Hamiltonian Formulation of Two Body Problem in Wheeler-Feynman electrodynamics

A Hamiltonian formulation for the classical problem of electromagnetic interaction of two charged relativistic particles is found.Comment: 22 pages, 8 Uuencoded Postscript figure

Tumour specific immunogenicity of methylcholanthrene-induced sarcoma cells after incubation in neuraminidase.

IT was previously suggested (Currie and Bagshawe, 1967) that effective antigenic expression by some types of tumour cell may be inhibited by the presence of sialic (N-acetylneuraminic) acid in the cell periphery. Treatment of the cells from several " non-specific " transplantable mouse tumours with neuraminidase results in a marked increase in their immunogenicity when subsequently injected into intact host mice and leads to a powerful anti-tumour immunity in these animals. So far this phenomenon has been reported using the Ehrlich (Lindenmann and- Klein, 1967), Landschuitz (Currie, 1967), and TA3 (Sanford, 1967) ascitic tumours. The antigenic discrepancies between these tumours and their respective host mice are probably related to strain-specific histocompatibility differences, i.e. these tumours are malignant allografts. Little of the information obtained from the study of such tumours is of immediate relevance to the growth and development of autochthonous tumours where the only tumour-host antigen discrepancy (if any) is specific to the tumour. The purpose of this paper is to report studies of the effects of incubation i

The pursuit of isotopic and molecular fire tracers in the polar atmosphere and cryosphere

We present an overview of recent multidisciplinary, multi-institutional efforts to identify and date major sources of combustion aerosol in the current and paleoatmospheres. The work was stimulated, in part, by an atmospheric particle \u27sample of opportunity\u27 collected at Summit, Greenland in August 1994, that bore the 14C imprint of biomass burning. During the summer field seasons of 1995 and 1996, we collected air filter, surface snow and snowpit samples to investigate chemical and isotopic evidence of combustion particles that had been transported from distant fires. Among the chemical tracers employed for source identification are organic acids, potassium and ammonium ions, and elemental and organic components of carbonaceous particles. Ion chromatography, performed by members of the Climate Change Research Center (University of New Hampshire), has been especially valuable in indicating periods at Summit that were likely to have been affected by the long range transport of biomass burning aerosol. Univariate and multivariate patterns of the ion concentrations in the snow and ice pinpointed surface and snowpit samples for the direct analysis of particulate (soot) carbon and carbon isotopes. The research at NIST is focusing on graphitic and polycyclic aromatic carbon, which serve as almost certain indicators of fire, and measurements of carbon isotopes, especially 14C, to distinguish fossil and biomass combustion sources. Complementing the chemical and isotopic record, are direct \u27visual\u27 (satellite imagery) records and less direct backtrajectory records, to indicate geographic source regions and transport paths. In this paper we illustrate the unique way in which the synthesis of the chemical, isotopic, satellite and trajectory data enhances our ability to develop the recent history of the formation and transport of soot deposited in the polar snow and ice

On the Number of Unbordered Factors

We illustrate a general technique for enumerating factors of k-automatic sequences by proving a conjecture on the number f(n) of unbordered factors of the Thue-Morse sequence. We show that f(n) = 4 and that f(n) = n infinitely often. We also give examples of automatic sequences having exactly 2 unbordered factors of every length