Materials Literature
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The properties of a novel complex between pyranine (a photoacid and an electron donor species) and methyl viologen (an efficient electron acceptor, MV +2 ) in aqueous and in micellar solutions were determined. On the basis of the electrostatic driven force for pyranine/methyl viologen (pyranine/MV 2+ ) complexation, t…
Nineteen oxybutylene/oxyethylene/oxybutylene triblock copolymers [B n /2 E m B n /2, E = oxyethylene, OCH 2 CH 2; B = oxybutylene, OCH 2 CH(CH 2 CH 3 )] were prepared and characterized. Twelve of the copolymers microphase-separated in the melt. Investigation of this microphase-separation behavior using small-angle X-r…
We report transformations of the Ruddlesden−Popper (R−P) oxide, K 2 La 2 Ti 3 O 10, to layered perovskite oxides, (Bi 2 O 2 )La 2 Ti 3 O 10, MLa 2 Ti 3 O 10 (M = Pb, Ba, Sr), and (VO)La 2 Ti 3 O 10, by a novel metathesis reaction with BiOCl, MCl 2, and VOSO 4 ·3H 2 O, respectively. The formation of (VO)La 2 Ti 3 O 10,…
Scrap tires are a growing environmental problem because they are not biodegradable and the components used to manufacture tires cannot readily be recovered. In this investigation, the thermochemical recycling of rubber from old tires by pyrolysis and hydropyrolysis has been studied using a swept fixed bed reactor. Thi…
The spontaneous breaking of a global discrete translational symmetry in the finite, lattice quantum sine-Gordon model is demonstrated by a density matrix renormalization group. A phase diagram in the coupling constant - inverse system size plane is obtained. Comparison of the phase diagram with a Woomany-Wyld finite-s…
Quenching of the photoluminescence (PL) emission from conjugated macromolecules by charge transfer to cationic electron acceptors is studied by changing the ion concentration in buffered aqueous solutions, by changing the concentration of acceptors, and by varying the temperature. A weakly bound complex is formed (in…
Ship-in-a-bottle synthesis of otherwise labile cyclic trimers of siloxanes in a self-assembled coordination cage, Ship-in-a-bottle synthesis of otherwise labile cyclic trimers of siloxanes in a self-assembled coordination cage
A new stelligeroid Cyclotella (Bacillariophyceae), Cyclotella mascarenica KLEE, HOUK et BIELSA nov. spec., from a pond on Reunion Island (France) is described here on the basis of LM and SEM studies. This species is strongly reminiscent of Cyclotella stelligera (CLEVE et GRUNOW) VAN HEURCK, however, it differs from it…
A series of new unsymmetrically substituted subphthalocyanines containing iodo or octylthioether substituents on the outer aromatic rings have been synthesized. The statistical reaction of one equivalent of 1,2-dicyano-3-iodobenzene whether with two equivalents of 1,2-dicyano-4-octylthiobenzene or with two equivalents…
Thermostimulated luminescence (TSL) of Li 2 B 4 O 7 and Li 2 B 4 O 7 :Eu single crystals in the temperature range 290-650K has been studied. Lithium tetraborate (LTB) doped with europium has been found to favour a further increase of the light sum storage of electroncaptured centres. Radiation-induced defects and thei…
The bulk materials of As 100-x S x (x = 71.4; 67; 62; 60; 58) composition were prepared by the direct synthesis according to the conventional melt-quenched method from 5N purity elements. Arsenic and sulfur were weighed and placed in precleaned and outgassed (by heating under vacuum to 900 C) quartz ampoules. The synt…
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Phytoplankton succession was studied weekly based on integrated samples from the euphotic zone (0-25 m) of the deep oligotrophic Lake Stechlin (Germany, Brandenburg) between 1994-1999. The rare centric diatom Stephanocostis chantaicus appeared regularly int he winter plankton building up population maximum int he wint…
[structure: see text] A series of novel poly-o-(bromomethyl)ated tetraarylporphyrins was synthesized. Their usefulness as building blocks for porphyrinic materials is demonstrated.
A series of three new fluorescent dendrimers containing a single, focally located dansyl group and 3 ( 1 ), 9 ( 2 ), and 27 ( 3 ) carboxylic acid groups in their peripheries were synthesized and characterized. The photophysical properties of these dendrimers were investigated in aqueous solution. The host−guest intera…
The multisubunit ligand 2 combines two complexation substructures known to undergo, with specific metal ions, distinct self-assembly processes to form a double-helical and a grid-type structure, respectively. The binding information contained in this molecular strand may be expected to generate, in a strictly predeter…
Reversible intramolecular cyclization reactions to form crown ethers are possible with photoactive anthracene derivatives containing two binding sites (see scheme). Different chemical inputs in the form of HgCl2 and Na+ ions result in changes in the efficiency and rate of the forward and reverse processes.
A high formaldehyde feed concentration and a low reaction temperature are among the advantages of using heteropolyacids (phosphotungstic acid and silicotungstic acid) as catalysts in the formation of trioxane; this cyclic trimer of formaldehyde (see scheme) is used in the industrial production of acetal resins. Compar…
p-TsOH-catalyzed condensation reactions of 1,1-diaryl-2-propyn-1-ol (1) and 2-naphthol (2) in the solid state gave 3, 3-diaryl-3H-naphtho[2,1-b]pyran (6) via Claisen rearrangement. Similar reactions of 1 with 2,6- (7) and 2,7-dihydroxynaphthalenes (8) afforded naphthodipyrane derivatives 9 and 10, respectively. Bis-na…
The spin crossover (SC) compounds [Fe(PM-AzA)2(NCX)2] and [Fe(PM-FIA)2(NCX)2] (with PM-AzA = N-2'-pyridylmethylene-4-(phe-nylazo)aniline, PM-FIA = N-2'-pyridylmethylene-4-(2-amino)fluorene, and X = S, Se) have been prepared. The SC regimes have been deduced from variable-temperature magnetic susceptibility data. The e…