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Particulate Materials (particulate + material)
Selected AbstractsThe biology and functional morphology of Arca noae (Bivalvia: Arcidae) from the Adriatic Sea, Croatia, with a discussion on the evolution of the bivalve mantle marginACTA ZOOLOGICA, Issue 1 2008Brian Morton Abstract In the Croatian Adriatic, Arca noae occurs from the low intertidal to a depth of 60 m; it can live for > 15 years and is either solitary or forms byssally attached clumps with Modiolus barbatus. The shell is anteriorly foreshortened and posteriorly elongate. The major inhalant flow is from the posterior although a remnant anterior stream is retained. There are no anterior but huge posterior byssal retractor muscles and both anterior and posterior pedal retractors. The ctenidia are of Type B(1a) and the ctenidial,labial palp junction is Category 3. The ctenidia collect, filter and undertake the primary sorting of potential food in the inhalant water. The labial palps are small with simple re-sorting tracks on the ridges of their inner surfaces. The ciliary currents of the mantle cavity appear largely concerned with the rejection of particulate material. The mantle margin comprises an outer and an (either) inner or middle fold. The outer fold is divided into outer and inner components that secrete the shell and are photo-sensory, respectively. The latter bears a large number of pallial eyes, especially posteriorly. The inner/middle mantle fold of A. noae, possibly representative of simpler, more primitive conditions, may have differentiated into distinct folds in other recent representatives of the Bivalvia. [source] Bioavailability of solid and non-aqueous phase liquid (NAPL)-dissolved phenanthrene to the biosurfactant-producing bacterium Pseudomonas aeruginosa 19SJENVIRONMENTAL MICROBIOLOGY, Issue 9 2001Marta García-Junco The biodegradation of phenanthrene by the biosurfactant-producing strain Pseudomonas aeruginosa 19SJ was investigated in experiments with the compound present either as crystals or dissolved in non-aqueous phase liquids (NAPLs). Growth on solid phenanthrene exhibited an initial phase not limited by dissolution rate and a subsequent, carbon-limited phase caused by exhaustion of the carbon source. Rhamnolipid biosurfactants were produced from solid phenanthrene and appeared in solution and particulate material (cells and phenanthrene crystals). During the carbon-limited phase, the concentration of rhamnolipids detected in culture exceeded the critical micelle concentration (CMC) determined with purified rhamnolipids. The biosurfactants caused a significant increase in dissolution rate and pseudosolubility of phenanthrene, but only at concentrations above the CMC. Externally added rhamnolipids at a concentration higher than the CMC increased the biodegradation rate of solid phenanthrene. Mineralization curves of low concentrations of phenanthrene initially dissolved in two NAPLs [2,2,4,4,6,8,8-heptamethylnonane and di(2-ethylhexyl)phthalate] were S-shaped, although no growth was observed in the population of suspended bacteria. Biosurfactants were not detected in solution under these conditions. The observed mineralization was attributed not only to suspended bacteria, but also to bacterial populations growing at the NAPL,water interface, mineralizing the compound at higher rates than predicted by abiotic partitioning. We suggest that rhamnolipid production and attachment increased the bioavailability of phenanthrene, so promoting biodegradation activity. [source] Extreme hydrochemical conditions in natural microcosms entombed within Antarctic iceHYDROLOGICAL PROCESSES, Issue 2 2004Martyn Tranter Abstract Cryoconite holes are near-vertical tubes that form in the surface of glaciers when solar-heated debris melts into the ice. Those that form in the McMurdo Dry Valleys of Antarctica are distinctive, in that they have ice lids and are closed to the atmosphere for periods of years to decades. Photoautotrophs and heterotrophs grow within this closed environment, perturbing the poorly buffered water chemistry, yet maintaining the potential for photosynthesis. Microbial excretion and decomposition of organic matter produces dissolved organic carbon (DOC): dissolved inorganic carbon ratios of ,1:2. Much of the dissolved nitrogen pool (80,100%) exists as dissolved organic nitrogen (DON). The DON:DOC ratio is ,1:11 (mol/mol), typical of organic particulate material at the Earth's surface. The combination of photoautotrophy, heterotrophy and weak chemical buffering within these microcosms promotes values of pH, pCO2, O2 saturation and percentage total dissolved nitrogen as DON that reach 10·99, 10,7·6 atm, 160% and 100% respectively, which are a unique combination among the surface waters on Earth. These ice-sealed cryoconite holes could be important analogues of refugia on Snowball Earth and other icy planets. Copyright © 2004 John Wiley & Sons, Ltd. [source] Hypoxia-like effect of Cobalt Chromium alloy micro particles on fibroblasts in vitroJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2010Bernadette K. Madathil Abstract