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Sample records for biological mixed colloids

  1. Probing self assembly in biological mixed colloids by SANS, deuteration and molecular manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Hjelm, R.P. [Los Alamos National Laboratory, NM (United States); Thiyagarajan, P. [Argonne National Laboratory, IL (United States); Hoffman, A. [Univ. of California, San Diego, CA (United States); Alkan-Onyuksel, H. [Univ. of Illinois, Chicago, IL (United States)

    1994-12-31

    Small-angle neutron scattering was used to obtain information on the form and molecular arrangement of particles in mixed colloids of bile salts with phosphatidylcholine, and bile salts with monoolein. Both types of systems showed the same general characteristics. The particle form was highly dependent on total lipid concentration. At the highest concentrations the particles were globular mixed micelles with an overall size of 50{Angstrom}. As the concentration was reduced the mixed micelles elongated, becoming rodlike with diameter about 50{Angstrom}. The rods had a radial core-shell structure in which the phosphatidylcholine or monoolein fatty tails were arranged radially to form the core with the headgroups pointing outward to form the shell. The bile salts were at the interface between the shell and core with the hydrophilic parts facing outward as part of the shell. The lengths of the rods increased and became more polydispersed with dilution. At sufficiently low concentrations the mixed micelles transformed into single bilayer vesicles. These results give insight on the physiological function of bile and on the rules governing the self assembly of bile particles in the hepatic duct and the small intestine.

  2. Probing self assembly in biological mixed colloids by SANS, deuteration and molecular manipulation

    International Nuclear Information System (INIS)

    Small-angle neutron scattering was used to obtain information on the form and molecular arrangement of particles in mixed colloids of bile salts with phosphatidylcholine, and bile salts with monoolein. Both types of systems showed the same general characteristics. The particle form was highly dependent on total lipid concentration. At the highest concentrations the particles were globular mixed micelles with an overall size of 50 Angstrom. As the concentration was reduced the mixed micelles elongated, becoming rodlike with diameter about 50 Angstrom. The rods had a radial core-shell structure in which the phosphatidylcholine or monoolein fatty tails were arranged radially to form the core with the headgroups pointing outward to form the shell. The bile salts were at the interface between the shell and core with the hydrophilic parts facing outward as part of the shell. The lengths of the rods increased and became more polydispersed with dilution. At sufficiently low concentrations the mixed micelles transformed into single bilayer vesicles. These results give insight on the physiological function of bile and on the rules governing the self assembly of bile particles in the hepatic duct and the small intestine

  3. Hydrodynamic Interactions in Colloidal and Biological Systems

    OpenAIRE

    Reichert, Michael

    2006-01-01

    Colloids are widely considered as model systems to elucidate fundamental processes in atomic systems. However, there is one feature truly specific to colloidal suspensions that distinguishes them fundamentally from atomic systems: hydrodynamic interactions, which can lead to fascinating collective behavior.In this thesis, we present analytical work and simulation results for several micron-scale colloidal and biological systems where the dynamics is predominantly governed by hydrodynamic inte...

  4. Engineering colloidal assembly via biological adhesion

    Science.gov (United States)

    Hiddessen, Amy Lynn

    Due to highly specialized recognition properties, biological receptor-ligand interactions offer valuable tools for engineering the assembly of novel colloidal materials. A unique sub-class of these macromolecules, called selectins, was exploited to develop binary suspensions where particles are programmed to associate reversibly or irreversibly via specific biomolecular cross-linking. Flow cytometry and videomicroscopy were used to examine factors controlling suspension assembly and structure, including biomolecular affinity and density, and individual and total particle volume fractions. By functionalizing small (RA = 0.47 mum) and larger (RB = 2.75 mum) particles with high surface densities of complementary E-selectin/sialyl Lewis X (sLeX) carbohydrate chemistry, a series of structures, from colloidal micelles (large particle coated with smaller particles) and clusters, to rings and elongated chains, was synthesized by decreasing the number ratio, NA/NB, of small (A) to large (B) particles (2 ≤ NA/NB ≤ 200) at low total volume fraction (10-4 ≤ φT ≤ 10-3 ). Using significantly lower surface densities, the low affinity binding between E-selectin and sLeX was exploited to create particles that interact reversibly, and average particle interaction lifetimes were tuned from minutes down to single selectin-carbohydrate bond lifetimes (≈1 s) by reducing sLeX density, a significant step toward assembling ordered microstructures. Particle binding lifetimes were analyzed with a receptor-ligand binding model, yielding estimates for molecular parameters, including on rate, 10-2 s-1 docking dynamics of particles. Finally, at significantly higher volume fraction (φ T ≥ 10-1) and low number ratio, the rheology of space-filling networks crosslinked by high affinity streptavidin-biotin chemistry was probed to acquire knowledge on bulk properties of biocolloidal suspensions. Flow curves (apparent viscosity (eta) versus shear rate ( ġ )) exhibited non

  5. Hybrid electrokinetics for separation, mixing, and concentration of colloidal particles

    Energy Technology Data Exchange (ETDEWEB)

    Sin, Mandy L Y; Shimabukuro, Yusuke; Wong, Pak Kin [Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ (United States)], E-mail: pak@email.arizona.edu

    2009-04-22

    The advent of nanotechnology has facilitated the preparation of colloidal particles with adjustable sizes and the control of their size-dependent properties. Physical manipulation, such as separation, mixing, and concentration, of these colloidal particles represents an essential step for fully utilizing their potential in a wide spectrum of nanotechnology applications. In this study, we investigate hybrid electrokinetics, the combination of dielectrophoresis and electrohydrodynamics, for active manipulation of colloidal particles ranging from nanometers to micrometers in size. A concentric electrode configuration, which is optimized for generating electrohydrodynamic flow, has been designed to elucidate the effectiveness of hybrid electrokinetics and define the operating regimes for different microfluidic operations. The results indicate that the relative importance of electrohydrodynamics increases with decreasing particle size as predicted by a scaling analysis and that electrohydrodynamics is pivotal for manipulating nanoscale particles. Using the concentric electrodes, we demonstrate separation, mixing, and concentration of colloidal particles by adjusting the relative strengths of different electrokinetic phenomena. The effectiveness of hybrid electrokinetics indicates its potential to serve as a generic technique for active manipulation of colloidal particles in various nanotechnology applications.

  6. Colloidal mesoporous silica nanoparticles enhance the biological activity of resveratrol.

    Science.gov (United States)

    Summerlin, Natalie; Qu, Zhi; Pujara, Naisarg; Sheng, Yong; Jambhrunkar, Siddharth; McGuckin, Michael; Popat, Amirali

    2016-08-01

    The naturally occurring polyphenol resveratrol (RES) has attracted increasing attention in recent years due to its antioxidant, anti-inflammatory, and anticancer activity. However, resveratrol's promising potential as a nutraceutical is hindered by its poor aqueous solubility, which limits its biological activity. Here we show that encapsulating resveratrol in colloidal mesoporous silica nanoparticles (MCM-48-RES) enhances its saturated solubility by ∼95% and increases its in vitro release kinetics compared to pure resveratrol. MCM-48-RES showed high loading capacity (20% w/w) and excellent encapsulation efficiency (100%). When tested against HT-29 and LS147T colon cancer cell lines, MCM-48-RES-mediated in vitro cell death was higher than that of pure resveratrol, mediated via the PARP and cIAP1 pathways. Finally, MCM-48-RES treatment also inhibited lipopolysaccharide-induced NF-κB activation in RAW264.7 cells, demonstrating improved anti-inflammatory activity. More broadly, our observations demonstrate the potential of colloidal mesoporous silica nanoparticles as next generation delivery carriers for hydrophobic nutraceuticals. PMID:27060664

  7. How a "pinch of salt" can tune chaotic mixing of colloidal suspensions

    CERN Document Server

    Deseigne, Julien; Stroock, Abraham D; Bocquet, Lydéric; Ybert, Christophe

    2014-01-01

    Efficient mixing of colloids, particles or molecules is a central issue in many processes. It results from the complex interplay between flow deformations and molecular diffusion, which is generally assumed to control the homogenization processes. In this work we demonstrate on the contrary that despite fixed flow and self-diffusion conditions, the chaotic mixing of colloidal suspensions can be either boosted or inhibited by the sole addition of trace amount of salt as a co-mixing species. Indeed, this shows that local saline gradients can trigger a chemically-driven transport phenomenon, diffusiophoresis, which controls the rate and direction of molecular transport far more efficiently than usual Brownian diffusion. A simple model combining the elementary ingredients of chaotic mixing with diffusiophoretic transport of the colloids allows to rationalize our observations and highlights how small-scale out-of-equilibrium transport bridges to mixing at much larger scales in a very effective way. Considering cha...

  8. Experimental Aspects of Colloidal Interactions in Mixed Systems of Liposome and Inorganic Nanoparticle and Their Applications

    Directory of Open Access Journals (Sweden)

    Michael Gradzielski

    2012-09-01

    Full Text Available In the past few years, growing attention has been devoted to the study of the interactions taking place in mixed systems of phospholipid membranes (for instance in the form of vesicles and hard nanoparticles (NPs. In this context liposomes (vesicles may serve as versatile carriers or as a model system for biological membranes. Research on these systems has led to the observation of novel hybrid structures whose morphology strongly depends on the charge, composition and size of the interacting colloidal species as well as on the nature (pH, ionic strength of their dispersing medium. A central role is played by the phase behaviour of phospholipid bilayers which have a tremendous influence on the liposome properties. Another central aspect is the incorporation of nanoparticles into vesicles, which is intimately linked to the conditions required for transporting a nanoparticle through a membrane. Herein, we review recent progress made on the investigations of the interactions in liposome/nanoparticle systems focusing on the particularly interesting structures that are formed in these hybrid systems as well as their potential applications.

  9. Formation of mixed Al-Fe colloidal sorbent and dissolved-colloidal partitioning of Cu and Zn in the Cement Creek - Animas River Confluence, Silverton, Colorado

    Science.gov (United States)

    Schemel, L.E.; Kimball, B.A.; Runkel, R.L.; Cox, M.H.

    2007-01-01

    Transport and chemical transformations of dissolved and colloidal Al, Fe, Cu and Zn were studied by detailed sampling in the mixing zone downstream from the confluence of Cement Creek (pH 4.1) with the Animas River (pH 7.6). Complete mixing resulted in circumneutral pH in the downstream reach of the 1300 m study area. All four metals were transported through this mixing zone without significant losses to the streambed, and they exhibited transformations from dissolved to colloidal forms to varying degrees during the mixing process. Nearly all of the Al formed colloidal hydrous Al oxides (HAO) as pH increased (4.8-6.5), whereas colloidal hydrous Fe oxides (HFO) were supplied by Cement Creek as well as formed in the mixing zone primarily at higher pH (>6.5). The short travel time through the mixing zone (approx. 40 min) and pH limited the formation of HFO from dissolved Fe2+ supplied by Cement Creek. Although the proportions of HAO and HFO varied as the streams mixed, the colloidal sorbent typically was enriched in HAO relative to HFO by a factor of 1.5-2.1 (by mole) in the pH range where dissolved-to-colloidal partitioning of Cu and Zn was observed. Model simulations of sorption by HFO (alone) greatly underestimated the dissolved-to-colloidal partitioning of Zn. Previous studies have shown that HAO-HFO mixtures can sorb greater amounts of Zn than HFO alone, but the high Zn-to-sorbent ratio in this mixing zone could also account for greater partitioning. In contrast to Zn, comparisons with model simulations did not show that Cu sorption was greater than that for HFO alone, and also indicated that sorption was possibly less than what would be expected for a non-interactive mixture of these two sorbents. These field results for Cu, however, might be influenced by (organic) complexation or other factors in this natural system. Laboratory mixing experiments using natural source waters (upstream of the confluence) showed that the presence of HFO in the mixed sorbent

  10. Transformation of organic carbon, trace element, and organo-mineral colloids in the mixing zone of the largest European Arctic river

    Directory of Open Access Journals (Sweden)

    O. S. Pokrovsky

    2013-10-01

    Full Text Available The estuarine behavior of organic carbon (OC and trace elements (TE was studied for the largest European sub-Arctic river, which is the Severnaya Dvina; this river is a deltaic estuary covered in ice during several hydrological seasons: summer (July 2010, 2012 and winter (March 2009 baseflow, and the November–December 2011 ice-free period. Colloidal forms of OC and TE were assessed using three pore size cutoff (1, 10, and 50 kDa using an in-situ dialysis procedure. Conventionally dissolved ( The most important result of this study is the elucidation of the behavior of the "truly" dissolved low molecular weight LMW fraction containing Fe, OC, and a number of insoluble elements. The concentration of the LMW fraction either remains constant or increases its relative contribution to the overall dissolved ( Overall, the observed decrease of the colloidal fraction may be related to the coagulation of organo-ferric colloids at the beginning of the mixing zone and therefore the replacement of the HMW1 kDa–0.22 μm portion by the LMW fraction. These patterns are highly reproducible across different sampling seasons, suggesting significant enrichment of the mixing zone by the most labile (and potentially bioavailable fraction of the OC, Fe and insoluble TE. The size fractionation of the colloidal material during estuarine mixing reflects a number of inorganic and biological processes, the relative contribution of which to element speciation varies depending on the hydrological stage and time of year. In particular, LMW ligand production in the surface horizons of the mixing zone may be linked to heterotrophic mineralization of allochthonous DOM and/or photodestruction. Given the relatively low concentration of particulate vs. dissolved load of most trace elements, desorption from the river suspended material was less pronounced than in other rivers in the world. As a result, the majority of dissolved components exhibited either a conservative (OC and

  11. Biological colloid engineering: Self-assembly of dipolar ferromagnetic chains in a functionalized biogenic ferrofluid

    Science.gov (United States)

    Ruder, Warren C.; Hsu, Chia-Pei D.; Edelman, Brent D.; Schwartz, Russell; LeDuc, Philip R.

    2012-08-01

    We have studied the dynamic behavior of nanoparticles in ferrofluids consisting of single-domain, biogenic magnetite (Fe3O4) isolated from Magnetospirillum magnetotacticum (MS-1). Although dipolar chains form in magnetic colloids in zero applied field, when dried upon substrates, the solvent front disorders nanoparticle aggregation. Using avidin-biotin functionalization of the particles and substrate, we generated self-assembled, linear chain motifs that resist solvent front disruption in zero-field. The engineered self-assembly process we describe here provides an approach for the creation of ordered magnetic structures that could impact fields ranging from micro-electro-mechanical systems development to magnetic imaging of biological structures.

  12. 9 CFR 114.6 - Mixing biological products.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Mixing biological products. 114.6 Section 114.6 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE VIRUSES, SERUMS, TOXINS, AND ANALOGOUS PRODUCTS; ORGANISMS AND VECTORS PRODUCTION REQUIREMENTS FOR BIOLOGICAL PRODUCTS § 114.6...

  13. Biological colloid engineering: Self-assembly of dipolar ferromagnetic chains in a functionalized biogenic ferrofluid.

    Science.gov (United States)

    Ruder, Warren C; Hsu, Chia-Pei D; Edelman, Brent D; Schwartz, Russell; Leduc, Philip R

    2012-08-01

    We have studied the dynamic behavior of nanoparticles in ferrofluids consisting of single-domain, biogenic magnetite (Fe(3)O(4)) isolated from Magnetospirillum magnetotacticum (MS-1). Although dipolar chains form in magnetic colloids in zero applied field, when dried upon substrates, the solvent front disorders nanoparticle aggregation. Using avidin-biotin functionalization of the particles and substrate, we generated self-assembled, linear chain motifs that resist solvent front disruption in zero-field. The engineered self-assembly process we describe here provides an approach for the creation of ordered magnetic structures that could impact fields ranging from micro-electro-mechanical systems development to magnetic imaging of biological structures. PMID:22952408

  14. Duplication: a Mechanism Producing Disassortative Mixing Networks in Biology

    Institute of Scientific and Technical Information of China (English)

    ZHAO Dan; LIU Zeng-Rong; WANG Jia-Zeng

    2007-01-01

    Assortative/disassortative mixing is an important topological property of a network. A network is called assortative mixing if the nodes in the network tend to connect to their connectivity peers, or disassortative mixing if nodes with low degrees are more likely to connect with high-degree nodes. We have known that biological networks such as protein-protein interaction networks (PPI), gene regulatory networks, and metabolic networks tend to be disassortative. On the other hand, in biological evolution, duplication and divergence are two fundamental processes. In order to make the relationship between the property of disassortative mixing and the two basic biological principles clear and to study the cause of the disassortative mixing property in biological networks, we present a random duplication model and an anti-preference duplication model. Our results show that disassortative mixing networks can be obtained by both kinds of models from uncorrelated initial networks.Moreover, with the growth of the network size, the disassortative mixing property becomes more obvious.

  15. Colloidal size spectra, composition and estuarine mixing behavior of DOM in river and estuarine waters of the northern Gulf of Mexico

    Science.gov (United States)

    Zhou, Zhengzhen; Stolpe, Björn; Guo, Laodong; Shiller, Alan M.

    2016-05-01

    Flow field-flow fractionation (FlFFF) coupled on-line with UV absorbance and fluorescence detectors was used to examine the colloidal composition and size distribution of optically active dissolved organic matter (DOM) in the lower Mississippi River (MR), the East Pearl River (EPR), the St. Louis Bay (SLB) estuary, and coastal waters of the northern Gulf of Mexico. In addition to field studies, laboratory mixing experiments using river and seawater end-members were carried out to study the processes controlling the estuarine mixing behavior and size partitioning of colloids with different sizes and composition. The colloidal size spectra of chromophoric DOM and humic-like DOM showed one dominant peak in the 0.5-4 nm size range, representing >75% of the total FlFFF-recoverable colloids. In contrast, protein-like DOM showed a bi-modal distribution with peaks at 0.5-4 nm and 4-8 nm, as well as a major portion (from ∼41% in the EPR to ∼72% in the Mississippi Bight) partitioned to the >20 nm size fraction. Bulk DOM was lower in abundance and molecular-weight in the MR compared with the EPR, while the proportion of colloidal protein-like DOM in the >20 nm size range was slightly larger in the MR compared with the EPR. These features are consistent with differences in land use, hydrological conditions, and water residence time between the two river basins, with more autochthonous DOM in MR waters. In the SLB estuary, different DOM components demonstrated different mixing behaviors. The abundance of colloidal chromophoric DOM decreased with increasing salinity and showed evident removal during estuarine mixing even though the bulk DOM appeared to be conservative. In contrast, colloidal humic-like DOM behaved conservatively inside SLB and during laboratory mixing experiments. The ratio of colloidal protein-like to humic-like DOM generally increased with increasing salinity, consistent with increasing autochthonous protein-like DOM and removal of terrestrially

  16. The influence of ionic strength and mixing ratio on the colloidal stability of PDAC/PSS polyelectrolyte complexes.

    Science.gov (United States)

    Zhang, Yanpu; Yildirim, Erol; Antila, Hanne S; Valenzuela, Luis D; Sammalkorpi, Maria; Lutkenhaus, Jodie L

    2015-10-01

    Polyelectrolyte complexes (PECs) form by mixing polycation and polyanion solutions together, and have been explored for a variety of applications. One challenge for PEC processing and application is that under certain conditions the as-formed PECs aggregate and precipitate out of suspension over the course of minutes to days. This aggregation is governed by several factors such as electrostatic repulsion, van der Waals attractions, and hydrophobic interactions. In this work, we explore the boundary between colloidally stable and unstable complexes as it is influenced by polycation/polyanion mixing ratio and ionic strength. The polymers examined are poly(diallyldimethylammonium chloride) (PDAC) and poly(sodium 4-styrenesulfonate) (PSS). Physical properties such as turbidity, hydrodynamic size, and zeta potential are investigated upon complex formation. We also perform detailed molecular dynamics simulations to examine the structure and effective charge distribution of the PECs at varying mixing ratios and salt concentrations to support the experimental findings. The results suggest that the colloidally stable/unstable boundary possibly marks the screening effects from added salt, resulting in weakly charged complexes that aggregate. At higher salt concentrations, the complexes initially form and then gradually dissolve into solution. PMID:26268471

  17. Evaluation of colloidal silica suspension as efficient additive for improving physicochemical and in vitro biological properties of calcium sulfate-based nanocomposite bone cement.

    Science.gov (United States)

    Borhan, Shokoufeh; Hesaraki, Saeed; Ahmadzadeh-Asl, Shaghayegh

    2010-12-01

    In the present study new calcium sulfate-based nanocomposite bone cement with improved physicochemical and biological properties was developed. The powder component of the cement consists of 60 wt% α-calcium sulfate hemihydrate and 40 wt% biomimetically synthesized apatite, while the liquid component consists of an aqueous colloidal silica suspension (20 wt%). In this study, the above mentioned powder phase was mixed with distilled water to prepare a calcium sulfate/nanoapatite composite without any additive. Structural properties, setting time, compressive strength, in vitro bioactivity and cellular properties of the cements were investigated by appropriate techniques. From X-ray diffractometer analysis, except gypsum and apatite, no further phases were found in both silica-containing and silica-free cements. The results showed that both setting time and compressive strength of the calcium sulfate/nanoapatite cement improved by using colloidal silica suspension as cement liquid. Meanwhile, the condensed phase produced from the polymerization process of colloidal silica filled the micropores of the microstructure and covered rodlike gypsum crystals and thus controlled cement disintegration in simulated body fluid. Additionally, formation of apatite layer was favored on the surfaces of the new cement while no apatite precipitation was observed for the cement prepared by distilled water. In this study, it was also revealed that the number of viable osteosarcoma cells cultured with extracts of both cements were comparable, while silica-containing cement increased alkaline phosphatase activity of the cells. These results suggest that the developed cement may be a suitable bone filling material after well passing of the corresponding in vivo tests. PMID:20972610

  18. Biological vs. physical mixing effects on benthic food web dynamics.

    Directory of Open Access Journals (Sweden)

    Ulrike Braeckman

    Full Text Available Biological particle mixing (bioturbation and solute transfer (bio-irrigation contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter assimilation by the metazoan lower part of the food web through niche establishment (i.e., ecosystem engineering or rather deprives them from food sources, is so far unclear. We investigated the effects of the ecosystem engineers Lanice conchilega (bio-irrigator and Abra alba (bioturbator compared to abiotic physical mixing events on survival and food uptake of nematodes after a simulated phytoplankton bloom. The (13C labelled diatom Skeletonema costatum was added to 4 treatments: (1 microcosms containing the bioturbator, (2 microcosms containing the bio-irrigator, (3 control microcosms and (4 microcosms with abiotic manual surface mixing. Nematode survival and subsurface peaks in nematode density profiles were most pronounced in the bio-irrigator treatment. However, nematode specific uptake (Δδ(13C of the added diatoms was highest in the physical mixing treatment, where macrobenthos was absent and the diatom (13C was homogenised. Overall, nematodes fed preferentially on bulk sedimentary organic material rather than the added diatoms. The total C budget (µg C m(-2, which included TO(13C remaining in the sediment, respiration, nematode and macrobenthic uptake, highlighted the limited assimilation by the metazoan benthos and the major role of bacterial respiration. In summary, bioturbation and especially bio-irrigation facilitated the lower trophic levels mainly over the long-term through niche establishment. Since the freshly added diatoms represented only a limited food

  19. Biological vs. physical mixing effects on benthic food web dynamics.

    Science.gov (United States)

    Braeckman, Ulrike; Provoost, Pieter; Moens, Tom; Soetaert, Karline; Middelburg, Jack J; Vincx, Magda; Vanaverbeke, Jan

    2011-01-01

    Biological particle mixing (bioturbation) and solute transfer (bio-irrigation) contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria) and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter assimilation by the metazoan lower part of the food web through niche establishment (i.e., ecosystem engineering) or rather deprives them from food sources, is so far unclear. We investigated the effects of the ecosystem engineers Lanice conchilega (bio-irrigator) and Abra alba (bioturbator) compared to abiotic physical mixing events on survival and food uptake of nematodes after a simulated phytoplankton bloom. The (13)C labelled diatom Skeletonema costatum was added to 4 treatments: (1) microcosms containing the bioturbator, (2) microcosms containing the bio-irrigator, (3) control microcosms and (4) microcosms with abiotic manual surface mixing. Nematode survival and subsurface peaks in nematode density profiles were most pronounced in the bio-irrigator treatment. However, nematode specific uptake (Δδ(13)C) of the added diatoms was highest in the physical mixing treatment, where macrobenthos was absent and the diatom (13)C was homogenised. Overall, nematodes fed preferentially on bulk sedimentary organic material rather than the added diatoms. The total C budget (µg C m(-2)), which included TO(13)C remaining in the sediment, respiration, nematode and macrobenthic uptake, highlighted the limited assimilation by the metazoan benthos and the major role of bacterial respiration. In summary, bioturbation and especially bio-irrigation facilitated the lower trophic levels mainly over the long-term through niche establishment. Since the freshly added diatoms represented only a limited food source

  20. Elaboration of hybrid materials by templating with mineral liquid crystals stabilization of a mixed sol of YSZ nanoparticles and V2O5 ribbon-like colloids

    International Nuclear Information System (INIS)

    The purpose of this PhD was to investigate innovative soft chemistry ways to prepare hybrid materials with ordered nano-structures. Concretely, research were conducted on the development of a hybrid material made of an yttria-stabilized zirconia (YSZ) matrix templated by a mineral liquid crystal, namely V2O5. In aqueous solutions, vanadium oxide exhibits ribbon-like colloids of typical dimensions 1 nm x 25 nm x 500 nm, stabilized by a strong negative surface charge. Above a critical concentration, the anisotropic colloids assemble into a nematic liquid crystal, whose domains can be oriented within the same direction over a macroscopic range under a weak magnetic field. The idea is to use V2O5 anisotropic colloids as a template for a hybrid material, taking advantage of their ordering behavior. Preliminary experiments revealed a strong reactivity between molecular compounds of zirconium and vanadium oxide. Therefore, the studies were directed toward the preparation of a mixed colloidal sol containing YSZ nanoparticles and vanadium oxide ribbon-like colloids, as a precursor sol for the intended hybrid material. The YSZ nanoparticles are obtained through an outstanding hydrothermal synthesis leading to a stable suspension of nanocrystalline particles of ca. 5 nm, in pure water. Providing a mixed sol of YSZ and V2O5 is a key challenge for it implies the co-stabilization of two types of colloids having different shape, size and surface properties. Besides, the existence of V2O5 in its ribbon-like form requires acidic conditions and very low ionic strength. The first part of this work was then dedicated to the study of electro-steric stabilization of zirconia suspension by addition of acidic poly-electrolytes. Different polymers with carboxylic and/or sulfonic acidic functions were investigated. Based on zeta potential measurements and adsorption isotherms, the influence of molecular weight and polymer charge were discussed. Among the studied polymers, poly vinylsulfonic

  1. Probing droplets with biological colloidal suspensions on smart surfaces by synchrotron radiation micro- and nano-beams

    Science.gov (United States)

    Marinaro, G.; Accardo, A.; Benseny-Cases, N.; Burghammer, M.; Castillo-Michel, H.; Cotte, M.; Dante, S.; De Angelis, F.; Di Cola, E.; Di Fabrizio, E.; Hauser, C.; Riekel, C.

    2016-01-01

    Droplets with colloidal biological suspensions evaporating on substrates with defined wetting properties generate confined environments for initiating aggregation and self-assembly processes. We describe smart micro- and nanostructured surfaces, optimized for probing single droplets and residues by synchrotron radiation micro- and nanobeam diffraction techniques. Applications are presented for Ac-IVD and β-amyloid (1-42) peptides capable of forming cross-β sheet structures. Complementary synchrotron radiation FTIR microspectroscopy addresses secondary structure formation. The high synchrotron radiation source brilliance enables fast raster-scan experiments.

  2. Probing droplets with biological colloidal suspensions on smart surfaces by synchrotron radiation micro- and nano-beams

    KAUST Repository

    Marinaro, Giovanni

    2015-03-01

    Droplets with colloidal biological suspensions evaporating on substrates with defined wetting properties generate confined environments for initiating aggregation and self-assembly processes. We describe smart micro- and nanostructured surfaces, optimized for probing single droplets and residues by synchrotron radiation micro- and nanobeam diffraction techniques. Applications are presented for Ac-IVD and β-amyloid (1-42) peptides capable of forming cross-β sheet structures. Complementary synchrotron radiation FTIR microspectroscopy addresses secondary structure formation. The high synchrotron radiation source brilliance enables fast raster-scan experiments. © 2015 Elsevier Ltd.

  3. Biological alkylation and colloid formation of selenium in methanogenic UASB reactors

    NARCIS (Netherlands)

    Lenz, M.; Smit, M.P.J.; Binder, P.; Aelst, van A.C.; Lens, P.N.L.

    2008-01-01

    Bioalkylation and colloid formation of selenium during selenate removal in upflow anaerobic sludge bed (UASB) bioreactors was investigated, The mesophilic (30 degrees C) UASB reactor (pH = 7.0) was operated for 175 d with lactate as electron donor at an organic loading rate of 2 g COD L-1 d(-1) and

  4. Colloid Transport and Retention

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander

    2012-01-01

    related to historical prospective, synthesis, characterization, theoretical modeling and application of unique class of colloidal materials starting from colloidal gold to coated silica colloid and platinum, titania colloids. This book is unique in its design, content, providing depth of science about......Book Description: Colloidal science and technology is one of the fastest growing research and technology areas. This book explores the cutting edge research in colloidal science and technology that will be usefull in almost every aspect of modern society. This book has a depth of information...... different colloidal materials and their applications in chemistry, physics, biological, medical sciences and environment. Graduate students, academic and industrial researchers and medical professionals will discover recently developed colloidal materials and their applications in many areas of human...

  5. Biological colloid engineering: Self-assembly of dipolar ferromagnetic chains in a functionalized biogenic ferrofluid

    OpenAIRE

    Ruder, Warren C.; Hsu, Chia-Pei D.; Edelman, Brent D.; Schwartz, Russell; Leduc, Philip R.

    2012-01-01

    We have studied the dynamic behavior of nanoparticles in ferrofluids consisting of single-domain, biogenic magnetite (Fe3O4) isolated from Magnetospirillum magnetotacticum (MS-1). Although dipolar chains form in magnetic colloids in zero applied field, when dried upon substrates, the solvent front disorders nanoparticle aggregation. Using avidin-biotin functionalization of the particles and substrate, we generated self-assembled, linear chain motifs that resist solvent front disruption in zer...

  6. Colloid dynamics and transport of major elements through a boreal river - brackish bay mixing zone

    DEFF Research Database (Denmark)

    Gustafsson, Ö.; Widerlund, A.; Andersson, P.; Ingri, J.; Roos, P.; Ledin, Anna

    A range of biogeochemical methodologies were applied to investigate how aggregation processes affected the phase distribution and mixing of Fe, Si, and organic carbon between the Kalix River and the Bothnic Bay, northernmost Baltic Sea salinityF3; the low-salinity zone LSZ. was stretching over 60...... organic C was occurring in the highly-resolved LSZ. While no conclusions may be drawn based solely on property–salinity plots over narrow salinity ranges, apparently linear graphs for Fe and Si over 3 separate years also suggest minimal removal in this regime. At the same time, size distributions both of...... elements —from cross-flow ultrafiltration — and of bulk suspended solids — from light scattering photon correlation spectroscopy wPCSx. — indicated that significant aggregation was taking place. The aggregation-without-significant-settling scenario in this low-salinity mixing regime, with a geochemistry...

  7. PEGylation of SPIONs by polycondensation reactions: a new strategy to improve colloidal stability in biological media

    International Nuclear Information System (INIS)

    In this study, we report on a new route of PEGylation of superparamagnetic iron oxide nanoparticles (SPIONs) by polycondensation reaction with carboxylate groups. Structural and magnetic characterizations were performed by X-ray diffractometry (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and vibrating sample magnetometry (VSM). The XRD confirmed the spinel structure with a crystallite average diameter in the range of 3.5–4.1 nm in good agreement with the average diameter obtained by TEM (4.60–4.97 nm). The TGA data indicate the presence of PEG attached onto the SPIONs’ surface. The SPIONs were superparamagnetic at room temperature with saturation magnetization (MS) from 36.7 to 54.1 emu/g. The colloidal stability of citrate- and PEG-coated SPIONs was evaluated by means of dynamic light scattering measurements as a function of pH, ionic strength, and nature of dispersion media (phosphate buffer and cell culture media). Our findings demonstrated that the PEG polymer chain length plays a key role in the coagulation behavior of the Mag-PEG suspensions. The excellent colloidal stability under the extreme conditions we evaluated, such as high ionic strength, pH near the isoelectric point, and cell culture media, revealed that suspensions comprising PEG-coated SPION, with PEG of molecular weight 600 and above, present steric stabilization attributed to the polymer chains attached onto the surface of SPIONs

  8. PEGylation of SPIONs by polycondensation reactions: a new strategy to improve colloidal stability in biological media

    Energy Technology Data Exchange (ETDEWEB)

    Viali, Wesley Renato; Silva Nunes, Eloiza da; Santos, Caio Carvalho dos [Universidade Estadual Paulista, Laboratorio de Materiais Magneticos e Coloides, Departamento de Fisico-quimica, Instituto de Quimica (Brazil); Silva, Sebastiao William da; Aragon, Fermin Herrera; Coaquira, Jose Antonio Huamani; Morais, Paulo Cesar [Universidade de Brasilia, Instituto de Fisica, Nucleo de Fisica Aplicada (Brazil); Jafelicci, Miguel, E-mail: jafeli@iq.unesp.br [Universidade Estadual Paulista, Laboratorio de Materiais Magneticos e Coloides, Departamento de Fisico-quimica, Instituto de Quimica (Brazil)

    2013-08-15

    In this study, we report on a new route of PEGylation of superparamagnetic iron oxide nanoparticles (SPIONs) by polycondensation reaction with carboxylate groups. Structural and magnetic characterizations were performed by X-ray diffractometry (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and vibrating sample magnetometry (VSM). The XRD confirmed the spinel structure with a crystallite average diameter in the range of 3.5-4.1 nm in good agreement with the average diameter obtained by TEM (4.60-4.97 nm). The TGA data indicate the presence of PEG attached onto the SPIONs' surface. The SPIONs were superparamagnetic at room temperature with saturation magnetization (M{sub S}) from 36.7 to 54.1 emu/g. The colloidal stability of citrate- and PEG-coated SPIONs was evaluated by means of dynamic light scattering measurements as a function of pH, ionic strength, and nature of dispersion media (phosphate buffer and cell culture media). Our findings demonstrated that the PEG polymer chain length plays a key role in the coagulation behavior of the Mag-PEG suspensions. The excellent colloidal stability under the extreme conditions we evaluated, such as high ionic strength, pH near the isoelectric point, and cell culture media, revealed that suspensions comprising PEG-coated SPION, with PEG of molecular weight 600 and above, present steric stabilization attributed to the polymer chains attached onto the surface of SPIONs.

  9. Preparation and characterization of silver particle encapsulated biopolymer nano-colloid substrate for surface enhanced raman scattering (SERS) for biological applications

    Science.gov (United States)

    To detect biological samples such as foodborne pathogens, Surface Enhanced Raman Scattering (SERS) substrate was prepared and its characteristics were analyzed in this work. Silver biopolymer nano colloidal substrate was prepared by adding silver nitrate to 2% polyvinyl alcohol (PVA) solution and ...

  10. Photocatalytic electrochemistry at a biological-membrane metal-colloid interface

    Science.gov (United States)

    Greenbaum, Elias

    1987-10-01

    A method for electrically contacting the electron-transport chain of photosynthesis is described. Colloidal platinum was prepared and precipitated directly onto photosynthetic thylakoid membranes from aqueous solution, and entrapped on fiberglass filter paper. This composition of matter was capable of sustained simultaneous photoevolution of hydrogen and oxygen when irradiated at any wavelength in the chlorophyll absorption spectrum. Experimental data support the interpretation that part of the platinum metal catalyst is precipitated adjacent to the photosystem-I reduction site of photosynthesis and the electron-transfer occurs across the interface between photosystem I and the catalyst. Photoactivity of the material was dependent on the nature of the ionic species from which the platinum was precipitated. When contacted with metal electrodes, the thylakoid-platinum combination is capable of generating a sustained flow of current through an external load resistor.

  11. Nanoparticle sensor for label free detection of swine DNA in mixed biological samples

    International Nuclear Information System (INIS)

    We used 40 ± 5 nm gold nanoparticles (GNPs) as colorimetric sensor to visually detect swine-specific conserved sequence and nucleotide mismatch in PCR-amplified and non-amplified mitochondrial DNA mixtures to authenticate species. Colloidal GNPs changed color from pinkish-red to gray-purple in 2 mM PBS. Visually observed results were clearly reflected by the dramatic reduction of surface plasmon resonance peak at 530 nm and the appearance of new features in the 620-800 nm regions in their absorption spectra. The particles were stabilized against salt-induced aggregation upon the adsorption of single-stranded DNA. The PCR products, without any additional processing, were hybridized with a 17-base probe prior to exposure to GNPs. At a critical annealing temperature (55 0C) that differentiated matched and mismatched base pairing, the probe was hybridized to pig PCR product and dehybridized from the deer product. The dehybridized probe stuck to GNPs to prevent them from salt-induced aggregation and retained their characteristic red color. Hybridization of a 27-nucleotide probe to swine mitochondrial DNA identified them in pork-venison, pork-shad and venison-shad binary admixtures, eliminating the need of PCR amplification. Thus the assay was applied to authenticate species both in PCR-amplified and non-amplified heterogeneous biological samples. The results were determined visually and validated by absorption spectroscopy. The entire assay (hybridization plus visual detection) was performed in less than 10 min. The LOD (for genomic DNA) of the assay was 6 μg ml-1 swine DNA in mixed meat samples. We believe the assay can be applied for species assignment in food analysis, mismatch detection in genetic screening and homology studies between closely related species.

  12. Nanoparticle sensor for label free detection of swine DNA in mixed biological samples

    Science.gov (United States)

    Ali, M. E.; Hashim, U.; Mustafa, S.; Che Man, Y. B.; Yusop, M. H. M.; Bari, M. F.; Islam, Kh N.; Hasan, M. F.

    2011-05-01

    We used 40 ± 5 nm gold nanoparticles (GNPs) as colorimetric sensor to visually detect swine-specific conserved sequence and nucleotide mismatch in PCR-amplified and non-amplified mitochondrial DNA mixtures to authenticate species. Colloidal GNPs changed color from pinkish-red to gray-purple in 2 mM PBS. Visually observed results were clearly reflected by the dramatic reduction of surface plasmon resonance peak at 530 nm and the appearance of new features in the 620-800 nm regions in their absorption spectra. The particles were stabilized against salt-induced aggregation upon the adsorption of single-stranded DNA. The PCR products, without any additional processing, were hybridized with a 17-base probe prior to exposure to GNPs. At a critical annealing temperature (55 °C) that differentiated matched and mismatched base pairing, the probe was hybridized to pig PCR product and dehybridized from the deer product. The dehybridized probe stuck to GNPs to prevent them from salt-induced aggregation and retained their characteristic red color. Hybridization of a 27-nucleotide probe to swine mitochondrial DNA identified them in pork-venison, pork-shad and venison-shad binary admixtures, eliminating the need of PCR amplification. Thus the assay was applied to authenticate species both in PCR-amplified and non-amplified heterogeneous biological samples. The results were determined visually and validated by absorption spectroscopy. The entire assay (hybridization plus visual detection) was performed in less than 10 min. The LOD (for genomic DNA) of the assay was 6 µg ml - 1 swine DNA in mixed meat samples. We believe the assay can be applied for species assignment in food analysis, mismatch detection in genetic screening and homology studies between closely related species.

  13. Nanoparticle sensor for label free detection of swine DNA in mixed biological samples

    Energy Technology Data Exchange (ETDEWEB)

    Ali, M E; Hashim, U [Institute of Nano Electronic Engineering (INNE), Universiti Malaysia Perlis, Lot 104-108, Tingkat 1, Block A, Taman Pertiwi Indah, Jalan Kangar-Alor Star, Seriab, 01000 Kangar, Perlis (Malaysia); Mustafa, S; Che Man, Y B; Yusop, M H M [Halal Products Research Institute, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Bari, M F [School of Materials Engineering, University Malaysia Perlis, Seriab 01000, Kangar, Perlis (Malaysia); Islam, Kh N [Department of Preclinical Sciences, Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Hasan, M F, E-mail: uda@unimap.edu.my [Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

    2011-05-13

    We used 40 {+-} 5 nm gold nanoparticles (GNPs) as colorimetric sensor to visually detect swine-specific conserved sequence and nucleotide mismatch in PCR-amplified and non-amplified mitochondrial DNA mixtures to authenticate species. Colloidal GNPs changed color from pinkish-red to gray-purple in 2 mM PBS. Visually observed results were clearly reflected by the dramatic reduction of surface plasmon resonance peak at 530 nm and the appearance of new features in the 620-800 nm regions in their absorption spectra. The particles were stabilized against salt-induced aggregation upon the adsorption of single-stranded DNA. The PCR products, without any additional processing, were hybridized with a 17-base probe prior to exposure to GNPs. At a critical annealing temperature (55 {sup 0}C) that differentiated matched and mismatched base pairing, the probe was hybridized to pig PCR product and dehybridized from the deer product. The dehybridized probe stuck to GNPs to prevent them from salt-induced aggregation and retained their characteristic red color. Hybridization of a 27-nucleotide probe to swine mitochondrial DNA identified them in pork-venison, pork-shad and venison-shad binary admixtures, eliminating the need of PCR amplification. Thus the assay was applied to authenticate species both in PCR-amplified and non-amplified heterogeneous biological samples. The results were determined visually and validated by absorption spectroscopy. The entire assay (hybridization plus visual detection) was performed in less than 10 min. The LOD (for genomic DNA) of the assay was 6 {mu}g ml{sup -1} swine DNA in mixed meat samples. We believe the assay can be applied for species assignment in food analysis, mismatch detection in genetic screening and homology studies between closely related species.

  14. Formation and colloidal behaviour of elemental sulphur produced from the biological oxidation of hydrogensulphide.

    OpenAIRE

    Janssen, A.J.H.

    1996-01-01

    The formation and aggregation of elemental sulphur from the microbiological oxidation of hydrogensulphide (H 2 S) by a mixed population of aerobic Thiobacillus -like bacteria has been investigated. Sulphide is formed during the anaerobic treatment of wastewaters which contain oxidized sulphur compounds such as thiosulphate, sulphite and sulphate. This sulphide has to be removed from the effluent solution of anaerobic reactors because of its detrimental characteristics e.g. toxicity, corrosive...

  15. Colloidal organization

    CERN Document Server

    Okubo, Tsuneo

    2015-01-01

    Colloidal Organization presents a chemical and physical study on colloidal organization phenomena including equilibrium systems such as colloidal crystallization, drying patterns as an example of a dissipative system and similar sized aggregation. This book outlines the fundamental science behind colloid and surface chemistry and the findings from the author's own laboratory. The text goes on to discuss in-depth colloidal crystallization, gel crystallization, drying dissipative structures of solutions, suspensions and gels, and similar-sized aggregates from nanosized particles. Special emphas

  16. Biological treatment of concentrated hazardous, toxic, and radionuclide mixed wastes without dilution

    OpenAIRE

    Stringfellow, William T.; Komada, Tatsuyuki; Chang, Li-Yang

    2004-01-01

    Approximately 10 percent of all radioactive wastes produced in the U. S. are mixed with hazardous or toxic chemicals and therefore can not be placed in secure land disposal facilities. Mixed wastes containing hazardous organic chemicals are often incinerated, but volatile radioactive elements are released directly into the biosphere. Some mixed wastes do not currently have any identified disposal option and are stored locally awaiting new developments. Biological treatment has been propo...

  17. Stories of staying and leaving: A mixed methods analysis of biology undergraduate choice, persistence, and departure

    Science.gov (United States)

    Lang, Sarah Adrienne

    Using a sequential, explanatory mixed methods design, this dissertation study compared students who persist in the biology major (persisters) with students who leave the biology major (switchers) in terms of how their pre-college experiences, college biology experiences, and biology performance figured into their choice of biology and their persistence in or departure from the biology major. This study combined (1) quantitative comparisons of biology persisters and switchers via a questionnaire developed for the study and survival analysis of a larger population of biology freshmen with (2) qualitative comparison of biology switchers and persisters via semi-structured life story interviews and homogenous focus groups. 319 students (207 persisters and 112 switchers) participated in the questionnaire and 36 students (20 persisters and 16 switchers) participated in life story and focus group interviews. All participants were undergraduates who entered The University of Texas at Austin as biology freshmen in the fall semesters of 2000 through 2004. Findings of this study suggest: (1) Regardless of eventual major, biology students enter college with generally the same suite of experiences, sources of personal encouragement, and reasons for choosing the biology major; (2) Despite the fact that they have also had poor experiences in the major, biology persisters do not actively decide to stay in the biology major; they simply do not leave; (3) Based upon survival analysis, biology students are most at-risk of leaving the biology major during the first two years of college and if they are African-American or Latino, women, or seeking a Bachelor of Arts degree (rather than a Bachelor of Science); (4) Biology switchers do not leave biology due to preference for other disciplines; they leave due to difficulties or dissatisfaction with aspects of the biology major, including their courses, faculty, and peers; (5) Biology performance has a differential effect on persistence in

  18. Biological carbon monoxide conversion to acetate production by mixed culture.

    Science.gov (United States)

    Nam, Chul Woo; Jung, Kyung A; Park, Jong Moon

    2016-07-01

    To utilize waste CO for mixed culture gas fermentation, carbon sources (CO, CO2) and pH were optimized in the batch system to find out the center point and boundary of response surface method (RSM) for higher acetate (HAc) production (center points: 25% CO, 40% CO2, and pH 8). The concentrations of CO and CO2, and pH had significant effects on acetate production, but the pH was the most significant on the HAc production. The optimum condition for HAc production in the gas fermentation was 20.81% CO, 41.38% CO2, 37.81% N2, and pH 7.18. The continuous gas fermentation under the optimum condition obtained 1.66g/L of cell DW, 23.6g/L HAc, 3.11g/L propionate, and 3.42g/L ethanol. PMID:27035481

  19. Biological treatment of concentrated hazardous, toxic, and radionuclide mixed wastes without dilution

    International Nuclear Information System (INIS)

    Approximately 10 percent of all radioactive wastes produced in the U. S. are mixed with hazardous or toxic chemicals and therefore can not be placed in secure land disposal facilities. Mixed wastes containing hazardous organic chemicals are often incinerated, but volatile radioactive elements are released directly into the biosphere. Some mixed wastes do not currently have any identified disposal option and are stored locally awaiting new developments. Biological treatment has been proposed as a potentially safer alternative to incineration for the treatment of hazardous organic mixed wastes, since biological treatment would not release volatile radioisotopes and the residual low-level radioactive waste would no longer be restricted from land disposal. Prior studies have shown that toxicity associated with acetonitrile is a significant limiting factor for the application of biotreatment to mixed wastes and excessive dilution was required to avoid inhibition of biological treatment. In this study, we demonstrate that a novel reactor configuration, where the concentrated toxic waste is drip-fed into a complete-mix bioreactor containing a pre-concentrated active microbial population, can be used to treat a surrogate acetonitrile mixed waste stream without excessive dilution. Using a drip-feed bioreactor, we were able to treat a 90,000 mg/L acetonitrile solution to less than 0.1 mg/L final concentration using a dilution factor of only 3.4. It was determined that the acetonitrile degradation reaction was inhibited at a pH above 7.2 and that the reactor could be modeled using conventional kinetic and mass balance approaches. Using a drip-feed reactor configuration addresses a major limiting factor (toxic inhibition) for the biological treatment of toxic, hazardous, or radioactive mixed wastes and suggests that drip-feed bioreactors could be used to treat other concentrated toxic waste streams, such as chemical warfare materiel

  20. Blade-mixing reactors in the biological treatment of contaminated soils

    International Nuclear Information System (INIS)

    The application of mixing reactors was expected to have a positive effect on the biological turnover of contaminants, especially for cohesive soils. During investigations using blade-mixing reactors, it appeared to be of utmost importance to inhibit or reduce pellet formation during the dynamic treatment of soils. In this connection, a comparison of the degradation kinetics in static and dynamic reactors is of great interest. Contaminants of concern were diesel fuel and lubricating oil

  1. Mixed cropping systems for biological control of weeds and pests in organic oilseed crops

    OpenAIRE

    Paulsen, Hans Marten; Schochow, Martin; Ulber, B; Kühne, Stefan; Rahmann, Gerold

    2006-01-01

    Agricultural advantages of mixed cropping are gained by biological effects like light competition, offering weed-suppressing capacities or by diversification of plant covers to break development cycles of pests. In a two-year project on mixed cropping with organic oilseed crops these effects were measured. It was found that weeds can be efficiently suppressed in organic linseed (Linum usitatissivum) in crop combinations with wheat (Triticum aestivum) or false flax (Camelina sativa). But linse...

  2. Biological treatment of concentrated hazardous, toxic, andradionuclide mixed wastes without dilution

    Energy Technology Data Exchange (ETDEWEB)

    Stringfellow, William T.; Komada, Tatsuyuki; Chang, Li-Yang

    2004-06-15

    Approximately 10 percent of all radioactive wastes produced in the U. S. are mixed with hazardous or toxic chemicals and therefore can not be placed in secure land disposal facilities. Mixed wastes containing hazardous organic chemicals are often incinerated, but volatile radioactive elements are released directly into the biosphere. Some mixed wastes do not currently have any identified disposal option and are stored locally awaiting new developments. Biological treatment has been proposed as a potentially safer alternative to incineration for the treatment of hazardous organic mixed wastes, since biological treatment would not release volatile radioisotopes and the residual low-level radioactive waste would no longer be restricted from land disposal. Prior studies have shown that toxicity associated with acetonitrile is a significant limiting factor for the application of biotreatment to mixed wastes and excessive dilution was required to avoid inhibition of biological treatment. In this study, we demonstrate that a novel reactor configuration, where the concentrated toxic waste is drip-fed into a complete-mix bioreactor containing a pre-concentrated active microbial population, can be used to treat a surrogate acetonitrile mixed waste stream without excessive dilution. Using a drip-feed bioreactor, we were able to treat a 90,000 mg/L acetonitrile solution to less than 0.1 mg/L final concentration using a dilution factor of only 3.4. It was determined that the acetonitrile degradation reaction was inhibited at a pH above 7.2 and that the reactor could be modeled using conventional kinetic and mass balance approaches. Using a drip-feed reactor configuration addresses a major limiting factor (toxic inhibition) for the biological treatment of toxic, hazardous, or radioactive mixed wastes and suggests that drip-feed bioreactors could be used to treat other concentrated toxic waste streams, such as chemical warfare materiel.

  3. Active colloids

    Science.gov (United States)

    Aranson, Igor S.

    2013-01-01

    A colloidal suspension is a heterogeneous fluid containing solid microscopic particles. Colloids play an important role in our everyday life, from food and pharmaceutical industries to medicine and nanotechnology. It is useful to distinguish two major classes of colloidal suspensions: equilibrium and active, i.e., maintained out of thermodynamic equilibrium by external electric or magnetic fields, light, chemical reactions, or hydrodynamic shear flow. While the properties of equilibrium colloidal suspensions are fairly well understood, active colloids pose a formidable challenge, and the research is in its early exploratory stage. One of the most remarkable properties of active colloids is the possibility of dynamic self-assembly, a natural tendency of simple building blocks to organize into complex functional architectures. Examples range from tunable, self-healing colloidal crystals and membranes to self-assembled microswimmers and robots. Active colloidal suspensions may exhibit material properties not present in their equilibrium counterparts, e.g., reduced viscosity and enhanced self-diffusivity, etc. This study surveys the most recent developments in the physics of active colloids, both in synthetic and living systems, with the aim of elucidation of the fundamental physical mechanisms governing self-assembly and collective behavior.

  4. Preservice Teachers' Epistemological Beliefs in Physics, Chemistry, and Biology: A Mixed Study

    Science.gov (United States)

    Topcu, Mustafa Sami

    2013-01-01

    The purposes of the study were to assess preservice teachers' domain-specific epistemological beliefs and to investigate whether preservice teachers distinguish disciplinary differences (physics, chemistry, and biology) in domain-specific epistemological beliefs. Mixed-method research design guided the present research. The researcher explored…

  5. EDITORIAL: Colloidal suspensions Colloidal suspensions

    Science.gov (United States)

    Petukhov, Andrei; Kegel, Willem; van Duijneveldt, Jeroen

    2011-05-01

    Colloid-polymer mixtures and depletion interactions Phase stability of a reversible supramolecular polymer solution mixed with nanospheres Remco Tuinier When depletion goes critical Roberto Piazza, Stefano Buzzaccaro, Alberto Parola and Jader Colombo Tuning the demixing of colloid-polymer systems through the dispersing solvent E A G Jamie, R P A Dullens and D G A L Aarts Polydispersity effects in colloid-polymer mixtures S M Liddle, T Narayanan and W C K Poon Colloidal dynamics and crystallization Crystallization and aging in hard-sphere glasses C Valeriani, E Sanz, E Zaccarelli, W C K Poon, M E Cates and P N Pusey Real-time monitoring of complex moduli from micro-rheology Taiki Yanagishima, Daan Frenkel, Jurij Kotar and Erika Eiser Brownian motion of a self-propelled particle B ten Hagen, S van Teeffelen and H Löwen Crystallization in suspensions of hard spheres: a Monte Carlo and molecular dynamics simulation study T Schilling, S Dorosz, H J Schöpe and G Opletal Structural signature of slow dynamics and dynamic heterogeneity in two-dimensional colloidal liquids: glassy structural order Takeshi Kawasaki and Hajime Tanaka

  6. Crack formation and prevention in colloidal drops

    Science.gov (United States)

    Kim, Jin Young; Cho, Kun; Ryu, Seul-a; Kim, So Youn; Weon, Byung Mook

    2015-01-01

    Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles. PMID:26279317

  7. Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems

    Directory of Open Access Journals (Sweden)

    V. Rossi

    2009-08-01

    Full Text Available Eastern Boundary Upwelling Systems (EBUS are characterized by a high productivity of plankton associated with large commercial fisheries, thus playing key biological and socio-economical roles. Since they are populated by several physical oceanic structures such as filaments and eddies, which interact with the biological processes, it is a major challenge to study this sub- and mesoscale activity in connection with the chlorophyll distribution. The aim of this work is to make a comparative study of these four upwelling systems focussing on their surface stirring, using the Finite Size Lyapunov Exponents (FSLEs, and their biological activity, based on satellite data. First, the spatial distribution of horizontal mixing is analysed from time averages and from probability density functions of FSLEs, which allow us to divide each areas in two different subsystems. Then we studied the temporal variability of surface stirring focussing on the annual and seasonal cycle. We also proposed a ranking of the four EBUS based on the averaged mixing intensity. When investigating the links with chlorophyll concentration, the previous subsystems reveal distinct biological signatures. There is a global negative correlation between surface horizontal mixing and chlorophyll standing stocks over the four areas. To try to better understand this inverse relationship, we consider the vertical dimension by looking at the Ekman-transport and vertical velocities. We suggest the possibility of a changing response of the phytoplankton to sub/mesoscale turbulence, from a negative effect in the very productive coastal areas to a positive one in the open ocean. This study provides new insights for the understanding of the variable biological productivity in the ocean, which results from both dynamics of the marine ecosystem and of the 3-D turbulent medium.

  8. Colloidal superballs

    OpenAIRE

    Rossi, L.

    2012-01-01

    This thesis is organized in four parts as follows. Part 1 focuses on the synthetic aspects of the colloidal model systems that will be used throughout the work described in this thesis. In Chapter 2 we describe synthetic procedures for the preparation of polycrystalline hematite superballs and superellipsoids. The internal structure of the particles is also investigated and will be used later to understand the magnetic properties of colloidal hematite. The same hematite particles are used as ...

  9. Topological colloids.

    Science.gov (United States)

    Senyuk, Bohdan; Liu, Qingkun; He, Sailing; Kamien, Randall D; Kusner, Robert B; Lubensky, Tom C; Smalyukh, Ivan I

    2013-01-10

    Smoke, fog, jelly, paints, milk and shaving cream are common everyday examples of colloids, a type of soft matter consisting of tiny particles dispersed in chemically distinct host media. Being abundant in nature, colloids also find increasingly important applications in science and technology, ranging from direct probing of kinetics in crystals and glasses to fabrication of third-generation quantum-dot solar cells. Because naturally occurring colloids have a shape that is typically determined by minimization of interfacial tension (for example, during phase separation) or faceted crystal growth, their surfaces tend to have minimum-area spherical or topologically equivalent shapes such as prisms and irregular grains (all continuously deformable--homeomorphic--to spheres). Although toroidal DNA condensates and vesicles with different numbers of handles can exist and soft matter defects can be shaped as rings and knots, the role of particle topology in colloidal systems remains unexplored. Here we fabricate and study colloidal particles with different numbers of handles and genus g ranging from 1 to 5. When introduced into a nematic liquid crystal--a fluid made of rod-like molecules that spontaneously align along the so-called 'director'--these particles induce three-dimensional director fields and topological defects dictated by colloidal topology. Whereas electric fields, photothermal melting and laser tweezing cause transformations between configurations of particle-induced structures, three-dimensional nonlinear optical imaging reveals that topological charge is conserved and that the total charge of particle-induced defects always obeys predictions of the Gauss-Bonnet and Poincaré-Hopf index theorems. This allows us to establish and experimentally test the procedure for assignment and summation of topological charges in three-dimensional director fields. Our findings lay the groundwork for new applications of colloids and liquid crystals that range from

  10. Preparation, Spectroscopic Investigation and Biological Activity of New Mixed Ligand Chelates

    International Nuclear Information System (INIS)

    Preparation and investigation of new Co(II), Ni(II), Zn(II) and Cr(III) chelates with mixed ligands including Schiff base (L1) formed from the condensation of 4-dimethylaminobenzaldehyde with 2-aminophenol and anthranilic acid (L2) were studied. The obtained Schiff base and mixed ligand chelates were subjected to several physiochemical techniques, in terms of CHN elemental analyses, molar conductivity, magnetic moment measurements, infrared, proton nuclear magnetic resonance, electronic and mass spectra. The analytical data showed the formation of the Schiff base compound and the ratio of metal to ligands of the chelates are 1:1:1(M:L1:L2). The infrared spectral data exhibited that the used ligands behaving as bidentate ligands towards the metal ions. The proton nuclear magnetic resonance spectral data showed the signals of the active groups in the ligands which entered in chelation with Zn(II) metal ion. The electronic spectral results showed the existence of pie (phenyl ring) and n = pie (C=N) of the ligands and suggested the geometrical structures of the chelates. Meanwhile, the mass spectral data revealed the fragmentations of the Schiff base, anthranilic acid and their Ni(II) mixed ligand chelate has been preformed the only chelate conducted for justification. All the prepared mixed chelates were non-electrolyte in nature. The antibacterial activity of the Schiff base, anthranilic acid, metal salts and mixed ligand chelates were studied and found to be that mixed ligand chelates have the most biological activity in comparison to the free ligands and salts. (author)

  11. Biological and Irradiation Treatment of Mix Industrial Wastewater in Flood Mitigation Pond at Prai Industrial Zone

    International Nuclear Information System (INIS)

    In this work, activated sludge process and E-Beam was used to treat mixed industrial waste water from mitigation pond A. The objectives of this study to analyze the effect of mix liquor volatile suspended solid (MLVSS) concentration on the properties of wastewater and duration of time taken to achieve steady stage condition for biological treatment. Besides that, effect of electron beam energy on the characteristic of wastewater after irradiation with electron beam machine EPS 3000 was studied as well. The result shows removal percentage of COD, suspended solid and color was linearly proportional with MLVSS. Maximum reduction values recorded for COD, suspended solid and color removal was 69.4, 73.0 and 43.7 % respectively with 3500 mg/l MLVSS at 48 h HRT. In irradiation treatment, significant reduction of COD was obtained with the increase of electron beam energy but the results for suspended solid and color was not favorable. (author)

  12. Radioactive colloids

    International Nuclear Information System (INIS)

    Different techniques for the characterization of radioactive colloids, used in nuclear medicine, have been evaluated and compared. Several radioactive colloids have been characterized in vitro and in vivo and tested experimentally. Colloid biokinetics following interstitial or intravenous injection were evaluated with a scintillation camera technique. Lymphoscintigraphy with a Tc-99-labelled antimony sulphur colloid was performed in 32 patients with malignant melanoma in order to evaluate the technique. Based on the biokinetic results, absorbed doses in tissues and organs were calculated. The function of the reticuloendothelial system has been evaluated in rats after inoculation with tumour cells. Microfiltration and photon correlation spectroscopy were found to be suitable in determining activity-size and particle size distributions, respectively. Maximal lymph node uptake following subcutaneous injection was found to correspond to a colloid particle size between 10 and 50 nm. Lymphoscintigraphy was found to be useful in the study of lymphatic drainage from the primary tumour site in patients with malignant melanoma on the trunk. Quantitative analysis of ilio-inguinal lymph node uptake in patients with malignant melanoma on the lower extremities was, however, found to be of no value for the detection of metastatic disease in lymph nodes. High absorbed doses may be received in lymph nodes (up to 1 mGy/MBq) and at the injection site (about 10 mGy/MBq). In an experimental study it was found that the relative colloid uptake in bone marrow and spleen depended on the total number of intravenously injected particles. This may considerably affect the absorbed dose in these organs. (author)

  13. Colloidal nematostatics

    Directory of Open Access Journals (Sweden)

    V.M. Pergamenshchik

    2010-01-01

    Full Text Available We give a review of the theory of large distance colloidal interaction via the nematic director field. The new area of nematic colloidal systems (or nematic emulsions has been guided by the analogy between the colloidal nematostatics and electrostatics. The elastic charge density representation of the colloidal nematostatics [V.M. Pergamenshchik, V.O. Uzunova, Eur. Phys. J. E, 2007, 23, 161; Phys. Rev. E, 2007, 76, 011707] develops this analogy at the level of charge density and Coulomb interaction. The analogy is shown to lie in common mathematics based on the solutions of Laplace equation. However, the 3d colloidal nematostatics substantially differs from electrostatics both in its mathematical structure and physical implications. The elastic charge is a vector fully determined by the torque exerted upon colloid, the role of Gauss' theorem is played by conservation of the torque components. Elastic multipoles consist of two tensors (dyads. Formulas for the elastic multipoles, the Coulomb-like, dipole-dipole, and quadrupole-quadrupole pair interaction potentials are derived and illustrated by particular examples. Based on the tensorial structure, we list possible types of elastic dipoles and quadrupoles. An elastic dipole is characterized by its isotropic strength, anisotropy, chirality, and its longitudinal component. An elastic quadrupole can be uniaxial and biaxial. Relation between the multipole type and its symmetry is discussed, sketches of some types of multipoles are given. Using the mirror image method of electrostatics as a guiding idea, we develop the mirror image method in nematostatics for arbitrary director tilt at the wall. The method is applied to the charge-wall and dipole-wall interaction.

