Measurement of the Top Quark Mass using Dilepton Events and a Neutrino Weighting Algorithm with the D0 Experiment at the Tevatron (Run II)

Elementary particle physics raises questions that are several thousand years old. What are the fundamental components of matter and how do they interact? These questions are linked to the question of what happened in the very first moments after the creation of the universe. Modern physics systematically tests nature to find answers to these and other fundamental questions. Precise theories are developed that describe various phenomena and at the same time are reduced to a few basic principals of nature. Simplification and reduction have always been guiding concepts of physics. The interplay between experimental data and theoretical descriptions led to the Standard Model of elementary particle physics. It summarizes the laws of nature and is one of most precise descriptions of nature achieved by mankind. Despite the great success of the Standard Model it is not the ultimate theory of everything. Models beyond the Standard Model try to unify all interactions in one grand unified theory. The number of free parameters is attempted to be reduced. Gravity is attempted to be incorporated. Extensions to the Standard Model like supersymmetry address the so-called hierarchy problem. Precision measurements are the key for searches of new particles and new physics. A powerful tool of experimental particle physics are particle accelerators. They provide tests of the Standard Model at smallest scales. New particles are produced and their properties are investigated. In 1995 the heaviest known elementary particle, called top quark, has been discovered at Fermilab. It differs from all other lighter quarks due to the high mass and very short lifetime. This makes the top quark special and an interesting object to be studied. A rich program of top physics at Fermilab investigates whether the top quark is really the particle as described by the Standard Model. The top quark mass is a free parameter of the theory that has been measured precisely. This thesis presents a precise measurement of the top quark mass by the D0 experiment at Fermilab in the dilepton final states. The comparison of the measured top quark masses in different final states allows an important consistency check of the Standard Model. Inconsistent results would be a clear hint of a misinterpretation of the analyzed data set. With the exception of the Higgs boson, all particles predicted by the Standard Model have been found. The search for the Higgs boson is one of the main focuses in high energy physics. The theory section will discuss the close relationship between the physics of the Higgs boson and the top quark

The importance of radiological controls of anastomoses after upper gastrointestinal tract surgery - a retrospective cohort study

<p>Abstract</p> <p>Introduction</p> <p>This study was designed to analyze whether routine radiological controls of anastomoses in the upper gastrointestinal tract an early detection of anastomotic leaks.</p> <p>Patients and Methods</p> <p>135 patients who underwent upper gastrointestinal tract surgery were retrospectively analyzed. Patients in the first group (n = 55) underwent routine radiological control of the anastomoses. In the second group (n = 80) the radiological control was only performed in case of clinical symptoms or signs of anastomotic leaks.</p> <p>Results</p> <p>The incidence of anastomotic leaks in the patients seen by us was 5.2%, equivalent to 7 of 135 patients In Group 1 leaks were seen in 4 of 55 patients (7,2%) in group 2 leaks were seen in 3 of 80 (3,8%). The radiological control of the anastomoses with contrast swallow showed the leakage in two cases. Twice the results were false negative. The sensitivity of computed tomography was 100%.</p> <p>Discussion</p> <p>Routine radiological control of anastomoses with contrast swallow only has low sensitivity. This procedure should not be performed routinely any more.</p> <p>The radiological control should be used in cases with signs of anastomotic leakage or with postoperatively impaired gastrointestinal passage.</p

Making environmental assessments of biomass production systems comparable worldwide

Global demand for agricultural and forestry products fundamentally affects regional land-use change associated with environmental impacts (EIs) such as erosion. In contrast to aggregated global metrics such as greenhouse gas (GHG) balances, local/regional EIs of different agricultural and forestry production regions need methods which enable worldwide EI comparisons. The key aspect is to control environmental heterogeneity to reveal man-made differences of EIs between production regions. Environmental heterogeneity is the variation in biotic and abiotic environmental conditions. In the present study, we used three approaches to control environmental heterogeneity: (i) environmental stratification, (ii) potential natural vegetation (PNV), and (iii) regional environmental thresholds to compare EIs of solid biomass production. We compared production regions of managed forests and plantation forests in subtropical (Satilla watershed, Southeastern US), tropical (Rufiji basin, Tanzania), and temperate (Mulde watershed, Central Germany) climates. All approaches supported the comparison of the EIs of different land-use classes between and within production regions. They also standardized the different EIs for a comparison between the EI categories. The EIs for different land-use classes within a production region decreased with increasing degree of naturalness (forest, plantation forestry, and cropland). PNV was the most reliable approach, but lacked feasibility and relevance. The PNV approach explicitly included most of the factors that drive environmental heterogeneity in contrast to the stratification and threshold approaches. The stratification approach allows consistent global application due to available data. Regional environmental thresholds only included arbitrarily selected aspects of environmental heterogeneity;they are only available for few EIs. Especially, the PNV and stratification approaches are options to compare regional EIs of biomass or crop production such as erosion, biodiversity, or water quality impacts worldwide and thereby complement existing metrics assessing global EIs such as GHG emissions

