Cooperative ordering of impurity dipoles in KNbO3 single crystals

The impurity atoms forming dipoles in the structure of KNbO₃ are arranged regularly in the structure. The locations of the dipole sites were observed by etching technique, when dilute HNO₃ was used as an etchant. The dipoles along with the domain structure with which they are associated are stable with respect to temperature, and retain the same sites at Curie temperature. Thus the regular cooperative ordering observed at room temperature also exists at the Curie transition. The importance of this ordering is discussed in terms of domain formation and the basic problem of ferroelectricity in crystals.     

Development and characterization of triazine based dendrimers for delivery of antitumor agent

In the present study we developed the novel kind of triazine dendrimers by utilizing differential reactivity of the cyanuric chloride (triazine trichloride) which overcome the limitations associated with the others classes of dendrimers like toxicity, low yield, high synthesis cost etc. Triazine dendrimers were synthesized by divergent method using triazine trichloride as core and diethanolamine as branching unit to avoid the use of protecting group and functional group interconversion up to third generation. These hydroxyl terminated dendrimers were characterized by FTIR, 1HNMR, 13CNMR, ES mass spectroscopy, and by elemental analysis. The yield of pure G3 dendrimers was 63%. This novel dendrimers increases the aqueous solubility of hydrophobic drug Paclitaxel up to 0.562 mg/ml as well as showed control release behavior. Hemolytic and toxicology studies of this dendrimer in mice showed no adverse toxicity to the kidneys and the liver up to 200 mg/kg dose (i.p). Triazine being a hydrophobic compound, the core of this dendrimer is hydrophobic and supposed to easily incorporate the hydrophobic guest while presence of hydroxyl group on periphery increases its water solubility and reduces its toxicity; and thus it is useful in various fields like gene delivery, MRI contrasting agents, vaccines or as solubilization tool.     

Advanced chrome-free organic–inorganic hybrid pretreatments for aerospace aluminum alloy 2024-T3—application of novel bis-ureasil sol–gel precursors

Effective pretreatment of aluminum alloys is very critical to success of protective coating systems for aerospace applications. While chromate-based pretreatments have been very successful for corrosion protection, they have been a target for replacement due to the increasingly stricter regulatory requirements arising from toxicity and carcinogenic nature of Cr(VI) used in such pretreatments. Among many approaches to develop alternative systems, the organic–inorganic hybrid (OIH) coatings based on sol–gel technology has advanced rapidly. We have successfully developed OIH coating systems by using suitably tailored organosilane precursors and sol–gel processing conditions. A series of novel bis-ureasil precursors have been developed and employed as organic precursor of OIH systems. Statistical design of experimental methodology (DoE) has been used to study and optimize compositional and process parameters using multifactor analysis of variance (ANOVA) analysis method. The corrosion resistance study (Potentiodynamic polarization, salt-spray corrosion test) shows that by proper choice of sol–gel precursors, cross-linkers, and reaction conditions, very dense, adherent and protective hybrid coatings, comparable in performance to chromate-based ones, can be obtained for aerospace aluminum alloy 2024-T3. This paper was awarded the Southern Society A.L. Hendry Award for best student paper. The paper was presented at FutureCoat! 2008, sponsored by Federation of Societies for Coatings Technology, held October 14–16, 2008, in Chicago, IL.     

Synthesis of H2SO4 doped polyaniline film by potentiometric method

H₂SO₄ doped polyaniline films were synthesized in aqueous acidic media. The polyaniline film deposited on platinum electrode exhibits highest conductivity. The conductivity of each H₂SO₄ doped polyaniline sample was determined by the four-probe technique. The current-voltage curve exhibits that polyaniline sample has an ohmic behaviour. Experiments were conducted to establish the conductivity of the sample from room temperature to 110°C. The current was set constant. It has been observed that at lower current as well as higher current conductivity of the polyaniline sample is due to the electrons transferred to the conduction band. It is observed that the concentration ratio of 0.2:1 of aniline and H₂SO₄ for synthesis of PANI film on platinum electrode shows good conductivity.     