Periprosthetic osteolysis leading to asceptic loosening remains the primary cause of failure of joint replacement. Although many inflammatory cell types have been implicated, the exact pathomechanisms of asceptic loosening have not been delineated. In the present study we have adopted a proteomic approach to elucidate the initial signals that are expressed to particulate material, using an in vitro cell culture system. Human lung fibroblasts MRC-5 were cultured with Cobalt Chromium (CoCr ASTM F-75, 1,7,µm) particles. Cells were harvested after 72,h incubation and total cellular proteins extracted for downstream analysis via 2D Gel Electrophoresis and tandem mass spectrometry using MALDI-TOF-TOF-MS. Thirteen protein spots showed greater than twofold increase, following 72,h incubation of fibroblast with CoCr particles. Four of these proteins were identified by tandem mass spectrometry. These were Annexin II, Pyruvate kinase, Triose phosphate isomerase, and N-myc downstream regulated gene 1 protein. Cobalt is a hypoxia mimicking agent and N-myc downstream regulated gene 1 protein, Triose phosphate isomerase, Pyruvate kinase, and Annexin II are important hypoxia regulated gene products that are found to be over expressed in cellular oxidative stress response. Our data indicates that exposure of fibroblast to CoCr alloy induces the transition of these cells into a hypoxia like state and oxidative stress even in normoxic culture conditions. The study reflects the possibility of the presence of a hypoxic environment in the periprosthetic tissue surrounding metallic implants. Published by Wiley Periodicals, Inc. J Orthop Res 28:1360,1367, 2010 [source] PRODUCTION OF PHYTOCHELATINS AND GLUTATHIONE BY MARINE PHYTOPLANKTON IN RESPONSE TO METAL STRESS,JOURNAL OF PHYCOLOGY, Issue 5 2006Silvia K. Kawakami Phytoplankton deal with metal toxicity using a variety of biochemical strategies. One of the strategies involves glutathione (GSH) and phytochelatins (PCs), which are metal-binding thiol peptides produced by eukaryotes and these compounds have been related to several intracellular functions, including metal detoxification, homeostasis, metal resistance and protection against oxidative stress. This paper assesses our state of knowledge on the production of PCs and GSH by marine phytoplankton in laboratory and field conditions and the possible applications of PCs for environmental purposes. Good relationships have been observed between metal exposure and PC production in phytoplankton in the laboratory with Cd, Pb, and Zn showing the greatest efficacy, thereby indicating that PCs have a potential for application as a biomarker. Fewer studies on PC distributions in particulate material have been undertaken in the field. These studies show that free Cu has a strong relationship with the levels of PC in the particulate material. The reason for this could be because Cu is a common contaminant in coastal waters. However it could also be due to the lack of measurements of other metals and their speciation. GSH shows a more complex relationship to metal levels both in the laboratory and in the field. This is most likely due to its multifunctionality. However, there is evidence that phytoplankton act as an important source of dissolved GSH in marine waters, which may form part of the strong organic ligands that control metal speciation, and hence metal toxicity. [source] A fish kill event, hypoxia and other limnological impacts associated with early wet season flow into a lake on the Mary River floodplain, tropical northern AustraliaLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 3-4 2003Simon A. Townsend Abstract The Mary River, in the Australian wet/dry tropics, flows seasonally to inundate a coastal floodplain. In the dry season, the river reduces to a series of disconnected lakes located along the main river channel. This paper examines the impact of riverine inflow, at the beginning of the wet season, on the limnology of Shady Camp Lake, and addresses broader water quality management issues. The first wet season flow of Mary River carried a high biological oxygen demand that reduced the lake's oxygen concentration. The resulting hypoxic conditions prompted fish avoidance behaviour and caused the death of at least 200 fish. There is no evidence of any direct anthropogenic pollution causing the event. After reaching near anoxic conditions, dissolved oxygen concentrations recovered several weeks later, although they remained low. The water quality of the Mary River was characterized by an initial pulse of water with high concentrations of organic carbon, suspended particulate material, colour, total nitrogen and total phosphorus. Phytoplankton biomass, measured as chlorophyll a, did not increase because of nitrogen limitation attributed to low nitrate and ammonia concentrations in the inflow waters. The low concentrations of available nitrogen were probably a result of denitrification, which would have been enhanced by the warm temperatures and low oxygen concentrations. The oxygen sag in Shady Camp Lake caused by the inflow of the Mary River exemplifies the vulnerability of floodplain