Three-dimensional structure at the base of the mantle beneath the central pacific

Forward modeling of differential travel times of phases sensitive to lowermost mantle beneath the central Pacific reveals lateral heterogeneity that is higher in amplitude than predicted by tomographic models. A broad zone of low S velocity (-4 percent with respect to standard models), which may correspond to the base of a thermal "plume," narrows and is deflected as it extends to about 1000 kilometers above the core-mantle boundary. To the east of this zone, a localized region of fast S velocity (+5 percent) suggests strong heterogeneity or anisotropy related to the presence of high pressure and temperature assemblages, which may or may not involve core material. Its presence could also explain the observation of precursors to core reflected phases in this region.

Viscosity of oceanic asthenosphere inferred from remote triggering of earthquakes

A sequence of large interplate earthquakes from 1952 to 1965 along the Aleutian arc and Kurile-Kamchatka trench released accumulated stresses along nearly the entire northern portion of the Pacific Plate boundary. The postseismic stress evolution across the northern Pacific and Arctic basins, calculated from a viscoelastic coupling model with an asthenospheric viscosity of 5 x 10(17) pascal seconds, is consistent with triggering of oceanic intraplate earthquakes, temporal patterns in seismicity at remote plate boundaries, and space-based geodetic measurements of anomalous velocity over an area 7000 by 7000 kilometers square during the 30-year period after the sequence.

Anisotropy in the Inner Core: Could It Be Due To Low-Order Convection?

A recently assembled data set of inner core-sensitive free oscillation splitting measurements and body wave differential travel times provides constraints on the patterns of anisotropy in the Earth's inner core. Applying a formalism that allows departures from radial symmetry and cylindrical anisotropy results in models with P-wave velocity distributions whose strength and pattern are incompatible with frozen-in anisotropy, but rather suggest a simple large-scale convection regime in the inner core.

[Chloroform concentration in drinking water of the Lódz municipal area]. / Stezenie chloroformu w wodzie do picia w aglomeracji lódzkiej.

Chloroform is one the most important pollutants, formed in the process of chlorination of water from surface intakes. The city of lódz is supplied with water mainly from surface intakes containing considerable amounts of organic material and from deep water intakes. The aim of this study was to determine concentrations of selected organic compounds including chloroform in raw water, water after chlorination and on different stages of purification as well as in water introduced to the municipal water supply system. Chloroform was analysed in n-pentane extracts by gas chromatography with ECD. The detection limit of the analytical method was 1 microgram/l. Concentrations of chloroform in raw water were very low, in most cases below the limit of detection. As a result of chlorination level of chloroform in water increased reaching as high as 120 micrograms/l. It has been shown that activated charcoal was not efficient in removing chloroform from water. Concentrations of chloroform were much lower in water from the municipal water supply system serving the northern part of town, where water from surface intakes was mixed with water from deep intakes. Concentrations exceeding 30 micrograms/l were determined only in the summer season. In both investigated parts of municipal water supply systems seasonal changes of chloroform concentration were observed with maximum values in June-August. The concentration of chloroform in water samples collected in different quarters of town were strictly correlated with its concentration in treated water from the municipal water supply system serving the quarter.

The cape mendocino, california, earthquakes of april 1992: subduction at the triple junction.

The 25 April 1992 magnitude 7.1 Cape Mendocino thrust earthquake demonstrated that the North America-Gorda plate boundary is seismogenic and illustrated hazards that could result from much larger earthquakes forecast for the Cascadia region. The shock occurred just north of the Mendocino Triple Junction and caused strong ground motion and moderate damage in the immediate area. Rupture initiated onshore at a depth of 10.5 kilometers and propagated up-dip and seaward. Slip on steep faults in the Gorda plate generated two magnitude 6.6 aftershocks on 26 April. The main shock did not produce surface rupture on land but caused coastal uplift and a tsunami. The emerging picture of seismicity and faulting at the triple junction suggests that the region is likely to continue experiencing significant seismicity.

Spatiotemporal patterns in the energy release of great earthquakes.

For the past 80 years, the energy released in great strike-slip and thrust earthquakes has occurred in alternating cycles of 20 to 30 years. This pattern suggests that a global transfer mechanism from poloidal to toroidal components of tectonic plate motions is operating on time scales of several decades. The increase in seismic activity in California in recent years may be related to an acceleration of global strike-slip moment release, as regions of shear deformation mature after being reached by stresses that have propagated away from regions of great subduction decoupling earthquakes in the 1960s.

[Reconstruction of the posterior cruciate ligament with Brückner's method. Principles of pre- and postoperative physiotherapeutic treatment]. / Rekonstrukcja tylnego wiezadla krzyzowego metoda Brücknera. Zasady przed- i pooperacyjnego leczenia fizjoterapeutycznego.

Description of a case of reconstruction of the posterior crucial ligament in the 27 year-old patient according to the method given by Brückner with the use of a free graft from the proper ligament of the patella is presented. The knee joint was reconstructed from two incisions: anterior--medial of Payr and a short posterior--medial. The principles of pre- and postoperative physiotherapy are included.

[Occupational exposure to toxic substances during the production of vinyl chloride and chlorinated organic solvents]. / Narazenie zawodowe na substancje toksyczne podczas produkcji chlorku winylu i rozpuszczalników chloroorganicznych.

Determinations of vinyl chloride and chlorinated organic solvent concentrations at the breathing zone of the industrial workers employed at the vinyl chloride synthesis process have revealed excessive exposure to certain chlorinated compounds. The average exposures of the operators of the vinyl chloride synthesis apparatus have been found to be 13 MAC for vinyl chloride and 2.5 MAC for 1,2-dichloroethane. The operators of the solvent synthesis apparatus have been exposed to average concentrations of carbon tetrachloride up to 3.5 MAC, the corresponding values for the fitters being 4.5 MAC for vinyl chloride, 3.5 MAC for 1,2-dichloroethane, and 3 MAC for carbon tetrachloride.

[Exposure to chromium compounds during processing of chromium iron ore]. / Narazenie na zwiazki chromu przy przetwórstwie rudy chromitowej w Polsce.

The work verifies data gathered by Occupational Hygiene departments of Sanitary-Epidemiological Stations about workers exposure to chromium compounds in the processing of chrome iron ore. Research showed that 7 plants were involved in the processing of chrome iron ore and that the number of workers directly employed in the process amounted to 215-230. About 150 workers were exposed to high concentrations of chromium compounds which exceeded hygienic standards. All of them were employed only in metallurgical plants. The remaining 80-100 workers subjected to the study exposed to relatively low chromium concentrations were employed in chemical plants and refractory materials plants.