Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Suspension

  • alumina suspension
  • bacterial suspension
  • batio3 suspension
  • bentonite suspension
  • calcium hydroxide suspension
  • cell suspension
  • ceramic suspension
  • clay suspension
  • colloidal suspension
  • concentrated suspension
  • conidial suspension
  • dense suspension
  • homogeneous suspension
  • hydroxide suspension
  • insulin lispro protamine suspension
  • lispro protamine suspension
  • magnetic suspension
  • nanoparticle suspension
  • oral suspension
  • particle suspension
  • protamine suspension
  • pulp suspension
  • single cell suspension
  • single-cell suspension
  • soil suspension
  • solid suspension
  • spore suspension
  • stable suspension
  • tail suspension
  • water suspension
  • yeast suspension

  • Terms modified by Suspension

  • suspension array
  • suspension bridge
  • suspension cell
  • suspension copolymerization
  • suspension culture
  • suspension feeder
  • suspension flow
  • suspension laryngoscopy
  • suspension polymerization
  • suspension suture
  • suspension system
  • suspension test

  • Selected Abstracts


    Keith O. Keplinger
    ABSTRACT: In early 1997, the Texas Edwards Aquifer Authority implemented a pilot Irrigation Suspension Program with the objectives of increasing springflow and providing relief to municipalities during drought. Irrigators were paid an average of $234 per acre to suspend water use, a price higher than regional land rental rates. Auction theory and program implementation details suggest that the program implementation partially caused inflated bids. The Irrigation Suspension Program is also compared to two alternative programs: (1) subsidizing more efficient irrigation technology and (2) buying land. The irrigation suspension is found to be more cost-effective relative to subsidizing improved irrigation efficiency because it can be put in place only when aquifer levels are low. Land purchase is a cheaper alternative if the bid levels remain at the levels observed. [source]


    ABSTRACT Three different techniques were applied to determine particle size distribution (PSD) of cloudy apple juice: sedimentation-photometry (S-F), scanning electron microscopy (SEM) and photon correlation spectroscopy (PCS). All the three techniques found particles in a range from about 0.05 to 3 micrometers (,m = 10,6m). While calculation of PSD by SEM was based on particle number, calculation of PSD by PCS and S-F were based on intensity of scattered light, and both weight (or volume) and projected area (or absorbed light), respectively. In order to compare results from these techniques, appropriate equations were used to convert distributions from one base to another. Three characteristic diameters were also obtained from each distribution: mean, median and modal. Characteristic diameters range from 0.88 to 2.50 ,m in weight basis, 0.77 to 2.50 ,m in projected area basis and 0.08 to 0.23 ,m in number basis. Differences between these diameters were due to asymmetry in the distributions. [source]

    Measurement and data analysis methods for field-scale wind erosion studies and model validation,

    Ted M. Zobeck
    Abstract Accurate and reliable methods of measuring windblown sediment are needed to con,rm, validate, and improve erosion models, assess the intensity of aeolian processes and related damage, determine the source of pollutants, and for other applications. This paper outlines important principles to consider in conducting ,eld-scale wind erosion studies and proposes strategies of ,eld data collection for use in model validation and development. Detailed discussions include consideration of ,eld characteristics, sediment sampling, and meteorological stations. The ,eld shape used in ,eld-scale wind erosion research is generally a matter of preference and in many studies may not have practical signi,cance. Maintaining a clear non-erodible boundary is necessary to accurately determine erosion fetch distance. A ,eld length of about 300 m may be needed in many situations to approach transport capacity for saltation ,ux in bare agricultural ,elds. Field surface conditions affect the wind pro,le and other processes such as sediment emission, transport, and deposition and soil erodibility. Knowledge of the temporal variation in surface conditions is necessary to understand aeolian processes. Temporal soil properties that impact aeolian processes include surface roughness, dry aggregate size distribution, dry aggregate stability, and crust characteristics. Use of a portable 2 tall anemometer tower should be considered to quantify variability of friction velocity and aerodynamic roughness caused by surface conditions in ,eld-scale studies. The types of samplers used for sampling aeolian sediment will vary depending upon the type of sediment to be measured. The Big Spring Number Eight (BSNE) and Modi,ed Wilson and Cooke (MWAC) samplers appear to be the most popular for ,eld studies of saltation. Suspension ,ux may be measured with commercially available instruments after modi,cations are made to ensure isokinetic conditions at high wind speeds. Meteorological measurements should include wind speed and direction, air temperature, solar radiation, relative humidity, rain amount, soil temperature and moisture. Careful consideration of the climatic, sediment, and soil surface characteristics observed in future ,eld-scale wind erosion studies will ensure maximum use of the data collected. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Fabrication of Al2O3/SiC Composite Microcomponents using Non-aqueous Suspension,

