Observation of two state behavior in the instability spectra of saturable nonlinear media

We investigate the modulational instability (MI) in the saturable nonlinear system (SNL). We identified the unique behavior of MI in the SNL system, which we called as the two state behavior. Unlike the case of Kerr type nonlinearity the so called critical modulational frequency does not monotonously increases, rather behaves in such way, that the increase in power increases the CMF upto the saturation power, and further increase in power decreases the CMF. This behavior is identified to be unusual in the context of MI and thus makes the study of MI interesting.     

Mixed convection in an inclined lid-driven cavity with non-uniform heating on both sidewalls

The present work reports a numerical simulation of mixed convection in an inclined square cavity. The vertical sidewalls are assumed to have a nonuniform temperature distribution. The finite volume method is used to solve dimensionless governing equations. Simulations are performed for different Richardson numbers, amplitude ratios, phase deviations, and cavity inclination angles. The results are presented graphically. The mean heat transfer significantly increases in the buoyancy-dominated mode on increasing cavity inclination angle if both walls have identical heating and cooling zones.     

Synthesis and characterization of Co(II), Ni(II), Cu(II) and Zn(II) complexes of tridentate Schiff base derived from vanillin and DL-alpha-aminobutyric acid

Co(II), Ni(II), Cu(II) and Zn(II) complexes of the Schiff base derived from vanillin and dl-alpha-aminobutyric acid were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements, powder XRD and biological activity. The analytical data show the composition of the metal complex to be [ML(H(2)O)], where L is the Schiff base ligand. The conductance data indicate that all the complexes are non-electrolytes. IR results demonstrate the tridentate binding of the Schiff base ligand involving azomethine nitrogen, phenolic oxygen and carboxylato oxygen atoms. The IR data also indicate the coordination of a water molecule with the metal ion in the complex. The electronic spectral measurements show that Co(II) and Ni(II) complexes have tetrahedral geometry, while Cu(II) complex has square planar geometry. The powder XRD studies indicate that Co(II) and Cu(II) complexes are amorphous, whereas Ni(II) and Zn(II) complexes are crystalline in nature. Magnetic measurements show that Co(II), Ni(II) and Cu(II) complexes have paramagnetic behaviour. Antibacterial results indicated that the metal complexes are more active than the ligand.     

Chemistry,Biosynthesis and Pharmacology of Sarsasapogenin: A Potential Natural Steroid Molecule for New Drug Design,Development and Therapy

Sarsasapogenin is a natural steroidal sapogenin molecule obtained mainly from Anemarrhena asphodeloides Bunge. Among the various phytosteroids present, sarsasapogenin has emerged as a promising molecule due to the fact of its diverse pharmacological activities. In this review, the chemistry, biosynthesis and pharmacological potentials of sarsasapogenin are summarised. Between 1996 and the present, the relevant literature regarding sarsasapogenin was obtained from scientific databases including PubMed, ScienceDirect, Scopus, and Google Scholar. Overall, sarsasapogenin is a potent molecule with anti-inflammatory, anticancer, antidiabetic, anti-osteoclastogenic and neuroprotective activities. It is also a potential molecule in the treatment for precocious puberty. This review also discusses the metabolism, pharmacokinetics and possible structural modifications as well as obstacles and opportunities for sarsasapogenin to become a drug molecule in the near future. More comprehensive preclinical studies, clinical trials, drug delivery, formulations of effective doses in pharmacokinetics studies, evaluation of adverse effects and potential synergistic effects with other drugs need to be thoroughly investigated to make sarsasapogenin a potential molecule for future drug development.     