channel lakes to riverine waters and underscores the need to manage catchment practices to minimize the concentration of labile organic material in the river and its associated oxygen demand. [source] Comparative Cellular Morphology Suggesting the Existence of Resident Dendritic Cells Within Immune Organs of SalmonidsTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 4 2008Jan Lovy Abstract This report is the first morphological description of cells that resemble dendritic cells, which appear to form resident populations within the spleen and anterior kidney of fish. Based on examination of three salmonid species, including, rainbow trout, brook trout, and Atlantic salmon, the cells were most abundant in the spleen, although they were always present in the anterior kidney. The cells appeared diffusely distributed, often near blood vessels of the spleen and kidney of healthy fish and within the epithelium, connective tissue, and blood vessels of rainbow trout gills with experimentally induced microsoporidial gill disease. The dendritic-like cells in this study contained granules that resemble Birbeck granules, which are considered to be morphological markers of Langerhans cells in mammals. The cells were approximately 6 ,m in diameter and contained Birbeck-like (BL) granules localized near centrioles. Although the dendritic-like cells in the three salmonid species shared many similarities, morphological differences were found in the fine structure of the rod portion of the BL granules. Rainbow trout BL granules contained amorphous material, while the other salmonid species contained particulate material arranged in a square-lattice arrangement. The BL granules in the cells of Atlantic salmon had a narrow diameter and contained four layers of particulate material when sectioned longitudinally; two layers enveloped by the granule membrane and two central layers making up a central lamella, which is common in mammalian Birbeck granules. Anat Rec, 291:456,462, 2008. © 2008 Wiley-Liss, Inc. [source] Geochemical changes in white seabream (Diplodus sargus) earth ponds during a production cycleAQUACULTURE RESEARCH, Issue 15 2007Dalila Serpa Abstract The knowledge of geochemical processes in fishponds is important in defining farming strategies and the carrying capacity of these systems, and is therefore essential for the management and sustainability of semi-intensive aquaculture in earth ponds. The main purpose of the present work, developed in the Aquaculture Research Station located in Ria Formosa, was to study the geochemical changes in semi-intensive earth ponds of white seabream Diplodus sargus L. during a production cycle, and relate it to farming conditions (fish biomass and feeding rate). Settled material and sediment samples were collected in a fish production pond and in a non-fish production pond during 2 years. The results obtained showed that particle-settling rates (S, g m,2 day,1) increased linearly with time (t, days): S=0.7t,34, in the fishpond. Increasing deposition of particulate material increased the organic matter content of bottom sediments, particularly during the second production year. Organic matter mineralization, during periods of high temperatures, led to high nutrient concentrations in porewater (NH4+, 965 ,M; NO3,, 40 ,M; HPO42,, 39 ,M) and subsequently to an increase in benthic primary production in the fishpond. The geochemical similarities between fishpond sediments and shallow coastal system's sediments, along with the high fish survival rate (94%), suggest that for the assayed farming conditions there were no environmental constraints within the pond. However, some impact on bottom sediments, namely, an increase in settled material, organic matter deposition, nutrients in porewater and microphytobentos production, was evident above a fish biomass of 500 g m,3 and a feeding rate of 150 kg month,1, indicating that pond environmental conditions should be carefully monitored from this point on. [source] Growth and survival of the scallop Lyropecten (=Nodipecten) nodosus (L. 1758) in suspended culture in the Cariaco Gulf (Venezuela) during a non-upwelling periodAQUACULTURE RESEARCH, Issue 9 2003L Freites Abstract Growth and survival of the scallop Lyropecten nodosus were studied in 1997 at two sites (inner and outer Turpialito Bay) during a non-upwelling period normally occurring between August and November. Individuals had an initial shell height of 4.86 cm (SD=1.64 cm). Both experimental groups were held in suspended plastic baskets at the same depth (4 m). Measurements of shell height and dry weights of shell, gonad, digestive gland, remaining tissues and shell biofouling were taken at monthly intervals. Environmental parameters, including temperature, phytoplanktonic biomass, total particulate material (TPM) and associated organic (POM) and inorganic (PIM) fractions, were recorded simultaneously. At the end of the study, significant differences in growth and survival of scallops were observed between the two experimental sites. Scallops maintained inside the bay showed a 22% greater increase in shell height (7.41±0.27 cm) than those