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Ca Content (ca + content)
Selected AbstractsEffect of earthworm activity (Aporrectodea giardi) on atrazine adsorption and biodegradationEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2006T. Alekseeva Summary We investigated the influence of earthworm (Aporrectodea giardi) activity on soil properties and on atrazine (AT) adsorption and biodegradation by comparing a coarse-textured smectite-free wetland soil (Brittany, France) with the earthworm casts derived from the top horizon of this soil. Casts are characterized by lower pH, are enriched in organic carbon (OC) and clay content, have a larger cation exchange capacity, and a greater exchangeable Ca content. The clay mineralogy of the soil studied and casts is characterized by a muscovite,kaolinite,chlorite association. In addition, the clay fraction of the soil contains lepidocrocite (,-FeOOH), which was not found in the casts. Atrazine adsorption isotherms were reasonably well described by the Freundlich equation and were all non-linear. The mean amounts of adsorbed AT for starting concentrations of 3,30 mg litre,1 ranged from 8 to 34%, being largest in earthworm casts. Soil AT adsorption capacity was well correlated with OC content. Non-decomposed organic matter present in the coarse size fractions and specific compounds present in earthworm casts (proteins, mono- and polysaccharides, polyphenols, sugars, lignin) and microbial and fungal biomass contribute to AT adsorption. Weak electrostatic (physical) sorption of AT on organic compounds and on mineral surfaces prevails. For casts, the formation of additional hydrophobic interactions between AT and SOM is proposed. We also studied AT biodegradation by the model bacterium Pseudomonas sp. strain ADP in the presence of soils or earthworm casts. An enhancement of the AT disappearance rate was observed in the presence of all the solid matrices tested compared with that obtained in an aqueous medium. The biodegradation rate was shown to be dependent not only on the OC content of the solid matrix, but mainly on its composition and structure. [source] Relative contributions from exposed inshore and estuarine nursery grounds to the recruitment of stone flounder, Platichthys bicoloratus, estimated using otolith Sr:Ca ratiosFISHERIES OCEANOGRAPHY, Issue 4 2000Yoh Yamashita In Sendai Bay, stone flounder larvae settle and spend their juvenile period in either shallow exposed inshore nursery grounds or estuarine nursery grounds. The purpose of this study is to examine the relative contributions of these two kinds of nursery grounds to the flounder population using otolith strontium:calcium ratios. Stone flounder juveniles were collected from both nursery grounds, and one- and two-year-old flounder were caught deeper in Sendai Bay. Sr and Ca content in the otoliths were measured by electron probe micro analysis. The Sr:Ca ratios in the otolith section corresponding to the early postsettlement period ranged from 3.06 to 3.85 for the exposed inshore areas with stable low temperature and high salinity conditions, and from 3.81 to 5.32 in brackish estuaries with high temperature and low salinity conditions but with large diel and tidal cyclical fluctuations. Values from an estuarine site with stable salinity ranged from 3.58 to 4.15 overlapping with both the above ranges. Rearing experiments supported our inference that the high otolith Sr:Ca ratios of juveniles inhabiting estuarine nursery grounds are attributable to higher temperature and physiological stress caused by the large diel temperature and salinity fluctuations within the estuaries. Estimation of the Sr:Ca ratio of recruited fish using the otolith section formed while in the nursery area showed that at least 20 out of 42 individuals examined originated from estuarine nursery grounds. The present study indicates that estuaries play an important role as nursery grounds for stone flounder, producing about half of the stock in spite of the small and restricted area compared with the wide expanse of the exposed inshore area. [source] Calcium balance in Daphnia grown on diets differing in food quantity, phosphorus and calciumFRESHWATER BIOLOGY, Issue 11 2009XUE-JIA HE Summary 1.,The influences of dietary phosphorus (P) and food concentration on the calcium (Ca) balance in Daphnia magna were examined in this study at two different ambient Ca concentrations (0.5 and 10 mg Ca L,1). Daphnia were grown by feeding the young adults differentially under contrasting dietary