Radiochemical Data Research Articles

Simplified Sensitivity Method for Uncertainty Evaluation in Decay-Heat Calculations due to Experimental Errors of Fission Yields

A simplified method to evaluate uncertainty of calculated decay heat is presented. Numerical analyses to provide the sensitivity coefficients were made only for uniform changes of the parameters used for the estimations of fractional yields. The deviations of the decay heat from the reference were approximately proportional to the magnitudes of the parameter changes. Then, a general formula for the sensitivity coefficients was theoretically derived from the first order approximation and the correlation due to the charge conservation law between complementary fragments was taken into account. The sensitivity for the charge distribution width σ A was less than 1/10 of that for the most probable charge ZP. The evaluation of experimental errors for ZP and σ A values were performed using radio-chemical data by Wahl and mass separator data by Clerc, and then the decay heat uncertainties were estimated by using the resultant ZP and σ A experimental errors. Evaluated uncertainties of the decay heat for thermal ne...

U-series isochron dating: A generalized method employing total-sample dissolution

The age of a sedimentary deposit can be determined by measuring 238U, 234U, 232Th, and 230Th in two or more samples of the deposit, with the requirement that these samples have different U/Th ratios but an identical 230Th 232Th ratio when deposited. This paper presents the theoretical and experimental aspects of the dating method. The latter involves techniques for securing samples of varied U/ Th ratios from the same deposit, plotting isochrons of the radiochemical data (obtained on totally dissolved samples) for age analysis, and estimating the errors involved. Although applications to impure carbonates and lacustrine evaporite sediments are given as examples in this paper, the method potentially can be generalized for dating a variety of authigenic deposits such as rock varnish, peat, opal, sulfate minerals, and marine phosphorites.

Voltammetric and radioactive labeling studies of single crystal and polycrystalline rhodium electrodes in sulfate-containing electrolytes

Adsorption of sulfate/bisulfate anions on single crystal Rh(111) (ordered/disordered) and polycrystalline rhodium electrodes in perchloric acid solution was studied by the use of cyclic voltammetry and the radioactive labeling method. The ordered Rh(111) surface was characterized by LEED and Auger spectroscopy to verify its well-defined character. Details of the surface chemistry of the anions interacting with the three rhodium substrates are different. This is considered as evidence that a long-range order of the metal electrodes alters the structure of chemisorbed hydrogen and oxygen significantly and that this structure is affected by the reversibly interacting species. Likewise, the adsorbed layer of sulfate anions on Rh(111) is more stable than that on other rhodium surfaces due to a favorable spatial configuration of the anions and surface water molecule network, which are proposed to be cross linked by hydrogen bonding. Overall, the adsorption reversibility of sulfate was confirmed with respect to the bulk concentration of the adsorbate and the electrode potential (provided that the surface oxidation is avoided). Radiochemical data reveal that, in the studied bulk concentration range (up to about 10 −3 M), the uptake of anions by Rh(111) is limited to ca. 40% of the theoretical maximum coverage. The interaction of sulfate with Pt(111), and corresponding voltammetry in perchloric acid electrolyte are also brought into focus. It is concluded that only a part of the Pt(111) “butterfly” can be accounted for by adsorption of high energy hydrogen. No high energy hydrogen has been found to exist on Rh(111), as inferred earlier in our laboratory.

Sedimentation dynamics in the Santa Monica-San Pedro Basin off Los Angeles: radiochemical, sediment trap and transmissometer studies