    Hany Hassanin
    This paper introduces a new process for fabrication of high resolution Al2O3/SiC composite microcomponents using softlithography and non-aqueous ceramic suspension. Polysilazane is used to provide both binding force and SiC composition. The shape retention and dimensions of the microcomponents were analyzed using a scanning electron microscope. Surface roughness, shrinkage, and density of the resultant sintered components were also discussed. [source]

    Relationship between stump treatment coverage using the biological control product PG Suspension, and control of Heterobasidion annosum on Corsican pine, Pinus nigra ssp. laricio

    FOREST PATHOLOGY, Issue 1 2008
    K. V. Tubby
    Summary The relationship between the proportion of the stump surface covered by the biological stump treatment agent PG Suspension, containing Phlebiopsis gigantea and its efficacy against the pathogen Heterobasidion annosum sensu stricto was studied during a first thinning of Corsican pine (Pinus nigra ssp. laricio) in Thetford Forest, UK. PG Suspension was manually applied to 100%, 75%, 50% or 0% of the surface of 150 stumps. Spores of H. annosum were inoculated onto 75 of the stumps, and the remaining stumps exposed to natural airborne spore deposition. The relationship between coverage and efficacy was found to be quantitative. Covering all the stump surface with PG Suspension completely excluded the pathogen, whereas stumps not treated with PG Suspension (the 0% treatment) became infected with H. annosum. Partial (75%) PG Suspension coverage resulted in the pathogen colonizing 40% of stumps following artificial inoculation with H. annosum, and just 7% of stumps exposed to ambient H. annosum spore infection. Decreasing levels of coverage allowed increasing areas of the stump surface to be colonized by H. annosum. Some small gaps in coverage were closed by lateral growth of P. gigantea, but it is recommended that operators aim for full stump coverage to give complete protection against H. annosum. [source]

    Photocatalytic Selective Oxidation of 4-Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home-Prepared Titanium Dioxide Catalyst

    Giovanni Palmisano
    Abstract The photocatalytic oxidation of 4-methoxybenzyl alcohol to p -anisaldehyde (PAA) was performed in water with organic-free suspensions of home-prepared and commercial titanium dioxide (TiO2) catalysts. The nanostructured TiO2 samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl4), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4-methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5,% mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116,%. A comparison with two commercial TiO2 samples showed that all the home-prepared catalysts exhibited a PAA yield higher than that of commercial ones. The only by-products present were traces of 4-methoxybenzoic acid and aliphatic products, carbon dioxide being the other main oxidation product. [source]


    ABSTRACT Peach pulp preserved by different methods, i.e., processing at 100C for 30 min, potassium metabisulphite (KMS; 2,000 ppm), sodium benzoate (750 ppm) and mixture of KMS and sodium benzoate (1,000 and 375 ppm) had no significant effect on total soluble solids (TSS), acidity, TSS : acid ratio, pH of carbonated as well as noncarbonated beverages. Carbonated beverages prepared from pulp with 750 ppm of sodium benzoate retained significantly (P , 0.05) higher carbon dioxide (CO2) content and CO2 gas : volume during storage. Color of the beverages prepared from peach pulp containing KMS was better but the beverages prepared from peach pulp preserved by processing and addition of sodium benzoate were organoleptically more acceptable. Both carbonated and noncarbonated drinks remained organoleptically acceptable throughout storage. Suspension of carbonated beverages was significantly (P , 0.05) higher during storage as compared with noncarbonated beverages. PRACTICAL APPLICATIONS Peaches are valued as a table fruit for a short period of time from end of April to end of May. The acceptability and utilization of this fruit can be increased by processing it into delicious carbonated and noncarbonated beverages. This will provide nutritious drink to the consumers and also help in increasing the fruit cultivation resulting in good returns to the growers. This study will also help to give a fillip to the establishment of a peach beverage industry world wide. [source]

    Suspension of Deportation Hearings and Measures of "Americanness"

    Susan Bibler Coutin
    Una forma de identificar las características que, según las autoridades y la ley, el ciudadano ideal debe de tener es estudiar casos de inmigración en corte. Por medio de observar la preparatión de tales casos, entrevistar a abogados y solicitantes, y asistir a audiencias en la corte federal de inmigración en Los Angeles, se analiza estas características. La investigatión se enfoca en los casos conocidos como "suspensión de deportatión". Para ganar, el solicitante tiene que haber vivido en los Estados Unidos por siete años, mostrar buen caracter moral y probar que deportation causarfa un dafio extremo al aplicante o a un pariente del aplicante. El anãlisis indica que, aunque no se menciona la raza ni la etnicidad del solicitante, las características preferidas se basan en la cultura anglosajóna, lo cual promueve un modelo anglosajón del cuidadano ideal. Por eso, aún cuando se ganan los casos, la ley impone requisitos que perjudican a ciertos sectores de la población. [source]

