Synthesis and properties of N-carbazole end-capped conjugated molecules

A series of novel N-carbazole end-capped π-conjugated molecules were synthesized by a divergent approach with the use of bromination, Suzuki cross-coupling, and Ullmann reactions and their physical properties were investigated. In dilute solution, UV-vis absorption spectra displayed bathochromic shift with respect to their conjugated backbones, and photoluminescence spectra showed emission maxima in the blue region. Thermal analysis revealed that they are thermally stable semi-crystalline and amorphous materials. All molecules exhibited good electrochemical stability with high-lying HOMO energy levels and have potential applications as hole-transporting and light-emitting layers in organic light-emitting diodes or as host materials for electrophosphorescent applications.     

Electrospun cellulose acetate fibers: effect of solvent system on morphology and fiber diameter

This paper reports an investigation of the effects of solvent system, solution concentration, and applied electrostatic field strength (EFS) on the morphological appearance and/or size of as-spun cellulose acetate (CA) products. The single-solvent systems were acetone, chloroform, N,N -dimethylformamide (DMF), dichloromethane (DCM), methanol (MeOH), formic acid, and pyridine. The mixed-solvent systems were acetone–DMAc, chloroform–MeOH, and DCM–MeOH. Chloroform, DMF, DCM, MeOH, formic acid, and pyridine were able to dissolve CA, forming clear solutions (at 5% w/v), but electrospinning of these solutions produced mainly discrete beads. In contrast, electrospinning of the solution of CA in acetone produced short and beaded fibers. At the same solution concentration of 5% (w/v) electrospinning of the CA solutions was improved by addition of MeOH to either chloroform or DCM. For all the solvent systems investigated smooth fibers were obtained from 16% (w/v) CA solutions in 1:1, 2:1, and 3:1 (v/v) acetone–DMAc, 14–20% (w/v) CA solutions in 2:1 (v/v) acetone–DMAc, and 8–12% (w/v) CA solutions in 4:1 (v/v) DCM–MeOH. For the as-spun fibers from CA solutions in acetone–DMAc the average diameter ranged between 0.14 and 0.37 μm whereas for the fibers from solutions in DCM–MeOH it ranged between 0.48 and 1.58 μm. After submersion in distilled water for 24 h the as-spun CA fibers swelled appreciably (i.e. from 620 to 1110%) but the physical integrity of the fibrous structure remained intact.     

Isolation and characterization of thermophilic benzothiophene-degrading Mycobacterium sp.

A bacterial strain, SWU-4, capable of using benzothiophene (BT) as a sole carbon and energy source was isolated from a petroleum-contaminated site in Thailand and identified by 16S rRNA gene sequence analysis to be in the genus of Mycobacterium. The strain was Gram-positive, nonspore former, and grew at 50° C. Colonies of the strain on nutrient agar were rod-shaped, smooth with a convex surface, slightly mucoid, and yellow pigmented. The thermophilic Mycobacterium sp. strain SWU-4 rapidly degraded 2% (w/v) BT at 50°C. Interestingly, this strain was able to degrade a wide variety of organosulfur compounds including thiophene, bromo(α)thiophene, and 3-methylthiophene in liquid minimum medium at 50°C, which will be beneficial for industrial applications.     

Efficient synthesis of ningalin C

[reaction: see text] A concise and efficient synthesis of the permethyl derivative of the marine alkaloid ningalin C (2) has been accomplished. The key step involves the formation of a pyrrolinone from an aminoquinone in one pot. An efficient route for the synthesis of the key aminoquinone has also been developed.     

Larval ultrastructure of Parasarcophaga dux (Thomson) (Diptera: Sarcophagidae)

Ultrastructure of all larval instars of Parasarcophaga dux (Thomson), a common flesh fly species in Thailand, is presented using scanning electron microscopy. Special attention is given to the structure of anterior and posterior spiracles since these are important features used to differentiate between other sarcophagids. Each anterior spiracle in second and third instars has a single row of papillae varying in number from 14 to 17. The posterior spiracular discs have incomplete peritremes, with a prominent inner arc. Three long, narrow spiracular slits are oriented more or less vertically in each spiracular disc of third instar. Posterior spiracular hairs lack extensive branching and emanate approximately midway down the length of each slit. Microscopic morphology of the mouthhooks markedly differs between the first and second instars. The structure of these mouthhooks supports this fly species as being necrophagous or capable of producing myiasis.     

Prestomal teeth of some flies of medical importance

Comparison of prestomal teeth of adult Chrysomya megacephala, Chrysomya rufifacies, Chrysomya nigripes, Lucilia cuprina, Parasarcophaga dux and Musca domestica was accomplished by use of scanning electron microscopy. The prestomal teeth of C. megacephala, C. rufifacies, L. cuprina and P. dux are all similar in appearance in having various degrees of bifurcation at their tips. In contrast, the tips of the prestomal teeth in C. nigripes are very shallowly serrated, but are comparatively more deeply serrated in M. domestica. These features may help account for the roles these flies may play in matters of medical or veterinary importance, such as causing physical irritation or acting as vectors of disease agents.     

Pt(IV)-catalyzed generation and [4+2]-cycloaddition reactions of o-quinone methides

Novel intermolecular and intramolecular generations of ortho-quinone methides and their formal [4+2]-cycloaddition reactions with olefins catalyzed by PtCl₄ and AuCl₃ under mild conditions have been developed. Good to excellent yields (up to 99%) and diastereoselectivity (up to >99:1) of the chromans were obtained. PtCl₄ was found to be effective and compatible with various functional groups present in the substrates. A mechanism accounting for its catalytic cycle is proposed and discussed.