Synthesis of a stable gold hydrosol by the reduction of chloroaurate ions by the amino acid, aspartic acid

Development of reliable protocols for the synthesis of nanoparticles of well-defined sizes and good monodispersity is an important aspect of nanotechnology. In this paper, we present details of the synthesis of gold nanoparticles of good monodispersity by the reduction of aqueous chloroaurate ions by the amino acid, aspartic acid. The colloidal gold solution thus formed is extremely stable in time, indicating electrostatic stabilization via nanoparticle surface-bound amino acid molecules. This observation has been used to modulate the size of the gold nanoparticles in solution by varying the molar ratio of chloroaurate ions to aspartic acid in the reaction medium. Characterization of the aspartic acid-reduced gold nanoparticles was carried out by UV-visible spectroscopy, thermogravimetric analysis and transmission electron microscopy. The use of amino acids in the synthesis and stabilization of gold nanoparticle in water has important implications in the development of new protocols for generation of bioconjugate materials.     

Induced Mesophases in Binary Systems of Non-Mesogens Where One of the Component is 1,2,4 Trisubstituted Benzene Derivatives

Abstract

Exhibition of mixed mesophases in binary systems where both the components are non-mesogens by themselves offer a very interesting study. In the present work four binary systems were studied where one of the components is non-mesogenic 1,2,4-trisubstituted benzene derivative while the other components are rod shaped non-mesogens. Induction of mesophases is observed in all the binary systems studied. Few compositions on cooling remain in liquid crystalline phase at the ambient temperatures for about 48 hours.     

New mesogens with a fluoro-substituted bent core

Ferroelectric properties in liquid crystals are no longer restricted to materials with a chiral molecular structure; ferroelectricity has been observed in a smectic phase formed by bent achiral molecules. Accordingly, two homologous series possessing a central biphenyl methane core have been synthesized, the central core having two lateral fluoro substituents. Both the series have six-ring structures and exhibit smectic mesophases of high thermal stability. The flexible biphenyl methane core imparts a slight curve to the molecules, giving them a bent shape.     

Mechanical desorption of immobilized proteins using carbon dioxide aerosols for reusable biosensors

Reusability of a biosensor has recently received considerable attention, and it is closely related with the effective desorption of probe molecules. We present a novel mechanical desorption technique to reuse biosensors by using periodic jets of carbon dioxide (CO₂) aerosols (a mixture of solid and gaseous CO₂), and demonstrate its feasibility by removing physically adsorbed and covalently bonded fluorescent proteins i.e., Escherichia coli fluorescein isothiocyanate antibody and bovine serum albumin (E. coli FITC–Ab and FITC–BSA) from silicon chips. The proteins on the chip surfaces were measured by fluorescent images before and after applying the aerosols. The removal efficiency of the aerosol treatment was measured for various concentrations (1–20 μg mL⁻¹) of E. coli FITC–Ab and FITC–BSA with two different removal cycles (5 and 11 cycles; each cycle: 8 s). We observed high removal efficiencies (>93.5% for physically adsorbed Ab and >84.6% for covalently bonded Ab) at 11 cycle aerosol treatment. This CO₂ aerosol treatment did not undermine re-functionalization, which was confirmed by the fluorescent images of FITC–Abs for fresh and reused chips. Desorption of the immobilized layers was validated by Fourier transform infrared and X-ray photoelectron spectroscopic analyses. We also conducted an experiment on the regeneration of E. coli sensing chips using this aerosol treatment, and the chips were re-used 5 times successfully. This mechanical desorption technique is a highly effective and novel strategy for reusable biosensors.     

Holographic digital data storage using phase-modulated pixels

We propose and demonstrate the use of phase images for holographic data storage. Use of phase images as input leads to uniform diffraction efficiency of multiplexed data pages. Use of binary phase-based data pages with 0 and π phase changes produces uniform spectral distribution at the Fourier plane. This in turn facilitates better recording of higher spatial frequencies. We experimentally demonstrate a phase-based holographic data storage system using shift multiplexing in a Fe:LiNbO₃ crystal, and use it for associative retrieval. Preliminary studies indicate high discrimination capabilities of phase-based holographic data storage system over the amplitude-based system in a content-addressable memory.     

Monotone iterative technique for neutral fractional differential equation with infinite delay

In this paper, we employ the method of lower and upper solutions coupled with the monotone iterative technique to obtain existence and uniqueness of extremal mild solutions to neutral fractional differential equation with infinite delay in an ordered Banach space. The results are obtained by using the theory of fractional calculus, monotone iterative technique, measure of noncompactness, and semigroup theory. Finally, we discuss an example to illustrate our results. Copyright © 2016 John Wiley & Sons, Ltd.     

On powers and centers of chordal graphs

A graph is chordal if every cycle of length strictly greater than three has a chord. A necessary and sufficient condition is given for all powers of a chordal graph to be chordal. In addition, it is shown that for connected chordal graphs the center (the set of all vertices with minimum eccentricity) always induces a connected subgraph. A relationship between the radius and diameter of chordal graphs is also established.     

Screening dependence of superconducting state parameters

Theoretical values of superconducting state parameters of a number of superconductors are presented here using linear potential with seven different forms of dielectric screening in order to exhibit the dielectric dependence of these parameters. Presently computed results on comparison with the available experimental data show that the R.P.A. screening provides the best explanation of the superconducting state in most of the metals. It has been observed that the use of a non-local pseudopotential is desirable in the case of complex metals like Al, Pb etc.