The application of a novel fluidised photo reactor under UV-Visible and natural solar irradiation in the photocatalytic generation of hydrogen

With advancements in the development of visible light responsive catalysts for H2 production frequently being reported, photocatalytic water splitting has become an attractive method as a potential ‘solar fuel generator’. The development of novel photo reactors which can enhance the potential of such catalyst, however, is rarely reported. This is particularly important as many reactor configurations are mass transport limited, which in term limits the efficiency of more effective photocatalysts in larger scale applications. This paper describes the performance of a novel fluidised photo reactor for the production of H2 over two catalysts under UV-Visible light and natural solar illumination. Catalysts Pt-C3N4 and NaTaO3.La were dispersed in the reactor and the rate of H2 was determined by GC-TCD analysis of the gas headspace. The unit was an annular reactor constructed from stainless steel 316 and quartz glass with a propeller located in the base to control fluidisation of powder catalysts. Reactor properties such as propeller rotational speed were found to enhance the photo activity of the system through the elimination of mass transport limitations and increasing light penetration. The optimum conditions for H2 evolution were found to be a propeller rotational speed of 1035 rpm and 144 W of UV-Visible irradiation, which produced a rate of 89 µmol h-1 g-1 over Pt-C3N4. Solar irradiation was provided by the George Ellery Hale Solar Telescope, located at the California Institute of Technology.

QUALITY OF 'SWEETHEART' CHERRY UNDER DIFFERENT STORAGE CONDITIONS

Abstract: In Portalegre, Portugal, sweet cherry production is very important to the region’s economic sustainability. The sweet cherry ‘Sweetheart’ has exhibited short shelf life in spite of being highly appreciated by consumers due to its organoleptic characteristics. In this trial, we evaluated fruit quality of ‘Sweetheart’ stored under different storage conditions: 1) cold conditions (1ºC and high humidity 95%), 2) cold conditions and polypropylene film bags (MA), and 3) controlled atmosphere (CA) (1°C, 95% humidity, 10% CO2 and 8% O2). Fruit physical and chemical parameters were evaluated after 0, 6, 13, 20 and 27 days of cold storage. Quality parameters tested included weight loss, external colour (L* a* b*), visual assessment of the epidermis, epidermis and mesocarp penetration test, soluble solids content (SSC), and titratable acidity (TA). We also performed sensory analyses. The results for textural properties, colour coordinates and sensory analysis suggest that ‘Sweetheart’ fruit can be stored under cold conditions, 1°C, 95% humidity, for up to 21 days without significant loss of quality. Controlled atmosphere maintained tissue turgidity during storage; however, this was not noticed by the panelists, who consistently classified fruits stored under CA conditions with lower overall ratings than fruits under cold conditions with or without film bags.

Characterization of bioactive compounds of dealcoholized wine: valuation of distillation process