    Suspension of high concentration slurry

    AICHE JOURNAL, Issue 6 2002
    Jie Wu
    First page of article [source]

    Measurement of Horizontal and Vertical Movement of Ralstonia solanacearum in Soil

    M. Satou
    Abstract Two model systems were constructed to measure horizontal and vertical movement of bacteria in soil. These systems were applied to measuring movement of Ralstonia solanacearum (race 1, biovar 3), a causal agent of bacterial wilt of tomato, in andosol and sand at 28°C. The first system was used to measure horizontal movement of the bacteria in soil packed in a narrow horizontal frame. Suspension of the pathogen was applied to soil at one end of the frame, and bacterial number per gram of soil was measured over distance from the inoculation point after 4 days. Horizontal movement of R. solanacearum in supersaturated soil, but without flow, was possibly due to diffusion and the front advanced at 2.2 cm/day in andosol, and at 8.1 cm/day in sand. Using the same experimental system, but applying water inflow to one end of the frame only, the bacterium was detected at the front of water in andosol and sand. The front of the distribution advanced at 20.4 cm/h in andosol and 66.3 cm/h in sand. In the second experimental system, a cylinder of soil packed in a short tube was soaked with water, and soil at the top of the tube was inoculated with bacterial suspension. Immediately, soil cylinders were turned upward, and the bacterial number per gram of soil was measured along vertical distance from the inoculation point after 7 days. Using the system with andosol, the capillary water front rose to 32.5 cm over 7 days after inoculation, and R. solanacearum reached to 18.8 cm height. In sand, capillary water rose to 20.0 cm and the bacteria reached to 16.3 cm height. [source]

    Kierkegaard's Teleological Suspension is Not a Bridge in Madison County

    Sheridan Hough
    First page of article [source]

    Room-Temperature Degradation of t -Zr(Pr)O2 in an Aqueous Suspension Revealed by Perturbed Angular Correlations

    María C. Caracoche
    This paper deals with the phase stability of an aqueous suspension of tetragonal Zr0.9Pr0.1O2 (20 wt%/vol%) at room temperature as a function of the aging time. The suspension is investigated in situ using the highly localized Perturbed Angular Correlations technique. The results indicate that an almost fully reversible degradation process toward monoclinic zirconia takes place through a first-order reaction of rate constant k=0.7 day,1. Two successive diffusion mechanisms are observed that are interpreted as OH, ions' migration in the grain surface and then, as proton defects' diffusion into the bulk. [source]

    Preparation of a Monodispersed Suspension of Barium Titanate Nanoparticles and Electrophoretic Deposition of Thin Films

    Juan Li
    A transparent and stable monodispersed suspension of nanocrystalline barium titanate was prepared by dispersing a piece of BaTiO3 gel into a mixed solvent of 2-methoxyethanol and acethylacetone. The results of high-resolution transmission electron microscopy (HR-TEM) and size analyzer confirmed that the BaTiO3 nanoparticles in the suspension had an average size of ,10 nm with a narrow size distribution. Crystal structure characterization via TEM and X-ray diffraction indicated BaTiO3 nanocrystallites to be a perovskite cubic phase. BaTiO3 thin films of controlled thickness from 100 nm to several micrometers were electrophoretic deposited compactly on Pt/Ti/SiO2/Si substrates. The deposited thin film had uniform nanostructure with a very smooth surface. [source]

    Synthesis and Electrorheological Characterization of Polyaniline/Barium Titanate Hybrid Suspension

    Fei Fei Fang
    Abstract As organic/inorganic composites having attracted much attention due to their heterogeneous physical properties, conducting polyaniline (PANI) and barium titanate (BaTiO3) which possesses large electronic resistance and excellent dielectric strength, were utilized to synthesize PANI/BaTiO3 hybrid which is applicable for an electrorheological (ER) material via ,in-situ' oxidative polymerization. Physical properties of the obtained PANI/BaTiO3 composites were characterized via Fourier-transform infrared spectra (FT-IR), thermogravimetry analysis (TGA), and scanning electron microscopy (SEM). The ER behaviors were investigated via a rotational rheometer, and their shear stresses were fitted using our previously proposed rheological equation of state. [source]

    Suspension of Particles from the Bottom of Pipes and Stirred Tanks by Gassed and Ungassed Flows