P conditions [molar C : P ratio = c. 900 and c. 90 as low P (LP) and high P (HP), respectively], ambient Ca concentrations [0.5 mg and 10 mg Ca L,1 as low Ca (LCa) or high Ca (HCa), respectively] and food levels [0.15 or 1.5 mg C L,1 as low food (LF) or high food (HF), respectively] for 5 days. 2.,The specific Ca contents of daphniids (1.9,6.5% of dry weight,1) increased with increasing Ca concentration, food level and dietary P content, although the food level did not affect the Ca content in the HPHCa treatment. A radioactive tracer method showed that the food level did not affect the influx of Ca from the water under LP conditions, but the Ca influx under HP conditions doubled with a HF level. A LP condition also led to a decrease in Ca influx with a HF level. 3.,During the 3 days of efflux, generally only a small proportion of Ca (2.6,3.3%) was retained by the daphniids, but this retention increased (14,23%) under low ambient Ca concentrations and under P-limitation. Excretion was the most important pathway for Ca loss (accounting for 50,60% of body Ca), followed by moulting (20,47%), but the relative contribution of these two pathways (excretion and moulting) did not vary among all the different treatments. The absolute loss of Ca through excretion and moulting, on the contrary, differed with different ambient Ca concentrations and dietary P conditions. A HF level led to an increase in the loss rates in most cases. 4.,Our study strongly suggested that there is an interaction between an essential metal (Ca) and macronutrients (C and P) in freshwater crustaceans with HCa and P contents. The results imply that variation in environmental nutrient conditions may change the Ca budget in crustaceans and may affect the dynamics of Ca in the epilimnion of freshwaters. [source] Effects of low calcium concentrations on two common freshwater crustaceans, Gammarus lacustris and Astacus astacusFUNCTIONAL ECOLOGY, Issue 3 2002N. A. Rukke Summary 1.,Field studies indicate that low Ca concentrations limit the distribution and success of Ca-demanding freshwater crustaceans in soft-water localities. A long-lasting depletion of Ca caused by reversed acidification could thus be detrimental to such species. 2.,Experimental studies of Gammarus lacustris and Astacus astacus revealed decreased survival and retarded growth at ambient Ca concentrations <5 mg l,1, compared with animals reared at 10 mg l,1. 3.,A significant proportion of the total body Ca content was lost during the moult, but moulting frequencies were not affected by ambient Ca concentration. Complete postmoult calcification of the carapace could not be achieved at ambient Ca concentrations <5 mg l,1, and individuals reared at such conditions had a lower specific Ca content than individuals reared at sufficient Ca levels. 4.,A juvenile bottleneck regarding the susceptibility to Ca deficiency was shown in G. lacustris, as neonates had a relatively higher mass-specific Ca content and a higher Ca threshold for survival than adults. 5.,Because of a short postmoult calcification period of less than 2 days, G. lacustris had limited ability to compensate for low water Ca levels by obtaining Ca from food. However, food might be an important source of Ca for A. astacus living at low ambient Ca, because eating could be resumed during the relatively long calcification period (>15 days). [source] Mineral absorption in tapirs (Tapirus spp.) as compared to the domestic horseJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 6 2009M. Clauss Summary To test whether mineral recommendations for horses are likely to guarantee adequate mineral provision for tapirs (Tapirus spp.), we investigated the apparent absorption (aA) of macro and micro-minerals in 18 tapirs from five zoological institutions in a total of 24 feeding trials with total faecal collection. Samples of feeds and faeces were analysed for Ca, P, Mg, Na, K, Fe, Cu and Zn. The resulting aA coefficients and the linear relationships of apparently absorbable dietary mineral content to total dietary mineral content (per 100 g dry matter) were compared with data for domestic horses. While there were no apparent differences in the absorption patterns for P, K, Na, Fe, Cu or Zn, the absorption of both Ca and Mg was distinctively higher in tapirs than in horses. Tapirs are browsers that are adapted to a diet of higher Ca content and higher Ca:P ratio than equids, and high absorptive efficiency for Ca might have evolved to ensure that high dietary Ca concentrations do not lead