Separation of microamounts of yttrium from strontium by using nitrobenzene solution of sodium dicarbollylcobaltate in the presence of 18-crown-6

A rapid extraction separation of trace amounts of yttrium from strontium with a nitrobenzene solution of sodium dicarbollylcobaltate (NaDCC) and 18-crown-6 in the presence of tetrasodium salt of ethylenediamine-N,N,N",N"- tetraacetic acid (Na₄L) in the aqueous phase was developed. The separation factor a(Sr/Y) was substantially higher than 10⁶. This water-nitrobenzene extraction system can be applied for efficient separation of carrier-free ⁹⁰Y from ⁹⁰Sr/⁹⁰Y generator.     

Extraction of microamounts of strontium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of dicyclohexyl-18-crown-6

Summary Extraction of microamounts of strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^-) in the presence of dicyclohexyl-18-crown-6 (DCH18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, HL, SrL²⁺and SrL are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

The formation of dislocations by a spark discharge

The arrangement of dislocations formed in a single crystal of the alloy Fe-4·2% Si by a spark discharge in air is studied. The dislocations are made visible by etching on the surfaces perpendicular and parallel to the axis of the crater. The results of the observations are explained on the basis of microphysical conceptions of plastic deformation.

---

, Fe— 4,2% Si . , . .

     

Transition‐Metal‐Catalyzed Direct Arylation of (Hetero)Arenes by C?H Bond Cleavage

The area of transition‐metal‐catalyzed direct arylation through cleavage of C? H bonds has undergone rapid development in recent years, and is becoming an increasingly viable alternative to traditional cross‐coupling reactions with organometallic reagents. In particular, palladium and ruthenium catalysts have been described that enable the direct arylation of (hetero)arenes with challenging coupling partners—including electrophilic aryl chlorides and tosylates as well as simple arenes in cross‐dehydrogenative arylations. Furthermore, less expensive copper, iron, and nickel complexes were recently shown to be effective for economically attractive direct arylations.     

Tetramethyl guanidine-assisted synthesis and thermal crosslinking of multifunctional benzoxazine monomers based on natural phloretic acid

An efficient strategy to synthesize novel biobased multifunctional benzoxazine compounds was developed using the 1,1,3,3-tetramethyl guanidine (TMG)-triggered esterification of natural phloretic acid with organic halides as a key synthetic step. First, phloretic acid was combined with either aniline or furfurylamine to prepare the corresponding carboxylic acid-functional monobenzoxazine monomer. Next, the use of TMG enabled an efficient esterification of these compounds with di-, tri-, and tetra-functional benzyl bromide compounds at room temperature to afford a series of new multi-benzoxazine monomers tethered to an aromatic core. The effect of the functionality of the monomers on the curing process was analyzed, indicating that the reactivity during the thermally induced ring-opening increases with the number of furan and oxazine rings in the monomers. The resulting thermosets revealed good correlation between the number of oxazine rings in the structure of the monomer and the properties of the crosslinked materials. Furfurylamine-based polybenzoxazines showed improved thermal behavior compared to the aniline-based systems, due to the role of furan rings. All materials showed high T_g, good thermal stability, and promising flame retardancy properties.     

Evolution of high-frequency gravitational waves in some cosmological models

We investigate Isaacson’s high-frequency gravitational waves which propagate in some relevant cosmological models, in particular the FRW spacetimes. Their time evolution in Fourier space is explicitly obtained for various metric forms of (anti-)de Sitter universe. Behaviour of high-frequency waves in the anisotropic Kasner spacetime is also described.     

Interaction of meso-tetrakis (4-sulfonatophenyl) porphyrin with cationic CTAC micelles investigated by small angle X-ray scattering (SAXS) and electron paramagnetic resonance (EPR)

Small angle X-ray scattering (SAXS) and electron paramagnetic resonance (EPR) have been used to investigate the interaction of the water-soluble meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS(4)) with cationic cethyltrimethylammonium chloride (CTAC) micelles. To evaluate if the porphyrin protonation state affects its interaction with the micelle, both SAXS and EPR measurements were performed at pH 4.0 and 9.0. The best-fit SAXS curves were obtained assuming for CTAC micelle a prolate ellipsoidal shape in the absence and upon incorporation of 2-10 mM TPPS(4). SAXS results show that the presence of porphyrin impacts on micellar hydrophobic core, leading to a micellar reassembling into smaller micelles. Lineshapes of EPR spectra of 5- and 16-doxyl stearic acids (5- and 16-DSA, respectively) bound to 100 mM CTAC micelles exhibited slight changes as a function of porphyrin concentration. Spectral simulations revealed an increase of mobility restriction for both spin probes, especially at higher porphyrin concentration, where a small reduction of environment polarity was also observed for 16-DSA. The spin labels monitored only slight differences between pH 4.0 and 9.0, in agreement with the SAXS results.     

Construction of Chiral Tri‐ and Tetra‐Arylmethanes Bearing Quaternary Carbon Centers: Copper‐Catalyzed Enantioselective Propargylation of Indoles with Propargylic Esters

Copper‐catalyzed enantioselective propargylation of indoles with propargylic esters and sequential Huisgen cycloaddition with azides lead to the construction of chiral triarylmethanes, bearing a quaternary carbon center, with high to excellent enantioselectivities. The result described herein can be used in the enantioselective preparation of a tetraarylmethane.     

Determination of total copper in haemodialysis water by differential-pulse anodic stripping voltammetry

An anodic stripping voltammetric method was developed in order to determine copper in the water used to prepare haemodialysis solutions. The interference from organic matter was overcome by high-pressure bomb mineralization. The electrochemical results were compared with those obtained by using graphite furnace atomic absorption spectrometry and the correlation was excellent (r = 0.983, p < 0.001). The detection limit was 0.2 μg l^?1 copper.     

Anhydrides as acylating agents in the enzymatic resolution of an intermediate of (-)-Paroxetine

A new chemoenzymatic method for the preparation of an intermediate of (-)-Paroxetine is reported. Cyclic anhydrides are used as acylating agents in the lipase-catalyzed esterification of trans-4-(4'-fluorophenyl)-3-hydroxymethyl-N-phenyloxycarbonylpiperidine in organic solvents. The best enantioselectivities are obtained with two different lipases from Candida antarctica. These two lipases show opposite stereochemical preference in these processes, so that both enantiomers can be obtained in their optically pure forms. The (3S,4R) isomer is an intermediate for the synthesis of (-)-Paroxetine.