Linear Low Density Polyethylene-Biodegradability Using Bacteria from Marine Benthic Environment and Photodegradability Using Ultraviolet Light

Various compositions of linear low density polyethylene(LLDPE) containing bio-filler(either starch or dextrin)of various particle sizes were prepared.The mechanical,thermal,FTIR,morphological(SEM),water absorption and melt flow(MFI) studies were carried out.Biodegradability of the compositions were determined using a shake culture flask containing amylase producing bacteria(vibrios),which were isolated from marine benthic environment and by soil burial test. The effect of low quantities of metal oxides and metal stearate as pro-oxidants in LLDPE and in the LLDPE-biofiller compositions was established by exposing the samples to ultraviolet light.The combination of bio-filler and a pro-oxidant improves the degradation of linear low density polyethylene.The maleation of LLDPE improves the compatibility of the c blend components and thepro-oxidants enhance the photodegradability of the compatibilised blends.The responsibility studies on the partially biodegradable LLDPE containing bio-fillers and pro-oxidants suggest that the blends could be repeatedly reprocessed without deterioration in mechanical properties.

Investigations on polyaniline based systems for technologically important applications and some novel polymers as prospective candidates for fabricating polymer light emitting diodes

Light emitting polymers (LEP) have drawn considerable attention because of their numerous potential applications in the field of optoelectronic devices. Till date, a large number of organic molecules and polymers have been designed and devices fabricated based on these materials. Optoelectronic devices like polymer light emitting diodes (PLED) have attracted wide-spread research attention owing to their superior properties like flexibility, lower operational power, colour tunability and possibility of obtaining large area coatings. PLEDs can be utilized for the fabrication of flat panel displays and as replacements for incandescent lamps. The internal efficiency of the LEDs mainly depends on the electroluminescent efficiency of the emissive polymer such as quantum efficiency, luminance-voltage profile of LED and the balanced injection of electrons and holes. Poly (p-phenylenevinylene) (PPV) and regio-regular polythiophenes are interesting electro-active polymers which exhibit good electrical conductivity, electroluminescent activity and high film-forming properties. A combination of Red, Green and Blue emitting polymers is necessary for the generation of white light which can replace the high energy consuming incandescent lamps. Most of these polymers show very low solubility, stability and poor mechanical properties. Many of these light emitting polymers are based on conjugated extended chains of alternating phenyl and vinyl units. The intra-chain or inter-chain interactions within these polymer chains can change the emitted colour. Therefore an effective way of synthesizing polymers with reduced π-stacking, high solubility, high thermal stability and high light-emitting efficiency is still a challenge for chemists. New copolymers have to be effectively designed so as to solve these issues. Hence, in the present work, the suitability of a few novel copolymers with very high thermal stability, excellent solubility, intense light emission (blue, cyan and green) and high glass transition temperatures have been investigated to be used as emissive layers for polymer light emitting diodes.

Blue, Green and Orange-Red Light Emitting Polymers: Synthesis, Characterization and Prospects of Applications in Optoelectronic Devices

Light emitting polymers (LEPs) are considered as the second generation of conducting polymers. A Prototype LEP device based on electroluminescence emission of poly(p-phenylenevinylene) (PPV) was first assembled in 1990. LEPs have progressed tremendously over the past 20 years. The development of new LEP derivatives are important because polymer light emitting diodes (PLEDs) can be used for the manufacture of next-generation displays and other optoelectronic applications such as lasers, photovoltaic cells and sensors. Under this circumstance, it is important to understand thermal, structural, morphological, electrochemical and photophysical characteristics of luminescent polymers. In this thesis the author synthesizes a series of light emitting polymers that can emit three primary colors (RGB) with high efficiency

Biological coagulation of skim latex using Acinetobacter sp. isolated from natural rubber latex centrifugation effluent

An Acinetobacter sp, isolated from latex centrifugation effluent, effectively coagulated skim rubber from skim latex. After coagulation for 48 h without the addition of any nutrients, at an optimum dilution of 1:10(v/v) and with an inoculum concentration of 6.4 mg dry cell /ml, the yield of the skim rubber was 8 % (w/v) and the COD of the residual solution was only 0.4 g/l. chemical coagulation at the same dilution resulted in 7 % (w/v) yield of dry rubber content and 2.2 g COD /l.

