foreign direct investment, but a notable absence from the discourse on the ‘Celtic Tiger’ has been any mention of the role of new business venture creation and entrepreneurship. In this paper we use unpublished Irish VAT data for the years 1988–2004 to provide the first detailed look at national trends in business birth and death rates in Ireland over the ‘take-off’ period. We also use sub-national VAT data to shed light on spatial trends in new venture creation. Our overall conclusions are that new business formation made no detectable contribution to the acceleration of Ireland’s growth in the late 1990s, although we do find evidence of spatial convergence in per capita business stocks.

Lessons for African economies from Irish and East Asian industry policy

When comparisons in terms of industrial policy lessons to be learned have taken place, it has tended to be solely vis-a-vis the ‘development state’ East Asian experience. This paper broadens the analysis and considers lessons which African countries can learn from other so-called ‘tiger’ economies including Ireland and the East and South Asian countries. We recognise that the latter are indeed clearly significant as many African countries at the time of independence had economic structures and levels of income quite similar to East Asian countries, yet have grown at vastly different rates since then. Exploring why this has been the case can thus offer important insights into possibilities for industrial policy. Yet this comes with some health warnings over East Asian experience. We suggest that another important contribution can come by looking at the Irish example, given its emphasis on corporatism rather than simply relying on state direction in the operation of industrial policy. The Irish model is also more democratic in some senses and has protected workers’ rights during the development process in contrast to the often highly dirigisite East Asian model. Overall we suggest that some immediate actions are needed, notably with regard to the financial system in small African economies. Without such changes, a poorly functioning financial system will continue to keep investment at low levels. In relation to the small size of the African economies, the paper recommends regional integration and sufficient overseas development assistance (ODA) for infrastructural development. It is also critical to note that the various small African economies each face their own industrial and economic development challenges, and that a ‘one size fits all’ approach is not appropriate; rather the key is to tailor policies and systems to the unique opportunities and development challenges in each African country.

The importance of institutions in expansionary fiscal consolidations. A critical assessment of non-Keynesian effects

The short-term effects of fiscal consolidation have attracted an increasing attention from both the academia and policy makers in the recent years. Authors in the literature on non- Keynesian effects usually put the emphasis on the need for the devaluation of the national currency, the accommodating reaction of the monetary authority and the favourable international economic conditions as the necessary accompanying tools of fiscal consolidation, in order to realise short-term expansionary effects. Some also add the necessity of large-scale adjustment; while others support the view that a high and increasing debt ratio or increasing government spending, by triggering an unavoidable adjustment, is the key to experiencing short-term expansionary effects. The composition of adjustment also became a crucial explanation for non-Keynesian effects. However, as the following critical assessment of the literature on expansionary fiscal consolidations will reveal, institutional conditions, such as the importance of the depth of financial intermediation and the influencing role of labour market structure, can prove to be crucial in the occurrence of the desired expansionary short-term effects.

Market reform and state paternalism in Hungary: a path-dependent approach

Hungary is one of the worst-hit countries of the current financial crisis in Central and Eastern Europe. The deteriorating economic performance of the country is, however, not a recent phenomenon. A relatively high ratio of redistribution, a high and persistent public deficit and accelerated indebtedness characterised the country not just in the last couple of years but also well before the transformation, which also continued in the postsocialist years. The gradualist success of the country – which dates back to at least 1968 – in the field of liberalisation, marketisation and privatisation was accompanied by a constant overspending in the general government. The paper attempts to explore the reasons behind policymakers’ impotence to reform public finances. By providing a path-dependent explanation, it argues that both communist and postcommunist governments used the general budget as a buffer to compensate losers of economic reforms, especially microeconomic restructuring. The ever-widening circle of net benefiters of welfare provisions paid from the general budget, however, has made it simply unrealistic to implement sizeable fiscal adjustment, putting the country onto a deteriorating path of economic development.

Social change in Central and Eastern Europe: General trends and national patterns

The paper addresses five issue areas. First it describes the plurality of trajectories in central and eastern European transformations, offering a broad typology. Then it addresses the drift between acceptance of democracy and the market, owing to growing inequalities. Third, problems of poverty and exclusion are addressed. Fourth, it is addressed if any known model of redistribution emerged in the post-transition economies. Fifth, consequences of the populist turn in European policies are being analyzed. Influences of the EU practices will be dealt with and some preliminary conclusions drawn. These suggest a strong intertwining between social and economic performance that limit theoretically conceivable – neoliberal, social democratic, postmodern or conservative - policy choices.

The relationship between alkaloid-based chemical defenses and diet in dendrobatid poison frogs