O vinho tinto é uma importante fonte de compostos fenólicos com atividade antioxidante e que estão relacionados com a prevenção de doenças cardiovasculares e cancro. Estes compostos são um sub-produto do processo de destilação vínica utilizado para produzir aguardente necessária para a produção de Vinho do Porto. Esta tese tem como objetivo valorizar os compostos fenólicos resultantes das destilarias de vinho, através do estudo da sua composição, das interações com o material polimérico do vinho, da sua estabilidade durante o armazenamento e avaliação dos seus potenciais efeitos biológicos in vitro. Isto irá permitir definir aplicações para estes compostos como ingredientes alimentares com propriedades funcionais. Dois vinhos tintos (RW1 e RW2) foram utilizados como fonte de compostos fenólicos. A fim de estudar estes compostos, cada vinho foi evaporado à pressão atmosférica, permitindo obter o respetivo vinho desalcolizado (DW1 e DW2). Os polissacarídeos e compostos fenólicos presentes nos vinhos desalcolizados foram fracionados por extração em fase sólida utilizando cartuchos C18 sep-pak. A fração hidrofóbica, rica em compostos fenólicos, foi separada em frações ricas em ácidos fenólicos, em procianidinas e em antocianinas, as quais foram usadas para avaliar a sua contribuição para a atividade antioxidante total e caracterização fenólica detalhada dos DW. Foram obtidas quantidades comparáveis de compostos fenólicos totais (1.3 g/L para RW1 e DW1, e 3.1 para RW2 e DW2), de taninos (1.2 g/L para RW1 e DW1 e 1.6 para RW2 e DW2) e de antocianinas (0.24 g/L para RW1 e DW1 e 0.41 para RW2 e DW2) para os vinhos e para os respetivos vinhos desalcolizados. A determinação da atividade antioxidante de RW e DW pelos métodos do DPPH e ABTS também originou valores semelhantes, permitindo inferir que o processo de destilação realizado não promoveu uma perda relevante de compostos fenólicos. A atividade antioxidante total de vinho deveu-se essencialmente à fração rica em antocianinas. Os dois DW foram dialisados para se obter o material polimérico dos vinhos (WPM1 e WPM2). O WPM1 e WPM2 apresentavam 1.1 e 1.3 g/L de material sólido, respetivamente. O WPM (WPM1 e WPM2) era composto por polissacarídeos (31 e 36%), proteínas (10 e 12%) e também por compostos fenólicos (32 e 43%). A análise de açúcares mostrou que as manoproteínas e as arabinogalactanas eram os principais polissacarídeos presentes. A extração do WPM com metanol deu origem a um material insolúvel em metanol (PMi) e a uma fração solúvel em metanol, que continuava a conter hidratos de carbono e compostos fenólicos, mostrando uma forte interação entre estes compostos. Para determinar a energia de ativação (Ea) da libertação dos compostos fenólicos de fracções de material polimérico do vinho, foram realizadas diálises do DW, WPM e PMi, utilizando-se quatro concentrações diferentes, a cinco temperaturas (5-40 °C). O valor da Ea foi 25 para o WPM e 61 kJ/mol para o PMi, mostrando que os compostos fenólicos do vinho podem estar associados de forma diferente à matriz polimérica e que uma fração pode estar, ainda, fortemente associada a esta matriz. A fim de avaliar a possível existência de interações seletivas com os compostos fenólicos, o WPM foi fracionado, permitindo a obtenção de uma fração rica em manoproteínas (MP), através de uma cromatografia de afinidade com concanavalina A e 3 frações ricas em arabinogalactanas (AG0, AG1 e AG2) obtidas por cromatografia de troca aniónica. Foi avaliada a difusão de nove antocianinas monoméricas através de uma membrana de diálise, em presença do WPM, e das frações ricas em MP e em AG. A diálise dos compostos fenólicos livres do vinho foi realizada como ensaio em branco. Todas as frações poliméricas mostraram capacidade para reter as antocianinas, embora em diferente extensão. Foi observada uma capacidade de retenção maior para as antocianinas acilglucosiladas do que para as antocianinas glucosiladas. A fração rica em AG teve uma maior contribuição para a capacidade de retenção das antocianinas pelo material polimérico vinho do que a fração rica em MP, principalmente quando as antocianinas estavam acetiladas. Com o objetivo de estudar formas para preservar, a longo prazo, as propriedades antioxidantes dos compostos fenólicos, o extrato de compostos fenólicos (PCE), em pó, foi armazenado em diferentes condições de luz e atmosfera, à temperatura ambiente durante 1 ano. Observou-se que o PCE armazenado no escuro, dentro de um exsicador sob atmosfera de azoto, preservou 95% da atividade antioxidante inicial. Também foram avaliadas as melhores condições para preservar as antocianinas quando em solução, armazenadas a duas temperaturas (5 e 30 ºC) durante 3 meses. A adição de 0.5 g/L de uma fração rica em polissacarídeos a um vinho armazenado a 30 ºC promoveu a proteção das antocianinas, especialmente das antocianinas cumaroiladas. Os potenciais efeitos biológicos dos compostos fenólicos foram avaliados em diferentes sistemas celulares in vitro utilizando as seguintes frações: WPM, WPS (polissacarídeos do vinho), WPC (compostos fenólicos do vinho), PA-E (fração rica em ácidos fenólicos), PR-E (fração rica em procianidinas) e APP-E (fração rica em antocianinas e procianidinas poliméricas). Foi observada uma maior viabilidade celular quando as células do carcinoma do cólon HT-29 foram expostas a dois agentes oxidantes (radiação UV e H2O2) em presença das frações PR-E e APP-E. Além disso, os extratos WPS, WPC, PR-E e APP-E mostraram propriedades anti-inflamatórias, avaliadas pela inibição da produção de NO por células de macrófagos RAW264.7, sendo o extrato APP-E (0.19 mg/mL) o que exibiu a maior capacidade anti-inflamatória. A fim de elucidar as propriedades antioxidantes dos extratos do vinho em células humanas, os glóbulos vermelhos (RBC) foram selecionados como um modelo metabolicamente simples. Os extratos WPM, WPS, WPC, PR-E, e APP-E mostraram efeito anti-hemolítico para a hemólise dos RBC provocada pelo peróxido de hidrogénio (H2O2) e pelo di-hidrocloreto de 2,2'-azo-bis(2-diaminopropano) (AAPH). Os resultados obtidos permitem concluir que o processo de desalcoolização dos vinhos à pressão atmosférica, preservou as principais características antioxidantes dos compostos fenólicos. Estes compostos podem contribuir para a defesa das células contra agentes oxidantes, nomeadamente por terem um potencial de atividades anti-inflamatória e anti-hemolítica, promovendo a viabilidade celular. A interação dos compostos fenólicos do vinho com o material polimérico permite inferir uma dosagem contínua e gradual das antocianinas vinho tinto após a sua ingestão, contribuindo para um período mais longo da sua exposição e, como consequência, dos seus potenciais benefícios para a saúde.

