Montmorillonite K-10 clay catalyzed solvent-free synthesis of bis-indolylindane-1,3-dione, 2-(1′,3′-dihydro-1H-[2,3′]biindolyl-2′-ylidene)-indan-1,3-dione and bisindolylindeno[1,2-b]quinoxaline under microwave irradiation

An environmentally benign protocol has been described for the synthesis of novel 2-(1′,3′-dihydro-1H-[2,3′]biindolyl-2′-ylidene)-indan-1,3-diones/bis-indolylindane-1,3-diones from ninhydrin and 3-substituted/unsubstituted indoles. It uses montmorillonite K-10 as catalyst in a solvent-free condition under microwave irradiation. The method was also used for the synthesis of novel bisindolylindeno[1,2-b]quinoxaline derivatives.     

Simultaneous occurrence of energy transfer and photoinduced electron transfer in interactions of hen egg white lysozyme with 4-nitroquinoline-1-oxide

The carcinogenic drug 4-nitroquinoline-1-oxide (4NQO) has been found to bind with the protein hen egg white lysozyme as evident from fluorescence quenching experiments. The binding constant and stoichiometry have been determined. The values of the thermodynamic parameters indicate that the interaction is an enthalpy-driven spontaneous phenomenon. The experimental value of change in free energy is similar to that obtained from the docking study. The far UV circular dichroism spectra show some changes in the secondary structure of protein. The high value of bimolecular quenching constant leads to the possibility of Förster resonance energy transfer (FRET). Along with FRET, the photoinduced electron transfer (PET) from tryptophan residue of protein to 4NQO has also been evident from the transient absorption spectra obtained in laser flash photolysis experiments. The simultaneous occurrence of FRET and PET is the key factor for quenching of intrinsic fluorescence of the protein as it binds with the drug.     

An improved algorithm for detecting point of impact in anisotropic inhomogeneous plates

Conventional triangulation techniques fail to correctly predict the acoustic source location in anisotropic plates due to the direction dependent nature of the elastic wave speeds. To overcome this problem, Kundu et al. [1] proposed an alternative method for acoustic source prediction based on optimizing an objective function. They defined an objective function that uses the time of flight information of the acoustic waves to the passive transducers attached to the plate and the wave propagation direction (θ) from the source point to the receiving sensors. Some weaknesses of the original algorithm proposed in Ref. [1] were later overcome by developing a modified objective function [2]. A new objective function is introduced here to further simplify the optimization procedure and improve the computational efficiency. A new algorithm for source location is also introduced here to increase the source location accuracy. The performance of the objective function and source location algorithm were experimentally verified on a homogeneous anisotropic plate and a non-homogeneous anisotropic plate with a doubler patch. Results from these experiments indicate that the new objective function and source location algorithm have improved performance when compared with those discussed in Refs. [1] and [2].     

Phase separation transition in a driven diffusive system with anti-ferromagnetic interaction

One-dimensional non-equilibrium systems with short-range interaction can undergo phase transitions from homogeneous states to phase separated states as interaction (?) among particles is increased. One of the model systems where such a transition has been observed is the extended Katz-Lebowitz-Spohn (KLS) model with ferromagnetically interacting particles at ?=4/5. Here, the system remains homogeneous for small interaction strength (?<4/5), and for anti-ferromagnetic interactions (?<0). We show that the phase separation transitions can also occur in anti-ferromagnetic systems if interaction among particles depends explicitly on the size of the block (n) they belong to. We study this transition in detail for a specific case ?=δ/n, where phase separation occurs for δ<−1.     

The role of ion-pairing in peak deformations in overloaded reversed-phase chromatography of peptides

The paper reports a study on the role of ion-pairing behind peak deformations, e.g. peak splitting and even peak disappearance, during the elution of a peptide at highly overloaded conditions in reversed-phase chromatography. Deformation of component peaks is not uncommon in chromatography. There are reports which discuss their occurrence, but mostly at analytical scale, while their occurrence is quite common also in the preparative scale, as in the case discussed in this work. This paper first describes the conditions leading to peak splitting and peak disappearance of an industrial peptide, then explains the plausible reasons behind such behaviour, and finally with experimental analysis demonstrates the role of ion-pairing in causing such behaviour.     

Attenuation and modal dispersion models for spatially multiplexed co-propagating helical optical channels in step index fibers

Spatial reuse of optical frequencies has been shown to be possible through a novel spatial domain multiplexing (SDM) technique that uses spatial multiplexer at the input end to launch multiple channels of the same wavelength inside a single strand of carrier fiber and then employs spatial filtering methods to de-multiplex the different optical channels at the output end. The individual SDM channels are confined to dedicated spatial locations inside the fiber while traversing through it owing to helical propagation of light. This presents attenuation and dispersion models of such a system. Experimentally obtained beam profile and resultant crosstalk of two such spatially multiplexed co-propagating SDM channels of the same wavelength over standard step index multimode optical fibers are also presented.     

Electro-osmotic flow of a viscoelastic fluid in a channel : Applications to physiological fluid mechanics

The paper presents a comprehensive theoretical study on the electro-osmotic flow of a viscoelastic fluid past a channel having stretching walls. An attempt has been made to investigate the effect of rheological and electro-osmotic parameters on the kinematics of the fluid. Results presented here pertain to the case where the channel height is much greater than the thickness of electrical double layer comprising the Stern and diffuse layers. The study reveals that an increase in electro-osmotic parameter leads to an increase in the axial velocity throughout the channel for a fluid having viscoelastic coefficient equal to that of blood. This aspect provides a source of novel insight into the process of designing bio-sensing and micro-fluidic devices.