Sr Profiles Research Articles

Temporal changes in interstitial water chemistry and calcite recrystallization in marine sediments

Recrystallization processes in marine sediments can alter the extent to which biogenic calcite composition serves as a proxy of oceanic chemical and isotopic history. Models of calcite recrystallization developed to date have resulted in significant insights into these processes, but are not completely adequate to describe the conditions of recrystallization. Marine sediments frequently have concentration gradients in interstitial dissolved calcium, magnesium, and strontium which have probably evolved during sediment accumulation. Realistic, albeit simplified, models of the temporal evolution of interstitial water profiles of Ca, Mg, and Sr were used with several patterns of recrystallization rate variation to predict the composition of recrystallized inorganic calcite. Comparison of predictions with measured Mg/Ca and Sr/Ca ratios in severely altered calcite samples from several Deep Sea Drilling Project sites demonstrates that models incorporating temporal variation in interstitial water composition more successfully predict observed calcite compositions than do models which rely solely on present-day interstitial water chemistry. Temporal changes in interstitial composition are particularly important in interpreting Mg/Ca ratios in conjunction with Sr/Ca ratios. Estimates of Mg distribution coefficients from previous observations in marine sediments, much lower than those in laboratory studies of inorganic calcite, are confirmed by these results. Evaluation of the effects of diagenetic alteration of biogenic calcium carbonate sediment must be a site-specific process, taking into account accumulation history, present interstitial chemistry and its variation in the past, and sample depths and ages.

Cerebral-activating (EEG) properties of two inverse agonists and of an antagonist at the benzodiazepine receptor in the rat

In order to assess the effects of inverse benzodiazepine agonists and antagonists on brain function, computerized EEG (CEEG) analysis was performed in rats following the i.p. administration of SR 95195 (7-phenyl-3-methyl-1,2,4 triazolo-[4,3-b]pyridazine) and CGS 8216 (2-phenylpyrazolo-[4,3c]-quinoline-3-[5H]-one) two benzodiazepine receptor inverse agonists (BRIAGs) and of flumazepil (Ro 15-1788), a benzodiazepine receptor antagonist (BRANT). The EEG effects of SR 95195 (3, 10, 30 and 60 mg/kg), CGS 8216 (10 and 30 mg/kg) and flumazepil (3, 10, 30 and 60 mg/kg) were compared to those of the psychostimulant drugs DL-amphetamine (0.1, 0.3 and 1 mg/kg), and caffeine (10 and 30 mg/kg) and those of aniracetam (100 and 300 mg/kg), a nootropic pyrrolidone derivative. The CEEG profiles of SR 95195, CGS 8216 and flumazepil were mainly characterized by a power increase in the 20-32 Hz frequency range and by a power reduction in the 8-16 Hz range. These effects were quite similar to those of the psychostimulants DL-amphetamine and caffeine as well as to those of the nootropic aniracetam. Other psychotropic drugs with CNS-depressant properties, namely diazepam (10 mg/kg p.o.), pentobarbital (30 mg/kg p.o.), chlorpromazine (10 mg/kg i.p.) and imipramine (10 mg/kg i.p.) induced quite different EEG power modifications. These results show that BRIAGs and BRANTs possess a marked intrinsic activity at the central level and suggest that this activity is CNS-activating in nature.

Occurrence of Key Chemical Elements in Late Cretaceous Adaville No. 1 Coal Seam, Kemmerer, Wyoming, Coal District: ABSTRACT

The distribution of key chemical elements across an approximately 35 m-thick section of the Adaville No. 1 subbituminous coal seam near Kemmerer, Wyoming, has been examined, using instrumental neutron activation analysis (INAA) and x-ray fluorescence analysis of whole coal samples. In comparing the mean element concentrations for 28 western coals the Adaville No. 1 contains (1) significantly higher concentrations of Br, Ca, Ga, Rb, Sr, and Zr, (2) significant lower concentrations of Al, Ce, Cr, La, and Na, and (3) similar concentrations of Sc, Ti, and V. Scanning electron microanalysis (SEM) of low temperature ash (LTA) revealed the presence of abundant clays and plagioclase feldspar; minor hematite, pyrite, quartz, gypsum, sylvite, amphibole, pyroxene, and rutile; and trace amounts of delafossite (the first recorded occurrence in a coal seam), calcite, cuprite, cassiterite, K-feldspar, and sphene. The cross-seam distribution of these minerals, combined with the similarity of the concentration profiles of Al, Ce, Cr, La, V, Rb, Sr, and Sc to that of LTA, suggest that all of the elements, except Br, Ga, and possible Zr, have significant mineralogical associations with the Adaville No. 1 coal. The presence of authigenic quartz, sylvite, delafossite, gypsum, and pyrite, and crystal solution features, suggest considerablemore » ion mobility during peat deposition and coalification. The mineralogy and trace-element chemistry of the Adaville No. 1 coal seam are consistent with a wave-dominated deltaic depositional environment, long-lived saline conditions during peat accumulation, and a siliceous igneous rock source terrane.« less

The fine structure of the dorsal column nucleus and the nucleus of bischoff of the python (Python reticulatus)