Innovative edible films to improve storage ability of fresh-cut apple cv. Bravo de Esmolfe

Dissertação de mestrado, Hortofruticultura, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

Biological membranes : biophysical properties and aquaporin function

Tese de doutoramento, Farmácia (Bioquímica), Universidade de Lisboa, Faculdade de Farmácia, 2014

Calculation of nondifferential properties for atomic ground states /

A new method for sampling the exact (within the nodal error) ground state distribution and nondiflPerential properties of multielectron systems is developed and applied to firstrow atoms. Calculated properties are the distribution moments and the electronic density at the nucleus (the 6 operator). For this purpose, new simple trial functions are developed and optimized. First, using Hydrogen as a test case, we demonstrate the accuracy of our algorithm and its sensitivity to error in the trial function. Applications to first row atoms are then described. We obtain results which are more satisfactory than the ones obtained previously using Monte Carlo methods, despite the relative crudeness of our trial functions. Also, a comparison is made with results of highly accurate post-Hartree Fock calculations, thereby illuminating the nodal error in our estimates. Taking into account the CPU time spent, our results, particularly for the 8 operator, have a relatively large variance. Several ways of improving the eflSciency together with some extensions of the algorithm are suggested.

POCN-type Pincer Complexes of NiII and NiIII : synthesis, reactivities, catalytic activities and physical properties

