Universiẗat, Diss., 1999--Kaiserslautern.

Trophic cascades involving large terrestrial mammals are very seldom empirically demonstrated. The high species diversity often associated with terrestrial systems is thought to modulate the strength of trophic cascades. In speciose systems, species often vary in vulnerability to consumption, hence some species are less responsive to top-down pressure. African large mammalian herbivores are highly diverse and vary greatly in body size, a characteristic linked to vulnerability to predation. Moreover, Africa is one of the last places to still support megaherbivores, species that have grown large enough to be practically impervious to non-human predation. Thus an African ecosystem is the ideal setting to explore trophic cascades in speciose terrestrial systems. In this study I explored patterns in trophic interaction amongst carnivores, vulnerable mesoherbivore and predator-invulnerable megaherbivores in an intact African savanna at a variety of spatial scales. I examined the mechanistic links between trophic levels at the patch scale through fine scale empirical manipulation of predation risk. In addition, I assessed the landscape scale biological relevance of these trophic interactions through correlative observations over large spatiotemporal scales. I present the first evidence of community level trophic cascades explicitly involving megaherbivores. I demonstrate how megaherbivores’ disregard of predation risk masks the effects of predator-triggered trophic cascades and weakens their impact on the ecosystem. The risk of predation triggered a spatial response in vulnerable species, driving them into safe areas, yet did not influence the space use of megaherbivores. This species-specific spatial response had contrasting effects on nutrient distribution. Vulnerable herbivores’ fear-induced foraging behaviour led to localised nutrient accumulation whereas the foraging behaviour of predator-invulnerable megaherbivores led to nutrient redistribution across the landscape. In addition, the fear-driven spatial differences in mesoherbivore grazing impact and nutrient deposition led to landscape scale changes in the distribution and persistence of herbivore maintained grass communities, so-called grazing lawns. However, the grazing activity of the in-vulnerable megagrazer, white rhino (Ceratotherium simum) weakened the effect of this trophic cascade by creating and maintaining grazing lawns within the risky habitat avoided by mesograzers. This study contributes to our understanding of what drives the variation among patterns of trophic control and provides the first evidence of the modulating influence that megaherbivores have on predator-triggered trophic cascades.

We investigated patterns of power within top management teams (TMTs) by addressing three research questions: What is the shape of TMT power distribution? Is TMT power distribution associated with firm performance? If so, are there distinguishing TMT characteristics between high and low performers? We evaluate these questions using survey data from top managers in 51 hospitals who identified power relationships among their team members. We find that while the CEO is almost always the most powerful TMT member, no teams in our sample have simply a dominant CEO surrounded by powerless team members. We find that the power inequality within a team is positively associated with firm performance. A TMT is more likely to be associated with strong performance when an executive pair garnered most of the power, and when that pair incorporated different world views, as indicated by differences in functional background and industry experience.

The Critical Path Method (CPM) is a widely used tool throughout the construction industry. Since its creation, the use and application of the Critical Path Method has grown tremendously. Up to date, three studies have been performed on how Engineering News Record's (ENR) Top 400 Contractor use CPM. The first study was performed by Edward Davis in 1974 and the second was performed by Amir Tavakoli and Roger Riachi in 1990. This paper is a summary of the third survey, which took place in 2003. The results from the three studies indicate that CPM use by the Top 400 Contractors is growing and the areas of use are expanding. The number one use of CPM throughout the years is detailed planning before the start of construction. Periodic control during construction is another large area of CPM use and has been a large area of growth due to the advances in technology, which make updating a schedule during construction easier and faster than was possible with a mainframe computer in the past. Another area of CPM growth is estimating and bidding for several reasons: use in this area has jumped from 19% to 54% in the past 30 years. An area of concern lately in CPM is the use of precedence diagramming instead of arrow diagramming. Despite the debate, the responding companies found precedence diagrams easier to read, provide more flexibility, and allow for easier use of "smart" relationships (i.e. start-start). / Master of Science

