15 research outputs found
Liquid 4He: contributions to first principles theory of quantized vortices, thermohydrodynamic properties, and the lambda transition
Liquid 4He has been studied extensively for almost a century, but there are
still a number of outstanding weak or missing links in our comprehension of it.
This paper reviews some of the principal paths taken in previous research and
then proceeds to fill gaps and create an integrated picture with more complete
understanding through first principles treatment of a realistic model that
starts with a microscopic, atomistic description of the liquid. Newly derived
results for vortex cores and thermohydrodynamic properties for a two-fluid
model are used to show that interacting quantized vortices may produce a lambda
anomaly in specific heat near the superfluid transition where flow properties
change. The nature of the order in the superfluid state is explained.
Experimental support for new calculations is exhibited, and a unique specific
heat experiment is proposed to test predictions of the theory. Relevance of the
theory to modern research in cosmology, astrophysics, and Bose-Einstein
condensates is discussed.Comment: 155 pages, 28 figure
Basic Methods for Computing Special Functions
This paper gives an overview of methods for the numerical evaluation of special functions, that is, the functions that arise in many problems from mathematical physics, engineering, probability theory, and other applied sciences. We consider in detail a selection of basic methods which are
frequently used in the numerical evaluation of special functions: converging and asymptotic series, including Chebyshev expansions, linear recurrence relations, and numerical quadrature. Several other methods are available and some of these will be discussed in less detail. We give examples of recent software for special functions where these methods are used. We mention a list of new publications on computational aspects of special functions available on our website
Where Does Campylobacter Come From? A Molecular Odyssey
Campylobacter is the most common bacterial cause of gastroenteritis, worldwide. Since the first description of the disease in the 1970 s (Skirrow, 1977 the incidence of human campylobacteriosis in the UK, measured in terms of laboratory reports, has risen steadily, peaking at 57,674 reports in the year 2000; with 46,603 reports in 2006 (http://www.hpa.org.uk). Although generally self limiting, this disease has an important economic impact (Skirrow and Blaser, 1992). More serious complications, such as motor neurone paralysis, arise in 1–2 cases per 100,000 people in the UK and USA (Nachamkin et al., 1998). The disease also has an appreciable, yet less defined, impact in developing countries. Approximately 90% of human infection is caused by C. jejuni, with C. coli accounting for much of the rest (Gillespie et al., 2002)