Cette thèse décrit la synthèse, la caractérisation, les réactivités, et les propriétés physiques de complexes divalents et trivalents de Ni formés à partir de nouveaux ligands «pincer» de type POCN. Les ligands POCN de type amine sont préparés d’une façon simple et efficace via l’amination réductrice de 3-hydroxybenzaldéhyde avec NaBH4 et plusieurs amines, suivie par la phosphination de l’amino alcool résultant pour installer la fonction phosphinite (OPR2); le ligand POCN de type imine 1,3-(i-Pr)2PC6H4C(H)=N(CH2Ph) est préparé de façon similaire en faisant usage de PhCH2NH2 en l’absence de NaBH4. La réaction de ces ligands «pincer» de type POCN avec NiBr2(CH3CN)x en présence d’une base résulte en un bon rendement de la cyclométalation du lien C-H situé en ortho aux fonctions amine et phosphinite. Il fut découvert que la base est essentielle pour la propreté et le haut rendement de la formation des complexes «pincer» désirés. Nous avons préparé des complexes «pincer» plan- carrés de type POCN, (POCNRR΄)NiBr, possédant des fonctions amines secondaires et tertiaires qui démontrent des réactivités différentes selon les substituants R et R΄. Par exemple, les complexes possédant des fonctions amines tertiaires ArCH2NR2 (NR2= NMe2, NEt2, and morpholinyl) démontrent des propriétés rédox intéressantes et pourraient être convertis en leurs analogues trivalents (POCNR2)NiBr2 lorsque réagis avec Br2 ou N-bromosuccinimide (NBS). Les complexes trivalents paramagnétiques à 17 électrons adoptent une géométrie de type plan-carré déformée, les atomes de Br occupant les positions axiale et équatoriale. Les analyses «DSC» et «TGA» des ces composés ont démontré qu’ils sont thermiquement stables jusqu’à ~170 °C; tandis que la spectroscopie d’absorption en solution a démontré qu’ils se décomposent thermiquement à beaucoup plus basse température pour regénérer les complexes divalents ne possédant qu’un seul Br; l’encombrement stérique des substitutants amines accélère cette route de décomposition de façon significative. Les analogues NMe2 et N(morpholinyl) de ces espèces de NiIII sont actifs pour catalyser la réaction d’addition de Kharasch, de CX4 à des oléfines telles que le styrène, tandis qu’il fut découvert que l’analogue le moins thermiquement stable (POCNEt2)Ni est complètement inerte pour catalyser cette réaction. Les complexes (POCNRH)NiBr possédant des fonctions amines secondaires permettent l’accès à des fonctions amines substituées de façon non symétrique via leur réaction avec des halogénures d’alkyle. Un autre avantage important de ces complexes réside dans la possibilité de déprotonation pour préparer des complexes POCN de type amide. De telles tentatives pour déprotoner les fonctions NRH nous ont permis de préparer des espèces dimériques possédant des ligands amides pontants. La nature dimérique des ces complexes [P,C,N,N-(2,6-(i-Pr)2PC6H3CH2NR)Ni]2 (R= PhCH2 et Ph) fut établie par des études de diffraction des rayons-X qui ont démontré différentes géométries pour les cœurs Ni2N2 selon le substituant N : l’analogue (PhCH2)N possède une orientation syn des substitutants benzyles et un arrangement ressemblant à celui du cyclobutane du Ni et des atomes d’azote, tandis que l’analogue PhN adopte un arrangement de type diamant quasi-planaire des atomes du Ni et des atomes d’azote et une orientation anti des substituants phényles. Les espèces dimériques ne se dissocient pas en présence d’alcools, mais elles promouvoient l’alcoolyse catalytique de l’acrylonitrile. De façon intéressante, les rendements de ces réactions sont plus élevés avec les alcools possédant des fonctions O-H plus acides, avec un nombre de «turnover» catalytique pouvant atteindre 2000 dans le cas de m-cresol. Nous croyons que ces réactions d’alcoolyse procèdent par activation hétérolytique de l’alcool par l’espèce dimérique via des liaisons hydrogènes avec une ou deux des fonctions amides du dimère. Les espèces dimériques de Ni (II) s’oxydent facilement électrochimiquement et par reaction avec NBS ou Br2. De façon surprenante, l’oxydation chimique mène à l’isolation de nouveaux produits monomériques dans lesquels le centre métallique et le ligand sont oxydés. Le mécanisme d’oxydation fut aussi investigué par RMN, «UV-vis-NIR», «DFT» et spectroélectrochimie.