  14. Multi-objective mixed integer strategy for the optimisation of biological networks.

    Science.gov (United States)

    Sendín, J O H; Exler, O; Banga, J R

    2010-05-01

    In this contribution, the authors consider multi-criteria optimisation problems arising from the field of systems biology when both continuous and integer decision variables are involved. Mathematically, they are formulated as mixed-integer non-linear programming problems. The authors present a novel solution strategy based on a global optimisation approach for dealing with this class of problems. Its usefulness and capabilities are illustrated with two metabolic engineering case studies. For these problems, the authors show how the set of optimal solutions (the so-called Pareto front) is successfully and efficiently obtained, providing further insight into the systems under consideration regarding their optimal manipulation. PMID:20500003

  15. The reduction of biological production induced by mesoscale mixing: a modelling study in the Benguela upwelling

    CERN Document Server

    Hernández-Carrasco, Ismael; Hernández-García, Emilio; Garçon, Veronique; López, Cristóbal

    2013-01-01

    Recent studies, both based on remote sensed data and coupled models, showed a reduction of biological productivity due to vigorous horizontal mixing in upwelling systems. In order to better understand this phenomenon, we have considered a system of oceanic flow in the Benguela area coupled with a simple biogeochemical model of Nutrient-Phyto-Zooplankton (NPZ) type. For the flow three different surface velocity fields are considered: one derived from satellite altimetry data, and the other two from a regional numerical model at two different spatial resolutions. We computed horizontal particle dispersion in terms of Lyapunov Exponents, and analyzed their correlations with phytoplankton concentrations. Our modelling approach confirms that in the south Benguela, there is a reduction of biological activity when stirring is increased. Two-dimensional offshore advection seems to be the dominant process involved. In the northern area, other factors not taken into account in our simulation are influencing the ecosyst...

  16. Colloidal superballs

    NARCIS (Netherlands)

    Rossi, L.

    2012-01-01

    This thesis is organized in four parts as follows. Part 1 focuses on the synthetic aspects of the colloidal model systems that will be used throughout the work described in this thesis. In Chapter 2 we describe synthetic procedures for the preparation of polycrystalline hematite superballs and super

  17. Integrative Approach for Producing Hydrogen and Polyhydroxyalkanoate from Mixed Wastes of Biological Origin.

    Science.gov (United States)

    Patel, Sanjay K S; Lee, Jung-Kul; Kalia, Vipin C

    2016-09-01

    In this study, an integrative approach to produce biohydrogen (H2) and polyhydroxyalkanoates (PHA) from the wastes of biological origin was investigated. A defined set of mixed cultures was used for hydrolysis and the hydrolysates were used to produce H2. The effluent from H2 production stage was used for PHA production. Under batch culture, a maximum of 62 l H2/kg of pure potato peels (Total solid, TS 2 %, w/v) and 54 l H2/kg of mixed biowastes (MBW1) was recorded. Using effluent from the H2 production stage of biowaste mixture (MBW1), Bacillus cereus EGU43 could produce 195 mg PHA/l and 15.6 % (w/w). Further, supplementation of GM-2 medium (0.1×) and glucose (0.5 %) in H2 production stage effluents, resulted in significant improvements of up to 11 and 41.7 % of PHA contents, respectively. An improvement of 3.9- and 17-fold in PHA yields as compared to with and without integrative H2 production from the MBW1 has been recorded. This integrative approach seems to be a suitable process to improve the yields of H2 and PHA by mixing biowastes. PMID:27407293

  18. Mixing regime as a key factor to determine DON formation in drinking water biological treatment.

    Science.gov (United States)

    Lu, Changqing; Li, Shuai; Gong, Song; Yuan, Shoujun; Yu, Xin

    2015-11-01

    Dissolved organic nitrogen (DON) can act as precursor of nitrogenous disinfection by-products formed during chlorination disinfection. The performances of biological fluidized bed (continuous stirred tank reactor, CSTR) and bio-ceramic filters (plug flow reactor, PFR) were compared in this study to investigate the influence of mixing regime on DON formation in drinking water treatment. In the shared influent, DON ranged from 0.71mgL(-1) to 1.20mgL(-1). The two biological fluidized bed reactors, named BFB1 (mechanical stirring) and BFB2 (air agitation), contained 0.12 and 0.19mgL(-1) DON in their effluents, respectively. Meanwhile, the bio-ceramic reactors, labeled as BCF1 (no aeration) and BCF2 (with aeration), had 1.02 and 0.81mgL(-1) DON in their effluents, respectively. Comparative results showed that the CSTR mixing regime significantly reduced DON formation. This particular reduction was further investigated in this study. The viable/total microbial biomass was determined with propidium monoazide quantitative polymerase chain reaction (PMA-qPCR) and qPCR, respectively. The results of the investigation demonstrated that the microbes in BFB2 had higher viability than those in BCF2. The viable bacteria decreased more sharply than the total bacteria along the media depth in BCF2, and DON in BCF2 accumulated in the deeper media. These phenomena suggested that mixing regime determined DON formation by influencing the distribution of viable, total biomass, and ratio of viable biomass to total biomass. PMID:25585870

  19. InteractoMIX: a suite of computational tools to exploit interactomes in biological and clinical research.

    Science.gov (United States)

    Poglayen, Daniel; Marín-López, Manuel Alejandro; Bonet, Jaume; Fornes, Oriol; Garcia-Garcia, Javier; Planas-Iglesias, Joan; Segura, Joan; Oliva, Baldo; Fernandez-Fuentes, Narcis

    2016-06-15

    Virtually all the biological processes that occur inside or outside cells are mediated by protein-protein interactions (PPIs). Hence, the charting and description of the PPI network, initially in organisms, the interactome, but more recently in specific tissues, is essential to fully understand cellular processes both in health and disease. The study of PPIs is also at the heart of renewed efforts in the medical and biotechnological arena in the quest of new therapeutic targets and drugs. Here, we present a mini review of 11 computational tools and resources tools developed by us to address different aspects of PPIs: from interactome level to their atomic 3D structural details. We provided details on each specific resource, aims and purpose and compare with equivalent tools in the literature. All the tools are presented in a centralized, one-stop, web site: InteractoMIX (http://interactomix.com). PMID:27284060

  20. Preparation of radioactive colloidal gold 198Au

    International Nuclear Information System (INIS)

    The preparation with simple equipment of radioactive colloidal gold of particle size about approximately 300 A from seed colloid stabilized by gelatine is described. Some physico-chemical parameters which can affect the process of formation of these colloidal particles are analysed; particle size has been meassured with an electron microscope. The colloid stability has been studied as a function of dilution, age and pH. Nucleation and growth of radioactive colloidal gold have been studied using spectrophotometry. Absorption spectra of the two ones are presented and compared. Quality control of the production process is verified through measurement of parameters, such as radioactive and radiochemical purity and biological distribution in laboratorial animals. This distribution was evalusted for rats injected endovenously with the gold colloidal solution.(Author)

  1. Mixed

    Directory of Open Access Journals (Sweden)

    Pau Baya

    2011-05-01

    Full Text Available Remenat (Catalan (Mixed, "revoltillo" (Scrambled in Spanish, is a dish which, in Catalunya, consists of a beaten egg cooked with vegetables or other ingredients, normally prawns or asparagus. It is delicious. Scrambled refers to the action of mixing the beaten egg with other ingredients in a pan, normally using a wooden spoon Thought is frequently an amalgam of past ideas put through a spinner and rhythmically shaken around like a cocktail until a uniform and dense paste is made. This malleable product, rather like a cake mixture can be deformed pulling it out, rolling it around, adapting its shape to the commands of one’s hands or the tool which is being used on it. In the piece Mixed, the contortion of the wood seeks to reproduce the plasticity of this slow heavy movement. Each piece lays itself on the next piece consecutively like a tongue of incandescent lava slowly advancing but with unstoppable inertia.

  2. Uranium accumulation in mixed-liquor suspended solids during biological wastewater treatment

    International Nuclear Information System (INIS)

    The accumulation of uranium by mixed liquor suspended solids (MLSS) has been of growing interest to regulatory officials and governmental agencies which process radioactive materials, especially in light of more stringent environmental standards and increasing liability concerns. Uranium uptake by MLSS can be significant, potentially creating a problem for disposal of the waste activated sludge. The goal of this research was to determine bioconcentration factors under different wastewater treatment operating conditions using continuous flow, stirred tank reactors with recycle. Wastewater, consisting of approximately 95% domestic sewage and 5% industrial waste which contained trace amounts of uranium, was used to study uranium build-up by the MLSS. A total of six biological reactors were included in the study, with three reactors operated at 20C and three reactors operated at 5C. Sludge ages of ∼ 5, 15, and 20 days were established in the reactors at the two operating temperatures. Uranium accumulation by the sludge solids was evaluated under different temperatures and sludge ages. Mixed-liquor samples were collected and separated into solid and supernatant fractions by centrifugation before uranium analysis. Uranium (both total and U235) was sequestered by the MLSS from the subject wastewater in all reactors during the study. Uranium uptake capacities ranged from 5-30μg/g dry solids, and distribution coefficients ranged from approximately 1,300 to 5,800 cm3/g . Due to higher than optimum pH and extremely low uranium concentration gradients, the observed specific uranium uptake capacities were much lower than those reported in the literature for laboratory biosorption experiments conducted at optimum pH values and large uranium concentration gradients. Total suspended solids concentration and sludge age influenced the specific uranium uptake as well as the total uranium sorbed

  3. Effect of chaotic mixing on enhanced biological growth and implications for wastewater treatment: A test case with Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Mixing patterns and modes have a great influence on the efficiency of biological treatment systems. A series of laboratory experiments was conducted with a controlled, small-scale analog of a pilot wastewater aeration tank, consisting of two eccentrically placed cylinders. By controlling the rotation direction and speed of the two cylinders, it has been possible to develop chaotic flow fields in the space between the walls of the cylinders. Our experiments utilized Saccharomyces cerevisiae as the biological oxidation organism and air bubbles as the mixing agent supplied by a large fine pore diffuser to the cells in their exponential growth phase. The effect of various mixing patterns on cell growth was studied at different cylinder eccentricities, rotation directions and speeds. It was found that chaotic advection flow patterns: (a) enhanced growth, and (b) sped up the onset of maximal growth of the organism by 15-18% and 14-20%, respectively

  4. Towards Directional Colloidal Interactions

    NARCIS (Netherlands)

    Kamp, M.

    2015-01-01

    Colloids are particles with a size on the scale of microns in at least one dimension. The central theme of this thesis is the synthesis of model colloids with anisotropic interactions - often called `patchy' colloids, as well as the search for new ways to assemble such colloids. Methods to build non

  5. Characterization and stability investigation of water dispersible colloids (WDCs) in natural soils

    OpenAIRE

    Jiang, Canlan

    2013-01-01

    In this work, surface properties, colloidal behaviours and mobilization processes of easily dispersed soil colloids or water dispersible colloids (WDCs) from three TERENO silt loam soils (arable, grassland and forest soils) have been investigated. Firstly, the colloidal behavior of soil mineral colloids (quartz and illite) was investigated in Na, Ca and mixed Na-Ca systems with photon correlation spectroscopy (PCS) and microeletrophoretic method, respectively. The critical coagulation concent...

  6. Synthesis, structural elucidation, biological, antioxidant and nuclease activities of some 5-Fluorouracil-amino acid mixed ligand complexes

    Science.gov (United States)

    Shobana, Sutha; Subramaniam, Perumal; Mitu, Liviu; Dharmaraja, Jeyaprakash; Arvind Narayan, Sundaram

    2015-01-01

    Some biologically active mixed ligand complexes (1-9) have been synthesized from 5-Fluorouracil (5-FU; A) and amino acids (B) such as glycine (gly), L-alanine (ala) and L-valine (val) with Ni(II), Cu(II) and Zn(II) ions. The synthesized mixed ligand complexes (1-9) were characterized by various physico-chemical, spectral, thermal and morphological studies. 5-Fluorouracil and its mixed ligand complexes have been tested for their in vitro biological activities against some pathogenic bacterial and fungal species by the agar well diffusion method. The in vitro antioxidant activities of 5-Fluorouracil and its complexes have also been investigated by using the DPPH assay method. The results demonstrate that Cu(II) mixed ligand complexes (4-6) exhibit potent biological as well as antioxidant activities compared to 5-Fluorouracil and Ni(II) (1-3) and Zn(II) (7-9) mixed ligand complexes. Further, the cleaving activities of CT DNA under aerobic conditions show moderate activity with the synthesized Cu(II) and Ni(II) mixed ligand complexes (1-6) while no activity is seen with Zn(II) complexes (7-9). Binding studies of CT DNA with these complexes show a decrease in intensity of the charge transfer band to the extent of 5-15% along with a minor red shift. The free energy change values (Δ‡G) calculated from intrinsic binding constants indicate that the interaction between mixed ligand complex and DNA is spontaneous.

  7. Electrochromism with colloidal WO3 and IrO2

    Science.gov (United States)

    Michalak, Franck; Rault, L.; Aldebert, Pierre

    1992-11-01

    Colloidal particles of WO3 and IrO2 are synthesized and dispersed within a gelatinous perfluorinated ionomer matrix. Experimental procedures are established in order to obtain percolation between the electrochromic particles. Colloidal particle sizes are measured by quasi elastic light scattering. Electrochemical properties of the mixed colloid electrodes are determined by cyclic voltammetry and impedance spectroscopy. Preliminary optical tests are performed in order to measure transmission and contrast of electrochromic half cells with a mixed colloid electrode, and also a sputtered oxide electrode.

  8. Enrichment of colloidal solutions by nanoparticles in underwater spark discharge

    International Nuclear Information System (INIS)

    The underwater spark discharge between manganese granules was studied. Optical emission spectroscopy methods were used for diagnostics of such discharge plasma. The colloidal solution with manganese nanoparticles was produced by this discharge. The biological applications of this colloid were analyzed. The mechanism of metallic nanoparticle action and their transformation at interacting with biological objects were studied in Alternaria alternata culture

  9. Colloidal Dispersions

    Science.gov (United States)

    Russel, W. B.; Saville, D. A.; Schowalter, W. R.

    1992-03-01

    The book covers the physical side of colloid science from the individual forces acting between submicron particles suspended in a liquid through the resulting equilibrium and dynamic properties. The relevant forces include Brownian motion, electrostatic repulsion, dispersion attraction, both attraction and repulsion due to soluble polymer, and viscous forces due to relative motion between the particles and the liquid. The balance among Brownian motion and the interparticle forces decides the questions of stability and phase behavior. Imposition of external fields produces complex effects, i.e. electrokinetic phenomena (electric field), sedimentation (gravitational field), diffusion (concentration/chemical potential gradient), and non-Newtonian rheology (shear field). The treatment aims to impart a sound, quantitative understanding based on fundamental theory and experiments with well-characterized model systems. This broad grasp of the fundamentals lends insight and helps to develop the intuitive sense needed to isolate essential features of technological problems and design critical experiments. Some exposure to fluid mechanics, statistical mechanics, and electricity and magnetism is assumed, but each subject is reintroduced in a self-contained manner.

  10. Hydrophobic-Sheath Segregated Macromolecular Fluorophores: Colloidal Nanoparticles of Polycaprolactone-Grafted Conjugated Polymers with Bright Far-Red/Near-Infrared Emission for Biological Imaging.

    Science.gov (United States)

    Yang, Cangjie; Liu, Hui; Zhang, Yingdan; Xu, Zhigang; Wang, Xiaochen; Cao, Bin; Wang, Mingfeng

    2016-05-01

    This article describes molecular design, synthesis and characterization of colloidal nanoparticles containing polycaprolactone-grafted conjugated polymers that exhibit strong far red/near-infrared (FR/NIR) fluorescence for bioimaging. Specifically, we synthesized two kinds of conjugated polymer bottle brushes (PFTB(out)-g-PCL and PFTB(in)-g-PCL) with different positions of the hexyl groups on the thiophene rings. A synthetic amphiphilic block copolymer PCL-b-POEGMA was employed as surfactants to encapsulate PFTB-g-PCL polymers into colloidal nanoparticles (denoted as "nanoREDs") in aqueous media. The chain length of the PCL side chains in PFTB-g-PCL played a critical role in determining the fluorescence properties in both bulk solid states and the colloidal nanoparticles. Compared to semiconducting polymer dots (Pdots) composed of PFTB(out) without grafted PCL, nanoRED(out) showed at least four times higher fluorescence quantum yield (∼20%) and a broader emission band centered at 635 nm. We further demonstrated the application of this new class of nanoREDs for effective labeling of L929 cells and HeLa cancer cells with good biocompatibility. This strategy of hydrophobic-sheath segregated macromolecular fluorophores is expected to be applicable to a broad range of conjugated polymers with tunable optical properties for applications such as bioimaging. PMID:27010718

  11. Lagrangian evolution of DMS during the Southern Ocean gas exchange experiment: The effects of vertical mixing and biological community shift

    Science.gov (United States)

    Yang, M.; Archer, S. D.; Blomquist, B. W.; Ho, D. T.; Lance, V. P.; Torres, R. J.

    2013-12-01

    Concentrations of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) are highly variable in time and space. What is driving the variability in DMS(P), and can those variability be explained by physical processes and changes in the biological community? During the Southern Ocean Gas Exchange Experiment (SO GasEx) in the austral fall of 2008, two 3He/SF6 labeled patches were created in the surface water. SF6 and DMS were surveyed continuously in a Lagrangian framework, while direct measurements of air-sea exchange further constrained the gas budgets. Turbulent diffusivity at the base of the mixed layer was estimated from SF6 profiles and used to calculate the vertical fluxes of DMS and nutrients. Increasing mixed layer nutrient concentrations due to mixing were associated with a shift in the phytoplankton community structure, which in turned likely affected the sulfur dynamics on timescales of days. DMS concentration as well as air-sea DMS flux appeared to be decoupled from the DMSP concentration, possibly due to grazing and bacterial DMS production. Contrary to expectations, in an environment with high winds and modest productivity, physical processes (air-sea exchange, photochemistry, vertical mixing) only accounted for a small fraction of DMS loss from the surface water. Among the DMS sinks, inferred biological consumption most likely dominated during SO GasEx.

  12. Biological behavior of mixed LMFBR-fuel-sodium aerosols in rodents

    International Nuclear Information System (INIS)

    Clearance of 239Pu from lung and other tissues was determined after nose-only exposure of rats to mixed aerosols of sodium-LMFBR fuel or to LMFBR fuels only. The rates of clearance from lung and from total body were both higher after exposure to the mixed sodium-fuel than after exposure to fuel-only aerosols

  13. NATO Advanced Study Institute on Mixed-Valence Compounds : Theory and Applications in Chemistry, Physics, Geology, and Biology

    CERN Document Server

    1980-01-01

    It has been a decade since two seminal reviews demonstrated that mixed-valence compounds share many unique and fascinating features. The insight pro­ vided by those early works has promoted a great deal of both experimental and theoretical study. As a result of extensive efforts, our understanding of the bonding and properties of mixed-valence compounds has advanced substantially. There has been no compre­ hensive treatment of mixed-valence compounds since 1967, and the meeting convened at Oxford in September, 1979, provided a unique opportunity to examine the subject and its many ramifications. Mixed-valence compounds play an important role in many fields. Although the major impact of the subject has been in chemistry, its importance has become increasingly clear in solid state physics, geology, and biology. Extensive interest and effort in the field of molecular metals has demonstrated that mixed-valency is a prerequisite for high elec­ trical conductivity. The intense colors of many minerals have been s...

  14. Colloidal Plasmas : Basic physics of colloidal plasmas

    Indian Academy of Sciences (India)

    C B Dwivedi

    2000-11-01

    Colloidal plasma is a distinct class of the impure plasmas with multispecies ionic composition. The distinction lies in the phase distribution of the impurity-ion species. The ability to tailor the electrostatic interactions between these colloidal particles provides a fertile ground for scientists to investigate the fundamental aspects of the Coulomb phase transition behavior. The present contribution will review the basic physics of the charging mechanism of the colloidal particles as well as the physics of the collective normal mode behavior of the general multi-ion species plasmas. Emphasis will be laid on the clarification of the prevailing confusing ideas about distinct qualities of the various acoustic modes, which are likely to exist in colloidal plasmas as well as in normal multi-ion species plasmas. Introductory ideas about the proposed physical models for the Coulomb phase transition in colloidal plasma will also be discussed.

  15. Efficacy of biological agents administered as monotherapy in rheumatoid arthritis: a Bayesian mixed-treatment comparison analysis

    Directory of Open Access Journals (Sweden)

    Migliore A

    2015-09-01

    Full Text Available Alberto Migliore,1 Emanuele Bizzi,1 Colin Gerard Egan,2 Mauro Bernardi,3 Lea Petrella4 1Rheumatology Unit, San Pietro Fatebenefratelli Hospital, Rome, 2Primula Multimedia SRL, Pisa, 3Department of Statistical Sciences, University of Padova, Padova, 4MEMOTEF Department, Sapienza University of Rome, Rome, Italy Background: Biological agents provide an important therapeutic alternative for rheumatoid arthritis patients refractory to conventional disease-modifying antirheumatic drugs. Few head-to-head comparative trials are available.Purpose: The aim of this meta-analysis was to compare the relative efficacy of different biologic agents indicated for use as monotherapy in rheumatoid arthritis.Methods: A systemic literature search was performed on electronic databases to identify articles reporting double-blind randomized controlled trials investigating the efficacy of biologic agents indicated for monotherapy. Efficacy was assessed using American College of Rheumatology (ACR 20, 50, and 70 criteria at 16–24 weeks. Relative efficacy was estimated using Bayesian mixed-treatment comparison models. Outcome measures were expressed as odds ratio and 95% credible intervals.Results: Ten randomized controlled trials were selected for data extraction and analysis. Mixed-treatment comparison analysis revealed that tocilizumab offered 100% probability of being the best treatment for inducing an ACR20 response versus placebo, methotrexate, adalimumab, or etanercept. Likewise, for ACR50 and ACR70 outcome responses, tocilizumab had a 99.8% or 98.7% probability of being the best treatment, respectively, compared to other treatments or placebo. Tocilizumab increased the relative probability of being the best treatment (vs methotrexate by 3.2-fold (odds ratio: 2.1–3.89 for all ACR outcomes.Conclusion: Tocilizumab offered the greatest possibility of obtaining an ACR20, ACR50, and ACR70 outcome vs other monotherapies or placebo. Keywords: biologics, meta

  16. Microfluidic colloid filtration.

    Science.gov (United States)

    Linkhorst, John; Beckmann, Torsten; Go, Dennis; Kuehne, Alexander J C; Wessling, Matthias

    2016-01-01

    Filtration of natural and colloidal matter is an essential process in today's water treatment processes. The colloidal matter is retained with the help of micro- and nanoporous synthetic membranes. Colloids are retained in a "cake layer" - often coined fouling layer. Membrane fouling is the most substantial problem in membrane filtration: colloidal and natural matter build-up leads to an increasing resistance and thus decreasing water transport rate through the membrane. Theoretical models exist to describe macroscopically the hydrodynamic resistance of such transport and rejection phenomena; however, visualization of the various phenomena occurring during colloid retention is extremely demanding. Here we present a microfluidics based methodology to follow filter cake build up as well as transport phenomena occuring inside of the fouling layer. The microfluidic colloidal filtration methodology enables the study of complex colloidal jamming, crystallization and melting processes as well as translocation at the single particle level. PMID:26927706

  17. Microfluidic colloid filtration

    Science.gov (United States)

    Linkhorst, John; Beckmann, Torsten; Go, Dennis; Kuehne, Alexander J. C.; Wessling, Matthias

    2016-03-01

    Filtration of natural and colloidal matter is an essential process in today’s water treatment processes. The colloidal matter is retained with the help of micro- and nanoporous synthetic membranes. Colloids are retained in a “cake layer” - often coined fouling layer. Membrane fouling is the most substantial problem in membrane filtration: colloidal and natural matter build-up leads to an increasing resistance and thus decreasing water transport rate through the membrane. Theoretical models exist to describe macroscopically the hydrodynamic resistance of such transport and rejection phenomena; however, visualization of the various phenomena occurring during colloid retention is extremely demanding. Here we present a microfluidics based methodology to follow filter cake build up as well as transport phenomena occuring inside of the fouling layer. The microfluidic colloidal filtration methodology enables the study of complex colloidal jamming, crystallization and melting processes as well as translocation at the single particle level.

  18. Evaluation of biological, physical and chemical properties of mineral trioxide aggregate mixed with 4-META/MMA-TBB

    Directory of Open Access Journals (Sweden)

    Rudra Kaul

    2013-01-01

    Full Text Available Aim: To evaluate the change in physical, chemical and biological properties when mineral trioxide aggregate (MTA is mixed with a resin 4-methacryloxyethyl trimellitate anhydride (4-META/methyl methacrylate-tri-n-butyl-borane (MMA-TBB. Materials and Methods: For biological evaluation MTA was inoculated in Wistar rat′s subcutaneous tissue and peripheral tissue response was checked after 72 h, 7 days, 15 days and 30 days. Setting time was evaluated using Gillmore needle. The Ca++ release at the end of 24 h was checked using ethylenediaminetetraacetic acid titration method. For all the trials MTA mixed with water was kept as a control and the ratio of MTA with resin was 1:1 by weight. Results: The biological reaction was verified by two observers and their readings were matched using kappa test and there was an excellent relevance. There was no significant difference in the tissue reaction at the end of 30 days where both the groups seemed to show healing. Setting time of MTA with 4-META/MMA-TBB was coming to a mean of 26 min (approx., which is almost 6 times lesser than that of MTA with water. After applying t test, the difference in Ca++ release was found significant (P = 0.00, with mean of 0.044 and 0.031 mol/L of MTA with water and MTA with 4-META/MMA-TBB respectively. Conclusion: Under the parameters of this study, this new experimental cement has better handling, physical and chemical properties. Even its subcutaneous tissue reaction is comparable to MTA mixed with water.

  19. EFFECT OF MIXING CONDITIONS ON FLOCCULATION KINETICS OF WASTEWATERS CONTAINING PROTEINS AND OTHER BIOLOGICAL COMPOUNDS USING FIBROUS MATERIALS AND POLYELECTROLYTES

    Directory of Open Access Journals (Sweden)

    L.A. CHEN

    1998-12-01

    Full Text Available The application of a combined system of a polyelectrolyte, carboxymethyl cellulose (CMC, and highly fibrillated fibrous materials, cellulose triacetate fibrets (CTF, for the recovery of proteins and other biological compounds from model and actual biological systems has been demonstrated . In the present work, reaction batches were scaled-up to a one-liter agitated vessel, with a standard configuration. The effect of mixing conditions on the adsorption and flocculation process was studied. It was observed that flocculation time was very fast, occurring within the period of polymer addition. Long term shearing did not result in floc breakage and the values of percentage light transmission and protein concentration of the final filtrate remained the same during the incubation period. Increasing the shear rate resulted in improved process efficiency, up to an optimum value, above which performance was poorer. Perikinetic and orthokinetic rate parameters were calculated and results analyzed in view of these parameters.

  20. Saturated Zone Colloid Transport

    International Nuclear Information System (INIS)

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, Rcol is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of Rcol that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, katt, and detachment rate constants, kdet, of colloids to the fracture surface have been measured for the fractured volcanics, and separate Rcol uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant retardation. Radionuclides irreversibly sorbed

  1. Oxidation of Mixed Active Pharmaceutical Ingredients in Biologically Treated Wastewater by ClO2

    DEFF Research Database (Denmark)

    Moradas, Gerly; Fick, Jerker; Ledin, Anna;

    2011-01-01

    Biologically treated wastewater containing a mixture of 53 active pharmaceutical ingredients (APIs)was treated with 0-20 mg/l chlorine dioxide (ClO2) solution. Wastewater effluents were taken from two wastewater treatment plants in Sweden, one with (low COD) and one without (high COD) extended...

  2. An efficient planar accordion-shaped micromixer: from biochemical mixing to biological application.

    Science.gov (United States)

    Cosentino, Armando; Madadi, Hojjat; Vergara, Paola; Vecchione, Raffaele; Causa, Filippo; Netti, Paolo Antonio

    2015-01-01

    Micromixers are the key component that allow lab-on-a-chip and micro total analysis systems to reach the correct level of mixing for any given process. This paper proposes a novel, simple, passive micromixer design characterized by a planar accordion-shape geometry. The geometrical characteristics of the presented design were analyzed numerically in the range of 0.01 experimentally investigated by means of fluorescence microscopy for a range of low diffusion coefficients, 10(-12) structure was fabricated in a simple single-step process using maskless lithography and soft lithography. The experimental results showed a very good agreement with the predicted numerical results. This micromixer design including a single serpentine unit (1-SERP) displayed an efficiency higher than 90% (mixing length = 6.4 mm) creating a pressure drop of about 500 Pa at Re = 0.1 and 60 kPa at Re = 10. A mixing efficiency of almost 100% was readily reached when three serpentine units were included (3-SERP). Finally, the potential diagnostic value of the presented microdevice was validated experimentally for Red Blood Cell (RBC) lysis. PMID:26658848

  3. Shape-shifting colloids via stimulated dewetting.

    Science.gov (United States)

    Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2016-01-01

    The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly. PMID:27426418

  4. Colloid process engineering

    CERN Document Server

    Peukert, Wolfgang; Rehage, Heinz; Schuchmann, Heike

    2015-01-01

    This book deals with colloidal systems in technical processes and the influence of colloidal systems by technical processes. It explores how new measurement capabilities can offer the potential for a dynamic development of scientific and engineering, and examines the origin of colloidal systems and its use for new products. The future challenges to colloidal process engineering are the development of appropriate equipment and processes for the production and obtainment of multi-phase structures and energetic interactions in market-relevant quantities. The book explores the relevant processes and for controlled production and how they can be used across all scales.

  5. Abundance of fluorescent biological aerosol particles at temperatures conducive to the formation of mixed-phase and cirrus clouds

    Science.gov (United States)

    Twohy, Cynthia H.; McMeeking, Gavin R.; DeMott, Paul J.; McCluskey, Christina S.; Hill, Thomas C. J.; Burrows, Susannah M.; Kulkarni, Gourihar R.; Tanarhte, Meryem; Kafle, Durga N.; Toohey, Darin W.

    2016-07-01

    Some types of biological particles are known to nucleate ice at warmer temperatures than mineral dust, with the potential to influence cloud microphysical properties and climate. However, the prevalence of these particle types above the atmospheric boundary layer is not well known. Many types of biological particles fluoresce when exposed to ultraviolet light, and the Wideband Integrated Bioaerosol Sensor takes advantage of this characteristic to perform real-time measurements of fluorescent biological aerosol particles (FBAPs). This instrument was flown on the National Center for Atmospheric Research Gulfstream V aircraft to measure concentrations of fluorescent biological particles from different potential sources and at various altitudes over the US western plains in early autumn. Clear-air number concentrations of FBAPs between 0.8 and 12 µm diameter usually decreased with height and generally were about 10-100 L-1 in the continental boundary layer but always much lower at temperatures colder than 255 K in the free troposphere. At intermediate temperatures where biological ice-nucleating particles may influence mixed-phase cloud formation (255 K ≤ T ≤ 270 K), concentrations of fluorescent particles were the most variable and were occasionally near boundary-layer concentrations. Predicted vertical distributions of ice-nucleating particle concentrations based on FBAP measurements in this temperature regime sometimes reached typical concentrations of primary ice in clouds but were often much lower. If convection was assumed to lift boundary-layer FBAPs without losses to the free troposphere, better agreement between predicted ice-nucleating particle concentrations and typical ice crystal concentrations was achieved. Ice-nucleating particle concentrations were also measured during one flight and showed a decrease with height, and concentrations were consistent with a relationship to FBAPs established previously at the forested surface site below. The vertical

  6. Integrated chemical/biological treatment of paint stripper mixed waste: Metals toxicity and separation

    International Nuclear Information System (INIS)

    The DOE complex has generated vast quantities of complex heterogeneous mixed wastes. Paint stripper waste (PSW) is a complex waste that arose from decontamination and decommissioning activities. It contains paint stripper, cheesecloth, cellulose-based paints with Pb and Cr, and suspect Pu. Los Alamos National Laboratory has 150--200 barrels of PSW and other national laboratories such as Rocky Flats Plant have many more barrels of heterogeneous waste. Few technologies exist that can treat this complex waste. Our approach to solving this problem is the integration of two established technologies: biodegradation and metals chelation

  7. Inventions Utilizing Microfluidics and Colloidal Particles

    Science.gov (United States)

    Marr, David W.; Gong, Tieying; Oakey, John; Terray, Alexander V.; Wu, David T.

    2009-01-01

    Several related inventions pertain to families of devices that utilize microfluidics and/or colloidal particles to obtain useful physical effects. The families of devices can be summarized as follows: (1) Microfluidic pumps and/or valves wherein colloidal-size particles driven by electrical, magnetic, or optical fields serve as the principal moving parts that propel and/or direct the affected flows. (2) Devices that are similar to the aforementioned pumps and/or valves except that they are used to manipulate light instead of fluids. The colloidal particles in these devices are substantially constrained to move in a plane and are driven to spatially order them into arrays that function, variously, as waveguides, filters, or switches for optical signals. (3) Devices wherein the ultra-laminar nature of microfluidic flows is exploited to effect separation, sorting, or filtering of colloidal particles or biological cells in suspension. (4) Devices wherein a combination of confinement and applied electrical and/or optical fields forces the colloidal particles to become arranged into three-dimensional crystal lattices. Control of the colloidal crystalline structures could be exploited to control diffraction of light. (5) Microfluidic devices, incorporating fluid waveguides, wherein switching of flows among different paths would be accompanied by switching of optical signals.

  8. Preparation of 99mTc- Tin colloid: a freeze-dried kit for liver imaging

    International Nuclear Information System (INIS)

    99mTc-tin-colloid was formulated as a useful agent for liver imaging. The radiochemical purity and stability of the labeled colloid were determined by paper chromatography and 85% methanol solvent, the labelling efficiency was > 95%. The comparative studies of the biological distribution of 99mTc-tin-colloid and 99Tc-Sulphur-colloid were made with Wistar rats. The results of organ distribution were similar in both products; > 90% liver uptake. (author)

  9. BIOLOGICAL NITROGEN REMOVAL FROM WASTEWATER BY DENITRIFICATION OF MIX-CULTURING FUNGI AND BACTERIA

    Institute of Scientific and Technical Information of China (English)

    TAKAYA; Naoki; SHOUN; Hirofumi

    2006-01-01

    Denitrificationis a biological processin which nitrateand/or nitrite is reduced to gaseous nitrogen,dinitrogen(N2)or nitrous oxide(N2O)while carbon dioxide is thesecond gaseous product of the process.This is one of themain mechanisms of the global nitrogen cycle,and playsanimportant role as the reverse reaction of nitrogen fixa-tion in maintaining global environmental homeostasis[1].Denitrification has beenlongthought to be a unique char-acteristic of prokaryotes[2,3].Anumber of bacteria(suchasPseudomonas s...

  10. Oxidation of Mixed Active Pharmaceutical Ingredients in Biologically Treated Wastewater by ClO2

    OpenAIRE

    Moradas, Gerly; Fick, Jerker; Ledin, Anna; Jansen, Jes la Cour; Andersen, Henrik Rasmus

    2011-01-01

    Biologically treated wastewater containing a mixture of 53 active pharmaceutical ingredients (APIs)was treated with 0-20 mg/l chlorine dioxide (ClO2) solution. Wastewater effluents were taken from two wastewater treatment plants in Sweden, one with (low COD) and one without (high COD) extended nitrogen removal. The removal of the APIs varied from no significant removal at the highest dose of ClO2 (20 mg/l) to 90% removal at a dose of 0.5 mg/l of the oxidant. From the low COD effluent, only 4 ...

  11. The influence of colloids on the migration of radionuclides

    International Nuclear Information System (INIS)

    For a concept of deep geological disposal of high level nuclear waste, the repository will be designed as a multiple-barrier system including bentonite as the buffer/backfill material and the host rock formation as the geological barrier. The engineered barrier (compacted bentonite) will be in contact with the host rock formation (e.g. granite). Consequently the bentonite will be saturated over time with formation groundwater, which will induce swelling and gel formation of the bentonite. At the gel-groundwater boundary, colloid detachment might be a possible colloid source and therefore might enhance the mobility of strong sorbing actinides. This work will focus on three aspects of colloidal transport: (a) Colloid stability in the mixing zone between granite groundwater and bentonite pore water, including its description with an extended DLVO model. (b) Colloid generation and erosion of the bentonite at the interface between compacted bentonite and granitic groundwater, as well as formation of new colloids in the mixing zone between the bentonite porewater and the granitic groundwater. (c) Colloid transport and the interaction of U, Th, Hf, Tb, Eu and Cm with bentonite colloids and fracture filling material, as well as their mobility in a natural fracture.

  12. Biological hydrogen production from probiotic wastewater as substrate by selectively enriched anaerobic mixed microflora

    Energy Technology Data Exchange (ETDEWEB)

    Sivaramakrishna, D.; Sreekanth, D.; Himabindu, V. [Centre for Environment, Institute of Science and Technology, Jawaharlal Nehru Technological University, Kukatpally, Hyderabad 500072, Andhra Pradesh (India); Anjaneyulu, Y. [TLGVRC, JSU Box 18739, JSU, Jackson, MS 32917-0939 (United States)

    2009-03-15

    Biohydrogen production from probiotic wastewater using mixed anaerobic consortia is reported in this paper. Batch tests are carried out in a 5.0 L batch reactor under constant mesophillic temperature (37 C). The maximum hydrogen yield 1.8 mol-hydrogen/mol-carbohydrate is obtained at an optimum pH of 5.5 and substrate concentration 5 g/L. The maximum hydrogen production rate is 168 ml/h. The hydrogen content in the biogas is more than 65% and no significant methane is observed throughout the study. In addition to hydrogen, acetate, propionate, butyrate and ethanol are found to be the main by-products in the metabolism of hydrogen fermentation. (author)

  13. Molecular mechanisms of the microsomal mixed function oxidases and biological and pathological implications

    Directory of Open Access Journals (Sweden)

    Arthur I. Cederbaum

    2015-04-01

    Full Text Available The cytochrome P450 mixed function oxidase enzymes play a major role in the metabolism of important endogenous substrates as well as in the biotransformation of xenobiotics. The liver P450 system is the most active in metabolism of exogenous substrates. This review briefly describes the liver P450 (CYP mixed function oxidase system with respect to its enzymatic components and functions. Electron transfer by the NADPH-P450 oxidoreductase is required for reduction of the heme of P450, necessary for binding of molecular oxygen. Binding of substrates to P450 produce substrate binding spectra. The P450 catalytic cycle is complex and rate-limiting steps are not clear. Many types of chemical reactions can be catalyzed by P450 enzymes, making this family among the most diverse catalysts known. There are multiple forms of P450s arranged into families based on structural homology. The major drug metabolizing CYPs are discussed with respect to typical substrates, inducers and inhibitors and their polymorphic forms. The composition of CYPs in humans varies considerably among individuals because of sex and age differences, the influence of diet, liver disease, presence of potential inducers and/or inhibitors. Because of such factors and CYP polymorphisms, and overlapping drug specificity, there is a large variability in the content and composition of P450 enzymes among individuals. This can result in large variations in drug metabolism by humans and often can contribute to drug–drug interactions and adverse drug reactions. Because of many of the above factors, especially CYP polymorphisms, there has been much interest in personalized medicine especially with respect to which CYPs and which of their polymorphic forms are present in order to attempt to determine what drug therapy and what dosage would reflect the best therapeutic strategy in treating individual patients.

  14. Interface colloidal robotic manipulator

    Energy Technology Data Exchange (ETDEWEB)

    Aronson, Igor; Snezhko, Oleksiy

    2015-08-04

    A magnetic colloidal system confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters. The colloidal system exhibits locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, structures can capture, transport, and position target particles.

  15. Colloid Transport and Retention

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander

    2012-01-01

    Book Description: Colloidal science and technology is one of the fastest growing research and technology areas. This book explores the cutting edge research in colloidal science and technology that will be usefull in almost every aspect of modern society. This book has a depth of information rela...

  16. Relative biological efficiency of powerful 252Cf mixed α-neutron radiation

    International Nuclear Information System (INIS)

    Comprehensive radiobiological studies of the relative biological and genetic efficacy (RBE and RGE) of powerful 252Cf radiation (the ANET-B unit) were conducted using research tools of various radiosensitivity (bacteria, Drosophila, Chinese hamster cells, murine thymocytes, human and murine bone marrow stem cells, human peripheral blood lymphocytes, Lewis lung carcinoma cells). It was shown in the tests of reproductive or interphase death and chromosome aberrations that the RBE and the RGE values of a sup(252)Cf new source varied within the same limits from 1.3 to 3.0 whereas in the tests of gene mutations the RGE of the source did not exceed the efficacy of 60Co γ-radiation and in some cases it was much lower. Thus the RBE of the new source in induced lethal and chromosome demages was 2-4 times lower than the efficacy of a low-activity sup(252)Cf source used now in radiotherapy

  17. A colloidal singularity reveals the crucial role of colloidal stability for nanomaterials in-vitro toxicity testing: nZVI-microalgae colloidal system as a case study.

    Directory of Open Access Journals (Sweden)

    Soledad Gonzalo

    Full Text Available Aggregation raises attention in Nanotoxicology due to its methodological implications. Aggregation is a physical symptom of a more general physicochemical condition of colloidal particles, namely, colloidal stability. Colloidal stability is a global indicator of the tendency of a system to reduce its net surface energy, which may be achieved by homo-aggregation or hetero-aggregation, including location at bio-interfaces. However, the role of colloidal stability as a driver of ENM bioactivity has received little consideration thus far. In the present work, which focuses on the toxicity of nanoscaled Fe° nanoparticles (nZVI towards a model microalga, we demonstrate that colloidal stability is a fundamental driver of ENM bioactivity, comprehensively accounting for otherwise inexplicable differential biological effects. The present work throws light on basic aspects of Nanotoxicology, and reveals a key factor which may reconcile contradictory results on the influence of aggregation in bioactivity of ENMs.

  18. Abundance of fluorescent biological aerosol particles at temperatures conducive to the formation of mixed-phase and cirrus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Twohy, C. H.; McMeeking, G. R.; DeMott, Paul J.; McCluskey, Christina; Hill, TC J.; Burrows, Susannah M.; Kulkarni, Gourihar R.; Tanarhte, M.; Kafle, D. N.; Toohey, D. W.

    2016-07-08

    Some types of biological particles are known to efficiently nucleate ice at relatively warm temperatures in the atmosphere, with the potential to influence cloud microphysical properties and climate. However, the prevalence of these particle types above the atmospheric boundary layer is not well known. Many types of biological particles fluoresce when exposed to ultraviolet light, and the Wideband Integrated Bioaerosol Sensor takes advantage of this characteristic to perform real-time measurements of fluorescent biological aerosol particles (FBAP). This relatively new instrument was flown on the National Center for Atmospheric Research Gulfstream-V aircraft to measure concentrations of fluorescent biological particles from different potential sources and at various altitudes over the U. S. western plains states in early autumn. Clear-air concentrations of FBAP larger than 0.8 µm in diameter usually decreased with height, and generally were about 10-100 L-1 in the continental boundary layer, but were always much lower in the free troposphere at temperatures colder than about 255K. Ice nucleating particle number concentrations measured during one flight also showed a decrease with height, and were consistent with a relationship to FBAP established previously at the surface at the same location. At intermediate ambient temperatures where biological ice nucleating particles may influence mixed-phase cloud formation (255K≤T≤270K), concentrations of fluorescent particles were the most variable, and were occasionally near boundary layer values. Predicted vertical profiles of ice nucleating particle concentrations based on FBAP measurements in this temperature regime sometimes reached typical ice crystal concentrations in clouds, but were often much lower. If convection was assumed to lift boundary layer FBAP particles without losses to the free troposphere, better agreement between predicted ice-nucleating particle concentrations and typical ice crystal number

  19. Saturated Zone Colloid Transport

    Energy Technology Data Exchange (ETDEWEB)

    H. S. Viswanathan

    2004-10-07

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R{sub col} is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R{sub col} that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k{sub att}, and detachment rate constants, k{sub det}, of colloids to the fracture surface have been measured for the fractured volcanics, and separate R{sub col} uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant

  20. Lock and key colloids.

    Science.gov (United States)

    Sacanna, S; Irvine, W T M; Chaikin, P M; Pine, D J

    2010-03-25

    New functional materials can in principle be created using colloids that self-assemble into a desired structure by means of a programmable recognition and binding scheme. This idea has been explored by attaching 'programmed' DNA strands to nanometre- and micrometre- sized particles and then using DNA hybridization to direct the placement of the particles in the final assembly. Here we demonstrate an alternative recognition mechanism for directing the assembly of composite structures, based on particles with complementary shapes. Our system, which uses Fischer's lock-and-key principle, employs colloidal spheres as keys and monodisperse colloidal particles with a spherical cavity as locks that bind spontaneously and reversibly via the depletion interaction. The lock-and-key binding is specific because it is controlled by how closely the size of a spherical colloidal key particle matches the radius of the spherical cavity of the lock particle. The strength of the binding can be further tuned by adjusting the solution composition or temperature. The composite assemblies have the unique feature of having flexible bonds, allowing us to produce flexible dimeric, trimeric and tetrameric colloidal molecules as well as more complex colloidal polymers. We expect that this lock-and-key recognition mechanism will find wider use as a means of programming and directing colloidal self-assembly. PMID:20336142

  1. Grimsel colloid exercise

    International Nuclear Information System (INIS)

    The Grimsel Colloid Exercise was an intercomparison exercise which consisted of an in situ sampling phase followed by a colloid characterisation step. The goal of this benchmark exercise, which involved 12 laboratories, was to evaluate both sampling and characterisation techniques with emphasis on the colloid specific size distribution. The sampling phase took place at the Grimsel Test Site between February 1 and 13, 1988 and the participating groups produced colloid samples using the following methods: 1. Cross-flow ultrafiltration with production of membranes loaded with colloids. 2. Tangential diaultrafiltration and production of colloid concentrates. 3. Filtrates produced by each group. 4. Unfiltered water was also collected by PSI in glass bottles, under controlled anaerobic conditions, and by the other sampling groups in various plastic bottles. In addition, on-line monitoring of pH, χ, [O-2] and T of the water and of [O-2] in the atmosphere of the sampling units was carried out routinely. All samples were shipped according to the CoCo Club scheme for characterisation, with emphasis on the size distribution. The exercise differentiates the colloid samples produced on site from those obtained after transfer of the fluid samples to the laboratories. The colloid concentration and size distribution can be determined by scanning electron microscopy (SEM), gravimetry (GRAV), chemical analysis of fluid samples after micro/ultrafiltration (MF/UF) and by transmission single particle counting (PC). The colloid concentration can also be evaluated by transmission electron microscopy (TEM), static and dynamic light scattering (SLS,DLS) and by laser-induced photoacoustic spectroscopy (LPAS). The results are discussed on the basis of the detection limit, lateral resolution and counting conditions of the technique (precision) as well as sample preparation, artefact production and measurement optimisation (accuracy). A good agreement between size distribution results was

  2. Colloids in Biotechnology

    CERN Document Server

    Fanun, Monzer

    2010-01-01

    Colloids have come a long way from when Thomas Graham coined the term colloid to describe 'pseudo solutions'. This book enables scientists to close the gap between extensive research and translation into commercial options in biomedicine and biotechnology. It covers biosurfactants and surface properties, phase behavior, and orientational change of surfactant mixtures with peptides at the interface. It also covers adsorption of polymers and biopolymers on the surface and interface, discusses colloidal nanoparticles and their use in biotechnology, and delves into bioadhesion and microencapsulati

  3. Colloids or artefacts?

    International Nuclear Information System (INIS)

    TVO (Teollisuuden Voima Oy, Finland) initiated a co-operative task with SKB (Swedish Nuclear Fuel and Waste Management Co.) to critically evaluate colloid sampling methods at the test site in Olkiluoto, SW Finland. Three different colloid sampling methods were compared when sampling at 613-618 m depth. The colloid sampling consisted of ordinary filtering (cross-flow filtering, 20-450 nm) in open air, inert filtering (cross-flow filtering, prefilter=2500 nm, separate filtration to three fractions 50,200 and 400 nm) by using N2 and ultrafiltration (tangential filtering, prefilter=1000 nm concentration to a single fraction 2-1000 nm) using N2. Two samples per method were taken with an interval of three weeks. For organic determination one sample was collected. Care was taken to avoid possible known artefacts in connection with the colloid sampling. (27 refs., 31 figs., 13 tabs.)

  4. Laboratory-generated mixtures of mineral dust particles with biological substances: characterization of the particle mixing state and immersion freezing behavior

    Science.gov (United States)

    Augustin-Bauditz, Stefanie; Wex, Heike; Denjean, Cyrielle; Hartmann, Susan; Schneider, Johannes; Schmidt, Susann; Ebert, Martin; Stratmann, Frank

    2016-05-01

    Biological particles such as bacteria, fungal spores or pollen are known to be efficient ice nucleating particles. Their ability to nucleate ice is due to ice nucleation active macromolecules (INMs). It has been suggested that these INMs maintain their nucleating ability even when they are separated from their original carriers. This opens the possibility of an accumulation of such INMs in soils, resulting in an internal mixture of mineral dust and INMs. If particles from such soils which contain biological INMs are then dispersed into the atmosphere due to wind erosion or agricultural processes, they could induce ice nucleation at temperatures typical for biological substances, i.e., above -20 up to almost 0 °C, while they might be characterized as mineral dust particles due to a possibly low content of biological material. We conducted a study within the research unit INUIT (Ice Nucleation research UnIT), where we investigated the ice nucleation behavior of mineral dust particles internally mixed with INM. Specifically, we mixed a pure mineral dust sample (illite-NX) with ice active biological material (birch pollen washing water) and quantified the immersion freezing behavior of the resulting particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). A very important topic concerning the investigations presented here as well as for atmospheric application is the characterization of the mixing state of aerosol particles. In the present study we used different methods like single-particle aerosol mass spectrometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), and a Volatility-Hygroscopicity Tandem Differential Mobility Analyser (VH-TDMA) to investigate the mixing state of our generated aerosol. Not all applied methods performed similarly well in detecting small amounts of biological material on the mineral dust particles. Measuring the hygroscopicity/volatility of the mixed particles with the VH-TDMA was the most

  5. Highly uniform polyhedral colloids formed by colloidal crystal templating

    Science.gov (United States)

    Wang, Yifan; McGinley, James; Crocker, John; Crocker Research Group Team

    2015-03-01

    We seek to create polyhedral solid particles by trapping oil droplets in a colloidal crystal, and polymerizing them in situ, resulting in polyhedral particles containing spherical dimples in an ordered arrangement. Specifically, highly monodisperse, micron-sized droplets of 3-methacryloxypropyl trimethoxysilane (TPM) were first prepared through a poly condensation reaction, following well established methods. The droplets were mixed with an excess of polystyrene(PS) particles (diameter in 2.58 μm), which formed close packed (FCC or HCP) colloidal crystals by natural sedimentation and compression under partial drying to an extent, with TPM oil droplets trapped into their tetrahedral and octahedral interstitial sites and wet PS particles. Depending on the initial particle volume fraction and extent of drying, a high yield of dimpled particles having different shapes including tetrahedra and cubes were obtained after oil initiated polymerization and dissolution of the host PS particles, as seen under SEM. The effects of TPM to PS particles size ratio, drying time, and other factors in relation to the yield of tetrahedral and cubic dimpled particles will be presented. Finally, fractionation techniques were used to obtain suspensions of uniform polyhedral particles of high purity.

  6. Doped Colloidal Artificial Ice

    OpenAIRE

    Libal, A.; Reichhardt, C. J. Olson; Reichhardt, C.

    2015-01-01

    We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Unlike magnetic artificial spin ices, colloidal and vortex artificial spin ice realizations allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is rai...

  7. In vitro and in vivo measurements of the dissolution parameters of uranium and plutonium mixed oxides in biological environment

    International Nuclear Information System (INIS)

    During the mixed-oxide fuel fabrication process, inhalation is potentially the main route of internal contamination. The International Commission on Radiological Protection recommends experimental measurement of parameters such as size and dissolution rate for specific industrial compounds. First, we validated the use of PERALS (Photon Electron Rejecting Alpha Liquid Scintillation) for alpha measurement in biological samples which, in some cases, could improve detection limit. We characterised physical chemical properties in terms of size, specific area and activity of 3 different powders: MOX made according to either the MIMAS process, which showed heterogeneous chemical composition, or the SOLGEL, which showed homogeneous chemical composition and industrial PuO2. Their dissolution parameters, fr and ss, as defined in the simplest model proposed by ICRP 66 were measured in vivo, after inhalation in the rat, and in vitro. The statistical variation of these values were expressed as standard deviation. Moreover, in vitro studies demonstrated variation of the ss value depending on the duration of the incubation. We also developed methods to characterise interactions between UO2 particles and phosphate ions which could be involved in the actinide toxicity. (author)

  8. Synthesis, Characterization, and Biological Activity Studies of Copper(II Mixed Compound with Histamine and Nalidixic Acid

    Directory of Open Access Journals (Sweden)

    Egla Yareth Bivián-Castro

    2009-01-01

    Full Text Available A mixed copper complex with deprotonated nalidixic acid (nal and histamine (hsm was synthesized and characterized by FTIR, UV-Vis, elemental analysis, and conductivity. The crystal structure of [Cu(hsm(nalH2O]Cl·3H2O (chn showed a pentacoordinated cooper(II in a square pyramidal geometry surrounded by two N atoms from hsm, two O atoms from the quinolone, and one apical water oxygen. Alteration of bacterial DNA structure and/or associated functions in vivo by [Cu(hsm(nalH2O]Cl·3H2O was demonstrated by the induction of a recA-lacZ fusion integrated at the amyE locus of a recombinant Bacillus subtilis strain. Results from circular dichroism and denaturation of calf thymus DNA (CT-DNA suggested that increased amounts of copper complex were able to stabilize the double helix of DNA in vitro mainly by formation of hydrogen bonds between chn and the sugars of DNA minor groove. In vivo and in vitro biological activities of the chn complex were compared with the chemical nuclease [Cu(phen(nalH2O]NO3·3H2O (cpn where phen is phenanthroline.

  9. Colloidal silver solutions with antimicrobial properties

    Energy Technology Data Exchange (ETDEWEB)

    Petica, A. [INCDIE ICPE-Advanced Research, Bucharest (Romania)], E-mail: petica@icpe-ca.ro; Gavriliu, S.; Lungu, M.; Buruntea, N. [INCDIE ICPE-Advanced Research, Bucharest (Romania); Panzaru, C. [Institute of Medicine and Pharmacy, Iassy (Romania)

    2008-08-25

    Some colloidal silver solutions involving the electrochemical technique with 'sacrificial anode method and different stabilizers and co-stabilizers' have been prepared. A constant current pulse generator with stirrer at different working times has been used. To achieve stable colloidal silver solutions, a mix of different tensioactive agents namely [poly (N-vinylpyrrolidone)], Na-naphthalene sulphonate, Na-lauryl sulfate and Na-dodecyl sulphonate were tested. The effects of these various mixes of polymer and ionic surfactants upon the Ag concentration and UV-vis spectra of silver nanoparticles were determined by spectrophotometer techniques. The nanoparticles sizes have been analyzed through dynamic light scattering technique and the silver nanoparticle morphology has been evidenced by transmission electron microscopy (TEM). Micobiological analysis has been made by determining minimal inhibitorial concentration upon the following germs: Staphylococcus aureus (ATCC) (Gram-positive cocci), Pseudomonas aeruginosa (ATTC), Escherichia coli (ATCC) and Acinetobacter spp. (Gram-negative coccobacillus). To evaluate the antifungal effect, the antibiogram method involving various tests using a fungi mix of Aspergillus, Penicillium and Trichoderma species has been used. The presented method allows obtaining of some stable colloidal solutions containing up to 35 ppm of Ag with very good antimicrobial and antifungal properties.

  10. Colloidal silver solutions with antimicrobial properties

    International Nuclear Information System (INIS)

    Some colloidal silver solutions involving the electrochemical technique with 'sacrificial anode method and different stabilizers and co-stabilizers' have been prepared. A constant current pulse generator with stirrer at different working times has been used. To achieve stable colloidal silver solutions, a mix of different tensioactive agents namely [poly (N-vinylpyrrolidone)], Na-naphthalene sulphonate, Na-lauryl sulfate and Na-dodecyl sulphonate were tested. The effects of these various mixes of polymer and ionic surfactants upon the Ag concentration and UV-vis spectra of silver nanoparticles were determined by spectrophotometer techniques. The nanoparticles sizes have been analyzed through dynamic light scattering technique and the silver nanoparticle morphology has been evidenced by transmission electron microscopy (TEM). Micobiological analysis has been made by determining minimal inhibitorial concentration upon the following germs: Staphylococcus aureus (ATCC) (Gram-positive cocci), Pseudomonas aeruginosa (ATTC), Escherichia coli (ATCC) and Acinetobacter spp. (Gram-negative coccobacillus). To evaluate the antifungal effect, the antibiogram method involving various tests using a fungi mix of Aspergillus, Penicillium and Trichoderma species has been used. The presented method allows obtaining of some stable colloidal solutions containing up to 35 ppm of Ag with very good antimicrobial and antifungal properties

  11. Colloid-borne uranium and other heavy metals in the water of a mine drainage gallery

    International Nuclear Information System (INIS)

    The water of a mine drainage gallery was investigated for its contents of colloid-borne heavy metals with emphasis on uranium. About 1 mg/L of colloid particles of 100 to 300 nm were found. They consist of a matrix of Fe and Al oxyhydroxides and are formed when anoxic slightly acidic shaft waters mix with oxic near-neutral gallery water. The colloid particles bear toxic trace elements such as As, Pb, and Cu. Almost 100% of the As and Pb and about 70% of the Cu contained in the water are colloid-borne. Carbonato complexes prevent the uranyl from being adsorbed on the colloids in the unaltered gallery water. Acidification destroys these complexes: up to 50% of the uranium is attached to the colloids in the slightly acidic pH region. Further acidification converts the uranyl again to a 'non-colloidal' form. (orig.)

  12. Biologic

    CERN Document Server

    Kauffman, L H

    2002-01-01

    In this paper we explore the boundary between biology and the study of formal systems (logic). In the end, we arrive at a summary formalism, a chapter in "boundary mathematics" where there are not only containers but also extainers ><, entities open to interaction and distinguishing the space that they are not. The boundary algebra of containers and extainers is to biologic what boolean algebra is to classical logic. We show how this formalism encompasses significant parts of the logic of DNA replication, the Dirac formalism for quantum mechanics, formalisms for protein folding and the basic structure of the Temperley Lieb algebra at the foundations of topological invariants of knots and links.

  13. Optimal Hydrodynamic Synchronization of Colloidal Rotors

    OpenAIRE

    Kotar, Jurij; Debono, Luke; Bruot, Nicolas; Box, Stuart; Phillips, David; Simpson, Stephen,; Hanna, Simon; Cicuta, Pietro

    2013-01-01

    Synchronization of driven oscillators is a key aspect of flow generation in artificial and biological filaments such as cilia. Previous theoretical and numerical studies have considered the “rotor” model of a cilium in which the filament is coarse grained into a colloidal sphere driven with a given force law along a predefined trajectory to represent the oscillating motion of the cilium. These studies pointed to the importance of two factors in the emergence of synchronization: the modulation...

  14. On the production of colloidal gold-198

    International Nuclear Information System (INIS)

    Colloidal gold-198 locally produced by the Noratom procedure which represents one-step method is compared with the product of another procedure which represents a two-step method. Quality control of the product of the two methods was carried out for ionic gold content, particle size and biological distribution in mice. The one-step method product proved to be better for liver scanning than that of the other procedure under the experimental conditions used. (author)

  15. Using a biological aerated filter to treat mixed water-borne volatile organic compounds and assessing its emissions

    Institute of Scientific and Technical Information of China (English)

    CHENG Wen-Hsi

    2009-01-01

    A biological aerated filter (BAF) was evaluated as a fixed-biofilm processes to remove water-borne volatile organic compounds (VOCs) from a multiple layer ceramic capacitor (MLCC) manufacturing plant in southern Taiwan.The components of VOC were identified to be toluene,1,2,4-trimethylbenzene,1,3,5-trimethylbenzene,bromodichloromethane and isopropanol (IPA).The full-scale BAF was constructed of two separate reactors in series,respectively using 10-cm and 15-cm diameter polypropylene balls as the packing materials and a successful preliminary bench-scale experiment was performed to feasibility.Performance results show that the BAF removed over 90% chemical oxygen demand (COD) from the influent with (1188 ± 605) mg/L of COD.A total organic loading of 2.76 kg biochemical oxygen demand (BOD)/(m~3 packing·d) was determined for the packed bed,in which the flow pattern approached that of a mixed flow.A limited VOC concentration of (0.97 ± 0.29) ppmv (as methane) was emitted from the BAF system.Moreover,the emission rate of VOC was calculated using the proposed formula,based on an air-water mass equilibrium relationship,and compared to the simulated results obtained using the Water 9 model.Both estimation approaches of calculation and model simulation using Water 9 evaluating VOC emissions reveal that 0.1% IPA (0.0031-0.0037 kg/d) was aerated into a gaseous phase,and 30% to 40% (0.006-0.008 kg/d) of the toluene was aerated.

  16. Synthesis characterization and biological evaluation of a novel mixed ligand 99mTc complex as potential brain imaging agent

    International Nuclear Information System (INIS)

    One approach in the design of neutral oxotechnetium complexes is based on the simultaneous substitution of a tridentate dianionic ligand and a monodentate monoanionic coligand on a [Tc(V)O]+3 precursor. Following this ''mixed ligand'' concept, a novel 99mTc complex with N,N-bis(2-mercaptoethyl)-N'N'-diethylethylenediamine as ligand and 1-octanethiol as coligand is prepared and evaluated as potential brain radiopharmaceutical. Preparation of the complex at tracer level was accomplished by using 99mTc-glucoheptonate as precursor. The substitution was optimized and a coligand/ligand ratio of 5 was selected. Under this conditions the labeling yield was over 80% and a major product (with radiochemical purity > 80%) was isolated by HPLC methods and used for biological evaluation. Chemical characterization at carrier level was developed using the corresponding rhenium complex as structural model. The Re complex was also prepared by substitution method and isolated as a crystalline product. The crystals were characterized by UV-vis and IR spectra and elemental analysis. Results were consistent with the expected ReOLC structure. X ray crystallographic study demonstrated that the complex adopts a distorted trigonal bipyramidal geometry. The basal plane is defined by the SS atoms of the ligand and the oxo group, while the N of the ligand and the S of the colligand occupy the two apical positions. All sulphur atoms underwent ionization leading to the formation of a neutral compound. 99Tc complex was also prepared. Although it was not isolated due to the small amount of reagents employed, the HPLC profile was identical to the one observed for the rhenium complex suggesting the same chemical structure. Biodistribution in mice demonstrated early brain uptake, fast blood clearance, excretion through hepatobiliary system and a brain/blood ratio that increased significantly with time. (author)

  17. Colloidal gold: Pt. 1

    International Nuclear Information System (INIS)

    Two basic approaches are used in the preparation of colloidal gold solutions. One is the disintegration of metallic gold rods by an electric arc operating in a liquid medium. The other more general approach is the synthesis of particles from gold salts using either appropriate reducing agents or radiation. X-rays with the results from electron microscopy were used for size determination. The growth, nucleation and coagulation of the particles were studied. The morphology and structure charateristics of colloidal gold particles were investigated by means of electron microscopy and are also described

  18. Colloid Release from Soil Aggregates

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad; Møldrup, Per; Schjønning, Per;

    2012-01-01

    The content of water-dispersible colloids (WDC) has a major impact on soil functions and structural stability. In addition, the presence of mobile colloids may increase the risk of colloid-facilitated transport of strongly sorbing environmental contaminants. The WDC content was measured in 39 soils...

