Design principles for autonomous agents: A case study of classification

Building artificial lifelike autonomous agents is still considered an art, rather than a science. A generally accepted precise methodology is missing, and—given the properties of the real world—it is doubtful whether such a methodology will ever be developed. Nevertheless, it is possible to define criteria and provide heuristics for good designs. We have developed a number of design principles which, when applied, lead to what we would consider good designs from a cognitive science or artificial life (ALife) perspective. The paper illustrates some of these principles using a case study of classification. Presented at the Internatial Symposium on Artificial Life and Robotics, Oita, Japan, February 18–20, 1996     

Immunohistochemical localization of netrin-1 in the embryonic chick nervous system

Netrin-1 has profound in vitro effects on the growth properties of vertebrate embryonic axons. In addition, netrin-1 mRNA is found in the floor plate of the embryonic nervous system, an intermediate target of many axons, including commissural axons that are affected by netrin-1 in vitro. Moreover, genetic studies of netrin-1 homologs in Caenorhabditis elegans and Drosophila implicate these proteins in commissure formation. We raised polyclonal antisera that recognize chick netrin-1 in fixed tissue sections. The antisera were used to immunohistochemically map netrin-1 in the embryonic spinal cord, brain, and retina. The relationship between netrin-1 localization and the growth of pioneering axons suggests roles for netrin-1 in the regulation of circumferential, commissural, and longitudinal axon growth in the spinal cord and brain. The data also suggest that the primary or sole effect of netrin-1 on pioneering spinal cord commissural axons is haptotactic. Furthermore, the pattern of netrin-1 localization raises the possibility that this protein helps mediate neuronal migration in the spinal cord, brain, and retina.     

Tissue distribution, elimination and metabolism of [3H]-leukotriene C4 in the American bullfrog, Rana catesbeiana

Tissue distribution, elimination, and metabolism of [3H]-leukotriene C4 were studied at 2.5 hours after injection in the conscious and anesthetized American bullfrog, Rana catesbeiana. Conscious frogs were injected via the dorsal lymph sac or the sciatic vein. Anesthetized frogs were injected via the abdominal vein. The organs containing the greatest percent of injected radioactivity at 2.5 hours after injection were liver, small intestine and kidney. Route of injection and anesthesia appears to alter distribution and elimination of leukotrienes. [3H]-leukotrienes were eliminated into bladder water and bile. In addition, 7.8 +/- 2.2 and 5.2 +/- 2.5 percent of the injected radioactivity was found in the pan water bathing the ventral surface of the venously and dorsally injected conscious frogs, respectively, suggesting transfer of radioactivity across the skin. At 2.5 hours, polar metabolites represented 50% of the radioactivity found in liver, bile, and bladder water. These polar metabolites were determined to be 18-carboxy-19,20-dinor-leukotriene E4, 20-carboxy-leukotriene E4, and 20-hydroxy-leukotriene E4. Of the non-oxidized leukotrienes, bile contained mainly LTD4 while bladder water contained primarily LTE4. N-acetyl LTE4 was not detected in any samples. The tissue distribution, elimination and metabolism of leukotrienes in the bullfrog was similar to mammalian studies and suggests evolutionary conservation of leukotriene processing.     

Untersuchungen an einem langzeitbeanspruchten 13 CrMo 44-Rohr

Beurteilung des Werkstoffzustandes eines vor 40 Jahren erschmolzenen warmfesten, niedriglegierten CrMo-Stahles nach einer Betriebsdauer von rd. 27 Jahren. Untersuchung der chemischen Zusammensetzung sowie der mechanischen Eigenschaften bei kurz- und langzeitiger Beanspruchung. Prüfung des Ausscheidungszustandes. Ermittlung der Restlebensdauer nach verschiedenen Extrapolationsverfahren.     

Mediastinal angiography. A helpful method to evaluate to operability of mediastinal and lung tumors (author's transl)

Preoperative mediastinal angiography, as a simple method, shows alterations of pulmonary and venous mediastinal circulation. It enables the surgeon to evaluate the operability of malignant thoracic neoplasms without performance of other diagnostic procedure with a higher rate of complications, e.g. mediastinoscopy or explorative thoractomy.     

Experience in HBM ESD testing of high pin count devices

HBM ESD sensitivity testing of high pin count devices is a challenge for current testers and the standardized test procedure. Alternative HBM test procedures are described for the test of devices with fewer tester channels than device pins. Experimental results for the “Split-IO” test method are presented and the risks of divergent results are discussed.     

Large‐Eddy Simulations and Particle‐Image Velocimetry Measurements of Tundish Flow

Large‐eddy simulations (LES) and digital particle‐image velocimetry (DPIV) of a tundish flow are performed to investigate the turbulent flow structures and vortex dynamics. The LES is carried out using an implicit approach. In implicitly filtered LES, the computational grid and the discretization operators are considered as the filtering tools of the governing equations. The numerical computations are performed by solving the viscous conservation equations for compressible fluids. An implicit dual‐time stepping scheme combined with low Mach number pre‐conditioning and a multigrid accelerating technique is implemented for LES computations. The impact of jet spreading, jet impingement on the wall, and wall jets on the flow field and steel quality is investigated. The characteristics of the flow field in a one‐strand tundish such as the time‐dependent turbulent flow structure and vortex dynamics are analysed and compared with experimental results. To validate the numerical results, DPIV measurements are performed in a reduced 1:1.7 scaled water model. The investigations focus on steady‐state casting conditions for the flow in a tundish. The results evidence a good agreement between the LES and experimental data. The LES solutions provide an extremely detailed insight into the highly intricate turbulent flow structure. Even phenomena like funnel‐shaped vortices downward the shroud jet are well captured.     

Lack of Major Genome-Wide DNA Methylation Changes in Succinate-Treated Human Epithelial Cells

The tricarboxylic acid (TCA) metabolite, succinate, is a competitive inhibitor of dioxygenase enzymes that require alpha ketoglutarate as a cofactor. One family of dioxygenases are the ten-eleven translocation (TET) proteins, which oxidize 5-methylcytosine to promote DNA demethylation. Inhibition of DNA demethylation is expected to lead to DNA hypermethylation, at least at genomic regions at which TET proteins are engaged. We treated human bronchial epithelial cells with succinate for five days and confirmed its effect on TET protein function by observing diminished formation of 5-hydroxymethylcytosine, the first oxidation product of the TET enzymatic reaction. We then analyzed global DNA methylation patterns by performing whole-genome bisulfite sequencing. Unexpectedly, we did not observe differentially methylated regions (DMRs) that reached genome-wide statistical significance. We observed a few regions of clustered DNA hypomethylation, which was also not expected based on the proposed mechanisms. We discuss potential explanations for our observations and the implications of these findings for tumorigenesis.