Molecular Networks Created by Charge-Assisted Hydrogen Bonds Between Bis(aminidinium) Cations and Carboxylates, Sulfonates, Phosphonates and Phosphates

L'objectif de cette étude est d'apprendre à créer de nouveaux matériaux moléculaires par design. À l'heure actuelle, il n'existe aucune méthode générale pour la prédiction des structures et des propriétés, mais des progrès importants ont été accomplis, en particulier dans la fabrication de matériaux moléculaires ordonnés tels que des cristaux. En ces matériaux, l'organisation peut être contrôlée efficacement par la stratégie de la tectonique moléculaire. Cette approche utilise des molécules appelées “tectons”, qui peuvent s’associer de manière dirigée par des interactions non covalentes prévisibles. De cette façon, la position de chaque molécule par rapport à ses voisins peut être programmée avec un degré élevé de fiabilité pour créer des cristaux et d'autres matériaux organisés avec des caractéristiques et des propriétés structurelles souhaitables. Le travail que nous allons décrire est axé sur l'utilisation de l'association des cations bis(aminidinium) avec des carboxylates, sulfonates, phosphonates et phosphates, afin de créer des réseaux moléculaires prévisibles. Ces réseaux promettent d'être particulièrement robuste, car ils sont maintenus ensemble par de multiples liaisons hydrogène assistées par des interactions électrostatiques.

Plasma Polymerised Organic Thin Films-A Study on the Structural, Electrical and Nonlinear Optical Properties for Possible Applications

This proposed thesis is entitled “Plasma Polymerised Organic Thin Films: A study on the Structural, Electrical, and Nonlinear Optical Properties for Possible Applications. Polymers and polymer based materials find enormous applications in the realm of electronics and optoelectronics. They are employed as both active and passive components in making various devices. Enormous research activities are going on in this area for the last three decades or so, and many useful contributions are made quite accidentally. Conducting polymers is such a discovery, and eversince the discovery of conducting polyacetylene, a new branch of science itself has emerged in the form of synthetic metals. Conducting polymers are useful materials for many applications like polymer displays, high density data storage, polymer FETs, polymer LEDs, photo voltaic devices and electrochemical cells. With the emergence of molecular electronics and its potential in finding useful applications, organic thin films are receiving an unusual attention by scientists and engineers alike. This is evident from the vast literature pertaining to this field appearing in various journals. Recently, computer aided design of organic molecules have added further impetus to the ongoing research activities in this area. Polymers, especially, conducting polymers can be prepared both in the bulk and in the thinfilm form. However, many applications necessitate that they are grown in the thin film form either as free standing or on appropriate substrates. As far as their bulk counterparts are concerned, they can be prepared by various polymerisation techniques such as chemical routes and electrochemical means. A survey of the literature reveals that polymers like polyaniline, polypyrrole, polythiophene, have been investigated with a view to studying their structural electrical and optical properties. Among the various alternate techniques employed for the preparation of polymer thin films, the method of plasma polymerisation needs special attention in this context. The technique of plasma polymerisation is an inexpensive method and often requires very less infra structure. This method includes the employment of ac, rf, dc, microwave and pulsed sources. They produce pinhole free homogeneous films on appropriate substrates under controlled conditions. In conventional plasma polymerisation set up, the monomer is fed into an evacuated chamber and an ac/rf/dc/ w/pulsed discharge is created which enables the monomer species to dissociate, leading to the formation of polymer thin films. However, it has been found that the structure and hence the properties exhibited by plasma polymerized thin films are quite different from that of their counterparts produced by other thin film preparation techniques such as electrochemical deposition or spin coating. The properties of these thin films can be tuned only if the interrelationship between the structure and other properties are understood from a fundamental point of view. So very often, a through evaluation of the various properties is a pre-requisite for tailoring the properties of the thin films for applications. It has been found that conjugation is a necessary condition for enhancing the conductivity of polymer thin films. RF technique of plasma polymerisation is an excellent tool to induce conjugation and this modifies the electrical properties too. Both oxidative and reductive doping can be employed to modify the electrical properties of the polymer thin films for various applications. This is where organic thin films based on polymers scored over inorganic thin films, where in large area devices can be fabricated with organic semiconductors which is difficult to achieve by inorganic materials. For such applications, a variety of polymers have been synthesized such as polyaniline, polythiophene, polypyrrole etc. There are newer polymers added to this family every now and then. There are many virgin areas where plasma polymers are yet to make a foray namely low-k dielectrics or as potential nonlinear optical materials such as optical limiters. There are also many materials which are not been prepared by the method of plasma polymerisation. Some of the materials which are not been dealt with are phenyl hydrazine and tea tree oil. The advantage of employing organic extracts like tea tree oil monomers as precursors for making plasma polymers is that there can be value addition to the already existing uses and possibility exists in converting them to electronic grade materials, especially semiconductors and optically active materials for photonic applications. One of the major motivations of this study is to synthesize plasma polymer thin films based on aniline, phenyl hydrazine, pyrrole, tea tree oil and eucalyptus oil by employing both rf and ac plasma polymerisation techniques. This will be carried out with the objective of growing thin films on various substrates such as glass, quartz and indium tin oxide (ITO) coated glass. There are various properties namely structural, electrical, dielectric permittivity, nonlinear optical properties which are to be evaluated to establish the relationship with the structure and the other properties. Special emphasis will be laid in evaluating the optical parameters like refractive index (n), extinction coefficient (k), the real and imaginary components of dielectric constant and the optical transition energies of the polymer thin films from the spectroscopic ellipsometric studies. Apart from evaluating these physical constants, it is also possible to predict whether a material exhibit nonlinear optical properties by ellipsometric investigations. So further studies using open aperture z-scan technique in order to evaluate the nonlinear optical properties of a few selected samples which are potential nonlinear optical materials is another objective of the present study. It will be another endeavour to offer an appropriate explanation for the nonlinear optical properties displayed by these films. Doping of plasma polymers is found to modify both the electrical conductivity and optical properties. Iodine is found to modify the properties of the polymer thin films. However insitu iodine doping is tricky and the film often looses its stability because of the escape of iodine. An appropriate insitu technique of doping will be developed to dope iodine in to the plasma polymerized thin films. Doping of polymer thin films with iodine results in improved and modified optical and electrical properties. However it requires tools like FTIR and UV-Vis-NIR spectroscopy to elucidate the structural and optical modifications imparted to the polymer films. This will be attempted here to establish the role of iodine in the modification of the properties exhibited by the films

