E. J. Lowe and Divine Causal Agency

In this essay, I apply Lowe’s theory of rational agency to God’s causal activity. I argue that Lowe’s account fits well the traditional notions that God acts in the world for reasons. In contrast to Lowe’s analysis of human causal agency, I argue that in the divine case, reasons for acting are not constituted by needs. They are constituted by God’s desires or plans. The fit between Lowe’s account of causal agency and the contours of divine causal agency motivate an argument in favor of Lowe’s theory. Any philosopher who is a theist ought to think Lowe’s account is likely to be true

Calculation of a Synthetic Gather using the Aki-Richards Approximation to the Zoeppritz Equations

A synthetic seismic gather showing amplitude versus offset can be analyzed by the interpretive geophysicist to predict rock properties useful in oil exploration. Reflection coefficients derived from measured well log data are convolved with a Ricker wavelet to create a synthetic seismic trace. The Zoeppritz equations describe the propagation of an acoustic wave across an interface between two viscous media of different acoustic impedances with respect to increasing offset angle. The Aki-Richards linear approximation is used to create a synthetic seismic gather with offset angles up to fifty degrees. This gather is compared to a synthetic gather created using commercially available software

The status of the northern Anchovy resource and its management

The northern anchovy, Engraulis mordax, has been the subject of increasing exploitation during the last 60 years. Concentrated studies of its biology and population dynamics has yielded population estimates of 5 to 8 million metric tons or about 5 to 10 times that existing during 1950-51. Continuing cooperative study programs between the State of California, the Federal Government and the government of Mexico are recommended. (15pp.

Stabilized Least Squares Migration

Before raw seismic data records are interpretable by geologists, geophysicists must process these data using a technique called migration. Migration spatially repositions the acoustic energy in a seismic record to its correct location in the subsurface. Traditional migration techniques used a transpose approximation to a true acoustic propagation operator. Conventional least squares migration uses a true inverse operator, but is limited in functionality by the large size of modern seismic datasets. This research uses a new technique, called stabilized least squares migration, to correctly migrate seismic data records using a true inverse operator. Contrary to conventional least squares migration, this new technique allows for errors over ten percent in the underlying subsurface velocity model, which is a large limitation in conventional least squares migration. The stabilized least squares migration also decreases the number of iterations required by conventional least squares migration algorithms by an average of about three iterations on the sample data tested in this research

Mounting structure

A mounting platform for heat producing instruments operated in a narrow equilibrium temperature range comprises a grid-like structure with relatively large openings therein. The instruments are secured to and thermally coupled with the grid surface facing the instruments. Excess heat from the instruments is selectively radiated to the ambient through openings in the grid, the grid surfaces at these openings exhibiting low thermal emissivity and adsorptivity. The remainder of the grid is maintained at the equilibrium temperature and is covered with a thermal insulating blanket. Thus, the entire system including the platform and instruments is maintained substantially isothermal, whereby the instruments remain in fixed physical relationship to one another

Near-zero-field nuclear magnetic resonance

We investigate nuclear magnetic resonance (NMR) in near-zero-field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J-coupling). This is in stark contrast to the high field case, where heteronuclear J-couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with non-trivial spectra.Comment: 5 pages, 5 figure

Frequency Locking by Analysis of Orthogonal Modes

We describe a method for frequency locking a laser and a cavity. Orthogonal modes from the laser are incident on a cavity such that only one mode is resonant at the desired frequency. The polarisation or spatial phase distribution of the light reflected from the cavity is analysed, yielding the phase between the modes - this is the locking signal. We compare this method with other locking techniques, and show this to be a natural progression from these. Simulations are presented for applications of interest, e.g., gravity wave interferometry (an empty cavity) and optical frequency conversion (a polarisation dependent cavity)