Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Uranium Compounds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources
PubMed1982

Perfusion fixation of lungs for structure-function analysis: credits and limitations.

The quality of tissue preservation in lungs fixed by vascular perfusion has been reevaluated. Excised rabbit lungs inflated to 60% of total lung capacity were perfused (zone III conditions) with different but widely used fixatives. The effects of the perfusates on pertinent physiological variables have been assessed by a continuous monitoring, the effects on the pulmonary microstructure by qualitative and morphometric analysis of electron micrographs. Important results include the following. 1) Perfusions with isotonic glutaraldehyde at flow rates within the physiological range produce large increases of perfusion pressure and lung weight that reflect intracellular, interstitial, and intra-alveolar edema. 2) No edema occurs if glutaraldehyde is added to isotonic buffer solutions (total osmolarity 510 mosM). 3) Glutaraldehyde as sole perfusate does not fully eliminate the retractive force of lung tissue. Upon release of transpulmonary pressure the lungs retract by an indeterminable amount. 4) Satisfactory results can be obtained by sequential perfusion with osmium tetroxide and uranyl acetate or glutaraldehyde (510 mosM) followed by osmium tetroxide and uranyl acetate. The latter combination yields optimal preparations to study the alveolar and capillary architecture but causes a hyperosmotic volume loss of lung cells (cell shrinkage).

Animals↗
PubMed1984

A comparison of standard lipid staining techniques used in electron microscopic studies of mammalian tissues.

Comparisons of several standard techniques for staining lipids in ultrastructural studies have been undertaken using the rat uterine epithelium as the experimental tissue. The best technique for clarity, retention of stain, and acceptability of cellular ultrastructure utilized p-phenylenediamine after primary fixation in glutaraldehyde and postfixation in osmium tetroxide. While osmium by itself stained only unsaturated lipids and p-phenylene-diamine stained no lipids in spot tests, when acting together, the staining of unsaturated lipids was enhanced and some staining of saturated lipids was seen. Further, the marked extraction of stained lipids normally found during dehydration did not then occur.

Animals↗
PubMed2001

Separation of uranium(VI) and transition metal ions with 4-(2-thiazolylazo)resorcinol by capillary electrophoresis.

A capillary electrophoresis method utilizing 4-(2-thiazolylazo)resorcinol (TAR) was developed to separate uranium, cobalt, cadmium, nickel, titanium and copper metal ions. TAR was chosen as the visible absorbing chelating ligand because of its ability to form stable complexes with a wide variety of metals. Several parameters that included pH, electrophoretic run buffer concentration, buffer type and the influence of chelating ligand in the electrophoretic run buffer were examined to determine the best separating conditions. Optimum separation of the six metal chelates was achieved in a 15 mM Na2B4O7-NaH2PO4, pH 8.3 buffer containing 0.1 mM TAR. Method validation included injection and method precision studies as well as detection limit and linear dynamic range determination. High-ppb to low-ppm (w/w ratio) detection limits were achieved with linear dynamic ranges between 0.1 and 75 ppm.

Azo Compounds↗
PubMed2005

Uptake and distribution of natural radioactivity in wheat plants from soil.

The uptake of naturally occurring uranium, thorium, radium and potassium by wheat plant from two morphologically different soils of India was studied under natural field conditions. The soil to wheat grain transfer factors (TF) were calculated and observed to be in the range of 4.0 x 10(-4) to 2.1 x 10(-3) for 238U, 6.0 x 10(-3) to 2.4 x 10(-2) for 232Th, 9.0 x 10(-3) to 1.6 x 10(-2) for 226Ra and 0.14-3.1 for 40K. Observed ratios (OR) of radionuclides with respect to calcium have been calculated to explain nearly comparable TF values in spite of differences in soil concentration of the different fields. They also give an idea about the discrimination exhibited by the plant in uptake of essential and nonessential elements. The availability of calcium and potassium in soil for uptake affects the uranium, thorium and radium content of the plant. The other soil factors such as illite clays of alluvial soil which trap potassium in its crystal lattice and phosphates which form insoluble compounds with thorium are seen to reduce their availability to plants. A major percentage (54-75%) of total 238U, 232Th and 226Ra activity in the plant is concentrated in the roots and only about 1-2% was distributed in the grains, whereas about 57% of 40K activity accumulated in the shoots and 16% in the grains. The intake of radionuclides by consumption of wheat grains from the fields studied contributes a small fraction to the total annual ingestion dose received by man due to naturally existing radioactivity in the environment.

Aluminum Silicates↗
PubMed2002

Differential pulse polarographic determination of uranium(VI) in complex materials after adsorption of its trifluoroethylxanthate cetyltrimethylammonium ion-associated complex on naphthalene adsorbent.