to the binding of dietary P in the intestine, making it unavailable for hindgut microbes. Similar to other hindgut fermenters, in tapirs, absorption coefficients for Ca increased with dietary Ca:P ratio, and urinary Ca:creatinine ratios increased with dietary Ca. Several zoo diets used were deficient in one or more minerals. When compared with faeces of free-ranging animals, faeces of zoo animals had higher concentrations of most minerals, probably indicating a lesser diluting effect of indigestible fibre in zoo animals. [source] Influence of different dietary calcium levels on the digestibility of Ca, Mg and P in Hermann's tortoises (Testudo hermanni)JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 11-12 2007A. Liesegang Summary Calcium and phosphorus are very important minerals in reptile nutrition, but many diets are still not balanced. To achieve optimal growth, including a healthy skeleton and a strong shell, a well-balanced supply with these minerals is prerequisite. The purpose of this study was to evaluate the apparent digestibility in Hermann's tortoises of diets with different calcium levels with special emphasis on the digestibility of minerals. Eight adult Hermann's tortoises of the veterinary faculty in Zurich were used. The animals were housed indoors at a mean temperature between 23 °C and 26 °C. The animals were fed a diet, which consisted of vegetables, herbs and different supplementation of calcium carbonate. Daily faecal samples of all tortoises were collected from day 8 to day 12. A proximate analysis was performed and the HCl-insoluble ash was used as an indigestible natural indicator (marker) for the determination of the apparent digestibility of minerals. The calcium content of the mixed feedstuffs of diet I was 0.64% on a dry matter basis, and the Ca:P ratio in the food was 3:1. In diet II the Ca content was 1.29% on a dry matter basis, and the Ca:P ratio in the food was 6:1. The digestibility of Ca in diet I was 57%. The other examined minerals, Mg and P, had a digestibility of 46% and 58% respectively. In diet II the digestibility of Ca was 79%, of Mg 52% and of P 52%. The results of this study indicated, that higher Ca concentrations in the diet led to an increased apparent digestibility of Ca and Mg. [source] Fractal structure of basic silica gels with low Ca contentJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000F. Gaboriaud Several gels were produced by addition of low amounts of calcium ions to strongly basic silico-alkaline sols. These gels, previously studied by small-angle x-ray scattering (SAXS), small-angle neutron scattering (SANS) and elastic light scattering (ELS), were analysed over a wide range of scattering vectors extending from 8 x 10,4Å,1 up to 2 x 10,4Å. The joint use of various scattering techniques allowed us the simultaneous characterisation of coarse, medium and fine structural features of the studied gels. Clear discrepancies between SANS and earlier ELS results were attributed to effects of multiple scattering on light scattering experiments. The experimental results demonstrate that the studied gels are composed of aggregates exhibiting a fractal structure within a scale range extending from less than 10 to more than 1000 Å, with the same fractal dimension over the whole scale range. The fractal dimension and so the mechanism of aggregation depend on the initial sol composition and Ca content. The mechanism responsible for gel formation in precursor sols with low calcium concentration ([Ca2+] = 0.3 mol.L,1) is reaction limited cluster-cluster aggregation (RLCA). [source] Influence of Ca content and oxygen partial pressure on microstructural evolution of (Co,Ca)O at elevated temperaturesJOURNAL OF MICROSCOPY, Issue 1 2006J. KUSINSKI Summary Ca-doped (1, 1.7, 5 and 10 mol% CaO) cobalt oxide single-crystal samples, with an [001] orientation, were annealed at elevated temperatures of 1000,1200 °C for different times and at different oxygen partial pressures. The microstructure was examined by means of transmission light and electron microscopy. High-temperature X-ray diffractometry was used, with the aim of determining the temperature of the CoO , Co3O4 transition in these materials. Extensive precipitation of Ca-free Co3O4 spinel crystals was observed with increasing Ca content and oxygen activity. It is suggested that the electrical conductivity changes in this material may be related to this precipitation, because it changes the electronic state of cobalt cations. [source] Effects of NGF on different