Look Ma, Backtracking without Recursion

Look Ma--no cancer.

'ICRF Human Tumour Innunology Group, University College and Middlesex School of Medicine, 91 Riding House Street, London WIP 8BT; 2Department of Oncology and Pathology, University of Copenhagen, Rigshospitalet, 2100 Copenhagen, Denmark; 3Department of Medical Oncology, Western General Infirmary, Edinburgh EH4 2XU; 'Department of Oncology, University College and Middlesex School of Medicine, 91 ...

Look, Ma! No pneumococcus!

Pneumococcal diseases, caused by the bacterium Streptococcus pneumoniae, include pneumonia and otitis media, which accounts for some 12 million doctor visits per year in the United States alone. Each year around the world, pneumococcus causes 1.2 million deaths due to pneumonia, 39% of which are in children under the age of five. In a three-year Phase III clinical trial involving 38,000 childre...

Another Look on Recursion Operators

Recursion operators of partial diierential equations are identiied with BB acklund auto-transformations of linearized diieties. Relations to the classical concept and its recent Guthrie's generalization are discussed. Traditionally,a recursion operator of a PDE is a linear operator L acting on symmetries: if f is a symmetry then so is Lf. This provides a convenient way to generate innnite famil...

Splitting Without Backtracking

Choices without Backtracking

ly, one possiblc3 mode of interaction bctwccn the the problLm solver and the dntn base is as follows. A list is maintained of c~cry ;\ssumptioll set disco\rcrcd to bc contradictory. Whcncvcr the problem solver discovers Iwo val~~cs with contt.adictr~ry assumptions, the combined assumption set is placed on this list, and cvcry vaIlIC b,iscd on it or any of its super sets is crascd from the daL\ ...