Some wave-propagation experiments in plasteline-clay rods

Compressional stress pulses have been propagated in plasteline-clay rods by detonating small charges of lead azide at one end. A capacitance gage at the other end was used to measure particle displacement associated with the pulses and the particle velocity was obtained by differentiation. The shapes and amplitudes of the pulses were determined in separate experiments using composite clay-steel rods where the steel acted, in effect, as a pressure transducer. The techniques employed permitted comparatively accurate determination of some aspects of the dynamic behavior of clay. On the basis of preliminary results, the behavior of clay has been compared to that of a linear viscoelastic solid with the tentative goal of studying the validity of a viscoelastic constitutive model.     

Heat capacity anomaly in Pr2(Co0.8Fe0.2)17

Heat capacity measurements of the alloy Pr₂(Co_0.8Fe_0.2)₁₇ in the temperature range 182.5–190.5 K show an anomaly around 188 K. This is associated with a rotation of the magnetization vector from the basal plane to the hexagonal c-axis.     

Experimental calibration and field investigation of the oxygen isotopic fractionation between biogenic aragonite and water

Marine molluscs have long been recognised as potential records of palaeoclimate change using the patterns and differences in the stable isotopic composition of the carbonate shells. The aim of this study is to improve the robustness of this approach for aragonitic molluscs by completing the first experimental calibration of the fractionation between water and biogenic aragonite. Fractionation factors were calibrated by growing specimens of the freshwater mollusc Lymnaea peregra under controlled conditions of water temperature and isotopic composition. Fifteen populations of L. peregra were maintained at constant temperature and isotopic conditions for five months (at five different temperatures and using three different water compositions). Water samples and temperature measurements were taken regularly throughout the experiment. The temperature dependence of the fractionation factor, between 8 and 24 degrees C, is given by: 1000 ln alpha=16.74x(1000T(-1))-26.39 (T in Kelvin) and the relationship between temperature (T), delta(18)O(carb) and delta(18)O(wat) is given by: T=21.36-4.83xdelta(+ degrees )O(carb)-delta(+ degrees )O(wat) (T is in degrees C, delta(18)O(carb) is with respect to Vienna Pee Dee Belemnite (PDB), the International Atomic Energy Agency (IAEA) replacement standard for PDB, and delta(18)O(wat) is with respect to Vienna standard mean ocean water (VSMOW)) The outcome of the controlled experiment is compared with previous studies on synthetic, and biogenic, calcite and aragonite from field and laboratory investigations. These comparisons suggest that although a vital offset exists between the fractionation of isotopes in synthetic and biogenic aragonite for molluscs in general, there is no vital effect that is specific either to freshwater, or to individual, genera. Therefore, the calibrated relationship may be used for any freshwater or marine mollusc to derive palaeotemperatures providing the isotopic composition of the environmental water can be reliably constrained. Copyright 1999 John Wiley & Sons, Ltd.     

The application of direct potential fitting to the X1sigma+ ground electronic states of LiCl, TlCl, RbF and CsF.

A procedure for directly fitting the potential energy curve of a diatomic molecule has been applied to the X1sigma+ ground states of LiCl, TlCl, RbF and CsF. Extensive, high-precision infrared and pure-rotational data sets for all isotopomers of the aforementioned molecules have been employed in direct least-squares fits of a radially dependent Hamiltonian operator. The Born-Oppenheimer potentials are represented by a modified Lennard-Jones function that is shown to be flexible and provide the proper behavior in the long-range region of the potential. While the potential fits of LiCl and TlCl required the inclusion of Born-Oppenheimer breakdown functions, no such functions were necessary for either RbF or CsF.     

Experiments on the space and wavelength dependence of speckle

A comprehensive series of speckle experiments is described for opal glass diffusers ranging in thickness from 10 to 500 μm. Wavelength decorrelation measurements are made using a cw dye laser source; and accurate square-law detection is provided by the use of an optic-fiber, photomultiplier combination rather than film. For this diffuser set intensity distribution functions, polarized and unpolarized, are plotted. Second-order correlation functions are presented for different apertures, relating diffuser motion and probe motion. Remote texture determination using contrast ratio and frequency decorrelation is illustrated.