Materials Literature
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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…
Thermographic phosphors may be used to measure surface temperatures in hostile and high temperature environments and have applications in gas turbine combustors and high temperature regions of the turbine. Most phosphors are excited by UV light and exhibit a temperature sensitive exponential decay in emission once exc…
Conformationally rigidified tetraCMPO derivatives have been prepared from calix[4]arene bis(crown ether) 4a in which adjacent oxygens are bridged at the narrow rim by two diethylene glycol links. Acylation of the tetraamine 4c with the CMPO-active ester 5b gave the tetraphosphine oxide 6a, while the tetraphosphinate 6…
Interaction with the zeolitic walls changes the structure of zeolite-encapsulated CuI(CO)3 cations (see picture), which were synthesized in situ by treating CuI-ZSM-5 zeolite with CO at 80 K, from the planar D3h form, typical of homogeneous analogues such as [Cu(CO)3]+AsF6−, to a C3v-symmetric bent form. This conclusi…
The structure and composition of fluorocarbon materials deposited in pulsed and continuous wave (CW) hexafluoropropylene oxide (HFPO) plasmas were investigated. Results indicate substantial dependence on substrate position relative to the rf coil. When the substrate was placed 8 cm downstream from the rf coil (25 W CW…
Novel peripherally heterogeneous dendrimers in which both ferrocene and cobaltocenium units are attached to the surface of poly(propylene imine) dendritic frameworks (see picture) were prepared. The presence of the two redox-active moieties allows the heterometallic dendrimers to be used as novel types of mediator in…
In this Letter, we show that at low temperatures, zero-point fluctuations of the plasmon modes of two mutually coupled 2-D planar Wigner crystals give rise to a novel long-range attractive force. For the case where the distance $d$ between two planar surfaces is large, this attractive force has an unusual power-law de…
In this paper, we present a unified physical picture for the electrostatic attraction between two coupled planar Wigner crystals at finite (but below their melting) temperature. At very low temperatures, we find a new regime where the attraction, arising from the long-wavelength excitation of the plasmon mode, scales…