Kinetics of reaction of C21 cycloaliphatic dicarboxylic acid and ethylenediamine

Kinetic studies were carried out on the reaction between ethylenediamine and C₂₁ cycloaliphatic dicarboxylic acid, prepared from dehydrated castor oil fatty acids and acrylic acid, in melt phase. The reaction was performed at six different temperatures ranging from 210 to 260°C and followed by determining the acid value of the product. The polyamidation reaction was found to follow an overall third order kinetics with an activation energy of 15.5 kcal/g mol.     

Quasi-linear assemblies of silver nanoparticles by highly localized anodic dissolution of copper in the hydrosol

The assembly of silver nanoparticles into quasi-linear superstructures in solution has been demonstrated. A small dc voltage applied to fine-tipped, L-shaped copper electrodes immersed in aqueous carboxylic acid-derivatized silver nanoparticle solution leads to the anodic dissolution of copper ions. The controlled release of Cu2+ ions within the gaps results in local screening of repulsive coulombic interactions between the silver nanoparticles and the consequent formation of aggregates that are extremely stable in time. Atomic force and transmission electron microscopy images of the silver nanoparticle solution after application of an electric field showed the presence of a large number of silver nanoparticle assemblies in open, quasi-linear structures. Such open structures do not form if Cu2+ ions are added directly to the silver nanoparticle solution.     

Nimesulide-modified gum karaya solid mixtures: preparation, characterization, and formulation development

Solid mixtures of nimesulide (NS) and modified gum karaya (MGK) were prepared to improve the dissolution rate of NS. The effect of drug-carrier ratio on dissolution rate of NS was investigated by preparing the solid mixtures of different ratios by cogrinding method. Solid mixtures were also prepared by physical mixing, kneading, and solid dispersion techniques to study the influence of method of preparation. Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and equilibrium solubility studies were performed to explain the results of in vitro dissolution rate studies. It was clearly evident from the results that the NS dissolution rate was dependent on the concentration of MGK in the solid mixtures, and optimum weight ratio was found to be 1:4 (NS:MGK). Though the dissolution rate of NS from all solid mixtures prepared by different methods improved significantly, maximum improvement in dissolution rate was observed with solid dispersions. The order of methods basing on their effect on dissolution efficiency is solid dispersion > kneading > cogrinding > physical mixing > pure NS. Tablets of pure drug and solid mixtures (1:4 w/w, NS:MGK) were prepared. Though the best results from the dissolution test were obtained for the tablets containing solid dispersions, tablets containing cogrinding mixture were found to be suitable, from a practical point of view, for commercialization.     

Preparation of GaAs films by the pulse plating technique

Electrodeposition of GaAs thin films by the pulse plating technique is reported for the first time. The films have been characterized by X-ray diffraction studies and the bandgap has been found to be 1.43 eV by the optical method.     

Structure of vacuum deposited SnSe films

Tin selenide (SnSe) thin films prepared on mica and glass substrates by vacuum sublimation technique and examined by scanning electron microscopy and transmission electron diffraction techniques showed epitaxial and polycrystalline nature respectively irrespective of substrate temperature. Grain size of the films deposited on glass substrate increased with increase in substrate temperature.     

Accurate recovery of three-dimensional shape from image focus

A new shape-from-focus method is described which is based on a new concept, named focused image surface (FIS). FIS of an object is defined as the surface formed by the set of points at which the object points are focused by a camera lens. According to paraxial-geometric optics, there is a one-to-one correspondence between the shape of an object and the shape of its FIS. Therefore, the problem of shape recovery can be posed as the problem of determining the shape of the FIS. From the shape of FIS the shape of the object is easily obtained. In this paper the shape of the FIS is determined by searching for a shape which maximizes a focus measure. In contrast to previous literature where the focus measure is computed over the planar image detector of the camera, here the focus measure is computed over the FIS. This results in more accurate shape recovery than the traditional methods. Also, using FIS, a more accurate focused image can be reconstructed from a sequence of images than is possible with traditional methods. The new method has been implemented on an actual camera system, and the results of shape recovery and focused image reconstruction are presented     

Interpretation of image flow: Rigid curved surfaces in motion

A new method is described for interpreting image flow (or optical flow) in a small field of view produced by a rigidly moving curved surface. The equations relating the shape and motion of the surface to the image flow are formulated. These equations are solved to obtainexplicit analytic expressions for the motion, orientation, and curvatures of the surface in terms of the spatial derivatives (up to second order) of the image flow. We state and prove somenew theoretical results concerning the existence of multiple interpretations. Numerical examples are given for some interesting cases where multiple solutions exist. The solution method described here is simpler and more direct than previous methods. The method and the representation described here are part of a unified approach for the interpretation of image motion in a variety of cases (e.g., planar/curved surfaces, constant/accelerated motion, etc.). Thus the representation and the method of analysis adopted here have some advantages in comparison with previous approaches.