Search results for "Solid"
showing 10 items of 3575 documents
Thermal, glass-forming, nonlinear optical and holographic properties of "push-pull" type azochromophores with triphenyl moieties containing isophoren…
2013
Molecular organic compounds with electron donating fragment bounded through π-conjugated system with electron acceptor fragment, as well as with incorporated triphenyl groups in their molecules show potential for creating cheap and simple solution processable materials with nonlinear optical properties. Additional insertion of azobenzene fragment in their structures makes them also possible to form holographic volume and surface relief gratings (SRG) after exposure to laser radiation, which could be useful for holographic data storage. For these purposes polymers are generally used. However, their application is complicated and challenging task as in every attempt to obtain the same polymer…
Anomalous diffraction profiles of alkali-halide-alkali-cyanide mixed crystals.
1986
The x-ray diffraction profiles of four mixed alkali halides-alkali cyanides have been studied. At the threshold concentration where the systems change over from ferroelastic ordering to the glass state, the profiles are highly unusual. The diffracted intensity of transverse scans along the cubic axes follows $I\ensuremath{\sim}\mathrm{exp}(\ensuremath{-}\ensuremath{\alpha}|\ensuremath{\xi}|)$, where $\ensuremath{\xi}$ is the reduced wave vector, measured from the line center.
M�ssbauer study of the spatial distribution of the active species in Cs doped Fe2O3-V2O5 catalysts
1995
From a Cs doped Fe2O3-V2O5 (Fe:V=1.4) catalyst exhibiting an inhomogeneous composition after calcination, three different fractions have been separated by visual inspection. One fraction has been found to consist of mainly α-Fe2O3, another one of mainly FeVO4. The third fraction (S1 in the text) is the catalytically most active fraction containing besides both of the former components an amorphous phase of FexVyOz and also the dopant. By combining the results from transmission and conversion electron Mossbauer spectra it has been concluded that the amorphous component is enriched in the surface region of the crystallites of the catalyst. In addition, the formation of a thin surface layer of…
Direct evaluation of the electron density correlation function of partially crystalline polymers
1980
A discussion of the general properties of the one-dimensional electron density correlation function K(z) of a partially crystalline polymer with lamellar structure shows that application of a graphical extrapolation procedure permits direct determination of the crystallinity, the specific inner surface, and the electron density difference ηc − ηa. The procedure is based upon the occurrence of a straight section in the “self-correlation” range of K(z). Curved and nonparallel lamellae do not invalidate the concept. In the case of heterogeneous samples composed of partially crystalline and totally amorphous regions, some of the parameters of the experimentally obtained correlation function, as…
Effect of Drying Condition on the Quality of Dry Late Peaches of Leonforte
2015
The Late Peach of Leonforte [Prunus persica (L.) Batsch] grown in Southern Italy matures in September and October and as late as November. Fruits are wrapped in paper bags to protect them from parasites and are harvested only when fully ripe. Protected inside the bags, they ripen late and take on a bright yellow colour with red streaks. Highly aromatic, the peach has yellow, firm flesh that is high in soluble solids and has a distinctive, slightly caramelized flavour. The aim of this work was to deter¬mine the best method of drying peach as a means of conserving the fruit after harvest due to its very limited shelf-life. Drying processes were carried out in a pilot plant utilising differen…
Structural studies of adsorbed protein (betalactoglobulin) on natural clay (montmorillonite)
2014
International audience; In this work, the adsorption of a small globular protein (betalactoglobulin, BLG), on a natural montmorillonite clay (Mt) was investigated in acidic buffer (pH = 3). The combination of different characterization techniques such as zetametry, X-ray diffraction, transmission electronic microscopy, fluorescence and solid state nuclear magnetic resonance spectroscopies shed light on the interaction mechanism between the clay mineral and the proteins. For low BLG concentration, a slight increase of the interlayer spacing of the clay mineral was noticed as well as structural changes of the protein. In contrast, as the concentration of BLG increased, the adsorption led to a…
C-Glycosyl amino acids through hydroboration-cross-coupling of exo-glycals and their application in automated solid-phase synthesis.
2013
O-Glycosylation is one of the most important post-translational modifications of proteins. The attachment of carbohydrates to the peptide backbone influences the conformation as well as the solubility of the conjugates and can even be essential for binding to specific ligands in cell-cell interactions or for active transport over membranes. This makes glycopeptides an interesting class of compounds for medical applications. To enhance the long-term availability of these molecules in vivo, the stabilization of the glycosidic bond between the amino acid residue and the carbohydrate is of interest. The described modular approach affords β-linked C-glycosyl amino acids by a sequence of Petasis …
Halonium ions as halogen bond donors in the solid state [xl2]y complexes
2015
The utilization of halogen bonding interactions is one of the most rapidly developing areas of supramolecular chemistry. While the other weak non-covalent interactions and their influence on the structure and chemistry of various molecules, complexes, and materials have been investigated extensively, the understanding, utilizations, and true nature of halogen bonding are still relatively unexplored. Thus its final impact in chemistry in general and in materials science has not yet been fully established. Because of the polarized nature of a Z–X bond (Z=electron-withdrawing atom or moiety and X=halogen atom), such a moiety can act as halogen bond donor when the halogen is polarized enough by…
Solid state halogen bonded networks vs. dynamic assemblies in solution: explaining N⋯X interactions of multivalent building blocks
2015
Tetrapyridine functionalized resorcinarene macrocycles were used as multivalent building blocks for the construction of halogen bonded networks with aryl halide linkers. In the solid state, resorcinarene macrocycles and aryl halide linker molecules assembled into interpenetrated, multidimensional halogen bonded networks with porous structure caused by the 3D block scaffold of the resorcinarenes. 19F NMR spectroscopy proved halogen bond formation also in solution, as either upfield or downfield shifts were observed depending on the bivalent or monovalent halogen bond binding mode. The binding mode in solution was explained by density functional theory computations. peerReviewed
The effect of pH on polymorph formation of the pharmaceutically active compound tianeptine.
2012
The anti-depressant pharmaceutical tianeptine has been investigated to determine the dynamics of polymorph formation under various pH conditions. By varying the pH two crystalline polymorphs were isolated. The molecular and crystal structures have been determined to identify the two polymorphs. One polymorph is an amino carboxylic acid and the other polymorph is a zwitterion. In the solid state the tianeptine moieties are bonded through hydrogen bonds. The zwitterion was found to be less stable and transformed to the acid form. During this investigation an amorphous form was identified.