Cation ordering of orthopyroxenes from the Skaergaard Intrusion: implications for the subsolidus cooling rates and permeabilities

 We have determined the quenched cation ordering states of five orthopyroxene crystals collected from the marginal border group and the lower zone a and b of the Skaergaard intrusion, and modeled these data to retrieve their closure temperatures (T _c) of Fe–Mg ordering and cooling rates. According to existing thermal models for the Skaergaard pluton, conductive cooling dominated the high and low temperature regimes, which were separated by an intermediate temperature regime in which the cooling was controlled primarily by convective fluid circulation. The cooling rates retrieved from the quenched cation ordering states of the orthopyroxene crystals strictly apply to temperatures around the closure temperatures of the ordering states, ∼340–400^° C, which fall at the transition from convective to the lower temperature conductive cooling. The cooling rates obtained from the cation ordering states of orthopyroxene vary from ∼1 to 270 K/ka. These results agree well with a thermal model calculated using an assumed average permeability of 10^-12 cm² for the pluton, but not completely with a model calculated on the basis of an average permeability of 10^-13 cm², although both values produced shifts of δ¹⁸O that are comparable to those observed in the pluton. Received: 27 February 1995/Accepted: 20 July 1995     

A solid state sensor for mapping and profiling stimulated bioluminescence in the marine environment

This paper describes the design and development of a solid state sensor for the measurement, in situ, of stimulable bioluminescence of marine organisms. It can be towed in the Undulating Oceanographic Recorder or used in vertical profiling mode from a stationary research vessel. The sensor can detect signals from 10⁹ quanta s⁻¹, from a single dinoflagellate flash, up to 10¹³ quanta s⁻¹, at cell densities of 10⁶ to 10⁸ m⁻³. Measurements of bioluminescence and associated environmental conditions are presented from a variety of deployments of the sensor in the Undulating Oceanographic Recorder.     

Physiologie des Phenolabbaus bei Rhodococcus spec. P1. Teil 2: Untersuchungen zur Regulation des Phenolabbaus

The phenol-degrading system which can be induced in Rhodococcus spec. P 1 brings about the metabolization of phenol via the β-ketoadipate path (ortho-cleavage of catechol). For the more precise characterization of the degradation performance investigations were made into the influences of different carbon sources: glucose, galactose, ribose, arabinose, xylose, acetate, citricacid, mandelic acid, protocatechoic acid, glycerol, tryptophane, phenylalanine and the complex substrate of nutrient broth as well as succinate, catechol and benzoate. Only the three last-named substances show an influence: succinate inhibits only the synthesis of phenol hydroxylase, catechol and benzoate inhibit the synthesis and activity of phenol hydroxylase. As a comparison of the results with literature shows, even at the same path of degradation there are different regulating mechanismus in the different microorganisms.     

Age and growth rate determinations for the atlantic ribbed mussel,Geukensia demissa Dillwyn (Bivalvia: Mytilidae)

Field studies were conducted in Westport, Connecticut, to determine linear shell growth rates forGeukensia demissa. These rates were then compared with those reported for the same species from other locations. Most shell deposition occurred from March through November of each year. Winter interruptions in growth were clearly recognized in all size mussels and the rings were a reliable method for determining age in mussels from Westport. No significant sexual dimorphism in mean annual growth rates was detected. Age-size relationships based on internal shell lines appear to be less reliable, probably because of the interference by shell erosion at the umbo in this species. No well-defined latitudinal patterns in growth could be established forGeukensia demissa.     

Effect of the solids retention time on the rate of biodegradation of organic compounds

The paper studies the effect of the solids retention time (SRT) on the rate of biodegradation of morpholine (M), sulfanilic acid (SA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA) in laboratory mixed culture systems, fed semicontinuously on a once-a-day feeding schedule. It has been found that the minimum values of SRT at which microorganisms degrading the above compounds were washed out from the cultivation systems were 3, 1, 1, and 20 days for M, SA, NTA, and EDTA systems, respectively. A critical value of SRT was defined as that below which the rate of substrate removal is lower than the rate of substrate application into the system. The critical values of SRT were found to be 8, 3, 2.5, and above 20 days for M, SA, NTA, and EDTA systems, respectively. In a range between the minimum and critical values of SRT the mixed culture system cannot give stable efficiency of a given compound removal and the effluent concentration can be expected to vary considerably. Above the critical value of SRT, every cultivation system has a potential capability of shock loading treatment.     

Asthenospheric parameters of dipping plate regions by magnetotelluric investigations

The multifrequency resolving capability of the electromagnetic surface impedance parameter, employed in magnetotelluric investigations, has been examined for an upper mantle model incorporating (1) a deep-seated lithosphere-asthenosphere boundary and (2) preferred orientations of olivine crystals in the lithosphere, usually associated with the subducting plate boundary zones. Numerical results display the quantitative errors in the resolution of various anisotropic and dipping plate conditions. It is found that (1) conductivity anisotropy, particularly with higher dips, causes a significant dispersion in the impedance values and higher resolving power, and (2) variations in the geometrical/physical parameters are reflected predominantly in the phase component of the surface impedance. The study has relevance to the understanding of the electrical nature of materials, its relationship with physical properties and associated geothermal and seismic activities in the dipping plate regions.