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A look at some of our fall athlete

Enriched weakness

The basic notions of category theory, such as limit, adjunction, and orthogonality, all involve assertions of the existence and uniqueness of certain arrows. Weak notions arise when one drops the uniqueness requirement and asks only for existence. The enriched versions of the usual notions involve certain morphisms between hom-objects being invertible; here we introduce enriched versions of the weak notions by asking that the morphisms between hom-objects belong to a chosen class of "surjections". We study in particular injectivity (weak orthogonality) in the enriched context, and illustrate how it can be used to describe homotopy coherent structures.Comment: 25 pages; v2 minor changes, to appear in JPA

Minimum wages and poverty in a developing country: simulations from Indonesia’s household survey

This study focuses on the efficiency of minimum wage policy for poverty reduction, taking Indonesia as a case study. A simulation approach assesses who benefits and who pays for minimum wage increases. On the benefits side, the rise in minimum wages boosts incomes in households with low wage workers. However, increases in wage costs are passed on through higher consumer prices. As a result, three out of four poor households lose in net terms, even when we assume no job losses. The findings suggest that minimum wages are unlikely to be an effective antipoverty instrument, at least for Indonesia

Enhanced 2-categories and limits for lax morphisms

We study limits in 2-categories whose objects are categories with extra structure and whose morphisms are functors preserving the structure only up to a coherent comparison map, which may or may not be required to be invertible. This is done using the framework of 2-monads. In order to characterize the limits which exist in this context, we need to consider also the functors which do strictly preserve the extra structure. We show how such a 2-category of weak morphisms which is "enhanced", by specifying which of these weak morphisms are actually strict, can be thought of as category enriched over a particular base cartesian closed category F. We give a complete characterization, in terms of F-enriched category theory, of the limits which exist in such 2-categories of categories with extra structure.Comment: 77 pages; v2 minor changes only, to appear in Advance

A colimit decomposition for homotopy algebras in Cat

Badzioch showed that in the category of simplicial sets each homotopy algebra of a Lawvere theory is weakly equivalent to a strict algebra. In seeking to extend this result to other contexts Rosicky observed a key point to be that each homotopy colimit in simplicial sets admits a decomposition into a homotopy sifted colimit of finite coproducts, and asked the author whether a similar decomposition holds in the 2-category of categories Cat. Our purpose in the present paper is to show that this is the case.Comment: Some notation changed; small amount of exposition added in intr

Categorified quantum sl(2) is an inverse limit of flag 2-categories

We prove that categorified quantum sl(2) is an inverse limit of Flag 2-categories defined using cohomology rings of iterated flag varieties. This inverse limit is an instance of a 2-limit in a bicategory giving rise to a universal property that characterizes the categorification of quantum sl(2) uniquely up to equivalence. As an application we characterize all bimodule homomorphisms in the Flag 2-category and prove that the categorified quantum Casimir of sl(2) acts appropriately on these 2-representations.Comment: 21 pages, with xypic diagrams. v2 corrects typo