Diese Dissertation beschreibt die Suche nach Resonanzen in der Erzeugung von Top-Quark-Antiquark-Paaren in Proton-Proton-Kollisionen bei einer Schwerpunktsenergie von 8 TeV. Die ausgewerteten Daten entsprechen einer integrierten Luminosität von 20.3 fb-1 und wurden mit dem ATLAS-Detektor am Large Hadron Collider aufgezeichnet. Die Analyse basiert auf Ereignissen mit genau einem geladenen Lepton, fehlendem Transversalimpuls und Teilchenjets im Endzustand. Mithilfe eines künstlichen neuronalen Netzes wird bei gleicher Signaleffizienz eine präzisere Identifikation von hochenergetischen, hadronisch zerfallenden Top-Quarks erzielt als mit bisher verwendeten Verfahren. Darauf aufbauend wird eine Ereignisselektion für die Erkennung von s-Kanal-Resonanzen mit Spin-1 optimiert. Eine verbesserte Abschätzung des erwarteten Untergrunds wird eingeführt, die den Einfluss der systematischen Unsicherheiten verringert. Die untersuchten Massenspektren der rekonstruierten Top-Quark-Paare weisen keine signifikante Abweichung von den Vorhersagen des Standardmodells auf. Im Vergleich zu schnittbasierten Suchstrategien lassen sich für Massen über 2 TeV etwa 30% bessere bayessche obere Ausschlussgrenzen auf den Wirkungsquerschnitt einer schmalen Resonanz eines leptophobischen Z'-Bosons in einem Technicolour-Modell sowie einer breiten Kaluza-Klein-Anregung des Gluons in einem Randall-Sundrum-Modell erzielen. Ausgehend von den beobachteten Ausschlussgrenzen auf den Wirkungsquerschnitt werden eine Z'-Resonanz bis zu einer Masse von 2.5 TeV und ein Randall-Sundrum Kaluza-Klein-Gluon bis zu einer Masse von 2.9 TeV ausgeschlossen. Dies stellt eine Verbesserung gegenüber bisherigen Suchen in vergleichbaren Datensätzen dar. / A search for new heavy particles that decay into top quark-antiquark pairs is presented using an integrated luminosity of 20.3 fb-1 of proton-proton collision data recorded at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the Large Hadron Collider. The analysis considers events with exactly one charged lepton, missing transverse momentum and jets in the final state. An artificial neural network is utilized to identify hadronically decaying top quarks with high Lorentz boost more precisely than established methods at the same signal efficiency. Based on this, a novel method optimized for the detection of s-channel resonances with spin 1 is created. An enhanced estimation of the background expectations is introduced, which reduces the impact of the systematic uncertainties on the analysis. No significant deviation from the background predicted by the Standard Model of particle physics is observed in the invariant mass spectrum of the top-quark pair candidates. Bayesian upper cross-section limits on a narrow resonance from a leptophobic Z' boson in the framework of a technicolour model and a broad Kaluza-Klein excitation of the gluon in a Randall-Sundrum model are both found to be about 30% better at resonance masses of at least 2 TeV relative to a cut-based search strategy. Based on the observed cross-section limits, a topcolour-assisted technicolour Z' boson up to a mass of 2.5 TeV and a Randall-Sundrum Kaluza-Klein gluon up to a mass of 2.9 TeV are excluded. These are the most stringent exclusion limits on the resonance mass as compared to other searches based on similar data sets.

The purpose of the study was to evaluate the impact of the Termination of Pregnancy (TOP) programme in South Africa, using Mpumalanga as focal area, with the view of developing guidelines to assist service providers in the implementation of the Choice on Termination of Pregnancy (CTOP), Act 92 of 1996. The study was conducted in two phases. In phase 1, a qualitative, quantitative, contextual, explorative, descriptive and case study research design was utilised. The purpose was to explore and describe TOP service providers and facility managers’ knowledge regarding the CTOP Act, as well as their experiences and feelings regarding TOP provision, and the feelings and experiences of health care consumers utilising TOP services. Records of attendance regarding the utilisation of the services were also reviewed. Data was collected using unstructured and semi-structured interviews. Phase 2 of the study focused on the development of guidelines to assist in the translation of the CTOP Act to action at service level. The findings revealed that although the TOP programme was operating within the reproductive health for women initiative, TOP service providers and facility managers were not knowledgeable on other legislation that supports the CTOP Act to integrate its implementation. All the participants experienced emotional, physical and psychological discomfort in providing TOP services. Lack of support of the programme also posed a major challenge. These findings formed the basis for the development of the guidelines. / Health Studies / (D.Litt. et Phil. (Health Studies))

