In the context of nutrient cycling in soil, plant-mediated mineralisation of carbon (C) and nitrogen (N) is poorly understood. The broad focus of this thesis was to investigate the potential importance of plant-mediated mineralisation (i.e.priming) on C and N mineralisation in soils with contrasting crop productivities. The studies focus on two soils, which had similar chemical and physical properties but contrasting plant productivities relating to their N supply capacity. These soils were used to investigate the potential importance of priming processes in contributing to the contrasting capacities of these soils to supply N for plant growth. 13C and 15N stable isotopes were used to measure specific gross C and N fluxes. Sole C or N and combined C with N treatments were established to disentangle the effect of carbon and nitrogen availability on plant-mediated mineralisation. The addition of labile C increased gross carbon and nitrogen fluxes from native soil organic matter (SOM) but the effect was soil specific. The addition of nitrogen did not affect SOM mineralisation in either soil. The much lower C-to-N ratio of the 'primed' flux compared to the 'basal' flux indicated that the primed flux utilises different OM pools highlighting that primed and basal mineralisation may be distinct processes. The priming response (i.e. positive or negative and associated mechanisms) was different depending on carbon and nitrogen supply to the microbial community. Overall, the studies in this thesis places the microbial community as the focal point of soil N supply. This data strongly supports the concept that the release of labile carbon from plant roots functions as a nutrient acquisition response, increasing mineralisation of SOM. From the data a conceptual model of priming mechanisms, based on nutrient availability to the microbial community, was established. This could be used as the foundation to develop key concepts for sustainable agricultural practice.

Normal coloring - an equivalent version of Petersen coloring - is a special proper 5-edge-coloring of cubic graphs. Every edge in a normally colored graph is normal, i.e. it uses together with its four neighbours either only three colors or all five colors. Jaeger conjectured that every bridgeless cubic graph has a normal coloring. This conjecture, if true, imply for example Cycle double cover conjecture. Here we solve a weakened version of Jaeger's problem. We are looking for a proper 5-edge-coloring such that at least a part of the edges is normal. We show a coloring of generalized prisms with two thirds of the edges normal and a coloring of graphs without short cycles with almost half of the edges normal. Then we propose a new approach to normal coloring - chains. We use chains to prove that there cannot be only one single mistake in an almost normally colored graph. We also prove some statements about cuts in a normally colored graph which also follow from nowhere-zero Petersen flow. Finally, we examine a four-cycle in a normally colored graph. 1

No description available.

Le travail présenté ici a pour but d’évaluer les mécanismes microstructuraux liés à l’amorçage de l’endommagement par fatigue d’un acier à usage pétrolier. Les microdéformations et les contraintes résiduelles (macrocontraintes) ont été déterminées par diffraction des rayons X en temps réel pendant des essais de fatigue en flexion alternée sur des éprouvettes plates prélevées dans la paroi d’un tube neuf. Les microdeformations sont estimées à partir de mesures de la largeur de corde à mi-hauteur (LCMH) d’un pic de diffraction et les contraintes résiduelles à partir du déplacement du pic. Les essais de fatigue sont réalisés pour cinq niveaux de contraintes différents. On observe trois stades de variation pendant l’évolution des microdeformations. On montre que leur amplitude et leur durée sont proportionnelles au niveau de contrainte alternée. Des variations similaires sont observées pour les contraintes résiduelles, avec des durées identiques à celles des microdéformations. Des évolutions dans la densité et la répartition des dislocations ont été observées par microscopie électronique en transmission à l’aide de la technique du faisceau d’ions focalisés. Pour comprendre le rôle de la structure initiale, des essais de fatigue sur éprouvettes recuites ont été réalisés dans les mêmes conditions d’essai. Là encore trois stades d’évolution sont observées mais avec un premier stade inversé du fait de l’état initial du réseau de dislocations. Les résultats obtenus sont très encourageants pour la prise en compte des évolutions microstructurales dans l’établissement d’un futur indicateur de dommage de la phase d’amorçage en fatigue à grand nombre de cycles des matériaux. / The present work aims to evaluate the microstructural mechanisms associated with the initiation of fatigue damage of steels used in the oil and gas industry. Microdeformations and residual stresses (macrostresses) were evaluated by X-ray diffraction in real time during alternating bending fatigue tests performed on flat test pieces taken from a pipe sample. Microdeformations were estimated from measurements of the full width at half maximum (FWHM) of the diffraction peak and residual stresses from the peak displacement. The fatigue tests were performed at five different stress levels. Three stages of changes during the evolution of microdeformation were detected. We show that their amplitude and duration are proportional to the level of alternating stress. Similar variations were observed for the residual stresses, with duration identical to those of the microdeformation. Changes in the density and distribution of dislocations were observed by transmission electron microscopy using the technique of focused ion beam. To understand the role of the initial structure, fatigue tests on annealed samples were performed under the same test conditions. Again, three stages of changes are observed but with an increase of the microdeformations instead of a decrease during the first stage due to the initial state of the dislocation network. The results are very encouraging for the consideration of the microstructural evolutions in the construction of a future counter of fatigue damage initiation in materials.