An Encoded Infrared Sheet Of Light Navigational Beacon System For Precise Localization Of Indoor Mobile Robot Vehicles

A new localization approach to increase the navigational capabilities and object manipulation of autonomous mobile robots, based on an encoded infrared sheet of light beacon system, which provides position errors smaller than 0.02m is presented in this paper. To achieve this minimal position error, a resolution enhancement technique has been developed by utilising an inbuilt odometric/optical flow sensor information. This system respects strong low cost constraints by using an innovative assembly for the digitally encoded infrared transmitter. For better guidance of mobile robot vehicles, an online traffic signalling capability is also incorporated. Other added features are its less computational complexity and online localization capability all these without any estimation uncertainty. The constructional details, experimental results and computational methodologies of the system are also described

Natural Rubber Latex Filler Masterbatch by Soap Sensitised Coagulation-Preparation, Processing and Evaluation

Sensitisation of natural rubber latex by addition of a small quantity of an anionic surfactant prior to the addition of a coacervant results in quick coagulation. The natural rubber prepared by the novel coagulation method shows improved raw rubber characteristics, better cure characteristics in gum and carbon black filled compounds and improved mechanical properties as compared to the conventionally coagulated natural rubber. Compounds based on dried masterbatches prepared by the incorporation of fluffy carbon black in different forms of soap sensitised natural rubber latices such as fresh latex, preserved field latex, centrifuged latex and a blend of preserved field latex and skim latex show improved cure characteristics and vucanizate properties as compared to an equivalent conventional dry rubber-fluffy carbon black based compound. The latex masterbatch based vulcanizates show higher level of crosslinking and better dispersion of filler. Vulcanizates based on fresh natural rubber latex- dual filler masterbatches containing a blend of carbon black and silica prepared by the modified coagulation process shows very good mechanical and dynamic properties that could be correlated to a low rolling resistance. The carbon black/silica/nanoclay tri-filler - fresh natural rubber latex masterbatch based vulcanizates show improved mechanical properties as the proportion of nanoclay increased up to 5 phr. The fresh natural rubber latex based carbon black-silica masterbatch/ polybutadiene blend vulcanizates show superior mechanical and dynamic properties as compared to the equivalent compound vulcanizates prepared from the dry natural rubber-filler (conventional dry mix)/polybutadiene blends

A STUDY OF THE MYTHICAL AND ARCHETYPAL ELEMENTS IN THE PDETICAL WORKS DF AJNEYA IN THE LIGHT OF THE THEORY PRDPDUNDED BY JUNG

Hindi

Synthesis and Photoluminescence Properties of Novel Red Phosphors for White Light Emitting Diode Applications

Several series of Eu3+ based red emitting phosphor materials were synthesized using solid state reaction route and their properties were characterized. The present studies primarily investigated the photoluminescence properties of Eu3+ in a family of closely related host structure with a general formula Ln3MO7. The results presented in the previous chapters throws light to a basic understanding of the structure, phase formation and the photoluminescence properties of these compounds and their co-relations. The variation in the Eu3+ luminescence properties with different M cations was studied in Gd3-xMO7 (M = Nb, Sb, Ta) system.More ordering in the host lattice and more uniform distribution of Eu3+ ions resulting in the increased emission properties were observed in tantalate system.Influence of various lanthanide ion (Lu, Y, Gd, La) substitutions on the Eu3+ photoluminescence properties in Ln3MO7 host structures was also studied. The difference in emission profiles with different Ln ions demonstrated the influence of long range ordering, coordination of cations and ligand polarizability in the emission probabilities, intensity and quantum efficiency of these phosphor materials. Better luminescence of almost equally competing intensities from all the 4f transitions of Eu3+ was noticed for La3TaO7 system. Photoluminescence properties were further improved in La3TaO7 : Eu3+ phosphors by the incorporation of Ba2+ ions in La3+ site. New red phosphor materials Gd2-xGaTaO7 : xEu3+ exhibiting intense red emissions under UV excitation were prepared. Optimum doping level of Eu3+ in these different host lattices were experimentally determined. Some of the prepared samples exhibited higher emission intensities than the standard Y2O3 : Eu3+ red phosphors. In the present studies, Eu3+ acts as a structural probe determining the coordination and symmetry of the atoms in the host lattice. Results from the photoluminescence studies combined with the powder XRD and Raman spectroscopy investigations helped in the determination of the correct crystal structures and phase formation of the prepared compounds. Thus the controversy regarding the space groups of these compounds could be solved to a great extent. The variation in the space groups with different cation substitutions were discussed. There was only limited understanding regarding the various influential parameters of the photoluminescence properties of phosphor materials. From the given studies, the dependence of photoluminescence properties on the crystal structure and ordering of the host lattice, site symmetries, polarizability of the ions, distortions around the activator ion, uniformity in the activator distribution, concentration of the activator ion etc. were explained. Although the presented work does not directly evidence any application, the materials developed in the studies can be used for lighting applications together with other components for LED lighting. All the prepared samples were well excitable under near UV radiation. La3TaO7 : 0.15Eu3+ phosphor with high efficiency and intense orange red emissions can be used as a potential red component for the realization of white light with better color rendering properties. Gd2GaTaO7 : Eu3+, Bi2+ red phosphors give good color purity matching to NTSC standards of red. Some of these compounds exhibited higher emission intensities than the standard Y2O3 : Eu3+ red phosphors. However thermal stability and electrical output using these compounds should be studied further before applications. Based on the studies in the closely related Ln3MO7 structures, some ideas on selecting better host lattice for improved luminescence properties could be drawn. Analyzing the CTB position and the number of emission splits, a general understanding on the doping sites can be obtained. These results could be helpful for phosphor designs in other host systems also, for enhanced emission intensity and efficiency.

