Uranium series dating applied to mammoth bones from the valley of Mexico

The purpose of this research is the dating of some mammoth bones from the Valley of Mexico, with the uranium-series method, which can determine the activity of the isotopic relationships ²³⁴U/²³⁸U and ²³⁰ Th/²³⁴U. Since not all samples could be dated by this method, it was necessary to apply other techniques as well. First of all, the total concentration of uranium was determined in mammoth bones by U. V. spectrometry, then a study of the conservation state of mammoth bone was carried out by scanning electron microscopy and X-ray diffraction. In this way the limiting factors at the application of this method for dating mammoth bones can be determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Lichtheimia blakesleeana as a new potencial producer of phytase and xylanase

Brazil is known for its great potential for production of renewable resources such as agro-industrial residues. These residues can be used as alternative sources of new products. Meanwhile, solid-state fermentation, with its advantages of energy conservation and pollution reduction, has been identified as a process of great potential for the production of bioactive compounds, especially enzymes. In the present work, a 2(3) factorial design was used to evaluate the effects of pH, temperature and moisture on the production of phytase and xylanase by Lichtheimia blakesleeana URM 5604 through the fermentation of citrus pulp. Statistical analyses of the results showed that the only the pH influenced the production of these enzymes, with the best phytase production (264.68 U/g) ocurring at pH 6.0, 34 °C, initial moisture 50%, after 48 hours of culture. The best conditions for xylanase production (397.82 U/g) were fermentation for 120 hours at pH 4.0, 26 °C and initial moisture of 70%. The best parameters for the simultaneous production of phytase (226.92 U/g) and xylanase (215.59 U/g) were determined to be initial moisture of 50%, pH 6.0, 26 °C, and 48 hours of fermentation.     

Spectrophotometric Determination of Uranium with Sorbohydroxamic Acid as Reagent

Sorbohydroxamic acid forms with uranium an orange red, water soluble complex. The mole ratio of uranyl ion to compound is 1 to 1 under the investigated conditions. The formation constant of this chelate was also determined by the Likussar—Boltz method at a constant ionic strength of 0.1 M at 30°C as 2.10×10². The recommended procedure obeys Beer's law between 3.98ppm and 166.6ppm of uranyl ion at pH 3.8±0.1. Tolerances to cerium (IV) and thorium have been investigated. The procedure for the determination of uranium are made more specific by applying preliminary extraction of uranium by ether.     

Uranium isotopes as a tracer of groundwater transport studies

The activity concentrations of ²³⁴U and ²³⁸U in thermal groundwater, deep well water and river water samples from Central Poland were determined. Concentration of ²³⁴U and ²³⁸U in the examined waters varied from <0.013 (LLD) to 16.8 mBq/dm³ and from <0.013 (LLD) to 45.5 mBq/dm³ respectively. The highest uranium activity concentrations were measured in the thermal groundwater from Mszczonow and Cieplice, while the lowest were observed in thermal ground water from Uniejow and Poddebice. In thermal groundwater from Skierniewice, uranium activity concentrations were below lower limit of detection (0.013 mBq/dm³). The ²³⁴U/²³⁸U activity ratio varied from 0.37 (Cieplice) to 1.30 (Poddebice well water).     

Investigation of radiocesium biokinetics in Manila clam (Ruditapes philippinarum)

This study was carried out to better understand the biokinetics of radiocesium in clams living in sediment. The accumulation and depuration kinetics of ¹³⁴Cs were investigated in the Manila clam (Ruditapes philippinarum) under controlled laboratory conditions. The concentration factor was found to be 3.0 for ¹³⁴Cs in the whole body; however, the concentration factor in the soft part of the clams (12) was significantly higher than those in the whole body and shell (0.80). The depuration kinetics of the radionuclide were described by a two-component exponential model for the whole body. The biological half-lives in the fast and slow components were found to be 0.63 and 22.1 days, respectively. The depuration kinetics for ¹³⁴Cs in the soft parts were described by a single-component exponential model with a resultant the biological half-life of 18.0 days.     

