Vacuum-ultraviolet photochemically initiated modification of polystyrene surfaces: morphological changes and mechanistic investigations

Vacuum-ultraviolet (VUV) irradiation (kexc: 172 ± 12 nm) of polystyrene films in the presence of oxygen produced not only oxidatively functionalized surfaces, but generated also morphological changes. Whereas OH- and C=O-functionalized surfaces might be used for e.g. secondary functionalization, enhanced aggregation or printing, processes leading to morphological changes open new possibilities of microstructurization. Series of experiments made under different experimental conditions brought evidence of two different reaction pathways: introduction of OH- and C=O-groups at the polystyrene pathways is mainly due to the reaction of reactive oxygen species (hydroxyl radicals, atomic oxygen, ozone) produced in the gas phase between the VUV-radiation source and the substrate. However, oxidative fragmentation leading to morphological changes, oxidation products of low molecular weight and eventually to mineralization of the organic substrate is initiated by electronic excitation of the polymer leading to C–C-bond homolysis and to a complex oxidation manifold after trapping of the C-centred radicals by molecular oxygen. The pathways of oxidative functionalization or fragmentation could be differentiated by FTIR-ATR analysis of irradiated polystyrene surfaces before and after washing with acetonitrile and microscopic fluorescence analysis of the surfaces secondarily functionalized with the N,N,N-tridodecyl-triaza-triangulenium (TATA) cation. Ozonization of the polystyrene leads to oxidative functionalization of the polymer surface but cannot initiate the fragmentation of the polymer backbone. Oxidative fragmentation is initiated by electronic excitation of the polymer (contact-mode AFM analysis), and evidence of the generation of intermediate C-centred radicals is given e.g. by experiments in the absence of oxygen leading to cross-linking (solubility effects, optical microscopy, friction-mode AFM) and disproportionation (fluorescence).

Somatic embryogenesis in Triticum aestivum L. Morphological observations on germination

Somatic embryos were induced from scutellar callus of immature zygotic embryos of T aestivum cv. Chinese Spring. Observations on precociously germinating somatic embryos revealed that: (i) In the initial stages the coleoptile is split, exposes the shoot apex and forms a green trichomatous leafy structure. In the germinating zygotic embryo, the coleoptile is tubular, (ii) Unlike what has been inferred earlier the leafy structure is the coleoptile and not the scutellum, (iii) Bipolarity of the embryoid is established later when root develops at the basal end.

Slot-Loaded Compact Microstrip Antenna for Dual-Frequency Operation

Dual frequency operation is achieved from a compact microstrip antenna by loading a pair of narrow slots close to its radiating edges. The two frequencies have parallel polarization planes and similar radiation characteristics. The ratio between the two operating frequencies can be tuned in the range (1.14-1. 24), which is much smaller than that of similar designs. The above excellent radiation characteristics are achieved along with an area reduction of - 75% compared to the standard rectangular patch

Slot coupled sqaure microstrip antenna for compact dual-frequency operation

A novel dual frequency design of a square microstrip antenna coaxially fed along the diagonal with a chip capacitor mounted at the bottom of the stub is introduced. This design provides enhanced area reduction and good cross-polarization levels. The antenna design can be used as a compact antenna system where limited size is a major requirement. The details of the antenna design and experimental results are presented

Compact Microstrip Slot Antenna for Broadband Operation

An arrow-shaped microstrip antenna with a pair of narrow slots embedded near the non-radiating edges gives wide impedance bandwidth. The experimental and simulated (!E3D) results show that antenna bandwidth is -3.5 times that of a conventional patch with the added advantage of reduced antenna size. The radiation characteristics are found to he uniform throughout the operating band

Integrated internal PIFA for UMTS operation of clamshell mobile phones

novel design of at internal PIFA integrated with an RF-shielding metal case for application in a clamshell or fielder-tvpe mobile phone is presented. The integrated PIFA has a bent and tapered radiating arm in order to easily fit in the casing of the clamshell mobile phone as an internal antenna. The integrated PlEA can also provide a wide operating bandwidth fir UM7S (1920-2170 MHz) operation. In addition, for the clamshell mobile phone in either the talk or standby condition, only a small effect on the operating bandwidth of the integrated PIFA is obtained. The experimental results of the proposed design are presented

Circular microstrip antenna with a sector-slot for dual-port operation

Design of a dual-port circular patch antenna with a sector-slot for dual-frequency operation is presented. The antenna resonates at two distinct frequencies with orthogonal polarizations and broad radiation characteristics. Unlike the conventional circular patch, this antenna can be microstrip-fed to operate at either of the resonances. The two polarizations can be simultaneously excited using two electromagnetically coupled ports with an isolation better than −30 dB between the ports. This antenna has the added advantage of size reduction of 44% compared to the conventional circular patch without any reduction in gain.

