The penetration of igneous basement in the Nazca Plate during DSDP Legs 16 and 34 provided samples of both fine-grained pillow-basalt and coarse-grained massive flow units. The magnetic mineral in these basalt samples is initially a titanomagnetite (Fe,Ti,O4) with a narrow range of composition of x = 0.62 f 0.05. Subsequent to formation, the titanomagnetite grains are generally subjected to low temperature oxidation to titanomaghemite with a corresponding rise in Curie temperature from the initial values of 120-150°C up to a maximum of 400°C. Both grain size and low-temperature oxidation state play important, and interrelated, roles in controlling the intensity and stability of magnetic remanence and other magnetic properties. Overall grain size can, in some cases, be related to oxidation state since some sections of the relatively impermeable massive flows can remain unoxidized for as long as 40 Myr while pillow basalts are extensively oxidized within 34 Myr. Low-temperature alteration in turn effects magnetic grain size since oxidation and subsequent Fe cation migration results in grain subdivision by the formation of shrinkage cracks. A five-stage sequence of the microscopic changes that are associated with progressive low-temperature oxidation is proposed and illustrated with photomicrographs from these basalt samples.A hierarchy in the intensity of magnetic remanence may exist with unoxidized pillow basalts having a much higher intensity and oxidized pillow basalts having a much lower intensity than the massive flow units. While pillow basalts are relatively immune to the addition of secondary components of magnetization, the coarse-grained massive flows readily acquire components of viscous remanence. Although they oxidize much more slowly than pillows, when oxidation does take place, components of chemical remanence can be acquired by the multi-domained grains in the massive flow units. 319319A 320 321

No abstract

Extragnathic xanthomas are seen in the bones or as soft tissue masses. They are often associated with hyperlipidemia and are considered as reactive or metabolic lesions. Only 19 cases of xanthomas of the jaws have been reported so far in the English literature. A total of ten cases of central xanthoma of the jaw bones were identified from the Oral and Maxillofacial Pathology biopsy services of the University of Washington and the Tufts University School of Dental Medicine, between the years 2000-2016. The demographic and clinical information on these cases was tabulated logically on the basis of age, gender, location and presence or absence of symptoms, extragnathic lesions and serum hyperlipidemia. Radiographic and histopathological features were also examined. The findings in these cases were correlated with those available from the previously reported cases. Majority of cases are seen in the second and third decades of life. There is no gender predilection. Jaw lesions presented as solitary radiolucencies with a predilection for the posterior mandible. Unlike maxillary lesions, pain and expansion are inconsistent findings in mandibular lesions. Jaw lesions are not associated with extragnathic bone or soft tissue involvement or a hyperlipidemia. The central xanthoma of the jaws is a unique benign tumor. Histopathologically, many other jaw lesions contain variable numbers of foamy histiocytes. Therefore, a diagnosis of a central xanthoma of the jaws must be made after excluding all other such histiocyte containing lesions. This requires correlation of histopathological findings with clinical and radiographic features.

The detailed study of 455 basement samples from DSDP Leg 37 reveals magnetic properties, particularly inclinations and intensities, different from those commonly considered representative of Layer 2. Non-dipole inclinations are the most common. The deepest hole (582 m) has a vector average intensity of 24.3 × 10−4 emu cm−3 (24.3 × 10−1 A/m) and an inclination of only −14.5°. Induced magnetization never dominates and is usually much less than remanent magnetization, with Q ratio averaging 35 for basalts and 2.6 for plutonic rocks. Viscous magnetization acquisition constant, S, ranges widely from 0.001 to 1 × 10−4 emu cm−3 (0.001 to 1 × 10−1A/m), but is very rarely sufficient to cause VRM to dominate NRM.The major carrier of NRM is cation-deficient titanomagnetite produced by low-temperature oxidation of stoichiometric titantomagnetite. There is no trend of alteration with depth. All the magnetic properties are controlled by conditions within the individual basalt pillows or more massive units. A high degree of cation deficiency is associated with reduced NRM intensity, initial susceptibility, saturation magnetization, and VRM acquisition and increased MDF, Q ratio, and Curie point. Zones of low cation deficiency are presently found only in parts of massive units. With the exception of rare individual samples pillow sequences are highly oxidized throughout.A discussion is given of the kinds of ocean crust drilling and laboratory experiments required to solve the problems of the magnetic structure of Layer 2 as seen at the Leg 37 sites.

Aerated n-dodecane as a liquid under 800-psig pressure has been passed over heated tubes at temperatures between 375 and 1000 °F (190-538 °C). The initial product, hydroperoxide, is stable to 550 °F (282 °C), but its decomposition at higher temperatures leads to alcohols, ketones, hydrogen, carbon monoxide, n-alkanes, and 1alkenes. Product yields increase only slightly between 725 and 900 °F (385-482 °C) since peroxide has completely disappeared at the lower temperature. Hydrocarbon pyrolysis reactions occur above 900 °F (482 °C) with greater yields for aerated n-dodecane than for oxygen-free liquid. Heater tubes fabricated from aluminum and two types of stainless steel, 304 and 316, yielded the same products and exhibited similar "temperature/ product concentration'' patterns.