Fluorescence Turn off Sensor for Brilliant Blue FCF- an Approach Based on Inner Filter Effect

A nanosensor with fluorometric readout based on L-cysteine capped cadmium sulphide quantum dots for discriminative detection and determination of Brilliant blue FCF (BB) (in 0.5 M Tris buffer solution of pH 9.5) over other synthetic food colourants is developed. Mechanism of the nanosensor is based on inner filter effect (IFE). The addition of BB into quantum dot solution might induce the quenching of fluorescence. The nanosensor described in this report reveals its simplicity and flexibility due to less laborious and more cost-effective synthesis. The developed fluorescence sensor showed excellent selectivity towards BB, and allows the detection as low as 3.50 × 10^?7 M. The developed sensor exhibited a linear concentration range of 4.00 × 10^?5 to 4.50 × 10^?6 M. More importantly, the proposed sensor exhibit sensitive responses toward BB in food samples such as sports drink and candies, demonstrating its potential in food analysis, which might be significant in food quality control in the future.     

Optical switching,photophysical, and electrochemical behaviors of pendant triazole‐linked indolylfulgimide polymer

Triazole‐linked 2‐indolylfulgimide polymer has been synthesized and its photochromic switching behavior has been characterized by NMR, IR, GPC, TGA, DSC, and UV–Vis spectroscopy. The synthesized photochromic polymer showed absorption peak maxima at 386 and 510 nm wherein the absorption at 510 nm was attributed to charge transfer from triazole ring nitrogen to carbonyl carbon of fulgimide unit. Fluorescence lifetime studies on exciting at 550 nm reveals triexponential behavior with fluorescence decay around 0.1, 1 and 4.2 ns, which correspond to open (E), closed (C) form of fulgimide and triazole ring, respectively. Whereas exciting at 470 nm evidences biexponential fit with fluorescence decay around 0.1 and 2.2 ns, which corresponds to the closed (C) form and triazole ring, respectively. Fluorescence decay of triazole ring was found to be influenced by the excitation wavelength. The cyclic voltammogram of open form of polymer depicts irreversible reductive wave at ?1.4 V. On illumination with 360‐nm light, the reduction wave of polymer was shifted toward less cathodic wave at ?0.9 V; this leads to formation of the closed form of fulgimide unit. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of some Schiff base transition metal complexes derived from vanillin and L(+)alanine

The cobalt(II), nickel(II), copper(II) and zinc(II)-vanillidene-L(+)alanine complexes were synthesized and characterized by elemental analysis, conductivity measurements, magnetic behavior, infrared, electronic spectral measurements, X-ray powder diffraction and biological studies. The conductance measurements indicate that all the complexes are non-electrolytes. The infrared spectra indicate the coordination of imino nitrogen, phenolic oxygen and carboxylato oxygen atoms. The electronic spectral measurements demonstrate that cobalt(II) and nickel(II)-vanillidene-L(+)alanine complexes are tetrahedral, while copper(II)-vanillidene-L(+)alanine complex has square planar geometry. The cobalt(II) complex is found to be ferromagnetic. The powder XRD studies confirm the crystalline nature of the complexes. The ligand and complexes were less active against PN, PA and BC, whereas copper complex shows moderate activity against AN.     

Photochromic switchable pendant indolyl fulgimide polypyrrole

The photochromic switchable 2-indolyl fulgimide functionalized pyrrole monomer is synthesized and ascertained by spectroscopic techniques. The absorption and emission band of monomer due to intramolecular charge transfer (ICT) state exhibit typical bathochromic shift from nonpolar to polar solvents. The molecular geometry and bandgap energy of monomer in open form as well as closed form are calculated by B3LYP/6-31 G (d) with Gaussian 03 program package. The functionalized pyrrole monomer is electropolymerized by cyclicvoltammetric method on an electrode. The polymer indicated a completely reversible photoswitching between two isomers of open and closed form 2-indolyl fulgimide moiety, which are stable over many cycles of operation by UV/visible light sources. The closed form of polymer exhibit fluorescence quenching attributed to the energy transfer from conductance band of polypyrrole to closed form of 2-indolyl fulgimides unit. This fluorescence quenching system controls the conductance of conducting polymer in molecular electronics and molecular switches.     

Quantification of α-Asarone in Acorus calamus by Validated HPTLC Densitometric Method

JPC – Journal of Planar Chromatography – Modern TLC -