placed outside the bay (6.37±0.41 cm). Survival of scallops inside the bay was 31% higher compared with scallops outside. The greater availability of food of phytoplanktonic origin during the first two experimental months (July and August) together with greater POM throughout the whole experimental period except September, at the inner bay site, probably explained survival and growth differences observed between the two locations. Results suggest that, during the non-upwelling period (characterized by low primary productivity and high water temperatures), POM of sedimentary origin may play an important role as an energy source required for metabolic and reproductive activities of L. nodosus. [source] The feeding behavior of Trichogramma brassicae: new evidence for selective ingestion of solid foodENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2000Z.X. Wu Abstract A descriptive study of the feeding behavior and structures of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was conducted. Based on direct observational and biochemical evidence, larvae feed predominantly on particulate materials, starting ca. 25 h post-oviposition. Feeding lasted for ca. 9 h, at 25±1 °C. During this feeding period the shape of the larvae changed from vermiform to pyriform and then to sacciform, resulting in a ca. 40-fold increase in body size. Larvae used elaborate feeding behaviors as they pulled solid food particles to their oral opening, broke small particles from larger ones, and took the particles into the stomodaeum, which is a powerful pump. In the stomodaeum, peristaltic movement further macerated the particles, which eventually passed through the cardiac valve into the midgut. As indicated by changes in fluorescently labeled casein, digestive enzymes aid in the extra-oral chemical digestion of food. The contents of the gut, during and shortly after feeding, were almost entirely closely packed solid particles. The behavioral activity of feeding larvae centered almost exclusively on processing and ingesting solid food particles. The rapid larval growth is much more plausibly explained by their feeding on the highly concentrated nutrients found in solid foods, rather than the extensive concentration required if dilute liquids were the principal source of nutrients. The implications of these findings for the development of practical artificial diets are discussed. [source] The implications of solar UV radiation exposure for fish and fisheriesFISH AND FISHERIES, Issue 3 2001Horacio E Zagarese Abstract Ultraviolet radiation (UVR) possesses three important properties that combine to make it a potent environmental force. These include the potential to induce damage: UVR carries more energy per photon than any other wavelength reaching the Earth's surface. Such highly energetic photons are known to damage many biological molecules, such as DNA and proteins. In addition, they can initiate a series of redox reactions to form reactive oxygen species (ROS), which cause oxidative stress to cells and tissues. The second property is ubiquity: owing to their dependence on light, primary producers and most visual predators, such as fish, are also necessarily exposed to damaging levels of UVR. Thirdly, the combined effect of UVR and additional environmental factors may result in synergistic effects, such as the photoactivation of organic pollutants and photosensitisation. In natural environments, the concentration of dissolved organic matter (DOM) and habitat depth are the two main factors controlling the degree of UVR exposure experienced by fish. Additional factors include vegetation coverage, particulate materials in suspension, pH and hydrological characteristics, and site location (latitude, elevation). The range of potential effects on fish includes direct DNA damage resulting in embryo and larval mortality, and adult and juvenile sunburn, as well as indirect oxidative stress, phototoxicity and photosensitisation. [source] Development of Cu and Zn Isotope MC-ICP-MS Measurements: Application to Suspended Particulate Matter and Sediments from the Scheldt EstuaryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2008Jérôme C.J. Petit isotopes de Cu et Zn; interférences spectrales et non spectrales; fractionnement de masse instrumental; MC-ICP-MS; sédiments The present study evaluates several critical issues related to precision and accuracy of Cu and Zn isotopic measurements with application to estuarine particulate materials. Calibration of reference materials (such as the IRMM 3702 Zn) against the JMC Zn and NIST Cu reference materials were performed in wet and/or dry plasma modes (Aridus I and DSN-100) on a Nu Plasma MC-ICP-MS. Different mass bias correction methods were compared. More than 100 analyses of certified reference materials suggested that the sample-calibrator bracketing correction and the empirical external normalisation methods provide the most reliable corrections, with long term external precisions of 0.06 and 0.07, (2SD), respectively. Investigation of the effect of variable analyte to spike concentration ratios on Zn and Cu isotopic determinations indicated that the