Showing papers by "James Cook University published in 1989"

The role of excitatory amino acids and NMDA receptors in traumatic brain injury.

Abstract: Brain injury induced by fluid percussion in rats caused a marked elevation in extracellular glutamate and aspartate adjacent to the trauma site. This increase in excitatory amino acids was related to the severity of the injury and was associated with a reduction in cellular bioenergetic state and intracellular free magnesium. Treatment with the noncompetitive N-methyl-D-aspartate (NMDA) antagonist dextrophan or the competitive antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid limited the resultant neurological dysfunction; dextrorphan treatment also improved the bioenergetic state after trauma and increased the intracellular free magnesium. Thus, excitatory amino acids contribute to delayed tissue damage after brain trauma; NMDA antagonists may be of benefit in treating acute head injury.

Porphyroblast inclusion trails: the key to orogenesis

Abstract: Detailed microstructural analysis of inclusion trails in hundreds of garnet porphyroblasts from rocks where spiral-shaped inclusion trails are common indicates that spiral-shaped trails did not form by rotation of the growing porphyroblasts relative to geographic coordinates. They formed instead by progressive growth by porphyroblasts over several sets of near-orthogonal foliations that successively overprint one another. The orientations of these near-orthogonal foliations are alternately near-vertical and near-horizontal in all porphyroblasts examined. This provides very strong evidence for lack of porphyroblast rotation. The deformation path recorded by these porphyroblasts indicates that the process of orogenesis involves a multiply repeated two-stage cycle of: (1) crustal shortening and thickening, with the development of a near-vertical foliation with a steep stretching lineation; followed by (2) gravitational instability and collapse of this uplifted pile with the development of a near-horizontal foliation, gravitational spreading, near-coaxial vertical shortening and consequent thrusting on the orogen margins. Correlation of inclusion trail overprinting relationships and asymmetry in porphyroblasts with foliation overprinting relationships observed in the field allows determination of where the rocks studied lie and have moved within an orogen. This information, combined with information about chemical zoning in porphyroblasts, provides details about the structural/metamorphic (P-T-t) paths the rocks have followed. The ductile deformation environment in which a porphyroblast can rotate relative to geographic coordinates during orogenesis is spatially restricted in continental crust to vertical, ductile tear/transcurrent faults across which there is no component of bulk shortening or transpression.

Inorganic nitrogen uptake by symbiotic marine cnidarians: a critical review

Abstract: The physiological data support host involvement in net ammonium uptake by intact symbioses. The evidence for nitrate assimilation by intact symbioses is equivocal. The depletion-diffusion model can account for net ammonium uptake by intact symbioses, but is inadequate to account for phosphate or nitrate uptake by symbioses. There is no evidence for nitrogen limitation as the means by which the host regulates algal growth in symbiosis; phosphorus limitation appears to be more likely.

The negative role of turbulence in estuarine mass transport

Abstract: It is competition between the various stratifying and mixing influences which determines the character of stratification in an estuary. Borrowing concepts which have been successfully applied to the discussion of stratification in shelf seas, a quantitative basis for determining the potential energy associated with vertical structure in estuaries is derived. The formulation, along similar lines to that of Bowden (1981) , provides a simple but comprehensive method of incorporating many relevant stratifying and mixing influences in a given problem, and is also shown to be capable of rearrangement into forms akin to the estuarine Richardson number which is commonly found in discussions of estuarine statification. The paper argues, based on a survey of the literature, that in wide, relatively well-mixed estuaries, the greatest longitudinal mass flux occurs at times when stratification is most developed, that is, when the turbulent kinetic energy in the water column is at a minimum. Modulation of turbulence, principally at various tidal frequencies, causes a pulsing of the mass flux in which the contribution of each pulse increases non-linearly as the period of the modulation increases. Some, possibly significant, changes to the state of stratification and to the corresponding mass transport may occur in association with slack water periods. However, the spring-neap cycle is proposed to have a far greater influence on stratification, mass transport and the long-term mass balance in estuaries, and recent observational studies lend support to this position.