M.Com. / In this treatise, research is done into the various theories with regard to the business phenomenon and the various phases of the business cycle according to various economic indicators. A characteristic of the South African economy as well as other capitalistic systems, is that business indicators have a unstable tendency. Times of prosperity are followed by times of recession when unemployment, production, prices, profits and economic welfare, decline. The recession is again followed by times of prosperity which are characterised by increases in job opportunities as well as rising prices, profits and living standards. This wave like movement in economic activity is known as the business phenomenon. There are certain forces which directly affect the business cycle - some of them force it upwards while others force it downwards. The direction of the business cycle depends on the dominant forces. As soon as the forces are exhausted, a turn in the cycle results. The series regarding the business cycle are classified according to specific schools of thought in order to investigate their development as well as the main causes of the wave like motion in economic activities. A simple classification can be made by dividing the theories into those which preceded the publication of J.M. Keynes' General Theory of Employment, Interest and Money in 1936 as the Classical or Pre-Keynesian, and those which form the Keynesian school of thought and which appeared since the thirties as the Post-Keynesian theories. Firstly the Pre-Keynesian business cycle theories are discussed with reference to amongst others the demand theories, supply theories, the monetary theories and. the impulse theories. Thereafter the Post-Keynesian business cycle theories are discussed, that is those of Hicks, Kalecki, Goodwin and Duesenberry. An examination of the different phases of the business cycle implies a study of the movement of economic data in a upward and downward direction. Four phases can be discerned within the business cycle namely: the upward phase, the upper turning point, the downward phase and the lower turning point. The position of the various indicators will determine in which phase a country's economy finds itself. Economic activities are never stagnant, with the result that a period of prosperity may be followed panicking or a pez'Lod of depression. Several economic indicators may indicate this sequence, for instance unemployment, declining output and profit margins, and the resulting loss of income on the national level. As soon as the lower turning point is reached, the economy starts to recover and a period of prosperity again follows. It can thus be argued that the business cycle is a result of interaction between demand and supply. The business cycle has a significant result on the economy as a whole. It influences the prosperity of the country and even that of the undertaking, its manpower position, its capacity occupation and its factors of production. Every individual is effected to the extend that his disposable income is directly determined by the position of the business cycle. The phases of the business cycle and the inclining and declining motion of economic data contains the nucleus of the effect of the external environment on the undertaking.

Thesis advisor: Ben Howard / The results in this dissertation are on the intersection behavior of certain special cycles on GSpin(n, 2) Shimura varieties for n > 1. In particular, we will determine when the intersection of the special cycles defined by a collection of special endomorphisms consists of isolated points in terms of the fundamental matrix of this collection. These generalize the corresponding results in the lower dimensional cases proved by Kudla and Rapoport. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Mathematics.