Uranium(VI) is adsorbed as a uranium trifluoroethylxanthate (TFEX)-cetyltrimethylammonium (CTMA) ion-pair complex on microcrystalline naphthalene quantitatively in the pH range 4.2 - 7.0. Without cetyltrimethylammonium as the counter ion, the adsorption is hardly 70%. The metal has been desorbed with HCI and determined with a differential pulse polarograph. Uranium can alternatively be quantitatively adsorbed on TFEX-CTMA-naphthalene adsorbent packed in a column at a flow rate of 1 - 5 ml/min and determined similarly. A well-defined peak has been obtained in this medium at -0.20 V versus a saturated calomel electrode. Cyclic voltammetry, differential pulse polarography and D.C. polarography studies indicate that uranium has been reduced irreversibly under these conditions. The detection limit is 0.30 microg/ml at the minimum instrumental settings (signal-to-noise ratio of 2) (with a preconcentration factor of 10, the detection limit would be 30 ng/ml for uranium when the volume in the cell is 15 ml). However if the volume in the cell is 5 ml, it would have been 10 ng/ml with a preconcentration factor of 30. Linearity is maintained in a concentration range of 0.5 - 19.0 microg/ml (2.1 - 79.83 x 10(-9) M) with a correlation factor of 0.9994 and a relative standard deviation of +/-1.1% (in this case 7.5 microg may be concentrated from 150 ml of the aqueous sample where its concentration is as low as 50 ng/ml). Various parameters, such as the effect of the pH, volume of the aqueous phase, flow rate and the interference of a large number of metal ions and anions on the determination of uranium, have been studied in detail to optimize the conditions for its trace determination in various complex materials, like alloys, coal fly ash, biological, synthetic, and waste-water samples.

Adsorption↗
PubMed2005

The uranium-nitrogen bond in U IV complexes supported by the hydrotris(3,5-dimethylpyrazolyl)borate ligand.

Insertion of benzonitrile and acetonitrile into the U-C bond of [U(Tp(Me2))Cl(2)(CH(2)SiMe(3))](Tp(Me2)= HB(3,5-Me(2)pz)(3)) gives the ketimide complexes [U(Tp(Me2))Cl(2){NC(R)(CH(2)SiMe(3))}](R = Ph (1); Me (2)). The identity of complex was ascertained by a single-crystal X-ray diffraction study. In the solid state exhibits octahedral geometry with a short U-N bond length to the ketimide ligand. We also report herein the synthesis and the X-ray crystal structures of the uranium amide complexes [U(Tp(Me2))Cl(2)(NR(2))](R = Et (3); Ph (4)). A detailed comparison of the U-N bond lengths in these compounds with other known U-N (and Th-N) distances in amide and ketimide actinide(IV) complexes is performed, confirming the short character of the U-N bond length in 1.

Journal Article↗
PubMed2003

Complexation of uranium (VI) by three eco-types of Acidithiobacillus ferrooxidans studied using time-resolved laser-induced fluorescence spectroscopy and infrared spectroscopy.

Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used to study the properties of uranium complexes (emission spectra and fluorescence lifetimes) formed by the cells of the three recently described eco-types of Acidithiobacillus ferrooxidans. The results demonstrated that these complexes have different lifetimes which increase in the same order as the capability of the strains to accumulate uranium. The complexes built by the cells of the eco-type II were the strongest, whereas, those of the eco-types I and III were significantly weaker. The emission spectra of all A. ferrooxidans complexes were almost identical to those of the uranyl organic phosphate compounds. The latter finding was confirmed by infrared spectroscopic analysis.

Biomass↗
PubMed2005

[Study on solid phase extraction and spectrophotometric determination of uranium in water with 2-(2-quinolylazo)-5-dimthylaminophenol].

A new chromogenic reagent 2-(2-quinolylazo)-5-Dimthylaminophenol (QADMAP) was synthesized, and its structure was verified by elemental analysis, infrared spectrum, 1H nuclear magnetic resonance spectrum, mass spectrumand UV-spectrum. The color reaction of QADMAP with uranium was studied. In the presence of pH 7.8 buffer solution, when fluorin ion and TritonX-100 medium exist, QADMAP can react with uranium and fluorin to form a stable 1 : 1 : 1 stable complex [F- :QADMAP : U(VI)]. The molar absorptivity is 1.05 x 10(5) L x mol(-1) x cm(-1) at 590 nm. Beer's law is obeyed in range of 0-20 microg/10 mL. The uranium in samples can be enriched and separated by solid phase extraction with TBP resin cartridge. This method is applied to the determination of uranium in water sample. The relative standard deviations are 2.2%-3.6%, and the recoveries are 94%-105%.

Aza Compounds↗
PubMed2004

Stereochemistry of new nitrogen containing heterocyclic compound XII. Polymeric uranyl complexes of hydrazone compounds.

Several dioxouranium(VI) heterochelates with tetradentate monobasic hydrazone compounds (HL(n)) have been synthesized. The heterochelates of the type [(UO2)2(HL(n))(L(n))2(OAc)2(OH2)2]n have been characterized on the basis of elemental analyses, IR and electronic spectra, conductance and magnetic susceptibility measurements. The complexes are polymeric, non-electrolytes, diamagnetic and eight-coordinated. Wilson, G.F. matrix method, Badger's formula, Jones and El-Sonbati equations were used to determine the stretching and interaction force constants from which the U-O bond distances were calculated. The bond distances of these complexes were also investigated.