accuracy of Cu measurements in dry plasma is very sensitive to the relative Cu and Zn concentrations, with deviations of ,65Cu from ,0.4, (Cu/Zn = 4) to +0.4, (Cu/Zn = 0.2). A quantitative assessment (with instrumental mass bias corrections) of spectral and non-spectral interferences (Ti, Cr, Co, Fe, Ca, Mg, Na) was performed. Titanium and Cr were the most severe interfering constituents, contributing to inaccuracies of ,5.1, and +0.60, on ,68/64Zn, respectively (for 500 ,g l,1 Cu and Zn standard solutions spiked with 1000 ,g l,1 of Ti or Cr). Preliminary isotopic results were obtained on contrasting sediment matrices from the Scheldt estuary. Significant isotopic fractionation of zinc (from 0.21, to 1.13, for ,66Zn) and copper (from ,0.38, to 0.23, for ,65Cu), suggest a control by physical mixing of continental and marine water masses, characterized by distinct Cu and Zn isotopic signatures. These results provide a stepping-stone to further evaluate the use of Cu and Zn isotopes as biogeochemical tracers in estuarine environments. L'étude présentée ici porte sur l'évaluation critique d'un certain nombre de paramètres contrôlant la précision et la justesse des mesures des isotopes de Cu et Zn, dans le cadre d'une application à du matériel particulaire estuarien. Une calibration de matériaux de référence (tels que le Zn IRMM 3702) par rapport aux matériaux de référence JMC Zn et NIST Cu a été effectuée avec des plasmas humides et secs (avec Aridus I et DSN-100) sur un MC-ICP-MS Nu. Différentes méthodes de correction de biais de masse ont été comparées. Plus de 100 analyses de matériaux de référence certifiés ont montré que la correction par l'intercalation d'un calibrateur entre chaque échantillon et la calibration externe empirique fournissaient les corrections les plus fiables, avec des précisions externes sur le long terme de 0.06 et 0.07, (2SD) respectivement. Les effets de la variation des rapports de concentrations entre analyte et spike sur les mesures des rapports isotopiques de Cu et Zn ont montré que la justesse des mesures pour Cu en plasma sec est très tributaire des concentrations relatives de Cu et Zn, avec des déviations de ,65Cu allant de ,0.4, (Cu/Zn = 4) à+0.4, (Cu/Zn = 0.2). Une estimation quantitative des interférences spectrales et non spectrales (Ti, Cr, Co, Fe, Ca, Mg, Na) a été faite. Ti et Cr se sont révélés être les constituants interférents les plus importants pouvant entraîner des erreurs de ,5.1, et +0.60, sur ,68/64Zn respectivement (pour des solutions standards à 500 ,g l,1 de Cu et Zn dopées avec 1000 ,g l,1 de Ti ou Cr). Des données isotopiques préliminaires ont été obtenues sur des matrices sédimentaires très différentes provenant de l'estuaire de Scheldt. Les fractionnements significatifs du zinc (de 0.21,à 1.13, pour ,66Zn) et du cuivre (de ,0.38,à 0.23, pour ,65Cu) suggèrent un contrôle par un processus physique de mélange entre des masses d'eaux continentales et marines ayant des signatures isotopiques de Cu et Zn distinctes. Ces résultats constituent un tremplin vers une utilisation future des isotopes de Cu et Zn comme traceurs biogéochimiques des environnements estuariens. [source] Hydrological and biogeochemical processes in a changing Amazon: results from small watershed studies and the large-scale biosphere-atmosphere experimentHYDROLOGICAL PROCESSES, Issue 12 2006Christopher Neill Abstract The Amazon Basin is the world's largest tropical forest region and one where rapid human changes to land cover have the potential to cause significant changes to hydrological and biogeochemical processes. The Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is a multidisciplinary, multinational research program led by Brazil. The goal of LBA is to understand how the Amazon Basin functions as a regional entity in the earth system and how these functions are changing as a result of ongoing human activity. This compilation of nine papers focuses on a central LBA question in the area of nutrient dynamics and surface water chemistry,how do changes in land use alter fluxes of dissolved and particulate materials from uplands across riparian zones and down the channels of river corridors? These papers cover work conducted in small watersheds on a wide range of topics within the spirit and geographical focus area of LBA: water balance and runoff generation, nutrient transformations in riparian zones and stream channels, carbon fluxes in water moving from land to water and the influence of soils on flowpath structure and stream chemistry. Important new insights can be gained from these and other studies. Forest clearing for pastures results in a decrease in soil hydraulic conductivity that forces water into surficial flowpaths throughout most of the rainy season across wide regions of the Amazon. Riparian zones along small forest streams appear to be very effective in removing nitrate arriving from the uplands, while forest streams take up nitrate at very low rates, allowing them to travel downstream for long distances. Although substantial, the contribution of dissolved organic C (DOC) to the carbon flux from forests to streams appears to be