    Rex B. Thorpe
    Abstract Widely accepted correlations and theoretical predictions for hydraulic conveying of solids in pipelines are compared with the literature on the suspension of particles in stirred tanks. Good agreement is found between the correlations and the theoretical predictions both within and between the two fields of study. The effect on the suspension velocity of introducing gas into the pipe and the stirred tank is remarkably similar. In both cases, the shear stress remains broadly unchanged when gas is added. Since the effect of the addition of gas on shear stress is quite well understood in both cases, this is a helpful result. Des corrélations et des prédictions théoriques largement acceptées pour le convoyage hydraulique de solides dans des conduites sont comparées à des données de la littérature scientifique sur la suspension des particules dans des réservoirs agités. Un bon accord est trouvé entre les corrélations et les prédictions théoriques dans et entre les deux champs d'étude. L'effet sur la vitesse de suspension de l'introduction de gaz dans la conduite et le réservoir agité est remarquablement similaire. Dans les deux cas, la contrainte de cisaillement reste largement inchangé lorsqu'il y a ajout de gaz. Ce résultat est utile car l'effet de l'ajout de gaz sur la contrainte de cisaillement est assez bien compris dans les deux cas. [source]

    The Effect of Adding Phosphate on the Size of Extremely Fine Needle-like Lepidocrocite Particles Prepared by Oxidizing an Aqueous Suspension of Ferrous Hydroxide

    Naoki Mihara
    Abstract Extremely fine particles of needle-like lepidocrocite (,-FeOOH) were synthesized by the oxidation of aqueous suspensions of ferrous hydroxide using a bubble column with draft tube at a constant temperature of 30°C, and the effects of the reaction conditions or the oxidation rate were investigated in order to determine the parameters that control the particle size. When the concentration of oxygen in the feed stream was varied under a constant gas velocity, the mean size based on the major axis of a needle-like particle decreased from 0.7 µm to 0.4 µm with increasing oxidation rate. By adding of NaH2PO4 to an aqueous Fe(OH)2 suspension, in concentrations up to 1.0 mol/m3 during the air oxidation, and up to 0.9 mol/m3 during the oxidation with 30% and 50% O2, the major axis could be reduced to ca. 0.3 µm with the minor axis and the oxidation rate remained almost unchanged. Des particules extra fines de lépidocrocite en forme d'aiguilles (,-FeOOH) ont été synthétisées par oxydation de suspensions aqueuses d'hydroxide ferreux à l'aide d'une colonne munie d'un tube d'aspiration à une température constante de 30°C et on a étudié les effets des conditions de réaction et de la vitesse d'oxydation afin de déterminer les paramètres qui contrôlent la taille de particule. Lorsqu'on fait varier la concentration d'oxygène dans le courant d'alimentation à une vitesse de gaz constante, la taille moyenne basée sur l'axe principal d'une particule en forme d'aiguille diminue de 0,7 µm à 0,4 µm avec l'augmentation de la vitesse d'oxydation. En ajoutant du NaH2PO4 à une suspension aqueuse de Fe(OH)2, à des concentrations atteignant 1,0 mol/m3 lors de l'oxydation de l'air et 0,9 mol/m3 lors de l'oxydation avec 30% et 50% de O2, l'axe principal pourrait être réduit à environ 0,3 µm, l'axe secondaire et la vitesse d'oxydation demeurant presque inchangés. [source]

    Performance Characterization of a Rotary Centrifugal Left Ventricular Assist Device With Magnetic Suspension

    ARTIFICIAL ORGANS, Issue 5 2008
    Said Jahanmir
    Abstract:, The MiTiHeart (MiTiHeart Corporation, Gaithersburg, MD, USA) left ventricular assist device (LVAD), a third-generation blood pump, is being developed for destination therapy for adult heart failure patients of small to medium frame that are not being served by present pulsatile devices. The pump design is based on a novel, patented, hybrid passive/active magnetic bearing system with backup hydrodynamic thrust bearing and exhibits low power loss, low vibration, and low hemolysis. Performance of the titanium alloy prototype was evaluated in a series of in vitro tests with blood analogue to map out the performance envelop of the pump. The LVAD prototype was implanted in a calf animal model, and the in vivo pump performance was evaluated. The animal's native heart imparted a strong pulsatility to the flow rate. These tests confirmed the efficacy of the MiTiHeart LVAD design and confirmed that the pulsatility does not adversely affect the pump performance. [source]

    Zum Kontaktverhalten zwischen suspensionsgestützten Ortbetonwänden und dem anstehenden Boden

