Studies on Catalysis by Titania

Scientists throughout the world are in search of a better methodology to reduce the use of environmentally hazardous chemicals common in industries .A significant contribution in this field is given by different redox catalysts in oxidation reactions. The oxidation of organic substrates represents one of the most important industrial chemical reactions, explaining the significant efforts invested in the research and development of new heterogeneous catalysts with increased activities and selectivities in these type reactions[l-4|. Hence liquid phase reactions like epoxidation of cylcohexene and hydroxylation of phenol were carried out with a new outlook in the challenge using CeO2/TiO;; and CuO/TiO2 catalysts denoted as TiO2-Ce as TiO2-Cu respectively in this work. Also different wt% of metals incorporated titania catalysts like 3, 6, 9 wt% CeO2/TiO; and CuO/TiO;were subjected to the present study .The interaction between metal oxides and the oxide supports have attracted much attention because of the wide applications of supported metal oxide systems[7,8]. It is well known that supported oxides of transition metals are widely used as catalysts for various reactions. Titania as well its metal modified catalysts systems afford high activity and selectivity in the liquid phase epoxidation of cyclohexene[9]. Cyclohexene epoxide is obtained as the major product during the reaction with small amounts of allylic substitution products.This chapter gives an idea about the liquid phase oxidation reactions like epoxidation of cylcohexene and hydroxylation of phenol in which many industrially important products are formed. Here discusses about the redox properties of the ceria and copper incorporated titania catalysts.The epoxidation of cyclohcxene is carried out efficiently over the prepared systems with the selective formation of cyclohexane epoxide. This reaction hints that it might be possible to create cleaner nylon chemistry. The total acidity of the prepared systems plays an important role in determining the catalytic activity in the dehydrogenation of cyclohexane and cyclohexene. The total acidity of the prepared systems plays an important role in determining the catalytic activity in the dehydrogenation of cyclohexane and cyclohexene.

Two-dimensional clusters of liquid 4He

The binding energies of two-dimensional clusters (puddles) of¿4He are calculated in the framework of the diffusion Monte Carlo method. The results are well fitted by a mass formula in powers of x=N-1/2, where N is the number of particles. The analysis of the mass formula allows for the extraction of the line tension, which turns out to be 0.121 K/Å. Sizes and density profiles of the puddles are also reported.

Freezing of 4He and its liquid-solid interface from density functional theory

We show that, at high densities, fully variational solutions of solidlike types can be obtained from a density functional formalism originally designed for liquid 4He . Motivated by this finding, we propose an extension of the method that accurately describes the solid phase and the freezing transition of liquid 4He at zero temperature. The density profile of the interface between liquid and the (0001) surface of the 4He crystal is also investigated, and its surface energy evaluated. The interfacial tension is found to be in semiquantitative agreement with experiments and with other microscopic calculations. This opens the possibility to use unbiased density functional (DF) methods to study highly nonhomogeneous systems, like 4He interacting with strongly attractive impurities and/or substrates, or the nucleation of the solid phase in the metastable liquid.

Comment on "Reappraisal of experimental values of third-order elastic constants of some cubic semiconductors and metals"

In a recent paper A. S. Johal and D. J. Dunstan [Phys. Rev. B 73, 024106 (2006)] have applied multivariate linear regression analysis to the published data of the change in ultrasonic velocity with applied stress. The aim is to obtain the best estimates for the third-order elastic constants in cubic materials. From such an analysis they conclude that uniaxial stress data on metals turns out to be nearly useless by itself. The purpose of this comment is to point out that by a proper analysis of uniaxial stress data it is possible to obtain reliable values of third-order elastic constants in cubic metals and alloys. Cu-based shape memory alloys are used as an illustrative example.

Studies on the Intercompartmental Exchange of Trace Metals in an Estuarine System

The present study is an attempt at investigating the intercompartmental exchange of trace metals (copper, cadmium, zinc, lead and nickel) in the Cochin estuary. The nature and extent of distribution in the different compartments with special reference to the transport from environmental compartments to biological compartments have been dealt with in detail. The suitability of the shells of Villorita cyprinoides var cochinensis (Hanely) in pollution monitoring activities has been assessed. A mathematical model (SAAMPLE - Shells in the Assessment of Aquatic Metal Pollution Levels) based on kinetic laws that govern the intercompartmental exchange has been proposed.

