Interactions of Puccinia hordei and Erysiphe graminis on barley

Imperial Users onl

Mutual Interlacing and Eulerian-like Polynomials for Weyl Groups

We use the method of mutual interlacing to prove two conjectures on the real-rootedness of Eulerian-like polynomials: Brenti's conjecture on $q$-Eulerian polynomials for Weyl groups of type $D$, and Dilks, Petersen, and Stembridge's conjecture on affine Eulerian polynomials for irreducible finite Weyl groups. For the former, we obtain a refinement of Brenti's $q$-Eulerian polynomials of type $D$, and then show that these refined Eulerian polynomials satisfy certain recurrence relation. By using the Routh--Hurwitz theory and the recurrence relation, we prove that these polynomials form a mutually interlacing sequence for any positive $q$, and hence prove Brenti's conjecture. For $q=1$, our result reduces to the real-rootedness of the Eulerian polynomials of type $D$, which were originally conjectured by Brenti and recently proved by Savage and Visontai. For the latter, we introduce a family of polynomials based on Savage and Visontai's refinement of Eulerian polynomials of type $D$. We show that these new polynomials satisfy the same recurrence relation as Savage and Visontai's refined Eulerian polynomials. As a result, we get the real-rootedness of the affine Eulerian polynomials of type $D$. Combining the previous results for other types, we completely prove Dilks, Petersen, and Stembridge's conjecture, which states that, for every irreducible finite Weyl group, the affine descent polynomial has only real zeros.Comment: 28 page

Existence of subgame perfect equilibrium with public randomization: A short proof

Consider a multi-stage game where each player has a compact choice set and payoffs are continuous in all such choices. Harris, Reny and Robson (1995) prove existence of a subgame perfect equilibrium as long as a public correlation device is added to each stage. They achieve this by showing that the subgame perfect equilibium path correspondence is upper hemicontinuous. The present paper gives a short proof of existence that focuses on equilibrium payoffs rather than paths.Existence

The Need for Speed: Impacts of Internet Connectivity on Firm Productivity

Fast internet access is widely considered to be a productivity-enhancing factor. Internet access speeds vary regionally within countries and even within cities. Despite articulate pleas for network upgrades to accelerate internet access, there is little rigorous research quantifying benefits to individual firms that arise from upgraded internet connectivity. We use a large New Zealand micro-survey of firms linked to unit record firm financial data to determine the impact that differing types of internet access have on firm productivity. Propensity score matching is used to control for factors, including the firm’s (lagged) productivity, that determine firms’ internet access choices. Having matched firms, we examine the productivity impacts that arise when a firm adopts different types (speeds) of internet connectivity. Broadband adoption is found to boost productivity but we find no productivity differences across broadband type. The results provide the first firm-level estimates internationally of the degree of productivity gains sourced from upgraded internet access.Internet, broadband, productivity

Re-examining the Determinants of Small- and Medium-sized Enterprises’ Performance Profitability and Growth: A Case of Ghana

Abstract This paper looks at the effects of the six main independent variables (sources of finance, social capital, ownership type, government policies, age and size, and human capital) on the main dependent variable (performance profitability and growth) of small and medium-sized enterprises (SMEs) in Ghana (the context for the project). The thesis is in three (3) parts. Project One (1) is the thematic literature review of the independent and dependent variables in this study. The review introduces the literature on the characteristics of SMEs in Ghana, and refers to SMEs in the developed world in order to compare the contributions and characteristics of SMEs worldwide. Information about the Ghanaian economy is provided, in order to set the context of the study. In addition, project one reviews the manufacturing and hospitality sectors and notes reasons for which they are the focus of this project. It ends with a presentation of summary of the review. Within this paper, the terms ‘firm’, ‘organisation’ and ‘enterprise’ are used interchangeably. Project Two (2) is concerned with the methodology. It is a cross-sectional study and uses interview for data collection. It emphasises the descriptive nature of the work, the suitability and importance of all the necessary processes like snowball technique, sampling methods, and data analysis. Nvivo 8, a computer assisted qualitative data analysis software (CAQDAS) is the primary software that is used for the analysis. Project Three (3) is the result of the study. It exposes the impermeable wall separating lenders and Government and SMEs as the former lack better knowledge of the latter. The reluctance of SMEs to outsource funding is consistent with the pecking order theory because of the negative consequences of borrowing on their performance profitability and growth. Unclear, unhelpful and unsuitable government policy framework has led to eschewal of such policies by SMEs. Social and human capitals affect the performance of the SMEs. Good social networks benefits SMEs as they reduce operating costs. Skilled and highly educated employees create positive value in the companies. The study is critical of the style of ownership structure of most SMEs. The “more is better” is very simplistic as age and size had mixed effect on SME performance profitability and growth in the study