    BAUTECHNIK, Issue 11 2007
    Anna Arwanitaki Dipl.-Ing.
    Eingangsparameter für analytische und numerische Berechnungen eines Baugrubenverbaus ist der Wandreibungswinkel. Dieser beschreibt die Fähigkeit, wieviel Schubspannungen aus dem Boden an der Grenzfläche Boden,Verbauwand von der Verbauwand bei einer vorgegebenen Normalspannung aufgenommen werden können. Die national gültigen Normen und Empfehlungen geben für Berechnungen im GZ1 einen Wandreibungswinkel von |,| , ,/2 vor. Für den Nachweis der Gebrauchstauglichkeit GZ2 hat sich die Methode der Finiten Elemente etabliert. Mit zunehmender Verfeinerung der Berechnungen stellt sich somit die Frage, ob der Ansatz von |,| , ,/2 noch zutreffend ist. Bei der Herstellung von Schlitzwänden sowie von unverrohrten Bohrpfahlwänden erfolgt der Bodenaushub im Schutze einer Stützflüssigkeit aus Wasser und Bentonit. Nach Erreichen der Schlitzendtiefe wird im Kontraktorbetonverfahren die Stützsuspension von unten nach oben verdrängt. Dabei können Reste der Suspension oder des entstehenden Filterkuchens in der Kontaktfläche Boden,Verbauwand verbleiben und den Wandreibungswinkel beeinflussen. In-situ-Proben des Filterkuchens einer Schlitzwandbaugrube zeigten, dass die Filterkuchenfestsubstanz ein Gemisch aus Bentonit und dem anstehenden Boden ist. Durch die Aushubarbeiten vermischt sich der anstehende Boden mit der Suspension, wobei die feinen Kornfraktionen durch die Fließgrenze der Suspension in Schwebe gehalten werden. Der durch den Filtrationsprozess an der Erdwandung entstehende Filterkuchen kann daher nicht mehr als Schmierschicht aus Bentonit bezeichnet werden, sondern besitzt eine beachtliche Scherfestigkeit. Dieser Beitrag stellt Ergebnisse von Baustellen- und Laboruntersuchungen zur Beschaffenheit des Filterkuchens und zur Ermittlung des Kontaktverhaltens des Boden-Schlitzwand-Systems vor. Skin friction of cast-in-place walls. Analytical and numerical calculations of retaining structures require the wall friction angle as an input parameter. It is specified as the maximal shear strength of the concrete-soil interface due to normal effective load. For the design of diaphragm walls the national engineering standards recommend an angle of wall skin friction of |,| , ,/2. In the framework of present design numerical calculations are performed to determine the deformation behaviour of structures, so that the contact formulation becomes fundamental. Bentonite suspensions are used to support the sides of excavation for diaphragm walls and uncased cast-in-place piles. When concrete is cast by tremie methods the filter cake remains adhering on side walls and becomes part of the concrete-soil interface and influences the characteristics of wall skin friction. In-situ specimens of the filter cake were taken from a diaphragm wall and examinations reveal that the filter cake consists of bentonite and fine soil particles. Due to the excavation process fine particles from the soil are suspended into the supporting fluid due to the liquid limit of the bentonite slurry. Thus, the suspension, in a process of filtration into the surrounding soil, forms a filter cake with a certain shear strength caused by the fine soil particles. This paper presents the results of field and laboratory tests for the investigation of the effective contact behaviour between cast-in-place walls and the surrounding soil. [source]

    Optimization of Rosmarinic Acid Production by Lavandula vera MM Plant Cell Suspension in a Laboratory Bioreactor

    Atanas I. Pavlov
    The all-round effect of dissolved oxygen concentration, agitation speed, and temperature on the rosmarinic acid production by Lavandula veraMM cell suspension was studied in a 3-L laboratory bioreactor by means of the modified Simplex method. Polynomial regression models were elaborated for description of the process of rosmarinic acid production (Y) in the bioreactor as a consequence of the variation of the dissolved oxygen (X1) concentration between 10% and 50%; agitation (X2) between 100 and 400 rpm; and temperature (X3) between 22 and 30 °C. The optimization made it possible to establish the optimal conditions for the biosynthesis of rosmarinic acid by L. veraMM: dissolved oxygen (X1*), 50% of air saturation; agitation (X2*), 400 rpm; and temperature (X3*), 29.9 °C, where maximal yield (Ymax) of 3489.4 mg/L of rosmarinic acid was achieved (2 times higher compared with the shake-flasks cultivation). [source]

    Electrode Reactions of Catechol at Tyrosinase-Immobilized Latex Suspensions

    ELECTROANALYSIS, Issue 8 2004
    Patsamon Rijiravanich
    Abstract Tyrosinase was immobilized on polystyrene latex particles in order to control amounts of the enzyme. The tyrosinase-coated latex particles were composed of the core polystyrene and four successive coating layers: polystyrene sulfonate, polyallylamine, tyrosinase and polyallylamine again, built up by the layer-by-layer technique. They showed catalytic currents for the enzymatic oxidation of catechol to o -quinone. The enzyme activity per particle was evaluated as 2.3×10,7 units from UV absorption of o -quinone. The relation between the catalytic current and the concentration of catechol leads to a Michaelis-Menten type kinetic equation. The layer-by-layer method was found to have a deactivating effect on enzyme catalysis. In spite of this, the catechol oxidation current was larger than the current from free tyrosinase at a common value of enzyme units per volume. This is ascribed to strong adsorption of the latex particles on the electrode, leading to the enhancement of the local concentration of tyrosinase. [source]

