Degradation of a polyester‐urethane coating: Physical properties

In this article we studied the evolution of thermomechanical properties of a polyester‐urethane coating during degradation under different degradation conditions, i.e., aerobic and anaerobic conditions with and without dry/wet cycling during degradation. Dynamic mechanical and thermal analyses show that under aerobic conditions the coatings become stiffer and more brittle in the glassy state. This stiffening is probably due to the increase in the amount of hydrogen bonding and the formation of oxidized groups which increase the polarity of the material and enhance the interactions of the polymer segments. However, oxidation reactions result in a considerable decrease in cross‐link density and stiffness in the rubbery state. Both changes, in the glassy and rubbery states, give rise to development of internal stresses. These stresses increase as the degradation process proceeds. Nevertheless, for samples exposed to anaerobic conditions, the stiffness remains constant in the glassy state and the cross‐link density slightly increases as a result of degradation. This reconfirms the dominance of the effect of oxidation reactions on the mechanical failure of the coatings. Oxygen permeation measurements show a more‐or‐less time‐independent diffusion coefficient and a gradual decrease in solubility of oxygen as a function of exposure time. This results in a slight decrease in oxygen permeation (mainly in the early stage of the degradation) as degradation proceeds. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 659–671     

Genetic diversity and haplotype structure of 21 Y‐STRs,including nine noncore loci,in South Tunisian Population: Forensic relevance

Y chromosome STRs (Y‐STRs) are being used frequently in forensic laboratories. Previous studies of Y‐STR polymorphisms in different groups of the Tunisian population identified low levels of diversity and discrimination capacity (DC) using various commercial marker sets. This definitely limits the use of such systems for Y‐STRs genotyping in Tunisia. In our investigation on South Tunisia, 200 unrelated males were typed for the 12 conventional Y‐STRs included in the PowerPlex® Y System. Additional set of nine noncore Y‐STRs including DYS446, DYS456, DYS458, DYS388, DYS444, DYS445, DYS449, DYS710, and DYS464 markers were genotyped and evaluated for their potential in improving DC. Allele frequency, gene diversity, haplotype diversity (HD), and DC calculation revealed that DYS464 was the most diverse marker followed by DYS710 and DYS449 markers. The standard panel of 12 Y‐STRs (DC = 80.5%) and the nine markers were combined to obtain DC of 99%. Among the 198 different haplotypes observed, 196 haplotypes were unique (HD = 99.999). Out of the nine noncore set, six Y‐STRs (DYS458, DYS456, DYS449, DYS710, DYS444, and DYS464) had the greatest impact on enhancing DC. Our data provided putative Y‐STRs combination to be used for genetic and forensic applications.     

On the viscous Allen-Cahn and Cahn-Hilliard systems with willmore regularization

We consider the viscous Allen-Cahn and Cahn-Hilliard models with an additional term called the nonlinear Willmore regularization. First, we are interested in the well-posedness of these two models. Furthermore, we prove that both models possess a global attractor. In addition, as far as the viscous Allen-Cahn equation is concerned, we construct a robust family of exponential attractors, i.e. attractors which are continuous with respect to the perturbation parameter. Finally, we give some numerical simulations which show the effects of the viscosity term on the anisotropic and isotropic Cahn-Hilliard equation.     

Synthesis and Biological Evaluation of New Fused Thiazolo[4,5-d] Pyridazine Derivatives

The synthesis of thiazolo[4,5-d]pyridazines and the unknown ring systems, thiazolo[4,5-d]-1,2,4-triazolo- and tetrazolo[4,3-b]pyridazines as well as thiazolo(4,5-d]pyridazino[2,3-c]2H triazines, has been achieved according to different pathways. Biological testing of the new tricyclic heterocycles revealed that some of these compounds possess remarkable antibacterial activity.     

Modification and validation of the mixed-format Engineering Concept Assessment for middle school students using many-facet Rasch measurement

Integrating engineering into the K-12 science curriculum continues to be a focus in national reform efforts in science education. Although there is an increasing interest in research in and practice of integrating engineering in K-12 science education, to date only a few studies have focused on the development of an assessment tool to measure students’ understanding of engineering design. Most of the existing measures focus only on knowledge and understanding of engineering design concepts using multiple-choice items with the exception of the mixed-format Engineering Concept Assessment (ECA). Also, advanced measurement models are lacking application in the testing of such mixed-format assessments in science education. This study applied many-faceted Rasch measurement to the modified ECA for eighth-grade (ECA/M8) and a newly constructed rubric applied by five judges across 497 eighth-grade students’ responses after experiencing an integrated learning unit on the engineering design process. The results supported the fit of the items and rubric rating scales to the Rasch specifications. Recommendations are made for item wording, and further reliability and validity testing of the ECA/M8, and use of the ECA/M8 in science education and research.     