A large number of sediment cores and sediment trap samples collected from different parts of the Santa Monica-San Pedro (SM-SP) Basin during 1985–1988 were studied for radionuclides, trace metals and other sedimentary components. The radiochemical data are presented here to give a basin-wide view of the sedimentation dynamics. 210Pb stratigraphy indicated that sedimentation rates were higher and more variable (30–80 mg cm −2y −1) in the more dynamic slope region, but were uniformly low (13.4–18.8 mg cm −2y −1) in the flat, deep basin. From the sediment record, it was suggested that sedimentation rates were decreasing and the area of anoxia had been expanding, at least during the past one to two centuries. Turbidite layers found in the sediment cores suggested higher frequency and more recent occurrence toward the basin margins. 210Pb geochronologies indicated that the recent turbidites might be related to major storms which occurred during the past two decades. Sediment traps deployed in the basin recorded very large short-term spatial and temporal variabilities of mass flux, with unusually high fluxes corresponding to recorded large wave events. Trap-measured near-bottom mass fluxes averaged over all collection periods (622 days) were consistent with 210Pb-based sediment accumulation rates. With few exceptions, trap-measured fluxes decreased offshore but increased with depth at any location, strongly suggesting lateral input of materials. Transmissometer data demonstrated the existence of nepheloid plumes off the eastern slope of the SM-SP Basin. The offshore decrease of sedimentation rate in the eastern part of the SM Basin was consistent with the fact that nepheloid plumes were confined to the basin slopes and that the major transport pathway of suspended particles, as indicated via progressive vector analysis, was alongshore from the SP Basin toward the SM Basin. Concentrations and fluxes of radionuclides measured in the near-bottom trap in the deep basin compared favorably with those registered in bottom sediments. Based on water column, sediment trap and sediment core data, self-consistent flux balances can be constructed for 228Th and 210Pb. Flux balances for 234Th were less well defined. The cyclic pattern of uranium profiles in deep basin sediments appeared to be in phase with the sedimentary record of CaCO 3 and the historical record of primary production and anchovy biomass. It is suggested that the removal of uranium from the water might be regulated by longterm regional changes in biological processes and sedimentation environments.

Gas chromatographic and gas chromatographic/tandem mass spectrometric characterization of precursors on the sesterterpene pathway for steroid biosynthesis.

An increasing amount of evidence is accumulating to support the proposal that steroidogenesis can occur by a sesterterpene pathway as well as the cholesterol pathway. Key intermediates on the sesterterpene pathway are 23,24-dinor-5-cholen-3 beta-ol (guneribol) and some of its metabolites, e.g. 23,24-dinor-4-cholen-3-one (guneribone). It has been reported that these intermediates are biosynthesized and converted to steroid hormones by a range of endocrine tissues in vitro. Monitoring the pentafluorobenzyloxime derivatives by negative ion chemical ionization mass spectrometry in the electron capture mode provided evidence for the presence of guneribone in extracts of bovine testicular and human adrenal tumour tissue. Complementary evidence was obtained from gas chromatographic/tandem mass spectrometric data generated on a triple-quadrupole instrument by monitoring daughter ions (in the multiple ion detection, MID mode) of the molecular anion of derivatized guneribone in both standards and tissue extracts. The present findings that sesterterpene pathway intermediates are present as endogenous compounds in tissue extracts, together with the previously reported radiochemical data, give further support to the sesterterpene pathway hypothesis.

Lysophosphatidylserine-dependent interaction between rat leukocytes and mast cells

The production of lysophosphatidylserine has been studied in a population of rat peritoneal cells; 67% polymorphonuclear and 33% mononuclear leukocytes. Pulse-chase experiments with l-[U- 14C]serine reveal a net lysophosphatidylserine production of 0.33 nmol/mg protein in 2 h of incubation. The source of lysophosphatidylserine is probably the phosphatidylserine of cells damaged during the incubation, since plasma membrane fragments obtained from the leukocytes yield higher lysophosphatidylserine production (1.9 nmol/mg protein in 1 h of incubation). Both leukocytes and plasma membranes show phosphatidylserine splitting activity when tested with vesicles of this phospholipid. In the presence of albumin a fraction of produced lysophosphatidylserine is recovered in the incubation medium. Under these conditions efficient incorporation of lysoderivative into surrounding leukocytes and conversion to phosphatidylserine requires cell activation by tetradecanoylphorbol acetate. In agreement with radiochemical data it is found that a suspension of leukocytes elicits histamine release when rat peritoneal mast cells and nerve growth factor are subsequently added. This typical, lysophosphatidylserine-dependent mast cell response is retained when leukocyte plasma membranes substitute the whole cells. These results suggest that leukocyte lysis at sites of tissue injury results in the production of a sufficient amount of lysophosphatidylserine to reach and activate surrounding mast cells.