Dissolution, solution transfer, diffusion versus fluid flow and volume loss during deformation/metamorphism

Abstract: Dissolution and solution transfer during deformation/metamorphism are controlled by the partitioning of deformation into progressive shearing and shortening components. Progressive shearing is readily accommodated by slip on the planar crystal structure of phyllosilicates and graphite without accumulating dislocation density gradients across grain boundaries. Progressive shortening is accommodated by the cores of most other minerals (including sulphides). These minerals develop strain, and hence dislocation density gradients, on their rims due to progressive shearing along grain boundaries. These gradients are particularly large when the mineral abuts phyllosilicate or graphite. The resulting chemical potential gradients between the core and rim drive dissolution, causing removal of the highly strained grain margins. Removal of dissolved material by solution transfer is aided by the geometry of shearing of phyllosilicates and graphite around other grains in an active anastomosing foliation. Interlayers and interfaces on boundaries lying at a low angle to the direction of shearing, and oriented relative to the sense of shear such that they can open, gape by small amounts. Water present in these interlayer spaces becomes destructured, considerably enhancing diffusion rates along the foliation. Penetrative volume loss, especially in deforming/metamorphosing pelitic rocks, is large at all metamorphic grades, increasing and becoming more penetrative with depth to at least the transition into granulite and eclogite facies. Transference of material by fluid flow from deep to high levels in the earth's crust is precluded because thousands to tens of thousands of rock volumes of fluid are required, necessitating continual recirculation of fluid from shallow to deep crustal levels in one large or several small sets of cells, unless some extremely large-scale form of fluid channelling is possible. Reassessment of diffusion mechanisms, and hence rates, during deformation and pervasive foliation generation in large volumes of rock where fluid channeling cannot provide enough fluid, indicates that diffusion can proceed with sufficient rapidity that massive recirculation of fluid is no longer required. The amount of fluid can be reduced sufficiently to allow large volume losses by a one-way flow of fluid to the earth's surface, in deforming/metamorphosing environments where the fluid pressure equals or exceeds the hydrostatic pressure. Deformation partitioning-controlled dissolution progressively changes the bulk chemistry of a rock containing phyllosilicates or graphite during deformation/metamorphism because matrix minerals, other than phyllosilicates and graphite, are preferentially removed. The large size of porphyroblasts, if present, tends to preserve them from dissolution. Hence, the bulk chemistry operative during subsequent porphyroblast growth can have changed considerably from that operative when the first porphyroblasts grew, in rocks in which bedding is still well preserved.

Horizontal distribution patterns of presettlement reef fish: are they influenced by the proximity of reefs?

Abstract: The distribution patterns of presettlement reef fish and how they were influenced by the proximity of reefs were investigated off the coast of Northland, New Zealand, from 1981–1986. We used ichthyoplankton tows and visual counts of fish. Distributions of presettlement fish of some species were influenced by the proximity of reefs, regardless of whether reefs were on the coast of the mainland or islands across the shelf. Presettlement fish of families that lay demersal eggs were most abundant near reefs: Gobiescocidae, Acanthoclinidae, Tripterygiidae, Eleotridae, and Gobiidae. The distribution of presettlement sparids, mullids (pelagic eggs), and blenniids and monacanthids (demersal eggs) was not determined in a predictable way by the proximity of reefs. High-frequency sampling over three days suggested that patches of presettlement sparids of 1 to 2 km in dimension may move quickly through a study area. High abundance of presettlement gobiescocids and tripterygiids were found in 0 to 2 m of water over rocky reefs at high and low tides. Presettlement eleotrids were associated with reefs in deeper water (3 to 20 m) and in some habitats with aggregations of mysids. The lack of general patterns of distribution for presettlement reef fish suggests that modelling patterns of drift of these fish as a single group is inappropriate; this concurs with evidence from tropical waters.

Effect of rate of inbreeding on inbreeding depression in Drosophila melanogaster.