  19. Chiral Colloidal Molecules And Observation of The Propeller Effect

    Science.gov (United States)

    2013-01-01

    Chiral molecules play an important role in biological and chemical processes, but physical effects due to their symmetry-breaking are generally weak. Several physical chiral separation schemes which could potentially be useful, including the propeller effect, have therefore not yet been demonstrated at the molecular scale. However, it has been proposed that complex nonspherical colloidal particles could act as “colloidal molecules” in mesoscopic model systems to permit the visualization of molecular phenomena that are otherwise difficult to observe. Unfortunately, it is difficult to synthesize such colloids because surface minimization generally favors the growth of symmetric particles. Here we demonstrate the production of large numbers of complex colloids with glancing angle physical vapor deposition. We use chiral colloids to demonstrate the Baranova and Zel’dovich (BaranovaN. B.Zel’dovichB. Y.Chem. Phys. Lett.1978, 57, 435) propeller effect: the separation of a racemic mixture by application of a rotating field that couples to the dipole moment of the enantiomers and screw propels them in opposite directions. The handedness of the colloidal suspensions is monitored with circular differential light scattering. An exact solution for the colloid’s propulsion is derived, and comparisons between the colloidal system and the corresponding effect at the molecular scale are made. PMID:23883328

  20. Viscosity of colloidal suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, E.G.D. [Rockefeller Univ., New York, NY (United States); Schepper, I.M. de [Delft Univ. of Technology (Netherlands)

    1995-12-31

    Simple expressions are given for the effective Newtonian viscosity as a function of concentration as well as for the effective visco-elastic response as a function of concentration and imposed frequency, of monodisperse neutral colloidal suspensions over the entire fluid range. The basic physical mechanisms underlying these formulae are discussed. The agreement with existing experiments is very good.

  1. Chaotic mixing in effective compressible flows

    CERN Document Server

    Volk, Romain; Bourgoin, Mickael; Cottin-Bizonne, Cécile; Ybert, Christophe; Raynal, Florence

    2014-01-01

    We study numerically joint mixing of salt and colloids by a chaotic velocity field $\\mathbf{V}$, and how salt inhomogeneities accelerate or delay colloid mixing by inducing a velocity drift $\\mathbf{V}_{\\rm dp}$ between colloids and fluid particles as proposed in recent experiments \\cite{Deseigne2013}. We demonstrate that because the drift velocity is no longer divergence free, small variations to the total velocity field drastically affect the evolution of colloid variance $\\sigma^2=\\langle C^2 \\rangle - \\langle C \\rangle^2$. A consequence is that mixing strongly depends on the mutual coherence between colloid and salt concentration fields, the short time evolution of scalar variance being governed by a new variance production term $P=- \\langle C^2 \

  2. Titanium in UK rural, agricultural and urban/industrial rivers: Geogenic and anthropogenic colloidal/sub-colloidal sources and the significance of within-river retention

    Energy Technology Data Exchange (ETDEWEB)

    Neal, Colin; Jarvie, Helen [Centre for Ecology and Hydrology, Wallingford, Crowmarsh Gifford, Wallingford, OXON, OX10 8BB (United Kingdom); Rowland, Philip, E-mail: apr@ceh.ac.uk [Centre for Ecology and Hydrology, Lancaster, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP (United Kingdom); Lawler, Alan; Sleep, Darren; Scholefield, Paul [Centre for Ecology and Hydrology, Lancaster, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP (United Kingdom)

    2011-04-15

    Operationally defined dissolved Titanium [Ti] (the < 0.45 {mu}m filtered fraction) in rivers draining rural, agricultural, urban and industrial land-use types in the UK averaged 2.1 {mu}g/l with a range in average of 0.55 to 6.48 {mu}g/l. The lowest averages occurred for the upland areas of mid-Wales the highest just downstream of major sewage treatment works (STWs). [Ti] in rainfall and cloud water in mid-Wales averaged 0.2 and 0.7 {mu}g/l, respectively. Average, baseflow and stormflow [Ti] were compared with two markers of sewage effluent and thus human population: soluble reactive phosphorus (SRP) and boron (B). While B reflects chemically conservative mixing, SRP declined downstream of STW inputs due to in-stream physico-chemical and biological uptake. The results are related to colloidal and sub-colloidal Ti inputs from urban/industrial conurbations coupled with diffuse background (geological) sources and within-river removal/retention under low flows as a result of processes of aggregation and sedimentation. The urban/industrial inputs increased background [Ti] by up to eleven fold, but the total anthropogenic Ti input might well have been underestimated owing to within-river retention. A baseline survey using cross-flow ultrafiltration revealed that up to 79% of the [Ti] was colloidal/nanoparticulate (> 1 kDa i.e. > c. 1-2 nm) for the rural areas, but as low as 28% for the urban/industrial rivers. This raises fundamental issues of the pollutant inputs of Ti, with the possibility of significant complexation of Ti in the sewage effluents and subsequent breakdown within the rivers, as well as the physical dispersion of fine colloids down to the macro-molecular scale. Although not directly measured, the particulate Ti can make an important contribution to the net Ti flux. - Research Highlights: {yields} Filtered Ti in agricultural, urban and industrial UK rivers described. {yields} Highest concentrations occur just downstream of STWs. {yields} The urban

  3. Colloidal Double Quantum Dots

    Science.gov (United States)

    2016-01-01

    Conspectus Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole–dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single

  4. Colloidal Double Quantum Dots.

    Science.gov (United States)

    Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan

    2016-05-17

    Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon

  5. Collective motion in populations of colloidal robots

    Science.gov (United States)

    Bartolo, Denis; Bricard, Antoine; Caussin, Jean-Baptiste; Dauchot, Olivier; Desreumaux, Nicolas

    2014-03-01

    Could the behavior of bacteria swarms, fish schools, and bird flocks be understood within a unified framework? Can one ignore the very details of the interaction mechanisms at the individual level to elucidate how strikingly similar collective motion emerges at the group level in this broad range of motile systems? These seemingly provocative questions have triggered significant advance in the physics and the biology, communities over the last decade. In the physics language these systems, made of motile individuals, can all be though as different realizations of ``active matter.'' In this talk, I will show how to gain more insight into this vivid field using self-propelled colloids as a proxy for motile organism. I will show how to motorize colloidal particles capable of sensing the orientation of their neighbors. Then, I will demonstrate that these archetypal populations display spontaneous transitions to swarming motion, and to global directed motion with very few density and orientation fluctuations.

  6. Ultrasmall colloidal PbS quantum dots

    International Nuclear Information System (INIS)

    Ultrasmall colloidal lead sulfide quantum dots can increase the open circuit voltages of quantum-dot-based solar cells because of their large energy gap. Their small size and visible or near infrared light-emitting property make them attractive to the applications of biological fluorescence labeling. Through a modified organometallic route, we can synthesize lead sulfide quantum dots as small as 1.6 nm in diameter. The low reaction temperature and the addition of a chloroalkane cosolvent decrease the reaction rate, making it possible to obtain the ultrasmall quantum dots. - Highlights: • Ultrasmall colloidal PbS quantum dots as small as 1.6 nm in diameter are synthesized. • The quantum dots emit red light with photoluminescence peak at 760 nm. • The growth temperature is as low as 50 °C. • Addition of cosolvent 1,2-dichloroethane in the reaction decreases the reaction rate

  7. Polypyrrole-silver colloids

    Czech Academy of Sciences Publication Activity Database

    Morávková, Zuzana; Omastová, M.; Bober, Patrycja; Hromádková, Jiřina; Trchová, Miroslava; Stejskal, Jaroslav

    Praha : Ioannes Marcus Marci Spectroscopic Society, 2014 - (Otruba, V.; Vašinová Galiová, M.). s. 208 ISBN 978-80-905704-1-2. [European Symposium on Atomic Spectrometry ESAS 2014 & Czech-Slovak Spectroscopic Conference /15./. 16.03.2014-21.03.2014, Prague] R&D Projects: GA ČR GAP205/12/0911 Institutional support: RVO:61389013 Keywords : polypyrrole * Raman spectroscopy * colloid Subject RIV: CD - Macromolecular Chemistry

  8. Viscosity of colloidal suspensions

    CERN Document Server

    Verberg, R; Cohen, E G D

    1997-01-01

    Simple expressions are given for the Newtonian viscosity \\eta_N(\\phi) as well as the viscoelastic behavior of the viscosity \\eta(\\phi,\\omega) of neutral monodisperse hard sphere colloidal suspensions as a function of volume fraction \\phi and frequency \\omega over the entire fluid range, i.e., for volume fractions 0 < \\phi < 0.55. These expressions are based on an approximate theory which considers the viscosity as composed as the sum of two relevant physical processes: \\eta (\\phi,\\omega) = \\eta_{\\infty}(\\phi) + \\eta_{cd}(\\phi,\\omega), where \\eta_{\\infty}(\\phi) = \\eta_0 \\chi(\\phi) is the infinite frequency (or very short time) viscosity, with \\eta_0 the solvent viscosity, \\chi(\\phi) the equilibrium hard sphere radial distribution function at contact, and \\eta_{cd}(\\phi,\\omega) the contribution due to the diffusion of the colloidal particles out of cages formed by their neighbors, on the P\\'{e}clet time scale \\tau_P, the dominant physical process in concentrated colloidal suspensions. The Newtonian viscos...

  9. TRLFS Studies on Indirect Determination of U(IV) in Biological Samples Containing Mixed U(IV/VI) Species

    International Nuclear Information System (INIS)

    The microbial-mediated metal reduction process has been viewed as a long-term remedial approach for in situ immobilization of radionuclide under anaerobic conditions in aquifers and saturated soils. Such approach depends on the fact that many radionuclides of concern including uranium are redox active and less soluble in their reduced form. Thus, the interaction of uranium with microorganisms has been the subject of considerable effort over the past decade. Uranium reduction occurs as a result of dynamic metabolic activity of microbials and biochemical reactions. The typical incubation system of uranium reducing bacteria such as sulfate-reducing Desulfovibrionales contains various geochemical components including electron donors (e.g., acetate, lactate, ethanol, thiol or glucose), anionic electron acceptors (sulfate and nitrate) and metal ions (Fe(II/III), Mn, Ni, etc.). The anoxic growth of bacteria results in uranium reduction by forming U(IV) aggregates or colloids. In most studies the isolation of U(IV) from U(VI) largely depends on filtration of precipitates and centrifugal separation of colloidal particles. Such U(IV) species were subsequently analyzed via ICP-MS for elemental uranium or kinetic phosphorescence analysis (KPA) in form of U(VI) although the relative proportion of U(IV) and U(VI) in the frozen samples can be estimated using X-ray absorption spectroscopy. However, recent studies report the formation of extracellular uranite nanoparticles, which may suspend in the resultant filtrate and supernatant solutions. Thus, the development of an analytical technique capable of estimating the dissolved or suspended U(IV) species is further required for better understanding of the bacterial-mediated uranium sequestration and dissolution process. In this study we explore the possibility of using TRLFS (time-resolved laser-induced fluorescence spectroscopy) to indirectly measure the concentration of U(IV) as well as that of U(VI) in bacterial culture media

  10. TECHNIQUES FOR MAKING BIOLOGICS AND MINERAL NITROGEN AND THEIR INFLUENCE ON THE YIELD OF THE MIXED CROPS IN THE CONDITIONS OF GREY FOREST SOILS

    Directory of Open Access Journals (Sweden)

    Shkotova O. N.

    2016-04-01

    Full Text Available In the conditions of grey forest soils in the Bryansk region among the fodder crops widespread mixed legume-cereal crops. The results showed that the photosynthetic activity of cereals and leguminous crops and their yields in mixed crops depended on made of biological and mineral nitrogen fertilizers. It is established that the nitrogen in the form of ammonium nitrate has a positive impact on the formation of assimilating leaf surface, photosynthetic potential and net productivity and yield of grain mixture in lupine-barley and soybean -barley cropping and pea-barley crops the use of nitrogen in the form of potassium nitrate was more favorable. It was found that in lupine-barley crops the active symbiotic potential has increased by 25,5% and the yield increased by 21,3% , in soybean-barley crops 28,5% and 19,2% respectively, due to the joint use of a mixture of symbiotic and associative rhizobacteria and mineral nitrogen in the form of ammonium nitrate in the dose of N60. In pea-barley agrocenosis it has improved the efficiency of cultivation of joint application of mixed inoculant symbiotic and associative rhizobacteria on the background of the application of mineral nitrogen in the form of potassium nitrate in the dose of N60, where there was an increase of the active symbiotic potential by 34,7% and grain yield by 24,7% compared to the option when adding the mixture of biological products

  11. Movie of phase separation during physics of colloids in space experiment

    Science.gov (United States)

    2002-01-01

    Still photographs taken over 16 hours on Nov. 13, 2001, on the International Space Station have been condensed into a few seconds to show the de-mixing -- or phase separation -- process studied by the Experiment on Physics of Colloids in Space. Commanded from the ground, dozens of similar tests have been conducted since the experiment arrived on ISS in 2000. The sample is a mix of polymethylmethacrylate (PMMA or acrylic) colloids, polystyrene polymers and solvents. The circular area in the video is 2 cm (0.8 in.) in diameter. The phase separation process occurs spontaneously after the sample is mechanically mixed. The evolving lighter regions are rich in colloid and have the structure of a liquid. The dark regions are poor in colloids and have the structure of a gas. This behavior carnot be observed on Earth because gravity causes the particles to fall out of solution faster than the phase separation can occur. While similar to a gas-liquid phase transition, the growth rate observed in this test is different from any atomic gas-liquid or liquid-liquid phase transition ever measured experimentally. Ultimately, the sample separates into colloid-poor and colloid-rich areas, just as oil and vinegar separate. The fundamental science of de-mixing in this colloid-polymer sample is the same found in the annealing of metal alloys and plastic polymer blends. Improving the understanding of this process may lead to improving processing of these materials on Earth.

  12. Phase separation during the Experiment on Physics of Colloids in Space

    Science.gov (United States)

    2003-01-01

    Still photographs taken over 16 hours on Nov. 13, 2001, on the International Space Station have been condensed into a few seconds to show the de-mixing -- or phase separation -- process studied by the Experiment on Physics of Colloids in Space. Commanded from the ground, dozens of similar tests have been conducted since the experiment arrived on ISS in 2000. The sample is a mix of polymethylmethacrylate (PMMA or acrylic) colloids, polystyrene polymers and solvents. The circular area is 2 cm (0.8 in.) in diameter. The phase separation process occurs spontaneously after the sample is mechanically mixed. The evolving lighter regions are rich in colloid and have the structure of a liquid. The dark regions are poor in colloids and have the structure of a gas. This behavior carnot be observed on Earth because gravity causes the particles to fall out of solution faster than the phase separation can occur. While similar to a gas-liquid phase transition, the growth rate observed in this test is different from any atomic gas-liquid or liquid-liquid phase transition ever measured experimentally. Ultimately, the sample separates into colloid-poor and colloid-rich areas, just as oil and vinegar separate. The fundamental science of de-mixing in this colloid-polymer sample is the same found in the annealing of metal alloys and plastic polymer blends. Improving the understanding of this process may lead to improving processing of these materials on Earth.

  13. Colloidal self-assembly at an interface

    Directory of Open Access Journals (Sweden)

    Ryan McGorty

    2010-06-01

    Full Text Available Mix a drop of water into a vial of oil. With some surfactant and a vigorous shake, that one droplet has become thousands, and the total interfacial area has increased by an order of magnitude or more. Like the folded membranes in our mitochondria, the alveoli in our lungs, and the catalytic converters in our cars, oil-water emulsions contain a vast reservoir of interfacial area that can be used to control and transform the things that encounter it. The oil-water interface is especially well-suited to directing the assembly of colloidal particles, which bind to it rapidly and often irreversibly.

  14. A Novel Sintered Porous Micromixer for the Effective Mixing of Biologics and Scale Model Investigation of Micromixing Mechanisms

    Directory of Open Access Journals (Sweden)

    J Stevens

    2012-01-01

    Full Text Available This paper presents a parametric investigation of a porous 3D micro-mixer as well as a 10:1 scale model of the same used to examine the influence of the contributions of both diffusion and advection to successful mixing of fluids of different viscosity. Experiments at both scales implement the laser induced fluorescence technique to capture the evolution of concentration gradients at the mixer outlet. Mixing performance strongly increases with flow rate in the micromixing apparatus but only moderately in the scale-up suggesting important scale-dependent manipulation of diffusion.

  15. Colloidal stability and chemical reactivity of complex colloids containing Fe³⁺.

    Science.gov (United States)

    van Leeuwen, Y M; Velikov, K P; Kegel, W K

    2014-07-15

    The reactivity of iron contained within insoluble colloidal metal-pyrophosphate salts was determined and compared to the reactivity of a soluble iron salt (FeCl3). As a model system for the reactivity of iron in food products, the formation of an iron-polyphenol complex was followed with spectrophotometry. Three types of systems were prepared and their colloidal stability and reactivity studied: Fe(3+) pyrophosphate, protein-coated Fe(3+) pyrophosphate and mixed-metal pyrophosphates containing Fe(3+) and a second cation M. The additional cation used was either monovalent (sodium) or divalent (M(2+)). It was found that: (i) incorporating iron in a colloidal salt reduced its reactivity compared to free Fe(3+) ions; (ii) coating the particles with a layer of hydrophobic protein (zein) increased stability and further decreased the reactivity. Finally, the most surprising result was that (iii) a mixed system containing more Fe(3+) than M actually increased the reactivity of the contained iron, while the reverse, a system containing excess M, inhibited the reactivity completely. PMID:24594169

  16. Size Control of 99mTc-tin Colloid Using PVP and Buffer Solution for Sentinel Lymph Node Detection

    OpenAIRE

    Kim, Eun-Mi; Lim, Seok Tae; Sohn, Myung-Hee; Jeong, Hwan-Jeong

    2015-01-01

    Colloidal particle size is an important characteristic that allows mapping sentinel nodes in lymphoscintigraphy. This investigation aimed to introduce different ways of making a 99mTc-tin colloid with a size of tens of nanometers. All agents, tin fluoride, sodium fluoride, poloxamer-188, and polyvinylpyrrolidone (PVP), were mixed and labeled with 99mTc. Either phosphate or sodium bicarbonate buffers were used to adjust the pH levels. When the buffers were added, the size of the colloids incre...

  17. Advanced Colloids Experiment (ACE) Science Overview

    Science.gov (United States)

    Meyer, William V.; Sicker, Ronald J.; Chiaramonte, Francis P.; Luna, Unique J.; Chaiken, Paul M.; Hollingsworth, Andrew; Secanna, Stefano; Weitz, David; Lu, Peter; Yodh, Arjun; Yunker, Peter; Lohr, Matthew; Gratale, Matthew; Lynch, Matthew; Kodger, Thomas; Piazza, Roberto; Buzzaccaro, Stefano; Cipelletti, Luca; Schall, Peter; Veen, Sandra; Wegdam, Gerhard; Lee, Chand-Soo; Choi, Chang-Hyung; Paul, Anna-Lisa; Ferl, Robert J.; Cohen, Jacob

    2013-01-01

    The Advanced Colloids Experiment is being conducted on the International Space Station (ISS) using the Light Microscopy Module (LMM) in the Fluids Integrated Rack (FIR). Work to date will be discussed and future plans and opportunities will be highlighted. The LMM is a microscope facility designed to allow scientists to process, manipulate, and characterize colloidal samples in micro-gravity where the absence of gravitational settling and particle jamming enables scientists to study such things as:a.The role that disordered and ordered-packing of spheres play in the phase diagram and equation of state of hard sphere systems,b.crystal nucleation and growth, growth instabilities, and the glass transition, c.gelation and phase separation of colloid polymer mixtures,d.crystallization of colloidal binary alloys,e.competition between crystallization and phase separation,f.effects of anisotropy and specific interactions on packing, aggregation, frustration and crystallization,g.effects of specific reversible and irreversible interactions mediated in the first case by hybridization of complementary DNA strands attached to separate colloidal particles,h.Lock and key interactions between colloids with dimples and spheres which match the size and shape of the dimples,i.finding the phase diagrams of isotropic and interacting particles,j.new techniques for complex self-assembly including scenarios for self-replication, k.critical Casimir forces,l.biology (real and model systems) in microgravity,m.etc. By adding additional microscopy capabilities to the existing LMM, NASA will increase the tools available for scientists that fly experiments on the ISS enabling scientists to observe directly what is happening at the particle level. Presently, theories are needed to bridge the gap between what is being observed (at a macroscopic level when photographing samples) with what is happening at a particle (or microscopic) level. What is happening at a microscopic level will be directly

  18. Polymers and colloids

    International Nuclear Information System (INIS)

    A wealth of structural information from colloid and polymer solutions on a large range of length scales can be obtained using small angle neutron scattering (SANS) experiments. After a general introduction to the field of soft condensed matter, I shall give a few selected examples on how SANS combined with suitable contrast variation schemes can be used to extract information on the size and conformation of polymer coils in solution and in the melt, and on the local structure and flexibility of polymerlike micelles and microemulsions. (author) 8 figs., tabs., 44 refs

  19. Polymers and colloids

    Energy Technology Data Exchange (ETDEWEB)

    Schurtenberger, P. [ETH Zurich, Inst. fuer Polymere, Zurich (Switzerland)

    1996-11-01

    A wealth of structural information from colloid and polymer solutions on a large range of length scales can be obtained using small angle neutron scattering (SANS) experiments. After a general introduction to the field of soft condensed matter, I shall give a few selected examples on how SANS combined with suitable contrast variation schemes can be used to extract information on the size and conformation of polymer coils in solution and in the melt, and on the local structure and flexibility of polymerlike micelles and microemulsions. (author) 8 figs., tabs., 44 refs.

  20. A mass-balance model to separate and quantify colloidal and solute redistributions in soil

    Science.gov (United States)

    Bern, C.R.; Chadwick, O.A.; Hartshorn, A.S.; Khomo, L.M.; Chorover, J.

    2011-01-01

    Studies of weathering and pedogenesis have long used calculations based upon low solubility index elements to determine mass gains and losses in open systems. One of the questions currently unanswered in these settings is the degree to which mass is transferred in solution (solutes) versus suspension (colloids). Here we show that differential mobility of the low solubility, high field strength (HFS) elements Ti and Zr can trace colloidal redistribution, and we present a model for distinguishing between mass transfer in suspension and solution. The model is tested on a well-differentiated granitic catena located in Kruger National Park, South Africa. Ti and Zr ratios from parent material, soil and colloidal material are substituted into a mixing equation to quantify colloidal movement. The results show zones of both colloid removal and augmentation along the catena. Colloidal losses of 110kgm-2 (-5% relative to parent material) are calculated for one eluviated soil profile. A downslope illuviated profile has gained 169kgm-2 (10%) colloidal material. Elemental losses by mobilization in true solution are ubiquitous across the catena, even in zones of colloidal accumulation, and range from 1418kgm-2 (-46%) for an eluviated profile to 195kgm-2 (-23%) at the bottom of the catena. Quantification of simultaneous mass transfers in solution and suspension provide greater specificity on processes within soils and across hillslopes. Additionally, because colloids include both HFS and other elements, the ability to quantify their redistribution has implications for standard calculations of soil mass balances using such index elements. ?? 2011.

  1. Colloidally deposited nanoparticle wires for biophysical detection

    Science.gov (United States)

    Shen, Sophie C.; Liu, Wen-Tao; Diao, Jia-Jie

    2015-12-01

    Among the techniques developed to prepare nanoparticle wires for multiple applications, the colloidal deposition method at interface has been regarded as cost-efficient and eco-friendly, and hence has attracted an increasing amount of research attention. In this report, the recent developments in preparing nanoparticle wires and integrated nanoparticle wire arrays using this technique have been reviewed. Furthermore, we have also discussed the application of these nanoparticle structures in detecting chemical and biological molecules. Project supported by the Fundamental Research Funds for the Central Universities through Xi’an Jiaotong University and the National Key Basic Research Program of China (Grant No. 2015CB856304).

  2. Shelf-life extension and improving micro-biological quality of mixed peas with diced carrot by gamma irradiation

    International Nuclear Information System (INIS)

    Mixed peas with diced carrot were collected and examined for their microbiological quality. All the examined samples had high level of microbial load. All examined samples contained Escherichia coli (E. coli) and Enterococcus faecalis (Ent. faecalis). Staphylococcus aureus (S. aureus) was detected in only 4 of samples (26.3%). The tested samples were free from Aeromonas hydrophila (A. hydrophila), Listeria monocytogenes (L monocytogenes) and Salmonella species. Gamma irradiation caused a great reduction in all microbial loads. During refrigerated storage, the counts of all microorganisms increased, but the rate of increase was slower as the irradiation dose increased. Irradiation dose of 3 kGy was the optimum dose for preservation of mixed peas with diced carrot which extended the refrigeration shelf-life up to 21 days and it was sufficient in eliminating pathogenic bacteria without affecting their sensory quality and with negligible effect on chemical quality.

  3. International workshop on colloids and colloid-facilitated transport of contaminants in soils and sediments

    International Nuclear Information System (INIS)

    The workshop was organized to review the present knowledge of colloid behavior and transport in porous media systems and the possibility of colloid-bound transport of contaminants, pesticide and nutrients in soil and groundwater. The four main topics at the workshop were 1) colloidal behavior and properties, 2) colloid mobilization and transport, 3) sorption onto colloids and facilitated transport of contaminants, and 4) modeling of colloidal and colloid-facilitated transport

  4. Public views on the donation and use of human biological samples in biomedical research: a mixed methods study

    OpenAIRE

    Lewis, C.; Clotworthy, M.; Hilton, S; MaGee, C.; Robertson, M. J.; Stubbins, L.J.; Corfield, J.

    2013-01-01

    Objective A mixed methods study exploring the UK general public's willingness to donate human biosamples (HBSs) for biomedical research. Setting Cross-sectional focus groups followed by an online survey. Participants Twelve focus groups (81 participants) selectively sampled to reflect a range of demographic groups; 1110 survey responders recruited through a stratified sampling method with quotas set on sex, age, geographical location, socioeconomic group and ethnicity. Main outcom...

  5. High School Biology Students' Transfer of the Concept of Natural Selection: A Mixed-Methods Approach

    Science.gov (United States)

    Pugh, Kevin J.; Koskey, Kristin L. K.; Linnenbrink-Garcia, Lisa

    2014-01-01

    The concept of natural selection serves as a foundation for understanding diverse biological concepts and has broad applicability to other domains. However, we know little about students' abilities to transfer (i.e. apply to a new context or use generatively) this concept and the relation between students' conceptual understanding and…

  6. Interaction between the biological effects of high- and low-LET radiation dose components in a mixed field exposure

    DEFF Research Database (Denmark)

    Mason, Anna J.; Giusti, Valerio; Green, Stuart;

    2011-01-01

    The relative biological effectiveness of two epithermal neutron sources, a reactor based source at Studsvik, Sweden, and a proton accelerator-based source in Birmingham, UK, was studied in relation to the proportional absorbed dose distribution as a function of neutron energy. Evidence for any...

  7. Evidence for anecdotes: Examining use of stories in introductory biology courses with a mixed-methods approach

    Science.gov (United States)

    Kreps, Jennifer Susan

    2005-11-01

    Instructional stories can be an effective way to teach science concepts. However, research has not examined the extent to which stories are being used, and how they are received. More research on the use of story in biology classes may lead to more conscious use of story by instructors, which may lead to a better understanding of biological concepts by students. The purpose of this study was to examine how instructors and students use stories in university introductory biology courses, and the degree to which these stories are perceived to be effective. To examine this phenomenon, a nationwide instructor survey, a university-wide student survey, and multiple case studies were used. Two case studies included observation of lectures, interviews with (36) students, and interviews with instructors (4) over two semesters of an organismal biology course. Instructor survey participants (N = 78) were gathered by posting email invitations, and student survey participants (N = 260) were volunteers from introductory biology courses at a middle-sized university. Several types of stories were observed, including personal experience stories, historical anecdotes, and "you" stories. Students reported increased affective learning when stories were told, and remembered mostly humorous stories. In the instructor survey, no significant differences emerged between genders, type of biology taught, or communicator style and instructional story frequency. However, reports of personal experience story frequency did increase significantly (p differences in story use by gender or ethnicity, although non-science majors reported that their instructors used stories significantly more frequently (p science majors. Simultaneous-entry multiple regression analyses indicated that there was a significant positive relationship between story use and cognitive and affective learning for all groups of students. Story use was a significant predictor of perceived learning loss for non-science majors, but

  8. Colloidal Bandpass and Bandgap Filters

    Science.gov (United States)

    Yellen, Benjamin; Tahir, Mukarram; Ouyang, Yuyu; Nori, Franco

    2013-03-01

    Thermally or deterministically-driven transport of objects through asymmetric potential energy landscapes (ratchet-based motion) is of considerable interest as models for biological transport and as methods for controlling the flow of information, material, and energy. Here, we provide a general framework for implementing a colloidal bandpass filter, in which particles of a specific size range can be selectively transported through a periodic lattice, whereas larger or smaller particles are dynamically trapped in closed-orbits. Our approach is based on quasi-static (adiabatic) transition in a tunable potential energy landscape composed of a multi-frequency magnetic field input signal with the static field of a spatially-periodic magnetization. By tuning the phase shifts between the input signal and the relative forcing coefficients, large-sized particles may experience no local energy barriers, medium-sized particles experience only one local energy barrier, and small-sized particles experience two local energy barriers. The odd symmetry present in this system can be used to nudge the medium-sized particles along an open pathway, whereas the large or small beads remain trapped in a closed-orbit, leading to a bandpass filter, and vice versa for a bandgap filter. NSF CMMI - 0800173, Youth 100 Scholars Fund

  9. Mixed hemimicelles solid-phase extraction of cephalosporins in biological samples with ionic liquid-coated magnetic graphene oxide nanoparticles coupled with high-performance liquid chromatographic analysis.

    Science.gov (United States)

    Wu, Jianrong; Zhao, Hongyan; Xiao, Deli; Chuong, Pham-Huy; He, Jia; He, Hua

    2016-07-01

    A novel mixed hemimicelles solid phase extraction based on magnetic graphene oxide (Fe3O4/GO) and ionic liquid (IL) was developed for the simultaneous extraction and determination of trace cephalosporins in spiked human urine. The high surface area and excellent adsorption capacity of the graphene oxide after modification with1-hexadecyl-3-methylmidazoliumbromide(C16mimBr) were utilized adequately in the solid phase extraction(SPE) process. A comprehensive study of the parameters affecting the extraction recovery, such as the zeta-potential of magnetic graphene oxide, amounts of magnetic graphene oxide and surfactant, pH of solution, ionic strength, extraction time, and desorption condition were optimized. A comparative study on the use of different surfacant-coated Fe3O4/GO NPs as sorbents was presented. Good linearity (R(2)>0.9987) for all calibration curves was obtained. The LODs were ranged between 0.6 and 1.9ng mL(-1) for the cephalosporins and the LOQs were 1.5 to 5.5, respectively. Satisfactory recoveries(84.3% to 101.7%)and low relative standard deviations from 1.7% to 6.3% in biological matrices were achieved. The mixed hemimicelles magnetic SPE (MSPE) method based on ILs and Fe3O4/GO NPs magnetic separation has ever been successfully used for pretreatment of complex biological samples. PMID:27266334

  10. Comparative radioanalytical and biokinetic studies of 99mTc-Tin and 99mTc-sulphur colloid kits

    International Nuclear Information System (INIS)

    Gel chromatography scanning technique (GCS) was used to study the radioanalytical behaviour of 99mTc-tin colloid and 99mTc-sulphur colloid kits. Sepharose has been found to be more accurate and versatile than the other conventional analytical procedures for radioanalytical evaluation of 99mTc-labelled colloids. The obtained radioanalytical results showed that 99mTc-sulphur colloid is more susceptible than the 99mTc-tin colloids to change due to the analytical environment. This is related to the nature of oxidation state of technetium atom in both colloids. The formation of 99mTc-tin colloid is achieved within few minutes after pertechnetate addition, while labeling of sulphur colloid is accomplished through a rather slow process. The organ distribution in mice shows that more than 90% of the injected dose of both colloids are accumulated in the liver, which proved the colloid labeling and optimal size particle. The minor size difference in the blood residual activity is due to the presence of hydrophilic stabilizer in 99mTc-sulphur colloid. The blood clearance study in rabbits showed that the biological half-times of activity disappearance of fast phase are longer periods extend to 125 and 65 minutes to 99mTc-tin and 99mTc-sulphur colloids, respectively. The in vitro plasma protein binding studies revealed by the GSC method showed that about 85% of 99mTc-tin colloid and 16% of 99mTc-sulphur colloid were bound to plasma protein, which proved that it does not influence the in vivo kinetics of both colloids

  11. Quantitative and qualitative examination of particle-particle interactions using colloidal probe nanoscopy.

    Science.gov (United States)

    D'Sa, Dexter; Chan, Hak-Kim; Kim, Hae-Won; Chrzanowski, Wojciech

    2014-01-01

    Colloidal Probe Nanoscopy (CPN), the study of the nano-scale interactive forces between a specifically prepared colloidal probe and any chosen substrate using the Atomic Force Microscope (AFM), can provide key insights into physical interactions present within colloidal systems. Colloidal systems are widely existent in several applications including, pharmaceuticals, foods, paints, paper, soil and minerals, detergents, printing and much more.1-3 Furthermore, colloids can exist in many states such as emulsions, foams and suspensions. Using colloidal probe nanoscopy one can obtain key information on the adhesive properties, binding energies and even gain insight into the physical stability and coagulation kinetics of the colloids present within. Additionally, colloidal probe nanoscopy can be used with biological cells to aid in drug discovery and formulation development. In this paper we describe a method for conducting colloidal probe nanoscopy, discuss key factors that are important to consider during the measurement, and show that both quantitative and qualitative data that can be obtained from such measurements. PMID:25080136

  12. Probing Interfacial Water on Nanodiamonds in Colloidal Dispersion.

    Science.gov (United States)

    Petit, Tristan; Yuzawa, Hayato; Nagasaka, Masanari; Yamanoi, Ryoko; Osawa, Eiji; Kosugi, Nobuhiro; Aziz, Emad F

    2015-08-01

    The structure of interfacial water layers around nanoparticles dispersed in an aqueous environment may have a significant impact on their reactivity and on their interaction with biological species. Using transmission soft X-ray absorption spectroscopy in liquid, we demonstrate that the unoccupied electronic states of oxygen atoms from water molecules in aqueous colloidal dispersions of nanodiamonds have a different signature than bulk water. X-ray absorption spectroscopy can thus probe interfacial water molecules in colloidal dispersions. The impacts of nanodiamond surface chemistry and concentration on interfacial water electronic signature are discussed. PMID:26267179

  13. The Design, Synthesis and Study of Mixed-Metal Ru,Rh and Os, Rh Complexes with Biologically Relevant Reactivity

    OpenAIRE

    Wang, Jing

    2013-01-01

    A series of mixed-metal bimetallic complexes [(TL)2M(dpp)RhCl2(TL)]3 (M = Ru and Os, terminal ligands (TL) = phen, Ph2phen, Me2phen and bpy, terminal ligands (TL) = phen, bpy and Me2bpy ), which couple one Ru or Os polyazine light absorber (LA) to a cis-RhIIICl2 center through a dpp bridging ligand (BL), were synthesized using a building block method. These are related to previously studied trimetallic systems [{(TL)2M(dpp)2RhCl2]5+, but the bimetallics are synthetically more complex to prepa...

  14. Surface Chemical Properties of Colloids in Main Soils of China

    Institute of Scientific and Technical Information of China (English)

    MAYI-JIE; YUANCHAO-LIANG

    1991-01-01

    Surface chemical properties of soil colloids are the important factor affecting soil fertility and genesis.To provide scientific basis for soil genetic classification,promotion of soil fertility and reasonable fertilizqation,the specific surface area and electric charge of soil colloids in relation to clay minerals and organic matter are further discussed on the basis of the results obtained from the studies on surface chemical properties of soil colloids in five main soils of China.Results from the studies show that the effect of clay minerals and organic matter on the surface chemical properties of soil colloids is very complicated because the siloxane surface,hydrated oxide surface and organic matter surface do not exist separately,but they are always mixed together and influenced each other.The understanding of the relationship among clay minerals,organic matter and surface chemical properties of soil colloids depends upon further study of the relevant disciplines of soil science,especially the study on the mechanisms of organo-mineral complexes.

  15. Shape control and compartmentalization in active colloidal cells.

    Science.gov (United States)

    Spellings, Matthew; Engel, Michael; Klotsa, Daphne; Sabrina, Syeda; Drews, Aaron M; Nguyen, Nguyen H P; Bishop, Kyle J M; Glotzer, Sharon C

    2015-08-25

    Small autonomous machines like biological cells or soft robots can convert energy input into control of function and form. It is desired that this behavior emerges spontaneously and can be easily switched over time. For this purpose we introduce an active matter system that is loosely inspired by biology and which we term an active colloidal cell. The active colloidal cell consists of a boundary and a fluid interior, both of which are built from identical rotating spinners whose activity creates convective flows. Similarly to biological cell motility, which is driven by cytoskeletal components spread throughout the entire volume of the cell, active colloidal cells are characterized by highly distributed energy conversion. We demonstrate that we can control the shape of the active colloidal cell and drive compartmentalization by varying the details of the boundary (hard vs. flexible) and the character of the spinners (passive vs. active). We report buckling of the boundary controlled by the pattern of boundary activity, as well as formation of core-shell and inverted Janus phase-separated configurations within the active cell interior. As the cell size is increased, the inverted Janus configuration spontaneously breaks its mirror symmetry. The result is a bubble-crescent configuration, which alternates between two degenerate states over time and exhibits collective migration of the fluid along the boundary. Our results are obtained using microscopic, non-momentum-conserving Langevin dynamics simulations and verified via a phase-field continuum model coupled to a Navier-Stokes equation. PMID:26253763

  16. Monomeric mixed cadmium-2,2‧-dipyridylamine complex derived from ferrocenecarboxylic acid: Structural, electrochemical and biological studies

    Science.gov (United States)

    Senthilkumar, Kabali; Gopalakrishnan, Mohan; Palanisami, Nallasamy

    2015-09-01

    A mixed Cd(II) complex {[Cd(FcCOO)2(dpyam)(H2O)][Cd(dpyam)2 (H2O)2]·(ClO4)2·CH3OH} (1) (where FcCOO = ferrocenecarboxylic acid and dpyam = 2,2‧-dipyridylamine), has been synthesized and characterized by FT-IR, 1H & 13C NMR, UV-Vis spectroscopy and elemental analysis. The molecular structure of compound 1 has been determined by the single crystal X-ray diffraction technique, which consists of mixed two different cadmium(II) complexes and two uncoordinated perchlorate ions. The crystal packing shows that the compound 1 self-assembled by intermolecular hydrogen bonding via pyridyl N-H⋯O and coordinated water O⋯H-O-H⋯O, to afford the molecule 2D supramolecular network. Compound 1 exhibits high-energy intraligand (π-π∗) fluorescence emission. In electrochemical studies of compound 1 shows negative potential compared with ferrocenecarboxylic acid due to formation of coordination complex with Cd ions. The antibacterial study against the distinct bacterial strains show compound 1 has significant activity.

  17. Monomeric mixed cadmium-2,2'-dipyridylamine complex derived from ferrocenecarboxylic acid: Structural, electrochemical and biological studies.

    Science.gov (United States)

    Senthilkumar, Kabali; Gopalakrishnan, Mohan; Palanisami, Nallasamy

    2015-09-01

    A mixed Cd(II) complex {[Cd(FcCOO)2(dpyam)(H2O)][Cd(dpyam)2 (H2O)2]·(ClO4)2·CH3OH} (1) (where FcCOO=ferrocenecarboxylic acid and dpyam=2,2'-dipyridylamine), has been synthesized and characterized by FT-IR, (1)H &(13)C NMR, UV-Vis spectroscopy and elemental analysis. The molecular structure of compound 1 has been determined by the single crystal X-ray diffraction technique, which consists of mixed two different cadmium(II) complexes and two uncoordinated perchlorate ions. The crystal packing shows that the compound 1 self-assembled by intermolecular hydrogen bonding via pyridyl N-H⋯O and coordinated water O⋯H-O-H⋯O, to afford the molecule 2D supramolecular network. Compound 1 exhibits high-energy intraligand (π-π(∗)) fluorescence emission. In electrochemical studies of compound 1 shows negative potential compared with ferrocenecarboxylic acid due to formation of coordination complex with Cd ions. The antibacterial study against the distinct bacterial strains show compound 1 has significant activity. PMID:25879985

  18. Colloidal aggregation in polymer blends.

    Science.gov (United States)

    Benhamou, M; Ridouane, H; Hachem, E-K; Derouiche, A; Rahmoune, M

    2005-06-22

    We consider here a low-density assembly of colloidal particles immersed in a critical polymer mixture of two chemically incompatible polymers. We assume that, close to the critical point of the free mixture, the colloids prefer to be surrounded by one polymer (critical adsorption). As result, one is assisted to a reversible colloidal aggregation in the nonpreferred phase, due the existence of a long-range attractive Casimir force between particles. This aggregation is a phase transition driving the colloidal system from dilute to dense phases, as the usual gas-liquid transition. We are interested in a quantitative investigation of the phase diagram of the immersed colloids. We suppose that the positions of particles are disordered, and the disorder is quenched and follows a Gaussian distribution. To apprehend the problem, use is made of the standard phi(4) theory, where the field phi represents the composition fluctuation (order parameter), combined with the standard cumulant method. First, we derive the expression of the effective free energy of colloids and show that this is of Flory-Huggins type. Second, we find that the interaction parameter u between colloids is simply a linear combination of the isotherm compressibility and specific heat of the free mixture. Third, with the help of the derived effective free energy, we determine the complete shape of the phase diagram (binodal and spinodal) in the (Psi,u) plane, with Psi as the volume fraction of immersed colloids. The continuous "gas-liquid" transition occurs at some critical point K of coordinates (Psi(c) = 0.5,u(c) = 2). Finally, we emphasize that the present work is a natural extension of that, relative to simple liquid mixtures incorporating colloids. PMID:16035822

  19. Liquid crystal boojum-colloids

    International Nuclear Information System (INIS)

    Colloidal particles dispersed in a liquid crystal (LC) lead to distortions of the director field. The distortions are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. The short-distance behaviour depends on the structure and dynamics of the topological defects nucleated near the colloidal particles and a full nonlinear theory is required to describe it. Spherical colloidal particles with strong planar degenerate anchoring nucleate a pair of antipodal surface topological defects, known as boojums. We use the Landau-de Gennes theory to resolve the mesoscopic structure of the boojum cores and to determine the pairwise colloidal interactions. We compare the results in three (3D) and two (2D) spatial dimensions for spherical and disc-like colloidal particles, respectively. The corresponding free energy functionals are minimized numerically using finite elements with adaptive meshes. Boojums are always point-like in 2D, but acquire a rather complex structure in 3D, which depends on the combination of the anchoring potential, the radius of the colloid, the temperature and the LC elastic anisotropy. We identify three types of defect cores in 3D that we call single, double and split-core boojums, and investigate the associated structural transitions. The split-core structure is favoured by low temperatures, strong anchoring and small twist to splay or bend ratios. For sufficiently strong anchoring potentials characterized by a well-defined uniaxial minimum, the split-core boojums are the only stable configuration. In the presence of two colloidal particles, we observe substantial re-arrangements of the inner defects in both 3D and 2D. These re-arrangements lead to qualitative changes in the force-distance profile when compared to the asymptotic quadrupole-quadrupole interaction. In line with the experimental results, the presence of the defects prevents coalescence of the colloidal particles in 2D, but not in 3D

  20. Controlling the Transient Interface Shape and Deposition Profile Left by Desiccation of Colloidal Droplets on Multiple Polymer Surfaces

    Science.gov (United States)

    Dunning, Peter David

    A colloidal suspension is a small constituent of insoluble solid particles suspended in a liquid medium. Control over the wetting, evaporation, and deposition patterns left by colloidal suspensions is valuable in many biological, medical, industrial, and agricultural applications. Understanding the governing principles of wetting and evaporative phenomena of these colloidal suspensions may lead to greater control over resultant deposition patterns. Perhaps the most familiar pattern forms when an initially heterogeneous colloidal suspension leaves a dark ring pattern at the edge of a drop. This pattern is referred to as a coffee-stain and it can be seen from dried droplets of spilled coffee. This coffee-stain effect was first investigated by Deegan et. al. who discovered that these patterns occur when outward radial flows driven by evaporation at the triple contact line dominate over other effects. While the presence of coffee-stain patterns is undesirable in many printing and medical diagnostic processes, it can also be advantageous in the production of low cost transparent conductive films, the deposition of metal vapor, and the manipulation of biological structures. Controlling the interactions between the substrate, liquid, vapor, and particles can lead to control over the size and morphology of evaporative deposition patterns left by aqueous colloidal suspensions. Several methods have been developed to control the evaporation of colloidal suspensions to either suppress or enhance the coffee stain effect. Electrowetting on Dielectric (EWOD) is one promising method that has been used to control colloidal depositions by applying either an AC or DC electric field. EWOD actuation has the potential to dynamically control colloidal deposition left by desiccated droplets to either suppress or enhance the coffee stain effect. It may also allow for independent control of the fluidic interface and deposition of particles via electrowetting and electrokinetic forces

  1. Colloids in Paints Colloids and Interface Science, Volume 6

    CERN Document Server

    Tadros, Tharwat F

    2011-01-01

    The first modern approach to relate fundamental research to the applied science of colloids, this series bridges academic research and practical applications, thus providing the information vital to both. Written by the very best scientists in their respective disciplines, this volume describes the role of colloids in paints, highlighting the importance of fundamental research in industrial applications.For surface, polymer and physicochemists, materials scientists, and chemical engineers.

  2. Effect of additives on properties of colloidal silica bonded Al2O3-SiC-C iron trough ramming mix%添加剂对硅溶胶结合 Al2O3-SiC-C 铁沟捣打料性能的影响

    Institute of Scientific and Technical Information of China (English)

    徐勇

    2015-01-01

    以特级矾土(粒径8~5、5~3和3~1 mm)、棕刚玉(粒径3~1、≤1和≤0.074 mm)、碳化硅(粒径≤1和≤0.074 mm)和球状沥青为主要原料,金属硅和碳化硼为抗氧化剂和促烧剂,添加超微粉或焦作黏土,以硅溶胶作结合剂,采用手工捣打成型工艺来制备 Al2 O3-SiC-C 铁沟捣打料。研究了硅微粉、α-Al2 O3微粉、焦作黏土和有机防爆纤维对硅溶胶结合 Al2 O3-SiC-C 铁沟捣打料性能的影响。结果表明:添加2%质量分数硅微粉、3%质量分数焦作黏土或0.05%质量分数有机防爆纤维对硅溶胶结合 Al2 O3-SiC-C 铁沟捣打料的体积密度影响不大。含9%质量分数α-Al2 O3微粉的试样和含6%质量分数α-Al2 O3微粉、3%质量分数焦作黏土的试样显示出更好的常温强度。合理的颗粒级配可以提高铁沟捣打料试样的抗高炉渣侵蚀性。含6%质量分数α-Al2 O3微粉、3%质量分数焦作黏土的试样的抗渣侵蚀性最好;含7%质量分数α-Al2 O3微粉、2%质量分数硅微粉的试样的抗渣侵蚀性次之;含9%质量分数α-Al2 O3微粉的试样的抗渣侵蚀性最差。有机防爆纤维提高了捣打料的烘后强度,但使抗渣性能有所降低。硅溶胶结合 Al2 O3-SiC-C 铁沟捣打料试样在1450℃煅烧后质量增加,有利于体积稳定性和抗渣性能。%The Al2 O3-SiC-C iron trough ramming mix was prepared using extra grade bauxite (particle size:8-5 ,5-3 and 3-1 mm),brown corundum (particle size:3-1、≤1 and ≤0.074 mm),silicon carbide (particle size:≤1 and ≤0.074 mm)and ball pitch as main starting materials,metallic silicon and boron carbide as antioxidant and sintering aid,adding ultra-micro powders or Jiaozuo clay,colloidal silica as binder,ramming and shaping.Effect of silica mi-cropowder,α-Al2 O3 micropowder,Jiaozuo clay and organic explosion-proof fiber on properties of colloidal silica bonded Al2 O3-SiC-C iron

  3. Biological efficiency of the Brookhaven Medical Research Reactor mixed neutron beam estimated from gene mutations in Tradescantia stamen hair cells assay

    International Nuclear Information System (INIS)

    The relative biological effectiveness (RBE) of low energy neutrons for the induction of various abnormalities in Tradescantia stamen hair mutation (Trad-SH) assay was studied using two clones (T-4430 and T-02), heterozygous for flower color. Dose response relationship for gene mutations induced in somatic cells of Trad-SH were investigated after irradiation with a mixed neutron beam of the Brookhaven Medical Research Reactor (BMRR), currently used in a clinical trial of boron neutron capture therapy (BNCT) for glioblastoma. To establish the RBE of the BMRR beam in the induction of various biological end-points in Tradescantia, irradiation with various doses of γ-rays was also performed. After irradiation all plants were cultivated several days at Brookhaven National Laboratory (BNL), then transported to Poland for screening the biological end-points. Due to the post-exposure treatment, all plants showed high levels of lethal events and alteration of the cell cycle. Plants of clone 4430 were more reactive to post-treatment conditions, resulting in decreased blooming efficiency that affected the statistics. Slope coefficients estimated from the dose response curves for gene mutation frequencies allowed the evaluation of ranges for the maximal RBE values of the applied beam vs. γ rays as 6.0 and 5.4 for the cells of T-02 and T-4430, respectively. Estimated fraction of doses from neutrons and corresponding biological effects for the clones T-02 and T-4430 allowed to evaluate the RBE values for neutrons part in the beam as 32.3 and 45.4, respectively. (author)

  4. Accelerated lattice Boltzmann model for colloidal suspensions rheology and interface morphology

    CERN Document Server

    Farhat, Hassan; Kondaraju, Sasidhar

    2014-01-01

    Colloids are ubiquitous in the food, medical, cosmetics, polymers, water purification, and pharmaceutical industries. The thermal, mechanical, and storage properties of colloids are highly dependent on their interface morphology and their rheological behavior. Numerical methods provide a convenient and reliable tool for the study of colloids. Accelerated Lattice Boltzmann Model for Colloidal Suspensions introduce the main building-blocks for an improved lattice Boltzmann–based numerical tool designed for the study of colloidal rheology and interface morphology. This book also covers the migrating multi-block used to simulate single component, multi-component, multiphase, and single component multiphase flows and their validation by experimental, numerical, and analytical solutions.   Among other topics discussed are the hybrid lattice Boltzmann method (LBM) for surfactant-covered droplets; biological suspensions such as blood; used in conjunction with the suppression of coalescence for investigating the...

  5. Active colloids in complex fluids

    CERN Document Server

    Patteson, Alison E; Arratia, Paulo E

    2016-01-01

    We review recent work on active colloids or swimmers, such as self-propelled microorganisms, phoretic colloidal particles, and artificial micro-robotic systems, moving in fluid-like environments. These environments can be water-like and Newtonian but can frequently contain macromolecules, flexible polymers, soft cells, or hard particles, which impart complex, nonlinear rheological features to the fluid. While significant progress has been made on understanding how active colloids move and interact in Newtonian fluids, little is known on how active colloids behave in complex and non-Newtonian fluids. An emerging literature is starting to show how fluid rheology can dramatically change the gaits and speeds of individual swimmers. Simultaneously, a moving swimmer induces time dependent, three dimensional fluid flows, that can modify the medium (fluid) rheological properties. This two-way, non-linear coupling at microscopic scales has profound implications at meso- and macro-scales: steady state suspension proper...

  6. Resonant phenomena in colloidal crystals

    OpenAIRE

    Palberg, Thomas; Würth, Mathias; König, Peter; Simnacher, Erwin; Leiderer, Paul

    1992-01-01

    Colloidal crystals of completely deionized suspensions of latex speres are subjected to oscillatory and steady shear, as well as to homogeneous and inhomogeneous electric fields. Various resonant phenomena observed in such experiments are reported.

  7. Studies on the biological behaviour of uranium-plutonium mixed oxide aerosols: Inhalation experiments with rats and in vitro studies with alveolar macrophages

    International Nuclear Information System (INIS)

    The retention of spherical and of irregularly shaped (U, Pu) mixed oxides in rat lung was analyzed after inhalation and intratracheal instillation. Their biological behaviour was relatively independent of particle shape and application route with only a few percent of radioactivity being transferred to other organs. In vivo and in vitro uptake and intracellular distribution in rat and bovine alveolar macrophages were analyzed as dependent on various parameters. In addition, detailed electron microscopic studies were performed demonstrating particles within membrane limited vacuoles as well as lying free in the cytoplasm. Under in vitro conditions the uptake process was finished after a few hours. After differential centrifugation of lung or macrophage homogenates the particles sedimented in the first (1000 g) fraction. (orig.)

  8. Magnetic silica colloids for catalysis

    OpenAIRE

    Claesson, E.M.; Mehendale, N.C.; Klein Gebbink, R. J. M.; van Koten, G; Philipse, A. P.

    2007-01-01

    Monodisperse magnetizable colloidal silica particles in a stable dispersion have been functionalized with a homogeneous catalyst: a PCP–pincer Pd-complex. In a proof-of-principle experiment we demonstrate the catalytic activity of the colloids in a C–C bond formation reaction. Advantages of the magnetic silica carriers are the large surface-to-volume ratio and the easy recovery by magnetic separation. After magnetic separation, the catalyst-loaded particles are readily redispersed for further...

  9. Re-shaping colloidal clusters

    Science.gov (United States)

    Kraft, Daniela

    2015-03-01

    Controlling the geometry and yield of anisotropic colloidal particles remains a challenge for hierarchical self-assembly. I will discuss a synthetic strategy for fabricating colloidal clusters by creating order in randomly aggregated polymer spheres using surface tension and geometrical constraints. The technique can be extended to a variety of charge-stabilized polymer spheres and offers control over the cluster size distribution. VENI grant from The Netherlands Organization for Scientific Research (NWO).

  10. Ferroelectric Ordering in Colloidal Nanocrystals

    OpenAIRE

    Polking, Mark Joseph

    2011-01-01

    The size-stability and fundamental nature of ferroelectric ordering in low-dimensional nanomaterials are explored using colloidal nanocrystals of the ferroelectric semiconductor germanium telluride (GeTe) and the archetypal perovskite ferroelectric barium titanate (BaTiO3). The synthesis of size-controlled colloidal GeTe nanocrystals is first explored, and the evolution of a polarization domain structure with increasing size is examined with transmission electron microscopy (TEM) and electro...

  11. Characterization of colloids in groundwater

    International Nuclear Information System (INIS)

    Natural colloids in the Gorleben aquifer systems have been investigated as for their chemical composition, quantification and size distribution. Humic substances appear to be the major organic materials in these groundwaters, generating humic colloids which are analysed to be humic acid (and fulvic acid) loaded with a large number of trace heavy metal ions. These metal ions include natural homologues of actinides and some fission products in trivalent, tetravalent and hexavalent state. Concentrations of trivalent and tetravalent heavy metal ions are linearly correlated with the dissolved organic carbon (DDC) concentration in different groundwaters. The DOC is found to be present as humic colloids. The Am3+ ions introduced in such a groundwater readily undergo the generation of its pseudocolloids through sorption or ion exchange reactions with humic colloids. The chemical behaviour of Am(III), being similar to the trivalent metal ions, e.g. Fe3+, REE etc. found in natural colloids, has been investigated by laser induced photoacoustic spectroscopy (LPAS). Groundwaters from Ispra, Markham Clinton and Felslabor Grimsel. Bidistilled water and one of Gorleben groundwaters, Gohy 1011, are taken for the purpose of comparison. This groundwater contains the least amount of natural colloids of all Gorleben groundwaters hitherto investigated. An indirect quantification is made by comparison of the LPAS results with experiment from Latex solution. (orig./IRB)

  12. Colloid migration in porous media

    International Nuclear Information System (INIS)

    Retention of radionuclides for long periods near waste repositories depends upon multiple barriers, one of which is adsorption to immobile solid surfaces. Since small particles and colloidal matter have high adsorption capacities per unit mass and can be mobile in subsurface flows, colloidal transport of waste components requires analysis. Theories for predicting colloid migration through porous media have been developed in the filtration literature. The applicability of filtration theories for predicting particle and colloid transport. Emphasis is on suspended matter much smaller than pore sizes, where physical and chemical forces control migration rather than size dependent physical straining. In general, experimentally verifiable theories exist for particle filtration by clean media, and a sensitivity analysis is possible on particle and media properties and fluid flow rate. When particle aggregates accumulate within pores, media permeability decreases, resulting in flow field alteration and possible radionuclide isolation. An analysis of the limited experimental data available indicates that present theories cannot predict long-term colloid transport when permeability reduction occurs. The coupling of colloid attachment processes and the hydrologic flow processes requires more extensive laboratory field research than has currently been carried out. An emphasis on the fundamental mechanisms is necessary to enhance long-term predictability

  13. STAR-POLYMER -- COLLOID MIXTURES

    Directory of Open Access Journals (Sweden)

    J.Dzubiella

    2002-01-01

    Full Text Available Recent results in theory and simulation of star-polymer--colloid mixtures are reviewed. We present the effective interaction between hard, colloidal particles and star polymers in a good solvent derived by monomer-resolved Molecular Dynamics simulations and theoretical arguments. The relevant parameters are the size ratio q between the stars and the colloids, as well as the number of polymeric arms f (functionality attached to the common center of the star. By covering a wide range of q's ranging from zero (star against a flat wall up to about 0.5, we establish analytical forms for the star-colloid interaction which are in excellent agreement with simulation results. By employing this cross interaction and the effective interactions between stars and colloids themselves, a demixing transition in the fluid phase is observed and systematically investigated for different arm numbers and size ratios. The demixing binodals are compared with experimental observations and found to be consistent. Furthermore, we map the full two-component system on an effective one-component description for the colloids, by inverting the two-component Ornstein-Zernike equations. Some recent results for the depletion interaction and freezing transitions are shown.

  14. Mixed hemimicelles solid-phase extraction based on sodium dodecyl sulfate (SDS)-coated nano-magnets for the spectrophotometric determination of Fingolomid in biological fluids

    Science.gov (United States)

    Azari, Zhila; Pourbasheer, Eslam; Beheshti, Abolghasem

    2016-01-01

    In this study, mixed hemimicelles solid-phase extraction (SPE) based on sodium dodecyl sulfate (SDS)-coated nano-magnets Fe3O4 was investigated as a novel method for the separation and determination of Fingolimod (FLM) in water, urine and plasma samples prior to spectrophotometeric determination. Due to the high surface area of these new sorbents and the excellent adsorption capacity after surface modification by SDS, satisfactory extraction recoveries can be produced. The main factors affecting the adsolubilization of analysts, such as pH, surfactant and adsorbent amounts, ionic strength, extraction time and desorption conditions were studied and optimized. Under the selected conditions, FLM has been quantitatively extracted. The accuracy of the method was evaluated by recovery measurements on spiked samples, and good recoveries of 96%, 95% and 88% were observed for water, urine and plasma respectively. Proper linear behaviors over the investigated concentration ranges of 2-26, 2-17 and 2-13 mg/L with good coefficients of determination, 0.998, 0.997 and 0.995 were achieved for water, urine and plasma samples, respectively. To the best of our knowledge, this is the first time that a mixed hemimicelles SPE method based on magnetic separation and nanoparticles has been used as a simple and sensitive method for monitoring of FLM in water and biological samples.

  15. Electron Transfer Between Colloidal ZnO Nanocrystals

    OpenAIRE

    Hayoun, Rebecca; Whitaker, Kelly M.; Gamelin, Daniel R.; Mayer, James M.

    2011-01-01

    Colloidal ZnO nanocrystals, capped with dodecylamine and dissolved in toluene, can be charged photochemically to give stable solutions in which electrons are present in the conduction bands of the nanocrystals. These conduction band electrons are readily monitored by EPR spectroscopy, with g* values that correlate with the nanocrystal sizes. Mixing a solution of charged small nanocrystals with a solution of uncharged large nanocrystals, e-CB:ZnO–S + ZnO–L, causes changes in the EPR spectrum i...

  16. Cellular solid behaviour of liquid crystal colloids. 2. Mechanical properties

    OpenAIRE

    Anderson, V.J.; Terentjev, E. M.

    2000-01-01

    This paper presents the results of a rheological study of thermotropic nematic colloids aggregated into cellular structures. Small sterically stabilised PMMA particles dispersed in a liquid crystal matrix densely pack on cell interfaces, but reversibly mix with the matrix when the system is heated above Tni. We obtain a remarkably high elastic modulus, G'~10^5 Pa, which is a nearly linear function of particle concentration. A characteristic yield stress is required to disrupt the continuity o...

  17. Charged colloids, polyelectrolytes and biomolecules viewed as strongly coupled Coulomb systems

    CERN Document Server

    Löwen, H; Likos, C N; Blaak, R; Dzubiella, J; Jusufi, A; Hoffmann, N; Harreis, H M

    2003-01-01

    A brief review is given on recent studies of charged soft matter solutions, as modelled by the 'primitive' approach of strongly coupled Coulomb systems, where the solvent just enters as a dielectric background. These include charged colloids, biological macromolecules such as proteins and DNA, polyelectrolytes and polyelectrolyte stars. Also some original results are presented on colloid-polyelectrolyte complex formation near walls and on the anomalous fluid structure of polyelectrolyte stars as a function of increasing concentration.

  18. Charged colloids, polyelectrolytes and biomolecules viewed as strongly coupled Coulomb systems

    International Nuclear Information System (INIS)

    A brief review is given on recent studies of charged soft matter solutions, as modelled by the 'primitive' approach of strongly coupled Coulomb systems, where the solvent just enters as a dielectric background. These include charged colloids, biological macromolecules such as proteins and DNA, polyelectrolytes and polyelectrolyte stars. Also some original results are presented on colloid-polyelectrolyte complex formation near walls and on the anomalous fluid structure of polyelectrolyte stars as a function of increasing concentration

  19. Colloidal gold--low density lipoprotein conjugates as membrane receptor probes.

    OpenAIRE

    Handley, D. A.; Arbeeny, C M; Witte, L D; Chien, S

    1981-01-01

    We have developed a method for conjugating low density lipoproteins (LDL) with colloidal gold. Conjugation, complete after 1 min, occurs by electrostatic adsorption of the LDL to the negatively charged gold particle. Each conjugate consists of approximately eight biologically active LDL molecules clustered around a central 19-nm gold granule. Acidic (pH 4), alkaline (pH 9), or high ionic (600 milliosmolar NaCl) environments do not dissociate the conjugate. Colloidal gold is an electron-dense,...