lower than the flux of dissolved inorganic C that is subsequently outgassed as CO2. Remaining key challenges within LBA will be to synthesize existing data sets on river networks, soils, climate, land use and planned infrastructure for the Amazon to develop models capable of predicting hydrologic and biogeochemical fluxes at a variety of scales relevant to the development of strategies for sustainable management of the Amazon's remarkable forest, soil and freshwater resources. Copyright © 2006 John Wiley & Sons, Ltd. [source] Discrete element method for modelling solid and particulate materialsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2007Federico A. Tavarez Abstract The discrete element method (DEM) is developed in this study as a general and robust technique for unified two-dimensional modelling of the mechanical behaviour of solid and particulate materials, including the transition from solid phase to particulate phase. Inter-element parameters (contact stiffnesses and failure criteria) are theoretically established as functions of element size and commonly accepted material parameters including Young's modulus, Poisson's ratio, ultimate tensile strength, and fracture toughness. A main feature of such an approach is that it promises to provide convergence with refinement of a DEM discretization. Regarding contact failure, an energy criterion based on the material's ultimate tensile strength and fracture toughness is developed to limit the maximum contact forces and inter-element relative displacement. This paper also addresses the issue of numerical stability in DEM computations and provides a theoretical method for the determination of a stable time-step. The method developed herein is validated by modelling several test problems having analytic solutions and results show that indeed convergence is obtained. Moreover, a very good agreement with the theoretical results is obtained in both elastic behaviour and fracture. An example application of the method to high-speed penetration of a concrete beam is also given. Copyright © 2006 John Wiley & Sons, Ltd. [source] Mechanics of column beds: I. Acquisition of the relevant parametersAICHE JOURNAL, Issue 3 2003Bee Gaik Yew The efficiency of chromatographic columns is adversely affected by large-scale radial variations of the packing density or void ratio of the material used to prepare the bed. This heterogeneity is due to wall friction effects that take place during the preparation of the column and to seepage effects operating during the packing process and the subsequent operation of the column. The dependence of the bed's void fraction on the stress applied during its consolidation was determined, as well as its permeability at various stages of the consolidation process and the coefficient of friction between typical packing materials and the stainless steel wall of chromatographic columns. These results are required to develop and use numerical models of the volumetric response to axial compression of the bed and models of the coupled mechanical-seepage rheology of particulate materials. [source] Physical Modeling and Electrodynamic Characterization of Dielectric Slurries by Impedance Spectroscopy (Part II)JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Vladimir Petrovsky Electrical characterization of dielectric slurries, as 0,3 composite systems, can provide valuable information on the dielectric properties of suspended particles. A new approach developed in our laboratory is based on impedance spectroscopy measurements of the slurries containing dispersed dielectric powders. Dielectric constants of the particles are determined through analysis of the low-frequency section of the impedance spectra. It was shown previously that this approach allows accurate and reliable measurement of dielectric constant of particles (,: ,100,2000) using host liquids (,: ,10,65). This study addresses the validation of this new method with physical model experiments using millimeter-sized sintered BaTiO3 model samples suspended in the liquid. Impedance spectra of barium titanate powder slurries were compared with the spectra of the model samples containing macroscopic cubes prepared by sintering of the same starting powder. This comparison shows a good agreement between the impedance spectra of powder and bulk BaTiO3 and validates the reliability of the new method to determine the dielectric constant of particulate materials. [source] Effect of cigarette smoke extract on the polymorphonuclear leukocytes chemiluminescence: influence of a filter containing glutathioneLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 2 2005B. Zappacosta Abstract Cigarette smoking is known to be a risk factor for several chronic and neoplastic diseases. Many compounds formed by cigarette burning, ranging from particulate materials to water solutes and gaseous extracts, are considered to be noxious agents, and many biochemical and molecular mechanisms have been proposed for the toxic effects of cigarette smoke. The oral cavity and the upper respiratory tract represent the first contact areas for smoke compounds; even a single cigarette