Abstract: This experiment was designed to study the relationship between rate of inbreeding and observed inbreeding depression of larval viability, adult fecundity and cold shock mortality in Drosophila melanogaster. Rates of inbreeding used were full-sib mating and closed lines of N=4 and N=20. Eight generations of mating in the N=20 lines, three generations in the N=4 lines and one generation of full-sib mating were synchronised to simultaneously produce individuals with an expected level of inbreeding coefficient (F) of approximately 0.25. Inbreeding depression for the three traits was significant at F=0.25. N=20 lines showed significantly less inbreeding depression than full-sib mated lines for larval viability at approximately the same level of F. A similar trend was observed for fecundity. No effect of rate of inbreeding depression was found for cold shock mortality, but this trait was measured with less precision than the other two. Natural selection acting on loci influencing larval viability and fecundity during the process of inbreeding could explain these results. Selection is expected to be more effective with slow rates of inbreeding because there are more generations and greater opportunity for selection to act before F=0.25 is reached. Selection intensities seem to have been different in the three traits measured. Selection was most intense for larval viability, less intense for fecundity and, perhaps, negligible at loci influencing cold shock mortality.

Occurrence and characteristics of unusual protistan symbionts from surgeonfishes (Acanthuridae) of the Great Barrier Reef, Australia

Abstract: The occurrence of unusual symbiotic microorganisms was examined in the intestines of a range of fish from the Great Barrier Reef, Australia. The fish taxa examined included 26 species of the family Acanthuridae, as well as representatives of phylogenetically related and herbivorous taxa. The microorganisms, referred to as protists, were only found in herbivorous and detritivorous members of the Acanthuridae. Protists were not found in planktivorous acanthurids, nor in any members of the families Kyphosidae, Pomacentridae, Scaridae, Zanclidae, Siganidae and Bleniidae we examined. In addition, protists were absent from the herbivorous acanthurids A. xanthopterus and A. nigricans. A range of protist forms, characterized by differences in size (8 to 417 μm), shape and mode of cell division (daughter-cell production and binary fission), was observed. The occurrence of these forms appeared to be correlated with host feedingecology. Large forms (>100 μm) of the protists were only found in acanthurids which fed over hard-reef substrata. Smaller forms were found in sand-grazing and detritivorous species. One of the protist forms appears identical to protists previously reported from Red Sea acanthurids.

Magnetic resonance imaging with adiabatic pulses using a single surface coil for RF transmission and signal detection

Abstract: In order to overcome the problems that arise from nonuniform B1, fields, there has been interest in developing pulses that are insensitive to large variations in RF power. Pulses derived from adiabatic passage principles that can execute spin inversion, excitation, and 90°and 180° plane rotations in the presence of B1, inhomogeneities have recently been described. When driven with optimized modulation functions, these pulses can execute uniform excitation, refocusing, and slice-selective inversion over a 10-fold or greater variation in B1 magnitude. This insensitivity to B1 strength enables the execution of T and/or T weighted spin-echo imaging experiments using coils, such as the surface coil, with extremely inhomogeneous B1 profiles. We have successfully acquired images with these pulses at 200 MHz using a single surface coil as the transmitter and receiver. Images of the slice definition, the region over which the excitation and refocusing pulses operate with a surface coil, and brain images obtained with slice planes perpendicular to the plane of the surface coil are presented. Results demonstrate that these pulses can be transmitted with a surface coil to yield high-quality T and/or T weighted images without B1, artifacts. © 1989 Academic Press, Inc.

Evidence from Sediments of Long-Term Acanthaster planci Predation on Corals of the Great Barrier Reef.

Abstract: Since 1962 the crown-of-thorns starfish, Acanthaster planci, has caused the devastation of living coral in large tracts of the Great Barrier Reef, Australia. Some authorities view this as a modern phenomenon, resulting from ecological disturbance caused by man. Evidence from skeletal remains in sediment suggests that large A. planci populations have been part of the Great Barrier Reef ecosystem for at least 8000 years. Coral predation by A. planci is likely to have influenced the morphological fabric of the Great Barrier Reef in its post-glacial development and may also have influenced species richness of the reef biota.