    Anaerobic degradation of benzene by a marine sulfate-reducing enrichment culture, and cell hybridization of the dominant phylotype

    Florin Musat
    Summary The anaerobic biodegradation of benzene, a common constituent of petroleum and one of the least reactive aromatic hydrocarbons, is insufficiently understood with respect to the involved microorganisms and their metabolism. To study these aspects, sulfate-reducing bacteria were enriched with benzene as sole organic substrate using marine sediment as inoculum. Repeated subcultivation yielded a sediment-free enrichment culture constituted of mostly oval-shaped cells and showing benzene-dependent sulfate reduction and growth under strictly anoxic conditions. Amplification and sequencing of 16S rRNA genes from progressively diluted culture samples revealed an abundant phylotype; this was closely related to a clade of Deltaproteobacteria that includes sulfate-reducing bacteria able to degrade naphthalene or other aromatic hydrocarbons. Cell hybridization with two specifically designed 16S rRNA-targeted fluorescent oligonucleotide probes showed that the retrieved phylotype accounted for more than 85% of the cells detectable via DAPI staining (general cell staining) in the enrichment culture. The result suggests that the detected dominant phylotype is the ,candidate species' responsible for the anaerobic degradation of benzene. Quantitative growth experiments revealed complete oxidation of benzene with stoichiometric coupling to the reduction of sulfate to sulfide. Suspensions of benzene-grown cells did not show metabolic activity towards phenol or toluene. This observation suggests that benzene degradation by the enriched sulfate-reducing bacteria does not proceed via anaerobic hydroxylation (mediated through dehydrogenation) to free phenol or methylation to toluene, respectively, which are formerly proposed alternative mechanisms for benzene activation. [source]

    Multiple influences of nitrate on uranium solubility during bioremediation of uranium-contaminated subsurface sediments

    Kevin T. Finneran
    Summary Microbiological reduction of soluble U(VI) to insoluble U(IV) has been proposed as a remediation strategy for uranium-contaminated groundwater. Nitrate is a common co-contaminant with uranium. Nitrate inhibited U(VI) reduction in acetate-amended aquifer sediments collected from a uranium-contaminated site in New Mexico. Once nitrate was depleted, both U(VI) and Fe(III) were reduced concurrently. When nitrate was added to sediments in which U(VI) had been reduced, U(VI) reappeared in solution. Parallel studies with the dissimilatory Fe(III)-, U(VI)- and nitrate-reducing microorganism, Geobacter metallireducens, demonstrated that nitrate inhibited reduction of Fe(III) and U(VI) in cell suspensions of cells that had been grown with nitrate as the electron acceptor, but not in Fe(III)-grown cells. Suspensions of nitrate-grown G. metallireducens oxidized Fe(II) and U(IV) with nitrate as the electron acceptor. U(IV) oxidation was accelerated when Fe(II) was also added, presumably due to the Fe(III) being formed abiotically oxidizing U(IV). These studies demonstrate that although the presence of nitrate is not likely to be an impediment to the bioremediation of uranium contamination with microbial U(VI) reduction, it is necessary to reduce nitrate before U(VI) can be reduced. These results also suggest that anaerobic oxidation of U(IV) to U(VI) with nitrate serving as the electron acceptor may provide a novel strategy for solubilizing and extracting microbial U(IV) precipitates from the subsurface. [source]

    Slip Casting of ZrB2,SiC Composite Aqueous Suspensions

    Valentina Medri
    Slip casting of concentrated aqueous suspensions was set up as forming technique for the production of crucibles from ZrB2,SiC composite powder. The dispersion effectiveness and the effect on the final microstructures of two commercial ammonium polyacrylates (Duramax D3005 and Dolapix PC33) used as dispersants were investigated. The first goal was pursued by evaluating the zeta potential of the powders in water at different concentrations of additives, while the second one was assessed by analyzing the microstructure. Duramax D3005 resulted more effective than Dolapix PC33 in electrostatically stabilize the suspensions. Correspondently, almost homogeneous microstructures and lower final porosity of the sintered crucibles were obtained with Duramax D3005, while ZrB2 layers on the vertical surfaces initially in contact with the plaster molds were observed using Dolapix PC33. Moreover, the use of this latter dispersant did not allow the preparation of thick crucible walls due to the sample rupture during the binders pyrolysis stage. [source]