phenotypes and genotypes of cholinergic murine SN56 cellsJOURNAL OF NEUROCHEMISTRY, Issue 2003H. Bielarczyk Nerve growth factor (NGF) is important for differentiation and maintenance of septal cholinergic neurons. It caused concentration-dependent increase of choline acetyltransferase (ChAT) activity ([EC50%] 1 ng/mL), acetylcholine (ACh) content and morphologic maturation of SN56TrkA(+)p75(+) but not TrkA(,)p75(+) cells. NGF added with cyclic AMP altered significantly differential effects of the latter neither in TrkA(,) nor TrkA(+). However, when cyclic AMP-predifferentiated cells were treated with NGF alone, it caused suppression of the cholinergic phenotype in both cell lines. Anti-p75 antibodies totally reversed inhibitory effects of NGF on ChAT activity. Differentiation was accompanied by increase whereas its reversal by decrease of intracellular Ca content. These data indicate that NGF may exert opposite effects on phenotype of cholinergic neurons by p75 receptor signaling pathways and changes in intracellular Ca. Acknowledgement: Supported by KBN project 6P05A 01020. [source] Dielectric and Structural Properties of Layer-Structured Sr1,xCaxBi2Nb2O9JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008Shiming Huang Sr1,xCaxBi2Nb2O9 (x=0, 0.2, 0.4, 0.6, 0.8 and 1) ceramics were prepared by a conventional solid-state reaction method. Their dielectric and structural properties were investigated. X-ray diffraction analysis indicated that single-phase layered perovskites were obtained. For Ca-substituted specimens, a dielectric relaxation peak is observed in the temperature range of 30°,150°C, and there is a broader para-ferroelectric phase transition peak. The temperature of the maximum dielectric constant Tm increases linearly with increasing Ca content. Raman spectra indicate that a small amount of Ca2+ is incorporated into Bi sites in the Bi2O2 layers, and an increase in the degree of distortion of NbO6 octahedra for Ca-substituted specimens should be one of the reasons for the increase in Tm compared with SrBi2Nb2O9. [source] Electrochemical Behavior of Gel-Derived Lanthanum Calcium Cobalt Ferrite Cathode in Contact with LAMOX ElectrolyteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Tsu-Yung Jin The electrochemical performance and structural features of (La1,yCay)(CoxFe1,x)O3 cathode prepared via a citrate acid gel route are studied when it is interfaced with the (La1.8Dy0.2)(Mo2,zWz)O9 electrolyte. The resistance and chemical capacitance of a low-frequency arc are extracted from the impedance results to evaluate its catalytic activity in oxygen reduction reaction (ORR). (La0.75Ca0.25)(Co0.8Fe0.2)O3 cathode exhibits the minimum area-specific resistance of 0.9 , cm2 and maximum capacitance of 5.7 mF/cm2 at 800°C among the compositions of x=0.1,0.9 and y=0.25. As the Co content increases, the decrease in resistance outweighs the increase in capacitance so that the product of resistance and capacitance (RC time constant) decreases. In contrast, when varying the Ca content of the A-site, the changes in resistance and the capacitance compensate each other; hence the RC time constant is virtually unchanged with respect to the calcium content. Thus, Co is a more influential element than Ca on the ORR catalytic activity. The pore structure study reveals a small amount of Mo diffuses from the electrolyte into the cathode, and its quantity is reduced when interfaced to an electrolyte of high W content. [source] Influence of Dietary Levels of Magnesium on Growth, Tissue Mineral Content, and Resistance of Channel Catfish Ictalurus punctatus Challenged with Edwardsiella ictaluriJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2003Chhorn Lim Juvenile channel catfish were fed purified diets supplemented with magnesium (Mg) from Mg sulfate at levels of 0, 200, 400, 600, 800, and 1,000 mg/kg and 0, 200, 400, 600, and 800 mg/kg in two separate feeding studies. In study I, the effect of dietary levels of Mg on growth response, vertebral mineral content, and macrophage chemotaxis were evaluated. Study II had similar objectives except that whole body mineral content was measured, and resistance of channel catfish to Edwardsiella ictaluri challenge was also determined. Fish with an average weight of 10.89 g were stocked at a rate of 50 fish/110-L aquarium (study I). In study II, fish with an average weight of 4.14 g were stocked at rates of 40 fish/110-L aquarium. Prior to stocking, each batch of fish was acclimated to laboratory conditions and fed the basal diet