Thermal stress fracture mode of CO2 laser cutting of aluminum nitride

A thermal stress fracture mode of material removal by laser cutting was conducted in 1-mm thick wafers of aluminum nitride (AlN) using a continuous wave CO₂ laser with a defocused beam. In this mode, a thin layer (10–20 μm) of AlN surface was melted in an oxygen environment to form aluminum oxide. Solidification of the melt layer coupled with thermal expansion mismatch generated thermal stresses that in turn created a crack along the middle path of the laser beam, resulting in material separation. Thermochemical modeling of laser heating, oxide forming, and subsequent cooling of AlN was performed to validate the formation of cracks as well as material separation through unstable crack propagation. A comparison with the conventional “evaporation/melt and blow” laser cutting method showed that the thermal stress method offers significant benefits such as improved precision, better cut quality, higher cutting speed, and lower energy losses.     

Effect of silver nanoelectrode ensembles on the electrocatalytic reduction of NO2 by zinc phthalocyanine

Ag nanoparticles anchored on mesoporous silica materials with and without zinc phthalocyanine (ZnPc) were prepared (Ag-MPS and Ag-MPS-ZnPc respectively). The morphology, structure and composition of the materials were characterized by transmission electron microscopy, X-ray diffraction, UV/vis diffuse reflectance spectra, and X-ray photoelectron spectroscopy techniques. The new materials were used for electrode modification and the nanoelectrode ensemble (NEE) behavior of Ag-MPS and Ag-MPS-ZnPc materials was semi-quantitatively evaluated by cyclic voltammetry. Further, electrocatalytic reduction of nitrite is demonstrated at these NEE.     

Span-60-based organogels as probable matrices for transdermal/topical delivery systems

The current study describes the preparation and characterization of thermoreversible span-60 and sunflower oil (SO)-based organogels as a matrix for drug delivery. Effect of gelator concentration on the properties of the organogels was studied by physical property evaluation, stability, light microscopy, FTIR spectroscopy, XRD, thermal analysis, pH, and hemocompatibility studies. The drug release kinetics and antimicrobial efficacy of the salicylic acid loaded organogels were studied. The rate of gelation of the gels was found to be quicker in organogels with higher gelator proportions. The gels were inherently stable when stored below 25°C. The micrographs indicated the presence of needle-shaped crystals which formed aggregates resulting in the formation of three-dimensional networked structures. FTIR indicated intermolecular hydrogen bonding amongst SO and span-60 molecules responsible for the gelation. There was an increase in the crystallinity and the melting point of the organogels as the proportion of the organogelator was increased. The pH of the organogels indicated nonirritant nature of the gels, which were also found to be hemocompatible. The release of SA from organogels followed Higuchian kinetics and showed prolonged antimicrobial activity. The preliminary results indicated that the organogels may be tried as a matrix for controlled drug delivery. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Recent advancements in visible-light-assisted photocatalytic removal of aqueous pharmaceutical pollutants

Clean Technologies and Environmental Policy - Pharmaceuticals are one of the persistent emerging contaminants that are ubiquitous in the aquatic environment due to their extensive application as...     

Effect of chemical modification of a natural polysaccharide on its inhibitory action on mild steel in 15% HCl solution

Many of the synthetic corrosion inhibitors being used currently, are toxic and therefore research for developing environmentally benign corrosion inhibitors is of great importance. Inhibitors such as natural polysaccharides of plant origin are popular due to its non-toxic nature. Here, the toxicity of a natural polysaccharide, guar gum, and its modified form, cationic guar gum was studied and their inhibitory effects were investigated by gravimetric, electrochemical and surface morphology studies. Both the inhibitors are found to be effective and their adsorption on metal is in accordance with the Langmuir adsorption isotherm. Experimental results are in consonance with the results of quantum chemical calculations by density functional theory.     

Synthesis and characterization of indium phosphide films prepared by co-evaporation technique

Polycrystalline indium phosphide films were successfully deposited on glass and Si substrates by co-evaporating indium and phosphorus from appropriate crucibles. Microstructural studies indicated the average crystallite size to be ∼78 nm. X-ray diffraction pattern indicated reflections from (111), (220) and (311) planes only. The surface roughness of the films was estimated to be 30 nm and the band gap as determined from the transmittance versus wavelength traces was found to be ∼1.42 eV. The PL spectrum measured at 300 K was dominated by a strong peak located ∼1.41 eV. The intensity of this peak increased significantly when recorded at lower (10 K) temperatures and shifted towards higher energy (∼1.54 eV). XPS studies indicated two peaks ∼444.5 eV and ∼451.9 eV, corresponding to peaks of 3d_5/2 and 3d_3/2 of In 3d core while the P 2p peak at ∼128.8 eV was assigned to only P in InP. Characteristics Raman peaks for InP at ∼303 cm⁻¹ (TO) and ∼342 cm⁻¹ (LO) were observed.     

Use of Portable Automated Ball Indentation System to Evaluate Mechanical Properties of Steel Pipes

In this study, portable automated ball indentation technique (PABI) has been applied to evaluate the few mechanical properties of steel pipes and excellent correlation has been obtained with conventional test results. A PABI system, developed and fabricated at National Metallurgical laboratory, India, was used to evaluate the mechanical properties. The operational parameters were optimized for various materials to measure yield strength, ultimate tensile strength, true-stress versus true-plastic-strain curve, strength coefficient (K), strain-hardening-exponent (n), hardness (BHN) and fracture toughness (K_JC). This unit can be mounted on components with curved or flat surfaces and properties of the material could be evaluated by making a very small indentation. Also it has provision to use small test specimens. Automation of the test, where a computer and test controller were used in innovative ways to control the test as well as to analyze test data made it simple, accurate, economical and highly reproducible. A LabVIEW BASED S/W was made to control the unit.     

A simplified watermarking algorithm based on lifting wavelet transform

Multimedia Tools and Applications - This paper presents a new blind image watermarking scheme using binary decimal sequence (d-sequence) and lifting wavelet transform (LWT) for copyright...     

Finding fluorescence polarization anisotropy from digital microimages of cells

Methods are developed to record and process microimages which are suitable to obtain quantitative information about the fluorescence polarization anisotropy caused by resonance energy transport between green fluorescent protein (GFP)-labeled proteins in a living cell. The methods allow for accurate detection of dimers and higher order associates for GFP-labeled proteins. Protein-protein interaction between subunits of the trimeric GFP protein was recorded. The sources of hardware inaccuracies were found and ways to eliminate them were proposed, which reduced the coefficients of data variation by an order of magnitude in comparison with the previously obtained values..