Synthesis,Voltammetric and Analytical Applications of Some Fluorine Substituted Spirosteroidalthiazolidin‐4‐one Derivatives of Sulfa Drugs

A new 5‐arylidene‐4‐oxo‐(sulfonamoyl phenyl)‐spiro[thiazolidinone‐2,2′‐steroids] series (7–10) was prepared by condensation of sulfanilamide, sulfapyridine and sulfadiazine sulfa drugs with testosterone, epiandrosterone and progesterone steroids, respectively. The resultant imino derivatives 1–3 upon cycloaddition with thioacetic acid in dry 1,4‐dioxane afforded 3‐sulfo‐namoylphenylspiro[4‐oxo‐thiazolidin‐2,2′steroids] (4–6). The latter compounds (4–6) upon condensation with p‐fluorobenzaldehyde in ethanol‐piperidine yielded the corresponding 4‐fluoroarylidene derivatives 7, 8 & 9, respectively. All the newly synthesized compounds were confirmed by UV, IR, ¹H NMR, ¹³C NMR, mass spectral data, elemental analysis and molecular weight determination. In vitro antimicrobial screening of some of the synthesized compounds showed good antimicrobial activities towards some pathogenic Gram‐positive, Gram‐negative bacteria and fungi vs. piperacillin and mycostatine antibiotics as standard antibacterial and antifungal agents, respectively. The voltammetric behavior of two newly spirothiazolidinone steroids ( 2a & 5a ) was critically studied. Compound 5a physically immobilized polyurethane foam solid sorbent was successfully used for removal and/or separation of bismuth(III) from water.     

1,2,4‐Triazine Chemistry Part IV: Synthesis and Chemical Behavior of 3‐Functionalized 5,6‐Diphenyl‐1,2,4‐triazines towards Some Nucleophilic and Electrophilic Reagents

The synthesis and chemical behavior of 3‐functionalized 5,6‐diphenyl‐1,2,4‐triazines towards some electrophilic and nucleophilic reagents are reviewed. The synthesis, unique features, and medicinal, pharmacological, and biological significance of these constituents are also reported.     

Kinetics of hydrolysis and self condensation reactions of silanes by NMR spectroscopy

The hydrolysis of four alkoxy-silane coupling agents, 3-methacryloxypropyl trimethoxy silane (MPMS), 3-mercaptopropyl trimethoxy silane (MRPMS), octyl triethoxy silane (OES) and 3-aminopropyl triethoxy silane (APES) was carried out in an ethanol/water 80/20 (w/w) solution under acidic, alkaline and neutral conditions and followed by ¹H, ¹³C and ²⁹Si NMR spectroscopy. It was found that the kinetic rate of the hydrolysis of the silanes under neutral conditions was very low, except for APES, which displayed the fastest reaction speed. The addition of TEA catalyzed both silane hydrolysis and self condensation reactions. Acidic conditions enhanced the hydrolysis and the ensuing silanol entities were quite stable. In fact, these conditions slowed down the rate of the self condensation reactions, as deduced from in situ ¹H and ¹³C NMR. Thanks to in situ ²⁹Si NMR spectroscopy, the nature of the intermediary species versus reaction time was established.     

Pyrazole Derivatives Part III Synthesis of Novel Naphtho[1,2-c]pyrazolebenzenesulfonylureas,Thioureas and Their Cycllzed Derivatives

Substituted p-(naphtho[1,2-c]pyrazol-2-yl)benzenesulfonylurea and thiourea derivatives 5–7 were prepared in three series. Cyclization of the thioureido group of compounds 7 by treating with ethyl bromoacetate, ethyl β-bromopropionate and α-bromoacetophenone afforded the corresponding thiazolidinone, thiazinone and thiazoline derivatives 8 , 9 and 10 respectively.     

Synthesis of Novel Cyclic Benzenesulfonylurea and Thiourea Derivatives

Treatment of the pyrazoline derivatives (1-6) with isocyanates or isothiocyanates afforded ureas (7-18) and thioureas (19-32) in a good yield. Subsequent treatment of the benzenesulfonylthioureas (19-32) with f - and g -halogenocarbonyl compounds gave the corresponding thiazolidines (33-41) and 1,3-thiazinones (42-46) respectively. When urea derivatives (7-18) were reacted with dimethyl malonate in sodium ethoxide, they gave the corresponding pyrazolebarbiturate derivatives (53-56) . The structure of the isolated product were determined by the spectral methods.