for 2 wk. The concentration of Mg in rearing water was 1.8 mg/L. Each diet was fed to fish in quadruplicate and triplicate aquaria to apparent satiation for 10 wk for studies I and II, respectively. Fish fed the basal diet started to die as early as 3 d after the study began (17 d of feeding the diet without Mg supplementation). In both studies, weight gain, survival, and feed efficiency were lowest for fish fed the basal diet but increased with increasing dietary levels of Mg. However, the differences between the values of each of these parameters for fish fed diets containing supplemental Mg were not always significant. Magnesium-deficiency signs observed were anorexia, sluggishness, convulsions, deformed snout, vertebral curvature, muscle flaccidity, and high mortality. Vertebral and whole body ash concentrations were high, but Mg content was low for fish fed the basal and the 200-mg Mg diets. Bone Ca content did not differ among fish fed different diets (study I), but whole body Ca tended to increase for fish fed the basal diet, suggesting the possibility of calcification of soft tissues. Macrophage chemotaxis in the presence of exoantigen was highest for fish fed diets supplemented with Mg at 400 and 200 mgkg for studies I and II, respectively. When expressed in terms of chemotaxis index, however, maximum or near maximum value was observed at a dietary Mg level of 400 mg/kg. Thus, a dietary level of Mg of 400 mg/kg from Mg sulfate was required for optimum growth and survival, maintaining high tissue levels of Mg, prevention of muscle flaccidity and skeletal deformity, and stimulating macrophage chemotaxis. Dietary levels of Mg had no effect on the resistance of juvenile channel catfish to Edwarsiella. ictaluri challenge. [source] Reduction of Botrytis cinerea sporulation in sweet basil by altering the concentrations of nitrogen and calcium in the irrigation solutionPLANT PATHOLOGY, Issue 4 2006U. Yermiyahu Current measures for suppressing grey mould (Botrytis cinerea) on sweet basil rely on fungicide applications and climate control. In this study, the nitrogen and calcium concentrations in the standard irrigation solution (7·2 and 1·3 mm, respectively) were varied in a series of experiments conducted in pots and large containers. Treatments differed in the N or Ca concentrations supplied, and effects on host response were determined in detached stem segments, individual plants and plots. Effects of the two elements on grey mould incidence, lesion size and rate of disease progression were erratic and rarely significant, but decreasing the concentration of N and increasing the concentration of Ca in the irrigation solution decreased sporulation of B. cinerea. In some cases, however, altering the standard irrigation solution resulted in significantly lower yields. Analyses of mineral contents in the shoots suggested that yields were not impaired when N content in the shoots was not reduced below 2·9% and Ca content was not raised above 1·3%. These findings were used to compose a modified irrigation solution containing half of the N (3·6 mm) and double of the Ca (2·55 mm) concentrations in the standard irrigation solution. The modified irrigation solution significantly reduced sporulation of B. cinerea without affecting crop yield. [source] Recruitment of Ca2+ release channels by calcium-induced Ca2+ release does not appear to occur in isolated Ca2+ release sites in frog skeletal muscleTHE JOURNAL OF PHYSIOLOGY, Issue 3 2002Karine Fénelon Ca2+ release from the sarcoplasmic reticulum (SR) in skeletal muscle in response to small depolarisations (e.g. to -60 mV) should be the sum of release from many isolated Ca2+ release sites. Each site has one SR Ca2+ release channel activated by its associated T-tubular voltage sensor. The aim of this study was to evaluate whether it also includes neighbouring Ca2+ release channels activated by Ca-induced Ca2+ release (CICR). Ca2+ release in frog cut muscle fibres was estimated with the EGTA/phenol red method. The fraction of SR Ca content ([CaSR]) released by a 400 ms pulse to -60 mV (denoted fCa) provided a measure of the average Ca2+ permeability of the SR associated with the pulse. In control experiments, fCa was approximately constant when [CaSR] was 1500-3000 ,m (plateau region) and then increased as [CaSR] decreased, reaching a peak when [CaSR] was 300-500 ,m that was 4.8 times larger on average than the plateau value. With 8 mm of the fast Ca2+ buffer BAPTA in the internal solution, fCa was 5.0-5.3 times larger on