Stefan F. Keller

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1. Overview Autonomous navigation in natural environments remains a considerable challenge, primarily because of the difficulty in describing the environment of the robot in a way that captures the variability of natural environments Error! Reference source not found.. While it is possible – although by no means trivial – to build models of smooth, 3-D(More)
As the World Wide Web is growing rapidly, it is getting increasingly challenging to gather representative information about it. Instead of crawling the web exhaustively one has to resort to other techniques like sampling to determine the properties of the web. A uniform random sample of the web would be useful to determine the percentage of web pages in a(More)
Clostridium difficile causes approximately 25% of nosocomial antibiotic-associated diarrheas and most cases of pseudomembranous colitis. We evaluated C. DIFF CHEK, a new screening test that detects glutamate dehydrogenase of C. difficile. Our results showed that this test was comparable to PCR in sensitivity and specificity and outperformed bacterial(More)
OBJECTIVE Examine the association between perceived stress and hunger continuously over a week in free-living individuals. METHODS Forty five young adults (70% women, 30% overweight/obese) ages 18 to 24 years (Mean = 20.7, SD = 1.5), with BMI between 17.4 and 36.3 kg/m(2) (Mean = 23.6, SD = 4.0) provided between 513 and 577 concurrent ratings of perceived(More)
The phenotyping of genetic mouse models for human disorders may greatly benefit from breath gas analysis as a noninvasive tool to identify metabolic alterations in mice. Phenotyping screens such as the German Mouse Clinic demand investigations in unrestrained mice. Therefore, we adapted a breath screen in which exhaled volatile organic compounds (VOCs) were(More)
The term ad hoc indicates the capability that two or several nodes can connect and communicate with each other independently of a centralized infrastructure. The disclaimer of such a central unit yields to the requirement of a self-organizing behavior of the network where the nodes organize themselves in a distributed manner. Knowing the geographical(More)