The Great Barrier Reef Marine Park: Dimensions and Regional Patterns

Abstract: A mapping programme of all reefs of the Great Barrier Reef Marine Park area and compilation of a computer-based gazetteer containing locational and morphological data have permitted the first comprehensive spatial and morphometric analysis of the Great Barrier Reef. As previously suspected the analysis shows that a degree of organisation exists in the complexity of the Reef and clear regional and latitudinal patterns are recognised Reasons for this, particularly in relation to regional structure and the influence of the pre-Holocene foundations of the modem reef, are discussed The usefulness of a morphometric approach is suggested and an example related to Acanthaster planci outbreaks presented

Self in wilderness: understanding the psychological benefits of individual-wilderness interaction through self control.

Abstract: In Australia people are increasingly spending more leisure time in wilderness settings and are willing to participate in guided wilderness adventures. It has been suggested that the wilderness environment is therapeutic, and psychological studies have attempted to demonstrate that meaningful changes take place within the individual as a consequence of being in that setting. Conceptual frameworks for understanding better why and how wilderness promotes psychological well being are scarce, however. This report provides a conceptual consideration of individual‐wilderness interactions that looks closely at the notion of perceived control. It is suggested that an alternative concept, self‐control, better characterizes individual‐wilderness relationships. Moreover, it is argued that the opportunity in wilderness for individuals to exert self‐control is psychologically rewarding. Properties of the wilderness setting that can facilitate self‐control are also discussed.

The role of deformation partitioning in the deformation and recrystallization of plagioclase and K‐feldspar in the Woodroffe Thrust mylonite zone, central Australia

Abstract: In the Woodroffe Thrust mylonite zone, central Australia, recrystallization in plagioclase and K-feldspar involved subgrain rotation, assisted by grain-boundary or kink band boundary bulging, without contribution from a change in the chemical composition from host grains to new grains. The size of subgrains and new grains changes across the mylonite zone, apparently as a function of the strain rate and the H2O content of the rock. The partitioning of deformation into zones of progressive shearing and progressive shortening controls the sites of recovery and recrystallization in feldspar during mylonitization. The size of feldspar porphyroclasts in well developed mylonites is governed by the scale of deformation partitioning reached in the earlier stages of mylonitization, before the formation of a large proportion of fine-grained matrix that can accommodate the progressive shearing component of the deformation. Recrystallization occurs in microcline, apparently without involving a translation to a monoclinic structure, as microcline-twinned new grains are common adjacent to microcline-twinned host grains. K-feldspar triclinicity values calculated from XRD traces increase from the margins to the interior of the mylonite zone, in conjunction with deformation intensity. K-feldspar host grains locally have cores of orthoclase or untwinned microcline, surrounded by mantles of twinned microcline, suggesting a relationship between the presence of microcline twinning and the degree of K-feldspar triclinicity.

Albite-rich, silica-depleted metasomatic rocks at Emuford, Northeast Queensland; mineralogical, geochemical, and fluid inclusion constraints on hydrothermal evolution and tin mineralization

