Spin trapping chemistry of sodium 2-sulfonatophenyl t-butyl nitrone . a negatively charged water-soluble spin trap

A new water-soluble negatively charged spin trap, sodium 2-sulfonatophenyl $\text{t}$-butyl nitrone is described.     

Synthesis of 2-Azobenzo[b]thiophene Derivatives and Their Application on Nylon Fibre

A series of novel monoazo disperse dyes derived from the coupling of diazotized 2-aminobenzo[b]thiophene derivatives with N-arylmaleimides is described. The monoazo disperse dyes applied to nylon fabric and their dyeing performance has been assessed. These dyes have been found to give light yellow to reddish pink color shades with very good depth and levelness on nylon fabric. The dyed fabric shows moderate light fastness and excellent washing, rubbing, perspiration, and sublimation fastness. The percentage dyebath exhaustion on nylon fabric has been found to be good and acceptable.     

Disperse dyes based on 2-aminothiazole derivatives for cellulose triacetate fabric

A range of azo disperse dyes was prepared by coupling diazotized 2-amino-4-(p-nitrophenyl)-5-nitrothiazole with various substituted arylamines. Spectral properties in the infrared and visible range of the dyes obtained were investigated. All the dyes, when applied on cellulose triacetate fabric as 2% shade, showed fairly good to very good light fastness and very good to excellent fastness to washing, perspiration, rubbing and sublimation. All the dyes gave a wide range of reddish brown to indigo shades with very good depth and levelness on fabric. The purity of dyes was checked by thin layer chromatography. The percentage dyebath exhaustion and fixation on fabric was reasonably good and acceptable.     

Single injection current in insulator with traps lying below the Fermi level

Analytical expressions for the current-voltage characteristics have been given for the insulator containing significant amount of traps lying below the Fermi level. The mobility of the current carriers is varying with concentration in the insulator. It is shown that the complete current-voltage characteristic can be divided into four regimes which are having power laws for the characteristic from linear law in pure Ohm's law regime to cube law in space-charge-limited trap-free regime. There is a very large change in current occurring over a restricted change in voltage.     

Geometrical confinement effects on the magnetization and polarization response in resonant magneto-optic rotator waveguides

Control of magnetization is central to the performance of magneto-optical switches and isolators. Photonic crystal technology on these devices can yield significant improvements in polarization rotation efficiency and an overall reduction in device dimensions. The optical response and field reversal characteristics of resonant magneto-optic polarization rotators fabricated on chip are presented herein and analyzed by micromagnetic simulation. By introducing domain-strip structures into the resonant cavity of Bragg gratings formed on magnetic garnet films, a bi-stable magnetic state is demonstrated and the enhancement of characteristic saturation field is studied. Domain closure loops between the strips affect the hysteresis response in the resonant cavity. Large magneto-optic rotations exceeding 45° are produced near resonance between 1500 and 1580 nm in the stop-bands, although the presence of linear birefringence in these gyrotropic waveguides strongly suppresses the Faraday rotation outside the stop-bands and degrades the linearity of the output polarization.     

Synthesis and Application of Disperse Dyes Based on 2-Aminothiazole Derivatives

A series of novel monoazo disperse dyes based on 2-amino-5-nitro-4-(p-nitrophenyl)thiazole were prepared using various N,N-dialkylaniline derivatives as the coupling components. The spectral properties in the IR and visible range of the dyes were investigated. The dyeing performance of these dyes was assessed on nylon fabric. These dyes were found to give a wide range of color shades from reddish brown to indigo with excellent brightness, levelness, and depth on nylon fabric. The dyed fabric showed fairly good light fastness, good to excellent fastness to wash and perspiration, and excellent fastness to sublimation. The dyebath exhaustion and fixation of the dyes on nylon were found to be very good and acceptable.     

Tunable photonic crystals based on ferroelectric and ferromagnetic materials by focused ion beam

By making photonic crystals in ferroelectric and ferromagnetic materials, field-provoked tunability of photonic crystals is broadening the interest in new applications of on-chip photonic devices. We report a nano-precise fabrication of various designs of photonic crystals in these non-conventional materials using the focused ion beam milling technique. Standard methods are developed and parameters for different materials are calibrated. Optical responses such as bandgaps and polarization status changing from planar film waveguide system with these patterns have been examined on ferromagnetic materials.     

13C-1H HSQC experiment of probe molecules aligned in thermotropic liquid crystals: sensitivity and resolution enhancement in the indirect dimension

The spectra of molecules oriented in liquid crystalline media are dominated by partially averaged dipolar couplings. In the 13C-1H HSQC, due to the inefficient hetero-nuclear dipolar decoupling in the indirect dimension, normally carried out by using a pi pulse, there is a considerable loss of resolution. Furthermore, in such strongly orienting media the 1H-1H and 13C-1H dipolar couplings leads to fast dephasing of transverse magnetization causing inefficient polarization transfer and hence the loss of sensitivity in the indirect dimension. In this study we have carried out 13C-1H HSQC experiment with efficient polarization transfer from 1H to 13C for molecules aligned in liquid crystalline media. The homonuclear dipolar decoupling using FFLG during the INEPT transfer delays and also during evolution period combined with the pi pulse heteronuclear decoupling in the t1 period has been applied. The studies showed a significant reduction in partially averaged dipolar couplings and thereby enhancement in the resolution and sensitivity in the indirect dimension. This has been demonstrated on pyridazine and pyrimidine oriented in the liquid crystal. The two closely resonating carbons in pyrimidine are better resolved in the present study compared to the earlier work [H.S. Vinay Deepak, Anu Joy, N. Suryaprakash, Determination of natural abundance 15N-1H and 13C-1H dipolar couplings of molecules in a strongly orienting media using two-dimensional inverse experiments, Magn. Reson. Chem. 44 (2006) 553-565].     

Steroid and antibacterial steroidal glycosides from marine green alga Codium iyengarii Borgesen

The ethyl acetate soluble part of methanolic extract of marine green alga Codium iyengarii collected from Karachi coast of Arabian Sea afforded a new steroid ([structure: see text], iyengadione) and two new steroidal glycosides [iyengaroside-A ([structure: see text]) and B ([structure: see text])] along with clerosterol galactoside ([structure: see text]). Their structures were elucidated with the aid of 1D-NMR spectroscopy and reconfirmed through HMBC experiments. The bactericidal activity of [structure: see text] was also explored and found positive response from iyengaroside-A ([structure: see text]) and clerosterol galactoside ([structure: see text]).     

A Model for the Construction of the Fusidic Acid Sidechain

The discovery of the antibiotic fusidic acid from Fusidium coccineum in 1962¹ provided a valuable new medicinal agent, highly active against staphylococcal infections. Though various modifications of the tetracyclic structure (I) have so far failed to furnish derivatives with enhanced antibiotic activity², no analogs of different skeletal configuration have yet been prepared for assessing the significance of the unique stereochemistry of the fusidane framework. For this purpose it would be desirable to have an effective method of attaching the fusidic acid sidechain to the 17-keto group of various steroids or to other ketones.