    Transplantation of an acutely isolated bone marrow fraction repairs demyelinated adult rat spinal cord axons

    GLIA, Issue 1 2001
    Masanori Sasaki
    Abstract The potential of bone marrow cells to differentiate into myelin-forming cells and to repair the demyelinated rat spinal cord in vivo was studied using cell transplantation techniques. The dorsal funiculus of the spinal cord was demyelinated by x-irradiation treatment, followed by microinjection of ethidium bromide. Suspensions of a bone marrow cell fraction acutely isolated from femoral bones in LacZ transgenic mice were prepared by centrifugation on a density gradient (Ficoll-Paque) to remove erythrocytes, platelets, and debris. The isolated cell fraction contained hematopoietic and nonhematopoietic stem and precursor cells and lymphocytes. The cells were transplanted into the demyelinated dorsal column lesions of immunosuppressed rats. An intense blue ,-galactosidase reaction was observed in the transplantation zone. The genetically labeled bone marrow cells remyelinated the spinal cord with predominately a peripheral pattern of myelination reminiscent of Schwann cell myelination. Transplantation of CD34+ hematopoietic stem cells survived in the lesion, but did not form myelin. These results indicate that bone marrow cells can differentiate in vivo into myelin-forming cells and repair demyelinated CNS. GLIA 35:26,34, 2001. © 2001 Wiley-Liss, Inc. [source]

    Nanoparticle Coating for Advanced Optical, Mechanical and Rheological Properties,

    F. Hakim
    Abstract Primary titania nanoparticles were coated with ultrathin alumina films using Atomic Layer Deposition (ALD). The deposited films were highly uniform and conformal with an average growth rate of 0.2,nm per coating cycle. The alumina films eliminated the surface photocatalytic activity of titania nanoparticles, while maintained their original extinction efficiency of ultraviolet light. Deposited films provided a physical barrier that effectively prevented the titania surface from oxidizing organic material whereas conserving its bulk optical properties. Parts fabricated from coated powders by pressureless sintering had a 13,% increase in surface hardness over parts similarly fabricated from uncoated particles. Owing to its homogeneous distribution, the secondary alumina phase suppressed excessive grain growth. Alumina films completely reacted during sintering to form aluminum titanate composites, as verified by XRD. Coated particles showed a pseudoplastic behavior at low shear rates due to modified colloidal forces. This behavior became similar to the Newtonian flow of uncoated nanoparticle slurries as the shear rate increased. Suspensions of coated particles also showed a decreased viscosity relative to the viscosity of uncoated particle suspensions. [source]

    Induction of colonic transmural inflammation by bacteroides fragilis.

    Implication of Matrix Metalloproteinases
    Abstract Background: Commensal bacteria are implicated in the pathophysiology of intestinal inflammation, but the precise pathogenetic mechanisms are not known. We hypothesized that Bacteroides fragilis -produced metalloproteinases (MMPs) are responsible for bacterial migration through the intestinal wall and transmural inflammation. Aim: To investigate the role of bacterial-MMP activity in an experimental model of colitis induced by the intramural injection of bacteria. Methods: Suspensions of viable B. fragilis or Escherichia coli were injected into the colonic wall, and the effect of the MMP inhibitor (phenantroline) on histologic lesion scores was tested. MMP activity in bacterial suspensions was measured by azocoll assay. Results: The inoculation with B. fragilis induced chronic inflammatory lesions that were preferentially located in the subserosa, whereas inoculation with E. coli induced acute-type inflammatory reactions, evenly distributed in both the submucosa and subserosa. Treatment with phenantroline significantly decreased subserosal lesion scores in rats inoculated with B. fragilis, but not in rats inoculated with E. coli. Bacterial suspensions of B. fragilis showed MMP activity, but E. coli suspensions did not. Sonication of B. fragilis reduced MMP activity and virulence to induce serosal lesions. Conclusion: Our data suggest that bacterial MMPs may be implicated in the serosal migration of B. fragilis and in the induction of transmural inflammation. [source]

    Efficacy of the injectable calcium phosphate ceramics suspensions containing magnesium, zinc and fluoride on the bone mineral deficiency in ovariectomized rats