Chemical defenses are common among organisms and represent some of the most complex adaptations for avoiding predation, yet our understanding of the ecological nature of these systems remains incomplete. Poison frogs are a group of chemically defended organisms that are dependent entirely on diet for chemical defense. In this study, I identified the dietary arthropods responsible for chemical defense in poison frogs, described spatial and temporal patterns in alkaloid composition of poison frogs, and established links between patterns of variation in alkaloid defense and arthropod diet in poison frogs. Identifying dietary sources and studying patterns of variation in alkaloid composition is fundamental to understanding the ecology and evolution of chemical defense in poison frogs. ^ The dendrobatid poison frog Oophaga pumilio shares many alkaloids in common with other poison frogs and is known to vary in alkaloid composition throughout its geographic range. I designed my dissertation to take advantage of these characteristics and use O. pumilio as a model species for the study of chemical defense in poison frogs. Here, I identified siphonotid millipedes as a source for spiropyrrolizidine alkaloids, formicine ants as a source for pumiliotoxin alkaloids, and oribatid mites as dietary sources for the majority of alkaloids found in poison frogs. I found that alkaloid composition varied spatially and temporally, on both small and large scales, within and among populations of O. pumilio. Alkaloid variation between populations was related to geographic distance, and closer populations tended to have alkaloid compositions more similar to each other than to distant populations. ^ The findings of my study suggest that oribatid mites are the most important dietary source of alkaloids in poison frogs. However, overall alkaloid defense in poison frogs is based on a combination of dietary arthropods, including mites, ants, millipedes, and beetles. Variation in chemical defenses of poison frogs is due to (1) spatial and temporal differences in the presence of alkaloids in certain arthropods and (2) differences in the availability of certain alkaloid-containing arthropods, which are likely the result of differences as well as successional changes in forest structure among locations and through time. ^

Radiative forcing of natural forest disturbances

Forest disturbances are major sources of carbon dioxide to the atmosphere, and therefore impact global climate. Biogeophysical attributes, such as surface albedo (reflectivity), further control the climate-regulating properties of forests. Using both tower-based and remotely sensed data sets, we show that natural disturbances from wildfire, beetle outbreaks, and hurricane wind throw can significantly alter surface albedo, and the associated radiative forcing either offsets or enhances the CO2 forcing caused by reducing ecosystem carbon sequestration over multiple years. In the examined cases, the radiative forcing from albedo change is on the same order of magnitude as the CO2 forcing. The net radiative forcing resulting from these two factors leads to a local heating effect in a hurricane-damaged mangrove forest in the subtropics, and a cooling effect following wildfire and mountain pine beetle attack in boreal forests with winter snow. Although natural forest disturbances currently represent less than half of gross forest cover loss, that area will probably increase in the future under climate change, making it imperative to represent these processes accurately in global climate models.

The role of teleost grazers in a relatively pristine seagrass ecosystem

Trophic downgrading of ecosystems necessitates a functional understanding of trophic cascades. Identifying the presence of cascades, and the mechanisms through which they occur, is particularly important for seagrass meadows, which are among the most threatened ecosystems on Earth. Shark Bay, Western Australia provides a model system to investigate the potential importance of top-down effects in a relatively pristine seagrass ecosystem. The role of megagrazers in the Shark Bay system has been previously investigated, but the role of macrograzers (i.e., teleosts), and their importance relative to megagrazers, remains unknown. The objective of my dissertation was to elucidate the importance of teleost macrograzers in transmitting top-down effects in seagrass ecosystems. Seagrasses and macroalgae were the main food of the abundant teleost Pelates octolineatus, but stable isotopic values suggested that algae may contribute a larger portion of assimilated food than suggested by gut contents. Pelates octolineatus is at risk from numerous predators, with pied cormorants (Phalacrocorax varius) taking the majority of tethered P. octolineatus. Using a combination of fish trapping and unbaited underwater video surveillance, I found that the relative abundance of P. octolineatus was greater in interior areas of seagrass banks during the cold season, and that the mean length of P. octolineatus was greater in these areas compared to along edges of banks. Finally, I used seagrass transplants and exclosure experiments to determine the relative effect of megagrazers and macrograzers on the establishment and persistence of three species of seagrasses in interior microhabitats. Teleost grazing had the largest impact on seagrass species with the highest nutrient content, and these impacts were primarily observed during the warm season. My findings are consistent with predictions of a behaviorally-mediated trophic cascade initiated by tiger sharks (Galeocerdo cuvier) and transmitted through herbivorous fishes and their predators.

Contrasting patterns of individual specialization and trophic coupling in two marine apex predators

1. Apex predators are often assumed to be dietary generalists and, by feeding on prey from multiple basal nutrient sources, serve to couple discrete food webs. But there is increasing evidence that individual level dietary specialization may be common in many species, and this has not been investigated for many marine apex predators. 2. Because of their position at or near the top of many marine food webs, and the possibility that they can affect populations of their prey and induce trophic cascades, it is important to understand patterns of dietary specialization in shark populations. 3. Stable isotope values from body tissues with different turnover rates were used to quantify patterns of individual specialization in two species of ‘generalist’ sharks (bull sharks, Carcharhinus leucas, and tiger sharks, Galeocerdo cuvier). 4. Despite wide population-level isotopic niche breadths in both species, isotopic values of individual tiger sharks varied across tissues with different turnover rates. The population niche breadth was explained mostly by variation within individuals suggesting tiger sharks are true generalists. In contrast, isotope values of individual bull sharks were stable through time and their wide population level niche breadth was explained by variation among specialist individuals. 5. Relative resource abundance and spatial variation in food-predation risk tradeoffs may explain the differences in patterns of specialization between shark species. 6. The differences in individual dietary specialization between tiger sharks and bull sharks results in different functional roles in coupling or compartmentalizing distinct food webs. 7. Individual specialization may be an important feature of trophic dynamics of highly mobile marine top predators and should be explicitly considered in studies of marine food webs and the ecological role of top predators.

Foster Hall, 1922 View

Foster Hall was named for Richard B. Foster who was the founder and first principal of Lincoln Institute. Foster Hall is a three story building. For several years it was the only dormitory for men on campus. It was renovated in phases from 1991 to 1994. It now houses the offices and laboratory facilities for Cooperative Research.