A sensitivity analysis of the prediction of the nitrogen fertilizer requirement of cauliflower crops using the HRI WELL_N computer model

HRI WELL_N is an easy to use computer model, which has been used by farmers and growers since 1994 to predict crop nitrogen (N) requirements for a wide range of agricultural and horticultural crops. A sensitivity analysis was carried out to investigate the model predictions of the N fertilizer requirement of cauliflower crops, and, at that rate, the yield achieved, yield response to the fertilizer applied, N uptake, NO3-N leaching below 30 and 90 cm and mineral N at harvest. The sensitivity to four input factors – soil mineral N before planting, mineralization rate of soil organic matter, expected yield and duration of growth – was assessed. Values of these were chosen to cover ranges between 40% and 160% of values typical for field crops of cauliflowers grown in East Anglia. The assessments were made for three soils – sand, sandy loam and silt – and three rainfall scenarios – an average year and years with 144% or 56% of average rainfall during the growing season. The sensitivity of each output variable to each of the input factors (and interactions between them) was assessed using a unique ‘sequential' analysis of variance approach developed as part of this research project. The most significant factors affecting N fertilizer requirement across all soil types/rainfall amounts were soil mineral N before planting and expected yield. N requirement increased with increasing yield expectation, and decreased with increasing amounts of soil mineral N before planting. The responses to soil mineral N were much greater when higher yields were expected. Retention of N in the rooting zone was predicted to be poor on light soils in the wettest conditions suggesting that to maximize N use, plants needed to grow rapidly and have reasonable yield potential. Assessment of the potential impacts of errors in the values of the input factors indicated that poor estimation of, in particular, yield expectation and soil mineral N before planting could lead to either yield loss or an increased level of potentially leachable soil mineral N at harvest. The research demonstrates the benefits of using computer simulation models to quantify the main factors for which information is needed in order to provide robust N fertilizer recommendations

The logical connection argument

Thesis (M.A.) -- University of Adelaide, Dept. of Philosophy, 197

Homeownership and Social Capital in New Zealand

Does homeownership affect individual social capital and thereby influence local outcomes? Following DiPasquale and Glaeser, a body of literature suggests that homeownership is positively related to social capital formation. Homeowners have an incentive to engage in the local community in order to preserve or enhance the value of their housing asset. Moreover, homeownership creates barriers to geographic mobility, which increases the present value of the expected stream of benefits from local community social capital. We test the homeownership hypothesis alongside other individual, household and locational determinants of social capital using unique data created by merging the 2006 and 2008 samples of the New Zealand Quality of Life survey. The measures of social capital used in our analysis include trust in others, participation in social networks, attitude towards local governance and sense of community. Since homeownership is not randomly assigned, we complement our regression models with propensity score matching to control for selection effects. The results confirm that homeownership exerts considerable positive impact in the formation of social capital in New Zealand communities. In raising accountability of local government it does, however, lead to reduced satisfaction by homeowners in the performance of local councils.social capital, homeownership, New Zealand, matching methods