Electrical impedance variation with water saturation in rock

We measured the electrical impedances of 22 sandstone samples during oil‐driving‐water tests using the two‐electrode method. Experiments show that the imaginary part X of the impedance (R + iX) of rock may respond well to water saturation in the frequency range 100 Hz–15 MHz. We found that the maximum −X values and their corresponding interfacial polarization frequencies are linear with water saturation. The lower critical frequency is found to vary with water saturation, in an unclear relationship with the characteristic length of rock. The dissipation factor at the interfacial polarization frequency remains quite stable and may be an indicator of the pore structure of rock. We used an equivalent circuit to explain the dispersive behavior of rock. More than one interfacial polarization frequency in the impedance Argand plot is predicted and can be observed if the measurement frequency range is wide enough.

Theoretical Characterization of Transition State Dynamical Resonances in Heavy–Light–Heavy Reactions

The resonant reactivity of three elementary Heavy–Light–Heavy reactions is presented and discussed. Collinear reactivity, in which a vibrational adiabatic model is constructed, is used for a detailed analysis of resonance phenomena, which appear as a direct consequence of transition state metastable states in the strong interaction region of the potential energy surface. Their influence on the detailed mechanism of the elementary process is also discussed. The shape of the resonant peak, and the phase and the Argand plot of the S-matrix are used for a further characterization.Three-dimensional approximate calculations are used to test the evolution of the energy dependent structure present in detailed quantities when sums and integrations over all partial waves contributing to reaction are taken into account to obtain the usual averaged global quantities such as integral state-to-state cross sections.

Resonance recognition in a Veneziano model

Suppose we agree that a resonance is a second-sheet pole in s of a partial wave amplitude T J T J ( s ) = B J ( s ) + R J / ( s R J − s ) . Here s R is the pole position (Im s R < 0, R J is the residue and B J (s) is everything else (‘background’). A narrow resonance gives a circular arc (Adair 1969) in the Argand plot of T J (s) . Similar arcs are found experimentally, but it is still not agreed exactly how to get resonance parameters from them. Many criteria have been suggested. (i) Top of the loop . The maximum of Im T give the resonance mass s = Re s R provided R is real and positive. The condition holds for elastic scattering if B is negligible (by unitarity), and is sometimes assumed more widely. For inelastic amplitudes, if R is real (but of either sign), s = Re s R may be correlated with either the top or the bottom of a loop.