None of the leading approaches to the migration of seismic sections—the Kirchhoff‐summation method, the finite‐difference method, or the frequency‐domain method—readily migrates seismic reflections to their proper positions when overburden velocities vary laterally. For inhomogeneous media, the diffraction curve for a localized, buried scatterer is no longer hyperbolic and its apex is displaced laterally from the position directly above the scatterer. Hubral observed that the Kirchhoff‐summation method images seismic data at emergent “image ray” locations rather than at the desired positions vertically above scatterers. In addition, distortions in diffraction shapes lead to incorrect imaging (i.e., incomplete diffraction collapse) and, hence, to further displacement errors for dipping reflections. The finite‐difference method has been believed to continue waves downward correctly through inhomogeneous media. In conventional implementations, however, both the finite‐difference method and frequency‐domain approach commit the same error that the Kirchhoff method does. Synthetic examples demonstrate how conventional migration fails to image events completely. Hubral’s solution to this migration problem is two‐ (or three‐) dimensional mapping of imaged time sections into depth. This mapping, “depth migration,” replaces simple vertical conversion from time to depth. Such depth migration can be postponed until after efficient image‐ray modeling has been performed to (1) support the final choice of velocity model, and (2) determine whether depth migration is necessary. Comparisons between depth‐migrated and conventionally depth‐converted sections of both synthetic and field data properly show that significant lateral displacement is often required to position reflectors properly. Monte Carlo studies show that the lateral corrections can be important not only in absolute terms but also in relation to errors expected from an inaccurate velocity model.

Measurements of remanent magnetization were made on cores prepared from 54 samples collected from a 50 mi2 area of the St. Francois Mountains, Missouri. The rocks studied are devitrified Precambrian volcanics. In some of these rocks, the stable magnetization has high coercivity and appears to reside in fine‐grained magnetite that was formed by devitrification and vapor‐phase crystallization. This magnetization is inferred to be chemical remanent magnetization. The remanent magnetization directions from all the samples are closely grouped after demagnetization in ac fields of 500 to 800 oersteds. The calculated mean direction is coincident with the mean directions of other Precambrian igneous rocks of the St. Francois Mountains. The calculated pole position is 141.0°W, 0.9°S.

Remanent magnetization (RM) properties have been determined at nineteen sites in two alkalic igneous complexes at Magnet Cove and Potash Sulphur Spring, Arkansas (34.5°N, 29.8°W). The Magnet Cove intrusion has been dated by K‐Ar, Rb‐Sr, and fission track methods. The average age from six age dates is 98 m.y. (early Late Cretaceous). All specimens were demagnetized in various alternating peak fields and yield 19 site‐mean RM directions. The paleomagnetic pole calculated from the mean of these 19 site‐means is at 65.1°N and 173.3°W with confidence oval semiaxes 8.8° and 12.5°, respectively. This pole agrees with other North American Cretaceous poles and hence further supports the conclusion that the geomagnetic field during Late Cretaceous is dipolar and stable. It also suggests that central Arkansas has been stable since early Late Cretaceous.

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A phytochemical investigation of the leaves and twigs of Glycosmis pentaphylla (Rutaceae), collected in Vietnam, yielded three new compounds named glyfuran (1), glyphyllamide (2), and glyphyllazole (3), along with twenty-five known compounds (4–28). The structures of isolates were determined by IR, MS, NMR, and UV data analyses. In the anti-diabetic activity screening, (+)-isoaltholacton (4), glycoborinine (17), 2′,4′-dihydroxy-4,6′-dimethoxychalcone (24), and flavokawain A (25) simultaneously exhibited inhibition of dipeptidyl peptidase-4 (DPP4) and stimulation of the glucagon-like peptide-1 (GLP-1) secretion on the murine intestinal secretin tumor cell line (STC-1).