Mechanism of the formation of the two epimeric diamino-hexose rings of neomycin B

By using variously tritiated hexoses and Streptomyces fradiae(a neomycin-producer), the mechanism and stereochemistry of the formation of various subunits of neomycin B were investigated. The results of the incorporation of (6RS)-D-[6-3H] glucose into neomycin B followed by specific degradation showed that during the formation of the aminomethyl group of the neosamine B ring one of the 6-3H atoms of the precursor was removed. The 3H remaining at C-6 of the neosamine B ring was shown to be located in the Hsi orientation through the isolation of the chiral centre as glycine and the analysis of the latter by using an exchange reaction catalysed by serine hydroxymethyltransferase. These results suggested that, as has been previously shown for neosamine C, the aminomethyl group of neosamine B is formed by an oxidation-transamination process; –CH2OH →–CHO →–CH2NH2 D-[5-3H]Glucose was prepared by an unambiguous method and incorporated into neomycin B. The radiochemical data on the various subunits of the antibiotic could be interpreted to suggest that the L-idose configuration at C-5 of the neosamine B ring is produced via an enolisation process involving a carbonyl group at either C-4 or C-6. The involvement of C-4 was then eliminated by feeding experiments in which it was shown that the hydrogen atom at C-4 of D-glucose was undisturbed during the incorporation of this position into the C-4 of neosamine B or C.

Growth of a manganese nodule from Peru Basin: A radiochemical anatomy

Attempts have been made to study the entire growth history of a manganese nodule from the northern part of Peru Basin in the Pacific using radiochemical profiles of 230Th 232Th , 227Th 230Th , and 10Be 9Be . Combined with the observations on Fe-Mn contents and textural variation, the radiochemical data indicate that the nodule grew more or less concentrically throughout most of its existence since it formed 1.5 my ago, receiving Mn from both bottom water and pore water. This condition appeared to have changed about 180 ky ago when the growth became asymmetric in that the top and bottom sides became fixed in their relative positions on the sea floor. Since then, the bottom side accreted with a fast rate of close to 200 mm/my, apparently fueled by the supply of diagenetically remobilized Mn in pore water from the sediment substrate. In the meantime, the top side accumulated at about 6 mm/my, a value which is in the normal range for deep-sea nodules having their Mn supplied from the hydrogenous source.

The α-recoil effects of uranium in the Oklo reactor

Until recently, it was thought that chemical elements were synthesized only in stars. The discovery of the Oklo phenomenon1–6 in 1972 revealed, however, that there was a nuclear ‘fire’ on the Earth 1,700 Myr ago. We have now carried out a series of acid-leaching experiments on a sample of uranium ore from reactor zone no. 10 of the Oklo mines in Gabon, Africa, and observe anomalously high 234U/238U ratios accompanied by modestly increased 235U/238U ratios in uranium fractions. These results, which can be interpreted as being due to the α-recoil effects of 238U and 239Pu, provide a convenient way of calculating the conversion factor (or the fraction of uranium atoms converted to plutonium) of the natural reactors from radiochemical data, obviating the necessity for mass-spectrometric measurements.