Micro-determination of Uranium using ammonium aurintricarboxylate as a colorimetric reagent

Summary The formation of a colored chelate between UO₂ ²⁺ and ammonium aurintricarboxylate has been used for the colorimetric determination of uranium on a microscale. The chelate has a maximum of absorbance at 540 nm (m). The stability of the color with time, temperature, and p_H has been studied. The interferences by a large number of cations and anions have been investigated, and the tolerance limit has been determined for each ion. It is recommended that a 50-fold molar excess of the reagent should be added, the p_H maintained at 5.5 ± 0.5, and the temperature held between 20° to 30° C.

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Zusammenfassung Die Bildung eines gefärbten Chelatkomplexes aus Uranylion und Ammoniumaurintricarboxylat (Aluminon) läßt sich mit Vorteil für die Mikrobestimmung von Uran verwenden. Dieser Komplex hat ein Absorptionsmaximum bei 540 nm. Die Beständigkeit der Farbe gegenüber Zeit, Temperatur und p_H wurde untersucht. Die störende Wirkung einer großen Zahl von Kationen und Anionen und deren Toleranzgrenze wurde quantitativ bestimmt. Es wird empfohlen, bei der Durchführung der Reaktion einen 50fachen Überschuß des Reagens zu verwenden, ein P_H von 5,5 ± 0,5 und eine Temperatur von 20 bis 30° einzuhalten.

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Résumé Il est possible d'utiliser avantageusement la formation d'un complexe chélaté coloré de l'ion uranyle et du tricarboxylate d'aurinammonium (Aluminon) pour le microdosage de l'uranium. Ce complexe présente un maximum d'absorption à 540 nm. On a étudié la stabilité de la couleur en fonction du temps, de la température et du P_H. L'action perturbatrice d'un grand nombre de cations et d'anions et les limites de tolérance correspondantes ont été déterminées quantitativement. Il est recommandé d'effectuer la réaction avec un excès de réactif 50 fois supérieur à la quantité nécessaire, à un Ph de 5,5 ± 0,5 et de maintenir une température de 20 à 30°.

     

阴极溶出伏安法测定含铀废水中的痕量铀

采用新型自动伏安极谱仪对含铀废水中的痕量铀进行测定。用浓硝酸和双氧水处理废水试样,以氯冉酸为铀络合剂,5 mmol/L的氯冉酸用量为0.1 mL;试液的pH值调节为2.4~2.6。以悬汞电极为工作电极,以微分脉冲为测定模式,标准加入法进行定量分析。在优化的实验条件下,方法的检出限为0.076 ng/mL,实际样品的加标回收率在80%~105%之间,测定结果的相对标准偏差为5.2%(n=6)。该方法操作简便,重现性好,试样用量少,可用于含铀废水中痕量铀的快速测定。     

Comparison between biokinetics of inhaled plutonium nitrate and gadolinium oxide in humans and animals

Due to the paucity of human data after inhalation of different chemical forms of radionuclides, the implications for human exposure are often based on animal studies. This paper describes biokinetic studies of plutonium nitrate and gadolinium oxide in human volunteers and rats. The results, together with information from other studies with radionuclides, suggests that animal studies can be used with advantage for assessing the biokinetic behavior in humans, and for providing guidance on the assessment of intake and optimal monitoring regimens.     

Determination of phytase activity in feed: interlaboratory study

An interlaboratory study was conducted to determine the performance characteristics of a new method for the determination of phytase activity in feed samples. The method is based on the principle that inorganic phosphate is released from the substrate phytate under defined assay conditions and has been validated for its suitability to measure the enzyme activity of various phytase products. Two different experimental designs of the study were applied, allowing for the estimation of the precision of the method under repeatability, intermediate precision and reproducibility conditions, respectively. The relative standard deviation for repeatability (RSDr) ranged from 2.2 to 10.6% and the RSD for reproducibility (RSDR) ranged from 5.4 to 15%. The suitability of the validated method for the intended purpose was demonstrated. The obtained performance profile of the method validated in this study was comparable to that of similar methods that were exclusively validated for one phytase product.     

Synthesis and DNA incorporation of an ethynyl-bridged cytosine C-nucleoside as guanosine surrogate

As a guanosine mimic that lacks the preference for syn or anti conformation a cytosine C-nucleoside was synthesized connecting the nucleobase at the anomeric center by an ethynyl linker. The key step was a Sonogashira cross coupling of 5-iodocytosine with 1'-ethynyl-2'-deoxyribose. The new C-nucleoside incorporated into G/C-alternating oligonucleotides emerged as guanosine substitute, however, with reduced duplex stability. B-Form DNA was strongly stabilized by the new surrogate even in typically Z-DNA forming sequences and in Z-form inducing environment.     

