Determination of uranium and radium in phosphate rock and technical phosphoric acid

Summary Uranium in phosphate rock can be determined radiometrically using gamma-counting and spectrophotometrically using arsenazo I. In the latter case the rock is dissolved in HNO₃, then uranium is extracted with tributyl phosphate, stripped with hot water and determined. For the determination of uranium in technical phosphoric acid, the fluorosilicate ion present as impurity must first be precipitated, the uranium separated on Amberlite IRA-400 in the sulfate form, then determined in the eluate spectrophotometrically by arsenazo I. Radium can be determined in leach solutions by the emanation method.

---

Bestimmung von Uran und Radium in Phosphatgestein und technischer Phosphorsäure

Zusammenfassung Uran kann in Phosphatgestein radiometrisch mit -Zählung und spektralphotometrisch mit Arsenazo I bestimmt werden. Zur spektralphotometrischen Bestimmung wird die Probe in Salpetersäure gelöst, dann das Uran mit Tributylphosphat extrahiert, in heißes Wasser überführt und bestimmt. Zur Uranbestimmung in technischer Phosphorsäure muß zuerst das als Verunreinigung vorhandene Fluorosilicat gefällt und dann das Uran mit Hilfe von Amberlit IRA-400 in der Sulfatform abgetrennt werden, bevor es im Eluat mit Arsenazo I bestimmt werden kann. Radium kann in Auslaugungslösungen mit Hilfe der Emanationsmethode bestimmt werden.

     

The control of lightning using lasers: properties of streamers and leaders in the presence of laser-produced ionization

This paper summarizes the research this team has performed over the past few years investigating laboratory electrical breakdown discharges in the presence of a plasma cylinder created by a single ultrashort laser pulse. This work is part of a feasibility study about the control of lightning using laser systems. Our experimental investigations have included discharges (i) in modest (30 cm) air gaps mediated by streamers, and (ii) in large (several meters) ambient air gaps for which the discharge took place through the formation of a leader, the mechanism relevant to large scale natural discharges such as lightning. In order to understand the observations, various physical models have been used, the main results of which are discussed in this paper. To cite this article: F. Vidal et al., C. R. Physique 3 (2002) 1361–1374.     

Nucleophilic addition to the tricarbonyl(η-cycloheptadienylium)iron cation by alkoxide ions. Formation of carboalkoxy intermediates

Nucleophilic addition the title compound by alkoxide ions (OR^?) at 0°C proceeds via a red intermediate probably involving metal-nucleophile interaction, and subsequent formation of the carboalkoxy compound C₇H₉Fe(CO)₂(CO₂R). On raising the temperature, the latter compound rearranges spontaneously by a dissociative mechanism to give the corresponding 5-exo-ring compound C₇H₉ORFe(CO)₃.     

Solvent effects in the synergistic solvent extraction of Co2+

The extraction of Co²⁺ from a 0.1M ionic strength aqueous phase (Na⁺, CH₃COOH) of pH=5.1 was studied using thenoyltrifluoroacetone, HTTA, in eight different solvents and HTTA+trioctylphosphine oxide, TOPO, in the same solvents. A comparisons of the effect of solvent dielectric constants on the equilibrium constant shows a synergism as a result of the increased hydrophobic character imparted to the metal complex due to the formation of the TOPO adduct.     

Pyrimidine derivatives and related compounds VI. A novel synthesis of 3,5-diacetamidopyrazole and of 2-aminopyrazolo [1,5-α] pyrimidines

3,5-Diaeetamidopyrazole (2) could be prepared via arylazo group decoupling from 3,5-diamino-4-arylazopyrazoles ( 1a-c ) by the action of acetic acid-sulfuric acid mixture. Arylazo group removal could also be effected when 2-amino-5-melhyl-7-oxo-6,7-dihydro-3-phenylazopyrazolo-[1,5-α]pyrimidine ( 5 ) was similarly treated. The 2-aminopyrazolo[1,5-α]pyrimridine derivative was obtained in this case. On the other hand, under the same experimental conditions compounds 7a-c and 8 were recovered almost unaffected. The mechanism of the reaction is discussed.     

Squarate complexes of some lanthanide ions in aqueous solution

The squarate complexes of Eu³⁺, Tb³⁺ and Tm³⁺ in aqueous solutions of 0.05M, 0.075M and 0.1M ionic strength are studied using the solvent extraction method. Effects of changes in the ionic strength on the stability constants of the complexes formed are discussed.     

Optimization of the preparation conditions of radioiodoepidepride: A dopamine D<Subscript>2</Subscript>receptor antagonist radioligand

Summary [¹²⁵I]iodepidepride, (s)-(-)-[(1-ethyl-2-pyrrolidinyl)methyl]-5-[¹²⁵I]-iodo-2,3-dimethoxybenzamide is the iodine substituted analogue of isoremoxipride, both of which are very potent dopamine D₂-antagonists. Epidepride was radioiodinated using different oxidizing agents such as chloramine-T, iodogen, iodogen glass frit and hydrogen peroxide. Chloramine-T is a powerful oxidizing agent compared to both iodogen and hydrogen peroxide so that the side products, especially the chlorinated epidepride, decreases the radiochemical yield. This chlorinated epidepride is minimized in the case of iodogen and iodogen glass frit and are not observed in case of the non-chlorinated oxidizing agent hydrogen peroxide. TLC and HPLC were used to analyze the reaction components and to estimate both the radiochemical yield and purity. The reaction parameters such as reaction time, pH, epidepride and oxidizing agent concentrations and the stabilty of the final product were studied to optimize the radiochemical yield and purity. The optimized radiochemical yield was about 90% and the radiochemical purity of the final product was 99.9%.     

2,2′-Dipyridyl and 1,10-phenanthroline in the synergetic extraction of Eu3+

The thermodynamics of the extraction of Eu³⁺ by thenoyltrifluoroacetone (HTTA) and by mixtures of HTTA and bidentate amine bases such as 2,2-dipyridyl (Dipy) and 1,10-phenanthroline (Phen) in benzene from an aqueous phase fixed to 0.1M ionic strength (NaClO₄), pH 3.9, has been investigated. Phenanthroline forms both the Eu(TTA)₃·Phen and Eu(TTA)₃·2Phen species, which are much stronger than the dipyridyl complexes. The diluent effect on the extraction is also studied.     

Synthesis and Biological Evaluation of Bicalutamide Analogues for the Potential Treatment of Prostate Cancer

The androgen receptor (AR) is a pivotal target for the treatment of prostate cancer (PC) even when the disease progresses toward androgen-independent or castration-resistant forms. In this study, a series of 15 bicalutamide analogues (sulfide, deshydroxy, sulfone, and O-acetylated) were prepared and their antiproliferative activity evaluated against four different human prostate cancer cell lines (22Rv1, DU-145, LNCaP, and VCap). Bicalutamide and enzalutamide were used as positive controls. Seven of these compounds displayed remarkable enhancement in anticancer activity across the four PC cell lines. The deshydroxy analogue (16) was the most active compound with IC₅₀ = 6.59–10.86 µM. Molecular modeling offers a plausible explanation of the higher activity of the sulfide analogues compared to their sulfone counterparts.