Further studies of the nature, composition and ages of contemporary phosphorite from the Namibian Shelf

Major and minor element and radiochemical data are examined for a set of phosphorite concretions and other phosphatic material from the Namibian Shelf. The concretions were separated on a morphological basis from grab samples taken in a transect of shallowing depth over the diatomaceous ooze belt. Compositional data indicate that the samples are fairly pure carbonate-fluorapatite, and trend towards a maximum 32% P 2O 5 content. A range of compositional variability similar to other samples from the Namibian Shelf is observed. Radiochemical systematics confirm that pelletal phosphorite and glauconitized pelletal phosphorite from depths > 170 m are at radioactive equilibrium, and are therefore old and reworked. The concretions, collected from depths shallower than 78 m, are entirely Recent, with maximum ages in the range 500–3800 years. They may be much younger. Despite distinct textural and small compositional differences, similar ages are found for separates from the same grab. Samples of fish scales and an unidentified high-magnesian phosphate mineral are also shown to have incorporated uranium recently.

Analysis of a longitudinal ripple from the Nova Scotian continental rise

A longitudinal ripple was obtained in a box core taken from the Nova Scotian continental rise in July 1982. Soft brown mud comprising 1.5—10% sand, ∼60% silt and ∼35% of <2 μm clay forms the 5 cm high and ∼40 cm wide ripple. A maximum thickness of 8 cm of this mud under the crest, thinning to 2 cm on the ripple's flank, overlies stiff muddy foram ooze. The vane shear strength of the brown mud is ∼0.4 kPa whereas that of the ooze is ∼4 kPa. X-radiographs show the mud to contain many fine burrows and a few larger ones as well as winnowed horizons rich in foraminifera of both benthonic and planktonic origin. Gentle wet sieving of the sand fraction on board ship showed the sand fraction to contain very few faecal pellets. Thus it appears unlikely that bedload movement played a large part in formation of the ripple. Rapid initial deposition from a concentrated suspension is suggested to have formed the structure, but this was followed by periods of erosion to yield winnowed horizons and further rebuilding with material deposited from suspension. Radiochemical data ( 234Th and 210Pb) and X-radiographs suggest intense particle mixing ( D B ∼90 cm 2 yr −1) and rapid sediment deposition (∼1.5 cm month −1). Thus it is possible that the bedform (and associated structures) are destroyed and recreated on a time-scale of a few months.

Modern sediment accumulation and strata formation on the Amazon continental shelf

Formation of fine-scale ( < 50 cm ) strata on the Amazon continental shelf was investigated using radiographic and radiochemical (e.g. 210Pb) techniques. Three distinct sedimentary environments are found within the inner shelf ( < 60 m water depth) mud deposit: (1) interbedded mud and sand in a corridor extending from the river mouth across the inner shelf; (2) faintly laminated muds on both flanks of the corridor; and (3) bioturbated muds comprising the remainder of the deposit. High rates of sediment accumulation ( > 2 cm/ yr ) are found in the region of interbedded mud and sand, and in the regions of faintly laminated muds. Accumulation rates in the region of bioturbated muds are relatively low (0.1–2 cm/yr), and an inverse relationship is observed between accumulation rate and extent of sedimentary structure alteration by benthic fauna. A first-order sediment budget indicates that sediment accumulation on the Amazon shelf (between the Brazil-French Guiana border and the Para River) is nearly equal to estimates of sediment discharged by the Amazon River ( 9 × 10 8 tons/yr ). The model of Amazon shelf sedimentation most consistent with the radiographic and radiochemical data suggests that the inner shelf mud deposit is a subaqueous delta prograding seaward over relict basal sands and that a turbulent jet emanates from the river mouth with competence (during some flood periods) to carry sand as bedload across the inner shelf. The presence of cross-bedded sands in the corridor of interbedded mud and sand supports the hypothesis of a turbulent jet. The faintly laminated muds probably represent suspended sediment rapidly deposited on both sides of the jet.

