Materials Literature
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A new chelating macrocycle, 1,5,9-triazacyclododecane-N,N’,N’’-triacetiacc id (DOTRA), has been synthesized, and its complexes \nwith Zn2’, Cd2+, Ca2+, Mg2+, and Mn2+ have been examined by potentiometry and NMR spectroscopy. The first protonation \nconstant of the free ligand (log K, = 12.8) was determined spe…
A crystal-state structutal analysis of pBrBz-(Aib-LAla)5-OMe tetrahydrate and pBrBz-(Aib-L-Ala)6-OMe dihydrate has been performed by X-ray diffraction. The decapeptide and dodecapeptide molecules are both basically α-helical with five and seven 1 â†� 5 intramolecular H-bonds, respectively. A similarity between the two…
The long sought after [2,2]azobenzenophane 1 has been prepared quite simply by reduction of l,2-bis(4-nitrophenyl)ethane. According to 1H-NMR and UV/VIS spectra the CNNC moiety in 1 is noticeably bent. Photochemically generated cis,cis-1 isomerizes 10000 times more slowly to the trans,trans-form than does the cis,t…
Liposomes can be produced by a variety of techniques such as sonication, high-pressure homogenization, detergent dialysis, reverse-phase evaporation and ether injection. The Microfluidizer is a high-pressure homogenizer which is capable of making small size multilamellar vesicles. The mean vesicle size of the liposome…
The temperature dependence and dispersion relation of phason and amplitudon relaxation times were measured in Sm-A and Sm-${C}^{\mathrm{*}}$ phases of the ferroelectric liquid crystal S-(+)-[4-(2'-methylbutyl) phenyl 4'-n-octylbiphenyl-4-carboxylate] (CE8) by photon correlation spectroscopy. In the Sm-A phase both mod…
Abstract
{5,5′;19,19′-Bi[phthalocyaninato(2–)]}titanium(IV)–1-chloronaphthalene(1/1 ), [TiL]·C10H7Cl, is obtained by the reaction of [Ti(pc)Cl2](pc = phthalocyaninato dianion, [C32H16N8]2–) with Na2(pc) in 1-chloronaphthalene at 190 °C, An X-ray single-crystal structure (monoclinic, space group C/2c, a= 16.327(3), b= 18.568(4)…
Quenching experiments on very thin films (≃ 1 000 Å) of symmetric diblock copolymer deposited on solid substrates result in the formation of circular relief domains at the free surface of the sample. It is due to the quantization of the possible thicknesses of the sample which accompanies the lamellar ordering of the…
Powder neutron diffraction studies confirm that D 2 S has 3 solid-state phases at ambient pressure. Phases I and II are cubic and orientationally disordered with space groups Fm [unk] m ( a = 5.8486(8) Å at 160 K) and P a [unk] ( a = 5.7647(6) Å at 120 K), respectively. The deuterium scattering density arising from th…
[NH4]2[MoO2{O2CC(S)Ph2}2]middot;2H2O has been prepared and its crystal structure solved, providing the first example of a co-ordinatively saturated molybdenum complex which reacts readily and reversibly with organophosphines at room temperature in water or methanol; its variable-temperature 13C{1H} NMR spectra and ele…
On joining of metals to ceramics, chemical reaction at the bonding interfaces is unavoidable in most of the combinations of ceramics and metals including brazes except for a few special cases. Thermodynamic possibility of the chemical reaction and the resulted interfacial structure are compared with the experimental r…
The complex anion obtained by crystallisation from an aqueous solution of molybdate and citric acid (H3cit) at pH ca. 3 is of the type (i), [(MoO2)4O3(cit)2]4−, as determined by X-ray analysis of the salt K4[Mo4O11(cit)2]·6H2O. Principal dimensions [ranges or means; estimated standard deviation (e.s.d.) 0.005 Å] are:…
High-surface-area amorphous Al2O3–AlPO4 samples (P/Al ratio: 0–0.17) have been prepared by reductive decomposition of aluminium nitrate in the presence of phosphoric acid. The materials obtained are amorphous up to 1100–1200 K and present “zeolitic-type” monomodal microporosity (r= 10–15 Å). They are weakly acidic. Th…
Reaction of MCl5(M = Nb or Ta) with p-butylcalix[4]arene, L-(OH)4, led, depending on the reaction conditions, either to mononuclear complexes [(AcO)–L–(O)3MCl2], or, in the case of niobium only, to the tetranuclear complex [{µ-L-(O)4}2Nb4O2Cl8], characterized by X-ray analysis.
Abstract
The corrosion rate of Nd-Fe-B magnets is found to vary with O, C, and N contents. The corrosion rate rapidly decreases with increasing oxygen content and reaches the minimum when the oxygen content is between 0.6 and 1.2%. The corrosion rate rapidly decreases as the carbon content increases up to about 0.06% and then…
Abstract A new laboratory plant for batch cooling crystallization is described, which allows to maintain the supersaturation at a constant level during an experimental run. A method for continuous supersaturation measurements has been developed, using a density meter and a hydrocyclone. Experimental results obtained f…
Traditionally, laboratory study of phytoplankton ecology and physiology has been performed in batch cultures. Such cultures are also commonly used when phytoplankton are needed as a food supply for herbivores in an experimental or aquaculture setting. The great advantage of batch culture is its simplicity; however, in…
We discuss the viscosity and the specific heat of glass forming systems near their glass transition in the framework of usual scaling theory at a second order transition. We define this transition through the Kauzmann paradox : i.e. we assume that all the entropy difference between the same crystal and the liquid phas…
The L-azetidine-2-carboxylic acid (Aze) residue can be incorporated into proteins in the place of L-proline, of which it is the lower homologue. This substitution alters the properties of proteins, especially of collagen. Conformational constraints in N-acetyl-Aze-N'-methylamide and in several dipeptides containing Az…