  20. Dielectrophoresis force of colloidal nanoparticles

    Science.gov (United States)

    Huang, Hao; Ou-Yang, Daniel

    Dielectrophoresis (DEP) is the motion of a polarizable colloidal particle in a non­uniform electric field. The magnitude of the DEP force is known to be proportional to the gradient of E2. The DEP force also depends on the relative polarizability of the particle to that of the surrounding medium. Due to its ease of use, DEP has been proposed for a variety of applications to manipulate colloidal particles in a microfluidic setting. However, accurate measurements of the DEP force on colloidal nanoparticles are lacking. A new method is proposed to measure accurately the DEP potential force of colloidal nanoparticles by using confocal fluorescence imaging to determine the density distributions of dilute colloidal nanoparticle in a DEP potential force field. The DEP potential field can be calculated from the particle density distributions since the spatial distribution of the particle number density follows the Boltzmann distribution of the DEP potential energy. The validity of the measured DEP force is tested by examining the force as a function of the E field strength and particle size. The classic Maxwell­Wagner­O'Konski is found to be inadequate to fully describe the frequency dependence of the DEP force. NSF 0928299, Emulsion Polymer Institute, Department of Physics of Lehigh University.

  1. Colloidal Plasmonic Titanium Nitride Nanoparticles: Properties and Applications

    CERN Document Server

    Guler, Urcan; Kildishev, Alexander V; Boltasseva, Alexandra; Shalaev, Vladimir M

    2014-01-01

    Optical properties of colloidal plasmonic titanium nitride nanoparticles are examined with an eye on their photothermal via transmission electron microscopy and optical transmittance measurements. Single crystal titanium nitride cubic nanoparticles with an average size of 50 nm exhibit plasmon resonance in the biological transparency window. With dimensions optimized for efficient cellular uptake, the nanoparticles demonstrate a high photothermal conversion efficiency. A self-passivating native oxide at the surface of the nanoparticles provides an additional degree of freedom for surface functionalization.

  2. Polymeric stabilization of colloidal asphaltenes

    Science.gov (United States)

    Hashmi, Sara; Firoozabadi, Abbas

    2010-03-01

    Asphaltenes, the heaviest component of crude oil, cause many problems in petroleum extraction and recovery. Operationally defined as insoluble in long chain alkanes but soluble in toluene, asphaltenes have been described by bulk thermodynamic models such as the Flory-Huggins theory. However, bulk models work well only for asphaltenes in good solvents. Characterization of asphaltenes in poor solvents remains elusive: molecular scale asphaltenes readily aggregate to the colloidal scale and become highly unstable in solution. We investigate the ability of polymers to stabilize colloidal asphaltene suspensions in heptane. In the absence of added polymer, sedimentation measurements reveal dynamics reminiscent of collapsing gels. Adding polymers to colloidal asphaltene suspensions can delay the characteristic sedimentation time by orders of magnitude. Light scattering results suggest that the mechanism of stabilization may be related to a decrease in both particle size and polydispersity as a function of added polymer.

  3. Entropy favours open colloidal lattices

    Science.gov (United States)

    Mao, Xiaoming; Chen, Qian; Granick, Steve

    2013-03-01

    Burgeoning experimental and simulation activity seeks to understand the existence of self-assembled colloidal structures that are not close-packed. Here we describe an analytical theory based on lattice dynamics and supported by experiments that reveals the fundamental role entropy can play in stabilizing open lattices. The entropy we consider is associated with the rotational and vibrational modes unique to colloids interacting through extended attractive patches. The theory makes predictions of the implied temperature, pressure and patch-size dependence of the phase diagram of open and close-packed structures. More generally, it provides guidance for the conditions at which targeted patchy colloidal assemblies in two and three dimensions are stable, thus overcoming the difficulty in exploring by experiment or simulation the full range of conceivable parameters.

  4. Dose calculation in biological samples in a mixed neutron-gamma field at the TRIGA reactor of the Univ. of Mainz

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, Tobias; Schuetz, Christian (Inst. for Nuclear Chemistry, Univ. of Mainz, Mainz (Germany)), E-mail: sctoschm@students.uni-mainz.de; Blaickner, Matthias (AIT Austrian Inst. of Technology GmbH, 2444 Seibersdorf (Austria)) (and others)

    2010-10-15

    To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the Univ. of Mainz (Germany), it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative biological effectiveness (RBE) of liver and cancer cells in our mixed neutron and gamma field. We work with alanine detectors in combination with Monte Carlo simulations, where we can measure and characterize the dose. To verify our calculations we perform neutron flux measurements using gold foil activation and pin-diodes. Material and methods. When L-a-alanine is irradiated with ionizing radiation, it forms a stable radical which can be detected by electron spin resonance (ESR) spectroscopy. The value of the ESR signal correlates to the amount of absorbed dose. The dose for each pellet is calculated using FLUKA, a multipurpose Monte Carlo transport code. The pin-diode is augmented by a lithium fluoride foil. This foil converts the neutrons into alpha and tritium particles which are products of the 7Li(n,a)3H-reaction. These particles are detected by the diode and their amount correlates to the neutron fluence directly. Results and discussion. Gold foil activation and the pin-diode are reliable fluence measurement systems for the TRIGA reactor, Mainz. Alanine dosimetry of the photon field and charged particle field from secondary reactions can in principle be carried out in combination with MC-calculations for mixed radiation fields and the Hansen and Olsen alanine detector response model. With the acquired data about the background dose and charged particle spectrum, and with the acquired information of the neutron flux, we are capable of calculating the dose to the tissue. Conclusion. Monte Carlo simulation of the mixed neutron and gamma field of the TRIGA Mainz is possible in order to characterize the neutron behavior in the thermal column. Currently we also speculate on

  5. Dose calculation in biological samples in a mixed neutron-gamma field at the TRIGA reactor of the University of Mainz.

    Science.gov (United States)

    Schmitz, Tobias; Blaickner, Matthias; Schütz, Christian; Wiehl, Norbert; Kratz, Jens V; Bassler, Niels; Holzscheiter, Michael H; Palmans, Hugo; Sharpe, Peter; Otto, Gerd; Hampel, Gabriele

    2010-10-01

    To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the University of Mainz, Germany, it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative biological effectiveness (RBE) of liver and cancer cells in our mixed neutron and gamma field. We work with alanine detectors in combination with Monte Carlo simulations, where we can measure and characterize the dose. To verify our calculations we perform neutron flux measurements using gold foil activation and pin-diodes. Material and methods. When L-α-alanine is irradiated with ionizing radiation, it forms a stable radical which can be detected by electron spin resonance (ESR) spectroscopy. The value of the ESR signal correlates to the amount of absorbed dose. The dose for each pellet is calculated using FLUKA, a multipurpose Monte Carlo transport code. The pin-diode is augmented by a lithium fluoride foil. This foil converts the neutrons into alpha and tritium particles which are products of the (7)Li(n,α)(3)H-reaction. These particles are detected by the diode and their amount correlates to the neutron fluence directly. Results and discussion. Gold foil activation and the pin-diode are reliable fluence measurement systems for the TRIGA reactor, Mainz. Alanine dosimetry of the photon field and charged particle field from secondary reactions can in principle be carried out in combination with MC-calculations for mixed radiation fields and the Hansen & Olsen alanine detector response model. With the acquired data about the background dose and charged particle spectrum, and with the acquired information of the neutron flux, we are capable of calculating the dose to the tissue. Conclusion. Monte Carlo simulation of the mixed neutron and gamma field of the TRIGA Mainz is possible in order to characterize the neutron behavior in the thermal column. Currently we also

  6. Dose calculation in biological samples in a mixed neutron-gamma field at the TRIGA reactor of the Univ. of Mainz

    International Nuclear Information System (INIS)

    To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the Univ. of Mainz (DE), it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative biological effectiveness (RBE) of liver and cancer cells in our mixed neutron and gamma field. We work with alanine detectors in combination with Monte Carlo simulations, where we can measure and characterize the dose. To verify our calculations we perform neutron flux measurements using gold foil activation and pin-diodes. Material and methods. When L-a-alanine is irradiated with ionizing radiation, it forms a stable radical which can be detected by electron spin resonance (ESR) spectroscopy. The value of the ESR signal correlates to the amount of absorbed dose. The dose for each pellet is calculated using FLUKA, a multipurpose Monte Carlo transport code. The pin-diode is augmented by a lithium fluoride foil. This foil converts the neutrons into alpha and tritium particles which are products of the 7Li(n,a)3H-reaction. These particles are detected by the diode and their amount correlates to the neutron fluence directly. Results and discussion. Gold foil activation and the pin-diode are reliable fluence measurement systems for the TRIGA reactor, Mainz. Alanine dosimetry of the photon field and charged particle field from secondary reactions can in principle be carried out in combination with MC-calculations for mixed radiation fields and the Hansen and Olsen alanine detector response model. With the acquired data about the background dose and charged particle spectrum, and with the acquired information of the neutron flux, we are capable of calculating the dose to the tissue. Conclusion. Monte Carlo simulation of the mixed neutron and gamma field of the TRIGA Mainz is possible in order to characterize the neutron behavior in the thermal column. Currently we also speculate on

  7. Gelatin-stabilized polyaniline-silver colloids

    Czech Academy of Sciences Publication Activity Database

    Bober, Patrycja; Humpolíček, P.; Stejskal, Jaroslav

    Bordeaux: European Colloid and Interface Society, 2015. P11-26. [Conference of the European Colloid and Interface Society /29./ - ECIS 2015. 06.09.2015-11.09.2015, Bordeaux] R&D Projects: GA ČR(CZ) GP14-05568P Institutional support: RVO:61389013 Keywords : polyaniline * colloid * silver nanoparticles Subject RIV: JI - Composite Materials

  8. Self-assembly mechanism in colloids: perspectives from statistical physics

    Science.gov (United States)

    Giacometti, Achille

    2012-06-01

    Motivated by recent experimental findings in chemical synthesis of colloidal particles, we draw an analogy between self-assembly processes occurring in biological systems (e.g. protein folding) and a new exciting possibility in the field of material science. We consider a self-assembly process whose elementary building blocks are decorated patchy colloids of various types, that spontaneously drive the system toward a unique and predetermined targeted macroscopic structure. To this aim, we discuss a simple theoretical model — the Kern-Frenkel model — describing a fluid of colloidal spherical particles with a pre-defined number and distribution of solvophobic and solvophilic regions on their surface. The solvophobic and solvophilic regions are described via a short-range square-well and a hard-sphere potentials, respectively. Integral equation and perturbation theories are presented to discuss structural and thermodynamical properties, with particular emphasis on the computation of the fluid-fluid (or gas-liquid) transition in the temperaturedensity plane. The model allows the description of both one and two attractive caps, as a function of the fraction of covered attractive surface, thus interpolating between a square-well and a hard-sphere fluid, upon changing the coverage. By comparison with Monte Carlo simulations, we assess the pros and the cons of both integral equation and perturbation theories in the present context of patchy colloids, where the computational effort for numerical simulations is rather demanding.

  9. Colloid properties in groundwaters from crystalline formations

    International Nuclear Information System (INIS)

    Colloids are present in all groundwaters. The role they may play in the migration of safety-relevant radionuclides in the geosphere therefore must be studied. Colloid sampling and characterisation campaigns have been carried out in Switzerland. On the bases of the results from studies in the Grimsel area, Northern Switzerland and the Black Forest, as well as those obtained by other groups concerned with crystalline waters, a consistent picture is emerging. The groundwater colloids in crystalline formations are predominantly comprised of phyllosilicates and silica originating from the aquifer rock. Under constant hydrogeochemical conditions, the colloid concentration is not expected to exceed 100 ng.ml-1 when the calcium concentration is greater than 10-4. However, under transient chemical or physical conditions, such as geothermal or tectonic activity, colloid generation may be enhanced and the colloid concentration may reach 10 μg.ml-1 or more, if both the calcium and sodium concentrations are low. In the Nagra Crystalline Reference Water the expected colloid concentration is -1. This can be compared, for example, to a colloid concentration of about 10 ng.ml-1 found in Zurzach water. The small colloid concentration in the reference water is a consequence of an attachment factor for clay colloids (monmorillonite) close to 1. A model indicates that at pH 8, the nuclide partition coefficients between water and colloid (Kp) must be smaller than 107 ml.g-1 if sorption takes place by surface complexation on colloids, = AIOH active groups forming the dominant sorption sites. This pragmatic model is based on the competition between the formation of nuclide hydroxo complexes in solution and their sorption on colloids. Experimental nuclide sorption data on colloids are compared with those obtained by applying this model. For a low colloid concentration, a sorption capacity of the order of 10-9 M and reversible surface complexation, their presence in the crystalline rock

  10. Microbial effects on colloidal agglomeration

    International Nuclear Information System (INIS)

    Colloidal particles are known to enhance the transport of radioactive metals through soil and rock systems. This study was performed to determine if a soil microorganism, isolated from the surface samples collected at Yucca Mountain, NV, could affect the colloidal properties of day particles. The agglomeration of a Wyoming bentonite clay in a sterile uninoculated microbial growth medium was compared to the agglomeration in the medium inoculated with a Pseudomonas sp. In a second experiment, microorganisms were cultured in the succinate medium for 50 h and removed by centrifugation. The agglomeration of the clay in this spent was compared to sterile uninoculated medium. In both experiments, the agglomeration of the clay was greater than that of the sterile, uninoculated control. Based on these results, which indicate that this microorganism enhanced the agglomeration of the bentonite clay, it is possible to say that in the presence of microorganisms colloidal movement through a rock matrix could be reduced because of an overall increase in the size of colloidal particle agglomerates. 32 refs

  11. Microbial effects on colloidal agglomeration

    Energy Technology Data Exchange (ETDEWEB)

    Hersman, L.

    1995-11-01

    Colloidal particles are known to enhance the transport of radioactive metals through soil and rock systems. This study was performed to determine if a soil microorganism, isolated from the surface samples collected at Yucca Mountain, NV, could affect the colloidal properties of day particles. The agglomeration of a Wyoming bentonite clay in a sterile uninoculated microbial growth medium was compared to the agglomeration in the medium inoculated with a Pseudomonas sp. In a second experiment, microorganisms were cultured in the succinate medium for 50 h and removed by centrifugation. The agglomeration of the clay in this spent was compared to sterile uninoculated medium. In both experiments, the agglomeration of the clay was greater than that of the sterile, uninoculated control. Based on these results, which indicate that this microorganism enhanced the agglomeration of the bentonite clay, it is possible to say that in the presence of microorganisms colloidal movement through a rock matrix could be reduced because of an overall increase in the size of colloidal particle agglomerates. 32 refs.

  12. Proteolytic stability in colloidal systems.

    NARCIS (Netherlands)

    Maste, M.C.L.

    1996-01-01

    Proteolytic enzymes in liquid detergents suffer from lack of stability in the sense that activity diminishes with time. Although the phenomenon could be attributed to several factors, the influence of colloidal surfaces on the enzymatic stability was investigated. Besides the types of surfaces that

  13. A short textbook of colloid chemistry

    CERN Document Server

    Jirgensons, B

    1962-01-01

    A Short Textbook of Colloid Chemistry, Second Revised Edition details the factual aspect of colloid chemistry that includes the basic facts, established empirical and mathematical relationships, and practical applications. The chapters of the title are organized into two parts. In the first part, the text discusses the general concepts of colloid chemistry, such as the history and scope, basic terms, and basic methods in experiment with colloids. Part Two covers the technical aspect of colloid chemistry, such as the optical properties, electrical properties, and viscosity. The book will be of

  14. Distorted colloidal arrays as designed template

    Science.gov (United States)

    Yu, Ye; Zhou, Ziwei; Möhwald, Helmuth; Ai, Bin; Zhao, Zhiyuan; Ye, Shunsheng; Zhang, Gang

    2015-01-01

    In this paper, a novel type of colloidal template with broken symmetry was generated using commercial, inductively coupled plasma reactive ion etching (ICP-RIE). With proper but simple treatment, the traditional symmetric non-close-packed colloidal template evolves into an elliptical profile with high uniformity. This unique feature can add flexibility to colloidal lithography and/or other lithography techniques using colloidal particles as building blocks to fabricate nano-/micro-structures with broken symmetry. Beyond that the novel colloidal template we developed possesses on-site tunability, i.e. the transformability from a symmetric into an asymmetric template. Sandwich-type particles with eccentric features were fabricated utilizing this tunable template. This distinguishing feature will provide the possibility to fabricate structures with unique asymmetric features using one set of colloidal template, providing flexibility and broad tunability to enable nano-/micro-structure fabrication with colloidal templates.

  15. Distorted colloidal arrays as designed template

    International Nuclear Information System (INIS)

    In this paper, a novel type of colloidal template with broken symmetry was generated using commercial, inductively coupled plasma reactive ion etching (ICP-RIE). With proper but simple treatment, the traditional symmetric non-close-packed colloidal template evolves into an elliptical profile with high uniformity. This unique feature can add flexibility to colloidal lithography and/or other lithography techniques using colloidal particles as building blocks to fabricate nano-/micro-structures with broken symmetry. Beyond that the novel colloidal template we developed possesses on-site tunability, i.e. the transformability from a symmetric into an asymmetric template. Sandwich-type particles with eccentric features were fabricated utilizing this tunable template. This distinguishing feature will provide the possibility to fabricate structures with unique asymmetric features using one set of colloidal template, providing flexibility and broad tunability to enable nano-/micro-structure fabrication with colloidal templates. (paper)

  16. Phase behaviour of a dispersion of charge-stabilised colloidal spheres with added non-adsorbing interacting polymer chains.

    Science.gov (United States)

    Gögelein, C; Tuinier, R

    2008-10-01

    We present a theory for the phase behaviour of mixtures of charge-stabilised colloidal spheres plus interacting polymer chains in good and theta -solvents within the framework of free-volume theory. We use simple but accurate combination rules for the depletion thickness around a colloidal particle and for the osmotic pressure up to the semi-dilute concentration regime. Hence, we obtain expressions for the free energy for mixtures of charged colloidal particles and non-adsorbing interacting polymers. From that, we calculate the phase behaviour, and discuss its topology in dependence on the competition between the charge-induced repulsion and the polymer-induced attraction. The homogeneous mixture of colloids and polymers becomes more stabilised against demixing when increasing the electrostatic repulsion. This charge-induced stabilisation is strongest for small polymer-to-colloid size ratios and is more pronounced for charged colloids mixed with polymers in a good solvent than for polymers in a theta -solvent. For the weakly charged regime we find that the phase diagram becomes salt-concentration-independent in the protein limit for charged colloids plus polymers in a theta -solvent. The liquid window, i.e., the concentration regimes where a colloidal liquid exists, is narrowed down upon increasing the charge-induced repulsion. Also this effect is more pronounced when charged colloids are mixed with polymer chains in a good solvent. In summary, we demonstrate that the solvent quality significantly influences the phase behaviour of mixtures of charged colloids plus non-adsorbing polymers if the range of the screened electrostatic repulsion becomes of the order of the range of the depletion-induced attraction. PMID:18791755

  17. Colloidal Photoluminescent Amorphous Porous Silicon, Methods Of Making Colloidal Photoluminescent Amorphous Porous Silicon, And Methods Of Using Colloidal Photoluminescent Amorphous Porous Silicon

    KAUST Repository

    Chaieb, Sahraoui

    2015-04-09

    Embodiments of the present disclosure provide for a colloidal photoluminescent amorphous porous silicon particle suspension, methods of making a colloidal photoluminescent amorphous porous silicon particle suspension, methods of using a colloidal photoluminescent amorphous porous silicon particle suspension, and the like.

  18. Interactions in Natural Colloid Systems "Biosolids" - Soil and Plant

    Science.gov (United States)

    Kalinichenko, Kira V.; Nikovskaya, Galina N.; Ulberg, Zoya R.

    2016-04-01

    The "biosolids" are complex biocolloid system arising in huge amounts (mln tons per year) from biological municipal wastewater treatment. These contain clusters of nanoparticles of heavy metal compounds (in slightly soluble or unsoluble forms, such as phosphates, sulphates, carbonates, hydroxides, and etc.), cells, humic substances and so on, involved in exopolysaccharides (EPS) net matrix. One may consider that biosolids are the natural nanocomposite. Due to the presence of nitrogen, phosphorus, potassium and other macro- and microelements (heavy metals), vitamins, aminoacids, etc., the biosolids are a depot of bioelements for plant nutrition. Thus, it is generally recognized that most rationally to utilize them for land application. For this purpose the biocolloid process was developed in biosolids system by initiation of microbial vital ability followed by the synthesis of EPS, propagation of ecologically important microorganisms, loosening of the structure and weakening of the coagulation contacts between biosolids colloids, but the structure integrity maintaining [1,2]. It was demonstrated that the applying of biosolids with metabolizing microorganisms to soil provided the improving soil structure, namely the increasing of waterstable aggregates content (70% vs. 20%). It occurs due to flocculation ability of biosolids EPS. The experimental modelling of mutual interactions in systems of soils - biosolids (with metabolizing microorganisms) were realized and their colloid and chemical mechanisms were formulated [3]. As it is known, the most harmonious plant growth comes at a prolonged entering of nutrients under the action of plant roots exudates which include pool of organic acids and polysaccharides [4]. Special investigations showed that under the influence of exudates excreted by growing plants, the biosolids microelements can release gradually from immobilized state into environment and are able to absorb by plants. Thus, the biosolids can serve as an active

  19. Statistical Physics of Colloidal Dispersions.

    Science.gov (United States)

    Canessa, E.

    Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the equilibrium statistical mechanics of colloidal dispersions which represent useful model systems for the study of condensed matter physics; namely, charge stabilized colloidal dispersions and polymer stabilized colloidal dispersions. A one-component macroparticle approach is adopted in order to treat the macroscopic and microscopic properties of these systems in a simple and comprehensive manner. The thesis opens with the description of the nature of the colloidal state before reviewing some basic definitions and theory in Chapter II. In Chapter III a variational theory of phase equilibria based on the Gibbs-Bogolyobov inequality is applied to sterically stabilized colloidal dispersions. Hard spheres are chosen as the reference system for the disordered phases while an Einstein model is used for the ordered phases. The new choice of pair potential, taken for mathematical convenience, is a superposition of two Yukawa functions. By matching a double Yukawa potential to the van der Waals attractive potential at different temperatures and introducing a purely temperature dependent coefficient to the repulsive part, a rich variety of observed phase separation phenomena is qualitatively described. The behaviour of the potential is found to be consistent with a small decrease of the polymer layer thickness with increasing temperature. Using the same concept of a collapse transition the non-monotonic second virial coefficient is also explained and quantified. It is shown that a reduction of the effective macroparticle diameter with increasing temperature can only be partially examined from the point of view of a (binary-) polymer solution theory. This chapter concludes with the description of the observed, reversible, depletion flocculation behaviour. This is accomplished by using the variational formalism and by invoking the double Yukawa potential to allow

  20. What happens when pharmaceuticals meet colloids.

    Science.gov (United States)

    Xing, Yingna; Chen, Xijuan; Zhuang, Jie; Chen, Xin

    2015-12-01

    Pharmaceuticals (PCs) have been widely detected in natural environment due to agricultural application of reclaimed water, sludge and animal wastes. Their potential risks to various ecosystems and even to human health have caused great concern; however, little was known about their environmental behaviors. Colloids (such as clays, metal oxides, and particulate organics) are kind of substances that are active and widespread in the environment. When PCs meet colloids, their interaction may influence the fate, transport, and toxicity of PCs. This review summarizes the progress of studies on the role of colloids in mediating the environmental behaviors of PCs. Synthesized results showed that colloids can adsorb PCs mainly through ion exchange, complexation and non-electrostatic interactions. During this process the structure of colloids and the stability of PCs may be changed. The adsorbed PCs may have higher risks to induce antibiotic resistance; besides, their transport may also be altered considering they have great chance to move with colloids. Solution conditions (such as pH, ionic strength, and cations) could influence these interactions between PCs and colloids, as they can change the forms of PCs and alter the primary forces between PCs and colloids in the solution. It could be concluded that PCs in natural soils could bind with colloids and then co-transport during the processes of irrigation, leaching, and erosion. Therefore, colloid-PC interactions need to be understood for risk assessment of PCs and the best management practices of various ecosystems (such as agricultural and wetland systems). PMID:26427370

  1. Application of ESEM to environmental colloids

    International Nuclear Information System (INIS)

    Environmental colloids are toxic or radioactive particles suspended in ground or surface water. These hazardous particles can facilitate and accelerate the transport of toxicants and enhance the threat to humans by exposure to pathogenic substances. The chemical and physical properties of hazardous colloids have not been well characterized nor are there standard colloid remediation technologies to prevent their deleterious effects. Colloid characterization requires measurement of their size distribution, zeta potential, chemical composition, adsorption capacity and morphology. The environmental scanning electron microscope (ESEM) by ElectroScan, Inc., analyzes particle sizes, composition, and morphology. It is also used in this study to identify the attachment of colloids onto packing or rock surfaces in the development of a colloid remediation process. The ESEM has confirmed the composition of groundwater colloids in these studies to be generally the same material as the surrounding rock. The morphology studies have generally shown that colloids are simply small pieces of the rock surface that have exfoliated into the surrounding water. However, in general, the source and chemical composition of groundwater colloids is site dependent. The authors have found that an ESEM works best as a valuable analysis tool within a suite of colloid characterization instruments

  2. Analytic studies of colloid transport in fractured porous media

    International Nuclear Information System (INIS)

    We analyze the interactive migration of radioactive colloids and solute in fractured rock. Two possible interactions between radionuclides as colloids and as solute are considered: solute sorption on nonradioactive colloids to form pseudocolloids, and dissolution of radioactive colloids. Previous studies have discussed the formation and transport of colloids in porous media, including removal of colloids by filtration and sedimentation. Colloids can migrate faster than solute because of weaker sorption on stationary solids and because of hydrochromatography of colloid particles in flow channels. However, the migration of colloids and pseudocolloids can be retarded by the interaction of colloids with solute, and the migration of solute in local equilibrium with colloids can be more rapid than if colloids were not present. Here we present a new quantative analysis to predict the interactive migration of colloids and solute in porous and fractured media. 4 figs

  3. CTCN: Colloid transport code -- nuclear

    International Nuclear Information System (INIS)

    This report describes the CTCN computer code, designed to solve the equations of transient colloidal transport of radionuclides in porous and fractured media. This Fortran 77 package solves systems of coupled nonlinear differential-algebraic equations with a wide range of boundary conditions. The package uses the Method of Lines technique with a special section which forms finite-difference discretizations in up to four spatial dimensions to automatically convert the system into a set of ordinary differential equations. The CTCN code then solves these equations using a robust, efficient ODE solver. Thus CTCN can be used to solve population balance equations along with the usual transport equations to model colloid transport processes or as a general problem solver to treat up to four-dimensional differential-algebraic systems

  4. Colloidal stability by surface modification

    Science.gov (United States)

    Kuchibhatla, Satyanarayana Vnt; Karakoti, A. S.; Seal, Sudipta

    2005-12-01

    The study of colloids is important in the design of materials for uses ranging from pot making to petroleum refining. This review presents the reasons for instability and different methods for attaining stability in various systems of interest. in this context, both steric and electrostatic stabilization are discussed. Also discussed are surface modification in core-shell technology and the importance of surfactants in emulsions.

  5. Colloidal Synthesis of Gold Semishells

    OpenAIRE

    Rodríguez-Fernández, Denis; Rodríguez-Fernández, Denis; Pérez-Juste, Jorge; Pérez-Juste, Jorge; Pastoriza-Santos, Isabel; Liz-Marzán, Luis M.; Liz-Marzán, Luis M.

    2012-01-01

    This work describes a novel and scalable colloid chemistry strategy to fabricate gold semishells based on the selective growth of gold on Janus silica particles (500 nm in diameter) partly functionalized with amino groups. The modulation of the geometry of the Janus silica particles allows us to tune the final morphology of the gold semishells. This method also provides a route to fabricating hollow gold semishells through etching of the silica cores with hydrofluoric acid. The optical proper...

  6. Americium and plutonium association with magnesium hydroxide colloids in alkaline nuclear industry process environments

    Science.gov (United States)

    Maher, Zoe; Ivanov, Peter; O'Brien, Luke; Sims, Howard; Taylor, Robin J.; Heath, Sarah L.; Livens, Francis R.; Goddard, David; Kellet, Simon; Rand, Peter; Bryan, Nick D.

    2016-01-01

    The behaviours of Pu, Am and colloids in feed solutions to the Site Ion-exchange Effluent Plant (SIXEP) at the Sellafield nuclear reprocessing site in the U.K. have been studied. For both Pu and Am, fractions were found to be associated with material in the colloidal size range, with ˜50% of the Pu in the range 1-200 nm. The concentration of soluble Pu (brucite (magnesium hydroxide) colloids of different sizes was studied under alkaline conditions representative of nuclear fuel storage pond and effluent feed solution conditions. The morphology of the brucite particles in the bulk material observed by ESEM was predominantly hexagonal, while that of the carbonated brucite consisted of hexagonal species mixed with platelets. The association of 241Am(III) with the brucite colloids was studied by ultrafiltration coupled with gamma ray-spectrometry. For carbonate concentrations up to 10-3 M, the 241Am(III) was mainly associated with larger colloids (>300 kDa), and there was a shift from the smaller size fractions to the larger over a period of 6 months. At higher carbonate concentrations (10-2 M), the Am was predominantly detected in the true solution fraction (<3 kDa) and in smaller size colloidal fractions, in the range 3-100 kDa.

  7. Colloidal thermoresponsive gel forming hybrids.

    Science.gov (United States)

    Liu, Ruixue; Tirelli, Nicola; Cellesi, Francesco; Saunders, Brian R

    2010-09-15

    Colloidal hybrids comprise organic and inorganic components and are attracting considerable attention in the literature. Recently, we reported hybrid anisotropic microsheets that formed thermoresponsive gels in polymer solutions [Liu et al., Langmuir, 25, 490, 2009]. Here, we investigate the composition and properties of these hybrid colloids themselves in detail for the first time. Three different cationic PNIPAm (N-isopropylacrylamide) graft copolymers and two inorganic nanoparticle types (laponite and Ludox silica) were used to prepare a range of hybrids. Anisotropic microsheets only formed when laponite particles were added to the copolymer implying directed self-assembly. Aqueous dispersions of the microsheets spontaneously formed gels at room temperature and these gels were thermoresponsive. They represent a new class of gel forming colloid and are termed thermoresponsive gel forming hybrids. The compositions of the hybrids were determined from thermogravimetric analysis and those that gave gel forming behaviour identified. Variable-temperature rheology experiments showed that the elasticity of the gels increased linearly with temperature. The reversibility of the thermally-triggered changes in gel elasticity was investigated. The concentration dependence of the rheology data was well described by elastic percolation scaling theory and the data could be collapsed onto a master curve. The concentration exponent for the elastic modulus was 2.5. The strong attractive interactions that exist between the dispersed gel forming hybrids was demonstrated by the formation of stable thermoresponsive hybrid hydrogels through casting of hybrid dispersions. PMID:20561633

  8. Implant materials modified by colloids

    Directory of Open Access Journals (Sweden)

    Zboromirska-Wnukiewicz Beata

    2016-03-01

    Full Text Available Recent advances in general medicine led to the development of biomaterials. Implant material should be characterized by a high biocompatibility to the tissue and appropriate functionality, i.e. to have high mechanical and electrical strength and be stable in an electrolyte environment – these are the most important properties of bioceramic materials. Considerations of biomaterials design embrace also electrical properties occurring on the implant-body fluid interface and consequently the electrokinetic potential, which can be altered by modifying the surface of the implant. In this work, the surface of the implants was modified to decrease the risk of infection by using metal colloids. Nanocolloids were obtained using different chemical and electrical methods. It was found that the colloids obtained by physical and electrical methods are more stable than colloids obtained by chemical route. In this work the surface of modified corundum implants was investigated. The implant modified by nanosilver, obtained by electrical method was selected. The in vivo research on animals was carried out. Clinical observations showed that the implants with modified surface could be applied to wounds caused by atherosclerotic skeleton, for curing the chronic and bacterial inflammations as well as for skeletal reconstruction surgery.

  9. Janus Nematic Colloids with Designable Valence

    Directory of Open Access Journals (Sweden)

    Simon Čopar

    2014-05-01

    Full Text Available Generalized Janus nematic colloids based on various morphologies of particle surface patches imposing homeotropic and planar surface anchoring are demonstrated. By using mesoscopic numerical modeling, multiple types of Janus particles are explored, demonstrating a variety of novel complex colloidal structures. We also show binding of Janus particles to a fixed Janus post in the nematic cell, which acts as a seed and a micro-anchor for the colloidal structure. Janus colloidal structures reveal diverse topological defect configurations, which are effectively combinations of surface boojum and bulk defects. Topological analysis is applied to defects, importantly showing that topological charge is not a well determined topological invariant in such patchy nematic Janus colloids. Finally, this work demonstrates colloidal structures with designable valence, which could allow for targeted and valence-conditioned self-assembly at micro- and nano-scale.

  10. Binodal Colloidal Aggregation Test - 4: Polydispersion

    Science.gov (United States)

    Chaikin, Paul M.

    2008-01-01

    Binodal Colloidal Aggregation Test - 4: Polydispersion (BCAT-4-Poly) will use model hard-spheres to explore seeded colloidal crystal nucleation and the effects of polydispersity, providing insight into how nature brings order out of disorder. Crewmembers photograph samples of polymer and colloidal particles (tiny nanoscale spheres suspended in liquid) that model liquid/gas phase changes. Results will help scientists develop fundamental physics concepts previously cloaked by the effects of gravity.

  11. Nonequilibrium Forces between Dragged Ultrasoft Colloids

    OpenAIRE

    Singh, S.P.; Winkler, R. G.; Gompper, G.

    2011-01-01

    The dynamical deformation of ultrasoft colloids as well as their dynamic frictional forces are numerically investigated, when one colloid is dragged past another at constant velocity. Hydrodynamic interactions are captured by a particle-based mesoscopic simulation method. At vanishing relative velocity, the equilibrium repulsive force-distance curve is obtained. At large drag velocities, in contrast, we find an apparent attractive force for departing colloids along the dragging direction. The...

  12. Doped Colloidal ZnO Nanocrystals

    OpenAIRE

    Yizheng Jin; Yuping Ren; MoTao Cao; Zhizhen Ye

    2012-01-01

    Colloidal ZnO nanocrystals are promising for a wide range of applications due to the combination of unique multifunctional nature and remarkable solution processability. Doping is an effective approach of enhancing the properties of colloidal ZnO nanocrystals in well-controlled manners. In this paper, we analyzed two synthetic strategies for the doped colloidal ZnO nanocrystals, emphasizing our understanding on the critical factors associated with the high temperature and nonaqueous approach....

  13. Oppositely charged colloids out of equilibrium

    OpenAIRE

    Vissers, T.

    2010-01-01

    Colloids are particles with a size in the range of a few nanometers up to several micrometers. Similar to atomic and molecular systems, they can form gases, liquids, solids, gels and glasses. Colloids can be used as model systems because, unlike molecules, they are sufficiently large to be studied directly with light microscopy and move sufficiently slow to study their dynamics. In this thesis, we study binary systems of polymethylmethacrylate (PMMA) colloidal particles suspended in low-polar...

  14. Attractions between charged colloids at water interfaces

    OpenAIRE

    Oettel, M.; Dominguez, A; Dietrich, S.

    2005-01-01

    The effective potential between charged colloids trapped at water interfaces is analyzed. It consists of a repulsive electrostatic and an attractive capillary part which asymptotically both show dipole--like behavior. For sufficiently large colloid charges, the capillary attraction dominates at large separations. The total effective potential exhibits a minimum at intermediate separations if the Debye screening length of water and the colloid radius are of comparable size.

  15. Soret Motion of a Charged Spherical Colloid

    OpenAIRE

    Rasuli, Seyyed Nader; Golestanian, Ramin

    2007-01-01

    The thermophoretic motion of a charged spherical colloidal particle and its accompanying cloud of counterions and co-ions in a temperature gradient is studied theoretically. Using the Debye-Huckel approximation, the Soret drift velocity of a weakly charged colloid is calculated analytically. For highly charged colloids, the nonlinear system of electrokinetic equations is solved numerically, and the effects of high surface potential, dielectrophoresis, and convection are examined. Our results ...

  16. Dietary bioavailability of Cu adsorbed to colloidal hydrous ferric oxide

    Science.gov (United States)

    Cain, Daniel J.; Croteau, Marie-Noële; Fuller, Christopher C.

    2013-01-01

    The dietary bioavailability of copper (Cu) adsorbed to synthetic colloidal hydrous ferric oxide (HFO) was evaluated from the assimilation of 65Cu by two benthic grazers, a gastropod and a larval mayfly. HFO was synthesized, labeled with 65Cu to achieve a Cu/Fe ratio comparable to that determined in naturally formed HFO, and then aged. The labeled colloids were mixed with a food source (the diatom Nitzschia palea) to yield dietary 65Cu concentrations ranging from 211 to 2204 nmol/g (dry weight). Animals were pulse fed the contaminated diet and assimilation of 65Cu from HFO was determined following 1–3 days of depuration. Mass transfer of 65Cu from HFO to the diatom was less than 1%, indicating that HFO was the source of 65Cu to the grazers. Estimates of assimilation efficiency indicated that the majority of Cu ingested as HFO was assimilated (values >70%), implying that colloidal HFO potentially represents a source of dietary Cu to benthic grazers, especially where there is active formation and infiltration of these particles into benthic substrates.

  17. Convection of colloidal suspensions stratified by thermodiffusion and gravity.

    Science.gov (United States)

    Smorodin, B L; Cherepanov, I N

    2014-11-01

    The convective stability thresholds and nonlinear evolution of convective rolls are numerically investigated in a plane horizontal layer of a colloidal suspension with positive separation ratio in the case of no-slip, impermeable horizontal boundaries. The characteristics of the steady and oscillatory patterns are analyzed under heating and gravity stratification. The standing and traveling waves are found as stable solutions within certain domains of parameters (on the plane of the Rayleigh and the Boltzmann numbers). Complex bifurcation and spatiotemporal properties are caused by the interaction of gravity sedimentation, Soret-induced gradients, and convective mixing of the fluid. PMID:25416242

  18. Nonequilibrium forces between dragged ultrasoft colloids.

    Science.gov (United States)

    Singh, Sunil P; Winkler, Roland G; Gompper, Gerhard

    2011-10-01

    The dynamical deformation of ultrasoft colloids as well as their dynamic frictional forces are numerically investigated, when one colloid is dragged past another at constant velocity. Hydrodynamic interactions are captured by a particle-based mesoscopic simulation method. At vanishing relative velocity, the equilibrium repulsive force-distance curve is obtained. At large drag velocities, in contrast, we find an apparent attractive force for departing colloids along the dragging direction. The deformation, in the close encounter of colloids, and the energy dissipation are examined as a function of the drag velocity and their separation. PMID:22107322

  19. Dynamics of Electrically Modulated Colloidal Droplet Transport.

    Science.gov (United States)

    Dey, Ranabir; Ghosh, Udita Uday; Chakraborty, Suman; DasGupta, Sunando

    2015-10-20

    Electrically actuated transport dynamics of colloidal droplets, on a hydrophobic dielectric film covering an array of electrodes, is studied here. Specifically, the effects of the size and electrical properties (zeta-potential) of the colloidal particles on such transport characteristics are investigated. For the colloidal droplets, the application of an electrical voltage leads to additional attenuation of the local dielectric-droplet interfacial tension. This is due to the electrically triggered enhanced colloidal particle adsorption at the dielectric-droplet interface, in the immediate vicinity of the droplet three-phase contact line (TPCL). The extent of such interfacial particle adsorption, and hence, the extent of the consequential reduction in the interfacial tension, is dictated by the combined effects of the three-phase contact line spreading, particle size, the interfacial electrostatic interaction between the colloidal particles (if charged) and the charged dielectric surface above the activated electrode, and the interparticle electrostatic repulsion. The electrical driving force of varying magnitude, stemming from this altered solid-liquid interfacial tension gradient in the presence of the colloidal particles, culminates in different droplet transport velocity and droplet transfer frequency for different colloidal droplets. We substantiate the inferences from our experimental results by a quasi-steady state force balance model for colloidal droplet transport. We believe that the present work will provide an accurate framework for determining the optimal design and operational parameters for digital microfluidic chips handling colloidal droplets, as encountered in a plethora of applications. PMID:26422170

  20. Conductivity maximum in a charged colloidal suspension

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, S

    2009-01-27

    Molecular dynamics simulations of a charged colloidal suspension in the salt-free regime show that the system exhibits an electrical conductivity maximum as a function of colloid charge. We attribute this behavior to two main competing effects: colloid effective charge saturation due to counterion 'condensation' and diffusion slowdown due to the relaxation effect. In agreement with previous observations, we also find that the effective transported charge is larger than the one determined by the Stern layer and suggest that it corresponds to the boundary fluid layer at the surface of the colloidal particles.

  1. Collective motion in populations of colloidal bots

    Science.gov (United States)

    Bartolo, Denis

    One of the origins of active matter physics was the idea that flocks, herds, swarms and shoals could be quantitatively described as emergent ordered phases in self-driven materials. From a somehow dual perspective, I will show how to engineer active materials our of colloidal flocks. I will show how to motorize colloidal particles capable of sensing the orientation of their neighbors and how to handle them in microfluidic chips. These populations of colloidal bots display a non-equilibrium transition toward collective motion. A special attention will be paid to the robustness of the resulting colloidal flocks with respect to geometrical frustration and to quenched disorder.

  2. Colloid Titration--A Rapid Method for the Determination of Charged Colloid.

    Science.gov (United States)

    Ueno, Keihei; Kina, Ken'yu

    1985-01-01

    "Colloid titration" is a volumetric method for determining charged polyelectrolytes in aqueous solutions. The principle of colloid titration, reagents used in the procedure, methods of endpoint detection, preparation of reagent solutions, general procedure used, results obtained, and pH profile of colloid titration are considered. (JN)

  3. Pharmacological study of radioactive-gold colloid transport by blood and by serous exudate

    International Nuclear Information System (INIS)

    After giving the essential physico-chemical properties of the colloids, the author considers the biological role of these substances and, in connection with their transport by the blood, their capture by elements of the reticula-endothelial system. A summary is given of present knowledge concerning the role of serous proteins in the transport of substances, particularly that of radio-active colloidal gold. The blood fractions which can take part in colloidal gold transport are the red blood corpuscles, the leukocytes and histiocytic elements as well as the plasma. The radioactive distribution in these various fractions is obtained by autoradiography of blood sediments. After showing the importance of the role of the plasma in radioactive particle transport, the author, describes the attempts made to detect a possible of colloidal gold 198 on the various serous proteins using various methods of separation. The ''in vitro'' and ''in vivo'' bonds between colloidal gold-198 particles and either the serous proteins or healthy specimens or the effusion liquids of pathological origin in man, or due to an experimental inflammation with carregenin in the rat, have been studied. The bonding appears to be effective because of the protective macromolecular layer formed by the gelatine. The different positions of the colloidal grains on the electrophoregram can only be explained by their different physico-chemical characteristics. Gold in the ionic form, on the other hand, is combined only with the albumen is the amount metal present does not exceed a certain value. (author)

  4. Analysis of colloid and tracer breakthrough curves

    Science.gov (United States)

    Grindrod, Peter; Edwards, Mark S.; Higgo, Jenny J. W.; Williams, Geoffrey M.

    1996-02-01

    We consider the dispersion and elution of colloids and dissolved nonsorbing tracers within saturated heterogeneous porous media. Since flow path geometry in natural systems is often ill-characterized macroscopic (mean) flow rates and dispersion tensors are utilized in order to account for the sub-model scale microscopic fluctuations in media structure (and the consequent hydrodynamic profile). Even for tracer migration and dispersal this issue is far from settled. Here we consider how colloid and tracer migration phenomena can be treated consistently. Theoretical calculations for model flow geometries yield two quantitative predictions for the transport of free (not yet captured) colloids with reference to a non-sorbing dissolved tracer within the same medium: the average migration velocity of the free colloids is higher than that of the tracer; and that the ratio of the equivalent hydrodynamic dispersion rates of colloids and tracer is dependent only upon properties of the colloids and the porous medium, it is independent of pathlengths and fluid flux, once length scales are large enough. The first of these is well known, since even in simple flow paths free colloids must stay more centre stream. The second, if validated suggests how solute and colloid dispersion may be dealt with consistently in macroscopic migration models. This is crucial since dispersion is usually ill-characterized and unaddressed by the experimental literature. In this paper we present evidence based upon an existing Drigg field injection test for the validity of these predictions. We show that starting from experimental data the fitted dispersion rates of both colloids and non-sorbing tracers increase with the measured elution rates (obeying slightly different rules for tracers and colloids); and that the ratio of colloid and nonsorbing tracer elution rates, and the ratio of colloid and nonsorbing tracer dispersion rates may be dependent upon properties of the colloids and the medium (not

  5. On the Equivalence of Trapped Colloids, Pinned Vortices, and Spin Ice

    Energy Technology Data Exchange (ETDEWEB)

    Nisoli, Cristiano [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-04-23

    We investigate the recently reported analogies between pinned vortices in nano-structured superconductors or colloids in optical traps, and spin ice materials. The frustration of the two models, one describing colloids and vortices, the other describing spin ice, differs essentially. However, their effective energetics is made identical by the contribution of an emergent field associated to a topological charge. This equivalence extends to the local low-energy dynamics of the ice manifold, yet breaks down in lattices of mixed coordination, because of topological charge transfer between sub-latices.

  6. Fabricating colloidal crystals and construction of ordered nanostructures

    Directory of Open Access Journals (Sweden)

    Sun Zhiqiang

    2006-01-01

    Full Text Available AbstractColloidal crystals of polymeric or inorganic microspheres are of extensive interest due to their potential applications in such as sensing, optics, photonic bandgap and surface patterning. The article highlights a set of approaches developed in our group, which are efficient to prepare colloidal crystals with ordered voids, patterned colloidal crystals on non-planar surfaces, heterogeneous colloidal crystals of different building blocks, colloidal crystals composed of non-spherical polyhedrons, and colloidal crystals of non-close-packed colloidal microspheres in particular. The use of these colloidal crystals as templates for different microstructures range from nanoscale to micron-scale is also summarized.

  7. Structured fluids polymers, colloids, surfactants

    CERN Document Server

    Witten, Thomas A

    2010-01-01

    Over the last thirty years, the study of liquids containing polymers, surfactants, or colloidal particles has developed from a loose assembly of facts into a coherent discipline with substantial predictive power. These liquids expand our conception of what condensed matter can do. Such structured-fluid phenomena dominate the physical environment within living cells. This book teaches how to think of these fluids from a unified point of view showing the far-reaching effects ofthermal fluctuations in producing forces and motions. Keeping mathematics to a minimum, the book seeks the simplest expl

  8. Frost Heave in Colloidal Soils

    KAUST Repository

    Peppin, Stephen

    2011-01-01

    We develop a mathematical model of frost heave in colloidal soils. The theory accountsfor heave and consolidation while not requiring a frozen fringe assumption. Two solidificationregimes occur: a compaction regime in which the soil consolidates to accommodate the ice lenses, and a heave regime during which liquid is sucked into the consolidated soil from an external reservoir, and the added volume causes the soil to heave. The ice fraction is found to vary inversely with thefreezing velocity V , while the rate of heave is independent of V , consistent with field and laboratoryobservations. © 2011 Society for Industrial and Applied Mathematics.

  9. Fluctuation interactions of colloidal particles

    International Nuclear Information System (INIS)

    For like-charged colloidal particles, two mechanisms of attraction between them survive when the interparticle distance is larger than the Debye screening length. One of them is the conventional van der Waals attraction and the second is the attraction mechanism mediated by thermal fluctuations of particle position. The latter is related to the effective variable mass (Euler mass) of the particles produced by the fluid motion. The strongest attraction potential (up to the value of the temperature T) corresponds to the case of uncharged particles and a relatively large Debye screening length. In this case, the third attraction mechanism is involved. It is mediated by thermal fluctuations of the fluid density.

  10. Organic and organo-mineral colloids in discontinuous permafrost zone

    Science.gov (United States)

    Pokrovsky, Oleg S.; Manasypov, Rinat M.; Loiko, Sergey V.; Shirokova, Liudmila S.

    2016-09-01

    On-going permafrost thaw in discontinuous permafrost regions produces significant amounts of small permafrost subsidence and depressions, while large lakes are likely to drain into streams and rivers. The intensification of permafrost thaw may alter the size distribution and chemical composition of organo-Fe-Al colloids in lakes and rivers. We used a continuum of surface water bodies, from permafrost subsidence, small depressions and thaw ponds to large lakes and rivers that drain the Western Siberia Lowland (WSL), to assess OC, major and the trace element size distribution between the 20-μm, 5-μm, 1.2-μm, 0.45-μm, 0.22-μm, 0.025-μm and 1-kDa (∼1.4 nm) size fractions. This approach allowed us to distinguish the organic and organo-ferric colloids that were responsible for the transport of trace elements in surface waters and address their evolution during possible physico-chemical and biological processes. Both conventionally dissolved (precipitation with Fe hydroxides in the presence of surface DOM at groundwater discharge sites within the riparian/hyporheic zones of rivers. Under a warming climate scenario, an increase in the thickness of the thawing depth will intensify the input of inorganic components from deep mineral horizons and possibly underground waters thus producing the enrichment of large lakes in Fe-rich colloids and particles. The speciation of divalent metal micronutrients (Cu, Ni, and Co) and toxic metals (Al, Cd, Pb, and U) that are complexed within DOM will most likely remain conservative. Overall, the WSL's surface water colloidal composition may shift from DOM-rich and DOM-Al-rich to Fe-rich, and the export of low-soluble trivalent and tetravalent hydrolysates from the soil to rivers will increase.

  11. Colloidal Plasmonic Titanium Nitride Nanoparticles: Properties and Applications

    DEFF Research Database (Denmark)

    Guler, Urcan; Suslov, Sergey; Kildishev, Alexander V.; Boltasseva, Alexandra; Shalaev, Vladimir M.

    2015-01-01

    Optical properties of colloidal plasmonic titanium nitride nanoparticles are examined with an eye on their photothermal and photocatalytic applications via transmission electron microscopy and optical transmittance measurements. Single crystal titanium nitride cubic nanoparticles with an average...... size of 50 nm, which was found to be the optimum size for cellular uptake with gold nanoparticles [1], exhibit plasmon resonance in the biological transparency window and demonstrate a high absorption efficiency. A self-passivating native oxide at the surface of the nanoparticles provides an additional...... degree of freedom for surface functionalization. The titanium oxide shell surrounding the plasmonic core can create new opportunities for photocatalytic applications....

  12. Oppositely charged colloids out of equilibrium

    NARCIS (Netherlands)

    Vissers, T.

    2010-01-01

    Colloids are particles with a size in the range of a few nanometers up to several micrometers. Similar to atomic and molecular systems, they can form gases, liquids, solids, gels and glasses. Colloids can be used as model systems because, unlike molecules, they are sufficiently large to be studied d

  13. Dynamics of colloidal crystals in shear flow

    NARCIS (Netherlands)

    Derks, D.; Wu, Y.L.; van Blaaderen, A.; Imhof, A.

    2009-01-01

    We investigate particle dynamics in nearly hard sphere colloidal crystals submitted to a steady shear flow. Both the fluctuations of single colloids and the collective motion of crystalline layers as a whole are studied by using a home-built counter rotating shear cell in combination with confocal m

  14. How do polydisperse repulsive colloids crystallize?

    Science.gov (United States)

    Botet, Robert; Cabane, Bernard; Goehring, Lucas; Li, Joaquim; Artzner, Franck

    2016-04-12

    A modified version of the Gibbs-ensemble Monte-Carlo method reveals how polydisperse charged colloidal particles can build complex colloidal crystals. It provides general rules that are applicable to this fractionated crystallization that stems from size segregation. It explains the spontaneous formation of complex crystals with very large unit-cells in suspensions of nanoparticles with a broad size distribution. PMID:26761364

  15. Size Control of (99m)Tc-tin Colloid Using PVP and Buffer Solution for Sentinel Lymph Node Detection.

    Science.gov (United States)

    Kim, Eun-Mi; Lim, Seok Tae; Sohn, Myung-Hee; Jeong, Hwan-Jeong

    2015-06-01

    Colloidal particle size is an important characteristic that allows mapping sentinel nodes in lymphoscintigraphy. This investigation aimed to introduce different ways of making a (99m)Tc-tin colloid with a size of tens of nanometers. All agents, tin fluoride, sodium fluoride, poloxamer-188, and polyvinylpyrrolidone (PVP), were mixed and labeled with (99m)Tc. Either phosphate or sodium bicarbonate buffers were used to adjust the pH levels. When the buffers were added, the size of the colloids increased. However, as the PVP continued to increase, the size of the colloids was controlled to within tens of nanometers. In all samples, phosphate buffer added PVP (30 mg) stabilized tin colloid ((99m)Tc-PPTC-30) and sodium bicarbonate solution added PVP (50 mg) stabilized tin colloid ((99m)Tc-BPTC-50) were chosen for in vitro and in vivo studies. (99m)Tc-BPTC-50 (PPTC-30 (>100 nm) mainly accumulated in the liver. When a rabbit was given a toe injection, the node uptake of (99m)Tc-PPTC-30 decreased over time, while (99m)Tc-BPTC-50 increased. Therefore, (99m)Tc-BPTC-50 could be a good candidate radiopharmaceutical for sentinel node detection. The significance of this study is that nano-sized tin colloid can be made very easily and quickly by PVP. PMID:26028937

  16. Colloid formation in groundwater by subsurface aeration: characterisation of the geo-colloids and their counterparts

    International Nuclear Information System (INIS)

    Subsurface aeration is used to oxidise Fe in situ in groundwater to make the water potable. In a groundwater system with pH > 7, subsurface aeration results in a non-mobile Fe precipitate and mobile Fe colloids. Since originally the goal of subsurface aeration is to remove Fe in situ, the formation of non-mobile Fe precipitate is the desired result. In addition to this intended effect, subsurface aeration may also strongly enhance the microbiological removal of NH4 in the purification station. A hypothesis is that mobile Fe colloids may be the link between subsurface aeration and the positive effect on the microbiological removal of NH4. The objective of this study is to characterise the mobile Fe colloids and to derive a synthetic substitute for the naturally formed Fe colloids in order to be able to apply the Fe colloids as a management tool to enhance the removal of NH4 in the process of producing drinking water from groundwater. At a purification station in The Netherlands natural Fe colloids from an aerated well were sampled. Furthermore, eight synthetic Fe colloids were prepared by oxidising synthetic solutions differing in elemental composition. The colloids were analysed using chemical analysis and electron microscopy (SEM and SEM-EDAX). The Fe colloids sampled in the field contained Fe, Ca, Na, PO4 and Mn. Also in the synthetic Fe colloids PO4, Ca, Na and Mn were the most important elements next to Fe. Phosphate and dissolved organic C strongly influenced the morphology of the synthetic Fe colloids. When both the elemental composition and the morphology of the Fe colloids are taken into account, the synthetic Fe colloids formed in the synthetic solution containing Fe, Mn, PO4, SiO4 and dissolved organic matter best match the Fe colloids from the field

  17. Stability of Ionic Colloidal Crystals (ICCs)

    Science.gov (United States)

    Maskaly, Garry R.; Garcia, R. Edwin; Carter, W. Craig; Chiang, Yet-Ming

    2003-03-01

    Ionic colloidal crystals (ICCs) are here defined as ordered multicomponent colloids formed by attractive electrostatic interactions. Compared to previous approaches to colloidal crystallization, the ICC approach holds the potential for self-assembly of a wide range of structures not easily accessible by other methods. In this work, the colloid-chemical conditions under which ICCs are stable have been theoretically analyzed. A model is presented in which two dimensionless parameters are found to fully characterize an ICC system. We calculate the Madelung constant for ICCs of several classical ionic crystal structures as a function of these two parameters, and discuss the parallels between the ICC Madelung constants and the classical ionic case. Experimentally accessible regions of surface charge, particle sizes, salt concentration, and temperature where ionic colloidal crystallization should be possible are identified.

  18. Shaping colloids for self-assembly

    Science.gov (United States)

    Sacanna, Stefano; Korpics, Mark; Rodriguez, Kelvin; Colón-Meléndez, Laura; Kim, Seung-Hyun; Pine, David J.; Yi, Gi-Ra

    2013-04-01

    The creation of a new material often starts from the design of its constituent building blocks at a smaller scale. From macromolecules to colloidal architectures, to granular systems, the interactions between basic units of matter can dictate the macroscopic behaviour of the resulting engineered material and even regulate its genesis. Information can be imparted to the building units by altering their physical and chemical properties. In particular, the shape of building blocks has a fundamental role at the colloidal scale, as it can govern the self-organization of particles into hierarchical structures and ultimately into the desired material. Herein we report a simple and general approach to generate an entire zoo of new anisotropic colloids. Our method is based on a controlled deformation of multiphase colloidal particles that can be selectively liquified, polymerized, dissolved and functionalized in bulk. We further demonstrate control over the particle functionalization and coating by realizing patchy and Janus colloids.

  19. Dynamics of the colloidal suspensions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hai-yan; MA Hong-ru

    2006-01-01

    This article offers a survey on our current knowledge of the dynamics of the colloidal suspension,where each particle experiences the friction force with solvent,hydrodynamic interaction,and potential force from surrounding particles and thermodynamic force.It further contains a summary of the basic concepts about microstructures and equilibrium properties,and of analytical and numerical methods,which are relevant for the theoretical description of the suspensions.The description of the dynamics of colloidal particles,based on the generalized Smoluchowski equation,is justified for the time scale accessible in DLS experiments.The combined influence of hard sphere or electrostatic potential and solvent-mediated hydrodynamic interaction on the short-time dynamics of monodisperse suspensions is investigated in detail.A thorough study of tracer-diffusion in hard sphere and charge-stabilized suspensions is presented.Mean-square displacements and long-time tracer-diffusion coefficients are calculated with two alternative approximations,i.e.,a mode-coupling scheme and a single relaxation time ansatz.

  20. Diffusion in active magnetic colloids

    International Nuclear Information System (INIS)

    Properties of active colloids of circle swimmers are reviewed. As a particular example of active magnetic colloids the magnetotactic bacteria under the action of a rotating magnetic field is considered. The relation for a diffusion coefficient due to the random switching of the direction of rotation of their rotary motors is derived on the basis of the master equation. The obtained relation is confirmed by the direct numerical simulation of random trajectory of a magnetotactic bacterium under the action of the Poisson type internal noise due to the random switching of rotary motors. The results obtained are in qualitative and quantitative agreement with the available experimental results and allow one to determine the characteristic time between the switching events of a rotary motor of the bacterium. - Highlights: • Magnetotactic bacteria in a rotating field behaves as circle swimmers. • Diffusion coefficient of these swimmers due to the random switching of rotary motors is calculated. • Results are in good qualitative and quantitative agreement with available experimental results

  1. Colloid-Associated Radionuclide Concentration Limits: ANL

    International Nuclear Information System (INIS)

    The purpose and scope of this report is to describe the analysis of available colloidal data from waste form corrosion tests at Argonne National Laboratory (ANL) to extract characteristics of these colloids that can be used in modeling their contribution to the source term for sparingly soluble radioelements (e.g., Pu). Specifically, the focus is on developing a useful description of the following waste form colloid characteristics: (1) composition, (2) size distribution, and (3) quantification of the rate of waste form colloid generation. The composition and size distribution information are intended to support analysis of the potential transport of the sparingly soluble radionuclides associated with the waste form colloids. The rate of colloid generation is intended to support analysis of the waste form colloid-associated radionuclide concentrations. In addressing the above characteristics, available data are interpreted to address mechanisms controlling colloid formation and stability. This report was developed in accordance with the ''Technical Work Plan for Waste Form Degradation Process Model Report for SR'' (CRWMS M and O 2000). Because the end objective is to support the source term modeling we have organized the conclusions into two categories: (1) data analysis conclusions and (2) recommendations for colloid source term modeling. The second category is included to facilitate use of the conclusions from the data analysis in the abstraction of a colloid source term model. The data analyses and conclusions that are presented in this report are based on small-scale laboratory tests conducted on a limited number of waste glass compositions and spent fuel types

  2. Diffusion of humic colloids in compacted bentonite

    International Nuclear Information System (INIS)

    In Sweden, as in many other countries, compacted bentonite will surround the encapsulated spent nuclear fuel in a deep bedrock repository. Bentonite gives mechanical support and minimizes the water flow over the deposition holes. The retardation for cationic radionuclides escaping a faulted canister is high in saturated compacted bentonite, since cationic radionuclides sorbs strongly on the bentonite surface, and the only plausible transport mechanism is diffusion. Sorption and diffusion of radionuclides in the bentonite barrier has been extensively studied, and sorption and diffusion coefficients are well established. There is a lack of knowledge as well as data for effects of colloids on radionuclide mobility and transport in the bentonite barrier. In a deep bedrock repository, colloids, particles in the size range of 1-1000 nm, will be present, however in very low concentrations. The colloids origin from eroded bedrock and filling material, mineral oxides, clay, degraded organic compounds and micro-organisms etc. The bentonite barrier is regarded to be an efficient filtering barrier for colloids. With the widely spread micro-structure with pores in between the montmorillonite flakes in the size range of nm, and the inter particle voids partly gel filled of sizes, colloid transport seems unlikely. In a Japanese diffusion study on gold colloids no breakthrough of the colloids was detected. However, to reject the possibility of enhancement of transport of radionuclides by colloids, more data from diffusion studies on other types of colloids in compacted bentonite are needed. Therefore diffusion experiments of Humic Colloids (HC), in the size range of 1-10 nm, were performed. (author)

  3. Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

    Institute of Scientific and Technical Information of China (English)

    M. Vinod; K.G.Gopchandran

    2014-01-01

    Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

  4. Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

    Directory of Open Access Journals (Sweden)

    M. Vinod

    2014-12-01

    Full Text Available Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

  5. Fluid-bicontinuous gels stabilized by interfacial colloids: low and high molecular weight fluids

    International Nuclear Information System (INIS)

    Carefully tuned composite materials can have properties wholly unlike those of their separate constituents. We review the development of one example: colloid-stabilized emulsions with bicontinuous liquid domains. These non-equilibrium structures resemble the sponge mesophase of surfactants; however, in the colloid-stabilized case the interface separating the liquid domains is itself semi-solid. The arrangement of domains is created by arresting liquid-liquid phase separation via spinodal decomposition. Dispersed colloids exhibiting partial wettability become trapped on the newly created interface and jam together as the domains coarsen. Similar structures have been created in polymer blends stabilized using either interfacial nanoparticles or clay platelets. Here it has been possible to create the domain arrangement either by phase separation or by direct mixing of the melt. The low molecular weight liquid and polymer based structures have been developed independently and much can be learnt by comparing the two. (topical review)

  6. Plutonium and Cesium Colloid Mediated Transport

    Science.gov (United States)

    Boukhalfa, H.; Dittrich, T.; Reimus, P. W.; Ware, D.; Erdmann, B.; Wasserman, N. L.; Abdel-Fattah, A. I.

