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Phase diagrams of urea inclusion compounds
2. Stearic acid and urea
Abstract
The stearic acid-urea binary system exhibits an unusual phase diagram, which, on the one hand, indicates an incongruently melting inclusion compound and on the other hand a miscibility gap in the liquid phases. The peritectic point lies near the melting point of urea and the unstable congruent melting point of the inclusion compound coincides with the melting point of urea. In addition to the processing of the phase diagram, the pure inclusion compound was prepared and its DSC curve, FTIR spectrum and X-ray diffractogram were recorded.
Novel zinc(II) benzoate complex compounds with caffeine and urea
Synthesis and characterization
Abstract
Novel zinc(II) complex compounds of general formula Zn(C6H5COO)2·L2 (where L=caffeine (caf) and urea (u)) were synthesized and characterized by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied during heating in air by thermogravimetry. It was found that the thermal decomposition of the anhydrous Zn(II) benzoate compounds with bioactive ligands was initiated by the release of organic ligands at various temperatures. On further heating of the compounds up to 400°C the thermal degradation of the benzoate anions took place. Zinc oxide was found as the final product of the thermal decomposition of all zinc(II) benzoate complex compounds heated to 600°C. Results of elemental analysis, infrared spectroscopy, mass spectroscopy and thermogravimetry are presented.
Abstract
The gel to liquid-crystal transition for vesicles in aqueous solution formed by dimethyldi-n-octadecylammonium bromide (DOAB) occurs at 44.7C. Moreover, the shapes of the scans recorded by a sensitive DSC microcalorimeter are very similar when the vesicular solutions are prepared starting with solid DOAB and comparable amounts of either solid urea or solid alkylureas. Therefore, the DOAB vesicles in aqueous solution accommodate this class of solutes without marked changes in the melting temperature and the enthalpy of the transition. The contrast with effects of added surfactants and simple organic solutes such as THF and ethanol is particularly significant.
Abstract
The adduct of Al(NO3)3·6CO(NH2)2 has been prepared and characterized by means of chemical analysis, IR spectroscopy, X-ray patterns and microscopy. A thermoanalytical study of Al(NO3)3·6CO(NH2)2 as well as urea, for comparison purposes, under conventional dynamic and quasi-isothermal—quasi-isobaric conditions in air has been carried out. It has been found that the adduct is thermally stable up to about 200°C, i.e. up to higher temperature than the decomposition temperature of the constituent compounds. The thermal decomposition mechanism of the adduct is complex, thus infrared spectroscopy and X-ray diffraction techniques have been used to determine the intermediate products. Aluminium oxide(III) is the final decomposition product.
Abstract
It is presented a study concerning the influence of guanidinium chloride (GuHCl) and urea on thermal stability of Bovine Pancreatic Ribonuclease A (RNAase A) at differentpH values. As expected, at increasing the denaturant concentration, the protein thermostability decreases. This is shown by a decrease of both the thermodynamic parameters, temperature and heat effect, characterising the denaturation process. In order to analyse the calorimetric curves we adopt a statistical thermodynamic approach. The individual one-dimensional DSC profiles have been expanded into another dimension by varying the GuHCl concentration, so that a heat capacity surface is defined for eachpH. By means of the ICARUS program, developed in our laboratory, we accomplish a two dimensional deconvolution of the experimental data linking the binding equilibrium to the denaturation process. This analysis provides a well founded and complete statistical thermodynamic characterisation of denaturation process of RNAase A in the presence of GuHCl and allows to calculate the thermodynamic parameters associated to the binding of denaturant molecule.
Abstract
Two bismuth ferrite potential precursors systems, namely Fe(NO3)3·9H2O-Bi(NO3)3·9H2O-glycine/urea with different metal nitrate/organic compound molar ratios have been investigated in order to evaluate their suitability as BiFeO3 precursors. The presence into the precursor of both reducing (glycine and urea) and oxidizing (NO3 −) components, modifies dramatically their thermal behaviour comparative with the raw materials, both from the decomposition stoichiometries and temperature occurrence intervals points of view. Also, the thermal behaviour is dependent on the fuel nature but practically independent with the fuel content. The fuel nature influences also some characteristics of the resulted oxides (phase composition, morphologies). In the case of the oxides prepared using urea as fuel, a faster evolution toward a single phase composition with the temperature rise is evidenced, the formation of the BiFeO3 perovskite phase being completed in the temperature range of 500–550°C.
Effects of three antagonistic fungi ( Paecilomyces lilacinus, Pochonia chlamydosporia , and Trichoderma harzianum ) alone and together with wastes materials (saw dust and neem leaf litter) and urea were studied on the growth of tomato and on the reproduction of Meloidogyne incognita in glass house experiments. Individually neem leaf litter was better in improving growth of plants without nematodes compared with any other single treatment. However, use of P. lilacinus against plants with M. incognita caused higher increase in plant growth than caused by P. chlamydosporia / T. harzianum or urea but similar to that caused by neem leaf litter or saw dust. Maximum increase in the growth of nematode inoculated plants was observed when P. lilacinus was used with neem leaf litter. P. lilacinus caused higher reduction in galling and nematode multiplication followed by P. chlamydosporia , neem leaf litter, urea, T. harzianum and saw dust. Maximum reduction in galling and nematode multiplication was observed when P. lilacinus was used with neem leaf litter.
Introduction Urea–formaldehyde resins are the most important type of the so-called amino plastic resins. Amino resins are often used to modify properties of other materials. These resins are added during the processing of
of cinnamic acid-urea single crystal. Experimental Synthesis The cinnamic acid–urea single crystals were prepared by digesting appropriate weighed amount of cinnamic acid in methanol of urea in