Abstract: Late Paleozoic fluorine-rich granites and their host metasediments in the Emuford district of the Herberton tin field contain small zones of intense albitization that host cassiterite mineralization. Sodium metasomatism was accompanied by hydrothermal leaching of granite quartz to form vuggy albite rocks (episyenites). Vugs created by quartz dissolution were filled in by hydrothermal minerals, including albite, K feldspar, and/or muscovite and cassiterite; late phases are dominated by quartz and fluorite. Swarms of parallel veinlets crosscut the albitized zones. These veinlets were formed by repeated fracturing in response to local fluid over-pressures. They contain infill mineralogy similar to the vugs and probably formed at least partly contemporaneously with vug infill.Due to the overprinting at various scales of alteration, vug infill, and vein formation stages, chemical changes associated with episyenite formation are only qualitatively constrained. However, the mineralogical and textural features of the alteration zones suggest that most major and trace elements had substantial mobility during their formation. Major chemical changes associated with episyenite formation include leaching of SiO 2 , K 2 O, Rb, and Ba, with introduction of Na 2 O and minor Sr. During vug-and vein-filling stages there was an introduction of SiO 2 , Al 2 O 3 , Na 2 O, K 2 O, CaO, F, and Sn. The erratic behavior of REE is probably related to the growth of fluorite and minor accessory phases (zircon, monazite, xenotime), with preferential enrichment of heavy REE in rocks with the highest fluorine concentrations.Fluid inclusion study indicates that vug- and vein-filling stages of the hydrothermal evolution involved two types of fluids. A high-salinity fluid (30-50 equiv wt % NaCl) of probable magmatic origin and homogenization temperatures up to 428 degrees C was associated with vug filling in the granite-hosted deposits. A lower salinity fluid (5-15 equiv wt % NaCl), containing variable amounts of CO 2 and having homogenization temperatures between 160 degrees and 420 degrees C, was associated with veinlet formation in the granite-hosted deposits and with vein and cavity filling in the metasediment-hosted deposit. This lower salinity fluid may represent a condensed vapor phase derived from boiling of the magmatic fluid or may be a mixture of magmatic and meteoric components.The close association of albitization and quartz dissolution suggests a genetic link between the two processes. It is proposed that exchange of Na for K in the fluorine-rich hydrothermal fluids caused a substantial increase in quartz solubility and led to quartz dissolution in the albitized rocks.

An evaluation of calf castration by intra‐testicular injection of a lactic acid solution

Abstract: This experiment evaluated intra-testicular injection of a sclerosing drug, lactic acid, for castration of bulls. Its use was compared in 58 Brahman cross calves (50 to 128kg) with the general practice of open surgical castration. Chemical castration appeared to be more painful than surgical castration, though post-operative swelling and pain appeared similar for both methods. Chemical castration took 3 times longer than surgical castration (58 sec v 20 sec; P less than 0.01). Scrotal necrosis occurred in 25% of chemically-castrated calves and appeared due to drug leakage from the testes under the high pressure of injection. Healing time for chemical castrates was approximately twice that for surgical castrates. Five chemically-castrated calves (18%) retained one testis. Though all 5 were rendered sterile, each maintained androgenesis. This led to secondary male behaviour which caused management problems. Castration method did not influence post-operative growth. It is concluded that lactic acid administration is not a suitable alternative to the open surgical technique for castration of Brahman cross calves.

Geologic Characteristics and Genetic Problems Associated with the Development of Granite-Hosted Deposits of Tantalum and Niobium

Abstract: Granite-hosted deposits of tantalum and niobium form massive or sheetlike zones of disseminated mineralization in the upper portions of some geochemically specialized granite plutons. Such mineralization usually reaches a maximum in association with albite and fluorite (±lithium)-rich zones in small, late-stage intrusions. These zones are formed in some cases by crystallization of fluorine-rich magmas, and in other cases may result from postmagmatic alteration.

Leaf shape and the host‐finding behaviour of two ovipositing monophagous butterfly species

Abstract: . 1. Ovipositing Eurema brigitta (Wallace) and Eurema herla (W. S. Macleay) butterflies were followed in the field to determine the nature and extent of the pre-alighting discrimination shown by these insects towards their only host plant, Cassia mimosoides (L). 2. Both species tended to search in areas where plants with long, thin leaves (primarily grasses) were less common, on average, than in randomly placed quadrats. Both species were also more likely to alight on non-host plants with leaves of a similar size and shape to those of the host plant than on non-hosts with leaf shapes dissimilar to that of the host. 3. The search behaviour of these monophagous insects was not so specialized that the butterflies never alighted on non-hosts; in fact the majority of alightings were on non-host plants and the pre-alighting discrimination shown by these insects is clearly not the prime behavioural determinant of their monophagy.