    2013-12-01

    Plutonium and cesium have been released to the environment at many different locations worldwide and are present in spent fuel at significant levels. Accurate understanding of the mechanisms that control their fate and transport in the environment is important for the management of contaminated sites, for forensic applications, and for the development of robust repositories for the disposal of spent nuclear fuel and nuclear waste. Plutonium, which can be present in the environment in multiple oxidations states and various chemical forms including amorphous oxy(hydr)oxide phases, adsorbs/adheres very strongly to geological materials and is usually immobile in all its chemical forms. However, when associated with natural colloids, it has the potential to migrate significant distances from its point of release. Like plutonium, cesium is not very mobile and tends to remain adhered to geological materials near its release point, although its transport can be enhanced by natural colloids. However, the reactivity of plutonium and cesium are very different, so their colloid-mediated transport might be significantly different in subsurface environments. In this study, we performed controlled experiments in two identically-prepared columns; one dedicated to Pu and natural colloid transport experiments, and the other to Cs and colloid experiments. Multiple flow-through experiments were conducted in each column, with the effluent solutions being collected and re-injected into the same column two times to examine the persistence and scaling behavior of the natural colloids, Pu and Cs. The data show that that a significant fraction of colloids were retained in the first elution through each column, but the eluted colloids collected from the first run transported almost conservatively in subsequent runs. Plutonium transport tracked natural colloids in the first run but deviated from the transport of natural colloids in the second and third runs. Cesium transport tracked natural

  7. Spontaneous Formation of Eutectic Crystal Structures in Binary and Ternary Charged Colloids due to Depletion Attraction.

    Science.gov (United States)

    Toyotama, Akiko; Okuzono, Tohru; Yamanaka, Junpei

    2016-01-01

    Crystallization of colloids has extensively been studied for past few decades as models to study phase transition in general. Recently, complex crystal structures in multi-component colloids, including alloy and eutectic structures, have attracted considerable attention. However, the fabrication of 2D area-filling colloidal eutectics has not been reported till date. Here, we report formation of eutectic structures in binary and ternary aqueous colloids due to depletion attraction. We used charged particles + linear polyelectrolyte systems, in which the interparticle interaction could be represented as a sum of the electrostatic, depletion, and van der Waals forces. The interaction was tunable at a lengthscale accessible to direct observation by optical microscopy. The eutectic structures were formed because of interplay of crystallization of constituent components and accompanying fractionation. An observed binary phase diagram, defined by a mixing ratio and inverse area fraction of the particles, was analogous to that for atomic and molecular eutectic systems. This new method also allows the adjustment of both the number and wavelengths of Bragg diffraction peaks. Furthermore, these eutectic structures could be immobilized in polymer gel to produce self-standing materials. The present findings will be useful in the design of the optical properties of colloidal crystals. PMID:26984298

  8. Spontaneous Formation of Eutectic Crystal Structures in Binary and Ternary Charged Colloids due to Depletion Attraction

    Science.gov (United States)

    Toyotama, Akiko; Okuzono, Tohru; Yamanaka, Junpei

    2016-03-01

    Crystallization of colloids has extensively been studied for past few decades as models to study phase transition in general. Recently, complex crystal structures in multi-component colloids, including alloy and eutectic structures, have attracted considerable attention. However, the fabrication of 2D area-filling colloidal eutectics has not been reported till date. Here, we report formation of eutectic structures in binary and ternary aqueous colloids due to depletion attraction. We used charged particles + linear polyelectrolyte systems, in which the interparticle interaction could be represented as a sum of the electrostatic, depletion, and van der Waals forces. The interaction was tunable at a lengthscale accessible to direct observation by optical microscopy. The eutectic structures were formed because of interplay of crystallization of constituent components and accompanying fractionation. An observed binary phase diagram, defined by a mixing ratio and inverse area fraction of the particles, was analogous to that for atomic and molecular eutectic systems. This new method also allows the adjustment of both the number and wavelengths of Bragg diffraction peaks. Furthermore, these eutectic structures could be immobilized in polymer gel to produce self-standing materials. The present findings will be useful in the design of the optical properties of colloidal crystals.

  9. Preparation and Optical Properties of Spherical Inverse Opals by Liquid Phase Deposition Using Spherical Colloidal Crystals

    Science.gov (United States)

    Aoi, Y.; Tominaga, T.

    2013-03-01

    Titanium dioxide (TiO2) inverse opals in spherical shape were prepared by liquid phase deposition (LPD) using spherical colloidal crystals as templates. Spherical colloidal crystals were produced by ink-jet drying technique. Aqueous emulsion droplets that contain polystyrene latex particles were ejected into air and dried. Closely packed colloidal crystals with spherical shape were obtained. The obtained spherical colloidal crystals were used as templates for the LPD. The templates were dispersed in the deposition solution of the LPD, i.e. a mixed solution of ammonium hexafluorotitanate and boric acid and reacted for 4 h at 30 °C. After the LPD process, the interstitial spaces of the spherical colloidal crystals were completely filled with titanium oxide. Subsequent heat treatment resulted in removal of templates and spherical titanium dioxide inverse opals. The spherical shape of the template was retained. SEM observations indicated that the periodic ordered voids were surrounded by titanium dioxide. The optical reflectance spectra indicated that the optical properties of the spherical titanium dioxide inverse opals were due to Bragg diffractions from the ordered structure. Filling in the voids of the inverse opals with different solvents caused remarkable changes in the reflectance peak.

  10. Investigation of uranium-colloid interactions in soil by dual field-flow fractionation/capillary electrophoresis hyphenated with inductively coupled plasma-mass spectrometry

    International Nuclear Information System (INIS)

    This paper deals with the study of uranium-colloid interactions in a carbonated soil. The work is focused on the immediately available fraction obtained after a leaching process, according to a normalized batch method. In order to characterize the different colloidal carriers, Asymmetrical Flow Field-Flow Fractionation (As-FI-FFF) coupled to different detectors (UV, Multi Angle laser Light Scattering (MALLS) and Inductively coupled Plasma-Mass Spectrometry (ICP-MS)) was used. The colloidal carriers are mainly inorganic particles (carbonated particles and clays) mixed with organic substances. Furthermore, dissolved and colloidal uranium species in the leaching solutions were monitored by Capillary Electrophoresis (CE) coupled to ICP-MS, in order to investigate the uranium/colloids interactions. According to the first results, uranium fate in this specific soil is controlled by sorption/desorption phenomena, strongly pH dependent. (authors)

  11. Structural evolution of Colloidal Gels under Flow

    Science.gov (United States)

    Boromand, Arman; Maia, Joao; Jamali, Safa

    Colloidal suspensions are ubiquitous in different industrial applications ranging from cosmetic and food industries to soft robotics and aerospace. Owing to the fact that mechanical properties of colloidal gels are controlled by its microstructure and network topology, we trace the particles in the networks formed under different attraction potentials and try to find a universal behavior in yielding of colloidal gels. Many authors have implemented different simulation techniques such as molecular dynamics (MD) and Brownian dynamics (BD) to capture better picture during phase separation and yielding mechanism in colloidal system with short-ranged attractive force. However, BD neglects multi-body hydrodynamic interactions (HI) which are believed to be responsible for the second yielding of colloidal gels. We envision using dissipative particle dynamics (DPD) with modified depletion potential and hydrodynamic interactions, as a coarse-grain model, can provide a robust simulation package to address the gel formation process and yielding in short ranged-attractive colloidal systems. The behavior of colloidal gels with different attraction potentials under flow is examined and structural fingerprints of yielding in these systems will be discussed.

  12. Towards conducting inks: Polypyrrole–silver colloids

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Composite colloidal particles combining conducting polymer and metal have been prepared. • Conducting colloids are suitable for printing applications. • Polypyrrole/silver colloids are prepared in a single reaction step. • The conductivity control is discussed and still needs improvement. - Abstract: The oxidation of pyrrole with silver nitrate in the presence of suitable water-soluble polymers yields composite polypyrrole–silver colloids. The polypyrrole–silver nanoparticles stabilized with poly(N-vinylpyrrolidone) have a typical size around 350 nm and polydispersity index 0.20, i.e. a moderate polydispersity in size. Similar results have been obtained with poly(vinyl alcohol) as stabilizer. The effect of stabilizer concentration on the particle size is marginal. In the present study, several types of stabilizers have been tested in addition to currently used poly(N-vinylpyrrolidone). Transmission electron microscopy and optical microscopy revealed the gemini morphology of polypyrrole and silver colloidal nanoparticles and confirmed their size and size-distribution determined by dynamic light scattering. The use of colloidal dispersions provides an efficient tool for the UV–vis and FT Raman spectroscopic characterization of polypyrrole, including the transition between polypyrrole salt and corresponding polypyrrole base. The dispersions were used for the preparation of coatings on polyethylene terephthalate foils, and the properties for polypyrrole–silver composites have been compared with those produced from polypyrrole colloids alone

  13. Synthesis and Analytical Centrifugation of Magnetic Model Colloids

    NARCIS (Netherlands)

    Luigjes, B.

    2012-01-01

    This thesis is a study of the preparation and thermodynamic properties of magnetic colloids. First, two types of magnetic model colloids are investigated: composite colloids and single-domain nanoparticles. Thermodynamics of magnetic colloids is studied using analytical centrifugation, including a s

  14. Colloidal QDs-polymer nanocomposites

    Science.gov (United States)

    Gordillo, H.; Suárez, I.; Rodríguez-Cantó, P.; Abargues, R.; García-Calzada, R.; Chyrvony, V.; Albert, S.; Martínez-Pastor, J.

    2012-04-01

    Nanometer-size colloidal semiconductor nanocrystals, or Quantum Dots (NQD), are very prospective active centers because their light emission is highly efficient and temperature-independent. Nanocomposites based on the incorporation of QDs inside a polymer matrix are very promising materials for application in future photonic devices because they combine the properties of QDs with the technological feasibility of polymers. In the present work some basic applications of these new materials have been studied. Firstly, the fabrication of planar and linear waveguides based on the incorporation of CdS, CdSe and CdTe in PMMA and SU-8 are demonstrated. As a result, photoluminescence (PL) of the QDs are coupled to a waveguide mode, being it able to obtain multicolor waveguiding. Secondly, nanocomposite films have been evaluated as photon energy down-shifting converters to improve the efficiency of solar cells.

  15. Carbon Nanomaterials as Antibacterial Colloids

    Directory of Open Access Journals (Sweden)

    Michael Maas

    2016-07-01

    Full Text Available Carbon nanomaterials like graphene, carbon nanotubes, fullerenes and the various forms of diamond have attracted great attention for their vast potential regarding applications in electrical engineering and as biomaterials. The study of the antibacterial properties of carbon nanomaterials provides fundamental information on the possible toxicity and environmental impact of these materials. Furthermore, as a result of the increasing prevalence of resistant bacteria strains, the development of novel antibacterial materials is of great importance. This article reviews current research efforts on characterizing the antibacterial activity of carbon nanomaterials from the perspective of colloid and interface science. Building on these fundamental findings, recent functionalization strategies for enhancing the antibacterial effect of carbon nanomaterials are described. The review concludes with a comprehensive outlook that summarizes the most important discoveries and trends regarding antibacterial carbon nanomaterials.

  16. Measurement of Colloidal Gold-198 and Phosphorus-32 Present in the Same Sample

    International Nuclear Information System (INIS)

    Colloidal 198Au and 32P are normally used separately in therapeutics. In comparative metabolism studies, however, the two colloids are sometimes administered together and hence found in the same biological sample. The simultaneous determination of the activity of each of the radioisotopes then poses a problem which the authors have attempted to solve, using the Bremsstrahlung of the 32P, by the following two methods: (1) Measurement of the 198Au and 32P after establishing their respective electromagnetic spectral curves and selecting favourable peaks; (2) Simultaneous radioactivity measurements using a photomultiplier with two distinct amplitude discrimination thresholds which give different yields for the two emissions. Both methods are evaluated with the help of standards, their validity is discussed, and the limits of their applicability are specified. The second method was employed in studying the reciprocal effects of colloidal 198Au and 32P on in vitro sedimentation in an ascitic fluid. (author)

  17. Three-dimensional ultrasonic colloidal crystals

    Science.gov (United States)

    Caleap, Mihai; Drinkwater, Bruce W.

    2016-05-01

    Colloidal assembly represents a powerful method for the fabrication of functional materials. In this article, we describe how acoustic radiation forces can guide the assembly of colloidal particles into structures that serve as microscopic elements in novel acoustic metadevices or act as phononic crystals. Using a simple three-dimensional orthogonal system, we show that a diversity of colloidal structures with orthorhombic symmetry can be assembled with megahertz-frequency (MHz) standing pressure waves. These structures allow rapid tuning of acoustic properties and provide a new platform for dynamic metamaterial applications. xml:lang="fr"

  18. Colloid and interface chemistry for nanotechnology

    CERN Document Server

    Kralchevsky, Peter

    2013-01-01

    Colloid and interface science dealt with nanoscale objects for nearly a century before the term nanotechnology was coined. An interdisciplinary field, it bridges the macroscopic world and the small world of atoms and molecules. Colloid and Interface Chemistry for Nanotechnology is a collection of manuscripts reflecting the activities of research teams that have been involved in the networking project Colloid and Interface Chemistry for Nanotechnology (2006-2011), Action D43, the European Science Foundation. The project was a part of the intergovernmental framework for Cooperation in Science an

  19. Characterization of natural groundwater colloids at Palmottu

    International Nuclear Information System (INIS)

    Characterization of groundwater colloids (size range from 2 nm to 500 nm) in the Palmottu natural analogue (for radioactive waste disposal in Finland) area was continued by sampling another drill hole, 346, at three depths. Results evaluated so far indicate the presence of both organic and inorganic colloids. In terms of chemical composition and morphology, the inorganic colloids differ from those found in previous studies. According to SEM/EDS and STEM/EDS they mostly contain Ca and are spherical in shape. At this stage further characterization and evaluation of results is provisional and does not allow very accurate conclusions to be drawn

  20. Site-specific functionalization of anisotropic nanoparticles: from colloidal atoms to colloidal molecules

    DEFF Research Database (Denmark)

    Li, Fan; Yoo, Won Cheol; Beernink, Molly B; Stein, Andreas

    2009-01-01

    -specific tethers. Amorphous sol-gel materials were molded by the template into shaped NPs that mimic tetravalent atoms but on the length scale of colloids. Synthetic methods were developed to modify only the tips of the tetrapods with a range of possible functional groups to generate anisotropic NPs capable of......Multipodal nanoparticles (NPs) with controlled tethers are promising principal building blocks, useful for constructing more complex materials, much like atoms are connected into more complex molecules. Here we report colloidal sphere templating as a viable means to create tetrapodal NPs with site...... directional bonding to other NPs. We also illustrate that sets of tethered "colloidal atoms" can assemble themselves into "colloidal molecules" with precise placement of the modifying colloids. The templating and tethering approaches to these anisotropic colloidal building blocks and the assembly methods are...

  1. A colloidal quantum dot spectrometer

    Science.gov (United States)

    Bao, Jie; Bawendi, Moungi G.

    2015-07-01

    Spectroscopy is carried out in almost every field of science, whenever light interacts with matter. Although sophisticated instruments with impressive performance characteristics are available, much effort continues to be invested in the development of miniaturized, cheap and easy-to-use systems. Current microspectrometer designs mostly use interference filters and interferometric optics that limit their photon efficiency, resolution and spectral range. Here we show that many of these limitations can be overcome by replacing interferometric optics with a two-dimensional absorptive filter array composed of colloidal quantum dots. Instead of measuring different bands of a spectrum individually after introducing temporal or spatial separations with gratings or interference-based narrowband filters, a colloidal quantum dot spectrometer measures a light spectrum based on the wavelength multiplexing principle: multiple spectral bands are encoded and detected simultaneously with one filter and one detector, respectively, with the array format allowing the process to be efficiently repeated many times using different filters with different encoding so that sufficient information is obtained to enable computational reconstruction of the target spectrum. We illustrate the performance of such a quantum dot microspectrometer, made from 195 different types of quantum dots with absorption features that cover a spectral range of 300 nanometres, by measuring shifts in spectral peak positions as small as one nanometre. Given this performance, demonstrable avenues for further improvement, the ease with which quantum dots can be processed and integrated, and their numerous finely tuneable bandgaps that cover a broad spectral range, we expect that quantum dot microspectrometers will be useful in applications where minimizing size, weight, cost and complexity of the spectrometer are critical.

  2. Magnetic assembly route to colloidal responsive photonic nanostructures.

    Science.gov (United States)

    He, Le; Wang, Mingsheng; Ge, Jianping; Yin, Yadong

    2012-09-18

    Responsive photonic structures can respond to external stimuli by transmitting optical signals. Because of their important technological applications such as color signage and displays, biological and chemical sensors, security devices, ink and paints, military camouflage, and various optoelectronic devices, researchers have focused on developing these functional materials. Conventionally, self-assembled colloidal crystals containing periodically arranged dielectric materials have served as the predominant starting frameworks. Stimulus-responsive materials are incorporated into the periodic structures either as the initial building blocks or as the surrounding matrix so that the photonic properties can be tuned. Although researchers have proposed various versions of responsive photonic structures, the low efficiency of fabrication through self-assembly, narrow tunability, slow responses to the external stimuli, incomplete reversibility, and the challenge of integrating them into existing photonic devices have limited their practical application. In this Account, we describe how magnetic fields can guide the assembly of superparamagnetic colloidal building blocks into periodically arranged particle arrays and how the photonic properties of the resulting structures can be reversibly tuned by manipulating the external magnetic fields. The application of the external magnetic field instantly induces a strong magnetic dipole-dipole interparticle attraction within the dispersion of superparamagnetic particles, which creates one-dimensional chains that each contains a string of particles. The balance between the magnetic attraction and the interparticle repulsions, such as the electrostatic force, defines the interparticle separation. By employing uniform superparamagnetic particles of appropriate sizes and surface charges, we can create one-dimensional periodicity, which leads to strong optical diffraction. Acting remotely over a large distance, magnetic forces drove the

  3. PRELIMINARY STUDY ON THE DISSOLVED AND COLLOIDAL ORGANIC CARBON IN THE ZHUJIANG RIVER ESTUARY

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper reports data on the dissolved and colloidal organic carbon in the Zhujiang (Pearl) River estuary. DOC concentration was 142 to 239 μmol/L in the freshwater taken in March 1997 from the four Zhujiang River tributaries flowing into the Lingdingyang estuary. High concentration was observed in the Humen tributary located near Guangzhou. The rapidly increased DOC concentration at low salinities (~5) may be attributed to the exchange between macroparticulate and dissolved organic matter during the early stage of estuarine mixing. DOC concentration overall followed the mixing line until salinity ~25, where the Deep Bay is located and where DOC was elevated. This elevated DOC may suggest a local organic matter source from Shenzhen. Using a cross-flow ultrafiltration (CFF) system equipped with a Millipore Prep-scale CFF 1 kD regenerated cellulose membrane, we also separated the colloidal organic matter from the truly dissolved fraction (<1 kD). CFF membranes were carefully evaluated for their applicability (retention characteristics, blank level and mass balance) to separate colloidal organic matter. COC in the study area ranged from 5 to 85 μmol/L, representing ~ 3%-32% of DOC. The highest COC percentage was found at low salinities (< 5) in both winter and summer. Evidence suggests in-situ production of colloidal material at this salinity range. Beyond this point, a very modest removal was observable until high salinities. Again, an increase in COC concentration was shown in the samples taken from the Deep Bay.

  4. Anisotropic Colloids: Synthesis and Phase Behavior of Eccentric, Dimer and String-like Colloids

    OpenAIRE

    Demirors, A.F.

    2010-01-01

    The research described in this thesis focuses on synthesis and phase behavior of anisotropic colloids prepared through different synthetic strategies. Namely, eccentric core-shell particles, dimers, string-like particles and core-shell particles are the systems investigated throughout this work. The synthesis routes are described for these colloidal systems and their physical/chemical properties are extensively characterized. Furthermore, potential applications of these colloidal systems in f...

  5. Colloid migration in groundwaters: Geochemical interactions of radionuclides with natural colloids

    International Nuclear Information System (INIS)

    The aim of this joint research programme is to determine the significance of groundwater colloids in far field radionuclide migration. This is based on the characterization, quantification and theoretical interpretation of colloidal transport of radionuclides in selected Gorleben aquifer systems. These aquifers were chosen for their well characterized hydrological and geological properties and because they contain substantial colloids of different chemical compositions in addition to considerable quantities of chemical homologues for the tri-, tetra- and hexavalent actinides. (orig./BBR)

  6. Self-assembly of microcapsules via colloidal bond hybridization and anisotropy.

    Science.gov (United States)

    Evers, Chris H J; Luiken, Jurriaan A; Bolhuis, Peter G; Kegel, Willem K

    2016-06-16

    Particles with directional interactions are promising building blocks for new functional materials and may serve as models for biological structures. Mutually attractive nanoparticles that are deformable owing to flexible surface groups, for example, may spontaneously order themselves into strings, sheets and large vesicles. Furthermore, anisotropic colloids with attractive patches can self-assemble into open lattices and the colloidal equivalents of molecules and micelles. However, model systems that combine mutual attraction, anisotropy and deformability have not yet been realized. Here we synthesize colloidal particles that combine these three characteristics and obtain self-assembled microcapsules. We propose that mutual attraction and deformability induce directional interactions via colloidal bond hybridization. Our particles contain both mutually attractive and repulsive surface groups that are flexible. Analogously to the simplest chemical bond--in which two isotropic orbitals hybridize into the molecular orbital of H2--these flexible groups redistribute on binding. Via colloidal bond hybridization, isotropic spheres self-assemble into planar monolayers, whereas anisotropic snowman-shaped particles self-assemble into hollow monolayer microcapsules. A modest change in the building blocks thus results in much greater complexity of the self-assembled structures. In other words, these relatively simple building blocks self-assemble into markedly more complex structures than do similar particles that are isotropic or non-deformable. PMID:27281213

  7. Self-assembly of microcapsules via colloidal bond hybridization and anisotropy

    Science.gov (United States)

    Evers, Chris H. J.; Luiken, Jurriaan A.; Bolhuis, Peter G.; Kegel, Willem K.

    2016-06-01

    Particles with directional interactions are promising building blocks for new functional materials and may serve as models for biological structures. Mutually attractive nanoparticles that are deformable owing to flexible surface groups, for example, may spontaneously order themselves into strings, sheets and large vesicles. Furthermore, anisotropic colloids with attractive patches can self-assemble into open lattices and the colloidal equivalents of molecules and micelles. However, model systems that combine mutual attraction, anisotropy and deformability have not yet been realized. Here we synthesize colloidal particles that combine these three characteristics and obtain self-assembled microcapsules. We propose that mutual attraction and deformability induce directional interactions via colloidal bond hybridization. Our particles contain both mutually attractive and repulsive surface groups that are flexible. Analogously to the simplest chemical bond—in which two isotropic orbitals hybridize into the molecular orbital of H2—these flexible groups redistribute on binding. Via colloidal bond hybridization, isotropic spheres self-assemble into planar monolayers, whereas anisotropic snowman-shaped particles self-assemble into hollow monolayer microcapsules. A modest change in the building blocks thus results in much greater complexity of the self-assembled structures. In other words, these relatively simple building blocks self-assemble into markedly more complex structures than do similar particles that are isotropic or non-deformable.

  8. Surface-enhanced Raman Scattering Activity Study of Molecule in Mixed Negatively and Positively Charged Silver Colloidal Solution%混合正、负电性银胶体系的表面增强拉曼散射活性研究

    Institute of Scientific and Technical Information of China (English)

    方靖淮; 黄云霞; 李霞; 窦晓明

    2004-01-01

    Both negatively and positively charged silver colloids were prepared in aqueous solution for surface-enhanced Raman scattering (SERS) by the reduction of silver nitrate with sodium citrate and hydrogen peroxide under basic condition, respectively. By means of transmission electron microscopy (TEM), the observation of morphologies of negatively charged silver colloid (NSC) and positively charged silver colloid (PSC) has been presented, and the aggregation behaviors of NSC and PSC as well as the mixture of NSC and PSC induced by the addition of fuchsine basic molecules examined. SERS from fuchsine basic molecules in above mentioned colloidal systems were recorded respectively and compared with each other. The results show that the mixture of NSC and PSC could form the aggregation morphology different from that of single NSC and PSC and bring about the favorable effect on SERS behavior for the adsorbed fuchsine basic.%通过化学还原的方法分别制备了具有正、负电性的纳米银胶.利用透射电子显微镜表征了正、负电性银胶以及混合银胶体系中加入碱性品红分子后的聚集行为.通过测定碱性品红分子在正、负电性银胶以及混合银胶体系中的表面增强拉曼光谱的变化,探讨了不同电性银胶基底对碱性品红表面增强拉曼活性的影响.实验结果表明,混合溶胶体系所具有的不同于单一溶胶的聚集特性能有效的改善单银胶体系的表面增强拉曼散射活性.

  9. Grimsel colloid exercise, an international intercomparison exercise on the sampling and characterization of groundwater colloids

    International Nuclear Information System (INIS)

    The Grimsel colloid exercise was an intercomparison exercise which consisted of an in situ sampling phase followed by a colloid characterization step. The goal of this benchmark exercise, which involved 12 laboratories, was to evaluate both sampling and characterization techniques with emphasis on the colloid specific size distribution. The sampling phase took place at the Grimsel test site between 1 and 13 February 1988 and the participating groups produced colloid samples using various methods. This work was carried out within the Community COCO Club, as a component of the Mirage project (second phase)

  10. Use of a New Ziprasidone-Selective Electrode in Mixed Solvents and Its Application in the Analysis of Pharmaceuticals and Biological Fluids

    OpenAIRE

    María Cuartero; Mª Soledad García; Mustafa Salem Abuherba; Ortuño, Joaquín A.

    2011-01-01

    The construction and characterization of a new ion-selective electrode for the determination of the antipsychotic ziprasidone in mixed solvents is presented. The electrode contains a plasticized polymeric membrane based on a ziprasidone-tetraphenylborate ion-exchanger. The influence of membrane composition on the electrode response towards ziprasidone in hydroalcoholic solutions was studied. The electrode displayed a stable response in a 2:3 (v/v) methanol/water medium from a ziprasidone conc...

  11. A Course in Colloid and Surface Science.

    Science.gov (United States)

    Scamehorn, John F.

    1984-01-01

    Describes a course for chemical engineers, chemists, and petroleum engineers that focuses on colloid and surface science. Major topic areas in the course include capillarity, surface thermodynamics, adsorption contact angle, micelle formation, solubilization in micelles, emulsions, foams, and applications. (JN)

  12. Linear Optical Properties of Gold Colloid

    Directory of Open Access Journals (Sweden)

    Jingmin XIA

    2015-12-01

    Full Text Available Gold colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid.

  13. Mobility of radioactive colloidal particles in groundwater

    International Nuclear Information System (INIS)

    Radiocolloids are a major factor in the rapid migration of radioactive waste in groundwater. For at least two Los Alamos National Laboratory (LANL) sites, researchers have shown that groundwater colloidal particles were responsible for the rapid transport of radioactive waste material in groundwater. On an international scale, a review of reported field observations, laboratory column studies, and carefully collected field samples provides compelling evidence that colloidal particles enhance both radioactive and toxic waste migration. The objective of this project is to understand and predict colloid-contaminant migration through fundamental mathematical models, water sampling, and laboratory experiments and use this information to develop an effective and scientifically based colloid immobilization strategy. The article focuses on solving the suspected radiocolloid transport problems at LANL's Mortandad Canyon site. (author) 6 figs., 5 tabs., 18 refs

  14. Polydispersity effects in colloid-polymer mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Liddle, S M; Poon, W C K [SUPA and School of Physics and Astronomy, The University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ (United Kingdom); Narayanan, T, E-mail: S.Liddle@ed.ac.uk, E-mail: narayan@esrf.fr, E-mail: w.poon@ed.ac.uk [European Synchrotron Radiation Facility, F-38043 Grenoble Cedex (France)

    2011-05-18

    We study phase separation and transient gelation experimentally in a mixture consisting of polydisperse colloids (polydispersity: {approx} 6%) and non-adsorbing polymers, where the ratio of the average size of the polymer to that of the colloid is {approx} 0.062. Unlike what has been reported previously for mixtures with somewhat lower colloid polydispersity ({approx} 5%), the addition of polymers does not expand the fluid-solid coexistence region. Instead, we find a region of fluid-solid coexistence which has an approximately constant width but an unexpected re-entrant shape. We detect the presence of a metastable gas-liquid binodal, which gives rise to two-stepped crystallization kinetics that can be rationalized as the effect of fractionation. Finally, we find that the separation into multiple coexisting solid phases at high colloid volume fractions predicted by equilibrium statistical mechanics is kinetically suppressed before the system reaches dynamical arrest.

  15. Linear Optical Properties of Gold Colloid

    Directory of Open Access Journals (Sweden)

    Jingmin XIA

    2015-11-01

    Full Text Available Gold colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9558

  16. Suspensions of colloidal particles and aggregates

    CERN Document Server

    Babick, Frank

    2016-01-01

    This book addresses the properties of particles in colloidal suspensions. It has a focus on particle aggregates and the dependency of their physical behaviour on morphological parameters. For this purpose, relevant theories and methodological tools are reviewed and applied to selected examples. The book is divided into four main chapters. The first of them introduces important measurement techniques for the determination of particle size and interfacial properties in colloidal suspensions. A further chapter is devoted to the physico-chemical properties of colloidal particles—highlighting the interfacial phenomena and the corresponding interactions between particles. The book’s central chapter examines the structure-property relations of colloidal aggregates. This comprises concepts to quantify size and structure of aggregates, models and numerical tools for calculating the (light) scattering and hydrodynamic properties of aggregates, and a discussion on van-der-Waals and double layer interactions between ...

  17. Inoculation of Plasmids Encoding Japanese Encephalitis Virus PrM-E Proteins with Colloidal Gold Elicits a Protective Immune Response in BALB/c Mice

    OpenAIRE

    Zhao, Zijiang; Wakita, Takaji; Yasui, Kotaro

    2003-01-01

    We established a simple and effective method for DNA immunization against Japanese encephalitis virus (JEV) infection with plasmids encoding the viral PrM and E proteins and colloidal gold. Inoculation of plasmids mixed with colloidal gold induced the production of specific anti-JEV antibodies and a protective response against JEV challenge in BALB/c mice. When we compared the efficacy of different inoculation routes, the intravenous and intradermal inoculation routes were found to elicit str...

  18. Crust formation in drying colloidal suspensions

    OpenAIRE

    Style, R. W.; Peppin, S. S. L.

    2010-01-01

    During the drying of colloidal suspensions, the desiccation process causes the suspension near the air interface to consolidate into a connected porous matrix or crust. Fluid transport in the porous medium is governed by Darcy’s law and the equations of poroelasticity, while the equations of colloid physics govern processes in the suspension. We derive new equations describing this process, including unique boundary conditions coupling the two regions, yielding a moving-boundary model of the ...

  19. Coarse-graining polymers as soft colloids

    OpenAIRE

    Louis, A. A.; Bolhuis, P. G.; Finken, R.; Krakoviack, V.; Meijer, E. J.; Hansen, J. P.

    2001-01-01

    We show how to coarse grain polymers in a good solvent as single particles, interacting with density-independent or density-dependent interactions. These interactions can be between the centres of mass, the mid-points or end-points of the polymers. We also show how to extend these methods to polymers in poor solvents and mixtures of polymers. Treating polymers as soft colloids can greatly speed up the simulation of complex many-polymer systems, including polymer-colloid mixtures.

  20. Autonomous colloidal crystallization in a galvanic microreactor

    Science.gov (United States)

    Punckt, Christian; Jan, Linda; Jiang, Peng; Frewen, Thomas A.; Saville, Dudley A.; Kevrekidis, Ioannis G.; Aksay, Ilhan A.

    2012-10-01

    We report on a technique that utilizes an array of galvanic microreactors to guide the assembly of two-dimensional colloidal crystals with spatial and orientational order. Our system is comprised of an array of copper and gold electrodes in a coplanar arrangement, immersed in a dilute hydrochloric acid solution in which colloidal micro-spheres of polystyrene and silica are suspended. Under optimized conditions, two-dimensional colloidal crystals form at the anodic copper with patterns and crystal orientation governed by the electrode geometry. After the aggregation process, the colloidal particles are cemented to the substrate by co-deposition of reaction products. As we vary the electrode geometry, the dissolution rate of the copper electrodes is altered. This way, we control the colloidal motion as well as the degree of reaction product formation. We show that particle motion is governed by a combination of electrokinetic effects acting directly on the colloidal particles and bulk electrolyte flow generated at the copper-gold interface.

  1. Density functional theory of charged colloidal systems

    International Nuclear Information System (INIS)

    The phase behavior of charged colloidal systems has been studied recently by the density functional theory formalism (DFT) [R. van Roij, M. Dijkstra, and J. P. Hansen, Phys. Rev. E >59, 2010 (1999)]. A key feature of this approach is the appearance of a density and temperature-dependent effective Hamiltonian between the charged colloids. Under certain approximations, the effective Hamiltonian is made up only of a sum of position-independent one-body or volume terms and two-body colloid-separation dependent terms. In the limit of low colloidal densities, the DFT results do not reduce to the familiar Debye-Huckel limiting law nor do the results agree with previous work based on an identical approach but were developed using traditional statistical-mechanical methods [B. Beresford-Smith, D. Y. C. Chan, and D. J. Mitchell J. Colloid Interface Sci. >105, 216 (1985)]. This paper provides a reconciliation of these differences and comments on the significance of the one-body volume terms in the effective Hamiltonian of a system of charged colloids in determining thermodynamics and phase behavior

  2. Complex coacervation between colloidal silica and polyacrylamide

    International Nuclear Information System (INIS)

    Complex coacervation introduced by gamma-ray induced polymerization of acrylamide in colloidal silica was studied. The complex coaservate was formed by polymerization of acrylamide dissolved in a colloidal silica and methanol mixture. Complex coacervation (two-phase separation of the mixture) was observed only when the concentration of methanol was between 33 and 41 percent by volume, and the concentration of colloidal silica did not affect it. Although two phase separation was not influenced by pH change, the content of polyacrylamide was bigger in the equilibrated solution in acidic regions. It was, however, bigger in the complex coacervate at neutral and in alkaline regions. The content of polyacrylamide was also calculated from the particle diameter of complex coacervate measured by small angle X-ray scattering, and the result was well coincided with the analytical result. The stability of the complex coacervate against the addition of salts was better than that of the untreated colloidal silica. The rate of electrophoretic transport of the complex coacervate was also lower than that of the colloidal silica. From these observation it was concluded that the hydrophobic colloidal silica particles were protected by the surrounding hydrophilic polyacrylamide. (author)

  3. Colloids generation from metallic uranium fuel

    International Nuclear Information System (INIS)

    The possibility of colloid generation from spent fuel in an unsaturated environment has significant implications for storage of these fuels in the proposed repository at Yucca Mountain. Because colloids can act as a transport medium for sparingly soluble radionuclides, it might be possible for colloid-associated radionuclides to migrate large distances underground and present a human health concern. This study examines the nature of colloidal materials produced during corrosion of metallic uranium fuel in simulated groundwater at elevated temperature in an unsaturated environment. Colloidal analyses of the leachates from these corrosion tests were performed using dynamic light scattering and transmission electron microscopy. Results from both techniques indicate a bimodal distribution of small discrete particles and aggregates of the small particles. The average diameters of the small, discrete colloids are ∼3--12 nm, and the large aggregates have average diameters of approximately100--200 nm. X-ray diffraction of the solids from these tests indicates a mineral composition of uranium oxide or uranium oxy-hydroxide

  4. Sterically stabilized colloids with tunable repulsions.

    Science.gov (United States)

    van Gruijthuijsen, Kitty; Obiols-Rabasa, Marc; Heinen, Marco; Nägele, Gerhard; Stradner, Anna

    2013-09-10

    When studying tunable electrostatic repulsions in aqueous suspensions of charged colloids, irreversible colloid aggregation or gelation may occur at high salt concentrations. For many commonly used synthetic colloids, such as polystyrene and silica particles, the reason for coagulation is the presence of unbalanced, strongly attractive, and short-ranged van der Waals (VDW) forces. Here, we present an aqueous polystyrene model colloid that is sterically stabilized against VDW attractions. We show that the synthesis procedure, based on a neutral initiator couple and a nonionic surfactant, introduces surface charges that can be further increased by the addition of charged comonomer methacrylic acid. Thus, the interactions between the polystyrene spheres can be conveniently tuned from hard-sphere-like to charge-stabilized with long-ranged electrostatic repulsions described by a Yukawa-type pair potential. The particle size, grafting density, core-shell structure, and surface charge are characterized by light and neutron scattering. Using X-ray and neutron scattering in combination with an accurate analytic integral equation scheme for the colloidal static structure factor, we deduce effective particle charges for colloid volume fractions ≥0.1 and salt concentrations in the range of 1.5 to 50 mM. PMID:23937718

  5. Self-replication with magnetic dipolar colloids

    Science.gov (United States)

    Dempster, Joshua M.; Zhang, Rui; Olvera de la Cruz, Monica

    2015-10-01

    Colloidal self-replication represents an exciting research frontier in soft matter physics. Currently, all reported self-replication schemes involve coating colloidal particles with stimuli-responsive molecules to allow switchable interactions. In this paper, we introduce a scheme using ferromagnetic dipolar colloids and preprogrammed external magnetic fields to create an autonomous self-replication system. Interparticle dipole-dipole forces and periodically varying weak-strong magnetic fields cooperate to drive colloid monomers from the solute onto templates, bind them into replicas, and dissolve template complexes. We present three general design principles for autonomous linear replicators, derived from a focused study of a minimalist sphere-dimer magnetic system in which single binding sites allow formation of dimeric templates. We show via statistical models and computer simulations that our system exhibits nonlinear growth of templates and produces nearly exponential growth (low error rate) upon adding an optimized competing electrostatic potential. We devise experimental strategies for constructing the required magnetic colloids based on documented laboratory techniques. We also present qualitative ideas about building more complex self-replicating structures utilizing magnetic colloids.

  6. Radio-active colloids in the functional exploration of the reticulo-endothelium system

    International Nuclear Information System (INIS)

    A historical review describes the reticulo-endothelial system (R.E.S.) and aims at defining it and at explaining its operation. The methods used for its examination and the colloids utilized are considered. The author has been led to prepare a special type of colloid: an albuminous complex containing radio-iodine, 'C.A. 131I', whose method of preparation and physical and biological examination are described. A human albumin, having a known optical density in solution, is heated until a change in the optical density indicates that an aggregation of the proteinic molecules has occurred. The denatured protein is iodated with 131I. Electrophoretic, ultracentrifuge and autoradiographic controls are then carried out. This atoxic and metabolisable preparation of biological origin is compared with the better defined colloidal gold which serves as reference. C.A.131I is injected into mice. It is shown by radioactivity measurements, auto-radiographies on sections of the whole animal, and anthropo-gamma-metric detections that a high concentration occurs in the S.R.E. of the liver. These static results are only of limited importance however compared to those obtained from an in vivo study of the phenomenon. The author records the changes in the radioactivity of the blood derived from the carotid artery using a well-scintillator. He obtains directly a curve of the radioactivity of blood having a decreasing exponential form; the mathematical expression describing this curve is given. The biological half-life T 1/2 of the colloid in the blood is a measure of its phagocytosis by the S.R.E. cells. A supplementary check is provided by the direct recording of the hepatic activity using a suitably collimated exterior detector. A curve of increasing-exponential form is obtained and its parameters are corollary to the preceding curve. These tests carried out on guinea-pigs and rats make it possible to give to the S.R.E. a phagocytic index which is characteristic of its state of activity

  7. High-density gold and silver colloids developed for coating material; Toryoyo ni kaihatsusareta konodo kin, gin koroido

    Energy Technology Data Exchange (ETDEWEB)

    Asada, M. [Dai Nippon Ink and Chemical, Inc., Tokyo (Japan)

    2000-08-05

    Gold and silver with the beautiful precious metal luster show red and yellow by the plasmon absorption, which differ from the original color, when the particle size becomes less than several decade nm, and they have been used for colorants of stained glass since the ancient times. Recently, the method for adjusting comparatively conveniently high-density gold and silver colloids was announced. Though this method was the general method for preparing gold colloids or silver colloids in which chloroauric acid or silver nitrate aqueous solution is reduced respectively, that the reduction was done by using a water insoluble high molecular weight dispersing agent as a protective colloid in the mixed solvent system of water soluble organic solvent such as the acetone and water was the feature. Using solid sol obtained by this method, the alkyd-melamine coating material was made, and it was baked at 140 degrees C, the coating film was obtained. The coating film of gold colloid was vivid red, and the absorption peak was observed near 530nm, whereas on the other hand the silver colloid was yellow, and the absorption peak was observed near 420nm. These values almost agreed with the values of the plasmon absorption of each metal. (NEDO)

  8. Colloidal transport of uranium in soil: Size fractionation and characterization by field-flow fractionation-multi-detection

    International Nuclear Information System (INIS)

    The aim of this study was to characterize colloids associated with uranium by using an on-line fractionation/multi-detection technique based on asymmetrical flow field-flow fractionation (As-Fl-FFF) hyphenated with UV detector, multi angle laser light scattering (MALLS) and inductively coupling plasma-mass spectrometry (ICP-MS). Moreover, thanks to the As-Fl-FFF, the different colloidal fractions were collected and characterized by a total organic carbon analyzer (TOC). Thus it is possible to determine the nature (organic or inorganic colloids), molar mass, size (gyration and hydrodynamic radii) and quantitative uranium distribution over the whole colloidal phase. In the case of the site studied, two populations are highlighted. The first population corresponds to humic-like substances with a molar mass of (1500 ± 300) g mol-1 and a hydrodynamic diameter of (2. 0 ± 0. 2) nm. The second one has been identified as a mix of carbonated nano-particles or clays with organic particles (aggregates and/or coating of the inorganic particles) with a size range hydrodynamic diameter between 30 and 450 nm. Each population is implied in the colloidal transport of uranium: maximum 1% of the uranium content in soil leachate is transported by the colloids in the site studied, according to the depth in the soil. Indeed, humic substances are the main responsible of this transport in sub-surface conditions whereas nano-particles drive the phenomenon in depth conditions. (authors)

  9. A colloidal singularity reveals the crucial role of colloidal stability for nanomaterials in-vitro toxicity testing: nZVI-microalgae colloidal system as a case study

    OpenAIRE

    Gonzalo, Soledad; Pulido-Reyes, Gerardo; Fernández-Piñas, Francisca; Bonzongo, Jean Claude; Leganés, Francisco; Rosal, Roberto; García-Calvo, Eloy; Rodea-Palomares, Ismael

    2014-01-01

    Aggregation raises attention in Nanotoxicology due to its methodological implications. Aggregation is a physical symptom of a more general physicochemical condition of colloidal particles, namely, colloidal stability. Colloidal stability is a global indicator of the tendency of a system to reduce its net surface energy, which may be achieved by homo-aggregation or hetero-aggregation, including location at bio-interfaces. However, the role of colloidal stability as a driver of ENM bioactivity ...

  10. Synthesis, Biological, and Quantum Chemical Studies of Zn(II) and Ni(II) Mixed-Ligand Complexes Derived from N,N-Disubstituted Dithiocarbamate and Benzoic Acid

    OpenAIRE

    Anthony C. Ekennia; Damian C. Onwudiwe; Aderoju A Osowole; Olasunkanmi, Lukman O.; Eno E. Ebenso

    2016-01-01

    Some mixed-ligand complexes of Zn(II) and Ni(II) derived from the sodium salt of N-alkyl-N-phenyl dithiocarbamate and benzoic acid have been prepared. The complexes are represented as ZnMDBz, ZnEDBz, NiMDBz, and NiEDBz (MD: N-methyl-N-phenyl dithiocarbamate, ED: N-ethyl-N-phenyl dithiocarbamate, and Bz: benzoate); and their coordination behavior was characterized on the basis of elemental analyses, IR, electronic spectra, magnetic and conductivity measurements, and quantum chemical calculatio...

  11. Colloid-Facilitated Transport of Radionuclides Through The Vadose Zone

    International Nuclear Information System (INIS)

    The main purpose of this project was to advance the basic scientific understanding of colloid and colloid-facilitated Cs transport of radionuclides in the vadose zone. We focused our research on the hydrological and geochemical conditions beneath the leaking waste tanks at the USDOE Hanford reservation. Specific objectives were (1) to determine the lability and thermodynamic stability of colloidal materials, which form after reacting Hanford sediments with simulated Hanford Tank Waste, (2) to characterize the interactions between colloidal particles and contaminants, i.e., Cs and Eu, (3) to determine the potential of Hanford sediments for in situ mobilization of colloids, (4) to evaluate colloid-facilitated radionuclide transport through sediments under unsaturated flow, (5) to implement colloid-facilitated contaminant transport mechanisms into a transport model, and (6) to improve conceptual characterization of colloid-contaminant-soil interactions and colloid-facilitated transport for clean-up procedures and long-term risk assessment

  12. Colloid's influences on microalgae growth as a potential environmental factor

    Institute of Scientific and Technical Information of China (English)

    赵新淮; 张正斌; 刘莲生

    2003-01-01

    The role of colloid as "colloid pump" in the ocean is well known. The important influence of colloid in seawater on the growth of microalga was found in our 1999-2000 study. Colloid concentrates were obtained by employing a cross-flow filtration systen to ultrafilter seawater (which had been pre-filtrated by 0.45 μm acetate cellulose membrane) successively with different membranes. Ultrafiltration retentions (we called them colloid concentrates ) together with control sample ( seawater without colloid) were then inoculated with two species of microalgae and cultivated in selected conditions. Monitoring of microalgae growth during cultivation showed that all colloid concentrates had obvious influence on the growth of the microalgae studied. Addition of Fe(OH)3 colloid or organic colloid (protein or carbohydrate) to the control sample enhanced the microalgae's growth.

  13. Stimulus-Responsive Heteroaggregation of Colloidal Dispersions: Reversible Systems and Composite Materials

    OpenAIRE

    Julian Eastoe; Melanie Bradley; Azwan Mat Lazim

    2011-01-01

    Heteroaggregation is the aggregation of mixed particle systems where the colloidal particles may differ in charge, size and chemical composition. The phenomenon of heteroaggregation is of great relevance in industrial processes and the natural environment. This review will focus on binary heteroaggregation where at least one of the particles is a stimulus-responsive smart particle. Aggregation under various conditions of pH, temperature, light and relative concentration can be induced by the ...

  14. A novel approach for scanning electron microscopy of colloidal gold- labeled cell surfaces

    OpenAIRE

    1984-01-01

    A method is described for the use of scanning electron microscopy on the surface of gold-labeled cells. It includes the use of 45- or 20-nm colloidal gold marker conjugated with Staphylococcal protein A. The marker is best recognized on the basis of its atomic number contrast by using the backscattered electron imaging mode of the scanning electron microscope. When the backscattered electron signal is mixed with the secondary electron signal, an optimum correlation between the distribution of...

  15. Effect of Solvation Film on the Viscosity of Colloidal Dispersions

    Institute of Scientific and Technical Information of China (English)

    PENG Chang-Sheng; GU Qing-Bao; SONG Shao-Xian

    2005-01-01

    Viscosity is one of the most important properties of colloids in mixing, transportation, stabilization, energy consumption, and so on. According to Einstein's viscosity equation, the viscosity of a colloidal dispersion increases with the increase of particle concentration. And the equation can be applicable to all micro-particle dispersions, because the effect of solvation films coated on particles can be neglectable in that case. But with the decrease of particle size to nano-scale, the formation of solvation films on nano-particles can greatly affect the viscosity of a dispersion, and Einstein's equation may not be applicable to this case. In this work, one kind of micro-size silica particle and two kinds of nano-size silica particles were used to investigate the effect of solvation films on dispersion viscosity, dispersed in water and ethyl alcohol solvents, respectively. The results of theoretical calculation and experimental investigation show that the increase of viscosity is contributed from solvation films by more than 95 percent for nano-particle dispersions, while less than 10 percent for micro-particle dispersions.

  16. Synthesis, Biological, and Quantum Chemical Studies of Zn(II and Ni(II Mixed-Ligand Complexes Derived from N,N-Disubstituted Dithiocarbamate and Benzoic Acid

    Directory of Open Access Journals (Sweden)

    Anthony C. Ekennia

    2016-01-01

    Full Text Available Some mixed-ligand complexes of Zn(II and Ni(II derived from the sodium salt of N-alkyl-N-phenyl dithiocarbamate and benzoic acid have been prepared. The complexes are represented as ZnMDBz, ZnEDBz, NiMDBz, and NiEDBz (MD: N-methyl-N-phenyl dithiocarbamate, ED: N-ethyl-N-phenyl dithiocarbamate, and Bz: benzoate; and their coordination behavior was characterized on the basis of elemental analyses, IR, electronic spectra, magnetic and conductivity measurements, and quantum chemical calculations. The magnetic moment measurement and electronic spectra were in agreement with the four proposed coordinate geometries for nickel and zinc complexes and were corroborated by the theoretical quantum chemical calculations. The quantum chemically derived thermodynamics parameters revealed that the formation of N-methyl-N-phenyl dithiocarbamate complexes is more thermodynamically favourable than that of the N-ethyl-N-phenyl dithiocarbamate complexes. The bioefficacy of the mixed-ligand complexes examined against different microbes showed moderate to high activity against the test microbes. The anti-inflammatory and antioxidant studies of the metal complexes showed that the ethyl substituted dithiocarbamate complexes exhibited better anti-inflammatory and antioxidant properties than the methyl substituted dithiocarbamate complexes.

  17. Colloid chemistry: available sorption models and the question of colloid adhesion

    International Nuclear Information System (INIS)

    A safety analysis of a radioactive waste repository should consider the possibility of nuclide transport by colloids. This would involve describing the sorption properties of the colloids and their transport in porous and fissured media. This report deals with a few selected aspects of the chemistry of this complex subject. Because the mechanisms of ion adsorption onto surfaces are material-specific, increased attention should be paid to identifying the material constitution of aquatic colloids. Suitable models already exist for describing reversible adsorption; these models describe sorption using mass action equations. The surface coordination model, developed for hydrous oxide surfaces, allows a uniform approach to be adopted for different classes of materials. This model is also predictive and has been applied successfully to natural systems. From the point of view of nuclide transport by colloids, irreversible sorption represents the most unfavourable situation. There is virtually no information available on the extent of reversibility and on the desorption kinetics of important nuclide/colloid combinations. Experimental investigations are therefore necessary in this respect. The only question considered in connection with colloid transport and its modelling is that of colloid sticking. Natural colloids, and the surfaces of the rock on which they may be collected, generally have negative surface charges so that colloid sticking will be difficult. The DLVO theory contains an approach for calculating the sticking factor from the surface potentials of the solid phases and the ionic strength of the water. However, it has been shown that this theory is inapplicable because of inherent shortcomings which lead to completely unrealistic predictions. The sticking probability of colloids should therefore be determined experimentally for systems which correspond as closely as possible to reality. (author) 66 figs., 12 tabs., 204 refs

  18. Biological synthesis of very small silver nanoparticles by culture supernatant of Klebsiella pneumonia: The effects of visible-light irradiation and the liquid mixing process

    International Nuclear Information System (INIS)

    This study has investigated different visible-light irradiation's effect on the formation of silver nanoparticles from silver nitrate using the culture supernatant of Klebsiella pneumonia. Our study shows that visible-light emission can significantly prompt the synthesis of silver nanoparticles. Also, the study experimentally investigated the liquid mixing process effect on silver nanoparticle synthesis by visible-light irradiation. This study successfully synthesized uniformly dispersed silver nanoparticles with a uniform size and shape in the range of 1-6 nm with an average size of 3 nm. Furthermore, the study investigated the mechanism of the reduction of silver ions by culture supernatant of K. pneumonia, and used X-ray diffraction to characterize silver chloride as an intermediate compound. Silver chloride was prepared synthetically and used as a substrate for the synthesis of silver nanoparticles by culture supernatant of K. pneumonia. The silver nanoparticles have been prepared from silver chloride during this investigation for the first time.

  19. Dose calculation in biological samples in a mixed neutron-gamma field at the TRIGA reactor of the University of Mainz

    DEFF Research Database (Denmark)

    Schmitz, T.; Blaickner, M.; Schütz, C.;

    2010-01-01

    To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the University of Mainz, Germany, it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative...... neutron fluence directly. Results and discussion. Gold foil activation and the pin-diode are reliable fluence measurement systems for the TRIGA reactor, Mainz. Alanine dosimetry of the photon field and charged particle field from secondary reactions can in principle be carried out in combination with MC...... simulation of the mixed neutron and gamma field of the TRIGA Mainz is possible in order to characterize the neutron behavior in the thermal column. Currently we also speculate on sensitizing alanine to thermal neutrons by adding boron compounds....

  20. Selective porous gates made from colloidal silica nanoparticles

    Directory of Open Access Journals (Sweden)

    Roberto Nisticò

    2015-11-01

    Full Text Available Highly selective porous films were prepared by spin-coating deposition of colloidal silica nanoparticles on an appropriate macroporous substrate. Silica nanoparticles very homogenous in size were obtained by sol–gel reaction of a metal oxide silica precursor, tetraethyl orthosilicate (TEOS, and using polystyrene-block-poly(ethylene oxide (PS-b-PEO copolymers as soft-templating agents. Nanoparticles synthesis was carried out in a mixed solvent system. After spin-coating onto a macroporous silicon nitride support, silica nanoparticles were calcined under controlled conditions. An organized nanoporous layer was obtained characterized by a depth filter-like structure with internal porosity due to interparticle voids. Permeability and size-selectivity were studied by monitoring the diffusion of probe molecules under standard conditions and under the application of an external stimulus (i.e., electric field. Promising results were obtained, suggesting possible applications of these nanoporous films as selective gates for controlled transport of chemical species in solution.

  1. Colloidal silica-grouting in demonstration tunnel 2 in ONKALO

    International Nuclear Information System (INIS)

    Posiva carried out grouting using colloidal silica as the grouting material and with the time stop method as the design approach.Three fans were pre-grouted at Posiva Oy's research space ONKALO demonstration tunnel 2 in autumn 2011 and early winter 2012. Colloidal silica is a mix of one-component colloidal silica and accelerator. Before gelling, colloidal silica behaves like a Newtonian liquid. Colloidal silica's efficiency of penetrating hydraulic apertures in small fractures in rock is significantly better than that of cement-based grout. The grouting design was based on an analytical calculation model. A new technique was used in the grouting implementation, which primarily differed from the previous technique in regard to vacuum pumping and packers. The goal of the first grouting fan in the demonstration tunnel was to check the functionality of the equipment and the method; therefore, the fan was drilled into rock mass with no hydraulic conducting fractures. The second grouting fan was drilled into rock mass with an observed fairly low hydraulic conductivity that was lower than the start criterion established in Posiva Oy's requirements to manage groundwater inflows. Nevertheless, the grouting was carried out. The sealing effect was estimated from the control holes, and a slight improvement in sealing was noted. The holes of the third grouting fan clearly penetrated a water conductive rock mass. The grouting was carried out in two phases, in which the new holes in the second phase were drilled between the existing ones that were drilled in the first phase. In the third fan, the grouting holes of the first phase were noted to be significantly crooked and the second phase grouting holes were drilled in locations that differed from the original design. The quantity of grouting holes was increased in the second phase. The sealing effect was estimated by monitoring the second phase holes and control holes. Based on observations from the control holes

  2. Colloidal silica-grouting in demonstration tunnel 2 in ONKALO

    Energy Technology Data Exchange (ETDEWEB)

    Hollmen, K.; Sievaenen, U. [Saanio and Riekkola Oy, Helsinki (Finland); Funehag, J.; Granberg, N. [Tyrens AB, Stockholm (Sweden); Lyytinen, T.; Syrjaenen, P. [ELY Management Oy, Espoo (Finland)

    2013-12-15

    Posiva carried out grouting using colloidal silica as the grouting material and with the time stop method as the design approach.Three fans were pre-grouted at Posiva Oy's research space ONKALO demonstration tunnel 2 in autumn 2011 and early winter 2012. Colloidal silica is a mix of one-component colloidal silica and accelerator. Before gelling, colloidal silica behaves like a Newtonian liquid. Colloidal silica's efficiency of penetrating hydraulic apertures in small fractures in rock is significantly better than that of cement-based grout. The grouting design was based on an analytical calculation model. A new technique was used in the grouting implementation, which primarily differed from the previous technique in regard to vacuum pumping and packers. The goal of the first grouting fan in the demonstration tunnel was to check the functionality of the equipment and the method; therefore, the fan was drilled into rock mass with no hydraulic conducting fractures. The second grouting fan was drilled into rock mass with an observed fairly low hydraulic conductivity that was lower than the start criterion established in Posiva Oy's requirements to manage groundwater inflows. Nevertheless, the grouting was carried out. The sealing effect was estimated from the control holes, and a slight improvement in sealing was noted. The holes of the third grouting fan clearly penetrated a water conductive rock mass. The grouting was carried out in two phases, in which the new holes in the second phase were drilled between the existing ones that were drilled in the first phase. In the third fan, the grouting holes of the first phase were noted to be significantly crooked and the second phase grouting holes were drilled in locations that differed from the original design. The quantity of grouting holes was increased in the second phase. The sealing effect was estimated by monitoring the second phase holes and control holes. Based on observations from the control holes

  3. Saturated Zone Colloid-Facilitated Transport

    Energy Technology Data Exchange (ETDEWEB)

    A. Wolfsberg; P. Reimus

    2001-12-18

    The purpose of the Saturated Zone Colloid-Facilitated Transport Analysis and Modeling Report (AMR), as outlined in its Work Direction and Planning Document (CRWMS M&O 1999a), is to provide retardation factors for colloids with irreversibly-attached radionuclides, such as plutonium, in the saturated zone (SZ) between their point of entrance from the unsaturated zone (UZ) and downgradient compliance points. Although it is not exclusive to any particular radionuclide release scenario, this AMR especially addresses those scenarios pertaining to evidence from waste degradation experiments, which indicate that plutonium and perhaps other radionuclides may be irreversibly attached to colloids. This report establishes the requirements and elements of the design of a methodology for calculating colloid transport in the saturated zone at Yucca Mountain. In previous Total Systems Performance Assessment (TSPA) analyses, radionuclide-bearing colloids were assumed to be unretarded in their migration. Field experiments in fractured tuff at Yucca Mountain and in porous media at other sites indicate that colloids may, in fact, experience retardation relative to the mean pore-water velocity, suggesting that contaminants associated with colloids should also experience some retardation. Therefore, this analysis incorporates field data where available and a theoretical framework when site-specific data are not available for estimating plausible ranges of retardation factors in both saturated fractured tuff and saturated alluvium. The distribution of retardation factors for tuff and alluvium are developed in a form consistent with the Performance Assessment (PA) analysis framework for simulating radionuclide transport in the saturated zone. To improve on the work performed so far for the saturated-zone flow and transport modeling, concerted effort has been made in quantifying colloid retardation factors in both fractured tuff and alluvium. The fractured tuff analysis used recent data

  4. Colloidal transport phenomena of milk components during convective droplet drying.

    Science.gov (United States)

    Fu, Nan; Woo, Meng Wai; Chen, Xiao Dong

    2011-10-15

    Material segregation has been reported for industrial spray-dried milk powders, which indicates potential material migration during drying process. The relevant colloidal transport phenomenon and the underlying mechanism are still under debate. This study extended the glass-filament single droplet drying technique to observe not only the drying behaviour but also the dissolution behaviour of the correspondingly dried single particle. At progressively longer drying stage, a solvent droplet (water or ethanol) was attached to the semi-dried milk particle and the interaction between the solvent and the particle was video-recorded. Based on the different dissolution and wetting behaviours observed, material migration during milk drying was studied. Fresh skim milk and fresh whole milk were investigated using water and ethanol as solvents. Fat started to accumulate on the surface as soon as drying was started. At the initial stage of drying, the fat layer remained thin and the solubility of the semi-dried milk particle was much affected by lactose and protein present underneath the fat layer. Fat kept accumulating at the surface as drying progressed and the accumulation was completed by the middle stage of drying. The results from drying of model milk materials (pure sodium caseinate solution and lactose/sodium caseinate mixed solution) supported the colloidal transport phenomena observed for the milk drying. When mixed with lactose, sodium caseinate did not form an apparent solvent-resistant protein shell during drying. The extended technique of glass-filament single droplet approach provides a powerful tool in examining the solubility of individual particle after drying. PMID:21703825

  5. Organic and organo-mineral colloids in discontinuous permafrost zone

    Science.gov (United States)

    Pokrovsky, Oleg S.; Manasypov, Rinat M.; Loiko, Sergey V.; Shirokova, Liudmila S.

    2016-09-01

    On-going permafrost thaw in discontinuous permafrost regions produces significant amounts of small permafrost subsidence and depressions, while large lakes are likely to drain into streams and rivers. The intensification of permafrost thaw may alter the size distribution and chemical composition of organo-Fe-Al colloids in lakes and rivers. We used a continuum of surface water bodies, from permafrost subsidence, small depressions and thaw ponds to large lakes and rivers that drain the Western Siberia Lowland (WSL), to assess OC, major and the trace element size distribution between the 20-μm, 5-μm, 1.2-μm, 0.45-μm, 0.22-μm, 0.025-μm and 1-kDa (∼1.4 nm) size fractions. This approach allowed us to distinguish the organic and organo-ferric colloids that were responsible for the transport of trace elements in surface waters and address their evolution during possible physico-chemical and biological processes. Both conventionally dissolved (alkaline earth elements and several micronutrients (Zn, Ba, Mn, and Ni), decreased the degree of their binding to DOM along the landscape continuum, whereas the majority of insoluble TEs (Al, Fe, Co, Cd, Cu, Pb, REEs, Th, and U) remained complexed with DOM in the LMWmetals and organo-Al entities to thaw ponds and lakes; and (ii) Fe2+ oxidation and TE co-precipitation with Fe hydroxides in the presence of surface DOM at groundwater discharge sites within the riparian/hyporheic zones of rivers. Under a warming climate scenario, an increase in the thickness of the thawing depth will intensify the input of inorganic components from deep mineral horizons and possibly underground waters thus producing the enrichment of large lakes in Fe-rich colloids and particles. The speciation of divalent metal micronutrients (Cu, Ni, and Co) and toxic metals (Al, Cd, Pb, and U) that are complexed within DOM will most likely remain conservative. Overall, the WSL's surface water colloidal composition may shift from DOM-rich and DOM-Al-rich to Fe

  6. Interparticle interactions and polarization effects in colloids

    Energy Technology Data Exchange (ETDEWEB)

    Hayter, J.B.

