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Author: Stoll, D. ×

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Now showing 1 - 5 of 5
  • Publication
    Mass spectrometric analysis of surfactant metabolism in human volunteers using deuteriated choline
    ( 2004)
    Bernhard, W.
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    Pynn, C.J.
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    Jaworski, A.
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    Rau, G.A.
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    Hohlfeld, J.M.
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    Freihorst, J.
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    Poets, C.F.
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    Stoll, D.
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    Postle, A.D.
    Surfactant reduces surface tension at pulmonary air-liquid interfaces. Although its major component is dipalmitoyl-phosphatidylcholine (PC16:0/16:0), other PC species, principally palmitoylmyristoyl-PC, palmitoylpalmitoleoyl-PC, and palmitoyloleoyl-PC, are integral components of surfactant. The composition and metabolism of PC species depend on pulmonary development, respiratory rate, and pathologic alterations, which have largely been investigated in animals using radiolabeled precursors. Recent advances in mass spectrometry and availability of precursors carrying stable isotopes make metabolic experiments in human subjects ethically feasible. We introduce a technique to quantify surfactant PC synthesis in vivo using deuteriated choline coupled with electrospray ionization tandem mass spectrometry. Endogenous PC from induced sputa of healthy volunteers comprised 54.0 +/- 1.5% PC16:0/16:0, 9.7 +/- 0.7% palmitoylmyristoyl-PC, 10.0 +/- 1.0% palmitoylpalmitoleoyl-PC, and 13.1 +/- 0.3% palmitoyloleoyl-PC. Infusion of deuteriated choline chloride (3.6 mg/kg body weight) over 3 hours resulted in linear incorporation into PC over 30 hours. After a plateau of 0.61 +/- 0.04% labeled PC between 30 and 48 hours, incorporation decreased to 0.30 +/- 0.02% within 7 days. Compared with native PC, fractional label was initially lower for PC16:0/16:0 (31.9 +/- 8.3%) but was higher for palmitoyloleoyl-PC (21.0 +/- 1.2%), and equilibrium was achieved after only 48 hours. We conclude that infusion of deuteriated choline and electrospray ionization tandem mass spectrometry is useful to investigate surfactant metabolism in humans in vivo.
  • Publication
    Systematic Improvement of Technical Reviews in Large-Scale Systems Development
    ( 2001)
    Laitenberger, O.
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    Leszak, M.
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    Brunck, W.
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    Stoll, D.
    Technical reviews are a cost-effective method commonly used for the early detection of product defects. To exploit their full potential, it is necessary to constantly monitor and improve the implemented review procedure. This paper describes a systematic improvement effort to amplify and leverage the benefits of reviews at Lucent Technologies Optical Networking Group (ONG) at Nuremberg, Germany. The motivation for the effort stems from root cause analysis results. These results reveal that defects detected in later development phases could have been found earlier by reviews. The improvement effort involved a sequence of four steps. In the first step, review data was analyzed, the current review process was observed, review participants were interviewed, and the existing review documentation was scrutinized. In a second step improvement suggestions were derived based on the collected information and incorporated in the existing approach. The third step involved the training of the participants in the revised approach. The final step consisted of the application of the revised approach in projects at Lucent/ONG.In essence, the improvement effort provides key insights in the challenges of today's reviews. It questions existing meeting-based review processes and suggests a non-meeting based alternative. In fact, this is one of the very few efforts that implemented non-meeting based reviews in industrial projects.
  • Publication
    A microarray enzyme-linked immunosorbent assay for autoimmune diagnostics
    ( 2000)
    Joos, T.O.
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    Schrenk, M.
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    Hopfl, P.
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    Kroger, K.
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    Chowdhury, U.
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    Stoll, D.
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    Schnorer, D.
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    Durr, M.
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    Herick, K.
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    Rupp, S.
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    Sohn, K.
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    Hammerle, H.
  • Publication
    Evaluating a Model for Review Success Factors in an Industrial Setting
    ( 1999)
    Laitenberger, O.
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    Leszak, M.
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    Stoll, D.
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    Emam, K. el
  • Publication
    Quantitative Modeling of Software Reviews in an Industrial Setting
    ( 1999)
    Laitenberger, O.
    ;
    Leszak, M.
    ;
    Stoll, D.
    ;
    Emam, K. el
    Technical reviews are a cost-effective method commonly used to detect software defects early. To exploit their full potential, it is necessary to collect measurement data to constantly monitor and improve the implemented review procedure. This paper postulates a model of the factors that affect the number of defects detected during a technical review, and tests the model empirically using data from a large software development organization. The data set comes from more than 300 specification, design, and code reviews that were performed at Lucent's Product Realization Center for Optical Networking (PRC-ON) in Nuernberg, Germany. Since development projects within PRC-ON usually spend between 12% and 18% of the total development effort on reviews, it is essential to understand the relationships among the factors that determine review success. One major finding of this study is that the number of detected defects is primarily determined by the preparation effort of reviewers rather than t he size of the reviewed artifact. In addition, the size of the reviewed artifact has only limited influence on review effort. Furthermore, we identified consistent ceiling effects in the relationship between size and effort with the number of defects detected. These results suggest that managers at PRC-ON must consider adequate preparation effort in their review planning to ensure high quality artifacts as well as a mature review process.