average than the plateau value obtained before adding BAPTA when [CaSR] was 300-500 ,m. In support of earlier results, 8 mm BAPTA did not affect Ca2+ release in the plateau region. At intermediate values of [CaSR], BAPTA resulted in a small, if any, increase in fCa, presumably by decreasing Ca inactivation of Ca2+ release. Since BAPTA never decreased fCa, the results indicate that neighbouring channels are not activated by CICR with small depolarisations when [CaSR] is 300-3000 ,m. [source] Relationship between Carbon Isotope Discrimination, Mineral Content and Gas Exchange Parameters in Vegetative Organs of Wheat Grown under Three Different Water RegimesJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2010L. Zhu Abstract Carbon isotope discrimination (,) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of high cost for , analysis, attempts have been made to identify alternative screening criteria. Ash content (ma) has been proposed as an alternative criterion for , in wheat and barley. A pot experiment was conducted to analyse the relationship between ,, mineral content and gas exchange parameters in seedlings and leaves of bread wheat (Triticum aestivum L.). Plants of 10 genotypes were cultivated under three different water regimes corresponding to moderate (T3), intermediate (T2) and severe drought (T1) stress obtained by maintaining soil humidity at 75 %, 55 % and 45 % of the humidity at field capacity respectively. , and ma in seedlings and leaves showed significant differences among the three water treatments. Significant positive correlations were found between , and ma in seedlings and leaves at elongation and anthesis stages in severe drought stress (T1). , was negatively associated with potassium (K) content in intermediate drought stress (T2) and positively with magnesium (Mg) content in T2 and T3 (moderate drought stress) in flag leaf at anthesis. There were negative correlations between , and single-leaf intrinsic water-use efficiency (WT) in T2 and T3 at anthesis stage. Stronger positive associations were noted between , and stomatal conductance (gs) in T1 and T2 than in T3 at anthesis. These results suggested that , is a good trait as an indirect selection criterion for genotypic improvement in transpiration efficiency, while ma is a possible alternative criterion of , in wheat vegetative organs, especially in stressed environments. Significant association was found between , and K, Mg and Ca contents that would merit being better investigated. [source] Relationship between Carbon Isotope Discrimination and Mineral Content in Wheat Grown under Three Different Water RegimesJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2008L. Zhu Abstract Carbon isotope discrimination (,) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of the high cost for , analysis, attempts have been carried out to identify alternative screening criteria. Ash content (ma) has been proposed as an alternative criterion for , in wheat and barley. A pot experiment was conducted to analyse the relationship between , and ma in flag leaf and grain. Plants of 10 genotypes were cultivated under three different water regimes corresponding to moderate, intermediate and severe drought stress obtained by maintaining soil humidity at 75 %, 55 % and 45 % of the humidity at field capacity, respectively. , and ma in flag leaf and grain showed significant differences between the moderate, intermediate and severe drought stress levels. Significant correlations were found among genotypes for , and ma in flag leaf under severe drought stress, and for , and ma in grain under intermediate and moderate drought stress. In flag leaf at anthesis, , was negatively associated to K content and positively to Mg content. At maturity, , in grain was negatively correlated with Mg and Ca contents in flag leaf and grain, respectively. These results suggested that these traits may be potentially useful traits, which could be surrogates for ,. [source] Elemental distributions in femoral bone of rat under osteoporosis preventive treatmentsJOURNAL OF MICROSCOPY, Issue 3 2006M. D. YNSA Summary One of the abnormalities of bone architecture is osteoporosis as occurring in post-menopausal women. Especially long bones, such as femur, become more fragile and more prone to fracture. The efficiency of several osteoporosis preventative treatments based on oestrogen and progestin in bone structure and mineral recovery was studied using ovariectomized Wistar rats as an osteoporosis experimental model. Diagonal