Theoretical study of the physicochemical properties of the light transactinides

A theoretical study of the physicochemical properties of elements 104, 105, and 106 and their compounds in the gas phase and aqueous solutions has been undertaken using relativistic atomic and molecular codes. Trends in properties such as bonding, ionization potentials, electron affinities, energies of electronic transitions, stabilities of oxidation states etc. have been defined within the corresponding chemical groups and within the transactinides. These trends are shown to be determined by increasing relativistic effects within the groups. The behaviour of some gas phase compounds and complexes in solutions is predicted for the gas chromatography and solvent extraction experiments. Redox potentials in aqueous solutions of these elements are estimated.

Time-resolved studies of neutral and ionized Na_n clusters with femtosecond light pulses

The real-time dynamics of Na_n (n=3-21) cluster multiphoton ionization and fragmentation has been studied in beam experiments applying femtosecond pump-probe techniques in combination with ion and electron spectroscopy. Three dimensional wave packet motions in the trimer Na_3 ground state X and excited state B have been observed. We report the first study of cluster properties (energy, bandwidth and lifetime of intermediate resonances Na_n^*) with femtosecond laser pulses. The observation of four absorption resonances for the cluster Na_8 with different energy widths and different decay patterns is more difficult to interpret by surface plasmon like resonances than by molecular structure and dynamics. Timeresolved fragmentation of cluster ions Na_n^+ indicates that direct photo-induced fragmentation processes are more important at short times than the statistical unimolecular decay.

Analytical Study of Light Propagation in Highly Nonlinear Media

The present dissertation is devoted to the construction of exact and approximate analytical solutions of the problem of light propagation in highly nonlinear media. It is demonstrated that for many experimental conditions, the problem can be studied under the geometrical optics approximation with a sufficient accuracy. Based on the renormalization group symmetry analysis, exact analytical solutions of the eikonal equations with a higher order refractive index are constructed. A new analytical approach to the construction of approximate solutions is suggested. Based on it, approximate solutions for various boundary conditions, nonlinear refractive indices and dimensions are constructed. Exact analytical expressions for the nonlinear self-focusing positions are deduced. On the basis of the obtained solutions a general rule for the single filament intensity is derived; it is demonstrated that the scaling law (the functional dependence of the self-focusing position on the peak beam intensity) is defined by a form of the nonlinear refractive index but not the beam shape at the boundary. Comparisons of the obtained solutions with results of experiments and numerical simulations are discussed.

Synthesis and Characterization of Novel Spiro-Starburst-Structures as Blue Light Emitters and Zeolites

Spiro-starburst-structures with symmetric globular structures in forms of first and second generations that readily form stable amorphous glasses have been synthesized and then characterised in this work. During the synthesis of these materials, possibilities of the extension of the chains of the phenyl rings in 2,2’,7 and 7’-positions of the central core of the spirobifluorene as well as the 2’,7 and 7’-positions of the terminal spirobifluorene units of the spiro-starburst-structures have been investigated so that solubilities and morphologies of the compounds are not negatively influenced. Their morphological properties have been explored by recording their decomposition temperature and glass transition temperature. These compounds possessing two perpendicular arrangement of the two molecular halves show high glass transition temperature (Tg), which is one of the most important parameter indicating the stability of the amorphous state of the material for optoelectronic devices like organic light emitting diodes. Within the species of second generation compounds, for example, 4-spiro3 shows the highest Tg (330 °C) and the highest branching degree. When one [4B(SBF)SBF-SBF 84] or two [4SBFSBF-SBF 79] terminal spirobifluorene units are removed, the Tg decreases to 318 °C and 307 °C respectively. Photo absorption and fluorescence spectra and cyclic voltammetry measurements are taken in account to characterize the optoelectronic properties of the compounds. Spiro-starburst-structures emit radiation in the blue region of the visible spectrum. The peak maxima of absorption and emission spectra are observed to be at higher wavelength in the molecules with longer chromophore chains than in the molecules with shorter chromophore chains. Excitation spectra are monitored with their emission peak maxima. The increasing absorbing species in molecule leads to increasing molar extinction coefficient. In the case of 4B(TP)SBF-SBF 53 and 4B(SBF)SBF-SBF 84, the greater values of the molar extinction coefficients (43*104 and 44*104 L mol-1 cm-1 respectively) are the evidences of the presence of four times octiphenyl conjugation rings and eight times terminal fluorene units respectively. The optical properties of solid states of these compounds in the form of thin film indicate that the intermolecular interaction and aggregation of individual molecules in neat amorphous films are effectively hindered by their sterically demanding structures. Accordingly, in solid state, they behave like isolated molecules in highly dilute solution. Cyclic voltammetry measurements of these compounds show electrochemically reversibility and stability. Furthermore, the zeolitic nature (host-guest) of the molecular sieve of the synthesized spiro-starburst-structures has been analysed by thermogravimetric analysis method.