    1987-01-01

    The physics of simple colloidal systems is usually dominated by three independent length scales: the particle size, the average interparticle distance, and the range of the interparticle potential. The dispersed particles typically have characteristic dimensions in the range 5 to 100 nm, often with spherical or cylindrical symmetry. Dispersion densities vary over volume fractions ranging from 0.5 to 10/sup -4/, with the corresponding mean interparticle distances ranging from about 1 to 10 diameters (in spherical systems). The interaction potential may be very short ranged (hard sphere), very long ranged (Coulomb or dipolar), or anywhere in between (screened Coulomb), and the correlations exhibited in the dispersion may be gas-like, liquid-like or crystalline, depending on the range of the potential relative to the interparticle distance. This rich phase behavior is responsible for the remarkable importance of colloidal studies in many areas of condensed matter physics and biophysics, but it poses often intractable problems in developing the statistical mechanical descriptions necessary for an understanding of scattering data from colloids. This paper will review the considerable recent progress in this field, in the context of SANS experiments on colloids in which the potentials are dominated by either screened Coulomb or magnetic dipolar interactions; in the case of magnetic colloids (ferrofluids), the use of polarization analysis will also be discussed. 32 refs., 4 figs.

  7. Interparticle interactions and polarization effects in colloids

    International Nuclear Information System (INIS)

    The physics of simple colloidal systems is usually dominated by three independent length scales: the particle size, the average interparticle distance, and the range of the interparticle potential. The dispersed particles typically have characteristic dimensions in the range 5 to 100 nm, often with spherical or cylindrical symmetry. Dispersion densities vary over volume fractions ranging from 0.5 to 10-4, with the corresponding mean interparticle distances ranging from about 1 to 10 diameters (in spherical systems). The interaction potential may be very short ranged (hard sphere), very long ranged (Coulomb or dipolar), or anywhere in between (screened Coulomb), and the correlations exhibited in the dispersion may be gas-like, liquid-like or crystalline, depending on the range of the potential relative to the interparticle distance. This rich phase behavior is responsible for the remarkable importance of colloidal studies in many areas of condensed matter physics and biophysics, but it poses often intractable problems in developing the statistical mechanical descriptions necessary for an understanding of scattering data from colloids. This paper will review the considerable recent progress in this field, in the context of SANS experiments on colloids in which the potentials are dominated by either screened Coulomb or magnetic dipolar interactions; in the case of magnetic colloids (ferrofluids), the use of polarization analysis will also be discussed. 32 refs., 4 figs

  8. Synthesis of Ag-colloids in sol-gel derived SiO2-coatings on glass

    OpenAIRE

    Mennig, Martin; Schmitt, Mike; Schmidt, Helmut K.

    1997-01-01

    Ag colloid-containing coatings on soda lime glass and fused silica are prepared via the sol-gel process. To incorporate Ag+-ions in the coatings homogeneously, they are stabilized by a functionalised silane (aminosilane) and then mixed with the basic sol prepared from 3-glycidoxypropyl trimethoxysilane (GPTS) and tetraethoxysilane (TEOS). Crack-free and transparent coatings with a thickness of 0.5 to 1.2 µm, are obtained by heat treatment between 120°C and 600°C. The Ag-colloid formatio...

  9. In vivo biodegradation of colloidal quantum dots by a freshwater invertebrate, Daphnia magna

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Dongwook; Kim, Min Jung; Park, Chansik; Park, Jaehong [Department of Chemistry, Hanyang University, Seoul 133-791 (Korea, Republic of); Choi, Kyungho [Department of Environmental Health, Seoul National University, Seoul 151-742 (Korea, Republic of); Yoon, Tae Hyun, E-mail: thyoon@gmail.com [Department of Chemistry, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2012-06-15

    Impacts of planktonic invertebrate, Daphnia magna, on the speciation of colloidal quantum dots (QD) were investigated using fluorescence spectromicroscopic technique. Well-dispersed {sup GA/TOPO}QD were prepared by forming a supramolecular assembly of hydrophobic {sup TOPO}QD with biomacromolecules (i.e., Gum Arabic, GA). Biological degradation of this nanomaterial was monitored by fluorescence spectromicroscopic methods. Our study confirmed the major uptake pathway of manufactured nanomaterials and in vivo biodegradation processes in a well-known toxicity test organism, D. magna. In addition, we also found that D. magna can induce significant deterioration of aquatic media by releasing fragments of partially degraded QD colloids. These biological processes may significantly change the predicted toxicities of nanomaterials in aquatic environments. Thus, we propose that the impacts of aquatic living organisms on the environmental fate of manufactured nanomaterials (MNs) should be carefully taken into account when assessing the risk of MNs to the environment and human health.

  10. In vivo biodegradation of colloidal quantum dots by a freshwater invertebrate, Daphnia magna

    International Nuclear Information System (INIS)

    Impacts of planktonic invertebrate, Daphnia magna, on the speciation of colloidal quantum dots (QD) were investigated using fluorescence spectromicroscopic technique. Well-dispersed GA/TOPOQD were prepared by forming a supramolecular assembly of hydrophobic TOPOQD with biomacromolecules (i.e., Gum Arabic, GA). Biological degradation of this nanomaterial was monitored by fluorescence spectromicroscopic methods. Our study confirmed the major uptake pathway of manufactured nanomaterials and in vivo biodegradation processes in a well-known toxicity test organism, D. magna. In addition, we also found that D. magna can induce significant deterioration of aquatic media by releasing fragments of partially degraded QD colloids. These biological processes may significantly change the predicted toxicities of nanomaterials in aquatic environments. Thus, we propose that the impacts of aquatic living organisms on the environmental fate of manufactured nanomaterials (MNs) should be carefully taken into account when assessing the risk of MNs to the environment and human health.

  11. Pickering emulsions stabilized by oppositely charged colloids: Stability and pattern formation

    Science.gov (United States)

    Christdoss Pushpam, Sam David; Basavaraj, Madivala G.; Mani, Ethayaraja

    2015-11-01

    A binary mixture of oppositely charged colloids can be used to stabilize water-in-oil or oil-in-water emulsions. A Monte Carlo simulation study to address the effect of charge ratio of colloids on the stability of Pickering emulsions is presented. The colloidal particles at the interface are modeled as aligned dipolar hard spheres, with attractive interaction between unlike-charged and repulsive interaction between like-charged particles. The optimum composition (fraction of positively charged particles) required for the stabilization corresponds to a minimum in the interaction energy per particle. In addition, for each charge ratio, there is a range of compositions where emulsions can be stabilized. The structural arrangement of particles or the pattern formation at the emulsion interface is strongly influenced by the charge ratio. We find well-mixed isotropic, square, and hexagonal arrangements of particles on the emulsion surface for different compositions at a given charge ratio. The distribution of coordination numbers is calculated to characterize structural features. The simulation study is useful for the rational design of Pickering emulsifications wherein oppositely charged colloids are used, and for the control of pattern formation that can be useful for the synthesis of colloidosomes and porous shells derived thereof.

  12. Phase I - Laboratory Study Effects of Cement Grout Structures on Colloid Formation from SRS Soils

    International Nuclear Information System (INIS)

    Studies were conducted to better understand the influence of grout structures and fills on colloid formation. Low-Level Waste is disposed in concrete vaults and trenches at the E-Area Low-Level Waste Facility (LLWF). Two types of enhanced trench disposal are approved for use including; Intimately-Mixed Cement-Stabilized waste forms, such as Ashcrete and Blowcrete resulting from operation of the Consolidated Incinerator Facility, and Cement-Stabilized Encapsulated waste, where waste forms (e.g., contaminated equipment) will be surrounded by a grout or other cementitious material. The presence of concrete structures and process of grouting in trenches are expected to generate colloids, both from the grout itself and as a result of the interactions of these cementitious materials and their degradation products with the surrounding soils. The extent of occurrence, mobility, and influence on contaminant transport of colloidal materials in aquifer systems is the subject of this study. The intent of this study is not to modify the PA but to aid in our understanding of the significance of this phenomenon. Information generated in this study will help in considering whether colloid-enhanced contaminant migration should be considered in establishing waste acceptance criteria and in the design and development of waste disposal systems

  13. Selected Ga-68-siderophores versus Ga-68-colloid and Ga-68-citrate: biodistribution and small animal imaging in mice

    Czech Academy of Sciences Publication Activity Database

    Petřík, M.; Vlčková, A.; Nový, Z.; Urbánek, Lubor; Haas, H.; Decristoforo, C.

    2015-01-01

    Roč. 159, č. 1 (2015), s. 60-66. ISSN 1213-8118 R&D Projects: GA MŠk(CZ) LO1304 Institutional support: RVO:61389030 Keywords : gallium-68 * siderophores * colloid Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.200, year: 2014

  14. Influence of heteroaggregation processes between intrinsic colloids and carrier colloids on cerium(III) mobility through fractured carbonate rocks.

    Science.gov (United States)

    Tran, Emily; Klein Ben-David, Ofra; Teutch, Nadya; Weisbrod, Noam

    2016-09-01

    Colloid facilitated transport of radionuclides has been implicated as a major transport vector for leaked nuclear waste in the subsurface. Sorption of radionuclides onto mobile carrier colloids such as bentonite and humic acid often accelerates their transport through saturated rock fractures. Here, we employ column studies to investigate the impact of intrinsic, bentonite and humic acid colloids on the transport and recovery of Ce(III) through a fractured chalk core. Ce(III) recovery where either bentonite or humic colloids were added was 7.7-26.9% Ce for all experiments. Greater Ce(III) recovery was observed when both types of carrier colloids were present (25.4-37.4%). When only bentonite colloids were present, Ce(III) appeared to be fractionated between chemical sorption to the bentonite colloid surfaces and heteroaggregation of bentonite colloids with intrinsic carbonate colloids, precipitated naturally in solution. However, scanning electron microscope (SEM) images and colloid stability experiments reveal that in suspensions of humic acid colloids, colloid-facilitated Ce(III) migration results only from the latter attachment mechanism rather than from chemical sorption. This observed heteroaggregation of different colloid types may be an important factor to consider when predicting potential mobility of leaked radionuclides from geological repositories for spent fuel located in carbonate rocks. PMID:27183207

  15. Neptunium Colloidal Behaviors in Present of Humic Acids

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>The colloidal-borne facilitated transport of actinides is an important part of radionuclide migration investigation in HLW geological disposal. In the present studies, Np colloidal behaviors in present of

  16. Inorganic passivation and doping control in colloidal quantum dot photovoltaics

    KAUST Repository

    Hoogland, Sjoerd H.

    2012-01-01

    We discuss strategies to reduce midgap trap state densities in colloidal quantum dot films and requirements to control doping type and magnitude. We demonstrate that these improvements result in colloidal quantum dot solar cells with certified 7.0% efficiency.

  17. Synthesis of functional nanomaterials via colloidal mask templating and glancing angle deposition (GLAD)”

    DEFF Research Database (Denmark)

    Dolatshahi-Pirouz, Alireza; Jensen, Thomas Bo; Vorup-Jensen, Thomas;

    2010-01-01

    We present a simple method for the fabrication of separated brush-like networks with both improved optical and biological properties. The brush networks were fabricated by combing the glancing angle deposition (GLAD) technique with colloidal mask templating. By changing the deposition angle durin...... of multifunctional nanomaterials which could have potential impact on devices where both controlled optical properties and cell surface interactions are needed (for instance controlled cell adhesion on optical biosensor materials)....

  18. Premelting at Defects Within Bulk Colloidal Crystals

    Science.gov (United States)

    Alsayed, A. M.; Islam, M. F.; Zhang, J.; Collings, P. J.; Yodh, A. G.

    2005-08-01

    Premelting is the localized loss of crystalline order at surfaces and defects at temperatures below the bulk melting transition. It can be thought of as the nucleation of the melting process. Premelting has been observed at the surfaces of crystals but not within. We report observations of premelting at grain boundaries and dislocations within bulk colloidal crystals using real-time video microscopy. The crystals are equilibrium close-packed, three-dimensional colloidal structures made from thermally responsive microgel spheres. Particle tracking reveals increased disorder in crystalline regions bordering defects, the amount of which depends on the type of defect, distance from the defect, and particle volume fraction. Our observations suggest that interfacial free energy is the crucial parameter for premelting in colloidal and atomic-scale crystals.

  19. Colloid Release From Differently Managed Loess Soil

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad; Schjønning, Per; Møldrup, Per;

    2012-01-01

    of NPK fertilizer had a destabilizing effect on the WSA and also caused a decrease in the cation exchange capacity of the soils. The mean tensile strength was positively correlated to the colloid release rate and the content of WDC after 2 min of shaking and therefore to the amount of clay not......The content of water-dispersible colloids (WDC) in a soil can have a major impact on soil functions, such as permeability to water and air, and on soil strength, which can impair soil fertility and workability. In addition, the content of WDC in the soil may increase the risk of nutrient loss and...... of colloid-facilitated transport of strongly sorbing compounds. In the present study, soils from the Bad Lauchstadt long-term static fertilizer experiment with different management histories were investigated to relate basic soil properties to the content of WDC, the content of water...

  20. Boundaries Matter for Confined Colloidal Glasses

    Science.gov (United States)

    Hunter, Gary; Edmond, Kazem V.; Weeks, Eric R.

    2012-02-01

    We confine dense colloidal suspensions within emulsion droplets to examine how confinement and properties of the confining medium affect the colloidal glass transition. Samples are imaged via fast confocal microscopy. By observing a wide range of droplet sizes and varying the viscosity of the external continuous phase, we separate finite size and boundary effects on particle motions within the droplet. Suspensions are composed of binary PMMA spheres in organic solvents while the external phases are simple mixtures of water and glycerol. In analogy with molecular super-cooled liquids and thin-film polymers, we find that confinement effects in colloidal systems are not merely functions of the finite size of the system, but are strongly dependent on the viscosity of the confining medium and interactions between particles and the interface of the two phases.

  1. Colloid migration in groundwaters: Geochemical interactions of radionuclides with natural colloids. Final report

    International Nuclear Information System (INIS)

    In this joint research programme the significance of groundwater colloids in far field radionuclide migration has been studied. The characterization, quantification and theoretical interpretation of colloid-borne transport phenomena for radionuclides were the main objectives of this research programme. Groundwaters, colloids and sediments were sampled from aquifer system overlying a saltdome in the Gorleben area in northern Germany and were characterized by various analytical methods (ICP-MS, ICP-AES, neutron activation analysis (NAA), DOC-Analyser, HPIC, potentiometric titration). Different natural isotopes (2H, 3H, 13C, 14C, 18O, 34S, U/Th decay series) were determined and their ratios were compared with one another in the order to ascertain the provenance of the groundwater colloids. The investigated groundwaters contain substantial amounts of colloids mainly composed of humic and fulvic acids loaded with various metal ions. The chemical interaction of radionuclide ions of various oxidation states (Am, Eu, for M(III), Th, Pu for M(IV), Np for M(V) and U for M(VI)) with groundwater colloids was investigated in order to elucidate the colloid facilitated migration behaviour of actinides in a given aquifer system. Transport process studies with generated pseudocolloids of radionuclides in various oxidation states were undertaken in scaled column experiments, pre-equilibrated with colloid rich Gorleben groundwater. A modelling programme was developed to predict chemical transport of radionuclides in the presence of humic colloids using a modified version of the CHEMTARD code. Modelling predictions have generated acceptable results for Eu, Am and U and poorer agreement between experimental and modelling results for Th and Np as a result of more limited data. (orig.)

  2. Colloidal interactions in two-dimensional nematic emulsions

    Indian Academy of Sciences (India)

    N M Silvestre; P Patrício; M M Telo Da Gama

    2005-06-01

    We review theoretical and experimental work on colloidal interactions in two-dimensional (2D) nematic emulsions. We pay particular attention to the effects of (i) the nematic elastic constants, (ii) the size of the colloids, and (iii) the boundary conditions at the particles and the container. We consider the interactions between colloids and fluid (deformable) interfaces and the shape of fluid colloids in smectic-C films.

  3. Displacement of Colloidal Dispersions in Porous Media: Experimental & Numerical Approaches

    OpenAIRE

    AHMADI-SENICHAULT, Azita; OMARI, Aziz; BERTIN, Henri

    2015-01-01

    The displacement of colloidal dispersions is of particular interest in many applications ranging from environmental issues to petroleum recovery. Natural porous media such as soils, aquifers or reservoirs contain colloidal particles of different nature (bacteria, viruses, clay, metal complexes …). Colloids can act as vehicles for micro organisms’ transport in aquifers causing danger for human health. In petroleum recovery techniques, water containing colloids is sometimes injected and their r...

  4. Preparation and Characterization of Polymer-Stabilized Ruthenium-Platinum and Ruthenium-Palladium Bimetallic Colloids and Their Catalytic Properties for Hydrogenation of o-Chloronitrobenzene.

    Science.gov (United States)

    Liu; Yu; Liu; Zheng

    1999-06-15

    Colloidal dispersions of poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium-platinum and ruthenium-palladium bimetallic colloids were prepared by NaBH4 reduction of the corresponding mixed-metal salts at room temperature and characterized by TEM, XPS, and XRD. The resulting bimetallic colloids were used as catalysts for the selective hydrogenation of o-chloronitrobenzene (o-CNB) in methanol at 303 K under 0.1 MPa of hydrogen. It was observed that the catalytic performance of PVP-stabilized ruthenium-platinum colloids (PVP-Ru/Pt) and ruthenium-palladium colloids (PVP-Ru/Pd) was dependent on their compositions and could be remarkably affected by some added metal cations. In the presence of cobalt ion, nearly 100% selectivity to o-chloroaniline (o-CAN) was achieved over PVP-Ru/Pt colloids at 100% conversion of o-CNB, with an activity two orders of magnitude higher than that of monometallic PVP-Ru colloid. Copyright 1999 Academic Press. PMID:10339363

  5. [Method of determining the colloidal status of the vitreous body].

    Science.gov (United States)

    Agafonov, V A; Anisimov, S I; Fedorov, S N

    1984-12-01

    A new method for the quantitative estimation of the vitreous body colloidal state has been suggested. For realization of the method a fragment of the vitreous body and an equal volume of water are dried out, and the drying time is registered. The higher is the ratio between the drying time of the vitreous body fragment and water, the higher is the density of the vitreous body gel. The drying out of the vitreous body fragment and water on the analytical balance cups permits the registration of the drying out process in the time course. Thus some additional parameters are obtained that characterize the object studied more completely. The method can be used in experimental and clinical investigations of the vitreous body and other biological liquids. PMID:6095956

  6. Fabrication of anisotropic multifunctional colloidal carriers

    Science.gov (United States)

    Jerri, Huda A.

    The field of colloidal assembly has grown tremendously in recent years, although the direct or template-assisted methods used to fabricate complex colloidal constructions from monodisperse micro- and nanoparticles have been generally demonstrated on model materials. In this work, novel core particle syntheses, particle functionalizations and bottom-up assembly techniques are presented to create functional colloidal devices. Using particle lithography, high-information colloidal vectors have been developed and modified with imaging and targeting agents. Localized nanoscale patches have been reliably positioned on microparticles to serve as foundations for further chemical or physical modifications. Site-specific placement of RGD targeting ligands has been achieved in these lithographed patches. Preferential uptake of these targeted vectors by RGD-specific 3T3 fibroblasts was verified using confocal laser scanning microscopy. A transition was made from the functionalization of model imaging core particles to the lithography of colloidal cartridges, in an effort to construct colloidal syringes with specialized, programmable release profiles. A variety of functional, pH-sensitive fluorescent cores were engineered to respond to solution conditions. When triggered, the diverse composite core microparticles and reservoir microcapsules released embedded fluorescent moieties such as dye molecules, and fluorophore-conjugated nanoparticles. The microcapsules, created using layer-by-layer polyelectrolyte deposition on sacrificial templates, were selectively modified with a robust coating. The pH-responsive anisotropic reservoir microcapsules were extremely stable in solution, and exhibited a "Lazarus" functionality of rehydrating to their original state following desiccation. A snapshot of focused-release of core constituents through the lone opening in colloidal monotremes has been obtained by anisotropically-functionalizing degradable cores with barrier shells. Additionally

  7. Self-assembly of colloidal surfactants

    Science.gov (United States)

    Kegel, Willem

    2012-02-01

    We developed colloidal dumbbells with a rough and a smooth part, based on a method reported in Ref. [1]. Specific attraction between the smooth parts occurs upon addition of non-adsorbing polymers of appropriate size. We present the first results in terms of the assemblies that emerge in these systems. [4pt] [1] D.J. Kraft, W.S. Vlug, C.M. van Kats, A. van Blaaderen, A. Imhof and W.K. Kegel, Self-assembly of colloids with liquid protrusions, J. Am. Chem. Soc. 131, 1182, (2009)

  8. Synthesis of Ionic Colloidal Crystals (ICCs)

    Science.gov (United States)

    Maskaly, Garry R.; Garcia, R. Edwin; Carter, W. Craig; Chiang, Yet-Ming

    2003-03-01

    Binary ionic colloidal crystals (ICCs) have been produced by ordered heterocoagulation of colloidal mixtures of silica (negative surface charge) and polystyrene functionalized with amidine (positive surface charge) suspended in isopropanol. Experimental conditions predicted by the theoretical model discussed in a separate talk have been implemented to obtain heterocoagulation of these particles in the rocksalt structure. To our knowledge, this is the first experimental demonstration of the ICC concept. The importance of various experimental parameters on ICC formation is discussed. Particle dynamics simulations are carried out to provide insight into the kinetics of ICCs. Potential applications are discussed.

  9. Dynamics of colloidal particles in ice

    KAUST Repository

    Spannuth, Melissa

    2011-01-01

    We use x-ray photon correlation spectroscopy (XPCS) to probe the dynamics of colloidal particles in polycrystalline ice. During freezing, the dendritic ice morphology and rejection of particles from the ice created regions of high particle density, where some of the colloids were forced into contact and formed disordered aggregates. The particles in these high density regions underwent ballistic motion, with a characteristic velocity that increased with temperature. This ballistic motion is coupled with both stretched and compressed exponential decays of the intensity autocorrelation function. We suggest that this behavior could result from ice grain boundary migration. © 2011 American Institute of Physics.

  10. Wetting reversal in colloid-polymer systems.

    Science.gov (United States)

    Blokhuis, Edgar M; Kuipers, Joris

    2010-05-01

    The wetting of a phase-separated colloid-polymer mixture in contact with a hard wall is analyzed using free volume theory in a Nakanishi-Fisher-type approach. We present results for the wetting phase diagram for several model approximations. Our analysis is compared with a previous analysis by Aarts [J. Chem. Phys. 120, 1973 (2004)]. We find that there is a crossover from wetting to drying at a threshold value for the colloid-polymer size ratio and that the transitions are close to the critical point and of second order in nature. PMID:20866234

  11. Binary Colloidal Alloy Test-5: Phase Separation

    Science.gov (United States)

    Lynch, Matthew; Weitz, David A.; Lu, Peter J.

    2008-01-01

    The Binary Colloidal Alloy Test - 5: Phase Separation (BCAT-5-PhaseSep) experiment will photograph initially randomized colloidal samples onboard the ISS to determine their resulting structure over time. This allows the scientists to capture the kinetics (evolution) of their samples, as well as the final equilibrium state of each sample. BCAT-5-PhaseSep studies collapse (phase separation rates that impact product shelf-life); in microgravity the physics of collapse is not masked by being reduced to a simple top and bottom phase as it is on Earth.

  12. Shape recognition of microbial cells by colloidal cell imprints

    NARCIS (Netherlands)

    Borovicka, J.; Stoyanov, S.D.; Paunov, V.N.

    2013-01-01

    We have engineered a class of colloids which can recognize the shape and size of targeted microbial cells and selectively bind to their surfaces. These imprinted colloid particles, which we called "colloid antibodies", were fabricated by partial fragmentation of silica shells obtained by templating

  13. A general method to coat colloidal particles with titiana

    NARCIS (Netherlands)

    Demirors, A.F.; van Blaaderen, A.; Imhof, A.

    2010-01-01

    We describe a general one-pot method for coating colloidal particles with amorphous titania. Various colloidal particles such as silica particles, large silver colloids, gibbsite platelets, and polystyrene spheres were successfully coated with a titania shell. Although there are several ways of coat

  14. Interplay between Colloids and Interfaces : Emulsions, Foams and Microtubes

    NARCIS (Netherlands)

    de Folter, J.W.J.

    2013-01-01

    The central theme of this thesis is the interplay between colloids and interfaces. The adsorption of colloids at fluid-fluid interfaces is the main topic and covers Chapters 2-6. Pickering emulsions where colloidal particles act as emulsion stabilizers in the absence of surfactants are studied in a

  15. Dimeric and dipolar ground state orders in colloidal molecular crystals

    OpenAIRE

    Emmanuel Trizac; Samir El Shawish; Jure Dobnikar

    2010-01-01

    A two dimensional colloidal suspension subject to a periodic substrate evolves into a colloidal molecular crystal under situationsofstrongconfinement. Wefocusonthelongrangeorientationalordertherebyemerging, inthegroundstate. We study by simulations the situations where in each trap lies a pair of identical colloids, or alternatively a pair of oppositelychargedmacroions. We consider square or triangular geometries for the periodic confinement, together with less symmetric distorted lattices.Um...

  16. Ultrasound Propagation in Colloidal Dispersions.

    Science.gov (United States)

    Sherman, Nigel E.

    Available from UMI in association with The British Library. This thesis describes apparatus and techniques for making ultrasonic measurements in fluids and applications of them to measurements of ultrasonic parameters in colloidal dispersions. A brief description of the properties and uses of ultrasound propagation in dispersions is followed by an extensive review of theories which relate the particulate properties of the dispersions to the measurable ultrasonic parameters, velocity (c) and attenuation (alpha ). Measurement principles are outlined related to the design of near-field measurement methods and the development of three techniques is described. These are shown to give results which are both highly self-consistent and in excellent agreement with a far-field method. Measurements of alpha and c for model dispersions of glass spheres in Newtonian liquids are shown to be in good agreement with the relevant theory when particle polydispersity is taken into account. For structured fluids as the continuous phase, the alpha and c data for suspensions of spheres are used to obtain the continuous phase viscosity ( eta). The alpha data agree approximately with the macroscopic viscosity, but the velocity data requires the introduction of a shear elastic term and the revision of theory in order to obtain agreement. Attenuation as a function of barite concentration in Newtonian liquids was investigated and the ultrasonic particle radius was found to be systematically larger than expected. This is attributed to particle rugosity. Measurements of alpha and c using non-gelling aqueous kaolinite suspensions are shown to agree well with theory when the eccentricity and the interactions of particles are taken into account. For gelling aqueous bentonite suspensions, alpha and c were found to be time-dependent over a period of several days following initial dispersion. The observed increases in both alpha and c are interpreted in terms of a growth in gel fraction and shear

  17. Proceedings of the fifth Asian conference on colloid and interface science

    International Nuclear Information System (INIS)

    Colloid and Interfacial (Surface) phenomena constitute a field of science which today embodies concepts that are fundamental to the understanding of both microscopic and macroscopic behaviors, and hence the design of a wide range of system of great potential interest. Now a days, this branch of science has entered a new era where modern development and knowledge of physics, chemistry, biology, material science, pharmacy, engineering, etc., have been extensively exploited and adopted. As a result, both fundamental and applied aspects of colloid and surface science have advanced over the years, for example, starting from tertiary oil recovery to nanotechnology to environmental science. These multifaceted fields also find applications in everyday life, and helps in understanding the intricacies of the life process. All these developments have enriched the field, which is considered to be the front-line/emerging area of research in the national and international scenario. Recent growth of modern colloid and interface science in Asian countries has encouraged the scientists to share in-depth discussions within the regional scientific community in Asia. Scientific topics covered by the conference were: Adsorption, Molecular Assemblies, Colloids and Dispersions, Gels, Surfaces and Interfaces, Thin Films, Membranes, Nanomaterials, Biomaterials, Devices and Applications etc. Papers relevant to INIS are indexed separately

  18. Gray Correlation Analysis on the Relationship Between Colloidal Structure and Chemical Component of Asphalt Colloid and Performance

    OpenAIRE

    Cao, X J; Y. J. Ding

    2015-01-01

    Asphalt is considered a colloidal material and it is important to study the relationship between its colloidal structure, chemical components and performance. The aromatic nucleus content of asphalt at different depth analysed by attenuated total reflection (ATR) was taken as the index of colloid structure. The gray correlation was used to analyse the relationship between colloidal structure and chemical components of asphalt gel and performance. The results show that the correlation degree b...

  19. Adjuvant therapy of Dukes' C colon cancer by intra-arterial P-32 colloid for internal radiation therapy of the liver

    Energy Technology Data Exchange (ETDEWEB)

    Grady, E.D.

    1984-09-01

    To prevent probable occult metastatic liver cancer from progressing to clinical disease, the author used internal radiation therapy as an effective adjuvant to surgical excision of primary Dukes' C colonic cancer. A calculated radiation dose of 5000 rads was delivered to the liver by injecting radioactive 32-P chromic phosphate colloid through the superior mesenteric and celiac arteries. When this was done, the colloid passed through the intestines and was mixed thoroughly with the blood and delivered to the liver by the portal vein. The Kupffer cells in the liver trapped the colloid, and a minimum amount passed through the liver and got into the general circulation. This kept the amount of colloid deposited in the bone marrow to a minimum. In a phase-I pilot study in which nine patients were treated, no serious side effects were noted. In eight patients, the liver has remained free of cancer for more than 1 year.

  20. Sorption of nuclides on organic colloids and their migration through porous media. (2)

    International Nuclear Information System (INIS)

    Model V and NICA-Donnan model, which can describe the interaction of humic acids with metals, were reviewed and CD-MUSIC model, which is a typical surface complexation model of metals with solid surfaces, was also introduced. In Model V, the equilibrium of chemicals among water in environment, sediments and solids is considered. In NICA-Donnan model, the electrostatic interactions due to the difference in the activities between humic acids and bulk is included and the heterogeneity of binding sites in humic acids is also taken into account. In this report, the problems of these models was summarized and the future development was discussed. In experimental part, the proton dissociation reaction and the interaction with Cu2+ were investigated, by titration experiments using Aldrich humic acids. Considering NICA-Donnan model, the interaction parameters of the proton dissociation reaction and the interaction with Cu2+ were evaluated. In calculation part, the mixing characteristics of water flow in fracture junctions was discussed by Real-coded Lattice Gas model. The mixing ratio at the outlet of fracture junctions was analyzed qualitatively and quantitatively as a function of Peclet number. Furthermore, the trajectory of colloid transport in the laminar flow at bending tube was calculated, and the effect of the mass of colloid was qualitatively studied. The random walk and diffusion phenomena of colloids were found to be successfully calculated by Real-coded Lattice Gas model developed in this work. (author)

  1. Sampling and analysis of groundwater colloids. A literature review

    International Nuclear Information System (INIS)

    The purpose of this literature study was to give basic information of colloids: their formation, colloid material, sampling and characterisation of groundwater colloids. Colloids are commonly refereed to as particles in the size range of 1 nm to 1000 nm. They are defined as a suspension of solid material in a liquid that does not appear to separate even after a long period of time. Colloids can be formed from a variety of inorganic or organic material. Inorganic colloids in natural groundwaters are formed by physical fragmentation of the host rock or by precipitation. The water chemistry strongly controls the stability of colloids. The amount of colloid particles in a solution tends to decrease with the increasing ionic strength of the solution. Increases in pH and organic material tend to increase the stability of colloids. The mobility of colloids in a porous medium is controlled mainly by groundwater movement, sedimentation, diffusion and interception. Factors controlling sampling artefacts are oxygen diffusion: leads to e.g. calcite precipitation, pumping rates and filtering techniques. Efforts to minimise artefact formation should be taken if the scope of the sampling programme is to study the colloid particles. The colloid phase size distribution can be determined by light scattering systems, laser induced break down or by single particle analysis using SEM micrographs. Elemental compositions can be analysed with EDS spectrometry from single colloid particles. Bulk compositions of the colloid phase can be analysed with e.g. ICP-MS analyser. The results of this study can be used as guidelines for groundwater colloid samplings. Recommendations for future work are listed in the conclusions of this report. (orig.)

  2. Turbulent mixing

    OpenAIRE

    Dimotakis, Paul E.

    2005-01-01

    The ability of turbulent flows to effectively mix entrained fluids to a molecular scale is a vital part of the dynamics of such flows, with wide-ranging consequences in nature and engineering. It is a considerable experimental, theoretical, modeling, and computational challenge to capture and represent turbulent mixing which, for high Reynolds number (Re) flows, occurs across a spectrum of scales of considerable span. This consideration alone places high-Re mixing phenomena beyond the reach o...

  3. Radio-active colloids in the functional exploration of the reticulo-endothelium system; Les colloides radioactifs dans l'exploration fonctionnelle du systeme reticulo-endothelial

    Energy Technology Data Exchange (ETDEWEB)

    Chivot, J.J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-03-01

    A historical review describes the reticulo-endothelial system (R.E.S.) and aims at defining it and at explaining its operation. The methods used for its examination and the colloids utilized are considered. The author has been led to prepare a special type of colloid: an albuminous complex containing radio-iodine, 'C.A. {sup 131}I', whose method of preparation and physical and biological examination are described. A human albumin, having a known optical density in solution, is heated until a change in the optical density indicates that an aggregation of the proteinic molecules has occurred. The denatured protein is iodated with {sup 131}I. Electrophoretic, ultracentrifuge and autoradiographic controls are then carried out. This atoxic and metabolisable preparation of biological origin is compared with the better defined colloidal gold which serves as reference. C.A.{sup 131}I is injected into mice. It is shown by radioactivity measurements, auto-radiographies on sections of the whole animal, and anthropo-gamma-metric detections that a high concentration occurs in the S.R.E. of the liver. These static results are only of limited importance however compared to those obtained from an in vivo study of the phenomenon. The author records the changes in the radioactivity of the blood derived from the carotid artery using a well-scintillator. He obtains directly a curve of the radioactivity of blood having a decreasing exponential form; the mathematical expression describing this curve is given. The biological half-life T 1/2 of the colloid in the blood is a measure of its phagocytosis by the S.R.E. cells. A supplementary check is provided by the direct recording of the hepatic activity using a suitably collimated exterior detector. A curve of increasing-exponential form is obtained and its parameters are corollary to the preceding curve. These tests carried out on guinea-pigs and rats make it possible to give to the S.R.E. a phagocytic index which is

  4. Responsivity improvement in PbS colloidal quantum dot photoconductors using colloidal gold nanoparticles

    OpenAIRE

    Heves, Emre; Öztürk, Cem; Ozturk, Cem; Gürbüz, Yaşar; Gurbuz, Yasar

    2013-01-01

    A study is presented on improving the absorption of the PbS colloidal quantum dot (CQD) films using plasmonic scattering. Unlike previous methods that include high temperature annealing, an integrated circuits (IC) compatible method of introducing colloidal gold nanoparticles to PbS film during the spin deposition process is developed. The devices are composed of eight layers of PbS and gold nanoparticles are spin cast after the fourth layer that places them in the middle, sandwiched between ...

  5. Colloidal models. A bit of history

    NARCIS (Netherlands)

    Lyklema, J.

    2015-01-01

    This paper offers an anthology on developments in colloid and interface science emphasizing themes that may be of direct or indirect interest to Interfaces Against Pollution. Topics include the determination of Avogadro’s number, development in the insight into driving forces for double layer format

  6. Dynamics of Colloids Confined in Microcylinders

    NARCIS (Netherlands)

    Ghosh, S.; Wijnperle, D.; Mugele, F.; Duits, M.H.G.

    2016-01-01

    We studied both global and local effects of cylindrical confinement on the diffusive behavior of hard sphere (HS) colloids. Using confocal scanning laser microscopy (CSLM) and particle tracking, we measured the mean squared displacement (MSD) of 1 micron sized silica particles in water–glycerol. Thi

  7. Geochemistry of colloid systems. For earth scientists

    NARCIS (Netherlands)

    Nickel, E.

    1979-01-01

    The second part of the title of this book gives an indication for whom it has been written. It is a real 'synthesizer'. Throughout ten chapters the reader is introduced into the highly complex matter of colloid chemistry and its role in geochemistry, pedology, oceanography, and geology.

  8. Nucleation in suspensions of anisotropic colloids

    NARCIS (Netherlands)

    Schilling, T.; Frenkel, D.

    2005-01-01

    We report Monte Carlo studies of liquid crystal nucleation in two types of anisotropic colloidal systems: hard rods and hard ellipsoids. In both cases we find that nucleation pathways differ strongly from the pathways in systems of spherical particles. Short hard rods show an effect of self-poisonin

  9. Advanced Colloids Experiment (ACE-T1)

    Science.gov (United States)

    Meyer, William V.; Sicker, Ron; Brown, Dan; Eustace, John

    2015-01-01

    Increment 45 - 46 Science Symposium presentation of Advanced Colloids Experiment (ACE-T1) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.

  10. Synthesis and properties of colloidal heteronanocrystals

    NARCIS (Netherlands)

    de Mello Donegá, C.

    2011-01-01

    Colloidal heteronanocrystals (HNCs) can be regarded as solution-grown inorganic–organic hybrid nanomaterials, since they consist of inorganic nanoparticles that are coated with a layer of organic ligand molecules. The hybrid nature of these nanostructures provides great flexibility in engineering th

  11. Towards conducting inks: polypyrrole-silver colloids

    Czech Academy of Sciences Publication Activity Database

    Omastová, M.; Bober, Patrycja; Morávková, Zuzana; Peřinka, N.; Kaplanová, M.; Syrový, T.; Hromádková, Jiřina; Trchová, Miroslava; Stejskal, Jaroslav

    2014-01-01

    Roč. 122, 10 March (2014), s. 296-302. ISSN 0013-4686 R&D Projects: GA TA ČR TE01020022; GA ČR(CZ) GA13-00270S Institutional support: RVO:61389013 Keywords : conducting inks * polypyrrole * colloids Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 4.504, year: 2014

  12. Dipolar structures in colloidal magnetite dispersions

    NARCIS (Netherlands)

    Klokkenburg, Mark

    2007-01-01

    Dipolar structures in liquid colloidal dispersions comprising well-defined magnetite (Fe3O4) nanoparticles with a permanent magnetic dipole moment are analyzed on a single-particle level by in situ cryogenic transmission electron microscopy (2D). Compared to conventional ferrofluids, these dispersio

  13. Photoelectrochromism in Tungsten Trioxide Colloidal Solutions

    Science.gov (United States)

    Chenthamarakshan, C. R.; Tacconi, N. R. de; Xu, Lucy; Rajeshwar, Krishnan

    2004-01-01

    Photophysical and photochemical properties of semiconductor metal oxide colloids are studied in the context of photoelectrochemical conversion and storage of solar energy. The experiment teaches the instrumental principles of UV-visible spectrophotometry, spectral acquisition and background subtraction strategies and diode array spectrometers.

  14. Molecular Photoacoustic Tomography with Colloidal Nanobeacons**

    OpenAIRE

    Pan, Dipanjan; Pramanik, Manojit; Senpan, Angana; Yang, Xinmai; Song, Kwang H.; Scott, Mike J.; Zhang, Huiying; Gaffney, Patrick J.; Wickline, Samuel A; Wang, Lihong V.; Lanza, Gregory M.

    2009-01-01

    Vascularly constrained, “soft” colloidal gold nanobeacons (GNB) demonstrate for the first time that GNBs can be characterized as exogenous photoacoustic contrast agents for targeted detection of fibrin, a major biochemical feature of thrombus. Fibrin-targeted GNBs provide a more than tenfold signal enhancement in photo acoustic tomography (PAT) in the NIR wavelength window, indicating their potential for diagnostic imaging with PAT.

  15. Nanometals and colloids as catalyst precursors

    Energy Technology Data Exchange (ETDEWEB)

    Boennemann, H.H. [Max-Planck-Institut fuer Kohlenforschung (Germany)

    1995-12-01

    Mono- or plurimetallic nanometals and colloids stabilized by surfactant molecules are discussed as pre-prepared precursors for heterogeneous catalysts. This {open_quotes}precursor concept{close_quotes} provides a novel access to supported metal catalysts having active components of controlled particle size, intermetallic ratio and particle structure on surfaces. Possible applications will also be presented.

  16. Radiolytic reduction reaction of colloidal silver bromide solution

    International Nuclear Information System (INIS)

    The reduction reaction of colloidal silver bromide (AgBr3)2- in nitrous oxide gas saturated solution of some alcohols: methanol, ethanol, 2-propanol and 2-methyl-2-propanol by γ-irradiation was studied spectrophotometrically in order to elucidate the mechanism of the formation of colloidal silver bromide (AgBr3)3- at ambient temperature. The amount of colloidal silver bromide formed increases in the order: i-PrOH, EtOH, MeOH. In t-BuOH, colloidal silver bromide did not form. The relative reactivities of alcohols for colloidal silver bromide was also studied kinetically. (author)

  17. Colloid stable sorbents for cesium removal: preparation and application of latex particles functionalized with transition metals ferrocyanides.

    Science.gov (United States)

    Avramenko, Valentin; Bratskaya, Svetlana; Zheleznov, Veniamin; Sheveleva, Irina; Voitenko, Oleg; Sergienko, Valentin

    2011-02-28

    In this paper we suggest a principally new approach to preparation of colloid stable selective sorbents for cesium uptake using immobilization of transition metals (cobalt, nickel, and copper) ferrocyanides in nanosized carboxylic latex emulsions. The effects of ferrocyanide composition, pH, and media salinity on the sorption properties of the colloid stable sorbents toward cesium ions were studied in solutions containing up to 200 g/L of sodium nitrate or potassium chloride. The sorption capacities of the colloid sorbents based on mixed potassium/transition metals ferrocyanides were in the range 1.3-1.5 mol Cs/mol ferrocyanide with the highest value found for the copper ferrocyanide. It was shown that the obtained colloid-stable sorbents were capable to penetrate through bulk materials without filtration that made them applicable for decontamination of solids, e.g. soils, zeolites, spent ion-exchange resins contaminated with cesium radionuclides. After decontamination of liquid or solid radioactive wastes the colloid-stable sorbents can be easily separated from solutions by precipitation with cationic flocculants providing localization of radionuclides in a small volume of the precipitates formed. PMID:21208744

  18. Colloidal Stability and Monodispersible Magnetic Iron Oxide Nanoparticles in Biotechnology Application

    Science.gov (United States)

    Shamili, K.; Rajesh, E. M.; Rajendran, R.; Madhan Shankar, S. R.; Elango, M.; Abitha Devi, N.

    2013-02-01

    Magnetic iron oxide nanoparticles are promising material for various biological applications. In the recent decades, magnetic iron oxide nanoparticles (MNPs) have great attention in biomedical applications such as drug delivery, magnetic resonance imaging (MRI) and magnetic fluid hyperthermia (MFH). This review focuses on the colloidal stability and monodispersity properties of MNPs, which pay more attention toward biomedical applications. The simplest and the most promising method for the synthesis of MNPs is co-precipitation. The biocompatible MNPs are more interested in MRI application. This review also apportions synthesis, characterization and applications of MNP in biological and biomedical as theranostics and imaging.

  19. Using gold colloid nanoparticles to modulate the surface enhanced fluorescence of Rhodamine B

    International Nuclear Information System (INIS)

    Enhanced fluorescence from Rhodamine B (RB) mixed with gold colloids has been observed under ultraviolet irradiation. Spectroscopic studies show that with the increasing gold colloids content, the fluorescence of RB at about 590 nm increases firstly and then decreases with slight red shift. These features observed in the experiment can be explained by the local electric field enhancement via surface plasmon resonance (SPR) of gold nanoparticles. Fluorescence enhancement is obtained when the emission frequency of RB lies within the bandwidth of local field enhancement from gold nanoparticles. Theoretical calculation results show that the local field band red shifts obviously with increase the thickness of dye shell which capped on gold particle, whereas the fluorescence band of RB is fixed around 590 nm. Therefore, the red shift and non-monotonic change of fluorescence intensity from RB is attributed to the dye shell dependent red shift of local field band of gold particles

  20. Colloidal processing of Fe-based metal ceramic composites with high content of ceramic reinforcement

    International Nuclear Information System (INIS)

    Major difficulties of processing metal-matrix composites by means of conventional powder metallurgy techniques are the lack of dispersion of the phases within the final microstructure. In this work, processing through colloidal techniques of the Fe-based metal-matrix composites, with a high content of a ceramic reinforcement (Ti(C,N) ), is presented for the first time in the literature. The colloidal approach allows a higher control of the powders packing and a better homogenization of phases since powders are mixed in a liquid medium. The chemical stability of Fe in aqueous medium determines the dispersion conditions of the mixture. The Fe slurries were formulated by optimising their zeta potential and their rheology, in order to shape bulk pieces by slip-casting. Preliminary results demonstrate the viability of this procedure, also opening new paths to the microstructural design of fully sintered Fe-based hard metal, with 50 vol. % of Ti(C,N) in its composition. (Author)

  1. Colloid suspension stability and transport through unsaturated porous media

    Energy Technology Data Exchange (ETDEWEB)

    McGraw, M.A.; Kaplan, D.I.

    1997-04-01

    Contaminant transport is traditionally modeled in a two-phase system: a mobile aqueous phase and an immobile solid phase. Over the last 15 years, there has been an increasing awareness of a third, mobile solid phase. This mobile solid phase, or mobile colloids, are organic or inorganic submicron-sized particles that move with groundwater flow. When colloids are present, the net effect on radionuclide transport is that radionuclides can move faster through the system. It is not known whether mobile colloids exist in the subsurface environment of the Hanford Site. Furthermore, it is not known if mobile colloids would likely exist in a plume emanating from a Low Level Waste (LLW) disposal site. No attempt was made in this study to ascertain whether colloids would form. Instead, experiments and calculations were conducted to evaluate the likelihood that colloids, if formed, would remain in suspension and move through saturated and unsaturated sediments. The objectives of this study were to evaluate three aspects of colloid-facilitated transport of radionuclides as they specifically relate to the LLW Performance Assessment. These objectives were: (1) determine if the chemical conditions likely to exist in the near and far field of the proposed disposal site are prone to induce flocculation (settling of colloids from suspension) or dispersion of naturally occurring Hanford colloids, (2) identify the important mechanisms likely involved in the removal of colloids from a Hanford sediment, and (3) determine if colloids can move through unsaturated porous media.

  2. Colloid suspension stability and transport through unsaturated porous media

    International Nuclear Information System (INIS)

    Contaminant transport is traditionally modeled in a two-phase system: a mobile aqueous phase and an immobile solid phase. Over the last 15 years, there has been an increasing awareness of a third, mobile solid phase. This mobile solid phase, or mobile colloids, are organic or inorganic submicron-sized particles that move with groundwater flow. When colloids are present, the net effect on radionuclide transport is that radionuclides can move faster through the system. It is not known whether mobile colloids exist in the subsurface environment of the Hanford Site. Furthermore, it is not known if mobile colloids would likely exist in a plume emanating from a Low Level Waste (LLW) disposal site. No attempt was made in this study to ascertain whether colloids would form. Instead, experiments and calculations were conducted to evaluate the likelihood that colloids, if formed, would remain in suspension and move through saturated and unsaturated sediments. The objectives of this study were to evaluate three aspects of colloid-facilitated transport of radionuclides as they specifically relate to the LLW Performance Assessment. These objectives were: (1) determine if the chemical conditions likely to exist in the near and far field of the proposed disposal site are prone to induce flocculation (settling of colloids from suspension) or dispersion of naturally occurring Hanford colloids, (2) identify the important mechanisms likely involved in the removal of colloids from a Hanford sediment, and (3) determine if colloids can move through unsaturated porous media

  3. Scattering from correlations in colloidal systems

    International Nuclear Information System (INIS)

    Colloidal suspensions typically exhibit spatial correlations over distances of order 10-104 A, corresponding either to the size of individual particles (e.g., polymer chains, surfactant micelles) or to the range of interaction between particles (e.g., charged polymer lattices at low ionic strength). Apart from having fundamental intrinsic interest, such systems are also extremely useful as model systems with which to study, for example, non-Newtonian hydrodynamics, since temporal correlations are generally much longer lived (10-8-10-3 sec) than those found in simple atomic or small molecular systems (10-13-10-10 sec). Colloids have long been the subject of macroscopic phenomenological research (on rheological properties, for example), but it is only recently that microscopic light, x-ray and neutron scattering techniques have been applied to their study, in large part because of theoretical difficulties in understanding the scattering from dense liquid-like systems of interacting particles. For spherical colloids, such theoretical problems have now been largely overcome, and for anisotropic colloids experimental techniques are being developed which circumvent the intractable theoretical areas. This paper will first review some static light and small-angle neutron scattering (SANS) results on colloidal suspensions, both at equilibrium and in steady-state non-equilibrium situations, and will then discuss some dynamic measurements on polymer solutions and melts made using the neutron spin-echo (NSE) technique. Emphasis is placed on experiments which have a possible counterpart in synchrotron radiation studies. In particular, NSE extends the results of photon correlation spectroscopy (PCS) to larger momentum transfers and shorter time-scales than are available with visible light, and the extension of PCS to short wavelength on a synchrotron source would be of similar fundamental interest

  4. Stable Colloidal Drug Aggregates Catch and Release Active Enzymes.

    Science.gov (United States)

    McLaughlin, Christopher K; Duan, Da; Ganesh, Ahil N; Torosyan, Hayarpi; Shoichet, Brian K; Shoichet, Molly S

    2016-04-15

    Small molecule aggregates are considered nuisance compounds in drug discovery, but their unusual properties as colloids could be exploited to form stable vehicles to preserve protein activity. We investigated the coaggregation of seven molecules chosen because they had been previously intensely studied as colloidal aggregators, coformulating them with bis-azo dyes. The coformulation reduced colloid sizes to sorafenib, tetraiodophenolphthalein (TIPT), or vemurafenib produced particles that are stable in solutions of high ionic strength and high protein concentrations. Like traditional, single compound colloidal aggregates, the stabilized colloids adsorbed and inhibited enzymes like β-lactamase, malate dehydrogenase, and trypsin. Unlike traditional aggregates, the coformulated colloid-protein particles could be centrifuged and resuspended multiple times, and from resuspended particles, active trypsin could be released up to 72 h after adsorption. Unexpectedly, the stable colloidal formulations can sequester, stabilize, and isolate enzymes by spin-down, resuspension, and release. PMID:26741163

  5. Preferences for colloid use in Scandinavian intensive care units

    DEFF Research Database (Denmark)

    Perner, A.; Aneman, A.; Guttormsen, A.B.; Karason, S.; Tenhunen, J.

    2008-01-01

    . Thirty-five ICUs had contraindications, which were mainly for the use of synthetic colloids (acute renal failure 25 units, bleeding 15 units). Most units based the use of colloids on theoretical knowledge and tradition. Sixty-five and 54 ICUs were ready to change colloid use based on data from randomised...... trials of ICU patients showing changes in mortality or renal function, respectively. CONCLUSION: Most Scandinavian ICUs use both synthetic and natural colloids, but HES 130/0.4 is by far the preferred colloid. Few units have protocols for colloid use, but most use them for hypovolaemia, and the majority...... have no contraindications. Most ICUs are ready to change colloid use if randomised trials in ICU patients show changes in mortality or renal function Udgivelsesdato: 2008/7...

  6. Mixing Ventilation

    DEFF Research Database (Denmark)

    Kandzia, Claudia; Kosonen, Risto; Melikov, Arsen Krikor;

    In this guidebook most of the known and used in practice methods for achieving mixing air distribution are discussed. Mixing ventilation has been applied to many different spaces providing fresh air and thermal comfort to the occupants. Today, a design engineer can choose from large selection of ...

  7. LONG-TERM COLLOID MOBILIZATION AND COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES IN A SEMI-ARID VADOSE ZONE

    Energy Technology Data Exchange (ETDEWEB)

    Markus Flury; James B. Harsh; Fred Zhang; Glendon W. Gee; Earl D. Mattson; Peter C. L

    2012-08-01

    The main purpose of this project was to improve the fundamental mechanistic understanding and quantification of long-term colloid mobilization and colloid-facilitated transport of radionuclides in the vadose zone, with special emphasis on the semi-arid Hanford site. While we focused some of the experiments on hydrogeological and geochemical conditions of the Hanford site, many of our results apply to colloid and colloid-facilitated transport in general. Specific objectives were (1) to determine the mechanisms of colloid mobilization and colloid-facilitated radionuclide transport in undisturbed Hanford sediments under unsaturated flow, (2) to quantify in situ colloid mobilization and colloid-facilitated radionuclidetransport from Hanford sediments under field conditions, and (3) to develop a field-scale conceptual and numerical model for colloid mobilization and transport at the Hanford vadose zone, and use that model to predict long-term colloid and colloid- facilitated radionuclide transport. To achieve these goals and objectives, we have used a combination of experimental, theoretical, and numerical methods at different spatial scales, ranging from microscopic investigationsof single particle attachment and detachment to larger-scale field experiments using outdoor lysimeters at the Hanford site. Microscopic and single particle investigations provided fundamental insight into mechanisms of colloid interactions with the air-water interface. We could show that a moving air water interface (such as a moving water front during infiltration and drainage) is very effective in removing and mobilizing particles from a stationary surface. We further demonstrated that it is particularly the advancing air-water interface which is mainly responsible for colloid mobilization. Forces acting on the colloids calculated from theory corroborated our experimental results, and confirm that the detachment forces (surface tension forces) during the advancing air-water interface

  8. Improvement Effects of Rice Straw Mixed with Biological Agent on Plastic Shed Continuous Cultivation Soil%稻草配施生物菌剂对大棚连作土壤的改良效果

    Institute of Scientific and Technical Information of China (English)

    韩玉珠; 宋述尧

    2012-01-01

    The decomposition characteristics in soil and the improvement effects of rice straw mixed with biological agent used in plastic shed continuous cultivation soil were studied. The results showed that, the decomposition of rice straw mixed with biological agent was rapidly in the beginning and then weaken. The decomposition efficiency of rice straw mixed with EM bacterium was higher. Soil capacity and solid fraction was decreased; soil moisture content and porosity was increased; and soil water infiltration was strengthened. The content of organic materials, total N, total P and available N, P and K was in-crensed. The pH and EC value of the soil decreased. The soil salinity was restrained to migrate to surface. The soil cation exchange ratio was increased; and the soil nutrient preserving capability was improved. The quantity of bacteria and action-mycetes and their ratio (B/F) increased. The plastic shed soil's continuous cultivation obstacle was relieved. From the comprehensive analysis of soil's improvement,0.8% rice straw mixed with 1.0% EM bacterium had great effect.%研究了稻草配合两种生物菌剂施入塑料大棚连作土壤后,在土壤中的分解特性及对连作土壤的改良效果.结果表明,稻草配施生物菌剂(EM菌、乐土菌)在大棚土壤中腐解,开始迅速,以后逐渐减缓,以稻草+EM菌处理腐解效率较高.稻草配施生物菌剂可降低土壤的容重和固相率,提高土壤的含水量和孔隙度,增加土壤通透性,改善了土壤结构;提高了土壤有机质、全氮、全磷含量及碱解氮、速效磷、速效钾含量,降低了土壤pH和EC,抑制了大棚土壤盐分的表聚,提高了土壤阳离子交换量,增强了土壤的保肥供肥能力;增加了土壤中细菌、放线菌的数量,B/F提高,可从根本上缓解大棚土壤连作的障碍.从大棚土壤改良效果的综合分析看,0.8%稻草与1.0%EM菌配施效果较好.

  9. Dissolved and colloidal trace elements in the Mississippi River delta outflow after Hurricanes Katrina and Rita

    Science.gov (United States)

    Shim, Moo-Joon; Swarzenski, Peter W.; Shiller, Alan M.

    2012-07-01

    The Mississippi River delta outflow region is periodically disturbed by tropical weather systems including major hurricanes, which can terminate seasonal bottom water hypoxia and cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, Hurricanes Katrina and Rita passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we collected water samples in the Mississippi River delta outflow, examining the distributions of trace elements to study the effect of Hurricanes Katrina and Rita. We observed limited stratification on the shelf and bottom waters that were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn-O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 μm) from colloidal (0.02-0.45 μm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the bioavailablity

  10. Dissolved and colloidal trace elements in the Mississippi River Delta outflow after Hurricanes Katrina and Rita

    Science.gov (United States)

    Shim, Moo-Joon; Swarzenski, Peter W.; Shiller, Alan M.

    2012-01-01

    The Mississippi River delta outflow region is periodically disturbed by tropical weather systems including major hurricanes, which can terminate seasonal bottom water hypoxia and cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, Hurricanes Katrina and Rita passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we collected water samples in the Mississippi River delta outflow, examining the distributions of trace elements to study the effect of Hurricanes Katrina and Rita. We observed limited stratification on the shelf and bottom waters that were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn–O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 μm) from colloidal (0.02–0.45 μm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the

  11. Hydrogel-colloid interfacial interactions: a study of tailored adhesion using optical tweezers.

    Science.gov (United States)

    Sheikhi, Amir; Hill, Reghan J

    2016-08-21

    Dynamics of colloidal particles adhering to soft, deformable substrates, such as tissues, biofilms, and hydrogels play a key role in many biological and biomimetic processes. These processes, including, but not limited to colloid-based delivery, stitching, and sorting, involve microspheres exploring the vicinity of soft, sticky materials in which the colloidal dynamics are affected by the fluid environment (e.g., viscous coupling), inter-molecular interactions between the colloids and substrates (e.g., Derjaguin-Landau-Verwey-Overbeek (DLVO) theory), and the viscoelastic properties of contact region. To better understand colloidal dynamics at soft interfaces, an optical tweezers back-focal-plane interferometry apparatus was developed to register the transverse Brownian motion of a silica microsphere in the vicinity of polyacrylamide (PA) hydrogel films. The time-dependent mean-squared displacements are well described by a single exponential relaxation, furnishing measures of the transverse interfacial diffusion coefficient and binding stiffness. Substrates with different elasticities were prepared by changing the PA crosslinking density, and the inter-molecular interactions were adjusted by coating the microspheres with fluid membranes. Stiffer PA hydrogels (with bulk Young's moduli ≈1-10 kPa) immobilize the microspheres more firmly (lower diffusion coefficient and position variance), and coating the particles with zwitterionic lipid bilayers (DOPC) completely eliminates adhesion, possibly by repulsive dispersion forces. Remarkably, embedding polyethylene glycol-grafted lipid bilayers (DSPE-PEG2k-Amine) in the zwitterionic fluid membranes produces stronger adhesion, possibly because of polymer-hydrogel attraction and entanglement. This study provides new insights to guide the design of nanoparticles and substrates with tunable adhesion, leading to smarter delivery, sorting, and screening of micro- and nano-systems. PMID:27425660

  12. In-situ Microfluidic Measurement of the Dielectric Constant of Colloidal Particles

    Science.gov (United States)

    Manafirasi, Setareh; Leary, Thomas; Maldarelli, Charles

    2015-11-01

    The ability to manipulate micron-sized colloidal particles or biological cells in a liquid medium in microfluidic geometries is necessary in lab on a chip devices for micro scale biological analysis and diagnostics for sorting and directing the trafficking of the particles. In dielectrophoresis, a nonuniform electric (E) field is applied to move the particles along the gradient of the field energy, and the velocity is a function of the particle's dielectric constant. Measurement of the dielectric constant is necessary in order to scale field strengths for applications, and it is important to undertake this measurement in-situ as the particle's dielectric content can be modified by the suspending medium (e.g. adsorption onto the particle surface). In this talk we measure directly the dielectric constant of colloids in a microfluidic channel by applying an electric field with ``V''-shaped and planar electrodes on opposite sides of the channel. The cusp of the ``V'' shape concentrates the field to provide a sufficient field intensity gradient which is designed to be uniform across the height of the channel and to vary only with its width. Optical measurements of the diffusiophoretic velocity of polymer colloids are compared to simulations based on numerical solution of the E-field and particle hydrodynamics to obtain the particle dielectric constant and investigate the effect of biomolecule adsorption on the particle surface.

  13. Colloids related to low level and intermediate level waste

    International Nuclear Information System (INIS)

    A comprehensive investigation has been undertaken to improve the understanding of the potential role of colloids in the context of disposal and storage of low and intermediate level waste immobilised in cement. Several topics have been investigated using a wide range of advanced physico-chemical and analytical techniques. These include: (a) the study of formation and characteristics of colloids in cement leachates, (b) the effects of the near-field aqueous chemistry on the characteristics of colloids in repository environments, (c) colloid sorption behaviour, (d) interactions of near-field materials with leachates, and (e) preliminary assessment of colloid migration behaviour. It has been shown that the generation of colloids in cement leachates can arise from a process of nucleation and growth leading to an amorphous phase which is predominantly calcium silicate hydrate. Such colloidal material has a capacity for association with polyvalent rare earths and actinides and these may be significant in the source term and processes involving radionuclide retention in the near field. It has also been shown that the near-field aqueous chemistry (pH, Ca2+ concentration) has a marked effect on colloid behaviour (deposition and stability). A mechanistic approach to predict colloid sorption affinity has been developed which highlights the importance of colloid characteristics and the nature of the ionic species. (author)

  14. From one to many: dynamic assembly and collective behavior of self-propelled colloidal motors.

    Science.gov (United States)

    Wang, Wei; Duan, Wentao; Ahmed, Suzanne; Sen, Ayusman; Mallouk, Thomas E

    2015-07-21

    The assembly of complex structures from simpler, individual units is a hallmark of biology. Examples include the pairing of DNA strands, the assembly of protein chains into quaternary structures, the formation of tissues and organs from cells, and the self-organization of bacterial colonies, flocks of birds, and human beings in cities. While the individual behaviors of biomolecules, bacteria, birds, and humans are governed by relatively simple rules, groups assembled from many individuals exhibit complex collective behaviors and functions that do not exist in the absence of the hierarchically organized structure. Self-assembly is a familiar concept to chemists who study the formation and properties of monolayers, crystals, and supramolecular structures. In chemical self-assembly, disorder evolves to order as the system approaches equilibrium. In contrast, living assemblies are typically characterized by two additional features: (1) the system constantly dissipates energy and is not at thermodynamic equilibrium; (2) the structure is dynamic and can transform or disassemble in response to stimuli or changing conditions. To distinguish them from equilibrium self-assembled structures, living (or nonliving) assemblies of objects with these characteristics are referred to as active matter. In this Account, we focus on the powered assembly and collective behavior of self-propelled colloids. These nano- and microparticles, also called nano- and micromotors or microswimmers, autonomously convert energy available in the environment (in the form of chemical, electromagnetic, acoustic, or thermal energy) into mechanical motion. Collections of these colloids are a form of synthetic active matter. Because of the analogy to living swimmers of similar size such as bacteria, the dynamic interactions and collective behavior of self-propelled colloids are interesting in the context of understanding biological active matter and in the development of new applications. The progression

  15. Cotransport of bismerthiazol and montmorillonite colloids in saturated porous media

    Science.gov (United States)

    Shen, Chongyang; Wang, Hong; Lazouskaya, Volha; Du, Yichun; Lu, Weilan; Wu, Junxue; Zhang, Hongyan; Huang, Yuanfang

    2015-06-01

    While bismerthiazol [N,N‧-methylene-bis-(2-amino-5-mercapto-1,3,4-thiadiazole)] is one of the most widely used bactericides, the transport of bismerthiazol in subsurface environments is unclear to date. Moreover, natural colloids are ubiquitous in the subsurface environments. The cotransport of bismerthiazol and natural colloids has not been investigated. This study conducted laboratory column experiments to examine the transport of bismerthiazol in saturated sand porous media both in the absence and presence of montmorillonite colloids. Results show that a fraction of bismerthiazol was retained in sand and the retention was higher at pH 7 than at pH 4 and 10. The retention did not change with ionic strength. The retention was attributed to the complex of bismerthiazol with metals/metal oxides on sand surfaces through ligand exchange. The transport of bismerthiazol was enhanced with montmorillonite colloids copresent in the solutions and, concurrently, the transport of montmorillonite colloids was facilitated by the bismerthiazol. The transport of montmorillonite colloids was enhanced likely because the bismerthiazol and the colloids competed for the attachment/adsorption sites on collector surfaces and the presence of bismerthiazol changed the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies between colloids and collectors. The transport of bismerthiazol was inhibited if montmorillonite colloids were pre-deposited in sand because bismerthiazol could adsorb onto the colloid surfaces. The adsorbed bismerthiazol could be co-remobilized with the colloids from primary minima by decreasing ionic strength. Whereas colloid-facilitated transport of pesticides has been emphasized, our study implies that transport of colloids could also be facilitated by the presence of pesticides.

