Stability criteria for nonlinear fully implicit differential-algebraic systems

This thesis contributes to the qualitative theory of differential-algebraic equations(DAEs) by providing new stability criteria for solutions of a class of nonlinear, fully implicit DAEs with a properly stated derivative term and tractability index one and two. A generalization of the Andronov-Witt Theorem addressing orbital stability is proved. To this purpose, a state space representation of differential-algebraic systems based on the tractability index is developed which has advantageous properties, e.g. moderate smoothness requirements, commutativity with linearization and an autonomous structure in case of autonomous DAEs. It allows a suitable definition of characteristic multipliers referring to the inherent dynamics, but given in terms of the DAE. Furthermore, the fundamentals of Lyapunov's direct method with respect to diffe- rential-algebraic systems are worked out. Novel denitions of Lyapunov functions for differentiable solution components of a DAE are stated, where the monotoni- cally decreasing total time derivative of a Lyapunov function along DAE solutions is expressed in terms of the original system. The topology of the domain of the inherent dynamics turns out to be decisive for nonlocal existence of solutions given a Lyapunov function. As a result, practical stability criteria for bounded solutions of autonomous DAEs and for general solutions of DAEs with bounded partial derivatives of the constitutive function arise. Known contractivity denitions for DAEs can be interpreted in the context of this approach

Cardiovascular Consequences of Unfair Pay

This paper investigates physiological responses to perceptions of unfair pay. In a simple principal agent experiment agents produce revenue by working on a tedious task. Principals decide how this revenue is allocated between themselves and their agents. In this environment unfairness can arise if an agent's reward expectation is not met. Throughout the experiment we record agents' heart rate variability. Our findings provide evidence of a link between perceived unfairness and heart rate variability. The latter is an indicator of stress-related impaired cardiac autonomic control, which has been shown to predict coronary heart diseases in the long run. Establishing a causal link between unfair pay and heart rate variability therefore uncovers a mechanism of how perceptions of unfairness can adversely affect cardiovascular health. We further test potential adverse health effects of unfair pay using data from a large representative data set. Complementary to our experimental findings we find a strong and highly significant association between health outcomes, in particular cardiovascular health, and fairness of pay.fairness, social preferences, inequality, heart rate variability, health, experiments, SOEP

Cardiovascular Consequences of Unfair Pay

This paper investigates physiological responses to perceptions of unfair pay. In a simple principal agent experiment agents produce revenue by working on a tedious task. Principals decide how this revenue is allocated between themselves and their agents. In this environment unfairness can arise if an agent's reward expectation is not met. Throughout the experiment we record agents' heart rate variability. Our findings provide evidence of a link between perceived unfairness and heart rate variability.The latter is an indicator of stressrelated impaired cardiac autonomic control, which has been shown to predict coronary heart diseases in the long run. Establishing a causal link between unfair pay and heart rate variability therefore uncovers a mechanism of how perceptions of unfairness can adversely affect cardiovascular health. Wefurther test potential adverse health effects of unfair pay using data from a large representative data set. Complementary to our experimental findings we find a strong and highly significant association between health outcomes, in particular cardiovascular health, and fairness of pay.Fairness, social preferences, inequality, heart rate variability, health, experiments, SOEP

Shiga toxin producing Escherichia coli: identification of non-O157:H7-Super-Shedding cows and related risk factors

<p>Abstract</p> <p>Background</p> <p>Shiga toxin producing <it>Escherichia coli </it>(STEC) are an important cause of human gastro-enteritis and extraintestinal sequelae, with ruminants, especially cattle, as the major source of infection and reservoir. In this study, the fecal STEC shedding of 133 dairy cows was analyzed over a period of twelve months by monthly sampling with the aim to investigate shedding patterns and risk factors.</p> <p>Results</p> <p>Overall, 24.7% (in total 407) of 1,646 fecal samples were tested positive for <it>stx </it>by PCR with inner-herd prevalences on the different farms of 11.1% to 32.3%. At individual levels, cows were <it>stx</it>-positive on zero to eight consecutive samplings. According to a strictly longitudinal definition of Super-Shedding, in the present study 14 cows were identified as Super-Shedders of non-O157 serotypes.</p> <p>Significant risk factors for the shedding of STEC were the month of sampling, the number of lactations and days in lactation, the nutritional condition, the somatic cell count and the content of protein in milk. Most notably, the presence of STEC Super-Shedding cows in the herd was a significant risk factor, revealing that STEC Super-Shedding is not restricted to STEC O157:H7 alone.</p> <p>Conclusions</p> <p>These data have implications for possible interventions, as removing single non-O157:H7 STEC Super-Shedding cattle from farms would significantly reduce STEC burden.</p

From Stable to Lab—Investigating Key Factors for Sudden Deaths Caused by Streptococcus suis

Swine stocks are endemically infected with the major porcine pathogen Streptococcus (S.) suis. The factors governing the transition from colonizing S. suis residing in the tonsils and the exacerbation of disease have not yet been elucidated. We analyzed the sudden death of fattening pigs kept under extensive husbandry conditions in a zoo. The animals died suddenly of septic shock and showed disseminated intravascular coagulopathy. Genotypic and phenotypic characterizations of the isolated S. suis strains, a tonsillar isolate and an invasive cps type 2 strain, were conducted. Isolated S. suis from dead pigs belonged to cps type 2 strain ST28, whereas one tonsillar S. suis isolate harvested from a healthy animal belonged to ST1173. Neither S. suis growth, induction of neutrophil extracellular traps, nor survival in blood could explain the sudden deaths. Reconstituted blood assays with serum samples from pigs of different age groups from the zoo stock suggested varying protection of individuals against pathogenic cps type 2 strains especially in younger pigs. These findings highlight the benefit of further characterization of the causative strains in each case by sequence typing before autologous vaccine candidate selection

Detection of stx1 and stx2 Genes in Pennsylvanian White-Tailed Deer

Shiga toxin-producing E. coli carrying the stx1 and/or stx2 genes can cause multi-symptomatic illness in humans. A variety of terrestrial and aquatic environmental reservoirs of stx have been described. Culture based detection of microbes in deer species have found a low percentage of samples that have tested positive for Stx-producing microbes, suggesting that while deer may contain these microbes, their overall abundance in deer is low. In this study, quantitative PCR (qPCR) was utilized to test for the presence of stx genes in white-tailed deer fecal matter in western Pennsylvania. In this culture independent screening, nearly half of the samples tested positive for the stx2 gene, with a bias towards samples that were concentrated with stx2. This study, while limited in scope, suggests that deer may be a greater reservoir for stx than was previously thought