cross-sections of the proximal epiphysis of femoral bones were analysed using nuclear microscopy techniques in order to map and determine the concentration profiles of P, Ca, S, Fe and Zn from the epiphysis to diaphysis and across the cortical and trabecular bone structures. In control animals (not ovariectomized), the S and Zn contents significantly characterized differences between cortical and trabecular bone structures, whereas P and Ca showed increased gradients from the epiphyseal region to the diaphysis. After ovariectomy the differences observed were differential according to the type of hormonal supplementation. A significant decrease in P and Ca contents and depletion of minor and trace minerals, such as S, Fe and Zn, were found for both cortical and trabecular bone structures after ovariectomy relative to controls. Bone mineral contents were reversed to control levels by synthetic oestrogen supplementation, and combined oestrogen and progesterone treatment. Recovery was more evident in the femoral epiphysis and neck than in the diaphysis. The use of oestrogen alone did not lead to bone recovery after ovariectomy. Alterations in bone mineral composition observed for animals receiving synthetic oestrogen and combined oestrogen and progesterone supplement might reflect beneficial structural changes in critical regions of long bones, mostly affected in post-menopausal osteoporosis. [source] The Cornubian Batholith: an Example of Magmatic Fractionation on a Crustal ScaleRESOURCE GEOLOGY, Issue 3 2006Bruce W. Chappell Abstract. The Cornubian Batholith comprises six major and several smaller bodies of S-type granite in southwestern England. These late-Variscan granites comprise two-mica granites, and much less abundant Li-mica granites that are restricted to one of the major bodies (St Austell) and smaller bodies. Some of these intrusive rocks are associated with major Sn mineralization. This paper is concerned with the geochemistry of the two-mica granites, which are felsic, strongly peraluminous, and have a high total alkali content and low Na:K. Rocks with very similar compositions to these granites occur elsewhere, including the Variscan granites of continental Europe, and in southeastern Australia. In detail all of the major plutons of this batholith have distinctive compositions, except for Bodmin Moor and Carnmenellis which cannot be discriminated from each other compositionally. A comparison with experimental data shows that the granites attained their major element composition under conditions of crystal-liquid equilibrium, with the final melt being saturated in H2O, at temperatures close to 770d,C and pressures about 50 MPa. That temperature estimate is in good agreement with values obtained from zircon saturation thermometry. The specific minimum-temperature composition excludes the possibility of widespread transfer of elements during hydrothermal alteration. Minor elements that are relatively very abundant are Li, B, Cs and U, while F, Ga, Ge, Rb, Sn, Ta, W and Tl are quite abundant and P is high for felsic rocks. Sr, Ba, and the trace transition metals Sc to Zn, are low, but not as low as they commonly are in very felsic granites. These trace element abundances, and the EL2O-saturation, resulted from the fractional crystallization of a melt derived by the partial melting of feldspathic greywackes in the crust. The Cornubian granites have compositions very similar to the more felsic rocks of the Koetong Suite of southeastern Australia, where a full range of granites formed at the various stages of magmatic fractionation postulated for the Cornubian granites, can be observed. The operation of fractional crystallization in the Cornubian granites is confirmed by the high P abundances in the feldspars, with P contents of the plagioclase crystals correlating with Ab-con-tent Most of the granites represent solidified melt compositions but within the Dartmoor pluton there is a significant component of granites that are cumulative, shown by their higher Ca contents. The Cornubian plutons define areas of high heat flow, of a magnitude which requires that fractionated magmas were transported laterally from their sources and concentrated in the exposed plutons. The generation of these granite plutons therefore involved magmatic fractionation during the stages of partial melting, removal of unmelted material from that melt, and fractional crystallization. During the later stages of those processes, movement of those magmas occurred on a crustal scale. [source] |