Prevalence and intensity of non‐strongyle intestinal parasites of horses in northern Queensland

Abstract: A quantitative post-mortem study of 57 horses from northern Queensland was done to determine the prevalence and intensity of non-strongyle intestinal parasites. The following species (% prevalence) were found: Draschia megastoma (39%); Habronema muscae (43%); Gasterophilus intestinalis (34%), G. nasalis (30%); Parascaris equorum (15%); Strongyloides westeri (6%); Probstmayria vivipara (2%); Oxyuris equi (26%); Anoplocephala magna (2%); A. perfoliata (32%). Mean parasite numbers of individual species ranged from 10 to 1310. Prevalence and intensity data were compared to recent studies in Western Australia and in the United States of America. Differences between stabled and paddocked horses were noted, particularly for botfly larvae and spiruroids. Climatic and seasonal changes in prevalence were restricted to H. muscae, G. nasalis and P. equorum with highest prevalence in the wet season or in horses from wet coastal areas. Only P. equorum showed any age effect being restricted to horses less than 5 years old. Breed and sex of horses was not important. The likelihood of changing parasite population dynamics with improved anthelmintic regimen is discussed.

Metabolic changes in rabbit spinal cord after trauma: magnetic resonance spectroscopy studies.

Abstract: Combined phosphorus and proton magnetic resonance spectroscopy (MRS), using double-tuned surface coils, was used to monitor certain metabolic changes in the L-3 spinal segment of anesthetized rabbits prior to and following experimental spinal cord trauma. Following severe trauma, resulting in spastic paraplegia, there was a delayed and progressive accumulation of lactic acid, a decline in intracellular pH, and a loss of high-energy phosphates. Maximal alterations occurred between 2 and 3 hours after the trauma, with little further change by 4 hours. Histological examination 2 weeks after trauma showed tissue necrosis and cavitation. These findings support the concept of secondary tissue injury after spinal cord trauma and suggest that early changes in metabolism, as shown by MRS, may predict irreversible tissue damage.

The Elura Ag-Pb-Zn mine in Australia; ore genesis in a slate belt by syndeformational metasomatism along hydrothermal fluid conduits

Abstract: The Ag-Pb-Zn ore deposit at the Elura mine, New South Wales, Australia, is situated in a Devonian slate belt and essentially consists of two vertically elongated, ellipsoidal bodies of massive sulfide. These are located above a zone of subeconomic vein mineralization. From the boundary of each orebody toward its core, the host sediment is progressively incorporated (as inclusions) in a deformed matrix of massive sulfide, but continuity of bedding attitudes is retained (across separate inclusions). Preserved bedding patterns and the sulfide deformation show that each orebody formed by metasomatism in the hinge of a developing anticline. The two anticlines are doubly plunging structures with superposed smaller folds, in which four generations of fold axial plane cleavages (S 1 -S 4 ) represent polyphase deformation (D 1 -D 4 ).The sulfide distribution in bedding-parallel outliers of the orebodies is controlled by the S 2 cleavage, but the style of D 2 folding within such horizons has been influenced by the presence of sulfide. Also, there are mesoscopic replicas of the orebodies with a shape and orientation that reflect the vertically elongated D 2 strain ellipsoid. Most replicas lie across hinges of D 2 folds, but locally their presence has affected the fold pattern. These, and other, complex relationships are explained as a consequence of relatively rapid metasomatism by sulfide during D 2 deformation.Synkinematic (syn-D 2 ) porphyroblasts of siderite mark an alteration halo around the ore. Alteration patterns indicate a coeval origin for the ore and its halo, which is further marked by vein-hosted breccias within a swarm of tension veins. Crack-seal microstructures in the latter indicate repeated microcracking during vertical stretching of the dome and basin folds at lithostatic pore fluid pressures. Structural relationships between the crack-seal veins and breccia veins are complex but suggest periodic release of the overpressured fluids by brecciation of sediment. The drops in fluid pressure triggered metasomatism by carbonates and sulfides in the two largest fold domes. The brecciation is attributed to dome collapse, following dilational rupture due to faulting in a system defined by shear zones and domains of bedding disruption.