Tetrazol-2-yl as a donor group for incorporation of a spin-crossover function based on Fe(II) ions into a coordination network

The coordination polymer {[Fe(pbtz)3](ClO4)2 . 2EtOH}infinity (1) has been prepared in a reaction between Fe(ClO4)2 . 6H2O and 1,3-di(tetrazol-2-yl)propane (pbtz). The formation of the second product {[Fe(pbtz)3](ClO4)2}infinity (2) was also noticed. Both complexes crystallize in the R3 space group. The single-crystal X-ray diffraction study of 1 (295, 90 and 230 K) revealed that the 2-substituted tetrazole rings (2tz) coordinate monodentately to the metal ions, forming Fe(2tz)6 cores. There are two crystallographically independent iron(II) ions in 1. At 295 K the Fe-N4 bond lengths are equal to 2.173(5) and 2.196(5) A for Fe1 and 2.176(5) and 2.190(4) A for Fe2. The pbtz ligand molecules act as N4,N4' connectors, bridging central atoms in the three directions, which leads to the formation of the 3D network. The crystal lattice of 1 is solvated by ethanol molecules. At 295 K the solvent and ligand molecules are disordered. The results of temperature-dependent magnetic susceptibility measurements (5-300 K), and the single-crystal X-ray diffraction studies (90 K) have exhibited that 1 undergoes the thermally induced spin transition HS<-->LS (SCO). The chiMT(T) dependence shows in the range 200-75 K gradual SCO. Below 75 K the transition is finished and approximately 20% of the HS fraction is present in the sample. The HS-->LS transition is accompanied by a shortening of the Fe-N bonds of 0.15 A. At 90 K the ligand molecules are ordered. The presence of 2 in the reaction product was disclosed accidentally, and only the X-ray diffraction studies (250, 90 K) were performed. Also in 2 iron(II) ions serve as topological nodes of the 3D network. Despite the same network topology, 2 crystallizes without ethanol molecules solvating the crystal lattice. The pbtz molecules bridge the neighboring iron(II) ions, coordinating through N4,N4' atoms of the 2-substituted tetrazole rings forming the Fe(2tz)6 cores. At 250 K the Fe-N bond lengths are equal to 2.208(5) and 2.218(5) A. In contrast to 1, the cooling of the crystal of 2 from 250 to 90 K does not involve the shortening of the Fe-N bond lengths. At this temperature, the Fe-N distances remain characteristic for the HS form of the complex and are equal to 2.203(3) and 2.208(3) A.     

Distribution of uranium in human bones

Uranium and calcium contents in human bones (skull, rib and femur) were determined by the fission track method and the inductively coupled plasma-atomic emission spectroscopic method (ICP-AES), respectively. The U/Ca concentration ratio in the bones was found to decrease in the order of rib greater than femur greater than skull, which is in accordance with the decreasing order of the mean annual replacement percentage of bone components. Several femur bones were cut into several longitudinal segments, and uranium and calcium contents in each segment were determined. Among these, the U/Ca ratio in the epiphysis was higher than those in the diaphysis.     

Polarography of Uranium in lactate medium

The polarography of uranium(Vl) in the lactate medium is studied at different pH values. At pH 1 the half-wave potential of the uranium(Vl) wave remains the same as that of the simple ion, but the limiting current increases with increasing concentration of lactate; disproportionation of uranium(V) at the electrode surface is suggested. The rate of disproportionation is calculated. Polarograms observed in the region of pH 5 and 6 are interpreted on the basis of complexation of UO₂²⁺.     

Determination of Oxygen to Uranium Ratio in Uranium Dioxide Nuclear Fuel by Differential Pulse Polarography

A differential pulse polarographic method for determination of oxygen to uranium ratio in uranium oxides is fully described. An accuracy ?2.62% to +4.35% was achieved by calibrating the method against standard U₃O₃, replicate test runs with UO₂, gave a precision of ±4.59% or better. The method is now successfully used in routine analysis for UO² fuel.     