Thesis advisor: Peter Ireland / My dissertation consists of three papers on business cycles in developing countries. All the papers are different from each other and emphasize different aspects of understanding economic fluctuations in developing countries. The first paper is titled `Medium Term Business Cycles in Developing Countries' (with Diego Comin, Norman Loayza and Luis Serven). This paper models the link between business cycle fluctuations in developed countries with fluctuations in developing countries. Business cycle fluctuations in developed economies tend to have large and persistent effects on developing countries. We study the transmission of business cycle fluctuations from developed to developing economies with a two-country asymmetric DSGE model with two important features: (i) endogenous and slow diffusion of technologies from the developed to the developing country, and (ii) adjustment costs to investment flows. Consistent with the model, we observe that the flow of technologies from developed to developing economies co-moves positively with output in both developed and developing countries. After calibrating the model to Mexico and the U.S., it can explain the following stylized facts: (i) U.S. and Mexican output co-move more than consumption; (ii) U.S. shocks have a larger effect on Mexico than in the U.S.; (iii) U.S. business cycles lead over medium term fluctuations in Mexico; (iv) Mexican consumption is more volatile than output. The second paper of my dissertation is based on a price setting survey conducted by the State Bank of Pakistan (Central Bank). The paper is titled `Price-Setting Discoveries: Results from a Developing Country' (with M. Ali Choudhary, Abdul Faheem, Nadeem Hanif, and Saima Naeem) present the results of 1189 structured face-to-face interviews about price-setting behavior of the formal firms in the manufacturing and services sector of Pakistan. The key findings of the survey are:the frequency of price change is high in Pakistan, lowering the real impact of monetary policy. Price rigidity is mainly explained by firms caring about relative prices and the persistence of shocks. The exchange-rate and cost shocks are more important than financial and demand shocks for both setting prices and also the readiness with which these shocks pass-through to the economy. Formal sector firms with connections to the informal sector, especially through demand, have a lower probability of price adjustment. The lack of taxes and compliance with tax regime, i.e. enforcement are held responsible for existence of the informal sector by formal sector firms. The results from this paper provided motivation for the last paper of my dissertation about understanding and modeling the business cycle fluctuations in a developing economy like Pakistan. The last paper of my dissertation is titled `Modeling Business Cycles in Pakistan: A First Step'. In this paper, I establish the nature of short-run fluctuations of the Pakistani economy over the period of 1960-2010. There have been significant changes in the nature of the Pakistani economy over the last few decades. Therefore, I focus my detailed analysis on the last few decades where it seems more appropriate to investigate the nature and causes of business cycles in Pakistan. Furthermore, I evaluate the performance of a typical RBC and an augmented RBC model with an exogenous FDI shock in explaining cyclical fluctuations experienced by the Pakistani economy. I find that a simple RBC model does badly in terms of matching relevant second order moments of short run fluctuations as depicted by the data. However, augmented RBC model performs better compared to the simple RBC model. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / One of the lessons from the recent global financial crisis is the importance of macro-financial linkage in the economy. Based on this background, this dissertation analyzes the effects of financial frictions on the aggregate activities of the economy, wealth distribution and business cycles. The first chapter investigates the effects of financial development on aggregate capital accumulation and wealth distribution by constructing a heterogeneous-agent general equilibrium model with two idiosyncratic risks, endogenous occupational choice and Holmstrom and Tirole (1999) type financial contracts to prevent moral hazard issue. The benchmark model is calibrated to match the empirical data, where the wealth distribution has a right-hand fat tail and a small number of entrepreneurs hold a large amount of wealth. We find that financial development measured by decrease of monitoring cost contributes to the economy's higher capital accumulation and lower wealth Gini coefficient. The second chapter develops a dynamic stochastic general equilibrium (DSGE) model with financial frictions arising from the moral hazard problem as in Holmstrom and Tirole (1997) together with regulatory capital requirements on the banks. In contrast with the standard BGG (1999) financial accelerator model, we consider the agency problem from hidden action and regulatory capital requirements on the banks in order to examine whether changes of regulatory capital requirements result in credit crunches in the transmissions of aggregate technology and monetary policy shocks. The third chapter explores quantitative experiments using the above DSGE model. We examine whether there exists a "financial accelerator" effect from these kinds of financial frictions and a "credit crunch" from shocks. We find that there exists a "financial accelerator" effect and that financial deepening measured by decrease of financial intermediary's monitoring costs could contribute to mitigating business cycle fluctuations. In particular, no financial frictions with zero monitoring cost could decrease the variance of aggregate investment to around 18.5%. We also find that imposing and increasing capital requirements on the banks could cause decrease of bank's lending ("credit crunch"), thereby amplifying business cycles. / 2031-01-02

Research report presented to the Unisa School of Business Leadership / The results of the study show that as posited in the research statement, media spend is positive in relation to both the direct and indirect business cycles variables. This pattern of increased media spend is only maintained during the up-phases of the business cycle, but tends to level off during the down-phases.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Alfred P. Sloan School of Management. / Vita. / Bibliography: leaves 257-265. / Ph.D.