The purpose of the study was to evaluate the impact of the Termination of Pregnancy (TOP) programme in South Africa, using Mpumalanga as focal area, with the view of developing guidelines to assist service providers in the implementation of the Choice on Termination of Pregnancy (CTOP), Act 92 of 1996. The study was conducted in two phases. In phase 1, a qualitative, quantitative, contextual, explorative, descriptive and case study research design was utilised. The purpose was to explore and describe TOP service providers and facility managers’ knowledge regarding the CTOP Act, as well as their experiences and feelings regarding TOP provision, and the feelings and experiences of health care consumers utilising TOP services. Records of attendance regarding the utilisation of the services were also reviewed. Data was collected using unstructured and semi-structured interviews. Phase 2 of the study focused on the development of guidelines to assist in the translation of the CTOP Act to action at service level. The findings revealed that although the TOP programme was operating within the reproductive health for women initiative, TOP service providers and facility managers were not knowledgeable on other legislation that supports the CTOP Act to integrate its implementation. All the participants experienced emotional, physical and psychological discomfort in providing TOP services. Lack of support of the programme also posed a major challenge. These findings formed the basis for the development of the guidelines. / Health Studies / (D.Litt. et Phil. (Health Studies))

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The first measurement of the production cross section for a single top quark in association with a W boson with the CMS experiment at the Large Hadron Collider is presented. The analysed data is from proton-proton collisions at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 4.9 fb-1. The analysis focuses on the leptonic final states of the process and implements a cut-based method. The final state consists of two leptons, two neutrinos and a jet from the fragmentation of a b-quark. The primary source of background events arises from tt(overbar) production, followed by Z/gamma* processes. The observed signal has a significance of 3:5sigma and corresponds to a cross section measurement of 14:9+5:0 -5:1 (stat + syst) pb, in agreement with the Standard Model expectations.

Multi-homing is a technology used by Internet Service Provider (ISP) to connect to the Internet via multiple networks. This connectivity enhances the network reliability and service quality of the ISP. However, using multi-networks may imply multiple costs on the ISP. To make full use of the underlying networks with minimum cost, a routing strategy is requested by ISPs. Of course, this optimal routing strategy depends on the pricing regime used by network providers. In this study we investigate a relatively new pricing regime – top-percentile pricing. Under top-percentile pricing, network providers divide the charging period into several fixed length time intervals and calculate their cost according to the traffic volume that has been shipped during the θ-th highest time interval. Unlike traditional pricing regimes, the network design under top-percentile pricing has not been fully studied. This paper investigates the optimal routing strategy in case where network providers charge ISPs according to top-percentile pricing. We call this problem the Top-percentile Traffic Routing Problem (TpTRP). As the ISP cannot predict next time interval’s traffic volume in real world application, in our setting up the TpTRP is a multi-stage stochastic optimisation problem. Routing decisions should be made at the beginning of every time period before knowing the amount of traffic that is to be sent. The stochastic nature of the TpTRP forms the critical difficulty of this study. In this paper several approaches are investigated in either the modelling or solving steps of the problem. We begin by exploring several simplifications of the original TpTRP to get an insight of the features of the problem. Some of these allow analytical solutions which lead to bounds on the achievable optimal solution. We also establish bounds by investigating several “naive” routing policies. In the second part of this work, we build the multi-stage stochastic programming model of the TpTRP, which is hard to solve due to the integer variables introduced in the calculation of the top-percentile traffic. A lift-and-project based cutting plane method is investigated in solving the SMIP for very small examples of TpTRP. Nevertheless it is too inefficient to be applicable on large sized instances. As an alternative, we explore the solution of the TpTRP as a Stochastic Dynamic Programming (SDP) problem by a discretization of the state space. This SDP model gives us achievable routing policies on small size instances of the TpTRP, which of course improve the naive routing policies. However, the solution approach based on SDP suffers from the curse of dimensionality which restricts its applicability. To overcome this we suggest using Approximate Dynamic Programming (ADP) which largely avoids the curse of dimensionality by exploiting the structure of the problem to construct parameterized approximations of the value function in SDP and train the model iteratively to get a converged set of parameters. The resulting ADP model with discrete parameter for every time interval works well for medium size instances of TpTRP, though it still requires too long to be trained for large size instances. To make the realistically sized TpTRP problem solvable, we improve on the ADP model by using Bezier Curves/Surfaces to do the aggregation over time. This modification accelerates the efficiency of parameter training in the solution of the ADP model, which makes the realistically sized TpTRP tractable.