Trace-element contents and cathodoluminescence of “trapiche” rubies from Mong Hsu, Myanmar (Burma): geological significance

Summary ?Mong Hsu rubies of the “trapiche” type are sporadically seen in the gem market. However, they have never been described in the field. The study of the nature of solid inclusions, the variation of trace-element contents, as well as the cathodoluminescence behaviour of six “trapiche” rubies permit the conclusion that these rubies crystallised in the same geological environment (marble-type deposit) as the normal rubies from Mong Hsu: (1) Cr and V are the main chromophorous elements in both ruby types; they act, together with Ti, as activators or quenchers for cathodoluminescence; (2) calcite, dolomite, rutile, mica, diaspore, apatite, chlorite, and feldspar are solid inclusions found in both ruby types; (3) the presence of bastn?site in trapiche ruby and fluorite in non-trapiche ruby indicates the circulation of F-bearing fluids during ruby deposition; (4) the distribution of trace-element contents in the crystal is similar for both ruby types. In the Cr₂O₃ vs. Fe₂O₃ and Cr₂O₃ vs. Fe₂O₃/TiO₂ diagrams, the population fields of Mong Hsu “trapiche” and non-“trapiche” rubies overlap. They are distinct from those of rubies and sapphires hosted in basalts from South-east Asia. Received October 30, 2001; revised version accepted March 25, 2002     

On the resonant spin flavor precession of the neutrino in the sun

This work deals with the possible solution of the solar neutrino problem in the framework of the resonant neutrino spin-flavor precession scenario. The event rate results from the solar neutrino experiments as well as the recoil electron energy spectrum from SuperKamiokande are used to constrain the free parameters of the neutrino in this model (Δm² and μ_ν). We consider two kinds of magnetic profiles inside the sun. For both cases, a static and a twisting field are discussed.     

Observations on the ecological importance of salt marshes in the Cumberland Basin,a macrotidal estuary in the Bay of Fundy

The Cumberland Basin, a 118 km² estuary at the head of the Bay of Fundy which has an average tidal range of about 11m, contains large tracts of salt marsh (15% of the area below highest high water). Low marsh (below about 0·9 m above mean high water) is composed almost exclusively of Spartina alterniflora while the vegetation on high marsh is more diverse but dominated by Spartina patens. Because of its higher elevation, high marsh is flooded infrequently for short periods by only extreme high tides. Low marsh is inundated much more frequently by water as much as 4m deep for periods as long as 4 h per tide. Temporal variability in the occurrence of extreme tides influences the flooding frequency of high marsh for any given month and year. Using a modification of Smalley's method, the mean annual net aerial primary production (NAPP) of low and high marsh is estimated to be 272 and 172 g C m^?2, respectively. Vegetation turnover times average 1·0 and 2·0 y for low and high marsh, respectively. Because of abundant tidal energy, much of the low marsh production appears to be exported and distributed widely about the estuary. Since high levels of turbidity suppress phytoplankton production, salt marshes produce approximately half of the carbon fixed photosynthetically in the Cumberland Basin. It is concluded that salt marshes play a major ecological role in the Cumberland Basin.     

A 2000-YEAR CONTEXT FOR MODERN CLIMATE CHANGE

ABSTRACT. Although considerable attention has been paid to the record of temperature change over the last few centuries, the range and rate of change of atmospheric circulation and hydrology remain elusive. Here, eight latitudinally well-distributed (pole-equator-pole), highly resolved (annual to decadal) climate proxy records are presented that demonstrate major changes in these variables over the last 2000 years. A comparison between atmospheric ¹⁴C and these changes in climate demonstrates a first-order relationship between a variable Sun and climate. The relationship is seen on a global scale.     

Kinetic studies of lead(II) uptake by the seagrass Zostera muelleri in water by radiotracing,atomic absorption spectrometry and electrochemical techniques

Evidence was found that uptake of lead from seawater in both model and natural systems by the leaves of the seagrass Zostera muelleri does occur for live, dead and scraped leaves at all the lead concentrations tested. Positive uptake of lead was measured using the three analytical techniques of radio-tracer, differential pulse anodic stripping voltammetry and atomic absorption spectrometry; similar uptake profiles were obtained for each technique. Profiles always showed an initial rapid uptake phase followed by a gradual transition to a plateau phase at which an approximate equilibrium between lead attached to seagrass and free ionic lead in seawater was reached. The presence of active lead uptake processes was indicated in experiments which attempted to remove lead from leaves by a chelating agent.     

Four-element CODAR beam forming

An HF radar called the Coastal Ocean Dynamics Applications Radar (CODAR) is presently being used in several forms to measure ocean surface parameters. The original version was developed by the National Oceanic and Atmospheric Administration (NOAA) and utilizes a four-element receive array. The array consists of four equally spaced elements arranged on a circle with a radius of 0.2151 wavelengths (at 25.4 MHz). It was designed to measure ocean currents using a direction-finding technique based on an extension to a simple two-element interferometer. The problem of determining the bearing of a radiating source can be readily shown to be equivalent to that incurred in spectral estimation. In an attempt to improve upon the processing of existing data, modern nonlinear spectral estimation techniques are applied in a beam-forming bearing estimation procedure and compared against several direction-finding algorithms. Enhancement of bearing estimators via analysis of the eigenstructure of a spatial correlation matrix is included. Antenna response patterns are calculated and used to investigate properties of direction-finding algorithms. Simulated data are used for a comparison of direction finding and beam forming. The asymmetrical bias of each method is investigated to determine its effect on the error in estimating the angle of arrival of a radar target.     

A note on turbulent perturbations of salinity in a partially mixed estuary

Measurements of salinity perturbations in a partially mixed estuary have been used to evaluate the usefulness of an inductive salinometer and to determine some of the characteristics of the salinity perturbations. The salinometer performed satisfactorily under most conditions. Although internal wave like effects were present, the turbulence fluctuations were dominant. The salinity fluctuations and the turbulent fluxes $\text{sw}$ and $\text{su}$ were found to behave in a manner similar to the density fluctuations in a thermally stratified atmospheric boundary layer and a laboratory open channel flow. A quadrant analysis suggested that the contribution of each quadrant to the turbulent flux changed with Ri. The turbulence parameters ν and c_γ were found to decrease and increase respectively as Ri increases.     

Chronology and evolution of the northern Iceland Plateau

New aeromagnetic data, K-Ar age determinations of dredged marine igneous rocks, as well as other geophysical evidence have shed light on the chronology, nature and evolution of the northern Iceland Plateau. Correspondence between seismic refraction profiles taken on the Jan Mayen Ridge and westward through Jan Mayen Island, suppressed aeromagnetic anomalies, earthquake surface wave studies, and ages of dredged igneous rocks suggest these strata may form an extended region of thickened crust, possibly of Caledonian age, extending westward toward the Kolbeinsey Ridge and northwest to the south wall of the Jan Mayen Fracture Zone.