A mobile robot usually estimates its position and orientation by a dead reckoning system. However under several kinds of uncertainties, e.g. inner/outer sensor errors and/or a slip, a mobile robot unfortunately misunderstands true position and orientation in a real world as false position and orientation in a computer world. Due to the difference, a mobile robot governed by sensor-based navigation sometimes gets lost in an unknown 2-D environment. On the observation, in this paper, we firstly improve previous metric sensor-based navigation algorithms in order for a mobile robot to deal with such uncertainties. Secondly, we name a class of errors a homeomorpic error, where true and false positions in real and computer worlds are projected each other by the homeomorphism. Finally, we theoretically show that generation of the homeomorpic error is the necessary and sufficient condition for a mobile robot not to enter into any limit cycle in every type of sensor-based navigation algorithm.
An endothelial nitric oxide synthase gene (NOS3) polymorphism in exon 7 (G894T), resulting in Glu298Asp substitution at protein level, has been associated with myocardial infarction, hypertension and coronary atherosclerosis in some populations. This polymorphism is usually identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). However, the procedures described to date do not eliminate the possibility of misclassification and either require confirmation by DNA sequencing or are timeconsuming. In this study, a PCR-RFLP procedure to detect the G894T polymorphism at the NOS3 was optimized by the introduction of a constitutive cleavage site in the amplification product. This cleavage site provides an internal control for enzymatic activity to avoid mistyping. The method was validated by the study of 35 white unrelated individuals with familial hypercholesterolemia and 70 controls. The frequency of the variant allele (T) was similar between both groups (27% vs. 22%, NS), and comparable to the frequency found in other white populations. However, future studies are necessary to confirm these data. In summary, the optimized procedure for detection of the G894T NOS3 polymorphism is rapid, simple, and does not require confirmatory tests. Using this method, we found no association between this polymorphism and familial hypercholesterolemia.