Fertility in a tropical beef herd divergently selected for pregnancy rate

Abstract: Selection on the basis of estimated breeding value for cow fertility was successful in establishing two distinct lines of high (H) and low (L) fertility in a herd of Droughtmaster (Brahman × Shorthorn) cattle. The average difference in pregnancy rates over 3 years between the H and L line was 12% (P < 0·01) in the selected cows. In lactating cows this difference was 17% indicating that lactational anoestrus was an important component of the line difference in fertility. The total calf losses between confirmed pregnancy and weaning were 17%, but there were no line differences. Cow mortalities were 5% higher (P < 0·01) in pregnant cows than in empty cows but were similar in the H and L 'lines.H cows were proportionately 0·06 lighter in body weight (P < 0·01) at mating and 0·075 lighter (P < 0·01) at weaning than L cows. Much of this difference was due to the greater number of calves carried and weaned by H cows during their lifetime. Smaller lactation effects on weight gains and weight losses in H cows indicated that these cows were less sensitive in terms of weight gain to seasonal fluctuations in nutrition. H cows conceived earlier than L cows in 2 out of the 3 years and reared calves which were proportionately 0·04 lighter at weaning (P < 0·01). It is suggested that lower milk production in H cows leading to shorter periods of lactational anoestrous, combined with lower sensitivity to nutritional stress, was responsible for their higher fertility.

Phosphorus Metabolism in the Coral-Zooxanthellae Symbiosis: Characterization and Possible Roles of Two Acid Phosphatases in the Algal Symbiont Symbiodinium sp.

Abstract: Cell-free extracts of zooxanthellae ( Symbiodinium sp.) from the hard coral Acropora formosa contained two acid phosphatases that were resolved by affinity chromatography on concanavalin-A-Sepharose. The enzymes had similar properties, with the exception that phosphatase P-1 hydrolysed polyphosphate and pyrophosphate, whereas phosphatase P-2 had no activity towards either. The high activity of phosphatase P-1 with polyphosphate implies that the physiological role of this enzyme may be the mobilization of this phosphate storage compound. The physiological substrate of phosphatase P-2 is unknown, but the most likely role of this enzyme is the hydrolysis of phosphate esters exterior to the plasmalemma, before uptake of the released inorganic phosphate by the algal transport system. Cultured zooxanthellae ( S. kawagutii ) contained phosphatase P-2 only; the significance of this difference is unknown. The activities of P-1 and P-2 were always high in freshly isolated zooxanthellae, and both activities were repressed after incubation in phosphate-supplemented media. The implication is therefore that the algae in the coral-zooxanthellae symbiosis may be phosphate limited.

Geochemistry of Granites Associated with Tantalum and Niobium Mineralization

Abstract: Tantalum and niobium mineralization is often associated with geochemically specialized granites which are characterized by enrichment in fluorine, and by the development of pervasive, postmagmatic alteration Three major varieties of granite can be recognized: 1 Alkali granites containing alkali pyroxenes and/or amphiboles which are characterized by high Fe, F, Nb, Zr, Rb, Sn and REE, and by low CaO, Ba, Sr and Ta/Nb These granites occur principally in anorogenic settings, and are associated mainly with niobium mineralization 2 Biotite and/or muscovite granites often containing Fe-Li micas which are characterized by high F, Rb and Sn, and by low CaO, Ba, Sr and Eu These granites occur in both anorogenic and postorogenic settings, and are associated principally with Nb-Ta(-Sn) mineralization 3 Lepidolite-albite granites often containing topaz which are characterized by high A12O3, F, Li, Rb, Sn, Ta and Ta/Nb, and by low Ba, Sr, Eu, Zr and REE These granites occur principally in postorogenic settings, but also form marginal facies varieties of biotite and/or muscovite granites in both anorogenic and postorogenic settings Lepidolite-albite granites are generally associated with Ta(-Nb-Sn) mineralization