Search results for "Urea"
showing 10 items of 888 documents
Structural and Optical Study of Ga3+ Substitution in CuInS2 Nanoparticles Synthesized by a One-Pot Facile Method
2014
A one-pot method was used to synthesize CuInxGa1–xS2 nanoparticles by substituting In3+ with Ga3+. The samples with composition of gallium ranging from 0% to 100% were synthesized by solving copper chloride, indium trichloride, gallium acetylacetonate, and thiourea as precursors in 1-octadecene, oleylamine, and oleic acid as noncoordinating, coordinating, and capping agent solvents, respectively. Depending on the chemical composition and synthesis conditions, the morphology of the as-synthesized nanoparticles obtained was trigonal, semitrigonal, hexagonal, and quasi-spherical. X-ray photoelectron spectroscopy and X-ray diffraction confirmed that Ga3+ substituted In3+ without any segregation…
The Use of Atomic Force Microscopy in Determining the Stiffness and Adhesion Force of Human Dentin After Exposure to Bleaching Agents
2009
Introduction: Oxidant bleaching agents may induce several alterations on mineralized teeth tissues. Our aim is to study,at the ultrastructurallevel,mechanicalmodifications induced on dentin after exposure to different bleaching agents.Methods: Nanoindentation performed with atomic force microscopy was used to measure changes in dentin stiffness as well as the adhesion force between the tip and the tissue both in intertubular and peritubulardentin.Foreachspecimen,dentinlocalization, and bleaching agent, 100 independent nanoindentations were performed. Carbamide peroxide (30%) and hydrogenperoxide(35%) wereusedasbleaching agents. Results: A significant reduction of both stiffness and adhesion…
Structural and optical properties of Fe and Zn substituted CuInS2 nanoparticles synthesized by a one-pot facile method
2015
We substitute indium present in the CuInS2 ternary compound by iron and zinc using a facile one-pot synthesis method. The quaternary compound of CuIn1−xMxS2 (M = Fe and Zn) was synthesized by dissolving CuCl, InCl3, FeCl3, Zn(ac)2 and SC(NH2)2 as precursors in 1-octadecene, oleylamine and oleic acid as non-coordinating, coordinating and capping agent solvents, respectively. Oleic acid, oleylamine and thiourea were used respectively as a hard Lewis base, borderline Lewis base (in comparison with oleic acid) and soft Lewis base to form appropriate complexes. The complex formation, structure, and optical properties of CuIn1−xMxS2 (M = Fe and Zn) nanoparticles were studied by Fourier transform …
Amoxicillin-loaded polyethylcyanoacrylate nanoparticles: influence of PEG coating on the particle size, drug release rate and phagocytic uptake.
2001
Polyethyleneglycol (PEG)-coated polyethylcyanoacrylate (PECA) nanoparticles loaded with amoxicillin were prepared and the influence of the PEG coating on the particle size, zeta potential, drug release rate and phagocytic uptake by murine macrophages was studied. Experimental results show that this colloidal drug delivery system could be useful for intravenous or oral administration. The profile of amoxicillin release from PECA nanoparticles system was studied under various conditions similar to those of some corporeal fluids. In all these experiments, amoxicillin release in the free form was studied by HPLC analysis. Experimental results showed that at pH 7.4 drug release rises when molecu…
Experimental and theoretical investigations of lignin-urea-formaldehyde wood adhesive: Density functional theory analysis
2021
Abstract In view of its chemical structure, lignin has recently become an interesting candidate for various applications. This work serves to optimize the isolation process of lignin from sugar industry by-product (bagasse can, molasses beet) applying alkali treatment. For this purpose, the effect of alkali and sulfuric acid concentrations have been studied ranging from 10% (w/v) to 20% (w/v) and 1.5 M–3 M, respectively. Moreover, the isolated lignins were characterized by different complementary analysis such as FT-IR and TGA/DTG. The aim behind this work is to reduce formaldehyde emissions and improving mechanical as well as physical properties of wood adhesive. Lignin was added with diff…
Enhanced bistability by guest inclusion in Fe(ii) spin crossover porous coordination polymers
2012
Inclusion of thiourea guest molecules in the tridimensional spin crossover porous coordination polymers {[Fe(pyrazine)[M(CN)(4)]} (M = Pd, Pt) leads to novel clathrates exhibiting unprecedented large thermal hysteresis loops of ca. 60 K wide centered near room temperature.
Valorization of Solanum Elaeagnifolium Cavanilles Weeds as a New Lignocellulosic Source for the Formulation of Lignin-Urea-Formaldehyde Wood Adhesive
2021
Solanum Elaeagnifolium Cavanilles (SE-Cav) is an invasive plant that has been developed in Mediterranean basin countries especially in Morocco. This weeds which belongs to lignocellulosic biomass a...
Lipid Metabolism during the Sexual Maturation of the Mealworm (Tenebrio molitor): Effect of Ingested Diflubenzuron
1997
Abstract Diflubenzuron (DFB), a benzoylphenylurea derivative, when fed to adult females of Tenebrio molitor during sexual maturation (i.e., from adult ?? to day 9), was found to accumulate in the fat body and to quantitatively and qualitatively affect lipid synthesis. DFB treatment decreased the overall lipid level in the fat body and caused perturbations in both the rate of incorporation and distribution of radiolabeled oleic acid in the different classes of lipids. Compared to untreated controls, a significant increase in the level of saturated fatty acids and a significant decrease in the level of unsaturated fatty acids were observed in the fat body. In the ovaries, the fatty acid compo…
An undergraduate thesis training course for faculty reduces variability in student evaluations
2020
Abstract Background The undergraduate thesis evaluation process is one of the most prevalent weak points in universities; the literature indicates the need to orient undergraduate thesis evaluators through specific training initiatives. Objectives The aim of this study was to analyze the discrepancies between the grades awarded by undergraduate thesis supervisors and by the panel of faculty examiners, and the effect of training targeted to faculty members. Design and methods A cross-sectional study was performed during the 2015–2016 academic year in a Spanish Nursing School. Settings and participants We analyzed the mean grades from undergraduate thesis evaluation rubrics and the effects of…
Typification of the Linnaean name Centaurea seridis (Asteraceae)
2014
The genus Centaurea Linnaeus (1753: 909) (Asteraceae) comprises a large number of taxa mainly occurring in the Mediterranean region and southwest Asia (Susanna & Garcia-Jacas 2007). Centaurea seridis Linnaeus (1753: 915) is distributed from south Europe (Spain incl. Balearic Islands, Italy incl. Sicily, France, Albania and Greece) to northwest Africa (Algeria, Morocco and Tunisia). From a nomenclatural standpoint, Centaurea seridis has not been typified (Jarvis 2007: 402). This paper proposes the designation of a lectotype for this Linnaean name, based on the analysis of the protologue and original material.