Three-Dimensional Ray Tracing and Geophysical Inversion in Layered Media

In this paper the problem of finding seismic rays in a three-dimensional layered medium is examined. The "layers" are separated by arbitrary smooth interfaces that can vary in three dimensions. The endpoints of each ray and the sequence of interfaces it encounters are specified. The problem is formulated as a nonlinear system of equations and efficient, accurate methods of solution are discussed. An important application of ray tracing methods, which is discussed, is the nonlinear least squares estimation of medium parameters from observed travel times. In addition the "type" of each ray is also determined by the least squares process—this is in effect a deconvolution procedure similar to that desired in seismic exploration. It enables more of the measured data to be used without filtering out the multiple reflections that are not pure P-waves

Variation in Ray Flowers of anthemis cotula and Other Composites

The object of this study was to determine the amount of variation occurring in the number of ray flowers of the Mayweed (Anthemis cotula L.), to compare the variations occurring in different localities, and also the variations in different plants of the same locality, and finally to compare this variation with that of a few other species of Compositae

The Viability of Weed Seeds under Different Conditions of Treatment, and a Study of Their Dormant Periods

The viability of a seed is its capacity to live after maturity, and its dormant period is the time required for the seed to germinate after being planted. A great deal of investigation has been carried on for many years past to determine the viability of seeds; more especially of cultivated seeds of the farm and garden, but not so much attention has been given to weed seeds. In 1897 Mr. C. R. Ball of this college published an article on Seed Testing; Its Importance, History and Some Results, With a Partial Bibliography. This article contains a long and valuable bibliography referring to all the most important literature before 1897

The Fe XXII I(11.92 A)/I(11.77 A) Density Diagnostic Applied to the Chandra High Energy Transmission Grating Spectrum of EX Hydrae

Using the Livermore X-ray Spectral Synthesizer, which calculates spectral models of highly charged ions based primarily on HULLAC atomic data, we investigate the temperature, density, and photoexcitation dependence of the I(11.92 A)/I(11.77 A) line ratio of Fe XXII. We find that this line ratio has a critical density n_c \approx 5x10^13 cm^-3, is approximately 0.3 at low densities and 1.5 at high densities, and is very insensitive to temperature and photoexcitation, so is a useful density diagnostic for sources like magnetic cataclysmic variables in which the plasma densities are high and the efficacy of the He-like ion density diagnostic is compromised by the presence of a bright ultraviolet continuum. Applying this diagnostic to the Chandra High Energy Transmission Grating spectrum of the intermediate polar EX Hya, we find that the electron density of its T_e \approx 12 MK plasma is n_e = 1.0^{+2.0}_{-0.5} x 10^14 cm^-3, orders of magnitude greater than that typically observed in the Sun or other late-type stars.Comment: 11 pages including 3 encapsulated postscript figures; LaTeX format, uses aastex.cls; accepted on 2003 April 3 for publication in The Astrophysical Journa

New Magnetic Excitations in the Spin-Density-Wave of Chromium

Low-energy magnetic excitations of chromium have been reinvestigated with a single-Q crystal using neutron scattering technique. In the transverse spin-density-wave phase a new type of well-defined magnetic excitation is found around (0,0,1) with a weak dispersion perpendicular to the wavevector of the incommensurate structure. The magnetic excitation has an energy gap of E ~ 4 meV and at (0,0,1) exactly corresponds to the Fincher mode previously studied only along the incommensurate wavevector.Comment: 4 pages, 4 figure

Experiences of the Pre and Post Retirement Period of Female Elite Artistic Gymnasts: An Exploratory Study

This study explored retirement experiences of eight, female, former elite artistic gymnasts. Particular attention was afforded to coping strategies employed and dynamics of gymnast’s relationships with significant members of their social support network, in light of identity impact, across the retirement transition period. Retrospective, semi-structured interviews were conducted, transcripts were analysed through content analysis, and represented via pen profiles. Pre-retirement planning emerged as fundamental to the quality of the retirement transition. Keeping in contact with sport was the most frequently cited coping strategy. Social support networks adjusted pre- to post-retirement, identifying parents and partners as the consistent members of these networks across the transition. Findings provide formative recommendations to enhance the post-career education within current lifestyle management programmes, and for the design of a transitional support programme for gymnasts. The study findings may be of relevance for policy and practice in elite sport transitions more generally