Electrical and Optical Properties of Znga2o4 Thin Films Deposited By Pulsed Laser Deposition

ZnGa2O4 spinel is a promising new UV transparent electronic conductor. Enhancing the electrical conductivity of this potential oxide phosphor can make it a promising transparent conducting oxide. In this paper, we have investigated the effects of processing and doping on the conductivity of semiconducting ZnGa2O4, particularly thin films. Crystalline zinc gallate thin films have been deposited on fused quartz substrates employing the pulsed laser deposition (PLD) technique at room temperature for an oxygen partial pressure of 0.1 Pa (0.001mbar). The films were found to be UV transparent, the band gap of which shifted to 4.75eV on hydrogen annealing. The band gap of the oxygen stoichiometric bulk powder samples (4.55eV) determined from diffuse reflection spectrum (DRS) shifted to 4.81eV on reduction in a hydrogen atmosphere. The electrical conductivity improved when Sn was incorporated into the ZnGa2O4 spinel. The conductivity of ZnGa2O4:Sn thin films was further improved on reduction.

Biochemical and Storage Characteristics of Myofibrillar Protein ( Surimi ) from Freshwater Major Carps

School of Industrial Fisheries, Cochin University of Science and Technology

Studies on Metallocene Polyolefin and Polyvinyl Chloride for Blood and Blood Component Storage Applications

Plasticized poly(vinyl chloride) (pPVC), although a major player in the medical field, is at present facing lot of criticism due to some of its limitations like the leaching out of the toxic plasticizer, di ethylhexyl phthalate (DEHP) to the medium and the emission of an environmental pollutant,dioxin gas,at the time of the post use disposal of PVC Products by incineration. Due to these reasons, efforts are on to reduce the use of pPVC considerably in the medical field and to find viable alternative materials. The present study has been undertaken in this context to find a suitable material for the manufacture of medical aids in place of pPVC. The main focus of this study has been to find out a non-DEHP material as plasticizer for pPVC and another suitable material for the complete repalcement of pPVC for blood/ blood component storage applications.Two approaches have been undertaken for this purpose-(1)the controversial plasticizer, DEHP has been partially replaced by polymeric plasticizers(2) an alternative material, namely, metallocene polyolefin (mPO) has been used and suitably modified to match the properties of flexible PVC used for blood and blood component storage applications.