Electrolytes↗
PubMed1993

Dissimilatory metal reduction.

Microorganisms can enzymatically reduce a variety of metals in metabolic processes that are not related to metal assimilation. Some microorganisms can conserve energy to support growth by coupling the oxidation of simple organic acids and alcohols, H2, or aromatic compounds to the reduction of Fe(III) or Mn(IV). This dissimilatory Fe(III) and Mn(IV) reduction influences the organic as well as the inorganic geochemistry of anaerobic aquatic sediments and ground water. Microorganisms that use U(VI) as a terminal electron acceptor play an important role in uranium geochemistry and may be a useful tool for removing uranium from contaminated environments. Se(VI) serves as a terminal electron acceptor to support anaerobic growth of some microorganisms. Reduction of Se(VI) to Se(O) is an important mechanism for the precipitation of selenium from contaminated waters. Enzymatic reduction of Cr(VI) to the less mobile and less toxic Cr(III), and reduction of soluble Hg(II) to volatile Hg(O) may affect the fate of these compounds in the environment and might be used as a remediation strategy. Microorganisms can also enzymatically reduce other metals such as technetium, vanadium, molybdenum, gold, silver, and copper, but reduction of these metals has not been studied extensively.

Bacteria↗
PubMedDate not supplied

Tracers in vascular casting resins enhance backscattering brightness.

Studying cast microvasculature with scanning electron microscopy has expanded our knowledge of many circulations, but need arises to determine the blood source of vascular beds that are supplied by two circulations. One way to do this is to mark the casting resin by adding a tracer compound that can be detected in the scanning electron microscope. A potential method of distinguishing different substances is to detect the backscattered electrons that are emitted from the tracer if the tracer is a heavier element, because heavier elements backscatter more electrons. To explore different tracers, we tested lead, titanium, iron, osmium, and uranium as solutions of different polarity and powders. The tracers were added to 1 ml of methyl methacrylate in log concentrations. Shrinkage, hardness, cast quality, and change in brightness from the tracer were compared with multivariate analysis at scanning electron microscopic working distances of 15 and 39 mm on carbon-coated and uncoated specimens. Several concentrations caused sedimentation of the tracer and prevented the resin from solidifying. Tetraethyl lead shortened the hardening time: uranyl acetate and osmium tetroxide prolonged it. Most tracers decreased shrinkage. When lead citrate and Reynolds solutions were removed, the brightness correlated with increasing atomic number, concentration of the tracer, and mean atomic number of the specimen (p <0.0001). The substances that increased contrast most were tetraethyl lead and uranium. Backscattering electron detection can distinguish methacrylate casts that have small amounts of heavier elements added to them, but an optimal tracer has not yet been established.

Animals↗
PubMed2004

Radioactivity distribution in some Permian sediments from the Iratí and Corumbataí Formations of the Paraná Basin, Southeastern Brazil.

In the city of Limeira, southeastern Brazil, an important exposure of Permian sediments of the Paraná basin was revealed by an open pit mine that exploits limestone for production of soil correction compounds and raw materials for the ceramic industry. The radioactivity of these sediments was investigated in some detail and the results provided a general view of the vertical distributions of uranium, thorium and potassium concentrations and of the element ratios U/K, U/Th and Th/K. In general, the concentrations of the main natural radioactive elements are low, with uranium being enriched in some limestone and shale levels. In addition the results showed that the 238U series is in radioactive disequilibrium in many of the analyzed samples. Although the origin of the observed disequilibrium has not been investigated, the results suggest that it is due to weathering processes and water interaction with the rock matrix.

Brazil↗
PubMed2001

Determination of radium-226 in aqueous solutions by alpha-spectrometry.

The new European legislation imposes a lower threshold for radioactivity in drinking water. This requires the development of more sensitive and reliable analytical methods. This work presents an improved alpha-spectrometric technique to determine the radium-226 activity in aqueous solution relying on the radium adsorption onto a thin manganese oxide layer followed by alpha-measurement. The preparation of the MnO2 deposit has been optimized as well as the radium adsorption conditions. Detection threshold and limit of 5 and 10 mBq x L(-1), respectively, with a 10% (95% confidence) uncertainty are currently reached. This paper reports on the overall technique and on its application to assess the radium-226 activity in 28 French mineral waters. In addition, the gross alpha- and beta-activities have been evaluated using proportional counting while the uranium concentrations were derived from ICPMS.

Algorithms↗
PubMed1995

Alpha pulse height distributions with ZnS(Ag) scintillator.

A flask coated with ZnS(Ag) scintillator is one of the most accurate detectors available for measuring 222Rn. To maintain this accuracy, the counting system consisting of a photomultiplier tube and associated electronics must be checked on a regular basis. A combination of an alpha source and a ZnS(Ag) scintillator is commonly used for these purposes. This paper compares the pulse height distributions of 4 alpha sources with the pulse height distribution from a 100 cm3 scintillation flask containing 222Rn. The source that most closely reproduced the distribution from an actual 222Rn sample in a 100 cm3 scintillation flask consisted of a sealed flask, of the same type, which contains a small piece of uranium-ore.

Alpha Particles↗