  16. Behavior of ionic and colloid forms of microelements in colloidal chemical extraction from humic acid solutions

    International Nuclear Information System (INIS)

    Speciation and extractability of humic acids (HAs) and humate complexes of microelements are studied using the colloidal chemical extraction method in combination with ICP MS, taking natural mineral water with high HA concentration (800-1200 mg l-1) collected from the Salekhard region as an example. Joint extraction behavior of ionic and colloid forms of anionic and cationic species of a large number of microelements, including Li, Sr, B, Sc, U(VI) and Th(IV), and HAs is examined at their natural abundance in mineral water, as influenced by pH and HA concentration. Humic acids proved to behave in natural water as a pool of ion-colloidal species, whose protonation results in precipitation at pH 2.0-3.5. In this case, some chemical elements are sorbed on the resulting solid and may be separated along with HAs by colloidal chemical extraction into isobutanol. In natural humate solutions, a considerable fraction (10-99 mol %) of chemical elements is associated with HAs in the form of colloid species extractable with isobutanol

  17. Crust formation in drying colloidal suspensions

    KAUST Repository

    Style, R. W.

    2010-06-30

    During the drying of colloidal suspensions, the desiccation process causes the suspension near the air interface to consolidate into a connected porous matrix or crust. Fluid transport in the porous medium is governed by Darcy\\'s law and the equations of poroelasticity, while the equations of colloid physics govern processes in the suspension. We derive new equations describing this process, including unique boundary conditions coupling the two regions, yielding a moving-boundary model of the concentration and stress profiles during drying. A solution is found for the steady-state growth of a nedimensional crust during constant evaporation rate from the surface. The solution is used to demonstrate the importance of the system boundary conditions on stress profiles and diffusivity in a drying crust. © 2011 The Royal Society.

  18. Colloid transport code-nuclear user's manual

    International Nuclear Information System (INIS)

    This report describes the CTCN computer code, designed to solve the equations of transient colloidal transport of radionuclides in porous and fractured media. This Fortran 77 package solves systems of coupled nonlinear differential equations with a wide range of boundary conditions. The package uses the Method of Lines technique with a special section which forms finite-difference discretizations in up to four spatial dimensions to automatically convert the system into a set of ordinary differential equations. The CTCN code then solves these equations using a robust, efficient ODE solver. Thus CTCN can be used to solve population balance equations along with the usual transport equations to model colloid transport processes or as a general problem solver to treat up to four-dimensional differential systems

  19. Structure and hydrodynamics of colloidal systems

    Science.gov (United States)

    Hayter, John B.

    1986-02-01

    Invited paperColloidal phases (for example, micellar solutions, latex suspensions, ferrofluids and microemulsions) provide excellent model systems with which to test structural and hydrodynamic theories of the liquid state. Interparticle potentials may be attractive or repulsive, and the experimentalist is often free to control the strength, range and symmetry of the interactions. Small-angle neutron scattering (SANS) and small-angle neutron spin-echo (SANSE) provide excellent complementary tools for studying the structure and time-dependence of these systems, where correlation lengths typically vary from about one to several tens of nm. Correlation times are usually in the nsec to μsec range, but may be of order minutes in certain systems. This paper will review some of the current theories and their recent experimental tests, using colloidal systems in which the direct interaction potentials may have spherical, dipolar or cylindrical symmetry and the hydrodynamic interactions may be weak or strong.

  20. Polymers at interfaces and in colloidal dispersions.

    Science.gov (United States)

    Fleer, Gerard J

    2010-09-15

    This review is an extended version of the Overbeek lecture 2009, given at the occasion of the 23rd Conference of ECIS (European Colloid and Interface Society) in Antalya, where I received the fifth Overbeek Gold Medal awarded by ECIS. I first summarize the basics of numerical SF-SCF: the Scheutjens-Fleer version of Self-Consistent-Field theory for inhomogeneous systems, including polymer adsorption and depletion. The conformational statistics are taken from the (non-SCF) DiMarzio-Rubin lattice model for homopolymer adsorption, which enumerates the conformational details exactly by a discrete propagator for the endpoint distribution but does not account for polymer-solvent interaction and for the volume-filling constraint. SF-SCF corrects for this by adjusting the field such that it becomes self-consistent. The model can be generalized to more complex systems: polydispersity, brushes, random and block copolymers, polyelectrolytes, branching, surfactants, micelles, membranes, vesicles, wetting, etc. On a mean-field level the results are exact; the disadvantage is that only numerical data are obtained. Extensions to excluded-volume polymers are in progress. Analytical approximations for simple systems are based upon solving the Edwards diffusion equation. This equation is the continuum variant of the lattice propagator, but ignores the finite segment size (analogous to the Poisson-Boltzmann equation without a Stern layer). By using the discrete propagator for segments next to the surface as the boundary condition in the continuum model, the finite segment size can be introduced into the continuum description, like the ion size in the Stern-Poisson-Boltzmann model. In most cases a ground-state approximation is needed to find analytical solutions. In this way realistic analytical approximations for simple cases can be found, including depletion effects that occur in mixtures of colloids plus non-adsorbing polymers. In the final part of this review I discuss a

  1. Interaction between colloidal particles. Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    Longcheng Liu; Neretnieks, Ivars (Royal Inst. of Technology, Stockholm (Sweden). School of Chemical Science and Engineering, Dept. of Chemical Engineering and Technology)

    2010-02-15

    This report summarises the commonly accepted theoretical basis describing interaction between colloidal particles in an electrolyte solution. The two main forces involved are the van der Waals attractive force and the electrical repulsive force. The report describes in some depth the origin of these two forces, how they are formulated mathematically as well as how they interact to sometimes result in attraction and sometimes in repulsion between particles. The report also addresses how the mathematical models can be used to quantify the forces and under which conditions the models can be expected to give fair description of the colloidal system and when the models are not useful. This report does not address more recent theories that still are discussed as to their applicability, such as ion-ion correlation effects and the Coulombic attraction theory (CAT). These and other models will be discussed in future reports

  2. Structure and hydrodynamics of colloidal systems

    Energy Technology Data Exchange (ETDEWEB)

    Hayter, J.B.

    1985-07-01

    Colloidal phases (for example, micellar solutions, latex suspensions, ferrofluids and microemulsions) provide excellent model systems with which to test structural and hydrodynamic theories of the liquid state. Interparticle potentials may be attractive or repulsive, and the experimentalist is often free to control the strength, range and symmetry of the interactions. Small-angle neutron scattering (SANS) and small-angle neutron spin-echo (SANSE) provide excellent complementary tools for studying the structure and time-dependence of these systems, where correlation lengths typically vary from about one to several tens of nm. Correlation times are usually in the nsec to ..mu..sec range, but may be of order minutes in certain systems. This paper will review some of the current theories and their recent experimental tests, using colloidal systems in which the direct interaction potentials may have spherical, dipolar or cylindrical symmetry and the hydrodynamic interactions may be weak or strong.

  3. Ultrasonic wave interactions with magnetic colloids

    CERN Document Server

    Chapman, J R

    2001-01-01

    fluids have been performed in an effort to determine the relative stability of the fluids. The experimental results have been compared with a combined scattering and hydrodynamic model (Allegra and Hawley 1972) and the ultrasonic anisotropy theory of Skumiel (1997). An on-line quality assurance process is proposed. Originally invented as a method for moving spacecraft fuel in weightless conditions, magnetic colloids or ferrofluids are now used in applications as diverse as the dissipation of heat in the voice coils of a loudspeaker, and for the separation of scrap metal. It has been found that aqueous ferrofluids become unstable after a period of time and with dilution. Therefore, there is a need to characterize the colloidal fluid to study the effects of degradation. Additionally, due to the high cost of ferrofluids and the large volumes required for some applications, the fluid is recycled. It is therefore necessary to develop a system for quality assurance for the fluid reclamation process. Ultrasonic meth...

  4. Interaction between colloidal particles. Literature Review

    International Nuclear Information System (INIS)

    This report summarises the commonly accepted theoretical basis describing interaction between colloidal particles in an electrolyte solution. The two main forces involved are the van der Waals attractive force and the electrical repulsive force. The report describes in some depth the origin of these two forces, how they are formulated mathematically as well as how they interact to sometimes result in attraction and sometimes in repulsion between particles. The report also addresses how the mathematical models can be used to quantify the forces and under which conditions the models can be expected to give fair description of the colloidal system and when the models are not useful. This report does not address more recent theories that still are discussed as to their applicability, such as ion-ion correlation effects and the Coulombic attraction theory (CAT). These and other models will be discussed in future reports

  5. Realizing the Physics of Motile Cilia Synchronization with Driven Colloids

    Science.gov (United States)

    Bruot, Nicolas; Cicuta, Pietro

    2016-03-01

    Cilia and flagella in biological systems often show large scale cooperative behaviors such as the synchronization of their beats in "metachronal waves." These are beautiful examples of emergent dynamics in biology, and are essential for life, allowing diverse processes from the motility of eukaryotic microorganisms, to nutrient transport and clearance of pathogens from mammalian airways. How these collective states arise is not fully understood, but it is clear that individual cilia interact mechanically, and that a strong and long-ranged component of the coupling is mediated by the viscous fluid. We review here the work by ourselves and others aimed at understanding the behavior of hydrodynamically coupled systems, and particularly a set of results that have been obtained both experimentally and theoretically by studying actively driven colloidal systems. In these controlled scenarios, it is possible to selectively test aspects of living motile cilia, such as the geometrical arrangement, the effects of the driving profile and the distance to no-slip boundaries. We outline and give examples of how it is possible to link model systems to observations on living systems, which can be made on microorganisms, on cell cultures or on tissue sections. This area of research has clear clinical application in the long term, as severe pathologies are associated with compromised cilia function in humans.

  6. Behavior of colloidal gold nanoparticles in different ionic strength media

    Energy Technology Data Exchange (ETDEWEB)

    Barreto, Ângela; Luis, Luis G. [University of Aveiro, Department of Biology & CESAM (Portugal); Girão, Ana V.; Trindade, Tito [University of Aveiro, Department of Chemistry & CICECO (Portugal); Soares, Amadeu M. V. M.; Oliveira, Miguel, E-mail: migueloliveira@ua.pt [University of Aveiro, Department of Biology & CESAM (Portugal)

    2015-12-15

    The increased applications of engineered nanoparticles (NPs) may lead to environmental release and transport to estuarine environments where NPs are expected to aggregate/agglomerate with increasing ionic strength. However, more stable NPs that may be resistant to high ionic strength media and more dispersed in the aquatic environment are being synthesized. Thus, understanding colloidal NPs’ behavior in different ionic strength media is crucial for the assessment of the consequences of their environmental release. This work assessed the behavior of gold nanoparticles (AuNPs), with diverse sizes and coatings, in media with different ionic strengths (from biological buffers to artificial seawater). Overall, in biological buffers and artificial seawater, citrate-coated AuNPs were unstable, displaying significantly increased sizes (between 100 and 400 nm), whereas no significant alterations (less than 5 % oscillation) were found for AuNPs with other coatings (bovine serum albumin, polyvinylpyrrolidone, and polyethylene glycol). Data suggest that coated AuNPs, and probably other NPs, may be dispersed in the environment from freshwater to estuarine systems.

  7. Behavior of colloidal gold nanoparticles in different ionic strength media

    International Nuclear Information System (INIS)

    The increased applications of engineered nanoparticles (NPs) may lead to environmental release and transport to estuarine environments where NPs are expected to aggregate/agglomerate with increasing ionic strength. However, more stable NPs that may be resistant to high ionic strength media and more dispersed in the aquatic environment are being synthesized. Thus, understanding colloidal NPs’ behavior in different ionic strength media is crucial for the assessment of the consequences of their environmental release. This work assessed the behavior of gold nanoparticles (AuNPs), with diverse sizes and coatings, in media with different ionic strengths (from biological buffers to artificial seawater). Overall, in biological buffers and artificial seawater, citrate-coated AuNPs were unstable, displaying significantly increased sizes (between 100 and 400 nm), whereas no significant alterations (less than 5 % oscillation) were found for AuNPs with other coatings (bovine serum albumin, polyvinylpyrrolidone, and polyethylene glycol). Data suggest that coated AuNPs, and probably other NPs, may be dispersed in the environment from freshwater to estuarine systems

  8. Ultrasound techniques for characterizing colloidal dispersions

    International Nuclear Information System (INIS)

    Interest in the interaction of acoustic waves with particulate mixtures has a long history-dating back to the work of Rayleigh in the 19th century. This interest has intensified over the last fifteen years as advances in electronics and instrumentation science have brought the possibility of using ultrasound to characterize colloidal mixtures both in the laboratory and in-process, and in both of these contexts a small number of instruments are currently in use. The characterization of colloidal mixtures by ultrasound requires a formal theoretical basis which relates the properties of the mixture, particularly the dispersed phase particle size distribution (PSD), to the complex wavenumber governing propagation. The number of theoretical treatments is vast, having evolved over more than a century. This paper is intended to provide a review of these developments in a form which will enable new researchers in the field to climb a very steep learning curve in a relatively short time. We discuss definitions and production techniques for colloidal mixtures and the basic physical phenomena underlying wave propagation through them. We identify two approaches to the propagation problem-scattering and coupled-phase; these are treated both separately and comparatively, particularly in relation to limitations that arise when the concentration of particles is high and the basic theories break down. We introduce the basic method for the measurement of PSD and show how dynamic effects such as flocculation and crystallization can be observed and modelled. The core of all ultrasonic characterization procedures is the physical measurement of the ultrasonic wave attenuation coefficient and phase velocity as functions of frequency; here we discuss these techniques on the basis that what is observable or measurable about a colloid depends on both its physical properties and the frequency bandwidth available for measurement. This paper concludes with our view on future developments of

  9. Non-Fickian diffusion in colloidal glasses

    OpenAIRE

    Hagen, M.H.J.; Frenkel, D.; Lowe, C.P.

    1998-01-01

    We have studied numerically the decay of the self-dynamic structure factor (SDSF) for a small particle diffusing in a colloidal glass. We show that, in line with theoretical predictions, the super-Burnett coefficient (characterizing the deviation of the fourth moment of the single particle distribution from its Gaussian value) is finite. However, our results also show that large scale deviations from Fick's law of diffusion should still be easy to detect experimentally. These deviations take ...

  10. The Silicon:Colloidal Quantum Dot Heterojunction

    KAUST Repository

    Masala, Silvia

    2015-10-13

    A heterojunction between crystalline silicon and colloidal quantum dots (CQDs) is realized. A special interface modification is developed to overcome an inherent energetic band mismatch between the two semiconductors, and realize the efficient collection of infrared photocarriers generated in the CQD film. This junction is used to produce a sensitive near infrared photodetector. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Shear modulus titration in crystalline colloidal suspensions

    OpenAIRE

    Palberg, Thomas; Kottal, Johannes; Bitzer, Franz; Simon, Rolf; Würth, Mathias; Leiderer, Paul

    1995-01-01

    We present the first direct experimental access to the actual surface charge number Z of colloidal particles under conditions of strong electrostatic interaction. We further calculate a renormalized charge number Z *(Z) using the modified DLVO approximation and the dependence of the shear modulus G(Z*) on the concentration of neutral electrolyte ns. The excellent agreement of predicted and measured values provides an experimental verification of the renormalization concept under variation of ...

  12. Colloidal suspensions as model liquids and solids

    OpenAIRE

    Palberg, Thomas; Simon, Rolf; Würth, Mathias; Leiderer, Paul

    1994-01-01

    We here review some of our recent results on fluid-like and crystalline ordered colloidal suspensions. We have investigated the structure and the dynamical properties of strongly interacting charged latex particles. The interaction can be varied experimentally over a wide range and in a precisely controlled way. It gives rise to pronounced correlations between the particles, leading to ordered mesoscopic structures which bear striking similarities with atomic or molecular liquids and solids. ...

  13. Geometric frustration in small colloidal clusters

    OpenAIRE

    Malins, Alex; Stephen R Williams; Eggers, Jens; Tanaka, Hajime; Royall, C. Patrick

    2009-01-01

    We study the structure of clusters in a model colloidal system with competing interactions using Brownian dynamics simulations. A short-ranged attraction drives clustering, while a weak, long-ranged repulsion is used to model electrostatic charging in experimental systems. The former is treated with a short-ranged Morse attractive interaction, the latter with a repulsive Yukawa interaction. We consider the yield of clusters of specific structure as a function of the strength of the interactio...

  14. Colloidal Electrostatic Interactions Near a Conducting Surface

    OpenAIRE

    Polin, Marco; Grier, David G.; Han, Yilong

    2006-01-01

    Charge-stabilized colloidal spheres dispersed in deionized water are supposed to repel each other. Instead, artifact-corrected video microscopy measurements reveal an anomalous long-ranged like-charge attraction in the interparticle pair potential when the spheres are confined to a layer by even a single charged glass surface. These attractions can be masked by electrostatic repulsions at low ionic strengths. Coating the bounding surfaces with a conducting gold layer suppresses the attraction...

  15. Strong electrostatic interactions in spherical colloidal systems

    OpenAIRE

    Messina, René; Holm, Christian; Kremer, Kurt

    2001-01-01

    We investigate spherical macroions in the strong Coulomb coupling regime within the primitive model in salt-free environment. We first show that the ground state of an isolated colloid is naturally overcharged by simple electrostatic arguments illustrated by the Gillespie rule. We furthermore demonstrate that in the strong Coulomb coupling this mechanism leads to ionized states and thus to long range attractions between like-charged spheres. We use molecular dynamics simulations to study in d...

  16. Logarithmic Relaxation in a Colloidal System

    OpenAIRE

    Sperl, Matthias

    2003-01-01

    The slow dynamics for a colloidal suspension of particles interacting with a hard-core repulsion complemented by a short-ranged attraction is discussed within the frame of mode-coupling theory for ideal glass transitions for parameter points near a higher-order glass-transition singularity. The solutions of the equations of motion for the density correlation functions are solved for the square-well system in quantitative detail by asymptotic expansion using the distance of the three control p...

  17. New materials for tunable plasmonic colloidal nanocrystals

    OpenAIRE

    Comin, Alberto; Manna, Liberato

    2014-01-01

    We present a review on the emerging materials for novel plasmonic colloidal nanocrystals. We start by explaining the basic processes involved in surface plasmon resonances in nanoparticles and then discuss the classes of nanocrystals that to date are particularly promising for tunable plasmonics: non-stoichiometric copper chalcogenides, extrinsically doped metal oxides, oxygen-deficient metal oxides and conductive metal oxides. We additionally introduce other emerging types of plasmonic nanoc...

  18. Repulsive depletion interactions in colloid polymer mixtures

    OpenAIRE

    Rudhardt, Daniel; Bechinger, Clemens; Leiderer, Paul

    1999-01-01

    Depletion forces in colloidal systems are known to be entirely attractive, as long as the background of macromolecules is small enough that an ideal gas approach is valid. At higher densities, however, structural correlation effects of the macromolecules which lead to additional repulsive parts in the depletion interaction, have to be taken into account. We have measured the depletion interaction between a single polystyrene sphere and a wall in the presence of non-ionic polymer coils. Althou...

  19. Photonic Binding in Silicon-Colloid Microcavities

    OpenAIRE

    Xifré-Pérez, E.; García de Abajo, Francisco Javier; Fenollosa Esteve, Roberto; Meseguer, Francisco

    2009-01-01

    Photonic binding between two identical silicon-colloid-based microcavities is studied by using a generalized multipolar expansion. In contrast with previous works, we focus on low-order cavity modes that resemble low-energy electronic orbitals. For conservative light intensities, the interaction between cavity modes with moderate Q factors produces extremely large particle acceleration values. Optical forces dominate over vanderWaals, gravity, and Brownian motion, and they show a binding-anti...

  20. Thermal Jamming of a Colloidal Glass

    KAUST Repository

    Agarwal, Praveen

    2011-12-01

    We investigate the effect of temperature on structure and dynamics of a colloidal glass created by tethering polymers to the surface of inorganic nanoparticles. Contrary to the conventional assumption, an increase in temperature slows down glassy dynamics of the material, yet causes no change in its static structure factor. We show that these findings can be explained within the soft glassy rheology framework if the noise temperature X of the glass phase is correlated with thermodynamic temperature. © 2011 American Physical Society.

  1. Depleted Bulk Heterojunction Colloidal Quantum Dot Photovoltaics

    KAUST Repository

    Barkhouse, D. Aaron R.

    2011-05-26

    The first solution-processed depleted bulk heterojunction colloidal quantum dot solar cells are presented. The architecture allows for high absorption with full depletion, thereby breaking the photon absorption/carrier extraction compromise inherent in planar devices. A record power conversion of 5.5% under simulated AM 1.5 illumination conditions is reported. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Gray Correlation Analysis on the Relationship Between Colloidal Structure and Chemical Component of Asphalt Colloid and Performance

    Directory of Open Access Journals (Sweden)

    X. J. Cao

    2015-01-01

    Full Text Available Asphalt is considered a colloidal material and it is important to study the relationship between its colloidal structure, chemical components and performance. The aromatic nucleus content of asphalt at different depth analysed by attenuated total reflection (ATR was taken as the index of colloid structure. The gray correlation was used to analyse the relationship between colloidal structure and chemical components of asphalt gel and performance. The results show that the correlation degree between the index of colloidal structure and saturates and resins is high, which proves that saturates and resins play an important role in asphalt colloid structure. With regard to the asphalt performance indexes, the complex modulus G* and the tangent of the phase angle (tan δ have good correlation with the index of colloidal structure at the temperature of 30 – 70 °C but poor correlation at the temperature of 70 – 90 °C. Low temperature performance has a good correlation with colloid structure index, and tg can better reflect the characteristics of colloidal structure. The analysis shows that the colloidal structure of asphalt is a complex system and it is necessary to use more than one index to characterize the performance.

  3. Silica colloids and their effect on radionuclide sorption - experimental study

    International Nuclear Information System (INIS)

    Non-cementitious grouts have been tested in ONKALO for the sealing of fractures with the small hydraulic aperture. A non-cementitious inorganic grout material for sealing the fractures of the apertures less than 0.05 mm is colloidal silica called silica sol. In this work, the release of silica colloids from the silica sol gel, the stability of silica sol colloids and sorption of Europium-152 on silica sol colloids were determined in saline OLSO and low salinity Allard groundwater simulates, de-ionized water and NaCl and CaCl2 solutions. The salinity of groundwater had a significant influence on the release and stability of silica colloids. In OLSO, particle size distribution was at first wide from nanometres to thousands of nanometres. According to the disappearance of large particles, aggregation and sedimentation had been occurred after one year. Zeta potential values around zero indicated the instability of colloids. In Allard, particle size distribution was narrow and the particle diameter remained less than 60 nm. High negative zeta potential values were in accordance with the existence of stable silica colloids. Europium sorption on silica sol colloids was significantly dependent on solution pH. The Kd-values were 2-10 m3 kg-1 for OLSO pH 7-8 and Allard pH 8-9 and 100-140 m3 kg-1 for OLSO pH 10-11. In OLSO pH 10-11 samples Eu-152 was rapidly sorbed onto silica sol colloids and measured radioactivity in a liquid phase was at the background level resulting in inaccurate Kd determination. The concentrations of the released silica colloids were some higher than concentrations of natural colloids determined in granitic groundwater. The main uncertainties remain in the quantification of colloid generation under realistic repository conditions and how mobile colloids are. Irreversible sorption on silica colloids may increase radionuclide transport if colloids are sufficiently stable. Under the prevailing medium saline to saline groundwater conditions in Olkiluoto

  4. Equilibrium crystal phases of triblock Janus colloids.

    Science.gov (United States)

    Reinhart, Wesley F; Panagiotopoulos, Athanassios Z

    2016-09-01

    Triblock Janus colloids, which are colloidal spheres decorated with attractive patches at each pole, have recently generated significant interest as potential building blocks for functional materials. Their inherent anisotropy is known to induce self-assembly into open structures at moderate temperatures and pressures, where they are stabilized over close-packed crystals by entropic effects. We present a numerical investigation of the equilibrium phases of triblock Janus particles with many different patch geometries in three dimensions, using Monte Carlo simulations combined with free energy calculations. In all cases, we find that the free energy difference between crystal polymorphs is less than 0.2 kBT per particle. By varying the patch fraction and interaction range, we show that large patches stabilize the formation of structures with four bonds per patch over those with three. This transition occurs abruptly above a patch fraction of 0.30 and has a strong dependence on the interaction range. Furthermore, we find that a short interaction range favors four bonds per patch, with longer range increasingly stabilizing structures with only three bonds per patch. By quantifying the effect of patch geometry on the stability of the equilibrium crystal structures, we provide insights into the fundamental design rules for constructing complex colloidal crystals. PMID:27609002

  5. Potential Distribution Around a Spherical Colloidal Particle

    International Nuclear Information System (INIS)

    When it is immersed into an electrolyte solution, surface of a colloidal particle will be charged. The charge creates repulsion force among particles. This causes that agglomeration among colloidal particles will be difficult to occur. This paper discusses in brief the surface charging process and then followed by calculation to determine the potential distribution, Ψ, around a spherical colloid particle. The particle has radius of a and zeta potential, ζ, at it's surface. The poisson-Boltzmann equation, εε0∇2Ψ= -σkN ezknk, that determines the potential distribution outside the particle will be solved analytically. Its nonlinearity causes that the equation only can be solved for symmetric, 1-1 electrolyte and with approximation that the double layer thickness is much less than the particle radius. Because of this, the area outside the particle can be divided into two regions, i.e. the electroneutral region far from the surface and the ion diffused region closed to the surface. Solutions to the PB equation will be determined for each region and constants in the solutions will be determined by matching. For the neutral region it is found that ψ = eζ/kTr exp (κa(1-r), with correction factor in the order of O (1/κa)

  6. C-cells in colloid goiter

    Directory of Open Access Journals (Sweden)

    Lima Marcus A.

    2003-01-01

    Full Text Available PURPOSE: The aim of this investigation was to quantitatively evaluate C-cells in colloid goiters, analyzing 36 thyroids that were obtained through thyroidectomy from 24 patients with goiter and 12 normal glands from adult patients without thyroid disease, which were used as the control group. MATERIAL AND METHODS: On average, 6 different thyroid areas were sampled and labeled by immunohistochemistry with a monoclonal anticalcitonin antibody, utilizing the avidin-biotin-peroxidase complex. C-cells were counted in fields measuring 1 square centimeter, and the mean number of cells per field was then calculated. Data were statistically analyzed using the Mann-Whitney test. RESULTS: In the colloid goiter group, the number of C-cells ranged from 0 to 23 per field, while in normal controls they ranged from 20 to 148 per field. CONCLUSIONS: These results demonstrate a significant decrease of C-cell number in the colloid goiter group compared with control group, indicating that the hyperplastic process is restricted to follicular cells, to the detriment of C-cells, which probably cease to receive trophic stimuli.

  7. Improving feed slurry rheology by colloidal techniques

    Energy Technology Data Exchange (ETDEWEB)

    Heath, W.O.; Ternes, R.L.

    1984-06-01

    Pacific Northwest Laboratory (PSN) has investigated three colloidal techniques in the laboratory to improve the sedimentation and flowability of Hanford simulated (nonradioactive) current acid waste (CAW) melter feed slurry: polymer-induced bridging flocculation; manipulating glass former (raw SiO/sub 2/ or frit) particle size; and alteration of nitric acid content. All three methods proved successful in improving the rheology of the simulated CAW feed. This initially had exhibited nearly worst-case flow and clogging properties, but was transformed into a flowable, resuspendable (nonclogging) feed. While each has advantages and disadvantages, the following three specific alternatives proved successful: addition of a polyelectrolyte in 2000 ppM concentration to feed slurry; substitution of a 49 wt % SiO/sub 2/ colloidal suspension (approx. 10-micron particle size) for the -325 mesh (less than or equal to 44-micron particle size) raw-chemical SiO/sub 2/; and increase of nitric acid content from the reference 1.06 M to optimum 1.35 M. The first method, polymer-induced bridging flocculation, results in a high sediment volume, nonclogging CAW feed. The second method, involving the use of colloidal silica particles results in a nonsedimenting feed that when left unagitated forms a gel. The third method, increase in feed acidity, results in a highly resuspendable (nonclogging) melter feed. Further research is therefore required to determine which of the three alternatives is the preferred method of achieving rheological control of CAW melter feeds.

  8. An evaporation model of colloidal suspension droplets

    Science.gov (United States)

    Sartori, Silvana; Li\\ Nán, Amable; Lasheras, Juan C.

    2009-11-01

    Colloidal suspensions of polymers in water or other solvents are widely used in the pharmaceutical industry to coat tablets with different agents. These allow controlling the rate at which the drug is delivered, taste or physical appearance. The coating is performed by simultaneously spraying and drying the tablets with the colloidal suspension at moderately high temperatures. The spreading of the coating on the pills surface depends on the droplet Webber and Reynolds numbers, angle of impact, but more importantly on the rheological properties of the drop. We present a model for the evaporation of a colloidal suspension droplet in a hot air environment with temperatures substantially lower than the boiling temperature of the carrier fluid. As the liquid vaporizes from the surface, a compacting front advances into the droplet faster than the liquid surface regresses, forming a shell of a porous medium where the particles reach their maximum packing density. While the surface regresses, the evaporation rate is determined by both the rate at which heat is transported to the droplet surface and the rate at which liquid vapor is diffused away from it. This regime continues until the compacting front reaches the center of the droplet, at which point the evaporation rate is drastically reduced.

  9. Synthesis of metal colloids in inverse microemulsions

    Science.gov (United States)

    Barnickel, P.; Wokaun, A.

    Colloidal silver and gold particles have been prepared by reduction of aqueous metal salt solutions in inverse microemulsions. The sols are characterized by absorption spectroscopy and electron microscopy. Ultrasound treatment during reduction results in a narrower size distribution of the colloidal particles, as evidenced by a narrower absorption band. Photochemical silver and gold sol formation, without the addition of a reducing agent, has been observed for inverse microemulsions of metal salt solutions in a medium consisting of dodecyl-heptaethyleneglycol-ether and hexane. The particle sizes determined from electron microscopy have been used as input parameters for the simulation of absorption spectra, based on the electromagnetic theory of localized surface plasmon excitation. For the gold sols a quantitative agreement between experimental and simulated spectra is obtained. With the silver colloids, the observed red-shift of the absorption maximum points to the presence of an ionic layer on the surface of the particles. When this layer is included in the theoretical model, good agreement with the experiment is achieved.

  10. Design and elaboration of colloidal molecules: an overview.

    Science.gov (United States)

    Duguet, Etienne; Désert, Anthony; Perro, Adeline; Ravaine, Serge

    2011-02-01

    The concept of colloidal molecules was first evoked by van Blaaderen in 2003 for describing small non-spherical colloids made of the aggregation of a small number of particles. He predicted original properties to the complex assemblies of such colloids, in particular in optics. This critical review deals with the different strategies reported for creating robust clusters of spherical particles which could mimic the space-filling models of simple conventional molecules. These routes concern either the controlled clustering of preformed colloids directed by coalescence, physical routes, chemical routes, or 2-D/3-D geometrical confinement, or strategies starting from a single colloid which is decorated by satellite colloids by taking advantage of controlled phase separation or nucleation and growth phenomena. These routes are compared from the viewpoint of the accessible shapes, their tunability and scalability (146 references). PMID:21212874

  11. Colloid migration in groundwaters: Geochemical interactions of radionuclides with natural colloids. 5. progress report

    International Nuclear Information System (INIS)

    The aim of the joint research programme is to determine the significance of groundwater colloids in far field radionuclide migration. The characterization, quantification and theoretical interpretation of colloid-borne transport phenomena of radionuclides in selected Gorleben aquifer systems are the main objectives of the present research programme. Gorleben aquifer systems are chosen because they are well characterized in terms of their hydrological and geological properties and because they contain substantial amounts of colloids of different chemical compositions as well as considerable quantities of chemical homologues and natural analogues of radionuclides, e.g. M(III), M(IV), M(VI), and Th and U decay series. The research tasks are investigated jointly by the four laboratories (listed below) in close coordination of experimental capacities of each laboratory. (orig.)

  12. Formation mechanisms of metal colloids

    Science.gov (United States)

    Halaciuga, Ionel

    Highly dispersed uniform metallic particles are widely used in various areas of technology and medicine and are likely to be incorporated into many other applications in the future. It is commonly accepted that size, shape and composition of the particles represent critical factors in most applications. Thus, understanding the mechanisms of formation of metal particles and the ways to control the physical (e.g. shape, size) and chemical (e.g. composition) properties is of great importance. In the current research, the formation of uniform silver spheres is investigated experimentally. The parameters that influence the formation of silver particles when concentrated iso-ascorbic acid and silver-polyamine complex solutions are rapidly mixed were studied in the absence of dispersants. We found that by varying the nature of the amine, temperature, concentration of reactants, silver/amine molar ratio, and the nature of the silver salt, the size of the resulting silver particles can be varied in a wide range (0.08--1.5 microm). The silver particles were formed by aggregation of nanosize subunits as substantiated by both electron microscopy and X-ray diffraction techniques and by the vivid rapid color changes during the chemical precipitation process. From the practical standpoint, the goal of this research was to prepare well dispersed spherical silver particles having a relatively smooth surface and a diameter of about 1 microm to satisfy the demands of the current electronic materials market. A two stage particle growth model previously developed to explain the narrow size distribution occurring in synthesis of gold spheres was applied to the present experimental system, and the parameters that control the size distribution characteristics were identified. The kinetic parameter required to match the final particle size was found to be in agreement with the one used previously in modeling formation of gold spheres, suggesting that similar kinetics governs the

  13. Surface forces studied with colloidal probe atomic force microscopy

    OpenAIRE

    Giesbers, M.

    2001-01-01

    Forces between surfaces are a determining factor for the performance of natural as well as synthetic colloidal systems, and play a crucial role in industrial production processes. Measuring these forces is a scientific and experimental challenge and over the years several techniques have been developed to measure the interaction between surfaces directly as a function of their separation distance. Colloidal probe atomic force microscopy (colloidal probe AFM) offers the possibility to study su...

  14. Colloidal Stability and Thermal Stability of Magnetic Fluids

    OpenAIRE

    I.M. Arefyev; T.A. Arefyeva; Yu.B. Kazakov

    2013-01-01

    Colloidal and thermal stabilities of magnetic fluids define the service life of magneto-liquid equipment. The results of the research into colloidal and thermal stabilities of original synthesized magnetic fluids based on kerosene, siloxane fluid and synthetic hydrocarbon oil are presented. The method of carrying agent substitution was used in the research into colloidal stability. The thermal tests were conducted in the research into thermal stability. The conclusions about the prospects of ...

  15. Reconfigurable multi-scale colloidal assembly on excluded volume patterns

    OpenAIRE

    Tara D. Edwards; Yuguang Yang; W. Neil Everett; Bevan, Michael A.

    2015-01-01

    The ability to create multi-scale, periodic colloidal assemblies with unique properties is important to emerging applications. Dynamically manipulating colloidal structures via tunable kT-scale attraction can provide the opportunity to create particle-based nano- and microstructured materials that are reconfigurable. Here, we report a novel tactic to obtain reconfigurable, multi-scale, periodic colloidal assemblies by combining thermoresponsive depletant particles and patterned topographical ...

  16. Short-wave infrared colloidal quantum dot photodetectors on silicon

    OpenAIRE

    Hu, Chen; Gassenq, Alban; Justo, Yolanda; Yakunin, Sergii; Heiss, Wolfgang; Hens, Zeger; Roelkens, Gunther

    2013-01-01

    In this paper, two kinds of colloidal quantum dots, PbS and HgTe, are explored for SWIR photodetectors application. The colloidal dots are prepared by hot injection chemical synthesis, with organic ligands around the dots keeping them stable in solution. For the purpose of achieving efficient carrier transport between the dots in a film, these long organic ligands are replaced by shorter, inorganic ligands. We report uniform, ultra-smooth colloidal QD films without cracks realized by dip-coat...

  17. Recent research progress in wettability of colloidal crystals

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The wettability of solid surfaces has attracted extensive interest in both theoretical research and industrial applications. This paper reviews recent research progress in the fabrication and applications of the colloidal crystals with special wettability. Based on the modified equation of Wenzel and Cassie, the colloidal crystals with special wettability have been obtained by either application of the intrinsic rough structure or modification of the surface chemical composition. Some typical applications of colloidal crystals with special wettability have also been demonstrated.

  18. Semi-analytical solution for soliton propagation in colloidal suspension

    Directory of Open Access Journals (Sweden)

    Senthilkumar Selvaraj

    2013-04-01

    Full Text Available We consider the propagation of soliton in colloidal nano-suspension. We derive the semi analytical solution for soliton propagation in colloidal nano-suspensions for both one and two spatial dimensions using variational method. This Variational method uses both Averaged Lagrangian and suitable trial functions. Finally we analyse about Rayleigh scattering loss in the soliton propagation through the colloidal nano-suspensions.

  19. Sodium meta-autunite colloids: Synthesis, characterization, stability

    OpenAIRE

    Zheng, Zuoping; Wan, Jiamin; Tokunaga, Tetsu K.

    2004-01-01

    Waste forms of U such as those in the United States Department of Energy's Hanford Site often contain high concentrations of Na and P. Low solubility sodium uranyl phosphates such as sodium meta-autunite have the potential to form mobile colloids that can facilitate transport of this radionuclide. In order to understand the geochemical behavior of uranyl phosphate colloids, we synthesized sodium meta-autunite colloids, and characterized their morphology, chemical composition, structure, ...

  20. General elastic interaction in nematic liquid crystals colloids

    OpenAIRE

    Chernyshuk, S. B.; Lev, B. I.

    2009-01-01

    The new free energy functional that describes general elastic interaction between colloidal particles and nematic liquid crystal has been proposed. It generalizes results of the paper \\cite{lupe} on the case of arbitrary orientation of colloidal particles and is valid for arbitrary surface anchoring strength. Formal analogies and differences between electric particles and colloidal particles in LC are found. It is first time shown that spur of the quadrupole moment tensor is different from ze...

  1. Oppositely charged colloids out of equilibrium

    Science.gov (United States)

    Vissers, T.

    2010-11-01

    Colloids are particles with a size in the range of a few nanometers up to several micrometers. Similar to atomic and molecular systems, they can form gases, liquids, solids, gels and glasses. Colloids can be used as model systems because, unlike molecules, they are sufficiently large to be studied directly with light microscopy and move sufficiently slow to study their dynamics. In this thesis, we study binary systems of polymethylmethacrylate (PMMA) colloidal particles suspended in low-polar solvent mixtures. Since the ions can still partially dissociate, a surface charge builds up which causes electrostatic interactions between the colloids. By carefully tuning the conditions inside the suspension, we make two kinds of particles oppositely charged. To study our samples, we use Confocal Laser Scanning Microscopy (CLSM). The positively and negatively charged particles can be distinguished by a different fluorescent dye. Colloids constantly experience a random motion resulting from random kicks of surrounding solvent molecules. When the attractions between the oppositely charged particles are weak, the particles can attach and detach many times and explore a lot of possible configurations and the system can reach thermodynamic equilibrium. For example, colloidal ‘ionic’ crystals consisting of thousands to millions of particles can form under the right conditions. When the attractions are strong, the system can become kinetically trapped inside a gel-like state. We observe that when the interactions change again, crystals can even emerge again from this gel-like phase. By using local order parameters, we quantitatively study the crystallization of colloidal particles and identify growth defects inside the crystals. We also study the effect of gravity on the growth of ionic crystals by using a rotating stage. We find that sedimentation can completely inhibit crystal growth and plays an important role in crystallization from the gel-like state. The surface

  2. Bletilla colloid as a vascular embolization agent: experimental studies

    International Nuclear Information System (INIS)

    Purpose: To study the efficacy, safety and related characteristics of bletilla colloid as a vascular embolization agent. Materials and methods: The authors prepared bletilla colloid as a vascular embolization agent from the stem tubers of bletilla of Chinese medicinal herb. Related characteristics of bletilla colloid were studied. In four pigs hepatic arterial embolization was performed with the bletilla colloid. Results: The bletilla colloid was a homogenous viscous colloid whose relative viscosity was 2324.6 mm2/s. It was easily injected through 4-F catheter and hyperattenuating under fluoroscopy, meanwhile, with good histocompatibility and hemo-compatibility, without pyrogenetic response and toxicity. In vitro, the mixture of bletilla colloid and MMC did not produce separation and suspension phenomena but released 50% of MMC at 1.8h and 100% at 3.4h. The bletilla colloid mainly embolized peripheral arteries, maintaining occlusion for 5 weeks and without formation of collateral circulation. The injuries of normal hepatic tissues were slight, without hepatic cytonecrosis. Conclusions: Bletilla colloid, safe and effective in use with angioembolic function and characteristics of carrier and slow-release, is a potential peripheral embolization agent

  3. Giant Leaking Colloid Cyst Presenting with Aseptic Meningitis

    DEFF Research Database (Denmark)

    Bakhtevari, Mehrdad Hosseinzadeh; Sharifi, Guive; Jabbari, Reza;

    2015-01-01

    BACKGROUND: Colloid cysts are benign third ventricle lesions that need to be diagnosed correctly because of their association with sudden death. Chemical or aseptic meningitis is a rare presentation of a colloid cyst. METHODS: We present a case of a 69-year-old man with fever, alteration of mental...... status, and meningismus. Microbiological examination of the cerebrospinal fluid revealed aseptic meningitis. Brain imaging revealed a third ventricular colloid cyst with hydrocephalus. RESULTS: The tumor was resected via endoscopic intervention. There were no persistent operative complications related to...... the endoscopic procedure. CONCLUSIONS: Chemical or aseptic meningitis is an unusual clinical manifestation of a colloid cyst, complicating the differential diagnosis, especially in the elderly....

  4. Laser-induced assembly of gold nanoparticles into colloidal crystals

    International Nuclear Information System (INIS)

    Micron-sized colloidal crystals comprised of gold nanospheres have been synthesized directly from a gold nanoparticle/methyl methacrylate colloid by application of a 514 nm laser at 500 mW. An array of colloidal crystals can be created by translation of the glass substrate under the laser beam, after 2 min of irradiation at each site. We demonstrate through a series of control experiments and calculations that plasmon-induced, localized heating of the gold nanoparticles contributes to the mechanism responsible for the formation of these colloidal crystals

  5. Optical properties of gold colloids formed in inverse micelles

    International Nuclear Information System (INIS)

    We discuss the formation of gold metal colloids in a variety of surfactant/solvent systems. Static and dynamic light scattering, small angle x-ray and neutron scattering, TEM analysis, and UV-visible absorbance are used to characterize the kinetics of formation and final colloid stability. These gold colloids exhibit a dramatic blueshift and broadening of the plasmon resonance with decreasing colloid size. Several types of reduction method are discussed and differences between micelle (water-free) or microemulsions as reaction media are compared. Use of inverse micelles allows smaller clusters to be formed with greater long-term stability

  6. Fabrication of bioinspired nanostructured materials via colloidal self-assembly

    Science.gov (United States)

    Huang, Wei-Han

    Through millions of years of evolution, nature creates unique structures and materials that exhibit remarkable performance on mechanicals, opticals, and physical properties. For instance, nacre (mother of pearl), bone and tooth show excellent combination of strong minerals and elastic proteins as reinforced materials. Structured butterfly's wing and moth's eye can selectively reflect light or absorb light without dyes. Lotus leaf and cicada's wing are superhydrophobic to prevent water accumulation. The principles of particular biological capabilities, attributed to the highly sophisticated structures with complex hierarchical designs, have been extensively studied. Recently, a large variety of novel materials have been enabled by natural-inspired designs and nanotechnologies. These advanced materials will have huge impact on practical applications. We have utilized bottom-up approaches to fabricate nacre-like nanocomposites with "brick and mortar" structures. First, we used self-assembly processes, including convective self-assembly, dip-coating, and electrophoretic deposition to form well oriented layer structure of synthesized gibbsite (aluminum hydroxide) nanoplatelets. Low viscous monomer was permeated into layered nanoplatelets and followed by photo-curing. Gibbsite-polymer composite displays 2 times higher tensile strength and 3 times higher modulus when compared with pure polymer. More improvement occurred when surface-modified gibbsite platelets were cross-linked with the polymer matrix. We observed ˜4 times higher strength and nearly 1 order of magnitude higher modulus than pure polymer. To further improve the mechanical strength and toughness of inorganicorganic nanocomposites, we exploited ultrastrong graphene oxide (GO), a single atom thick hexagonal carbon sheet with pendant oxidation groups. GO nanocomposite is made by co-filtrating GO/polyvinyl alcohol suspension on 0.2 im pore-sized membrane. It shows ˜2 times higher strength and ˜15 times higher

  7. Mixed Movements

    DEFF Research Database (Denmark)

    Brabrand, Helle

    2010-01-01

    levels than those related to building, and this exploration is a special challenge and competence implicit artistic development work. The project Mixed Movements generates drawing-material, not primary as representation, but as a performance-based media, making the body being-in-the-media felt and appear......Mixed Movements is a research project engaged in performance-based architectural drawing. Architectonic implementation questions relations between the human body and a body of architecture by the different ways we handle drawing materials. A drawing may explore architectonic problems at other...

  8. Methods for preparing colloidal nanocrystal-based thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kagan, Cherie R.; Fafarman, Aaron T.; Choi, Ji-Hyuk; Koh, Weon-kyu; Kim, David K.; Oh, Soong Ju; Lai, Yuming; Hong, Sung-Hoon; Saudari, Sangameshwar Rao; Murray, Christopher B.

    2016-05-10

    Methods of exchanging ligands to form colloidal nanocrystals (NCs) with chalcogenocyanate (xCN)-based ligands and apparatuses using the same are disclosed. The ligands may be exchanged by assembling NCs into a thin film and immersing the thin film in a solution containing xCN-based ligands. The ligands may also be exchanged by mixing a xCN-based solution with a dispersion of NCs, flocculating the mixture, centrifuging the mixture, discarding the supernatant, adding a solvent to the pellet, and dispersing the solvent and pellet to form dispersed NCs with exchanged xCN-ligands. The NCs with xCN-based ligands may be used to form thin film devices and/or other electronic, optoelectronic, and photonic devices. Devices comprising nanocrystal-based thin films and methods for forming such devices are also disclosed. These devices may be constructed by depositing NCs on to a substrate to form an NC thin film and then doping the thin film by evaporation and thermal diffusion.

  9. Flavor mixing

    International Nuclear Information System (INIS)

    Recently, some researchers have been talking about the so-called 'fifth force'. This name suggests that four forces are already known to exist, which are generally called the strong, electromagnetic, weak, and gravitational interactions. However, the standard model of particle physics tells a different story; they are the gauge interactions, Yukawa interactions, Higgs interactions, and gravity. Of the first three, only the gauge interactions have been verified experimentally. However, the other two are truly necessary ingredients of the standard model to make it work. The present report discusses such matters as Kobayashi-Maskawa matrix, KM matrix elements, CP violation, particle antiparticle mixing, flavor-charging neutral current decays, generation crossover, FCNC decay, and lepton flavor mixing. It is concluded that the Kobayashi-Maskawa scheme for the quark mixing is in good shape. So far five out of nine matrix elements are experimentally determined. Nonzero value of the sixth matrix element Kub is essential for the KM scenario of CP violation. The observed large B-B-bar mixing suggests a heavy top quark. A lot of work is still needed towards the understanding of 'flavor'. (N.K.)

  10. Activation energies of colloidal particle aggregation: towards a quantitative characterization of specific ion effects.

    Science.gov (United States)

    Tian, Rui; Yang, Gang; Li, Hang; Gao, Xiaodan; Liu, Xinmin; Zhu, Hualing; Tang, Ying

    2014-05-21

    A quantitative description of specific ion effects is an essential and focused topic in colloidal and biological science. In this work, the dynamic light scattering technique was employed to study the aggregation kinetics of colloidal particles in the various alkali ion solutions with a wide range of concentrations. It indicated that the activation energies could be used to quantitatively characterize specific ion effects, which was supported by the results of effective hydrodynamic diameters, aggregation rates and critical coagulation concentrations. At a given concentration of 25 mmol L(-1), the activation energies for Li(+) are 1.2, 5.7, 28, and 126 times as much for Na(+), K(+), Rb(+), and Cs(+), respectively. Most importantly, the activation energy differences between two alkali cation species increase sharply with decrease of electrolyte concentrations, implying the more pronounced specific ion effects at lower concentrations. The dominant role of electrolyte cations during the aggregation of negatively charged colloidal particles was confirmed by alternative anions. Among the various theories, only the polarization effect can give a rational interpretation of the above specific ion effects, and this is substantially supported by the presence of strong electric fields from montmorillonite surfaces and its association mainly with electrolyte cations and montmorillonite particles. The classical induction theory, although with inclusion of electric field, requires significant corrections because it predicts an opposite trend to the experimentally observed specific ion effects. PMID:24603654

  11. Rapid adhesion and proliferation of keratinocytes on the gold colloid/chitosan film scaffold

    International Nuclear Information System (INIS)

    The gold colloid/chitosan film scaffold, which could enhance the attached ratio and accelerate proliferation of newborn mice keratinocytes, was fabricated by nanotechnology and self-assembly technology. This nanometer scaffold was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The keratinocytes were cultured and observed on three different extracellular matrices (ECM): gold colloid/chitosan film scaffold, chitosan film and cell culture plastic (control groups). 6 h, 12 h, 24 h after inoculation, the cell attached ratios were calculated respectively. In comparison to control groups, this scaffold could significantly (P < 0.01) increase the attached ratio of keratinocytes and promote their growth. Meanwhile, there were not any fusiform fibroblasts growing on this scaffold. The rapidly proliferating keratinocytes were indentified and characterized by immunohistochemistry and transmissive electron microscope (TEM), which showed the cells maintain their biological activity well. The results indicated that gold colloid/chitosan film scaffold was nontoxic to keratinocytes, and was a good candidate for wound dressing in skin tissue engineering.

  12. Luminescence properties of II/VI semiconductor colloidal nanocrystals at collective and single scales

    Energy Technology Data Exchange (ETDEWEB)

    Vion, Celine; Barthou, Carlos; Coolen, Laurent; Bennaloul, Paul; MaItre, Agnes [Institut des NanoSciences de Paris, Unite Mixte de Recherche-CNRS 7588, Universite Pierre et Marie Curie, Paris (France); Vu Duc Chinh; Pham Thuy Linh; Vu Thi Bich; Pham Thu Nga [Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi (Viet Nam)], E-mail: celine.vion@insp.jussieu.fr

    2009-09-01

    Colloidal nanocrystals are crystalline spheres of semiconductors of a few nanometers, obtained by chemical synthesis. At this size scale, lower than Bohr radius of the exciton, emission properties are dominated by quantum confinement effects and depend crucially on the nanocrystal radius, which can be controlled by adjusting the synthesis parameters. Nanocrystals present high photostability and good quantum efficiency, even at room temperature. Their emission wavelength can be tuned over the whole visible range, making them very attractive solid state light sources which are already used in optoelectronic devices or for biological labeling. The luminescence properties of CdSe colloidal nanocrystals synthesized at the Institute of Materials Science in Hanoi are presented. At collective scale, the emission properties reveal the synthesis quality. Temperature effects from ambient to 4 K on spectra and decay rates will be presented and analyzed in terms of emitting level fine structure. The study of CdSe colloidal quantum dots at the single emitter scale is of great interest as it reveals properties which are hidden by collective studies, such as luminescence 'blinking', a random switching from a fluorescent to a non fluorescent state, which is closely related to the crystalline defects of a nanocrystal and its interaction with its environment. We will present the blinking properties of the prepared nanocrystals, and relate them to the nanocrystals synthesis quality and shell quality.

  13. Generation of stable colloidal gold nanoparticles by ultrashort laser-induced melting and fragmentation

    Science.gov (United States)

    Vasa, Parinda; Sharma, Rahul; Singh, Mamraj; Dharmadhikari, Aditya K.; Dharmadhikari, Jayashree A.; Mathur, Deepak

    2014-09-01

    We report on generation of stable colloidal gold nanoparticles by ultrashort laser-induced melting and fragmentation. Irradiation of colloidal gold nanoparticles (of initial size larger than 25 nm) by 56 fs long, near-IR pulses of moderate fluence (1.3-5.3 J cm-2) generates very small (2.5 nm) nanoparticles with a narrow size distribution (±0.5 nm). Systematic measurements show the final size of fragmented nanoparticles to be (i) very weakly dependent on the original size and particle shape as well as of pump laser wavelength (800 nm, 1200 nm and 1350 nm), but (ii) strongly dependent on laser parameters; moreover, fragmentation is effectively controllable by pulse fluence and irradiation time. The fragmented particles appear to be contaminant free and have high crystalline quality. We find that the fragmented particles are stable over a time period of more than three months. Stable, contaminant-free, crystalline colloidal gold nanoparticles of sizes around 3 nm, with very narrow size distribution, have potential utility in diverse nanotechnological applications, ranging from biologically relevant imaging to nanoscopic generators of high-frequency mechanical vibrations in the GHz range.

  14. Generation of stable colloidal gold nanoparticles by ultrashort laser-induced melting and fragmentation

    International Nuclear Information System (INIS)

    We report on generation of stable colloidal gold nanoparticles by ultrashort laser-induced melting and fragmentation. Irradiation of colloidal gold nanoparticles (of initial size larger than 25 nm) by 56 fs long, near-IR pulses of moderate fluence (1.3–5.3 J cm−2) generates very small (2.5 nm) nanoparticles with a narrow size distribution (±0.5 nm). Systematic measurements show the final size of fragmented nanoparticles to be (i) very weakly dependent on the original size and particle shape as well as of pump laser wavelength (800 nm, 1200 nm and 1350 nm), but (ii) strongly dependent on laser parameters; moreover, fragmentation is effectively controllable by pulse fluence and irradiation time. The fragmented particles appear to be contaminant free and have high crystalline quality. We find that the fragmented particles are stable over a time period of more than three months. Stable, contaminant-free, crystalline colloidal gold nanoparticles of sizes around 3 nm, with very narrow size distribution, have potential utility in diverse nanotechnological applications, ranging from biologically relevant imaging to nanoscopic generators of high-frequency mechanical vibrations in the GHz range. (paper)

  15. Physicochemical Characterization and Cytotoxicity Screening of a Novel Colloidal Nanogold-Based Phenytoin Conjugate

    Science.gov (United States)

    Suneetha, Susan Cleave A; Raghupathy, Bala Praveen Chakkravarthy; Suresh, P. K.

    2014-01-01

    Abstract A novel, colloidal nanogold-based drug delivery system for phenytoin, a well-known anti-epileptic drug with an enhanced efflux via P-glycoprotein, has been proposed in this study. The vital physical properties that would aid in predicting the biological interaction of this system were profiled using various techniques such as UV-Vis, DLS, and TEM in corroboration with theoretical calculations. It was significant to note that the binding of phenytoin to colloidal nanogold was strongly pH-dependent with the optimum at pH 5.5 and a consistently reproducible spectral shift. Analysis of the conjugate by FTIR revealed that the imide functional group of phenytoin mediated a dative coordinate bond to colloidal nanogold at the optimum pH. The amount of the drug bound to the gold was quantified to be 85.8±2.5% (w/v) by HPLC. Hypothetically, the surface charge of the conjugate could possibly imply charge-mediated uptake across the cell membrane. Further, the novel conjugate was screened for its cytotoxicity in two cell lines and the dosage range was identified. Subsequent development, thorough evaluations in suitable model systems, and the potential for bioimaging to track the payload would validate our hypothesis on the conjugate for better intracellular retention at the site of action, and thereby achieve the targeted delivery. PMID:26171330

  16. Scanning electron and atomic force microscopy investigation of extracellular polymeric substances, hematite and EPS-hematite colloids and aggregates

    Science.gov (United States)

    Wieczorek, Arkadiusz K.; Narvekar, Sneha; Totsche, Kai Uwe

    2013-04-01

    Natural colloids are involved in a multitude of biogeochemical and physicochemical processes in aqueous systems. However, the chemical composition, mineralogical diversity and morphological variability of natural colloids are the reasons for the difficulty to understand their formation, stability and mechanisms of interaction with other solutes. In this study we explore the effects of different amount of extracellular polymeric substances (EPS) of Bacillus subtilis on the aggregation and stability of hematite colloids. The hematite colloids were synthesized using Schwertmann and Cornell method [1], where ferric nitrite solution slowly drops into the boiling water. Bacillus subtilis EPS was obtained using Omoike and Chorover method [2], where EPS was precipitated from the supernatant solution by using three volumes of cold ethanol. Then the mixture was centrifuged and dialyzed to remove ethanol and residual media components and stored at -20C. Synthetic hematite was mixed with different amounts of EPS resulting in solutions with EPS/hematite ratios of 1:5, 1:2, 1:0.5 and 1:0.2. Droplets of the colloidal suspension were put on silicon wafer and subject to air drying. The wafers were then analyzed by Scanning Electron Microscopy (SEM) with energy-dispersive Xray spectroscopy and Atomic Force Microscopy (AFM). A control sample with pure synthetic hematite colloid was also prepared and analyzed. Pure hematite colloids form homogenic distribution of relatively small aggregates of 40 to 100 nm size. Theses aggregates loosely connect to each other creating skeletal or fisher-net like structures. The smallest amount of EPS results in coagulation of hematite in very large (up to 80 µm) islands/aggregates of tightly packed hematite nanoparticles. Adding EPS decreases the size of islands to the point where again only 40 to 100 nm size aggregates are visible, but they are strictly separated in comparison to the pure hematite colloid. Although separation of hematite aggregates

  17. Anisotropic Colloids: Synthesis and Phase Behavior of Eccentric, Dimer and String-like Colloids

    NARCIS (Netherlands)

    Demirors, A.F.

    2010-01-01

    The research described in this thesis focuses on synthesis and phase behavior of anisotropic colloids prepared through different synthetic strategies. Namely, eccentric core-shell particles, dimers, string-like particles and core-shell particles are the systems investigated throughout this work. The

  18. Explorative analysis of microbes, colloids and gases

    Energy Technology Data Exchange (ETDEWEB)

    Hallbeck, Lotta; Pedersen, Karsten (Microbial Analytics Sweden AB, Goeteborg (Sweden))

    2008-08-15

    The overall objectives of the hydrogeochemical description for Forsmark are to establish a detailed understanding of the hydrogeochemical conditions at the site and to develop models that fulfil the needs identified by the safety assessment groups during the site investigation phase. Issues of concern to safety assessment are radionuclide transport and technical barrier behaviour, both of which are dependent on the chemistry of groundwater and pore water and their evolution with time. In this report, part of the final hydrogeochemical evaluation work of the site investigation at the Forsmark site, is presented. The work was conducted by SKB's hydrogeochemical project group, ChemNet, which consists of independent consultants and Univ. researchers with expertise in geochemistry, hydrochemistry, hydrogeochemistry, microbiology, geomicrobiology, analytical chemistry etc. The resulting site descriptive model version, mainly based on 2.2 data and complementary 2.3 data, was carried out during September 2006 to December 2007. This report focuses on microbiology, colloids and gases: - Microbes (Chapter 1): Several methods must be used to characterize active microbial communities in groundwater. Microbial parameters of interest are the total number of cells (TNC) and the presence of various metabolic groups of microorganisms. Different microbial groups influence the environment in different ways, depending on what metabolic group is dominant. Typically, the following redox couples are utilized by bacteria in granitic groundwater: H{sub 2}O/O{sub 2}, NO{sub 3}-/N{sub 2}, Mn2+/Mn(IV), Fe2+/Fe(III), S2-/SO{sub 4}2-, CH{sub 4}/CO{sub 2}, CH{sub 3}COOH/CO{sub 2}, and H{sub 2}/H+. The data will indicate the activity of specific microbial populations at particular sites and how they may affect the geochemistry. - Colloids (Chapter 2): Particles in the size range from 1 to 1x10-3 mum are regarded as colloids. Their small size prohibits them from settling, which gives them the

  19. Explorative analysis of microbes, colloids and gases

    International Nuclear Information System (INIS)

    The overall objectives of the hydrogeochemical description for Forsmark are to establish a detailed understanding of the hydrogeochemical conditions at the site and to develop models that fulfil the needs identified by the safety assessment groups during the site investigation phase. Issues of concern to safety assessment are radionuclide transport and technical barrier behaviour, both of which are dependent on the chemistry of groundwater and pore water and their evolution with time. In this report, part of the final hydrogeochemical evaluation work of the site investigation at the Forsmark site, is presented. The work was conducted by SKB's hydrogeochemical project group, ChemNet, which consists of independent consultants and Univ. researchers with expertise in geochemistry, hydrochemistry, hydrogeochemistry, microbiology, geomicrobiology, analytical chemistry etc. The resulting site descriptive model version, mainly based on 2.2 data and complementary 2.3 data, was carried out during September 2006 to December 2007. This report focuses on microbiology, colloids and gases: - Microbes (Chapter 1): Several methods must be used to characterize active microbial communities in groundwater. Microbial parameters of interest are the total number of cells (TNC) and the presence of various metabolic groups of microorganisms. Different microbial groups influence the environment in different ways, depending on what metabolic group is dominant. Typically, the following redox couples are utilized by bacteria in granitic groundwater: H2O/O2, NO3-/N2, Mn2+/Mn(IV), Fe2+/Fe(III), S2-/SO42-, CH4/CO2, CH3COOH/CO2, and H2/H+. The data will indicate the activity of specific microbial populations at particular sites and how they may affect the geochemistry. - Colloids (Chapter 2): Particles in the size range from 1 to 1x10-3 μm are regarded as colloids. Their small size prohibits them from settling, which gives them the potential to transport radionuclides in groundwater. The aim of

  20. Transport and Deposition of Variably Charged Soil Colloids in Saturated Porous Media

    DEFF Research Database (Denmark)

    Sharma, Anu; Kawamoto, Ken; Møldrup, Per; de Jonge, Lis Wollesen; Komatsu, Toshiko

    2011-01-01

    A series of column experiments was conducted to investigate the transport and deposition of variably charged colloids in saturated porous media. Soil colloids with diameters <1 mm were extracted from a volcanic-ash soil from Nishi-Tokyo (referred to here as VAS colloids) and a red-yellow soil from...... of both soil colloids and sand grains, thereby increasing colloid deposition. This study emphasizes that the pH-dependent surface charge of both mobile colloids and receiving porous media needs more consideration in models for colloid and colloid-facilitated transport in soil....