Effect of some toxic metals on selected phytoplankton of Kerala water

The extraction and use of metals has been the mainstay for the sustained development and progress of a nation. Metals, though fairly stable in the natural environment are found in trace quantities in water bodies. Attention has therefore been focused to identify the metals that impair the water quality. In the last few decades the concern about the fate of these metals in the aquatic system has been gaining momentum, particularly in the industrial belts. The disasters caused by metal poisoning in recent times have prompted an indepth study of the interaction of metals with aquatic biota. Kerala, basically an agriculture oriented state has witnessed the upsurgence of various industries as a part of the nationwide economic development programme. Cochin has been identified as the industrial capital of the state.The present study is an attempt towards a better understanding of the metal-phytoplankton interactions with special reference to the physiological changes in the species. various parameters such as temperature, salinity, pH, nutrients, number of cells, photosynthetic pigments, carbohydrates, protein and lipid are studied to highlight the complexity of metal..phytoplankton interaction

Studies on the effect of selected metals on the productivity of two species of algae

The thesis embodies the results of a study on the variations in the parameters of productivity of two test species, a chlorophycean alga and a diatom. The chlorophycean alga Scenedesmus abundans was isolated from a fresh water pond whereas the diatom Nitzschia clausii was from the Cochin backwaters. Their growth parameters and their variations due to the effect of addition of some heavy metals have been studied. The growth parameters include biomass, production, respiration, photosynthetic pigments and end products of photosynthesis. The cell numbers were estimated by using a haemocytometer and production and respiration by oxygen light and dark technique. Spectrophotometric analysis for pigments, anthrone method for carbohydrate and heated biuret method for protein were the different methods employed in the present investigation. The present study is confined to nickel, cobalt, trivalent and hexavalent chromium. Different metals are discharged from various industries in and around Cochin. The effects of these metals individually and in combination are studied. Experiments to determine the effects of interaction of metals in combination enabled the assessment of the antagonistic and synergistic effect of metals on test species. The concentration or accumulation of metals on algae was determined by Atomic Absorption Spectrophotometry. The thesis has been divided into seven chapters. The introductory chapter explains the relevance of the present investigation. Chapter two presents the review of literature based on the work in relation to toxicity. Third chapter gives a detailed description of the material and specialized methods followed for the study. The effects of various metals selected for study - nickel, cobalt, trivalent and hexavalent chromium on the qualitative and quantitative aspects of productivity forms the subject of matter of the fourth chapter. The fifth chapter gives the impact of metals in combination on two species of algae. A general discussion and summary are included in the sixth and seventh chapters

Sub-Lethal effects of heavy metals on perna indica ( Kuriakose & Nair) and donax incarnatus gmelin

The present scientific investigation of the effects of copper, mercury and cadmium has focussed on their effects on two commercially important marine bivalve species, Perna indica (brown mussel) and Donax incarnatus (wedge clam), conspicuous representatives of the tropical intertidal areas. The investigation centred around delineating the cause and effects of heavy metal stress, individually and in combination on these species under laboratory conditions. A clear understanding of the cause and effect can be had only if laboratory experiments are conducted employing sub-lethal concentrations of the above toxicants. Therefore, during the course of the investigation, sub-lethal concentrations of copper, mercury and cadmium were employed to assess the concentration dependent effects on survival, ventilation rate, O:N ratio and tissues. The results obtained are compared with the already available information and partitioned in sections to make a meaningful presentation.The thesis is presented in five chapters comprising INTRODUCTION, ACUTE TOXICITY, VENTILATION RATE, OXYGEN : NITROGEN RATIO and HISTOPATHOLOGY. Each chapter has been divided into various sections such as INTRODUCTION, REVIEW OF LITERATURE, MATERIAL AND METHODS, RESULTS and DISCUSSION

Cavitation in 3He-4He liquid mixtures at low temperatures

Bubble formation in solutions of 3He and 4He is studied within a density-functional approach. In particular, the temperature dependence of the cavitation pressure for different 3He concentrations is calculated at low temperatures and compared to that of pure 4He. The presence of Andreev states lowers the surface tension and, consequently, nucleation barriers are drastically reduced. This fact means that even at low 3He concentrations the cavitation process takes place at higher pressures than the spinodal pressure, which is not the case for pure 4He.