Synthesis of 1-Tosyl-4,6-dihydrothieno[3,4-d]pyrazole 5,5-Dioxides as Precursors to Pyrazole Analogue of o-Quinodimethane

A facile synthesis of 3-substituted 1-tosyl-4,6-dihydrothieno[3,4-d]pyrazole 5,5-dioxides from readily prepared 3-(phenylthio)-4-acyl-3-sulfolenes and their use as precursors to o-dimethylene pyrazole in [4 + 2] cycloaddition are described.     

Synthesis and Characterization of Base‐catalyzed Phenyl Modified PDMS/PHMS Copolymers

A series of phenyl modified polydimethylsiloxane (PDMS) / polyhydrogenmethylsiloxane (PHMS) random copolymers containing both internal Si‐H and terminal SiH₂ and T (MeSiO_3/2) units was synthesized in one step through n‐BuLi‐catalyzed ring‐opening polymerization of cyclic comonomers and characterized by GPC, IR and ¹H and ²⁹Si NMR. Sequential microstructures of these copolymers were determined by ²⁹Si‐NMR spectroscopy. Epoxy‐modified polysiloxanes were prepared and used as comparable standards for the assignment of the NMR spectra. A hydride‐transfer mechanism has been proposed to account for the formation of terminal Si‐H and T group. Detailed sequential analyses and chemical shifts of ²⁹Si‐NMR for various siloxane units are reported for the first time.     

Determination of Ethion Residues in Soil by Extraction and by Mass Spectrometry Using Different Procedures

Optimized experimental procedures including time of extraction, extraction solvent in Soxhlet extraction technique were sought for detection of trace ethion residues in soil. The largest recoveries over 96% were achieved with a 1:1 mixture of methanol and acetone as extraction solvent for three hours. In comparing EI, CI, EI-CAD, and PCI-CAD modes of a four sector mass spectrometry for detection ethion, it was shown the best monitoring mode to be EI monitoring of the M⁺ of ethion, m/z 384, which fragments to give the m/z 231 product ion. The limit of detection obtained was 170 pg/g in soil.     

Meaningful image sharing scheme using toral automorphism

In recent years, image sharing scheme has attracted much attention for researchers due to the characteristics of security and easy implementation. In 2011, Wang and Lee proposed a random grid-based sharing scheme with identifiable shares to protect the security of the secret images. Their method has several disadvantages that must be improved. First, the constructed shares are meaningless ones which are difficult to manage. Second, the original secret image cannot be completely recovered which can cause the misjudgment of information. Wang et al. proposed a sharing method with verification ability in 2011. However, the constructed shares are also meaningless ones. This paper proposes a meaningful image sharing scheme to improve the above-mentioned disadvantages. Furthermore, we utilize toral automorphism to enhance the security of the secret image. Experimental results can show the feasibility of the proposed method.     

Spontaneous Hierarchical Assembly of Crown Ether‐like Macrocycles into Nanofibers and Microfibers Induced by Alkali‐Metal and Ammonium Salts

Schiff base macrocycle 1 , which has a crown ether like central pore, was combined with different alkali‐metal and ammonium salts in chloroform, resulting in one‐dimensional supramolecular aggregates. The ion‐induced self‐assembly was studied with solid‐state NMR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). It was found that the lengths and widths of the superstructures depend on the cation and counteranion of the salts. Among the salts being used, Na⁺ and NH₄⁺ ions with BF₄^? ions showed the most impressive fibrous structures that can grow up to 1 μm in diameter and hundreds of microns in length. In addition, the size of the fibers can be controlled by the evaporation rate of the solvent. A new macrocycle with bulky triptycenyl substituents that prevent supramolecular assembly was prepared and did not display any nanofibers with alkali‐metal ions in chloroform when studied with TEM.     

A Straightforward Synthesis of Polythiophene-fused-3-sulfolenes from Methyl 3-Hydroxy-4,6-dihydrothieno[3,4-b]thiophene-2-carboxylate

A straightforward synthesis of substituted polythiophene-fused-3-sulfolenes from the readily prepared methyl 3-hydroxy-4,6-dihydrothieno[3,4-b]thiophene-2-carboxylate will be presented. Upon thermolysis in the presence of N-phenylmaleimide, these new substrates serve as precursors of reactive polythiophene o-quinodimethanes to give the corresponding Diels-Alder adducts in high yields.     

Bidirectional iterative synthesis of alternating benzene-furan oligomers towards molecular wires

Reaction of propargylic dithioacetal 2a with BuLi gives the sulfur-substituted allenyllithium 3a which is allowed to react with a dialdehyde to yield the corresponding alternating benzene-furan oligoaryls 6. Functional group transformation converts the ester groups in 6 to dialdehyde 8 which can be used for the synthesis of higher homologues towards molecular wires. A combination of this furan annulation, Heck reaction and Sonogashira coupling leads to a variety of benzene-furan-alkene/alkyne conjugated oligomers of precise length.     

Hydrodynamics of two-phase flow in vertical up and down-flow across a horizontal tube bundle

Flow patterns, void fraction and friction pressure drop measurements were made for an adiabatic, vertical up-and-down, two-phase flow of air–water mixtures across a horizontal in-line, 5×20 tube bundle with a pitch-to-diameter ratio of 1.28. The flow patterns in the cross-flow zones were obtained and flow pattern maps were constructed. The data of average void fraction were less than the values predicted by a homogenous flow model and showed a strong mass velocity effect, but were well-correlated in terms of the Martinelli parameter X_tt and liquid-only Froude number Fr_LO. The two-phase friction multiplier data could be well-correlated with the Martinelli parameter.