  1. Sulfate—Exchange Alkalinity of Ferralsol Colloid

    Institute of Scientific and Technical Information of China (English)

    ZHANGGANGYA; ZHANGXIAONIAN

    1999-01-01

    The amount of OH- replaced by sulfate,i.e.,sulfate-exchange alkalinity,from the electric double layer of ferralsol colloid was measured quantitatively in different conditions with an automatic titration equipment.The amount of OH- release increased with the amount of Na2SO4 added and decreased with raising pH in the suspension of ferralsol colloid.The exchange acidity was displayed as pH was higher than 5.6,If the negative effect of sodium ions was offset,the amount of OH- replaced by sulfate was larger than the original amount of OH- released in the pH range of lower than 5.8.The amount of OH- released decreased rapidly as pH was higher than 6.0 and dropped to zero when pH reached 6.5.In the solution of 2.0molL-1 NaClO4,the amount of OH- repleaced by sulfate from the surface of ferralsol colloid could be considered as the amount of OH- adsorbed by ligand exchange reaction.The amount of OH- released in the solution of NaClO4 concentration below 2.0mol L-1 from which the amount of OH- adsorbed by ligand exchange reaction was subtracted could be conidered as the OH- adsorbed by electrostatic force,The OH- adsorbed by electrostatic force decreased with increases in the concentration of NaClO4 and pH and increased almost linearly with the increasing amount of Na2SON4 added.The percentages of OH- adsorbed by electrostatic force in water and in the electrolyte solutions of 0.05 and 0.5mol L-1 NaClO4 in the total OH- released were calculated,respectively.

  2. Generation, stability and migration of montmorillonite colloids in aqueous systems

    International Nuclear Information System (INIS)

    In Sweden the encapsulated nuclear waste will be surrounded by compacted bentonite in the granitic host rock. In contact with water-bearing fractures the bentonite barrier may release montmorillonite colloids that may be further transported in groundwater. If large amounts of material are eroded from the barrier, the buffer functionality can be compromised. Furthermore, in the scenario of a leaking canister, strongly sorbing radionuclides, can be transported by montmorillonite colloids towards the biosphere. This thesis addresses the effects of groundwater chemistry on the generation, stability, sorption and transport of montmorillonite colloids in water bearing rock fractures. To be able to predict quantities of montmorillonite colloids released from the bentonite barrier in contact with groundwater of varying salinity, generation and sedimentation test were performed. The aim is first to gain understanding on the processes involved in colloid generation from the bentonite barrier. Secondly it is to test if concentration gradients of montmorillonite colloids outside the barrier determined by simple sedimentation experiments are comparable to generation tests. Identical final concentrations and colloid size distributions were achieved in both types of tests. Colloid stability is strongly correlated to the groundwater chemistry. The impact of pH, ionic strength and temperature was studied. Aggregation kinetics experiments revealed that for colloid aggregation rate increased with increasing ionic strength. The aggregation rate decreased with increasing pH. The temperature effect on montmorillonite colloid stability is pH-dependent. At pH≤4, the rate constant for colloid aggregation increased with increasing temperature, regardless of ionic strength. At pH≥10, the aggregation rate constant decreased with increasing temperature. In the intermediate pH interval, the aggregation rate constant decreased with increasing temperature except at the highest ionic strength

  3. Room temperature synthesis of colloidal platinum nanoparticles

    Indian Academy of Sciences (India)

    G Sarala Devi; V J Rao

    2000-12-01

    Efficient preparation of stable dispersions of platinum nanoparticles from platinous chloride (K2PtCl4) was achieved by simultaneous addition of capping polymer material. The size of platinum nanoparticles was controlled by changing the ratio of concentration of capping polymer material to the concentration of platinum cation used. The morphology of colloidal particles were studied by means of UV-visible spectrophotometry and transmission electron microscopy (TEM). Particle size increased with low reagent concentration. The change in absorption spectra with the particle size was observed, i.e. blue shift attributed to decrease in particle size.

  4. Structure and Frictional Properties of Colloid Gel

    OpenAIRE

    Masayuki Tokita

    2014-01-01

    Polymer gels are known to be opaque when the preparation conditions, such as the reaction temperature and the composition, are changed. The increase of the opaqueness of the gel suggests strongly the change of network structure. Here, we are going to review the recent studies on the structure and the frictional study of the opaque poly(acrylamide) gel. The results indicate that the opaque poly(acrylamide) gel consists of the fractal aggregate of the colloidal particles of sub-micrometer in si...

  5. Three-dimensional lock and key colloids.

    Science.gov (United States)

    Wang, Yu; Wang, Yufeng; Zheng, Xiaolong; Yi, Gi-Ra; Sacanna, Stefano; Pine, David J; Weck, Marcus

    2014-05-14

    Colloids with well-defined multicavities are synthesized through the hydrolytic removal of silica cluster templates from organo-silica hybrid patchy particles. The geometry of the cavities stems from the originally assembled cluster templates, displaying well-defined three-dimensional symmetries, ranging from spherical, linear, triangular, tetrahedral, trigonal dipyramidal, octahedral, to pentagonal dipyramidal. The concave surface of the cavities is smooth, and the cavity shallowness and size can be varied. These particles with multicavities can act as "lock" particles with multiple "key holes". Up to n "key" particles can self-assemble into the lock particles via depletion interaction, resulting in multivalent, site-specific, reversible, and flexible bonding. PMID:24785203

  6. Size determinations of colloidal fat emulsions

    DEFF Research Database (Denmark)

    Kuntsche, Judith; Klaus, Katrin; Steiniger, Frank

    2009-01-01

    Size and size distributions of colloidal dispersions are of crucial importance for their performance and safety. In the present study, commercially available fat emulsions (Lipofundin N, Lipofundin MCT and Lipidem) were analyzed by photon correlation spectroscopy, laser diffraction with adequate...... slightly smaller size was indicated by all methods for Lipidem. Sub-micron resolution was best in the Coulter LS but the fraction of larger particles in the upper nm-range was presumably underestimated. The emulsions could be analyzed in a highly reproducible manner by asymmetrical flow field...

  7. Fractal-like structures in colloid science.

    Science.gov (United States)

    Lazzari, S; Nicoud, L; Jaquet, B; Lattuada, M; Morbidelli, M

    2016-09-01

    The present work aims at reviewing our current understanding of fractal structures in the frame of colloid aggregation as well as the possibility they offer to produce novel structured materials. In particular, the existing techniques to measure and compute the fractal dimension df are critically discussed based on the cases of organic/inorganic particles and proteins. Then the aggregation conditions affecting df are thoroughly analyzed, pointing out the most recent literature findings and the limitations of our current understanding. Finally, the importance of the fractal dimension in applications is discussed along with possible directions for the production of new structured materials. PMID:27233526

  8. Behaviour of colloidal silicas during uniaxial compaction

    OpenAIRE

    Ehrburger, Françoise; Lahaye, Jacques

    1989-01-01

    The pressure P transmitted by colloidal silica samples during low speed uniaxial compaction, is measured as a function of the volume fraction f of solid. In the case of pyrogenic silicas, two domains are evidenced. A first one below f ~ 0.065, is characterized by a percolation type behaviour P ~ (f - fc)k. For higher volume fractions (second domain) P scales as the void volume Vp, P ~ (Vp)- α with α ~ 3. It appears that the behaviour of the precipitated silica is very different. The P(f) curv...

  9. Colloid research for the Nevada Test Site

    International Nuclear Information System (INIS)

    Research is needed to understand the role of particulates in the migration of radionuclides away from the sites of nuclear tests at the Nevada Test Site. The process of testing itself may produce a reservoir of particles to serve as vectors for the transport of long-lived radionuclides in groundwater. Exploratory experiments indicate the presence of numerous particulates in the vicinity of the Cambric test but a much lower loading in a nearby well that has been pumped continuously for 15 years. Recent groundwater colloid research is briefly reviewed to identify sampling and characterization methods that may be applicable at the Nevada Test Site

  10. Colloidal optical waveguides structured by light

    Czech Academy of Sciences Publication Activity Database

    Brzobohatý, Oto; Kaňka, Jan; Chvátal, Lukáš; Ježek, Jan; Zemánek, Pavel

    New York : City College of New York, 2015. ISBN 978-2-9545460-7-0. [META’15. International Conference on Metamaterials, Photonic Crystals and Plasmonics /6./. New York (US), 04.08.2015-07.08.2015] R&D Projects: GA ČR(CZ) GA14-16195S; GA TA ČR TE01020233; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : colloidal optical waveguides Subject RIV: BH - Optics, Masers, Lasers

  11. Biological Threats

    Science.gov (United States)

    ... Workplace Plans School Emergency Plans Main Content Biological Threats Biological agents are organisms or toxins that can ... for Disease Control and Prevention . Before a Biological Threat Unlike an explosion, a biological attack may or ...

  12. Enhanced fluorescence imaging performance of hydrophobic colloidal ZnO nanoparticles by a facile method

    International Nuclear Information System (INIS)

    Highlights: • A dual phase hydrothermal method was developed to synthesize ZnO nanoparticles. • ZnO nanoparticles show a stability and solubility in the aqueous environment. • ZnO nanoparticles with a blue emission wavelength at around 420 nm and small size (30 nm). • ZnO nanoparticles as biological labeling agent was also shown. - Abstract: A facile synthesis method for the formation of ZnO nanoparticles by using a double-phase reaction was demonstrated in this paper. The morphology of the synthesized ZnO nanoparticles shows a flower-shape. Hydrogen peroxide was used as a unique oxygenic source to promote the formation of ZnO in the presence of organic zinc precursor. The as-synthesized ZnO nanoparticles also show a stability and solubility in the aqueous environment. The structure and properties of ZnO nanoparticles were investigated by the transmission electron microscopy (TEM) and X-ray diffraction (XRD) as well as UV–vis and photoluminescence spectroscopy. The as-prepared hydrophobic colloidal ZnO nanoparticles could be modified to become water-soluble via ligand exchange with amineothanethiol⋅HCl while retaining the photoluminescence properties. In addition, the potential application for biological label of water-soluble ZnO nanoparticles were also demonstrated. These results not only have applications towards using colloidal ZnO nanoparticles effectively in biological fluorescence imaging, but also promote its application in the field of targeted drug delivery

  13. Pharmacological study of radioactive-gold colloid transport by blood and by serous exudate; Contribution a l'etude pharmacologique du transport des colloides d'or radioactif par le sang et les exsudats sereux

    Energy Technology Data Exchange (ETDEWEB)

    Rousselet, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-06-01

    After giving the essential physico-chemical properties of the colloids, the author considers the biological role of these substances and, in connection with their transport by the blood, their capture by elements of the reticula-endothelial system. A summary is given of present knowledge concerning the role of serous proteins in the transport of substances, particularly that of radio-active colloidal gold. The blood fractions which can take part in colloidal gold transport are the red blood corpuscles, the leukocytes and histiocytic elements as well as the plasma. The radioactive distribution in these various fractions is obtained by autoradiography of blood sediments. After showing the importance of the role of the plasma in radioactive particle transport, the author, describes the attempts made to detect a possible of colloidal gold 198 on the various serous proteins using various methods of separation. The ''in vitro'' and ''in vivo'' bonds between colloidal gold-198 particles and either the serous proteins or healthy specimens or the effusion liquids of pathological origin in man, or due to an experimental inflammation with carregenin in the rat, have been studied. The bonding appears to be effective because of the protective macromolecular layer formed by the gelatine. The different positions of the colloidal grains on the electrophoregram can only be explained by their different physico-chemical characteristics. Gold in the ionic form, on the other hand, is combined only with the albumen is the amount metal present does not exceed a certain value. (author) [French] Apres avoir enonce les proprietes physicochimiques essentielles des colloides nous etudions le devenir biologique de ces substances et, en relation avec leur transport par le sang, leur captation par les elements du Systeme Reticulo-Endothelial. Nous resumons les connaissances acquises jusqu'alors sur le role des proteines seriques dans le transport des

  14. Use and abuse of mixing models (MixSIAR)

    Science.gov (United States)

    Background/Question/MethodsCharacterizing trophic links in food webs is a fundamental ecological question. In our efforts to quantify energy flow through food webs, ecologists have increasingly used mixing models to analyze biological tracer data, often from stable isotopes. Whil...

  15. Aqueous Synthesis of PEGylated Quantum Dots with Increased Colloidal Stability and Reduced Cytotoxicity.

    Science.gov (United States)

    Ulusoy, Mehriban; Jonczyk, Rebecca; Walter, Johanna-Gabriela; Springer, Sergej; Lavrentieva, Antonina; Stahl, Frank; Green, Mark; Scheper, Thomas

    2016-02-17

    Ligands used on the surface of colloidal nanoparticles (NPs) have a significant impact on physiochemical properties of NPs and their interaction in biological environments. In this study, we report a one-pot aqueous synthesis of 3-mercaptopropionic acid (MPA)-functionalized CdTe/CdS/ZnS quantum dots (Qdots) in the presence of thiol-terminated methoxy polyethylene glycol (mPEG) molecules as a surface coordinating ligand. The resulting mPEG-Qdots were characterized by using ζ potential, FTIR, thermogravimetric (TG) analysis, and microscale thermophoresis (MST) studies. We investigated the effect of mPEG molecules and their grafting density on the Qdots photophysical properties, colloidal stability, protein binding affinity, and in vitro cellular toxicity. Moreover, cellular binding features of the resulting Qdots were examined by using three-dimensional (3D) tumor-like spheroids, and the results were discussed in detail. Promisingly, mPEG ligands were found to increase colloidal stability of Qdots, reduce adsorption of proteins to the Qdot surface, and mitigate Qdot-induced side effects to a great extent. Flow cytometry and confocal microscopy studies revealed that PEGylated Qdots exhibited distinctive cellular interactions with respect to their mPEG grafting density. As a result, mPEG molecules demonstrated a minimal effect on the ZnS shell deposition and the Qdot fluorescence efficiency at a low mPEG density, whereas they showed pronounced effect on Qdot colloidal stability, protein binding affinity, cytotoxicity, and nonspecific binding at a higher mPEG grafting amount. PMID:26567697

  16. Bismuth oxide aqueous colloidal nanoparticles inhibit Candida albicans growth and biofilm formation

    Directory of Open Access Journals (Sweden)

    Hernandez-Delgadillo R

    2013-04-01

    Full Text Available Rene Hernandez-Delgadillo,1 Donaji Velasco-Arias,3 Juan Jose Martinez-Sanmiguel,2 David Diaz,3 Inti Zumeta-Dube,3 Katiushka Arevalo-Niño,1 Claudio Cabral-Romero2 1Facultad de Ciencias Biológicas, Instituto de Biotecnologia, Universidad Autonoma de Nuevo Leon, UANL, Monterrey, Mexico; 2Facultad de Odontología, Universidad Autonoma de Nuevo Leon, UANL, Monterrey, México; 3Facultad de Quimica, Universidad Nacional Autonoma de Mexico, UNAM, Distrito Federal, México Abstract: Multiresistance among microorganisms to common antimicrobials has become one of the most significant concerns in modern medicine. Nanomaterials are a new alternative to successfully treat the multiresistant microorganisms. Nanostructured materials are used in many fields, including biological sciences and medicine. Recently, it was demonstrated that the bactericidal activity of zero-valent bismuth colloidal nanoparticles inhibited the growth of Streptococcus mutans; however the antimycotic potential of bismuth nanostructured derivatives has not yet been studied. The main objective of this investigation was to analyze the fungicidal activity of bismuth oxide nanoparticles against Candida albicans, and their antibiofilm capabilities. Our results showed that aqueous colloidal bismuth oxide nanoparticles displayed antimicrobial activity against C. albicans growth (reducing colony size by 85% and a complete inhibition of biofilm formation. These results are better than those obtained with chlorhexidine, nystatin, and terbinafine, the most effective oral antiseptic and commercial antifungal agents. In this work, we also compared the antimycotic activities of bulk bismuth oxide and bismuth nitrate, the precursor metallic salt. These results suggest that bismuth oxide colloidal nanoparticles could be a very interesting candidate as a fungicidal agent to be incorporated into an oral antiseptic. Additionally, we determined the minimum inhibitory concentration for the synthesized

  17. Studies on the preparation and evaluation of colloidal chromic phosphate - 32P for possible therapeutic use

    International Nuclear Information System (INIS)

    Radionuclide therapy has become the focus of recent attention in nuclear medicine, thanks to the emergence of new therapeutic radionuclides as well as the known prospects of local instillation approach and the exciting promise of targeted therapy concept. This has naturally led to a revived interest in the use of established products of earlier generation also, for example 32P compounds. In response to such a demand of nuclear medicine physicians in India, 32P labelled colloidal chromic phosphate suspension (CCPS) was prepared by suitable modifications to a reported procedure. 51Cr was used as tracer for initial studies of standardisation, in order to avail the benefits of relatively greater ease and higher efficiency of assay of gamma activity at low levels. Recovery of the colloid and purification were accomplished by dialysis leading to about 60% radiochemical (RC) yield. The RC purity of the CCPS formulated in 30% dextrose solution was over 98% as assessed by paper chromatography. The particle size was below 5μM, with nearly 99% of the particles present in the size range of 0.6-2.5 μM. The stability of the colloid was found to be not less than 7 days, in terms of soluble phosphate content of the CCPS. The consistency of biological behaviour of CCPS was attempted to be studied by i.v. administration in test animals, although the envisaged end use is only by local instillation. The animal studies revealed prominent lung uptake ( 70%) indicating the presence of >10μM particles formed in vivo, most probably due to agglomeration in serum. The easy reliable preparation of CCPS in acceptable yield, purity and particle size distribution demonstrated in the present study, considered along with the added advantages of abundant, economic availability and convenient production logistics of no-carrier-added 32P, would merit further investigations on CCPS and similar *M(III)-phosphate colloids for possible therapeutic applications. (author)

  18. A Stochastic Model for Colloid Transport and Deposition

    Science.gov (United States)

    Profiles of retained colloids in porous media have frequently been observed to be hyper-exponential or nonmonotonic with transport depth under unfavorable attachment conditions, whereas filtration theory predicts an exponential profile. In this work we present a stochastic model for colloid transpo...

  19. Coherent Acoustic Phonons in Colloidal Semiconductor Nanocrystal Superlattices.

    Science.gov (United States)

    Poyser, Caroline L; Czerniuk, Thomas; Akimov, Andrey; Diroll, Benjamin T; Gaulding, E Ashley; Salasyuk, Alexey S; Kent, Anthony J; Yakovlev, Dmitri R; Bayer, Manfred; Murray, Christopher B

    2016-01-26

    The phonon properties of films fabricated from colloidal semiconductor nanocrystals play a major role in thermal conductance and electron scattering, which govern the principles for building colloidal-based electronics and optics including thermoelectric devices with a high ZT factor. The key point in understanding the phonon properties is to obtain the strength of the elastic bonds formed by organic ligands connecting the individual nanocrystallites. In the case of very weak bonding, the ligands become the bottleneck for phonon transport between infinitively rigid nanocrystals. In the opposite case of strong bonding, the colloids cannot be considered as infinitively rigid beads and the distortion of the superlattice caused by phonons includes the distortion of the colloids themselves. We use the picosecond acoustics technique to study the acoustic coherent phonons in superlattices of nanometer crystalline CdSe colloids. We observe the quantization of phonons with frequencies up to 30 GHz. The frequencies of quantized phonons depend on the thickness of the colloidal films and possess linear phonon dispersion. The measured speed of sound and corresponding wave modulus in the colloidal films point on the strong elastic coupling provided by organic ligands between colloidal nanocrystals. PMID:26696021

  20. Statistical Mechanics of Superparamegnetic Colloidal Dispersions Under Magnetic Fields

    OpenAIRE

    Andreu, Jordi

    2013-01-01

    Colloidal dispersions, a term coined by the Scottish scientist Thomas Graham in 1861, have been the subject of interest in different scientific areas during more than a century. A colloidal dispersion is characterized by the existence of a dispersed phase uniformly distributed throughout a dispersion medium.

  1. Fluorescent colloidal silica rods - synthesis and phase behavior

    NARCIS (Netherlands)

    Kuijk, A.

    2012-01-01

    Although the experimental study of spherical colloids has been extensive, similar studies on rod-like particles are rare because suitable model systems are scarce. To fulfill this need, we present the synthesis of monodisperse rod-like silica colloids with tunable dimensions. Rods were produced with

  2. Formation, characterization, and stability of plutonium (IV) colloid

    International Nuclear Information System (INIS)

    Plutonium is expected to be a major component of the waste element package in any high-level nuclear waste repository. Plutonium(IV) is known to form colloids under chemical conditions similar to those found in typical groundwaters. In the event of a breach of a repository, these colloids represent a source of radionuclide transport to the far-field environment, in parallel with the transport of dissolved waste element species. In addition, the colloids may decompose or disaggregate into soluble ionic species. Thus, colloids represent an additional term in determining waste element solubility limits. A thorough characterization of the physical and chemical properties of these colloids under relevant conditions is essential to assess the concentration limits and transport mechanisms for the waste elements at the proposed Yucca Mountain Repository site. This report is concerned primarily with recent results obtained by the Yucca Mountain Project (YMP) Solubility Determination Task pertaining to the characterization of the structural and chemical properties of Pu(IV) colloid. Important results will be presented which provides further evidence that colloidal plutonium(IV) is structurally similar to plutonium dioxide and that colloidal plutonium(IV) is electrochemically reactive. 13 refs., 7 figs

  3. Extinction and Scattering of Light by Magnetic Colloidal Nanoparticles

    Directory of Open Access Journals (Sweden)

    C.V. Yerin

    2015-12-01

    Full Text Available The peculiarities of scattering and extinction of light by colloids with different concentrations of magnetite nanoparticles are investigated. The light absorption effect on spectral dependencies of optical density of magnetic colloid are observed. According to dynamic light scattering experiments, particle size distributions for samples with different concentration of nanoparticles are defined.

  4. Colloid-Facilitated Plutonium Transport in Saturated Alluvium

    International Nuclear Information System (INIS)

    Natural groundwater colloids have been recognized as possible agents for enhancing the subsurface transport of strongly-sorbing radionuclides. To evaluate this mechanism, packed-bed column experiments were conducted comparing the simultaneous transport of dissolved plutonium (Pu), Pu sorbed onto natural colloids, 190-nm and 500-nm diameter fluorescent CML microspheres, and tritiated water in saturated alluvium. Experiments were conducted in two columns having slightly different porosities at two flow rates, resulting in average linear velocities (vz) of 0.6 to 3.65 cm/hr in one column and 0.57 to 2.85 cm/hr in the other. In all experiments, Pu associated with natural colloids transported through alluvium essentially unretarded, while dissolved Pu was entirely retained. These results were consistent with the strong sorption of Pu to alluvium and the negligible desorption from natural colloids, observed in separate batch experiments, over time scales exceeding those of the column experiments. Breakthroughs of natural colloids preceded tritiated water in all experiments, indicating a slightly smaller effective pore volume for the colloids. The enhancement of colloids transport over tritiated water decreased with vz, implying ∼ 40% enhancement at vz = 0. The 500-nm CML microspheres were significantly attenuated in the column experiments compared to the 190-nm microspheres, which exhibited slightly more attenuation than natural colloids

  5. Particle Trapping and Banding in Rapid Colloidal Solidification

    KAUST Repository

    Elliott, J. A. W.

    2011-10-11

    We derive an expression for the nonequilibrium segregation coefficient of colloidal particles near a moving solid-liquid interface. The resulting kinetic phase diagram has applications for the rapid solidification of clay soils, gels, and related colloidal systems. We use it to explain the formation of bandlike defects in rapidly solidified alumina suspensions. © 2011 American Physical Society.

  6. Fabrication and Characterization of Colloidal Crystal Thin Films

    Science.gov (United States)

    Rodriguez, I.; Ramiro-Manzano, F.; Meseguer, F.; Bonet, E.

    2011-01-01

    We present a laboratory experiment that allows undergraduate or graduate students to get introduced to colloidal crystal research concepts in an interesting way. Moreover, such experiments and studies can also be useful in the field of crystallography or solid-state physics. The work concerns the growth of colloidal crystal thin films obtained…

  7. Reversible assembly of oppositely charged hairy colloids in water

    NARCIS (Netherlands)

    Spruijt, E.; Bakker, H.E.; Kodger, T.E.; Sprakel, J.H.B.; Stuart, M.A.C.; Gucht, van der J.

    2011-01-01

    We present an experimental study of the fully reversible assembly of oppositely charged colloidal particles in aqueous solutions. Our polystyrene colloids are charged by a grafted polyelectrolyte brush on their surface and stabilized at all salt concentrations by a neutral adsorbed polymer layer. Be

  8. Avalanches, plasticity, and ordering in colloidal crystals under compression

    Science.gov (United States)

    McDermott, D.; Reichhardt, C. J. Olson; Reichhardt, C.

    2016-06-01

    Using numerical simulations we examine colloids with a long-range Coulomb interaction confined in a two-dimensional trough potential undergoing dynamical compression. As the depth of the confining well is increased, the colloids move via elastic distortions interspersed with intermittent bursts or avalanches of plastic motion. In these avalanches, the colloids rearrange to minimize their colloid-colloid repulsive interaction energy by adopting an average lattice constant that is isotropic despite the anisotropic nature of the compression. The avalanches take the form of shear banding events that decrease or increase the structural order of the system. At larger compression, the avalanches are associated with a reduction of the number of rows of colloids that fit within the confining potential, and between avalanches the colloids can exhibit partially crystalline or anisotropic ordering. The colloid velocity distributions during the avalanches have a non-Gaussian form with power-law tails and exponents that are consistent with those found for the velocity distributions of gliding dislocations. We observe similar behavior when we subsequently decompress the system, and find a partially hysteretic response reflecting the irreversibility of the plastic events.

  9. Predicting colloid transport through saturated porous media: A critical review

    Science.gov (United States)

    Molnar, Ian L.; Johnson, William P.; Gerhard, Jason I.; Willson, Clinton S.; O'Carroll, Denis M.

    2015-09-01

    Understanding and predicting colloid transport and retention in water-saturated porous media is important for the protection of human and ecological health. Early applications of colloid transport research before the 1990s included the removal of pathogens in granular drinking water filters. Since then, interest has expanded significantly to include such areas as source zone protection of drinking water systems and injection of nanometals for contaminated site remediation. This review summarizes predictive tools for colloid transport from the pore to field scales. First, we review experimental breakthrough and retention of colloids under favorable and unfavorable colloid/collector interactions (i.e., no significant and significant colloid-surface repulsion, respectively). Second, we review the continuum-scale modeling strategies used to describe observed transport behavior. Third, we review the following two components of colloid filtration theory: (i) mechanistic force/torque balance models of pore-scale colloid trajectories and (ii) approximating correlation equations used to predict colloid retention. The successes and limitations of these approaches for favorable conditions are summarized, as are recent developments to predict colloid retention under the unfavorable conditions particularly relevant to environmental applications. Fourth, we summarize the influences of physical and chemical heterogeneities on colloid transport and avenues for their prediction. Fifth, we review the upscaling of mechanistic model results to rate constants for use in continuum models of colloid behavior at the column and field scales. Overall, this paper clarifies the foundation for existing knowledge of colloid transport and retention, features recent advances in the field, critically assesses where existing approaches are successful and the limits of their application, and highlights outstanding challenges and future research opportunities. These challenges and opportunities

  10. Asymmetrical phase separation and gelation in binary mixtures of oppositely charged colloids

    Science.gov (United States)

    Zong, Yiwu; Yuan, Guangcui; Han, Charles C.

    2016-07-01

    Two types of colloidal particles, which are nearly the same in chemical composition but carry opposite surface charges, are mixed in water. Depending on the relative proportion of the oppositely charged particles, the process of aggregation leads to the formation of discrete clusters of various sizes in dilute dispersions, and to the development of particle gel networks in more concentrated systems. Due to the significant difference in the absolute values of surface charges (negative particle: -48 mV, positive particle: +24 mV), the phase separation and the gelation behaviors are asymmetric with respect to the mixing ratio. Mixtures with excess negative particles are more stable, while mixtures with excess positive particles are easily affected by phase separation. The hetero-aggregation triggered by the addition of microscopically large macro-ions is similar to what is often observed in a mono-component charged colloidal system, i.e., phase separation occurs through addition of small electrolyte ions. Within the concentration region investigated here, it is clear that the gel line is buried inside the phase separation region. Gelation occurs only when the number and size of the clusters are large and big enough to connect up into a space-spanning network. Our results indicate that, in this binary mixture of oppositely charged colloids, although the interaction between unlike species is attractive and that between like species is repulsive, the onset of gelation is in fact governed by the equilibrium phase separation, as in the case of purely attractive systems with short-range isotropic interaction.

  11. Marketing mix

    OpenAIRE

    Staniková, Aneta

    2013-01-01

    Summary This diploma thesis focuses on the design of marketing mix emerging object. The building is located in the village Hejtmankovice in Broumov. Originally a farm house undergoing complete renovation in 2011. Now the owner's aim is to establish this object like accommodation establishments. This thesis is not only focused on this aim, but is extended by providing additional options and catering services. The thesis is completed with the analysis of micro and macro environment, pricing ...

  12. [Mixed marriages].

    Science.gov (United States)

    Harmsen, C N

    1998-08-01

    The author examines the extent and characteristics of mixed marriages in the Netherlands. "Nine out of ten married persons born in Turkey or Morocco have a partner who was born in the same country. The majority of married Surinamese also have a partner originating from the same country. Those who spend (a part of) their youth in Indonesia (the former Dutch East Indies), on the other hand, are mostly married to someone born in the Netherlands." (EXCERPT) PMID:12294179

  13. Studies of colloids and their importance for repository performance assessment

    International Nuclear Information System (INIS)

    The processes, parameters and data used to evaluate the potential of nuclide transport by a colloid facilitated mechanism are reviewed and discussed in this report. Both steady-state (present situation) and possible future non-steady-state hydrogeochemistry in the geosphere are covered. In the steady-state scenario, the colloid (clay, silica, iron(III)hydroxide) concentration is around 20-45 micrograms/l which is considered to be a low value. The low colloid concentration is justified by the large attachment factor to the rock which reduces the stability of the colloids in the aquifer. Both reversible and irreversible sorption processes are reviewed. In the non-steady-state scenario, changes of hydrogeochemical properties may induce larger colloid concentrations. The increase of concentration is however limited and relaxation is always observed after any change. Emphasis is placed on the glaciation-deglaciation scenario. 53 refs, 12 figs, 3 tabs

  14. Long-time self-diffusion of charged colloids

    International Nuclear Information System (INIS)

    Using a recently developed mode-coupling scheme we calculate the long-time self-diffusion coefficient of colloids in charge-stabilized dispersions, such as globular proteins or micelles. All ionic species (colloids, counterions and salt ions) are treated on the same footing, that is as overdamped charged hard spheres in a structureless dielectric solvent. More importantly, we include the effects of hydrodynamic interactions, up to the far-field level. It is found that hydrodynamics is essential for a correct description of colloidal self-diffusion, and that the effects of the finite size of the electrolyte ions are relevant only for colloid-electrolyte ion size ratios typically less than five. The theory describes self-diffusion over the entire range of salt concentration and colloidal volume fraction and recovers the relevant limiting laws for very thin and thick electric double layers. (author)

  15. Colloids related to low level and intermediate level waste

    International Nuclear Information System (INIS)

    A comprehensive research investigation has been undertaken to improve the understanding of the potential role of colloids in the context of disposal and storage of low level and intermediate level waste immobilized in cement. Several topics have been investigated which include: (a) the study of the formation and characteristics of colloids in cement leachates; (b) the effects of the near-field aqueous chemistry on the characteristics of colloids in repository environments; (c) colloid sorption behaviour; (d) interactions of near-field materials with leachates; (e) characteristics of near-field materials in EC repository simulation tests; and (f) colloid migration behaviour. These experimental investigations should provide data and a basis for the development of transport models and leaching mechanisms, and thus relate directly to the part of the Task 3 programme concerned with migration and retention of radionuclides in the near field. 114 Figs.; 39 Tabs.; 12 Refs

  16. The effects of corrosion product colloids on actinide transport

    International Nuclear Information System (INIS)

    This report assesses the possible effects of colloidal corrosion products on the transport of actinides from the near field of radioactive waste repositories. The desorption of plutonium and americium from colloidal corrosion products of iron and zirconium was studied under conditions simulating a transition from near-field to far-field environmental conditions. Desorption of actinides occurred slowly from the colloids under far-field conditions. Measurements of particle stability showed all the colloids to be unstable in the near field. Stability increased under far-field conditions or as a result of the evolution of the near field. Migration of colloids from the near field is unlikely except in the presence of organic materials. (Author)

  17. Colloidal layers in magnetic fields and under shear flow

    International Nuclear Information System (INIS)

    The behaviour of colloidal mono- and bilayers in external magnetic fields and under shear is discussed and recent progress is summarized. Superparamagnetic colloidal particles form monolayers when they are confined to a air-water interface in a hanging water droplet. An external magnetic field allows us to tune the strength of the mutual dipole-dipole interaction between the colloids and the anisotropy of the interaction can be controlled by the tilt angle of the magnetic field relative to the surface normal of the air-water interface. For sufficiently large magnetic field strength crystalline monolayers are found. The role of fluctuations in these two-dimensional crystals is discussed. Furthermore, clustering phenomena in binary mixtures of superparamagnetic particles forming fluid monolayers are predicted. Finally, we address sheared colloidal bilayers and find that the orientation of confined colloidal crystals can be tailored by a previously applied shear direction

  18. Single-File Escape of Colloidal Particles from Microfluidic Channels.

    Science.gov (United States)

    Locatelli, Emanuele; Pierno, Matteo; Baldovin, Fulvio; Orlandini, Enzo; Tan, Yizhou; Pagliara, Stefano

    2016-07-15

    Single-file diffusion is a ubiquitous physical process exploited by living and synthetic systems to exchange molecules with their environment. It is paramount to quantify the escape time needed for single files of particles to exit from constraining synthetic channels and biological pores. This quantity depends on complex cooperative effects, whose predominance can only be established through a strict comparison between theory and experiments. By using colloidal particles, optical manipulation, microfluidics, digital microscopy, and theoretical analysis we uncover the self-similar character of the escape process and provide closed-formula evaluations of the escape time. We find that the escape time scales inversely with the diffusion coefficient of the last particle to leave the channel. Importantly, we find that at the investigated microscale, bias forces as tiny as 10^{-15}  N determine the magnitude of the escape time by drastically reducing interparticle collisions. Our findings provide crucial guidelines to optimize the design of micro- and nanodevices for a variety of applications including drug delivery, particle filtering, and transport in geometrical constrictions. PMID:27472142

  19. Single-File Escape of Colloidal Particles from Microfluidic Channels

    Science.gov (United States)

    Locatelli, Emanuele; Pierno, Matteo; Baldovin, Fulvio; Orlandini, Enzo; Tan, Yizhou; Pagliara, Stefano

    2016-07-01

    Single-file diffusion is a ubiquitous physical process exploited by living and synthetic systems to exchange molecules with their environment. It is paramount to quantify the escape time needed for single files of particles to exit from constraining synthetic channels and biological pores. This quantity depends on complex cooperative effects, whose predominance can only be established through a strict comparison between theory and experiments. By using colloidal particles, optical manipulation, microfluidics, digital microscopy, and theoretical analysis we uncover the self-similar character of the escape process and provide closed-formula evaluations of the escape time. We find that the escape time scales inversely with the diffusion coefficient of the last particle to leave the channel. Importantly, we find that at the investigated microscale, bias forces as tiny as 10-15 N determine the magnitude of the escape time by drastically reducing interparticle collisions. Our findings provide crucial guidelines to optimize the design of micro- and nanodevices for a variety of applications including drug delivery, particle filtering, and transport in geometrical constrictions.

  20. Colloidal-based additive manufacturing of bio-inspired composites

    Science.gov (United States)

    Studart, Andre R.

    Composite materials in nature exhibit heterogeneous architectures that are tuned to fulfill the functional demands of the surrounding environment. Examples range from the cellulose-based organic structure of plants to highly mineralized collagen-based skeletal parts like bone and teeth. Because they are often utilized to combine opposing properties such as strength and low-density or stiffness and wear resistance, the heterogeneous architecture of natural materials can potentially address several of the technical limitations of artificial homogeneous composites. However, current man-made manufacturing technologies do not allow for the level of composition and fiber orientation control found in natural heterogeneous systems. In this talk, I will present two additive manufacturing technologies recently developed in our group to build composites with exquisite architectures only rivaled by structures made by living organisms in nature. Since the proposed techniques utilize colloidal suspensions as feedstock, understanding the physics underlying the stability, assembly and rheology of the printing inks is key to predict and control the architecture of manufactured parts. Our results will show that additive manufacturing routes offer a new exciting pathway for the fabrication of biologically-inspired composite materials with unprecedented architectures and functionalities.

  1. Radionuclide transport facilitated by polydispersed pseudo-colloids in the fractured rock media

    International Nuclear Information System (INIS)

    One dimensional analytic transport model in the fractured rock media which incorporates advective-dispersive transport, sorption onto stationary solid medium, pseudo-colloid formation, polydispersity of colloids, and radioactive decay was developed by assuming equilibrium sorption of radionuclide and colloids onto the solid medium and constant concentration of natural colloids in the fracture. It was resulted from this model study that transport of radionuclides in a fractured rock medium was accelerated by the presence of colloids and the polydispersity of colloids increased the mobility of radionuclides in the fracture, although the maximum concentration was decreased, comparing to the case of monodispersed colloids. Also it was noted that the effects of pseudo-colloid formation constant and concentration of natural colloids are of great importance in the transport of colloids. This model study could help to evaluate the significance of colloid presence in groundwater and to assess the overall behavior of radionuclides in groundwater. (author)

  2. Phase transformations in binary colloidal monolayers.

    Science.gov (United States)

    Yang, Ye; Fu, Lin; Marcoux, Catherine; Socolar, Joshua E S; Charbonneau, Patrick; Yellen, Benjamin B

    2015-03-28

    Phase transformations can be difficult to characterize at the microscopic level due to the inability to directly observe individual atomic motions. Model colloidal systems, by contrast, permit the direct observation of individual particle dynamics and of collective rearrangements, which allows for real-space characterization of phase transitions. Here, we study a quasi-two-dimensional, binary colloidal alloy that exhibits liquid-solid and solid-solid phase transitions, focusing on the kinetics of a diffusionless transformation between two crystal phases. Experiments are conducted on a monolayer of magnetic and nonmagnetic spheres suspended in a thin layer of ferrofluid and exposed to a tunable magnetic field. A theoretical model of hard spheres with point dipoles at their centers is used to guide the choice of experimental parameters and characterize the underlying materials physics. When the applied field is normal to the fluid layer, a checkerboard crystal forms; when the angle between the field and the normal is sufficiently large, a striped crystal assembles. As the field is slowly tilted away from the normal, we find that the transformation pathway between the two phases depends strongly on crystal orientation, field strength, and degree of confinement of the monolayer. In some cases, the pathway occurs by smooth magnetostrictive shear, while in others it involves the sudden formation of martensitic plates. PMID:25677504

  3. Convective Cage Release in Model Colloidal Glasses.

    Science.gov (United States)

    Jacob, Alan R; Poulos, Andreas S; Kim, Sunhyung; Vermant, Jan; Petekidis, George

    2015-11-20

    The mechanism of flow in glassy materials is interrogated using mechanical spectroscopy applied to model nearly hard sphere colloidal glasses during flow. Superimposing a small amplitude oscillatory motion orthogonal onto steady shear flow makes it possible to directly evaluate the effect of a steady state flow on the out-of-cage (α) relaxation as well as the in-cage motions. To this end, the crossover frequency deduced from the viscoelastic spectra is used as a direct measure of the inverse microstructural relaxation time, during flow. The latter is found to scale linearly with the rate of deformation. The microscopic mechanism of flow can then be identified as a convective cage release. Further insights are provided when the viscoelastic spectra at different shear rates are shifted to scale the alpha relaxation and produce a strain rate-orthogonal frequency superposition, the colloidal analogue of time temperature superposition in polymers with the flow strength playing the role of temperature. Whereas the scaling works well for the α relaxation, deviations are observed both at low and high frequencies. Brownian dynamics simulations point to the origins of these deviations; at high frequencies these are due to the deformation of the cages which slows down the short-time diffusion, while at low frequency, deviations are most probably caused by some mild hydroclustering. PMID:26636876

  4. Colloidal Quantum Dot Photovoltaics: A Path Forward

    KAUST Repository

    Kramer, Illan J.

    2011-11-22

    Colloidal quantum dots (CQDs) offer a path toward high-efficiency photovoltaics based on low-cost materials and processes. Spectral tunability via the quantum size effect facilitates absorption of specific wavelengths from across the sun\\'s broad spectrum. CQD materials\\' ease of processing derives from their synthesis, storage, and processing in solution. Rapid advances have brought colloidal quantum dot photovoltaic solar power conversion efficiencies of 6% in the latest reports. These achievements represent important first steps toward commercially compelling performance. Here we review advances in device architecture and materials science. We diagnose the principal phenomenon-electronic states within the CQD film band gap that limit both current and voltage in devices-that must be cured for CQD PV devices to fulfill their promise. We close with a prescription, expressed as bounds on the density and energy of electronic states within the CQD film band gap, that should allow device efficiencies to rise to those required for the future of the solar energy field. © 2011 American Chemical Society.

  5. Critical Casimir forces for colloidal assembly

    International Nuclear Information System (INIS)

    Critical Casimir forces attract increasing interest due to their opportunities for reversible particle assembly in soft matter and nano science. These forces provide a thermodynamic analogue of the celebrated quantum mechanical Casimir force that arises from the confinement of vacuum fluctuations of the electromagnetic field. In its thermodynamic analogue, solvent fluctuations, confined between suspended particles, give rise to an attractive or repulsive force between the particles. Due to its unique temperature dependence, this effect allows in situ control of reversible assembly. Both the force magnitude and range vary with the solvent correlation length in a universal manner, adjusting with temperature from fractions of the thermal energy, k B T, and nanometre range to several ten kT and micrometer length scale. Combined with recent breakthroughs in the synthesis of complex particles, critical Casimir forces promise the design and assembly of complex colloidal structures, for fundamental studies of equilibrium and out-of-equilibrium phase behaviour. This review highlights recent developments in this evolving field, with special emphasis on the dynamic interaction control to assemble colloidal structures, in and out of equilibrium. (topical review)

  6. Colloidal Quantum dot photovoltaics: Tuning optoelectronic properties

    International Nuclear Information System (INIS)

    Full text: Colloidal quantum dots combine processing from the solution phase with tunability of the bandgap. Via the size-effect the optical properties can be matched to the solar spectrum for a wide-range photon harvesting. To engineer photovoltaic devices, quantum dots are compressed from their colloidal form into a close-packed nanocrystal matrix, while undergoing a systematic layer-by-layer process. The resulting quantum dot solid is treated as semiconductor medium - one having electron-hole mobilites, free carrier densities and a dielectric constant. While the size-effect determined the band-gap before, it is now the nature of ligand and the treatment route, that influences mentioned electronic parameters. We took the view on the processing steps and found a concept for analysing trap states, moblility and device performance in real quantum dot solids. Our findings emphasize the interplay of mobility and trap-distribution with routes that take special care on the nanocrystal surface and hence conserve optoelectronic qualities of quantum dots for efficient photovoltaic cells. (author)

  7. Critical Casimir forces for colloidal assembly

    Science.gov (United States)

    Nguyen, V. D.; Dang, M. T.; Nguyen, T. A.; Schall, P.

    2016-02-01

    Critical Casimir forces attract increasing interest due to their opportunities for reversible particle assembly in soft matter and nano science. These forces provide a thermodynamic analogue of the celebrated quantum mechanical Casimir force that arises from the confinement of vacuum fluctuations of the electromagnetic field. In its thermodynamic analogue, solvent fluctuations, confined between suspended particles, give rise to an attractive or repulsive force between the particles. Due to its unique temperature dependence, this effect allows in situ control of reversible assembly. Both the force magnitude and range vary with the solvent correlation length in a universal manner, adjusting with temperature from fractions of the thermal energy, k B T, and nanometre range to several ten kT and micrometer length scale. Combined with recent breakthroughs in the synthesis of complex particles, critical Casimir forces promise the design and assembly of complex colloidal structures, for fundamental studies of equilibrium and out-of-equilibrium phase behaviour. This review highlights recent developments in this evolving field, with special emphasis on the dynamic interaction control to assemble colloidal structures, in and out of equilibrium.

  8. Visualization of dislocation dynamics in colloidal crystals.

    Science.gov (United States)

    Schall, Peter; Cohen, Itai; Weitz, David A; Spaepen, Frans

    2004-09-24

    The dominant mechanism for creating large irreversible strain in atomic crystals is the motion of dislocations, a class of line defects in the crystalline lattice. Here we show that the motion of dislocations can also be observed in strained colloidal crystals, allowing detailed investigation of their topology and propagation. We describe a laser diffraction microscopy setup used to study the growth and structure of misfit dislocations in colloidal crystalline films. Complementary microscopic information at the single-particle level is obtained with a laser scanning confocal microscope. The combination of these two techniques enables us to study dislocations over a range of length scales, allowing us to determine important parameters of misfit dislocations such as critical film thickness, dislocation density, Burgers vector, and lattice resistance to dislocation motion. We identify the observed dislocations as Shockley partials that bound stacking faults of vanishing energy. Remarkably, we find that even on the scale of a few lattice vectors, the dislocation behavior is well described by the continuum approach commonly used to describe dislocations in atomic crystals. PMID:15448265

  9. Structure and Frictional Properties of Colloid Gel

    Directory of Open Access Journals (Sweden)

    Masayuki Tokita

    2014-03-01

    Full Text Available Polymer gels are known to be opaque when the preparation conditions, such as the reaction temperature and the composition, are changed. The increase of the opaqueness of the gel suggests strongly the change of network structure. Here, we are going to review the recent studies on the structure and the frictional study of the opaque poly(acrylamide gel. The results indicate that the opaque poly(acrylamide gel consists of the fractal aggregate of the colloidal particles of sub-micrometer in size. The density of the colloid particle is calculated from the structural parameters and is found to be of the order of about 1 g/cm3. The results indicate that the main chain component and the cross-linker is densely cross-linked into the particle. The frictional property of poly(acrylamide gel is analyzed in terms of the structural parameters of the gel. It is found that the frictional property of the opaque gel is well explained in terms of the structural parameters of the opaque gel.

  10. Dynamics and Rheology of Soft Colloidal Glasses

    KAUST Repository

    Wen, Yu Ho

    2015-01-20

    © 2015 American Chemical Society. The linear viscoelastic (LVE) spectrum of a soft colloidal glass is accessed with the aid of a time-concentration superposition (TCS) principle, which unveils the glassy particle dynamics from in-cage rattling motion to out-of-cage relaxations over a broad frequency range 10-13 rad/s < ω < 101 rad/s. Progressive dilution of a suspension of hairy nanoparticles leading to increased intercenter distances is demonstrated to enable continuous mapping of the structural relaxation for colloidal glasses. In contrast to existing empirical approaches proposed to extend the rheological map of soft glassy materials, i.e., time-strain superposition (TSS) and strain-rate frequency superposition (SRFS), TCS yields a LVE master curve that satis fies the Kramers-Kronig relations which interrelate the dynamic moduli for materials at equilibrium. The soft glassy rheology (SGR) model and literature data further support the general validity of the TCS concept for soft glassy materials.

  11. Dynamics of colloidal particles in ice

    Science.gov (United States)

    Spannuth, Melissa; Mochrie, S. G. J.; Peppin, S. S. L.; Wettlaufer, J. S.

    2011-03-01

    Solidification of the solvent phase of a colloidal suspension occurs in many natural and technological settings and is becoming a popular technique for creating microporous structures and composite materials. During freezing, regions of high particle density can form as particles are rejected from the growing solid and guided into a variety of macroscopic morphologies. The particles in the high density regions form an amorphous colloidal solid that deforms in response to internal and external stresses. Using X-ray Photon Correlation Spectroscopy, we studied this deformation for silica particles in polycrystalline ice. We found that the particles in the high density regions underwent ballistic motion coupled with a non-exponential decay of the intensity autocorrelation function (ACF) that transitions from a stretched to a compressed exponential with increasing scattering vector q. While ballistic motion and a compressed exponential decay of the ACF is common, the coupling with a stretched exponential decay is very rare and a transition with increasing q has not previously been reported. We explain this behavior in terms of ice grain boundary migration.

  12. Two-dimensional magnetic colloids under shear.

    Science.gov (United States)

    Mohorič, Tomaž; Dobnikar, Jure; Horbach, Jürgen

    2016-04-01

    Complex rheological properties of soft disordered solids, such as colloidal gels or glasses, inspire a range of novel applications. However, the microscopic mechanisms of their response to mechanical loading are not well understood. Here, we elucidate some aspects of these mechanisms by studying a versatile model system, i.e. two-dimensional superparamagnetic colloids in a precessing magnetic field, whose structure can be tuned from a hexagonal crystal to a disordered gel network by varying the external field opening angle θ. We perform Langevin dynamics simulations subjecting these structures to a constant shear rate and observe three qualitatively different types of material response. In hexagonal crystals (θ = 0°), at a sufficiently low shear rate, plastic flow occurs via successive stress drops at which the stress releases due to the formation of dislocation defects. The gel network at θ = 48°, on the contrary, via bond rearrangement and transient shear banding evolves into a homogeneously stretched network at large strains. The latter structure remains metastable after switching off of the shear. At θ = 50°, the external shear makes the system unstable against phase separation and causes a failure of the network structure leading to the formation of hexagonal close packed clusters interconnected by particle chains. At a microcopic level, our simulations provide insight into some of the mechanisms by which strain localization as well as material failure occur in a simple gel-like network. Furthermore, we demonstrate that new stretched network structures can be generated by the application of shear. PMID:26877059

  13. Shaken, and stirred: oscillatory segmented flow for controlled size-evolution of colloidal nanomaterials.

    Science.gov (United States)

    Abolhasani, Milad; Oskooei, Ali; Klinkova, Anna; Kumacheva, Eugenia; Günther, Axel

    2014-07-01

    We introduce oscillatory segmented flow as a compact microfluidic format that accommodates slow chemical reactions for the solution-phase processing of colloidal nanomaterials. The strategy allows the reaction progress to be monitored at a dynamic range of up to 80 decibels (i.e., residence times of up to one day, equivalent to 720-14,400 times the mixing time) from only one sensing location. A train of alternating gas bubbles and liquid reaction compartments (segmented flow) was initially formed, stopped and then subjected to a consistent back-and-forth motion. The oscillatory segmented flow was obtained by periodically manipulating the pressures at the device inlet and outlet via square wave signals generated by non-wetted solenoid valves. The readily implementable format significantly reduced the device footprint as compared with continuous segmented flow. We investigated mixing enhancement for varying liquid segment lengths, oscillation amplitudes and oscillation frequencies. The etching of gold nanorods served as a case study to illustrate the utility of the approach for dynamic characterization and precise control of colloidal nanomaterial size and shape for 5 h. Oscillatory segmented flows will be beneficial for a broad range of lab-on-a-chip applications that require long processing times. PMID:24828153

  14. Effects of kaolinite colloids on Cd2 + transport through saturated sand under varying ionic strength conditions: Column experiments and modeling approaches

    Science.gov (United States)

    Wikiniyadhanee, Rakkreat; Chotpantarat, Srilert; Ong, Say Kee

    2015-11-01

    Column experiments were performed under various ionic strengths (0.0-0.9 mM) using 10 mg L- 1 of Cd2 + without kaolinite colloids and 10 mg L- 1 Cd2 + mixed with 100 mg L- 1 kaolinite colloids. The nonequilibrium two-site model (TSM) described the behavior of both Cd2 + transport and Cd2 + co-transported with kaolinite colloids better than the equilibrium model (CDeq) (R2 = 0.978-0.996). The results showed that an increase in ionic strength negatively impacted the retardation factors (R) of both Cd2 + and Cd2 + mixed with kaolinite colloids. The presence of kaolinite colloids increased the retardation factors of Cd2 + from 7.23 to 7.89, 6.76 to 6.61 and 3.79 to 6.99 for ionic strengths of 0.225, 0.45 and 0.9 mM, respectively. On the other hand, the presence of kaolinite colloids decreased the retardation factor of Cd2 + from 8.13 to 7.83 for ionic strength of 0.0 mM. The fraction of instantaneous sorption sites (f) parameters, kinetic constant for sorption sites (α) and Freundlich constant (Kf) were estimated from HYDRUS-1D of TSM for Cd2 + transport. The fraction of instantaneous sorption sites was found to increase for an increase in ionic strength. Kf values of Cd2 + transport without kaolinite colloids for 0.0, 0.225 and 0.45 mM were found to be higher than those of Cd2 + transport with kaolinite colloids, except for ionic strength of 0.9 mM. Hence, the presence of kaolinite colloids probably retarded the mobility of Cd2 + in porous media for higher ionic strengths. Furthermore, retardation factors and Kf values of both Cd2 + transport and Cd2 + co-transport were shown to decrease when ionic strength increased. Interestingly, according to TSM, the fraction of instantaneous sorption sites tends to increase for an increase in ionic strength, which imply that the mechanism of Cd2 + sorption onto quartz sand can be better described using equilibrium sorption rather than nonequilibrium sorption for an increase in ionic strength.

  15. Effects of kaolinite colloids on Cd²⁺ transport through saturated sand under varying ionic strength conditions: Column experiments and modeling approaches.

    Science.gov (United States)

    Wikiniyadhanee, Rakkreat; Chotpantarat, Srilert; Ong, Say Kee

    2015-11-01

    Column experiments were performed under various ionic strengths (0.0-0.9 mM) using 10 mg L(-1) of Cd(2+) without kaolinite colloids and 10 mg L(-1) Cd(2+) mixed with 100 mg L(-1) kaolinite colloids. The nonequilibrium two-site model (TSM) described the behavior of both Cd(2+) transport and Cd(2+) co-transported with kaolinite colloids better than the equilibrium model (CD(eq)) (R(2)=0.978-0.996). The results showed that an increase in ionic strength negatively impacted the retardation factors (R) of both Cd(2+) and Cd(2+) mixed with kaolinite colloids. The presence of kaolinite colloids increased the retardation factors of Cd(2+) from 7.23 to 7.89, 6.76 to 6.61 and 3.79 to 6.99 for ionic strengths of 0.225, 0.45 and 0.9 mM, respectively. On the other hand, the presence of kaolinite colloids decreased the retardation factor of Cd(2+) from 8.13 to 7.83 for ionic strength of 0.0 mM. The fraction of instantaneous sorption sites (f) parameters, kinetic constant for sorption sites (α) and Freundlich constant (K(f)) were estimated from HYDRUS-1D of TSM for Cd(2+) transport. The fraction of instantaneous sorption sites was found to increase for an increase in ionic strength. K(f) values of Cd(2+) transport without kaolinite colloids for 0.0, 0.225 and 0.45 mM were found to be higher than those of Cd(2+) transport with kaolinite colloids, except for ionic strength of 0.9 mM. Hence, the presence of kaolinite colloids probably retarded the mobility of Cd(2+) in porous media for higher ionic strengths. Furthermore, retardation factors and K(f) values of both Cd(2+) transport and Cd(2+) co-transport were shown to decrease when ionic strength increased. Interestingly, according to TSM, the fraction of instantaneous sorption sites tends to increase for an increase in ionic strength, which imply that the mechanism of Cd(2+) sorption onto quartz sand can be better described using equilibrium sorption rather than nonequilibrium sorption for an increase in ionic strength. PMID

  16. Large-scale assembly of colloidal particles

    Science.gov (United States)

    Yang, Hongta

    This study reports a simple, roll-to-roll compatible coating technology for producing three-dimensional highly ordered colloidal crystal-polymer composites, colloidal crystals, and macroporous polymer membranes. A vertically beveled doctor blade is utilized to shear align silica microsphere-monomer suspensions to form large-area composites in a single step. The polymer matrix and the silica microspheres can be selectively removed to create colloidal crystals and self-standing macroporous polymer membranes. The thickness of the shear-aligned crystal is correlated with the viscosity of the colloidal suspension and the coating speed, and the correlations can be qualitatively explained by adapting the mechanisms developed for conventional doctor blade coating. Five important research topics related to the application of large-scale three-dimensional highly ordered macroporous films by doctor blade coating are covered in this study. The first topic describes the invention in large area and low cost color reflective displays. This invention is inspired by the heat pipe technology. The self-standing macroporous polymer films exhibit brilliant colors which originate from the Bragg diffractive of visible light form the three-dimensional highly ordered air cavities. The colors can be easily changed by tuning the size of the air cavities to cover the whole visible spectrum. When the air cavities are filled with a solvent which has the same refractive index as that of the polymer, the macroporous polymer films become completely transparent due to the index matching. When the solvent trapped in the cavities is evaporated by in-situ heating, the sample color changes back to brilliant color. This process is highly reversible and reproducible for thousands of cycles. The second topic reports the achievement of rapid and reversible vapor detection by using 3-D macroporous photonic crystals. Capillary condensation of a condensable vapor in the interconnected macropores leads to the

  17. Linking carbon and iron cycles by investigating transport, fate and mineralogy of iron-bearing colloids from peat-draining rivers - Scotland as model for high-latitude rivers

    Science.gov (United States)

    Wood, Deborah; Crocket, Kirsty; Brand, Tim; Stutter, Marc; Wilson, Clare; Schröder, Christian

    2016-04-01

    Linking carbon and iron cycles by investigating transport, fate and mineralogy of iron-bearing colloids from peat-draining rivers - Scotland as model for high-latitude rivers Wood, D.A¹, Crocket, K², Brand, T², Stutter, M³, Wilson, C¹ & Schröder, C¹ ¹Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA ²Scottish Association for Marine Science, University of the Highlands and Islands, Dunbeg, Oban, PA37 1QA ³James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH The biogeochemical iron cycle exerts significant control on the carbon cycle¹. Iron is a limiting nutrient in large areas of the world's oceans and its bioavailability controls CO2 uptake by marine photosynthesizing microorganisms. While atmospheric iron inputs to the open ocean have been extensively measured, global river inputs have likely been underestimated because most major world rivers exhibit extensive iron removal by flocculation and sedimentation during seawater mixing. Iron minerals and organic matter mutually stabilise each other², which results in a 'rusty carbon sink' in sediments³ on the one hand but may also enhance transport beyond the salinity gradient on the other. Humic-rich, high latitude rivers have a higher iron-carrying capacity⁴‑⁶ but are underrepresented in iron flux calculations. The West Coast sea lochs in Scotland are fed by predominantly peatland drainage catchments, and the rivers entering the sea lochs carry a high load of organic matter. The short distance between many of these catchments and the coastal ocean facilitates source-to-sea research investigating transport, fate and mineralogy of iron-bearing colloids providing a good analogue for similar high latitude fjordic systems. We use SeaFAST+ICP-MS and Mössbauer spectroscopy to survey trace metal concentrations, with emphasis on iron concentrations, speciation and mineralogy, across salinity gradients. In combination with ultra-filtration techniques, this allows

  18. The use of colloidal nano gold as an effective modifier for the determination of antimony, arsenic and lead by ETAAS

    International Nuclear Information System (INIS)

    Complete text of publication follows. Colloidal nano gold was prepared and used as a modifier for the determination of antimony, arsenic and lead by electrothermal atomic absorption spectrometry. The effects of pyrolysis and atomization temperature, the amounts of interferants and modifier on the sensitivities of antimony, arsenic and lead in the presence of modifier were investigated. In addition, the contribution of another modifying reagent Mg(NO3)2 mixed with colloidal nano gold was also investigated. The modifier allows the use of pyrolysis temperatures between 1200 deg C and 1300 deg C for antimony, arsenic and lead. In the presence of colloidal nano gold modifier, the tolerance limits of NaCl and Na2SO4 for the quantitative recoveries of antimony, arsenic and lead were investigated. After optimization of experimental conditions, the three elements were successfully determined in some model solutions containing some sulphate and chloride salts as well as in CRM water samples at 95% confidence level using pure aqueous standards. The effectiveness of modifier was compared with that of the mixed universal modifier (Mg+Pd).

  19. EDITORIAL: Colloidal dispersions in external fields Colloidal dispersions in external fields

    Science.gov (United States)

    Löwen, Hartmut

    2012-11-01

    Colloidal dispersions have long been proven as pivotal model systems for equilibrium phase transition such as crystallization, melting and liquid-gas phase transition. The last decades have revealed that this is also true for nonequilibrium phenomena. In fact, the fascinating possibility to track the individual trajectories of colloidal particles has greatly advanced our understanding of collective behaviour in classical many-body systems and has helped to reveal the underlying physical principles of glass transition, crystal nucleation, and interfacial dynamics (to name just a few typical nonequilibrium effects). External fields can be used to bring colloids out of equilibrium in a controlled way. Different kinds of external fields can be applied to colloidal dispersions, namely shear flow, electric, magnetic and laser-optical fields, and confinement. Typical research areas can be sketched with the by now traditional complexity diagram (figure 1). The complexity of the colloidal system itself as embodied in statistical degrees of freedom is shown on the x-axis while the complexity of the problem posed, namely bulk, an inhomogeneity in equilibrium, steady state nonequilibrium and full time-dependent nonequilibrium are shown on the y-axis. The different external fields which can be imposed are indicated by the different hatched areas. figure1 Figure 1. Diagram of complexity for colloidal dispersions in external fields: while the x-axis shows the complexity of the system, the y-axis shows the complexity of the problem. Regions which can be accessed by different kinds of external fields are indicated. The arrows indicate recent research directions. Active particles are also indicated with a special complexity of internal degrees of freedom [1]. This collection of papers reflects the scientific programme of the International Conference on Colloidal Dispersions in External Fields III (CODEF III) which took place in Bonn-Bad Godesberg from 20-23 March 2012. This was the

  20. Extraction and characterisation of colloids in waste repository leachate

    International Nuclear Information System (INIS)

    Inorganic colloids are ubiquitous in environmental waters and are thought to be potential transporters of radionuclides and other toxic metals. Colloids present large surface areas to pollutants and contaminants present in waters and are therefore capable of sorbing and transporting them via groundwater and surface water movement. Much research has been and is currently being undertaken to understand more fully the stability of colloids in different water chemistries, factors which affect metal sorption onto colloids, and the processes which affect metal-colloid transport. This thesis first investigates groundwater and surface water sampling and characterisation techniques for the investigation of the colloids present in and around a low-level waste repository. Samples were collected anaerobically using micro-purge low-flow methodology (MPLF) and then subjected to sequential ultrafiltration, again anaerobically. After separation into size fractions the solids were analysed for radiochemical content, colloid population and morphology. It was found that colloids were present in large numbers in the groundwaters extracted from the trench waste burial area (anaerobic environment), but in the surface drain waters (aerobic environment) colloid population was comparable to levels found in waters extracted from above the trenches. There was evidence that the non-tritium activity was associated with the colloids and particulates in the trenches, but outside of the trenches the evidence was not conclusive because the activity and colloid concentrations were low. Secondly this thesis investigates the stability of inorganic colloids, mainly haematite, in the presence of humic acid, varying pH and electrolyte concentrations. The applicability of the SchuIze-Hardy rule to haematite and haematite/humic acid mixtures was investigated using photon correlation spectroscopy to measure the rate of fast and slow coagulation after the addition of mono, di and trivalent ions. It was