Search

Discusses Lewis acid-catalyzed hydrostannation of acetylenes. Regio- and stereoselective trans-addition of tributyltin hydride and dibutyltin dihydride; Use of nonpolar solvents for obtaining high stereoselectivity and chemical yield; Reactions of internal acetylenes.

• The photo-sensitive micellar systems have improved biodegradability and less toxicity. • Photo-responsive systems based on mixed cationic/anionic surfactants are superior. • Mixed photo-sensitive additives have the advantages of both the constituent additives. • Photo-responsive systems are based on low concentrations of surfactants and additives. A method to construct photo-responsive wormlike micellar systems with high photo-responsive efficiency and strong photo-responsive ability and reduced impact on the environment by mixed cationic/anionic surfactants and mixed photo-sensitive additives has been proposed. For this purpose, a cleavable cationic ester-containing gemini surfactant, N , N '-bis(2-(dodecanoyloxy)ethyl)- N , N , N ', N '-tetramethyl-1,3-propane diammonium dibromide (C 12 DEG 3), and five anionic biocompatible carboxylate surfactants, have been selected. The mixed photo-sensitive additives are composed of sodium trans -ortho-methoxycinnamate (trans -NaOMCA) and sodium trans -cinnamate (trans -NaCA). The mixed cationic/anionic surfactants are superior to the single cationic surfactant C 12 DEG 3 in constructing UV light-responsive wormlike micellar systems due to their stronger self-assembly ability. The molecular structure of anionic surfactant, such as the length of hydrophobic tail, the introduction of the N-methylated amide group between the hydrophobic tail and carboxylate headgroup, and the number of hydroxyl group in bile salts, is important factor influencing the self-assembly ability of the mixed systems. For single C 12 DEG 3 or the mixed cationic/anionic surfactants, the mixed photo-sensitive additives have the advantages of both trans -NaCA and trans -NaOMCA. The fast reaction rate of the trans -to- cis photoisomerization of NaOMCA leads to the high photo-responsive efficiency of the wormlike micellar systems. The addition of t rans -NaCA promotes the growth of wormlike micelles and leads to larger difference between viscosities before and after UV irradiation, demonstrating higher photo-responsive ability. The experimental results reveal that the UV light induced trans -to- cis isomerization of NaOMCA is the main reason inducing the microstructural transition from wormlike micelles to coexistence of spherical and short rodlike micelles and thus causing reduction in shear viscosities by 3–4 orders of magnitude. [ABSTRACT FROM AUTHOR]

A quantitative multi-phase-field model for non-isothermal and polycrystalline solidification was developed and applied to dilute multicomponent alloys with hexagonal close-packed structures. The effects of Lewis coefficient and undercooling on dendrite growth were investigated systematically. Results show that large Lewis coefficients facilitate the release of the latent heat, which can accelerate the dendrite growth while suppress the dendrite tip radius. The greater the initial undercooling, the stronger the driving force for dendrite growth, the faster the growth rate of dendrites, the higher the solid fraction, and the more serious the solute microsegregation. The simulated dendrite growth dynamics are consistent with predictions from the phenomenological theory but significantly deviate from the classical JMAK theory which neglects the soft collision effect and mutual blocking among dendrites. Finally, taking the Mg-6Gd-2Zn (wt.%) alloy as an example, the simulated dendrite morphology shows good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Cold tolerance and the green period are key traits in the breeding of zoysiagrass (Zoysia Willd.). Identifica-tion of molecular markers associated with cold tolerance and the green period of zoysiagrass will contribute to efficient selection of elite cultivars. These two traits were measured in 96 zoysiagrass accessions in 2004 and 2005-2006, respectively. The mapping population was screened with 29 pairs of simple sequence repeat (SSR) primers and 54 pairs of sequence-related amplified polymorphism (SRAP) primers. A multi-loci in silico mapping approach implemented with an empirical Bayes method was applied for association mapping of cold tolerance and green period. We detected 254 SSR polymorphic loci and 338 SRAP polymorphic loci, among which three SSR loci (Xgwml31-3B-187, Xgwm469-6D-194 and Xgwm234-5B-244) and one SRAP locus (MellEm7-406) were significantly associated with cold tolerance with effect values of 57.83%, 38.05%, 36.92% and 37%, respectively. Three SSR loci (Xgwml32-6B-225, Xgwml 11-7D-34 and Xgwml02-2D-97) and two SRAP loci (Mel9Em5-359 and Mel6Em8-483) were significantly associated with the green period with effect values of 79.54%, 62.59%, 99.04%, 49.01% and 82.57%. These markers will be useful for genetic improvement of the cold tolerance and green period of zoysiagrass by marker-assisted breeding. [ABSTRACT FROM AUTHOR]