can produce marked effects on some components of the oral cavity, either chemical compounds, such as glutathione and enzymes, or cellular elements, such as polymorphonuclear leukocytes. Several studies suggest a protective role of glutathione against the noxious effects of tobacco smoke; the sulphydril groups of glutathione, in fact, could react with some smoke products, such as unsaturated aldehydes, leading to the formation of harmless intermediate compounds and simultaneously preventing the inactivation of metabolically essential molecules, such as some enzymes. In this paper we analyse the effect of a filter containing glutathione on the respiratory burst of polymorphonuclear leukocytes exposed to aqueous extract of cigarette smoke, measuring their chemiluminescence activity. The results of this paper indicate that the GSH--containing filter has a likely protective effect against the inhibition of cigarette smoke extract on polymorphonuclear leukocyte activity. Copyright © 2005 John Wiley & Sons, Ltd. [source] An evaluation of the solid hold-up distribution in a fluidized bed of nanoparticles using radioactive densitometry and fibre opticsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2008Babak Esmaeili Abstract An experimental study was conducted to assess the solid hold-up distribution in a fluidized bed of zirconia and aluminum nanoparticles. For this purpose, two different techniques, radioactive densitometry and fibre optic measurement, were used. The results showed that while the fluidization of these nanoparticles occurs in the agglomeration state, it performs homogeneously in terms of phase concentration. This matter is important especially when a polymerization reaction should take place uniformly on the surface of nanoparticles, where the monomer is the fluidizing gas. Both techniques presented uniform solid hold-up distribution over the cross-section, although the fibre optic method overestimated the overall solid concentration, which was obtained based on bed expansion results. The radioactive densitometry was, however, capable of properly predicting the phase concentration within the bed according to the bed expansion observation. Finally, the effect of bulk density on the fluidization of nanoparticles was discussed by comparing the fluidization of different types of particulate materials. On a mené une étude expérimentale pour évaluer la distribution de rétention de solide dans un lit fluidisé de nano particules de zircon et d'aluminium. À cette fin, deux techniques différentes, la densimétrie radioactive et la mesure par fibres optiques, ont été utilisées. Les résultats montrent qu'alors que la fluidisation de ces nano particules survient à l'état d'agglomération, elle est relativement performante en termes de concentration de phase. Cet aspect est important, car une réaction de polymérisation devrait se produire uniformément à la surface des nano particules, le monomère étant le gaz fluidifiant. Les deux techniques ont mis en évidence une distribution de rétention de solide uniforme dans la section transversale, bien que la méthode par fibres optiques ait surestimé la concentration de solide globale, obtenue à partir des résultats d'expansion du lit. Cependant, la densimétrie radioactive est capable de prédire de manière correcte la concentration de phase dans le lit d'après l'observation de l'expansion de lit. Enfin, l'effet de la masse volumique apparente sur la fluidisation des nano particules est examiné en comparant la fluidisation de différents types de matériaux particulaires. [source] Formation of Biofilm on Different Particulate Media Using Modified Kitchen Waste Extract as Initial Growth Substrate for Use in PCB DegradationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2005J. Auresenia Abstract This study describes the formation of biofilm on two different particulate media using modified kitchen waste extract as initial growth medium, and the subsequent testing of the this biofilm to biodegrade polychlorinated biphenyls (PCBs). Two parallel completely mixed fluidized bed reactors, one using cement balls and the other using sand as particulate media, were operated in order to produce the biofilm. Modified kitchen waste extract was used as a growth substrate instead of the more expensive complex substrate. The medium was inoculated with microorganisms from tannery wastes. Performance of the biofilms formed in the two reactors were compared based on BOD and COD degradation rates, biomass growth rate, biofilm thickness and ease offluidization. The results demonstrate that a stable biofilm can be formed on readily available particulate materials using cheap substrate from kitchen wastes extracts. Furthermore, cement balls proved to be more suitable as particulate media compared to sand, possessing superior biofilm-forming characteristics. The biofilm formed on cement balls was tested for the degradation of PCBs. Initial PCB batch degradation tests showed that about 70% of PCBs degraded within six hours. Kinetics of PCB degradation followed the Monod model with Km = 561.98 mg/l and m,max=0.07 1/h. [source] | |||||||||||||||||||