Three types of neuronal perikaryal profiles were identified in the dorsal column nucleus and the nucleus of Bischoff of the python (Python reticulatus). Type I neuronal profiles are large (diameters 12-20 μm) with a deeply indented uncleus. The cisterns of rough endoplasmic reticulum (rER) are mostly randomly dispersed. Axosomatic synapses are few. Type II neuronal profiles (9-11 μm) have a smooth, round, or slightly oval nucleus. Several small stacks of rER are present. Type III neuronal profiles (8-10 μm) have little cytoplasm. The nuclear margin is irregular but not deeply infolded. The rER usually consists of a single long perinuclear ribosome-studded cistern. Two types of astrocytic profiles have been identified. Both types contain abundant filaments. Type I astrocytes are large cells, and the nucleus is very irregular in shape. Type II astrocytes are smaller and are found among the myelinated axons in the dorsal funiculus. Two classes of axon terminals have been identified. One class contains round synaptic vesicles (R profiles) and the other flattened vesicles (F profiles). Some R profiles are small (SR profiles), others are large (LR profiles). Some R profiles also contain a few large, dense-cored vesicles. The R and F profiles establish axodendritic and axoaxonal synapses, some of which are located in the synaptic glomeruli and others in the extraglomerular neuropil. In most of the axoaxonal synapses, the presynaptic element is an F profile and the post synaptic element an LR profile. Occasionally, LR profiles are presynaptic to F profiles. The findings in the python are compared with those of the dorsal column nuclei of the rat, cat, and monkey.

Quantitative electroencephalographic profile of 3-(4-hydroxy-1-piperidinyl)-6-(2,4-dichlorophenyl)-pyridazine (SR 41378) in the rat.

Quantitative electroencephalographic (QEEG) analysis was performed in rats following the oral administration of SR 41378 [3-(4-hydroxy-1-piperidinyl)-6-(2,4-dichlorophenyl)-pyridazine], a novel aminopyridazine derivative, which has been shown to possess anticonvulsant, antianxiety and hypnotic activities in mice and rats. The EEG effects of SR 41378 (10, 30 and 100 mg/kg) were compared to those of secobarbital (30 and 60 mg/kg) and diazepam (1, 3 and 10 mg/kg). SR 41378 and secobarbital increased the power of the middle-frequencies (8-16 Hz) of the EEG, reduced that of 4-8 Hz (theta) activities and did not affect 1-4 Hz (delta) activities. Diazepam also increased the power of middle-frequency activities and decreased that of both delta and theta activities. Quantitative EEG profiles were calculated from the mean integrated power (MIP) of selected frequency bands. The QEEG profile of SR 41378 was found to share common characteristics with those of secobarbital and diazepam: dose-dependent decrease of theta band MIP and increase of 8-20 Hz (middle beta bands) MIP. However, both SR 41378 and secobarbital induced a reduction of the 28-32 Hz (fast beta bands) MIP, whereas diazepam diminished the delta band. These results suggest that SR 41378, a novel chemical structure, shares common psychotropic properties with barbiturates and benzodiazepines.

Volcanism of shoshonite to high-K andesite affinity in an Archean are environment, Oxford Lake, Manitoba

Volcanic rocks of the Archean Oxford Lake Group are characterized by a stratigraphic progression from mafic to felsic compositions, accompanied by a systematic decrease in incompatible element abundances. This, coupled with high abundances of Sr, Rb, K2O, and La, high (La/Yb)n, and unfractionated (flat to concave) heavy-REE (rare earth element) profiles, distinguishes these rocks as an Archean shoshonite to high-K andesite – dacite–rhyolite series, directly comparable to modern analogues formed in convergent tectonic settings. The trace-element data support a model of petrogenesis in which an Archean mantle source region was modified by volatiles rich in large-ion-lithophile elements, the modified mantle was subjected to partial melting forming a parental liquid of shoshonitic character, and this liquid principally underwent amphibole fractionation to form the evolved rock compositions. This process is envisaged as terminal magmatism during the final (senile) stage of activity in an arc setting. The Rb–Sr age (2650 ± 80 Ma) and initial-Sr ratio (0.70145 ± 38) of the Oxford Lake Group are in accord with this model; when coupled with the 2.7 Ga age for the underlying Hayes River Group volcanics, these data indicate a short interval (<50 Ma?) for Archean crustal development in the area.

Comparison of emission and absorption core profiles of Sr and Ba resonance lines in an air-acetylene flame

Under optically thin conditions, the core of emission-line profiles of the resonance lines ( 1 P 1- 1 S 0 transition) of Sr and Ba have been measured with a pressure-scanned Fabry-Pe´rot interferometer in a laminar, pre-mixed, shielded air-acetylene flame at 1 atm ( T = 2275 K). Under identical experimental conditions, where Doppler and collisional broadening are almost equally important, these profiles are compared with Zeeman-scanned absorption profiles of the same resonance lines. The values for the full width at one-half maximum (FWHM) and the shift of the emission and absorption core profiles for Sr and Ba proved to be identical within an experimental scatter of 5 and 20%, respectively. Obviously the radiation emitted by the Sr and Ba atoms in the flame is thermal, which means that the spectral shape of the line is consistent with Maxwell-Boltzmann equilibrium.