Effect Of Urea Derivatives Research Articles

Effect of urea derivatives on the volume shrinkage during curing of cyanate ester and epoxy resins with polymeric hardener based on phenol‐amine salt

AbstractEffect of urea derivatives (UDs) on volume shrinkage during the curing of bisphenol A diglycidyl ether (BAGE)/bisphenol E cyanate ester (DCBE)/thermal latent polymeric hardener based on phenol‐amine salt (PAH) was investigated. The UDs with NH bonds and bulky substituents reduced the volume shrinkage effectively. The UDs were just dispersed in the compositions before the curing, whereas the UDs dissolved in the cured compounds by the collapse of the dense packing of UDs based on hydrogen‐bonding interaction and/or π‐stacking after the curing. Besides, the curing behavior and the structure of cured materials were examined by DSC and IR. The results revealed that the UDs hardly affected the curing of the DCBE/BAGE/PAH system.

Effects of auxin and urea derivatives on adventitious rooting in chestnut and oak microshoots

The present study investigated how auxin concentration and the method of application affected the formation of adventitious roots in microshoots of chestnut (Castanea sativa) and oak (Quercus robur). The activity of two urea derivatives (2, 3-MDPU and 3, 4-MDPU) was also evaluated. Microshoots were derived from basal sprouts of two mature chestnut trees (P1 and P2) and one adult oak genotype (Sainza). In chestnut, rooting percentage was positively affected by auxin in a dose-dependent manner, particularly in shoots treated with the hormone for 24 h. The effect of auxin on rooting also differed depending on the application method. In shoots treated for 24 h, the highest concentration of auxin produced the healthiest rooted plantlets, in terms of the root system and shoot quality. By contrast, in shoots treated by the basal quick-dip method, the shoot quality was best at the lowest auxin concentration. The effect of urea derivatives on the root system depended on the species as well as on the auxin concentration and application period. Use of the MDPUs improved the root system architecture of auxin-treated shoots by promoting lateral root development and triggering the synchronous initiation of root primordia at the base of the shoot. Shoot quality was also improved by MDPUs, which promoted resumption of growth and reduced shoot-tip necrosis.

Effect of urea derivatives on the critical micelle concentration of polyoxyethylated nonionic surfactant

The critical micelle concentrations (CMCs) of aqueous solutions of a nonionic surfactant, polyoxyl 23 lauryl ether in the presence of various concentration of urea and its derivatives were measured. The CMC of the surfactant increased in proportion to the concentration of the additives, and the CMC-raising activities increased with more and longer alkyl groups substituted in urea. The CMC shift values were successfully correlated with the cloud point shift values and the protein-denaturing activities of the additives, respectively. These results suggest that the micelle formation, clouding of the surfactant and the protein denaturation are a closely related phenomenon, and a common mechanism is operating which might be the hydrophobic interaction.

Transformations and effects of urea derivatives in soil

AbstractThe application of urea phosphate, urea nitrate and thoiurea to a silty clay soil from Nile Delta (pH 7.4, 1,9% CaCO3) inhibited soil urease activity if compared to urea. The nitrification process of ammonia formed from urea hydrolysis was retarded. The use of these urea derivatives eliminated nitrite accumulation and greatly retarded nitrate formation with increased recovery of urea‐N throughout the experimental period. Gaseous losses of urea‐N as ammonia or by denitrification were reduced. These derivatives may be much more advantageous than urea if fertilizer effeciency is to be increased.

Effect of urea derivatives and analgetics on the permeability to water and electrical properties of the urinary bladder of the toad.

Four urea derivatives and six analgetics examined here, when added to the serosal medium bathing the urinary bladder of the toad, Bufo vulgaris japo-nicus, increased the permeability to water despite the presence or the absence of vasopressin and this effect was completely inhibited by 10-55M epinephrine. Oxyphenbutazone on the serosal side inhibited the, response to cyclic 3', 5'-AMP, while in contrast phenylmethylurea, acetaminophen and aminopyrine slightly enhanced this response. Potential difference, short-circuit current and conductance across the bladder were depressed by these compounds. In brief the mode of action of these compounds seems to be similar to that of chlorpropamide, but theophylline-like action could not be excluded. A common chemical structure was also discussed.