Industrial concentration and competition in Indonesian manufacturing

This thesis examines the interrelationship between market structures, firm rivalry, and government intervention in the Indonesian manufacturing sector over the period 1975 to 1995. Two empirical methodologies are used in this study. First, the Structure. Conduct - Performance (S-C-P) approach to industrial organisation provides the basic framework for our analysis in the first part of the study. The second research methodology is indus•ry case studies. Two industry studies presented in this study are cigarettes and cement. The study begins with an overview of the evolution of Indonesian trade and industrial policies and the salient features of the manufacturing sector. An analysis of the trends in seller concentration over the period 1975 to 1993 is also provided. The descriptive analysis on seller concentration shows that there is a long-term declining trend in industrial concentration, particularly in those industries that were highly concentrated in the mid-1970s. This provides the backdrop into subsequent statistical analysis of the interrelationship between concentration and other aspects of structure and performance. For this purpose, we specify and estimate a simultaneous equations model of industry structure, conduct and performance. The interrelationships among six key variables (concentration, profitability, foreign ownership, export intensity, import penetration and trade policy) are estimated for two different policy periods; (1) pre-1986 period of heavy trade and industry policy intervention, and (2) post-1986 period of trade and industry liberalisation. A number of interesting findings emerged from the analysis. Trade protection, interacted with seller concentration, was a major determinant of high profitability in concentrated industries in the pre-liberalisation period. This relationship significantly weakened as a result of the late 1980s trade liberalisation. High concentration had a positive influence on effective trade protection, providing some support for the interest group model, which asserts that highly concentrated industries find it easier to lobby government for protection. However, the level of concentration had no significant influence on export intensity or import penetration over and above the other variables considered in the analysis. Finally, our results suggest that market structure factors (economies of scale, capital costs, product differentiation, market size and regional market segmentation) are the major determinants of industrial concentration in Indonesian manufacturing. We could not find a direct relationship between trade policy, regulation and concentration. These insignificant results probably arise due to limitations inherent in cross-sectional tests of the effect of trade policy and regulation on market structure. We tested the effect of international influences (export intensity, import penetration and foreign ownership) on concentration. However, the results turned out to be statistically insignificant in both the pre - and post-liberalisation periods. The study extends the analysis to include the determinants of changes in leading firms' market shares. Changes in market shares are a good indicator of firm rivalry. The results show that regulations in several industries are associated with stable market shares, suggesting that they have reduced competition in these industries. The second part of thesis presents two industry case studies. The focus of the case studies is on the nature of competition among firms, and the influence of regulation on this process. In cement, until the industry was deregulated in 1998, government regulations - distribution and price controls - had created a market structure that closely resembled a cartel. The second case study is cigarettes. This study estimates the effect of advertising expenditure on seven leading firms' market shares, using monthly advertising and market share data. Our results show that advertising competition reallocates sales between leading firms. An important finding of our study is that an equal percentage increase in advertising by all firms will change the distribution of market shares in favour of the more successful, larger firms in the long-run. This arises because larger firms have an 'image advantage' over the smaller firms. This image advantage is an asymmetry that constitutes a barrier to upward mobility of smaller, less-favoured existing firms

The Evolution of the Use of Serum Alpha-fetoprotein in Clinical Liver Cancer Surveillance

Liver cancer is the 6(th) most common cancer and 2(nd) leading cause of cancer-related mortality. In order to improve patient survival early tumor detection is required and this necessitates accurate screening of at risk individuals. In this article we concisely review the methodologies employed for Hepatocellular Carcinoma (HCC) surveillance and how their use has evolved over the last three decades. We focus attention to serum biomarkers, particularly alpha-fetoprotein. We propose that by using an increasingly sophisticated approach to assess dynamic rates of change in biomarkers tailored to individual patients that screening accuracy may be improved. Additional improvements may also be possible by the incorporation of patient clinical data into such personalised screening assessments. These possibilities may hold the promise of improving cancer detection and early curative therapy for the increasing worldwide population at risk of HCC development

The effects of scattering-layer composition, animal size, and numerical density on the frequency response of volume backscatter

Land-associated, sound-scattering layers of mesopelagic micronekton surround the Hawaiian Islands. These animals undergo diel migrations during which they split into multiple, distinct layers that have differences in animal density, taxonomic composition, and size. A video-camera system capable of quantitatively estimating the biological constituency of the layers was combined with a four-frequency, vessel-mounted, echosounder system (38, 70, 120, and 200 kHz) to examine the effects of layer features on the frequency response of volume backscatter. Volume scattering was correlated with animal density at all frequencies, but the effects of animal length and layer composition were frequency-specific. Only scattering at 70 kHz matched the predictions of volume scattering based on the mean echo strengths and densities estimated from camera profiles, suggesting different scattering mechanisms at other frequencies. Differences in volume scattering between pairs of frequencies, however, did strongly correlate with animal length and layer composition and could be used as measures of the biological properties of layers. Applying this technique to the data shows strong partitioning of habitat by taxa and animal size in space and time, indicating the importance of competition in structuring the community.Keywords: Multifrequency, Scattering layer, Acoustics, Volume backscatter, Fisheries, MyctophidsKeywords: Multifrequency, Scattering layer, Acoustics, Volume backscatter, Fisheries, Myctophid