Removal of Orange G from aqueous solution by hematite: Isotherm and mass transfer studies

The efficiency of hematite for the removal of Orange G from aqueous solution has been studied at various concentrations as a function of time, temperatures and pH. It was found that the low initial concentration, low temperature and low pH favor the removal process. The maximum adsorption of the dye on hematite has been recorded at 25 mg/l concentration, 303 K temperature and pH 3. The negative values of change in free energy and enthalpy indicate the spontaneous and exothermic nature of the process, respectively. Fixation and immobilization of the dye molecules at the surface of hematite as a result of adsorption are responsible for the negative entropy effect. The effect of pH was described by considering coulombic attraction and aqua complex formation approaches. The applicability of various adsorption isotherms—Langmuir, Freundlich and Jossens—was tested in order to find the most suitable isotherm. The Freundlich isotherm was fitted with the data of the present study.     

Precursor Dependent Structural Phase Evolution in Hydrothermally Prepared Cu<Subscript>2</Subscript>O Octahedrons and Cu Micro-Flakes and Their Structural and Optical Properties

Cuprous oxide (Cu₂O) and metallic copper particles with different microstructures have been prepared by a single-step hydrothermal method by using copper acetate monohydrate and sodium hydroxide as precursors, d-glucose as reducing agent, and poly (vinylpyrrolidone) as stabilizing agent. It was found that the concentration of the NaOH in the reactant solution played a significant role in the structural phase formation of the product. Further, it was also optimized to get either the single phase of Cu₂O or Cu or the mixed phase of Cu₂O and Cu depending on the NaOH content in the reaction mixture. The product material was systematically investigated by x-ray diffraction (XRD), Rietveld refinement, UV–Vis, Raman spectroscopies, scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (XEDS). A thorough analysis of the XRD patterns in a standard method as well as by Rietveld refinement have shown the cubic phases for both Cu₂O and Cu. The same phases have been retained in the mixed phase sample also. Optical band gap was determined through Tauc plot to be 1.95 eV. Microstructural studies by SEM showed that the Cu particles were formed as micro flakes whereas the Cu₂O particles were formed with the well-defined octahedral morphology. The XEDS analysis confirmed the chemical composition in Cu₂O. This work reports the dependence of NaOH concentration in the reactant solution on the type of product (single phase or a mixed phases of Cu₂O and Cu) and their structural and optical properties.     

Potentiometric study of polyaniline film synthesized with various dopants and composite-dopant: A comparative study

The potentiometric study of polyaniline (PANI) film synthesized with dopants viz. polyvinyl sulfonic acid (PVS),p-toluene sulfonic acid (p TS), dodecyl benzene sulfonic acid (DBS) and composite-dopants viz. PVS-p TS and PVS-DBS, has been carried out. The synthesized PANI films were characterized by electrochemical technique, UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and conductivity measurement. It was found that the PANI doped with PVS gives good electrochemical properties, conductivity as well as surface morphology as compared to p TS and DBS, whereas in composite dopants the PANI doped with PVS-pTS gives good polymer matrix as compared to PVS-DBS.     

Experiences of designing a sophisticated network monitor

This paper describes the design of a network monitor that captures connections information in a network. The real-time performance requirement makes the design significantly more challenging than that of a simple monitor that only counts packet types. Although we developed the monitor for DECnet, most of the lessons we learned are protocol-independent and are thus applicable to designing such a monitor for a different protocol. In addition to reviewing the functionality, we report a first-cut performance evaluation of the monitor software. We also describe some of our early experiences in using the monitor and review some current applications of the monitor in the areas of network configuration planning and performance management.     

Upgradation of a spectral irradiance measurement facility at National Physical Laboratory,India

This report describes the details of a recently upgraded spectral irradiance measurement facility in optical radiation standards at National Physical Laboratory, India. This facility provides the calibration of spectral irradiance in the wavelength range 280 nm – 2500 nm. PTB, Braunschweig, Germany calibrated five numbers of 1000 W quartz halogen lamps, which are used as reference standards for spectral irradiance scale. In addition to providing the details of instruments, the procedure of calibration and evaluation of uncertainties is also described. For checking the fidelity, repeatability and reproducibility of the upgraded system, calibration of one of the PTB calibrated lamps, was done against the other four PTB calibrated lamps. These measurements not only provide confidence on the upgraded system but also verify the retention of the PTB certificate values after a lapse of two years after their calibration.