A Study of Morphological Operators with Applications

The present work deals with the A study of morphological opertors with applications. Morphology is now a.necessary tool for engineers involved with imaging applications. Morphological operations have been viewed as filters the properties of which have been well studied (Heijmans, 1994). Another well-known class of non-linear filters is the class of rank order filters (Pitas and Venetsanopoulos, 1990). Soft morphological filters are a combination of morphological and weighted rank order filters (Koskinen, et al., 1991, Kuosmanen and Astola, 1995). They have been introduced to improve the behaviour of traditional morphological filters in noisy environments. The idea was to slightly relax the typical morphological definitions in such a way that a degree of robustness is achieved, while most of the desirable properties of typical morphological operations are maintained. Soft morphological filters are less sensitive to additive noise and to small variations in object shape than typical morphological filters. They can remove positive and negative impulse noise, preserving at the same time small details in images. Currently, Mathematical Morphology allows processing images to enhance fuzzy areas, segment objects, detect edges and analyze structures. The techniques developed for binary images are a major step forward in the application of this theory to gray level images. One of these techniques is based on fuzzy logic and on the theory of fuzzy sets.Fuzzy sets have proved to be strongly advantageous when representing in accuracies, not only regarding the spatial localization of objects in an image but also the membership of a certain pixel to a given class. Such inaccuracies are inherent to real images either because of the presence of indefinite limits between the structures or objects to be segmented within the image due to noisy acquisitions or directly because they are inherent to the image formation methods.

Studies on L-glutamic acid Production using Brevibacterium sp.

The thesis comprises a set of experiments mainly focused on the improvement of L-glutamic acid fennentation. Much attention has been given to use of locally available raw materials, culturing the organism on inert solid substrates and also immobilization of the bacterial cells from the view point of long term utilization of biocatalyst and continuous operation of the stabilized system. Studies were also carried out for the down stream processing for the extraction and purification of L-glutamic acid. An attempt was made to study the morphological features of the microorganism including the cell premeability. In relation with the accumulation of glutamic acid within the cells an approach was made to study the behaviour of the Brevibacterium cells when they are exposed to hyper osmotic environment. Attempts were also made to study the requirement of iron and production of siderophores by this microbial strain. The search for a suitable nitrogen source for glutamate fermentation ended with a promising result that they got a potent urease activity and it can be utilized for many biotransfonnation studies. The entire thesis is presented in three sections, viz. introductory section, experimental section and the concluding section

Planning And Operation Problems Of Indian Major Ports With Special Emphasis On Cochin Port

Rapid changes in the technological environment of marine logistics and the increasing integration of waterborne, air and land transport systems have fostered a revolution in the design and operations of transport vehicles, cargo handling technology, and terminal facilities. This in turn has caused major changes in the functions of and uses of ports. From literature, it was found that these changes were very slow in case of Indian ports and the performances of port operations were poor when compared with similar ports in the same region. It was also found that a very few studies were conducted to identify the reasons for slow improvements in the performances of Indian major ports. In this thesis, an attempt is made to find out the operational problems of Indian major ports and to analyze the reasons for it. Some solutions have also been found out using management tools

Morphological filtering on hypergraphs

The focus of this article is to develop computationally efficient mathematical morphology operators on hypergraphs. To this aim we consider lattice structures on hypergraphs on which we build morphological operators. We develop a pair of dual adjunctions between the vertex set and the hyper edge set of a hypergraph H, by defining a vertex-hyperedge correspondence. This allows us to recover the classical notion of a dilation/erosion of a subset of vertices and to extend it to subhypergraphs of H. Afterward, we propose several new openings, closings, granulometries and alternate sequential filters acting (i) on the subsets of the vertex and hyperedge set of H and (ii) on the subhypergraphs of a hypergraph

Structural And Surface Morphological Investigation Of Formation Stages Of Highly (002) Oriented Zno Films On Glass Substrates By Spray Pyrolysis Method

ZnO thin films were coated on amorphous glass substrate at various temperatures in the range 160-500 0C by spray pyrolysis method. The as deposited films were characterised by using XRD and SEM. Wurtzite phase of ZnO was formed at a substrate temperature of 400 0C, highly oriented (002) phase was developed with respect to increase of substrate temperature from 450 to 500 0C. Morphological and growth mode of these films were analyzed with respect to structural orientation of films from wurtzite to highly (002) oriented phase. Present study reveals that substrate temperature was one of the important parameters which determine the crystalline quality, population of defects, grain size, orientation and morphology of the films

Automatic Segmentation Framework for Primary Tumors From Brain MRIs Using Morphological Filtering Techniques

This paper describes a novel framework for automatic segmentation of primary tumors and its boundary from brain MRIs using morphological filtering techniques. This method uses T2 weighted and T1 FLAIR images. This approach is very simple, more accurate and less time consuming than existing methods. This method is tested by fifty patients of different tumor types, shapes, image intensities, sizes and produced better results. The results were validated with ground truth images by the radiologist. Segmentation of the tumor and boundary detection is important because it can be used for surgical planning, treatment planning, textural analysis, 3-Dimensional modeling and volumetric analysis