Identification and Characterization of Alkaline Uranyl(2 +) Phosphates

The spontaneous precipitation in the systems U02(N03)2- -MOH-HaP04--H20 and U02(N03)2-MNOa-H3P04- H20 (M = = Li, Na, K, Rb, Cs) is examined. The formation of alkaline- uranyl(2+) phosphates polyhydrates is detected: M[U02P04] · · n H20 (n = 4 for M = Li, n = 3 for M = Na, K, Rb and n = 2.5 for M =Cs). The X-ray powder patterns of these compounds are determined and compared with that of H30[U02P04] · 3 H20. A close structural relation within this series is observed. The size of the alkaline ionic species in the particular compound affects the content of crystalline water in the unit cell

Spontaneous Precipitation in the System Uranyl(2+ )nitrate Potassium Hydroxide - Phosphoric Acid - Water

The precipitation system U02(NOs)2-KOH-H3P04-H20 (at 298 K) aged for 1 day and for 30 days is examined ([U02(NOs)2] = = 1 · 10-a mol dm-3, [KOH] varied from 1 · 10-6 to 6 · 10-1 mol dm-3, [H3P04] from 2 · 10-4 to 6 · 10-1 mol dm-3 and 1.5 <pH< 11.5). The precipitation and phase boundaries are determined. The solid phases U02HP04 · 4 H20(s) and (U02)s(P04)2 · 8 H20 are stable at [KOH] < 1 · 10-3 mol dm-3, 1.5 <pH < 4.0. Uranates precipitate at pH > 9.5. The stability region of KU02P04 · 3 H20(s) is found at high concentrations of KOH and H3P04. X-ray diffraction pattern of this compound is given. According to the precipitation boundary after 30 days (equilibrium conditions) the solubility product of KU02P04 · 3 H20 is determined: log ([K+] · · [U022+] [P043-]) = -- 26.28 (at I =0 mol dm-3)

Precipitation and Solubility of Uranyl - Orthophosphates. I. Heterogeneous Equilibria in Solutions of: U02(NOa)2 - HaP04

The precipitation and dissolution of uranium(VI) from aqueous solutions of orthophosphoric acid (2 X 10-a to 6 M) and uranyl nitrate (3 X 10- 5 to 0.5 M) has been investigated by turbidimetric and chemical analyses, fluorescent and electron microscopy. The concentration ranges where (U02 )g(P04 h and U02HP04 precipitates were observed 24 hours and 30 days after mixing are represented by typical precipitation bodies. The morphology of the precipitated particles is shown by electron micrographs. At equilibrium conditions (U02)a(P04 ) 2 is stable at concentrations of total phosphate in the mother liquor lower than 1.5 X 10-3 M. At total phosphate concentrations higher than 5 X 10- 3 M, U02 HP0 1 is stable

Precipitation and Solubility of Uranyl Orthophosphates. II. Heterogeneous Equilibria in Solutions of: U02(NO3)2 - H3P04 - HNO3

The precipitation and dissolution of uranium(VI) from aqueous solutions containing 10-3 M uranyl nitrate and various concentrations of orthophosphoric and nitric acid is / surveyed. The concentration regions where (U02)s(P04h and U02HP04 are precipitated and/or dissolved are presented by means of typical precipitation bodies. The influence of the initial concentration ratio of nitric/ orthophosphoric acid in the precipitation system on the morphology of (U02la(P04)2 particles formed is shown by electron micrograps

Nucleation of Calcium Phosphate from Solutions at Physiological pH

In a previous paper1 it was shown that when phase transition from aqueous solutions occurs at metastable equilibrium, the stoichiometry of the nucleating phase can be conveniently evaluated from the precipitation boundary2 • The method was applied to calcium phosphates nucleating in the pH range 6.3 , to 9.1 from solutions containing calcium chloride and sodium phosphate at constant total phosphate concentration 1 X 10-3 M. The calcium phosphate ratio of the nucleating phase was found to be 1.5 and the formation of an amorphous metastable precursor to hydroxyap atite was concluded. Because of its implications on biological calcification it was of interest to reexamine this result restricting the experiments to the physiological pH region (pH 7.25-7.5), but taking into account possible variations of total phosphate and total calcium concentrations. This was done as part of more extensive investigations of the precipitation of calcium phosphates from aqu eous solutions and from media containing 0.15 M sodium chlorid e

Chemical Defence in a Millipede: Evaluation and Characterization of Antimicrobial Activity of the Defensive Secretion from Pachyiulus hungaricus (Karsch, 1881) (Diplopoda, Julida, Julidae)

The chemical defence of the millipede Pachyiulus hungaricus is reported in the present paper, in which a chemical characterization is given and antimicrobial activity is determined. In total, independently of sex, 44 compounds were identified. All compounds belong to two groups: quinones and pentyl and hexyl esters of long-chain fatty acids. The relative abundances of quinones and non-quinones were 94.7% vs. 5.3% (males) and 87.3% vs. 12.7% (females), respectively. The two dominant quinones in both sexes were 2-methyl-1,4,-benzoquinone and 2-methoxy-3-methyl-1,4-benzoquinone. Antibacterial and antifungal activity of the defensive secretion was evaluated in vitro against seven bacterial strains and eight fungal species. With the aid of a dilution technique, the antimicrobial potential of the secretion and high sensitivity of all tested strains were confirmed. The lowest minimum concentrations of these compounds (0.20-0.25 mg/mL) were sufficient for inhibition of Aeromonas hydrophila, Listeria monocytogenes and Methicillin resistant Staphylococcus aureus (MRSA). The growth of eight tested fungal species was inhibited by slightly lower concentrations of the secretion, with Fusarium equisetias the most sensitive fungus and Aspergillus flavus as the most resistant. Values of MIC and MFC in the employed microdilution assay ranged from 0.10 to above 0.35 mg/m L. The given extract contains antimicrobial components potentially useful as therapeutic agents in the pharmaceutical and agricultural industries

A formal account of the dual extension of knowledge and concept in C-K design theory

The paper presents a contribution to the formalization efforts of C-K design theory. First, we analyze the notion of "dual expansion of concepts and knowledge" in C-K design theory and we discuss how such a reasoning process can be modeled using first-order logic. Then, we present a basic formal account of this notion. This framework is complementary to previous work formalizing the interaction of concepts and knowledge. Finally an attempt is made to sketch some possible extensions of the basic formal framework

Keep IT Real: On Tools, Emotion, Cognition and Intentionality in Design

Keep IT real, create, build, and develop design tools that support designers during the early phases of design processing. This paper investigates how, and whether, current technology can afford real-time interaction and affective computing in a HDT(E) design tool that integrates and blends realities through physical and virtual interaction. Interaction design (IxD) is crucial to the usability (UX) and engagement (UE), concepts and terminology are introduced, after which an interaction framework is set up that takes into account the multi-modal Human Computer Interaction (HCI) with a HDT(E)

Recursive Secessions in Former Yugoslavia: too Hard a Case for Theories of Secession?

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