Glucoamylase immobilized on montmorillonite: influence of nature of binding on surface properties of clay-support and activity of enzyme

Glucoamylase was immobilized on acid activated montmorillonite clay via two different procedures namely adsorption and covalent binding. The immobilized enzymes were characterized by XRD, NMR and N2 adsorption measurements and the activity of immobilized glucoamylase for starch hydrolysis was determined in a batch reactor. XRD shows intercalation of enzyme into the clay matrix during both immobilization procedures. Intercalation occurs via the side chains of the amino acid residues, the entire polypeptide backbone being situated at the periphery of the clay matrix. 27Al NMR studies revealed the different nature of interaction of enzyme with the support for both immobilization techniques. N2 adsorption measurements indicated a sharp drop in surface area and pore volume for the covalently bound glucoamylase that suggested severe pore blockage. Activity studies were performed in a batch reactor. The adsorbed and covalently bound glucoamylase retained 49% and 66% activity of the free enzyme respectively. They showed enhanced pH and thermal stabilities. The immobilized enzymes also followed Michaelis–Menten kinetics. Km was greater than the free enzyme that was attributed to an effect of immobilization. The immobilized preparations demonstrated increased reusability as well as storage stability.

Electrical conductivity, dielectric constant and phase transitions in pure and doped diammonium hydrogen phosphate

DC and AC electrical conductivity measurements in single crystals of diammonium hydrogen phosphate along the c axis show anomalous variations at 174, 246 and 416 K. The low-frequency dielectric constant also exhibits peaks exactly at these temperatures with a thermal hysteresis of 13 degrees C for the peak at 416 K. These specific features of the electrical properties are in agreement with earlier NMR second-moment data and can be identified with three distinct phase transitions that occur in the crystal. The electrical conductivity values have been found to increase linearly with impurity concentration in specimens doped with a specific amount of SO42- ions. The mechanisms of the phase transition and of the electrical conduction process are discussed in detail.

Packaging materials for shrimp, fish and fish products, their properties, selection and effect of different packaging materials on their shelf life

Packaging is important not only in extending the shellife of fish and fishery products but also improving their marketability. In the recent years, significant development have taken place in the packaging industry. During the past decade in India, there is almost a packaging revolution with the availability of variety packaging materials, thus generating better packaging consciousness in other producer/manufacturing industries. But unfortunately, such realisation is not forthcoming in the fisheries sector and packaging techniques for local and export trade continues to be on traditional lines with their inherent drawbacks and limitations. Better packaging ensures improved quality and presentation of the products and ensures higher returns to the producer. Among several packaging materials used in fishery industry, ISI specifications had been formulated only for corrugated fibre board boxes for export of seafoods and froglegs. This standard was formulated before containersiation came into existance in the export of marine products. Before containerisation, the standards were stringent in view of the rough handling, transportation and storage. Two of the common defects reported in the master cartons exported from India are low mechanical strength and tendency to get wet. They are weakened by the deposits of moisture caused by temperature fluctuations during loading, unloading and other handling stages. It is necessary to rectify the above defects in packaging aquatic products and hence in the present study extensive investigations are carried out to find out the reasons for the damage of master cartons, to evolve code of practice for the packaging oi frozen shrimp for exports, development of alternative style of packaging for the shipping container, development of suitable consumer packaging materials for fish soup powder, cured dried mackeral, fish pickles in oil and frozen shrimp. For the development of suitable packaging materials, it is absolutely essential to know the properties of packaging materials, effect of different packaging materials on theirshelf life and their suitability for food contact applications.