Uranium(VI) Sorption Complexes on Montmorillonite as a Function of Solution Chemistry

We have investigated the effect of changes in solution chemistry on the nature of uranyl sorption complexes on montmorillonite (SAz-1) at different surface coverages (1.43-53.6 μmol/g). Uranyl uptake onto SAz-1 between pH 3 and 7 was determined in both titration and batch-mode experiments. These pH values result in solutions that contain a range of monomeric and oligomeric aqueous uranyl species. Continuous-wave and time-resolved emission spectroscopies were used to investigate the nature of U(VI) sorbed to SAz-1. A discrete set of uranyl surface complexes has been identified over a wide range of pH values at these low to moderate coverages. For all samples, two surface complexes are detected with spectral characteristics commensurate with an inner-sphere complex and an exchange-site complex; the relative abundance of these two species is similar over these pH values at low coverage (1.43-2.00 μmol/g). In addition, surface species having spectra consistent with polymeric hydroxide-like sorption complexes form at the moderate coverages ( approximately 34-54 μmol/g), increasing in abundance as the capacity of the amphoteric surface sites is exceeded. Furthermore, a species with spectral characteristics anticipated for an outer-sphere surface complex is observed for wet paste samples at low pH (3.7-4.4) and both low ( approximately 2 μmol/g) and moderate ( approximately 40 μmol/g) coverage. There are only subtle differences in the nature of sorption complexes formed at different pH values but similar coverages, despite markedly different uranyl speciation in solution. These results indicate that the speciation in the solution has minimal influence on the nature of the sorption complex under these experimental conditions. The primary control on the nature and abundance of the different uranyl sorption complexes appears to be the relative abundance and reactivity of the different sorption sites. Copyright 2001 Academic Press.     

Solubilization of oligosaccharides into chloroform by their incorporation into polystyrene as pendant groups

Solubilization of hydrophilic saccharide chains into organic solvents has been attempted by incorporating saccharide-substituted styrene unit into polystyrene main chain. Lactose-, maltopentaose, and amylose-substituted styrene monomers were copolymerized with styrene. Resulting chloroform-soluble copolymers were characterized, and structural formation was investigated. Copolymers of lactose-substituted styrene and maltopentaose-substituted styrene with styrene were dissolved into chloroform. The chloroform-soluble polymers contained about 12 disaccharide lactose chains or 1.7 maltopentaose chains as the pendant groups in one polystyrene molecule. Chloroform-insoluble methyl orange was dissolved into chloroform with the help of chloroform-soluble polystyrene having some saccharide chains. On the other hand, when an amylose-substituted styrene unit was inserted in a polystyrene chain, the resulting polymer became insoluble into chloroform. Amylose polysaccharide of DP_n = ∼24 was not dissolved into chloroform by this method.     

Direct incorporation of gaseous carbon dioxide into solid‐state copolymer containing oxirane and quaternary ammonium halide structure as self‐catalytic function

We established a self‐catalyst system for solid phase incorporation of gaseous carbon dioxide into terpolymers prepared by polymerization of glycidyl methacrylate, N‐benzyl‐N‐[2‐(methacryrolroxy)ethyl]‐N,N‐dimethylammonium bromide, and methyl methacrylate. Terpolymer composition affected the incorporation behavior where the terpolymer with higher oxirane content exhibited higher efficiency of carbon dioxide incorporation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4941–4947, 2004     

铀床氚残留量的测量

分别采用直接测量法、同位素交换法和溶解法测量铀床中的氚残留量, 并分析了这三种测量方法在本实验条件下的误差. 直接测量法测量铀床的氚残留量的结果如下: 铀床的氚残留量为2.68%, 即每克铀含(0.0308±0.0003) mmol 氚气; 当压力读数在1500～133332 Pa之间时, 基于理想气体状态方程的测量方法(简称PVT法)的标准差小于0.95%. 同位素交换法测量铀床氚的结果如下: 加热充分解吸过的铀床经多次同位素交换后, 其交换效率仅为2.84%, 即不到3%(摩尔分数)的氚被氘气载带出来, 其同位素交换法测量的标准差为7.35%. 溶解法能够彻底地测量铀床中残留的氚, 其溶解法测量的标准差为6.49%.