    Makoto Otsuka
    Abstract The purpose of this study was to evaluate the therapeutic efficacy of a new calcium phosphate (CaP)-based formulation in improving the bone mineral deficiency in ovariectomized (OVX) rats. The ions release experiments for CaP preparations (G2: 0.46% Mg, 5.78% Zn, and 2.5% F; G3:3.1% Mg, 0.03% Zn, and 3.01% F; G4: 1.25% Mg, 1.77% Zn, 1.35% F) and of a Zn-TCP (G1: 6.17% Zn) powders, the initial Mg and Zn ion release rates of MZF-CaPs were performed in acetate buffer at pH 4.5 (37°C). Wistar rats were divided into six groups including a normal (not OVX) group (GN) and a control, OVX group (GC). Rats in groups GC, G1, G2, G3, G4 were OVX. Suspensions consisting of CaP preparations (G2, G3, G4) and of a Zn-TCP (G1) powders were injected in the right thighs of OVX rats in all groups except for GN and GC, once a week for 4 weeks. GN and GC rats were injected with saline solutions. Plasma was analyzed for Zn land alkaline phosphatase levels. The bone mineral density (BMD) was measured using DEXA and the bone (femur) strength determined using three-point-bending analysis. G1 and G2 groups showed high plasma Zn levels. The area under the curve of plasma Zn was significantly greater in the G1, G2, and GN groups than in the G3, G4, and GC groups (p,<,0.05). The BMD and bone mechanical strength of the right femur were significantly higher in the G1, G2, G3, and G4 groups than GC group on day 28. The right femur had significantly greater BMD and bone mechanical strength than the left femur in G1, G2, G3, and G4 groups. However, there was no significant difference in the BMD of the right femur between the G1, G2, G3, and G4 groups. Results indicate that the new injectable CaP formulations are effective in improving bone properties of OVX rats and may be useful in osteoporosis therapy. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:421,432, 2008 [source]

    Effects of microstructure on the compressive yield stress

    AICHE JOURNAL, Issue 1 2000
    Glenn M. Channell
    The effects of microstructure on the compressive properties of aggregated alumina suspensions are determined by intentionally introducing heterogeneities into the suspension. Suspensions are prepared at a high volume fraction and diluted with low shear hand mixing to a series of initial concentrations. As the initial concentration is increased, larger heterogeneities are introduced, and the suspension becomes more compressible relative to the compressive yield stress of the uniform suspension. A simple model is proposed in which the heterogeneous suspensions compress by rearrangement of the dense aggregates until a critical concentration (,c, which coincides with the volume fraction prior to dilution) is reached. Above ,c, the suspensions consolidate identically to the uniform suspension. With a single fitting parameter (the size of the heterogeneities), the model shows semiquantitative agreement with the experimental data. [source]

    Bacterial Culture and DNA Checkerboard for the Detection of Internal Contamination in Dental Implants

    Rodrigo Edson Santos Barbosa DDS
    Abstract Purpose: The aim of this in vitro study was to evaluate the bacterial leakage along the implant,abutment interface by the conventional bacterial culture and DNA Checkerboard hybridization method. Materials and Methods: Twenty Branemark-compatible implants with a 3.75-mm diameter and external hexagonal platform were randomly placed in two groups of ten implant,abutment assemblies each. One group was used to analyze bacterial counts by DNA Checkerboard hybridization and the other by a conventional bacterial culture. Suspensions of Fusobacterium nucleatum (3 ,l) were injected into the grooved internal cylinders of each implant assembly, and the abutment was connected by a 32 Ncm torque. The combined implant,abutments were individually placed in tubes containing the CaSaB culture medium and incubated in a bacteriological constant temperature oven for 14 days. The samples were observed daily as to the presence of turbidity, and after the designated time the microorganisms were collected from the implant interiors and analyzed by the two methods. Results: After 14 days, six implant,abutment assemblies showed turbidity. Both methods indicated reduced microorganism counts in samples from the interior of the implant,abutment assemblies after incubation in the culture medium; however, the number of counts of F. nucleatum was higher by the DNA Checkerboard method when compared to the group analyzed by conventional bacterial cultures (p < 0.05). Conclusion: The DNA Checkerboard method was shown to be more sensitive than conventional cultures in the detection of microorganisms. [source]

    In Situ X-Ray Radiography and Tomography Observations of the Solidification of Aqueous Alumina Particle Suspensions,Part I: Initial Instants

    Sylvain Deville
    This paper investigates by in situ high-resolution X-ray radiography and tomography the behavior of colloidal suspensions of alumina partic les during directional solidification by freezing. The combination of these techniques provided both qualitative and quantitative information about the propagation kinetic of the solid/liquid interface, the particle redistribution between the crystals and a particle-enriched phase, and the three-dimensional organization of the ice crystals. In this first part of two companion papers, the precursor phenomena leading to directional crystallization during the first instants of solidification are studied. Mullins,Sekerka instabilities are not necessary to explain the dynamic evolution of the interface pattern. Particle redistribution during these first instants is dependent on the type of crystals growing into the suspension. The insights gained into the mechanisms of solidification of colloidal suspensions may be valuable for the materials processing routes derived for this type of directional solidification (freeze-casting), and of general interest for those interested in the interactions between solidification fronts and inert particles. [source]