Making environmental assessments of biomass production systems comparable worldwide

Global demand for agricultural and forestry products fundamentally affects regional land-use change associated with environmental impacts (EIs) such as erosion. In contrast to aggregated global metrics such as greenhouse gas (GHG) balances, local/regional EIs of different agricultural and forestry production regions need methods which enable worldwide EI comparisons. The key aspect is to control environmental heterogeneity to reveal man-made differences of EIs between production regions. Environmental heterogeneity is the variation in biotic and abiotic environmental conditions. In the present study, we used three approaches to control environmental heterogeneity: (i) environmental stratification, (ii) potential natural vegetation (PNV), and (iii) regional environmental thresholds to compare EIs of solid biomass production. We compared production regions of managed forests and plantation forests in subtropical (Satilla watershed, Southeastern US), tropical (Rufiji basin, Tanzania), and temperate (Mulde watershed, Central Germany) climates. All approaches supported the comparison of the EIs of different land-use classes between and within production regions. They also standardized the different EIs for a comparison between the EI categories. The EIs for different land-use classes within a production region decreased with increasing degree of naturalness (forest, plantation forestry, and cropland). PNV was the most reliable approach, but lacked feasibility and relevance. The PNV approach explicitly included most of the factors that drive environmental heterogeneity in contrast to the stratification and threshold approaches. The stratification approach allows consistent global application due to available data. Regional environmental thresholds only included arbitrarily selected aspects of environmental heterogeneity;they are only available for few EIs. Especially, the PNV and stratification approaches are options to compare regional EIs of biomass or crop production such as erosion, biodiversity, or water quality impacts worldwide and thereby complement existing metrics assessing global EIs such as GHG emissions

From Visualization to Visually Enabled Reasoning

Interactive Visualization has been used to study scientific phenomena, analyze data, visualize information, and to explore large amounts of multi-variate data. It enables the human mind to gain novel insights by empowering the human visual system, encompassing the brain and the eyes, to discover properties that were previously unknown. While it is believed that the process of creating interactive visualizations is reasonably well understood, the process of stimulating and enabling human reasoning with the aid of interactive visualization tools is still a highly unexplored field. We hypothesize that visualizations make an impact if they successfully influence a thought process or a decision. Interacting with visualizations is part of this process. We present exemplary cases where visualization was successful in enabling human reasoning, and instances where the interaction with data helped in understanding the data and making a better informed decision. We suggest metrics that help in understanding the evolution of a decision making process. Such a metric would measure the efficiency of the reasoning process, rather than the performance of the visualization system or the user. We claim that the methodology of interactive visualization, which has been studied to a great extent, is now sufficiently mature, and we would like to provide some guidance regarding the evaluation of knowledge gain through visually enabled reasoning. It is our ambition to encourage the reader to take on the next step and move from information visualization to visually enabled reasoning

Infection after Acute Ischemic Stroke: Risk Factors, Biomarkers, and Outcome

Background. The activation of inflammatory cascades triggered by ischemic stroke may play a key role in the development of infections. Methods. Patients admitted with ischemic stroke within 24 hours were prospectively enrolled. Biomarkers of infection were measured on days 1, 3, and 5. The patients were continuously monitored for predefined infections. Results. Patients with infection were older (OR 1.06 per year, 95% CI 1.01–1.11) and had a higher National Institute of Health Stroke Scale Score (NIHSS, OR 1.21, 95% CI 1.10–1.34), localization in the insula, and higher stroke volumes on diffusion-weighted imaging. The maximum temperature on days 1 and 3, leukocytes, interleukin-6, lipopolysaccharide-binding protein on days 1, 3, and 5, C-reactive protein on days 3 and 5, and procalcitonin on day 5 were higher and HLA-DR-expression on monocytes on days 1, 3, and 5 lower in patients with infection. Age and NIHSS predicted the development of infections. Infection was an independent predictor of poor functional outcome. Conclusions. Severe stroke and increasing age were shown to be early predictors for infections after stroke