Regional brain distribution of d-amphetamine in lead-exposed rats

The present study was designed to examine the time course of distribution of d-[ 3H]amphetamine ( d-amph) in various brain regions and plasma in lead-intoxicated rats. Measurements of d-amph-induced locomotor activity were also recorded in these same animals. The protocol involved exposing lactating dams to either 0, 0.1, or 0.2% lead acetate Pb(Ac) 2, in their drinking water and thus neonates indirectly to lead-contaminated milk. At weaning, control litters and half of the litters from the 0.1% Pb(Ac) 2 group were placed on distilled water while the remaining litters received the maternal regimen. Assessment of locomotor activity at 90 days of age revealed a significantly attenuated d-amph response (1.0 mg/kg, sulfate salt, sc) in the 0.2% but not in the 0.1% Pb(Ac) 2 group (both sexes). Subsequent analyses of brain d-amph distribution revealed that the 0.2% Pb(Ac) 2 group (both sexes) also had significantly decreased concentrations (10 to 12%) of d-amph in the hippocampus, striatum, and hypothalamus at 15, 30, and 90 min postinjection. Concentrations in medulla and plasma did not differ from controls. However, the time courses for the significant behavioral and radiochemical data did not coincide and correlations between d-amph concentration and locomotor activity were negligible. These data suggest that the alterations in d-amph-induced locomotor activity observed in the 0.2% Pb(Ac) 2 group animals may result in part from an inability to concentrate and/or maintain critical levels of the d-amph in specific regions in the CNS.

Acute inhibition of intestinal lipid transport by Pluronic L-81 in the rat.

Lymph fistula rats were used to determine the acute effects of the hydrophobic surfactant, Pluronic L-81, on lipid transport by the small bowel. Animals were infused intraduodenally with a lipid emulsion containing [3H]triolein and Pluronic L-81, and the rate of intestinal transport of absorbed lipid into lymph was studied using liquid scintillation spectrometry. With this technique, various dose levels of Pluronic L-81 were analyzed for a possible inhibitory effect on lipid transport. Also, the rate at which this agent produced inhibition of intestinal lipid transport was determined. Results were correlated with electron microscopic studies of jejunal enterocytes and lipoprotein particles recovered in intestinal lymph. Infusion of Pluronic L-81 at a rate of 0.25 mg/h had no effect, but infusion at 0.5 and 1 mg/h produced a dramatic reduction in lipid transport by the small bowel. The rate of inhibition of lymphatic lipid output was rapid, with a t1/2 of 69 min for the 0.5 mg/h dose and 35 min for the 1 mg/h dose. This inhibition of lipid transport was associated with marked mucosal accumulation of lipid as demonstrated by radiochemical and morphological data. By electron microscopic analysis, only very low-density lipoprotein-sized particles were transported into lymph by enterocytes exposed to an effective dose of Pluronic L-81. It is concluded that small amounts of Pluronic L-81 produce a striking inhibition in the intracellular transport of chylomicron-sized particles, thereby blocking secretion of chylomicrons by the enterocytes. Furthermore, this action is very rapidly produced by effective doses of this agent.

Nodules and associated sediments in the Madagascar Basin

Several buried nodule beds have been found in a sediment core sampled in the Madagascar Basin. 14C, 230Th, 231Pa and paleomagnetic measurements on sediments and nodules from several layers in the core show good agreement with data given by other investigators using microfaunal stratigraphic methods. The radiochemical data, on a carbonate-free basis, give low and regular sedimentation rates ( 1 mm 10 3 yr. ). The same measurements performed on nodules from three beds give identical accretion rates of ∼ 1 mm 10 6 yr . The implications of the results are briefly discussed in terms of nodule accretion rates: slow growth rates for which bioturbation is needed to allow nodules to escape from burial or rapid growth rates before burial in the sedimentary column.

Mass number and prompt neutron emission of individual fission fragments as functions of nuclear charge, both involving parameters determinable from radiochemical data

Mass number and prompt neutron emission of individual fission fragments as functions of nuclear charge, both involving parameters determinable from radiochemical data

Search for a new reaction mechanism in the system132Xe+natFe

Thin targets of natural Fe have been irradiated with132xe ions at beam energies of 5.00, 5.90, and 7.15 MeV/u. Mass yields for projectile-like and symmetric products were evaluated, and their ratio as a function of beam energy determined. The results are consistent with previously-determined thick-target radiochemical data, and are not consistent with published on-line counter data for the same system.

Regulation of 3T3-L1 fibroblast differentiation by prostacyclin (prostaglandin I 2)

Prostaglandin biosynthesis and prostaglandin-stimulated cyclic AMP accumulation were studied in 3T3-L1 fibroblasts as they differentiated into adipocytes. Incubation of 3T3-L1 membranes with [1- 14C]prostaglandin H 2, and subsequent radio-TLC analysis, showed that prostacyclin (prostaglandin L 2) is the principal enzymatically synthesized prostaglandin in this cell line. Confirmation of the radiochemical data was obtained by demonstrating the presence of 6-keto-prostaglandin F 1α, the stable hydrolysis product of prostaglandin I 2, by gas chromatography-mass spectrometry. In support of previous work, indomethacin, the prostaglandin endoperoxide synthetase (EC 1.14.99.1) inhibitor, accelerated 3T3-L1 differentiation. More importantly, the incubation of 3T3-L1 cells with insulin and the prostaglandin I 2 synthetase inhibitor 9,11-azoprosta-5,13-dienoic acid (azo analog I) also enhanced the rate of cellular differentiation, even though this compound does not inhibit the synthesis of other prostaglandins. The repeated addition of exogenous prostaglandin I 2 to 3T3-L1 cells inhibited insulin- and indomethacin-mediated differentiation. When 3T3-L1 cells were exposed to various prostaglandins and the cyclic AMP levels were measured, prostaglandin I 2 proved to be the most potent stimulator of cyclic AMP accumulation, followed by prostaglandin E 1 > prostaglandin H 2 > prostaglandin E 2, while prostaglandin D 2 was inactive. As 3T3-L1 cells differentiate, the ability of prostaglandin I 2 or prostaglandin H 2 to stimulate cyclic AMP accumulation progressively diminishes. It is suggested that 3T3-L1 differentiation may be controlled by the rate of prostaglandin I 2 synthesis and/or sensitivity of the adenylate cyclase to prostaglandin I 2.

Radiochemical and electrophoretic studies on the CNS of crabs parasitized with rhizocephalans: comparison with healthy crabs

Abstract 1. 1. The incorporation of 3H-Leucine into the CNS of healthy and parasitized Carcinus with Sacculina shows that the protein synthesis and release in the brain and ventral ganglionic mass, and the transfer of material to the eyestalks are reduced into the infested animals. 2. 2. The presence of a Sacculinidae or injections of its root homogenates modify the electrophoregrams of the VGM of R. harrisii: (a) Fractions appear with the same mobility as some of the root's pattern; (b) a characteristic slow migrating fraction is found, suggesting a reaction against the parasite. 3. 3. The radiochemical and electrophoretic data agree with the hypothesis that the male gametogenic perturbations of infested crab are the result of neuroendocrin alterations induced by the Sacculinidae, directly or via a diffusible substance.

Formula omitted]: A selective inhibitor of thromboxane synthetase

Imidazole inhibits the enzymatic conversion of the endoperoxides (PGG 2 and PGH 2) to thromboxane A 2 by platelet microsomes (IC 50: 22 μg/ml; determined by bioassay). The inhibitor is selective, for prostaglandin cyclo-oxygenase is only affected at high doses. Radiochemical data confirms that imidazole blocks the formation of 14C-thromboxane B 2 from 14C-PHG 2. Several imidazole analogues and other substances were tested but only 1-methyl-imidadole was more potent that imidazole iteself. The use of imidazole of inhibit thromboxane formation could help to elucidate the role of thromboxanes in physiology or pathophysiology.